Energy utilization integrated system and method for coupling photovoltaic power generation and compressed air energy storage

Abstract

The invention discloses a photovoltaic power generation and compressed air energy storage coupled energy comprehensive utilization system and method. The system comprises a photovoltaic power generation unit, a compressed air energy storage unit, a sludge treatment unit, a biogas power generation unit and an electric energy management unit. The photovoltaic power generation unit is arranged in a sewage treatment plant; the photovoltaic power generation unit is connected with the compressed air energy storage unit and the sludge treatment unit through the electric energy management unit; the output end of the compressed air energy storage unit is connected with the sewage treatment unit through the electric energy management unit; the output end of the biogas power generation unit is connected with the sewage treatment unit through the electric energy management unit; through the synergistic effect of photovoltaic power generation and compressed air energy storage, energy generated by sewage treatment is coupled, self-sufficiency of energy of a sewage treatment plant is achieved, dependence on an external power grid is reduced, meanwhile, traditional fossil energy is replaced with clean renewable energy and biogas generated by sludge digestion, and the carbon footprint of the sewage treatment plant is remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical fields of photovoltaic power generation and compressed air energy storage, and particularly relates to an energy comprehensive utilization system for coupling photovoltaic power generation and compressed air energy storage in a sewage treatment plant. Background Art

[0002] Sewage treatment plants are large energy consumers. Traditional sewage treatment processes rely on external power supply, with high operating costs and large carbon emissions. Due to the reasons of sewage treatment processes, sewage treatment plants usually cover a large area and are equipped with the conditions for installing distributed photovoltaic power generation systems, and the installed capacity is usually in the MW level. After installing the photovoltaic power generation system, sewage treatment plants usually adopt the operation mode of "spontaneous use for self and surplus electricity on-grid", that is, a part of the generated electricity is supplied for the self-use of the sewage treatment plant, and the remaining part is directly sold on the grid. Investigations show that the proportion of surplus electricity on-grid in some sewage treatment plants can reach 40%. Due to the large difference between the on-grid electricity price and the off-grid electricity price, for sewage treatment plants, surplus electricity on-grid cannot generate the maximum economic benefits. At the same time, due to the influence of weather, photovoltaic power generation is naturally intermittent and unstable, and direct application in sewage treatment plants may lead to mismatches between energy supply and demand. Compressed air energy storage technology, as an efficient energy storage method, can effectively solve the problem of unbalanced energy supply and demand. "Sewage treatment plant + photovoltaic energy storage" has become the only way for the long-term development of sewage treatment plants. Therefore, if an energy comprehensive utilization system that couples photovoltaic power generation and energy storage can be developed in combination with the special process flow of sewage treatment plants, it is of great significance for reducing the energy consumption and carbon emissions of sewage treatment plants.

[0003] Sludge anaerobic digestion is a very effective sludge treatment process that uses facultative bacteria and anaerobic bacteria to carry out anaerobic biochemical reactions to decompose organic substances in sludge and achieve sludge stabilization. Hydrolysis is a sludge anaerobic digestion pretreatment method with high efficiency. This method can dissolve the organic substances in sludge by using high temperature and high pressure to destroy the structure of cell walls and extracellular polymers, thereby improving the subsequent anaerobic digestion performance. According to the relevant process requirements of sewage treatment plants, the reaction temperature of the hydrolysis system is 160 - 200 °C, the reaction pressure is 0.6 - 1.6 MPa, and the hydrolyzed sludge should be cooled to meet the sludge inlet requirements of the subsequent digestion tank before entering the digestion tank.

[0004] Sludge anaerobic digestion will produce a large amount of biogas. Theoretically, every 1 kg of COD degraded can produce 0.35 Nm 3methane. Biogas power generation is one of the most common ways to utilize biogas in sewage treatment plants. It mainly consists of a biogas internal combustion engine, a waste heat boiler, a condensing extraction steam turbine generator set, etc. The exhaust gas temperature of the biogas internal combustion engine is usually between 400°C and 600°C. After heat exchange in the steam generator of the waste heat boiler, the exhaust gas temperature is generally 220°C - 250°C. After passing through the economizer of the waste heat boiler, the exhaust gas temperature needs to be higher than the flue gas dew point (about 120°C - 140°C).

[0005] Currently, the adiabatic compression scheme is usually adopted in the built non-supplementary combustion compressed air energy storage power plants, and the heat storage system generally uses 180°C high-temperature hot water or 330°C heat-conducting oil for heat storage. Although the overall efficiency of the power plant increases with the increase of the heat storage temperature, the investment cost of high-temperature heat-conducting oil is significantly higher than that of high-temperature hot water. For sewage treatment plants, using 180°C high-temperature hot water (corresponding saturated pressure is 1MPa) for heat storage is more cost-effective, and 180°C high-temperature hot water can match the temperature and pressure range of sludge hydrothermal hydrolysis.

[0006] In summary, the compression heat of compressed air energy storage can be used for sludge hydrothermal hydrolysis. The methane generated after sludge hydrothermal hydrolysis digestion can be used for power generation, and the waste heat after power generation can be used to increase the temperature of compressed air, thereby improving the efficiency of the expander. Therefore, for the sludge treatment process of sewage treatment plants, on the basis of supporting the construction of photovoltaic power generation and compressed air energy storage, it is necessary to develop a comprehensive energy utilization system to couple the waste heat of each link to improve the energy utilization efficiency of sewage treatment plants, reduce the energy consumption cost, and reduce carbon emissions. Summary of the Invention

[0007] The purpose of the present invention is to provide a comprehensive energy utilization system and method for coupling photovoltaic power generation and compressed air energy storage in sewage treatment plants, which can optimize energy supply and storage, reduce the operating cost of sewage treatment plants, and improve energy utilization efficiency.

[0008] To achieve the above purpose, the technical solution of the present invention is as follows:

[0009] A comprehensive energy utilization system for coupling photovoltaic power generation and compressed air energy storage in a sewage treatment plant, comprising: a sludge treatment unit, and further comprising a photovoltaic power generation unit, a compressed air energy storage unit, a biogas power generation unit, and an electric energy management unit;

[0010] The photovoltaic power generation unit is arranged in the sewage treatment plant;

[0011] The photovoltaic power generation unit is connected to the compressed air energy storage unit and the sludge treatment unit through the electric energy management unit;

[0012] The output end of the compressed air energy storage unit is connected to the sewage treatment unit through the electric energy management unit;

[0013] The output end of the biogas power generation unit is connected to the sewage treatment unit through an electric energy management unit.

[0014] Furthermore, the photovoltaic power generation unit is arranged on the roof of the sewage treatment plant building or above the aeration tank.

[0015] Furthermore, the compressed air energy storage unit includes a high-pressure gas storage tank. During the peak load of the sewage treatment plant, the compressed air in the high-pressure gas storage tank is released to drive the turbine to rotate, driving the generator to generate electric energy, and the electric energy is supplied to the sewage treatment unit through the electric energy management unit.

[0016] Furthermore, the sludge treatment unit includes a sludge hydrothermal hydrolysis reactor. The sludge hydrothermal hydrolysis reactor is connected to a sludge-water heat exchanger through a pipeline, and the sludge-water heat exchanger is connected to an anaerobic digester through a pipeline. The biogas generated by the anaerobic digester is transported through a pipeline to the biogas internal combustion engine included in the biogas power generation unit.

[0017] Furthermore, the biogas power generation unit includes a biogas internal combustion engine, a waste heat boiler, and a condensing extraction steam turbine generator set. The biogas generated by the sludge treatment unit is sent into the biogas internal combustion engine for power generation. The flue gas generated by the power generation is used to heat the feed water in the waste heat boiler to generate steam, and the steam is sent into the condensing extraction steam turbine generator set for power generation.

[0018] An energy comprehensive utilization method for the energy comprehensive utilization system described above, the method includes:

[0019] When there is no remaining power in the photovoltaic power generation unit, the power management unit automatically shuts down the power supply circuit to the compressed air energy storage unit, the compressed air energy storage unit cuts out the operating state, and the sewage treatment unit and the biogas power generation unit are in the main circuit operating state; the power management unit supplies power to the sewage treatment unit for sludge treatment;

[0020] When there is remaining power in the photovoltaic power generation unit, the power management unit automatically starts the power supply circuit to the compressed air energy storage unit, the compressed air energy storage unit is put into the operating state, and the sewage treatment unit and the biogas power generation unit are in the bypass operating state; the photovoltaic power generation unit supplies power to the compressed air energy storage unit through the power management unit; the electric energy generated by the operation of the compressed air energy storage unit is supplied to the sewage treatment unit through the power management unit; the biogas generated by the operation of the sewage treatment unit is transported to the biogas power generation unit for power generation, and the electric energy generated by the biogas power generation unit is supplied to the sewage treatment unit for use through the power management unit, and the excess electric energy is stored through the power management unit.

[0021] Furthermore, when there is no remaining power in the photovoltaic power generation unit, the heat source of the sludge hydrolysate reactor included in the sewage treatment unit switches to the main path operation mode. The first valve is closed, the second valve is opened, and steam is extracted from the extraction condensing steam turbine unit and supplied to the sludge hydrolysate reactor. The cooling water of the sludge-water heat exchanger switches to the main path operation mode. The third valve is closed, the fourth valve is opened, and the condensed water of the extraction condensing steam turbine unit is used for sludge-water cooling to increase the temperature of the condensed water. The feed water heated by the sludge-water heat exchanger is sent to the economizer of the waste heat boiler. The feed water of the economizer of the waste heat boiler switches to the main path operation mode. The fifth valve is closed, the sixth valve is opened, and all the feed water enters the steam generator of the waste heat boiler to generate superheated steam and send it to the extraction condensing steam turbine generator set for power generation.

[0022] Furthermore, when there is remaining power in the photovoltaic power generation unit and the compressed air energy storage unit is put into operation, the multi-stage compressor uses the electric energy generated by the photovoltaic power generation to compress the air under atmospheric pressure in stages. The compressed air enters the high-pressure gas storage tank. The cooling water flows through the first-stage cooler, the second-stage cooler, and the third-stage cooler respectively, and then enters the sludge hydrolysate reactor. The multi-stage expander uses the high-pressure air released from the high-pressure gas storage tank to expand and do work to drive the generator to generate electricity. Among them, the air flows through the high-pressure expander, the first-stage heater, the low-pressure expander, and the second-stage heater in sequence. The high-temperature water flows through the first-stage heater and the second-stage heater respectively and then returns to the low-temperature cold water tank.

[0023] The heat source of the sludge hydrolysate reactor switches to the bypass operation mode. The second valve is closed, the first valve is opened, and the high-temperature saturated water heated by the multi-stage intermediate cooler of the compressed air energy storage unit is supplied to the sludge hydrolysate reactor. The high-temperature saturated water reduces in pressure and flashes to become steam, providing a steam source for sludge hydrolysis. The cooling water of the sludge-water heat exchanger switches to the full operation mode. The third valve is opened, the fourth valve is opened, and the cold water in the low-temperature cold water tank and the condensed water of the extraction condensing steam turbine unit are used for sludge-water cooling to increase the water temperature. The cold water heated by the sludge-water heat exchanger is sent to the economizer of the waste heat boiler. The feed water of the economizer of the waste heat boiler switches to the full operation mode. The fifth valve and the sixth valve are opened simultaneously. A part of the feed water enters the high-temperature hot water tank, and the other part enters the steam generator of the waste heat boiler to generate superheated steam and send it to the extraction condensing steam turbine generator set for power generation.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. Improve energy utilization efficiency: Through the synergistic effect of photovoltaic power generation and compressed air energy storage, the present invention couples the energy generated by sewage treatment to achieve the self-sufficiency of energy in the sewage treatment plant and reduce the dependence on the external power grid.

[0026] 2. Reduce operating costs: Utilize clean and renewable energy to reduce electricity expenses, and at the same time achieve economic benefits through the peak-valley electricity price difference.

[0027] 3. Reduce carbon emissions: Utilize clean and renewable energy and biogas generated from sludge digestion to replace traditional fossil fuels, significantly reducing the carbon footprint of wastewater treatment plants.

[0028] 4. Enhance the operational stability of the sludge treatment plant: Compressed air energy storage effectively smooths out the fluctuations in photovoltaic power generation, ensuring the stable operation of the wastewater treatment plant.

[0029] 5. Save land resources:

[0030] Make full use of the existing space in the wastewater treatment plant to arrange photovoltaic power generation units and compressed air energy storage units, without the need to occupy additional land. Brief Description of the Drawings

[0031] Figure 1 It is the overall flowchart of the present invention

[0032] Figure 2 It is the schematic diagram of comprehensive utilization of waste heat of the present invention Detailed Embodiment

[0033] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific examples described herein are some embodiments of the present invention, rather than all embodiments, and are not intended to limit 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 fall within the scope of protection of the present invention.

[0034] The embodiment of the present invention provides an energy comprehensive utilization system for a wastewater treatment plant coupled with photovoltaic power generation and compressed air energy storage, including a photovoltaic power generation unit 1, a compressed air energy storage unit 2, a sludge treatment unit 3, a biogas power generation unit 4, and an electric energy management unit 5.

[0035] The photovoltaic power generation unit 1 is used to convert solar energy into electric energy. The photovoltaic power generation unit 1 is arranged on the roofs of wastewater treatment plant buildings, above aeration tanks and other available spaces, and at least includes a photovoltaic array, an inverter and a control system. The generated electric energy is sent to the electric energy management system 5 of the wastewater treatment plant.

[0036] The compressed air energy storage unit 2 is used for storing and releasing electric energy. The compressed air energy storage unit 2 mainly utilizes the electric energy generated by photovoltaic power generation during the low load period of the sewage treatment plant to compress air, and stores it in the high-pressure gas storage tank 231, and releases it during the high load period of the sewage treatment plant to drive the air turbine to generate electricity. Driving the air turbine to generate electricity is a technology that compresses air to push the turbine to rotate, and then drives the generator to generate electric energy. The compressed air energy storage unit 2 is arranged in the sewage treatment plant building, and the energy storage system capacity is determined according to factors such as the design scale of the sewage treatment plant, the installed capacity of photovoltaic power generation, and the electricity load of the sewage treatment plant. The compressed air energy storage unit 2 at least includes a multi-stage compressor, a multi-stage intercooler, a heat storage system, a high-pressure gas storage system, a multi-stage expander, a multi-stage intermediate heater, and its attached pumps, pipelines, valves, control systems, etc. The multi-stage compressor includes a low-pressure compressor 201, a medium-pressure compressor 202, and a high-pressure compressor 203; the multi-stage intercooler includes a first-stage cooler 211, a second-stage cooler 212, and a third-stage cooler 213. The intercooler adopts a shell-and-tube heat exchanger, and the shell-and-tube heat exchanger includes a tube-side pipeline and a shell-side pipeline. Among them, the compressed air passes through the tube-side pipeline, and the circulating cooling water passes through the shell-side pipeline; the heat storage system includes a low-temperature cold water tank 221 and a high-temperature hot water tank 222; the high-pressure gas storage system includes a high-pressure gas storage tank 231; the multi-stage expander includes a high-pressure expander 241 and a low-pressure expander 242; the multi-stage intermediate heater includes a first-stage heater 251 and a second-stage heater 252. The intermediate heater adopts a shell-and-tube heat exchanger, and the shell-and-tube heat exchanger includes a tube-side pipeline and a shell-side pipeline. Among them, the high-pressure air passes through the tube-side pipeline, and the heat storage medium passes through the shell-side pipeline. In the present invention, the compressed air gas storage tank uses a high-pressure steel gas storage tank as the gas storage space.

[0037] Such as Figure 1As shown, the output end of the low-pressure compressor 201 is connected to the inlet of the tube side pipeline of the first-stage cooler 211 through a pipeline, and the outlet of the shell side pipeline of the first-stage cooler 211 is connected to the sludge hydrothermal reactor 301 through a pipeline. The outlet of the tube side pipeline of the first-stage cooler 211 is connected to the input end of the medium-pressure compressor 202 through a connecting pipeline, the output end of the medium-pressure compressor 202 is connected to the inlet of the tube side pipeline of the second-stage cooler 212 through a pipeline, and the outlet of the shell side pipeline of the second-stage cooler 212 is connected to the sludge hydrothermal reactor 301 through a pipeline. The outlet of the tube side pipeline of the second-stage cooler 212 is connected to the input end of the high-pressure compressor 203 through a connecting pipeline, the output end of the high-pressure compressor 203 is connected to the inlet of the tube side pipeline of the third-stage cooler 213 through a pipeline, the outlet of the shell side pipeline of the third-stage cooler 213 is connected to the sludge hydrothermal reactor 301 through a pipeline, and the outlet of the tube side pipeline of the third-stage cooler 213 is connected to the input end of the high-pressure gas storage tank 231. Air flows through the low-pressure compressor 201, the first-stage cooler 211, the medium-pressure compressor 202, the second-stage cooler 212, the high-pressure compressor 203, and the third-stage cooler 213 in sequence, and then enters the high-pressure gas storage tank 231; the inlets of the shell side pipelines of the first-stage cooler 211, the second-stage cooler 212, and the third-stage cooler 213 are all connected to the cooling water source through pipelines. After the cooling water in the first-stage cooler 211, the second-stage cooler 212, and the third-stage cooler 213 completes the heat exchange, its temperature rises, and the cooling water in the first-stage cooler 211 flows into the sludge hydrothermal reactor 301 after completing the heat exchange; the cooling water in the second-stage cooler 212 flows into the sludge hydrothermal reactor 301 after completing the heat exchange; the cooling water in the third-stage cooler 213 flows into the sludge hydrothermal reactor 301 after completing the heat exchange. The first valve 601 is arranged on the pipeline connecting the outlets of the shell side pipelines of the first-stage cooler 211, the second-stage cooler 212, and the third-stage cooler 213 to the sludge hydrothermal reactor 301. When the first valve 601 is opened, the liquid in the first-stage cooler 211, the second-stage cooler 212, and the third-stage cooler 213 can flow into the sludge hydrothermal reactor 301, and when the first valve 601 is closed, the liquid in the first-stage cooler 211, the second-stage cooler 212, and the third-stage cooler 213 cannot flow into the sludge hydrothermal reactor 301.

[0038] The multi-stage expander utilizes the high-pressure air released from the high-pressure gas storage tank 231 to expand and do work, driving the generator to generate electricity. The output end of the high-pressure gas storage tank 231 is connected to the inlet of the tube side pipeline of the first-stage heater 251 through a pipeline. The outlet of the shell side pipeline of the first-stage heater 251 is connected to the inlet of the low-temperature cold water tank 221 through a pipeline; the outlet of the tube side pipeline of the first-stage heater 251 is connected to the input end of the high-pressure expander 241 through a pipeline. The output end of the high-pressure expander 241 is connected to the inlet of the tube side pipeline of the second-stage heater 252 through a pipeline. The outlet of the shell side pipeline of the second-stage heater 252 is connected to the inlet of the low-temperature cold water tank 221 through a pipeline; the outlet of the tube side pipeline of the second-stage heater 252 is connected to the input end of the low-pressure expander 242 through a pipeline. The compressed air in the low-pressure expander 242 is used to drive the air turbine to generate electricity. The outlet end of the high-temperature hot water tank 222 is connected to the inlets of the shell side pipelines of both the first-stage heater 251 and the second-stage heater 252. Among them, the high-pressure air in the high-pressure gas storage tank 231 flows through the first-stage heater 251, the high-pressure expander 241, the second-stage heater 252, and the low-pressure expander 242 in sequence. The high-temperature water flow in the first-stage heater 251 has its temperature reduced after heat exchange and returns to the low-temperature cold water tank 221 through a pipeline. The high-temperature water flow in the second-stage heater 252 has its temperature reduced after heat exchange and returns to the low-temperature cold water tank 221 through a pipeline. The low-temperature cold water tank 221 is connected to the shell side pipeline inlets of the first-stage cooler 211, the second-stage cooler 212, and the third-stage cooler 213 through pipelines.

[0039] The heat storage medium of the compressed air energy storage and heat storage system uses 180°C high-temperature saturated demineralized water, and the 180°C high-temperature saturated demineralized water flows in the shell side pipelines of the first-stage heater 251 and the second-stage heater 252. To maintain the non-vaporization of the 180°C water, nitrogen is used for constant pressure to maintain the pressures of the low-temperature cold water and the high-temperature hot water at 1 MPa.

[0040] In the present invention, the output end of the compressed air energy storage unit 2 is connected to the sewage treatment unit 3 through the power management unit 5. During the peak load of the sewage treatment plant, the compressed air in the high-pressure gas storage tank 231 is released to push the turbine to rotate, driving the generator to generate electricity, and the electric energy can supply power to the sewage treatment unit 3.

[0041] The sludge treatment unit 3 only focuses on the process flows, equipment, and buildings related to the present invention. The sludge treatment unit 3 involves a sludge pyrolysis system, a sludge anaerobic digestion system, a biogas collection and storage system, etc., and is used for anaerobic digestion of sludge to produce biogas. The sludge treatment unit 3 mainly includes a sludge hydrothermal reactor 301, a sludge-water heat exchanger 302, and an anaerobic digester 303. The system feeds the dewatered sludge (with a moisture content of about 80%) into the sludge hydrothermal reactor 301 through a pump or a conveying device, and injects high-temperature steam / saturated water into the reactor 301 to rapidly heat up the sludge. Under high temperature and high pressure conditions, the microbial cell walls in the sludge rupture, releasing intracellular organic matter, and at the same time, macromolecular organic matter decomposes into small-molecular substances. In the present invention, after the cooling water in the first-stage cooler 211, the second-stage cooler 212, and the third-stage cooler 213 completes heat exchange, its temperature rises. After the water with the increased temperature flows out of the first-stage cooler 211, the second-stage cooler 212, and the third-stage cooler 213, it flows into the sludge hydrothermal reactor 301 to heat up the sludge. The output end of the sludge hydrothermal reactor 301 is connected to the input end of the sludge-water heat exchanger 302 through a pipeline, the output end of the sludge-water heat exchanger 302 is connected to the input end of the anaerobic digester 303 through a pipeline, and the output end of the anaerobic digester 303 is connected to the input end of the biogas internal combustion engine 401. The sludge-water mixture generated by the sludge hydrothermal reactor 301 needs to be cooled by the sludge-water heat exchanger 302 before it can enter the anaerobic digester 303, and the sludge generates biogas in the anaerobic digester 303.

[0042] In the present invention, the output end of the anaerobic digester 303 is connected to the input end of the biogas internal combustion engine 401 through a pipeline, and the biogas generated by the anaerobic digester 303 is transported into the biogas internal combustion engine 401 to realize biogas power generation.

[0043] The biogas power generation unit 4 is used for biogas power generation and waste heat utilization. The biogas power generation unit 4 only focuses on the process flows and equipment related to the present invention. The biogas power generation unit mainly includes a biogas internal combustion engine 401, a waste heat boiler 402, a condensing extraction steam turbine generator set 403 and its related systems. The waste heat boiler 402 includes a waste heat boiler steam generator 4021 and a waste heat boiler economizer 4022. The output end of the biogas internal combustion engine 401 is connected to the input end of the waste heat boiler 402 through a pipeline, and the high-temperature flue gas discharged from the biogas internal combustion engine 401 is directly introduced into the flue gas inlet of the waste heat boiler 402 through a high-temperature resistant pipeline. The output end of the waste heat boiler 402 is connected to the input end of the condensing extraction steam turbine generator set 403 through a pipeline, and the steam generated by the waste heat boiler 402 is transported to the steam inlet of the condensing extraction steam turbine generator set 403 through the main steam pipeline.

[0044] In the present invention, the extraction condensing steam turbine unit 403 is connected to the sludge hydrothermal hydrolysis reactor 301 through a pipeline. The second valve 602 is arranged on the pipeline connecting the extraction condensing steam turbine unit 403 and the sludge hydrothermal hydrolysis reactor 301. When the second valve 602 is in the open state, steam at about 0.8 MPa and 180 °C can be extracted from the extraction condensing steam turbine unit 403 and supplied to the sludge hydrothermal hydrolysis reactor 301.

[0045] The low-temperature cold water tank 221 is connected to the mud-water heat exchanger 302 through a pipeline. The third valve 611 is arranged on the pipeline connecting the low-temperature cold water tank 221 and the mud-water heat exchanger 302. When the third valve 611 is opened, the cooling water in the low-temperature cold water tank 221 can flow into the mud-water heat exchanger 302. The mud-water heat exchanger 302 is connected to the extraction condensing steam turbine unit 403 through a pipeline. The fourth valve 612 is arranged on the pipeline connecting the output end of the extraction condensing steam turbine unit 403 and the input end of the mud-water heat exchanger 302. When the fourth valve 612 is opened, the condensate water of the extraction condensing steam turbine unit 403 can be used for cooling the mud and water in the mud-water heat exchanger 302.

[0046] The output end of the mud-water heat exchanger 302 is connected to the input end of the high-temperature hot water tank 222 through a pipeline. The fifth valve 621 is arranged on the pipeline connecting the mud-water heat exchanger 302 and the high-temperature hot water tank 222. When the fifth valve 621 is in the open state, the liquid that has completed heat exchange in the mud-water heat exchanger 302 can flow through the pipeline to the high-temperature hot water tank 222. The waste heat boiler steam generator 4021 and the waste heat boiler economizer 4022 are connected through a pipeline. The sixth valve 622 is arranged on the pipeline connecting the waste heat boiler steam generator 4021 and the waste heat boiler economizer 4022.

[0047] The biogas generated by the anaerobic digester 303 included in the sludge treatment unit 3 is sent to the biogas internal combustion engine 401 through a pipeline after being collected, purified, and pressurized for power generation. The flue gas generated by power generation is used to heat feed water through the waste heat boiler 402 to generate steam, and the steam is transported to the extraction condensing steam turbine generator set 403 for power generation. In the present invention, the electric energy generated by the biogas power generation unit 4 can be supplied to the sewage treatment unit 3 for use through the electric energy management unit 5.

[0048] The electric energy management unit 5 is mainly used for electric energy distribution and balancing the electricity load of the sewage treatment plant, including sending the surplus electric energy of the photovoltaic power generation unit 1 to the compressed air energy storage unit 2, distributing the electric energy generated by the biogas power generation unit 4, etc. The output end of the photovoltaic power generation unit 1 is connected to the sewage treatment unit 3 and the compressed air energy storage unit 2 respectively through the electric energy management unit 5. The photovoltaic power generation unit 1 can supply power to the sewage treatment unit 3 and the compressed air energy storage unit 2. The output end of the compressed air energy storage unit 2 is connected to the sewage treatment unit 3 through the electric energy management unit 5. The biogas generated by the sewage treatment unit 3 can be used for power generation by the biogas power generation unit 4. The output end of the biogas power generation unit 4 is connected to the sewage treatment unit 3 through the electric energy management unit 5.

[0049] The present invention also provides an operation mode of an integrated energy utilization system for coupling photovoltaic power generation and compressed air energy storage in a sewage treatment plant. In the present invention, the main circuit operation means that the sewage treatment unit 3 needs to draw power from the external power grid, and the bypass operation means that the sewage treatment unit 3 is powered by the photovoltaic power generation unit 1. The integrated energy utilization system of the present invention is pre-installed. The operation mode of the present invention includes:

[0050] (1) When the photovoltaic power generation unit has no surplus power

[0051] When the photovoltaic power generation system does not work at night or the power generation power of the photovoltaic power generation unit 1 is less than or equal to the sewage treatment power load during the day, the power management unit 5 automatically closes the power supply circuit to the compressed air energy storage unit 2, and the compressed air energy storage unit 2 cuts out the operation state and does not operate. The sewage treatment unit 3 and the biogas power generation unit 4 are in the main circuit operation state and need to draw power from the external power grid. The heat source of the sludge hydrolysate reactor 301 is switched to the main circuit operation mode. The first valve 601 is closed, and the second valve 602 is opened to extract steam at about 0.8 MPa and 180 °C from the extraction condensing steam turbine unit 403 and supply it to the sludge hydrolysate reactor 301. The cooling water of the sludge-water heat exchanger 302 is switched to the main circuit operation mode. The third valve 611 is closed, and the fourth valve 612 is opened to use the condensate water of the extraction condensing steam turbine unit 403 for sludge-water cooling to increase the temperature of the condensate water. The feed water heated by the sludge-water heat exchanger 302 is sent to the economizer 4022 of the waste heat boiler. The feed water of the economizer 4022 of the waste heat boiler is switched to the main circuit operation mode. The fifth valve 621 is closed, and the sixth valve 622 is opened, and all the feed water enters the steam generator 4021 of the waste heat boiler to generate superheated steam and send it to the extraction condensing steam turbine generator set 403 for power generation.

[0052] (2) When the photovoltaic power generation unit has surplus power

[0053] When the power generation power of the daytime photovoltaic power generation unit 1 is greater than the sewage treatment power load, the power management unit 5 automatically starts the power supply circuit to the compressed air energy storage unit 2, the compressed air energy storage unit 2 is put into operation, and the sewage treatment unit 3 and the biogas power generation unit 4 are in the bypass operation state.

[0054] When the compressed air energy storage unit 2 is put into operation, the multi-stage compressor uses the electric energy generated by photovoltaic power generation to compress the air under atmospheric pressure in stages. At the same time, the high-temperature and high-pressure air after compression is cooled in stages by the cooling water sent by the low-temperature cold water tank 221. The air flows through the low-pressure compressor 201, the first-stage cooler 211, the medium-pressure compressor 202, the second-stage cooler 212, the high-pressure compressor 203, and the third-stage cooler 213 in sequence, and then enters the high-pressure gas storage tank 231; the cooling water flows through the first-stage cooler 211, the second-stage cooler 212, and the third-stage cooler 213 and enters the sludge hydrothermal reactor 301. The multi-stage expander uses the high-pressure air released from the high-pressure gas storage tank 231 to expand and do work to drive the generator to generate electricity. The air flows through the first-stage heater 251, the high-pressure expander 241, the second-stage heater 252, and the low-pressure expander 242 in sequence. The high-temperature water flows through the first-stage heater 251 and the second-stage heater 252 and then returns to the low-temperature cold water tank 221.

[0055] The heat source of the sludge hydrothermal reactor 301 is switched to the bypass operation mode. The second valve 602 is closed, and the first valve 601 is opened. The high-temperature saturated water (1.0 MPa, 180 °C) heated by the multi-stage intermediate cooler of the compressed air energy storage unit is supplied to the sludge hydrothermal reactor 301. At this time, the high-temperature saturated water flashes into steam due to the sudden drop in pressure, providing a steam source for sludge hydrothermal hydrolysis. The cooling water of the mud-water heat exchanger 302 is switched to the full operation mode. The third valve 611 is opened, and the fourth valve 612 is opened. The cold water in the low-temperature cold water tank 221 and the condensate water of the extraction condensing steam turbine unit 403 are used for mud-water cooling and the water temperature is increased. The cold water heated by the mud-water heat exchanger 302 is sent to the economizer 4022 of the waste heat boiler. The feed water of the economizer 4022 of the waste heat boiler is switched to the full operation mode. At the same time, the fifth valve 621 is opened, and the sixth valve 622 is opened. Part of the feed water enters the high-temperature hot water tank 222, and the other part enters the steam generator 4021 of the waste heat boiler to generate superheated steam and send it to the extraction condensing steam turbine generator set for power generation. The hot water in the high-temperature hot water tank 222 is used to heat the air at the expander inlet during the operation of the multi-stage expander to improve the expander efficiency.

[0056] The present invention couples photovoltaic power generation with compressed air energy storage, uses a specific process for sewage treatment plant sludge treatment, comprehensively analyzes the energy consumption and production links, establishes an integrated energy utilization system to improve energy utilization efficiency, enhance system stability, reduce carbon emissions, lower the operating costs of sewage treatment plants, save land resources, and contribute to the realization of the "dual carbon" goal.

[0057] The above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or alterations can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. The obvious changes or alterations derived therefrom still fall within the protection scope of the present invention.

Claims

1. An energy comprehensive utilization system for coupling photovoltaic power generation and compressed air energy storage in a sewage treatment plant, comprising: The sludge treatment unit (3) is characterized in that it further comprises a photovoltaic power generation unit (1), a compressed air energy storage unit (2), a biogas power generation unit (4), and an electric energy management unit (5); The photovoltaic power generation unit (1) is arranged in the sewage treatment plant; The photovoltaic power generation unit (1) is connected to the compressed air energy storage unit (2) and the sludge treatment unit (3) through the electric energy management unit (5); The output end of the compressed air energy storage unit (2) is connected to the sewage treatment unit (3) through the electric energy management unit (5); The output end of the biogas power generation unit (4) is connected to the sewage treatment unit (3) through the electric energy management unit (5).

2. The integrated energy utilization system for sewage treatment plants coupled with photovoltaic power generation and compressed air energy storage according to claim 1, characterized in that: The photovoltaic power generation unit (1) is arranged on the roof of the sewage treatment plant building or above the aeration tank.

3. The energy comprehensive utilization system for coupling photovoltaic power generation and compressed air energy storage in a sewage treatment plant according to claim 1, characterized in that: The compressed air energy storage unit (2) includes a high-pressure gas storage tank (231). During the peak load of the sewage treatment plant, the compressed air in the high-pressure gas storage tank (231) is released to drive the turbine to rotate, driving the generator to generate electric energy, and the electric energy is supplied to the sewage treatment unit (3) through the electric energy management unit (5).

4. An energy comprehensive utilization system for coupling photovoltaic power generation and compressed air energy storage in a sewage treatment plant according to claim 1, characterized in that: The sludge treatment unit (3) includes a sludge hydrothermal hydrolysis reactor (301). A first valve (601) is provided on the connecting pipeline between the sludge hydrothermal hydrolysis reactor (301) and the multi-stage intermediate cooler; the multi-stage intermediate cooler and the sludge hydrothermal hydrolysis reactor (301) are connected to the sludge-water heat exchanger (302) through a pipeline, and a third valve (611) is provided on the connecting pipeline between the low-temperature cold water tank (221) and the sludge-water heat exchanger (302); the sludge-water heat exchanger (302) is connected to the anaerobic digester (303) through a pipeline, and the biogas generated by the anaerobic digester (303) is transported through a pipeline into the biogas internal combustion engine (401) included in the biogas power generation unit (4).

5. The energy comprehensive utilization system for coupling photovoltaic power generation and compressed air energy storage in a sewage treatment plant according to claim 1, characterized in that: The biogas power generation unit (4) includes a biogas internal combustion engine (401), a waste heat boiler (402), and a condensing extraction steam turbine generator set (403). The biogas generated by the sludge treatment unit (3) is sent into the biogas internal combustion engine (401) for power generation. The flue gas generated by the power generation is used to heat the feed water in the waste heat boiler (402) to generate steam, and the steam is sent into the condensing extraction steam turbine generator set (403) for power generation. A second valve (602) is provided on the connecting pipeline between the condensing extraction steam turbine generator set (403) and the sludge hydrothermal hydrolysis reactor (301), and on the pipeline connecting the sludge-water heat exchanger (302) and the condensing extraction steam turbine generator set 403; a fourth valve (612) is provided on the connecting pipeline between the sludge-water heat exchanger (302) and the condensing extraction steam turbine generator set (403).

6. An energy comprehensive utilization method for the energy comprehensive utilization system according to any one of claims 1-5, the method comprising: When the photovoltaic power generation unit (1) has no remaining power, the power management unit (5) automatically closes the power supply circuit to the compressed air energy storage unit (2), the compressed air energy storage unit cuts out the operating state, and the sewage treatment unit (3) and the biogas power generation unit (4) are in the main circuit operating state; the power management unit (5) supplies power to the sewage treatment unit (3) for sludge treatment; When the photovoltaic power generation unit (1) has surplus power, the power management unit (5) automatically activates the power supply circuit to the compressed air energy storage unit (2), and the compressed air energy storage unit (2) is put into the operating state. The sewage treatment unit (3) and the biogas power generation unit (4) are in the bypass operating state. The photovoltaic power generation unit (1) supplies power to the compressed air energy storage unit (2) through the power management unit (5). The electric energy generated by the operation of the compressed air energy storage unit (2) supplies power to the sewage treatment unit (3) through the power management unit (5). The biogas generated by the operation of the sewage treatment unit (3) is transported to the biogas power generation unit (4) for power generation, and the electric energy generated by the biogas power generation unit (4) is supplied to the sewage treatment unit (3) for use through the power management unit (5), and the surplus electric energy is stored through the power management unit (5).

7. An energy comprehensive utilization method according to claim 6, characterized in that: When the photovoltaic power generation unit (1) has no surplus power, the heat source of the sludge hydrolysate reactor (301) included in the sewage treatment unit (3) switches to the main circuit operation mode. The first valve (601) is closed, and the second valve (602) is opened to extract steam from the extraction condensing steam turbine unit (403) and supply it to the sludge hydrolysate reactor (301). The cooling water of the sludge-water heat exchanger (302) switches to the main circuit operation mode. The third valve (611) is closed, and the fourth valve (612) is opened to use the condensate water of the extraction condensing steam turbine unit (403) for sludge-water cooling to increase the temperature of the condensate water. The feed water heated by the sludge-water heat exchanger (302) is sent to the economizer (4022) of the waste heat boiler. The feed water of the economizer (4022) of the waste heat boiler switches to the main circuit operation mode. The fifth valve (621) is arranged on the connecting pipeline between the sludge-water heat exchanger (302) and the high-temperature hot water tank (222), and the sixth valve (622) is arranged on the connecting pipeline between the steam generator (4021) of the waste heat boiler and the economizer (4022) of the waste heat boiler. The fifth valve (621) is closed, and the sixth valve (622) is opened, and all the feed water enters the steam generator (4021) of the waste heat boiler to generate superheated steam and send it to the extraction condensing steam turbine generator set (403) for power generation.

8. An energy comprehensive utilization method according to claim 6, characterized in that: When the photovoltaic power generation unit (1) has surplus power and the compressed air energy storage unit (2) is put into operation, the multi-stage compressor uses the electric energy of photovoltaic power generation to compress the air under atmospheric pressure in stages. The compressed air enters the high-pressure gas storage tank (231). The cooling water flows into the sludge hydrolysate reactor (301). The multi-stage expander uses the high-pressure air released from the high-pressure gas storage tank (231) to expand and do work to drive the generator to generate electricity. The high-temperature water flows through the first-stage heater (251) and the second-stage heater (252) respectively and then returns to the low-temperature cold water tank (221). The heat source of the sludge hydrothermal reactor (301) is switched to the bypass operation mode. The second valve (602) is closed and the first valve (601) is opened. The high-temperature saturated water heated by the multi-stage intermediate cooler of the compressed air energy storage unit is supplied to the sludge hydrothermal reactor (301). The pressure of the high-temperature saturated water drops and flash evaporation occurs, turning it into steam, which provides the steam source for sludge hydrothermal hydrolysis. The cooling water of the sludge-water heat exchanger (302) is switched to the full operation mode. The third valve (611) is opened and the fourth valve (612) is opened. The cold water in the low-temperature cold water tank (221) and the condensate water of the extraction condensing steam turbine unit (403) are used for sludge-water cooling to raise the water temperature. The cold water heated by the sludge-water heat exchanger (302) is sent to the economizer (4022) of the waste heat boiler. The feed water of the economizer (4022) of the waste heat boiler is switched to the full operation mode. The fifth valve (621) and the sixth valve (622) are opened simultaneously. Part of the feed water enters the high-temperature hot water tank (222), and the other part enters the steam generator (4021) of the waste heat boiler to generate superheated steam, which is sent to the extraction condensing steam turbine generator set for power generation.

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