SU861441A1 - Method of producing semicellulose - Google Patents

Description

The invention relates to methods for producing hemicellulose and can be used in the pulp and paper industry in the manufacture of woven, fibrous semi-finished products for the manufacture of various types of paper and cardboard. A known method for producing semi-whole lulose by boiling the source lignocellulosic material with an aqueous solution containing either a mixture of it with NartS (green liquor; with a ratio of these components in the mixture (in mass%): Na ,, CO, - 70-99, NajS 1, 30 1. However, due to the low pH at the end of the cooking process, this method causes the formation of significant quantities of malodorous (sulfur-containing) substances. The closest to the technical essence and the achieved result is the method of producing semi-cellulose by boiling wood chips Liquor in the presence of an oxidizing agent 2. Molecular oxygen is used as an oxidizing agent, contributing to the oxidation of foul-smelling (sulfur-containing) substances formed during the cooking process. In this case, the molecular oxygen is introduced into the digester after the welded mass is cooled. for technological difficulties arising from the oxidation of sulfur-containing compounds with molecular oxygen and, in particular, the need to use the increased consumption of said oxidizing agent, complex a paraturnogo clearance process and long duration of the cooling process and the liquor cooked mass, resulting in prolonged boiling cooking process as a whole. In addition, the yield of the target product is not high enough. The aim of the invention is to reduce the amount of foul-smelling substances, increase the yield of the target product and intensify the process. The goal is achieved by the fact that in the method for producing cellulose by cooking wood chips with green liquor in the presence of an oxidizing agent at elevated temperatures and pressures according to the invention, the spent liquor from the oxy-alkaline bleached fiber semi-finished product is used as the oxidant, while the waste liquor is fed to the cooking in conjunction with green liquor Organic and inorganic distortions contained in waste silk from the oxygen-healing bleaching steps effectively oxidize Sulfi bottom sulfur in the initial cooking solution, which leads to a decrease in the number of foul-smelling (sulfur-containing) substances formed during the cooking of hemicellulose. In addition, during cooking, peroxide compounds are involved in the delignification process, speeding up the process and increasing its selectivity. At the same time, there is an increase in the yield of hemicellulose by 1.5-2.0%.

Example 1. 750 g of chips are steamed and filled with a personal l solution consisting of a mixture of green liquor and spent liquor oxygen. but alkaline bleaching stage with a volume ratio of 1: 4.5. The concentration of the cooking liquor in total alkali is 21.6 g / l, the hydraulic module is 3.7-1.

This corresponds to the consumption of chemicals for cooking, constituting 8% of the mass of absolutely dry wood.

The circulation of the cooking liquor and the electrical heating of the autoclave are included. The temperature is then raised to 175 ° C over a period of 20 1 liter and cooked at this temperature for 25 minutes.

The result is semi-cellulose, the quality indicators of which are given in table. 2

The analysis of liquor is presented in table. one.

EXAMPLE 2: 750 g of chips are boiled under the same conditions as in example 1, except for the amount of added liquor from oxygen-base alkaline bleaching, which

is in volume ratio to green liquor 2: 1.

The result is semi-cellulose, the quality indicators of which are presented in table 2.

The analysis of liquors is given in table. one

Example 3 750 g of chips are cooked in the same way as in example 1, but without the addition of spent liquor from oxygen-base bleaching stage to green liquor (according to the prototype). The result is semi-cellulose, the quality indicators of which are given in table 2. The analysis of the liquor is presented in table. one.

From tab. 1, it can be seen that the content of sodium sulfide in the initial cooking solution according to the proposed method is reduced by about 1.5 times, which will also reduce the odorous (sulfur-containing) substances by 1.5 times.

As can be seen from the table. 2, according to the proposed method, hemicellulose is obtained with a high yield from wood by 1, 5-2.0%, with a greater degree of penetration, its mechanical strength indicators are at the level of semi-cellulose indicators obtained in a known manner.

Thus, the application of the proposed method of semi-cellulose cooking will reduce the amount of foul-smelling substances, increase the yield of the semifinished product, speed up the delignification process and increase its selectivity and reduce the total cooking time, as well as ensure the return of chemicals to the production from spent liquors of the oxygen-alkaline bleaching stage.

For the application of the proposed method, no investment is required for the installation of additional equipment, the whole process is carried out on the existing equipment of the semi-pulp mill.

T a b l and c a i

Invention

1: 4.5 12.4

1: 2.0 -12.4

12.4

The method of production of cellulose by boiling wood chips with green liquor in the presence of an oxidizing agent at elevated temperature and pressure, 45

21.6

14.8

4.10 8.4

0.50

21.6. 5.20 8.0

14.0

0.60 Prototype

13.1. 0.80

6.60 7.6

21.6 Table 2

- in order to reduce the amount of black-haired substances, increase the yield of the target product and intensify the process, used lye from oxygen is used as an oxidant78614418

but alkaline fiber bleaching1, US Patent 3811995, cl. 162-19,

semifrifrikata, which is served on the var - pub. 1974. ku with green liquor.

Sources of information, 2. US patent 3969184, CL. 162-19,

taken into account in the examination of the publication. 1976 - PROTOTYPE.

Claims (1)

The claims are 60 in that, in order to reduce the amount of dope when - cessa, as an oxidizing agent used at elevated temperature and pressure, 65 is used spent liquor from oxygen-alkaline bleaching of fibrous semi-finished product, which is fed to cooking together with green liquor.