A multi-component potassium dihydrogen phosphate multi-stage crystallization device

Abstract

The utility model relates to potassium dihydrogen phosphate technical field, specifically to a kind of multi-component potassium dihydrogen phosphate multistage crystallization device, including primary evaporation crystallizer, secondary evaporation crystallizer and tertiary cooling crystallizer, the high-level overflow pipe of primary evaporation crystallizer is connected the feed pipe of secondary evaporation crystallizer by pipeline, the bottom discharge port of secondary evaporation crystallizer is connected centrifugal separator by pipeline, the liquid material outlet of centrifugal separator is connected mother liquor tank by pipeline, and mother liquor tank is connected tertiary cooling crystallizer by pipeline;First, second crystallization is carried out in primary evaporation crystallizer and secondary evaporation crystallizer under higher temperature, effectively avoid the precipitation of potassium chloride, ammonium phosphate salt and other impurity salt, to improve the purity of product;Cooling crystallization is carried out in tertiary cooling crystallizer, further reduce the solubility of potassium dihydrogen phosphate in mother liquor.

Description

Technical Field

[0001] This utility model relates to the field of potassium dihydrogen phosphate technology, specifically to a multi-component potassium dihydrogen phosphate multi-stage crystallization device. Background Technology

[0002] Currently, domestic production of potassium dihydrogen phosphate mainly employs neutralization and metathesis methods. The neutralization method requires refined phosphoric acid with extremely low metal impurity content (less than 5 ppm) as raw material, but the preparation process of refined phosphoric acid (such as TBP solvent extraction) is complex and costly. The metathesis method suffers from low product purity; the resulting potassium dihydrogen phosphate product typically has a purity below 98%, with high impurity content, reducing product value.

[0003] In recent years, the process of directly producing potassium dihydrogen phosphate using wet-process phosphoric acid and potassium chloride as direct raw materials via organic amine solvent extraction has shown cost advantages. However, the initial potassium dihydrogen phosphate solution obtained by this method contains impurity ions such as Cl⁻ (0.8-1.5%) and NH₄⁺ (approximately 0.3%). During the concentration and crystallization process, these impurity ions co-crystallize with potassium dihydrogen phosphate in the form of potassium chloride, ammonium phosphate, etc., severely affecting the purity and yield of the final product. Existing single crystallization techniques are insufficient to effectively separate these impurities, making it impossible to simultaneously achieve both high-purity product and economic viability of raw materials. Utility Model Content

[0004] The purpose of this invention is to provide a multi-component potassium dihydrogen phosphate multi-stage crystallization device, which achieves high purity and high yield of potassium dihydrogen phosphate product through staged crystallization, thereby solving the defects mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution: A multi-component potassium dihydrogen phosphate multi-stage crystallization device includes a primary evaporator crystallizer, a secondary evaporator crystallizer, and a tertiary cooling crystallizer. Both the primary and secondary evaporators crystallize in a crystallization vessel, which is equipped with a feed pipe, a high-level overflow pipe, and a bottom outlet. The high-level overflow pipe of the primary evaporator crystallizer is connected to the feed pipe of the secondary evaporator crystallizer via a pipeline. The bottom outlet of the secondary evaporator crystallizer is connected to a centrifugal separator via a pipeline. The liquid material outlet of the centrifugal separator is connected to a mother liquor tank via a pipeline. The mother liquor tank is connected to the tertiary cooling crystallizer via a pipeline.

[0006] As a further improvement, the three-stage cooling crystallizer includes a crystallization tank, which is connected to the material inlet of the cooler via a pipeline, and the material outlet of the cooler is connected to the crystallization tank via a pipeline. A cooling crystallization circulation pump for driving the material to circulate between the crystallization tank and the cooler is also provided on the pipeline between the crystallization tank and the cooler. The bottom of the crystallization tank is also connected to the centrifugal separator via a pipeline.

[0007] As a further improvement, the top of the crystallization vessel is provided with an air outlet. The air outlet of the first-stage evaporation crystallizer is connected to the tube-side inlet of the first condenser through a pipeline. The air outlet of the second-stage evaporation crystallizer is connected to the tube-side inlet of the second condenser through a pipeline. The tube-side outlets of the first condenser and the second condenser are respectively connected to a condensate tank through pipelines. A vacuum pump is also connected to the tube-side of the second condenser through a pipeline.

[0008] As a further improvement, a stirring shaft driven by a motor is rotatably installed inside the crystallization vessel. The stirring shaft extends vertically, and a stirrer is fixedly installed on the stirring shaft inside the crystallization vessel. The bottom discharge port is coaxially arranged with the stirring shaft, and a cleaning rod coaxially arranged with the stirring shaft is vertically slidably installed at the lower end of the stirring shaft. A scraper for scraping off the material on the inner wall of the bottom discharge port is fixedly installed on the cleaning rod.

[0009] As a further improvement, the scraper is spirally arranged around the cleaning rod.

[0010] As a further improvement, the bottom discharge port is an inverted cone shape with a larger diameter at the top and a smaller diameter at the bottom, and the scraper fits against the inner wall of the bottom discharge port; the lower end of the stirring shaft is provided with an installation cavity, and the bottom wall of the installation cavity is provided with a guide hole that extends downwards, the cleaning rod is vertically slidably installed in the guide hole, and a stop block is fixedly installed on the cleaning rod located in the installation cavity, and a spring is connected between the top of the stop block and the inner wall of the installation cavity.

[0011] Compared with the prior art, the beneficial effects of this utility model are: By carrying out the first and second stage crystallization at higher temperatures in the primary and secondary evaporation crystallizers, the precipitation of impurity salts such as potassium chloride and ammonium phosphate is effectively avoided, thereby improving the purity of the product. By performing cooling crystallization in a three-stage cooling crystallizer, the solubility of potassium dihydrogen phosphate in the mother liquor is further reduced, causing it to crystallize and precipitate, which significantly improves the total yield of potassium dihydrogen phosphate. After vacuum evaporation crystallization through the primary and secondary evaporation crystallizers, the temperature of the liquid is reduced, which in turn effectively reduces the cooling load of the external cooler of the tertiary cooling crystallizer and reduces the system energy consumption. By setting a spiral scraper on the cleaning rod, the spring force makes the scraper stick tightly to the inverted conical inner wall of the bottom outlet. The stirring shaft drives the cleaning rod and scraper to rotate, and the scraper scrapes off the material adhering to the inner wall of the bottom outlet, thereby avoiding blockage of the bottom outlet and improving the material discharge efficiency. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a structural schematic diagram of an embodiment of the present utility model; Figure 2 This is a schematic diagram of the structure of the crystallization vessel according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the cleaning rod according to an embodiment of the present invention; Figure 4 This is a top view schematic diagram of the scraper according to an embodiment of the present utility model.

[0014] In the diagram: 1-First-stage evaporator crystallizer; 2-Second-stage evaporator crystallizer; 3-Third-stage cooling crystallizer; 4-Feed pipe; 5-High-level overflow pipe; 6-Bottom outlet; 7-Gas outlet; 8-First condenser; 9-Second condenser; 10-Condensate tank; 11-Vacuum pump; 12-Centrifuge; 13-Mother liquor tank; 14-Crystallization tank; 15-Cooler; 16-Cooling crystallization circulation pump; 17-Crystallization discharge pump; 18-Motor; 19-Stirring shaft; 20-Stirrer; 21-Cleaning rod; 22-Support rod; 23-Scraper; 24-Mounting cavity; 25-Guide hole; 26-Block; 27-Spring; 28-Crystallization vessel; 29-Mother liquor pump. Detailed Implementation

[0015] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0016] like Figures 1 to 4 As shown, a multi-component potassium dihydrogen phosphate multi-stage crystallization device includes a primary evaporator crystallizer 1, a secondary evaporator crystallizer 2, and a tertiary cooling crystallizer 3.

[0017] Both the primary evaporator crystallizer 1 and the secondary evaporator crystallizer 2 include a crystallization vessel 28. A feed pipe 4 and a high-level overflow pipe 5 are located on the top side of the crystallization vessel 28, and a bottom outlet 6 is located at the bottom of the crystallization vessel 28. A discharge valve is installed below the bottom outlet 6. The high-level overflow pipe 5 of the primary evaporator crystallizer 1 is connected to the feed pipe 4 of the secondary evaporator crystallizer 2 via a pipeline.

[0018] The top of the crystallization vessel 28 is provided with an outlet 7. The outlet 7 of the first-stage evaporator crystallizer 1 is connected to the tube inlet of the first condenser 8 through a pipeline. The outlet 7 of the second-stage evaporator crystallizer 2 is connected to the tube inlet of the second condenser 9 through a pipeline. The tube outlets of the first condenser 8 and the second condenser 9 are respectively connected to the condensate tank 10 through pipelines. Cooling water circulates in the shell side of the first condenser 8 and the second condenser 9. The steam in the first-stage evaporator crystallizer 1 and the second-stage evaporator crystallizer 2 is eliminated through the first condenser 8 and the second condenser 9, so that the system maintains a vacuum environment. The steam in the first-stage evaporator crystallizer 1 and the second-stage evaporator crystallizer 2 is condensed into liquid and then recovered to the condensate tank 10.

[0019] The tube side of the second condenser 9 is also connected to a vacuum pump 11 via a pipeline. The vacuum pump 11 is located near the secondary evaporator crystallizer 2, creating a pressure gradient between the primary evaporator crystallizer 1 and the secondary evaporator crystallizer 2. The pressure in the primary evaporator crystallizer 1 is relatively high, and the boiling point of the material is relatively high; the pressure in the secondary evaporator crystallizer 2 is relatively low, and the boiling point of the material is relatively low.

[0020] The bottom outlet 6 of the secondary evaporator crystallizer 2 is connected to the centrifuge 12 through a pipeline. The centrifuge 12 is used for solid-liquid separation. The centrifuge 12 has a solid material outlet and a liquid material outlet. The liquid material outlet of the centrifuge 12 is connected to the mother liquor tank 13 through a pipeline. The mother liquor tank 13 is equipped with a stirrer. The mother liquor tank 13 is connected to the tertiary cooling crystallizer 3 through a pipeline.

[0021] The three-stage cooling crystallizer 3 includes a crystallization tank 14, which is equipped with a stirrer. The crystallization tank 14 is connected to the material inlet of a cooler 15 via a pipeline, and the material outlet of the cooler 15 is connected to the crystallization tank 14 via a pipeline. A cooling crystallization circulation pump 16 is also installed on the pipeline between the crystallization tank 14 and the material inlet of the cooler 15 to drive the material to circulate between the crystallization tank 14 and the cooler 15. A mother liquor tank 13 is connected to a mother liquor pump 29 via a pipeline, and the outlet end of the mother liquor pump 29 is connected to the pipeline on the material outlet side of the cooler 15 via a pipeline. The mother liquor in the mother liquor tank 13 is transported to the crystallization tank 14 by the mother liquor pump 29, and the cooling crystallization circulation pump 16 drives the mother liquor to circulate between the crystallization tank 14 and the cooler 15 for cooling and crystallization. The bottom of the crystallization tank 14 is also connected to a centrifuge 12 via a pipeline. A crystallization discharge pump 17 is installed on the pipeline between the crystallization tank 14 and the centrifuge 12 to transport the crystal slurry in the crystallization tank 14 to the centrifuge 12 for solid-liquid separation.

[0022] The crystallization process using the above-mentioned multi-component potassium dihydrogen phosphate multi-stage crystallization device is as follows: 1. A 95-98℃, 48-50% potassium dihydrogen phosphate solution from the concentration system enters the first-stage evaporator crystallizer 1 for cooling and crystallization, where the temperature drops to 70-75℃. 2. The liquid material that has been cooled and crystallized in the first-stage evaporator crystallizer 1 overflows into the second-stage evaporator crystallizer 2 through the high-level overflow pipe 5 of the first-stage evaporator crystallizer 1 for further cooling and crystallization, and the temperature will be reduced to 60-65℃. 3. The crystal slurry that has been cooled and crystallized in the secondary evaporator crystallizer 2 is discharged through the bottom outlet 6 of the secondary evaporator crystallizer 2 and enters the centrifugal separator 12 for solid-liquid separation. The solid wet potassium dihydrogen phosphate after centrifugal separation is transported to the subsequent drying system. By carrying out the first and second crystallization at a high temperature, the precipitation of impurity salts such as potassium chloride and ammonium phosphate is effectively avoided, and a potassium dihydrogen phosphate product with extremely high purity is obtained, in which P2O5>52%, K2O>34%, Cl⁻<0.1%, N<0.05%, which can be used in industrial or high-end agricultural fields. 4. The potassium dihydrogen phosphate solution separated by centrifuge 12 enters the three-stage cooling crystallizer 3, where it circulates, cools, and crystallizes between crystallization tank 14 and cooler 15. When the temperature drops to 30-35℃, the crystal slurry is transported back to centrifuge 12. The separated potassium dihydrogen phosphate product is then sent to the subsequent drying system for further processing. The third-stage cooling crystallization further reduces the solubility of potassium dihydrogen phosphate in the mother liquor, causing it to crystallize and precipitate, significantly improving the total yield of potassium dihydrogen phosphate. This part of the product can reach the fertilizer-grade superior standard, with P2O5>51%, K2O>33.8%, Cl⁻<1%, and N<0.4%, realizing product gradation and maximizing resource utilization.

[0023] In addition, such as Figures 2 to 4 As shown, a stirring shaft 19 driven by a motor 18 is rotatably installed inside the crystallization vessel 28. The stirring shaft 19 extends vertically and is coaxially arranged with the crystallization vessel 28. The stirring shaft 19 is rotatably installed on the top wall of the crystallization vessel 28 through bearings. A motor bracket is provided on the top of the crystallization vessel 28. The motor 18 is installed on the motor bracket by bolts. The upper end of the stirring shaft 19 extends out of the outside of the crystallization vessel 28 and is connected to the motor shaft of the motor 18 through a coupling. An agitator 20 is fixedly installed on the stirring shaft 19 located inside the crystallization vessel 28.

[0024] The bottom discharge port 6 is coaxially arranged with the stirring shaft 19. A cleaning rod 21, coaxially arranged with the stirring shaft 19, is vertically slidably mounted on the lower end of the stirring shaft 19. The lower end of the cleaning rod 21 extends into the bottom discharge port 6. A support rod 22 extending radially is welded to the outer side of the lower end of the cleaning rod 21. The end of the support rod 22 away from the cleaning rod 21 is fixed by bolts or welded with a scraper 23 for scraping off the material on the inner wall of the bottom discharge port 6. While the stirring shaft 19 rotates to stir the material in the crystallization vessel 28, the stirring shaft 19 drives the cleaning rod 21 to rotate. The cleaning rod 21 drives the scraper 23 to scrape off the material adhering to the inner wall of the bottom discharge port 6, thereby preventing the accumulation of crystals in the bottom discharge port 6 and causing blockage of the bottom discharge port 6.

[0025] The scraper 23 is spirally arranged around the cleaning rod 21. During the process of discharging the crystal slurry by opening the discharge valve below the bottom discharge port 6, the spiral scraper 23 rotates and conveys the material downward, thereby improving the discharge efficiency of the material in the crystallizing kettle 28.

[0026] The bottom discharge port 6 is an inverted cone shape with a larger diameter at the top and a smaller diameter at the bottom. The side of the scraper 23 away from the cleaning rod 21 is in contact with the inner wall of the bottom discharge port 6. The lower end of the stirring shaft 19 is provided with an installation cavity 24. The bottom wall of the installation cavity 24 is provided with a guide hole 25 that extends downward. The cleaning rod 21 is vertically slidably installed in the guide hole 25. The cleaning rod 21 is specifically a polygonal prism-shaped cleaning rod. The guide hole 25 matches the cross-sectional shape of the cleaning rod 21, which can prevent the cleaning rod 21 from deflecting relative to the stirring shaft 19. A stop block 26 is fixedly installed on the cleaning rod 21 located in the installation cavity 24 by bolts. A spring 27 is connected between the top of the stop block 26 and the inner wall of the installation cavity 24. The spring 27 provides a downward pushing force to the stop block 26 and the scraper 23, so that the scraper 23 can press down tightly against the inverted cone-shaped inner wall of the bottom discharge port 6, thereby improving the scraping efficiency of the scraper 23 on the inner wall of the bottom discharge port 6.

[0027] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A multi-component potassium dihydrogen phosphate multi-stage crystallization device, characterized in that: The system includes a primary evaporator crystallizer (1), a secondary evaporator crystallizer (2), and a tertiary cooling crystallizer (3). Both the primary evaporator crystallizer (1) and the secondary evaporator crystallizer (2) include a crystallization vessel (28). The crystallization vessel (28) is equipped with a feed pipe (4), a high-level overflow pipe (5), and a bottom outlet (6). The high-level overflow pipe (5) of the primary evaporator crystallizer (1) is connected to the feed pipe (4) of the secondary evaporator crystallizer (2) through a pipeline. The bottom outlet (6) of the secondary evaporator crystallizer (2) is connected to a centrifuge (12) through a pipeline. The liquid material outlet of the centrifuge (12) is connected to a mother liquor tank (13) through a pipeline. The mother liquor tank (13) is connected to the tertiary cooling crystallizer (3) through a pipeline.

2. The multi-component potassium dihydrogen phosphate multi-stage crystallization apparatus as described in claim 1, characterized in that: The three-stage cooling crystallizer (3) includes a crystallization tank (14), which is connected to the material inlet of the cooler (15) via a pipeline. The material outlet of the cooler (15) is connected to the crystallization tank (14) via a pipeline. A cooling crystallization circulation pump (16) for driving the material to circulate between the crystallization tank (14) and the cooler (15) is also provided on the pipeline between the crystallization tank (14) and the cooler (15). The bottom of the crystallization tank (14) is also connected to the centrifuge (12) via a pipeline.

3. The multi-component potassium dihydrogen phosphate multi-stage crystallization apparatus as described in claim 1, characterized in that: The crystallization vessel (28) is provided with an outlet (7) at the top. The outlet (7) of the first-stage evaporator crystallizer (1) is connected to the tube inlet of the first condenser (8) through a pipeline. The outlet (7) of the second-stage evaporator crystallizer (2) is connected to the tube inlet of the second condenser (9) through a pipeline. The tube outlet of the first condenser (8) and the tube outlet of the second condenser (9) are respectively connected to the condensate tank (10) through pipelines. The tube side of the second condenser (9) is also connected to a vacuum pump (11) through a pipeline.

4. The multi-component potassium dihydrogen phosphate multi-stage crystallization apparatus as described in claim 1, characterized in that: The crystallization vessel (28) is rotatably installed with a stirring shaft (19) driven by a motor (18). The stirring shaft (19) extends vertically, and a stirrer (20) is fixedly installed on the stirring shaft (19) inside the crystallization vessel (28). The bottom outlet (6) is coaxially arranged with the stirring shaft (19). A cleaning rod (21) is vertically slidably installed at the lower end of the stirring shaft (19) and is coaxially arranged with it. A scraper (23) for scraping off the material on the inner wall of the bottom outlet (6) is fixedly installed on the cleaning rod (21).

5. The multi-component potassium dihydrogen phosphate multi-stage crystallization apparatus as described in claim 4, characterized in that: The scraper (23) is spirally arranged around the cleaning rod (21).

6. The multi-component potassium dihydrogen phosphate multi-stage crystallization apparatus as described in claim 5, characterized in that: The bottom outlet (6) is an inverted cone with a larger diameter at the top and a smaller diameter at the bottom. The scraper (23) is in contact with the inner wall of the bottom outlet (6). The lower end of the stirring shaft (19) is provided with an installation cavity (24). The bottom wall of the installation cavity (24) is provided with a guide hole (25) that extends downward. The cleaning rod (21) is vertically slidably installed in the guide hole (25). A stop block (26) is fixedly installed on the cleaning rod (21) located in the installation cavity (24). A spring (27) is connected between the top of the stop block (26) and the inner wall of the installation cavity (24).

Images