A device for combined waste heat recovery, white plume elimination and wastewater concentration

Abstract

The present invention discloses a device for combined waste heat recovery, white smoke elimination and wastewater concentration. This device is used to solve the problems of waste heat recovery from power plant flue gas and wastewater concentration, and is composed of an absorption heat pump system, a wastewater concentration system, an evaporation and drying system, etc. This device utilizes the waste heat of flue gas from coal-fired power plants or other industries for wastewater concentration. The concentration process has little impact on the humidity of the flue gas, turns the wastewater into usable water, and finally transfers the recovered flue gas heat to the low-pressure heater system to achieve cascaded utilization of thermal energy. The highly concentrated wastewater after concentration and reduction can be sent to the evaporation and drying system, greatly reducing the heat required by the evaporation and drying system and reducing the impact on the unit. The entire system has the advantages of low energy consumption, low investment, and low operating costs.

Description

Technical Field

[0001] The present invention belongs to the field of environmental protection technologies, and particularly relates to a device for combined waste heat recovery and white plume elimination and wastewater concentration, and more particularly to a method and device for deep waste heat recovery from flue gas in a thermal power plant, white plume elimination, water collection, and coordinated wastewater treatment, or for deep waste heat recovery from flue gas, white plume elimination, water collection, and coordinated wastewater treatment in other fields. Background Art

[0002] Currently, the mainstream white plume elimination technologies all involve arranging a flue gas condenser, a spray tower behind the desulfurization tower or adding a slurry cooler to the slurry circulation pipeline to cool the flue gas at the outlet of the desulfurization tower to precipitate moisture, and using the sensible heat of the raw flue gas to heat the clean flue gas. Such technologies not only cannot deeply recover the large latent heat of water vapor in the clean flue gas, but also waste the sensible heat of the raw flue gas. At the same time, the condensation and precipitation of moisture in the flue gas require external refrigerant, resulting in a great waste of energy. To remove the latent heat of the clean flue gas, a large amount of cooling circulating water is required, and the cold source is a problem that the current mainstream technologies must face. Especially in areas where the flue gas temperature and moisture content at the outlet of the desulfurization tower are specified, not only is condensation required in winter, but even in summer, flue gas condensation is also required. During summer in a power plant, the cooling water tower often operates at full load and cannot provide an effective cold source. If a new cooling water tower is built, additional investment is required, and at the same time, it will result in exchanging good water for wastewater, without achieving the water-saving effect. If a mechanical draft cooling tower is newly built, the construction cost is extremely high and unaffordable for the power plant.

[0003] The treatment of wet desulfurization wastewater mainly adopts the triple box pretreatment + clarifier + dewatering machine technology, which can remove some heavy metals, reduce some SS and turbidity, but cannot remove chloride ions, and there is no outlet for the treated wastewater. Currently, the technologies under research include deep pretreatment + concentration reduction + evaporation and drying. Deep pretreatment includes dosing, clarification, and filtration; concentration reduction can utilize thermal methods (MED, MVR, NED) and membrane methods (UF / RO); evaporation and drying use steam or flue gas waste heat for drying. Using steam evaporation can produce recoverable salts and realize the reuse of water in the wastewater. Its disadvantage is the recovery of low-grade salts, which is difficult to reuse. Its evaporation process requires high-quality steam, with high energy consumption, large investment, and high operating requirements. The flue gas waste heat evaporation scheme has lower investment and operating costs, and can improve the dust removal efficiency of the downstream. Its disadvantage is the consumption of high-quality flue gas waste heat, which affects the flue gas temperature of the air preheater, resulting in a reduction in the unit efficiency. At the same time, it will increase the load of the dust removal equipment. If concentration reduction is not carried out, a large amount of moisture will enter the desulfurization system, resulting in a reduction in the evaporation capacity of the desulfurization tower, affecting the desulfurization flushing water volume, and the treated wastewater volume will also be limited by the flue gas temperature and load.

[0004] Due to the above problems of energy and water resource waste, large investment costs, and only investment without return in white plume elimination in the current conventional white plume elimination technologies, and problems such as consumption of high-quality thermal energy, high energy consumption, large investment costs, high operating requirements, and adverse effects on the unit efficiency in the desulfurization wastewater concentration technology. Summary of the Invention

[0005] Therefore, the technical problems to be solved by the present invention are the deep recovery of waste heat from power plant flue gas, the elimination of wet plume, and the treatment of desulfurization wastewater. The flue gas after wet desulfurization is saturated flue gas at about 50°C, carrying a large amount of saturated water and free water. If directly discharged from the chimney, it will cause visual pollution of the wet plume, and at the same time waste a large amount of water resources and the latent heat of water vapor in the flue gas. Reducing and concentrating the desulfurization wastewater requires a large amount of high-quality steam or flue gas, with high energy consumption. Whether using the extraction steam of the unit or the waste heat of the flue gas before the air preheater will have an adverse impact on the unit. Thus, a device for combined waste heat recovery, plume elimination, and wastewater concentration is proposed.

[0006] For this reason, the technical solutions provided by the present invention are as follows:

[0007] The device for combined waste heat recovery, plume elimination, and wastewater concentration provided by the present invention includes:

[0008] An absorption heat pump system, including an absorption unit, a first circulation loop, and a first heat exchanger provided on the first circulation loop. The liquid inlet end of the first circulation loop is connected to the lower part of the absorption unit, and the liquid outlet end is connected to the upper part of the absorption unit;

[0009] A wastewater concentration system, including a wastewater flash tank, a wastewater cooler, and a sedimentation device connected in sequence. The wastewater flash tank is connected to the first heat exchanger or the fifth heat exchanger, so that the liquid at the outlet end exchanges heat with the desulfurization wastewater from the outside in the first heat exchanger or the fifth heat exchanger, and then the heated desulfurization wastewater is sent to the wastewater flash tank, wastewater cooler, and sedimentation device in sequence;

[0010] An evaporation and drying system, connected to the sedimentation device, so that the concentrated desulfurization wastewater from the sedimentation device enters the evaporation and drying system.

[0011] Furthermore, it further includes a second heat exchanger, a third heat exchanger, and a fifth heat exchanger;

[0012] The second heat exchanger and the third heat exchanger are connected in sequence, and the second heat exchanger is also connected to the first heat exchanger, so that the water from the heat network or the intermediate heat transfer medium water passes through the first heat exchanger, the second heat exchanger, and the third heat exchanger in sequence to form the return water of the heat network or the intermediate heat transfer medium water; the second heat exchanger or the third heat exchanger is also connected to the fifth heat exchanger to send part of the water from the heat network or the intermediate heat transfer medium water into the fifth heat exchanger to heat the desulfurization wastewater;

[0013] The fifth heat exchanger is arranged on the intermediate heat medium water circulation pipe and connected to the waste water flash evaporation tank. The intermediate heat medium water first exchanges heat with the dilute absorption liquid through the first heat exchanger, then enters the second heat exchanger, and then enters the fifth heat exchanger to exchange heat with the desulfurized waste water. Or it continuously passes through the second heat exchanger and the third heat exchanger for heat exchange and then enters the fifth heat exchanger to exchange heat with the desulfurized waste water. It is led out after the second heat exchanger or the third heat exchanger according to the temperature and vacuum degree required for flash evaporation. The desulfurized waste water is heated and then enters the waste water flash evaporation tank for flash evaporation. This operation mode improves the temperature of the intermediate heat medium water by utilizing the heat of the primary steam condensate and the secondary steam of the heat pump system, thereby increasing the temperature of the desulfurized waste water entering the flash evaporation tank and reducing the vacuum degree required for the waste water flash evaporation tank.

[0014] Furthermore, it further includes a second circulation loop and a regeneration system arranged on the second circulation loop. The liquid inlet end of the second circulation loop is communicated with the lower part of the absorption unit, and the liquid outlet end is communicated with the upper part of the absorption unit, so that the liquid at the liquid outlet end enters the absorption unit after being regenerated by the regeneration system and contacts the flue gas entering the absorption unit in a countercurrent manner.

[0015] Furthermore, the regeneration system includes a solution flash evaporation tank, which is provided with a dilute solution inlet in the middle, a steam outlet at the upper part, and a concentrated solution outlet at the lower part;

[0016] The seventh heat exchanger, the lower part of the absorption unit, the seventh heat exchanger and the dilute solution inlet are communicated in sequence;

[0017] The compressor and the saturator, the steam outlet, the compressor, the saturator and the seventh heat exchanger are communicated in sequence, so that in the non-heating season, the dilute solution at the lower part of the absorption unit exchanges heat with the secondary steam in the seventh heat exchanger and then enters the solution flash evaporation tank.

[0018] Furthermore, it further includes a sixth heat exchanger arranged on the second circulation loop. The lower part of the absorption unit, the sixth heat exchanger, the seventh heat exchanger and the dilute solution inlet are communicated in sequence, so as to exchange heat between the dilute solution from the absorption unit and the concentrated solution from the concentrated solution outlet in the sixth heat exchanger, and the concentrated solution after heat exchange enters the absorption unit.

[0019] Furthermore, the sedimentation device includes at least two-stage sedimentation units to perform multi-stage precipitation on the cooled concentrated waste water;

[0020] The upper part of the sedimentation device is communicated with the first heat exchanger or the fifth heat exchanger, so that the supernatant liquid in the sedimentation device and / or the externally added desulfurized waste water enters the first heat exchanger or the fifth heat exchanger and exchanges heat with the dilute solution from the absorption unit or the intermediate heat medium water.

[0021] Further, it further includes an air preheater, a dust removal unit, and a desulfurization unit that are connected in sequence. The desulfurization unit is connected to the lower part of the absorption unit.

[0022] Further, an economizer is also provided between the dust removal unit and the desulfurization unit. Preferably, the economizer is a low-low temperature economizer.

[0023] Further, the evaporation and drying system is a flue gas spray evaporator. Along the flow direction of the flue gas, the flue gas spray evaporator is arranged in the flue between the air preheater and the dust removal unit; or,

[0024] The evaporation and drying system is a rotary spray evaporator. A high-temperature dry flue gas inlet is arranged at its upper part. Along the flow direction of the flue gas, the high-temperature dry flue gas inlet is connected to the upstream flue of the air preheater, so that the high-temperature dry flue gas in the upstream flue of the air preheater enters the rotary spray evaporator to exchange heat with the concentrated desulfurized wastewater. A high-temperature wet flue gas outlet is arranged at the lower part of the rotary spray evaporator. The high-temperature wet flue gas outlet is connected to the flue between the air preheater and the dust removal unit. The connection point of the sedimentation device and the rotary spray evaporator is located at the upper part of the rotary spray evaporator.

[0025] Further, a condenser is also included, which is connected to the secondary steam outlet at the upper part of the wastewater flash tank. The condenser is also connected to the wastewater cooler, so that the heated heat exchange medium from the wastewater cooler enters the condenser and exchanges heat with the secondary steam from the wastewater flash tank again.

[0026] Further, a fourth heat exchanger is also included, which is arranged on the second circulation loop and is used for heat exchange of the concentrated solution again.

[0027] Further, a chimney is also included, and the chimney is connected to the desulfurization unit;

[0028] The dust removal unit is an electrostatic precipitator; the desulfurization unit is a desulfurization tower.

[0029] The technical solution of the present invention has the following advantages: By setting up an absorption heat pump system, the moisture content of the net flue gas can be greatly reduced. During the absorption process, the steam releases latent heat due to phase change, which increases the dryness and temperature of the flue gas. It can simultaneously achieve the elimination of wet plume, deep water extraction, reduction of dust content in the flue gas, and recovery of low-quality latent heat of water vapor in the flue gas. Further, a part of the dilute solution after absorption is concentrated into a concentrated solution through a regeneration system, and the other part can heat the heat network water or intermediate heat medium water through the first heat exchanger. The flow rates of the two are adjusted according to specific requirements. After the heat network water or intermediate heat medium water is heated and temperature-raised through the first heat exchanger, it exchanges heat with the second heat exchanger and the third heat exchanger, reaching the temperature requirement of the heat network water during the heating season to form the return water of the heat network. During the non-heating season, it can be used to heat the desulfurized wastewater of the low-pressure heater, thus realizing the effect of increasing the heating area of the unit during the heating season and treating wastewater with waste heat during the non-heating season;

[0030] By setting up a wastewater concentration system and an evaporation and drying system, the heat recovered from the flue gas is used to increase the temperature of the desulfurized wastewater. The heated wastewater undergoes flashing in the wastewater flash tank, thereby achieving the concentration of the desulfurized wastewater. The flash tank is in a negative pressure state, and its vacuum degree is provided by a vacuum pump. The heat recovered from the flue gas is carried out with the concentrated wastewater and secondary steam. The heat contained in the concentrated wastewater and the condensed secondary steam is recovered by the condensate of the low-pressure heater, and finally this heat returns to the low-pressure heater condensate system. Without losing the recovered heat, the use of heat is expanded, realizing the cascade utilization of thermal energy. The condensed water of the secondary steam after condensation can be used for process water replenishment in the desulfurization system. The concentrated wastewater is sent to a precipitation device (specifically, a wastewater sedimentation tank) by a wastewater pump. After multi-stage precipitation, the supernatant is recycled to the first heat exchanger or the fifth heat exchanger (specifically, a wastewater heater) together with the newly entered desulfurized wastewater, and a small amount of high-concentration wastewater is sent to the evaporation and drying system to control the chloride ion concentration of the wastewater in the concentration system. When it is sent to the flue gas spray evaporator, the atomized concentrated water is evaporated into water vapor by using the high-temperature waste heat flue gas in the flue. The vapor enters the desulfurization tower together with the dust-removed flue gas, and the evaporation crystallization product enters the dust removal unit (specifically, an electrostatic precipitator) together with the dust and is discharged with the ash; or it is sent to an independent rotary spray evaporator for evaporation and drying. A small part of the flue gas at the outlet of the denitration SCR is extracted to the rotary spray evaporator. The desulfurized wastewater is sprayed into the rotary spray evaporator, and the atomized concentrated water is evaporated into water vapor in it by using the heat of the flue gas. The flue gas at the outlet of the rotary spray evaporator enters the inlet flue of the dust removal unit, and the vapor enters the desulfurization unit (specifically, a desulfurization absorption tower) together with the dust-removed flue gas; the evaporation crystallization product enters the dust removal unit (specifically, an electrostatic precipitator) together with the dust and is captured and discharged with the ash;

[0031] Finally, the problems of eliminating wet plumes in coal-fired power plants or other industries and the lack of return on investment in the deep water extraction system are solved through an absorption heat pump system, a wastewater concentration system, and an evaporation and drying system. The wastewater concentration system (low-temperature phase change wastewater concentration system) uses the latent heat recovered by the absorption heat pump system (open absorption heat pump system) to evaporate the desulfurized wastewater, achieving wastewater concentration. This system has the advantages of low energy consumption, low investment, and low operating costs, and achieves high-efficiency energy conservation and environmental protection effects such as emission reduction, having good social and economic impacts. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 FIG. is a schematic structural diagram of a device for combined waste heat recovery and white plume elimination and wastewater concentration in an embodiment of the present invention;

[0034] Figure 2 FIG. is another schematic structural diagram of a device for combined waste heat recovery and white plume elimination and wastewater concentration in an embodiment of the present invention;

[0035] Figure 3 FIG. is a schematic structural diagram of an absorption unit in an embodiment of the present invention;

[0036] Figure 4 FIG. is a schematic structural diagram of a regeneration system in an embodiment of the present invention;

[0037] Figure 5 FIG. is a schematic structural diagram of a wastewater concentration system in an embodiment of the present invention;

[0038] Among them, the reference numerals are represented as follows:

[0039] 0 - air preheater; 1 - dust removal unit; 2 - desulfurization unit; 3 - absorption unit; 3a - first spray unit; 3b - second spray unit; 3c - demister; 4 - economizer; 5 - chimney; 6 - solution filtration and conditioning system; 7 - first heat exchanger; 8 - second heat exchanger; 9 - third heat exchanger; 10 - fourth heat exchanger; 11 - fifth heat exchanger; 12 - sixth heat exchanger; 13 - saturator; 14 - seventh heat exchanger; 15 - solution flash tank; 16 - sedimentation device; 17 - wastewater flash tank; 18 - condenser; 19 - wastewater cooler; 20 - nozzle; 21 - compressor; 22 - rotary spray evaporator. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative work belong to the protection scope of the present invention.

[0041] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0042] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0043] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0044] Embodiment 1

[0045] This embodiment provides a device for waste heat recovery, white smoke elimination and wastewater concentration, as shown in Figure 1 、 3 、4 and 5. The absorption heat pump system includes an air preheater 0, a dust removal unit 1, an economizer 4, a desulfurization unit 2, and a chimney 5 that are connected in sequence. It also includes a first circulation loop and a first heat exchanger 7 provided on the first circulation loop. The liquid inlet end of the first circulation loop is connected to the lower part of the absorption unit 3, and the liquid outlet end is connected to the upper part of the absorption unit 3; in this embodiment, the dust removal unit 1 is an electrostatic precipitator, the economizer 4 is a low-low temperature economizer, and the desulfurization unit 2 is a desulfurization tower; the absorption unit 3 can be an absorption tower, and the absorption tower can be an empty tower or a packed tower. When it is a packed tower, the packing can be single-layer or multi-layer;

[0046] Wastewater concentration system, including a wastewater flash tank 17, a wastewater cooler 19 and a sedimentation device 16 connected in sequence. The wastewater flash tank 17 is connected to the first heat exchanger 7 or the fifth heat exchanger, so that the liquid at the outlet end exchanges heat with the desulfurized wastewater from the outside in the first heat exchanger 7 or the fifth heat exchanger, and then the heated desulfurized wastewater is sent into the wastewater flash tank 17, the wastewater cooler 19 and the sedimentation device 16 in sequence; Specifically, the sedimentation device 16 includes at least two - stage sedimentation units to perform multi - stage precipitation on the cooled concentrated wastewater; Further, it also includes a second heat exchanger 8, a third heat exchanger 9 and a fifth heat exchanger 11. The second heat exchanger 8 and the third heat exchanger 9 are connected in sequence, and the second heat exchanger 8 is also connected to the first heat exchanger 7, so that the heat network incoming water passes through the first heat exchanger 7, the second heat exchanger 8 and the third heat exchanger 9 in sequence to form heat network return water; The second heat exchanger 8 or the third heat exchanger 9 is also connected to the fifth heat exchanger 11 to send part of the heat network return water into the fifth heat exchanger 11 to heat the desulfurized wastewater;

[0047] The fifth heat exchanger 11 is arranged on the intermediate heat medium water circulation pipe and is connected to the wastewater flash tank. The intermediate heat medium water first exchanges heat with the dilute absorbent solution through the first heat exchanger, then enters the second heat exchanger 8, and then enters the fifth heat exchanger to exchange heat with the desulfurized wastewater, or continuously passes through the second heat exchanger 8 and the third heat exchanger 9 for heat exchange and then enters the fifth heat exchanger to exchange heat with the desulfurized wastewater, and is led out after the second heat exchanger or the third heat exchanger according to the temperature and vacuum degree required for flashing. The desulfurized wastewater is heated and then enters the wastewater flash tank for flashing. This operation mode improves the temperature of the intermediate heat medium water by using the heat of the primary steam condensate and the secondary steam of the heat pump system, thereby increasing the temperature of the desulfurized wastewater entering the wastewater flash tank and reducing the vacuum degree required for the wastewater flash tank.

[0048] The upper part of the sedimentation device 16 is connected to the first heat exchanger 7 or the fifth heat exchanger 11, so that the supernatant liquid and / or the additional desulfurized wastewater in the sedimentation device 16 enter the first heat exchanger or the fifth heat exchanger 11 and exchange heat with the dilute solution from the absorption unit 3; More specifically, as Figure 5 shown, the sedimentation device 16 is a wastewater sedimentation tank with three - stage sedimentation units connected in sequence. The multi - stage precipitation form is adopted to ensure that only a small amount of concentrated wastewater needs to be sent to the evaporation and drying system to reduce the impact on the overall efficiency of the unit;

[0049] An evaporation drying system is connected to the sedimentation device 16, specifically communicating with the lower part of the sedimentation device 16, so that the concentrated desulfurized wastewater from the sedimentation device 16 enters the evaporation drying system; in this embodiment, the evaporation drying system is a flue spray evaporator (such as the nozzle 20), and along the flow direction of the flue gas, the flue spray evaporator is arranged in the flue between the air preheater 0 and the dust removal unit 1, using the high-temperature waste heat flue gas in the flue to evaporate the atomized concentrated water into water vapor. The vapor enters the desulfurization tower along with the flue gas after dust removal, and the evaporation crystallization product enters the electrostatic precipitator along with the dust and is discharged outside with the ash, controlling the chloride ion concentration in the wastewater sedimentation tank.

[0050] Furthermore, it further includes a second circulation loop and a regeneration system arranged on the second circulation loop. The liquid inlet end of the second circulation loop communicates with the lower part of the absorption unit 3, and the liquid outlet end communicates with the upper part of the absorption unit 3, so that the liquid at the liquid outlet end enters the absorption unit 3 after being regenerated by the regeneration system and contacts the flue gas entering the absorption unit 3 in a countercurrent manner; specifically, the regeneration system includes a solution flash evaporation tank 15, with a dilute solution inlet arranged in the middle, a steam outlet arranged at the upper part, and a concentrated solution outlet arranged at the lower part; a seventh heat exchanger 14, the lower part of the absorption unit 3, the seventh heat exchanger 14, and the dilute solution inlet are connected in sequence; a compressor 21 and a saturator 13, the steam outlet, the compressor 21, the saturator 13, and the seventh heat exchanger 14 are connected in sequence, so that in the non-heating season, the dilute solution at the lower part of the absorption unit 3 exchanges heat with the secondary steam in the seventh heat exchanger 14 and then enters the solution flash evaporation tank 15; it further includes a sixth heat exchanger 12 arranged on the second circulation loop, the lower part of the absorption unit 3, the sixth heat exchanger 12, the seventh heat exchanger 14, and the dilute solution inlet are connected in sequence, so that the dilute solution from the absorption unit 3 exchanges heat with the concentrated solution from the concentrated solution outlet in the sixth heat exchanger 12, and the heat-exchanged concentrated solution enters the absorption unit 3.

[0051] By setting up the regeneration system, no modification is made to the desulfurization tower of the raw flue gas system. An absorption tower is arranged behind the desulfurization tower. The clean flue gas enters from the bottom of the absorption tower and counterflows with the concentrated absorption liquid sprayed from the top of the absorption tower. The concentrated absorption liquid absorbs the moisture in the flue gas and becomes dilute. The latent heat released during the phase change of the separated water vapor heats the flue gas and the absorption liquid, heating the flue gas and the absorption liquid to 55°C - 70°C. The return water of the heat network exchanges heat with the dilute solution and is heated to 40 - 65°C. Part of the dilute solution enters the sixth heat exchanger 12, the dilute and concentrated solutions exchange heat and increase in temperature, then part of it enters the seventh heat exchanger 14 and vaporizes, and finally enters the solution flash evaporation tank 15 for flashing, turning the absorbed water into secondary steam. The concentrated solution at the bottom enters the sixth heat exchanger 12 (dilute and concentrated solution heat exchanger) for heat exchange and then returns to the top of the absorber for spraying. This process recovers the latent heat of the clean flue gas through the heat released by the absorption liquid absorbing water, so that 1 part of the driving steam entering the open absorption heat pump system becomes 1.7 parts of heat when leaving the open absorption heat pump system, thereby increasing the heating area of the unit.

[0052] Specifically, the first spraying unit 3a is disposed inside and near the upper part of the absorption unit 3, and the first spraying unit 3a is communicated with the liquid outlet end of the first circulation loop; specifically, as Figure 1 shown, the number of the first spraying units 3a is 1-2, and is 1 in this embodiment. When there are two, they are divided into upper and lower spraying layers, preferably two layers; the first spraying unit 3a is communicated with the liquid outlet end of the second circulation loop;

[0053] At least one stage of the second spraying unit 3b is disposed inside and near the upper part of the absorption unit 3, and the second spraying unit 3b is communicated with the liquid outlet end of the first circulation loop; specifically, the number of the second spraying units 3b is 2-4, and is two in this embodiment, and is divided into upper and lower spraying layers, preferably three layers;

[0054] It further includes a demister 3c, which is disposed at the top end of the absorption unit 3.

[0055] Further, in order to filter and condition the concentrated solution as the absorption liquid in the absorption unit 3, a solution filtering and conditioning system 6 is further included. The lower part of the absorption unit 3, the solution filtering and conditioning system 6, the first heat exchanger 7 and the second spraying unit 3b are sequentially communicated and arranged to send the dilute solution to the second spraying unit 3b after filtering, conditioning and heat exchange; specifically, the solution filtering and conditioning system 6 is composed of a cyclone + filter which are sequentially communicated.

[0056] In addition, the specific number of the first spraying unit 3a and the second spraying unit 3b can be determined according to the flue gas volume of the project. Each circulation loop is provided with a heat exchanger or a circulation pump separately, and the dynamic equipment is reserved according to relevant specifications. The solution at the bottom of the lower section of the absorption tower is divided into three parts: the first part is responsible for system regeneration through the second circulation loop (outer circulation); the second part is responsible for maintaining the balance state of the absorption system through the first circulation loop (inner circulation); the third part enters the solution filtration and conditioning unit, and a filtration and conditioning unit is provided at the bottom of the lower section of the absorption tower. On the one hand, solid particulate matters and generated crystal salts (such as sulfates, carbonates, etc.) accumulated in the solution in the absorption tower can be removed through a cyclone + filtration device, so that the pollutants and impurities in the absorption tower solution are controlled to a certain extent; on the other hand, calcium-based salts are added to adjust the pH of the solution, maintain the absorption capacity of the solution, and reduce the corrosiveness of the solution at the same time. The absorption liquid enters from the top of the absorption tower and undergoes countercurrent convection with the clean flue gas entering from the bottom of the absorption tower through uniform spraying. The water vapor in the clean flue gas is absorbed by the concentrated solution. Spare layers can be provided for the upper and lower spraying layers respectively to improve the reliability of the absorption tower. By adjusting the small circulation solution volume in the lower section of the absorption tower, the water absorption capacity per unit mass of the salt solution can be controlled. The absorption tower is arranged after the desulfurization tower. Since the moisture content of the flue gas at the bottom of the absorption tower is high, most of the water absorption occurs in this part. A small circulation is set at the bottom of the absorption tower, and the balance temperature of the lower section of the absorption tower is controlled by reducing the temperature of the small circulation solution, so as to improve the water absorption capacity per unit mass of the solution. The concentration of the dilute solution after absorption is reduced by 1%-10% relative to the concentrated solution. The ratio of the small circulation volume (the first circulation loop) to the regeneration circulation volume (the second circulation loop) can be 1:1 - 10:1.

[0057] When there is no heating demand in the non-heating season, environmental protection and white smoke elimination need to be satisfied. In order to reduce the system operation energy consumption, the secondary steam upgraded by the regeneration system (MVR system) is used as the driving heat source. The secondary steam is discharged from the top of the solution flash tank and enters the compressor. The saturated secondary steam after pressurization, temperature increase and spraying is used as the driving heat source of the regenerator. After the secondary steam exchanges heat with the concentrated solution and releases the latent heat, it becomes condensed water. The intermediate heat medium water (low-pressure heater condensed water) is heated to about 65°C. The condensed secondary steam condensate is used for the process water supply of the desulfurization tower. Part of the vaporized concentrated absorption liquid undergoes flash evaporation in the solution flash tank for gas-liquid separation. The flashed secondary steam is recycled to the compressor of the MVR system. The concentrated absorption liquid at the bottom of the solution flash tank is sent to the sixth heat exchanger 12 (dilute and concentrated solution heat exchanger) for heat exchange and finally recycled to the top of the absorber.

[0058] The concentrated wastewater at the bottom of the wastewater flash tank enters the wastewater cooler to exchange heat with the condensate of the low-pressure heater. The cooled concentrated wastewater enters the wastewater sedimentation tank. After hierarchical sedimentation, the supernatant and the newly incoming desulfurized wastewater are recycled to the wastewater heater again. A small amount of concentrated wastewater at the bottom of the wastewater sedimentation tank is sent to the flue gas spray evaporator in front of the electrostatic precipitator. The high-temperature waste heat flue gas in the flue is used to evaporate the atomized concentrated water into water vapor. The vapor enters the desulfurization tower along with the flue gas after dust removal, and the evaporation dry matter enters the electrostatic precipitator together with the dust and is discharged outside with the ash.

[0059] Example 2

[0060] This embodiment provides a device for waste heat recovery, white smoke elimination and wastewater concentration, as Figure 2 shown. On the basis of the above-mentioned Embodiment 1, as a variable implementation mode, the evaporation and drying system is a rotary spray evaporator 22, and a high-temperature dry flue gas inlet is arranged on its upper part. Along the flow direction of the flue gas, the high-temperature dry flue gas inlet is communicated with the upstream flue of the air preheater 0, so that the high-temperature dry flue gas in the upstream flue of the air preheater 0 enters the rotary spray evaporator to exchange heat with the concentrated desulfurized wastewater; specifically, the high-temperature dry flue gas inlet is communicated with the inlet flue of the air preheater 0;

[0061] A high-temperature wet flue gas outlet is arranged at the lower part of the rotary spray evaporator. The high-temperature wet flue gas outlet is communicated with the flue between the air preheater 0 and the dust removal unit 1. Specifically, the high-temperature wet flue gas outlet is communicated with the inlet flue of the dust removal unit 1, and relative to the connection point of the high-temperature dry flue gas inlet and the upstream flue, the connection point of the high-temperature wet flue gas outlet and the upstream flue is close to the dust removal unit 1. The connection point of the sedimentation device 16 and the rotary spray evaporator is located at the upper part of the rotary spray evaporator. Specifically, the connection point of the sedimentation device 16 and the rotary spray evaporator is located at the top of the rotary spray evaporator.

[0062] In actual working conditions, the evaporation and drying system can adopt an independently rotating spray drying tower. The independently rotating spray drying tower is arranged outside the flue gas system. The cooled concentrated wastewater enters the wastewater sedimentation tank. After hierarchical sedimentation, the supernatant and the newly incoming desulfurized wastewater are recycled to the wastewater heater again. A small amount of concentrated wastewater at the bottom of the wastewater sedimentation tank is sent to the independently rotating spray evaporation tower for evaporation and drying. A flue gas bypass is set up to extract a small part of the flue gas at the outlet of the denitration SCR to the spray drying tower. The desulfurized wastewater is sprayed into the spray drying tower and the atomized concentrated water is evaporated into water vapor in the spray drying tower by using the heat of the flue gas. The flue gas at the outlet of the spray drying tower enters the inlet flue of the dust removal unit. The vapor enters the desulfurization tower along with the flue gas after dust removal. The evaporation crystallization product enters the electrostatic precipitator together with the dust and is captured and discharged outside with the ash. The concentrated and dried solid salt is discharged from the bottom of the spray drying tower.

[0063] Example 3

[0064] This embodiment provides a device for combined waste heat recovery and white smoke elimination and wastewater concentration. On the basis of the above-mentioned Embodiment 1 or 2, it further includes a condenser 18, which is connected to the secondary steam outlet at the upper part of the wastewater flash tank 17. The condenser 18 is also connected to the wastewater cooler 19, so that the heated heat exchange medium from the wastewater cooler 19 enters the condenser 18 and exchanges heat with the secondary steam from the wastewater flash tank 17 again;

[0065] Furthermore, it further includes a fourth heat exchanger 10, which is arranged on the second circulation loop and is used for heat exchange of the concentrated solution again.

[0066] During the heating season, the intermediate heat medium water exchanges heat with the absorption liquid from the absorber. The heat network water leaving the first heat exchanger (primary heat network heat exchanger) exchanges heat with the steam extraction condensate water entering the second heat exchanger (secondary heat exchanger). The heat network water leaving the secondary heat network heat exchanger exchanges heat with the secondary steam entering the second heat exchanger (tertiary heat exchanger) again. Finally, the temperature of the heat network water can be raised to 70 - 90 °C. A part of the heat network water leaving the secondary heat network heat exchanger or the tertiary heat exchanger is diverted to the fifth heat exchanger (wastewater heater), and its heat is transferred to the desulfurization wastewater through the wastewater heater. The other part is sent to the heat network head station for continuous heating or directly used for municipal heating. During the non - heating season, the intermediate heat medium water exchanges heat with the absorption liquid from the absorber. The intermediate heat medium water leaving the primary heat network heat exchanger exchanges heat with the secondary steam condensate water entering the secondary heat exchanger. Finally, the temperature of the intermediate heat medium water can be raised to 50 - 65 °C. Then it enters the wastewater heater to heat the desulfurization wastewater, and the desulfurization wastewater can be heated to about 63 °C. The heat used for heating the desulfurization wastewater throughout the year is the latent heat recovered from the clean flue gas. This heat is used to provide the latent heat for the flash evaporation of the desulfurization wastewater, thus avoiding using fresh steam or high - quality flue gas as the heat source for wastewater concentration. The desulfurization wastewater can also directly exchange heat with the absorption liquid through the primary heat network heat exchanger of the heat network water, which can reduce the heat transfer temperature difference loss and make the temperature of the wastewater rise higher, such as Figure 1 and 2 the dotted - line heat exchange route in

[0067] Embodiment 4

[0068] This embodiment provides a device for combined waste heat recovery, white smoke elimination and wastewater concentration. On the basis of the above-mentioned Embodiment 1, 2 or 3, it further includes a first pump, which is connected to the wastewater flash tank 17 and is used to keep the inside of the wastewater flash tank 17 in a negative pressure state and control the vacuum degree therein. That is, in order to ensure that the wastewater after heating can be flash-concentrated, the low-temperature phase-change concentration system needs to be equipped with a vacuum pump (i.e., the first pump). The vacuum pump is connected in series with the wastewater flash tank and the condenser and is located behind the condenser. The secondary steam is first cooled in the condenser, and a negative pressure is generated during its cooling process due to phase change, which can maintain the negative pressure state of the system by itself. However, for system startup and maintaining the stability of the vacuum degree, a vacuum pump needs to be set. The vacuum pump evacuates the air when starting up. During the operation process, it only needs to extract the non-condensable gas separated from the condensate of the secondary steam, reducing the power consumption of the vacuum pump while ensuring the stability of the system vacuum degree;

[0069] A second pump, which is arranged on the pipeline between the sedimentation device 16 and the fifth heat exchanger 11 to send the supernatant and / or the externally added desulfurized wastewater into the fifth heat exchanger 11;

[0070] A third pump, which is arranged on the pipeline between the sedimentation device 16 and the evaporation and drying system.

[0071] A fourth pump, which is arranged on the pipeline between the wastewater flash tank 17 and the condenser 18;

[0072] A fifth pump, which is arranged on the return pipeline or the incoming water pipeline of the low-pressure heater condensate.

[0073] In addition, the heat recovered by the open absorption heat pump system is sent by the heat network water or the intermediate heat medium water to the wastewater heater to heat the desulfurized wastewater. The heated wastewater enters the wastewater flash tank. The flash tank is in a negative pressure state, and its vacuum degree is provided by the vacuum pump. The size of the vacuum degree is related to the wastewater temperature and the required evaporation amount. The vacuum pump is connected in series with the condenser and is located behind the condenser. The recovered flue gas heat is carried out with the concentrated wastewater and the secondary steam. The low-pressure heater condensate is used to recover the heat contained in the concentrated wastewater and the condensed secondary steam. Finally, the heat returns to the low-pressure heater condensate system. After being reheated, the low-pressure heater condensate returns to the low-pressure heater circulating water system with a temperature close to it. With almost no loss of the recovered heat, the cascade utilization of thermal energy is realized. The condensed water of the secondary steam can be used for process water replenishment of the desulfurization system. The condensate of the secondary steam is used for process water replenishment of the desulfurization system.

[0074] The absorber of the open absorption heat pump is responsible for heat and moisture recovery, and the regeneration system restores the dilute solution to the original concentration. The low-temperature phase-change wastewater concentration system and the evaporation and crystallization system are responsible for treating the desulfurized wastewater. This device has the advantage of using waste to eliminate waste by recovering the latent heat of the clean flue gas to increase the heating area in the heating season or concentrate the desulfurized wastewater.

[0075] In addition, it should be noted that, as Figure 1 and Figure 2。An absorber is arranged after the desulfurization tower of the power plant. The absorber is equipped with 2 - 6 spray layers according to the flue gas volume. Generally, 2 layers of external circulation and 3 layers of internal circulation are set. The concentrated salt solution at the top of the absorber absorbs the moisture in the flue gas and becomes diluted. During the phase change of the precipitated moisture, latent heat is released, heating the flue gas and the absorption liquid. The heated absorption liquid exchanges heat through plate heat exchangers on each branch of the internal circulation, and the balance state in the absorber is controlled by the amount of heat carried away. The heated absorption liquid enters the primary heat exchanger of the heat network to exchange heat with the heat network water (heating season) or the intermediate heat transfer medium water (non - heating season). The external circulation is generally one in use and one in reserve, and the external circulation can carry the moisture absorbed by the absorber to the regeneration system for regeneration. The diluted absorption liquid that becomes diluted after absorbing water at the bottom of the absorber is sent to the dilute - concentrated solution heat exchanger to exchange heat with the concentrated absorption liquid. After heat exchange, the dilute solution enters the plate evaporator to continue heating up. The heat source in the heating season is the steam extracted from the unit. The steam condensate enters the secondary heat exchanger of the heat network to exchange heat, and the condensate after heat exchange returns to the deaerator. Part of the vaporized concentrated solution enters the solution flash tank for vapor - liquid separation. The flash tank is at a slightly negative pressure, and the negative pressure is provided by a vacuum pump. The vacuum pump is connected in series with the condenser and is located behind the condenser. The evaporated secondary steam is sent from the top of the flash tank to the tertiary heat exchanger of the heat network to exchange heat with the heat network water. The condensate of the secondary steam after heat exchange is used for the makeup water of the desulfurization process. The concentrated absorption liquid at the bottom of the flash tank is sent to the dilute - concentrated solution heat exchanger for heat exchange, and finally circulates to the top of the absorber. The latent heat of the clean flue gas is recovered through an open - type absorption heat pump to increase the heating area.

[0076] When there is no heating demand in the non - heating season, environmental protection de - whitening needs to be satisfied. In order to reduce the operating energy consumption of the system, the secondary steam upgraded by the MVR system is used as the driving heat source. The secondary steam is discharged from the top of the flash tank and enters the compressor, and the pressurized and heated secondary steam is sprayed as saturated secondary steam as the driving heat source of the regenerator. After the secondary steam exchanges heat with the concentrated solution and releases latent heat, it becomes condensate, which can heat the intermediate heat transfer medium water (low - pressure heater condensate) to about 65°C. The condensate of the secondary steam after condensation is used for the makeup water of the desulfurization tower process. Part of the vaporized concentrated solution undergoes flash evaporation in the flash tank for vapor - liquid separation. The flashed secondary steam is recycled to the compressor of the MVR system. The concentrated absorption liquid at the bottom of the flash tank is sent to the dilute - concentrated solution heat exchanger for heat exchange, and finally circulates to the top of the absorber.

[0077] During the heating season, the heat network water exchanges heat with the absorption liquid from the absorber. The heat network water exiting the primary heat exchanger of the heat network exchanges heat with the condensate of the steam extraction from the steam turbine entering the secondary heat exchanger. The heat network water exiting the secondary heat exchanger of the heat network exchanges heat with the secondary steam entering the tertiary heat exchanger. A portion of the heat network water exiting the secondary or tertiary heat exchanger of the heat network is diverted to the waste water heater, where its heat is transferred to the desulfurization waste water, and the other portion is sent to the heat network head station for further heating or directly used for municipal heating. During the non-heating season, the intermediate heat transfer water exchanges heat with the absorption liquid from the absorber. The intermediate heat transfer water exiting the primary heat exchanger of the heat network exchanges heat with the condensate of the secondary steam entering the secondary heat exchanger, and then enters the waste water heater to heat the desulfurization waste water. The heat used to heat the desulfurization waste water throughout the year is the latent heat recovered from the clean flue gas. This portion of the heat is used to provide the latent heat for the flash evaporation of the desulfurization waste water, thus avoiding the use of fresh steam or high-quality flue gas as the heat source for waste water concentration.

[0078] The heat recovered by the open absorption heat pump system is sent by the heat network water or the intermediate heat transfer water to the waste water heater to heat up the waste water sent from the waste water sedimentation tank. The heated waste water enters the waste water flash tank. The flash tank is in a negative pressure state, and its vacuum degree is provided by a vacuum pump. The vacuum pump is connected in series with the condenser and is located behind the condenser. The concentrated waste water after flashing enters the waste water cooler from the bottom of the flash tank, and the heat it carries is used to initially heat the condensate of the low-pressure heater. The cooled concentrated waste water enters the waste water sedimentation tank. After classified sedimentation, the supernatant and the newly incoming desulfurization waste water are recycled to the waste water heater again. A small amount of concentrated waste water at the bottom of the waste water sedimentation tank is sent to the flue gas spray evaporator in front of the electrostatic precipitator, where the atomized concentrated water is evaporated into water vapor by the high-temperature waste heat flue gas in the flue. The vapor enters the desulfurization tower along with the flue gas after dust removal, and the evaporation dry matter enters the electrostatic precipitator together with the dust and is discharged with the ash; or it is sent to an independent rotary spray evaporation tower for evaporation and drying. A small portion of the flue gas at the outlet of the denitration SCR is extracted to the evaporation tower, and the desulfurization waste water is sprayed into the evaporation tower, where the atomized concentrated water is evaporated into water vapor by the heat of the flue gas in the evaporation tower. The flue gas at the outlet of the evaporation tower enters the inlet flue of the dust collector, and the vapor enters the desulfurization absorption tower along with the flue gas after dust removal; the evaporation crystallization product enters the electrostatic precipitator together with the dust and is captured and discharged with the ash. The secondary steam obtained by flashing exits from the top of the flash tank and enters the condenser, where the condensate of the low-pressure heater is reheated. The condensate of the low-pressure heater after being reheated returns to the low-pressure heater circulating water system with a temperature close to it, and the condensate of the secondary steam is used for the process make-up water of the desulfurization system. Through this system, the flue gas heat recovered by the open absorption heat pump is first used for desulfurization waste water concentration, solving the drawbacks of using high-quality heat energy for evaporation in the conventional route. At the same time, after the waste water is concentrated, the heat it contains is transferred to the condensate system of the low-pressure heater. Almost no loss of the recovered flue gas heat occurs during the process, except that its quality decreases, realizing the cascade utilization of energy, thereby reducing the unit energy consumption. Both the concentration system and the evaporation crystallization system are independent of the flue gas system and can be adjusted according to the change of the unit load.

[0079] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. An apparatus for combined waste heat recovery, white plume elimination and wastewater concentration, characterized in that, including, an absorption heat pump system including an absorption unit, a first circulation loop, and a first heat exchanger disposed on the first circulation loop, wherein the liquid inlet end of the first circulation loop communicates with the lower part of the absorption unit, and the liquid outlet end communicates with the upper part of the absorption unit; a wastewater concentration system including a wastewater flash tank, a wastewater cooler, and a sedimentation device connected in sequence, wherein the wastewater flash tank is connected to the first heat exchanger or the fifth heat exchanger, so that the liquid at the outlet end exchanges heat with the desulfurized wastewater from the outside in the first heat exchanger or the fifth heat exchanger, and then the heated desulfurized wastewater is sent to the wastewater flash tank, the wastewater cooler, and the sedimentation device in sequence; an evaporation and drying system connected to the sedimentation device, so that the concentrated desulfurized wastewater from the sedimentation device enters the evaporation and drying system; a second heat exchanger; a third heat exchanger, the second heat exchanger and the third heat exchanger are connected in sequence, and the second heat exchanger is also connected to the first heat exchanger, so that the heat network supply water or the intermediate heat transfer medium water passes through the first heat exchanger, the second heat exchanger, and the third heat exchanger in sequence to form the heat network return water or the intermediate heat transfer medium water; the second heat exchanger or the third heat exchanger is also connected to the fifth heat exchanger to send part of the heat network supply water or the intermediate heat transfer medium water into the fifth heat exchanger to heat the desulfurized wastewater; a fifth heat exchanger disposed on the intermediate heat transfer medium water circulation pipe and connected to the wastewater flash tank, the intermediate heat transfer medium water first exchanges heat with the dilute absorption liquid through the first heat exchanger, then enters the second heat exchanger, and then enters the fifth heat exchanger to exchange heat with the desulfurized wastewater, or continuously passes through the second heat exchanger and the third heat exchanger for heat exchange and then enters the fifth heat exchanger to exchange heat with the desulfurized wastewater, and the desulfurized wastewater is heated and then enters the wastewater flash tank for flashing; the sedimentation device includes at least two - stage sedimentation units to perform multi - stage precipitation on the cooled concentrated wastewater, the upper part of the sedimentation device communicates with the first heat exchanger or the fifth heat exchanger, so that the supernatant liquid and / or the additional desulfurized wastewater in the sedimentation device enters the first heat exchanger or the fifth heat exchanger and exchanges heat with the dilute solution or the intermediate heat transfer medium water from the absorption unit; a condenser, which communicates with the secondary steam outlet at the upper part of the wastewater flash tank, and the condenser is also connected to the wastewater cooler, so that the heated heat transfer medium from the wastewater cooler enters the condenser and exchanges heat with the secondary steam from the wastewater flash tank again.

2. The apparatus according to claim 1, characterized in that, further including, a second circulation loop and a regeneration system disposed on the second circulation loop, the liquid inlet end of the second circulation loop communicates with the lower part of the absorption unit, and the liquid outlet end communicates with the upper part of the absorption unit, so that the liquid at the outlet end enters the absorption unit after being regenerated by the regeneration system and contacts the flue gas entering the absorption unit in a counter - current manner.

3. The apparatus according to claim 2, characterized in that, the regeneration system includes, a solution flash tank having a dilute solution inlet in the middle, a steam outlet at the upper part, and a concentrated solution outlet at the lower part; a seventh heat exchanger, the lower part of the absorption unit, the seventh heat exchanger, and the dilute solution inlet are connected in sequence; A compressor and a saturator, the steam outlet, the compressor, the saturator and the seventh heat exchanger are connected in sequence, so that in the non-heating season, the dilute solution at the lower part of the absorption unit exchanges heat with the secondary steam in the seventh heat exchanger and then enters the solution flash tank.

4. The apparatus according to claim 3, characterized in that, It further includes A sixth heat exchanger, which is arranged on the second circulation loop. The lower part of the absorption unit, the sixth heat exchanger, the seventh heat exchanger and the dilute solution inlet are connected in sequence, so as to exchange heat between the dilute solution from the absorption unit and the concentrated solution from the concentrated solution outlet in the sixth heat exchanger, and the concentrated solution after heat exchange enters the absorption unit.

5. The apparatus according to claim 1, characterized in that, It further includes an air preheater, a dust removal unit and a desulfurization unit which are connected in sequence, and the desulfurization unit is connected to the lower part of the absorption unit.

6. The apparatus according to claim 5, characterized in that, The evaporation and drying system is a flue gas spray evaporator. Along the flow direction of the flue gas, the flue gas spray evaporator is arranged in the flue between the air preheater and the dust removal unit; or The evaporation and drying system is a rotary spray evaporator, and a high-temperature dry flue gas inlet is arranged at its upper part. Along the flow direction of the flue gas, the high-temperature dry flue gas inlet is communicated with the upstream flue of the air preheater, so that the high-temperature dry flue gas in the upstream flue of the air preheater enters the rotary spray evaporator to exchange heat with the concentrated desulfurized wastewater; a high-temperature wet flue gas outlet is arranged at the lower part of the rotary spray evaporator, and the high-temperature wet flue gas outlet is communicated with the flue between the air preheater and the dust removal unit, and the connection point of the sedimentation device and the rotary spray evaporator is located at the upper part of the rotary spray evaporator.

7. The apparatus according to claim 2, characterized in that, It further includes a fourth heat exchanger, which is arranged on the second circulation loop and is used for reheating the concentrated solution.

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