Natural gas pressure energy power generation and pressure regulation device and method

Abstract

The invention belongs to the technical field of natural gas pressure energy recycling, and provides a natural gas pressure energy power generation and pressure regulation device and method.The device comprises a main pipeline which is sequentially provided with a control valve, a heat exchange unit, a first pressure regulation unit and a second pressure regulation unit, and the first pressure regulation unit comprises a first pressure regulation module and an expansion machine which are sequentially connected; the first pressure regulating module is used for regulating the natural gas pressure and flow of the main pipeline before expansion power generation; and the second pressure regulating unit is used for regulating the pressure of the natural gas after expansion power generation and monitoring the temperature of the natural gas after expansion power generation. By using the heat exchange unit, the pipeline can be preheated before the expansion machine generates power, so that natural gas quickly achieves power generation, and the power generation efficiency is improved; by using the heat exchange bypass, the flow of the heat exchange bypass can be adjusted according to the temperature before expansion and the temperature after expansion, so that the conditions that the temperature of natural gas before expansion is too low and the main pipeline is frosted and frozen are dealt with.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas pressure energy recovery and utilization, and in particular relates to a natural gas pressure energy power generation and pressure regulating device and method. Background Art

[0002] At present, the downstream natural gas pipeline pressure regulation of the natural gas industry still uses the traditional pressure regulation method to reduce the pressure, resulting in the kinetic energy and potential energy of natural gas in the pressure reduction process not being reasonably utilized and wasted. At present, with the rapid development of natural gas in the pipeline network, the efficient use of natural gas resources is an important way to develop a low-carbon economy. As a new energy-saving technology in the gas industry, natural gas pressure energy power generation technology can not only efficiently utilize natural gas pressure energy, but also bring considerable economic benefits and energy-saving and emission reduction benefits, and achieve energy conservation and consumption reduction for enterprises. As a node in the operation of the gas pipeline network, each pressure regulating station is an area where pressure energy is concentrated. The use of natural gas pressure energy power generation can utilize this part of pressure energy to improve the overall value utilization rate of natural gas. The existing natural gas pressure energy application projects are mainly designed for large and medium-sized pressure regulating stations, mainly focusing on the comprehensive utilization of large-scale pressure energy, and the natural gas pressure, temperature and flow rate all have large fluctuations. In the process of natural gas pressure energy expansion power generation, there are also problems such as large natural gas pressure fluctuations and large changes in intake flow, which make the expander in a variable operating state for a long time, resulting in the generator set not being able to operate safely and stably, prone to failures and emergency braking, and unstable power supply voltage and current, and poor power quality. Due to changes in gas consumption and pressure load requirements of downstream gas users, the gas supply pressure after expansion and power generation often cannot meet the gas demand of downstream users, causing depressurization of the downstream pipeline network. Summary of the invention

[0003] In order to solve at least one problem in the background technology, the present invention provides a natural gas pressure energy power generation and pressure regulating device and method.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A natural gas pressure energy power generation and pressure regulating device, comprising:

[0006] The main pipeline is provided with a control valve, a heat exchange unit, a first pressure regulating unit and a second pressure regulating unit in sequence;

[0007] The central control unit is connected to the heat exchange unit, the first pressure regulating unit and the second pressure regulating unit respectively, and is used to control the working states of the heat exchange unit, the first pressure regulating unit and the second pressure regulating unit;

[0008] The control valve is used to control the flow of natural gas entering the main pipeline;

[0009] The heat exchange unit is used to preheat the natural gas entering the main pipeline;

[0010] The first pressure regulating unit includes a first pressure regulating module and an expander connected in sequence, the first pressure regulating module is used to adjust the natural gas pressure and flow rate of the main pipeline before expansion and power generation, and monitor the temperature of the natural gas before expansion and power generation;

[0011] The second pressure regulating unit is used to regulate the pressure of the natural gas after expansion and power generation and to monitor the temperature of the natural gas after expansion and power generation.

[0012] Preferably, the heat exchange unit comprises a circulation pump, a frequency converter, a heat source, a heat exchanger and a circulation branch;

[0013] The water inlet and outlet of the cold pipe of the heat exchanger are both connected to the main pipe;

[0014] The water inlet and outlet of the heat pipe of the heat exchanger are both connected to the circulation branch;

[0015] The circulation pump and the heat source are arranged in series in the circulation branch;

[0016] The frequency converter is electrically connected to the circulation pump.

[0017] Preferably, the frequency converter and the heat source are both electrically connected to the central control unit.

[0018] Preferably, the main pipeline is also connected to a heat exchange bypass, the inlet of the heat exchange bypass is located on the main pipeline between the control valve and the heat exchange unit, and the outlet is connected to the heat source;

[0019] A heat exchange regulating valve is installed on the heat exchange bypass.

[0020] Preferably, the first pressure regulating unit comprises a regulating valve, an expander, a first pressure regulating device and an inlet temperature sensor;

[0021] In the main pipeline, the control valve, the first pressure regulating device, the inlet temperature sensor and the expander are arranged in sequence.

[0022] Preferably, the expander is electrically connected to a generator, and the generator is electrically connected to a controller;

[0023] The regulating valve, the controller, the first pressure regulating device and the inlet temperature sensor are all electrically connected to the central control unit.

[0024] Preferably, the main line is also connected to a pressure regulating bypass, the inlet of the pressure regulating bypass is located on the main line between the heat exchange unit and the first pressure regulating unit, and the outlet is located on the main line between the first pressure regulating unit and the second pressure regulating unit;

[0025] A pressure regulating valve and a check valve are sequentially installed on the pressure regulating bypass.

[0026] Preferably, the second pressure regulating unit comprises a second pressure regulating device and an outlet temperature sensor connected in series on the main pipe;

[0027] The second pressure regulating device and the outlet temperature sensor are both electrically connected to the central control unit.

[0028] A natural gas pressure energy power generation and pressure regulation method, used in the above-mentioned natural gas pressure energy power generation and pressure regulation device, comprises the following steps:

[0029] Control the total amount of natural gas entering the main pipeline through the control valve;

[0030] When the temperature of the natural gas passing through the first pressure regulating unit is lower than the first preset temperature, adjusting the natural gas flow of the heat exchange unit until the temperature of the natural gas passing through the first pressure regulating unit reaches the first preset temperature;

[0031] When the natural gas pressure and flow rate of the main pipeline before expansion power generation are lower than the first preset working value, the natural gas pressure and flow rate of the main pipeline before expansion power generation are adjusted by the first pressure regulating unit until the first preset working value of the pressure and flow rate is met;

[0032] When the temperature of the natural gas passing through the second pressure regulating unit is lower than the second preset temperature, adjusting the natural gas flow of the heat exchange unit until the temperature of the natural gas passing through the second pressure regulating unit reaches the second preset temperature;

[0033] When the natural gas pressure and flow rate of the main pipeline after expansion and power generation are lower than the second preset working value, the second pressure regulating unit adjusts the natural gas pressure and flow rate of the main pipeline after expansion and power generation until the second preset working value of pressure and flow is met.

[0034] Preferably, the first preset temperature is a preheating temperature of the main pipe, and the second preset temperature is a temperature for preventing frost on the main pipe.

[0035] Preferably, a pressure regulating bypass is provided so that the inlet of the pressure regulating bypass is located on the main pipe between the heat exchange unit and the first pressure regulating unit, and the outlet is located on the main pipe between the first pressure regulating unit and the second pressure regulating unit;

[0036] When the natural gas pressure and flow rate of the main pipeline after expansion and power generation are lower than the second preset working value, the natural gas pressure and flow rate of the main pipeline after expansion and power generation are jointly adjusted by the second pressure regulating unit and the pressure regulating bypass until the second preset working value of the pressure and flow rate is met;

[0037] When the natural gas flow rate of the expander entering the first pressure regulating unit is greater than the processing capacity of the expander, the excess flow rate directly enters the second pressure regulating unit through the pressure regulating bypass;

[0038] When the pressure demand load of the main pipeline downstream of the second pressure regulating unit increases or the main pipeline loses pressure, the heat exchange unit and the first pressure regulating unit are closed, so that the natural gas in the main pipeline enters the downstream main pipeline of the second pressure regulating unit from the pressure regulating bypass;

[0039] When the pressure demand load of the main pipeline downstream of the second pressure regulating unit decreases, the heat exchange unit and the first pressure regulating unit are opened to reduce the natural gas flow of the pressure regulating bypass and increase the natural gas flow entering the first pressure regulating unit, so that the expander in the first pressure regulating unit can perform work.

[0040] Beneficial effects of the present invention:

[0041] 1. The present invention uses a heat exchange unit to preheat the pipeline before the expander generates electricity, so that the natural gas can quickly reach the power generation point, thereby improving the power generation efficiency;

[0042] 2. The present invention uses a heat exchange bypass, and can adjust the flow of the heat exchange bypass according to the temperature before expansion and the temperature after expansion, so as to cope with the situation that the natural gas temperature before expansion is too low and frost and ice appear in the main pipeline;

[0043] 3. The present invention uses the first pressure regulating unit to adjust the pressure and flow rate of the main line before expansion so that it meets the working parameters before expansion;

[0044] 4. The present invention uses a pressure regulating bypass. When the pressure before expansion is too high or the pressure of the downstream pipeline is insufficient, the pressure can be regulated by the pressure regulating bypass to meet the working needs;

[0045] 5. The present invention uses a second pressure regulating unit to monitor the pressure and temperature parameters of the natural gas after expansion, and then adjusts them according to control instructions.

[0046] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 A structural schematic diagram of a natural gas pressure energy power generation and pressure regulating device of the present invention is shown.

[0049] In the figure: 1. High-pressure inlet natural gas; 2. Control valve; 3. Pressure regulating valve; 4. Control valve; 5. Check valve; 6. Circulation pump; 7. Frequency converter; 8. Heat source; 9. Expander; 10. Controller; 11. Generator; 12. First pressure regulating device; 13. Second pressure regulating device; 14. Heat exchanger; 15. Inlet temperature sensor; 16. Heat exchange regulating valve; 17. Central control unit; 18. Low-pressure outlet natural gas; 19. Outlet temperature sensor; 20. Heat exchange bypass; 21. Pressure regulating bypass. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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. 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.

[0051] A natural gas pressure energy power generation and pressure regulating device, such as Figure 1 As shown, it includes a main line and a central control unit 17, wherein the main line is sequentially provided with a control valve 2, a heat exchange unit, a first pressure regulating unit and a second pressure regulating unit; the central control unit 17 is respectively connected to the heat exchange unit, the first pressure regulating unit and the second pressure regulating unit, and is used to control the working status of the heat exchange unit, the first pressure regulating unit and the second pressure regulating unit, mainly monitors the index parameters of the entire pressure energy power generation process, receives the transmitted data and sends feedback instructions to each module to adjust the corresponding index parameters. The control valve 2 is used to control the flow of natural gas entering the main line; the heat exchange unit is used to preheat the natural gas entering the main line. The first pressure regulating unit includes a first pressure regulating module and an expander 9 connected in sequence, the first pressure regulating module is used to adjust the natural gas pressure and flow of the main line before expansion power generation, and monitor the temperature of the natural gas before expansion power generation; the second pressure regulating unit is used to adjust the pressure of the natural gas after expansion power generation and monitor the temperature of the natural gas after expansion power generation.

[0052] It should be noted that in Figure 1 The medium-high pressure natural gas 1 enters the main pipeline through the inlet on the left, and then the first pressure regulating unit uses the pressure energy generated by the pressure reduction of the high pressure natural gas 1 to generate electricity. The inlet end is connected to the control valve 2, and the outlet end is connected to the second pressure regulating device 13. The first pressure regulating unit and the second pressure regulating unit are both equipped with pressure regulating devices, which are mainly used to adjust the natural gas pressure and flow and stabilize them.

[0053] It should be further explained that the expander 9 can replace the traditional pressure regulating structure to recover the pressure energy of natural gas. The mechanical energy generated by the expansion and decompression of high-pressure natural gas is used to directly drive the generator 11 to generate electricity. According to the principle of thermodynamics, It is the state parameter of natural gas, which is the maximum amount of its energy that can be reversibly converted into work in theory, and the enthalpy of gas per unit mass. for:

[0054] e x,h =h-h0-T0(s-s0);

[0055] In the formula, e x,h Represents the specific enthalpy of a gas The unit is kJ / kg; s and s0 represent the specific enthalpy of the gas before the state change and in the ambient state, and the unit is kJ / kg; T0 represents the ambient temperature, and the unit is K; h0, h1 represent the specific entropy of the gas before the state change and in the ambient state, and the unit is kJ / (kg·K).

[0056] When natural gas enters the expander 9, it can be considered to undergo approximately isentropic expansion. During this process, the high-pressure natural gas will drive the blades of the expander 9 to rotate to complete the transfer of mechanical energy, and the rotor of the synchronous generator 11 will rotate through the coupling to achieve the conversion of mechanical energy into electrical energy. The first pressure regulating unit also converts the natural gas pressure energy into electrical energy during the process of reducing the pressure of natural gas. The natural gas pipeline network is regarded as an open system. In the process of natural gas changing from the state before pressure regulation to the stable state after pressure regulation, the pressure of natural gas is also converted into electrical energy. Changes to:

[0057]

[0058] Among them, e x,h1 、e x,h2 Indicates the specific enthalpy of natural gas before and after pressure regulation, in kJ / kg; C p It represents the specific heat capacity of gas at constant pressure, in kJ / (kg·K); T1, T2, T0 represent the temperature of natural gas before and after pressure regulation and the ambient temperature, in K; P1, P2 represent the absolute pressure of natural gas before and after pressure regulation, in MPa; M represents the molar mass of gas.

[0059] The higher the natural gas pressure in the pipeline network, The larger the value. The method can effectively analyze that the maximum work that can be output by natural gas from high pressure state P1 to low pressure state P2 is the maximum amount of its energy that can be reversibly converted into work in theory. Therefore, the pressure drop process can be used to convert the internal energy of natural gas into mechanical energy to do external work, and the mechanical energy output by the expander 9 drives the generator 11 to generate electricity, realizing the conversion of natural gas internal energy into electrical energy and completing the power generation of natural gas pressure energy.

[0060] Furthermore, the heat exchange unit includes a circulation pump 6, a frequency converter 7, a heat source 8, a heat exchanger 14 and a circulation branch; wherein the water inlet and outlet of the cold pipe of the heat exchanger 14 are both connected to the main pipe; and the water inlet and outlet of the hot pipe of the heat exchanger 14 are both connected to the circulation branch, and the circulation pump 6 and the heat source 8 are arranged in series in the circulation branch; and the frequency converter 7 is electrically connected to the circulation pump 6, and the frequency converter 7 and the heat source 8 are both electrically connected to the central control unit 17.

[0061] It should be noted that in the heat exchange unit, natural gas can heat the circulating medium in the heat source 8, and then the circulating pump 6 transports the heat medium to the heat pipe in the heat exchanger 14, and then the natural gas in the heat pipe and the cold pipe exchange heat to achieve the preheating effect of the natural gas in the cold pipe. In this process, the central control unit 17 can issue control instructions to the frequency converter 7 and the heat source 8. In addition, the central control unit 17 is the software in the computer, which monitors the parameters of the whole process and can monitor and adjust the relevant parameters through the software. The circulating pump 6 is connected to the frequency converter 7, and the frequency converter 7 is connected to the central control unit 17. The central control unit 17 transmits signals to control the frequency converter 7, and then controls the circulating pump 6.

[0062] Furthermore, the main line is also connected to a heat exchange bypass 20 , the inlet of the heat exchange bypass 20 is located on the main line between the control valve 2 and the heat exchange unit, and the outlet is connected to the heat source 8 ; a heat exchange regulating valve 16 is installed on the heat exchange bypass 20 .

[0063] It should be noted that the heat exchange bypass 20 controls the flow through the heat exchange regulating valve 16. In the working state, the natural gas flow in the heat exchange bypass 20 can be adjusted as needed. For example, when the flow of the heat exchange bypass 20 is increased, the natural gas flow entering the first pressure regulating unit will be reduced accordingly.

[0064] Further, in Figure 1 The first pressure regulating unit includes a regulating valve 4, an expander 9, a first pressure regulating device 12 and an inlet temperature sensor 15; in the main pipeline, the regulating valve 4, the first pressure regulating device 12, the inlet temperature sensor 15 and the expander 9 are arranged in sequence. The expander 9 is electrically connected to a generator 11, and the generator 11 is electrically connected to a controller 10; and the regulating valve 4, the controller 10, the first pressure regulating device 12 and the inlet temperature sensor 15 are all electrically connected to the central control unit 17.

[0065] It should be noted that in the first pressure regulating unit, the control valve 4 can control the flow of natural gas, the first pressure regulating device 12 can regulate the pressure of natural gas and the flow, and the inlet temperature sensor 15 can monitor the temperature of natural gas. At the same time, the central control unit 17 will obtain the pressure, flow and temperature data of the first pressure regulating unit in real time to perform regulation. In addition, the controller 10 is used to receive the control instructions of the central control unit 17 and control the speed of the expander 9 and the speed of the generator 11 by controlling the excitation current.

[0066] Furthermore, the main line is also connected to a pressure regulating bypass 21, the inlet of the pressure regulating bypass 21 is located on the main line between the heat exchange unit and the first pressure regulating unit, and the outlet is located on the main line between the first pressure regulating unit and the second pressure regulating unit. A pressure regulating valve 3 and a check valve 5 are installed on the pressure regulating bypass 21 in sequence.

[0067] It should be noted that the main function of the pressure regulating bypass 21 is to regulate the pressure of the natural gas entering the first pressure regulating unit and the second pressure regulating unit, and to perform pressure regulation according to different working conditions.

[0068] Furthermore, the second pressure regulating unit includes a second pressure regulating device 13 and an outlet temperature sensor 19 connected in series on the main pipe; the second pressure regulating device 13 and the outlet temperature sensor 19 are both electrically connected to the central control unit 17 .

[0069] It should be noted that the natural gas discharged by the second pressure regulating unit is low-pressure outlet natural gas 18, which is subsequently transported to the downstream pipeline network for users to use. Therefore, the second pressure regulating unit can monitor the pressure, flow and temperature of the natural gas when it is transported to the downstream pipeline network, and transmit the information to the central control unit 17, which then issues control instructions for regulation.

[0070] It should be further explained that the first pressure regulating device 12 and the second pressure regulating device 13 both include pressure and flow sensors as well as pressure and flow control elements and other control elements, and the elements can be made movable through the central control. The pressure and flow signals are received by the sensors and transmitted to the central control unit 17, which controls the opening of the pressure control element, the flow control element and other control mechanisms, thereby controlling the speed and amount of the fluid passing through (the pressure can be coordinated through the pressure regulating bypass 21 to reduce the pressure loss in this process and ensure the downstream pipeline pressure) so that the pressure and flow reach the set value, and the outlet flow is stabilized, thereby stabilizing the natural gas flow entering the expander 9.

[0071] The above-mentioned natural gas pressure energy power generation and pressure regulation device corresponds to a natural gas pressure energy power generation and pressure regulation method, which includes the following steps:

[0072] The total amount of natural gas entering the main pipeline is controlled by the control valve 2; specifically, the control valve 2 is opened to allow the high-pressure inlet natural gas 1 to enter the main pipeline, and the heat exchange regulating valve 16 is opened at the same time to allow part of the high-pressure inlet natural gas 1 to enter the heat exchange bypass 20.

[0073] When the temperature of the natural gas passing through the first pressure regulating unit is lower than the first preset temperature, the natural gas flow of the heat exchange unit is adjusted until the temperature of the natural gas passing through the first pressure regulating unit reaches the first preset temperature; specifically, the circulation pump 6 in the heat exchange unit provides heat medium to the heat exchanger 14 through the circulatory working medium, and the frequency converter 7 controls the flow of heat medium entering the heat exchanger 14 by controlling the running speed of the circulation pump 6. The inlet temperature sensor 15 monitors the natural gas temperature of the main pipeline in real time. When its temperature is lower than the set value T1, the electrical signal is transmitted to the central control unit 17. The central control unit 17 sends feedback information to the heat exchange bypass 20 according to the instruction, adjusts the opening of the heat exchange regulating valve 16, and increases the high-pressure natural gas intake in the heat exchange bypass 20. The frequency converter 7 increases the flow of heat medium entering the heat exchanger 14, so that the high-pressure pipeline network natural gas is greater than the first preset temperature T1, thereby realizing the preheating of the natural gas and making it have the enthalpy value required for the natural gas pressure to generate electricity.

[0074] When the natural gas pressure and flow rate of the main pipeline before expansion and power generation are lower than the first preset working value, the natural gas pressure and flow rate of the main pipeline before expansion and power generation are adjusted by the first pressure regulating unit until the first preset working value of the pressure and flow rate are met; specifically, the first pressure regulating device 12 receives feedback information from the central control unit 17 to adjust the natural gas pressure and flow rate of the main pipeline so that the pressure and flow rate of the natural gas entering the expander 9 are stabilized at the first preset working value, thereby achieving stable power generation and supplying stable current and voltage.

[0075] When the temperature passing through the second pressure regulating unit is lower than the second preset temperature, the natural gas flow of the heat exchange unit is adjusted until the temperature of the natural gas passing through the second pressure regulating unit reaches the second preset temperature; specifically, the outlet temperature sensor 19 monitors whether the temperature of the natural gas after expansion and power generation is lower than the frost temperature, and the heat exchange regulating valve 16 is adjusted by the central control unit 17 to increase the temperature of the natural gas so that its temperature after expansion and power generation (the second preset temperature) is greater than the frost temperature to avoid frost in the main pipeline.

[0076] When the natural gas pressure and flow rate of the main pipeline after expansion and power generation are lower than the second preset working value, the second pressure regulating unit adjusts the natural gas pressure and flow rate of the main pipeline after expansion and power generation until the second preset working value of pressure and flow rate is met. Specifically, the second pressure regulating device 13 monitors whether the natural gas pressure and flow rate after expansion and power generation at the outlet of the expander 9 are sufficient to supply the needs of downstream users. When it is insufficient to supply the gas needs of downstream users, the second pressure regulating device 13 feeds back the pressure and flow rate to the central control unit 17 in the form of an electrical signal. The central control system adjusts the second pressure regulating device 13 to supplement the natural gas pressure and flow rate of the downstream pipeline network.

[0077] Furthermore, the pressure regulating bypass 21 can work together with the second pressure regulating unit, and its working process is as follows;

[0078] When the natural gas pressure and flow rate of the main pipeline after expansion and power generation are lower than the second preset working value, the second pressure regulating unit and the pressure regulating bypass 21 jointly adjust the natural gas pressure and flow rate of the main pipeline after expansion and power generation until the second preset working value of pressure and flow is met.

[0079] When the natural gas flow rate of the expander 9 entering the first pressure regulating unit is greater than the processing capacity of the expander 9 , the excess flow rate directly enters the second pressure regulating unit through the pressure regulating bypass 21 .

[0080] When the pressure demand load of the main pipeline downstream of the second pressure regulating unit increases or the main pipeline loses pressure, the heat exchange unit and the first pressure regulating unit are closed, so that the natural gas in the main pipeline enters the downstream main pipeline of the second pressure regulating unit from the pressure regulating bypass 21. Specifically, when the downstream pressure demand load increases sharply or the pipeline loses pressure, the central control system closes the heat exchange regulating valve 16 and the first pressure regulating device 12, so that the natural gas in the main pipeline enters the downstream pipeline from the pressure regulating bypass 21, and the natural gas demand of the downstream users can be met by stopping power generation. At the same time, when the expander 9 is under maintenance, the natural gas can directly enter the downstream pipeline through the pressure regulating bypass 21 so as not to affect the gas use of downstream users.

[0081] When the pressure demand load of the main pipeline downstream of the second pressure regulating unit decreases, the heat exchange unit and the first pressure regulating unit are opened to reduce the natural gas flow of the pressure regulating bypass 21, increase the natural gas flow entering the first pressure regulating unit, and make the expander 9 in the first pressure regulating unit work. Specifically, when the gas load of the downstream user is small, the second pressure regulating device 13 feeds back the pressure and flow information to the central control unit 17, and the central control unit 17 reopens the first pressure regulating device 12 and the heat exchange regulating valve 16, adjusts the pressure regulating valve 3 to control the gas flow of the pressure regulating bypass 21, stabilizes the natural gas pressure and flow through the first pressure regulating device 12 and enters the expander 9, and realizes the natural gas pressure energy power generation again. The function of the check valve 5 is to prevent the natural gas after expansion and power generation from flowing back to the pressure regulating bypass 21, and avoid the pressure energy loss caused by the collision with the natural gas coming out of the pressure regulating bypass 21 due to the backflow.

[0082] The working process of the device of the present invention is described below in combination with the above method:

[0083] When high-pressure natural gas enters, a part of it enters the heat source 8 through the heat exchange bypass 20, and the circulatory working fluid in the heating circulation pump 6 provides heat medium to the heat exchanger 14. The frequency converter 7 controls the flow of heat medium entering the heat exchanger 14 through the circulation pump 6. The inlet temperature sensor 15 monitors the temperature of the natural gas in the main pipeline in real time. When its temperature is lower than the set value T1, it transmits an electrical signal to the central control unit 17. The central control unit 17 sends feedback information to the heat exchange bypass 20 according to the instruction, adjusts the opening of the heat exchange regulating valve 16, and increases the intake amount of high-pressure natural gas in the heat exchange bypass 20. The frequency converter 7 increases the flow of heat medium entering the heat exchanger 14, so that the high-pressure pipeline network natural gas is greater than the set value T1, and the natural gas is preheated.

[0084] The preheated high-pressure natural gas enters the first pressure regulating device 12, which monitors the natural gas pressure and flow in the pipeline in real time. When it is greater than the natural gas pretreatment pressure and flow of the expander 9, the first pressure regulating device 12 sends a signal to the central control unit 17, and the central control unit 17 sends a feedback signal to the first pressure regulating device 12 and the pressure regulating bypass 21 according to the set pressure and flow information. The first pressure regulating device 12 makes an adjustment response according to the feedback signal to make the natural gas pressure at the inlet end reach the set value P1 and stabilize it, so that the natural gas with stable pressure and flow enters the expander 9. The pressure regulating bypass 21 adjusts the opening of the pressure regulating valve 3 according to the feedback signal, so that part of the natural gas directly enters the low-pressure pipeline network through the pressure regulating bypass 21, realizes the diversion of natural gas and supplements the natural gas pressure of the downstream pipeline network, and at the same time reduces the pressure energy waste caused by the pressure regulation of the pressure regulating device.

[0085] After being regulated by the pressure regulating device, the natural gas with stable pressure and flow enters the expander 9, driving the impeller of the expander 9 to rotate, thereby realizing the conversion of internal energy into mechanical energy. The expander 9 drives the rotor of the generator 11 to rotate through the coupling, thereby realizing the conversion of mechanical energy into electrical energy. The controller 10 adjusts the excitation current according to the speed set by the central control unit 17 to adjust the speed of the generator 11 and the expander 9, thereby stabilizing the output current and voltage.

[0086] The downstream pipeline network monitors the outlet natural gas temperature in real time through the outlet temperature sensor 19. When the temperature is lower than the natural gas frost or ice temperature, the outlet temperature sensor 19 transmits the information to the central control unit 17, and the central control unit 17 makes an adjustment response, adjusts the opening of the heat exchange regulating valve 16, increases the high-pressure natural gas intake in the heat exchange bypass 20 and the heat medium flow in the heat exchanger 14, until the low-pressure pipeline network natural gas temperature after expansion and pressure reduction is greater than the set value T2 (T2 temperature is greater than the natural gas frost or ice temperature). At this time, the central control unit 17 has a higher priority for adjusting the response to T2 than T1 to meet the requirement that T2 temperature is greater than the frost or ice temperature to avoid frost in the downstream pipeline network.

[0087] The second pressure regulating device 13 monitors the pressure and flow rate at the downstream pipeline network in real time, and appropriately supplements the natural gas pressure of the downstream pipeline network through the pressure regulating bypass 21, so as to avoid the expansion machine 9 being in a variable operating state due to the pressure difference fluctuation caused by the gas demand of the downstream users. When the gas load of the downstream pipeline network users increases sharply and the pressure of the downstream pipeline network is about to reach the pressure loss level, the second pressure regulating device 13 sends an adjustment instruction to the central control unit 17. The central control unit 17 makes a feedback instruction according to the signal, closes the control valve 4 and the heat exchange regulating valve 16, keeps the valve of the pressure regulating bypass 21 fully open, and realizes that the high-pressure pipeline network natural gas directly enters the downstream pipeline network through the pressure regulating bypass 21 instead of entering the expansion machine 9. The central control unit 17 stops the rotation of the generator 11 and the expansion machine 9 through the controller 10 to avoid failure. The needs of downstream users are met by stopping expansion and power generation, avoiding the time and maintenance cost loss caused by the failure of the expansion machine 9 and the generator 11 due to excessive pressure fluctuations, and also avoiding the loss of pressure in the downstream pipeline network. When the gas load of the downstream pipeline network decreases and the pressure gradually rises to the pressure value P2 set by the central control unit 17, the central control unit 17 reopens the heat exchange regulating valve 16 and the regulating valve 4, reduces the valve opening of the pressure regulating bypass 21, and makes the pressure and flow of the first pressure regulating device 12 reach the set level. At this time, the high-pressure pipeline network natural gas re-enters the expander 9, drives the expander 9 to expand and generate electricity, and the central control unit 17 controls the speed of the generator 11 and the expander 9 through the controller 10, so that the entire natural gas pressure energy power generation system can generate electricity safely and stably again.

[0088] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A natural gas pressure energy power generation and pressure regulating device, characterized in that: include: The main pipeline is provided with a control valve (2), a heat exchange unit, a first pressure regulating unit and a second pressure regulating unit in sequence; A central control unit (17) is connected to the heat exchange unit, the first pressure regulating unit and the second pressure regulating unit respectively, and is used to control the working states of the heat exchange unit, the first pressure regulating unit and the second pressure regulating unit; The control valve (2) is used to control the flow of natural gas entering the main pipeline; The heat exchange unit is used to preheat the natural gas entering the main pipeline; The first pressure regulating unit comprises a first pressure regulating module and an expander (9) connected in sequence, the first pressure regulating module being used to regulate the pressure and flow of the natural gas in the main pipeline before expansion and power generation, and to monitor the temperature of the natural gas before expansion and power generation; The second pressure regulating unit is used to regulate the pressure of the natural gas after expansion and power generation and to monitor the temperature of the natural gas after expansion and power generation.

2. A natural gas pressure energy power generation and pressure regulating device according to claim 1, characterized in that: The heat exchange unit comprises a circulation pump (6), a frequency converter (7), a heat source (8), a heat exchanger (14) and a circulation branch; The water inlet and outlet of the cold pipe of the heat exchanger (14) are both connected to the main pipe; The water inlet and outlet of the heat pipe of the heat exchanger (14) are both connected to the circulation branch; The circulation pump (6) and the heat source (8) are arranged in series in a circulation branch; The frequency converter (7) is electrically connected to the circulation pump (6).

3. A natural gas pressure energy power generation and pressure regulating device according to claim 2, characterized in that: The frequency converter (7) and the heat source (8) are both electrically connected to the central control unit (17).

4. A natural gas pressure energy power generation and pressure regulating device according to claim 2 or 3, characterized in that: The main pipeline is also connected to a heat exchange bypass (20), the inlet of the heat exchange bypass (20) is located on the main pipeline between the control valve (2) and the heat exchange unit, and the outlet is connected to the heat source (8); A heat exchange regulating valve (16) is installed on the heat exchange bypass (20).

5. The natural gas pressure energy power generation and pressure regulating device according to claim 1, characterized in that: The first pressure regulating unit comprises a regulating valve (4), an expander (9), a first pressure regulating device (12) and an inlet temperature sensor (15); In the main pipeline, the control valve (4), the first pressure regulating device (12), the inlet temperature sensor (15) and the expander (9) are arranged in sequence.

6. A natural gas pressure energy power generation and pressure regulating device according to claim 5, characterized in that: The expander (9) is electrically connected to a generator (11), and the generator (11) is electrically connected to a controller (10); The regulating valve (4), the controller (10), the first pressure regulating device (12) and the inlet temperature sensor (15) are all electrically connected to the central control unit (17).

7. A natural gas pressure energy power generation and pressure regulating device according to claim 5 or 6, characterized in that: The main pipeline is also connected to a pressure regulating bypass (21), the inlet of the pressure regulating bypass (21) is located on the main pipeline between the heat exchange unit and the first pressure regulating unit, and the outlet is located on the main pipeline between the first pressure regulating unit and the second pressure regulating unit; A pressure regulating valve (3) and a check valve (5) are sequentially installed on the pressure regulating bypass (21).

8. A natural gas pressure energy power generation and pressure regulating device according to claim 7, characterized in that: The second pressure regulating unit comprises a second pressure regulating device (13) and an outlet temperature sensor (19) connected in series on the main pipe; The second pressure regulating device (13) and the outlet temperature sensor (19) are both electrically connected to the central control unit (17).

9. A natural gas pressure energy power generation and pressure regulation method, characterized in that: A natural gas pressure energy power generation and pressure regulating device as claimed in any one of claims 1 to 8, comprising the following steps: The total amount of natural gas entering the main pipeline is controlled by a control valve (2); When the temperature of the natural gas passing through the first pressure regulating unit is lower than the first preset temperature, adjusting the natural gas flow of the heat exchange unit until the temperature of the natural gas passing through the first pressure regulating unit reaches the first preset temperature; When the natural gas pressure and flow rate of the main pipeline before expansion power generation are lower than the first preset working value, the natural gas pressure and flow rate of the main pipeline before expansion power generation are adjusted by the first pressure regulating unit until the first preset working value of the pressure and flow rate is met; When the temperature of the natural gas passing through the second pressure regulating unit is lower than the second preset temperature, adjusting the natural gas flow of the heat exchange unit until the temperature of the natural gas passing through the second pressure regulating unit reaches the second preset temperature; When the natural gas pressure and flow rate of the main pipeline after expansion and power generation are lower than the second preset working value, the second pressure regulating unit adjusts the natural gas pressure and flow rate of the main pipeline after expansion and power generation until the second preset working value of pressure and flow is met.

10. A natural gas pressure energy power generation and pressure regulation method according to claim 9, characterized in that: The first preset temperature is a preheating temperature of the main pipe, and the second preset temperature is a temperature for preventing frost on the main pipe.

11. A natural gas pressure energy power generation and pressure regulation method according to claim 9, characterized in that: A pressure regulating bypass (21) is provided, wherein the inlet of the pressure regulating bypass (21) is located on the main pipe between the heat exchange unit and the first pressure regulating unit, and the outlet of the pressure regulating bypass (21) is located on the main pipe between the first pressure regulating unit and the second pressure regulating unit; When the natural gas pressure and flow rate of the main pipeline after expansion and power generation are lower than a second preset working value, the natural gas pressure and flow rate of the main pipeline after expansion and power generation are jointly adjusted by the second pressure regulating unit and the pressure regulating bypass (21) until the second preset working values ​​of the pressure and flow rate are met; When the natural gas flow rate entering the expander (9) of the first pressure regulating unit is greater than the processing capacity of the expander (9), the excess flow rate directly enters the second pressure regulating unit through the pressure regulating bypass (21); When the pressure demand load of the main pipeline downstream of the second pressure regulating unit increases or the main pipeline loses pressure, the heat exchange unit and the first pressure regulating unit are closed, so that the natural gas in the main pipeline enters the main pipeline downstream of the second pressure regulating unit from the pressure regulating bypass (21); When the pressure demand load of the main pipeline downstream of the second pressure regulating unit decreases, the heat exchange unit and the first pressure regulating unit are opened, the natural gas flow rate of the pressure regulating bypass (21) is reduced, and the natural gas flow rate entering the first pressure regulating unit is increased, so that the expansion machine (9) in the first pressure regulating unit performs work.

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