CN114775324A - Dissolving pulp and preparation method thereof - Google Patents
Dissolving pulp and preparation method thereof Download PDFInfo
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- CN114775324A CN114775324A CN202210268169.XA CN202210268169A CN114775324A CN 114775324 A CN114775324 A CN 114775324A CN 202210268169 A CN202210268169 A CN 202210268169A CN 114775324 A CN114775324 A CN 114775324A
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- 229920000875 Dissolving pulp Polymers 0.000 title claims abstract description 63
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 238000005406 washing Methods 0.000 claims abstract description 96
- 238000004061 bleaching Methods 0.000 claims abstract description 91
- 239000002002 slurry Substances 0.000 claims abstract description 85
- 239000002023 wood Substances 0.000 claims abstract description 84
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims abstract description 80
- 238000010411 cooking Methods 0.000 claims abstract description 77
- 239000002351 wastewater Substances 0.000 claims abstract description 54
- 238000000034 method Methods 0.000 claims abstract description 35
- 239000003513 alkali Substances 0.000 claims description 56
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 51
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 42
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 27
- 239000001301 oxygen Substances 0.000 claims description 27
- 229910052760 oxygen Inorganic materials 0.000 claims description 27
- 239000003795 chemical substances by application Substances 0.000 claims description 20
- 238000010306 acid treatment Methods 0.000 claims description 15
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 10
- -1 polyoxyethylene Polymers 0.000 claims description 9
- 238000004073 vulcanization Methods 0.000 claims description 9
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 6
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 6
- 229910052979 sodium sulfide Inorganic materials 0.000 claims description 6
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims description 6
- 235000014113 dietary fatty acids Nutrition 0.000 claims description 5
- 239000000194 fatty acid Substances 0.000 claims description 5
- 229930195729 fatty acid Natural products 0.000 claims description 5
- 150000002191 fatty alcohols Chemical class 0.000 claims description 3
- 230000003204 osmotic effect Effects 0.000 claims 2
- 239000011347 resin Substances 0.000 abstract description 23
- 229920005989 resin Polymers 0.000 abstract description 23
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 description 42
- 239000004155 Chlorine dioxide Substances 0.000 description 21
- 235000019398 chlorine dioxide Nutrition 0.000 description 21
- 239000007788 liquid Substances 0.000 description 12
- 239000000126 substance Substances 0.000 description 12
- 102100030386 Granzyme A Human genes 0.000 description 11
- 101001009599 Homo sapiens Granzyme A Proteins 0.000 description 11
- 239000002253 acid Substances 0.000 description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
- 238000006243 chemical reaction Methods 0.000 description 10
- 238000009897 hydrogen peroxide bleaching Methods 0.000 description 10
- 230000007062 hydrolysis Effects 0.000 description 9
- 238000006460 hydrolysis reaction Methods 0.000 description 9
- 244000166124 Eucalyptus globulus Species 0.000 description 8
- 230000003647 oxidation Effects 0.000 description 8
- 238000007254 oxidation reaction Methods 0.000 description 8
- 241000278701 Acacia mangium Species 0.000 description 7
- 235000017631 Acacia mangium Nutrition 0.000 description 7
- 239000003814 drug Substances 0.000 description 7
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 6
- 239000000460 chlorine Substances 0.000 description 6
- 229910052801 chlorine Inorganic materials 0.000 description 6
- 230000003749 cleanliness Effects 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 229920005610 lignin Polymers 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 229910021645 metal ion Inorganic materials 0.000 description 5
- FMMSEFNIWDFLKK-UHFFFAOYSA-N [O].OO Chemical compound [O].OO FMMSEFNIWDFLKK-UHFFFAOYSA-N 0.000 description 4
- 230000018044 dehydration Effects 0.000 description 4
- 238000006297 dehydration reaction Methods 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- 230000007613 environmental effect Effects 0.000 description 4
- 239000011121 hardwood Substances 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000004064 recycling Methods 0.000 description 4
- 241000220479 Acacia Species 0.000 description 3
- 229920000742 Cotton Polymers 0.000 description 3
- 235000010643 Leucaena leucocephala Nutrition 0.000 description 3
- 239000002027 dichloromethane extract Substances 0.000 description 3
- 238000011068 loading method Methods 0.000 description 3
- HGUFODBRKLSHSI-UHFFFAOYSA-N 2,3,7,8-tetrachloro-dibenzo-p-dioxin Chemical compound O1C2=CC(Cl)=C(Cl)C=C2OC2=C1C=C(Cl)C(Cl)=C2 HGUFODBRKLSHSI-UHFFFAOYSA-N 0.000 description 2
- 229920003043 Cellulose fiber Polymers 0.000 description 2
- 229920001131 Pulp (paper) Polymers 0.000 description 2
- 229920000297 Rayon Polymers 0.000 description 2
- 230000000711 cancerogenic effect Effects 0.000 description 2
- 231100000315 carcinogenic Toxicity 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 125000005456 glyceride group Chemical group 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000004627 regenerated cellulose Substances 0.000 description 2
- RSWGJHLUYNHPMX-UHFFFAOYSA-N Abietic-Saeure Natural products C12CCC(C(C)C)=CC2=CCC2C1(C)CCCC2(C)C(O)=O RSWGJHLUYNHPMX-UHFFFAOYSA-N 0.000 description 1
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 1
- 235000017491 Bambusa tulda Nutrition 0.000 description 1
- 229920002488 Hemicellulose Polymers 0.000 description 1
- 229920000433 Lyocell Polymers 0.000 description 1
- 244000082204 Phyllostachys viridis Species 0.000 description 1
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 1
- KHPCPRHQVVSZAH-HUOMCSJISA-N Rosin Natural products O(C/C=C/c1ccccc1)[C@H]1[C@H](O)[C@@H](O)[C@@H](O)[C@@H](CO)O1 KHPCPRHQVVSZAH-HUOMCSJISA-N 0.000 description 1
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 229920006221 acetate fiber Polymers 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 239000011425 bamboo Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 150000004665 fatty acids Chemical class 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 235000021588 free fatty acids Nutrition 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 238000011534 incubation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000007127 saponification reaction Methods 0.000 description 1
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical compound [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 1
- 229910001948 sodium oxide Inorganic materials 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 239000011550 stock solution Substances 0.000 description 1
- 238000005486 sulfidation Methods 0.000 description 1
- KHPCPRHQVVSZAH-UHFFFAOYSA-N trans-cinnamyl beta-D-glucopyranoside Natural products OC1C(O)C(O)C(CO)OC1OCC=CC1=CC=CC=C1 KHPCPRHQVVSZAH-UHFFFAOYSA-N 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
Images
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
- D21H11/02—Chemical or chemomechanical or chemothermomechanical pulp
-
- 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
- D21C1/00—Pretreatment of the finely-divided materials before digesting
- D21C1/02—Pretreatment of the finely-divided materials before digesting with water or steam
-
- 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
- D21C7/00—Digesters
-
- 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
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
- D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Paper (AREA)
Abstract
The invention discloses dissolving pulp and a preparation method thereof, wherein the preparation method of the dissolving pulp comprises the following steps: obtaining wood chips to be treated, and washing the wood chips to be treated through washing wastewater; carrying out steam prehydrolysis on wood chips to be treated; cooking the wood chips to be treated after steam prehydrolysis to obtain initial slurry; and carrying out ozone bleaching on the initial pulp, and washing the initial pulp after the ozone bleaching to obtain dissolving pulp and washing wastewater. The method can reduce the resin content of the dissolving pulp and improve the yield of the dissolving pulp.
Description
Technical Field
The invention relates to the technical field of dissolving pulp preparation, in particular to dissolving pulp and a preparation method thereof.
Background
Dissolving pulp is a special chemical pulp composed of high-purity cellulose, and is a raw material of various regenerated cellulose fibers and films such as viscose, lyocell, acetate fiber and the like, and products can be divided into two categories according to the raw materials, namely cotton pulp and wood pulp. Cotton pulp is subject to cotton yield limitations and environmental policy, with yields slipping year after year, and wood dissolving pulp is the main trend for making regenerated cellulose fibers.
The resin content in the dissolving pulp has great influence on the preparation of viscose fibers, and the resin content is higher, so that saponification reaction is generated during alkali impregnation, uneven alkali liquor absorption is caused, insoluble substances in spinning stock solution are too high, filtration and deaeration are difficult, spinnability is reduced, whiteness of finished fibers is reduced, and other negative problems are caused. During cooking, the resin and lignin are easy to condense, which causes difficulty in removing lignin, increases the amount of residue, reduces the yield of pulp, and consumes cooking agents.
The prior dissolving pulp preparation is difficult to reduce the resin content.
Disclosure of Invention
The invention provides dissolving pulp and a preparation method thereof, which aim to solve the problem of overhigh resin content in the dissolving pulp.
In order to solve the technical problem, the invention provides a preparation method of dissolving pulp, which comprises the following steps: obtaining wood chips to be treated, and washing the wood chips to be treated through washing wastewater; carrying out steam prehydrolysis on wood chips to be treated; cooking the wood chips to be treated after steam prehydrolysis to obtain initial slurry; and carrying out ozone bleaching on the initial pulp, and washing the initial pulp after the ozone bleaching to obtain dissolving pulp and washing wastewater.
Wherein, the steps of carrying out ozone bleaching on the initial pulp and washing the initial pulp after the ozone bleaching to obtain dissolving pulp and washing wastewater comprise: and sequentially carrying out oxygen delignification treatment, acid treatment, ozone bleaching, alkali treatment and pressure hydrogen peroxide treatment on the initial pulp, and washing the initial pulp after ozone bleaching to obtain dissolving pulp and washing wastewater.
Wherein the step of sequentially subjecting the initial slurry to oxygen delignification treatment, acid treatment, ozone bleaching, alkali treatment and pressure hydrogen peroxide treatment to obtain a dissolving slurry comprises: performing oxygen delignification treatment on the initial slurry; carrying out acid treatment on the initial slurry after oxygen delignification treatment by using sulfuric acid; carrying out ozone bleaching on the initial slurry after the acid treatment by using ozone; carrying out alkali treatment on the initial slurry after ozone bleaching by using sodium hydroxide; carrying out at least one section of pressure hydrogen peroxide treatment on the initial slurry after the alkali treatment to obtain bleaching wastewater and bleaching slurry; dissolving pulp is obtained based on the bleached pulp.
Wherein the ozone dosage range of the ozone bleaching is 0.2-1.5%, and the ozone bleaching temperature range is 30-70 ℃.
Wherein, the step of cooking the wood chips to be treated after steam prehydrolysis to obtain initial slurry comprises the following steps: and (3) cooking the wood chips to be treated after the steam prehydrolysis through sodium hydroxide, sodium sulfide and a permeable cooking agent to obtain initial slurry.
Wherein the penetrating type cooking agent at least comprises one or more of polyoxyethylene fatty acid ester, polyoxyethylene fatty alcohol ether and fatty glyceride.
Wherein the dosage range of the penetrating type cooking agent is 0.05-0.20%.
Wherein the alkali consumption range of the cooking is 15-25%, and the vulcanization degree range of the cooking is 15-35%.
Wherein the step of steam prehydrolysis of wood chips to be treated further comprises: and in response to the temperature of steam prehydrolysis reaching a preset condition, performing at least two times of steam release treatment on the wood chips to be treated.
In order to solve the technical problems, the invention also provides dissolving pulp which is prepared by the preparation method of the dissolving pulp.
The invention has the beneficial effects that: different from the situation of the prior art, the wood chips to be treated are obtained, and are washed by washing wastewater; carrying out steam prehydrolysis on wood chips to be treated; cooking the wood chips to be treated after steam prehydrolysis to obtain initial slurry; the initial slurry is subjected to ozone bleaching, and the initial slurry after the ozone bleaching is washed to obtain dissolving slurry and washing wastewater, and the initial slurry is subjected to ozone oxidation, so that the resin content in the initial slurry can be greatly reduced. And the ozone oxidation does not influence the gray scale and the metal ion content of the initial slurry, so that the resin content in the slurry can be reduced, and the whiteness of the slurry can be improved. And the washing wastewater is recycled, so that the wood chips to be treated can be washed by using the temperature of the washing wastewater and washing substances, and the washing cleanliness of the wood chips to be treated is improved under the condition of recycling the washing wastewater.
Drawings
FIG. 1 is a schematic flow chart showing an example of a method for producing dissolving pulp according to the present invention;
FIG. 2 is a schematic flow chart showing another embodiment of the method for producing dissolving pulp of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, fig. 1 is a schematic flow chart of an embodiment of a method for preparing dissolving pulp according to the present invention.
Step S11: obtaining wood chips to be treated, and washing the wood chips to be treated through washing wastewater.
Obtaining the wood chips to be treated for preparing dissolving pulp. The wood chips to be treated in this embodiment may be any wood, and include hardwood, for example: eucalyptus, acacia, etc. the dissolving pulp prepared from hardwood as a raw material has a relatively large resin content because the resin component of hardwood includes some esterified fatty acids, and few free fatty acids and a small amount of rosin acids, but the method for preparing dissolving pulp of this example can reduce the resin content in the dissolving pulp prepared from hardwood.
The wood chips to be treated are washed by the washing wastewater obtained by the washing step in the step S14 in this embodiment, so that the washing wastewater can be recycled, thereby saving the production cost of dissolving pulp.
Step S12: the wood chips to be treated are subjected to steam prehydrolysis.
The wood chips to be treated are subjected to steam prehydrolysis, wherein the steam prehydrolysis refers to a process of pretreating with water, steam or dilute acid in a closed container at a certain temperature and pressure.
The wood chips to be treated are subjected to steam prehydrolysis, so that air in the wood chips to be treated can be discharged, the temperature is increased and stabilized, the wood chips to be treated can absorb liquid medicine quickly after entering a subsequent cooking procedure, the temperature of the wood chips to be treated is higher, the temperature rise time of the bamboo chips in the subsequent cooking procedure can be saved, and the preparation efficiency of dissolving pulp is improved.
Step S13: and (4) cooking the wood chips to be treated after steam prehydrolysis to obtain initial slurry.
And (4) cooking the wood chips to be treated after steam prehydrolysis to obtain initial slurry.
In a specific application scenario, the wood chips to be treated can be cooked by using sodium hydroxide and sodium sulfide and controlling the temperature, and the emphasis of the cooking section is controlled by the H factor, so as to obtain the initial slurry. Wherein the H factor defines: the relative reaction rate constant at each cooking temperature is a constant integral over the cooking time.
Step S14: and carrying out ozone bleaching on the initial pulp, and washing the initial pulp after the ozone bleaching to obtain dissolving pulp and washing wastewater.
After obtaining the initial slurry, the initial slurry is subjected to ozone bleaching, wherein in the embodiment, the resin content in the initial slurry can be greatly reduced by performing ozone oxidation on the initial slurry. And the ozone oxidation does not influence the gray scale and the metal ion content of the initial slurry, so that the resin content in the slurry can be reduced, and the whiteness of the slurry can be improved.
In addition, in the embodiment, the ozone is used for bleaching, so that the bleaching by adopting chlorine-containing substances is avoided, the chlorine-containing bleaching has the defects that the water consumption for bleaching is large, the wastewater is difficult to treat, and carcinogenic substances such as dioxin exist, and the like, and the ozone bleaching replaces the chlorine-containing bleaching, so that the water consumption for bleaching can be further reduced, and the environmental protection property and the safety of the preparation of the dissolving pulp are improved.
After the ozone bleaching, washing the initial slurry after the ozone bleaching to obtain dissolving slurry and washing wastewater. The washing wastewater obtained in the step can be used for washing the wood chips to be treated in the step S11, so that the wood chips to be treated can be washed by using the temperature of the washing wastewater and the washing substances, and the washing cleanliness of the wood chips to be treated is improved under the condition of recycling the washing wastewater.
Through the steps, the wood chips to be treated are obtained, and the wood chips to be treated are washed through the washing wastewater; carrying out steam prehydrolysis on wood chips to be treated; cooking the wood chips to be treated after steam prehydrolysis to obtain initial slurry; the initial slurry is subjected to ozone bleaching, and the initial slurry after the ozone bleaching is washed to obtain dissolving slurry and washing wastewater, and the initial slurry is subjected to ozone oxidation, so that the resin content in the initial slurry can be greatly reduced. And the ozone oxidation does not influence the gray scale and the metal ion content of the initial slurry, so that the resin content in the slurry can be reduced, and the whiteness of the slurry can be improved. And the washing wastewater is recycled, so that the wood chips to be treated can be washed by using the temperature of the washing wastewater and washing substances in the washing of the wood chips to be treated, and the washing cleanliness of the wood chips to be treated is improved under the condition of recycling the washing wastewater.
Referring to fig. 2, fig. 2 is a schematic flow chart of another embodiment of the dissolving pulp preparation method of the present invention.
Step S21: obtaining wood chips to be treated, and washing the wood chips to be treated through washing wastewater.
This step is the same as step S11 in the previous embodiment, and please refer to the foregoing description, which is not repeated herein.
Step S22: and (3) carrying out steam prehydrolysis on the wood chips to be treated, and carrying out at least two times of steam release treatment on the wood chips to be treated in response to the temperature of the steam prehydrolysis reaching a preset condition.
After washing the wood chips, performing steam prehydrolysis on the wood chips to be treated, wherein the range of the P factor (prehydrolysis factor) in the prehydrolysis stage is 400-700, specifically 400, 450, 500, 550, 600, 650, or 700, and the like, which can be specifically set based on actual situations and is not limited herein.
And in response to the temperature of the steam prehydrolysis reaching the preset condition, performing at least two times of steam release treatment on the wood chips to be treated. The preset conditions comprise that multi-stage preset temperature or multi-stage preset temperature ranges are met, and the difference between the preset temperature or the preset temperature ranges of each stage is 10-20 degrees. When the temperature of steam prehydrolysis reaches a preset temperature at a certain stage, steam discharging treatment is carried out. The number of the stages of the preset temperature is at least two, and specifically, the number of the stages of the preset temperature can be 2, 4, 5, 6, 7, and the like. The preset temperature and the specific temperature of the preset temperature range may be set based on the kind of wood chips to be treated and other practical conditions, and are not limited herein.
In a specific application scenario, when the wood chips to be treated are subjected to steam prehydrolysis, after the hydrolysis temperature rises to reach a stable state for 10-30 minutes, when the temperature reaches 120-plus-150 ℃, steam is released for 5-10 minutes for the first time, when the temperature reaches 130-plus-170 ℃, steam is released for the second time, and the temperature is kept for 20-80 minutes.
In the step, ester substances in the resin can be discharged partially along with the steam through small steam release of presteaming. Compared with the steam discharging of the alkaline cooking section, the steam discharging of the steam prehydrolysis stage has less pollution to the environment, and can reduce the discharge of part of effective substances such as cellulose, hemicellulose, medicines and the like dissolved out by the steam discharging of the alkaline cooking section along with the steam, thereby reducing the yield of dissolving pulp, reducing the effective rate of medicine use, influencing the production environment, reducing the resin content in the wood chips to be treated, improving the yield of dissolving pulp to a certain extent, improving the effective rate of medicine use and ensuring the production environment.
Step S23: and (3) cooking the wood chips to be treated after the steam prehydrolysis through sodium hydroxide, sodium sulfide and a permeable cooking agent to obtain initial slurry.
And (3) cooking the wood chips to be treated after the steam prehydrolysis by using sodium hydroxide, sodium sulfide and a permeable cooking agent to obtain initial slurry. Wherein the alkali consumption range in the cooking process is 15-25%, and the vulcanization degree range is 15-35%. Wherein the alkali dosage is a general term in the industry and represents the ratio of the mass of alkali (sodium hydroxide in the present invention) to the oven dry mass of the cooked sample, expressed as mass percent. The degree of sulfidation is the percentage of sodium sulfide to active base (in this invention sodium hydroxide) in terms of sodium oxide.
Wherein, in the cooking process, the penetration type cooking agent is added for co-cooking. The permeable cooking agent at least comprises one or more of polyoxyethylene fatty acid ester, polyoxyethylene fatty alcohol ether and fatty glyceride. The dosage of the permeable cooking agent is 0.05-0.20%, and specifically may be 0.05%, 0.08%, 0.12%, 0.16%, 0.18%, or 0.20%, and the like, which is not limited herein.
The permeable cooking agent is added in the cooking process, so that extractable substances can be dispersed in a guide pipe or a capillary of wood to be treated, the liquid medicine can be deeply permeated, the permeation speed is accelerated, the liquid medicine can quickly permeate into the capillary to reach the inside of a material sheet, and the liquid medicine reacts with lignin to generate soluble lignin with small molecular weight, so that the lignin is easier to diffuse and wash, and simultaneously, delignification and alkali consumption reduction are facilitated. And the permeable cooking agent has biodegradability and does not cause burden on wastewater treatment. The permeable cooking agent is a high molecular organic matter which can enter an alkali recovery system along with the black liquor and can not affect the alkali recovery system.
In a specific application scenario, the initial pulp may be diluted to 1-6g/L concentration by black liquor (washing liquid for washing digested pulp in the process of making pulp by sulfate method or soda method) or hot water, the alkali concentration in the digestion stage is 40-100g/L, and the liquor ratio is 1: 3-1: 5 (liquid ratio: the ratio of the weight of the absolutely dry raw materials to the volume of the total liquid of the cooking), and the temperature is 150 ℃ and 170 ℃.
Wherein, the end point of the cooking stage is controlled to 500-1300 by an H factor, which can be 500, 560, 320, 680, 750, 793, 855, 900, 986, 1052, 1124, 1256 or 1300, etc., wherein the H factor refers to: the relative reaction rate constant at each cooking temperature is a constant integral over the cooking time.
Step S24: and sequentially carrying out oxygen delignification treatment, acid treatment, ozone bleaching, alkali treatment and pressure hydrogen peroxide treatment on the initial pulp, and washing the initial pulp to obtain dissolving pulp and washing wastewater.
The method comprises the steps of carrying out oxygen delignification treatment on initial pulp, carrying out acid treatment on the initial pulp after the oxygen delignification treatment by using sulfuric acid, carrying out ozone bleaching on the initial pulp after the acid treatment by using ozone, carrying out alkali treatment on the initial pulp after the ozone bleaching by using sodium hydroxide, carrying out at least one section of pressure hydrogen peroxide treatment on the initial pulp after the alkali treatment to obtain bleaching waste water and bleaching pulp, and obtaining dissolving pulp based on the bleaching pulp.
In the embodiment, the ozone is used for bleaching, so that the bleaching by adopting chlorine-containing substances is avoided, the chlorine-containing bleaching has the defects that the water consumption for bleaching is large, the wastewater is difficult to treat, and carcinogenic substances such as dioxin exist, and the like, and the ozone bleaching replaces the chlorine-containing bleaching, so that the water consumption for bleaching can be further reduced, and the environmental protection property and the safety of the preparation of the dissolving pulp are improved.
After the ozone bleaching, washing the initial slurry after the ozone bleaching to obtain dissolving slurry and washing wastewater. The washing wastewater obtained in the step can be used for washing the wood chips to be treated in the step S11, so that the wood chips to be treated can be washed by using the temperature of the washing wastewater and the residual hydrogen peroxide, the utilization rate of the hydrogen peroxide is improved and the washing cleanliness of the wood chips to be treated is improved under the condition that the washing wastewater and the hydrogen peroxide are recycled, and the hydrogen peroxide can also remove the resin in the wood chips to be treated to a certain degree, thereby further reducing the resin content in the dissolving pulp.
During oxygen delignification, the concentration range of the initial slurry is 10-20%, the alkali dosage range is 1.5-4.5%, the oxygen pressure range is 0.8-1.0MPa, the temperature range is 95-110 ℃, and the heat preservation time range is 60-80 minutes. The concentration of the initial slurry may be 10%, 12%, 15%, 18%, 20%, etc., and the amount of the alkali may be 1.5%, 1.9%, 2.1%, 2.5%, 2.8%, 3.4%, 3.9%, 4.0%, 4.3%, or 4.5%. The oxygen pressure may be specifically 0.8MPa, 0.9MPa or 1.0 MPa. The temperature may be 95 deg.C, 98 deg.C, 101 deg.C, 103 deg.C, 105 deg.C, 106 deg.C, 109 deg.C or 110 deg.C. The incubation time may be specifically 60 minutes, 65 minutes, 72 minutes, 76 minutes, 79 minutes or 80 minutes. And are not limited herein.
After the oxygen delignification treatment, carrying out acid treatment on the initial slurry, wherein the acid treatment adopts sulfuric acid, and in the acid treatment process, the concentration range of the initial slurry is 10-20%, the pH range is 1.5-3.5, the temperature range is 70-80 ℃, and the time range is 60-80 minutes. Specifically, the concentration of the initial slurry may be 10%, 12%, 15%, 18%, 20%, or the like, and the pH may be 1.5, 1.8, 2.1, 2.5, 2.9, 3.2, 3.5, or the like. The temperature may be 70 ℃, 72 ℃, 73 ℃, 75 ℃, 76 ℃, 79 ℃ or 80 ℃ and the time may be 60 minutes, 64 minutes, 69 minutes, 72 minutes, 76 minutes, 79 minutes or 80 minutes. And are not limited herein.
After the acid treatment, the initial pulp is subjected to ozone bleaching, wherein the dosage range of ozone is 0.2-1.5%, and the temperature range is 30-70 ℃. The ozone may be used in an amount of 0.2%, 0.4%, 0.5%, 0.7%, 0.9%, 1.1%, 1.2%, or 1.5%, and the temperature may be 30 ℃, 35 ℃, 40 ℃, 46 ℃, 50 ℃, 53 ℃, 59 ℃, 62 ℃, 68 ℃, or 70 ℃. And is not limited thereto. Ozone bleaching within this parameter range can meet the bleaching requirements for the initial pulp.
After the ozone reaction is finished, alkali treatment is carried out, the alkali consumption range is 1-2%, the temperature range is 70-80 ℃, the concentration range of initial slurry is 10-20%, and the time range is 30-45 minutes. The alkali content may be 1.0%, 1.5%, or 2.0%, and the temperature may be 70 deg.C, 72 deg.C, 73 deg.C, 75 deg.C, 76 deg.C, 79 deg.C, or 80 deg.C. The concentration of the initial slurry may be specifically 10%, 12%, 15%, 18%, 20%, or the like, and the time may be specifically 30 minutes, 33 minutes, 35 minutes, 37 minutes, 40 minutes, 42 minutes, 45 minutes, or the like. And are not limited herein.
After the alkali treatment is finished, one-stage or two-stage pressure hydrogen peroxide bleaching (PO) is carried out, the oxygen pressure range is 0.2-0.3MPa, the concentration range of the initial slurry is 10-20%, the temperature range is 105-120 ℃, and the bleaching time range is 60-90 minutes. The oxygen pressure may be 0.2 or 0.3MPa, the concentration of the initial slurry may be 10%, 12%, 15%, 18%, or 20%, and the temperature may be 105 ℃, 108 ℃, 113 ℃, 115 ℃, 119 ℃, or 120 ℃. And are not limited herein. The hydrogen peroxide bleaching can realize the bleaching of initial slurry under the condition of safety and environmental protection, and can also ensure that the washed washing wastewater contains hydrogen peroxide, so that the hydrogen peroxide is recycled and the cleanliness of wood chips to be treated is improved when the wood chips to be treated are washed by the washing wastewater containing hydrogen peroxide.
The preparation method and performance of the dissolving pulp with the above ratio according to the present invention will be examined through a plurality of specific examples. The wood chips to be treated in the following experiments included eucalyptus australis and acacia wood chips, with a chip size of 15 x 2mm (length, width, height), ash content of 0.4%, metal ion content of 0.17%. The alkaline water pH for wood chips washing was 10. The cooking stage permeable cooking agent used was soriss PK 9000. Dilute sulfuric acid, pH 1.5, was used for the acid pretreatment. The alkali treatment is NaOH, and the alkali amount is calculated relative to the absolute dry amount of the slurry.
Example 1:
washing eucalyptus pieces by using washing wastewater, then putting the eucalyptus pieces into a pot, setting the P factor of a prehydrolysis stage to be 500, performing primary steam release when the temperature reaches 120 ℃ after the hydrolysis temperature rise reaches a stable state for 10 minutes, performing secondary steam release when the temperature reaches 155 ℃ for 5 minutes, performing secondary steam release when the temperature reaches the secondary temperature rise and continuing to preserve heat for 60 minutes. The alkali consumption and the vulcanization degree of the cooking section are respectively 20 percent and 30 percent, the end point of the cooking section is controlled by an H factor to be 590, a permeable cooking agent is added into the cooking section, the consumption is 0.12 percent, the alkali concentration of the cooking section is 135g/L, and the liquor ratio is 1: 4, the temperature is 170 ℃. After oxygen delignification, pulp is subjected to acid pretreatment and ozone bleaching, the acid pretreatment process adopts the steps that the pH value is 1.5, the temperature is 70 ℃, the pulp concentration is 10 percent, the time is 60 minutes, then dehydration and concentration are carried out until the pulp concentration reaches 30 percent, dispersion is carried out, and the pulp is placed in an ozone mixing reactor for ozone bleaching, wherein the ozone dosage is as follows: 1 percent. And (3) the ozone stays for 7 minutes after being introduced into the reactor, the reaction is stopped, the reactor is opened, the slurry is taken out, and alkali treatment is carried out: the alkali consumption is 1%, the temperature is 70 ℃, the pulp concentration is 10%, and the time is 30 minutes. And then washing the pulp by using deionized water. The pressure oxygen-hydrogen peroxide bleaching is carried out in two sections, and the first section of the pressure hydrogen peroxide bleaching process comprises the following steps: the using amount of the hydrogen peroxide is 2 percent, the using amount of the sodium hydroxide is 3 percent, the pulp concentration is 10 percent, the oxygen pressure is 0.2MPa, the temperature is 110 ℃, and the time is 60 minutes; the second stage of hydrogen peroxide bleaching process has hydrogen peroxide amount of 1.5%, sodium hydroxide amount of 2.5%, pulp concentration of 10%, oxygen pressure of 0.2MPa, temperature of 110 deg.c and time of 60 min. And (4) after the reaction is finished, washing the pulp to obtain dissolving pulp, and using the washing wastewater after washing for washing the wood chips.
Example 2:
washing the eucalyptus pieces by using the washing wastewater, then putting the eucalyptus pieces into a pot, wherein the P factor in the prehydrolysis stage is 500, after the temperature rises after hydrolysis and reaches a stable state for 10 minutes, performing primary steam release when the temperature reaches 120 ℃, releasing steam for 5 minutes, performing secondary steam release when the temperature rises to 145 ℃, releasing steam for 10 minutes, and continuously preserving heat for 60 minutes. The alkali consumption and the vulcanization degree of the cooking section are respectively 20 percent and 30 percent, the end point of the cooking section is controlled by an H factor to be 590, a permeable cooking agent is added into the cooking section, the consumption is 0.1 percent, the alkali concentration of the cooking section is 50g/L, and the liquid ratio is 1: 4, the temperature is 170 ℃. After oxygen delignification, pulp is subjected to acid pretreatment and ozone bleaching, the acid pretreatment process adopts the steps of pH of 1.5, temperature of 70 ℃, pulp concentration of 10 percent and time of 60 minutes, then dehydration concentration is carried out until the pulp concentration reaches 30 percent, dispersion is carried out, and the pulp is placed in an ozone mixing reactor for ozone bleaching, wherein the ozone dosage is as follows: 0.6 percent. And (3) introducing ozone into the reactor, then staying for 5-8 minutes, stopping, opening the reactor, taking out slurry, and performing alkali treatment: the alkali consumption is 1%, the temperature is 70 ℃, the pulp concentration is 10%, and the time is 30 minutes. And then washing the pulp by using deionized water. Single-stage pressure oxygen-hydrogen peroxide bleaching, wherein the consumption of hydrogen peroxide is 8 percent, the sodium hydroxide is 3 percent, the pulp concentration is 10 percent, the oxygen pressure is 0.3MPa, the temperature is 110 ℃, and the time is 120 minutes. And (4) after the reaction is finished, washing the pulp to obtain dissolved pulp, and using the washed waste water for washing wood chips.
Comparative example 1:
and (3) loading the eucalyptus pieces into a pot, wherein the P factor in the prehydrolysis stage is 500, releasing steam when the temperature reaches 120 ℃ after the hydrolysis temperature rise reaches a stable state for 10 minutes, releasing steam for 5 minutes, and preserving heat for 60 minutes when the hydrolysis temperature rise reaches 155 ℃. The alkali consumption and the vulcanization degree of the cooking section are respectively 20 percent and 30 percent, the end point of the cooking section is controlled by an H factor to be 590, the alkali concentration of the cooking section is 135g/L, and the liquid ratio is 1: 4, the temperature is 170 ℃. The bleaching comprises 3 stages of chlorine dioxide bleaching and one stage of alkali extraction, specifically, the dosage of chlorine dioxide in the first stage of chlorine dioxide bleaching is 0.5 percent, the temperature is 75 ℃, the time is 120 minutes, the pH is 2.0, and the pulp concentration is 10 percent. Then alkali treatment is carried out, wherein the alkali consumption is 1%, the temperature is 70 ℃, the pulp concentration is 10%, and the time is 30 minutes. And after the first-stage chlorine dioxide bleaching, performing second-stage chlorine dioxide bleaching, wherein the consumption of the second-stage chlorine dioxide bleaching is 0.3%, the temperature is 80 ℃, the time is 120 minutes, the pH is 4.5, and the pulp concentration is 10%. And after the second stage of chlorine dioxide bleaching, performing third stage of chlorine dioxide bleaching, wherein the consumption of the chlorine dioxide in the third stage of chlorine dioxide bleaching is 0.1%, the temperature is 80 ℃, the time is 120 minutes, the pH is 4.0, and the pulp concentration is 10%. After the reaction, a dissolving pulp is obtained.
Example 3:
after balancing the moisture of the acacia mangium pieces, washing the acacia mangium pieces through washing wastewater, then loading the acacia mangium pieces into a pot, wherein the P factor in the prehydrolysis stage is 500, after the hydrolysis temperature rises to a stable state for 10 minutes, performing primary steam release when the temperature reaches 120 ℃, releasing steam for 5 minutes, performing secondary steam release when the temperature rises to 155 ℃ for two times, releasing steam for 10 minutes, and continuously keeping the temperature for 60 minutes. The alkali consumption and the vulcanization degree of the cooking section are respectively 20 percent and 30 percent, the end point of the cooking section is controlled by an H factor to be 1190, a permeable cooking agent is added into the cooking section, the consumption is 0.12 percent, the alkali concentration of the cooking section is 60g/L, and the liquid ratio is 1: 4, the temperature is 170 ℃. After oxygen delignification, pulp is subjected to acid pretreatment and ozone bleaching, the acid pretreatment process adopts the steps that the pH value is 1.5, the temperature is 70 ℃, the pulp concentration is 10 percent, the time is 60 minutes, then dehydration and concentration are carried out until the pulp concentration reaches 30 percent, dispersion is carried out, and the pulp is placed in an ozone mixing reactor for ozone bleaching, wherein the ozone dosage is as follows: 1 percent. And (3) introducing ozone into the reactor, then staying for 5-8 minutes, stopping, opening the reactor, taking out slurry, and performing alkali treatment: the alkali consumption is 1%, the temperature is 70 ℃, the pulp concentration is 10%, and the time is 30 minutes. And then washing the pulp by using deionized water. Single-stage pressure oxygen-hydrogen peroxide bleaching, wherein the consumption of hydrogen peroxide is 8 percent, the sodium hydroxide is 3 percent, the pulp concentration is 10 percent, the oxygen pressure is 0.3MPa, the temperature is 110 ℃, and the time is 120 minutes. And (4) after the reaction is finished, washing the pulp to obtain dissolved pulp, and using the washed waste water for washing wood chips.
Comparative example 2:
and (3) filling the acacia mangium chips into a pot, wherein the P factor of the prehydrolysis stage is 500, after the hydrolysis temperature rise reaches a stable state for 10 minutes, releasing steam when the temperature reaches 120 ℃, releasing steam for 5 minutes, and after the hydrolysis temperature rise reaches 155 ℃, preserving the heat for 60 minutes. The alkali consumption and the vulcanization degree of the cooking section are respectively 20 percent and 30 percent, the end point of the cooking section is controlled to 1190 by an H factor, the alkali concentration of the cooking section is 135g/L, and the liquid ratio is 1: 4, the temperature is 170 ℃. The bleaching comprises 3 stages of chlorine dioxide bleaching and one stage of alkali extraction, specifically, the dosage of chlorine dioxide in the first stage of chlorine dioxide bleaching is 0.5%, the temperature is 75 ℃, the time is 120 minutes, the pH is 2.0, and the pulp concentration is 10%. Then alkali treatment is carried out, wherein the alkali consumption is 1%, the temperature is 70 ℃, the pulp concentration is 10%, and the time is 30 minutes. And after the first stage of chlorine dioxide bleaching, performing second stage of chlorine dioxide bleaching, wherein the consumption of the chlorine dioxide in the second stage of chlorine dioxide bleaching is 0.3%, the temperature is 80 ℃, the time is 120 minutes, the pH is 4.5, and the pulp concentration is 10%. And after the second stage of chlorine dioxide bleaching, performing third stage of chlorine dioxide bleaching, wherein the consumption of the chlorine dioxide in the third stage of chlorine dioxide bleaching is 0.1%, the temperature is 80 ℃, the time is 120 minutes, the pH is 4.0, and the pulp concentration is 10%. After the reaction is finished, dissolving pulp is obtained.
Example 4:
after balancing the moisture of the acacia mangium chips, washing the acacia mangium chips through washing wastewater, then loading the acacia mangium chips into a pot, wherein the P factor of the prehydrolysis stage is 500, after the hydrolysis temperature rises to a stable state for 10 minutes, performing primary steam release when the temperature reaches 120 ℃, releasing steam for 5 minutes, performing secondary steam release when the secondary temperature rises to 145 ℃, releasing steam for 10 minutes, and continuously keeping the temperature for 60 minutes. The alkali consumption and the vulcanization degree of the cooking section are respectively 20 percent and 30 percent, the end point of the cooking section is controlled by an H factor to be 1200, a permeable cooking agent is added into the cooking section, the consumption is 0.1 percent, the alkali concentration of the cooking section is 50g/L, and the liquid ratio is 1: 4, the temperature is 170 ℃. After oxygen delignification, pulp is subjected to acid pretreatment and ozone bleaching, the acid pretreatment process adopts the steps of pH of 1.5, temperature of 70 ℃, pulp concentration of 10 percent and time of 60 minutes, then dehydration concentration is carried out until the pulp concentration reaches 30 percent, dispersion is carried out, and ozone bleaching is carried out in a rotary ozone mixing reactor, wherein the ozone dosage is as follows: 1 percent. And (3) introducing ozone into the reactor, then staying for 5-8 minutes, stopping, opening the reactor, taking out slurry, and performing alkali treatment: alkali consumption of 1%, temperature: the slurry concentration was 10% at 70 ℃ for 30 minutes. And then washing the pulp by using deionized water. The pressure oxygen-hydrogen peroxide bleaching is carried out in two stages, and the first stage of pressure hydrogen peroxide bleaching process comprises the following steps: the using amount of the hydrogen peroxide is 2 percent, the using amount of the sodium hydroxide is 3 percent, the pulp concentration is 10 percent, the oxygen pressure is 0.3MPa, the temperature is 110 ℃, and the time is 60 minutes; the hydrogen peroxide dosage of the second stage hydrogen peroxide bleaching process is 1.5 percent, the sodium hydroxide dosage is 2.5 percent, the pulp concentration is 10 percent, the oxygen pressure is 0.3MPa, the temperature is 110 ℃, and the time is 60 minutes. And (4) after the reaction is finished, washing the pulp to obtain dissolved pulp, and using the washed waste water for washing wood chips.
Part of the process and results test data for the above examples and comparative examples are as follows:
from the test results, it can be seen that, by the method of the present invention, under the same P factor and H factor conditions, compared with examples 1 and 2 and comparative example 1, the DCM extract content, i.e. the resin content, is greatly reduced, and the reduction respectively reaches 84.4% and 68.3%, and simultaneously the whiteness of the slurry is improved. Examples 3 and 4 compared with comparative example 2, the DCM extract of eucalyptus dissolving pulp decreased 47.8% and 42.3% respectively. The data result proves that the DCM extract content of the acacia wood dissolving pulp is greatly reduced by 40-80% in the embodiment, and meanwhile, the whiteness of the pulp is improved by 1-2% ISO.
Through the steps, the wood chips to be treated are obtained, and the wood chips to be treated are washed through the washing wastewater; carrying out steam prehydrolysis on wood chips to be treated; cooking the wood chips to be treated after steam prehydrolysis to obtain initial slurry; the initial slurry is subjected to ozone bleaching, and the initial slurry after the ozone bleaching is washed to obtain dissolving slurry and washing wastewater, and the initial slurry is subjected to ozone oxidation, so that the resin content in the initial slurry can be greatly reduced. And the ozone oxidation does not influence the gray scale and the metal ion content of the initial slurry, so that the resin content in the slurry can be reduced, and the whiteness of the slurry can be improved. And the washing wastewater is recycled, so that the wood chips to be treated can be washed by using the temperature of the washing wastewater and washing substances, and the washing cleanliness of the wood chips to be treated is improved under the condition of recycling the washing wastewater.
Based on the same inventive concept, the application also provides dissolving pulp prepared by the preparation method of the dissolving pulp in any embodiment, so that the resin content of the dissolving pulp can be reduced, and the yield of the dissolving pulp is improved.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A method for preparing dissolving pulp is characterized by comprising the following steps:
obtaining wood chips to be treated, and washing the wood chips to be treated through washing wastewater;
carrying out steam prehydrolysis on the wood chips to be treated;
cooking the wood chips to be treated after steam prehydrolysis to obtain initial slurry;
and carrying out ozone bleaching on the initial slurry, and washing the initial slurry after the ozone bleaching to obtain the dissolving pulp and the washing wastewater.
2. The method of claim 1, wherein the steps of ozone bleaching the initial slurry and washing the ozone-bleached initial slurry to obtain the dissolving pulp and the washing wastewater comprise:
and sequentially carrying out oxygen delignification treatment, acid treatment, ozone bleaching, alkali treatment and pressure hydrogen peroxide treatment on the initial pulp, and washing the initial pulp to obtain the dissolving pulp and the washing wastewater.
3. The method of preparing dissolving pulp according to claim 2, wherein said step of sequentially subjecting said initial slurry to oxygen delignification treatment, acid treatment, ozone bleaching, alkali treatment and pressurized hydrogen peroxide treatment to obtain said dissolving pulp comprises:
subjecting the initial slurry to an oxygen delignification treatment;
carrying out acid treatment on the initial slurry after oxygen delignification treatment by using sulfuric acid;
carrying out ozone bleaching on the initial slurry after the acid treatment by using ozone;
carrying out alkali treatment on the initial slurry after ozone bleaching by using sodium hydroxide;
carrying out at least one section of pressure hydrogen peroxide treatment on the initial slurry after the alkali treatment to obtain bleaching wastewater and bleaching slurry;
obtaining the dissolving pulp based on the bleaching pulp.
4. The method of producing dissolving pulp according to claim 3,
the ozone dosage range of the ozone bleaching is 0.2-1.5%, and the ozone bleaching temperature range is 30-70 ℃.
5. The process for the preparation of dissolving pulp according to claim 1, characterized in that the step of cooking the wood chips to be treated after the steam prehydrolysis to obtain an initial pulp comprises:
and (3) cooking the wood chips to be treated after the steam prehydrolysis by using sodium hydroxide, sodium sulfide and a permeable cooking agent to obtain the initial slurry.
6. The method of claim 5, wherein the osmotic cooking agent comprises at least one or more of polyoxyethylene fatty acid ester, polyoxyethylene fatty alcohol ether, and fatty acid glyceride.
7. The method of claim 5, wherein the osmotic cooking agent is used in an amount ranging from 0.05 to 0.20%.
8. The method of producing dissolving pulp according to claim 5,
the alkali consumption range of the cooking is 15-25%, and the vulcanization degree range of the cooking is 15-35%.
9. The dissolving pulp preparing method according to claim 1, wherein the step of steam prehydrolyzing the wood chips to be treated further comprises:
and responding to the temperature of the steam prehydrolysis to reach a preset condition, and performing at least two times of steam release treatment on the wood chips to be treated.
10. Dissolving pulp, characterized in that it is prepared by the method for preparing dissolving pulp according to any one of claims 1 to 9.
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Application publication date: 20220722 |