A continuous reaction crystallizer for the production of potassium dihydrogen phosphate from wet-process phosphoric acid

Abstract

The utility model discloses a kind of for wet-process phosphoric acid preparation potassium dihydrogen phosphate continuous reaction crystallizer, including cylinder, driving device, flow guide cylinder, liquid distributor and overflow tank, the upper portion of cylinder is crystallization section, lower portion is conical sedimentation section and is equipped with crystal slurry outlet.Driving device drives stirring shaft and the rotation of impeller located in flow guide cylinder.The core innovation of the utility model is that flow guide cylinder is double-wall structure, forms sealed jacket cavity, cooling medium inlet and outlet are equipped on it, so that flow guide cylinder has double functions of flow guiding and high-efficiency heat exchange;Liquid distributor is arranged below flow guide cylinder for uniform liquid distribution, overflow tank is used for separating and discharging fine crystal;It can also include built-in coil coiled on the outside of flow guide cylinder to strengthen heat exchange;Efficient, continuous operation of reaction crystallization process is realized, with the advantages of high heat exchange efficiency, uniform temperature field, narrow product crystal particle size distribution, easy to automate control, especially suitable for wet-process phosphoric acid system preparation high-quality potassium dihydrogen phosphate.

Description

Technical Field

[0001] This utility model relates to a continuous reaction crystallizer for the wet process of phosphoric acid to prepare potassium dihydrogen phosphate, belonging to the field of phosphoric acid technology. Background Technology

[0002] Potassium dihydrogen phosphate (KH2PO4) is a high-value phosphorus and potassium compound fertilizer, and also an important raw material for the food, pharmaceutical, and electronics industries. Traditional production processes mainly use a thermal process to neutralize phosphoric acid with potassium hydroxide or potassium carbonate. Although this method produces high-purity products, it is costly and energy-intensive.

[0003] The production of potassium dihydrogen phosphate using the wet-process phosphoric acid method can significantly reduce raw material costs and is an important development direction for the industry. However, wet-process phosphoric acid has a complex composition, containing various impurities such as iron, aluminum, magnesium, and fluorine, and direct reaction can seriously affect product quality. Existing technologies typically employ a batch process of purification followed by reaction, which suffers from problems such as long process flow, large equipment investment, high energy consumption, unstable product quality, and inability to achieve continuous automated production.

[0004] In particular, the crystallization section often uses ordinary cooling crystallizers, which have disadvantages such as low heat exchange efficiency, uneven temperature field, wide crystal size distribution (CSD), easy scaling, and inability to discharge continuously. These disadvantages have become a bottleneck restricting the production of high-quality potassium dihydrogen phosphate by wet process phosphoric acid.

[0005] Therefore, there is an urgent need to develop a continuous reaction crystallizer specifically for this system. It can efficiently remove the heat of reaction and the heat of crystallization, achieve precise temperature control, provide a stable supersaturated environment to generate uniform crystals, and enable continuous material feeding and unloading, thereby meeting the requirements of continuous, efficient, and green production in modern chemical industry. Utility Model Content

[0006] The technical problem to be solved by this utility model is to provide a continuous reaction crystallizer for the wet process of phosphoric acid to prepare potassium dihydrogen phosphate, so as to solve the problems of intermittent operation, low efficiency, uneven product particle size, and high energy consumption.

[0007] This utility model is achieved through the following scheme: a continuous reaction crystallizer for the wet process of phosphoric acid to prepare potassium dihydrogen phosphate, comprising a cylinder, a driving device, a guide cylinder, a liquid distributor and an overflow box; The upper part of the cylinder is a crystallization section, and the lower part is a conical settling section. The bottom end of the conical settling section is provided with a crystal slurry outlet. The drive device is fixed to the top of the cylinder, and its output end is connected to the stirring shaft. The stirring shaft is equipped with an impeller located inside the guide tube. The guide tube is coaxially disposed inside the crystallization section. The guide tube has a double-wall structure, with a sealed jacket cavity formed between its inner and outer walls. The jacket cavity is provided with a cooling medium inlet and a cooling medium outlet. The liquid distributor is located below the guide tube and is connected to the feed pipe; The overflow box is located on the outside of the cylinder and is connected to the upper part of the crystallization section through an overflow pipe. The overflow box is provided with a clear liquid outlet.

[0008] It also includes a built-in coil, which is coiled around the outside of the guide tube and inside the tube body, and the built-in coil is connected to a coil inlet and a coil outlet.

[0009] The built-in coil has a double helix structure and is symmetrically coiled around the outer periphery of the guide tube.

[0010] The cooling medium inlet is located at the lower part of the guide tube jacket cavity, and the cooling medium outlet is located at the upper part of the guide tube jacket cavity.

[0011] The impeller is an axial flow impeller.

[0012] The liquid distributor is a ring-shaped tube structure with several liquid distribution holes on its tube wall.

[0013] The overflow tank is equipped with a baffle to stabilize the liquid flow.

[0014] The crystal slurry outlet is connected to the crystal slurry pump via a pipeline.

[0015] The beneficial effects of this utility model are as follows: 1. This utility model discloses a continuous reaction crystallizer for the wet-process phosphoric acid preparation of potassium dihydrogen phosphate. Designed for a wet-process phosphoric acid system, it integrates the neutralization reaction and cooling crystallization process into a single device. The reaction solution from the previous stage can be directly introduced through a distributor, utilizing the crystallizer's powerful heat exchange capacity to rapidly remove the heat of reaction and directly enter the crystallization stage, simplifying the process and reducing equipment investment. 2. The present invention provides a continuous reaction crystallizer for the wet process of phosphoric acid to prepare potassium dihydrogen phosphate. The guide tube is used as the core heat exchange component. Its double-layer jacket structure maximizes the heat exchange area, and the heat exchange surface is directly located on the core channel of fluid circulation. The heat transfer coefficient is extremely high, which can quickly and uniformly remove the heat of crystallization, accurately control the supersaturation, and fundamentally avoid local supercooling and explosive nucleation. 3. The continuous reaction crystallizer for the preparation of potassium dihydrogen phosphate by wet process phosphoric acid adopts a dual main heat exchange method. The two heat exchange methods can be flexibly selected or combined according to the concentration of wet process phosphoric acid raw materials, the heat of reaction and the changes in water temperature in different seasons, so as to ensure stable and reliable temperature control under any production conditions and ensure stable product quality. 4. The continuous reaction crystallizer for wet phosphoric acid preparation of potassium dihydrogen phosphate of this utility model adopts an axial flow impeller and a guide tube to form a stable and flat circulating flow field in the equipment, which provides a uniform environment for crystal growth and effectively inhibits secondary nucleation. The potassium dihydrogen phosphate crystals produced have the characteristics of uniform particle size, complete crystal shape and high purity. Attached Figure Description

[0016] Figure 1 This is a front view cross-sectional schematic diagram of a continuous reaction crystallizer for the wet process preparation of potassium dihydrogen phosphate according to the present invention.

[0017] Figure 2 This is a three-dimensional structural diagram of the liquid distributor of a continuous reaction crystallizer for the wet process of phosphoric acid to prepare potassium dihydrogen phosphate according to the present invention.

[0018] Figure 3 This is a front view schematic diagram of a continuous reaction crystallizer for the wet process preparation of potassium dihydrogen phosphate according to the present invention, which is a second embodiment of the present invention.

[0019] In the diagram: 100 is the cylinder, 101 is the crystallization section, 102 is the conical settling section, 103 is the crystal slurry outlet, 200 is the drive device, 201 is the stirring shaft, 202 is the impeller, 300 is the guide tube, 301 is the jacket cavity, 302 is the cooling medium inlet, 303 is the cooling medium outlet, 400 is the liquid distributor, 401 is the feed pipe, 402 is the liquid distribution hole, 500 is the overflow box, 501 is the overflow pipe, 502 is the clear liquid outlet, 503 is the baffle, 600 is the built-in coil, 601 is the coil inlet, and 602 is the coil outlet. Detailed Implementation

[0020] The following is combined Figure 1-3 The present invention will be further described below, but the scope of protection of the present invention is not limited to the contents described herein.

[0021] Example 1 Reference Figure 1 and Figure 2 This embodiment provides a continuous reaction crystallizer for the wet process of phosphoric acid to prepare potassium dihydrogen phosphate, which mainly includes a cylinder 100, a driving device 200, a guide cylinder 300, a liquid distributor 400, and an overflow box 500.

[0022] The cylinder 100 is arranged vertically, with a cylindrical crystallization section 101 at the top and a conical settling section 102 at the bottom. A crystal slurry outlet 103 is provided at the bottom center of the conical settling section 102 for continuously discharging the crystallized product.

[0023] The drive device 200 is fixedly mounted on the top flange of the cylinder 100 via a frame, and its output end is connected to the stirring shaft 201 via a coupling. The stirring shaft 201 extends vertically into the cylinder 100, and an impeller 202 is installed at its lower end.

[0024] The guide tube 300 is coaxially positioned at the center of the crystallization section 101 via a support rod. The guide tube 300 is made of double-layer stainless steel plate by rolling and welding, forming a sealed annular jacketed cavity 301 between its inner and outer walls. A cooling medium inlet 302 is provided on one side of the bottom of the jacketed cavity 301, and a cooling medium outlet 303 is provided on the other side of the top, thus forming a heat exchange structure integrated on the guide tube.

[0025] The liquid distributor 400 is horizontally installed directly below the guide tube 300 and near the bottom of the cylinder 100. The liquid distributor 400 has an annular tube structure and is connected to an external feeding system through a feed pipe 401. The annular tube of the liquid distributor 400 has several downward-facing distribution holes 402 evenly distributed to ensure uniform material distribution.

[0026] The overflow box 500 is located on the outside of the cylinder 100 and is connected to the upper side wall of the crystallization section 101 through the overflow pipe 501. The overflow box 500 is equipped with a vertical baffle 503 to reduce the fluctuation of the overflow liquid, and a clear liquid outlet 502 is provided at the bottom of the box.

[0027] In this embodiment, the arrangement of the cooling medium inlet 302 located at the lower part of the guide tube jacket cavity 301 and the cooling medium outlet 303 located at the upper part facilitates the cooling medium to fill the cavity from bottom to top, expel gas, achieve counter-current heat exchange, and improve heat exchange efficiency. The impeller 202 is preferably an axial flow impeller, which can provide strong axial circulation power, enabling the crystal slurry to form a stable and controllable circulation flow inside and outside the guide tube. The crystal slurry outlet 103 is connected to an external crystal slurry pump through a pipeline to achieve continuous and controllable discharge of the crystal slurry.

[0028] Example 2 Reference Figure 3 This embodiment further optimizes the structure described in Embodiment 1. To better control the crystallization temperature, especially suitable for operating conditions with high heat load, this embodiment adds a built-in coil 600.

[0029] The built-in coil 600 is coiled around the outside of the guide tube 300 and located in the internal space of the cylinder 100. The built-in coil 600 is made of corrosion-resistant metal tube bent into shape, and its coil inlet 601 and coil outlet 602 pass through the wall of the cylinder 100 and are connected to the external cooling system.

[0030] The built-in coil 600 serves as an auxiliary heat exchange unit, which can work in conjunction with or independently of the guide tube jacket cavity 301 to remove the heat of crystallization, greatly enhancing the heat exchange capacity and operational flexibility of the entire crystallizer and enabling it to meet a wider range of process requirements.

[0031] Example 3 The built-in coil 600 adopts a double spiral coil structure, which is formed by two tube bundles with symmetrical starting points coiled side by side and arranged symmetrically around the periphery of the guide tube 300.

[0032] This double-helix symmetrical arrangement allows the coils to be distributed more evenly within the cylinder, avoiding uneven local cooling and fluid short-circuiting that may be caused by a single coil. This provides uniform and gentle cooling across the entire crystallization section cross-section, further optimizing the supersaturation distribution during the crystallization process and facilitating the production of potassium dihydrogen phosphate products with more concentrated particle size distribution and more perfect crystal shape.

[0033] Although the technical solutions of this utility model have been described and enumerated in detail, it should be understood that modifications to the above embodiments or the adoption of equivalent alternatives are obvious to those skilled in the art. Such modifications or improvements made without departing from the spirit of this utility model are all within the scope of protection claimed by this utility model.

Claims

1. A continuous reaction crystallizer for the wet-process preparation of potassium dihydrogen phosphate from phosphoric acid, characterized in that, It includes a cylinder (100), a drive unit (200), a guide tube (300), a liquid distributor (400), and an overflow box (500). The upper part of the cylinder (100) is a crystallization section (101), and the lower part is a conical settling section (102). The bottom end of the conical settling section (102) is provided with a crystal slurry outlet (103). The drive device (200) is fixed to the top of the cylinder (100), and its output end is connected to the stirring shaft (201). The stirring shaft (201) is provided with an impeller (202) located inside the guide tube (300). The guide tube (300) is coaxially disposed inside the crystallization section (101). The guide tube (300) has a double-wall structure, and a sealed jacket cavity (301) is formed between its inner wall and outer wall. The jacket cavity (301) is provided with a cooling medium inlet (302) and a cooling medium outlet (303). The liquid distributor (400) is located below the guide tube (300) and is connected to the feed pipe (401); The overflow box (500) is located outside the cylinder (100) and is connected to the upper part of the crystallization section (101) through the overflow pipe (501). The overflow box (500) is provided with a clear liquid outlet (502).

2. A continuous reaction crystallizer for the wet-process phosphoric acid preparation of potassium dihydrogen phosphate according to claim 1, characterized in that... It also includes a built-in coil (600), which is coiled around the outside of the guide tube (300) and the inside of the cylinder (100). The built-in coil (600) is connected to a coil inlet (601) and a coil outlet (602).

3. A continuous reaction crystallizer for the wet-process phosphoric acid preparation of potassium dihydrogen phosphate according to claim 2, characterized in that... The built-in coil (600) has a double helix structure and is symmetrically coiled around the outer periphery of the guide tube (300).

4. A continuous reaction crystallizer for the wet-process phosphoric acid preparation of potassium dihydrogen phosphate according to claim 1, characterized in that... The cooling medium inlet (302) is located at the lower part of the guide tube jacket cavity (301), and the cooling medium outlet (303) is located at the upper part of the guide tube jacket cavity (301).

5. A continuous reaction crystallizer for the wet-process phosphoric acid preparation of potassium dihydrogen phosphate according to claim 1, characterized in that... The impeller (202) is an axial flow impeller.

6. A continuous reaction crystallizer for the wet-process phosphoric acid preparation of potassium dihydrogen phosphate according to claim 1, characterized in that... The liquid distributor (400) is an annular tube structure with several liquid distribution holes (402) on its tube wall.

7. A continuous reaction crystallizer for the wet-process phosphoric acid preparation of potassium dihydrogen phosphate according to claim 1, characterized in that... The overflow tank (500) is equipped with a baffle (503) for stabilizing the liquid flow.

8. A continuous reaction crystallizer for the wet-process phosphoric acid preparation of potassium dihydrogen phosphate according to claim 1, characterized in that... The crystal slurry outlet (103) is connected to the crystal slurry pump via a pipeline.

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