SU924189A1 - Method for regenerating spin bath in viscose production - Google Patents

Description

The invention relates to the production of viscose ^fibers: in particular the coagulation bath to regenerate the viscose production.

When molding viscose fibers, water and sodium sulfate ⁵ accumulate in the precipitation bath. The main amount of water is introduced into the viscose precipitation bath. Sodium sulphate is formed by reacting sulfuric acid spin bath with sodium hydroxide, ¹⁰ co powers in viscose.

A known method of regeneration of the precipitation bath, according to which water is evaporated, and sodium sulfate is crystallized. The evaporation of water is carried out by heating the bath with flue gases or steam, for which purpose, respectively, the installation of contact vapors and vacuum evaporators are used. The crystallization of sodium sulfate is carried out at low temperature with the release of the Glauber's salt, go with the increased

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perature with the release of anhydrous product [11.

The disadvantages of this method of regeneration of the precipitation bath are high energy consumption, pollution of the atmosphere of the source water with toxic substances, the presence of impurities of metal salts in marketable sodium sulfate.

Closest to the proposed method is the regeneration of the precipitation bath of viscose production by the release of sodium sulfate by crystallization during cooling to 5-8 ° C. The mother liquor is returned to the general circulating system of the precipitation bath, which is evaporated by heating under vacuum [21.

The main disadvantage of this method of regeneration is associated with the return of the mother liquor to the general circulating system of the precipitation bath, which necessitates the evaporation of water from the bath. For evaporation of a necessary amount of water (5000 -

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8000 kg per 1 ton of fiber) consume significant amounts of energy (58 million kcal / ton of fiber). Flow of cooling "in boiling water vapor condensation (200-350 m ^b / ton of fiber) as yavlyaet- ⁵ Xia essential. When the ambient temperature is high, it is excessively large, which causes considerable difficulties. To reduce the water flow is cooled in heat exchanger ¹⁰ via brine nicknames that involve additional energy and other costs. When water evaporates from the bath, the waste water and air are contaminated with carbon disulfide, hydrogen sulfide and sulfuric acid. Commercial sodium sulfate contains salts of polyvalent metals (zinc, aluminum, etc., depending on the composition of the baths) as an impurity. The yield of sodium sulfate is 20 not high enough. It decreases with an increase in acid in the bath.

The purpose of the invention is to reduce energy consumption and increase the purity of the commodity

. sodium sulfate. 25

This goal is achieved by the fact that when using the method of regeneration of the precipitation bath of viscose production by the release of sodium sulfate

*; crystallization during cooling, carbonate is introduced into the bath before crystallization

sodium to neutralize it and remove the resulting precipitate.

This precipitate is reused as an additive in the viscose or precipitating bath _35, and the mother liquor after crystallization is used for dissolving the cellulose xanthate. Depending on the composition of the bath, when it is neutralized with alkali, hydroxides of ₄₀ corresponding polyvalent metals, for example, aluminum, iron, zinc, cadmium, precipitate out. When neutralized with sodium carbonate, the precipitate may contain polyvalent metal carbonates. The precipitate is easily dissolved in the precipitation bath without any treatment, and it is introduced into the main circulation loop of the precipitation bath. When the aluminum-containing bath is neutralized, the precipitate formed is dissolved in an alkaline solution. Therefore, it is advisable to introduce it into the viscose together with the alkali solution used

for dissolving cellulose xanthate.

PRI me R 1. Excess precipitation bath containing, kg / m ^ sulfuric acid 75; sodium sulfate 300; aluminum sulfate 24 and having 50 ^e C, neutralized with sodium carbonate. Dropped out

the precipitate, consisting mainly of aluminum hydroxide and sodium sulfate is filtered off. The solution is sent to crystallization, for which it is cooled to 20 ° C. During crystallization, Glauber salt Mag $ OX * 10 Ng.O. is released from the solution. Polyvalent metals were not found in the resulting sodium sulfate.

The mother liquor is alkalinized to a sodium hydroxide content of 28 kg / m ^a and then the precipitate separated out during neutralization of the precipitation bath is dissolved in it. The resulting solution is used to dissolve cellulose xanthate. Viscose; containing,%: alpha cellulose .8,4; sodium hydroxide 5.9; sodium sulfate 10.5; sodium aluminate 0.75, molded into. precipitation bath of the composition indicated above. Forming speed 50 m / min. The finished fiber has a strength of 34 gf / tex and an elongation of 20%.

PRI mme R 2. Excess precipitation bath containing, kg / m: sulfuric acid 40; sodium sulfate 200; aluminum sulphate 80 and having 30 ’C is neutralized with sodium carbonate. The precipitate, aluminum hydroxide is filtered. The solution is sent to crystallization, for which ςρο is cooled to 10 ° C. Glauber salt is precipitated from the solution during crystallization. Polyvalent metals were not found in the resulting sodium sulfate.

The mother liquor is used to dissolve cellulose xanthate. The precipitate of aluminum hydroxide is dissolved in a precipitation bath. Viscose containing,%: alpha-cellulose 6,9; sodium hydroxide 5.5. <and sodium sulfate 6,1 molded into a precipitation bath of the above composition. Forming speed 40 m / min. The finished fiber has a strength of 35 gf / tex and an elongation of 16%.

Thus, the use of the present invention allows to significantly reduce energy costs for evaporation of water and crystallization of sodium sulfate from the bath, to reduce environmental pollution and the consumption of fresh softened water for the preparation of viscose, improve the conditions for forming the fiber while reducing acid consumption, eliminate impurities polyvalent metals in sodium sulfate and increase the output of sodium sulfate by reducing its content in the mother liquor without lowering the temperature.

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Claims (1)

Claim A method of regeneration of a viscose production precipitation bath by the release of sodium sulfate by crystallization upon cooling, characterized in that, in order to reduce the energy consumption and increase the purity of marketable sodium sulfate, sodium carbonate is introduced into the bath before crystallization neutralize and remove the resulting precipitate.