CA2090338A1 - Process for treatment of lignocellulosic pulp and apparatus for performance of the process - Google Patents
Process for treatment of lignocellulosic pulp and apparatus for performance of the processInfo
- Publication number
- CA2090338A1 CA2090338A1 CA002090338A CA2090338A CA2090338A1 CA 2090338 A1 CA2090338 A1 CA 2090338A1 CA 002090338 A CA002090338 A CA 002090338A CA 2090338 A CA2090338 A CA 2090338A CA 2090338 A1 CA2090338 A1 CA 2090338A1
- Authority
- CA
- Canada
- Prior art keywords
- washing
- treatment
- enzyme
- pulp
- stock
- 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.)
- Abandoned
Links
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
- D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
- D21C5/005—Treatment of cellulose-containing material with microorganisms or enzymes
-
- 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
- D21C9/02—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Biochemistry (AREA)
- Microbiology (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
- Chemical And Physical Treatments For Wood And The Like (AREA)
Abstract
A process for treatment of lignocellulosic pulp comprising a multistage washing of the unbleached kraft brown stock and a xylanase treatment. The xylanase treatment is carried out in a holding tank introduced upstream the first washing unit or downstream one or more of the other washing units except for the last washing unit.
Description
~ 92/03608 2 ~ 9 0 3 3 8 PCI/DK91/OU239 PROCESS FOR TREATMENT OF UGNOCELLULOSIC PULP
AND APPARATUS FOR PERFORMANCE OF THE PROCESS
~.
A common stage in the treatment of wood chips for paper production is chemical pulping, e.g. the so-called kraft process which is an alkaline sulphate 5 cooking of the wood chips. The native wood chips contain around 30% lignin, -and at the end of the chemical cooking process less than 5% of the lignin compounds is still left in the pulp. Due to the strong brown color of the remaining lignin and its tendency to darken in UV light or by oxidation this has to be removed in order to obtain a white pulp without the tendency to color reversion.10 After the sulphate cooking a multistage washing of the unbleached kraft brownstock takes place. The well washed brown stock can then be treated with an enzyme preparation followed by a subsequent wash before entering the bleach plant.
The invention comprises an improvement of this conventional 15 multistage washing of the unbleached kraft brown stock, followed by the enzyme treatment with the subsequent wash, whereby this improvement is a modification, which improves the economy and facilitates the processing.
i ~ After a multistage washing of the unbleached kraft brown stock followed by an enzyme treatment with the subsequent wash the brown color can 20 be removed by a multistage bleaching using e.g. chlorine and/or chlorine dioxide.
Due to the ever increasing environmental concern, the dosage of chlorine and/or chlorine dioxide has to be kept at a minimum, and it is for that reason that theenzymatic treatment of the kraft cooked pulp has been introduced, vide e.g. The third InteMational Conference on Biotechnology in the Pulp and Paper Industry, 2s Stockholm, 16~-19.6, 1986, page 67-69.
Thus, the sequence of the prior art processes in regard to paper - .
pulping is the following:
1) kraft cooking of the wood chips, : -2) multistage washing of the unbleached kraft brown stock 30 3) ~ enzymatic treatment of the washed brown stock - 4) bleaching.
: . .
.
WO 92/03608 PCr/DK9l/00239 2 ~ 3 8 2 The invention comprises the above indicated processes 2) and 3) and is an improvement thereof, as explained in more detail in the following.
Hitherto the multistage washing of the unbleached kraft brown stock . has been performed as indicated on the flow sheet of Fig. 1. In addition to the 5 process stages indicated on Fig. 1 an oxygen delignification stage with subsequent washing may be included either before or after the enzyme stage.
This prior art process with an enzyme treatment introduced between the cooking and the bleaching sections has some serious drawbacks, e.g. (1) the enzyme stage includes a washing stage, which is a unit operation that represents a large 10 capital investrnent, and (2) pH adjustment of the pulp may be needed if enzymes with acid pH optimum are used.
Thus, the purpose of the invention is the provision of a process for treatment of lignocellulosic pulp which requires a less expensive apparatus or stated otherwise the provision of a reduction of the price of the prior art method 15 for treatment of lignocellulosic pulp comprising a multistage washing of the unbleached brown kraft stock with subsequent enzyme treatment, washing and bleaching, and a corresponding apparatus for performance of the process.
Now, according to the invention it has been found that the purpose of the invention can be fulfilled, if the enzymatic treatment with the subsequent wash 20 is abandoned altogether and the enzymatic treatment is introduced after one or more of the single washing units in the multistage washings of the unbleached kraft brown stock, or stated otherwise if the enzyme treatment is introduced upstream the prior art position of the enzyme treatment in the multistage washing, in such manner that the multistage washing for washing out of impurities from the 25 kraft cooking and washing out of the residues from the enzyme treatment is combined.
Thus, the process for treatment of lignocellulosic pulp.according to the invention comprising a multistage washing of the unbleached kraft brown stock and a xylanase treatment is characterized by the fact that the xylanase 30 treatment is introduced upstream the prior art position of the xylanase treatment in such manner that the stock from the kraft cooking or the washed stock from the outlet side of one or more of the washing units is-transported to a holding .. .. . .. .. .. .. ... ...... ~ .. .. .~. . . . . . . .
92~113608 2 0 9 0 3 3 8 PCI/DK91/U0~39 tank, that a xylanase with high pH activity and stability and high heat stability is added directly upstream the holding tank, and that the enzyme treated stock is passed further on in the process to the next washing unit. Also in relation to the process according to the invention (Fig. 2) another non-chlorine bleaching stage, 5 e.g. an oxygen delignification stage or an ozone stage may be included either before or after the enzyme stage.
By comparison of Fig. 1 (prior art) and Fig. 2 (invention) it clearly appears that the invention requires one washing unit less than the prior art process, and thus, the process according to the invention fulfils the purpose of10 the invention. Furthermore, as the tank on Fig. 1 used for the enzyme treatment normally also serves as buffer tank between the kraft cooking and the bleaching plant the residence time of the pulp in the tank often varies within a wide range, e.g. between 30 minutes and 24 hours. In the invention the tank is an integratedpart of the washing process. It only serves the need for holding time for the 15 enzyme treatment, which makes it much easier to control the enzyme treatment time. Finally, the invention provides a much better connection to the existing wash water streams. The entire amount of wash water obtained in the process according to the invention will end up in the recovery system for the kraft cooking process, which means that everything that is solubilized during the enzyme 20 treatment will be burned in the recovery boiler whereby the BODs load from the enzyme stage on the effluent streams is eliminated. This is not the case in the prior art system. In the prior art system the wash water from the washing stage after the enzyme treatment normally has to be sewered. The enzyme treatment according to the invention also releases more cooking chemicals from the pulp 25 than a conventional wash with water. This makes it possible to obtain an even better recovery of cooking chemicals than normally obtained.
The three washing units on Fig. 2 are not limiting to the invention, but just an example. Each single unit can represent more than one washing stage.
With three washing units one, two or three enzyme treatment units can be 30 introduced according to the invention; just one enzyme treatment unit is shown on Fig. 2.
. ,' ', .. .1, ' ' ".' '`." ' ' ' ~ . . . ' ' ' ,'' ~`., . ;' .
'~ ', : , '. ,' . ' ' ' , ., . : ' .
WO 92/03608 PCI'/DK91/00239~, 2~338 ~
The xylanase with high pH activity and stability and with high heat stability, which is used in the process according to the invention, has to show a bleach boosting effect under the conditions present just prior to the last washing unit.
The bleach boosting effect is measured as the kappa number reduction of pulp after an enzyme treatment followed by a C/D-E bleaching compared to a control which is treated in the same way but without addition of . -enzyme: (Bleach boosting Effect = Kappa number after C/D-E bleaching of - :enzyme treated pulp minus kappa number after C/D-E bleaching of pulp treated 10 without enzyme).
Also, the invention comprises an apparatus for performance of the process according to the invention. The apparatus according to the invention is characterized by the fact that a holding tank with piping with facilities for introduction of enzyme is introduced upstream the first washing unit or 15 downstream one or more of the other washing units except for the last washingunit, that piping is provided for further transport of the stock to the next washing unit, and that the conventional enzyme treatment unit downstream the washing unit is abandoned.
It is to be understood that at least one holding tank with accessories 20 is introduced, and that the maximum number of holding tanks with accessories,which can be introduced into the sequence according to the invention equals the number of washing units in the multistage washing process. ~.
The following example illustrates the invention in comparison to prior art.
: ' 2s EXAMPLE 1 In order to illustrate the invention an unbleached and unwashed softwood pulp identified as P was washed in one stage as follows: ~-The pulp P was diluted with fresh water to a consistency of 1% DS
and then reconcentrated to a consistency of approximately 20% on a wire screen.
-92/03608 2 0 9 0 3 3 8 PCI /DK9l /00239 ' :
This washing sequence is the standard washing stage used throughout thisexample. After the washing the pH of the pulp was 9.7.
This pulp sample was divided into two halves.
The first half of this one stage washed pulp was xylanase treated under the following conditions without pH adjustment prior to the enzyme addition.
Temperature : 70C -pH : 9.7 Consistency : 10%
Time : 3 hours Xylanase : Streptomyces olivochromogenes, vide Example 6 in WO 91/02839 Enzyme dosage : 5000 EXU/kg dry pulp ; , ' ; . :
15 The definition of the EXU xylanase activity unit appears from AF
293.9/1, obtainable on request from NOVO NORDISK A/S, Novo Allé, DK-2880 Bagsvaerd, Denmark.
The xylanase stage was carried out as follows. The pulp was diluted to the desireq consistency by addition of fresh water. The enzyme solution was 20 added and mixed into the pulp by vigorous mixing. The pulp was then placed in -a water bath to ensure constant temperature for the remainder of the treatment time. The pulp was not mixed during the three hours of holding time.
After the enzyme stage the pulp was carried through two standard washing stages. This pulp sample which was enzyme treated between the first ~i ~ 25 and the second washing stage, was carried out according to the invention and will be referred to later as inv 1-2 The second half of the one stage washed pulp was carried through another standard washing stage. After washing the pH of the pulp suspension was 8.7.
WO 92/03608 PC~/DK91/00239 2 ~ ;) 8 6 This two stage washed pulp was enzyme treated without pH
adjustment prior to the enzyme addition under the following conditions:
Temperature : 70C
pH : 8.7 Consistency : 10%
Time : 3 hours Enzyme : Streptomyces olivochromogenes, vide -- Example 6 in WO 91/02839 Enzyme dosage : 2000 EXU/kg dry pulp The enzyme treatment was carried out as described above.
After the enzyme stage the pulp was carried through one standard washing stage. This sample of pulp, which was enzyme treated between the second and third washing stage, was carried out according to the invention and will be referred to later as inv 2-3.
In order to illustrate the corresponding prior art the pulp P was first carried through three standard washing stages. Then the pH of the pulp was owered to 6.5 by addition of sulfuric acid and an enzyme stage was carried out under~the following conditions.
Temperature : 50"C
20 pH : 6.5 Consistency : 10%
Time : 3 hours Enzyme : PulpzymerMHA
Enzyme dosage : 275 FXU/kg dry pulp , .
The definition of FXU xylanase activity unit appears from AF 293.6/1, obtainable on request from NOVO NORDISK A/S, Novo Allé, DK-2880 Bagsvaerd, :
Denmark.
The enzyme treatment was made as described above.
~ .
~ 92/03608 2 0 9 0 3 3 8 PCr/DK91/00239 , .
After the enzyme stage the pulp was washed in an extra standard washing stage according to the prior art. This pulp sample will be referred to later as prior.
The above experiment used to illustrate prior art was repeated except 5 that no enzyme was added. This experiment served as a control to demonstrate that the enzyme stage really has an effect on the pulp and will be referred to later as control.
The xylanases used in this example were selected according to their .
pH optimum in relation to the pH of the pulp.
After enzyme treatments and washings all the pulps were bleached according to the same two stage bleaching sequence (D50 C50) E.
The bleachings were carried out under the following conditions:
(D50 C50):
Temperature : 50C
Consistency : 5%
Time : 20 minutes active Cl dosage : 5.7% (w/w) on dry pulp E: :~
Temperature : 60C
Consistency : 10%
rlme : 1 hour NaOH dosage : 4.2% (w/w) on dry pulp ~ .
; After the bleaching the kappa number of all four pulps were determined.
. ' :~
WO 92/03608 PCl-/DK91/00239 2~903~8 8 Results Kappa number of the pulps after the (D50 C50) E bleachings:
Kappa numberdelta Kappa number %
5 Control 2.85 Prior 2.52 11.6 inv 1-2 2.50 12.3 inv 2-3 2.31 19.0 ~. '.
It is observed that the kappa number of the enzyme treated pulps are 10 reduced compared to the control. This demonstrates that the enzyme treatment in all three sequences, the prior art and the two inventive sequences, has showna bleach boosting èffect.
It is also seen that the kappa numbers obtained by the two sequences carried out according to the invention are lower than the kappa s numbers for the prior art sequence.
This demonstrates that the sequence described by the invention besides giving the technical advantages of avoiding one washing unit gives just as good~ a kappa number reduction or even a better kappa number reduction as -the prior art sequence. .:
~:
: .
AND APPARATUS FOR PERFORMANCE OF THE PROCESS
~.
A common stage in the treatment of wood chips for paper production is chemical pulping, e.g. the so-called kraft process which is an alkaline sulphate 5 cooking of the wood chips. The native wood chips contain around 30% lignin, -and at the end of the chemical cooking process less than 5% of the lignin compounds is still left in the pulp. Due to the strong brown color of the remaining lignin and its tendency to darken in UV light or by oxidation this has to be removed in order to obtain a white pulp without the tendency to color reversion.10 After the sulphate cooking a multistage washing of the unbleached kraft brownstock takes place. The well washed brown stock can then be treated with an enzyme preparation followed by a subsequent wash before entering the bleach plant.
The invention comprises an improvement of this conventional 15 multistage washing of the unbleached kraft brown stock, followed by the enzyme treatment with the subsequent wash, whereby this improvement is a modification, which improves the economy and facilitates the processing.
i ~ After a multistage washing of the unbleached kraft brown stock followed by an enzyme treatment with the subsequent wash the brown color can 20 be removed by a multistage bleaching using e.g. chlorine and/or chlorine dioxide.
Due to the ever increasing environmental concern, the dosage of chlorine and/or chlorine dioxide has to be kept at a minimum, and it is for that reason that theenzymatic treatment of the kraft cooked pulp has been introduced, vide e.g. The third InteMational Conference on Biotechnology in the Pulp and Paper Industry, 2s Stockholm, 16~-19.6, 1986, page 67-69.
Thus, the sequence of the prior art processes in regard to paper - .
pulping is the following:
1) kraft cooking of the wood chips, : -2) multistage washing of the unbleached kraft brown stock 30 3) ~ enzymatic treatment of the washed brown stock - 4) bleaching.
: . .
.
WO 92/03608 PCr/DK9l/00239 2 ~ 3 8 2 The invention comprises the above indicated processes 2) and 3) and is an improvement thereof, as explained in more detail in the following.
Hitherto the multistage washing of the unbleached kraft brown stock . has been performed as indicated on the flow sheet of Fig. 1. In addition to the 5 process stages indicated on Fig. 1 an oxygen delignification stage with subsequent washing may be included either before or after the enzyme stage.
This prior art process with an enzyme treatment introduced between the cooking and the bleaching sections has some serious drawbacks, e.g. (1) the enzyme stage includes a washing stage, which is a unit operation that represents a large 10 capital investrnent, and (2) pH adjustment of the pulp may be needed if enzymes with acid pH optimum are used.
Thus, the purpose of the invention is the provision of a process for treatment of lignocellulosic pulp which requires a less expensive apparatus or stated otherwise the provision of a reduction of the price of the prior art method 15 for treatment of lignocellulosic pulp comprising a multistage washing of the unbleached brown kraft stock with subsequent enzyme treatment, washing and bleaching, and a corresponding apparatus for performance of the process.
Now, according to the invention it has been found that the purpose of the invention can be fulfilled, if the enzymatic treatment with the subsequent wash 20 is abandoned altogether and the enzymatic treatment is introduced after one or more of the single washing units in the multistage washings of the unbleached kraft brown stock, or stated otherwise if the enzyme treatment is introduced upstream the prior art position of the enzyme treatment in the multistage washing, in such manner that the multistage washing for washing out of impurities from the 25 kraft cooking and washing out of the residues from the enzyme treatment is combined.
Thus, the process for treatment of lignocellulosic pulp.according to the invention comprising a multistage washing of the unbleached kraft brown stock and a xylanase treatment is characterized by the fact that the xylanase 30 treatment is introduced upstream the prior art position of the xylanase treatment in such manner that the stock from the kraft cooking or the washed stock from the outlet side of one or more of the washing units is-transported to a holding .. .. . .. .. .. .. ... ...... ~ .. .. .~. . . . . . . .
92~113608 2 0 9 0 3 3 8 PCI/DK91/U0~39 tank, that a xylanase with high pH activity and stability and high heat stability is added directly upstream the holding tank, and that the enzyme treated stock is passed further on in the process to the next washing unit. Also in relation to the process according to the invention (Fig. 2) another non-chlorine bleaching stage, 5 e.g. an oxygen delignification stage or an ozone stage may be included either before or after the enzyme stage.
By comparison of Fig. 1 (prior art) and Fig. 2 (invention) it clearly appears that the invention requires one washing unit less than the prior art process, and thus, the process according to the invention fulfils the purpose of10 the invention. Furthermore, as the tank on Fig. 1 used for the enzyme treatment normally also serves as buffer tank between the kraft cooking and the bleaching plant the residence time of the pulp in the tank often varies within a wide range, e.g. between 30 minutes and 24 hours. In the invention the tank is an integratedpart of the washing process. It only serves the need for holding time for the 15 enzyme treatment, which makes it much easier to control the enzyme treatment time. Finally, the invention provides a much better connection to the existing wash water streams. The entire amount of wash water obtained in the process according to the invention will end up in the recovery system for the kraft cooking process, which means that everything that is solubilized during the enzyme 20 treatment will be burned in the recovery boiler whereby the BODs load from the enzyme stage on the effluent streams is eliminated. This is not the case in the prior art system. In the prior art system the wash water from the washing stage after the enzyme treatment normally has to be sewered. The enzyme treatment according to the invention also releases more cooking chemicals from the pulp 25 than a conventional wash with water. This makes it possible to obtain an even better recovery of cooking chemicals than normally obtained.
The three washing units on Fig. 2 are not limiting to the invention, but just an example. Each single unit can represent more than one washing stage.
With three washing units one, two or three enzyme treatment units can be 30 introduced according to the invention; just one enzyme treatment unit is shown on Fig. 2.
. ,' ', .. .1, ' ' ".' '`." ' ' ' ~ . . . ' ' ' ,'' ~`., . ;' .
'~ ', : , '. ,' . ' ' ' , ., . : ' .
WO 92/03608 PCI'/DK91/00239~, 2~338 ~
The xylanase with high pH activity and stability and with high heat stability, which is used in the process according to the invention, has to show a bleach boosting effect under the conditions present just prior to the last washing unit.
The bleach boosting effect is measured as the kappa number reduction of pulp after an enzyme treatment followed by a C/D-E bleaching compared to a control which is treated in the same way but without addition of . -enzyme: (Bleach boosting Effect = Kappa number after C/D-E bleaching of - :enzyme treated pulp minus kappa number after C/D-E bleaching of pulp treated 10 without enzyme).
Also, the invention comprises an apparatus for performance of the process according to the invention. The apparatus according to the invention is characterized by the fact that a holding tank with piping with facilities for introduction of enzyme is introduced upstream the first washing unit or 15 downstream one or more of the other washing units except for the last washingunit, that piping is provided for further transport of the stock to the next washing unit, and that the conventional enzyme treatment unit downstream the washing unit is abandoned.
It is to be understood that at least one holding tank with accessories 20 is introduced, and that the maximum number of holding tanks with accessories,which can be introduced into the sequence according to the invention equals the number of washing units in the multistage washing process. ~.
The following example illustrates the invention in comparison to prior art.
: ' 2s EXAMPLE 1 In order to illustrate the invention an unbleached and unwashed softwood pulp identified as P was washed in one stage as follows: ~-The pulp P was diluted with fresh water to a consistency of 1% DS
and then reconcentrated to a consistency of approximately 20% on a wire screen.
-92/03608 2 0 9 0 3 3 8 PCI /DK9l /00239 ' :
This washing sequence is the standard washing stage used throughout thisexample. After the washing the pH of the pulp was 9.7.
This pulp sample was divided into two halves.
The first half of this one stage washed pulp was xylanase treated under the following conditions without pH adjustment prior to the enzyme addition.
Temperature : 70C -pH : 9.7 Consistency : 10%
Time : 3 hours Xylanase : Streptomyces olivochromogenes, vide Example 6 in WO 91/02839 Enzyme dosage : 5000 EXU/kg dry pulp ; , ' ; . :
15 The definition of the EXU xylanase activity unit appears from AF
293.9/1, obtainable on request from NOVO NORDISK A/S, Novo Allé, DK-2880 Bagsvaerd, Denmark.
The xylanase stage was carried out as follows. The pulp was diluted to the desireq consistency by addition of fresh water. The enzyme solution was 20 added and mixed into the pulp by vigorous mixing. The pulp was then placed in -a water bath to ensure constant temperature for the remainder of the treatment time. The pulp was not mixed during the three hours of holding time.
After the enzyme stage the pulp was carried through two standard washing stages. This pulp sample which was enzyme treated between the first ~i ~ 25 and the second washing stage, was carried out according to the invention and will be referred to later as inv 1-2 The second half of the one stage washed pulp was carried through another standard washing stage. After washing the pH of the pulp suspension was 8.7.
WO 92/03608 PC~/DK91/00239 2 ~ ;) 8 6 This two stage washed pulp was enzyme treated without pH
adjustment prior to the enzyme addition under the following conditions:
Temperature : 70C
pH : 8.7 Consistency : 10%
Time : 3 hours Enzyme : Streptomyces olivochromogenes, vide -- Example 6 in WO 91/02839 Enzyme dosage : 2000 EXU/kg dry pulp The enzyme treatment was carried out as described above.
After the enzyme stage the pulp was carried through one standard washing stage. This sample of pulp, which was enzyme treated between the second and third washing stage, was carried out according to the invention and will be referred to later as inv 2-3.
In order to illustrate the corresponding prior art the pulp P was first carried through three standard washing stages. Then the pH of the pulp was owered to 6.5 by addition of sulfuric acid and an enzyme stage was carried out under~the following conditions.
Temperature : 50"C
20 pH : 6.5 Consistency : 10%
Time : 3 hours Enzyme : PulpzymerMHA
Enzyme dosage : 275 FXU/kg dry pulp , .
The definition of FXU xylanase activity unit appears from AF 293.6/1, obtainable on request from NOVO NORDISK A/S, Novo Allé, DK-2880 Bagsvaerd, :
Denmark.
The enzyme treatment was made as described above.
~ .
~ 92/03608 2 0 9 0 3 3 8 PCr/DK91/00239 , .
After the enzyme stage the pulp was washed in an extra standard washing stage according to the prior art. This pulp sample will be referred to later as prior.
The above experiment used to illustrate prior art was repeated except 5 that no enzyme was added. This experiment served as a control to demonstrate that the enzyme stage really has an effect on the pulp and will be referred to later as control.
The xylanases used in this example were selected according to their .
pH optimum in relation to the pH of the pulp.
After enzyme treatments and washings all the pulps were bleached according to the same two stage bleaching sequence (D50 C50) E.
The bleachings were carried out under the following conditions:
(D50 C50):
Temperature : 50C
Consistency : 5%
Time : 20 minutes active Cl dosage : 5.7% (w/w) on dry pulp E: :~
Temperature : 60C
Consistency : 10%
rlme : 1 hour NaOH dosage : 4.2% (w/w) on dry pulp ~ .
; After the bleaching the kappa number of all four pulps were determined.
. ' :~
WO 92/03608 PCl-/DK91/00239 2~903~8 8 Results Kappa number of the pulps after the (D50 C50) E bleachings:
Kappa numberdelta Kappa number %
5 Control 2.85 Prior 2.52 11.6 inv 1-2 2.50 12.3 inv 2-3 2.31 19.0 ~. '.
It is observed that the kappa number of the enzyme treated pulps are 10 reduced compared to the control. This demonstrates that the enzyme treatment in all three sequences, the prior art and the two inventive sequences, has showna bleach boosting èffect.
It is also seen that the kappa numbers obtained by the two sequences carried out according to the invention are lower than the kappa s numbers for the prior art sequence.
This demonstrates that the sequence described by the invention besides giving the technical advantages of avoiding one washing unit gives just as good~ a kappa number reduction or even a better kappa number reduction as -the prior art sequence. .:
~:
: .
Claims (2)
1. Process for treatment of lignocellulosic pulp comprising a multistage washing of the unbleached kraft brown stock and a xylanase treatment, characterized by the fact that the xylanase treatment is introduced upstream theprior art position of the xylanase treatment in such manner that the stock from the kraft cooking or the washed stock from the outlet side of one or more of the washing units is transported to a holding tank, that a xylanase with high pH
activity and stability and high heat stability is added directly upstream the holding tank, and that the enzyme treated stock is passed further on in the process to the next washing unit.
activity and stability and high heat stability is added directly upstream the holding tank, and that the enzyme treated stock is passed further on in the process to the next washing unit.
2. Apparatus for performance of the process according to Claim 1, characterized by the fact that a holding tank with piping with facilities for introduction of enzyme is introduced upstream the first washing unit or downstream one or more of the other washing units except for the last washing unit, that piping is provided for further transport of the stock to the next washing tank, and that the conventional enzyme treatment unit downstream the washing unit is abandoned.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DK2034/90 | 1990-08-24 | ||
| DK203490A DK203490D0 (en) | 1990-08-24 | 1990-08-24 | PROCEDURE FOR TREATING LIGNOCELLULOS PULP AND APPARATUS FOR PERFORMING THE PROCESS |
| PCT/DK1991/000239 WO1992003608A1 (en) | 1990-08-24 | 1991-08-21 | Process for treatment of lignocellulosic pulp and apparatus for performance of the process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2090338A1 true CA2090338A1 (en) | 1992-02-25 |
Family
ID=8109613
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002090338A Abandoned CA2090338A1 (en) | 1990-08-24 | 1991-08-21 | Process for treatment of lignocellulosic pulp and apparatus for performance of the process |
Country Status (11)
| Country | Link |
|---|---|
| EP (1) | EP0547100B1 (en) |
| JP (1) | JPH05509137A (en) |
| AT (1) | ATE118842T1 (en) |
| BR (1) | BR9106763A (en) |
| CA (1) | CA2090338A1 (en) |
| DE (1) | DE69107620D1 (en) |
| DK (1) | DK203490D0 (en) |
| ES (1) | ES2069307T3 (en) |
| FI (1) | FI930803A0 (en) |
| NZ (1) | NZ239501A (en) |
| WO (1) | WO1992003608A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| MXPA03011194A (en) | 2001-06-06 | 2004-02-26 | Novozymes As | Endo-beta-1,4-glucanase from bacillus. |
| CN101967490B (en) | 2002-06-14 | 2014-07-16 | 先正达公司 | Xylanases, nucleic adics encoding them and methods for making and using them |
| DK1989302T3 (en) | 2006-02-14 | 2018-07-23 | Bp Corp North America Inc | XYLANASES, NUCLEIC ACID CODING THEM AND PROCEDURES FOR THEIR PREPARATION AND USE |
| WO2009073709A1 (en) | 2007-12-06 | 2009-06-11 | Novozymes A/S | Polypeptides having acetylxylan esterase activity and polynucleotides encoding same |
| DK2483403T3 (en) | 2009-09-29 | 2018-02-12 | Novozymes Inc | POLYPEPTIDES WITH XYLANASE ACTIVITY AND POLYNUCLEOTIDES CODING THEM |
| CA2780198A1 (en) | 2009-11-06 | 2011-05-12 | Novozymes, Inc. | Polypeptides having xylanase activity and polynucleotides encoding same |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0373107B1 (en) * | 1988-11-23 | 1994-03-23 | Sandoz Ag | Use of enzymes of Aureobasidium pullulans in pulp bleaching |
| FI90888B (en) * | 1989-02-14 | 1993-12-31 | Enso Gutzeit Oy | Method for bleaching cellulose pulp |
-
1990
- 1990-08-24 DK DK203490A patent/DK203490D0/en not_active Application Discontinuation
-
1991
- 1991-08-21 JP JP3514774A patent/JPH05509137A/en active Pending
- 1991-08-21 AT AT91915560T patent/ATE118842T1/en not_active IP Right Cessation
- 1991-08-21 BR BR919106763A patent/BR9106763A/en not_active Application Discontinuation
- 1991-08-21 DE DE69107620T patent/DE69107620D1/en not_active Expired - Lifetime
- 1991-08-21 WO PCT/DK1991/000239 patent/WO1992003608A1/en active IP Right Grant
- 1991-08-21 EP EP91915560A patent/EP0547100B1/en not_active Expired - Lifetime
- 1991-08-21 CA CA002090338A patent/CA2090338A1/en not_active Abandoned
- 1991-08-21 ES ES91915560T patent/ES2069307T3/en not_active Expired - Lifetime
- 1991-08-22 NZ NZ239501A patent/NZ239501A/en unknown
-
1993
- 1993-02-23 FI FI930803A patent/FI930803A0/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| NZ239501A (en) | 1993-01-27 |
| BR9106763A (en) | 1993-06-29 |
| FI930803A (en) | 1993-02-23 |
| JPH05509137A (en) | 1993-12-16 |
| DK203490D0 (en) | 1990-08-24 |
| ATE118842T1 (en) | 1995-03-15 |
| EP0547100A1 (en) | 1993-06-23 |
| FI930803A0 (en) | 1993-02-23 |
| DE69107620D1 (en) | 1995-03-30 |
| WO1992003608A1 (en) | 1992-03-05 |
| EP0547100B1 (en) | 1995-02-22 |
| ES2069307T3 (en) | 1995-05-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 19970821 |