SU889765A1 - Method of delignifying cellulose-containing raw product - Google Patents

Description

(C) METHOD OF DELEGNIFICATION OF A PULMERUS CONTAINING

I

This invention relates to methods for delignifying cellulose-containing semifinished products and can be used in the pulp and paper industry in the production of high yield pulp for various types of paper and paperboard.

There is a known method for delignifying a cellulose-containing semifinished product by suspending the semifinished product in an aqueous solution of sodium chloride, followed by electrolysis of the resulting suspension in the electrolyzer. The electrolysis is carried out at an initial pH of 2-2.5 and the process is carried out in an electrolyzer with vertically arranged electrodes, in which the ratio of surface areas of the anode and cathode is 1: 2, with an electrolyte concentration of 6 and anode current density of 0.20-0, A / cm 1.

However, this method leads to a high cost of electrical energy and does not provide for the production of CELL-UPE-PRODUCT

left product with a high degree of delignification.

The aim of the invention is to increase the degree of delignification while intensifying the process.

The goal is achieved by the method of delignifying a cellulose-containing semi-finished product by suspending the semi-finished product in an aqueous solution of sodium chloride, followed by electrolysis of the resulting suspension in the electrolyzer, the electrolysis is carried out at initial pH 6, in the electrolyzer with heated anode and vertical cathodes at an initial pH of 6, in the electrolyzer with heated anode and vertical cathodes at an initial pH of 6, in the electrolyzer with heated horizontal anode and vertical cathodes, it is carried out at an initial pH of 6; the anode surface area of each cathode is 1: 1 -1: 1.5.

20

The electrolysis is carried out at an anode current density of 0.22-0.25 A / cm.

In the proposed method, a semi-finished product with a high content of lignin 16-20 is used as the initial cellulose-containing 38 psmg / faboiklta:. The electrolysis is carried out in a 6% aqueous solution of sodium chloride in the proposed electrolyzer under the specified conditions for 2-20 minutes. This ensures the production of active chlorine 1.4-3, V g / l (or, in terms of hypochlorite 3.8- 8 g / l), including, Qk, S g / l hypochlorite. The horizontal position of the anode at the bottom of the electrolyzer ensures maximum penetration and entry into the delignification reaction of the oxidants formed during the electrolysis and their minimum loss into the environment. Electrochemical reactions at the anode of lignin degradation products that have gone into solution as a result of chemical reactions with the resulting oxidants are also possible. Depending on the electrolysis time, the pH of the solutions after electrolysis is 6-9, and the smaller the longer the electrolysis time. After electrolysis, it remains in the electrolyte with up to 1 g / l of active chlorine (this amount also depends on the time of electrolysis - the longer, the more unused chloride is (about 5.3%), so the electrolyte can be reused after deligification. After electrochemical processing of the semi-finished product is expediently subjected to the addition and finishing by the usual technology.The delignification is subjected to a cellulose-containing fibrous semi-finished product previously obtained from larch wood under the following conditions. : within 15 min, hydronic module 4: 1. Alkaline impregnation: 170 ° C for 60 min, hydromodule 4: 1, alkali consumption 14.5 to the weight of absolutely dry wood (by NanO). Oxidative treatment: mass concentration.3% , temperature 20 ° С, duration 180 min. Consumption of ULO. 10, (with an alkaline stabilizing solution of NanSiOn + NaOH.) The prepared 1.5 suspension of said fibrous cellulose-containing semi-finished product in a 6% solution of sodium chloride (initial pH 6.37) is placed in the electrolyzer, set the anode current density of 0.22-0.25 A / cm and lead to electrolysis with periodic re eshivanii cellulosic suspension during different time. After electrolysis, the pulp is filtered from the electrolyte, washed with water and dried. The initial pulp-containing semi-finished product before delignification has the following indicators: Lignin content 16.4% Delignification degree by the P4.5 permanganate number. In the examples given, the parameters for the implementation of specific electrolysis conditions according to the proposed technology in different variants, as well as indicators of the target product, are indicated. Example 1. Electrolysis time 4 min. The amount of electricity missed 0,13 AH / g semi-finished product. pH after electrolysis is 8.9. The amount of active chlorine obtained in the blank test is 1.35 g / l (or, in terms of hypochlorite, 2.83 g / l), including hypochlorite, 2.09 g / l. Residual amount of chlorine after electrolysis with cellulosic suspension (working experience) Traces Residual lignin content,% 12.9 Degree of lignin removal, 421.3 Residual permanganate number 61.7 Reduction of permanent number,% 46,1 Example 2. Electrolysis time 8 min . The amount of electricity missed 0.27 AH / g. The amount of active chlorine obtained in the blank experiment is 2.63 g / l (or 5.58 g / l in terms of hypochlorite), including hypochlorite 2.53 g / l. Residual amount of active chlorine in the blank experiment 0.41 g / l Residual lignin content,% 10.9 Degree of lignin removal, 33.5 Residual permanganate number 45.3 Reduction of permanganate number,% 60.4 Example 3. Electrolysis time 2 min . Amount of electricity skipped 0.4 Ah / g. The amount of active chlorine obtained in the blank experiment is 3.06 g / l (or in terms of hypochlorite 6.1 g / l), including hypochlorite 3.7 g / l.

Residual

lignin,

Degree of removal

lignin,% 65,8

Residual permanganate number 13.9 Reduction of permanganate number,% 87.7 The proposed method is more effective than the known one, since the delignification proceeds more intensively and the content of lignin in the process of processing decreases by 16% to 5.8 - 12.9, t. e. at 3.5-9.6, whereas in the known method only at, in addition, the proposed method is less long and leads to a reduction in power consumption.

Claims (2)

Claim 1. A method for delignifying a pulp-containing semifinished product by suspension. semi-finished product in an aqueous solution of sodium chloride, followed by electrolysis of the resulting suspension in the electrolyzer, characterized in that, in order to increase the degree of delignification of the target product while simultaneously intensifying the process, the electrolysis is carried out at an initial pH of 6, S-7 in an electrolytic cell with a horizontal anode and vertical cathodes, in which the ratio of the surface area of the anode to the area of each of the cathodes is 1: 1.2 - 1: 1.5. 2. The method according to claim 1, wherein the electrolysis is carried out at an anode current density of 0.220, 25 A / cm. Sources of information taken into account in the examination I. USSR copyright certificate If 555190, cl. D 21 from 9/10, 1975.