US3888726A - Process for determining alkali content in alkaline pulping liquor by a calorimetric measurement of the heat of partial neutralization of the pulping liquor - Google Patents

Process for determining alkali content in alkaline pulping liquor by a calorimetric measurement of the heat of partial neutralization of the pulping liquor Download PDF

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US3888726A
US3888726A US377856A US37785673A US3888726A US 3888726 A US3888726 A US 3888726A US 377856 A US377856 A US 377856A US 37785673 A US37785673 A US 37785673A US 3888726 A US3888726 A US 3888726A
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alkali
cooking
liquor
pulping
pulping liquor
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Bengt Goran Hultman
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Mo och Domsjo AB
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    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/22—Other features of pulping processes
    • D21C3/228—Automation of the pulping processes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
    • G01N25/48—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity on solution, sorption, or a chemical reaction not involving combustion or catalytic oxidation

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  • Domsjoverken, Sweden Assignee: Mooeh Domsjo Aktiebolag, 404-407.
  • this is due to the complexity of the cellulosic material, and the variations in the reactivity of the cellulosic material according to the natural product in which it is found, and the complexity of the chemical reactions that may take place, simultaneously or concurrently, in the reaction mixture.
  • This complexity is increased if, for example, the cellulosic material is being degraded by alkali attack as in the chemical pulping of cellulose. since the alkali can react not only with the cellulosic material but also with the degradation products produced in consequence of this attack on the cellulosic material.
  • Conductometric techniques can be used for determination of alkali concentration. If a direct conduc-tometric measurement is made in the pulping liquid the correlation between alkali concentration and the conductivity of the sample is poor. On the other hand ifa conductometric titration is made, a very complex apparatus is needed in order to obtain accurate results. Potentiometers using ion selective electrodes are liable to drift, and provide unreliable results. Moreover, the signal given by such an electrodeis dependent upon the alkali content in a logarithmic relation, which requires a high degree of accuracy in the measurement of electrode potential, if the process is to be useful commercially.
  • a basic difficulty in determining alkali content by conductivity of the reaction mixture is that ions other than those contributing to alkali content also carry an electric current.
  • An apparatus constructed for this analysis is relatively complicated, since it is necessary to record and evaluate a complete course of titration sequences. It is also difficult to make continuous measurements of alkali content using such techniques, which is a disadvantage in determining alkali concentration using a continuous pulping process.
  • the analysis is to be fully automatic. some provision must be made to somehow select the end point of a given titration. If a computer is used for this purpose, the cost of the analytical equipment is correspondingly increased. It is obvious that this technique is complicated, but it can be used to obtain accurate measurements of the alkali concentration in pulping liquors, for instance, black liquor.
  • alkali content is found to be in a logarithmic relationship to electrode potential which makes it difficult to measure the alkali concentration directly with sufficient accuracy. Moreover, it is difficult to maintain pH electrodes in good condition when immersed in the corrosive highly alkaline pulping liquor.
  • effective alkali is meant the alkali evidencing its presence by reaction with a suitably chosen alkaline buffer, which acts as an acid towards the more alkaline pulping liquor.
  • the method of the present invention makes it possible to determine effective alkali content of pulping liquor accurately and continuously, without the need for expensive instrumentation, thereby making it possible to continuously control a pulping sequence according to its alkali content at any given stage. It has been found that the effective alkali determined by reaction with a buffer and calorimetric analysis is a good measurement of effective alkali according to the first mentioned definition, if the buffer has a pH in the range of 9.5-l2.5. Consequently, the calorimetrically determined concentration of effective alkali can be used to control pulping processes.
  • the heat liberated by a pulping liquor in the partial neutralization of the alkali by an acidic substance is determined calorimetrically after mixing a sample of the pulping liquor with a buffer in an amount to provide a pH within the range from about 9.5 to about 12.5, and preferably within the range from about 10.5 to about 11.5, in the resulting mixture. It has been determined in accordance with the invention that the heat liberated by partial neutralization of the alkaline pulping liquor only to this extent is an accurate measure of the effective alkali content of the pulping liquor at the time of the measurement. Thus, by sampling the pulping liquor at any stage of the pulping process, continuously or intermittently, one can obtain information on the effective alkali content which is sufficient to enable one to modify the pulping conditions so as to control the pulping as desired.
  • the particular final pH selected for the measurement is not critical, but for reproducible measurements in any given cook, it is desirable to select and utilize for the measurements throughout the cook a fixed final pH for the buffer-pulping liquor mixture. This is important in order to obtain reproducible results, that are meaningful in comparison to previous and subsequent alkali determinations in a given cook. This can be done by using the same buffer solutions throughout, and the same proportions between the sample volume of pulping liquor and the volume of buffer solution.
  • a sample of the alkaline pulping liquor is diluted to a suitable concentration at which the reaction with the buffer can take place.
  • This concentration is in no way critical, and any desired concentration can be used, without exception.
  • the concentration range of alkali as NaOH in normal undiluted pulping liquor is from about 1 to about g NaOH per liter at the end of the cook, at the beginning of a cook from about 50 to about 90 g NaOI-I per liter.
  • the pulping liquor is diluted with from 3 to times its volume of water, and preferably with from 8 to 12 times its volume of water.
  • the diluted sample is then mixed with an amount of an acidreacting buffer sufficient to bring the pH of the resulting mixture within the range from about 9.5 to about 12.5, and preferably from about 10.5 to 11.5.
  • an acidreacting buffer sufficient to bring the pH of the resulting mixture within the range from about 9.5 to about 12.5, and preferably from about 10.5 to 11.5.
  • Neither the amount of buffer used nor its pH are critical, provided both are at least sufficient to bring the pH of the mixture to within this range. It is not even necessary to control the amount of buffer added, provided an excess of buffer is added, and the relative proportions of buffer and sample are always the same, since an excess of buffer itself having a pH within this range prior to mixing with the pulping liquor merely ensures that the resulting mixture will also have this certain pH within this range.
  • the buffer solution does not change appreciably in pH as a result of the mixing, the pulping liquor changes from a pH in excess of 12 to a considerably lower pH, according to the buffer used and its pH.
  • the pH of the pulping liquor is reduced because hydroxyl ions of the effective alkali are reacting with hydrogen ions supplied from the acid component of the buffer, resulting in the formation of water in an equivalent amount. Accordingly, the consumption of the acid component of the buffer, converted to sodium hydroxide concentration by calculation, provides a good measurement of the effective alkali content of the sample of pulping liquor, and therefore presents a characteristic feature of the pulping liquor at the selected stage of the pulping at which the sample is taken.
  • the pulping liquor is titrated by acid to an arbitrarily selected partial neutralization end point represented by any desired pH within the range from about 9.5 to about 12.5 in a single step, by mixing the pulping liquor with the buffer, the end point 'of the titration being determined by the pH of the buffer and being the pH of the buffer when an excess of buffer is used. The heat liberated in so doing is then measured calorimetrically.
  • any changes in the content of hydroxyl ions based on the pulping liquor sample will be difficult to establish, because of the presence of other ions in the liquor which also contribute to conductivity.
  • the change in hydroxyl ion content is measured directly, and this change can be measured accurately, because there is a linear relationship between the heat of partial neutralization of the pulping liquor and the alkali content thereof.
  • reaction carried out in the process of the invention resulting in the formation of water from hydrogen ions of the buffer and hydroxyl ions in the pulping liquor is not a full neutralization between a large excess of strong acid and a small quantity of alkali, in which case the excess acid determines that the final pH be on the acid side, but partial neutralization of the effective alkali with an acid-reacting buffer (in its behavior towards the alkaline sample), where an alkaline terminal pH within the range from about 9.5 to about 12.5 is selected as the end point. If the titration is effected with an excess of acid, lignin would precipitate out, upsetting the measurement results, and clogging the apparatus.
  • the absolute alkali defined by neutralization to pH 7 is not required. It is only the effective alkali content that needs to be determined, and this is what is measured in accordance with the process of the invention, by titration to a pH within the range from about 9.5 to about 12.5, using an acid-reacting buffer.
  • Buffers which can be used in the process of the invention are known, and form no part of the instant invention. Pure acids are not included, but acid mixtures with their corresponding bases are, which in aqueous solution impart a pH within the range from about 9.5 to about 12.5, preferably from 10.5 to 11.5.
  • buffers are mixtures of alkali metal phosphates with monohydrogen phosphates, and/or dihydrogen phosphates; mixtures of alkali metal carbonates with bicarbonates; mixtures of alkali metal borates and hydrogen borates; mixtures of ammonium phosphates, carbonates or borates and ammonia; quaternary ammonium compounds; organic amines; and mixtures of two or more of these systems.
  • the relative proportions of these salts in the mixtures are selected so that the aqueous buffer solution has a pH within the range from about 9.5 to about 12.5, as stated.
  • the pH of the phosphate-hydrogen phosphate buffer is given by the expression:
  • This buffer has its maximum buffer capacity at the pH pK for the equilibrium HPO, H P that is at pH 11.
  • the buffer used in accordance with the invention has the same molar concentration of PO- 4 5 which is a base, and of HPO which is an acid. Consequently this buffer is acid-reacting when it is mixed with the sample of pulping liquor.
  • acid reacting buffer refers to a buffer which acts as an acid towards the sample of alkaline pulping liquor.
  • the determination of effective alklali content in accordance with this process is then used to select appropriate pulping conditions to obtain the desired cellulose pulp.
  • the quantity of effective alkali in the pulping liquor sample at a suitable point of time or stage in the pulping reaction is determined, it is possible to establish a suitable time-temperature sequence for the cook, so that a pulp having the desired degree of delignification is obtained, by applying the socalled H factor, as defined by Vroom, Pulp and Paper Magazine of Canada 1957 pages 228 to 231, the disclosure of which is hereby incorporated by reference.
  • wood can be pulped to a desired Kappa value under pulping conditions established on the basis of H factor determined from a graph of H factor against Kappa value over a range of alkalinities (in terms of g/l. NaOH) corresponding to the alkalinites required for the pulping of the type of wood selected.
  • alkalinities in terms of g/l. NaOH
  • the alkalinity of one or more samples taken at an early stage from a pulping liquor used to digest the same type of wood is determined by the calorimetric method according to the invention.
  • the alkalinity of the sample obtained by this measurement establishes the curve of the reference graph applicable to this sample of wood, and from this curve that is thus selected, the H factor applicable to obtain a sulfate cellulose pulp having a predetermined Kappa value is read off.
  • the H factor in turn establishes cooking time and/or cooking temperature for the selected degree of delignification.
  • the sulfate cooking is begun in the conventional manner, by charging and thoroughly mixing wood chips and alkaline cooking liquor in the digester.
  • a sulfate cooking liquor is an aqueous solution of alkali, usually NaOH, and Na S.
  • the digestion is then begun, and allowed to continue for an initial cooking period during which at least 20% of the alkali added initially up to about of the alkali added initially, preferably from 40% to 75%, has been consumed, after which a sample of the cooking liquor is taken, and titrated with an acid-reacting buffer to an end pH within the range from about 9.5 to about 12.5.
  • Either a gradually or rapidly increasing temperature during the initial cook can be used as desired, but approximately the same rate of increase would be used afterwards as before.
  • the determination is usually valid only for initial heating rates and temperatures approximating those used in obtaining the sample.
  • the rate of temperature increase during the initial digestion stages can be within the range from about O.1 C/minute to about 25 C/minute, preferably from about O.5 to about 10 C/minute.
  • the calorimetric determination of alkali concentration makes it possible to select the correct curve to determine H factor for a given (desired) Kappa value on the reference graph.
  • the reference graph is composed of a family of curves, one for each alkali concentration (NaOH in g/l) at which a cooking can be carried out over the entire range of useful alkali concentrations.
  • One reference graph is set up for each type of wood to be digested, for instance, spruce, fir, pine, birch, eucalyptus, beech, oak, maple, aspen, cedar, hemlock, cherry, chestnut, locust, elm, and the curves are based on the Kappa values obtained for pulps processed at given H factors in the digestor to be used.
  • each plant would establish its own reference graph empirically, based on actual digestion experience for the type of wood to be pulped.
  • the H factor for the Kappa value of pulp desired can be read off, and from the H factor the cooking temperature and cooking time can be ascertained.
  • the H factor corresponds to a unit of digestion, and represents the number of hours of digestion at C. At a higher temperature, more units of digestion can be completed within a given time, and at a lower temperature, less. Thus, H factor is a measure of how much digestion is needed at 100C., or at temperatures above and below 100C.
  • any digestion temperature can be used in the process of the invention, within the range from about to about 180C., and the cooking times also can be widely varied, from about 1 minute to about 10 hours, preferably from about to about C. for from about 15 minutes to about 3 hours.
  • the H factor determines how long the cook must be at a selected temperature, and vice versa, for a given Kappa value, at the alkali concentration determined in the calorimetric analysis.
  • the first step in the development of the H factor by Vroom was the establishment of relative reaction rate values corresponding to a range of temperature levels. Vroom quite arbitrarily chose the reaction rate at 100C. as unity, and rates at all other temperatures were releted to this standard.
  • the Arrhenius equation was used in the form where k reaction rate,
  • the H factor represents the number of units of digestion per hour at 100C.
  • the total number of digestion units needed, the H factor value from the reference graph curve, can be obtained using the above table as a multiple of the lower number of units per hour at lower temperatures, or as a fraction of the higher number of units per hour at higher temperatures.
  • the H factor indicated by the reference graph curve is 401.
  • the desired Kappa value will be obtained after the equivalent of a 1 hour cook at 160C, or a two hour cook at 152C, or a 3 hour cook at 147C; or a one-half hour cook at 168C.
  • This is an oversimplification because as a practical matter, however, the cook is not carried out solely at the temperature of the table, but over a gradual heating to the cooking temperature, and the H factor represents the units of digestion over the entire cooking cycle.
  • the computation is slightly more complicated, and in fact the H factor for any cooking cycle represents the area under a relative reaction rate versus time curve.
  • the H factor determines the shape of any of an infinite number of curves that can be used for a given cook.
  • the H factor is 1594.
  • a cooking cycle of 1% hours in the rising temperature stage from C to 170C, and 1% hours at 170C in the final cooking stage This is shown by the following computation:
  • any conditions of cooking temperature and time which give the H factor that has been determined can be used.
  • a computer can be used for calculating the H-factor and the cooking conditions from the H factor, and the computer can also be adapted to control the cooking automatically by sending direct signals to the control board establishing the cooking conditions.
  • the same temperature and time schedule is used for all cooks, in a batch operation, or continuously, from day to day, in the continuous operation.
  • the cooking conditions for each batch, in a batch operation, or continuously, in a continuous operation are varied according to the H factor determined for the particular lot of work being pulped, as shown by the sample.
  • Such variation can be effected in cooking temperature or in cooking time, or both, and thistype of variation is the usual one, but it is also possible to adjust the alkali concentration by adding either water, black liquor or alkali to move to a different alkali concentration curve in the reference graph, and so obtain a more favorable or more convenient H factor. It may be desirable, but it is not essential, to take another sample, if more alkali is added, since the presence of a higher alkali concentration may affect the wood in a different way. If the additional alkali is added at a later stage of the digestion, however, the effect is minimal, and another sample is unnecessary.
  • the chips are fed through a preheater where they are heated by steam and hot gases led from a digester and gas evaporator and are then passed continuously via a high-pressure feeder into the digester by means of circulating cooking liquor.
  • the excess of chips and cooking liquor, if any, is recirculated.
  • the digester is a long reactor through which the chips and liquor progress at a steady rate.
  • the temperature is adjusted at the heaters of the fluid taken from the cooking zones and circulated to achieve the desired rate of temperature increase and cooking temperature.
  • Liquor sample lines go to a calorimetric analyzer of the type shown in FIG. 1 or FIG. 2 which determines effective alkali content.
  • the calorimeter can be made to signal a computer which is programmed to adjust the temperature at the heaters and in this way control the cookby prescribed variations in cooking temperature.
  • the pulp is removed at the bottom of the digester and is fed to a blow tank. Spent black liquor is led to the re-. covery plant and the evaporators, while the hot gases from the evaporators are led to the condensers and preheater.
  • the pulp has a substantially constant Kappa number, due to the control of the cooking conditions in accordance with the invention.
  • the calorimetric method makes it possible to carry out the analysis of effective alkali content of the pulping liquor continuously, which is of particular importance with continuous pulping processes. This means that one can continuously meter the effective alkali content of the pulping liquor from the start to the end of the pulping process with a very short time lag, due only to the transport time for pumping the sample to the calorimetric analyzer.
  • the calorimeter is of simple construction, and gives strong signals using, for example, thermal emf measurements from thermopiles, or resistance changes from thermistors. There is moreover a linear relationship between the signal and the effectivealkali content, which makes it possible to determine the effective alkali content, which makes it possible to determine the effective content with a considerable degree of accuracy.
  • FIG. 1 illustrates diagramatically one embodiment of an isothermal calorimeter suitable for the calorimetric effective alkali analysis of alkaline pulping liquor
  • FIG. 2 illustrates diagrammatically one embodiment of adiabatic calorimeter, suitable for the calorimetric effective alkali analysis of alkaline pulping liquor;
  • FIG. 3 is a typical titration curve showing analytical results obtainable with the instrument of FIG. 1;
  • FIG. 4 is a titration curve showing analytical results obtainable with the instrument of FIG. 2.
  • the calorimeter of FIG. 1 utilizes the principles of isothermal calorimetry, and includes a three-line peristaltic pump 4, and thermostat coils 6, 6' arranged in a thermostat bath 12 together with a mixing vessel 7 and a reaction vessel 8.
  • a thermopile 9 is in heatreceiving relation to the reaction vessel 8, and the thermopile 9 in turn is in heat-conducting contact with a metal vessel 10, immersed in the thermostat bath 12 and surrounding the mixing vessel 7 and reaction vessel 8.
  • Reaction heat liberated in the reaction vessel 8 thus can be conducted through the thermopile to the thermostat bath, and the signal voltage developed as a result of this heat exchange can be taken out through the line 13 from the thermopile, as a measurement of the heat of partial neutralization conducted from the reaction vessel 8 to the thermostat bath 12.
  • Line 1 conducts buffer solution to the peristaltic pump 4.
  • Line 2 conducts pulping liquor to the peristaltic pump 4.
  • Line 3 conducts a reference solution to the peristaltic pump 4.
  • the valves 5,5 in lines 2, 3 on the other side of the peristaltic pump make it possible to pass either a pulping liquor solution or a reference solution through the thermostat coil 6' to the mixing vessel 7, while the line 1 passes an acid-reacting buffer solution through the thermostat coil 6 to the mixing vessel 7.
  • thermopile 9 The mixture is then removed through the outlet line 11.
  • the signal obtained at 13 when the acid-reacting buffer solution and reference solution are mixed can be taken as a base or zero line.
  • the calorimeter illustrated in FIG. 2 is adapted for adiabatic calorimetric measurements.
  • the apparatus includes a peristaltic pump 24, thermostat coils 26,26, a mixing vessel 27, a reaction vessel 28, thermistors 33, 34 in the thermostat bath at the outlet ends of the thermostat coils 26,26 and at the reaction vessel 28, and a thermostat bath 32.
  • the inlet line 21 leads buffer solution to the peristaltic pump 24, and then through the thermostat coil 26 to the mixing vessel 27.
  • the inlet line 22 leads a cooking liquor sample solution to the peristaltic pump 24, whence (according to the position of the valve 25) the solution passes through the thermostat coil 26 to the mixing vessel 27, while the inlet line 23 leads a reference solution (according to the position of valve 25') through the thermostat coil 26 to the mixing vessel 27.
  • the thermistors 33, 34 will register a small rise in temperature owing among other things to friction in the mixing vessel, and to the fact that the buffer and reference solutions can liberate a small heat of dilution.
  • a very large amount of heat is liberated, in proportion.
  • Pine wood chips were charged to a 30 liter circulating digester, and cooked with a sulphate pulping liquor under the following conditions:
  • pulping liquor samples were taken at 110, 130, 150, 160 and 170C during the cook. Samples were also taken after 1 hour at the maximum cooking temperature of 170C. The pulping liquor samples were then analyzed by an accurate conductometric titration, adiabatic calorimetric analysis using the apparatus of FIG. 2, and isothermal calorimetric analysis using the apparatus of FIG. 1.
  • the pulping liquor sample solutions were diluted to times their volume with 0.6 molar sodium sulphate solution.
  • the diluted samples were then pumped at a flow rate of 1.8 ml/min to the calorimeters.
  • the buffer solution was an aqueous solution of disodium monohydrogen phosphate and trisodium phosphate, having the composition 0.2 molar Na I-IPO plus 0.2 molar Na PO 'l2 11 0 to 2 liters of buffer solution.
  • the ionic strength of the buffer was 1.8.
  • the reference solution was 0.6 molar sodium sulphate whose ionic strength was 1.8. Thus, these three solutions, the buffer, the cooking liquor sample and the reference solution, all had the same ionic strength. Sodium sulphate was used as the reference solution and as a diluent because of the small amount of heat of dilution liberated thereby. The flow of buffer and reference solution was 1.8 ml per min. for each.
  • a process for determining the effective alkali content of an alkaline pulping liquor comprising an alkali metal hydroxide and an alkali metal sulfide which comprises taking a sample of the alkaline pulping liquor, mixing the sample with an acid reacting buffer having a pH less than the pH of the alkaline pulping liquor, in an amount to bring the pH of the resulting mixture to within the range from about 9.5 to about 12.5, measuring the heat liberated in the resulting partial neutralization of the effective alkali calorimetrically, and from such measurement determining the effective alkali content of the pulping liquor.
  • the acid-reacting buffer is selected from the group consisting of acid-reacting mixtures of alkali metal borates and hydrogen borates; mixtures of alkali metal carbonates with bicarbonates; mixtures of alkali metal phosphates with monohydrogen phosphates or dihydrogen phosphates; mixtures of ammonium phosphates, carbonates or borates and ammonia; quaternary ammonium compounds; organic amines; and mixturesv thereof, the relative proportions of the mixtures being selected so that the aqueous solution has a pH within the range from about 9.5 to about 12.5.
  • alkali metal hydroxide is sodium hydroxide
  • alkali metal sulfide is sodium sulfide
  • a process for preparing sulfate pulps of relatively uniform quality having a desired Kappa number which comprises pulping wood using an alkaline pulping liquor comprising alkali metal hydroxide and alkali metal sulfide at a cooking temperature and for a cooking time established on the basis of H factor determined by a graph of H factor against Kappa value at an alkali concentration corresponding to the effective alkali concentration determined calorimetrically for the alkaline pulping liquor used for pulping of the type of wood selected by the process of claim 1.
  • the sulfate cooking is begun by charging and mixing wood chips and alkaline cooking liquor in the digester, the digestion is then begun, and allowed to continue for an initial cooking period during which at least 20% of the alkali added initially up to about of the alkali added initially has been consumed, using an increasing temperature, after which a sample of the cooking liquor is taken and mixed with acidreacting buffer and the effective alkali content determined and then the pulping is carried out at approximately the same rate of temperature increase during the initial stages until the final cooking temperature is reached.
  • a process for determining the conditions needed in controllably obtaining a predetermined degree of de lignification and therefore a predetermined Kappa number in the manufacture of sulfate pulp, using an alkaline pulping liquor comprising an alkali metal hydroxide and an alkali metal sulfide which comprises taking a sample of alkaline pulping liquor at an early stage in the pulping of wood of the type to be digested, determining the effective alkali content of the sample according to the process of claim 1, and from this alkali content determining the H factor at the desired Kappa value in the finished sulfate pulp, and from the H factor determining the cooking time and temperature relationship needed to obtain the pulp of this Kappa value.
  • sample is prepared by mixing wood chips and alkaline sulfate cooking liquor, and continuing the digestion for an initial cooking period while consuming alkali until an amount within the range from about 20% to about 85% of the alkali added initially has been consumed.

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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3941649A (en) * 1972-07-14 1976-03-02 Mo Och Domsjo Aktiebolag Process for obtaining a predetermined Kappa number in sulfate pulping
US4012197A (en) * 1975-11-07 1977-03-15 Measurex Corporation Titration apparatus and method therefor
US4042328A (en) * 1976-04-06 1977-08-16 Seymour George W On-line analyzer
US4138313A (en) * 1976-04-14 1979-02-06 Mo Och Domsjo Aktiebolag Method and apparatus for continuously washing fibrous suspensions and controlling the volume of wash liquid
US4151252A (en) * 1976-09-13 1979-04-24 Commissariat A L'energie Atomique Device for the analysis of samples by measurement of the heat flux released at the time of contacting of each sample with a reagent
US4192708A (en) * 1974-09-05 1980-03-11 Mo Och Domsjo Aktiebolag Method for controlling the addition of active chemical for delignifying and/or bleaching cellulose pulp suspended in a liquor containing chemicals reactive with the delignifying and/or bleaching chemical
US4251497A (en) * 1976-09-11 1981-02-17 Dowa Mining Co. Ltd. Method for measuring the basic amount in basic aluminum sulfate solution for removal of SO2 gas
US4345913A (en) * 1980-01-18 1982-08-24 Eur-Control Kalle Ab Method and apparatus for determining the lignin content in pulp
US4846584A (en) * 1987-12-17 1989-07-11 Pennwalt Corporation Automated calorimeter and methods of operating the same
US4929307A (en) * 1985-11-29 1990-05-29 A. Ahlstrom Corporation Method of decreasing black liquor viscosity
US4933292A (en) * 1986-09-08 1990-06-12 Savcor-Consulting Oy Method for controlling and measuring cellulose digestion
US5456799A (en) * 1989-01-19 1995-10-10 Mo Och Domsjo Aktiebolag Method for controlling activation of lignocellulosic material in the presence of a nitrate containing liquid
US6606901B1 (en) * 1999-09-02 2003-08-19 Teijin Twaron B.V. Process for determining the acidity of a washing solution for fibers
WO2012003553A1 (en) * 2010-07-08 2012-01-12 Katholieke Universiteit Leuven Adiabatic scanning calorimeter

Citations (6)

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US3941649A (en) * 1972-07-14 1976-03-02 Mo Och Domsjo Aktiebolag Process for obtaining a predetermined Kappa number in sulfate pulping
US4192708A (en) * 1974-09-05 1980-03-11 Mo Och Domsjo Aktiebolag Method for controlling the addition of active chemical for delignifying and/or bleaching cellulose pulp suspended in a liquor containing chemicals reactive with the delignifying and/or bleaching chemical
US4012197A (en) * 1975-11-07 1977-03-15 Measurex Corporation Titration apparatus and method therefor
US4104028A (en) * 1975-11-07 1978-08-01 Measurex Corporation Method of titrating liquor
US4042328A (en) * 1976-04-06 1977-08-16 Seymour George W On-line analyzer
US4138313A (en) * 1976-04-14 1979-02-06 Mo Och Domsjo Aktiebolag Method and apparatus for continuously washing fibrous suspensions and controlling the volume of wash liquid
US4251497A (en) * 1976-09-11 1981-02-17 Dowa Mining Co. Ltd. Method for measuring the basic amount in basic aluminum sulfate solution for removal of SO2 gas
US4151252A (en) * 1976-09-13 1979-04-24 Commissariat A L'energie Atomique Device for the analysis of samples by measurement of the heat flux released at the time of contacting of each sample with a reagent
US4345913A (en) * 1980-01-18 1982-08-24 Eur-Control Kalle Ab Method and apparatus for determining the lignin content in pulp
US4929307A (en) * 1985-11-29 1990-05-29 A. Ahlstrom Corporation Method of decreasing black liquor viscosity
US4933292A (en) * 1986-09-08 1990-06-12 Savcor-Consulting Oy Method for controlling and measuring cellulose digestion
US4846584A (en) * 1987-12-17 1989-07-11 Pennwalt Corporation Automated calorimeter and methods of operating the same
US5456799A (en) * 1989-01-19 1995-10-10 Mo Och Domsjo Aktiebolag Method for controlling activation of lignocellulosic material in the presence of a nitrate containing liquid
US6606901B1 (en) * 1999-09-02 2003-08-19 Teijin Twaron B.V. Process for determining the acidity of a washing solution for fibers
WO2012003553A1 (en) * 2010-07-08 2012-01-12 Katholieke Universiteit Leuven Adiabatic scanning calorimeter
US9310263B2 (en) 2010-07-08 2016-04-12 Katholieke Universiteit Leuven Adiabatic scanning calorimeter

Also Published As

Publication number Publication date
FI54344B (fi) 1978-07-31
FR2193116A1 (pl) 1974-02-15
ZA734424B (en) 1974-03-27
FI54344C (fi) 1978-11-10
BR7305271D0 (pt) 1974-09-05
FR2193116B1 (pl) 1976-05-07
SE377348B (pl) 1975-06-30
CA998502A (en) 1976-10-19
JPS4957101A (pl) 1974-06-03
JPS5140162B2 (pl) 1976-11-01

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