Refrigerant dehydration system and dehydration method for removing low-temperature pollutants from flue gas

Abstract

The invention discloses a refrigerant dehydration system and a dehydration method for removing low-temperature pollutants from flue gas. The system comprises a refrigerant buffer tank, a three-stage circulation pump and a three-stage circulation cooler which are sequentially connected to a refrigerant circulating liquid outlet arranged on a flue gas cooling tower. The outlet of the three-stage circulation cooler is connected to a refrigerant circulating liquid inlet. The flue gas outlet of the flue gas cooling tower is connected to an adsorber, which is connected to the flue gas inlet of a refrigerant dehydration tower through a flue gas pipeline. The outlet of the three-stage circulation pump is divided into two paths, one of which is connected to the circulating liquid inlet of the three-stage circulation cooler, and the other is connected to the circulating liquid inlet of the refrigerant dehydration tower. The invention brings desulfurized and denitrified dry flue gas into countercurrent contact with the refrigerant, uses the dry flue gas to take away the moisture in the refrigerant, can effectively and continuously remove the moisture in the refrigerant, does not increase the energy consumption of the system, and the device is simple and easy to implement.

Description

Technical Field

[0001] The invention belongs to the technical field of flue gas pollutant purification, and in particular relates to a refrigerant dehydration system and a dehydration method for removing low-temperature pollutants from flue gas. Background Art

[0002] In the field of integrated removal of low-temperature flue gas pollutants, in order to increase the adsorption capacity of unit adsorbent and reduce the filling volume of adsorbent, it is necessary to cool the flue gas from high temperature to sub-zero temperature in stages. Due to the water content in the flue gas, when the flue gas continues to cool below zero degrees Celsius, if the method of indirect heat exchange between the flue gas and the refrigerant is adopted, as the operating time increases, the moisture in the flue gas will freeze on the flue gas side of the heat exchanger, increasing the resistance of the heat exchanger and even clogging it. If the method of direct heat exchange between the flue gas and the refrigerant is adopted, as the operating time increases, the refrigerant will be diluted by the moisture in the flue gas, resulting in an increase in the freezing point of the refrigerant, requiring the addition or replacement of fresh refrigerant, affecting the stability of system operation, and increasing the consumption of refrigerant and operating costs.

[0003] Traditional refrigerant dehydration methods generally use desiccant drying or direct heating evaporation. In the process of regeneration or heating evaporation of the desiccant after absorbing water, a large amount of heat energy is consumed, resulting in energy waste, and a series of heating and cooling equipment need to be added, and the process is relatively cumbersome. Therefore, the development of a new refrigerant dehydration system suitable for the integrated removal of low-temperature pollutants in flue gas has become the focus of research. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a refrigerant dehydration system and a dehydration method for removing low-temperature pollutants in flue gas. The system can effectively and continuously remove moisture from the refrigerant without affecting the stability of the operation of the integrated flue gas low-temperature pollutant removal process, without increasing the system energy consumption, and the device is simple and easy to implement.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a refrigerant dehydration system for removing low-temperature pollutants from flue gas, comprising a flue gas cooling tower, wherein a primary cooling spray device, a secondary cooling spray device and a tertiary cooling spray device are sequentially arranged in the flue gas airflow direction in the flue gas cooling tower, the flue gas outlet of the flue gas cooling tower is connected with an adsorber, the adsorber is used to remove sulfur and nitrate components in the flue gas, the outlet of the adsorber is connected to the flue gas inlet of the refrigerant dehydration tower through a flue gas pipeline, the circulating liquid outlet of the tertiary cooling spray device is connected to the inlet of a tertiary circulating pump through a pipeline via a refrigerant buffer tank, the outlet of the tertiary circulating pump is divided into two paths, one of which is connected to the circulating liquid inlet of the tertiary circulating cooler, and the other is connected to the circulating liquid inlet of the refrigerant dehydration tower, the circulating liquid inlet of the tertiary cooling spray device is connected to the circulating liquid outlet of the tertiary circulating cooler, the circulating liquid outlet of the refrigerant dehydration tower is connected to the refrigerant buffer tank, and the circulating liquid used by the tertiary cooling spray device is a refrigerant.

[0006] A further solution is that a cold energy recovery device is provided on the flue gas duct, and the cold energy recovery device is used to recover the cold energy in the flue gas.

[0007] A further solution is that the circulating liquid outlet of the primary cooling spray device is connected to the primary circulating pump through a pipeline, the outlet of the primary circulating pump is connected to the circulating liquid inlet of the primary circulating cooler, the outlet of the primary circulating cooler is connected to the circulating liquid inlet of the cold recovery device, the circulating liquid outlet of the cold recovery device is connected to the circulating liquid inlet of the primary cooling spray device, and the circulating liquid used by the primary cooling spray device is cooling water.

[0008] A further solution is that the cooling water inlet of the primary circulating cooler is connected to the circulating cooling water supply pipe of the power plant, and the cooling water outlet of the primary circulating cooler is connected to the circulating cooling water return pipe of the power plant.

[0009] A further solution is that the circulating liquid outlet of the secondary cooling spray device is connected to the secondary circulating pump through a pipeline, the outlet of the secondary circulating pump is connected to the inlet of the secondary circulating cooler, the outlet of the secondary circulating cooler is connected to the circulating liquid inlet of the secondary cooling spray device, and the circulating liquid used by the secondary cooling spray device is cooling water.

[0010] A further solution is that the cooling water inlet and outlet of the secondary circulation cooler are connected to the inlet and outlet of the first refrigerator; the cooling water inlet and outlet of the tertiary circulation cooler are connected to the inlet and outlet of the second refrigerator.

[0011] A further solution is that the coolant is a salt coolant.

[0012] A further solution is that a bypass pipe connected to the chimney is provided on the flue gas pipe, and the flue gas outlet of the refrigerant dehydration tower is connected to the chimney.

[0013] A further solution is that the ratio of the brine flow rate to the brine water removal tower to the total outlet flow rate of the primary circulation pump is 2-20%.

[0014] The refrigerant dehydration method for removing low-temperature pollutants from flue gas specifically includes:

[0015] After entering the flue gas cooling tower, the high-temperature flue gas undergoes primary cooling, secondary cooling and tertiary cooling in sequence. After the flue gas temperature drops below 5°C, it enters the adsorber, which desulfurizes and denitrates the low-temperature dry flue gas.

[0016] The low-temperature dry flue gas with sulfur and nitrate components removed goes to the cold recovery device to recover cold. After recovering cold, the flue gas at about 30-40°C is divided into two paths, one enters the refrigerant dehydration tower, and the other goes to the chimney. The one going to the chimney is directly discharged into the atmosphere; at the same time, a part of the refrigerant coming out of the refrigerant buffer tank also enters the refrigerant dehydration tower, and contacts with the dry flue gas in countercurrent. After the dry flue gas takes away the water enriched in the refrigerant, the refrigerant flows back to the refrigerant buffer tank.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: the traditional refrigerant dehydration method generally adopts a desiccant drying method or a direct heating evaporation method. In the process of regeneration of the desiccant after absorbing water or heating evaporation, a large amount of heat energy is consumed, resulting in energy waste, and a series of heating and cooling equipment need to be added. The process is relatively cumbersome. The present invention recovers the cold energy of the cooled dry flue gas through a cold energy recovery device, and then the dry flue gas at about 30 to 40°C is in countercurrent contact with the refrigerant, and the moisture in the refrigerant is taken away by the dry flue gas. The device can effectively and continuously remove the moisture in the refrigerant, and does not affect the stability of the operation of the integrated flue gas low-temperature pollutant removal process, does not increase the system energy consumption, and the device is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the process flow of the present invention.

[0019] Figure numerals: 1. Flue gas cooling tower, 2. Primary circulation pump, 3. Secondary circulation pump, 4. Third-stage circulation pump, 5. Primary circulation cooler, 6. Cold recovery device, 7. Secondary circulation cooler, 8. First refrigerator, 9. Third-stage circulation cooler, 10. Second refrigerator, 11. Refrigerant buffer tank, 12. Adsorber, 13. Refrigerant dehydration tower. DETAILED DESCRIPTION

[0020] The present invention will be described in more detail below in conjunction with the accompanying drawings and specific embodiments.

[0021] See attached Figure 1 A refrigerant dehydration system for removing low-temperature pollutants from flue gas comprises a flue gas cooling tower 1 connected to the high-temperature flue gas after dust removal in a power plant. A primary cooling spray device, a secondary cooling spray device and a tertiary cooling spray device are sequentially arranged in the flue gas cooling tower 1 along the flue gas flow direction from bottom to top. The circulating liquid outlet of the primary cooling spray device is connected to the inlet of a primary circulating pump 2, and the outlet of the primary circulating pump 2 is connected to the circulating liquid inlet of a primary circulating cooler 5. The circulating liquid outlet of the primary circulating cooler 5 is connected to the circulating liquid inlet of a cold recovery device 6, and the circulating liquid outlet of the cold recovery device 6 goes to the circulating liquid inlet of the primary cooling spray device. The primary circulating pump 2 is used to provide power so that the circulating liquid forms a cycle in the primary cooling spray device; the cooling water inlet of the primary circulating cooler 5 is connected to the circulating cooling water supply pipe of the power plant, and the cooling water outlet of the primary circulating cooler 5 is connected to the circulating cooling water return pipe of the power plant. The cooling capacity of the primary circulating cooler 5 is provided by the circulating cooling water of the power plant. The circulating liquid used in the first-stage cooling spray device is cooling water. When the flue gas enters the first-stage cooling spray device from bottom to top, the cooling water is sprayed from top to bottom. The two are in countercurrent contact and heat exchange. The cooling water and the flue gas are fully exchanged with each other. After the cooled flue gas temperature drops to about 40°C, it enters the second-stage cooling spray device.

[0022] In this embodiment, the circulating liquid outlet of the secondary cooling spray device is connected to the inlet of the secondary circulation pump 3, the outlet of the secondary circulation pump 3 is connected to the circulating liquid inlet of the secondary circulation cooler 7, the circulating liquid outlet of the secondary circulation cooler 7 goes to the circulating liquid inlet of the secondary cooling spray device, the secondary circulation pump 3 is used to provide power, so that the circulating liquid forms a cycle in the secondary cooling spray device; the refrigerant inlet of the secondary circulation cooler 7 is connected to the refrigerant outlet of the first refrigerator 8, the refrigerant outlet of the secondary circulation cooler 7 is connected to the refrigerant inlet of the first refrigerator 8, and the cooling capacity of the secondary circulation cooler 7 is provided by the first refrigerator 8. The circulating liquid used in the secondary cooling spray device is also cooling water. When the flue gas enters the secondary cooling spray device from bottom to top, the cooling water is sprayed from top to bottom, and the two are in countercurrent contact and heat exchange, and sufficient heat exchange is carried out between the cooling water and the flue gas. After the cooled flue gas temperature drops to about 5°C, it enters the tertiary cooling spray device.

[0023] In this embodiment, the circulating liquid outlet of the tertiary cooling spray device is connected to the upper end of the refrigerant buffer tank 11, and the lower end of the refrigerant buffer tank 11 is connected to the inlet of the tertiary circulating pump 4. The outlet of the tertiary circulating pump 4 is divided into two paths, one of which is connected to the upper end of the refrigerant dehydration tower 13, and the other is connected to the circulating liquid inlet of the tertiary circulating cooler 9. The refrigerant flow rate to the refrigerant dehydration tower 13 accounts for 2% to 20% of the total outlet flow of the tertiary circulating pump 4. The amount of water absorbed by the refrigerant in the flue gas can be judged by observing the change in the liquid level of the refrigerant buffer tank 11, thereby adaptively adjusting the refrigerant flow rate to the refrigerant dehydration tower 13. The circulating liquid outlet of the tertiary circulating cooler 9 is connected to the circulating liquid inlet of the tertiary cooling spray device. The tertiary circulating pump 4 is used to provide power so that the circulating liquid forms a cycle in the tertiary cooling spray device. The refrigerant inlet of the tertiary circulating cooler 9 is connected to the refrigerant outlet of the second refrigerator 10. The circulating liquid used in the tertiary cooling spray device is a salt refrigerant, preferably a calcium chloride solution. When the flue gas enters the tertiary cooling spray device from bottom to top, the refrigerant is sprayed from top to bottom, and the two are in countercurrent contact for heat exchange. The cooling water and the refrigerant are fully exchanged with each other. At the same time, the refrigerant will be diluted by the moisture in the flue gas, taking away the moisture in the flue gas. The cooled flue gas temperature drops to below 5°C before entering the adsorber 12.

[0024] In this embodiment, after the low-temperature flue gas enters the adsorber 12, the adsorber 12 removes sulfur, nitrate and other components in the flue gas, and then the flue gas outlet of the adsorber 12 is connected to the flue gas inlet of the cold recovery device 6, and the clean cold flue gas goes to the cold recovery device 6 to recover cold energy. After recovering the cold energy, the temperature rises to about 30-40°C, and the flue gas outlet of the cold recovery device 6 is divided into two paths, one path goes to the chimney and is directly discharged into the air, and the other path goes to the lower end of the refrigerant dehydration tower 13, and contacts with the refrigerant in countercurrent. The dry flue gas takes away the water enriched in the refrigerant and is discharged into the air through the chimney. The refrigerant after dehydration in the refrigerant dehydration tower 13 returns to the refrigerant buffer tank 11.

[0025] The present invention provides a refrigerant dehydration method for integrated removal of low-temperature pollutants in flue gas, which specifically comprises:

[0026] After entering the flue gas cooling tower 1, the high-temperature flue gas undergoes primary cooling, secondary cooling and tertiary cooling in sequence. After the flue gas temperature drops below 5°C, it enters the adsorber 12, which performs desulfurization and denitrification treatment on the low-temperature dry flue gas.

[0027] The low-temperature dry flue gas with sulfur and nitrate components removed goes to the cold recovery device 6 to recover cold energy. After recovering cold energy, the flue gas at about 30-40°C is divided into two paths, one path enters the refrigerant dehydration tower 13, and the other path goes to the chimney. The path going to the chimney is directly discharged into the atmosphere; at the same time, a part of the refrigerant coming out of the refrigerant buffer tank 11 also enters the refrigerant dehydration tower 13, and contacts with the dry flue gas in countercurrent. After the dry flue gas takes away the water enriched in the refrigerant, the refrigerant flows back to the refrigerant buffer tank 11.

[0028] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A refrigerant dehydration system for removing low-temperature pollutants from flue gas, comprising a flue gas cooling tower (1), wherein a primary cooling spray device, a secondary cooling spray device and a tertiary cooling spray device are sequentially arranged in the flue gas cooling tower (1) along the flue gas flow direction, and characterized in that: The flue gas outlet of the flue gas cooling tower (1) is connected to an adsorber (12), and the adsorber (12) is used to remove sulfur and nitrate components in the flue gas. The outlet of the adsorber (12) is connected to the flue gas inlet of the coolant dehydration tower (13) through a flue gas pipeline. The circulating liquid outlet of the three-stage cooling spray device is connected to the inlet of the three-stage circulating pump (4) through a pipeline via the coolant buffer tank (11). The outlet of the three-stage circulating pump (4) is divided into two paths, one of which is connected to the circulating liquid inlet of the three-stage circulating cooler (9), and the other is connected to the circulating liquid inlet of the coolant dehydration tower (13). The circulating liquid inlet of the three-stage cooling spray device is connected to the circulating liquid outlet of the three-stage circulating cooler (9), and the circulating liquid outlet of the coolant dehydration tower (13) is connected to the coolant buffer tank (11). The circulating liquid used by the three-stage cooling spray device is coolant; wherein, The flue gas pipeline is provided with a cold recovery device (6), and the cold recovery device (6) is used to recover the cold in the flue gas. The circulating liquid outlet of the primary cooling spray device is connected to the primary circulation pump (2) through a pipeline, and the outlet of the primary circulation pump (2) is connected to the circulating liquid inlet of the primary circulation cooler (5), and the outlet of the primary circulation cooler (5) is connected to the circulating liquid inlet of the cold recovery device (6). The circulating liquid outlet of the cold recovery device (6) is connected to the circulating liquid inlet of the primary cooling spray device. The circulating liquid used by the primary cooling spray device is cooling water. A part of the coolant coming out of the coolant buffer tank (11) also enters the coolant dehydration tower (13) and contacts with the dry flue gas in countercurrent. After the dry flue gas takes away the water enriched in the coolant, the coolant flows back to the coolant buffer tank (11). The coolant is a salt coolant.

2. The refrigerant dehydration system for low-temperature flue gas pollutant removal according to claim 1 is characterized in that: The cooling water inlet of the primary circulating cooler (5) is connected to the circulating cooling water supply pipeline of the power plant, and the cooling water outlet of the primary circulating cooler (5) is connected to the circulating cooling water return pipeline of the power plant.

3. The refrigerant dehydration system for removing low-temperature pollutants from flue gas according to claim 1 is characterized in that: The circulating liquid outlet of the secondary cooling spray device is connected to the secondary circulating pump (3) through a pipeline, the outlet of the secondary circulating pump (3) is connected to the inlet of the secondary circulating cooler (7), the outlet of the secondary circulating cooler (7) is connected to the circulating liquid inlet of the secondary cooling spray device, and the circulating liquid used by the secondary cooling spray device is cooling water.

4. The refrigerant dehydration system for removing low-temperature pollutants from flue gas according to claim 3 is characterized in that: The cooling water inlet and outlet of the secondary circulation cooler (7) are connected to the inlet and outlet of the first refrigerator (8); the cooling water inlet and outlet of the tertiary circulation cooler (9) are connected to the inlet and outlet of the second refrigerator (10).

5. The refrigerant dehydration system for removing low-temperature pollutants from flue gas according to claim 1, characterized in that: The flue gas pipeline is provided with a bypass pipeline connected to the chimney, and the flue gas outlet of the coolant dehydration tower (13) is connected to the chimney.

6. The refrigerant dehydration system for removing low-temperature pollutants from flue gas according to claim 1, characterized in that: The ratio of the brine flow rate to the brine dewatering tower (13) to the total outlet flow rate of the tertiary circulation pump (4) is 2-20%.

7. A refrigerant dehydration method for removing low-temperature pollutants from flue gas, the refrigerant dehydration method being applied to the refrigerant dehydration system for removing low-temperature pollutants from flue gas as claimed in claim 1, characterized in that: Specifically, the high-temperature flue gas enters a flue gas cooling tower (1) and undergoes primary cooling, secondary cooling and tertiary cooling in sequence. After the flue gas temperature drops to below 5° C., it enters an adsorber (12), and the adsorber (12) performs desulfurization and denitrification treatment on the low-temperature dry flue gas. The low-temperature dry flue gas from which sulfur and nitrate components have been removed is sent to a cold energy recovery device (6) to recover cold energy. After the cold energy is recovered, the flue gas at 30 to 40°C is divided into two paths, one path entering a refrigerant dehydration tower (13) and the other path going to a chimney. The path going to the chimney is directly discharged into the atmosphere. At the same time, a portion of the refrigerant coming out of the refrigerant buffer tank (11) also enters the refrigerant dehydration tower (13) to come into countercurrent contact with the dry flue gas. After the dry flue gas takes away the water enriched in the refrigerant, the refrigerant flows back into the refrigerant buffer tank (11).

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