WO1984004937A1 - A process for the chemical pulping of lignocellulosic material - Google Patents

A process for the chemical pulping of lignocellulosic material Download PDF

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Publication number
WO1984004937A1
WO1984004937A1 PCT/EP1983/000144 EP8300144W WO8404937A1 WO 1984004937 A1 WO1984004937 A1 WO 1984004937A1 EP 8300144 W EP8300144 W EP 8300144W WO 8404937 A1 WO8404937 A1 WO 8404937A1
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Prior art keywords
nitrate
aluminum
pulping
alkaline
parts
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PCT/EP1983/000144
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German (de)
French (fr)
Inventor
Eric S Prior
Original Assignee
Eric S Prior
Priority date (The priority date 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 date listed.)
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Publication date
Application filed by Eric S Prior filed Critical Eric S Prior
Priority to JP58502065A priority Critical patent/JPS60501509A/en
Priority to BR8307728A priority patent/BR8307728A/en
Priority to EP83901918A priority patent/EP0148815A1/en
Priority to PCT/EP1983/000144 priority patent/WO1984004937A1/en
Priority to AU16099/83A priority patent/AU1609983A/en
Publication of WO1984004937A1 publication Critical patent/WO1984004937A1/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
    • D21C3/222—Use of compounds accelerating the pulping processes

Definitions

  • This invention relates to an improved process for the chemical pulping of lignocellulosic material, particularly wood chips, but it is equally applicable to straw, bamboo, bagasse etc.
  • EP-A-12 775 discloses a process for the chemical pulping of lignocellulosic material utilizing an acidic nitrate cooking procedure in the presence of aluminum sulfate, or an alkaline nitrate cooking procedure in the absence of aluminum sulfate.
  • EP-A-22 881 and WO 81/00267 relate to a similar subject matter disclosing aluminum salts other than aluminum sulfate to be used in the acidic nitrate cooking procedure. In both latter publications the alkaline nitrate cooking procedure utilizing a pH of 11 to 13 is also carried out in the absence of an aluminum salt.
  • the invention relates to an improved process for the chemical pulping of lignocellulosic material, particularly wood chips, straw, bamboo and bagasse, wherein said lignocellulosic material is subjected to an alkaline nitrate cooking procedure at a pH of 11 to 13.5, preferably pH 12 to 13, which process is characterized in that the pulping is carried out in the presence of an aluminum salt, preferably aluminum sulfate.
  • the aluminum salt to be utilized in the present invention should be soluble in the pulping liquor.
  • Aluminum sulfate (alum) is preferred and the commercial products having varying amounts of crystal water (13 to 18 moles of waterper Al 2 (SO 4 ) 3 ) can readily be used.
  • Other suitable aluminum salts are reported in WO 81/00267 incorporated in by reference.
  • the pulping is carriedout in an alkaline nitrate solution at a pH of 11 to 13.5, preferably 12 to 13.
  • alkalis and / or earth alkalis can be used, such as caustic soda, potassium hydroxide, ammonium hydroxide and calcium hydroxide.
  • caustic soda is used. The necessary amount is determined by the above stated pH which is to be reached.
  • the nitrate ion concentration in the alkaline pulping liquor which is neccessary for achieving the intended ob ⁇ Ject is at least 0.05 percent, generally from 0.1 to 1.0 percent and preferably from 0.1 to 0.5 percent, each by weight of the total pulping liquor. It can be achieved by adding a suitable amount of either nitric acid or nitrate salts, such as sodium nitrate, potassium nitrate or ammonium nitrate to the alkaline pulping liquor.
  • the aluminum salt in particular alum, is preferably premixed with the nitric acid before the addition to the pulping liquor.
  • the aluminum salt can be added to the pulping liquor simultaneously with the nitric acid or immediately thereafter, e.g. within a few minutes, but premixing of the nitric acid with the aluminum salt is preferred.
  • alkali and nitrate source usually is determined by the rate of activity desired, cost, safety and choice of residual chemical ions. Normally the most practical for pulping for paper products will be a combination of NaOH and HNO 3 .
  • the amount of alum, as the preferred aluminum salt, used is for example 1 part by weight of alum per 10 parts by weight of ENT 3 (100%). In terms of aluminum concentration this means that about 0.08 parts by weight of aluminum and aluminum ions, respectively, are present for each 10 parts by weight of nitrate (NO 3 -).
  • the pre ferred rzane of aluminum is from 0.04 to 0.16, more preferably from 0.6 to 0.12 parts by weight of aluminum per each 10 parts by weight of NO 3 , a value of about 0.08 giving desirable results in the practice of the process of the invention.
  • the latter value of 0.08 parts by weight of aluminum, in terms of alum (Al 2 (SO 4 ) 3 x 18 H 2 O) corresponds to 1 part by weight of alum per 10 parts by weight of
  • the alkaline nitrate pulping process of the invention is carried out at temperatures of up to 100 ° C, preferably 85 to 100 ° C, specifically 95 to 99 ° C, e.g. 96 ° C for wood chips, without the appliance of pressure or vacuum being necessary, although pressure or vacuum can be applied for Special purposes, if desired. Pressure can be permitted but temperature should be held close to a maximum of 100 ° C. Higher temperatures want degrade pulp quality.
  • pulping time varies from a few minutes to a few hours, e.g. 15 minutes to 4 hours. Pulping time should be selected carefully to optimize subsequent defibration, i.e. pulp quality levels, energy input, and where necessary, as in printing paper pulps, minimal chemical action to maximize pulp brightness and opacity.
  • the process of the invention can be carried out in open vessels as one-step process providing a fiber yield of 85 - 90% of the woody material treated.
  • the process of the present invention provides a high quality pulp in the above mentioned high yield having a high tear and high bursting strength, in particular as shown in the following comparison in regard to the economic and strength benefits of the pulp product of this pulping system expressed in the following table by fiber length fractionation, energy requirement and yield percentage.
  • the present invention has the advantage of reducing pollution problems to a minimum since the formation of gases or odors which affect the environment can be avoided or, even if produced, can be easily controlled and eliminated.
  • the residual pulping liquor can be recycled and made up again to strength with the necessary amounts of the three necessary chemicals (alkali, nitrate and aluminum). After having recycled it 25 times the liquor can be either neutralized and discarded as an effluent (eg into thebiologically treated sewage system) or used again, after concentration, in the paper making process as additive to the fiber furnish or burned as in the conventional kraft pulping system.
  • the material to be pulped can be passed through an initial impregnation step in water, if desired, at a temperature of 100 ° C or nearly 100 ° C, or more expeditiously with steam.
  • the impregnation time can vary from 15 minutes up to
  • 3 hours preferably it ranges from 0.5 to 1.5 hours.
  • the alkaline pulping liquor alone to the material to be pulped after carrying out the impregnation step (if any) with hot water.
  • the aluminum salt / nitric acid mixture should then be added immediately or shortly following, eg, within 1 to 2 minutes.
  • Spruce wood chips in the amount of 1300 g A.D., equivalent to 1000 g B.D., are immersed in a pulping solution of 5000 ml and held at 100 ° C in a non-pressure container for 4 hours.
  • the pulping liquor is made up as follows:

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Abstract

A process for the chemical pulping of lignocellulosic material, wherein said lignocellulosic material is subjected to an alkaline nitrate cooking procedure at a pH of 11 to 13,5 in the presence of an aluminium salt.

Description

D e s c r i p t i o n D e s c r i p t i o n
------------------------------------------------------------------------------------------------------------------------------------------------------------------ -------------------------------------------------- ------------
A Process for the Chemical Pulping ofA Process for the Chemical Pulping of
Lignocellulosic Material -----------------------------------------------------------------------------------------------------------Lignocellulosic material ------------------------------------------------ -------------------------------------------------- ---------
This invention relates to an improved process for the chemical pulping of lignocellulosic material, particularly wood chips, but it is equally applicable to straw, bamboo, bagasse etc.This invention relates to an improved process for the chemical pulping of lignocellulosic material, particularly wood chips, but it is equally applicable to straw, bamboo, bagasse etc.
EP-A-12 775 discloses a process for the chemical pulping of lignocellulosic material utilizing an acidic nitrate cooking procedure in the presence of aluminum sulfate, or an alkaline nitrate cooking procedure in the absence of aluminum sulfate. EP-A-22 881 and WO 81/00267 relate to a similar subject matter disclosing aluminum salts other than alumi¬num sulfate to be used in the acidic nitrate cooking procedure. In both latter publications the alkaline nitrate cooking procedure utilizing a pH of 11 to 13 is also carried out in the absence of an aluminum salt. From US-A-1,717,798 a process for the chemical pulping of lignocellulosic material is known, wherein cooking with a neutral pH alkali nitrate solution i s used. The cooking is accomplished with pressures of about 6 to 8 bar and at temperatures of about 150°C for a at Least 2 hours followed by draining andsevera a cold solution of chemical leached from the cookin
Figure imgf000003_0001
g It has now been found that the alkaline nitrate cooking process can be accelerated and provides a fully defibered chemical type pulp if it is carried out in the presence of an aluminum salt, such as aluminum sulfate.EP-A-12 775 discloses a process for the chemical pulping of lignocellulosic material utilizing an acidic nitrate cooking procedure in the presence of aluminum sulfate, or an alkaline nitrate cooking procedure in the absence of aluminum sulfate. EP-A-22 881 and WO 81/00267 relate to a similar subject matter disclosing aluminum salts other than aluminum sulfate to be used in the acidic nitrate cooking procedure. In both latter publications the alkaline nitrate cooking procedure utilizing a pH of 11 to 13 is also carried out in the absence of an aluminum salt. From US-A-1,717,798 a process for the chemical pulping of lignocellulosic material is known, wherein cooking with a neutral pH alkali nitrate solution is used. The cooking is accomplished with pressures of about 6 to 8 bar and at temperatures of about 150 ° C for a at Least 2 hours followed by draining andsevera a cold solution of chemical leached from the cookin
Figure imgf000003_0001
G It has now been found that the alkaline nitrate cooking process can be accelerated and provides a fully defibered chemical type pulp if it is carried out in the presence of an aluminum salt, such as aluminum sulfate.
Accordingly, the invention relates to an improved process for the chemical pulping of lignocellulosic material, particularly wood chips, straw, bamboo and bagasse, wherein said lignocellulosic material is subjected to an alkaline nitrate cooking procedure at a pH of 11 to 13,5, preferably pH 12 to 13, which process is characterized in that the pulping is carried out in the presence of an aluminum salt, preferably aluminum sulfate.Accordingly, the invention relates to an improved process for the chemical pulping of lignocellulosic material, particularly wood chips, straw, bamboo and bagasse, wherein said lignocellulosic material is subjected to an alkaline nitrate cooking procedure at a pH of 11 to 13.5, preferably pH 12 to 13, which process is characterized in that the pulping is carried out in the presence of an aluminum salt, preferably aluminum sulfate.
The aluminum salt to be utilized in the present invention should be soluble in the pulping liquor. Aluminum sulfate (alum) is preferred and the commercial products having varying amounts of crystal water (13 to 18 moles of waterper Al2(SO4)3 ) can readily be used. Other suitable aluminum salts are reported in WO 81/00267 incorporated herein by reference.The aluminum salt to be utilized in the present invention should be soluble in the pulping liquor. Aluminum sulfate (alum) is preferred and the commercial products having varying amounts of crystal water (13 to 18 moles of waterper Al 2 (SO 4 ) 3 ) can readily be used. Other suitable aluminum salts are reported in WO 81/00267 incorporated in by reference.
With the process of the invention the pulping is carriedout in an alkaline nitrate solution at a pH of 11 to 13,5 , preferably 12 to 13. To reach the basic pH as mentioned above, usual and normally available alkalis and/or earth alkalis can be used, such as caustic soda, potassium hydroxide, ammonium hydroxide and calcium hydroxide. Preferably caustic soda is used. The necessary amount is determined by the above stated pH which is to be reached.With the process of the invention the pulping is carriedout in an alkaline nitrate solution at a pH of 11 to 13.5, preferably 12 to 13. To reach the basic pH as mentioned above, usual and normally available alkalis and / or earth alkalis can be used, such as caustic soda, potassium hydroxide, ammonium hydroxide and calcium hydroxide. Preferably caustic soda is used. The necessary amount is determined by the above stated pH which is to be reached.
The nitrate ion concentration in the alkaline pulping liquor which is neccessary for achieving the intended ob¬Ject is at least 0.05 percent, generally from 0.1 to 1.0 percent and preferably from 0.1 to 0.5 percent, each by weight of the total pulping liquor. It can be achieved by adding a suitable amount of either nitric acid or nitrate salts, such as sodium nitrate, potassium nitrate or ammonium nitrate to the alkaline pulping liquor.The nitrate ion concentration in the alkaline pulping liquor which is neccessary for achieving the intended ob¬Ject is at least 0.05 percent, generally from 0.1 to 1.0 percent and preferably from 0.1 to 0.5 percent, each by weight of the total pulping liquor. It can be achieved by adding a suitable amount of either nitric acid or nitrate salts, such as sodium nitrate, potassium nitrate or ammonium nitrate to the alkaline pulping liquor.
It is preferred to provide the above stated nitrate ion concentration by the addition of the respective amount of nitric acid to the alkaline pulping liquor. In this case, the aluminum salt, in particular alum, is preferably premixed with the nitric acid before the addition to the pulping liquor. Alternatively, the aluminum salt can be added to the pulping liquor simultaneously with the nitric acid or immediately thereafter, e.g. within a few minutes, but premixing of the nitric acid with the aluminum salt is preferred.It is preferred to provide the above stated nitrate ion concentration by the addition of the respective amount of nitric acid to the alkaline pulping liquor. In this case, the aluminum salt, in particular alum, is preferably premixed with the nitric acid before the addition to the pulping liquor. Alternatively, the aluminum salt can be added to the pulping liquor simultaneously with the nitric acid or immediately thereafter, e.g. within a few minutes, but premixing of the nitric acid with the aluminum salt is preferred.
The choice of alkali and nitrate source usually is determined by the rate of activity desired, cost, safety and choice of residual chemical ions. Normally the most practical for pulping for paper products will be a combination of NaOH and HNO3.The choice of alkali and nitrate source usually is determined by the rate of activity desired, cost, safety and choice of residual chemical ions. Normally the most practical for pulping for paper products will be a combination of NaOH and HNO 3 .
For obtaining practically desirable results, the amount of alum, as the preferred aluminum salt, used is for example 1 part by weight of alum per 10 parts by weight of HNO3 (100 %). In terms of aluminum concentration this means that about 0.08 parts by weight of aluminum and aluminum ions, respectively, are present for each 10 parts by weight of nitrate (NO3-) .For obtaining practically desirable results, the amount of alum, as the preferred aluminum salt, used is for example 1 part by weight of alum per 10 parts by weight of ENT 3 (100%). In terms of aluminum concentration this means that about 0.08 parts by weight of aluminum and aluminum ions, respectively, are present for each 10 parts by weight of nitrate (NO 3 -).
While it has been noted that there is a minimum amount of aluminum to achieve a remarkable effect, e.g. 0.01 , 0.02 , 0.03 or 0.04 parts by weight of aluminum per each 10 parts of NO3-, there is actually no strict upper limit, and the aluminum concentration could go far beyond 0.08, for example up to 0.10, 0.15, 0.2, or even more each per 10 parts of NO3-. It has been found, however, that with exceeding a certain aluminum level no further advantage as to time reduction is obtained so that higher amounts are not desirable under economic and environmental pollution point of views. Also, sometimes with a very high aluminum concentration the quality of the end product is affected. Thus, the pre ferred ränge of aluminum is from 0.04 to 0.16, more preferably from 0.6 to 0.12 parts by weight of aluminum per each 10 parts by weight of NO3 , a value of about 0.08 giving desirable results in the practice of the process of the invention. The latter value of 0.08 parts by weight of aluminum, in terms of alum (Al2(SO4)3 x 18 H2O) corresponds to 1 part by weight of alum per 10 parts by weight ofWhile it has been noted that there is a minimum amount of aluminum to achieve a remarkable effect, eg 0.01, 0.02, 0.03 or 0.04 parts by weight of aluminum per each 10 parts of NO 3 -, there is actually no strict upper limit, and the aluminum concentration could go far beyond 0.08, for example up to 0.10, 0.15, 0.2, or even more each per 10 parts of NO 3 -. It has been found, however, that with exceeding a certain aluminum level no further advantage as to time reduction is obtained so that higher amounts are not desirable under economic and environmental pollution point of views. Also, sometimes with a very high aluminum concentration the quality of the end product is affected. Thus, the pre ferred ränge of aluminum is from 0.04 to 0.16, more preferably from 0.6 to 0.12 parts by weight of aluminum per each 10 parts by weight of NO 3 , a value of about 0.08 giving desirable results in the practice of the process of the invention. The latter value of 0.08 parts by weight of aluminum, in terms of alum (Al 2 (SO 4 ) 3 x 18 H 2 O) corresponds to 1 part by weight of alum per 10 parts by weight of
'nitrate.'nitrates.
The alkaline nitrate pulping process of the invention, depending on the lignocellulosic material to be pulped and the planned end use, is carried out at temperatures of up to 100°C, preferably 85 to 100°C, specifically 95 to 99°C, e.g. 96°C for wood Chips, without the appliance of pressure or vacuum being necessary, although pressure or vacuum can be applied for Special purposes, if desired. Pressure can be permitted but temperature should be held close to a maximum of 100°C. Higher temperatures will degrade pulp quality. Depending on the type of fiber to be pulped and the planned end use, pulping time varies from a few minutes to a few hours, e.g. 15 minutes to 4 hours. Pulping time should be selected carefully to optimize subsequent defibration, i.e. pulp quality levels, energy input, and where necessary, as in printing paper pulps, minimal chemical action to maximize pulp brightness and opacity.The alkaline nitrate pulping process of the invention, depending on the lignocellulosic material to be pulped and the planned end use, is carried out at temperatures of up to 100 ° C, preferably 85 to 100 ° C, specifically 95 to 99 ° C, e.g. 96 ° C for wood chips, without the appliance of pressure or vacuum being necessary, although pressure or vacuum can be applied for Special purposes, if desired. Pressure can be permitted but temperature should be held close to a maximum of 100 ° C. Higher temperatures want degrade pulp quality. Depending on the type of fiber to be pulped and the planned end use, pulping time varies from a few minutes to a few hours, e.g. 15 minutes to 4 hours. Pulping time should be selected carefully to optimize subsequent defibration, i.e. pulp quality levels, energy input, and where necessary, as in printing paper pulps, minimal chemical action to maximize pulp brightness and opacity.
The process of the invention can be carried out in open vessels as one-step process providing a fiber yield of 85 - 90% of the woody material treated.The process of the invention can be carried out in open vessels as one-step process providing a fiber yield of 85 - 90% of the woody material treated.
The process of the present invention provides a high quality pulp in the above mentioned high yield having a high tear and high bursting strength, in particular as shown in the following comparison in regard to the economic and strength benefits of the pulp product of this pulping system expressed in the following table by fiber length fractionation, energy requirement and yield percentage. U.S.Southern Spruce Spruce Pine Thermo- InvenKraft Process mechanical tion Pulp Pulp PulpThe process of the present invention provides a high quality pulp in the above mentioned high yield having a high tear and high bursting strength, in particular as shown in the following comparison in regard to the economic and strength benefits of the pulp product of this pulping system expressed in the following table by fiber length fractionation, energy requirement and yield percentage. USSouthern Spruce Spruce Pine Thermo-InvenKraft Process mechanical tion Pulp Pulp Pulp
1. Fiber Fraction (McNett) Screw R 14 - Long Figer 74.1 % 5.0-7.0 % 65,58 % " R 30 - Medium Fiber 11.5 24.0-27.0 13,621. Fiber Fraction (McNett) Screw R 14 - Long Figer 74.1% 5.0-7.0% 65.58% "R 30 - Medium Fiber 11.5 24.0-27.0 13.62
2. Energy H.P. Days/Ton 10 130 302. Energy H.P. Days / Ton 10 130 30
3. Yield 55-65 % 90-92 % 91 %3. Yield 55-65% 90-92% 91%
In addition, the present invention has the advantage of reducing pollution problems to a minimum since the formation of gases or odors which affect the environment can be avoided or, even if produced, can be easily controlled and eliminated. The residual pulping liquor can be recycled and made up again to strength with the necessary amounts of the three necessary chemicals (alkali, nitrate and aluminum). After having recycled it 25 times the liquor can be either neutralized and discarded as an effluent (e.g. into thebiologically treated sewage system) or used again, after concentration, in the paper making process as additive to the fiber furnish or burned as in the conventional kraft pulping system. According to the process of the invention the material to be pulped can be passed through an initial impregnation step in water, if desired, at a temperature of 100°C or nearly 100°C, or more expeditiously with steam. Depending on the fibrous material to be pulped and the intended end use, the impregnation time can vary from 15 minutes up toIn addition, the present invention has the advantage of reducing pollution problems to a minimum since the formation of gases or odors which affect the environment can be avoided or, even if produced, can be easily controlled and eliminated. The residual pulping liquor can be recycled and made up again to strength with the necessary amounts of the three necessary chemicals (alkali, nitrate and aluminum). After having recycled it 25 times the liquor can be either neutralized and discarded as an effluent (eg into thebiologically treated sewage system) or used again, after concentration, in the paper making process as additive to the fiber furnish or burned as in the conventional kraft pulping system. According to the process of the invention the material to be pulped can be passed through an initial impregnation step in water, if desired, at a temperature of 100 ° C or nearly 100 ° C, or more expeditiously with steam. Depending on the fibrous material to be pulped and the intended end use, the impregnation time can vary from 15 minutes up to
3 hours, preferably it ranges from 0.5 to 1.5 hours.3 hours, preferably it ranges from 0.5 to 1.5 hours.
With the process of the invention it is preferred to add the alkaline pulping liquor alone to the material to be pulped after carrying out the impregnation step (if any) with hot water. The aluminum salt/nitric acid mixture should then be added immediately or shortly following, e.g., within 1 to 2 minutes.With the process of the invention it is preferred to add the alkaline pulping liquor alone to the material to be pulped after carrying out the impregnation step (if any) with hot water. The aluminum salt / nitric acid mixture should then be added immediately or shortly following, eg, within 1 to 2 minutes.
Taking specifically the use of U.S. Southern Pine pulping, for example, takes place at an alkali concentration star¬ting at 2.88 % and ending at 2.08 %, each calculated as NaOH, with a starting nitrate ion concentration of 0.3 % and an aluminum sulfate concentration of 0.02 % (0.67 parts by weight of alum per 10 parts by weight of nitrate), each by weight of pulping liquor, which is a typical formulationfor most fibrous structures to be pulped. Preimpregnation with hot water or steam and time period of cooking are the main variables in effecting ease of defibering. The following example further illustrates the invention.Taking specifically the use of U.S. Southern Pine pulping, for example, takes place at an alkali concentration star¬ting at 2.88% and ending at 2.08%, each calculated as NaOH, with a starting nitrate ion concentration of 0.3% and an aluminum sulfate concentration of 0.02% (0.67 parts by weight of alum per 10 parts by weight of nitrate), each by weight of pulping liquor, which is a typical formulation for most fibrous structures to be pulped. Preimpregnation with hot water or steam and time period of cooking are the main variables in effecting ease of defibering. The following example further illustrates the invention.
E x a m p l eE x a m p l e
Spruce wood chips in the amount of 1300 g A.D., equivalent to 1000 g B.D., are immersed in a pulping solution of 5000 ml and held at 100°C in a non-pressure Container for 4 hours.Spruce wood chips in the amount of 1300 g A.D., equivalent to 1000 g B.D., are immersed in a pulping solution of 5000 ml and held at 100 ° C in a non-pressure container for 4 hours.
The pulping liquor is made up as follows:The pulping liquor is made up as follows:
NaOH, 50 % 150 mlNaOH, 50% 150 ml
HNO3, 50 % (containingENT 3 , 50% (containing
1 g alum per 10 parts of1 g alum per 10 parts of
HNO3 (100 %) ) 15 mlHNO 3 (100%)) 15 ml
Water, added to 5000 mlWater, added to 5000 ml
After the end of the pulping period the black liquor is drained from the Chips and recycled. The obtained fiber is soft, very light in color and shows a relatively low percentage of delignification. The yield is 89 %. Test results on defibered, screened pulp (hand sheet) were as follows: TestAfter the end of the pulping period the black liquor is drained from the chips and recycled. The obtained fiber is soft, very light in color and shows a relatively low percentage of delignification. The yield is 89%. Test results on defibered, screened pulp (hand sheet) were as follows: test
Basis weight, g/m2 117.5 132 122.5 121Basis weight, g / m 2 117.5 132 122.5 121
Schopper Riegler, degree 40 36 34 43Apparent Density, g/cm3 0.522 0.530 0.506 0.519Schopper Riegler, degree 40 36 34 43 Apparent Density, g / cm 3 0.522 0.530 0.506 0.519
Burst, kPa 431 451 416 416Burst, kPa 431 451 416 416
Elmendorf Tear, mN 1815 2266 1844 1972Elmendorf Tear, mN 1815 2266 1844 1972
Tensile, m 5149 4090 4707 5124Tensile, m 5149 4090 4707 5124
Elongation, % 2.2 2.7 2.3 2.3Elongation,% 2.2 2.7 2.3 2.3
Ring Crush, kN/m;Ring crush, kN / m;
1.10 1.23 1.27 1.29
Figure imgf000009_0001
1.10 1.23 1.27 1.29
Figure imgf000009_0001

Claims

C L A I M S
1. A process for the chemical pulping of lignocellulosic material, wherein said lignocellulosic material is subjected to an alkaline nitrate cooking procedure at a pH of 11 to 13,5 , c h a r a c t e r i z e d i n that the pulping is carried out in the presence of an aluminum salt.1. A process for the chemical pulping of lignocellulosic material, wherein said lignocellulosic material is subjected to an alkaline nitrate cooking procedure at a pH of 11 to 13.5, c h a r a c t e r i z e d i n that the pulping is carried out in the presence of an aluminum salt.
2. The process of claim 1 characterized in that said aluminum salt is aluminum sulfate.2. The process of claim 1 characterized in that said aluminum salt is aluminum sulfate.
3. The process of claim 1 or 2 characterized in that said alkaline nitrate pulping liquor has a nitrate ion concentration from 0.1 to 1 percent, preferably 0.1 to 0.5 percent, each based on the weight of the total pulping liquor.3. The process of claim 1 or 2 characterized in that said alkaline nitrate pulping liquor has a nitrate ion concentration from 0.1 to 1 percent, preferably 0.1 to 0.5 percent, each based on the weight of the total pulping liquor.
4. The process according to any of Claims 1 to 3 characterized in that said aluminum salt is present in an amount: from 0.04 to 0.16 parts by weight of aluminum per each 10 parts of nitrate. 4. The process according to any of Claims 1 to 3 characterized in that said aluminum salt is present in an amount: from 0.04 to 0.16 parts by weight of aluminum per each 10 parts of nitrate.
5. The process of claim 4 characterized in that said aluminum salt is present in an amount from 0.06 to 0.12 parts by weight of aluminum per each 10 parts of nitrate.5. The process of claim 4 characterized in that said aluminum salt is present in an amount from 0.06 to 0.12 parts by weight of aluminum per each 10 parts of nitrate.
6. The process of any of Claims 1 to 5 characterized in that said nitrate is provided by the addition of nitric acid to said alkaline pulping liquor.6. The process of any of Claims 1 to 5 characterized in that said nitrate is provided by the addition of nitric acid to said alkaline pulping liquor.
7. The process of Claims 2 and 6 characterized in that aluminum sulfate and nitric acid are added simultaneously or shortly one after another to said alkaline pulping liquor.7. The process of Claims 2 and 6 characterized in that aluminum sulfate and nitric acid are added simultaneously or shortly one after another to said alkaline pulping liquor.
8. The process of claim 7 characterized in that said aluminum sulfate and nitric acid are premixed before being added to the pulping liquor.8. The process of claim 7 characterized in that said aluminum sulfate and nitric acid are premixed before being added to the pulping liquor.
9. The process of any of Claims 1 to 8 characterized in that said alkaline pH is provided by caustic soda.9. The process of any of Claims 1 to 8 characterized in that said alkaline pH is provided by caustic soda.
10. The process of any of Claims 1 to 9 characterized by applying temperatures from 95 to 99°C. 10. The process of any of Claims 1 to 9 characterized by applying temperatures from 95 to 99 ° C.
PCT/EP1983/000144 1983-06-06 1983-06-06 A process for the chemical pulping of lignocellulosic material WO1984004937A1 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
JP58502065A JPS60501509A (en) 1983-06-06 1983-06-06 Chemical pulping method for lignocellulosic materials
BR8307728A BR8307728A (en) 1983-06-06 1983-06-06 A PROCESS FOR CHEMICAL REDUCTION OF LIGNOCELLULOSIC MATERIAL PULP
EP83901918A EP0148815A1 (en) 1983-06-06 1983-06-06 A process for the chemical pulping of lignocellulosic material
PCT/EP1983/000144 WO1984004937A1 (en) 1983-06-06 1983-06-06 A process for the chemical pulping of lignocellulosic material
AU16099/83A AU1609983A (en) 1983-06-06 1983-06-06 A process for the chemical pulping of lignocellulosic material

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PCT/EP1983/000144 WO1984004937A1 (en) 1983-06-06 1983-06-06 A process for the chemical pulping of lignocellulosic material
AU16099/83A AU1609983A (en) 1983-06-06 1983-06-06 A process for the chemical pulping of lignocellulosic material

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE410824C (en) * 1923-03-07 1925-03-10 Richard Wolffenstein Dr Process for the preparation of pulp from wood and lignified materials
FR2333892A1 (en) * 1975-12-04 1977-07-01 Vaugue Armand Cellulose extraction from vegetable prods. - by delignification with sodium hydroxide soln. contg. e.g. aluminium sulphate
EP0022881A1 (en) * 1979-07-19 1981-01-28 Eric S. Prior Accelerated pulping process
GB2076034A (en) * 1980-05-16 1981-11-25 Natural Fibres Uk Ltd Process for treating lignocellulosic material

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE410824C (en) * 1923-03-07 1925-03-10 Richard Wolffenstein Dr Process for the preparation of pulp from wood and lignified materials
FR2333892A1 (en) * 1975-12-04 1977-07-01 Vaugue Armand Cellulose extraction from vegetable prods. - by delignification with sodium hydroxide soln. contg. e.g. aluminium sulphate
EP0022881A1 (en) * 1979-07-19 1981-01-28 Eric S. Prior Accelerated pulping process
GB2076034A (en) * 1980-05-16 1981-11-25 Natural Fibres Uk Ltd Process for treating lignocellulosic material

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AU1609983A (en) 1985-01-04
EP0148815A1 (en) 1985-07-24

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