A process for producing caustic soda, soda ash and barium sulfate by co-production of salt carrier and witherite

Abstract

A process for the co-production of caustic soda, soda ash and barium sulfate by a salt carrier and witherite, wherein a salt carrier solution or a salt carrier is used as a raw material, mixed with a light brine and evaporated to obtain a high-purity salt product and a salt-making mother liquor; the high-purity salt product is exported, or dissolved to obtain a high-purity brine, and the high-purity brine or the salt carrier solution is decalcified and magnesium is removed to obtain a primary brine; the primary brine is refined to obtain a secondary brine; the secondary brine is electrolyzed to obtain a liquid caustic soda product, light brine and hydrochloric acid; ammonium brine is mixed with a salt-making mother liquor and an ammonium precipitation mother liquor and evaporated at high temperature to obtain refined salt and a salt-precipitation mother liquor; the refined salt is exported, or mixed brine is obtained, and caustic soda and soda ash solutions are added to obtain refined brine; the refined brine is subjected to double decomposition reaction to obtain baking soda and a heavy alkali mother liquor; the salt precipitation mother liquor is evaporated at low temperature to obtain ammonium chloride and an ammonium precipitation mother liquor; the ammonium brine is deaminated and evaporated at high temperature to obtain a salt-ammonium co-saturated salt mother liquor, or the ammonium precipitation mother liquor is steam distilled with lime to obtain ammonia and distillation waste liquid; the distillation waste liquid, gypsum and witherite are reacted to obtain calcium carbonate and a decalcified mother liquor.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic chemical industry, in particular to a process for producing caustic soda, soda ash and barium sulfate by co-production of salt carrier and witherite. Background Art

[0002] At present, the country requires zero-emission treatment for seawater desalination brine, chemical salt-containing nitrate wastewater, mother liquor, waste salt, and waste residue. These seawater desalination brine, chemical salt-containing nitrate wastewater, mother liquor, and waste residue produce tens of millions of tons of by-product salt, nitrate, magnesium chloride, and calcium chloride (including sodium chloride (NaCl), sodium sulfate (Na2SO4), magnesium chloride (MgCl2), calcium chloride (CaCl2), COD and other components) every year. These huge amounts of by-product salt, nitrate, magnesium chloride, and calcium chloride have caused new secondary pollution and serious environmental problems due to the difficulty in finding a market of suitable scale. Sodium chloride and sodium sulfate are the basic raw materials for the chemical production of caustic soda and soda ash.

[0003] The known sodium chloride caustic soda production process of the ion membrane method produces a large amount of chlorine as a by-product, and the industrial chain process using chlorine is long and complicated; the export of chlorine is affected by many factors such as market, distance, and safety. The known sodium chloride production process of soda ash has the problem of high cost due to the cold combined alkali production method, which requires high-quality solid sodium chloride, and the frozen crystallization of ammonium chloride consumes a lot of electricity. The known sodium chloride production process of soda ash has a by-product of about 10m3 / ton of alkali product. 3 The distillation waste liquid containing calcium chloride and sodium chloride is difficult to use and dispose of, which poses a serious environmental problem.

[0004] Therefore, the above-mentioned seawater desalination brine, saltpeter wastewater, mother liquor, waste salt and waste residue as raw materials for producing caustic soda and soda ash processes have limitations in the application of the extended industrial chain of actual environmental protection projects. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a process for the co-production of caustic soda, soda ash and barium sulfate by using salt carrier and witherite, which uses salt carrier and witherite as raw materials to co-produce high value-added products such as caustic soda, soda ash and barium sulfate, and has the characteristics of comprehensive utilization of seawater desalination brine, waste salt nitrate brine, waste salt nitrate mother liquor, waste salt and waste residue, and no waste residue, waste water, waste gas or waste liquid discharge, which is brand new green, low-carbon, zero emission and good environmental benefits.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A process for producing caustic soda, soda ash and barium sulfate by co-production of salt carrier and witherite comprises the following steps:

[0008] 1) Using a salt carrier solution or a salt carrier as a raw material, dilute brine and the salt carrier solution or the salt carrier are mixed and evaporated to obtain a high-purity salt product and a salt-making mother liquor;

[0009] 2) The high-purity salt product is exported, or dissolved with condensed water to obtain the first high-purity brine, and the first high-purity brine or salt carrier solution is added with caustic soda or soda ash solution to remove calcium and magnesium to obtain primary brine;

[0010] 3) The primary brine is further adsorbed and refined to obtain secondary brine;

[0011] 4) Secondary brine electrolysis to obtain liquid caustic soda product, light brine and by-product hydrochloric acid;

[0012] 5) 0-100% by weight of ammonium salt water is mixed with salt-making mother liquor and 0-100% by weight of ammonium precipitation mother liquor, and the mixture is evaporated at high temperature to obtain refined salt and salt-precipitation mother liquor;

[0013] 6) The refined salt is exported, or added to the salt water to obtain the second high purity salt water, or added to the condensed water or fresh water or calcium precipitation mother liquor or barium removal salt water to obtain the mixed salt water;

[0014] 7) adding caustic soda and soda ash solution to the mixed brine to remove calcium and magnesium to obtain refined brine;

[0015] 8) Refined brine undergoes double decomposition reaction with ammonium bicarbonate or ammonia and carbon dioxide to obtain baking soda and heavy alkali mother liquor;

[0016] 9) calcining baking soda to obtain soda ash product and carbon dioxide;

[0017] 10) 0-100% by weight of the heavy alkali mother liquor reacts with hydrochloric acid to obtain ammonium salt water and carbon dioxide;

[0018] 11) 0-100% by weight of ammonium brine goes to lime distillation;

[0019] 12) low temperature evaporation of the salt precipitation mother liquor to obtain ammonium chloride and ammonium precipitation mother liquor;

[0020] 13) 0-100% by weight of the ammonium precipitation mother liquor is circulated to the high temperature evaporation salt production process in step 5);

[0021] 14) deammoniating a heavy alkali mother liquor with a weight ratio of 0-100% at high temperature to obtain aqueous ammonia and deammoniated mother liquor;

[0022] 15) evaporating the deammoniation mother liquor to obtain a salt mother liquor saturated with salt and ammonium salt; salt removal step 6);

[0023] 16) The ammonium co-saturated salt mother liquor is directly (lime and ammonium precipitation mother liquor, steam are directly mixed for heat transfer) or indirectly (lime and ammonium precipitation mother liquor are indirectly exchanged with steam for heat transfer) is steam distilled to obtain ammonia and distillation waste liquid;

[0024] 17) reacting the salt carrier solution or the salt carrier with the distillation waste liquid to obtain calcium sulfate and calcium precipitation mother liquor;

[0025] 18) The calcium precipitation mother liquor is supplied externally, or returned to step 6) and mixed with condensed water for refined salt or fresh water solution to obtain mixed brine;

[0026] 19) regularly or continuously removing a small amount of the mother liquor rich in heavy metals and COD salts from the system for drying;

[0027] 20) reacting the distilled waste liquid, gypsum and witherite to obtain calcium carbonate and decalcified mother liquor;

[0028] 21) Calcination of calcium carbonate to obtain lime and carbon dioxide;

[0029] 22) the salt carrier reacts with the calcium removal mother solution to obtain barium sulfate and barium-removing brine;

[0030] 23) supplying except the barium salt water, or returning to step 6) and mixing with the refined salt condensate or fresh water solution to obtain a mixed salt water;

[0031] 24) The ammonia and carbon dioxide obtained in the above steps are recycled and used for the double decomposition reaction in step 8).

[0032] Furthermore, the salt carrier is a refined brine obtained by treating concentrated brine obtained by reverse osmosis of seawater: concentrated brine is obtained by reverse osmosis of seawater, and the concentrated brine is nanofiltered to obtain high brine containing high concentrations of magnesium sulfate and magnesium chloride and low brine containing high concentrations of sodium chloride; the low brine and the high brine are concentrated and mechanically compressed or multi-effect evaporated to be concentrated to 25°Bé saturated brine respectively; soda ash is added to the saturated brine of the high brine to obtain a light magnesium carbonate product and magnesium-removed brine, and the magnesium-removed brine is circulated to the nanofiltration process; the saturated brine of the low brine is acidified, oxidized, blown out, absorbed by alkali solution, and distilled to obtain bromine and bromine production waste liquid; the bromine production waste liquid adopts a two-alkali method to remove calcium and magnesium ions, and caustic soda and soda ash are added to react in two steps, and solid-liquid separation is performed to obtain magnesium hydroxide, calcium carbonate and a refined brine respectively.

[0033] Furthermore, the seawater contains NaCl 20-40g / l and KCl, NaBr, CaSO4, MgSO4, MgCl2, CaCl2 and COD impurities; the concentrated brine, the high brine and the low brine contain NaCl 40-120g / l and KCl, NaBr, CaSO4, MgSO4, MgCl2, CaCl2 and COD impurities; the saturated brine, the magnesium-removing brine and the bromine production waste liquid contain NaCl 280-350g / l and KCl, NaBr, CaSO4, MgSO4, MgCl2, CaCl2 and COD impurities; the contents of each component in the primary refined brine are NaCl 300-320g / l, Na2SO4≤10g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD≤120ppm.

[0034] Furthermore, the salt carrier solution contains NaCl 10-360 g / l, Na2SO4 10-360 g / l and CaSO4, MgSO4, MgCl2, CaCl2 and COD impurities; the salt carrier contains sodium chloride, sodium sulfate and calcium sulfate, magnesium sulfate, magnesium chloride, calcium chloride and COD impurities.

[0035] Furthermore, the contents of the components in the light salt water are NaCl 180-240 g / l, Na2SO4 0.2-10 g / l, CaSO4≤0.05 ppm, MgSO4≤0.02 ppm and COD≤120 ppm).

[0036] Furthermore, the contents of the components in the first high-purity brine and the second high-purity brine are NaCl 300-320 g / l, Na2SO4≤10 g / l, CaSO4≤68 ppm, MgSO4≤50 ppm and COD≤120 ppm.

[0037] Furthermore, the contents of each component in the primary brine are NaCl 300-320 g / l, Na2SO4≤10 g / l, CaSO4≤68 ppm, MgSO4≤50 ppm and COD≤120 ppm; the contents of each component in the secondary brine are NaCl 300-320 g / l, Na2SO4≤10 g / l, CaSO4≤0.05 ppm, MgSO4≤0.02 ppm and COD≤120 ppm.

[0038] Furthermore, the contents of each component in the ammonium precipitation mother liquor are NaCl 110-220g / l, NH4Cl 180-580g / l, Na2SO4≤60g / l, CaSO4≤6g / l, MgSO4≤60g / l and COD≤80000ppm; the contents of each component in the salt precipitation mother liquor are NaCl 100-220g / l, NH4Cl 200-620g / l, Na2SO4≤60g / l, CaSO4≤6g / l, MgSO4≤60g / l and COD≤80000ppm.

[0039] Furthermore, the contents of the components in the calcium precipitation mother liquor are NaCl 100-220 g / l, NH4Cl 200-620 g / l, Na2SO4≤60 g / l, CaSO4≤6 g / l, MgSO4≤60 g / l and COD≤80000 ppm.

[0040] Furthermore, the substitute for sodium chloride in the raw material is sodium sulfate carrier calcium glauberite, decahydrated nitre, saltpeter brine; the substitute for ammonium chloride is ammonium sulfate. The substitute for hydrochloric acid produced as a byproduct of caustic soda that reacts with the heavy alkali mother liquor in this process can be purchased hydrochloric acid, the substitute for ammonium carbonate in this process can be ammonia (NH3) and carbon dioxide (CO2), and the substitute for heavy alkali mother liquor in this process can be purchased ammonium carbonate. The substitute for sodium chloride in waste brine or waste salt in this process can be sodium sulfate carrier calcium glauberite, decahydrated nitre, saltpeter brine and other inorganic salt solutions or waste residues. In this case, the substitute for ammonium chloride product in this process can be ammonium sulfate.

[0041] The beneficial effects of the present invention are:

[0042] 1) The present invention uses salt carriers (containing impurities such as sodium chloride (NaCl), sodium sulfate (Na2SO4), calcium sulfate (CaSO4), magnesium sulfate (MgSO4), magnesium chloride (MgCl2), calcium chloride (CaCl2) and COD) and witherite (containing impurities such as barium carbonate (BaCO3), calcium sulfate (CaSO4), magnesium sulfate (MgSO4)) as raw materials, and can realize the co-production of caustic soda, soda ash and barium sulfate high value-added products using brine as raw material;

[0043] 2) The heavy alkali mother liquor in the process of the present invention (containing ammonium chloride (NH4Cl), sodium chloride (NaCl), ammonium bicarbonate (NH4HCO3), ammonium carbonate ((NH4)2CO3), sodium bicarbonate (NaHCO3), sodium sulfate (Na2SO4), and ammonium sulfate ((NH4)2SO4)) is converted into ammonium brine and carbon dioxide by electrolysis with the by-product hydrochloric acid of the secondary brine. The heavy alkali mother liquor is deaminated with hydrochloric acid to solve the major problems of the long industrial chain of caustic soda by-product chlorine gas production and processing and the difficulty in selling liquid chlorine and hydrochloric acid;

[0044] 3) The present invention can alleviate the long-standing problem of salt and nitrate by-products from seawater desalination and chemical industry wastewater being difficult to find markets, thus forming a new serious environmental problem, and obtain high value-added caustic soda, soda ash, and barium sulfate products, generating huge environmental protection and circular economic benefits;

[0045] 4) The present invention can solve the serious environmental problem caused by the large amount of calcium chloride produced by the ammonia-soda process in producing soda ash, which has low added value and is difficult to utilize;

[0046] 5) The present invention has the characteristics of comprehensive utilization of seawater desalination concentrated brine, waste salt nitrate brine, waste salt nitrate mother liquor, waste salt and waste residue, and no waste residue, waste water, waste gas or waste liquid discharge, which is brand new, green, low-carbon, zero emission and good environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic flow diagram of the process for co-producing caustic soda, soda ash and barium sulfate from a salt carrier and witherite of the present invention. DETAILED DESCRIPTION

[0048] The structure of the present invention and the technical effects to be achieved will be described below with specific embodiments in combination with the accompanying drawings. However, the selected embodiments are only used for illustration and explanation and are not intended to limit the scope of the present invention.

[0049] like Figure 1 As shown, the present invention provides a process for producing caustic soda, soda ash and barium sulfate by co-producing salt carrier and witherite, comprising the following steps:

[0050] 1) Using a salt carrier solution or a salt carrier as a raw material, dilute brine and the salt carrier solution or the salt carrier are mixed and evaporated to obtain a high-purity salt product and a salt-making mother liquor;

[0051] 2) The high-purity salt product is exported, or dissolved with condensed water to obtain the first high-purity brine, and the first high-purity brine or salt carrier solution is added with caustic soda or soda ash solution to remove calcium and magnesium to obtain primary brine;

[0052] 3) The primary brine is further adsorbed and refined to obtain secondary brine;

[0053] 4) Secondary brine electrolysis to obtain liquid caustic soda product, light brine and by-product hydrochloric acid;

[0054] 5) 0-100% by weight of ammonium salt water is mixed with salt-making mother liquor and 0-100% by weight of ammonium precipitation mother liquor, and the mixture is evaporated at high temperature to obtain refined salt and salt-precipitation mother liquor;

[0055] 6) The refined salt is exported, or added to the salt water to obtain the second high purity salt water, or added to the condensed water or fresh water or calcium precipitation mother liquor or barium removal salt water to obtain the mixed salt water;

[0056] 7) adding caustic soda and soda ash solution to the mixed brine to remove calcium and magnesium to obtain refined brine;

[0057] 8) Refined brine undergoes double decomposition reaction with ammonium bicarbonate or ammonia and carbon dioxide to obtain baking soda and heavy alkali mother liquor;

[0058] 9) calcining baking soda to obtain soda ash product and carbon dioxide;

[0059] 10) 0-100% by weight of the heavy alkali mother liquor reacts with hydrochloric acid to obtain ammonium salt water and carbon dioxide;

[0060] 11) 0-100% by weight of ammonium brine goes to lime distillation;

[0061] 12) low temperature evaporation of the salt precipitation mother liquor to obtain ammonium chloride and ammonium precipitation mother liquor;

[0062] 13) 0-100% by weight of the ammonium precipitation mother liquor is circulated to the high temperature evaporation salt production process in step 5);

[0063] 14) deammoniating a heavy alkali mother liquor with a weight ratio of 0-100% at high temperature to obtain aqueous ammonia and deammoniated mother liquor;

[0064] 15) evaporating the deammoniation mother liquor to obtain a salt mother liquor saturated with salt and ammonium salt; salt removal step 6);

[0065] 16) The ammonium co-saturated salt mother liquor is directly (lime and ammonium precipitation mother liquor, steam are directly mixed for heat transfer) or indirectly (lime and ammonium precipitation mother liquor are indirectly exchanged with steam for heat transfer) is steam distilled to obtain ammonia and distillation waste liquid;

[0066] 17) reacting the salt carrier solution or the salt carrier with the distillation waste liquid to obtain calcium sulfate and calcium precipitation mother liquor;

[0067] 18) The calcium precipitation mother liquor is supplied externally, or returned to step 6) and mixed with condensed water for refined salt or fresh water solution to obtain mixed brine;

[0068] 19) regularly or continuously removing a small amount of the mother liquor rich in heavy metals and COD salts from the system for drying;

[0069] 20) reacting the distilled waste liquid, gypsum and witherite to obtain calcium carbonate and decalcified mother liquor;

[0070] 21) Calcination of calcium carbonate to obtain lime and carbon dioxide;

[0071] 22) the salt carrier reacts with the calcium removal mother solution to obtain barium sulfate and barium-removing brine;

[0072] 23) supplying except the barium salt water, or returning to step 6) and mixing with the refined salt condensate or fresh water solution to obtain a mixed salt water;

[0073] 24) The ammonia and carbon dioxide obtained in the above steps are recycled and used for the double decomposition reaction in step 8).

[0074] Several specific embodiments are listed below to illustrate the present invention in detail.

[0075] Embodiment 1 (salt nitre solution, thermal alkali route):

[0076] 1) 10m 3 Salt solution (NaCl 100g / l, Na2SO4 12g / l, CaSO4 0.10g / l, MgSO4 0.05g / l and COD 2500ppm) is used as raw material, 3.07m 3 Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and 10m 3Salt nitrate solution (NaCl 100g / l, Na2SO4 12g / l, CaSO40.10g / l, MgSO4 0.05g / l and COD 2500ppm) was mixed and evaporated (temperature 50℃) to obtain 0.98 tons of high-purity salt products (containing NaCl ≥ 96.93%, Na2SO4 ≤ 0.19%, a small amount of CaSO4, MgSO4 and COD ≤ 370ppm, H2O ≤ 3%) and 2.26m 3 Salt production mother liquor (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.25g / l and COD≤11225ppm);

[0077] 2) 0.98 tons of high-purity salt product (containing NaCl ≥ 96.93%, Na2SO4 ≤ 0.19%, a small amount of CaSO4, MgSO4 and COD ≤ 370ppm, H2O ≤ 3%) uses 2.73m 3 Condensate solution to obtain 3.07m 3 High-purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amounts of CaSO4, MgSO4 and COD ≤ 120ppm); 3.07m 3 High-purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amounts of CaSO4, MgSO4 and COD≤120ppm) is added with caustic soda (NaOH) and soda ash (Na2CO3) solutions to obtain primary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD≤120ppm);

[0078] 3) The primary brine (NaCl 310 g / l, Na2SO4≤0.60 g / l, CaSO4≤68 ppm, MgSO4≤50 ppm and COD≤120 ppm) is further adsorbed and refined to obtain secondary brine (NaCl 310 g / l, Na2SO4≤0.60 g / l, CaSO4≤0.05 ppm, MgSO4≤0.02 ppm and COD≤120 ppm);

[0079] 4) Secondary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) was electrolyzed to obtain 0.66 tons of liquid caustic soda (containing 32% NaOH) and 3.07m 3Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and by-product 0.64 tons of hydrochloric acid (containing 30% HCl);

[0080] 5)4.08m 3 Ammonium brine (NaCl 100g / l, NH4Cl 224g / l, Na2SO4 29.41g / l, small amounts of CaSO4, MgSO4 and COD) and 3.97m 3 Ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤6244ppm), 2.26m 3 The mother liquor of salt production (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.025g / l and COD≤11225ppm) was mixed and evaporated at high temperature (temperature 100℃) to obtain 0.84 tons of refined salt (containing NaCl≥82.5%, NH4Cl≤2%, Na2SO4≤14.3%, H2O≤3%, a small amount of CaSO4, MgSO4 and COD) and 4.85m 3 Salt precipitation mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4≤60g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm);

[0081] 6) 0.84 tons of refined salt (containing NaCl ≥ 82.5%, NH4Cl ≤ 2%, Na2SO4 ≤ 14.3%, H2O ≤ 3%, a small amount of CaSO4, MgSO4 and COD) is added to 2.97 tons of condensed water or fresh water to obtain 3.55 m 3 Mixed brine (NaCl 310 g / l, Na2SO4 33.80 g / l, small amounts of CaSO4, MgSO4 and COD);

[0082] 7)3.55m 3 Mixed brine (NaCl 310g / l, Na2SO4 33.80g / l, a small amount of CaSO4, MgSO4 and COD) is added with caustic soda (NaOH) and soda ash (Na2CO3) solution to remove calcium and magnesium to obtain 3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 33.80g / l, CaSO4 ≤ 68ppm, MgSO4 ≤ 50ppm and COD);

[0083] 8)3.55m3 Refined brine (NaCl 310g / l, Na2SO4 33.80g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD) and 1.38 tons of ammonium bicarbonate (containing 98.5% NH4HCO3) were subjected to double decomposition reaction (reaction time 3 hours) to obtain 1.01 tons of baking soda (containing 99% NaHCO3) and 3.55 tons of sodium bicarbonate. 3 Heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 33.80g / l, small amounts of CaSO4, MgSO4 and COD);

[0084] 9) 1.01 tons of baking soda (containing 99% NaHCO3) was calcined to obtain 0.64 tons of soda ash (containing 99% Na2CO3) product and carbon dioxide (CO2);

[0085] 10)3.55m 3 The heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 33.80g / l, a small amount of CaSO4, MgSO4 and COD) reacts with 0.64 tons of hydrochloric acid (containing 30% HCl) to obtain 4.08m 3 Ammonium brine (NaCl 100g / l, NH4Cl 224g / l, Na2SO4 29.41g / l, small amounts of CaSO4, MgSO4 and COD) and carbon dioxide (CO2);

[0086] 11)4.85m 3 The mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4≤60g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm) was evaporated at low temperature (temperature 50℃) to obtain 0.95 tons of ammonium chloride (containing NH4Cl≥96%, H2O≤3%, a small amount of NaCl, Na2SO4, (NH)2SO4, CaSO4, MgSO4 and COD) and 3.97m 3 Ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤70g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm);

[0087] 12)3.97m 3The ammonium precipitation mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤80000ppm) is circulated to the high temperature evaporation (temperature 100°C) process;

[0088] 13) The ammonia (NH3) and carbon dioxide (CO2) obtained by the above system are recycled for use in the double decomposition reaction process;

[0089] 14)0.3125m 3 The mixed salt mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤80000ppm) is dried.

[0090] Embodiment 2 (salt nitre, thermal method combined alkali route):

[0091] 1) Using 1.15 tons of saltpeter (NaCl 86.7%, Na2SO4 10.39%, H2O 3%, trace amounts of calcium sulfate (CaSO4), magnesium sulfate (MgSO4) and COD and other impurities) as raw materials, 3.07m 3 Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and 1.15 tons of saltpeter (NaCl 90%, Na2SO4 7%, H2O 3%, trace amounts of calcium sulfate (CaSO4), magnesium sulfate (MgSO4) and COD and other impurities) are mixed and evaporated (temperature 50°C) to obtain 0.98 tons of high-purity salt products (containing NaCl ≥96.93%, Na2SO4 ≤0.19%, a small amount of CaSO4, MgSO4 and COD ≤370ppm, H2O ≤3%) and 2.26 tons of 3 Salt production mother liquor (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.25g / l and COD≤11225ppm);

[0092] 2) 0.98 tons of high-purity salt product (containing NaCl ≥ 96.93%, Na2SO4 ≤ 0.19%, a small amount of CaSO4, MgSO4 and COD ≤ 370ppm, H2O ≤ 3%) uses 2.73m 3 Condensate solution to obtain 3.07m 3 High purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amount of CaSO4, MgSO4 and COD ≤ 120ppm); 3.07m 3High-purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amounts of CaSO4, MgSO4 and COD≤120ppm) is added with caustic soda (NaOH) and soda ash (Na2CO3) solutions to obtain primary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD≤120ppm);

[0093] 3) The primary brine (NaCl 310 g / l, Na2SO4≤0.60 g / l, CaSO4≤68 ppm, MgSO4≤50 ppm and COD≤120 ppm) is further adsorbed and refined to obtain secondary brine (NaCl 310 g / l, Na2SO4≤0.60 g / l, CaSO4≤0.05 ppm, MgSO4≤0.02 ppm and COD≤120 ppm);

[0094] 4) Secondary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) was electrolyzed to obtain 0.66 tons of liquid caustic soda (containing 32% NaOH) and 3.07m 3 Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and by-product 0.64 tons of hydrochloric acid (containing HCl30%);

[0095] 5)4.08m 3 Ammonium brine (NaCl 100g / l, NH4Cl 224g / l, Na2SO4 29.41g / l, small amounts of CaSO4, MgSO4 and COD) and 3.97m 3 Ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤6244ppm), 2.26m 3 The mother liquor of salt production (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.025g / l and COD≤11225ppm) was mixed and evaporated at high temperature (temperature 100℃) to obtain 0.84 tons of refined salt (containing NaCl≥82.5%, NH4Cl≤2%, Na2SO4≤14.3%, H2O≤3%, a small amount of CaSO4, MgSO4 and COD) and 4.85m 3Salt precipitation mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4≤60g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm);

[0096] 6) 0.84 tons of refined salt (containing NaCl ≥ 82.5%, NH4Cl ≤ 2%, Na2SO4 ≤ 14.3%, H2O ≤ 3%, a small amount of CaSO4, MgSO4 and COD) is added to 2.97 tons of condensed water or fresh water to obtain 3.55 m 3 Mixed brine (NaCl 310 g / l, Na2SO4 33.80 g / l, small amounts of CaSO4, MgSO4 and COD);

[0097] 7)3.55m 3 Mixed brine (NaCl 310g / l, Na2SO4 33.80g / l, a small amount of CaSO4, MgSO4 and COD) is added with caustic soda (NaOH) and soda ash (Na2CO3) solution to remove calcium and magnesium to obtain 3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 33.80g / l, CaSO4 ≤ 68ppm, MgSO4 ≤ 50ppm and COD);

[0098] 8)3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 33.80g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD) and 1.38 tons of ammonium bicarbonate (containing 98.5% NH4HCO3) were subjected to double decomposition reaction (reaction time 3 hours) to obtain 1.01 tons of baking soda (containing 99% NaHCO3) and 3.55 tons of sodium bicarbonate. 3 Heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 33.80g / l, small amounts of CaSO4, MgSO4 and COD);

[0099] 9) 1.01 tons of baking soda (containing 99% NaHCO3) was calcined to obtain 0.64 tons of soda ash (containing 99% Na2CO3) product and carbon dioxide (CO2);

[0100] 10)3.55m 3 The heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 33.80g / l, a small amount of CaSO4, MgSO4 and COD) reacts with 0.64 tons of hydrochloric acid (containing 30% HCl) to obtain 4.08m 3Ammonium brine (NaCl 100g / l, NH4Cl 224g / l, Na2SO4 29.41g / l, small amounts of CaSO4, MgSO4 and COD) and carbon dioxide (CO2);

[0101] 11)4.85m 3 The mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4≤60g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm) was evaporated at low temperature (temperature 50℃) to obtain 0.95 tons of ammonium chloride (containing NH4Cl≥96%, H2O≤3%, a small amount of NaCl, Na2SO4, (NH)2SO4, CaSO4, MgSO4 and COD) and 3.97m 3 Ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤70g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm);

[0102] 12)3.97m 3 The ammonium mother liquor (NaCl 160g / l, NH4Cl3 20g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤80000ppm) is circulated to the high temperature evaporation (temperature 100°C) process;

[0103] 13) The ammonia (NH3) and carbon dioxide (CO2) obtained by the above system are recycled for use in the double decomposition reaction process;

[0104] 14)0.3125m 3 The mixed salt mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤80000ppm) is dried.

[0105] Embodiment 3 (salt nitre solution, salt nitre, thermal alkali route):

[0106] 1) 5m 3 Saltpeter solution (NaCl 100g / l, Na2SO4 12g / l, CaSO4 0.10g / l, MgSO4 0.05g / l and COD 2500ppm) and 0.575 tons of saltpeter (NaCl 86.7%, Na2SO4 10.39%, H2O 3%, trace amounts of calcium sulfate (CaSO4), magnesium sulfate (MgSO4) and COD and other impurities) are used as raw materials, 3.07m 3Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and 5m 3 Saltpeter solution (NaCl 100g / l, Na2SO4 12g / l, CaSO4 0.10g / l, MgSO4 0.05g / l and COD 2500ppm) and 1.15 tons of saltpeter (NaCl 86.7%, Na2SO4 10.39%, H2O 3%, trace amounts of calcium sulfate (CaSO4), magnesium sulfate (MgSO4) and COD and other impurities) are mixed and evaporated (temperature 50°C) to obtain 0.98 tons of high-purity salt products (containing NaCl ≥ 96.93%, Na2SO4 ≤ 0.19%, a small amount of CaSO4, MgSO4 and COD ≤ 370ppm, H2O ≤ 3%) and 2.26 tons of 3 Salt production mother liquor (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.25g / l and COD≤11225ppm);

[0107] 2) 0.98 tons of high-purity salt product (containing NaCl ≥ 96.93%, Na2SO4 ≤ 0.19%, a small amount of CaSO4, MgSO4 and COD ≤ 370ppm, H2O ≤ 3%) uses 2.73m 3 Condensate solution to obtain 3.07m 3 High purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amount of CaSO4, MgSO4 and COD ≤ 120ppm); 3.07m 3 High-purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amounts of CaSO4, MgSO4 and COD ≤ 120ppm) was added with caustic soda (NaOH) and soda ash (Na2CO3) to obtain 3.07m 3 Primary brine (NaCl 310 g / l, Na2SO4 ≤ 0.60 g / l, CaSO4 ≤ 68 ppm, MgSO4 ≤ 50 ppm and COD ≤ 120 ppm);

[0108] 3)3.07m 3 The primary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD≤120ppm) was further purified by adsorption to obtain 3.07m 3 Secondary brine (NaCl 310 g / l, Na2SO4 ≤ 0.60 g / l, CaSO4 ≤ 0.05 ppm, MgSO4 ≤ 0.02 ppm and COD ≤ 120 ppm);

[0109] 4)3.07m 3 Secondary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) was electrolyzed to obtain 0.66 tons of liquid caustic soda (containing 32% NaOH) and 3.07m 3 Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and by-product 0.64 tons of hydrochloric acid (containing 30% HCl);

[0110] 5)4.08m 3 Ammonium brine (NaCl 100g / l, NH4Cl 224g / l, Na2SO4 29.41g / l, small amounts of CaSO4, MgSO4 and COD) and 3.97m 3 Ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤6244ppm), 2.26m 3 The mother liquor of salt production (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.025g / l and COD≤11225ppm) was mixed and evaporated at high temperature (temperature 100℃) to obtain 0.84 tons of refined salt (containing NaCl≥82.5%, NH4Cl≤2%, Na2SO4≤14.3%, H2O≤3%, a small amount of CaSO4, MgSO4 and COD) and 4.85m 3 Salt precipitation mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4≤60g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm);

[0111] 6) 0.84 tons of refined salt (containing NaCl ≥ 82.5%, NH4Cl ≤ 2%, Na2SO4 ≤ 14.3%, H2O ≤ 3%, a small amount of CaSO4, MgSO4 and COD) is added to 2.97 tons of condensed water or fresh water to obtain 3.55 m 3 Mixed brine (NaCl 310 g / l, Na2SO4 33.80 g / l, small amounts of CaSO4, MgSO4 and COD);

[0112] 7)3.55m 3Mixed brine (NaCl 310g / l, Na2SO4 33.80g / l, a small amount of CaSO4, MgSO4 and COD) is added with caustic soda (NaOH) and soda ash (Na2CO3) solution to remove calcium and magnesium to obtain 3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 33.80g / l, CaSO4 ≤ 68ppm, MgSO4 ≤ 50ppm and COD);

[0113] 8)3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 33.80g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD) and 1.38 tons of ammonium bicarbonate (containing 98.5% NH4HCO3) were subjected to double decomposition reaction (reaction time 3 hours) to obtain 1.01 tons of baking soda (containing 99% NaHCO3) and 3.55 tons of sodium bicarbonate. 3 Heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 33.80g / l, small amounts of CaSO4, MgSO4 and COD);

[0114] 9) 1.01 tons of baking soda (containing 99% NaHCO3) was calcined to obtain 0.64 tons of soda ash (containing 99% Na2CO3) product and carbon dioxide (CO2);

[0115] 10)3.55m 3 The heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 33.80g / l, a small amount of CaSO4, MgSO4 and COD) reacts with 0.64 tons of hydrochloric acid (containing 30% HCl) to obtain 4.08m 3 Ammonium brine (NaCl 100g / l, NH4Cl 224g / l, Na2SO4 29.41g / l, small amounts of CaSO4, MgSO4 and COD) and carbon dioxide (CO2);

[0116] 11)4.85m 3 The mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4≤60g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm) was evaporated at low temperature (temperature 50℃) to obtain 0.95 tons of ammonium chloride (containing NH4Cl≥96%, H2O≤3%, a small amount of NaCl, Na2SO4, (NH)2SO4, CaSO4, MgSO4 and COD) and 3.97m 3Ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤70g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm);

[0117] 12)3.97m 3 The ammonium precipitation mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤80000ppm) is circulated to the high temperature evaporation (temperature 100°C) process;

[0118] 13) The ammonia (NH3) and carbon dioxide (CO2) obtained by the above system are recycled for use in the double decomposition reaction process;

[0119] 14)0.3125m 3 The mixed salt mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤80000ppm) is dried.

[0120] Embodiment 4 (salt-nitre solution, ammonia-soda process route):

[0121] 1) 10m 3 Salt solution (NaCl 100g / l, Na2SO4 12g / l, CaSO4 0.10g / l, MgSO4 0.05g / l and COD 2500ppm) is used as raw material, 3.07m 3 Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and mixed evaporation (temperature 50℃) to obtain 0.98 tons of high-purity salt products (containing NaCl≥96.93%, Na2SO4≤0.19%, a small amount of CaSO4, MgSO4 and COD≤370ppm, H2O≤3%) and 2.26m 3 Salt production mother liquor (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.25g / l and COD≤11225ppm);

[0122] 2) 0.98 tons of high-purity salt product (containing NaCl ≥ 96.93%, Na2SO4 ≤ 0.19%, a small amount of CaSO4, MgSO4 and COD ≤ 370ppm, H2O ≤ 3%) uses 2.73m 3 Condensate solution to obtain 3.07m 3High-purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amounts of CaSO4, MgSO4 and COD ≤ 120ppm); 3.07m 3 High-purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amounts of CaSO4, MgSO4 and COD≤120ppm) is added with caustic soda (NaOH) and soda ash (Na2CO3) solutions to obtain primary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD≤120ppm);

[0123] 3) The primary brine (NaCl 310 g / l, Na2SO4≤0.60 g / l, CaSO4≤68 ppm, MgSO4≤50 ppm and COD≤120 ppm) is further adsorbed and refined to obtain secondary brine (NaCl 310 g / l, Na2SO4≤0.60 g / l, CaSO4≤0.05 ppm, MgSO4≤0.02 ppm and COD≤120 ppm);

[0124] 4) Secondary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) was electrolyzed to obtain 0.66 tons of liquid caustic soda (containing 32% NaOH) and 3.07m 3 Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and by-product 0.64 tons of hydrochloric acid (containing HCl30%);

[0125] 5)4.08m 3 Ammonium brine (NaCl 100g / l, NH4Cl 224g / l, Na2SO4 29.41g / l, small amounts of CaSO4, MgSO4 and COD) and 2.26m 3 The mother liquor of salt production (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.025g / l and COD≤11225ppm) was mixed and evaporated at high temperature (temperature 100℃) to obtain 0.99 tons of refined salt (containing NaCl≥82.5%, NH4Cl≤2%, Na2SO4≤14.3%, H2O≤3%, a small amount of CaSO4, MgSO4 and COD) and 2.21m 3Salt precipitation mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4 ≤ 60g / l, CaSO4 ≤ 1.0g / l, MgSO4 ≤ 6g / l and COD ≤ 80000ppm);

[0126] 6) 0.99 tons of refined salt (containing NaCl ≥ 82.5%, NH4Cl ≤ 2%, Na2SO4 ≤ 14.3%, H2O ≤ 3%, a small amount of CaSO4, MgSO4 and COD) for export, 3.55m 3 Calcium precipitation mother liquor (NaCl 310g / l, CaSO4 6g / l and COD ≤ 80000ppm) is 3.55m 3 Mixed brine (NaCl 310g / l, CaSO4 6g / l and COD ≤ 80000ppm);

[0127] 7)3.55m 3 Mixed brine (NaCl 310g / l, CaSO4 6g / l and COD ≤ 80000ppm) was added with caustic soda (NaOH) and soda ash (Na2CO3) solution to remove calcium and magnesium to obtain 3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 6.26g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD);

[0128] 8)3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 6.26g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD) and 1.38 tons of ammonium bicarbonate (containing 98.5% NH4HCO3) were subjected to double decomposition reaction (reaction time 3 hours) to obtain 1.01 tons of baking soda (containing 99% NaHCO3) and 3.55m 3 Heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 6.26g / l, small amounts of CaSO4, MgSO4 and COD);

[0129] 9) 1.01 tons of baking soda (containing 99% NaHCO3) was calcined to obtain 0.64 tons of soda ash (containing 99% Na2CO3) product and carbon dioxide (CO2);

[0130] 10)3.55m 3 The heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 6.26g / l, a small amount of CaSO4, MgSO4 and COD) reacts with 0.64 tons of hydrochloric acid (containing 30% HCl) to obtain 4.08m3 Ammonium brine (NaCl 100 g / l, NH4Cl 224 g / l, Na2SO4 29.41 g / l, small amounts of CaSO4, MgSO4 and COD) and carbon dioxide (CO2);

[0131] 11)2.21m 3 The mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4≤60g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm) was evaporated at low temperature (temperature 50℃) to obtain 0.35 tons of ammonium chloride (containing NH4Cl≥96%, H2O≤3%, a small amount of NaCl, Na2SO4, (NH)2SO4, CaSO4, MgSO4 and COD) and 1.81m 3 Ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤70g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm);

[0132] 12)1.81m 3 The ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤80000ppm) was distilled by steam (distillation temperature 100℃) to obtain 0.19 tons of ammonia (NH3) and 3.15m 3 Distillation waste liquid (NaCl 92g / l, CaCl2 191g / l, CaO≤4g / l, CaCO3≤20g / l, Mg(OH)2≤10g / l, SiO2≤5g / l and COD≤80000ppm, and other solid substances (calcium carbonate, magnesium hydroxide, calcium sulfate, ferric oxide and others)≤35g / l);

[0133] 13) 0.82 tons of saltpeter (NaCl 2%, Na2SO4 95%, a small amount of CaSO4, MgSO4 and COD, H2O3%) and 3.15 m 3 The waste liquid (NaCl 92g / l, CaCl2 191g / l, CaO≤4g / l, CaCO3≤20g / l, Mg(OH)2≤10g / l, SiO2≤5g / l and COD≤80000ppm, and other solid substances (calcium carbonate, magnesium hydroxide, calcium sulfate, ferric oxide and others)≤35g / l) was distilled and reacted (reaction time 0.5 hours) to obtain 0.743 tons of calcium sulfate (absolute dry 100% CaSO4) and 3.55m 3Calcium precipitation mother liquor (NaCl 310g / l, CaSO4 6g / l and COD≤80000ppm);

[0134] 14) 0.99 tons of refined salt (containing NaCl ≥ 82.5%, NH4Cl ≤ 2%, Na2SO4 ≤ 14.3%, H2O ≤ 3%, a small amount of CaSO4, MgSO4 and COD) for export, 3.55m 3 Calcium precipitation mother liquor (NaCl 310g / l, CaSO4 6g / l and COD ≤ 80000ppm) is mixed brine (NaCl 310g / l, CaSO4 6g / l and COD ≤ 80000ppm), 3.55m 3 Mixed brine (NaCl 310g / l, CaSO4 6g / l and COD ≤ 80000ppm) was added with caustic soda (NaOH) and soda ash (Na2CO3) solution to remove calcium and magnesium to obtain 3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 6.26g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD) decomposition reaction process;

[0135] 15) The ammonia (NH3) and carbon dioxide (CO2) obtained in the above system are recycled for use in the double decomposition reaction process.

[0136] Embodiment 5 (salt-salt solution, ammonia-soda method, barium sulfate route):

[0137] 1) 10m 3 Salt solution (NaCl 100g / l, Na2SO4 12g / l, CaSO4 0.10g / l, MgSO4 0.05g / l and COD 2500ppm) is used as raw material, 3.07m 3 Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and mixed evaporation (temperature 50℃) to obtain 0.98 tons of high-purity salt products (containing NaCl≥96.93%, Na2SO4≤0.19%, a small amount of CaSO4, MgSO4 and COD≤370ppm, H2O≤3%) and 2.26m 3 Salt production mother liquor (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.25g / l and COD≤11225ppm);

[0138] 2) 0.98 tons of high-purity salt product (containing NaCl ≥ 96.93%, Na2SO4 ≤ 0.19%, a small amount of CaSO4, MgSO4 and COD ≤ 370ppm, H2O ≤ 3%) uses 2.73m 3 Condensate solution to obtain 3.07m 3 High purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amount of CaSO4, MgSO4 and COD ≤ 120ppm); 3.07m 3 High-purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amounts of CaSO4, MgSO4 and COD≤120ppm) is added with caustic soda (NaOH) and soda ash (Na2CO3) solutions to obtain primary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD≤120ppm);

[0139] 3) The primary brine (NaCl 310 g / l, Na2SO4≤0.60 g / l, CaSO4≤68 ppm, MgSO4≤50 ppm and COD≤120 ppm) is further adsorbed and refined to obtain secondary brine (NaCl 310 g / l, Na2SO4≤0.60 g / l, CaSO4≤0.05 ppm, MgSO4≤0.02 ppm and COD≤120 ppm);

[0140] 4) Secondary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) was electrolyzed to obtain 0.66 tons of liquid caustic soda (containing 32% NaOH) and 3.07m 3 Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and by-product 0.64 tons of hydrochloric acid (containing 30% HCl);

[0141] 5)4.08m 3 Ammonium brine (NaCl 100g / l, NH4Cl 224g / l, Na2SO4 29.41g / l, small amounts of CaSO4, MgSO4 and COD) and 2.26m 3The mother liquor of salt production (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.025g / l and COD≤11225ppm) was mixed and evaporated at high temperature (temperature 100℃) to obtain 0.99 tons of refined salt (containing NaCl≥82.5%, NH4Cl≤2%, Na2SO4≤14.3%, H2O≤3%, a small amount of CaSO4, MgSO4 and COD) and 2.21m 3 Salt precipitation mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4 ≤ 60g / l, CaSO4 ≤ 1.0g / l, MgSO4 ≤ 6g / l and COD ≤ 80000ppm);

[0142] 6) 0.99 tons of refined salt (containing NaCl ≥ 82.5%, NH4Cl ≤ 2%, Na2SO4 ≤ 14.3%, H2O ≤ 3%, a small amount of CaSO4, MgSO4 and COD) for export, 3.55m 3 Calcium precipitation mother liquor (NaCl 310g / l, CaSO4 6g / l and COD ≤ 80000ppm) is 3.55m 3 Mixed brine (NaCl 310g / l, CaSO4 6g / l and COD ≤ 80000ppm);

[0143] 7)3.55m 3 Mixed brine (NaCl 310g / l, CaSO4 6g / l and COD ≤ 80000ppm) was added with caustic soda (NaOH) and soda ash (Na2CO3) solution to remove calcium and magnesium to obtain 3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 6.26g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD);

[0144] 8)3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 6.26g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD) and 1.38 tons of ammonium bicarbonate (containing 98.5% NH4HCO3) were subjected to double decomposition reaction (reaction time 3 hours) to obtain 1.01 tons of baking soda (containing 99% NaHCO3) and 3.55m 3 Heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 6.26g / l, small amounts of CaSO4, MgSO4 and COD);

[0145] 9) 1.01 tons of baking soda (containing 99% NaHCO3) was calcined to obtain 0.64 tons of soda ash (containing 99% Na2CO3) product and carbon dioxide (CO2);

[0146] 10)3.55m 3 The heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 6.26g / l, a small amount of CaSO4, MgSO4 and COD) reacts with 0.64 tons of hydrochloric acid (containing 30% HCl) to obtain 4.08m 3 Ammonium brine (NaCl 100 g / l, NH4Cl 224 g / l, Na2SO4 29.41 g / l, small amounts of CaSO4, MgSO4 and COD) and carbon dioxide (CO2);

[0147] 11)2.21m 3 The mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4≤60g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm) was evaporated at low temperature (temperature 50℃) to obtain 0.35 tons of ammonium chloride (containing NH4Cl≥96%, H2O≤3%, a small amount of NaCl, Na2SO4, (NH)2SO4, CaSO4, MgSO4 and COD) and 1.81m 3 Ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤70g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm);

[0148] 12)1.81m 3 The ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤80000ppm) was distilled by steam (distillation temperature 100℃) to obtain 0.19 tons of ammonia (NH3) and 3.15m 3 Distillation waste liquid (NaCl 92g / l, CaCl2 191g / l, CaO≤4g / l, CaCO3≤20g / l, Mg(OH)2≤10g / l, SiO2≤5g / l and COD≤80000ppm, and other solid substances (calcium carbonate, magnesium hydroxide, calcium sulfate, ferric oxide and others)≤35g / l);

[0149] 13) 1.11 tons of witherite (2% NaCl, 97% BaCO3, small amounts of CaSO4 and MgSO4) and 3.15 m3 The waste liquid (NaCl 92g / l, CaCl2 191g / l, CaO≤4g / l, CaCO3≤20g / l, Mg(OH)2≤10g / l, SiO2≤5g / l and COD≤80000ppm, and other solid substances (calcium carbonate, magnesium hydroxide, calcium sulfate, ferric oxide and others)≤35g / l) was distilled and reacted (reaction time 0.5 hours) to obtain 0.55 tons of calcium carbonate (absolute dry 100% CaCO3) and 3.1 ... 3 Decalcification mother liquor (NaCl99g / l, BaCl2 359g / l, trace amounts of CaSO4, MgSO4, COD and other impurities);

[0150] 14) 0.55 tons of calcium carbonate (100% CaCO3) was calcined to obtain 0.37 tons of lime (Ca(OH)2) and 0.24 tons of carbon dioxide (CO2);

[0151] 15)6.46m 3 Salt solution (NaCl 200g / l, Na2SO4 120g / l, CaSO4 0.10g / l, MgSO4 0.05g / l and COD 2500ppm) and 3.15m 3 The calcium removal mother liquor (NaCl 99g / l, BaCl2 359g / l, trace amounts of CaSO4, MgSO4 and COD and other impurities) was reacted to obtain 1.27 tons of barium sulfate (BaSO4) and 9.61m 3 Remove barium brine (NaCl 233g / l, trace amounts of CaSO4, MgSO4, COD and other impurities);

[0152] 16)9.61m 3 In addition to barium brine (NaCl 233g / l, trace amounts of CaSO4, MgSO4 and COD and other impurities);

[0153] 17) The ammonia (NH3) and carbon dioxide (CO2) obtained in the above system are recycled and used in the double decomposition reaction process.

[0154] Embodiment 6 (seawater desalination and concentrated brine, thermal process and alkali route):

[0155] 1) Reverse osmosis of seawater obtains concentrated brine; the concentrated brine is nanofiltered to obtain high brine containing high concentrations of magnesium sulfate and magnesium chloride and low brine containing high concentrations of sodium chloride. The nanofiltration low brine and high brine are concentrated by mechanical compression or multi-effect evaporation to 25°Bé saturated brine. Soda ash is added to the saturated brine of the high brine to obtain a light magnesium carbonate product and magnesium-removed brine, and the magnesium-removed brine is circulated to the nanofiltration process; the saturated brine of the low brine is acidified, oxidized, blown out, absorbed by alkaline solution, and distilled to obtain bromine and bromine production waste liquid. The bromine production waste liquid adopts the two-alkali method to remove calcium and magnesium ions. Caustic soda and soda ash are added to the bromine production waste liquid for two-step reaction, and solid-liquid separation is performed to obtain magnesium hydroxide, calcium carbonate and primary refined brine (NaCl 300g / l, Na2SO4 12g / l, CaSO4 0.10g / l, MgSO4 0.05g / l and COD 2500ppm);

[0156] 2) 3.23m 3 Salt solution (NaCl 300g / l, Na2SO4 12g / l, CaSO4 0.10g / l, MgSO4 0.05g / l and COD 2500ppm) is used as raw material, 3.07m 3 Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and 3.23m 3 Saltpeter solution (NaCl 300g / l, Na2SO4 12g / l, CaSO40.10g / l, MgSO4 0.05g / l and COD 2500ppm) was mixed and evaporated (temperature 50℃) to obtain 0.98 tons of high-purity salt products (containing NaCl ≥ 96.93%, Na2SO4 ≤ 0.19%, a small amount of CaSO4, MgSO4 and COD ≤ 370ppm, H2O ≤ 3%) and 2.26m 3 Salt production mother liquor (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.25g / l and COD≤11225ppm);

[0157] 2) 0.98 tons of high-purity salt product (containing NaCl ≥ 96.93%, Na2SO4 ≤ 0.19%, a small amount of CaSO4, MgSO4 and COD ≤ 370ppm, H2O ≤ 3%) uses 2.73m 3 Condensate solution to obtain 3.07m 3 High-purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amounts of CaSO4, MgSO4 and COD ≤ 120ppm); 3.07m 3High-purity brine (NaCl 310g / l, Na2SO4 0.60g / l, small amounts of CaSO4, MgSO4 and COD ≤ 120ppm) was added with caustic soda (NaOH) and soda ash (Na2CO3) to obtain 3.07m 3 Primary brine (NaCl 310 g / l, Na2SO4 ≤ 0.60 g / l, CaSO4 ≤ 68 ppm, MgSO4 ≤ 50 ppm and COD ≤ 120 ppm);

[0158] 3)3.07m 3 The primary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD≤120ppm) was further purified by adsorption to obtain 3.07m 3 Secondary brine (NaCl 310 g / l, Na2SO4 ≤ 0.60 g / l, CaSO4 ≤ 0.05 ppm, MgSO4 ≤ 0.02 ppm and COD ≤ 120 ppm);

[0159] 4)3.07m 3 Secondary brine (NaCl 310g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) was electrolyzed to obtain 0.66 tons of liquid caustic soda (containing 32% NaOH) and 3.07m 3 Brine (NaCl 210g / l, Na2SO4≤0.60g / l, CaSO4≤0.05ppm, MgSO4≤0.02ppm and COD≤120ppm) and by-product 0.64 tons of hydrochloric acid (containing 30% HCl);

[0160] 5)4.08m 3 Ammonium brine (NaCl 100g / l, NH4Cl 224g / l, Na2SO4 29.41g / l, small amounts of CaSO4, MgSO4 and COD) and 3.97m 3 Ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤6244ppm), 2.26m 3The mother liquor of salt production (NaCl 306g / l, Na2SO4≤54g / l, CaSO4≤0.45g / l, MgSO4≤0.025g / l and COD≤11225ppm) was mixed and evaporated at high temperature (temperature 100℃) to obtain 0.84 tons of refined salt (containing NaCl≥82.5%, NH4Cl≤2%, Na2SO4≤14.3%, H2O≤3%, a small amount of CaSO4, MgSO4 and COD) and 4.85m 3 Salt precipitation mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4≤60g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm);

[0161] 6) 0.84 tons of refined salt (containing NaCl ≥ 82.5%, NH4Cl ≤ 2%, Na2SO4 ≤ 14.3%, H2O ≤ 3%, a small amount of CaSO4, MgSO4 and COD) is added to 2.97 tons of condensed water or fresh water to obtain 3.55 m 3 Mixed brine (NaCl 310 g / l, Na2SO4 33.80 g / l, small amounts of CaSO4, MgSO4 and COD);

[0162] 7)3.55m 3 Mixed brine (NaCl 310g / l, Na2SO4 33.80g / l, a small amount of CaSO4, MgSO4 and COD) is added with caustic soda (NaOH) and soda ash (Na2CO3) solution to remove calcium and magnesium to obtain 3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 33.80g / l, CaSO4 ≤ 68ppm, MgSO4 ≤ 50ppm and COD);

[0163] 8)3.55m 3 Refined brine (NaCl 310g / l, Na2SO4 33.80g / l, CaSO4≤68ppm, MgSO4≤50ppm and COD) and 1.38 tons of ammonium bicarbonate (containing 98.5% NH4HCO3) were subjected to double decomposition reaction (reaction time 3 hours) to obtain 1.01 tons of baking soda (containing 99% NaHCO3) and 3.55 tons of sodium bicarbonate. 3 Heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 33.80g / l, small amounts of CaSO4, MgSO4 and COD);

[0164] 9) 1.01 tons of baking soda (containing 99% NaHCO3) was calcined to obtain 0.64 tons of soda ash (containing 99% Na2CO3) product and carbon dioxide (CO2);

[0165] 10)3.55m 3 The heavy alkali mother liquor (NaCl 115g / l, NH4Cl 178g / l, NH4HCO3 118g / l, Na2SO4 33.80g / l, a small amount of CaSO4, MgSO4 and COD) reacts with 0.64 tons of hydrochloric acid (containing 30% HCl) to obtain 4.08m 3 Ammonium brine (NaCl 100g / l, NH4Cl 224g / l, Na2SO4 29.41g / l, small amounts of CaSO4, MgSO4 and COD) and carbon dioxide (CO2);

[0166] 11)4.85m 3 The mother liquor (NaCl 131g / l, NH4Cl 414g / l, Na2SO4≤60g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm) was evaporated at low temperature (temperature 50℃) to obtain 0.95 tons of ammonium chloride (containing NH4Cl≥96%, H2O≤3%, a small amount of NaCl, Na2SO4, (NH)2SO4, CaSO4, MgSO4 and COD) and 3.97m 3 Ammonium mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤70g / l, CaSO4≤1.0g / l, MgSO4≤6g / l and COD≤80000ppm);

[0167] 12)3.97m 3 The ammonium precipitation mother liquor (NaCl 160g / l, NH4Cl 320g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤80000ppm) is circulated to the high temperature evaporation (temperature 100°C) process;

[0168] 13) The ammonia (NH3) and carbon dioxide (CO2) obtained by the above system are recycled for use in the double decomposition reaction process;

[0169] 14)0.3125m 3 The mixed salt mother liquor (NaCl 160g / l, NH4Cl3 20g / l, Na2SO4≤54g / l, CaSO4≤0.2g / l, MgSO4≤6g / l and COD≤80000ppm) is dried.

[0170] The present invention is defined by the claims, but based on this, a person skilled in the art may make various obvious changes or modifications, which should be within the main spirit and scope of protection of the present invention.

Claims

1. A process for producing caustic soda, soda ash and barium sulfate by using a salt carrier and witherite, characterized in that: The following steps are involved: 1) Using salt carrier solution or salt carrier as raw material, light brine and salt carrier solution or salt carrier are mixed and evaporated to obtain high-purity salt product and salt-making mother liquor; the salt carrier is a refined brine obtained by reverse osmosis of seawater to obtain concentrated brine; the salt carrier is a refined brine obtained by reverse osmosis of seawater to obtain concentrated brine: seawater reverse osmosis obtains concentrated brine, and the concentrated brine is nanofiltered to obtain high brine containing high concentrations of magnesium sulfate and magnesium chloride and low brine containing high concentrations of sodium chloride; the low brine and the high brine are concentrated and mechanically compressed or multi-effect evaporation is respectively concentrated to 25°Bé saturated brine; soda ash is added to the saturated brine of the high brine to obtain a light magnesium carbonate product and magnesium-removed brine, and the magnesium-removed brine is circulated to the nanofiltration process; the saturated brine of the low brine is acidified, oxidized, blown out, absorbed by alkali solution, and distilled to obtain bromine and bromine-making waste liquid; the bromine-making waste liquid adopts a two-alkali method to remove calcium and magnesium ions, and caustic soda and soda ash are added to react in two steps, and solid-liquid separation is performed to obtain magnesium hydroxide, calcium carbonate and a refined brine respectively; 2) The high-purity salt product is exported, or dissolved with condensed water to obtain the first high-purity brine, and the first high-purity brine or salt carrier solution is added with caustic soda or soda ash solution to remove calcium and magnesium to obtain primary brine; 3) The primary brine is further adsorbed and refined to obtain secondary brine; 4) Secondary brine electrolysis to obtain liquid caustic soda product, light brine and by-product hydrochloric acid; 5) 0-100% by weight of ammonium salt water is mixed with salt-making mother liquor and 0-100% by weight of ammonium precipitation mother liquor, and the mixture is evaporated at high temperature to obtain refined salt and salt-precipitation mother liquor; 6) The refined salt is exported, or added to the salt water to obtain the second high purity salt water, or added to the condensed water or fresh water or calcium precipitation mother liquor or barium removal salt water to obtain the mixed salt water; 7) adding caustic soda and soda ash solution to the mixed brine to remove calcium and magnesium to obtain refined brine; 8) Refined brine undergoes double decomposition reaction with ammonium bicarbonate or ammonia and carbon dioxide to obtain baking soda and heavy alkali mother liquor; 9) calcining baking soda to obtain soda ash product and carbon dioxide; 10) 0-100% by weight of the heavy alkali mother liquor reacts with hydrochloric acid to obtain ammonium salt water and carbon dioxide; 11) 0-100% by weight of ammonium brine goes to lime distillation; 12) low temperature evaporation of the salt precipitation mother liquor to obtain ammonium chloride and ammonium precipitation mother liquor; 13) 0-100% by weight of the ammonium precipitation mother liquor is circulated to the high temperature evaporation salt production process in step 5); 14) deammoniating a heavy alkali mother liquor with a weight ratio of 0-100% at high temperature to obtain aqueous ammonia and deammoniated mother liquor; 15) evaporating the deammoniation mother liquor to obtain a salt mother liquor saturated with salt and ammonium salt; salt removal step 6); 16) The ammonium co-saturated mother liquor, the ammonium separation mother liquor, and the lime are directly mixed with steam for heat transfer, or the ammonium co-saturated mother liquor, the ammonium separation mother liquor, and the lime are indirectly exchanged with steam for heat transfer, and ammonia and distillation waste liquid are obtained by steam distillation; 17) reacting the salt carrier solution or the salt carrier with the distillation waste liquid to obtain calcium sulfate and calcium precipitation mother liquor; 18) The calcium precipitation mother liquor is supplied externally, or returned to step 6) and mixed with condensed water for refined salt or fresh water solution to obtain mixed brine; 19) regularly or continuously removing a small amount of the ammonium precipitation mother liquor rich in heavy metals and COD in step 12) from the system for drying; 20) reacting the distilled waste liquid, gypsum and witherite to obtain calcium carbonate and decalcified mother liquor; 21) Calcination of calcium carbonate to obtain lime and carbon dioxide; 22) the salt carrier reacts with the calcium removal mother solution to obtain barium sulfate and barium-removing brine; 23) supplying except the barium salt water, or returning to step 6) and mixing with the refined salt condensate or fresh water solution to obtain a mixed salt water; 24) The ammonia and carbon dioxide obtained in the above steps are recycled and used for the double decomposition reaction in step 8).

2. The process for co-producing caustic soda, soda ash and barium sulfate from salt carrier and witherite according to claim 1, characterized in that: The seawater contains 20-40 g / l of NaCl and impurities of KCl, NaBr, CaSO4, MgSO4, MgCl2, CaCl2 and COD; the concentrated brine, the high brine and the low brine contain 40-120 g / l of NaCl and impurities of KCl, NaBr, CaSO4, MgSO4, MgCl2, CaCl2 and COD; the saturated brine, the magnesium-removing brine and the bromine production waste liquid contain 280-350 g / l of NaCl and impurities of KCl, NaBr, CaSO4, MgSO4, MgCl2, CaCl2 and COD; the contents of each component in the primary refined brine are NaCl 300-320 g / l, Na2SO4≤10 g / l, CaSO4≤68 ppm, MgSO4≤50 ppm and COD≤120 ppm.

3. The process for co-producing caustic soda, soda ash and barium sulfate from salt carrier and witherite according to claim 1, characterized in that: The salt carrier solution contains NaCl 10-360g / l, Na2SO4 10-360g / l and CaSO4, MgSO4, MgCl2, CaCl2 and COD impurities; the salt carrier contains sodium chloride, sodium sulfate and calcium sulfate, magnesium sulfate, magnesium chloride, calcium chloride and COD impurities.

4. The process for co-producing caustic soda, soda ash and barium sulfate from salt carrier and witherite according to claim 1, characterized in that: The contents of the components in the light salt water are NaCl 180-240 g / l, Na2SO4 0.2-10 g / l, CaSO4≤0.05 ppm, MgSO4≤0.02 ppm and COD≤120 ppm).

5. The process for co-producing caustic soda, soda ash and barium sulfate from salt carrier and witherite according to claim 1, characterized in that: The contents of the components in the first high-purity brine and the second high-purity brine are NaCl 300-320 g / l, Na2SO4≤10 g / l, CaSO4≤68 ppm, MgSO4≤50 ppm and COD≤120 ppm.

6. The process for co-producing caustic soda, soda ash and barium sulfate from salt carrier and witherite according to claim 1, characterized in that: The contents of the components in the primary brine are NaCl 300-320 g / l, Na2SO4≤10 g / l, CaSO4≤68 ppm, MgSO4≤50 ppm and COD≤120 ppm; the contents of the components in the secondary brine are NaCl 300-320 g / l, Na2SO4≤10 g / l, CaSO4≤0.05 ppm, MgSO4≤0.02 ppm and COD≤120 ppm.

7. The process for co-producing caustic soda, soda ash and barium sulfate from salt carrier and witherite according to claim 1, characterized in that: The contents of the components in the ammonium precipitation mother liquor are NaCl 110-220 g / l, NH4Cl 180-580 g / l, Na2SO4≤60 g / l, CaSO4≤6 g / l, MgSO4≤60 g / l and COD≤80000 ppm; the contents of the components in the salt precipitation mother liquor are NaCl 100-220 g / l, NH4Cl 200-620 g / l, Na2SO4≤60 g / l, CaSO4≤6 g / l, MgSO4≤60 g / l and COD≤80000 ppm.

8. The process for co-producing caustic soda, soda ash and barium sulfate from salt carrier and witherite according to claim 1, characterized in that: The contents of the components in the calcium precipitation mother liquor are NaCl 100-220 g / l, NH4Cl 200-620 g / l, Na2SO4≤60 g / l, CaSO4≤6 g / l, MgSO4≤60 g / l and COD≤80000 ppm.

9. The process for co-producing caustic soda, soda ash and barium sulfate from salt carrier and witherite according to claim 1, characterized in that: The substitutes for sodium chloride in the raw materials are sodium sulfate carriers such as calcium glauberite, decahydrated nitre, and saltpeter brine; the substitute for ammonium chloride is ammonium sulfate.

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