SU1730300A1 - Method of producing cellulose - Google Patents

Abstract

The invention relates to the technology of producing cellulosic semi-finished products and allows improving the physicomechanical properties of cellulose and increasing the content of reducing substances in the final spent liquor. The wood chips are varied in two steps with the removal of spent liquor after each of them. The first stage cooking is carried out with an aqueous solution of sodium pyrosulfite with an S02 content of 2.2-2.4% in it at a temperature of 135-140 ° C for 1.5-2.0 hours. The second stage of cooking is carried out 2.8-3.0% aqueous solution of sulfur dioxide at a temperature of 135-140 ° C for 2.0-2.5 hours. 1 s. f-ly, 1 tab.

Description

Yo

The invention relates to a technology for producing pulp semi-finished products and can be used in the pulp and paper industry in the manufacture of pulp for various types of paper and cardboard.

A known method for producing cellulose by boiling cellulose-containing raw material with a cooking solution containing sodium pyrosulfite for 2-3 hours at a temperature of 160-170 ° C and a pH of 3-5. The disadvantage of the method is the low mechanical properties of cellulose.

There is also known a method for producing cellulose by boiling wood raw material with a cooking solution containing sodium pyrosulfite when heated from 80 to 120 ° C for one hour, from 120 to 160 ° C - for

2 h and keeping at 160 ° C for

3h The disadvantages of this method are

low value of tear resistance and low content of reducing substances (PB) in liquor.

The closest analogue of the invention is a method for producing cellulose, which involves boiling wood chips in two stages, the second of which is carried out with an aqueous solution of sulfur dioxide, and removing spent liquors after each stage. 8-3.0% at a temperature of 147-155 ° C. At the second stage, an aqueous solution of SOa is used as a cooking solution, and at a temperature of 140-145 ° C for 2.0-2.5 hours the cooking is completed. The disadvantages of the method are the low physico-mechanical parameters of cellulose and the relatively low content of reducing substances (PB) in the final waste liquor.

Oj

about

Oj

about

about

The aim of the invention is to improve the physicomechanical properties of cellulose and increase the RV content in the final spent liquor.

To achieve this goal, a two-step cooking of wood chips is carried out using an aqueous solution of sodium pyrosulfite with CO2 content of 2.2-2.4% in it at the first stage with heating for 1.5 hours from 60 to 135-140 ° C. temperature for 1.5-2.0 hours. In the second stage, an aqueous solution of CO2 with a concentration of 2.8-3.0% is used for cooking at a temperature of 135-140 ° C for 2.0-2.5 hours. The choice of sodium pyrosulfite solution as a cooking one at the first cooking stage is due to its high reactivity in the lignin sulphurization reaction characteristic of the initial cooking stage. The use of an aqueous solution of S02 in the second stage of cooking is caused by the significant rate of dissolution of sulfonated lignin in an acidic medium. The temperature range of 135-140 ° C in the first stage of cooking is selected on the basis that at a temperature below 135 ° C the process of sulfonation of lignin with pyrosulfite-sodium is slowed down and a significant increase in the duration of cooking will be required to obtain cellulose. At temperatures above 140 ° C, in the first stage of cooking, the cellulose component of wood will be subjected to decomposition, which will markedly reduce the yield of cellulose from wood.

Example. Get cellulose from spruce chips. A pyrosulfite cooking solution for the first cooking stage is prepared by dissolving a portion of sodium pyrosulfite (GOST 10575-63) in water. The aqueous solution S02 for the second stage of cooking is prepared by saturating the water with gaseous S02. Hydraulic module cooking 1: 5. After each cooking stage, the spent cooking liquor is removed.

Cookings are carried out at different values of the total S02 content in the aqueous solution of sodium pyrosulfite, the temperatures and the duration of each cooking stage. Cooking conditions, as well as pulp indicators and RV content in the waste

liquor presented in the table.

At the same time, the experiment was carried out according to the method of the prototype, using sodium bisulfite as a cooking solution at the first stage. The conditions of the pulping and pulp and liquor indicators are also presented in the table.

As can be seen from the table, the prototype and the proposed method of cooking the obtained semi-finished products of approximately the same yield and degree of delignification. However, when cooking by the proposed method compared to the prototype, the resistance to fracture increases by 3.2-3.3 times and the resistance to tearing by 2 times. Wherein

discontinuity and resistance to bursting are not reduced.

The proposed method also allows, in comparison with the prototype, to increase the RV indicator of the spent final liquor.

almost doubled, which is very important for further chemical processing of liquor.

Claims (2)

1. A method for producing pulp, which involves boiling wood chips in two stages, the second of which is carried out with an aqueous solution of sulfur dioxide, and removing spent liquor after each stage of cooking, characterized in that In order to improve the physicomechanical properties of cellulose and increase the content of reducing substances in the final waste liquor, the first stage of cooking is carried out with an aqueous solution of pyrosulfite sodium with S02 content of 2.2-2.4% at a temperature of 135-140 ° C for 1.5-2.0 hours. 2. A method according to claim 1, characterized in that the second cooking step is carried out at the concentration of an aqueous solution of sulfur dioxide 2.8-3.0% and a temperature of 135-140 ° C for 2.0-2.5 hours Table continuation