Natural gas differential pressure power generation system utilizing photo-thermal heating and use method

Abstract

The invention relates to a natural gas differential pressure power generation system utilizing photo-thermal heating and a using method, the system comprises a natural gas excess pressure utilization loop, a cooling water circulation loop and a solar heat collection lifting loop, and the natural gas excess pressure utilization loop comprises a first natural gas heat exchanger, an expansion power generator, an air temperature type gasifier and a second natural gas heat exchanger; the cooling water circulation loop comprises a cooling water tank, a first water heat exchanger, a tee joint and a flow control valve; the second natural gas heat exchanger is connected between the cooling water tank and the flow control valve. The first natural gas heat exchanger is connected with the tee joint and the cooling water tank. The solar heat collection lifting loop comprises a refrigerant compressor, a refrigerant J-T valve, a solar heat collector, a circulating water pump and a hot water storage tank; the hot water storage tank, the refrigerant compressor, the first water heat exchanger and the refrigerant J-T valve are sequentially and circularly connected; solar heat collection heat energy is utilized to heat a natural gas pipeline for power generation, the risk of ice blockage of the pipeline of a power generation system caused by hydrates is reduced, and efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas excess pressure utilization, and specifically relates to a natural gas pressure difference power generation system utilizing photothermal heating and a method of using the system. Background Art

[0002] Natural gas is a flammable gas released from underground. It is mainly used as fuel. It can be used to make carbon black, chemicals and liquefied petroleum gas. Propane and butane produced from natural gas are important raw materials for modern industry. Natural gas mined from underground has a high pressure energy. Natural gas is transported to the pressure regulating station, where the pressure of natural gas is distributed and then transported to the actual user pipeline.

[0003] Long-distance natural gas transportation mainly adopts the form of high-pressure long-distance pipelines. The upstream high-pressure natural gas can enter the urban area only after the pressure is reduced by the pressure regulating station outside the city. The above pressure reduction process is generally achieved by throttle valves, which makes it impossible to recycle the pressure energy of natural gas, resulting in huge energy waste.

[0004] In the existing technology, turbines are used instead of throttle valves to expand high-pressure natural gas for power generation, which is widely used. However, the low-temperature and low-pressure gas after decompression will form hydrates, which will cause the risk of ice blockage in the power generation system pipeline, reduce power generation efficiency, and even damage equipment. Summary of the invention

[0005] In response to at least one of the problems in the above-mentioned prior art, the purpose of the present invention is to provide a natural gas pressure difference power generation system using solar thermal heating and a method of use. The system heats the natural gas pipeline for power generation by utilizing the thermal energy collected by solar energy, thereby reducing the risk of hydrates causing ice blockage in the power generation system pipeline and greatly improving the system efficiency of the natural gas pressure difference power generation system.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A natural gas pressure difference power generation system using photothermal heating, comprising:

[0008] A natural gas residual pressure utilization circuit includes a first natural gas heat exchanger, an expansion generator, an air-temperature vaporizer, and a second natural gas heat exchanger connected in sequence;

[0009] A cooling water circulation loop comprises a cooling water tank, a first water heat exchanger, a tee and a flow control valve connected in sequence; the second natural gas heat exchanger is connected between the cooling water tank and the flow control valve, and the first natural gas heat exchanger is connected to the tee and the cooling water tank respectively;

[0010] The solar thermal collection boosting circuit includes a refrigerant compressor, a refrigerant JT valve, and a solar thermal collector, a circulating water pump, and a hot water storage tank that are connected in a cycle in sequence; the hot water storage tank, the refrigerant compressor, the first water heat exchanger, and the refrigerant JT valve are connected in a cycle in sequence.

[0011] Preferably, the natural gas excess pressure utilization circuit is further provided with a circuit connected in parallel therewith, and the parallel circuit is provided with a heating furnace and a pressure reducing valve connected in sequence.

[0012] Preferably, the front ends of the natural gas excess pressure utilization circuit and the circuits connected in parallel are both connected to a natural gas pipeline network.

[0013] Preferably, the expansion generator is a centrifugal expansion generator, a dual-rotor expansion generator or an integrated expansion generator for pipelines.

[0014] A method for using a natural gas pressure difference power generation system using photothermal heating comprises the following steps:

[0015] In the natural gas excess pressure utilization loop, the natural gas in the natural gas pipeline network is first heated by the first natural gas heat exchanger, and then enters the expansion generator to expand and generate electricity, and then the pressure energy of the natural gas is recovered for pressure difference power generation, and then the natural gas is passed into the air-temperature gasifier for reheating, and then the natural gas is passed into the second natural gas heat exchanger for further reheating to a set temperature, so that the natural gas enters the downstream pipeline network;

[0016] In the cooling water circulation loop, after the cooling water is pumped out from the cooling water tank, the cooling water passes through the first water heat exchanger, and is heated by the refrigerant in the solar heat collection lifting loop, and then passes through the tee;

[0017] In the solar thermal collection and lifting circuit, the solar energy is converted into thermal energy by the solar thermal collector during the day, and then the thermal energy is stored in the hot water in the hot water storage tank by the circulating water pump; after the hot water passes through the compressed refrigerant of the refrigerant compressor, the heat is released in the first water heat exchanger, and then it is cooled in the refrigerant JT valve, and after throttling and reducing the pressure to liquefy, it enters the hot water storage tank for heating, and then enters the refrigerant compressor to form a closed cycle.

[0018] Preferably, in summer mode, the flow control valve is closed so that the cooling water transfers heat to the natural gas in the first natural gas heat exchanger and then enters the cooling water tank for circulation.

[0019] Preferably, in winter mode, the flow control valve is opened, and after passing through the second natural gas heat exchanger, the opening of the flow control valve is adjusted according to the natural gas outlet temperature to adjust the flow of the cooling water branch; when the natural gas outlet temperature is lower than the first set temperature, the opening of the flow control valve is increased to further reheat the natural gas; when the natural gas outlet temperature is higher than the second set temperature, the opening of the flow control valve is reduced to improve the efficiency of the natural gas pressure difference power generation system.

[0020] Preferably, the set temperature of the natural gas introduced into the second natural gas heat exchanger for further reheating is above 0°C.

[0021] Preferably, the first set temperature is 2°C.

[0022] Preferably, the second set temperature is 5°C.

[0023] The present invention adopts the above technical solution, which has the following advantages:

[0024] 1. The natural gas pressure difference power generation system using photothermal heating and the method of use provided by the present invention, the natural gas pressure difference power generation system heats the natural gas pipeline for power generation by using the heat energy collected by solar energy, thereby reducing the risk of ice blockage of the pipeline of the power generation system caused by hydrates, and greatly improving the system efficiency of the natural gas pressure difference power generation system; at the same time, it has the functions of solar energy collection and boosting and natural gas residual pressure power generation, fully utilizing the residual pressure of natural gas for power generation and neutralizing the cold generated by the residual pressure power generation by solar energy collection; it is suitable for the natural gas pressure difference power generation system, and improves the thermal energy effect of the natural gas pressure difference power generation system by performing solar energy collection and boosting the thermal energy of the circuit, while increasing the power output of the pressure difference power generation system, fully considering the matching of the internal energy cycle of the natural gas pressure difference power generation system and the solar energy collection and boosting circuit, and the input power can be used by the factory area.

[0025] 2. The natural gas pressure difference power generation system and method of use using photothermal heating provided by the present invention can reduce the preheating cost to a minimum by optimizing the expansion ratio and compression ratio under various working conditions in real time; at the same time, it can use solar energy thermal storage to ensure the thermal balance of the system throughout the year, so that the system can continue to operate efficiently and stably; and using solar energy thermal storage, the system can be heated throughout the year and a water source heat pump can be used to further increase the heat, which is more suitable for the application scenario of the natural gas expansion power generation system for heating throughout the year. At receiving stations, long-distance pipeline distribution stations, urban gas gate stations, high and medium pressure regulating stations, and industrial direct supply user regulating stations, by combining the natural gas pressure difference power generation system and the solar thermal power generation system, low-quality waste cooling and low-quality waste heat can be combined, which can simultaneously improve the system efficiency of the natural gas pressure difference power generation and reduce the investment cost and operating cost of additional reheating.

[0026] 3. The natural gas pressure difference power generation system and method of use provided by the present invention use a water source heat pump to improve the quality of heat, thereby greatly improving the system efficiency of the natural gas pressure difference power generation system. By improving the quality of thermal energy, the efficiency of the overall system is improved. Efficiency, and save the heating system of natural gas pressure difference power generation, reducing the operating cost of the overall system; the first natural gas heat exchanger is set in front of the expansion generator in the cooling water circulation loop to provide a heat source, which increases the output of the expansion generator in the natural gas pressure difference power generation system, thereby improving the system efficiency. The overall system complements the heat and cold of natural gas pressure energy power generation and solar energy collection. The solar energy collection and lifting device increases the enthalpy difference of upstream and downstream natural gas, increases the power generation of natural gas pressure energy power generation, and solves the problem of converting natural gas pressure energy into electricity and producing cold energy as a by-product. There is no need to add an additional heating system for the natural gas pressure difference power generation system, which improves the efficiency of the overall system and reduces the investment of the overall system. It has excellent use effect and has high use and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a natural gas pressure difference power generation system using photothermal heating provided by one embodiment of the present invention.

[0028] Figure 2 It is a flow chart of a method for using a natural gas pressure difference power generation system using photothermal heating provided by one embodiment of the present invention.

[0029] Markings in the accompanying drawings:

[0030] 1 is a heating furnace, 2 is a pressure reducing valve, 3 is a first natural gas heat exchanger, 4 is an expansion generator, 5 is an air-temperature vaporizer, 6 is a second natural gas heat exchanger, 11 is a first water heat exchanger, 12 is a three-way valve, 13 is a flow control valve, 14 is a cooling water tank, 21 is a solar collector, 22 is a circulating water pump, 23 is a hot water storage tank, 24 is a refrigerant compressor, and 25 is a refrigerant JT valve. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "front", "backward", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the system or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention. The arrows in the accompanying drawings represent the flow direction of the substance.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "assembly", "setting", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] The present invention provides a natural gas pressure difference power generation system using photothermal heating and a method for using the system. The natural gas pressure difference power generation system is provided with a natural gas excess pressure utilization loop, a cooling water circulation loop and a solar thermal collection and lifting loop, and the natural gas pipeline for power generation is heated by utilizing the heat energy collected by solar thermal energy, thereby reducing the risk of hydrates causing ice blockage in the pipeline of the power generation system and greatly improving the system efficiency of the natural gas pressure difference power generation system.

[0035] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] Example 1

[0037] Please refer to Figure 1 The embodiment provides a natural gas pressure difference power generation system using photothermal heating, including a natural gas excess pressure utilization loop, a cooling water circulation loop and a solar heat collection lifting loop. The natural gas excess pressure utilization loop includes a first natural gas heat exchanger 3, an expansion generator 4, an air-temperature vaporizer 5 and a second natural gas heat exchanger 6 connected in sequence; the cooling water circulation loop includes a cooling water tank 14, a first water heat exchanger 11, a three-way 12 and a flow control valve 13 connected in sequence; the second natural gas heat exchanger 6 is connected between the cooling water tank 14 and the flow control valve 13, and the first natural gas heat exchanger 3 is connected to the three-way 12 and the cooling water tank 14 respectively; the solar heat collection lifting loop includes a refrigerant compressor 24, a refrigerant JT valve 25 and a solar collector 21, a circulating water pump 22 and a hot water storage tank 23 connected in a cycle in sequence; the hot water storage tank 23, the refrigerant compressor 24, the first water heat exchanger 11 and the refrigerant JT valve 25 are connected in a cycle in sequence.

[0038] Among them, the cooling water circulation loop is in circulation operation, and serves to connect the natural gas excess pressure utilization loop and the solar thermal collection and lifting loop. The heat in the solar thermal collection and lifting recovery loop is brought into the cooling water circulation loop through the first water heat exchanger 11. The heat of the cooling water circulation loop is brought into the front end of the natural gas excess pressure utilization loop through the first natural gas heat exchanger 3, the second natural gas heat exchanger 6, and the flow control valve 13, or into the front and rear ends at the same time. The solar thermal collection and lifting loop and the natural gas excess pressure utilization loop are operated simultaneously, and the cooling water circulation loop serves as a bridge connecting the two, recycling the excess heat in the solar thermal collection and lifting loop and the excess cold in the natural gas excess pressure utilization loop.

[0039] The first water heat exchanger 11, the refrigerant compressor 24 and the refrigerant JT valve 25 form a water source heat pump. The heat in the solar heat collection and boosting loop comes from solar energy. Since solar energy only exists during the day, the heat energy can be stored in the hot water storage tank 23, and the quality of heat collection can be improved by the water source heat pump.

[0040] The expansion generator 4 in the natural gas surplus pressure utilization loop can generate electricity, and the electricity can be self-generated and used for the factory area or the surplus electricity can be connected to the power supply network.

[0041] A first natural gas heat exchanger 3 is arranged before the expansion generator 4 in the cooling water circulation loop to provide a heat source, thereby increasing the work output of the expansion generator 4 in the natural gas pressure difference power generation system, thereby improving the system efficiency.

[0042] The JT valve is a Joule-Thomson throttling expansion valve, and the refrigerant JT valve 25 can be a product of the prior art.

[0043] Specifically, the natural gas excess pressure utilization circuit is further provided with a circuit connected in parallel therewith, and the parallel circuit is provided such that the heating furnace 1 and the pressure reducing valve 2 are connected in sequence.

[0044] The parallel circuit enters the downstream pipe network through the pressure reducing valve 2 and has a front-end heating function. The natural gas excess pressure utilization circuit enters the downstream pipe network through the expansion generator 4 and has the dual functions of front-end heating and rear-end reheating. The parallel circuit can operate independently or simultaneously with the natural gas excess pressure utilization circuit.

[0045] Specifically, the front ends of the natural gas surplus pressure utilization loop and its parallel loop are connected to the natural gas pipeline network.

[0046] Specifically, the expansion generator 4 is a centrifugal expansion generator, a dual-rotor expansion generator or an integrated expansion generator for pipelines.

[0047] Example 2

[0048] Please refer to Figure 1 and Figure 2This embodiment provides a method for using the natural gas pressure difference power generation system using photothermal heating of embodiment 1, comprising the following steps:

[0049] Step S1, in the natural gas excess pressure utilization loop, the natural gas in the natural gas pipeline network is first heated by the first natural gas heat exchanger 3, and then enters the expansion generator 4 for expansion and power generation, and then the pressure energy of the natural gas is recovered for pressure difference power generation, and then the natural gas is passed into the air-temperature gasifier 5 for reheating, and then the natural gas is passed into the second natural gas heat exchanger 6 for further reheating to the set temperature, so that the natural gas enters the downstream pipeline network;

[0050] Step S2, in the cooling water circulation loop, after the cooling water is pumped out from the cooling water tank 14, the cooling water passes through the first water heat exchanger 11, and is heated by the refrigerant in the solar heat collection lifting loop, and then passes through the tee 12;

[0051] Step S3, in the solar energy collection and lifting loop, solar energy is converted into thermal energy during the day through the solar collector 21, and then the thermal energy is stored in the hot water in the hot water storage tank 23 through the circulating water pump 22; the hot water passes through the compressed refrigerant of the refrigerant compressor 24, releases heat in the first water heat exchanger 11, and then is cooled in the refrigerant JT valve 25, and after throttling and reducing the pressure to liquefy, it enters the hot water storage tank 23 for heating, and then enters the refrigerant compressor 24 to form a closed cycle.

[0052] Specifically, in the summer mode, the flow control valve 13 is closed, so that the cooling water transfers heat to the natural gas in the first natural gas heat exchanger 3 and then enters the cooling water tank 14 for circulation;

[0053] Specifically, in the winter mode, the flow control valve 13 is opened, and after passing through the second natural gas heat exchanger 6, the opening of the flow control valve 13 is adjusted according to the natural gas outlet temperature to adjust the flow of the cooling water branch; when the natural gas outlet temperature is lower than the first set temperature, the opening of the flow control valve 13 is increased to further reheat the natural gas; when the natural gas outlet temperature is higher than the second set temperature, the opening of the flow control valve 13 is reduced, so that the efficiency of the natural gas pressure difference power generation system is improved;

[0054] Specifically, the set temperature of the natural gas introduced into the second natural gas heat exchanger 6 for further reheating is above 0°C.

[0055] Specifically, the first set temperature is 2°C.

[0056] Specifically, the second set temperature is 5°C.

[0057] Among them, the natural gas residual pressure utilization circuit can realize two operation modes:

[0058] 1. In the normal mode, the natural gas in the natural gas pipeline network directly passes through the pressure reducing valve 2 to produce the coke soup effect, and then is reduced in pressure and enters the downstream pipeline network; this normal mode wastes a large amount of pressure energy of the natural gas.

[0059] 2. In bypass mode, natural gas enters the downstream pipeline network after being reduced in pressure by the expansion generator 4; since the refrigeration effect of expansion and pressure reduction is more significant than the refrigeration effect of the coke effect, the temperature drop of natural gas in bypass mode is more significant than that in normal mode, and it is more difficult to reach the set temperature requirement of the natural gas downstream pipeline network, such as above 0°C, and therefore multiple forms of rewarming are required.

[0060] It can be seen that in the bypass mode, the natural gas in the pipeline network is first heated by the first natural gas heat exchanger 3, and then enters the expansion generator 4 for expansion and power generation, and the pressure energy of the natural gas is recovered for pressure difference power generation, and then enters the air-temperature gasifier 5 for reheating, and then enters the second natural gas heat exchanger 6 for further reheating to above 0°C before entering the downstream pipeline network. While utilizing the natural gas pressure energy, it avoids the adverse effect of excessive cooling of the natural gas on the downstream pipeline network.

[0061] In addition, by controlling the flow control valve 13 in the cooling water circulation loop, two operation modes can be achieved:

[0062] 1. In summer mode, by closing the flow control valve 13, the cooling water passes through the tee 12, directly enters the first natural gas heat exchanger 3, and then returns to the cooling water tank 14 for circulation;

[0063] 2. In winter mode, the ambient temperature may be lower than 0°C, and the air-temperature vaporizer 5 is not sufficient to reheat the natural gas to above 0°C, so it is necessary to open the flow control valve 13, and control the opening of the flow control valve 13 by the outlet temperature of the natural gas, thereby adjusting the flow of the cooling water branch. When the outlet temperature of the natural gas is lower than the first set value of, for example, 2°C, the opening of the flow control valve 13 is increased, thereby increasing the flow of the cooling water circulation bypass, and more heat of the cooling water is used to further reheat the natural gas in the second natural gas heat exchanger 6; when the outlet temperature of the natural gas is higher than the second set value of, for example, 5°C, the opening of the flow control valve 13 is reduced, thereby reducing the flow of the cooling water circulation bypass, and more heat of the cooling water is used to heat the natural gas in the first natural gas heat exchanger 3, thereby increasing the work output of the expansion generator 4.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A natural gas pressure difference power generation system using photothermal heating, characterized in that: include: A natural gas residual pressure utilization circuit comprises a first natural gas heat exchanger (3), an expansion generator (4), an air-temperature vaporizer (5) and a second natural gas heat exchanger (6) which are connected in sequence; A cooling water circulation loop comprises a cooling water tank (14), a first water heat exchanger (11), a tee (12) and a flow control valve (13) which are connected in sequence; the second natural gas heat exchanger (6) is connected between the cooling water tank (14) and the flow control valve (13), and the first natural gas heat exchanger (3) is connected to the tee (12) and the cooling water tank (14) respectively; The solar heat collection boosting circuit comprises a refrigerant compressor (24), a refrigerant JT valve (25), and a solar heat collector (21), a circulating water pump (22), and a hot water storage tank (23) which are connected in a circular manner in sequence; the hot water storage tank (23), the refrigerant compressor (24), the first water heat exchanger (11), and the refrigerant JT valve (25) are connected in a circular manner in sequence.

2. The natural gas pressure difference power generation system using photothermal heating according to claim 1 is characterized in that: The natural gas excess pressure utilization circuit is also provided with a circuit connected in parallel therewith, and the parallel circuit is provided with a heating furnace (1) and a pressure reducing valve (2) connected in sequence.

3. The natural gas pressure difference power generation system using photothermal heating according to claim 2 is characterized in that: The front ends of the natural gas excess pressure utilization circuit and the circuits connected in parallel are both connected to the natural gas pipeline network.

4. The natural gas pressure difference power generation system using photothermal heating according to any one of claims 1 to 3, characterized in that: The expansion generator (4) is a centrifugal expansion generator, a dual-rotor expansion generator or an integrated expansion generator for pipelines.

5. A method for using a natural gas pressure difference power generation system using photothermal heating as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: In the natural gas excess pressure utilization loop, the natural gas in the natural gas pipeline network is first heated by the first natural gas heat exchanger (3), and then enters the expansion generator (4) for expansion and power generation, and then the pressure energy of the natural gas is recovered for pressure difference power generation, and then the natural gas is passed into the air-temperature gasifier (5) for reheating, and then the natural gas is passed into the second natural gas heat exchanger (6) for further reheating to a set temperature, so that the natural gas enters the downstream pipeline network; In the cooling water circulation loop, after the cooling water is pumped out from the cooling water tank (14), the cooling water passes through the first water heat exchanger (11), and is heated by the refrigerant in the solar energy heat collection lifting loop, and then passes through the tee (12); In the solar thermal collection and lifting circuit, the solar energy is converted into thermal energy during the day by the solar thermal collector (21), and then the thermal energy is stored in the hot water in the hot water storage tank (23) by the circulating water pump (22); the hot water passes through the compressed refrigerant of the refrigerant compressor (24), releases heat in the first water heat exchanger (11), is cooled in the refrigerant JT valve (25), and after throttling and reducing pressure to liquefy, enters the hot water storage tank (23) to be heated, and then enters the refrigerant compressor (24) to form a closed cycle.

6. The method for using the natural gas pressure difference power generation system using photothermal heating according to claim 5 is characterized in that: In summer mode, the flow control valve (13) is closed so that the cooling water transfers heat to the natural gas in the first natural gas heat exchanger (3) and then enters the cooling water tank (14) for circulation.

7. The method for using the natural gas pressure difference power generation system using photothermal heating according to claim 5 is characterized in that: In winter mode, the flow control valve (13) is opened, and after passing through the second natural gas heat exchanger (6), the opening of the flow control valve (13) is adjusted according to the natural gas outlet temperature to adjust the flow of the cooling water branch; when the natural gas outlet temperature is lower than the first set temperature, the opening of the flow control valve (13) is increased to further reheat the natural gas; when the natural gas outlet temperature is higher than the second set temperature, the opening of the flow control valve (13) is reduced to increase the efficiency of the natural gas pressure difference power generation system.

8. The method for using the natural gas pressure difference power generation system using photothermal heating according to claim 5 is characterized in that: The set temperature of the natural gas introduced into the second natural gas heat exchanger (6) for further reheating is above 0°C.

9. The method for using the natural gas pressure difference power generation system using photothermal heating according to claim 5, characterized in that: The first set temperature is 2°C.

10. The method for using the natural gas pressure difference power generation system using photothermal heating according to claim 9, characterized in that: The second set temperature is 5°C.

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