Ejecting type heat pump flue gas waste heat recovery system for graded flash evaporation of desulfurization slurry

Abstract

The utility model discloses an injection type heat pump flue gas waste heat recovery system for desulfurization slurry grading flash evaporation, and belongs to the technical field of coal-fired boiler waste heat heat supply. Desulfurization slurry grading flash evaporation and an injection type heat pump technology are combined, deep flue gas waste heat recovery is achieved, the water temperature of a heat supply network is greatly increased, and the process includes the steps that desulfurization slurry is firstly fed into a front flash evaporation tank to be subjected to first-stage negative pressure flash evaporation, and flash evaporation steam is used for first-stage preheating of return water of the heat supply network; the first-stage concentrated slurry is sent to an injection flash tank for second-stage negative pressure flash evaporation, flash steam is sent to a negative pressure injector and is driven by heat supply steam to be pressurized into medium-pressure steam, and then second-stage large-temperature-difference heating is conducted on heat supply network return water; returning the secondary concentrated slurry to a desulfurized water system; non-condensable gas with high SO2 content on the liquid level of front flash steam condensed water is vacuumized by the ejector, so that the temperature of front slurry can be greatly reduced, and the temperature of flue gas is greatly reduced; and the pressure of the injection medium-pressure exhaust steam is higher, so that the non-condensable gas can be condensed by adopting a conventional vacuum pump.

Description

Technical Field

[0001] The utility model relates to an ejector heat pump flue gas waste heat recovery system for desulfurized slurry staged flash evaporation, belonging to the technical field of waste heat heating of coal-fired boilers. Background Technique

[0002] A large amount of high-temperature flue gas is discharged during the heat production process of boilers. Recycling the waste heat of flue gas can not only reduce the heat loss of boilers, but also reduce fuel consumption and pollutant emissions such as greenhouse gases, and improve the thermal efficiency of boilers. Existing flue gas waste heat recovery systems mainly include three categories: (1) The first category is to use a shell-and-tube heat exchanger to achieve flue gas waste heat recovery, that is, to use a low-temperature economizer or an economizer, etc. Install a heat exchanger with a tubular structure or the like on the boiler outlet flue to recover the flue gas waste heat and heat the boiler feed water or heating return water. This method has a simple system and a relatively low total cost. The disadvantage is that the waste heat recovery rate is low. Affected by the changes in the inlet temperature of the heated water, the flue gas discharge temperature, etc., the actual temperature difference is usually only about 20-30°C, which is about 1%-2% of the boiler heat output. It is impossible to recover the latent heat of vaporization of the water vapor in the flue gas, so deep heat recovery cannot be achieved. (2) The second category is to use the absorption heat pump flue gas deep recovery technology. Use the absorption heat pump to recover the flue gas waste heat and heat the network return water, etc. The flue gas temperature can be greatly reduced to about 30°C, and the waste heat recovery amount is equivalent to 8%-15% of the boiler heat output. Therefore, deep heat recovery can be achieved. However, the absorption heat pump needs to consume high-level heat sources such as steam to drive, and a large amount of acidic condensate will be generated in the flue gas, and an anti-corrosion heat exchanger needs to be used, and the equipment investment is relatively high. (3) The third category is the total heat exchange recovery technology based on air-flue gas. By humidifying the air, the dew point temperature of the flue gas is increased, and the condensation heat of the flue gas is recovered in the tail flue. This method has a simple system structure, does not require an additional driving heat source, and has a low investment cost. In recent years, the "steam-carrying boiler flue gas waste heat recovery" series of patented technologies jointly developed by Tsinghua University and Beijing Qingda Tianguang Energy Technology Research Institute (patent numbers CN104110675B, CN107166420A, CN206929794U, etc.) have been widely promoted and applied at present and have good application prospects. However, its normal-pressure flue gas waste heat spray tower usually extracts heat from the flue gas by intermediate water, and the size of the flue gas waste heat spray tower is very large, and a certain resistance will be added to the flue gas side. If the outlet pressure margin of the original induced draft fan is insufficient, the fan needs to be replaced or a booster induced draft fan needs to be set up. The above situations will all increase the cost, and sometimes the site does not have the implementation conditions.

[0003] In recent years, in the second type of flue gas waste heat recovery method, a method of using desulfurized slurry flash evaporation + absorption heat pump has emerged, that is, abandoning the flue gas waste heat exchanger, extracting the heat in the flue gas from the desulfurized slurry through a flash tank, sending the flash steam into the heat pump for waste heat recovery, heating the return water of the heat network or other process water, and returning the concentrated liquid to the desulfurized circulating water. Its advantages are: there is no need to transform the flue gas system, reducing the on-site implementation difficulty; the quality of the condensate water is good, which is convenient for recycling. However, the disadvantages are also very obvious: the flue gas temperature can usually only be reduced to 42 - 45 °C, recovering about half of the flue gas waste heat, which does not belong to deep heat recovery and can only be regarded as a half-finished project. There is still a large amount of flue gas waste heat escaping from the flue gas, and secondary transformation is still required in the future to achieve deep heat recovery. The cost calculated for the unit waste heat recovery amount is relatively high, and the investment payback period is long. The fundamental reasons why it cannot reduce the flue gas temperature to the 30 °C level and achieve deep heat recovery are as follows: First, the desulfurized slurry flash evaporation complete set of equipment is a vacuum equipment, its system integration is relatively complex, the guarantee requirements are high, and the lower the flash steam temperature, the larger the specific volume, the larger the equipment volume, and the higher the cost; Second, a large amount of non-condensable gases such as SO2 will escape during the desulfurized slurry flash evaporation process. The flash steam is sent into the absorption heat pump, and it is difficult to evacuate during the condensation heat release process in the horizontal evaporator of the heat pump. The absolute pressure during actual operation can only be maintained at about 7 - 8 kPa. It is very difficult to further improve the vacuum degree with the existing equipment and conditions, and it is impossible to further increase the vacuum degree like a normal condenser. Therefore, the saturation temperature of the flash steam can only be reduced to the 38 - 40 °C level, resulting in the flue gas temperature can only be reduced to the 40 - 45 °C level; Third, this technical method still belongs to the heat pump method in essence, only the heat extraction device is different. It still requires a large amount of driving steam, with high operating costs, deteriorating the thermal power flexibility adjustment problem of the power plant, and even sometimes seriously affecting the technical and economic benefits of the power plant. Summary of the Invention

[0004] The object and task of the present invention are, aiming at the respective inherent technical limitations of the above various flue gas waste heat recovery systems and their impacts on the economy of the power plant, and aiming at the scenario where the return water temperature of the heat network is relatively low, combining the ejector heat pump technology, to construct a brand-new integrated flue gas waste heat recovery system.

[0005] The specific description of the present utility model is: an ejector heat pump flue gas waste heat recovery system for desulfurized slurry staged flash evaporation, which is composed of an original desulfurization tower subsystem and a desulfurized slurry staged flash evaporation and heated process water subsystem. The original desulfurization tower subsystem includes an original desulfurization tower 1, an original flue gas inlet pipe 2 and an original slurry pump 3. It is characterized in that the desulfurized slurry staged flash evaporation and heated process water subsystem includes a pre-flash tank 21, a pre-heater 26, an ejector flash tank 11, an ejector 15, an ejector heater 16, a vacuum pump 18 and connecting pipelines and components. Among them, the slurry inlet of the pre-flash tank 21 is connected to the waste heat slurry outlet of the bottom desulfurization slurry tank of the original desulfurization tower 1 through a waste heat slurry pump 10, and the primary concentrated slurry outlet of the pre-flash tank 21 is connected to the slurry inlet of the ejector flash tank 11. The secondary concentrated slurry outlet of the ejector flash tank 11 is connected to the inlet of the original slurry pump 3; a flash steam pre-demister 22 and a pre-washing spray layer 23 are arranged in the upper part inside the pre-flash tank 21. Its flash steam outlet is connected to the steam inlet of the pre-heater 26 through a pre-connection pipe 25. The condensate outlet of the pre-heater 26 is connected to the inlet of a pre-condensate pump 27. The outlet of the pre-condensate pump 27 is respectively connected to the inlets of the pre-washing spray layer 23 and the ejector washing spray layer 13, and is communicated with the outlet pipe of the pre-external discharged condensate W1; a flash steam ejector demister 12 and an ejector washing spray layer 13 are arranged in the upper part inside the ejector flash tank 11. Its flash steam outlet is connected to the low-pressure steam inlet pipe 15b of the ejector 15. The high-pressure steam inlet pipe 15a of the ejector 15 is communicated with the steam supply pipe of the heating steam Q through an ejector regulating valve 14. The medium-pressure exhaust pipe 15c of the ejector 15 is connected to the steam inlet of the ejector heater 16. The condensate outlet of the ejector heater 16 is connected to the inlet of an ejector condensate pump 17. The outlet of the ejector condensate pump 17 is communicated with the outlet pipe of the ejector external discharged condensate W; the low-temperature water inlet of the pre-heater 26 is communicated with the incoming water pipe of the return water from the heat network H1. The low-temperature water outlet of the pre-heater 26 is respectively connected to the incoming water pipe of the return water from the heat network H1, the return water pipe of the return water from the heat network H2 and the low-temperature water inlet of the ejector heater 16 through a heat network water series-parallel valve group 28. The low-temperature water outlet of the ejector heater 16 is respectively connected to the low-temperature water inlet of the ejector heater 16 and the return water pipe of the return water from the heat network H2; the outlet of the pre-non-condensable gas S of the pre-heater 26 is connected to the low-pressure steam inlet pipe 15b of the ejector 15 through a non-condensable gas regulating valve 29; the outlet of the ejector non-condensable gas S1 of the ejector heater 16 is connected to the air inlet of the vacuum pump 18. The exhaust outlet of the vacuum pump 18 is communicated with the original flue gas inlet pipe 2 of the original desulfurization tower 1; the upstream of the original flue gas inlet pipe 2 is the inlet of the original flue gas Y1, and the downstream is the flue gas inlet of the original desulfurization tower 1. The top of the original desulfurization tower 1 is the outlet of the clean flue gas Y2;The circulating liquid outlets of the bottom desulfurization slurry pool of the original desulfurization tower 1 are respectively communicated with the inlet of the original slurry pump 3, the water inlet pipe of desulfurization make-up water B, and the outlet of the final-stage concentrated slurry of the final-stage flash evaporation tank 31. The outlet of the original slurry pump 3 is connected to the circulating slurry inlet of the original desulfurization tower 1. The sewage outlet of the bottom desulfurization slurry pool of the original desulfurization tower 1 is communicated with the drain pipe of desulfurization wastewater P.

[0006] The preheater 26 and the ejector heater 16 respectively adopt a vertical tube heat exchange structure, with a condensate hot well arranged at the bottom, and a non-condensable gas discharge port arranged above the liquid level of the hot well.

[0007] The inside of the preflash evaporation tank 21 is set as a primary heat exchange area or an N-stage heat exchange area, where N is greater than or equal to 2. When setting the N-stage heat exchange area, the flash evaporation concentrated slurry outlet of each stage of the heat exchange area is connected to the slurry inlet of its next stage, and the low-temperature water inlet is connected to the low-temperature water outlet of its next stage.

[0008] The ejector 15 adopts a high-efficiency wide-range negative pressure ejector structure with an internal flow cross-sectional area adjusted in nearly equal proportion.

[0009] The heating steam Q is steam greater than atmospheric pressure or negative pressure steam; the outlet pipe of the ejector external drainage condensate W is respectively communicated with the desulfurization make-up water B, the water inlet pipe of the heat network return water H1 and / or the outlet pipe of the pre-ejector external drainage condensate W1.

[0010] The beneficial effects of the present utility model are as follows.

[0011] (1) Heat is taken from the desulfurization slurry without adding a flue gas waste heat exchanger and its flue gas resistance; the hierarchical flash evaporation + ejector heat pump technology is adopted. The heat network return water is directly heated through the primary flash evaporation, and the heat network return water is continuously heated by the ejector heat pump composed of ejectors in the secondary flash evaporation, so as to realize the deep heat recovery of the flue gas. The flue gas temperature can be reduced to the 30°C level, fundamentally avoiding the inherent disadvantages of the existing desulfurization slurry flash evaporation + absorption heat pump technology method, and the maximum heat recovery amount can reach 2-3 times.

[0012] (2) An ejector heat pump system is composed of equipment components such as the ejector flash evaporation tank 11, the ejector 15, and the ejector heater 16 to recover a part of the desulfurization slurry waste heat. The ejector 15 adopts a high-efficiency wide-range negative pressure ejector structure with an internal flow cross-sectional area adjusted in nearly equal proportion, so that the ejector heat pump can flexibly adapt to the changes in technical conditions such as the inlet and outlet temperatures, pressures, and flows on the desulfurization slurry flash evaporation side and the heat network return water heating side, and always maintain a very high system energy efficiency ratio.

[0013] (3) Maximize the recovery of the waste heat of the desulfurization slurry by direct heat exchange, and preheat the return water of the heat network and the boiler inlet air; the ejector heat pump system can also maintain a very high energy efficiency ratio, thus greatly reducing the steam consumption of the driving steam. Its steam consumption is only a fraction of that of the conventional desulfurization slurry flashing + absorption heat pump method. Therefore, the comprehensive energy efficiency ratio of the entire waste heat recovery system can reach 2 to 4 times, far higher than the conventional method.

[0014] (4) A large amount of SO2 and the like are contained in the non-condensable gas of the preheater 26. Instead of setting up a dedicated vacuum pump, it is directly extracted by the ejector 15, which can maintain a very high vacuum degree (reduced to the absolute pressure level of 2 - 4 kPa when necessary). Therefore, the preflash tank 21 can achieve a very high vacuum degree, which is beneficial to significantly reduce the temperature of the desulfurization slurry, and then significantly reduce the flue gas temperature, realizing deep flue gas waste heat recovery and maximizing the recovery of flue gas waste heat.

[0015] (5) The steam side pressure of the ejector heater 16 is inherently high, so the technical requirements for the vacuum pump 18 for extracting non-condensable gas are reduced; at the same time, the preheater 26 and the ejector heater 16 respectively adopt a vertical tube heat exchange structure, which is also beneficial to improving the extraction of non-condensable gas by the vacuum pump 18 and maintaining a higher vacuum degree.

[0016] (6) Using the condensate water of the flash steam to wash the demister in each flash tank can maintain a higher demisting effect and supplement water to the desulfurization slurry to replace a part or all of the original desulfurization makeup water B. The makeup water source of the latter is often wastewater with a very high chloride ion content. After replacing it with the condensate water of the flash steam, it can help significantly reduce the external discharge flow of the desulfurization wastewater P and greatly reduce the secondary pollution and operation and maintenance costs caused by it, improving the operation effect of the desulfurization system.

[0017] (7) The condensate water of the flash steam can also be used as makeup water for the return water of the heat network, which helps to significantly reduce the production volume and cost of softened water; at the same time, the comprehensive recovery and utilization of the condensate water also correspondingly greatly reduces the consumption of water resources.

[0018] (8) This solution and system can be widely applied to the flue gas waste heat recovery and heating system of thermal power plants and boiler houses, promoting the realization of the comprehensive technical and economic benefits of energy conservation and environmental protection integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the system of the present utility model.

[0020] Figure 1 The numbers and names of each component in it are as follows.

[0021] Original desulfurization tower 1, original flue gas inlet pipe 2, original slurry pump 3, waste heat slurry pump 10, ejector flash evaporation tank 11, flash steam ejector demister 12, ejector washing spray layer 13, ejector regulating valve 14, ejector 15, high-pressure steam inlet pipe 15a, low-pressure steam inlet pipe 15b, medium-pressure exhaust pipe 15c, ejector heater 16, ejector condensate pump 17, vacuum pump 18, preflash evaporation tank 21, flash steam pre-demister 22, prewashing spray layer 23, preconnection pipe 25, preheater 26, precondensate pump 27, heat network water series-parallel valve group 28, non-condensable gas regulating valve 29, desulfurization make-up water B, heat network return water incoming water H1, heat network return water discharging water H2, desulfurization wastewater P, heating steam Q, pre non-condensable gas S, ejector non-condensable gas S1, ejector external discharged condensate water W, pre external discharged condensate water W1, original flue gas Y1, clean flue gas Y2. Detailed implementation manners

[0022] Figure 1 It is the system schematic diagram and embodiment of the present utility model.

[0023] The specific embodiment of the present utility model is as follows.

[0024] The specific description of the embodiments of the present utility model is as follows: The specific description of the present utility model is: An ejector heat pump flue gas waste heat recovery system for desulfurized slurry staged flash evaporation, which consists of an original desulfurization tower subsystem and a desulfurized slurry staged flash evaporation and heating process water subsystem. The original desulfurization tower subsystem includes an original desulfurization tower 1, an original flue gas inlet pipe 2, and an original slurry pump 3. It is characterized in that the desulfurized slurry staged flash evaporation and heating process water subsystem includes a pre-flash tank 21, a pre-heater 26, an ejector flash tank 11, an ejector 15, an ejector heater 16, a vacuum pump 18, and connecting pipelines and components. Among them, the slurry inlet of the pre-flash tank 21 is connected to the waste heat slurry outlet of the bottom desulfurization slurry tank of the original desulfurization tower 1 through a waste heat slurry pump 10, and the first-stage concentrated slurry outlet of the pre-flash tank 21 is connected to the slurry inlet of the ejector flash tank 11. The second-stage concentrated slurry outlet of the ejector flash tank 11 is connected to the inlet of the original slurry pump 3; a flash steam pre-demister 22 and a pre-washing spray layer 23 are arranged in the upper part inside the pre-flash tank 21. Its flash steam outlet is connected to the steam inlet of the pre-heater 26 through a pre-connection pipe 25. The condensate outlet of the pre-heater 26 is connected to the inlet of a pre-condensate pump 27. The outlet of the pre-condensate pump 27 is respectively connected to the inlets of the pre-washing spray layer 23 and the ejector washing spray layer 13, and is communicated with the outlet pipe of the pre-external discharged condensate W1; a flash steam ejector demister 12 and an ejector washing spray layer 13 are arranged in the upper part inside the ejector flash tank 11. Its flash steam outlet is connected to the low-pressure steam inlet pipe 15b of the ejector 15. The high-pressure steam inlet pipe 15a of the ejector 15 is communicated with the steam supply pipe of the heating steam Q through an ejector regulating valve 14. The medium-pressure exhaust pipe 15c of the ejector 15 is connected to the steam inlet of the ejector heater 16. The condensate outlet of the ejector heater 16 is connected to the inlet of an ejector condensate pump 17. The outlet of the ejector condensate pump 17 is communicated with the outlet pipe of the ejector external discharged condensate W; the low-temperature water inlet of the pre-heater 26 is communicated with the incoming water pipe of the heat network return water H1. The low-temperature water outlet of the pre-heater 26 is respectively connected to the incoming water pipe of the heat network return water H1, the return water pipe of the heat network return water H2, and the low-temperature water inlet of the ejector heater 16 through a heat network water series-parallel valve group 28. The low-temperature water outlet of the ejector heater 16 is respectively connected to the low-temperature water inlet of the ejector heater 16 and the return water pipe of the heat network return water H2; the outlet of the pre-non-condensable gas S of the pre-heater 26 is connected to the low-pressure steam inlet pipe 15b of the ejector 15 through a non-condensable gas regulating valve 29; the outlet of the ejector non-condensable gas S1 of the ejector heater 16 is connected to the air inlet of the vacuum pump 18. The exhaust outlet of the vacuum pump 18 is communicated with the original flue gas inlet pipe 2 of the original desulfurization tower 1; the upstream of the original flue gas inlet pipe 2 is the inlet of the original flue gas Y1, and the downstream is the flue gas inlet of the original desulfurization tower 1. The top of the original desulfurization tower 1 is the outlet of the clean flue gas Y2;The circulating liquid outlets of the bottom desulfurization slurry pool of the original desulfurization tower 1 are respectively communicated with the inlets of the original slurry pump 3, the water inlet pipe of desulfurization make-up water B, and the outlet of the final-stage concentrated slurry of the final-stage flash tank 31. The outlet of the original slurry pump 3 is connected to the circulating slurry inlet of the original desulfurization tower 1. The sewage outlet of the bottom desulfurization slurry pool of the original desulfurization tower 1 is communicated with the drain pipe of desulfurization wastewater P.;

[0025] The preheater 26 and the ejector heater 16 respectively adopt a vertical tube-type heat exchange structure, with a condensate hot well provided at the bottom and a non-condensable gas discharge port provided above the liquid level of the hot well.

[0026] The interior of the pre-flash tank 21 is set as a first-stage heat exchange area or an N-stage heat exchange area, where N is greater than or equal to 2. When the N-stage heat exchange area is set, the flash-concentrated slurry outlet of each stage of the heat exchange area is connected to the slurry inlet of the next stage of the heat exchange area, and the low-temperature water inlet is connected to the low-temperature water outlet of the next stage of the heat exchange area.

[0027] The ejector 15 adopts a high-efficiency wide-range negative-pressure ejector structure with an approximately equal-proportion adjustment of the internal flow cross-sectional area.

[0028] The heating steam Q is steam greater than atmospheric pressure or negative-pressure steam; the outlet pipe of the ejected external condensate W is respectively communicated with the desulfurization make-up water B, the water inlet of the make-up water pipe of the return water H1 of the heat network, and / or the outlet pipe of the pre-ejected external condensate W1.

[0029] It should be noted that the present utility model is based on key technologies such as multi-stage flash evaporation of desulfurization slurry, pressurized heat exchange of flash steam by an ejector heat pump, vacuum pumping by an ejector, and using clean condensate as desulfurization make-up water to reduce the external discharge flow of desulfurization wastewater, and proposes a complete set of new integrated systems and operation strategies for flash evaporation of desulfurization slurry for deep flue gas waste heat recovery. According to this overall solution, there can be different specific implementation measures and specific implementation devices with different structures. The above specific implementation manners are only one of them. Any other similar simple deformed implementation manners, such as simple deformations of flash steam and heat exchangers and simple adjustments of pipelines, or simple changes in vacuum pumping methods and condensate recovery and utilization methods, all fall within the protection scope of the present utility model.

Claims

1. An ejector heat pump flue gas waste heat recovery system for desulfurized slurry staged flashing, which is composed of an original desulfurization tower subsystem and a desulfurized slurry staged flashing and heating process water subsystem. The original desulfurization tower subsystem includes an original desulfurization tower (1), an original flue gas inlet pipe (2), and an original slurry pump (3), and is characterized in that, The described desulfurized slurry staged flash evaporation and heated process water subsystem includes a preflash tank (21), a preheater (26), an ejector flash tank (11), an ejector (15), an ejector heater (16), a vacuum pump (18) and connecting pipelines and components. Among them, the slurry inlet of the preflash tank (21) is connected to the waste heat slurry outlet of the bottom desulfurized slurry tank of the original desulfurization tower (1) through a waste heat slurry pump (10), and the first-stage concentrated slurry outlet of the preflash tank (21) is connected to the slurry inlet of the ejector flash tank (11), and the second-stage concentrated slurry outlet of the ejector flash tank (11) is connected to the inlet of the original slurry pump (3); inside the upper part of the preflash tank (21), there are a preflash steam demister (22) and a prewashing spray layer (23). Its flash steam outlet is connected to the steam inlet of the preheater (26) through a pre-connection pipe (25). The condensate outlet of the preheater (26) is connected to the inlet of a pre-condensate pump (27). The outlet of the pre-condensate pump (27) is respectively connected to the inlets of the prewashing spray layer (23) and the ejector washing spray layer (13), and is also connected to the outlet pipe of the pre-external discharge condensate (W1); inside the upper part of the ejector flash tank (11), there are an ejector flash steam demister (12) and an ejector washing spray layer (13). Its flash steam outlet is connected to the low-pressure steam inlet pipe (15b) of the ejector (15). The high-pressure steam inlet pipe (15a) of the ejector (15) is connected to the steam supply pipe of the heating steam (Q) through an ejector regulating valve (14). The medium-pressure exhaust pipe (15c) of the ejector (15) is connected to the steam inlet of the ejector heater (16). The condensate outlet of the ejector heater (16) is connected to the inlet of an ejector condensate pump (17). The outlet of the ejector condensate pump (17) is connected to the outlet pipe of the ejector external discharge condensate (W); the low-temperature water inlet of the preheater (26) is connected to the incoming water pipe of the return water from the heat network (H1). The low-temperature water outlet of the preheater (26) is respectively connected to the incoming water pipe of the return water from the heat network (H1), the drain pipe of the return water from the heat network (H2) and the low-temperature water inlet of the ejector heater (16) through a heat network water series-parallel valve group (28). The low-temperature water outlet of the ejector heater (16) is respectively connected to the low-temperature water inlet of the ejector heater (16) and the drain pipe of the return water from the heat network (H2); the outlet of the pre-non-condensable gas (S) of the preheater (26) is connected to the low-pressure steam inlet pipe (15b) of the ejector (15) through a non-condensable gas regulating valve (29); the outlet of the ejector non-condensable gas (S1) of the ejector heater (16) is connected to the air inlet of the vacuum pump (18). The exhaust outlet of the vacuum pump (18) is connected to the original flue gas inlet pipe (2) of the original desulfurization tower (1); the upstream of the original flue gas inlet pipe (2) is the inlet of the original flue gas (Y1), and the downstream is the flue gas inlet of the original desulfurization tower (1). The top of the original desulfurization tower (1) is the outlet of the clean flue gas (Y2);The circulating liquid outlet of the bottom desulfurization slurry pool of the original desulfurization tower (1) is respectively communicated with the inlet of the original slurry pump (3), the water inlet pipe of desulfurization make-up water (B), and the outlet of the final-stage concentrated slurry of the final-stage flash tank (31). The outlet of the original slurry pump (3) is connected to the circulating slurry inlet of the original desulfurization tower (1). The blowdown port of the bottom desulfurization slurry pool of the original desulfurization tower (1) is communicated with the drain pipe of desulfurization wastewater (P).; 2. The ejector heat pump flue gas waste heat recovery system for staged flash evaporation of desulfurization slurry according to claim 1, characterized in that The described preheater (26) and ejector heater (16) respectively adopt a vertical tube-and-shell heat exchange structure, with a condensate hot well provided at the bottom and a non-condensable gas discharge port provided above the liquid level of the hot well.

3. The ejector heat pump flue gas waste heat recovery system for the classified flash evaporation of desulfurized slurry according to claim 1, characterized in that The interior of the described preflash tank (21) is set as a primary heat exchange zone or an N-stage heat exchange zone, where N is greater than or equal to 2. When an N-stage heat exchange zone is set, the flash-concentrated slurry outlet of each stage of the heat exchange zone is connected to the slurry inlet of its next stage, and the low-temperature water inlet is connected to the low-temperature water outlet of its next stage.

4. The ejector heat pump flue gas waste heat recovery system for staged flash evaporation of desulfurization slurry according to claim 1, characterized in that The described ejector (15) adopts a high-efficiency wide-range negative-pressure ejector structure with a nearly equal-proportion adjustment of the internal flow cross-sectional area.

5. The ejector heat pump flue gas waste heat recovery system for desulfurized slurry staged flash evaporation according to claim 1, characterized in that The described heating steam (Q) is steam greater than atmospheric pressure or negative-pressure steam; the outlet pipes of the ejector-discharged condensate (W) are respectively communicated with the make-up water pipes of the desulfurization make-up water (B), the return water of the heat network (H1), and / or the outlet pipes of the pre-discharged condensate (W1).

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