High-pressure and high-pressure-ratio natural gas differential pressure power generation system and turbo expander device applied to high-pressure and high-pressure-ratio natural gas differential pressure power generation system

Abstract

The invention discloses a high-pressure large-pressure-ratio natural gas differential pressure power generation system and a turbo expander device applied to the system. The high-pressure large-pressure-ratio natural gas differential pressure power generation system comprises a main gas conveying pipeline and branches. The branch comprises a plurality of pressure sections which are connected in series; the pressure section comprises a turbo expander, a turbo expander air inlet pipeline connected with the air inlet end of the turbo expander, a turbo expander air outlet pipeline connected with the air outlet end of the turbo expander, and a bypass pressure reducing valve connected with the turbo expander in parallel. The pressure section comprises at least one heat exchanger; the turbine expander air outlet pipeline comprises a user and an air inlet connecting pipeline; the air inlet pipeline of the turbo expander of the adjacent pressure section is connected with the air inlet connecting pipeline of the previous pressure section; and the gas inlet pipeline of the turbo expander at the uppermost pressure section is connected with a main gas pipeline. The method has the advantages of small transformation and short period, and the system shutdown time is shortened to the greatest extent; the device is suitable for high-pressure environments; and gas pressure and temperature of upstream and downstream pipelines are maintained through cooperative control with a bypass, and continuous downstream gas supply is ensured.

Description

Technical Field

[0001] The present invention relates to the field of residual pressure power generation, in particular to a high-pressure and large-pressure-ratio natural gas pressure difference power generation system and a turbine expander device applied to the system. Background Art

[0002] With the implementation of the overall layout of the country's ecological civilization construction of carbon peak and carbon neutrality, building a clean, low-carbon, safe and efficient energy system, controlling the total amount of fossil energy, focusing on improving energy efficiency, and promoting the transformation and upgrading of the energy structure have become development trends in the power industry. Countries will shift their strategic goals to energy conservation and efficiency improvement of traditional energy and the development and popularization of new energy.

[0003] There is abundant pressure energy in the natural gas pipeline transportation process. How to achieve pipeline pressure reduction and efficient recovery of green pressure energy has become a difficult topic of current research. The outlet pressure of natural gas wells is generally 20~26MPa, the temperature is close to room temperature, the gas composition is complex, the gas flow is large and the downstream demand is different. It can be reduced to 10~6MPa for industrial gas, or reduced to 2.5MPa~4MPa for urban trunk lines, or reduced to 0.1~0.4MPa for regional users. The original process pipeline uses the main gas pipeline to transport to downstream plants and stations.

[0004] As an energy recovery device, the differential pressure turbine expander can replace the pressure reducing valve between the traditional high-pressure gas transmission pipeline and the low-pressure gas distribution pipeline, so that this part of the gas pressure can be converted into mechanical energy in the turbine, which can directly drive the generator to generate electricity, or serve as a prime mover to drive various compressors; it can be widely used in the field of natural gas pipeline transportation, petrochemical production, etc. The electricity generated after recovery by the turbine expander can meet the factory's own electricity needs, and the surplus electricity can be connected to the grid for power generation, greatly reducing production energy consumption, increasing energy utilization, and improving overall economic benefits.

[0005] In actual use, when using a differential pressure turbine expander for power generation, it is necessary to deal with high pressure, large pressure ratio and other scenarios. For example, gas wells with high pressure and large pressure ratio; when setting up a differential pressure turbine expander, Conventional settings require modifications to the original piping system, which often involves large modifications, long cycles, and long system downtime. At the same time, the large pressure difference can cause low temperatures at the turbine expander outlet, which is prone to ice blockage, making it impossible to ensure uninterrupted downstream gas supply. Summary of the invention

[0006] The purpose of the present invention is to provide a high-pressure and high-pressure ratio natural gas pressure difference power generation system and a turbine expander device applied to the system in view of the deficiencies of the prior art. The present invention requires little modification to the original process pipeline system, has a short cycle, and minimizes the system downtime; it is suitable for high-pressure environments such as natural gas wellhead stations; it can replace the original pressure reducing valve group, recover pressure energy to achieve power generation, and has high-pressure step-by-step pressure reduction means. A single set of pressure difference expander equipment can achieve multi-stage pressure output and fully combine industrial waste heat to achieve online power generation. At the same time, coordinated control with bypass can maintain the gas pressure and temperature of upstream and downstream pipelines to ensure uninterrupted downstream gas supply.

[0007] The technical purpose of the present invention is achieved by the following technical solutions: A high-pressure, large-pressure-ratio natural gas pressure-difference power generation system comprises a main gas transmission pipeline and a branch connected to the main gas transmission pipeline; the branch comprises a plurality of pressure sections and the pressure sections are connected in series; the pressure section comprises a turbine expander, a turbine expander inlet pipeline connected to the turbine expander inlet end, a turbine expander outlet pipeline connected to the turbine expander outlet end, and a bypass pressure reducing valve connected in parallel with the turbine expander; the pressure section comprises at least one heat exchanger; the turbine expander outlet pipeline of each pressure section comprises a user connecting pipeline connected to a downstream user and an intake connecting pipeline connected to the turbine expander inlet pipeline of the next pressure section; the turbine expander inlet pipeline of an adjacent pressure section is connected to the intake connecting pipeline of the turbine expander outlet pipeline of the previous pressure section, wherein the turbine expander inlet pipeline of the uppermost pressure section is connected to the main gas transmission pipeline.

[0008] The main gas transmission pipeline is provided with a filtering unit for processing natural gas impurities, and the filtering unit is arranged before the inlet of the turbine expander air intake pipeline.

[0009] The heat exchanger is an interstage heat exchanger or an outlet heat exchanger.

[0010] The interstage heat exchanger is directly connected to the turboexpander.

[0011] The outlet heat exchanger is arranged at the gas outlet end of the turbo expander.

[0012] A turbine expander device applied to a high-pressure, large-pressure-ratio natural gas pressure-difference power generation system comprises a multi-shaft gearbox and a plurality of clutches; the multi-shaft gearbox comprises an output shaft connected to the generator and an input shaft connected to the turbine expander; the output shaft and the input shaft are connected via gear transmission; the number of the input shafts corresponds to the number of the pressure sections, the input shafts are connected to the turbine expanders of the pressure sections in a one-to-one correspondence, and a clutch is provided between the input shaft and the turbine expander.

[0013] The multi-shaft gearbox, generator, clutch and various pressure sections with turbine expanders are uniformly arranged on a base / in a device skid.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention requires little modification to the original process pipeline system, has a short cycle, and minimizes the system downtime; it is suitable for high-pressure environments such as natural gas wellhead stations; it can replace the original pressure reducing valve group, and the recovered pressure can be used to generate electricity. It has a high-pressure step-by-step pressure reduction method. A single set of pressure differential expander equipment can not only achieve multi-stage pressure output, but also fully combine industrial waste heat to achieve grid-connected power generation. At the same time, coordinated control with the bypass can maintain the gas pressure and temperature of the upstream and downstream pipelines to ensure uninterrupted downstream gas supply.

[0015] 2. The branch circuit of the present invention includes multiple pressure sections and the pressure sections are connected in series. A branch circuit is set on the main gas transmission pipeline, and the pressure is reduced by turbine step by step and section by section. There are multiple pressure sections from the upstream gas supply to the downstream gas consumption room. In order to meet various pressure requirements, each pressure section can be output separately.

[0016] 3. The pressure section of the present invention comprises a turbine expander, a turbine expander air inlet pipe connected to the turbine expander air inlet end, a turbine expander air outlet pipe connected to the turbine expander air outlet end, and a bypass pressure reducing valve connected in parallel with the turbine expander. The bypass pressure reducing valve can be adjusted in full flow or in coordination with the turbine split flow.

[0017] 4. The outlet pipe of the turbine expander of each pressure section of the present invention includes a user connection pipe connected to the downstream user and an intake connection pipe connected to the intake pipe of the turbine expander of the next pressure section. This technical measure can meet the needs of users in different regions and avoid ice blockage at the outlet due to excessive pressure difference in a single pressure section.

[0018] 5. The pressure section of the present invention includes at least one heat exchanger. The heat exchanger is an interstage heat exchanger or an outlet heat exchanger. By setting the heat exchanger, the natural gas from the outlet of the turbine expander is reheated and heated to prevent the natural gas temperature at the outlet of the turbine expander from being too low and to avoid the occurrence of dew point. The system uses a turbine expander instead of a pressure reducing valve to achieve pressure energy recovery and power generation, improve the operation economy of the pipeline network, and use industrial waste heat to heat natural gas, achieve energy complementarity, and further improve energy utilization.

[0019] 6. The complete set of turbine expander device of the present invention is mainly composed of turbine expanders of each pressure section, multi-axis gearbox, clutch, generator, etc. The input shaft of the multi-axis gearbox is connected to the turbine expanders of each pressure section, and a set of clutch is configured between each set of turbine expanders and the input shaft of the gearbox, and the output shaft of the multi-axis gearbox is connected to the generator. During operation, the natural gas that has been decompressed step by step works in each section of the turbine expander, changes the speed to 3000rpm through the gearbox and drives the generator to connect to the grid for power generation. The speed of the turbine expander of each pressure section can be designed differently according to the segmentation parameters to maximize the power generation efficiency. If a single set of turbine expanders needs to be shut down, the corresponding bypass pressure reducing valve can be coordinated to run at full flow. At this time, the corresponding clutch is actuated to disengage the input shaft of the turbine expander and the gearbox to complete the shutdown of a single device. Other pressure section units can continue to operate. One or several groups of turbine expanders can be disconnected from the gearbox independently for shutdown and maintenance without affecting the normal operation of other groups of turbine expanders. It is highly practical and can significantly improve the pressure energy utilization efficiency of the station.

[0020] 7. The present invention integrates all the turbo expanders and unifies all the pressure sections on a base / device skid, achieving simplicity, high efficiency and small footprint. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 yes Figure 1 Structural diagram of the medium pressure section; Figure 3 is a schematic structural diagram of a turbo expander device applied to the present invention; Reference numerals: 1—main gas transmission pipeline; 2—pressure section; 21—turbine expander; 22—turbine expander air inlet pipe; 23—turbine expander air outlet pipe; 231—user connection pipe; 232—air inlet connection pipe; 24—bypass pressure reducing valve; 25—interstage heat exchanger; 26—exit heat exchanger; 3—multi-axis gearbox; 31—output shaft; 32—input shaft; 4—Clutch; 5—Generator. DETAILED DESCRIPTION

[0022] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0023] 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 invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In addition, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0025] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0026] 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 invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In addition, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0028] like Figure 1 — Figure 2As shown, a high-pressure and large-pressure-ratio natural gas pressure difference power generation system comprises a main gas transmission pipeline 1 and a branch connected to the main gas transmission pipeline 1; the branch comprises a plurality of pressure sections 2 and the pressure sections 2 are connected in series; the pressure section 2 comprises a turbine expander 21, a turbine expander inlet pipeline 22 connected to the inlet end of the turbine expander 21, a turbine expander outlet pipeline 22 connected to the outlet end of the turbine expander 21, and a bypass pressure reducing valve 24 connected in parallel with the turbine expander 21; the pressure section 2 comprises at least one heat exchanger; the turbine expander outlet pipeline 22 of each pressure section 2 comprises a user connecting pipeline 231 connected to a downstream user and an intake connecting pipeline 232 connected to the turbine expander inlet pipeline 22 of the next pressure section 2; the turbine expander inlet pipeline 22 of the adjacent pressure section 2 is connected to the intake connecting pipeline 232 of the turbine expander outlet pipeline 22 of the previous pressure section 2, wherein the turbine expander inlet pipeline 22 of the uppermost pressure section 2 is connected to the main gas transmission pipeline 1.

[0029] In actual use, by combining the original process pipeline, a branch is set on the main gas transmission pipeline 1, and the branch is composed of multiple pressure sections 2 connected in series. By adopting this technical measure, the turbine expander 21 is used for decompression step by step and section by section. There are multiple pressure sections 2 from the upstream gas supply to the downstream gas consumption room. In order to meet various pressure requirements, each pressure section 2 can be output separately; each pressure section 2 includes a set of turbine expanders 21 and a bypass pressure reducing valve 24 connected in parallel with the turbine expander 21. Among them, the pressure section 2 is provided with a heat exchanger arranged in coordination with the turbine expander 21 to perform reheating and temperature rise to prevent the turbine outlet natural gas temperature from being too low and avoid the occurrence of dew point. The bypass pressure reducing valve 24 can be adjusted at full flow or in coordination with the turbine diversion. The turbine expander outlet pipeline 22 of each pressure section 2 includes a user connection pipeline 231 connected to the downstream user and an intake connection pipeline 232 connected to the turbine expander intake pipeline 22 of the next pressure section 2. Designing multiple pressure sections 2 in this way can meet the needs of users in different regions. At the same time, it avoids the phenomenon of ice blockage at the outlet caused by excessive pressure difference in a single pressure section 2. The adoption of this technical measure requires little modification to the original process pipeline system, with a short cycle, and minimizes the system downtime; it is suitable for high-pressure environments such as natural gas wellhead stations; it can replace the original pressure reducing valve group, and the recovered pressure can achieve power generation. It has high-pressure step-by-step pressure reduction means. A single set of pressure differential expander equipment can achieve multi-stage pressure output and fully combine industrial waste heat to achieve online power generation. At the same time, coordinated control with bypass can maintain the gas pressure and temperature of upstream and downstream pipelines to ensure uninterrupted downstream gas supply.

[0030] like Figure 1As shown, a filtering unit for treating natural gas impurities is provided on the main gas pipeline 1, and the filtering unit is provided before the inlet of the turbine expander intake pipeline 22. One end of the main gas pipeline 1 is connected to the upstream of the natural gas pipeline, and the other end is connected to the original natural gas main pipeline; the branch is connected to the main gas pipeline 1. A filtering unit is provided before the inlet of the flat expander intake pipeline 22 of the first pressure section 2 connected to the main gas pipeline 1 to treat natural gas impurities. When the system is running, high-pressure natural gas is output from the gas well, and after passing through the filtering and impurity removal unit at the front end of the system, it is transported to the pressure section 2 of the branch and the original natural gas main pipeline.

[0031] like Figure 1 As shown, the branch includes multiple pressure sections 2 and the pressure sections 2 are connected in series. In actual use, the number of pressure sections 2 is generally three to five. For example, the first pressure section is directly connected to the main gas pipeline 1, and the second pressure section is connected to the first pressure section. From top to bottom, the third pressure section, the fourth pressure section, the fifth pressure section, etc. are arranged in sequence. A branch consisting of multiple pressure sections 2 connected in series is arranged on the main gas pipeline 1, and the pressure is reduced step by step and section by section by turbine. There are multiple pressure sections 2 from the upstream gas supply to the downstream gas consumption room. In order to meet various pressure requirements, each pressure section 2 can be output separately.

[0032] like Figure 2 As shown, the pressure section 2 includes a turbine expander 21, a turbine expander inlet pipe 22 connected to the inlet end of the turbine expander 21, a turbine expander outlet pipe 22 connected to the outlet end of the turbine expander 21, and a bypass pressure reducing valve 24 connected in parallel with the turbine expander 21. In actual use, the bypass pressure reducing valve 24 can be adjusted in full flow or in coordination with the turbine expander 21 for diversion.

[0033] The turbine expander outlet pipe 22 of each pressure section 2 includes a user connection pipe 231 connected to a downstream user and an intake connection pipe 232 connected to the turbine expander intake pipe 22 of the next pressure section 2. This technical measure can meet the needs of users in different regions and avoid ice blockage at the outlet caused by excessive pressure difference in a single pressure section 2.

[0034] like Figure 1 As shown, the turbine expander air inlet pipe 22 of the first pressure section 2 is directly connected to the main gas pipeline 1; that is, the turbine expander air inlet pipe 22 of the uppermost pressure section 2 is connected to the main gas pipeline 1. The turbine expander air inlet pipes 22 of the remaining adjacent pressure sections 2 are connected to the air inlet connecting pipe 232 of the turbine expander air outlet pipe 22 of the upper pressure section 2. That is, the turbine expander air inlet pipe 22 of the second pressure section is connected to the air inlet connecting pipe 232 of the turbine expander air outlet pipe 22 of the first pressure section. The air inlet connecting pipes 232 of the third pressure section, the fourth pressure section, and the fifth pressure section are connected in the same manner as the second pressure section.

[0035] like Figure 1 As shown, the pressure section 2 includes at least one heat exchanger. The heat exchanger is an interstage heat exchanger 25 or an outlet heat exchanger 26. Specifically, the heat exchanger includes an interstage heat exchanger 25 directly connected to the turbine expander 21. The heat exchanger includes an outlet heat exchanger 26 arranged at the outlet end of the turbine expander 21. The outlet heat exchanger 26 is arranged on the turbine expander outlet pipe 23 at the outlet end of the turbine expander 21. By setting the heat exchanger, the natural gas from the outlet end of the turbine expander 21 is reheated and heated to prevent the outlet temperature of the turbine expander 21 from being too low, thereby avoiding the occurrence of dew point. This system uses the turbine expander 21 instead of the pressure reducing valve to realize pressure energy recovery power generation, improve the operating economy of the pipeline network, and use industrial waste heat to heat the natural gas, realize energy complementarity, and further improve energy utilization.

[0036] When the system is in operation, high-pressure natural gas is output from the gas well, and the high-pressure natural gas is transported from the upstream of the natural gas pipeline to the original natural gas main pipeline through the main gas transmission pipeline 1; the high-pressure natural gas passes through the filtering and impurity removal unit at the front end of the system and reaches the first pressure section 2, and coordinates with the bypass pressure reducing valve 24 and the turbine expander 21 to ensure timely adjustment of the unit power generation under stable pressure conditions; the gas after the turbine expander 21 does work has a lower temperature and needs to be heated by the interstage heat exchanger 25 or the outlet heat exchanger 26 at the outlet end of the turbine expander 21. After fully utilizing the industrial waste heat to heat the natural gas, it is transported to downstream users or enters the next pressure section 2, and so on. The natural gas meets the needs of users in each section and completes the pressure reduction.

[0037] like Figure 3 As shown, in order to adapt to the operation of the above system and realize the integration of the high-pressure natural gas decompression turbine expansion unit, all pressure sections 2 are unified in the device skid. Using the divided speed and multi-axis arrangement scheme, a multi-axis gearbox 3 is connected to the turbine expander 21 of each pressure section 2 to achieve coordinated driving of the generator 5 and grid-connected power generation.

[0038] Specifically, a turbine expander device applied to a high-pressure, large-pressure-ratio natural gas pressure-difference power generation turbine expander system comprises a multi-shaft gearbox 3 and a plurality of clutches 4; the multi-shaft gearbox 3 comprises an output shaft 31 connected to a generator 5 and an input shaft 32 connected to a turbine expander 21; the output shaft 31 and the input shaft 32 are connected via gear transmission; the number of input shafts 32 corresponds to the number of pressure sections 2, the input shafts 32 are connected one-to-one with the turbine expanders 21 of the pressure sections 2, and a clutch 4 is provided between the input shaft 32 and the turbine expander 21.

[0039] like Figure 3As shown, the multi-axis gearbox 3 includes an output shaft 31 connected to the generator 5 and four input shafts 32 arranged longitudinally on both sides of the output shaft 31. In actual use, the number and position of the input shafts 32 can be increased, decreased and adjusted according to actual conditions. The number of input shafts 32 is the same as the number of pressure sections 2, that is, when there are three pressure sections 2, the number of input shafts 32 is three. The input shaft 32 can be arranged longitudinally and transversely. The output shaft 31 and the input shaft 32 are driven by gears. The whole set of turbine expander device is mainly composed of the turbine expander 21 of each pressure section 2, the multi-axis gearbox 3, the clutch 4, the generator 5, etc. The input shaft 32 of the multi-axis gearbox 3 is connected to the turbine expander 21 of each pressure section 2, and a set of clutch 4 is configured between each set of turbine expanders 21 and the input shaft 32 of the gearbox, and the output shaft 31 of the multi-axis gearbox 3 is connected to the generator 5. During operation, the natural gas that has been gradually decompressed does work in each section of the turbine expander 21, changes the speed to 3000 rpm through the gearbox and drives the generator 5 to connect to the grid for power generation. The speed of the turbine expander 21 of each pressure section 2 can be designed differently according to the segmentation parameters to maximize the power generation efficiency. If a single set of turbine expanders 21 needs to be shut down, the corresponding bypass pressure reducing valve 24 can be coordinated to operate at full flow. At this time, the corresponding clutch 4 is actuated to disengage the turbine expander 21 of this group from the input shaft 32 of the multi-axis gearbox 3 to complete the shutdown of a single device. The other pressure section 2 units can continue to operate. A single or several sets of turbine expanders 21 can be independently disconnected from the gearbox for shutdown and maintenance without affecting the normal operation of other sets of turbine expanders 21, which is highly practical and can significantly improve the pressure energy utilization efficiency of the station.

[0040] Among them, the multi-shaft gearbox 3, the generator 5, the clutch 4 and each pressure section 2 provided with the turbine expander 21 are uniformly arranged on a base / in a device skid. By integrating all the turbine expanders 21, all the pressure sections 2 are unified on a base / in a device skid, achieving the advantages of simplicity, high efficiency and small footprint.

[0041] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A high-pressure and high-pressure ratio natural gas pressure difference power generation system, characterized in that: It includes a main gas transmission pipeline and a branch connected to the main gas transmission pipeline; the branch includes a plurality of pressure sections and the pressure sections are connected in series; The pressure section includes a turbine expander, a turbine expander air inlet pipeline connected to the turbine expander air inlet end, a turbine expander air outlet pipeline connected to the turbine expander air outlet end, and a bypass pressure reducing valve connected in parallel with the turbine expander; the pressure section includes at least one heat exchanger; The turbine expander outlet pipeline of each pressure section includes a user connection pipeline connected to a downstream user and an intake connection pipeline connected to the turbine expander intake pipeline of the next pressure section; the turbine expander intake pipeline of the adjacent pressure section is connected to the intake connection pipeline of the turbine expander outlet pipeline of the previous pressure section, Among them, the air inlet pipeline of the turbine expander in the uppermost pressure section is connected to the main gas transmission pipeline.

2. The high-pressure and large-pressure-ratio natural gas pressure difference power generation system according to claim 1 is characterized in that: The main gas transmission pipeline is provided with a filtering unit for processing natural gas impurities, and the filtering unit is arranged before the inlet of the turbine expander air intake pipeline.

3. The high-pressure and large-pressure-ratio natural gas pressure difference power generation system according to claim 1 is characterized in that: The heat exchanger is an interstage heat exchanger or an outlet heat exchanger.

4. The high-pressure and large-pressure-ratio natural gas pressure difference power generation system according to claim 3 is characterized in that: The interstage heat exchanger is directly connected to the turboexpander.

5. The high-pressure and large-pressure-ratio natural gas pressure difference power generation system according to claim 3 is characterized in that: The outlet heat exchanger is arranged at the gas outlet end of the turbo expander.

6. A turbine expander device used in the high-pressure and large-pressure-ratio natural gas pressure differential power generation system according to claim 1, characterized in that: including a multi-shaft gearbox and multiple clutches; The multi-shaft gearbox comprises an output shaft connected to the generator and an input shaft connected to the turbine expander; the output shaft and the input shaft are driven by gears; The number of the input shafts corresponds to the number of the pressure sections, the input shafts are connected to the turbine expanders of the pressure sections in a one-to-one correspondence, and a clutch is provided between the input shafts and the turbine expanders.

7. The turboexpander device according to claim 6, characterized in that: The multi-shaft gearbox, generator, clutch and various pressure sections with turbine expanders are uniformly arranged on a base / in a device skid.

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