A natural gas pipeline network high pressure energy conversion device

Abstract

The utility model discloses a natural gas pipe network high pressure energy conversion device, including expansion generator unit, gas bearing, bearing buffer subassembly and variable flow control component, expansion generator unit includes primary expansion impeller, secondary expansion impeller and alternator, primary expansion impeller and secondary expansion impeller are arranged at the both sides of alternator and with alternator coaxial arrangement, gas bearing sets up in primary expansion impeller and secondary expansion impeller inside, bearing buffer subassembly includes buffer jar and filter, and bearing buffer subassembly is connected with the high pressure natural gas pipeline of expansion generator unit upstream, and the gas export of gas bearing and alternator cooling air confluence and flow out expansion generator unit, the utility model discloses a natural gas pipe network high pressure energy conversion device, and the regulation and control precision are accurate, and the surplus energy in the decompression process of natural gas high pressure pipe network is fully utilized, and multiple protection measures are set up simultaneously, guarantee that the device is stable operation in the use process.

Description

Technical Field

[0001] This utility model relates to the field of high-pressure energy conversion technology, specifically to a high-pressure energy conversion device for natural gas pipeline networks. Background Technology

[0002] With the rapid growth of domestic natural gas demand, the construction of my country's natural gas pipeline network has accelerated, with long distances, large diameters, high pressures, and network connectivity becoming the general development trend. When the pipeline pressure is 10 MPa and the user-end pressure is 0.8 MPa, the maximum recoverable pressure energy reaches 359.12 kJ / kg, containing a significant amount of pressure energy. Recovering and utilizing this energy can effectively reduce pressure energy loss and achieve efficient energy utilization. Currently, the main methods for recovering and utilizing residual pressure and energy from natural gas pipelines are residual pressure power generation and refrigeration applications. Residual pressure power generation primarily includes direct expansion power generation and combined cycle power generation. Domestically, the utilization of residual pressure and energy from natural gas pipelines remains largely theoretical, with practical engineering applications not yet fully realized. Therefore, there is still considerable room for exploration in the engineering application of residual pressure and energy utilization from natural gas pipelines. Summary of the Invention

[0003] This invention addresses the lack of engineering applications for utilizing residual pressure and energy in natural gas pipelines in the existing technology. It proposes a high-pressure energy conversion device for natural gas pipelines that features precise control, fast response speed, and full utilization of residual energy during the decompression process of high-pressure natural gas pipelines.

[0004] This utility model is achieved through the following technical solution: A high-pressure energy conversion device for a natural gas pipeline includes an expansion generator set, an air-bearing bearing, a bearing buffer assembly, and a converter control assembly, wherein the expansion generator set is installed on a high-pressure natural gas pipeline; The expander generator set includes a primary expander impeller, a secondary expander impeller, and an AC generator. The primary expander impeller and the secondary expander impeller are arranged on both sides of the AC generator and are coaxially mounted with the AC generator. The converter control assembly is electrically connected to the AC generator. The air bearing is disposed inside the primary expansion impeller and the secondary expansion impeller; The expansion generator set includes inlet A, inlet B, outlet C1, outlet C2 and outlet D. Inlet A introduces high-pressure natural gas from the high-pressure natural gas pipeline into the inlet of the first-stage expansion impeller. The outlet of the first-stage expansion impeller is divided into two paths, one of which is connected to the inlet of the second-stage expansion impeller, and the other path enters the alternator to provide cooling air for the alternator. The outlet of the secondary expansion impeller is connected to the outlet D, and the outlet D is connected to the downstream natural gas pipeline; The bearing buffer assembly includes a buffer tank and a filter. The bearing buffer assembly is connected to the high-pressure natural gas pipeline upstream of the expansion generator set and leads the gas to inlet B. The priming gas from inlet B supplies the operation of the air-bearing bearing. The gas outlet of the air-bearing bearing merges with the cooling air of the alternator and flows out of the expansion generator set through outlet C1 and outlet C2.

[0005] As a further improvement of this utility model, a filter separator, a natural gas metering system and a safety shut-off valve are sequentially installed upstream of the expansion generator set. The outlet of the safety shut-off valve divides the high-pressure natural gas pipeline into a main stream, a first bypass branch and a second bypass branch. The main stream is connected to the inlet A and the first bypass branch is connected to the bearing buffer assembly. The second bypass branch is connected to the natural gas pipeline downstream of the outlet D.

[0006] As a further improvement of this utility model, a main regulating valve and a secondary regulating valve are provided on the upstream high-pressure natural gas pipeline of the inlet A, and the main regulating valve and the secondary regulating valve are connected in parallel. A ball valve is installed on the second bypass branch.

[0007] As a further improvement of this utility model, the bearing buffer assembly also includes a check valve, a solenoid valve, and a PV regulating valve. The check valve is located upstream of the buffer tank and connected to a branch of the high-pressure natural gas pipeline. The filter is located downstream of the buffer tank. The solenoid valve and the PV regulating valve are connected in parallel downstream of the filter and connected to the inlet B.

[0008] As a further improvement of this utility model, the converter control component includes a PWM rectifier, a protection module, a power leakage circuit, a PWM inverter, a grid-connected filter, and a frequency converter. The PWM rectifier is electrically connected to the AC generator, the PWM inverter is electrically connected to the PWM rectifier and the external power grid respectively, and the frequency converter and the grid-connected filter are both connected to the PWM inverter. The protection module is located between the PWM rectifier and the PWM inverter.

[0009] As a further improvement of this utility model, the protection module includes a first fast-response switch, a second fast-response switch, a first mechanical switch, and a second mechanical switch. The first fast-response switch and the first mechanical switch are connected in parallel between the connection circuit of the PWM rectifier and the PWM inverter, and the second fast-response switch and the second mechanical switch are connected in parallel between the rectifier and the energy leakage circuit.

[0010] As a further improvement of this utility model, the first fast response switch and the second fast response switch of the protection module are insulated gate bipolar transistor (IGBT) switches.

[0011] As a further improvement of this utility model, the energy dissipation circuit is a DC braking resistor.

[0012] As a further improvement of this utility model, the natural gas metering system includes a straight pipe section, an ultrasonic flow meter, a temperature sensor, and a pressure sensor.

[0013] Compared with the prior art, the beneficial effects of this utility model are: it transforms the utilization of residual energy in high-pressure natural gas pipelines into engineering technology, and makes full use of the residual energy in the decompression process of high-pressure natural gas pipelines. At the same time, it sets up multiple protection measures to ensure the stable operation of the device during use. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the accompanying drawings required in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 This is a system diagram of the high-pressure energy conversion device for natural gas pipeline networks according to this utility model; Figure 2 This is a schematic diagram of the internal structure of the expansion generator set of the high-pressure energy conversion device for natural gas pipeline networks according to this utility model; Figure 3 This is a schematic diagram illustrating the power generation and grid connection principle of the high-pressure energy conversion device for natural gas pipeline networks according to this utility model; Figure 4 This is a diagram of the three-phase bridge PWM control rectifier circuit for the high-pressure energy conversion device of the natural gas pipeline network of this utility model; Figure 5 This is a three-phase full-bridge PWM control inverter circuit diagram for a high-pressure energy conversion device for natural gas pipeline networks according to this utility model; Figure 6 This is the electrical diagram of the high-pressure energy conversion device for natural gas pipeline networks according to this utility model; Figure 7 This is a schematic diagram of the switch installation for the rapid switching of the protection module of the high-pressure energy conversion device for natural gas pipeline networks according to this utility model. Detailed Implementation

[0016] The technical solutions of various embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0017] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0018] A high-pressure energy conversion device for a natural gas pipeline network includes an expansion generator set 1, an air-floating bearing 2, a bearing buffer assembly, and a converter control assembly. The expansion generator set 1 is installed on a high-pressure natural gas pipeline. The expander generator set 1 includes a first-stage expander impeller 3, a second-stage expander impeller 4, and an AC generator. Both the first-stage expander impeller 3 and the second-stage expander impeller 4 are radial expander impellers. The first-stage expander impeller 3 and the second-stage expander impeller 4 are arranged on both sides of the AC generator and are coaxial with the AC generator. The converter control component is electrically connected to the AC generator. The air bearing 2 is installed inside the primary expansion impeller 3 and the secondary expansion impeller 4; The expander generator set 1 includes inlet A, inlet B, outlet C1, outlet C2 and outlet D. Inlet A introduces high-pressure natural gas from the high-pressure natural gas pipeline into the inlet of the first-stage expander impeller 3. The outlet of the first-stage expander impeller 3 is divided into two paths. One path is connected to the inlet of the second-stage expander impeller 4, and the other path enters the alternator to provide cooling air for the alternator. The outlet of the secondary expansion impeller 4 is connected to outlet D, and outlet D is connected to the downstream natural gas pipeline; The high-pressure natural gas used in the expander generator set 1 is divided into two streams: power gas and bearing gas. The power gas enters the first-stage expander impeller 3 through the main regulating valve at inlet A to do work. After expansion and work, the temperature decreases. Then, a portion of the natural gas enters the generator chamber to cool the stator coil and is discharged from ports C1 and C2. The majority of the remaining power gas enters the second-stage expander impeller 4 through the interstage connecting pipe to continue doing work. Port B is used separately to supply the air bearing 2 for operation. At the same time, due to the high gas pressure in the chambers of the first-stage expander impeller 3 and the second-stage expander impeller 4, the bearing gas enters the stator and rotor chambers and is discharged from outlets C1 and C2 along with the cooling gas. After merging with the exhaust gas from the second-stage expander impeller 4, it flows downstream into the main stream.

[0019] The bearing buffer assembly includes a buffer tank 6 and a filter 7. The bearing buffer assembly is connected to the high-pressure natural gas pipeline upstream of the expansion generator set 1 and leads the gas to inlet B. The induced gas from inlet B supplies the operation of the air-bearing bearing 2. The gas outlet of the air-bearing bearing 2 merges with the cooling air of the alternator and flows out of the expansion generator set 1 through outlet C1 and outlet C2.

[0020] An upstream filter separator 8 is installed in the expansion generator set 1. A natural gas metering system 9 and a safety shut-off valve 10 are installed downstream of the filter separator 8. The natural gas metering system 9 includes a straight pipe section, an ultrasonic flow meter, a temperature sensor, and a pressure sensor. The outlet of the safety shut-off valve 10 divides the high-pressure natural gas pipeline into a main stream 11, a first bypass branch 12, and a second bypass branch 13. The main stream 11 is connected to the inlet A. The first bypass branch 12 is connected to the bearing buffer assembly. The second bypass branch is connected to the natural gas pipeline downstream of the outlet D. The natural gas metering system 9 is used to meter and regulate the natural gas in the second bypass branch 13.

[0021] A main regulating valve 14 and a secondary regulating valve 15 are installed on the upstream high-pressure natural gas pipeline of inlet A. The main regulating valve 14 and the secondary regulating valve 15 are connected in parallel. The main regulating valve 14 is configured for power-flow cascade regulation and also has a second bypass branch 13 with flow (height limit) and outlet pressure (height limit) monitoring and limiting regulation functions to ensure gas transmission. Pressure sensors are installed before and after the main regulating valve 14 to detect the pressure before and after regulation. The secondary regulating valve 15 is used for pressure balancing and primary flow impact regulation when the expansion generator set 1 starts up, and also works with the main regulating valve 14 for fine regulation. A ball valve 16 is provided on the second bypass branch. After the safety shut-off valve 10 is closed or fails, it will quickly balance the pressure difference between the two ends of the expansion generator set 1 to reduce the speed of the expansion generator set 1 and prevent the expansion generator set 1 from running away.

[0022] The bearing buffer assembly also includes a check valve 17, a solenoid valve 18, and a PV regulating valve 19. The check valve 17 is a DN25 check valve, which is located upstream of the buffer tank 6 and connected to the first bypass branch 12 to ensure that the stock in the buffer tank 6 will not be lost in reverse. The filter 7 is located downstream of the buffer tank 6. The buffer tank 6 and the filter 7 are set up mainly to ensure that the stock in the buffer tank 6 is used to ensure the bearing air required by the air bearing 2 when the expansion generator set 1 coasts from the rated speed to the shutdown in the case of branch cut-off or venting, while ensuring the cleanliness of the bearing air.

[0023] Solenoid valve 18 and PV regulating valve 19 are connected in parallel downstream of filter 7 and connected to inlet B. They are controlled by coarse adjustment of PV valve and fine adjustment of solenoid valve 18 to ensure that the pressure difference between the two ends of air bearing 2 is kept balanced. Two pressure transmitters are installed downstream of bearing air branch outlet C1 and outlet C2. The two transmitters are combined with the pressure on the cooling air branch to calculate the bearing air pressure difference.

[0024] The expander generator set 1 is equipped with sensors to measure signals such as coil temperature, axial vibration, and radial vibration. Combined with temperature, pressure, and flow sensors on various pipeline systems, these measurements are transmitted in real-time to the main control system for online monitoring and control of the operating status. Specifically, two pressure sensors are installed in the cooling gas branches at outlets C1 and C2, which, together with the pressure sensor in the bearing gas branch, calculate the bearing gas pressure difference. The expander cooling gas flow rate is measured and adjusted using a flow meter, regulating valve, and temperature transmitter, and the relationship between power generation, cooling gas flow rate, and coil temperature is monitored. The main outlet D circuit of expander generator set 1 is equipped with two temperature sensors to monitor the outlet gas temperature after expansion, preventing excessively low temperatures; one pressure sensor is installed to monitor the outlet gas pressure; and a check valve is used to prevent downstream backflow from affecting the operation of expander generator set 1. A vent branch is installed downstream of outlet D, equipped with one manual ball valve and one electric shut-off valve for safe venting.

[0025] In this embodiment, the converter control component includes a PWM rectifier 20, a protection module, a power leakage circuit, a PWM inverter 21, a grid-connected filter, and a frequency converter, which are used to realize AC-DC-AC conversion.

[0026] In this embodiment, the AC-DC conversion process is implemented through a three-phase bridge PWM-controlled rectifier circuit, specifically within the PWM rectifier. The SVPWM method is used to control the rectification process. Through spatial current vector distribution calculation, comparison of spatial vector synthesis methods (including various single-triangle and double-triangle modes), and modulation process design, the SVPWM control method is optimized to improve the power factor of the conversion process and control harmonic distortion. Based on the instantaneous reactive power theory of three-phase circuits, harmonics in the rectifier circuit are detected, and the difference between the harmonics and the standard complete sine wave is calculated. Finally, an external harmonic compensation device is set according to the difference, and the compensation power is adjusted to eliminate or prevent harmonic generation.

[0027] The inversion process from rectified direct current to alternating current is achieved through a three-phase full-bridge PWM-controlled inverter circuit, specifically within the PWM inverter. The SVPWM method is used to control the inversion process. Through spatial voltage vector distribution calculation, spatial vector synthesis calculation and wave function derivation, comparisons are made between discontinuous pulse width modulation zero vector allocation methods (including single zero vector method, double zero vector method, and optimal zero vector method) and continuous pulse width modulation methods. Combined with MATLAB simulation, the SVPWM control method is optimized to improve DC utilization in the conversion process, control voltage and current harmonic generation, reduce switching frequency and losses in the circuit, and adjust the three-phase voltage and frequency to match the external power grid.

[0028] The complete electrical diagram of the AC-DC-AC conversion and protection module is as follows: Figure 6 as shown in

[0029] The protection module in this embodiment includes a first fast response switch (TS1), a second fast response switch (TS2), a first mechanical switch (PS1), and a second mechanical switch (PS2). The first fast response switch (TS1) and the first mechanical switch (PS1) are connected in parallel between the connecting circuit of the PWM rectifier and the PWM inverter, and the second fast response switch (TS2) and the second mechanical switch (PS2) are connected in parallel between the rectifier and the energy discharge circuit. The first fast response switch and the second fast response switch are insulated-gate bipolar transistor (IGBT) switches. Insulated-gate bipolar transistors can achieve millisecond-level response, which can meet the requirement that the protection module intervenes quickly to prevent accidents. The installation of the fast switching switch of the protection module is as Figure 6 shown in

[0030] Since the first fast response switch (TS1) and the second fast response switch (TS2) have millisecond-level response, they can be applied to high-frequency circuits and act prior to common mechanical switches. When the protection module operates, the driving circuit drives the first fast response switch (TS1) and the second fast response switch (TS2) to act to achieve fast switching. After the first mechanical switch (PS1) and the second mechanical switch (PS2) complete their actions, the driving circuit then turns off the first fast response switch (TS1) and the second fast response switch (TS2), so as to achieve the goal of quickly switching the circuit to the energy discharge circuit when the power station end is off-grid. In this embodiment, a three-phase voltage detection algorithm at the power generation end can be constructed, a voltage threshold for switch action can be established, the sampling circuit, control circuit and driving circuit matching the circuit can be designed, and the main parameters of each circuit can be optimized based on matlab simulation.

[0031] In this embodiment, the energy discharge circuit is a DC braking resistor. When disconnected from the external power grid, the electricity generated in the natural gas power station is consumed through the DC braking resistor to ensure the safety of the power grid and power generation equipment.

[0032] Finally, it should be noted that the above embodiments are only used to explain the technical solution of the present utility model, not to limit it; although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solution described in the foregoing embodiments, or equivalently replace some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solution depart from the technical solution of the embodiments of the present utility model.

Claims

1. A high-pressure energy conversion device for a natural gas pipeline network, comprising an expander generator set, an air-bearing bearing, a bearing buffer assembly, and a converter control assembly, wherein the expander generator set is installed on a high-pressure natural gas pipeline, characterized in that: The expander generator set includes a primary expander impeller, a secondary expander impeller, and an AC generator. The primary expander impeller and the secondary expander impeller are arranged on both sides of the AC generator and are coaxially mounted with the AC generator. The converter control assembly is electrically connected to the AC generator. The air bearing is disposed inside the primary expansion impeller and the secondary expansion impeller; The expansion generator set includes inlet A, inlet B, outlet C1, outlet C2 and outlet D. Inlet A introduces high-pressure natural gas from the high-pressure natural gas pipeline into the inlet of the first-stage expansion impeller. The outlet of the first-stage expansion impeller is divided into two paths, one of which is connected to the inlet of the second-stage expansion impeller, and the other path enters the alternator to provide cooling air for the alternator. The outlet of the secondary expansion impeller is connected to the outlet D, and the outlet D is connected to the downstream natural gas pipeline; The bearing buffer assembly includes a buffer tank and a filter. The bearing buffer assembly is connected to the high-pressure natural gas pipeline upstream of the expansion generator set and leads the gas to inlet B. The priming gas from inlet B supplies the operation of the air-bearing bearing. The gas outlet of the air-bearing bearing merges with the cooling air of the alternator and flows out of the expansion generator set through outlet C1 and outlet C2.

2. The high-pressure energy conversion device for natural gas pipelines according to claim 1, characterized in that: Upstream of the expansion generator set, a filter separator, a natural gas metering system, and a safety shut-off valve are installed in sequence. The outlet of the safety shut-off valve divides the high-pressure natural gas pipeline into a main stream, a first bypass branch, and a second bypass branch. The main stream is connected to the inlet A, and the first bypass branch is connected to the bearing buffer assembly. The second bypass branch is connected to the natural gas pipeline downstream of the outlet D.

3. The high-pressure energy conversion device for natural gas pipelines according to claim 2, characterized in that: The upstream high-pressure natural gas pipeline of inlet A is equipped with a main regulating valve and a secondary regulating valve, which are connected in parallel. A ball valve is installed on the second bypass branch.

4. The high-pressure energy conversion device for natural gas pipelines according to claim 2, characterized in that: The bearing buffer assembly also includes a check valve, a solenoid valve, and a PV regulating valve. The check valve is located upstream of the buffer tank and connected to the first bypass branch. The filter is located downstream of the buffer tank. The solenoid valve and the PV regulating valve are connected in parallel downstream of the filter and connected to the inlet B.

5. The high-pressure energy conversion device for natural gas pipelines according to claim 1, characterized in that: The converter control component includes a PWM rectifier, a protection module, a power leakage circuit, a PWM inverter, a grid-connected filter, and a frequency converter; The PWM rectifier is electrically connected to the AC generator, the PWM inverter is electrically connected to the PWM rectifier and the external power grid respectively, and the frequency converter and the grid-connected filter are both connected to the PWM inverter. The protection module is located between the PWM rectifier and the PWM inverter.

6. The high-pressure energy conversion device for natural gas pipelines according to claim 5, characterized in that: The protection module includes a first fast-response switch, a second fast-response switch, a first mechanical switch, and a second mechanical switch. The first fast-response switch and the first mechanical switch are connected in parallel between the connection circuit of the PWM rectifier and the PWM inverter, and the second fast-response switch and the second mechanical switch are connected in parallel between the rectifier and the energy leakage circuit.

7. The high-pressure energy conversion device for natural gas pipelines according to claim 6, characterized in that: The first and second fast-response switches of the protection module are insulated gate bipolar transistor (IGBT) switches.

8. The high-pressure energy conversion device for natural gas pipelines according to claim 5, characterized in that: The energy dissipation circuit is a DC braking resistor.

9. The high-pressure energy conversion device for natural gas pipelines according to claim 2, characterized in that: The natural gas metering system includes a straight pipe section, an ultrasonic flow meter, a temperature sensor, and a pressure sensor.

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