Continuous crystallization process and equipment for large-particle ammonium sulfate

Abstract

The invention relates to the technical field of ammonium sulfate evaporative crystallization, in particular to a continuous crystallization process and equipment for large-particle ammonium sulfate, and the equipment comprises an MVR evaporative crystallization unit, an evaporation-cooling coupling crystallization unit and a solid-liquid separation-retreatment unit; the MVR evaporative crystallization unit comprises a vapor compressor, an ammonia gas absorption tower, an evaporation chamber, a fine grain culture chamber, a first forced circulation heat exchange pump, a first heat exchanger and a fine grain extraction pump; the evaporation-cooling coupling crystallization unit comprises a flash chamber, a large-particle crystal raising chamber, a second forced circulation heat exchange pump, a second heat exchanger, a fine crystal circulating pump and a large-particle extraction pump; an ammonium sulfate solution is subjected to fractional crystallization through the MVR evaporative crystallization unit and the evaporation-cooling coupling crystallization unit, the MVR evaporative crystallization unit firstly performs primary crystallization on an ammonium sulfate raw material, then fine crystals are conveyed to the evaporation-cooling coupling crystallization unit for secondary crystallization, and the generated crystals are uniform in particle size distribution and uniform in particle size distribution. And continuous production of large-particle ammonium sulfate crystals is realized.

Description

Technical Field

[0001] The invention relates to the technical field of ammonium sulfate evaporation and crystallization, and in particular to a continuous crystallization process and equipment for large-particle ammonium sulfate. Background Art

[0002] Large-particle ammonium sulfate is a fertilizer and industrial raw material with a specific physical form and application advantages. Its particle size is typically between 2-5mm. Compared to traditional powdered or small-particle products, it has good fluidity, is less prone to agglomeration, and has long-lasting fertilizer effects. It is often used as a basic nitrogen source and combined with phosphorus and potassium fertilizers to produce high-concentration compound fertilizers, thereby increasing product added value. Ferric phosphate is primarily produced by the reaction of ferrous sulfate and ammonium phosphate. The production process produces large amounts of sulfate and ammonium ions, which exactly constitute the chemical composition of ammonium sulfate, eliminating the need for additional nitrogen and sulfur resources. Pretreatment and membrane concentration remove calcium, magnesium, iron, aluminum, calcium phosphate, and other nutrients, providing the raw materials for the formation of ammonium sulfate crystals.

[0003] MVR, or mechanical vapor recompression, works by compressing low-temperature steam through a compressor, raising its temperature and pressure, increasing its enthalpy. The steam then enters a heat exchanger to exchange heat with the material, fully utilizing the steam's latent heat. This eliminates the need for additional raw steam during the evaporation process, reducing external steam consumption, resulting in energy savings and increased steam utilization by over 40%. MVR reduces operating costs by replacing steam input with electrical power.

[0004] The main ammonium sulfate crystallization processes include evaporation crystallization and cooling crystallization. Evaporation crystallization can achieve high yields, but the product quality is poor, with rod-shaped or even needle-shaped crystals. Cooling crystallization produces better crystal habit and larger particle size, but the solubility of ammonium sulfate changes slowly with temperature, resulting in a low yield using cooling crystallization. By effectively combining the advantages of evaporation crystallization and cooling crystallization, large ammonium sulfate crystals with a high yield and stable morphology can be obtained.

[0005] In order to increase the proportion of large-particle ammonium sulfate products with a size of 2-4 mm, Chinese patent CN115520880A crystallizes an ammonium sulfate liquid to be crystallized in the presence of heterogeneous seed particles to obtain a mixed liquid containing small particles and medium-sized or larger crystals; the obtained mixed liquid is then separated once or multiple times to obtain an ammonium sulfate crystal mixed liquid and small-particle ammonium sulfate crystals; the obtained ammonium sulfate crystal mixed liquid is then crystallized to obtain large-particle ammonium sulfate crystals; crystals with a particle size distribution of 2-4 mm can only be obtained through multiple separations and crystallizations, and the operation process is cumbersome, making it difficult to achieve continuous production.

[0006] Chinese patent CN114832424A proposes a crystallization system in which an evaporation chamber for boiling and evaporating water from the slurry and a crystallization chamber for growing slurry crystals are connected in series. Two independent heating systems are set on the evaporation concentrator and crystallizer devices, and raw steam needs to be continuously added to maintain the operation of the system. The energy consumption required by the evaporation system is relatively large. The main particle size of ammonium sulfate crystals is 1-2.5mm, accounting for more than 72%, and the number of large-particle crystals with a crystal particle size distribution of 2-4mm is relatively small.

[0007] Traditional crystallization systems require preheated and highly concentrated raw materials, resulting in slow crystal growth, uneven crystal size distribution, and the inability to add crystallization aids. These factors make it difficult to achieve the continuous crystallization of large-particle ammonium sulfate. Therefore, the challenge of continuously producing large-particle ammonium sulfate from low-concentration ferric phosphate wastewater using an evaporation-cooling crystallization system is a pressing issue. Summary of the Invention

[0008] The object of the present invention is to provide a continuous crystallization process and equipment for large-particle ammonium sulfate, which has a high content of large-particle ammonium sulfate crystals, so as to solve the problems of low quality and small crystal size of large-particle ammonium sulfate products obtained in the prior art.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A continuous crystallization device for large-particle ammonium sulfate, comprising an MVR evaporation crystallization unit, an evaporation-cooling coupled crystallization unit, and a solid-liquid separation-reprocessing unit; the MVR evaporation crystallization unit comprises a steam compressor, an ammonia absorption tower, an evaporation chamber, a fine crystal growth chamber, a first forced circulation heat exchange pump, a first heat exchanger, and a fine crystal extraction pump; the evaporation-cooling coupled crystallization unit comprises a flash chamber, a large-particle growth chamber, a second forced circulation heat exchange pump, a second heat exchanger, a fine crystal circulation pump, and a large-particle extraction pump; the inlet of the ammonia absorption tower is connected to the top of the evaporation chamber, and the bottom of the evaporation chamber is connected to the fine crystal growth chamber; the inlet side of the first forced circulation heat exchange pump is connected to one side of the top of the fine crystal growth chamber, and the outlet side is connected to the tube-side inlet of the first heat exchanger, and the tube-side outlet of the first heat exchanger is connected to one side of the evaporation chamber; The inlet side of the steam compressor is connected to the air outlet of the ammonia absorption tower, and the outlet side is connected to the shell side inlet of the first heat exchanger; the inlet side of the fine crystal extraction pump is connected to the bottom of the fine crystal cultivation chamber, and the outlet side is connected to one side of the large particle cultivation chamber; the top of the flash chamber is connected to the vacuum system, and the bottom of the flash chamber is connected to the large particle cultivation chamber; the inlet side of the fine crystal circulation pump is connected to one side of the top of the large particle cultivation chamber, and the outlet side is connected to the evaporation chamber; the inlet side of the second forced circulation heat exchange pump is connected to one side of the top of the large particle cultivation chamber, and the outlet side is connected to the tube side inlet of the second heat exchanger, and the tube side outlet of the second heat exchanger is connected to one side of the flash chamber; the inlet side of the large particle extraction pump is connected to the bottom of the large particle cultivation chamber, and the outlet side is connected to the solid-liquid separation-reprocessing unit.

[0011] As a further improvement, the solid-liquid separation-reprocessing unit includes a thick cooler, a centrifuge, a mother liquor tank, a mother liquor pump, a sedimentation tank, and a clear liquid pump; the outlet side of the large particle extraction pump is connected to the feed port of the thick cooler; the inlet of the centrifuge is connected to the discharge port of the thick cooler, the liquid material outlet of the centrifuge is connected to the mother liquor tank, and the solid material outlet is connected to the vibrating fluidized bed; the inlet side of the mother liquor pump is connected to the mother liquor tank, and the outlet side is connected to the sedimentation tank; the inlet side of the clear liquid pump is connected to the sedimentation tank, and the outlet side is connected to the evaporation chamber; the sedimentation tank is provided with a flocculant addition port; and a filter is provided on the outlet pipeline of the clear liquid pump.

[0012] As a further improvement, the MVR evaporation crystallization unit also includes a condensate tank and a condensate pump, the shell side outlet of the first heat exchanger is connected to the condensate tank, the inlet side of the condensate pump is connected to the condensate tank, and the outlet side is connected to the shell side inlet of the second heat exchanger; the MVR evaporation crystallization unit also includes a centrifugal pump, the inlet side of the centrifugal pump is connected to the top side of the fine crystal growing chamber, and the outlet side is connected to the flash chamber.

[0013] As a further improvement, a liquid feed port is provided on the outlet side pipeline of the tube side of the first heat exchanger; and a solid feed port is provided on the top of the fine crystal growing chamber.

[0014] As a further improvement, the inner diameter of the large particle growing chamber decreases gradually from top to bottom.

[0015] As a further improvement, a plurality of extraction ports at different heights are provided on the lower side wall of the large particle crystal growing chamber, and the plurality of extraction ports are all connected to the inlet side of the large particle extraction pump, and an ultrasonic solid content detector is provided on the extraction port.

[0016] A continuous crystallization process for large-particle ammonium sulfate, using the continuous crystallization equipment for granular ammonium sulfate, comprises the following steps:

[0017] S1, concentrated ammonium sulfate solution is obtained from pretreated ferric phosphate wastewater as raw material, part of the raw material is transported to the fine crystal growth chamber of the MVR evaporation crystallization unit to start crystallization operation; the remaining part of the raw material is transported to the large particle growth chamber of the evaporation-cooling coupled crystallization unit;

[0018] In step S2, the solution in the fine crystal incubation chamber is transported to the first heat exchanger through the first forced circulation heat exchange pump, and then flows to the evaporation chamber for heat exchange. The saturated solution is continuously evaporated and concentrated in the evaporation chamber to form crystal nuclei in the fine crystal incubation chamber and continuously grows. During the process, the steam generated in the evaporation chamber is passed through the ammonia absorption tower to recover the ammonia in the steam. The steam then enters the steam compressor and is heated by secondary steam compression to serve as the heat source for the first heat exchanger.

[0019] S3, the solid-liquid mixture in the fine crystal growing chamber is transported to the large particle growing chamber by the fine crystal extraction pump, and then circulated in the flash chamber and the large particle growing chamber by the second forced circulation heat exchange pump, and then the vacuum system on the top of the flash chamber is turned on, and the concentrated solution is evaporated for a second time by the operation of the vacuum system, and the crystals fall into the large particle growing chamber, grow in the large particle growing chamber and settle in the large particle growing chamber, and the crystals with smaller particles and the ammonium sulfate solution continue to circulate and grow in the flash chamber and the large particle growing chamber by the second forced circulation heat exchange pump, and the fine crystals that fail to grow are transported to the evaporation chamber by the fine crystal circulation pump;

[0020] S4, the crystals settled at the bottom of the large-particle crystal cultivation chamber are transported to a thick cooler by a large-particle extraction pump, where they are cooled and slowly stirred to ensure slow growth of the crystal particles, solidification of the crystals, and prevent adhesion of the crystals; the crystals settled in the thick cooler enter a centrifuge, and the ammonium sulfate solution after centrifugal separation enters a mother liquor tank for temporary storage. The separated large-particle ammonium sulfate crystals enter a vibrating fluidized bed, and the dried large-particle ammonium sulfate crystals are the product;

[0021] S5, the ammonium sulfate solution temporarily stored in the mother liquor tank is transported to the sedimentation tank through the mother liquor pump, a flocculant is added to the sedimentation tank and filtered to remove some impurities in the solution that affect crystal growth, and the clear liquid is transported to the evaporation chamber through the clear liquid pump to continue evaporation and concentration.

[0022] As a further improvement, the proportion of raw materials in S1 entering the fine grain growing chamber is 80%-100%, and the proportion entering the large grain growing chamber is 0-20%.

[0023] As a further improvement, the temperature of the ammonium sulfate solution in the evaporation chamber of S2 is 85-95°C; the temperature of the ammonium sulfate solution in the fine crystal growth chamber of S2 is 80-90°C; the temperature of the ammonium sulfate solution in the flash chamber of S3 is 70-80°C; the temperature of the ammonium sulfate solution in the large particle growth chamber of S3 is 65-75°C; the temperature of the ammonium sulfate solution in the thick cooler of S4 is 55-65°C.

[0024] As a further improvement, the vacuum degree of the flash chamber in S3 is -25kPa to -50kPa.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention performs fractional crystallization on the ammonium sulfate solution through an MVR evaporation crystallization unit and an evaporation-cooling coupled crystallization unit. The MVR evaporation crystallization unit first performs primary crystallization on the ammonium sulfate raw material, and then transports the fine crystals to the evaporation-cooling coupled crystallization unit for secondary crystallization. Finally, a small amount of fine crystals suspended in the large-particle crystal cultivation chamber are extracted and sent to the MVR evaporation crystallization unit for crystallization. The circulation system solves the problem of material accumulation in the central tube of a single crystallization unit. At the same time, the establishment of the evaporation-cooling coupled crystallization unit makes it easier to control the crystallization temperature and rate, while effectively improving the large-particle rate of crystallization, making the growth of ammonium sulfate crystals more stable, and the generated crystals have a uniform particle size distribution, thereby realizing the continuous production of large-particle ammonium sulfate crystals.

[0027] 2. The inner diameter of the large-particle crystal growing chamber of the present invention decreases gradually from top to bottom, forming flow velocity differences at different positions in the large-particle crystal growing chamber, allowing crystals of different particle sizes to be distributed gradiently from bottom to top. Crystals with small particle sizes continue to grow in a cycle in the crystallization chamber, and large-particle crystals are extracted at multiple extraction ports to ensure uniform and stable crystal particle size during continuous production.

[0028] 3. The present invention sets a solid feed port at the top of the fine crystal growth chamber, and adds small-particle ammonium sulfate crystals after centrifugal drying as seed crystals to increase the crystallization rate; at the same time, a sedimentation tank is set after the mother liquor tank, and by adding flocculants and setting a filtering device, the influence of impurities on crystallization is reduced during the system circulation process, thereby improving the quality of large-particle ammonium sulfate crystals;

[0029] 4. The present invention utilizes the MVR evaporation crystallization unit and uses the condensed water from the first heat exchanger as the heat source for the second heat exchanger, thereby greatly reducing energy consumption. Compared with the traditional evaporator, the temperature difference is much smaller, and the crystals after two evaporation crystallizations are cooled and crystallized in the thick cooler and then grow again, thereby maximizing the particle size and morphology of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 It is a structural diagram of an embodiment of the present invention;

[0032] Figure 2 2 is a schematic structural diagram of an MVR evaporation crystallization unit according to an embodiment of the present invention;

[0033] Figure 3 Schematic diagram of the structure of a fine grain growing chamber and a large grain growing chamber according to an embodiment of the present invention;

[0034] Figure 4 2 is a schematic structural diagram of an evaporation-cooling coupled crystallization unit and a solid-liquid separation-reprocessing unit according to an embodiment of the present invention;

[0035] Figure 5 1 is a flow chart of a continuous crystallization process for large-particle ammonium sulfate according to an embodiment of the present invention.

[0036] In the figure: 101-evaporation chamber; 102-fine crystal growth chamber; 103-first heat exchanger; 104-first forced circulation heat exchange pump; 105-steam compressor; 106-ammonia absorption tower; 107-condensate tank; 108-condensate pump; 110-centrifugal pump; 111-fine crystal extraction pump; 112-liquid feed port; 113-solid feed port; 114-first central pipe; 201-flash chamber; 202-large particle growth chamber; 203-second heat exchanger; 204-second forced circulation heat exchange pump; 205-thick cooler; 206-centrifuge; 207-mother liquor tank; 208-sedimentation tank; 209-fine crystal circulation pump; 210-large particle extraction pump; 211-mother liquor pump; 212-clear liquid pump; 213-extraction port; 214-second central pipe. DETAILED DESCRIPTION

[0037] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0038] like Figures 1 to 5 As shown, a continuous crystallization equipment for large-particle ammonium sulfate includes an MVR evaporation crystallization unit, an evaporation-cooling coupled crystallization unit, and a solid-liquid separation-reprocessing unit.

[0039] The MVR evaporation crystallization unit includes a steam compressor 105, an ammonia absorption tower 106, a condensed water tank 107, a condensed water pump 108, an evaporation chamber 101, a fine crystal growth chamber 102, a first forced circulation heat exchange pump 104, a first heat exchanger 103, and a fine crystal extraction pump 111.

[0040] The evaporation-cooling coupled crystallization unit includes a flash chamber 201 , a large particle crystal growing chamber 202 , a second forced circulation heat exchange pump 204 , a second heat exchanger 203 , a fine crystal circulation pump 209 , and a large particle extraction pump 210 .

[0041] The solid-liquid separation-reprocessing unit includes a thick cooler 205 , a centrifuge 206 , a mother liquor tank 207 , a mother liquor pump 211 , a sedimentation tank 208 , and a clear liquid pump 212 .

[0042] The entire equipment uses 40% ammonium sulfate solution produced by ferric phosphate production as raw material, which is transported to the MVR evaporation crystallization unit and the evaporation-cooling coupled crystallization unit.

[0043] The inlet of the ammonia absorption tower 106 is connected to the top of the evaporation chamber 101, and the bottom of the evaporation chamber 101 is connected to the fine crystal growth chamber 102. The bottom of the evaporation chamber 101 is connected to the first central tube 114, and the first central tube 114 extends downward to the bottom of the fine crystal growth chamber 102; the inlet side of the first forced circulation heat exchange pump 104 is connected to the top side of the fine crystal growth chamber 102, and the outlet side is connected to the tube side inlet of the first heat exchanger 103, and the tube side outlet of the first heat exchanger 103 is connected to one side of the evaporation chamber 101; the inlet side of the steam compressor 105 is connected to the air outlet of the ammonia absorption tower 106, and the outlet side is connected to the shell side inlet of the first heat exchanger 103. The steam after absorbing ammonia in the ammonia absorption tower 106 is The first heat exchanger 103 provides a heat source; the shell side outlet of the first heat exchanger 103 is connected to the condensate tank 107, the inlet side of the condensate pump 108 is connected to the condensate tank 107, and the outlet side is connected to the shell side inlet of the second heat exchanger 203. The condensate generated by the first heat exchanger 103 is temporarily stored in the condensate tank 107, and then sent to the second heat exchanger 203 of the evaporation-cooling coupled crystallization unit by the condensate pump 108 to provide a heat source for it; the inlet side of the fine crystal production pump 111 is connected to the bottom of the fine crystal growth chamber 102, and the outlet side is connected to one side of the large particle growth chamber 202. A plurality of production pipelines of different heights are arranged at the bottom of the fine crystal growth chamber 102, and the plurality of production pipelines are all connected to the inlet side of the fine crystal production pump 111.

[0044] The top of the flash chamber 201 is connected to the vacuum system, the bottom of the flash chamber 201 is connected to the large particle crystal growing chamber 202, the bottom of the flash chamber 201 is connected to the second central tube 214, and the second central tube 214 extends downward to the bottom of the large particle crystal growing chamber 202; the inlet side of the fine crystal circulation pump 209 is connected to the top side of the large particle crystal growing chamber 202, and the outlet side is connected to the evaporation chamber 101, and the outlet side of the fine crystal circulation pump 209 is connected to the outlet side of the evaporation chamber 101 through pipelines. One side of the bottom and one side of the upper end of the first central tube 114; the inlet side of the second forced circulation heat exchange pump 204 is connected to the top side of the large particle crystal growing chamber 202, and the outlet side is connected to the tube side inlet of the second heat exchanger 203, and the tube side outlet of the second heat exchanger 203 is connected to one side of the flash chamber 201. The connection position of the inlet side of the second forced circulation heat exchange pump 204 and the large particle crystal growing chamber 202 is lower than the connection position of the fine crystal circulation pump 209 and the large particle crystal growing chamber 202.

[0045] The inlet side of the large particle extraction pump 210 is connected to the bottom of the large particle crystal cultivation chamber 202, and the outlet side is connected to the feed port at the top of the thick cooler 205. The lower part of the large particle crystal cultivation chamber 202 is provided with multiple extraction ports 213 of different heights. The multiple extraction ports 213 are all connected to the inlet side of the large particle extraction pump 210. An ultrasonic solid content detector is provided on the extraction port 213. The inlet of the centrifuge 206 is connected to the discharge port at the bottom of the thick cooler 205. The liquid material of the centrifuge 206 is connected to the discharge port at the bottom of the thick cooler 205. The outlet is connected to the mother liquor tank 207, and the solid material outlet is connected to the vibrating fluidized bed; the inlet side of the mother liquor pump 211 is connected to the mother liquor tank 207, and the outlet side is connected to the sedimentation tank 208; the inlet side of the clear liquid pump 212 is connected to the sedimentation tank 208, and the outlet side is connected to the evaporation chamber 101. The outlet body of the clear liquid pump 212 is connected to the pipeline on the inlet side of the first forced circulation heat exchange pump 104 through a pipeline, and the sedimentation tank 208 transports the clear liquid to the MVR evaporation crystallization unit through the clear liquid pump 212.

[0046] A liquid feed port 112 is provided on the outlet side pipeline of the first heat exchanger 103 for adding liquid crystallization aid to the system; a solid feed port 113 is provided on the top of the fine crystal growing chamber 102 for adding crystal seeds or solid crystallization aid; a flocculant addition port is provided on the top of the sedimentation tank 208, which can be used to add flocculants or pH regulators to the mother liquor generated during the crystallization process, to remove impurities in the mother liquor and improve the crystallization environment.

[0047] The evaporation chamber 101, the flash chamber 201, the fine crystal growth chamber 102 and the large particle growth chamber 202 are all provided with multiple sight glasses to facilitate observation of the internal crystal growth conditions; a No. 1 stirring device is provided in the thick cooler 205; a No. 2 stirring device is provided in the mother liquor tank 207; a No. 3 stirring device is provided in the sedimentation tank 208; and a filter is provided on the outlet side pipeline of the clear liquid pump 212.

[0048] The MVR evaporation crystallization unit also includes a centrifugal pump 110, the inlet side of the centrifugal pump 110 is connected to the top side of the fine crystal growing chamber 102, and the outlet side is connected to the pipeline on the tube side outlet of the second heat exchanger 203. The connection position of the centrifugal pump 110 and the fine crystal growing chamber 102 is higher than the connection position of the inlet side of the first forced circulation heat exchange pump 104 and the fine crystal growing chamber 102. The clear liquid on the upper layer of the fine crystal growing chamber 102 is transported to the tube side outlet pipeline of the second heat exchanger 203 through the centrifugal pump 110.

[0049] A No. 1 electromagnetic flowmeter is installed on the outlet side pipeline of the fine crystal extraction pump 111 to monitor the flow rate of the ammonium sulfate solid-liquid mixture transported to the large particle crystallization system after the primary crystallization. The flow rate is related to the system operation status and the flow rate range is 7-10m 3 / h; for example: 7m 3 / h、8m 3 / h、9m3 / h、10m 3 / h. A No. 2 electromagnetic flowmeter is installed on the outlet pipeline of the fine crystal circulation pump 209, with a control range of 3-5m 3 / h; for example: 3m 3 / h、3.5m 3 / h、4m 3 / h、4.5m 3 / h、5m 3 / h. A No. 3 electromagnetic flowmeter is installed on the outlet pipeline of the large particle extraction pump 210, with a control range of 4-6m 3 / h; for example: 4m 3 / h、4.5m 3 / h、5m 3 / h、5.5m 3 / h、6m 3 In this solution, the flow rate at each location is controlled by adjusting the frequency conversion of the pump connected to its pipeline.

[0050] In this scheme, the large particle extraction flow rate is determined by the number of crystals in the large particle crystal growing chamber 202. By extracting large particle crystals, better growth space can be provided for subsequent crystals. Therefore, real-time extraction of large particle crystals is crucial to the continuous operation of the entire device.

[0051] The temperature control of each stage of the crystallization operation mainly relies on heat exchangers and evaporation control, and the temperature difference is small. The temperature of the ammonium sulfate solution in the evaporation chamber 101 is 85-95°C, such as 85°C, 88°C, 93°C, and 95°C. The temperature of the ammonium sulfate solution in the fine crystal growth chamber 102 is 80-90°C, such as 80°C, 83°C, 86°C, and 90°C. The temperature of the ammonium sulfate solution in the flash chamber 201 is 70-80°C, such as 70°C, 73°C, 76°C, and 80°C. The temperature of the ammonium sulfate solution in the large particle growth chamber 202 is 65-75°C, such as 65°C, 68°C, 72°C, and 75°C.

[0052] The liquid level control range of evaporation chamber 101 is 50%-80%, for example: 50%, 60%, 70%, 80%. In this solution, the liquid level in evaporation chamber 101 is kept within the control range by controlling the feed rate of the raw liquid, the flow rate of the fine crystal extraction pump 111, and the flow rate of the fine crystal circulation pump 209. The liquid level control range of flash chamber 201 is 50%-70%, for example: 50%, 55%, 60%, 65%, 70%. In this solution, the liquid level of flash chamber 201 is controlled by the flow rate at the outlet of the fine crystal extraction pump 111, the flow rate at the outlet of the fine crystal circulation pump 209, and the flow rate at the outlet of the large particle extraction pump 210, ensuring that the crystallization process has sufficient saturated solution to provide driving force for crystal growth.

[0053] The vacuum system at the top of the flash chamber 201 is mainly used to adjust the vacuum degree to control the evaporation rate. The vacuum degree is controlled between -20kPa and -50kPa; for example: -20kPa, -30kPa, -40kPa, -50kPa.

[0054] As large crystals are extracted and transported to thickening cooler 205, they pass through an ultrasonic solids detector installed at extraction port 213. This real-time measurement of the extracted solids content helps control the percentage of large crystals removed, within a range of 25%-40% (e.g., 25%, 30%, 35%, or 40%). The solids content is controlled by adjusting the valve opening of extraction port 213, and the extraction rate is stabilized by using extraction ports 213 at different locations, ensuring continuous operation and preventing pipeline blockage due to excessive large particles, which could affect the system's continuous operation.

[0055] Large crystals are transported to thickening cooler 205 via large crystal extraction pump 210, where they are slowly stirred to prevent crystal adhesion and the temperature is slowly lowered to ensure slow crystal growth. As the large crystals settle to the bottom of thickening cooler 205, the supernatant flows through the overflow port into mother liquor tank 207 for temporary storage.

[0056] Large crystals that settle to the bottom of the thick cooler 205 flow through a pipe with a controllable valve to the centrifuge 206, where they undergo solid-liquid separation. The liquid flows into the mother liquor tank 207 for temporary storage. The solids are then piped into a vibrating fluidized bed for drying to obtain large ammonium sulfate crystals. This solution screens these crystals, and smaller crystals are used as seeds, which are added through the solid additive inlet of the fine crystal incubation chamber 102, significantly accelerating crystal formation.

[0057] The ammonium sulfate solution temporarily stored in the mother liquor tank 207 is transported to the sedimentation tank 208 through the mother liquor pump 211, and flocculant is added thereto to effectively reduce the content of impurity ions in the circulated ammonium sulfate solution. The ammonium sulfate solution after impurity removal is then transported to the fine crystal growth chamber 102 through the clear liquid pump 212 for crystallization.

[0058] In this embodiment, the flow rate and temperature of each device affect each other, and it is necessary to pay attention to different indicators simultaneously to ensure continuous production of the device. The particle size distribution of the large-particle ammonium sulfate product obtained in this embodiment is 65-85% in the range of 2-4 mm.

[0059] Example 1

[0060] Step 1: The pretreated iron phosphate wastewater is used to obtain a 40% ammonium sulfate solution as raw material, and 90% of it is transported to the fine crystal growth chamber 102 of the MVR evaporation crystallization unit to start the crystallization operation; 10% of the raw materials are transported to the large particle growth chamber 202 of the evaporation-cooling coupled crystallization unit.

[0061] Step 2: The solution in the fine crystal growing chamber 102 is transported to the first heat exchanger 103 through the first forced circulation heat exchange pump 104, and then flows to the evaporation chamber 101 after heat exchange. A saturated solution is formed through continuous evaporation and concentration. The saturated solution produces crystal nuclei in the fine crystal growing chamber 102 and continues to grow. In order to promote crystal growth, manganese sulfate is added to the fine crystal growing chamber 102 as a crystallization aid. During the process, the steam generated in the evaporation chamber 101 passes through the ammonia absorption tower 106 to recover the ammonia in the steam, and then the steam enters the steam compressor 105. After secondary steam compression and heating, it is used as the heat source of the first heat exchanger 103, continuously providing driving force for the evaporation chamber 101.

[0062] Step three: transport the solid-liquid mixture in the fine crystal growing chamber 102 to the large particle growing chamber 202 through the fine crystal extraction pump 111, and then circulate the solid-liquid mixture in the flash chamber 201 and the large particle growing chamber 202 through the second forced circulation heat exchange pump 204, and then turn on the vacuum system on the top of the flash chamber, and evaporate the concentrated solution for the second time through the operation of the vacuum system. The crystals are settled at the bottom of the large particle growing chamber 202 through the second central tube 214 connecting the flash chamber 201 and the large particle growing chamber 202, and the smaller crystals and the ammonium sulfate solution continue to circulate and grow in the flash chamber 201 and the large particle growing chamber 202 through the second forced circulation heat exchange pump 204. The fine crystals that have not grown up and are located in the upper layer of the large particle growing chamber 202 are transported to the evaporation chamber 101 through the fine crystal circulation pump 209.

[0063] Step 4: The crystals settled at the bottom of the large-particle crystal growing chamber 202 are transported to the thick cooler 205 through the large-particle extraction pump 210, and are cooled and slowly stirred to ensure that the crystal particles grow slowly while preventing the crystals from sticking together; the crystals settled in the thick cooler 205 enter the centrifuge 206, and the ammonium sulfate solution after centrifugal separation enters the mother liquor tank 207 for temporary storage. The separated large-particle ammonium sulfate crystals enter the vibrating fluidized bed, and the dried large-particle ammonium sulfate crystals are the product.

[0064] Step 5: The ammonium sulfate solution temporarily stored in the mother liquor tank 207 is transported to the sedimentation tank 208 through the mother liquor pump 211, and Al2(SO4)3 is added to the sedimentation tank as a flocculant to remove Fe in the solution. 3+ The plasma is filtered and the clear liquid is transported to the inlet of the first forced circulation heat exchange pump 104 through the clear liquid pump 212, and continues to be evaporated and concentrated in the evaporation chamber 101 to ensure continuous operation of the system.

[0065] The temperature of the ammonium sulfate solution in the evaporation chamber 101 in S2 is 91.2°C; the temperature of the ammonium sulfate solution in the fine crystal growth chamber 102 in S2 is 87.4°C; the temperature of the ammonium sulfate solution in the flash chamber 201 in S3 is 79.1°C; the temperature of the ammonium sulfate solution in the large particle growth chamber 202 in S3 is 73.9°C; the temperature of the ammonium sulfate solution in the thick cooler 205 in S4 is 62.7°C; the vacuum degree of the flash chamber 201 in S3 is -47.2kPa.

[0066] In this embodiment, by controlling 10% of the raw materials to enter the large particle crystal growing chamber 202, the concentration of the solution in the large particle crystal growing chamber 202 can be effectively controlled, so that the crystallization process proceeds more smoothly.

[0067] In this embodiment, by adding crystal seeds into the fine crystal growing chamber 102, the growth time of the crystal is greatly shortened and the crystallization efficiency is improved.

[0068] In this embodiment, Al2(SO4)3 is added to the sedimentation tank 208 as a flocculant to 3+ Impurities that affect crystallization are removed to ensure that the accumulation of impurity ions does not affect the crystal quality during the cycle.

[0069] The evaporation chamber 101 and the fine crystal growth chamber 102 mainly carry out primary crystallization, and the obtained ammonium sulfate crystals have a particle size greater than 1 mm, accounting for 97.3%. Then the crystals obtained in the primary crystallization process are transported to the flash chamber 201 and the large-particle crystal growth chamber 202 for secondary crystallization operation, and finally large-particle ammonium sulfate crystals with a particle size greater than 2 mm, accounting for 78.4%. Then, the large-particle ammonium sulfate product can be obtained through centrifugal separation and vibration fluidized bed drying.

[0070] Example 2

[0071] Step 1: The pretreated iron phosphate wastewater is used to obtain a 40% ammonium sulfate solution as raw material, and 87% of it is transported to the fine crystal growth chamber 102 of the MVR evaporation crystallization unit to start the crystallization operation; 13% of the raw material is transported to the large particle growth chamber 202 of the evaporation-cooling coupled crystallization unit.

[0072] Step 2: The solution in the fine crystal growing chamber 102 is transported to the first heat exchanger 103 through the first forced circulation heat exchange pump 104, and then flows to the evaporation chamber 101 after heat exchange. A saturated solution is formed through continuous evaporation and concentration. The saturated solution produces crystal nuclei in the fine crystal growing chamber 102 and continues to grow. In order to promote crystal growth, manganese sulfate is added to the fine crystal growing chamber 102 as a crystallization aid. During the process, the steam generated in the evaporation chamber 101 passes through the ammonia absorption tower 106 to recover the ammonia in the steam, and then the steam enters the steam compressor 105. After secondary steam compression and heating, it is used as the heat source of the first heat exchanger 103, continuously providing driving force for the evaporation chamber 101.

[0073] Step three: transport the solid-liquid mixture in the fine crystal growing chamber 102 to the large particle growing chamber 202 through the fine crystal extraction pump 111, and then circulate the solid-liquid mixture in the flash chamber 201 and the large particle growing chamber 202 through the second forced circulation heat exchange pump 204, and then turn on the vacuum system on the top of the flash chamber, and evaporate the concentrated solution for the second time through the operation of the vacuum system. The crystals are settled at the bottom of the large particle growing chamber 202 through the second central tube 214 connecting the flash chamber 201 and the large particle growing chamber 202, and the smaller crystals and the ammonium sulfate solution continue to circulate and grow in the flash chamber 201 and the large particle growing chamber 202 through the second forced circulation heat exchange pump 204. The fine crystals that have not grown up and are located in the upper layer of the large particle growing chamber 202 are transported to the evaporation chamber 101 through the fine crystal circulation pump 209.

[0074] Step 4: The crystals settled at the bottom of the large-particle crystal growing chamber 202 are transported to the thick cooler 205 through the large-particle extraction pump 210, and are cooled and slowly stirred to ensure that the crystal particles grow slowly while preventing the crystals from sticking together; the crystals settled in the thick cooler 205 enter the centrifuge 206, and the ammonium sulfate solution after centrifugal separation enters the mother liquor tank 207 for temporary storage. The separated large-particle ammonium sulfate crystals enter the vibrating fluidized bed, and the dried large-particle ammonium sulfate crystals are the product.

[0075] Step 5: The ammonium sulfate solution temporarily stored in the mother liquor tank 207 is transported to the sedimentation tank 208 through the mother liquor pump 211, and Al2(SO4)3 is added to the sedimentation tank as a flocculant to remove Fe in the solution. 3+ The plasma is filtered and the clear liquid is transported to the inlet of the first forced circulation heat exchange pump 104 through the clear liquid pump 212, and continues to be evaporated and concentrated in the evaporation chamber 101 to ensure continuous operation of the system.

[0076] The temperature of the ammonium sulfate solution in the evaporation chamber 101 in S2 is 88.9°C; the temperature of the ammonium sulfate solution in the fine crystal growth chamber 102 in S2 is 84.1°C; the temperature of the ammonium sulfate solution in the flash chamber 201 in S3 is 74.5°C; the temperature of the ammonium sulfate solution in the large particle growth chamber 202 in S3 is 69.0°C; the temperature of the ammonium sulfate solution in the thick cooler 205 in S4 is 60.3°C; the vacuum degree of the flash chamber 201 in S3 is -37.6 kPa.

[0077] In this embodiment, by controlling 13% of the raw materials to enter the large-particle crystal growing chamber 202, the concentration of the solution in the large-particle crystal growing chamber 202 can be effectively controlled, so that the crystallization process proceeds more smoothly.

[0078] In this embodiment, by adding crystal seeds into the fine crystal growing chamber 102, the growth time of the crystal is greatly shortened and the crystallization efficiency is improved.

[0079] In this embodiment, Al2(SO4)3 is added to the sedimentation tank 208 as a flocculant to 3+ Impurities that affect crystallization are removed to ensure that the accumulation of impurity ions does not affect the crystal quality during the cycle.

[0080] The evaporation chamber 101 and the fine crystal growth chamber 102 mainly carry out primary crystallization, and most of the ammonium sulfate crystals obtained have a particle size greater than 1 mm, accounting for 96.4%. Then the crystals obtained in the primary crystallization process are transported to the flash chamber 201 and the large-particle crystal growth chamber 202 for secondary crystallization operation, and finally large-particle ammonium sulfate crystals with a particle size greater than 2 mm, accounting for 73.5%. Then, large-particle ammonium sulfate products can be obtained through centrifugal separation and vibrating fluidized bed drying.

[0081] Example 3

[0082] Step 1: The pretreated iron phosphate wastewater is used to obtain a 40% ammonium sulfate solution as raw material, and 80% of it is transported to the fine crystal growth chamber 102 of the MVR evaporation crystallization unit to start the crystallization operation; 20% of the raw materials are transported to the large particle growth chamber 202 of the evaporation-cooling coupled crystallization unit.

[0083] Step 2: The solution in the fine crystal growing chamber 102 is transported to the first heat exchanger 103 through the first forced circulation heat exchange pump 104, and then flows to the evaporation chamber 101 after heat exchange. A saturated solution is formed through continuous evaporation and concentration. The saturated solution produces crystal nuclei in the fine crystal growing chamber 102 and continues to grow. In order to promote crystal growth, manganese sulfate is added to the fine crystal growing chamber 102 as a crystallization aid. During the process, the steam generated in the evaporation chamber 101 passes through the ammonia absorption tower 106 to recover the ammonia in the steam, and then the steam enters the steam compressor 105. After secondary steam compression and heating, it is used as the heat source of the first heat exchanger 103, continuously providing driving force for the evaporation chamber 101.

[0084] Step three: transport the solid-liquid mixture in the fine crystal growing chamber 102 to the large particle growing chamber 202 through the fine crystal extraction pump 111, and then circulate the solid-liquid mixture in the flash chamber 201 and the large particle growing chamber 202 through the second forced circulation heat exchange pump 204, and then turn on the vacuum system on the top of the flash chamber, and evaporate the concentrated solution for the second time through the operation of the vacuum system. The crystals are settled at the bottom of the large particle growing chamber 202 through the second central tube 214 connecting the flash chamber 201 and the large particle growing chamber 202, and the smaller crystals and the ammonium sulfate solution continue to circulate and grow in the flash chamber 201 and the large particle growing chamber 202 through the second forced circulation heat exchange pump 204. The fine crystals that have not grown up and are located in the upper layer of the large particle growing chamber 202 are transported to the evaporation chamber 101 through the fine crystal circulation pump 209.

[0085] Step 4: The crystals settled at the bottom of the large-particle crystal growing chamber 202 are transported to the thick cooler 205 through the large-particle extraction pump 210, and are cooled and slowly stirred to ensure that the crystal particles grow slowly while preventing the crystals from sticking together; the crystals settled in the thick cooler 205 enter the centrifuge 206, and the ammonium sulfate solution after centrifugal separation enters the mother liquor tank 207 for temporary storage. The separated large-particle ammonium sulfate crystals enter the vibrating fluidized bed, and the dried large-particle ammonium sulfate crystals are the product.

[0086] Step 5: The ammonium sulfate solution temporarily stored in the mother liquor tank 207 is transported to the sedimentation tank 208 through the mother liquor pump 211, and Al2(SO4)3 is added to the sedimentation tank as a flocculant to remove Fe in the solution. 3+ The plasma is filtered and the clear liquid is transported to the inlet of the first forced circulation heat exchange pump 104 through the clear liquid pump 212, and continues to be evaporated and concentrated in the evaporation chamber 101 to ensure continuous operation of the system.

[0087] The temperature of the ammonium sulfate solution in the evaporation chamber 101 in S2 is 86.3°C; the temperature of the ammonium sulfate solution in the fine crystal growth chamber 102 in S2 is 83.1°C; the temperature of the ammonium sulfate solution in the flash chamber 201 in S3 is 74.1°C; the temperature of the ammonium sulfate solution in the large particle growth chamber 202 in S3 is 68.3°C; the temperature of the ammonium sulfate solution in the thick cooler 205 in S4 is 64.2°C; the vacuum degree of the flash chamber 201 in S3 is -41.4 kPa.

[0088] In this embodiment, by controlling 20% of the raw materials to enter the large particle crystal growing chamber 202, the concentration of the solution in the large particle crystal growing chamber 202 can be effectively controlled, so that the crystallization process can proceed more smoothly.

[0089] In this embodiment, by adding crystal seeds into the fine crystal growing chamber 102, the growth time of the crystal is greatly shortened and the crystallization efficiency is improved.

[0090] In this embodiment, Al2(SO4)3 is added to the sedimentation tank 208 as a flocculant to 3+ Impurities that affect crystallization are removed to ensure that the accumulation of impurity ions does not affect the crystal quality during the cycle.

[0091] The evaporation chamber 101 and the fine crystal growth chamber 102 mainly carry out primary crystallization, and most of the ammonium sulfate crystals obtained have a particle size greater than 1 mm, accounting for 91.5%. Then the crystals obtained in the primary crystallization process are transported to the flash chamber 201 and the large-particle crystal growth chamber 202 for secondary crystallization operation, and finally large-particle ammonium sulfate crystals with a particle size greater than 2 mm, accounting for 68.3%. Then, large-particle ammonium sulfate products can be obtained through centrifugal separation and vibration fluidized bed drying.

[0092] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A continuous crystallization device for large-particle ammonium sulfate, characterized in that: It includes MVR evaporation crystallization unit, evaporation-cooling coupled crystallization unit, solid-liquid separation-reprocessing unit; The MVR evaporation crystallization unit comprises a steam compressor (105), an ammonia absorption tower (106), an evaporation chamber (101), a fine crystal cultivation chamber (102), a first forced circulation heat exchange pump (104), a first heat exchanger (103), and a fine crystal extraction pump (111); The evaporation-cooling coupled crystallization unit comprises a flash chamber (201), a large particle crystal cultivation chamber (202), a second forced circulation heat exchange pump (204), a second heat exchanger (203), a fine crystal circulation pump (209), and a large particle extraction pump (210); The inlet of the ammonia absorption tower (106) is communicated with the top of the evaporation chamber (101), and the bottom of the evaporation chamber (101) is communicated with the fine crystal growing chamber (102); the inlet side of the first forced circulation heat exchange pump (104) is communicated with one side of the top of the fine crystal growing chamber (102), and the outlet side is communicated with the tube side inlet of the first heat exchanger (103), and the tube side outlet of the first heat exchanger (103) is communicated with one side of the evaporation chamber (101); the inlet side of the steam compressor (105) is communicated with the gas outlet of the ammonia absorption tower (106), and the outlet side is communicated with the shell side inlet of the first heat exchanger (103); the inlet side of the fine crystal extraction pump (111) is communicated with the bottom of the fine crystal growing chamber (102), and the outlet side is communicated with one side of the large particle growing chamber (202); The top of the flash chamber (201) is connected to the vacuum system, and the bottom of the flash chamber (201) is connected to the large particle crystal growing chamber (202); the inlet side of the fine crystal circulation pump (209) is connected to one side of the top of the large particle crystal growing chamber (202), and the outlet side is connected to the evaporation chamber (101); the inlet side of the second forced circulation heat exchange pump (204) is connected to one side of the top of the large particle crystal growing chamber (202), and the outlet side is connected to the pipe side inlet of the second heat exchanger (203), and the pipe side outlet of the second heat exchanger (203) is connected to one side of the flash chamber (201); the inlet side of the large particle extraction pump (210) is connected to the bottom of the large particle crystal growing chamber (202), and the outlet side is connected to the solid-liquid separation-reprocessing unit.

2. The continuous crystallization device for large-particle ammonium sulfate according to claim 1, wherein: The solid-liquid separation-reprocessing unit includes a thick cooler (205), a centrifuge (206), a mother liquor tank (207), a mother liquor pump (211), a sedimentation tank (208), and a clear liquid pump (212); the outlet side of the large particle extraction pump (210) is connected to the feed port of the thick cooler (205); the inlet of the centrifuge (206) is connected to the discharge port of the thick cooler (205), and the liquid material outlet of the centrifuge (206) is connected to the The mother liquor tank (207) is connected, and the solid material outlet is connected to the vibrating fluidized bed; the inlet side of the mother liquor pump (211) is connected to the mother liquor tank (207), and the outlet side is connected to the sedimentation tank (208); the inlet side of the clear liquid pump (212) is connected to the sedimentation tank (208), and the outlet side is connected to the evaporation chamber (101); the sedimentation tank (208) is provided with a flocculant addition port; and a filter is provided on the outlet side pipeline of the clear liquid pump (212).

3. The continuous crystallization device for large-particle ammonium sulfate according to claim 1, wherein: The MVR evaporation crystallization unit also includes a condensate tank (107) and a condensate pump (108), the shell-side outlet of the first heat exchanger (103) is connected to the condensate tank (107), the inlet side of the condensate pump (108) is connected to the condensate tank (107), and the outlet side is connected to the shell-side inlet of the second heat exchanger (203); the MVR evaporation crystallization unit also includes a centrifugal pump (110), the inlet side of the centrifugal pump (110) is connected to the top side of the fine crystal growth chamber (102), and the outlet side is connected to the flash chamber (201).

4. The continuous crystallization device for large-particle ammonium sulfate according to claim 1, wherein: A liquid feed port (112) is provided on the pipe line at the outlet side of the first heat exchanger (103); and a solid feed port (113) is provided on the top of the fine crystal nurturing chamber (102).

5. The continuous crystallization device for large-particle ammonium sulfate according to claim 1, wherein: The inner diameter of the large particle growing chamber (202) decreases gradually from top to bottom.

6. The continuous crystallization device for large-particle ammonium sulfate according to claim 1, wherein: A plurality of extraction ports (213) at different heights are provided on the lower side wall of the large particle crystal growing chamber (202), and the plurality of extraction ports (213) are all connected to the inlet side of the large particle extraction pump (210). An ultrasonic solid content detector is provided on the extraction port (213).

7. A continuous crystallization process for large-particle ammonium sulfate, using the continuous crystallization equipment for large-particle ammonium sulfate according to any one of claims 1 to 6, characterized in that: The process includes the following steps: S1, using ammonium sulfate solution obtained from pretreated iron phosphate wastewater as raw material, part of the raw material is transported to the fine crystal growth chamber (102) of the MVR evaporation crystallization unit to start the crystallization operation; the remaining part of the raw material is transported to the large particle growth chamber (202) of the evaporation-cooling coupled crystallization unit; S2, the solution in the fine crystal growth chamber (102) is transported to the first heat exchanger (103) through the first forced circulation heat exchange pump (104) and flows to the evaporation chamber (101) after heat exchange, and is continuously evaporated and concentrated in the evaporation chamber (101) to form a saturated solution. The saturated solution generates crystal nuclei in the fine crystal growth chamber (102) and continuously grows; during the process, the steam generated in the evaporation chamber (101) passes through the ammonia absorption tower (106) to recover ammonia in the steam, and then the steam enters the steam compressor (105), and is heated by secondary steam compression to serve as a heat source for the first heat exchanger (103); S3, the solid-liquid mixture in the fine crystal growing chamber (102) is transported to the large particle growing chamber (202) through the fine crystal extraction pump (111), and then the solid-liquid mixture is circulated in the flash chamber (201) and the large particle growing chamber (202) through the second forced circulation heat exchange pump (204), and then the vacuum system on the top of the flash chamber (201) is turned on, and the concentrated solution is evaporated for a second time through the operation of the vacuum system, and the crystals fall into the large particle growing chamber (202), grow in the large particle growing chamber (202) and settle in the large particle growing chamber (202), and the crystals with smaller particles continue to circulate and grow together with the ammonium sulfate solution in the flash chamber (201) and the large particle growing chamber (202) through the second forced circulation heat exchange pump (204), and the fine crystals that fail to grow are transported to the evaporation chamber (101) through the fine crystal circulation pump (209); S4, the crystals settled at the bottom of the large-particle crystal cultivation chamber (202) are transported to the thick cooler (205) through the large-particle extraction pump (210), and are subjected to cooling and slow stirring in the thick cooler (205) to ensure that the crystal particles grow slowly and solidify under cold conditions, while preventing the crystals from sticking together; the crystals settled in the thick cooler (205) enter the centrifuge (206), and the ammonium sulfate solution after centrifugal separation enters the mother liquor tank (207) for temporary storage, and the separated large-particle ammonium sulfate crystals enter the vibrating fluidized bed, and the dried large-particle ammonium sulfate crystals are the product; In step S5, the ammonium sulfate solution temporarily stored in the mother liquor tank (207) is transported to the sedimentation tank (208) via the mother liquor pump (211). A flocculant is added to the sedimentation tank and filtered to remove some impurities in the solution that affect crystal growth. The clear liquid is transported to the evaporation chamber (101) via the clear liquid pump (212) to continue evaporation and concentration.

8. The continuous crystallization process for large-particle ammonium sulfate according to claim 7, wherein: The proportion of the raw materials in S1 entering the fine grain crystal growing chamber (102) is 80%-100%, and the proportion entering the large grain crystal growing chamber (202) is 0-20%.

9. The continuous crystallization process for large-particle ammonium sulfate according to claim 7, wherein: The temperature of the ammonium sulfate solution in the evaporation chamber (101) in S2 is 85-95°C; the temperature of the ammonium sulfate solution in the fine crystal growth chamber (102) in S2 is 80-90°C; the temperature of the ammonium sulfate solution in the flash chamber (201) in S3 is 70-80°C; the temperature of the ammonium sulfate solution in the large particle growth chamber (202) in S3 is 65-75°C; and the temperature of the ammonium sulfate solution in the thick cooler (205) in S4 is 55-65°C.

10. The continuous crystallization process for large-particle ammonium sulfate according to claim 7, wherein: The vacuum degree of the flash chamber (201) in S3 is -25 kPa to -50 kPa.

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