Device and method for removing non-condensable gas through negative pressure and coupling flash evaporation waste heat utilization

Abstract

The invention provides a device and method for removing non-condensable gas through negative pressure and coupling flash evaporation waste heat utilization, and belongs to the technical field of energy saving. The device comprises a heat collector, a desulfurizing tower, a flash evaporation device and a heat pump which are connected in sequence, the flash evaporation device comprises a first-stage flash evaporation tank and a second-stage flash evaporation tank which are communicated through a through-flow device, and the heat collector is communicated with the heat pump through an auxiliary heater; and the heat pump is communicated with a heat supply pipe network. A large amount of non-condensed gas is separated out from the slurry in the first-stage flash tank, only low-temperature steam is flashed out from the slurry in the second-stage flash tank under vacuum negative pressure, the low-temperature steam enters a heat pump evaporator to be subjected to phase change, and phase change heat can be completely absorbed by a heat pump. Smoke sensible heat in front of an absorption tower is extracted to serve as a driving heat source of a heat pump, and smoke waste heat is effectively utilized to the maximum extent.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy conservation, and in particular relates to a device and method for negative pressure removal of non-condensable gas coupled with flash evaporation waste heat utilization. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Coal-fired heating in autumn and winter will lead to increased pollutant emissions in the atmosphere, which is one of the reasons for the severe haze in winter. Waste heat heating is an important technical means to control winter haze. Waste heat heating is based on waste heat from high-energy-consuming industrial enterprises such as power plants and steel mills. After being heated by heat pumps, it can stably and effectively meet the heating needs of surrounding residents in autumn and winter, thereby significantly reducing coal-fired heating consumption and reducing the emission of atmospheric pollutants.

[0004] Among the various heat losses of the boiler system, exhaust loss accounts for more than 50% of the total heat loss. Most coal-fired power plants use wet desulfurization technology. During the desulfurization process, a large amount of water evaporates into the flue gas. After desulfurization, the flue gas is saturated and the sensible heat of the flue gas is converted into latent heat of water vapor. Realizing the deep utilization of flue gas latent heat is of great practical significance for energy conservation, emission reduction, water conservation, and reducing environmental pollution. Summary of the invention

[0005] Based on the current technical status, the purpose of the present invention is to provide a device and method for negative pressure removal of non-condensable gases coupled with flash evaporation waste heat utilization, which can efficiently remove non-condensable gases in slurry and avoid the impact of non-condensable gases on the thermal efficiency of absorption heat pumps. At the same time, the exhaust steam condensate produced by flash evaporation of slurry is of high quality and can be used to supplement the heating network system and desulfurization system, playing a significant role in saving water.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] In a first aspect, a device for negative pressure removal of non-condensable gases coupled with flash evaporation waste heat utilization comprises a heat collector, a desulfurization tower, a flash evaporation device and a heat pump connected in sequence; the flash evaporation device comprises a primary flash tank and a secondary flash tank connected by a flow device, the heat collector is connected to the heat pump via an auxiliary heater; the heat pump is connected to a heating network.

[0008] Optionally, the slurry outlet of the desulfurization tower is connected to the flash spray layer of the primary flash tank, the primary flash tank includes a primary slurry pool, and the primary slurry pool is connected to the secondary flash tank through a flow device; the secondary flash tank includes a secondary slurry pool, and the secondary slurry pool is connected to the slurry spray device of the desulfurization tower; most of the non-condensable gases are separated out in the primary flash tank, and the non-condensable gases contained in the primary slurry in the primary flash tank are greatly reduced, and the flash exhaust steam (low-temperature steam) in the secondary flash tank is completely formed by the primary slurry, which basically does not contain non-condensable gases, thereby preventing the non-condensable gases from entering the heat pump evaporator and affecting the heat exchange efficiency, causing the heat pump COP value to seriously deviate from the design value.

[0009] In a second aspect, a method for utilizing waste heat of flash evaporation by coupling negative pressure removal of non-condensable gas based on the above-mentioned device for utilizing waste heat of flash evaporation by coupling negative pressure removal of non-condensable gas comprises the following process:

[0010] S1. The desulfurization slurry accumulated in the desulfurization tower enters the primary flash tank and is converted into primary slurry and non-condensable gas. The primary slurry enters the secondary flash tank through the flow device and is converted into secondary slurry and low-temperature steam. The low-temperature steam enters the heat pump to release latent heat, and the secondary slurry returns to the desulfurization tower;

[0011] S2, the heat collector absorbs the heat of the original flue gas entering the desulfurization tower to heat the circulating medium, and the circulating medium is input into the heat pump as a driving heat source of the heat pump;

[0012] S3. The heat pump realizes heating through a heating pipe network.

[0013] The beneficial effects of the present invention are:

[0014] 1. The present invention sets a primary slurry flash tank to remove non-condensable gases and eliminate the impact on the operation of the vacuum system and the output of the heat pump. A large amount of non-condensable gases are precipitated in the slurry in the primary flash tank, and the primary vacuum pump extracts the non-condensable gases and discharges them into the atmosphere. The slurry after the non-condensable gases are removed in the primary flash system enters the secondary flash tank. The slurry in the secondary flash tank only flashes out low-temperature steam under vacuum negative pressure. The low-temperature steam enters the heat pump evaporator and undergoes phase change. The phase change heat can be completely absorbed by the heat pump. The sensible heat of the flue gas before the absorption tower is extracted as the driving heat source of the heat pump, and the waste heat of the flue gas is effectively utilized to the greatest extent, and the energy consumption of the flash system is reduced. A steam auxiliary heater is set on the outlet hot water pipeline of the heat collector. When the heat extraction of the heat collector is insufficient and the COP of the heat pump is lower than the design value, steam is introduced into the steam auxiliary heater to supplement the driving heat required by the heat pump.

[0015] 2. The design of the heat pump system of the present invention can meet the needs of large-flow and low-flow heating water respectively, and ensure the safe and stable operation of the heat pump. During the heating season, the heating capacity heats large-flow heating network water; during the non-heating season, the heat pump heating capacity is used to heat low-flow boiler condensate and low-flow air heater. The heat pump output under variable operating conditions is mainly implemented using the logic of multi-objective PID control. The outlet temperature of the heated water is set in the control system as the main adjustment target of the heat pump. The control system will calculate and evaluate the various working parameters inside the heat pump under the new boundary conditions, so as to achieve safe and autonomous adjustment of the heat pump under variable operating conditions and meet the user's requirements for the output of the heat pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 This is a schematic diagram of the structure of the device for removing non-condensable gas by negative pressure coupled with flash evaporation waste heat utilization in Example 1.

[0018] Among them, 1. Heat collector; 2. Desulfurization tower; 3. Slurry spray device; 4. Slurry pump; 5. Bypass valve; 6. Return regulating valve; 7. Flash tank inlet regulating valve; 8. First-stage flash tank; 9. Cyclone defogger; 91. Cyclone plate; 92. Cyclone outer wall; 93. Cyclone center tube; 94. Cyclone partition; 10. Flash spray layer; 11. First-stage slurry pool; 12. Low-temperature steam pipeline; 13. Second-stage slurry pool; 14. First-stage vacuum pump ; 15. Slurry return pump; 16. Secondary vacuum pump; 17. Total vapor-liquid separator; 18. Heat pump; 19. Condensate heat exchanger; 20. Warm air heat exchanger; 21. Primary gas-liquid separator; 22. Secondary gas-liquid separator; 23. Steam auxiliary heater switch valve; 24. Steam auxiliary heater bypass valve; 26. Steam auxiliary heater; 27. Steam regulating valve; 28. Steam trap; 29. ​​Flow device; 30. Secondary flash tank. DETAILED DESCRIPTION

[0019] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0020] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0021] A device for negative pressure removal of non-condensable gas coupled with flash evaporation waste heat utilization, comprising a heat collector, a desulfurization tower, a flash evaporation device and a heat pump connected in sequence; the flash evaporation device comprises a primary flash tank and a secondary flash tank connected by a flow device, the heat collector is connected to the heat pump through an auxiliary heater; the heat pump is connected to a heating network.

[0022] Through the above arrangement, a large amount of non-condensable gas is precipitated in the slurry in the first-stage flash tank, and the first-stage vacuum pump extracts the non-condensable gas and discharges it into the atmosphere. The slurry after the non-condensable gas is removed in the first-stage flash system enters the second-stage flash tank. The slurry in the second-stage flash tank only flashes out low-temperature steam under vacuum negative pressure, and the low-temperature steam enters the heat pump evaporator to undergo phase change. The phase change heat can be completely absorbed by the heat pump. Since the non-condensable gas does not enter the heat pump, the efficiency of the heat pump is stable and easy to control.

[0023] Optionally, the slurry outlet of the desulfurization tower is connected to the flash spray layer of the primary flash tank, the primary flash tank includes a primary slurry pool, and the primary slurry pool is connected to the secondary flash tank through a flow device; the secondary flash tank includes a secondary slurry pool, and the secondary slurry pool is connected to the slurry spray device of the desulfurization tower; most of the non-condensable gases are separated out in the primary flash tank, and the non-condensable gases contained in the primary slurry in the primary flash tank are greatly reduced, and the low-temperature steam in the secondary flash tank is completely formed by the primary slurry, which basically does not contain non-condensable gases, thereby preventing the non-condensable gases from entering the heat pump evaporator and affecting the heat exchange efficiency, causing the heat pump COP value to seriously deviate from the design value.

[0024] Optionally, the first-stage flash tank is connected to a first-stage vacuum pump, and negative pressure is formed by the first-stage vacuum pump.

[0025] Optionally, a cyclone demisting device is provided in the first-stage flash tank, which is used to remove entrained droplets in the non-condensable gas.

[0026] Optionally, the cyclone defogger is composed of a cyclone plate, a cyclone outer wall, a cyclone center tube and a cyclone partition. The defogger mechanism of the cyclone defogger is as follows: after the airflow carrying a large number of droplets passes through the cyclone, the direction of the airflow changes, generating a rotating airflow, and the chasing effect produced by large droplets and small droplets causes the droplets to grow, thereby achieving the demisting effect.

[0027] Optionally, a primary gas-liquid separator is provided between the primary flash tank and the primary vacuum pump, for removing the secondary entrained droplets in the non-condensable gas to prevent the droplets from causing adverse effects on the vacuum pump.

[0028] Optionally, the secondary flash tank is connected to a secondary vacuum pump through the heat pump to ensure that the secondary flash tank flashes out the required low-temperature steam flow, temperature and pressure under negative pressure, and the flashed low-temperature steam enters the evaporator of the heat pump through the low-temperature steam pipeline, and the heat pump absorbs the heat of the exhaust steam; the condensed water formed by the low-temperature steam is supplemented into the auxiliary heating pipeline or the heat network pipeline.

[0029] Optionally, a secondary gas-liquid separator is provided between the heat pump and the secondary vacuum pump to prevent a small amount of non-condensable gas from carrying liquid droplets and affecting the output of the secondary vacuum pump.

[0030] Optionally, the auxiliary heater is a steam auxiliary heater, which is connected to external steam; when the heat collector does not take in enough heat, causing the COP of the heat pump to be lower than the design value, the steam auxiliary heater introduces steam to supplement the driving heat required by the heat pump.

[0031] Optionally, the heat pump is connected to a heating network for heating in winter.

[0032] Optionally, the heat pump is connected to a heater heat exchanger for exchanging heat with the boiler heater pipeline to realize waste heat utilization in seasons when heating is not required.

[0033] Optionally, the heat pump is connected to a condensate heat exchanger for exchanging heat with a boiler condensate pipeline to realize waste heat utilization in seasons when heating is not required.

[0034] Optionally, the primary vacuum pump and the secondary vacuum pump are connected to the atmosphere via a total vapor-liquid separator; the total vapor-liquid separator is provided to prevent residual droplets discharged into the atmosphere from polluting the environment when the ambient temperature is low.

[0035] A method for utilizing waste heat by coupling negative pressure removal of non-condensable gas and flash evaporation based on the above-mentioned device for utilizing waste heat by coupling negative pressure removal of non-condensable gas and flash evaporation comprises the following steps:

[0036] S1. The desulfurization slurry accumulated in the desulfurization tower enters the primary flash tank and is converted into primary slurry and non-condensable gas. The primary slurry enters the secondary flash tank through the flow device and is converted into secondary slurry and low-temperature steam. The low-temperature steam enters the heat pump to release latent heat, and the secondary slurry returns to the desulfurization tower;

[0037] S2, the heat collector absorbs the heat of the original flue gas entering the desulfurization tower to heat the circulating medium, and the circulating medium is input into the heat pump as a driving heat source of the heat pump;

[0038] S3. The heat pump realizes heating through a heating pipe network.

[0039] Optionally, in S1, non-condensable gas and droplets are separated from the primary gas-liquid separator by a cyclone demisting device, and the non-condensable gas is discharged by a primary vacuum pump.

[0040] Optionally, in S1, condensed water formed by low-temperature steam after releasing latent heat is added to the auxiliary heating pipeline or the heating network pipeline.

[0041] Optionally, when the heat of the heat collector in S2 is insufficient, the auxiliary heater is started to heat the circulating medium.

[0042] Example 1

[0043] The desulfurization slurry of the wet desulfurization tower contains a large amount of non-condensable gases such as CO2 and N2. During the vacuum negative pressure flash evaporation process, a large amount of non-condensable gases will precipitate from the slurry and enter the heat pump system together with the low-temperature steam. In the process of low-temperature steam releasing latent heat, the non-condensable gases will not condense but continue to exist in the form of gas. The non-condensable gases will affect the stable operation of the entire flash tank vacuum system and reduce the output of the heat pump.

[0044] This embodiment provides a device for removing non-condensable gas by negative pressure and utilizing flash evaporation waste heat, such as Figure 1 As shown, it includes a heat collector 1, a desulfurization tower 2, a flash device and a heat pump 18 connected in sequence; the flash device includes a primary flash tank 8 and a secondary flash tank 30 connected through a flow device 29, and the heat collector 1 is connected to the heat pump 18 through a steam auxiliary heater 26; the heat pump 18 is connected to the heating network.

[0045] A large amount of non-condensable gas is precipitated in the slurry in the first-stage flash tank 8, and the first-stage vacuum pump 14 extracts the non-condensable gas to be discharged into the atmosphere; the slurry after the non-condensable gas is removed in the first-stage flash system enters the second-stage flash tank 30, and the slurry in the second-stage flash tank 30 only flashes out low-temperature steam under vacuum negative pressure, and the low-temperature steam enters the evaporator of the heat pump 18 to undergo phase change, and the phase change heat energy can be completely absorbed by the heat pump 18. Since the non-condensable gas does not enter the heat pump 18, the efficiency of the heat pump 18 is stable and easy to control.

[0046] The slurry outlet of the desulfurization tower 2 is connected to the flash spray layer 10 of the primary flash tank 8 through the slurry pump 4. The primary flash tank 8 includes a primary slurry pool 11, which is connected to the secondary flash tank 30 through the flow device 29; the secondary flash tank 30 includes a secondary slurry pool 13, which is connected to the slurry spray device 3 of the desulfurization tower 2; most of the non-condensable gases are separated out in the primary flash tank 8, and the non-condensable gases that can be dissolved in the primary slurry accumulated in the primary slurry pool 11 are greatly reduced. The low-temperature steam in the secondary flash tank 30 is completely formed by the primary slurry, which basically does not contain non-condensable gases, thereby preventing the non-condensable gases from entering the evaporator of the heat pump 18 and affecting the heat exchange efficiency, causing the COP value of the heat pump 18 to seriously deviate from the design value.

[0047] The flow device 29 includes a plurality of flow holes with multiple apertures, so that the slurry in the primary pulp pool 11 enters the secondary flash tank 30 and atomizes the slurry in the form of a screen structure; the design takes into account that the slurry in the primary pulp pool 11 will not flow into the secondary flash tank 30 quickly to prevent the liquid level of the primary pulp pool 11 from being unable to be maintained, and also takes into account that the slurry will not scale in the flow device 29 and will not be atomized in the secondary flash tank 30.

[0048] A flash tank slurry inlet regulating valve 7 is arranged between the slurry outlet of the desulfurization tower 2 and the flash spray layer 10, a slurry return pump 15 and a return regulating valve 6 are arranged between the secondary slurry pool 13 and the slurry spray device 3 of the desulfurization tower 2, and the slurry outlet pipeline of the desulfurization tower 2 and the inlet of the slurry spray device 3 are connected by a pipeline equipped with a bypass valve 5, which is used to adjust the proportion of the desulfurization slurry of the desulfurization tower 2 entering the primary flash tank 8 and the proportion of the secondary slurry in the secondary slurry pool 13 flowing back into the desulfurization tower 2.

[0049] The primary slurry pool 11 serves as a buffer pool for the slurry. The slurry pool design takes into account the angle between the slope of the slurry pool and the horizontal level of 15°, which not only stabilizes the negative pressure of the primary flash tank 8, but also ensures that the slurry does not settle.

[0050] The secondary slurry pool 13 is used as a buffer pool for the slurry. The design takes into account the angle of 20° between the slope of the slurry pool and the horizontal. It not only stabilizes the negative pressure of the secondary flash tank 30, but also ensures that the slurry does not settle. The primary and secondary flash tanks are both arranged in an elevated manner. A slurry return pump 15 is set below the secondary slurry pool 13. After the slurry temperature drops by 5-10°C after flashing, the cold slurry returns to the slurry spray device 3 through the slurry return pump 15 to be atomized and heat exchanged with the saturated wet flue gas in the desulfurization tower 2, absorbing the latent heat of vaporization in the wet flue gas. The cold slurry controls the flow rate of heat exchange with the saturated wet flue gas through the return regulating valve 6 to achieve the best energy-saving effect.

[0051] The primary flash tank 8 is connected to the primary vacuum pump 14 , and negative pressure is formed by the primary vacuum pump 14 .

[0052] A cyclone demisting device 9 is provided in the primary flash tank 8 , which is used to remove entrained droplets in the non-condensable gas discharged from the primary flash tank 8 .

[0053] The cyclone defogger 9 is composed of a cyclone plate, a cyclone outer wall, a cyclone central tube and a cyclone partition. The cyclone central tube can rotate around the central axis. A plurality of cyclone plates are installed on the periphery of the cyclone central tube, and the cyclone plates are surrounded by a cyclone outer wall as a fixing device; the cyclone plates, the cyclone outer wall and the cyclone central tube constitute a cyclone, and the cyclone is installed in a frame composed of a plurality of cyclone partitions; the cyclone plates of two adjacent cyclones are both clockwise or counterclockwise, so the intersection and coupling area of ​​the two adjacent cyclones produces an airflow countercurrent effect, a large number of small droplets in the airflow collide with the small droplets in the oncoming airflow, resulting in primary polymerization, secondary polymerization or even multiple polymerization between the droplets to form large droplet particles, thereby achieving the best demisting efficiency; the demisting mechanism of the cyclone defogger 9 is: after the airflow carrying a large number of droplets passes through the cyclone, the airflow direction changes to generate a rotating airflow, and the pursuit effect generated by the large droplets and the small droplets causes the droplets to grow, thereby achieving the demisting effect.

[0054] A primary gas-liquid separator 21 is provided between the primary flash tank 8 and the primary vacuum pump 14, and is used to remove the mist droplets entrained in the non-condensable gas for the second time, so as to avoid the mist droplets from causing adverse effects on the vacuum pump.

[0055] The secondary flash tank 30 is connected to the secondary vacuum pump 16 through the heat pump 18 to ensure that the secondary flash tank 30 flashes out the required low-temperature steam flow, temperature and pressure under negative pressure. The flashed low-temperature steam enters the evaporator of the heat pump 18 through the low-temperature steam pipe 12, and the heat pump 18 absorbs the heat of the low-temperature steam; the condensed water formed by the low-temperature steam is supplemented into the auxiliary heating pipeline or the heat network pipeline.

[0056] A secondary gas-liquid separator 22 is provided between the heat pump 18 and the secondary vacuum pump 16 to prevent a small amount of non-condensable gas from carrying liquid droplets and affecting the output of the secondary vacuum pump 16 .

[0057] The steam auxiliary heater 26 is an auxiliary heater, and the steam auxiliary heater 26 is connected to external steam through a steam regulating valve 27 and a steam trap 28; when the heat extraction of the heat collector 1 is insufficient and causes the COP of the heat pump to be lower than the design value, steam is introduced into the steam auxiliary heater 26 to supplement the driving heat required by the heat pump 18; the flow rate of steam is controlled by the steam regulating valve 27, and the steam condensate after work enters the steam trap 28 and is discharged; the front and rear ends of the steam auxiliary heater 26 are respectively provided with steam auxiliary heater switch valves 23, and the steam auxiliary heater 26 is connected in parallel with the steam auxiliary heater bypass valve 24. By adjusting the steam auxiliary heater bypass valve 24 and the two steam auxiliary heater switch valves 23, the steam auxiliary heater 26 can be cut in / out.

[0058] The heat pump 18 is connected to the heating network for heating in winter.

[0059] The heat pump 18 is connected to the heater heat exchanger 20 for exchanging heat with the boiler heater pipeline to realize waste heat utilization in seasons when heating is not required.

[0060] The heat pump 18 is connected to the condensate heat exchanger 19 for exchanging heat with the boiler condensate pipeline to realize waste heat utilization in seasons when heating is not required.

[0061] The primary vacuum pump 14 and the secondary vacuum pump 16 are connected to the atmosphere through a total vapor-liquid separator 17; the total vapor-liquid separator 17 is provided to prevent residual droplets discharged into the atmosphere from polluting the environment when the ambient temperature is low.

[0062] The negative pressure removal of non-condensable gas coupled with flash evaporation waste heat utilization method of the device for negative pressure removal of non-condensable gas coupled with flash evaporation waste heat utilization according to this embodiment includes the following process:

[0063] S1. The desulfurization slurry accumulated in the desulfurization tower 2 enters the primary flash tank 8 and is converted into primary slurry and non-condensable gas. The non-condensable gas and droplets are separated from the primary gas-liquid separator by the cyclone demisting device 9, and the non-condensable gas is discharged by the primary vacuum pump 14; the primary slurry enters the secondary flash tank 30 through the flow device 29 and is converted into secondary slurry and low-temperature steam. The low-temperature steam enters the heat pump 18 to release latent heat, and the secondary slurry returns to the desulfurization tower 2; the condensed water formed by the low-temperature steam after releasing the latent heat is supplemented into the auxiliary heating pipeline or the heat network pipeline.

[0064] S2, the heat collector 1 absorbs the heat of the original flue gas entering the desulfurization tower 2 to heat the circulating medium, and the circulating medium is input into the heat pump 18 as the driving heat source of the heat pump 18. When the heat of the heat collector 1 is insufficient, the steam auxiliary heater 26 is started to heat the circulating medium;

[0065] S3. The heat pump 18 realizes heating through the heating pipe network.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for removing non-condensable gas by negative pressure coupled with flash evaporation waste heat utilization, characterized in that: It includes a heat collector, a desulfurization tower, a flash device and a heat pump which are connected in sequence; the flash device includes a primary flash tank and a secondary flash tank which are connected through a flow device, the heat collector is connected to the heat pump through an auxiliary heater; the heat pump is connected to a heating network.

2. The device for removing non-condensable gas by negative pressure coupled with flash evaporation waste heat utilization as claimed in claim 1, characterized in that: The slurry outlet of the desulfurization tower is connected to the flash spray layer of the primary flash tank. The primary flash tank includes a primary slurry pool, which is connected to the secondary flash tank through a flow device; the secondary flash tank includes a secondary slurry pool, which is connected to the slurry spray device of the desulfurization tower.

3. The device for removing non-condensable gas by negative pressure coupled with flash evaporation waste heat utilization as claimed in claim 1, characterized in that: The primary flash tank is connected to a primary vacuum pump.

4. The device for removing non-condensable gas by negative pressure coupled with flash evaporation waste heat utilization as claimed in claim 3, characterized in that: A primary gas-liquid separator is arranged between the primary flash tank and the primary vacuum pump.

5. The device for removing non-condensable gas by negative pressure coupled with flash evaporation waste heat utilization as claimed in claim 1, characterized in that: The secondary flash tank is connected to a secondary vacuum pump through the heat pump; a secondary gas-liquid separator is arranged between the heat pump and the secondary vacuum pump.

6. The device for removing non-condensable gas by negative pressure coupled with flash evaporation waste heat utilization as claimed in claim 1, characterized in that: The auxiliary heater is a steam auxiliary heater, and the steam auxiliary heater is connected to external steam.

7. The device for removing non-condensable gas by negative pressure coupled with flash evaporation waste heat utilization as claimed in claim 1, characterized in that: The heat pump is connected to a heating network; optionally, the heat pump is connected to a heater heat exchanger; optionally, the heat pump is connected to a condensate heat exchanger.

8. A method for utilizing waste heat by coupling negative pressure removal of non-condensable gas and flash evaporation based on the device for utilizing waste heat by coupling negative pressure removal of non-condensable gas and flash evaporation according to any one of claims 1 to 7, characterized in that: The process includes: S1. The desulfurization slurry accumulated in the desulfurization tower enters the primary flash tank and is converted into primary slurry and non-condensable gas. The primary slurry enters the secondary flash tank through the flow device and is converted into secondary slurry and low-temperature steam. The low-temperature steam enters the heat pump to release latent heat, and the secondary slurry returns to the desulfurization tower; S2, the heat collector absorbs the heat of the original flue gas entering the desulfurization tower to heat the circulating medium, and the circulating medium is input into the heat pump as a driving heat source of the heat pump; S3. The heat pump realizes heating through a heating pipe network.

9. A method for utilizing the residual heat of flash evaporation coupled with the negative pressure removal of non-condensable gas as claimed in claim 8, characterized in that: In S1, condensed water formed by low-temperature steam after releasing latent heat is added to the auxiliary heating pipeline or the heat network pipeline.

10. The method for utilizing waste heat by coupling flash evaporation with removal of non-condensable gas by negative pressure as claimed in claim 8, characterized in that: When the heat of the heat exchanger in S2 is insufficient, the auxiliary heater is started to heat the circulating medium.

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