A heat recovery system for coal gas condensate water

Abstract

The application discloses a heat recycling system of coal gas condensate water and belongs to the technical field of light metal smelting. The application comprises a coal economizer, the inlet of the coal economizer is connected with the outlet of coal gas, and the outlet of the coal economizer is connected with a bag-type dust collector through a gas outlet pipe; a first cooling pipe is arranged in the coal economizer, the first cooling pipe is used for cooling the coal gas, one end of the first cooling pipe is connected with a water pool through a first liquid inlet pipe, a water pump is arranged on the first liquid inlet pipe, the other end of the first cooling pipe is connected with a hot water heater through a first liquid outlet pipe, and the hot water heater is used for heating red mud settling washing water; the inlet of the hot water heater is also connected with a red mud settling washing water source and a heating steam source respectively, and the outlet of the hot water heater is connected with a red mud separation washing unit. The application reduces the use amount of heating steam and saves energy. Meanwhile, the hot water can also be used as make-up water and is used for laying the foundation for the red mud separation washing step.

Description

Technical Field

[0001] This invention belongs to the field of light metal smelting technology, specifically relating to a heat recovery and utilization system for coal gas condensate. Background Technology

[0002] The alumina plant has a gasification station that supplies fuel to the calcination workshop. The gas produced at the gasification station must pass through a baghouse dust collector for dust removal before it can be used. The gas itself is relatively hot, and directly entering the baghouse dust collector would damage it. Therefore, the gas is usually cooled by an economizer before entering the baghouse dust collector. When the gas load changes, the temperature of the gas entering the baghouse dust collector may become too high, damaging the filter bags and affecting the safe operation of the gas system. Summary of the Invention

[0003] To address the above shortcomings, this invention provides a heat recovery and utilization system for gas condensate, which can effectively utilize the heat of hot water and save energy.

[0004] This invention protects a heat recovery and utilization system for coal gas condensate, including an economizer, wherein the inlet of the economizer is connected to the outlet of the coal gas, and the outlet of the economizer is connected to a bag filter through an outlet pipe.

[0005] The economizer is equipped with a first cooling pipe for cooling the coal gas. One end of the first cooling pipe is connected to a water tank through a first liquid inlet pipe, and a water pump is installed on the first liquid inlet pipe. The other end of the first cooling pipe is connected to a hot water heater through a first liquid outlet pipe, and the hot water heater is used to heat the red mud settling wash water.

[0006] The inlet of the hot water heater is connected to both the red mud settling and washing water source and the heating steam source, and the outlet of the hot water heater is connected to the red mud separation and washing unit.

[0007] The heating steam provided by the heating steam source enters from the bottom of the hot water heater, and the hot water in the first outlet pipe enters from the top of the hot water heater, with the steam and hot water transferring heat in opposite directions.

[0008] Furthermore, the water in the pool is coal gas condensate, which contains ammonia nitrogen; the ammonia nitrogen content in the coal gas condensate is 3000-5000 mg / L.

[0009] Furthermore, a first TIC valve is provided on the first liquid inlet pipe; the opening degree of the first TIC valve is controlled according to the gas temperature in the gas outlet pipe, and the gas temperature in the gas outlet pipe is proportional to the opening degree of the first TIC valve.

[0010] Furthermore, the first outlet pipe and the first inlet pipe are connected by a connecting pipe, and a second TIC valve is provided on the connecting pipe; the opening degree of the second TIC valve is controlled according to the liquid temperature in the first outlet pipe, and the liquid temperature in the first outlet pipe is inversely proportional to the opening degree of the second TIC valve.

[0011] Furthermore, a dew point analyzer is installed on the air outlet pipe.

[0012] Furthermore, the economizer is equipped with a second cooling pipe. One end of the second cooling pipe is connected to a low-temperature demineralized water source through a second liquid inlet pipe, and the other end of the second cooling pipe is connected to a steam drum through a second liquid outlet pipe.

[0013] Furthermore, the second inlet pipe is equipped with an LIC valve; the opening degree of the LIC valve is controlled according to the liquid level in the steam drum, and the liquid level in the steam drum is inversely proportional to the opening degree of the LIC valve.

[0014] Beneficial effects:

[0015] (1) By setting up a hot water heater, the hot water after cooling the economizer flows directly into the hot water heater. The hot water heater is also connected to the red mud settling and washing water source. The hot water can heat the red mud settling and washing water, reducing the amount of heating steam used and saving energy consumption. At the same time, the hot water can also be used as makeup water to prepare for the red mud separation and washing steps.

[0016] (2) The present invention selects coal gas condensate as the cooling water in the economizer, which can reuse the coal gas condensate. In addition, the coal gas condensate contains ammonia nitrogen and the red mud settling wash water contains sodium carbonate, which is an alkaline environment that is conducive to the decomposition of ammonia nitrogen in the coal gas condensate. There is no need to set up a separate process or add separate reagents for decomposition of the coal gas condensate, which simplifies the steps and saves costs. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a heat recovery and utilization system for coal gas condensate in one embodiment of the present invention.

[0018] In the diagram: 1. Economizer; 2. First liquid outlet pipe; 3. Second TIC valve; 4. First TIC valve; 5. Gas outlet pipe; 6. Bag filter; 7. Water tank; 8. First liquid inlet pipe; 9. Water pump; 10. Connecting pipe; 11. Hot water heater; 12. Second liquid inlet pipe; 13. LIC valve; 14. Steam drum; 15. Second liquid outlet pipe; 16. Dew point analyzer. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] refer to Figure 1 This invention protects a heat recovery and utilization system for coal gas condensate, including an economizer 1, the inlet of which is connected to coal gas, and the outlet of which is connected to a bag filter 6 through an outlet pipe 5.

[0021] The economizer 1 is equipped with a first cooling pipe, which is used to cool the coal gas. One end of the first cooling pipe is connected to the water tank 7 through the first liquid inlet pipe 8. A water pump 9 is installed on the first liquid inlet pipe 8. The other end of the first cooling pipe is connected to the hot water heater 11 through the first liquid outlet pipe 2. The hot water heater 11 is used to heat the red mud settling wash water.

[0022] The inlet of the hot water heater 11 is connected to both the red mud settling and washing water source and the heating steam source, and the outlet of the hot water heater 11 is connected to the red mud separation and washing unit. The heating steam provided by the heating steam source enters from the bottom of the hot water heater 11, and the hot water in the first outlet pipe 2 enters from the top of the hot water heater 11, with the steam and hot water transferring heat in opposite directions.

[0023] In the red mud separation and washing process of an alumina plant, hot water is required as washing water. To prevent red mud from solidifying, the red mud settling wash water generally needs to be heated to above 90°C. Therefore, a hot water heater 5 is installed in the process section. The heating medium of the hot water heater 5 is steam, and the heated medium is the red mud settling wash water. The higher the makeup water temperature, the lower the steam consumption and the lower the alumina energy consumption. Therefore, this invention allows the hot water after cooling the economizer to flow directly into the hot water heater to heat the red mud settling wash water, reducing the amount of heating steam used and saving energy consumption. At the same time, the hot water can also be used as makeup water to prepare for the red mud separation and washing steps.

[0024] In one specific embodiment, the water in pool 7 is coal gas condensate, which contains ammonia nitrogen; the ammonia nitrogen content in the coal gas condensate is 3000-5000 mg / L.

[0025] Wet coal gas contains water vapor, and condensate will form when the pressure or temperature decreases. (This is based on a 40000Nm...) 3Taking the condensate from a circulating fluidized bed gasifier at atmospheric pressure as an example, typical components are as follows: flow rate Q = 3t / h, temperature 40℃, pH 8.9, ammonia nitrogen 3000-5000 mg / L, COD ≤ 200 mg / L. The condensate contains a high concentration of ammonia nitrogen, which is not permitted to be directly discharged into natural waterways as it would have a serious impact on the environment. In previous projects, treating the high concentration of ammonia nitrogen in the condensate required specialized equipment and the addition of chemicals. The treated condensate was then discharged only after meeting emission standards, which increased equipment investment and operating costs, resulting in a waste of water resources. In this embodiment, the condensate from the wet gas condensation in other equipment within the plant is transported by tanker truck to water tank 7, serving as cooling water for the tubes in the economizer 1. In this way, the coal gas condensate can be reused. In addition, the coal gas condensate contains ammonia nitrogen, and the red mud settling wash water contains sodium carbonate, which is an alkaline environment that is conducive to the decomposition of ammonia nitrogen in the coal gas condensate. There is no need to set up a separate process or add separate decomposition agents for the coal gas condensate, which simplifies the process and saves costs.

[0026] In one specific embodiment, a first TIC valve 4 is provided on the first liquid inlet pipe 8. The opening degree of the first TIC valve 4 is controlled according to the gas temperature in the gas outlet pipe 5, and the gas temperature in the gas outlet pipe 5 is directly proportional to the opening degree of the first TIC valve 4. The higher the gas temperature in the gas outlet pipe 5, the larger the opening degree of the first TIC valve 4, in order to increase the water flow and cool the gas; similarly, the lower the gas temperature in the gas outlet pipe 5, the smaller the opening degree of the first TIC valve 4, in order to reduce the water flow and ensure the temperature of the water entering the hot water heater 11.

[0027] In one specific embodiment, the first outlet pipe 2 and the first inlet pipe 8 are connected by a connecting pipe 10, on which a second TIC valve 3 is provided. The opening degree of the second TIC valve 3 is controlled according to the liquid temperature in the first outlet pipe 2, and the liquid temperature in the first outlet pipe 2 is inversely proportional to the opening degree of the second TIC valve 3. When the liquid temperature in the first outlet pipe 2 is high, the opening degree of the second TIC valve 3 is small, allowing hot water to flow directly into the hot water heater 11. When the liquid temperature in the first outlet pipe 2 is low, the opening degree of the second TIC valve 3 is large, allowing the liquid to flow back into the economizer 1 for heat exchange.

[0028] In one specific embodiment, a lower economizer outlet gas temperature is more beneficial for waste heat recovery. However, a low economizer outlet gas temperature may cause water vapor in the gas to condense and dust in the gas to adhere to the bag filter 6, affecting the safe operation of the bag filter 6. A dew point analyzer 16 is installed on the outlet pipe 5. The dew point analyzer 16 is an online detector, interlocked with the TIC valve 4, maximizing the utilization of waste heat from the gas while ensuring no condensation.

[0029] In one specific embodiment, the economizer 1 is equipped with a second cooling pipe. One end of the second cooling pipe is connected to a low-temperature demineralized water source via a second liquid inlet pipe 12, and the other end is connected to a steam drum 14 via a second liquid outlet pipe 15. In this embodiment, the economizer 1 is divided into a high-temperature zone and a low-temperature zone. The high-temperature zone is located near the gas inlet, and the second cooling pipe is installed in the high-temperature zone to heat the low-temperature demineralized water into steam for storage. The low-temperature zone is equipped with a first cooling pipe to heat the gas condensate into hot water, which is used to heat the red mud settling wash water.

[0030] In one specific embodiment, the second liquid inlet pipe 12 is equipped with an LIC valve 13; the opening degree of the LIC valve 13 is controlled according to the liquid level in the steam drum 14, and the liquid level in the steam drum 14 is inversely proportional to the opening degree of the LIC valve 13. The higher the liquid level in the steam drum 14, the smaller the opening degree of the LIC valve 13, to prevent liquid from overflowing from the steam drum.

[0031] The following are specific examples.

[0032] Example 1

[0033] In this embodiment, the above system is used, and 3 t / h of coal gas condensate is added to water tank 7. The ammonia nitrogen content in the coal gas condensate is 3000-5000 mg / L, saving 26 x 10 4 kcal / h, saving 40 kg / h of ammonia nitrogen treatment agent.

[0034] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A heat recovery system for coal gas condensate water, characterized by, The coal economizer (1) is connected with the outlet of the coal gas, and the outlet of the coal economizer (1) is connected with the bag-type dust collector (6) through the gas outlet pipe (5); The first cooling pipe is arranged in the coal economizer (1) and used for cooling the coal gas, one end of the first cooling pipe is connected with the water pool (7) through the first liquid inlet pipe (8), the water pump (9) is arranged on the first liquid inlet pipe (8), the other end of the first cooling pipe is connected with the hot water heater (11) through the first liquid outlet pipe (2), and the hot water heater (11) is used for heating the red mud settling washing water; The inlet of the hot water heater (11) is also connected with the red mud settling washing water source and the heating steam source respectively, and the outlet of the hot water heater (11) is connected with the red mud separation washing unit; the water in the water pool (7) is the coal gas condensate water, the coal gas condensate water contains ammonia nitrogen, and the ammonia nitrogen content in the coal gas condensate water is 3000-5000 mg / L.

2. The system for heat recovery of coal gas condensate water according to claim 1, characterized by, The first TIC valve (4) is arranged on the first liquid inlet pipe (8); The opening degree of the first TIC valve (4) is controlled according to the temperature of the coal gas in the gas outlet pipe (5), and the temperature of the coal gas in the gas outlet pipe (5) is proportional to the opening degree of the first TIC valve (4).

3. The system for heat recovery of coal gas condensate water according to claim 1, characterized by, The first liquid outlet pipe (2) and the first liquid inlet pipe (8) are communicated through the communication pipe (10), and the second TIC valve (3) is arranged on the communication pipe (10); The opening degree of the second TIC valve (3) is controlled according to the temperature of the liquid in the first liquid outlet pipe (2), and the temperature of the liquid in the first liquid outlet pipe (2) is inversely proportional to the opening degree of the second TIC valve (3).

4. The system for heat recovery of coal gas condensate water according to claim 1, wherein The dew point analyzer (16) is arranged on the gas outlet pipe (5).

5. The system for heat recovery of coal gas condensate water according to claim 1, wherein The second cooling pipe is arranged in the coal economizer (1), one end of the second cooling pipe is connected with the low-temperature desalted water source through the second liquid inlet pipe (12), and the other end of the second cooling pipe is connected with the steam drum (14) through the second liquid outlet pipe (15).

6. The system for heat recovery of coal gas condensate water according to claim 5, wherein The LIC valve (13) is arranged on the second liquid inlet pipe (12); The opening degree of the LIC valve (13) is controlled according to the liquid level height in the steam drum (14), and the liquid level height in the steam drum (14) is inversely proportional to the opening degree of the LIC valve (13).

Images