A process for co-producing potassium sulfate and sodium bicarbonate from municipal solid waste fly ash and waste salt.

Abstract

This invention discloses a process for co-producing potassium sulfate and sodium bicarbonate from municipal solid waste fly ash waste salt, belonging to the technical field of municipal solid waste fly ash treatment. Using the waste heavy liquid obtained from municipal solid waste fly ash after water-soluble treatment as raw material, calcium is removed to obtain decalcified brine; the decalcified brine is then added to caustic soda and soda ash for further deammoniation and refining to obtain magnesium hydroxide and calcium carbonate solids, ammonia gas, and deammoniation brine; the deammoniation brine is evaporated to obtain salt and potassium-rich mother liquor; the potassium-rich mother liquor is cooled to precipitate potassium chloride, and then mixed with slurry and reacted with added sodium sulfate and water to obtain potassium sulfate and potassium sulfate mother liquor; the potassium sulfate is dissolved in water to control the equilibrium separation of sodium sulfate and potassium sulfate to obtain potassium sulfate product and potassium sulfate mother liquor; the potassium sulfate mother liquor and potassium sulfate mother liquor are recycled to the calcium removal process; the salt is dissolved in water and ammonia is absorbed to obtain ammonia brine; the ammonia brine reacts with carbon dioxide to obtain sodium bicarbonate product and heavy alkali mother liquor; the heavy alkali mother liquor is recycled to the calcium removal process. This invention achieves waste salt reduction, harmlessness, and resource utilization.

Description

Technical Field

[0001] This invention relates to a process for co-producing potassium sulfate and sodium bicarbonate from waste salts in municipal solid waste fly ash, belonging to the technical field of municipal solid waste fly ash treatment. Background Technology

[0002] Currently, rigid and flexible landfill methods are commonly used to treat fly ash from municipal solid waste (which mainly contains sodium chloride, calcium chloride, potassium chloride, as well as heavy metal ions and COD). Here, "COD" refers to Chemical Oxygen Demand, an indicator that measures the amount of reducing substances in a water sample that need to be oxidized. It is determined chemically and expressed as milligrams of oxidant consumed per liter. A higher COD concentration indicates more severe organic pollution in the water. Landfill methods are influenced by factors such as land availability, location, cost, and groundwater availability. Furthermore, the large amounts of inorganic salts like sodium chloride, sodium sulfate, and calcium chloride present in landfills represent a waste of land, capital, and chemical resources.

[0003] Therefore, finding reasonable processes for reducing, rendering harmless, and recycling fly ash from municipal solid waste is a major issue that the environmental protection industry urgently needs to address. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to provide a process for co-producing potassium sulfate and sodium bicarbonate from fly ash waste salt of municipal solid waste, so as to achieve waste salt reduction, harmlessness and resource utilization, and produce high value-added products potassium sulfate and sodium bicarbonate.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A process for co-producing potassium sulfate and sodium bicarbonate from municipal solid waste fly ash and waste salt includes the following steps:

[0007] (1) The waste liquid obtained by water-soluble treatment of domestic waste fly ash is used as raw material. It is mixed with sodium sulfate and recycled potassium sulfate mother liquor, potassium sulfate mother liquor and heavy alkali mother liquor to form a balanced reaction. The reaction temperature is 20-40℃ and the reaction time is 0.1-8 hours. Calcium chloride in the waste liquid is removed to obtain calcium sulfate and calcium carbonate solids and calcium-removed brine.

[0008] (2) Add caustic soda and soda ash to the calcium-dehydrated brine, then remove ammonia and refine to obtain magnesium hydroxide and calcium carbonate solids, ammonia gas and deammoniated brine; the deammoniated brine is subjected to multi-effect evaporation to obtain salt and potassium-rich mother liquor, with an evaporation temperature of 40-130℃;

[0009] (3) After the potassium-rich mother liquor is cooled to 20-40℃ and potassium chloride is precipitated, the mixed slurry and the added sodium sulfate and water undergo a metathesis reaction to obtain potassium mirabilite and potassium mirabilite mother liquor. The potassium mirabilite mother liquor is recycled to step (1) to participate in the calcium removal reaction.

[0010] (4) Potassium sulfate and potassium sulfate mother liquor are obtained by dissolving potassium sulfate in water at a temperature of 35-100℃; the potassium sulfate mother liquor is recycled to step (1) to participate in the calcium removal reaction.

[0011] (5) The salt obtained in step (2) is dissolved in water to obtain brine, and the brine absorbs ammonia to obtain ammonia brine;

[0012] (6) The reaction of ammonia salt water with carbon dioxide yields sodium bicarbonate product and heavy alkali mother liquor; the heavy alkali mother liquor is recycled to step (1) to participate in the calcium removal reaction.

[0013] In the process of this invention, the waste liquid contains: NaCl 5-290 g / L, CaCl 25-300 g / L, KCl 5-350 g / L, and COD 10-1500 ppm.

[0014] In the process of this invention, the sodium sulfate mainly contains: 5-98% Na2SO4 and 1-95% NaCl.

[0015] In the process of this invention, the potassium sulfate mother liquor contains: NaCl 100-300 g / L, CaSO4 0.1-6.0 g / L, KCl 10-250 g / L, K2SO4 10-250 g / L, and COD 100-30000 ppm; the potassium sulfate mother liquor contains: NaCl 1-5 g / L, CaSO4 0.1-0.5 g / L, KCl 1-5 g / L, Na2SO4 70-350 g / L, K2SO4 50-200 g / L, and COD 1-2000 ppm; the heavy alkali mother liquor contains: NaCl 30-100 g / L, NH4HCO3 50-130 g / L, NH4Cl 60-200 g / L, and COD 10-100 ppm.

[0016] In the process of this invention, the calcium-removing brine contains: NaCl 5-280 g / L, CaSO4 5-6 g / L, KCl 1-350 g / L, K2SO4 0.55-200 g / L, NH4Cl 70-220 g / L, and COD 10-1500 ppm.

[0017] In the process of this invention, the deammoniation brine contains: NaCl 75-330 g / L, KCl 1-290 g / L, K2SO4 0.55-200 g / L, and COD 10-1500 ppm.

[0018] In the process of this invention, the potassium-rich mother liquor contains: NaCl 10-300 g / L, KCl 10-300 g / L, K2SO4 10-300 g / L, and COD 100-30000 ppm.

[0019] In the process of the present invention, in step (5), the brine contains: NaCl 300-330 g / L, COD 10-100 ppm; the ammonia brine contains NH3 65-74 g / L, NaCl 300-330 g / L, COD 10-100 ppm.

[0020] In the process of the present invention, the raw materials may also contain one or two soluble impurities selected from MgCl and MgSO4.

[0021] The advantages of this invention are:

[0022] This invention uses the waste liquid obtained from the water-soluble treatment of municipal solid waste fly ash as raw material. After calcium removal, it yields calcium sulfate and calcium carbonate solids, as well as a calcium-removing brine containing potassium chloride, potassium sulfate, sodium chloride, ammonium chloride, and calcium sulfate. The calcium-removing brine is then treated with caustic soda and soda ash for further deammoniation and refining to obtain magnesium hydroxide and calcium carbonate solids, ammonia, and ammonia-removing brine. The ammonia-removing brine is evaporated to obtain salt and potassium-rich mother liquor. The potassium-rich mother liquor is cooled and reacted with sodium sulfate in a double decomposition reaction to obtain potassium sulfate and potassium sulfate mother liquor. The potassium sulfate mother liquor is recycled to the calcium removal process. Potassium sulfate is dissolved in water to control the equilibrium separation of sodium sulfate and potassium sulfate, yielding potassium sulfate product and potassium sulfate mother liquor. The potassium sulfate mother liquor is recycled to the calcium removal process. Salt is dissolved in water to obtain brine that absorbs ammonia, which is then reacted with carbonation to obtain sodium bicarbonate product and heavy alkali mother liquor. The heavy alkali mother liquor is recycled to the calcium removal process. This invention features waste salt reduction, harmlessness, and resource utilization, and can produce high-value-added products such as potassium sulfate and sodium bicarbonate. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the co-production of potassium sulfate and sodium bicarbonate from municipal solid waste fly ash and waste salt of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this does not imply any limitation on the scope of protection of the present invention.

[0025] like Figure 1As shown, this invention uses the waste liquid obtained from the water-soluble treatment of municipal solid waste fly ash as raw material. After calcium removal, calcium sulfate and calcium carbonate solids are obtained, as well as calcium-removing brine containing potassium chloride, potassium sulfate, sodium chloride, ammonium chloride, and calcium sulfate. The calcium-removing brine is then added to caustic soda and soda ash for further deammoniation and purification to obtain magnesium hydroxide and calcium carbonate solids, ammonia gas, and deammoniation brine. The deammoniation brine is evaporated to obtain salt and potassium-rich mother liquor. After cooling, the potassium-rich mother liquor undergoes a double decomposition reaction with sodium sulfate to obtain potassium sulfate and potassium sulfate mother liquor. The potassium sulfate mother liquor is recycled to the calcium removal process. Potassium sulfate is added to water to control the dissolution of sodium sulfate and potassium sulfate to achieve equilibrium separation, resulting in potassium sulfate product and potassium sulfate mother liquor. The potassium sulfate mother liquor is recycled to the calcium removal process. The brine obtained by dissolving salt in water absorbs ammonia to obtain ammonia brine. The ammonia brine undergoes a carbonation reaction to obtain sodium bicarbonate product and heavy alkali mother liquor. The heavy alkali mother liquor is recycled to the calcium removal process.

[0026] As the raw material of the present invention, the waste heavy liquid is obtained by dissolving and separating solids and liquids in a multi-stage countercurrent process using water to dissolve fly ash from municipal solid waste.

[0027] Example 1

[0028] Take 60 m 3 Waste heavy liquid (containing NaCl 53 g / L, CaCl2 100 g / L, KCl 10.00 g / L, COD 500 ppm) was used as raw material; 60 m 3 The waste heavy liquid was mixed with 2.44 tons of sodium sulfate (containing 98% Na₂SO₄ and 1% NaCl) and 4.26 m³ of recycled wastewater. 3 Potassium sulfate mother liquor (containing NaCl 262.5 g / L, CaSO4 1.0 g / L, KCl 70 g / L, K2SO4 17.5 g / L, COD ≤15750ppm), 0.64 m 3 Potassium sulfate mother liquor (containing 1 g / L NaCl, 0.10 g / L CaSO4, 300 g / L Na2SO4, 60 g / L K2SO4, 1.1 g / L KCl, COD ≤500 ppm), 46.93 m 3 The heavy alkali mother liquor (containing 90 g / L NaCl, 127 g / L NH4HCO3, 180 g / L NH4Cl, and 30 ppm COD) was mixed and equilibrated (reaction temperature 25℃, reaction time 4 hours) to remove calcium chloride from the waste heavy liquor, yielding calcium sulfate (CaSO4) and calcium carbonate (CaCO3) solid precipitates and 111.83 m... 3 Calcium-free brine (containing NaCl 133.62 g / L, NH4Cl 111.29 g / L, CaSO4 5.0 g / L, KCl 8.04 g / L, K2SO4 1.01 g / L, COD ≤900 ppm); 111.83 m 3After adding appropriate amounts of caustic soda (NaOH) and soda ash (NaCO3) to the calcium-free brine, followed by deammoniation and purification, magnesium hydroxide (Mg(OH)2) and calcium carbonate (CaCO3) solid precipitates, ammonia (NH3), and approximately 111.83 m 3 Deammoniation-free brine (containing NaCl 255.41 g / L, KCl 8.04 g / L, K₂SO₄ 1.01 g / L, COD ≤600 ppm); approximately 111.83 m 3 Multi-effect evaporation of deammoniated brine (evaporation temperature 110℃) yielded 9.67 tons of industrial salt (99% NaCl) and 4.26 m³ of [unclear - possibly a specific product or product name]. 3 Potassium-rich mother liquor (containing NaCl 129.11 g / L, KCl 211.06 g / L, K₂SO₄ 19.83 g / L, COD ≤15750 ppm); 4.26 m 3 After cooling the potassium-rich mother liquor (to 30°C), water was added and reacted with 0.58 tons of sodium sulfate (Na₂SO₄ 99%) to obtain 0.95 tons of potassium mirabilite (Na₂SO₄·3K₂SO₄) and 4.26 m 3 Potassium sulfate mother liquor (containing NaCl 262.5 g / L, CaSO4 1.0 g / L, KCl 70 g / L, K2SO4 17.5 g / L, COD ≤15750 ppm); 4.26 m 3 The potassium sulfate mother liquor is recycled to the calcium removal process to participate in the calcium removal reaction; 0.95 tons of potassium sulfate are dissolved in water (dissolution temperature 35℃) to obtain 0.71 tons of potassium sulfate (K2SO4) and 0.64 m 3 Potassium sulfate mother liquor (containing NaCl 1 g / L, CaSO4 0.10 g / L, Na2SO4 300 g / L, K2SO4 60 g / L, KCl 1.1 g / L, COD ≤500 ppm); 0.64 m 3 Potassium sulfate mother liquor is recycled to the calcium removal process to participate in the calcium removal reaction; 9.67 tons of salt (containing 99% NaCl) is dissolved in water to a concentration of 31.91 m³. 3 Ammonia (NH3) was adsorbed by brine (containing 300 g / L NaCl and 30 ppm COD) to obtain 31.91 m. 3 Ammonia-containing saline solution (containing NH3 65 g / L, NaCl 300 g / L, COD 30 ppm); 31.91 m 3 Ammonia brine was carbonated with a suitable amount of carbon dioxide (CO2) to yield 14.03 tons of sodium bicarbonate (containing 99% NaHCO3) product and 46.93 m³ of sodium bicarbonate solution. 3 Heavy alkali mother liquor (containing NaCl 90 g / L, NH4HCO3 127 g / L, NH4Cl 180 g / L, COD 30 ppm); 46.93 m3 The mother liquor of heavy alkali is recycled to the calcium removal process to participate in the calcium removal reaction.

[0029] Example 2

[0030] Take 60 m 3 Waste heavy liquid (containing NaCl 50 g / L, CaCl2 95 g / L, KCl 20.00 g / L, COD 500 ppm) was used as raw material; 60 m 3 The waste heavy liquid was mixed with 2.43 tons of sodium sulfate (containing 97.5% Na₂SO₄ and 1.50% NaCl) and 8.50 m³ of recycled wastewater. 3 Potassium sulfate mother liquor (containing NaCl 255 g / L, CaSO4 0.80 g / L, KCl 75 g / L, K2SO4 20 g / L, COD 30000 ppm), 1.30m 3 Potassium sulfate mother liquor (containing NaCl 1 g / L, CaSO4 0.10 g / L, Na2SO4 295 g / L, K2SO4 65 g / L, KCl 1.5 g / L, COD 300 ppm), 50 m 3 The heavy alkali mother liquor (containing 92 g / L NaCl, 120 g / L NH4HCO3, 185 g / L NH4Cl, and 30 ppm COD) underwent a mixed equilibrium reaction (reaction temperature 30℃, reaction time 2 hours) to remove calcium chloride from the waste heavy liquor, yielding calcium sulfate (CaSO4) and calcium carbonate (CaCO3) solid precipitates and 119.8 m... 3 Calcium-free brine (containing NaCl 134 g / L, NH4Cl 111 g / L, CaSO4 5.05 g / L, KCl 15.35 g / L, K2SO4 1.01 g / L, COD ≤1461ppm); 119.8 m 3 After adding appropriate amounts of caustic soda (NaOH) and soda ash (NaCO3) to the calcium-free brine, followed by deammoniation and purification, magnesium hydroxide (Mg(OH)2) and calcium carbonate (CaCO3) solid precipitates, ammonia (NH3), and approximately 119.8 m... 3 Deammoniation-free brine (containing NaCl 255 g / L, KCl 10.0 g / L, K₂SO₄ 2.12 g / L, COD ≤974 ppm); approximately 119.8 m 3 Multi-effect evaporation of deammoniated brine (evaporation temperature 115℃) yielded 9.73 tons of industrial salt (NaCl 99%) and 8.50 m³ of [unclear - possibly a specific product or product name]. 3 Potassium-rich mother liquor (containing NaCl 114.06 g / L, KCl 216 g / L, K₂SO₄ 29.94 g / L, COD 30000 ppm); 8.50 m 3After cooling the potassium-rich mother liquor (to 25°C), water was added and reacted with 1.78 tons of sodium sulfate (Na₂SO₄ 99%) to obtain 1.90 tons of potassium mirabilite (Na₂SO₄·3K₂SO₄) and 8.50 m 3 Potassium sulfate mother liquor (containing NaCl 255 g / L, CaSO4 0.5-1.0 g / L, KCl 75 g / L, K2SO4 20 g / L, COD 30000 ppm); 8.50 m 3 The potassium sulfate mother liquor is recycled to the calcium removal process to participate in the calcium removal reaction; 1.90 tons of potassium sulfate are dissolved in condensate (dissolution temperature 35℃) to obtain 1.42 tons of potassium sulfate (K2SO4) and 1.30 m 3 Potassium sulfate mother liquor (containing NaCl 1 g / L, CaSO4 0.10 g / L, Na2SO4 295 g / L, K2SO4 65 g / L, KCl 1.5 g / L, COD 300 ppm); 1.30 m 3 Potassium sulfate mother liquor is recycled to the calcium removal process to participate in the calcium removal reaction; 9.73 tons of salt (containing 99% NaCl) is dissolved in water to a concentration of 32.11 m³. 3 Ammonia (NH3) was adsorbed by brine (containing 300 g / L NaCl and 30 ppm COD) to obtain 32.11 m. 3 Ammonia-containing saline solution (containing NH3 65 g / L, NaCl 300 g / L, COD 30 ppm); 32.11 m 3 Ammonia brine was carbonated with a suitable amount of carbon dioxide (CO2) to yield 14.12 tons of sodium bicarbonate (containing 99% NaHCO3) product and 50 m³ of sodium bicarbonate solution. 3 Heavy alkali mother liquor (containing NaCl 92 g / L, NH4HCO3 120 g / L, NH4Cl 185 g / L, COD 30 ppm); 50 m 3 The mother liquor of heavy alkali is recycled to the calcium removal process to participate in the calcium removal reaction.

[0031] Example 3

[0032] Take 60 m 3 Waste heavy liquid (containing NaCl 50 g / L, CaCl2 105 g / L, KCl 15.00 g / L, COD 500 ppm) was used as raw material; 60 m 3 The waste heavy liquid was mixed with 2.50 tons of sodium sulfate (containing 99% Na₂SO₄ and 0.50% NaCl) and 6.45 m³ of recycled wastewater. 3 Potassium sulfate mother liquor (containing NaCl 257.5 g / L, CaSO4 0.30 g / L, KCl 72.5 g / L, K2SO4 22 g / L, COD 10000ppm), 0.90 m 3Potassium sulfate mother liquor (containing NaCl 1.5 g / L, CaSO4 0.15 g / L, Na2SO4 298 g / L, K2SO4 63 g / L, KCl 1.5 g / L, COD 100 ppm), 50 m 3 The heavy alkali mother liquor (containing NaCl 92 g / L, NH4HCO3 125 g / L, NH4Cl 180 g / L, COD 30 ppm) was mixed and equilibrated (reaction temperature 30℃, reaction time 3 hours) to remove calcium chloride from the waste heavy liquor, yielding calcium sulfate (CaSO4) and calcium carbonate (CaCO3) solid precipitates and 117.4 m 3 Calcium-free brine (containing NaCl 131.66 g / L, NH4Cl 117.38 g / L, CaSO4 5.50 g / L, KCl 11.67 g / L, K2SO4 0.59 g / L, COD ≤472 ppm); 117.4 m 3 After adding appropriate amounts of caustic soda (NaOH) and soda ash (NaCO3) to the calcium-free brine, followed by deammoniation and purification, magnesium hydroxide (Mg(OH)2) and calcium carbonate (CaCO3) solid precipitates, ammonia (NH3), and approximately 117.4 m³ of [unspecified substance] were obtained. 3 Deammoniation-free brine (containing NaCl 260 g / L, KCl 11.67 g / L, K₂SO₄ 0.59 g / L, COD ≤472 ppm); approximately 117.4 m 3 Multi-effect evaporation of deammoniated brine (evaporation temperature 115℃) yielded 9.79 tons of industrial salt (99% NaCl) and 6.45 m³ of sodium chloride. 3 Potassium-rich mother liquor (containing NaCl 114.82 g / L, KCl 214.34 g / L, K₂SO₄ 30.84 g / L, COD 10000 ppm); 6.45m 3 After cooling the potassium-rich mother liquor (to 30°C), water was added and reacted with 1.35 tons of sodium sulfate (Na₂SO₄ 99%) to obtain 1.44 tons of potassium sulfate (Na₂SO₄·3K₂SO₄) and 6.45 m 3 Potassium sulfate mother liquor (containing NaCl 257.5 g / L, CaSO4 0.30 g / L, KCl 72.5 g / L, K2SO4 22 g / L, COD 10000 ppm); 6.45 m 3 The potassium sulfate mother liquor is recycled to the calcium removal process to participate in the calcium removal reaction; 1.44 tons of potassium sulfate are dissolved in water (dissolution temperature 35℃) to obtain 1.08 tons of potassium sulfate (K2SO4) and 0.90 m 3Potassium sulfate mother liquor (containing NaCl 1.5 g / L, CaSO4 0.15 g / L, Na2SO4 298 g / L, K2SO4 63 g / L, KCl 1.5 g / L, COD 100 ppm); 0.30 m 3 Potassium sulfate mother liquor is recycled to the calcium removal process to participate in the calcium removal reaction; 9.79 tons of salt (containing 99% NaCl) is dissolved in water to a concentration of 32.31 m³. 3 Ammonia (NH3) was adsorbed by brine (containing 300 g / L NaCl and 30 ppm COD) to obtain 32.31 m. 3 Ammonia-containing brine (containing NH3 65 g / L, NaCl 300 g / L, COD 30 ppm); 32.31 m 3 Ammonia brine was carbonated with a suitable amount of carbon dioxide (CO2) to yield 14.21 tons of sodium bicarbonate (containing 99% NaHCO3) product and 50 m³ of sodium bicarbonate solution. 3 Heavy alkali mother liquor (containing NaCl 92 g / L, NH4HCO3 125 g / L, NH4Cl 180 g / L, COD 30 ppm); 50 m 3 The mother liquor of heavy alkali is recycled to the calcium removal process to participate in the calcium removal reaction.

Claims

1. A process for co-production of potassium sulphate and baking soda from municipal solid waste fly ash waste salt, characterized by, The process comprises the following steps: (1) The raw material is the water-soluble treated household garbage fly ash, which is mixed with added sodium sulfate and recycled potassium mirabilite mother liquor, potassium sulfate mother liquor, and heavy alkali mother liquor for balance reaction. The reaction temperature is 20-40℃, and the reaction time is 0.1-8 hours. The calcium chloride in the raw material is removed to obtain calcium sulfate and calcium carbonate solids and calcium-removed salt water; (2) Soda ash and soda ash are added to the calcium-removed salt water, and then deamination and refining are performed to obtain magnesium hydroxide and calcium carbonate solids, ammonia gas, and deamination salt water. The deamination salt water is subjected to multi-effect evaporation to obtain salt and potassium-rich mother liquor, and the evaporation temperature is 40-130℃; (3) The potassium-rich mother liquor is cooled to 20-40℃ to precipitate potassium chloride, and then the mixed slurry is subjected to double decomposition reaction with added sodium sulfate and water to obtain potassium mirabilite and potassium mirabilite mother liquor. The potassium mirabilite mother liquor is recycled to step (1) for calcium removal reaction; (4) The potassium mirabilite is dissolved with water to obtain potassium sulfate and potassium sulfate mother liquor, and the dissolution temperature is 35-100℃. The potassium sulfate mother liquor is recycled to step (1) for calcium removal reaction; (5) The salt obtained in step (2) is dissolved with water to obtain salt water, and the salt water is subjected to ammonia absorption to obtain ammonia salt water; (6) The ammonia salt water is reacted with carbon dioxide to obtain baking soda product and heavy alkali mother liquor. The heavy alkali mother liquor is recycled to step (1) for calcium removal reaction.

2. The process for co-production of potassium sulphate and baking soda from MSW fly ash waste salt as claimed in claim 1, wherein, The calcium-removed raw waste liquid contains: NaCl 5-290 g / L, CaCl2 5-300 g / L, KCl 5-350 g / L, and COD 10-1500 ppm.

3. The process for co-production of potassium sulphate and baking soda from waste salts of municipal solid incinerated fly ash as claimed in claim 1 or 2 wherein, The sodium sulfate contains: Na2SO4 5-98%, and NaCl 1-95%.

4. The process for co-production of potassium sulphate and baking soda from MSW fly ash waste salt as claimed in claim 2 wherein, The potassium mirabilite mother liquor contains: NaCl 100-300 g / L, CaSO4 0.1-6.0 g / L, KCl 10-250 g / L, K2SO4 10-250 g / L, and COD 100-30000 ppm. The potassium sulfate mother liquor contains: NaCl 1-5 g / L, CaSO4 0.1-0.5 g / L, KCl 1-5 g / L, Na2SO4 70-350 g / L, K2SO4 50-200 g / L, and COD 1-2000 ppm. The heavy alkali mother liquor contains: NaCl 30-100 g / L, NH4HCO3 50-130 g / L, NH4Cl 60-200 g / L, and COD 10-100 ppm.

5. The process for co-production of potassium sulphate and baking soda from MSW fly ash waste salt as claimed in claim 2, wherein, The calcium-removed salt water contains: NaCl 5-280 g / L, CaSO4 5-6 g / L, KCl 1-350 g / L, K2SO4 0.55-200 g / L, NH4Cl 70-220 g / L, and COD 10-1500 ppm.

6. The process for co-production of potassium sulphate and baking soda from MSW fly ash waste salt as claimed in claim 2, wherein, The deamination salt water contains: NaCl 75-330 g / L, KCl 1-290 g / L, K2SO4 0.55-200 g / L, and COD 10-1500 ppm.

7. The process for co-production of potassium sulphate and baking soda from MSW fly ash waste salt as claimed in claim 2, wherein, The potassium-rich mother liquor contains: NaCl 10-300 g / L, KCl 10-300 g / L, K2SO4 10-300 g / L, COD 100-30000 ppm.

8. The process for co-production of potassium sulphate and baking soda from MSW fly ash waste salt as claimed in claim 2, wherein, In the step (5), the salt water contains: NaCl 300-330 g / L, COD 10-100 ppm; the ammonia salt water contains NH365-74 g / L, NaCl 300-330 g / L, COD 10-100 ppm.

9. The process for co-production of potassium sulphate and baking soda from waste salts of municipal solid waste fly ash as claimed in claim 1 or 2 wherein, The raw material also contains one or both of MgCl and MgSO4 soluble impurities.

Images