Method for comprehensive utilization of ammonia evaporation waste liquid and salted salt after bitter brine in soda production by ammonia alkali method

Abstract

The application discloses a method for comprehensive utilization of soda waste clear liquid and salted salt post bitter brine. The salted salt post bitter brine and ammonia distillation waste liquid are pretreated through an ultrafiltration membrane, the bitter brine and the ammonia distillation waste clear liquid are mixed in proportion, the obtained calcium sulfate dihydrate suspension liquid is subjected to solid-liquid separation, the liquid after centrifugation is subjected to an electrodialysis stage, and magnesium chloride solution and sodium chloride solution are obtained through the electrodialysis; the solid after centrifugation is washed, pressure-filtered, and then made into a slurry, a crystal modifier is added for crystal transformation, and through centrifugation and drying, calcium sulfate hemihydrate whiskers are finally obtained. The method uses the salted salt post bitter brine and the ammonia distillation waste clear liquid as raw materials to produce the calcium sulfate hemihydrate whiskers, and the two low-grade solutions of the magnesium chloride solution and the sodium chloride solution are reused, so that the high-value-added products are produced, no waste water is discharged, and the ecological environment and the economic benefits are both won.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater recycling, and particularly relates to a method for comprehensive utilization of ammonia evaporation waste liquid generated by pure alkali process after salt evaporation. BACKGROUND

[0002] The large-scale salt production of salt enterprises leads to the year-by-year increase of by-product bitterns, and the treatment cost of bitterns is high. At present, a large amount of bitterns is discharged into the sea, which causes serious pollution to the ecological environment of the sea. The traditional process for bitterns utilization has problems such as high energy consumption, low product yield and poor economic benefit. With the increasing environmental protection pressure, exploring the high-efficiency utilization process of bitterns has become a current hotspot.

[0003] Bitterns contain sodium, magnesium, potassium, sulfate and other components (see Table 1 for details). At present, researchers mainly take magnesium as the extraction target according to the components of bitterns, and the utilization rate of bitterns is about 20%-30%. In the traditional magnesium-based product extraction process, bitterns needs to go through processes such as pre-cooling, freezing crystallization, heat preservation settlement and product washing, which has high energy consumption and low product added value. The low-end products such as magnesium chloride and magnesium hydroxide produced from bitterns still have technical barriers in the production of high-end high-purity and ultra-high-purity magnesium-based products. Compared with the traditional extraction method, the utilization rate of bitterns is greatly improved, and the process is simple to operate, which can produce high-quality products with high economic benefit.

[0004] Ammonia evaporation waste liquid is the largest amount of waste liquid generated in the production of pure alkali by ammonia-soda process, which is mainly high-salt wastewater, and the main components are inorganic salts such as sodium chloride and calcium chloride. At present, it is concentrated by airing, and then enters the calcium chloride preparation plant for crystallization. However, this method has great harm to the environment, and a large amount of land is needed. Moreover, the concentrated liquid after airing and concentration is unstable and has many impurities, which is not conducive to the evaporation crystallization of calcium chloride. The disposal of ammonia evaporation waste liquid has been one of the factors restricting the sustainable development of enterprises producing alkali by ammonia-soda process. The utilization rate of calcium in the present application is more than 85%, and basically realizes zero discharge, which greatly reduces the pollution to the environment.

[0005]

[0006] The two low-grade wastewater is used to produce high-quality gypsum products, which have excellent performance and can replace traditional building materials. At present, there are few gypsum products meeting the high-quality requirements in China, and the domestic market is in short supply. The high-quality gypsum produced by the present application has higher whiteness and purity than the existing products on the market, and has more excellent performance. At the same time, the solution after reaction is reused, which truly realizes the resource utilization of pure alkali waste liquid, and helps to solve the environmental protection and discharge problems of ammonia evaporation waste liquid by ammonia-soda process.

[0007] In recent years, the research on comprehensive utilization of brine and other systems has also gradually increased. The Chinese invention patent document with the publication number CN102874851A discloses a method for co-production of magnesium hydroxide and calcium sulfate whiskers by using brine. The method uses refined brine as the starting material, adds appropriate amount of calcium chloride to obtain calcium sulfate, and then adds calcium hydroxide to the filtrate to obtain magnesium hydroxide. The method uses refined brine as the starting material, uses bitter brine as the magnesium source, needs to newly add a large amount of calcium chloride solution and calcium hydroxide emulsion as the calcium source to generate calcium sulfate product, only solves the utilization of one waste liquid, and has more added specific materials and higher cost.

[0008] The Chinese invention patent document with the publication number CN109607572A discloses a method for producing refined salt water and calcium-magnesium compounds by comprehensively utilizing underground brine. The method uses high-salinity seawater as the raw material, removes impurities in the raw material by adding a precipitating agent, and then further refines to obtain refined salt; the removed impurities are further separated, purified and refined to obtain magnesium hydroxide, calcium carbonate and calcium sulfate byproducts. The invention can effectively remove calcium and magnesium ions and sulfate ions in underground brine, and simultaneously produce high-value-added products such as magnesium hydroxide, calcium carbonate and calcium sulfate. However, the method uses high-salinity seawater as the raw material, which is the comprehensive utilization of underground brine, not a waste liquid recycling technology. Moreover, the invention needs to add multiple precipitating agents, coagulating agents and other reagents multiple times, and the process is complex and the operation is cumbersome. SUMMARY

[0009] The technical problem to be solved by the present application is to provide a method for comprehensively utilizing ammonia evaporation waste liquid produced in soda ash production by ammonia-soda process and bitter brine after salt evaporation. The method can improve the comprehensive utilization rate of bitter brine after salt evaporation and ammonia evaporation waste liquid produced in soda ash production process, and extract calcium sulfate dihydrate, magnesium chloride and sodium chloride from bitter brine and ammonia evaporation waste liquid. The main components of bitter brine and ammonia evaporation waste liquid are comprehensively utilized by using multiple process integration, and the comprehensive utilization rate of waste liquid is greatly improved.

[0010] To solve the above technical problems, the technical scheme of the present application is a method for comprehensively utilizing soda ash waste clear liquid and bitter brine after salt evaporation, which specifically comprises the following steps:

[0011] (1) The bitter brine after salt evaporation and the ammonia evaporation waste liquid are pretreated by ultrafiltration respectively to remove solid insoluble substances, and then the pretreated bitter brine after salt evaporation and the ammonia evaporation waste liquid are mixed and reacted to obtain a calcium sulfate dihydrate suspension;

[0012] (2) The calcium sulfate dihydrate suspension is subjected to solid-liquid separation to obtain calcium sulfate dihydrate crude product and mother liquor;

[0013] (3) The calcium sulfate dihydrate crude product is sent into a pressure filtration system with water for water washing and pressure filtration to obtain chlorine-containing washed water and calcium sulfate dihydrate solid;

[0014] (4) The chlorine-containing washing water obtained in step (3) is sequentially separated by a nanofiltration-reverse osmosis device to obtain permeate and concentrate. The concentrate is mixed with the mother liquor in step (2) and then fed into an electrodialysis system to obtain magnesium chloride solution and sodium chloride solution respectively.

[0015] (5) Add water to the calcium sulfate dihydrate solid obtained in step (3) to form a slurry, then add a crystallization agent to the slurry to perform crystallization, then centrifuge and dry to obtain calcium sulfate hemihydrate whiskers and crystallization liquid. The crystallization liquid is transported to the crystallization liquid collection tank and reused for crystallization.

[0016] Furthermore, in step (1), the pretreated bittern from salt production and the ammonia stripping waste liquid are mixed and reacted to control the SO4 content in the bittern from salt production. 2- With Ca in ammonia stripping waste liquid 2+ The molar ratio is (1-1.5):1.

[0017] Furthermore, in step (3), the water washing and pressure filtration are three-stage water washing and pressure filtration, and the chloride ion mass concentration in the water after the third stage of washing is controlled to be less than 200 ppm. The water after the first, second and third stages of washing are mixed to obtain chlorine-containing water after washing.

[0018] Furthermore, in step (4), the electrodialysis system uses a monovalent selective cation exchange membrane and a homogeneous anion exchange membrane. 2% sodium chloride solution is used as the electrode liquid in both electrode chambers of the electrodialysis system, and the initial liquid in the salt chamber is pure water. The circulation flow rate of the concentrate chamber and the salt chamber is 400-600 L / h, the circulation flow rate of the electrode chamber is 400-600 L / h, the inlet pressure is 0.4-0.6 MPa, the membrane voltage is 1.5-1.8 V, and the current is 0.4-0.6 A.

[0019] Furthermore, in step (4), the nanofiltration-reverse osmosis system is a combination of two-stage nanofiltration and reverse osmosis, with Ca being selected for the first-stage nanofiltration. 2+ Retention rate 20%~40%, SO4 2- Nanofiltration membranes with a rejection rate of 80%~90%, with Ca2+ selected for secondary nanofiltration. 2+ Retention rate 65%~85%, SO4 2- Nanofiltration membranes with a rejection rate of 95%~99% are used for nanofiltration, and reverse osmosis membranes with a desalination rate of 99%~99.8% are used for reverse osmosis. Chlorine-containing wash water is dechlorinated through the nanofiltration-reverse osmosis system, and the recovery rate of the permeate is 50%~70%.

[0020] Further, in step (5), the slurry contains 10%-30% calcium sulfate dihydrate by mass; the crystallizing agent is a mixture of inorganic salt and surfactant, wherein the inorganic salt is one or two of magnesium chloride, sodium carbonate, and sodium sulfate, and the surfactant is one of sodium oleate, sodium stearate, and sodium dodecylbenzene sulfonate; the mixing ratio of the inorganic salt and surfactant is (2-8):1.

[0021] Further, in step (5), the total amount of crystallization agent added is 0.02~0.15g / l, and the crystallization conditions are: reaction temperature of 95~150℃, reaction pressure of 0.15~0.5MPa, stirring speed of 100~300r / min, and reaction time of 1~4h.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) This invention makes full use of two low-grade liquids, bittern and ammonia stripping waste liquid. Based on the process of preparing calcium sulfate whiskers, the resulting centrifugal mother liquor is used to produce magnesium chloride solution and sodium chloride solution through electrodialysis technology. The product recovery rate is high, realizing the separation and utilization of saline wastewater. At the same time, the washing water in the dechlorination process of calcium sulfate dihydrate is selectively separated and reused through a nanofiltration-reverse osmosis system, realizing the concentration and reuse of chloride ions and the recycling of washing water.

[0024] (2) This invention utilizes the effective components in bittern and ammonia stripping waste liquid in a tiered manner, producing calcium sulfate whiskers, magnesium chloride solution, and sodium chloride solution. The prepared calcium sulfate whiskers have high purity, high whiteness, high aspect ratio, and uniform particle size, resulting in high added value. This method not only solves the environmental problem of large-scale storage of waste liquid at the end of the process of preparing soda ash from bittern and ammonia-soda after salt drying, but also greatly improves the comprehensive utilization rate of resources, resulting in significant cost advantages. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process flow according to an embodiment of the present invention.

[0026] Figure 2 This is a microscope image (100x magnification) of calcium sulfate hemihydrate whisker A prepared in Example 1 of the present invention.

[0027] Figure 3 This is a microscope image (100x magnification) of calcium sulfate hemihydrate whiskers B prepared in Example 2 of the present invention.

[0028] Figure 4 This is a microscopic image (100x magnification) of calcium sulfate hemihydrate whiskers prepared in Example 3 of the present invention.

[0029] Figure 5This is a microscopic image (100x magnification) of the calcium sulfate hemihydrate whiskers prepared in Example 4 of this invention. Detailed Implementation

[0030] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples. However, the present invention is not limited to these embodiments.

[0031] Example 1

[0032] Reference Figure 1 The pretreated bittern and ammonia stripping waste liquid were mixed according to the SO4 content in the bittern. 2- With Ca in ammonia stripping waste liquid 2+ The mixture was reacted at a molar ratio of 1:1, with a stirring speed of 100 r / min, at room temperature for 1 hour. The crude calcium sulfate dihydrate and the reaction solution were then centrifuged to separate the solids and liquids. Deionized water was added to dechlorinate the calcium sulfate dihydrate, with a wash water to crude calcium sulfate dihydrate mass ratio of 2:1. After a first-stage pressure filtration, the chloride ion concentration in the chlorinated wash water decreased from 153791 ppm to 16000 ppm. After a second-stage pressure filtration, the chloride ion concentration decreased from 16000 ppm to 500 ppm. After a third-stage pressure filtration, the chloride ion concentration decreased from 500 ppm to 170 ppm. The filtered liquid entered a wash water collection tank and then entered a nanofiltration-reverse osmosis system. The product water index was Ca. 2+ The content was 13 ppm, SO4 2- The ion content is 1 ppm, Cl - The ion content is 264 ppm.

[0033] The washed and centrifuged calcium sulfate dihydrate solid was mixed with water to prepare a calcium sulfate dihydrate slurry, with calcium sulfate dihydrate accounting for 10% of the total slurry mass. Sodium carbonate (0.016 g / L) and sodium stearate (0.004 g / L) were added. The temperature was raised to 95℃ and the pressure to 0.15 MPa. After 2 hours, the mixture was centrifuged and dried to obtain calcium sulfate hemihydrate whiskers A. Figure 2 It can be seen that the calcium sulfate hemihydrate whiskers obtained in this embodiment have a high aspect ratio, uniform particle size, high rigidity, and high strength. Moreover, the crystal structure is relatively complete, resulting in superior reinforcing performance.

[0034] The reacted solution entered an electrodialysis system employing a monovalent selective cation exchange membrane and a homogeneous anion exchange membrane. The electrode water was a 2% sodium sulfate solution, and the initial liquid in the salt chamber was pure water. The circulation flow rates in the concentrate and salt chambers were 460 L / h, and the circulation flow rate in the electrode chambers was 450 L / h. The inlet pressure was 0.46 MPa, the membrane voltage was 1.58 V, and the current was 0.46 A. The magnesium chloride recovery rate was 85.8%, and the sodium chloride recovery rate was 85.4%.

[0035] Example 2

[0036] The pretreated bittern and ammonia stripping waste liquid were mixed according to the SO4 content in the bittern. 2- With Ca in ammonia stripping waste liquid 2+ The mixture was reacted at a molar ratio of 1:1.2, with a stirring speed of 200 r / min, at room temperature for 4 hours. The crude calcium sulfate dihydrate and the reaction solution were then centrifuged to separate the solids and liquids. Deionized water was added to dechlorinate the crude calcium sulfate dihydrate, with a wash water to calcium sulfate dihydrate solid mass ratio of 2:1. After a first-stage pressure filtration, the chloride ion concentration in the chlorinated wash water decreased from 175,131 ppm to 15,000 ppm. After a second-stage pressure filtration, the chloride ion concentration decreased from 15,000 ppm to 400 ppm. After a third-stage pressure filtration, the chloride ion concentration decreased from 400 ppm to 85 ppm. The filtered liquid entered a wash water collection tank and then entered a nanofiltration-reverse osmosis system. The product water index was Ca. 2+ The content is 12 ppm, SO4 2- The ion content is 1 ppm, Cl - The ion content is 244 ppm.

[0037] The washed and centrifuged calcium sulfate dihydrate solid was mixed with water to prepare a calcium sulfate dihydrate slurry, with calcium sulfate dihydrate accounting for 20% of the total slurry mass. Sodium sulfate (0.1 g / L) and sodium dodecylbenzenesulfonate (0.05 g / L) were added, the temperature was raised to 150℃, and the pressure was 0.25 MPa. After 3 hours, the mixture was centrifuged and dried to obtain calcium sulfate hemihydrate whiskers B. Figure 3 It can be seen that the calcium sulfate hemihydrate whiskers obtained in this embodiment are similar to those in Example 1.

[0038] After the reaction, the solution entered the electrodialysis system, employing a monovalent selective cation exchange membrane and a homogeneous anion exchange membrane. The electrode water was a 2% sodium sulfate solution, and the initial liquid in the salt chamber was pure water. The circulation flow rates in the concentrate and salt chambers were 480 L / h, and the circulation flow rate in the electrode chambers was 470 L / h. The inlet pressure was 0.52 MPa, the membrane voltage was 1.61 V, and the current was 0.51 A. The recovery rates were 86.5% for magnesium chloride and 86.3% for sodium chloride.

[0039] Example 3

[0040] The pretreated bittern and ammonia stripping waste liquid were mixed according to the SO4 content in the bittern. 2- With Ca in ammonia stripping waste liquid 2+The mixture was reacted at a molar ratio of 1:1.5, with a stirring speed of 300 r / min, at room temperature for 2.5 hours. The crude calcium sulfate dihydrate and the reaction solution were then centrifuged for solid-liquid separation. Deionized water was added to dechlorinate the crude calcium sulfate dihydrate, with a wash water to crude calcium sulfate dihydrate mass ratio of 2:1. After a first-stage pressure filtration, the chloride ion concentration in the chlorinated wash water decreased from 162,345 ppm to 14,000 ppm. After a second-stage pressure filtration, the chloride ion concentration decreased from 14,000 ppm to 450 ppm. After a third-stage pressure filtration, the chloride ion concentration decreased from 450 ppm to 50 ppm. The filtered liquid entered the wash water collection tank and then entered the nanofiltration-reverse osmosis system. The product water index was Ca. 2+ The content was 11 ppm, SO4 2- The ion content is 1 ppm, Cl - The ion content is 232 ppm.

[0041] The washed and centrifuged calcium sulfate dihydrate solid was mixed with water to prepare a calcium sulfate dihydrate slurry, with calcium sulfate dihydrate accounting for 30% of the total slurry mass. Sodium sulfate (0.06 g / L), sodium carbonate (0.02 g / L), and sodium stearate (0.01 g / L) were added to the slurry. The temperature was raised to 120°C, the pressure was 0.5 MPa, and after 4 hours, the mixture was centrifuged and dried to obtain calcium sulfate hemihydrate whiskers C. Figure 4 It can be seen that the calcium sulfate hemihydrate whiskers obtained in this embodiment are similar to those in Example 1.

[0042] After the reaction, the solution entered the electrodialysis system, employing a monovalent selective cation exchange membrane and a homogeneous anion exchange membrane. The electrode water was a 2% sodium sulfate solution, and the initial liquid in the salt chamber was pure water. The circulation flow rates in the concentrate and salt chambers were 520 L / h, and the circulation flow rate in the electrode chambers was 480 L / h. The inlet pressure was 0.54 MPa, the membrane voltage was 1.68 V, and the current was 0.55 A. The recovery rates were 87.3% for magnesium chloride and 86.2% for sodium chloride.

[0043] Example 4

[0044] The pretreated bittern and ammonia stripping waste liquid were mixed according to the SO4 content in the bittern. 2- With Ca in ammonia stripping waste liquid 2+The mixture was reacted at a molar ratio of 1:1.5, with a stirring speed of 300 r / min, at room temperature for 2.5 hours. The crude calcium sulfate dihydrate and the reaction solution were then centrifuged for solid-liquid separation. Deionized water was added to dechlorinate the crude calcium sulfate dihydrate, with a wash water to crude calcium sulfate dihydrate mass ratio of 2:1. After a first-stage pressure filtration, the chloride ion concentration in the chlorinated wash water decreased from 166,115 ppm to 14,307 ppm. After a second-stage pressure filtration, the chloride ion concentration decreased from 14,307 ppm to 431 ppm. After a third-stage pressure filtration, the chloride ion concentration decreased from 431 ppm to 55 ppm. The filtered liquid entered the wash water collection tank and then entered the nanofiltration-reverse osmosis system. The product water index Ca... 2+ The content was 13 ppm, SO4 2- The ion content is 1 ppm, Cl - The ion content is 220 ppm.

[0045] The washed and centrifuged calcium sulfate dihydrate solid was mixed with water to prepare a calcium sulfate dihydrate slurry, with calcium sulfate dihydrate accounting for 30% of the total slurry mass. Magnesium chloride 0.06 g / L and sodium oleate 0.02 g / L were added. The temperature was raised to 120℃ and the pressure to 0.5 MPa. After 4 hours, the mixture was centrifuged and dried to obtain calcium sulfate hemihydrate whiskers D. Figure 5 It can be seen that the calcium sulfate hemihydrate whiskers obtained in this embodiment are similar to those in Example 2.

[0046] The reacted solution was fed into an electrodialysis system using a monovalent selective cation exchange membrane and a homogeneous anion exchange membrane. The electrode water was a 2% sodium sulfate solution, and the initial liquid in the salt chamber was pure water. The circulation flow rates in the concentrate and salt chambers were 520 L / h, and the circulation flow rate in the electrode chambers was 480 L / h. The inlet pressure was 0.54 MPa, the membrane voltage was 1.68 V, and the current was 0.55 A. The magnesium chloride recovery rate was 87.0%, and the sodium chloride recovery rate was 86.05%.

Claims

1. A method for the comprehensive utilization of ammonia stripping waste liquid and bittern from salt production using the ammonia-soda process, characterized in that, Includes the following steps: (1) The bittern and ammonia stripping waste liquid after salt production are pretreated by ultrafiltration to remove solid insoluble matter. Then the pretreated bittern and ammonia stripping waste liquid are mixed and reacted to obtain calcium sulfate dihydrate suspension. (2) The calcium sulfate dihydrate suspension was subjected to solid-liquid separation to obtain crude calcium sulfate dihydrate and mother liquor; (3) Add water to the crude calcium sulfate dihydrate and send it into the pressure filter system for washing and pressure filtration to obtain chlorine-containing washing water and calcium sulfate dihydrate solid; (4) The chlorine-containing washing water obtained in step (3) is sequentially separated by a nanofiltration-reverse osmosis system to obtain permeate and concentrate. The concentrate is mixed with the mother liquor in step (2) and then fed into an electrodialysis system to obtain magnesium chloride solution and sodium chloride solution respectively. (5) Add water to the calcium sulfate dihydrate solid obtained in step (3) to form a slurry, then add a crystallization agent to the slurry to perform crystallization, then centrifuge and dry to obtain calcium sulfate hemihydrate whiskers and crystallization solution. The crystallization solution is refluxed for crystallization. In step (1), the pretreated bittern from salt production and the ammonia stripping waste liquid are mixed and reacted to control the SO4 content in the bittern. 2- With Ca in ammonia stripping waste liquid 2+ The molar ratio is 1 to 1.5:1; In step (4), the electrodialysis process uses a monovalent selective cation exchange membrane and a homogeneous anion exchange membrane. Both electrode chambers of the electrodialysis system use a 2% sodium sulfate solution as the electrode liquid, and the initial liquid in the salt chamber is pure water. The circulation flow rate of the concentrate chamber and salt chamber is 400–600 L / h, the circulation flow rate of the electrode chamber is 400–600 L / h, the inlet pressure is 0.4–0.6 MPa, the membrane voltage is 1.5–1.8 V, and the current is 0.4–0.6 A. The nanofiltration-reverse osmosis system is a combination of two-stage nanofiltration and reverse osmosis. The first-stage nanofiltration uses Ca2+. 2+ Retention rate 20%~40%, SO4 2- Nanofiltration membranes with a rejection rate of 80%~90%, with Ca2+ selected for secondary nanofiltration. 2+ Retention rate 65%~85%, SO4 2- Nanofiltration membranes with a rejection rate of 95%~99% are used for nanofiltration, and reverse osmosis membranes with a desalination rate of 99%~99.8% are used for reverse osmosis. Chlorine-containing wash water is dechlorinated through the nanofiltration-reverse osmosis system, and the recovery rate of the permeate is 50%~70%.

2. The method for comprehensive utilization of ammonia stripping waste liquid and bittern after salt evaporation in the ammonia-soda process for producing soda ash according to claim 1, characterized in that, In step (3), the water washing and pressure filtration are three-stage water washing and pressure filtration. The mass concentration of chloride ions in the water after the third stage of washing is controlled to be less than 200 ppm. The water after the first, second and third stages of washing are mixed to obtain chlorine-containing water after washing.

3. The method for comprehensive utilization of ammonia stripping waste liquid and bittern after salt evaporation in the ammonia-soda process for producing soda ash according to claim 1, characterized in that, In step (5), the calcium sulfate dihydrate accounts for 10%-30% of the total slurry by mass; the crystallizing agent is a mixture of inorganic salt and surfactant, wherein the inorganic salt is one or two of magnesium chloride, sodium carbonate, and sodium sulfate, and the surfactant is one of sodium oleate, sodium stearate, and sodium dodecylbenzene sulfonate; the mass ratio of inorganic salt to surfactant is 2-8:

1.

4. The method for comprehensive utilization of ammonia stripping waste liquid and bittern after salt evaporation in the ammonia-soda process for producing soda ash according to claim 1, characterized in that, In step (5), the total amount of crystallization agent added is 0.02~0.15 g / l, and the crystallization conditions are: reaction temperature of 95~150℃, reaction pressure of 0.15~0.5MPa, stirring speed of 100~300r / min, and reaction time of 1~4h.

Images