SU1074929A1 - Method of producing sulphate digesting acid for pulp production - Google Patents

Abstract

METHOD FOR PREPARATION OF SULPHITIC ACID FOR THE PRODUCTION OF CELLULOSE, including szh. that, in order to improve the delignifying properties of cooking acid, before the absorption of sulfur dioxide, the spent solution p of oxygen-alkali deinking pulp was treated sequentially with hydrochloric acid to pH 1-3 at 15-30 ° C and diethyl ether C at a rate of 15-25 vol.%. at € 15-30 ° C followed by separation of the precipitate formed.

Description

WITH

Yu

; o Invention refers to the pulp and paper industry and can be used in the production of pulp by the sulphite method. A known method for the preparation of sulphite cooking acid for the production of pulp, according to which the cooking acid for sulphite cooking of pulp is obtained from spent liquor from sulphite cooking. The spent sodium-based liquor is burned in a reducing atmosphere. Sulfuric acid is added to the melt obtained to produce an acidic solution, followed by lime, as well as blowing sulfur dioxide gas. The resulting calvaceous sulphate is separated, and the sodium sulphate is directed to the preparation of sulphite cooking acid l. However, this method of preparing sulphite cooking acid does not prevent tar deposits on the equipment in the process. The closest to the invention of the technical essence and the achieved result is a method involving the burning of sulfur or pyrite with obtaining sulfur dioxide, gas purification from harmful impurities, gas cooling , absorption of sulfurous anhydride in absorption apparatuses, where the used solution from oxygen-alkaline cellulose refining is used as an absorber, saturation is obtained Crude acid sulphite products blowings 2. However, when passing sulfuric anhydride through lye from oxygen-alkaline refining, the solution becomes noticeably cloudy. The fine t cloud is stable, not filtering with conventional methods, including centrifugation, which reduces the stability of the acid and worsens its delignifying properties. The purpose of the invention is to improve the delignifying properties of cooking acid. This goal is achieved in that according to the method of preparing cooking acid for pulp production, including burning sulfur-containing products to obtain a gaseous product containing sulfurous anhydride, cleaning the gaseous product, cooling, absorbing sulfuric anhydride with a spent solution from oxygen-alkaline refining of cellulose to obtain crude sulfite acid and saturation by the last products of the blowdown, before absorption, of sulfur dioxide, the spent solution from oxygen-alkali th deinking pulp was treated sequentially with hydrochloric acid to pH 1-3 at 15-30 C, and diethyl ether at a rate of 15-25 vol.% at 15-30 ° C followed by separation of the formed precipitate. The method is carried out as follows. The sulfur-containing product is burned, the resulting sulfur dioxide is purified from impurities, and the gas is cooled. The spent liquor is taken from the oxygen-base cellulose refining and fed through a heat exchanger to the reactor, where it is treated with hydrochloric acid until the pH of the medium is 1-3. Then the liquor with the formed suspended substances is treated with diethyl ether at a rate of 15-25% by volume at 15-30 ° C and atmospheric pressure for 2-7 hours, preferably 3-5 hours. After the indicated time has elapsed, the solution is separated from the precipitate and after the heat exchanger is sent to a distillation column, where diethyl ether is distilled off at 35-50 ° C. The oxygen-alkaline refining liquors thus treated are fed into a feed tank, where a solution of soda ash is added, the sodium base is adjusted to 0, 80-0.85%. N320. This solution is fed to packed absorbers to absorb sulfur dioxide. The amount of B alkaline solution absorber is adjusted by the ratio controller in accordance with the incoming gas. The crude acid obtained in the acid compartment is pumped into tanks or tanks for storage before being used for pulping. Example 1. Sulfur pyrite is burned under production conditions, the resulting gaseous product containing sulfur dioxide is purified in a scrubber and cooled. The spent solution from the oxygen-alkaline refining of spruce sulphite pulp is obtained from refining according to the following conditions: temperature 100 ° С, sodium hydroxide consumption 6% per unit. Ne20, processing time 85 min. The composition of the liquor from oxygen-alkaline refining, ppm,% to liquor: Dry substances 2.43 Organic substances1., 36 Volatile acids0.33 , 76 N a 2 O,% in units, 1.07 Ash content,% RV,% 0.04 PH. 12.0 Density, kg / m 1013 10800 Acidibility, mg / l COD, mg 16000 VPK5 mg O2 / L 3950 Next, 500 ml of the spent solution (pH 9, b) are treated with 12% hydrochloric acid until pH of the medium is reached 1 at. Next, in a separating funnel, 500 mp of alkaline pH 1 is treated with diethyl ether at a rate of 15 vol.% At 15 ° C. After settling the solution for 2 hours, the bottom of the separatory funnel coagulates the flocculated precipitate which is removed. The characteristics of the processed lye from the oxygen-alkaline refining are shown in Table. 1, For comparison, data relating to a known method is recorded. As follows from the data table. 1, the content of resinous substances in the liquor after processing by the proposed method is significantly reduced, which contributes to reducing the deposition of resins in the equipment. At the same time, the content of reactive Na20 in the lye does not change from the alkali oxygen upgrading, indicating that it is possible to successfully use such lye as the base of sulfite cooking acid. Liquids from oxygen-alkaline refining in the amount of 70% of the volume of acid required for cooking are used to absorb sulfur dioxide. Along with this lye, O, 76% of alkali is fed into the cooking acid. Na. The remaining amount of alkali to bring the base content to 0.83% Ma20 is introduced in the form of soda ash. The resulting sulfite acid cheese is saturated with blows to a total S02 content of 8%. Sulfite cooking is carried out at a water ratio of 5: 1 under the following conditions: temperature rise to - 2 hours, stand at 105 ° C 2, 5 hours, temperature rise to 2 hours, stand at - 1 hour 45 minutes, Indicate the quality of sulphite unbleached pulp in comparison with the known are given in table. 2. From the data table. 2 it follows that the proposed treatment of liquors from oxygen-alkaline refining improves the efficiency of the cooking process and improves the quality of the fibrous semi-finished product. Example 2. Analogously to example 1, receive sulfur dioxide. 500 ml of waste solution obtained by oxygen-alkaline refining of aspen wood pulp, as in Example 1, having the composition, ppm % of {whole: Dry substances 1.60 Organic matter 1.02 Volatile acids 0.15 Including acetic acid 0.09 formic 0.06 Non-volatile acids 1.09 MetaNolSledi Ethanol 0.01 Substances extracted with diethyl ether 0.06 Substances insoluble in mineral acids 0,03 Reactive N320,%, in units - Ash content,% 0,58 RV,% 0.08 Density, kg / m 1006 pH11.5 Oxidability, mg / l 4700 COD, mg O / l 7200 BOD5, mg 0 „/ l2530 treated with 12% hydrochloric acid until a pH of 3 is reached at. Next in the separatory funnel. 500 ml of alkali with pH 3 is treated with diethyl ether at a rate of 25 vol.% At. After settling the solution for 7 hours, coagulated at the bottom of the separatory funnel, the precipitate is removed. The characteristics of the processed by the proposed method of liquor from oxygen-alkaline refining are given in table. 1. (example 2). The liquor treated in this way is used to absorb sulfurous anhydride to produce sulphite cooking acid and pulping as in Example 1. Cellulose is obtained with the quality indicators shown in Table 2. 2 (example 2). Example 3. Liquor from oxygen-alkaline refining of cellulose from birch wood of composition, ppm,% to liquor is used:

Dry matter2.92

Organic matter2,07

Volatiles0.31 Including

acetic acid 0,19 formic 0.12 Non-volatile acids1.08 Methanol Spec. Ethanol.Sledi Extractable substances. diethyl ether0.04 Substances insoluble in mineral acids0.02 Reactive NajrOj% in units, N3200.76 Ash content,% - 0.85 RV,% 0.06 PH -12.5 Density, kg / m1014 Oxidability, mg / l 8990 COD , mg 02 / l15600 BOD, mg C2 / L5060

500 MP of the spent liquor, analogously to Example 1, are treated with 12% hydrochloric acid until pH 2 is reached at 20 ° C. Then in a separating funnel, 500 ml. alkali with pH 2 is treated with diethyl ether at a rate of 20 vol.% at 20 ° C. After settling the solution for 5 hours, the precipitate which coagulates at the bottom of the separatory funnel is removed. The characteristics of the lye from the oxygen-alkaline refining processed by the proposed method are shown in Table 1 (Example 3). The liquor treated in this way is used to prepare sulphite cooking acid and perform pulping as in Example 1. Cellulose is obtained with quality indicators shown in Table 1 (Example 3),

The data presented in Tables 1 and 2 indicate that the proposed method for the preparation of sulphite cooking acid makes it possible to improve its delignification properties. 1T a b l i: c a 1

Mass fraction of reactive Nag O,% in unc Nag Nag O

Mass fraction of substances extracted by diethyl ether,% to liquor

Mass fraction of nonvolatile acids% to liquor

Mass fraction of substances insoluble in mineral acids% to liquor

The output of cellulose,% by weight.with. wood

Rigidity of cellulose, perm. Mass fraction of lignin,%

0.76

0.76

0.76

0.76

0.0

Traces

Traces . Traces

1 D5

1.02

0.90

0.90

0.02

Table 2 Method

46.6

46.6 49

50

1.20

0.95

Mass fraction of extractives,%

Ash content of cellulose,% Viscosity of cellulose, Pa "s

Continued table. 2

0.21

0.21

0.23 0.16 0.16 0.16 24.8 24.7 24.8

Claims (1)

METHOD FOR PREPARING SULPHITE BOILING ACID FOR CELLULOSE PRODUCTION, including burning sulfur-containing products to produce a gaseous product containing sulfur dioxide, purifying the gaseous product, cooling, absorbing sulfur dioxide using the spent solution from oxygen-alkaline refluxing, and differentiating the cellulose with refluxing it; in order to improve the delignifying properties of cooking acid, before the absorption of sulphurous anhydride, the spent acid solution Hydrogen-alkaline refinement of cellulose is treated sequentially with hydrochloric acid to pH 1-3 at 15-30 ° C and diethyl ether with a flow rate of 15-25 vol.%. at 15-30 ° C followed by separation of the precipitate formed. ί