Cellulose delignification process

FIELD: paper-and-pulp industry.

SUBSTANCE: cellulose delignification process comprises alkali treatment, delignification with hydrogen peroxide with sodium hydroxide and sodium silicate additive, and acid treatment. Alkali treatment consumes 0.5% hydrogen peroxide and 2.0% sodium hydroxide based on the weight of absolutely dry cellulose and is conducted for 2.0-2.5 h at 60-90°C. Acid treatment of delignified product is accomplished with aqueous hydrochloric acid, which is consumed in amount 1.0% based on the weight of absolutely dry fibers, while treatment is conducted for 30-60 min at ambient temperature.

EFFECT: enhanced economical efficiency without loss cellulose characteristics.

2 tbl, 11 ex

 

The invention relates to a method of bleaching cellulose and can be used in the pulp and paper industry.

There is a method of bleaching sulphate hardwood pulp, including the treatment of cellulose with hydrochloric acid and peroxide delignification of hydrogen, while the treatment with hydrochloric acid is carried out at 70-95°C, concentration of 10-20 mass%. Before delignification pulp is washed. The delignification hydrogen peroxide is carried out at 70-95°C, pH of 9.5 to 10.5 with a flow rate of 0.5-2.5% of hydrogen peroxide; and 1.0% of sodium hydroxide; 3% sodium silicate by weight of absolutely dry cellulose (RF patent No. 1193192, CL D21 9/10, publ. 23.11.85 year).

The disadvantage of this method is carrying out acid treatment at high temperature, which contributes to the degradation of cellulose and, consequently, reduces the mechanical strength of the pulp.

The closest way to the same destination to the claimed invention on the totality of symptoms is the way the bleaching of hardwood sulphate pulp, including the processing of the original cellulose mineral acid at 70-95°With alkaline treatment on the basis of NaOH when the flow rate of 2-4% in% NaOH by weight of absolutely dry pulp for 1,1-2,0 h, the delignification hydrogen peroxide with the addition of sodium hydroxide and sodium silicate at a flow rate of hydrogen peroxide 0,5-2,5, sodium hydroxide 0.5 to 1.2% of sodium silicate 2-5% of the mass of absolutely dry pulp. After each treatment is washing pulp (RF patent No. 2019613, CL D21 9/16, 9/10, publ. 15.09.94 year). This method is adopted for the prototype.

The disadvantages of this method, taken as a prototype, is the duration of delignification (total duration of 7.1 to 8 h) at elevated temperature (70-95° (C), as well as the increased consumption of steam for heating of the mass, as you three times to heat the mass to a temperature of 70-95°C.

The characteristics of the prototype, which is common with the claimed invention, acid treatment, alkaline treatment, delignification hydrogen peroxide with the addition of sodium hydroxide and sodium silicate.

The objective of the invention is to increase the efficiency of the method of delignification of the pulp while maintaining the same results.

The problem is solved due to the fact that in the known method, including acid treatment, alkaline treatment, the delignification hydrogen peroxide with the addition of sodium hydroxide and sodium silicate, alkaline treatment is carried out in the presence of hydrogen peroxide (oxidative bucking - PS) when the flow rate of 0.5% sodium hydroxide at a flow rate of 2.0% of the mass of absolutely dry pulp at a temperature of 75°C for 30 min, the peroxide delignification is odorata (PD) are at a flow rate of hydrogen peroxide 1,0-3,0%, sodium hydroxide and 2.0%, sodium silicate - 3,0%, trylon B - 0.3% of the mass of absolutely dry pulp at a temperature of 60-90°C for 2.0 to 2.5 h, and the acid treatment is carried out after delignification hydrogen peroxide hydrochloric acid when the flow rate of 1.0% by weight of the absolutely dry fiber at room temperature for 30-60 minutes

Signs, distinctive features of the prototype, the alkaline treatment is carried out in the presence of hydrogen peroxide when the flow rate of 0.5% sodium hydroxide at a flow rate of 2.0% of the mass of absolutely dry pulp at a temperature of 75°C for 30 min; the delignification hydrogen peroxide is carried out at a flow rate of hydrogen peroxide 1,0-3,0%, sodium hydroxide and 2.0%, sodium silicate - 3,0%, trylon B - 0.3% of the mass of absolutely dry pulp at a temperature of 60-90°C for 2.0 to 2.5 h; the acid treatment is carried out after delignification hydrogen peroxide hydrochloric acid when the flow rate of 1.0% by weight of the absolutely dry fiber at room temperature for 30-60 minutes Distinguishing features allow to increase the efficiency of the method of delignification of the pulp.

It was established that in the peroxide delignification occurs swelling of the inner wall of the fiber, with the increase of the specific surface of the fiber, which promotes an intensive transfer of residual lignin, low-molecular fra the Nations of polysaccharides and extractives from cellulose in solution.

Intermediate kislovka mass contributes to the contraction (compression) of the fiber. Shrinkage of the fiber decreases the diameter of the capillary and wicking ability, delayed the micro-cavities formed in lignohydrocarbon matrix when the removal of lignin and hemicelluloses. When this occurs, the displacement of the inner capillary space residues delignification solution and dissolved substances. In subsequent dobelli by hydrogen peroxide in alkaline medium fiber swells again. When this occurs, the absorption into the fiber of fresh bleaching chemicals and as a consequence, the process of delignification and bleaching are more intense due to the update of the reaction surface and increase the concentration of the reacting substances.

The proposed method is as follows.

A portion of the cellulose weight of 40 g of absolutely dry fibers disintegrate in water, wring out, put in a porcelain Cup and poured the required amount of alkali and hydrogen peroxide. Oxidative bucking carried out at a temperature of 75°C for 30 min and the concentration of the mass of 8%. After the process is complete, the pulp mass is washed with a Buechner funnel and hold the delignification hydrogen peroxide when the flow rate of 1,0-3,0%, the consumption of sodium hydroxide and 2.0%, sodium silicate - 3,0%, trylon B to 0.3% by weight and is absolutely dry fibers within 2.0 to 2.5 hours at a temperature of 60-90° C. After delignification, the pulp is washed with a Buechner funnel. Next, perform the acid treatment of the mass with hydrochloric acid at a flow rate of 1.0% for 30-60 min at room temperature.

Examples of specific performance.

Example 1. Cellulose by weight of 40 g of absolutely dry fiber stiffness 80-90 pad, white 62,0% by mass of resins and fats 1,55% disintegrate in water, wring out a Buechner funnel and placed in a porcelain Cup, which is heated in a thermostat to maintain constant temperature. The mass is heated to a temperature of 75°and poured the solution containing sodium hydroxide and 2.0%hydrogen peroxide and 0.5% by weight of absolutely dry pulp. Oxidative bucking carried out for 30 min at a temperature of 75°C.

After oxidative be cellulose washed with water in a Buechner funnel and placed in a porcelain Cup, which is heated in a thermostat. When the temperature reached 90°With the mass of the poured solution consisting of hydrogen peroxide in the amount of 3.0%, sodium hydroxide and 2.0%, sodium silicate - 3,0%, trylon B - 0.3% of the mass of absolutely dry fiber. The treatment is carried out for 2.5 hours After the treatment the pulp is washed with water and subjected to acid treatment with hydrochloric acid, with its consumption of 1% by weight of the absolutely dry fiber at room temperature for 30-60 minutes

the reamers 2-11 carried out analogously to example 1.

Operation parameters of the method, as well as indicators of the quality of the pulp after delignification are shown in table 1. Table 2 shows the performance of cellulose after dobelli hydrogen peroxide in one step (scheme PS-PD-K-P-K).

From the table it is seen that after delignification (GSR-PD-K) white pulp is 80.6-85,4%, the mechanical strength is quite high level. Subsequent dabelko pulp with hydrogen peroxide in one step to achieve a white 86,3-97,6% depending on the conditions of peroxide delignification.

Conditions dobelli hydrogen peroxide: the consumption of peroxide hydrogen to 1.7%, the consumption of sodium hydroxide and 0.75%, sodium silicate is 1.75%, the trylon B - 0.2% of the mass of absolutely dry fibers; temperature 90°s; duration of 2.5 hours

The advantages of the proposed method for the delignification of cellulose:

- creation of early-stage bleaching conditions, contributing to a more efficient delignification and bleaching of cellulose at subsequent stages of bleaching due to the inclusion in the scheme-stage pre-oxidizing be in the presence of hydrogen peroxide;

intermediate processing of mass between the levels of peroxide delignification and peroxide bleaching acid promotes internal changes substructure fibers, reinforcing the subsequent EXT is the LCA of pulp with hydrogen peroxide the effect of delignification and bleaching;

- mild oxidative effects of hydrogen peroxide on cellulose fibers compared to conventional chlorine-containing reagents;

- greening schemes bleaching;

a significant decrease in the content in the pulp mass fraction resins and fats, which effectively solves the problem with pitch problems in paper production;

- reducing the consumption of steam for heating the mass and reducing the duration of delignification of the pulp.

This demonstrates the high efficiency of the proposed method of delignification of the pulp.

Table 1

Results pulp bleaching
# exampleOptions stage PDIndicators of cellulose after delignification PS-PD-To
Temperature, °Duration, hThe consumption of H2About2, % by weight of the abs. dry. celluloseWhite, %Rigidity, pegBreaking length, mOutput, % of unbleached pulp
1902,53,085,449820095,0
2902,5 1,084,653835095,5
3902,02,084,055825095,4
4752,03,082,757825096,0
5752,01,081,959830096,3
6752,52,083,354825096,0
7602,53,082,056815096,5
8602,51,081,256820096,8
9602,02,080,660815096,9

Output, % of unbleached pulp
Table 2
# exampleIndicators of cellulose after dobelli in one step (scheme PS-PD-K-P-K)
White, %Rigidity, pegBreaking length, mMass fraction of resins and fats, %
190,110785093,50,53
2to 89.5158000a 94.20,58
389,216795094,00,60
4at 88.128795094,40,62
597,631800094,70,62
688,726795094,50,60
7of 87.817780095,10,60
886,9167850for 95.20,65
986,3327800for 95.30,65

The method of delignification of pulp, including acid treatment, alkali treatment and delignification hydrogen peroxide with the addition of sodium hydroxide and sodium silicate, characterized in that the alkaline treatment is carried out in the presence of hydrogen peroxide when the flow rate of 0.5% and sodium hydroxide p and the consumption - 2.0% of the mass of absolutely dry pulp at a temperature of 75°C for 30 min, the delignification hydrogen peroxide is carried out at a flow rate of hydrogen peroxide 1,0-3,0%, sodium hydroxide and 2.0%, sodium silicate - 3,0%, trylon B - 0.3% of the mass of absolutely dry pulp at a temperature of 60-90°C for 2.0 to 2.5 h, and the acid treatment is carried out after delignification hydrogen peroxide hydrochloric acid when the flow rate of 1.0% by weight of the absolutely dry fiber at room temperature for 30-60 minutes



 

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SUBSTANCE: unbleached sulfate cellulose obtained from hardwood is subjected oxygen-alkali delignification, after which treated with chlorine dioxide in presence of oxyethylidenediphosphonic acid and then consecutively hydrogen peroxide and chlorine dioxide solutions. Process may be used in production of bleached fibrous intermediates.

EFFECT: increased whiteness and strength characteristics of cellulose and improved environmental safety of bleaching process.

2 cl, 1 tbl

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1 tbl, 17 ex

FIELD: pulp-and-paper industry, in particular method for PULP whitening.

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1 tbl, 9 ex

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1 tbl, 17 ex

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1 tbl, 9 ex

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2 tbl, 18 ex

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2 tbl, 18 ex

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