A gas-supercritical carbon dioxide combined cycle generator

Abstract

The application discloses a gas-supercritical carbon dioxide combined cycle generator set, and relates to the technical field of cycle power generation systems.The gas-supercritical carbon dioxide combined cycle generator set comprises a gas-supercritical carbon dioxide combined cycle power generation system, a natural gas expansion power generation system, a gas turbine generator set waste heat utilization system and a molten salt energy storage circulation system.The gas-supercritical carbon dioxide combined cycle power generation system and the natural gas expansion power generation system are connected through two groups of heat exchangers and two groups of heaters to realize heat energy conversion and utilization.The application takes the gas turbine generator set as the core, combines supercritical carbon dioxide power generation, natural gas expansion power generation, molten salt-supercritical carbon dioxide energy storage and other technologies, improves the thermal medium circulation process of the combined cycle power generation system, realizes efficient recycling of residual energy such as waste heat, residual pressure and cold energy in the system, avoids additional energy consumption, improves energy utilization rate, comprehensively reduces carbon emission and realizes energy saving and carbon reduction.

Description

Technical Field

[0001] This invention relates to the field of combined cycle power generation systems, specifically to a gas-supercritical carbon dioxide combined cycle power generation unit. Background Technology

[0002] Liquefied natural gas (LNG) has a lower storage pressure and a higher compression and vaporization ratio, resulting in a higher energy storage density. Furthermore, it is not dependent on city gas pipeline networks. Therefore, most gas turbine generator sets use LNG as their combustion energy source. However, LNG needs to be heated and vaporized, and its pressure adjusted, to be converted into gaseous natural gas (CNG) before it can be used as fuel to power gas turbine generator sets. The traditional method involves using a heated vaporizer to heat the LNG with a primary heat source, vaporizing it into high-pressure CNG. Then, an expander or pressure regulator is used to absorb the residual pressure, bringing the CNG up to the gas turbine generator set's supply standards. This process requires additional heat energy and results in a significant amount of pressure energy remaining unutilized.

[0003] Gas turbine generator sets generate a significant amount of high-quality waste heat during operation, which is currently primarily recovered and utilized through gas-steam combined cycle (GSCB) power generation technology or Organic Rankine (ORC) low-temperature waste heat power generation technology. However, compared to water vapor and various organic working fluids in the aforementioned GSCBs, supercritical carbon dioxide, as a heat transfer medium, boasts higher pressure, enthalpy, thermal efficiency, specific heat capacity, energy storage density, and cycle efficiency. It also exhibits excellent thermal stability and high thermal efficiency. Furthermore, its critical conditions are easier to achieve, storage is less challenging, safety is higher, and overall manufacturing and operating costs are lower. Therefore, in recent years, gas-supercritical carbon dioxide GSCB power generation technology has been proposed to replace gas-steam and gas-ORC GSCB systems. Simultaneously, the application of supercritical carbon dioxide in power generation systems also helps reduce carbon emissions, achieving energy conservation and carbon reduction. However, existing GSCB power generation systems have relatively low waste heat recovery and utilization rates. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a gas turbine-supercritical carbon dioxide combined cycle generator set to improve the utilization efficiency of waste heat from the gas turbine generator set and make full use of the residual energy inside the system.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a gas-supercritical carbon dioxide combined cycle generator set, including a gas-supercritical carbon dioxide combined cycle power generation system and a natural gas expansion power generation system. The two power generation systems achieve thermal energy conversion between energy through two sets of heat exchangers and two sets of heaters. Each set of heat exchangers includes a condenser and an evaporator.

[0006] The gas-supercritical carbon dioxide combined cycle power generation system includes a carbon source, a first air compressor, a first gas-liquid separator, a first condenser in the first group of heat exchangers, a carbon dioxide heating pipeline, a supercritical carbon dioxide storage tank, a molten salt boiler, a carbon dioxide expansion generator set, a first heater, a second heater, a second air compressor, and a second condenser in the second group of heat exchangers, wherein the second condenser is connected again to the aforementioned carbon dioxide heating pipeline via a pipeline.

[0007] The natural gas expansion power generation system includes, in sequence, an LNG storage tank, an LNG throttle valve, a No. 1 evaporator in the first group of heat exchangers, a No. 2 gas-liquid separator, an LNG transfer pump, a No. 2 evaporator in the second group of heat exchangers, a No. 1 control valve, a No. 1 CNG throttle valve, a first heater, a natural gas expansion generator set, a second heater, and a No. 1 natural gas compressor. The No. 1 natural gas compressor is then connected to the No. 2 evaporator in the second group of heat exchangers.

[0008] The above technical solution enables the gas-supercritical carbon dioxide combined cycle power generation system and the natural gas expansion power generation system to operate together through a heat exchanger. This allows the waste heat and pressure energy that are not fully utilized when they operate separately to be converted and utilized together, thereby improving energy efficiency.

[0009] Furthermore, it also includes a gas turbine generator set waste heat utilization system and a molten salt energy storage and circulation system, wherein the gas turbine generator set waste heat utilization system includes a gas turbine generator set and a waste heat boiler, and the flue gas outlet end of the waste heat boiler is connected to the No. 1 gas-liquid separator via a pipeline.

[0010] The molten salt energy storage circulation system includes a molten salt boiler, a low-temperature molten salt storage tank, a low-temperature molten salt pump, a molten salt heating pipe, a No. 1 high-temperature molten salt pump, a high-temperature molten salt storage tank, and a No. 2 high-temperature molten salt pump, all connected in a ring. The molten salt heating pipe and the carbon dioxide heating pipe are both located inside the waste heat boiler.

[0011] Furthermore, the carbon source in the gas-supercritical carbon dioxide combined cycle power generation system includes, but is not limited to, purified carbon dioxide obtained through natural capture, air separation, and flue gas treatment.

[0012] Furthermore, in the gas-supercritical carbon dioxide combined cycle power generation system, the supercritical carbon dioxide produced through the carbon dioxide heating pipeline not only enters the supercritical carbon dioxide storage tank, but is also directly connected to the carbon dioxide expansion generator unit through pipelines.

[0013] Furthermore, the carbon dioxide expansion generator set includes a carbon dioxide turbine expansion turbine and a generator. The carbon dioxide turbine expansion turbine is mainly used to convert the internal energy, thermal energy and pressure energy of supercritical carbon dioxide into mechanical energy through turbine expansion, thereby driving the generator to rotate. The generator mainly converts the mechanical energy transmitted by the carbon dioxide turbine expansion turbine into electrical energy output.

[0014] Furthermore, the second heat exchanger includes an LNG vaporization pipeline and a CNG heating pipeline in the No. 2 evaporator. The LNG transfer pump is connected to the LNG vaporization pipeline via a pipeline, and the liquid outlet of the LNG vaporization pipeline is connected again to the inlet of the LNG transfer pump via a pipeline.

[0015] Furthermore, in the natural gas expansion power generation system, the BOG in the LNG storage tank is connected to the No. 3 natural gas compressor via a pipeline. The No. 3 natural gas compressor is equipped with a No. 2 control valve at its outlet. The LNG obtained after compression enters the LNG storage tank via a pipeline. The uncompressed BOG is connected to the aforementioned CNG heating pipeline via a pipeline. The outlet end of the CNG heating pipeline is connected to the No. 2 natural gas compressor via a pipeline. The No. 2 natural gas compressor is connected to the gas turbine generator set.

[0016] Furthermore, the gas outlet of the No. 2 gas-liquid separator is connected to the aforementioned No. 3 natural gas compressor via a pipeline.

[0017] Furthermore, the first control valve is also connected to a second CNG throttle valve, which is connected in parallel with the first CNG throttle valve, and its outlet end is connected to the second heater through a pipeline; the outlet end of the second CNG throttle valve is also connected to the first CNG throttle valve through a pipeline.

[0018] Furthermore, the natural gas expansion generator set includes a natural gas turbine expansion turbine and a second generator. The natural gas turbine expansion turbine is mainly used to convert the internal energy and pressure energy of high-pressure natural gas into mechanical energy through turbine expansion, thereby driving the second generator to rotate. The second generator mainly converts the mechanical energy transmitted by the natural gas turbine expansion turbine into electrical energy output.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) This invention takes gas turbine generator set as the core and combines supercritical carbon dioxide power generation, natural gas expansion power generation, molten salt-supercritical carbon dioxide energy storage and other technologies to realize the efficient recovery and utilization of residual energy such as waste heat, waste pressure and cold energy in the system, thereby improving energy utilization rate.

[0021] (2) Based on the physical characteristics of supercritical carbon dioxide, the heat working fluid circulation process of the combined cycle power generation system is improved, the flue gas emitted by the gas turbine generator set is fully recovered and utilized, and carbon emissions are comprehensively reduced, thus achieving energy conservation and carbon reduction.

[0022] (3) To address the issue of utilizing the residual pressure of high-pressure CNG, a natural gas expansion generator set is added to the process. This not only enables the recovery and utilization of natural gas residual pressure energy, but also makes full use of cold energy, thus avoiding additional energy consumption during the gasification process.

[0023] (4) To address the high energy consumption problem of LNG gasification, the waste heat of the gas turbine generator set is used to replace the primary heat source, realizing cascade utilization in the overall system cycle process, which significantly improves the utilization rate and thermal efficiency of waste heat.

[0024] (5) In addition, a molten salt energy storage system is added to make full use of the waste heat and waste pressure of the gas turbine generator set, while realizing the integration of power supply and storage, reducing energy waste and further improving energy utilization. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process structure of the present invention;

[0026] In the diagram: blue represents the carbon dioxide cycle process; green represents the LNG gasification cycle process; red represents the waste heat recovery system process of the gas turbine generator set; and orange represents the molten salt energy storage cycle system process. Detailed Implementation

[0027] It is important to note that

[0028] In the specific embodiments proposed in this invention, unless otherwise specified, carbon dioxide, natural gas, etc., are all gaseous forms of the substance. If there are descriptions such as "liquid" or "supercritical", they refer to the physical form of the substance under certain conditions.

[0029] In the specific implementation examples proposed in this invention, the descriptions such as "high temperature", "medium temperature", "low temperature" and "high pressure" are only used as comparative descriptions in the process of explaining the principle, and do not represent the actual temperature, pressure and other parameters in the specific implementation process.

[0030] In the specific implementation examples proposed in this invention, the structures shown in the figures are only for illustrating the principle and do not represent actual application methods.

[0031] The specific implementation examples presented in this invention represent only one possible solution that can be implemented by this invention, and do not represent all possible solutions that can be implemented by this invention.

[0032] In the specific implementation examples proposed in this invention, the terms "first," "second," "number one," "number two," etc., are used for descriptive purposes only and do not specifically refer to any order or sequence, nor are they intended to limit this invention. They are merely used to distinguish components or operations described with the same technical terms.

[0033] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings:

[0034] like Figure 1 As shown, a gas-supercritical carbon dioxide combined cycle generator set includes a gas-supercritical carbon dioxide combined cycle power generation system, a natural gas expansion power generation system, a gas turbine generator set waste heat utilization system, and a molten salt energy storage cycle system. The gas-supercritical carbon dioxide combined cycle power generation system and the natural gas expansion power generation system achieve energy conversion and utilization of thermal energy through two sets of heat exchangers and two sets of heaters, wherein each set of heat exchangers includes a condenser and an evaporator.

[0035] The gas-supercritical carbon dioxide combined cycle power generation system includes a carbon source, a No. 1 air compressor (air compressor I), a No. 1 gas-liquid separator (gas-liquid separator I), a No. 1 condenser (condenser I) in the first group of heat exchangers (heat exchanger I), a carbon dioxide heating pipeline, a supercritical carbon dioxide storage tank, a molten salt boiler, a carbon dioxide expansion generator set, a first heater (heater I), a second heater (heater II), a No. 2 air compressor (air compressor II), and a No. 2 condenser (condenser II) in the second group of heat exchangers (heat exchanger II). The No. 2 condenser (condenser II) is connected again to the aforementioned carbon dioxide heating pipeline via a pipeline. The aforementioned carbon dioxide heating pipeline is also directly connected to the carbon dioxide expansion generator set via a pipeline.

[0036] The carbon source mentioned above is the source of carbon dioxide, including but not limited to purified carbon dioxide obtained through natural capture, air separation, and flue gas treatment. This carbon dioxide enters the No. 1 air compressor through pipeline 101.

[0037] The No. 1 air compressor and the No. 2 air compressor are mainly used to increase the pressure of carbon dioxide for its transport. The carbon dioxide, after being pressurized by the No. 1 air compressor, enters the No. 1 gas-liquid separator via pipeline 102. The No. 1 gas-liquid separator is mainly used to separate the liquid components (water vapor) mixed in with the carbon dioxide that have low-temperature freezing properties, preventing them from freezing and clogging subsequent pipelines, thus completing the drying process. It then enters the No. 1 condenser via pipeline 103.

[0038] In the first condenser, carbon dioxide releases its heat energy to the corresponding evaporator, lowering the temperature of the carbon dioxide entering and converting it into liquid carbon dioxide. This liquid carbon dioxide then flows through pipe 104 into pipe 105, and is transported to the aforementioned carbon dioxide heating pipe for heating and vaporization. As the temperature and pressure rise, exceeding the critical point (31.3℃, 7.38MPa), it is converted into supercritical carbon dioxide. The resulting supercritical carbon dioxide is output through pipe 106, with a portion flowing into pipe 107 and directly transported to the carbon dioxide expansion generator set, and another portion flowing through pipe 701 into the supercritical carbon dioxide storage tank for adiabatic storage, completing pressure energy storage.

[0039] The aforementioned carbon dioxide expansion generator set includes a carbon dioxide turbine expansion turbine and a generator (generator I). The carbon dioxide turbine expansion turbine is mainly used to convert the internal energy, thermal energy, and pressure energy of supercritical carbon dioxide into mechanical energy through turbine expansion, thereby driving the generator (generator I) to rotate. The generator I mainly converts the mechanical energy transmitted by the carbon dioxide turbine expansion turbine into electrical energy output.

[0040] The supercritical carbon dioxide stored in the supercritical carbon dioxide storage tank is transported to the molten salt boiler through pipeline 702, where the supercritical carbon dioxide is heated by high-temperature molten salt; then it is transported to the aforementioned carbon dioxide expansion generator set through pipeline 703 into pipeline 107.

[0041] After being expanded by the carbon dioxide turbine, the supercritical carbon dioxide pressure and temperature decrease, transforming into high-temperature carbon dioxide, which is then transported to the first heater through pipeline 108 to release heat and provide thermal energy output for the first heater.

[0042] After the first heater is used, the carbon dioxide temperature decreases and is converted into medium-temperature carbon dioxide. The output medium-temperature carbon dioxide is transported to the second heater through pipeline 109, where it releases heat and provides thermal energy output for the second heater, thus realizing cascade utilization.

[0043] After the second heater is used, the carbon dioxide temperature decreases again, turning into room temperature carbon dioxide. The output room temperature carbon dioxide is transported to the second air compressor via pipeline 110. The carbon dioxide, after being pressurized by the second air compressor, is transported to the second condenser in the second heat exchanger via pipeline 111, where it releases its heat and condenses into liquid carbon dioxide. After condensing into liquid carbon dioxide, it is connected to pipeline 105 via pipeline 112 and re-enters the carbon dioxide heating pipeline, forming a circulation pipeline to achieve carbon dioxide circulation.

[0044] The natural gas expansion power generation system includes, sequentially connected via pipelines, an LNG storage tank, an LNG throttle valve, a first evaporator (evaporator I) and a second gas-liquid separator (gas-liquid separator II) within the first group of heat exchangers (heat exchanger I), an LNG transfer pump, a second evaporator (evaporator II) within the second group of heat exchangers (heat exchanger II), a first control valve (control valve I), a first CNG throttle valve (CNG throttle valve I), a first heater (heater I), a natural gas expansion generator set, a second heater (heater II), and a first natural gas compressor (natural gas compressor I). The second evaporator contains both an LNG vaporization pipeline and a CNG heating pipeline. The LNG transfer pump is connected to the LNG vaporization pipeline via pipeline 205, and the liquid outlet of the LNG vaporization pipeline is connected again to the inlet of the LNG transfer pump via pipeline 215. The first natural gas compressor is connected to the CNG heating pipeline via pipeline 212.

[0045] The aforementioned LNG storage tank contains insulated liquefied natural gas and can transport liquefied natural gas to other locations via pipeline 201.

[0046] An LNG throttle valve is installed at the output end of pipeline 201 to regulate the output flow of liquefied natural gas. The LNG is then transported through pipeline 202 to the aforementioned No. 1 evaporator, where the heat released from the No. 1 condenser heats and evaporates the LNG. Part of the liquefied natural gas absorbs heat and vaporizes, transforming into boil-off gas (BOG), which mixes with the liquefied natural gas to form a gas-liquid mixture.

[0047] Subsequently, the gas-liquid mixed natural gas enters the No. 2 gas-liquid separator through pipeline 203. The No. 2 gas-liquid separator separates liquefied natural gas (LNG) from boiled natural gas (BOG). The separated LNG is transported to the LNG transfer pump through pipeline 204. The separated BOG is then combined with the BOG discharged from the LNG storage tank through pipeline 301 via pipeline 302, and then transported together through pipeline 303 to the No. 3 natural gas compressor (natural gas compressor III) for pressurization and compression (because the boiled natural gas generated in the LNG storage tank has a low temperature and strong compressibility, the No. 3 natural gas compressor can re-liquefy the boiled natural gas by increasing its pressure, converting it into liquefied natural gas). The compressed mixed natural gas is split through pipeline 304 and the No. 2 control valve (control valve II). The liquefied liquefied natural gas (LNG) enters the LNG storage tank again through pipeline 306 for adiabatic storage, while the gaseous natural gas (CNG) is transported to the CNG heating pipeline in the No. 2 evaporator through pipeline 305.

[0048] The liquefied natural gas (LNG) entering the LNG transfer pump is transported through pipeline 205 to the LNG vaporization pipeline inside the No. 2 evaporator. The heat energy released by the No. 2 condenser is used to vaporize the LNG and heat the CNG heating pipeline.

[0049] As the LNG temperature rises above the critical temperature (-162℃), it vaporizes and expands, transforming into high-pressure natural gas. High-pressure CNG is output through pipeline 206. The flow rate and velocity of the natural gas within the pipeline are regulated by control valve No. 1, and the gas is then split, connecting to CNG throttle valve No. 1 via pipeline 207 and CNG throttle valve No. 2 (CNG throttle valve II) via pipeline 401. After entering CNG throttle valve No. 2, the gas is split again. A portion of the high-pressure CNG that meets the requirements re-enters CNG throttle valve No. 1 via pipeline 402 for further flow rate and velocity regulation, entering the subsequent cycle.

[0050] After the flow rate and velocity of the natural gas are regulated by the No. 1 CNG throttle valve, it enters the first heater through pipeline 208. The high temperature of the carbon dioxide is used to heat and pressurize the natural gas, so that the pipeline and the high-pressure CNG in the pipeline are heated to above 5°C to prevent them from freezing and blocking at the inlet of the natural gas expansion generator set. Then it enters the natural gas expansion generator set through pipeline 209.

[0051] The natural gas expansion generator set includes a natural gas turbine expansion turbine and a second generator (generator II). The natural gas turbine expansion turbine is mainly used to convert the internal energy and pressure energy of high-pressure natural gas into mechanical energy through turbine expansion, which drives the second generator to rotate. The second generator mainly converts the mechanical energy transmitted by the natural gas turbine expansion turbine into electrical energy output.

[0052] After depressurization, the natural gas cools down and becomes low-temperature CNG. The CNG that was diverted through the No. 2 CNG throttle valve is then mixed through pipelines 210 and 403 and enters the second heater. The second heater uses the temperature carried by the medium-temperature flammable gas to heat the natural gas to above 5°C to prevent the natural gas from freezing and clogging.

[0053] The low-temperature CNG output from the second heater is then transported via pipeline 211 to the No. 1 natural gas compressor. The No. 1 natural gas compressor pressurizes the natural gas and then transports it via pipeline 212 to the CNG heating pipeline inside the No. 2 evaporator. The CNG heating pipeline raises the temperature of the low-temperature CNG, converting it to ambient temperature CNG. It is then transported via pipeline 213 to the No. 2 natural gas compressor (Natural Gas Compressor II). After being pressurized again by the compressor, it is transported via pipeline 214 to the gas turbine generator set, becoming the starting fuel for the gas turbine generator set.

[0054] The first and second heaters are both located close to the natural gas expansion generator set.

[0055] The molten salt energy storage circulation system includes a molten salt boiler, a low-temperature molten salt storage tank, a low-temperature molten salt pump, a molten salt heating pipeline, a first high-temperature molten salt pump (high-temperature molten salt pump I), a high-temperature molten salt storage tank, and a second high-temperature molten salt pump (high-temperature molten salt pump II) connected in a ring. The molten salt boiler uses high-temperature molten salt to heat the supercritical carbon dioxide flowing through it. After absorbing heat, the temperature of the molten salt decreases, and it is converted into low-temperature molten salt. It is then transported to the low-temperature molten salt storage tank through pipeline 606 for insulated storage of the low-temperature molten salt.

[0056] Under conditions of sufficient waste heat supply, the cryogenic molten salt in the cryogenic molten salt storage tank is connected to the cryogenic molten salt pump via pipeline 607, and then transported to the molten salt heating pipeline via pipeline 608. There, it is heated together with the external solid salt transported via pipeline 601, transforming into high-temperature molten salt. The produced high-temperature molten salt is transported to the first high-temperature molten salt pump via pipeline 602, and then transported to the high-temperature molten salt storage tank via pipeline 603 for insulated storage, completing the thermal energy storage.

[0057] Under conditions of insufficient supercritical carbon dioxide production, the high-temperature molten salt in the high-temperature molten salt storage tank is transported to the second high-temperature molten salt pump via pipeline 604, and then to the aforementioned molten salt boiler via pipeline 605, forming a cycle. Meanwhile, the supercritical carbon dioxide storage tank, through pressure differential diffusion and pumping, transports supercritical carbon dioxide to the molten salt boiler via pipeline 702. In the molten salt boiler, the high-temperature molten salt heats the supercritical carbon dioxide, completing the output of thermal energy storage.

[0058] The waste heat utilization system of the gas turbine generator set includes the aforementioned gas turbine generator set and a waste heat boiler. The gas turbine generator set is mainly used to burn the aforementioned natural gas and the starting fuel transported through pipeline 501. After being pressurized by the No. 2 natural gas compressor to meet the fuel supply standards of the gas turbine generator set, it is transported through pipeline 214 to the gas turbine generator set for combustion to generate electricity and output electrical energy, while also providing waste heat and flue gas. The high-temperature flue gas generated is transported to the aforementioned waste heat boiler through pipeline 502.

[0059] The aforementioned carbon dioxide heating pipe and the aforementioned molten salt heating pipe are both installed inside the aforementioned waste heat boiler. They are heated by utilizing the temperature of the high-temperature flue gas inside the waste heat boiler to meet the corresponding heating requirements, thereby reducing the flue gas temperature.

[0060] The flue gas outlet of the waste heat boiler is connected to the No. 1 gas-liquid separator via pipes 503 and 504, providing purified carbon dioxide (flue gas produced by natural gas combustion, which consists of carbon dioxide and water vapor) obtained after flue gas treatment for recycling.

[0061] The natural gas flow control method involved in the above embodiments is as follows:

[0062] When the gas turbine generator set operates at low power, its fuel consumption is low, requiring a reduction in the natural gas flow rate in the pipeline. However, reducing the natural gas flow rate will affect the normal operation of the natural gas expansion generator set.

[0063] Under low flow conditions, the pressure of natural gas in the pipeline decreases due to the expansion effect. At this time, in order to ensure the normal operation of the natural gas expansion generator set, it is necessary to increase the pressure in the pipeline.

[0064] Pipes 401 and 402 are throttling pipes, with the diameter of pipe 401 being smaller than that of the main pipe and the diameter of pipe 402 being smaller than that of pipe 401, which can gradually reduce the pressure drop caused by the expansion effect.

[0065] Control valve No. 1 and CNG throttle valve No. 1 work together to close pipeline 207, while control valve No. 1 opens pipeline 401, through which natural gas is delivered to CNG throttle valve No. 2. CNG throttle valve No. 2 adjusts the flow rate and velocity of natural gas in the pipeline, thereby adjusting the pressure within the pipeline, and then delivers natural gas to CNG throttle valve No. 1 through pipeline 402. CNG throttle valve No. 1 adjusts the flow rate and velocity of natural gas in the pipeline, thereby adjusting the pressure within the pipeline, and then delivers natural gas to the first heater through pipeline 208.

[0066] During the adjustment of CNG throttle valve No. 1 and CNG throttle valve No. 2, it should be ensured that the natural gas flow rate in the pipeline is not lower than the minimum flow rate driving the natural gas expansion generator set, and the natural gas pressure in the pipeline is not lower than the minimum pressure driving the natural gas expansion generator set.

[0067] The diameter of the aforementioned pipe 208 is larger than that of pipes 401 and 402, but its length is shorter, resulting in a less pronounced expansion effect and a smaller pressure drop in natural gas.

[0068] Natural gas is heated in the first heater, and the pressure increases during the heating process, which can make up for the pressure drop in pipeline 208. Then it is transported to the natural gas expansion generator unit through pipeline 209 for power generation.

[0069] The natural gas used for power generation is transported to the second heater via pipeline 210.

[0070] After being heated in the second heater, the natural gas is transported to the No. 1 natural gas compressor via pipeline 211. The No. 1 natural gas compressor increases the pressure of the natural gas and transports it to the No. 2 evaporator via pipeline 212.

[0071] After being heated in the No. 2 evaporator, the natural gas is transported to the No. 3 natural gas compressor via pipeline 213. The No. 3 natural gas compressor increases the natural gas pressure and transports it to the gas turbine generator set via pipeline 214, thus completing the adjustment of the natural gas flow rate.

[0072] Under high flow conditions, excessive flow can damage the natural gas expansion generator set. In this case, in order to protect the natural gas expansion generator set, it is necessary to divert the natural gas.

[0073] Control valve 1 opens both pipeline 207 and pipeline 401 simultaneously.

[0074] The No. 1 CNG throttle valve closes pipeline 402, and at the same time reduces the flow of natural gas from pipeline 207 into pipeline 208 to the safe flow range of the natural gas expansion generator set.

[0075] The second CNG throttle valve closes pipe 402 and opens pipe 403.

[0076] Natural gas is diverted to pipeline 401, reducing the flow in pipelines 207 and 208, and then merges into pipeline 210 through pipeline 403, bypassing the natural gas expansion generator set to complete the protection operation.

[0077] The solid salt mentioned in the above embodiments is the solid form of molten salt. When the solid salt is heated to its melting point in the waste heat boiler, it will be converted into liquid molten salt. Limited by the temperature range of 400℃ to 600℃ of the flue gas of the gas turbine generator set, the solid salt mentioned in this invention includes, but is not limited to, single molten salts such as sodium nitrate, potassium nitrate, and lithium chloride with melting points within the above temperature range or below 400℃, as well as mixed molten salts such as lithium-potassium chloride mixtures and sodium-aluminum-fluoride mixtures with eutectic points within the above temperature range or below 400℃. Potassium nitrate is used as an example in the above embodiments.

[0078] The starting fuel mentioned in the above embodiments is defined as the fuel used during the start-up process of the gas turbine generator set, including but not limited to the natural gas mentioned above, as well as methane, hydrogen, ethanol, diesel, pulverized coal, etc.

[0079] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A gas-supercritical carbon dioxide combined cycle generator set, characterized in that: It includes a gas-supercritical carbon dioxide combined cycle power generation system and a natural gas expansion power generation system. The two power generation systems achieve energy conversion between each other through two sets of heat exchangers and two sets of heaters. Each set of heat exchangers includes a condenser and an evaporator. The gas-supercritical carbon dioxide combined cycle power generation system includes a carbon source, a first air compressor, a first gas-liquid separator, a first condenser in the first heat exchanger group, a carbon dioxide heating pipeline, a supercritical carbon dioxide storage tank, a molten salt boiler, a carbon dioxide expansion generator set, a first heater, a second heater, a second air compressor, and a second condenser in the second heat exchanger group, wherein the second condenser is connected again to the aforementioned carbon dioxide heating pipeline via a pipeline. The natural gas expansion power generation system includes, in sequence, an LNG storage tank, an LNG throttle valve, a No. 1 evaporator in the first group of heat exchangers, a No. 2 gas-liquid separator, an LNG transfer pump, a No. 2 evaporator in the second group of heat exchangers, a No. 1 control valve, a No. 1 CNG throttle valve, a first heater, a natural gas expansion generator set, a second heater, and a No. 1 natural gas compressor. The No. 1 natural gas compressor is then connected to the No. 2 evaporator in the second group of heat exchangers.

2. The gas-supercritical carbon dioxide combined cycle generator set according to claim 1, characterized in that: It also includes a gas turbine generator set waste heat utilization system and a molten salt energy storage and circulation system. The gas turbine generator set waste heat utilization system includes a gas turbine generator set and a waste heat boiler. The flue gas outlet of the waste heat boiler is connected to the No. 1 gas-liquid separator via a pipeline. The molten salt energy storage circulation system includes a molten salt boiler, a low-temperature molten salt storage tank, a low-temperature molten salt pump, a molten salt heating pipe, a No. 1 high-temperature molten salt pump, a high-temperature molten salt storage tank, and a No. 2 high-temperature molten salt pump, all connected in a ring. The molten salt heating pipe and the carbon dioxide heating pipe are both located inside the waste heat boiler.

3. The gas-supercritical carbon dioxide combined cycle generator set according to claim 1, characterized in that: The carbon source in the gas-supercritical carbon dioxide combined cycle power generation system includes, but is not limited to, purified carbon dioxide obtained through natural capture, air separation, and flue gas treatment.

4. A gas-supercritical carbon dioxide combined cycle generator set according to claim 1, characterized in that: In the gas-supercritical carbon dioxide combined cycle power generation system, the supercritical carbon dioxide produced through the carbon dioxide heating pipeline enters not only the supercritical carbon dioxide storage tank, but is also directly connected to the carbon dioxide expansion generator unit through pipelines.

5. A gas-supercritical carbon dioxide combined cycle generator set according to claim 1, characterized in that: The carbon dioxide expansion generator set includes a carbon dioxide turbine expansion turbine and a generator.

6. A gas-supercritical carbon dioxide combined cycle generator set according to claim 2, characterized in that: The second heat exchanger group has an LNG vaporization pipeline and a CNG heating pipeline in the No. 2 evaporator. The LNG transfer pump is connected to the LNG vaporization pipeline through a pipeline, and the liquid outlet of the LNG vaporization pipeline is connected to the inlet of the LNG transfer pump through a pipeline.

7. A gas-supercritical carbon dioxide combined cycle generator set according to claim 6, characterized in that: In the natural gas expansion power generation system, the BOG in the LNG storage tank is connected to the No. 3 natural gas compressor via a pipeline. The No. 3 natural gas compressor is equipped with a No. 2 control valve at its outlet. The LNG obtained after compression enters the LNG storage tank via a pipeline. The uncompressed BOG is connected to the aforementioned CNG heating pipeline via a pipeline. The outlet end of the CNG heating pipeline is connected to the No. 2 natural gas compressor via a pipeline. The No. 2 natural gas compressor is connected to the gas turbine generator set.

8. A gas-supercritical carbon dioxide combined cycle generator set according to claim 7, characterized in that: The gas outlet of the No. 2 gas-liquid separator is connected to the No. 3 natural gas compressor via a pipeline.

9. A gas-supercritical carbon dioxide combined cycle generator set according to claim 1, characterized in that: The first control valve is also connected to a second CNG throttle valve, which is connected in parallel with the first CNG throttle valve. Its outlet end is connected to the second heater through a pipeline. The outlet end of the second CNG throttle valve is also connected to the first CNG throttle valve through a pipeline.

10. A gas-supercritical carbon dioxide combined cycle generator set according to claim 1, characterized in that: The natural gas expansion generator set includes a natural gas turbine expansion turbine and a generator.

Images