A method and system for producing ammonium dihydrogen phosphate

Abstract

The application discloses a production method and system of ammonium dihydrogen phosphate, and the method comprises the following steps: first, reacting and dissolving phosphate ore slurry with phosphoric acid, filtering the liquid after the reaction to obtain solution A; second, defluorinating the solution A; third, mixing saturated solution B prepared from ammonium sulfate with the defluorinated solution A in a certain proportion, and stirring to generate white precipitate; fourth, realizing solid-liquid separation of the white precipitate in the third step and the liquid, and washing to obtain pure white precipitate D and ammonium dihydrogen phosphate solution E. The system comprises a phosphoric acid calcium phosphate aqueous solution preparation part, a phosphoric acid calcium phosphate aqueous solution defluorination part, a neutralization reaction part and a solid-liquid separation part. The application has the advantages that ammonium dihydrogen phosphate is produced by simply and effectively utilizing ammonium sulfate.

Description

Technical Field

[0001] This invention relates to the field of inorganic phosphorus chemical production and preparation, and discloses a method and system for producing ammonium dihydrogen phosphate by utilizing the properties of ammonium sulfate. Background Technology

[0002] Ammonium sulfate is an acidic agricultural fertilizer, but due to the large quantities of ammonium sulfate produced as a byproduct of the chemical industry and ammonia-based flue gas desulfurization industry, its price is currently lower than that of the raw materials. In the production of phosphoric acid and ammonium dihydrogen phosphate, sulfuric acid and ammonia are used respectively. Sulfuric acid is the main raw material for wet-process phosphoric acid production, while ammonia is one of the main raw materials for ammonium dihydrogen phosphate production. Using ammonium sulfate in the production of ammonium dihydrogen phosphate would greatly alleviate the current surplus of ammonium sulfate in my country and also help industries that produce ammonium sulfate as a byproduct to absorb the large quantities of ammonium sulfate produced.

[0003] In order to find a low-cost method for producing ammonium dihydrogen phosphate from ammonium sulfate, this invention makes full use of the components of ammonium sulfate to achieve low-cost recycling, fundamentally reducing the production cost of ammonium dihydrogen phosphate and solving the problem of unsold ammonium sulfate. Summary of the Invention

[0004] This invention provides a simple and effective method and system for producing ammonium dihydrogen phosphate using ammonium sulfate.

[0005] To achieve the above objectives, this invention provides a method and system for producing ammonium dihydrogen phosphate while consuming ammonium sulfate, the details of which are as follows: A method for producing ammonium dihydrogen phosphate includes the following steps: Step 1: React and dissolve the phosphate rock slurry with phosphoric acid. After the reaction, filter the liquid to obtain solution A. Step 2: Defluorinate solution A; Step 3: Mix the saturated solution B made of ammonium sulfate with the defluorinated solution A in a certain proportion and stir to generate a white precipitate; Step 4: Separate the white precipitate from Step 3 from the liquid to obtain white precipitate D and ammonium dihydrogen phosphate solution E.

[0006] Furthermore, the method also includes the following steps; Step 5: Evaporate and concentrate the ammonium dihydrogen phosphate solution E from step 4, cool and crystallize, and separate the solid and liquid to obtain ammonium dihydrogen phosphate.

[0007] Furthermore, in the second step, defluorination is performed using defluorinating agents and / or physical methods.

[0008] Furthermore, in the third step, the defluorinated solution A and solution B are mixed and reacted at a solute molar ratio of 1:2, and a white precipitate is generated by stirring.

[0009] Furthermore, the defluorinating agent is a mixture of sodium sulfate and quartz glass powder.

[0010] Furthermore, in the first step, the reaction temperature is 0-100℃.

[0011] Furthermore, in the first step, the reaction time is 2-10 hours.

[0012] A system for producing ammonium dihydrogen phosphate includes a calcium phosphate aqueous solution preparation unit, a calcium phosphate aqueous solution defluorination unit, a neutralization reaction unit, and a solid-liquid separation unit; The calcium phosphate aqueous solution preparation unit includes a phosphoric acid dissolver and a first filtration device. The first filtration device can be located inside or outside the phosphoric acid dissolver. The phosphate rock slurry and phosphoric acid react in the phosphoric acid dissolver. The first filtration device filters the liquid generated by the reaction in the phosphoric acid dissolver. The filtered liquid is solution A. The defluorination section of the calcium phosphate aqueous solution includes a defluorinator, which is connected to the first filtration device, and defluorinates solution A in the defluorinator. The neutralization reaction section includes a neutralization reactor, in which a defluorinated solution A is neutralized with a saturated solution B made of ammonium sulfate to generate a solid-liquid mixture. The solid-liquid separation section includes a solid-liquid separator, in which a solid-liquid mixture is separated into solid and liquid components. The solid is a white precipitate D, and the liquid is an ammonium dihydrogen phosphate solution E.

[0013] Furthermore, the system also includes an evaporation and crystallization section, which includes an evaporator, a cooler, and a crystallizer. Ammonium dihydrogen phosphate is evaporated and concentrated in the evaporator. After being cooled by the cooler, the concentrated ammonium dihydrogen phosphate is crystallized in the crystallizer to form ammonium dihydrogen phosphate.

[0014] The advantages of this invention are:

[0015] The reaction process is simple and easy to perform. A simplified reaction process means fewer operational steps and a lower probability of error. The reaction process of this invention is simple, requiring no cumbersome steps, greatly reducing the technical requirements for operators, improving production efficiency, and laying a solid foundation for industrialization. Significantly reducing raw material production costs by approximately 200 yuan per ton of product (ammonium dihydrogen phosphate raw material) is a considerable amount. For example, a factory with an annual production capacity of 100,000 tons could save 20 million yuan annually. This cost reduction not only enhances the product's price competitiveness in the market but also brings greater profit margins to the enterprise. Solving the Ammonium Sulfate Surplus Problem in the Chemical Industry: The surplus of ammonium sulfate in the chemical industry has always been a thorny issue. This invention successfully finds a way to utilize the surplus ammonium sulfate, effectively alleviating inventory pressure within the industry.

[0016] Capable of producing high-purity gypsum High-purity gypsum has extremely high application value in many fields. For example, in the construction industry, high-purity gypsum can be used to produce high-quality gypsum boards, which have better strength and stability and can meet higher building standards and requirements; in the medical field, high-purity gypsum can be used to make precision gypsum molds, providing more accurate fixation and treatment for fracture patients. In summary, this invention demonstrates outstanding advantages in terms of reaction process, cost control, industry problem solving, and product quality, and has great application value and market prospects. Attached Figure Description

[0017] The accompanying drawings further describe the various steps of the present invention and are part of the specification. They are also used to better explain the present invention in specific operations. The present invention does not limit the specific equipment used in the process.

[0018] Figure 1 This is a schematic diagram of the method of the present invention.

[0019] Figure 2 This is a system schematic diagram of the present invention.

[0020] As shown in the figure, the calcium phosphate aqueous solution preparation unit 1, the calcium phosphate aqueous solution defluorination unit 2, the second filtration device 3, the neutralization reaction unit 4, the solid-liquid separation unit 5, the evaporation and crystallization unit 6, the phosphoric acid dissolver 11, the first filtration device 12, the evaporator 61, the cooler 62, and the crystallizer 63 are all part of the solution. Detailed Implementation

[0021] like Figure 1 As shown, a method for producing ammonium dihydrogen phosphate includes the following steps: Step 1: React and dissolve the phosphate rock slurry with phosphoric acid. After the reaction, filter the liquid to obtain solution A. Preferably, the reaction temperature is 0-100℃ and the reaction time is 2-10 hours. Step 2: Defluorinate solution A. Preferably, defluorination is performed using a defluorinating agent and / or physical methods. Generally, the defluorinating agent is a mixture of sodium sulfate and quartz glass powder. Step 3: Mix the saturated solution B made of ammonium sulfate with the defluorinated solution A in a certain proportion and stir to generate a white precipitate; Step 4: Separate the white precipitate from Step 3 from the liquid to obtain white precipitate D and ammonium dihydrogen phosphate solution E; Step 5: Evaporate and concentrate the ammonium dihydrogen phosphate solution E from step 4, cool and crystallize, and separate the solid and liquid to obtain ammonium dihydrogen phosphate.

[0022] Furthermore, in the second step, defluorination is performed using defluorinating agents and / or physical methods.

[0023] Furthermore, in the third step, the defluorinated solution A and solution B are mixed and reacted at a solute molar ratio of 1:2, and a white precipitate is generated by stirring.

[0024] The following is a small-scale laboratory test example:

[0025] Example 1 First, place 100g of phosphate rock slurry with a solid content of 60% into a 2-liter beaker, then dilute it with 90g of 85% phosphoric acid and 1000g of water. The mixture was stirred continuously and placed in a 60°C hot water bath to accelerate the reaction. After 8 hours, it was removed and vacuum filtered to obtain calcium phosphate aqueous solution and gray filter cake, respectively. The gray filter cake was filtered off to form calcium phosphate aqueous solution, thus obtaining solution A. In the second step, 5g of sodium sulfate and 5g of quartz glass powder were added to the obtained solution A, and the reaction was carried out for 4 hours. The precipitate was filtered out from solution A. The third step is to slowly add 180g of saturated ammonium sulfate solution B at 20℃ to solution A obtained in the second step, and stir continuously while a white precipitate is formed. The fourth step involves filtering the liquid-solid two-phase mixture obtained from the reaction under vacuum to obtain a wet white precipitate of gypsum and liquid E. Fifth step: Mix the white precipitate gypsum washing solution with liquid E, evaporate and concentrate until crystals appear, then stop the concentration. Then cool and stir the liquid in a constant temperature water bath at 30℃. When the temperature of liquid E drops to 40℃, stop cooling and vacuum filter to obtain white crystals, weighing 191.4g. Dehydrate the crystals in a 200℃ oven for 2 hours, and weigh to obtain 166.9g of solid. The analysis shows that the content of ammonium dihydrogen phosphate is 62.8% and the nitrogen content is 11.9%.

[0026] Example 2 First, place 100g of phosphate rock slurry with a solid content of 50% into a 2-liter beaker, then dilute it with 80g of 85% phosphoric acid and 1000g of water. The mixture was stirred continuously and placed in a 70°C hot water bath to accelerate the reaction. After 8 hours, it was removed and vacuum filtered to obtain calcium phosphate aqueous solution and gray filter cake, respectively. The gray filter cake was filtered off to form calcium phosphate aqueous solution, thus obtaining solution A. In the second step, 4.5g of sodium sulfate and 4.5g of quartz glass powder were added to the obtained solution A, and the reaction was carried out for 4 hours. The precipitate was filtered out from solution A. The third step involves slowly adding 160g of saturated ammonium sulfate solution B at 20℃ to the second obtained solution A, while continuously stirring to produce a white precipitate. The fourth step involves filtering the liquid-solid two-phase mixture obtained from the reaction under vacuum to obtain a wet white precipitate of gypsum and liquid E. Fifth step: Mix the white precipitate gypsum washing solution with liquid E, evaporate and concentrate until crystals appear, then stop the concentration. Then cool and stir the liquid in a constant temperature water bath at 32℃. When the temperature of liquid E drops to 40℃, stop cooling and vacuum filter to obtain white crystals, weighing 184.4g. Dehydrate the crystals in an oven at 200℃ for 2 hours, and weigh to obtain 159.9g of solid. The analysis shows that the content of ammonium dihydrogen phosphate is 62.7% and the nitrogen content is 11.8%.

[0027] like Figure 2 A system for producing ammonium dihydrogen phosphate includes a calcium phosphate aqueous solution preparation unit 1, a calcium phosphate aqueous solution defluorination unit 2, a neutralization reaction unit 4, and a solid-liquid separation unit 5. The calcium phosphate aqueous solution preparation unit 1 includes a phosphoric acid dissolver 11 and a first filter device 12. The first filter device 12 can be located inside or outside the phosphoric acid dissolver. The phosphate rock slurry and phosphoric acid react in the phosphoric acid dissolver 11. The first filter device 11 filters the liquid generated by the reaction in the phosphoric acid dissolver. The filtered liquid is solution A. The calcium phosphate aqueous solution defluorination section 2 includes a defluorinator connected to the first filter device 12. Solution A is defluorinated in the defluorinator and filtered through the second filter device 3 to remove fluoride precipitate from solution A. The neutralization reaction section 4 includes a neutralization reactor, in which the defluorinated solution A is neutralized with a saturated solution B made of ammonium sulfate to generate a solid-liquid mixture. The solid-liquid separation unit 5 includes a solid-liquid separator, in which a solid-liquid mixture is separated into solid and liquid components. The solid is a white precipitate D and the liquid is an ammonium dihydrogen phosphate solution E. Preferably, the evaporation and crystallization section 6 includes an evaporator 61, a cooler 62, and a crystallizer 63. Ammonium dihydrogen phosphate E is evaporated and concentrated in the evaporator 61. After being cooled by the cooler 62, the evaporated and concentrated ammonium dihydrogen phosphate is crystallized in the crystallizer 63 to form ammonium dihydrogen phosphate.

[0028] The first step involves adding 500 kg of 60% phosphate rock slurry to the phosphoric acid dissolver 11, then diluting it with 400 kg of 85% phosphoric acid and 5000 kg of water, while continuously stirring. The heater is used to raise the reaction temperature in the phosphoric acid dissolver 11 to 65°C. After 7 hours, the mixture is passed through the first filter 12 to obtain a calcium phosphate aqueous solution and a gray filter cake. The gray filter cake is then filtered out to form a calcium phosphate aqueous solution, resulting in solution A. In the second step, solution A, 25 kg of sodium sulfate, and 25 kg of quartz glass powder are added to the defluorination section 2 of the calcium phosphate aqueous solution. After reacting for 4.2 hours, solution A passes through the second filtration device 3 to precipitate out, forming defluorinated solution A. In the third step, the solution A obtained in the second step is input into the neutralization reaction section 4, and at the same time, 900 kg of saturated ammonium sulfate solution B at 20°C is slowly added and continuously stirred, accompanied by the formation of a white precipitate. In the fourth step, the liquid and solid obtained from the reaction are filtered in the solid-liquid separation section 5 to obtain a wet white precipitate of gypsum and liquid E. In the fifth step, liquid E is evaporated and concentrated in evaporator 61 until crystals appear, then the concentration is stopped. The liquid is then cooled and stirred in cooler 62. When the temperature of liquid E drops to 40°C, cooling is stopped. White crystals are obtained by vacuum filtration in crystallizer 63, weighing 952 kg. The crystals are then dehydrated in an oven at 200°C for 2 hours, and 823.2 kg of solid is obtained. The analysis shows that the content of ammonium dihydrogen phosphate is 61.2% and the nitrogen content is 11.1%.

[0029] In this invention, ammonium sulfate is prepared into a liquid to ensure complete reaction, but is not limited to a liquid.

[0030] This article mainly describes the various steps of the invention, without excessive control over the quality of the product. The amount of reactants used meets the requirements for chemical equilibrium.

Claims

1. A method for producing ammonium dihydrogen phosphate, characterized in that: The method includes the following steps: Step 1: React and dissolve the phosphate rock slurry with phosphoric acid. After the reaction, filter the liquid to obtain solution A. Step 2: Defluorinate solution A; Step 3: Mix the saturated solution B made of ammonium sulfate with the defluorinated solution A in a certain proportion and stir to generate a white precipitate; Step 4: Separate the white precipitate from Step 3 from the liquid to obtain a pure white precipitate D and an ammonium dihydrogen phosphate solution E by washing.

2. The method for producing ammonium dihydrogen phosphate according to claim 1, characterized in that: The method further includes the following steps; Step 5: Evaporate and concentrate the ammonium dihydrogen phosphate solution E from step 4, cool and crystallize, and separate the solid and liquid to obtain ammonium dihydrogen phosphate.

3. The method for producing ammonium dihydrogen phosphate according to any one of claims 1-2, characterized in that: In the second step, defluorination is performed using defluorinating agents and / or physical methods.

4. The method for producing ammonium dihydrogen phosphate according to any one of claims 1-2, characterized in that: In the third step, the defluorinated solution A and solution B are mixed and reacted at a solute molar ratio of 1:2, and a white precipitate is generated by stirring.

5. The method for producing ammonium dihydrogen phosphate according to claim 3, characterized in that: The defluorinating agent is a mixture of sodium sulfate and quartz glass powder.

6. The method for producing ammonium dihydrogen phosphate according to any one of claims 1-2, characterized in that: In the first step described above, the reaction temperature is 0-100℃.

7. The method for producing ammonium dihydrogen phosphate according to any one of claims 1-2, characterized in that: In the first step, the reaction time is 2-6 hours.

8. A system for producing ammonium dihydrogen phosphate, characterized in that: The system includes a calcium phosphate aqueous solution preparation section, a calcium phosphate aqueous solution defluorination section, a neutralization reaction section, and a solid-liquid separation section. The calcium phosphate aqueous solution preparation unit includes a phosphoric acid dissolver and a first filtration device. The first filtration device can be located inside or outside the phosphoric acid dissolver. The phosphate rock slurry and phosphoric acid react in the phosphoric acid dissolver. The first filtration device filters the liquid generated by the reaction in the phosphoric acid dissolver. The filtered liquid is solution A. The defluorination section of the calcium phosphate aqueous solution includes a defluorinator, which is connected to the first filtration device, and defluorinates solution A in the defluorinator. The neutralization reaction section includes a neutralization reactor, in which a defluorinated solution A is neutralized with a saturated solution B made of ammonium sulfate to generate a solid-liquid mixture. The solid-liquid separation section includes a solid-liquid separator, in which a solid-liquid mixture is separated into solid and liquid components. The solid is a white precipitate D, and the liquid is an ammonium dihydrogen phosphate solution E.

9. A system for producing ammonium dihydrogen phosphate according to claim 8, characterized in that: The system also includes an evaporation and crystallization section, which includes an evaporator, a cooler, and a crystallizer. Ammonium dihydrogen phosphate is evaporated and concentrated in the evaporator. After being cooled by the cooler, the concentrated ammonium dihydrogen phosphate is crystallized in the crystallizer to form ammonium dihydrogen phosphate.

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