Water and electricity cogeneration peak shaving system and operation method

Abstract

The invention discloses a water and electricity cogeneration peak shaving system and an operation method, and relates to the technical field of energy power. The water and electricity cogeneration peak shaving system comprises an ASU subsystem, an Allam subsystem and a refrigerated centrifugal desalination subsystem, and electric power generated by the Allam subsystem is used for being transmitted to the ASU subsystem, the refrigerated centrifugal desalination subsystem and a user side; the refrigeration centrifugal desalination subsystem can make supercooled water into ice slurry, and the ice slurry can exchange heat with backflow carbon dioxide, so that the backflow carbon dioxide is liquefied, and the ice slurry subjected to heat exchange forms fresh water. Allam circulation, an energy storage peak regulation technology and a refrigerated centrifugal desalination technology can be combined, so that efficient utilization of energy, stable supply of electric power and effective production of fresh water are realized.

Description

Technical Field

[0001] This invention relates to the field of energy and power technology, and in particular to a combined hydropower peak-shaving system and its operation method. Background Technology

[0002] The Allam cycle is an energy conversion technology that uses supercritical carbon dioxide (sCO2) as the working fluid. However, the Allam cycle still faces some challenges in practical applications. When operating under variable load conditions, its power regulation range is limited to only 40% to 100% due to the constraints of the air separation unit (ASU), making it difficult to meet more flexible power regulation requirements. Furthermore, its performance is limited by the critical characteristics of CO2 and its high sensitivity to cooling temperature, especially in high-temperature environments where system performance is easily degraded.

[0003] The emergence of energy storage peak-shaving technology offers a new approach to solving the aforementioned problems. This technology can store excess energy generated during variable load operation of generating units and release it during peak electricity demand periods. It boasts significant advantages such as low operating costs and high economic benefits, effectively balancing electricity supply and demand and improving the stability and reliability of the power system. Combining energy storage peak-shaving technology (cold storage) with the Allam cycle is expected to compensate for the Allam cycle's shortcomings in power regulation and high-temperature environments, further leveraging its advantages in energy conversion.

[0004] In the field of freshwater supply, cryogenic centrifugal desalination technology, which combines the advantages of freezing and centrifugation, has demonstrated unique value. Through the synergistic effect of phase change separation and centrifugal enhancement, this technology retains the advantages of simple pretreatment and low equipment corrosion rate of cryogenic methods, while achieving efficient separation of ice crystals and salt through centrifugal force field enhancement. This effectively overcomes the drawback of traditional freezing methods requiring secondary treatment, providing a more economical and reliable technological option for seawater desalination.

[0005] Currently, there is a lack of a technical solution that can combine Allam cycle, energy storage peak shaving technology, and refrigerated centrifugal desalination technology to achieve efficient energy utilization, stable power supply, and effective freshwater production. Summary of the Invention

[0006] The purpose of this invention is to provide a combined hydropower peak shaving system and its operation method to solve the problems existing in the prior art. It can combine Allam cycle, energy storage peak shaving technology and refrigerated centrifugal desalination technology to achieve efficient energy utilization, stable power supply and effective freshwater production.

[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides a combined hydropower peak-shaving system, comprising: The ASU subsystem is capable of separating oxygen from the air; The Allam subsystem can mix and burn natural gas with oxygen separated from the ASU subsystem, and use the working fluid produced by combustion to generate electricity; after the working fluid has done work, water is separated to form reflux carbon dioxide, which can be pressurized by the circulation module and mixed with the oxygen separated and delivered by the ASU subsystem for reheating, and then mixed and burned with natural gas again; The refrigerated centrifugal desalination subsystem, connected to the circulation module, can use the reflux carbon dioxide pressurized by the circulation module to exchange heat with seawater, so that the seawater becomes subcooled water. The reflux carbon dioxide after heat exchange can be returned to the circulation module for repressurization. The repressurized reflux carbon dioxide is used for heat exchange with seawater or for mixing and reheating with the oxygen separated and transported by the ASU subsystem, and then mixing and burning with natural gas. The electricity generated by the Allam subsystem is used to supply the ASU subsystem, the cryogenic centrifugal desalination subsystem, and the user end; the cryogenic centrifugal desalination subsystem can turn supercooled water into ice slurry, which can exchange heat with reflux carbon dioxide to liquefy the reflux carbon dioxide and form fresh water from the heat-exchanged ice slurry.

[0008] Preferably, the ASU subsystem includes an air separation unit and a mixing compressor connected in series. The air separation unit is capable of separating oxygen from the air and delivering it to the mixing compressor. The mixing compressor is capable of mixing and pressurizing pressurized reflux carbon dioxide with oxygen and delivering the mixed and pressurized material to the Allam subsystem.

[0009] Preferably, the Allam subsystem includes a combustion expansion module, a regenerative heating module, a gas-liquid separation module, and a circulation module, wherein the circulation module is a carbon dioxide compression module; when the Allam subsystem is running, natural gas and oxygen provided by the ASU subsystem are mixed and burned in the combustion expansion module to produce a high-temperature and high-pressure working fluid, which then expands in a cooled turbine, and the cooled turbine drives a generator to generate electricity. After generating electricity, the working fluid enters the regenerative heating module to exchange heat with the mixed and pressurized material. The heat-exchanged material is then transported to the combustion expansion module. The heat-exchanged working fluid flows into the gas-liquid separation module, where water is separated to form reflux carbon dioxide. After removing the incremental carbon dioxide from the circulation, the reflux carbon dioxide enters the carbon dioxide compression module to be pressurized to the required pressure. Finally, it returns to the combustion expansion module via the regenerative heating module.

[0010] Preferably, the combustion expansion module includes a natural gas compressor, a burner, a cooled turbine, and a generator connected in sequence via pipelines; the natural gas compressor can compress natural gas from the natural gas pipeline and deliver it to the burner; after the reflux carbon dioxide is pressurized and mixed with oxygen for reheating, it is delivered to the burner via a reheating module; the burner can deliver the combusted working fluid to the cooled turbine for driving the generator to generate electricity.

[0011] Preferably, the regenerative heating module includes a regenerator and a bypass compressor; the output end of the cooled turbine is connected to the heat release section of the regenerator through two carbon dioxide branches, which can transport the working fluid after power generation to the regenerator; the output end of the heat release section of the regenerator is connected to three output branches, two of which are connected to the gas-liquid separation module, and the third output branch is connected to the bypass compressor, the output end of which is connected to the heat release section of the regenerator; the output end of the heat absorption section of the regenerator is connected to the burner and the cooled turbine through branches, and the input end of the heat absorption section of the regenerator is connected to the output ends of the mixing compressor and the carbon dioxide compression module, respectively.

[0012] Preferably, the gas-water separation module includes a first gas-water separator and a second gas-water separator arranged in parallel. The water outlets of the first gas-water separator and the second gas-water separator are connected to a fresh water storage tank, and the gas outlets of the first gas-water separator and the second gas-water separator are connected to the carbon dioxide compression module. The inputs of the first gas-water separator and the second gas-water separator are connected to the output of the heat release section of the regenerator.

[0013] Preferably, the carbon dioxide compression module includes a carbon dioxide compressor unit, a low-pressure carbon dioxide pump, a medium-pressure carbon dioxide pump, and a high-pressure carbon dioxide pump. The outlet of the first gas-liquid separator is connected in series with the first-stage compressor, second-stage compressor, third-stage compressor, and fourth-stage compressor of the carbon dioxide compressor unit via a pipeline. The end of the fourth-stage compressor is connected to the medium-pressure carbon dioxide pump via a first circuit, and the end of the fourth-stage compressor is connected to the refrigerated centrifugal desalination subsystem via a second circuit. A first valve is provided on the second circuit. A second valve is provided on the pipeline between the first-stage compressor and the second-stage compressor. A third circuit is provided on the pipeline between the first-stage compressor and the second valve. A third valve, a condenser, and the low-pressure carbon dioxide pump are sequentially provided on the third circuit. The output of the low-pressure carbon dioxide pump is connected to the first circuit and the second circuit, respectively. The outlet of the second gas-liquid separator is connected to the first circuit via a pipeline. The medium-pressure carbon dioxide pump is connected to the input end of the heat absorption section of the regenerator via a pipeline connected to the high-pressure carbon dioxide pump. The medium-pressure carbon dioxide pump is also connected to the input end of the heat absorption section of the regenerator via a pipeline connected to the mixing compressor.

[0014] Preferably, the refrigerated centrifugal desalination subsystem includes a refrigeration module, a refrigerated centrifugal cold storage module, and a desalination cold release module; The refrigeration module includes a carbon dioxide compressor unit in a carbon dioxide compression module and a refrigeration compressor, an evaporator, and a throttle valve arranged sequentially on the second circuit; the end of the second circuit away from the first valve is connected to the first stage compressor. The refrigeration centrifugal cold storage module includes a water intake pump, a filter, an ice crystal generator, a centrifuge, and a freshwater ice crystal storage tank. One end of the water intake pump is connected to a seawater source, and the other end is connected to the filter. The filter is connected to the inlet of the evaporator and can deliver filtered seawater into the evaporator to form subcooled water. The outlet of the evaporator is sequentially connected to the ice crystal generator, the centrifuge, and the freshwater ice crystal storage tank. The desalination and cooling module includes a water pump, a condenser, an ice slurry pump, and a freshwater storage tank; the freshwater ice crystal storage tank is connected to the condenser through a pipeline equipped with a fourth valve and an ice slurry pump, and the water outlet of the condenser is connected to the freshwater storage tank; the freshwater storage tank is connected to the freshwater ice crystal storage tank through a pipeline equipped with a fifth valve and a water pump.

[0015] Preferably, a first-stage intercooler is provided between the second valve and the second-stage compressor, a second-stage intercooler is provided between the second-stage compressor and the third-stage compressor, a third-stage intercooler is provided between the third-stage compressor and the fourth-stage compressor, and a fourth-stage intercooler is provided for the fourth-stage compressor. The end of the fourth-stage intercooler is connected to the first circuit and the second circuit, respectively.

[0016] The present invention also provides an operation method for the aforementioned combined hydropower peak-shaving system, comprising the following steps: During periods of low electricity demand, the refrigerated centrifugal cold storage module operates in energy storage mode. At this time, apart from the carbon dioxide compressor unit running at full load, other components of the Allam subsystem operate at minimum load. Simultaneously, the first valve opens, and pressurized return carbon dioxide flows into the refrigeration module of the refrigerated centrifugal desalination subsystem to produce cold energy. The refrigerated centrifugal cold storage module is then used to produce freshwater ice crystals, which are stored in the freshwater ice crystal storage tank. The refrigeration module and the carbon dioxide compressor unit share the compression components, and the carbon dioxide compressor unit maintains full load operation. The refrigeration module and the refrigerated centrifugal cold storage module consume the electricity produced by the Allam subsystem and store it as cold energy in the freshwater ice crystal storage tank. During peak electricity demand periods, the Allam subsystem operates under overload conditions, and the refrigerated centrifugal cold storage module is in energy release mode. Since liquid fluids are more easily compressed than gaseous fluids, the pump's energy consumption is lower than the compressor's energy consumption when increasing the same pressure. The cold energy stored during off-peak electricity demand periods is used to liquefy the reflux carbon dioxide in the Allam subsystem, thereby boosting the working fluid at the outlet of the first-stage compressor to the required pressure.

[0017] The present invention achieves the following technical effects compared to the prior art: This invention integrates Allam cycle, cold storage peak shaving, and cryogenic centrifugal desalination technologies to construct a combined heat and power (CHP) system. The Allam cycle's high-efficiency power generation provides the power for seawater desalination, while the cryogenic centrifugal desalination system uses a cold storage / release mechanism to regulate the Allam cycle's power output, forming a closed-loop "energy-water" synergistic production system. Cold storage technology converts excess electrical energy from the Allam cycle into stored cold energy, releasing it during peak electricity demand to reduce carbon dioxide compression power consumption. This overcomes the power regulation limitations of traditional Allam cycles, enhancing the system's responsiveness to grid load fluctuations, and is particularly suitable for peak shaving needs in power systems with a high proportion of renewable energy. The cold storage system provides a cooling source, effectively addressing the Allam cycle's sensitivity to cooling temperatures due to the carbon dioxide criticality, mitigating system performance degradation in high-temperature environments, and improving its operational stability in tropical regions.

[0018] By combining the advantages of refrigeration and centrifugation methods, and leveraging the synergistic effect of phase change separation and centrifugation, the pretreatment process is simplified, equipment corrosion rate is reduced, and desalination efficiency and economy are significantly improved. The carbon dioxide compressor unit and refrigeration module are shared, allowing the compressor unit to operate at full capacity during off-peak electricity demand periods, increasing equipment utilization. This reduces investment costs in the refrigeration system and provides a buffer for peak electricity demand through cold energy storage, achieving multi-functionality and efficient operation throughout the entire lifecycle. It can also simultaneously achieve combined electricity and water production, making it particularly suitable for areas with water and electricity shortages.

[0019] Through intelligent switching between cold storage and cold release modules, the system can dynamically adjust its operating mode (power generation priority or water production priority) according to power demand, meeting diverse energy product demands and enhancing market adaptability.

[0020] In summary, this invention, through multi-technology coupling and system-level innovation, effectively solves the bottleneck problems of narrow peak-shaving range and poor high-temperature performance of the Allam cycle while maintaining its high efficiency and low carbon advantages, and expands the function of combined hydropower, providing a competitive technical solution for energy structure adjustment and water security. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram showing the relationship between the ASU subsystem, the Allam subsystem, and the cryogenic centrifugal desalination subsystem in one or more embodiments of the present invention. Figure 2 This is a schematic diagram of a combined hydropower peak-shaving system in one or more embodiments of the present invention.

[0023] In the diagram: 1-Air separation unit, 2-Natural gas compressor, 3-Burner, 4-Cooled turbine, 5-First gas-liquid separator, 6-Second gas-liquid separator, 7-Water pump, 8-Low-pressure carbon dioxide pump, 9-Medium-pressure carbon dioxide pump, 10-High-pressure carbon dioxide pump, 11-Mix compressor, 12-Bypass compressor, 13-Regenerator, 14-First-stage compressor, 15-Second-stage compressor, 16-Third-stage compressor, 17-Fourth-stage compressor, 18-First-stage intercooler 19-Second-stage intercooler, 20-Third-stage intercooler, 21-Fourth-stage intercooler, 22-Condenser, 23-Evaporator, 24-Freshwater ice crystal storage tank, 25-Freshwater storage tank, 26-Throttle valve, 27-Refrigeration compressor, 28-Filter, 29-Ice crystal generator, 30-Centrifuge, 31-First valve, 32-Second valve, 33-Third valve, 34-Fourth valve, 35-Fifth valve, 36-Water intake pump, 37-Ice slurry pump. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The purpose of this invention is to provide a combined hydropower peak shaving system and its operation method to solve the problems existing in the prior art. It can combine Allam cycle, energy storage peak shaving technology and refrigerated centrifugal desalination technology to achieve efficient energy utilization, stable power supply and effective freshwater production.

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] This invention provides a combined hydropower peak-shaving system, such as... Figure 1 and Figure 2As shown, the system includes an ASU subsystem, or Air Separation Unit, which primarily separates oxygen from the air using methods such as cryogenic distillation or pressure swing adsorption. The Allam subsystem mixes natural gas with the oxygen separated by the ASU subsystem for combustion, and uses the combustion product as a working fluid for power generation. In this invention, the circulating working fluid between the combustion chamber and the gas-liquid separator is simply referred to as the working fluid. The circulating working fluid after the gas-liquid separator is a mixture with a carbon dioxide concentration greater than 90%, hence the abbreviation "recirculated carbon dioxide." After the working fluid has been used for power generation, water is separated to form recirculated carbon dioxide. This recirculated carbon dioxide can be pressurized by the circulation module and mixed with the oxygen separated and transported by the ASU subsystem for reheating, and then remixed with natural gas for combustion. The system also includes a refrigerated separation unit. The desalination subsystem connects to the circulation module, enabling heat exchange between pressurized reflux carbon dioxide from the circulation module and seawater to create subcooled water. The refluxed carbon dioxide is then returned to the circulation module for repressurization. This repressurized carbon dioxide is used for heat exchange with seawater or mixed with oxygen from the ASU subsystem for reheating before being mixed with natural gas for combustion. The electricity generated by the Allam subsystem is supplied to the ASU subsystem, the refrigerated centrifugal desalination subsystem, and the user end. The refrigerated centrifugal desalination subsystem produces ice slurry from the subcooled water. This ice slurry exchanges heat with the refluxed carbon dioxide, liquefying it and creating fresh water. The refrigerated centrifugal desalination subsystem regulates the power output of the Allam subsystem through a cold storage device. Together, these three systems provide electricity and fresh water to the user.

[0028] The ASU subsystem of this invention uses electricity to separate air and produce oxygen required for combustion in the Allam subsystem. The Allam subsystem consumes natural gas and oxygen from the ASU subsystem to produce electricity, while simultaneously capturing the high concentration of carbon dioxide produced through a bypass. Part of the electricity generated is supplied to the ASU subsystem and the cryogenic centrifugal desalination subsystem, and the remainder is transmitted to users through the power grid. The cryogenic centrifugal desalination subsystem uses excess electricity during periods of low electricity demand to freeze and centrifuge seawater to produce freshwater ice crystals. At the same time, it uses cold storage equipment to transfer cold energy to periods of high electricity demand for use in the carbon dioxide liquefaction of the Allam subsystem, thus achieving freshwater production while regulating the power output of the Allam subsystem.

[0029] The ASU subsystem includes a connected air separation unit and a mixing compressor 11. The air separation unit separates oxygen from the air and delivers it to the mixing compressor 11. The mixing compressor 11 mixes and pressurizes the pressurized reflux carbon dioxide with oxygen, and then delivers the mixed and pressurized material to the Allam subsystem. Because the Allam cycle requires a high O2 purity (≥99.5 mol%), the commercially available large-scale, high-concentration O2 air separation technology is cryogenic distillation air separation. Therefore, the air separation unit employs cryogenic air separation technology. Furthermore, because the oxygen leaves the ASU subsystem at a low pressure, it needs to be mixed and pressurized with the reflux carbon dioxide before entering the combustion chamber of the Allam subsystem for combustion.

[0030] The Allam subsystem comprises a combustion expansion module, a regenerative heating module, a gas-liquid separation module, and a circulation module, with the circulation module being a carbon dioxide compression module. During operation, natural gas and oxygen supplied by the ASU subsystem mix and burn in the combustion expansion module, generating a high-temperature, high-pressure working fluid that expands to drive a generator. The working fluid, after performing work, enters the regenerative heating module, where it exchanges heat with the working fluid in subsequent processes, improving energy utilization efficiency. Next, the working fluid flows into the gas-liquid separation module to separate moisture, and the incremental carbon dioxide is transported to a sealed storage tank or the output end. Finally, the remaining working fluid enters the carbon dioxide compression module to be pressurized to the required pressure, and after being heated by the regenerative heating module, it returns to the combustion expansion module. This achieves sCO2 circulation and efficient energy conversion.

[0031] The combustion expansion module includes a natural gas compressor 2, a burner 3, a cooled turbine 4, and a generator connected sequentially via pipelines. The natural gas compressor 2 compresses natural gas from the pipeline to 30 MPa and delivers it to the burner 3. Recirculated carbon dioxide is pressurized, mixed with oxygen, and reheated before being delivered to the burner 3 via a reheating module. The burner 3 delivers the combusted working fluid to the cooled turbine 4 to drive the generator. Since the exhaust temperature at the burner 3 outlet reaches 1150 ℃, exceeding the material temperature limit of the turbine blades (860 ℃), cooling of the turbine blades is necessary to ensure safe and stable system operation. Therefore, partially recirculated carbon dioxide is introduced into the reheater 13 to cool the turbine.

[0032] The regenerative heating module includes a regenerator 13 and a bypass compressor 12. The output of a cooled turbine 4 is connected to the heat release section of the regenerator 13 via two carbon dioxide branches, enabling the delivery of the working fluid after power generation to the regenerator 13. The output of the heat release section of the regenerator 13 is connected to three output branches, two of which are connected to the gas-liquid separation module, and the third output branch is connected to the bypass compressor 12. The output of the bypass compressor 12 is connected to the heat release section of the regenerator 13. The output of the heat absorption section of the regenerator 13 is connected to the burner 3 and the cooled turbine 4 via branches, respectively. The input of the heat absorption section of the regenerator 13 is connected to the output of the mixing compressor 11 and the carbon dioxide compression module, respectively. The regenerator 13 contains three hot fluids and three cold fluids, making it a typical multi-flow heat exchanger. The low-pressure gas discharged from the cooled turbine 4 is divided into two streams and enters the regenerator 13 for heat recovery. Considering that the heat recovery is insufficient, one stream passes through the bypass compressor 12 to increase the temperature and returns to the regenerator 13 to release the heat of compression.

[0033] The gas-water separation module includes a first gas-water separator 5 and a second gas-water separator 6 arranged in parallel. The water outlets of the first gas-water separator 5 and the second gas-water separator 6 are connected to a freshwater storage tank 25, and the gas outlets of the first gas-water separator 5 and the second gas-water separator 6 are connected to a carbon dioxide compression module. The inputs of the first gas-water separator 5 and the second gas-water separator 6 are connected to the output of the heat release section of the regenerator 13. The first gas-water separator 5 is a low-pressure side separator with an operating pressure of 3.3 MPa; the second gas-water separator 6 is a high-pressure side separator with an operating pressure of 8 MPa. Water produced during combustion is removed from the separators and stored in the freshwater storage tank 25.

[0034] The carbon dioxide compression module includes a carbon dioxide compressor unit, a low-pressure carbon dioxide pump 8, a medium-pressure carbon dioxide pump 9, and a high-pressure carbon dioxide pump 10. The outlet of the first gas-liquid separator 5 is connected in series via pipelines to the first-stage compressor 14, the second-stage compressor 15, the third-stage compressor 16, and the fourth-stage compressor 17 of the carbon dioxide compressor unit. The end of the fourth-stage compressor 17 is connected to the medium-pressure carbon dioxide pump 9 via a first circuit, and the end of the fourth-stage compressor 17 is connected to a refrigerated centrifugal desalination subsystem via a second circuit. A first valve 31 is installed on the second circuit. The first-stage compressor 14 and the second-stage compressor 15... A second valve 32 is installed on the pipeline between the first-stage compressor 14 and the second valve 32. A third loop is installed on the pipeline between the first-stage compressor 14 and the second valve 32. The third loop is equipped with a third valve 33, a condenser 22, and a low-pressure carbon dioxide pump 8 in sequence. The output end of the low-pressure carbon dioxide pump 8 is connected to the first loop and the second loop respectively. The outlet end of the second gas-liquid separator 6 is connected to the first loop through a pipeline. The medium-pressure carbon dioxide pump 9 is connected to the input end of the heat absorption section of the regenerator 13 through a pipeline connected to the high-pressure carbon dioxide pump 10. The medium-pressure carbon dioxide pump 9 is also connected to the input end of the heat absorption section of the regenerator 13 through a pipeline connected to the mixing compressor 11. The high-concentration carbon dioxide separated by the first gas-liquid separator 5 first enters the carbon dioxide compressor unit for pressurization. When the pressure rises to 8MPa, it merges with the high-concentration carbon dioxide separated by the second gas-liquid separator 6, and then flows into the medium-pressure carbon dioxide pump 9 and the high-pressure carbon dioxide pump 10 in sequence to be pressurized to 30MPa. The carbon dioxide compressor unit is a compressor unit with interstage cooling. A first-stage intercooler 18 is provided between the second valve 32 and the second-stage compressor 15. A second-stage intercooler 19 is provided between the second-stage compressor 15 and the third-stage compressor 16. A third-stage intercooler 20 is provided between the third-stage compressor 16 and the fourth-stage compressor 17. A fourth-stage intercooler 21 is provided for the fourth-stage compressor 17. The end of the fourth-stage intercooler 21 is connected to the first circuit and the second circuit respectively. The compression heat of each stage is removed by the cooler after that stage, so that the inlet temperature of each stage compressor is the lowest temperature of the cycle, thereby significantly reducing the power consumption of the compression process.

[0035] The refrigerated centrifugal desalination subsystem includes a refrigeration module, a refrigerated centrifugal cold storage module, and a desalination cold release module. During periods of low electricity demand, the refrigeration module consumes excess electricity to produce low-temperature cold energy, while the refrigerated centrifugal cold storage module uses the generated cold energy to produce fluid ice and further consumes excess electricity to produce freshwater ice crystals, which are stored in the freshwater ice crystal storage tank 24. During periods of high electricity demand, the carbon dioxide compression module in the Allam subsystem uses the cold energy in the freshwater ice crystals to liquefy carbon dioxide, reducing the power consumption for carbon dioxide pressurization and increasing the system output power. At the same time, the freshwater ice crystals absorb heat and liquefy to produce freshwater, which is stored in the freshwater storage tank 25.

[0036] The refrigeration module includes a refrigeration compressor 27, an evaporator 23, and a throttling valve 26 sequentially arranged in the second circuit. The end of the second circuit furthest from the first valve 31 is connected to the first-stage compressor 14. The refrigerant, namely high-concentration carbon dioxide, generates cold energy in the evaporator 23 after a phase change for the production of fluid ice. The refrigeration module and the carbon dioxide compression module share a carbon dioxide compressor unit. During periods of low electricity demand, the carbon dioxide compressor unit in a conventional Allam cycle operates at low load, resulting in low efficiency. However, in the Allam cycle proposed in this invention, the carbon dioxide compressor unit operates at full load, effectively improving the efficiency of the compression system and reducing the cost of the refrigeration system. The refrigeration centrifugal cold storage module includes a water intake pump 36, a filter 28, an ice crystal generator 29, a centrifuge 30, and a freshwater ice crystal storage tank 24. One end of the water intake pump 36 is connected to a seawater source, and the other end is connected to the filter 28. The filter 28 is connected to the inlet of the evaporator 23, which can transport the filtered seawater into the evaporator 23 and form subcooled water in the evaporator 23. The outlet of the evaporator 23 is connected in sequence to the ice crystal generator 29, the centrifuge 30, and the freshwater ice crystal storage tank 24. During periods of low electricity demand, the water intake pump 36 draws water from the seawater source inlet, then passes through the filter 28 to remove impurities such as silt, and enters the evaporator 23 to form subcooled water. Then, it enters the ice crystal generator 29 to generate fluid ice, and then enters the centrifuge 30 for centrifugal desalination. The resulting freshwater ice crystals are stored in the freshwater ice crystal storage tank 24. The desalination and cooling module includes a water pump 7, a condenser 22, an ice slurry pump 37, and a freshwater storage tank 25. A freshwater ice crystal storage tank 24 is connected to the condenser 22 via a pipeline equipped with a fourth valve 34 and the ice slurry pump 37. The outlet of the condenser 22 is connected to the freshwater storage tank 25. The freshwater storage tank 25 is connected to the freshwater ice crystal storage tank 24 via a pipeline equipped with a fifth valve 35 and the water pump 7. During peak electricity demand periods, if the ice crystal storage tank contains only ice crystals and no ice slurry, a small amount of freshwater is drawn from the freshwater storage tank 25 and injected into the freshwater ice crystal storage tank 24 using the water pump 7 to generate ice slurry. If ice slurry is present, no freshwater injection is required. The ice slurry is injected into the condenser 22 using the ice slurry pump 37. The released cold energy liquefies the low-pressure carbon dioxide in the Allam subsystem, allowing the returned carbon dioxide to be pressurized to 8 MPa using the low-pressure carbon dioxide pump 8. This process reduces the energy consumption of carbon dioxide compression and also produces fresh water, enabling the new system to achieve combined hydropower. The types of air compressors and expanders involved in this invention are not limited; they can be piston, axial, centrifugal, screw, etc., or combinations of different types. The form of the heat exchanger is not limited; it can be shell-and-tube, tube-and-shell, jacketed, regenerative, tube-fin, or plate-fin type.

[0037] The present invention also provides an operation method for a combined hydropower peak-shaving system, comprising the following steps: During periods of low electricity demand, to balance power generation with user demand, it is necessary to minimize the output power on the generation side. Therefore, the combined hydropower peak-shaving system operates in a reduced-load state, with the cold storage module in energy storage mode. At this time, except for the carbon dioxide compressor unit operating at full load, other components of the Allam subsystem operate at minimum load. First, the Allam subsystem operates at reduced load to decrease fuel flow. This leads to a reduction in the power generation of the Allam subsystem. ,in This represents the rated power generation of the Allam subsystem during periods of stable power demand. Simultaneously, the first valve 31 opens, and the system... The carbon dioxide circulating working fluid flows into the refrigeration module of the refrigerated centrifugal desalination subsystem to produce cold energy, and utilizes the refrigerated centrifugal cold storage module to produce freshwater ice crystals, which are stored in the freshwater ice crystal storage tank 24. Since the refrigeration module shares compression components with the carbon dioxide compressor unit, the carbon dioxide compressor unit still operates at full load. The compression components within the refrigeration module and the refrigerated centrifugal cold storage module further consume approximately [amount missing] of the electricity generated by the Allam subsystem. It is stored as cold energy in a cold storage tank. Therefore, in energy storage mode, the output power of the entire system is as low as ( ) .

[0038] During peak electricity demand periods, to balance power generation with user demand, the output power of the power generation side needs to be increased. Therefore, the system operates under overload conditions, with the cold storage equipment in energy release mode. Since liquids are more compressible than gases, the pump consumes less energy than the compressor when increasing the pressure. Utilizing the cold energy stored during off-peak electricity demand periods to liquefy the carbon dioxide mixture returning to the Allam subsystem allows the working fluid at the outlet of the first-stage compressor 14 to be pressurized to the required pressure via a pump, thus saving significant compression work. This energy saving is the increased output power of the integrated system.

[0039] The implementation process of the above method of the present invention is as follows: During periods of stable electricity demand, only the second valve 32 is opened, while the other valves remain closed. Natural gas from the pipeline is pressurized by the natural gas compressor 2 and then enters the burner 3, where it mixes and burns with oxygen from the air separation unit 1. The high-temperature, high-pressure gas produced by combustion enters the cooled turbine 4 for expansion, reducing its pressure to 3.3 MPa, which drives the generator to produce electricity. After completing its work, the high-temperature, low-pressure gas splits into two streams that enter the regenerator 13. One stream leaves the regenerator 13 and is compressed by the bypass compressor 12, increasing its pressure to 8 MPa before re-entering the regenerator 13. All the fluids entering the regenerator 13 release heat to the returning carbon dioxide and oxygen. The carbon dioxide, after releasing heat, is then separated from the combustion-produced water by the first gas-water separator 5 and the second gas-water separator 6. The separated water flows into the freshwater storage tank 25. After the water is removed, a high-concentration carbon dioxide of 3.3 MPa is formed. Part of the carbon dioxide (carbon dioxide circulation increment) is bypassed for storage or other purposes, while the remaining high-concentration carbon dioxide continues to be compressed by the carbon dioxide compressor unit. When the pressure rises to 8 MPa, it merges with the high-concentration carbon dioxide leaving the second gas-water separator 6, and then enters the carbon dioxide medium-pressure pump 9 for further pressurization. Afterward, the carbon dioxide is further divided into two streams: one stream is pre-mixed with oxygen and pressurized before being sent to the burner 3; the other stream is pressurized to the turbine's cooling pressure by the carbon dioxide high-pressure pump 10 and then split again. The stream pressurized to the turbine's cooling pressure splits into two streams, which, after being heated by the regenerator 13, enter the cooled turbine 4 and burner 3 respectively for cooling.

[0040] During periods of low electricity demand, only valves 31 and 32 are opened, while the remaining valves remain closed. Initially, the Allam subsystem operates at reduced load to decrease fuel flow. The flow rate of carbon dioxide returning to the combustion chamber needs to be reduced. Therefore, excess carbon dioxide in the system (i.e., The carbon dioxide, after leaving the carbon dioxide compressor unit, enters the refrigeration module through the first valve 31. The high-pressure carbon dioxide is cooled and expanded to the evaporation pressure through the throttling valve 26, then enters the evaporator 23, where it absorbs heat from the seawater and vaporizes. The reheated carbon dioxide mixture is compressed by the refrigeration compressor 27 to a pressure of 3.3 MPa at the outlet of the gas-liquid separator, and then enters the carbon dioxide compressor unit for continuous pressurization and cooling, finally returning to the throttling valve 26 to participate in the next cycle. Simultaneously, the water pump 36 draws seawater from the water source, which, after passing through the filter 28, enters the evaporator 23 to transfer heat to the carbon dioxide, while the seawater forms chilled water. This chilled water then enters the ice crystal generator 29 to form fluid ice, which then enters the centrifuge 30 for centrifugal desalination. The resulting freshwater ice crystals are stored in the freshwater ice crystal storage tank 24.

[0041] During peak electricity demand periods, only valves 33 and 34 are opened, while the remaining valves remain closed. Initially, the Allam subsystem operates at full load, with the operating status of the first-stage compressor 14 within the carbon dioxide compressor unit remaining unchanged. Valve 33 opens, allowing high-concentration carbon dioxide leaving the compressor to enter the condenser 22, transferring heat to the ice slurry. The high-concentration carbon dioxide liquefies and is pressurized to 8 MPa using the low-pressure carbon dioxide pump 8. It then sequentially enters the medium-pressure carbon dioxide pump 9 and the high-pressure carbon dioxide pump 10, returning to the burner 3 after reheating. In the condenser 22, the high-concentration carbon dioxide exchanges heat with the ice slurry taken from the freshwater ice crystal storage tank 24. If the ice crystal storage tank contains only ice crystals and no ice slurry, a small amount of freshwater is drawn from the freshwater storage tank 25 and injected into the freshwater ice crystal storage tank 24 using the water pump 7 to generate ice slurry. If ice slurry is present, no freshwater injection is required. Then, using the ice slurry pump 37, ice slurry is injected into the condenser 22. The released cold energy liquefies the low-pressure carbon dioxide in the Allam subsystem, and the resulting fresh water is collected in the fresh water storage tank 25 to meet the user's water needs.

[0042] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A combined hydropower peak-shaving system, characterized in that: Comprise: ASU subsystem, which can separate oxygen from air; Allam subsystem, which can mix natural gas with oxygen separated from the ASU subsystem and burn, and use the working fluid generated by the burning to generate electricity; the working fluid after the electricity generation is separated from water to form backflow carbon dioxide, which can be pressurized by a circulation module and mixed with oxygen separated and delivered from the ASU subsystem for heat recovery, and then mixed with natural gas for burning again; A refrigeration centrifugal desalination subsystem connected with the circulation module, which can use the backflow carbon dioxide pressurized by the circulation module to exchange heat with seawater to form supercooled water, and the backflow carbon dioxide after the heat exchange can return to the circulation module for re-pressurization, and the backflow carbon dioxide after the re-pressurization is used to exchange heat with seawater or to exchange heat with oxygen separated and delivered from the ASU subsystem for heat recovery, and then mixed with natural gas for burning; The electricity generated by the Allam subsystem is used to deliver to the ASU subsystem, the refrigeration centrifugal desalination subsystem and the user end; the refrigeration centrifugal desalination subsystem can make the supercooled water into ice slurry, and the ice slurry can exchange heat with the backflow carbon dioxide to liquefy the backflow carbon dioxide and make the ice slurry after the heat exchange into fresh water.

2. The combined heat and power peak shaving system of claim 1, wherein: The ASU subsystem comprises a communication air separation unit and a mixing compressor, the air separation unit can separate oxygen from air and deliver to the mixing compressor, the mixing compressor can mix and pressurize the backflow carbon dioxide and oxygen after pressurization, and deliver the mixed and pressurized material to the Allam subsystem.

3. The CCHP peak shaving system according to claim 2, characterized in that: The Allam subsystem comprises a combustion expansion module, a heat recovery and temperature rising module, a gas-water separation module and a circulation module, the circulation module is a carbon dioxide compression module; when the Allam subsystem operates, natural gas mixes and burns with oxygen provided by the ASU subsystem in the combustion expansion module, and after the high-temperature and high-pressure working fluid is generated, the working fluid expands in the turbine with cooling, and the turbine with cooling drives the generator to generate electricity; The working fluid after the electricity generation enters the heat recovery and temperature rising module to exchange heat with the mixed and pressurized material, the material after the heat exchange is delivered to the combustion expansion module; the working fluid after the heat exchange flows into the gas-water separation module to separate water and form backflow carbon dioxide, and after the backflow carbon dioxide removes the circulation increment carbon dioxide, it enters the carbon dioxide compression module to be pressurized to the required pressure, and returns to the combustion expansion module through the heat recovery and temperature rising module.

4. The CCHP peak shaving system according to claim 3, characterized in that: The combustion expansion module comprises a natural gas compressor, a burner, a turbine with cooling and a generator connected by pipelines in sequence; the natural gas compressor can compress the natural gas from the natural gas pipeline and deliver to the burner; the backflow carbon dioxide after the pressurization and the heat recovery with oxygen is delivered to the burner through the heat recovery and temperature rising module; the burner can deliver the working fluid after the burning to the turbine with cooling to drive the generator to generate electricity.

5. The CCHP peak shaving system according to claim 4, characterized in that: The heat recovery temperature raising module comprises a heat regenerator and a bypass compressor; the output end of the turbine with cooling is communicated with the heat releasing section of the heat regenerator through two carbon dioxide branches, and can deliver the working medium after power generation to the heat regenerator; the output end of the heat releasing section of the heat regenerator is connected with three output branches, two of which are connected with the gas-water separation module, and the third is connected with the bypass compressor, the output end of which is communicated with the heat releasing section of the heat regenerator; the output end of the heat absorbing section of the heat regenerator is communicated with the combustor and the turbine with cooling through branches respectively, and the input end of the heat absorbing section of the heat regenerator is connected with the output end of the mixed compressor and the carbon dioxide compression module.

6. The CCHP peak shaving system according to claim 4, characterized in that: The gas-water separation module comprises a first gas-water separator and a second gas-water separator arranged in parallel, the water outlet of the first gas-water separator and the second gas-water separator is connected with a fresh water storage tank, and the gas outlet of the first gas-water separator and the second gas-water separator is connected with the carbon dioxide compression module; the input end of the first gas-water separator and the second gas-water separator is connected with the output end of the heat releasing section of the heat regenerator.

7. The CCHP peak shaving system according to claim 6, characterized in that: The carbon dioxide compression module comprises a carbon dioxide compressor set, a carbon dioxide low pressure pump, a carbon dioxide medium pressure pump and a carbon dioxide high pressure pump; the gas outlet of the first gas-water separator is connected with the first stage compressor, the second stage compressor, the third stage compressor and the fourth stage compressor of the carbon dioxide compressor set in series through a pipeline, the fourth stage compressor is connected with the carbon dioxide medium pressure pump through a first loop, and the fourth stage compressor is connected with the refrigeration centrifugal desalination subsystem through a second loop, and a first valve is arranged on the second loop; a second valve is arranged on the pipeline between the first stage compressor and the second stage compressor, a third loop is arranged on the pipeline between the first stage compressor and the second valve, a third valve, a condenser and the carbon dioxide low pressure pump are arranged on the third loop in sequence, and the output end of the carbon dioxide low pressure pump is connected with the first loop and the second loop respectively; the gas outlet of the second gas-water separator is communicated with the first loop through a pipeline; the carbon dioxide medium pressure pump is communicated with the input end of the heat absorbing section of the heat regenerator through a pipeline connected with the carbon dioxide high pressure pump, and the carbon dioxide medium pressure pump is communicated with the input end of the heat absorbing section of the heat regenerator through a pipeline connected with the mixed compressor.

8. The CCHP peak shaving system according to claim 7, characterized in that: The refrigeration centrifugal desalination subsystem comprises a refrigeration module, a refrigeration centrifugal cold storage module and a desalination cold release module; The refrigeration module comprises the carbon dioxide compressor set in the carbon dioxide compression module and a refrigeration compressor, an evaporator and a throttling valve arranged on the second loop in sequence; one end of the second loop away from the first valve is communicated with the first stage compressor; The freezing centrifugal cold storage module comprises a water pump, a filter, an ice crystal generator, a centrifuge and a fresh water ice crystal storage tank; one end of the water pump is connected with a seawater source, the other end is connected with the filter, the filter is connected with the water inlet end of the evaporator, the filtered seawater can be delivered into the evaporator to form supercooled water in the evaporator; the water outlet end of the evaporator is sequentially connected with the ice crystal generator, the centrifuge and the fresh water ice crystal storage tank; The desalination cold release module comprises a water pump, a condenser, an ice slurry pump and a fresh water storage tank; the fresh water ice crystal storage tank is connected with the condenser through a pipeline provided with a fourth valve and an ice slurry pump, the water outlet end of the condenser is connected with the fresh water storage tank; the fresh water storage tank is connected with the fresh water ice crystal storage tank through a pipeline provided with a fifth valve and a water pump.

9. The CCHP peak shaving system according to claim 7, characterized in that: A first-stage intermediate cooler is arranged between the second valve and the second-stage compressor, a second-stage intermediate cooler is arranged between the second-stage compressor and the third-stage compressor, a third-stage intermediate cooler is arranged between the third-stage compressor and the fourth-stage compressor, and the fourth-stage compressor is provided with a fourth-stage intermediate cooler, and the fourth-stage intermediate cooler is connected with the first loop and the second loop at the tail end.

10. A method for operating a system for combined heat and power and peak shaving according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: During the low power demand period, the freezing centrifugal cold storage module is in the energy storage mode, at this time, the Allam subsystem is in the minimum load operation except that the carbon dioxide compressor set is in full load operation; meanwhile, the first valve is opened, the pressurized backflow carbon dioxide flows into the refrigeration module of the freezing centrifugal desalination subsystem to produce cold energy, and the freezing centrifugal cold storage module produces fresh water ice crystals which are stored in the fresh water ice crystal storage tank; the refrigeration module and the carbon dioxide compressor set share the compression components, and the carbon dioxide compressor set remains in the full load operation state; the refrigeration module and the freezing centrifugal cold storage module consume the electricity produced by the Allam subsystem and store it in the fresh water ice crystal storage tank in the form of cold energy; During the peak power demand period, the Allam subsystem is in the overload operation state, and the freezing centrifugal cold storage module is in the energy release mode; since liquid fluid is more easily compressed than gas fluid, the energy consumption of the pump is lower than that of the compressor when the same pressure is increased, and the backflow carbon dioxide in the Allam subsystem is liquefied by using the cold energy stored during the low power demand period, and the working medium at the outlet of the first-stage compressor is pressurized to the required pressure.

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