CNG (compressed natural gas) discharging system adopting variable-frequency regulation and control rotary compressor

Abstract

The utility model discloses a CNG (compressed natural gas) discharging system adopting a variable-frequency regulation and control rotary compressor, and belongs to the technical field of natural gas compression and recovery. The CNG gas discharging system adopting the variable-frequency regulation and control rotary compressor comprises a gas discharging column connected with a tank car gas cylinder through a pipeline, a high-pressure gas discharging branch, a cooling and pressurizing branch and a main controller, and a gas discharging column pressure sensor is connected to the gas discharging column; the high-pressure gas discharging branch comprises a first remote control stop valve and a pressure reducing valve which are sequentially connected between a gas discharging column pressure sensor and a CNG pipe network through pipelines, and the cooling and pressurizing branch comprises a second remote control stop valve, a rotary compressor and a heat exchanger which are sequentially connected between the gas discharging column pressure sensor and the CNG pipe network through pipelines. And the main controller is in signal connection with the gas discharging column pressure sensor, the first remote control stop valve, the second remote control stop valve and the motor. The CNG gas discharging system adopting the variable-frequency regulation and control rotary compressor can improve the energy utilization rate and achieve rapid and deep gas discharging of a tank car.

Description

Technical Field

[0001] The utility model relates to the technical field of natural gas compression recovery, in particular to a CNG gas unloading system adopting a variable frequency controlled rotary compressor. Background Art

[0002] The addition of scattered well natural gas to the natural gas pipeline network, achieving separation between production sites and users, can maximize the economic benefits of natural gas and has good technical and economic feasibility. The current approach to collecting gas resources from scattered wells is to use compressor technology to fill tank trucks, which are then transported to loading points for unloading into the pipeline network. The unloading and loading of CNG tank trucks into the pipeline network at the station is currently in its infancy. The pipeline backpressure and loading capacity vary significantly between stations, and the overall technology needs to be improved. The unloading process of tank trucks in private locations is plagued by problems such as slow unloading speeds, insufficient unloading volumes, and low transfer efficiency. Utility Model Content

[0003] The purpose of the utility model is to overcome the problems in the prior art and provide a CNG gas unloading system using a variable frequency controlled rotary compressor to improve energy utilization and achieve rapid and deep gas unloading of tank trucks.

[0004] The utility model provides a CNG gas unloading system using a variable frequency controlled rotary compressor, which is used to increase the natural gas from scattered wells in the tank truck gas cylinder to the CNG pipeline network. It includes a gas unloading column connected to the tank truck gas cylinder through a pipeline, and a gas unloading column pressure sensor is connected to the gas unloading column, and also includes:

[0005] The high-pressure gas unloading branch includes a first remote-controlled shut-off valve and a pressure reducing valve connected in sequence between the gas unloading column pressure sensor and the CNG pipe network through a pipeline. The pressure reducing valve is used to reduce the incoming gas pressure to the control pressure and control the system flow;

[0006] The cooling and pressurizing branch includes a second remote-controlled shut-off valve, a rotary compressor, and a heat exchanger connected in sequence between the gas unloading column pressure sensor and the CNG pipeline network through a pipeline, wherein the rotor of the rotary compressor is connected to the main shaft of a motor;

[0007] The main controller is signal-connected with the gas unloading column pressure sensor, the first remote-controlled shut-off valve, the second remote-controlled shut-off valve and the motor.

[0008] Preferably, a compressor inlet buffer tank is connected to the rotary compressor and the second remote-controlled shut-off valve through a pipeline, and a compressor outlet buffer tank is connected to the rotary compressor and the heat exchanger through a pipeline, so that the gas flowing through the unloading column is diverted according to the pressure state, and the high-pressure gas enters the high-pressure unloading branch to achieve pressure reduction and flow stabilization of the high-pressure gas through the pressure reducing valve, and the low-pressure gas enters the cooling and pressurizing branch to change the working volume through the rotational motion of the rotor of the rotary compressor in the cylinder to achieve power transmission of the gas, and the compressed high-temperature and high-pressure gas is cooled through the heat exchanger, and finally the high-pressure and low-pressure gases are combined to flow into the pipeline network.

[0009] Preferably, a pressure protection valve is connected between the first remote-controlled shut-off valve and the pressure reducing valve through a pipeline, and a first pressure sensor is connected between the pressure reducing valve and the CNG pipeline network. The first pressure sensor and the pressure protection valve are connected through a main controller signal to ensure that the gas pressure is within a reasonable range after the gas flows through the pressure reducing valve 14 and is relieved. If the gas back pressure of the pressure reducing valve 14 exceeds or is lower than the allowable pressure range, the pressure protection valve 13 will be cut off.

[0010] Preferably, a second pressure sensor is connected between the rotary compressor and the second remote shut-off valve, and a third pressure sensor is connected between the heat exchanger and the CNG pipeline network. The motor is connected to the second pressure sensor and the third pressure sensor through the main controller signal to measure the pressure of the gas before and after entering the rotary compressor, and the main controller is used to control and adjust the speed of the motor accordingly to fully utilize the power provided by the rotary compressor, thereby improving the natural gas transportation capacity of the system.

[0011] Preferably, an electric heater is connected between the pressure reducing valve and the metering skid through a pipeline, so as to heat the gas in the high-pressure gas unloading branch through the electric heater to prevent hydrate freezing and blockage caused by low temperature in the pipeline after pressure reduction.

[0012] Preferably, a first temperature sensor is connected between the electric heater and the pressure reducing valve, and a second temperature sensor is connected between the electric heater and the CNG pipe network. The electric heater is connected to the first temperature sensor and the second temperature sensor through a main controller signal. The first temperature sensor and the second temperature sensor are respectively used to measure the temperature of the gas before and after flowing through the electric heater, so as to control the power of the electric heater through the main controller and heat the gas to an appropriate temperature.

[0013] Preferably, a third temperature sensor is connected between the rotary compressor and the second remote shut-off valve, a fourth temperature sensor is connected between the heat exchanger and the rotary compressor, and a fifth temperature sensor is connected between the rotary compressor and the CNG pipeline network. The heat exchanger and the third temperature sensor, the fourth temperature sensor and the fifth temperature sensor are all connected through the main controller signal. The fourth temperature sensor and the fifth temperature sensor are respectively used to measure the gas temperature before and after flowing through the heat exchanger, so as to control the power of the heat exchanger through the main controller and reduce the gas to an appropriate temperature.

[0014] Preferably, a first filter is connected between the gas unloading column and the tank truck gas cylinder through a pipeline, a second filter is provided between the first remote-controlled shut-off valve and the pressure reducing valve, and a third filter is connected between the second remote-controlled shut-off valve and the rotary compressor through a pipeline to purify and filter the incoming gas.

[0015] Preferably, the outlet of the high-pressure gas unloading branch is connected to the inlet of a first flowmeter through a pipeline, the outlet of the cooling and pressurizing branch is connected to the inlet of a second flowmeter through a pipeline, the inlet of the CNG pipe network is connected to the outlet of a third flowmeter through a pipeline, the outlets of the first flowmeter and the second flowmeter are commonly connected to the inlet of the third flowmeter, and the first flowmeter, the second flowmeter and the third flowmeter are all connected to the display signal through the main controller to measure the high-pressure gas unloading branch, the cooling and pressurizing branch and the total gas unloading flow respectively.

[0016] Preferably, a safety valve is connected between the tank truck gas cylinder and the gas unloading column through a pipeline, and a gas unloading column temperature sensor is also connected to the gas unloading column. A remote-controlled safety valve is provided between the gas unloading column and the first remote-controlled shut-off valve and the second remote-controlled shut-off valve. The gas unloading column temperature sensor is connected to the main controller signal to achieve safe transmission of gas.

[0017] Compared with the prior art, the present invention has at least the following advantages:

[0018] 1. This utility model combines the new rotary compressor technology suitable for a single gas unloading column with the CNG pipeline network boosting system. This gas unloading system can effectively solve the problems of slow gas unloading speed, small gas unloading volume, unstable gas unloading speed, and large gas residue in tank trucks.

[0019] 2. The utility model controls the motor speed based on the frequency conversion idea, dynamically integrates constant power regulation, optimizes the compressor parameters, can adapt to the variable pressure ratio unloading process, improve energy utilization, and realize deep unloading of the tank truck.

[0020] 3. Compared with traditional large compressors, the rotary compressor of the utility model has a compact structure, is easy to install and simple to maintain. It saves space, and has lower initial investment and maintenance costs, especially for small-scale stations with limited space. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of a CNG unloading system using a variable frequency controlled rotary compressor.

[0022] Description of reference numerals:

[0023] 1. Tank truck gas cylinder; 2. Main controller; 3. Display; 4. Safety valve; 5. First filter; 6. Unloading column; 7. Unloading column pressure sensor; 8. Unloading column temperature sensor; 9. Remote safety valve; 10. First ball valve; 11. First remote shut-off valve; 12. Second filter; 13. Pressure protection valve; 14. Pressure reducing valve; 15. First pressure sensor; 16. First temperature sensor; 17. Electric heater; 18. Second temperature sensor; 19. Second ball valve; 20. First flow meter; 21. Third ball valve; 22. Second remote shut-off valve; 23. Third filter; 24. Second pressure Force sensor; 25. Third temperature sensor; 26. Compressor inlet buffer tank; 27. Motor; 28. Rotary compressor; 29. ​​Outlet buffer tank; 30. Fourth temperature sensor; 31. Heat exchanger; 32. Third pressure sensor; 33. Fifth temperature sensor; 34. Fourth ball valve; 35. Second flow meter; 36. First maintenance safety valve; 37. First manual gate valve; 38. Second maintenance safety valve; 39. Second manual gate valve; 40. Third maintenance safety valve; 41. Third manual gate valve; 42. Fifth ball valve; 43. Air release valve; 44. Third flow meter; 45. Sixth ball valve. DETAILED DESCRIPTION

[0024] The following is combined with Figure 1 , the specific embodiments of the present invention are described in detail, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] The utility model provides a CNG gas unloading system using a variable frequency controlled rotary compressor, which combines a new rotary compressor technology suitable for a single gas unloading column with a CNG pipeline network boosting system. The rotary compressor has the advantages of compact structure, easy installation, simple maintenance, high efficiency and low noise. By variable frequency control of the rotary compressor, its power output is continuously maintained in a stable state, thereby improving energy utilization and realizing rapid and deep gas unloading of the tank truck.

[0026] A CNG tanker unloading system using variable frequency controlled rotary compressor, such as Figure 1 As shown, the tank truck gas cylinder 1 is connected to the safety valve 4, the first filter 5, the gas unloading column 6, the gas unloading column pressure sensor 7, the gas unloading column temperature sensor 8, and the remote control safety valve 9 in sequence through pipelines;

[0027] The high-pressure gas unloading branch includes a first ball valve 10, a first remote shut-off valve 11, a second filter 12, a pressure protection valve 13, a pressure reducing valve 14, a first pressure sensor 15, a first temperature sensor 16, an electric heater 17, a second temperature sensor 18, a second ball valve 19, and a first flow meter 20, which are connected in sequence;

[0028] The cooling and pressurizing branch includes a third ball valve 21, a second remote shut-off valve 22, a third filter 23, a second pressure sensor 24, a third temperature sensor 25, a compressor inlet buffer tank 26, a motor 27, a rotary compressor 28, an outlet buffer tank 29, a fourth temperature sensor 30, a heat exchanger 31, a third pressure sensor 32, a fifth temperature sensor 33, a fourth ball valve 34, and a second flow meter 35, which are connected in sequence;

[0029] The natural gas collected from the two branches is connected to the fifth ball valve 42, the third flow meter 44, and the sixth ball valve 45 in sequence through a pipeline;

[0030] The gas unloading column pressure sensor 7, the gas unloading column temperature sensor 8, the first pressure sensor 15, the first temperature sensor 16, the second temperature sensor 24, the first flowmeter 20, the second pressure sensor 24, the third temperature sensor 25, the fourth temperature sensor 30, the third pressure sensor 32, the fifth temperature sensor 33, the second flowmeter 35, and the third flowmeter 44 are connected to the main controller through wires for collecting temperature, pressure, and flow signals;

[0031] The remote safety valve 9, the first remote shut-off valve 11, the pressure protection valve 13, the second remote shut-off valve 22, and the motor 27 are connected to the main controller 2 via wires to control the opening and closing of each branch and the operation of the compressor. The main controller 2 is connected to the display 3 via an HDMI interface.

[0032] The inlet of the air release valve 43 is connected with the outlet of the fifth ball valve 42 and the inlet of the third flowmeter 44, and is used for CNG pressure relief or air release. The first maintenance safety valve 36, the first manual gate valve 37, the second maintenance safety valve 38, the second manual gate valve 39, the third maintenance safety valve 40 and the third manual gate valve 41 are sequentially connected. The inlet of the first maintenance safety valve 36 is connected with the outlet of the first remote cut-off valve 11 and the inlet of the second filter 12. The inlet of the second maintenance safety valve 38 is connected with the outlet of the second remote cut-off valve 22 and the inlet of the third filter 23. The outlet of the first manual gate valve 37, the outlet of the second manual gate valve 39 and the outlet of the third manual gate 41 are connected with a vent pipe network. The inlet of the third maintenance safety valve 40 is connected with the outlet of the first manual gate valve 37 and the outlet of the second manual gate valve 39, and is used for maintenance and auxiliary exhaust of the natural gas pipeline.

[0033] Working principle:

[0034] Firstly, the tank car gas cylinder 1 carries 20Mpa natural gas. The tank car gas cylinder is connected with the pressure relief column through a pipeline. The high-pressure natural gas flows through the safety valve 4, enters the first filter 5 for filtering and impurity removal, flows through the pressure relief column pressure sensor 7 and the pressure relief column temperature sensor 8 for pressure and temperature measurement, flows through the remote control safety valve 9, and then enters the heating and pressure regulating pry.

[0035] The gas entering the heating and pressure regulating pry is divided into two paths. When the pressure measured by the pressure relief column pressure sensor 7 is greater than the pipeline network pressure, the first remote cut-off valve 11 is opened, the second remote cut-off valve 22 is closed, and the compressor motor 27 is closed. The natural gas enters the high-pressure pressure relief process. When the pressure measured by the pressure relief column pressure sensor 7 is less than the pipeline network pressure, the first remote cut-off valve 11 is closed, the second remote cut-off valve 22 is opened, and the compressor motor 27 is opened. The gas enters the pressure boosting and gas extraction process.

[0036] In the high-pressure pressure relief process, the gas passes through the first ball valve 10 and the first remote cut-off valve 11, and then passes through the second filter 12 for water and impurity removal. Then the gas passes through the pressure protection valve 13. The pressure protection valve 13 is connected with the first pressure sensor 15 through the main control unit and the wire, so as to ensure that the gas pressure is within a reasonable range after the gas passes through the pressure relief valve 14 for pressure relief. If the back pressure of the pressure relief valve 14 exceeds or is lower than the allowable pressure range, the pressure protection valve 13 will be cut off.

[0037] The pressure set by the pressure relief valve 14 needs to be slightly higher than the pipeline network pressure, which is used for gas flow and overcoming the resistance along the way and locally. The gas after pressure relief is heated to 5℃ in the electric heater 17. The heating power of the electric heater 17 is PID controlled according to the temperature of the second temperature sensor. The gas after heating and pressure regulation flows through the second ball valve 19 and the first flowmeter 20 for flow measurement.

[0038] During the pressurized gas extraction process, the gas passes through the third ball valve 21 and the second remote-controlled shut-off valve 22, and passes through the third filter 23 to remove water and impurities. Before entering the rotary compressor, it flows through the second pressure sensor 24 and the third temperature sensor 25 for temperature and pressure measurement, and then passes through the inlet buffer tank 26 to enter the compressor.

[0039] When the power is turned on, motor 27 starts. Motor 27 drives the rotor of rotary compressor 28 to rotate. The blades or screw at the front of the rotor generate centrifugal force as they rotate, drawing in gas. This drawn-in gas is carried to the rear end as the rotor rotates. During this process, the gas is compressed by the rotor blades or screw, reducing its volume and increasing its pressure. The compressed gas is carried to the exhaust port as the rotor rotates, where it is discharged through an exhaust pipe and passes through an outlet buffer tank 29.

[0040] The gas exiting the compressor is then passed through a heat exchanger 31 for cooling. A fourth temperature sensor 30 and a fifth pressure sensor 32, located at the inlet and outlet of the heat exchanger, measure the gas temperature at the compressor outlet and before entering the pipeline network. After pressurization and cooling, the gas flows through a fourth ball valve 34 and a second flowmeter 35 for flow measurement.

[0041] The high-pressure unloading process and the pressurized gas extraction process both need to be connected to the metering skid. The fifth ball valve 42, the third flow meter 44, and the sixth ball valve 45 are connected in sequence for measuring the total unloading gas flow rate. The aggregated gas is introduced into the CNG uploading pipeline network. The inlet of the vent valve 43 is connected to the outlet of the fifth ball valve 42 and the inlet of the third flow meter 44 for CNG pressure relief or gas release.

[0042] The first maintenance safety valve 36 and the first manual gate valve 37 are connected in sequence, the second maintenance safety valve 38 and the second manual gate valve 39 are connected in sequence, the third maintenance safety valve 40 and the third manual gate valve 41 are connected in sequence, and the outlet of the first manual gate valve 37, the outlet of the second manual gate valve 39, and the outlet of the third manual gate 41 are connected to the vent network for maintenance and auxiliary exhaust of the natural gas pipeline.

[0043] In the description of the utility model, it is necessary to explain that in this article, relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "include", "contain" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent in such process, method, article or equipment. Without more limitations, the element defined by the sentence "including a …" does not exclude the existence of other identical elements in the process, method, article or equipment including the element.

[0044] In the description of the utility model, it is also necessary to explain that, unless otherwise expressly specified and limited, the terms "set", "mount", "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected, it can be mechanically connected, or it can be electrically connected, it can be directly connected, or it can be indirectly connected through an intermediate medium, it can be the communication inside two elements. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0045] Although the embodiments of the utility model have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the utility model, the scope of the utility model is defined by the appended claims and their equivalents.

Claims

1. A CNG unloading system using a variable frequency controlled rotary compressor for increasing the natural gas from scattered wells in a tank truck cylinder (1) to a CNG pipeline network, comprising a unloading column (6) connected to the tank truck cylinder (1) via a pipeline, characterized in that: The gas unloading column (6) is connected to a gas unloading column pressure sensor (7), and further comprises: The high-pressure gas unloading branch comprises a first remote-controlled shut-off valve (11) and a pressure reducing valve (14) which are sequentially connected between the gas unloading column pressure sensor (7) and the CNG pipe network through pipelines; The cooling and pressurizing branch comprises a second remote-controlled shut-off valve (22), a rotary compressor (28), and a heat exchanger (31) connected in sequence between the gas unloading column pressure sensor (7) and the CNG pipe network through a pipeline, wherein the rotor of the rotary compressor (28) is connected to the main shaft of a motor (27); The main controller (2) is signal-connected to the gas discharge column pressure sensor (7), the first remote-controlled shut-off valve (11), the second remote-controlled shut-off valve (22) and the motor (27).

2. The CNG gas unloading system using a variable frequency controlled rotary compressor according to claim 1, characterized in that: A compressor inlet buffer tank (26) is connected between the rotary compressor (28) and the second remote shut-off valve (22) via a pipeline, and a compressor outlet buffer tank (29) is connected between the rotary compressor (28) and the heat exchanger (31) via a pipeline.

3. The CNG gas unloading system using a variable frequency controlled rotary compressor according to claim 1, characterized in that: A pressure protection valve (13) is connected between the first remote-controlled shut-off valve (11) and the pressure reducing valve (14) via a pipeline, a first pressure sensor (15) is connected between the pressure reducing valve (14) and the CNG pipe network, and the first pressure sensor (15) and the pressure protection valve (13) are connected via a main controller (2) signal.

4. The CNG gas unloading system using a variable frequency controlled rotary compressor according to claim 1, characterized in that: A second pressure sensor (24) is connected between the rotary compressor (28) and the second remote shut-off valve (22), a third pressure sensor (32) is connected between the heat exchanger (31) and the CNG pipe network, and the motor (27) is connected to the second pressure sensor (24) and the third pressure sensor (32) via a main controller signal.

5. The CNG gas unloading system using a variable frequency controlled rotary compressor according to claim 1, characterized in that: An electric heater (17) is connected between the pressure reducing valve (14) and the metering skid via a pipeline.

6. The CNG gas unloading system using a variable frequency controlled rotary compressor according to claim 5, characterized in that: A first temperature sensor (16) is connected between the electric heater (17) and the pressure reducing valve (14), a second temperature sensor (18) is connected between the electric heater (17) and the CNG pipe network, and the electric heater (17) is connected to the first temperature sensor (16) and the second temperature sensor (18) via a main controller (2) signal.

7. The CNG gas unloading system using a variable frequency controlled rotary compressor according to claim 1, characterized in that: A third temperature sensor (25) is connected between the rotary compressor (28) and the second remote shut-off valve (22), a fourth temperature sensor (30) is connected between the heat exchanger (31) and the rotary compressor (28), and a fifth temperature sensor (33) is connected between the rotary compressor (28) and the CNG pipe network. The heat exchanger (31) is connected to the third temperature sensor (25), the fourth temperature sensor (30), and the fifth temperature sensor (33) via signals from the main controller (2).

8. The CNG gas unloading system using a variable frequency controlled rotary compressor according to claim 1, characterized in that: A first filter (5) is connected between the gas unloading column (6) and the tank truck gas cylinder (1) via a pipeline, a second filter (12) is provided between the first remote-controlled shut-off valve (11) and the pressure reducing valve (14), and a third filter (23) is connected between the second remote-controlled shut-off valve (22) and the rotary compressor (28) via a pipeline.

9. The CNG gas unloading system using a variable frequency controlled rotary compressor according to claim 1, characterized in that: The outlet of the high-pressure gas unloading branch is connected to the inlet of a first flowmeter (20) through a pipeline, the outlet of the cooling and pressurizing branch is connected to the inlet of a second flowmeter (35) through a pipeline, and the inlet of the CNG pipe network is connected to the outlet of a third flowmeter (44) through a pipeline. The outlets of the first flowmeter (20) and the second flowmeter (35) are commonly connected to the inlet of the third flowmeter (44), and the first flowmeter (20), the second flowmeter (35) and the third flowmeter (44) are all connected to the display (3) through the main controller (2).

10. The CNG gas unloading system using a variable frequency controlled rotary compressor according to claim 1, characterized in that: A safety valve (4) is connected between the tank truck gas cylinder (1) and the gas unloading column (6) via a pipeline. A gas unloading column temperature sensor (8) is also connected to the gas unloading column (6). A remote safety valve (9) is provided between the gas unloading column (6) and the first remote shut-off valve (11) and the second remote shut-off valve (22). The gas unloading column temperature sensor (8) is connected to a main controller (2) for signal transmission.

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