Desulfurization slurry waste heat recovery system and method based on absorption-compression combined drive

Abstract

The present application belongs to the technical field of desulfurization slurry waste heat recovery, and particularly relates to a desulfurization slurry waste heat recovery system and method based on absorption-compression combined driving. The present application is provided with a two-stage flash tank, through the upper chamber first-stage flash to remove CO2 and other non-condensable gases, and the lower chamber second-stage flash to generate 30-40℃ pure exhaust steam; the exhaust steam enters a compression sub-cycle evaporator, is lifted to 80-90℃ by a compressor, and then is used to drive an absorption sub-cycle generator together with plant ≤0.1MPa ultra-low pressure steam, so as to make the lithium bromide dilute solution boil to generate refrigerant steam; the refrigerant steam enters an absorber after condensation and spray evaporation, is absorbed by the lithium bromide concentrated solution to release absorption heat, and heats the heat network return water to above 85℃. The present application realizes efficient separation of non-condensable gases, step-by-step utilization of ultra-low pressure exhaust steam, and high-grade recovery of waste heat, and significantly improves the energy efficiency and economy of the system.

Description

Technical Field

[0001] This invention belongs to the field of waste heat recovery technology for desulfurization slurry, specifically relating to a waste heat recovery system and method for desulfurization slurry based on absorption-compression composite drive. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Limestone-gypsum wet desulfurization technology is widely used in industries such as thermal power generation, steel, and chemicals. The temperature of the slurry after desulfurization is usually 45~55℃, containing a large amount of low-grade waste heat, which has significant recovery value.

[0004] Currently, some solutions utilize flash evaporation technology coupled with heat pumps to recover this low-temperature waste heat, but significant technical bottlenecks remain. On one hand, non-condensable gases such as CO2 are released during flash evaporation. If these gases enter the heat pump evaporator with the exhaust steam, they form a gas film on the heat exchange surface, severely degrading the heat pump's heat transfer efficiency and affecting system stability. On the other hand, conventional absorption heat pumps typically employ a single-stage generation cycle, requiring steam pressures of 0.3 MPa or higher to drive the generator; to output high-temperature steam, the quality of the driving heat source must be even higher. Furthermore, due to limitations in the cycle principle, traditional single-effect or double-effect absorption heat pumps struggle to stably produce heat transfer media at temperatures above 85°C when utilizing such low-temperature exhaust steam, limiting the direct application of waste heat recovery in industrial process heating and other scenarios.

[0005] Therefore, ensuring that the heat pump obtains a clean and stable air source, reducing drive energy consumption, and improving the quality of output heat energy have become the key to the in-depth promotion of this technology and the improvement of economic benefits. Summary of the Invention

[0006] This invention addresses the shortcomings of existing flash evaporation-heat pump coupled systems, including heat transfer degradation due to non-condensable gases, excessively high requirements for the grade of heat pump-driven steam, limited overall heating temperature, and difficulty in efficiently utilizing ultra-low pressure (≤0.1MPa) waste steam within the plant. To address these issues, this invention provides a desulfurization slurry waste heat recovery system and method based on absorption-compression composite drive. It employs an absorption-compression composite cycle, a high-efficiency regenerative process, and an evaporator structure adapted to high-flow-rate waste steam. The system utilizes the condensation heat of the compression sub-cycle and ultra-low pressure steam (with an absolute pressure not exceeding 0.1MPa) to drive the generation process, significantly reducing dependence on a single high-grade driving heat source. This invention can efficiently and stably recover and upgrade the waste heat of desulfurization slurry into high-temperature hot water (above 85℃) that can be directly used in industrial processes, effectively improving system energy efficiency and economy.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a desulfurization slurry waste heat recovery system based on absorption-compression composite drive, including a desulfurization tower 1, a slurry circulation pump 2, a secondary flash tank 3, a slurry return pump 4, a cooler 5, a vacuum pump group 6, and an absorption-compression composite heat pump unit; the absorption-compression composite heat pump unit includes a generator 7, an absorber sub-circulation condenser 8, a refrigerant pump 9, an absorber sub-circulation evaporator 10, an absorber 11, a solution heat exchanger 12, a throttle valve 13, a solution pump 14, a compressor sub-circulation evaporator 18, a compressor 19, a throttle valve 17, a condensate flash tank (20), and an ultra-low pressure steam supply pipeline.

[0008] Furthermore, the refrigerant-side outlet of the compression sub-cycle evaporator 18 is sequentially connected to the compressor 19, the first part of the heat exchange tubes in the generator 7, the second set of heat exchange tubes in the absorption sub-cycle evaporator 10, and the throttle valve 17, and then connected back to the refrigerant-side inlet of the compression sub-cycle evaporator 18 to form a compression sub-cycle.

[0009] Furthermore, the dilute lithium bromide solution outlet at the bottom of the absorber 11 is connected to the inlet of the solution pump 14, the outlet of the solution pump 14 is connected to the shell-side inlet of the solution heat exchanger 12, and the shell-side outlet of the solution heat exchanger 12 is connected to the solution inlet of the generator 7; the concentrated solution outlet of the generator 7 is connected to the tube-side inlet of the solution heat exchanger 12, and the tube-side outlet of the solution heat exchanger 12 is connected to the top spray inlet of the absorber 11 via the throttle valve 13, forming a lithium bromide solution loop connection for the absorber cycle.

[0010] Furthermore, the refrigerant vapor outlet at the top of the generator 7 is connected to the inlet of the absorber cycle condenser 8, the outlet of the absorber cycle condenser 8 is connected to the inlet of the refrigerant pump 9, and the outlet of the refrigerant pump 9 is connected to the shell-side spray device of the absorber cycle evaporator 10; the shell-side vapor outlet of the absorber cycle evaporator 10 is connected to the refrigerant vapor inlet of the absorber 11, thus forming a refrigerant loop connection for the absorber cycle.

[0011] Secondly, the present invention provides a method for recovering waste heat from desulfurization slurry in a desulfurization slurry waste heat recovery system based on absorption-compression composite drive, comprising the following steps: S1. The 50-55℃ warm slurry discharged from the desulfurization tower 1 is sent to the upper chamber 31 of the secondary flash tank 3 by the slurry circulation pump 2. Under the negative pressure of 8-10kPa, the first-stage flash evaporation occurs, and non-condensable gas is released. The gas is then discharged through the cooler 5 and the vacuum pump 6. The degassed slurry enters the lower chamber 32 through the liquid collection bowl 33. Under the negative pressure of 5-7kPa, the second-stage flash evaporation occurs, producing low-temperature pure exhaust steam at 30-40℃. S2. The 30~40℃ low-temperature pure exhaust steam enters the compressor sub-circulation evaporator 18, heats the liquid refrigerant in its heat exchange tubes to make it evaporate, and the generated refrigerant vapor is compressed by the compressor 19 to become high-temperature and high-pressure refrigerant vapor. The high-temperature and high-pressure refrigerant vapor flows sequentially through the first set of heat exchange tubes in the generator 7 and the second set of heat exchange tubes in the absorption sub-circulation evaporator 10 to release condensation heat. S3. Ultra-low pressure steam with an absolute pressure ≤0.1MPa is introduced into the second set of heat exchange tubes of generator 7, and together with the condensation heat described in step S2, it heats the dilute lithium bromide solution in generator 7, causing it to boil in generator 7 and generate refrigerant steam; the condensate of ultra-low pressure steam enters the condensate flash tank 20 for depressurization flash evaporation, and the generated flash steam is used to preheat the dilute lithium bromide solution before entering generator 7. S4. The refrigerant vapor generated by the generator 7 is condensed by the absorber cycle condenser 8 and then sprayed into the absorber cycle evaporator 10 by the refrigerant pump 9. It absorbs the residual condensation heat from the compressor cycle and evaporates. The generated refrigerant vapor enters the absorber 11. The concentrated lithium bromide solution from the generator 7 is cooled by the solution heat exchanger 12 and depressurized by the throttle valve 13 before being sprayed into the absorber 11. It absorbs the refrigerant vapor and releases the absorbed heat, heating the approximately 40°C return water of the heating network flowing through the tube side of the absorber 11 to above 85°C, thus completing the waste heat recovery.

[0012] The working principle of the desulfurization slurry waste heat recovery system based on absorption-compression composite drive is as follows: The warm slurry discharged from the desulfurization tower first undergoes primary flash evaporation in the upper chamber (8~10kPa) of the secondary flash tank, releasing dissolved non-condensable gases such as CO2 and venting them. The degassed slurry then enters the lower chamber (5~7kPa) for secondary flash evaporation, generating low-temperature pure exhaust steam at 30~40℃. This exhaust steam serves as a low-temperature heat source and enters the compressor sub-circulation evaporator to heat the liquid refrigerant, causing it to evaporate. The generated refrigerant vapor is then compressed by the compressor to a high-temperature and high-pressure state of 80~90℃, and then flows sequentially through the condenser I and the absorber sub-circulation evaporator in the generator. The condenser II inside the generator releases high-grade condensation heat. At the same time, ultra-low pressure steam with a plant pressure ≤0.1MPa is also introduced into the generator, which, together with the condensation heat from compression, heats the dilute lithium bromide solution in the generator, causing it to boil and generate refrigerant vapor. The refrigerant vapor generated by the generator is condensed, pressurized, and sprayed before evaporating in the absorber circulation evaporator by absorbing the residual condensation heat from the compression circulation. The generated refrigerant vapor enters the absorber, where it is strongly absorbed by the concentrated lithium bromide solution from the generator and releases the absorption heat. This heats the return water of the heat network flowing through the absorber tubes from about 40°C to over 85°C, achieving efficient recovery and grade improvement of the waste heat from the desulfurization slurry.

[0013] The beneficial effects of this invention are: 1. This invention combines two-stage flash evaporation with an absorption-compression composite cycle to convert low-temperature exhaust steam heat (30-40°C) into a high-grade heat source (above 85°C). This system not only overcomes the heat transfer degradation problem caused by non-condensable gases, but also, through further optimization of cycle parameters and equipment design, has the potential to raise the heat source temperature by 70-80°C, achieving high-temperature heat energy output above 110°C, thus broadening the application prospects of low-grade waste heat in higher-temperature industrial processes.

[0014] 2. The heat pump unit adopts a combined drive mode of compression condensation heat and ultra-low pressure steam, which significantly reduces the dependence on high-grade drive steam and can directly utilize the surplus ultra-low pressure waste steam in the plant, resulting in outstanding energy-saving benefits. The integrated condensate flash tank's regenerative design and the horizontal air-inlet evaporator optimized for large-flow steam deeply tap the thermal energy potential within the system, improve the overall thermal economy, and enhance the system's operational stability and adjustment flexibility under varying operating conditions.

[0015] 3. This system boasts high industrial applicability and integration. The vertical, integrated two-stage flash tank features a compact design, addressing non-condensable gas interference at its source. The entire system seamlessly integrates with existing power plant desulfurization systems and low-pressure steam networks, facilitating retrofit implementation. While achieving deep waste heat recovery and reducing heating costs, it also minimizes the emission of low-grade waste gas within the plant, offering both environmental and economic benefits. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0017] Figure 1 This is a schematic diagram of the desulfurization slurry waste heat recovery system based on absorption-compression composite drive in Example 1.

[0018] Among them, 1: desulfurization tower; 2: slurry circulation pump; 3: secondary flash tank; 4: slurry return pump; 5: cooler; 6: vacuum pump; 7: generator; 8: absorber circulation condenser; 9: refrigerant pump; 10: absorber circulation evaporator; 11: absorber; 12: solution heat exchanger; 13: throttle valve; 14: solution pump; 15: compressor circulation condenser I; 16: compressor circulation condenser II; 17: throttle valve; 18: compressor circulation evaporator; 19: compressor; 20: condensate flash tank; 31: upper chamber; 32: lower chamber; 33: liquid collection bowl; 34: tank cooler. Detailed Implementation

[0019] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

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

[0021] This invention provides a desulfurization slurry waste heat recovery system based on absorption-compression composite drive, including a desulfurization tower 1, a slurry circulation pump 2, a secondary flash tank 3, a slurry return pump 4, a cooler 5, a vacuum pump group 6, and an absorption-compression composite heat pump unit; the absorption-compression composite heat pump unit includes a generator 7, an absorber sub-circulation condenser 8, a refrigerant pump 9, an absorber sub-circulation evaporator 10, an absorber 11, a solution heat exchanger 12, a throttle valve 13, a solution pump 14, a compressor sub-circulation evaporator 18, a compressor 19, and a throttle valve 17.

[0022] In some specific embodiments of the present invention, the refrigerant-side outlet of the compression sub-cycle evaporator 18 is sequentially connected to the compressor 19, the first part of the heat exchange tubes in the generator 7, the second set of heat exchange tubes in the absorption sub-cycle evaporator 10, and the throttle valve 17, and then connected back to the refrigerant-side inlet of the compression sub-cycle evaporator 18 to form a compression sub-cycle.

[0023] In some specific embodiments of the present invention, the dilute lithium bromide solution outlet at the bottom of the absorber 11 is connected to the inlet of the solution pump 14, the outlet of the solution pump 14 is connected to the shell-side inlet of the solution heat exchanger 12, and the shell-side outlet of the solution heat exchanger 12 is connected to the solution inlet of the generator 7; the concentrated solution outlet of the generator 7 is connected to the tube-side inlet of the solution heat exchanger 12, and the tube-side outlet of the solution heat exchanger 12 is connected to the top spray inlet of the absorber 11 via the throttle valve 13, forming a lithium bromide solution loop connection for the absorber cycle.

[0024] In some specific embodiments of the present invention, the refrigerant vapor outlet at the top of the generator 7 is connected to the inlet of the absorber cycle condenser 8, the outlet of the absorber cycle condenser 8 is connected to the inlet of the refrigerant pump 9, and the outlet of the refrigerant pump 9 is connected to the shell-side spray device of the absorber cycle evaporator 10; the shell-side vapor outlet of the absorber cycle evaporator 10 is connected to the refrigerant vapor inlet of the absorber 11, thus forming a refrigerant loop connection of the absorber cycle.

[0025] In some specific embodiments of the present invention, the slurry outlet of the desulfurization tower 1 is connected to the inlet of the slurry circulation pump 2, and the outlet of the slurry circulation pump 2 is connected to the liquid inlet of the secondary flash tank 3; the pure exhaust steam outlet of the secondary flash tank 3 is connected to the heat source side inlet of the compressor sub-circulation evaporator 18.

[0026] In some specific embodiments of the present invention, the secondary flash tank 3 is a vertical structure, and its interior is divided into an upper chamber 31 and a lower chamber 32 by a liquid collection bowl 33; the upper side wall of the upper chamber 31 is provided with a tangential liquid inlet and a non-condensable gas outlet at the top; the liquid collection bowl 33 is inverted conical and has a guide hole in the center; an in-tank cooler (34) is provided in the lower chamber (32) for further cooling of the flash slurry; the upper side wall of the lower chamber 32 is provided with a pure exhaust steam outlet and a slurry outlet at the bottom, which is connected to the inlet of the slurry return pump 4, and the outlet of the slurry return pump 4 is connected to the slurry return port of the desulfurization tower 1.

[0027] In some specific embodiments of the present invention, the working pressure of the upper chamber 31 is 8~10 kPa, which is used for primary flash evaporation and separation of non-condensable gases; the working pressure of the lower chamber 32 is 5~7 kPa, which is used for secondary flash evaporation and generation of low-temperature pure exhaust steam at 30~40°C.

[0028] In some specific embodiments of the present invention, the ultra-low pressure steam supply pipeline is connected to the inlet of the second set of heat exchange tubes of the generator 7, the condensate outlet of the second set of heat exchange tubes of the generator 7 is connected to the inlet of the condensate flash tank 20, and the cooling water pipeline of the absorber 11 is connected to the heating network water circuit.

[0029] In some specific embodiments of the present invention, the flash steam outlet of the condensate flash tank 20 is connected to the lithium bromide dilute solution inlet of the solution heat exchanger 12. Alternatively, the flash steam outlet of the condensate flash tank 20 is connected to a separate preheater located between the solution heat exchanger 12 and the generator 7 for preheating the lithium bromide dilute solution from the absorber.

[0030] In some specific embodiments of the present invention, the absolute pressure of the ultra-low pressure steam is not higher than 0.1 MPa.

[0031] In some specific embodiments of the present invention, the operating pressure of the generator 7 is 70~90 kPa, the operating pressure of the absorber circulating evaporator 10 is maintained at 50~70 kPa by the refrigerant pump 9, and the operating pressure of the absorber 11 is 80~100 kPa.

[0032] The present invention also provides a method for recovering waste heat from desulfurization slurry in the aforementioned absorption-compression composite driven desulfurization slurry waste heat recovery system, comprising the following steps: S1. The 50-55℃ warm slurry discharged from the desulfurization tower 1 is sent to the upper chamber 31 of the secondary flash tank 3 by the slurry circulation pump 2. Under the negative pressure of 8-10kPa, the first-stage flash evaporation occurs, and non-condensable gas is released. The gas is then discharged through the cooler 5 and the vacuum pump 6. The degassed slurry enters the lower chamber 32 through the liquid collection bowl 33. Under the negative pressure of 5-7kPa, the second-stage flash evaporation occurs, producing low-temperature pure exhaust steam at 30-40℃. S2. The 30~40℃ low-temperature pure exhaust steam enters the compressor sub-circulation evaporator 18, heats the liquid refrigerant in its heat exchange tubes to make it evaporate, and the generated refrigerant vapor is compressed by the compressor 19 to become high-temperature and high-pressure refrigerant vapor. The high-temperature and high-pressure refrigerant vapor flows sequentially through the first set of heat exchange tubes in the generator 7 and the second set of heat exchange tubes in the absorption sub-circulation evaporator 10 to release condensation heat. S3. Ultra-low pressure steam with an absolute pressure ≤0.1MPa is introduced into the second set of heat exchange tubes of generator 7, and together with the condensation heat described in step S2, it heats the dilute lithium bromide solution in generator 7, causing it to boil in generator 7 and generate refrigerant steam; the condensate of ultra-low pressure steam enters the condensate flash tank 20 for depressurization flash evaporation, and the generated flash steam is used to preheat the dilute lithium bromide solution before entering generator 7. S4. The refrigerant vapor generated by the generator 7 is condensed by the absorber cycle condenser 8 and then sprayed into the absorber cycle evaporator 10 by the refrigerant pump 9. It absorbs the residual condensation heat from the compressor cycle and evaporates. The generated refrigerant vapor enters the absorber 11. The concentrated lithium bromide solution from the generator 7 is cooled by the solution heat exchanger 12 and depressurized by the throttle valve 13 before being sprayed into the absorber 11. It absorbs the refrigerant vapor and releases the absorbed heat, heating the approximately 40°C return water of the heating network flowing through the tube side of the absorber 11 to above 85°C, thus completing the waste heat recovery.

[0033] Example 1 The desulfurization slurry waste heat recovery system based on absorption-compression composite drive provided in this embodiment, such as Figure 1 As shown, it includes a desulfurization tower 1, a slurry circulation pump 2, a secondary flash tank 3, a slurry return pump 4, a cooler 5, a vacuum pump group 6, and an absorption-compression composite heat pump unit.

[0034] The absorption-compression combined heat pump unit includes a generator 7, an absorber sub-circulation condenser 8, a refrigerant pump 9, an absorber sub-circulation evaporator 10, an absorber 11, a solution heat exchanger 12, a throttle valve 13, a solution pump 14, a compressor sub-circulation evaporator 18, a compressor 19, and a throttle valve 17.

[0035] The system also includes a ≤0.1 MPa ultra-low pressure steam supply pipeline that provides an auxiliary driving heat source for the generator 7, a condensate flash tank 20 for recovering waste heat from the driving steam, a hot water circuit, and corresponding connecting pipes.

[0036] The slurry outlet of desulfurization tower 1 is connected to the inlet of slurry circulation pump 2, and the outlet of slurry circulation pump 2 is connected to the inlet of secondary flash tank 3. Secondary flash tank 3 is a vertical structure, internally divided into an upper chamber 31 and a lower chamber 32 by a collection bowl 33. The upper side wall of the upper chamber 31 has a tangential inlet to receive warm slurry from the desulfurization tower; the top of the upper chamber 31 has a non-condensable gas outlet, which is sequentially connected to cooler 5 and vacuum pump group 6; the collection bowl 33 is inverted conical in shape, with a central guide hole for slurry to flow into the lower chamber; the upper side wall of the lower chamber 32 has a pure exhaust gas outlet, and the bottom has a slurry outlet, which is connected to the inlet of slurry return pump 4, and the outlet of slurry return pump 4 is connected to the slurry return port of desulfurization tower 1.

[0037] The compression sub-cycle uses environmentally friendly refrigerants such as R134a and comprises a throttling valve 17, a compression sub-cycle evaporator 18, a compressor 19, and a generator 7 and an absorber sub-cycle evaporator 10, which serve as its condensers. The generator 7 and the absorber sub-cycle evaporator 10 also function as condensers for the compression sub-cycle. Specifically, the generator 7 has a first heat exchange tube section serving as the compression sub-cycle condenser I 15; the absorber sub-cycle evaporator 10 has a second heat exchange tube section serving as the compression sub-cycle condenser II 16.

[0038] The heat source side inlet of the compressor sub-cycle evaporator 18 is connected to the pure exhaust steam outlet of the lower chamber 32. The refrigerant side outlet of the compressor sub-cycle evaporator 18 is connected to the suction port of the compressor 19. The discharge port of the compressor 19 is sequentially connected to the first part of the heat exchange tubes in the generator 7 and the second part of the heat exchange tubes in the absorption sub-cycle evaporator 10, and then connected back to the refrigerant side inlet of the compressor sub-cycle evaporator 18 through the throttle valve 17, thus forming a compressor sub-cycle.

[0039] The generator 7 is designed as a composite heat source driven generator, with its tube side divided into two parts: the first part is connected to the high-pressure refrigerant vapor outlet of the compressor sub-cycle to receive the condensation heat of the compressor sub-cycle; the second part is connected to the ultra-low pressure steam supply pipeline. The ultra-low pressure steam supply pipeline provides steam with an absolute pressure ≤0.1 MPa, which can be taken from the plant's low-pressure steam network or low-grade waste heat steam in the industrial process. The ultra-low pressure steam supply pipeline is connected to the auxiliary steam inlet of the generator 7, and the condensate outlet of the generator 7 is connected to the inlet of the condensate flash tank 20; the flash steam outlet of the condensate flash tank 20 is connected to the lithium bromide dilute solution side inlet of the solution heat exchanger 12 (or connected to an independent preheater located between the solution heat exchanger and the generator) for preheating the lithium bromide dilute solution from the absorber.

[0040] The absorber cycle of the absorption-compression composite heat pump unit adopts a lithium bromide-water working fluid pair, including a generator 7, an absorber cycle condenser 8, a refrigerant pump 9, an absorber cycle evaporator 10, an absorber 11, a solution heat exchanger 12, a solution pump 14, and a throttling valve 13.

[0041] The solution loop connection of the absorber cycle is as follows: the dilute lithium bromide solution outlet at the bottom of absorber 11 is connected to the inlet of solution pump 14, the outlet of solution pump 14 is connected to the shell-side inlet of solution heat exchanger 12, and the shell-side outlet of solution heat exchanger 12 is connected to the solution inlet of generator 7; the concentrated solution outlet of generator 7 is connected to the tube-side inlet of solution heat exchanger 12, and the tube-side outlet of solution heat exchanger 12 is connected to the top spray inlet of absorber 11 via throttle valve 13.

[0042] The refrigerant circuit connection of the absorber cycle is as follows: the refrigerant vapor outlet at the top of the generator 7 is connected to the inlet of the absorber cycle condenser 8, the outlet of the absorber cycle condenser 8 is connected to the inlet of the refrigerant pump 9, the outlet of the refrigerant pump 9 is connected to the shell-side spray device of the absorber cycle evaporator 10, and the shell-side vapor outlet of the absorber cycle evaporator 10 is connected to the refrigerant vapor inlet of the absorber 11.

[0043] The cooling water pipe of the absorber 11 is connected to the heat network water circuit (return water in). The heat network return water first enters the tube side of the absorber 11, absorbs heat, and is then output to the heat network water supply pipe (high temperature hot water out).

[0044] In this embodiment, the core of the absorption-compression composite cycle lies in actively constructing a pressure field using refrigerant pumps and solution pumps, making the absorber the highest point of the system's thermodynamic state, thereby directly outputting high-grade thermal energy. Taking the case of using 30~40℃ low-temperature exhaust steam as a heat source and aiming to produce hot water exceeding 85℃ as an example, the pressure levels of each device are set as follows: the working pressure of the upper chamber 31 is maintained at 8~10 kPa to achieve primary flash evaporation and efficient separation of non-condensable gases; the working pressure of the lower chamber 32 is maintained at 5~7 kPa to achieve secondary flash evaporation and generate low-temperature pure exhaust steam at 30~40℃. The generator 7 operates in the medium-pressure zone of 70~90 kPa under the combined drive of compression condensation heat and ≤0.1 MPa ultra-low pressure steam. The refrigerant pump 9 is responsible for pressurizing the condensate to 50~70 kPa and sending it into the absorber sub-cycle evaporator 10, raising its saturation temperature to 80~90℃, thereby better matching it with the high-temperature condensation heat from the compression sub-cycle. Absorber 11 is a high-pressure zone, with its operating pressure maintained at 80~100kPa. The corresponding high saturation temperature ensures that it can output high-temperature hot water. Solution pump 14 pressurizes the dilute lithium bromide solution from absorber 11 to 110~130kPa to overcome all the resistance flowing through solution heat exchanger 12 and pipelines, ensuring that the solution can smoothly enter generator 7. Finally, the concentrated solution flowing out of generator 7 is depressurized to 60~80kPa through throttle valve 13, ensuring that the concentrated solution can be effectively injected and absorb heat. This pressure gradient makes the absorber the pressure and temperature peak of the entire thermodynamic system, and only a small amount of pump power is needed to effectively improve the heat energy quality. In addition, the absorber circulation evaporator (10) adopts a horizontal shell and tube structure and a horizontal air inlet with a large cross-section on the side wall, so that the high-pressure refrigerant vapor from the compressor is horizontally and uniformly flushed with the horizontal tube bundle. This design can reduce flow resistance, enhance heat transfer through condensation outside the tubes, and work together with the above-mentioned pressure system to ensure the large temperature rise performance of the cycle.

[0045] Example 2 The desulfurization slurry waste heat recovery method based on the absorption-compression composite driven desulfurization slurry waste heat recovery system of Example 1 includes the following steps: The 50-55℃ warm slurry discharged from desulfurization tower 1 is tangentially pumped by slurry circulation pump 2 into the upper chamber 31 of the secondary flash tank 3. Under a vacuum environment of 8-10 kPa, the slurry undergoes primary flash evaporation, and non-condensable gases such as CO2 dissolved in the slurry are released. After being cooled by cooler 5, the slurry is processed by vacuum pump group 6 and then discharged into the atmosphere. The degassed slurry is guided to the lower chamber 32 by liquid collection bowl 33, where secondary flash evaporation occurs under a pressure of 5-7 kPa, producing low-temperature pure exhaust steam at 30-40℃.

[0046] The 30-40°C low-temperature pure exhaust vapor enters the compressor sub-cycle evaporator 18, driving the compressor sub-cycle to start. Specifically, the connection process of the compressor sub-cycle is as follows: liquid refrigerant (such as R134a) is heated and evaporated by the 30-40°C pure exhaust vapor in the heat exchange tube of the compressor sub-cycle evaporator 18. The resulting low-temperature, low-pressure refrigerant vapor is compressed by the compressor 19 and transformed into 80-90°C high-temperature, high-pressure refrigerant vapor. The 80-90°C high-temperature, high-pressure refrigerant vapor flows sequentially through the compressor sub-cycle condenser I 15 in the generator 7 and the compressor sub-cycle condenser II 16 in the absorption sub-cycle evaporator 10. During this process, it releases high-grade condensation heat to drive the absorption sub-cycle and is completely condensed into liquid. After the liquid is depressurized by the throttle valve 17, it returns to the compressor sub-cycle evaporator 18, completing the compressor sub-cycle.

[0047] Simultaneously, ultra-low pressure steam (≤0.1MPa) from the plant area is introduced into the second heat exchange tube side of generator 7, where it, together with the aforementioned compression condensation heat, heats the dilute lithium bromide solution within generator 7, causing it to boil and generate refrigerant vapor. The high-temperature condensate formed by the ultra-low pressure steam in generator 7 enters the condensate flash tank 20 for depressurized flash evaporation. The resulting low-pressure flash steam is used to preheat the dilute lithium bromide solution before it enters generator 7 in solution heat exchanger 12, achieving deep energy recovery.

[0048] Furthermore, the solution loop connection of the absorber cycle is as follows: the dilute lithium bromide solution flowing out of absorber 11 is pumped by solution pump 14 and enters the shell side of solution heat exchanger 12, where it is heated by flash steam discharged from condensate flash tank 20 and concentrated lithium bromide solution from generator 7, and finally enters generator 7; or, the dilute lithium bromide solution is pumped by solution pump 14 and enters the shell side of solution heat exchanger 12, where it is first heated once by concentrated lithium bromide solution, then passes through an independent preheater (optional component), where it is heated a second time by flash steam discharged from condensate flash tank 20 flowing through the preheater, and finally enters generator 7. The concentrated lithium bromide solution at the bottom of generator 7 is cooled by the tube side of solution heat exchanger 12 and depressurized by throttle valve 13, and then returns to the top of absorber 11 for spraying.

[0049] The refrigerant loop of the absorber cycle is as follows: the refrigerant vapor generated by generator 7 is condensed by absorber cycle condenser 8 and then sprayed into absorber cycle evaporator 10 by refrigerant pump 9. It absorbs the residual condensation heat from the compressor cycle and evaporates, and the generated refrigerant vapor enters absorber 11. The concentrated lithium bromide solution from generator 7 is cooled by solution heat exchanger 12 and depressurized by throttling valve 13 before being sprayed into absorber 11. It strongly absorbs the refrigerant vapor and releases the absorbed heat, heating the heat network return water flowing through the tubes of absorber 11 from about 40°C to above 85°C, completing the waste heat recovery and upgrading, and outputting it for industrial heat or heating.

[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A desulfurization slurry waste heat recovery system based on absorption-compression composite drive, characterized in that, It includes a desulfurization tower (1), a slurry circulation pump (2), a secondary flash tank (3), a slurry return pump (4), a cooler (5), a vacuum pump group (6), and an absorption-compression composite heat pump unit; the absorption-compression composite heat pump unit includes a generator (7), an absorber sub-circulation condenser (8), a refrigerant pump (9), an absorber sub-circulation evaporator (10), an absorber (11), a solution heat exchanger (12), a throttle valve (13), a solution pump (14), a compressor sub-circulation evaporator (18), a compressor (19), a throttle valve (17), a condensate flash tank (20), and an ultra-low pressure steam supply pipeline; The refrigerant-side outlet of the compression sub-cycle evaporator (18) is sequentially connected to the compressor (19), the first part of the heat exchange tubes in the generator (7), the second set of heat exchange tubes in the absorption sub-cycle evaporator (10), and the throttle valve (17), and then connected back to the refrigerant-side inlet of the compression sub-cycle evaporator (18) to form a compression sub-cycle; The lithium bromide dilute solution outlet at the bottom of the absorber (11) is connected to the inlet of the solution pump (14), the outlet of the solution pump (14) is connected to the shell-side inlet of the solution heat exchanger (12), the shell-side outlet of the solution heat exchanger (12) is connected to the solution inlet of the generator (7); the concentrated solution outlet of the generator (7) is connected to the tube-side inlet of the solution heat exchanger (12), and the tube-side outlet of the solution heat exchanger (12) is connected to the top spray inlet of the absorber (11) via the throttle valve (13), forming a lithium bromide solution loop connection for the absorber cycle.

2. The desulfurization slurry waste heat recovery system based on absorption-compression composite drive according to claim 1, characterized in that, The refrigerant vapor outlet at the top of the generator (7) is connected to the inlet of the absorber cycle condenser (8), the outlet of the absorber cycle condenser (8) is connected to the inlet of the refrigerant pump (9), and the outlet of the refrigerant pump (9) is connected to the shell-side spray device of the absorber cycle evaporator (10); the shell-side vapor outlet of the absorber cycle evaporator (10) is connected to the refrigerant vapor inlet of the absorber (11), thus forming the refrigerant loop connection of the absorber cycle.

3. The desulfurization slurry waste heat recovery system based on absorption-compression composite drive according to claim 1, characterized in that, The slurry outlet of the desulfurization tower (1) is connected to the inlet of the slurry circulation pump (2), and the outlet of the slurry circulation pump (2) is connected to the liquid inlet of the secondary flash tank (3); the pure exhaust steam outlet of the secondary flash tank (3) is connected to the heat source side inlet of the compressor sub-circulation evaporator (18).

4. The desulfurization slurry waste heat recovery system based on absorption-compression composite drive according to claim 1, characterized in that, The secondary flash tank (3) is a vertical structure, and its interior is divided into an upper chamber (31) and a lower chamber (32) by a liquid collection bowl (33). The upper chamber (31) has a tangential liquid inlet on the upper side wall and a non-condensable gas outlet at the top. The liquid collection bowl (33) is inverted conical and has a guide hole in the center. The lower chamber (32) has a pure exhaust gas outlet on the upper side wall and a slurry outlet at the bottom. The slurry outlet is connected to the inlet of the slurry return pump (4), and the outlet of the slurry return pump (4) is connected to the slurry return port of the desulfurization tower (1).

5. The desulfurization slurry waste heat recovery system based on absorption-compression composite drive according to claim 4, characterized in that, The upper chamber (31) has a working pressure of 8~10 kPa and is used for primary flash evaporation and separation of non-condensable gases; the lower chamber (32) has a working pressure of 5~7 kPa and is used for secondary flash evaporation and generation of low-temperature pure exhaust steam at 30~40℃.

6. The desulfurization slurry waste heat recovery system based on absorption-compression composite drive according to claim 1, characterized in that, The ultra-low pressure steam supply pipeline is connected to the inlet of the second set of heat exchange tubes of the generator (7), the condensate outlet of the second set of heat exchange tubes of the generator (7) is connected to the inlet of the condensate flash tank (20), and the cooling water pipeline of the absorber (11) is connected to the heating network water circuit.

7. The desulfurization slurry waste heat recovery system based on absorption-compression composite drive according to claim 6, characterized in that, The flash outlet of the condensate flash tank (20) is connected to the lithium bromide dilute solution side inlet of the solution heat exchanger (12). Alternatively, the flash outlet of the condensate flash tank (20) is connected to a separate preheater located between the solution heat exchanger (12) and the generator (7) for preheating the dilute lithium bromide solution from the absorber.

8. The desulfurization slurry waste heat recovery system based on absorption-compression composite drive according to claim 6, characterized in that, The absolute pressure of the ultra-low pressure steam is not higher than 0.1 MPa.

9. The desulfurization slurry waste heat recovery system based on absorption-compression composite drive according to claim 1, characterized in that, The working pressure of the generator (7) is 70~90kPa, the working pressure of the absorber circulating evaporator (10) is maintained at 50~70kPa by the refrigerant pump (9), and the working pressure of the absorber (11) is 80~100kPa.

10. The method for recovering waste heat from desulfurization slurry based on an absorption-compression composite driven desulfurization slurry waste heat recovery system according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. The 50~55℃ warm slurry discharged from the desulfurization tower (1) is sent to the upper chamber (31) of the secondary flash tank (3) by the slurry circulation pump (2). Under the negative pressure of 8~10kPa, the first-stage flash evaporation occurs, and non-condensable gas is released. It is discharged through the cooler (5) and the vacuum pump (6). The degassed slurry enters the lower chamber (32) through the liquid collection bowl (33). Under the negative pressure of 5~7kPa, the second-stage flash evaporation occurs, and low-temperature pure exhaust steam of 30~40℃ is generated. S2. The 30~40℃ low temperature pure exhaust steam enters the compressor sub-circulation evaporator (18), heats the liquid refrigerant in its heat exchange tubes to make it evaporate, and the generated refrigerant vapor is compressed by the compressor (19) to become high temperature and high pressure refrigerant vapor. The high temperature and high pressure refrigerant vapor flows sequentially through the first set of heat exchange tubes in the generator (7) and the second set of heat exchange tubes in the absorption sub-circulation evaporator (10) to release condensation heat. S3. Ultra-low pressure steam with an absolute pressure ≤ 0.1 MPa is introduced into the second set of heat exchange tubes of the generator (7) and heated together with the condensation heat described in step S2 to heat the dilute lithium bromide solution in the generator (7), causing it to boil in the generator (7) and generate refrigerant steam; the condensate of the ultra-low pressure steam enters the condensate flash tank (20) for depressurization flash evaporation, and the generated flash steam is used to preheat the dilute lithium bromide solution before entering the generator (7); S4. The refrigerant vapor generated by the generator (7) is condensed by the absorber cycle condenser (8) and sent by the refrigerant pump (9) to the absorber cycle evaporator (10) for spraying. It absorbs the residual condensation heat from the compression cycle and evaporates. The generated refrigerant vapor enters the absorber (11). The lithium bromide concentrated solution from the generator (7) is cooled by the solution heat exchanger (12) and depressurized by the throttle valve (13) and then sprayed into the absorber (11). It absorbs the refrigerant vapor and releases the absorbed heat, heating the approximately 40°C heat network return water flowing through the absorber (11) tube to above 85°C, thus completing the waste heat recovery.

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