阅读说明：本技术 一种磷石膏制备硫酸钾、碳酸钙及氯化铵的方法与系统装置 (Method and system device for preparing potassium sulfate, calcium carbonate and ammonium chloride from phosphogypsum ) 是由 周仕飞 于 2020-06-05 设计创作，主要内容包括：本发明涉及一种磷石膏资源化的方法,其中磷石膏与加入的氨、合成氨副产的CO<Sub>2</Sub>作为原料,得到硫酸铵与含杂质的碳酸钙沉淀,其中硫酸铵溶液加入氯化钾进行复分解反应,得到硫酸钾产品和氯化钾与氯化铵的混合溶液,将氯化钾和氯化铵的混合溶液与含杂质的碳酸钙沉淀在特定的蒸氨反应器中进行碳酸钙与氯化铵的分解反应,得到的溶液为氯化钾与氯化钙的混合物,经过滤后冷却结晶,得到的氯化钾作为生产硫酸钾的原料循环使用,氯化钙溶液与氨、CO<Sub>2</Sub>进行反应,得到轻质碳酸钙产品和氯化铵溶液,氯化铵溶液进行蒸发结晶得到氯化铵产品。本发明还提供了实现所述方法的系统装置,整个工艺过程核心为氯化铵与碳酸钙的反应,得到氯化钙的同时,实现了氨与CO<Sub>2</Sub>的循环利用。(The invention relates to a method for recycling phosphogypsum, wherein the phosphogypsum, added ammonia and CO as a byproduct of synthetic ammonia 2 The method comprises the steps of obtaining ammonium sulfate and calcium carbonate sediment containing impurities as raw materials, adding potassium chloride into an ammonium sulfate solution to perform double decomposition reaction to obtain a potassium sulfate product and a mixed solution of potassium chloride and ammonium chloride, performing decomposition reaction of calcium carbonate and ammonium chloride on the mixed solution of potassium chloride and ammonium chloride and the calcium carbonate sediment containing the impurities in a specific ammonia evaporation reactor to obtain a solution which is a mixture of potassium chloride and calcium chloride, filtering, cooling and crystallizing to obtain potassium chloride which is recycled as a raw material for producing potassium sulfate, and recycling the calcium chloride solution, ammonia and CO 2 Reacting to obtain light calcium carbonate product and ammonium chloride solution, evaporating and crystallizing the ammonium chloride solution to obtainAmmonium chloride product. The invention also provides a system device for realizing the method, the core of the whole process is the reaction of ammonium chloride and calcium carbonate to obtain calcium chloride, and simultaneously, the ammonia and CO are realized 2 The recycling of (2).)

1. A method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum is characterized by comprising the following steps: the process flow of the method adopts the following steps:

(1) carrying out an ammoniation reaction on phosphogypsum and ammonia water with the mass concentration of 20-25%, dissolving calcium sulfate in ammonia, and then introducing CO₂Reacting the gas to obtain calcium carbonate precipitate and an ammonium sulfate solution with the mass concentration of 30-35%, wherein impurities contained in the phosphogypsum enter the calcium carbonate in the process, and the reaction temperature is 25-35 ℃;

(2) adding industrial potassium chloride and recycled potassium chloride into the ammonium sulfate solution filtered in the step (1) to perform double decomposition reaction, crystallizing potassium sulfate from the solution by virtue of salting-out action of high-concentration ammonium sulfate, and performing centrifugal separation to obtain a potassium sulfate product, wherein the solution after the reaction is a mixed solution of potassium chloride and ammonium chloride;

(3) adding the potassium chloride and ammonium chloride mixed solution obtained in the step (2) into the calcium carbonate obtained in the step (1) for mixing, introducing steam for high-temperature decomposition at the decomposition temperature of 150-170 ℃, and obtaining ammonia and CO in a gas phase₂The mixture with the water vapor is concentrated by a rectifying section at the top of the reactor to obtain ammonia water and CO with the mass concentration of 15-20%₂Gas, wherein the solution after ammonia evaporation is a mixed liquid of potassium chloride and calcium chloride, the temperature reaches 120-140 ℃, heat preservation and filtration are carried out, the filtered solution is cooled to 50-65 ℃ for high-temperature crystallization, and the obtained potassium chloride crystals are recycled to the step (2);

(4) ammonia water and CO obtained in step (3)₂Carrying out carbonation reaction with the calcium chloride solution obtained in the step (3) to obtain calcium carbonate precipitateFiltering and drying to obtain light calcium carbonate product, and evaporating and crystallizing the obtained ammonium chloride solution to obtain ammonium chloride product.

2. The method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum as claimed in claim 1, which is characterized in that: preparation of phosphogypsum, ammonia water and by-product CO of synthetic ammonia from ammonium sulfate₂Reacting raw materials at 25-35 ℃;

preferably, CaSO is contained in the phosphogypsum in the step (1)₄·2H₂The mass percentage of O is 42-48%, such as 42%, 44%, 46% and 48%.

Preferably, the mass concentration of ammonia water in the step (1) is 20-25%, and more preferably: 20%, 21%, 22%, 23%, 24%, 25%.

Preferably, CO is used in step (1)₂The volume fraction is 80-95%, more preferably 80%, 85%, 90%, 95%.

Preferably, NH is added to the ammoniacal water in step (1)₃SO in phosphogypsum₄The molar ratio is 1.04-1.1: 1, and more preferably, 1.04: 1, 1.06: 1, 1.08: 1, 1.1: 1;

preferably, the phosphogypsum and ammonia water in the step (1) are mixed and stirred for 15-20min, more preferably 15min, 18min and 20 min.

Preferably, the carbonation reaction time of the step (1) and the step (4) is 30-50min, more preferably 30min, 40min and 50 min.

3. The method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum as claimed in claim 1, which is characterized in that: the potassium chloride raw material used in the potassium sulfate preparation tank meets the following requirements: k₂The mass percentage of O is more than or equal to 55 percent, and in addition, the crystal product KCl after ammonia distillation reaction is also included.

4. The method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum as claimed in claim 1, which is characterized in that: the ammonia distillation reaction takes steam as a heating heat source to realize the decomposition of ammonium chloride, the subsequent mixed gas of ammonia and water steam is concentrated by a rectifying section arranged at the upper part of the ammonia distillation reactor,while obtaining qualified ammonia water, CO₂Precipitated, compressed and decarbonated.

Preferably, the ammonia distillation reaction temperature is 150-170 ℃, more preferably 150 ℃, 155 ℃, 160 ℃, 165 ℃ and 170 ℃.

Preferably, the mass concentration of the ammonia water obtained after ammonia distillation is 15-20%, more preferably 15%, 16%, 17%, 18%, 19%, 20%.

5. The method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum as claimed in claim 1, which is characterized in that: after ammonia evaporation, the solution is mixed liquid of potassium chloride and calcium chloride, the temperature reaches 120-140 ℃, heat preservation and filtration are carried out, impurities such as silicon, iron and the like in the solution are separated through filtration, the solution of the potassium chloride and the calcium chloride is obtained, high-temperature crystallization is carried out after the solution of the potassium chloride and the calcium chloride is cooled, and the potassium chloride is crystallized from the calcium chloride;

preferably, the mixed solution of potassium chloride and calcium chloride is cooled to 50-65 ℃, more preferably 50 ℃, 55 ℃, 60 ℃ and 65 ℃.

6. The method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum as claimed in claim 1, which is characterized in that: the carbonation process is to distill ammonia to obtain ammonia water and CO₂Reacting with calcium chloride solution to obtain calcium carbonate precipitate.

Preferably, the carbonation reaction temperature is 30-40 ℃, more preferably 30 ℃, 35 ℃ and 40 ℃.

Preferably, the carbonation reaction time is 30-50min, more preferably 30min, 40min and 50 min.

7. The utility model provides a system's device of ardealite preparation potassium sulfate, calcium carbonate and ammonium chloride, the system's device includes: (1) preparing an ammonium sulfate preparation kettle; (2) an ammonium sulfate solution pump; (3) a filter residue filter press; (4) a potassium sulfate preparation tank; (5) a potassium sulfate centrifuge; (6) an ammonia distillation reactor; (7) a condenser; (8) CO 2₂A compressor; (9) an ammonia evaporation pump; (10) a filter residue filter press; (11) cooling the potassium chloride by an air cooler; (12) a potassium chloride centrifuge; (13) a carbonation reactor; (14) a carbonation pump; (15) a calcium carbonate filter press; (16) A calcium carbonate dryer; (17) an ammonium chloride evaporative crystallizer;

wherein, the outlet of the ammonium sulfate preparation kettle (1) is connected with the inlet of an ammonium sulfate solution pump (2), the outlet of the ammonium sulfate solution pump (2) is connected with the inlet of a filter residue filter press (3), the liquid outlet of the filter residue filter press (3) is connected with the inlet of a potassium sulfate preparation tank (4), the solid outlet of the filter residue filter press (3) is connected with the inlet of an ammonia evaporation reactor (6), the outlet of the potassium sulfate preparation tank (4) is connected with the inlet of a potassium sulfate centrifuge (5), the outlet of the potassium sulfate centrifuge (5) is connected with the liquid inlet of the ammonia evaporation reactor (6), the gas outlet of the ammonia evaporation reactor (6) is connected with the inlet of a condenser (7), the outlet of the condenser (7) is connected with the inlet of a CO solution pump (2₂Inlet connection of compressor (8), CO₂The outlet of the compressor (8) is connected with the inlet of the carbonating reactor (13), the liquid outlet of the ammonia steaming reactor (6) is connected with the inlet of the ammonia steaming pump (9), the outlet of the ammonia steaming pump (9) is connected with the inlet of the filter residue filter press (10), the outlet of the filter residue filter press (10) is connected with the inlet of the potassium chloride air cooling machine (11), the outlet of the potassium chloride air cooling machine (11) is connected with the inlet of the potassium chloride centrifugal machine (12), the liquid outlet of the potassium chloride centrifugal machine (12) is connected with the inlet of the carbonating reactor (13), the solid outlet of the potassium chloride centrifugal machine (12) is connected with the potassium sulfate preparation tank (4), the outlet of the carbonating reactor (13) is connected with the inlet of the carbonating pump (14), the outlet of the carbonating pump (14) is connected with the inlet of the calcium carbonate filter press (15), the solid outlet of the calcium carbonate filter press (15) is connected with the inlet of the calcium carbonate, the liquid outlet of the calcium carbonate filter press (15) is connected with the inlet of the ammonium chloride evaporative crystallizer (17).

8. The system apparatus of claim 7, wherein: the preparation of the ammonium sulfate is carried out in a reaction kettle;

preferably, the ammonium sulfate preparation kettle is made of stainless steel;

preferably, the ammonium sulfate preparation kettle is reaction equipment for phosphogypsum and carbonated ammonia water;

wherein, the ammonia distillation reaction is carried out in an ammonia distillation reactor.

Preferably, the ammonia distillation reactor is made of stainless steel;

preferably, the ammonia distillation reactor takes steam as a heat source and is reaction equipment of ammonium chloride and calcium carbonate;

wherein the carbonation reaction is carried out in a reaction kettle.

Preferably, the carbonation reactor is stainless steel;

preferably, the carbonation reactor is a reaction device of calcium chloride and carbonated ammonia water.

9. The process according to any one of claims 1 to 6, characterized in that it comprises the following steps:

(1) adding phosphogypsum and ammonia water with mass concentration of 20-25% into an ammonium sulfate preparation kettle, and introducing CO with the content of a synthetic ammonia byproduct of 80-95%₂Reacting at 25-35 ℃ to obtain calcium carbonate precipitate and ammonium sulfate solution with mass concentration of 30-35%;

(2) filtering the reaction slurry obtained in the step (1) by a filter residue filter press to obtain an ammonium sulfate solution, carrying out double decomposition reaction on the ammonium sulfate solution, industrial potassium chloride and recycled potassium chloride in a potassium sulfate preparation tank, and carrying out solid-liquid separation by a centrifugal machine to obtain potassium sulfate crystals and a mixed solution of potassium chloride and ammonium chloride;

(3) carrying out pyrolysis on the potassium chloride and ammonium chloride mixed solution obtained in the step (2) and the calcium carbonate obtained in the step (1) in an ammonia distillation reactor, wherein the pyrolysis temperature is 150-170 ℃, and obtaining ammonia and CO in a gas phase₂The mixture with the water vapor is condensed by a condenser after being concentrated by a rectifying section at the top of the ammonia distillation reactor to obtain ammonia water and CO with the mass concentration of 15-20 percent₂A gas. Performing heat preservation and filtration on the mixed liquid of potassium chloride and calcium chloride by using a filter residue filter press, cooling the filtered solution to 50-65 ℃ by using an air cooling machine for high-temperature crystallization, performing solid-liquid separation by using a centrifugal machine to obtain a calcium chloride solution and potassium chloride crystals, and recycling the potassium chloride crystals to the step (2);

(4) the ammonia obtained in the step (3) and CO compressed by a compressor₂Carrying out carbonation reaction with the calcium chloride solution obtained in the step (3) in the carbonation reaction, and filtering by a filter press to obtain calcium carbonate precipitate and ammonium chloride solution, wherein the calcium carbonate precipitate and the ammonium chloride solution are calcium carbonateDrying the precipitate by a dryer to obtain a light calcium carbonate product, and evaporating and crystallizing the ammonium chloride solution by an evaporation crystallizer to obtain an ammonium chloride product.

Technical Field

The invention belongs to the technical field of environmental protection, and relates to a method and a system device for preparing potassium sulfate, calcium carbonate and ammonium chloride by using a solid waste phosphogypsum.

Background

The main component of the phosphogypsum is calcium sulfate dihydrate (CaSO)₄·2H₂O), the content thereof is very high. Phosphogypsum impurities fall into two broad categories: 1. insoluble impurities such as quartz, undecomposed apatite, insoluble P₂O₅Eutectic crystal P₂O₅Fluorides and phosphates and sulfates of fluorine, aluminum, magnesium. 2. Soluble impuritiesWater soluble P as a substance₂O₅Lower solubility fluorides and sulfates. In addition, the phosphogypsum also contains arsenic, copper, zinc, iron, manganese, lead, cadmium, mercury and radioactive elements which are all extremely trace, most of the elements are insoluble solids, and the hazard is negligible. Fluoride, free phosphoric acid, P contained in phosphogypsum₂O₅And impurities such as phosphate are main factors causing environmental pollution of the phosphogypsum in the stockpiling process.

Besides producing building materials, industrial application of phosphogypsum draws attention from the industry, and the main research contents comprise:

(1) preparation of sulfuric acid and joint production of cement by phosphogypsum

The phosphogypsum is properly treated, coke, auxiliary raw materials and the like are added into a rotary kiln, and the rotary kiln is calcined into clinker and SO-containing material at high temperature₂The clinker is mixed with blast furnace slag and gypsum after being treated, the mixture is ground into cement, and SO generated by decomposition is generated₂Used for producing sulfuric acid. The calcination of the phosphogypsum raw material is the key of the production, namely the SO is prepared₂High and stable concentration, and meets the kiln gas for sulfuric acid production, and the clinker meeting the requirements is obtained to produce high-strength grade cement. Because of the shortage of domestic sulfur resources, with the development of wet-process phosphoric acid, a large amount of sulfuric acid is required to be consumed, and under the condition, the preparation of sulfuric acid and the co-production of cement by using phosphogypsum is undoubtedly an effective way which can make up the shortage of sulfur resources and solve the problem of the coming-out of phosphogypsum so as to comprehensively utilize the resources. At present, three, four and six projects for preparing sulfuric acid and co-producing cement by phosphogypsum are built in multiple enterprises such as the North-Lu chemical industry group in China, and the technology becomes mature through years of practice. The method has the advantages that: the yield of the sulfuric acid is increased, 85 to 90 percent of the sulfuric acid used in the production of the phosphoric acid is recycled, and the phosphogypsum does not need a storage yard and is not transported outside. The disadvantages are that: long flow, more equipment, large investment and certain requirements on the quality of the phosphogypsum. According to the calculation of the 'three, four and six' engineering of producing sulfuric acid and co-producing cement by using phosphogypsum, the total engineering investment is about 1 hundred million yuan RMB, and the phosphogypsum is treated by about 100 kt/a.

(2) Preparation of ammonium sulfate from phosphogypsum

Ammonium sulfate is an important sulfur and nitrogen fertilizer and is widely used in agricultural production. The main processes for preparing ammonium sulfate from phosphogypsum comprise the pretreatment of phosphogypsum, the preparation of ammonium carbonate solution, the conversion of phosphogypsum, the filtration and separation of calcium carbonate, the evaporative crystallization of ammonium sulfate solution, the drying of ammonium sulfate crystal and the packaging of finished products. The method has the advantages that part of ammonium bicarbonate products are converted into ammonium sulfate which is easy to be sold out, and the phosphogypsum does not need to be stockpiled or transported outside. The disadvantages are that: long flow, more equipment, larger investment and certain requirements on the quality of the phosphogypsum. With the development of ammonium nitrate and urea production and the increase of the quantity of ammonium sulfate byproducts, the production of ammonium sulfate prepared by phosphogypsum is gradually reduced, and only some enterprises in India and Indonesia are still producing at present.

(3) Preparation of potassium sulfate from phosphogypsum

The potassium sulfate is an important chlorine-free potassium fertilizer, the domestic demand is large, and the research on producing the potassium sulfate and the sulfur compound fertilizer by the phosphogypsum is many in the world. At present, the method for preparing potassium sulfate by a gypsum conversion method mainly comprises a one-step method and a two-step method: the one-step method is that in a high-concentration ammonia solution, phosphogypsum and potassium chloride react in one step to prepare potassium sulfate; the two-step method is to replace ammonia solution with ammonium bicarbonate (or ammonium carbonate), and the reaction system is carried out in two steps. The method comprises the following steps of ammonia absorption, limestone calcination, carbonization, gypsum conversion, potassium sulfate crystallization and drying, gypsum precipitation, distillation and the like.

The problems of preparing potassium sulfate by using phosphogypsum are mainly as follows: 1. the product is out of the way, for example, the by-product calcium chloride can not be sold as the product; 2. the conversion rate problem, including that the conversion rate of potassium sulfate formed by potassium chloride can only reach 60%, and the mixture of ammonium chloride and potassium chloride as by-product can only be sold as mixed salt after being evaporated, so that it is difficult to produce benefit.

Disclosure of Invention

The invention aims to solve the problems of low conversion rate and calcium chloride output in the process of preparing potassium sulfate by phosphogypsum, and provides a method and a system device for preparing potassium sulfate, calcium carbonate and ammonium chloride by phosphogypsum, wherein the phosphogypsum, added ammonia and CO as a byproduct of synthetic ammonia₂As a raw material, ammonium sulfate and calcium carbonate precipitate containing impurities are obtained, wherein the ammonium sulfateAdding potassium chloride into the solution to carry out double decomposition reaction to obtain a potassium sulfate product and a mixed solution of potassium chloride and ammonium chloride, precipitating the mixed solution of potassium chloride and ammonium chloride and calcium carbonate containing impurities in a specific ammonia distillation reactor to carry out decomposition reaction of calcium carbonate and ammonium chloride to obtain a solution which is a mixture of potassium chloride and calcium chloride, filtering, cooling and crystallizing to obtain potassium chloride which is recycled as a raw material for producing potassium sulfate, and reacting the calcium chloride solution with ammonia distillation to obtain ammonia and CO₂And carrying out reaction to obtain a light calcium carbonate product and an ammonium chloride solution, and carrying out evaporation crystallization on the ammonium chloride solution to obtain an ammonium chloride product. The core process of the whole process is the reaction of ammonium chloride and calcium carbonate to obtain calcium chloride and realize the reaction of ammonia and CO₂And (4) recycling.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum, wherein the method adopts the following process flow:

(1) carrying out an ammoniation reaction on phosphogypsum and ammonia water with the mass concentration of 20-25%, dissolving calcium sulfate in ammonia, and then introducing CO₂And reacting the gas to obtain calcium carbonate precipitate and an ammonium sulfate solution with the mass concentration of 30-35%, wherein impurities contained in the phosphogypsum enter the calcium carbonate in the process, and the reaction temperature is 25-35 ℃.

(2) Adding industrial potassium chloride and recycled potassium chloride into the ammonium sulfate solution filtered in the step (1) to perform double decomposition reaction, crystallizing potassium sulfate from the solution by virtue of salting-out action of high-concentration ammonium sulfate, and performing centrifugal separation to obtain a potassium sulfate product. The solution after the reaction is a mixed solution of potassium chloride and ammonium chloride.

(3) Adding the potassium chloride and ammonium chloride mixed solution obtained in the step (2) into the calcium carbonate obtained in the step (1) for mixing, introducing steam for high-temperature decomposition at the decomposition temperature of 150-170 ℃, and obtaining ammonia and CO in a gas phase₂The mixture with the water vapor is concentrated by a rectifying section at the top of the reactor to obtain ammonia water and CO with the mass concentration of 15-20%₂A gas. The solution after ammonia distillation is potassium chloride and chlorineAnd (3) carrying out heat preservation and filtration on the mixed liquid of calcium chloride when the temperature reaches 120-140 ℃, cooling the filtered solution to 50-65 ℃ for high-temperature crystallization, and recycling the obtained potassium chloride crystal to the step (2).

(4) Ammonia water and CO obtained in step (3)₂And (4) carrying out carbonation reaction with the calcium chloride solution obtained in the step (3) to obtain calcium carbonate precipitate, filtering and drying to obtain a light calcium carbonate product, and evaporating and crystallizing the obtained ammonium chloride solution to obtain an ammonium chloride product.

The invention relates to a method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum, wherein phosphogypsum, ammonia water and a byproduct CO of synthetic ammonia are prepared by using ammonium sulfate₂Reacting raw materials at 25-35 ℃;

preferably, CaSO is contained in the phosphogypsum in the step (1)₄·2H₂The mass percentage of O is 42-48%, such as 42%, 44%, 46% and 48%.

Preferably, the mass concentration of ammonia water in the step (1) is 20-25%, such as 20%, 21%, 22%, 23%, 24%, 25%.

Preferably, CO is used in step (1)₂The volume fraction is 80-95%, for example 80%, 85%, 90%, 95%.

Preferably, NH is added to the ammoniacal water in step (1)₃SO in phosphogypsum₄The molar ratio is 1.04-1.1: 1, such as 1.04: 1, 1.06: 1, 1.08: 1, 1.1: 1;

preferably, the phosphogypsum in the step (1) is mixed with the ammonia water and stirred for 15-20min, such as 15min, 18min and 20 min.

Preferably, the carbonation reaction time of step (1) and step (4) is 30-50min, such as 30min, 40min, 50 min.

In the method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum, the potassium chloride raw material used in the potassium sulfate preparation tank meets the standard of qualified products in the national standard GB 6549-2011 potassium chloride, wherein K is₂The mass percentage of O is more than or equal to 55 percent, and in addition, a crystallization product KCl after ammonia distillation reaction is also included;

the method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsumThe method comprises the steps that steam is used as a heating heat source in the ammonia distillation reaction to realize the decomposition of ammonium chloride, the subsequent mixed gas of ammonia and water vapor is concentrated by a rectifying section arranged at the upper part of an ammonia distillation reactor to obtain qualified ammonia water, and CO is added into the concentrated mixed gas₂Precipitated, compressed and decarbonated.

Preferably, the reaction temperature of ammonia distillation is 150-170 ℃, such as 150 ℃, 155 ℃, 160 ℃, 165 ℃ and 170 ℃.

Preferably, the ammonia water obtained after ammonia distillation has a mass concentration of 15-20%, such as 15%, 16%, 17%, 18%, 19%, 20%.

In the method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum, ammonia evaporation is carried out, the solution is mixed liquid of potassium chloride and calcium chloride, the temperature reaches 120-140 ℃, heat preservation and filtration are carried out, impurities such as silicon, iron and the like in the solution are separated through filtration, the solution of potassium chloride and calcium chloride is obtained, high-temperature crystallization is carried out after the solution of potassium chloride and calcium chloride is cooled, and potassium chloride is crystallized from calcium chloride.

Preferably, the mixed solution of potassium chloride and calcium chloride is cooled to 50-65 ℃, for example, 50 ℃, 55 ℃, 60 ℃ and 65 ℃.

The method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum comprises the step of performing carbonation to obtain ammonia water and CO by ammonia distillation₂Reacting with calcium chloride solution to obtain calcium carbonate precipitate.

Preferably, the carbonation reaction temperature is 30 to 40 ℃, for example 30 ℃, 35 ℃, 40 ℃.

Preferably, the carbonation reaction time is 30-50min, such as 30min, 40min, 50 min.

In a second aspect, the present invention provides a system apparatus for preparing potassium sulfate, calcium carbonate and ammonium chloride from phosphogypsum, wherein the system apparatus comprises: (1) preparing an ammonium sulfate preparation kettle; (2) an ammonium sulfate solution pump; (3) a filter residue filter press; (4) a potassium sulfate preparation tank; (5) a potassium sulfate centrifuge; (6) an ammonia distillation reactor; (7) a condenser; (8) CO 2₂A compressor; (9) an ammonia evaporation pump; (10) a filter residue filter press; (11) cooling the potassium chloride by an air cooler; (12) a potassium chloride centrifuge; (13) a carbonation reactor; (14) a carbonation pump; (15) a calcium carbonate filter press;(16) a calcium carbonate dryer; (17) ammonium chloride evaporative crystallizers. Wherein, the outlet of the ammonium sulfate preparation kettle (1) is connected with the inlet of an ammonium sulfate solution pump (2), the outlet of the ammonium sulfate solution pump (2) is connected with the inlet of a filter residue filter press (3), the liquid outlet of the filter residue filter press (3) is connected with the inlet of a potassium sulfate preparation tank (4), the solid outlet of the filter residue filter press (3) is connected with the inlet of an ammonia evaporation reactor (6), the outlet of the potassium sulfate preparation tank (4) is connected with the inlet of a potassium sulfate centrifuge (5), the outlet of the potassium sulfate centrifuge (5) is connected with the liquid inlet of the ammonia evaporation reactor (6), the gas outlet of the ammonia evaporation reactor (6) is connected with the inlet of a condenser (7), the outlet of the condenser (7) is connected with the inlet of a CO solution pump (2₂Inlet connection of compressor (8), CO₂The outlet of the compressor (8) is connected with the inlet of the carbonating reactor (13), the liquid outlet of the ammonia steaming reactor (6) is connected with the inlet of the ammonia steaming pump (9), the outlet of the ammonia steaming pump (9) is connected with the inlet of the filter residue filter press (10), the outlet of the filter residue filter press (10) is connected with the inlet of the potassium chloride air cooling machine (11), the outlet of the potassium chloride air cooling machine (11) is connected with the inlet of the potassium chloride centrifugal machine (12), the liquid outlet of the potassium chloride centrifugal machine (12) is connected with the inlet of the carbonating reactor (13), the solid outlet of the potassium chloride centrifugal machine (12) is connected with the potassium sulfate preparation tank (4), the outlet of the carbonating reactor (13) is connected with the inlet of the carbonating pump (14), the outlet of the carbonating pump (14) is connected with the inlet of the calcium carbonate filter press (15), the solid outlet of the calcium carbonate filter press (15) is connected with the inlet of the calcium carbonate, the liquid outlet of the calcium carbonate filter press (15) is connected with the inlet of the ammonium chloride evaporative crystallizer (17).

The system device for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum is characterized in that the ammonium sulfate is prepared in a reaction kettle.

Preferably, the ammonium sulfate preparation kettle is made of stainless steel;

preferably, the ammonium sulfate preparation kettle is reaction equipment for phosphogypsum and carbonated ammonia water.

The system device for preparing potassium sulfate, calcium carbonate and ammonium chloride by using the phosphogypsum is characterized in that the ammonia distillation reaction is carried out in an ammonia distillation reactor.

Preferably, the ammonia distillation reactor is made of stainless steel;

preferably, the ammonia distillation reactor takes steam as a heat source and is a reaction device of ammonium chloride and calcium carbonate.

The system device for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum is characterized in that the carbonation reaction is carried out in the reaction kettle.

Preferably, the carbonation reactor is stainless steel;

preferably, the carbonation reactor is a reaction device of calcium chloride and carbonated ammonia water.

The above processing method, wherein the method comprises the steps of:

(1) adding phosphogypsum and ammonia water with mass concentration of 20-25% into an ammonium sulfate preparation kettle, and introducing CO with the content of a synthetic ammonia byproduct of 80-95%₂Reacting at 25-35 ℃ to obtain calcium carbonate precipitate and ammonium sulfate solution with mass concentration of 30-35%;

(2) and (2) filtering the reaction slurry obtained in the step (1) by using a filter residue filter press to obtain an ammonium sulfate solution, carrying out double decomposition reaction on the ammonium sulfate solution, industrial potassium chloride and recycled potassium chloride in a potassium sulfate preparation tank, and carrying out solid-liquid separation by using a centrifugal machine to obtain potassium sulfate crystals and a mixed solution of potassium chloride and ammonium chloride.

(3) Carrying out pyrolysis on the potassium chloride and ammonium chloride mixed solution obtained in the step (2) and the calcium carbonate obtained in the step (1) in an ammonia distillation reactor, wherein the pyrolysis temperature is 150-170 ℃, and obtaining ammonia and CO in a gas phase₂The mixture with the water vapor is condensed by a condenser after being concentrated by a rectifying section at the top of the ammonia distillation reactor to obtain ammonia water and CO with the mass concentration of 15-20 percent₂A gas. And (3) carrying out heat preservation and filtration on the mixed liquid of potassium chloride and calcium chloride by using a filter residue filter press, cooling the filtered solution to 50-65 ℃ by using an air cooling machine for high-temperature crystallization, carrying out solid-liquid separation by using a centrifugal machine to obtain a calcium chloride solution and potassium chloride crystals, and recycling the potassium chloride crystals to the step (2).

(4) The ammonia obtained in the step (3) and CO compressed by a compressor₂Carrying out carbonation reaction with the calcium chloride solution obtained in the step (3) in the carbonation reaction, and filtering by a filter press to obtain carbonic acidCalcium carbonate precipitation and an ammonium chloride solution, wherein the calcium carbonate precipitation is dried by a dryer to obtain a light calcium carbonate product, and the ammonium chloride solution is evaporated and crystallized by an evaporation crystallizer to obtain an ammonium chloride product.

Compared with the prior art, the invention has the following beneficial effects:

(1) the method utilizes the phosphogypsum to prepare the potassium sulfate, the calcium carbonate and the ammonium chloride, and has remarkable economic benefit;

(2) the invention realizes the reaction of ammonia and CO₂The recycling of the process is realized, and three wastes are not discharged.

(3) The invention realizes the resource utilization of the phosphogypsum and eliminates the hidden trouble of the environment.

Drawings

FIG. 1 is a process flow diagram of a method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum;

FIG. 2 is a schematic structural diagram of a system device for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum;

wherein: (1) preparing an ammonium sulfate preparation kettle; (2) an ammonium sulfate solution pump; (3) a filter residue filter press; (4) a potassium sulfate preparation tank; (5) a potassium sulfate centrifuge; (6) an ammonia distillation reactor; (7) a condenser; (8) CO 2₂A compressor; (9) an ammonia evaporation pump; (10) a filter residue filter press; (11) cooling the potassium chloride by an air cooler; (12) a potassium chloride centrifuge; (13) a carbonation reactor; (14) a carbonation pump; (15) a calcium carbonate filter press; (16) a calcium carbonate dryer; (17) ammonium chloride evaporative crystallizers.

Detailed Description

The method for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum is realized in the way, and is specifically described by combining the attached drawing.

The specific embodiment of the present invention is implemented using the process flow shown in fig. 1. The process flow mainly comprises the following steps:

(1) carrying out an ammoniation reaction on phosphogypsum and ammonia water with the mass concentration of 20-25%, dissolving calcium sulfate in ammonia, and then introducing CO₂Reacting the gas to obtain calcium carbonate precipitate and an ammonium sulfate solution with the mass concentration of 30-35%, wherein impurities contained in the phosphogypsum enter the calcium carbonate in the process, and the reaction temperature is 25-35 DEG C。

(2) Adding industrial potassium chloride and recycled potassium chloride into the ammonium sulfate solution filtered in the step (1) to perform double decomposition reaction, crystallizing potassium sulfate from the solution by virtue of salting-out action of high-concentration ammonium sulfate, and performing centrifugal separation to obtain a potassium sulfate product. The solution after the reaction is a mixed solution of potassium chloride and ammonium chloride.

(3) Adding the potassium chloride and ammonium chloride mixed solution obtained in the step (2) into the calcium carbonate obtained in the step (1) for mixing, introducing steam for high-temperature decomposition at the decomposition temperature of 150-170 ℃, and obtaining ammonia and CO in a gas phase₂The mixture with the water vapor is concentrated by a rectifying section at the top of the reactor to obtain ammonia water and CO with the mass concentration of 15-20%₂A gas. And (3) the solution after ammonia evaporation is a mixed liquid of potassium chloride and calcium chloride, the temperature reaches 120-140 ℃, heat preservation and filtration are carried out, the filtered solution is cooled to 50-65 ℃ for high-temperature crystallization, and the obtained potassium chloride crystals are recycled to the step (2).

(4) Ammonia water and CO obtained in step (3)₂And (4) carrying out carbonation reaction with the calcium chloride solution obtained in the step (3) to obtain calcium carbonate precipitate, filtering and drying to obtain a light calcium carbonate product, and evaporating and crystallizing the obtained ammonium chloride solution to obtain an ammonium chloride product.

In the specific embodiment of the present invention, a system apparatus for preparing potassium sulfate, calcium carbonate and ammonium chloride by using phosphogypsum as shown in fig. 2 is adopted, and the system apparatus comprises: (1) preparing an ammonium sulfate preparation kettle; (2) an ammonium sulfate solution pump; (3) a filter residue filter press; (4) a potassium sulfate preparation tank; (5) a potassium sulfate centrifuge; (6) an ammonia distillation reactor; (7) a condenser; (8) CO 2₂A compressor; (9) an ammonia evaporation pump; (10) a filter residue filter press; (11) cooling the potassium chloride by an air cooler; (12) a potassium chloride centrifuge; (13) a carbonation reactor; (14) a carbonation pump; (15) a calcium carbonate filter press; (16) a calcium carbonate dryer; (17) ammonium chloride evaporative crystallizers. Wherein, the outlet of the ammonium sulfate preparation kettle (1) is connected with the inlet of an ammonium sulfate solution pump (2), the outlet of the ammonium sulfate solution pump (2) is connected with the inlet of a filter residue filter press (3), the liquid outlet of the filter residue filter press (3) is connected with the inlet of a potassium sulfate preparation tank (4), the solid outlet of the filter residue filter press (3) is connected with an ammonia distillation reactor (6)The outlet of the potassium sulfate preparation tank (4) is connected with the inlet of a potassium sulfate centrifuge (5), the outlet of the potassium sulfate centrifuge (5) is connected with the liquid inlet of an ammonia evaporation reactor (6), the gas outlet of the ammonia evaporation reactor (6) is connected with the inlet of a condenser (7), and the outlet of the condenser (7) is connected with CO₂Inlet connection of compressor (8), CO₂The outlet of the compressor (8) is connected with the inlet of the carbonating reactor (13), the liquid outlet of the ammonia steaming reactor (6) is connected with the inlet of the ammonia steaming pump (9), the outlet of the ammonia steaming pump (9) is connected with the inlet of the filter residue filter press (10), the outlet of the filter residue filter press (10) is connected with the inlet of the potassium chloride air cooling machine (11), the outlet of the potassium chloride air cooling machine (11) is connected with the inlet of the potassium chloride centrifugal machine (12), the liquid outlet of the potassium chloride centrifugal machine (12) is connected with the inlet of the carbonating reactor (13), the solid outlet of the potassium chloride centrifugal machine (12) is connected with the potassium sulfate preparation tank (4), the outlet of the carbonating reactor (13) is connected with the inlet of the carbonating pump (14), the outlet of the carbonating pump (14) is connected with the inlet of the calcium carbonate filter press (15), the solid outlet of the calcium carbonate filter press (15) is connected with the inlet of the calcium carbonate, the liquid outlet of the calcium carbonate filter press (15) is connected with the inlet of the ammonium chloride evaporative crystallizer (17).

The phosphogypsum adopted by the invention is from a phosphorus-making group in Guizhou, and the main components of the phosphogypsum are shown in the following table.

Composition (I)	CaSO4·2H2O	P2O5	SiO2	H2O	MgO	Fe2O3	Others
								Composition wt%	42-48	1.3-2.5	12-18	25-35	0.2-0.5	1.0-2.0	1.5-2.0

The potassium chloride adopted by the invention is from Qinghai Guerba, and the main component composition thereof is shown in the following table.

Composition (I)	K2O	H2O	NaCl	Ca+Mg	Water insoluble substance	Others
							Composition wt%	55-57	5-6	0.8-1.5	1.0-1.5	0.2-0.5	2.0-3.0

The technical indexes of the agricultural potassium sulfate national standard GB 20406-2006 are shown in the following table.

The technical indexes of the industrial light calcium carbonate standard HG/T2226-2010 are shown in the following table.

The technical indexes of the national standard GB/T2946-.