Method for producing sodium carbonate by using sodium-containing material

Abstract

The invention discloses a method for producing sodium carbonate by using a sodium-containing material, and belongs to the technical field of chemical engineering. The method comprises the following steps: producing sodium carbonate by taking sodium chloride, CO2, NH3 and water as raw materials and adopting a combined alkali preparation method, putting a byproduct ammonium chloride and calcium carbonate into a solution containing calcium chloride, and carrying out ammonium chloride transformation to obtain mixed gas containing CO2 and NH3 and calcium chloride slurry; the calcium chloride slurry is used for producing a calcium-containing compound; or, calcium carbonate and ammonium chloride are mixed and roasted, ammonium chloride transformation is carried out, and mixed gas containing CO2 and NH3 and a byproduct calcium chloride product are obtained; and returning the mixed gas of CO2 and NH3 for cyclic utilization. According to the method, ammonium chloride obtained in the alkali preparation process through calcium carbonate decomposition is adopted, recycling of NH3 in the alkali preparation process is achieved, a CO2 gas source needed by alkali preparation is provided, and the method has the advantages of being wide in raw material application range, simple in process, high in production efficiency, good in economic benefit and the like.

Description

Technical Field

[0001] The present invention relates to a method for producing sodium carbonate from sodium-containing materials, belonging to the field of chemical engineering technology. Background Art

[0002] Sodium carbonate, commonly known as soda ash, is a basic industrial raw material with a very wide range of uses. At present, most of the sodium carbonate in the world is artificially synthesized, and the industrial synthesis methods of sodium carbonate include the ammonia-soda method and the combined method.

[0003] The production of soda ash by the ammonia-soda method was first invented by Solvay, also known as the Solvay soda process. It uses salt (sodium chloride), limestone, and ammonia as raw materials. Limestone is calcined to obtain CaO and CO 2 , salt is dissolved in water to obtain a sodium chloride solution, the sodium chloride solution absorbs ammonia to obtain ammoniacal brine, and the ammoniacal brine is carbonated to precipitate heavy soda (sodium bicarbonate). After filtration, sodium bicarbonate crystals and their crystallization mother liquor are obtained. The sodium bicarbonate crystals are thermally decomposed to obtain sodium carbonate, and the sodium bicarbonate crystallization mother liquor is added with lime and evaporated to recover ammonia, so it is called the ammonia-soda method. The basic principle of the ammonia-soda method is: 2 NaCl + NH

[0004] NaCl + NH 3 + CO 2 + H 2 O = NaHCO 3 ↓ + NH 4 Cl

[0005] CaCO 3 = high temperature = CaO + CO 2 ↑

[0006] CaO + H 2 O = Ca(OH) 2

[0007] 2NH 4 Cl + Ca(OH) 2 = 2NH 3 ↑ + CaCl 2 + 2H 2 O

[0008] 2NaHCO 3 =Δ= Na 2 CO 3 + CO 2 ↑ + H 2 O↑

[0009] The advantages of the ammonia-soda method are easy raw material sources, simple varieties, low costs, and pure quality, which are suitable for large-scale continuous production. The disadvantages are low utilization rate of salt (only about 75%) and difficult treatment of ammonia evaporation waste liquid. For every 1 t of soda ash produced, there are 9 - 10 m3 Waste liquid discharge puts enormous pressure on environmental protection.

[0010] The combined process for producing soda ash uses sodium chloride, carbon dioxide, ammonia and water as raw materials. While producing soda ash, ammonium chloride is produced as a by-product. The main reaction of the combined alkali production process is the carbonization reaction, that is, the ammoniacal brine reacts with carbon dioxide to obtain sodium bicarbonate crystals (heavy alkali) and alkali production mother liquor. The sodium bicarbonate crystals are pyrolyzed to obtain sodium carbonate products and carbon dioxide gas, and the carbon dioxide gas is recovered for carbonization reaction. The obtained alkali production mother liquor is crystallized and separated from the ammonium chloride by the "cold method" according to the principle of cooling and salting out, or the ammonium chloride is crystallized and separated by the evaporation process, that is, the "hot method" to produce ammonium chloride. Therefore, the process produces two products, sodium carbonate and ammonium chloride, so it is called the combined alkali production process. The advantage of the combined alkali production process is that it retains the advantages of the ammonia-soda process, overcomes its disadvantages, and increases the utilization rate of salt to more than 96%; in addition, it comprehensively utilizes the carbon dioxide from the ammonia plant and the Cl in the sodium chloride. - ions, and at the same time, soda ash and ammonium chloride are produced. The disadvantage is that an ammonia plant must be built at the same time as a soda ash plant, and the ammonium chloride produced is mainly used as agricultural fertilizer, while the Cl in ammonium chloride - The ions are harmful to many crops, which has caused serious unsalability of ammonium chloride.

[0011] Another difference between the Solvay process and the combined process is that the Solvay process can use both solid salt and bittern as raw materials, while the combined process can only use refined salt as raw materials, and neither can use salt with high nitrate content or other sodium-containing materials with high impurities as production raw materials. In addition, the industrial waste salt generated by the large-scale use of soda ash and its related products cannot be consumed. In many places, industrial waste salt has piled up like a mountain, posing a huge threat to the ecological environment. Summary of the invention

[0012] In view of the problems existing in the above-mentioned prior art, one of the purposes of the present invention is to provide a method for producing sodium carbonate from sodium-containing materials, which adopts a combined alkali production process to produce sodium carbonate, and uses calcium carbonate to decompose the ammonium chloride obtained in the alkali production process, which not only realizes the production of NH 3 It is recycled in the alkali production process and also provides the CO required for alkali production. 2 The present invention inherits the advantages of the ammonia-soda method and the combined method for alkali production, overcomes the disadvantages of both methods, has the advantages of wide raw material adaptability, simple process, high production efficiency, good economic benefits, convenient operation, etc., and is suitable for large-scale industrial production of sodium carbonate from sodium-containing materials.

[0013] To achieve the above object, the first aspect of the present invention is to provide a method for producing sodium carbonate from sodium-containing materials, comprising the following steps:

[0014] (1) Using sodium chloride, CO 2 , NH 3 and water as raw materials to produce sodium carbonate by the combined soda process, and by-product ammonium chloride;

[0015] (2) Placing calcium carbonate and ammonium chloride in a solution containing calcium chloride to carry out ammonium chloride transformation to obtain a mixed gas containing CO 2 and NH 3 and a calcium chloride slurry; using the calcium chloride slurry for the production of calcium-containing compounds;

[0016] Alternatively, mixing and roasting calcium carbonate and ammonium chloride to carry out ammonium chloride transformation to obtain a mixed gas containing CO 2 and NH 3 and a by-product calcium chloride product;

[0017] (3) Returning the mixed gas of CO 2 and NH 3 to step (1) for recycling;

[0018] Alternatively, making the mixed gas of CO 2 and NH 3 into ammonium carbonate or ammonium bicarbonate products.

[0019] The present invention ingeniously uses ammonium chloride obtained from the process of decomposing calcium carbonate to produce soda, generating a mixed gas containing CO 2 and NH 3 , and also by-producing calcium-containing compounds. The present invention simultaneously produces a mixed gas of CO 2 and NH 3 . First, the presence of CO 2 can prevent the formation of hydrogen bonds between NH 3 and H 2 O. Since NH 3 is alkaline and CO 2 is acidic, once NH 3 combines with CO 2 , it loses the ability to form hydrogen bonds with H 2 O. Second, CO 2 can play a good role in carrying the volatilization of NH 3 , significantly accelerating the volatilization of NH 3 in the solution, avoiding the hindrance of the decomposition of ammonium chloride due to the accumulation of NH 3 , and making the volatilization of NH 3 easier. Further, the present invention not only realizes NH 3Recycled in the alkali-making process, and also provides the CO required for alkali-making 2 gas source. Meanwhile, calcium-containing compounds are also by-produced. The present invention has the advantages of wide raw material adaptability, simple process, high production efficiency, good economic benefits, convenient operation, etc.

[0020] The principle of using ammonium chloride obtained from the calcium carbonate decomposition alkali-making process is as follows:

[0021] Ammonium chloride reacts with calcium carbonate to obtain calcium-containing products and a mixed gas containing NH 3 and CO 2 . The obtained NH 3 and CO 2 mixed gas is directly used as the production raw material for alkali-making, or the NH 3 and CO 2 mixed gas is made into ammonium carbonate salt products:

[0022] CaCO 3 + 2NH 4 Cl =Δ= CaCl 2 + 2NH 3 ↑ + CO 2 ↑ + H 2 O↑ (3)

[0023] 2NH 3 + CO 2 + H 2 O = (NH 4 ) 2 CO 3 (4)

[0024] (NH 4 ) 2 CO 3 + CO 2 + H 2 O = 2NH 4 HCO 3 (5)

[0025] Using the NH 3 and CO 2 mixed gas generated by the reaction to prepare ammonium bicarbonate can not only simplify the carbonation process of brine, but also optimize the equipment configuration in the process, and improve the operation efficiency and production capacity of the equipment.

[0026] In the present invention, the calcium-containing products include solid calcium chloride, liquid calcium chloride, calcium carbonate and other products.

[0027] Meanwhile, the present invention selects a solution containing calcium chloride as the reaction bottom liquid, mainly because the reaction of ammonium chloride decomposing calcium carbonate in an aqueous solution belongs to the endothermic reaction type. The purpose of selecting a solution containing calcium chloride as the reaction bottom liquid is as follows: Utilize the characteristic that the boiling point of the CaCl 2 solution increases with the increase of its concentration. When the concentration of the calcium chloride solution reaches a certain concentration, the boiling point temperature of the CaCl 2 solution can be increased to ≥105 °C, which can meet the process temperature required for the rapid decomposition of calcium carbonate by ammonium chloride in the solution, and the product obtained by the reaction is also CaCl 2 , which facilitates its recovery and utilization.

[0028] As a preferred embodiment, the sodium chloride is prepared by a method comprising the following steps:

[0029] Dissolve the solid material containing sodium salt to form a nearly saturated salt solution or a saturated salt solution. Add ammonium chloride to the nearly saturated salt solution or saturated salt solution and stir while heating. Wait until the ammonium chloride is dissolved to reach or nearly reach saturation. Utilize the common ion effect of Cl - ions to force Na + ions to transform into NaCl and selectively crystallize out. Filter and separate to obtain sodium chloride crystals and the post-salting-out liquid. The sodium chloride crystals are directly used as raw materials for producing sodium carbonate, or are washed and filtered to obtain refined sodium chloride products; the post-salting-out liquid is cooled and crystallized to precipitate ammonium chloride crystals, and then filtered and separated to obtain ammonium chloride crystals and ammonium chloride crystallization mother liquor. The ammonium chloride crystals are returned to the salting-out process for recycling, and the ammonium chloride crystallization mother liquor is returned to the solid material dissolution process containing sodium salt for continuous use until it significantly hinders the dissolution of the solid material containing sodium salt, and then is discharged for comprehensive recovery; the addition amount of ammonium chloride is 1 to 3 times the amount required to reach saturation in the nearly saturated salt solution or saturated salt solution.

[0030] As a preferred embodiment, the sodium salt in the solid material containing sodium salt is selected from at least one of sodium chloride, sodium sulfate, and sodium nitrate.

[0031] As a preferred embodiment, the dissolution temperature of the solid material containing sodium salt is 25 to 65 °C, and the temperature at which sodium chloride selectively crystallizes out is 65 to 115 °C.

[0032] The basic principle of preparing refined sodium chloride by transforming the solid material containing sodium salt with ammonium chloride is as follows:

[0033] 2NH 4 Cl (in excess) + Na 2 SO 4 =Δ= 2NaCl↓ + (NH 4 ) 2 SO 4 (1)

[0034] NH 4 Cl (excess) + NaNO 3 =Δ= NaCl↓ + NH 4 NO 3 (2)

[0035] There are already mature theories and production processes for preparing heavy alkali by carbonating ammoniated brine. And it has long been known that adding solid NaCl to the middle of the carbonating tower can improve the utilization rate of sodium in the process. However, the added NaCl must be refined salt that has removed Ca 2+ and Mg 2 + impurities. However, the cost of refined salt has limited the industrial application of this technology. The present invention ingeniously uses ammonium chloride as a transformation agent to convert sodium-containing materials into refined sodium chloride. This not only significantly reduces the production cost of refined NaCl, but also greatly improves the quality of refined sodium chloride. Moreover, when carbonating with the obtained dissolved solution of refined sodium chloride, neither calcium nor magnesium precipitates are generated, nor will ammonium sulfate or ammonium nitrate accumulate in the carbonation filtrate mother liquor, because the purity of the obtained refined sodium chloride can reach more than 99.6%, which is higher than the standard of the first-class product of refined industrial salt in the national standard.

[0036] As a preferred solution, when the solid material containing sodium salt contains organic impurities and / or other inorganic impurities, impurity removal pretreatment is required, and the impurity removal pretreatment includes at least one of the following methods:

[0037] When the solid material containing sodium salt contains organic impurities, first pyrolyze or oxidize the solid material containing sodium salt and then dissolve it;

[0038] When the solid material containing sodium salt contains insoluble inorganic impurities, filter the nearly saturated salt solution or saturated salt solution formed by dissolving the solid material containing sodium salt;

[0039] When the solid material containing sodium salt contains water-soluble inorganic impurities, perform anion impurity removal treatment and cation impurity removal treatment on the nearly saturated salt solution or saturated salt solution formed by dissolving the solid material containing sodium salt: first add ferric salt and / or aluminum salt to the nearly saturated salt solution or saturated salt solution according to 1 - 1.5 times of the stoichiometry and adjust the solution pH to 3.5 - 6.5, stir at 50 - 70 °C for 0.5 - 1.5 h to remove the anion impurities therein, then add lime milk - soda ash or lime milk - calcium chloride, and adjust the pH value of the solution to 9 - 11, stir for 0.5 - 1 h to remove the cation impurities therein, and then use hydrochloric acid to callback the pH to 5 - 7; the ferric salt is selected from at least one of ferric sulfate, ferric nitrate and ferric chloride; the aluminum salt is selected from at least one of aluminum sulfate, aluminum nitrate and aluminum chloride.

[0040] As a preferred embodiment, the anionic impurities include phosphate and / or silicate.

[0041] As a preferred embodiment, the cationic impurities include Mg 2+ , Fe 3+ , Mn 2+ , Zn 2+ and Cu 2+ and at least one of the cations therein.

[0042] As a preferred embodiment, when using lime milk - soda ash to remove cationic impurities, the molar ratio of Ca(OH) 2 / NaCO 3 is 1:1 - 2.

[0043] As a preferred embodiment, when using lime milk - calcium chloride to remove cationic impurities, the molar ratio of Ca(OH) 2 / CaCl 2 is 1:1 - 3.

[0044] The present invention has no special requirements for the temperature when removing cations, and the temperature that can be adopted is 5 - 95 °C.

[0045] As a preferred embodiment, the molar dosage ratio of ammonium chloride to calcium carbonate is 1:0.5 - 1.5;

[0046] And the operation of transforming ammonium chloride specifically includes:

[0047] First, preheat the temperature of the solution containing calcium chloride to above 110 °C as the reaction bottom liquid, then add calcium carbonate and ammonium chloride to the preheated solution containing calcium chloride. After the feeding is completed, keep calcium carbonate stirred at a constant temperature of 110 - 175 °C for 0.5 - 0.25 h to generate a calcium chloride slurry and a mixed gas containing NH 3 and CO 2 ; the calcium chloride concentration in the solution containing calcium chloride is ≥ 30 wt.%;

[0048] It should be noted that there are essential differences between decomposing ammonium chloride with calcium carbonate in a calcium chloride solution at a temperature as high as above 110 °C and steaming ammonia with lime milk in the mother liquor for soda production obtained by the ammonia - soda method. During the reaction process, the former simultaneously generates NH 3 and CO 2 gases, while the latter only generates NH 3 . As is well known, NH 3 can form hydrogen bonds with H 2 O, which makes the volatilization of NH 3 in the aqueous solution difficult, especially in the later stage of ammonia steaming, which severely restricts the operation efficiency of ammonium chloride decomposition. However, NH 3and CO 2 The situation is different when both are produced simultaneously. First, the presence of CO 2 can prevent the formation of hydrogen bonds between NH 3 and H 2 O. Since NH 3 is alkaline and CO 2 is acidic, once NH 3 combines with CO 2 , it loses the ability to form hydrogen bonds with H 2 O. Second, CO 2 can play a good role in carrying the volatilization of NH 3 , which can significantly accelerate the volatilization of NH 3 in the solution and avoid the hindrance of the decomposition of ammonium chloride due to the accumulation of NH 3 . In addition, although the decomposition temperature of ammonium chloride in the former is higher than that in the latter when compared, its energy consumption is much lower than that in the latter, because only a high-concentration (concentration ≥ 30 wt.%) calcium chloride solution can raise its temperature above 110°C, and the high-concentration calcium chloride solution has strong water absorption, making it difficult to evaporate water from the high-concentration calcium chloride solution. Therefore, for decomposing the same mass of ammonium chloride, the water evaporation amount in the former is much smaller than that in the latter.

[0049] In the calcium chloride-containing solution of the present invention, the calcium chloride concentration is further preferably 30 wt.% - 60 wt.%.

[0050] As a preferred embodiment, the operation of ammonium chloride transformation specifically includes: after mixing calcium carbonate and ammonium chloride, roasting at a temperature of 350 - 650°C for 0.5 - 3 h to obtain a mixed gas containing CO 2 and NH 3 and anhydrous calcium chloride.

[0051] As a preferred embodiment, the particle size of the calcium carbonate is < 60 μm.

[0052] As a preferred embodiment, the method of using the obtained calcium chloride solution for the production of calcium-containing compounds includes: keeping the generated calcium chloride slurry warm and clarified, and directly returning the obtained supernatant to be used as the reaction bottom liquid. The bottom sludge is stirred, washed, filtered, and the obtained washing water is returned to be used as a regulator for the concentration or temperature of the reaction slurry.

[0053] As a preferred embodiment, the method of using the obtained calcium chloride solution for the production of calcium-containing compounds includes: first filtering the generated calcium chloride slurry to remove suspended solids, and then separating and recovering chlorine and calcium in the filtrate. The specific steps of recovering chlorine and calcium in the filtrate include: adding sulfuric acid to the filtrate to convert calcium chloride therein into anhydrite and HCl gas or hydrochloric acid, or introducing NH 3 and CO2 The gas converts calcium chloride therein into light calcium carbonate and ammonium chloride, or ammonium sulfate is added to the filtrate to convert calcium chloride therein into calcium sulfate dihydrate and ammonium chloride.

[0054] As a preferred embodiment, the method of using the obtained calcium chloride solution for the production of calcium-containing compounds includes: diluting the generated calcium chloride slurry with water to a CaCl 2 concentration of 25-45 wt%, filtering while keeping warm at a hot temperature, cooling the filtrate to crystallize out ammonium chloride therein, filtering to obtain ammonium chloride crystals or a mixed crystal of ammonium chloride and calcium chloride and its crystallization mother liquor, the ammonium chloride crystals or the mixed crystal of ammonium chloride and calcium chloride are returned to the ammonium chloride transformation process for recycling, and the crystallization mother liquor is the liquid calcium chloride product.

[0055] As a more preferred embodiment, the liquid calcium chloride is evaporated and concentrated to obtain a solid calcium chloride product.

[0056] As a preferred embodiment, the comprehensive recovery is selected from at least one of the following methods:

[0057] When the solid material containing sodium salt contains nitrate and / or sulfate, the ammonium chloride crystallization mother liquor is evaporated and concentrated to separate and recover sodium chloride, ammonium chloride, ammonium sulfate and / or ammonium nitrate therein;

[0058] When the solid material containing sodium salt contains sulfate, according to SO 4 2- / Ca 2+ The molar ratio of 1:0.9-1.5, calcium chloride is added to the ammonium chloride crystallization mother liquor for denitrification, filtered, washed and dried to obtain a precipitated calcium sulfate product, and then hydrochloric acid is added to adjust the pH value of the filtrate back to 5-7.

[0059] Compared with the prior art, the present invention has at least the following advantages:

[0060] In the present invention, ammonium chloride is used as a transformation agent to first convert all non-chlorinated sodium salts in the sodium-containing material into refined sodium chloride, broadening the adaptability of the alkali-making process to raw materials. Then, the obtained sodium chloride is used as a raw material, and the combined soda process is used to produce sodium carbonate. Calcium carbonate powder is used to decompose ammonium chloride obtained in the alkali-making process under heating conditions. Not only is the recycling of NH 3 realized in the alkali-making process, but also the CO 2 gas source required for alkali-making is provided, and calcium-containing compound products are by-produced. Compared with the ammonia-soda method, it neither produces ammonia stilling waste liquid nor requires a large amount of equipment investment for lime burning. Compared with the combined method, it not only saves the cost of building a supporting ammonia plant, but also eliminates the worry of unsalable ammonium chloride.

[0061] The present invention inherits the advantages of the ammonia-soda process and the combined soda-making process, overcomes the disadvantages of both, and has the advantages of wide raw material adaptability, simple process, high production efficiency, good economic benefits, convenient operation, etc. It is suitable for large-scale industrial production of sodium carbonate from sodium-containing materials. Detailed implementation mode

[0062] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0063] The following further illustrates the present invention in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative efforts still fall within the protection scope of the present invention.

[0064] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0065] Example 1

[0066] Using 5000 g of first-grade refined industrial salt as the raw material for soda production, the combined soda-making process is adopted (the refined industrial salt is first dissolved in water and ammonia is charged to prepare ammoniacal brine, and then CO is charged into the ammoniacal brine 2 Carbonation, crystallization to precipitate sodium bicarbonate, filtration to obtain heavy soda and mother liquor for soda production). The heavy soda obtained in the process is filtered, washed, and thermally decomposed to obtain first-grade industrial sodium carbonate with a purity of 98.8%. The mother liquor for soda production obtained is used to produce ammonium chloride by the "cold method". After the obtained ammonium chloride crystals are washed, filtered, and dried with saturated ammonium chloride solution, the ammonium chloride is pyrolyzed at a temperature of 500 °C to form a mixed gas of NH 3 and HCl, and the HCl in it is countercurrently adsorbed by particles with a particle size of 0.3 - 2.3 cm made of limestone powder with a CaCO 3 content of 94.7% (ammonium chloride and calcium carbonate are fed according to the stoichiometric ratio of the chemical reaction, specifically 1:1.1), and the contact time is 0.5 h, so that it is converted into anhydrous calcium chloride and a mixed gas of NH 3 and CO 2 The effective utilization rate of CaCO 3 in the adsorption process is 96.4%, the adsorption rate of HCl reaches 99.8%, and the NH 3 and CO 2The mixed gas is collected and returned as a production raw material for soda production. The obtained anhydrous calcium chloride has a purity of 95.2%, meeting the standard of Type I anhydrous calcium chloride specified in GB / T 26520-2021.

[0067] Example 2

[0068] Using mechanically mined rock salt containing 95.16% NaCl, 3.87% NaSO 4 3, 0.64% CaCl 2 0, 0.31% MgCl 2 as raw materials to prepare refined sodium chloride: The rock salt is added with water, stirred and dissolved, and the temperature is raised to prepare a saturated NaCl solution at 65°C. Then, ferric chloride solution is added (1.5 times the stoichiometric amount for forming iron phosphate), and the pH of the solution is adjusted to 4.3. Stir at a constant temperature for 1 h (65°C), and filter to remove anionic impurities such as phosphate and silicate ions. Then, lime milk-sodium carbonate slurry (the molar ratio of Ca(OH) 2 / NaCO 3 is 1:1.6) is added to remove cationic impurities such as calcium and magnesium. The obtained purified solution is heated and stirred, and ammonium chloride crystals are added as a salting-out agent according to 1.5 times the solubility of ammonium chloride at 65°C. When the solution temperature rises to 85°C and it is confirmed that the ammonium chloride is completely dissolved, filter while hot to obtain sodium chloride crystals and its post-salting-out liquid. The sodium chloride crystals are washed, filtered, and dried to obtain refined sodium chloride with a purity of 99.8% and the contents of Ca and Mg both <0.01%. The obtained post-salting-out liquid is cooled and crystallized to precipitate ammonium chloride, and the ammonium chloride crystals are filtered to obtain ammonium chloride crystals and its post-crystallization liquid. The ammonium chloride crystals are returned to continue to be used as a salting-out agent, and the ammonium chloride post-crystallization liquid is directly returned to the original salt dissolution process for continued use, or after adding calcium chloride for denitrification (SO 4 2- / Ca 2+ The molar ratio is 1:1.3), and then it is returned to the original salt dissolution process for continued use. The effective utilization rate of sodium in the cyclic refining process is 99.31%.

[0069] Using the obtained refined sodium chloride as a raw material to produce sodium carbonate: 1000 g of refined sodium chloride is added with water to dissolve to obtain saturated refined brine. The refined brine is carbonated with ammonium bicarbonate to prepare baking soda. According to NaCl / NH 4 HCO 3Ammonium bicarbonate is added to saturated brine in a molar ratio of 1:1.2 in batches with stirring slowly, so that sodium bicarbonate crystallizes out. The sodium bicarbonate is filtered, washed, and thermally decomposed to obtain an industrial high-quality sodium carbonate product with a purity of 99.3%. The mother liquor of soda production is heated to 65 °C and evaporated under negative pressure for 0.5 h, so that the residual ammonium bicarbonate and sodium bicarbonate therein are converted into ammonium carbonate and sodium carbonate. Then, refined sodium chloride is added to dissolve it to saturation, cooled, and ammonium chloride is selectively crystallized out. The ammonium chloride crystals and their mother liquor are obtained by filtration. The mother liquor is returned to the saturated brine preparation process for recycling. After the obtained ammonium chloride crystals are washed with saturated ammonium chloride solution, they are slowly added to a calcium chloride solution (concentration: 50 wt.%) at a temperature of 135 °C, and CaCO 3 with a stoichiometric amount (molar ratio of ammonium chloride to calcium carbonate is 2:1) of -360 mesh CaCO 3 limestone powder with a content of 96.7% is added, so that it is rapidly decomposed and converted into a calcium chloride solution and a mixed gas of NH 3 and CO 2 . The decomposition temperature is 135 °C and the time is 2.5 h. The effective utilization rate of the added ammonium chloride reaches 99.6%. The mixed gas of NH 3 and CO 2 produced by the reaction is collected and merged with the thermal decomposition gas of sodium bicarbonate for the production of ammonium bicarbonate. The obtained ammonium bicarbonate is returned to the carbonation process for utilization. After the reaction slurry is clarified, part of the supernatant is returned to continue to be used as the reaction bottom liquid for ammonium chloride decomposition, and the rest of the supernatant is diluted with water to a CaCl 2 concentration of 30 wt%, filtered while hot and kept warm. The filtrate is cooled to crystallize ammonium chloride therein. The mixed crystals of ammonium chloride and calcium chloride and their mother liquor are obtained by filtration. The mixed crystals of ammonium chloride and calcium chloride are returned to the ammonium chloride transformation process for recycling, and the mother liquor is sold as a liquid calcium chloride product. The utilization rate of refined sodium chloride in the soda production process is 98.72%.

[0070] Example 3

[0071] Using waste salt residue containing 86.38% NaCl; 5.74% Na 2 SO 4 , 0.47% of metal impurities such as (calcium, magnesium, iron), 5.38% of moisture, and 2.01% of organic matter as raw materials to prepare refined sodium chloride: The waste salt residue is first thermally decomposed at 380 °C to remove organic matter, then dissolved in water to obtain a saturated sodium chloride solution at 60 °C. Then, lime milk is added to the solution to causticize the sodium carbonate solution (Ca(OH) 2 / NaCO 3The slurry obtained with a molar ratio of 1:1.3), after removing metal ion impurities such as calcium, magnesium, and iron therein, the obtained purified liquid is heated, and ammonium chloride crystals are added to the solution with stirring as a salting-out agent at 1.6 times the solubility of ammonium chloride at 60 °C. After the solution temperature rises to 95 °C and it is confirmed that the ammonium chloride is completely dissolved, it is filtered while hot and kept warm to obtain sodium chloride crystals and the liquid after salting out. The sodium chloride crystals are washed, filtered, and dried to obtain refined sodium chloride with a purity of 99.9% and the contents of Ca and Mg both <0.01%. The liquid after salting out is cooled and crystallized to precipitate ammonium chloride, and the ammonium chloride crystals are filtered to obtain ammonium chloride crystals and the liquid after crystallization. The ammonium chloride crystals are returned to continue to be used as the salting-out agent for sodium chloride, and the liquid after crystallization of ammonium chloride is directly returned to the dissolution process for continued use, or calcium chloride is added for denitrification (SO 4 2- / Ca 2+ with a molar ratio of 1:1.1), and then returned to the dissolution process for continued use. The effective utilization rate of sodium in the cyclic refining process is 99.18%.

[0072] Using the obtained refined sodium chloride as a raw material to produce sodium carbonate: 600 g of refined sodium chloride is dissolved in water to obtain saturated refined brine. The refined brine is carbonated with NH 3 and CO 2 gases to prepare sodium bicarbonate. After filtration, washing, and heat decomposition, industrial high-quality sodium carbonate with a purity of 99.2% is obtained (the refined brine is first filled with ammonia to prepare ammoniacal brine, and then CO 2 gas is carbonated to precipitate sodium bicarbonate). The mother liquor for soda making is heated to 80 °C and evaporated at normal pressure for 1 h to convert the residual ammonium bicarbonate and sodium bicarbonate therein into ammonium carbonate and sodium carbonate. Then, refined sodium chloride is added to dissolve the sodium chloride to saturation, cooled, and ammonium chloride is selectively crystallized out. The ammonium chloride crystals are filtered to obtain ammonium chloride crystals and the mother liquor after crystallization. The mother liquor after crystallization is returned to the refined brine preparation process for cyclic use. The obtained ammonium chloride crystals are washed with saturated ammonium chloride solution, and then according to the Cl / Ca molar ratio of 2:1 and -600-mesh CaCO 3 limestone powder with a content of 95.8% is added with water and mixed to make ore pellets with a particle size of 1.5 - 2.5 cm. After the ore pellets are dried in the air, they are added to a continuous in-and-out vertical kiln at 350 - 650 °C and roasted for 2 h to obtain anhydrous calcium chloride with a content of 96.1%. The regeneration rate of NH 2 during the roasting process is 99.3%. The flue gas containing NH 3 and CO 3 and CO 2 is collected and sent to the refined brine carbonation process for cyclic absorption. The utilization rate of refined sodium chloride in the soda making process is 98.41%.

[0073] Example 4

[0074] Using mechanically mined Na 2 SO 424.91%, NaCO 3 Using natural mirabilite with 0.08%, NaCl 1.79%, water-insoluble matter 48.65%, and moisture 24.58% as raw materials to prepare refined sodium chloride: First, hydrate the mirabilite with water, filter to remove insoluble impurities to obtain a saturated sodium sulfate solution at 40 - 50 °C, and slowly add ammonium chloride crystals as a transformation agent and salting-out agent according to twice the solubility of ammonium chloride at 50 °C, stir and heat. When the solution temperature rises to 90 °C, filter while hot and keep warm to obtain sodium chloride crystals and its post-salting-out liquid. The sodium chloride crystals are washed with saturated sodium chloride solution, filtered, and dried to obtain refined sodium chloride with a purity of 99.7%. For the obtained post-salting-out liquid, first cool and crystallize to separate ammonium chloride, and return it to the transformation process for recycling. Then, add calcium chloride to the post-salting-out liquid according to the molar ratio of SO 4 2- / Ca 2+ 1:0.9 for heating and stirring to remove nitrate, filter to obtain precipitated calcium sulfate and its post-precipitation liquid. The post-precipitation liquid is cooled and crystallized, filtered to obtain ammonium chloride and post-nitrate-removal liquid, and the post-nitrate-removal liquid is returned to the mirabilite dissolution process for recycling. The effective utilization rate of sodium in the refining process is 98.26%.

[0075] Using the obtained refined sodium chloride as raw material to produce sodium carbonate: Dissolve 1200 g of refined sodium chloride in water to obtain saturated refined brine. The refined brine is carbonated with NH 3 and CO 2 gases to prepare sodium bicarbonate. After filtration, washing, and thermal decomposition, industrial sodium carbonate of first-class quality with a purity of 98.9% is obtained (the refined brine is first filled with ammonia to prepare ammoniacal brine, and then filled with CO 2 gas for carbonation to precipitate sodium bicarbonate). The obtained mother liquor for soda production is heated to 75 °C and evaporated at normal pressure for 1.5 h to convert the remaining ammonium bicarbonate and sodium bicarbonate into ammonium carbonate and sodium carbonate. Then, refined sodium chloride is added to make the sodium chloride dissolve close to saturation, cooled, and ammonium chloride is selectively crystallized out. After filtration, ammonium chloride crystals and its crystallization mother liquor are obtained. The crystallization mother liquor is returned to the refined brine preparation process for recycling. The obtained ammonium chloride crystals are mixed with -1000-mesh CaCO 3 powder with a CaCO 3 content of 96.3% in a ratio of Cl / Ca molar ratio of 2:1 and mixed with water to form a dough, roasted at 550 °C for 1 h. The NH 2 and CO

[0076] flue gas generated during roasting is sent to the soda production process for utilization. The obtained roasted sand containing calcium chloride is returned to the post-mirabilite transformation liquid for nitrate removal, realizing the recycling of chlorine elements in the process of producing sodium carbonate from mirabilite. The utilization rate of refined sodium chloride in the soda production process is 98.34%.The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for producing sodium carbonate with sodium-containing materials, characterized in that: The following steps are involved: (1) Using sodium chloride, CO2, NH3 and water as raw materials, a combined alkali production process is used to produce sodium carbonate, and ammonium chloride is produced as a by-product; (2) placing calcium carbonate and ammonium chloride in a solution containing calcium chloride, performing ammonium chloride transformation, and obtaining a mixed gas containing CO2 and NH3 and a calcium chloride slurry; using the calcium chloride slurry for the production of calcium-containing compounds; Alternatively, calcium carbonate and ammonium chloride are mixed and roasted to transform the ammonium chloride to obtain a mixed gas containing CO2 and NH3 and a by-product calcium chloride product; (3) returning the mixed gas of CO2 and NH3 to step (1) for recycling; Alternatively, the mixed gas of CO2 and NH3 is made into ammonium carbonate or ammonium bicarbonate product.

2. A method for producing sodium carbonate from sodium-containing materials according to claim 1, characterized in that: The sodium chloride is prepared by a method comprising the following steps: The solid material containing sodium salt is dissolved to form a nearly saturated salt solution or a saturated salt solution, and ammonium chloride is added to the nearly saturated salt solution or the saturated salt solution under heating and stirring, and the ammonium chloride is dissolved until it reaches or approaches saturation, and Cl - The common ion effect of ions forces Na + The ions are converted into NaCl, which is selectively crystallized and separated by filtration to obtain sodium chloride crystals and a salting-out liquid. The sodium chloride crystals are directly used as raw materials for producing sodium carbonate, or are washed and filtered to obtain a refined sodium chloride product. The salting-out liquid is cooled and crystallized to precipitate ammonium chloride crystals, which are filtered and separated to obtain ammonium chloride crystals and an ammonium chloride crystallization mother liquor. The ammonium chloride crystals are returned to the salting-out step for recycling, and the ammonium chloride crystallization mother liquor is returned to the sodium salt-containing solid material dissolution step for continued use until it has a significant inhibitory effect on the dissolution of the sodium salt-containing solid material, and the circuit is opened for comprehensive recovery. The amount of ammonium chloride added is 1 to 3 times the amount required to dissolve in the nearly saturated salt solution or the saturated salt solution to reach saturation.

3. A method for producing sodium carbonate from sodium-containing materials according to claim 2, characterized in that: The sodium salt in the sodium salt-containing solid material is selected from at least one of sodium chloride, sodium sulfate and sodium nitrate.

4. A method for producing sodium carbonate from sodium-containing materials according to claim 2, characterized in that: The dissolution temperature of the solid material containing sodium salt is 25-65°C, and the temperature for selective crystallization of sodium chloride is 65-115°C.

5. A method for producing sodium carbonate from sodium-containing materials according to claim 2, characterized in that: When the sodium salt-containing solid material contains organic impurities and / or other inorganic impurities, it is necessary to perform impurity removal pretreatment, and the impurity removal pretreatment includes at least one of the following methods: When the solid material containing sodium salt contains organic impurities, the solid material containing sodium salt is first subjected to pyrolysis treatment or oxidation treatment and then dissolved; When the sodium salt-containing solid material contains insoluble inorganic impurities, filtering the nearly saturated salt solution or saturated salt solution formed by dissolving the sodium salt-containing solid material; When the sodium salt-containing solid material contains water-soluble inorganic impurities, the near-saturated salt solution or saturated salt solution formed by dissolving the sodium salt-containing solid material is subjected to anion impurity removal treatment and cationic impurity removal treatment: first, iron salt and / or aluminum salt are added to the near-saturated salt solution or saturated salt solution at 1-1.5 times the stoichiometric amount, and the pH of the solution is adjusted to 3.5-6.5, and stirred at 50-70° C. for 0.5-1.5 h to remove anion impurities therein, and then lime milk-soda ash or lime milk-calcium chloride is added, and the pH value of the solution is adjusted to 9-11, stirred for 0.5-1 h to remove cationic impurities therein, and then hydrochloric acid is used to adjust the pH to 5-7; the iron salt is selected from at least one of ferric sulfate, ferric nitrate and ferric chloride; the aluminum salt is selected from at least one of aluminum sulfate, aluminum nitrate and aluminum chloride.

6. A method for producing sodium carbonate from sodium-containing materials according to claim 5, characterized in that: When lime milk-soda ash is used to remove cationic impurities, the molar ratio of Ca(OH)2 / NaCO3 is 1:1~2; When lime milk-calcium chloride is used to remove cationic impurities, the molar ratio of Ca(OH)2 / CaCl2 is 1:1~3.

7. A method for producing sodium carbonate from sodium-containing materials according to any one of claims 1 to 6, characterized in that: The molar ratio of the ammonium chloride to the calcium carbonate is 1:0.5-1.5; And the operation of the ammonium chloride transformation specifically includes: First, the temperature of the solution containing calcium chloride is preheated to above 110°C as a reaction base liquid, and then calcium carbonate and ammonium chloride are added to the preheated solution containing calcium chloride. After the addition is completed, the calcium carbonate is stirred at a constant temperature of 110-175°C for 0.5-0.25h to generate calcium chloride slurry and a mixed gas containing NH3 and CO2; the calcium chloride concentration in the calcium chloride solution is ≥30wt.%; Alternatively, the calcium carbonate and ammonium chloride are mixed and calcined at a temperature of 350-650° C. for 0.5-3 h to obtain a mixed gas containing CO 2 and NH 3 and anhydrous calcium chloride.

8. A method for producing sodium carbonate from sodium-containing materials according to claim 7, characterized in that: The method for producing the obtained calcium chloride solution as a calcium-containing compound comprises: The generated calcium chloride slurry is kept warm and clarified, the obtained supernatant is directly returned as the reaction bottom liquid, the bottom mud is stirred, washed, filtered, and the obtained washing water is returned as a concentration or temperature regulator of the reaction slurry; or, The generated calcium chloride slurry is first filtered to remove suspended matter, and then the chlorine and calcium in the filtrate are separated and recovered. The specific steps of recovering the chlorine and calcium in the filtrate include: adding sulfuric acid to the filtrate to convert the calcium chloride therein into anhydrite and HCl gas or hydrochloric acid, or passing NH3 and CO2 gas into the filtrate to convert the calcium chloride therein into light calcium carbonate and ammonium chloride, or adding ammonium sulfate to the filtrate to convert the calcium chloride therein into calcium sulfate dihydrate and ammonium chloride; or, The generated calcium chloride slurry is diluted with water to a CaCl2 concentration of 25-45wt%, and filtered while hot. The filtrate is cooled to allow the ammonium chloride crystals therein to precipitate, and ammonium chloride crystals or mixed crystals of ammonium chloride and calcium chloride and their crystallization mother liquor are filtered out. The ammonium chloride crystals or mixed crystals of ammonium chloride and calcium chloride are returned to the ammonium chloride transformation process for recycling, and the crystallization mother liquor is the liquid calcium chloride product.

9. A method for producing sodium carbonate from sodium-containing materials according to claim 8, characterized in that: The liquid calcium chloride is evaporated and concentrated to obtain a solid calcium chloride product.

10. A method for producing sodium carbonate from sodium-containing materials according to claim 2, characterized in that: The comprehensive recovery is selected from at least one of the following methods: When the sodium salt-containing solid material contains nitrate and / or sulfate, the ammonium chloride crystallization mother liquor is evaporated and concentrated to separate and recover the sodium chloride, ammonium chloride, ammonium sulfate and / or ammonium nitrate therein; When the solid material containing sodium salt contains sulfate, according to SO4 2- / Ca 2+ The molar ratio is 1:0.9-1.5, and calcium chloride is added to the ammonium chloride crystal mother liquor for denitration, and the product of precipitated calcium sulfate is obtained by filtering, washing and drying, and then hydrochloric acid is added to adjust the pH value of the filtrate to 5-7.