CA1173602A - Process for producing special high alpha-cellulose pulps by means of a multistage cook including an acid prehydrolysis - Google Patents
Process for producing special high alpha-cellulose pulps by means of a multistage cook including an acid prehydrolysisInfo
- Publication number
- CA1173602A CA1173602A CA000391377A CA391377A CA1173602A CA 1173602 A CA1173602 A CA 1173602A CA 000391377 A CA000391377 A CA 000391377A CA 391377 A CA391377 A CA 391377A CA 1173602 A CA1173602 A CA 1173602A
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- wood
- hydrolysate
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- dry matter
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C13—SUGAR INDUSTRY
- C13K—SACCHARIDES OBTAINED FROM NATURAL SOURCES OR BY HYDROLYSIS OF NATURALLY OCCURRING DISACCHARIDES, OLIGOSACCHARIDES OR POLYSACCHARIDES
- C13K1/00—Glucose; Glucose-containing syrups
- C13K1/02—Glucose; Glucose-containing syrups obtained by saccharification of cellulosic materials
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23K—FODDER
- A23K10/00—Animal feeding-stuffs
- A23K10/30—Animal feeding-stuffs from material of plant origin, e.g. roots, seeds or hay; from material of fungal origin, e.g. mushrooms
- A23K10/32—Animal feeding-stuffs from material of plant origin, e.g. roots, seeds or hay; from material of fungal origin, e.g. mushrooms from hydrolysates of wood or straw
-
- 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
- D21C3/26—Multistage processes
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- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Polymers & Plastics (AREA)
- Health & Medical Sciences (AREA)
- Biotechnology (AREA)
- Organic Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Botany (AREA)
- Molecular Biology (AREA)
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- Physiology (AREA)
- Animal Husbandry (AREA)
- Zoology (AREA)
- Emergency Medicine (AREA)
- Food Science & Technology (AREA)
- Paper (AREA)
Abstract
\
Abstract The process according to the invention is related to the production of high alpha-cellulose pulps suitable for chemical processing and special papers by means of a multi-stage cook.
Steamed chips are prehydrolyzed by using a strong acid, e.g.
sulfuric acid, whereby 20 to 30 % of the dry matter of the wood is dissolved under suitable process conditions. The pre-hydrolysis liquor is removed from the cooker by means of a counter-current wash, whereafter the chips are conveyed to the actual sulfate cook.
The hydrolysate is separated with a high dry matter content and efficiently. In addition to this, the process is charac-terized in that the furfural content of the prehydrolysis liquor is very low, which makes the further processing of the prehydrolysis liquor easier.
Abstract The process according to the invention is related to the production of high alpha-cellulose pulps suitable for chemical processing and special papers by means of a multi-stage cook.
Steamed chips are prehydrolyzed by using a strong acid, e.g.
sulfuric acid, whereby 20 to 30 % of the dry matter of the wood is dissolved under suitable process conditions. The pre-hydrolysis liquor is removed from the cooker by means of a counter-current wash, whereafter the chips are conveyed to the actual sulfate cook.
The hydrolysate is separated with a high dry matter content and efficiently. In addition to this, the process is charac-terized in that the furfural content of the prehydrolysis liquor is very low, which makes the further processing of the prehydrolysis liquor easier.
Description
~736(~
. .
'I
process for_producing special high alpha-cellulose pulps by means of a multistage cook including an acid prehydrolysis When producing high-quality celluIose pulps~ a two-stage cooking process is o~ten used, the first stage of which is a prehydrolysis carried out with water or steam at the tem-perature of 170 to 175 C. After the prehydrolysis and an eventual remo~al of t~e hydrolysate, white liquor is added to the cooker and a normal sulfate cook is carried out, ~hereby high-quality pulp is obtained, the alpha-cellulose contant of which is over 90 % before bleacing. The high alpha number is achieved due to the prehydrolysis stage, as there the hemi-cellulose which can be easily hydrolyzed, is almost comple-tely dissolvedr and the only task which remains for the sulfate cook is to remove lignin.
The hydrolysis and the dissolving of the hemicellulose of wood requires acidic conditions. When the hydrolysis is carried out by means of water or steam, the acidity is achieved by organic acids, such as acetic, formic or propionic acid, which are derived from the wood itself. As the above mentioned organic acids are weak acids, the pH cannot go very low in the pxehydrolysis react1on. The low acidity of the reaction conditions must thus be compensated by quite a high temperature, in order to achieve a sufficiently rapid hydro-lysis.
When producing high alpha-cellulose pulps for chemical pro cessing, the most common way is water prehydrolysis at a temperature of 170 to 175 C with a reaction time of from 40 to ~20 minutes at the maximum temperature. The prehydro-lysis loss is then, depending on the species of wood, from 18 to 25 %. When softwood is used, lignin may condensate noticeably, whereby the kappa number after the cook increases much and the bleaching consumes disproportionate amounts of p~
;
:~ ~73~
c~lorine or chlorine oxide.
Steam prehydrolysis principally resembles water prehydrolysis and requires the same reaction conditions. As in steam pre-hydrolysis the liq~lid-to-wood ratio is considerably smaller than in the latter, less thermal energy is needed. ~lso-the required cooker volume and investing costs are smaller.
The biggest risk factor when using steam pre~ydrolysis is the quality of the pulp where there ~an be irreguIarities due to the small liquid-to-wood ratio.
The dry matter of wood dissolving in the prehydrolysis is thus primarily hemicellulose and it consists of pentoses or hexose~ ost of the hemicellulose is decomposed in the prehydrolysis and 50 to 60 ~ of the dry matter of the hydro-lysate is monosaccharides. Part of these are, however, still in the form of oligo- or polysaccharides. In addition to these, a considerable amount of organic acids as well as furfural are formed in the process from the pentoses of the wood. ~rhe formation of acetic acid and furfural in particular increases rapidly as the temperature oE the hydrolysis rises in the range above 150C~
The hydrolysate formed in the prehydrolysis stage including, in addition to sugars and polysaccharides, also organic acids and furfural, is valuable and its utilization improves the profitability of pulping.
In addition to what has been mentioned, the utilization of the hydrolysate is important also because when it is discharged unused, it causes sewage problems which are difficult to handle. Factories in which the utilization of the hydrolysate as a raw material for chemical products or in the production of energy has not been completely solved, have unreasonably high sewage purification costs.
~1736~
~s ~ consider~ble part of the hemicellulose in watex or steam pxehy~rol~sis re~ain'~ in the oli~o- or pol~s~ccharide stage and simu~taneously large ~mounts of 'fur'fural, w~ich is partly converted into 'fur'~uran resins, is formed, it is difficult to handle the formed hydrolysate. It is characterized by a so called caramellizing tendency which is caused by the poly-saccharides and the 'fur'furan resins that are being formed.
Already as a we~k'so'lution, the hydrolysate tends to form on the equipment deposits and layers which are difficult to remoVe; these disadvantages are emphasi~ed when hydrolysate is evaporated. The difficulties in the evaporation plant are often reflected as an increased pollution load and as increased handling costs. In case hydrolysate is used as a raw material for biochemical processes, evaporation is often not necessary.
If the prehydrolysis is carried out under very acidic conditions, the hydrolysis temperature can be lowered. The formation of furfural decreases as does natural'ly the formation of furfuran resins as well. Due to the low pH, the polysaccharides are decomposed almost completely to mono-and disaccharides.
The use of strong mineral acids as the hydrolyzing agent has been known for a long tim~. The Swedish paten-t No. 11357~
discloses e.g. the production of viscose pulp from straw by using prehydrolysis with less than 1 % of sulfuric acid at a temperature of 100 to 130 C followed by a sulfate cook.
The Swedish patent No. 113580 discloses the production of viscose pulp from softwood chips under similar conditions.
The use of a strong S02 so'lution in the prehydrolysis has been disclosed in several U.S. patents.
The hydrolysate thus formed does not have the tendency to caramellize, neither does it have any other troublesome properties; it can be stored without any problems for long periods of time, p~nped and in particular, it can be evaporat~d O
1~736~)~
to ~ hig~ dry ~atter eo~tent, whexe~Y i~$ us~bility and its proee~sin~ possih'llities arç imp~o~ed decisively.
Thç' use of ~tron~ aeids is not, however,'uneomplieated, e.g.
due to dif'fieuIt eoxrosion eonditions and the faet that the variations in the yield and quality of puIp are at low pH-Yalues steeper than u'sual'ly. As far as is known, the above mentioned patents are nowhere appliçd to in pulp produetion.
It is extremely diffieult to get the aeid to absorb into the ehips so evenly that the entire wood material is prehydrolyzed in thç same way, whieh is neeessary in consideration of the uniform quality of the pulp. The uniformity of absorption ean be improved by using smaller ehips than usually, but then the circulation of the eooking liquid in the eooker beeomes more difficult partieularly 'during the alkaline stage following the hydrolysis.
The present invention relates to a process for produeing high-quality puIps suitable for ehemical processing by means of a multi-stage cook which is characterized in that the prehydro-lysis is carried out under strictly eontrolled, comparatively acidie eonditions. In order to ensure the even absorbance of the prehydrolysis agent into the chips, they are steamed for 5 to 10 minutes at a temperature of 110 to 120 C. The optimum length of the chips does not have to be shorter than 20 to 21 mm which does not yet have an effeet on the eireula-tion of the cooking liquid. Excessively eoarse, over 25 mm long chips should, however, be earefully screened away. E.g.
sulfuric acid is used from 1 to 2 % of the weight of the wood, whereby the sulfuric aeid content of the prehydrolysis liquid is 0,3 to 0,6 ~. When sulfur dioxide is used, the most suitable amount is 0,3 ~o 1,0 ~ based on the weight of wood.
The prehydrolysis temperature is 140 to 150 C and the hydro~
lysis time 30 to 60 minutes.
When sulfuric aeid i5 used a~ a hydrolysis agent, sugar acids ~ 3~0;~ 1 a,nd li~nosulpho~ cids are formed, Which together with SO2 are effec~i~e ~u~ ost of the xe~ction time. This is how an efficie~t hydrolysis is carried out, in which the actual cellulose is not da~aged, part of the lignin is dissolved and it is possible to obtain high-quality pulp in a sulfate cook following the ~ydrolysis'under mild conditions. The lignosulph,onic acids which are formed in the process assist in obtaining a sufficiently low p~. It is known that sulfuric acid also decomposes sugars more than other mineral acids. At the same time, ligno'sulphonic acids cause the hydrolysate not to form deposits in the after tre~tment.
By intensifying either one or more of the above mentioned conditions within given limits, the prehydrolysis loss can be increased, this in turn resulting in chips including less hemicellulose than before. In the alkaline cook following this stage, these chips will yield pulp which is cleaner and has an extremely high alpha number.
A counter-current wash with a recovery grade of 70 to 80 %
of the prehydrolyzed chips is an essential feature of the method. Then the conditions of the alkaline cook can be controlled with su~fient accuracy, as substantially no alkali is spent for the neutralization of the hydrolysate. Also hydrolysate from a previous hydrolysis with a dry matter content of e.g. 7 to 8 % can be added to the hydrolysis staye. The dry matter content of the hydrolysate can thus be increased by recirculation, whereby the evaporation costs of the hydrolysate are decreased essentially.
When using hardwood, e.g. birch, for the processing of which this method is particularly suitable, by adjusting the above mentioned hydrolysis conditions within the given limits, with a prehydrolysis loss o~ 20 to 30 % and with.a sulfate cook chemical dosage of 14 to 15 % Na2O, a high-quality pulp is obtained, the pentosan content of which is 2 to 8 % as un-', ~ 3 ~0'~
bleached, ~app~ numbe~ 8 t~ 12 ~nd ~ie~d o~ w~od 32 t~ 36 %.When the ~u~p is blç~ched otherwise no~ma~ but by using at lçast 75 % ~cti~e c~lorine dioxide in the ~irst stage, high-alpha pulps (alpha number 90 to 97'% depending on the residu~l pentosans) suitable for che~ic~l Processing are produced without an intensi~ied ho~ or cold alkali treatment.
Due to the strict'ly controlled conditions and the eVen absorp-tion of the hydrolysis liquid,' unadvanta~eous condensation of li~nin in t~e chips can be avoided also when ~ydrolyzing soft-wood, and consequently, the bleaching is relatively easy.
.
The hydrolysate which has been carefully separated from the chips includes the dissolved hemicel'luIose, most of which is decomposed to monosaccharidesl the mineral acid used as agent and organic acids.
When using birch, most of the monosaccharides are xyloses and when'using softwood, hexoses. The dry matter content of the hydrolysate is 6 to 8 % and due to the special hydrolysis conditions - the hemicel'luIose is primarily in the form of monosaccharides and the amount of furfurai formed is minimal its further treatment, e.g. evaporation, is easy and caramellizing does not occur.
Prehydrolysis carried out in this way rnakes the production of high~quality pulp easier, as the condensation of lignin is insignificant at the low hydrolysis temperature and therefore the sulfate cook is easily carried out after the prehydro-lysis. A small dosage of alkali is sufficient and a low cooling temperature is employed, wherefore the energy consumption of the process decreases also in the sulfate cook.
The amount of alkali used is small also bec`ause of the efficient intermediate wash which consumes only a littie alkali for the neutralization of the hydrolysate.
~736~
It is also within the scope of the invention to carry out a method wherein the hydrolys,ate formed as described above and containing mostly mono- and disaccharides and having a low furfural content, is neutralized in order to bind the organic acids, and concentrated by means of evaporation until it contains 60 to 70~ dry matter, whereafter it can be economic-ally used as cattle feed or raw material for chemical processes.
. .
'I
process for_producing special high alpha-cellulose pulps by means of a multistage cook including an acid prehydrolysis When producing high-quality celluIose pulps~ a two-stage cooking process is o~ten used, the first stage of which is a prehydrolysis carried out with water or steam at the tem-perature of 170 to 175 C. After the prehydrolysis and an eventual remo~al of t~e hydrolysate, white liquor is added to the cooker and a normal sulfate cook is carried out, ~hereby high-quality pulp is obtained, the alpha-cellulose contant of which is over 90 % before bleacing. The high alpha number is achieved due to the prehydrolysis stage, as there the hemi-cellulose which can be easily hydrolyzed, is almost comple-tely dissolvedr and the only task which remains for the sulfate cook is to remove lignin.
The hydrolysis and the dissolving of the hemicellulose of wood requires acidic conditions. When the hydrolysis is carried out by means of water or steam, the acidity is achieved by organic acids, such as acetic, formic or propionic acid, which are derived from the wood itself. As the above mentioned organic acids are weak acids, the pH cannot go very low in the pxehydrolysis react1on. The low acidity of the reaction conditions must thus be compensated by quite a high temperature, in order to achieve a sufficiently rapid hydro-lysis.
When producing high alpha-cellulose pulps for chemical pro cessing, the most common way is water prehydrolysis at a temperature of 170 to 175 C with a reaction time of from 40 to ~20 minutes at the maximum temperature. The prehydro-lysis loss is then, depending on the species of wood, from 18 to 25 %. When softwood is used, lignin may condensate noticeably, whereby the kappa number after the cook increases much and the bleaching consumes disproportionate amounts of p~
;
:~ ~73~
c~lorine or chlorine oxide.
Steam prehydrolysis principally resembles water prehydrolysis and requires the same reaction conditions. As in steam pre-hydrolysis the liq~lid-to-wood ratio is considerably smaller than in the latter, less thermal energy is needed. ~lso-the required cooker volume and investing costs are smaller.
The biggest risk factor when using steam pre~ydrolysis is the quality of the pulp where there ~an be irreguIarities due to the small liquid-to-wood ratio.
The dry matter of wood dissolving in the prehydrolysis is thus primarily hemicellulose and it consists of pentoses or hexose~ ost of the hemicellulose is decomposed in the prehydrolysis and 50 to 60 ~ of the dry matter of the hydro-lysate is monosaccharides. Part of these are, however, still in the form of oligo- or polysaccharides. In addition to these, a considerable amount of organic acids as well as furfural are formed in the process from the pentoses of the wood. ~rhe formation of acetic acid and furfural in particular increases rapidly as the temperature oE the hydrolysis rises in the range above 150C~
The hydrolysate formed in the prehydrolysis stage including, in addition to sugars and polysaccharides, also organic acids and furfural, is valuable and its utilization improves the profitability of pulping.
In addition to what has been mentioned, the utilization of the hydrolysate is important also because when it is discharged unused, it causes sewage problems which are difficult to handle. Factories in which the utilization of the hydrolysate as a raw material for chemical products or in the production of energy has not been completely solved, have unreasonably high sewage purification costs.
~1736~
~s ~ consider~ble part of the hemicellulose in watex or steam pxehy~rol~sis re~ain'~ in the oli~o- or pol~s~ccharide stage and simu~taneously large ~mounts of 'fur'fural, w~ich is partly converted into 'fur'~uran resins, is formed, it is difficult to handle the formed hydrolysate. It is characterized by a so called caramellizing tendency which is caused by the poly-saccharides and the 'fur'furan resins that are being formed.
Already as a we~k'so'lution, the hydrolysate tends to form on the equipment deposits and layers which are difficult to remoVe; these disadvantages are emphasi~ed when hydrolysate is evaporated. The difficulties in the evaporation plant are often reflected as an increased pollution load and as increased handling costs. In case hydrolysate is used as a raw material for biochemical processes, evaporation is often not necessary.
If the prehydrolysis is carried out under very acidic conditions, the hydrolysis temperature can be lowered. The formation of furfural decreases as does natural'ly the formation of furfuran resins as well. Due to the low pH, the polysaccharides are decomposed almost completely to mono-and disaccharides.
The use of strong mineral acids as the hydrolyzing agent has been known for a long tim~. The Swedish paten-t No. 11357~
discloses e.g. the production of viscose pulp from straw by using prehydrolysis with less than 1 % of sulfuric acid at a temperature of 100 to 130 C followed by a sulfate cook.
The Swedish patent No. 113580 discloses the production of viscose pulp from softwood chips under similar conditions.
The use of a strong S02 so'lution in the prehydrolysis has been disclosed in several U.S. patents.
The hydrolysate thus formed does not have the tendency to caramellize, neither does it have any other troublesome properties; it can be stored without any problems for long periods of time, p~nped and in particular, it can be evaporat~d O
1~736~)~
to ~ hig~ dry ~atter eo~tent, whexe~Y i~$ us~bility and its proee~sin~ possih'llities arç imp~o~ed decisively.
Thç' use of ~tron~ aeids is not, however,'uneomplieated, e.g.
due to dif'fieuIt eoxrosion eonditions and the faet that the variations in the yield and quality of puIp are at low pH-Yalues steeper than u'sual'ly. As far as is known, the above mentioned patents are nowhere appliçd to in pulp produetion.
It is extremely diffieult to get the aeid to absorb into the ehips so evenly that the entire wood material is prehydrolyzed in thç same way, whieh is neeessary in consideration of the uniform quality of the pulp. The uniformity of absorption ean be improved by using smaller ehips than usually, but then the circulation of the eooking liquid in the eooker beeomes more difficult partieularly 'during the alkaline stage following the hydrolysis.
The present invention relates to a process for produeing high-quality puIps suitable for ehemical processing by means of a multi-stage cook which is characterized in that the prehydro-lysis is carried out under strictly eontrolled, comparatively acidie eonditions. In order to ensure the even absorbance of the prehydrolysis agent into the chips, they are steamed for 5 to 10 minutes at a temperature of 110 to 120 C. The optimum length of the chips does not have to be shorter than 20 to 21 mm which does not yet have an effeet on the eireula-tion of the cooking liquid. Excessively eoarse, over 25 mm long chips should, however, be earefully screened away. E.g.
sulfuric acid is used from 1 to 2 % of the weight of the wood, whereby the sulfuric aeid content of the prehydrolysis liquid is 0,3 to 0,6 ~. When sulfur dioxide is used, the most suitable amount is 0,3 ~o 1,0 ~ based on the weight of wood.
The prehydrolysis temperature is 140 to 150 C and the hydro~
lysis time 30 to 60 minutes.
When sulfuric aeid i5 used a~ a hydrolysis agent, sugar acids ~ 3~0;~ 1 a,nd li~nosulpho~ cids are formed, Which together with SO2 are effec~i~e ~u~ ost of the xe~ction time. This is how an efficie~t hydrolysis is carried out, in which the actual cellulose is not da~aged, part of the lignin is dissolved and it is possible to obtain high-quality pulp in a sulfate cook following the ~ydrolysis'under mild conditions. The lignosulph,onic acids which are formed in the process assist in obtaining a sufficiently low p~. It is known that sulfuric acid also decomposes sugars more than other mineral acids. At the same time, ligno'sulphonic acids cause the hydrolysate not to form deposits in the after tre~tment.
By intensifying either one or more of the above mentioned conditions within given limits, the prehydrolysis loss can be increased, this in turn resulting in chips including less hemicellulose than before. In the alkaline cook following this stage, these chips will yield pulp which is cleaner and has an extremely high alpha number.
A counter-current wash with a recovery grade of 70 to 80 %
of the prehydrolyzed chips is an essential feature of the method. Then the conditions of the alkaline cook can be controlled with su~fient accuracy, as substantially no alkali is spent for the neutralization of the hydrolysate. Also hydrolysate from a previous hydrolysis with a dry matter content of e.g. 7 to 8 % can be added to the hydrolysis staye. The dry matter content of the hydrolysate can thus be increased by recirculation, whereby the evaporation costs of the hydrolysate are decreased essentially.
When using hardwood, e.g. birch, for the processing of which this method is particularly suitable, by adjusting the above mentioned hydrolysis conditions within the given limits, with a prehydrolysis loss o~ 20 to 30 % and with.a sulfate cook chemical dosage of 14 to 15 % Na2O, a high-quality pulp is obtained, the pentosan content of which is 2 to 8 % as un-', ~ 3 ~0'~
bleached, ~app~ numbe~ 8 t~ 12 ~nd ~ie~d o~ w~od 32 t~ 36 %.When the ~u~p is blç~ched otherwise no~ma~ but by using at lçast 75 % ~cti~e c~lorine dioxide in the ~irst stage, high-alpha pulps (alpha number 90 to 97'% depending on the residu~l pentosans) suitable for che~ic~l Processing are produced without an intensi~ied ho~ or cold alkali treatment.
Due to the strict'ly controlled conditions and the eVen absorp-tion of the hydrolysis liquid,' unadvanta~eous condensation of li~nin in t~e chips can be avoided also when ~ydrolyzing soft-wood, and consequently, the bleaching is relatively easy.
.
The hydrolysate which has been carefully separated from the chips includes the dissolved hemicel'luIose, most of which is decomposed to monosaccharidesl the mineral acid used as agent and organic acids.
When using birch, most of the monosaccharides are xyloses and when'using softwood, hexoses. The dry matter content of the hydrolysate is 6 to 8 % and due to the special hydrolysis conditions - the hemicel'luIose is primarily in the form of monosaccharides and the amount of furfurai formed is minimal its further treatment, e.g. evaporation, is easy and caramellizing does not occur.
Prehydrolysis carried out in this way rnakes the production of high~quality pulp easier, as the condensation of lignin is insignificant at the low hydrolysis temperature and therefore the sulfate cook is easily carried out after the prehydro-lysis. A small dosage of alkali is sufficient and a low cooling temperature is employed, wherefore the energy consumption of the process decreases also in the sulfate cook.
The amount of alkali used is small also bec`ause of the efficient intermediate wash which consumes only a littie alkali for the neutralization of the hydrolysate.
~736~
It is also within the scope of the invention to carry out a method wherein the hydrolys,ate formed as described above and containing mostly mono- and disaccharides and having a low furfural content, is neutralized in order to bind the organic acids, and concentrated by means of evaporation until it contains 60 to 70~ dry matter, whereafter it can be economic-ally used as cattle feed or raw material for chemical processes.
Claims (10)
1. Process for producing special high alpha-cellulose pulps suitable for chemical processing and special papers by means of a multistage cook, characterized in that in a first stage wood chips are steamed for 5 to 10 minutes at a temperature of 110 to 120°C, whereafter in a prehydrolysis stage strong acid, in an amount of 1 to 2% based on the weight of the wood, and water are added so that the liquor-to-wood ratio is from 1:2,5 to 1:3,5 and the chips are kept in this stage at a temp-erature from 140 to 150°C for 30 to 60 minutes, whereby 20 to 30%
of the dry matter of the wood is dissolved, whereafter the hydro-lysate is taken out of the reaction vessel and the recovery is intensified with a counter-current wash of the wood chips, where-after white liquor is added and a normal, comparatively mild sulfate cook is carried out for the chips at a temperature of 165 to 170°C with an active alkali dosage of 14 to 15% Na2O based on abs. dry wood.
of the dry matter of the wood is dissolved, whereafter the hydro-lysate is taken out of the reaction vessel and the recovery is intensified with a counter-current wash of the wood chips, where-after white liquor is added and a normal, comparatively mild sulfate cook is carried out for the chips at a temperature of 165 to 170°C with an active alkali dosage of 14 to 15% Na2O based on abs. dry wood.
2. Process as claimed in claim 1, wherein the wood chips are 20 to 21 mm long.
3. Process as Rosetta in claim 1 or 2, characterized in that instead of an acid, residual acid from a chlorine dioxide plant obtained when chlorine dioxide is prepared from sodium chlorate, is used in the hydrolysis.
4. Process as recited in claim 1 or 2, characterized in that 0.3 to 1.0% SO2 based on the dry weight of the wood is used as the hydrolysis agent.
5. Process as recited in claim 1 or 2, characterized in that either hydrolysate from the same process, spent liquor of a high-yield cook or spent liquor obtained from a mechanical fiberizing process is used instead of water in the prehydro-lysis stage.
6. The process as recited in claim 1, further including the step, wherein the hydrolysate, containing mostly mono- and disaccharides and having a low furfural content, is neutralized in order to bind the organic acids and concentrated by means of evaporation until it contains 60 to 70% dry matter, whereafter it can be economically used as cattle feed or raw material for chemical processes.
7. The process as recited in claim 2, further including the step wherein the hydrolysate containing mostly mono- and disaccharides and having a low furfural content, is neutralized in order to bind the organic acids and concentrated by means of evaporation until it contains 60 to 70% dry matter, whereafter it can be economically used as cattle feed or raw material for chemical processes.
8. The process as recited in claim 1 or 2, characterized in that instead of an acid, residual acid from a chlorine dioxide plant obtained when chlorine dioxide is prepared from sodium chlorate, is used in the hydrolysis, said process further including the step wherein the hydrolysate, containing mostly mono- and disaccharides and having a low furfural content, is neutralized in order to bind the organic acids and concentrated by means of evaporation until it contains 60 to 70% dry matter, whereafter it can be economically used as cattle feed or raw material for chemical processes.
9. The process as recited in claim 1 or 2, characterized in that 0.3 to 1.0% SO2 based on the dry weight of the wood is used as the hydrolysis agent said process further including the step, wherein the hydrolysate containing mostly mono- and disaccharides and having a low furfural content, is neutralized in order to bind the organic acids and concentrated by means of evaporation until it contains 60 to 70% dry matter, whereafter it can be economically used as cattle feed or raw material for chemical processes.
10. The process of claim 1 or 2, characterized in that either hydrolysate from the same process, spent liquor of a high-yield cook or spent liquor obtained from a mechanical fiberizing process is used instead of water in the prehydrolysis stage, said process further including the step wherein the hydrolysate containing mostly mono- and disaccharides and having a low furfural content, is neutralized in order to bind the organic acids and concentrated by means of evaporation until it contains 60 to 70% dry matter, whereafter it can be economically used as cattle feed or raw material for chemical processes.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI803802 | 1980-12-08 | ||
| FI803802A FI63267B (en) | 1980-12-08 | 1980-12-08 | FOERFARANDE FOER FRAMSTAELLNING AV SPECIALCELLULOSA MED HOEGT ALFATAL GENOM FLERSTEGSKOKNING INNEFATTANDE SYRAFOERHYDROLYS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1173602A true CA1173602A (en) | 1984-09-04 |
Family
ID=8513967
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000391377A Expired CA1173602A (en) | 1980-12-08 | 1981-12-02 | Process for producing special high alpha-cellulose pulps by means of a multistage cook including an acid prehydrolysis |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS57121688A (en) |
| CA (1) | CA1173602A (en) |
| FI (1) | FI63267B (en) |
| FR (1) | FR2495654B1 (en) |
| SE (1) | SE8107247L (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010046532A1 (en) | 2008-10-21 | 2010-04-29 | Danisco A/S | Process of producing xylose and dissolving pulp |
| US8262854B2 (en) | 2006-02-10 | 2012-09-11 | Metso Paper, Inc. | Method for recovering hydrolysis products |
| WO2017142445A1 (en) * | 2016-02-16 | 2017-08-24 | Valmet Ab | Method for recovering concentrated hydrolysate after hydrolysis of cellulose material |
| WO2020204793A1 (en) | 2019-04-01 | 2020-10-08 | Valmet Ab | Method for extracting hemicellulose from lignocellulosic material |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4436586A (en) * | 1982-01-22 | 1984-03-13 | Kamyr, Inc. | Method of producing kraft pulp using an acid prehydrolysis and pre-extraction |
| CN1099501C (en) * | 1999-09-21 | 2003-01-22 | 中国科学院广州化学研究所 | Pulping technology by dissolving eucalyptus |
| US9260818B2 (en) * | 2007-05-23 | 2016-02-16 | Andritz Inc. | Single vessel reactor system for hydrolysis and digestion of wood chips with chemical enhanced wash method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE442623A (en) * | 1939-12-13 | |||
| SE389520B (en) * | 1973-09-03 | 1976-11-08 | Kamyr Ab | APPARATUS FOR CONTINUOUS EXTRACTION OF HYDROLYSATE FROM FINELY DISTRIBUTED FIBER MATERIAL |
-
1980
- 1980-12-08 FI FI803802A patent/FI63267B/en not_active Application Discontinuation
-
1981
- 1981-12-02 CA CA000391377A patent/CA1173602A/en not_active Expired
- 1981-12-03 SE SE8107247A patent/SE8107247L/en unknown
- 1981-12-04 FR FR8122762A patent/FR2495654B1/en not_active Expired
- 1981-12-08 JP JP56196428A patent/JPS57121688A/en active Pending
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8262854B2 (en) | 2006-02-10 | 2012-09-11 | Metso Paper, Inc. | Method for recovering hydrolysis products |
| WO2010046532A1 (en) | 2008-10-21 | 2010-04-29 | Danisco A/S | Process of producing xylose and dissolving pulp |
| WO2017142445A1 (en) * | 2016-02-16 | 2017-08-24 | Valmet Ab | Method for recovering concentrated hydrolysate after hydrolysis of cellulose material |
| CN108699768A (en) * | 2016-02-16 | 2018-10-23 | 维美德公司 | Method for the recycling concentration hydrolysate after cellulosic material hydrolysis |
| EP3417102A4 (en) * | 2016-02-16 | 2019-10-30 | Valmet AB | Method for recovering concentrated hydrolysate after hydrolysis of cellulose material |
| CN108699768B (en) * | 2016-02-16 | 2020-10-27 | 维美德公司 | Process for recovering a concentrated hydrolysate after hydrolysis of cellulosic material |
| US10947669B2 (en) | 2016-02-16 | 2021-03-16 | Valmet Ab | Method for recovering concentrated hydrolysate after hydrolysis of cellulose material |
| WO2020204793A1 (en) | 2019-04-01 | 2020-10-08 | Valmet Ab | Method for extracting hemicellulose from lignocellulosic material |
| EP3947809A4 (en) * | 2019-04-01 | 2023-01-04 | Valmet Ab | Method for extracting hemicellulose from lignocellulosic material |
Also Published As
| Publication number | Publication date |
|---|---|
| FI803802L (en) | 1982-06-09 |
| FI63267B (en) | 1983-01-31 |
| JPS57121688A (en) | 1982-07-29 |
| FR2495654A1 (en) | 1982-06-11 |
| FR2495654B1 (en) | 1986-07-04 |
| SE8107247L (en) | 1982-06-09 |
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| MKEX | Expiry |