CN114132950A

CN114132950A - Method for preparing ammonium chloride by co-production of sodium bicarbonate

Info

Publication number: CN114132950A
Application number: CN202111449257.1A
Authority: CN
Inventors: 刘松林; 刘金坤; 刘瀚宇
Original assignee: Hengyang Aijie Technology Co ltd
Current assignee: Hengyang Aijie Technology Co ltd
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2022-03-04

Abstract

The invention discloses a method for preparing ammonium chloride by co-producing sodium bicarbonate, which comprises the following steps: 1) precipitating sodium bicarbonate at first stage to obtain crude sodium bicarbonate and crude mother liquor M1; 2) precipitating sodium: adding sodium chloride into the crude mother liquor M1 to enable residual ammonium bicarbonate in the crude mother liquor M1 to have double decomposition reaction with the sodium chloride again, filtering to obtain a refined mother liquor M1 and baking soda, and returning the baking soda to the step 1); 3) performing cold separation and crystallization; 4) salting out and crystallizing; 5) secondary sodium bicarbonate precipitation; 6) and circulating the mother liquor. In the sodium precipitation step, the residual ammonium bicarbonate in the crude mother liquor M1 is further reacted with sodium chloride, and the ammonium bicarbonate is decomposed before the subsequent cold separation crystallization, so that the phenomenon that the baking soda generated by the reaction of the crude mother liquor and the sodium chloride in the subsequent cold separation process is difficult to separate from the ammonium chloride under the low-temperature condition due to the high content of the ammonium bicarbonate in the crude mother liquor is avoided, the content of sodium salt in the ammonium chloride is reduced, the content of ammonia in the ammonium chloride is improved, and the yield of the baking soda is also effectively improved.

Description

Method for preparing ammonium chloride by co-production of sodium bicarbonate

Technical Field

The invention relates to the technical field of chemical production, in particular to a method for preparing ammonium chloride by co-production of sodium bicarbonate.

Background

Baking soda is also called as sodium bicarbonate, is an inorganic salt, is white crystalline powder, is odorless, is soda-tasted, is easily soluble in water, and is widely applied to the industries of pharmaceutical industry, food processing, fire-fighting equipment and the like.

There are many improvements in the prior art for the co-production of ammonium chloride from sodium bicarbonate, such as a cyclic production method of co-production of ammonium chloride from sodium bicarbonate with patent application No. CN201910000924.4, which comprises sequentially performing primary sodium bicarbonate precipitation, cold precipitation crystallization, salting-out crystallization, mother liquor circulation, and is characterized in that: the method also comprises a step of secondary sodium bicarbonate precipitation between the salting-out crystallization and the mother liquor circulation, which is used for further precipitating sodium bicarbonate from the sodium bicarbonate mother liquor (I-II) generated after the salting-out crystallization, and comprises the following specific steps: (1) first-stage separation of sodium bicarbonate: adding saturated brine and ammonium bicarbonate into a reaction kettle for double decomposition reaction to generate sodium bicarbonate, filtering the obtained sodium bicarbonate, washing, dehydrating and drying; (2) and (3) cold separation and crystallization: taking brine generated by the baking soda generated in the separation step (1) as baking soda mother liquor (I), conveying the baking soda mother liquor into a crystallization kettle, adding ammonium sulfate serving as a divalent anion accelerant into the crystallization kettle, controlling the temperature to be 15-20 ℃, freezing for 2.5-4 h, crystallizing and separating out ammonium chloride, and filtering and dehydrating the obtained ammonium chloride; (3) salting out and crystallizing: overflowing sodium bicarbonate mother liquor (I-I) generated after cold separation crystallization from the crystallization kettle to a salting-out kettle, simultaneously adding sodium chloride into the salting-out kettle, controlling the temperature to be 20-25 ℃, further crystallizing and separating out ammonium chloride, settling to a crystal pulp outlet of the salting-out kettle, and returning ammonium chloride crystal pulp to the crystallization kettle in the step (2); (4) and (3) secondary sodium bicarbonate precipitation: sodium bicarbonate mother liquor (I-II) generated after salting-out crystallization overflows to a thickening tank from a salting-out kettle, flows to a heating kettle through the bottom of the thickening tank, is separated out at the temperature of 35-45 ℃, and is dehydrated and dried; (5) mother liquor circulation: and (3) collecting brine generated by separating ammonium chloride and brine generated by separating the baking soda in the second stage in the separation step (4) into a second-stage liquid storage tank, and returning supernatant in the second-stage liquid storage tank as baking soda mother liquor (II) to the step (1) for recycling.

When the method is adopted to prepare the baking soda and separate the ammonium chloride, the following problems mainly exist:

(1) the ammonium chloride prepared by the method and the device has high content of nitrogen-containing low and sodium salt, and the reason is that: the mother liquor M1 obtained by separating the sodium bicarbonate prepared by the first-stage sodium bicarbonate precipitation device in the device is high in carbonate content and higher than Na and HCO in a phase diagram₃Cross plot, NaHCO formed at Low temperature₃Cannot be separated from ammonium chloride, and enters an ammonium chloride treatment device from the bottom of the crystallization kettle to be carried into an ammonium chloride product together with ammonium chloride through cold separation and coprecipitation, so that the sodium salt in the ammonium chloride product is increased and the nitrogen content is low;

in addition, because a large amount of sodium chloride solid salt is added into the salting-out kettle in the salting-out process, when ammonium chloride crystal slurry crystallized from the salting-out kettle is directly input into the crystallization kettle through a crystal slurry taking-out port, sodium chloride directly enters the crystallization kettle along with ammonium chloride, so that sodium ions in an ammonium chloride product crystallized from the crystallization kettle exceed the standard, the ammonium chloride is difficult to reach the agricultural standard, and the product quality of the ammonium chloride is reduced;

2) the baking soda product prepared by the method has high content of ammonium salt, and the reason is that: because the concentration of sodium ions becomes dilute at the later stage of the double decomposition reaction, the double decomposition reaction tends to be mild violently, an atmosphere which is not suitable for the double decomposition reaction of sodium chloride and ammonium bicarbonate is formed, a part of ammonium bicarbonate in the double decomposition reaction tends to lack reaction power, and the ammonium bicarbonate and baking soda coexist in the form of solid crystals, and the ammonium bicarbonate and the baking soda enter a drying procedure after being filtered and centrifugally separated, while the temperature when the baking soda is dried is 50-60 ℃, the ammonium bicarbonate crystals are difficult to decompose into free ammonia and volatilize at the drying temperature, so that the ammonium bicarbonate is remained in the baking soda product, however, the method does not comprise a step of reducing the content of ammonium salt in the baking soda, and further the content of the ammonium salt in the baking soda product exceeds the standard; the other part of ammonium bicarbonate is directly dissolved and can not collide with double decomposition ions under the low-sodium condition to form crystal nucleus, so that the crystal nucleus is slowly formed, the crystal growth is slower, the crystallization is finer, and the subsequent filtering effect is reduced to influence the yield of the baking soda;

3) after the external cooler in the method is operated for a long time, a large amount of scar blocks formed by ammonium chloride crystals are attached to the inner wall of the external cooler and the outer wall of the exchange tube in the external cooler, so that part of ammonium chloride is lost, the cleaning difficulty of the external cooler and the exchange tube is increased, and the preparation efficiency of baking soda and ammonium chloride and the yield of ammonium chloride are further reduced.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method has the advantages of reducing the content of ammonium salt in the prepared sodium bicarbonate product, improving the yield of the sodium bicarbonate, reducing the content of sodium salt in the ammonium chloride product, and improving the content and the yield of ammonia in the ammonium chloride.

The technical scheme adopted by the invention for solving the technical problems is as follows: a method for preparing ammonium chloride by co-producing sodium bicarbonate comprises the following steps: 1) precipitating sodium bicarbonate at first stage to obtain crude sodium bicarbonate and crude mother liquor M1; 2) precipitating sodium: adding sodium chloride into the crude mother liquor M1 to enable residual ammonium bicarbonate in the crude mother liquor M1 to have double decomposition reaction with the sodium chloride again, filtering to obtain a refined mother liquor M1 and baking soda, and returning the baking soda to the step 1); 3) performing cold separation and crystallization; 4) salting out and crystallizing; 5) secondary sodium bicarbonate precipitation; 6) mother liquor circulation: and (3) collecting the brine generated by separating the ammonium chloride in the step 3) and the brine generated in the step 5), and returning the collected supernatant to the step 1) as mother liquor M2 for recycling.

Further, the specific operation steps of step 1) are as follows: adding saturated brine and ammonium bicarbonate into a mixing reaction kettle, carrying out double decomposition reaction under the stirring action, allowing the mixture to flow through a crystal nucleus growing kettle, a particle growing kettle and a reaction equilibrium kettle, reacting for 1-1.30h to generate sodium bicarbonate, and filtering, washing and dehydrating the obtained sodium bicarbonate to obtain crude sodium bicarbonate and mother liquor M1.

Further, the specific operation steps of step 2) are as follows: inputting the crude mother liquor M1 and sodium chloride into a first sodium precipitation kettle to carry out double decomposition reaction again, wherein the mass ratio of ammonium bicarbonate in the crude mother liquor M1 to the added sodium chloride is as follows: 75-95:7, controlling the temperature in the first sodium precipitation kettle to be 22-25 ℃, flowing through the second sodium precipitation kettle, controlling the temperature in the second sodium precipitation kettle to be 35-40 ℃, and precipitating sodium for 1-1.5 h; and filtering the slurry reacted in the second sodium precipitation kettle to obtain mother liquor M1 and sodium bicarbonate.

Preferably, the mass ratio of ammonium bicarbonate in the crude mother liquor M1 to the added sodium chloride is: 80:7.

Further, the specific operation steps of step 3) are as follows: conveying the refined mother liquor M1 to a crystallization kettle, adding ammonium sulfate as a divalent anion accelerant into the crystallization kettle, circularly communicating the crystallization kettle with an ice machine through an external cooler, controlling the temperature to be 8-10 ℃, freezing for 6-8 hours, and crystallizing and separating out ammonium chloride.

Further, the specific operation steps of step 4) are as follows: overflowing overflow liquid generated after cold separation crystallization from the crystallization kettle to the salting-out kettle, simultaneously adding sodium chloride into the salting-out kettle, controlling the temperature to be 10-12 ℃, salting out for 6-8 h, further crystallizing and separating out ammonium chloride, and settling to a crystal paddle taking outlet of the salting-out kettle.

Further, a salt separation step is also included between the step 4) and the step 5), and the specific operation steps are as follows: and (3) conveying the ammonium chloride settled to the crystal slurry taking-out port of the salting-out kettle into the salt separation kettle, settling the sodium chloride remained on the ammonium chloride crystals into the bottom of the salt separation kettle, dissolving the sodium chloride, returning the dissolved sodium chloride to the salting-out kettle for recycling, floating the ammonium chloride crystals to the slurry taking-out port of the salt separation kettle, returning the ammonium chloride crystals to the crystallization kettle in the step 3) from the slurry taking-out port, converging the ammonium chloride crystals and the ammonium chloride crystals frozen and separated out from the crystallization kettle, filtering and dehydrating.

Further, the specific operation steps of step 5) are as follows: overflowing liquid generated after salting-out crystallization from the salting-out kettle to a thickening tank, flowing into a heating kettle through the bottom of the thickening tank, separating out baking soda at the temperature of 35-45 ℃, and dehydrating and drying the obtained baking soda.

Further, the step 6) is followed by a step 7) of deamination: mixing the mother liquor M2 with the crude sodium bicarbonate to carry out double decomposition reaction again to generate fine soda, and filtering, washing, dehydrating and drying the obtained fine soda to obtain the sodium bicarbonate with low ammonium salt content.

Further, the specific operation steps of step 7) are as follows: mother liquor M2 and crude baking soda were mixed according to a solid-to-liquid ratio of 2.5: inputting the sodium bicarbonate solution 1 into a first deamination kettle to carry out double decomposition reaction again, enabling the sodium bicarbonate solution to flow through a second deamination kettle and a third deamination kettle, carrying out deamination for 1-1.3h at the temperature of 25-35 ℃ to generate fine soda, filtering and washing the obtained fine soda to obtain solid, washing liquid and semi-brine, dehydrating and drying the solid to obtain a product sodium bicarbonate, and returning the semi-brine to the step 2) to be collected with crude mother liquor M1 for sodium removal treatment.

Further, the method further comprises a cleaning step: conveying the washing liquid obtained by washing in the step 7) into an external cooler, repeatedly washing the inner wall of the external cooler and the outer pipe wall of an exchange tube in the external cooler, and finally conveying the final washing liquid into a crystallization kettle for cold crystallization.

The method for preparing ammonium chloride by co-producing sodium bicarbonate has the beneficial effects that:

(1) according to the method, by adding the step of sodium precipitation, the ammonium bicarbonate remained in the crude mother liquor M1 and the added sodium chloride are further reacted to generate the baking soda, the baking soda is filtered and then is input into the step of primary baking soda precipitation, and the ammonium bicarbonate is decomposed before the subsequent cold precipitation crystallization, so that the phenomenon that the baking soda generated by the reaction of the crude mother liquor and the sodium chloride is difficult to separate from the ammonium chloride at low temperature due to the high content of the ammonium bicarbonate in the crude mother liquor is avoided, the content of sodium salt in the ammonium chloride is reduced, the content of ammonia in the ammonium chloride is improved, and the yield of the baking soda is also effectively improved;

(2) according to the method, the step of deamination is added, the mother liquor M2 and the crude sodium bicarbonate are subjected to double decomposition reaction to obtain the sodium bicarbonate, the unreacted ammonium bicarbonate remained on the crude sodium bicarbonate is effectively decomposed, the yield of the sodium bicarbonate is improved, the content of ammonium salt in the sodium bicarbonate product is reduced, and the product quality of the sodium bicarbonate reaches the national food standard; meanwhile, due to the addition of the mother liquor M2, the residual ammonium chloride crystals can be further diluted, the solubility of ammonium chloride is improved, the separation of ammonium chloride and baking soda is facilitated, and the content of ammonium salt in the baking soda is reduced;

(3) the washing liquid obtained in the deamination step is used for washing the external cooler, so that the phenomenon that the waste liquid discharge does not reach the standard due to the direct discharge of the washing liquid can be avoided, the phenomenon that the inner wall of the external cooler and the outer wall of the exchange tube are scabbed is avoided, the cleaning difficulty of the external cooler and the exchange tube is reduced, and the smooth preparation of sodium bicarbonate and ammonium chloride is ensured; the liquid after the washing is conveyed to the crystallization kettle through the replacement groove, so that the ammonium chloride in the washing liquid can be effectively recovered, the loss of the ammonium chloride is reduced, and the yield of the ammonium chloride is improved;

(4) according to the method, by adding the salt separation step, the ammonium chloride crystal carrying the solid salt obtained by salting out crystallization enters the salt separation kettle, and is separated from sodium chloride in the salt separation kettle and then enters the cold precipitation crystallization, so that the phenomenon that the ammonium chloride obtained by directly inputting the ammonium chloride crystal carrying the solid salt obtained by salting out crystallization into the crystallization kettle is high in salt content after being output from the bottom of the crystallization kettle and treated by the ammonium chloride is avoided, the phenomenon that the sodium ions in the ammonium chloride product exceed the standard is prevented, the produced ammonium chloride reaches the agricultural standard, and the product quality of the ammonium chloride is effectively improved;

(5) in the step of precipitating the baking soda in the first stage, the baking soda prepared by double decomposition reaction sequentially enters the mixing reaction kettle, the crystal nucleus growing kettle, the particle growing kettle and the reaction balance kettle to crystallize step by step, so that the crystallization time is prolonged, the growing space of each crystal grain is increased, the phenomena of poor subsequent filtering effect and low efficiency caused by over-fine crystal grains after the crystallization is finished are avoided, the yield and the preparation efficiency of the baking soda are improved, and the preparation cost of the baking soda is reduced.

Drawings

FIG. 1 is a schematic structural diagram of an apparatus for co-producing sodium bicarbonate and preparing ammonium chloride according to the present invention;

FIG. 2-is an enlarged schematic view of the first stage sodium bicarbonate evolving apparatus and the first solid-liquid separation apparatus of FIG. 1;

FIG. 3 is an enlarged schematic view of the deamination apparatus and a third solid-liquid separation apparatus of FIG. 1;

FIG. 4-is a schematic diagram of the process at the sodium precipitation unit and the second solid-liquid separation unit in FIG. 1;

FIG. 5-is an enlarged schematic view of the cooling apparatus and salting-out apparatus of FIG. 1;

FIG. 6-is an enlarged schematic view of the secondary sodium bicarbonate evolving plant and ammonium chloride treatment plant of FIG. 1;

fig. 7-is an enlarged schematic view at the drying apparatus in fig. 1.

1-a first-stage sodium bicarbonate precipitation device, 2-a first solid-liquid separation device, 3-a sodium precipitation device, 4-a second solid-liquid separation device, 5-a second-stage sodium bicarbonate precipitation device, 6-a deamination device, 7-a stirring slurry, 8-a heat exchange pipe, 9-a cold precipitation device, 10-a salting-out device, 11-an ammonium chloride treatment device, 12-a first deamination kettle, 13-a second deamination kettle, 14-a third deamination kettle, 15-a third solid-liquid separation device, L1101-a mixing reaction kettle, L1102-a crystal nucleus growth kettle, L1103-a particle growth kettle, L1104-a reaction balance kettle, T1102-a brine tank, an N103-ammonium bicarbonate feeding device, X101, X102, X124-a vacuum filter, P101, X129, P102, S122-a centrifugal machine and V104-a separation tank, v106-a primary liquid storage tank, X103-a belt filter, P103-a water washing tank, F109-a drying device, K110, K130-a bag sewing machine, T1116-a crystallization kettle, Y115-an external cooler, P113-an ice maker, T1118-a salting-out kettle, B120-a salt feeding device, V121-a dense tank, L2121-1-a heating kettle, V125-a tertiary liquid storage tank, V117-a low tank, L2105-a first sodium precipitation kettle, L2106-a second sodium precipitation kettle, a salt metering scale L1107, V108-a separation tank, V109-a secondary liquid storage tank, V112-a salt separation kettle, V110-a semi-brine tank, V107-an external washing tank and V111-a replacing tank. In the figure, PL denotes a liquid and PS denotes a solid.

Detailed Description

The invention is further illustrated with reference to the following figures and examples, which are not intended to limit the scope of the invention in any way.

Example 1

A method for preparing baking soda with low ammonium salt content by co-producing baking soda and ammonium chloride comprises the following steps:

1) first-stage separation of sodium bicarbonate: directly adding 8.5 cubic meters of unpurified saturated brine into a mixed reaction kettle L1101 with the capacity of 11 cubic meters through a brine tank T1102, heating to 35 ℃, adding 2200 kilograms of ammonium bicarbonate into the mixed reaction kettle L1101 through an ammonium bicarbonate feeding device N103 ammonium bicarbonate metering belt, and controlling the temperature to be 25 ℃ under the stirring action to perform double decomposition reaction; when the mixing reaction kettle L1101 is nearly full, a valve at the kettle bottom of the mixing reaction kettle L1101 is opened, a pump is started, slurry is sent into a crystal nucleus growth kettle L1102, stirring is continued, and the temperature is controlled to be 28 ℃; when the crystal nucleus growing kettle L1102 is about to be full, a valve at the bottom of the crystal nucleus growing kettle L1102 is opened, a pump is started, slurry is sent into the particle growing kettle L1103, stirring is continued, and the temperature is controlled to be 28 ℃; when the particle growth kettle L1103 is nearly full, a valve at the bottom of the particle growth kettle L1103 is opened, a pump is started, slurry is sent to a reaction equilibrium kettle L1104, the temperature is kept at 29 ℃, the total reaction time is 1.30h, baking soda is generated, the slurry containing the baking soda is filtered by a vacuum filter X101, and then a centrifuge P101 is used for dehydrating to obtain crude baking soda and crude mother liquor M1;

the double decomposition reaction and the baking soda crystallization in the step are carried out step by step in a mixing reaction kettle L1101, a crystal nucleus growing kettle L1102, a particle growing kettle L1103 and a reaction equilibrium kettle L1104, when the previous kettle body is full, part of feed liquid is conveyed to the next kettle, the baking soda crystallization time is prolonged, and compared with the operation of simultaneously carrying out reaction and crystallization by only adopting one kettle body, the crystal grain growing space is increased, the obtained baking soda crystals are thicker, the filtering effect is effectively improved, the baking soda preparation efficiency is improved, and the baking soda yield is effectively improved;

2) precipitating sodium: the method comprises the steps of collecting crude mother liquor M1 to a first-stage liquid storage tank V106, conveying the crude mother liquor into a first sodium precipitation kettle L2105, adding sodium chloride into the first sodium precipitation kettle L2105 through a salt metering scale L1107, wherein the mass ratio of ammonium bicarbonate in the crude mother liquor M1 to the added sodium chloride is as follows: 80:7, further carrying out double decomposition reaction on ammonium bicarbonate and sodium chloride remained in the crude mother liquor M1, controlling the temperature in the first sodium precipitation kettle L2105 to be 22 ℃, opening a valve at the bottom of the first sodium precipitation kettle L2105 when the first sodium precipitation kettle L2105 is about to be full, conveying the slurry into the second sodium precipitation kettle L2106, controlling the temperature of the second sodium precipitation kettle L2106 to be 35 ℃, and setting the sodium precipitation time to be 1.5 h; filtering the slurry reacted in the second sodium precipitation kettle L2106 by a filter X102, and then sequentially conveying the slurry to a filter to obtain a refined mother liquor M1 and baking soda, wherein the baking soda is returned to the mixed reaction kettle L1101;

according to the invention, by arranging a sodium precipitation step, the residual ammonium bicarbonate in the crude mother liquor M1 obtained by separation in the step 1) and the added sodium chloride are further subjected to double decomposition reaction, the sodium bicarbonate obtained by filtration and separation is returned to the mixing reaction kettle L1101 in the step 1), and the obtained refined mother liquor M1 is conveyed to the cold separation crystallization in the subsequent step 3), so that the ammonium bicarbonate is decomposed by the crude mother liquor M1 before entering the cold separation crystallization, the content of ammonium bicarbonate in the refined mother liquor M1 entering the cold separation crystallization is effectively reduced, the reaction of ammonium bicarbonate and sodium chloride in the cold separation process is prevented, the phenomenon that the sodium bicarbonate and the ammonium chloride formed in the cold separation process are difficult to separate is further avoided, the content of sodium salt in the ammonium chloride is reduced, the content of ammonia in the ammonium chloride is improved, and the yield of the sodium bicarbonate is also effectively improved;

3) and (3) cold separation and crystallization: collecting the refined mother liquor M1 to a secondary liquid storage tank V107, directly conveying the refined mother liquor into a 9 cubic meter crystallization kettle T1116, simultaneously adding ammonium sulfate serving as a divalent anion activator into the crystallization kettle T1116, circularly communicating the crystallization kettle T1116 with an ice maker P113 through an external cooler Y115, controlling the temperature to be 8 ℃, freezing for 6 hours, crystallizing and separating out ammonium chloride, filtering the ammonium chloride by a vacuum filter X124, dehydrating the ammonium chloride by a centrifuge X129, and packaging the ammonium chloride by a bag sewing machine X129 to obtain a finished product ammonium chloride;

4) salting out and crystallizing: overflowing the cold-separated and crystallized overflow liquid from the crystallization kettle T1116 to a salting-out kettle T1118, simultaneously adding sodium chloride into the salting-out kettle T1118 through a salt feeding device B120, controlling the temperature at 10 ℃, salting out for 6h, further crystallizing and separating out ammonium chloride, and settling to an outlet at the middle lower part of the salting-out kettle T1118, namely a crystal paddle taking outlet of a suspension section;

6) salt separation: conveying ammonium chloride which is deposited into the salt separation kettle V112 from a crystal slurry taking-out port of the salt separation kettle T1118 to the salt separation kettle V112, precipitating sodium chloride remained on ammonium chloride crystals into the bottom of the salt separation kettle V112, dissolving the sodium chloride and then returning the ammonium chloride to the salt separation kettle T1118 for recycling, floating the ammonium chloride crystals to the slurry taking-out port of the salt separation kettle V112, returning the ammonium chloride crystals to the crystallization kettle T1116 from the slurry taking-out port, collecting the ammonium chloride crystals with the ammonium chloride crystals which are frozen and separated out from the crystallization kettle T1116, conveying the ammonium chloride crystals to a low-level tank V117, filtering the ammonium chloride crystals by a vacuum filter X124, dehydrating by a centrifuge X129, and packaging by a bag sewing machine X129 to obtain a finished product of ammonium chloride;

7) and (3) secondary sodium bicarbonate precipitation: the supernatant in the salting-out kettle T1118 overflows to a thickening tank V121, flows to a heating kettle L2121-1 through the bottom of the thickening tank V121, baking soda is further separated out at the temperature of 35 ℃, the obtained baking soda is dehydrated by a centrifuge S122 and then is conveyed to a drying device F109 for drying, and the dried baking soda is packaged by a bag sewing machine K110 to obtain the finished product baking soda;

8) mother liquor circulation: collecting the brine generated by separating ammonium chloride in the steps 3) and 6) and the brine generated in the step 7) into a three-stage liquid storage tank V125, allowing the suspension to sink to the bottom under the action of stirring, returning to a heating kettle L2121-1, allowing clear liquid to float upwards to serve as mother liquid M2, heating to 35 ℃, returning a part of the mother liquid M2 to a mixing reaction kettle L1101, performing double decomposition reaction with ammonium bicarbonate to produce sodium bicarbonate, repeatedly operating, and recycling, so as to achieve the purpose of no wastewater discharge; the other part of mother liquor M2 is input into a deamination device 6 to carry out the subsequent deamination step;

9) and (3) deamination: feeding the crude baking soda into a first deamination kettle 12, mixing the crude baking soda with mother liquor M2 input into the first deamination kettle 12, and carrying out double decomposition reaction again to further carry out double decomposition reaction on ammonium bicarbonate remained in the crude baking soda and sodium chloride in the mother liquor M2, wherein the solid-to-liquid ratio is 2.5:1, when the first deamination kettle 12 is about to be full, opening a valve at the bottom of the first deamination kettle 12, and feeding the slurry into a second deamination kettle 13; when the second deamination kettle 13 is about to be full, a valve at the bottom of the second deamination kettle 13 is opened, slurry is sent into a third deamination kettle 14, the total deamination time is 1-1.3h, the temperature is controlled to be 25 ℃, fine soda is generated, the fine soda is filtered by a belt filter X103 and then washed by 100L of deionized water or saturated soda water at the temperature of 35 ℃, the first half-section filtrate obtained by filtering is used as semi-brine and sent into a first sodium precipitation kettle L2105, the washing liquid obtained by washing is used for subsequently washing an external cooler, the solid obtained by filtering is dewatered by a centrifugal machine P102 and dried by a drying device F109 drying furnace, and the dried sodium bicarbonate is packaged by a bag sewing machine K110 to obtain a finished product of sodium bicarbonate;

10) cleaning: conveying the washing liquid obtained by washing in the step 9) into an external cooler Y1115, repeatedly washing the inner wall of the external cooler Y1115 and the outer wall of an exchange tube in the external cooler Y1115, and finally conveying the final washing liquid into a crystallization kettle T1116 for cold crystallization;

the components in the crude mother liquor M1 are controlled as follows: NaCl 100-₄HCO₃ 100-110g/L、NH₄Cl 190-210g/L、SO₄ ^2-1-8 g/L; the components in the mother liquor M1 are controlled as follows: NaCl 130-₄HCO₃ 50-60g/L、NH₄Cl 190-210g/L、SO₄ ^2-1-8 g/L; the components in the mother liquor M2 are controlled as follows: NaCI 230-₄CI 60g-100g/L、NH₄HCO₃ 30g-70g/L、SO₄ ^2- 1-8g/L。

The device used in the method comprises a first-stage sodium bicarbonate precipitation device 1, a first solid-liquid separation device 2, a sodium precipitation device 3, a second solid-liquid separation device 4, an ammonium chloride preparation device, a second-stage sodium bicarbonate precipitation device 5 and a mother liquor circulation device which are sequentially communicated, wherein the first solid-liquid separation device 2 is also connected with a deamination device 6.

Baking soda device 1 is appeared including the mixed reation kettle L1101, crystal nucleus growth cauldron L1102, the long cauldron L1103 of particle and the reaction balance cauldron L1104 that communicate in proper order, mixed reation kettle L1101 still is connected with brine groove T1102 and ammonium bicarbonate feeding device N103 respectively through the pipeline, brine groove T1102 is used for storing brine and passes through the pipeline with brine and carry to mixed reation kettle L1101 in, ammonium bicarbonate feeding device N103 is used for carrying ammonium bicarbonate to mixed reation kettle L1101 in, reaction balance cauldron L1104 and first solid-liquid separation equipment 2 intercommunication.

All be equipped with the feed inlet on mixing reation kettle L1101, crystal nucleus growth cauldron L1102, particle growth cauldron L1103 and reaction balance cauldron L1104's the kettle cover, mixing reation kettle L1101, crystal nucleus growth cauldron L1102, particle growth cauldron L1103 and reaction balance cauldron L1104's cauldron body bottom all is equipped with the discharge gate.

The first-stage sodium bicarbonate precipitation device 1 of the invention adopts four kettles, namely a mixing reaction kettle L1101, a crystal nucleus growing kettle L1102, a particle growing kettle L1103 and a reaction balance kettle L1104, to replace one kettle in the prior art, in the double decomposition reaction process, reactants (ammonium bicarbonate and sodium chloride in brine) are firstly stirred and mixed in the mixing reaction kettle L1101, the stirred and mixed solution enters the crystal nucleus growing kettle L1102 from the mixing reaction kettle L1101, crystals with large crystal structures are firstly conveyed into the particle growing kettle L1103 from the bottom of the crystal nucleus growing kettle L1102 through a pipeline, the crystals with small crystal structures continue to grow and slowly crystallize in the crystal nucleus growing kettle L1102, and the like, the crystals with large crystal structures in each kettle are conveyed into the next kettle, so that the growing space of the crystals with small crystal structures in the kettle is enlarged, the crystallization time is prolonged, and the phenomena that the nucleation rate is high due to crystallization in one kettle are effectively avoided, The phenomenon of large crystal nucleus quantity and high crystallization speed reduces the formation of fine crystals, further improves the filtration and separation effect of subsequent baking soda crystals, further improves the yield and preparation efficiency of baking soda, and reduces the preparation cost of baking soda.

Mixing reation kettle L1101, crystal nucleus growth cauldron L1102, particle growth cauldron L1103 and reaction balance cauldron L1104's kettle cover's top all installs agitator motor, agitator motor is connected with the (mixing) shaft, in the bottom of (mixing) shaft stretches into mixing reation kettle L1101, crystal nucleus growth cauldron L1102, particle growth cauldron L1103 and reaction balance cauldron L1104 respectively, and be equipped with a plurality of stirring thick liquids 7 on it, stirring thick liquid 7 sets up respectively in the height of the three difference of (mixing) shaft, and the contained angle that is located between not co-altitude stirring thick liquid 7 and the horizontal plane reduces along the direction of top to bottom of (mixing) shaft gradually. The method specifically comprises the following steps: the stirring paddles 7 at the uppermost level are at an angle of 30 to 32 (see a in fig. 1) (31 in this embodiment), the stirring paddles 7 at the intermediate level are at an angle of 24 to 26 (see b in fig. 1) (25 in this embodiment), and the stirring paddles 7 at the lowermost level are at an angle of 22 to 24 (see c in fig. 1) (23 in this embodiment) with respect to the horizontal plane.

According to the invention, the included angles between the stirring paddles 7 at different heights and the horizontal plane are gradually reduced along the direction from the top to the bottom of the stirring shaft, so that the contact area between the crystals above the kettle bodies and the corresponding stirring shaft and the shearing stress generated by the solution on the stirring shaft are larger than those below the crystals, the number of crystal nuclei in the kettle is ensured to meet the production requirement, the number of new crystal nuclei formed by particles on the crystals below due to the shearing stress and the contact with the stirring shaft can be effectively reduced, the growth space of each crystal grain below the kettle body is increased, the crystal grains below the kettle body are coarsened and then conveyed to the next kettle body for continuous crystallization, and meanwhile, the growth space is also reserved for the growth of each crystal grain above the kettle body.

The reaction balance kettle L1104 is further connected with a heat exchange device, the heat exchange device comprises a heat exchange tube 8 and a steam boiler (not shown in the figure), the heat exchange tube 8 is coiled in the reaction balance kettle L1104, an air inlet of the heat exchange tube is connected with an air outlet of the steam boiler, and an air outlet of the heat exchange tube is connected with an air inlet of the steam boiler. The solution in the reaction equilibrium kettle L1104 is heated by a heat exchange device, so that the dissolution of ammonium chloride in the solution and the crystallization and precipitation of baking soda are promoted, and the preparation is made for the subsequent filtration of crystal mush.

First solid-liquid separation equipment 2 specifically is the centrifuge P101 of vacuum filter X101 and vacuum filter X101 intercommunication that communicates in proper order, vacuum filter X101 and reaction balance cauldron L1104 intercommunication for the magma after reaction balance cauldron L1104 filters, and it still is connected with knockout drum V104, knockout drum V104 intercommunication has one-level liquid storage pot V106, centrifuge P101 is connected with one-level liquid storage pot V106, be used for carrying the liquid that thick tassels centrifugal dehydration obtained to one-level liquid storage pot V106 in, one-level liquid storage pot V106 with sink sodium device intercommunication, and its storage has this liquid as thick mother liquor M1 of liquid through vacuum filter X101 and centrifuge P101 separation in it, centrifuge P101 still has deamination device 6 through pipe connection.

The sodium precipitation device 3 comprises a first sodium precipitation kettle L2105 and a second sodium precipitation kettle L2106 which are sequentially communicated, wherein the top end of the first sodium precipitation kettle L2105 is connected with a salt metering scale L1107 for conveying sodium chloride into the first sodium precipitation kettle L2105, the feed end of the first sodium precipitation kettle L2105 is connected with a primary liquid storage tank V106 of the first solid-liquid separation device 2, the primary liquid storage tank V106 is used for conveying crude mother liquid M1 in the primary liquid storage tank V106 into the first sodium precipitation kettle L2105 to further react the sodium chloride with residual ammonium bicarbonate in the crude mother liquid M1, and the discharge end of the second sodium precipitation kettle L2106 is communicated with a second solid-liquid separation device 4 and used for separating slurry output from the second sodium precipitation kettle L2106 to obtain baking soda and refined mother liquid M1.

The second solid-liquid separation device 4 is respectively communicated with the ammonium chloride preparation device and the first-stage sodium bicarbonate precipitation device 1, and is used for respectively inputting the refined mother liquor M1 obtained by separation of the second solid-liquid separation device 4 and sodium bicarbonate into the ammonium chloride preparation device and the first-stage sodium bicarbonate precipitation device 1, and the method specifically comprises the following steps: the vacuum filter X102, the separating tank V108 and the secondary liquid storage tank V109 are sequentially communicated, the vacuum filter X102 is further communicated with a second sodium precipitation kettle L2106 through a pipeline, is used for filtering crystal slurry input into the second sodium precipitation kettle L2106, is further communicated with a mixing reaction kettle L1101, is used for returning baking soda obtained through filtering separation into the mixing reaction kettle L1101, and is communicated with an ammonium chloride preparation device, and is used for conveying a refined mother solution M1 into the ammonium chloride preparation device to prepare ammonium chloride.

The second sodium precipitation kettle L2106 is also connected with a heat exchange device, the structure of the heat exchange device is the same as that of the heat exchange device connected with the reaction balance kettle L1104, a heat exchange tube 6 of the heat exchange device is coiled in the second sodium precipitation kettle L2106, the air inlet of the heat exchange device is connected with the air outlet of a steam boiler, and the air outlet of the heat exchange device is connected with the air inlet of the steam boiler.

According to the invention, by arranging the sodium precipitation device 3 and the second solid-liquid separation device 4, the residual ammonium bicarbonate in the crude mother liquor M1 separated by the first solid-liquid separation device 2 and the added sodium chloride can further undergo a double decomposition reaction to generate the baking soda, the baking soda separated by the second solid-liquid separation device 4 is returned to the mixing reaction kettle L1101, and the obtained refined mother liquor M1 is conveyed to the ammonium chloride preparation device, so that the content of ammonium bicarbonate in the refined mother liquor M1 in the cold separation and crystallization process performed by the ammonium chloride preparation device is effectively reduced, the reaction of ammonium bicarbonate and sodium chloride in the cold separation process is prevented, the phenomenon that the baking soda and the ammonium chloride formed in the cold separation process are difficult to separate is further avoided, the content of sodium salt in the ammonium chloride is reduced, the content of ammonia in the ammonium chloride is improved, and the yield of the baking soda is also effectively improved.

The ammonium chloride preparation device comprises a cold separation device 9, a salting-out device 10 and an ammonium chloride treatment device 11, wherein the cold separation device 9 is used for carrying out cold separation crystallization on the refined mother liquor M1 obtained by separation of the second solid-liquid separation device 4 and comprises a crystallization kettle T1116, an external cooler Y115 and an ice machine P113, the crystallization kettle T1116 is respectively communicated with the external cooler Y115 and the secondary liquid storage tank V109, and clear liquid at the upper end in the crystallization kettle T1116 is conveyed to the external cooler Y115, cooled by the external cooler Y115 and returned to the crystallization kettle T1116 for cold separation crystallization; the external cooler Y115 is circularly communicated with the ice maker P113, an exchange tube is arranged in the external cooler Y115, the ammonium chloride treatment device 11 is communicated with the cold separation device 9 and used for filtering, dehydrating and drying the ammonium chloride separated out in the cold separation device 9, and the ammonium chloride treatment device comprises a vacuum filter X124, a centrifuge X129 and a sack closer K130 which are sequentially connected.

The salting-out device 10 is used for collecting overflow liquid discharged by the cold-separating device 9 and carrying out salting-out crystallization on the overflow liquid, the salting-out device 10 comprises a salting-out kettle T1118 and a salt feeding device B120, the salt feeding device B120 is communicated with the salting-out kettle T1118 and is used for adding reaction salt into the salting-out kettle T1118, and the feeding end of the salting-out kettle T1118 is communicated with the crystallization kettle T1116 and is used for collecting overflow liquid discharged by the crystallization kettle T1116 and carrying out salting-out crystallization on the overflow liquid.

Salting out cauldron T1118 includes clear liquid section, linkage segment and suspension section, the height of suspension section is 3m, the clear liquid section is equipped with the overflow mouth, overflow mouth and second grade are appeared and are linked up with baking soda device 5, the side of linkage segment is 60 with the contained angle of vertical direction, the suspension section is equipped with two magma and takes out the mouth, the magma is taken out the mouth and is set up apart from suspension section top 3/4 department, the magma is taken out the mouth and is connected with and divides salt cauldron V112, divides the feed end and the magma at salt cauldron V112 top to take out the mouth intercommunication, be equipped with the center tube in the salt cauldron V112, the pipeline that the magma of salting out cauldron T1118 was taken out the mouth and is connected with and divides salt cauldron V112 top stretches into in the center tube through the feed end at salt cauldron V112 top for with the ammonium chloride magma input after salting out cauldron T1118 crystallization divides in the salt cauldron V112.

The middle part of the side wall of the salt separation kettle V112 is provided with a slurry taking port, and the bottom of the salt separation kettle V112 is communicated with the salting-out kettle T1118 through a pipeline, so that solid salt dissolved in the salt separation kettle V112 is returned to the salting-out kettle T1118 to be recycled, and the ammonium chloride preparation cost is saved; get the thick liquid mouth and be connected through the pipeline with the top of crystallization kettle T1116 for in carrying the ammonium chloride crystal to crystallization kettle T1116, for crystallization kettle T1116 provides the ammonium chloride crystal nucleus, promote the ammonium chloride crystal growth in the crystallization kettle T1116, precipitate the ammonium chloride crystal in making crystallization kettle T1116 fast, energy-conserving festival.

The salt separation kettle V112 is also connected with the crystal slurry taking-out port of the salting-out kettle T1118, the crystal slurry containing ammonium chloride crystals and solid salt after being salted out from the salting-out kettle T1118 can be conveyed into the salt separation kettle V112 through the crystal slurry taking-out port, the ammonium chloride crystals are light in shape, the volume of the salting-out kettle T1118 is large, the pressure discharged by the salting-out kettle T1118 is large, the ammonium chloride is suspended in the salt separation kettle V112, the solid salt is precipitated at the bottom of the salt separation kettle V112 and dissolved, the ammonium chloride crystals are separated from the solid salt after being suspended and conveyed into the crystallization kettle T1116 from the pulp taking port, the increase of the ammonium chloride crystals in the crystallization kettle T1116 is promoted, the phenomenon that the salt content of the ammonium chloride in the ammonium chloride product from the crystallization kettle T1116 is high due to the fact that the crystal slurry containing the ammonium chloride crystals and the solid salt is directly conveyed into the crystallization kettle T1116 can be effectively avoided, and the phenomenon that the sodium ions in the ammonium chloride product from the crystallization kettle T1116 exceed the standard can be prevented, the produced ammonium chloride reaches the agricultural standard, effectively improves the product quality of the ammonium chloride.

The secondary sodium bicarbonate precipitation device 5 comprises a concentration tank V121, a heating kettle L2121-1 and a centrifuge S122 which are sequentially communicated, wherein the concentration tank V121 is used for collecting overflow liquid overflowing from the salting kettle T1118, and the heating kettle L2121-1 is used for heating the overflow liquid to further precipitate sodium bicarbonate; the centrifuge S122 is used for separating the baking soda further precipitated in the heating kettle L2121-1 from the mother liquor, and the baking soda separated by the centrifuge S122 enters a drying device F109 and a bag sewing machine K110 for drying and packaging to obtain the baking soda.

The mother liquor circulating device comprises a three-stage liquid storage tank V125, a stirrer is arranged in the three-stage liquid storage tank V125 at a position far from the bottom 1/4, the bottom of the stirrer is communicated with a heating kettle L2121-1 and is used for returning suspension at the bottom in the three-stage liquid storage tank V125 to the heating kettle L2121-1, the stirrer is also communicated with a centrifugal machine S122, a vacuum filter X124 and a centrifugal machine X129 through pipelines respectively, the stirrer is used for collecting mother liquor obtained by separating the centrifugal machine S122 of the second-stage sodium bicarbonate separating device 5, the mother liquor obtained by separating the vacuum filter X124 and the centrifugal machine X129 of the ammonium chloride processing device 11, and supernatant of the mother liquor is returned to a brine tank T1102 and the deamination device for cyclic utilization as mother liquor M2.

Deamination device 6 is including the first deamination cauldron 12, second deamination cauldron 13 and the third deamination cauldron 14 that communicate in proper order, the feed end and the centrifuge P101 intercommunication of first deamination cauldron 7 for carry the coarse baking soda that obtains through centrifuge P101 centrifugation to first deamination cauldron 12 in, and first deamination cauldron 12 passes through pipeline and mother liquor circulating device intercommunication, be used for further with the coarse baking soda reaction in the first deamination cauldron 12 in carrying mother liquor M2 that mother liquor circulating device collected to first deamination cauldron 12.

According to the invention, the deamination device 6 is arranged, the secondary sodium bicarbonate precipitation device 5 and the mother liquor M2 generated by the ammonium chloride preparation device are conveyed into the first deamination kettle 12 to further react with the crude sodium bicarbonate in the first deamination kettle 12, so that the undecomposed solid sodium bicarbonate remained in the crude sodium bicarbonate further reacts with the sodium chloride in the mother liquor M2 to generate the sodium bicarbonate, the content of ammonium salt in the sodium bicarbonate is effectively reduced, the content of the ammonium salt in the sodium bicarbonate is ensured to be lower than 1000ppM, the yield of the sodium bicarbonate is improved, and the quality of the sodium bicarbonate product is improved; the three deamination kettles are arranged, so that the residual ammonium bicarbonate reacts with sodium chloride step by step, the growth space of crystal grains is enlarged, the reaction time is prolonged, the contact between the brine and the ammonium bicarbonate is effectively promoted, the formation of baking soda is promoted, and the yield of the baking soda is improved; in addition, the addition of the mother liquor M2 can further dilute the residual ammonium chloride on the crude baking soda, thereby reducing the difficulty of subsequent washing, improving the solubility of the ammonium chloride and facilitating the separation of the ammonium chloride and the baking soda.

The third deamination kettle 14 is also connected with a heat exchange device, the structure of the heat exchange device is the same as that of the heat exchange device connected with the reaction balance kettle L1104, a heat exchange tube 8 of the heat exchange device is coiled in the third deamination kettle 14, the air inlet of the heat exchange device is connected with the air outlet of a steam boiler, and the air outlet of the heat exchange device is connected with the air inlet of the steam boiler.

The bottom of the third deamination kettle 14 is sequentially connected with a third solid-liquid separation device 15 and a drying device F109 through pipelines, the third solid-liquid separation device 15 is used for separating mother liquor and fine soda generated in the third deamination kettle 9 to obtain semi-brine, fine soda and washing liquor, and specifically comprises a belt filter X103 and a centrifuge P102 communicated with the belt filter X103, a liquid outlet of the belt filter X103 is connected with a washing water tank P103 through a pipeline, the top of the belt filter X103 is also connected with a semi-brine tank V110, the semi-brine tank V110 is communicated with a first sodium precipitation kettle L2105 and used for returning front half-section filtrate filtered by the belt filter X103 as semi-brine to the first sodium precipitation kettle for recycling, a water outlet of the washing water tank P103 is connected with a spray header of the belt filter X103 through a pipeline, and a water outlet of the washing water tank is also connected with an outer washing tank V107 through a pipeline and used for storing the washing liquor into the outer washing tank V107, and then the washing liquid is conveyed into the external cooler to wash the external cooler and the exchange tubes in the external cooler. It should be noted that the belt filter of the present invention is a belt filter having a washing or rinsing function as in the prior art, such as the belt filter disclosed in patent application No. CN 201820348308.9.

The drying device F109 is used for drying the separated baking soda, and is communicated with a sack closer K110 and used for packaging the dried baking soda to obtain the finished baking soda.

The outer washing groove V107 is circularly communicated with the outer cooler Y115 through a pipeline, and the specific structure is as follows: the lower part of the side wall of the outer wash tank V107 is communicated with the top of the outer cooler Y115 through a pipeline, the top of the outer wash tank V107 is communicated with the bottom of the outer cooler Y115 through a pipeline, wash liquor stored in the outer wash tank V107 is conveyed from the top of the outer cooler Y115 through the pipeline from the outer wash tank V107, then is returned to the outer wash tank V107 from the pipeline at the bottom of the outer cooler Y115 after being conveyed from the top of the outer cooler Y115 through the pipeline, and is used for circularly and repeatedly washing scar blocks attached to the inner wall of the outer cooler Y115 and the outer wall of the exchange tube.

According to the invention, the outer washing tank V107 for storing the washing liquid obtained by separation of the third solid-liquid separation device 15 is arranged, the outer washing tank V107 is communicated with the outer cooler Y115 in a circulating manner through the pipeline, and the washing liquid in the outer washing tank V107 is adopted to wash the ammonium chloride crystals scarred on the inner wall of the outer cooler Y115 and the outer wall of the exchange column pipe in a reciprocating circulating manner.

The bottom of the external cooler Y115 is also connected with a replacement tank V111 through a pipeline, the replacement tank V111 is communicated with the crystallization kettle T1116 through a pipeline, the final flushing liquid can be stored in the replacement tank V111 after being cleaned, and is conveyed into the crystallization kettle T1116 from the replacement tank V111 through a pipeline, so that ammonium chloride crystals in the flushing liquid are further crystallized in the crystallization kettle T1116, the aim of zero discharge of the flushing liquid is fulfilled, and the problem that the discharge of waste liquid cannot reach the discharge standard due to direct discharge of the flushing liquid in the prior art is avoided; and the washing liquid is recycled to the crystallization kettle T1116 internal medicine to effectively recycle the ammonium chloride in the washing liquid, so that the loss of the ammonium chloride is reduced, and the yield of the ammonium chloride is improved.

Comparative example 1

This comparative example differs from example 1 in that: step 1): directly adding 8.5 cubic meters of unpurified saturated brine into a mixed reaction kettle L1101 with the capacity of 11 cubic meters through a brine tank T1102, heating to 35 ℃, adding 2200 kilograms of ammonium bicarbonate into the mixed reaction kettle L1101 through an ammonium bicarbonate feeding device N103 ammonium bicarbonate metering belt, controlling the temperature to be 25 ℃ under the stirring action to perform double decomposition reaction to generate sodium bicarbonate, filtering slurry containing the sodium bicarbonate by using a vacuum filter X101, and dehydrating by using a centrifuge P101 to obtain crude sodium bicarbonate and a crude mother liquor M1; the method comprises the steps of 2) sodium precipitation, 6) salt separation, 9) deamination and 10) cleaning. The other steps were the same as in example 1. The adopted device can be correspondingly adjusted on the basis of the embodiment 1 according to the difference between the method in the comparative example 1 and the embodiment 1, and the details are not repeated here.

Comparative example 2

This comparative example differs from example 1 in that: step 1): directly adding 8.5 cubic meters of unpurified saturated brine into a mixed reaction kettle L1101 with the capacity of 11 cubic meters through a brine tank T1102, heating to 35 ℃, adding 2200 kilograms of ammonium bicarbonate into the mixed reaction kettle L1101 through an ammonium bicarbonate feeding device N103 ammonium bicarbonate metering belt, controlling the temperature to be 25 ℃ under the stirring action to perform double decomposition reaction to generate sodium bicarbonate, filtering slurry containing the sodium bicarbonate by a vacuum filter X101, and dehydrating by a centrifuge P101 to obtain crude sodium bicarbonate and a crude mother liquor M1. The other steps were the same as in example 1. The adopted device can be correspondingly adjusted on the basis of the embodiment 1 according to the difference between the method in the comparative example 1 and the embodiment 1, and the details are not repeated here.

Comparative example 3

This comparative example differs from example 1 in that: the sodium precipitation in the step 2) is not included, the crude mother liquor prepared in the step 1) is directly input into the step of cold separation and crystallization, and other steps are the same as those in the example 1. The adopted device can be correspondingly adjusted on the basis of the embodiment 1 according to the difference between the method in the comparative example 1 and the embodiment 1, and the details are not repeated here.

Comparative example 4

This comparative example differs from example 1 in that: the salt separation in the step 6) is not included, and the ammonium chloride obtained by salting out in the salting-out kettle is directly returned to the crystallization kettle, and other steps are the same as those in the example 1. The adopted device can be correspondingly adjusted on the basis of the embodiment 1 according to the difference between the method in the comparative example 1 and the embodiment 1, and the details are not repeated here.

Comparative example 5

This comparative example differs from example 1 in that: step 9) deamination is not included, and the external cooler is washed by clear water.

Comparative example 6

This comparative example differs from example 1 in that: and step 10), washing the external cooler by using clear water.

The present inventors measured the yields of baking soda, the ammonium salt content and the ammonium chloride yield of baking soda, the nitrogen content of ammonium chloride, and the sodium salt content of ammonium chloride prepared in example 1 and comparative examples 1 to 6, and the measurement results are shown in the following table:

as can be seen from the above table, compared with comparative examples 1-6, the method of the present application can significantly improve the yield of baking soda and ammonium chloride, effectively increase the nitrogen content in ammonium chloride, reduce the ammonium salt content in baking soda and the sodium salt content in ammonium chloride, make the prepared baking soda product and ammonium chloride product more in line with the national use standard, and improve the quality of the product.

It will be further understood that the terms "first," "second," "third," "fourth," and the like, may be used herein to describe various elements, but these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

As used herein, the terms "upper," "lower," "left," "right," and the like are used for convenience of description based on the orientation as shown in the figures of the drawings, which may vary from one actual device to another depending on the manner in which the device is arranged.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A method for preparing ammonium chloride by co-producing sodium bicarbonate is characterized by comprising the following steps: the method comprises the following steps: 1) precipitating sodium bicarbonate at first stage to obtain crude sodium bicarbonate and crude mother liquor M1; 2) precipitating sodium: adding sodium chloride into the crude mother liquor M1 to enable residual ammonium bicarbonate in the crude mother liquor M1 to have double decomposition reaction with the sodium chloride again, filtering to obtain a refined mother liquor M1 and baking soda, and returning the baking soda to the step 1); 3) performing cold separation and crystallization; 4) salting out and crystallizing; 5) secondary sodium bicarbonate precipitation; 6) mother liquor circulation: and (3) collecting the brine generated by separating the ammonium chloride in the step 3) and the brine generated in the step 5), and returning the collected supernatant to the step 1) as mother liquor M2 for recycling.

2. The method for coproducing baking soda and preparing ammonium chloride according to claim 1, which is characterized in that: the specific operation steps of the step 1) are as follows: adding saturated brine and ammonium bicarbonate into a mixing reaction kettle, carrying out double decomposition reaction under the stirring action, allowing the mixture to flow through a crystal nucleus growing kettle, a particle growing kettle and a reaction equilibrium kettle, reacting for 1-1.30h to generate sodium bicarbonate, and filtering, washing and dehydrating the obtained sodium bicarbonate to obtain crude sodium bicarbonate and mother liquor M1.

3. The method for coproducing baking soda and preparing ammonium chloride according to claim 1, which is characterized in that: the specific operation steps of the step 2) are as follows: inputting the crude mother liquor M1 and sodium chloride into a first sodium precipitation kettle to carry out double decomposition reaction again, wherein the mass ratio of ammonium bicarbonate in the crude mother liquor M1 to the added sodium chloride is as follows: 75-95:7, controlling the temperature in the first sodium removing kettle to be 22-25 ℃, flowing through the second sodium precipitating kettle, controlling the temperature in the second sodium precipitating kettle to be 35-40 ℃, and precipitating sodium for 1-1.5 h; and filtering the slurry reacted in the second sodium precipitation kettle to obtain mother liquor M1 and sodium bicarbonate.

4. The method for coproducing baking soda and preparing ammonium chloride according to claim 1, which is characterized in that: the specific operation steps of the step 3) are as follows: conveying the refined mother liquor M1 to a crystallization kettle, adding ammonium sulfate as a divalent anion accelerant into the crystallization kettle, circularly communicating the crystallization kettle with an ice machine through an external cooler, controlling the temperature to be 8-10 ℃, freezing for 6-8 hours, and crystallizing and separating out ammonium chloride.

5. The process for co-producing ammonium chloride from baking soda as claimed in claim 4, wherein: the specific operation steps of the step 4) are as follows: overflowing overflow liquid generated after cold separation crystallization from the crystallization kettle to the salting-out kettle, simultaneously adding sodium chloride into the salting-out kettle, controlling the temperature to be 10-12 ℃, salting out for 6-8 h, further crystallizing and separating out ammonium chloride, and settling to a crystal paddle taking outlet of the salting-out kettle.

6. The process for co-producing ammonium chloride from baking soda as claimed in claim 5, wherein: the method also comprises a salt separation step between the step 4) and the step 5), and the specific operation steps are as follows: and (3) conveying the ammonium chloride settled to the crystal slurry taking-out port of the salting-out kettle into the salt separation kettle, settling the sodium chloride remained on the ammonium chloride crystals into the bottom of the salt separation kettle, dissolving the sodium chloride, returning the dissolved sodium chloride to the salting-out kettle for recycling, floating the ammonium chloride crystals to the slurry taking-out port of the salt separation kettle, returning the ammonium chloride crystals to the crystallization kettle in the step 3) from the slurry taking-out port, converging the ammonium chloride crystals and the ammonium chloride crystals frozen and separated out from the crystallization kettle, filtering and dehydrating.

7. The method for coproducing baking soda and preparing ammonium chloride according to claim 1, which is characterized in that: the specific operation steps of the step 5) are as follows: overflowing liquid generated after salting-out crystallization from the salting-out kettle to a thickening tank, flowing into a heating kettle through the bottom of the thickening tank, separating out baking soda at the temperature of 35-45 ℃, and dehydrating and drying the obtained baking soda.

8. The process for co-producing ammonium chloride from baking soda as claimed in claim 4, wherein: the step 6) is followed by a step 7) of deamination: mixing the mother liquor M2 with the crude sodium bicarbonate to carry out double decomposition reaction again to generate fine soda, and filtering, washing, dehydrating and drying the obtained fine soda to obtain the sodium bicarbonate with low ammonium salt content.

9. The process for co-producing ammonium chloride from baking soda as claimed in claim 3, wherein: the specific operation steps of the step 7) are as follows: mother liquor M2 and crude baking soda were mixed according to a solid-to-liquid ratio of 2.5: inputting the sodium bicarbonate solution 1 into a first deamination kettle to carry out double decomposition reaction again, enabling the sodium bicarbonate solution to flow through a second deamination kettle and a third deamination kettle, carrying out deamination for 1-1.3h at the temperature of 25-35 ℃ to generate fine soda, filtering and washing the obtained fine soda to obtain solid, washing liquid and semi-brine, dehydrating and drying the solid to obtain a product sodium bicarbonate, and returning the semi-brine to the step 2) to be collected with crude mother liquor M1 for sodium removal treatment.

10. The process for co-producing baking soda and preparing ammonium chloride as claimed in claim 9, wherein: the method further comprises a cleaning step: conveying the washing liquid obtained by washing in the step 7) into an external cooler, repeatedly washing the inner wall of the external cooler and the outer pipe wall of an exchange tube in the external cooler, and finally conveying the final washing liquid into a crystallization kettle for cold crystallization.