Heat pump and heat storage coupling system for recovering exhaust steam waste heat of coal-fired power plant

Abstract

The invention discloses a heat pump and heat storage coupling system for coal-fired power plant exhaust steam waste heat recovery. The system comprises an air cooling unit thermodynamic system and a heat pump system. The air cooling unit thermodynamic system comprises a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a generator, a high-pressure heater, a water feeding pump, a deaerator, a low-pressure heater, a condensate pump and a condenser. The heat pump system comprises a filter, a heat regenerator, a compressor, a condenser, an expansion machine, a heat storage tank, a heat exchanger, a cold storage tank and a motor. Through the heat pump system, surplus electric power of the coal-fired power plant in the electric power trough period is consumed, and the deep peak regulation capacity of the coal-fired power plant is improved; by additionally arranging the heat storage tank and the cold storage tank, heat is stored and transferred, and the energy utilization rate is increased; the condenser of the air cooling unit is used for replacing an evaporator of the heat pump system, the transformation cost of the heat pump system is saved, and compared with normal-temperature air serving as a heat source of the evaporator of the heat pump system, the performance coefficient of the heat pump system is improved.

Description

Technical Field

[0001] The present invention relates to the field of energy technology, and in particular to a heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant. Background Art

[0002] With the continuous growth of global energy demand and the improvement of environmental protection awareness, improving energy utilization efficiency and reducing energy waste have become urgent issues that the power industry needs to solve. In traditional coal-fired power plants, a large amount of waste heat is generated during the power generation process, especially in air-cooled units, where exhaust steam waste heat is usually directly discharged into the atmosphere after air cooling. This practice not only causes a large amount of energy waste, but also increases environmental thermal pollution.

[0003] How to effectively recover the waste heat from coal-fired power plants, improve energy utilization, and reduce environmental pollution is a technical problem that needs to be urgently solved by existing technologies. Summary of the invention

[0004] In order to solve at least one technical problem in the above-mentioned background technology, the present invention proposes a heat pump and heat storage coupling system for recovering waste heat from exhaust steam of a coal-fired power plant, the system comprising:

[0005] Thermal system and heat pump system of air-cooled unit; thermal system of air-cooled unit includes: boiler, high-pressure cylinder, medium-pressure cylinder, low-pressure cylinder, generator, high-pressure heater, feed water pump, deaerator, low-pressure heater, condensate pump and condenser; heat pump system includes: filter, regenerator, compressor, condenser, expander, heat storage tank, heat exchanger, cold storage tank and motor;

[0006] In the thermal system of the air-cooled unit, the boiler, high-pressure cylinder, medium-pressure cylinder, low-pressure cylinder, condenser, condensate pump, low-pressure heater, deaerator, feedwater pump, and high-pressure heater are connected in series to form a loop, and the high-pressure cylinder, medium-pressure cylinder, low-pressure cylinder, and generator are connected in series in sequence. The steam extraction ports of the high-pressure cylinder and the medium-pressure cylinder are connected to the high-pressure heater, and the steam extraction ports of the medium-pressure cylinder and the low-pressure cylinder are connected to the low-pressure heater;

[0007] In the heat pump system, the filter, regenerator, compressor, condenser, and expander are connected in sequence, and the condenser, heat storage tank, heat exchanger, and cold storage tank are connected in series to form a loop. One end of the compressor is connected to the motor, and the other end is connected to the expander.

[0008] Optionally, the boiler is used to send steam into the high-pressure cylinder to perform work, the high-pressure cylinder is used to reduce the pressure and temperature of the steam to the levels required by the medium-pressure cylinder, and send the steam into the medium-pressure cylinder to perform work, the medium-pressure cylinder is used to reduce the pressure and temperature of the steam to the levels required by the low-pressure cylinder, and send the steam into the low-pressure cylinder to perform work, and the low-pressure cylinder is used to enable the steam to drive the generator to generate electricity; the high-pressure heater uses the steam extracted from the high-pressure cylinder and the medium-pressure cylinder to heat the feed water; the deaerator is used to remove oxygen from the feed water to ensure the quality of the feed water; the feed pump is used to increase the feed water pressure to meet the boiler feed water demand; the low-pressure heater uses the steam extracted from the medium-pressure cylinder and the low-pressure cylinder to heat the condensate; the condenser is used to condense the steam sent from the low-pressure cylinder into water, and establish and maintain a vacuum at the exhaust of the low-pressure cylinder; the condensate pump is used to increase the pressure of the condensate at the outlet of the condenser and send it to the heat recovery cycle.

[0009] Optionally, the condenser is used to exchange heat between two cold and hot working fluids from the heat exchanger outlet and the compressor outlet; the regenerator is used to exchange heat between two cold and hot working fluids from the filter outlet and the condenser outlet; the heat storage tank is used to store the hot molten salt after heat exchange through the condenser, and output heat to the outside when there is a heat demand; the cold storage tank is used to store the cold molten salt after heat exchange; the heat exchanger is used to exchange heat between the working fluid from the heat storage tank outlet and condensate, and the working fluid after heat exchange returns to the thermal system of the air-cooled unit to form a closed cycle; the expander is used to recover the waste heat of the circulating working fluid at the regenerator outlet.

[0010] Optionally, the heat pump system is an air heat pump, which utilizes part of the low-temperature hot air at the condenser outlet as the circulating working fluid of the heat pump system.

[0011] Optionally, the air at the condenser outlet is filtered through a filter and then enters the regenerator, exchanges heat with the circulating working fluid at the condenser outlet and then enters the compressor for pressurization, then enters the condenser and exchanges heat with the condensed water at the heat exchanger outlet and then flows into the regenerator for secondary heat exchange, and then enters the expansion machine to form a cycle. The air expanded by the expander becomes superheated steam and is discharged into the atmosphere.

[0012] Optionally, the electrical energy required by the electric motor is generated by a generator.

[0013] Optionally, the heat storage medium is molten salt. When storing heat, the cold molten salt in the cold storage tank is heated by the heat pump system to turn it into hot molten salt, and stored in the heat storage tank. When releasing heat, the heat pump system stops running, and the hot molten salt in the heat storage tank returns to the cold storage tank after exchanging heat through the heat exchanger, forming a closed cycle to achieve the recycling of molten salt.

[0014] Optionally, the cold flow entering the heat exchanger comes from condensed water after the outlet of the feedwater pump and before the inlet of the high-pressure heater.

[0015] Optionally, the air entering the regenerator is filtered through a filter to remove dust, fine particles, impurities or pollutants in the air to avoid clogging or corrosion of the regenerator, thereby improving the efficiency and life of the equipment and ensuring the normal operation of the heat pump system.

[0016] Optionally, the steam extraction port of the intermediate pressure cylinder is connected to a deaerator.

[0017] The beneficial effects of the present invention are:

[0018] The present invention proposes a heat pump and heat storage coupling system for recovering waste heat from exhaust steam of a coal-fired power plant. The heat pump system consumes the surplus electricity of the coal-fired power plant during the power off-peak period, thereby improving the deep peak-shaving capacity of the coal-fired power plant. Heat is stored and transferred by adding a heat storage tank and a cold storage tank, thereby improving the energy utilization rate. The condenser of an air-cooled unit is used to replace the evaporator of the heat pump system, thereby saving the cost of heat pump system modification. Compared with normal temperature air as the heat source of the evaporator of the heat pump system, the COP (Coefficient of Performance) of the heat pump system is improved by utilizing the waste heat of hot air. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0020] Figure 1 It is a schematic diagram of a heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant according to an embodiment of the present invention.

[0021] In the figure: 1- thermal system of air-cooling unit, 2- heat pump system, 3- boiler, 4- high-pressure cylinder, 5- medium-pressure cylinder, 6- low-pressure cylinder, 7- generator, 8- high-pressure heater, 9- feed water pump, 10- deaerator, 11- low-pressure heater, 12- condensate pump, 13- condenser, 14- filter, 15- regenerator, 16- compressor, 17- condenser, 18- expander, 19- heat storage tank, 20- heat exchanger, 21- cold storage tank, 22- motor. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a series of products or devices are not necessarily limited to those units explicitly listed, but may include other units that are not explicitly listed or inherent to these products or devices.

[0024] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] Figure 1 Schematic diagram of a heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant according to an embodiment of the present invention. Figure 1 As shown, in one embodiment of the present invention, the heat pump and heat storage coupling system for recovering exhaust heat from a coal-fired power plant of the present invention comprises: an air-cooling unit thermal system 1 and a heat pump system 2.

[0026] like Figure 1 As shown, the thermal system 1 of the air-cooling unit includes: a boiler 3, a high-pressure cylinder 4, a medium-pressure cylinder 5, a low-pressure cylinder 6, a generator 7, a high-pressure heater 8, a feed water pump 9, a deaerator 10, a low-pressure heater 11, a condensate pump 12 and a condenser 13.

[0027] like Figure 1 As shown, the heat pump system 2 includes: a filter 14 , a regenerator 15 , a compressor 16 , a condenser 17 , an expander 18 , a heat storage tank 19 , a heat exchanger 20 , a cold storage tank 21 and a motor 22 .

[0028] like Figure 1 As shown, in the thermal system 1 of the air-cooling unit, the boiler 3, the high-pressure cylinder 4, the medium-pressure cylinder 5, the low-pressure cylinder 6, the condenser 13, the condensate pump 12, the low-pressure heater 11, the deaerator 10, the feed water pump 9, and the high-pressure heater 8 are connected in series in sequence to form a loop. The high-pressure cylinder 4, the medium-pressure cylinder 5, the low-pressure cylinder 6, and the generator 7 are connected in series in sequence. The steam extraction ports of the high-pressure cylinder 4 and the medium-pressure cylinder 5 are connected to the high-pressure heater 8, and the steam extraction ports of the medium-pressure cylinder 5 and the low-pressure cylinder 6 are connected to the low-pressure heater 11.

[0029] like Figure 1As shown, in the heat pump system 2, the filter 14, the regenerator 15, the compressor 16, the condenser 17, and the expander 18 are connected in sequence. The condenser 17, the heat storage tank 19, the heat exchanger 20, and the cold storage tank 21 are connected in series in sequence to form a loop. One end of the compressor 16 is connected to the motor 22, and the other end is connected to the expander 18.

[0030] In one embodiment of the present invention, the boiler 3 is used to send steam into the high-pressure cylinder 4 to do work, the high-pressure cylinder 4 is used to reduce the pressure and temperature of the steam to the level required by the medium-pressure cylinder 5, and send the steam into the medium-pressure cylinder 5 to do work, the medium-pressure cylinder 5 is used to reduce the pressure and temperature of the steam to the level required by the low-pressure cylinder 6, and send the steam into the low-pressure cylinder 6 to do work, and the low-pressure cylinder 6 is used to enable the steam to drive the generator 7 to generate electricity. The high-pressure heater 8 uses the steam extracted from the high-pressure cylinder 4 and the medium-pressure cylinder 5 to heat the feed water. The deaerator 10 is used to remove oxygen from the feed water to ensure the quality of the feed water. The feed water pump 9 is used to increase the feed water pressure to meet the boiler feed water demand. The low-pressure heater 11 uses the steam extracted from the medium-pressure cylinder 5 and the low-pressure cylinder 6 to heat the condensate. The condenser 13 is used to condense the steam sent from the low-pressure cylinder 6 into water, and establish and maintain vacuum at the exhaust of the low-pressure cylinder 6. The condensate pump 12 is used to increase the pressure of the condensate at the outlet of the condenser 13 and send it to the heat recovery cycle.

[0031] In one embodiment of the present invention, the condenser 17 is used to exchange heat between two cold and hot working fluids from the outlet of the heat exchanger 20 and the outlet of the compressor 16. The regenerator 15 is used to exchange heat between two cold and hot working fluids from the outlet of the filter 14 and the outlet of the condenser 17. The heat storage tank 19 is used to store the hot molten salt after heat exchange in the condenser 17, and output heat to the outside when there is a heat demand. The cold storage tank 21 is used to store the cold molten salt after heat exchange. The heat exchanger 20 is used to exchange heat between the working fluid at the outlet of the heat storage tank 19 and condensed water, and the working fluid after heat exchange returns to the thermal system 1 of the air-cooled unit to form a closed cycle. The expander 18 is used to recover the waste heat of the circulating working fluid at the outlet of the regenerator 15.

[0032] It can be seen that the heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant of the present invention has the following characteristics:

[0033] 1. The system of the present invention replaces the evaporator of the heat pump system with the condenser of the thermal system of the air-cooled unit, which can effectively recover and utilize the waste heat discharged by the power station, improve the utilization rate of energy, achieve the purpose of energy conservation and emission reduction, and simplify the system structure and save construction costs compared with the traditional heat pump system.

[0034] 2. The system of the present invention sets a heat exchanger to transfer the waste heat of exhaust steam in the low-temperature circulating cooling water into the boiler feed water after heat exchange. By heating the boiler feed water, fuel consumption is reduced and the circulation thermal efficiency of the thermal system of the air-cooled unit is improved.

[0035] In one embodiment of the present invention, one end of the compressor 16 is connected to the motor 22 , and the other end is coaxially connected to the expander 18 .

[0036] In one embodiment of the present invention, the steam extraction ports of the high-pressure cylinder 4, the medium-pressure cylinder 5, and the low-pressure cylinder 6 are connected to the high-pressure heater 8, the deaerator 10, and the low-pressure heater 11, respectively.

[0037] In one embodiment of the present invention, the heat pump system 2 is an air heat pump, and part of the low-temperature hot air at the outlet of the condenser 13 is used as the circulating working medium of the heat pump system 2 .

[0038] The present invention can effectively recover and utilize the low-temperature waste heat that might have been discharged by introducing the low-temperature hot air at the outlet of the condenser 13 into the heat pump system 2. This not only reduces the heat loss of air discharge, but also converts the low-temperature waste heat into usable thermal energy, thereby improving the overall energy utilization rate. The heat pump system of the present invention uses air as a circulating working fluid. Compared with traditional working fluids, air is easy to obtain and has low cost. At the same time, the fluidity and thermodynamic properties of the air working fluid are fully utilized in the system, so that the heat pump system can maintain good operating performance under different working conditions. The present invention extracts low-temperature air from the condenser 13 into the heat pump system, and the working fluid undergoes compression, condensation, expansion, heat exchange and other processes to form a closed cycle. This design reduces the loss of heat, and stores and regulates the heat through the heat storage tank 19 and the cold storage tank 21 to ensure that there is sufficient heat supply at different times. The present invention uses low-temperature hot air as a circulating working fluid, and this air-type heat pump solution further improves the heat recovery efficiency of the system, achieving a more energy-saving and environmentally friendly operation mode.

[0039] In one embodiment of the present invention, the air at the outlet of the condenser 13 is filtered by the filter 14 and then enters the regenerator 15. After heat exchange with the circulating working fluid at the outlet of the condenser 17, it enters the compressor 16 for pressurization. Then, it enters the condenser 17, exchanges heat with the condensed water at the outlet of the heat exchanger 20, and then flows into the regenerator 15 for secondary heat exchange. Then, it enters the expander 18 to form a cycle. After the air is expanded by the expander 18, it becomes superheated steam and is discharged into the atmosphere.

[0040] The low-temperature hot air at the outlet of the condenser 13 of the present invention first passes through the filter 14 to remove impurities to ensure that the air entering the heat pump system is clean. The filtered air enters the regenerator 15, where it undergoes the first heat exchange with the circulating working medium at the outlet of the condenser 17. In this process, the air is preheated by the high-temperature circulating working medium coming out of the condenser 17 to increase its temperature and make it more suitable for subsequent compression processing.

[0041] The air after the preliminary heat exchange flows into the compressor 16, where the air is further compressed, and its temperature and pressure are significantly increased. Through compression, the thermodynamic properties of the air are significantly improved, making it have more potential thermal energy.

[0042] The pressurized high-temperature and high-pressure air enters the condenser 17 and exchanges heat with the condensed water at the outlet of the heat exchanger 20. At this time, the condensed water has a lower temperature and can effectively absorb the heat in the air, while the air is further cooled. This process of the condenser 17 transfers the heat of the air to the condensed water, making it a heat source that can be used in other system processes.

[0043] The air coming out of the condenser 17 flows into the regenerator 15 again to exchange heat with the working medium in the system (such as molten salt in the heat storage tank). This process can not only further recover the residual heat in the air, but also increase the overall thermal efficiency of the system through repeated heat exchange processes, making full use of the energy of each part.

[0044] After the secondary heat exchange in the regenerator, the air flows into the expander 18. In the expander, the air pressure drops rapidly, expands, releases mechanical energy and part of the heat energy, and the temperature drops sharply, becoming superheated steam. The superheated steam after expansion is finally discharged into the atmosphere, completing a complete cycle.

[0045] The air of the present invention undergoes two heat exchanges (regenerator and condenser), making full use of waste heat, and storing the heat in condensed water or molten salt, thereby maximizing the recovery of waste heat. During the circulation process in multiple heat exchangers, heat is exchanged and utilized multiple times, reducing the energy loss of the system and enhancing the heat recovery efficiency of the entire system. The design of the expander allows the air to become superheated steam when it is finally discharged into the atmosphere, further releasing heat while reducing the cooling burden on the environment. The combination of air pressurization, heat exchange and expansion processes achieves efficient operation of the heat pump system, while also reducing the cooling load and energy consumption of the entire power station system. The air-type heat pump system design of the present invention achieves efficient heat management through a sophisticated heat exchange and compression process, maximizes the utilization of waste heat, and further improves the overall efficiency and environmental performance of the system.

[0046] In one embodiment of the present invention, the electric energy required by the motor 22 is generated by the generator 7, thereby improving the deep peak regulation capability of the coal-fired power plant during the power off-peak period.

[0047] During the off-peak period when electricity demand is low, power plants usually face the problem of reduced power generation load. The present invention can effectively digest this excess electricity by utilizing the excess electricity generated by the generator 7 during the off-peak period to drive the motor 22 in the heat pump system, thereby reducing the impact of frequent start and stop of power generation equipment on equipment life and efficiency. This design of the present invention can not only maintain the operating efficiency of the generator set, but also stabilize the grid load and improve the peak-shaving capacity of the coal-fired power plant. During the off-peak period, the present invention uses the electricity generated by the generator 7 to drive the motor 22 of the heat pump system, which can effectively utilize the excess electricity generated during the power generation process and reduce energy waste. In addition, the heat pump system can recover waste heat and store heat (such as through a heat storage tank 19), and can release the stored heat when the electricity demand rises for heating or power generation, thereby improving the flexibility and response speed of the system.

[0048] In one embodiment of the present invention, a heat storage tank 19 and a cold storage tank 21 are additionally provided in the system of the present invention, and the heat storage medium is molten salt. When storing heat, the cold molten salt in the cold storage tank 21 is heated by the heat pump system 2 to turn it into hot molten salt, and the hot molten salt is stored in the heat storage tank 19. When releasing heat, the heat pump system 2 stops running, and the hot molten salt in the heat storage tank 19 returns to the cold storage tank 21 after exchanging heat through the heat exchanger 20, forming a closed cycle, thereby realizing the recycling of molten salt.

[0049] As a heat storage medium, molten salt has good thermophysical properties and can store a large amount of heat while maintaining high thermal stability. Molten salt does not undergo significant physical or chemical changes at high temperatures and is suitable as a long-term heat storage medium. During the heat storage process, molten salt can store heat at a higher temperature, and during the heat release process, molten salt can effectively transfer heat to the working fluid or other system equipment through the heat exchanger, ensuring full utilization of thermal energy.

[0050] The present invention uses a closed cycle of molten salt between the heat storage tank 19 and the cold storage tank 21, so that the system can repeatedly perform heat storage and heat release operations without frequent replacement or addition of new media. This design greatly simplifies operation management and reduces waste of energy and materials. The present invention can effectively recover waste heat and store it, and release it when needed, avoiding waste heat. By utilizing the high heat storage capacity of molten salt and the efficient operation of the heat pump, the energy efficiency of the entire system can be significantly improved. The recycling of molten salt can not only reduce heat emissions to the outside world, but also reduce dependence on traditional coal burning through waste heat recovery and reuse, thereby reducing the emission of greenhouse gases and other pollutants, and contributing to environmental protection.

[0051] The addition of the heat storage tank 19 and the cold storage tank 21 of the present invention enables the efficient use of molten salt as a heat storage medium, forming a closed circulation system. This solution of the present invention greatly improves the heat storage and management capabilities, ensuring the flexible operation of the heat pump system under different working conditions. Through the recycling of molten salt, the system achieves efficient waste heat recovery and energy storage, enhances the peak-shaving capacity of coal-fired power plants, reduces energy waste, and reduces environmental impact.

[0052] In one embodiment of the present invention, the cold flow entering the heat exchanger 20 comes from the condensed water after the outlet of the feed water pump 9 and before the inlet of the high-pressure heater 8.

[0053] The present invention utilizes the condensed water between the outlet of the feed water pump 9 and the inlet of the high-pressure heater 8 as the cold flow. This part of the cold flow has a relatively low temperature when entering the heat exchanger 20, and can effectively absorb the heat of the high-temperature air returning from the heat pump system. The heat exchanger 20 transfers part of the heat to this part of the cold flow condensed water by exchanging heat with the working fluid of the heat pump system. After the temperature of the cold flow condensed water increases, it enters the high-pressure heater 8 and is further used to heat the feed water. This process not only fully recovers the heat of the heat pump system, but also preheats the condensed water before entering the high-pressure heater 8, reducing the load of the high-pressure heater 8.

[0054] The present invention introduces the condensed water between the outlet of the feed water pump 9 and the inlet of the high-pressure heater 8 as a cold flow into the heat exchanger 20, which not only effectively utilizes the cold energy of the condensed water, but also improves the waste heat recovery efficiency of the heat pump system. At the same time, this design also reduces the load of the high-pressure heater, optimizes the thermal cycle of the entire power generation system, and significantly improves the energy utilization efficiency and the overall stability of the system.

[0055] In one embodiment of the present invention, the air entering the regenerator 15 is filtered through a filter 14 to remove dust, fine particles, impurities or pollutants in the air to avoid clogging or corrosion of the regenerator 15, thereby improving the efficiency and life of the equipment and ensuring the normal operation of the heat pump system 2.

[0056] If impurities, dust and fine particles in the air enter the regenerator without being filtered, they may adhere to the heat exchange surface, causing the heat exchanger to be blocked and affecting the heat exchange efficiency. In addition, certain chemicals or impurities may react with the material of the equipment, causing corrosion, further reducing the service life of the equipment. In the present invention, these pollutants in the air are effectively removed through the filter 14, preventing them from clogging and corroding the regenerator, thereby improving the working efficiency and durability of the regenerator.

[0057] In addition, when the surface of the heat exchanger is clean and free of contamination, the heat exchange efficiency between the air and the working medium will be higher. If impurities are attached to the heat exchange surface, the heat transfer performance of the heat exchanger may be reduced, reducing the energy recovery effect of the system. The use of the filter 14 ensures that the air entering the heat exchanger is clean, thereby ensuring the heat transfer efficiency of the heat exchanger and improving the working performance of the entire heat pump system 2.

[0058] In one embodiment of the present invention, the steam extraction port of the intermediate pressure cylinder 5 is connected to the deaerator 10 .

[0059] It can be seen from the above embodiments that the present invention proposes a heat pump and heat storage coupling system for recovering waste heat from exhaust steam of coal-fired power plants. Through the heat pump system, the surplus electricity of coal-fired power plants during power off-peak periods is consumed to improve the deep peak-shaving capacity of coal-fired power plants; heat is stored and transferred by adding heat storage tanks and cold storage tanks, thereby improving the utilization rate of energy; the condenser of the air-cooled unit is used instead of the evaporator of the heat pump system, thereby saving the cost of heat pump system modification. Compared with normal temperature air as the heat source of the evaporator of the heat pump system, the COP of the heat pump system is improved by utilizing the waste heat of hot air. At the same time, the stored heat can heat feed water, reheat cold section steam or generate main steam to reduce turbine extraction and increase unit output. The present invention can broaden the load operation range of coal-fired power generation systems, improve the operating flexibility of the system, and has good application prospects in the field of thermal power generation.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant, characterized in that: include: Air cooling unit thermal system (1) and heat pump system (2); The thermal system (1) of the air-cooling unit includes: a boiler (3), a high-pressure cylinder (4), a medium-pressure cylinder (5), a low-pressure cylinder (6), a generator (7), a high-pressure heater (8), a feed water pump (9), a deaerator (10), a low-pressure heater (11), a condensate pump (12) and a condenser (13); the heat pump system (2) includes: a filter (14), a regenerator (15), a compressor (16), a condenser (17), an expander (18), a heat storage tank (19), a heat exchanger (20), a cold storage tank (21) and a motor (22); In the thermal system (1) of the air-cooling unit, the boiler (3), the high-pressure cylinder (4), the medium-pressure cylinder (5), the low-pressure cylinder (6), the condenser (13), the condensate pump (12), the low-pressure heater (11), the deaerator (10), the feed water pump (9), and the high-pressure heater (8) are sequentially connected in series to form a loop; the high-pressure cylinder (4), the medium-pressure cylinder (5), the low-pressure cylinder (6), and the generator (7) are sequentially connected in series; the steam extraction ports of the high-pressure cylinder (4) and the medium-pressure cylinder (5) are connected to the high-pressure heater (8); and the steam extraction ports of the medium-pressure cylinder (5) and the low-pressure cylinder (6) are connected to the low-pressure heater (11); In the heat pump system (2), the filter (14), the regenerator (15), the compressor (16), the condenser (17), and the expander (18) are connected in sequence, and the condenser (17), the heat storage tank (19), the heat exchanger (20), and the cold storage tank (21) are connected in series in sequence to form a loop. One end of the compressor (16) is connected to the motor (22), and the other end is connected to the expander (18).

2. The heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant according to claim 1 is characterized in that: The boiler (3) is used to send steam into the high-pressure cylinder (4) to perform work. The high-pressure cylinder (4) is used to reduce the pressure and temperature of the steam to the level required by the medium-pressure cylinder (5), and send the steam into the medium-pressure cylinder (5) to perform work. The medium-pressure cylinder (5) is used to reduce the pressure and temperature of the steam to the level required by the low-pressure cylinder (6), and send the steam into the low-pressure cylinder (6) to perform work. The low-pressure cylinder (6) is used to drive the steam to drive the generator (7) to generate electricity. The high-pressure heater (8) uses the steam extracted from the high-pressure cylinder (4) and the medium-pressure cylinder (5) to heat the feed water. The deaerator (10) is used to remove oxygen from the feed water to ensure the quality of the feed water; the feed water pump (9) is used to increase the feed water pressure to meet the boiler feed water demand; the low-pressure heater (11) uses the steam extracted from the medium-pressure cylinder (5) and the low-pressure cylinder (6) to heat the condensate; the condenser (13) is used to condense the steam sent from the low-pressure cylinder (6) into water, and to establish and maintain a vacuum at the exhaust of the low-pressure cylinder (6); the condensate pump (12) is used to increase the pressure of the condensate at the outlet of the condenser (13) and send it to the heat recovery cycle.

3. The heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant according to claim 1 is characterized in that: The condenser (17) is used to exchange heat between two cold and hot working fluids at the outlet of the heat exchanger (20) and the outlet of the compressor (16); the regenerator (15) is used to exchange heat between two cold and hot working fluids at the outlet of the filter (14) and the outlet of the condenser (17); the heat storage tank (19) is used to store the hot molten salt after heat exchange in the condenser (17) and output heat to the outside when there is a heat demand; the cold storage tank (21) is used to store the cold molten salt after heat exchange; the heat exchanger (20) is used to exchange heat between the working fluid at the outlet of the heat storage tank (19) and condensed water, and the working fluid after heat exchange returns to the thermal system (1) of the air cooling unit to form a closed cycle; the expander (18) is used to recover the waste heat of the circulating working fluid at the outlet of the regenerator (15).

4. The heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant according to claim 1 is characterized in that: The heat pump system (2) is an air-type heat pump, which utilizes part of the low-temperature hot air at the outlet of the condenser (13) as the circulating working fluid of the heat pump system (2).

5. The heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant according to claim 1, characterized in that: The air at the outlet of the condenser (13) is filtered by the filter (14) and then enters the regenerator (15). After heat exchange with the circulating medium at the outlet of the condenser (17), the air enters the compressor (16) for pressurization. The air then enters the condenser (17) for heat exchange with the condensed water at the outlet of the heat exchanger (20) and then flows into the regenerator (15) for secondary heat exchange. The air then enters the expander (18) to form a cycle. After expansion in the expander (18), the air becomes superheated steam and is discharged into the atmosphere.

6. The heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant according to claim 1, characterized in that: The electric energy required by the electric motor (22) is generated by the generator (7).

7. The heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant according to claim 1, characterized in that: The heat storage medium is molten salt. When storing heat, the cold molten salt in the cold storage tank (21) is heated by the heat pump system (2) to turn it into hot molten salt, which is then stored in the heat storage tank (19). When releasing heat, the heat pump system (2) stops running, and the hot molten salt in the heat storage tank (19) returns to the cold storage tank (21) after exchanging heat through the heat exchanger (20), thereby forming a closed cycle and realizing the recycling of the molten salt.

8. The heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant according to claim 1, characterized in that: The cold flow entering the heat exchanger (20) comes from the condensed water after the outlet of the feed water pump (9) and before the inlet of the high-pressure heater (8).

9. The heat pump and heat storage coupling system for exhaust heat recovery of coal-fired power plants according to claim 1, characterized in that: The air entering the regenerator (15) is filtered through a filter (14) to remove dust, fine particles, impurities or pollutants in the air to avoid clogging or corrosion of the regenerator (15), thereby improving the efficiency and life of the equipment and ensuring the normal operation of the heat pump system (2).

10. The heat pump and heat storage coupling system for recovering waste heat from exhaust steam from a coal-fired power plant according to claim 1, characterized in that: The steam extraction port of the medium pressure cylinder (5) is connected to the deaerator (10).

Images