Multi-stage expander differential pressure power generation system

Abstract

This invention proposes a multi-stage expander differential pressure power generation system comprising N stages of expander units and a generator set. Each stage of the expander unit includes a free plunger expander, a pressure relay, and a three-position three-way solenoid valve. The expander unit is used to output mechanical energy to the generator set during the expansion and depressurization process of high-pressure gas. The inlet end of the first-stage free plunger expander is connected to the high-pressure gas input end. The outlet end of the i-th stage free plunger expander is connected to the inlet end of the i-th pressure relay and the i-th three-position three-way solenoid valve. The inlet end of the (i+1)-th stage free plunger expander is connected to the first working end of the i-th three-position three-way solenoid valve. The second working ends of all N three-position three-way solenoid valves are connected to the low-pressure gas output end. The pressure relay is used to monitor the gas pressure at the outlet end of each stage of the free plunger expander. The generator set is connected to the energy output end of each stage of the free plunger expander and is used to convert the mechanical energy output by the expander unit into electrical energy.

Description

Technical Field

[0001] This invention relates to the field of differential pressure power generation technology, and in particular to a multi-stage expander differential pressure power generation system. Background Technology

[0002] In the process of natural gas extraction, processing, and transportation, there are many pressure reduction stages. Natural gas extracted from the wellhead has a pressure of 10–20 MPa, enters the pipeline at 10 MPa, and is delivered to the city gate station at approximately 4–6 MPa. From there, it is further reduced to below 0.8 MPa before being delivered to end users. These processes result in significant pressure energy losses. The natural gas industry typically uses expanders to recover the pressure energy lost during pressure regulation. However, the pressure drop at each stage varies, and the operating conditions of each expander differ. To efficiently recover pressure energy, different types and sizes of expanders need to be matched to different pressure regulation conditions. In some cases, expanders may even need to be redesigned to fully recover the pressure energy lost during natural gas pressure regulation. This not only increases the cost of pressure energy recovery but also adds complexity to the expander selection process. Summary of the Invention

[0003] The present invention aims to at least partially solve one of the technical problems in the related art.

[0004] To address this, this invention proposes a multi-stage expander differential pressure power generation system. This system employs a combination of multi-stage free piston expanders and pressure relays, allowing the hydraulic energy output from each expander unit to flow in parallel into the same pipeline to the hydraulic motor. This avoids installing a generator at each stage, saving costs, fully utilizing gas pressure, and increasing the efficiency of pressure energy recovery.

[0005] To achieve the above objectives, this invention proposes a multi-stage expander differential pressure power generation system, comprising: N-stage expander units and a generator set; wherein each stage of the expander unit includes a free plunger expander, a pressure relay, and a three-position three-way solenoid valve, and the expander unit is used to output mechanical energy to the generator set during the expansion and depressurization process of high-pressure gas; wherein the inlet end of the first-stage free plunger expander is connected to the high-pressure gas input end, the outlet end of the i-th stage free plunger expander is connected to the inlet end of the i-th pressure relay and the i-th three-position three-way solenoid valve, the inlet end of the (i+1)-th stage free plunger expander is connected to the first working end of the i-th three-position three-way solenoid valve, and the second working ends of the N three-position three-way solenoid valves are all connected to the low-pressure gas output end; the N pressure relays are used to monitor the gas pressure at the outlet end of each stage of the free plunger expander; wherein, if the i-th pressure relay detects the i-th stage... If the gas pressure at the outlet of the free plunger expander is higher than the corresponding preset pressure threshold, the first working end of the i-th three-position three-way solenoid valve is connected to the inlet of the i-th stage free plunger expander to allow the gas discharged from the outlet of the i-th stage free plunger expander to enter the (i+1)-th stage free plunger expander. If the i-th pressure relay detects that the gas pressure at the outlet of the i-th stage free plunger expander is not higher than the corresponding preset pressure threshold, the second working end of the i-th three-position three-way solenoid valve is connected to the outlet of the i-th stage free plunger expander to allow the gas after expansion and depressurization treatment by the i-th stage free plunger expander to be discharged through the low-pressure gas output end. A generator set is connected to the energy output end of each stage of the free plunger expander to convert the mechanical energy output by the expander set into electrical energy. Wherein, N is a positive integer greater than or equal to 2, i is a positive integer greater than or equal to 1, and N > i.

[0006] The multi-stage expander differential pressure power generation system of this invention includes: N-stage expander units and a generator set; wherein each stage of the expander unit includes a free plunger expander, a pressure relay, and a three-position three-way solenoid valve, and the expander unit is used to output mechanical energy to the generator set during the expansion and depressurization process of high-pressure gas; wherein the inlet end of the first-stage free plunger expander is connected to the high-pressure gas input end, the outlet end of the i-th stage free plunger expander is connected to the inlet end of the i-th pressure relay and the i-th three-position three-way solenoid valve, the inlet end of the (i+1)-th stage free plunger expander is connected to the first working end of the i-th three-position three-way solenoid valve, and the second working ends of the N three-position three-way solenoid valves are all connected to the low-pressure gas output end; the N pressure relays are used to monitor the gas pressure at the outlet end of each stage of the free plunger expander; wherein, if the i-th pressure... If the relay detects that the gas pressure at the outlet of the i-th stage free plunger expander is higher than the corresponding preset pressure threshold, it controls the first working end of the i-th three-position three-way solenoid valve to connect with the inlet of the i-th stage free plunger expander, so that the gas discharged from the outlet of the i-th stage free plunger expander enters the (i+1)-th stage free plunger expander; if the i-th pressure relay detects that the gas pressure at the outlet of the i-th stage free plunger expander is not higher than the corresponding preset pressure threshold, it controls the second working end of the i-th three-position three-way solenoid valve to connect with the outlet of the i-th stage free plunger expander, so that the gas after expansion and depressurization treatment by the i-th stage free plunger expander is discharged through the low-pressure gas output end; the generator set is connected to the energy output end of each stage of the free plunger expander and is used to convert the mechanical energy output by the expander set into electrical energy. Therefore, the system adopts a combination of multi-stage free piston expanders and pressure relays, so that the hydraulic energy output from each stage is connected in parallel and flows into the same pipeline to the hydraulic motor, avoiding the need to install a generator in each stage, saving costs, making full use of gas pressure energy, and increasing the efficiency of pressure energy recovery.

[0007] In addition, the multi-stage expander differential pressure power generation system proposed in this embodiment of the invention may also have the following additional technical features:

[0008] According to one embodiment of the present invention, the expander units at each stage further include:

[0009] There are N first units, and the i-th first unit controls the free piston in the i-th stage free piston expander so that the free piston of the i-th stage free piston expander returns according to a predetermined stroke during operation.

[0010] There are N second units, and the i-th second unit controls the flow direction of the oil in the energy recovery chamber of the i-th stage free plunger expander so that the oil in the i-th stage free plunger expander flows in a predetermined direction during the energy recovery process.

[0011] According to one embodiment of the present invention, the i-th first unit includes:

[0012] The first energy storage device is used to store and release energy;

[0013] A pressure gauge is connected to the first accumulator and is used to monitor the pressure inside the first accumulator.

[0014] A hydraulic pump, one end of which is connected to a first accumulator via a first check valve, and the other end of which is connected to a first oil tank, the hydraulic pump being used to provide and regulate pressure;

[0015] A first relief valve is disposed between the first accumulator and the other end of the hydraulic pump, and is used to limit the pressure of the liquid flowing out of the first accumulator;

[0016] The first two-position two-way solenoid valve has one end connected to the first accumulator and the other end connected to the high-pressure inlet of the i-th stage free plunger expander, and is used to control the supply of hydraulic fluid to the i-th stage free plunger expander.

[0017] A second one-way valve is connected to the first energy recovery end of the first accumulator and the i-th stage free plunger expander to prevent fluid backflow.

[0018] The first oil tank, as an oil storage and recovery device, receives return oil from the hydraulic pump and the first relief valve;

[0019] The first unit regulates the system pressure by controlling the output pressure and flow of the hydraulic pump and combining the energy storage and release functions of the first accumulator. Through the combined use of the first two-position two-way solenoid valve and the second one-way valve, it controls the direction and flow of hydraulic fluid supplied to the i-th stage free piston expander, thereby controlling the return stroke of the free piston in the i-th stage free piston expander.

[0020] According to one embodiment of the present invention, the i-th second unit includes:

[0021] The third one-way valve and the second oil tank are located between the second energy recovery end of the i-th stage free plunger expander and the second oil tank.

[0022] The second unit controls the third one-way valve to make the oil in the energy recovery chamber of the i-th stage free plunger expander flow in a predetermined direction, thereby realizing energy recovery and conversion.

[0023] According to one embodiment of the present invention, the i-th second unit further includes:

[0024] A fourth check valve is provided between the generator set and the energy output end of the i-th stage free plunger expander.

[0025] According to one embodiment of the present invention, the first-stage expander unit further includes:

[0026] The second two-position two-way solenoid valve has one end connected to the air inlet of the first-stage free plunger expander and the other end connected to the high-pressure gas input. The second two-position two-way solenoid valve is used to control the flow rate of high-pressure gas entering the first-stage free plunger expander from the high-pressure gas input.

[0027] According to one embodiment of the present invention, the generator set includes:

[0028] Flow meters are used to monitor the flow rate of fluid entering a generator set.

[0029] The second energy storage device is used to store and release energy;

[0030] A pressure sensor, used to monitor the pressure inside the second accumulator in real time;

[0031] The second overflow valve is disposed between the second accumulator and the third oil tank and is used to limit the pressure flowing out of the second accumulator;

[0032] A hydraulic motor, wherein the hydraulic motor is used to receive hydraulic energy from a free piston expander and regulated by a second accumulator, and convert the hydraulic energy into mechanical energy;

[0033] A torque sensor is mounted on the output shaft of the hydraulic motor to measure and transmit torque information of the hydraulic motor.

[0034] A generator connected to the output of a hydraulic motor for converting mechanical energy into electrical energy;

[0035] The third oil tank serves as an oil storage and recovery device, receiving return oil from the second overflow valve and the hydraulic motor.

[0036] According to one embodiment of the present invention, the gas is natural gas.

[0037] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0039] Figure 1 This is a schematic diagram of a multi-stage expander differential pressure power generation system according to an embodiment of the present invention;

[0040] The reference numerals in the attached figures are as follows:

[0041] First-stage expander unit 1, first-stage free piston expander 1.1, first accumulator 1.2, pressure gauge 1.3, first two-position two-way solenoid valve 1.4, first check valve 1.5, hydraulic pump 1.6, second check valve 1.7, first relief valve 1.8, first oil tank 1.9, third check valve 1.10, second oil tank 1.11, fourth check valve 1.12, pressure relay 1.13, three-position three-way solenoid valve 1.14, second two-position two-way solenoid valve 1.15;

[0042] 2. Second-stage expander unit; 2.1. Second-stage free piston expander; 2.2. First accumulator; 2.3. Pressure gauge; 2.4. First two-position two-way solenoid valve; 2.5. First check valve; 2.6. Hydraulic pump; 2.7. Second check valve; 2.8. First relief valve; 2.9. First oil tank; 2.10. Third check valve; 2.11. Second oil tank; 2.12. Fourth check valve; 2.13. Pressure relay; 2.14. Three-position three-way solenoid valve.

[0043] 3. Third-stage expander unit 3, 3.1 Third-stage free piston expander 3, 3.2 First accumulator 3, 3.3 Pressure gauge 3, 3.4 First two-position two-way solenoid valve 3, 3.5 First check valve 3, 3.6 Hydraulic pump 3, 3.7 Second check valve 3, 3.8 First relief valve 3, 3.9 First oil tank 3, 3.10 Third check valve 3, 3.11 Second oil tank 3, 3.12 Fourth check valve 3, 3.13 Pressure relay 3, 3.14 Three-position three-way solenoid valve;

[0044] Flow meter 4, accumulator 5, pressure sensor 6, relief valve 7, hydraulic motor 8, torque sensor 9, generator 10, third oil tank 11. Detailed Implementation

[0045] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0046] The multi-stage expander differential pressure power generation system of the present invention will be described below with reference to the accompanying drawings.

[0047] Figure 1This is a schematic diagram of a multi-stage expander differential pressure power generation system according to an embodiment of the present invention.

[0048] like Figure 1 As shown, the multi-stage expander differential pressure power generation system of this invention includes: N-stage expander units and a generator set; wherein, each stage of expander unit i includes a free plunger expander i.1, a pressure relay i.13, and a three-position three-way solenoid valve i.14, and expander unit i is used to output mechanical energy to the generator set during the expansion and depressurization process of high-pressure gas (such as natural gas); wherein, the inlet end of the first-stage free plunger expander i.1 is connected to the high-pressure gas input end, and the outlet end of the i-th stage free plunger expander i.1 is connected to... The inlet of the i-th pressure relay i.13 and the i-th three-position three-way solenoid valve i.14 are connected. The inlet of the (i+1)-th stage free plunger expander (i+1).14 is connected to the first working end of the i-th three-position three-way solenoid valve i.14. The second working ends of all N three-position three-way solenoid valves i.14 are connected to the low-pressure gas output end. The N pressure relays i.13 are used to monitor the gas pressure at the outlet of each stage of the free plunger expander i.1. If the i-th pressure relay i.13 detects the i-th stage free plunger expander i.14, the pressure relay i.13 will be connected to the inlet of the i-th stage free plunger expander i.14. If the gas pressure at the outlet of the first-stage free plunger expander i.1 is higher than the corresponding preset pressure threshold, then the first working end of the i-th three-position three-way solenoid valve i.14 is connected to the inlet of the i-th-stage free plunger expander i.1 to allow the gas discharged from the outlet of the i-th-stage free plunger expander i.1 to enter the (i+1)-th stage free plunger expander (i+1).14; if the i-th pressure relay i.13 detects that the gas pressure at the outlet of the i-th-stage free plunger expander i.1 is not higher than the corresponding preset pressure threshold, then... If the force threshold is set, the second working end of the i-th three-position three-way solenoid valve i.14 is connected to the outlet end of the i-th stage free plunger expander i.1, so that the gas after expansion and depressurization treatment by the i-th stage free plunger expander i.1 is discharged through the low-pressure gas output end; the generator set is connected to the energy output end of each stage free plunger expander i.1, and is used to convert the mechanical energy output by the expander set i into electrical energy; where N is a positive integer greater than or equal to 2, i is a positive integer greater than or equal to 1, and N > i.

[0049] For example, such as Figure 1As shown, the first-stage expander unit 1 includes a first-stage free piston expander 1.1, a first accumulator 1.2, a pressure gauge 1.3, a first two-position two-way solenoid valve 1.4, a first check valve 1.5, a hydraulic pump 1.6, a second check valve 1.7, a first relief valve 1.8, a first oil tank 1.9, a third check valve 1.10, a second oil tank 1.11, a fourth check valve 1.12, a pressure relay 1.13, a three-position three-way solenoid valve 1.14, and a second two-position two-way solenoid valve 1.15. The second-stage expander unit 2 includes a second-stage free piston expander 2.1, a first accumulator 2.2, a pressure gauge 2.3, a first two-position two-way solenoid valve 2.4, a first check valve 2.5, a hydraulic pump 2.6, a second check valve 2.7, a first relief valve 2.8, a first oil tank 2.9, a third check valve 2.10, a second oil tank 2.11, a fourth check valve 2.12, a pressure relay 2.13, and a three-position three-way solenoid valve 2.14. The third-stage expander unit 3 includes a third-stage free piston expander 3.1, a first accumulator 3.2, a pressure gauge 3.3, a first two-position two-way solenoid valve 3.4, a first check valve 3.5, a hydraulic pump 3.6, a second check valve 3.7, a first relief valve 3.8, a first oil tank 3.9, a third check valve 3.10, a second oil tank 3.11, a fourth check valve 3.12, a pressure relay 3.13, and a three-position three-way solenoid valve 3.14.

[0050] like Figure 1 As shown, each stage of the expander unit i also includes: N first units, the i-th first unit corresponding to control the free plunger in the i-th stage free plunger expander i.1, so that the free plunger in the i-th stage free plunger expander i.1 performs a return motion according to a predetermined stroke during operation; and N second units, the i-th second unit corresponding to control the flow direction of the oil in the energy recovery chamber of the i-th stage free plunger expander i.1, so that the oil in the i-th stage free plunger expander i.1 flows in a predetermined direction during energy recovery.

[0051] like Figure 1As shown, the i-th first unit includes: a first accumulator i.2, used to store and release energy; a pressure gauge i.3, connected to the first accumulator i.2, used to monitor the pressure inside the first accumulator i.2; a hydraulic pump i.6, one end of which is connected to the first accumulator i.2 via a first check valve i.5, and the other end of which is connected to a first oil tank i.9, used to provide and regulate pressure; a first relief valve i.8, located between the first accumulator i.2 and the other end of the hydraulic pump i.6, used to limit the pressure of the liquid flowing out of the first accumulator i.2; and a first two-position two-way solenoid valve i.4, one end of which is connected to the first accumulator i.2, and the other end of which is connected to the i-th stage free... The high-pressure inlet of the plunger expander i.1 is used to control the supply of hydraulic fluid to the i-th stage free plunger expander i.1; the second check valve i.7 is connected to the first energy recovery end of the first accumulator i.2 and the i-th stage free plunger expander i.1 to prevent fluid backflow; the first oil tank i.9 serves as an oil storage and recovery device, receiving return oil from the hydraulic pump i.6 and the first relief valve i.8; wherein, the first unit regulates the system pressure by controlling the output pressure and flow rate of the hydraulic pump i.6, combined with the energy storage and release function of the first accumulator i.2, and controls the direction and flow rate of the hydraulic fluid supplied to the i-th stage free plunger expander i.1 through the coordinated use of the first two-position two-way solenoid valve i.4 and the second check valve i.7, thereby controlling the return stroke of the free plunger in the i-th stage free plunger expander i.1.

[0052] like Figure 1 As shown, the i-th second unit includes: a third one-way valve i.10 and a second oil tank i.11. The third one-way valve i.10 is located between the second energy recovery end of the i-th stage free plunger expander i.1 and the second oil tank i.11. The second unit controls the third one-way valve i.10 to make the oil in the energy recovery chamber of the i-th stage free plunger expander i.1 flow in a predetermined direction, thereby realizing energy recovery and conversion.

[0053] like Figure 1 As shown, the i-th second unit also includes: a fourth one-way valve i.12, which is disposed between the generator set and the energy output end of the i-th stage free plunger expander i.1.

[0054] like Figure 1As shown, the first-stage expander unit 1 also includes: a second two-position two-way solenoid valve 1.15, one end of which is connected to the air inlet of the first-stage free plunger expander 1.1, and the other end of which is connected to the high-pressure gas input end. The second two-position two-way solenoid valve 1.15 is used to control the flow rate of high-pressure gas entering the first-stage free plunger expander 1.1 from the high-pressure gas input end.

[0055] like Figure 1 As shown, the generator set includes: a flow meter 4 for monitoring the flow rate of fluid entering the generator set; a second accumulator 5 for storing and releasing energy; a pressure sensor 6 for real-time monitoring of the pressure inside the second accumulator 5; a second relief valve 7 located between the second accumulator 5 and the third oil tank 11 for limiting the pressure flowing out of the second accumulator 5; a hydraulic motor 8 for receiving hydraulic energy from the free piston expander and regulated by the second accumulator 5, and converting the hydraulic energy into mechanical energy; a torque sensor 9 located on the output shaft of the hydraulic motor 8 for measuring and transmitting the torque information of the hydraulic motor 8; a generator 10 connected to the output end of the hydraulic motor 8 for converting mechanical energy into electrical energy; and a third oil tank 11, which serves as an oil storage and recovery device, receiving return oil from the second relief valve 7 and the hydraulic motor 8.

[0056] In the first stage of expansion, the second two-position two-way solenoid valve 1.15 opens, and high-pressure natural gas enters the first-stage free plunger expander 1.1. The first-stage free plunger expander 1.1 converts the gas pressure energy of the high-pressure natural gas into hydraulic energy, which passes through the fourth check valve 1.12, flow meter 4, and hydraulic motor 8, and finally returns to the third oil tank 11. The hydraulic motor 8 converts the hydraulic energy into mechanical energy to drive the generator 10 to rotate and generate electrical energy.

[0057] After the first stage of expansion, the pressure of the natural gas is measured by the pressure relay 1.13. If the pressure after the first stage of expansion is lower than the preset pressure threshold set by the pressure sensor 1.13, the second working end (left position) of the three-position three-way solenoid valve 1.14 is energized, and the gas enters the low-pressure pipeline for discharge. If the pressure after the first stage of expansion is higher than the preset pressure threshold set by the pressure sensor 1.13, the first working end (right position) of the three-position three-way solenoid valve 1.14 is energized, and the gas enters the second stage expander unit 2.

[0058] In the second-stage expander 2, similar to the first-stage expander 1, the gas after secondary expansion enters the low-pressure exhaust pipe or the third-stage expander 3. The high-pressure natural gas undergoes multiple stages of expansion until the pressure is reduced to meet the requirements, and finally enters the low-pressure pipe and is discharged through the low-pressure gas output end.

[0059] Therefore, the system of the present invention can make full use of natural gas pressure and increase the efficiency of pressure energy recovery; the free plunger expander has the characteristics of being resistant to two-phase flow, pollution-resistant, and wide operating conditions, which broadens the application scenarios of multi-stage expander differential pressure power generation system; by using a free plunger and hydraulic system for energy recovery, the hydraulic energy output from each stage is connected in parallel and flows into the same pipeline to the hydraulic motor, avoiding the need to install a generator in each stage and saving costs.

[0060] In summary, the multi-stage expander differential pressure power generation system of this invention includes: N-stage expander units and a generator set; wherein each stage of the expander unit includes a free plunger expander, a pressure relay, and a three-position three-way solenoid valve, and the expander unit is used to output mechanical energy to the generator set during the expansion and depressurization process of high-pressure gas; wherein, the inlet end of the first-stage free plunger expander is connected to the high-pressure gas input end, the outlet end of the i-th stage free plunger expander is connected to the inlet end of the i-th pressure relay and the i-th three-position three-way solenoid valve, the inlet end of the (i+1)-th stage free plunger expander is connected to the first working end of the i-th three-position three-way solenoid valve, and the second working ends of the N three-position three-way solenoid valves are all connected to the low-pressure gas output end; the N pressure relays are used to monitor the gas pressure at the outlet end of each stage of the free plunger expander; wherein, if the i-th stage... If the pressure relay detects that the gas pressure at the outlet of the i-th stage free plunger expander is higher than the corresponding preset pressure threshold, it controls the first working end of the i-th three-position three-way solenoid valve to connect with the inlet of the i-th stage free plunger expander, so that the gas discharged from the outlet of the i-th stage free plunger expander enters the (i+1)-th stage free plunger expander; if the pressure relay detects that the gas pressure at the outlet of the i-th stage free plunger expander is not higher than the corresponding preset pressure threshold, it controls the second working end of the i-th three-position three-way solenoid valve to connect with the outlet of the i-th stage free plunger expander, so that the gas after expansion and depressurization treatment by the i-th stage free plunger expander is discharged through the low-pressure gas output end; the generator set is connected to the energy output end of each stage free plunger expander and is used to convert the mechanical energy output by the expander set into electrical energy. Therefore, this system adopts a combination of multi-stage free piston expanders and pressure relays, so that the hydraulic energy output from each stage is connected in parallel and flows into the same pipeline to the hydraulic motor, avoiding the need to install a generator in each stage, saving costs, making full use of gas pressure energy, and increasing the efficiency of pressure energy recovery; it converts the pressure energy of natural gas into easily usable hydraulic energy, recovering and utilizing energy that would otherwise be wasted, which has beneficial effects on the comprehensive utilization of natural gas and energy conservation and emission reduction; this device adopts a multi-stage pressure reduction system, which makes the pressure energy recovery efficiency higher and is more suitable for the pressure energy recovery of high-pressure natural gas; the hydraulic system realizes energy recovery and reset, and the high-pressure gas enters the expansion chamber and expands rapidly, releasing a large amount of energy in a short time. The hydraulic system can act as a spring, making the piston run smoothly, and the hydraulic system has high power transmission efficiency, which can realize functions such as buffering and safety protection; the hydraulic components in the hydraulic circuit are small in size and have a fast response speed, which can make the overall mechanism layout more compact.

[0061] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0062] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A multi-stage expander differential pressure power generation system, characterized in that, include: N-stage expander unit and generator set; wherein, each stage of the expander unit (i) includes a free plunger expander (i.1), a pressure relay (i.13), and a three-position three-way solenoid valve (i.14), and the expander unit (i) is used to output mechanical energy to the generator set during the expansion and depressurization process of high-pressure gas; wherein, The inlet of the first-stage free plunger expander (1.1) is connected to the high-pressure gas input end. The outlet of the i-th stage free plunger expander (i.1) is connected to the inlet of the i-th pressure relay (i.13) and the i-th three-position three-way solenoid valve (i.14). The inlet of the (i+1)-th stage free plunger expander ((i+1).14) is connected to the first working end of the i-th three-position three-way solenoid valve (i.14). The second working ends of N of the three-position three-way solenoid valves (i.14) are all connected to the low-pressure gas output end. N pressure relays (i.13) are used to monitor the gas pressure at the outlet of each stage of the free plunger expander (i.1). If the i-th pressure relay (i.13) detects that the gas pressure at the outlet of the i-th stage free plunger expander (i.1) is higher than the corresponding preset pressure threshold, then the first working end of the i-th three-position three-way solenoid valve (i.14) is connected to the inlet of the i-th stage free plunger expander (i.1) to allow the gas discharged from the outlet of the i-th stage free plunger expander (i.1) to pass through. The gas enters the (i+1)th stage free plunger expander ((i+1).14); if the i-th pressure relay (i.13) detects that the gas pressure at the outlet of the i-th stage free plunger expander (i.1) is not higher than the corresponding preset pressure threshold, then the second working end of the i-th three-position three-way solenoid valve (i.14) is connected to the outlet of the i-th stage free plunger expander (i.1) so that the gas after expansion and depressurization treatment by the i-th stage free plunger expander (i.1) is discharged through the low-pressure gas output end; A generator set, which is connected to the energy output end of a series of free plunger expanders (i.1), is used to convert the mechanical energy output by the expander set (i) into electrical energy; Where N is a positive integer greater than or equal to 2, i is a positive integer greater than or equal to 1, and N > i; The expander units (i) at each level also include: There are N first units, and the i-th first unit controls the free piston in the i-th stage free piston expander (i.1) so that the free piston of the i-th stage free piston expander (i.1) will return according to a predetermined stroke during operation; There are N second units, and the i-th second unit controls the flow direction of the oil in the energy recovery chamber of the i-th stage free plunger expander (i.1) so that the oil in the i-th stage free plunger expander (i.1) flows in a predetermined direction during the energy recovery process; The i-th second unit also includes: A fourth check valve (i.12) is disposed between the generator set and the energy output end of the i-th stage free plunger expander (i.1); The first-stage expander unit (1) also includes: The second two-position two-way solenoid valve (1.15) has one end connected to the air inlet of the first-stage free plunger expander (1.1) and the other end connected to the high-pressure gas input. The second two-position two-way solenoid valve (1.15) is used to control the flow rate of high-pressure gas entering the first-stage free plunger expander (1.1) from the high-pressure gas input.

2. The system according to claim 1, characterized in that, The i-th first unit includes: The first energy storage device (i.2) is used to store and release energy; Pressure gauge (i.3), which is connected to the first accumulator (i.2), is used to monitor the pressure inside the first accumulator (i.2); A hydraulic pump (i.6) is provided, one end of which is connected to a first accumulator (i.2) via a first check valve (i.5), and the other end of which is connected to a first oil tank (i.9). The hydraulic pump (i.6) is used to provide and regulate pressure. The first overflow valve (i.8) is disposed between the first accumulator (i.2) and the other end of the hydraulic pump (i.6) to limit the pressure of the liquid flowing out of the first accumulator (i.2); The first two-position two-way solenoid valve (i.4) is connected at one end to the first accumulator (i.2) and at the other end to the high-pressure inlet of the i-th stage free piston expander (i.1), and is used to control the supply of hydraulic fluid to the i-th stage free piston expander (i.1). The second one-way valve (i.7) is connected to the first energy recovery end of the first accumulator (i.2) and the i-th stage free plunger expander (i.1) to prevent fluid backflow; The first oil tank (i.9) serves as an oil storage and recovery device, receiving return oil from the hydraulic pump (i.6) and the first relief valve (i.8); The first unit regulates the system pressure by controlling the output pressure and flow of the hydraulic pump (i.6) and combining the energy storage and release functions of the first accumulator (i.2). Through the coordinated use of the first two-position two-way solenoid valve (i.4) and the second one-way valve (i.7), it controls the direction and flow of hydraulic fluid supplied to the i-th stage free piston expander (i.1), thereby controlling the return stroke of the free piston in the i-th stage free piston expander (i.1).

3. The system according to claim 1, characterized in that, The i-th second unit includes: The third check valve (i.10) and the second oil tank (i.11) are located between the second energy recovery end of the i-th stage free plunger expander (i.1) and the second oil tank (i.11). The second unit controls the third one-way valve (i.10) to make the oil in the energy recovery chamber of the i-th stage free plunger expander (i.1) flow in a predetermined direction, thereby realizing energy recovery and conversion.

4. The system according to claim 1, characterized in that, The generator set includes: Flow meter (4) is used to monitor the flow rate of fluid entering the generator set; The second energy storage device (5) is used to store and release energy; Pressure sensor (6), the pressure sensor (6) is used to monitor the pressure inside the second accumulator (5) in real time; The second overflow valve (7) is located between the second accumulator (5) and the third oil tank (11) to limit the pressure flowing out of the second accumulator (5); Hydraulic motor (8), the hydraulic motor (8) is used to receive hydraulic energy from the free piston expander and regulated by the second accumulator (5), and convert the hydraulic energy into mechanical energy; A torque sensor (9) is installed on the output shaft of the hydraulic motor (8) to measure and transmit torque information of the hydraulic motor (8); A generator (10) is connected to the output of a hydraulic motor (8) for converting mechanical energy into electrical energy; The third oil tank (11) serves as an oil storage and recovery device, receiving return oil from the second overflow valve (7) and the hydraulic motor (8).

5. The system according to claim 1, characterized in that, The gas is natural gas.

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