CN-122013580-A - Preparation method of pulp

CN122013580ACN 122013580 ACN122013580 ACN 122013580ACN-122013580-A

Abstract

The present disclosure provides a method of preparing pulp, comprising the steps of: the method comprises the steps of obtaining wood chips as stewing raw materials, preparing stewing liquid, adopting two-stage stewing to obtain coarse pulp, carrying out alkali treatment on the coarse pulp to obtain alkali treatment pulp, carrying out primary chlorine dioxide bleaching D0, alkali extraction bleaching E1 and secondary bleaching D1 on the alkali treatment pulp in sequence to obtain bleaching pulp, and carrying out acid treatment on the bleaching pulp to obtain pulp.

Inventors

GONG CHEN
NI JIANPING
LI NAN
FAN SHUJIE
YAN JIPENG
ZHANG YU
YANG BIN
SU ZHENHUA

Assignees

中国制浆造纸研究院有限公司

Dates

Publication Date: 20260512
Application Date: 20260313

Claims (4)

1. A method for preparing pulp, comprising the steps of: Obtaining wood chips as cooking raw materials, and screening and washing the cooking raw materials; Preparing a cooking solution, cooking by adopting a sulfate method, preparing a mixed solution of sodium hydroxide and sodium sulfide, wherein the alkali content is 15-25% of the weight of absolute dry materials by using Na 2 O, and the vulcanizing degree is 20-40% by using Na 2 O; the method comprises the steps of steaming and boiling by adopting a two-stage method to obtain coarse pulp, wherein the temperature of the first stage is raised to 130-140 ℃ from 25 ℃ for 60-70 min, the temperature of the second stage is raised to 160-170 ℃ from 130-140 ℃ and the temperature of the first stage is raised to 15-20 min, the temperature of the second stage is raised to 30-90 min, the sum of the temperature of the first stage and the temperature of the second stage is 1-3 h, and the kappa number of the coarse pulp is 15-20; Alkali treatment is carried out on the crude slurry to obtain alkali treatment slurry, wherein alkali liquid is at least one of sodium hydroxide and potassium hydroxide, the concentration of the alkali liquid is 1-10%, the temperature is 20-60 ℃, and the time is 30-120 min; Sequentially carrying out primary bleaching D0 of chlorine dioxide, alkaline extraction bleaching E1 and secondary bleaching D1 of chlorine dioxide on the alkaline treated pulp to obtain bleached pulp, wherein, The technological condition of the primary bleaching D0 of chlorine dioxide is that the pulp concentration is 10 to 20 weight percent, the time is 60 to 120 minutes, the temperature is 70 to 95 ℃, the consumption of the chlorine dioxide is 1.0 to 2.5 percent relative to the absolute dry pulp mass, and the residual chlorine after bleaching is 0 to 0.1g/L; The technological conditions of the alkali extraction bleaching E1 are that the pulp concentration is 10 to 20 weight percent, the time is 60 to 120 minutes, the temperature is 70 to 95 ℃, and the dosage of sodium hydroxide is 1.0 to 2.0 percent relative to the mass of absolute dry pulp; The process conditions of the chlorine dioxide secondary bleaching D1 are that the pulp concentration is 10-20wt%, the time is 60-120 min, the temperature is 70-95 ℃, the chlorine dioxide consumption is 0.5-1.5% relative to the absolute dry pulp mass, and the residual chlorine after bleaching is 0-0.1g/L; And (3) carrying out acid treatment on the bleached pulp to obtain pulp, wherein the consumption of sulfuric acid is more than 0 and less than or equal to 0.5% and the consumption of DTPA is 0.1% -2% relative to the mass of absolute dry pulp.
2. The method of producing pulp according to claim 1, wherein the liquid ratio in the cooking is 1:3 to 1:6.
3. The method of producing pulp according to claim 1, wherein the wood chips after screening have a wood chip length of 15mm to 30mm, a width of not more than 20mm and a thickness of 3mm to 5mm.
4. The method of producing pulp according to claim 1, wherein the pulp has an α -cellulose content of 98% or more, an intrinsic viscosity of 500mL/g or more, a degree of polymerization of 700 or more, and a whiteness of 90% or more.

Description

Preparation method of pulp Technical Field The present disclosure relates to the field of pulping technology, and more particularly, to a method for preparing pulp. Background As a high-purity cellulose carrier, dissolving pulp is usually prepared from lignocellulose biomass as a raw material through chemical treatment processes such as digestion, bleaching and the like. In the pulping process flow, the cooking and bleaching are key procedures, namely, the cooking is to treat plant fiber raw materials by adopting chemical liquid medicine under certain temperature and pressure conditions, so that lignin, hemicellulose, grease, resin and other non-cellulose components are dissolved out, and the separation and dissociation of cellulose are realized, and the bleaching is to further treat the pulp obtained by the cooking to remove residual impurities and pigments, so that the purity and whiteness of the cellulose are improved. Cellulose products suitable for specific industrial applications can be obtained by the above procedure. However, existing digestion and bleaching techniques have the following problems: Firstly, the main production method for preparing dissolving pulp from wood/non-wood fiber raw materials at the present stage comprises a sulfite method and a prehydrolysis sulfate method, and is limited by equipment, waste liquid treatment and the like, the domestic dissolving pulp mainly adopts the prehydrolysis sulfate pulp method, namely, a prehydrolysis section is added before the traditional sulfate pulping section, so that the aim of targeted hemicellulose removal is fulfilled, but the prepared pulp has lower yield which is generally only 30% -35% (relative to fiber raw materials) and is 12% -15% lower than that of common pulp, so that the raw material cost per ton of pulp is increased by about 33% compared with that of common pulp, and the profit margin of the dissolving pulp is greatly reduced. Secondly, in the prior art, one-step high-temperature cooking is often adopted, namely, the temperature is directly increased from 25 ℃ to 170 ℃, the temperature is kept for 1-3 hours at 170 ℃, although part of hemicellulose can be removed, the high temperature inevitably leads to severe degradation of cellulose, the viscosity is reduced, the yield is reduced, and the peak energy consumption is high. Third, in the prior art, conventional bleaching processes typically employ oxygen delignification in combination with elemental chlorine-free bleaching (e.g., DED bleaching sequences). However, the oxygen delignification process has insufficient selective removal capability on lignin, which is easy to cause excessive degradation of cellulose and lower the viscosity of pulp, while the conventional DED bleaching has limited bleaching efficiency, and the whiteness is difficult to be improved to more than 90% on the premise of not damaging fibers. Fourth, those skilled in the art generally consider that extending the treatment time or increasing the temperature is the only way to increase purity and whiteness, but this necessarily sacrifices the degree of fiber polymerization. Accordingly, there is a need to provide a method for preparing pulp capable of solving the above-mentioned first to fourth technical problems. Disclosure of Invention In view of the above, the present disclosure provides a method for preparing pulp, which is used for solving the first to fourth technical problems in the prior art. The preparation method of the pulp provided by the disclosure comprises the following steps: Obtaining wood chips as cooking raw materials, and screening and washing the cooking raw materials; Preparing a cooking solution, cooking by adopting a sulfate method, preparing a mixed solution of sodium hydroxide and sodium sulfide, wherein the alkali content is 15-25% of the weight of absolute dry materials by using Na 2 O, and the vulcanizing degree is 20-40% by using Na 2 O; the method comprises the steps of steaming and boiling by adopting a two-stage method to obtain coarse pulp, wherein the temperature of the first stage is raised to 130-140 ℃ from 25 ℃ for 60-70 min, the temperature of the second stage is raised to 160-170 ℃ from 130-140 ℃ and the temperature of the first stage is raised to 15-20 min, the temperature of the second stage is raised to 30-90 min, the sum of the temperature of the first stage and the temperature of the second stage is 1-3 h, and the kappa number of the coarse pulp is 15-20; Alkali treatment is carried out on the crude slurry to obtain alkali treatment slurry, wherein alkali liquid is at least one of sodium hydroxide and potassium hydroxide, the concentration of the alkali liquid is 1-10%, the temperature is 20-60 ℃, and the time is 30-120 min; Sequentially carrying out primary bleaching D0 of chlorine dioxide, alkaline extraction bleaching E1 and secondary bleaching D1 of chlorine dioxide on the alkaline treated pulp to obtain bleached pulp, wherein, The technological condition of the p