CA1070056A - Process for oxygen alkali delignification of wood pulp - Google Patents
Process for oxygen alkali delignification of wood pulpInfo
- Publication number
- CA1070056A CA1070056A CA238,381A CA238381A CA1070056A CA 1070056 A CA1070056 A CA 1070056A CA 238381 A CA238381 A CA 238381A CA 1070056 A CA1070056 A CA 1070056A
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- oxygen
- improved process
- process according
- ammonia
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- 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
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/1026—Other features in bleaching processes
- D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
Abstract
IMPROVED PROCESS FOR OXYGEN-ALKALI
DELIGNIFICATION OF WOOD PULP
Abstract of the Disclosure An improved process for increasing the yields of wood pulp and improving the viscosity of the pulp during oxygen-alkali delignification is provided whereby, in a rela-tively low consistency alkaline pulp, there are present small amounts of ammonia or a compound which releases ammonia under the alkaline conditions of the process.
DELIGNIFICATION OF WOOD PULP
Abstract of the Disclosure An improved process for increasing the yields of wood pulp and improving the viscosity of the pulp during oxygen-alkali delignification is provided whereby, in a rela-tively low consistency alkaline pulp, there are present small amounts of ammonia or a compound which releases ammonia under the alkaline conditions of the process.
Description
I. P. 2102 IMPROVED PROCESS FOR OXYGEN-ALKALI
DELIGNIFICATION OF WOOD PULP
Background of the Invention _ The present invention relates to an improved process for improving the yields of fibrous materials, such as wood pulp, and of increasing the viscosity of the delignified pulp, during an oxygen-alkali delignification or bleaching treatment.
In the process, conducted at relatively low consistency, there ~re present small amounts of ammonia or a compound which will release ammonia under ~he alkaline conditions of the oxygen-alkali delignification.
Current interest in the paper industry has emphasized the desirability of delignifying wood pulp and other cellulosic ibrous materials using oxygen-alkali treatments. Such processes are desirable because they avoid the use of the traditional chlorination bleaching which uses a more expensive chemical and introduces complications due to the need to remove chlorine-containing by-products from the effluent streams. ~his requires expensive rhemical recovery systems so as to abate stream and environmental pollution problems. A number of oxygen-aikali delignification processes have been presented, such as those of ~ichter U. S. patent 1,860,432; Graangard et al. u. S. patents
DELIGNIFICATION OF WOOD PULP
Background of the Invention _ The present invention relates to an improved process for improving the yields of fibrous materials, such as wood pulp, and of increasing the viscosity of the delignified pulp, during an oxygen-alkali delignification or bleaching treatment.
In the process, conducted at relatively low consistency, there ~re present small amounts of ammonia or a compound which will release ammonia under ~he alkaline conditions of the oxygen-alkali delignification.
Current interest in the paper industry has emphasized the desirability of delignifying wood pulp and other cellulosic ibrous materials using oxygen-alkali treatments. Such processes are desirable because they avoid the use of the traditional chlorination bleaching which uses a more expensive chemical and introduces complications due to the need to remove chlorine-containing by-products from the effluent streams. ~his requires expensive rhemical recovery systems so as to abate stream and environmental pollution problems. A number of oxygen-aikali delignification processes have been presented, such as those of ~ichter U. S. patent 1,860,432; Graangard et al. u. S. patents
2,92S,114 and 3,024,158; Gaschke et al. U. S. patent 3,274,049s ~eylan et al. U. 5. pztent 3,384,533; Watanabe U. S. patent
3,~51,730; Rerolle et al. U. S~ patent 3,423,282; Farley U. S.
patent 3,661j~99; and French patents 1,130,248 and 1,387,853.
, A more recent process which has been found to be particularly advantageous~is that o Roymoulik et al. U. S~ patent 3,~32,276.
~C~7~
The-Roymoulik e~ al. patent process is a highly satisfactory processO However, the paper industry continues to strive to improve pulp yields and to improve the quality of the pulp. It is known, for example, that oxygen-alkali delignification ox bleaching methods tend to reduce the pulp viscosity. To counteract this problem, and to strive for optimum yields, various additives have been suggested in the oxygen-alkali treatments, such as magnesium salts, chelating agents and sequestering agents, have been employed in the systems in order to redu~e the cellulose degradation which causes the unwanted reduction in pulp viscosities.
Yield loss during delignifica~ion or bleaching is not unique to oxygen-alkali delignification processes. It is encountered in many pulp treatments of cellulosic materials.
With the increasing costs of the source of cellulosic materials, such as txee logs, the reduction of yield losses becomes of increasin~ importancP to the paper industry. The search for means of reducing yield losses and viscosity losses has been going on for many years, even going back prior to the advent of oxygen-alkali delignification treatments.
One such suggested means of preventing viscosity reduction due to cellulose depolymerization or degradation is ~eald U. S. patent 3,36~,935. That patent is directed to a sulfite pulping process where urea is employed in the cooking liquor to control pH and prevent depolymerization of the cellulose. Sulfite cooking liquor3 are, however, an entirely different system from an oxygen-alkali bleaching system. The reaction mechanisms in the two processes are entirely different.
Baudisch U. SD patent 2,271,218 describes a method of producing textile fibers by treating corn straw in a solution .
~7~
of alkali and urea. The process is a two-stage pulping pro~
cess in which corn straw is treated with alkali and urea in the first staye and defiberized mechanically in the second stage. Such a treatment is quite different from an oxygen-alkali delignification treatment~
Liebergott et al. U. S. paten~ 3,740,311 describes a process for the delignification of wood pu]p in which the pulp is treated at a relatively high consistency with ammonia and oxygen. In the processl ammonia is the sole source of llkalinity. Gaschke et al. U. S. patent 3,274,049 is similar to the Liebergott patent and differs in that it is directed to the treatment of bagasse, but it also employs ammonia as the sole source of alkalinity.
A publication by Lyman C. Aldrich, "Cellulose Degra-dation Inhibitors for the Chlorination Stage", TAPPI, Vol. 51,No. 3, pp. 71A-74A (March 1968) describes the use of urea and ammonium hydroxide (actually ammonium chloride,which is formed by the instantaneous reaction with ammonium hydroxide on the chlorine-containing acidic treatment liquor) during chlcrine bleaching to inhiblt cellulose degradation. While the addition of urea and ammonium hydroxide improves pulp viscosity ~o some extent, it also produces pulps having higher permanganate num ~ers, re~lecting a higher lignin content than the controls.
Thus, in the chlorination bleaching treatment of the Aldrich publica~ion, the addition of urea and ammonium hydroxide at levels of additive above 0.25% actually reduced the amount of deligniication. This is a serious disadvantage in a proc~ss .
whose sole purpose is to r mo~e lignin from the pulp and so that if any subsequent chemical trea~ment is involved, such as the use of chlorine dioxide in a subsequent treatment of the ' pulp, that treatment can be minimized. In the acidic chlori-nation conditions employed by Aldrich, the nitrogenous com-pounds react with the chlorine in the bl~aching solutions to form chloro derivatives of the nitrogen compound, thus wasting bleaching chemical. Thus, the addition of urea or ammonia servesno useful purpose insofar as delignification is involved.
A paper by Tobar, "Sulfamic Acid in the Chlorination and Hypochlorite Bleaching of Pulp", TAPPI, Vol. 47, No. 11 pp. 688-691, and Tobar U. S. patent 3,308,012, d~scribe the use of urea and ammonium chloride as cellulose st~bilizers during alkaline hypochlorite bleac~ing. On page 691 of the publication, Tobar states that in a hypochlorite bleaching sys-tem, the addition of urea or ammonium chloride produced both a loss in brightness and a loss in pulp viscosity, thereby showing that these agents in such a system actually produce undesirable results.
Gudivaka et al., "Inhibitors in Pulp Bleaching", Indian Pulp and Paper, pp. 447-452, (January 1971) describe the use of urea, ammonia and sulfamic ac~d in~the bleaching of pulp by chlorine or hypochlorite. Such a system is, of course, quite different chemically from oxygen-a1kali bleaching system.
The results obtained by the authors were inconclusive.
Viscosity repr~sents a measurement of the average degree of polymerization of the cellulose in the pulp sample, i.e~, the average chain length of the cellulose. Thus, decreases in ~iscosity values represen~ ~he extent of depol~merization or degradation caused by the bleaching process. Excessive degra-dation is to be avoided since it provides undesirable physical ....
properties in any paper made from the pulp.
.
.
~i7~5~
Kappa No. is determined by the potassium permanganate consumed by a sample of pulp and represents a measurement of its retained lignin content. The higher the Kappa No., the less bleached and delignified is the pulp. By comparing Kappa Nos.
of samples before and after bleaching treatment, one can obtaln an evaluation of the extent of delignification wh;ch has taken place.
It is, therefore, an object of the pres~nt invention to provide an improved process for the delignification or bleaching of pulp by the oxygen-alkali process.
It is another objec~ of the present invention ~o provide a method of delignifying wood pulp which will reduce yield losses and provide a pulp of improved viscosity.
Further objects will be apparent to those skilled in the art from the present description, taken in conjunction with the appended drawing, which is a graph comparing the shrinkage or yield loss in the oxygen-alkali treabment of wood pulp with various concentrations of ammonia in the pulp.
General Description o the Invention We have now discovered that unexpectedly improved pulp yields and higher pulp viscosities can be obtained in the oxygen-al~ali delignifica~ion of pulp by introducing into the alkaline pulp at least about 0~1% by weight (based on oven-dried pulp) of ammonia or a compound which will release ammonia under the~alkaline conditions of the process. In the alkaline condi-tions contemplatedl the alkali solution, containing pulp, shall have a pH of be~ween about 9 and 13. In the case of ammonia, amounts o up to about 3% by weight of oven-dried pulp have been found to provide excellent results and amounts above that provide no advantage and result in 105s in economy. Preerred . .
~: :' S ~
- ~ ~7~al5~;
amounts of ammonia are between about 0.4~ and 1~ by weight with the optimum amoun~ being about 0.6%. In the case of uxea, and compounds r~leasing ammonia, amount:s up to about 6~ by weight provide satisfactory results and amounts in excess of this provide no economical advantage. When urea is employed as the compound resulting in ammonia, the preferred amount is from about 1~ to 4% by weight of oven-dri~d pulp.
In the process, temperatures of bet.ween about 200 and 260~F. are desixable with the preferred temperature range being between about 210 and 220F. The pressure of elemental oxygen in the system is desirably between about 30 and 300 psig. with the preferred partial pressure range being between about 120 and 130 psig. The amount of oxygen employed is desirably between about 1 and 10% based on oven-dried pulp.
Air can be used as the source o~ oxygen, but this requires longer reaction times and the use of higher pressures.
The amount of alkali, such as sodium and potassilIm hydroxides, or carbonates, or mixtures thereof, employed is sufficient to provide a pH range of between about 9 and 13, preEerred between about 11.5 and 12.5. The amounts of sodium or potassium hydroxides generally employed are between about 0.5 and 8 grams per liter, preferably about 2 to 4 grams per liter.
As presently contemplated, the process can be con-ducted in a time inter~al of from about 1 to 120 minutes, but usually 2~ to 40 minutes 15 ~he most satisfactory time period.
The consistency of the pulp is lower than that employed in most prior~art bleaching or delignification processes and the desirable range is between about 1% and 10~ based on oven-dried pulp,~ with the preferable range b ing between a~out 3%
~ and 5%.
.
.
. .. . . . .
In addition to ammonia, per se~ ammonium sa~ts such as the chloride, carbonate sulfite, nitrate or sulfate may be em~ployed. Also, ammonia-releasing compounds may be employed, such as urea, sodium cyana~e, hydrazine and substituted hydra-zines such as alkyl substituted hydra2ines, cyanuric acid, nrimary amides such as methyl and propyl amide, hydroxylamine, sodium or magnesium nitrides, sulfamic acid, etc.
The oxygen-alkali delignifica~ion treatment may desirably be conducted in accordance ~ith ~he process and apparatus disclosed in R~moulik et al. U. S. patent 3,832,276.
However, i~ is not necessary to employ these conditions. The alkaline pulp, containing the source of ammonia, is dèsirably mixed with oxygen in a high-shear mixing device so as to bring the oxygen into intimate contact with the alkaline pulp. ~igh-shear, high-speed mixing devices, such as the Lightnin' type mix~r, are highly suitab~e for this purpo~e. Desirably, the alkaline aqueous pulp is briefly subjected to a high-pressure oxygen pre-treatment and thereafter the pressuxe is gradually reduce~ during t~e delignification process.
The wood chips or pulp may first be impregnated with `I
a source of ammonia before ~eing expo~ed to the alkaline solu- j tion and o~ygen.
In one aspect of this invention there is provided an improved process for increasing the yields of wood pulp and improving the viscosity of the pulp during oxygen-alkali delignification. The process comprises treating a pulp contain-ing at least about 0.1~ by weight of oven-dried pulp of a member selected from the class consisting of ammonia and compounds r~leasing ammonia at a pH o~ between about 9 and 13. The pulp has a ~onsistency of between about 1 and 10% based on oven-dried *Trade Mark ~ - 7 -~ .
~ , .
~7~5~
.
pulp. The pulp has a pH within the range of between about 9 and 13. The treatment is carried out at a temperature between ut 200 and 260F at an oxygen pressuxe of between about 30 and 3000 psig.
As shown in the accompanying drawing~ shrinkage or reduction in yield varies with the concentrlation of ammonia in the process. As shown, the yield loss is minimized at a concentration of approxima~ely 0.6% ammonia. The data for the graph were obtained by employing the procedure of Example 1 hereinbelow.
. .. ... .
.
-......
- 7~a) -~.
: . . : . .: : . : : .
. : : . , , Detailed Description of the Invention In order to disclose more clearly the nature of the present invention, the following examples illustrating the invention are given. It should be understood, however, that this is done solely by way of example and is intended neither to delineate the scope of the invention nGr limit tile ambit of the appended claims~ In the examples which follow, and throughout the specification, the quantities of material are expressed in terms of parts by weight, unless otherwise ~pecified.
Kraft hardwood pulp was subjected to oxygen-alkali bleachiny, using various concentrations of urea. In the runs, the pulp consistency was approximately 2% by weight of oven-dried pulp. The alkaline delignification solution contained4 grams per liter vf sodium hydroxide. The delignification was carried out at a temperature of 205F. in a pressure reac-tor having intimately mixed with the alkaline pulp, oxygen at an initial pressure of 100 psig. That pressure was maintained for approximately 10 minutes fol~owed by venting to 36 psig.
pressure, followed by gradual reduction to æero psig. over a period of 42 minutes. The experiments were repeated at each concentration of urea for between 4 and 7 repetitions. The result~ are set forth in Tablo 1 below.
' ., . .: , .
:
~.
.
~7~5~
Table 1 Average Values . .
Kappa Viscosity Yield Number of Experiment Number cp, at 0.5% % on OD Pulp Runs Starting Pulp 19 .1 33 . 0 Control 11.0 23.0 95.3 6 0.5~ Urea 11.2 24.9 \` 96.7 5 1.0% Urea 10.8 25.9 96.2 4 2.0~ Urea 11.3 26.2 96.8 7
patent 3,661j~99; and French patents 1,130,248 and 1,387,853.
, A more recent process which has been found to be particularly advantageous~is that o Roymoulik et al. U. S~ patent 3,~32,276.
~C~7~
The-Roymoulik e~ al. patent process is a highly satisfactory processO However, the paper industry continues to strive to improve pulp yields and to improve the quality of the pulp. It is known, for example, that oxygen-alkali delignification ox bleaching methods tend to reduce the pulp viscosity. To counteract this problem, and to strive for optimum yields, various additives have been suggested in the oxygen-alkali treatments, such as magnesium salts, chelating agents and sequestering agents, have been employed in the systems in order to redu~e the cellulose degradation which causes the unwanted reduction in pulp viscosities.
Yield loss during delignifica~ion or bleaching is not unique to oxygen-alkali delignification processes. It is encountered in many pulp treatments of cellulosic materials.
With the increasing costs of the source of cellulosic materials, such as txee logs, the reduction of yield losses becomes of increasin~ importancP to the paper industry. The search for means of reducing yield losses and viscosity losses has been going on for many years, even going back prior to the advent of oxygen-alkali delignification treatments.
One such suggested means of preventing viscosity reduction due to cellulose depolymerization or degradation is ~eald U. S. patent 3,36~,935. That patent is directed to a sulfite pulping process where urea is employed in the cooking liquor to control pH and prevent depolymerization of the cellulose. Sulfite cooking liquor3 are, however, an entirely different system from an oxygen-alkali bleaching system. The reaction mechanisms in the two processes are entirely different.
Baudisch U. SD patent 2,271,218 describes a method of producing textile fibers by treating corn straw in a solution .
~7~
of alkali and urea. The process is a two-stage pulping pro~
cess in which corn straw is treated with alkali and urea in the first staye and defiberized mechanically in the second stage. Such a treatment is quite different from an oxygen-alkali delignification treatment~
Liebergott et al. U. S. paten~ 3,740,311 describes a process for the delignification of wood pu]p in which the pulp is treated at a relatively high consistency with ammonia and oxygen. In the processl ammonia is the sole source of llkalinity. Gaschke et al. U. S. patent 3,274,049 is similar to the Liebergott patent and differs in that it is directed to the treatment of bagasse, but it also employs ammonia as the sole source of alkalinity.
A publication by Lyman C. Aldrich, "Cellulose Degra-dation Inhibitors for the Chlorination Stage", TAPPI, Vol. 51,No. 3, pp. 71A-74A (March 1968) describes the use of urea and ammonium hydroxide (actually ammonium chloride,which is formed by the instantaneous reaction with ammonium hydroxide on the chlorine-containing acidic treatment liquor) during chlcrine bleaching to inhiblt cellulose degradation. While the addition of urea and ammonium hydroxide improves pulp viscosity ~o some extent, it also produces pulps having higher permanganate num ~ers, re~lecting a higher lignin content than the controls.
Thus, in the chlorination bleaching treatment of the Aldrich publica~ion, the addition of urea and ammonium hydroxide at levels of additive above 0.25% actually reduced the amount of deligniication. This is a serious disadvantage in a proc~ss .
whose sole purpose is to r mo~e lignin from the pulp and so that if any subsequent chemical trea~ment is involved, such as the use of chlorine dioxide in a subsequent treatment of the ' pulp, that treatment can be minimized. In the acidic chlori-nation conditions employed by Aldrich, the nitrogenous com-pounds react with the chlorine in the bl~aching solutions to form chloro derivatives of the nitrogen compound, thus wasting bleaching chemical. Thus, the addition of urea or ammonia servesno useful purpose insofar as delignification is involved.
A paper by Tobar, "Sulfamic Acid in the Chlorination and Hypochlorite Bleaching of Pulp", TAPPI, Vol. 47, No. 11 pp. 688-691, and Tobar U. S. patent 3,308,012, d~scribe the use of urea and ammonium chloride as cellulose st~bilizers during alkaline hypochlorite bleac~ing. On page 691 of the publication, Tobar states that in a hypochlorite bleaching sys-tem, the addition of urea or ammonium chloride produced both a loss in brightness and a loss in pulp viscosity, thereby showing that these agents in such a system actually produce undesirable results.
Gudivaka et al., "Inhibitors in Pulp Bleaching", Indian Pulp and Paper, pp. 447-452, (January 1971) describe the use of urea, ammonia and sulfamic ac~d in~the bleaching of pulp by chlorine or hypochlorite. Such a system is, of course, quite different chemically from oxygen-a1kali bleaching system.
The results obtained by the authors were inconclusive.
Viscosity repr~sents a measurement of the average degree of polymerization of the cellulose in the pulp sample, i.e~, the average chain length of the cellulose. Thus, decreases in ~iscosity values represen~ ~he extent of depol~merization or degradation caused by the bleaching process. Excessive degra-dation is to be avoided since it provides undesirable physical ....
properties in any paper made from the pulp.
.
.
~i7~5~
Kappa No. is determined by the potassium permanganate consumed by a sample of pulp and represents a measurement of its retained lignin content. The higher the Kappa No., the less bleached and delignified is the pulp. By comparing Kappa Nos.
of samples before and after bleaching treatment, one can obtaln an evaluation of the extent of delignification wh;ch has taken place.
It is, therefore, an object of the pres~nt invention to provide an improved process for the delignification or bleaching of pulp by the oxygen-alkali process.
It is another objec~ of the present invention ~o provide a method of delignifying wood pulp which will reduce yield losses and provide a pulp of improved viscosity.
Further objects will be apparent to those skilled in the art from the present description, taken in conjunction with the appended drawing, which is a graph comparing the shrinkage or yield loss in the oxygen-alkali treabment of wood pulp with various concentrations of ammonia in the pulp.
General Description o the Invention We have now discovered that unexpectedly improved pulp yields and higher pulp viscosities can be obtained in the oxygen-al~ali delignifica~ion of pulp by introducing into the alkaline pulp at least about 0~1% by weight (based on oven-dried pulp) of ammonia or a compound which will release ammonia under the~alkaline conditions of the process. In the alkaline condi-tions contemplatedl the alkali solution, containing pulp, shall have a pH of be~ween about 9 and 13. In the case of ammonia, amounts o up to about 3% by weight of oven-dried pulp have been found to provide excellent results and amounts above that provide no advantage and result in 105s in economy. Preerred . .
~: :' S ~
- ~ ~7~al5~;
amounts of ammonia are between about 0.4~ and 1~ by weight with the optimum amoun~ being about 0.6%. In the case of uxea, and compounds r~leasing ammonia, amount:s up to about 6~ by weight provide satisfactory results and amounts in excess of this provide no economical advantage. When urea is employed as the compound resulting in ammonia, the preferred amount is from about 1~ to 4% by weight of oven-dri~d pulp.
In the process, temperatures of bet.ween about 200 and 260~F. are desixable with the preferred temperature range being between about 210 and 220F. The pressure of elemental oxygen in the system is desirably between about 30 and 300 psig. with the preferred partial pressure range being between about 120 and 130 psig. The amount of oxygen employed is desirably between about 1 and 10% based on oven-dried pulp.
Air can be used as the source o~ oxygen, but this requires longer reaction times and the use of higher pressures.
The amount of alkali, such as sodium and potassilIm hydroxides, or carbonates, or mixtures thereof, employed is sufficient to provide a pH range of between about 9 and 13, preEerred between about 11.5 and 12.5. The amounts of sodium or potassium hydroxides generally employed are between about 0.5 and 8 grams per liter, preferably about 2 to 4 grams per liter.
As presently contemplated, the process can be con-ducted in a time inter~al of from about 1 to 120 minutes, but usually 2~ to 40 minutes 15 ~he most satisfactory time period.
The consistency of the pulp is lower than that employed in most prior~art bleaching or delignification processes and the desirable range is between about 1% and 10~ based on oven-dried pulp,~ with the preferable range b ing between a~out 3%
~ and 5%.
.
.
. .. . . . .
In addition to ammonia, per se~ ammonium sa~ts such as the chloride, carbonate sulfite, nitrate or sulfate may be em~ployed. Also, ammonia-releasing compounds may be employed, such as urea, sodium cyana~e, hydrazine and substituted hydra-zines such as alkyl substituted hydra2ines, cyanuric acid, nrimary amides such as methyl and propyl amide, hydroxylamine, sodium or magnesium nitrides, sulfamic acid, etc.
The oxygen-alkali delignifica~ion treatment may desirably be conducted in accordance ~ith ~he process and apparatus disclosed in R~moulik et al. U. S. patent 3,832,276.
However, i~ is not necessary to employ these conditions. The alkaline pulp, containing the source of ammonia, is dèsirably mixed with oxygen in a high-shear mixing device so as to bring the oxygen into intimate contact with the alkaline pulp. ~igh-shear, high-speed mixing devices, such as the Lightnin' type mix~r, are highly suitab~e for this purpo~e. Desirably, the alkaline aqueous pulp is briefly subjected to a high-pressure oxygen pre-treatment and thereafter the pressuxe is gradually reduce~ during t~e delignification process.
The wood chips or pulp may first be impregnated with `I
a source of ammonia before ~eing expo~ed to the alkaline solu- j tion and o~ygen.
In one aspect of this invention there is provided an improved process for increasing the yields of wood pulp and improving the viscosity of the pulp during oxygen-alkali delignification. The process comprises treating a pulp contain-ing at least about 0.1~ by weight of oven-dried pulp of a member selected from the class consisting of ammonia and compounds r~leasing ammonia at a pH o~ between about 9 and 13. The pulp has a ~onsistency of between about 1 and 10% based on oven-dried *Trade Mark ~ - 7 -~ .
~ , .
~7~5~
.
pulp. The pulp has a pH within the range of between about 9 and 13. The treatment is carried out at a temperature between ut 200 and 260F at an oxygen pressuxe of between about 30 and 3000 psig.
As shown in the accompanying drawing~ shrinkage or reduction in yield varies with the concentrlation of ammonia in the process. As shown, the yield loss is minimized at a concentration of approxima~ely 0.6% ammonia. The data for the graph were obtained by employing the procedure of Example 1 hereinbelow.
. .. ... .
.
-......
- 7~a) -~.
: . . : . .: : . : : .
. : : . , , Detailed Description of the Invention In order to disclose more clearly the nature of the present invention, the following examples illustrating the invention are given. It should be understood, however, that this is done solely by way of example and is intended neither to delineate the scope of the invention nGr limit tile ambit of the appended claims~ In the examples which follow, and throughout the specification, the quantities of material are expressed in terms of parts by weight, unless otherwise ~pecified.
Kraft hardwood pulp was subjected to oxygen-alkali bleachiny, using various concentrations of urea. In the runs, the pulp consistency was approximately 2% by weight of oven-dried pulp. The alkaline delignification solution contained4 grams per liter vf sodium hydroxide. The delignification was carried out at a temperature of 205F. in a pressure reac-tor having intimately mixed with the alkaline pulp, oxygen at an initial pressure of 100 psig. That pressure was maintained for approximately 10 minutes fol~owed by venting to 36 psig.
pressure, followed by gradual reduction to æero psig. over a period of 42 minutes. The experiments were repeated at each concentration of urea for between 4 and 7 repetitions. The result~ are set forth in Tablo 1 below.
' ., . .: , .
:
~.
.
~7~5~
Table 1 Average Values . .
Kappa Viscosity Yield Number of Experiment Number cp, at 0.5% % on OD Pulp Runs Starting Pulp 19 .1 33 . 0 Control 11.0 23.0 95.3 6 0.5~ Urea 11.2 24.9 \` 96.7 5 1.0% Urea 10.8 25.9 96.2 4 2.0~ Urea 11.3 26.2 96.8 7
4.0% Urea 11.6 26.5 96.6 The experiment of Example 1 was repeated emp:Loying various concentrations of ammonia, based on weiyht of oven-dried pulp, in place of ~he urea. Six runs were conducted for each concentration of ammonia. The results are shown below in ~able ~ .
. ~ Table 2 -Average Values .
Kappa Viscosity Yieid Brightness Experiment ~umber cp, at G.5% % on OD Pulp ~, Elrepho Sta~ting Pulp 19.1 33.0 -- 26.3 Control 11.0 23.0 g5.3 45.2 .
: 0.3% Ammonia 10.5 26.3 96.7 46.8 ~ -0.6% Ammonia ll.Q 25.7 .97.0 , 4604 1~0% ~mmonia 10~5 26r3 96~7 46~1 . EXAMPLE 3 A pîlot plant run was conducted employing 0.6% ammo-nia in an oxygen-alkali system tr~ating hardwood dissolv:ing : pulp of a consistency~of 3% based on weight of ovlen-dried pulp~
The pilot plan-t run was conducted in two parts. In one part referred to as "Gonventional", the pulp, having a consistency of 3% based on oven-dried pulp, containing 1.8 grams per liter of sodium hydroxide, was mixed intimately with elemental oxygen to provide an initial pressure of 100 psig. and the pulp was maintained at a temperature oE 205F. for 10 minutes. Thereafter, the system was vented to 36 psig. pressure, the pressure was then gradually reduced to zero psig. over a period of 42 minutes. In the second portion of the pilot plant run conducted under what is referred to as "Split Flow" whereby the initial pulp consistency was 4.7% based on oven-dried pulp, containing 1.2 grams per liter of sodium hydroxide and the pulp treated at 230F. at an initial oxygen pressure of lQ0 psig. After 16 minutes the temperature was reduced to 205F., the consistency reduced to 3% by the addition of water, and the pressure reduced to 36 psig. and over 42 minutes the pressure was gradually reduced to ~ero psig. These pilot plant runs were conducted continuously for periods of 8 to 12 hours at the rate of 1 to 1.5 tons per day production of delignified pulp. The results are shown below in Table 3.
Table 3 Pilot Plant Trials Using Ammonia-Kraft Dissolving Pulp Average -Flow Permanganate Permanganate Viscosity-- Viscosity--Treatment No. -- StartNo. -- Final S-tart Final :
Split Flow Control 5.4 2.9 32.8 12.7 0.6% Ammonia 5.5 3.3 33.8 21.7 Conventional Control 6.6 4.1 33.4 13.1 0.6% ~mmonia 6.5 4.7 40.4 26.4 ., - . .. . :
~7q~56 As will be apparent to those skilled in the art from the present description, in the foregoing examples the ammonia and the a~ea may be replaced by appropriate amounts of other compounds releasing ammonia, such as ammonium chloride, carbonate, sulfite, nitrate or sulfate, sodium cyanate, hydra~
zine, cyar.uric acid, methylamide, hydroxylami.ne, sulfamic acid, and sodium or magnesium nitrides, etc.
The terms and expressions which have b~en employed are used as terms of description and not of limitation, and there is no intention in the use o such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifi-cations a~e possible within the scope of ~he invention claimed.
:; ~ . ' 1 1
. ~ Table 2 -Average Values .
Kappa Viscosity Yieid Brightness Experiment ~umber cp, at G.5% % on OD Pulp ~, Elrepho Sta~ting Pulp 19.1 33.0 -- 26.3 Control 11.0 23.0 g5.3 45.2 .
: 0.3% Ammonia 10.5 26.3 96.7 46.8 ~ -0.6% Ammonia ll.Q 25.7 .97.0 , 4604 1~0% ~mmonia 10~5 26r3 96~7 46~1 . EXAMPLE 3 A pîlot plant run was conducted employing 0.6% ammo-nia in an oxygen-alkali system tr~ating hardwood dissolv:ing : pulp of a consistency~of 3% based on weight of ovlen-dried pulp~
The pilot plan-t run was conducted in two parts. In one part referred to as "Gonventional", the pulp, having a consistency of 3% based on oven-dried pulp, containing 1.8 grams per liter of sodium hydroxide, was mixed intimately with elemental oxygen to provide an initial pressure of 100 psig. and the pulp was maintained at a temperature oE 205F. for 10 minutes. Thereafter, the system was vented to 36 psig. pressure, the pressure was then gradually reduced to zero psig. over a period of 42 minutes. In the second portion of the pilot plant run conducted under what is referred to as "Split Flow" whereby the initial pulp consistency was 4.7% based on oven-dried pulp, containing 1.2 grams per liter of sodium hydroxide and the pulp treated at 230F. at an initial oxygen pressure of lQ0 psig. After 16 minutes the temperature was reduced to 205F., the consistency reduced to 3% by the addition of water, and the pressure reduced to 36 psig. and over 42 minutes the pressure was gradually reduced to ~ero psig. These pilot plant runs were conducted continuously for periods of 8 to 12 hours at the rate of 1 to 1.5 tons per day production of delignified pulp. The results are shown below in Table 3.
Table 3 Pilot Plant Trials Using Ammonia-Kraft Dissolving Pulp Average -Flow Permanganate Permanganate Viscosity-- Viscosity--Treatment No. -- StartNo. -- Final S-tart Final :
Split Flow Control 5.4 2.9 32.8 12.7 0.6% Ammonia 5.5 3.3 33.8 21.7 Conventional Control 6.6 4.1 33.4 13.1 0.6% ~mmonia 6.5 4.7 40.4 26.4 ., - . .. . :
~7q~56 As will be apparent to those skilled in the art from the present description, in the foregoing examples the ammonia and the a~ea may be replaced by appropriate amounts of other compounds releasing ammonia, such as ammonium chloride, carbonate, sulfite, nitrate or sulfate, sodium cyanate, hydra~
zine, cyar.uric acid, methylamide, hydroxylami.ne, sulfamic acid, and sodium or magnesium nitrides, etc.
The terms and expressions which have b~en employed are used as terms of description and not of limitation, and there is no intention in the use o such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifi-cations a~e possible within the scope of ~he invention claimed.
:; ~ . ' 1 1
Claims (13)
1. An improved process for increasing the yields of wood pulp and improving the viscosity of the pulp during oxygen-alkali delignification, which comprises treating a pulp containing at least about 0.1% by weight of oven-dried pulp of a member selected from the class consisting of up to 3% of ammonia, and up to 6% of compounds releasing ammonia at a pH
of between about 9 and 13, said pulp having a consistency of between about 1 and 10% based on oven-dried pulp, said pulp having a pH within the range of between about 9 and 13, at a temperature between about 200 and 260°F. at an oxygen pressure of between about 30 and 300 psig.
of between about 9 and 13, said pulp having a consistency of between about 1 and 10% based on oven-dried pulp, said pulp having a pH within the range of between about 9 and 13, at a temperature between about 200 and 260°F. at an oxygen pressure of between about 30 and 300 psig.
2. An improved process according to Claim 1 wherein the amount of ammonia is between about 0.4 and 1% by weight of oven-dried pulp.
3. An improved process according to Claim 1 wherein the amount of compound releasing ammonia is between about 1 and 4% by weight of oven-dried pulp.
4. An improved process according to Claim 1, 2 or 3, wherein the temperature is between about 210 and 220°F.
5. An improved process according to Claim 1, 2 or 3 wherein the oxygen pressure is between about 120 and 130 psig.
6. An improved process according to Claim 1, 2 or 3 wherein the pulp consistency is between about 3 and 5% by weight of oven-dried pulp.
7. An improved process according to Claim 1, 2 or 3 wherein the pH is between about 11.5 and 12.5.
8. An improved process according to Claim 1, 2 or 3 wherein the oxygen-alkali delignification is conducted over a time interval of from about 1 to 120 minutes.
9. An improved process according to Claim 1, 2 or 3 wherein the oxygen-alkali delignification is conducted over a time interval of from about 20 to 40 minutes.
10. An improved process according to Claim 1, 2 or 3 wherein the pressure during the oxygen-alkali delignification is gradually reduced.
11. An improved process according to Claim 1, 2 or 3 wherein the oxygen is intimately dispersed and subdivided into the pulp by means of a high-shear agitator.
12. An improved process according to Claim 1 wherein the ammonia is present in an amount of about 0.6%.
13. An improved process according to Claim 1, 2 or 3 wherein a member selected from the class consisting of sodium and potassium hydroxides and carbonates is employed for the oxygen-alkali delignification.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/621,355 US4002526A (en) | 1975-10-10 | 1975-10-10 | Oxygen-alkali delignification of low consistency wood pulp |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070056A true CA1070056A (en) | 1980-01-22 |
Family
ID=24489828
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA238,381A Expired CA1070056A (en) | 1975-10-10 | 1975-10-27 | Process for oxygen alkali delignification of wood pulp |
Country Status (11)
| Country | Link |
|---|---|
| US (1) | US4002526A (en) |
| JP (1) | JPS6024875B2 (en) |
| AT (1) | AT349883B (en) |
| AU (1) | AU502921B2 (en) |
| BR (1) | BR7603292A (en) |
| CA (1) | CA1070056A (en) |
| FI (1) | FI65096C (en) |
| FR (1) | FR2327357A1 (en) |
| NO (1) | NO143752C (en) |
| SE (1) | SE436584B (en) |
| ZA (1) | ZA762574B (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI773597A (en) * | 1976-12-01 | 1978-06-02 | New Zealand Dev Finance | FOERFARANDE FOER BEHANDLING AV LIGNOCELLULOSA-ELLER CELLULOSAFIBERMASSA SAO ATT BEHANDLINGEN FRAEMJAR KROEKNING AV MASSANS FIBERS OCH FOERBAETTRAR PAPPRETS RIVHAOLLFASTHET |
| US4622100A (en) * | 1984-10-01 | 1986-11-11 | International Paper Company | Process for the delignification of lignocellulosic material with oxygen, ferricyanide, and a protector |
| AU7739794A (en) * | 1993-06-16 | 1995-01-03 | Hans-Peter Call | Multicomponent bleaching system |
| AU5558196A (en) * | 1995-04-20 | 1996-11-07 | R-J Holding Company | Pulping process |
| US20030150065A1 (en) * | 1998-12-30 | 2003-08-14 | Sheng-Hsin Hu | Liquid ammonia explosion treatment of wood fibers |
| WO2009138090A2 (en) * | 2008-05-14 | 2009-11-19 | Rådet For Agroindustri | A process for the production of hydrolysed plant material |
| EP2977511B1 (en) * | 2013-03-21 | 2020-02-12 | Japan Tobacco Inc. | Production method for black liquor and production method for liquid containing flavoring component |
| US11154087B2 (en) | 2016-02-02 | 2021-10-26 | R.J. Reynolds Tobacco Company | Method for preparing flavorful compounds isolated from black liquor and products incorporating the flavorful compounds |
Family Cites Families (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2071304A (en) * | 1934-12-04 | 1937-02-16 | Great Western Electro Chemical Co | Process of manufacture of products of ground wood pulp |
| US2271218A (en) * | 1937-08-31 | 1942-01-27 | Baudisch Friedrich | Method of decomposing maize straw for textile purposes |
| NL54060C (en) * | 1939-03-22 | 1942-10-15 | ||
| US2361639A (en) * | 1940-07-15 | 1944-10-31 | Henry A Wallace | Process for defibering lignocellulosic materials |
| US2372561A (en) * | 1941-06-19 | 1945-03-27 | Joseph C Elgin | Process of treating low rank textile fibers |
| US2394989A (en) * | 1942-03-11 | 1946-02-19 | Bonard Claude | Manufacture of cellulose |
| US3161562A (en) * | 1960-12-13 | 1964-12-15 | Champion Papers Inc | Pulping cellulose material with an alkaline cooking liquor containing hydrazine |
| US3308012A (en) * | 1963-08-19 | 1967-03-07 | Du Pont | Use of sulfamic acid in chlorination step of multistage bleaching process |
| US3368935A (en) * | 1964-10-12 | 1968-02-13 | Sonoco Products Co | Sulfite pulping process with urea |
| US3507743A (en) * | 1965-02-23 | 1970-04-21 | Fmc Corp | Bleaching of wood pulps with reductive bleaching agents and thiourea |
| US3274049A (en) * | 1965-02-25 | 1966-09-20 | Pullman Inc | Process for pulping bagasse with ammonium hydroxide and oxygen |
| US3401076A (en) * | 1965-08-12 | 1968-09-10 | Allied Chem | Increasing kraft pulp yield with hydroxylamine |
| CA752864A (en) * | 1965-10-12 | 1967-02-14 | Pulp And Paper Research Institute Of Canada | Extraction of fibrous cellulosic material with ammonia following treatment with chlorine, chlorine dioxide or other reagents |
| FR1531616A (en) * | 1967-05-24 | 1968-07-05 | Azote Office Nat Ind | Fast textile bleaching process |
| CA864409A (en) * | 1969-04-14 | 1971-02-23 | H. Andrews Douglas | Pulp bleaching process |
| ZA697269B (en) * | 1969-10-15 | 1971-04-28 | Air Liquide Sa Exploit Des Pro | Improvements in or relating to the delignification and bleaching of cellulose pulp with oxygen gas |
| GB1310835A (en) * | 1970-05-28 | 1973-03-21 | Pulp Paper Research Inst Of Ca | Treatment of chemical cellulosic pulp |
| US3740311A (en) * | 1971-05-24 | 1973-06-19 | Pulp Paper Res Inst | Delignification of cellulosic pulp with ammonia gas followed by heating in the presence of oxygen |
| FI52877B (en) * | 1972-11-16 | 1977-08-31 | Ahlstroem Oy | |
| US3832276A (en) * | 1973-03-07 | 1974-08-27 | Int Paper Co | Delignification and bleaching of a cellulose pulp slurry with oxygen |
-
1975
- 1975-10-10 US US05/621,355 patent/US4002526A/en not_active Expired - Lifetime
- 1975-10-27 CA CA238,381A patent/CA1070056A/en not_active Expired
-
1976
- 1976-02-19 SE SE7601934A patent/SE436584B/en unknown
- 1976-04-28 AU AU13413/76A patent/AU502921B2/en not_active Expired
- 1976-04-29 ZA ZA762574A patent/ZA762574B/en unknown
- 1976-05-25 BR BR7603292A patent/BR7603292A/en unknown
- 1976-05-26 FR FR7616069A patent/FR2327357A1/en not_active Withdrawn
- 1976-05-28 JP JP51062189A patent/JPS6024875B2/en not_active Expired
- 1976-05-28 NO NO761808A patent/NO143752C/en unknown
- 1976-05-28 FI FI761526A patent/FI65096C/en not_active IP Right Cessation
- 1976-05-31 AT AT398976A patent/AT349883B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| NO143752B (en) | 1980-12-29 |
| FI65096C (en) | 1984-03-12 |
| FI761526A (en) | 1977-04-11 |
| NO761808L (en) | 1977-04-13 |
| ZA762574B (en) | 1977-04-27 |
| JPS6024875B2 (en) | 1985-06-14 |
| AU502921B2 (en) | 1979-08-16 |
| AT349883B (en) | 1979-04-25 |
| US4002526A (en) | 1977-01-11 |
| FR2327357A1 (en) | 1977-05-06 |
| FI65096B (en) | 1983-11-30 |
| JPS5253004A (en) | 1977-04-28 |
| ATA398976A (en) | 1978-09-15 |
| SE7601934L (en) | 1977-04-11 |
| SE436584B (en) | 1985-01-07 |
| AU1341376A (en) | 1977-11-03 |
| BR7603292A (en) | 1977-05-24 |
| NO143752C (en) | 1981-04-08 |
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