Ammonium sulfate crystallization wastewater recycling device

Abstract

The utility model relates to the technical field of caprolactam production, and particularly provides an ammonium sulfate crystallization wastewater recycling device which comprises a stripping tower, a wastewater feeding hole is formed in the upper part of the stripping tower, a steam feeding hole is formed in the lower part of the stripping tower, a gas phase outlet is formed in the top of the stripping tower, and the gas phase outlet is connected to a cooler through a pipeline and then connected to a return tank; a gas phase outlet of the reflux tank is connected to an ammonia gas washing tower, a desalted water inlet is formed in the upper part of the ammonia gas washing tower, a discharge port in the lower part of the ammonia gas washing tower is connected with ammonium sulfate crystallization equipment through a pipeline and a discharge pump, and the discharge pump is further connected to the desalted water inlet through a pipeline to form a circulation loop; and a liquid-phase discharge port of the return tank is connected to a return port at the upper part of the stripping tower through a pipeline and a circulating pump. The device can be used for treating the wastewater, recovering ammonia nitrogen in the wastewater and directly recycling the wastewater to an ammonium sulfate neutralization and crystallization process of caprolactam.

Description

Technical Field

[0001] This utility model belongs to the field of caprolactam production technology and relates to a device for recycling ammonium sulfate crystallization wastewater. Background Technology

[0002] Caprolactam is a monomer used in the synthesis of nylon 6 fibers and has wide applications in the field of polymer materials. Currently, the main domestic production process for caprolactam involves the aminooxime conversion of cyclohexanone followed by the Beckmann rearrangement. This process is lengthy and complex, producing numerous byproducts, including a high yield of ammonium sulfate, resulting in poor economic viability of the raw materials. In this process, the crystallization and neutralization reaction is a crucial step, and the large amount of wastewater generated from this reaction, with an ammonia nitrogen content of approximately 1600 mg / L, cannot be directly utilized.

[0003] Currently, the treatment of high ammonia nitrogen wastewater mainly employs a combined physiochemical and biological approach. The physiochemical method primarily uses physical and chemical methods to treat high-concentration ammonia nitrogen wastewater, without needing to consider the toxic effects of the wastewater on microorganisms. This mainly includes methods such as stripping, membrane separation, breakpoint chlorination, chemical precipitation, sulfuric acid absorption, and chemical oxidation. However, these methods generally suffer from high equipment investment, high energy consumption, and high operating costs, hindering their further development.

[0004] CN 117263416 A discloses a device and method for treating caprolactam wastewater. The wastewater is fed into a wet oxidation reactor for pretreatment to remove most of the COD. Then, it is filtered through a membrane and then enters the wet oxidation reactor again. Under the action of high temperature, high pressure, oxygen and catalyst, the COD and ammonia nitrogen in the wastewater are removed. Finally, ammonia nitrogen is removed by electrodialysis. The method is costly and the ammonia nitrogen cannot be recovered. Summary of the Invention

[0005] This invention provides a device for recycling ammonium sulfate crystallization wastewater, which can treat the wastewater, recover the ammonia nitrogen, and directly reuse it in the ammonium sulfate neutralization and crystallization process of caprolactam.

[0006] The technical solution of this utility model is to provide a wastewater recovery and utilization device for ammonium sulfate crystallization, including a stripping tower with a wastewater inlet at the top, a steam inlet at the bottom, and a gas phase outlet at the top. The gas phase outlet is connected to a cooler via a pipeline, and then to a reflux tank. The gas phase outlet of the reflux tank is connected to an ammonia scrubbing tower. The ammonia scrubbing tower has a demineralized water inlet at the top, and its lower outlet is connected to an ammonium sulfate crystallization device via a pipeline and a discharge pump. The discharge pump is also connected to the demineralized water inlet via a pipeline to form a circulation loop. The liquid phase outlet of the reflux storage tank is connected to the return port at the top of the stripping tower via a pipeline and a circulation pump.

[0007] Furthermore, the device also includes a wastewater preheater, and the wastewater feed pipe is connected to the stripping tower wastewater inlet after passing through the wastewater preheater.

[0008] Furthermore, the bottom of the stripping tower is also equipped with a discharge port, which is connected to the wastewater preheater via a bottom pump. After exchanging heat with the wastewater to be treated, the wastewater is discharged from the device.

[0009] Furthermore, a branch pipe is provided between the bottom pump and the wastewater preheater to connect to the return port of the stripping tower.

[0010] Furthermore, the stripping tower is provided with a ceramic packing layer or a structured packing layer.

[0011] Furthermore, the wastewater inlet is connected to a liquid distributor, which is located above the packing layer.

[0012] Furthermore, the ammonia scrubbing tower is provided with a gas distributor, a packing layer, a liquid sprayer, and a demister from bottom to top.

[0013] Furthermore, the cooler is a shell-and-tube heat exchanger, and its heat exchange medium channel is connected to a circulating water pipe or a wastewater pipe.

[0014] This utility model has the following beneficial effects:

[0015] Wastewater from the ammonium sulfate unit, containing a certain concentration of ammonia nitrogen, has a temperature of approximately 40-45℃, making direct reuse impossible. Directly transporting it to the wastewater treatment unit would also result in ammonia waste. The device provided by this invention introduces this wastewater into a stripping tower. Through steam heating, the ammonia and water vapor evaporated at the top of the tower are condensed and enter a reflux storage tank. Part of the water condenses, and the ammonia gas enters an ammonia scrubbing tower for washing and absorption. The ammonia water from the ammonia scrubbing tower is circulated and washed until a certain concentration and level are reached, after which it is used as raw material to replenish the ammonium sulfate crystallization equipment, thus reducing ammonia loss. The wastewater at the bottom of the stripping tower, after ammonia recovery, is discharged from the system. Before being discharged, the wastewater can be preheated to recover residual heat. This portion of water can be reused as process water or transported to the water treatment unit for further treatment. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model. Detailed Implementation

[0017] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0018] like Figure 1As shown, this utility model provides a wastewater recovery and utilization device for ammonium sulfate crystallization, including a stripping tower 1. The tower has a wastewater inlet 1-1 at the top, a steam inlet 1-2 at the bottom, and a gas phase outlet 1-3 at the top. The gas phase outlet is connected to a cooler 2 via a pipeline, and then to a reflux tank 3. The gas phase outlet of the reflux tank is connected to the ammonia feed pipe 4-3 of an ammonia scrubbing tower 4. The ammonia scrubbing tower has a demineralized water inlet 4-1 at the top, and its lower outlet 4-2 is connected to an ammonium sulfate crystallization device 6 via a pipeline and a discharge pump 5. The discharge pump is also connected to the demineralized water inlet via a pipeline to form a circulation loop. The liquid phase outlet of the reflux tank is connected to the return inlet 1-5 at the top of the stripping tower via a pipeline and a circulation pump. When the ammonia water in the reflux tank reaches a certain concentration, it can also be introduced into the ammonium sulfate crystallization device.

[0019] In some embodiments, the device further includes a wastewater preheater 7, with the wastewater feed pipe connected to the stripping tower wastewater inlet after passing through the wastewater preheater. In a more preferred embodiment, the bottom of the stripping tower also has an outlet 1-4, which is connected to the wastewater preheater via a bottom pump 8, exchanging heat with the wastewater to be treated before being discharged from the device. The wastewater temperature is approximately 40-45°C, while the temperature of the liquid at the bottom of the stripping tower reaches over 100°C, fully utilizing the preheating of the hot water before it enters the stripping tower, reducing the wastewater's residual heat before entering the stripping tower to approximately 90°C. The heat source for this device is external low-pressure steam; in some embodiments, a reboiler can also be installed at the bottom of the stripping tower, introducing steam into the reboiler to heat the wastewater.

[0020] In a more preferred embodiment, a branch pipe is provided between the bottom pump and the wastewater preheater, connecting to the return port of the stripping tower, to circulate and strip the bottom wastewater, fully removing ammonia nitrogen and avoiding waste. This return port can be located below the wastewater inlet 1-1, and preferably is equipped with a liquid distributor.

[0021] In some embodiments, the stripping tower is provided with a ceramic packing layer or a structured packing layer; a structured packing layer is preferred. It has a large specific surface area and high mass transfer efficiency, which can improve the processing capacity of a single tower.

[0022] In a more preferred embodiment, the wastewater inlet is connected to a liquid distributor, which is located above the packing layer.

[0023] In some embodiments, the ammonia scrubbing tower is provided from bottom to top with a gas distributor, a packing layer, a liquid sprayer, and a demister. The tail gas outlet at the top of the ammonia scrubbing tower can be directly vented or enter the tail gas treatment system.

[0024] In some embodiments, the cooler is a shell-and-tube heat exchanger, and its heat exchange medium channel is connected to a circulating water pipe or a wastewater pipe.

[0025] The wastewater from the caprolactam ammonium sulfate crystallization process contains ammonia nitrogen at 1200-1800 mg / L, COD at approximately 3500-8000 mg / L, and a temperature of 40-45℃. When using this device for wastewater treatment, the ammonia water is preheated and then fed into a stripping tower. Steam is introduced into the bottom of the stripping tower for heating, causing the ammonia nitrogen in the wastewater to be discharged from the gas phase outlet. After condensation, the gas phase enters a reflux tank, and the gas phase further enters an ammonia scrubbing tower for washing and recovery with demineralized water. When the ammonia water in the scrubbing liquid reaches a certain concentration, it is introduced as raw material into the ammonium sulfate crystallization equipment. The treated wastewater can have its ammonia nitrogen level reduced to below 500 mg / L, enabling the recovery and reuse of ammonia nitrogen in the wastewater, reducing ammonia loss, saving energy and protecting the environment, and saving costs.

[0026] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including combining the various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed by the present invention and all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be determined by the appended claims.

Claims

1. A device for recycling and utilizing ammonium sulfate crystallization wastewater, characterized in that: The system includes a stripping tower with a wastewater inlet at the top, a steam inlet at the bottom, and a gas phase outlet at the top. The gas phase outlet is connected to a cooler via a pipeline, and then to a reflux tank. The gas phase outlet of the reflux tank is connected to an ammonia scrubbing tower. The ammonia scrubbing tower has a demineralized water inlet at the top, and its lower outlet is connected to an ammonium sulfate crystallization device via a pipeline and a discharge pump. The discharge pump is also connected to the demineralized water inlet via a pipeline to form a circulation loop. The liquid phase outlet of the reflux tank is connected to the return port at the top of the stripping tower via a pipeline and a circulation pump.

2. The apparatus according to claim 1, characterized in that: The device also includes a wastewater preheater, and the wastewater feed pipe is connected to the wastewater feed inlet of the stripping tower after passing through the wastewater preheater.

3. The apparatus according to claim 2, characterized in that: The bottom of the stripping tower is also equipped with a discharge port, which is connected to the wastewater preheater via a bottom pump. After exchanging heat with the wastewater to be treated, the wastewater is discharged from the device.

4. The apparatus according to claim 3, characterized in that: A branch pipe is also provided between the bottom pump and the wastewater preheater, connecting to the return port of the stripping tower.

5. The apparatus according to any one of claims 1 to 4, characterized in that: The stripping tower is equipped with a ceramic packing layer or a structured packing layer.

6. The apparatus according to claim 5, characterized in that: The wastewater inlet is connected to a liquid distributor, which is located above the packing layer.

7. The apparatus according to any one of claims 1 to 4, characterized in that: The ammonia scrubbing tower is equipped with a gas distributor, a packing layer, a liquid sprayer, and a demister from bottom to top.

8. The apparatus according to claim 1, characterized in that: The cooler is a shell-and-tube heat exchanger, and its heat exchange medium channel is connected to the circulating water pipeline or the wastewater pipeline.

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