CN112726249A - Dissolving pulp prepared from corn straw skins and method - Google Patents
Dissolving pulp prepared from corn straw skins and method Download PDFInfo
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- CN112726249A CN112726249A CN202011602531.XA CN202011602531A CN112726249A CN 112726249 A CN112726249 A CN 112726249A CN 202011602531 A CN202011602531 A CN 202011602531A CN 112726249 A CN112726249 A CN 112726249A
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- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 title claims abstract description 84
- 235000002017 Zea mays subsp mays Nutrition 0.000 title claims abstract description 84
- 235000005822 corn Nutrition 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title claims abstract description 41
- 229920000875 Dissolving pulp Polymers 0.000 title claims abstract description 40
- 240000008042 Zea mays Species 0.000 title claims description 82
- 239000010902 straw Substances 0.000 title claims description 50
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 claims abstract description 84
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 79
- 239000002002 slurry Substances 0.000 claims abstract description 70
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 66
- 238000005406 washing Methods 0.000 claims abstract description 59
- 239000004155 Chlorine dioxide Substances 0.000 claims abstract description 42
- 235000019398 chlorine dioxide Nutrition 0.000 claims abstract description 42
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 41
- 238000004061 bleaching Methods 0.000 claims abstract description 41
- 239000007864 aqueous solution Substances 0.000 claims abstract description 34
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 claims abstract description 24
- 230000007935 neutral effect Effects 0.000 claims abstract description 23
- PYKYMHQGRFAEBM-UHFFFAOYSA-N anthraquinone Natural products CCC(=O)c1c(O)c2C(=O)C3C(C=CC=C3O)C(=O)c2cc1CC(=O)OC PYKYMHQGRFAEBM-UHFFFAOYSA-N 0.000 claims abstract description 20
- 150000004056 anthraquinones Chemical class 0.000 claims abstract description 20
- 238000010411 cooking Methods 0.000 claims abstract description 13
- 238000001816 cooling Methods 0.000 claims abstract description 12
- 229910052943 magnesium sulfate Inorganic materials 0.000 claims abstract description 12
- 235000019341 magnesium sulphate Nutrition 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 6
- 239000000243 solution Substances 0.000 claims abstract description 6
- 230000018044 dehydration Effects 0.000 claims description 15
- 238000006297 dehydration reaction Methods 0.000 claims description 15
- 238000004321 preservation Methods 0.000 claims description 6
- 239000007844 bleaching agent Substances 0.000 claims description 2
- 241000209149 Zea Species 0.000 abstract 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 24
- 239000000203 mixture Substances 0.000 description 13
- 239000007788 liquid Substances 0.000 description 11
- 239000003513 alkali Substances 0.000 description 9
- 238000000605 extraction Methods 0.000 description 9
- 208000003643 Callosities Diseases 0.000 description 8
- 206010020649 Hyperkeratosis Diseases 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 238000005520 cutting process Methods 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- 238000009897 hydrogen peroxide bleaching Methods 0.000 description 6
- 239000002699 waste material Substances 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 5
- 229920000742 Cotton Polymers 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 230000003301 hydrolyzing effect Effects 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000004537 pulping Methods 0.000 description 4
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 3
- 235000017491 Bambusa tulda Nutrition 0.000 description 3
- 241001330002 Bambuseae Species 0.000 description 3
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 3
- 239000011425 bamboo Substances 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000002023 wood Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229920002488 Hemicellulose Polymers 0.000 description 2
- 229920001131 Pulp (paper) Polymers 0.000 description 2
- 229920000297 Rayon Polymers 0.000 description 2
- 239000012752 auxiliary agent Substances 0.000 description 2
- 239000006172 buffering agent Substances 0.000 description 2
- 150000001720 carbohydrates Chemical class 0.000 description 2
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 229920005610 lignin Polymers 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
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- 230000001590 oxidative effect Effects 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 239000003381 stabilizer Substances 0.000 description 2
- 229920000298 Cellophane Polymers 0.000 description 1
- YZCKVEUIGOORGS-OUBTZVSYSA-N Deuterium Chemical compound [2H] YZCKVEUIGOORGS-OUBTZVSYSA-N 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- 239000000020 Nitrocellulose Substances 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 229920006221 acetate fiber Polymers 0.000 description 1
- 238000012271 agricultural production Methods 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229920001220 nitrocellulos Polymers 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003895 organic fertilizer Substances 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
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Classifications
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C3/00—Pulping cellulose-containing materials
- D21C3/22—Other features of pulping processes
- D21C3/222—Use of compounds accelerating the pulping processes
-
- 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
- D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/1026—Other features in bleaching processes
- D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
-
- 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
- D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
-
- 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
- D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
- D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
- D21C9/144—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites with ClO2/Cl2 and other bleaching agents in a multistage process
-
- 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
- D21C9/16—Bleaching ; Apparatus therefor with per compounds
- D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
-
- 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
- D21C9/18—De-watering; Elimination of cooking or pulp-treating liquors from the pulp
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- Wood Science & Technology (AREA)
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- Paper (AREA)
Abstract
The invention relates to dissolving pulp prepared by using corn stalk skins and a method, wherein the method comprises the following steps of 1, insulating the corn stalk skins by using water, cooling, washing the pulp and dehydrating to obtain pulp; step 2, adding KOH and anthraquinone aqueous solution, cooking the obtained mixed system, washing and drying to obtain the absolute dry slurry; step 3, adding water to adjust the concentration of the pulp to 8% -12%, adjusting the pH to 4-4.5, bleaching with a chlorine dioxide aqueous solution, and washing the pulp with water until the pulp is neutral and dehydrated; step 4, adding water to adjust the concentration of the pulp to 8-12%, adjusting the pH value to be more than or equal to 10, extracting and bleaching by using a sodium hydroxide solution and a hydrogen peroxide solution, and washing the pulp by water until the pulp is neutral and dehydrated; and 5, bleaching with a chlorine dioxide aqueous solution, washing and dehydrating, adjusting the concentration of the pulp to be 8-12%, adjusting the pH value to be more than or equal to 10, adding a hydrogen peroxide aqueous solution and a magnesium sulfate aqueous solution, bleaching for 90-110 min, washing the pulp to be neutral with water, and dehydrating to obtain dissolved pulp.
Description
Technical Field
The invention belongs to the technical field of pulping, and particularly relates to dissolving pulp prepared by using corn straw skins and a method.
Background
The dissolving pulp belongs to high-purity refined pulp and is mainly used for producing viscose rayon, nitrocellulose, acetate fiber, cellophane and other products, and the raw materials for preparing the dissolving pulp at present mainly comprise cotton linters and wood.
Due to the serious shortage of forest resources and the increasing amount of cotton for spinning in China, people pay attention to the preparation of dissolving pulp by using other cellulose resources to replace cotton linters and wood, a new variety of paper pulp raw materials is developed, and the maximum utilization of annual plant raw materials is a good idea. Corn is a main crop in agricultural production, the yield of corn straws is considerable, about 1.7 hundred million tons of corn straws can be collected every year, and the corn straws account for 48 percent of national corn straw resources. But the total utilization rate is less than 50 percent due to the lack of scientific and technological innovation support. The fuel is mainly used for combustion at present, and great resource waste and environmental pollution are caused.
The Chinese patent with the patent number ZL02112175.3 relates to a method for modifying insoluble bamboo pulp, namely, the papermaking bamboo pulp is further boiled by NaOH to prepare viscose bamboo pulp. The method is characterized in that the raw materials are subjected to secondary cooking, the primary cooking is combined, and the raw materials are essentially subjected to pulping by a NaOH method, the total experiment time is long, the process is repeated, the material waste is serious, the production load and the environmental load are large, and the production cost is high. Chinese patent publication No. CN101158122A relates to a sulfate pulping method, which eliminates the prehydrolysis step, shortens the superficial flow path, but eliminates all pentosan as waste, resulting in waste of resources.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the dissolving pulp prepared by using the corn straw skins and the method thereof, the pollution is small, the waste liquid is easy to recycle, the production cost is low, and the whiteness and the alpha-cellulose content of the obtained dissolving pulp reach the quality index.
The invention is realized by the following technical scheme:
a method for preparing dissolving pulp by utilizing corn stalk skins comprises the following steps:
and 5, bleaching the pulp bleached in the second step by using a chlorine dioxide aqueous solution again, then washing and dehydrating the pulp, adding water into the obtained pulp to adjust the concentration to be 8-12%, then adjusting the pH of the pulp to be more than or equal to 10, adding a hydrogen peroxide aqueous solution and a magnesium sulfate aqueous solution, bleaching the pulp for 90-110 min at 80-90 ℃, washing the pulp to be neutral by using water, and finally dehydrating the pulp to obtain dissolved pulp.
Preferably, the ratio of the corn stalk skins to the water in the step 1 is 1kg (4-7) L.
Further, in the step 1, the corn straw skin is heated to 150-170 ℃ in water and then is kept warm for 90-120 min.
Preferably, after the aqueous solution of KOH and anthraquinone is added into the pretreated slurry in the step 2, the proportion of the corn straw skin to the water in the mixed system is 1kg (4-7) L.
Preferably, the mixed system is cooked at the temperature for 90-120 min in the step 2 to obtain black liquor.
Preferably, in the step 3, the concentration of the chlorine dioxide aqueous solution is 10%, the mass of the chlorine dioxide aqueous solution is 2% -7% of that of the oven-dried pulp, and the pulp is bleached by the chlorine dioxide at the temperature of 60-80 ℃ for 50-70 min.
Preferably, in the step 4, the mass of the sodium hydroxide is 3% -8% of the mass of the oven-dry pulp, the mass of the hydrogen peroxide is 2% -6% of the mass of the oven-dry pulp, and the pulp is bleached by the sodium hydroxide and the hydrogen peroxide for 60-80 min at the temperature of 60-80 ℃.
Preferably, the bleaching process of the pulp bleached in the second step by the aqueous chlorine dioxide solution in the step 5 comprises the following steps:
adding water into the pulp bleached in the second step to adjust the concentration of the pulp to be 8-12%, then adjusting the pH of the obtained pulp to be 4-4.5, then adding a chlorine dioxide aqueous solution, bleaching at the temperature of 70-90 ℃ for 60-100 min, wherein the concentration of the chlorine dioxide aqueous solution is 10%, and the mass of the chlorine dioxide aqueous solution is 1-3% of that of the oven dry pulp.
Preferably, in the step 5, the mass of the hydrogen peroxide is 1-6% of the mass of the oven-dry slurry, and the mass of the magnesium sulfate is 0.5-2% of the mass of the oven-dry slurry.
The dissolving pulp obtained by the method for preparing the dissolving pulp by using the corn straw skins.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention relates to a method for preparing dissolving pulp by using corn stalk skins, which comprises the steps of carrying out heat preservation treatment on the corn stalk skins in water, carrying out prehydrolysis on the corn stalk skins by the water, then cooling, washing and dehydrating the pulp to obtain pulp, wherein the prehydrolysis is beneficial to improving the content of alpha-cellulose in the pulp, promoting the removal of lignin in the corn stalk skins and reducing the content of hemicellulose in the corn stalk skins, then obtaining black liquor by adopting an alkaline cooking process, washing the black liquor, drying to obtain an absolute dry pulp, and finally obtaining the absolute dry pulpSequentially carrying out chlorine dioxide bleaching and pulp washing dehydration, alkali extraction and pulp washing dehydration, chlorine dioxide bleaching and pulp washing dehydration and hydrogen peroxide bleaching, and adding H in the alkali extraction stage2O2Auxiliary bleaching as auxiliary agent, H2O2The method is beneficial to oxidizing the carboxyl end group of carbohydrate, reducing peeling reaction, strengthening the effect of delignification and improving the whiteness of the bleached pulp, and magnesium sulfate is added in the final hydrogen peroxide bleaching as a stabilizing agent and a buffering agent to finally obtain the dissolving pulp. The invention uses the corn straw to replace cotton linter and wood to prepare dissolving pulp, develops a new variety of paper pulp raw materials, realizes a high-valued approach for the utilization of the corn straw, reduces the environmental pollution and lowers the production cost. The invention adopts alkaline pulping, uses KOH to adjust the composition of the black liquor, is expected to improve the utilization efficiency of a nitrogen source in the black liquor, and is beneficial to the conversion of waste liquid organic fertilizer.
Drawings
FIG. 1 is a diagram of a mass index of dissolving pulp in the prior art.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
The invention relates to a method for preparing dissolving pulp by using corn stalk skins, which comprises the following steps:
adding water into 100-500 g of corn straw skin, and stirring, wherein the weight kg of the corn straw skin/the total liquid volume L) (namely the liquid ratio) is 1: (4-7) the ratio of the weight of the absolutely dry raw materials (kg or t) to the total volume of the liquor (L or m)3) The total liquid is water, then the temperature is raised to the highest temperature of 150-170 ℃, the temperature is kept for 90-120 min, the corn straw skin is prehydrolyzed by the water in the process, and the pulp is washed and dehydrated after cooling to obtain pretreated pulp;
the prehydrolysis is helpful for improving the content of alpha-cellulose in the slurry, promoting the removal of lignin in the corn straw skins, and reducing the content of hemicellulose in the corn straw skins.
placing the pretreated slurry in a cooking pot, dissolving KOH and anthraquinone (AQ for short) in water in advance, stirring to obtain a mixed solution, adding the mixed solution into the cooking pot, heating to 150-170 ℃, and then preserving heat for 90-120 min, wherein the mass of KOH is 17% -30% of the mass of corn straw skins, the weight kg of the corn straw skins/the total liquid volume L) (namely the liquid ratio) is 1 (4-7), the mass of AQ is 0.02% -0.08% of the mass of the corn straw skins, pouring out black liquid after cooling, washing the obtained slurry, and drying to obtain the drying-resistant slurry.
And 4, bleaching the mixture,
taking 10g of the absolute dry pulp as a reference, bleaching the pulp in four steps by using a beaker in a constant-temperature water bath kettle to obtain the dissolving pulp.
Four-stage bleaching is adopted, namely D-stage bleaching, E-stage bleaching, D-stage bleaching and P-stage bleaching, but for the convenience of understanding, the first step, the second step, the third step and the fourth step are still described later.
The first step is chlorine dioxide bleaching and pulp washing dewatering:
adding water to adjust the concentration of the obtained slurry to be 8-12%, adding hydrochloric acid to adjust the pH value of a system to be 4-4.5, wherein the influence of the hydrochloric acid on the concentration of the slurry is negligible due to the small use amount of the hydrochloric acid, adding a chlorine dioxide aqueous solution, bleaching for 50-70 min at the temperature of 60-80 ℃, wherein the concentration of the chlorine dioxide aqueous solution is 10%, the mass of the chlorine dioxide aqueous solution is 2-7% of that of the oven-dry slurry, washing the slurry to be neutral by using water, and dewatering;
the second step is alkali extraction and pulp washing dehydration:
adding water to adjust the concentration of the slurry to be 8-12%, adding sodium hydroxide to adjust the pH value of a system to be more than or equal to 10, adding a sodium hydroxide solution and a hydrogen peroxide solution, reacting at the temperature of 60-80 ℃ for 60-80 min, washing the slurry to be neutral by water, and dehydrating, wherein the mass of the sodium hydroxide is 3-8% of that of the oven-dry slurry, and the mass of the hydrogen peroxide is 2-6% of that of the oven-dry slurry;
in the alkaline extraction stageAddition of H2O2Auxiliary bleaching as auxiliary agent, H2O2The method is beneficial to oxidizing the carboxyl end group of carbohydrate, reduces peeling reaction, can strengthen the effect of delignification and can improve the whiteness of bleached pulp.
The third step is chlorine dioxide bleaching and pulp washing dehydration:
adding water to adjust the concentration of the slurry to be 8-12%, adding hydrochloric acid to adjust the pH value of a system to be 4-4.5, wherein the influence of the hydrochloric acid on the concentration of the slurry is negligible due to the small use amount of hydrochloric acid, adding a chlorine dioxide aqueous solution, bleaching for 60-100 min at the temperature of 70-90 ℃, wherein the concentration of the chlorine dioxide aqueous solution is 10%, the mass of the chlorine dioxide aqueous solution is 1-3% of that of the absolutely dry slurry, washing the slurry to be neutral by water, and dewatering;
the fourth step is hydrogen peroxide bleaching:
adding water to adjust the concentration of the pulp to be 8-12%, then adding sodium hydroxide to adjust the pH value of a system to be more than or equal to 10, then adding aqueous hydrogen peroxide solution and aqueous magnesium sulfate solution to bleach for 90-110 min at the temperature of 80-90 ℃, wherein the magnesium sulfate is a stabilizer and a buffering agent, the mass of the hydrogen peroxide is 1-6% of that of the oven-dry pulp, the mass of the magnesium sulfate is 0.5-2% of that of the oven-dry pulp, then washing the pulp to be neutral by water, and then dehydrating to obtain dissolving pulp.
The invention detects the yield, the bleachability, the hardness, the viscosity and the like of the dissolving pulp, and obtains the dissolving pulp with good performance.
Control protocol
It should be noted that the applicant also conducted experiments without adding hydrogen peroxide in the second alkali extraction step, and then conducted the same steps and parameters as above, and obtained the corresponding dissolving pulp for comparative illustration.
Example 1
The invention relates to a method for preparing dissolving pulp by using corn stalk skins, which comprises the following steps:
adding water (liquid ratio is 1:4) into 100g of corn straw skin, stirring, preserving heat for 90min at the highest temperature of 150 ℃, carrying out prehydrolysis on the corn straw skin by using water in the process, and carrying out pulp washing and dehydration after cooling to obtain pretreated pulp;
placing the pretreated pulp in a cooking pot, dissolving KOH and Anthraquinone (AQ) in water in advance, stirring, heating, keeping the temperature, cooling, pouring out black liquor, washing and dehydrating the obtained pulp to obtain the absolute dry pulp.
The mass of KOH is 17 percent of the mass of the corn straw skin, the mass ratio of the corn straw skin to water is 1:4, the mass of AQ is 0.02 percent of the mass of the corn straw skin, the temperature is 150 ℃, and the heat preservation time is 90 min.
And 4, bleaching the mixture,
the first step is chlorine dioxide bleaching and pulp washing dewatering:
adding water to adjust the concentration of the slurry to 8%, adding hydrochloric acid to adjust the pH of the system to 4.5, wherein the mass of chlorine dioxide is 2% of that of the oven-dried slurry, at the temperature of 60 ℃, for 50min, washing the slurry to be neutral by water, and then dehydrating;
the second step is alkali extraction and pulp washing dehydration:
adding water to adjust the concentration of the slurry to 10%, adding sodium hydroxide to adjust the pH value of a system to 11, wherein the mass of the sodium hydroxide is 3% of the absolute dry slurry, the mass of the hydrogen peroxide is 4% of the absolute dry slurry, performing washing at 60 ℃ for 60min, and then, washing the slurry to be neutral by water, and then, dehydrating;
the third step is chlorine dioxide bleaching and pulp washing dehydration:
adding water to adjust the concentration of the slurry to 8%, then adding hydrochloric acid to adjust the pH of the slurry to 4.5, wherein the mass of chlorine dioxide is 1% of that of the oven-dried slurry, at the temperature of 70 ℃, for 60min, then washing the slurry to be neutral by water, and then dehydrating;
the fourth step is hydrogen peroxide bleaching:
adding water to adjust the concentration of the slurry to 8%, adding sodium hydroxide to adjust the pH value of a system to 11, adding 1% of hydrogen peroxide and 0.5% of magnesium sulfate in the mass of the oven-dried slurry, washing the slurry to be neutral by water at the temperature of 80 ℃ for 90min, and dehydrating to obtain dissolved slurry.
Example 2
The invention relates to a method for preparing dissolving pulp by using corn stalk skins, which comprises the following steps:
adding water (liquid ratio is 1:6) into 300g of corn straw skin, stirring, preserving heat for 100min at the highest temperature of 160 ℃, carrying out prehydrolysis on the corn straw skin by using water in the process, and carrying out pulp washing and dehydration after cooling to obtain pretreated pulp;
placing the pretreated pulp in a cooking pot, dissolving KOH and Anthraquinone (AQ) in water in advance, stirring, heating, keeping the temperature, cooling, pouring out black liquor, washing and dehydrating the obtained pulp to obtain the absolute dry pulp.
The mass of KOH is 25 percent of the mass of the corn straw skin, the mass ratio of the corn straw skin to water is 1:6, the mass of AQ is 0.05 percent of the mass of the corn straw skin,
the temperature is 160 ℃, and the heat preservation time is 100 min.
And 4, bleaching the mixture,
the first step is chlorine dioxide bleaching and pulp washing dewatering:
adding water to adjust the concentration of the slurry to 10%, then adding hydrochloric acid to adjust the pH of the system to 4.5, wherein the mass of chlorine dioxide is 5% of that of the oven-dried slurry, at the temperature of 70 ℃, for 60min, then washing the slurry to be neutral by water, and then dehydrating;
the second step is alkali extraction and pulp washing dehydration:
adding water to adjust the concentration of the slurry to 10%, adding sodium hydroxide to adjust the pH value of a system to 11, wherein the mass of the sodium hydroxide is 6% of the absolute dry slurry, the mass of the hydrogen peroxide is 4% of the absolute dry slurry, performing washing at 70 ℃ for 70min, neutralizing the slurry, and dehydrating;
the third step is chlorine dioxide bleaching and pulp washing dehydration:
adding water to adjust the concentration of the slurry to 10%, then adding hydrochloric acid to adjust the pH of the system to 4.5, wherein the mass of chlorine dioxide is 2% of that of the oven-dried slurry, at the temperature of 80 ℃, for 90min, then washing the slurry to be neutral by water, and then dehydrating;
the fourth step is hydrogen peroxide bleaching:
adding water to adjust the concentration of the slurry to 10%, adding sodium hydroxide to adjust the pH value of a system to 11, adding hydrogen peroxide to 4% of the mass of the oven-dry slurry, adding magnesium sulfate to 1% of the mass of the oven-dry slurry, performing washing at 85 ℃ for 100min, neutralizing the slurry with water, and dehydrating to obtain dissolved slurry.
Example 3
The invention relates to a method for preparing dissolving pulp by using corn stalk skins, which comprises the following steps:
adding water (liquid ratio is 1:7) into 500g of corn stalk skins, stirring, preserving heat for 120min at the highest temperature of 170 ℃, carrying out prehydrolysis on the corn stalk skins by using water in the process, cooling, washing pulp and dehydrating to obtain pretreated pulp;
placing the pretreated pulp in a cooking pot, dissolving KOH and Anthraquinone (AQ) in water in advance, stirring, heating, keeping the temperature, cooling, pouring out black liquor, washing and dehydrating the obtained pulp to obtain the absolute dry pulp.
The mass of KOH is 30 percent of the mass of the corn straw skin, the mass ratio of the corn straw skin to water is 1:7, the mass of AQ is 0.05 percent of the mass of the corn straw skin,
the temperature is 170 ℃, and the heat preservation time is 120 min.
And 4, bleaching the mixture,
the first step is chlorine dioxide bleaching and pulp washing dewatering:
adding water to adjust the concentration of the slurry to 12%, adding hydrochloric acid to adjust the pH of the system to 4.5, wherein the mass of chlorine dioxide is 7% of that of the oven-dried slurry, at the temperature of 80 ℃, for 70min, washing the slurry to be neutral by water, and then dehydrating;
the second step is alkali extraction and pulp washing dehydration:
adding water to adjust the concentration of the slurry to 12%, adding sodium hydroxide to adjust the pH value of a system to 11, wherein the mass of the sodium hydroxide is 8% of the absolute dry slurry, the mass of the hydrogen peroxide is 6% of the absolute dry slurry, keeping the temperature at 80 ℃, keeping the temperature for 80min, washing the slurry to be neutral by water, and then dehydrating;
the third step is chlorine dioxide bleaching and pulp washing dehydration:
adding water to adjust the concentration of the slurry to 12%, then adding hydrochloric acid to adjust the pH of the system to 4.5, wherein the mass of chlorine dioxide is 3% of that of the oven-dried slurry, at the temperature of 90 ℃, for 100min, then washing the slurry to be neutral by water, and then dehydrating;
the fourth step is hydrogen peroxide bleaching:
adding water to adjust the concentration of the slurry to 12%, adding sodium hydroxide to adjust the pH value of a system to 11, adding 6% of hydrogen peroxide and 2% of magnesium sulfate in the mass of the oven-dry slurry, washing the slurry to be neutral at 90 ℃ for 110min, and dehydrating to obtain dissolved slurry.
The optimal process is as in example 2, the KOH consumption is 25%, the liquor ratio is 1:6, the cooking liquor ratio is 1:6, the AQ consumption is 0.05%, the highest cooking temperature is 160 ℃, the temperature is kept for 100min, the kappa number of the obtained black liquor is calculated to be as low as 5.76, the black liquor yield is 36.40%, and the residual effective alkali in the black liquor is 3.18 g/L. The intrinsic viscosity is 776.23mL/g, the polymerization degree is 1135, the whiteness is 84.37ISO, the ash content is 0.65 percent, and the content of alpha-cellulose is 92.7 percent. As can be seen from the data in FIG. 1, both the whiteness and the alpha-cellulose content achieved the quality index of the dissolving pulp.
In the contrast scheme, the whiteness of paper made of the finally obtained dissolving pulp is stabilized at 40-79% ISO, and the difference is still existed between the requirement of the dissolving pulp on the whiteness.
In the invention, H is added in the alkali extraction stage2O2The whiteness of paper made of the obtained dissolving pulp can be controlled at 84-89% ISO by carrying out auxiliary bleaching through the test of the above embodiment.
Claims (10)
1. A method for preparing dissolving pulp by utilizing corn stalk skins is characterized by comprising the following steps:
step 1, carrying out heat preservation treatment on corn straw skins in water, carrying out prehydrolysis on the corn straw skins by the water, and then carrying out pulp washing and dehydration after cooling to obtain pretreated slurry;
step 2, adding aqueous solution of KOH and anthraquinone into the pretreated slurry, wherein the mass of the KOH is 17% -30% of that of the corn straw skins, the mass of the anthraquinone is 0.02% -0.08% of that of the corn straw skins to obtain a mixed system, cooking the mixed system at the temperature of 150-170 ℃, removing black liquor, washing and drying to obtain the absolutely dry slurry;
step 3, adding water into the oven-dried pulp, adjusting the concentration of the obtained pulp to be 8% -12%, then adjusting the pH of the pulp to be 4-4.5, then bleaching the pulp by using a chlorine dioxide aqueous solution, then washing the pulp to be neutral by using water, and finally dewatering to obtain the pulp bleached in the first step;
step 4, adding water into the pulp bleached in the first step to adjust the concentration of the pulp to be 8-12%, then adjusting the pH value of the pulp to be more than or equal to 10, then respectively extracting and bleaching the pulp by using a sodium hydroxide solution and a hydrogen peroxide solution, then washing the pulp to be neutral by using water, and finally dehydrating to obtain the pulp bleached in the second step;
and 5, bleaching the pulp bleached in the second step by using a chlorine dioxide aqueous solution again, then washing and dehydrating the pulp, adding water into the obtained pulp to adjust the concentration to be 8-12%, then adjusting the pH of the pulp to be more than or equal to 10, adding a hydrogen peroxide aqueous solution and a magnesium sulfate aqueous solution, bleaching the pulp for 90-110 min at 80-90 ℃, washing the pulp to be neutral by using water, and finally dehydrating the pulp to obtain dissolved pulp.
2. The method for preparing dissolving pulp by using the corn stalk skins as claimed in claim 1, wherein the ratio of the corn stalk skins to the water in the step 1 is 1kg (4-7) L.
3. The method for preparing dissolving pulp by utilizing the corn stalk skins as claimed in claim 2, wherein the corn stalk skins in the step 1 are heated to 150-170 ℃ in water and then are kept warm for 90-120 min.
4. The method for preparing dissolving pulp by using the corn stalk skins as claimed in claim 1, wherein the ratio of the corn stalk skins to water in the mixed system is 1kg (4-7) L after the aqueous solution of KOH and anthraquinone is added into the pretreated pulp in the step 2.
5. The method for preparing dissolving pulp by utilizing the corn straw skins as claimed in claim 4, wherein the step 2 is to steam and boil the mixed system at the temperature for 90-120 min to obtain black liquor.
6. The method for preparing dissolving pulp by utilizing the corn straw skins as claimed in claim 1, wherein the concentration of the chlorine dioxide aqueous solution in the step 3 is 10%, the mass of the chlorine dioxide aqueous solution is 2% -7% of that of the oven dry pulp, and the pulp is bleached by the chlorine dioxide at the temperature of 60-80 ℃ for 50-70 min.
7. The method for preparing dissolving pulp by using corn stalk skins as claimed in claim 1, wherein the mass of the sodium hydroxide in the step 4 is 3% -8% of the mass of the oven dry pulp, the mass of the hydrogen peroxide is 2% -6% of the mass of the oven dry pulp, and the sodium hydroxide and the hydrogen peroxide bleach the pulp at the temperature of 60-80 ℃ for 60-80 min.
8. The method for preparing dissolving pulp by using corn straw skins as claimed in claim 1, wherein the bleaching of the second-step bleached pulp by the aqueous solution of chlorine dioxide in the step 5 comprises the following steps:
adding water into the pulp bleached in the second step to adjust the concentration of the pulp to be 8-12%, then adjusting the pH of the obtained pulp to be 4-4.5, then adding a chlorine dioxide aqueous solution, bleaching at the temperature of 70-90 ℃ for 60-100 min, wherein the concentration of the chlorine dioxide aqueous solution is 10%, and the mass of the chlorine dioxide aqueous solution is 1-3% of that of the oven dry pulp.
9. The method for preparing dissolving pulp by utilizing the corn straw skins as claimed in claim 1, wherein the mass of the hydrogen peroxide in the step 5 is 1% -6% of the mass of the absolute dry pulp, and the mass of the magnesium sulfate is 0.5% -2% of the mass of the absolute dry pulp.
10. A dissolving pulp obtained by the method for preparing dissolving pulp by using corn stalk skins as claimed in any one of claims 1 to 9.
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| WO2023222948A1 (en) * | 2022-05-18 | 2023-11-23 | Teknologian Tutkimuskeskus Vtt Oy | Pulp production utilizing bark-containing residues as raw material |
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