A post cooling system for ammonia stripping wastewater in a coke ammonia stripping process

Abstract

The utility model discloses a kind of post-cooling systems of ammonia distillation wastewater in coking ammonia distillation process, including ammonia distillation tower, wastewater pump, ammonia water heat exchanger, oil separation tank, residual oil pump, wastewater intermediate tank, wastewater booster pump, cooler and oil-water separator;The ammonia distillation wastewater outlet of the ammonia distillation tower is connected with the inlet of oil separation tank after wastewater pump and ammonia water heat exchanger, and the overflow port of oil separation tank is connected with the inlet of wastewater intermediate tank;The outlet of the wastewater intermediate tank is connected with the inlet of cooler by wastewater booster pump, and the outlet of cooler is connected with biological section;The tar outlet of the oil separation tank is connected with the inlet of oil-water separator by residual oil pump, and the outlet of oil-water separator is connected with biological section.The cooling function of the system will be placed in biological section after ammonia distillation wastewater, and the oil separation tank is used to remove oil from wastewater before cooling, to solve the problem of tar blockage, and the first-stage cooling of wastewater uses biological external water instead of circulating water, to reduce the use of coking circulating water.

Description

Technical Field

[0001] This utility model relates to the field of coking wastewater treatment technology, and in particular to a post-cooling system for ammonia stripping wastewater in the coking ammonia stripping process. Background Technology

[0002] During the coking process, coal is dry distilled at high temperature in the coke oven under air-isolated conditions. The nitrogen in the coal is converted into ammonia (NH3) through pyrolysis. At the same time, the organic matter in the coal decomposes to produce a large amount of raw coal gas containing tar, benzene, phenols and various volatile substances. Some chemically bound water is also generated, and the water evaporates along with the raw coal gas, forming raw coal gas containing water, ammonia, tar, phenols and other components.

[0003] The raw coal gas extracted from the coke oven carbonization chamber is approximately 700°C. It is cooled to 80-90°C by spraying circulating ammonia water into the gas collecting pipe. A small amount of ammonia water evaporates, carrying away the heat from the raw coal gas. The unevaporated ammonia water continues to absorb ammonia from the raw coal gas. As production continues, the amount of ammonia water increases, and excess ammonia water needs to be discharged from the circulating ammonia water system; this excess ammonia water is called waste ammonia water. Because the ammonia nitrogen content in the waste ammonia water is as high as 2000-5000 mg / L, the biological treatment section cannot handle such a high concentration of ammonia nitrogen wastewater. Therefore, the waste ammonia water needs to undergo ammonia stripping treatment to reduce the ammonia nitrogen concentration before biological treatment.

[0004] Ammonia removal from residual ammonia water is generally achieved using steam distillation, or simply ammonia stripping. Ammonia stripping utilizes steam distillation to remove dissolved ammonia nitrogen from the ammonia water into steam, thus achieving the purpose of removing ammonia nitrogen from the ammonia water. To further reduce the ammonia nitrogen concentration in the wastewater, sodium hydroxide solution needs to be added to the residual ammonia water to decompose fixed ammonium salts (NH4Cl, (NH4)2SO4, etc.) in the residual ammonia water.

[0005] The traditional and most widely used ammonia stripping process involves first exchanging heat with the ammonia stripping wastewater to raise the temperature to around 90°C. Then, it is mixed with sodium hydroxide alkaline solution and added to the upper part of the ammonia stripping tower. The ammonia water comes into countercurrent contact with the steam introduced at the bottom of the tower. Under the steam blowing, the ammonia in the ammonia water evaporates and overflows to the top of the tower. The wastewater collected at the bottom of the ammonia stripping tower is pressurized by a wastewater pump and exchanged heat with the remaining ammonia water. Then, after a first stage of circulating water cooling and a second stage of low-temperature water cooling to a temperature of 30°C, it is sent to the biological treatment section.

[0006] In traditional ammonia stripping processes, the tar present in the wastewater solidifies and adheres to the heat exchangers and pipes in the first and second stage coolers and wastewater pipelines due to the temperature drop, causing equipment blockage. This necessitates frequent chemical cleaning of the heat exchangers and pipes, hindering stable production operation. Simultaneously, to meet the wastewater temperature requirements of the biological treatment section, the first stage cooler consumes a large volume of circulating water. Utility Model Content

[0007] The technical problem to be solved by this utility model is to provide a post-cooling system for ammonia stripping wastewater in the coking ammonia stripping process, so as to solve the problems of equipment blockage and high consumption of circulating water in the existing ammonia stripping wastewater treatment process.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: It includes an ammonia stripping tower, a wastewater pump, an ammonia-water heat exchanger, an oil separator, a sludge oil pump, an intermediate wastewater tank, a wastewater booster pump, a cooler, and an oil-water separator; the ammonia stripping wastewater outlet of the ammonia stripping tower is connected to the inlet of the oil separator after passing through the wastewater pump and the ammonia-water heat exchanger, and the overflow outlet of the oil separator is connected to the inlet of the intermediate wastewater tank; the outlet of the intermediate wastewater tank is connected to the inlet of the cooler through the wastewater booster pump, and the outlet of the cooler is connected to the biological treatment section; the tar outlet of the oil separator is connected to the inlet of the oil-water separator through the sludge oil pump, and the outlet of the oil-water separator is connected to the biological treatment section.

[0009] Furthermore, the lower part of the oil separator is a slag hopper, and the tar outlet is located at the bottom of the slag hopper; a coil heater is installed inside the slag hopper.

[0010] Furthermore, the oil separator is equipped with a liquid distributor.

[0011] Furthermore, the cooling medium inlet of the ammonia heat exchanger is connected to the remaining ammonia pipeline of the cooling drum section.

[0012] Furthermore, the cooler includes a first-stage cooler and a second-stage cooler connected in series.

[0013] Furthermore, the cooling medium inlet of the aforementioned cooler is connected to the external greywater pipeline of the bio-process section.

[0014] Furthermore, the cooling medium inlet of the two-stage cooler is connected to a low-temperature water pipeline.

[0015] The beneficial effects of adopting the above technical solution are as follows: This utility model reasonably optimizes the wastewater treatment process of the ammonia stripping section and the biological section. The cooling function of the ammonia stripping wastewater is placed in the biological section. At the same time, the oil removal function of the oil separator in the biological section is used to remove oil from the wastewater before cooling, which solves the problem of tar blockage. The first stage of wastewater cooling uses biological externally supplied water to replace the circulating water, reducing the amount of coking circulating water used.

[0016] This invention utilizes a coil heater installed inside the slag hopper to maintain the wastewater temperature at 70-80℃ during the transport of ammonia-containing wastewater to the biological treatment section. This ensures that the tar in the wastewater maintains good fluidity and does not solidify or adhere to the ammonia-water heat exchange equipment and pipelines, preventing blockages. Furthermore, the tar is removed from the oil separator in the biological treatment section before cooling, avoiding tar blockage of the heat exchangers during the subsequent two cooling stages. Simultaneously, the initial cooling of the ammonia-containing wastewater uses recycled water from the biological treatment section as the cooling medium, saving on the coking plant's circulating water consumption and reducing the cooling and water supply load of the circulating water system, resulting in significant energy savings.

[0017] This utility model is novel and practical, which can improve the service life of pipelines and heat exchange equipment, reduce maintenance costs, and ensure long-term continuous and stable production operation. Attached Figure Description

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0019] Figure 1 This is a schematic diagram of the system structure of this utility model.

[0020] In the diagram: 1. Ammonia stripping tower; 2. Wastewater pump; 3. Ammonia water heat exchanger; 4. Oil separator; 5. Sludge oil pump; 6. Intermediate wastewater tank; 7. Wastewater lift pump; 8. Primary cooler; 9. Secondary cooler; 10. Equalization tank; 11. Oil-water separator; 12. Biological effluent tank; 13. External water pump; 14. Liquid distributor; 15. Coil heater; 16. Low-temperature water pipeline; 17. Residual ammonia water pipeline; 18. Tank body; 19. Sludge hopper. Detailed Implementation

[0021] Figure 1As shown, the post-cooling system for ammonia stripping wastewater in this coking ammonia stripping process includes an ammonia stripping tower 1, a wastewater pump 2, an ammonia-water heat exchanger 3, an oil separator 4, a sludge-oil pump 5, an intermediate wastewater tank 6, a wastewater booster pump 7, a cooler, and an oil-water separator 11. The cooler includes a primary cooler 8 and a secondary cooler 9. The ammonia stripping wastewater outlet at the bottom of the ammonia stripping tower 1 is connected to the inlet of a heat exchange path in the ammonia-water heat exchanger 3 via the wastewater pump 2. The outlet of the heat exchange path is connected to the inlet of the oil separator 4. The overflow outlet of the oil separator 4 is connected to the inlet of the intermediate wastewater tank 6, and the overflow outlet of the oil separator 4 is 2 meters higher than the inlet of the intermediate wastewater tank 6. The outlet of the intermediate wastewater tank 6 is connected to the inlet of the primary cooler 8 via the wastewater booster pump 7. The outlet of the primary cooler 8 is connected to the inlet of the secondary cooler 9. The outlet of the secondary cooler 9 is connected to the equalization tank 10 of the biological treatment section. The inlet of another heat exchange passage of the ammonia heat exchanger 3 is connected to the residual ammonia pipeline of the cooling drum section, and the outlet of this heat exchange passage is connected to the residual ammonia inlet of the ammonia stripping tower 1 via the residual ammonia pipeline 17. The cooling medium inlet of the first-stage cooler 8 is connected to the external greywater pipeline of the biological process section, that is, the external greywater pipeline transported by the biological effluent tank 12 in the biological process section via the external water pump 13. The cooling medium inlet of the second-stage cooler 9 is connected to the low-temperature water pipeline 16 after the coking plant refrigeration unit.

[0022] Figure 1 As shown, the post-cooling system for ammonia stripping wastewater in this coking ammonia stripping process includes an oil separator 4 equipped with a liquid distributor 14. The lower part of the oil separator 4 is a slag hopper 19, with a tar outlet at the bottom. A coil heater 15 is installed inside the slag hopper 19. The tar outlet of the oil separator 4 is connected to the inlet of an oil-water separator 11 via a slag-oil pump 5. The outlet of the oil-water separator 11 is connected to the equalization tank 10 of the biological treatment section.

[0023] Figure 1 As shown, the operation process of the post-cooling system for ammonia stripping wastewater in this coking ammonia stripping process is as follows:

[0024] (1) The primary heat exchange and transportation of ammonia stripping wastewater is completed in the ammonia stripping section. The ammonia stripping wastewater discharged from the bottom of the ammonia stripping tower 1 is pumped out by the wastewater pump 2 and sent to the ammonia water heat exchanger 3 to exchange heat with the remaining ammonia water from the cooling drum section. The temperature of the ammonia stripping wastewater drops to 70-80℃. After the remaining ammonia water is heated by heat exchange, it enters the upper part of the ammonia stripping tower 1 through the remaining ammonia water pipeline 17. The ammonia stripping wastewater after preliminary cooling is sent to the oil separator 4 of the biological section.

[0025] (2) The ammonia stripping wastewater from the ammonia stripping section enters the oil separator 4 and is evenly distributed by the liquid distributor 14. Relying on gravity, the tar in the wastewater is deposited at the bottom of the slag hopper 19 in the oil separator 4. The wastewater overflows from the top of the oil separator 4 to the wastewater intermediate tank 6 by the height difference. The tar at the bottom of the slag hopper 19 is periodically pumped to the oil-water separator 11 by the slag oil pump 5 for further oil-water separation.

[0026] (3) The wastewater in the intermediate wastewater tank 6 is sent to the first-stage cooler 8 and the second-stage cooler 9 by the wastewater lift pump 7 for cooling, and then discharged into the regulating tank 10.

[0027] (4) The water in the biological effluent tank 12 in the biological section is wastewater that has undergone deep treatment and meets the water quality standards for reclaimed water. It is sent to other reclaimed water users by the external water pump 13. The cooling water in the first stage wastewater cooler 8 is this water. The cooling water after heat exchange is still discharged to the external water main pipe, and its cooling water flow rate is controlled by the valve.

[0028] (5) The process cooling water for the wastewater secondary cooler 9 is 16℃ low temperature water produced by the coking plant refrigeration machine. It is supplied by the low temperature water system through the low temperature water pipeline 16, and the cooling return water is sent to the low temperature water return network.

[0029] (6) The cooling water of the first-stage cooler 8 is connected to the main water pipe of the external water pump 13. The cooling water after heat exchange is still discharged to the external water pipe, and its cooling water flow rate is regulated by valve.

[0030] (7) A steam coil heater 15 is provided at the bottom slag hopper 19 of the oil separator 4 to indirectly heat the bottom deposited tar with steam and prevent the tar from solidifying.

[0031] (8) The tar separated by sedimentation in slag hopper 19 is pumped to oil-water separator 11 by slag oil pump 5 for further oil-water separation. The wastewater at the top of oil-water separator 11 is discharged into regulating tank 10, and the tar at the bottom is discharged and sent to coking coal for coking.

[0032] An embodiment of this utility model is as follows:

[0033] Ammonia stripping tower: tower diameter 2000mm, tower height 20450mm;

[0034] Wastewater pump: Model CZ65-200;

[0035] Ammonia heat exchanger: 70m² 2 ;

[0036] Grease trap: 7.0m x 7.0m x 7.5m (length x width x height);

[0037] Sludge pump: Model ZYB-4.2 / 5.5;

[0038] Intermediate wastewater tank: 300m³ 3 ;

[0039] Wastewater lift pump: Model IS100-80-125;

[0040] First-stage cooler: area 3×100m² 2 ;

[0041] Second-stage cooler: area 3×60m² 2;

[0042] External water pump: Model TQL150-400A;

[0043] Regulating tank: 31.0m x 21.0m x 6.0m (length x width x height);

[0044] Biological effluent tank: 12.0 × 6.0 × 5.7 m (length × width × height)

[0045] Coil heater: 25mm diameter, 20m² heat exchange area 2 ;

[0046] Oil-water separator: diameter Φ1500mm, height 2500mm.

Claims

1. A post-cooling system for ammonia stripping wastewater in a coking ammonia stripping process, characterized in that: The system includes an ammonia stripping tower (1), a wastewater pump (2), an ammonia water heat exchanger (3), an oil separator (4), a sludge oil pump (5), a wastewater intermediate tank (6), a wastewater booster pump (7), a cooler, and an oil-water separator (11). The ammonia stripping wastewater outlet of the ammonia stripping tower (1) is connected to the inlet of the oil separator (4) via the wastewater pump (2) and the ammonia water heat exchanger (3). The overflow outlet of the oil separator (4) is connected to the inlet of the wastewater intermediate tank (6). The outlet of the wastewater intermediate tank (6) is connected to the inlet of the cooler via the wastewater booster pump (7). The outlet of the cooler is connected to the biological process section. The tar outlet of the oil separator (4) is connected to the inlet of the oil-water separator (11) via the sludge oil pump (5). The outlet of the oil-water separator (11) is connected to the biological process section.

2. The post-cooling system for ammonia stripping wastewater in a coking ammonia stripping process according to claim 1, characterized in that: The lower part of the oil separator (4) is a slag hopper (19), and the tar outlet is located at the bottom of the slag hopper (19); a coil heater (15) is provided inside the slag hopper (19).

3. The post-cooling system for ammonia stripping wastewater in a coking ammonia stripping process according to claim 1, characterized in that: The oil separator (4) is equipped with a liquid distributor (14).

4. The post-cooling system for ammonia stripping wastewater in a coking ammonia stripping process according to claim 1, characterized in that: The cooling medium inlet of the ammonia heat exchanger (3) is connected to the remaining ammonia pipeline of the cold drum section.

5. A post-cooling system for ammonia stripping wastewater in a coking ammonia stripping process according to any one of claims 1-4, characterized in that: The cooler includes a first-stage cooler (8) and a second-stage cooler (9) connected in series.

6. The post-cooling system for ammonia stripping wastewater in a coking ammonia stripping process according to claim 5, characterized in that: The cooling medium inlet of the first-stage cooler (8) is connected to the external water supply pipeline of the bio-process section.

7. The post-cooling system for ammonia stripping wastewater in a coking ammonia stripping process according to claim 5, characterized in that: The cooling medium inlet of the two-stage cooler (9) is connected to the low-temperature water pipeline (16).

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