USH1479H - Liquid composition analyzer and method - Google Patents

Liquid composition analyzer and method Download PDF

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Publication number
USH1479H
USH1479H US07/881,327 US88132792A USH1479H US H1479 H USH1479 H US H1479H US 88132792 A US88132792 A US 88132792A US H1479 H USH1479 H US H1479H
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United States
Prior art keywords
liquor
components
analyzer
concentration
sulfide
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Abandoned
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US07/881,327
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English (en)
Inventor
Michael A. Paulonis
Debasish Mondal
Aravamuthan Krishnagopalan
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Auburn University
Auburn Research Foundation Auburn University
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Auburn University
Auburn Research Foundation Auburn University
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Priority to US07/881,327 priority Critical patent/USH1479H/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N35/00—Automatic analysis not limited to methods or materials provided for in any single one of groups G01N1/00 - G01N33/00; Handling materials therefor
    • G01N35/10—Devices for transferring samples or any liquids to, in, or from, the analysis apparatus, e.g. suction devices, injection devices
    • G01N35/1095—Devices for transferring samples or any liquids to, in, or from, the analysis apparatus, e.g. suction devices, injection devices for supplying the samples to flow-through analysers
    • G01N35/1097—Devices for transferring samples or any liquids to, in, or from, the analysis apparatus, e.g. suction devices, injection devices for supplying the samples to flow-through analysers characterised by the valves
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C7/00—Digesters
    • D21C7/12—Devices for regulating or controlling
    • 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
    • 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 pulp

Definitions

  • the Wallin U.S. Pat, No. 3,941,649 describes an attempt to control the pulping time and pulping temperature by taking a sample of the pulping liquor after initial digestion has occurred.
  • the pulping sample is titrated to provide an alkaline content of the liquor. From this alkaline content, the pulping intensity expressed as "H" factor is determined and used to obtain the desired KAPPA number.
  • the Hultman et al U.S. Pat. No. 4,236,960 describes a process for controlling the degree of causticization of white liquor.
  • the process of the Hultman et al patent includes determining the sodium carbonate concentration of green liquor fed to the causticization, then determining the sodium carbonate concentration of white liquor resulting from the causticization and thereby controlling the degree of causticization within a predetermined range while taking both sodium carbonate concentrations into account.
  • the Bertelsen U.S. Pat. No. 4,536,253 describes a process for controlling the properties of white liquor by measuring the electric conductivity of the green liquor before causticization in addition to measuring of the conductivity of the white liquor.
  • the conductivity of the green liquor is measured both before the slaker and gradually as it passes through the slaker to determine the reaction of the carbonate.
  • the present invention includes a method for determining the concentration of each of at least three components intermixed in a homogeneous solution.
  • the white or green liquor composition includes three major components, sodium hydroxide, sodium sulfide, and sodium carbonate.
  • the method includes identifying characteristics of the components that are quantitatively detectable in relation to the concentration of the components.
  • a mathematical relationship is then developed between the concentration of each of the components and the detectable characteristics using the characteristics as independent variables.
  • the solution is then sensed using detectors to obtain quantitative data for each of the characteristics.
  • the quantitative data is then employed in the mathematical relationship to obtain the concentration of each of the components.
  • the present invention also includes an analyzer having detectors which sense the three components and provide quantifiable data to a computer for employment in the mathematical relationship that was developed.
  • an analyzer having detectors which sense the three components and provide quantifiable data to a computer for employment in the mathematical relationship that was developed.
  • a sample is extracted from the process and analyzed by the detectors.
  • the process solution is continuously passed by the detectors for analysis.
  • FIG. 1 is a schematic diagram of a liquid analyzer of the present invention.
  • FIG. 2 is a graphical view of a typical response of the analyzer of FIG. 1 to a kraft liquor.
  • FIG. 3 is a graphical view illustrating deviations between titrated and predicted industrial white liquor compositions using the analyzer of FIG. 1.
  • FIG. 4 is a graphical view of the deviations between titrated and predicted industrial green liquor compositions using the analyzer of FIG. 1.
  • FIG. 5 is a schematic diagram of an alternative embodiment of the liquor analyzer of the present invention.
  • FIG. 6 is a graphical view of a comparison between the titrated and predicted sodium sulfide concentrations for the analyzer of FIG. 5 for white liquor-type solutions.
  • FIG. 7 is a graphical view of the comparison between titrated and predicted sodium hydroxide concentrations for the analyzer of FIG. 5 for white liquor-type solutions.
  • FIG. 8 is a graphical view of the comparison between of the titrated and predicted sodium carbonate concentrations for the analyzer of FIG. 5 for white liquor-type solutions.
  • FIG. 9 is a graphical view of the comparison between the titrated and predicted sodium sulfide concentrations for the analyzer of FIG. 5 for green liquor-type solutions.
  • FIG. 10 is a graphical view of the comparison between the titrated and predicted sodium hydroxide concentrations for the analyzer of FIG. 5 for green liquor-type solutions.
  • FIG. 11 is a graphical view of the comparison between the titrated and predicted sodium carbonate concentrations for the analyzer of FIG. 5 for green liquor-type solutions.
  • FIG. 12 is a diagrammatical view of one example of a control system using the analyzer of the present invention.
  • the present invention includes an on-line automatic liquor analyzer for a kraft pulp-paper mill application. Timely knowledge of liquor composition is necessary for close control of the digesting and recovery operations in a pulping process.
  • the process described herein is a kraft (alkali based) process
  • the analyzer of the present invention may very well be used in other processes such as a sulfite process.
  • the three primary components of the liquor include sodium hydroxide, sodium sulfide, and sodium carbonate.
  • the present invention provides a non-invasive type of measurement of the green liquor (the liquor exiting the recovery furnace) or the white liquor (the liquor exiting the causticizer) or green, white, or weak liquor solutions in other parts of the process can also be measured.
  • Detectors are chosen for sensing a characteristic of each of the components. For example, in one of the preferred embodiments, UV absorption at 254 nm was used to detect sodium sulfide which hydrolyzes into sodium hydrosulfide in kraft liquors. Conductivity and refractive index were used to detect sodium hydroxide, sodium sulfide, and sodium carbonate in differing proportions.
  • the present invention also includes a process for obtaining the concentrations of components of a process solution by initially identifying the characteristics of the components that are quantitatively detectable in relation to the concentration of the component.
  • a mathematical technique such as regression analysis is used to develop a mathematical relationship between the relative concentration of the components and the detectable characteristics. For example, equations are developed using the detectable characteristics as independent variables.
  • a sample of the solution is then analyzed to obtain quantitative data for each of the detectable characteristics. That quantitative data is then employed in the mathematical relationship developed previously to obtain the concentration of each of the components in the sample.
  • white or green liquor is drawn without interrupting the process or contaminating the process solution. Since a sample can be taken at any time and an analysis done quickly, for example in less than three minutes, the present invention provides for close monitoring of the process that was previously not possible.
  • the analyzer of the present invention can be used in at least one of two preferred modes. In a first mode, a sample is extracted from the process and analyzed. In a second mode, the process solution is continuously passed by the detectors.
  • the extractive sample analyzer 30 is illustrated in FIG. 1.
  • the analyzer 30 includes a Valco EC6W 6-port sample injection valve with electric actuator 32 for extracting a sample from a sample stream at 34 from the process of the present invention.
  • a Waters 510 HPLC pump 36 is used to pump water 38 into the valve 32.
  • a Waters zero dead volume tee 40 is disposed upstream from a Waters high pressure gradient mixer 42.
  • a Waters 510 HPLC pump 44 pumps water 46 through the tee 40.
  • a Waters column heater 48 is disposed downstream from the mixer for maintaining a selected temperature of the extracted sample.
  • a Waters 481 variable wavelength UV spectrophotometer 50 Located downstream from the heater are a Waters 481 variable wavelength UV spectrophotometer 50, a Waters 430 enhanced conductivity detector 52, and a Waters 410 differential refractometer 54. Data from the three detectors 50, 52, and 54 is collected by a Keithley 570 data acquisition system 56 and a Zenith 248 microcomputer 58.
  • the operation of the analyzer proceeds as follows.
  • a liquor stream is run through the extractive valve 32 and a very small sample (5 microliters) is captured in a constant volume loop in the valve 32.
  • the sample is flushed from the valve 32 by a stream of distilled, degassed water 38 provided by pump 36.
  • the flowing sample is diluted by additional distilled, degassed water 46 entering through the tee 40.
  • the resulting sample is mixed thoroughly in the gradient mixer 42.
  • the mixed sample is heated to a uniform temperature by passing through the column heater 48.
  • the sample then flows through the UV spectrophotometer 50, conductivity detector 52, and differential refractometer 54.
  • the responses from the detectors are sent to the computer 58 by the data acquisition system 56 where the responses are integrated over time.
  • the areas are calculated by the computer in units of volt-sec ⁇ 10.
  • the concentrations of sodium hydroxide, sodium sulfide, and sodium carbonate in the liquor are then calculated by correlations with the detector response areas.
  • test solutions were prepared from concentrated stock solutions of the individual compounds.
  • the stock solutions were prepared in distilled, degassed water, using reagent grade chemicals. These solutions were kept tightly capped and the runs were made within 10 days of stock solution preparation.
  • the concentrations of the stock solutions were determined by titration with HCl.
  • the solution densities were determined by weighing known volumes. The concentration and density of each solution were periodically checked and no changes were detected during the course of the experiments.
  • test solutions were prepared by mixing specific masses of the stock solutions and water, if necessary, to produce the desired concentration of each component.
  • the solutions were injected into the analyzer 30 immediately after preparation to minimize any compositional changes due to sulfide oxidation, carbonate formation, or evaporation.
  • the operating parameters for the analyzer components are listed in Table 1.
  • the inputs to the data acquisition system were carried by twisted, shielded pairs, and filtered by first-order RC filters with a 2.7 K ohm resistor and a 10 ⁇ F non-polar capacitor.
  • the detector responses were recorded for five minutes by the data acquisition system.
  • a sample response is illustrated in FIG. 2.
  • the response shows a dead time of just over one minute, where the sample zone was traveling from the injection valve to the tee.
  • the analysis was run for over a minute after the responses returned to the baseline although this additional time is not necessary.
  • the minimum analysis time per sample is approximately three minutes.
  • RI differential refractometer response
  • UV UV spectrophotometer response
  • Equations (4, 5, and 6) result in an approximate 90% confidence interval of ⁇ 0.5 g/l for both sodium hydroxide and sodium sulfide, and ⁇ 0.8 g/l for sodium carbonate.
  • the results from the industrial white liquor analysis are shown in FIG. 3.
  • the results indicate that each component is generally overpredicted when using the correlations developed for pure white liquor.
  • the sodium hydroxide estimate is the least affected by the impurities. The observed deviations are reasonable considering the types of impurities which may be present. Some thiosulfates and polysulfides may be present which would contribute to the absorbance at 254 nm. This would result in overprediction of sodium sulfide. Sodium sulfate and sulfite would basically appear to the detectors as sodium carbonate. Sodium sulfate and sulfide are species with low conductivity contribution, but significant refractive index contribution. The average deviations for the industrial white liquors are shown in Table 5.
  • the results from the industrial green liquor analyses are shown in FIG. 4.
  • the results are similar to the industrial white liquor analysis.
  • the sodium carbonate is always overpredicted. This is again caused by the influence of impurities having small contributions to solution conductivity.
  • the sodium sulfide error is smaller, and the sodium hydroxide error is larger than that of the white liquor.
  • the average deviations for industrial green liquors are shown in Table 6.
  • the analyzer 60 includes a Rosemount Model 222 Toroidal Conductivity Sensor with a Model 1054T Toroidal Conductivity Analyzer/Transmitter 62, a Micro Motion Model D25 Mass Flow Meter with a Micro Motion DMS Liquid Densitometer 64, and a Rosemount Model 340A Selective Ion Sensor with a Model 1033 Selective Ion Analyzer/Transmitter with a Phoenix Silver/Sulfide Ion Electrode 66.
  • Temperature data was transmitted through a Rosemount Series 78S platinum RTD with a Model 444 Temperature Transmitter 82. Data acquisition was accomplished with a Keithley 570 data acquisition system 68 and a Zenith 248 microcomputer 70.
  • the conductivity sensor 62, the densitometer 64 and the sulfide electrode 66 are disposed serially along a bypass conduit 72 that provides a stream of liquor from a vessel 80.
  • the bypass stream 72 is maintained at a uniform temperature by a heater 74 with temperature control 76.
  • a pump 78 provides the mode of force for circulating the bypass stream 72.
  • the analyzer operation involves pumping the liquor through the various sensors and processing the sensor data to calculate liquor composition.
  • aqueous solutions containing sodium hydroxide, sodium sulfide, and sodium carbonate were divided into two groups, white liquor type solutions and green liquor type solutions.
  • the white liquor solutions contained between 50 and 100 g/l of NaOH, 50 to 40 g/l of Na 2 S, and 0 to 25 g/l of Na 2 Co 3 , all expressed as Na 2 O equivalents.
  • the green liquor solutions contained between 65 and 105 g/l of Na 2 CO 3 , 0 to 30 g/l of NaOH, and 5 to 35 g/l of Na 2 S, all expressed as Na 2 O equivalents.
  • the solutions were prepared from reagent grade chemicals in distilled water and were used immediately after preparation.
  • a liquor sample was taken from the vessel 74 and titrated in duplicate using HCl before each experiment was begun.
  • the vessel 80 was capped and the contents heated sequentially to 70°, 80°, and 90° C. This temperature range was chosen because it is the typical temperature range in which white and green liquors are transported throughout a pulp mill.
  • the liquor was held at each temperature until all of the sensor responses had stabilized. In each case, the sulfide electrode had the slowest, and thus limiting, response time.
  • Sensor data was recorded at ten second intervals throughout each experiment as averages of ten consecutive readings. The data acquisition rate was 3.33 Hz.
  • the process transmitters were configured to provide good signal resolution over the expected range of liquor concentrations.
  • Each transmitter output was connected to the data acquisition system as a 4-20 mA current loop.
  • a load resistor of 250 ohms was used to convert the signal into a voltage of 1-5 V.
  • the transmitter ranges and maximum signal resolutions are shown in Table 7.
  • the procedure for reducing the data into correlations involved two steps. First, the temperature effect on the detector responses was determined. This allowed the final regression to be made on temperature compensated data. This approach was chosen based on the eventual field application of the analyzer. In the field, the temperature compensation could possibly be performed prior to data transmission.
  • the liquor temperature is not a significant factor in the sulfide electrode response for the white liquor solutions in the range of 70°-90° C.
  • the data indicates that there is a small deviation of the electrode response within this region, but no trend was observed with temperature.
  • V sulfide electrode voltage (mV)
  • V o reference potential (mV)
  • the activity coefficient relating the activity and the concentration is dependent upon the total ionic strength of the liquor being measured. This indicates that additional terms involving the other components in the liquor may be required to adequately fit the electrode response to measured sulfide concentration.
  • the best regression equations for sulfide concentration in the white liquor composition range are:
  • V sulfide electrode voltage (-mV)
  • Equation (17) is the best fit for liquor only at 80° C.
  • equation (18) is best for the temperature range 70°-90° C.
  • the prediction ability of the sulfide electrode is shown in FIG. 6.
  • the error at 80° C. expressed as a 90% confidence interval is approximately ⁇ 2.3 g/l, while that over 70°-90° C. is nearly ⁇ 3 g/l. Both errors are substantial.
  • the regressions involving sodium hydroxide and sodium carbonate were carried out for three different cases.
  • the sodium sulfide concentration was assumed to be known with accuracy corresponding to that of the liquor titration.
  • the second case involved regression of the data at 80° C. using equation (17) for sulfide prediction.
  • the third case was a regression of all data using equation (18) for sulfide prediction.
  • the equation form determined by stepwise regression to be optimum was:
  • V sulfide electrode voltage (-mV)
  • Equation (22) is similar to equation (17) for white liquor. However, the ionic strength correction in this case is density rather than conductivity. This dependence reflects the effect of sodium carbonate, the primary green liquor component, on density elevation rather than conductivity elevation.
  • the standard deviation of the prediction with equation (22) is 2.54 g/l, resulting in a 90% confidence interval of ⁇ 4.60 g/l for sodium sulfide.
  • the prediction ability is excellent if the sulfide concentration is known.
  • the sulfide predictions adversely effect the NaOH and Na 2 CO 3 predictions when the correlation is used. If the sodium sulfide measurement could be made with accuracy of ⁇ 1.0 g/l or better, then sodium hydroxide and sodium carbonate measurements would be within 90% confidence intervals of ⁇ 0.7 g/l. Mathematical manipulation of sodium sulfide data shows this to be true.
  • the Na 2 S prediction results are shown in FIG. 9.
  • the results for NaOH and Na 2 CO 3 are shown in FIGS. 10 and 11.
  • the novel extractive sample liquor analyzer of the present invention has the ability to analyze kraft white and green liquor samples for sodium hydroxide, sodium sulfide, and sodium carbonate concentrations with accuracy comparable to titration.
  • the in-situ liquor analyzer also has comparable accuracy if a reliable sulfide electrode that can withstand the continuous hostile environment is developed.
  • the design of both types of analyzers permits handling of other pulp mill liquors based on the same components such as soda, soda-AQ, neutral and alkaline sulfite, and controlled alkali semi-chemical liquors. It will be further understood that the analyzer of this invention may be used in processes other than paper pulping processes.
  • the liquor analyzer of the present invention is suitable for use in both feed forward and feed back control systems. Many types of control systems can be configured to help control the concentration of the green liquor in a kraft paper process.
  • One simple control system is illustrated in FIG. 12.
  • Control for a causticizer 80 includes analysis of the green liquor stream 82 entering the causticizer and the liquor stream 84 exiting the causticizer.
  • the addition of lime 86 is regulated by a computer control system 88 which uses the data received from detectors 90.
  • the minimum analysis time for the extractive sample liquor analyzer is approximately three minutes.
  • the 90% confidence intervals for white and green liquors are approximately ⁇ 0.5 g/l for sodium hydroxide and sodium sulfide, and ⁇ 0.8 g/l for sodium carbonate expressed as equivalents of Na 2 O.
  • the analyzer of this invention has features which make it advantageous as compared to current types of analysis.
  • One advantage is speed.
  • the time for analysis is approximately three minutes. This is significantly faster than automatic titrators or ion chromatography.
  • Another advantage is that a minimal amount of maintenance is required.
  • the accuracy of analysis is also good over a wide range of operating conditions.
  • the in-situ liquor analyzer specifically the conductivity and density portion, has the advantages of continuous liquor monitoring and simplicity of design.
  • the question of temperature compensation has been answered, and the accuracy could be comparable to that of the extractive sample analyzer once a sulfide electrode is developed to withstand the harsh environment for an extended period of time.

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US07/881,327 1990-05-01 1992-05-07 Liquid composition analyzer and method Abandoned USH1479H (en)

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US07/881,327 USH1479H (en) 1990-05-01 1992-05-07 Liquid composition analyzer and method

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20010031501A1 (en) * 2000-03-15 2001-10-18 Kanto Kagaku Kabushiki Kaisha Method and apparatus for detecting concentration of solution, and apparatus for diluting and preparing agents
WO2007006150A1 (en) * 2005-07-13 2007-01-18 Fpinnovations Method for quantitative determination of individual polysulphide species in oxidized white liquors by means of raman spectroscopy
US20160281708A1 (en) * 2015-03-24 2016-09-29 Avl List Gmbh System for measuring temporally resolved through-flow processes of fluids
US11397170B2 (en) * 2018-04-16 2022-07-26 Ecolab Usa Inc. Repetition time interval adjustment in adaptive range titration systems and methods
US11397171B2 (en) 2017-09-18 2022-07-26 Ecolab Usa Inc. Adaptive range flow titration systems and methods with sample conditioning
US11454619B2 (en) * 2018-04-09 2022-09-27 Ecolab Usa Inc. Methods for colorimetric endpoint detection and multiple analyte titration systems

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SE503605C2 (sv) * 1992-01-09 1996-07-15 Svenska Traeforskningsinst Analysförfarande med UV-absorptionsmätning
US5282931A (en) * 1992-07-08 1994-02-01 Pulp And Paper Research Institute Of Canada Determination and control of effective alkali in kraft liquors by IR spectroscopy
US5330621A (en) * 1992-09-23 1994-07-19 A. Ahlstrom Corporation Continuous elemental analysis of process flows
US5616214A (en) * 1995-09-12 1997-04-01 Pulp And Paper Research Institute Of Canada Determination of sodium sulfide and sulfidity in green liquors and smelt solutions
US6023065A (en) * 1997-03-10 2000-02-08 Alberta Research Council Method and apparatus for monitoring and controlling characteristics of process effluents
CA2216046A1 (en) * 1997-09-18 1999-03-18 Kenneth Boegh In-line sensor for colloidal and dissolved substances
US6339222B1 (en) 1998-11-12 2002-01-15 Kvaerner Canada Inc. Determination of ionic species concentration by near infrared spectroscopy
US6281689B1 (en) * 1999-04-12 2001-08-28 Honeywell-Measurex Corporation Means of correcting a measurement of a property of a material with a sensor that is affected by a second property of the material
CN102879356A (zh) * 2012-09-28 2013-01-16 邢台钢铁线材精制有限责任公司 测量电镀钝化槽液浓度的方法

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US4536253A (en) * 1981-09-25 1985-08-20 Kemotron A/S Process for controlling the properties of white liquor
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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20010031501A1 (en) * 2000-03-15 2001-10-18 Kanto Kagaku Kabushiki Kaisha Method and apparatus for detecting concentration of solution, and apparatus for diluting and preparing agents
US6706533B2 (en) * 2000-03-15 2004-03-16 Kanto Kagaku Kabushiki Kaisha Method for detecting a concentration of a solution
WO2007006150A1 (en) * 2005-07-13 2007-01-18 Fpinnovations Method for quantitative determination of individual polysulphide species in oxidized white liquors by means of raman spectroscopy
US20160281708A1 (en) * 2015-03-24 2016-09-29 Avl List Gmbh System for measuring temporally resolved through-flow processes of fluids
US10094378B2 (en) * 2015-03-24 2018-10-09 Avl List Gmbh System for measuring temporally resolved through-flow processes of fluids
US11397171B2 (en) 2017-09-18 2022-07-26 Ecolab Usa Inc. Adaptive range flow titration systems and methods with sample conditioning
US11454619B2 (en) * 2018-04-09 2022-09-27 Ecolab Usa Inc. Methods for colorimetric endpoint detection and multiple analyte titration systems
US11397170B2 (en) * 2018-04-16 2022-07-26 Ecolab Usa Inc. Repetition time interval adjustment in adaptive range titration systems and methods

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BR9106402A (pt) 1993-05-04
EP0527900A1 (en) 1993-02-24

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