A system and operation method for deep recovery of flue gas water heat

Abstract

The present invention belongs to the field of energy conservation and environmental protection, and specifically discloses a system and an operating method for deeply recovering water and heat from flue gas. The system for deeply recovering water and heat from flue gas comprises a second desulfurization tower, an absorption tower, a first flash tank, a second flash tank, a first absorption heat pump and a second absorption heat pump; the low-temperature flue gas outlet of the second desulfurization tower is connected to the low-temperature flue gas inlet of the absorption tower, the outlet of the absorption tower is connected to the inlet of the first flash tank, the negative-pressure steam outlet of the first flash tank is connected to the negative-pressure steam inlet of the first absorption heat pump, the outlet of the first flash tank is connected to the inlet of the second flash tank, and the negative-pressure steam outlet of the second flash tank is connected to the negative-pressure steam inlet of the second absorption heat pump; the system achieves the purpose of fully recovering moisture and heat in low-temperature flue gas with low moisture content, greatly improves the water and heat recovery rate, and ultimately significantly reduces the temperature and water vapor content of the low-temperature dry flue gas discharged into the atmosphere, thereby achieving the purpose of eliminating white smoke plumes.

Description

Technical Field

[0001] The present invention belongs to the field of energy conservation and environmental protection, and specifically relates to a system for deep recovery of flue gas water heat and an operating method. Background Art

[0002] For cogeneration units, recovering waste heat from the system is one of the best ways to increase heating capacity without expanding the unit size. Currently, power plants typically use water spraying to cool flue gas to 50-60°C before discharging it, without recovering the heat, resulting in energy waste. Furthermore, the saturated, wet flue gas discharged after spraying still contains some heat and a significant amount of water vapor, which easily forms a white plume when released into the air. This has also been a contributing factor to the recent smog.

[0003] Although the existing technology has achieved the purpose of recycling and utilizing the waste heat and water of low-temperature flue gas with high moisture content, the existing technology does not fully utilize the waste heat in low-temperature flue gas with low moisture content, and does not fully recover the water vapor in the low-temperature flue gas. The water heat recovery rate is low and the energy utilization rate is low, resulting in the flue gas temperature and water vapor content discharged into the atmosphere still being high, the white plume phenomenon is still relatively obvious, and causing waste of water and heat. Summary of the Invention

[0004] The purpose of the present invention is to provide a system and operation method for deep recovery of flue gas water heat to solve the technical problems existing in the prior art.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical means: a system for deep recovery of flue gas water heat, comprising a second desulfurization tower, an absorption tower, a first flash tank, a second flash tank, a first absorption heat pump and a second absorption heat pump; the low-temperature flue gas outlet of the second desulfurization tower is connected to the low-temperature flue gas inlet of the absorption tower, the outlet of the absorption tower is connected to the inlet of the first flash tank, the negative pressure steam outlet of the first flash tank is connected to the negative pressure steam inlet of the first absorption heat pump, the outlet of the first flash tank is connected to the inlet of the second flash tank, and the negative pressure steam outlet of the second flash tank is connected to the negative pressure steam inlet of the second absorption heat pump.

[0006] Furthermore, the first flash tank is divided into a first area and a second area by a partition, and the desulfurization slurry in the first area does not contact the absorption liquid in the second area; the second flash tank is divided into a third area and a fourth area by a partition, and the desulfurization slurry in the third area does not contact the absorption liquid in the fourth area; the outlet of the absorption tower is connected to the inlet of the second area, the outlet of the second area is connected to the inlet of the fourth area, and the outlet of the fourth area is connected to the inlet of the absorption tower.

[0007] Furthermore, it also includes a first desulfurization tower, the outlet of the first desulfurization tower is connected to the inlet of the first area, and the outlet of the first area is connected to the inlet of the first desulfurization tower.

[0008] Furthermore, the medium-temperature saturated wet flue gas outlet of the first desulfurization tower is connected to the medium-temperature saturated wet flue gas inlet of the second desulfurization tower, the outlet of the second desulfurization tower is connected to the inlet of the third area, and the outlet of the third area is connected to the inlet of the second desulfurization tower.

[0009] Furthermore, the first desulfurization tower is provided with a medium-temperature desulfurization slurry, which is used to exchange moisture and heat with the flue gas; the second desulfurization tower is provided with a low-temperature desulfurization slurry, which is used to exchange moisture and heat with the medium-temperature saturated wet flue gas; the absorption tower is provided with a concentrated absorption liquid, which is used to absorb moisture and heat in the low-temperature flue gas.

[0010] Furthermore, the first desulfurization tower is provided with a smoke inlet for the entry of flue gas.

[0011] A method for operating a system for deep recovery of flue gas water and heat, wherein the flue gas enters a first desulfurization tower from a smoke inlet, and the flue gas exchanges water and heat with a medium-temperature desulfurization slurry to generate a high-temperature desulfurization slurry and a medium-temperature saturated wet flue gas; the high-temperature desulfurization slurry enters a first region from the outlet of the first desulfurization tower, flashes in a vacuum environment, and generates medium-temperature flash steam and medium-temperature desulfurization slurry; the medium-temperature desulfurization slurry flows from the outlet of the first region into the inlet of the first desulfurization tower, and the medium-temperature flash steam enters the negative-pressure steam inlet of the first absorption heat pump from the negative-pressure steam outlet of the first flash tank.

[0012] Furthermore, the medium-temperature saturated wet flue gas enters the second desulfurization tower from the first desulfurization tower, and the medium-temperature saturated wet flue gas exchanges water and heat with the low-temperature desulfurization slurry to generate medium- and high-temperature desulfurization slurry and low-temperature flue gas; the medium- and high-temperature desulfurization slurry flows into the third area from the outlet of the second desulfurization tower, flashes under a vacuum environment, and generates low-temperature flash steam and low-temperature desulfurization slurry; the low-temperature desulfurization slurry flows into the inlet of the second desulfurization tower from the outlet of the third area, and the low-temperature flash steam enters the negative-pressure steam inlet of the second absorption heat pump from the negative-pressure steam outlet of the second flash tank.

[0013] Furthermore, the low-temperature flue gas enters the absorption tower from the second desulfurization tower, and the low-temperature flue gas exchanges moisture and heat with the concentrated absorption liquid to generate dilute absorption liquid and low-temperature dry flue gas; the dilute absorption liquid enters the second area from the absorption tower outlet, flashes under a vacuum environment, and generates medium absorption liquid and flash steam, and the flash steam enters the first absorption heat pump negative pressure steam inlet from the first flash tank negative pressure steam outlet, and the medium absorption liquid enters the fourth area from the second area outlet, flashes under a vacuum environment to generate concentrated absorption liquid and flash steam, and the flash steam enters the second absorption heat pump negative pressure steam inlet from the second flash tank negative pressure steam outlet, and the concentrated absorption liquid enters the absorption tower inlet from the fourth area outlet.

[0014] Furthermore, the first absorption heat pump and the second absorption heat pump are driven by driving steam, and all flash steam is condensed into condensed water in the absorption heat pump, and the condensed water is discharged from the condensed water outlet. The return water of the heating network serves as a cold source and is heated by the second absorption heat pump and the first absorption heat pump in sequence to become the supply water of the heating network.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: after the low-temperature flue gas enters the absorption tower from the second desulfurization tower, the moisture and heat in the low-temperature flue gas are absorbed by the concentrated absorption liquid to generate a dilute absorption liquid and low-temperature dry flue gas, and then the temperature and water vapor content of the low-temperature dry flue gas discharged into the atmosphere are greatly reduced, thereby achieving the purpose of eliminating white smoke plume; the dilute absorption liquid that has absorbed the moisture and heat in the low-temperature flue gas enters the first flash tank and the second flash tank in turn for flash evaporation, and flash steam is generated. After the flash steam enters the first absorption heat pump and the second absorption heat pump respectively, the flash steam condenses into condensed water in the absorption heat pump. At the same time, the heat in the flash steam also provides energy for the absorption heat pump, thereby achieving the purpose of fully recovering the moisture and heat in the low-humidity low-temperature flue gas, greatly improving the water and heat recovery rate, and reducing energy waste.

[0016] Furthermore, the present invention performs flash evaporation of desulfurized slurry and flash regeneration of absorption liquid in different zones in the same flash tank, thereby not only realizing the regeneration and recycling of absorption liquid, but also improving the utilization efficiency of vacuum pumps, reducing the number of required vacuum pumps, and greatly reducing equipment costs and power consumption of vacuum pumps.

[0017] Furthermore, after the flue gas enters the first desulfurization tower, it exchanges moisture and heat with the medium-temperature desulfurization slurry to generate high-temperature desulfurization slurry and medium-temperature saturated wet flue gas. The heat is transferred from the flue gas to the high-temperature desulfurization slurry. After the high-temperature desulfurization slurry enters the first flash tank, it flashes to generate medium-temperature flash steam and medium-temperature desulfurization slurry. The heat is transferred from the high-temperature desulfurization slurry to the medium-temperature flash steam. The low-temperature flash steam enters the first absorption heat pump and condenses into condensed water, thereby achieving the purpose of preliminary recovery of moisture and heat in the flue gas. After the medium-temperature saturated wet flue gas enters the second desulfurization tower, it exchanges moisture and heat with the low-temperature desulfurization slurry to generate medium-high-temperature desulfurization slurry and low-temperature flue gas. After the medium-high-temperature desulfurization slurry enters the second flash tank, it flashes to generate low-temperature flash steam and low-temperature desulfurization slurry. The heat is transferred from the medium-high-temperature desulfurization slurry to the low-temperature flash steam. The low-temperature flash steam enters the second absorption heat pump and condenses into condensed water, thereby achieving the purpose of recovering moisture and heat in the medium-temperature saturated wet flue gas. For the purpose of recycling and utilization, the low-temperature flue gas enters the absorption tower from the second desulfurization tower, and the moisture and heat in the low-temperature flue gas are absorbed by the concentrated absorption liquid to generate dilute absorption liquid and low-temperature dry flue gas, and then the temperature and water vapor content of the low-temperature dry flue gas discharged into the atmosphere are greatly reduced, thereby achieving the purpose of eliminating white smoke plume; the dilute absorption liquid that has absorbed the moisture and heat in the low-temperature flue gas enters the first flash tank and the second flash tank in turn for flash evaporation, and flash steam is generated. After the flash steam enters the first absorption heat pump and the second absorption heat pump respectively, the flash steam condenses into condensed water in the absorption heat pump, and at the same time, the heat in the flash steam also provides energy for the absorption heat pump, thereby achieving the purpose of fully recovering the moisture and heat in the low-humidity low-temperature flue gas, and finally achieving deep recovery of flue gas water and heat, and the temperature and water vapor content of the low-temperature dry flue gas discharged into the atmosphere are greatly reduced, thereby achieving the purpose of eliminating white smoke plume, and with significant economic benefits.

[0018] Furthermore, the flash steam is condensed into condensed water through an absorption heat pump. The condensed water has good water quality and is pure water with trace impurities. It can be used for chemical water replenishment, process water or desulfurization tower water replenishment, reducing the water consumption of the present invention.

[0019] Furthermore, the present invention effectively improves the recovery rate of water heat in flue gas through the organic combination of two-stage desulfurization slurry flash evaporation water heat recovery method and absorption liquid absorption, and further reduces the water content and flue gas temperature in the flue gas. The recovered heat is used to provide heating for residents, increasing the heating capacity of the unit, and has significant economic benefits.

[0020] Furthermore, the present invention combines the two-stage regeneration of the absorption liquid with the two-stage flash evaporation heat raising of the desulfurized slurry, thereby effectively improving the regeneration effect of the absorption liquid and reducing the comprehensive regeneration energy consumption, thereby having significant economic benefits.

[0021] The operation method of this system realizes the recovery of moisture and heat in flue gas through the cooperation of the first desulfurization tower, the first flash tank and the first absorption heat pump, further realizes the recovery of moisture and heat in medium-temperature saturated wet flue gas through the cooperation of the second desulfurization tower, the second flash tank and the second absorption heat pump, and realizes the recovery of moisture and heat in low-temperature flue gas through the cooperation of the absorption tower, the flash tank and the absorption heat pump; this method effectively improves the recovery rate of water and heat in flue gas and further reduces the water content and flue gas temperature in flue gas through the organic combination of two-stage desulfurization slurry flash evaporation water heat recovery method and absorption liquid absorption. By performing desulfurization slurry flash evaporation and absorption liquid flash evaporation regeneration in the same flash tank in different areas, the utilization efficiency of the vacuum pump is improved, the number of vacuum pumps required is reduced, and the equipment cost and vacuum pump power consumption are greatly reduced; by combining the two-stage regeneration of the absorption liquid with the two-stage flash evaporation heat raising of the desulfurization slurry, the absorption liquid regeneration effect is effectively improved, and the comprehensive regeneration energy consumption is reduced, which has significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, 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.

[0023] In the attached figure:

[0024] Figure 1 This is a structural schematic diagram of a system for deep recovery of flue gas water heat according to the present invention.

[0025] In the figure: 1. First desulfurization tower; 2. Second desulfurization tower; 3. Absorption tower; 4. Second flash tank; 5. First flash tank; 6. Second absorption heat pump; 7. First absorption heat pump; 8. Flue gas; 9. Medium-temperature saturated wet flue gas; 10. High-temperature desulfurization slurry; 11. Low-temperature flue gas; 12. Low-temperature dry flue gas; 13. Low-temperature desulfurization slurry; 14. Low-temperature flash steam; 15. Concentrated absorption liquid; 16. Medium-temperature desulfurization slurry; 17. Medium absorption liquid; 18. Medium-temperature flash steam; 19. Dilute absorption liquid; 20. Medium- and high-temperature desulfurization slurry; 21. Driving steam; 22. Driving steam condensate; 23. Heating network return water; 24. Heating network water supply; 25. Condensate; 26. Medium-temperature heating network water; 41. Third area; 42. Fourth area; 51. First area; 52. Second area DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0027] The following detailed description is an exemplary description and is intended to provide further detailed description of the present invention. Unless otherwise indicated, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention.

[0028] See Figure 1 As shown, the present invention provides a system for deep recovery of flue gas water heat, comprising a first desulfurization tower 1, a second desulfurization tower 2, an absorption tower 3, a second flash tank 4, a first flash tank 5, a first absorption heat pump 7 and a second absorption heat pump 6;

[0029] The first desulfurization tower 1 is provided with a smoke inlet for the flue gas 8 to enter, and the first desulfurization tower 1 is provided with a medium-temperature saturated wet flue gas outlet for discharging the medium-temperature saturated wet flue gas 9; a medium-temperature desulfurization slurry 16 is provided in the first desulfurization tower 1, and the medium-temperature desulfurization slurry 16 is used to exchange moisture and heat with the flue gas 8; the first desulfurization tower 1 is provided with a first desulfurization tower inlet and a first desulfurization tower outlet, the first flash tank 5 is provided with a first flash tank negative pressure steam outlet, the first flash tank 5 also includes a first area 51 and a second area 52, the first area 51 is provided with a first area inlet and a first area outlet, the second area 52 is provided with a second area inlet and a second area outlet, the first absorption heat pump 7 is provided with a first absorption heat pump negative pressure steam inlet; the first desulfurization tower outlet is connected to the first area inlet, the first flash tank negative pressure steam outlet is connected to the first absorption heat pump negative pressure steam inlet, and the first area outlet is connected to the first desulfurization tower inlet.

[0030] The second desulfurization tower 2 is provided with a low-temperature desulfurization slurry 13, which is used to exchange moisture and heat with the medium-temperature saturated wet flue gas 9; the first desulfurization tower 1 is connected to the second desulfurization tower 2, and the second desulfurization tower 2 is provided with a medium-temperature saturated wet flue gas inlet for the medium-temperature saturated wet flue gas 9 to enter, the medium-temperature saturated wet flue gas outlet of the first desulfurization tower 1 is connected to the medium-temperature saturated wet flue gas inlet of the second desulfurization tower 2, and the second desulfurization tower 2 is provided with a low-temperature flue gas outlet for discharging the low-temperature flue gas 11; the second desulfurization tower 2 is provided with a second desulfurization tower outlet and a second desulfurization tower inlet. The second flash tank 4 is provided with a second flash tank negative pressure steam outlet, and the second flash tank 4 further includes a third area 41 and a fourth area 42, the third area 41 is provided with a third area inlet and a third area outlet, and the fourth area 42 is provided with a fourth area inlet and a fourth area outlet; the second absorption heat pump 6 is provided with a second absorption heat pump negative pressure steam inlet; the second desulfurization tower outlet is connected to the third area inlet, the second flash tank negative pressure steam outlet is connected to the second absorption heat pump negative pressure steam inlet, and the third area outlet is connected to the second desulfurization tower inlet.

[0031] A concentrated absorption liquid 15 is provided in the absorption tower 3, and the concentrated absorption liquid 15 is used to absorb moisture and heat in the low-temperature flue gas 11; the low-temperature flue gas outlet of the second desulfurization tower 2 is connected with the low-temperature flue gas inlet of the absorption tower 3, and the absorption tower 3 is provided with a low-temperature flue gas inlet for the entry of the low-temperature flue gas 11; the absorption tower 3 is provided with an absorption tower outlet and an absorption tower inlet; the absorption tower outlet is connected with the inlet of the first flash tank, the absorption tower outlet is connected with the second area inlet of the first flash tank, the first flash tank outlet is connected with the second flash tank inlet, the second area outlet of the first flash tank is connected with the fourth area inlet of the second flash tank, and the fourth area outlet is connected with the absorption tower inlet.

[0032] The absorption heat pump is driven by driving steam 21 , and includes a driving steam inlet, a driving steam condensate outlet, a condensate outlet, a heating network return water inlet, and a heating network supply water outlet.

[0033] A method for operating a system for deep recovery of flue gas water heat, comprising:

[0034] Flue gas 8 enters the first desulfurization tower 1 from the flue gas inlet, and the flue gas 8 exchanges moisture and heat with the medium-temperature desulfurization slurry 16 to generate high-temperature desulfurization slurry 10 and medium-temperature saturated wet flue gas 9;

[0035] The high-temperature desulfurization slurry 10 enters the first area 51 from the outlet of the first desulfurization tower, flashes in a vacuum environment, and produces medium-temperature flash steam 18 and medium-temperature desulfurization slurry 16. Heat is transferred from the high-temperature desulfurization slurry 10 to the medium-temperature flash steam 18. The medium-temperature desulfurization slurry 16 flows from the outlet of the first area into the inlet of the first desulfurization tower, and the medium-temperature flash steam 18 enters the negative-pressure steam inlet of the first absorption heat pump from the negative-pressure steam outlet of the first flash tank.

[0036] The medium-temperature saturated wet flue gas 9 enters the second desulfurization tower 2 from the first desulfurization tower 1 through the medium-temperature saturated wet flue gas outlet and the medium-temperature saturated wet flue gas inlet. The medium-temperature saturated wet flue gas 9 exchanges water and heat with the low-temperature desulfurization slurry 13 in the second desulfurization tower 2 to generate medium-temperature and high-temperature desulfurization slurry 20 and low-temperature flue gas 11.

[0037] The medium- and high-temperature desulfurization slurry 20 flows from the outlet of the second desulfurization tower into the third area 41, flashes under a vacuum environment, and generates low-temperature flash steam 14 and low-temperature desulfurization slurry 13. Heat is transferred from the medium- and high-temperature desulfurization slurry 20 to the low-temperature flash steam 14. In a preferred embodiment of the present invention, the medium- and high-temperature desulfurization slurry 20 flashes under a higher vacuum degree, which can achieve better heat recovery and concentration of the generated flash steam and desulfurization slurry. The low-temperature desulfurization slurry 13 flows from the outlet of the third area into the inlet of the second desulfurization tower, and the low-temperature flash steam 14 enters the negative-pressure steam inlet of the second absorption heat pump from the negative-pressure steam outlet of the second flash tank.

[0038] The low-temperature flue gas 11 enters the absorption tower 3 from the second desulfurization tower 2 through the low-temperature flue gas outlet and the low-temperature flue gas inlet. The low-temperature flue gas 11 exchanges moisture and heat with the concentrated absorption liquid 15 to generate a dilute absorption liquid 19 and a low-temperature dry flue gas 12.

[0039] The dilute absorption liquid 19 enters the second area 52 from the outlet of the absorption tower, and flash evaporates under a vacuum environment to produce a medium absorption liquid 17 and flash steam. The flash steam enters the negative pressure steam inlet of the first absorption heat pump from the negative pressure steam outlet of the first flash tank. The medium absorption liquid 17 enters the fourth area 42 from the outlet of the second area, and is flash evaporated and concentrated under a vacuum environment with a higher vacuum degree to generate a concentrated absorption liquid 15 and flash steam. The flash steam enters the negative pressure steam inlet of the second absorption heat pump from the negative pressure steam outlet of the second flash tank. The concentrated absorption liquid 15 enters the absorption tower inlet from the outlet of the fourth area.

[0040] The driving steam 21 enters from the driving steam inlet, and the driving steam 21 serves as a high-temperature heat source for the first absorption heat pump 7 and the second absorption heat pump 6. The driving steam 21 drives the first absorption heat pump 7 and the second absorption heat pump 6 to operate. The driving steam 21 condenses in the absorption heat pump to form driving steam condensate 22, and the driving steam condensate 22 is discharged from the driving steam condensate outlet and returned to the clean water tank; the low-temperature flash steam 14 generated after flash evaporation in the third area 41, the medium-temperature flash steam 18 generated after flash evaporation in the first area 51, and the flash steam flashed in the second area 52 and the fourth area 42 are all condensed into condensate 25, and the condensate 25 is discharged from the first absorption heat pump through the condensate outlet. 7 and the second absorption heat pump 6. In a preferred embodiment of the present invention, the condensed water 25 has good quality and is pure water with trace impurities. It can be recycled and used for chemical make-up water, process water or desulfurization tower make-up water, reducing the water consumption of the present invention; the hot network return water 23 serves as the cold source of the absorption heat pump and is heated to a specified temperature by two-stage absorption heat pumps in sequence to become the hot network supply water 24 for heating residents. The hot network return water 23 enters the second absorption heat pump 6 from the hot network return water inlet and is heated to generate medium-temperature hot network water 26. The medium-temperature hot network water 26 then enters the first absorption heat pump 7 from the second absorption heat pump 6 and is heated to become the hot network supply water 24. The hot network supply water 24 flows out from the hot network water supply outlet for heating residents.

[0041] In a preferred embodiment of the present invention, the flue gas 8 comes from the power plant boiler; the driving steam 21 is drawn from the power plant turbine extraction steam, the specific source of which can be determined by the power plant itself, and can be three-stage steam extraction, four-stage steam extraction or five-stage steam extraction.

[0042] In a preferred embodiment of the present invention, the first flash tank 5 is separated into a first area 51 and a second area 52 by a partition, and the second flash tank 4 is separated into a third area 41 and a fourth area 42 by a partition. The desulfurization slurry in the first area 51 does not contact the absorption liquid in the second area 52, and the desulfurization slurry in the third area 41 does not contact the absorption liquid in the fourth area 42. The flash steam generated by the flash evaporation of the absorption liquid merges with the flash steam generated by the flash evaporation of the desulfurization slurry, and then the merged flash steam enters the first absorption heat pump 7 from the negative pressure steam outlet of the first flash tank, the flash steam generated by the flash evaporation of the absorption liquid merges with the flash steam generated by the flash evaporation of the desulfurization slurry, and then the merged flash steam enters the second absorption heat pump 6 from the negative pressure steam outlet of the second flash tank; in a preferred embodiment of the present invention, the partition is vertically fixed to the bottom end surface in the first flash tank 5, and the bottom of the partition is welded to the inner surface of the first flash tank 5. The bottom end surfaces are seamlessly connected together, the top of the partition does not contact the first flash tank 5, and there is a space between the top of the partition and the top of the first flash tank 5. The flash steam generated by the flash evaporation of the desulfurization slurry in the first area 51 and the flash steam generated by the flash evaporation of the absorption liquid in the second area 52 merge in the space and enter the first absorption heat pump 7 from the negative pressure steam outlet of the first flash tank; in a preferred embodiment of the present invention, the partition is vertically fixed to the bottom end surface of the second flash tank 4, the bottom of the partition is seamlessly connected to the bottom end surface of the second flash tank 4 by welding, the top of the partition does not contact the second flash tank 4, and there is a space between the top of the partition and the top of the second flash tank 4. The flash steam generated by the flash evaporation of the desulfurization slurry in the third area 41 and the flash steam generated by the flash evaporation of the absorption liquid in the fourth area 42 merge in the space and enter the second absorption heat pump 6 from the negative pressure steam outlet of the second flash tank.

[0043] In a preferred embodiment of the present invention, the partition is made of a polymer material plate, and the polymer material plate is made of a material resistant to acid and alkali corrosion, and the polymer material plate is made of peek material or PTFE material, which can extend the service life of the flash tank and reduce equipment maintenance costs.

[0044] In a preferred embodiment of the present invention, the temperature range of the medium-temperature saturated wet flue gas 9 is 50°C to 55°C, the temperature range of the low-temperature flue gas 11 is 45°C to 50°C, the temperature range of the low-temperature dry flue gas 12 is 40°C to 45°C, the temperature range of the low-temperature desulfurization slurry 13 is 40°C to 45°C, the temperature range of the medium-temperature desulfurization slurry 16 is 42°C to 47°C, the temperature range of the medium- and high-temperature desulfurization slurry 20 is 45°C to 50°C, the temperature range of the high-temperature desulfurization slurry 10 is 48°C to 53°C, the temperature range of the low-temperature flash steam 14 is 40°C to 45°C, and the temperature range of the medium-temperature flash steam 18 is 45°C to 50°C;

[0045] In a preferred embodiment of the present invention, the components of the absorption liquid include CaCl2 solution, the CaCl2 concentration of the concentrated absorption liquid 15 is 30% to 60%, the CaCl2 concentration of the medium absorption liquid 17 is 15% to 40%, and the CaCl2 concentration of the dilute absorption liquid 19 is 5% to 30%.

[0046] In a preferred embodiment of the present invention, the driving steam 21 can be driven steam extracted from different steam turbines according to actual needs.

[0047] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A system for deep recovery of flue gas water heat, characterized in that: It comprises a second desulfurization tower (2), an absorption tower (3), a first flash tank (5), a second flash tank (4), a first absorption heat pump (7) and a second absorption heat pump (6); The low-temperature flue gas outlet of the second desulfurization tower (2) is connected to the low-temperature flue gas inlet of the absorption tower (3), the absorption tower outlet is connected to the first flash tank inlet, the first flash tank negative pressure steam outlet is connected to the first absorption heat pump negative pressure steam inlet, the first flash tank outlet is connected to the second flash tank inlet, and the second flash tank negative pressure steam outlet is connected to the second absorption heat pump negative pressure steam inlet; The first flash tank (5) is divided into a first area (51) and a second area (52) by a partition, and the desulfurization slurry in the first area (51) does not contact the absorption liquid in the second area (52); the second flash tank (4) is divided into a third area (41) and a fourth area (42) by a partition, and the desulfurization slurry in the third area (41) does not contact the absorption liquid in the fourth area (42); The absorption tower outlet is communicated with the second region inlet, the second region outlet is communicated with the fourth region inlet, and the fourth region outlet is communicated with the absorption tower inlet.

2. The system for deep recovery of flue gas water heat according to claim 1, characterized in that: It also includes a first desulfurization tower (1), the outlet of the first desulfurization tower is connected to the inlet of the first area, and the outlet of the first area is connected to the inlet of the first desulfurization tower.

3. The system for deep recovery of flue gas water heat according to claim 2, characterized in that: The medium-temperature saturated wet flue gas outlet of the first desulfurization tower (1) is connected to the medium-temperature saturated wet flue gas inlet of the second desulfurization tower (2), the outlet of the second desulfurization tower is connected to the inlet of the third area, and the outlet of the third area is connected to the inlet of the second desulfurization tower.

4. The system for deep recovery of flue gas water heat according to claim 2, characterized in that: The first desulfurization tower (1) is provided with a medium-temperature desulfurization slurry (16), and the medium-temperature desulfurization slurry (16) is used to exchange moisture and heat with the flue gas (8); the second desulfurization tower (2) is provided with a low-temperature desulfurization slurry (13), and the low-temperature desulfurization slurry (13) is used to exchange moisture and heat with the medium-temperature saturated wet flue gas (9); the absorption tower (3) is provided with a concentrated absorption liquid (15), and the concentrated absorption liquid (15) is used to absorb moisture and heat in the low-temperature flue gas (11).

5. The system for deep recovery of flue gas water heat according to claim 2, characterized in that: The first desulfurization tower (1) is provided with a smoke inlet for the entry of flue gas (8).

6. A method for operating a system for deep recovery of flue gas water heat, characterized in that: A system for deep recovery of flue gas water heat according to any one of claims 1 to 5, wherein flue gas (8) enters a first desulfurization tower (1) from a flue gas inlet, and the flue gas (8) exchanges water and heat with a medium-temperature desulfurization slurry (16) to generate a high-temperature desulfurization slurry (10) and a medium-temperature saturated wet flue gas (9); The high-temperature desulfurization slurry (10) enters the first area (51) from the outlet of the first desulfurization tower, flashes in a vacuum environment, and generates medium-temperature flash steam (18) and medium-temperature desulfurization slurry (16); the medium-temperature desulfurization slurry (16) flows from the outlet of the first area into the inlet of the first desulfurization tower, and the medium-temperature flash steam (18) enters the negative-pressure steam inlet of the first absorption heat pump from the negative-pressure steam outlet of the first flash tank.

7. The method for operating a system for deep recovery of flue gas water heat according to claim 6, characterized in that: The medium-temperature saturated wet flue gas (9) enters the second desulfurization tower (2) from the first desulfurization tower (1), and the medium-temperature saturated wet flue gas (9) exchanges water and heat with the low-temperature desulfurization slurry (13) to generate medium-temperature and high-temperature desulfurization slurry (20) and low-temperature flue gas (11); The medium- and high-temperature desulfurization slurry (20) flows from the outlet of the second desulfurization tower into the third area (41), flashes under a vacuum environment, and generates low-temperature flash steam (14) and low-temperature desulfurization slurry (13); the low-temperature desulfurization slurry (13) flows from the outlet of the third area into the inlet of the second desulfurization tower, and the low-temperature flash steam (14) enters the negative-pressure steam inlet of the second absorption heat pump from the negative-pressure steam outlet of the second flash tank.

8. The method for operating a system for deep recovery of flue gas water heat according to claim 7, characterized in that: The low-temperature flue gas (11) enters the absorption tower (3) from the second desulfurization tower (2), and the low-temperature flue gas (11) exchanges water and heat with the concentrated absorption liquid (15) to generate a dilute absorption liquid (19) and a low-temperature dry flue gas (12); The dilute absorption liquid (19) enters the second region (52) from the outlet of the absorption tower, flashes under a vacuum environment, and generates a medium absorption liquid (17) and flash steam. The flash steam enters the negative pressure steam inlet of the first absorption heat pump from the negative pressure steam outlet of the first flash tank. The medium absorption liquid (17) enters the fourth region (42) from the outlet of the second region, flashes under a vacuum environment, and generates a concentrated absorption liquid (15) and flash steam. The flash steam enters the negative pressure steam inlet of the second absorption heat pump from the negative pressure steam outlet of the second flash tank. The concentrated absorption liquid (15) enters the absorption tower inlet from the outlet of the fourth region.

9. The method for operating a system for deep recovery of flue gas water heat according to claim 8, characterized in that: The first absorption heat pump (7) and the second absorption heat pump (6) are driven by driving steam (21). All flash steam condenses into condensed water (25) in the absorption heat pump. The condensed water (25) is discharged from the condensed water outlet. The heat network return water (23) serves as a cold source and is heated by the second absorption heat pump (6) and the first absorption heat pump (7) in sequence to become the heat network supply water (24).

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