SU1454262A3 - Periodic method of producing cellulose - Google Patents

Abstract

The multi-stage pulping process is performed in a single digester (10) in a batch type operation. The wood chips to be cooked are introduced into the digester (10) and soaked with a warm black liquor to remove most of the air from the digester (10) and the chips. This warm black liquor is thereafter displaced from the digester (10) with a mixture of a first stage hot black liquor and hot white liquor, the proportionate amount of hot white liquor being relatively high. The temperature of the digester contents is then raised to a cooking temperature for a predetermined amount of time. The original cooking liquor is then displaced with a mixture of a second hot black liquor and hot white liquor, the proportionate amount of hot white liquor in this second cooking liquor being less than in the first. Again, the temperature of the digester (10) is raised to a cooking temperature and the cooking is carried out for a shorter period of time than in the first cooking stage. After the required number of cooks which may be preferably three but may be as low as two or more than three, the cooking liquor is displaced from the digester with a liquid filtrate (47) derived from pulp washing. Finally, the contents of the digester (10) are emptied by applying gas under pressure to the interior of the digester (10).

Description

SP

four;

N9

ten

15

The invention relates to the pulp and paper industry and can be used for pulping various cooking solutions.

The purpose of the invention is to reduce the process time and steam consumption.

The proposed batch process for pulping involves feeding wood chips to a digester, impregnating it with black liquor at a temperature below the boiling temperature, displacing the impregnating black liquor from the boiler with a preheated mixture of black and white liquor, raising the temperature of the reaction mixture, boiling the chips with the final mixture at the final temperature , replacement of the spent liquor at the end of cooking with the filtrate from the washing stage and unloading the contents of the cooking boiler by supplying gas under pressure to its internal Part. Cooking is carried out in three stages, the first of which is carried out for 35 minutes when the content of white liquor in the mixture is 69% of its total consumption for cooking, the second for 15 minutes when the content of white liquor in the mixture is 22%, and the third during 10 min when the content of white liquor is 9% of its total consumption for cooking.

The total amount of white liquor used for multi-stage cooking is 25% of the capacity of the digester without the volume of chips in the digester.

The proposed method is carried out as follows.

Chips are loaded into the digester 0 with a removable lid, then warm black liquor is pumped from the black liquor base to the ntenbi soak into the base of the digester of the digester 13, and the contents of the boiler can be heated to the boiling point by pumping the steam condensate.

14542622

The system for implementing the method includes a tank for storing fresh hot white liquor heated by heat exchange by draining part of the hot liquor, and accumulators of hot liquors for the first, second and third cooking stages, respectively, obtained by supplying black and white liquors through flow regulators into the drive and representing the necessary mixture of black and white liquors.

After the impregnation is completed, the liquor is successively replaced with hot liquor of the first cooking stage, after the first cooking stage has expired with the second stage liquor, and after the second stage has passed with the third stage cooking liquor.

The fibrous semi-finished product obtained as a result of a three-stage cooking process is washed, the filtrate is heated by heat exchange with hot liquor and fed to the storage tank of hot filtrate, then to the digester.

20

25

35

To unload the contents of the digester, an exhaust valve is provided, which opens after the end of cooking and injection into the boiler through the air inlet duct or other fluid.

The proposed sequential use of different cooking solutions in the process of one multi-stage cooking is possible in the implementation of sulphate or soda cooking and provides a more complete delignification of the fibrous semi-finished product.

Example. A peridic method for producing sulphate pulp from soft wood chips is carried out in the manner described in a 6000 cubic meter digester. feet with process parameters listed in Table. one.

Table 1

0

five

To discharge the contents of the digester, an exhaust valve is provided, which opens after the end of cooking and injection into the boiler through the air inlet duct or other fluid.

The proposed sequential use of different cooking solutions in the process of one multi-stage cooking is possible in the implementation of sulphate or soda cooking and provides a more complete delignification of the fibrous semi-finished product.

Example. A peridic method for producing sulphate pulp from soft wood chips is carried out in the manner described in a 6000 cubic meter digester. feet with process parameters listed in Table. one.

Table 1

3U54262

At the same time, the data on the long-term, thus the invention of various operations of the three-stage process, to effectively carry out the sulphate method for the production of sulphate and cellulose pulping in relatively small amounts are given in Table. 2, a cooking cycle of short duration, i.e. improve productivity Table2process.

Operations

Continue the firmament, min

Chip loading

Warm liquor impregnation

Fill with first liquor

First stage cooking

Filling with second liquor

Second cooking stage

Filling with the third hot liquor

Third stage cooking

Replacement of high and low liquor

Purge Reserve

Claims (1)

Formula invented t i n five 0 five Periodic method of pulp production, including feeding wood chips into the digester, impregnating it with black liquor at a temperature below the boiling temperature, displacing the black liquor impregnating liquor from the boiler with a preheated mixture of black and white liquors, raising the temperature of the reaction mixture, boiling the chips with this mixture at the end temperature, replacement of the spent liquor at the end of cooking with the filtrate. stages of unloading and unloading the contents of the digester by supplying gas under pressure to its inner part, characterized in that, in order to shorten the process time and steam consumption, the cooking is carried out in three stages, the first of which is carried out for white liquor in a mixture of 69% of its total consumption for cooking, the second lead for 15 min when the content of white liquor in a mixture of 22% of 5 of its total cooking cost, and a third is carried out for 10 minutes with a white liquor content of 9% of its total cooking cost.