CN115246649A - Method for preparing fertilizer-grade potassium chloride from potassium chloride organic hazardous waste salt - Google Patents
Method for preparing fertilizer-grade potassium chloride from potassium chloride organic hazardous waste salt Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/14—Purification
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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
- C01D5/16—Purification
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- C01—INORGANIC CHEMISTRY
- 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 discloses a method for preparing fertilizer-grade potassium chloride from potassium chloride organic hazardous waste salt, belonging to the technical field of organic hazardous waste salt treatment. Drying and dehydrating organic dangerous waste salt containing potassium chloride, then carrying out low-temperature anaerobic critical carbonization treatment, preparing the obtained carbonized waste salt into a sub-saturated potassium chloride solution, carrying out decarbonization and impurity removal on the solution, adjusting the pH value of the treated sub-saturated potassium chloride solution, carrying out primary crystallization and recrystallization by a cooling crystallization method to obtain wet potassium chloride, and drying the wet potassium chloride to remove water to obtain a fertilizer-grade potassium chloride product. The method has the advantages of low treatment temperature, high safety, wide raw material source, low raw material cost and manufacturing cost, simple conversion, easy control of purity, and easy post treatment of other waste materials generated after treatment, is particularly suitable for industrial batch treatment of the dangerous waste salt to prepare the potassium chloride, and can solve the problem of utilization of the existing organic waste salt containing the potassium chloride.
Description
Technical Field
The invention relates to a preparation method of potassium chloride, in particular to a method for preparing fertilizer-grade potassium chloride from potassium chloride organic hazardous waste salt, and belongs to the technical field of organic hazardous waste salt treatment.
Background
With the development of economic technology, the demand of industrial salt in China is greatly increased, and further a large amount of waste salt byproduct is generated. The waste salt is mainly industrial waste salt which takes halogenated salt such as sodium chloride, potassium chloride, sodium fluoride, potassium fluoride, sodium bromide, potassium bromide and the like as main components, and mainly comes from various industries such as coal chemical industry, pesticide, medicine, fine chemical industry, dye, chemical fertilizer and the like. The waste salt is often incapable of being directly reused in industrial production due to large amount of organic matters and toxic and harmful components, and is classified as dangerous waste by national relevant legal documents, generally called organic dangerous waste salt. The organic hazardous waste salt has complex components and high harmfulness, so that the self-treatment and consignment treatment cost of enterprises is very high, and huge economic burden and potential safety hazards are brought to enterprise operation.
Among such a large number of industrial waste salt residues, the most common waste salt residue is halogenated waste salt such as potassium chloride. In general, in waste water generated by acid-base neutralization in the industries of fine chemicals, medicines, pesticides, dyes and the like, the waste water cannot be treated by a common biochemical method because the waste water contains a large amount of inorganic salts and high-content organic matters, the waste water is required to be changed into incineration residues after passing through an incinerator, the residues mainly contain halogenated salts, the content of the halogenated salts is more than 70%, and the other waste water contains burning ash, inorganic salts and a small amount of organic matters. The incinerated salt ash is generally disposed of in landfills after being paid and stored by a third party with disposal qualification as dangerous solid waste. Moreover, the landfill treatment not only occupies a large amount of land resources, but also often causes secondary pollution and potential safety hazard of land and underground water resource environments due to different characteristics of hazardous wastes, and entrusted treatment cost and environmental protection pressure of the landfill treatment also often become important factors restricting sustainable development of enterprises.
At present, the preparation method of potassium chloride in the prior art mainly comprises the following steps:
recrystallization method: rock salt carnallite (carnalite) with magnesium chloride and potassium chloride as main components is crushed and mixed with 75% of water, superheated steam is introduced, and potassium chloride is separated out after cooling. The method is simple to operate, is suitable for the production of industrial potassium chloride, and has the advantages of single condition and small benefit.
A flotation method: crushing sylvite ore (or sand crystal salt) by a ball mill, adding 1% of octadecylamine flotation agent while stirring, adding 2% of cellulose for flotation, and performing centrifugal separation to obtain a potassium chloride finished product. The conversion method is used more frequently, the purity is difficult to control, and the post-treatment of the flotation reagent after flotation is difficult.
The method for neutralizing potassium hydroxide by hydrochloric acid comprises the following steps: adding stoichiometric pure hydrochloric acid into pure potassium hydroxide water solution, slightly excessive acid to make the solution slightly acidic, heating and concentrating to make the solution still be acidic, cooling, precipitating potassium chloride, suction filtering, placing the obtained precipitate in evaporating dish, placing on sand bath, stirring and heating and drying so as to obtain the potassium chloride crystal. The method is prepared by utilizing the principle of acid-base neutralization to generate salt, has higher preparation cost and almost has no industrial significance.
Cold decomposition method: after being crushed, carnallite is put into a decomposer and water, mother liquor and a flotation agent are added for decomposition, and crude potassium slurry discharged from the lower part of the decomposer is pumped into a settler. And discharging the settled slurry from the bottom of the device, performing centrifugal separation, and removing the mother liquor to obtain crude sylvite. Feeding the crude potassium salt into a washer, dissolving sodium chloride contained in the crude potassium salt into water at room temperature, and settling, centrifugally separating and drying the slurry again to obtain a potassium chloride finished product; the clear liquid is used as refined potassium mother liquor for recycling. The method has wide source of raw materials, but has strong locality, and is only suitable for wide application of raw materials in production places.
By combining the common halogenated waste salt with high yield in the organic hazardous waste salt, how to develop a suitable process technology, and the harmless treatment with low investment, low cost and environmental protection and the resource utilization of the potassium chloride organic hazardous waste salt to prepare the potassium chloride are combined, so that the requirements of sustainable environment-friendly green development of enterprises are met, the technical problem of resource treatment of the potassium chloride hazardous waste salt in the environment-friendly industry is solved, and the method has important significance.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for preparing fertilizer grade potassium chloride from potassium chloride organic hazardous waste salt.
The technical scheme of the invention is as follows:
a method for preparing fertilizer-grade potassium chloride from potassium chloride organic hazardous waste salt mainly comprises the following steps: drying and dehydrating organic hazardous waste salt containing potassium chloride, performing low-temperature oxygen-free critical carbonization treatment on the obtained dry hazardous waste salt, preparing the obtained carbonized waste salt into a sub-saturated potassium chloride solution, and performing decarbonization and impurity removal on the solution; adjusting the pH value of the sub-saturated potassium chloride solution subjected to decarbonization and impurity removal to subacidity, carrying out primary crystallization and recrystallization by a cooling crystallization method to obtain wet potassium chloride, and drying the wet potassium chloride to remove moisture to obtain the fertilizer grade potassium chloride.
The further technical scheme is as follows:
the low-temperature carbonization temperature of the dry hazardous waste salt during the low-temperature anaerobic critical carbonization treatment is 450-550 ℃, and the dry hazardous waste salt is in an anaerobic environment.
The further technical scheme is as follows:
and smoke generated when the dry hazardous waste salt is subjected to low-temperature oxygen-free critical carbonization treatment is sequentially cooled by a quench tower, subjected to cyclone dust collection and subjected to cloth bag dust collection, then enters a combustion chamber to be fully combusted, and is sprayed by alkali liquor in a spray tower to reach the emission standard.
The further technical scheme is as follows:
the preparation of the sub-saturated potassium chloride solution and the decarbonization of the carbonized sewage salt are carried out, and the carbonized sewage salt is dissolved in water with the temperature of 85-90 ℃ and then filtered to remove the carbon.
The further technical scheme is as follows:
the step of removing impurities from the sub-saturated potassium chloride solution comprises the steps of firstly adding potassium hydroxide into the decarbonized sub-saturated potassium chloride solution to adjust the pH value of the solution to be more than 11.0, then sequentially adding quantitative calcium chloride powder and potassium carbonate into the solution in sequence, respectively carrying out constant-temperature stirring reaction, and then carrying out hot filtration to realize the removal of impurities.
The further technical scheme is as follows:
adding hydrochloric acid into the sub-saturated potassium chloride solution after impurity removal to adjust the pH value to 4.5-6.0, filtering, cooling the obtained filtrate to 60-65 ℃, adding potassium chloride crystals to carry out primary crystallization, then continuously cooling to room temperature, standing to wait for completion of primary crystallization, and filtering to obtain crude potassium chloride crystals.
The further technical scheme is as follows:
and (3) recycling the mother liquor obtained by primary crystallization for preparing a sub-saturated potassium chloride solution, and cooling and crystallizing after the content of sodium sulfate in the mother liquor reaches saturation to obtain a sodium sulfate product.
The further technical scheme is as follows:
dissolving the crude potassium chloride crystal obtained by primary crystallization in deionized water at 85-90 ℃, cooling to 70-75 ℃, adding analytically pure potassium chloride for recrystallization, cooling to room temperature, standing for recrystallization, and filtering to obtain wet potassium chloride.
The further technical scheme is as follows:
and the mother liquor obtained by recrystallization is recycled to the recrystallization process to be used as a solution for dissolving the next batch of crude potassium chloride crystals.
The further technical scheme is as follows:
and slowly drying the wet potassium chloride at 100-105 ℃ to obtain the fertilizer grade potassium chloride.
The beneficial technical effects of the invention are as follows:
1. when the fertilizer-grade potassium chloride is prepared from the hazardous waste salt containing organic substances, mainly comprising potassium chloride, the organic substances in the hazardous waste salt are removed by a low-temperature anaerobic critical carbonization treatment mode, the method is low in treatment temperature and high in safety, and the hazardous waste salt is in an anaerobic environment in the treatment process, so that the metal components in the hazardous waste salt in the carbonization process can be prevented from reacting with oxygen to form new impurities which are difficult to remove.
2. According to the invention, the potassium chloride solution prepared from carbonized polluted salt is sequentially and respectively subjected to primary crystallization and recrystallization after decarbonization and impurity removal, so that potassium chloride components in the polluted salt can be completely extracted, and mother liquor generated by primary crystallization and recrystallization can be recycled in the treatment process, thereby greatly reducing material waste; in addition, the method can prepare fertilizer-grade potassium chloride and simultaneously obtain a sodium sulfate byproduct, so that the utilization rate of hazardous waste salt is increased.
3. The method has wide sources, organic hazardous waste salt containing organic matters and containing potassium chloride and generated in the industries of food, pesticide and printing and dyeing can be used as an initial raw material, the raw material cost and the manufacturing cost are low, the conversion is simple, the purity is easy to control, the post treatment of other waste materials generated after treatment is relatively easy, the method is particularly suitable for preparing the potassium chloride by industrially treating the hazardous waste salt in batches, and the problem of utilization of the existing organic waste salt containing the potassium chloride can be solved.
Drawings
FIG. 1 is a schematic process flow diagram of the process of the present invention.
Detailed Description
The invention relates to a method for preparing fertilizer grade potassium chloride by using potassium chloride organic hazardous waste salt, which mainly comprises the following steps:
1. drying and dehydrating organic hazardous waste salt containing potassium chloride, performing low-temperature oxygen-free critical carbonization treatment on the obtained dry hazardous waste salt, preparing the obtained carbonized waste salt into a sub-saturated potassium chloride solution, and performing decarbonization and impurity removal on the solution.
Wherein before the organic hazardous waste salt containing potassium chloride is dried and dehydrated, the organic hazardous waste salt can be mixed and proportioned, namely, the organic hazardous waste salt with low organic matter content and the organic hazardous waste salt with high organic matter content are mixed, so that the content of organic matters in the mixed organic hazardous waste salt is 5-8wt.%.
Wherein the low-temperature carbonization temperature of the dry hazardous waste salt subjected to low-temperature anaerobic critical carbonization treatment is 450-550 ℃, and the dry hazardous waste salt is in an anaerobic environment; meanwhile, flue gas generated in the process sequentially passes through a quenching tower for cooling, cyclone dust collection and cloth bag dust collection, then enters a combustion chamber for full combustion, and is sprayed by alkali liquor in a spray tower and then is discharged up to the standard. And after the reaction is finished, analyzing the carbonized mixture (mainly comprising solid carbon and salt), collecting and temporarily storing the mixture for treatment.
When the sub-saturated potassium chloride solution is prepared and decarbonized, the obtained carbonized sewage salt is dissolved in water with the temperature of 85-90 ℃, and then the solid carbon is removed by filtration.
Wherein the step of removing impurities from the sub-saturated potassium chloride solution is to add an alkaline substance which is heated to at least 85 ℃ into the decarbonized sub-saturated potassium chloride solution to adjust the pH value of the solution to be more than 11.0 and then remove impurities. Specifically, potassium hydroxide is added to prepare a solution with the pH value larger than 11.0, then, quantitative calcium chloride powder and potassium carbonate are sequentially added into the solution in sequence, constant-temperature stirring reaction is carried out respectively, and then, heat filtration is carried out to realize impurity removal, wherein the impurity removal in the step mainly comprises removal of impurities such as P, si, fe, cu, ni and the like.
2. Adjusting the pH value of the sub-saturated potassium chloride solution subjected to decarbonization and impurity removal to subacidity, carrying out primary crystallization and recrystallization by a cooling crystallization method to obtain wet potassium chloride, and drying the wet potassium chloride to remove moisture to obtain the fertilizer grade potassium chloride.
Adding hydrochloric acid into the sub-saturated potassium chloride solution after impurity removal to adjust the pH value to 4.5-6.0, filtering, cooling the obtained filtrate to 60-65 ℃, adding potassium chloride crystals to carry out primary crystallization, then continuously cooling to room temperature, standing to wait for completion of primary crystallization, and filtering to obtain crude potassium chloride crystals. And (3) recycling the mother liquor obtained by primary crystallization for preparing a sub-saturated potassium chloride solution, and cooling and crystallizing after the content of sodium sulfate in the mother liquor reaches saturation to obtain a sodium sulfate product.
Dissolving crude potassium chloride crystals obtained by primary crystallization in deionized water at 85-90 ℃ to prepare a saturated potassium chloride solution, then cooling to 70-75 ℃, adding analytically pure potassium chloride for recrystallization, cooling to room temperature, standing for completion of recrystallization, filtering to obtain high-purity wet potassium chloride, and slowly drying the high-purity wet potassium chloride at 100-105 ℃ to obtain fertilizer-grade potassium chloride. And the mother liquor obtained by recrystallization is recycled to the recrystallization process to be used as a solution for dissolving the next batch of crude potassium chloride crystals.
In order to make the technical means of the present invention clearer and to make the technical means of the present invention capable of being implemented according to the content of the specification, the following detailed description of the embodiments of the present invention is made with reference to the accompanying drawings and examples, which are provided for illustrating the present invention and are not intended to limit the scope of the present invention.
Detailed description of the preferred embodiment
S1, 800kg of industrial waste salt generated in the production process of a certain plant, wherein the industrial waste salt contains 5.5wt.% of organic matters, 8978 wt.% of potassium chloride, 8978 wt.% of zxft 8978 wt.%, 2.8wt.% of sodium sulfate and 9.59wt.% of water. Drying and dehydrating the industrial waste salt;
s2, drying the hazardous waste salt obtained after drying, wherein the hazardous waste salt is uniform and has no caking phenomenon, and the hazardous waste salt enters a low-temperature carbonization furnace in a spiral feeding mode. The low-temperature carbonization furnace adopts closed and anaerobic operation, the temperature is controlled to be 500-550 ℃ for carbonization, the carbonization time is 5 hours, and the carbonization enters a cooling stage. The flue gas generated in the low-temperature oxygen-free critical carbonization treatment process mainly comprises water vapor and trace dust, the water vapor and the trace dust are subjected to quenching tower, cyclone dust collection and cloth bag dust collection and then enter a combustion chamber, and the flue gas after combustion is sprayed by alkali liquor and then is discharged up to the standard.
S3, cooling the obtained carbonized polluted salt to 70 ℃, sampling, and cooling the rest for later use; the sample is cooled to room temperature and then is left for analysis, and the analysis result is as follows: potassium salt weight 667.28g with potassium chloride content 96.3wt.%, sodium sulfate content 3.23wt.%, and other material content 0.42wt.%.
S4, dissolving 550g of potassium salt in 1000ml of tap water at 90 ℃, filtering to remove carbon after dissolving, adding 1.5g of potassium hydroxide to adjust the pH value to be more than 11.0, stirring for 10min, adding 0.8g of calcium chloride powder, continuously stirring at constant temperature for 20min, adding 0.55g of potassium carbonate, and continuously stirring at constant temperature for 30min; and after stirring, carrying out hot filtration, adding hydrochloric acid into the filtrate to adjust the pH value back to 5.0-5.5, and obtaining 4.19g of filter residue.
And S5, stirring and cooling the filtrate by a water bath method, adding 1g of potassium chloride crystals when the temperature is reduced to 60-65 ℃, finding that a large amount of crystals are separated out from the solution, continuously cooling to 30 ℃, and stopping continuously cooling. Filtration afforded 371.7g of wet potassium chloride crystals. And (3) recycling the mother liquor obtained by primary crystallization for preparing a sub-saturated potassium chloride solution, and cooling and crystallizing after the content of sodium sulfate in the mother liquor reaches saturation to obtain a sodium sulfate product.
S6, adding 317.7g of wet potassium chloride crystals into 430ml of deionized water with the temperature of 85 ℃, stirring for 10min, completely dissolving, adding 2g of analytically pure potassium chloride when the temperature is reduced to 75 ℃, continuously reducing the temperature to 25 ℃, stirring for 5min, and filtering to obtain 79.88g of wet potassium chloride. And the mother liquor obtained by filtering is recycled to the recrystallization process to be used as a solution for dissolving the next batch of crude potassium chloride crystals.
S7, drying 79.88g of the obtained wet potassium chloride for 2 hours at 105 ℃ to obtain 72.5g of fertilizer-grade potassium chloride.
Specific example 2
S1, 1000kg of industrial waste salt generated in the production process of a certain pesticide factory, wherein the industrial waste salt contains 5.5wt.% of organic matters, 88.8wt.% of potassium chloride, 4.8wt.% of sodium sulfate and 13.88wt.% of water. Drying and dehydrating the industrial waste salt;
s2, drying the hazardous waste salt obtained after drying, wherein the hazardous waste salt is uniform and has no caking phenomenon, and the hazardous waste salt enters a low-temperature carbonization furnace in a spiral feeding mode. The low-temperature carbonization furnace adopts closed and anaerobic operation, the temperature is controlled to be 500-550 ℃ for carbonization, the carbonization time is 6 hours, and the carbonization enters a cooling stage. The flue gas generated in the low-temperature oxygen-free critical carbonization treatment process mainly comprises water vapor and trace dust, the water vapor and the trace dust are subjected to quenching tower, cyclone dust collection and cloth bag dust collection and then enter a combustion chamber, and the flue gas after combustion is sprayed by alkali liquor and then is discharged up to the standard.
S3, cooling the obtained carbonized dirt salt to 60 ℃, sampling, and cooling the rest for later use; the sample is cooled to room temperature and then is left for analysis, and the analysis result is as follows: potassium salt weight 812.50g with potassium chloride content 93.11wt.%, sodium sulfate content 5.01wt.%, and other material content 1.88wt.%.
S4, dissolving 750g of cooled potassium salt in 1450ml of tap water at 85 ℃, filtering to remove carbon after dissolving, adding 1.5g of potassium hydroxide to adjust the pH value to be more than 11.0, stirring for 10min, adding 1.1g of calcium chloride powder, continuously stirring at constant temperature for 20min, adding 0.7g of potassium carbonate, and continuously stirring at constant temperature for 30min; and after stirring, carrying out hot filtration, adding hydrochloric acid into the filtrate to adjust the pH value back to 4.5-5.0, and obtaining 15.3g of filter residue.
And S5, stirring and cooling the filtrate by a water bath method, adding 1g of potassium chloride crystals when the temperature is reduced to 60-65 ℃, finding that a large amount of crystals are separated out from the solution, continuously cooling to 30 ℃, and stopping continuously cooling. Filtration afforded 328.46g of wet potassium chloride crystals. And (3) recycling the mother liquor obtained by primary crystallization for preparing a sub-saturated potassium chloride solution, and cooling and crystallizing after the content of sodium sulfate in the mother liquor reaches saturation to obtain a sodium sulfate product.
S6, adding 328.46g of wet potassium chloride crystals into 400ml of deionized water with the temperature of 85 ℃, stirring for 10min, completely dissolving, adding 3g of analytically pure potassium chloride when the temperature is reduced to 75 ℃, continuously reducing the temperature to 25 ℃, stirring for 5min, and filtering to obtain 96.5g of wet potassium chloride. And the mother liquor obtained by filtering is recycled to the recrystallization process to be used as a solution for dissolving the next batch of crude potassium chloride crystals.
S7, drying 79.88g of the obtained wet potassium chloride for 2 hours at 105 ℃ to obtain 81.5g of fertilizer-grade potassium chloride.
Specific example 3
S1, 2000kg of industrial waste salt generated in the production process of a certain chemical plant, wherein the industrial waste salt contains 6.5wt.% of organic matters, 89.8wt.% of potassium chloride, 2.21wt.% of sodium sulfate and 12.88wt.% of water. Drying and dehydrating the industrial waste salt;
s2, drying the hazardous waste salt obtained after drying, wherein the hazardous waste salt is uniform and has no caking phenomenon, and the hazardous waste salt enters a low-temperature carbonization furnace in a spiral feeding mode. The low-temperature carbonization furnace adopts closed and anaerobic operation, the temperature is controlled to be 500-550 ℃ for carbonization, the carbonization time is 5.5 hours, and the carbonization is carried out before entering a cooling stage. The flue gas generated in the low-temperature oxygen-free critical carbonization treatment process mainly comprises water vapor and trace dust, the water vapor and the trace dust are subjected to quenching tower, cyclone dust collection and cloth bag dust collection and then enter a combustion chamber, and the flue gas after combustion is sprayed by alkali liquor and then is discharged up to the standard.
S3, cooling the obtained carbonized polluted salt to 60 ℃, sampling, and cooling the rest for later use; after the sample is cooled to room temperature, the sample is left for analysis, and the analysis result is as follows: potassium salt weight 1629.01g with potassium chloride content 97.01wt.%, sodium sulfate content 2.35wt.%, and other material content 0.64wt.%.
S4, dissolving 1500g of potassium salt in 2800ml of tap water at 90 ℃, filtering to remove carbon after dissolving, adding 3.15g of potassium hydroxide to adjust the pH value to be more than 11.0, stirring for 10min, adding 2.1g of calcium chloride powder, continuously stirring at constant temperature for 20min, adding 1.5g of potassium carbonate, and continuously stirring at constant temperature for 30min; and (3) after stirring, carrying out hot filtration, adding hydrochloric acid into the filtrate to adjust the pH value back to 4.5-5.0, and obtaining 10.5g of filter residue.
And S5, stirring and cooling the filtrate by a water bath method, adding 1.6g of potassium chloride crystals when the temperature is reduced to 60-65 ℃, finding that a large amount of crystals are separated out from the solution, continuously cooling to 20 ℃, and stopping continuously cooling. The wet potassium chloride crystals 559.8g were obtained by filtration. And (3) recycling the mother liquor obtained by primary crystallization for preparing a sub-saturated potassium chloride solution, and cooling and crystallizing after the content of sodium sulfate in the mother liquor reaches saturation to obtain a sodium sulfate product.
S6, adding 559.8g of wet potassium chloride crystals into 1050ml of deionized water at 90 ℃, stirring for 10min, completely dissolving, adding 4g of analytically pure potassium chloride when the temperature is reduced to 75 ℃, continuously reducing the temperature to 25 ℃, stirring for 5min, and filtering to obtain 159.41g of wet potassium chloride. And the mother liquor obtained by filtering is recycled to the recrystallization process to be used as a solution for dissolving the next batch of crude potassium chloride crystals.
S7, drying 159.41g of the obtained wet potassium chloride for 2 hours at 105 ℃ to obtain 135.5g of fertilizer-grade potassium chloride.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A method for preparing fertilizer-grade potassium chloride from potassium chloride organic hazardous waste salt is characterized by mainly comprising the following steps: drying and dehydrating organic hazardous waste salt containing potassium chloride, performing low-temperature oxygen-free critical carbonization treatment on the obtained dry hazardous waste salt, preparing the obtained carbonized waste salt into a sub-saturated potassium chloride solution, and performing decarbonization and impurity removal on the solution; adjusting the pH value of the sub-saturated potassium chloride solution subjected to decarbonization and impurity removal to subacidity, carrying out primary crystallization and recrystallization by a cooling crystallization method to obtain wet potassium chloride, and drying the wet potassium chloride to remove moisture to obtain the fertilizer grade potassium chloride.
2. The method of claim 1, wherein: the low-temperature carbonization temperature of the dry hazardous waste salt during the low-temperature anaerobic critical carbonization treatment is 450-550 ℃, and the dry hazardous waste salt is in an anaerobic environment.
3. The method of claim 1, wherein: and smoke generated when the dry hazardous waste salt is subjected to low-temperature oxygen-free critical carbonization treatment is sequentially cooled by a quench tower, subjected to cyclone dust collection and subjected to cloth bag dust collection, then enters a combustion chamber to be fully combusted, and is sprayed by alkali liquor in a spray tower to reach the emission standard.
4. The method of claim 1, wherein: the preparation and decarbonization steps of the subsaturated potassium chloride solution are carried out on the carbonized sewage salt, and the carbonized sewage salt is dissolved in water with the temperature of 85-90 ℃ and then is filtered and decarbonized.
5. The method of claim 1, wherein: the step of removing impurities from the sub-saturated potassium chloride solution is to add potassium hydroxide into the decarbonized sub-saturated potassium chloride solution to adjust the pH value of the solution to be more than 11.0, sequentially add quantitative calcium chloride powder and potassium carbonate into the solution in sequence, respectively carry out constant-temperature stirring reaction, and then carry out hot filtration to realize the impurity removal.
6. The method of claim 1, wherein: adding hydrochloric acid into the sub-saturated potassium chloride solution after impurity removal to adjust the pH value to 4.5-6.0, filtering, cooling the obtained filtrate to 60-65 ℃, adding potassium chloride crystals to carry out primary crystallization, then continuously cooling to room temperature, standing to wait for completion of primary crystallization, and filtering to obtain crude potassium chloride crystals.
7. The method of claim 6, wherein: and (3) recycling the mother liquor obtained by primary crystallization for preparing a sub-saturated potassium chloride solution, and cooling and crystallizing after the content of sodium sulfate in the mother liquor reaches saturation to obtain a sodium sulfate product.
8. The method of claim 1, wherein: dissolving the crude potassium chloride crystal obtained by primary crystallization in deionized water at 85-90 ℃, cooling to 70-75 ℃, adding analytically pure potassium chloride for recrystallization, cooling to room temperature, standing for recrystallization, and filtering to obtain wet potassium chloride.
9. The method of claim 8, wherein: and the mother liquor obtained by recrystallization is recycled to the recrystallization process to be used as a solution for dissolving the next batch of crude potassium chloride crystals.
10. The method of claim 1, wherein: and slowly drying the wet potassium chloride at 100-105 ℃ to obtain the fertilizer grade potassium chloride.
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