A dinitrate crystallization purification device and process

Abstract

The invention relates to the technical field of chemical production, and discloses a dinitrate crystallization purification device and process, comprising a purification device body, wherein the purification device body comprises a crystallizer 1, a crystallizer 2, a crystallizer 3, a crystallizer 4, a crystallizer 5, a circulating water tank, a crystallization circulating water pump, a crystallization plate heat exchanger A, a crystallization plate heat exchanger B, a crystallization mother liquid tank, a primary finished product tank and a secondary finished product tank. The purification device effectively realizes multiple crystallization purification of dinitrate through segmented operation of the crystallizer 1 to the crystallizer 5. The design of the multi-stage crystallization process, combined with precise temperature control, enables the temperature in each crystallizer to be gradually reduced or increased as needed, thereby ensuring that the dinitrate is crystallized under optimal conditions in different crystallizers.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, and in particular to a dinitrate crystallization purification device and process. Background Art

[0002] Dinitrobenzene refers to dinitro compounds, such as dinitroaniline or other similar compounds. Its purity directly affects the quality and performance of downstream products. Dinitrobenzene refers to organic compounds containing two nitro groups in the molecule. Common dinitro compounds include dinitrobenzene, dinitrotoluene, dinitroaniline, etc. These compounds have high chemical reactivity and have important applications in many fields such as chemical industry, medicine and agriculture.

[0003] According to the Chinese patent authorization announcement: CN104225952B, the disclosed high-purity isophthaloyl chloride purification device and purification method include a heat exchange tube coiled in a crystallizer body, the crystallizer body is provided with a feed port, a discharge port, and a circulating water inlet and a circulating water outlet connected to the heat exchange tube, a circulating water thermometer is installed on the circulating water inlet pipeline, and an internal thermometer is installed inside the crystallizer body. The invention has reasonable structural design, simple preparation process, low energy consumption, can realize low-temperature operation, high reaction yield, and can provide a purification device and purification method for high-purity isophthaloyl chloride with a product purity of more than 99.97%. However, the purification process still has some problems in use. The traditional dinitr crystallization purification process usually uses a single crystallizer for operation, lacks a multi-stage crystallization step, and this single crystallization process often cannot fully control the crystallization conditions of dinitr, resulting in low crystallization efficiency. Due to the imprecise control of temperature, pressure and other conditions, part of the dinitr cannot be completely crystallized and precipitated, affecting the purity and output of the final product. In addition, the traditional process fails to effectively manage the discharge and reuse of the mother liquor, resulting in a large amount of uncrystallized dinitr being discharged from the system, increasing material waste. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a dinitrate crystallization purification device and process, which solves the problems of low efficiency, poor purity, large waste and lack of multi-stage crystallization control in the traditional dinitrate purification process.

[0005] To achieve the above objectives, the present invention is implemented through the following technical scheme: a dinitrate crystallization purification device, including a purification device body, the purification device body includes crystallizer 1, crystallizer 2, crystallizer 3, crystallizer 4, crystallizer 5, a circulating water tank, a crystallization circulating water pump, a crystallization plate heat exchanger A, a crystallization plate heat exchanger B, a crystallization mother liquor tank, a primary finished product tank and a secondary finished product tank, the crystallizer 1, crystallizer 2, crystallizer 3, crystallizer 4 and crystallizer 5 are respectively connected to a circulating water tank, a crystallization circulating water pump, a crystallization plate heat exchanger A and a crystallization plate heat exchanger B, the discharge port of the crystallizer 1 is connected to the crystallization mother liquor tank through a pipeline, the discharge port of the crystallization mother liquor tank is connected to the primary finished product tank, and the discharge ports of the crystallizer 4 and the crystallizer 5 are respectively connected to the secondary finished product tank through pipelines.

[0006] Preferably, the crystallizer 1, crystallizer 2, crystallizer 3, crystallizer 4 and crystallizer 5 are all connected to corresponding circulating water tanks through pipelines, and the circulating water tanks are used to store and provide circulating water.

[0007] Preferably, the crystallization circulating water pump is used to pump circulating water from the circulating water tank into the crystallizer 1 to cool or heat the material in the crystallizer 1; The crystallization plate heat exchanger A is connected to the crystallization circulating water pump and is used to cool the circulating water with low-temperature water, and the cooling temperature range is 30-50°C; The crystallization plate heat exchanger B is connected to the crystallization circulating water pump and is used to heat the circulating water by steam, and the heating temperature range is 45-85°C.

[0008] Preferably, the discharge port of the crystallization mother liquid tank is connected to a mother liquid pump, and the mother liquid pump is used to transport the mother liquid in the crystallization mother liquid tank to the product tank 70; The discharge port of the first-level finished product tank is connected to the second-level finished product tank through a pipeline, and the discharge port of the second-level finished product tank is connected to the second-level finished product pump, and the second-level finished product pump is used to transport the material in the second-level finished product tank to the 99 product tank.

[0009] The present invention also provides a dinitrate crystallization purification process, comprising the following steps: S1: Feeding and initial crystallization: Feed the dinitro raw material into the crystallizer 1 through the feed pump. When the liquid level reaches the upper limit, stop feeding, start the crystallization circulating water pump of the crystallizer 1, open the low-temperature water valve in the crystallization plate heat exchanger A, and cool the material in the crystallizer 1; S2: Mother liquor discharge: When the temperature of the dinitrate solution in the crystallizer 1 decreases and most of the dinitrate has been crystallized, the mother liquor discharge pipeline valve is automatically opened, and the unsolidified mother liquor flows into the crystallization mother liquor tank; when the liquid level of the crystallization mother liquor tank reaches the upper limit, the mother liquor pump is started to transport the mother liquor to the 70 product tank; S3: Material heating and discharging: After the mother liquor is discharged, close the mother liquor pipe valve, close the low-temperature water valve, open the steam valve, keep the steam temperature at 120°C ± 5°C, heat the circulating water through the crystallization plate heat exchanger B, raise the circulating water temperature to 80°C ± 3°C, and then transport it to the crystallizer 1 through the crystallization circulating water pump, raise the temperature of the material in the crystallizer 1 to 60°C ± 2°C, and ensure that the dinitrate in the crystallizer 1 is completely melted; S4: Secondary crystallization: the materials in the first-level finished product tank are fed into crystallizer 2, crystallizer 3, crystallizer 4 and crystallizer 5 in sequence, and secondary crystallization operation is performed in crystallizer 2, crystallizer 3, crystallizer 4 and crystallizer 5, and the temperature is controlled to be gradually reduced to improve the purity of dinitrate and ensure crystallization efficiency and product purity; S5: Secondary finished product collection: After the secondary crystallization operation of crystallizer 4 and crystallizer 5 is completed, the material flows into the secondary finished product tank. When the preset liquid level is reached, the flow is automatically stopped, and the secondary finished product pump is started to transport the material to the 99 product tank. Beneficial Effects

[0010] The present invention provides a dinitrate crystallization purification device. Compared with the prior art, it has the following beneficial effects: In the present invention, the purification device effectively realizes multiple crystallization purification of dinitrate through the segmented operation of crystallizer 1 to crystallizer 5. The design of this multi-stage crystallization process, combined with precise temperature control, allows the temperature in each crystallizer to be gradually reduced or increased as needed, thereby ensuring that dinitrate is crystallized under optimal conditions in different crystallizers. For example, through the initial cooling crystallization in crystallizer 1, the temperature of the dinitrate solution can be quickly reduced, so that most of the dinitrate is crystallized and precipitated in a short time. Subsequently, through the step-by-step cooling operation, secondary crystallization is carried out in crystallizers 2, 3, 4 and 5, effectively improving the purity of the product. Such a segmented crystallization design not only improves the crystallization efficiency, but also greatly reduces the processing time of the solution, ensuring an efficient dinitrate crystallization purification process. Through the recycling and separate discharge of the crystallization mother liquor, the material loss is further reduced, so that the residual dinitrate in the mother liquor is also fully utilized. This design also reduces the demand for energy in the production process. By optimizing the low-temperature water and steam circulation of heat exchangers A and B, the energy utilization rate of the entire system is higher, reducing the operating cost of the process.

[0011] 2. In the present invention, the dinitrate crystallization purification device not only improves the crystallization efficiency, but also effectively reduces the loss of equipment and prolongs the service life of the device through the segmented operation of multiple crystallizers and precise temperature control. In the traditional crystallization purification process, the temperature and pressure fluctuate greatly, which easily leads to thermal fatigue and mechanical damage of the equipment materials. In the present invention, by reasonably setting the operating temperature and pressure range of crystallizers 1 to 5, the equipment is avoided from working at too high or too low temperature for a long time, thereby reducing the possibility of equipment wear and failure. Specifically, the crystallization plate heat exchangers A and B are responsible for cooling and heating tasks respectively. By accurately controlling the temperature range (for example, cooling temperature 30-50°C, heating temperature 45-85°C), the heat shock caused by drastic temperature changes in the heat exchanger is effectively avoided. In addition, the use of a circulating water tank and a crystallization circulating water pump to stabilize the water flow and temperature also reduces the load on the equipment. This design not only ensures the stability of the system, but also reduces the frequency and cost of equipment maintenance. Through these measures, the operating cost of the equipment is reduced, the downtime is reduced, and the production efficiency is improved. At the same time, the extended equipment service life means less equipment replacement and investment, which significantly reduces the capital expenditure of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A process flow diagram of a part of a crystallizer of a dinitrate crystallization purification device and process proposed by the present invention; Figure 2 A schematic diagram of the process flow of two parts of a crystallizer of a dinitrate crystallization purification device and process proposed by the present invention; Figure 3 A schematic diagram of the process flow of three parts of a crystallizer of a dinitrate crystallization purification device and process proposed by the present invention; Figure 4 A schematic diagram of the process flow of four parts of a crystallizer of a dinitrate crystallization purification device and process proposed by the present invention; Figure 5 A schematic diagram of a process flow of five parts of a crystallizer of a dinitrate crystallization purification device and process proposed by the present invention; Figure 6 The present invention provides a purification process flow chart of a dinitrate crystallization purification device and process.

[0013] Legend: 1. Purification device body; 101. Crystallizer 1; 102. Crystallizer 2; 103. Crystallizer 3; 104. Crystallizer 4; 105. Crystallizer 5; 2. Crystallization mother liquor tank; 3. Primary finished product tank; 4. Crystallization plate heat exchanger A; 5. Crystallization plate heat exchanger B; 6. Crystallization circulating water pump; 7. Mother liquor pump; 8. Circulating water tank; 9. Secondary finished product tank; 10. Secondary finished product pump. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 are within the scope of protection of the present invention.

[0015] See also Figure 1 - Figure 6 The present invention provides two technical solutions, which specifically include the following embodiments: Embodiment 1

[0016] A dinitrate crystallization and purification device, comprising a purification device body 1, the purification device body 1 comprises a crystallizer 101, a crystallizer 2 102, a crystallizer 3 103, a crystallizer 4 104, a crystallizer 5 105, a circulating water tank 8, a crystallization circulating water pump 6, a crystallization plate heat exchanger A4, a crystallization plate heat exchanger B5, a crystallization mother liquor tank 2, a primary finished product tank 3 and a secondary finished product tank 9, the crystallizers 101 to 105 are respectively connected to a circulating water tank 8, a crystallization circulating water pump 6, a crystallization plate heat exchanger A4 and a crystallization plate heat exchanger B5, the discharge port of the crystallizer 101 is connected to the crystallization mother liquor tank 2 through a pipeline, the discharge port of the crystallization mother liquor tank 2 is connected to the primary finished product tank 3, the crystallizer 4 The discharge ports of crystallizer 104 and crystallizer five 105 are respectively connected to the secondary finished product tank 9 through pipelines, wherein crystallizer one 101, crystallizer two 102, crystallizer three 103, crystallizer four 104 and crystallizer five 105 are all key equipment for performing staged crystallization operation of dinitrate, and the designs of crystallizer one 101, crystallizer two 102, crystallizer three 103, crystallizer four 104 and crystallizer five 105 take different crystallization stages into consideration to ensure that dinitrate can crystallize under optimal conditions at different stages.

[0017] Crystallizer 1 101, crystallizer 2 102, crystallizer 3 103, crystallizer 4 104 and crystallizer 5 105 are all connected to the corresponding circulating water tank 8 through pipelines, and the circulating water tank 8 is used to store and provide circulating water. Crystallizer 1 101, crystallizer 2 102, crystallizer 3 103, crystallizer 4 104 and crystallizer 5 105 are all connected to the corresponding circulating water tank 8 through pipelines, and the circulating water tank 8 is responsible for storing and providing circulating water required for cooling or heating, ensuring that the temperature control of crystallizer 1 101, crystallizer 2 102, crystallizer 3 103, crystallizer 4 104 and crystallizer 5 105 reaches the optimal state; The crystallization circulating water pump 6 is used to pump circulating water from the circulating water tank 8 to the crystallizer 101 to cool or heat the material in the crystallizer 101, wherein the crystallization circulating water pump 6 is used to pump circulating water from the circulating water tank 8 to each crystallizer to adjust the temperature of the material in the crystallizer 101 to achieve the desired cooling or heating effect. These pumps have efficient fluid transmission capabilities to ensure stable and accurate flow of circulating water; The crystallization plate heat exchanger A4 is connected to the crystallization circulating water pump 6 and is used to cool the circulating water with low temperature water. The cooling temperature range is 30-50°C. The crystallization plate heat exchanger A4 is connected to the crystallization circulating water pump 6 and is mainly used to cool the circulating water with low temperature water. The heat exchanger A can reduce the temperature of the circulating water to 30-50°C. This temperature range helps to control the initial crystallization process of dinitrate in the crystallizer and ensure the crystallization efficiency and quality. The crystallization plate heat exchanger B5 is connected to the crystallization circulating water pump 6 and is used to heat the circulating water by steam. The heating temperature range is 45-85°C. The heat exchanger B heats the circulating water to 45-85°C. This heating range can increase the temperature of the crystallizer when necessary, so that the dinitrate melts at a higher temperature, ensuring the smooth progress of the crystallization process.

[0018] During operation, in the whole process, crystallizer 101, crystallizer 2 102, crystallizer 3 103, crystallizer 4 104, crystallizer 5 105 all play different roles to realize the primary crystallization and multiple purification of raw materials. First, the dinitro raw material enters the crystallizer 101 through the feed pump, and the feeding is stopped when the liquid level reaches the set value. The crystallization circulating water pump 6 and the crystallization plate heat exchanger A4 are cooled to gradually reduce the temperature, thereby promoting the occurrence of the crystallization process. This cooling method not only improves the crystallization rate, but also reduces the solubility of impurities in the solution, so that more pure dinitro is precipitated. After completing the primary crystallization, the unsolidified mother liquor is transported to the crystallization mother liquor tank 2, ensuring efficient liquid-solid separation. Then, the temperature of the control crystallizer 101 is raised to 60°C ± 2°C by steam heating circulating water, so that the residual dinitro is completely melted, and preparation is made for the next step of purification. During the secondary crystallization process, the materials in the first-level finished product tank 3 enter the crystallizer 2 102 to the crystallizer 5 105 in sequence, and the temperature is gradually reduced. By reducing the temperature step by step, the crystallization is more thorough, and the purity of dinitrate is effectively improved. The entire process utilizes the difference in solubility of dinitrate in the solution under different temperature conditions to achieve efficient separation and purification. Through multiple crystallizations and the synergistic effects of crystallizer 1 101, crystallizer 2 102, crystallizer 3 103, crystallizer 4 104, and crystallizer 5 105, the high purity and high quality of the final product are ensured, which not only improves the crystallization efficiency, but also greatly improves the purity and quality of the product, meeting the needs of industrial production. Embodiment 2

[0019] On the basis of Example 1, the discharge port of the crystallization mother liquid tank 2 is connected to the mother liquid pump 7, which is used to transport the mother liquid in the crystallization mother liquid tank 2 to the product tank 70, wherein the mother liquid tank is connected to the discharge port of the crystallizer 101 through a pipeline to receive and store the mother liquid discharged from the crystallizer 101. The tank can temporarily store the uncrystallized mother liquid to ensure that the mother liquid can be properly processed and utilized; The mother liquor pump 7 is connected to the outlet of the crystallization mother liquor tank 2 to transport the mother liquor from the crystallization mother liquor tank 2 to the product tank 70. This process ensures the timely transfer and treatment of the mother liquor, effectively reducing the material loss in the production process.

[0020] The discharge port of the primary finished product tank 3 is connected to the secondary finished product tank 9 through a pipeline, and the discharge port of the secondary finished product tank 9 is connected to the secondary finished product pump 10. The secondary finished product pump 10 is used to transport the material in the secondary finished product tank 9 to the 99 product tank, wherein the primary finished product tank 3 is connected to the crystallization mother liquor tank 2, and is used to receive the primary finished product dinitrate transferred from the crystallization mother liquor tank 2. The primary finished product tank 3 is a place for preliminary collection and storage of the preliminary crystallized dinitrate. The secondary finished product tank 9 is connected to the primary finished product tank 3 through a pipeline, and is used to further process the material in the primary finished product tank 3 and transfer the material to the secondary finished product tank 9 through the pipeline. The function of this tank is to collect the dinitrate after secondary crystallization for further purification. The secondary finished product pump 10 is connected to the discharge port of the secondary finished product tank 9, and is responsible for transporting the material in the secondary finished product tank 9 to the 99 product tank.

[0021] Working principle: The crystallization mother liquor tank 2 is connected to the discharge port of the crystallizer 101 to temporarily store the uncrystallized mother liquor discharged from the crystallizer 101 for subsequent processing. The mother liquor pump 7 is connected to the discharge port of the mother liquor tank to transport the mother liquor to the 70 product tank to achieve timely transfer of the mother liquor and reduce material loss. The first-level finished product tank 3 is connected to the crystallization mother liquor tank 2 to collect the initially crystallized dinitrate and store the material to be further processed. The second-level finished product tank 9 is connected to the first-level finished product tank 3 through a pipeline to receive and process the material that has undergone secondary crystallization to further improve the product purity. Finally, the second-level finished product pump 10 transports the high-purity dinitrate in the second-level finished product tank 9 to the 99 product tank to prepare for final packaging and processing.

[0022] The present invention also provides a dinitrate crystallization purification process, comprising the following steps: S1: Feeding and initial crystallization: Feed the dinitrate raw material into the crystallizer 101 through the feed pump. When the liquid level reaches the upper limit, stop feeding, start the crystallization circulating water pump 6 of the crystallizer 101, open the low-temperature water valve in the crystallization plate heat exchanger A4, cool the material in the crystallizer 101, and feed the dinitrate raw material into the crystallizer 101 through the feed pump. The function of the feed pump is to ensure that the raw material is transported to the crystallizer at a stable flow rate. During the feeding process, the liquid level sensor monitors the liquid level of the crystallizer 101. When the liquid level reaches the preset upper limit, the feed pump automatically stops feeding. At this time, start the crystallization circulating water pump 6 of the crystallizer 101 to start the flow of circulating water. The low-temperature water valve in the crystallization plate heat exchanger A4 is opened, allowing the low-temperature water to enter the heat exchanger A and exchange heat with the circulating water, thereby reducing the temperature of the material in the crystallizer 101. This cooling process causes the dinitrate in the solution to begin to crystallize and form preliminary solid particles; S2: Mother liquor discharge: When the temperature of the dinitrate solution in the crystallizer 101 decreases and most of the dinitrate has been crystallized, the mother liquor discharge pipeline valve is automatically opened, and the unsolidified mother liquor flows into the crystallization mother liquor tank 2; when the liquid level in the crystallization mother liquor tank 2 reaches the upper limit, the mother liquor pump 7 is started to transport the mother liquor to the 70 product tank. When the temperature of the dinitrate solution in the crystallizer 101 decreases, most of the dinitrate has been crystallized. At this time, the automation system will open the mother liquor discharge pipeline valve to discharge the uncrystallized mother liquor to the crystallization mother liquor tank 2. The liquid level sensor of the crystallization mother liquor tank 2 monitors the liquid level in real time. When the liquid level reaches the upper limit, the mother liquor pump 7 is started to pump the mother liquor from the crystallization mother liquor tank 2 to the 70 product tank. This operation ensures that the mother liquor can be processed in time and reduces the loss of materials, and also prepares for subsequent processing steps; S3: Material heating and discharging: After the mother liquor is discharged, the mother liquor pipe valve is closed, the low-temperature water valve is closed, and the steam valve is opened to keep the steam temperature at 120°C ± 5°C. The circulating water is heated by the crystallization plate heat exchanger B5. After the circulating water temperature is raised to 80°C ± 3°C, it is transported to the crystallizer 101 through the crystallization circulating water pump 6, and the material in the crystallizer 101 is heated to 60°C ± 2°C to ensure that the dinitrate in the crystallizer 101 is completely melted; S4: secondary crystallization: the material in the first-level finished product tank 3 is sequentially fed into the second crystallizer 102, the third crystallizer 103, the fourth crystallizer 104 and the fifth crystallizer 105, and a secondary crystallization operation is performed in the second crystallizer 102, the third crystallizer 103, the fourth crystallizer 104 and the fifth crystallizer 105, and the temperature is controlled to be gradually reduced to improve the purity of dinitrate and ensure the crystallization efficiency and product purity; S5: Collection of secondary finished products: After the secondary crystallization operation of crystallizer four 104 and crystallizer five 105 is completed, the material flows into the secondary finished product tank 9. When the preset liquid level is reached, the flow is automatically stopped, and the secondary finished product pump 10 is started to transport the material to the 99 product tank. After the secondary crystallization operation of crystallizer four 104 and crystallizer five 105 is completed, the material will flow into the secondary finished product tank 9. At this time, the liquid level monitoring system of the secondary finished product tank 9 will automatically detect the liquid level, and when the liquid level reaches the preset high limit, the inflow of materials will be automatically stopped. Then, the secondary finished product pump 10 is started to transport the high-purity dinitrate in the secondary finished product tank 9 to the 99 product tank. This operation ensures that the final product can be smoothly transferred and stored, providing a high-purity dinitrate product for final packaging and processing.

[0023] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the application should be included in the protection scope of the present application.

Claims

1. A dinitrate crystal purification device, comprising a purification device body (1), characterized in that: The purification device body (1) comprises a crystallizer 1 (101), a crystallizer 2 (102), a crystallizer 3 (103), a crystallizer 4 (104), a crystallizer 5 (105), a circulating water tank (8), a crystallization circulating water pump (6), a crystallization plate heat exchanger A (4), a crystallization plate heat exchanger B (5), a crystallization mother liquid tank (2), a primary finished product tank (3) and a secondary finished product tank (9), wherein the crystallizer 1 (101), the crystallizer 2 (102), the crystallizer 3 (103), the crystallizer 4 (104), the crystallizer 5 (105), a circulating water tank (8), a crystallization circulating water pump (6), a crystallization plate heat exchanger A (4), a crystallization plate heat exchanger B (5), a crystallization mother liquid tank (2), a primary finished product tank (3) and a secondary finished product tank (9). The crystallizer 1 (104) and the crystallizer 5 (105) are respectively connected to a circulating water tank (8), a crystallization circulating water pump (6), a crystallization plate heat exchanger A (4) and a crystallization plate heat exchanger B (5); the discharge port of the crystallizer 1 (101) is connected to the crystallization mother liquor tank (2) through a pipeline, the discharge port of the crystallization mother liquor tank (2) is connected to the primary finished product tank (3), and the discharge ports of the crystallizer 4 (104) and the crystallizer 5 (105) are respectively connected to the secondary finished product tank (9) through pipelines.

2. A dinitrate crystallization purification device according to claim 1, characterized in that: The crystallizer 1 (101), the crystallizer 2 (102), the crystallizer 3 (103), the crystallizer 4 (104) and the crystallizer 5 (105) are all connected to the corresponding circulating water tank (8) through a pipeline, and the circulating water tank (8) is used to store and provide circulating water.

3. A dinitrate crystallization purification device according to claim 1, characterized in that: The crystallization circulating water pump (6) is used to pump circulating water from the circulating water tank (8) into the crystallizer 1 (101) to cool or heat the material in the crystallizer 1 (101); The crystallization plate heat exchanger A (4) is connected to the crystallization circulating water pump (6) and is used to cool the circulating water with low-temperature water, and the cooling temperature range is 30-50°C; The crystallization plate heat exchanger B (5) is connected to the crystallization circulating water pump (6) and is used to heat the circulating water by steam, with the heating temperature ranging from 45 to 85°C.

4. A dinitrate crystallization purification device according to claim 1, characterized in that: The discharge port of the crystallization mother liquid tank (2) is connected to a mother liquid pump (7), and the mother liquid pump (7) is used to transport the mother liquid in the crystallization mother liquid tank (2) to a product tank 70; The discharge port of the first-level finished product tank (3) is connected to the second-level finished product tank (9) through a pipeline, and the discharge port of the second-level finished product tank (9) is connected to the second-level finished product pump (10), and the second-level finished product pump (10) is used to transport the material in the second-level finished product tank (9) to the 99 product tank.

5. A dinitrate crystallization purification process, implemented according to the dinitrate crystallization purification device according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: Feeding and initial crystallization: The dinitrogen raw material is fed into the crystallizer 1 (101) through the feed pump. When the liquid level reaches the upper limit, the feeding is stopped, the crystallization circulation water pump (6) of the crystallizer 1 (101) is started, and the low-temperature water valve in the crystallization plate heat exchanger A (4) is opened to cool the material in the crystallizer 1 (101); S2: Mother liquor discharge: When the temperature of the dinitrate solution in the crystallizer 1 (101) decreases and most of the dinitrate has been crystallized, the valve of the mother liquor discharge pipeline is automatically opened, and the unsolidified mother liquor flows into the crystallization mother liquor tank (2); when the liquid level of the crystallization mother liquor tank (2) reaches the upper limit, the mother liquor pump (7) is started to transport the mother liquor to the product tank 70; S3: Material heating and discharging: After the mother liquor is discharged, the mother liquor pipe valve is closed, the low-temperature water valve is closed, and the steam valve is opened to keep the steam temperature at 120°C ± 5°C. The circulating water is heated by the crystallization plate heat exchanger B (5) to raise the circulating water temperature to 80°C ± 3°C, and then the circulating water is transported to the crystallizer 1 (101) through the crystallization circulating water pump (6). The material in the crystallizer 1 (101) is heated to 60°C ± 2°C to ensure that the dinitrate in the crystallizer 1 (101) is completely melted; S4: secondary crystallization: the material in the first-stage finished product tank (3) is fed into the second crystallizer (102), the third crystallizer (103), the fourth crystallizer (104) and the fifth crystallizer (105) in sequence, and secondary crystallization is performed in the second crystallizer (102), the third crystallizer (103), the fourth crystallizer (104) and the fifth crystallizer (105), and the temperature is controlled to be gradually lowered to improve the purity of dinitrate and ensure the crystallization efficiency and product purity; S5: Secondary finished product collection: After the secondary crystallization operation of crystallizer four (104) and crystallizer five (105) is completed, the material flows into the secondary finished product tank (9). When the preset liquid level is reached, the flow is automatically stopped and the secondary finished product pump (10) is started to transport the material to the 99 product tank.

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