CN102745720A - Denitration method in caustic soda technology - Google Patents

Abstract

A denitration method in caustic soda technology comprises the following steps: firstly cooling dechlorinated light salt brine from an electrolytic workshop section, removing residual free chlorine by an active carbon filter, adjusting the pH value to 3-7, removing large particles by a security filter to prevent the large particles from entering a film group; pumping the pretreated dechlorinated light salt brine into the film group system by a charging high pressure pump, separating the light salt brine into penetrating fluid poor in nitrate and penetrating fluid rich in nitrate, wherein the film group adopts three-level film filtration, filtering the penetrating fluid poor in nitrate through each level to obtain decreasing flow, combining the filtrates together, filtering the penetrating fluid rich in nitrate through the three levels for gradual concentration so as to obtain the concentrate at the third level; finally, crystallizing and separating sodium sulfate from the concentrate by a freezing cooling method. The method of the invention is low in operation cost, simple in operation, and high in automation degree, brings no new impurities into the treated salt brine, and causes no pollution.

Description

The nitre method of removing in a kind of process of caustic soda

Technical field

The present invention relates to the nitre method of removing in a kind of process of caustic soda.

Background technology

In production of caustic soda, sulfate radical can enrichment in the salt solution of system, and too high sulfate radical can increase side reaction in the electrolytic process, reduces purity of chlorine gas feeding, current efficiency is descended.Sulfate radical mainly gets into systems by 3 approach, promptly crude salt (or bittern), changing salt solution, dechlorination, to add S-WAT oxidized and produce, and is main with what bring in the raw material salt (or bittern) wherein.The removal method of sulfate anion in brine system has barium method, calcium method, cold method, ion exchange method and membrane separation process etc. at present.The shortcoming of barium method is that working cost is high, bariumchloride is that violent in toxicity, waste residue can produce secondary pollution.Calcium method shortcoming is because the calcium sulfate that generates is micro-soluble material, and the salt slurry amount is increased.The shortcoming of cold method is that investment is high, and energy consumption is high.

Summary of the invention

In order to overcome the deficiency of above-mentioned prior art, the object of the present invention is to provide the nitre method of removing in a kind of process of caustic soda, effective, cost is low.

To achieve these goals, the technical scheme of the present invention's employing is:

The nitre method of removing in a kind of process of caustic soda comprises the steps:

Step 1, pre-treatment

Be water-cooled to 35～50 ℃ to the dechlorination light salt brine that comes from electrolysis workshop section with interchanger, utilize activated charcoal filter to remove residual free chlorine; Adjustment pH value to 3～7: remove macrobead with security personnel's strainer, prevent to get into the film group;

Step 2, membrane filtration

Through the dechlorination light salt brine after the pre-treatment, squeeze into the film group system through the charging HPP, separate into poor nitre penetrating fluid and rich nitre liquid concentrator to light salt brine, said film group arrangement mode is 4-2-2; Promptly three grades of membrane filtrations are respectively 4,2,2 putaminas, each 4 film; Totally 32 films, poor nitre penetrating fluid come out from every grade, and flow successively decreases; Gather at last, rich nitre liquid concentrator progressively concentrates through three grades, comes out the third stage;

Step 3, aftertreatment

In rich nitre liquid concentrator, add alkali adjustment pH value, flow into the liquid concentrator basin, with pump the liquid concentrator extraction is delivered to 2 interchanger and carries out precooling 9～11; Refrigerant is from the freezing low nitre cool brine that removes behind the nitre-5 ℃ of cool brine jar, and the liquid concentrator temperature after the precooling is 12～15 ℃, interchanger, carries out heat exchange with the chilled brine that comes from cooling plant then; The back flows in the saltpetre sinking device, and the liquid concentrator after freezing contains a large amount of saltcake, and muddy liquid concentrator flows automatically to the saltpetre sinking device core barrel; In core barrel, the saltcake crystal grain is grown up gradually, and liquid concentrator drops to the core barrel lower part outlet along core barrel; Flow in the staving of saltpetre sinking device, at this moment the saltcake in the liquid concentrator sinks under the effect of gravity gradually, finally is deposited in the awl bottom; And the low nitre liquid concentrator of isolating saltcake rises to the top of saltpetre sinking device along staving, is back to the hydrops case, and overflow flows in the cool brine basin; And do the refrigerant of pre-cooler by pump delivery to 2 platen formula interchanger, and make temperature bring up to 30 ℃ of sending to salt, after being discharged by the awl end, the higher nitre mud of the solid content at the saltpetre sinking device awl end flows automatically in the whizzer; After centrifugal, pack, obtain the saltcake that the quality mark is lower than 60% (comprising crystal water).

Compared with prior art, the present invention is that working cost is lower, simple to operate, level of automation is high, brings new impurity into can for the salt solution of handling, and is pollution-free.

Embodiment

Below in conjunction with embodiment the present invention is explained further details.

The nitre method of removing in a kind of process of caustic soda comprises the steps:

Step 1, pre-treatment

Be water-cooled to 35～50 ℃ to the dechlorination light salt brine that comes from electrolysis workshop section with interchanger, utilize activated charcoal filter to remove residual free chlorine; Adjustment pH value to 3～7: remove macrobead with security personnel's strainer, prevent to get into the film group;

Step 2, membrane filtration

Through the dechlorination light salt brine after the pre-treatment, squeeze into the film group system through the charging HPP, separate into poor nitre penetrating fluid and rich nitre liquid concentrator to light salt brine, said film group arrangement mode is 4-2-2; Promptly three grades of membrane filtrations are respectively 4,2,2 putaminas, each 4 film; Totally 32 films, poor nitre penetrating fluid come out from every grade, and flow successively decreases; Gather at last, rich nitre liquid concentrator progressively concentrates through three grades, comes out the third stage;

Step 3, aftertreatment

In rich nitre liquid concentrator, add alkali adjustment pH value, flow into the liquid concentrator basin, with pump the liquid concentrator extraction is delivered to 2 interchanger and carries out precooling 9～11; Refrigerant is from the freezing low nitre cool brine that removes behind the nitre-5 ℃ of cool brine jar, and the liquid concentrator temperature after the precooling is 12～15 ℃, interchanger, carries out heat exchange with the chilled brine that comes from cooling plant then; The back flows in the saltpetre sinking device, and the liquid concentrator after freezing contains a large amount of saltcake, and muddy liquid concentrator flows automatically to the saltpetre sinking device core barrel; In core barrel, the saltcake crystal grain is grown up gradually, and liquid concentrator drops to the core barrel lower part outlet along core barrel; Flow in the staving of saltpetre sinking device, at this moment the saltcake in the liquid concentrator sinks under the effect of gravity gradually, finally is deposited in the awl bottom; And the low nitre liquid concentrator of isolating saltcake rises to the top of saltpetre sinking device along staving, is back to the hydrops case, and overflow flows in the cool brine basin; And do the refrigerant of pre-cooler by pump delivery to 2 platen formula interchanger, and make temperature bring up to 30 ℃ of sending to salt, after being discharged by the awl end, the higher nitre mud of the solid content at the saltpetre sinking device awl end flows automatically in the whizzer; After centrifugal, pack, obtain the saltcake that the quality mark is lower than 60% (comprising crystal water).

Claims (1)

1. the nitre method of removing in the process of caustic soda is characterized in that, comprises the steps:

Step 1, pre-treatment

Be water-cooled to 35～50 ℃ to the dechlorination light salt brine that comes from electrolysis workshop section with interchanger, utilize activated charcoal filter to remove residual free chlorine; Adjustment pH value to 3～7: remove macrobead with security personnel's strainer, prevent to get into the film group;

Step 2, membrane filtration

Through the dechlorination light salt brine after the pre-treatment, squeeze into the film group system through the charging HPP, separate into poor nitre penetrating fluid and rich nitre liquid concentrator to light salt brine, said film group arrangement mode is 4-2-2; Promptly three grades of membrane filtrations are respectively 4,2,2 putaminas, each 4 film; Totally 32 films, poor nitre penetrating fluid come out from every grade, and flow successively decreases; Gather at last, rich nitre liquid concentrator progressively concentrates through three grades, comes out the third stage;

Step 3, aftertreatment

In rich nitre liquid concentrator, add alkali adjustment pH value, flow into the liquid concentrator basin, with pump the liquid concentrator extraction is delivered to 2 interchanger and carries out precooling 9～11; Refrigerant is from the freezing low nitre cool brine that removes behind the nitre-5 ℃ of cool brine jar, and the liquid concentrator temperature after the precooling is 12～15 ℃, interchanger, carries out heat exchange with the chilled brine that comes from cooling plant then; The back flows in the saltpetre sinking device, and the liquid concentrator after freezing contains a large amount of saltcake, and muddy liquid concentrator flows automatically to the saltpetre sinking device core barrel; In core barrel, the saltcake crystal grain is grown up gradually, and liquid concentrator drops to the core barrel lower part outlet along core barrel; Flow in the staving of saltpetre sinking device, at this moment the saltcake in the liquid concentrator sinks under the effect of gravity gradually, finally is deposited in the awl bottom; And the low nitre liquid concentrator of isolating saltcake rises to the top of saltpetre sinking device along staving, is back to the hydrops case, and overflow flows in the cool brine basin; And do the refrigerant of pre-cooler by pump delivery to 2 platen formula interchanger, and make temperature bring up to 30 ℃ of sending to salt, after being discharged by the awl end, the higher nitre mud of the solid content at the saltpetre sinking device awl end flows automatically in the whizzer; After centrifugal, pack, obtain the saltcake that the quality mark is lower than 60% (comprising crystal water).