Method for preparing industrial-grade monopotassium phosphate by using double decomposition extraction method

Abstract

The invention relates to a method for preparing industrial-grade monopotassium phosphate by using a double decomposition extraction method, and belongs to the technical field of fine chemical engineering. The monopotassium phosphate product is prepared from phosphate, sylvite and sulfuric acid through double decomposition and extraction processes. According to the technology, in the reaction process, generated monopotassium phosphate is dissolved in a water phase, generated calcium sulfate dihydrate is precipitate, and the monopotassium phosphate and the calcium sulfate dihydrate can be separated through a simple solid-liquid separation method. A small amount of hydrochloric acid contained in the filtrate can be separated through extraction, so that a byproduct ammonium chloride product is obtained while a high-quality industrial-grade monopotassium phosphate product is obtained. The preparation method disclosed by the invention has the advantages in cost and product quality, the process is easy to realize, and meanwhile, the extraction agent can be recycled.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemicals, and in particular to a method for preparing industrial-grade potassium dihydrogen phosphate by utilizing a double decomposition extraction method. Background Art

[0002] Potassium dihydrogen phosphate is widely used in food, industry, animal husbandry and other industries. At present, there are many production processes for potassium dihydrogen phosphate, such as neutralization method, double decomposition method, solvent extraction method, direct method, ion exchange method, electrolysis method, etc. Among them, the neutralization method has the advantages of simple process and good product quality. At present, 90% of industrial-grade potassium dihydrogen phosphate products are produced by the neutralization method. This method uses high-quality industrial-grade phosphoric acid and industrial-grade potassium hydroxide as raw materials to produce industrial-grade potassium dihydrogen phosphate. The raw material is industrial-grade phosphoric acid. Whether it is hot phosphoric acid or wet phosphoric acid, the production cost is relatively high. The product quality of potassium dihydrogen phosphate produced by hot phosphoric acid is higher than that of wet phosphoric acid.

[0003] However, the production of thermal phosphoric acid has the problems of high energy consumption and high pollution, and is now gradually replaced by wet phosphoric acid. However, there are many types of impurity ions in wet phosphoric acid, and the content of some metal ions is high. The production of industrial-grade potassium dihydrogen phosphate products using wet phosphoric acid has the problems of difficult control of process indicators and unstable product quality. Other methods for producing potassium dihydrogen phosphate also have more or less problems and have not been promoted and applied on a large scale. For example, the production of potassium dihydrogen phosphate products by a single extraction method has problems such as poor separation effect, high extraction cost, and difficulty in recycling the extractant; the ion exchange method is currently immature, not very operable, and is still in the exploratory stage.

[0004] The above methods for producing potassium dihydrogen phosphate all have the problems of high cost, high impurity content, low product purity, unstable quality, etc., and it is urgent to find a potassium dihydrogen phosphate production process with low cost, low energy consumption and high product quality. Summary of the invention

[0005] In view of the problems that the existing neutralization method for producing potassium dihydrogen phosphate has high requirements for the grade of phosphate ore, large energy consumption, and relatively high cost, the present invention provides a method for preparing industrial-grade potassium dihydrogen phosphate using a double decomposition extraction method to solve the above problems. The present invention uses phosphate, potassium salt and sulfuric acid raw materials to prepare potassium dihydrogen phosphate products through double decomposition and extraction processes, which has more advantages in cost and product quality, is easy to implement, and the extractant can be recycled and reused, reducing production costs.

[0006] The technical solution of the present invention is as follows: A method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction method comprises the following steps: (1) Potassium chloride is fed into the reactor, and then calcium phosphate is added to the reactor, and then 98% sulfuric acid solution is added to the reactor at a specified speed through a peristaltic pump for reaction; hydrogen chloride is extracted during the reaction, the pH of the reaction system is maintained at 4.2-4.5, the reaction temperature is 55-65°C, and the reaction time is 60-90 minutes; the reaction formula is as follows: Ca 3 (PO 4 ) 2 +3H 2 SO 4 +2KCl+6H 2 O=3CaSO 4 ·2H 2 O+2KH 2 PO 4 +2HCl; (2) The material obtained in step (1) is subjected to filter pressing while hot, and the filter residue is phosphogypsum, and the filtrate is a potassium dihydrogen phosphate solution containing hydrochloric acid; (3) extracting the potassium dihydrogen phosphate solution containing hydrochloric acid in step (2) with an extractant, wherein the oil-water ratio of the extract phase is 3 to 9:1, to obtain an extracted organic phase and an aqueous phase, respectively; the main component of the aqueous phase is potassium dihydrogen phosphate; The extractant consists of three components: A, B and C, wherein A is trioctylamine or triethylamine; B is trioctyldecyl tertiary amine or di-2-ethylhexyl phosphate; and C is dodecane or kerosene.

[0007] (4) The aqueous phase obtained in step (3) is concentrated, and the temperature is controlled to be 165-175° C. The concentrated potassium dihydrogen phosphate filtrate is cooled to 40-50° C. to obtain potassium dihydrogen phosphate slurry, and the potassium dihydrogen phosphate wet product is obtained by centrifugal separation, and the mother liquor is returned to the reactor; the wet product is dried to finally obtain the potassium dihydrogen phosphate product.

[0008] Furthermore, in step (3), the extraction temperature is 25-60°C, the extraction time is 15-30 min, and the stirring speed is 150-300 r / min.

[0009] Furthermore, in step (1), the content of potassium oxide in potassium chloride is 58% to 62%; and the content of phosphorus pentoxide in calcium phosphate is 35% to 41%.

[0010] Furthermore, the 98% sulfuric acid solution is pumped into the reaction system at a speed of 30-50 ml / min.

[0011] Furthermore, the volume ratio of the three components A, B, and C is 3~8:3~8:2~4.

[0012] Furthermore, in step (4), the cooling rate of the concentrated potassium dihydrogen phosphate filtrate is 0.2-0.8°C / min.

[0013] Furthermore, the extracted organic phase in step (3) is stripped with 25% to 28% aqueous ammonia, the aqueous phase after stripping is an ammonium chloride solution, and the organic phase is a regenerated extractant; the oil-water ratio (O / A) of the stripping phase is 4 to 9:1, the stripping temperature is 25 to 65°C, the stripping time is 15 to 30 min, and the stirring speed is 150 to 300 r / min.

[0014] Furthermore, the hydrogen chloride produced in step (1) is adsorbed by aqueous ammonia to obtain an ammonium chloride solution; the ammonium chloride solution is then combined with the aqueous phase of the stripping and concentrated, the temperature is controlled to be 70-80°C, and after concentrating, cooling and crystallizing, the ammonium chloride is obtained by solid-liquid separation.

[0015] The beneficial effects of the present invention are: (1) Compared with the prior art, the present invention replaces the traditional production process using phosphoric acid and potassium hydroxide as raw materials, and uses phosphate, potassium salt and sulfuric acid raw materials to produce potassium dihydrogen phosphate products through double decomposition and extraction processes, which has more advantages in cost and product quality, is easy to implement, and the extractant can be recovered and reused.

[0016] (2) In the process of the present invention, during the reaction, the generated potassium dihydrogen phosphate is dissolved in the aqueous phase, and the generated calcium sulfate dihydrate is a precipitate, and the two can be separated by a simple solid-liquid separation method. The small amount of hydrochloric acid contained in the filtrate can be separated by extraction, and a high-quality industrial-grade potassium dihydrogen phosphate product is obtained while an ammonium chloride product is produced as a by-product. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 It is a preparation flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0020] Example 1 A method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction method comprises the following steps: (1) Weigh 200 g of potassium chloride with a potassium oxide content of 60% and feed it into a reactor, then add 477.03 g of calcium phosphate with a phosphorus pentoxide content of 38% into the reactor, and then add 98% sulfuric acid solution into the reactor at a rate of 35 ml / min through a peristaltic pump; extract hydrogen chloride gas through a vacuum pump, control the vacuum degree at 0.087 MPa, and absorb it with ammonia water to obtain a dilute ammonium chloride solution; maintain the pH of the reaction system at 4.2, the reaction temperature at 55°C, and the reaction time at 60 min; (2) The material obtained in step (1) is subjected to filter pressing while hot, and the filter residue is phosphogypsum, and the filtrate is a potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid; (3) extracting the potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid in step (2) with an extractant, the extraction temperature is 25° C., the oil-water ratio (O / A) of the extraction phase is 3:1, the extraction time is 15 min, and the stirring speed is 150 r / min, to obtain an extracted organic phase and an aqueous phase respectively; the main component of the aqueous phase is potassium dihydrogen phosphate; The extractant consists of trioctylamine, trioctyldecyl tertiary amine and dodecane in a volume ratio of 3:3:2.

[0021] (4) The aqueous phase obtained in step (3) is concentrated, and the temperature is controlled to be 165°C. The concentrated potassium dihydrogen phosphate filtrate is cooled to 40°C at a cooling rate of 0.2°C / min to obtain potassium dihydrogen phosphate slurry, which is centrifuged to obtain a potassium dihydrogen phosphate wet product, and the mother liquor is returned to the reactor; the wet product is dried to obtain a potassium dihydrogen phosphate product. The test data of the potassium dihydrogen phosphate product is shown in Table 1.

[0022] (5) The organic phase of step (3) is stripped with 27% ammonia water, the oil-water ratio (O / A) of the stripping phase is 4:1, the stripping temperature is 25°C, the stripping time is 15 min, the stirring speed is 150 r / min, the aqueous phase after stripping is an ammonium chloride solution, and the organic phase is a regenerated extractant, which is returned to the extraction system for repeated use. The aqueous phase and the dilute ammonium chloride solution after ammonia absorption in the double decomposition step are combined and concentrated, the temperature is controlled at 70°C, and after concentration, cooling and crystallization, the by-product of ammonium chloride is obtained by centrifugation. The ammonium chloride detection data is shown in Table 2.

[0023] Example 2 A method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction method comprises the following steps: (1) Weigh 300 g of potassium chloride with a potassium oxide content of 60% and feed it into a reactor, then add 679.81 g of calcium phosphate with a phosphorus pentoxide content of 40% into the reactor, and then add 98% sulfuric acid solution into the reactor at a rate of 45 ml / min through a peristaltic pump; extract hydrogen chloride gas through a vacuum pump, control the vacuum degree at 0.090 MPa, and absorb it with ammonia water to obtain a dilute ammonium chloride solution; maintain the pH of the reaction system at 4.3, the reaction temperature at 60°C, and the reaction time at 75 min; (2) The material obtained in step (1) is subjected to filter pressing while hot, and the filter residue is phosphogypsum, and the filtrate is a potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid; (3) extracting the potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid in step (2) with an extractant, the extraction temperature is 35° C., the oil-water ratio (O / A) of the extraction phase is 5:1, the extraction time is 20 min, and the stirring speed is 200 r / min, to obtain an extracted organic phase and an aqueous phase respectively; the main component of the aqueous phase is potassium dihydrogen phosphate; The extractant consists of triethylamine, di-2-ethylhexyl phosphate and kerosene in a volume ratio of 5:5:3.

[0024] (4) The aqueous phase obtained in step (3) is concentrated, and the temperature is controlled to be 170°C. The concentrated potassium dihydrogen phosphate filtrate is cooled to 40°C at a cooling rate of 0.2°C / min to obtain potassium dihydrogen phosphate slurry, and the potassium dihydrogen phosphate wet product is obtained by centrifugal separation. The mother liquor is returned to the reactor; the wet product is dried to obtain a potassium dihydrogen phosphate product. The test data of the potassium dihydrogen phosphate product is shown in Table 1.

[0025] (5) The organic phase of step (3) is stripped with 26% ammonia water, the oil-water ratio (O / A) of the stripping phase is 6:1, the stripping temperature is 35°C, the stripping time is 20 min, the stirring speed is 200 r / min, the aqueous phase after stripping is an ammonium chloride solution, and the organic phase is a regenerated extractant, which is returned to the extraction system for repeated use. The aqueous phase and the dilute ammonium chloride solution after ammonia absorption in the double decomposition step are combined and concentrated, the temperature is controlled at 70°C, and after concentration, cooling and crystallization, the by-product of ammonium chloride is obtained by centrifugation. The ammonium chloride detection data is shown in Table 2.

[0026] Example 3 A method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction method comprises the following steps: (1) Weigh 250 g of potassium chloride with a potassium oxide content of 59% and feed it into a reactor, then add 571.34 g of calcium phosphate with a phosphorus pentoxide content of 39% into the reactor, and then add 98% sulfuric acid solution into the reactor at a rate of 48 ml / min through a peristaltic pump; extract hydrogen chloride gas through a vacuum pump, control the vacuum degree at 0.093 MPa, and absorb it with ammonia water to obtain a dilute ammonium chloride solution; maintain the pH of the reaction system at 4.4, the reaction temperature at 65°C, and the reaction time at 90 min; (2) The material obtained in step (1) is subjected to filter pressing while hot, and the filter residue is phosphogypsum, and the filtrate is a potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid; (3) extracting the potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid in step (2) with an extractant, the extraction temperature is 45° C., the oil-water ratio (O / A) of the extraction phase is 7:1, the extraction time is 25 min, and the stirring speed is 300 r / min, to obtain an extracted organic phase and an aqueous phase respectively; the main component of the aqueous phase is potassium dihydrogen phosphate; The extractant consists of triethylamine, trioctyldecyl tertiary amine and dodecane in a volume ratio of 5:6:3.

[0027] (4) The aqueous phase obtained in step (3) is concentrated, and the temperature is controlled to be 170°C. The concentrated potassium dihydrogen phosphate filtrate is cooled to 40°C at a cooling rate of 0.3°C / min to obtain potassium dihydrogen phosphate slurry, and the potassium dihydrogen phosphate wet product is obtained by centrifugal separation. The mother liquor is returned to the reactor; the wet product is dried to obtain a potassium dihydrogen phosphate product. The test data of the potassium dihydrogen phosphate product is shown in Table 1.

[0028] (5) The organic phase of step (3) is stripped with 26% aqueous ammonia, the oil-water ratio (O / A) of the stripping phase is 6:1, the stripping temperature is 35°C, the stripping time is 25 min, the stirring speed is 300 r / min, the aqueous phase after stripping is an ammonium chloride solution, and the organic phase is a regenerated extractant, which is returned to the extraction system for repeated use. The aqueous phase and the dilute ammonium chloride solution after ammonia absorption in the double decomposition step are combined and concentrated, the temperature is controlled at 75°C, and after concentration, cooling and crystallization, the by-product of ammonium chloride is obtained by centrifugation. The ammonium chloride detection data is shown in Table 2.

[0029] Example 4 A method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction method comprises the following steps: (1) Weigh 200 g of potassium chloride with a potassium oxide content of 58% and feed it into a reactor, then add 461.13 g of calcium phosphate with a phosphorus pentoxide content of 38% into the reactor, and then add 98% sulfuric acid solution into the reactor at a rate of 43 ml / min through a peristaltic pump; extract hydrogen chloride gas through a vacuum pump, control the vacuum degree at 0.090 MPa, and absorb it with ammonia water to obtain a dilute ammonium chloride solution; maintain the pH of the reaction system at 4.5, the reaction temperature at 60°C, and the reaction time at 80 min; (2) The material obtained in step (1) is subjected to filter pressing while hot, and the filter residue is phosphogypsum, and the filtrate is a potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid; (3) extracting the potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid in step (2) with an extractant, the extraction temperature is 30° C., the oil-water ratio (O / A) of the extraction phase is 5:1, the extraction time is 30 min, and the stirring speed is 250 r / min, to obtain an extracted organic phase and an aqueous phase respectively; the main component of the aqueous phase is potassium dihydrogen phosphate; The extractant is composed of trioctylamine, trioctyldecyl tertiary amine and kerosene in a volume ratio of 6:7:4.

[0030] (4) The aqueous phase obtained in step (3) is concentrated, and the temperature is controlled to be 170°C. The concentrated potassium dihydrogen phosphate filtrate is cooled to 45°C at a cooling rate of 0.5°C / min to obtain potassium dihydrogen phosphate slurry, and the potassium dihydrogen phosphate wet product is obtained by centrifugal separation. The mother liquor is returned to the reactor; the wet product is dried to obtain a potassium dihydrogen phosphate product. The test data of the potassium dihydrogen phosphate product is shown in Table 1.

[0031] (5) The organic phase of step (3) is stripped with 28% ammonia water, the oil-water ratio (O / A) of the stripping phase is 8:1, the stripping temperature is 30°C, the stripping time is 30 min, the stirring speed is 250 r / min, the aqueous phase after stripping is an ammonium chloride solution, and the organic phase is a regenerated extractant, which is returned to the extraction system for repeated use. The aqueous phase and the dilute ammonium chloride solution after ammonia absorption in the double decomposition step are combined and concentrated, the temperature is controlled at 75°C, and after concentration, cooling and crystallization, the by-product of ammonium chloride is obtained by centrifugation. The ammonium chloride detection data is shown in Table 2.

[0032] Test Case The potassium dihydrogen phosphate products prepared in Examples 1 to 4 were tested, and the specific results are shown in Table 1 below: Table 1 - Potassium dihydrogen phosphate test results

[0033] The byproduct ammonium chloride prepared in Examples 1 to 4 was tested, and the specific results are shown in Table 2 below: Table 2 - Ammonium chloride test results

[0034] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction, characterized in that: The following steps are involved: (1) Potassium chloride is fed into the reactor, and then calcium phosphate is added to the reactor, and then 98% sulfuric acid solution is added to the reactor at a prescribed speed through a peristaltic pump to react; hydrogen chloride is extracted during the reaction, and the pH of the reaction system is maintained at 4.2-4.5, the reaction temperature is 55-65°C, and the reaction time is 60-90 minutes; (2) The material obtained in step (1) is subjected to hot filter press, the filter residue is phosphogypsum, and the filtrate is a potassium dihydrogen phosphate solution containing hydrochloric acid; (3) extracting the potassium dihydrogen phosphate solution containing hydrochloric acid in step (2) with an extractant, wherein the oil-water ratio of the extraction phase is 3 to 9:1, to obtain an extracted organic phase and an aqueous phase, respectively; the main component of the aqueous phase is potassium dihydrogen phosphate; The extractant is composed of three components: A, B, and C, wherein A is trioctylamine or triethylamine; B is trioctyldecyl tertiary amine or di-2-ethylhexyl phosphate; and C is dodecane or kerosene. (4) The aqueous phase obtained in step (3) is concentrated, and the temperature is controlled to be 165-175° C. The concentrated potassium dihydrogen phosphate filtrate is cooled to 40-50° C. to obtain potassium dihydrogen phosphate slurry, which is centrifuged to obtain a potassium dihydrogen phosphate wet product, and the wet product is dried to obtain potassium dihydrogen phosphate.

2. The method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction as claimed in claim 1, characterized in that: In step (3), the extraction temperature is 25-60°C, the extraction time is 15-30 min, and the stirring speed is 150-300 r / min.

3. The method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction as claimed in claim 1, characterized in that: In step (1), the content of potassium oxide in potassium chloride is 58% to 62%; the content of phosphorus pentoxide in calcium phosphate is 35% to 41%.

4. The method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction as claimed in claim 1, wherein: The 98% sulfuric acid solution is pumped into the reaction system at a rate of 30-50 ml / min.

5. The method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction as claimed in claim 1, characterized in that: The volume ratio of the three components A, B, and C is 3~8:3~8:2~4.

6. The method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction as claimed in claim 1, characterized in that: In step (4), the cooling rate of the concentrated potassium dihydrogen phosphate filtrate is 0.2~0.8℃ / min.

7. The method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction as claimed in claim 1, characterized in that: The extracted organic phase in step (3) is stripped with 25% to 28% ammonia water, and the organic phase is used as the regeneration extractant; the oil-water ratio of the stripping phase is 4 to 9:1, the stripping temperature is 25 to 65°C, the stripping time is 15 to 30 minutes, and the stirring speed is 150 to 300 r / min.

8. The method for preparing industrial-grade potassium dihydrogen phosphate by double decomposition extraction as claimed in claim 7, characterized in that: The hydrogen chloride produced in step (1) is adsorbed with aqueous ammonia to obtain an ammonium chloride solution; the ammonium chloride solution is then combined with the aqueous phase of the stripping reaction and concentrated, the temperature is controlled at 70-80°C, and after concentration, cooling and crystallization, ammonium chloride is obtained by solid-liquid separation.

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