US3886034A - Process for determining the conditions needed in controllably obtaining sulfate pulp having a predetermined kappa number - Google Patents

Process for determining the conditions needed in controllably obtaining sulfate pulp having a predetermined kappa number Download PDF

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US3886034A
US3886034A US402697A US40269773A US3886034A US 3886034 A US3886034 A US 3886034A US 402697 A US402697 A US 402697A US 40269773 A US40269773 A US 40269773A US 3886034 A US3886034 A US 3886034A
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pulping
sample
acid
wood
digester
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Sture Erik Olof Noreus
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Mo och Domsjo AB
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Mo och Domsjo AB
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Priority claimed from SE06795/70A external-priority patent/SE367451B/xx
Priority to DE2123497A priority Critical patent/DE2123497C3/de
Priority to CA112,925A priority patent/CA944905A/en
Priority to FR7117562A priority patent/FR2091637A5/fr
Priority to AT423771A priority patent/AT319735B/de
Application filed by Mo och Domsjo AB filed Critical Mo och Domsjo AB
Priority to US402697A priority patent/US3886034A/en
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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

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  • ABSTRACT A process is provided for determining the conditions needed in controllably obtaining a predetermined degree of delignification and therefore a predetermined Kappa number in the manufacture of sulfate pulp
  • a sample is taken of the alkaline pulping liquor at an early stage in the pulping of wood of the type to be pulped, the sample is titrated with an acid to the end point at which the conductivity of the sample has decreased to a relatively constant value, the NaOH (g/l) concentration is determined, and from this NaOl-l concentration at the desired Kappa value in the finished sulfate pulp the H factor is determined, which prescribed the pulping time and temperature relationship needed to obtain pulp of this Kappa value. Then the pulping time and cooking temperature are controlled during the pulping in accordance with such M factor.
  • the objective of a pulping process is to free the cellulose fibers from the wood, with the least amount of damage to the cellulose content thereof.
  • the wood is treated at a high temperature with an alkaline cooking liquor consisting substantially of sodium hydroxide and sodium sulfide in order to extract the lignin from the wood, and thereby free the cellulose fibers.
  • This process is called delignification. Delignification also makes it possible to obtain a strong cellulose pulp having a high degree of brightness and durability, after the cellulose pulp has been treated with bleaching chemicals.
  • the degree of delignification that is required depends upon the use to which the sulfate pulp is to be put, although the cost of the raw materials also plays an important part.
  • the desired degree of dilignification is determined in part by the cost of the wood and the bleaching chemicals, and in part by the technical properties of the pulp for the end use required, such as m the manufacture of paper.
  • the greater the degree of delignification obtained in the digester the less bleaching chemicals are needed to obtain a certain degree of brightness in the pulp.
  • the resulting reduction in chemicals consumption is counteracted by an impaired pulp yield, and a reduction in the strength of the pulp.
  • the degree of delignification is less, the result is an increase in the cost of bleaching chemicals, and at the same time an Increase in the volume of chemical waste, which is undesirable from the standpoint of care and protection of the environment.
  • the degree of delignification is determined by the quality of the wood, the amount of chemicals charged to the system per ton of dry wood, the woodlo-liquid ratio, and the intensity of the pulping condit ons, i.e., the digestion or cooking time, and the digestion or cooking temperature.
  • the quality of the wood is meant primarily how much alkali is required to delignify the pulp to a specific Kappa number under standardized conditions.
  • the requisite amount of alkali is dependent on the condition of the wood, such as the proportion of knots, and bark content, as well as on the chemical composition of the wood. It is, however, difficult to determine prior pulping how much alkali is required for pulping any particular batch of wood, and consequently it is difficult to determine in advance how much alkali is needed to obtain pulp of a desired Kappa number.
  • the amount of chemicals charged to the system per ton of dry wood is primarily determined by three variables, namely, the amount of dry wood charged to the system, the amount of white liquor charged to the system, and the composition and strength of the white liquor.
  • the quality of white liquor charged to e system and the strength and composition of the liquor can be determined with a fair degree of accuracy, but the quantity of dry wood in the digester is much more difficult to determine accurately.
  • the most important being the diff"- culty in estimating the moisture content of the chips, and the variations in volumetric weight of the wood, i.e., its density, and the degree of packing of the chips in the digester.
  • the intensity of the pulping process greatly influences the delignification. It is therefore important to maintain good control over both temperature and time during the pulping.
  • batch pulping processes have normally been carried out in accordance with a fixed time and temperature schedule, the degree of delignification obtained with pulp in a pilot run using a specific pulping process being used as a measure to determine the requisite amount of alkali for a number of succeeding batches, to obtain a desired degree of delignification.
  • This procedure results in pulp of nonuniform quality, because the wood is nonuniform from batch to batch.
  • a process for determining with considerable accuracy the conditions required for any desired degree of delignification, and thus make it possible to reproducibly prepare sulfate pulps of uniform quality.
  • the wood is pulped to a desired Kappa value under pulping conditions established on he asi of H factor determined from a graph of H factor against Kappa value over a range of alkalinities (in terms of g/ NaOl-l) corresponding to the alkalinities required for the pulping of the type of wood selected.
  • alkalinities in terms of g/ NaOl-l
  • alkalinity of one or more samples taken at an early stage from a pulping liquor used to pulp the same type of wood is determined by titration with an acid, to an end point determined as the limiting relatively constant value of the conductivity of the sample that is reached as conductivity decreases during the acid titration.
  • 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 l-I" factor applicable to obtain a sulfate cellulose pulp having a predetermined Kappa value is read off.
  • the H" factor in turn establishes pulping time and/or pulping temperature for the selected degree of delignification.
  • the sulfate pulping is begun in the conventional manner, by charging and thoroughly mixing wood chips and alkaline pulping liquor in the digester.
  • a sulfate pulping liquor is an aqueous solution of alkali, usually NaOH, and Na s.
  • the pulping is then begun, and allowed to continue for an initial pulping period during which at least 20 percent of the alkali added initially up to about 85 percent of the alkali added initially, preferably from 40 percent to 75 percent, has been consumed. after which a sample of the pulping liquor is taken, and titrated with an acid to the end point determined as the limiting conductivity of the sample.
  • the rate of temperature increase during the initial pulping states can be within the range from about O.lC/minute to about 25C/minute, preferably from about 0.5 to about lOC/minute.
  • the curve obtained when graphing conductivity as a function in the quantity of acid charged to the sample is asymptotic, and very characteristic.
  • conductivity decreases rapidly, but after a certain quantity of acid has been reached (which quantity is dependent on the alkalinity of the samples), the change in conductivity with addition of more acid becomes very small, or disappears altogether.
  • the point at which the change in conductivity diminishes or disappears constitutes the end point, and this point is marked by a change in slope of the curve. This point is referred to as the limiting value in the conductivity, and is the point where conductivity becomes relatively constant.
  • the accuracy of this method is in contrast to the accuracy of a method for determining total OH concentration based on differential conductivity, such as is disclosed in Rivers US. Pat. No. 3,553,075.
  • differential conductivity being an absolute conductivity value determination, reflects the presence of any ion that conducts a current. Since there are other ions present in alkaline pulping liquor in addition to OH, it is not possible to accurately determine total OH concentration in this way.
  • a series of comparative analyses using the titration technique of this invention and the differential conductivity method of Rivers has shown that the differential conductivity method is accurate only within the range of i 4.0 grams per liter, measured as NaOH.
  • FIG. 1-1 represents the curve followed by conductivity during the titration of alkaline sulfate pulping liquor by acid.
  • FIGS. l-2 compares the conductrimetric titration technique of this invention with the differential conductivity technique of Rivers, US. Pat. No. 3,553,075.
  • FIGS. 1A to IE represent typical acid titration curves obtained in accordance with the process of the invention, in which conductivity is graphed against the amount of acid added. The point at which conductivity reaches or approaches a limiting value is taken as the end point, and is marked P in the Figures. There is one figure for each working Example 1A to IE, and the data in the Figures are taken from the working Examples 1A to IE, as will be seen from the disclosure thereof, infra.
  • FIG. 2 represents a graph of H" factor against percent alkali as NaOH.
  • FIG. 3 represents a reference graph, showing a family of curves of H" factor against Kappa number for a series of alkali concentrations ranging from l2.5 g/l. to 40 g/l. NaOH.
  • FIG. 4 is a schematic view of apparatus useful in carrying out the process of the invention.
  • the device or meter by which the conductivity is determined is not critical. Any convenient conductivitymeasuring device or meter can be used.
  • One useful conductivity meter is provided with a reference electrode, for example the Kemotron four-electrode type, which registers electrical conductivity at different acid charges.
  • the acid employed in the titration is an organic or inorganic acid, preferably an inorganic acid, and preferably an acid which is nonoxidizing under the titration conditions.
  • the acid is used in dilute aqueous solution.
  • the normality of the solution is not critical, and can be within the range from about 0.1 to about 6N.
  • Preferred acids are sulfuric acid and hydrochloric acid.
  • Sulfuric acid has the advantage of a high sulfur content, which corresponds to the pulping liquor.
  • Other inorganic acids such as orthophosphoric acid, hydrobromic acid, hydroiodic acid, metaphosphoric acid and pyrophosphoric acid also can be used, as well as organic acids such as acetic, formic, trichloroacetic, and propionic acids. Strong oxidizing acids such as persulfuric acid and nitric acid may be used under some conditions, but usually should be avoided.
  • the amount of acid added during the titration to the end point corresponds to the amount of alkali present, and the latter can therefore be determined by calculation from the amount of acid.
  • the alkali content is calculated as NaOH in g/l.
  • the 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 pulping 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 digester to be used.
  • each plant would establish its own reference graph empirically, based on actual pulping 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 pulping temperature and pulping time can be ascertained.
  • the I-I factor corresponds to a unit of pulping, and represents the number of hours of pulping at C. At a higher temperature, more units of pulping can be completed within a given time, and at a lower temperature, less.
  • H factor is a measure of how much pulping is needed at 100C, or at temperatures above and below 100C.
  • any pulping temperature can be used in the process of the invention, within the range from about 1 10 to about 180C, and the pulping times also can be widely varied, from about 1 minute to about 10 hours, preferably from about 160 to about 180C. for from about minutes to about 3 hours.
  • the H factor determines how long the pulping must be at a selected temperature, and vice versa, for a given Kappa value, at the alkali concentration determined in the titration.
  • 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 related 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. Then, the desired Kappa value will be obtained after the equivalent of a 1 hour pulping at 160C, or a 2 hour pulping at 152C, or a 3 hour pulping at 147C; or a 12 hour pulping at 168C. This is an oversimplification because as a practical matter, however, the pulping is not carried out solely at the temperature of the Table, but over a gradual heating to the pulping temperature, and the H" factor represents the units of digestion over the entire pulping cycle.
  • the H" factor determines the shape of any of an 1nfil 103 34 133 51 1 163 nite number of curves that can be used for a given pulp- 18g 37 134 563 12 4 mg 1 135 610 H 2 106 45 136 661 166
  • the H 2 107 49 137 716 167 factor is 1594.
  • one 2 108 54 138 777 168 k h th risin tem- 3 109 139 855 169 can use a pulplng cycle of 1 ours in e g g 110 66 140 927 170 perature stage from C to 170C, and 1% hours at 111 73 141 1005 171 o shown b t e 4 112 79 142 1039 172 170 C m the final pulping stage.
  • any conditions of pulping temperature and time which give the H" factor that has been determined can be used.
  • the same temperature and time schedule is used for all pulpings, from day to day, for each batch, in a batch operation, or continuously, in the continuous operation.
  • the pulping 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 pulping temperature or in pulping time, or both, and this type 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 effect the wood in a different way. If the additional alkali is added at a later stage of the pulping, however, the effect is minimal, and another sample is unnecessary.
  • the apparatus shown in FIG. 4 is designed for a continuous pulping process.
  • the chips are fed through a preheater 2 where they are heated by steam and hot gases led by lines 25, 22 from a digester 1, and gas evaporator 20, and are then passed continuously via the high-pressure feeder l and the line 3 into the digester l by means of pulping liquor circulating in the line 11.
  • the excess of chips and pulping liquor, if any, is recirculated by line 12.
  • the digester is a long reactor through which the chips and liquor progress at a steady rate.
  • the temperature is adjusted at the steam-heated heaters 4 of the fluid taken from the pulping zones 5 and circulated via lines 6, 7, 8, 9 to achieve the desired rate of temperature increase and pulping temperature.
  • Liquor sample lines goes from line 8, 9 to an analyzer 13 for alkali which analyzer meters the conductivity of the liquor.
  • the meter signals a computer (not shown) 5 which is programmed to adjust the temperature at the steam-heated heaters 4, and in this way control the pulping by prescribed variations in pulping temperature.
  • pulp is removed at the bottom of the digester and is fed to the blow tank via valve 16 and line 17.
  • Spent black liquor is led to the recovery plant via lines l8, l9 and the evaporators 20, 21, while the hot gases from the evaporators are led by lines 22, 23, 24 to the condensers and preheater.
  • the pulp has a substantially constant Kappa number
  • Alkali charge active alkali (as NaOH) Sulfidity Wood-to-liquid ratio kg/l Rate of temperature increase in the initial stage from to l'lOC O.5C/min.
  • This batch digester had previously been used to establish the reference graphs shown in FIGS. 2 and 3 by carrying out a series of digestions, using pine wood chips, under the same pulping conditions, i.e., a pulping liquor to wood ratio of 3 5, a rate of temperature increase from 80C to the pulping temperature of 0.5C/min., and a final pulping temperature of 170C, and the Kappa numbers of the pulps obtained noted.
  • Kappa number was graphed against H" factor, for each alkali concentration from 12.5 g/l. to 49 g/l. NaOH, and the reference graph appears as FIG. 3.
  • Alkali concentration was also graphed against H" factor, and this graph appears as FIG. 2.
  • Pulping conditions for each of batches A to E are readily determined to produce pulp of a desired Kappa number by selecting the curve in FIG. 3 corresponding to the alkali concentration of the batch, selecting the Kappa number, and then reading the H factor off the curve.
  • k k and k depend on the rate of increase in temperature before the sample is taken, and the pulping temperature and time at which the sample is taken, and have to be determined empirically for each profile of pulping conditions. However, the formula is applicable for all pulping conditions that can be used.
  • Alkali charge 24% alkali (as NaOH) Sulfidity 30% Wood-to-Iiquid ratio 1:3.5 kg/l Rate of temperature increase,
  • pine chips taken from the same batch of chips were pulped for 2 hours at a maximum temperature of 170C.
  • the conditions in other respects were the same as those described above.
  • the Kappa number of the pulp obtained was l9.9, which is far from the desired value.
  • Example 2 was repeated, using pine chips taken from the same batch of chips as that used in Example 2.
  • the temperature of the pulping had reached 140C, a sample of the pulping liquor was taken, and the H factor required to obtain a pulp having a Kappa number of 33 was determined to be I300, using the formula above.
  • This l-l" factor corresponds to a pulping time of I20 minutes, at a maximum temperature of 164C.
  • the process was then carried out as described, and when the temperature of the pulping had reached 164C, the temperature was maintained for 120 minutes, after which the pulping was interrupted.
  • the pulp obtained by this pulping had a Kappa number of 32, which was satisfactorily close to the projected value of 33.
  • a process for determining the conditions needed in controllably obtaining a predetermined degree of delignification and therefore a predetermined Kappa number in the manufacture of sulfate pulp from wood, and then pulping the wood under the conditions thereby determined, 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 the wood to be pulped at which from at least 20 percent up to about 85 percent of the alkali added initially has been consumed, titrating the sample with an acid to the end point at which the conductivity of the sample has decreased to a relatively constant value, determining from the amount of acid added during the titration the alkali concentration at this end point, and from this alkali concentration determining the H" factor at the desired Kappa value in the finished sulfate pulp, and from the H" factor determining the pulping time and temperature relationship needed to obtain pulp of this Kappa value, and
  • a process for determining the alkali concentration 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 at a stage at which from at least 20% up to about of the alkali added initially has been consumed, titrating the sample with an acid to the end point at which the conductivity of the sample has decreased to a relatively constant value, and determining the alkali concentration at the end point from the amount of titrating acid added to the end point.
  • 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 pulping temperature and for a pulping time established by taking a sample of alkaline pulping liquor at an early stage in the pulping of the wood to be pulped at which from at least 20 percent up to about 85 percent of the alkali added initially has been consumed, titrating the sample with an acid to the end point at which the conductivity of the sample has decreased to a relatively constant value, determining from the amount of acid added during the titration the alkali concentration at this end point, and from this alkali concentration determining the H factor at the desired Kappa value in the finished sulfate pulp, and from the *H" factor determining the pulping time and temperature relationship needed to obtain pulp of this Kappa value.
  • Apparatus for the continuous preparation of sulfate pulps of relatively uniform quality having a desired Kappa number comprising, in positive flow connection and in combination, a digester arranged for the through passage of particulate wood while converting the wood in transit to pulp by pulping with alkaline sulfate pulping liquor, means in fluid flow communication with the digester for introducing wood and alkaline pulping liquor at one end of the digester, means in fluid flow communication with the digester for withdrawing wood pulp at another end of the digester, means for heating the digester, means in fluid flow communication with the digester for withdrawing a sample of pulping liquor at a position along the digester corresponding to an early stage of pulping at which from at least 20 percent 16 up to about percent of the alkali added initially has been consumed, means in fluid flow communication with the digester for measuring the conductivity of the sample, means in fluid flow communication with the digester for titrating the sample with acid to an end point at which conductivity has been decreased to a relatively constant value, and means connected
  • Apparatus according to claim 19 including a preheater for heating the particulate wood prior to passage through the digester.
  • Apparatus according to claim 19 including a gas evaporator for concentrating spent alkaline liquor, and means for recycling hot gases from the evaporator to a preheater for the particulate wood.
  • Apparatus according to claim 19, including means for adding alkali to the liquor in the digester at a position along the digester corresponding to a later stage of the digestion.

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Priority Applications (5)

Application Number Priority Date Filing Date Title
DE2123497A DE2123497C3 (de) 1970-05-15 1971-05-12 Verfahren zur Herstellung von Sulfatpulpen zur Erzielung von Pulpen mit einem vorherbestimmten Maß an Delignifizierung
CA112,925A CA944905A (en) 1970-05-15 1971-05-13 Obtaining sulfate pulp having a predetermined kappa number
FR7117562A FR2091637A5 (de) 1970-05-15 1971-05-14
AT423771A AT319735B (de) 1970-05-15 1971-05-14 Verfahren zur Herstellung von Sulfatzellstoff mit vorbestimmtem Delignifizierungsgrad
US402697A US3886034A (en) 1970-05-15 1973-10-02 Process for determining the conditions needed in controllably obtaining sulfate pulp having a predetermined kappa number

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SE06795/70A SE367451B (de) 1970-05-15 1970-05-15
US14222671A 1971-05-11 1971-05-11
US402697A US3886034A (en) 1970-05-15 1973-10-02 Process for determining the conditions needed in controllably obtaining sulfate pulp having a predetermined kappa number

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AT (1) AT319735B (de)
CA (1) CA944905A (de)
DE (1) DE2123497C3 (de)
FR (1) FR2091637A5 (de)

Cited By (9)

* 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
US4933292A (en) * 1986-09-08 1990-06-12 Savcor-Consulting Oy Method for controlling and measuring cellulose digestion
USD377844S (en) * 1996-01-16 1997-02-04 Industrial Molding Corporation Light support stake
USD378439S (en) * 1995-11-21 1997-03-11 Industrial Molding Corporation Light support stake
WO1997013916A3 (de) * 1995-10-09 1997-07-17 Siemens Ag Verfahren zur bestimmung des endpunktes der zellstoffkochung und anordnung zum steuern der kochzeit bei der zellstoffkochung in einem reaktor
US6174409B1 (en) * 1997-09-19 2001-01-16 American Air Liquide Inc. Method to improve final bleached pulp strength properties by adjusting the CI02:03 ration within a single (D/Z) stage of the bleaching process
WO2001088257A1 (en) * 2000-05-14 2001-11-22 U.S. Borax Inc. Methods for analyzing boron-containing alkaline pulping liquors
US6339222B1 (en) 1998-11-12 2002-01-15 Kvaerner Canada Inc. Determination of ionic species concentration by near infrared spectroscopy
US20100286387A1 (en) * 2009-05-06 2010-11-11 Hashaikeh Raed Crystalline sulphated cellulose ii and its production from sulphuric acid hydrolysis of cellulose

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE9017325U1 (de) * 1990-12-21 1992-01-02 Siemens AG, 8000 München Prozeßleitsystem zur Steuerung der Herstellung von Zellstoff
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

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2950177A (en) * 1956-02-27 1960-08-23 Ici Ltd Apparatus for the determination and control of compositions in chemical processes
US3553075A (en) * 1968-04-01 1971-01-05 Calgon Corp Method for controlling the hydroxide ion concentration in pulp digestion liquor

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2950177A (en) * 1956-02-27 1960-08-23 Ici Ltd Apparatus for the determination and control of compositions in chemical processes
US3553075A (en) * 1968-04-01 1971-01-05 Calgon Corp Method for controlling the hydroxide ion concentration in pulp digestion liquor

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
US4933292A (en) * 1986-09-08 1990-06-12 Savcor-Consulting Oy Method for controlling and measuring cellulose digestion
WO1997013916A3 (de) * 1995-10-09 1997-07-17 Siemens Ag Verfahren zur bestimmung des endpunktes der zellstoffkochung und anordnung zum steuern der kochzeit bei der zellstoffkochung in einem reaktor
USD378439S (en) * 1995-11-21 1997-03-11 Industrial Molding Corporation Light support stake
USD377844S (en) * 1996-01-16 1997-02-04 Industrial Molding Corporation Light support stake
US6174409B1 (en) * 1997-09-19 2001-01-16 American Air Liquide Inc. Method to improve final bleached pulp strength properties by adjusting the CI02:03 ration within a single (D/Z) stage of the bleaching process
US6339222B1 (en) 1998-11-12 2002-01-15 Kvaerner Canada Inc. Determination of ionic species concentration by near infrared spectroscopy
WO2001088257A1 (en) * 2000-05-14 2001-11-22 U.S. Borax Inc. Methods for analyzing boron-containing alkaline pulping liquors
US6635147B1 (en) 2000-05-14 2003-10-21 U.S. Borax Inc. Method for analyzing boron-containing alkaline pulping liquors
US20040055718A1 (en) * 2000-05-14 2004-03-25 Hsu Wu-Hwa Wesley Methods for analyzing boron-containing alkaline pulping liquors
US6913672B2 (en) 2000-05-14 2005-07-05 U.S. Borax Inc. Methods for analyzing boron-containing alkaline pulping liquors
AU2001259769B2 (en) * 2000-05-14 2005-10-06 U.S. Borax Inc. Methods for analyzing boron-containing alkaline pulping liquors
US20100286387A1 (en) * 2009-05-06 2010-11-11 Hashaikeh Raed Crystalline sulphated cellulose ii and its production from sulphuric acid hydrolysis of cellulose
US8309708B2 (en) 2009-05-06 2012-11-13 Fpinnovations Crystalline sulphated cellulose II and its production from sulphuric acid hydrolysis of cellulose

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DE2123497C3 (de) 1978-08-03
CA944905A (en) 1974-04-09
DE2123497B2 (de) 1977-11-24
AT319735B (de) 1975-01-10
DE2123497A1 (de) 1971-11-25
FR2091637A5 (de) 1972-01-14

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