Liquid Compressed Air Energy Storage System Coupled with the Thermal System of Coal-Fired Power Generation Units

Abstract

The present invention belongs to a liquid compressed air energy storage system, and solves the two main schemes for the compression heat release and expansion heat absorption of air in the process of compressed energy storage and power generation in the existing liquid compressed air energy storage system, which either have the problems of large initial investment and poor variable operating condition performance, or high fuel consumption and large pollutant emissions. A liquid compressed air energy storage system coupled with a thermal system of a coal-fired power generation unit is provided, comprising an air compressor, an air cooler, a refrigeration expander, a gas-liquid separator, a liquefied air storage device, a liquid booster pump and a plurality of air heaters connected in sequence; wherein the heating temperatures of the plurality of air heaters are increased in sequence; the plurality of air heaters are respectively connected to a plurality of steam source points of a steam turbine in the coal-fired power generation unit, and the pressure and temperature of each steam source point are different.

Description

Technical Field

[0001] The present invention belongs to a liquid compressed air energy storage system, and in particular, to a liquid compressed air energy storage system coupled with a thermal system of a coal-fired power generation unit.

Background Art

[0002] As of the end of 2019, the cumulative installed capacities of photovoltaic and wind power reached 205 million and 210 million kilowatts respectively, accounting for 10.2% and 10.4% of the total installed capacity (2.01 billion kilowatts); the annual total power generations reached 224.3 billion and 405.7 billion kWh respectively, accounting for 3% and 5.5% of the annual total power generation (7,325.3 billion kWh). The proportion of power generation is significantly less than the proportion of installed capacity, indicating that there is still a large amount of waste in new energy power. New energy power will develop rapidly and significantly in the future. Therefore, it is required that thermal power units further explore the peak shaving potential on the current basis.

[0003] The large-scale grid connection of renewable energy electric energy with the characteristics of volatility and intermittency puts forward higher requirements for the peak shaving and valley filling of the power grid and the safe and stable operation level. Building large-scale energy storage devices and improving the operation flexibility and safety of the power system are effective ways to solve the problem of high proportion of new energy consumption.

[0004] Currently, the energy storage technologies mainly include pumped storage, compressed air energy storage, and electrochemical energy storage. The pumped storage technology is mature and has high efficiency, but there are problems such as geographical location restrictions and it is difficult to be promoted on a large scale; the electrochemical energy storage technology has fast response, small volume, and short construction period, but has disadvantages such as short overall life and large industrial pollution; the liquid compressed air energy storage technology has the characteristics of long life, small environmental pollution, and low operation and maintenance costs, and has the potential for large-scale promotion and application.

[0005] However, for the liquid compressed air energy storage systems reported publicly at present, there are mainly two treatment schemes for the compression heat release and expansion heat absorption of air during the compression energy storage and power generation processes: 1) setting up a heat storage system to store the released heat during the air compression process and use it for preheating before the expander during the expansion energy release and power generation link; 2) discharging the compression heat externally and supplying the expansion heat absorption by means of fuel supplementary combustion. Among them, the heat storage scheme has disadvantages such as large initial investment and poor off-design performance; the heat supplementary scheme has problems such as fuel consumption and pollutant emissions.

Summary of the Invention

[0006] The purpose of the present invention is to solve the problems that in the existing liquid compressed air energy storage system, the two main treatment schemes for the compression heat release and expansion heat absorption of air during the compression energy storage and power generation processes either have large initial investment and poor off-design performance, or have high fuel consumption and large pollutant emissions, and to provide a liquid compressed air energy storage system coupled with a thermal system of a coal-fired power generation unit.

[0007] To achieve the above object, the present invention is implemented by the following technical solutions:

[0008] A liquid compressed air energy storage system coupled with the thermal system of a coal-fired power generation unit, comprising an air compressor, an air cooler, a refrigeration expander, a gas-liquid separator, a liquefied air storage device, a liquid booster pump, and a plurality of air heaters connected in sequence; wherein, the heating temperatures of the plurality of air heaters increase in sequence;

[0009] After the air is pressurized by the air compressor, it is cooled by the air cooler, then enters the refrigeration expander, and the gas-liquid separation is completed in the gas-liquid separator. The liquid part enters the liquefied air storage device, is boosted by the liquid booster pump, and then enters the air expansion generator to do work and generate electricity after being heated by the plurality of air heaters in sequence;

[0010] The plurality of air heaters are respectively connected to a plurality of steam source points of the steam turbine in the coal-fired power generation unit, and the pressure and temperature of each steam source point are different.

[0011] A further improvement of the present invention lies in:

[0012] It further includes an air preheater, a warm air blower, and a boiler forced draft fan connected in sequence;

[0013] The air preheater is connected to the boiler of the coal-fired power generation unit;

[0014] A circulating water pipeline is provided between the warm air blower and the air cooler, and a circulating water booster pump is provided on the circulating water pipeline.

[0015] The new steam at the outlet of the boiler in the coal-fired power generation unit returns to the reheater in the boiler after doing work in the high-pressure cylinder of the steam turbine, and then enters the intermediate-pressure cylinder and the low-pressure cylinder of the steam turbine in sequence to do work and drive the generator to generate electricity.

[0016] The air heaters include a primary air heater, a secondary air heater, a tertiary air heater, and a quaternary air heater arranged in sequence from the liquid booster pump to the air expansion generator;

[0017] The heat source of the quaternary air heater is extracted from the new steam at the outlet of the reheater in the boiler of the coal-fired power generation unit;

[0018] The heat source of the tertiary air heater is extracted from a certain stage extraction steam of the intermediate-pressure cylinder of the steam turbine in the coal-fired power generation unit;

[0019] The heat source of the secondary air heater is extracted from the exhaust steam of the intermediate-pressure cylinder of the steam turbine in the coal-fired power generation unit;

[0020] The heat source of the primary air heater is extracted from a certain stage extraction steam of the low-pressure cylinder of the steam turbine in the coal-fired power generation unit.

[0021] The drain water after the steam of the primary air heater, secondary air heater, tertiary air heater, and quaternary air heater releases heat and condenses all flows back to the condenser of the coal-fired power generation unit.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The liquid compressed air energy storage system coupled with the thermal system of the coal-fired power generation unit in the present invention efficiently couples the heat generated by air compression in the liquid compressed air energy storage link and the heating heat source required in the energy release and power generation link with heat sources having similar qualities in the thermal cycle process of the coal-fired power generation unit. Compared with the existing liquid compressed air energy storage system, the heat storage system or the fuel supplementary heating link is cancelled, and is replaced by a gas-water heat exchanger and a steam-gas heat exchanger. The heat released during compression and the heat absorbed during expansion in the air compression energy storage and power generation processes of the air are exchanged with heat users having similar qualities to those of the coal-fired power generation unit, reducing system investment and effectively improving the overall efficiency.

[0024] 2. In the present invention, a flow cycle is carried out between the air cooler and the air preheater, transferring the heat of the air at the outlet of the air compressor to the cold air at the outlet of the boiler forced draft fan, increasing the air temperature at the inlet of the air preheater, improving the operating environment of the air preheater, being able to improve the safety and reliability of the equipment, and enhancing the boiler efficiency.

[0025] 3. There are four levels of air heaters in the present invention, and the heat source comes from different steam source points of the steam turbine. The system structure is compact and the overall utilization rate is high.

[0026] 4. In the present invention, the drain water after the steam of each level of heater releases heat and condenses all flows back to the condenser of the coal-fired power generation unit, ensuring the steam-water mass balance of the overall system.

Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic diagram of an embodiment of the compressed air energy storage system coupled with the thermal system of the coal-fired power generation unit of the present invention.

[0029] Wherein: 1 - boiler; 2 - high-pressure cylinder of steam turbine; 3 - intermediate-pressure cylinder of steam turbine; 4 - low-pressure cylinder of steam turbine; 5 - generator; 6 - air preheater; 7 - air heater; 8 - boiler forced draft fan; 9 - closed-loop water booster pump; 10 - air compressor; 11 - air cooler; 12 - refrigeration expander; 13 - gas-liquid separator; 14 - liquefied air storage device; 15 - liquid booster pump; 16 - primary air heater; 17 - secondary air heater; 18 - tertiary air heater; 19 - quaternary air heater; 20 - air expansion generator.

Detailed implementation manners

[0030] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. The components of the embodiments of the present invention usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0032] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0033] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0034] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0035] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] The present invention will be further described in detail below with reference to the accompanying drawings:

[0037] See Figure 1 , the present invention provides a liquid compressed air energy storage system coupled with the thermal system of a coal-fired power generation unit. By making full use of the huge heat carrier of the steam-water thermal cycle of the coal-fired power generation unit, an air-water heat exchanger, an air-steam heat exchanger and corresponding pipelines are set. Using closed-circuit circulating water as the heat carrier, the heat released during the air compression energy storage process is used to heat the cold air at the inlet of the air preheater 6 of the boiler 1, improving the operating environment of the air preheater 6, enhancing the safety and reliability of the equipment, and increasing the efficiency of the boiler 1. At the same time, steam of different qualities is used to increase the temperature of the air entering the air expansion generator 20 in each stage of the air heater.

[0038] The liquid compressed air energy storage system coupled with the thermal system of the coal-fired power generation unit includes an air preheater 6, a warm air blower 7 and a boiler forced draft fan 8 that are connected in sequence; an air compressor 10, an air cooler 11, a refrigeration expander 12, a gas-liquid separator 13, a liquefied air storage device 14, a liquid booster pump 15 and multiple air heaters that are connected in sequence. Among them, the multiple air heaters include a primary air heater 16, a secondary air heater 17, a tertiary air heater 18 and a quaternary air heater 19 that are arranged in sequence from the liquid booster pump 15 to the air expansion generator 20.

[0039] In the coal-fired power generation unit, the new steam at the outlet of the boiler 1 does work in the high-pressure cylinder 2 of the steam turbine and then returns to the boiler 1 for secondary temperature increase in the reheater, and then enters the intermediate-pressure cylinder 3 and the low-pressure cylinder 4 of the steam turbine to do work to drive the generator 5 to generate electricity. The steam turbine is provided with regenerative extraction steam of different pressure and temperature levels.

[0040] In the liquid compressed air energy storage link, after the air is pressurized by the compressor 10 and releases heat in the air cooler 11, it then enters the refrigeration expander 12 to achieve deep cooling, and the liquid-gas separation of the air is realized in the gas-liquid separator 13. Then, the liquid enters the liquefied air storage device 14, which is the liquefaction and compression energy storage process of the air.

[0041] The power generation and energy release process of the energy storage system is as follows: The liquid air at the outlet of the liquid air storage device 14 is pressurized by the liquid booster pump 15, and then sequentially passes through the primary air heater 16, the secondary air heater 17, the tertiary air heater 18, and the quaternary air heater 19 for stepwise temperature rise, and then enters the air expansion generator 20 to generate electricity by doing work. The exhaust gas is discharged into the atmospheric environment.

[0042] In addition, in the air compression energy storage process, the air cooler 11 and the air preheater 7 of the boiler 1 are set, and their structural forms are both air-water surface heat exchangers. Using the closed-circuit circulating water as the heat carrier, driven by the closed-circuit water booster pump 9, it circulates between the air cooler 11 and the air preheater 7, transfers the heat of the air at the outlet of the air compressor 10 to the cold air at the outlet of the boiler forced draft fan 8, increases the inlet air temperature of the air preheater 6, improves the operating environment of the air preheater 6 to improve the safety and reliability of the equipment, and improves the efficiency of the boiler 1.

[0043] In the air expansion power generation and energy release process, the four air heaters set are all steam-air heat exchangers, and steam with four different pressures and temperatures is extracted from different steam sources of the steam turbine: the steam extracted by the quaternary air heater 19, the tertiary air heater 18, the secondary air heater 17, and the primary air heater 16 are the reheated steam, the third-stage extraction steam (a certain stage of the intermediate pressure cylinder 3 of the steam turbine), the extraction steam from the middle exhaust (the exhaust of the intermediate pressure cylinder 3 of the steam turbine), and the sixth-stage extraction steam (a certain stage of the low pressure cylinder 4 of the steam turbine) respectively. Among them, the reheated steam is the new steam at the outlet of the reheater of the boiler 1, with the highest temperature, and is used as the heating steam source for the last-stage air heater; the third-stage extraction steam is the extraction steam of a certain stage of the intermediate pressure cylinder 3 of the steam turbine, with a temperature lower than the reheated steam but higher than the extraction steam from the middle exhaust and the sixth-stage extraction steam, and is used as the heating steam source for the tertiary air heater 18; the extraction steam from the middle exhaust and the sixth-stage extraction steam are used as the heating steam sources for the secondary air heater 17 and the primary air heater 16 respectively. The low-temperature air at the outlet of the liquid booster pump 15 sequentially flows through the primary air heater 16, the secondary air heater 17, the tertiary air heater 18, and the quaternary air heater 19 for stepwise temperature rise, and then enters the air expander 20 to generate electricity by doing work. The condensed water of the steam released by the four-stage air heaters flows back to the condenser of the coal-fired power generation unit to ensure the steam-water mass balance of the overall system.

[0044] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A liquid compressed air energy storage system coupled with the thermal system of a coal-fired power generation unit, characterized in that, it includes an air compressor (10), an air cooler (11), a refrigeration expander (12), a gas-liquid separator (13), a liquefied air storage device (14), a liquid booster pump (15) and multiple air heaters that are connected in sequence; wherein, the heating temperatures of the multiple air heaters increase sequentially; After the air is pressurized by the air compressor (10), it is cooled by the air cooler (11), then enters the refrigeration expander (12), and gas-liquid separation is completed in the gas-liquid separator (13). The liquid part enters the liquefied air storage device (14), is boosted by the liquid booster pump (15), and then enters the air expansion generator (20) to do work and generate electricity after being heated by the multiple air heaters in sequence; The multiple air heaters are respectively connected to multiple steam source points of the steam turbine in the coal-fired power generation unit, and the pressure and temperature of each steam source point are different; It also includes an air preheater (6), a warm air blower (7) and a boiler forced draft fan (8) that are connected in sequence; The air preheater (6) is connected to the boiler of the coal-fired power generation unit; A circulating water pipeline is provided between the warm air blower (7) and the air cooler (11), and a circulating water booster pump (9) is provided on the circulating water pipeline; The new steam at the outlet of the boiler (1) in the coal-fired power generation unit returns to the reheater in the boiler (1) after doing work in the high-pressure cylinder (2) of the steam turbine, and then enters the intermediate-pressure cylinder (3) and the low-pressure cylinder (4) of the steam turbine in sequence to do work, driving the generator (5) to generate electricity; The air heaters include a primary air heater (16), a secondary air heater (17), a tertiary air heater (18) and a quaternary air heater (19) that are arranged in sequence from the liquid booster pump (15) to the air expansion generator (20); The heat source of the quaternary air heater (19) is extracted from the new steam at the outlet of the boiler reheater in the coal-fired power generation unit; The heat source of the tertiary air heater (18) is extracted from a certain stage of extraction steam in the intermediate-pressure cylinder of the coal-fired power generation unit steam turbine; The heat source of the secondary air heater (17) is extracted from the exhaust steam of the intermediate-pressure cylinder of the coal-fired power generation unit steam turbine; The heat source of the primary air heater (16) is extracted from a certain stage of extraction steam in the low-pressure cylinder of the coal-fired power generation unit steam turbine; The condensed drain water after the steam of the primary air heater (16), secondary air heater (17), tertiary air heater (18) and quaternary air heater (19) releases heat all flows back to the condenser of the coal-fired power generation unit.

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