A combined cycle power generation system for wastewater treatment plants based on the ideal Ericsson cycle principle

Abstract

This invention relates to a combined cycle power generation system for wastewater treatment plants based on the ideal Ericsson cycle principle, comprising: a biogas turbine power generation module, an aeration tank photovoltaic power generation module, a carbon dioxide cycle power generation module, and a thermal storage module. The carbon dioxide cycle power generation module, based on the ideal Ericsson cycle principle, generates electricity through isothermal compression and expansion, and isobaric heat absorption and release processes. During off-peak electricity demand, carbon dioxide is compressed and stored through photovoltaic power generation or off-peak grid electricity, and then heated using waste heat from the gas turbine and the thermal storage module before entering the expander for power generation. Compared with existing technologies, this invention not only optimizes energy utilization in wastewater treatment plants but also effectively reduces dependence on fossil fuels, resulting in higher environmental and economic benefits. The effective combination of the biogas turbine, compressed carbon dioxide cycle power generation, aeration tank photovoltaic power generation, and thermal storage system achieves efficient energy utilization and dynamic peak shaving.

Description

Technical Field

[0001] This invention relates to the field of energy technology, and in particular to a combined cycle power generation system for wastewater treatment plants based on the ideal Ericsson cycle principle. Background Technology

[0002] Wastewater treatment plants generate large amounts of sludge during the wastewater treatment process. The organic matter in sludge undergoes anaerobic fermentation to produce biogas. Traditional wastewater treatment plants typically only use biogas as fuel for heating or for direct power generation, but this method has low energy efficiency. Furthermore, traditional electricity supply often relies on fossil fuels, which not only consumes non-renewable energy sources but also places a burden on the environment.

[0003] With the development of renewable energy technologies, photovoltaic (PV) power generation has become an effective green energy solution. However, in many facilities, the space and energy conversion efficiency of PV power generation remain limited. During peak electricity demand periods, the stability and efficiency of power supply are critical issues, making the development of efficient energy storage systems and dynamic peak-shaving solutions particularly important.

[0004] Existing carbon dioxide cycle power generation technologies, such as the ideal Ericsson cycle, theoretically possess high energy conversion efficiency. However, in practical applications, due to system complexity and high operating costs, they have not yet been widely adopted in wastewater treatment plants. Therefore, effectively integrating carbon dioxide cycle power generation technology with existing wastewater treatment plant resources has become crucial for improving power generation efficiency and resource utilization. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a system that not only optimizes energy utilization in wastewater treatment plants but also effectively reduces dependence on fossil fuels, resulting in high environmental and economic benefits. By integrating multiple power generation and energy storage technologies into one system, a highly efficient and environmentally friendly power generation solution is provided. This system effectively combines biogas turbines, compressed carbon dioxide cycle power generation, aeration tank photovoltaic power generation, and thermal storage systems, achieving efficient energy utilization and dynamic peak shaving.

[0006] This invention provides a combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle, comprising: a biogas gas turbine power generation module, an aeration tank photovoltaic power generation module, a carbon dioxide cycle power generation module, and a heat storage module;

[0007] The biogas generator module uses biogas produced by the fermentation of sludge from the sewage treatment plant as fuel to drive the biogas generator to generate electricity, thus making full use of the biogas resources generated in the sewage treatment plant.

[0008] The carbon dioxide cycle power generation module is based on the ideal Ericsson cycle principle, generating electricity through isothermal compression and expansion, and isobaric heat absorption and release processes. During off-peak electricity demand, carbon dioxide is compressed and stored through photovoltaic power generation or off-peak grid electricity, and heated using waste heat from the gas turbine and a heat storage module before entering the expander to generate electricity. The carbon dioxide cycle power generation module includes: an energy storage unit, a high-pressure expander, a low-pressure expander, a high-pressure heater, a low-pressure heater, and a generator; the high-pressure expander, low-pressure expander, and generator are connected in sequence; the energy storage unit includes: a high-pressure compressor, a low-pressure... The system includes a compressor, a high-pressure carbon dioxide storage tank, and a low-pressure carbon dioxide storage tank. Pipelines at the flue gas outlets of the high-pressure and low-pressure heaters are connected to the sludge drying tank, allowing the waste heat from the superheated flue gas in the heaters to provide the necessary heat to the sludge to be dried, thus meeting the drying temperature requirements. A carbon dioxide-to-carbon dioxide heat exchanger and a heat storage fluid-to-carbon dioxide heat exchanger are installed between the high-pressure heater and the energy storage unit. Pipelines at the outlets of the carbon dioxide-to-carbon dioxide heat exchangers are connected in series with heat exchangers in the sludge anaerobic digestion tank, providing the necessary heat to the sludge to be heated, thus meeting the anaerobic digestion conditions.

[0009] In the photovoltaic power generation module of the aeration tank, a photovoltaic power generation unit is installed on the aeration tank to compress carbon dioxide using photovoltaic power generation or off-peak electricity from the power grid and store it in a high-pressure gas storage tank.

[0010] The heat storage module is used to store waste heat from the gas turbine and releases this heat to heat carbon dioxide during peak electricity demand, thereby increasing power generation. The heat storage module includes a cold tank, a hot tank, a cold heat storage fluid, and a waste heat flue gas heat exchanger. The heat storage module is located after the biogas gas turbine power generation module. The cold tank is a cold heat storage fluid storage tank, and the hot tank is a hot heat storage fluid storage tank.

[0011] Furthermore, in the energy storage unit, a first carbon dioxide and cooling water heat exchanger is provided between the high-pressure compressor and the low-pressure compressor, so that the heat exchanged between the circulating cooling water and the compressed carbon dioxide in the first carbon dioxide and cooling water heat exchanger is used to provide temperature conditions for the anaerobic digestion of sludge to produce biogas.

[0012] A second carbon dioxide and cooling water heat exchanger is provided between the high-pressure compressor and the high-pressure carbon dioxide storage tank, so that the carbon dioxide is stored in the high-pressure carbon dioxide storage tank.

[0013] Furthermore, in the carbon dioxide cycle power generation module, a third carbon dioxide and cooling water heat exchanger is arranged in the pipelines of the high-pressure expander and the low-pressure expander, so that the compression and expansion process in the carbon dioxide cycle is close to an ideal isothermal process. The heat exchanged between the circulating cooling water and the compressed carbon dioxide in the third carbon dioxide and cooling water heat exchanger is used to provide temperature conditions for the anaerobic digestion of sludge to produce biogas.

[0014] Furthermore, in the carbon dioxide cycle power generation module, the high-pressure heater is a waste heat flue gas and high-pressure carbon dioxide heat exchanger, and the low-pressure heater is a waste heat flue gas and low-pressure carbon dioxide heat exchanger.

[0015] Furthermore, a carbon dioxide-air heat exchanger is provided between the third carbon dioxide and cooling water heat exchanger and the low-pressure carbon dioxide storage tank, so that the carbon dioxide after work is stored in the low-pressure carbon dioxide storage tank.

[0016] Furthermore, the waste heat flue gas outlet pipeline of the biogas turbine is equipped with a first flue gas shut-off valve and a second flue gas shut-off valve, which are used to control the heat storage process and heat carbon dioxide, respectively.

[0017] Furthermore, in the heat storage module, a first carbon dioxide shut-off valve is installed at the inlet pipe of the high-pressure carbon dioxide storage tank, a second carbon dioxide shut-off valve is installed at the inlet pipe of the low-pressure carbon dioxide storage tank, a first carbon dioxide flow control valve is installed at the outlet pipe of the high-pressure carbon dioxide storage tank, and a second carbon dioxide flow control valve is installed at the outlet pipe of the low-pressure carbon dioxide storage tank. The flow control valves are adjusted according to the temperature and flow rate of the waste heat flue gas from the biogas generator, thereby dynamically adjusting the carbon dioxide levels.

[0018] Furthermore, a first heat storage fluid flow control valve is installed at the outlet of the cold tank. The first heat storage fluid flow control valve is controlled according to the waste heat temperature and flow rate of the biogas generator, thereby adjusting the outlet flow rate of the heat storage fluid in the cold tank.

[0019] A second thermal storage fluid flow control valve is installed at the outlet of the hot tank. The flow rate of the thermal storage fluid at the outlet of the hot tank is controlled by the flow rate of carbon dioxide.

[0020] Furthermore, a flue gas flow control valve is installed at the flue gas inlet of the low-pressure heater. The flue gas flow control valve is adjusted according to the temperature and flow rate of the waste heat flue gas from the biogas generator, thereby dynamically adjusting the flue gas flow rate.

[0021] Furthermore, a second heat storage fluid shut-off valve is provided between the cold tank, the heat storage fluid and the carbon dioxide heat exchanger, and a first heat storage fluid shut-off valve is provided between the cold heat storage fluid and the waste heat flue gas heat exchanger and the hot tank.

[0022] The flow control method of the present invention:

[0023] Dynamic adjustment: Based on the flue gas flow rate and temperature of the biogas generator, the carbon dioxide flow rate and flue gas flow rate are adjusted to ensure that the carbon dioxide outlet temperature in the high / low pressure heater reaches the set value, thereby maintaining the cycle power generation efficiency.

[0024] Heat storage and heat release stage control: During the heat storage stage, the flow rate of the heat storage fluid at the outlet of the cold tank is adjusted to maintain the heat storage at the optimal level; during the heat release stage, the flow rate at the outlet of the hot tank is controlled according to the set temperature of carbon dioxide.

[0025] The operation process of this invention:

[0026] During off-peak electricity usage: start the low-pressure gas storage tank outlet and compressor to compress and store carbon dioxide; at the same time, store the waste heat from the biogas generator in the hot tank through heat exchange.

[0027] During peak electricity demand: The compression and heat storage processes are stopped, and the valves at the high-pressure gas storage tank, the hot tank outlet, and the high / low-pressure flue gas inlet are opened to heat the heat storage fluid and carbon dioxide gas, which is then fed into the high / low-pressure expander for power generation. After power generation, the carbon dioxide gas is cooled by heat exchange and stored in the low-pressure gas storage tank.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] (1) The system of the present invention not only optimizes energy utilization in wastewater treatment plants, but also effectively reduces dependence on fossil fuels, thus possessing high environmental benefits and economic value. By integrating multiple power generation and energy storage technologies into one system, it provides an efficient and environmentally friendly power generation solution. This system effectively combines biogas turbines, compressed carbon dioxide cycle power generation, aeration tank photovoltaic power generation, and thermal storage systems, achieving efficient energy utilization and dynamic peak shaving.

[0030] (2) Comprehensive utilization of resources: The biogas from the sewage treatment plant is used to generate electricity, and combined with the photovoltaic power generation system of the aeration tank and the carbon dioxide cycle power generation technology, the energy utilization efficiency and power generation capacity are improved.

[0031] (3) Dynamic peak shaving and energy storage: Carbon dioxide is compressed and stored through photovoltaic power generation or off-peak electricity from the grid, and the stored energy is released to generate electricity during peak electricity demand, thereby achieving dynamic peak shaving and effective energy storage.

[0032] (4) Waste heat utilization: The waste heat of the gas turbine and high / low pressure heater is used to dry the waste sludge, thereby maximizing the utilization of heat and improving the overall energy utilization efficiency of the system.

[0033] (5) Improve power generation efficiency: By precisely adjusting the carbon dioxide flow rate, flue gas flow rate and the operation of the thermal storage system, the system can maintain the best power generation efficiency under different load conditions.

[0034] (6) Reduce system power consumption: The inlet temperature of the low-pressure gas storage tank is reduced by the radiator, thereby reducing the power consumption of the compressor and improving the efficiency of the cycle power generation. Attached Figure Description

[0035] Figure 1This is a schematic diagram of a combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle.

[0036] Figure reference numerals: 1-Low-pressure compressor, 2-First carbon dioxide and cooling water heat exchanger, 3-High-pressure compressor, 4-Second carbon dioxide and cooling water heat exchanger, 5-First carbon dioxide shut-off valve, 6-High-pressure carbon dioxide storage tank, 7-First carbon dioxide flow control valve, 8-Carbon dioxide and carbon dioxide heat exchanger, 9-Heat storage fluid and carbon dioxide heat exchanger, 10-Waste heat flue gas and high-pressure carbon dioxide heat exchanger, 11-High-pressure expander, 12-Waste heat flue gas and low-pressure carbon dioxide heat exchanger, 13-Low-pressure expander, 14-Third carbon dioxide and cooling water heat exchanger 15-Water heat exchanger, 16-Carbon dioxide and air heat exchanger, 17-Second carbon dioxide shut-off valve, 18-Low-pressure carbon dioxide storage tank, 19-Second carbon dioxide flow control valve, 20-Cold heat storage fluid storage tank, 21-First heat storage fluid flow control valve, 22-Cold heat storage fluid and waste heat flue gas heat exchanger, 23-First heat storage fluid shut-off valve, 24-Hot heat storage fluid storage tank, 25-Second heat storage fluid flow control valve, 26-Second heat storage fluid shut-off valve, 27-First flue gas shut-off valve, 28-Second flue gas shut-off valve. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0038] Example 1

[0039] This embodiment provides a combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle, such as... Figure 1 As shown, it includes: a biogas gas turbine power generation module, an aeration tank photovoltaic power generation module, a carbon dioxide cycle power generation module, and a heat storage module;

[0040] The biogas generator module uses biogas produced by the fermentation of sludge from the sewage treatment plant as fuel to drive the biogas generator to generate electricity, thus making full use of the biogas resources generated in the sewage treatment plant.

[0041] The carbon dioxide cycle power generation module is based on the ideal Ericsson cycle principle, generating electricity through isothermal compression and expansion, and isobaric heat absorption and release processes. During off-peak electricity demand, carbon dioxide is compressed and stored through photovoltaic power generation or off-peak grid electricity, and heated using waste heat from the gas turbine and a heat storage module before entering the expander for power generation. The carbon dioxide cycle power generation module includes: an energy storage unit, a high-pressure expander 11, a low-pressure expander 13, a high-pressure heater, a low-pressure heater, and a generator; the high-pressure expander 11, the low-pressure expander 13, and the generator are connected in sequence; the energy storage unit includes: a high-pressure compressor 3, a low-pressure heater 4, a high-pressure heater 5, a low-pressure heater 6, and a generator 7. The system includes a compressor 1, a high-pressure carbon dioxide storage tank 6, and a low-pressure carbon dioxide storage tank 17. The flue gas outlets of the high-pressure heater and the low-pressure heater are connected to the sludge drying tank, allowing the waste heat flue gas from the heaters, which undergoes superheat exchange with carbon dioxide, to provide the sludge to be dried with the appropriate heat to meet the drying temperature requirements. A carbon dioxide-to-carbon dioxide heat exchanger 8 and a heat storage fluid-to-carbon dioxide heat exchanger 9 are provided between the high-pressure heater and the energy storage unit. The outlet of the carbon dioxide-to-carbon dioxide heat exchanger 8 is connected in series with a heat exchanger in the sludge anaerobic digestion tank, and the carbon dioxide in the pipeline provides the sludge to be heated with the appropriate heat to meet the anaerobic digestion conditions.

[0042] In the photovoltaic power generation module of the aeration tank, a photovoltaic power generation unit is installed on the aeration tank to compress carbon dioxide using photovoltaic power generation or off-peak electricity from the power grid and store it in a high-pressure gas storage tank.

[0043] The heat storage module is used to store waste heat from the gas turbine and releases this heat to heat carbon dioxide during peak electricity demand, thereby increasing power generation. The heat storage module includes a cold tank, a hot tank, a cold heat storage fluid, and a waste heat flue gas heat exchanger 22. The heat storage module is located after the biogas gas turbine power generation module. The cold tank is a cold heat storage fluid storage tank 20, and the hot tank is a hot heat storage fluid storage tank 24.

[0044] In a specific embodiment, in the energy storage unit, a first carbon dioxide and cooling water heat exchanger 2 is provided between the high-pressure compressor 3 and the low-pressure compressor 1, so that the heat exchanged between the circulating cooling water and the compressed carbon dioxide in the first carbon dioxide and cooling water heat exchanger 2 is used to provide temperature conditions for the anaerobic digestion of sludge to produce biogas.

[0045] A second carbon dioxide and cooling water heat exchanger 4 is provided between the high-pressure compressor 3 and the high-pressure carbon dioxide storage tank 6, so that carbon dioxide is stored in the high-pressure carbon dioxide storage tank 6.

[0046] In a specific embodiment, in the carbon dioxide cycle power generation module, a third carbon dioxide and cooling water heat exchanger 14 is arranged in the pipeline of the high-pressure expander 11 and the low-pressure expander 13, so that the compression and expansion process in the carbon dioxide cycle is close to the ideal isothermal process. The heat exchanged between the circulating cooling water and the compressed carbon dioxide in the third carbon dioxide and cooling water heat exchanger 14 is used to provide temperature conditions for the anaerobic digestion of sludge to produce biogas.

[0047] In a specific embodiment, in the carbon dioxide cycle power generation module, the high-pressure heater is a waste heat flue gas and high-pressure carbon dioxide heat exchanger 10, and the low-pressure heater is a waste heat flue gas and low-pressure carbon dioxide heat exchanger 12.

[0048] In a specific embodiment, a carbon dioxide and air heat exchanger 15 is provided between the third carbon dioxide and cooling water heat exchanger 14 and the low-pressure carbon dioxide storage tank 17, so that the carbon dioxide after work is stored in the low-pressure carbon dioxide storage tank 17.

[0049] In a specific embodiment, the waste heat flue gas outlet pipe of the biogas turbine is provided with a first flue gas shut-off valve 27 and a second flue gas shut-off valve 28, which are used to control the heat storage process and heat carbon dioxide, respectively.

[0050] In a specific implementation, the heat storage module includes a first carbon dioxide shut-off valve 5 installed at the inlet pipe of the high-pressure carbon dioxide storage tank 6, a second carbon dioxide shut-off valve 16 installed at the inlet pipe of the low-pressure carbon dioxide storage tank 17, a first carbon dioxide flow control valve 7 installed at the outlet pipe of the high-pressure carbon dioxide storage tank 6, and a second carbon dioxide flow control valve 18 installed at the outlet pipe of the low-pressure carbon dioxide storage tank 17. The flow control valves are adjusted according to the temperature and flow rate of the waste heat flue gas from the biogas generator, thereby dynamically adjusting the carbon dioxide levels.

[0051] In a specific embodiment, a first heat storage fluid flow control valve 21 is installed at the outlet of the cold tank. The first heat storage fluid flow control valve 21 is controlled according to the waste heat temperature and flow rate of the biogas generator, thereby adjusting the outlet flow rate of the heat storage fluid in the cold tank.

[0052] A second thermal storage fluid flow control valve 25 is installed at the outlet of the hot tank. The flow rate of the thermal storage fluid at the outlet of the hot tank is controlled by the flow rate of carbon dioxide.

[0053] In a specific embodiment, a flue gas flow control valve 19 is installed at the flue gas inlet of the low-pressure heater. The flue gas flow control valve 19 is adjusted according to the temperature and flow rate of the waste heat flue gas from the biogas generator, thereby dynamically adjusting the flue gas flow rate.

[0054] In a specific embodiment, a second heat storage fluid shut-off valve 26 is provided between the cold tank, the heat storage fluid and the carbon dioxide heat exchanger 9, and a first heat storage fluid shut-off valve 23 is provided between the cold heat storage fluid and the waste heat flue gas heat exchanger 22 and the hot tank.

[0055] The specific work process is as follows:

[0056] During periods of low electricity demand, electricity generated from off-peak power grids or from photovoltaic devices installed in the aeration tank of the wastewater treatment plant is used to control the low-temperature, low-pressure carbon dioxide in the low-pressure carbon dioxide storage tank 17 via the second carbon dioxide flow control valve 18. This carbon dioxide is then compressed in the low-pressure compressor 1, reaching a certain pressure before entering the first carbon dioxide and cooling water heat exchanger 2 for cooling. The circulating cooling water in the first carbon dioxide and cooling water heat exchanger 2 provides the necessary temperature conditions for biogas fermentation by surrounding the sludge anaerobic digester in the wastewater treatment plant through pipelines. After exchanging heat with the cooling water in the carbon dioxide and cooling water heat exchanger 2, the carbon dioxide enters the high-pressure compressor 3 and is compressed to a specified pressure. Then, the carbon dioxide enters the second carbon dioxide and cooling water heat exchanger 4 to exchange heat with the cooling water. The inlet and outlet circulating cooling water in the second carbon dioxide and cooling water heat exchanger 4 surrounds the anaerobic sludge consumption pond in the sewage treatment plant through pipelines, providing the temperature conditions for biogas fermentation of the sludge in the pond. After exchanging heat with the cooling water in the second carbon dioxide and cooling water heat exchanger 4, the high-pressure carbon dioxide is stored in the high-pressure carbon dioxide storage tank 6 through the first carbon dioxide shut-off valve 5. Simultaneously, the second flue gas shut-off valve 28 is closed, and the first flue gas shut-off valve 27 is open. The waste heat flue gas from the biogas generator enters the cold heat storage fluid and waste heat flue gas heat exchanger 22, where it exchanges heat with the heat storage fluid in the cold heat storage fluid storage tank 20, which passes through the first heat storage fluid flow control valve 21. The heat storage fluid, after absorbing the waste heat from the flue gas, flows through the first heat storage fluid shut-off valve 23 into the hot heat storage fluid storage tank 24.

[0057] During peak electricity consumption periods, the high-pressure carbon dioxide storage tank 6 dynamically monitors and controls the carbon dioxide outlet flow rate of the first carbon dioxide flow control valve 7 based on the flow rate and temperature of the waste heat flue gas from the biogas turbine. After exchanging heat with the carbon dioxide after it has done work in the carbon dioxide heat exchanger 8, it enters the heat storage fluid heat exchanger 9 to exchange heat with the heat storage fluid. At this time, the outlet flow rate of the second heat storage fluid flow control valve 25 is controlled according to the set temperature of the carbon dioxide outlet of the preheater. The heat-exchanged heat storage fluid flows back to the cold heat storage fluid storage tank 20 through the second heat storage fluid shut-off valve 26 for the next heat storage process. Afterwards, the system controls the outlet flue gas flow rate of the flue gas flow valve 19 according to the set carbon dioxide temperature to ensure that the outlet temperature of the waste heat flue gas is consistent with that of the high-pressure carbon dioxide heat exchanger 10 and the low-pressure carbon dioxide heat exchanger 12. The carbon dioxide exiting the heat storage fluid and carbon dioxide heat exchanger 9 enters the waste heat flue gas and high-pressure carbon dioxide heat exchanger 10, raising its temperature to a specified level. There, it performs work in the high-pressure expander 11. Simultaneously, the carbon dioxide after performing work in the high-pressure expander 11 exchanges heat with another portion of the high-temperature waste heat flue gas from the biogas generator in the waste heat flue gas and low-pressure carbon dioxide heat exchanger 12, raising its temperature again to a specified level. This carbon dioxide then enters the low-pressure expander 13 to perform work, simultaneously driving the generator to produce electricity along with the high-pressure expander 11. The waste heat flue gas from both the high-pressure and low-pressure carbon dioxide heat exchangers 10 and 12, after heat exchange with carbon dioxide, is uniformly recovered and transported through pipelines for use in drying sludge at the wastewater treatment plant. The carbon dioxide that has completed its work in the low-pressure expander 13 enters the carbon dioxide-carbon dioxide heat exchanger 8, where it transfers heat to the cold-end carbon dioxide before it enters the heat storage fluid-carbon dioxide heat exchanger 9, raising its temperature. The cooled, medium-temperature carbon dioxide then transfers its heat through pipelines for use in drying sludge in the wastewater treatment plant. After this process, the carbon dioxide enters the third carbon dioxide-cooling water heat exchanger 14 to exchange heat with the cooling water. The circulating cooling water in the inlet and outlet of the third carbon dioxide-cooling water heat exchanger 14 surrounds the sludge anaerobic digester in the wastewater treatment plant through pipelines, providing the temperature conditions for biogas fermentation. After exchanging heat with the third carbon dioxide-cooling water heat exchanger 14, the low-pressure carbon dioxide exiting the heat exchanger enters the carbon dioxide-air heat exchanger 15, where it is cooled to ambient temperature. After flowing through the second carbon dioxide shut-off valve 16, it is sent to the low-pressure carbon dioxide storage tank 17. This completes the process of photovoltaic power generation in the co-generation and storage peak-shaving aeration tank of the wastewater treatment plant, and the combined power generation of biogas and carbon dioxide through the anaerobic consumption of sludge.

[0058] Components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0059] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle, characterized in that, include: Biogas gas turbine power generation module, aeration tank photovoltaic power generation module, carbon dioxide cycle power generation module, and thermal storage module; The biogas generator module uses biogas produced by the fermentation of sludge from the sewage treatment plant as fuel to drive the biogas generator to generate electricity. The carbon dioxide cycle power generation module is based on the ideal Ericsson cycle principle and generates electricity through isothermal compression and expansion, isobaric heat absorption and release processes. During off-peak hours, carbon dioxide is compressed and stored through photovoltaic power generation or off-peak electricity from the grid, and the waste heat from the gas turbine and the heat storage module are used to heat the carbon dioxide before it enters the expander to generate electricity. The carbon dioxide cycle power generation module includes: an energy storage unit, a high-pressure expander (11), a low-pressure expander (13), a high-pressure heater, a low-pressure heater, and a generator; the high-pressure expander (11), the low-pressure expander (13), and the generator are connected in sequence; the energy storage unit includes: a high-pressure compressor (3), a low-pressure compressor (1), a high-pressure carbon dioxide storage tank (6), and a low-pressure carbon dioxide storage tank (17); the flue gas outlets of the high-pressure heater and the low-pressure heater are connected to the sludge drying tank, so that the waste heat flue gas in the heater that has undergone superheat exchange with carbon dioxide provides the corresponding heat for the sludge to be dried to meet the drying temperature conditions; a carbon dioxide-to-carbon dioxide heat exchanger (8) and a heat storage fluid-to-carbon dioxide heat exchanger (9) are provided between the high-pressure heater and the energy storage unit; the outlet of the carbon dioxide-to-carbon dioxide heat exchanger (8) is connected in series with the heat exchanger in the sludge anaerobic digestion tank, and the carbon dioxide in the pipeline provides the corresponding heat for the sludge to be heated to meet the anaerobic digestion conditions; In the photovoltaic power generation module of the aeration tank, a photovoltaic power generation unit is installed on the aeration tank to compress carbon dioxide using photovoltaic power generation or off-peak electricity from the power grid and store it in a high-pressure gas storage tank. The heat storage module is used to store the waste heat of the gas turbine and release the heat to heat carbon dioxide during peak electricity demand, thereby increasing the power generation. The heat storage module includes: a cold tank, a hot tank, a cold heat storage fluid and a waste heat flue gas heat exchanger (22). The heat storage module is located after the biogas gas turbine power generation module.

2. The combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle according to claim 1, characterized in that, In the energy storage unit, a first carbon dioxide and cooling water heat exchanger (2) is provided between the high-pressure compressor (3) and the low-pressure compressor (1), so that the heat exchanged between the circulating cooling water and the compressed carbon dioxide in the first carbon dioxide and cooling water heat exchanger (2) is used to provide temperature conditions for the anaerobic digestion of sludge to produce biogas. A second carbon dioxide and cooling water heat exchanger (4) is provided between the high-pressure compressor (3) and the high-pressure carbon dioxide storage tank (6) so that carbon dioxide is stored in the high-pressure carbon dioxide storage tank (6).

3. The combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle according to claim 1, characterized in that, In the carbon dioxide cycle power generation module, a third carbon dioxide and cooling water heat exchanger (14) is arranged in the pipelines of the high-pressure expander (11) and the low-pressure expander (13), so that the compression and expansion process in the carbon dioxide cycle is close to the ideal isothermal process. The heat exchanged between the circulating cooling water and the compressed carbon dioxide in the third carbon dioxide and cooling water heat exchanger (14) is used to provide temperature conditions for the anaerobic digestion of sludge to produce biogas.

4. A combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle according to claim 1, characterized in that, In the carbon dioxide cycle power generation module, the high-pressure heater is a waste heat flue gas and high-pressure carbon dioxide heat exchanger (10), and the low-pressure heater is a waste heat flue gas and low-pressure carbon dioxide heat exchanger (12).

5. A combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle according to claim 3, characterized in that, A carbon dioxide and air heat exchanger (15) is provided between the third carbon dioxide and cooling water heat exchanger (14) and the low-pressure carbon dioxide storage tank (17), so that the carbon dioxide after work is stored in the low-pressure carbon dioxide storage tank (17).

6. A combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle according to claim 1, characterized in that, The waste heat flue gas outlet pipe of the biogas turbine is equipped with a first flue gas shut-off valve (27) and a second flue gas shut-off valve (28), which are used to control the heat storage process and heat carbon dioxide, respectively.

7. A combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle according to claim 1, characterized in that, In the heat storage module, a first carbon dioxide shut-off valve (5) is installed at the inlet pipe of the high-pressure carbon dioxide storage tank (6), a second carbon dioxide shut-off valve (16) is installed at the inlet pipe of the low-pressure carbon dioxide storage tank (17), a first carbon dioxide flow control valve (7) is installed at the outlet pipe of the high-pressure carbon dioxide storage tank (6), and a second carbon dioxide flow control valve (18) is installed at the outlet pipe of the low-pressure carbon dioxide storage tank (17).

8. A combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle according to claim 1, characterized in that, A first heat storage fluid flow control valve (21) is installed at the outlet of the cold tank. The first heat storage fluid flow control valve (21) is controlled according to the waste heat temperature and flow rate of the biogas generator, thereby adjusting the outlet flow rate of the heat storage fluid in the cold tank. A second thermal storage fluid flow control valve (25) is installed at the outlet of the hot tank. The flow rate of the second thermal storage fluid is controlled according to the carbon dioxide flow rate, thereby controlling the outlet flow rate of the thermal storage fluid at the outlet of the hot tank.

9. A combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle according to claim 1, characterized in that, A flue gas flow control valve (19) is installed at the flue gas inlet of the low-pressure heater. The flue gas flow control valve (19) is adjusted according to the temperature and flow rate of the waste heat flue gas from the biogas generator, thereby dynamically adjusting the flue gas flow rate.

10. A combined cycle power generation system for a wastewater treatment plant based on the ideal Ericsson cycle principle according to claim 1, characterized in that, A second heat storage fluid shut-off valve (26) is provided between the cold tank, the heat storage fluid and the carbon dioxide heat exchanger (9), and a first heat storage fluid shut-off valve (23) is provided between the cold heat storage fluid and the waste heat flue gas heat exchanger (22) and the hot tank.

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