Bidirectional circulation high-stability LNG (Liquefied Natural Gas) flow standard device based on dynamic mass method

Abstract

The invention relates to the technical field of LNG and other low-temperature fluid metering, in particular to a two-way circulation high-stability LNG flow standard device based on a dynamic mass method. The device comprises a first storage tank and a second storage tank, the first storage tank is connected with the second storage tank, the installation height of the first storage tank is smaller than that of the second storage tank, a reversing execution mechanism is arranged between the first storage tank and the second storage tank, the first storage tank is connected with a supercooling system, the supercooling system is connected with a low-temperature pump unit, and the low-temperature pump unit is connected with a detected flowmeter. A proportioning valve is arranged between the low-temperature pump unit and the detected flow meter, the bottom end of the second storage tank is a weighing unit, the top end of the second storage tank is connected with a gas mass flow meter and an ejector, and the two sides of the ejector are connected with a high-pressure gas source and a special exhaust pipeline respectively. The bidirectional circulation high-stability LNG flow standard device based on the dynamic mass method is high in applicability, high in practical operation performance and high in precision, and a foundation is provided for development of domestic LNG standard devices.

Description

Technical Field

[0001] The invention relates to the technical field of LNG and other cryogenic fluid metering, and in particular to a bidirectional circulation high-stability LNG flow standard device based on a dynamic mass method. Background Art

[0002] Natural gas is a clean, environmentally friendly, high-quality energy source that contains almost no sulfur, dust, or other harmful substances, resulting in a low greenhouse effect, thus fundamentally improving environmental quality. Natural gas, with its advantages of flexibility, safety, cleanliness, and low carbon, can play a key supporting role in the process of "carbon peak" and "carbon neutrality". As an important part of global carbon reduction, natural gas is closely related to the global clean energy trade situation and the smooth progress of "carbon reduction".

[0003] Natural gas fuel is one of the earliest widely used alternative fuels. It is divided into compressed natural gas (CNG) and liquefied natural gas (LNG). Natural gas is further purified during the liquefaction process and contains almost no carbon dioxide and sulfide. It is colorless, odorless and non-toxic. Compared with natural gas, LNG has a higher unit calorific value, no secondary pollution after combustion, and flexible transportation methods. LNG has become an ideal urban energy source.

[0004] The entire LNG industry chain can be roughly divided into three sections: upstream purification and liquefaction; midstream transportation; and downstream, namely, customer terminals. At present, research on LNG mainly focuses on the liquefaction of natural gas and the storage and transportation of LNG. The LNG flow metering system has not yet been established. There are relatively few studies on the performance testing and flow measurement of LNG products, and there are only a handful of domestic and foreign flow meters that can be used to directly measure LNG. However, with the national layout and rapid development of the clean energy industry, accurate flow metering is required for LNG storage and transportation and various trade handover links. The accuracy of flow metering is one of the shortcomings that restrict the development of the LNG industry. The existing low-temperature flow metering standard device lacks mature performance detection and test methods, and there are also major deficiencies in flow stability, especially the stability of the device under small flow. Therefore, in response to the above deficiencies, a bidirectional circulation high-stability LNG flow standard device based on the dynamic mass method is proposed. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The present invention provides a bidirectional circulation high-stability LNG flow standard device based on the dynamic mass method, which effectively solves the problems of real-flow verification and flow calibration of deep-cold and low-temperature LNG flowmeters. Through the bidirectional circulation technology, the continuous generation and controllability of the standard flow are guaranteed, and the high-accuracy traceability of the LNG flow is realized.

[0007] (II) Technical solution

[0008] In order to solve the above problems, the present invention provides a bidirectional circulation high-stability LNG flow standard device based on a dynamic mass method, comprising:

[0009] A first storage tank, a second valve and a second storage tank, the interior of the first storage tank is a test medium LNG, the LNG is liquefied natural gas, the installation height of the first storage tank is less than the installation height of the second storage tank, the first storage tank and the second storage tank are connected, a reversing actuator is provided between the first storage tank and the second storage tank, the first storage tank is connected to a supercooling system, the supercooling system is connected to a cryogenic pump unit, the cryogenic pump unit is connected to a flow meter to be tested, a proportional regulating valve is provided between the cryogenic pump unit and the flow meter to be tested, the proportional regulating valve adjusts the size of the LNG flow, and the flow meter to be tested is connected to a reversing actuator;

[0010] The first storage tank drives LNG to flow into the second storage tank through a cryogenic pump unit, and the second storage tank can return LNG to the first storage tank through a height difference. The bottom end of the second storage tank is a weighing unit, and the weighing unit dynamically monitors the weighing data of the second storage tank. The top end of the second storage tank is respectively connected to a gas mass flow meter and an injector, and both sides of the injector are respectively connected to a high-pressure gas source and a special exhaust pipeline.

[0011] Preferably, the first storage tank is provided with an automatic loop inlet, the second storage tank is provided with a second liquid inlet, the automatic loop inlet is connected to the second liquid inlet, and a reversing actuator is provided between the automatic loop inlet and the second liquid inlet.

[0012] Preferably, the reversing actuator includes a first reversing actuator valve and a second reversing actuator valve, the first reversing actuator valve is connected to the automatic loop inlet, the first reversing actuator valve is connected to the second reversing actuator valve, the second reversing actuator valve is connected to the second liquid inlet, the outlet pipeline of the flow meter under test is connected to the pipeline between the first reversing actuator valve and the second reversing actuator valve, and the first reversing actuator valve and the second reversing actuator valve can be opened simultaneously or alternately.

[0013] Preferably, a second valve is provided next to the flow meter being tested, and the second valve is a bypass valve, one end of the second valve is connected to the pipeline between the proportional control valve and the flow meter being tested, and the other end of the second valve is connected to the pipeline between the automatic loop inlet and the first reversing execution valve.

[0014] Preferably, the special exhaust pipe is connected to the ejector, and a one-way valve is provided on the special exhaust pipe and the ejector, and the special exhaust pipe is an exhaust pipe.

[0015] Preferably, an outlet pipeline of the gas mass flow meter is connected to a pipeline between the injector and the one-way valve.

[0016] Preferably, the ejector comprises a first ejector suction port, a second ejector suction port and an ejector outlet, the first ejector suction port is connected to a high-pressure gas source, the second ejector suction port is connected to a second storage tank, and the ejector outlet is connected to a special exhaust pipe.

[0017] Preferably, the cryopump unit comprises a cryopump and a first valve, the cryopump and the first valve are connected in parallel, and the first valve is a bypass valve.

[0018] Preferably, the calculation formula of the LNG flow rate is:

[0019]

[0020] Among them, Q B is the LNG flow rate, Δm B is the mass difference before and after adding liquid, Δt is the adding time, Δm g is the mass of exhaust gas obtained by the gas mass flow meter.

[0021] (III) Beneficial effects

[0022] The bidirectional circulation high-stability LNG flow standard device based on the dynamic mass method provided by the present invention has strong applicability and high practical operating performance. The installation height of the second storage tank is higher than that of the first storage tank, forming a certain height difference, so that the LNG in the second storage tank can return to the first storage tank by its own gravity, and cooperate with the first storage tank to drive the LNG to flow into the second storage tank through the low-temperature pump unit, thereby effectively realizing bidirectional circulation, and cooperating with the proportional control valve to achieve high stability effect under a wide range of LNG flow rate, with high accuracy, which provides a basis for the development of domestic LNG standard devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of a bidirectional circulation high-stability LNG flow standard device based on a dynamic mass method according to an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of a first storage tank system according to an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of a second storage tank system according to an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of a reversing actuator between a first storage tank and a second storage tank in an embodiment of the present invention.

[0027] Among them: 1-first storage tank; 2-subcooling system; 3-cryogenic pump; 4-proportional control valve; 5-first valve; 6-second valve; 7-tested flow meter; 8-reversing actuator; 9-weighing unit; 10-second storage tank; 11-gas mass flow meter; 12-high pressure gas source; 12-injector; 14-check valve; 15-special drainage pipeline;

[0028] 101-first liquid inlet; 102-liquid inlet valve; 103-first safety valve; 104-first thermometer; 105-first pressure gauge; 106-liquid outlet; 107-self-circulation loop inlet;

[0029] 201-liquid outlet valve;

[0030] 801-first reversing actuating valve; 802-second reversing actuating valve;

[0031] 1001-second thermometer; 1002-second pressure gauge; 1003-second safety valve; 1004-special exhaust pipe valve; 1005-exhaust valve; 1006-second liquid inlet; 1007-exhaust port; 1008-special exhaust port;

[0032] 1201-gas source outlet; 1202-third valve;

[0033] 1301 - suction port of the first ejector; 1302 - suction port of the second ejector; 1303 - ejector outlet. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0035] In the description of the present invention, it is necessary to understand that the orientations or positional relationships indicated by “upper”, “lower”, “inside”, “outside”, “top”, “bottom”, etc. are all based on the orientations or positional relationships shown in the accompanying drawings. The purpose is only to facilitate the description of the present invention and simplify the description. It does not indicate or imply that the referred parts must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0036] Figure 1 FIG. 1 is a schematic diagram of the structure of a bidirectional circulation high-stability LNG flow standard device based on a dynamic mass method according to an embodiment of the present invention. Figure 1 As shown, the present invention provides a bidirectional circulation high-stability LNG flow standard device based on a dynamic mass method, comprising:

[0037] A first storage tank 1, a second valve 6 and a second storage tank 10, wherein the interior of the first storage tank 1 is a test medium LNG, wherein the LNG is liquefied natural gas, the installation height of the first storage tank 1 is less than the installation height of the second storage tank 10, the first storage tank 1 and the second storage tank 10 are connected, a reversing actuator 8 is provided between the first storage tank 1 and the second storage tank 10, the first storage tank 1 is connected to a subcooling system 2, the subcooling system 2 is connected to a cryogenic pump unit, the cryogenic pump unit is connected to a flow meter 7 to be tested, a proportional regulating valve 5 is provided between the cryogenic pump unit and the flow meter to be tested, the proportional regulating valve 5 adjusts the size of the LNG flow, and the flow meter 7 to be tested is connected to the reversing actuator 8;

[0038] The first storage tank 1 drives LNG to flow into the second storage tank 10 through a cryogenic pump unit. The second storage tank 10 can return LNG to the first storage tank 1 through a height difference. The bottom end of the second storage tank 10 is a weighing unit 9. The weighing unit 9 dynamically monitors the weighing data of the second storage tank 10. The top end of the second storage tank 10 is respectively connected to a gas mass flow meter 11 and an injector 13. Both sides of the injector 13 are respectively connected to a high-pressure gas source 12 and a special exhaust pipe 15.

[0039] In practical applications, Figure 2 Schematic diagram of the first storage tank system according to an embodiment of the present invention, as shown in Figure 2 As shown, a first safety valve 103 is provided on the left side of the first storage tank 1, a first thermometer 104 and a first pressure gauge 105 are provided on the other side of the first storage tank 1, a self-circulating loop inlet 107 is provided at the lower end of the right side of the first storage tank 1, one end of the bottom of the first storage tank 1 is connected to a liquid inlet pipeline, a liquid inlet valve 102 is provided on the liquid inlet pipeline, an opening of the liquid inlet pipeline is a first liquid inlet 101, and the first liquid inlet 101 is switched by the liquid inlet valve 102, a liquid outlet 106 is provided at the center of the bottom end of the first storage tank 1, the liquid outlet 106 is connected to the subcooling system 2 through a liquid outlet pipeline, and a liquid outlet 106 is provided on the liquid outlet pipeline. An outlet valve 201 is provided, through which the liquid outlet of the first storage tank 1 is controlled. The other side of the outlet valve 201 is a subcooling system 2. The subcooling system 2 is connected to a cryogenic pump unit. A pressure gauge and a thermometer are provided on the outlet pipeline of the subcooling system 2. The cryogenic pump unit is a parallel unit of a cryogenic pump 3 and a first valve 4. The first valve 4 is a bypass valve. The cryogenic pump unit is connected to a flow meter 7 to be tested. A proportional regulating valve 5 is provided between the cryogenic pump unit and the flow meter 7 to be tested. The proportional regulating valve 5 can adjust the size of the LNG flow rate. The flow meter 7 to be tested is connected to a reversing actuator 8.

[0040] In this device, the standard flow rate is precisely controlled by the cryogenic pump 3 in conjunction with the proportional control valve 5, and LNG calibration flow points of different sizes can be obtained. Within the flow range of the cryogenic pump 3, stepless regulation can be achieved, and the standard flow rate and timing system are combined with the start-stop compensation algorithm.

[0041] In practical applications, Figure 3 Schematic diagram of the second storage tank system according to an embodiment of the present invention, Figure 3 As shown, the second liquid inlet 1006 is at the left end of the bottom of the second storage tank 10, the bottom end of the second storage tank 10 is a weighing unit 9, a second safety valve 1003 is provided on the left side of the second storage tank 10, a second thermometer 1001 and a second pressure gauge 1002 are provided on the right side of the second storage tank 10, an exhaust port 1007 and a special exhaust port 1008 are provided on both sides of the top of the second storage tank 10, the second storage tank 10 is connected to the gas mass flowmeter 11 through the exhaust port 1007, an exhaust valve 1005 is provided between the exhaust port 1007 and the gas mass flowmeter 11, and the second storage tank 10 is connected to the injector 13 through the special exhaust port 1008.

[0042] In this device, the ejector 13 is provided with a first ejector suction port 1301, a second ejector suction port 1302 and an ejector outlet 1303. The second ejector suction port 1302 is connected to the special discharge port 1008 of the second storage tank 10. A special discharge pipeline valve 1004 is provided between the special discharge port 1008 and the second ejector suction port 1302. The first ejector suction port 1301 is connected to the gas source outlet 1201 of the high-pressure gas source 12. A third valve 1202 is provided between the gas source outlet 1201 and the high-pressure gas source 12. A thermometer and a pressure gauge are also provided on the outlet pipeline of the high-pressure gas source 12. The ejector outlet 1303 is connected to the special discharge pipeline 15. A one-way valve 14 is provided between the ejector outlet 1303 and the special discharge pipeline 15. The one-way valve 14 controls the ejector 13 to pass to the special discharge pipeline 15.

[0043] It should be noted that the outlet pipeline of the gas mass flow meter 11 is connected to the pipeline between the injector 13 and the one-way valve 14 .

[0044] In addition, the first storage tank 1 is provided with an automatic loop inlet 107, and the second storage tank 10 is provided with a second liquid inlet 1006. The automatic loop inlet 107 is connected to the second liquid inlet 1006. A reversing actuator 8 is provided between the automatic loop inlet 107 and the second liquid inlet 1006. It should be noted that a thermometer and a pressure gauge are provided on the connecting pipeline of the automatic loop inlet 107.

[0045] It should be noted that Figure 4 Schematic diagram of the reversing actuator between the first storage tank and the second storage tank according to an embodiment of the present invention. Figure 4As shown, the reversing actuator 8 includes a first reversing actuator valve 801 and a second reversing actuator valve 802, the first reversing actuator valve 801 and the second reversing actuator valve 802 are connected, the outlet pipeline of the flow meter 7 to be tested is connected to the pipeline between the first reversing actuator valve 801 and the second reversing actuator valve 802, a thermometer and a pressure gauge are arranged on the outlet pipeline of the flow meter 7 to be tested, the first reversing actuator valve 801 is connected to the automatic loop inlet 107 of the first storage tank 1, the second reversing actuator valve 802 is connected to the second liquid inlet 1006 of the second storage tank 10, the first reversing actuator valve 801 and the second reversing actuator valve 802 can be opened simultaneously or alternately.

[0046] In actual application, a second valve 6 is provided next to the flow meter 7 under test, one end of the second valve 6 is connected to the pipeline between the proportional control valve 5 and the flow meter 7 under test, and the other end of the second valve 6 is connected to the pipeline between the first reversing execution valve 801 and the automatic loop inlet 107.

[0047] In actual applications, the interior of the first storage tank 1 is the test medium LNG, which is liquefied natural gas. The installation height of the second storage tank 10 is higher than that of the first storage tank 1, and a certain height difference is formed between the two storage tanks. In conjunction with the reversing actuator 8, the device can realize two-way circulation of LNG. The LNG inside the first storage tank 1 can flow into the second storage tank 10, and the LNG in the second storage tank 10 can also flow into the first storage tank 1. At the same time, the LNG in the pipeline is in a supercooled state during the flow verification and calibration process. The supercooling system 2 can be composed of a liquid nitrogen tank or a refrigerator, and may not be limited to the above method. The supercooling system 2 makes the LNG in a supercooled state to ensure that the flow test pipeline of the LNG flow standard device is in a full liquid state.

[0048] It should be noted that both the first storage tank 1 and the second storage tank 10 use a static or dynamic high-vacuum insulation structure to reduce heat conduction. At the same time, a high-reflection, low-absorption insulation layer is added to the inside of the cold end of the tank body, and a low-reflection, high-absorption surface material is arranged on the tank body wall at the normal temperature end, which greatly reduces radiation heat exchange and inhibits LNG gasification. In addition, the vacuum layer of the two storage tanks, the inside of the tank body and the flow test pipe section are equipped with necessary thermometers and pressure gauges for real-time safety monitoring, and are equipped with safety valves to ensure system safety in emergency situations such as insulation failure, to avoid excessive pressure in pipelines and storage tanks, and the supply tank can be used through a self-pressurizing device in conjunction with a liquid level gauge, a pressure gauge, etc. to replenish the LNG in the two storage tanks in time.

[0049] In addition, the weighing unit 9 can measure the mass of LNG in the second storage tank 10. In fact, it measures the mass of LNG flowing from the storage tank 1 into the storage tank 2. By adding the weighing unit 9, the dynamic weighing data of the second storage tank 10 in the entire flow test process can be obtained, thereby obtaining the mass difference between the first storage tank 1 and the second storage tank 10 before and after the liquid is filled and discharged, thereby improving the test accuracy. The high-pressure gas source 12 can be a high-pressure nitrogen bottle or two storage tanks with a compressor. On the one hand, it can purge the storage tanks and pipelines of the LNG flow standard device, and on the other hand, it can provide high-pressure inert gas for the ejector. The special exhaust pipeline 15 is a dedicated exhaust pipeline for the system. During the purging and pre-cooling stage, the nitrogen and gas impurities in the pipeline are discharged into the special exhaust pipeline after the pipeline is purged.

[0050] In practical applications, the precooling system pipeline and the test section of the flow meter under test are equipped with thermometers and pressure gauges to measure the pipeline fluid in real time, providing a basis for standard flow correction and uncertainty assessment.

[0051] It should be noted that all sensor signals and flow signals of this LNG flow standard device are received, stored and calculated through a unified software platform, which generates a calibration technical report while performing real-time monitoring and safety warning of the overall system functions.

[0052] In actual applications, the LNG flow is driven by the cryogenic pump 3, so that the LNG in the first storage tank 1 flows to the second storage tank 10, and the proportional control valve 5 is cooperated to achieve a high stability effect under a wide range of LNG flow rates with high accuracy. Based on the principle of dynamic mass method, the installation height difference between the first storage tank 1 and the second storage tank 10 is utilized to enable the LNG in the second storage tank 10 to flow back to the first storage tank 1, effectively realizing the two-way circulation of the system. The flow standard device is easy to operate and has precise control in different stages such as purging, precooling, detection, two-way circulation resetting, and emptying, providing a foundation for the development of domestic LNG standard devices.

[0053] The dynamic mass method bidirectional circulation high stability LNG flow standard device mainly includes the detection stage, the bidirectional circulation reset stage and the emptying stage, as follows:

[0054] (1) Detection stage

[0055] In this embodiment, after the overall pre-cooling of the device and the LNG filling are completed, before the flow standard device calibrates the flow meter flow, the liquid inlet valve 102 of the first storage tank 1 is closed, the liquid outlet 106 of the first storage tank 1 is opened, the cryogenic pump 3 and the proportional regulating valve 5 are turned on, and the LNG in the first storage tank 1 is driven to flow through the cooling system 2, the cryogenic pump 3, and the flow meter 7 under test flows into the second storage tank 10.

[0056] In actual application, when the LNG flow standard device starts to calibrate the flow of the flow meter 7 to be tested, the second reversing actuator valve 802 on the side of the second storage tank 10 is cut off and the first reversing actuator valve 801 on the side of the first storage tank 1 is opened to realize the self-circulation flow of LNG in the flow standard device, so that the LNG in the return liquid pipeline flows to the first storage tank 1, providing a stable flow field for the flow test; after waiting for the flow state of LNG in the self-circulation to stabilize, the second reversing actuator valve 802 on the side of the second storage tank 10 is opened, and the first reversing actuator valve 801 on the side of the first storage tank 1 is closed, and the timing system synchronously records the current moment, and the LNG in the first storage tank 1 flows through the flow meter 7 to be tested, and stably adds liquid to the second storage tank 10 on the weighing unit 9, thereby generating a standard LNG flow and a standard cumulative flow.

[0057] After the detection is completed, the second reversing execution valve 802 on the second storage tank 10 side is closed, and the first reversing execution valve 801 on the first storage tank 1 side is opened. The timing system synchronously records the end time of the detection. After the detection is completed, the flow of the cryogenic pump 3 is readjusted and the next detection is started after the flow stabilizes.

[0058] In this embodiment, during the entire detection and calibration process, the time point when the second reversing execution valve 802 on the second storage tank 10 side is opened after the self-circulating flow is stabilized is used as the starting point of the timing, and the time point when the second reversing execution valve 802 on the second storage tank 10 side is closed is used as the end point of the timing.

[0059] In practical applications, the calculation formula for LNG flow is:

[0060]

[0061] Among them, Q B is the LNG flow rate, Δm B is the mass difference before and after adding liquid, Δt is the adding time, Δm g is the mass of exhaust gas obtained by the gas mass flow meter.

[0062] (2) Bidirectional cycle reset stage

[0063] In the bidirectional circulation reset stage of the LNG flow standard device, when the liquid level in the second storage tank 10 reaches the safety line, the two reversing valves in the reversing actuator 8 are opened at the same time, and the liquid outlet valve 201 of the first storage tank 1 is closed. The second storage tank 10 uses the pressure difference generated by its own height difference to re-flow the LNG in the second storage tank 10 into the first storage tank 1 through the circulation loop, and the system reaches the initial state again, achieving high operating efficiency of the device while saving material costs.

[0064] (3) Emptying stage

[0065] After the entire calibration process is completed, if the LNG flow standard device is not used for a long time, it is necessary to drain all the LNG in the system for safety reasons.

[0066] In this embodiment, the gas source outlet 1201 is connected to the first ejector suction port 1301, the second ejector suction port 1302 is connected to the special discharge outlet 1004 of the second storage tank 10, the ejector outlet 1303 is connected to the one-way valve 14 and the special discharge pipe 15, and the high-pressure gas source 12 is a high-pressure nitrogen cylinder.

[0067] During the emptying stage, the nitrogen in the high-pressure gas source 12 flows into the first ejector suction port 1301 through the gas source outlet 1201, and the second ejector secondary suction port 1302 continuously absorbs the gas in the second storage tank 10, and is discharged into the special discharge pipe 15 after safe mixing.

[0068] It should be noted that, during the discharge phase of LNG in the first storage tank 1, the LNG can be first discharged into the second storage tank 10, and then the above-mentioned LNG emptying process in the second storage tank 10 can be repeated. In addition, the emptying scheme of the first storage tank 1 can also adopt the emptying scheme of the second storage tank 10, that is, a special discharge pipe 15 and a corresponding ejector 13 can be added to the first storage tank 1 to achieve the same effect.

[0069] After the device is finally emptied, the nitrogen purge process is carried out again to fill the entire device with nitrogen to achieve the nitrogen sealing effect of the LNG flow standard device.

[0070] In practical applications, the monitoring instruments such as weighing unit, safety valve, thermometer, pressure gauge and liquid level gauge in the dynamic mass method bidirectional circulation high-stability LNG flow standard device are responsible for the safety monitoring of the entire device, and can obtain indicators such as the internal pressure, temperature, and safety parameters of the device, thereby achieving a safe, stable and reliable effect for the entire device during the LNG flow detection process.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] First, the standard flow range generated is precisely adjusted by a cryogenic pump in conjunction with a proportional control valve, which can detect the performance of flow meters at different flow rates, especially ensuring the flow stability of the LNG flow standard device at small flow rates. The proportional control valve has a wide adjustment margin, and within the flow range of the cryogenic pump, large and small flow rates can be measured and more stable; second, the installation height of the second storage tank is higher than that of the first storage tank, forming a certain height difference, so that the LNG in the second storage tank can return to the first storage tank by its own gravity, and cooperate with the first storage tank to drive the LNG into the second storage tank through the cryogenic pump, effectively realizing two-way circulation, and real-flow verification and calibration can be performed repeatedly; third, during real-flow verification, LNG is passed through the second storage tank. When filling at the bottom of the storage tank, the LNG flow rate fluctuates slightly and the measurement accuracy is high. There is a certain height difference when the LNG in the first storage tank flows into the second storage tank. There is a certain back pressure during the flow measurement of the flow standard device, so that the LNG meets the supercooling condition and avoids the gasification of LNG inside the pipeline caused by small heat leakage, ensuring that the LNG inside the pipeline is in a full liquid state during the flow detection and calibration process; Fourth, during the detection and calibration of the LNG flow standard device, the pressure inside the second storage tank increases. During the detection, the exhaust port of the second storage tank is weighed with a gas mass flowmeter or a gas collector to calculate the gas mass, reduce the uncertainty of the device, and ensure the measurement accuracy of the LNG flow standard device.

[0073] The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A bidirectional circulation high-stability LNG flow standard device based on dynamic mass method, characterized in that: include: A first storage tank (1), a second valve (6) and a second storage tank (10), wherein the interior of the first storage tank (1) contains a test medium LNG, which is liquefied natural gas; the installation height of the first storage tank (1) is less than the installation height of the second storage tank (10); the first storage tank (1) and the second storage tank (10) are connected; a reversing actuator (8) is provided between the first storage tank (1) and the second storage tank (10); the first storage tank (1) is connected to a supercooling system (2); the supercooling system (2) is connected to a cryogenic pump unit; the cryogenic pump unit is connected to a flow meter (7) to be tested; a proportional regulating valve (5) is provided between the cryogenic pump unit and the flow meter (7); the proportional regulating valve (5) regulates the flow of LNG; the flow meter (7) to be tested is connected to the reversing actuator (8); The first storage tank (1) drives LNG to flow into the second storage tank (10) through a cryogenic pump unit, and the second storage tank (10) can return LNG to the first storage tank (1) through a height difference. The bottom end of the second storage tank (10) is a weighing unit (9), and the weighing unit (9) dynamically monitors the weighing data of the second storage tank (10). The top end of the second storage tank (10) is respectively connected to a gas mass flow meter (11) and an ejector (13), and the two sides of the ejector (13) are respectively connected to a high-pressure gas source (12) and a special exhaust pipe (15).

2. According to the bidirectional circulation high-stable LNG flow standard device based on the dynamic mass method according to claim 1, the first storage tank (1) is provided with an automatic loop inlet (107), the second storage tank (10) is provided with a second liquid inlet (1006), the automatic loop inlet (107) is connected to the second liquid inlet (1006), and a reversing actuator (8) is provided between the automatic loop inlet (107) and the second liquid inlet (1006).

3. The bidirectional circulation high-stability LNG flow standard device based on the dynamic mass method according to claim 2 is characterized in that: The reversing actuator (8) comprises a first reversing actuator valve (801) and a second reversing actuator valve (802), wherein the first reversing actuator valve (801) is connected to the automatic loop inlet (107), the first reversing actuator valve (801) is connected to the second reversing actuator valve (802), the second reversing actuator valve (802) is connected to the second liquid inlet (1006), the outlet pipeline of the flow meter (7) to be tested is connected to the pipeline between the first reversing actuator valve (801) and the second reversing actuator valve (802), and the first reversing actuator valve (801) and the second reversing actuator valve (802) can be opened simultaneously or staggered.

4. The bidirectional circulation high-stability LNG flow standard device based on the dynamic mass method according to claim 3 is characterized in that: A second valve (6) is provided next to the flow meter (7) being tested. The second valve (6) is a bypass valve. One end of the second valve (6) is connected to the pipeline between the proportional control valve (5) and the flow meter (7) being tested, and the other end of the second valve (6) is connected to the pipeline between the automatic loop inlet (107) and the first reversing execution valve (801).

5. The bidirectional circulation high-stability LNG flow standard device based on the dynamic mass method according to claim 1 is characterized in that: The special exhaust pipe (15) is connected to the ejector (13), and a one-way valve (14) is provided between the special exhaust pipe (15) and the ejector (13). The special exhaust pipe (15) is an exhaust pipe.

6. According to the bidirectional circulation high-stable LNG flow standard device based on the dynamic mass method according to claim 5, the outlet pipeline of the gas mass flow meter (11) is connected to the pipeline between the injector (13) and the one-way valve (14).

7. The bidirectional circulation high-stability LNG flow standard device based on the dynamic mass method according to claim 5 is characterized in that: The ejector (13) comprises a first ejector suction port (1301), a second ejector suction port (1302) and an ejector outlet (1303), wherein the first ejector suction port (1301) is connected to a high-pressure gas source (12), the second ejector suction port (1302) is connected to a second storage tank (10), the ejector outlet (1303) is connected to a special exhaust pipe (15), and a connecting pipeline of the ejector outlet (1303) is connected to a connecting pipeline of a gas mass flow meter (11).

8. The bidirectional circulation high-stability LNG flow standard device based on the dynamic mass method according to claim 1 is characterized in that: The cryopump unit comprises a cryopump (3) and a first valve (4); the cryopump (3) and the first valve (4) are connected in parallel, and the first valve (3) is a bypass valve.

9. The bidirectional circulation high-stability LNG flow standard device based on the dynamic mass method according to claim 1 is characterized in that: The calculation formula of the LNG flow is: Among them, Q B is the LNG flow rate, ΔmB is the mass difference before and after adding liquid, Δt is the adding time, Δm g is the mass of exhaust gas obtained by the gas mass flow meter.

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