A method for preparing soda ash or baking soda by utilizing concentrated brine from coal chemical industry

Abstract

The present invention provides a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine, the method comprising: removing harmful impurities from coal chemical concentrated brine by induced crystallization, acidolysis and thermally stimulated oxidation to obtain mixed salt and mixed salt mother liquor; separating sodium nitrate from the mixed salt mother liquor, double decomposing and evaporating the mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor to obtain sodium sulfate mixed crystals and ammonium chloride enriched solution; obtaining ammonium chloride and ammonium chloride mother liquor from the ammonium chloride enriched solution; dissolving and salting out the sodium sulfate mixed crystals and sodium bicarbonate mother liquor to obtain a saturated sodium sulfate solution and crude ammonium sulfate; obtaining ammonium sulfate and ammonium sulfate mother liquor from crude ammonium sulfate; double decomposing the saturated sodium sulfate solution and ammonium bicarbonate to obtain a sodium bicarbonate product and a sodium bicarbonate mother liquor. The method provided by the present invention obtains baking soda and co-produces high-value ammonium salt products from coal chemical concentrated brine in a short process and at a low cost, thereby realizing the reduction, harmlessness and resource utilization of coal chemical wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of coal chemical wastewater treatment, and relates to a method for treating coal chemical concentrated brine, and in particular to a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine. Background Art

[0002] In the production process of coal chemical industry, such as gasification, liquefaction and coking, a large amount of wastewater is usually generated. The main components of coal chemical wastewater are sodium sulfate and sodium chloride, which is called coal chemical brine. It also includes organic pollutants such as phenols, benzene, polycyclic aromatic hydrocarbons, heterocyclic compounds, and inorganic pollutants such as nitrates, potassium, fluorine, silicon, calcium, magnesium, and cyanide. Coal chemical brine has the characteristics of complex composition, high concentration of pollutants, difficult degradation, and high salinity, which has become one of the core environmental problems of coal chemical industry.

[0003] CN116354541A discloses a zero-emission high-concentration brine resource utilization and processing system for coal chemical industry. The system performs pretreatment by decarbonization, ozone advanced oxidation, silicon removal, and ultrafiltration, and then obtains sodium sulfate and sodium chloride products by nanofiltration evaporation and salt separation. However, the processing flow of this method is long and the investment and maintenance costs of the ozone oxidation nanofiltration salt separation section are high, and the added value of the obtained sodium sulfate and sodium chloride products is low.

[0004] CN113929117A discloses a system and method for preparing sodium bicarbonate and co-producing nitrogen fertilizer by resource utilization of coal chemical concentrated brine, wherein the method comprises the following steps: evaporating and concentrating the coal chemical concentrated brine, removing impurities, performing double decomposition with carbon dioxide, ammonia or ammonium carbonate to obtain baking soda, performing ammonia evaporation on the sodium bicarbonate mother liquor, and then evaporating and crystallizing the mother liquor to obtain ammonium sulfate and filtrate 2, evaporating filtrate 2 again to obtain impurity salts and filtrate 3, and cooling and crystallizing filtrate 3 to obtain ammonium chloride. The method requires three high-temperature evaporation processes, has high energy consumption, and the loss of ammonia in the ammonia evaporation process is also relatively serious. Chloride ions circulate in the entire system, and the equipment material requirements are high and the investment cost is increased.

[0005] CN113636576A, CN116161683A, etc. disclose a method for preparing sodium bicarbonate and nitrogen fertilizer using coal chemical miscellaneous salt as raw material, wherein the coal chemical miscellaneous salt is first subjected to double decomposition reaction with ammonium bicarbonate or by passing ammonia and carbon dioxide to obtain sodium bicarbonate, and then the ammonium salt is subjected to salt separation treatment. This method mainly has the following problems: when sodium sulfate and sodium chloride react with ammonium bicarbonate or by passing ammonia and carbon dioxide, sodium sulfate is converted into solid particles due to the salting-out effect of sodium chloride on sodium sulfate, making the conversion of sodium sulfate difficult and the purity of sodium bicarbonate low; at the same time, when ammonium chloride is separated from ammonium sulfate, due to the influence of sodium sulfate and ammonium sulfate, ammonium chloride is crystallized together with sodium sulfate and ammonium sulfate double salt during the crystallization process, thereby failing to achieve the separation of ammonium chloride and ammonium sulfate.

[0006] The existing resource utilization process for coal chemical concentrated brine often has problems such as low resource added value, low raw material utilization rate, complicated process or insufficient product quality. Therefore, based on the above problems, the present invention provides a method for preparing soda ash or baking soda from coal chemical concentrated brine. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine, so as to realize resource utilization of coal chemical concentrated brine and prepare high-value products of baking soda or soda ash and nitrogen fertilizer through a short-process technology.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine, the method comprising the following steps:

[0010] (1) using a silicon-fluoride removal agent to carry out a crystallization reaction on coal chemical concentrated brine under the action of a crystal seed, using an acid and a flocculant to carry out an acid hydrolysis precipitation reaction, and using an oxidant to carry out a thermally excited oxidation reaction, wherein the crystallization reaction, the acid hydrolysis precipitation reaction, and the thermally excited oxidation reaction are not in any particular order, and after the reaction is completed, a purified mother liquor, a silicon-fluoride precipitate, and an acid hydrolysis precipitate are finally obtained;

[0011] (2) evaporating and crystallizing the purified mother liquor to obtain a mixed salt and a mixed salt mother liquor after solid-liquid separation;

[0012] (3) mixing the mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor for double decomposition and evaporation, evaporating the water introduced by the ammonium sulfate mother liquor, and obtaining sodium sulfate mixed crystals and ammonium chloride enriched liquid after solid-liquid separation;

[0013] The mixed salt mother liquor is cooled and crystallized, and solid-liquid separation is performed to obtain a sodium nitrate product;

[0014] (4) cooling and crystallizing the ammonium chloride enriched solution, and obtaining an ammonium chloride product and an ammonium chloride mother liquor after solid-liquid separation, wherein the ammonium chloride mother liquor is recycled to step (3);

[0015] The sodium sulfate mixed crystals are mixed with a sodium bicarbonate mother liquor to be dissolved and salted out, and a saturated sodium sulfate solution and crude ammonium sulfate are obtained after solid-liquid separation;

[0016] (5) mixing the crude ammonium sulfate with the ammonium sulfate evaporation condensate for evaporation and crystallization, collecting the volatile components generated during the evaporation and crystallization process, condensing the ammonium sulfate evaporation condensate, and recycling it to the evaporation and crystallization; and performing solid-liquid separation after evaporation and crystallization to obtain an ammonium sulfate product and an ammonium sulfate mother liquor, wherein the ammonium sulfate mother liquor is recycled to step (3);

[0017] The saturated sodium sulfate solution is subjected to double decomposition reaction with ammonium bicarbonate solid or a mixed gas of ammonia and carbon dioxide to obtain a sodium bicarbonate product and a sodium bicarbonate mother liquor after solid-liquid separation. The sodium bicarbonate mother liquor is recycled to step (4).

[0018] In the present invention, the sodium carbonate product is obtained by calcining the sodium bicarbonate product.

[0019] In the present invention, the remaining mother liquor after cooling and crystallization of the mixed salt mother liquor in step (3) is dried to obtain the impure salt.

[0020] The resource utilization method of coal chemical concentrated brine provided by the present invention adopts a short process and low-cost method to remove impurities such as fluorine, silicon, and organic matter therein, overcomes the shortcomings of traditional organic matter removal methods such as long time, complicated procedures, and low efficiency, obtains pure crystalline mixed salt, and then directly prepares sodium bicarbonate through a circulating salt separation process and co-produces high-value products such as ammonium sulfate and ammonium chloride, and separates a sodium nitrate product from the mixed salt mother liquor, overcomes the low-value products of sodium sulfate and sodium chloride obtained by direct salt separation of traditional coal chemical wastewater, overcomes the problems of high raw material requirements, easy damage of membranes, and high costs in membrane salt separation, is easy to implement the industrial process, and has high purity. The total alkali content of the sodium bicarbonate product meets the requirements of industrial sodium bicarbonate-III in GB / T1606-2008, the total alkali content of the sodium carbonate product meets the requirements of industrial sodium carbonate qualified products in GB / T 210-2022, the nitrogen content of the ammonium chloride product meets the requirements of agricultural ammonium chloride qualified products in GB / T2946-2018, and the nitrogen content of the ammonium sulfate product meets the requirements of GB / T 535-2020 The requirements of medium fertilizer grade ammonium sulfate-Class I qualified products all meet the requirements of industrial qualified products, achieving the reduction, harmlessness and resource utilization of coal chemical wastewater.

[0021] In the coal chemical concentrated brine, the mass ratio of sodium sulfate to sodium chloride is >1.

[0022] The impurity composition of the coal chemical concentrated brine includes: carbonate ≤0.8%, bicarbonate ≤0.75%, fluorine ≤0.06%, silicon ≤0.02%, and COD ≤0.95%.

[0023] Preferably, the seed crystals in step (1) include any one of cryolite, fluoride, iron oxide or silicon dioxide, or a combination of at least two of them. Typical but non-limiting combinations include a combination of cryolite and fluoride, a combination of fluoride and iron oxide, a combination of iron oxide and silicon dioxide, a combination of cryolite, fluoride and iron oxide, a combination of fluoride, iron oxide and silicon dioxide, or a combination of cryolite, fluoride, iron oxide and silicon dioxide.

[0024] Exemplarily, the fluoride includes any one of sodium fluoride, calcium fluoride, calcium fluorosilicate or calcium fluorophosphate, or a combination of at least two thereof.

[0025] Exemplarily, the iron oxide includes ferric oxide and / or ferrous oxide.

[0026] Preferably, the silicon-fluoride removal agent in step (1) comprises any one of polyaluminium chloride, polyaluminium sulfate, ferric sulfate, sodium aluminate or polyferric sulfate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of polyaluminium chloride and polyaluminium sulfate, a combination of polyaluminium sulfate and ferric sulfate, a combination of sodium aluminate and polyferric sulfate, a combination of polyaluminium chloride, polyaluminium sulfate and ferric sulfate, or a combination of polyaluminium sulfate, ferric sulfate, sodium aluminate and polyferric sulfate.

[0027] Preferably, the amount of the silicon-fluorine removal agent added in step (1) is 500-6000 mg / L based on coal chemical concentrated brine, for example, it can be 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, 2500 mg / L, 3000 mg / L, 3500 mg / L, 4000 mg / L, 4500 mg / L, 5000 mg / L, 5500 mg / L or 6000 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, the pH value of the crystallization reaction in step (1) is 4-9, for example, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5 or 9, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the temperature of the crystallization reaction in step (1) is 20-90°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, the acid in step (1) comprises any one of sulfuric acid, hydrochloric acid or nitric acid, or a combination of at least two of them. Typical but non-limiting combinations include a combination of sulfuric acid and hydrochloric acid, a combination of hydrochloric acid and nitric acid, a combination of sulfuric acid and nitric acid, or a combination of sulfuric acid, hydrochloric acid and nitric acid.

[0031] Preferably, the flocculant in step (1) comprises polyacrylamide and / or sodium polyacrylate.

[0032] Preferably, the dosage of the flocculant in step (1) is 5-200 mg / L based on coal chemical concentrated brine, for example, 5 mg / L, 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L or 200 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the pH value of the acid hydrolysis precipitation reaction in step (1) is 0.5-5, for example, it can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the oxidant in step (1) comprises any one of air, ozone, hydrogen peroxide, ammonium persulfate or sodium persulfate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of air and ozone, a combination of hydrogen peroxide and ammonium persulfate, a combination of ammonium persulfate and sodium persulfate, a combination of ozone, hydrogen peroxide and ammonium persulfate, or a combination of air, ozone, hydrogen peroxide, ammonium persulfate and sodium persulfate.

[0035] Preferably, the mass ratio of the oxidant in step (1) to the COD in the coal chemical concentrated brine is (0.5-15):1, for example, it can be 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the temperature of the thermally excited oxidation reaction in step (1) is 50-100°C, for example, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the time of the thermally excited oxidation reaction in step (1) is 0.5-4 h, for example, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h or 4 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the temperature for evaporating and crystallizing the purified mother liquor in step (2) is 70-100°C, for example, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Preferably, during the evaporation crystallization process in step (2), the pH is maintained at ≥ 2, for example, it can be 2, 4, 5, 6, 8, 10, 12 or 14, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, the mass percentage of sodium nitrate in the mixed salt mother liquor of step (2) is in the range of 20-60%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, in the mixing of the mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor in step (3), the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor is controlled to be (0.6-1.5):1, for example, it can be 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the temperature of the double decomposition and evaporation in step (3) is 60-110°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C or 110°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, the terminal temperature of the mixed salt mother liquor cooling crystallization in step (3) is 0-40°C, for example, it can be 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C or 40°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] Preferably, the terminal temperature of the ammonium chloride enriched solution during cooling and crystallization in step (4) is 10-40°C, for example, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C or 40°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] Preferably, the temperature of dissolving and salting out in step (4) is 10-45°C, for example, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C or 45°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] Preferably, the temperature of the evaporation crystallization in step (5) is 70-100°C, for example, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] Preferably, in the double decomposition reaction of step (5), the molar ratio of bicarbonate to sodium ion in the control system is (0.9-1.3):1, for example, it can be 0.9:1, 1.0:1, 1.1:1, 1.2:1 or 1.3:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] Preferably, the temperature of the metathesis reaction in step (5) is 30-60°C, for example, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0049] As a preferred technical solution of the method provided by the present invention, the method comprises the following steps:

[0050] (1) using a desiliconizing and fluorinating agent to carry out a crystallization reaction on the coal chemical concentrated brine under the action of a crystal seed, wherein the amount of the desiliconizing and fluorinating agent is 500-6000 mg / L based on the coal chemical concentrated brine, the pH value of the crystallization reaction is 4-9, the temperature of the crystallization reaction is 20-90°C, and solid-liquid separation is carried out after the crystallization reaction; using an acid and a flocculant to carry out an acid hydrolysis precipitation reaction on the coal chemical concentrated brine, wherein the amount of the flocculant is 5-200 mg / L based on the coal chemical concentrated brine, the pH value of the acid hydrolysis precipitation reaction is 0.5-5, and flotation separation is carried out after the acid hydrolysis reaction is completed; using an oxidant to carry out a thermally excited oxidation reaction on the coal chemical concentrated brine, wherein the mass ratio of the oxidant to the COD in the coal chemical concentrated brine is (0.5-15):1, the temperature of the thermally excited oxidation reaction is 50-100°C, and the time of the thermally excited oxidation reaction is 0.5-4h. The crystallization reaction, acid hydrolysis precipitation reaction and thermally excited oxidation reaction are not in any particular order, and after the reaction is completed, a purified mother liquor, a silicon-fluorine precipitate and an acid hydrolysis precipitate are finally obtained;

[0051] (2) evaporating and crystallizing the purified mother liquor at 70-100° C. to obtain a mixed salt and a mixed salt mother liquor after solid-liquid separation;

[0052] (3) mixing the mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor, controlling the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor to be (0.6-1.5):1, performing double decomposition and evaporation at 60-110° C., evaporating the water introduced by the ammonium sulfate mother liquor, and obtaining sodium sulfate mixed crystals and ammonium chloride enriched liquid after solid-liquid separation;

[0053] The mass percentage of sodium nitrate in the mixed salt mother liquor is in the range of 20-60%, the mixed salt mother liquor is cooled and crystallized to an end point temperature of 0-40° C. to obtain a sodium nitrate product, and the remaining mother liquor after cooling and crystallization is dried to obtain impurity salt;

[0054] (4) cooling and crystallizing the ammonium chloride enriched solution to an end point temperature of 10-40° C., and obtaining an ammonium chloride product and an ammonium chloride mother liquor after solid-liquid separation, wherein the ammonium chloride mother liquor is reused in step (3);

[0055] The sodium sulfate mixed crystals are mixed with a sodium bicarbonate mother liquor at 10-45° C. for dissolution and salting out, and a saturated sodium sulfate solution and crude ammonium sulfate are obtained after solid-liquid separation;

[0056] (5) mixing the crude ammonium sulfate with the ammonium sulfate evaporation condensate at 70-100° C. for evaporation and crystallization, collecting the volatile components generated during the evaporation and crystallization process, condensing the ammonium sulfate evaporation condensate, and recycling it to the evaporation and crystallization, and performing solid-liquid separation after evaporation and crystallization to obtain an ammonium sulfate product and an ammonium sulfate mother liquor, and recycling the ammonium sulfate mother liquor to step (3);

[0057] The saturated sodium sulfate solution is subjected to a double decomposition reaction with solid ammonium bicarbonate or a mixed gas of ammonia and carbon dioxide, the molar ratio of bicarbonate to sodium ion in the system is controlled to be (0.9-1.3):1, the temperature of the double decomposition reaction is 30-60° C., and a sodium bicarbonate product and a sodium bicarbonate mother liquor are obtained after solid-liquid separation, and the sodium bicarbonate mother liquor is reused in step (4).

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The method provided by the present invention adopts a short-process and low-cost method to remove impurities from coal chemical concentrated brine and utilize it as resources to produce baking soda or soda ash and co-produce high-value products such as ammonium chloride and ammonium sulfate, thereby achieving the reduction, harmlessness and resource utilization of coal chemical wastewater. The obtained product has high purity and meets the requirements of industrial qualified products. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a process flow chart of the method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine provided in Example 1. DETAILED DESCRIPTION

[0061] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0062] Example 1

[0063] This embodiment provides a Figure 1 The method for preparing soda ash or baking soda by resource utilization of concentrated brine from coal chemical industry comprises the following steps:

[0064] (1) After adding sodium carbonate and sodium hydroxide to coal chemical concentrated brine to remove calcium and magnesium, seed cryolite and polyaluminium sulfate as a desiliconizing and defluorinating agent are added thereto to remove silicon and fluorine. The amount of desiliconizing and defluorinating agent added is 4000 mg / L. The pH value during desiliconizing and defluorinating is 6.5 and the temperature is 40°C. After filtering, a desiliconizing and defluorinating purified liquid and a desiliconizing and defluorinating precipitate are obtained;

[0065] (2) adding sulfuric acid to the obtained purified liquid for silicon and fluorine removal to adjust the pH to 3, and adding cationic polyacrylamide (CPAM-1200) as a flocculant in an amount of 40 mg / L, and then flotation separation is performed to obtain an acid hydrolysis mother liquor and an acid hydrolysis precipitate;

[0066] (3) adding sodium persulfate as an oxidant to the obtained acid hydrolysis mother liquor, wherein the mass ratio of the oxidant to the COD in the acid hydrolysis mother liquor is 8:1, and controlling the temperature to 90°C for a thermally excited oxidation reaction for 2 hours. After the reaction is completed, a purified mother liquor is obtained;

[0067] (4) evaporating and crystallizing the obtained purified mother liquor at 85° C., maintaining the solution pH value greater than or equal to 2 during evaporation and crystallization, and adding sodium hydroxide to adjust the pH value when the pH value is lower than 2 to prevent the residual oxidant from oxidizing the chloride ions, thereby obtaining a mixed salt of sodium sulfate and sodium chloride and a mixed salt mother liquor, wherein the mass percentage of sodium nitrate in the mixed salt mother liquor is 30%;

[0068] (5) mixing the obtained mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor, controlling the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor to be 1:1, performing double decomposition and evaporation, the temperature of double decomposition and evaporation is 85° C., evaporating the water introduced by the ammonium sulfate mother liquor, and then filtering to obtain sodium sulfate mixed crystals and ammonium chloride hot solution;

[0069] The obtained mixed salt mother liquor is cooled and crystallized to 30°C, filtered to obtain the sodium nitrate product, and the remaining mother liquor after filtration is dried to obtain the impurity salt;

[0070] (6) cooling the hot ammonium chloride solution obtained in step (5) to 30° C. for crystallization, filtering to obtain an ammonium chloride product and an ammonium chloride mother liquor, and the ammonium chloride mother liquor is reused in step (5);

[0071] The sodium sulfate mixed crystals obtained in step (5) are mixed with sodium bicarbonate mother liquor at 30°C for dissolution and salting out, and a saturated sodium sulfate solution and crude ammonium sulfate crystals (Na2SO4·(NH4)2SO4·4H2O) are obtained after filtration;

[0072] (7) mixing the crude ammonium sulfate crystals obtained in step (6) with the ammonium sulfate evaporation condensate for evaporation crystallization at a temperature of 90° C. collecting the volatile components generated during the evaporation crystallization process, condensing the ammonium sulfate evaporation condensate, and recycling it to the evaporation crystallization of the crude ammonium sulfate crystals. After filtering, an ammonium sulfate product and an ammonium sulfate mother liquor are obtained, and the ammonium sulfate mother liquor is recycled to step (5);

[0073] The saturated sodium sulfate solution obtained in step (6) is added to solid ammonium bicarbonate for double decomposition reaction. The amount of ammonium bicarbonate added is controlled so that the molar ratio of bicarbonate to sodium in the solution system is 1:1. The temperature of the double decomposition reaction is 40° C. After filtration, a sodium bicarbonate product and a sodium bicarbonate mother liquor are obtained. The sodium bicarbonate mother liquor is reused in step (6). The sodium bicarbonate product is calcined to obtain a sodium carbonate product.

[0074] Example 2

[0075] This embodiment provides a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine, the method comprising the following steps:

[0076] (1) After adding sodium carbonate and sodium hydroxide to coal chemical concentrated brine to remove calcium and magnesium, sodium fluoride seed and polyferric sulfate as a silicon and fluorine removal agent are added thereto, the amount of silicon and fluorine removal agent added is 5000 mg / L, the pH value during silicon and fluorine removal is 7.5, the temperature is 40°C, and after filtering, silicon and fluorine removal purified liquid and silicon and fluorine precipitate are obtained;

[0077] (2) Adding hydrochloric acid to the obtained silicon-fluoride-removing purified liquid to adjust the pH to 3, and adding cationic polyacrylamide (CPAM-1200) as a flocculant, the amount of which is 40 mg / L, and then performing flotation separation to obtain an acid hydrolysis mother liquor and an acid hydrolysis precipitate;

[0078] (3) adding ozone as an oxidant to the obtained acid hydrolysis mother liquor, wherein the mass ratio of the oxidant to the COD in the acid hydrolysis mother liquor is 10:1, and controlling the temperature to 95°C for a thermally excited oxidation reaction for 3 hours. After the reaction is completed, a purified mother liquor is obtained;

[0079] (4) evaporating and crystallizing the obtained purified mother liquor at 100° C., maintaining the solution pH at a value greater than or equal to 2 during the evaporation and crystallization, and adding sodium hydroxide to adjust the pH when the pH is lower than 2 to prevent the residual oxidant from oxidizing the chloride ions, thereby obtaining a mixed salt of sodium sulfate and sodium chloride and a mixed salt mother liquor, wherein the mass percentage of sodium nitrate in the mixed salt mother liquor is 30%;

[0080] (5) mixing the obtained mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor, controlling the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor to be 1:1, performing double decomposition and evaporation, the temperature of double decomposition and evaporation is 100° C., evaporating the water introduced by the ammonium sulfate mother liquor, and then filtering to obtain sodium sulfate mixed crystals and ammonium chloride hot solution;

[0081] The obtained mixed salt mother liquor is cooled and crystallized to 40°C, filtered to obtain the sodium nitrate product, and the remaining mother liquor after filtration is dried to obtain the impurity salt;

[0082] (6) cooling the hot ammonium chloride solution obtained in step (5) to 40° C. for crystallization, filtering to obtain an ammonium chloride product and an ammonium chloride mother liquor, and the ammonium chloride mother liquor is reused in step (5);

[0083] The sodium sulfate mixed crystals obtained in step (5) are mixed with sodium bicarbonate mother liquor at 45°C for dissolution and salting out, and a saturated sodium sulfate solution and crude ammonium sulfate crystals (Na2SO4·(NH4)2SO4·4H2O) are obtained after filtration;

[0084] (7) mixing the crude ammonium sulfate crystals obtained in step (6) with the ammonium sulfate evaporation condensate for evaporation crystallization at a temperature of 100° C. collecting the volatile components generated during the evaporation crystallization process, condensing the ammonium sulfate evaporation condensate, and recycling it to the evaporation crystallization of the crude ammonium sulfate crystals. After filtering, obtaining an ammonium sulfate product and an ammonium sulfate mother liquor, and recycling the ammonium sulfate mother liquor to step (5);

[0085] The saturated sodium sulfate solution obtained in step (6) is added to solid ammonium bicarbonate for double decomposition reaction. The amount of ammonium bicarbonate added is controlled so that the molar ratio of bicarbonate to sodium in the solution system is 1.3:1. The temperature of the double decomposition reaction is 50° C. After filtration, a sodium bicarbonate product and a sodium bicarbonate mother liquor are obtained. The sodium bicarbonate mother liquor is reused in step (6). The sodium bicarbonate product is calcined to obtain a sodium carbonate product.

[0086] Example 3

[0087] This embodiment provides a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine, the method comprising the following steps:

[0088] (1) After adding sodium carbonate and sodium hydroxide to coal chemical concentrated brine to remove calcium and magnesium, seed silicon dioxide and a silicon-fluoride removal agent sodium aluminate are added thereto, the amount of silicon-fluoride removal agent added is 4000 mg / L, the pH value during silicon and fluoride removal is 6.5, the temperature is 40°C, and after filtering, a silicon-fluoride removal purified liquid and silicon-fluoride precipitate are obtained;

[0089] (2) adding sulfuric acid to the obtained purified liquid for silicon and fluorine removal to adjust the pH to 5, and adding cationic polyacrylamide (CPAM-1200) as a flocculant in an amount of 40 mg / L, and then flotation separation is performed to obtain an acid hydrolysis mother liquor and an acid hydrolysis precipitate;

[0090] (3) adding hydrogen peroxide as an oxidant to the obtained acid hydrolysis mother liquor, wherein the mass ratio of the oxidant to the COD in the acid hydrolysis mother liquor is 12:1, and controlling the temperature to 95°C for a thermally excited oxidation reaction for 4 hours. After the reaction is completed, a purified mother liquor is obtained;

[0091] (4) evaporating and crystallizing the obtained purified mother liquor at 70° C., maintaining the solution pH value greater than or equal to 2 during evaporation and crystallization, and adding sodium hydroxide to adjust the pH value when the pH value is lower than 2 to prevent the residual oxidant from oxidizing the chloride ions, thereby obtaining a mixed salt of sodium sulfate and sodium chloride and a mixed salt mother liquor, wherein the mass percentage of sodium nitrate in the mixed salt mother liquor is 30%;

[0092] (5) mixing the obtained mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor, controlling the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor to be 1:1, performing double decomposition and evaporation at a temperature of 70° C., evaporating water introduced by the ammonium sulfate mother liquor, and then filtering to obtain sodium sulfate mixed crystals and ammonium chloride hot solution;

[0093] The obtained mixed salt mother liquor is cooled and crystallized to 0°C, filtered to obtain the sodium nitrate product, and the remaining mother liquor after filtration is dried to obtain the impurity salt;

[0094] (6) cooling the hot ammonium chloride solution obtained in step (5) to 10° C. for crystallization, filtering to obtain an ammonium chloride product and an ammonium chloride mother liquor, and the ammonium chloride mother liquor is reused in step (5);

[0095] The sodium sulfate mixed crystals obtained in step (5) are mixed with sodium bicarbonate mother liquor at 10° C. for dissolution and salting out, and a saturated sodium sulfate solution and crude ammonium sulfate crystals (Na2SO4·(NH4)2SO4·4H2O) are obtained after filtration;

[0096] (7) mixing the crude ammonium sulfate crystals obtained in step (6) with the ammonium sulfate evaporation condensate for evaporation crystallization at a temperature of 70° C. collecting the volatile components generated during the evaporation crystallization process, condensing the ammonium sulfate evaporation condensate, and recycling it to the evaporation crystallization of the crude ammonium sulfate crystals. After filtering, obtaining an ammonium sulfate product and an ammonium sulfate mother liquor, and recycling the ammonium sulfate mother liquor to step (5);

[0097] The saturated sodium sulfate solution obtained in step (6) is added to solid ammonium bicarbonate for double decomposition reaction. The amount of ammonium bicarbonate added is controlled so that the molar ratio of bicarbonate to sodium in the solution system is 1.0:1. The temperature of the double decomposition reaction is 50° C. After filtration, a sodium bicarbonate product and a sodium bicarbonate mother liquor are obtained. The sodium bicarbonate mother liquor is reused in step (6). The sodium bicarbonate product is calcined to obtain a sodium carbonate product.

[0098] Example 4

[0099] This embodiment provides a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine, the method comprising the following steps:

[0100] (1) After adding sodium carbonate and sodium hydroxide to coal chemical concentrated brine to remove calcium and magnesium, seed cryolite and polyaluminium sulfate as a desiliconizing and defluorinating agent are added thereto to remove silicon and fluorine. The amount of desiliconizing and defluorinating agent added is 500 mg / L. The pH value during desiliconizing and defluorinating is 9 and the temperature is 20°C. After filtering, desiliconizing and defluorinating purified liquid and siliconizing and defluorinating precipitate are obtained;

[0101] (2) adding sulfuric acid to the obtained silicon-fluoride-removing purified liquid to adjust the pH to 0.5, and adding a flocculant cationic polyacrylamide (CPAM-1200) in an amount of 100 mg / L, and then flotation separation is performed to obtain an acid hydrolysis mother liquor and an acid hydrolysis precipitate;

[0102] (3) adding sodium persulfate as an oxidant to the obtained acid hydrolysis mother liquor, with the mass ratio of the oxidant to the COD in the acid hydrolysis mother liquor being 0.5:1, controlling the temperature to 100°C for thermally excited oxidation reaction, and the reaction time being 0.5h, and obtaining a purified mother liquor after the reaction is completed;

[0103] (4) evaporating and crystallizing the obtained purified mother liquor at 85° C., maintaining the solution pH value greater than or equal to 2 during evaporation and crystallization, and adding sodium hydroxide to adjust the pH value when the pH value is lower than 2 to prevent the residual oxidant from oxidizing the chloride ions, thereby obtaining a mixed salt of sodium sulfate and sodium chloride and a mixed salt mother liquor, wherein the mass percentage of sodium nitrate in the mixed salt mother liquor is 20%;

[0104] (5) mixing the obtained mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor, controlling the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor to be 0.6:1, performing double decomposition and evaporation, the temperature of double decomposition and evaporation is 60° C., evaporating the water introduced by the ammonium sulfate mother liquor, and then filtering to obtain sodium sulfate mixed crystals and ammonium chloride hot solution;

[0105] The obtained mixed salt mother liquor is cooled and crystallized to 30°C, filtered to obtain the sodium nitrate product, and the remaining mother liquor after filtration is dried to obtain the impurity salt;

[0106] (6) cooling the hot ammonium chloride solution obtained in step (5) to 30° C. for crystallization to obtain an ammonium chloride product and an ammonium chloride mother liquor, and the ammonium chloride mother liquor is reused in step (5);

[0107] The sodium sulfate mixed crystals obtained in step (5) are mixed with sodium bicarbonate mother liquor at 30°C for dissolution and salting out, and a saturated sodium sulfate solution and crude ammonium sulfate crystals (Na2SO4·(NH4)2SO4·4H2O) are obtained after filtration;

[0108] (7) mixing the crude ammonium sulfate crystals obtained in step (6) with the ammonium sulfate evaporation condensate for evaporation crystallization at a temperature of 90° C. collecting the volatile components generated during the evaporation crystallization process, condensing the ammonium sulfate evaporation condensate, and recycling it to the evaporation crystallization of the crude ammonium sulfate crystals. After filtering, an ammonium sulfate product and an ammonium sulfate mother liquor are obtained, and the ammonium sulfate mother liquor is recycled to step (5);

[0109] The saturated sodium sulfate solution obtained in step (6) is added to solid ammonium bicarbonate for double decomposition reaction. The amount of ammonium bicarbonate added is controlled so that the molar ratio of bicarbonate to sodium in the solution system is 1:1. The temperature of the double decomposition reaction is 30° C. After filtration, a sodium bicarbonate product and a sodium bicarbonate mother liquor are obtained. The sodium bicarbonate mother liquor is reused in step (6). The sodium bicarbonate product is calcined to obtain a sodium carbonate product.

[0110] Example 5

[0111] This embodiment provides a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine, the method comprising the following steps:

[0112] (1) After adding sodium carbonate and sodium hydroxide to coal chemical concentrated brine to remove calcium and magnesium, seed cryolite and polyaluminium sulfate as a desiliconizing and defluorinating agent are added thereto to remove silicon and fluorine. The amount of desiliconizing and defluorinating agent added is 6000 mg / L. The pH value during desiliconizing and defluorinating is 4 and the temperature is 90°C. After filtering, desiliconizing and defluorinating purified liquid and siliconizing and defluorinating precipitate are obtained;

[0113] (2) adding sulfuric acid to the obtained silicon-fluoride-removing purified liquid to adjust the pH to 2, and adding cationic polyacrylamide (CPAM-1200) as a flocculant, the amount of which is 5 mg / L, and then flotation separation is performed to obtain an acid hydrolysis mother liquor and an acid hydrolysis precipitate;

[0114] (3) adding sodium persulfate as an oxidant to the obtained acid hydrolysis mother liquor, wherein the mass ratio of the oxidant to the COD in the acid hydrolysis mother liquor is 15:1, and controlling the temperature to 50°C for a thermally excited oxidation reaction for 4 hours. After the reaction is completed, a purified mother liquor is obtained;

[0115] (4) evaporating and crystallizing the obtained purified mother liquor at 85° C., maintaining the solution pH value greater than or equal to 2 during evaporation and crystallization, and adding sodium hydroxide to adjust the pH value when the pH value is lower than 2 to prevent the residual oxidant from oxidizing the chloride ions, thereby obtaining a mixed salt of sodium sulfate and sodium chloride and a mixed salt mother liquor, wherein the mass percentage of sodium nitrate in the mixed salt mother liquor is 40%;

[0116] (5) mixing the obtained mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor, controlling the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor to be 1.5:1, performing double decomposition and evaporation at a temperature of 110° C., evaporating water introduced by the ammonium sulfate mother liquor, and then filtering to obtain sodium sulfate mixed crystals and ammonium chloride hot solution;

[0117] The obtained mixed salt mother liquor is cooled and crystallized to 30°C, filtered to obtain the sodium nitrate product, and the remaining mother liquor after filtration is dried to obtain the impurity salt;

[0118] (6) cooling the hot ammonium chloride solution obtained in step (5) to 30° C. for crystallization to obtain an ammonium chloride product and an ammonium chloride mother liquor, and the ammonium chloride mother liquor is reused in step (5);

[0119] The sodium sulfate mixed crystals obtained in step (5) are mixed with sodium bicarbonate mother liquor at 30°C for dissolution and salting out, and a saturated sodium sulfate solution and crude ammonium sulfate crystals (Na2SO4·(NH4)2SO4·4H2O) are obtained after filtration;

[0120] (7) mixing the crude ammonium sulfate crystals obtained in step (6) with the ammonium sulfate evaporation condensate for evaporation crystallization at a temperature of 90° C. collecting the volatile components generated during the evaporation crystallization process, condensing the ammonium sulfate evaporation condensate, and recycling it to the evaporation crystallization of the crude ammonium sulfate crystals. After filtering, an ammonium sulfate product and an ammonium sulfate mother liquor are obtained, and the ammonium sulfate mother liquor is recycled to step (5);

[0121] The saturated sodium sulfate solution obtained in step (6) is added to solid ammonium bicarbonate for double decomposition reaction. The amount of ammonium bicarbonate added is controlled so that the molar ratio of bicarbonate to sodium in the solution system is 1:1. The temperature of the double decomposition reaction is 60° C. After filtration, a sodium bicarbonate product and a sodium bicarbonate mother liquor are obtained. The sodium bicarbonate mother liquor is reused in step (6). The sodium bicarbonate product is calcined to obtain a sodium carbonate product.

[0122] Example 6

[0123] This embodiment provides a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine. Compared with Example 1, the amount of silicon-fluorine removal agent added in step (1) is controlled to be 6000 mg / L, and the rest is the same as Example 1.

[0124] Example 7

[0125] This embodiment provides a method for preparing soda ash or baking soda from coal chemical concentrated brine resources. Compared with Example 1, the terminal temperature of the cooling crystallization of the hot ammonium chloride solution in step (6) is controlled to be 20°C, and the rest is the same as Example 1.

[0126] Example 8

[0127] This embodiment provides a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine. Compared with Example 1, the amount of ammonium bicarbonate added in step (7) is controlled so that the molar ratio of bicarbonate to sodium in the solution system is 1.2:1. The rest is the same as Example 1.

[0128] Example 9

[0129] This embodiment provides a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine. Compared with Example 1, in the control step (5), the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor is 0.5:1, and the rest is the same as Example 1.

[0130] Example 10

[0131] This embodiment provides a method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine. Compared with Example 1, in the control step (5), the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor is 1.6:1, and the rest is the same as Example 1.

[0132] Embodiment 11

[0133] This embodiment provides a method for preparing soda ash or baking soda from coal chemical concentrated brine resources. Compared with Example 1, the temperature of the evaporation and crystallization of ammonium sulfate in step (7) is controlled to be 60° C., and the rest is the same as Example 1.

[0134] Example 12

[0135] This embodiment provides a method for preparing soda ash or baking soda from coal chemical concentrated brine. Compared with Example 1, the temperature of the double decomposition reaction in step (7) is controlled to be 20° C., and the rest is the same as Example 1.

[0136] Comparative Example 1

[0137] This comparative example provides a method for preparing soda ash or baking soda by resource utilization of concentrated brine from coal chemical industry. Compared with Example 1, no seed crystal is added in step (1) for removing silicon and fluorine, and the rest is the same as Example 1.

[0138] Comparative Example 2

[0139] This comparative example provides a method for preparing soda ash or baking soda by resource utilization of concentrated brine from coal chemical industry. Compared with Example 1, step (1) of removing silicon and fluorine is not performed, and the rest is the same as Example 1.

[0140] Comparative Example 3

[0141] This comparative example provides a method for preparing soda ash or baking soda from concentrated brine in coal chemical industry. Compared with Example 1, the acid hydrolysis in step (2) is not performed, and the rest is the same as Example 1.

[0142] Comparative Example 4

[0143] This comparative example provides a method for preparing soda ash or baking soda from concentrated brine in coal chemical industry. Compared with Example 1, the thermally stimulated oxidation reaction in step (3) is not performed, and the rest is the same as Example 1.

[0144] Comparative Example 5

[0145] This comparative example provides a method for preparing soda ash or baking soda by resource utilization of concentrated brine in coal chemical industry, the method comprising the following steps:

[0146] (1) After adding sodium carbonate and sodium hydroxide to coal chemical concentrated brine to remove calcium and magnesium, seed cryolite and polyaluminium sulfate as a desiliconizing and defluorinating agent are added thereto to remove silicon and fluorine. The amount of desiliconizing and defluorinating agent added is 4000 mg / L. The pH value during desiliconizing and defluorinating is 6.5 and the temperature is 40°C. After filtering, a desiliconizing and defluorinating purified liquid and a desiliconizing and defluorinating precipitate are obtained;

[0147] (2) adding sulfuric acid to the obtained silicon-fluoride-removing purified liquid to adjust the pH to 3, and adding a flocculant and a flocculation aid cationic polyacrylamide (CPAM-1200) at a flocculant addition amount of 40 mg / L, and then flotation separation is performed to obtain an acid hydrolysis mother liquor and an acid hydrolysis precipitate;

[0148] (3) adding sodium persulfate as an oxidant to the obtained acid hydrolysis mother liquor, wherein the mass ratio of the oxidant to the COD in the acid hydrolysis mother liquor is 8:1, and controlling the temperature to 90°C for a thermally excited oxidation reaction for 2 hours. After the reaction is completed, a purified mother liquor is obtained;

[0149] (4) Evaporating and crystallizing the obtained purified mother liquor at 85° C., maintaining the solution pH greater than or equal to 2 during evaporation and crystallization, and adding sodium hydroxide to adjust the pH when the pH is lower than 2 to prevent the residual oxidant from oxidizing the chloride ions, thereby obtaining a mixed salt of sodium sulfate and sodium chloride and an evaporation mother liquor, and drying the evaporation mother liquor to discharge the impurities;

[0150] (5) mixing the ammonium bicarbonate solid, the mixed sodium salt, the deammonium solid and the cooled mother liquor, and controlling the molar ratio of total nitrogen to total sodium in the reaction system to be 1.1:1, performing a double decomposition reaction at 35° C. for 75 min, first separating by sedimentation and then filtering to obtain sodium bicarbonate and a double decomposition mother liquor; and calcining the obtained sodium bicarbonate to obtain sodium carbonate;

[0151] (6) subjecting the obtained metathesis mother liquor to ammonia evaporation at 85° C. to obtain a mixed gas of ammonia and carbon dioxide and an ammonia evaporation mother liquor, and the obtained mixed gas is recycled to step (5);

[0152] (7) Concentrating and crystallizing the obtained ammonia evaporation mother liquor at 85° C., and obtaining a mixed salt and a concentrated mother liquor after centrifugal separation;

[0153] (8) cooling and crystallizing the concentrated mother liquor at 15°C, first by sedimentation separation and then by centrifugation to obtain ammonium chloride and a cooled mother liquor, and the cooled mother liquor is reused in step (5);

[0154] (9) mixing the evaporated mother liquor and the mixed salt obtained in step (7), enriching the mixture with ammonium sulfate at 95° C., and centrifuging to obtain an ammonium sulfate-rich solution and a deammonium-free solid, and the deammonium-free solid is reused in step (5);

[0155] (10) The obtained ammonium sulfate-rich solution is evaporated and crystallized at 95° C., and then subjected to hydrocyclone separation and centrifugal separation to obtain ammonium sulfate and an evaporation mother liquor, and the obtained evaporation mother liquor is returned to step (9).

[0156] That is, the operations from step (1) to step (4) are the same as those in Example 1.

[0157] Comparative Example 6

[0158] This comparative example provides a method for preparing soda ash or baking soda by resource utilization of concentrated brine in coal chemical industry, the method comprising the following steps:

[0159] (1) After adding sodium carbonate and sodium hydroxide to coal chemical concentrated brine to remove calcium and magnesium, seed cryolite and polyaluminium sulfate as a desiliconizing and defluorinating agent are added thereto to remove silicon and fluorine. The amount of desiliconizing and defluorinating agent added is 4000 mg / L. The pH value during desiliconizing and defluorinating is 6.5 and the temperature is 40°C. After filtering, a desiliconizing and defluorinating purified liquid and a desiliconizing and defluorinating precipitate are obtained;

[0160] (2) adding sulfuric acid to the obtained silicon-fluoride-removing purified liquid to adjust the pH to 3, and adding a flocculant and a flocculation aid cationic polyacrylamide (CPAM-1200) at a flocculant addition amount of 40 mg / L, and then flotation separation is performed to obtain an acid hydrolysis mother liquor and an acid hydrolysis precipitate;

[0161] (3) adding sodium persulfate as an oxidant to the obtained acid hydrolysis mother liquor, wherein the mass ratio of the oxidant to the COD in the acid hydrolysis mother liquor is 8:1, and controlling the temperature to 90°C for a thermally excited oxidation reaction for 2 hours. After the reaction is completed, a purified mother liquor is obtained;

[0162] (4) Evaporating and crystallizing the obtained purified mother liquor at 85° C., maintaining the solution pH greater than or equal to 2 during evaporation and crystallization, and adding sodium hydroxide to adjust the pH when the pH is lower than 2 to prevent the residual oxidant from oxidizing the chloride ions, thereby obtaining a mixed salt of sodium sulfate and sodium chloride and an evaporation mother liquor, and drying the evaporation mother liquor to discharge the impurities;

[0163] (5) reacting the obtained mixed salt with ammonium sulfate solution at 40° C. for 180 min, and filtering to obtain a first mother liquor and crude sodium sulfate;

[0164] (6) reacting the ammonium sulfate solution with the obtained crude sodium sulfate at 60° C. for 1 hour, and filtering to obtain a saturated sodium sulfate solution and a sodium sulfate-ammonium sulfate double salt;

[0165] The obtained first mother liquor is cooled and crystallized to an end point temperature of -5°C, and filtered to obtain ammonium chloride and a second mother liquor;

[0166] The second mother liquor is mixed with sodium sulfate-ammonium sulfate double salt and recycled to the primary reaction of step (5);

[0167] (7) subjecting the obtained saturated sodium sulfate solution to a secondary reaction with solid ammonium bicarbonate at 30° C. for 100 min, wherein the molar ratio of the sodium atom in the saturated sodium sulfate solution to the molar ratio of the nitrogen atom in the ammonium bicarbonate in the secondary reaction is 0.8:1, and filtering to obtain sodium bicarbonate and a third mother liquor, wherein the third mother liquor is recycled to step (6) as an ammonium sulfate solution for reaction crystallization;

[0168] The solvent is mixed with the obtained sodium sulfate-ammonium sulfate double salt and then enriched at 110° C. for 20 min, the mass ratio of the solvent to the double salt is 1:1, and the fourth mother liquor and deammonium solid are obtained after filtration. The deammonium solid is recycled to step (6) as a crude sodium sulfate product for reaction crystallization;

[0169] (8) The fourth mother liquor obtained is evaporated and crystallized at 80° C., and filtered to obtain ammonium sulfate and a fifth mother liquor. The fifth mother liquor is recycled to step (7) and used as a solvent for enrichment.

[0170] Performance Testing

[0171] The sodium bicarbonate product, sodium carbonate product, ammonium sulfate product, ammonium chloride product and sodium nitrate product prepared in the examples and comparative examples were dried and then subjected to performance tests. The results are listed in Table 1.

[0172] The total alkali content of sodium bicarbonate is measured according to the method of "Industrial Sodium Bicarbonate (GB / T 1606-2008)".

[0173] The total alkali content of sodium carbonate is measured according to the method in "Industrial Sodium Carbonate (GB / T210-2022)".

[0174] The particle size of sodium bicarbonate was measured by sieving method.

[0175] The nitrogen content of ammonium sulfate and ammonium chloride is measured according to the method in "Fertilizer Grade Ammonium Sulfate (GB / T535-2020)".

[0176] The fluorine content was measured using the fluorine electrode method.

[0177] Table 1

[0178]

[0179]

[0180] “ / ” in the table means no data.

[0181] As can be seen from Table 1, the coal chemical concentrated brine treatment process provided by the present invention can effectively remove calcium, magnesium, fluorine, silicon and organic impurities in wastewater, realize inorganic salt separation in wastewater through a short-process circulation process, and separate sodium bicarbonate / sodium carbonate, and high-value products of sodium nitrate, ammonium chloride and ammonium sulfate. No additional auxiliary or reinforcing reagents are required in the salt separation. The obtained product has high purity and meets the use requirements of industrial chemicals. In addition, the sodium bicarbonate product has a higher crystal size and good crystal quality.

[0182] Compared with Example 1, in Comparative Example 1, no defluorination seed is added, and the defluorination depth is low, which will aggravate the corrosion of the ammonium chloride crystallization system and cause the fluorine content in the subsequent product to be high; in Comparative Example 2, no defluorination silicon is performed, the impurity content of the system is high, the presence of fluorine aggravates the corrosion of the ammonium chloride and ammonium sulfate crystallization systems, and the presence of silicon makes the filtering performance of sodium bicarbonate worse, washing is difficult, and it is difficult to obtain qualified products; in Comparative Examples 3 and 4, when acid hydrolysis or thermally excited oxidation is not performed, it is difficult to decompose organic matter, and some organic matter enters the mixed salt, further affecting the purity of sodium bicarbonate and sodium carbonate. At the same time, the residual organic matter content in the mixed salt mother liquor is high. In order to ensure that the organic matter content in the mixed salt is as low as possible, the evaporation depth can only be reduced, so that the sodium nitrate content in the mother liquor is low, and it is difficult to obtain sodium nitrate crystals by cooling crystallization; in Comparative Example 5, The technical route of first separating sodium bicarbonate and then separating ammonium salt is adopted. Due to the salting-out effect of sodium chloride on sodium sulfate, sodium sulfate is difficult to dissolve and react, and is easy to crystallize. Sodium sulfate solid is often entrained in sodium bicarbonate, and the particle size of the sodium bicarbonate product is fine. At the same time, chloride ions remain in the system for a long time, there is a problem of equipment corrosion, and the separation of ammonium salt has the problem of high energy consumption; in addition, during cooling and crystallization, a small amount of sodium sulfate and ammonium sulfate double salt will be entrained in the ammonium chloride crystals, and the quality of the ammonium chloride product is poor; in Comparative Example 6, the substance used to prepare ammonium chloride by double decomposition of sodium chloride and ammonium sulfate in the previous process is sodium sulfate-ammonium sulfate double salt. The sodium sulfate particles generated in the double salt conversion process are fine and easy to entrain chloride ions, so that the chloride ion content in the solution of the subsequent soda ash preparation and ammonium sulfate crystallization process is high, and the equipment is seriously corroded.

[0183] In summary, the method provided by the present invention adopts a short-process, low-cost method to remove impurities from coal chemical concentrated brine and utilize it as a resource to produce baking soda or soda ash and co-produce high-value products such as ammonium chloride and ammonium sulfate, thereby achieving the reduction, harmlessness and resource utilization of coal chemical wastewater. The obtained product has high purity and meets the requirements of industrial qualified products.

[0184] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing soda ash or baking soda by resource utilization of coal chemical concentrated brine, characterized in that: The method comprises the following steps: (1) using a silicon-fluoride removal agent to carry out a crystallization reaction on coal chemical concentrated brine under the action of a crystal seed, using an acid and a flocculant to carry out an acid hydrolysis precipitation reaction, and using an oxidant to carry out a thermally excited oxidation reaction, wherein the crystallization reaction, the acid hydrolysis precipitation reaction, and the thermally excited oxidation reaction are not in any particular order, and after the reaction is completed, a purified mother liquor, a silicon-fluoride precipitate, and an acid hydrolysis precipitate are finally obtained; Wherein, the seed crystal includes any one of cryolite, fluoride, iron oxide or silicon dioxide or a combination of at least two thereof; the silicon fluoride removal agent includes any one of polyaluminium chloride, polyaluminium sulfate, ferric sulfate, sodium metaaluminate or polyferric sulfate or a combination of at least two thereof; the temperature of the thermally excited oxidation reaction is 50-100°C; (2) evaporating and crystallizing the purified mother liquor to obtain a mixed salt and a mixed salt mother liquor after solid-liquid separation, wherein the mass percentage of sodium nitrate in the mixed salt mother liquor is in the range of 20-60%; (3) mixing the mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor for double decomposition and evaporation, wherein the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor is controlled to be (0.6-1.5):1, and evaporating water introduced by the ammonium sulfate mother liquor to obtain sodium sulfate mixed crystals and ammonium chloride enriched liquid after solid-liquid separation; The mixed salt mother liquor is cooled and crystallized, and solid-liquid separation is performed to obtain a sodium nitrate product; (4) cooling and crystallizing the ammonium chloride enriched solution, and obtaining an ammonium chloride product and an ammonium chloride mother liquor after solid-liquid separation, wherein the ammonium chloride mother liquor is recycled to step (3); The sodium sulfate mixed crystals are mixed with a sodium bicarbonate mother liquor to be dissolved and salted out, and a saturated sodium sulfate solution and crude ammonium sulfate are obtained after solid-liquid separation; (5) mixing the crude ammonium sulfate with the ammonium sulfate evaporation condensate for evaporation and crystallization at a temperature of 70-100° C., collecting the volatile components generated during the evaporation and crystallization process, condensing the ammonium sulfate evaporation condensate, and recycling it to the evaporation and crystallization process. After evaporation and crystallization, solid-liquid separation is performed to obtain an ammonium sulfate product and an ammonium sulfate mother liquor, and the ammonium sulfate mother liquor is recycled to step (3); The saturated sodium sulfate solution is subjected to double decomposition reaction with ammonium bicarbonate solid or a mixed gas of ammonia and carbon dioxide to obtain a sodium bicarbonate product and a sodium bicarbonate mother liquor after solid-liquid separation. The sodium bicarbonate mother liquor is recycled to step (4).

2. The method according to claim 1, characterized in that The amount of the silicon-fluorine removal agent added in step (1) is 500-6000 mg / L based on coal chemical concentrated brine.

3. The method according to claim 1, characterized in that: The pH value of the crystallization reaction in step (1) is 4-9; The temperature of the crystallization reaction in step (1) is 20-90°C.

4. The method according to claim 1, characterized in that: The flocculant in step (1) includes polyacrylamide and / or sodium polyacrylate; The dosage of the flocculant in step (1) is 5-200 mg / L based on the coal chemical concentrated brine; The pH value of the acid hydrolysis precipitation reaction in step (1) is 0.5-5.

5. The method according to claim 1, characterized in that The oxidant in step (1) comprises any one of air, ozone, hydrogen peroxide, ammonium persulfate or sodium persulfate, or a combination of at least two thereof; The mass ratio of the oxidant in step (1) to the COD in the coal chemical concentrated brine is (0.5-15):

1.

6. The method according to claim 1, characterized in that The time of the thermally excited oxidation reaction in step (1) is 0.5-4h.

7. The method according to claim 1, characterized in that The terminal temperature of the mixed salt mother liquor cooling crystallization in step (3) is 0-40°C.

8. The method according to claim 1, characterized in that The temperature of the double decomposition and evaporation in step (3) is 60-110°C.

9. The method according to claim 1, characterized in that: The method comprises the following steps: (1) using a silicon-fluoride removal agent to perform a crystallization reaction on the coal chemical concentrated brine under the action of a seed crystal, wherein the amount of the silicon-fluoride removal agent is 500-6000 mg / L based on the coal chemical concentrated brine, the pH value of the crystallization reaction is 4-9, the temperature of the crystallization reaction is 20-90°C, and solid-liquid separation is performed after the crystallization reaction; using an acid and a flocculant to perform an acid hydrolysis precipitation reaction on the coal chemical concentrated brine, wherein the amount of the flocculant is 5-200 mg / L based on the coal chemical concentrated brine, the pH value of the acid hydrolysis precipitation reaction is 0.5-5, and flotation separation is performed after the acid hydrolysis reaction is completed; using an oxidant to perform a thermally excited oxidation reaction on the coal chemical concentrated brine, wherein the mass ratio of the oxidant to the COD in the coal chemical concentrated brine is (0.5-15):1, the temperature of the thermally excited oxidation reaction is 50-100°C, and the time of the thermally excited oxidation reaction is 0.5-4h. The crystallization reaction, acid hydrolysis precipitation reaction and thermally excited oxidation reaction are not in any particular order, and after the reaction is completed, a purified mother liquor, silicon-fluoride precipitate and acid hydrolysis precipitate are finally obtained; (2) evaporating and crystallizing the purified mother liquor at 70-100° C. to obtain a mixed salt and a mixed salt mother liquor after solid-liquid separation; (3) mixing the mixed salt, ammonium chloride mother liquor and ammonium sulfate mother liquor, controlling the molar ratio of chlorine in the mixed system to ammonium ions in the ammonium sulfate mother liquor to be (0.6-1.5):1, performing double decomposition and evaporation at 60-110° C., evaporating the water introduced by the ammonium sulfate mother liquor, and obtaining sodium sulfate mixed crystals and ammonium chloride enriched liquid after solid-liquid separation; The mass percentage of sodium nitrate in the mixed salt mother liquor is in the range of 20-60%, the mixed salt mother liquor is cooled and crystallized to an end point temperature of 0-40° C. to obtain a sodium nitrate product, and the remaining mother liquor after cooling and crystallization is dried to obtain impurity salt; (4) cooling and crystallizing the ammonium chloride enriched solution to an end point temperature of 10-40° C., and obtaining an ammonium chloride product and an ammonium chloride mother liquor after solid-liquid separation, wherein the ammonium chloride mother liquor is reused in step (3); The sodium sulfate mixed crystals are mixed with a sodium bicarbonate mother liquor at 10-45° C. for dissolution and salting out, and a saturated sodium sulfate solution and crude ammonium sulfate are obtained after solid-liquid separation; (5) mixing the crude ammonium sulfate with the ammonium sulfate evaporation condensate at 70-100° C. for evaporation and crystallization, collecting the volatile components generated during the evaporation and crystallization process, condensing the ammonium sulfate evaporation condensate, and recycling it to the evaporation and crystallization, and performing solid-liquid separation after evaporation and crystallization to obtain an ammonium sulfate product and an ammonium sulfate mother liquor, and recycling the ammonium sulfate mother liquor to step (3); The saturated sodium sulfate solution is subjected to a double decomposition reaction with solid ammonium bicarbonate or a mixed gas of ammonia and carbon dioxide, the molar ratio of bicarbonate to sodium ion in the system is controlled to be (0.9-1.3):1, the temperature of the double decomposition reaction is 30-60° C., and a sodium bicarbonate product and a sodium bicarbonate mother liquor are obtained after solid-liquid separation, and the sodium bicarbonate mother liquor is reused in step (4).

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