Ammoximation wastewater double-effect deamination and heat energy recovery system

Abstract

The double-effect deamination and heat energy recovery system comprises a wastewater tank, a wastewater feeding pump, a heat exchanger, an atmospheric tower, a normal-pressure discharging pump, a pressurizing tower, a pressurizing discharging pump, a wastewater cooler, a condenser, an ammonia water cooler, an ammonia water tank, an ammonia water discharging pump, an alkane washing tower, a tail gas absorption tower and a reboiler, the wastewater tank is sequentially communicated with a wastewater feeding pump, a heat exchanger tube pass, an atmospheric tower, a normal-pressure discharging pump, a pressurizing tower, a pressurizing discharging pump, a heat exchanger shell pass and a wastewater cooler through pipelines; the top of the atmospheric tower is sequentially communicated with a condenser, an ammonia water cooler, an ammonia water tank, an ammonia water discharge pump and an alkane washing tower through pipelines; a gas phase outlet of the condenser is communicated with a tail gas absorption tower through a pipeline; the top of the pressurizing tower is sequentially communicated with a reboiler shell pass, an ammonia water condensation tank, an ammonia water condensation discharge pump and an alkane washing tower through pipelines; and the reboiler shell pass is communicated with an atmospheric tower. The cyclohexanone ammoximation wastewater treatment device is used for solving the problems of high energy consumption, high ammonia nitrogen emission and heat energy waste in cyclohexanone ammoximation wastewater treatment in existing caprolactam production.

Description

Technical Field

[0001] This utility model relates to a dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater. Background Technology

[0002] In the caprolactam production process, the cyclohexanone ammoniation reaction generates a large amount of ammonia-containing wastewater, with an ammonia content of approximately 3%, mainly derived from the water contained in hydrogen peroxide and the water produced during the reaction. Currently, the treatment of this wastewater primarily relies on single-effect ammonia stripping tower technology, but this technology has several problems. On the one hand, a single-effect ammonia stripping tower consumes approximately 160 kg of steam to treat each ton of wastewater. Taking a 400,000-ton / year caprolactam plant as an example, with 45 tons of wastewater produced per hour, the steam consumption reaches as high as 7.2 t / h, significantly increasing production costs. In the current context of energy scarcity and the critical importance of cost control, this high energy consumption has become a key factor restricting the industry's development. On the other hand, the ammonia content of the wastewater after treatment by the single-effect ammonia stripping tower is still as high as 200-250 ppm, resulting in an excessively high ammonia nitrogen load in the wastewater, making it difficult to meet increasingly stringent environmental standards and placing enormous environmental pressure on enterprises. Furthermore, in terms of thermal energy utilization, the existing technology suffers from serious waste. The wastewater at the top of the tower, reaching approximately 90°C, is directly cooled using circulating water, while the wastewater at the bottom needs to be cooled to 40°C with chilled water before being sent out. A significant amount of heat from vaporization remains unutilized, and the cooling process consumes substantial amounts of cooling energy, further increasing production costs. Currently, the industry commonly uses atmospheric pressure towers for ammonia removal, which not only consumes a lot of steam but also has poor ammonia nitrogen removal efficiency, failing to meet the needs of enterprises for energy conservation, emission reduction, and cost reduction. Therefore, developing a highly efficient, energy-saving, and environmentally friendly wastewater ammonia removal and heat recovery technology has become a critical issue urgently needing to be addressed in the caprolactam industry. Utility Model Content

[0003] The purpose of this invention is to provide a dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater, which solves the problems of high energy consumption, high ammonia nitrogen emissions, and heat waste in the treatment of cyclohexanone ammonia oxime wastewater in existing caprolactam production.

[0004] To solve the above problems, the technical solution of this utility model is as follows:

[0005] A dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater includes a wastewater tank, a wastewater feed pump, a heat exchanger, an atmospheric pressure tower, an atmospheric pressure discharge pump, a pressurized tower, a pressurized discharge pump, a wastewater cooler, a condenser, an ammonia water cooler, an ammonia water tank, an ammonia water discharge pump, an alkane washing tower, a tail gas absorption tower, and a reboiler. The wastewater tank is connected sequentially to the wastewater feed pump, the tube side of the heat exchanger, the atmospheric pressure tower, the atmospheric pressure discharge pump, the pressurized tower, the pressurized discharge pump, the shell side of the heat exchanger, and the wastewater cooler via pipelines. The top of the atmospheric pressure tower is connected sequentially to the condenser, the ammonia water cooler, the ammonia water tank, the ammonia water discharge pump, and the alkane washing tower via pipelines. The vapor phase outlet of the condenser is connected to the tail gas absorption tower via a pipeline. The top of the pressurized tower is connected sequentially to the shell side of the reboiler, the ammonia water condenser tank, the ammonia water condensate discharge pump, and the alkane washing tower via pipelines. The tube side of the reboiler is connected to the atmospheric pressure tower.

[0006] Furthermore, the top of the ammonia tank is connected to the condenser and the atmospheric pressure tower via a first return water pipe, and a first water supply valve is installed on the first return water pipe.

[0007] Furthermore, the top of the ammonia condenser is connected to the reboiler and the pressurization tower via a second return water pipe, and a second water supply valve is installed on the second return water pipe.

[0008] The beneficial effects of this utility model are as follows:

[0009] 1. Significantly Reduced Steam Consumption: This system utilizes a double-effect ammonia stripping tower technology, using the secondary steam from the pressurized tower as the heat source for the atmospheric tower, achieving highly efficient utilization of thermal energy and significantly reducing steam consumption. Compared to a traditional single-effect ammonia stripping tower, steam consumption is reduced by nearly half, saving 3.6 tons of steam per hour. Based on 8,000 hours of annual operation, this translates to annual savings of 2.88 million yuan in steam costs (at a steam price of 100 yuan / ton).

[0010] 2. Reduced ammonia content in wastewater: This system optimizes the design and process of the ammonia stripping tower, reducing the ammonia content in the wastewater at the bottom of the tower to below 100 ppm. Compared to the 200-250 ppm ammonia content after treatment by traditional single-effect towers, this significantly reduces the ammonia nitrogen load in the wastewater, simplifies wastewater treatment, and meets increasingly stringent environmental protection requirements.

[0011] 3. Reduced cooling requirements: Utilizing the heat of vaporization of wastewater at the top of the tower as a heat source avoids directly cooling high-temperature wastewater with circulating water, reducing the cooling capacity required by the cooler and thus lowering electricity consumption and circulating water costs. Based on an annual operating time of 8,000 hours, this can save 364,800 yuan in circulating water costs annually (based on a circulating water unit price of 0.12 yuan / ton).

[0012] 4. Save ammonia resources: Through the efficient ammonia removal process, ammonia waste is reduced, saving 0.0045 tons / hour of ammonia per year. Based on an annual operating time of 8,000 hours, this can save 75,600 yuan of ammonia resources (based on an ammonia price of 2,100 yuan / ton). Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings:

[0014] Figure 1 This is a schematic diagram of the structure of this utility model.

[0015] In the diagram: 1. Wastewater feed pump; 2. Filter; 3. Pressurized discharge pump; 4. Packing; 5. Ammonia condenser; 6. Ammonia condenser discharge pump; 7. Alkane washing tower; 8. Atmospheric discharge pump; 9. First water supply valve; 10. Ammonia tank; 11. Ammonia discharge pump; 12. Ammonia cooler; 13. Tail gas absorption tower; 14. Condenser; 15. Atmospheric tower; 16. Reboiler; 17. Second water supply valve; 18. Pressurized tower; 19. Heat exchanger; 20. Wastewater cooler; 21. Sewage treatment pond; 22. Wastewater tank. Detailed Implementation

[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0017] like Figure 1 As shown, a dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater includes a wastewater tank 22, a wastewater feed pump 1, a heat exchanger 19, an atmospheric pressure tower 15, an atmospheric pressure discharge pump 8, a pressurized tower 18, a pressurized discharge pump 3, a wastewater cooler 20, a condenser 14, an ammonia water cooler 12, an ammonia water tank 10, an ammonia water discharge pump 11, an alkane washing tower 7, a tail gas absorption tower 13, and a reboiler 16.

[0018] Wastewater tank 22 is connected in sequence to wastewater feed pump 1, tube side of heat exchanger 19, atmospheric pressure tower 15, atmospheric pressure discharge pump 8, pressurized tower 18, pressurized discharge pump 3, shell side of heat exchanger 19 and wastewater cooler 20 through pipelines.

[0019] The top of the atmospheric pressure tower 15 is connected in sequence to the condenser 14, the ammonia water cooler 12, the ammonia water tank 10, the ammonia water discharge pump 11 and the alkane washing tower 7 via pipelines. The gas phase outlet of the condenser 14 is connected to the tail gas absorption tower 13 via a pipeline.

[0020] The top of the pressurized tower 18 is connected in sequence to the shell side of the reboiler 16, the ammonia condenser 5, the ammonia condensate discharge pump 6, and the alkane washing tower 7 via pipelines. The tube side of the reboiler 16 is connected to the atmospheric tower 15.

[0021] The specific working process is as follows: Wastewater from wastewater tank 22 (temperature approximately 40-45℃) is pumped by wastewater feed pump 1 to the tube side of heat exchanger 19, where it is preheated to approximately 90℃ before entering the upper part of atmospheric pressure tower 15. Ammonia gas collected from the top of atmospheric pressure tower 15 is condensed to approximately 45℃ by circulating water in condenser 14, and then cooled by chilled water in ammonia water cooler 12 to produce ammonia water with a concentration of approximately 20%. A small amount of non-condensable gas in condenser 14 enters tail gas absorption tower 13 for treatment. Wastewater containing a portion of ammonia from atmospheric pressure tower 15 is pumped into the upper part of pressurized tower 18 by atmospheric pressure discharge pump 8. Live steam is added to pressurized tower 18 to raise the temperature to 140-150℃, and the pressure is controlled at 0.3 MPa (G). The secondary steam from the top of pressurized tower 18 is sent to the shell side of reboiler 16 as a heat source to raise the temperature of atmospheric pressure tower 15. The ammonia water condensed in the ammonia water condenser 5 is sent to the alkane washing tower 7 by the ammonia water condensate discharge pump 6. The wastewater at the bottom of the pressurized tower 18 is sent to the sewage treatment pond by the pressurized discharge pump 3. During this process, the wastewater passes through the shell side of the heat exchanger 19 and the wastewater cooler 20. When passing through the shell side of the heat exchanger 19, the wastewater pumped to the atmospheric tower 15 by the wastewater tank 22 is preheated. When passing through the wastewater cooler 20, the wastewater is cooled to 40°C and then sent to the sewage treatment pond 21.

[0022] The top of the ammonia tank 10 is connected to the condenser 14 and the atmospheric pressure tower 15 through a first return water pipe, and a first water supply valve 9 is installed on the first return water pipe.

[0023] The top of the ammonia condensate tank 5 is connected to the reboiler 16 and the pressurization tower 18 via a second return water pipe. A second water supply valve 17 is installed on the second return water pipe. The first water supply valve 9 and the second water supply valve 17 can discharge the condensed ammonia water in the pipeline in a timely manner, avoid water hammer, reduce pipeline corrosion, and prevent ammonia leakage.

[0024] Furthermore, the heat exchanger 19 is a spiral plate heat exchanger 19. Its heat transfer coefficient is 20%-50% higher than that of a conventional shell and tube heat exchanger 19, which can achieve heat exchange more efficiently and improve the heat energy recovery and utilization rate.

[0025] Furthermore, a filter 2 is installed between the wastewater feed pump 1 and the tube side of the heat exchanger 19. The filter 2 has a filtration accuracy of 5-10μm, which can effectively remove solid impurities in the wastewater, prevent them from clogging and wearing the system equipment, and extend the service life of the equipment.

[0026] Furthermore, packing material 4 is provided in the atmospheric pressure tower 15 and the pressurized tower 18. The specific surface area of ​​the packing material 4 is 200-500 m² / m³, and the porosity is 0.8-0.95, which can effectively enhance the heat and mass transfer efficiency and improve the ammonia removal effect.

[0027] Furthermore, the reboiler 16 is a thermosiphon reboiler 16. This reboiler 16 does not have an additional circulation pump, has a compact structure, occupies a small area, and can save equipment space.

[0028] The embodiments described in this specification are merely examples of implementations of the inventive concept. The scope of protection of this utility model should not be considered as limited to the specific forms described in the embodiments. The scope of protection of this utility model also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater, characterized in that: The system includes a wastewater tank, wastewater feed pump, heat exchanger, atmospheric pressure tower, atmospheric pressure discharge pump, pressurized tower, pressurized discharge pump, wastewater cooler, condenser, ammonia cooler, ammonia tank, ammonia discharge pump, alkane scrubbing tower, tail gas absorption tower, and reboiler. The wastewater tank is connected sequentially to the wastewater feed pump, heat exchanger tube side, atmospheric pressure tower, atmospheric pressure discharge pump, pressurized tower, pressurized discharge pump, heat exchanger shell side, and wastewater cooler via pipelines. The top of the atmospheric pressure tower is connected sequentially to the condenser, ammonia cooler, ammonia tank, ammonia discharge pump, and alkane scrubbing tower via pipelines. The vapor phase outlet of the condenser is connected to the tail gas absorption tower via a pipeline. The top of the pressurized tower is connected sequentially to the reboiler shell side, ammonia condenser tank, ammonia condensate discharge pump, and alkane scrubbing tower via pipelines. The reboiler tube side is connected to the atmospheric pressure tower.

2. The dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater according to claim 1, characterized in that: The top of the ammonia tank is connected to the condenser and the atmospheric pressure tower via a first return water pipe, and a first water supply valve is installed on the first return water pipe.

3. The dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater according to claim 1, characterized in that: The top of the ammonia condenser is connected to the reboiler and the pressurization tower via a second return water pipe, and a second water supply valve is installed on the second return water pipe.

4. The dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater according to claim 1, characterized in that: The heat exchanger is a spiral plate heat exchanger.

5. The dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater according to claim 1, characterized in that: A filter is installed between the wastewater feed pump and the heat exchanger tubes.

6. The dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater according to claim 1, characterized in that: Packing material is installed in both the atmospheric pressure tower and the pressurized tower.

7. The dual-effect ammonia removal and heat recovery system for ammonia oxime wastewater according to claim 1, characterized in that: The reboiler is a thermosiphon reboiler.

Images