Device for stably recycling pressure energy and cold energy of natural gas

Abstract

The utility model provides a device for stably recycling pressure energy and cold energy of natural gas. An inlet of the device is connected with upstream pipeline conveying natural gas, the device comprises a differential pressure generator set, a heat exchange unit and an expansion machine bypass pressure stabilizing unit, the differential pressure generator set and the heat exchange unit are connected in series and then connected with the expansion machine bypass pressure stabilizing unit in parallel, and the differential pressure generator set and the expansion machine bypass pressure stabilizing unit are connected into downstream natural gas using equipment after being gathered. The expansion machine bypass voltage stabilization unit comprises a first voltage stabilization and regulation unit, a second voltage stabilization and regulation unit and a third voltage stabilization and regulation unit, and the first voltage stabilization and regulation unit, the second voltage stabilization and regulation unit and the third voltage stabilization and regulation unit are connected in parallel. On the premise of ensuring normal and stable gas utilization of downstream gas utilization equipment, the device is comprehensively applied by combining an ingenious combination mode with an advanced control method, and abundant energy of natural gas can be fully recycled. And the working requirements of upstream incoming gas under the harsh working conditions of large flow and large pressure difference fluctuation change can be met.

Description

Technical Field

[0001] The utility model relates to the technical field of comprehensive energy recovery of natural gas, and in particular to a device for stably recovering and utilizing pressure energy and cold energy of natural gas. Background Art

[0002] At present, the technology of natural gas pressure regulating stations is becoming more and more mature, but the application of related advanced process technologies supporting natural gas is still incomplete. In particular, the comprehensive utilization rate of energy efficiency in the process of reducing and stabilizing pressure in traditional gas-fired power plants is not high. There is still a lot of room for optimization in terms of energy conservation and environmental protection, the application of intelligent control technology, and reliability improvement. Due to the large number of gas source components mined, the volume percentage of each gas in the component varies within a certain range; at the same time, there are many overhead sections in the long-distance natural gas pipeline. Due to the superposition of day and night temperature differences and seasonal factors, the gas will expand and contract in the pipeline, and a certain range of pressure fluctuations will occur in the pipeline; in addition, the mid- and upstream gate stations dynamically adjust the gas transmission and distribution plan according to the season and the actual needs of users. After superimposing comprehensive factors such as the peaks and valleys of residential and commercial gas use, it will directly lead to a large range of numerical fluctuations in the natural gas finally received by the gas-fired power plants in the middle and downstream in a short period of time, which is difficult to achieve precise adjustment and does not meet the requirements of stable production in the downstream. Usually, the upstream gate station uses a large-flow high-pressure dedicated pipeline to supply natural gas, while the gas pressure actually required by the gas turbine or other gas-using equipment at the end is generally low. Objectively, the prerequisites of large flow and high pressure difference are met. However, the abundant energy stored in this pressure regulation process is wasted because it is not well utilized, which is a pity.

[0003] There are no similar mature cases to learn from for some important supporting devices or core technology control methods of gas power plant pressure regulating stations, especially the joint recovery and application of natural gas pressure energy and cold energy, and the continuous and stable gas supply technology of gas turbines. There is a lack of experience in the comprehensive recovery and application of natural gas pressure energy and cold energy. Compared with existing solutions, most of them only select one of the characteristics for recycling, which will lead to insufficient recovery and utilization of the abundant energy of natural gas. When the upstream pipeline natural gas is transported at a large flow rate (40,500~145,000Nm 3 / h), high pressure difference (5-9MPa) and parameter fluctuations, it is extremely difficult and challenging to ensure smooth, accurate and reliable gas transmission to downstream equipment and to realize the combined recovery of pressure energy and cold energy of natural gas. Utility Model Content

[0004] In view of the defects in the prior art, the purpose of the utility model is to provide a device for stably recovering and utilizing natural gas pressure energy and cold energy with high energy utilization rate and high power generation efficiency.

[0005] To solve the above problems, the technical solution of the utility model is:

[0006] A device for stably recovering and utilizing natural gas pressure energy and cold energy, wherein the inlet of the device is connected to upstream pipeline natural gas, and the device comprises a differential pressure generator set, a heat exchange unit, and an expander bypass pressure stabilizing unit. The differential pressure generator set is connected in series with the heat exchange unit and then connected in parallel with the expander bypass pressure stabilizing unit, and then connected to natural gas downstream gas-using equipment after being aggregated. The expander bypass pressure stabilizing unit comprises a first pressure stabilizing and regulating unit, a second pressure stabilizing and regulating unit, and a third pressure stabilizing and regulating unit, and the first pressure stabilizing and regulating unit, the second pressure stabilizing and regulating unit, and the third pressure stabilizing and regulating unit are connected in parallel with each other.

[0007] Preferably, the differential pressure generator set includes a pneumatic isolation valve, a filter, a pressure sensor, a temperature sensor, an electric butterfly valve, a flat turbine expander, a generator and a grid-connected cabinet, and a check valve. The pneumatic isolation valve, filter, pressure sensor, temperature sensor, and electric butterfly valve are connected to the natural gas inlet of the flat turbine expander in sequence. The generator and the grid-connected cabinet are directly connected to the output shaft of the flat turbine expander to obtain sufficient torque required for power generation. The natural gas outlet of the flat turbine expander is connected to the pressure sensor, temperature sensor, pneumatic isolation valve, and check valve in sequence.

[0008] Preferably, the filter is a cone filter for coarse filtration to prevent large particles of impurities from damaging the equipment.

[0009] Preferably, the heat exchange unit includes a single-tube heat exchanger, the natural gas outlet of the differential pressure generator set is connected to the natural gas inlet of the single-tube heat exchanger through a pressure pipeline element, the air-conditioning cooling water outlet is connected to the temperature sensor, the pressure sensor, and the valve group in sequence to the water inlet of the single-tube heat exchanger through the pressure pipeline element, the water outlet of the single-tube heat exchanger is connected to the temperature sensor, the temperature switch, the flow switch, the valve group in sequence through the pressure pipeline element, and then to the air-conditioning chilled water outlet, and the natural gas that has been heated by heat exchange is collected in parallel with the expander bypass pressure stabilizing unit through the outlet of the single-tube heat exchanger, and then connected to other downstream gas-consuming equipment.

[0010] Preferably, the first voltage-stabilizing and regulating unit is sequentially connected in series with a pneumatic isolation valve, a pressure gauge, a monitoring pressure regulator including a shut-off valve, a working pressure regulator, a pressure gauge, and a pneumatic isolation valve; the second voltage-stabilizing and regulating unit is sequentially connected in series with a pneumatic isolation valve, a pressure gauge, a monitoring pressure regulator including a shut-off valve, a working pressure regulator, a pressure gauge, and a pneumatic isolation valve; the third voltage-stabilizing and regulating unit is sequentially connected in series with a pneumatic isolation valve, a pressure gauge, a monitoring pressure regulator including a shut-off valve, a working pressure regulator, a pressure gauge, and a pneumatic isolation valve; and the compressed air is passed through the pressure pipeline element. The pneumatic actuators in the first pressure-stabilizing and pressure-regulating unit, the second pressure-stabilizing and pressure-regulating unit, and the third pressure-stabilizing and pressure-regulating unit are respectively transmitted as the valve torque input source to control the opening and closing actions of the pneumatic isolation valves. The monitoring pressure regulator and the working pressure regulator containing the cut-off valve in the first pressure-stabilizing and pressure-regulating unit, the second pressure-stabilizing and pressure-regulating unit, and the third pressure-stabilizing and pressure-regulating unit respectively use pressure-leading pipes on the natural gas pipeline to take pressure. After comparing with the pressure value set by the spring inside the pressure regulator, the valve opening will be automatically adjusted to achieve precise pressure regulation.

[0011] Preferably, the working pressure ranges of the first voltage stabilizing and regulating unit, the second voltage stabilizing and regulating unit, and the third voltage stabilizing and regulating unit are pre-set in a gradient ratio from low to high.

[0012] Preferably, the pressure, flow rate and other parameters of the natural gas inlet and outlet of the device are collected in real time, and the optimal control mode is quickly selected through the specific program logic operation and judgment of the control system. By changing the opening and closing states of the front and rear pneumatic isolation valves of the first pressure stabilizing and regulating unit, the second pressure stabilizing and regulating unit, and the third pressure stabilizing and regulating unit, the working path is quickly and flexibly switched. According to different situations, the control mode of pressure stabilization and pressure regulation specifically includes:

[0013] When it is detected that the upstream gas volume is small but the pressure is relatively low: the front and rear valves of the differential pressure generator set are closed, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the first pressure stabilizing and regulating unit are opened;

[0014] When it is detected that the upstream gas volume is small and the pressure is relatively moderate: the front and rear valves of the differential pressure generator set are closed, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the second pressure stabilizing and regulating unit are opened;

[0015] When it is detected that the upstream gas volume is small but the pressure is relatively high: the front and rear valves of the differential pressure generator set are closed, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the third pressure stabilizing and regulating unit are opened;

[0016] When it is detected that the upstream gas volume is moderate but the pressure is relatively low: the front and rear valves of the differential pressure generator set are opened, and the front and rear valves of all the pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed;

[0017] When it is detected that the upstream gas volume is moderate and the pressure is relatively moderate: the front and rear valves of the differential pressure generator set are both opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the first pressure stabilizing and regulating unit are both opened;

[0018] When it is detected that the upstream gas volume is moderate but the pressure is relatively high: the front and rear valves of the differential pressure generator set are both opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the second pressure stabilizing and regulating unit are both opened;

[0019] When it is detected that the upstream gas volume is large but the pressure is relatively low: the front and rear valves of the differential pressure generator set are both opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the first pressure stabilizing and regulating unit are both opened;

[0020] When it is detected that the upstream gas volume is large and the pressure is relatively moderate: the front and rear valves of the differential pressure generator set are both opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the second pressure stabilizing and regulating unit are both opened;

[0021] When it is detected that the upstream gas volume is large but the pressure is relatively high: the front and rear valves of the differential pressure generator set are opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the third pressure stabilizing and regulating unit are opened;

[0022] When the first voltage stabilizing and regulating unit fails and is automatically cut off, the control system will automatically enable the second voltage stabilizing and regulating unit to work;

[0023] When the second voltage stabilizing and regulating unit fails and is automatically cut off, the control system will automatically enable the third voltage stabilizing and regulating unit to work;

[0024] When the third voltage stabilizing and regulating unit fails and is automatically cut off, the control system will automatically enable the first voltage stabilizing and regulating unit and the second voltage stabilizing and regulating unit to work simultaneously in parallel.

[0025] Compared with the prior art, the device of the utility model fully recycles and utilizes the abundant pressure energy and cold energy contained in the natural gas in the process of gas power plant pressure regulating station through the comprehensive application of ingenious combination and advanced control methods, under the premise of ensuring the normal and stable gas consumption of downstream gas-using equipment. The electric energy is transmitted to the power grid through the generator and the grid-connected cabinet, which further reduces the cost of the factory electricity price, benefits the society and improves the economic benefits. The device has the characteristics of high energy utilization rate and high power generation efficiency. While improving energy efficiency, it can also save energy and protect the environment, saving unnecessary energy expenditure costs. In view of the large fluctuations in the flow rate and pressure range of the upstream gas, it is also considered that the differential pressure generator set cannot achieve controllable pressure regulation. The utility model also adds an expander bypass voltage stabilizing unit to meet the needs of working under the harsh conditions of large flow rate and large pressure difference fluctuations of the upstream gas. The degree of intelligent control is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0027] Figure 1 It is the principle diagram of the utility model. DETAILED DESCRIPTION

[0028] The utility model is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the utility model, but do not limit the utility model in any form. It should be pointed out that for those of ordinary skill in the art, several changes and improvements can be made without departing from the concept of the utility model. These all belong to the protection scope of the utility model.

[0029] Specifically, the utility model provides a device for stably recovering and utilizing the pressure energy and cold energy of natural gas, such as Figure 1 As shown, the inlet of the device is connected to the upstream pipeline natural gas, and the device includes a differential pressure generator set and a heat exchange unit connected in series with the differential pressure generator set. The differential pressure generator set is connected in series with the heat exchange unit and then connected in parallel with the expander bypass pressure stabilizing unit, and then connected to the natural gas downstream gas consumption equipment after being aggregated.

[0030] Among them, pressure energy recovery is mainly achieved through the differential pressure generator set, which includes a pneumatic isolation valve 1, a filter 2, a pressure sensor 3, a temperature sensor 4, an electric butterfly valve 5, a flat diaphragm expander 6, a generator and a grid-connected cabinet 7, and a check valve 8. The pneumatic isolation valve 1, the filter 2, the pressure sensor 3, the temperature sensor 4, and the electric butterfly valve 5 are connected to the natural gas inlet of the flat diaphragm expander 6 in sequence. The filter 2 is a cone filter for coarse filtration to prevent large particles of impurities from damaging the equipment. The generator and the grid-connected cabinet 7 are directly connected to the output shaft of the flat diaphragm expander 6 to obtain sufficient torque required for power generation. The natural gas outlet of the flat diaphragm expander 6 is connected to the pressure sensor 3, the temperature sensor 4, the pneumatic isolation valve 1, and the check valve 8 in sequence.

[0031] Among them, cold energy recovery is mainly achieved through the heat exchange unit, which includes a single-tube heat exchanger 9. The pipeline is connected to the gas inlet 9A of the single-tube heat exchanger 9 by utilizing the characteristic that the volume of natural gas increases while the temperature decreases after expansion and depressurization by the expander. A valve group is connected to the water inlet 9C of the single-tube heat exchanger 9, and the valve group is connected in parallel by redundant electric stop valve 12 and manual stop valve 13. According to the size of the expander outlet temperature, the electric stop valve is preferentially used to achieve accurate control of the heat exchange medium. When the electric stop valve fails, the manual stop valve can be temporarily used to adjust the flow of the heat exchange medium. Then the pressure sensor 3 and the temperature sensor 4 are connected in sequence, and finally connected to the air conditioning cooling water outlet. The water outlet 9D of the single-tube heat exchanger 9 is connected with the temperature sensor 4, the temperature switch 14, and the flow switch 15 in sequence, and then a valve group is connected, and the valve group is also connected to the air conditioning refrigeration water outlet in the form of parallel connection of the electric stop valve 12 and the manual stop valve 13. Finally, the natural gas heated by heat exchange is collected through the outlet 9B of the single-tube heat exchanger 9 and the bypass pressure stabilizing unit of the expander, and then connected to other downstream gas-consuming equipment. The natural gas discharge port 9E of the single-tube heat exchanger 9 is connected to the manual ball valve 10 and the safety valve 11 in sequence through the pressure pipeline component. When the natural gas pressure in the equipment reaches the safe discharge pressure value, the safety valve will be automatically opened and intermittently discharged through the discharge pipeline, which can avoid the failure or explosion of the container due to overpressure.

[0032] In the device of the utility model, the expander bypass pressure stabilizing unit is provided with three different pressure stabilizing and regulating unit branches, namely, the first pressure stabilizing and regulating unit A, the second pressure stabilizing and regulating unit B, and the third pressure stabilizing and regulating unit C, which are in parallel relationship with each other, and each pressure stabilizing and regulating unit branch is similar in equipment configuration, namely, the first pressure stabilizing and regulating unit A is connected in series with a pneumatic isolation valve 1A, a pressure gauge 16A, a monitoring pressure regulator 17A with a cut-off valve, a working pressure regulator 18A, a pressure gauge 16A, and a pneumatic isolation valve 1A. The second pressure stabilizing and regulating unit B is connected in series with a pneumatic isolation valve 1B, a pressure gauge 16B, a monitoring pressure regulator 17B with a cut-off valve, a working pressure regulator 18B, a pressure gauge 16B, and a pneumatic isolation valve 1B. The third pressure stabilizing and regulating unit C is connected in series with a pneumatic isolation valve 1C, a pressure gauge 16C, a monitoring pressure regulator 17C with a cut-off valve, a working pressure regulator 18C, a pressure gauge 16C, and a pneumatic isolation valve 1C. Compressed air is delivered to the pneumatic actuators on the pneumatic isolation valves 1A, 1B, and 1C through pressure pipeline components as the torque output source for the valve opening and closing. The monitoring pressure regulators 17A, 17B, and 17C, and the working pressure regulators 18A, 18B, and 18C of the cut-off valves are respectively pressured by pressure pipes on the natural gas pipelines. The valve opening is automatically adjusted after pressure comparison by the spring inside the pressure regulator, thereby achieving precise pressure regulation.

[0033] In view of the characteristics of the mechanical structure of the voltage regulator itself, when the voltage regulator is set, there will be a fixed working range. In order to meet the characteristics of large pressure range fluctuations, multiple voltage stabilizing and regulating branches need to be set, that is, the parameter values ​​set by the voltage regulator on each voltage stabilizing and regulating unit branch are different, and each has a different working range. In order to facilitate better intelligent control, in the setting of the working range, the action parameters are preset according to a certain gradient distribution, that is, each voltage stabilizing and regulating circuit has a clear and appropriate working condition processing range, which ensures that the pressure stabilization accuracy of the outlet is within a relatively controllable range. At the same time, the pressure working range of the two adjacent voltage regulators must have an intersection of more than 1 / 4 of the area, and there must be no gaps. Each voltage stabilizing and regulating branch flexibly switches the working path through the opening and closing state of the front and rear pneumatic isolation valves. The opening and closing instructions of the pneumatic isolation valves are given by an intelligent control system. The automatic data acquisition instrument collects the pressure, temperature, and flow parameters of the natural gas before and after the differential pressure generator set in real time, and uploads them to the intelligent control system as parameters for calculation and analysis through the preset algorithm. According to the final control execution plan, by changing the opening and closing states of the pneumatic isolation valves before and after each voltage stabilizing and regulating unit branch, the following multiple modes can be combined. The specific control process is summarized as follows:

[0034] 1. When it is detected that the upstream gas volume is small but the pressure is relatively low: the front and rear valves of the differential pressure generator set are closed, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the first pressure stabilizing and regulating unit A are opened;

[0035] 2. When it is detected that the upstream gas volume is small and the pressure is relatively moderate: the front and rear valves of the differential pressure generator set are closed, and the front and rear valves of the second pressure stabilizing and regulating unit B in the expander bypass pressure stabilizing unit are closed;

[0036] 3. When it is detected that the upstream gas volume is small but the pressure is relatively high: the front and rear valves of the differential pressure generator set are closed, and the front and rear valves of the third pressure regulating unit C in the expander bypass pressure regulating unit are opened, and the front and rear valves of the other pressure regulating units are closed;

[0037] 4. When it is detected that the upstream gas volume is moderate but the pressure is relatively low: the front and rear valves of the differential pressure generator set are opened, and the front and rear valves of all the pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed;

[0038] 5. When it is detected that the upstream gas volume is moderate and the pressure is relatively moderate: the front and rear valves of the differential pressure generator set are opened, and the front and rear valves of the first pressure stabilizing and regulating unit A in the expander bypass pressure stabilizing unit are opened, and the front and rear valves of the other pressure stabilizing and regulating units are closed;

[0039] 6. When it is detected that the upstream gas volume is moderate but the pressure is relatively high: the front and rear valves of the differential pressure generator set are opened, and the front and rear valves of the second pressure regulating unit B in the expander bypass pressure regulating unit are closed;

[0040] 7. When it is detected that the upstream gas volume is large but the pressure is relatively low: the front and rear valves of the differential pressure generator set are opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except for the front and rear valves of the first pressure stabilizing and regulating unit A;

[0041] 8. When it is detected that the upstream gas volume is large and the pressure is relatively moderate: the front and rear valves of the differential pressure generator set are opened, and the front and rear valves of the second pressure stabilizing and regulating unit B in the expander bypass pressure stabilizing unit are closed;

[0042] 9. When it is detected that the upstream gas volume is large but the pressure is relatively high: the front and rear valves of the differential pressure generator set are opened, and the front and rear valves of the third pressure regulating unit C in the expander bypass pressure regulating unit are closed;

[0043] 10. When the first voltage stabilizing and regulating unit A fails and is automatically cut off, the control system will automatically enable the second voltage stabilizing and regulating unit B;

[0044] 11. When the second voltage stabilizing and regulating unit B fails and is automatically cut off, the control system will automatically enable the third voltage stabilizing and regulating unit C;

[0045] 12. When the third voltage stabilizing and regulating unit C fails and is automatically cut off, the control system will automatically enable the first voltage stabilizing and regulating unit A and the second voltage stabilizing and regulating unit B at the same time, and work simultaneously in parallel.

[0046] It should be added that, in addition to meeting certain voltage stabilization gradient requirements, the voltage stabilization processing capability of the selected voltage regulator and the feasibility of failure replacement should also be considered when setting parameters. Therefore, the following conditions must be met in terms of processing capability: (voltage stabilization and voltage regulation units A and B) > voltage stabilization and voltage regulation unit C > voltage stabilization and voltage regulation unit B > voltage stabilization and voltage regulation unit A.

[0047] In summary, the utility model device uses a clever combination method and advanced control methods to comprehensively apply, while achieving pressure reduction and voltage stabilization, fully recovering and utilizing the abundant pressure energy and cold energy contained in the natural gas in the process of gas power plant pressure regulating station. The device transmits electric energy to the power grid through the generator and the grid-connected cabinet, which further reduces the ex-factory electricity price cost while improving the power generation efficiency, benefiting the society. The recycling of cold energy has the characteristics of energy saving and emission reduction, and green environmental protection. While saving energy consumption, it also saves unnecessary energy expenditure costs, and has a very high social demonstration effect. In view of the large fluctuations in the flow rate and pressure range of the upstream gas, the traditional energy recovery device cannot take into account the needs of the stable operation of the downstream gas-using equipment at the same time. The utility model breaks through this defect, by adding an expander bypass voltage stabilization unit in the system, and through a specific control method, it can meet the intelligent working requirements under the harsh conditions of large flow rate and large pressure difference fluctuations of the upstream gas. It is creative, advanced, practical and reliable.

[0048] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other at will.

Claims

1. A device for stably recovering and utilizing natural gas pressure energy and cold energy, characterized in that: The inlet of the device is connected to the upstream pipeline natural gas. The device includes a differential pressure generator set, a heat exchange unit and an expander bypass pressure stabilizing unit. The differential pressure generator set is connected in series with the heat exchange unit and then connected in parallel with the expander bypass pressure stabilizing unit. After being aggregated, they are connected to the natural gas downstream gas-using equipment. The expander bypass pressure stabilizing unit includes a first pressure stabilizing and regulating unit, a second pressure stabilizing and regulating unit, and a third pressure stabilizing and regulating unit. The first pressure stabilizing and regulating unit, the second pressure stabilizing and regulating unit, and the third pressure stabilizing and regulating unit are connected in parallel with each other.

2. The device for stably recovering and utilizing natural gas pressure energy and cold energy according to claim 1, characterized in that: The differential pressure generator set includes a pneumatic isolation valve, a filter, a pressure sensor, a temperature sensor, an electric butterfly valve, a flat turbine expander, a generator and a grid-connected cabinet, and a check valve. The pneumatic isolation valve, filter, pressure sensor, temperature sensor, and electric butterfly valve are connected to the natural gas inlet of the flat turbine expander in sequence. The generator and the grid-connected cabinet are directly connected to the output shaft of the flat turbine expander to obtain sufficient torque required for power generation. The natural gas outlet of the flat turbine expander is connected to the pressure sensor, temperature sensor, pneumatic isolation valve, and check valve in sequence.

3. The device for stably recovering and utilizing natural gas pressure energy and cold energy according to claim 2, characterized in that: The filter is a cone filter, which is used for coarse filtration to prevent large particles of impurities from damaging equipment.

4. The device for stably recovering and utilizing natural gas pressure energy and cold energy according to claim 1, characterized in that: The heat exchange unit includes a single-tube heat exchanger. The natural gas outlet of the differential pressure generator set is connected to the natural gas inlet of the single-tube heat exchanger through a pressure pipeline element. The air-conditioning cooling water outlet is connected to the temperature sensor, the pressure sensor, and the valve group in sequence to the water inlet of the single-tube heat exchanger through the pressure pipeline element. The water outlet of the single-tube heat exchanger is connected to the temperature sensor, the temperature switch, the flow switch, the valve group in sequence through the pressure pipeline element, and then to the air-conditioning chilled water outlet. The natural gas that has been heated by heat exchange is collected in parallel with the expander bypass pressure stabilizing unit through the outlet of the single-tube heat exchanger, and then connected to other downstream gas-using equipment.

5. The device for stably recovering and utilizing natural gas pressure energy and cold energy according to claim 1, characterized in that: The first voltage-stabilizing and regulating unit is connected in series with a pneumatic isolation valve, a pressure gauge, a monitoring pressure regulator with a cut-off valve, a working pressure regulator, a pressure gauge, and a pneumatic isolation valve; the second voltage-stabilizing and regulating unit is connected in series with a pneumatic isolation valve, a pressure gauge, a monitoring pressure regulator with a cut-off valve, a working pressure regulator, a pressure gauge, and a pneumatic isolation valve; the third voltage-stabilizing and regulating unit is connected in series with a pneumatic isolation valve, a pressure gauge, a monitoring pressure regulator with a cut-off valve, a working pressure regulator, a pressure gauge, and a pneumatic isolation valve; and the compressed air is respectively connected through the pressure pipeline components. The pneumatic actuators transmitted to the first pressure stabilizing and pressure regulating unit, the second pressure stabilizing and pressure regulating unit, and the third pressure stabilizing and pressure regulating unit are used as the valve torque input source to control the opening and closing actions of the pneumatic isolation valves. The monitoring pressure regulators and working pressure regulators containing cut-off valves in the first pressure stabilizing and pressure regulating unit, the second pressure stabilizing and pressure regulating unit, and the third pressure stabilizing and pressure regulating unit respectively use pressure pipes to take pressure on the natural gas pipeline. After comparing with the pressure value set by the spring inside the pressure regulator, the valve opening will be automatically adjusted to achieve precise pressure regulation.

6. The device for stably recovering and utilizing natural gas pressure energy and cold energy according to claim 5, characterized in that: The working pressure ranges of the first voltage stabilizing and regulating unit, the second voltage stabilizing and regulating unit, and the third voltage stabilizing and regulating unit are pre-set in a gradient ratio from low to high.

7. The device for stably recovering and utilizing natural gas pressure energy and cold energy according to claim 6, characterized in that: The pressure, flow and other parameters of the natural gas inlet and outlet of the device are collected in real time. After the specific program logic operation and judgment of the control system, the optimal control mode will be quickly selected. By changing the opening and closing states of the front and rear pneumatic isolation valves of the first pressure stabilizing and regulating unit, the second pressure stabilizing and regulating unit, and the third pressure stabilizing and regulating unit, the working path can be quickly and flexibly switched. According to different situations, the control methods of pressure stabilization and pressure regulation specifically include: When it is detected that the upstream gas volume is small but the pressure is relatively low: the front and rear valves of the differential pressure generator set are closed, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the first pressure stabilizing and regulating unit are opened; When it is detected that the upstream gas volume is small and the pressure is relatively moderate: the front and rear valves of the differential pressure generator set are closed, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the second pressure stabilizing and regulating unit are opened; When it is detected that the upstream gas volume is small but the pressure is relatively high: the front and rear valves of the differential pressure generator set are closed, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the third pressure stabilizing and regulating unit are opened; When it is detected that the upstream gas volume is moderate but the pressure is relatively low: the front and rear valves of the differential pressure generator set are opened, and the front and rear valves of all the pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed; When it is detected that the upstream gas volume is moderate and the pressure is relatively moderate: the front and rear valves of the differential pressure generator set are both opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the first pressure stabilizing and regulating unit are both opened; When it is detected that the upstream gas volume is moderate but the pressure is relatively high: the front and rear valves of the differential pressure generator set are both opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the second pressure stabilizing and regulating unit are both opened; When it is detected that the upstream gas volume is large but the pressure is relatively low: the front and rear valves of the differential pressure generator set are both opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the first pressure stabilizing and regulating unit are both opened; When it is detected that the upstream gas volume is large and the pressure is relatively moderate: the front and rear valves of the differential pressure generator set are both opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the second pressure stabilizing and regulating unit are both opened; When it is detected that the upstream gas volume is large but the pressure is relatively high: the front and rear valves of the differential pressure generator set are opened, and the front and rear valves of the other pressure stabilizing and regulating units in the expander bypass pressure stabilizing unit are closed except that the front and rear valves of the third pressure stabilizing and regulating unit are opened; When the first voltage stabilizing and regulating unit fails and is automatically cut off, the control system will automatically enable the second voltage stabilizing and regulating unit to work; When the second voltage stabilizing and regulating unit fails and is automatically cut off, the control system will automatically enable the third voltage stabilizing and regulating unit to work; When the third voltage stabilizing and regulating unit fails and is automatically cut off, the control system will automatically enable the first voltage stabilizing and regulating unit and the second voltage stabilizing and regulating unit to work simultaneously in parallel.

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