Differential pressure power generation system of natural gas treatment station

Abstract

The invention discloses a differential pressure power generation system of a natural gas treatment station, and belongs to the technical field of natural gas transportation. Comprising an inlet separation metering subsystem, a differential pressure power generation subsystem and a high-pressure emptying subsystem which are all connected with a control system. The inlet separation metering subsystem comprises a separation unit and a metering unit; the separation unit comprises a first horizontal separator connected with an upstream single well or a gas inlet port of a gas gathering station, and a liquid phase outlet of the first horizontal separator is connected with a port to a condensate oil stabilizing device; the metering unit comprises a vertical separator connected with an upstream single well or a gas inlet port of a gas gathering station, and a gas phase outlet of the vertical separator is connected with an inlet of the first horizontal separator; through control of the control system and interaction and cooperation of the subsystems, continuous and safe conveying of natural gas can be guaranteed, the process requirements of the treatment station are met, and meanwhile pressure energy is effectively utilized to generate clean electric power.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas transportation and relates to a differential pressure power generation system for a natural gas treatment station. Background Art

[0002] Natural gas is a clean high-quality energy source and chemical raw material. However, most gas fields producing natural gas are located in remote areas, far from the main gas-consuming cities. Therefore, continuous and airtight high-pressure long-distance pipelines are mostly used to transport natural gas from gas fields in China to gas-consuming cities. However, due to limitations such as pipeline materials and construction costs, the operating pressure of most high-pressure long-distance pipelines in China is lower than 12 MPa. However, the wellhead pressure of natural gas produced from ultra-deep gas fields in China may be as high as 70 MPa. Therefore, the gathering pipeline between the natural gas wellhead and the long-distance pipeline generally needs to be pressure-regulated multiple times. Among them, in natural gas centralized treatment stations, the existing pressure-regulation process often uses a J-T valve to reduce pressure, without making full use of the pressure potential energy of natural gas itself, wasting a large amount of energy. In recent years, in order to make full use of the pressure potential energy during natural gas transportation, expansion power generation technology has been gradually developed and applied. The existing expansion power generation technologies mainly include the following three types: turboexpander technology, dual-rotor expander technology, and screw expander technology. Among them, the efficiency of turboexpander technology during power generation is generally greater than 80%, significantly higher than the other two technologies. Therefore, it is an optimal option to use turboexpander technology in natural gas treatment stations to utilize the pressure potential energy of natural gas.

[0003] However, the existing systems and equipment in the energy field that use turbine expander technology for pressure difference power generation have some technical defects. For example, the Chinese invention patent with publication number CN114673566A discloses "A pressure difference power generation device and system for natural gas pipeline pressure energy recovery", but the disadvantage of the system is that the temperature of the natural gas after power generation is relatively low, and additional heating equipment is required to heat the natural gas; the Chinese invention patent with authorization announcement number CN104234752B discloses "Expander pressure difference power generation system and control method thereof", but it is mainly aimed at the special situation when the expander is shut down in an emergency; the Chinese invention patent with publication number CN103334891A discloses "A natural gas pressure regulating power generation device", but the device is a simple parallel structure, which does not take into account the maintenance of the device and the need to vent the natural gas during maintenance; the Chinese invention patent with publication number CN103334891A discloses "A natural gas pressure regulating power generation device", but the device is a simple parallel structure, which does not take into account the maintenance of the device and the need to vent the natural gas during maintenance; The Chinese invention patent CN115681040A discloses "A photovoltaic-thermal coupled pressure differential power generation energy comprehensive utilization system and method", which uses the waste heat after solar power generation to provide low-grade heat for pressure differential power generation, but it is only a simple combination of photovoltaic, thermal, pressure differential power generation and other concepts, and the main consideration is how to form the complementarity of several technologies, and it cannot maximize the benefits of the pressure differential power generation system; the Chinese invention patent with the publication number CN115434776A discloses "A natural gas expansion pressure differential power generation system" to control 4 power generation modes according to the principle of the highest economic benefit to produce electricity, compressed natural gas or liquefied natural gas to achieve the maximum utilization of natural gas pressure energy, but this solution is mainly aimed at situations where the gas transmission volume may fluctuate greatly. When it is applied to a processing station with a stable gas source, it will face the problems of excessive investment and equipment redundancy. SUMMARY OF THE INVENTION

[0004] The purpose of the present invention is to solve the technical problems in the prior art that the pressure difference power generation system of the natural gas processing station has no natural gas heating equipment, cannot vent the natural gas during maintenance, and has unreasonable equipment redundancy in the structural design, and provide a pressure difference power generation system for the natural gas processing station.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The present invention provides a pressure difference power generation system for a natural gas processing station, including an inlet separation metering subsystem, a pressure difference power generation subsystem and a high-pressure venting subsystem, all of which are connected to a control system;

[0007] The inlet separation metering subsystem includes a separation unit and a metering unit; the separation unit includes a first horizontal separator connected to the gas inlet port of the upstream single well or gas gathering station, the liquid phase outlet of the first horizontal separator is connected to the port leading to the condensate stabilization unit, and the gas phase outlet of the first horizontal separator is connected to a second horizontal separator through a gas-liquid heat exchanger and a first gas-gas heat exchanger; the metering unit includes a vertical separator connected to the gas inlet port of the upstream single well or gas gathering station, the gas phase outlet of the vertical separator is connected to the inlet of the first horizontal separator; the liquid phase outlet of the vertical separator is connected to the port leading to the condensate stabilization unit; a gas flowmeter is provided at the gas phase outlet of the vertical separator, and a liquid flow observer is provided at the liquid phase outlet.

[0008] The differential pressure power generation subsystem includes a differential pressure generator skid connected to the gas phase outlet of the second horizontal separator, and the gas phase outlet of the differential pressure generator skid is connected to a third horizontal separator; a reserved port before the differential pressure power generation system is provided between the first gas-gas heat exchanger and the second horizontal separator, the reserved port before the differential pressure power generation system is connected to the third horizontal separator, a reserved port after the differential pressure power generation system is provided between the reserved port before the differential pressure power generation system and the third horizontal separator, and a J-T valve is provided between the reserved port before the differential pressure power generation system and the reserved port after the differential pressure power generation system; the third horizontal separator is connected to the port leading to the export pipeline after passing through the first gas-gas heat exchanger and the second gas-gas heat exchanger in sequence; the differential pressure generator skid is connected to a power grid connection system.

[0009] The high-pressure venting subsystem includes a venting pipeline connecting the gas phase outlet of the differential pressure generator skid to the port leading to the high-pressure venting device.

[0010] A further improvement of the present invention lies in:

[0011] It further includes a condensate recovery subsystem; the condensate recovery subsystem includes a port leading to the condensate recovery device connected to the gas-liquid mixed outlet of the second horizontal separator; the gas inlet port of the condensate recovery device is connected to the gas phase inlet of the third horizontal separator through the second gas-gas heat exchanger, and the gas-liquid mixed outlet of the third horizontal separator is connected to the port leading to the condensate recovery device.

[0012] It further includes an antifreeze working subsystem; the antifreeze working subsystem includes an antifreeze addition port provided between the first horizontal separator and the gas-liquid heat exchanger, and after the antifreeze flows along the pipeline into the second horizontal separator and the third horizontal separator for separation, it flows along the pipeline into the port leading to the sewage treatment device or the port leading to the antifreeze recovery device.

[0013] The antifreeze is methanol, ethylene glycol, ethanol or propylene glycol.

[0014] It further includes a heating subsystem; the heating subsystem includes a liquid inlet of the gas-liquid heat exchanger connected to a liquid inlet port of a heating system through a pipeline, and the heating water flows to a heating system port after heat exchange in the gas-liquid heat exchanger.

[0015] The gas phase outlet of the second horizontal separator is connected to the sealed chamber of the differential pressure generator skid for sealing the differential pressure generator skid.

[0016] Each device is connected through a pipeline, and valves are provided on the pipeline.

[0017] The gas phase flow observer adopts an ultrasonic flowmeter, a turbine flowmeter, a vortex street flowmeter, a precession flowmeter, a differential pressure flowmeter or an orifice plate flowmeter; the liquid phase flow observer adopts an electromagnetic flowmeter, a differential pressure flowmeter, a turbine flowmeter, a volumetric flowmeter or a contact flowmeter.

[0018] The condensate oil stabilizing device is replaced by an oil-water mixture treatment device.

[0019] The control system is a DCS control system, and the DCS control system is used to monitor the temperature, pressure and flow rate of the differential pressure power generation system of the natural gas treatment station, and regulate the fluid flow rate in the differential pressure power generation system through valves.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention discloses a differential pressure power generation system for a natural gas treatment station, including an inlet separation and metering subsystem, a differential pressure power generation subsystem and a high-pressure blowdown subsystem all connected to a control system; through the operation of the control system and the interaction and cooperation of multiple subsystems, it can achieve the effective utilization of pressure energy to generate clean electricity while ensuring the continuous and safe transportation of natural gas and meeting the process requirements of the treatment station; at the inlet of the treatment station, two sets of pipelines and equipment for separation and metering are adopted, which can effectively meet the two requirements of metering and treatment of the treatment station at the same time. And it can initially remove the liquid phase contained in the natural gas, achieving the purpose of meeting both the quality requirements of the differential pressure power generation and the external transportation quality requirements of the treatment station. The differential pressure power generation system can not only utilize the pressure potential energy in the natural gas by using the differential pressure generator skid, but also meet the bypass pressure reduction requirements in special cases through the J-T valve device, meeting the continuous and safe operation requirements of the treatment station. It is particularly suitable for natural gas centralized treatment stations that have already been provided with J-T valves and have stable gas volumes. By arranging a horizontal separator before and after the differential pressure generator skid, the liquid phase such as antifreeze and condensate contained in the natural gas can be fully removed, improving the separation and recovery ability of the liquid phase such as antifreeze and condensate, thereby reducing the operation and maintenance costs and increasing the benefits.

[0022] Furthermore, the differential pressure power generation system of the natural gas treatment station in the present invention further includes a condensate recovery subsystem, which makes full use of the heat of the incoming natural gas to heat the supply water pipeline and the exported natural gas, and exchanges heat between the gas from the condensate recovery device and the exported natural gas, thereby increasing the temperature of the heating water and the exported natural gas. There is no need to add additional heating equipment, which greatly improves the heat utilization efficiency, and the process is relatively simple and the equipment has good stability, facilitating maintenance and repair.

[0023] Furthermore, the gas phase outlet of the second horizontal separator is connected to the sealed chamber of the differential pressure generator skid for sealing the differential pressure generator skid. Using natural gas as the raw material gas or the instrument air system in the treatment station to provide sealing gas for the differential pressure generator skid can reduce the setting of nitrogen sealing devices and pipelines, thereby reducing the investment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic structural diagram of a differential pressure power generation system of a natural gas treatment station in the present invention;

[0026] Figure 2 It is a schematic diagram of the inlet metering and separation subsystem in a differential pressure power generation system of a natural gas treatment station in the present invention;

[0027] Figure 3 It is a schematic diagram of the differential pressure power generation subsystem in a differential pressure power generation system of a natural gas treatment station in the present invention;

[0028] Figure 4 It is a schematic diagram of the antifreeze recovery subsystem in a differential pressure power generation system of a natural gas treatment station in the present invention;

[0029] Figure 5 It is a schematic diagram of the condensate recovery subsystem in a differential pressure power generation system of a natural gas treatment station in the present invention;

[0030] Figure 6 It is a schematic diagram of the high-pressure venting subsystem in a differential pressure power generation system of a natural gas treatment station in the present invention;

[0031] Figure 7 It is a schematic diagram of the heating subsystem in a differential pressure power generation system of a natural gas treatment station in the present invention.

[0032] Wherein: 1 - Gas inlet port from upstream single well or gas gathering station; 2 - Port to condensate stabilization unit; 3 - Port to sewage treatment unit; 4 - Port to antifreeze recovery unit; 5 - Liquid inlet port from heating system; 6 - Port to heating system; 7 - Port to export pipeline; 8 - Port to high-pressure venting unit; 9 - Gas inlet port from condensate recovery unit; 10 - Port to condensate recovery unit; 11 - Differential pressure generator skid; 12 - Reserved port before differential pressure power generation system; 13 - Reserved port after differential pressure power generation system; 101 - Inlet manifold; 102 - Inlet metering branch pipe; 103 - Inlet main pipe; 104 - Liquid phase metering branch pipe; 105 - Gas phase metering branch pipe; 106 - Separated liquid phase main pipe; 107 - Separated gas phase main pipe; 201 - Feed gas inlet main pipe; 202 - Dry gas seal inlet branch pipe; 203 - Feed gas outlet main pipe; 204 - Dry gas outlet main pipe; 205 - Condensate recovery gas inlet pipe; 206 - Bypass pressure reduction branch pipe; 301 - Antifreeze recovery branch pipe; 302 - Antifreeze recovery main pipe; 303 - Antifreeze recovery pipe; 304 - Drainage pipe; 401 - Condensate recovery main pipe; 402 - Condensate recovery branch pipe; 501 - Leakage gas recovery branch pipe; 502 - Flare gas recovery branch pipe; 503 - High-pressure venting main pipe; 601 - Heating water pipe; 1001 - First electric ball valve; 1002 - Second electric ball valve; 1003 - First pneumatic ball valve; 1004 - First electric control valve; 1005 - First control valve; 1006 - Vertical separator; 1007 - First horizontal separator; 1008 - Second horizontal separator; 1009 - Gas phase flow monitor; 1010 - Liquid phase flow monitor; 2001 - Second pneumatic ball valve; 2002 - Second control valve; 2003 - J-T valve; 2004 - Third pneumatic ball valve; 2005 - First ball valve; 2006 - Third control valve; 2007 - First check valve; 2008 - Fourth pneumatic ball valve; 2009 - Third horizontal separator; 2010 - First pressure monitor; 2011 - Second pressure monitor; 2012 - Third pressure monitor; 2013 - First temperature monitor; 2014 - Second temperature monitor; 2015 - First gas-gas heat exchanger; 2016 - Second gas-gas heat exchanger; 3001 - Fourth control valve; 3002 - Fifth control valve; 4001 - Sixth control valve; 5001 - Second electric control valve; 6001 - Gas-liquid heat exchanger. Detailed implementation manners

[0033] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0035] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not require further definition and explanation in subsequent drawings.

[0036] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is customarily placed during use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0037] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0038] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are 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 directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0039] The present invention will be further described in detail below with reference to the accompanying drawings:

[0040] See Figure 1 , an embodiment of the present invention discloses a differential pressure power generation system for a natural gas treatment station, including an inlet separation and metering subsystem, a differential pressure power generation subsystem, a high-pressure blowdown subsystem, a condensate recovery subsystem, an antifreeze working subsystem, and a heating subsystem, all of which are connected to a control system.

[0041] See Figure 2, the inlet separation and metering subsystem includes a separation unit and a metering unit; the separation unit includes a first horizontal separator 1007 connected to the gas inlet port 1 of the upstream single well or gas gathering station. The liquid phase outlet of the first horizontal separator 1007 is connected to the port 2 leading to the condensate stabilization unit. The gas phase outlet of the first horizontal separator 1007 is connected to a second horizontal separator 1008 through a gas-liquid heat exchanger 6001 and a first gas-gas heat exchanger 2015; the metering unit includes a vertical separator 1006 connected to the gas inlet port 1 of the upstream single well or gas gathering station. The gas phase outlet of the vertical separator 1006 is connected to the inlet of the first horizontal separator 1007; the liquid phase outlet of the vertical separator 1006 is connected to the port 2 leading to the condensate stabilization unit; a gas phase flowmeter 1009 is provided at the gas phase outlet of the vertical separator 1006, and a liquid phase flow observer 1010 is provided at the liquid phase outlet.

[0042] The inlet separation equipment and pipelines refer to that the natural gas entering the station passes through multiple valves and gas-liquid separators, and a large amount of liquid phase is separated and sent to the condensate stabilization unit, and the natural gas containing a small amount of liquid phase is sent to the differential pressure power generation subsystem. The inlet separation equipment and pipelines are the main transmission channels for the natural gas entering the station, mainly composed of an inlet header 101, an intake main pipe 103, a first horizontal separator 1007, a separated liquid main pipe 106, a separated gas main pipe 107 and the valves on the pipelines.

[0043] The inlet metering equipment and pipelines refer to that after the natural gas entering the station enters the vertical separator 1006 through the intake metering branch pipe 102, the gas phase and liquid phase in the natural gas containing a large amount of liquid phase are separated and measured by a gas phase flow observer 1009 and a liquid phase flow observer 1010 respectively. Then the gas phase is transported to the first horizontal separator 1007 through the gas phase metering branch pipe 105 for further separation, and the liquid phase is transported to the separated liquid main pipe 106 through the liquid phase metering branch pipe 104 and then sent to the condensate stabilization unit together. The inlet metering equipment and pipelines are the main metering channels for the natural gas entering the station, mainly composed of an intake metering branch pipe 102, a vertical separator 1006, a liquid phase metering branch pipe 104, a gas phase metering branch pipe 105, a gas phase flowmeter 1009, a liquid phase flow observer 1010 and the valves on the pipelines.

[0044] Optionally, the vertical separator 1006 can also be a horizontal separator.

[0045] Optionally, the gas phase flow observer 1009 can be an ultrasonic flowmeter, a turbine flowmeter, a vortex street flowmeter, a swirl flowmeter, a differential pressure flowmeter, an orifice flowmeter, etc. The liquid phase flow observer 1010 can be an electromagnetic flowmeter, a differential pressure flowmeter, a turbine flowmeter, a volumetric flowmeter, a contact flowmeter, etc.

[0046] It should be noted that the first electric ball valve 1001 and the second electric ball valve 1002 are not allowed to be opened simultaneously in principle, that is, the incoming natural gas cannot enter the separation pipeline and the metering pipeline at the same time.

[0047] The first electric ball valve 1001 and the second electric ball valve 1002 are used to adjust the opening and closing of the pipeline. The first pneumatic ball valve 1003 is used to adjust the flow rate. The first electric control valve 1004 and the first control valve 1005 are used to adjust the flow rate.

[0048] The separated liquid phase is generally condensate or an oil-water mixture. Optionally, the condensate stabilization unit to which it goes can also be an oil-water mixture treatment unit.

[0049] The DCS control system mainly centrally manages the equipment and various valves in the gas transmission station yard and dispersedly controls the equipment and valves in the gas transmission station yard. The DCS control system can implement alarm functions and control functions according to data such as monitored pressure, flow rate, and temperature. Intuitively, the DCS control system can control the valves.

[0050] See Figure 3 , the differential pressure power generation subsystem includes a differential pressure generator skid 11 connected to the gas phase outlet of the second horizontal separator 1008. The gas phase outlet of the differential pressure generator skid 11 is connected to a third horizontal separator 2009. A pre-reservation port 12 for the differential pressure power generation system is provided between the first gas-gas heat exchanger 2015 and the second horizontal separator 1008. The pre-reservation port 12 for the differential pressure power generation system is connected to the third horizontal separator 2009. A post-reservation port 13 for the differential pressure power generation system is provided between the pre-reservation port 12 for the differential pressure power generation system and the third horizontal separator 2009. A J-T valve 2003 is provided between the pre-reservation port 12 for the differential pressure power generation system and the post-reservation port 13 for the differential pressure power generation system. The third horizontal separator 2009 is connected to an outgoing transmission pipeline port 7 after passing through the first gas-gas heat exchanger 2015 and the second gas-gas heat exchanger 2016 in sequence. The differential pressure generator skid 11 is connected to a power grid connection system;

[0051] The differential pressure power generation subsystem includes a differential pressure generator skid, a power grid connection system, a gas phase transmission pipeline, a J-T valve, a horizontal separator, a heat exchanger, and connected pipelines and valves.

[0052] The differential pressure generator skid is a complete modular-configured differential pressure power generation skid-mounted device, including a turbine expander, an asynchronous generator, a lubricating oil system, a cooling system, a control system, and supporting auxiliary equipment such as thermal resistors and pressure transmitters, as well as wiring between skids.

[0053] The turboexpander of the differential pressure generator skid is designed based on the natural gas thermodynamic calculation data in the processing station, considering parameters such as the pressure drop, temperature drop across the J-T valve, and the flow rate of the natural gas processed in the station. The asynchronous generator needs to be combined with the gas transmission station environment and the requirement of low maintenance, and a generator set with wide market application, mature technology, simple structure, high reliability, and not restricted by the usage place is adopted. The lubricating oil system adopts a three-pump oil supply method of main oil pump MOP + auxiliary oil pump AOP + emergency oil pump EOP, and no elevated oil tank is set. The cooling system adopts air cooling. The control system is a complete control system for the turboexpander generator set, including system design, hardware manufacturing, cabinet integration, system configuration, testing, etc. The function of the control system is to be isolated when an accident occurs in the turboexpander (such as overspeed, lack of lubricating oil, abnormal pressure increase, etc.), so as to ensure the safety of the skid-mounted unit.

[0054] The sealing of the differential pressure generator skid is mainly completed by means of the instrument air system in the natural gas treatment station, and nitrogen is generally used as the sealing gas. Dry gas separated by the second horizontal separator 1008 can also be used and enters the seal chamber through the dry gas seal inlet branch pipe 202.

[0055] Due to the limitations of materials and processes, the differential pressure generator skid cannot achieve absolute sealing, and there is still a small amount of leakage gas passing through the secondary seal and entering the leakage gas recovery branch pipe 501 through the outlet.

[0056] The power grid connection system refers to the power generated by the differential pressure generator skid, which is transmitted to the high-voltage distribution room of the natural gas treatment station through high-voltage cables. Through the grid connection system, the energy relationship between the grid power and the differential pressure power generation is automatically adjusted and controlled to achieve a combined power supply mode of grid power and differential pressure power generation. The differential pressure power generation is preferentially used to supply power to the electrical equipment in the processing station, and the grid power is used as a beneficial supplement.

[0057] The grid connection system should have functions of complementary self-regulation with grid power, anti-islanding protection, and emergency fault power-off.

[0058] Complementary self-regulation function with grid power: The phase sequence of the generated electric energy should be the same as that of the grid power return bus; the effective value of the voltage of the generated electric energy should be close to or equal to that of the grid power, and the waveforms should be the same; the frequency of the generated electric energy should be basically equal to that of the power system; the voltage phase of the generated electric energy should be equal to the voltage phase of the power system power supply; according to the amount of generated electric energy, complementary self-regulation with grid power is realized to supply power to the natural gas treatment station.

[0059] Grid-connected anti-islanding protection function: When overvoltage, undervoltage, excessive frequency, low frequency, frequency mutation, reverse power, external tripping, system power failure, frequency mutation blocking low frequency, automatic closing with voltage, simulated tripping, etc. occur, the grid-connected system can be automatically controlled to achieve the separation and protection of grid power and differential pressure power generation.

[0060] Emergency fault power-off function: To ensure power supply safety and reliability and enable the differential pressure generator set to operate stably and reliably after being grid-connected, the unit should be equipped with a safety protection device. Once faults such as overload fault, overspeed fault, pressure fault, temperature fault, power direction fault, and emergency stop device occur in the unit, it should automatically trip, disconnect from the grid, and automatically shut down.

[0061] The high-voltage cable of the grid-connected system is laid in a direct buried manner, protected by a power pipe throughout the process, and covered with sand and a protection board. The connection between the cable and the differential pressure generator skid uses an explosion-proof cable sealing head with a double-layer sealing structure.

[0062] The gas-phase transmission pipeline mainly includes a raw gas inlet main pipe 201, a raw gas outlet main pipe 203, and a dry gas outlet main pipe 204.

[0063] The J-T valve 2003 refers to a Joule-Thomson throttling expansion valve, which is a throttle valve designed based on the Joule-Thomson throttling expansion principle and is located on the 1020 bypass pressure-reducing branch pipe.

[0064] Optionally, the J-T valve 2003 can also be replaced by other components with the same throttling, pressure-reducing, and temperature-reducing effects. Such components with the same effects should have the same Joule-Thomson throttling expansion principle.

[0065] The horizontal separators include a second horizontal separator 1008 and a third horizontal separator 2009, which have the same function, that is, to remove liquid-phase media such as antifreeze, oil, and water from natural gas and convert natural gas containing a small amount of liquid droplets into dry gas that can be exported.

[0066] The heat exchangers include a first gas-gas heat exchanger 2015 and a second gas-gas heat exchanger 2016. They both exchange heat between high-temperature gas and low-temperature gas, so that the heat of the high-temperature gas is transferred to the low-temperature gas to improve the heat utilization efficiency.

[0067] Among them, the first gas-gas heat exchanger 2015 exchanges heat between natural gas with a relatively high temperature containing a small amount of liquid and the exported dry gas after throttling, pressure-reducing, and temperature-reducing, so as to increase the temperature of the exported natural gas. The second gas-gas heat exchanger 2016 exchanges heat between natural gas with a relatively high temperature containing a small amount of liquid droplets coming from the condensate recovery device and the exported natural gas, so as to further increase the temperature of the exported natural gas.

[0068] It is worth noting that the third regulating valve 2006 and the first ball valve 2005 can be opened at the same time, that is, the raw gas can serve as the sealing gas of the pressure difference generator skid.

[0069] The second pneumatic ball valve 2001, the third pneumatic ball valve 2004, and the fourth pneumatic ball valve 2008 are used to adjust the opening and closing of the pipeline. The first ball valve 2005 is used to adjust the flow. The JT valve 2003 and the third regulating valve 2006 are used to adjust the pressure. The first check valve 2007 is used to prevent the natural gas from flowing back into the pressure difference generator skid.

[0070] The first pressure observer 2010 and the second pressure observer 2011 are used to observe the pressure before and after the third regulating valve 2006, and the third pressure observer 2012 is used to observe the pressure at the outlet of the pressure difference generator.

[0071] The first temperature observer 2013 and the second temperature observer 2014 are used to observe the temperature of the pressure difference generator skid inlet and outlet respectively.

[0072] See also Figure 4 , the antifreeze working subsystem includes an antifreeze inlet provided between the first horizontal separator 1007 and the gas-liquid heat exchanger 601. The antifreeze flows along the pipeline into the second horizontal separator 1008 and the third horizontal separator 2009 for separation, and then flows along the pipeline to the sewage treatment device port 3 or to the antifreeze recovery device port 4.

[0073] The antifreeze working subsystem includes the addition, separation and recovery of antifreeze, as well as the connecting pipelines and valves.

[0074] Optionally, the antifreeze agent may be methanol, ethylene glycol, ethanol, propylene glycol, etc.

[0075] The antifreeze inlet is generally located on the separation gas phase main pipe 107, between the gas-liquid heat exchanger 6001 and the first horizontal separator 1007.

[0076] The separation of antifreeze mainly relies on the second horizontal separator 1008 and the third horizontal separator 2009. A large amount of antifreeze separated from the second horizontal separator 1008 passes through the antifreeze recovery main pipe 302, generally leading to the antifreeze recovery pipe 303, and goes to the antifreeze recovery device. In special cases, it can also lead to the sewage pipe 304 and go to the sewage treatment device. A small amount of antifreeze separated from the third horizontal separator 2009 is collected in the antifreeze recovery main pipe 302 through the antifreeze recovery branch pipe 301.

[0077] The fourth regulating valve 3001 is used to control the flow of the antifreeze recovery main pipe 302.

[0078] See also Figure 5The condensate recovery subsystem includes 9 and a port 10 for a condensate recovery device connected to the gas-liquid mixed outlet of the second horizontal separator 1008; the gas inlet port 9 of the condensate recovery device is connected to the gas phase inlet of the third horizontal separator 2009 through the second gas-gas heat exchanger 2016, and the gas-liquid mixed outlet of the third horizontal separator 2009 is connected to the port 10 for a condensate recovery device.

[0079] The condensate recovery subsystem includes equipment, pipelines and valves for sending the condensate separated from the natural gas to the condensate recovery device, and equipment, pipelines and valves for sending the higher temperature natural gas separated from the condensate recovery device to the third horizontal separator 2009.

[0080] Condensate refers to a liquid hydrocarbon mixture recovered from natural gas and not stabilized, generally including ethane, propane, butane and some stable light hydrocarbon components.

[0081] The condensate separated by the second horizontal separator 1008 passes through the condensate recovery main pipe 401 to the condensate recovery device. The third horizontal separator 2009 collects the condensate separated from the natural gas through the condensate recovery branch pipe 402 and into the condensate recovery main pipe 401.

[0082] Optionally, due to the pressure reduction and temperature reduction effect of the pressure difference generator skid, the temperature and pressure at the outlet of the pressure difference generator skid are significantly lower than those at the inlet, so the pressure and temperature in the third horizontal separator 2009 are significantly lower than those in the second horizontal separator 1008, so that the condensate separated from the third horizontal separator 2009 is generally more than the condensate separated from the second horizontal separator 1008. Therefore, the primary and secondary distinctions of the condensate recovery main pipe 401 and the condensate recovery branch pipe 402 are only used to distinguish the pipeline connection mode, but not to distinguish the flow rate, that is, the condensate recovery main pipe and the condensate recovery branch pipe are just names and can be interchanged.

[0083] The natural gas with a higher temperature separated from the condensate recovery device is transported through the condensate recovery gas pipeline 205, and after heat exchange with the external natural gas at the second gas-to-gas heat exchanger 2016, it is merged into the raw gas outlet main pipe 203 and leads to the third horizontal separator 2009.

[0084] The fifth regulating valve 3002 and the sixth regulating valve 4001 are used to adjust the flow rate.

[0085] See also Figure 6 , the high-pressure venting subsystem includes a venting pipeline connecting the gas phase outlet of the pressure difference generator skid 11 with the port 8 to the high-pressure venting device.

[0086] The high-pressure venting subsystem includes a leaked gas recovery branch pipe 501, a vented gas recovery branch pipe 502, a high-pressure venting main pipe 503 and valves thereof.

[0087] Function of the vent gas recovery branch pipe 502: When the pressure difference power generation system makes an emergency stop or is under maintenance, it is used to release the flammable and explosive natural gas in the system, so as to ensure the safety of the pressure difference power generation system; the released natural gas enters the vent gas recovery branch pipe and leads to the high-pressure vent main pipe.

[0088] Function of the leaked gas recovery branch pipe 501: Although a tight sealing system has been adopted, due to the limitation of the process level, there is still a small amount of natural gas working medium leaking from inside the pressure difference generator skid. The leaked gas recovery branch pipe is used to introduce the leaked small amount of gas into the vent gas recovery branch pipe and then lead to the high-pressure vent main pipe.

[0089] The high-pressure vent main pipe 503 mainly leads the high-pressure natural gas that leaks or needs to be released to the high-pressure vent device, so as to meet the requirement of removing the combustible natural gas in the device.

[0090] Optionally, the high-pressure vent device can also be a vent gas recovery device to recover the leaked or released natural gas. The specific selection should be comprehensively considered according to factors such as economy and environmental protection requirements.

[0091] See Figure 7 , the heating subsystem includes the liquid inlet port 5 of the heating system connected by a pipeline to the liquid phase inlet of the gas-liquid heat exchanger 6001, and the heating water flows to the heating system port 6 after heat exchange in the gas-liquid heat exchanger 6001.

[0092] The described heating subsystem refers to pipelines, heat exchangers, valves, etc. used to exchange heat between the heating water in the living area and the natural gas with a relatively high temperature when entering the station. It mainly includes the heating water pipeline 601 and the gas-liquid heat exchanger 6001.

[0093] Exchanging heat between the heating water pipeline and the natural gas with a relatively high temperature when entering the station is beneficial to saving the gas consumption in the living area.

[0094] Optionally, energy supplement can be provided for the heating water pipeline in forms such as photovoltaic power generation, solar thermal heating, air source heat pump, water source heat pump, etc., but economic efficiency needs to be considered emphatically.

[0095] The working principle of the present invention is as follows:

[0096] The described inlet separation and metering subsystem is used for: through the control of the DCS control system, completing the metering and preliminary separation of the natural gas containing a large amount of liquid phase entering the processing station. The separated natural gas containing a small amount of liquid phase enters the pressure difference power generation subsystem; the separated large amount of liquid phase leads to the condensate stabilization unit.

[0097] The described differential pressure power generation subsystem is used for: providing a stable, reliable, economical and practical process to fully utilize the pressure potential energy of natural gas to generate electric energy, and fully utilizing the heat in the station to provide heat for the natural gas after pressure reduction to meet the requirements such as temperature and pressure for the external transportation of natural gas.

[0098] The described antifreeze working subsystem is used for: adding antifreeze to the natural gas transported in the station pipeline to lower its freezing point, improve the antifreeze ability, and prevent the formation of hydrates in natural gas during the cooling process and blockage of pipelines or equipment due to freezing. The separated antifreeze is also recycled through a separator to achieve the recycling of antifreeze, thereby saving costs.

[0099] The described condensate recovery subsystem is used for: separating the condensate with high economic value contained in natural gas and sending it to the condensate recovery device for centralized treatment. The natural gas with relatively low pressure and relatively high temperature separated from the condensate recovery device is sent to the differential pressure power generation subsystem and is externally transported after being separated again.

[0100] The described high-pressure venting subsystem is used for: when the differential pressure power generation system of the natural gas treatment station needs to be overhauled or the leakage of the sealing gas needs to be released, transporting the natural gas in the system to the venting device through the high-pressure venting pipeline.

[0101] The described heating subsystem is used for: exchanging heat between the low-temperature heating water in the living area of the treatment station and the high-temperature natural gas entering the station to lower the temperature of the natural gas and raise the temperature of the heating water, saving heating costs.

[0102] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A pressure difference power generation system for a natural gas processing station, characterized in that: It includes an inlet separation metering subsystem, a pressure difference generating subsystem and a high-pressure venting subsystem, all of which are connected to the control system; The inlet separation and metering subsystem comprises a separation unit and a metering unit; the separation unit comprises a first horizontal separator (1007) connected to the gas inlet port (1) of an upstream single well or a gas gathering station, the liquid phase outlet of the first horizontal separator (1007) is connected to the port (2) to the condensate oil stabilization device, and the gas phase outlet of the first horizontal separator (1007) is connected to the second horizontal separator (1008) through the gas-liquid heat exchanger (6001) and the first gas-gas heat exchanger (2015); the metering unit comprises a first horizontal separator (1007) connected to the gas inlet port (1007) of the upstream single well or the gas gathering station, the liquid phase outlet of the first horizontal separator (1007) is connected to the port (2) to the condensate oil stabilization device, and the gas phase outlet of the first horizontal separator (1007) is connected to the second horizontal separator (1008) through the gas-liquid heat exchanger (6001) and the first gas-gas heat exchanger (2015); The measuring unit comprises a vertical separator (1006) connected to the gas inlet port (1) of an upstream single well or a gas gathering station, the gas phase outlet of the vertical separator (1006) being connected to the inlet of the first horizontal separator (1007); the liquid phase outlet of the vertical separator (1006) being connected to the port (2) for the condensate oil stabilization device; a gas phase flow meter (1009) is provided at the gas phase outlet of the vertical separator (1006), and a liquid phase flow observer (1010) is provided at the liquid phase outlet; The pressure difference power generation subsystem comprises a pressure difference power generation skid (11) connected to the gas phase outlet of the second horizontal separator (1008), and the gas phase outlet of the pressure difference power generation skid (11) is connected to the third horizontal separator (2009); a pressure difference power generation system front reserved port (12) is provided between the first gas-to-gas heat exchanger (2015) and the second horizontal separator (1008), and the pressure difference power generation system front reserved port (12) is connected to the third horizontal separator (2009), and the pressure difference power generation system front reserved port (12) is connected to the third horizontal separator (2009). A rear reserved port (13) of the pressure difference power generation system is arranged between the port (12) and the third horizontal separator (2009), and a JT valve (2003) is arranged between the front reserved port (12) of the pressure difference power generation system and the rear reserved port (13) of the pressure difference power generation system; the third horizontal separator (2009) is connected to a port (7) for an external transmission pipeline after passing through the first gas-to-gas heat exchanger (2015) and the second gas-to-gas heat exchanger (2016) in sequence; the pressure difference generator skid (11) is connected to a power grid connection system; The high-pressure venting subsystem comprises a venting pipeline connecting the gas phase outlet of the pressure difference generator skid (11) with a port (8) leading to the high-pressure venting device.

2. The pressure difference power generation system of the natural gas processing station according to claim 1, characterized in that: It also includes a condensate recovery subsystem; the condensate recovery subsystem includes (9) and a port (10) to a condensate recovery device connected to the gas-liquid mixed outlet of the second horizontal separator (1008); the gas inlet port (9) of the condensate recovery device is connected to the gas phase inlet of the third horizontal separator (2009) through the second gas-to-gas heat exchanger (2016), and the gas-liquid mixed outlet of the third horizontal separator (2009) is connected to the port (10) to the condensate recovery device.

3. The pressure difference power generation system of the natural gas processing station according to claim 1, characterized in that: It also includes an antifreeze working subsystem; the antifreeze working subsystem includes an antifreeze inlet arranged between the first horizontal separator (1007) and the gas-liquid heat exchanger (601); the antifreeze flows along the pipeline into the second horizontal separator (1008) and the third horizontal separator (2009) for separation, and then flows along the pipeline to the sewage treatment device port (3) or to the antifreeze recovery device port (4).

4. The pressure difference power generation system of the natural gas processing station according to claim 3, characterized in that: Antifreeze is methanol, ethylene glycol, ethanol or propylene glycol.

5. The pressure difference power generation system of the natural gas processing station according to claim 1, characterized in that: It also includes a heating subsystem; the heating subsystem includes a heating system liquid inlet port (5) connected to the liquid phase inlet of the gas-liquid heat exchanger (6001) through a pipeline, and the heating water flows to the heating system port (6) after heat exchange in the gas-liquid heat exchanger (6001).

6. The pressure difference power generation system of a natural gas processing station according to claim 1, characterized in that: The gas phase outlet of the second horizontal separator (1008) is connected to the sealing chamber of the pressure difference generator skid (11) for sealing the pressure difference generator skid (11).

7. The pressure difference power generation system of a natural gas processing station according to any one of claims 1 to 6, characterized in that: The devices are connected through pipelines, and valves are arranged on the pipelines.

8. The pressure difference power generation system of the natural gas processing station according to claim 7, characterized in that: The gas phase flow observer (1009) adopts an ultrasonic flowmeter, a turbine flowmeter, a vortex flowmeter, a swirl flowmeter, a differential pressure flowmeter or an orifice flowmeter; the liquid phase flow observer (1010) adopts an electromagnetic flowmeter, a differential pressure flowmeter, a turbine flowmeter, a volumetric flowmeter or a contact flowmeter.

9. The pressure difference power generation system of a natural gas processing station according to claim 7, characterized in that: The condensate oil stabilization device is replaced by an oil-water mixture processing device.

10. The pressure difference power generation system of a natural gas processing station according to claim 7, characterized in that: The control system is a DCS control system, which is used to monitor the temperature, pressure and flow of the pressure difference power generation system of the natural gas processing station and adjust the fluid flow in the pressure difference power generation system through valves.

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