High back pressure unit deep flue gas waste heat utilization cascade heating heat supply system

Abstract

The application discloses a high-back-pressure unit deep flue gas waste heat utilization cascade heating heat supply system, comprising a low-temperature flue gas waste heat recovery system including a desulfurization tower and a spray tower; a medium-temperature flue gas waste heat recovery system including a negative pressure flash tank; a low-temperature loop of a double-stage compression heat pump unit being connected with the spray tower; a medium-temperature loop of the double-stage compression heat pump unit being connected with the negative pressure flash tank; a heat network heater of the double-stage compression heat pump unit passing through a high-back-pressure unit being connected with a water supply pipeline of a network circulating water system, and a condenser of the double-stage compression heat pump unit passing through the high-back-pressure unit being connected with a return water pipeline of the network circulating water system; the system makes up for the disadvantage of insufficient flexibility of the high-back-pressure heat supply unit in deep peak regulation, improves heat efficiency and heat supply capacity of the unit, has higher thermal economy, reduces pollutant emission, deeply reduces power generation load under the premise of guaranteeing heating heat load, gives out accommodation space for new energy on-grid, and realizes energy saving and carbon reduction, flexibility and high efficiency.

Description

Technical Field

[0001] This invention belongs to the field of thermal power unit heating retrofit technology, and particularly relates to a cascade heating system for deep flue gas waste heat utilization in high back pressure units. Background Technology

[0002] To meet the ever-increasing heat load demand in the heating area, achieve the energy conservation and carbon reduction goals of coal-fired cogeneration units, improve the operational flexibility and energy utilization rate of the units, enable them to meet the deep peak shaving needs of the power grid while ensuring heating supply, make room for the grid connection of wind and solar new energy, and create a good space for the long-term survival and development of power generation companies, it is necessary to carry out the transformation of the units to simultaneously meet the requirements of heating supply, energy conservation and flexibility, so as to improve the economic efficiency of the unit's heating operation and enhance the regional heating security capacity. High back-pressure turbine units, as conventional heating units in northern regions, make full use of the waste heat from the cold end of the steam turbine, improving the turbine's thermal efficiency and heating capacity, and meeting the requirements of heating system renovation and energy-saving renovation. However, their flexibility is limited. During the deep peak shaving period of the heating season, they cannot simultaneously meet the heating load of urban areas and the peak shaving requirements of the power grid, resulting in wind and solar power curtailment in the local power grid. In addition to the waste heat from the cold end, coal-fired cogeneration units also have waste heat from the tail flue gas that can be deeply recovered and utilized. After the boiler exhaust is desulfurized by spraying in the desulfurization tower, it becomes saturated moisture-containing flue gas, which contains a large amount of low-grade water vapor latent heat. How to heat and utilize this latent heat, and how to deeply recover and utilize the low-temperature flue gas waste heat through flexible renovation, is the main breakthrough direction to make up for the current lack of flexibility of high back-pressure turbine units. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention aims to provide a cascade heating system for deep flue gas waste heat utilization in high back-pressure units. By introducing an electrically driven two-stage compression heat pump coupled with a two-stage flue gas waste heat deep recovery system, the problem of insufficient flexibility in back-pressure retrofit units is solved.

[0004] This invention is achieved through the following technical solution:

[0005] A cascade heating system for deep flue gas waste heat utilization in high back-pressure turbine units, comprising:

[0006] Low-temperature flue gas waste heat recovery system, medium-temperature flue gas waste heat recovery system, two-stage compression heat pump unit;

[0007] The low-temperature flue gas waste heat recovery system includes a desulfurization tower and a spray tower; the medium-temperature flue gas waste heat recovery system includes a negative pressure flash tank.

[0008] The flue gas side of the spray tower is connected to the flue gas side of the desulfurization tower; the water side of the spray tower is connected to the water side of the desulfurization tower; the low-temperature loop of the two-stage compression heat pump unit is connected to the spray tower; the medium-temperature loop of the two-stage compression heat pump unit is connected to the negative pressure flash tank; the heating medium side of the two-stage compression heat pump unit is connected to the water supply pipeline of the primary circulating water system through the heat network heater of the high back pressure unit; the low-temperature heat source side of the two-stage compression heat pump unit is connected to the return water pipeline of the primary circulating water system through the condenser of the high back pressure unit.

[0009] Preferably, the two-stage compression heat pump unit includes a condenser, a first pressure-reducing valve, a working fluid heat exchanger, an intermediate heat exchanger, a high-pressure stage compressor, a second pressure-reducing valve, an evaporator, and a low-pressure stage compressor;

[0010] The condenser, high-pressure stage compressor, low-pressure stage compressor, evaporator, second pressure-reducing valve, and working fluid heat exchanger are connected in sequence to form a low-temperature loop; the evaporator is connected to the desulfurization tower.

[0011] The condenser, high-pressure stage compressor, intermediate heat exchanger, first pressure reducing valve, and working fluid heat exchanger are sequentially connected to form a medium-temperature loop; the intermediate heat exchanger is connected to the negative pressure flash tank.

[0012] Preferably, the water-side inlet of the condenser is connected to the return water pipe of the primary circulating water system through the condenser of the high back pressure unit; the water-side outlet of the condenser is connected to the water supply pipe of the primary circulating water system through the heat network heater of the high back pressure unit; one path of the low-temperature waste heat side of the condenser is connected to the water-side inlet of the condenser; and the other path of the low-temperature waste heat side of the condenser is connected to the water side of the heat network heater.

[0013] Preferably, a first check valve is provided on the pipeline between the condenser and the heating network heater; a first ball valve is provided on the pipeline between the condenser and the condenser; and a second ball valve is provided on the pipeline between the condenser and the heating network heater.

[0014] Preferably, one water-side outlet pipe of the intermediate heat exchanger is connected to a condensate tank, and the other is connected to a negative pressure flash tank; a first electric regulating valve is installed at the inlet of the condensate tank; a condensate pump is installed on the water-side outlet pipe of the intermediate heat exchanger; and a second electric regulating valve is installed on the water-side inlet pipe of the negative pressure flash tank.

[0015] Preferably, the negative pressure flash tank is equipped with a vacuum pump, and a flash spray pump is installed at the slurry-side inlet of the negative pressure flash tank; a slurry return pump is installed at the slurry-side outlet of the negative pressure flash tank; and flash spray nozzles are installed on the spray pipe inside the negative pressure flash tank.

[0016] Preferably, one inlet of the heating network heater is connected to the heating steam extraction pipe; a second check valve is provided between the heating network heater and the heating steam extraction pipe; one outlet of the heating network heater is connected to the heating network water supply pipe; and a heating network water supply pump is provided on the heating network water supply pipe.

[0017] Preferably, a heating network circulating water pump is installed on the return water pipe of the circulating water system.

[0018] Preferably, a spray water pump is installed on the bottom circulating water output pipe of the spray tower; and spray tower nozzles are installed on the internal spray pipe of the spray tower.

[0019] Preferably, the internal spray pipe of the desulfurization tower is equipped with a slurry spray nozzle, and the external pipeline between the bottom of the desulfurization tower and the slurry spray nozzle is equipped with a slurry spray pump; a third electric regulating valve is installed on the pipeline between the water side of the spray tower and the water side of the desulfurization tower.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] This invention aims to provide a cascade heating system for deep flue gas waste heat recovery in high back-pressure turbine units. Addressing the lack of flexibility in high back-pressure turbine retrofitting, it introduces an electrically driven two-stage compression heat pump coupled with a two-stage deep flue gas waste heat recovery system. The waste heat recovery method is divided into medium-temperature and low-temperature types. The low-temperature waste heat recovery method is a flue gas spraying method. A spray tower is installed on the flue gas side of the desulfurization tower outlet, and closed-loop circulating water is used to spray and cool the outlet flue gas, causing water vapor in the flue gas to condense and release its latent heat, which falls into the spray tower. The sprayed condensate is then sent to the low-temperature loop of the two-stage compression heat pump to extract waste heat. The medium-temperature waste heat recovery method is a negative-pressure flash evaporation method. The desulfurization slurry after spraying from the desulfurization tower is sent to a newly built negative-pressure flash evaporation tank. By reducing the pressure inside the tank, the desulfurization slurry flashes out water vapor, and the concentrated solution falls to the bottom of the tank and is sent back to the desulfurization tower to continue spraying the flue gas. Flash steam enters the intermediate loop of the two-stage compression heat pump to extract waste heat. Condensate can be recovered or returned to the bottom of the tank to maintain the concentration of desulfurization slurry from becoming too high. The two-stage flue gas deep waste heat recovery coupled with a two-stage electric compression heat pump system serves as a flexible supplementary unit for high back-pressure heating units, compensating for the lack of flexibility in deep peak shaving of high back-pressure heating units, improving the unit's thermal efficiency and heating capacity, achieving higher thermal economy, reducing pollutant emissions, and allowing for a deep reduction in power generation load while ensuring heating load, thus creating space for the grid connection of new energy sources and achieving energy conservation, carbon reduction, flexibility, and high efficiency. By placing the two-stage compression heat pump heating unit between the condenser and the heating network heater, the heating load that the condenser needs to bear and the temperature rise of the heating network circulating water can be reduced, thereby lowering the outlet temperature of the heating network circulating water on the condenser water side, reducing the condenser back pressure, increasing the unit's power generation under the same heat supply, reducing power generation coal consumption, and optimizing overall economic efficiency.

[0022] Furthermore, the waste heat of the flue gas at the tail end of the detachment tower is recovered by spraying, which deeply recovers the low-grade waste heat contained in the flue gas, improves the thermal efficiency and economy of the unit, and solves the problem of deep waste heat recovery of flue gas.

[0023] Furthermore, the low-grade heat energy contained in the desulfurization slurry is recovered by negative pressure flash evaporation, which is to indirectly recover the waste heat of the tail flue gas, improve the energy-saving potential and heating capacity of the unit, and reduce heating costs and pollutant emissions.

[0024] Furthermore, the two-stage compression heat pump, by setting up a two-stage compressor, compresses the working fluid of the low-temperature waste heat recovery loop at low pressure and mixes it with the working fluid of the medium-temperature waste heat recovery loop. Then, they are sent together to the high-pressure stage compressor. After compression, the heat is released by condensation in the heat exchanger and transferred to the circulating water of the heating network. Both the high-pressure and low-pressure stage compressors are powered by the electricity generated by the coal-fired cogeneration unit. This increases the waste heat recovery capacity and the unit's heating capacity while reducing the unit's electricity consumption. The degree of waste heat recovery and the power consumption of the compressor are adjustable within a certain range. When coupled with a high back-pressure unit, it can realize the three-way linkage of heating transformation, energy-saving transformation, and flexibility transformation, reduce the unit's coal consumption, reduce power generation and heating costs and pollutant emissions, and achieve the goals of energy saving, emission reduction, flexibility and efficiency. Attached Figure Description

[0025] Figure 1 A schematic diagram of a cascade heating system for utilizing waste heat from deep flue gas in high back-pressure turbine units.

[0026] In the diagram: 1-Heating network circulating water pump; 2-Condenser; 3-First ball valve; 4-First check valve; 5-Second ball valve; 6-Heating network heater; 7-Second check valve; 8-Heating network drain pump; 9-Condenser; 10-First pressure reducing valve; 11-Working fluid heat exchanger; 12-Intermediate heat exchanger; 13-High-pressure stage compressor; 14-Second pressure reducing valve; 15-Evaporator; 16-Low-pressure stage compressor; 17-Condenser 18-Condensate pump; 19-First electric regulating valve; 20-Second electric regulating valve; 21-Negative pressure flash tank; 22-Vacuum pump; 23-Flash spray pump; 24-Flash spray nozzle; 25-Slurry return pump; 26-Spray water pump; 27-Spray tower; 28-Spray nozzle; 29-Third electric regulating valve; 30-Desulfurization tower; 31-Slurry spray pump; 32-Slurry spray nozzle. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0028] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0029] This invention aims to provide a cascade heating system for deep flue gas waste heat recovery in high back-pressure turbine units. Addressing the lack of flexibility in retrofitting high back-pressure units, it introduces an electrically driven two-stage compression heat pump coupled with a two-stage deep flue gas waste heat recovery system. The waste heat recovery method is divided into medium-temperature and low-temperature types. The low-temperature method involves flue gas spraying, where a spray tower is installed on the flue gas side of the desulfurization tower outlet. A closed-loop circulating water system sprays and cools the outlet flue gas, causing water vapor in the flue gas to condense and release its latent heat, which falls into the spray tower. The sprayed condensate is then sent to the low-temperature loop of the two-stage compression heat pump to extract waste heat. The medium-temperature method involves negative-pressure flash evaporation, where the desulfurization slurry after spraying from the desulfurization tower is sent to a newly constructed negative-pressure flash tank. By reducing the pressure inside the tank, the desulfurization slurry flashes out water vapor, and the concentrated solution falls to the bottom of the tank and is returned to the desulfurization tower. The flue gas continues to be sprayed, and the flash steam enters the intermediate loop of the two-stage compression heat pump to extract waste heat. The condensate can be recovered or sent back to the bottom of the tank to keep the concentration of the desulfurization slurry from becoming too high. The two-stage compression heat pump is equipped with a two-stage compressor. The working fluid of the low-temperature waste heat recovery loop is compressed at low pressure and then mixed with the working fluid of the medium-temperature waste heat recovery loop. They are then sent together to the high-pressure stage compressor. After compression, the heat is released by condensation in the heat exchanger and transferred to the circulating water of the heating network. Both the high-pressure and low-pressure stage compressors are powered by the electricity generated by the coal-fired cogeneration unit. This increases the waste heat recovery capacity and the unit's heating capacity while reducing the unit's electricity consumption. The degree of waste heat recovery and the power consumption of the compressor are adjustable within a certain range. After coupling with the high back-pressure unit, it can realize the three-way linkage of heating transformation, energy-saving transformation and flexibility transformation, reduce the unit's coal consumption, reduce power generation and heating costs and pollutant emissions, and achieve the goals of energy saving, emission reduction, flexibility and efficiency.

[0030] Specifically, including, such as Figure 1 As shown, there are low-temperature flue gas waste heat recovery systems, medium-temperature flue gas waste heat recovery systems, and two-stage compression heat pumps.

[0031] The low-temperature flue gas waste heat recovery system includes a desulfurization tower 30 and a spray tower 27; the medium-temperature flue gas waste heat recovery system includes a negative pressure flash tank 21.

[0032] The flue gas side of the spray tower 30 is connected to the flue gas side of the desulfurization tower 27; the water side of the spray tower 30 is connected to the water side of the desulfurization tower 27; the low-temperature loop of the two-stage compression heat pump unit is connected to the spray tower 27; the medium-temperature loop of the two-stage compression heat pump unit is connected to the negative pressure flash tank 21; the heating medium side of the two-stage compression heat pump unit is connected to the water supply pipeline of the primary circulating water system through the heat network heater 6 of the high back pressure unit; the low-temperature heat source side of the two-stage compression heat pump unit is connected to the return water pipeline of the primary circulating water system through the condenser 2 of the high back pressure unit.

[0033] The two-stage compression heat pump unit includes a condenser 9, a first pressure-reducing valve 10, a working fluid heat exchanger 11, an intermediate heat exchanger 12, a high-pressure stage compressor 13, a second pressure-reducing valve 14, an evaporator 15, and a low-pressure stage compressor 16.

[0034] The condenser 9, high-pressure stage compressor 13, low-pressure stage compressor 16, evaporator 15, second pressure reducing valve 14 and working fluid heat exchanger 11 are connected in sequence to form a low-temperature loop; the evaporator 15 is connected to the desulfurization tower 27.

[0035] The condenser 9, high-pressure stage compressor 13, intermediate heat exchanger 12, first pressure reducing valve 10 and working fluid heat exchanger 11 are connected in sequence to form a medium-temperature loop; the intermediate heat exchanger 12 is connected to the negative pressure flash tank 21.

[0036] The water-side inlet of the condenser 9 is connected to the return water pipe of the primary circulating water system through the condenser 2 of the high back pressure unit; the water-side outlet of the condenser 9 is connected to the water supply pipe of the primary circulating water system through the heat network heater 6 of the high back pressure unit; one path of the low-temperature waste heat side of the condenser 2 is connected to the water-side inlet of the condenser 9; the other path of the low-temperature waste heat side of the condenser 2 is connected to the water side of the heat network heater 6.

[0037] A first check valve 4 is installed on the pipeline between the condenser 9 and the heat network heater 6; a first ball valve 3 is installed on the pipeline between the condenser 2 and the condenser 9; and a second ball valve 5 is installed on the pipeline between the condenser 2 and the heat network heater 6.

[0038] One water-side outlet pipe of the intermediate heat exchanger 12 is connected to the condensate tank 19, and the other is connected to the negative pressure flash tank 21; a first electric regulating valve 18 is provided at the inlet of the condensate tank 19; a condensate pump 17 is provided on the water-side outlet pipe of the intermediate heat exchanger 12; and a second electric regulating valve 20 is provided on the water-side inlet pipe of the negative pressure flash tank 21.

[0039] The negative pressure flash tank 21 is equipped with a vacuum pump 22, and a flash spray pump 23 is installed at the slurry side inlet of the negative pressure flash tank 21; a slurry return pump 25 is installed at the slurry side outlet of the negative pressure flash tank 21; and a flash spray nozzle 24 is installed on the spray pipe inside the negative pressure flash tank 21.

[0040] One inlet of the heating network heater 6 is connected to the heating steam extraction pipe; a second check valve 7 is installed between the heating network heater and the heating steam extraction pipe; one outlet of the heating network heater 6 is connected to the heating network water supply pipe; a heating network water supply pump 8 is installed on the heating network water supply pipe.

[0041] A heating network circulating water pump 1 is installed on the return water pipe of the circulating water system.

[0042] A spray water pump 26 is installed on the bottom circulating water output pipe of the spray tower 27; a spray tower nozzle 28 is installed on the internal spray pipe of the spray tower 27.

[0043] The internal spray pipe of the desulfurization tower 30 is equipped with a slurry spray nozzle 32, and the external pipeline between the bottom of the desulfurization tower 30 and the slurry spray nozzle 32 is equipped with a slurry spray pump 31; a third electric regulating valve 29 is installed on the pipeline between the water side of the spray tower 27 and the water side of the desulfurization tower 30.

[0044] Example 1 describes the specific operation process as follows:

[0045] In the high-back-pressure unit's deep flue gas waste heat utilization cascade heating system, when in operation, the return water from the heating network is pressurized by the heating network circulating water pump 1 and enters the condenser 2. In the condenser 2, it absorbs waste heat from the exhaust steam of the turbine's low-pressure cylinder and is then heated before entering the condenser 9 of the two-stage compression heat pump via the first ball valve 3. It is then heated further before entering the heating network heater 6 via the first check valve 4 and being heated by the heating extraction steam. Finally, it is supplied to heat users through the primary network. When the heat pump is not in operation, the first ball valve 3 is closed and the second ball valve 5 is opened. In the low-temperature flue gas waste heat recovery section, the flue gas first undergoes desulfurization in the desulfurization tower 30, and the slurry spray pump 31 sprays the bottom of the desulfurization tower... The slurry is extracted and sent to the slurry spray nozzle 32 to spray the flue gas for desulfurization. After desulfurization, the flue gas enters the spray tower 27. The spray water pump 26 extracts the circulating water in the tower and sends it to the heat pump evaporator 15 to absorb heat and cool down. Then it is sent back to the tower and sprayed on the flue gas at the outlet of the desulfurization tower through the spray nozzle. In the medium-temperature flue gas waste heat recovery section, the desulfurization slurry in the desulfurization tower is sprayed through the slurry spray nozzle 23 and then pumped to the slurry spray nozzle 24 in the negative pressure flash tank 21 for spraying. The vacuum pump 22 is used to maintain the negative pressure in the tank. After the slurry evaporates into water vapor in the flash tank 21, it enters the intermediate heat exchanger 12 to condense and release heat. Then it is pumped out by the condensate pump 17 and sent back to the flash tank. Inside 21, when the liquid level in the tank is too high, excess condensate is sent into the condensate tank 19. The first electric regulating valve 18 and the second electric regulating valve 20 are used to regulate the distribution of condensate returning to the flash tank 21 and the condensate tank 19. The slurry return pump 25 sends the desulfurization slurry after continuous spraying and cooling in the tower back into the desulfurization tower to continue spraying the flue gas. The above-mentioned two-stage compression heat pump consists of a condenser 9, a first pressure reducing valve 10, a working fluid heat exchanger 11, an intermediate heat exchanger 12, a high-pressure stage compressor 13, a second pressure reducing valve 14, an evaporator 15, and a low-pressure stage compressor 16. When the internal working fluid is circulating, the working fluid condenses and releases in the condenser 9. The heat is transferred to the circulating water of the heating network. The outlet working fluid is divided into two paths. One path expands, depressurizes, and cools down through the first pressure-reducing valve 10, and then enters the working fluid heat exchanger 11 to absorb the heat of the other working fluid. It then enters the intermediate heat exchanger 12 to absorb the medium-temperature waste heat of the flash steam, and then mixes with the other working fluid. The other working fluid is first cooled down through the working fluid heat exchanger 11, and then expands, depressurizes, and cools down through the second pressure-reducing valve 14. It then evaporates through the evaporator 15 to absorb the low-temperature waste heat of the spray water. After being compressed by the low-pressure stage compressor 16, it mixes with the medium-temperature loop working fluid. The mixed working fluids enter the high-pressure stage compressor 13 for compression, and then enter the condenser 9 to complete the cycle.

[0046] A two-stage deep waste heat recovery system coupled with a two-stage electric compression heat pump system is adopted as a flexible supplementary unit for the high back pressure heating unit. A spray-type waste heat recovery tower is used as the low-temperature waste heat recovery part of the system, and a negative pressure flash-type waste heat recovery tank is used as the medium-temperature waste heat recovery part of the system. The two-stage compressor consumes the power generated by the high back pressure unit to drive the heat pump to recover waste heat from the flue gas for heating. The spray-type flue gas waste heat recovery tower utilizes the characteristic that the saturated moisture content of flue gas decreases with decreasing temperature. A spray tower is installed on the flue gas side at the outlet of the desulfurization tower, using closed-loop circulating water to spray and cool the tail flue gas. As the tail flue gas temperature decreases, the saturated moisture content also decreases, causing some water vapor in the flue gas to condense and release heat. This condensate falls to the bottom of the spray tower, forming spray condensate carrying low-grade waste heat. The condensate is then sent to the low-temperature loop of a two-stage compression heat pump to extract waste heat. The negative-pressure flash-type flue gas waste heat recovery tank utilizes the characteristic that the saturated temperature of water decreases with decreasing pressure. Desulfurization slurry is introduced into the flash tank for spraying. By establishing a negative pressure vacuum inside the flash tank, the water in the slurry evaporates into water vapor carrying low-grade heat energy. This water vapor enters the medium-temperature loop of a two-stage compression heat pump to be extracted. Waste heat is released through condensation. Part of the condensate is returned to the tower, and part is sent to the condensate tank. The condensate in the tank has good quality and can be used as makeup water for the heating network. The two-stage compression heat pump divides the internal circulating working fluid into two paths by setting up a two-stage compressor, which recovers medium-temperature waste heat and low-temperature waste heat respectively. This allows for the cascade utilization of waste heat from the flue gas, improving energy efficiency. At the same time, the two-stage compressor reduces power consumption compared to a single-stage compressor, increasing the COP of the heat pump. It consumes less electricity to recover the same amount of waste heat, reducing heating costs and improving the thermal economy of the unit. The return water from the heating network first recovers waste heat from the exhaust steam in the condenser and is then heated by the two-stage compression heat pump. Finally, it is heated by the heating network heater to the required supply water temperature before being supplied to the outside. The two-stage waste heat recovery system not only improves the unit's heating capacity but also enhances operational flexibility.

[0047] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0048] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or it can be in a centered component. When a component is said to be "connected to" another component, it can be directly connected to the other component or it may also be in a centered component. When a component is said to be "set to" another component, it can be directly set on the other component or it may also be in a centered component.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A high back pressure unit deep flue gas waste heat utilization cascade heating heat supply system, characterized in that, include, Low-temperature flue gas waste heat recovery system, medium-temperature flue gas waste heat recovery system, two-stage compression heat pump unit; The low-temperature flue gas waste heat recovery system includes a desulfurization tower (30) and a spray tower (27); the medium-temperature flue gas waste heat recovery system includes a negative pressure flash tank (21). The flue gas side of the spray tower (27) is connected to the flue gas side of the desulfurization tower (30); the water side of the spray tower (27) is connected to the water side of the desulfurization tower (30); the low temperature loop of the two-stage compression heat pump unit is connected to the spray tower (27); the medium temperature loop of the two-stage compression heat pump unit is connected to the negative pressure flash tank (21); the heating medium side of the two-stage compression heat pump unit is connected to the water supply pipeline of the primary circulating water system through the heat network heater (6) of the high back pressure unit; the low temperature heat source side of the two-stage compression heat pump unit is connected to the return water pipeline of the primary circulating water system through the condenser (2) of the high back pressure unit. The two-stage compression heat pump unit includes a condenser (9), a first pressure reducing valve (10), a working fluid heat exchanger (11), an intermediate heat exchanger (12), a high-pressure stage compressor (13), a second pressure reducing valve (14), an evaporator (15), and a low-pressure stage compressor (16). The condenser (9), high-pressure stage compressor (13), low-pressure stage compressor (16), evaporator (15), second pressure reducing valve (14) and working fluid heat exchanger (11) are connected in sequence to form a low-temperature loop; the evaporator (15) is connected to the desulfurization tower (30); The condenser (9), high-pressure stage compressor (13), intermediate heat exchanger (12), first pressure reducing valve (10) and working fluid heat exchanger (11) are connected in sequence to form a medium-temperature loop; the intermediate heat exchanger (12) is connected to the negative pressure flash tank (21); The water-side inlet of the condenser (9) is connected to the return water pipe of the primary circulating water system through the condenser (2) of the high back pressure unit; the water-side outlet of the condenser (9) is connected to the water supply pipe of the primary circulating water system through the heat network heater (6) of the high back pressure unit; one low-temperature waste heat side of the condenser (2) is connected to the water-side inlet of the condenser (9); the other low-temperature waste heat side of the condenser (2) is connected to the water side of the heat network heater (6).

2. The high back-pressure unit deep flue gas waste heat utilization cascade heating system according to claim 1, characterized in that, A first check valve (4) is installed on the pipeline between the condenser (9) and the heat network heater (6); a first ball valve (3) is installed on the pipeline between the condenser (2) and the condenser (9); and a second ball valve (5) is installed on the pipeline between the condenser (2) and the heat network heater (6).

3. The high back-pressure unit deep flue gas waste heat utilization cascade heating system according to claim 1, characterized in that, One of the water-side outlet pipes of the intermediate heat exchanger (12) is connected to the condensate tank (19), and the other is connected to the negative pressure flash tank (21); a first electric regulating valve (18) is provided at the inlet of the condensate tank (19); a condensate pump (17) is provided on the water-side outlet pipe of the intermediate heat exchanger (12); a second electric regulating valve (20) is provided on the water-side inlet pipe of the negative pressure flash tank (21).

4. A high back-pressure unit deep flue gas waste heat utilization cascade heating system according to claim 1, characterized in that, A vacuum pump (22) is installed on the negative pressure flash tank (21), and a flash spray pump (23) is installed at the slurry side inlet of the negative pressure flash tank (21); a slurry return pump (25) is installed at the slurry side outlet of the negative pressure flash tank (21); and a flash spray nozzle (24) is installed on the spray pipe inside the negative pressure flash tank (21).

5. A high back-pressure unit deep flue gas waste heat utilization cascade heating system according to claim 1, characterized in that, The inlet of one side of the heat network heater (6) is connected to the heating steam extraction pipe; a second check valve (7) is provided between the heat network heater and the heating steam extraction pipe; the outlet of one side of the heat network heater (6) is connected to the heat network water supply pipe; a heat network water supply pump (8) is provided on the heat network water supply pipe.

6. A high back-pressure unit deep flue gas waste heat utilization cascade heating system according to claim 1, characterized in that, A heating network circulating water pump (1) is installed on the return water pipe of the circulating water system.

7. A high back-pressure unit deep flue gas waste heat utilization cascade heating system according to claim 1, characterized in that, A spray water pump (26) is installed on the bottom circulating water output pipe of the spray tower (27); a spray tower nozzle (28) is installed on the internal spray pipe of the spray tower (27).

8. A high back-pressure unit deep flue gas waste heat utilization cascade heating system according to claim 1, characterized in that, The internal spray pipe of the desulfurization tower (30) is equipped with a slurry spray nozzle (32), and the external pipeline between the bottom of the desulfurization tower (30) and the slurry spray nozzle (32) is equipped with a slurry spray pump (31); a third electric regulating valve (29) is installed on the pipeline between the water side of the spray tower (27) and the water side of the desulfurization tower (30).

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