Device for preparing monopotassium phosphate by double decomposition method

Abstract

A device for preparing monopotassium phosphate by a double decomposition method comprises an industrial monoammonium delivery pump and a potassium chloride delivery pump which are respectively connected with a reaction tank through pipelines, the reaction tank is connected with a first plate-and-frame filter press through a reaction tank discharge pump, and a solid outlet of the first plate-and-frame filter press is connected with a first dissolving tank; the first dissolving tank is connected with a second plate-and-frame filter press through a solution delivery pump, a liquid outlet of the second plate-and-frame filter press is connected with a recrystallization tank, the recrystallization tank is connected with a third plate-and-frame filter press through a crystallization pump, a solid outlet of the third plate-and-frame filter press is connected with the second dissolving tank, and the second dissolving tank is connected with an extraction tank through a saturated liquid delivery pump. The extraction tank is connected with a fourth plate-and-frame filter press through an extraction tank discharge pump, and a liquid outlet of the fourth plate-and-frame filter press is connected with the methanol distillation tower through an extract delivery pump. According to the device, materials are recycled, the cost can be effectively reduced, the device has recyclability, basically no three wastes are generated, and the development requirements of a green and circular economy mode are met.

Description

Technical Field

[0001] The utility model relates to the field of chemical equipment, in particular to a device for preparing potassium dihydrogen phosphate by double decomposition method. Background Art

[0002] Potassium dihydrogen phosphate is an inorganic compound with the chemical formula KH2PO4. It is deliquescent and melts into a transparent liquid when heated to 400°C. It solidifies into an opaque glassy potassium metaphosphate after cooling. It is stable in the air, soluble in water, and insoluble in ethanol. It is used as a buffer and culture agent in industry, as a flavoring agent for synthetic sake, a raw material for potassium metaphosphate, a culture agent, a fortifier, a bulking agent, and a fermentation aid for brewing yeast, and as a high-efficiency phosphorus-potassium compound fertilizer in agriculture.

[0003] There are few potassium dihydrogen phosphate manufacturers in my country and they are small in scale. Nearly 50% of potassium dihydrogen phosphate needs to be imported from abroad. At present, the main production methods of potassium dihydrogen phosphate at home and abroad include neutralization method, solvent extraction method, double decomposition method and crystallization method.

[0004] The neutralization method uses phosphoric acid and potassium hydroxide as raw materials. If there is a lack of low-cost raw material sources, the production cost will be high, which greatly limits large-scale production. The solvent extraction method has a complex process flow, and the organic solvents used are mostly alcohols, amines, lipids, ketones, sulfoxides, alkyl phosphine, etc., which are expensive and cause great pollution to the environment. The implementation process also has a high safety risk. The double decomposition method using calcium hydrogen phosphate and potassium hydrogen sulfate as raw materials has a low raw material utilization rate, resulting in a waste of resources. During the production process, calcium sulfate will be generated to wrap the potassium dihydrogen phosphate, and a large amount of water will be consumed to wash the product. The treatment of washing water will also increase economic investment. The crystallization method uses phosphoric acid and potassium chloride as raw materials, and the introduction of chloride ions causes the chloride ion content in the product to exceed the standard. It cannot be used in the production of fertilizers for chlorine-sensitive crops, which limits the sales of the product. In addition, the process uses 180°C evaporation crystallization, which has high energy consumption. Summary of the invention

[0005] The technical problem to be solved by the utility model is to provide a device for preparing potassium dihydrogen phosphate by double decomposition method, taking industrial monoammonium and potassium chloride as raw materials, adopting multi-stage recrystallization combined with methanol extraction technology to produce high-quality potassium dihydrogen phosphate, the materials in this process are recycled, and the cost is effectively reduced; the process route is recyclable, and basically no "three wastes" are generated, which meets the development requirements of green and circular economic models.

[0006] In order to solve the above technical problems, the technical scheme adopted by the utility model is as follows: an industrial ammonium delivery pump and a potassium chloride delivery pump are respectively connected to a reaction tank through pipelines, the reaction tank is connected to a first plate-frame filter press through a reaction tank discharge pump, the solid outlet of the first plate-frame filter press is connected to a first dissolving tank, the first dissolving tank is connected to a second plate-frame filter press through a solution delivery pump, the liquid outlet of the second plate-frame filter press is connected to a recrystallization tank, the recrystallization tank is connected to a third plate-frame filter press through a crystallization pump, the solid outlet of the third plate-frame filter press is connected to the second dissolving tank, the second dissolving tank is connected to an extraction tank through a saturated liquid delivery pump, the extraction tank is connected to a fourth plate-frame filter press through an extraction tank discharge pump, the liquid outlet of the fourth plate-frame filter press is connected to a methanol distillation tower through an extraction liquid delivery pump, the gas outlet of the methanol distillation tower is connected to a heat exchanger, and the heat exchanger is connected to a methanol storage tank.

[0007] The liquid outlet of the third plate-frame filter press is connected to the reaction tank through a residual liquid circulation pump.

[0008] The liquid outlet of the methanol distillation tower is also connected to the reaction tank through a residual liquid circulation pump.

[0009] The methanol storage tank is connected to the extraction tank through a methanol circulation pump.

[0010] The methanol storage tank is connected to the liquid inlet of the methanol distillation tower.

[0011] As a preferred embodiment, the recrystallization tank is provided with a density meter for accurately controlling the degree of concentrated crystallization.

[0012] In a preferred embodiment, the methanol distillation tower is a packed tower, and the packing material in the tower is polytetrafluoroethylene packing.

[0013] Beneficial effects of the utility model:

[0014] (1) The reaction of preparing potassium dihydrogen phosphate using industrial ammonium monoammonium and potassium chloride has mild reaction conditions compared with other synthesis methods; the raw materials are recycled, the utilization rate is high, and the cost is effectively reduced; the system operates in a cycle and has industrial conditions;

[0015] (2) The by-products can be further utilized to create economic benefits, and the system does not produce "three wastes", which meets the development requirements of a green and circular economy model. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of the utility model.

[0017] In the figure: 1. Industrial monoammonium delivery pump; 2. Potassium chloride delivery pump; 3. Reaction tank; 4. Reaction tank discharge pump; 5. First plate and frame filter press; 6. First dissolving tank; 7. Solution delivery pump; 8. Second plate and frame filter press; 9. Recrystallization tank; 10. Crystallization pump; 11. Third plate and frame filter press; 12. Second dissolving tank; 13. Saturated liquid delivery pump; 14. Extraction tank; 15. Extraction tank discharge pump; 16. Fourth plate and frame filter press; 17. Raffinate delivery pump; 18. Methanol distillation tower; 19. Heat exchanger; 20. Methanol storage tank; 21. Methanol circulation pump; 22. Residual liquid circulation pump. DETAILED DESCRIPTION

[0018] The utility model is further described in detail below based on the accompanying drawings and specific embodiments.

[0019] Example 1

[0020] The invention discloses a device for preparing potassium dihydrogen phosphate by double decomposition method, comprising an industrial ammonium delivery pump 1 and a potassium chloride delivery pump 2, which are respectively connected to a reaction tank 3 through pipelines; the reaction tank 3 is connected to a first plate-frame filter press 5 through a reaction tank discharge pump 4; the solid outlet of the first plate-frame filter press 5 is connected to a first dissolving tank 6; the first dissolving tank 6 is connected to a second plate-frame filter press 8 through a solution delivery pump 7; the liquid outlet of the second plate-frame filter press 8 is connected to a recrystallization tank 9; the recrystallization tank 9 is connected to a third plate-frame filter press 11 through a crystallization pump 10; the solid outlet of the third plate-frame filter press 11 is connected to a second dissolving tank 12; the second dissolving tank 12 is connected to an extraction tank 14 through a saturated liquid delivery pump 13; the extraction tank 14 is connected to a fourth plate-frame filter press 16 through an extraction tank discharge pump 15; the liquid outlet of the fourth plate-frame filter press 16 is connected to a methanol distillation tower 18 through an extracting liquid delivery pump 17; the gas outlet of the methanol distillation tower 18 is connected to a heat exchanger 19; and the heat exchanger 19 is connected to a methanol storage tank 20.

[0021] The liquid outlet of the third plate-frame filter press 11 is connected to the reaction tank 3 via a residual liquid circulation pump 22 .

[0022] The liquid outlet of the methanol distillation tower 18 is also connected to the reaction tank 3 through a residual liquid circulation pump 22 .

[0023] The methanol storage tank 20 is connected to the extraction tank 14 via a methanol circulation pump 21 .

[0024] The methanol storage tank 20 is connected to the liquid inlet of the methanol distillation tower 18 .

[0025] Furthermore, the recrystallization tank 9 is provided with a density meter for accurately controlling the degree of concentrated crystallization.

[0026] Furthermore, the methanol distillation tower 18 is a packed tower, and the packing material in the tower is polytetrafluoroethylene packing.

[0027] Example 2

[0028] The device described in Example 1 is used, and the steps of using the device are as follows:

[0029] Step 1: Raw material reaction

[0030] 2-4 mol / L of industrial monoammonium and potassium chloride are delivered to a reaction tank 3 through an industrial monoammonium delivery pump 1 and a potassium chloride delivery pump 2, wherein the molar ratio of industrial monoammonium and potassium chloride is 1:1-1.5, and the mixture is stirred evenly for reaction at a temperature of 85°C-110°C for 0.5-2.5 hours. After the reaction is completed and cooled to 25-60°C, the mixed solution is delivered to a first plate-frame filter press 5 through a reaction tank discharge pump 4 for separation to obtain a crude potassium dihydrogen phosphate solid and an ammonium chloride solution, the ammonium chloride solution is delivered to other sections, and the crude potassium dihydrogen phosphate solid is delivered to a 1# dissolving tank 6;

[0031] Step 2: Multiple crystallization

[0032] Water is added to the first dissolving tank 6 to dissolve the crude potassium dihydrogen phosphate solid, wherein the solid-liquid ratio is 1:3-6, and the dissolved liquid is sent to the second plate-frame filter press 8 through the solution delivery pump 7, and the filtrate is sent to the recrystallization tank 9 for recrystallization purification after removing insoluble impurities, and the density of the material at the recrystallization end point is controlled at 1.15g / mL-1.25g / mL. After the crystallization is completed, the solid-liquid mixture is pumped to the third plate-frame filter press 11 through the crystallization pump 10, and the filtrate is sent to the reaction tank 3 for recycling through the residual liquid circulation pump 22, and the potassium dihydrogen phosphate solid with a purity of 90% is sent to the 2# dissolving tank 12 for further dissolution.

[0033] Step 3: Extraction and purification

[0034] Water is added to the second dissolving tank 12 to dissolve the solid, wherein the solid-liquid ratio is 1:2-5, and the solution is then pumped to the extraction tank 14 in sequence by the saturated liquid delivery pump 13, and then methanol is introduced into the extraction tank 14 for extraction, during which the volume ratio of the solution to methanol is 1:0.5-1.5, the extraction temperature is 20-35°C, the extraction time is 10-60min, and the potassium dihydrogen phosphate solid and the methanol-salt mixed solution are obtained. The mixed solution is pumped into the fourth plate and frame filter press 16 through the extraction tank discharge pump 15 to separate and obtain a high-purity potassium dihydrogen phosphate product.

[0035] Step 4: Methanol Recovery

[0036] The methanol-containing mixed liquid is delivered to the middle feed port of the methanol distillation tower 18 by the raffinate delivery pump 17 for distillation. The distillation temperature is controlled at 80°C-105°C. The methanol gas at the top of the methanol distillation tower 18 is condensed by the heat exchanger 19 and enters the methanol storage tank 20. The methanol circulation pump 21 delivers it to the extraction tank 14 for recycling. The residual liquid at the bottom of the methanol distillation tower 18 returns to the reaction tank 3 as a raw material to continue to participate in the reaction.

[0037] Through this device, high-quality industrial potassium dihydrogen phosphate products can be produced. The reaction conditions of this process are mild; the raw materials are recycled, and the system does not produce "three wastes", which meets the development requirements of a green and circular economic model.

Claims

1. A device for preparing potassium dihydrogen phosphate by double decomposition method, characterized in that: The invention comprises an industrial monoammonium delivery pump (1) and a potassium chloride delivery pump (2) which are respectively connected to a reaction tank (3) through pipelines; the reaction tank (3) is connected to a first plate-frame filter press (5) through a reaction tank discharge pump (4); the solid outlet of the first plate-frame filter press (5) is connected to a first dissolving tank (6); the first dissolving tank (6) is connected to a second plate-frame filter press (8) through a solution delivery pump (7); the liquid outlet of the second plate-frame filter press (8) is connected to a recrystallization tank (9); the recrystallization tank (9) is connected to a third plate-frame filter press (11) through a crystallization pump (10). The solid outlet of the third plate-frame filter press (11) is connected to the second dissolving tank (12), the second dissolving tank (12) is connected to the extraction tank (14) via a saturated liquid delivery pump (13), the extraction tank (14) is connected to the fourth plate-frame filter press (16) via an extraction tank discharge pump (15), the liquid outlet of the fourth plate-frame filter press (16) is connected to the methanol distillation tower (18) via an extraction liquid delivery pump (17), the gas outlet of the methanol distillation tower (18) is connected to the heat exchanger (19), and the heat exchanger (19) is connected to the methanol storage tank (20).

2. The device for preparing potassium dihydrogen phosphate by double decomposition method according to claim 1, characterized in that: The liquid outlet of the third plate-frame filter press (11) is connected to the reaction tank (3) via a residual liquid circulation pump (22).

3. The device for preparing potassium dihydrogen phosphate by double decomposition method according to claim 1, characterized in that: The liquid outlet of the methanol distillation tower (18) is also connected to the reaction tank (3) via a residual liquid circulation pump (22).

4. The device for preparing potassium dihydrogen phosphate by double decomposition method according to claim 1, characterized in that: The methanol storage tank (20) is connected to the extraction tank (14) via a methanol circulation pump (21).

5. The device for preparing potassium dihydrogen phosphate by double decomposition method according to claim 1, characterized in that: The methanol storage tank (20) is connected to the liquid inlet of the methanol distillation tower (18).

Images