Production method for jointly preparing sodium carbonate and ammonium chloride

Abstract

The invention discloses a production method for jointly preparing sodium carbonate and ammonium chloride, which comprises the following steps: (1) preparing a mixed solution of supersaturated sodium chloride from a cooled ammonium chloride mother solution and sodium chloride waste salt, then introducing ammonia gas for ammoniation treatment, and then introducing carbon dioxide gas for carbonization treatment to obtain a mixed solution containing bicarbonate; (2) carrying out heat preservation crystallization and separation on the bicarbonate-containing mixed solution to obtain sodium bicarbonate and a sodium bicarbonate mother solution; (3) adding sodium hydroxide solid into the sodium bicarbonate mother liquor for reaction, then cooling and crystallizing for the first time, then adding sodium chloride for salting-out crystallization, cooling and crystallizing for the second time, and separating to obtain ammonium chloride and cooled ammonium chloride mother liquor; calcining the sodium bicarbonate to obtain a sodium carbonate product, and recycling the cooled ammonium chloride mother liquor in the step (1). According to the method, the problem that the quality of an ammonium chloride product cannot reach the standard due to the fact that sodium bicarbonate is precipitated along with ammonium chloride due to supersaturation is effectively solved.

Description

Technical Field

[0001] The invention relates to a production method for jointly preparing sodium carbonate and ammonium chloride, and belongs to the technical field of chemical process recycling. Background Art

[0002] Sodium chloride is a common compound and an important industrial raw material. In recent years, the output of sodium chloride waste salt in the chemical industry and other industries has increased year by year. Realizing the resource recycling of industrial by-product sodium chloride is a necessary development trend. The traditional combined alkali production method uses brine as the raw material of sodium chloride resources. After the brine is purified, ammonia and carbon dioxide are used as auxiliary materials to directly convert sodium chloride into sodium bicarbonate and co-produce ammonium chloride. The overall reaction equation is: NaCl+NH3+CO2+H2O→NaHCO3↓+NH4Cl. The sodium bicarbonate mother liquor after sodium bicarbonate crystallization and filtration contains NaCl, NaHCO3, and NH4Cl, among which sodium bicarbonate is in a saturated state. When preparing ammonium chloride, one is to use evaporation to recover ammonium chloride, but the energy consumption is very high, because there is no cogeneration facility, and bituminous coal is used as fuel, and local environmental protection does not allow it, so there is no feasibility of practical application. The second is to use NaCl to salt out NH4Cl in the sodium bicarbonate mother liquor. Sodium bicarbonate is also precipitated with ammonium chloride due to supersaturation, resulting in the quality of ammonium chloride product not meeting the standard, and sodium bicarbonate cannot be recovered, and the sodium carbonate production yield is also affected. Summary of the invention

[0003] Aiming at at least one problem existing in the above-mentioned prior art, the present invention provides a production method for jointly preparing sodium carbonate and ammonium chloride, wherein bicarbonate in a sodium bicarbonate mother liquor is converted into carbonate, and on the premise that the type of cation remains unchanged, the generation of mixed crystals of sodium bicarbonate and ammonium chloride is avoided, and ammonium chloride is used to cool the mother liquor and sodium chloride waste salt to form a supersaturated sodium chloride aqueous solution, and the sodium carbonate remaining in the solid phase generates sodium bicarbonate solid in a subsequent reaction, which is then calcined to obtain a sodium carbonate product, and then the problem of saturated sodium bicarbonate mother liquor crystallizing with ammonium chloride is solved, and then the ammonium chloride product is salted out and crystallized.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme: a production method for jointly preparing sodium carbonate and ammonium chloride, comprising the following steps:

[0005] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas to perform ammoniation treatment to convert it into ammoniated brine, and the ammoniated waste brine is then transported to a carbonization tower and introduced with carbon dioxide gas to perform carbonization treatment to obtain a mixed solution containing bicarbonate;

[0006] (2) the mixed solution containing bicarbonate is subjected to heat preservation crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor;

[0007] (3) adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, first cooling and crystallizing until no crystals are produced, then adding sodium chloride for salting out crystallization, then cooling and crystallizing for a second time, and separating the solid from the liquid to obtain ammonium chloride and cooling the ammonium chloride mother liquor;

[0008] The sodium bicarbonate is calcined to obtain a sodium carbonate product, and the carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower; the ammonium chloride mother liquor is cooled and reused in step (1).

[0009] Preferably, in step (1), the temperature is controlled at 30-35° C., and the concentration of the supersaturated sodium chloride mixed solution, calculated as sodium ions, is finally controlled at 235-248 g / L.

[0010] Preferably, in step (1), the temperature of the ammoniation treatment is 35-40° C., the molar ratio of sodium ions to ammonia is 1:1.1-1.2, and the pressure is 0.2-0.3 MPa.

[0011] Preferably, in step (1), the temperature of the carbonization treatment is 55-60° C., the molar ratio of sodium ions to sodium carbonate is 1:1-1.1, and the pressure is 0.2-0.3 MPa.

[0012] Preferably, in step (2), the crystallization temperature is 50-55°C.

[0013] Preferably, in step (3), the molar ratio of the amount of sodium hydroxide added to the amount of heavy sodium ions in the sodium bicarbonate mother liquor is 1:0.95-1.

[0014] Preferably, in step (3), the first cooling crystallization temperature is 30-35°C, and the second cooling crystallization temperature is 10-15°C.

[0015] Preferably, in step (3), sodium chloride is added for salting out and crystallization, and the endpoint concentration of sodium ions is controlled at 216.5 to 219.8 g / L.

[0016] Preferably, in step (3), the endpoint concentration of ammonium ions in the cooled ammonium chloride mother liquor is less than 47 g / L.

[0017] Compared with the prior art, the invention has the following beneficial effects: the method of the invention converts bicarbonate in the sodium bicarbonate mother liquor into carbonate, and on the premise that the type of cation remains unchanged, the generation of mixed crystals of sodium bicarbonate and ammonium chloride is avoided; the method of the invention effectively solves the problem that the quality of the ammonium chloride product does not meet the standard because sodium bicarbonate is precipitated together with the ammonium chloride due to supersaturation, and at the same time, the ammonium chloride mother liquor is cooled and recycled, thereby improving the production yield of sodium carbonate; the total alkali content of the sodium carbonate of the invention is more than 98.5%, and the mass percentage of the ammonium chloride is more than 99%; the invention reduces energy consumption, improves economic benefits, and is environmentally friendly. DETAILED DESCRIPTION

[0018] The following is a clear and complete description of the technical solutions in the implementation of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents, instruments, and components used, they are all conventional products that can be purchased commercially.

[0019] The present invention provides a production method for jointly preparing sodium carbonate and ammonium chloride, comprising the following steps:

[0020] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, calculated as 235-248 g / L in terms of sodium ions, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas for ammoniation treatment at a temperature of 35-40° C., a molar ratio of sodium ions to ammonia gas of 1:1.1-1.2, and a pressure of 0.2-0.3 MPa, to convert it into ammoniated brine, and the ammoniated waste brine is then transported to a carbonation tower and introduced with carbon dioxide gas for carbonization treatment at a temperature of 55-60° C., a molar ratio of sodium ions to sodium carbonate of 1:1-1.1, and a pressure of 0.2-0.3 MPa, to obtain a mixed solution containing bicarbonate;

[0021] (2) the mixed solution containing bicarbonate is kept warm at 50-55° C. for crystallization, and solid-liquid separation is performed to obtain sodium bicarbonate and sodium bicarbonate mother liquor;

[0022] (3) adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, wherein the molar ratio of the amount of sodium hydroxide solid added to the heavy sodium ion of the sodium bicarbonate mother liquor is 1:0.95-1, then cooling and crystallizing for the first time at 30-35° C. until no crystals are generated, adding sodium chloride, and controlling the end point concentration of sodium ions at 216.5-219.8 g / L, performing salting-out crystallization, and then cooling and crystallizing for the second time at 10-15° C., and performing solid-liquid separation to obtain ammonium chloride and cooled ammonium chloride mother liquor;

[0023] The sodium bicarbonate is calcined to obtain a sodium carbonate product, and the carbon dioxide gas after the calcination is collected and compressed and sent to a carbonization tower; the ammonium chloride mother liquor is cooled and reused in step (1), and the end point concentration of ammonium ions in the cooled ammonium chloride mother liquor is less than 47 g / L.

[0024] Example 1

[0025] A production method for jointly preparing sodium carbonate and ammonium chloride comprises the following steps:

[0026] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, calculated as 235 g / L based on sodium ions, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas for ammoniation treatment, the temperature is 35° C., the molar ratio of sodium ions to ammonia gas is 1:1.1, the pressure is 0.2 MPa, and the mixed solution is converted into ammoniated brine, and the ammoniated waste brine is then transported to a carbonation tower and introduced with carbon dioxide gas for carbonization treatment, the temperature is 55° C., the molar ratio of sodium ions to sodium carbonate is 1:1, and the pressure is 0.2 MPa, to obtain a mixed solution containing bicarbonate;

[0027] (2) the mixed solution containing bicarbonate is kept warm at 50° C. for crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor. The sodium bicarbonate is calcined to obtain a sodium carbonate product. The carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower;

[0028] (3) After adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, the molar ratio of the amount of sodium hydroxide solid added to the heavy sodium ion of the sodium bicarbonate mother liquor is 1:0.95, and then cooling and crystallizing for the first time at 30° C. until no crystals are generated, adding sodium chloride, and controlling the endpoint concentration of sodium ions to 216.5 g / L, performing salting-out crystallization, and then cooling and crystallizing for the second time at 10° C., solid-liquid separation, to obtain ammonium chloride and a cooled ammonium chloride mother liquor, the cooled ammonium chloride mother liquor is reused in step (1), and the endpoint concentration of ammonium ions in the cooled ammonium chloride mother liquor is less than 47 g / L.

[0029] Example 2

[0030] A production method for jointly preparing sodium carbonate and ammonium chloride comprises the following steps:

[0031] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, calculated as 240 g / L based on sodium ions, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas for ammoniation treatment, the temperature is 32° C., the molar ratio of sodium ions to ammonia gas is 1:1.15, the pressure is 0.25 MPa, and the mixed solution is converted into ammoniated brine, and the ammoniated waste brine is then transported to a carbonation tower and introduced with carbon dioxide gas for carbonization treatment, the temperature is 58° C., the molar ratio of sodium ions to sodium carbonate is 1:1.05, and the pressure is 0.25 MPa, to obtain a mixed solution containing bicarbonate;

[0032] (2) the mixed solution containing bicarbonate is kept at 52° C. for crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor. The sodium bicarbonate is calcined to obtain a sodium carbonate product. The carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower;

[0033] (3) After adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, the molar ratio of the amount of sodium hydroxide solid added to the heavy sodium ion of the sodium bicarbonate mother liquor is 1:0.98, and then cooling and crystallizing for the first time at 33° C. until no crystals are generated, adding sodium chloride, and controlling the endpoint concentration of sodium ions at 217.6 g / L, performing salting-out crystallization, and then cooling and crystallizing for the second time at 12° C., and controlling the endpoint concentration of ammonium ions at 56.3 g / L, performing solid-liquid separation, obtaining ammonium chloride and cooled ammonium chloride mother liquor, and recycling the cooled ammonium chloride mother liquor to step (1), wherein the endpoint concentration of ammonium ions in the cooled ammonium chloride mother liquor is less than 47 g / L.

[0034] Example 3

[0035] A production method for jointly preparing sodium carbonate and ammonium chloride comprises the following steps:

[0036] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, calculated as 245 g / L based on sodium ions, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas for ammoniation treatment, the temperature is 40° C., the molar ratio of sodium ions to ammonia gas is 1:1.2, the pressure is 0.3 MPa, and converting it into ammoniated brine, the ammoniated waste brine is then transported to a carbonation tower and introduced with carbon dioxide gas for carbonization treatment, the temperature is 60° C., the molar ratio of sodium ions to sodium carbonate is 1:1.1, and the pressure is 0.3 MPa, to obtain a mixed solution containing bicarbonate;

[0037] (2) the mixed solution containing bicarbonate is kept warm at 55° C. for crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor. The sodium bicarbonate is calcined to obtain a sodium carbonate product. The carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower;

[0038] (3) After adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, the molar ratio of the amount of sodium hydroxide solid added to the heavy sodium ion of the sodium bicarbonate mother liquor is 1:1, and then cooling and crystallizing for the first time at 30° C. until no crystals are generated, adding sodium chloride, and controlling the endpoint concentration of sodium ions at 218.9 / L, performing salting out crystallization, and then cooling and crystallizing for the second time at 10° C., solid-liquid separation, to obtain ammonium chloride and cooled ammonium chloride mother liquor, the cooled ammonium chloride mother liquor is reused in step (1), and the endpoint concentration of ammonium ions in the cooled ammonium chloride mother liquor is less than 47 g / L.

[0039] Example 4

[0040] A production method for jointly preparing sodium carbonate and ammonium chloride comprises the following steps:

[0041] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, calculated as 248 g / L based on sodium ions, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas for ammoniation treatment, the temperature is 40° C., the molar ratio of sodium ions to ammonia gas is 1:1.1, the pressure is 0.3 MPa, and the mixed solution is converted into ammoniated brine, and the ammoniated waste brine is then transported to a carbonation tower and introduced with carbon dioxide gas for carbonization treatment, the temperature is 55° C., the molar ratio of sodium ions to sodium carbonate is 1:1.1, and the pressure is 0.2 MPa, to obtain a mixed solution containing bicarbonate;

[0042] (2) the mixed solution containing bicarbonate is kept warm at 55° C. for crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor. The sodium bicarbonate is calcined to obtain a sodium carbonate product. The carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower;

[0043] (3) After adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, the molar ratio of the amount of sodium hydroxide solid added to the heavy sodium ion of the sodium bicarbonate mother liquor is 1:1, and then cooling and crystallizing for the first time at 30° C. until no crystals are generated, adding sodium chloride, and controlling the endpoint concentration of sodium ions to be 219.8 g / L, performing salting-out crystallization, and then cooling and crystallizing for the second time at 10° C., solid-liquid separation, to obtain ammonium chloride and a cooled ammonium chloride mother liquor, the cooled ammonium chloride mother liquor is reused in step (1), and the endpoint concentration of ammonium ions in the cooled ammonium chloride mother liquor is less than 47 g / L.

[0044] Comparative Example 1

[0045] A production method for jointly preparing sodium carbonate and ammonium chloride comprises the following steps:

[0046] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, calculated as 250 g / L in terms of sodium ions, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas for ammoniation treatment at a temperature of 35° C., a molar ratio of sodium ions to ammonia gas of 1:1.1, and a pressure of 0.2 MPa, to convert it into ammoniated brine, and the ammoniated waste brine is then transported into a carbonation tower and introduced with carbon dioxide gas for carbonization treatment at a temperature of 55° C., a molar ratio of sodium ions to sodium carbonate of 1:1, and a pressure of 0.2 MPa to obtain a mixed solution containing bicarbonate;

[0047] (2) the mixed solution containing bicarbonate is kept warm at 50° C. for crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor. The sodium bicarbonate is calcined to obtain a sodium carbonate product. The carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower;

[0048] (3) After adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, the molar ratio of the amount of sodium hydroxide solid added to the heavy sodium ion of the sodium bicarbonate mother liquor is 1:0.95, and then cooling and crystallizing for the first time at 30° C. until no crystals are generated, adding sodium chloride, and controlling the endpoint concentration of sodium ions to 216.5 g / L, performing salting-out crystallization, and then cooling and crystallizing for the second time at 10° C., solid-liquid separation, to obtain ammonium chloride and a cooled ammonium chloride mother liquor, the cooled ammonium chloride mother liquor is reused in step (1), and the endpoint concentration of ammonium ions in the cooled ammonium chloride mother liquor is less than 47 g / L.

[0049] Comparative Example 2

[0050] A production method for jointly preparing sodium carbonate and ammonium chloride comprises the following steps:

[0051] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, calculated as 235 g / L based on sodium ions, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas for ammoniation treatment, the temperature is 35° C., the molar ratio of sodium ions to ammonia gas is 1:1.1, the pressure is 0.2 MPa, and the mixed solution is converted into ammoniated brine, and the ammoniated waste brine is then transported to a carbonation tower and introduced with carbon dioxide gas for carbonization treatment, the temperature is 55° C., the molar ratio of sodium ions to sodium carbonate is 1:1, and the pressure is 0.2 MPa, to obtain a mixed solution containing bicarbonate;

[0052] (2) the mixed solution containing bicarbonate is kept warm at 45° C. for crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor. The sodium bicarbonate is calcined to obtain a sodium carbonate product. The carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower;

[0053] (3) After adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, the molar ratio of the amount of sodium hydroxide solid added to the heavy sodium ion of the sodium bicarbonate mother liquor is 1:0.9, and then cooling and crystallizing for the first time at 30° C. until no crystals are generated, adding sodium chloride, and controlling the endpoint concentration of sodium ions to be 216.5 g / L, performing salting-out crystallization, and then cooling and crystallizing for the second time at 10° C., solid-liquid separation, to obtain ammonium chloride and a cooled ammonium chloride mother liquor, the cooled ammonium chloride mother liquor is reused in step (1), and the endpoint concentration of ammonium ions in the cooled ammonium chloride mother liquor is less than 47 g / L.

[0054] Comparative Example 3

[0055] A production method for jointly preparing sodium carbonate and ammonium chloride comprises the following steps:

[0056] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, calculated as 235 g / L based on sodium ions, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas for ammoniation treatment, the temperature is 35° C., the molar ratio of sodium ions to ammonia gas is 1:1.1, the pressure is 0.2 MPa, and the mixed solution is converted into ammoniated brine, and the ammoniated waste brine is then transported to a carbonation tower and introduced with carbon dioxide gas for carbonization treatment, the temperature is 55° C., the molar ratio of sodium ions to sodium carbonate is 1:1, and the pressure is 0.2 MPa, to obtain a mixed solution containing bicarbonate;

[0057] (2) the mixed solution containing bicarbonate is kept warm at 50° C. for crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor. The sodium bicarbonate is calcined to obtain a sodium carbonate product. The carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower;

[0058] (3) After adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, the molar ratio of the amount of sodium hydroxide solid added to the heavy sodium ion of the sodium bicarbonate mother liquor is 1:0.95, and then cooling and crystallizing at 30° C. until no crystals are generated, adding sodium chloride, and controlling the endpoint concentration of sodium ions to be 216.5 g / L, performing salting out crystallization, and solid-liquid separation to obtain ammonium chloride and cooled ammonium chloride mother liquor, and the cooled ammonium chloride mother liquor is reused in step (1), and the endpoint concentration of ammonium ions in the cooled ammonium chloride mother liquor is greater than 60 g / L.

[0059] Comparative Example 4

[0060] A production method for jointly preparing sodium carbonate and ammonium chloride comprises the following steps:

[0061] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, calculated as 235 g / L based on sodium ions, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas for ammoniation treatment, the temperature is 35° C., the molar ratio of sodium ions to ammonia gas is 1:1.1, the pressure is 0.2 MPa, and the mixed solution is converted into ammoniated brine, and the ammoniated waste brine is then transported to a carbonation tower and introduced with carbon dioxide gas for carbonization treatment, the temperature is 55° C., the molar ratio of sodium ions to sodium carbonate is 1:1, and the pressure is 0.2 MPa, to obtain a mixed solution containing bicarbonate;

[0062] (2) the mixed solution containing bicarbonate is kept warm at 50° C. for crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor. The sodium bicarbonate is calcined to obtain a sodium carbonate product. The carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower;

[0063] (3) After adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, the molar ratio of the amount of sodium hydroxide solid added to the heavy sodium ion of the sodium bicarbonate mother liquor is 1:0.95, and then cooling and crystallizing for the first time at 30° C. until no crystals are generated, adding sodium chloride, and controlling the endpoint concentration of sodium ions to 215.3 g / L, performing salting-out crystallization, and then cooling and crystallizing for the second time at 10° C., solid-liquid separation, to obtain ammonium chloride and a cooled ammonium chloride mother liquor, the cooled ammonium chloride mother liquor is reused in step (1), and the endpoint concentration of ammonium ions in the cooled ammonium chloride mother liquor is greater than 51 g / L.

[0064] Comparative Example 5

[0065] A production method for jointly preparing sodium carbonate and ammonium chloride comprises the following steps:

[0066] (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, calculated as 235 g / L based on sodium ions, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas for ammoniation treatment, the temperature is 35° C., the molar ratio of sodium ions to ammonia gas is 1:1.1, the pressure is 0.2 MPa, and the mixed solution is converted into ammoniated brine, and the ammoniated waste brine is then transported to a carbonation tower and introduced with carbon dioxide gas for carbonization treatment, the temperature is 55° C., the molar ratio of sodium ions to sodium carbonate is 1:1, and the pressure is 0.2 MPa, to obtain a mixed solution containing bicarbonate;

[0067] (2) the mixed solution containing bicarbonate is kept warm at 50° C. for crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor. The sodium bicarbonate is calcined to obtain a sodium carbonate product. The carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower;

[0068] (3) After adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, the molar ratio of the amount of sodium hydroxide solid added to the heavy sodium ion of the sodium bicarbonate mother liquor is 1:0.95, and then cooling and crystallizing for the first time at 30° C. until no crystals are generated, adding sodium chloride, and controlling the endpoint concentration of sodium ions to 220.5 g / L, performing salting-out crystallization, and then cooling and crystallizing for the second time at 10° C., solid-liquid separation, to obtain ammonium chloride and a cooled ammonium chloride mother liquor, the cooled ammonium chloride mother liquor is reused in step (1), and the endpoint concentration of ammonium ions in the cooled ammonium chloride mother liquor is less than 47 g / L.

[0069] The test results of the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1.

[0070] Table 1

[0071] Total alkali content of sodium carbonate / % Ammonium chloride mass percentage / % Example 1 98.6 99.2 Example 2 99.1 99.3 Example 3 98.9 99.1 Example 4 99.0 99.1 Comparative Example 1 97.6 99.0 Comparative Example 2 98.2 98.9 Comparative Example 3 98.0 99.1 Comparative Example 4 98.1 99.2 Comparative Example 5 98.8 98.4

[0072] As shown in Table 1, the present invention adopts ammonium chloride cooling mother liquor and sodium chloride waste salt to form a sodium chloride aqueous solution in a supersaturated state, and the sodium carbonate remaining in the solid phase produces sodium bicarbonate solid in the subsequent reaction, and then obtains a sodium carbonate product after calcination, and then uses sodium hydroxide to convert the bicarbonate in the sodium bicarbonate mother liquor into carbonate, and under the premise that the type of cation remains unchanged, the generation of mixed crystals of sodium bicarbonate and ammonium chloride is avoided, and the problem that sodium bicarbonate is precipitated together with ammonium chloride due to supersaturation, resulting in the quality of ammonium chloride product failing to meet the standard is effectively solved; sodium hydroxide is used to convert the bicarbonate in the sodium bicarbonate mother liquor into carbonate, and the ammonium chloride cooling mother liquor is used as a circulating raw material, which can also effectively improve the sodium carbonate production yield, and also make the total alkali content of sodium carbonate above 98.5%; and the sodium bicarbonate mother liquor is cooled and crystallized for the second time after the first cooling crystallization and salting out, so that the mass percentage of ammonium chloride is 99% or above.

[0073] Compared with Comparative Example 1, it can be found that the sodium ion content of the mixed solution of supersaturated sodium chloride is too high, which will cause ammonium chloride to precipitate with sodium bicarbonate, and have a certain influence on the sodium carbonate alkali amount; in addition, the sodium ion content is too small, the sodium carbonate production yield will be reduced, and the production efficiency is low; Compared with Comparative Example 2, it can be found that the mixed solution containing bicarbonate has a low crystallization temperature, which will also cause ammonium chloride to precipitate with sodium bicarbonate; Compared with Comparative Example 3, after salting out, the content of ammonium chloride in the cooling ammonium chloride mother liquor is high without the second cooling crystallization, and the circulating material specific gravity is large. When recycling, due to the supersaturation of sodium chloride, ammonium chloride is precipitated with sodium bicarbonate; Compared with Comparative Example 4, the sodium ion endpoint concentration after salting out crystallization is low, and the content of ammonium chloride in the cooling ammonium chloride mother liquor is high. When recycling, due to the supersaturation of sodium chloride, ammonium chloride is precipitated with sodium bicarbonate; Compared with Comparative Example 5, the sodium ion endpoint concentration after salting out crystallization is high, and it will precipitate with ammonium chloride during the second cooling crystallization, which has a certain influence on the ammonium chloride mass fraction.

[0074] In summary, the method of the present invention effectively solves the problem that the quality of the ammonium chloride product does not meet the standard because sodium bicarbonate is precipitated together with ammonium chloride due to supersaturation, and at the same time, the mother liquor of ammonium chloride is cooled and recycled, thereby improving the production yield of sodium carbonate.

[0075] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit and essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0076] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for jointly preparing sodium carbonate and ammonium chloride, characterized in that: The following steps are involved: (1) cooling ammonium chloride mother liquor and sodium chloride waste salt to prepare a supersaturated sodium chloride mixed solution, sending the supersaturated sodium chloride mixed solution into an ammonia absorber and introducing ammonia gas to perform ammoniation treatment to convert it into ammoniated brine, and the ammoniated waste brine is then transported to a carbonization tower and introduced with carbon dioxide gas to perform carbonization treatment to obtain a mixed solution containing bicarbonate; (2) the mixed solution containing bicarbonate is subjected to heat preservation crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor; (3) adding sodium hydroxide solid to the sodium bicarbonate mother liquor for reaction, first cooling and crystallizing until no crystals are produced, then adding sodium chloride for salting out crystallization, then cooling and crystallizing for a second time, and separating the solid from the liquid to obtain ammonium chloride and cooling the ammonium chloride mother liquor; The sodium bicarbonate is calcined to obtain a sodium carbonate product, and the carbon dioxide gas after calcination is collected and compressed and sent to a carbonization tower; the ammonium chloride mother liquor is cooled and reused in step (1).

2. A method for jointly preparing sodium carbonate and ammonium chloride according to claim 1, characterized in that: In step (3), the molar ratio of the amount of sodium hydroxide added to the amount of heavy sodium ions in the sodium bicarbonate mother liquor is 1:0.95-1.

3. A method for jointly preparing sodium carbonate and ammonium chloride according to claim 1, characterized in that: In step (1), the temperature is controlled at 30-35° C., and the concentration of the supersaturated sodium chloride mixed solution, calculated as sodium ions, is finally controlled at 235-248 g / L.

4. A method for jointly preparing sodium carbonate and ammonium chloride according to claim 3, characterized in that: In step (2), the crystallization temperature is kept at 50-55°C.

5. A method for jointly preparing sodium carbonate and ammonium chloride according to claim 4, characterized in that: In step (3), the first cooling crystallization temperature is 30-35°C, and the second cooling crystallization temperature is 10-15°C.

6. A method for jointly preparing sodium carbonate and ammonium chloride according to claim 4, characterized in that: In step (3), sodium chloride is added for salting out and crystallization, and the endpoint concentration of sodium ions is controlled at 216.9 to 219.8 g / L.

7. A method for jointly preparing sodium carbonate and ammonium chloride according to claim 1, characterized in that: In step (3), sodium chloride is added for salting out and crystallization, and the endpoint concentration of sodium ions is controlled to be less than 47 g / L.

8. A method for jointly preparing sodium carbonate and ammonium chloride according to claim 1, characterized in that: In step (1), the temperature of the ammoniation treatment is 35-40° C., the molar ratio of sodium ions to ammonia gas is 1:1.1-1.2, and the pressure is 0.2-0.3 MPa.

9. A method for jointly preparing sodium carbonate and ammonium chloride according to claim 1, characterized in that: In step (1), the temperature of the carbonization treatment is 55-60° C., the molar ratio of sodium ions to sodium carbonate is 1:1-1.1, and the pressure is 0.2-0.3 MPa.