A power generation system based on a gas-liquid integrated free plunger expander

Abstract

The present invention relates to the technical field of expander and natural gas pressure difference energy utilization, and specifically to a power generation system based on a gas-liquid integrated free-piston expander: comprising an energy recovery and conversion unit group, a return accumulator unit group and a constant frequency generator group, the energy recovery and conversion unit group comprising an exhaust phase of a free-piston expander group, an expansion phase of a free-piston expander group and an intake phase of a free-piston expander group, the number of intake phases of the free-piston expander group is at least one, and due to the setting of parallel and series control valves, the power generation system based on the gas-liquid integrated free-piston expander can realize the matching of parallel expanders with large wellhead flow and the matching of series expanders with high or ultra-high wellhead pressure, and has the advantages of flexible expander arrangement, wide adaptability to working conditions, high conversion efficiency, safety and stability, and high power generation quality, and is conducive to the implementation and promotion of recovery of wellhead natural gas pressure difference energy.

Description

Technical Field

[0001] The present invention relates to the technical field of expanders and natural gas pressure difference energy utilization, and in particular to a power generation system based on a gas-liquid integrated free plunger expander. Background Art

[0002] As a clean and environmentally friendly fossil energy source, natural gas produces less carbon dioxide when burned than other fossil fuels. When natural gas flows from the wellhead, due to its high pressure, typically reaching 20 MPa or above, it needs to be throttled down to a pressure range of 6-10 MPa that can be handled by the gas gathering station.

[0003] Currently, the main method of reducing the pressure of high-pressure natural gas from the wellhead to the gas gathering station or the gathering and transmission pipeline is to use a throttle valve, but this pressure reduction method will waste a lot of energy. Summary of the Invention

[0004] The purpose of the present invention is to provide a power generation system based on a gas-liquid integrated free-piston expander to solve the problem that in the process of transferring high-pressure natural gas from the wellhead to the gas gathering station or the gathering and transmission pipeline, the main method of reducing the pressure of natural gas is a throttle valve, but this pressure reduction method will waste a lot of energy.

[0005] To achieve the above objectives, the present invention provides a power generation system based on a gas-liquid integrated free-piston expander, the power generation system based on the gas-liquid integrated free-piston expander comprising an energy recovery and conversion unit group, a return accumulator unit group, and a constant-frequency generator group, wherein the return chamber of the energy recovery and rotation unit group is connected to the return accumulator unit group, and the output end of the energy recovery and rotation unit group is connected to the constant-frequency generator group;

[0006] The energy recovery and conversion unit group includes a free plunger expansion unit exhaust phase, a free plunger expansion unit expansion phase and a free plunger expansion unit intake phase, the number of the free plunger expansion unit intake phase is at least 1, the free plunger expansion unit exhaust phase, the free plunger expansion unit expansion phase and the free plunger expansion unit intake phase are all composed of a gas-liquid integrated free plunger expander, the free plunger expansion unit exhaust phase, the free plunger expansion unit expansion phase and the free plunger expansion unit The number of the gas-liquid integrated free-piston expanders in the intake phase is at least one, each of the gas-liquid integrated free-piston expanders is connected to the high-pressure wellhead natural gas through an intake control valve, each of the gas-liquid integrated free-piston expanders is connected to the low-pressure gathering pipeline through an exhaust control valve, each of the gas-liquid integrated free-piston expanders is connected to the return accumulator unit group through a first one-way valve and an oil pipe, and each of the gas-liquid integrated free-piston expansion mechanisms is connected to the constant frequency generator set through a second one-way valve.

[0007] Among them, when there are multiple gas-liquid integrated free piston expanders set on the exhaust phase of the free piston expansion unit, the expansion phase of the free piston expansion unit and the intake phase of the free piston expansion unit, two adjacent gas-liquid integrated free piston expanders are connected through parallel and series control valves.

[0008] Among them, a high-pressure natural gas inlet and a low-pressure natural gas exhaust are respectively provided on both sides of the bottom of each of the gas-liquid integrated free plunger expanders, an isolation valve core is provided in the middle of the top of each of the gas-liquid integrated free plunger expanders, and a plunger is provided inside each of the gas-liquid integrated free plunger expanders. The cross-section of the plunger is U-shaped, and an expansion chamber is formed between the plunger and the inner bottom of the gas-liquid integrated free plunger expander. The top of the plunger is provided on the outside of the bottom of the isolation valve core, and a return oil chamber is provided inside the plunger. The top of the isolation valve core is provided with a return oil chamber inlet and outlet, and an energy recovery chamber is formed between the top of the plunger and the outer wall of the isolation valve core. The energy recovery chamber oil inlet and the energy recovery chamber oil discharge are respectively provided on both sides of the top of each of the gas-liquid integrated free plunger expanders.

[0009] Among them, the inner wall of each of the gas-liquid integrated free piston expanders is provided with a high-pressure hydraulic sealing ring, a low-pressure gas-liquid sealing ring and a high-pressure air pressure sealing ring in sequence from top to bottom, and the inner wall of each of the gas-liquid integrated free piston expanders is also provided with an air release chamber and an oil release chamber, the air release chamber is located between the high-pressure air pressure sealing ring and the low-pressure gas-liquid sealing ring, and the oil release chamber is located between the low-pressure gas-liquid sealing ring and the high-pressure hydraulic sealing ring.

[0010] In which, the return accumulator unit group includes an accumulator, a first pressure gauge, a third one-way valve, an oil replenishment pump, a first oil tank and a relief valve. The accumulator is connected to the multiple return oil chamber inlets and outlets through a pipeline. The first pressure gauge is provided on the pipeline connecting the accumulator and the multiple return oil chamber inlets and outlets. The accumulator is respectively connected to the first oil tank and the multiple energy recovery chamber oil inlets through pipelines. The third one-way valve and the oil replenishment pump are sequentially provided on the pipeline connecting the accumulator and the first oil tank. The first oil tank and the first pressure gauge are connected by a pipeline, and the relief valve is provided on the pipeline connecting the first oil tank and the first pressure gauge.

[0011] In which, the constant frequency generator set includes a flow meter, a filter accumulator, a second pressure gauge, a safety valve, a variable motor, a torque sensor, a generator, a synchronizer, a constant frequency alternating current and a second oil tank. Multiple energy recovery chamber oil drain ports are connected to the second oil tank through pipes. The flow meter, the filter accumulator, the second pressure gauge and the variable motor are sequentially arranged between the pipes connecting the multiple energy recovery chamber oil drain ports and the second oil tank. The second oil tank is connected to the filter accumulator pipe. The safety valve is arranged on the pipe connecting the second oil tank and the filter accumulator. The variable motor is sequentially connected to the torque sensor and the generator. The generator outputs constant frequency alternating current through the synchronizer.

[0012] The present invention provides a power generation system based on a gas-liquid integrated free-piston expander, comprising an energy recovery and conversion unit group, a return accumulator unit group and a constant-frequency generator group, wherein the energy recovery and conversion unit group comprises an exhaust phase of a free-piston expander group, an expansion phase of a free-piston expander group and an intake phase of a free-piston expander group, the number of intake phases of the free-piston expander group is at least one, and the number of the gas-liquid integrated free-piston expanders on the exhaust phase of the free-piston expander group, the expansion phase of the free-piston expander group and the intake phase of the free-piston expander group is at least one. Due to the setting of the parallel and series control valves, the power generation system based on the gas-liquid integrated free-piston expander can realize the matching of parallel expanders with large wellhead flow and series expanders with high or ultra-high wellhead pressure, and has the advantages of flexible expander arrangement, wide adaptability to working conditions, high conversion efficiency, safety and stability, and high power generation quality, which is conducive to the implementation and promotion of recovery of wellhead natural gas pressure difference energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 It is a structural schematic diagram of a power generation system based on a gas-liquid integrated free plunger expander provided by the present invention.

[0015] Figure 2 It is a cross-sectional view of the internal structure of the gas-liquid integrated free plunger expander provided by the present invention.

[0016] 1-Exhaust phase of free plunger expansion unit, 2-Expansion phase of free plunger expansion unit, 3-First intake phase of free plunger expansion unit, i-Second intake phase of free plunger expansion unit, 4-Accumulator, 5-First pressure gauge, 6-Third check valve, 7-Fuel charge pump, 8-Relief valve, 9-First fuel tank, 10-Flow meter, 11-Filter accumulator, 12-Second pressure gauge, 13-Safety valve, 14-Variable motor, 15-Torque sensor, 16-Generator, 17-Synchronizer, 18-Constant frequency AC power, 19-Second fuel tank, 20-High-pressure natural gas inlet , 21-expansion chamber, 22-low-pressure natural gas exhaust port, 23-plunger, 24-return oil chamber, 25-air relief chamber, 26-oil relief chamber, 27-high-pressure air sealing ring, 28-low-pressure gas-liquid sealing ring, 29-high-pressure hydraulic sealing ring, 30-energy recovery chamber oil inlet, 31-return oil chamber oil inlet and outlet, 32-energy recovery chamber oil drain port, 33-isolating valve core, 34-energy recovery chamber, 35-gas-liquid integrated free plunger expander, 36-intake control valve, 37-exhaust control valve, 38-first one-way valve, 39-second one-way valve, 40-parallel series control valve. DETAILED DESCRIPTION

[0017] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0018] See also Figure 1 and Figure 2 The present invention provides a power generation system based on a gas-liquid integrated free-piston expander, the power generation system based on the gas-liquid integrated free-piston expander comprising an energy recovery and conversion unit group, a return accumulator unit group, and a constant-frequency generator group, wherein the return chamber of the energy recovery and rotation unit group is connected to the return accumulator unit group, and the output end of the energy recovery and rotation unit group is connected to the constant-frequency generator group;

[0019] The energy recovery and conversion unit group includes a free plunger expansion unit exhaust phase 1, a free plunger expansion unit expansion phase 2 and a free plunger expansion unit intake phase. The number of the free plunger expansion unit intake phase is at least 1. If the number of the free plunger expansion unit intake phase is multiple, the free plunger expansion unit intake phase includes a free plunger expansion unit first intake phase 3 and a free plunger expansion unit second intake phase i (i≥3). The free plunger expansion unit exhaust phase 1, the free plunger expansion unit expansion phase 2 and the free plunger expansion unit intake phase are all composed of a gas-liquid integrated free plunger expander 35. The free plunger expansion The number of the gas-liquid integrated free plunger expanders 35 in the exhaust phase 1 of the unit, the expansion phase 2 of the free plunger expander unit, and the intake phase of the free plunger expander unit is at least one. Each of the gas-liquid integrated free plunger expanders 35 is connected to the high-pressure wellhead natural gas through an intake control valve 36. Each of the gas-liquid integrated free plunger expanders 35 is connected to the low-pressure gathering pipeline through an exhaust control valve 37. Each of the gas-liquid integrated free plunger expanders 35 is connected to the return accumulator unit group through a first one-way valve 38 and an oil pipe. Each of the gas-liquid integrated free plunger expanders 35 is connected to the constant frequency generator set through a second one-way valve 39.

[0020] When there are multiple gas-liquid integrated free piston expanders 35 installed on the exhaust phase 1 of the free piston expander group, the expansion phase 2 of the free piston expander group and the intake phase of the free piston expander group, two adjacent gas-liquid integrated free piston expanders 35 are connected through a parallel and series control valve 40.

[0021] In this embodiment, due to the setting of the parallel and series control valve 40, the power generation system based on the gas-liquid integrated free-piston expander can achieve parallel expander matching of large wellhead flow and series expander matching of high wellhead pressure or ultra-high pressure, which has the advantages of flexible expander arrangement, wide adaptability to working conditions, high conversion efficiency, safety and stability, and high power generation quality, which is conducive to the implementation and promotion of recovery of wellhead natural gas pressure difference energy.

[0022] Furthermore, the phase difference calculation formula of the free plunger expander exhaust phase 1, the free plunger expander expansion phase 2 and the free plunger expander intake phase is: 360° / i. Since the working cycle of the gas-liquid integrated free plunger expander 35 can be divided into three stages, including the intake stage (such as Figure 1 The free plunger expander unit intake phase), expansion phase (such as Figure 1 The free piston expander in the expansion phase 2) and exhaust phase (as Figure 1The free plunger expander exhaust phase 1), so the phase i value should be greater than or equal to 3, and the larger the value of i, the smaller the flow pulsation. The specific value depends on the wellhead natural gas operating conditions.

[0023] Furthermore, since the working cycle of the gas-liquid integrated free piston expander 35 arranged on the free piston expansion unit exhaust phase 1, the free piston expansion unit expansion phase 2 and the free piston expansion unit intake phase includes the intake stage, the expansion stage and the exhaust stage, the free piston expansion unit exhaust phase 1, the free piston expansion unit expansion phase 2, the free piston expansion unit first intake phase 3 and the free piston expansion unit second intake phase i can all switch between the three stages of exhaust, expansion and intake during actual operation. Therefore, the free piston expansion unit exhaust phase 1 is not limited to the exhaust stage, the free piston expansion unit expansion phase 2 is not limited to the expansion stage, the free piston expansion unit first intake phase 3 and the free piston expansion unit second intake phase i are not limited to the intake stage.

[0024] Furthermore, a high-pressure natural gas inlet 20 and a low-pressure natural gas exhaust 22 are respectively provided on both sides of the bottom of each of the gas-liquid integrated free plunger expanders 35, an isolation valve core 33 is provided in the middle of the top of each of the gas-liquid integrated free plunger expanders 35, and a plunger 23 is provided inside each of the gas-liquid integrated free plunger expanders 35. The cross-section of the plunger 23 is U-shaped, and an expansion chamber 21 is formed between the plunger 23 and the inner bottom of the gas-liquid integrated free plunger expander 35. The top of the plunger 23 is provided on the outside of the bottom of the isolation valve core 33, and a return oil chamber 24 is provided inside the plunger 23. The top of the isolation valve core 33 is provided with a return oil chamber inlet and outlet 31, and an energy recovery chamber 34 is formed between the top of the plunger 23 and the outer wall of the isolation valve core 33. An energy recovery chamber 34 is respectively provided with an energy recovery chamber oil inlet 30 and an energy recovery chamber oil outlet 32 ​​on both sides of the top of each of the gas-liquid integrated free plunger expanders 35.

[0025] In this embodiment, the cross-section of the plunger 23 provided on each of the gas-liquid integrated free plunger expanders 35 is U-shaped, so the structure of the gas-liquid integrated free plunger expander 35 is compact, resistant to high pressure, resistant to multiphase flow, and has strong anti-pollution energy, and the top dead point of each of the plungers 23 is not restricted, and can expand freely.

[0026] Specifically, a high-pressure hydraulic sealing ring 29, a low-pressure gas-liquid sealing ring 28 and a high-pressure air pressure sealing ring 27 are sequentially arranged on the inner wall of each of the gas-liquid integrated free piston expanders 35 from top to bottom, and an air release chamber 25 and an oil release chamber 26 are also arranged on the inner wall of each of the gas-liquid integrated free piston expanders 35. The air release chamber 25 is located between the high-pressure air pressure sealing ring 27 and the low-pressure gas-liquid sealing ring 28, and the oil release chamber 26 is located between the low-pressure gas-liquid sealing ring 28 and the high-pressure hydraulic sealing ring 29.

[0027] Furthermore, the return accumulator unit group includes an accumulator 4, a first pressure gauge 5, a third one-way valve 6, an oil replenishment pump 7, a first oil tank 9 and an overflow valve 8. The accumulator 4 is connected to the multiple return oil chamber inlet and outlet ports 31 through a pipeline, and the first pressure gauge 5 is provided on the pipeline connecting the accumulator 4 to the multiple return oil chamber inlet and outlet ports 31. The accumulator 4 is connected to the first oil tank 9 and the multiple energy recovery chamber oil inlet ports 30 through pipelines respectively, and the third one-way valve 6 and the oil replenishment pump 7 are sequentially provided on the pipeline connecting the accumulator 4 to the first oil tank 9. The first oil tank 9 and the first pressure gauge 5 are connected by a pipeline, and the overflow valve 8 is provided on the pipeline connecting the first oil tank 9 and the first pressure gauge 5.

[0028] Furthermore, the constant frequency generator set includes a flow meter 10, a filter accumulator 11, a second pressure gauge 12, a safety valve 13, a variable motor 14, a torque sensor 15, a generator 16, a synchronizer 17, a constant frequency AC power 18 and a second oil tank 19. The multiple energy recovery chamber oil drain ports 32 are connected to the second oil tank 19 through pipes. The flow meter 10, the filter accumulator 11, the second pressure gauge 12 and the variable motor 14 are sequentially arranged between the pipes connecting the multiple energy recovery chamber oil drain ports 32 and the second oil tank 19. The second oil tank 19 is connected to the filter accumulator 11 by a pipe. The safety valve 13 is provided on the pipe connecting the second oil tank 19 and the filter accumulator 11. The variable motor 14 is sequentially connected to the torque sensor 15 and the generator 16. The generator 16 outputs constant frequency AC power 18 through the synchronizer 17.

[0029] In this embodiment, the variable motor 14 can automatically change the displacement according to the input and output flow to achieve constant speed output, thereby driving the generator 16 to emit constant frequency current; the variable motor 14 is connected to the torque sensor 15 and the generator 16 through a coupling.

[0030] In summary, the working principles of the free plunger expansion unit exhaust phase 1, the free plunger expansion unit expansion phase 2 and the free plunger expansion unit intake phase 3 are as follows: the intake control valve 36 is opened, and the high-pressure wellhead natural gas enters the expansion chamber 21, which will push the plunger 23 to start moving upward; the intake control valve 36 is closed, and the high-pressure wellhead natural gas expands and performs work in the expansion chamber 21, continuing to push the plunger 23 to move upward; the exhaust control valve 37 is opened, and under the action of the return pressure oil of the return accumulator unit group, the plunger 23 moves downward, and the low-pressure natural gas in the expansion chamber 21 is discharged into the low-pressure gathering pipeline, and the gas-liquid integrated free plunger expander 35 completes a working cycle; when the plunger 23 moves upward, it is the pressure difference energy recovery stage, and the plunger 23 compresses the hydraulic oil in the energy recovery chamber 34 to drive the variable motor 14 to rotate, thereby driving the generator 16 to generate electricity.

[0031] Among them, since the number of the gas-liquid integrated free-plunger expanders 35 on each phase is at least one (determined according to the production and pressure of the wellhead), and when there are multiple gas-liquid integrated free-plunger expanders 35 on a phase, the two adjacent gas-liquid integrated free-plunger expanders 35 are connected by a parallel-series control valve 40, and the parallel and series connection of the expanders on each phase is achieved by switching the parallel-series control valve 40 (the initial position is parallel); the parallel connection of the expanders can match the large flow (i.e., production) of the natural gas wellhead, and the series connection can match the pressure or ultra-high pressure of the natural gas wellhead, realizing multi-stage expansion, preventing ice blockage and excessive temperature drop, resulting in the need to reheat the expanded natural gas before entering the low-pressure gathering pipeline.

[0032] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of the rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A power generation system based on a gas-liquid integrated free plunger expander, characterized in that: It includes an energy recovery and conversion unit group, a return accumulator unit group and a constant frequency generator group, the return chamber of the energy recovery and rotation unit group is connected to the return accumulator unit group, and the output end of the energy recovery and rotation unit group is connected to the constant frequency generator group; The energy recovery and conversion unit group includes a free plunger expansion unit exhaust phase, a free plunger expansion unit expansion phase and a free plunger expansion unit intake phase, the number of the free plunger expansion unit intake phase is at least 1, the free plunger expansion unit exhaust phase, the free plunger expansion unit expansion phase and the free plunger expansion unit intake phase are all composed of a gas-liquid integrated free plunger expander, the free plunger expansion unit exhaust phase, the free plunger expansion unit expansion phase and the free plunger expansion unit The number of the gas-liquid integrated free-plunger expanders in the intake phase is at least one, each of the gas-liquid integrated free-plunger expanders is connected to the high-pressure wellhead natural gas through an intake control valve, each of the gas-liquid integrated free-plunger expanders is connected to the low-pressure gathering pipeline through an exhaust control valve, each of the gas-liquid integrated free-plunger expanders is connected to the return accumulator unit group through a first one-way valve and an oil pipe, and each of the gas-liquid integrated free-plunger expansion mechanisms is connected to the constant-frequency generator set through a second one-way valve; When there are multiple gas-liquid integrated free plunger expanders provided on the exhaust phase of the free plunger expander group, the expansion phase of the free plunger expander group, and the intake phase of the free plunger expander group, two adjacent gas-liquid integrated free plunger expanders are connected via a parallel-series control valve; A high-pressure natural gas inlet and a low-pressure natural gas exhaust are respectively provided on both sides of the bottom of each of the gas-liquid integrated free-plunger expanders, an isolation valve core is provided in the middle of the top of each of the gas-liquid integrated free-plunger expanders, a plunger is provided inside each of the gas-liquid integrated free-plunger expanders, the cross section of the plunger is U-shaped, an expansion chamber is formed between the plunger and the inner bottom of the gas-liquid integrated free-plunger expander, the top of the plunger is provided on the outside of the bottom of the isolation valve core, a return oil chamber is provided inside the plunger, the top of the isolation valve core is provided with a return oil chamber inlet and outlet, an energy recovery chamber is formed between the top of the plunger and the outer wall of the isolation valve core, an energy recovery chamber is respectively provided with an energy recovery chamber oil inlet and an energy recovery chamber oil discharge on both sides of the top of each of the gas-liquid integrated free-plunger expanders; A high-pressure hydraulic sealing ring, a low-pressure gas-liquid sealing ring and a high-pressure gas-pressure sealing ring are arranged on the inner wall of each of the gas-liquid integrated free-piston expanders in sequence from top to bottom. An air release chamber and an oil release chamber are also arranged on the inner wall of each of the gas-liquid integrated free-piston expanders. The air release chamber is located between the high-pressure gas-pressure sealing ring and the low-pressure gas-liquid sealing ring, and the oil release chamber is located between the low-pressure gas-liquid sealing ring and the high-pressure hydraulic sealing ring.

2. The power generation system based on the gas-liquid integrated free plunger expander according to claim 1, characterized in that: The return accumulator unit group includes an accumulator, a first pressure gauge, a third one-way valve, an oil replenishment pump, a first oil tank and a relief valve. The accumulator is connected to the multiple return oil chamber inlets and outlets through a pipeline. The first pressure gauge is provided on the pipeline connecting the accumulator and the multiple return oil chamber inlets and outlets. The accumulator is respectively connected to the first oil tank and the multiple energy recovery chamber oil inlets through pipelines. The third one-way valve and the oil replenishment pump are sequentially provided on the pipeline connecting the accumulator and the first oil tank. The first oil tank and the first pressure gauge are connected by a pipeline, and the relief valve is provided on the pipeline connecting the first oil tank and the first pressure gauge.

3. The power generation system based on the gas-liquid integrated free plunger expander according to claim 2, characterized in that: The constant frequency generator set includes a flow meter, a filter accumulator, a second pressure gauge, a safety valve, a variable motor, a torque sensor, a generator, a synchronizer, a constant frequency alternating current and a second oil tank. Multiple energy recovery chamber oil drain ports are connected to the second oil tank through pipelines. The flow meter, the filter accumulator, the second pressure gauge and the variable motor are sequentially arranged between the pipelines connecting the multiple energy recovery chamber oil drain ports and the second oil tank. The second oil tank is connected to the filter accumulator pipeline. The safety valve is arranged on the pipeline connecting the second oil tank and the filter accumulator. The variable motor is sequentially connected to the torque sensor and the generator. The generator outputs constant frequency alternating current through the synchronizer.

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