WO1984004597A1 - Method and apparatus for determining carbonate/sulfide concentration - Google Patents

Method and apparatus for determining carbonate/sulfide concentration Download PDF

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Publication number
WO1984004597A1
WO1984004597A1 PCT/US1984/000740 US8400740W WO8404597A1 WO 1984004597 A1 WO1984004597 A1 WO 1984004597A1 US 8400740 W US8400740 W US 8400740W WO 8404597 A1 WO8404597 A1 WO 8404597A1
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Prior art keywords
sample
liquor
gas
acid
reaction chamber
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Application number
PCT/US1984/000740
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French (fr)
Inventor
Jerry Robert Speaks
Ronald Paul Warrick
Thomas Gordon Rozwod
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Weyerhaeuser Co
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Filing date
Publication date
Application filed by Weyerhaeuser Co filed Critical Weyerhaeuser Co
Publication of WO1984004597A1 publication Critical patent/WO1984004597A1/en
Priority to FI850234A priority Critical patent/FI850234A0/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/34—Paper
    • G01N33/343—Paper paper pulp
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods

Definitions

  • the process actually starts with the recovery furnace.
  • the black liquor consisting of organic and inorganic chemicals and water is charged to the furnace where the water is evaporated, the organic components are burned and inorganic components are recovered in the form of a molten smelt.
  • the molten smelt containing mostly sodium carbonate and sodium sulfide is continuously decanted from the furnace bed and dissolved in water
  • a typical green liquor composition is about 60-65% sodium carbonate and 25-28% sodium sulfide by weight (% of solids) expressed as Na»0.
  • a typical solids content of green liquor is around 18% of total liquor weight.
  • the green liquor is pumped from the dissolving tank or tanks to a green liquor clarifier where the dregs settle out.
  • the dregs are impurities, i.e., undissolved solids from the furnace. These are mainly carbon, calcium, magnesium and iron compounds.
  • the green liquor is mixed with reburned lime from the kiln in the slaker. Usually the amount of lime is adjusted to maintain a specified white liquor concentration.
  • Makeup lime in the form of fresh lime (or limestone burned in the kiln) is added to the reburned lime to replace lime losses in the system.
  • Grits large, unreacted lime particles
  • OMPI OMPI . liquor to form calcium hydroxide and this in turn reacts with the sodium carbonate in the green liquor to form sodium hydroxide and calcium carbonate, which then flows to the causticizing cells.
  • Causticizing cells are used to allow enough time for the causticizing reaction that starts in the slaker to approach completion.
  • the slurry is pumped to the white liquor clarifier (or a pressure filter) to separate the white liquor from the lime mud, calcium carbonate.
  • the clarified white liquor is pumped to storage and then to the digester house to pulp wood chips.
  • the mud or calcium carbonate in the bottom of the clarifier is pumped to a mud washer where it is washed with water from the mud filter and the dregs washer.
  • the overflow water from the mud washer is called weak wash and this is used at the dissolving tank or tanks to dissolve the smelt to form raw green liquor.
  • the causticizing reaction is usually controlled by chemical analysis (titration) of the white liquor taken from a causticizing cell or from the white liquor clarifier overflow.
  • Lime feed, green liquor density at the dissolving tank or tanks or a combination of the two is usually changed to maintain a white liquor strength within a mill's specification.
  • the specifica ⁇ tion is generally expressed as the sodium hydroxide and sodium sulfide concentration in the white liquor, i.e., AA (active alkali) or EA (effective alkali).
  • White liquor AA or EA concentration does vary considerably because of changes in lime availability (CaO content), reactivity (rate of hydration), mass flow rate of lime to the slaker or combinations of these.
  • Sodium carbonate concentration changes in the green liquor feed will also affect the resulting white liquor strength.
  • TTA total titratable alkali
  • TTA is a measurement of sodium hydroxide, sodium carbonate, and sodium sulfide, and is, therefore, only an indirect, approximate determination of the Na 2 CO 3 concentration in the liquor.
  • ABC test colorimetric titration
  • TAPPI test T624 OS-68 Parts 9, 10 and 11
  • Titration end points are not identified by a crisp color change. Rather, there is a gradual change in color from, for example, orange to red or from green to blue depending on which indicator is used. This "diffuse" end point determination results in much uncertainty in the liquor concentrations which are the only variables which are measured regularly. There have been attempts to solve these problems. Hultman, et al, U.S. Patents 4,236,960 and 4,311,666 describe a different type of process for controlling the degree of causticizion.
  • TAPPI test T624 OS-68 describes tests for the analysis of soda and sulfite white and green liquors.
  • Test 12 describes the sodium carbonate (evaluation method) test.
  • the proposed process control logic reduces or eliminates most of the above-mentioned process control problems. It is based on the idea that a kraft mill slaker is really a carbonate reactor, i.e., carbonate ions in the green liquor are crystallized from solution with hydrated lime, and sodium hydroxide is generated in the process. Specifically the causticizing control logic is based on determining the concentration of sodium carbonate and sodium sulfide in the green liquor, in the white liquor-mud slurry at the slaker or first causticizer and in the white liquor being sent to the digester house and using this information to control the entire process. This logic is much different than present practice.
  • OMPI s_ - W1PO The reason for measuring the concentration of sodium sulfide in the green liquor is not to control the slaking/causticizing process, but to indicate inefficiencies in the process and to take steps to control them.
  • An increase in sulfide concentration will tend to decrease the efficiency of the causticizing reaction.
  • Knowledge of the concentration of sodium sulfide entering the slaker will indicate to the operator or process computer the optimum causticizing efficiency that can be expected from his recausticiz- ing plant.
  • the changes in sulfide concentration will also indicate changes in recovery boiler sodium sulfide reduction efficiency and will allow steps to be taken to better control boiler sodium sulfide reduction efficiency.
  • Variations in the Na 2 CO 3 concentration in the liquor at the slaker or causticizer are the result of variations in the concentration and flow rate of lime and green liquor.
  • Lime quality and quantity can be variable and difficult to control - changes in mass flow rate, availability (% CaO) and lime reactivity (how fast hydration occurs) affect the Na « CO3 concentration in the slaker/causticizer liquor, but are extremely difficult to measure and control.
  • the concentration and flow rate of the green liquor may be measured and controlled quite easily.
  • the proposed strategy will control the green liquor flow rate to the slaker to maintain the desired Na ⁇ COg concentration in the slaker/causticizer liquor despite variations which occur in the lime.
  • the green liquor concentration is also controlled in a control loop.
  • a constant, desired concentration of Na 2 C0 3 is controlled early in the slaking/causticizing reaction, ensuring safe, efficient operation.
  • the slaking/causticizing process is controlled by adjusting the flow rate and concentration of the green liquor, which is technically quite easy to accomplish. Controlling the concentration, activity, and flow rate of the lime is technically difficult and therefore is allowed to vary within normal limits and the green liquor flow rate is adjusted in response to these variations. This strategy provides much more precise control than do strategies which attempt to adjust lime flow rate in response to changes in liquor flow rate and concentration.
  • This strategy will control the process based on direct measurements of the critical component in the system, sodium carbonate. This provides much more precise control than do strategies based on TTA liquor conductivity, liquor density or other indirect, approximate indications of a 2 CO 3 in process liquors.
  • the overall liquor room production rate (amount of white liquor generated per minute) will be controlled by the flow rate of lime to the slaker. As the production rate needs to be increased or decreased in order to maintain an overall mill liquor balance, the flow rate of lime added to the slaker is correspondingly increased or decreased.
  • the green liquor flow rate will be automatically adjusted by a control loop to maintain the desired
  • N- ⁇ Og concentration in the white liquor N- ⁇ Og concentration in the white liquor. Both chemical inventory (lime and liquor storage levels) and mill production rates can be maintained by this strategy. Chemical inventory and/or production rate may be controlled either manually or automatically.
  • the last measurement is to determine the concentrations of sodium hydroxide, sodium carbonate, and sodium sulfide in the white liquor which is sent to the digester house to be used in the cooking process. It is important to measure the sodium hydroxide and sodium sulfide concentrations in the white liquor so that the amount of liquor to be charged in the digester(s) may be correctly determined. Changes in sodium sulfide concentration (generated at the recovery boiler) can affect white liquor AA/EA concentration.
  • the apparatus takes a sample from an appropriate line - green liquor, slaker/causticizer liquor, or white liquor to the digester - filters the sample if necessary, takes a measured quantity, reacts that measured quantity with an acid to generate hydrogen sulfide and carbon dioxide and measures the quantities of these gases in a gas chromatograph.
  • the apparatus has four main circuits: the filter circuit, the sampling circuit, the reactor circuit and the gas chromatograph circuit.
  • a mud separation eircuit is also utilized if the apparatus is to analyze liquor from the slaker or causticizing cells. A number of operations or modes are performed in each of these circuits during a test cycle. These modes are sequenced differently depending upon the different operation of the mill.
  • the unit must operate consistently over a long period of time and must give reproducible results.
  • the liquor is corrosive and can also plug lines.
  • the inventors have devised an apparatus which eliminates corrosion and reduces line plugging to a minimum. This required a great deal of lab and mill testing and redesign to accomplish. During the testing, it was found that the liquor being analyzed, the degree of completion of the reaction and the temperature of the reactive gases would cause changes in the results which would lead to an inability to control the process. Again, a great deal of time and laboratory and mill testing was required before the problem was recognized, the sources of the problem discovered and corrective measures taken.
  • the present apparatus and control logic is the result of several man-years of work extending over a several-year period and the present application represents the inventor's understanding as of the date of the application of the problem and the solution. The work is continuing.
  • Figure 1 is a diagram of the principal components of the test unit.
  • Figure 2 is a diagram of the filter circuit for the apparatus.
  • Figure 3 is a diagram of a three-filter circuit unit for the apparatus when operating in a three-component configuration.
  • Figure 4 is a diagram of the mud separation circuit.
  • Figure 5 is a cross-sectional view of the reactor for the apparatus.
  • Figure 6 is a top plan view of the reactor for the apparatus.
  • Figure 7 is an interior side plan view partially in cross section showing the magnetic spin bar driver and the spin bar in the reactor chamber.
  • Figure 8 is a cross-sectional view along line 8-8 of Figure 7.
  • Figure 9 is a plot of a gas chromatograph voltage output over the course of gas analysis resulting from a typical green liquor sample.
  • Figure 10 is a schematic diagram of a data collection circuit.
  • Figure 11 is a diagram of a single loop apparatus in a pulp mill.
  • Figure 12 is a diagram of a double loop apparatus in a pulp mill.
  • Figure 13 is a diagram of a triple loop apparatus in a pulp mill.
  • Figure 14 is a diagram of a cascaded control.
  • the apparatus has four main circuits: the filter circuit, the sampling circuit, the reactor circuit and the gas chromatograph circuit.
  • a mud separation circuit is also used if the apparatus is to be utilized to analyze liquor from the slaker or causticizing cells.
  • Each of these circuits has a number of operations or modes which are performed during one test cycle. These modes are sequenced differently depending upon the particular operation of a mill. The parts and modes will be described for each of the circuits. A possible sequence will then be described. It should be noted that most of the operable valves throughout the unit are two-position valves. This is for ease and simplicity of operation. Three-position valves or multiple port valves are used in several specific applications. Where so used, the use of these valves is noted.
  • Filter Circuit The purpose of the filter circuit is to remove particulate material from the liquor to prevent both the plugging of the test equipment and the chemical side reactions that would mask the true composition of the liquor.
  • the following description is directed to the filter circuit of Figures 2 and 3.
  • Each of the filter circuits in the three circuit array shown in Figure 3 would have the same parts and operating sequence, so the same reference numerals will be used for the individual elements in these circuits.
  • the circuit has the following components: Major components F - Filter. FS - Filter shock dome. Lines
  • ML - Mill liquor line in the causticizing system between the green liquor clarifier and the slaker, between the slaker and first causticizer, between the first and second caustic ⁇ zers or between the clear white liquor storage tank and the digester, depending on the liquor being sampled.
  • L22 Sampling line from the filter outlet line L30A to the sampling circuit.
  • L28 Liquor return line from the filter circuit to the clarifier, slaker or causticizer depending on liquor being sampled.
  • L30 - Filter outlet line from the upper part of the filter F to the liquor return line L28.
  • L30A Filter outlet line from the fUter F to the sampling line L22.
  • L30B Filter outlet line from the filter outlet line L30A to the filter backflush line L31.
  • L30C Filter outlet line from the filter outlet line L30B to the liquor return line L28.
  • L31 Filter backflush line from the valve V28 to the filter outlet line L30C.
  • L32 Filter bypass line from the filter circuit inlet line L29 to the liquor return line L28.
  • L33 Air inlet line to the top of the filter shock dome FS.
  • L33A Air inlet line from the air supply to the water backflush line L37.
  • L33B Air and water inlet line between the water backflush line L37 and the top of the filter shock dome FS.
  • L34 Filter inlet and filter backflush outlet line between the valve V28 and the bottom of the filter F.
  • L35 Inlet line from the filter circuit liquor supply line L29 to the valve V28.
  • L36 Water supply line.
  • V26 - Valve in the air inlet line L33A Two positions: open; closed. • V28 - Filter inlet-backflush three-way T valve at juncture of the filter backflush line L31, the filter inlet line L34 and the inlet line L35. Two positions: position one (backflush) (IB) - open to the filter backflush line L31 and the filter backflush outlet line L34, closed to the inlet line L35; position two (filter) (2F) - open to the filter inlet line L34 and the inlet line L35, closed to the filter backflush line L31.
  • IB backflush
  • V23 Check valve in the filter backflush line L31 to prevent flow through the line L31 into the filter F.
  • Pressure valve (open or partially open, manually operable)
  • V20 - Back pressure valve in the filter outlet line L30B to provide pressure in the filter F and to induce preferential flow into the sampling line L22 when the valve V22 is open.
  • Pressure relief valve (normally closed, automatically openable)
  • V27 Pressure relief valve on the filter F. Repair valves (normally open, manually operable) V19 - Repair valve in the liquor return line L28. V25 - Repair valve in the filter circuit liquor supply line
  • the filter circuit has several operating modes. Bypass mode (no liquor to filter) (Bypass)
  • the first mode is a liquor bypass mode in which the liquor is taken from the mill liquor line, through the bypass line and returned to the slaker or causticizer without passing through the filter. Lines involved
  • L28 Liquor return line from the filter circuit.
  • L29 Liquor supply line from the mill liquor line ML to the filter eircuit.
  • L32 Filter bypass line from the f ilter circuit inlet line L29 to the filter eircuit outlet line L28. Valves involved Operating valves/position
  • the second mode is a liquor filtering mode in which the liquor is taken from the mill liquor line, filtered in the filter F and returned to the return line in order to establish steady state filtering of the liquor.
  • Major components involved are involved
  • F - Filter Lines involved ML - Mill liquor line.
  • L29 -_ Liquor supply line from the ⁇ iill liquor line ML to the filter circuit.
  • L30 - Filter outlet line from the upper part of the filter F to the return line L28.
  • VI 8 Check valve in the filter outlet line L 3 OB to prevent flow through the line L30 into the filter F.
  • a filter cycle is immediately performed to provide a liquor sample for the first reaction.
  • the filter cycle is started at a time determined by an action somewhere else in the system. It can be started by a sequencer output which is energized when a new liquor sample is desired. This could be signaled by completion of filling the acid pump AP2 or opening the valve which applies pressure to the reactor Rl. Time
  • the third mode is a liquor sampling mode in which the liquor is taken from the mill liquor line, filtered and sent to the sampling circuit to provide the test sample.
  • the parts, lines, valves and valve positions are the same in this mode as in the second mode, the filter mode, except for the following change.
  • F - Filter Lines involved L22 - Sampling line from the filter outlet line L30A to the sampling circuit.
  • V22 Valve in the sampling line L22/open.
  • Pressure valves V20 - Back pressure valve in the filter outlet line L30B provides back pressure to cause preferential diver ⁇ sion of the filtered liquor into the sampling line L22.
  • the fourth mode is a stop sampling mode which is a pause to allow the sample valve V22 in the sampling circuit to change position.
  • the parts, lines, valves, valve positions and flows are the same as in the second mode - the filter mode.
  • Liquor backflush mode The fifth mode is a liquor backflush mode, in which the liquor is used to backflush or backwash particulate matter in the filter from the filter to the return line. It takes place in two stages. Stage 1 (Backflush 1)
  • stage 1 the filter outlet valve V21 is closed and liquor from the mill liquor line ML fills the filter to the middle of the filter shock dome FS.
  • ML - Mill liquor line ML - Mill liquor line.
  • L29 Liquor supply line from the mill liquor line ML to the filter circuit.
  • L33 Air inlet line to the top of the filter shock dome FS.
  • L34 Filter inlet line from the valve V28 to the bottom of the filter F.
  • V22 Valve in the sampling line L22/closed.
  • V24 Valve in the filter bypass line L32/closed.
  • V26 Valve in the air inlet line L33A/closed.
  • V 8 Filter inlet-backflush valve/position two (filter) (2F) - open to the filter Inlet line L34 and the inlet line L35, closed to the filter backflush line L31.
  • V29 Valve in the water backflush line L3 /closed. Repair valves
  • V25 - Repair valve in the filter eircuit liquor supply line L29 V25 - Repair valve in the filter eircuit liquor supply line L29.
  • stage 2 air admitted at the top of the filter shock dome FS, drives the liquor through the filter element of the filter F, out the inlet to the filter element, through the filter backflush outlet line
  • V22 Valve in the sampling line L22/closed.
  • V24 Valve in the filter bypass line L32/open.
  • V26 Valve in the air inlet line L33 A/open.
  • V28 Filter inlet-backflush valve/position one (backflush) (IB) - open to the filter backflush line L31 and the filter backflush outlet line L34, closed to the inlet line L35.
  • V23 Check valve in the backflush line L31 to prevent flow through the line L31 into the filter F.
  • Repair valves VI 9 Repair valve in the filter circuit liquor return line
  • the sixth mode is a water backflush mode in which water is introduced at the top of the filter shock dome FS and washes particulate matter from the filter element, out the bottom of the filter through the filter backflush outlet line L34, the backflush line L31, the filter outlet line L30C, and the filter circuit liquor return line L28.
  • the water backflush mode would normally occur in place of a first mode, a bypass mode, and would follow a fifth mode, the liquor backflush mode. It is used any time the filter is excessively dirty with particulate matter.
  • the liquor supply would normally be turned off.
  • the parts, lines, valves and valve positions are the same as in stage 2 of the fifth mode, stage 2 of the liquor backflush mode, with the following additions and changes. Lines involved
  • L33B Inlet line from the water backflush line L37 to the top of the filter shock dome FS.
  • L36 Water supply line.
  • L37 Water backflush line from the water supply line L36 to the inlet line L33B. Valves involved
  • Mud separation circuit - slaker/causticizer white liquor It is often desirable for control applications to obtain liquor samples directly from the slaker or causticizer for analysis.
  • This liquor contains 8-10% by weight suspended calcium carbonate mud solids, which must be removed prior to analysis.
  • the level of solids loading present in this liquor is too high to be introduced immediately to the filter circuit since severe plugging of the filter element would result.
  • the purpose of the mud separation unit is to remove the bulk of the solids from the liquor and yield
  • OMPI a "clear" liquor containing 1% or less suspended mud solids. This "clear” liquor is filterable and becomes the liquor supply to the filter circuit. It should be noted that the mud separation unit in no way interferes with subsequent operation of the analyzer system.
  • the filter, sample, reactor, and gas chromatograph circuits operate exactly as they do when no mud separation circuit is utilized. The mud separation circuit merely ensures that an acceptable liquor sample is provided to the filter eircuit.
  • the best method of mud separation has been found to involve the use of a continuous settling cone.
  • This device receives unclarified liquor from the slaker or causticizer, separates the mud from the liquor, returns the mud to the slaker or causticizer, and supplies a continuous "clear" liquor supply to the filter circuit.
  • the advantages of this apparatus and method are simplicity, reliability, ease of operation and a fresh, uninterrupted supply of liquor to the filter circuit so that operation of the filter circuit is not disturbed.
  • the settling cone itself is a no ⁇ mechanical thickener of a type commonly used for continuous liquid-solid separations in low volume appli ⁇ cations.
  • the details of the construction and operation of these units are well known and will not be given in detail here, but may be found in Perry, J. H. (Ed.) Chemical Engineers Handbook, 3rd Ed., McGraw-Hill Book Co., Inc. New York, 1950, pp. 940-941.
  • the mud separation unit should be designed for a capacity that will deliver a desirable flow of "clear" liquor (approximately 2-3 liters/minute) to the filter circuit.
  • the following description is of the mud separation circuit shown in Figure 4.
  • the circuit consists of the following components: Major components
  • SP1 Unclarified liquor supply pump from unclarified liquor supply line L39 to unclarified liquor supply line L40.
  • SP2 Clear liquor supply pump in filter circuit liquor
  • L29 Liquor supply line to the filter circuit.
  • L39 Unclarified liquor supply line from slaker (or causti ⁇ cizer) to unclarified liquor supply pump SP1.
  • L40 Unclarified liquor supply line from unclarified liquor supply pump SP1 to junction of settling cone inlet line L41 and settling cone bypass line L42.
  • L41 Settling cone inlet line from unclarified liquor supply line L40 to settling cone Tl.
  • L42 Settling cone bypass line from unclarified liquor supply line L40 to slaker (or causticizer) return line L50.
  • L43 Clear liquor supply line from bustle pipe/launder ring apparatus Bl to junction of clear liquor tank inlet line L44 and clear liquor tank bypass line L46.
  • L44 Clear liquor tank inlet line from clear liquor supply line L43 to clear liquor tank T2.
  • L45 Clear liquor tank overflow line from clear liquor tank T2 to clear liquor bypass/overflow line L48.
  • L46 Clear liquor tank bypass line from clear liquor supply line L43 to clear liquor bypass/overflow line L48.
  • L47 Clear liquor tank outlet line from clear liquor tank T2 to junction of filter circuit liquor supply line L29 and clear liquor tank drain line L51.
  • L48 Clear liquor tank bypass/overflow line from junction of clear liquor tank bypass line L46 and clear liquor tank overflow line L45 to slaker (causticizer) return line L50.
  • L49 Settling cone mud discharge line from settling cone
  • V30 - Settling cone inlet valve in settling cone inlet line L41 Two positions: open, closed.
  • V31 Settling cone bypass valve in settling cone bypass line L42. Two positions: open, closed.
  • V32 Clear liquor tank bypass valve in clear liquor tank bypass line L46. Two positions: open, closed.
  • V33 Clear liquor tank inlet valve in clear liquor tank inlet line L44. Two positions: open, closed.
  • V34 Clear liquor tank outlet valve in fftter circuit liquor supply line L29. Two positions: open, closed.
  • V35 Clear liquor tank drain valve in clear liquor tank drain line L51. Two positions: open, closed.
  • V36 Water flush valve in water flush line L52. Two positions: open, closed.
  • V37 Unclarified liquor supply valve in unclarified liquor supply line L39..
  • the mud separation unit has five modes of operation, these being the normal operating mode, the clear liquor tank bypass mode, the settling cone bypass mode, the circuit shutdown/water flush mode, and the circuit shutdown/standby mode.
  • Normal operating mode The first mode is the normal operating mode. The circuit will normally remain in this mode. The circuit will be removed from this mode only as necessitated by the need for repairs to the mud separation or filter circuits, or upon shutdown of the slaking/causticizing process.
  • Major parts involved Tl - Continuous settling cone.
  • T2 Clear liquor tank.
  • SP1 Unclarified liquor supply pump/on.
  • SP2 Clear liquor supply pump/on.
  • Bl Bustle pipe/launder ring apparatus. Lines involved
  • L43 Clear liquor supply line.
  • L44 Clear liquor tank inlet line.
  • V30 - Settling cone inlet valve/open V30 - Settling cone inlet valve/open.
  • V31 - Settling cone bypass valve/closed V31 - Settling cone bypass valve/closed.
  • V32 Clear liquor tank bypass valve/closed (or throttled).
  • V34 Clear liquor tank outlet valve/open.
  • V35 Clear liquor tank drain valve/closed.
  • the time will vary.
  • the circuit will normally be in this mode, being removed from this mode only for maintenance of this circuit or the filter circuit or upon shutdown of the slaking and causticizing process.
  • the second mode is the clear liquor tank bypass mode. This mode is utilized when it is necessary to stop the flow of clear liquor to the clear liquor tank. This may be necessitated by the need for repairs to this part of the circuit, or by the need for repairs to the filter circuit which require that the flow of clear liquor to the filter circuit be stopped.
  • Tl Continuous settling cone.
  • T2 Clear liquor tank.
  • SP1 Unclarified liquor supply pump/on.
  • L41 Settling cone inlet line.
  • L43 Clear liquor supply line.
  • L46 Clear liquor tank bypass line.
  • L47 Clear liquor tank outlet line.
  • L48 Clear liquor tank bypass/overflow line.
  • L49 Settling cone mud discharge line.
  • L50 Slaker (or causticizer) return line.
  • L51 Clear liquor tank drain line.
  • Operating valves/position V30 Settling cone inlet valve/open.
  • V31 Settling cone bypass valve/ closed.
  • V32 Clear liquor tank bypass valve/open.
  • V33 Clear liquor tank inlet valve/closed.
  • V34 Clear liquor tank outlet valve/closed
  • V35 Clear liquor tank drain valve/open.
  • V36 Water flush valve/closed.
  • V37 Unclarified liquor supply valve/open.
  • the third mode is the settling cone bypass mode. . This mode is utilized when it is necessary to stop operation of the settling cone in order to repair this part of the circuit. The flow of clear liquor will be interrupted in this mode and there will be no sample flow to the filter eircuit and analyzer.
  • V31 - Settling tank bypass valve/open V31 - Settling tank bypass valve/open.
  • Circuit Shutdown/Water Flush Mode The fourth mode is the circuit shutdown/water flush mode. This mode is used when it is necessary to entirely shut down the circuit for maintenance or in response to a shutdown of the slaking/causticizing process. The flow of unclarified liquor to the system is stopped and all lines and major parts are flushed with water to ensure that they are clean and unplugged.
  • Tl Settling cone.
  • T2 Clear liquor tank.
  • SP1 Unclarified liquor supply pump/on.
  • SP2 Clear liquor supply pump/on.
  • L40 Unclarified liquor supply line.
  • L41 Settling tank inlet line.
  • L42 Settling tank bypass line.
  • L43 - Clear liquor supply line L44 - Clear liquor tank inlet line.
  • L48 Clear liquor tank bypass/overflow line.
  • L49 Settling cone mud discharge line.
  • L50 Return line to slaker or causticizer.
  • L51 Clear liquor tank drain line.
  • L52 Water flush line. Operating valves/position
  • V30 Settling cone inlet valve/open.
  • V31 Settling cone bypass valve/open.
  • V32 Clear liquor tank bypass valve/open.
  • V33 Clear liquor tank inlet valve/open.
  • V34 Clear liquor tank outlet valve/open.
  • V35 Clear liquor tank drain valve/open.
  • V36 Water flush valve/open.
  • V37 Unclarified liquor supply valve/closed.
  • the fifth mode is the circuit shutdown/standby mode. This mode is used after the circuit has been flushed with water. The circuit is in a "standby" condition and will remain in this condition until restarted. Major components involved
  • V30 Settling tank inlet valve/open.
  • V31 Settling tank bypass valve/closed.
  • V32 Clear liquor tank bypass valve/closed.
  • V33 Clear liquor tank inlet valve/open.
  • V34 Clear liquor supply valve/open.
  • V35 Clear liquor tank drain valve/closed.
  • V36 Water flush valve/closed.
  • V3 Unclarified liquor supply valve/closed.
  • the sample loop obtains a 10 cc sample of the filtered liquor and the acid pump obtains a 50 cc sample of 10% sulfuric acid by volume (approximately 2.2 N).
  • the acid pump strokes to deliver a full 50 cc of acid but only 40 cc goes to reactor.
  • the rest is left in the sample loop SL2 and is washed out when fresh liquor displaces the acid in the liquor sampling mode.
  • SL2 Sample loop for obtaining a 10 ' cc filtered liquor sample. It is connected to the ports P5 and P6 of the sample valve VI 4.
  • API The air piston for operating the piston in the positive displacement acid pump AP2. Two posi ⁇ tions: position one (acid in or fill) (IF); position two (acid out or transfer) (2T).
  • AP2 Positive displacement acid pump for obtaining a 50 cc sample of 10% sulfuric acid. Two positions: position one (acid fill and standby) (IF); position two (acid out or transfer) (2T). Lines
  • LI 6 Air line from the valve Vll to the port P2 of the sample valve V14 for supplying air to move the sample valve V14 to position two (transferring) (2T).
  • L17 Sample line from the port P4 of the sample valve V14 to the port R9 of the reactor Rl.
  • L19 Acid line from the acid line L21 to the port P3 of the sample valve V14.
  • L20 Acid supply line from the acid supply to the acid line L21.
  • L21 Acid line from the juncture of acid lines LI 9 and
  • L22 Sample line from the filter system to the port P8 of the sample valve V14.
  • L23 Sample line from the port P7 of the sample valve V14 to the sewer.
  • Vll - Solenoid operated air valve connecting the air line L14 to either the air line LI 5 or the air line LI 6 to position the sample valve V14.
  • V14 - Air operated sample valve has two operational ports.
  • V17 - Solenoid operated air valve connecting air line L26 to either the air line L24 or the air line L25.
  • V12 - Check valve in the sample line L17 prevents material or gas from returning through the line LI 7 from the reactor Rl to the sampling circuit.
  • V15 - Check valve in the acid line LI 9 prevents baekflow of acid from L19 through L20 into AP2 during the acid pump fill mode.
  • the sample valve and its associated sample loop receives and holds a measured liquor sample.
  • the acid system receives and holds a measured amount of acid separate from the liquor sample. These are held until the reactor can accept the sample and the acid.
  • the eircuit then transports the sample, followed by the acid, to the reactor Rl. During this latter step, the acid passes through the sample loop SL2. This accomplishes two objectives: (1) the sample is transported to the reactor assembly by the acid and (2) the sample loop is cleaned by the acid during the injection.
  • the sampling circuit has several operating modes. In many of these modes the valving arrangement is the same.
  • An initial acid flush cycle (Modes 1-4) is performed at start-up to ensure that the sample system is clean and filled with acid before sample analysis begins. At start-up, there may or may not be a sample in the sample loop depending upon the status of the sample system at shutdown.
  • the first mode is a standby mode in which there is acid or liquor in the sample loop SL2, depending on the status of the sample circuit at shutdown.
  • API Air operated piston for operating the piston in the acid pump/position one (acid fill) (IF).
  • AP2 Acid pump/position one (acid fill) (IF).
  • L24 Air line from the valve V17 to the inner side of the piston in API.
  • L26 Air line from the air supply line L27 to the valve V17.
  • L2 Air supply line.
  • Vll - Solenoid operated air valve/position one (sampling) (IS): connecting the air lines L14 and L15.
  • AR2 Pressure regulation valve in the air line L26.
  • AR3 Pressure regulation valve in the air line L14.
  • Sample valve repositioning mode (Reposition 1)
  • the second mode is a sample valve repositioning mode. The sample valve is moved from the sample receiving position to the sample transferring position.
  • API Air operated piston for operating the piston in the acid pump/position one (acid ill) (IF).
  • AP2 Positive displacement acid pump/position one (acid fill) (IF).
  • V14 Air operated sample valve/position two (transfer ⁇ ring) (2T): connecting the ports P3, P4, P5 and P6.
  • VI 5 - Check valve in the acid line LI 9 holds acid in the line L19.
  • VI 6 - Cheek valve in the acid supply line L20 holds acid in the acid lines L20 and L21.
  • AR2 Pressure regulation valve in the air line L26.
  • AR3 Pressure regulation valve in the air line L14. Flow Air L27 through AR3 through L14 through Vll through L16 through P2 into V14.
  • the third mode is a transfer mode in which the acid pump forces the 50 cc of acid in the acid pump AP2 through the sample loop SL2 and into the reactor. An initial flushing of the system with acid is performed to ensure that the system is cleaned and filled with acid before sample analysis commences.
  • LI 6 Air line from the valve Vll to the port P2 of the sample valve V14.
  • L17 Sample line from the port P4 of the sample valve V14 to the port R9 of the reactor Rl.
  • L19 Acid line from the acid line L21 to the port P3 of the sample valve VI 4.
  • V12 - Check valve in the sample line L17 prevents the liquor and acid from returning to the sample circuit once it has entered the reactor.
  • VI 5 - Check valve in the acid line LI 9 allows acid to flow from AP2 through L21 through LI 9 into V14.
  • V16 - Check valve in the acid line L20 prevents acid from returning to the acid supply system when AP2 transfers the acid.
  • AR2 Pressure regulation valve in the air line L26.
  • AR3 Pressure regulation valve in the air line LI 4.
  • the fourth mode is a second sample valve repositioning mode to move the sample valve from position two (transferring) to position one (sampling), and to move the acid pump from position two (acid transfer) to position one (acid fill) to fill the acid pump with acid and antiflocculant. It is necessary to add antiflocculant to the reaction mixture to prevent flocculation and deposition of sulfur in the reactor. It is best to add a known amount of antiflocculant to each reaction by mixing antiflocculant solution with acid when the acid pump refills.
  • the proportions of acid and antiflocculant drawn into the acid pump AP2 will be such as to ensure a desirable concentration of antiflocculant in the reaction mixture.
  • API Air operated piston for operating the piston in the acid pump/position one (acid fill) (IF).
  • API - Positive displacement acid pump/position one (acid fill) (IF).
  • VI 6 - Check valve in the acid supply line L20 allows acid to flow from L20 through L21 into AP2.
  • Pressure regulation valves AR2 - Pressure regulation valve in the air line L26 are Pressure regulation valves AR2 - Pressure regulation valve in the air line L26.
  • the fifth mode is a second standby mode (Standby 2) in which the sample valve waits to receive a sample from the filter circuit. It is identical to the first mode (Standby 1) and will not be given in detail again.
  • Its time is 12 minutes, but may change depending on the operation of a particular system.
  • the sixth mode is a sample collecting mode in which a sample is collected from the filter circuit.
  • API Air operated piston for operating the piston in the acid pump/position one (acid fill) (IF).
  • AP2 Positive displacement acid pump/position one (acid fill) (IF).
  • IS Air operated sample valve/position one (sampling)
  • IS connecting the ports P5, P6, P7 and P8.
  • VI Solenoid operated air valve/position one (acid fill)
  • VI 5 - Check valve in the acid line LI 9 holds the acid in the line L19.
  • V16 - Cheek valve in the acid supply line L20 holds the acid in the lines L20 and L21.
  • AR2 Pressure regulation valve in the air line L26.
  • AR3 Pressure regulation valve in the air line L14.
  • the seventh mode is a third standby mode (Standby 3) in which the sample circuit waits for the reactor circuit to receive the sample. It is identical to the first and fifth modes (Standby 1 and Standby 2) and will not be given in detail.
  • the sample loop is filled with liquor rather than acid at this stage.
  • the eighth mode is a third sample valve repositioning mode
  • the ninth mode is a second transfer mode (Transfer 2) in which the acid pump forces the 50 cc of acid through the sample loop and into the reactor. This carries the sample into the reactor also. Acid remains in the sample loop to clean the sample loop of any material that may have coated on the tubing during the seventh mode (Standby 3). This acid and the residue will be removed from the system during the next sample collecting mode. It is identical in operation to the third mode (Transfer 1) and will not be given in detail.
  • the tenth mode is a fourth repositioning mode (Reposition 4) in which the sample valve V14 is moved from position two (transferring) to position one (sampling) and the acid pump AP2 is filled with acid and antiflocculant. It is identical to the fourth mode (Reposition 2) and its time is the same. Reactor circuit
  • the reactor is shown in Figures 5 and 6 and the reactor circuit is shown in the bottom left hand section of Figure 1.
  • the reactor Rl has a reactor compartment R2 which is defined by a cover member R3, sidewalls R4 and a base R5.
  • the cover member R3 has four ports: R6 for the vent gas from the reactor to the sewer line, R7 for the wash water to the reactor, R8 both for the reactor gas from the reactor to the gas chromatograph and for gas under pressure to pressurize the reaction chamber, and R9 for the sample and acid to the reactor.
  • the base R5 defines the bottom R10 of the chamber R2.
  • the bottom R10 is sloped toward the central outlet valve V13 so that the reaction chamber R2 may be washed and drained easily after each reaction.
  • the magnetic spin bar R13 provides turbulence and mixing of the reaction mixture.
  • the base R5 rests on a pressure chamber Rll and pressure within the chamber Rll is maintained by the rubber diaphragm R12 between the base R5 and the pressure chamber Rll.
  • the valve VI 3 drops into its lower position allowing the reaction chamber R2 to be drained.
  • the liquid goes into outlet line LI 8 to be sewered or otherwise treated.
  • the reactor circuit has the following components: Major components
  • LI Air line from the valve V10 to the reactor outlet pressure chamber Rll.
  • L2 Line to the gas chromatograph GC.
  • L2A Line between the reactor gas line L ⁇ and the gas chromatograph GC.
  • L2B Line between the reactor pressurization line L10 and the line L2A.
  • L3 Air line between the air supply line L27 and the line Lll.
  • L4 Water supply line between the water supply and the port R7 of the reactor Rl.
  • L5 Vent line from the port R6 of the reactor Rl to the sewer.
  • L6 Reaction gas line from the line L13 to the line L2A.
  • L27 and lines L8 and L2B Lll - Connecting line between the air line L3 and the gauge line L12, and the reactor gas line L6, the air pressure line L8 and the reactor line LI 3.
  • L12 Gauge line between the air line L3 and the connect ⁇ ing line Lll, and the gauge protector Gl and the pressure gauge G2.
  • L13 Reactor line between the port R8 of the reactor Rl and the juncture of the reactor gas line L6, the reactor pressurization line L8 and the connecting line Lll.
  • LI 4 Air line between the air supply line L27 and the valve V10.
  • L17 Sample line between the sample valve V14 and the port R9 of the reactor Rl.
  • L18 Outlet line from the valve VI 3 of the reactor Rl. Valves
  • V10 - Valve between the air line L14 and the air line LI Two positions: open; closed. Operating valves (air operated)
  • V12 - Check valve in the sample line L17 preventing either the sample, the reaction gas or air from flowing back through the sample line L17.
  • AR1 Pressure regulation valve in the air line LI.
  • AR3 Pressure regulation valve in the air line LI 4.
  • AR4 Pressure regulation valve in the air line L3.
  • the acid and sample are placed in the reactor and the reaction starts.
  • the reactor is placed under pressure using a precise air pressure regulator. This is important if a direct relationship between gas chromato ⁇ graph output and liquor concentration is to be obtained.
  • the final reactor pressure should be about 2 psi above the highest total reactor pressure resulting from the sum of all the partial pressures or the expected components or 26 psi above the ambient pressure. This is to compensate for the dependence of reactor pressure on liquor concentration which would provide an incorrect reading if there was no compensation.
  • reaction gas is transferred to the gas chromatograph.
  • the time of transfer must be long enough to obtain a representative sample of gas in the sample loop SL1 of the gas chromatograph. This usually requires 40-50 seconds.
  • the cycle takes approximately 19 minutes, but will vary according to the characteristics of each individual system.
  • the first mode of the reactor circuit is a standby mode in which the reactor is waiting to receive the sample. It usually occurs only at start ⁇ up.
  • the reactor contains whatever was present in it at shutdown. This can be the old reaction mixture, wash water, etc. Major components involved
  • V4 Valve in the water line L4/closed.
  • V5 Valve in the vent line L 5 /closed.
  • V6 Valve in the reaction gas line L6/closed.
  • V8 Valve in the air pressure line L8/closed.
  • V10 Valve between the air lines L14 and Ll/open.
  • Vent mode The second mode is a vent mode.
  • the reactor is vented when the sample valve V14 is repositioned from position one (sampling) to position two (transferring). This allows the pressure in the reaction chamber to reach atmospheric pressure prior to sample injection.
  • the gas in the reactor contains, at most, minor amounts of carbon dioxide and hydrogen sulfide. Major components involved
  • VIO Valve between the air lines L14 and Ll/open to hold the outlet valve VI 3 of the reactor Rl closed.
  • VI 3 Outlet valve from the reactor Rl/closed.
  • Pressure regulation valves AR1 Pressure regulation valve in the air line LI.
  • Drain mode Drain
  • the third mode is a reactor drain mode. During the washing cycle the reactor is drained either of reaction products or of wash water.
  • L3 Air line from the air supply line L27 to the connecting line Lll.
  • Lll Connecting line from the air line L3 to the reactor line LI 3.
  • LI 3 Reactor line from the connecting line Lll to the port R8 of the reactor Rl.
  • LI 8 Outlet line from the reactor Rl.
  • L2 Air supply line. Valves involved Operating valves/position
  • V12 - Check valve in the sample line L17 prevents air from escaping through the sample line L17.
  • the fourth mode is the reactor fill mode. During the wash cycle, the reactor is filled with wash water. Major components involved
  • V4 Valve in the water line L4/open.
  • V5 Valve in the vent line L5/open.
  • V6 Valve in the reaction gas line L6/closed.
  • V8 Valve in the air pressure line L8/closed.
  • VIO Valve between the air lines L14 and Ll/open.
  • V12 - Check valve in the sample line L17 prevents air from entering the sample circuit.
  • the sixth mode is the sample transferring mode.
  • the sample is received from the sampling circuit.
  • Major components involved Rl - Reactor.
  • LI Air line from the valve VIO to the outlet valve 13 of the reactor Rl.
  • L14 Air line from the air supply line L27 to the valve VIO.
  • V3 Valve in the air line L3/closed.
  • V4 Valve in the water line L4/closed.
  • V5 Valve in the vent line L5/closed.
  • V6 Valve in the reaction gas line L6/elosed.
  • V8 Valve in the air pressure line L8/closed.
  • V12 - Check valve in the sample line L17 prevents the sample or reaction gases from returning through line
  • Reaction mode The seventh mode is the reaction mode. The reaction between the acid and the sample takes place in the reaction chamber. There are two stages in the reaction mode, reaction 1 and reaction 2. Reaction 2 is the continuation of reaction 1 after pressure has been applied to the reaction chamber and is identical to reaction 1. Major components involved
  • V4 Valve in the water line L4/closed.
  • V5 Valve in the vent line L5/closed.
  • V6 Valve in the reaction gas line L6/closed.
  • V8 Valve in the air pressure line L8/closed.
  • V10 Valve between air lines L14 and Ll/open.
  • V12 - Cheek valve in the sample line L17 prevents the reaction gas from entering the sample circuit through the sample line L17.
  • AR1 Pressure regulation valve in line LI.
  • AR3 Pressure regulation valve in air line L14. Flow Air L27 through AR3 through L14 through VIO through LI through AR1 into Rll to hold VI 3 closed. Time
  • the total time of the reaction is about 15 minutes. It is divided into the two parts before and after pressure is applied.
  • the eighth mode is a pressurization mode. Eleven minutes after the reaction begins, air pressure is applied through a precise regulator to the reaction chamber to maintain a constant final reactor pressure. It was decided to pressurize 11 minutes into the reaction, because at this time:
  • the time of pressurization may be changed as needed in response to the characteristics of individual reactor systems.
  • the pressurization step was added in response to observations made during the development of the system. In order to make valid comparisons among samples, it is necessary to have a constant final gas pressure. If this is not done, then the experience of our experiments will be repeated. In these experiments, the final gas pressure inside the reactor was allowed to remain at whatever pressure existed due to the release of carbon dioxide and hydrogen sulfide from the reaction. This pressure varied according to the amounts of sodium carbonate and sodium sulfide in the liquor sample. It was observed that, although an increase in sodium carbonate concentration in the liquor did cause an increase in the carbon dioxide peak area generated by the gas chromatograph, the relationship was not directly proportional.
  • the carbon dioxide peak area was influenced by the amount of Na « s ⁇ the liquor, which resulted in erroneous sodium carbonate measurements due to changes in the sodium sulfide concentration in the liquor.
  • the measurement of sodium sulfide in the liquor was affected in the same manner. After this was realized, it was decided to adjust the pressure so that there would be the same total moles of gas in the system for each measurement. This ean be done by maintaining the reaction gas in the reactor at a constant pressure at the completion of the reaction. The addition of air will act as a diluent, and the total moles of gas will remain fixed among a number of samples.
  • L8 and the port R8 of the reactor Rl L14 - Air line between the air supply line L27 and the valve VIO.
  • V3 Valve in the air line L3/closed.
  • V4 Valve in the water line L4/closed.
  • V5 Valve in the vent line L5/closed.
  • V6 Valve in the reaction gas line L6/elosed.
  • V8 Valve in the reactor pressurization line L8/open.
  • VIO Valve between the air lines L14 and Ll/open.
  • VI 3 Outlet valve in the reactor Rl/elosed.
  • V12 - Check valve in the sample line L17 prevents reac ⁇ tion gases from entering the sample circuit through the sample line.
  • AR5 - Pressure regulation valve having a precision of + .02 psi in the reactor pressurization line L10.
  • the ninth mode is the reaction gas transfer mode.
  • the reaction gas is transferred to the gas chromatograph (G.C). This requires enough time to allow a representative sample to be received in the sample loop SLl of the gas chromatograph.
  • LI Air line between the valve VIO and the reactor outlet valve V13.
  • L2A Line between the reaction gas line L6 and the gas chromatograph.
  • L6 Reaction gas line between the reactor line LI 3 and the gas chromatograph line L2A.
  • LI 3 Reactor line between the port R8 of the reactor Rl and the reaction gas line L6.
  • L14 Air line between the air supply line L27 and the valve VIO.
  • V5 Valve in the vent line L5/closed.
  • V6 Valve in the reaction gas line L6/open.
  • V8 Valve in the air pressure line L8/elosed.
  • VIO Valve between the air lines L14 and Ll/open.
  • VI 3 Outlet valve in the Reactor Rl /closed.
  • V12 - Check valve in the sample line L17 prevents reac ⁇ tion gas from entering the sample circuit through the sample line L17.
  • AR1 Pressure regulation valve in the air line LI.
  • AR3 Pressure regulation valve in the air line LI 4.
  • the tenth mode is the stop transfer mode.
  • the reaction gas valve V6 is closed. Time is allowed for the pressure in the gas chromatograph system to equalize.
  • V3 Valve in the air line L3/elosed.
  • V4 Valve in the water line L4/closed.
  • V5 Valve in the vent line L5/closed.
  • V6 Valve in the reaction gas line L6/closed.
  • V8 Valve in the air pressure line L8/closed.
  • V12 - Check valve in the sample line L17 prevents reac- tion gas from entering the sampling system through the sample line.
  • the liquor within the reactor chamber R2 is stirred by the mixing rod R13 within the reactor and resting on the drain valve V13 in the bottom of the reactor.
  • This rod is magnetically coupled with and rotated by the magnetic spin bar driver M2 in chamber Ml.
  • the magnetic spin bar driver is shown in Figures 7 and 8.
  • a powerful horseshoe magnet M3 faces upwardly toward the spin bar R13.
  • the horseshoe magnet M3 is mounted on a rotating plate M4. Any type of mounting may be used. It may be adhered to the plate M4 with epoxy or other type of adhesive. It is shown mounted in an arcuate depression in the upper face of the plate M4.
  • the plate M4 rests on a base M5. Both the rotating plate M4 and the base M5 are shown as being circular in cross section.
  • the base M5 has an upper flat horizontal supporting surface M6 around its periphery.
  • a circular recessed section M7 is within the periphery. The recessed section
  • M7 also has a flat horizontal surface below surface M6 and a vertical side wall that extends from its surface to the supporting surface M6.
  • a circular further recessed section M8 is within section M7.
  • the surface of recessed section M8 is also flat and below the surface of section M7.
  • the section M8 also has a vertical side wall that extends from its surface to the surface of section M7.
  • the periphery of the base M5, the periphery of the section M7 and the periphery of the section M8 are concentric.
  • the section M8 holds a nylon and glass ball bearing M9.
  • M4 has a cylindrical shaft M10 that fits and rotates within bearing M9.
  • a motor section Mil of the plate M4 fits and rotates within the recessed section M7 of the base M5. There is a clearance between the motor section
  • the motor section Mil is circular and concentric with both the cylindrical shaft M10 and the outer circular periphery M12 of the plate M5.
  • the periphery M13 of the motor section Mil is broken by equally spaced radial slots or indentations M14.
  • An air line M15 extends through the base M5 below the recessed section M8.
  • Two secondary air passages Ml 6 extend from air line M15 angularly upwardly to the surface of the recessed section M7.
  • the outlets of the secondary air passage Ml 6 are aligned with the radial slots M14 to allow air to impinge against the side walls of the radial slots M14 and rotate the plate M4.
  • the outlets of the secondary air passages M16 are shown as 180° apart and on opposite sides of air line M15.
  • the outlets may be parallel to a tangent to the periphery of recessed section M7 or be angled toward the periphery.
  • the outlets may be, as shown, near the periphery of recessed section M7.
  • Air from air line L7 passes through line M15 and passages M16 to impinge against the walls of the radial slots Ml 4 to rotate the plate M4.
  • the escaping air from the secondary air passages Ml 6 also acts as a bearing for the plate M5 between the surface M17 of the plate M4 and the supporting surface M6 of the base M5. The air eventually escapes along the surface M6 and out through the gap between the base and the revolving plate.
  • the rotation of plate M4 rotates the magnet M3.
  • the rotating magnet M3 rotates the spin bar R13.
  • the magnetic spin bar drive has the following components and operation:
  • the magnetic spin bar drive may also be turned off and on depending on whether the reactor chamber is filled or empty by changing the valve V7 to a solenoid operated on/off valve and operating it on the same cycle as valve VIO which controls the outlet valve V13 of the reactor. Valves V7 and VIO would open and close together.
  • the green liquor or white liquor is reacted with acid to form carbon dioxide and hydrogen sulfide gases.
  • the concentration of these gases is measured in the gas chromatograph.
  • the chromatograph outputs a continuous analog signal corresponding to the flow rate of gas through the detector of the chromatograph. By integrating this signal for the proper time intervals (corresponding to the time of appearance of carbon dioxide and hydrogen sulfide at the detector), the concentrations of carbon dioxide and hydrogen sulfide in the reaction gas are measured. Calibration of the reactor/gas chromatograph system using liquors of known concentration allows the carbon dioxide and hydrogen sulfide measurements to be converted directly to a determination of sodium carbonate and sodium sulfide in the liquor sample.
  • the analysis process takes about four minutes for both carbon dioxide and hydrogen sulfide. It may be necessary to analyze only for carbon dioxide in the green liquor and causticizer white liquor samples. This would reduce the analysis time for these samples to one and one-half minutes.
  • the gas chromatograph may be used to successively analyze the reaction gases from a number of reactors. For one slaking/causticizing line, three liquor samples should be analyzed, resulting in a three-reactor analyzer system. For this reason the valve VI is a four position valve having four inlets from the reactors or other outside sources and one outlet to the gas chromatograph. It cycles through the four positions until is is at the proper position to receive reaction gas from the selected reactor. It requires approximately five seconds to move from one position to the next. Another five seconds is allowed to electronically check the position of the valve.
  • mode 1A bypass
  • mode IB gas transfer
  • mode 1C purge
  • position two analyze
  • SLl Sample loop for the gas chromatograph. Lines
  • L2 - Line to the gas chromatograph L2A - Line from the reaction gas line L6 to the gas chromatograph GC.
  • L2B Line from the calibration gas line L7 to the gas chromatograph line L2A.
  • L2C Line from the air pressure line L10 to the gas chromatrograph line L2B.
  • L6 Reaction gas line from the reactor Rl to the gas chromatograph line L2A.
  • L7 Calibration gas line from the calibration gas supply to the gas chromatograph line L2B.
  • L10 Air pressure line from the air supply line L27 to the gas chromatograph line L2C.
  • L14 Air line from air supply line L2 to air line L53.
  • L27 Air supply line.
  • VI - Valve in the gas chromatograph line L2A Four positions to bring sample into gas chromatograph: position one (reactor one); position two (reactor two); position three (reactor three); position four (spare).
  • V2 - Valve in the high pressure air line L2C Two positions: open; closed.
  • V6 - Valve in the reaction gas line L6 Two positions: open; closed.
  • the gas chromatograph takes a gas sample into the sample loop SLl, analyzes the gas sample, purges the sample from the system and backflushes the system. It then waits for a new sample to be supplied.
  • the first mode is a standby mode.
  • the gas chromatograph is waiting for a sample from the reactor eircuit. Major components involved
  • VI - Valve in gas chromatograph line L2A/position four (closed). This is exemplary. The valve may be in any position at start-up. It will depend upon the valve position when the system was shut down. V2 - Valve in high pressure air line L2C/elosed. V6 - Valve in the reaction gas line L6/closed. V7 - Valve in the calibration gas line L7/closed. Flow
  • the second mode is a reposition mode (Reposition).
  • the valve VI is repositioned around its four positions until it is lined up with the right reactor. It moves in the same direction, either clockwise or counter ⁇ clockwise, requiring five seconds to move. An additional five seconds is alloted for the system to check the position of the valve. If its location is not right, it will move again and be checked again. This will continue until it is in the right position. The other valves and the gas chromatograph remain as they are.
  • the third mode is a new Standby mode (Standby 2) in which all the valves remain in their positions until the reactor circuit is ready to transfer a gas sample.
  • the fourth mode is a reaction gas transfer mode.
  • the gas chromatograph is internally valved so that the reaction gas goes through the sample loop and then to the vent to sewer. The time of this transfer is long enough for a representative sample to be received.
  • the initial gas entering the sample loop SLl will usually not be representative of the bulk of gas in the reactor.
  • the lines from the reactor to the gas chromatograph are initially filled with air from the previous air purge mode. Air must be flushed from these lines and the sample loop to ensure a representative sample of reaction gas is obtained. It requires a period of time to obtain a steady state sample in the sample loop. Consequently the time will vary depending on the several factors influencing the gas transfer to the sample loop.
  • These factors may include the arrangement and dimensions of the tubing between the reactor and the sample loop, the sample purge condi- tions, and the conditions of pressure, gas composition, etc. existing in the reactor itself at the time of gas transfer.
  • the time is usually between 40 and 60 seconds.
  • Stop sample mode (Stop)
  • the fifth mode is a stop sampling mode in which the reaction gas he gas chromatograph is stopped and the gas pressure in the sample loop llowed to equalize with atmospheric pressure.
  • VI - Valve in gas chromatograph line L2A/position one (reactor circuit one).
  • the sixth mode is an analysis mode in which the sample is analyzed in the gas chromatograph. There is no change in the external circuit. The change is in the internal system of the gas chromatograph. It switches from position two (gas transfer) to position three (analyze). Major components involved
  • Sample purge mode The seventh mode is a gas purge mode in which high pressure air is used to purge the sample from the sample loop and the lines between the sample loop and reactor.
  • L10 to the sample loop SLl Includes lines L2A, L2B and L2C.
  • VI - Valve in the gas chromatograph line L2A/position one (reactor circuit one).
  • the gas chromatograph output circuitry generates voltage "peaks" which correspond to the appearance of each gas component at the detector of the gas chromatograph.
  • the time interval (from the start of the analysis) during which each component (air, carbon dioxide and hydrogen sulfide) will pass through the detector is a characteristic of each component gas. This time interval during which each component appears at the detector is very reproducible and is easily established for each gas.
  • the gas chromatograph output circuitry generates a continuous 0-1 volt analog signal which is proportional to the flow of gas through the detector. During the time interval each component passes through the detector, a voltage "peak" is generated in response to the appearance of the component.
  • Figure 9 is a plot of G.C. voltage output over the course of a gas analysis resulting from a typical green liquor sample.
  • Each component of the gas sample is identified, and the time interval during which it appears is noted.
  • the voltage "peaks" for each component are easily observed from the figure.
  • the integrated voltage for each component (which is equal to the area under each peak) is proportional to the amount of the component in the gas sample.
  • the carbon dioxide and hydrogen sulfide integrated voltages are proportional to the sodium carbonate and sodium sulfide concentrations in the liquor.
  • the integrated peak areas for CO « and H 2 S are therefore a measure of the Na 2 CO 3 and Na 2 S concentrations in the liquor sample.
  • the data collection circuit enables the carbonate/sulfide analyzer to convert the voltage peaks generated by the gas chromatograph into values which correspond to the concentrations of Na 2 CO 3 and Na 2 S in the liquor.
  • the data collection circuit consists of the following major components:
  • FIG. 10 A schematic of the data collection circuit is shown in Figure 10.
  • the associated wiring and components needed to link the major components are known and are therefore not illustrated.
  • the CO 2 and H 2 S voltage peaks must be integrated. There are many methods which may be utilized to accomplish the integra ⁇ tion.
  • the preferred method of peak integration is to utilize a voltage-to- frequency converter (VCO) to convert the 0-1 volt G.C. output signal to a 0-10,000 HZ frequency signal.
  • VCO voltage-to- frequency converter
  • the continuous series of electronic pulses thus generated is utilized as input to a digital microcomputer.
  • the time intervals corresponding to the appearance of the CO 2 and H S peaks are programmed into the microcomputer software.
  • the microcomputer counts the total number of pulses generated by the VCO for the peak period.
  • the number of pulses thus counted is a measure of the peak area.
  • the peak area measurements thus obtained for CO 2 and H 2 S are proportional to the concentrations of Na 2 CO 3 and Na 2 S, respectively, in the liquor sample.
  • the microcomputer furthermore, allows for calibration of the analyzer by providing the ability to convert the pulse count measurements to direct determinations of Na 2 CO 3 and Na 2 S in the liquor.
  • the pulse count is directly proportional to the concentration of chemical in the liquor.
  • These conversion factors are then stored in the micro ⁇ computer software.
  • the conversion factors are applied to the pulse counts for all subsequent liquor samples to provide direct determinations of Na «CO 3 and NaippoS in the liquor.
  • the liquor concentrations may be given as printed data or converted to analog signals for use as input to control devices. Methods of generating such outputs are varied and are well known. Reactor temperature measurement system
  • the measurement of sodium carbonate and sodium sulfide gener ⁇ ated by the carbonate/sulfide analyzer have been observed to be affected by the temperature at which the reaction occurs.
  • the reaction temperature is primarily governed by the temperature inside the analyzer cabinet.
  • the measurements generated by the analyzer vary in direct proportion with the cabinet temperature. As the cabinet temperature increases, the resultant measurements of sodium carbonate and sodium sulfide correspondingly increase. There must be compensation for this phenomena if accurate measurements are to be obtained for all samples despite reactor tempera ⁇ ture variations.
  • T actual temperature of gas from reactor As an example if the reference temperature is 30°C and the actual temperature is 27°C, then for Na 2 CO 3
  • the temperature measurement system uses a resistance tempera ⁇ ture detector (RTD) mounted inside the cabinet, and a relay which closes to allow the detector to be sampled by the analyzer data collection system.
  • the relay closes to allow sampling of the detector immediately upon completion of the transfer of reactor gases to the gas chromatograph sample chamber. It remains closed for 20 seconds or as needed to obtain an accurate temperature measurement.
  • the RTD signal is converted to a temperature measurement in the data collection software.
  • a resistance temperature detector has been found to be the best suited temperature measuring device.
  • the detector element exhibits an electrical resistance which varies directly with temperature. This resis ⁇ tance is easily measured electronically and is easily converted to a temperature reading since the calibration of these elements is well docu- mented.
  • Other devices, such as thermocouples or thermistors, which exhibit electrical properties that vary as a function of temperature could also be utilized in this application. Materials of construction
  • the reactor's top and base is constructed of P.V.C. (poly vinyl chloride).
  • the fixture at top of pump is P.V.C.
  • the mounting board for all solenoids, etc. is P.V.C.
  • the magnetic spin bar driver is P.V.C.
  • the reactor cylinder and the acid pump cylinder are glass. All tubing that is in direct contact with acid or the gases is teflon, all other tubing is nylon. All fittings that are in direct contact with acid or the gases are nylon. The reactor gas to gas chromatograph and the vent solenoids are teflon. All cheek valves are teflon. The sample loop is nylon.
  • the acid pump piston is teflon coated 316 S.S. (stainless steel).
  • the fittings that come into indirect contact with gases or those that are flushed with air or water are 316 S.S. All fittings, tubing, valves, columns, etc. within the gas chromatograph are 316 S.S.
  • the gas isolation valve mounted on front of gas chromatograph is 316 S.S.
  • the air, water, pressurization and purge solenoids are 304 S.S.
  • V22 C V6 C V24 O V8 C V26 C * V10 O * V28 IB V13 C *
  • V14 IS * V4 c
  • Use Figures 11, 12 and 13 are schematic diagrams showing the use of the apparatus in the causticizing system.
  • Control loop 1 seen in Figure 11 discloses the use of the analyzer in controlling the sodium carbonate concentration in the green liquor to the slaker.
  • green liquor from the green liquor clarifier GLC flows through the mill liquor line MLl and is pumped by the green liquor pump GLP to the slaker S. Lime is added to the green liquor at the slaker S.
  • the line L28/29 designates two lines, L29 which carries the liquor from the mill liquor line MLl to the reactor system RSI and L28 which returns the liquor from the reactor system RSI to the mill liquor line
  • Each of the reactor systems - RSI, RS2 and RS3 - includes a filter
  • the line L2 carries the reaction gas from the reactor system RSI to the gas chromatograph/analyzer GC/A in which the gas is analyzed for carbon dioxide (resulting from sodium carbonate in the liquor) and hydrogen sulfide (resulting from sodium sulfide) as described above.
  • the analyzer using the carbon dioxide analysis, outputs a signal through the control line CL1 to the controller which operates the valve V40 to increase or decrease the amount of weak wash flowing through line L40 into MLl in order to maintain a constant sodium carbonate concentration in the green liquor going to the slaker.
  • the hydrogen sulfide analysis has several uses. It is an indication of the reduction efficiency in the recovery boiler.
  • the sodium sulfide concentration can be given to the recovery boiler operator to confirm to him that the reduction efficiency is good or to allow him to make corrections to improve the reduction efficiency. It is also an indication of the potential efficiency in the causticizing operation. As the concentration of sodium carbonate or sodium sulfide in the green liquor increases, the efficiency of the causticizing operation decreases. This will give the operator information about the causticizing reaction that the green liquor is about to undergo and allow the causticizing operator to take corrective action.
  • the second control loop of this system is shown in Figure 12.
  • This loop controls the balance of green liquor and lime, and in fact controls the entire slaking operation.
  • a "clear" liquor sample is taken from the calcium carbonate mud separator at either the slaker or first causticizer.
  • This "clear” liquid is then filtered to remove all the remaining calcium carbonate mud.
  • the sodium carbonate and sodium sulfide concentration in this filtered liquor is then measured in the GC/A from the reaction gas from the second reactor system, RS2.
  • the control loop logic will contain a set point for the desired sodium carbonate concentration in the liquor.
  • OMPI leaving the slaker There are two ways of controlling the sodium carbonate concentration in the slaker or first causticizer. One is the usual method of controlling the amount of lime being added to the slaker. The other, and the method the inventors consider to be significantly better, is shown in Figure 12. In this method the amount of sodium carbonate in the green liquor is controlled by loop 1 as is described above. The amount of this green liquor added to the slaker is controlled by loop 2. The amount of sodium carbonate and sodium sulfide in the white liquor from the first causticizer or slaker is determined by the GC/A from the reaction gases from RS2. A signal, based on the sodium carbonate, is then sent through control line CL2 to the controller which operates the valve V41 to increase or decrease the amount of green liquor flowing through MLl into the slaker S.
  • the measurement of the chemical concentrations in the white liquor is taken from the line between the clear white liquor storage tank and the digester or digesters.
  • concentrations of sodium sulfide and sodium carbonate in the white liquor are determined directly by analysis by the GC/A of the reaction gases from the third reaction system, RS3.
  • the amount of sodium hydroxide in the white liquor must be deter- mined indirectly. There are three pieces of information which must be combined to yield the sodium hydroxide concentration in the white liquor.
  • the sodium hydroxide concentration in the green liquor Measurements 1 and 2 are used to determine the amount of carbonate in the green liquor which, in the slaking/causticizing operation, has been converted to sodium hydroxide in the white liquor.
  • the difference between the amount of Na «CO 3 entering the system with the green liquor and the amount of Na 2 CO 3 leaving with the white liquor is the concentration of NaOH which has been produced in the white liquor due to the causticizing reaction. All chemical concentrations are expressed on a sodium oxide (Na 2 O) basis.
  • Some sodium hydroxide also enters the system with the green liquor. This sodium hydroxide passes unchanged through the system to the white liquor and must be accounted or.
  • This source of NaOH in the system is relatively stable - a periodic (every eight hour) determination of NaOH in the green liquor may be manually performed by an operator and entered into the analyzer software.
  • the determination of the NaOH in the green liquor may be performed directly in titration of a green liquor sample. It may alter ⁇ natively be determined indirectly by titrating the NaOH in the white liquor.
  • the amount of NaOH in the white liquor which cannot be accounted for by the amount of NaOH generated in recausticizing is the amount of NaOH which has entered with the green liquor. It is recommended that the NaOH in the green liquor be determined by the indirect method, which has the advantage of reducing errors caused by time lags in the process.
  • the amount of NaOH associated with the green liquor is then stored in the microprocessor memory until updated by another titration. This value is used to update each subsequent white liquor sodium hydroxide determination.
  • the analyzer will solve the following equation for each succeed ⁇ ing sample to determine the sodium hydroxide concentration in the white liquor:
  • the carbonate analysis is updated with each sample every 19 minutes.
  • the determination of sodium hydroxide in the green liquor is updated by manual titration of a green or white liquor sample when necessary, usually every eight hours.
  • An updated, complete clarified white liquor analysis (determination of sodium hydroxide, sodium sulfide, and sodium carbonate) is provided to the digester operator or digester process computer every 12 to 19 minutes.
  • the system software must also take into consideration the time delays in the slaking, causticizing and clarification operations in order to correctly determine the current NaOH concentration in the white liquor. This will determine the amount of chemicals to be added to the digester In order to control the pulping process. Cascaded Control Opportunities
  • the ratio of sodium carbonate to total chemicals in the process stream will vary with time, resulting in improper determinations of sodium carbonate concentration and less precise control of the process than could be obtained if sodium carbonate was measured directly.
  • the changes which influence the calibration of these devices in measuring sodium carbonate concentration occur slowly - certainly greater than the 15-20 minute sampling period generated by the earbonate/sulfide analyzer.
  • the direct measurements of sodium carbonate generated by the earbonate/sulfide analyzer may be used as a set point control input to each primary control device. This practice will have the effect of adjusting the calibration of the primary device (conductivity probe, density gauge, etc.) every 15-20 minutes so that it is an accurate indicator of Na.CO concentration despite the previously mentioned variations in the ratio of Na 2 CO /total chemicals.
  • a cascaded control strategy of this type will have the advantage of having both an accurate method of determining sodium carbonate concentrations in the process and the ability to respond immedi- ately to changes in the process.
  • the main items are the dissolving tank DT, the green liquor clarifier GLC, the green liquor pump GLP, the slaker S and the first causticizer Cl.
  • Mill liquor line MLl carries green liquor from dissolving tank DT to the green liquor clarifier GLC
  • mill liquor line ML2 carries green liquor from the green liquor clarifier GLC to the slaker S.
  • the principal weak wash line L42 carries weak wash to lines L40 and L41.
  • the weak wash in line L41 is used to dissolve the smelt in the dissolving tank DT.
  • the amount of weak wash going to the dissolving tank DT through line L41 is controlled by valve V41.
  • the amount of weak wash is determined by the density of the green liquor from the dissolving tank DT. This is monitored in mill line MLl by the density meter DM1.
  • the signal from the density meter DM1 is carried through control line CL1 to the valve controller CN1.
  • the valve V41 is controlled by CN1 with a signal which passes through control line CL2. This is a standard local control loop in which a local direct measurement is used to monitor the process conditions.
  • Figure 14 also illustrates the use of local conditions to monitor and control the amount of weak wash entering ML2 to maintain the carbonate level in the green liquor. However, in this instance the gas chromatograph/analyzer is used to determine the set points for this local control.
  • the valve V40 is used to control the flow of weak wash in line L40, which is the amount of weak wash which will enter the mill liquor line ML2. This is monitored locally be a density meter DM2 which sends a signal through control line CL3 to the control unit CN2. CN2 operates the control valve V40 to increase or decrease the flow of weak wash to maintain the density in ML2 at a specified level.
  • the density of the liquor is not a direct indication of sodium carbonate in the liquor.
  • a sample of the density-controlled liquor from ML2 is taken and analyzed for sodium carbonate concentration by reactor system RSI and the gas chromatograph/analyzer unit GC/A. This direct determination of sodium carbonate is utilized to send a set point signal through control line CLS to CN2 in order to adjust the density set point so that the density more accurately reflects the sodium carbonate concentration in the liquor.

Abstract

A process and apparatus for measuring carbonate and sulfide concentrations in white and green pulp mill liquor and in the slaker/causticizing cells and controlling the causticizing reaction and other stages using this information. Specifically the causticizing control logic is based on determining the concentration of sodium carbonate and sodium sulfide in the green liquor, in the white liquor-mud slurry at the slaker (S) or first causticizer (C1) and in the white liquor being sent to the digester house and using this information to control the entire process. The apparatus takes a sample from an appropriate line, filters the sample if necessary, takes a measured quantity, reacts that measured quantity with an acid to generate hydrogen sulfide and carbon dioxide and measures the quantities of these gases in a gas chromatograph (GC). The apparatus has four main circuits: the filter circuit, the sampling circuit, the reactor circuit and the gas chromatograph circuit. A mud separation circuit is also utilized if the apparatus is to analyze liquor from the slaker or causticizing cells.

Description

METHOD AND APPARATUS FOR DETERMINING CARBONATE/SULFIDE CONCENTRATION
BACKGROUND OF THE INVENTION Field of the Invention
Analyzing green liquor, slaker and causticizing cells, and white liquor chemicals and controlling pulp mill operations from the analysis. Other Art A good diagram of the causticizing process may be found in Pulp and Paper Manufacture, 2nd Ed., Volume I, The Pulping of Wood, 1969, prepared under the direction of the Joint Textbook Committee of the Paper Industry, R. G. MacDonald, editor, and J. N. Franklin, technical editor, the McGraw Hill Book Company, New York, publisher. The diagram is Figure 9-72 on page 535.
The process actually starts with the recovery furnace. The black liquor consisting of organic and inorganic chemicals and water is charged to the furnace where the water is evaporated, the organic components are burned and inorganic components are recovered in the form of a molten smelt. The molten smelt containing mostly sodium carbonate and sodium sulfide is continuously decanted from the furnace bed and dissolved in water
(weak wash) at the dissolving tank or tanks to form green liquor. A typical green liquor composition is about 60-65% sodium carbonate and 25-28% sodium sulfide by weight (% of solids) expressed as Na»0. A typical solids content of green liquor is around 18% of total liquor weight. The green liquor is pumped from the dissolving tank or tanks to a green liquor clarifier where the dregs settle out. The dregs are impurities, i.e., undissolved solids from the furnace. These are mainly carbon, calcium, magnesium and iron compounds. Following clarification, the green liquor is mixed with reburned lime from the kiln in the slaker. Usually the amount of lime is adjusted to maintain a specified white liquor concentration. Makeup lime in the form of fresh lime (or limestone burned in the kiln) is added to the reburned lime to replace lime losses in the system. Grits (large, unreacted lime particles) are removed from the slaked lime slurry in the classifier section of the slaker.
In the slaker the lime or calcium oxide reacts with the water in the green
-ξ TREAlT
OMPI . liquor to form calcium hydroxide and this in turn reacts with the sodium carbonate in the green liquor to form sodium hydroxide and calcium carbonate, which then flows to the causticizing cells. Causticizing cells are used to allow enough time for the causticizing reaction that starts in the slaker to approach completion. From the eausticizers, the slurry is pumped to the white liquor clarifier (or a pressure filter) to separate the white liquor from the lime mud, calcium carbonate. The clarified white liquor is pumped to storage and then to the digester house to pulp wood chips. The mud or calcium carbonate in the bottom of the clarifier is pumped to a mud washer where it is washed with water from the mud filter and the dregs washer. The overflow water from the mud washer is called weak wash and this is used at the dissolving tank or tanks to dissolve the smelt to form raw green liquor.
In the usual process then, weak wash is used at the dissolving tank or tanks to dissolve the molten sodium salts exiting from the recovery boiler. The resulting raw green liquor is then clarified to remove the dregs and then pumped to the slaker. Lime feed to the slaker is generally based on the total flow of green liquor and the slaker temperature, the slaker temperature specification being such as to maintain a specified white liquor strength and safe operating conditions.
The causticizing reaction is usually controlled by chemical analysis (titration) of the white liquor taken from a causticizing cell or from the white liquor clarifier overflow. Lime feed, green liquor density at the dissolving tank or tanks or a combination of the two is usually changed to maintain a white liquor strength within a mill's specification. The specifica¬ tion is generally expressed as the sodium hydroxide and sodium sulfide concentration in the white liquor, i.e., AA (active alkali) or EA (effective alkali). These expressions are defined and discussed on pp. 358-363 of MacDonald and Franklin, supra. White liquor AA or EA concentration does vary considerably because of changes in lime availability (CaO content), reactivity (rate of hydration), mass flow rate of lime to the slaker or combinations of these. Sodium carbonate concentration changes in the green liquor feed will also affect the resulting white liquor strength. The presence of this number of uncontrolled variables makes it very difficult to control the slaking/ causticizing reaction. Present practice uses a total titratable alkali (TTA) measure¬ ment to control liquor strength and causticizing efficiency. TTA is a measurement of sodium hydroxide, sodium carbonate, and sodium sulfide, and is, therefore, only an indirect, approximate determination of the Na2CO3 concentration in the liquor.
Another variable that makes slaker control difficult is the colorimetric titration (ABC test) used to analyze the liquor. The ABC test is found in TAPPI test T624 OS-68 (Parts 9, 10 and 11). It may be modified to fit specific mill conditions. Titration end points are not identified by a crisp color change. Rather, there is a gradual change in color from, for example, orange to red or from green to blue depending on which indicator is used. This "diffuse" end point determination results in much uncertainty in the liquor concentrations which are the only variables which are measured regularly. There have been attempts to solve these problems. Hultman, et al, U.S. Patents 4,236,960 and 4,311,666 describe a different type of process for controlling the degree of causticizion. Sutinan and Haapoja, "Causti¬ cizing Plant and Lime Kiln Computer Control" describes a Nokia Autolime system. TAPPI test T624 OS-68 describes tests for the analysis of soda and sulfite white and green liquors. Test 12 describes the sodium carbonate (evaluation method) test.
SUMMARY OF THE INVENTION A process and apparatus for measuring carbonate and sulfide concentrations in white and green pulp mill liquor and in the slaker and causticizing cells and controlling the causticizing reaction and other stages using this information.
The proposed process control logic reduces or eliminates most of the above-mentioned process control problems. It is based on the idea that a kraft mill slaker is really a carbonate reactor, i.e., carbonate ions in the green liquor are crystallized from solution with hydrated lime, and sodium hydroxide is generated in the process. Specifically the causticizing control logic is based on determining the concentration of sodium carbonate and sodium sulfide in the green liquor, in the white liquor-mud slurry at the slaker or first causticizer and in the white liquor being sent to the digester house and using this information to control the entire process. This logic is much different than present practice.
- REXC?*
OMPI s_ - W1PO The reason for measuring the concentration of sodium sulfide in the green liquor is not to control the slaking/causticizing process, but to indicate inefficiencies in the process and to take steps to control them. An increase in sulfide concentration will tend to decrease the efficiency of the causticizing reaction. Knowledge of the concentration of sodium sulfide entering the slaker will indicate to the operator or process computer the optimum causticizing efficiency that can be expected from his recausticiz- ing plant. The changes in sulfide concentration will also indicate changes in recovery boiler sodium sulfide reduction efficiency and will allow steps to be taken to better control boiler sodium sulfide reduction efficiency.
It is desired that as much of the sodium carbonate in the green liquor as possible be converted to sodium hydroxide in the slaker and eausticizers. It is impossible to completely convert all the sodium carbon¬ ate to sodium hydroxide - some sodium carbonate will remain in the white liquor. The ultimate limit as to how much sodium carbonate may be converted to sodium hydroxide is governed by the equilibrium causticizing efficiency. A discussion of the factors governing the equilibrium causticiz¬ ing efficiency may be found on pp. 532-534 of MacDonald and Franklin, supra. It Is desirable to maintain the final white liquor at a composition very close to that determined by the equilibrium causticizing efficiency. If this is performed correctly, the benefits will be high efficiency of operation due to efficient conversion of sodium carbonate to sodium hydroxide, and low sodium carbonate "deadload" in the white liquor, which has many benefits throughout digestion, evaporation and recovery. In order to achieve this, it is necessary to closely balance the amounts of lime and green liquor being added to the slaker. An excess of green liquor to lime will result in low conversion efficiency of sodium carbonate to sodium hydroxide. An excess of lime to green liquor will impair the settling and filtering characteristics of the calcium carbonate "mud," which must be removed from the white liquor before it can be used in the digesters.
Variations in the Na2CO3 concentration in the liquor at the slaker or causticizer are the result of variations in the concentration and flow rate of lime and green liquor. Lime quality and quantity can be variable and difficult to control - changes in mass flow rate, availability (% CaO) and lime reactivity (how fast hydration occurs) affect the Na«CO3 concentration in the slaker/causticizer liquor, but are extremely difficult to measure and control. However, the concentration and flow rate of the green liquor may be measured and controlled quite easily. The proposed strategy will control the green liquor flow rate to the slaker to maintain the desired Na^COg concentration in the slaker/causticizer liquor despite variations which occur in the lime. The green liquor concentration is also controlled in a control loop. The advantages of this strategy are as follows:
1. A constant, desired concentration of Na2C03 is controlled early in the slaking/causticizing reaction, ensuring safe, efficient operation. 2. The slaking/causticizing process is controlled by adjusting the flow rate and concentration of the green liquor, which is technically quite easy to accomplish. Controlling the concentration, activity, and flow rate of the lime is technically difficult and therefore is allowed to vary within normal limits and the green liquor flow rate is adjusted in response to these variations. This strategy provides much more precise control than do strategies which attempt to adjust lime flow rate in response to changes in liquor flow rate and concentration.
3. This strategy will control the process based on direct measurements of the critical component in the system, sodium carbonate. This provides much more precise control than do strategies based on TTA liquor conductivity, liquor density or other indirect, approximate indications of a2CO3 in process liquors.
The overall liquor room production rate (amount of white liquor generated per minute) will be controlled by the flow rate of lime to the slaker. As the production rate needs to be increased or decreased in order to maintain an overall mill liquor balance, the flow rate of lime added to the slaker is correspondingly increased or decreased. The green liquor flow rate will be automatically adjusted by a control loop to maintain the desired
N-^ Og concentration in the white liquor. Both chemical inventory (lime and liquor storage levels) and mill production rates can be maintained by this strategy. Chemical inventory and/or production rate may be controlled either manually or automatically.
The last measurement is to determine the concentrations of sodium hydroxide, sodium carbonate, and sodium sulfide in the white liquor which is sent to the digester house to be used in the cooking process. It is important to measure the sodium hydroxide and sodium sulfide concentrations in the white liquor so that the amount of liquor to be charged in the digester(s) may be correctly determined. Changes in sodium sulfide concentration (generated at the recovery boiler) can affect white liquor AA/EA concentration. The apparatus takes a sample from an appropriate line - green liquor, slaker/causticizer liquor, or white liquor to the digester - filters the sample if necessary, takes a measured quantity, reacts that measured quantity with an acid to generate hydrogen sulfide and carbon dioxide and measures the quantities of these gases in a gas chromatograph. The apparatus has four main circuits: the filter circuit, the sampling circuit, the reactor circuit and the gas chromatograph circuit. A mud separation eircuit is also utilized if the apparatus is to analyze liquor from the slaker or causticizing cells. A number of operations or modes are performed in each of these circuits during a test cycle. These modes are sequenced differently depending upon the different operation of the mill.
The unit must operate consistently over a long period of time and must give reproducible results. For example, the liquor is corrosive and can also plug lines. The inventors have devised an apparatus which eliminates corrosion and reduces line plugging to a minimum. This required a great deal of lab and mill testing and redesign to accomplish. During the testing, it was found that the liquor being analyzed, the degree of completion of the reaction and the temperature of the reactive gases would cause changes in the results which would lead to an inability to control the process. Again, a great deal of time and laboratory and mill testing was required before the problem was recognized, the sources of the problem discovered and corrective measures taken. The present apparatus and control logic is the result of several man-years of work extending over a several-year period and the present application represents the inventor's understanding as of the date of the application of the problem and the solution. The work is continuing.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram of the principal components of the test unit.
Figure 2 is a diagram of the filter circuit for the apparatus. Figure 3 is a diagram of a three-filter circuit unit for the apparatus when operating in a three-component configuration. Figure 4 is a diagram of the mud separation circuit. Figure 5 is a cross-sectional view of the reactor for the apparatus.
Figure 6 is a top plan view of the reactor for the apparatus. Figure 7 is an interior side plan view partially in cross section showing the magnetic spin bar driver and the spin bar in the reactor chamber.
Figure 8 is a cross-sectional view along line 8-8 of Figure 7. Figure 9 is a plot of a gas chromatograph voltage output over the course of gas analysis resulting from a typical green liquor sample.
Figure 10 is a schematic diagram of a data collection circuit. Figure 11 is a diagram of a single loop apparatus in a pulp mill. Figure 12 is a diagram of a double loop apparatus in a pulp mill. Figure 13 is a diagram of a triple loop apparatus in a pulp mill. Figure 14 is a diagram of a cascaded control.
DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus has four main circuits: the filter circuit, the sampling circuit, the reactor circuit and the gas chromatograph circuit. A mud separation circuit is also used if the apparatus is to be utilized to analyze liquor from the slaker or causticizing cells. Each of these circuits has a number of operations or modes which are performed during one test cycle. These modes are sequenced differently depending upon the particular operation of a mill. The parts and modes will be described for each of the circuits. A possible sequence will then be described. It should be noted that most of the operable valves throughout the unit are two-position valves. This is for ease and simplicity of operation. Three-position valves or multiple port valves are used in several specific applications. Where so used, the use of these valves is noted. Filter Circuit The purpose of the filter circuit is to remove particulate material from the liquor to prevent both the plugging of the test equipment and the chemical side reactions that would mask the true composition of the liquor.
The following description is directed to the filter circuit of Figures 2 and 3. Each of the filter circuits in the three circuit array shown in Figure 3 would have the same parts and operating sequence, so the same reference numerals will be used for the individual elements in these circuits. The circuit has the following components: Major components F - Filter. FS - Filter shock dome. Lines
ML - Mill liquor line in the causticizing system between the green liquor clarifier and the slaker, between the slaker and first causticizer, between the first and second causticϊzers or between the clear white liquor storage tank and the digester, depending on the liquor being sampled. L22 - Sampling line from the filter outlet line L30A to the sampling circuit. L28 - Liquor return line from the filter circuit to the clarifier, slaker or causticizer depending on liquor being sampled. L29 - Liquor supply line from the mill liquor line ML to the filter circuit. L30 - Filter outlet line from the upper part of the filter F to the liquor return line L28.
L30A - Filter outlet line from the fUter F to the sampling line L22. L30B - Filter outlet line from the filter outlet line L30A to the filter backflush line L31. L30C - Filter outlet line from the filter outlet line L30B to the liquor return line L28. L31 - Filter backflush line from the valve V28 to the filter outlet line L30C. L32 - Filter bypass line from the filter circuit inlet line L29 to the liquor return line L28.
L33 - Air inlet line to the top of the filter shock dome FS. L33A - Air inlet line from the air supply to the water backflush line L37. L33B - Air and water inlet line between the water backflush line L37 and the top of the filter shock dome FS. L34 - Filter inlet and filter backflush outlet line between the valve V28 and the bottom of the filter F. L35 - Inlet line from the filter circuit liquor supply line L29 to the valve V28. L36 - Water supply line.
L37 - Water backflush line from the water supply line L36 to the inlet line L33B. Valves
Operating valves (solenoid operated) V21 - Valve in the filter outlet line L30A. Two positions: open; closed. V22 - Valve in the sampling line L22. Two positions: open; closed. V24 - Valve in the filter bypass line L32. Two positions: open; closed.
V26 - Valve in the air inlet line L33A. Two positions: open; closed. • V28 - Filter inlet-backflush three-way T valve at juncture of the filter backflush line L31, the filter inlet line L34 and the inlet line L35. Two positions: position one (backflush) (IB) - open to the filter backflush line L31 and the filter backflush outlet line L34, closed to the inlet line L35; position two (filter) (2F) - open to the filter inlet line L34 and the inlet line L35, closed to the filter backflush line L31.
V29 - Valve in the water backflush line L37. Two posi¬ tions: open; closed. Check valves
V18 - Check valve in the filter outlet line L30B to prevent flow through the line L30 into the filter F.
V23 - Check valve in the filter backflush line L31 to prevent flow through the line L31 into the filter F. Pressure valve (open or partially open, manually operable) V20 - Back pressure valve in the filter outlet line L30B to provide pressure in the filter F and to induce preferential flow into the sampling line L22 when the valve V22 is open. Pressure relief valve (normally closed, automatically openable)
V27 - Pressure relief valve on the filter F. Repair valves (normally open, manually operable) V19 - Repair valve in the liquor return line L28. V25 - Repair valve in the filter circuit liquor supply line
L29. The filter circuit has several operating modes. Bypass mode (no liquor to filter) (Bypass)
The first mode is a liquor bypass mode in which the liquor is taken from the mill liquor line, through the bypass line and returned to the slaker or causticizer without passing through the filter. Lines involved
ML - Mill liquor line.
L28 - Liquor return line from the filter circuit. L29 - Liquor supply line from the mill liquor line ML to the filter eircuit. L32 - Filter bypass line from the f ilter circuit inlet line L29 to the filter eircuit outlet line L28. Valves involved Operating valves/position
V21 - Valve in the filter outlet line L30A/closed. V22 - Valve in the sampling line L22/closed. V24 - Valve in the filter bypass line L32/open. V26 - Valve in the air inlet line L33A/closed. V28 - Filter inlet-backflush valve/position one (backflush)
(IB) - open to the filter backflush line L31 and the filter backflush outlet line L34, closed to the inlet line L35. V29 - Valve in the water backflush line L37/cIosed. Check valves
V18 - Check valve in the filter outlet line L30B to prevent flow through the line L30 into the filter F. V23 - Check valve in the filter backflush line L31 to prevent flow through the line L31 into the filter F. Repair valves
V19 - Repair valve in the liquor return line L28. V25 - Repair valve in the filter circuit liquor supply line L29. Flow
ML through V25 through L29 through V24 through L32 through V19 through L28.
Time
The time will vary. Liquor filtering mode (Filter)
The second mode is a liquor filtering mode in which the liquor is taken from the mill liquor line, filtered in the filter F and returned to the return line in order to establish steady state filtering of the liquor. Major components involved
F - Filter Lines involved ML - Mill liquor line.
L28 - Return line from the filter circuit.
L29 -_ Liquor supply line from the πiill liquor line ML to the filter circuit. L30 - Filter outlet line from the upper part of the filter F to the return line L28.
L34 - Filter inlet line from the valve V28 to the bottom of the filter F. L35 - Inlet line from the filter circuit liquor supply line L29 to the valve V28. Valves involved
Operating valves/position
V21 - Valve in the filter outlet line L30A/open. V22 - Valve in the sampling line L22/closed. V24 - Valve in the filter bypass line L32/closed. V26 - Valve in the air inlet line L33 A/closed.
V28 - Filter inlet-backflush valve/position two (filter) (2F) - open to the filter inlet line L34 and the inlet line L35, closed to the. filter backflush line L31. V29 - Valve in the water backflush line L37/closed. Check valves
VI 8 - Check valve in the filter outlet line L 3 OB to prevent flow through the line L30 into the filter F. V23 - Cheek valve in the filter backflush line L31 to prevent flow through the line L31 into the filter F. Pressure valve
V20 - Back pressure valve in the filter outlet line L30B. Repair valves
VI 9 - Repair valve in the filter circuit liquor return line
L28. V25 - Repair valve in the filter circuit liquor supply line L29. Flow
ML through V25 through L29 through L35 through V28 through L34 through F through V21 through L30 through V20 through V18 through V19 through L28. Note: When first starting up the analyzer, a filter cycle is immediately performed to provide a liquor sample for the first reaction. For all subsequent reactions, the filter cycle is started at a time determined by an action somewhere else in the system. It can be started by a sequencer output which is energized when a new liquor sample is desired. This could be signaled by completion of filling the acid pump AP2 or opening the valve which applies pressure to the reactor Rl. Time
60 seconds - will vary depending on time required to fill lower part of filter with liquor and provide an adequate flow in L30 to provide a consistent liquor sample to the sample line L22. Liquor sampling mode (sample)
The third mode is a liquor sampling mode in which the liquor is taken from the mill liquor line, filtered and sent to the sampling circuit to provide the test sample. The parts, lines, valves and valve positions are the same in this mode as in the second mode, the filter mode, except for the following change.
Major components involved
F - Filter Lines involved L22 - Sampling line from the filter outlet line L30A to the sampling circuit.
OMPI Valves involved
Operating valves/position
V22 - Valve in the sampling line L22/open. Pressure valves V20 - Back pressure valve in the filter outlet line L30B provides back pressure to cause preferential diver¬ sion of the filtered liquor into the sampling line L22. Flow
ML through V25 through L29 through L35 through V28 through L34 through F through V21 through L30A: part through V22 through L22 to sampling circuit, part through V20 through L30B through VI 8 through L30C through VI 9 through L28. Time 60 seconds - will vary depending on time needed to com¬ pletely flush and fill sample circuit with new liquor. Stop sampling mode (Stop)
The fourth mode is a stop sampling mode which is a pause to allow the sample valve V22 in the sampling circuit to change position. The parts, lines, valves, valve positions and flows are the same as in the second mode - the filter mode. Time
5 seconds or as needed to ensure closure of valve V22. Liquor backflush mode The fifth mode is a liquor backflush mode, in which the liquor is used to backflush or backwash particulate matter in the filter from the filter to the return line. It takes place in two stages. Stage 1 (Backflush 1)
In stage 1 the filter outlet valve V21 is closed and liquor from the mill liquor line ML fills the filter to the middle of the filter shock dome FS.
Major components involved F - Filter
FS - Filter shock dome. Lines involved
ML - Mill liquor line. L29 - Liquor supply line from the mill liquor line ML to the filter circuit. L33 - Air inlet line to the top of the filter shock dome FS. L34 - Filter inlet line from the valve V28 to the bottom of the filter F.
L35 - Inlet line from the filter circuit liquor supply line L29 to the valve V28. Valves involved
Operating valves/position V21 - Valve in the filter outlet line L30A/closed.
V22 - Valve in the sampling line L22/closed. V24 - Valve in the filter bypass line L32/closed. V26 - Valve in the air inlet line L33A/closed. V 8 - Filter inlet-backflush valve/position two (filter) (2F) - open to the filter Inlet line L34 and the inlet line L35, closed to the filter backflush line L31. V29 - Valve in the water backflush line L3 /closed. Repair valves
V25 - Repair valve in the filter eircuit liquor supply line L29.
Flow
ML through V25 through L29 through L35 through V28 through L34 into F to middle of FS. Time 10 seconds or as needed to provide sufficient liquor to backwash filter. Stage 2 (Backflush 2)
In stage 2 air, admitted at the top of the filter shock dome FS, drives the liquor through the filter element of the filter F, out the inlet to the filter element, through the filter backflush outlet line
L34, the backflush line L31, the filter outlet line L30C, and the filter eircuit liquor return line L28. Major components involved F - Filter Lines involved
L28 - Liquor return line from the filter circuit.
■ jHE D* OMPI L30C- Filter outlet line from the filter backflush line L31 to the filter circuit liquor return line L28. L31 - Filter backflush line from the valve V28 to the filter outlet line L30C. L33 - Air inlet line to the top of the filter shock dome FS.
L34 - Filter backflush outlet line from the bottom of the filter F to the valve V28. Valves involved
Operating valves/position V21 - Valve in the filter outlet line L30A/closed.
V22 - Valve in the sampling line L22/closed. V24 - Valve in the filter bypass line L32/open. V26 - Valve in the air inlet line L33 A/open. V28 - Filter inlet-backflush valve/position one (backflush) (IB) - open to the filter backflush line L31 and the filter backflush outlet line L34, closed to the inlet line L35. V29 - Valve in the water backflush line L37/closed. Check valves V18 - Check valve in the filter outlet line L30B to prevent flow through the line L30 into the filter F. V23 - Check valve in the backflush line L31 to prevent flow through the line L31 into the filter F. Repair valves VI 9 - Repair valve in the filter circuit liquor return line
L28. Flow Air
V26 through L33 into F. Liquor
F through L34 through V28 through V23 through L31 through L30C through V19 through L28. Time
15 seconds or as needed to adequately backflush filter. Water backflush mode '
The sixth mode is a water backflush mode in which water is introduced at the top of the filter shock dome FS and washes particulate matter from the filter element, out the bottom of the filter through the filter backflush outlet line L34, the backflush line L31, the filter outlet line L30C, and the filter circuit liquor return line L28. The water backflush mode would normally occur in place of a first mode, a bypass mode, and would follow a fifth mode, the liquor backflush mode. It is used any time the filter is excessively dirty with particulate matter. The liquor supply would normally be turned off. The parts, lines, valves and valve positions are the same as in stage 2 of the fifth mode, stage 2 of the liquor backflush mode, with the following additions and changes. Lines involved
L33A- Air line to the filter shock dome not used.
L33B- Inlet line from the water backflush line L37 to the top of the filter shock dome FS. L36 - Water supply line. L37 - Water backflush line from the water supply line L36 to the inlet line L33B. Valves involved
Operating valves/position
V26 - Valve in the air inlet line L33A/closed. V29 - Valve in the water backflush line L37/open.
Flow Water:
L36 through V29 through L37 through L33B through F through L34 through V28 through V23 through L31 through L30C through VI 9 through L 28.
Time
60 seconds or as needed to provide a complete washing of the filter element.
Mud separation circuit - slaker/causticizer white liquor It is often desirable for control applications to obtain liquor samples directly from the slaker or causticizer for analysis. This liquor contains 8-10% by weight suspended calcium carbonate mud solids, which must be removed prior to analysis. The level of solids loading present in this liquor is too high to be introduced immediately to the filter circuit since severe plugging of the filter element would result. The purpose of the mud separation unit is to remove the bulk of the solids from the liquor and yield
OMPI a "clear" liquor containing 1% or less suspended mud solids. This "clear" liquor is filterable and becomes the liquor supply to the filter circuit. It should be noted that the mud separation unit in no way interferes with subsequent operation of the analyzer system. The filter, sample, reactor, and gas chromatograph circuits operate exactly as they do when no mud separation circuit is utilized. The mud separation circuit merely ensures that an acceptable liquor sample is provided to the filter eircuit.
The best method of mud separation has been found to involve the use of a continuous settling cone. This device receives unclarified liquor from the slaker or causticizer, separates the mud from the liquor, returns the mud to the slaker or causticizer, and supplies a continuous "clear" liquor supply to the filter circuit. The advantages of this apparatus and method are simplicity, reliability, ease of operation and a fresh, uninterrupted supply of liquor to the filter circuit so that operation of the filter circuit is not disturbed.
The settling cone itself is a noπmechanical thickener of a type commonly used for continuous liquid-solid separations in low volume appli¬ cations. The details of the construction and operation of these units are well known and will not be given in detail here, but may be found in Perry, J. H. (Ed.) Chemical Engineers Handbook, 3rd Ed., McGraw-Hill Book Co., Inc. New York, 1950, pp. 940-941. The mud separation unit should be designed for a capacity that will deliver a desirable flow of "clear" liquor (approximately 2-3 liters/minute) to the filter circuit.
The following description is of the mud separation circuit shown in Figure 4. The circuit consists of the following components: Major components
Tl - Continuous settling cone. T2 - Clear liquor tank.
SP1 - Unclarified liquor supply pump from unclarified liquor supply line L39 to unclarified liquor supply line L40. SP2 - Clear liquor supply pump in filter circuit liquor
• supply line L29. Bl - Bustle pipe and launder ring apparatus from settling cone Tl to clear liquor supply line L43.
OMPI
- WIPO ,fr Lines
L29 - Liquor supply line to the filter circuit. L39 - Unclarified liquor supply line from slaker (or causti¬ cizer) to unclarified liquor supply pump SP1. L40 - Unclarified liquor supply line from unclarified liquor supply pump SP1 to junction of settling cone inlet line L41 and settling cone bypass line L42. L41 - Settling cone inlet line from unclarified liquor supply line L40 to settling cone Tl. L42 - Settling cone bypass line from unclarified liquor supply line L40 to slaker (or causticizer) return line L50. L43 - Clear liquor supply line from bustle pipe/launder ring apparatus Bl to junction of clear liquor tank inlet line L44 and clear liquor tank bypass line L46.
L44 - Clear liquor tank inlet line from clear liquor supply line L43 to clear liquor tank T2. L45 - Clear liquor tank overflow line from clear liquor tank T2 to clear liquor bypass/overflow line L48. L46 - Clear liquor tank bypass line from clear liquor supply line L43 to clear liquor bypass/overflow line L48. L47 - Clear liquor tank outlet line from clear liquor tank T2 to junction of filter circuit liquor supply line L29 and clear liquor tank drain line L51.
L48 - Clear liquor tank bypass/overflow line from junction of clear liquor tank bypass line L46 and clear liquor tank overflow line L45 to slaker (causticizer) return line L50. L49 - Settling cone mud discharge line from settling cone
Tl to slaker (causticizer) return line L50. L50 - Slaker (causticizer) return line returning flows from clear liquor tank bypass/overflow line L48, mud discharge line L49, and settling cone bypass line L42 to the slaker (or causticizer).
L51 - Clear liquor tank drain line from clear liquor tank outlet line L47 to return line L50.
j —OMPI . L52 - Water flush line from mill water supply to unclari¬ fied liquor supply line L39. Operating and repair valves (manually operable)
V30 - Settling cone inlet valve in settling cone inlet line L41. Two positions: open, closed.
V31 - Settling cone bypass valve in settling cone bypass line L42. Two positions: open, closed. V32 - Clear liquor tank bypass valve in clear liquor tank bypass line L46. Two positions: open, closed. V33 - Clear liquor tank inlet valve in clear liquor tank inlet line L44. Two positions: open, closed. V34 - Clear liquor tank outlet valve in fftter circuit liquor supply line L29. Two positions: open, closed. V35 - Clear liquor tank drain valve in clear liquor tank drain line L51. Two positions: open, closed.
V36 - Water flush valve in water flush line L52. Two positions: open, closed. V37 - Unclarified liquor supply valve in unclarified liquor supply line L39.. Two positions: open, closed. The mud separation unit has five modes of operation, these being the normal operating mode, the clear liquor tank bypass mode, the settling cone bypass mode, the circuit shutdown/water flush mode, and the circuit shutdown/standby mode. Normal operating mode The first mode is the normal operating mode. The circuit will normally remain in this mode. The circuit will be removed from this mode only as necessitated by the need for repairs to the mud separation or filter circuits, or upon shutdown of the slaking/causticizing process. Major parts involved Tl - Continuous settling cone.
T2 - Clear liquor tank. SP1 - Unclarified liquor supply pump/on. SP2 - Clear liquor supply pump/on. Bl - Bustle pipe/launder ring apparatus. Lines involved
L29 - Liquor supply line to filter circuit. L39 - Unclarified liquor supply line.
L40 - Unclarified liquor supply line.
L41 - Settling cone inlet line.
L43 - Clear liquor supply line. L44 - Clear liquor tank inlet line.
L45 - Clear liquor tank overflow line.
L48 - Clear liquor tank bypass/overflow line.
L49 - Settling cone mud discharge line.
L50 - Slaker (causticizer) return line. Operating valves/position
V30 - Settling cone inlet valve/open.
V31 - Settling cone bypass valve/closed.
V32 - Clear liquor tank bypass valve/closed (or throttled).
May be throttled partially open when circuit is in operation in order to direct some clear liquor to the return line L50 to ensure that L50 does not become plugged.
V33 - Clear liquor tank inlet valve/open.
V34 - Clear liquor tank outlet valve/open. V35 - Clear liquor tank drain valve/closed.
V36 - Water flush valve/ closed.
V37 - Unclarified liquor supply valve/open. Flow
Unclarified liquor From slaker (or causticizer) through V37 through L39 through SP1 through L40 through V30 through L41 into Tl. Clear liquor
From Tl through Bl through L43 through V33 through L44 into T2 through L47 through V34 through SP2 through L29. Mud
From Tl through L49 through L50 to slaker (or causticizer). Time
The time will vary. The circuit will normally be in this mode, being removed from this mode only for maintenance of this circuit or the filter circuit or upon shutdown of the slaking and causticizing process.
* * AΪ Clear liquor tank bypass mode
The second mode is the clear liquor tank bypass mode. This mode is utilized when it is necessary to stop the flow of clear liquor to the clear liquor tank. This may be necessitated by the need for repairs to this part of the circuit, or by the need for repairs to the filter circuit which require that the flow of clear liquor to the filter circuit be stopped.
Major components involved
Tl - Continuous settling cone. T2 - Clear liquor tank. SP1 - Unclarified liquor supply pump/on.
SP2 - Clear liquor supply pump/off. Bl - Bustle pipe/launder ring apparatus. Lines involved
L39 - Unclarified liquor supply line. L40 - Unclarified liquor supply line.
L41 - Settling cone inlet line. L43 - Clear liquor supply line. L46 - Clear liquor tank bypass line. L47 - Clear liquor tank outlet line. L48 - Clear liquor tank bypass/overflow line.
L49 - Settling cone mud discharge line. L50 - Slaker (or causticizer) return line. L51 - Clear liquor tank drain line. Operating valves/position V30 - Settling cone inlet valve/open.
V31 - Settling cone bypass valve/ closed. V32 - Clear liquor tank bypass valve/open. V33 - Clear liquor tank inlet valve/closed. V34 - Clear liquor tank outlet valve/closed V35 - Clear liquor tank drain valve/open.
V36 - Water flush valve/closed. V37 - Unclarified liquor supply valve/open. Flows
Unclarified liquor From slaker or causticizer through V37 through L39 through SP1 through L40 through V30 through L41 into Tl. Clear liquor
From Tl through Bl through L43 through V32 through L46 through L48 through L50 to slaker or causticizer. From T2 through L47 through L35 through L51 through L50 into slaker or causticizer.
Mud
From Tl through L49 through L50 to slaker or causticizer. Time
Varies as required to repair maintenance problem necessi¬ tating clear liquor tank bypass.
Settling Cone Bypass Mode
The third mode is the settling cone bypass mode. . This mode is utilized when it is necessary to stop operation of the settling cone in order to repair this part of the circuit. The flow of clear liquor will be interrupted in this mode and there will be no sample flow to the filter eircuit and analyzer.
Major components involved
SP1 - Unclarified liquor supply pump/on. SP2 - Clear liquor supply pump/off. Lines involved
L39 - Unclarified liquor supply line.
L40 - Unclarified liquor supply line.
L42 - Settling tank bypass line.
L47 - Clear liquor tank outlet line.
L50 - Slaker or causticizer return line.
L51 - Clear liquor tank drain line. Operating valves/position
V30 - Settling tank inlet valve/closed.
V31 - Settling tank bypass valve/open.
V32 - Clear liquor tank bypass valve/closed.
V33 - Clear liquor tank inlet valve/open.
V34 - Clear liquor supply valve/open.
V35 - Clear liquor tank drain valve/open.
V36 - Water flush valve/open.
V3 - Unclarified liquor supply valve/open,
OMPI Flows
Unclarified liquor
From slaker or causticizer through V37 through L39 through SP1 through L40 through V31 through L42 through L50 to slaker or causticizer.
Time
Varies as needed to complete maintenance repairs necessi¬ tating bypass of settling cone. Circuit Shutdown/Water Flush Mode The fourth mode is the circuit shutdown/water flush mode. This mode is used when it is necessary to entirely shut down the circuit for maintenance or in response to a shutdown of the slaking/causticizing process. The flow of unclarified liquor to the system is stopped and all lines and major parts are flushed with water to ensure that they are clean and unplugged.
Major components involved Tl - Settling cone. T2 - Clear liquor tank. SP1 - Unclarified liquor supply pump/on. SP2 - Clear liquor supply pump/on.
Bl - Bustle pipe/launder ring. Lines involved
L40 - Unclarified liquor supply line. L41 - Settling tank inlet line. L42 - Settling tank bypass line.
L43 - Clear liquor supply line. L44 - Clear liquor tank inlet line. L45 - Clear liquor tank overflow line. L46 - Clear liquor tank bypass line. L47 - Clear liquor tank outlet line.
L48 - Clear liquor tank bypass/overflow line. L49 - Settling cone mud discharge line. L50 - Return line to slaker or causticizer. L51 - Clear liquor tank drain line. L52 - Water flush line. Operating valves/position
V30 - Settling cone inlet valve/open. V31 - Settling cone bypass valve/open. V32 - Clear liquor tank bypass valve/open. V33 - Clear liquor tank inlet valve/open.
V34 - Clear liquor tank outlet valve/open. V35 - Clear liquor tank drain valve/open. V36 - Water flush valve/open. V37 - Unclarified liquor supply valve/closed. Flow
Water
Through L52 through V36 through L39 through SP1 through L40 through:
V31 through L42 through L50 into slaker or causticizer. V30 through L41 into Tl.
From Tl through L49 through L50 into slaker or causticizer.
From Tl through Bl through L43 through:
V32 through L46 through L48 through L50 into slaker or causticizer.
V33 through L44 into T2 through L47 through: V34 through SP2 through L29. V35 through L51 through L50 into slaker or causticizer. Time
15 minutes or as needed to completely flush circuit with water.
Note
This operation, as described, will completely flush the entire eircuit with water. Selected valves may be closed as desired to direct wash, water only through selected lines and parts of the circuit. It is not always necessary or desirable to flush the entire circuit. Circuit Shutdown/Standby Mode
The fifth mode is the circuit shutdown/standby mode. This mode is used after the circuit has been flushed with water. The circuit is in a "standby" condition and will remain in this condition until restarted. Major components involved
All components are in "standby." All tanks are drained and all pumps are off. Lines All lines have been flushed and drained and remain in a standby mode. Operating valves/position
V30 - Settling tank inlet valve/open. V31 - Settling tank bypass valve/closed. V32 - Clear liquor tank bypass valve/closed.
V33 - Clear liquor tank inlet valve/open. V34 - Clear liquor supply valve/open. V35 - Clear liquor tank drain valve/closed. V36 - Water flush valve/closed. V3 - Unclarified liquor supply valve/closed.
Flow
No flow in circuit once tanks and lines empty and drain. To restart the circuit and return to the first or normal operating mode, the urielarified liquor supply valve V29 is opened and pumps SP1 and SP2 are turned on. The circuit will then resume normal operation. The circuit should be started and be running at least 30 minutes prior to starting the rest of the analyzer system in order to ensure that all tanks have been filled and the circuit has reached equilibrium. Sampling circuit The purpose of the sampling circuit is to obtain a measured liquor sample and a measured amount of acid, to hold them separately until the reactor can receive them, and to transport them to the reactor. It has two main sections, a sample valve and an associated sample loop shown in the upper central part of Figure 1, and an acid section shown in the right hand side of Figure 1. The sample loop obtains a 10 cc sample of the filtered liquor and the acid pump obtains a 50 cc sample of 10% sulfuric acid by volume (approximately 2.2 N). The acid pump strokes to deliver a full 50 cc of acid but only 40 cc goes to reactor. The rest is left in the sample loop SL2 and is washed out when fresh liquor displaces the acid in the liquor sampling mode.
It has the following components:
OMPI Major components
SL2 - Sample loop for obtaining a 10' cc filtered liquor sample. It is connected to the ports P5 and P6 of the sample valve VI 4. API - The air piston for operating the piston in the positive displacement acid pump AP2. Two posi¬ tions: position one (acid in or fill) (IF); position two (acid out or transfer) (2T). AP2 - Positive displacement acid pump for obtaining a 50 cc sample of 10% sulfuric acid. Two positions: position one (acid fill and standby) (IF); position two (acid out or transfer) (2T). Lines
L9 - Antif locculant line from the antiflocculant supply to the acid supply line L20.
L14 - Air line from the air supply line L27 to the valve
Vll. L15 - Air line from the valve Vll to the port PI of the sample valve V14 for supplying air to move the sample valve V14 to position one (sampling) (IS).
LI 6 - Air line from the valve Vll to the port P2 of the sample valve V14 for supplying air to move the sample valve V14 to position two (transferring) (2T). L17 - Sample line from the port P4 of the sample valve V14 to the port R9 of the reactor Rl.
L19 - Acid line from the acid line L21 to the port P3 of the sample valve V14. L20 - Acid supply line from the acid supply to the acid line L21. L21 - Acid line from the juncture of acid lines LI 9 and
L20 to the acid pump AP2. L22 - Sample line from the filter system to the port P8 of the sample valve V14. L23 - Sample line from the port P7 of the sample valve V14 to the sewer.
^ JRl
OMPI L24 - Air line from the valve V17 to the inner side of the piston in API to move the piston outwardly to position one (acid fill) (IF). L25 - Air line from the valve V17 to the outer side of the piston in API to move the piston inwardly to posi¬ tion two (acid transfer) (2T). L26 - Air line from the air supply line L27 to the valve
V17. L2 - Air supply line. Valves
Operating valves
Vll - Solenoid operated air valve connecting the air line L14 to either the air line LI 5 or the air line LI 6 to position the sample valve V14. Two positions: position one (sampling) (IS) - the air line L14 con¬ nected to the air line LI 5; position two (transferring) (2T) - the air line LI 4 connected to the air line LI 6. V14 - Air operated sample valve has two operational ports.
PI - Connected to the air line L15 to allow air to move the valve to position one (sampling), and P2 - Connected to the air line LI 6 to allow air to move the valve to position two (transferring).
And six sample ports: P3 - Connected to the acid line LI 9, P4 - Connected to the sample line L17, P5 - Inlet to the sample loop SL2, P6 - Outlet from the sample loop SL2,
P7 - Connected to the sewer line L23, P8 - Connected to the sample line L22. It has two positions:
Position one (sampling) (IS) - receiving the sample from the filter circuit into the sample loop SL2.
Connects ports P5, P6, P7 and P8.
-g T EAlT
OMPI
/^> WIPO Position two (transferring) (2T) - sending the sample from the sample loop SL 2 to the reactor Rl. Connects ports P3, P4, P5 and P6 and sends acid charge from AP2 through sample loop SL2 to reactor Rl.
V17 - Solenoid operated air valve connecting air line L26 to either the air line L24 or the air line L25. Two positions: position one (acid fill) (IF): the air line
L26 connected to the air line L25; position two (acid transfer) (2T): the air line L26 connected to the air line L24. Check valves
V12 - Check valve in the sample line L17 prevents material or gas from returning through the line LI 7 from the reactor Rl to the sampling circuit.
V15 - Check valve in the acid line LI 9 prevents baekflow of acid from L19 through L20 into AP2 during the acid pump fill mode.
VI 6 - Check valve in the acid supply line L20 prevents baekflow of acid through the acid supply line L20 during the acid transfer mode. Pressure regulation valves
AR2 - Pressure regulation valve in the air line L26.
AR3 - Pressure regulation valve in the air line L14. The sample valve and its associated sample loop receives and holds a measured liquor sample. The acid system receives and holds a measured amount of acid separate from the liquor sample. These are held until the reactor can accept the sample and the acid. The eircuit then transports the sample, followed by the acid, to the reactor Rl. During this latter step, the acid passes through the sample loop SL2. This accomplishes two objectives: (1) the sample is transported to the reactor assembly by the acid and (2) the sample loop is cleaned by the acid during the injection.
After the transfer some acid remains in the loop and will dissolve any residue that may remain in the loop. Cleaning the sample loop before each liquor analysis is important because the liquor being handled tends to crystallize out on any surfaces with which it comes in contact. During the next sample reception, the sample is circulated through the sample loop SL2 and out of the system through line L23. This requires 60 to 100 seconds to ensure that all of the acid and any residue that may be present is removed from the sample loop, and that the new sample is a representative sample of the liquor currently being utilized by the process.
The sampling circuit has several operating modes. In many of these modes the valving arrangement is the same.
An initial acid flush cycle (Modes 1-4) is performed at start-up to ensure that the sample system is clean and filled with acid before sample analysis begins. At start-up, there may or may not be a sample in the sample loop depending upon the status of the sample system at shutdown.
Standby mode (Standby 1)
The first mode is a standby mode in which there is acid or liquor in the sample loop SL2, depending on the status of the sample circuit at shutdown.
Major components involved
SL2 - Sample loop/filled with 10 cc of acid or liquor. API - Air operated piston for operating the piston in the acid pump/position one (acid fill) (IF). AP2 - Acid pump/position one (acid fill) (IF).
Lines involved
L14 - Air line from the air supply line L27 to the valve
Vll. LI 5 - Air line from the valve Vll to the port PI of the sample valve VI 4.
L24 - Air line from the valve V17 to the inner side of the piston in API. L26 - Air line from the air supply line L27 to the valve V17. L2 - Air supply line.
Valves involved
Operating valves/position
Vll - Solenoid operated air valve/position one (sampling) (IS): connecting the air lines L14 and L15. V14 - Air operated sample valve/position one (sampling)
(IS): connecting the ports P5, P6, P7 and P8. V17 - Solenoid operated air valve/position one (acid fill) (IF): connecting the air lines L26 and L24. Check valves
VI 5 - Check valve in the acid line LI 9 holds acid in the line LI 9.
V16 - Check valve in the acid supply line L20 holds acid in the acid lines L20 and L21. Pressure regulation valves
AR2 - Pressure regulation valve in the air line L26. AR3 - Pressure regulation valve in the air line L14.
Flow Air
L27 through AR3 through L14 through Vll through L15 through PI into VI 4. L27 through AR2 through L26 through V17 through L24 into
API. Liquor
No flow. Sample valve repositioning mode (Reposition 1) The second mode is a sample valve repositioning mode. The sample valve is moved from the sample receiving position to the sample transferring position.
Major components involved
SL2 - Sample loop/10 cc of acid present. API - Air operated piston for operating the piston in the acid pump/position one (acid ill) (IF). AP2 - Positive displacement acid pump/position one (acid fill) (IF). Lines involved L14 - Air line from the air supply line L27 to the valve
Vll. L16 - Air line from the valve Vll to the port P2 of the sample valve VI 4. L24 - Air line from the valve V17 to the inner side of the piston in API.
L26 - Air line from the air supply line L2 to the valve V17. L27 - Air supply line. Valves involved
Operating valves/position
Vll - Solenoid operated air valve/position two (trans- f erring) (2T): connecting the air lines L14 and LI 6.
V14 - Air operated sample valve/position two (transfer¬ ring) (2T): connecting the ports P3, P4, P5 and P6. V17 - Solenoid operated air valve/position one (acid fill) (IF): connecting the air lines L26 and L25. Check valves
VI 5 - Check valve in the acid line LI 9 holds acid in the line L19. VI 6 - Cheek valve in the acid supply line L20 holds acid in the acid lines L20 and L21. Pressure regulation valves
AR2 - Pressure regulation valve in the air line L26. AR3 - Pressure regulation valve in the air line L14. Flow Air L27 through AR3 through L14 through Vll through L16 through P2 into V14.
L27 through AR2 through L26 through V17 through L24 into API. Time 5 seconds or as needed to ensure V14 has completed switching. Acid transferring mode (Transfer 1)
The third mode is a transfer mode in which the acid pump forces the 50 cc of acid in the acid pump AP2 through the sample loop SL2 and into the reactor. An initial flushing of the system with acid is performed to ensure that the system is cleaned and filled with acid before sample analysis commences.
Major components involved SL2 - Sample loop. API - Air operated piston for operating the piston in the acid pump/position two (acid transfer) (2T).
OMPI
/ *> WIPO « AP2 - Positive displacement acid pump/position two (acid transfer) (2T). Lines involved
L14 - Air line from the air supply line L27 to the valve Vll.
LI 6 - Air line from the valve Vll to the port P2 of the sample valve V14. L17 - Sample line from the port P4 of the sample valve V14 to the port R9 of the reactor Rl. L19 - Acid line from the acid line L21 to the port P3 of the sample valve VI 4. L21 - Acid line from the acid pump AP2 to the acid line
L19. L25 - Air line from the valve V17 to the outer side of the piston in API.
L26 - Air line from the air supply line L27 to the valve
V17. L2 - Air supply line. Valves involved Operating valves/position
Vll - Solenoid operated air valve/position two (trans¬ ferring) (2T): connecting the air lines L14 and L16. V14 - Air operated sample valve/position two (transf¬ erring) (2T): connecting the ports P3, P4, P5 and P6.
V17 - Solenoid operated air valve/position two (acid trans¬ fer) (2T): connecting the air lines L26 and L24. Check valves
V12 - Check valve in the sample line L17 prevents the liquor and acid from returning to the sample circuit once it has entered the reactor. VI 5 - Check valve in the acid line LI 9 allows acid to flow from AP2 through L21 through LI 9 into V14. V16 - Check valve in the acid line L20 prevents acid from returning to the acid supply system when AP2 transfers the acid. Pressure regulation valves
AR2 - Pressure regulation valve in the air line L26. AR3 - Pressure regulation valve in the air line LI 4. Flow Air
L27 through AR3 through L14 through Vll through LI 6 through P2 into VI 4.
L27 through AR2 through L26 through V17 through L25 into API to move piston upwardly. Liquid
AP2 through L21 through V15 through L19 through P3 through P5 through SL2 through P6 through P4 through V12 through L17 into Rl. Time 30 seconds or as needed to ensure AP2 has completed its stroke. Sample valve repositioning mode 2 (Reposition 2)
The fourth mode is a second sample valve repositioning mode to move the sample valve from position two (transferring) to position one (sampling), and to move the acid pump from position two (acid transfer) to position one (acid fill) to fill the acid pump with acid and antiflocculant. It is necessary to add antiflocculant to the reaction mixture to prevent flocculation and deposition of sulfur in the reactor. It is best to add a known amount of antiflocculant to each reaction by mixing antiflocculant solution with acid when the acid pump refills.
By proper choice of antiflocculant storage concentration and proper sizing of antiflocculant lines L9 and acid supply line L20, the proportions of acid and antiflocculant drawn into the acid pump AP2 will be such as to ensure a desirable concentration of antiflocculant in the reaction mixture. Sufficient turbulence exists in L20, L21 and AP2 during the acid fill step to ensure adequate dissolution of antiflocculant in the acid. Major components involved
SL2 - Sample loop/approximately 10 cc acid. API - Air operated piston for operating the piston in the acid pump/position one (acid fill) (IF).
API - Positive displacement acid pump/position one (acid fill) (IF).
^J EA "
OMPI r WIPO Lines involved
L9 - Antiflocculant supply line from antiflocculant storage to acid supply line L20.
L14 - Air valve from the air supply line to the valve Vll. L15 - Air line from the valve Vll to the port PI of the sample valve VI 4.
L20 - Acid supply line from the acid supply to the line
L21.
L21 - Acid line from the acid supply line L20 to the acid pump AP2.
L24 - Air line from the valve V17 to the inner side of the piston in API.
L26 - Air lines from the air supply line L27 to the valve
V17. L2 - Air supply line.
Valves involved
Operating valves/position
Vll - Solenoid operated air valve/position one (sampling)
(IS). V14 - Air operated sample valve/position one (sampling)
(IS): connecting the ports P5, P6, P7 and P8.
V17 - Solenoid operated air valve/position one (acid fill)
(IF): connecting the air lines L26 and L25.
Check valves VI 5 - Check valve in the acid line L19 prevents baekflow of acid from L19 through L21 into AP2.
VI 6 - Check valve in the acid supply line L20 allows acid to flow from L20 through L21 into AP2.
Pressure regulation valves AR2 - Pressure regulation valve in the air line L26.
AR3 - Pressure regulation valve in the air line L14.
Flow
Air
L27 through AR3 through L14 through Vll through L15 through PI into V14.
L27 through AR2 through L26 through V17 through L24 into
API.
-^ EAlT" OMPI efa WIPO Acid
L20 through V16 through L21 into AP2. Antiflocculant
L9 through L20 through VI 6 through L21 into AP2. Time
5 seconds
Note: Time not really important - a great excess of time (approximately 12 minutes for the system described) is available for the pump to fill and valve to switch. Standby mode (Standby 2)
The fifth mode is a second standby mode (Standby 2) in which the sample valve waits to receive a sample from the filter circuit. It is identical to the first mode (Standby 1) and will not be given in detail again.
Its time is 12 minutes, but may change depending on the operation of a particular system.
Sample collecting mode (Sample)
The sixth mode is a sample collecting mode in which a sample is collected from the filter circuit.
Major components involved SL2 - Sample loop/initially filled with 10 cc acid from last sample transfer mode. API - Air operated piston for operating the piston in the acid pump/position one (acid fill) (IF). AP2 - Positive displacement acid pump/position one (acid fill) (IF).
Lines involved
L14 - Air line from the air supply line L27 to the valve
Vll. L15 - Air supply line from the valve Vll to the port PI of the sample valve V14.
L22 - Liquor sample line from the filter system to the port P8 of the sample valve VI 4. L23 - Sample line from the port P7 of the sample valve V14 to the sewer. L24 - Air line from the valve V17 to the inner side of the piston in API.
OMPI -a- L26 - Air line from the air supply line L27 to the valve
V17. L2 - Air supply line. Valves involved Operating valves/position
Vll - Solenoid operated air valve/position one (sampling)
(IS): connecting the air lines L14 and L15. V14 - Air operated sample valve/position one (sampling) (IS): connecting the ports P5, P6, P7 and P8. VI - Solenoid operated air valve/position one (acid fill)
(IF): connecting the air lines L26 and L25. Check valves
VI 5 - Check valve in the acid line LI 9 holds the acid in the line L19. V16 - Cheek valve in the acid supply line L20 holds the acid in the lines L20 and L21. Pressure regulation valves
AR2 - Pressure regulation valve in the air line L26. AR3 - Pressure regulation valve in the air line L14. Flow
Air
L27 through AR3 through L14 through Vll through L15 through PI into VI 4.
L27 through AR2 through L26 through V17 through L24 into API.
Liquor
L22 through P8 through P5 through SL2 through P6 through P7 through L23. Time 60 seconds or as needed to ensure complete flushing and filling of sample loop with a fresh liquor sample. Standby mode (Standby 3)
The seventh mode is a third standby mode (Standby 3) in which the sample circuit waits for the reactor circuit to receive the sample. It is identical to the first and fifth modes (Standby 1 and Standby 2) and will not be given in detail. The sample loop is filled with liquor rather than acid at this stage.
OMPI Sample valve repositioning mode (Reposition 3)
The eighth mode is a third sample valve repositioning mode
(Reposition 3) in which the sample valve V14 is moved from position one
(sampling) to position two (transferring). It is identical to the second mode (Reposition 1) and will not be given in detail. Its time is the same as
Reposition 1.
Acid transferring mode (Transfer 2)
The ninth mode is a second transfer mode (Transfer 2) in which the acid pump forces the 50 cc of acid through the sample loop and into the reactor. This carries the sample into the reactor also. Acid remains in the sample loop to clean the sample loop of any material that may have coated on the tubing during the seventh mode (Standby 3). This acid and the residue will be removed from the system during the next sample collecting mode. It is identical in operation to the third mode (Transfer 1) and will not be given in detail.
Sample valve repositioning mode (Reposition 4)
The tenth mode is a fourth repositioning mode (Reposition 4) in which the sample valve V14 is moved from position two (transferring) to position one (sampling) and the acid pump AP2 is filled with acid and antiflocculant. It is identical to the fourth mode (Reposition 2) and its time is the same. Reactor circuit
The reactor is shown in Figures 5 and 6 and the reactor circuit is shown in the bottom left hand section of Figure 1. As may be seen in Figure 5, the reactor Rl has a reactor compartment R2 which is defined by a cover member R3, sidewalls R4 and a base R5. The cover member R3 has four ports: R6 for the vent gas from the reactor to the sewer line, R7 for the wash water to the reactor, R8 both for the reactor gas from the reactor to the gas chromatograph and for gas under pressure to pressurize the reaction chamber, and R9 for the sample and acid to the reactor. The base R5 defines the bottom R10 of the chamber R2. The bottom R10 is sloped toward the central outlet valve V13 so that the reaction chamber R2 may be washed and drained easily after each reaction. The magnetic spin bar R13 provides turbulence and mixing of the reaction mixture. The base R5 rests on a pressure chamber Rll and pressure within the chamber Rll is maintained by the rubber diaphragm R12 between the base R5 and the pressure chamber Rll. Air enters the pressure chamber Rll through air line LI and the air pressure holds the valve VI 3 in its upper closed position to maintain liquid within the reaction chamber R2. When the air pressure is bled from the line LI, the valve VI 3 drops into its lower position allowing the reaction chamber R2 to be drained. The liquid goes into outlet line LI 8 to be sewered or otherwise treated. The reactor circuit has the following components: Major components
Rl - Reactor Ml - Magnetic spin bar driver for reactor mixer.
Lines
LI - Air line from the valve V10 to the reactor outlet pressure chamber Rll. L2 - Line to the gas chromatograph GC. L2A - Line between the reactor gas line Lδ and the gas chromatograph GC. . L2B - Line between the reactor pressurization line L10 and the line L2A. L3 - Air line between the air supply line L27 and the line Lll.
L4 - Water supply line between the water supply and the port R7 of the reactor Rl. L5 - Vent line from the port R6 of the reactor Rl to the sewer. L6 - Reaction gas line from the line L13 to the line L2A.
L7 - Air line between air line LI 4 and the spin bar driver
Ml. L8 - Reactor pressurization line between the reactor pressurization line L10 and the reactor line L13. L10 - Reactor pressurization line between air supply line
L27 and lines L8 and L2B. Lll - Connecting line between the air line L3 and the gauge line L12, and the reactor gas line L6, the air pressure line L8 and the reactor line LI 3. L12 - Gauge line between the air line L3 and the connect¬ ing line Lll, and the gauge protector Gl and the pressure gauge G2. L13 - Reactor line between the port R8 of the reactor Rl and the juncture of the reactor gas line L6, the reactor pressurization line L8 and the connecting line Lll. LI 4 - Air line between the air supply line L27 and the valve V10. L17 - Sample line between the sample valve V14 and the port R9 of the reactor Rl. L18 - Outlet line from the valve VI 3 of the reactor Rl. Valves
Operating valves (solenoid operated)
V3 - Valve in the air line L3. Two position: open; closed. V4 - Valve in the water line L4. Two positions: open; closed. V5 - Valve in the vent line L5. Two positions: open; closed. V6 - Valve in the reaction gas line L6. Two positions: open; closed. V8 - Valve in the reactor pressurization line L8. Two positions: open; closed.
V10 - Valve between the air line L14 and the air line LI. Two positions: open; closed. Operating valves (air operated)
VI 3 - Outlet valve in the reactor Rl between the reaction chamber R2 and the outlet line LI 8. It is operated by air pressure from the line LI. Two positions: closed when the air is on; open when the air is off. Check valves
V12 - Check valve in the sample line L17 preventing either the sample, the reaction gas or air from flowing back through the sample line L17. Pressure regulation valves
AR1 - Pressure regulation valve in the air line LI. AR3 - Pressure regulation valve in the air line LI 4. AR4 - Pressure regulation valve in the air line L3.
AR5 - Pressure regulation valve in the reactor pressuriza¬ tion line L10.
-ψ ϊlEAlr OMPI Repair valves (normally open, manually operable) V7 - Repair valve in the air line L7. Ports
R6 - Port in the reactor Rl for the vent line L5. R7 - Port in the reactor Rl or the water line L4.
R8 - Port in the reactor Rl for the reactor line LI 3. R9 - Port in the reactor Rl for the sample line L17. The operating sequence of the reactor is as follows:
(1) The reactor is cleaned: (a) The reactor is drained.
(b) The reactor is filled with water.
(c) The reactor is again drained.
(d) The reactor is again filled with water.
(e) The reactor is again drained. (f) The reactor is again filled with water.
(g) The reactor is again drained.
(2) The reactor is vented for 5 seconds, then resealed.-
(3) The acid and sample are placed in the reactor and the reaction starts. (4) After approximately 11 minutes, the reactor is placed under pressure using a precise air pressure regulator. This is important if a direct relationship between gas chromato¬ graph output and liquor concentration is to be obtained. The final reactor pressure should be about 2 psi above the highest total reactor pressure resulting from the sum of all the partial pressures or the expected components or 26 psi above the ambient pressure. This is to compensate for the dependence of reactor pressure on liquor concentration which would provide an incorrect reading if there was no compensation.
(5) The reaction is allowed to go to completion.
(6) The reaction gas is transferred to the gas chromatograph. The time of transfer must be long enough to obtain a representative sample of gas in the sample loop SL1 of the gas chromatograph. This usually requires 40-50 seconds.
The cycle takes approximately 19 minutes, but will vary according to the characteristics of each individual system.
OMPI ™p° Standby mode (Standby)
The first mode of the reactor circuit is a standby mode in which the reactor is waiting to receive the sample. It usually occurs only at start¬ up. The reactor contains whatever was present in it at shutdown. This can be the old reaction mixture, wash water, etc. Major components involved
Rl - Reactor Lines involved
LI - Air line from the valve V10 to the valve V13. L14 - Air line from the air supply line L27 to the valve
V10. L27 - Air supply line. Valves involved
Operating valves/position V3 - Valve in the air line L3/closed.
V4 - Valve in the water line L4/closed. V5 - Valve in the vent line L 5 /closed. V6 - Valve in the reaction gas line L6/closed. V8 - Valve in the air pressure line L8/closed. V10 - Valve between the air lines L14 and Ll/open.
V13 - Outlet valve in the reactor Rl/closed. Pressure regulation valves
AR1 - Pressure regulation valve in the air line LI. AR3 - Pressure regulation valve in the air line L14. Flow
Air
L27 through AR3 through L14 through VI 0 through LI through AR1 into Rll to hold VI 3 closed. Vent mode (Vent) The second mode is a vent mode. The reactor is vented when the sample valve V14 is repositioned from position one (sampling) to position two (transferring). This allows the pressure in the reaction chamber to reach atmospheric pressure prior to sample injection. The gas in the reactor contains, at most, minor amounts of carbon dioxide and hydrogen sulfide. Major components involved
Rl - Reactor Lines involved
LI - Air line from the valve VIO to the chamber Rll of the reactor Rl. L5 - Vent line from the port R6 of the reactor Rl to the atmosphere.
L14 - Air line between the air supply line L27 and the valve VIO. L2 - Air supply line. Valves involved Operating valves/position
V3 - Valve in the air line L 3 /closed. V4 - Valve in the water line L4/elosed. V5 - Valve in the vent line L 5 /open. V6 - Valve in the reaction gas line L6/closed. V8 - Valve in the pressure line L8/closed.
VIO - Valve between the air lines L14 and Ll/open to hold the outlet valve VI 3 of the reactor Rl closed. VI 3 - Outlet valve from the reactor Rl/closed. Pressure regulation valves AR1 - Pressure regulation valve in the air line LI.
AR3 - Pressure regulation valve in the air line L14. Flow Air
Rl through R6 through V5 through L5 to vent line to sewer. L27 through AR3 through L14 through VIO through LI through AR1 into Rll to hold VI 3 closed. Time
5 seconds as needed for air in reactor to reach equilibrium with atmospheric pressure. In the vent mode prior to the introduction of the sample, the vent mode must end prior to introduction, of sample into reactor to ensure no loss of reaction gas products. . Drain mode (Drain)
The third mode is a reactor drain mode. During the washing cycle the reactor is drained either of reaction products or of wash water.
OMPI Major components involved
Rl - Reactor Lines involved
LI - Air line from the valve VIO to the outlet valve VI 3 of the reactor Rl.
L3 - Air line from the air supply line L27 to the connecting line Lll. Lll - Connecting line from the air line L3 to the reactor line LI 3. LI 3 - Reactor line from the connecting line Lll to the port R8 of the reactor Rl. LI 8 - Outlet line from the reactor Rl. L2 - Air supply line. Valves involved Operating valves/position
V3 - Valve in the air line L3/open. V4 - Valve in the water line L4/closed. V5 - Valve in the vent line L5/closed. V6 - Valve in the reaction gas line L6/closed. V8 - Valve in the air pressure line L8/closed.
VIO - Valve between the air lines L14 and Ll/closed to bleed air from the line LI to open the valve V13. V13 - Outlet valve of the reactor Rl/open to drain the reactor through the outlet line LI 8. Check valves
V12 - Check valve in the sample line L17 prevents air from escaping through the sample line L17. Pressure regulation valves
AR4 - Pressure regulation valve in the air line L3. Flow
Air
No flow in line LI.
L27 through AR4 through L3 through V3 through Lll through LI 3 through R8 into Rl. Liquid
Rl through VI 3 through L18.
OMPI Time
10 seconds or as needed to completely drain reactor. Fill mode (Fill)
The fourth mode is the reactor fill mode. During the wash cycle, the reactor is filled with wash water. Major components involved
Rl - Reactor Lines involved
LI - Air line from the valve VIO to the chamber Rll of the reactor Rl.
L4 - Water line between the water supply and the port
R7 of the reactor Rl. L5 - Vent line from the port R6 of the reactor Rl to the atmosphere. L14 - Air line from the air supply line L27 to the valve
VIO. L2 - Air supply line. Valve involved
Operating valves/position V3 - Valve in the air line L3/closed.
V4 - Valve in the water line L4/open. V5 - Valve in the vent line L5/open. V6 - Valve in the reaction gas line L6/closed. V8 - Valve in the air pressure line L8/closed. VIO - Valve between the air lines L14 and Ll/open.
VI 3 - Outlet valve of the reactor Rl/closed. Check valves
V12 - Check valve in the sample line L17 prevents air from entering the sample circuit. Pressure regulation valves
AR1 - Pressure regulation valve in the air line LI. AR3 - Pressure regulation valve in the air line L14. Flow Air Rl through R6 through V5 through L5 to vent line to sewer.
L27 through AR3 through LI 4 through V10 through LI through AR1 into Rll to hold V13 closed. g _ REA OMPI Water
L4 through V4 through R7 into Rl. Time
20 seconds or as needed to sufficiently fill reactor with water.
Sample transferring mode (Transfer)
The sixth mode is the sample transferring mode. The sample is received from the sampling circuit. Major components involved Rl - Reactor.
Lines involved
LI - Air line from the valve VIO to the outlet valve 13 of the reactor Rl. L14 - Air line from the air supply line L27 to the valve VIO.
L17 - Sample line from the sample circuit to the port R9 of the reactor Rl. L27 - Air supply line. Valves involved Operating valves/position
V3 - Valve in the air line L3/closed. V4 - Valve in the water line L4/closed. V5 - Valve in the vent line L5/closed. V6 - Valve in the reaction gas line L6/elosed. V8 - Valve in the air pressure line L8/closed.
VIO - Valve between the air lines L14 and Ll/open. V13 - Outlet valve from the reactor Rl/closed. Check valves
V12 - Check valve in the sample line L17 prevents the sample or reaction gases from returning through line
L17. Pressure regulation valves
AR1 - Pressure regulation valve in the air line LI. AR3 - Pressure regulation valve in the air line L14.
- J RE »
OMPI Λ WIPO Flow Air
L27 through AR3 through L14 through VIO through LI through AR1 into Rll to hold V13 closed. Liquor
SL2 through V14 through L17 through V12 through R9 into Rl. Acid
AP2 through L21 through VI 5 through L19 through V14 through SL2 through L17 through V12 through R9 into Rl.
Time
30 seconds or as needed to ensure complete transfer of acid and sample. Reaction mode (Reaction) The seventh mode is the reaction mode. The reaction between the acid and the sample takes place in the reaction chamber. There are two stages in the reaction mode, reaction 1 and reaction 2. Reaction 2 is the continuation of reaction 1 after pressure has been applied to the reaction chamber and is identical to reaction 1. Major components involved
Rl - Reactor Lines involved
LI - Air line from the valve VIO to the outlet valve VI 3 of the reactor Rl. L14 - Air line from the air supply line L27 to the valve
V O. L27 - Air supply line. Valves involved
Operating valves/position V3 - Valve in the air line L3/closed.
V4 - Valve in the water line L4/closed. V5 - Valve in the vent line L5/closed. V6 - Valve in the reaction gas line L6/closed. V8 - Valve in the air pressure line L8/closed. V10 - Valve between air lines L14 and Ll/open.
VI 3 - Outlet valve in the reactor Rl/closed.
*ς*TSLEA~ * OMPI Check valves
V12 - Cheek valve in the sample line L17 prevents the reaction gas from entering the sample circuit through the sample line L17. Pressure regulation valves
AR1 - Pressure regulation valve in line LI. AR3 - Pressure regulation valve in air line L14. Flow Air L27 through AR3 through L14 through VIO through LI through AR1 into Rll to hold VI 3 closed. Time
The total time of the reaction is about 15 minutes. It is divided into the two parts before and after pressure is applied.
Pressurization mode (Pressure)
The eighth mode is a pressurization mode. Eleven minutes after the reaction begins, air pressure is applied through a precise regulator to the reaction chamber to maintain a constant final reactor pressure. It was decided to pressurize 11 minutes into the reaction, because at this time:
1) the reaction is essentially complete and no further pressure rise is anticipated;
2) four minutes of reaction time remain, which allows the air which has been added in the pressurization step to become well mixed with the reaction gases to yield a homogeneous reaction gas sample at the end of the reaction.
The time of pressurization may be changed as needed in response to the characteristics of individual reactor systems. The pressurization step was added in response to observations made during the development of the system. In order to make valid comparisons among samples, it is necessary to have a constant final gas pressure. If this is not done, then the experience of our experiments will be repeated. In these experiments, the final gas pressure inside the reactor was allowed to remain at whatever pressure existed due to the release of carbon dioxide and hydrogen sulfide from the reaction. This pressure varied according to the amounts of sodium carbonate and sodium sulfide in the liquor sample. It was observed that, although an increase in sodium carbonate concentration in the liquor did cause an increase in the carbon dioxide peak area generated by the gas chromatograph, the relationship was not directly proportional. Furthermore, the carbon dioxide peak area was influenced by the amount of Na«s ∞ the liquor, which resulted in erroneous sodium carbonate measurements due to changes in the sodium sulfide concentration in the liquor. The measurement of sodium sulfide in the liquor was affected in the same manner. After this was realized, it was decided to adjust the pressure so that there would be the same total moles of gas in the system for each measurement. This ean be done by maintaining the reaction gas in the reactor at a constant pressure at the completion of the reaction. The addition of air will act as a diluent, and the total moles of gas will remain fixed among a number of samples. It has been found that the total pressure of air, carbon dioxide and hydrogen sulfide, under the conditions existing in the reactor, will not exceed 24 psi. By adding additional air to obtain a 26 psi pressure, it is possible to obtain gas samples each containing a constant total number of moles of gas. The air has substantially no carbon dioxide or hydrogen sulfide and does not affect the readings for carbon dioxide or hydrogen sulfide generated in the reaction. The peak areas for carbon dioxide and hydrogen sulfide will then be directly proportional to the concentrations of sodium carbonate and sodium sulfide, respectively, in the liquor. Furthermore, sodium carbonate measurements will not be affected by the sodium sulfide concentration in the liquor, nor will the sodium sulfide measurements be affected by the sodium carbonate concentration. The measurements of sodium carbonate and sodium sulfide are then used to control the process.
Major components involved Rl - Reactor
Lines involved
LI - Air line between the valve VIO and the outlet valve
V13 of the reactor Rl. L8 - Reactor pressurization line between the reactor pressurization line L10 and the reactor line L13.
L10 - Reactor pressurization line between the reactor pressurization line L8 and the air supply line L27.
-^URIX;
OMPI Lll - Connecting line between the reactor pressurization line L8 and the pressure gauge line L12. L12 - Pressure gauge line from the connecting line Lll to the gauge protector Gl and the air pressure gauge G2.
L13 - Reactor line between the reactor pressurization line
L8 and the port R8 of the reactor Rl. L14 - Air line between the air supply line L27 and the valve VIO. L2 - Air supply line.
Valves involved
Operating valves/position
V3 - Valve in the air line L3/closed. V4 - Valve in the water line L4/closed. V5 - Valve in the vent line L5/closed.
V6 - Valve in the reaction gas line L6/elosed. V8 - Valve in the reactor pressurization line L8/open. VIO - Valve between the air lines L14 and Ll/open. VI 3 - Outlet valve in the reactor Rl/elosed. Check valves
V12 - Check valve in the sample line L17 prevents reac¬ tion gases from entering the sample circuit through the sample line. Pressure regulation valves AR1 - Pressure regulation valve in the air line LI.
AR3 - Pressure regulation valve in the air line L14. AR5 - Pressure regulation valve having a precision of + .02 psi in the reactor pressurization line L10. Flow Air
L27 through AR2 through L14 through V10 through LI through AR1 into Rll to hold VI 3 closed. L27 through AR5 through L10 through V8 through L8 through LI 3 through R8 into Rl. Reaction gas transfer mode (Gas to G.C.)
The ninth mode is the reaction gas transfer mode. The reaction gas is transferred to the gas chromatograph (G.C). This requires enough time to allow a representative sample to be received in the sample loop SLl of the gas chromatograph.
Major components involved Rl - Reactor Lines involved
LI - Air line between the valve VIO and the reactor outlet valve V13. L2A - Line between the reaction gas line L6 and the gas chromatograph. L6 - Reaction gas line between the reactor line LI 3 and the gas chromatograph line L2A. LI 3 - Reactor line between the port R8 of the reactor Rl and the reaction gas line L6. L14 - Air line between the air supply line L27 and the valve VIO.
L2 - Air supply line. Valves involved
Operating valves/position
V3 - Valve in the air line L3/closed. V4 - Valve in the water line L4/closed.
V5 - Valve in the vent line L5/closed. V6 - Valve in the reaction gas line L6/open. V8 - Valve in the air pressure line L8/elosed. VIO - Valve between the air lines L14 and Ll/open. VI 3 - Outlet valve in the Reactor Rl /closed.
Cheek valves
V12 - Check valve in the sample line L17 prevents reac¬ tion gas from entering the sample circuit through the sample line L17. Pressure regulation valves
AR1 - Pressure regulation valve in the air line LI. AR3 - Pressure regulation valve in the air line LI 4. Flow Air L27 through AR3 through L14 through VIO through LI through AR1 into Rll to hold VI 3 closed. Reaction gas
Rl through R8 through L13 through V6 through L6 through L2A to gas chromatograph. Time 40 seconds or as needed to ensure that the gas chromato¬ graph has received a representative reaction gas sample. Stop transfer mode (Stop)
The tenth mode is the stop transfer mode. The reaction gas valve V6 is closed. Time is allowed for the pressure in the gas chromatograph system to equalize.
Major components involved
Rl - Reactor Lines involved
LI - Air line between the valve VIO and the reactor outlet valve VI 3.
L14 - Air line between the air supply line L27 and the valve VIO. L27 - Air supply line. Valves involved ' Operating valves/position
V3 - Valve in the air line L3/elosed. V4 - Valve in the water line L4/closed. V5 - Valve in the vent line L5/closed. V6 - Valve in the reaction gas line L6/closed. V8 - Valve in the air pressure line L8/closed.
VIO - Valve between the air lines LI 4 and Ll/open* V13 - Outlet valve in the Reactor Rl/closed. Check valves
V12 - Check valve in the sample line L17 prevents reac- tion gas from entering the sampling system through the sample line. Pressure regulation valves
AR1 - Pressure regulation valve in air line LI. AR3 - Pressure regulation valve in air line L14. Flow Air
L27 through AR3 through L14 through VIO through LI through AR1 into Rll to hold V13 closed. Time
5 seconds or as needed for the pressure in the gas chroma¬ tograph sample chamber to equilibrate. Magnetic spin bar driver
The liquor within the reactor chamber R2 is stirred by the mixing rod R13 within the reactor and resting on the drain valve V13 in the bottom of the reactor. This rod is magnetically coupled with and rotated by the magnetic spin bar driver M2 in chamber Ml.
The magnetic spin bar driver is shown in Figures 7 and 8. A powerful horseshoe magnet M3 faces upwardly toward the spin bar R13. The horseshoe magnet M3 is mounted on a rotating plate M4. Any type of mounting may be used. It may be adhered to the plate M4 with epoxy or other type of adhesive. It is shown mounted in an arcuate depression in the upper face of the plate M4.
The plate M4 rests on a base M5. Both the rotating plate M4 and the base M5 are shown as being circular in cross section. The base M5 has an upper flat horizontal supporting surface M6 around its periphery. A circular recessed section M7 is within the periphery. The recessed section
M7 also has a flat horizontal surface below surface M6 and a vertical side wall that extends from its surface to the supporting surface M6. A circular further recessed section M8 is within section M7. The surface of recessed section M8 is also flat and below the surface of section M7. The section M8 also has a vertical side wall that extends from its surface to the surface of section M7. The periphery of the base M5, the periphery of the section M7 and the periphery of the section M8 are concentric. The section M8 holds a nylon and glass ball bearing M9. The plate
M4 has a cylindrical shaft M10 that fits and rotates within bearing M9. A motor section Mil of the plate M4 fits and rotates within the recessed section M7 of the base M5. There is a clearance between the motor section
Mil and the surfaces of the recessed section M7. The motor section Mil is circular and concentric with both the cylindrical shaft M10 and the outer circular periphery M12 of the plate M5. The periphery M13 of the motor section Mil is broken by equally spaced radial slots or indentations M14.
OMPI
Figure imgf000054_0001
An air line M15 extends through the base M5 below the recessed section M8. Two secondary air passages Ml 6 extend from air line M15 angularly upwardly to the surface of the recessed section M7. The outlets of the secondary air passage Ml 6 are aligned with the radial slots M14 to allow air to impinge against the side walls of the radial slots M14 and rotate the plate M4. The outlets of the secondary air passages M16 are shown as 180° apart and on opposite sides of air line M15. The outlets may be parallel to a tangent to the periphery of recessed section M7 or be angled toward the periphery. The outlets may be, as shown, near the periphery of recessed section M7.
Air from air line L7 passes through line M15 and passages M16 to impinge against the walls of the radial slots Ml 4 to rotate the plate M4. The escaping air from the secondary air passages Ml 6 also acts as a bearing for the plate M5 between the surface M17 of the plate M4 and the supporting surface M6 of the base M5. The air eventually escapes along the surface M6 and out through the gap between the base and the revolving plate.
The rotation of plate M4 rotates the magnet M3. The rotating magnet M3 rotates the spin bar R13. The magnetic spin bar drive has the following components and operation:
Major components involved
Ml - Magnetic spin bar mixer chamber. M2 - Magnetic spin bar mixer driver. Lines involved
L7 - Air line from the air line L14 to the chamber Ml. L14 - Air line from the air supply line L27 to the air line
L7. L27 - Air supply line. Valves involved
Pressure regulation valves
AR3 - Pressure regulation valve in the air line L14. Repair valves
V7 - Repair valve in the air pressure line L7. Flow
L27 through AR3 through LI 4 through V7 through L7 into Ml to operate M2.
"^ftU R -C OMPI , WIPO It will be appreciated that the magnetic spin bar drive may also be turned off and on depending on whether the reactor chamber is filled or empty by changing the valve V7 to a solenoid operated on/off valve and operating it on the same cycle as valve VIO which controls the outlet valve V13 of the reactor. Valves V7 and VIO would open and close together. Gas Chromatograph System
In the reactor the green liquor or white liquor is reacted with acid to form carbon dioxide and hydrogen sulfide gases. The concentration of these gases is measured in the gas chromatograph. The chromatograph outputs a continuous analog signal corresponding to the flow rate of gas through the detector of the chromatograph. By integrating this signal for the proper time intervals (corresponding to the time of appearance of carbon dioxide and hydrogen sulfide at the detector), the concentrations of carbon dioxide and hydrogen sulfide in the reaction gas are measured. Calibration of the reactor/gas chromatograph system using liquors of known concentration allows the carbon dioxide and hydrogen sulfide measurements to be converted directly to a determination of sodium carbonate and sodium sulfide in the liquor sample.
The analysis process takes about four minutes for both carbon dioxide and hydrogen sulfide. It may be necessary to analyze only for carbon dioxide in the green liquor and causticizer white liquor samples. This would reduce the analysis time for these samples to one and one-half minutes.
The gas chromatograph may be used to successively analyze the reaction gases from a number of reactors. For one slaking/causticizing line, three liquor samples should be analyzed, resulting in a three-reactor analyzer system. For this reason the valve VI is a four position valve having four inlets from the reactors or other outside sources and one outlet to the gas chromatograph. It cycles through the four positions until is is at the proper position to receive reaction gas from the selected reactor. It requires approximately five seconds to move from one position to the next. Another five seconds is allowed to electronically check the position of the valve.
The inner details of a gas chromatograph will not be given. It is a standard piece of equipment and its details, other than allowing time for it to cycle through its procedure and the results of its analysis are not important here. There are a number of valves in the gas chromatograph that allow the sample loop to be filled, the gas sample to be carried to the analysis column, and the sample loop and analysis column to be purged and backflushed. This discussion will not include the standard helium flush and backflush that occurs within the gas chromatograph itself since these are normal functions of the instrument. We will merely note that these valves and operations exist in any gas chromatograph and will give only a general overview of the process and the apparatus. The only procedures that will be described in detail are the external procedures. The chromatrograph circuit has few parts. These are:
Components
Major components
GC - Gas chromatograph/two positions: position one
(standby) is used in three different modes - mode 1A (bypass); mode IB (gas transfer); mode 1C (purge) - position two (analyze). SLl - Sample loop for the gas chromatograph. Lines
L2 - Line to the gas chromatograph L2A - Line from the reaction gas line L6 to the gas chromatograph GC. L2B - Line from the calibration gas line L7 to the gas chromatograph line L2A. L2C - Line from the air pressure line L10 to the gas chromatrograph line L2B.
L6 - Reaction gas line from the reactor Rl to the gas chromatograph line L2A. L7 - Calibration gas line from the calibration gas supply to the gas chromatograph line L2B. L10 - Air pressure line from the air supply line L27 to the gas chromatograph line L2C. L14 - Air line from air supply line L2 to air line L53. L27 - Air supply line.
L53 - Air line from air line L14 to valve VI to operate the valve. Valves
Operating valves
VI - Valve in the gas chromatograph line L2A. Four positions to bring sample into gas chromatograph: position one (reactor one); position two (reactor two); position three (reactor three); position four (spare). V2 - Valve in the high pressure air line L2C. Two positions: open; closed. V6 - Valve in the reaction gas line L6. Two positions: open; closed. V7 - Valve in the calibration gas line L7. Two positions: open; closed. Pressure regulation valves AR3 - Pressure regulation valve in air line L14.
AR5 - Pressure regulation valve in high pressure air line
L10.
In the sequence of operations, the gas chromatograph takes a gas sample into the sample loop SLl, analyzes the gas sample, purges the sample from the system and backflushes the system. It then waits for a new sample to be supplied.
Standby mode (Standby)
The first mode is a standby mode. The gas chromatograph is waiting for a sample from the reactor eircuit. Major components involved
GC - Gas chromatograph/position one (standby) Valves involved
Operating valves/position
VI - Valve in gas chromatograph line L2A/position four (closed). This is exemplary. The valve may be in any position at start-up. It will depend upon the valve position when the system was shut down. V2 - Valve in high pressure air line L2C/elosed. V6 - Valve in the reaction gas line L6/closed. V7 - Valve in the calibration gas line L7/closed. Flow
No flow of reaction gases. Reposition mode (Reposition)
The second mode is a reposition mode (Reposition). The valve VI is repositioned around its four positions until it is lined up with the right reactor. It moves in the same direction, either clockwise or counter¬ clockwise, requiring five seconds to move. An additional five seconds is alloted for the system to check the position of the valve. If its location is not right, it will move again and be checked again. This will continue until it is in the right position. The other valves and the gas chromatograph remain as they are.
Standby mode (Standby 2)
The third mode is a new Standby mode (Standby 2) in which all the valves remain in their positions until the reactor circuit is ready to transfer a gas sample.
Reaction gas transfer mode (Gas to G.C.)
The fourth mode is a reaction gas transfer mode. The gas chromatograph is internally valved so that the reaction gas goes through the sample loop and then to the vent to sewer. The time of this transfer is long enough for a representative sample to be received. The initial gas entering the sample loop SLl will usually not be representative of the bulk of gas in the reactor. The lines from the reactor to the gas chromatograph are initially filled with air from the previous air purge mode. Air must be flushed from these lines and the sample loop to ensure a representative sample of reaction gas is obtained. It requires a period of time to obtain a steady state sample in the sample loop. Consequently the time will vary depending on the several factors influencing the gas transfer to the sample loop. These factors may include the arrangement and dimensions of the tubing between the reactor and the sample loop, the sample purge condi- tions, and the conditions of pressure, gas composition, etc. existing in the reactor itself at the time of gas transfer. The time is usually between 40 and 60 seconds.
Major components involved
GC - Gas chromatograph/mode 1A (gas transfer). SLl - Sample loop for the gas chromatograph.
-g JREATT" OMPI Lines involved
L2A - Gas chromatograph line from the reaction gas line
Lδ to the sample loop SLl. L6 - Reaction gas line from the reactor to the line L2A. L13 - Reactor line from the port R8 of the reactor Rl to the line L6. Valves involved
Operating valves/position
VI - Valve in gas chromatograph line L2A/position one (reactor cireuit one).
V2 - Valve in high pressure air line L2C/closed. V6 - Valve in reaction gas line L6/open. V7 - Valve in the calibration gas line L7/closed. Flow Reacton gas
Rl through R6 through L13 through V6 through L6 through L2A through VI through SLl to sewer. Time
40 seconds or as needed to obtain a representative sample of reaction gas in the sample loop. The time of 40 seconds is representative. The length of time is the time required to obtain a representative sample of reaction gas in the sample loop SLl. Stop sample mode (Stop) The fifth mode is a stop sampling mode in which the reaction gas he gas chromatograph is stopped and the gas pressure in the sample loop llowed to equalize with atmospheric pressure. Major components involved
GC - Gas chromatograph/mode IB (gas transfer). SLl - Sample loop of the gas chromatograph.
Valves involved
Operating valves/position
VI - Valve in gas chromatograph line L2A/position one (reactor circuit one). V2 - Valve in high pressure air line L2A/elosed.
V6 - Valve in reaction gas line Lδ/closed.
Figure imgf000060_0001
V7 - Valve in calibration gas line L7/closed.
Flow No flow Time 5 seconds or as needed for conditions in sample loop to equilibrate. Analysis mode (Analyze)
The sixth mode is an analysis mode in which the sample is analyzed in the gas chromatograph. There is no change in the external circuit. The change is in the internal system of the gas chromatograph. It switches from position two (gas transfer) to position three (analyze). Major components involved
GC - Gas chromatograph/position two (analyze). SLl - Sample loop of the gas chromatograph. Valves involved
Operating valves/position
VI - Valve in gas chromatograph line L2A/position one
(reactor circuit one). V2 - Valve in high pressure air line L2A/closed. V6 - Valve in the reaction gas line Lδ/closed.
V7 - Valve in the calibration gas line L7/closed.
Flow
Helium through sample loop carries reactor gas through column past detector out vent. Time
4 minutes depending on elutriation time of carbon dioxide and hydrogen sulfide through column. The time may be more or less than 4 minutes depending on the length of the column, column packing characteristics, helium flow rate, etc. The time will be one and one-half minutes if the analysis is only of carbon dioxide. Again, the time may be more or less than one and one-half minutes because of other factors. Sample purge mode (Purge) The seventh mode is a gas purge mode in which high pressure air is used to purge the sample from the sample loop and the lines between the sample loop and reactor.
^UREA*
OMPI Major components involved
GC - Gas chromatograph/mode 1C (purge). SLl - Sample loop for gas chromatograph. Lines involved L2 - Gas chromatograph line from high pressure air line
L10 to the sample loop SLl. Includes lines L2A, L2B and L2C. L10 - High pressure line between air supply line L2 and the gas chromatograph line L2. L2 - Air supply line.
Valves involved
Operating valves/position
VI - Valve in the gas chromatograph line L2A/position one (reactor circuit one). V2 - Valve in the high pressure air line L2C/open.
V6 - * Valve in the reaction gas line Lδ/closed. V7 - Valve in the calibration gas line L /closed. Pressure regulation valves
AR5 - Pressure regulation valve in the high pressure air line L10.
Flow Air
L27 through AR5 through L10 through V2 through L2 through SLl to vent to sewer. Time
1 minute 5 seconds or as needed to adequately purge lines and loop. During the time that the liquor sample in reactor 1 is completing its reaction, the valve VI would move to postions 2 and 3, and the gas chromatograph would be analyzing the gas samples from the second and third reactors. Data collection and analysis
The gas chromatograph output circuitry generates voltage "peaks" which correspond to the appearance of each gas component at the detector of the gas chromatograph. The time interval (from the start of the analysis) during which each component (air, carbon dioxide and hydrogen sulfide) will pass through the detector is a characteristic of each component gas. This time interval during which each component appears at the detector is very reproducible and is easily established for each gas. The gas chromatograph output circuitry generates a continuous 0-1 volt analog signal which is proportional to the flow of gas through the detector. During the time interval each component passes through the detector, a voltage "peak" is generated in response to the appearance of the component. Figure 9 is a plot of G.C. voltage output over the course of a gas analysis resulting from a typical green liquor sample. Each component of the gas sample is identified, and the time interval during which it appears is noted. The voltage "peaks" for each component are easily observed from the figure. The integrated voltage for each component (which is equal to the area under each peak) is proportional to the amount of the component in the gas sample. Furthermore, the carbon dioxide and hydrogen sulfide integrated voltages are proportional to the sodium carbonate and sodium sulfide concentrations in the liquor. The integrated peak areas for CO« and H2S are therefore a measure of the Na2CO3 and Na2S concentrations in the liquor sample.
The data collection circuit enables the carbonate/sulfide analyzer to convert the voltage peaks generated by the gas chromatograph into values which correspond to the concentrations of Na2CO3 and Na2S in the liquor. The data collection circuit consists of the following major components:
GC - Gas chromatograph output circuitry VCO - Voltage-to-frequency converter
M - Microcomputer
A schematic of the data collection circuit is shown in Figure 10. The associated wiring and components needed to link the major components are known and are therefore not illustrated. In order to calculate the concentration of Na„CO„ and Na2S in the liquor sample, the CO2 and H2S voltage peaks must be integrated. There are many methods which may be utilized to accomplish the integra¬ tion. The preferred method of peak integration is to utilize a voltage-to- frequency converter (VCO) to convert the 0-1 volt G.C. output signal to a 0-10,000 HZ frequency signal. The continuous series of electronic pulses thus generated is utilized as input to a digital microcomputer. The time intervals corresponding to the appearance of the CO2 and H S peaks are programmed into the microcomputer software. During the discrete time intervals corresponding to the peak for each component, the microcomputer counts the total number of pulses generated by the VCO for the peak period. The number of pulses thus counted is a measure of the peak area. The peak area measurements thus obtained for CO2 and H2S are proportional to the concentrations of Na2CO3 and Na2S, respectively, in the liquor sample.
The microcomputer, furthermore, allows for calibration of the analyzer by providing the ability to convert the pulse count measurements to direct determinations of Na2CO3 and Na2S in the liquor. The pulse count is directly proportional to the concentration of chemical in the liquor. By analyzing several liquors of known concentrations, and measuring the pulse counts generated from these known liquors, one can easily establish the correct conversion factors to convert the pulse counts to concentration measurements. These conversion factors are then stored in the micro¬ computer software. The conversion factors are applied to the pulse counts for all subsequent liquor samples to provide direct determinations of Na«CO3 and Na„S in the liquor. The liquor concentrations may be given as printed data or converted to analog signals for use as input to control devices. Methods of generating such outputs are varied and are well known. Reactor temperature measurement system
The measurement of sodium carbonate and sodium sulfide gener¬ ated by the carbonate/sulfide analyzer have been observed to be affected by the temperature at which the reaction occurs. The reaction temperature is primarily governed by the temperature inside the analyzer cabinet. The measurements generated by the analyzer vary in direct proportion with the cabinet temperature. As the cabinet temperature increases, the resultant measurements of sodium carbonate and sodium sulfide correspondingly increase. There must be compensation for this phenomena if accurate measurements are to be obtained for all samples despite reactor tempera¬ ture variations.
It has been determined that the best method of eliminating measurement errors due to reactor temperature variations is to apply a correction factor to each measurement based on the cabinet termperature during the reaction. In order to determine the proper factor for each measurement, the cabinet temperature is measured at the completion of
OMPI each reaction. The proper correction factors, based on the cabinet temperature, are then automatically computed for each sample and applied to the "raw" or "uncorrected" values generated by the gas chromatograph. This strategy has been found to be an effective method of eliminating errors caused by reaction temperature variations.
It has been found that for each 1°C deviation from a reference temperature the G.C. measured area for Na„CO3 increases or decreases 0.4% and the G.C. measured area for Na2S increases or decreases 0.7%. The correction for Na2CO3 is: CA = MA il + 0.004 (To - TH and for Na S is:
CA = MA il + 0.007 (To - T)i CA = corrected area MA = G.C. measured area To = reference temperature
T = actual temperature of gas from reactor As an example if the reference temperature is 30°C and the actual temperature is 27°C, then for Na2CO3
CA = MA il + 0.004 (30 - 27)4 = 0.988 MA and for Na2S
CA = MA il + 0.007 (30 - 27)4 = 0.979 MA
The temperature measurement system uses a resistance tempera¬ ture detector (RTD) mounted inside the cabinet, and a relay which closes to allow the detector to be sampled by the analyzer data collection system. The relay closes to allow sampling of the detector immediately upon completion of the transfer of reactor gases to the gas chromatograph sample chamber. It remains closed for 20 seconds or as needed to obtain an accurate temperature measurement. The RTD signal is converted to a temperature measurement in the data collection software. A resistance temperature detector has been found to be the best suited temperature measuring device. The detector element exhibits an electrical resistance which varies directly with temperature. This resis¬ tance is easily measured electronically and is easily converted to a temperature reading since the calibration of these elements is well docu- mented. Other devices, such as thermocouples or thermistors, which exhibit electrical properties that vary as a function of temperature could also be utilized in this application. Materials of construction
All materials have been selected to ensure maximum service¬ ability and resistance to the effects of heat, pressure, and the corrosive properties of the liquid and gas streams. We have found the following materials to be the best for the specific applications listed below:
The reactor's top and base is constructed of P.V.C. (poly vinyl chloride). The fixture at top of pump is P.V.C. The mounting board for all solenoids, etc. is P.V.C. The magnetic spin bar driver is P.V.C.
The reactor cylinder and the acid pump cylinder are glass. All tubing that is in direct contact with acid or the gases is teflon, all other tubing is nylon. All fittings that are in direct contact with acid or the gases are nylon. The reactor gas to gas chromatograph and the vent solenoids are teflon. All cheek valves are teflon. The sample loop is nylon. The acid pump piston is teflon coated 316 S.S. (stainless steel).
The fittings that come into indirect contact with gases or those that are flushed with air or water are 316 S.S. All fittings, tubing, valves, columns, etc. within the gas chromatograph are 316 S.S. The gas isolation valve mounted on front of gas chromatograph is 316 S.S. The air, water, pressurization and purge solenoids are 304 S.S.
All fittings on the air and water lines that are on inlet sides of solenoid or regulators are brass. All regulators are aluminum. The liquor/acid sample valve is Hastalloy C. Operation In an overall system these circuits would operate together. The precise operation will depend upon the mill configuration. A typical operation for one reactor eircuit is shown in the following table. In this table, the operating valves, the valve positions - open (O), closed (C) or position (1, 2) -, the change of position (*), and the time are given. For an analyzer utilizing multiple reactor circuits, the time of start-up of each eircuit would be offset so as to result in no overlap of gas chromatograph operation. Otherwise the logic and sequencing for each circuit will in general be identical, although minor modifications could be made to each individual reactor circuit in response to differences in liquor strength or other characteristics without adversely affecting the overall system operation. Table I
Time Filter Sample Reactor Gas Chrom.
00:00
Bypass Standby 1 Standby Standby
V21 C Vll IS V3 C VI 4
V22 C V14 IS V4 C V2 C
V24 O VI IF V5 C V6 C
V26 C AP2 IF V6 c V7 C
V28 IB (00:05) V8 c GC 1
V29 C V10 O (20:35)
(00:40) VI 3 c
00:05 00:05 00:05
Reposition 1 Vent
Vll 2T * V3 c
V14 2T * V4 c
V17 IF V5 O
AP2 IF V6 c
00:10 00:05 V8 c
Transfer V10 O
Vll 2T VI 3 C
V14 2T (00:35)
V17 2T *
AP2 2T *
00:40 00:40 00:3C ) 00:35 Filter Reposition 2 Standby V21 O Vll IS * V3 C V22 C V14 IS * V4 C V24 C V17 IF * V5 C V26 C AP2 IF * V6 C
00:45 V28 2F 00:05 V8 C V29 C Standby 2 V10 O ( 01:00) Vll IS V13 C
V14 IS (02:15)
V17 IF
AP2 IF
01:40 01:00 00:55
Sample Sample V21 O Vll IS •
V22 O V14 IS
V24 C V17 IF
V26 C. AP2 IF
V28 2F (01:00)
V29 C 02:40 01:00 01:00
Stop Standby 3 V21 O Vll IS
V22 C V14 IS
V24 C V17 IF
V26 C AP2 IF
V28 2F (01:55)
V29 C
OMPI Time Filter Sample Reactor Gas Chrom.
02:45 00:05 Backflush 1
V21 C * V22 C V24 C V26 C V28 2F
V29 C
02:55 00:10 02:15
Back lush 2 Drain V21 C V3 O * V22 C V4 C
V24 O * V5 C V26 O * V6 C V28 IB * V8 C V29 C V10 C * (00:15) V13 O *
03:05 00:10
Fill
03:10 00:15 W- C *
Bypass V4 O * V21 C V5 O *
V22 C . V6 C V24 O V8 C V26 C * V10 O * V28 IB V13 C *
03:25 V29 C 00:20
(13:00) Drain
V3 O *
V4 C *
V5 C *
V6 C
V8 C
Figure imgf000068_0001
V13 O *
03:35 00:10
Fill
V3 C *
V4 O *
V5 O *
V6 C
V8 C
V10 O *
V13 C *
03:55 00:20
Drain
V3 O *
V4 c * V5 c * V6 c V8 c V10 σ *
V13 o Gas Chrom.
*
Figure imgf000069_0001
V4 O *
V5 O *
V6 C
V8 c
V10 O *
V13 c *
04:25 00:20
Drain
V3 O *
V4 c *
V5 c *
V6 σ
V8 c
V10 c *
V13 O *
04:35 01:55 00:10
Reposition 3 Vent Vll 2T * V3 c *
V14 2T * V4 c
V17 IF V5 O *
AP2 IF V6 c
(00:05) . V8 c
V10 O *
V13 c * 04:40 00:05 00:05
Transfer Transfer
Vll 2T V3 c
V14 2T V4 c
V17 2T * V5 c *
AP2 2T * V6 c
(00:30) V8 c
V10 O
V13 c
05:10 00:30 00:3. 1
Reposition 4 Reaction 1 Vll IS * V3 C
V14 IS * V4 c
V17 IF * V5 c
AP2 IF * V6 c 05:15 00:05 V8 c
Standby 2 V10 O Vll IS V13 c
Figure imgf000069_0002
V26 C V6 c
V28 2F * V8 O *
V29 C V10 O
Figure imgf000069_0003
Time Filter Sample Reactor Gas Chrom.
16:20 00:10 Reaction 2
17:10 01:00 11:55 V3 C
Sample Sample V4 C V21 O Vll IS V5 C
V22 O * V14 IS V6 C
V24 C V17 IF V8 C *
V26 C AP2 IF V10 O
V28 2F (01:00) VI 3 C
V29 C (04:25)
18:10 01:00 01:00 1
Stop Standby 3 V21 O Vll IS
V22 C * V14 IS
V24 C VI 6 IF
V26 C AP2 IF
V28 2F (05:10)
V29 C
18:15 00:05
Backflush 1
V21 C *
V22 C
V24 C
V26 C
V28 2F
V29 C
18:25 00:10
Backflush 2
V21 C
V22 C
V24 O *
V26 O *
V28 IB *
V29 C
18:40 00:15
Bypass
20:35 V21 C 20:35 V22 C Reposition V24 O VI 1 * V26 C * V2 C V28 IB V6 C V29 C V7 C (16:15) GC 1 0:40 00:05
Standby VI 1 V2 C V6 C V7 C GC 1
Figure imgf000071_0001
V6 O * V7 C
V8 C GC 1
VIO O (00:40)
V13 C
21:25 00:40 00:40
Stop Stop
V3 C VI 1
V4 C V2 C
V5 C V6 C *
V6 C * V7 C
V8 C GC 1
V10 O (00:05)
V13 C
21:30 00:05 00:05
Drain Analyze
V3 O * Vi i
V4 C V2 C
V5 C V6 C
V6 C V7 C
V8 C GC 2
V10 C * (04:00)
V13 O * 21:40 00:10
Fill
V3 C *
V4 O *
V5 O *
V6 C
V8 C
V10 O * <
V13 C *
22:00 00:20
Drain
V3 O *
V4 C *
V5 C *
V6 C
V8 C
V10 C *
V13 O * Time Filter Sample Reactor Gas Chrom.
22:10 00:10
Fill
V3 C *
V4 O
V5 O *
V6 C
V8 c
V10 O *
V13 c
22:30 00:20
Drain
V3 O *
V4 c *
V5 c *
V6 c
V8 c
V10 c *
VI 3 O *
22:40 00:10
Fill
V3 c *
V4 O *
V5 O *
V6 c
V8 c
V10 O *
V13 c 23:00 00:20
Drain
V3 O *
V4 c *
V5 c *
V6 c
V8 c
V10 c
VI 3 O
23:10 05:10 00:10
Reposition 3 Tent" Vll 2T * V3 c V14 2T * V4 c V17 IF V5 O AP2 IF V6 c (00:05) V8 c
V10 O *
V13 c * Time Filter Sample Reactor Gas Chrom.
23:15 00:05 00:05 Transfer Transfer
Vll 2T V3 C
V14 2T V4 C
V17 2T * V5 C *
AP2 2T * V6 C
(00:30) V8 C
V10 O
V13 C
23:45 00:30 00:3C 1
Reposition 4 Reaction 1
Vll IS * V3 C
V14 IS * V4 C
V17 IF * V5 C
AP2 IF * V6 C
23:50 00:05 V8 c Standby 2 V10 O
25:30 Vll IS VI 3 c 04:00
V14 IS (11:00) Purge
V17 IF VI 1
AP2 IF V2 O *
(11:55) V6 C V7 C GC 1 *
26:35 01:05 Standby
34:45 16:15 11:00 V2 C *
Filter Pressure
Continues Continues Continues Continues
Use Figures 11, 12 and 13 are schematic diagrams showing the use of the apparatus in the causticizing system.
Control loop 1 seen in Figure 11 discloses the use of the analyzer in controlling the sodium carbonate concentration in the green liquor to the slaker. In this diagram green liquor from the green liquor clarifier GLC flows through the mill liquor line MLl and is pumped by the green liquor pump GLP to the slaker S. Lime is added to the green liquor at the slaker S.
There is an additional line in this diagram. That is line L40 which carries a portion of the weak wash into the mill liquor line MLl.
The line L28/29 designates two lines, L29 which carries the liquor from the mill liquor line MLl to the reactor system RSI and L28 which returns the liquor from the reactor system RSI to the mill liquor line
MLl. Each of the reactor systems - RSI, RS2 and RS3 - includes a filter
<£ T EA OMPI circuit, a sample circuit and a reactor circuit. These circuits are shown in Figures 1-3. The line L2 carries the reaction gas from the reactor system RSI to the gas chromatograph/analyzer GC/A in which the gas is analyzed for carbon dioxide (resulting from sodium carbonate in the liquor) and hydrogen sulfide (resulting from sodium sulfide) as described above. The analyzer, using the carbon dioxide analysis, outputs a signal through the control line CL1 to the controller which operates the valve V40 to increase or decrease the amount of weak wash flowing through line L40 into MLl in order to maintain a constant sodium carbonate concentration in the green liquor going to the slaker.
The hydrogen sulfide analysis has several uses. It is an indication of the reduction efficiency in the recovery boiler. The sodium sulfide concentration can be given to the recovery boiler operator to confirm to him that the reduction efficiency is good or to allow him to make corrections to improve the reduction efficiency. It is also an indication of the potential efficiency in the causticizing operation. As the concentration of sodium carbonate or sodium sulfide in the green liquor increases, the efficiency of the causticizing operation decreases. This will give the operator information about the causticizing reaction that the green liquor is about to undergo and allow the causticizing operator to take corrective action.
The second control loop of this system is shown in Figure 12. This loop controls the balance of green liquor and lime, and in fact controls the entire slaking operation. A "clear" liquor sample is taken from the calcium carbonate mud separator at either the slaker or first causticizer. This "clear" liquid is then filtered to remove all the remaining calcium carbonate mud. The sodium carbonate and sodium sulfide concentration in this filtered liquor is then measured in the GC/A from the reaction gas from the second reactor system, RS2. The control loop logic will contain a set point for the desired sodium carbonate concentration in the liquor. This set point a2CO3 concentration will, as proven by mill experience, result in the best combina¬ tion of high conversion efficiency of Na2CO3 to NaOH, low Na2CO3 "deadload," and acceptable mud settling characteristics. The loop will then control the slaker operation via mass flow of sodium carbonate to the slaker so as to maintain and control this concentration of Na„CO3 in the ^quor
- ϋ EA
OMPI leaving the slaker. There are two ways of controlling the sodium carbonate concentration in the slaker or first causticizer. One is the usual method of controlling the amount of lime being added to the slaker. The other, and the method the inventors consider to be significantly better, is shown in Figure 12. In this method the amount of sodium carbonate in the green liquor is controlled by loop 1 as is described above. The amount of this green liquor added to the slaker is controlled by loop 2. The amount of sodium carbonate and sodium sulfide in the white liquor from the first causticizer or slaker is determined by the GC/A from the reaction gases from RS2. A signal, based on the sodium carbonate, is then sent through control line CL2 to the controller which operates the valve V41 to increase or decrease the amount of green liquor flowing through MLl into the slaker S.
The measurement of the chemical concentrations in the white liquor is taken from the line between the clear white liquor storage tank and the digester or digesters. The concentrations of sodium sulfide and sodium carbonate in the white liquor are determined directly by analysis by the GC/A of the reaction gases from the third reaction system, RS3. The amount of sodium hydroxide in the white liquor, however, must be deter- mined indirectly. There are three pieces of information which must be combined to yield the sodium hydroxide concentration in the white liquor.
1. The sodium carbonate concentration in the white liquor;
2. The sodium carbonate concentration in the green liquor;
3. The sodium hydroxide concentration in the green liquor. Measurements 1 and 2 are used to determine the amount of carbonate in the green liquor which, in the slaking/causticizing operation, has been converted to sodium hydroxide in the white liquor. The difference between the amount of Na«CO3 entering the system with the green liquor and the amount of Na2CO3 leaving with the white liquor is the concentration of NaOH which has been produced in the white liquor due to the causticizing reaction. All chemical concentrations are expressed on a sodium oxide (Na2O) basis. Some sodium hydroxide also enters the system with the green liquor. This sodium hydroxide passes unchanged through the system to the white liquor and must be accounted or. This source of NaOH in the system is relatively stable - a periodic (every eight hour) determination of NaOH in the green liquor may be manually performed by an operator and entered into the analyzer software.
i E ^ OMPI .. The determination of the NaOH in the green liquor may be performed directly in titration of a green liquor sample. It may alter¬ natively be determined indirectly by titrating the NaOH in the white liquor. The amount of NaOH in the white liquor which cannot be accounted for by the amount of NaOH generated in recausticizing is the amount of NaOH which has entered with the green liquor. It is recommended that the NaOH in the green liquor be determined by the indirect method, which has the advantage of reducing errors caused by time lags in the process. The amount of NaOH associated with the green liquor is then stored in the microprocessor memory until updated by another titration. This value is used to update each subsequent white liquor sodium hydroxide determination.
The analyzer will solve the following equation for each succeed¬ ing sample to determine the sodium hydroxide concentration in the white liquor:
NaOH (white liquor) = Na2CO3 (green liquor) - Na2CO3 (white liquor)
+ NaOH (green liquor) The carbonate analysis is updated with each sample every 19 minutes. The determination of sodium hydroxide in the green liquor is updated by manual titration of a green or white liquor sample when necessary, usually every eight hours. An updated, complete clarified white liquor analysis (determination of sodium hydroxide, sodium sulfide, and sodium carbonate) is provided to the digester operator or digester process computer every 12 to 19 minutes. The system software must also take into consideration the time delays in the slaking, causticizing and clarification operations in order to correctly determine the current NaOH concentration in the white liquor. This will determine the amount of chemicals to be added to the digester In order to control the pulping process. Cascaded Control Opportunities
In many applications it will be sufficient and desirable to utilize carbonate/sulfide analyzer measurements as the primary input to process control devices. However, in some applications it may be advantageous to control the process directly with a measurement device providing a more immediate but less accurate (in terms of sodium carbonate concentration) response to process changes. If these devices are utilized, measurements from the earbonate/sulfide analyzer should be used as set point control signals for the primary controllers. This "cascaded" type control system will greatly improve the accuracy of the primary control measurement devices and improve control of the process. Several measurement devices such as conductivity probes, density gauges, etc. provide rapid response to process changes. However, these devices provide only indirect measurements of the sodium carbonate concentration - they respond to the concentration of all chemicals in the process stream. The ratio of sodium carbonate to total chemicals in the process stream will vary with time, resulting in improper determinations of sodium carbonate concentration and less precise control of the process than could be obtained if sodium carbonate was measured directly. However, the changes which influence the calibration of these devices in measuring sodium carbonate concentration occur slowly - certainly greater than the 15-20 minute sampling period generated by the earbonate/sulfide analyzer. The direct measurements of sodium carbonate generated by the earbonate/sulfide analyzer may be used as a set point control input to each primary control device. This practice will have the effect of adjusting the calibration of the primary device (conductivity probe, density gauge, etc.) every 15-20 minutes so that it is an accurate indicator of Na.CO concentration despite the previously mentioned variations in the ratio of Na2CO /total chemicals. A cascaded control strategy of this type will have the advantage of having both an accurate method of determining sodium carbonate concentrations in the process and the ability to respond immedi- ately to changes in the process.
This is illustrated in Figure 14. The main items are the dissolving tank DT, the green liquor clarifier GLC, the green liquor pump GLP, the slaker S and the first causticizer Cl. Mill liquor line MLl carries green liquor from dissolving tank DT to the green liquor clarifier GLC, and mill liquor line ML2 carries green liquor from the green liquor clarifier GLC to the slaker S. The principal weak wash line L42 carries weak wash to lines L40 and L41.
The weak wash in line L41 is used to dissolve the smelt in the dissolving tank DT. The amount of weak wash going to the dissolving tank DT through line L41 is controlled by valve V41. The amount of weak wash is determined by the density of the green liquor from the dissolving tank DT. This is monitored in mill line MLl by the density meter DM1. The signal from the density meter DM1 is carried through control line CL1 to the valve controller CN1. The valve V41 is controlled by CN1 with a signal which passes through control line CL2. This is a standard local control loop in which a local direct measurement is used to monitor the process conditions.
Figure 14 also illustrates the use of local conditions to monitor and control the amount of weak wash entering ML2 to maintain the carbonate level in the green liquor. However, in this instance the gas chromatograph/analyzer is used to determine the set points for this local control.
The valve V40 is used to control the flow of weak wash in line L40, which is the amount of weak wash which will enter the mill liquor line ML2. This is monitored locally be a density meter DM2 which sends a signal through control line CL3 to the control unit CN2. CN2 operates the control valve V40 to increase or decrease the flow of weak wash to maintain the density in ML2 at a specified level. However, the density of the liquor is not a direct indication of sodium carbonate in the liquor. A sample of the density-controlled liquor from ML2 is taken and analyzed for sodium carbonate concentration by reactor system RSI and the gas chromatograph/analyzer unit GC/A. This direct determination of sodium carbonate is utilized to send a set point signal through control line CLS to CN2 in order to adjust the density set point so that the density more accurately reflects the sodium carbonate concentration in the liquor.

Claims

1. A process for determining the carbonate content of a liquor comprising removing suspended solids from said liquor to form a filtered liquor, placing said filtered liquor in a sample container to obtain as a sample a specific quantity of said filtered liquor, using a measured quantity of acid to remove and clean said sample from said sample container and transfer said sample to a closed reaction chamber, allowing said acid and said sample to react in said reaction chamber for a first period of time, collecting in said reaction chamber a first gas generated from said reaction of said acid and said sample, said first gas comprising carbon dioxide, providing a constant pressure in said reaction chamber at the completion of said first period of time by adding a second gas to said reaction chamber, said second gas being substantially free of carbon dioxide, continuing said reaction of said acid and said sample in said reaction chamber for a second period of time and continuing to collect in said reaction chamber said first gas from said reaction, said first and second gases comprising a gas mixture, transferring said gas mixture in said reaction chamber to a gas chromatograph, analyzing said gas mixture for its carbon dioxide content, and purging said gas mixture from said gas chromatograph.
2. The process of claim 1 further comprising allowing a second quantity of said acid to remain in said sample container after said transfer of said sample to further remove any residue that may remain in said sample container.
3. The process of claim 2 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor, using said second filtered liquor to remove said second quantity of acid and said residue from said sample container, and
^fO E "^ OMPI fa wpo , obtaining as a second sample a measured quantity of said second filtered liquor in said sample container.
4. The process of claim 1 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor, placing said second filtered liquor in said sample container to obtain as a second sample a specific quantity of said second filtered liquor, said second sample quantity being equal to said first sample quantity, using a second measured quantity of said acid to remove and clean said second sample from said sample container and transfer said seeond sample to said closed reaction chamber, said second acid quantity being equal to said first acid quantity, allowing said second acid quantity and said second sample to react in a second reaction in said reaction chamber for a third period of time equal to said first period of time, collecting in said reaction chamber a third gas generated from said second reaction, said third gas comprising carbon dioxide, providing a constant pressure in said reaction chamber at the completion of said third period of time by adding a second quantity of said second gas, said seeond gas addition providing for each sample a total molar quantity of gas in said reaction chamber that is equal for all samples and is greater than the total potential moles of gas that might be generated from said reaction of each said sample and each quantity of said acid, continuing said second reaction in said reaction chamber for a fourth period of time equal to said second period of time and continuing to collect in said reaction chamber said third gas from said seeond reaction, said second and third gases comprising a second gas mixture, transferring said second gas mixture in said reaction chamber to said gas chromatograph, analyzing said second gas mixture for its carbon dioxide content, and purging said second gas mixture from said gas chromatograph.
5. The process of claim 4 further comprising allowing a third quantity of said acid to remain in said sample container after said transfer of said first sample to further remove any residue that may remain in said sample container.
WIP
6. The process of claim 5 further comprising using said second filtered liquor to remove said third quantity of acid and said residue from said sample container.
7. The process of claim 1 further comprising prior to said transfer of said acid and said sample to said reaction chamber, said reaction chamber contains a gas containing a minor quantity of carbon dioxide, and the pressure of said contained gas is allowed to become equal to atmospheric pressure just prior to said transfer of said acid and said sample to said reaction chamber. .
8. The process of claim 1 further comprising washing said reaction chamber following transfer of said gas mixture to said gas chromatograph.
9. The process of claim 1 further comprising adding an antiflocculant agent to said sample.
10. The process of claim 9 in which said antiflocculant agent is added to said acid.
11. The process of claim 1 further comprising converting said carbon dioxide gas quantities to sodium carbonate liquor concentrations.
12. The process of claim 1 in which said liquor is selected from the group consisting of pulp mill green liquor, pulp mill slaker liquor, pulp mill causticizing liquor and pulp mill clarified white liquor.
13. The process of claim 12 further comprising allowing a second quantity of said acid to remain in said sample container to further remove any residue that may remain in said sample container.
14. The process of claim 13 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor, using said second filtered liquor to remove said second quantity of acid and said residue from said sample container, and obtaining as a second sample a measured quantity of said second filtered liquor in said sample container.
15. The process of claim 12 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor, placing said second filtered liquor in said sample container to obtain as a second sample a specific quantity of said second filtered liquor, said second sample quantity being equal to said first sample quantity, using a second measured quantity of said acid to remove and clean said second sample from said sample container and transfer said second sample to said closed reaction chamber, said second acid quantity being equal to said first acid quantity, allowing said second acid quantity and said second sample to react in a seeond reaction in said reaction chamber for a third period of time equal to said first period of time, collecting in said reaction chamber a third gas generated from said second reaction, said third gas comprising carbon dioxide, providing a constant pressure in said reaction chamber at the completion of said third period of time by adding a second quantity of said second gas, said second gas addition providing for each sample a total molar quantity of gas in said reaction chamber that is equal for all samples and is greater than the total potential moles of gas that might be generated from said reaction of each said sample and said acid, continuing said second reaction in said reaction chamber for a fourth period of time equal to said second period of time and continuing to collect in said reaction chamber said third gas from said second reaction, said second and third gases comprising a second gas mixture, transferring said second gas mixture in said reaction chamber to a gas chromatograph, analyzing said seeond gas mixture for its carbon dioxide content, and purging said second gas mixture from said gas chromatograph.
16. The process of claim 15 further comprising allowing a third quantity of said acid to remain in said sample container after said transfer of said first sample to further remove any residue that may remain in said sample container.
17. The process of claim 16 further comprising using said second filtered liquor to remove said third quantity of acid and said residue from said sample container.
18. The process of claim 12 further comprising prior to said transfer of said acid and said sample to said reaction chamber, said reaction chamber contains a gas containing a minor quantity of carbon dioxide, and the pressure of said contained gas is allowed to become equal to atmospheric pressure just prior to said transfer of said acid and said sample to said reaction chamber.
19. The process of claim 12 further comprising washing said reaction chamber following said transfer of said gas mixture to said gas chromatograph.
20. The process of claim 12 further comprising adding an antiflocculant agent to said sample.
21. The process of claim 20 in which said antiflocculant agent is added to said acid.
22. The process of claim 12 further comprising converting said carbon dioxide gas quantities to sodium carbonate liquor concentrations.
23. The process of claim 22 further comprising determining the sodium carbonate concentration in said green liquor and said white liquor, and determining part of the sodium hydroxide concentration in said white liquor by determining the difference between the sodium carbonate concentration in said green liquor and the sodium carbonate concentration in said white liquor.
24. The process of claim 12 in which said liquor is selected from the group consisting of pulp mill slaker liquor and pulp mill causticizing liquor, and further comprising removing said suspended solids from said liquor by sedimentation followed by filtration.
25. The process of claim 24 further comprising allowing a second quantity of said acid to remain in said sample container after said transfer of said first sample to further remove any residue that may remain in said sample container.
26. The process of claim 25 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor,
-^TfREA.
OMPI *. WIPO _ using said second filtered liquor to remove said second quantity of acid and said residue from said sample container, and obtaining as a second sample a measured quantity of said second filtered liquor in said sample container.
27. The process of claim 24 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor, placing said second filtered liquor in said sample container to obtain as a second sample a specific quantity of said second filtered liquor, said second sample quantity being equal to said first sample quantity, using a second measured quantity of said acid to remove and clean said second sample from said sample container and transfer said second sample to said closed reaction chamber, said second acid quantity being equal to said first acid quantity, allowing said second acid quantity and said second sample to react in a seeond reaction in said reaction chamber for a third period of time equal to said first period of time, collecting in said reaction chamber a third gas generated from said second reaction, said third gas comprising carbon dioxide, providing a constant pressure in said reaction chamber at the completion of said third period of time by adding a second quantity of said second gas, said second gas addition providing for each sample a total molar quantity of gas in said reaction chamber that is equal for all samples and is greater than the total potential moles of gas that might be generated from said reaction of each said sample and each quantity of said acid, continuing said second reaction in said reaction chamber for a fourth period of time equal to said second period of time and continuing to collect in said reaction chamber said third gas from said seeond reaction, said second and third gases comprising a second gas mixture, transferring said second gas mixture in said reaction chamber to said gas chromatograph, analyzing said second gas mixture for its carbon dioxide content, and purging said second gas mixture from said gas chromatograph.
28. The process of claim 27 further comprising allowing a third quantity of said acid to remain in said sample container after said transfer of said first sample to further remove any residue that may remain in said sample container.
29. The process of claim 28 further comprising using said second filtered liquor to remove said third quantity of acid and said residue from said sample container.
30. The process of claim 24 further comprising prior to said transfer of said acid and said sample to said reaction chamber, said reaction chamber contains a gas containing a minor quantity of carbon dioxide, and the pressure of said contained gas is allowed to become equal to atmospheric pressure just prior to said transfer of said acid and said sample to said reaction chamber.
31. The process of claim 24 further comprising washing said reaction chamber following transfer of said first and second gases to said gas chromatograph.
32. The process of claim 24 further comprising adding an antiflocculant agent to said sample.
33. The process of claim 32 in which said antiflocculant agent is added to said acid.
34. The process of claim 24 further comprising converting said carbon dioxide gas quantities to sodium carbonate liquor concentrations.
35. The process of claim 1 for determining the carbonate and sulfide content of a liquor further comprising said gases from said reaction chamber containing carbon dioxide and hydrogen sulfide, said second gas being substantially free of carbon dioxide and hydrogen sulfide, and analyzing said gas mixture for its carbon dioxide and hydrogen sulfide content.
36. The process of claim 35 further comprising allowing a second quantity of said acid to remain in said sample container to further remove any residue that may remain in said sample container.
37. The process of claim 36 further comprising
- ORE
OMPI removing suspended solids from a new supply of said liquor to form a second filtered liquor, using said second filtered liquor to remove said second quantity of acid and said residue from said sample container, and obtaining as a second sample a measured quantity of said second filtered liquor in said sample container.
38. The process of claim 35 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor, placing said second filtered liquor in said sample container to obtain as a second sample a specific quantity of said second filtered liquor, said second sample quantity being equal to said first sample quantity, using a second measured quantity of said acid to remove and clean said second sample from said sample container and transfer said second sample to said closed reaction chamber, said second acid quantity being equal to said first acid quantity, allowing said second acid quantity and said second sample to react in a second reaction in said reaction chamber for a third period of time equal to said first period of time, collecting in said reaction chamber a third gas generated from said second reaction, said third gas comprising carbon dioxide and hydrogen sulfide, providing a constant pressure In said reaction chamber at the completion of said third period of time by adding a second quantity of said second gas, said second gas addition providing for each sample a total molar quantity of gas in said reaction chamber that is equal for all samples and is greater than the total potential moles of gas that might be generated from said reaction of each said sample and each quantity of said acid, continuing said second reaction in said reaction chamber for a fourth period of time equal to said second period of time and continuing to collect in said reaction chamber said third gas from said second reaction, said second and third gases comprising a seeond gas mixture, transferring said second gas mixture in said reaction chamber to said gas chromatograph, analyzing said second gas mixture for its carbon dioxide and hydrogen sulfide content, and purging said second gas mixture from said gas chromatograph.
39. The process of claim 38 further comprising allowing a third quantity of said acid to remain in said sample container after said transfer of said first sample to further remove any residue that may remain in said sample container.
40. The process of claim 39 further comprising using said second filtered liquor to remove said second quantity of acid and said residue from said sample container.
41. The process of claim 35 further comprising prior to said transfer of said acid and said sample to said reaction chamber, said reaction chamber contains a gas containing minor quantities of carbon dioxide and hydrogen sulfide, and the pressure of said contained gas is allowed to become equal to atmospheric pressure just prior to said transfer of said acid and said sample to said reaction chamber.
42. The process of claim 35 further comprising washing said reaction chamber following transfer of said gas mixture to said gas chromatograph.
43. The process of claim 35 further comprising adding an antiflocculant agent to said sample.
44. The process of claim 43 in which said antiflocculant agent is added to said acid.
45. The process of claim 35 further comprising converting said carbon dioxide and hydrogen sulfide gas quantities to sodium carbonate and sodium sulfide liquor concentrations.
46. The process of claim 35 in which said liquor is selected from the group consisting of pulp mill green liquor and pulp mill clarified white liquor.
47. The process of claim 46 further comprising allowing a second quantity of said acid to remain in said sample container after said transfer of said sample to further remove any residue that may remain in said sample container.
48. The process of claim 47 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor, using said second filtered liquor to remove said second quantity of acid and said residue from said sample container, and obtaining as a second sample a measured quantity of said seeond filtered liquor in said sample container.
49. The process of claim 46 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor, placing said second filtered liquor in said sample container to obtain as a second sample a specific quantity of said second filtered liquor, said second sample quantity being equal to said first sample quantity, using a second measured quantity of said acid to remove and clean said second sample from said sample container and transfer said second sample to said closed reaction chamber, said seeond acid quantity being equal to said first acid quantity, allowing said second acid quantity and said second sample to react in a second reaction in said reaction chamber for a third period of time equal to said first period of time, collecting in said reaction chamber a third gas generated from said second reaction, said third gas comprising carbon dioxide and hydrogen sulfide, providing a constant pressure in said reaction chamber at the completion of said third period of time by adding a second quantity of said second gas, said second gas addition providing for each sample a total molar quantity of gas in said reaction chamber that is equal for all samples and is greater than the total potential moles of gas that might be generated from said reaction of each said sample and each quantity of said acid, continuing said second reaction in said reaction chamber for a fourth period of time equal to said seeond period of time and continuing to collect in said reaction chamber said third gas from said second reaction, said second and third gases comprising a second gas mixture, transferring said second gas mixture in said reaction chamber to said gas chromatograph, analyzing said second gas mixture for its carbon dioxide and hydrogen sulfide content, and purging said second gas mixture from said gas chromatograph.
50. The process of claim 49 further comprising allowing a third quantity of said acid to remain in said sample container after said transfer of said first sample to further remove any residue that may remain in said sample container.
51. The process of claim 50 further comprising using said second filtered liquor to remove said third quantity of acid and said residue from said sample container.
52. The process of claim 46 further comprising prior to said transfer of said acid and said sample to said reation chamber, said reaction chamber contains a gas containing minor quantities of carbon dioxide and hydrogen sulfide, and the pressure of said contained gas is allowed to become equal to atmospheric pressure just prior to said transfer of said acid and said sample to said reaction chamber.
53. The process of claim 46 further comprising washing said reaction chamber following said transfer of said gas mixture to said gas chromatograph.
54. The process of claim 46 further comprising adding an antiflocculant agent to said sample.
55. The process of claim 54 in which said antiflocculant agent is added to said acid.
56. The process of claim 46 further comprising converting said carbon dioxide and hydrogen sulfide gas quantities to sodium carbonate and sodium sulfide liquor concentrations.
57. The process of claim 35 in which said liquor is selected from the group consisting of pulp mill slaker liquor and pulp mill causticizing liquor, further comprising removing said suspended solids from said liquor by sedimentation followed by filtration.
58. The process of claim 57 further comprising allowing a second quantity of said acid to remain in said sample container after said transfer of said sample to further remove any residue that may remain in said sample container.
59. The process of claim 58 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor, using said second filtered liquor to remove said second quantity of acid and said residue from said sample container, and
^ JREA
OMPI fa^ IPO obtaining as a second sample a measured quantity of said second filtered liquor in said sample container.
60. The process of claim 57 further comprising removing suspended solids from a new supply of said liquor to form a second filtered liquor, placing said second filtered liquor in said sample container to obtain as a second sample a specific quantity of said seeond filtered liquor, said second sample quantity being equal to said first sample quantity, using a second measured quantity of said acid to remove and clean said second sample from said sample container and transfer said second sample to said closed reaction chamber, said second acid quantity being equal to said first acid quantity, allowing said second acid quantity and said second sample to react in a second reaction in said reaction chamber for a third period of time equal to said first period of time, collecting in said reaction chamber a third gas generated from said second reaction, said third gas comprising carbon dioxide and hydrogen sulfide, providing a constant pressure in said reaction chamber at the completion of said third period of time by adding a second quantity of said second gas, said second gas addition providing for each sample a total molar quantity of gas in said reaction chamber that is equal for all samples and is greater than the total potential moles of gas that might be generated from said reaction of each said sample and each quantity of said acid, continuing said second reaction in said reaction chamber for a fourth period of time equal to said second period of time and continuing to collect in said reaction chamber said third gas from said second reaction, said second and third gases comprising a second gas mixture, transferring said seeond gas mixture in said reaction chamber to said gas chromatograph, analyzing said seeond gas mixture for its carbon dioxide and hydrogen sulfide content, and purging said second gas mixture from said gas chromatograph.
61. The process of claim 60 further comprising allowing a third quantity of said acid to remain in said sample container after the transfer of said first sample to further remove any residue that may remain in said sample container.
62. The process of claim 61 further comprising using said second filtered liquor to remove said third quantity of acid and said residue from said sample container.
63. The process of claim 57 further comprising prior to said transfer of said acid and said sample to said reaction chamber, said reaction chamber contains a gas containing minor quantities of carbon dioxide and hydrogen sulfide, and the pressure of said contained gas is allowed to become equal to atmospheric pressure just prior to said transfer of said acid and said sample to said reaction chamber.
64. The process of claim 57 further comprising washing said reaction chamber following transfer of said gas mixture to said gas chromatograph.
65. The process of claim 57 further comprising adding an antiflocculant agent to said sample.
66. The process of claim 65 in which said antiflocculant agent is added to said acid.
67. The process of claim 57 further comprising converting said carbon dioxide and hydrogen sulfide gas quantities to sodium carbonate and sodium sulfide liquor concentrations.
68. An apparatus for determining the carbonate and sulfide content of a liquor comprising first means for removing suspended solids from said liquor, second means for obtaining a measured sample of liquor from said first means, third means for allowing a reaction between an acid and said sample and collecting the gases from said reaction, fourth means for collecting a measured sample of acid and transferring the contents of said second and fourth means to said third means, fifth means connecting said first and second means, sixth means connecting said second and said fourth means, seventh means for alternately connecting said second means with either said fifth or said sixth means, eighth means for connecting said second and said third means, ninth means for adding a gas to said third means, a gas chromatograph for analyzing the constituents of the gases from said reaction, tenth means for connecting said third means and said gas chromatograph.
69. The apparatus to claim 68 further comprising eleventh means for equalizing the interior pressure of said third means and atmospheric pressure.
70. The apparatus of claim 68 further comprising eleventh means for connecting said second means to a sewer, and said seventh means connecting said second and eleventh means when it connects said second and fifth means and also connecting said eighth and second means when it connects said sixth and second means.
71. The apparatus of claim 68 further comprising eleventh means for connecting wash water to said third means, and twelfth means for draining said third means.
72. The apparatus of claim 68 further comprising eleventh means for connecting an antiflocculant agent to said fourth means.
73. An apparatus for determining the carbonate and sulfide content of a liquor comprising first means for removing suspended solids from said liquor, second means for obtaining a measured sample of liquor from said first means, third means for allowing a reaction between an acid and said sample and collecting the gases from said reaction, fourth means for collecting a measured sample of aeid and transferring the contents of said second and fourth means to said third means, fifth means connecting said first and second means, sixth means for connecting said second means to said sewer, seventh means connecting said second and said fourth means, eighth means for connecting said second and said third means, ninth means for alternately connecting said second means with either said fifth or said seventh means, said ninth means connecting said second and sixth means when it connects said second and fifth means and also connecting said eighth and second means when it connects said seventh and second means, tenth means for adding a gas to said third means, a gas chromatograph for analyzing the constituents of the gases from said reaction, eleventh means for connecting said third means and said gas chromatograph.
74. The apparatus of claim 73 further comprising twelfth means for connecting wash water to said third means, and thirteenth means for draining said third means.
75. The apparatus of claim 73 further comprising twelfth means for connecting an antiflocculant agent to said fourth means.
76. The apparatus to claim 73 further comprising twelfth means for equalizing the interior pressure of said third means and atmospheric pressure.
- EAΓ
OMPI
PCT/US1984/000740 1983-05-18 1984-05-16 Method and apparatus for determining carbonate/sulfide concentration WO1984004597A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
FI850234A FI850234A0 (en) 1983-05-18 1985-01-18 CARBONATE SULFID ANALYZER AND STYRFOERFARANDE.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US49586383A 1983-05-18 1983-05-18

Publications (1)

Publication Number Publication Date
WO1984004597A1 true WO1984004597A1 (en) 1984-11-22

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PCT/US1984/000740 WO1984004597A1 (en) 1983-05-18 1984-05-16 Method and apparatus for determining carbonate/sulfide concentration

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EP (1) EP0143844A4 (en)
JP (1) JPS60501328A (en)
FI (1) FI850234A0 (en)
NO (1) NO850151L (en)
WO (1) WO1984004597A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4740473A (en) * 1986-11-25 1988-04-26 Sampling Technology, Inc. Sodium sulfide analyzer
WO1995035490A2 (en) * 1994-06-20 1995-12-28 Lenzing Aktiengesellschaft Process, devices and use of said devices for measuring extinction of turbid suspensions
WO2003057980A1 (en) * 2002-01-14 2003-07-17 L'air Liquide - Societe Anonyme A Directoire Et Conseil De Surveillance Pour L'etude Et L'exploitation Des Procedes Georges Claude Polysulfide measurement methods using colorimetric techniques

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2754587B2 (en) * 1988-08-29 1998-05-20 株式会社島津製作所 Gas chromatograph
CN103698437B (en) * 2014-01-13 2015-04-08 福建农林大学 Method for quickly detecting starch coated amount in modified calcium carbonate filler through headspace gas chromatography

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3801281A (en) * 1971-12-10 1974-04-02 Amoco Prod Co Critical carbonate minerals in geochemical prospecting
US4063891A (en) * 1975-07-31 1977-12-20 Bayer Aktiengesellschaft Method for determining the inorganic carbon content of aqueous liquids
US4236960A (en) * 1978-07-18 1980-12-02 Mo Och Domsjo Aktiebolag Process for controlling the degree of causticization in the preparation of white liquid from the chemicals recovered from black liquor
JPS5647759A (en) * 1979-09-27 1981-04-30 Fuji Sekiyu Kk Analyzing method for acid gas constituent of liquid
US4397957A (en) * 1982-02-24 1983-08-09 The Dow Chemical Company Specific-ion gas-sensing carbonate analyzer

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3801281A (en) * 1971-12-10 1974-04-02 Amoco Prod Co Critical carbonate minerals in geochemical prospecting
US4063891A (en) * 1975-07-31 1977-12-20 Bayer Aktiengesellschaft Method for determining the inorganic carbon content of aqueous liquids
US4236960A (en) * 1978-07-18 1980-12-02 Mo Och Domsjo Aktiebolag Process for controlling the degree of causticization in the preparation of white liquid from the chemicals recovered from black liquor
US4311666A (en) * 1978-07-18 1982-01-19 Mo Och Domsjo Aktiebolag Apparatus for controlling the degree of causticization in the preparation of white liquor from the chemicals recovered from black liquor
JPS5647759A (en) * 1979-09-27 1981-04-30 Fuji Sekiyu Kk Analyzing method for acid gas constituent of liquid
US4397957A (en) * 1982-02-24 1983-08-09 The Dow Chemical Company Specific-ion gas-sensing carbonate analyzer

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP0143844A4 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4740473A (en) * 1986-11-25 1988-04-26 Sampling Technology, Inc. Sodium sulfide analyzer
WO1995035490A2 (en) * 1994-06-20 1995-12-28 Lenzing Aktiengesellschaft Process, devices and use of said devices for measuring extinction of turbid suspensions
WO1995035490A3 (en) * 1994-06-20 1996-02-15 Chemiefaser Lenzing Ag Process, devices and use of said devices for measuring extinction of turbid suspensions
WO2003057980A1 (en) * 2002-01-14 2003-07-17 L'air Liquide - Societe Anonyme A Directoire Et Conseil De Surveillance Pour L'etude Et L'exploitation Des Procedes Georges Claude Polysulfide measurement methods using colorimetric techniques
US6875414B2 (en) 2002-01-14 2005-04-05 American Air Liquide, Inc. Polysulfide measurement methods using colormetric techniques

Also Published As

Publication number Publication date
JPS60501328A (en) 1985-08-15
EP0143844A4 (en) 1985-09-26
FI850234L (en) 1985-01-18
EP0143844A1 (en) 1985-06-12
FI850234A0 (en) 1985-01-18
NO850151L (en) 1985-01-14

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