High and low temperature heat pump system for producing steam based on flue gas cascade waste heat of coal-fired unit

Abstract

The application discloses a high-low temperature heat pump system for preparing steam based on flue gas cascade waste heat of a coal-fired unit. The system mainly comprises a tail flue of a coal-fired power station, a high-temperature heat pump, a low-temperature heat pump and an air preheating device. The tail flue of the coal-fired power station comprises a flue gas deep cooler, an electrostatic precipitator, an induced draft fan, a desulfurization tower, a desulfurization process water tank, a flue gas condenser, a flue gas reheater and a chimney. The air preheating device comprises a warm air blower and a regenerator. The low-temperature heat pump converts electric energy into heat energy, recovers low-grade heat energy after the desulfurization tower and obtains hot water and warm air. The high-temperature heat pump recovers waste heat after the flue gas deep cooler and obtains low-pressure steam for external heat supply. The two-stage heat pump utilizes heat energy of different grades in cascade, which not only has a remarkable energy-saving effect, but also finally deeply utilizes the waste heat of the power station and improves energy utilization efficiency.

Description

Technical Field

[0001] This invention belongs to the field of waste heat recovery technology of coal-fired power plants, specifically involving a high and low temperature heat pump system for producing steam based on the cascade waste heat of flue gas from coal-fired units. Background Technology

[0002] As a crucial energy infrastructure facility in my country, coal-fired power plants play an irreplaceable role in ensuring energy supply. However, the current power generation efficiency of coal-fired power plants is only 35-42%, with most of the waste heat being directly discharged into the environment through boiler flue gas and cooling towers, resulting in a significant waste of heat. Deeply utilizing the heat from the low-grade flue gas of coal-fired units would be of great significance to my country's energy conservation and emission reduction strategy.

[0003] Based on differences in energy grade, flue gas temperatures can be classified into three categories: low-temperature, medium-temperature, and high-temperature. For the latter two categories, which have higher energy grades, conventional treatment methods include using waste heat boilers to recover energy from medium-temperature and high-temperature flue gas, and then using steam turbines to generate electricity. However, for the low-grade energy, i.e., the waste heat after the desulfurization system and economizer, there is currently a lack of effective utilization methods. Therefore, this invention employs a heat pump to assist in the recovery of low-grade energy, converting low-grade energy into low-pressure steam.

[0004] Under the "dual carbon" context, actively carrying out the "three-pronged approach" of energy-saving and consumption-reducing retrofits, heating system upgrades, and flexibility upgrades for coal-fired power units is an important means to improve energy efficiency, reduce coal consumption, and promote the consumption of clean energy. It is also an inevitable choice for coal-fired power units to improve their adaptability and regulation capabilities. Among these, heating system upgrades include external energy supply such as heating and industrial hot water / steam. Heat pumps can be used to recover low-grade waste heat, enabling energy-saving heating technologies through energy cascade utilization.

[0005] A heat pump is a technology that uses electricity or heat energy to improve the quality of heat energy. From the perspective of current industrial energy consumption, heat pumps have great application potential. Furthermore, with the advancement of electrification, heat pumps are being deployed rapidly across various industries. While residential ambient temperature heat pump technology is relatively mature and its deployment in building heating is progressing quickly, high-temperature heat pump technology for industrial applications is still under development and has not yet been widely adopted in the industrial sector. In industrial processes, a large amount of low-grade waste heat is generated during production. If this heat can be recovered to generate low-pressure steam and reused in the production process, significant energy-saving effects will be achieved. With suitable heat pump technology, the improvement and recovery of industrial waste heat can be realized.

[0006] Single-stage heat pumps heat cold water (-10–30°C) to low-pressure steam (30–150°C). However, these systems require significant investment, have low COP (Coefficient of Performance), demanding refrigerant requirements, and exhibit unstable operating parameters. In contrast, low-temperature heat pumps recover low-grade heat energy from the flue gas after the desulfurization tower, converting the consumed electrical energy into several times that amount of heat energy to produce hot water and warm air. High-temperature heat pumps recover waste heat from the flue gas before the desulfurization tower, combining with low-temperature heat pumps to obtain low-pressure steam or high-temperature hot water for external heating. These systems offer a high single-stage COP, lower investment, and a shorter payback period. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention aims to provide a high-low temperature heat pump system for producing steam from the cascaded waste heat of flue gas from coal-fired power units. This system utilizes heat pumps of varying heat capacities coupled with a flue gas waste heat recovery system to recover heat from low-grade flue gas after the desulfurization tower, producing hot water / steam. By utilizing heat energy of different grades in stages, the energy quality is improved, enabling external heat supply, ultimately reducing coal consumption and increasing energy efficiency.

[0008] To solve the above problems, the present invention adopts the following technical solution:

[0009] A high-low temperature heat pump system based on the staged waste heat of flue gas from a coal-fired power unit to produce steam includes: a flue gas deep cooler 1, an electrostatic precipitator 2, an induced draft fan 3, a desulfurization tower 4, a desulfurization process water tank 5, a first flue gas condenser 6, a second flue gas condenser 6', a flue gas reheater 7, a chimney 8, a low-temperature heat pump condenser 9, a low-temperature heat pump throttling valve 10, a low-temperature heat pump evaporator 11, a low-temperature heat pump compressor 12, a high-temperature heat pump condenser 13, a high-temperature heat pump throttling valve 14, a high-temperature heat pump evaporator 15, a high-temperature heat pump compressor 16, a warm air heat exchanger 17, a regenerator 18, an air preheater 19, a first three-way valve 20, and a second three-way valve 21.

[0010] The low-temperature heat pump condenser 9, low-temperature heat pump throttling valve 10, low-temperature heat pump evaporator 11 and low-temperature heat pump compressor 12 are connected in sequence through pipes to form a low-temperature heat pump refrigerant circulation loop; the shell-side inlet of the low-temperature heat pump condenser 9 is connected to the tube-side outlet of the second flue gas condenser 6', and the shell-side of the low-temperature heat pump evaporator 11 is connected to the tube-side of the first flue gas condenser 6, and the medium is circulating water or refrigerant.

[0011] The high-temperature heat pump condenser 13, high-temperature heat pump throttle valve 14, high-temperature heat pump evaporator 15 and high-temperature heat pump compressor 16 are connected in sequence through pipes to form a high-temperature heat pump refrigerant circulation loop; the shell side of the high-temperature heat pump evaporator 15 is connected to the pipe side of the flue gas deep cooler 1, and the medium is circulating water or refrigerant.

[0012] The water outlet on the tube side of the low-temperature heat pump condenser 9 is connected to the shell-side inlet of the regenerator 18 and / or the tube-side inlet of the flue gas reheater 7 via a second three-way valve 21. The shell-side outlet of the regenerator 18 is connected to the tube-side water inlet of the high-temperature heat pump condenser 13. Cold air enters the tube side of the warm air heat exchanger 17, and the hot air outlet on the tube side of the warm air heat exchanger 17 is connected to the inlet of the air preheater 19. The outlet of the air preheater 19 is connected to the boiler. The cold air first enters the warm air heat exchanger 17 for heating. The heated air exchanges heat with the hot water generated after the low-temperature heat pump condenser 9 in the regenerator 18 for further heating to obtain warm air. The cold water first enters the tube side of the second flue gas condenser 6' for heating. Part of the heated water enters the shell side of the low-temperature heat pump condenser 9, and after being heated again, enters the shell side of the high-temperature heat pump condenser 13, and superheated steam is obtained at the outlet. Part of the hot water enters the tube side of the flue gas reheater 7 to heat the flue gas and eliminate wet plumes.

[0013] The boiler flue gas passes sequentially through the flue gas deep cooler 1, electrostatic precipitator 2, induced draft fan 3, and desulfurization tower 4. The flue gas exiting the desulfurization tower 4 is divided into three paths through the first three-way valve 20. The first path enters the shell-side inlet of the warm air heat exchanger 17, the second path enters the shell-side inlet of the second flue gas condenser 6', and the third path enters the shell-side inlet of the first flue gas condenser 6. The flue gas from the shell-side outlets of the warm air heat exchanger 17, the second flue gas condenser 6', and the first flue gas condenser 6 enters the shell side of the flue gas reheater 7 and then enters the chimney 8. The drainage from the bottom of the desulfurization tower 4 enters the desulfurization process water tank 5.

[0014] The heat source of the low-temperature heat pump refrigerant circulation loop is the low-temperature flue gas after the desulfurization tower 4, and the cold source is cold water. The low-temperature heat pump compressor 12 compresses and transports refrigerant vapor, maintaining the low-pressure in the low-temperature heat pump evaporator 11 and the high-pressure in the low-temperature heat pump condenser 9. The low-temperature heat pump throttling valve 10 throttles and reduces the pressure of the refrigerant. The low-temperature heat pump evaporator 11 outputs cooling capacity to reduce the flue gas temperature and recover waste heat from the flue gas. The low-temperature heat pump condenser 9 outputs heat to increase the temperature of the input cold water.

[0015] The heat source of the high-temperature heat pump refrigerant circulation loop is the high-temperature flue gas after the flue gas deep cooler 1, and the cold source is the hot water heated by the low-temperature heat pump refrigerant circulation loop. The high-temperature heat pump compressor 16 compresses and transports refrigerant vapor, maintaining the low pressure in the high-temperature heat pump evaporator 15 and the high pressure in the high-temperature heat pump condenser 13. The high-temperature heat pump throttling valve 14 throttles and reduces the pressure of the refrigerant. The high-temperature heat pump evaporator 15 outputs cooling capacity, reduces the flue gas temperature, and recovers the waste heat of the flue gas. The high-temperature heat pump condenser 13 outputs heat, increases the temperature of the inlet hot water, and generates superheated steam.

[0016] The wet saturated flue gas at 50°C after desulfurization tower 4 is divided into three branches, which pass through the first flue gas condenser 6, the second flue gas condenser 6', and the warm air heat exchanger 17, respectively. The temperature of the condensed flue gas is 40-48°C. The cold water inlet temperature is -10-30°C. After low-temperature heating, the water temperature reaches 70-100°C. After being heated by the high-temperature heat pump refrigerant circulation loop, the superheated steam temperature is 120-150°C. The cold air inlet temperature is the outdoor air temperature. After being heated by the warm air heat exchanger 17, the air temperature reaches 30-40°C.

[0017] The hot air heated by the heat exchanger 17 is further heated by the regenerator 18 to achieve a temperature increase of 30-80°C.

[0018] The dry flue gas at 140-180°C after the deep flue gas cooler 1 is cooled to 90-120°C after passing through the high-temperature heat pump evaporator 15. The hot water at 70-100°C is heated to 130-150°C after passing through the high-temperature heat pump refrigerant circulation loop.

[0019] Cold water enters the tube side of the second flue gas condenser 6' and the shell side of the low-temperature heat pump condenser 9 to improve the heat energy grade, and then enters the tube side of the flue gas reheater 7 to heat the flue gas, thereby eliminating the wet plume at the tail of the coal-fired unit. After operation, the cold water is circulated and re-enters the second flue gas condenser 6'. The shell side of the low-temperature heat pump evaporator 11 is connected to the tube side of the first flue gas condenser 6, and absorbs the low-grade waste heat in the flue gas through circulating water.

[0020] Waste heat from the boiler outlet flue gas is recovered by connecting a high-temperature heat pump refrigerant circulation loop in series with the flue gas deep cooler 1 and the second flue gas deep cooler 1'. Cold water is first heated to 70-100°C by the shell side of the high-temperature heat pump condenser 13, and then enters the tube side of the flue gas deep cooler 1 to directly exchange heat with the flue gas to obtain superheated steam. The shell side of the high-temperature heat pump evaporator 15 is connected to the tube side of the second flue gas deep cooler 1, and absorbs high-grade waste heat from the flue gas through circulating water.

[0021] Waste heat from the boiler outlet flue gas is recovered by connecting a high-temperature heat pump refrigerant circulation loop in parallel with the flue gas deep cooler 1 and the second flue gas deep cooler 1'. The heat working fluid is directly heated through the flue gas deep cooler 1, and cold water enters the shell side of the high-temperature heat pump condenser 13 to be heated, and then enters the tube side of the flue gas deep cooler 1' to directly exchange heat with the flue gas to obtain superheated steam. The shell side of the high-temperature heat pump evaporator 15 is connected to the tube side of the second flue gas deep cooler 1', and high-grade waste heat in the flue gas is absorbed through circulating water.

[0022] The warm air heat exchanger 17 is a finned heat exchanger or a plate heat exchanger; the regenerator 18 is a finned heat exchanger or a plate heat exchanger; the first flue gas condenser 6 and the second flue gas condenser 6' are indirect heat exchangers or shell-and-tube heat exchangers, and are equipped with a condensate collection device.

[0023] Compared with existing technologies, the innovations, advantages, and positive effects of this invention are:

[0024] 1) This invention provides a high and low temperature heat pump system for producing steam from waste heat of flue gas from coal-fired power units. It directly utilizes different heat pump stages to recover low-grade waste heat from the flue gas of coal-fired power units and provides high-grade hot water / high-grade industrial steam to the outside world, thereby improving the adaptability and regulation capability of coal-fired power units.

[0025] 2) In order to adapt to the transformation and upgrading of existing units and the heating demand of users, this invention provides a variety of solutions, which can achieve "one policy for each plant and one policy for each unit".

[0026] 3) In actual operation, the heat pumps at each stage of the high and low temperature heat pump system have large heating capacity, high coefficient of performance (COP), long service life, are environmentally friendly and energy-saving, resulting in significant economic benefits and the ability to recover the investment in the renovation in a short period of time.

[0027] 4) This invention combines the use of heat pumps to recover the waste heat of low-grade flue gas from coal-fired power units with a condensation reheat system to eliminate plumes. This eliminates wet plumes at the tail end of coal-fired power units without the need to introduce a heat source, thus achieving energy saving and consumption reduction in the system. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a high-low temperature heat pump system and method for producing steam based on the waste heat of flue gas from a coal-fired power unit.

[0029] Figure 2 This is a schematic diagram of a series steam generation method based on the waste heat of flue gas from a coal-fired power unit.

[0030] Figure 3 This is a schematic diagram of a parallel steam generation method based on the waste heat of flue gas from a coal-fired power unit. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] Example 1, see Figure 1This invention provides a high-low temperature heat pump system for producing steam from the waste heat of flue gas from a coal-fired power plant, comprising a flue gas deep cooler 1, an electrostatic precipitator 2, an induced draft fan 3, a desulfurization tower 4, a desulfurization process water tank 5, a first flue gas condenser 6, a second flue gas condenser 6', a flue gas reheater 7, a chimney 8, a low-temperature heat pump condenser 9, a low-temperature heat pump throttling valve 10, a low-temperature heat pump evaporator 11, a low-temperature heat pump compressor 12, a high-temperature heat pump condenser 13, a high-temperature heat pump throttling valve 14, a high-temperature heat pump evaporator 15, a high-temperature heat pump compressor 16, a warm air heat exchanger 17, a regenerator 18, an air preheater 19, a first three-way valve 20, and a second three-way valve 21.

[0033] The boiler flue gas sequentially passes through a deep flue gas cooler 1, an electrostatic precipitator 2, an induced draft fan 3, and a desulfurization tower 4. The 50°C wet saturated flue gas after desulfurization tower 4 is divided into three branches by a first three-way valve 20, passing through a first flue gas condenser 6, a second flue gas condenser 6', and a warm air heat exchanger 17, respectively. The flue gas from the shell-side outlets of the warm air heat exchanger 17, the second flue gas condenser 6', and the first flue gas condenser 6 enters the shell-side of the flue gas reheater 7 and then enters the chimney 8. The drainage from the bottom of desulfurization tower 4 enters the desulfurization process water tank 5. Preferably, the first flue gas condenser 6 and the second flue gas condenser 6' are indirect heat exchangers or shell-and-tube heat exchangers, with a condensate collection device afterward. The advantages of this heat exchanger are high heat exchange efficiency, low heat loss, compact structure, small footprint, and convenient installation and cleaning, enabling full utilization of the waste heat from the wet saturated flue gas after the desulfurization tower. The heating air heat exchanger 17 is a finned heat exchanger or a plate heat exchanger, which has high gas-liquid heat exchange efficiency and can fully heat the cold air.

[0034] The low-temperature heat pump condenser 9, low-temperature heat pump throttling valve 10, low-temperature heat pump evaporator 11, and low-temperature heat pump compressor 12 are connected in sequence through pipes to form a low-temperature refrigerant circulation loop. The shell-side inlet of the low-temperature heat pump condenser 9 is connected to the tube-side outlet of the second flue gas condenser 6', and the shell-side of the low-temperature heat pump evaporator 11 is connected to the tube-side of the first flue gas condenser 6. The medium is circulating water or refrigerant. The high-temperature heat pump condenser 13, high-temperature heat pump throttling valve 14, high-temperature heat pump evaporator 15, and high-temperature heat pump compressor 16 are connected in sequence through pipes to form a high-temperature refrigerant circulation loop. The shell-side of the high-temperature heat pump evaporator 15 is connected to the tube-side of the flue gas deep cooler 1. The medium is circulating water or refrigerant.

[0035] Cold water first enters the tube side of the second flue gas condenser 6' for heating. Part of the heated water enters the shell side of the low-temperature heat pump condenser 9, and after being heated again, it enters the shell side of the high-temperature heat pump condenser 13, where superheated steam is obtained. Part of the hot water enters the tube side of the flue gas reheater 7 to heat the flue gas and eliminate wet plumes.

[0036] The cold air first enters the warm air heat exchanger 17 to be heated. The heated air then exchanges heat with the hot water produced by the low-temperature heat pump condenser 9 in the regenerator 18, further increasing its temperature by 30-80°C, thus obtaining warm air. The regenerator 18 is a finned heat exchanger or a plate heat exchanger, which has high gas-liquid heat exchange efficiency and can fully heat the cold air.

[0037] Example 2, reference Figure 2 This embodiment proposes a high-low temperature heat pump system for producing steam from the cascade waste heat of coal-fired power plant flue gas. Figure 2 The system includes a flue gas deep cooler 1, a second flue gas deep cooler 1', an electrostatic precipitator 2, an induced draft fan 3, a desulfurization tower 4, a desulfurization process water tank 5, a flue gas condenser 6, a flue gas reheater 7, a chimney 8, a high-temperature heat pump condenser 13, a high-temperature heat pump throttling valve 14, a high-temperature heat pump evaporator 15, and a high-temperature heat pump compressor 16. The flue gas deep cooler 1 and the second flue gas deep cooler 1' are connected in series, utilizing high-temperature flue gas to reheat chilled water into superheated steam. The chilled water is first heated by passing through the shell side of the high-temperature heat pump condenser 13, and then enters the tube side of the flue gas deep cooler 1 to directly exchange heat with the flue gas, obtaining superheated steam. The shell side of the high-temperature heat pump evaporator 15 is connected to the tube side of the flue gas deep cooler 1, absorbing high-grade waste heat from the flue gas through circulating water.

[0038] Example 3, reference Figure 3 This embodiment proposes a high-low temperature heat pump system for producing steam from the cascade waste heat of coal-fired power plant flue gas. Figure 3 The system includes a flue gas deep cooler 1, a second flue gas deep cooler 1', an electrostatic precipitator 2, an induced draft fan 3, a desulfurization tower 4, a desulfurization process water tank 5, a flue gas condenser 6, a flue gas reheater 7, a chimney 8, a high-temperature heat pump condenser 13, a high-temperature heat pump throttling valve 14, a high-temperature heat pump evaporator 15, and a high-temperature heat pump compressor 16. The flue gas deep cooler 1 and the second flue gas deep cooler 1' are connected in parallel. The cooling medium is directly heated through the second flue gas deep cooler 1' to obtain the heating medium, which can be water or air. A portion of the water enters the shell side of the high-temperature heat pump condenser 13 for heating, and then enters the tube side of the flue gas deep cooler 1 to directly exchange heat with the flue gas, obtaining superheated steam. The shell side of the high-temperature heat pump evaporator 15 is connected to the tube side of the flue gas deep cooler 1, absorbing high-grade waste heat from the flue gas through circulating water.

Claims

1. A high- and low-temperature heat pump system for producing steam from the cascade waste heat of flue gas from a coal-fired power unit, characterized in that, The system includes: a flue gas deep cooler (1), an electrostatic precipitator (2), an induced draft fan (3), a desulfurization tower (4), a desulfurization process water tank (5), a first flue gas condenser (6), a second flue gas condenser (6'), a flue gas reheater (7), a chimney (8), a low-temperature heat pump condenser (9), a low-temperature heat pump throttle valve (10), a low-temperature heat pump evaporator (11), a low-temperature heat pump compressor (12), a high-temperature heat pump condenser (13), a high-temperature heat pump throttle valve (14), a high-temperature heat pump evaporator (15), a high-temperature heat pump compressor (16), a warm air heat exchanger (17), a regenerator (18), an air preheater (19), a first three-way valve (20), and a second three-way valve (21). The low-temperature heat pump condenser (9), low-temperature heat pump throttle valve (10), low-temperature heat pump evaporator (11) and low-temperature heat pump compressor (12) are connected in sequence through pipes to form a low-temperature heat pump refrigerant circulation loop; the shell-side inlet of the low-temperature heat pump condenser (9) is connected to the pipe-side outlet of the second flue gas condenser (6'), and the shell-side of the low-temperature heat pump evaporator (11) is connected to the pipe-side of the first flue gas condenser (6). The medium is circulating water or refrigerant. The high-temperature heat pump condenser (13), high-temperature heat pump throttle valve (14), high-temperature heat pump evaporator (15) and high-temperature heat pump compressor (16) are connected in sequence through pipes to form a high-temperature heat pump refrigerant circulation loop; the shell side of the high-temperature heat pump evaporator (15) is connected to the pipe side of the flue gas deep cooler (1), and the medium is circulating water or refrigerant. The water outlet on the tube side of the low-temperature heat pump condenser (9) is connected to the shell-side inlet of the regenerator (18) and / or the tube-side inlet of the flue gas reheater (7) via a second three-way valve (21). The shell-side outlet of the regenerator (18) is connected to the tube-side water inlet of the high-temperature heat pump condenser (13). Cold air enters the tube side of the warm air heat exchanger (17), and the hot air outlet on the tube side of the warm air heat exchanger (17) is connected to the inlet of the air preheater (19). The outlet of the air preheater (19) is connected to the boiler. The cold air first enters the warm air heat exchanger (17) for heating. The heated air exchanges heat with the hot water generated after the low-temperature heat pump condenser (9) in the regenerator (18) for further heating to obtain warm air. The cold water first enters the second flue gas condenser (6'). The water is heated on the tube side of the heat pump condenser (9), and after being heated, part of the water enters the shell side of the low-temperature heat pump condenser (9). After being heated again, it enters the shell side of the high-temperature heat pump condenser (13), and superheated steam is obtained at the outlet. Part of the hot water enters the tube side of the flue gas reheater (7) to heat the flue gas and eliminate wet plumes. The boiler flue gas passes through the flue gas deep cooler (1), electrostatic precipitator (2), induced draft fan (3) and desulfurization tower (4) in sequence. The flue gas at the outlet of the desulfurization tower (4) is divided into three paths through the first three-way valve (20). The first path enters the shell-side inlet of the warm air heat exchanger (17), the second path enters the shell-side inlet of the second flue gas condenser (6'), and the third path enters the shell-side inlet of the first flue gas condenser (6). The flue gas from the shell-side outlets of the warm air heat exchanger (17), the second flue gas condenser (6'), and the first flue gas condenser (6) enters the shell side of the flue gas reheater (7) and then enters the chimney (8). The drainage at the bottom of the desulfurization tower (4) enters the desulfurization process water tank (5).

2. The high-low temperature heat pump system for producing steam from the cascade waste heat of coal-fired power plant flue gas according to claim 1, characterized in that, The heat source of the low-temperature heat pump refrigerant circulation loop is the low-temperature flue gas after the desulfurization tower (4), and the cold source is cold water. The low-temperature heat pump compressor (12) compresses and transports refrigerant vapor, maintains the low pressure in the low-temperature heat pump evaporator (11) and the high pressure in the low-temperature heat pump condenser (9), the low-temperature heat pump throttling valve (10) plays a throttling and pressure-reducing role on the refrigerant, the low-temperature heat pump evaporator (11) outputs cold energy, reduces the flue gas temperature, recovers the waste heat of the flue gas, and the low-temperature heat pump condenser (9) outputs heat, increasing the temperature of the input cold water.

3. The high-low temperature heat pump system for producing steam from the cascade waste heat of coal-fired power plant flue gas according to claim 1, characterized in that, The heat source of the high-temperature heat pump refrigerant circulation loop is the high-temperature flue gas after the flue gas deep cooler (1), and the cold source is the hot water heated by the low-temperature heat pump refrigerant circulation loop; wherein the high-temperature heat pump compressor (16) compresses and transports refrigerant vapor, maintains the low pressure in the high-temperature heat pump evaporator (15) and the high pressure in the high-temperature heat pump condenser (13), the high-temperature heat pump throttling valve (14) plays a throttling and pressure-reducing role on the refrigerant, the high-temperature heat pump evaporator (15) outputs cold energy, reduces the flue gas temperature, recovers the waste heat of the flue gas, and the high-temperature heat pump condenser (13) outputs heat, increases the temperature of the inlet hot water, and generates superheated steam.

4. The high-low temperature heat pump system for producing steam from the cascade waste heat of coal-fired power plant flue gas according to claim 1, characterized in that, The wet saturated flue gas at 50°C after the desulfurization tower (4) is divided into three branches, which pass through the first flue gas condenser (6), the second flue gas condenser (6'), and the warm air heat exchanger (17), respectively. The temperature of the flue gas after condensation is 40~48°C. The inlet temperature of the cold water is -10~30°C. After low-temperature heating, the water temperature reaches 70~100°C. After being heated by the high-temperature heat pump refrigerant circulation loop, the superheated steam temperature is 120~150°C. The inlet temperature of the cold air is the outdoor air temperature. After being heated by the warm air heat exchanger (17), the air temperature reaches 30~40°C.

5. The high-low temperature heat pump system for producing steam from the cascade waste heat of coal-fired power unit flue gas according to claim 1, characterized in that, The hot air heated by the heat exchanger (17) is further heated by the regenerator (18) to achieve a temperature increase of 30~80℃.

6. The high-low temperature heat pump system for producing steam from the cascade waste heat of coal-fired power unit flue gas according to claim 1, characterized in that, Cold water enters the tube side of the second flue gas condenser (6') and the shell side of the low-temperature heat pump condenser (9) to improve the heat energy grade, and then enters the tube side of the flue gas reheater (7) to heat the flue gas, thereby eliminating the wet plume at the tail of the coal-fired unit. After working, the cold water is circulated and re-enters the second flue gas condenser (6'). The shell side of the low-temperature heat pump evaporator (11) is connected to the tube side of the first flue gas condenser (6), and absorbs the low-grade waste heat in the flue gas through circulating water.

7. The high-low temperature heat pump system for producing steam from the cascade waste heat of coal-fired power unit flue gas according to claim 1, characterized in that, The structure of the warm air heat exchanger (17) is a finned heat exchanger or a plate heat exchanger; the structure of the regenerator (18) is a finned heat exchanger or a plate heat exchanger; the structure of the first flue gas condenser (6) and the second flue gas condenser (6') is a shell-and-tube heat exchanger, and a condensate collection device is provided at the rear.

Images