SU988938A1 - Method of producing cellulose pulp for chemical treatment - Google Patents

Description

The invention relates to the pulp and paper industry and can be used in the production of pulp for the chemical industry.

A method of producing pulp for chemical processing is known, which combines sulphate cooking and cold-hot bleaching during bleaching 1.

However, the high consumption of alkali for cold refining makes this method unprofitable.

A method is also known that involves the two-step treatment of a cellulose-containing material with an alkaline cooking solution at a temperature and pressure, with the first cooking step being carried out with sodium carbonate or green liquor to contain 15-40% of the dissolved organic wood components in the liquor 2.

However, the obtained cellulose is not reactive to viscose formation, it has a low mass fraction of alpha cellulose.

The closest to the invention to the technical essence and the achieved result is a method involving preliminary aqueous hydrolysis

wood at 158-165 C for 8040 minutes, removal of prehydrolyzate and sulphate cooking at 170-180 C, for 90-15 minutes with the consumption of active alkali 20-21% in units. by weight of absolutely dry wood. Unbleached pulp is sorted and bleached as a result, viscose sulfate pulp 13.

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The disadvantages of this method are reduced pulp yield in cooking (33-35%), a long T cooking cycle of 8-9 hours (water prednd and sulphate cooking 4-4.5 hours),

15a, in the Kamur continuous cooking system, the process was discontinued due to the scorching of the ligno-carbohydrate complex of caramel on the screens due to a sharp change in the pH of the liquid in the heating apparatus between the prehydrolysis zone and the cooking zone.

The purpose of the invention is to increase the yield of pulp and intensify the process.

25

The goal is achieved by the fact that according to the method of producing cellulose for chemical processing, including the processing of cellulose-containing cheese & cooking solutions in two stages, the second of which is carried out by

sulphate pulping at pH 11-13, the first stage of processing is carried out by sulphate pulping of cellulose-containing raw materials to pH 5-9 with the consumption of cooking reagent 4-40% by weight of its total consumption.

Example 1. Conducting a series of industrial birch wood cooking. The liquor sulfide is 14.3%. The total consumption of active alkali is 26% in units. by weight of absolutely dry wood, while the alkali consumption for the first and second stages of processing in different experiments is 1.0: 25.0; 5:21 and 10: 16% in units by weight of absolutely dry wood and corresponds to the ratio

the cost of cooking reagents in the mass% 4:96, 20:80 and 39:61.

Processing mode:

Stage 1 - hydronic module 2,6: 1, temperature rise from 7 О to 160-95 min, standing at 16 ° C for 40 min.

The step n - the hydromodule 4: 1, the temperature rise after entering the cooking reagent up to 170 С 10 min, standing at 170 ° 90 min.

After washing and sorting the pulp, fine wool is separated at the fractionator.

The results of the experiment are presented in table 1.

Table

Consumption of active alkali in units by weight of absolutely dry wood, in May. %:

1 stage P stage

The ratio of the cost of cooking reagent on the 1st and 2nd stage of the total consumption, in May.%,

UAH of waste liquid at the end of the 1st processing stage

The concentration of active alkali at the end of cooking, g / l units.

The yield of cellulose,% Stiffness, p.

Viscosity 1% copper-ammonium cellulose solution, mPas

Mass fraction of alpha-cellulose,% Turnover of the cooking cycle, min

In the back of the cooking cycle, the duration of general operations is not taken into account (chips loading, mass transfer and

DR.).

As follows from the data table. 1, the cooking by the proposed method allows to significantly increase the yield of cellulose relative to the prototype while maintaining the required quality indicators. It should also be noted that the turnover of the cooking cycle

10 16

1.0

5.0 21.0 25.0

20:80

39:61

4:96 8.8

5.05 6.2

3.8.

20.9

23.5

7.5

24.1

43.1 42.9

42.7 5.9 57 60

61

24.1

20.8 21.1

5.6 93.8. 94.0 93.9 4.6 235 235 235 15

by the proposed method, it was reduced by 28%, which significantly allows to intensify the aarka process.

Example 2. Conduct a series of cooking as applied to continuous process conditions in Kamur apparatuses. Sulfide cooking liquor of 27.8%. The total consumption of active alkali - 26% in units. by weight of absolutely dry wood. Alkali cost ratio

Between the first and second stages of treatment is 5:21% in units. by weight of wood, which corresponds to a ratio of 20:80. Entering the cooking solution to the first stage is carried out after the boiler is loaded with chips, to the second stage immediately after the end of the first stage.

The mode of the first stage of processing is similar to the mode in example 1.

The second stage of treatment is carried out at a water ratio of 4: 1; lifting those-10

Duration of standing at, min

The concentration of active alkali at the end of treatment, g / l

The yield of cellulose,% The stiffness of the pulp, .ed.

The viscosity of 1% copper-ammonia cellulose solution, mPaS

Mass dol alpha tselyuP r i me R 3. Experiment provo5p t with bleaching of cellulose.

The processing mode is carried out analogously to example I — the ratio of the cost of cooking liquor to the I and P stages, with respectively 5:21% in units by weight of absolutely dry wood. Sulfide cooking liquor 25%. Get unbleached pulp. With quality indicators

The yield of cellulose,% 43,5

Stiffness, p. 47

Viscosity 1% copper ammonium cellulose solution, mPa-c 23.8

Massowa Dol

Alpha Cellulose-in

cellulose,% 93,9

The mixture is heated to 170 ° C for 10 minutes, the drain at 170 ° C for 90 minutes, then the pulp is cooled down and kept at this temperature for 40 and 60 minutes. ..

After washing and sorting unbleached pulp, the fine fiber is separated in a fractionator. The results of the experiments are presented in table. 3 and correspond to the requirements for unbleached viscose pulp.

table 2

60

40

22.0

22,8

42.6

42.8 62 63

23.5

21.8

23.6

The pulp is divided into two samples, which are bleached according to the following schemes.

Test: chlorination and alkalization hypochlorite, chlorine dioxide alkalization - chlorine dioxide - acid

Test: chlorine dioxide / chlorine - alkali - hypochlorite - chlorine dioxide - alkali - chlorine dioxide - acid.

The chlorine dioxide / chlorine ratio is 4: 1.

Indicators of the quality of bleached pulp are presented in table. 3. .Table3

Bleaching of unbleached pulp obtained by the proposed method does not cause difficulties. At the same time, a henbane cellulose with a high reactivity was obtained (CS / NaOH is 90/11, retardation is 7 and 11 s). The obtained henbane pulp meets the requirements for sulfate viscose pulp according to the main quality indicators.

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The process can be used both in batch and continuous boilers. Using the proposed method for producing cellulose for cereal processing, compared with the prototype method, the yield of the target product is increased, the cooking process is intensified by a sharp decrease in turnover, the cooking pot (by 27-43%), the problem of caramelization in the production of pulp for chemical processing is reduced and simplifying the technological implementation of the method.

Claims (3)

1. Nepenin Yu.N. and Muzychenko MP Upgrading sulphate pulp. Refective information Chemical processing of wood. M., Lesna promnitshnnosti, 1965, 9 29, p. 6-8. 2. US patent 3811995, cl. D 21 C 3 / 26j publ. 1974. 3. USSR author's certificate 382783 cl. O 21 C 3/02, 1971rototip).