SU1490084A1 - Method of crystallizing sodium sulfate - Google Patents

Abstract

The invention relates to the field of regeneration of technological solutions in the production of viscose fibers, in particular to methods for the crystallization of sodium sulfate from technological solutions in vacuum crystallizers, and can be applied in the chemical and other industries. The invention allows to reduce energy consumption and increase the specific removal of the Glauber's salt from spent technological solutions of viscose productions due to the fact that in the method of salt crystallization from technological solutions with their preliminary cooling to 18 - 20 ° C and subsequent stepwise cooling by adiabatic evaporation of the solvent under vacuum in a multistage crystallizer in each of its sections serves additionally continuously or with a periodic sequence of feed pulses and a duty cycle of 3 - 5 s the initial salt solution at the temperature of the process solution 50 - 100 ° * C. The specific removal of the product is 78–80 kg / m ^{3 of the} regenerated solution.

Description

The invention relates to the regeneration of process solutions for the production of viscose fibers, in particular, to methods for the crystallization of sodium sulfate from process solutions in vacuum crystallizers, and can be used in the chemical and other industries.

The aim of the invention is to reduce energy consumption and increase the specific removal of the product.

When forming the hydrated cellulose fibers obtained by the viscose method, an excess amount of sodium sulfate, which is formed as a result of the interaction of sulfuric acid precipitators with caustic soda, contained in a spin solution, accumulates in the circulation loop of the sedimentation bath. Excess sodium sulfate is withdrawn from the shaping loop along with the precipitation bath. Therefore, it becomes necessary to regenerate the precipitation bath in order to extract excess sulphate from it. sodium and return to the production cycle of valuable components - sulfuric acid, zinc sulfate, etc.

The process is carried out as follows.

The main stream of the regenerated process solution with a temperature of 50 ° C is cooled in the pre-coolant to 18-20 ° C and in the state of saturation enters the 4-section vacuum crystallizer, first

four

with

oo

go section. The passage of the crystallizer section, the regenerated solution, due to the adiabatic evaporation of water from the solution and maintaining in the sections of the corresponding residual pressure while removing the resulting steam, is cooled stepwise to section temperatures of 15-18 ° C, 10-12 ° C; 7-8 ° C;

5-6 ° C and it is in a state of boiling at these temperatures. Already in the first section of the crystallizer, the solution attains the state of crossbreeding and glauber salt crystallizes to form the germinal phase. In the subsequent sections of the crystallizer, the nucleus grows to the size of production crystals of the Glauber's salt. Another smaller stream of the initial regenerated solution with an initial temperature of 50 ° C or heated to a higher temperature T up to 100 s) is introduced into each section of the crystallizer, in the lower part

slurry layer through a distribution device, for example through a perforated collector. At the outlet of the switchgear, it is overheated with respect to the conditions in the section of the solution:

The solution is cooled to the temperature of the suspension layer in the section, and the excess heat of the flow is spent on the formation of juice vapor in the depth of the suspension layer. growth medium for already 40 formed embryos and crystals. Lift up, the vapor bubbles mix the suspension layer, preventing the crystalline phase from settling. Example 1. Initial regenerated solution of the precipitation bath (main stream) of viscose fiber production, g / l: Na2S04 270; H ,, S04 135; ZnSO 17; the other, with a density of p 1290 kg / m, with a temperature of 50 C, is cooled in the pre cooler to 18 ° C and the amount of 38728 kg / h enters the 4-section horizontal vacuum crystallizer, in the first section. Topics II II - III - IV-5 ° C. Method of creating vacuum in sections of a steam ejector mold C12 steam ejectors) with condensation of a mixture of juice and working steam ejectors with water in a barometric mixing condenser. 1298 kg / h with temperature

154;

50 С (mixing additional flow), including in sections: I - зы to the bottom of the crystallizer and 45 kg / h; II - 330 kg / h, III 288 kg / h, IV - 260 kg / h. amount

Wu recrystallization of small crystals and the growth of large crystals.

Another way to implement the invention is to pulsed an additional stream of superheated process solution in the section of the mold.

In order to evenly distribute the crystals in the volume of the suspension, to prevent the coalescence of bubbles, the emission of crystals and the mother liquor from the suspension layer, to throw them into the vacuum tube and to carry it away with suction vapors from the crystallizer 50

55

1073 kg / h of vapor evaporated from the crystallizer sections. Consumption of working steam for the work of steam ejectors 2855 kg / h. A total of 3928 kg / h of water vapor is condensed in the mixing condenser. Water consumption with a temperature of 28 ° C to a barometric condenser for condensation of 3928 kg / h of water vapor is 783.6 m / h. The amount of production suspension from the last IV section of the catalyst is 38,925 kg / h. After conducting all the subsequent stages of the process of this amount

0

50

five

30 perurarat solution in sections:

jj 40

The overflow of the superheated precipitation bath is fed to the crystallizer sections in pulses. By selecting the frequency of the pulses following, their duration depending on the amount of the main flow of the precipitation bath, the amount of overheating of the additional flow of the precipitation bath and the residual pressure in the section of the crystallizer, you can get the best results in mixing the suspension without ejection of crystals and mother liquor into the supracetal space, increasing the specific removal of crystallisation - that per unit volume of the regenerated solution and increase the productivity of the mold.

Example 1. The initial regenerated solution of the precipitation bath (main stream) of the production of viscose fiber composition, g / l: Na2S04 270; H ,, S04 135; ZnSO 17; the rest, with a density of 1290 kg / m, with a temperature of 50 ° C, is cooled in the pre-cooler to 18 ° C and the amount of 38,728 kg / h enters the 4-section horizontal vacuum crystallizer, in the first section. Topics II II - III - IV-5 ° C. Method of creating vacuum in sections of a steam ejector mold C12 steam ejectors) with condensation of a mixture of juice and working steam ejectors with water in a barometric mixing condenser. 1298 kg / h with temperature

154;

50 С (mixing additional flow), including in sections: I - 45 kg / h; II - 330 kg / h, III 0

five

1073 kg / h of vapor evaporated from the crystallizer sections. Consumption of working steam for the work of steam ejectors 2855 kg / h. A total of 3928 kg / h of water vapor is condensed in the mixing condenser. Water consumption with a temperature of 28 ° C to a barometric condenser for condensation of 3928 kg / h of water vapor is 783.6 m / h. The amount of production suspension from the last IV section of the catalyst is 38,925 kg / h. After conducting all the subsequent stages of the process of this amount

5I /,

the production suspension of the Glauber's salt in the mother liquor gives 2AOO kg / h (57.6 tons / day) of commodity sodium sulfate. The specific removal of salable sodium sulfate is 78 kg / m of the regenerated solution.

Example 2 Similar to Example 1 by the method of stirring a suspension with a superheated initial solution of a precipitation bath and a steam ejector by creating a vacuum, but the condensation of a mixture of juice and working steam of steam ejectors is carried out in a surface brine condenser. The initial regenerated solution of the precipitation bath (the main flow of the production of viscose textile yarn composition, g / l: 270; 140; ZnSO 15; the rest, p 1290. kg / m, with a temperature of 75 C is cooled in a fuse before and in the amount of 38728 kg / h enters the A-section horizontal vacuum Hbrfi crystallizer, first along the section. Solution temperature in sections: I - 15 ° C; II-III-74 IV - 5 C. Supply of additional flow of the initial precipitation bath with temperature in the crystallizer section is 1298 kg / h, in tons per hour in sections; I - A20 kg / h; II - 330 kg / h; III - 288 kg / h ; IV - 260 kg / h. The amount of vapor exhausted from the crystallizer sections is 1073 kg / h. The consumption of working steam for the work of steam injectors is 2855 kg / h. In total, 3928 kg / h of water vapor is condensed in a surface condenser. The condensing agent is a brine with a temperature O - +2 C. Required for 2

condensation top 96.4 m. The amount of production suspension from the IV section of the crystallizer is 38925 kg / h. After all the subsequent stages of the process, 2400 kg / h (57.6 t / day) of marketable sodium sulfate are produced from this amount of the production of the α-suspension of the Glauber's salt in the mother liquor. The specific removal of sodium sulfate 77 kg / m of the recovery bath solution is obtained.

Example 3. Analogous to example 1 with a steam-ejector method of creating a vacuum and vapor condensation in a barometric mixing condenser with irrigated water, but the supply is additional 0084b

The hot stream of the osalitic bath with a temperature of 100 C in the section of the mold is pulsed with a pulse duration of 3 s and a duty cycle of 3 s. The original regenerated solution precipitation bath. (mainstream) production of viscose technical composition,

10 g / l: Na, S04 220; 00; ZnS04 90, the rest, p 1290 kg / m, with a temperature of 30 C is cooled in a fuse up to 18 C and in the amount of 42601 kg / h enters a 4-section

15 horizon;: a new vacuum crystallizer, in the first section along the way. Solution temperature in sections: I - 5 С; II -, III - 7 С; . } 1 pulse feed extra

20 of the flow of the initial precipitation bath with a temperature of 100 ° C in the section of crystallisation.rar is 1,428 kg / h, incl. in sections: I - 462 kg / h; II- 363 kg / h; P1 - 311 kg / h; IV-286 kg / h.

25 Number of suction from sections

crystallizer vapor 1181 kg / h. Consumption of working steam for steam ejectors work 3145 kg / h. In total, 4326 kg / h of water vapor is condensed in the mixing condenser. The flow rate of water with a temperature of 28 ° C to the barometric mixing condenser for condensation of 4326 kg / h of water vapor is 865 m / h. The amount of production suspension from the last IV section of the crystallizer is 42,601 kg / h. After carrying out all the subsequent stages of the process of this amount of production suspension of the Glauber's salt in the mother liquor

40 get 2,640 kg / h (63.3 tons / day) of marketable sodium sulfate. Specific j removal of salable sodium sulfate 80 kg / m of the regenerated solution.

35

Example 4. Similar to example 1, but the temperature of the solution in sections: I - 18 ° C; II - 12 s; III - 8 ° C; IV - b s and the supply of an additional flow of a precipitation bath with a temperature of 50 C in the section of the mold is pulsed with a pulse duration of 5 s and a duty cycle of 5 s. The amount of production suspension from the last IV section

crystallizer 38925 kg / h, the output of salable sodium sulphate 2400 kg / h (57.6 t / day, the specific removal of salable sodium sulfate was 78 kg / m of the regenerated solution.

Example 5. Analogous to example 1 ,. but the temperature of the solution in sections: I - II - PCh; III -J c; IV - 5, 5 and the supply of an additional stream of a precipitation bath with a temperature in the section of the mold is pulsed with a pulse duration of 4 s and a velocity of 4 s. The amount of production suspension from the last IV section of the mold is 38,925 kg / h, the output of marketable sodium sulfate is 2,400 kg / h (57.6 tons / day), the specific removal of salable sodium sulfate is 78 kg / m of the regenerated solution

The invention allows to increase the specific removal of salable sodium sulfate from 70 to 78 kg / m of the initial solution, to reduce steam consumption by 9.92 and water by 29%, and the productivity of the method for anhydrous sodium sulfate will increase by 14%,

Claims (1)

Invention Formula The method of crystallization of sodium sulfate from waste solutions of viscose production, including pre-cooling the initial solution to 18-20 ° C and subsequent stepwise cooling to 5-10 ° C by adiabatic evaporation under vacuum in a sectional crystallizer with stirring, characterized in and increase the specific removal of the crystalline product, in each section of the mold are additionally introduced continuously or with a periodic sequence of feed pulses and wells 3-5 s of the original solution with a temperature of 50-100 C in the amount of 4-14 kg per 1 m of the initial solution for crystallization. Compiled L.Temirova Editor T.Parfenova Tehred M.Didyk Proofreader S.Shekmar Order 3639/25 Circulation 433 VINILI of the State Committee on Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, 4/5 Raushsk nab. Production and Publishing Combine Patent, Uzhgorod, st. Gagarin, 101 Subscription