SU1567700A1 - Method of preliminary hydrolysis of wood before sulfate boiling of cellulose - Google Patents

Abstract

The invention relates to the production of cellulose for chemical processing and allows an increase in the yield of cellulose and the mass fraction of α-cellulose while simultaneously intensifying the process. Wood chips are treated with a hydrolyzing agent in two steps, the first of which is carried out at a temperature of 130-165 ° C for 20-50 minutes, and the second at a temperature of 160-175 ° C for 30-120 minutes. As a hydrolysing agent, water or steam, or a mixture thereof, or an aqueous solution of sulfur dioxide at a flow rate of the last 0.01-12% in units is used. SO ₂ from the mass of absolutely dry chips. 2 hp f-ly, 4 tab.

Description

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

The aim of the invention is to increase the yield of cellulose and the mass fraction (α-cellulose while simultaneously intensifying the process.

In the proposed method of preliminary hydrolysis of wood flake before sulfate pulping, which includes two steps of treating wood chips with a hydrolyzing agent with a temperature rise between the steps, the first step of treatment is performed at 130-165 ° C for

20-50 min, and the second stage at 160-175 ° C for 30-120 minutes

In the first and second stages, water is used as a hydrolysing agent using water and / or steam, or a water thief SO with a consumption of the last 0.01-12% in units. SOrj, from the mass of absolutely dry chips.

The proposed method allows for a more uniform prehydrolysis process. The need for stepwise pre-hydrolysis under the specified conditions is explained by the fact that in the process of stationing at the first stage temperature equalization occurs.

cl

WITH&

J |

contents of the boiler and a more complete uniform removal of lightly hydrolyzed, polysaccharides. Acetic acid and formic acid are formed due to the heat of acetyl and formyl groups of wood, which act as catalysts in the second stage of hydrolysis. Thus, the peculiarities of carrying out the first step of prehydrolysis create favorable conditions for the second stage. The achievement of the specified final temperature of hydrolysis at the second stage is the final stage of the prehydrolysis process, at which further hydrolysis of the partially finished cell-containing raw material occurs.

The combination of different temperatures and their duration is possible in a consistent and more in-depth process of dissolving hemicellulose, affecting the structure of lignin at different temperatures. This is confirmed by the results of subsequent sulphate cooking. With the same consumption of alkali for cooking, the degree of penetration of cellulose and the mass fraction of Y-cellulose in it according to the proposed method is higher.

The proposed method of prehydrolysis is technologically simple and does not require additional retrofit of the digester. The method is most effective in steam prehydrolysis, the use of which with known methods practically does not allow to achieve uniformity of the process without any additional equipment in the boiler.

Example 1. Unbleached pulp is produced for the production of cold-treated cord cord.

Cooking is done on pine wood. The proposed hydrolysis method is carried out in the vapor phase. Steam hydrolysis: supply of a hydrolyzing agent - steam down the boiler. Stage I: temperature rise 30–40 min, standing at 125, 145, 160, 165 and 170 ° g 0 and 40 min. Stage II: 170 n 175 ° C duration, respectively, 60 and 30 minutes, temperature rise from stage I to stage II 10 minutes.

Sulfate cooking: active alkali consumption 21% from abs. dry wood. Hydraulic module (FN) 4: 1, impregnation at 135 ° С 30 min, rise from 135 to 170 ° D 60 min, standing at

ten

15

20

15677004

170 With 90 min (experiments 3-11 - the proposed method, 2 and 12 control).

For comparison, the hydrolysis is carried out in prototype to obtain viscose pulp. At stage I, wood chips are processed, larch is treated with water at 100 ° C for 240 minutes, then the temperature is raised to 150 ° C, and stand at this temperature for 60 minutes (II stage processing). The data obtained are presented in table.1.

As can be seen from Table 1, the proposed method, in addition to experiments 2 and 12, which are control ones, allows, with a shorter hydrolysis time and an equal consumption of active alkali for cooking, a higher degree of penetration and mass fraction (-cellulose while maintaining the required viscosity. The temperature of the first stage of hydrolysis is 125 ° C, even with a duration of 40 min (experiment 2) is not sufficient to obtain a higher penetration of cellulose as compared with experiments 3-6. Increasing the temperature of stage I to 170CC (experiment 12) also reduces the degree penetration with a decrease in viscosity. Hydrolysis takes place more intensively due to high temperatures, confirmation is therefore a decrease in the viscosity of cellulose.

EXAMPLE 2. Larch wood is used for cooking. The proposed method is carried out in an aqueous medium.

Water hydrolysis: GM 3.8: 1; Stage I: 150 and C) () ° C with a duration of 20 and 40 microns (rise to the final temperature of 35 min). Stage II: 170 ° C with a duration of 60 and 7S min.

Sulfate cooking: active alkali consumption 19% from dry wood. Temperature, as in example 1.

25

thirty

35

40

45

50

55

The results are reported in table 2.

The data presented in Table 2 shows that, compared with the prototype, the proposed method allows to obtain unbleached pulp of higher quality while reducing the duration of hydrolysis with an increase in the yield and mass fraction of Cellulose.

Example 3 An unbleached pulp from larch wood is produced for the production of hot pulp.

0

five

The results are reported in table 2.

The data presented in Table 2 shows that, compared with the prototype, the proposed method allows to obtain unbleached pulp of higher quality while reducing the duration of hydrolysis with an increase in the yield and mass fraction of Cellulose.

Example 3 An unbleached pulp from larch wood is produced for the production of hot pulp.

five

Water hydrolysis:, 8.1. I level: 150 С-40 min, 160 ° С - 20 and 40 min. Stage II: 170 ° С - 45 and 60 min, 175 ° С - 30 min.

Sulfate cooking, as in example 1 The consumption of active alkali for cooking 22% units. NaaO from the mass abs.sukhoy wood.

The results are presented in table 3.

As can be seen from Table 3, a reduction in the total duration of hydrolysis of the proposed method as compared with the prototype allows one to obtain the required quality of unbleached pulp, which increases the yield and content (Y-cellulose.

Example 4 An unbleached pulp is obtained from larch wood for high modulus fiber.

Water hydrolysis with the addition of GM 3.8. 1. Consumption S0 0.03% of abs. dry wood. Stage I: 130 ° C - 50 min and 145CC 30 min; Stage II: 150 ° С - 180 minutes, 160 ° С - 120 minutes and 180 ° С - 30 minutes.

Sulfate cooking, as in example 3. The data obtained are presented in table 4.

As follows from table 4, the proposed method prehydrolysis in aqueous medium with the additive. with the same

00

the consumption of alkali for cooking ensures the required quality of unbleached pulp with a shorter duration of hydrolysis as compared with the prototype with a higher content of the mass fraction of C-cellulose.

Claims (3)

1. The method of preliminary guide-. the release of wood before sulphate pulping, which includes two stages of processing wood chips with a hydrolyzing agent with a temperature rise between stages, characterized in that, from a whole, increasing the yield of cellulose and the mass fraction of c-cellulose while simultaneously intensifying the process, the first stage of treatment is carried out at 130 -165 ° C for 20-50 min, and the second stage at 160-175 ° C. 2. A method according to claim 1, characterized in that the second stage is carried out for 30-120 minutes. 3. Method Pop.1, I differ by the fact that water or steam, or a mixture of them, or an aqueous solution of sulfur dioxide at a flow rate of 0.01-12% per unit of water, is used as a hydraulic agent. 50 from the mass of absolutely dry chips. Table 2 Table TablnicaD