Ammonium sulfate wastewater treatment system and method thereof

Abstract

This invention discloses an ammonium sulfate wastewater treatment system and method, comprising an ammonium sulfate wastewater storage tank for collecting ammonium sulfate wastewater; a calcium hydroxide preparation system for preparing calcium hydroxide solution; an evaporator and a first circulating heater for reacting and evaporating the ammonium sulfate wastewater and calcium hydroxide; a first crystallizer and a second circulating heater, a second crystallizer, and a third circulating heater for two-stage evaporation and crystallization; the final concentrated liquid is filtered and flows into a mother liquor collection tank for convenient wastewater treatment, while the evaporated ammonia gas is absorbed by a cooling absorption tower and a condensate collection tank to form ammonia water; the condensate from the second heat exchanger, the first circulating heater, the second circulating heater, and the third circulating heater is also returned to the condensate collection tank. This wastewater treatment system and method distill and crystallizes ammonium sulfate wastewater with calcium hydroxide solution, thereby recovering calcium sulfate and ammonia water, thus achieving waste utilization.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to an ammonium sulfate wastewater treatment system and method. Background Technology

[0002] The industrial production and utilization of ammonium sulfate generates a large amount of ammonium sulfate wastewater, which easily leads to water environment deterioration. Therefore, the discharge of ammonium sulfate wastewater is strictly restricted. Thus, how to treat ammonium sulfate wastewater is a technical problem that urgently needs to be solved by those skilled in the art. Currently, ammonium sulfate wastewater is generally mixed directly with other wastewater and then treated using activated sludge or biological methods. However, this often results in excessive ammonia nitrogen levels in the wastewater, increasing the difficulty of wastewater treatment. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an ammonium sulfate wastewater treatment system, which distills and crystallizes ammonium sulfate wastewater with calcium hydroxide solution to recover calcium sulfate and ammonia water, thereby realizing waste utilization.

[0004] Another technical problem to be solved by the present invention is to provide a method for treating ammonium sulfate wastewater, which uses the above-mentioned ammonium sulfate wastewater treatment system and can recover calcium sulfate and ammonia water, thereby realizing waste utilization.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: an ammonium sulfate wastewater treatment system, comprising...

[0006] An ammonium sulfate wastewater storage tank is used to collect ammonium sulfate wastewater. The storage tank is connected to the wastewater inlet of a first heat exchanger via a first wastewater delivery pipeline. The wastewater outlet of the first heat exchanger is connected to the wastewater inlet of a second heat exchanger. The wastewater outlet of the second heat exchanger is connected to the wastewater inlet of an evaporator via a first liquid inlet pipeline. The second heat exchanger also has a steam inlet, a steam outlet, and a condensate outlet. A first bottom circulation pipeline is provided at the bottom of the evaporator, connecting to the bottom of the tube side of a first circulating heater. The top of the evaporator is connected to the steam inlet of the second heat exchanger via a steam return pipeline. The steam outlet of the second heat exchanger is connected to the main steam return pipe. The top of the tube side of the first circulating heater is connected to the top of the evaporator via a first top circulation pipeline. The shell-side inlet of the first circulating heater is connected to the steam supply system. The shell-side outlet of the first circulating heater is connected to the main steam return pipe.

[0007] A first crystallizer and a second circulating heater are connected. The bottom of the first crystallizer is connected to the bottom tube side of the second circulating heater via a second bottom circulating pipe. The concentrated liquid outlet on the evaporator is connected to the second bottom circulating pipe via a first concentrated liquid outlet pipe. The top of the tube side of the second circulating heater is connected to the top of the first crystallizer via a second top circulating pipe. The shell side inlet of the second circulating heater is connected to the steam supply system. The shell side outlet of the second circulating heater is connected to the steam return main pipe.

[0008] A second crystallizer and a third circulating heater are connected. The bottom of the second crystallizer is connected to the bottom tube side of the third circulating heater via a third bottom circulating pipe. The concentrated liquid outlet of the first crystallizer is connected to the third bottom circulating pipe via a second concentrated liquid outlet pipe. The top of the tube side of the third circulating heater is connected to the top of the second crystallizer via a third top circulating pipe. The shell side inlet of the third circulating heater is connected to the steam outlet at the top of the first crystallizer. The shell side outlet of the third circulating heater and the top steam outlet of the second crystallizer are both connected to a steam reflux main pipe. The steam reflux main pipe is connected to the steam inlet of the first heat exchanger, and the outlet of the first heat exchanger is connected to a negative pressure system. The third bottom circulating pipe is connected to a concentrated liquid drain pipe, which is connected to a filter and a mother liquor collection tank.

[0009] The cooling absorption tower and the condensate collection tank are connected together. The steam reflux main pipe is connected to the cooling absorption tower. The bottom of the cooling absorption tower is connected to the condensate collection tank through the condensate outlet pipe. The condensate collection tank is connected to the top spray port of the cooling absorption tower through the condensate circulation pipeline.

[0010] The condensate outlet of the second heat exchanger is connected to the inlet of the third circulating heater through a condensate outlet pipe. The outlet of the first circulating heater is connected to the inlet of the second circulating heater through a first outlet pipe. The outlet of the second circulating heater is connected to the inlet of the third circulating heater through a second outlet pipe. The outlet of the third circulating heater is connected to the cooling pool through a third outlet pipe.

[0011] A calcium hydroxide preparation system is used to prepare a calcium hydroxide solution, and the calcium hydroxide preparation system is connected to an evaporator, a first crystallizer, and a second crystallizer.

[0012] Preferably, the treatment system further includes a third heat exchanger, the wastewater inlet of which is connected to the wastewater outlet of the first heat exchanger, the wastewater outlet of which is connected to the wastewater inlet of the second heat exchanger, and the liquid inlet and liquid outlet of the third heat exchanger are connected to the third liquid outlet pipe. Therefore, the heat energy in the condensate can be fully utilized by the third heat exchanger to further enhance the heat exchange of the ammonium sulfate wastewater and improve the heat energy utilization efficiency.

[0013] Preferably, the wastewater outlet on the second heat exchanger is connected to the top of the first crystallizer via a second liquid inlet pipe. Therefore, a portion of the wastewater after heat exchange in the second heat exchanger can also enter the first crystallizer for evaporation and crystallization, thereby improving the efficiency of evaporation and crystallization.

[0014] Preferably, the top of the evaporator is also connected to the shell-side inlet of the first circulating heater via a steam reuse pipeline, thus reusing the energy in the steam evaporated by the evaporator and further improving the energy utilization rate.

[0015] Preferably, the calcium hydroxide preparation system includes a calcium hydroxide preparation tank, which is equipped with a stirring device. The outlet of the calcium hydroxide preparation tank is connected to a calcium hydroxide solution storage tank via a calcium hydroxide delivery pipeline. The calcium hydroxide solution storage tank is equipped with an aeration device. The calcium hydroxide solution storage tank is connected to an evaporator, a first crystallizer, and a second crystallizer via calcium hydroxide solution supply branch pipelines. Each calcium hydroxide solution supply branch pipeline is equipped with a flow meter. The calcium hydroxide is prepared and stirred before being fed into the calcium hydroxide solution storage tank. Aeration and stirring in the calcium hydroxide solution storage tank prevent sedimentation. The saturated solution can then be easily fed into the evaporator, the first crystallizer, and the second crystallizer. Furthermore, the flow rate can be accurately controlled by the flow meter, thereby precisely controlling the pH value.

[0016] After adopting the above technical solution, the effects of this invention are as follows: In this treatment system, wastewater and calcium hydroxide solution enter the evaporator according to the ratio. The evaporator and the first circulating heater circulate and heat the evaporator, thereby releasing hot ammonia. The calcium sulfate obtained from the reaction flows into the first crystallizer with the concentrate, while the condensate flows into the final condensate collection tank for collection and is used to circulate and absorb ammonia to form ammonia water. The concentrate is then concentrated and crystallized again in the first and second crystallizers. The P value during evaporation and crystallization is precisely controlled to facilitate the generation of ammonia. Finally, the ammonia is absorbed by spraying to form ammonia water, which can be used for desulfurization and denitrification in power plants. After filtration, the calcium sulfate in the concentrate can be used for gypsum production, while the liquid can re-enter a conventional wastewater treatment system. This separates the ammonia from the ammonium sulfate, reducing the difficulty of subsequent wastewater treatment, and also recovers calcium sulfate and ammonia water.

[0017] To solve the second technical problem mentioned above, the solution of the present invention is: a method for treating ammonium sulfate wastewater, which uses the aforementioned ammonium sulfate wastewater treatment system and includes the following steps:

[0018] S1. Collect ammonium sulfate wastewater into an ammonium sulfate wastewater storage tank; prepare calcium hydroxide solution using a calcium hydroxide preparation system;

[0019] S2. The ammonium sulfate wastewater undergoes a first heat exchange with the steam in the steam return main pipe in the first heat exchanger, and then enters the second heat exchanger for a second heat exchange with the steam discharged from the top of the evaporator. Finally, it enters the evaporator in a measured amount. Calcium hydroxide solution is metered into the evaporator to react with the ammonium sulfate wastewater. The pH value in the evaporator is monitored and controlled between 9 and 10. The concentrated liquid after the reaction circulates between the tube side of the first circulating heater and the evaporator. Part of the steam evaporated in the evaporator enters the shell side of the second circulating heater, and the other part enters the second heat exchanger.

[0020] S3. The concentrated liquid after evaporation enters the circulating evaporation crystallization process between the first crystallizer and the second circulating heater through the second bottom circulation pipeline. Calcium hydroxide solution is added to the first crystallizer as needed to control the pH value between 9 and 10. The shell side of the second circulating heater is also heated by the steam supply system. The concentrated liquid in the tube side of the second circulating heater is sent to the first crystallizer. The condensate in the first circulating heater enters the second circulating heater through the first outlet pipe.

[0021] S4. Steam from the top of the first crystallizer is supplied to the shell side of the third circulating heater; the concentrated liquid after concentration in the first crystallizer enters the circulating evaporation crystallization process between the second crystallizer and the third circulating heater through the third bottom circulation pipe; calcium hydroxide solution is added to the second crystallizer as needed to control the pH value between 9 and 10; the condensate from the second circulating heater enters the third circulating heater through the second outlet pipe; the condensate from the second heat exchanger also enters the third circulating heater through the condensate outlet pipe.

[0022] S5. The steam from the top of the second crystallizer, the steam from the first circulating heater, the second circulating heater, and the third circulating heater are fed into the steam reflux main pipe and finally enter the cooling absorption tower for cooling before being collected in the condensate collection tank; the concentrated liquid at the bottom of the second crystallizer is filtered by a filter and then collected in the mother liquor collection tank; the outlet of the third circulating heater is connected to the cooling tank through the third outlet pipe.

[0023] Preferably, after the first heat exchange and before the second heat exchange, the ammonium sulfate wastewater undergoes enhanced heat exchange. After the first heat exchange, the ammonium sulfate wastewater enters the third heat exchanger and undergoes enhanced heat exchange with the condensate discharged from the third circulating heater. The cooling water after heat exchange in the third heat exchanger flows into the cooling pool. The condensate from the first heat exchanger also flows into the third heat exchanger.

[0024] After adopting the above technical solution, the effect of the present invention is as follows: The treatment method uses the above treatment system to react ammonium sulfate wastewater with calcium hydroxide, and separates and recovers ammonia and calcium sulfate by heating and evaporation crystallization. It makes full use of heat energy while controlling the pH value of the evaporation and crystallization reaction, which is more conducive to the generation of ammonia and also conducive to the crystallization and dehydration of calcium sulfate. The final concentrated liquid has a low ammonia content, so it does not affect the subsequent sewage treatment. Attached Figure Description

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] Figure 1 This is a partial system diagram of an embodiment of the present invention;

[0027] Figure 2 This is a system diagram of the remaining part of the system in an embodiment of the present invention;

[0028] In the attached diagram: 1. Calcium hydroxide preparation tank; 2. Stirring device; 3. Calcium hydroxide solution storage tank; 4. Aeration device; 5. Ammonium sulfate wastewater storage tank; 6. First wastewater conveying pipeline; 7. Wastewater conveying pump; 8. First heat exchanger; 9. Second heat exchanger; 10. First inlet pipeline; 11. Evaporator; 12. First bottom circulation pipeline; 13. First circulation heater; 14. First top circulation pipeline; 15. Steam supply system; 16. Steam reuse pipeline; 17. Steam return main pipe; 18. Second inlet pipeline; 19. First crystallizer; 20. Second circulation heater; 21. Second bottom circulation pipeline; 22. First concentrate outlet pipeline; 23. Second top circulation pipeline; 24. Second concentrate outlet pipeline; 25. Third bottom circulation pipeline; 26. Third top circulation pipeline; 27. Vacuum pump; 28. Concentrate drain pipe; 29. ​​Filter; 30. Mother liquor collection tank; 31. Condensate collection tank; 32. Third heat exchanger; 33. Cooling absorption tower; 34. Condensate outlet pipe; 35. First outlet pipe; 36. Second outlet pipe; 37. Third outlet pipe; 38. Wastewater flow meter; 39. Calcium hydroxide supply main pipe; 40. Second crystallizer; 41. Third circulating heater; 42. Condensate outlet pipe; 43. Condensate circulation pipeline. Detailed Implementation

[0029] The present invention will be further described in detail below through specific embodiments.

[0030] like Figure 1 and Figure 2 As shown, Figure 1 and Figure 2 This diagram illustrates an ammonium sulfate wastewater treatment system.

[0031] Because the system is quite complex, it is divided into... Figure 1 and Figure 2 ,in Figure 1 and Figure 2 The same letters in the diagram represent the same pipe. Specifically, a1 and a2, b1 and b2, c1 and c2, d1 and d21, e1 and e2, f1 and f2, g1 and g2, h1 and h2, and i1 and i2 are two ends cut from a single pipe. In the actual system, they are interconnected.

[0032] An ammonium sulfate wastewater storage tank 5 is used to collect ammonium sulfate wastewater 5. The ammonium sulfate wastewater storage tank 5 is connected to the wastewater inlet of the first heat exchanger 8 through a first wastewater conveying pipe 6. A wastewater flow meter 38 and a wastewater conveying pump 7 are installed on the first wastewater conveying pipe 6. The wastewater outlet of the first heat exchanger 8 is connected to the wastewater inlet of the second heat exchanger 9. The wastewater outlet of the second heat exchanger 9 is connected to the wastewater inlet of the evaporator 11 through a first liquid inlet pipe 10. The second heat exchanger 9 is also provided with a steam inlet, a steam outlet and a condensate outlet. The first heat exchanger 8 and the second heat exchanger 9 are conventional tube-type heat exchangers.

[0033] The bottom of the evaporator 11 is provided with a first bottom circulation pipe 12, which is connected to the bottom of the tube side of the first circulating heater 13. The top of the evaporator 11 is connected to the steam inlet of the second heat exchanger 9 through a steam return pipe 16, and the steam outlet of the second heat exchanger 9 is connected to the steam return main pipe 17. The top of the tube side of the first circulating heater 13 is connected to the top of the evaporator 11 through a first top circulation pipe 14, and the shell side inlet of the first circulating heater 13 is connected to the steam supply system 15. The shell side outlet of the first circulating heater 13 is connected to the steam return main pipe 17.

[0034] A first crystallizer 19 and a second circulating heater 20 are connected. The bottom of the first crystallizer 19 is connected to the bottom tube side of the second circulating heater 20 via a second bottom circulation pipe 21. The concentrated liquid outlet on the evaporator 11 is connected to the second bottom circulation pipe 21 via a first concentrated liquid outflow pipe 22. The top of the tube side of the second circulating heater 20 is connected to the top of the first crystallizer 19 via a second top circulation pipe 23. The shell side inlet of the second circulating heater 20 is connected to the steam supply system 15. The shell side outlet of the second circulating heater 20 is connected to the steam return main pipe 17.

[0035] The second crystallizer 40 and the third circulating heater 41 are connected. The bottom of the second crystallizer 40 is connected to the bottom tube side of the third circulating heater 41 via the third bottom circulation pipe 25. The concentrated liquid outlet of the first crystallizer 19 is connected to the third bottom circulation pipe 25 via the second concentrated liquid outflow pipe 24. The top of the tube side of the third circulating heater 41 is connected to the top of the second crystallizer 40 via the third top circulation pipe 26. The shell side inlet of the third circulating heater 41 is connected to the steam outlet at the top of the first crystallizer 19. The shell side outlet of the third circulating heater 41 and the top steam outlet of the second crystallizer 40 are both connected to the steam return main pipe 17. The steam return main pipe 17 is connected to the steam inlet of the first heat exchanger 8. The outlet of the first heat exchanger 8 is connected to the negative pressure system. The third bottom circulation pipe 25 is connected to a concentrated liquid drain pipe 28, which is connected to a filter 29 and a mother liquor collection tank 30.

[0036] The cooling absorption tower 33 and the condensate collection tank 31 are connected. The steam reflux main pipe 17 is connected to the cooling absorption tower 33. The bottom of the cooling absorption tower 33 is connected to the condensate collection tank 31 through the condensate outlet pipe 42. The condensate collection tank 31 is connected to the top spray port of the cooling absorption tower 33 through the condensate circulation pipe 43. The negative pressure system includes a vacuum pump 27. A gas-liquid separator is also connected to the negative pressure absorption tower. The gas phase port of the gas-liquid separator is connected to the vacuum pump 27, and the liquid phase port is connected to the condensate outlet pipe 42.

[0037] The condensate outlet of the second heat exchanger 9 is connected to the inlet of the third circulating heater through the condensate outlet pipe 34. The outlet of the first circulating heater 13 is connected to the inlet of the second circulating heater 20 through the first outlet pipe 35. The outlet of the second circulating heater 20 is connected to the inlet of the third circulating heater 41 through the second outlet pipe 36. The outlet of the third circulating heater 41 is connected to the cooling pool through the third outlet pipe 37.

[0038] A calcium hydroxide preparation system is used to prepare calcium hydroxide solution. The system is connected to an evaporator 11, a first crystallizer 19, and a second crystallizer 40. The system includes a calcium hydroxide preparation tank 1, which is equipped with a stirring device 2. The outlet of the preparation tank 1 is connected to a calcium hydroxide solution storage tank 3 via a calcium hydroxide delivery pipeline. The storage tank 3 is equipped with an aeration device 4. The storage tank 3 is connected to the evaporator 11, the first crystallizer 19, and the second crystallizer 40 via a main calcium hydroxide supply pipeline 39 and branch calcium hydroxide solution supply pipelines. Each branch pipeline is equipped with a flow meter. The calcium hydroxide, after being prepared and stirred, is fed into the storage tank 3. Aeration and stirring in the storage tank 3 prevent sedimentation. The saturated solution can then be easily fed into the evaporator 11, the first crystallizer 19, and the second crystallizer 40. The flow meters allow for precise control of the incoming flow rate and thus the pH value.

[0039] Among them, such as Figure 2 As shown, the treatment system also includes a third heat exchanger 32. The wastewater inlet of the third heat exchanger 32 is connected to the wastewater outlet of the first heat exchanger 8, and the wastewater outlet of the third heat exchanger 32 is connected to the wastewater inlet of the second heat exchanger 9. The liquid inlet and liquid outlet of the third heat exchanger 32 are connected to the third liquid outlet pipe 37. Therefore, the heat energy in the condensate in the third liquid outlet pipe 37 can be fully utilized by the third heat exchanger 32 to further enhance the heat exchange of ammonium sulfate wastewater and improve the heat energy utilization efficiency.

[0040] The wastewater outlet on the second heat exchanger 9 is connected to the top of the first crystallizer 19 via the second inlet pipe 18. In this way, after the ammonium sulfate wastewater is heated by the second heat exchanger 9, a portion of it can flow into the first crystallizer 19, thereby sharing the evaporation and crystallization pressure of the evaporator 11.

[0041] The top of the evaporator 11 is also connected to the shell-side inlet of the first circulating heater 13 via a steam reuse pipeline 16, thus reusing the energy in the steam evaporated by the evaporator 11 and further improving the energy utilization rate.

[0042] In addition, the present invention also discloses a method for treating ammonium sulfate wastewater, which uses the above-mentioned ammonium sulfate wastewater treatment system and includes the following steps:

[0043] S1. Collect ammonium sulfate wastewater into ammonium sulfate wastewater storage tank 5; prepare calcium hydroxide solution using calcium hydroxide preparation system;

[0044] S2. The ammonium sulfate wastewater undergoes a first heat exchange with the steam in the steam return main pipe 17 in the first heat exchanger 8, and then enters the second heat exchanger 9 for a second heat exchange with the steam discharged from the top of the evaporator 11. Finally, it enters the evaporator 11 in a measured amount. Calcium hydroxide solution is introduced into the evaporator 11 in a measured amount to react with the ammonium sulfate wastewater. The pH value in the evaporator 11 is monitored and controlled between 9 and 10. The concentrated liquid after the reaction circulates between the tube side of the first circulating heater 13 and the evaporator 11. Part of the steam evaporated in the evaporator 11 enters the shell side of the second circulating heater 20, and the other part enters the second heat exchanger 9.

[0045] S3. The concentrated liquid after evaporation 11 enters the circulating evaporation crystallization process between the first crystallizer 19 and the second circulating heater 20 through the second bottom circulation pipe 21. Calcium hydroxide solution is added to the first crystallizer 19 as needed to control the pH value between 9 and 10. The shell side of the second circulating heater 20 is also supplemented with steam from the steam supply system 15 for heating. The concentrated liquid in the tube side of the second circulating heater 20 is sent to the first crystallizer 19. The condensate from the first circulating heater 13 enters the second circulating heater 20 through the first outlet pipe 35.

[0046] S4. Steam from the top of the first crystallizer 19 is supplied to the shell side of the third circulating heater 41. The concentrated liquid from the first crystallizer 19 enters the circulating evaporation crystallization process between the second crystallizer 40 and the third circulating heater 41 through the third bottom circulation pipe 25. Calcium hydroxide solution is added to the second crystallizer 40 as needed to control the pH value between 9 and 10. The condensate from the second circulating heater 20 enters the shell side of the third circulating heater 41 through the second outlet pipe 36. The condensate from the second heat exchanger 9 also enters the shell side of the third circulating heater 41 through the condensate outlet pipe 34.

[0047] S5. Steam from the top of the second crystallizer 40, steam from the first circulating heater 13, the second circulating heater 20, and the third circulating heater 41 are fed into the steam return main pipe 17 and finally enter the cooling absorption tower 33 for cooling, and are then collected by the condensate collection tank 31. The concentrated liquid at the bottom of the second crystallizer 40 is filtered by the filter 29 and then collected by the mother liquor collection tank 30. The outlet of the third circulating heater 41 is connected to the cooling tank through the third outlet pipe 37. The ammonium sulfate wastewater undergoes enhanced heat exchange after the first heat exchange and before the second heat exchange. After the first heat exchange, the ammonium sulfate wastewater enters the third heat exchanger 32 and undergoes enhanced heat exchange with the condensate discharged from the third circulating heater 41. The cooling water after heat exchange in the third heat exchanger 32 flows into the cooling tank. The condensate from the first heat exchanger 8 also flows into the third heat exchanger 32.

[0048] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications and alterations made to the technical solutions of the present invention without departing from the spirit of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. An ammonium sulfate wastewater treatment system, characterized in that: include An ammonium sulfate wastewater storage tank is used to collect ammonium sulfate wastewater. The storage tank is connected to the wastewater inlet of a first heat exchanger via a first wastewater delivery pipeline. The wastewater outlet of the first heat exchanger is connected to the wastewater inlet of a second heat exchanger. The wastewater outlet of the second heat exchanger is connected to the wastewater inlet of an evaporator via a first liquid inlet pipeline. The second heat exchanger also has a steam inlet, a steam outlet, and a condensate outlet. A first bottom circulation pipeline is provided at the bottom of the evaporator, connecting to the bottom of the tube side of a first circulating heater. The top of the evaporator is connected to the steam inlet of the second heat exchanger via a steam return pipeline. The steam outlet of the second heat exchanger is connected to the main steam return pipe. The top of the tube side of the first circulating heater is connected to the top of the evaporator via a first top circulation pipeline. The shell-side inlet of the first circulating heater is connected to the steam supply system. The shell-side outlet of the first circulating heater is connected to the main steam return pipe. A first crystallizer and a second circulating heater are connected. The bottom of the first crystallizer is connected to the bottom tube side of the second circulating heater via a second bottom circulating pipe. The concentrated liquid outlet on the evaporator is connected to the second bottom circulating pipe via a first concentrated liquid outlet pipe. The top of the tube side of the second circulating heater is connected to the top of the first crystallizer via a second top circulating pipe. The shell side inlet of the second circulating heater is connected to the steam supply system. The shell side outlet of the second circulating heater is connected to the steam return main pipe. A second crystallizer and a third circulating heater are connected. The bottom of the second crystallizer is connected to the bottom tube side of the third circulating heater via a third bottom circulating pipe. The concentrated liquid outlet of the first crystallizer is connected to the third bottom circulating pipe via a second concentrated liquid outlet pipe. The top of the tube side of the third circulating heater is connected to the top of the second crystallizer via a third top circulating pipe. The shell side inlet of the third circulating heater is connected to the steam outlet at the top of the first crystallizer. The shell side outlet of the third circulating heater and the top steam outlet of the second crystallizer are both connected to a steam reflux main pipe. The steam reflux main pipe is connected to the steam inlet of the first heat exchanger, and the outlet of the first heat exchanger is connected to a negative pressure system. The third bottom circulating pipe is connected to a concentrated liquid drain pipe, which is connected to a filter and a mother liquor collection tank. The cooling absorption tower and the condensate collection tank are connected together. The steam reflux main pipe is connected to the cooling absorption tower. The bottom of the cooling absorption tower is connected to the condensate collection tank through the condensate outlet pipe. The condensate collection tank is connected to the top spray port of the cooling absorption tower through the condensate circulation pipeline. The condensate outlet of the second heat exchanger is connected to the inlet of the third circulating heater through a condensate outlet pipe. The outlet of the first circulating heater is connected to the inlet of the second circulating heater through a first outlet pipe. The outlet of the second circulating heater is connected to the inlet of the third circulating heater through a second outlet pipe. The outlet of the third circulating heater is connected to the cooling pool through a third outlet pipe. A calcium hydroxide preparation system is used to prepare a calcium hydroxide solution, and the calcium hydroxide preparation system is connected to an evaporator, a first crystallizer, and a second crystallizer.

2. The ammonium sulfate wastewater treatment system as described in claim 1, characterized in that: The treatment system also includes a third heat exchanger, the wastewater inlet of which is connected to the wastewater outlet of the first heat exchanger, the wastewater outlet of which is connected to the wastewater inlet of the second heat exchanger, and the liquid inlet and liquid outlet of the third heat exchanger are connected to the third liquid outlet pipe.

3. The ammonium sulfate wastewater treatment system as described in claim 2, characterized in that: The wastewater outlet on the second heat exchanger is connected to the top of the first crystallizer via a second liquid inlet pipe.

4. The ammonium sulfate wastewater treatment system as described in claim 3, characterized in that: The top of the evaporator is also connected to the shell-side inlet of the first circulating heater via a steam reuse pipeline.

5. The ammonium sulfate wastewater treatment system as described in claim 4, characterized in that: The calcium hydroxide preparation system includes a calcium hydroxide preparation tank, which is equipped with a stirring device. The outlet of the calcium hydroxide preparation tank is connected to a calcium hydroxide solution storage tank via a calcium hydroxide delivery pipeline. The calcium hydroxide solution storage tank is equipped with an aeration device. The calcium hydroxide solution storage tank is connected to an evaporator, a first crystallizer, and a second crystallizer via calcium hydroxide solution supply branch pipelines. Each calcium hydroxide solution supply branch pipeline is equipped with a flow meter.

6. A method for treating ammonium sulfate wastewater, characterized in that: The treatment method uses an ammonium sulfate wastewater treatment system as described in any one of claims 1 to 5, and includes the following steps: S1. Collect ammonium sulfate wastewater into an ammonium sulfate wastewater storage tank; prepare calcium hydroxide solution using a calcium hydroxide preparation system; S2. The ammonium sulfate wastewater undergoes a first heat exchange with the steam in the steam return main pipe in the first heat exchanger, and then enters the second heat exchanger for a second heat exchange with the steam discharged from the top of the evaporator. Finally, it enters the evaporator in a measured amount. Calcium hydroxide solution is metered into the evaporator to react with the ammonium sulfate wastewater. The pH value in the evaporator is monitored and controlled between 9 and 10. The concentrated liquid after the reaction circulates between the tube side of the first circulating heater and the evaporator. Part of the steam evaporated in the evaporator enters the shell side of the second circulating heater, and the other part enters the second heat exchanger. S3. The concentrated liquid after evaporation enters the circulating evaporation crystallization process between the first crystallizer and the second circulating heater through the second bottom circulation pipeline. Calcium hydroxide solution is added to the first crystallizer as needed to control the pH value between 9 and 10. The shell side of the second circulating heater is also heated by the steam supply system. The concentrated liquid in the tube side of the second circulating heater is sent to the first crystallizer. The condensate in the first circulating heater enters the second circulating heater through the first outlet pipe. S4. Steam from the top of the first crystallizer is supplied to the shell side of the third circulating heater; the concentrated liquid from the first crystallizer enters the circulating evaporation crystallization process between the second crystallizer and the third circulating heater through the third bottom circulation pipe; calcium hydroxide solution is added to the second crystallizer as needed to control the pH value between 9 and 10; the condensate from the second circulating heater enters the third circulating heater through the second outlet pipe; the condensate from the second heat exchanger also enters the third circulating heater through the condensate outlet pipe. S5. The steam from the top of the second crystallizer, the steam from the first circulating heater, the second circulating heater, and the third circulating heater are fed into the steam reflux main pipe and finally enter the cooling absorption tower for cooling before being collected in the condensate collection tank; the concentrated liquid at the bottom of the second crystallizer is filtered by a filter and then collected in the mother liquor collection tank; the outlet of the third circulating heater is connected to the cooling tank through the third outlet pipe.

7. The method for treating ammonium sulfate wastewater as described in claim 6, characterized in that: The ammonium sulfate wastewater undergoes enhanced heat exchange after the first heat exchange and before the second heat exchange. After the first heat exchange, the ammonium sulfate wastewater enters the third heat exchanger and undergoes enhanced heat exchange with the condensate discharged from the third circulating heater. The cooling water after heat exchange in the third heat exchanger flows into the cooling pool. The condensate from the first heat exchanger also flows into the third heat exchanger.

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