CN113896209B - Method for preparing sodium carbonate and byproducts potassium sulfate, ammonium sulfate and ammonium chloride from waste salt - Google Patents
Method for preparing sodium carbonate and byproducts potassium sulfate, ammonium sulfate and ammonium chloride from waste salt Download PDFInfo
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- CN113896209B CN113896209B CN202111498227.XA CN202111498227A CN113896209B CN 113896209 B CN113896209 B CN 113896209B CN 202111498227 A CN202111498227 A CN 202111498227A CN 113896209 B CN113896209 B CN 113896209B
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- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D7/00—Carbonates of sodium, potassium or alkali metals in general
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/16—Halides of ammonium
- C01C1/164—Ammonium chloride
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/24—Sulfates of ammonium
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
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- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
The invention provides a method for preparing sodium carbonate with waste salt and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which is characterized in that waste salt is separated after pulping to obtain dilute-phase slurry and concentrated-phase slurry; respectively carrying out solid-liquid separation on the dilute-phase slurry and the concentrated-phase slurry to obtain insoluble organic matters, prefabricated salt and treatment liquid; the pre-prepared salt is treated in the preparation process of sodium carbonate and ammonium salt to respectively obtain sodium carbonate, ammonium sulfate and ammonium chloride; carrying out oxidation treatment on the obtained treatment liquid to obtain a purified solution; when purifying K in solution+Performing precipitation treatment after the concentration reaches a preset value to obtain potassium-containing precipitate and a potassium-removing solution; the potassium-containing precipitate enters a potassium sulfate preparation procedure; the potassium-removing solution returns to the pulping step for recycling. The method has the advantages of clean process, simple flow and low cost, the utilization rate of sodium is not less than 90.8 percent, the purity of sodium carbonate is not less than 97 percent by weight, and the purity of the obtained potassium sulfate, ammonium sulfate and ammonium chloride can meet certain use requirements.
Description
Technical Field
The invention belongs to the technical field of chemical engineering environmental protection, relates to a method for preparing sodium carbonate with byproducts of potassium sulfate, ammonium sulfate and ammonium chloride by using salt, and particularly relates to a method for purifying waste salt and preparing sodium carbonate, potassium sulfate, ammonium sulfate and ammonium chloride.
Background
At present, the chemical waste salt taking sodium chloride and sodium sulfate as main components has huge yield and higher treatment cost, and the high treatment cost greatly increases the production and operation cost of related enterprises, thereby greatly restricting the technical upgrading and sustainable development of the related enterprises.
At present, the conventional treatment method of chemical waste salt mainly separates sodium sulfate and sodium chloride, mainly comprises a salt-nitrate method separation method and a nanofiltration separation method, wherein the salt-nitrate method separation method is divided into a hot method and a cold method. The nanofiltration separation method can separate sodium chloride and sodium sulfate to a certain extent, but cannot realize complete separation of two ions, so sodium sulfate and sodium chloride products with high quality cannot be obtained, and the process has high energy consumption and is not economical. In addition, sodium sulfate and sodium chloride are mainly upstream raw materials in the chemical industry, are used as byproducts of solid waste treatment, have low market acceptance and limited market absorption capacity due to lack of relevant standards, are mainly stockpiled, and have serious threat to the environment due to soluble salts. At present, in the face of increasingly severe environmental protection supervision, the problem of waste salt has become an important bottleneck restricting the development of related enterprises, so that related technologies are urgently needed at present to really realize resource utilization of waste salt and assist the enterprises to realize technology upgrading and sustainable development.
Although chemical waste salt belongs to typical solid waste, the chemical waste salt also belongs to a resource rich in inorganic salt, and according to the analysis of an industrial chain, sodium carbonate, ammonium chloride and ammonium sulfate are important downstream products of the chemical waste salt, and the sodium carbonate is an important chemical product and has wide application in the fields of nonferrous metallurgy, glass, food processing and the like; because of high nitrogen content, ammonium chloride is often used as an additive of nitrogen in compound fertilizers and is widely applied in the agricultural field. Ammonium sulfate is an important agricultural nitrogen fertilizer, is mainly a byproduct in chemical fiber industry and coking industry, and has huge annual demand in global markets. If the sodium carbonate, the ammonium sulfate and the ammonium chloride can be directly prepared into downstream bulk chemical products, namely the sodium carbonate, the ammonium sulfate and the ammonium chloride, the market absorption space can be effectively expanded, and the resource utilization of the waste salt is really realized.
CN109748296A discloses a technology and a method for preparing potassium sulfate products and co-producing lime and ammonium chloride by using phosphogypsum, firstly, the phosphogypsum and ammonium bicarbonate are added into a reaction tank according to a proportion, the materials after reaction pass through a rotary table filter, and the filtered slag is calcium carbonate and co-produces lime; the solution is ammonium sulfate solution, the ammonium sulfate solution and potassium chloride are dissolved in a dissolving tank, filtered by a plate filter, crystallized by a crystallizer and filtered to produce ammonium chloride solution and potassium sulfate crystals, and the ammonium chloride solution is separated by a triple effect concentration centrifuge and dried by a dryer to prepare an ammonium chloride product; and drying the potassium sulfate crystal by a dryer to prepare the potassium sulfate product required by the market.
CN1775679A discloses a new method for coproducing sodium carbonate, potassium sulfate and ammonium chloride, which comprises that firstly, sodium sulfate solution and ammonium bicarbonate (carbonized ammonia water) react in a sodium bicarbonate reaction kettle to generate sodium bicarbonate and ammonium sulfate; secondly, adding potassium chloride into the mother liquor I, introducing ammonia gas, and crystallizing and separating potassium sulfate; and thirdly, cooling the mother liquor II after ammonia evaporation to separate out crystalline ammonium chloride, adding ammonium bicarbonate into the cold separated mother liquor to separate out crystalline ammonium chloride, and sending the mother liquor III to a sodium bicarbonate reaction kettle to enter the next circulation.
In summary, how to provide a method for realizing resource utilization of chemical waste salt is a problem to be solved urgently at present.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a method for preparing sodium carbonate with waste salts and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which optimizes a recycling route according to the components contained in the waste salts and the properties of the components, and obtains downstream products with application values such as potassium sulfate, ammonium sulfate and ammonium chloride while preparing sodium carbonate, thereby realizing resource utilization and having better economic benefit.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for preparing sodium carbonate and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride from waste salt, which comprises the following steps:
(1) separating the waste salt after pulping to obtain dilute-phase slurry and concentrated-phase slurry; carrying out first solid-liquid separation on the dilute-phase slurry to obtain insoluble organic matters and a treatment solution; carrying out second solid-liquid separation on the concentrated phase slurry to obtain a prefabricated salt and a treatment solution; the pre-prepared salt enters a preparation process of sodium carbonate and ammonium salt for treatment, and sodium carbonate, ammonium sulfate and ammonium chloride are obtained respectively;
(2) carrying out oxidation treatment on the treatment solution obtained in the step (1) to obtain a purified solution;
(3) when K is in the purified solution in the step (2)+Performing precipitation treatment after the concentration reaches a preset value to obtain potassium-containing precipitate and a potassium-removing solution; the potassium-containing precipitate enters a potassium sulfate preparation procedure to obtain potassium sulfate; and (3) returning the potassium removal solution to the step (1) for recycling.
According to the method, the route of recycling the waste salt is reasonably optimized, the potassium sulfate is prepared by washing the waste salt, degrading organic matters and recycling the potassium element through precipitation, and the sodium carbonate, the ammonium chloride and the ammonium sulfate are prepared by using the treated waste salt. The method has the advantages of clean process, short flow and low energy consumption, really realizes the resource utilization of waste salt and the zero emission of solid waste, and has obvious economic benefit and environmental benefit.
In the invention, the waste salt comprises organic matters, a potassium source, a sodium source and a nitrogen source; the potassium source includes soluble potassium salts such as potassium chloride and the like; the sodium source includes soluble sodium salts such as sodium sulfate, sodium chloride, and the like; the nitrogen source includes nitrates such as sodium nitrate and the like.
In the invention, the separation in the step (1) can be carried out by adopting a cyclone separator, and the mixed slurry is divided into dilute phase slurry and concentrated phase slurry under the action of centrifugal force. The dilute phase slurry refers to a mixture of a solution and organic matters; dense phase slurry refers to a mixture of salt and solution after removal of organic matter.
In the invention, the preparation process of the sodium carbonate and the ammonium salt comprises the following operations: and carrying out double decomposition reaction on the prepared salt and ammonium bicarbonate to prepare sodium bicarbonate, and crystallizing the sodium bicarbonate mother liquor to prepare ammonium chloride and ammonium sulfate. This part of the operation is prior art and will not be described further here. Furthermore, the operation of preparing potassium sulfate from potassium-containing precipitates is also prior art and is not described in detail here.
In the invention, the insoluble organic matters obtained in the step (1) are intensively degraded.
The following technical solutions are preferred technical solutions of the present invention, but not limited to the technical solutions provided by the present invention, and technical objects and advantageous effects of the present invention can be better achieved and achieved by the following technical solutions.
In a preferred embodiment of the present invention, the waste salt in step (1) is first pulped with water, and the liquid-solid ratio of water to the waste salt in the first pulping process is 1.8:1 to 2.5:1mL/g, for example, 1.8:1mL/g, 2:1mL/g, 2.2:1mL/g or 2.5:1mL/g, but the ratio is not limited to the recited values, and other values not recited in the numerical range are also applicable.
In the invention, the liquid-solid ratio of fresh water and waste salt during the first pulping directly influences the separation effect and economy of salt and organic matters. If the liquid-solid ratio is too low, organic matters are difficult to separate from inorganic salts, so that subsequent treatment is influenced; if the liquid-solid ratio is too high, a large amount of inorganic salt is dissolved, and the recovery rate of the salt is reduced.
In a preferred embodiment of the present invention, the temperature of the pulping in step (1) is 60 to 90 ℃, for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃ or 90 ℃, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range of values are also applicable.
In the invention, the temperature of pulping needs to be controlled. If the temperature is too low, the viscosity of the solution is increased, and the difficulty in separating organic matters from inorganic salts is increased; if the temperature is too high, dissolution of the salt increases, so that the sodium recovery rate decreases.
As a preferred technical solution of the present invention, the oxidizing agent used in the oxidation treatment in step (2) includes any one or a combination of at least two of sodium persulfate, ammonium persulfate, chlorine gas, sodium hypochlorite, sodium chlorate, sodium perchlorate, hydrogen peroxide, potassium permanganate, oxygen gas, or ozone, and the combination is typically but not limited to: combinations of sodium chlorate and sodium perchlorate, combinations of sodium persulfate and ammonium persulfate, combinations of hydrogen peroxide and potassium permanganate, and the like.
In a preferred embodiment of the present invention, the amount of the oxidizing agent added is 5 to 10 times, for example, 5 times, 6 times, 7 times, 8 times, 9 times, or 10 times the total amount of COD in the solution, but the amount is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, and preferably 5 to 7 times.
In a preferred embodiment of the present invention, the temperature of the oxidation treatment is 50 to 100 ℃, for example, 50 ℃, 60 ℃, 70 ℃, 75 ℃, 80 ℃, 85, 90 ℃, 95 ℃ or 100 ℃, preferably 70 to 90 ℃; the time of the oxidation treatment is 30 to 90min, for example, 30min, 40min, 50min, 60min, 70min, 80min, or 90min, and preferably, the selection of the above values is not limited to the recited values for 30 to 60min, and other values not recited in the respective numerical ranges are also applicable.
In the present invention, the temperature of the oxidation treatment also needs to be controlled. If the temperature is too low, incomplete oxidation can be caused, and some groups cannot be decomposed; if the temperature is too high, the decomposition rate is too high, a large amount of foam is generated, and the operation is not easy.
As a preferred embodiment of the present invention, K in the step (3)+The preset value of the concentration is K+The concentration is not less than 10g/L, for example, 10g/L, 11g/L, 12g/L, 13g/L, 14g/L or 15g/L, etc., but is not limited to the recited values, and other values not recited within the range of values are also applicable.
As a preferred technical solution of the present invention, the precipitation treatment in step (3) is performed by using a precipitant, which includes any one or a combination of at least two of sulfuric acid, hydrochloric acid, ferric sulfate, ferrous sulfate or aluminum sulfate, and the combination is typically but not limited to: combinations of sulfuric acid and ferric sulfate, ferric sulfate and ferrous sulfate, sulfuric acid and aluminum sulfate, and the like.
In a preferred embodiment of the present invention, the amount of the precipitant added is 4 to 10 times, for example, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, or 10 times the total mass of potassium ions, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range of values are also applicable, preferably 5 to 10 times, and more preferably 5 to 7 times.
In a preferred embodiment of the present invention, the precipitation treatment in step (3) is carried out at a temperature of 20 to 100 ℃, for example, 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃ or 100 ℃, but not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, preferably 25 to 95 ℃.
In the present invention, the temperature of the precipitation treatment also needs to be controlled. If the temperature is too low, ferrous potassium alum can not be generated, potassium can not be precipitated and separated, and for the potassium alum, the viscosity is too high, the potassium alum is seriously entrained, and the quality of a potassium sulfate product is poor; if the temperature is too high, no jarosite can be formed.
Compared with the prior art, the invention has the following beneficial effects:
(1) the method of the invention comprises+，NO3-The mixed salt of sodium sulfate and sodium chloride of organic matters is used as a raw material, a recycling route of waste salt is designed and optimized, and the operation conditions are controlled, so that the utilization rate of sodium in the mixed salt is more than 90.8 percent, the purity of sodium carbonate in a product is more than 97 percent, the content of potassium oxide in a potassium sulfate product is not less than 45.9 percent, the requirement of a powdery crystalline potassium sulfate qualified product in GB/T20406-containing 2017 is met, the content of nitrogen in an ammonium sulfate product is not less than 20.3 percent, the requirement of the I-type standard in GB/T535-containing 2020 is met, the content of nitrogen in an ammonium chloride product is not less than 24.1 percent, and the standard requirement of an agricultural grade superior product in the GB/T2946-containing 2018 standard is met;
(2) the method has the advantages of clean process, short process section and low energy consumption, really realizes the resource utilization of the waste salt and the zero emission of solid waste, and has obvious economic benefit and environmental benefit.
Drawings
Fig. 1 is a process flow chart of a method for preparing sodium carbonate and by-producing potassium sulfate, ammonium sulfate and ammonium chloride from waste salt according to embodiment 1 of the present invention.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the present invention, which is defined by the claims.
The components and contents of the waste salts used in the following examples are shown in Table 1, in which the contents of the components are given in mass fraction.
TABLE 1
The following are typical but non-limiting examples of the invention:
example 1:
the embodiment provides a method for preparing sodium carbonate and coproducing potassium sulfate, ammonium sulfate and ammonium chloride from waste salt, and a process flow chart of the method is shown in figure 1.
The method comprises the following steps:
(1) mixing waste salt with the potassium-removing solution obtained in the step (3) (when the waste salt is subjected to primary pulping, the liquid-solid ratio of fresh water to the waste salt is 1.8: 1), stirring at 90 ℃ for pulping, performing stirring reaction for 30min, separating the pulp by using a cyclone, performing first solid-liquid separation on the separated dilute-phase pulp to obtain insoluble organic matters and treatment liquid, and performing second solid-liquid separation on the separated concentrated-phase pulp to obtain pre-prepared salt and treatment liquid; treating the obtained preformed salt in the preparation process of sodium carbonate and ammonium salt, treating the treatment liquid in the next process, and performing centralized degradation treatment on the insoluble organic matters;
(2) adding sodium persulfate into the treatment liquid in the step (1), wherein the addition amount of the sodium persulfate is 5 times of the total amount of COD, reacting at 90 ℃ for 30min after the sodium persulfate is added, obtaining a purified solution after the reaction is finished, and returning the purified solution to the step (1) for recycling; when the concentration of potassium ions in the purified solution reaches 15g/L, entering a potassium sulfate precipitation and recovery process;
(3) adding anhydrous aluminum sulfate into the purified solution obtained in the step (2), wherein the addition amount of the anhydrous aluminum sulfate is 5 times of the total mass of potassium ions, reacting the solution at 25 ℃ for 30min, after the reaction is finished, carrying out liquid-solid separation to obtain potassium alum and a potassium removal solution, returning the potassium removal solution to the step (1) for recycling, and using the potassium alum as a raw material for preparing potassium sulfate.
The preparation process of sodium carbonate and ammonium salt in this example includes: carrying out double decomposition reaction on the prepared salt and ammonium bicarbonate to obtain sodium bicarbonate slurry after reaction, carrying out liquid-solid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor, and calcining the sodium bicarbonate to obtain sodium carbonate; and (2) carrying out flash evaporation and recondensation on unreacted ammonium bicarbonate in the sodium bicarbonate mother liquor, then carrying out double decomposition reaction for recycling, cooling and crystallizing the solution subjected to flash evaporation and the ammonium sulfate mother liquor obtained subsequently to normal temperature to obtain cooling liquid and cooling salt, returning the cooling salt to the double decomposition reaction, carrying out deep cooling on the cooling liquid to obtain ammonium chloride, and carrying out evaporative crystallization on the deep cooling liquid to obtain ammonium sulfate.
The preparation procedure of potassium sulfate in this example includes: reacting potassium alum with potassium hydroxide to generate aluminum hydroxide precipitate and potassium sulfate solution, and crystallizing the potassium sulfate solution to obtain potassium sulfate.
Example 2:
the embodiment provides a method for preparing sodium carbonate and coproducing potassium sulfate, ammonium sulfate and ammonium chloride from waste salt, which comprises the following steps:
(1) mixing the waste salt with the potassium-removing solution obtained in the step (3) (when the waste salt is prepared into pulp for the first time, the liquid-solid ratio of fresh water to the waste salt is 2.5: 1), stirring and preparing the pulp at 85 ℃, after stirring and reacting for 60min, separating the pulp by a swirler, carrying out first solid-liquid separation on the separated dilute phase pulp to obtain insoluble organic matters and treatment liquid, and carrying out second solid-liquid separation on the separated concentrated phase pulp to obtain pre-prepared salt and treatment liquid; treating the obtained preformed salt in the preparation process of sodium carbonate and ammonium salt, treating the treatment liquid in the next process, and performing centralized degradation treatment on the insoluble organic matters;
(2) adding sodium hypochlorite into the treatment solution obtained in the step (1), wherein the addition amount of the sodium hypochlorite is 7 times of the total amount of COD, adding the sodium hypochlorite, reacting at 90 ℃ for 60min to obtain a purified solution after the reaction is finished, and returning the purified solution to the step (1) for recycling; when the concentration of potassium ions in the purified solution reaches 10g/L, entering a potassium sulfate precipitation and recovery process;
(3) and (3) adding anhydrous ferric sulfate into the purified solution in the step (2), wherein the addition amount of the anhydrous ferric sulfate is 6 times of the total mass of potassium ions, reacting the solution at 90 ℃ for 60min, after the reaction is finished, carrying out liquid-solid separation to obtain jarosite and a potassium removal solution, returning the potassium removal solution to the step (1) for recycling, and using the jarosite as a raw material for preparing potassium sulfate.
The preparation process of sodium carbonate and ammonium salt in this example includes: carrying out double decomposition reaction on the prepared salt and ammonium bicarbonate to obtain sodium bicarbonate slurry, carrying out liquid-solid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor, and calcining the sodium bicarbonate to obtain sodium carbonate. And (2) carrying out flash evaporation and recondensation on unreacted ammonium bicarbonate in the sodium bicarbonate mother liquor, then carrying out double decomposition reaction for recycling, cooling and crystallizing the solution subjected to flash evaporation and the ammonium sulfate mother liquor obtained subsequently to normal temperature to obtain cooling liquid and cooling salt, returning the cooling salt to the double decomposition reaction, carrying out deep cooling on the cooling liquid to obtain ammonium chloride, and carrying out evaporative crystallization on the deep cooling liquid to obtain ammonium sulfate.
The preparation procedure of potassium sulfate in this example includes: the jarosite and the potassium hydroxide react to generate ferric hydroxide solid and potassium sulfate solution, and the potassium sulfate is crystallized to obtain the potassium sulfate.
Example 3:
the embodiment provides a method for preparing sodium carbonate and coproducing potassium sulfate, ammonium sulfate and ammonium chloride from waste salt, which comprises the following steps:
(1) mixing waste salt with the potassium-removing solution obtained in the step (3) (when the waste salt is subjected to primary pulping, the liquid-solid ratio of fresh water to the waste salt is 2.0: 1), stirring at 85 ℃ for pulping, after stirring reaction is carried out for 60min, separating the materials by a cyclone, carrying out first solid-liquid separation on the separated dilute-phase slurry to obtain insoluble organic matters and treatment liquid, and carrying out second solid-liquid separation on the separated concentrated-phase slurry to obtain pre-prepared salt and treatment liquid; treating the obtained preformed salt in the preparation process of sodium carbonate and ammonium salt, treating the treatment liquid in the next process, and performing centralized degradation treatment on the insoluble organic matters;
(2) adding hydrogen peroxide into the treatment liquid in the step (1), wherein the addition amount of the hydrogen peroxide is 10 times of the total amount of COD, adding the hydrogen peroxide, reacting at 50 ℃ for 60min to obtain a purified solution after the reaction is finished, and returning the purified solution to the step (1) for recycling; when the concentration of potassium ions in the purified solution reaches 20g/L, entering a potassium sulfate precipitation and recovery process;
(3) and (3) adding anhydrous ferric sulfate into the purified solution obtained in the step (2), wherein the addition amount of the anhydrous ferric sulfate is 6 times of the total mass of potassium ions, reacting the solution at 90 ℃ for 60min, after the reaction is finished, carrying out liquid-solid separation to obtain jarosite and a potassium removal solution, returning the potassium removal solution to the step (1) for recycling, and using the jarosite as a raw material for preparing potassium sulfate.
The preparation process of sodium carbonate and ammonium salt in this example includes: carrying out double decomposition reaction on the prepared salt and ammonium bicarbonate to obtain sodium bicarbonate slurry, carrying out liquid-solid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor, and calcining the sodium bicarbonate to obtain sodium carbonate. And (2) carrying out flash evaporation and recondensation on unreacted ammonium bicarbonate in the sodium bicarbonate mother liquor, then carrying out double decomposition reaction for recycling, cooling and crystallizing the solution subjected to flash evaporation and the ammonium sulfate mother liquor obtained subsequently to normal temperature to obtain cooling liquid and cooling salt, returning the cooling salt to the double decomposition reaction, carrying out deep cooling on the cooling liquid to obtain ammonium chloride, and carrying out evaporative crystallization on the deep cooling liquid to obtain ammonium sulfate.
The preparation procedure of potassium sulfate in this example includes: the jarosite and the potassium hydroxide react to generate ferric hydroxide solid and potassium sulfate solution, and the potassium sulfate is crystallized to obtain the potassium sulfate.
Example 4:
the embodiment provides a method for preparing sodium carbonate and coproducing potassium sulfate, ammonium sulfate and ammonium chloride from waste salt, which comprises the following steps:
(1) mixing waste salt with the potassium-removing solution obtained in the step (3) (when the waste salt is subjected to primary pulping, the liquid-solid ratio of fresh water to the waste salt is 2.2: 1), stirring and pulping at 80 ℃, after stirring and reacting for 90min, separating the materials by a cyclone, performing first solid-liquid separation on the separated dilute-phase slurry to obtain insoluble organic matters and treatment liquid, and performing second solid-liquid separation on the separated concentrated-phase slurry to obtain pre-prepared salt and treatment liquid; treating the obtained preformed salt in the preparation process of sodium carbonate and ammonium salt, treating the treatment liquid in the next process, and performing centralized degradation treatment on the insoluble organic matters;
(2) adding ozone into the treatment liquid in the step (1), reacting at 80 ℃ for 30min, wherein the introduction amount of the ozone is 0.5L/min, obtaining a purified solution after the reaction is finished, and returning the purified solution to the step (1) for recycling; when the concentration of potassium ions in the purified solution reaches 20g/L, entering a potassium sulfate precipitation and recovery process;
(3) and (3) adding anhydrous ferric sulfate into the purified solution obtained in the step (2), wherein the addition amount of the anhydrous ferric sulfate is 6 times of the total mass of potassium ions, reacting the solution at 90 ℃ for 60min, after the reaction is finished, carrying out liquid-solid separation to obtain jarosite and a potassium removal solution, returning the potassium removal solution to the step (1) for recycling, and using the jarosite as a raw material for preparing potassium sulfate.
The preparation process of sodium carbonate and ammonium salt in this example includes: carrying out double decomposition reaction on the prepared salt and ammonium bicarbonate to obtain sodium bicarbonate slurry, carrying out liquid-solid separation to obtain sodium bicarbonate and sodium bicarbonate mother liquor, and calcining the sodium bicarbonate to obtain sodium carbonate. And (2) carrying out flash evaporation and recondensation on unreacted ammonium bicarbonate in the sodium bicarbonate mother liquor, then carrying out double decomposition reaction for recycling, cooling and crystallizing the solution subjected to flash evaporation and the ammonium sulfate mother liquor obtained subsequently to normal temperature to obtain cooling liquid and cooling salt, returning the cooling salt to the double decomposition reaction, carrying out deep cooling on the cooling liquid to obtain ammonium chloride, and carrying out evaporative crystallization on the deep cooling liquid to obtain ammonium sulfate.
The preparation procedure of potassium sulfate in this example includes: the jarosite and the potassium hydroxide react to generate ferric hydroxide solid and potassium sulfate solution, and the potassium sulfate is crystallized to obtain the potassium sulfate.
Example 5:
this example provides a method for preparing sodium carbonate with waste salts and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which is as described in example 1, except that: when the pulp is prepared for the first time in the step (1), the liquid-solid ratio of the fresh water to the waste salt is 1:1 mL/g.
Example 6:
this example provides a method for preparing sodium carbonate with waste salts and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which is as described in example 2, except that: when the pulp is prepared for the first time in the step (1), the liquid-solid ratio of the fresh water to the waste salt is 5:1 mL/g.
Example 7:
this example provides a method for preparing sodium carbonate with waste salts and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which is as described in example 1, except that: the temperature for pulping in the step (1) is 100 ℃.
Example 8:
this example provides a method for preparing sodium carbonate with waste salts and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which is as described in example 4, except that: the temperature for pulping in the step (1) is 60 ℃.
Example 9:
this example provides a method for preparing sodium carbonate with waste salts and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which is as described in example 4, except that: the temperature for pulping in the step (1) is 40 ℃.
Example 10:
this example provides a method for preparing sodium carbonate with waste salts and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which is as described in example 3, except that: the temperature of the oxidation treatment in the step (2) was 40 ℃.
Example 11:
this example provides a method for preparing sodium carbonate with waste salts and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which is as described in example 1, except that: the temperature of the oxidation treatment in the step (2) was 110 ℃.
Example 12:
this example provides a method for preparing sodium carbonate with waste salts and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which is as described in example 1, except that: the temperature of the precipitation treatment in the step (3) was 110 ℃.
Example 13:
this example provides a method for preparing sodium carbonate with waste salts and byproducts of potassium sulfate, ammonium sulfate and ammonium chloride, which is as described in example 2, except that: the temperature of the precipitation treatment in the step (3) was 20 ℃.
The results of examining the products obtained in examples 1 to 13, including the sodium utilization rate, the sodium carbonate product purity, the nitrogen content in ammonium chloride, the ammonium sulfate product purity, and the potassium sulfate product purity, are shown in table 2.
TABLE 2
As can be seen from Table 2, in the first pulping process, compared with example 1, the fresh water addition amount in example 5 is too small, so that organic matters and salt are difficult to separate, and the product quality is poor; in example 6, the inorganic salt was completely dissolved and the sodium recovery rate was low because the amount of the inorganic salt added was too large as compared with example 2. The temperature needs to be reasonably selected in the pulping process; compared with the embodiment 1, the pulping temperature is overhigh, the salt dissolution amount is large, and the sodium recovery rate is low in the embodiment 7; compared with example 4, the pulping temperature in example 9 is too low, which affects the separation of organic substances and salt, and the product purity is poor. The temperature of the oxidation treatment and the precipitation treatment are also important, and compared with the temperature of the oxidation treatment in the embodiment 3, the temperature of the oxidation treatment in the embodiment 10 is too low, the decomposition rate of impurities such as organic matters is low, and the impurities are accumulated in a system to influence the product quality and the sodium recovery rate; compared with the example 1, the temperature of the oxidation treatment in the example 11 is too high, a large amount of foam is generated, and the operation is difficult, but the sodium recovery rate and the product quality are not influenced; in example 12, the temperature of the precipitation treatment was too high to form potassium alum, compared to example 1; in example 13, the precipitation treatment temperature was too low to form jarosite, compared with example 2.
As can be seen from a combination of the examples and comparative examples described above, the process according to the invention is characterized by the fact that it contains K+，NO3-The mixed salt of sodium sulfate and sodium chloride of organic matters is used as a raw material, a recycling route of waste salt is designed and optimized, and the operation conditions are controlled, so that the utilization rate of sodium in the mixed salt is more than 90.8 percent, the purity of sodium carbonate in a product is more than 97 percent, the content of potassium oxide in a potassium sulfate product is not less than 45.9 percent, the requirement of a powdery crystalline potassium sulfate qualified product in GB/T20406-containing 2017 is met, the content of nitrogen in an ammonium sulfate product is not less than 20.3 percent, the requirement of the I-type standard in GB/T535-containing 2020 is met, the content of nitrogen in an ammonium chloride product is not less than 24.1 percent, and the standard requirement of an agricultural grade superior product in the GB/T2946-containing 2018 standard is met; the method has the advantages of clean process, flow section and low energy consumption, really realizes resource utilization of waste salt and zero emission of solid waste, and has obvious economic benefit and environmental benefit.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It will be apparent to those skilled in the art that any modifications to the present invention, equivalents thereof, additions of additional operations, selection of specific ways, etc., are within the scope and disclosure of the present invention.
Claims (7)
1. A method for preparing sodium carbonate and coproducing potassium sulfate, ammonium sulfate and ammonium chloride from waste salt is characterized by comprising the following steps:
(1) separating the waste salt after pulping to obtain dilute-phase slurry and concentrated-phase slurry; carrying out first solid-liquid separation on the dilute-phase slurry to obtain insoluble organic matters and a treatment solution; carrying out second solid-liquid separation on the concentrated phase slurry to obtain a prefabricated salt and a treatment solution; the pre-prepared salt is treated in the preparation process of sodium carbonate and ammonium salt to respectively obtain sodium carbonate, ammonium sulfate and ammonium chloride;
the waste salt in the step (1) is pulped for the first time by adopting water, and in the process of pulping for the first time, the liquid-solid ratio of the water to the waste salt is 1.8: 1-2.5: 1 mL/g;
the temperature of pulping in the step (1) is 60-90 ℃;
(2) carrying out oxidation treatment on the treatment solution obtained in the step (1) to obtain a purified solution;
the temperature of the oxidation treatment is 50-100 ℃;
(3) when K is in the purified solution in the step (2)+Performing precipitation treatment after the concentration reaches a preset value to obtain potassium-containing precipitate and a potassium-removing solution; the potassium-containing precipitate enters a potassium sulfate preparation procedure to obtain potassium sulfate; returning the potassium removal solution to the step (1) for recycling;
k in the step (3)+The preset value of the concentration is K+The concentration is not less than 10 g/L;
by using the method, the utilization rate of sodium in the waste salt reaches more than 90.8 percent.
2. The method according to claim 1, wherein the oxidizing agent used in the oxidation treatment in step (2) comprises any one or a combination of at least two of sodium persulfate, ammonium persulfate, chlorine gas, sodium hypochlorite, sodium chlorate, sodium perchlorate, hydrogen peroxide, potassium permanganate, oxygen gas and ozone.
3. The method according to claim 2, wherein the amount of the oxidant added is 5 to 10 times of the total amount of COD in the solution.
4. The method according to claim 1, wherein the time of the oxidation treatment is 30 to 90 min.
5. The method of claim 1, wherein the precipitation treatment in step (3) is performed with a precipitating agent comprising any one of or a combination of at least two of sulfuric acid, hydrochloric acid, ferric sulfate, ferrous sulfate, or aluminum sulfate.
6. The method according to claim 5, wherein the amount of the precipitant added is 4 to 10 times the total mass of potassium ions.
7. The method according to claim 1, wherein the precipitation treatment in step (3) is carried out at a temperature of 20 to 100 ℃.
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