Natural gas hydrogen-doped or pure hydrogen verification and calibration loop and calibration method

Abstract

The invention discloses a natural gas hydrogen-doped or pure hydrogen verification and calibration loop. The loop comprises a gas supplementing and exhausting device, a filtering device, a circulating fan, a heat exchanger, a temperature control system, a bypass adjusting device, a working-grade standard device, a detected device, a transmission turbine device and a verification control system which are sequentially connected according to a gas flowing sequence to form the loop, the calibration method comprises the following steps: step 1, analyzing an obtained gas component xi by a mass spectrum analyzer; 2, calculating a contrast density function # imgabs0 # and a contrast temperature function # imgabs1 #; 3, assuming the molar density rho value of the gas mixture to obtain the contrast density delta and the reciprocal tau of the contrast temperature of the gas mixture; and 4, calculating to obtain comparison Helmholtz free energy # imgabs2 # binary comparison Helmholtz free energy # imgabs3 # and ideal Helmholtz free energy # imgabs4 #. The loop and the calibration method effectively solve the problems of verification and calibration of the detected flowmeter for trade measurement of natural gas doped hydrogen or pure hydrogen gas.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas and hydrogen verification and calibration, and in particular to a natural gas hydrogen-blended or pure hydrogen verification and calibration loop and a calibration method. Background Art

[0002] Hydrogen, with its clean, efficient, widely available, and renewable advantages, is a widely used, green, and safe fuel, and has gradually become a key energy development priority for major economies worldwide. However, hydrogen storage and transportation are costly. Blending hydrogen into existing natural gas pipelines can reduce carbon dioxide emissions, lower hydrogen storage and transportation costs, and enable low-cost, large-scale, long-distance hydrogen transportation.

[0003] Flowmeters for natural gas blended with hydrogen or pure hydrogen used for trade measurement must be sent to authorized calibration agencies for actual flow calibration. Currently, there are no specialized calibration agencies in China for natural gas blended with hydrogen or pure hydrogen flowmeters. Existing natural gas blended with hydrogen flowmeters are generally sent to natural gas calibration stations for calibration. However, natural gas blended with hydrogen or pure hydrogen does not fully comply with natural gas calculation standards. Therefore, the uncertainty and indication error of the flowmeter data after calibration are relatively large, affecting the final trade settlement and easily leading to significant disagreements between upstream and downstream parties on the measurement results.

[0004] Traditional natural gas calibration stations use the gas source from the upstream gas transmission station for calibration, which is easily affected by the upstream and downstream working conditions. For example, the incoming gas pressure is low, while the flow meter requires a high pressure; the incoming gas flow is small and cannot reach the calibration flow of the flow meter. Therefore, the calibration requirements cannot be met.

[0005] The working-grade standard flow meters used during calibration need to be dismantled and inspected regularly. However, there are many working-grade standard flow meters, which are large in diameter, size and weight. They are not convenient to dismantle and transport, and traceability is troublesome. Regular dismantling and inspection will be very cumbersome and difficult, and there will be transportation safety risks. Summary of the Invention

[0006] The present invention aims to provide a natural gas hydrogen-blended or pure hydrogen verification and calibration loop and calibration method, which solves the verification and calibration problems of flow meters used for natural gas hydrogen-blended or pure hydrogen gas trade measurement.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A natural gas hydrogen-blended or pure hydrogen calibration loop, comprising a gas supply and exhaust device, a filter device, a circulating fan, a heat exchanger, a temperature control system, a bypass adjustment device, a working level standard device, a device to be tested, a transfer turbine device, and a calibration control system, which are sequentially connected in a gas flow order to form a loop;

[0009] The air supply and exhaust device is installed at the air inlet of the loop and is equipped with a pressure regulating valve, which is used to supply air and regulate the pressure or exhaust and release the pressure of the gas in the loop; the filtering device is used to filter gas impurities; the circulating fan is used to provide power for the loop and regulate the flow; the heat exchanger is used to take away the heat in the loop; the temperature control system is used to cool the gas in the loop; the bypass adjustment device is used to ensure stable operation of low flow rate in the loop; the working-level standard device is used for calibrating the device under test; a flow meter under test is set at the device under test; the transfer turbine device is used to calibrate the device under test; the calibration control system is installed in the control room to collect the instrument signals of the loop for metrological calibration and process control.

[0010] Preferably, the filtering device includes a filter, a pressure transmitter, a temperature transmitter, a differential pressure transmitter, a pressure gauge and a thermometer; the filter is used to filter impurities in the gas, and the differential pressure transmitter is used to detect the differential pressure at both ends of the filter.

[0011] Preferably, the bypass regulating device includes a flow regulating valve, a mass flow meter, a temperature transmitter and a pressure transmitter.

[0012] Preferably, the working-level standard device includes at least two standard pipelines arranged in parallel, and an electric forced sealing ball valve is provided at the inlet and outlet ends of the standard pipeline. The standard pipeline is connected in series with an electric forced sealing ball valve, a pressure gauge, a verification mass flow meter and a working-level standard flow meter in the direction of gas flow from the inlet to the outlet, and a rectifier is connected at both ends of the verification mass flow meter.

[0013] Preferably, the inspected device includes at least two inspected pipelines arranged in parallel, and an electric forced sealing ball valve is provided at the inlet and outlet ends of the inspected pipeline. The inspected pipeline is connected in series with the first inspected station, the second inspected station, the expansion joint and the pressure gauge in the direction of gas flow from the inlet to the outlet. A rectifier is connected at both ends of the first inspected station, and inspected flow meters are placed at the first inspected station and the second inspected station.

[0014] Preferably, the transfer turbine device includes a bypass pipeline and at least one transfer turbine pipeline, the bypass pipeline and the transfer turbine pipeline are connected in parallel, and an electric forced sealing ball valve is provided at the inlet end and the outlet end of the transfer turbine pipeline; the transfer turbine pipeline is connected in series with a pressure gauge and two transfer turbine flow meters, and a rectifier is connected to the front end of each transfer turbine flowmeter.

[0015] Preferably, the calibration control system includes a metrological calibration system workstation and a process control system workstation; the metrological calibration system workstation is used to complete flow calculation and calibrate the flow meter under test; the process control system workstation includes regulation and control of gas medium flow, valve switching, fan control system and temperature control system calibration.

[0016] A calibration method for a natural gas hydrogen-blended or pure hydrogen calibration loop comprises the following steps:

[0017] Step 1: Gas component x obtained by mass spectrometry analysis i ;

[0018] Step 2: Calculate the contrast density function and contrast temperature function

[0019] Step 3: Assuming the molar density ρ of the gas mixture, obtain the relative density δ and the inverse of the relative temperature τ of the gas mixture;

[0020] Step 4: Calculate the comparative Helmholtz free energy Binary contrast Helmholtz free energy and ideal Helmholtz free energy

[0021] Step 5: Calculate the ideal Helmholtz free energy α o and the residual Helmholtz free energy α r , substitute the dimensionless Helmholtz free energy α with respect to the inverse of the molar density ρ of the gas mixture and obtain P 计算 ;

[0022] Step 6: Check whether |P is satisfied 计算 -P 输入 |<10 -6 If it is satisfied, proceed to step 7. If it is not satisfied, return to step 3 and re-assume the molar density ρ value of the gas mixture, where P 输入 Obtained by pressure transmitter;

[0023] Step 7: Calculate the compression factors of the working-level standard flow meter and the flow meter under test respectively;

[0024] Step 8: Calculate the flow indication error between the flow meter under test and the working-level standard flow meter based on the compression factor, and calibrate the flow meter under test based on the flow indication error.

[0025] In the present invention, the flow meter under test for measuring natural gas mixed with hydrogen or pure hydrogen gas can be verified or calibrated, which can reduce the dependence of the verification station on the upstream gas source and is not affected by the pressure and flow of the natural gas mixed with hydrogen or pure hydrogen gas transported downstream. It can expand the verification capability of the natural gas mixed with hydrogen or pure hydrogen flow metering and verification station and further improve the flow value traceability system.

[0026] This loop offers high metering accuracy and can verify flowmeters down to Class 0.5. Compared to existing calibration devices for natural gas and hydrogen, the loop design reduces the calibration station's reliance on upstream gas sources and is unaffected by the pressure and flow rate of downstream natural gas blended with hydrogen or pure hydrogen. This expands the calibration capabilities of natural gas blended with hydrogen or pure hydrogen flowmetering stations and further improves the flow rate traceability system.

[0027] The calibration control system uses the GERG-2008 equation to calculate the gas compressibility factor. The calculation results are more accurate than the AGA8-92DC equation, resulting in high measurement accuracy. The relative expanded uncertainty of the working-level standard device calibrated with a transfer turbine flowmeter is better than 0.16% (k=2), and it can test flowmeters up to 0.5 level. The working-level standard flowmeter does not need to be disassembled for inspection. Instead, the smaller-caliber transfer turbine flowmeter can be sent to an authorized calibration agency for traceability to a higher-precision standard device. This makes the transfer turbine flowmeter more convenient to disassemble and transport. The traceable transfer turbine flowmeter can be used to transfer the value of the working-level standard flowmeter, saving labor and economic costs.

[0028] The compression factor is a parameter used to convert the flow rate of a working-level standard flow meter into the flow rate under the same temperature and pressure conditions as the flow meter under test. The flow rate of the converted working-level standard flow meter and the flow rate of the flow meter under test are used for calculation to obtain the flow indication error between the standard flow meter and the flow meter under test, and the flow meter under test is calibrated based on the flow indication error.

[0029] Existing natural gas calibration stations use the AGA8-92DC equation to calculate the compressibility of natural gas. This equation is applicable when the hydrogen concentration in natural gas is less than 10%. Above 10%, the error is large. The present invention relies on a framework based on dimensionless Helmholtz free energy and its first- and second-order differentials. Pressure, temperature, and gas composition are used as input parameters. Pressure and temperature are acquired by pressure and temperature transmitters adjacent to the flowmeter, while gas composition is analyzed by a mass spectrometer. Based on the relevant formulas of this method, the compressibility of natural gas blended with hydrogen or pure hydrogen can be accurately calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall process of the present invention;

[0031] Figure 2This is the topology diagram of the verification control system of the present invention;

[0032] Figure 3 It is a schematic diagram of the overall structure of the present invention;

[0033] In the figure: 1. Air supply and exhaust device; 2. Filter device; 3. Circulation fan; 4. Heat exchanger; 5. Temperature control system; 6. Bypass adjustment device; 7. Working level standard device; 8. Device under test; 9. Transfer turbine device; 10. Verification control system; 11. Printer; 12. Switch; 13. Process control system PLC controller; 14. Electric forced seal ball valve; 15. Pressure transmitter; 16. Temperature transmitter; 17. Combustible gas detector; 18. Mass spectrometer; 2 0. Differential pressure transmitter; 30. Fan circulation control system; 60. Flow control valve; 70. Verification mass flowmeter; 71. Working-level standard flowmeter; 80. Tested flowmeter; 90. Transfer turbine flowmeter; 101. Process control system workstation; 102. Database server; 103. Metrology and verification system workstation; 115. Metrology and verification system data acquisition controller; 120. Metrology compensated pressure transmitter; 121. Metrology compensated temperature transmitter; 180. Analytical instrument. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings:

[0035] like Figures 1 to 3 The natural gas blended with hydrogen or pure hydrogen calibration loop shown includes an air supply and exhaust device 1, a filter device 2, a circulating fan 3, a heat exchanger 4, a temperature control system 5, a bypass adjustment device 6, a working level standard device 7, a device to be tested 8, a transfer turbine device 9 and a calibration control system 10, forming a loop.

[0036] The air supply and exhaust device 1 is installed at the air inlet of the loop, and the filter device 2, the circulating fan 3, the heat exchanger 4, the temperature control system 5, the bypass adjustment device 6, the working level standard device 7, the inspected device 8 and the transfer turbine device 9 are connected in sequence according to the flow order of the gas.

[0037] The verification control system 10 is installed in the control room to collect the instrument signals of the loop for measurement verification and process control.

[0038] like Figure 2As shown, the calibration control system 10 utilizes two systems: a process control system workstation 101 and a metrological calibration system workstation 103. The core device of the process control system workstation 101 is a PLC controller, although a DCS controller can also be used. The loop's electric forced-seal ball valve 14, flow control valve 60, differential pressure transmitter 20, pressure transmitter 15, temperature transmitter 16, combustible gas detector 17, mass spectrometer 18, analytical instrument 180, temperature control system 5, and fan circulation control system 30 are connected to the AI, AO, DI, DO, and RS485 channels of the process control system PLC controller 13 using cables. Analytical instrument 180 includes an online methane detector, an online hydrogen detector, and an online oxygen detector. The process control system PLC controller 13 is connected to the switch 12 with a network cable, and the switch 12 is connected to the process control system workstation 101 with a network cable. On the screen of the process control system workstation 101, the pressure, temperature, and flow of the gas medium in the loop can be adjusted and controlled, valves can be switched, and state parameters can be collected, monitored, and displayed. It can also interact with the fan circulation control system 30 and the temperature control system 5 to complete automatic calibration and other tasks.

[0039] The core device of the metrology and verification system workstation 103 is the data acquisition controller. The flowmeter under test 80, transfer turbine flowmeter 90, working-level standard flowmeter 71, verification mass flowmeter 70, metrology-compensated pressure transmitter 120, and metrology-compensated temperature transmitter 121 are connected via cables to the HART, PI, and AI channels of the metrology and verification system data acquisition controller 115. The metrology and verification system data acquisition controller 115 is connected to the switch 12 via a network cable, which in turn is connected to the database server 102, the metrology and verification system workstation 103, and the printer 11 via network cables. The database server 102 is mainly responsible for all data collection, processing and database storage related to the calibration of flow meters, temperature transmitters and pressure transmitters. The measurement and calibration system workstation 103 can display the flow meter flow rate and measurement values such as temperature, pressure, gas component values and fault alarm information in real time. It is responsible for the configuration and issuance of calibration tasks, pipeline selection, calculation of calibration data, storage of calibration data, comparison and viewing of inspection data, generation of calibration certificate reports and other functions. The printer 11 is used to print calibration certificates.

[0040] The gas supply and exhaust device 1 is used to supply and regulate the pressure of natural gas mixed with hydrogen or pure hydrogen within the loop, or to exhaust and release the pressure. A pressure regulating valve is installed within the gas supply and exhaust device 1 to ensure that the pressure of the gas within the loop reaches a predetermined experimental pressure. When the gas pressure within the loop reaches the set value, the on-off valve connecting the gas supply and exhaust device 1 to the loop is closed, stopping the gas supply to the loop pipeline. When the gas within the loop needs to be discharged, the exhaust function can be used to extract the gas from the loop.

[0041] The filtering device 2 includes a filter, a pressure transmitter, a temperature transmitter, a differential pressure transmitter 20, a pressure gauge, a thermometer and a bypass valve; the filtering device 2 relies on the filter to filter impurities in the gas to prevent damage to downstream equipment, and the differential pressure transmitter 20 is used to detect the differential pressure at both ends of the filter. When the differential pressure is large, it indicates that the filter is clogged. In order not to affect normal calibration, it can be switched to bypass.

[0042] Circulation fan 3 includes a frequency converter control system and at least one external motor with a magnetically coupled fan. Circulation fan 3 is the core equipment. Its functions are: first, to provide power for the circulation of the test gas in the loop, compensating for frictional losses caused by the gas flowing within the annular pipeline and pressure losses caused by the fluid passing through various devices; second, to provide a certain working condition test flow rate for the loop, allowing flow regulation; and third, to meet different compression ratios under various pressure and flow conditions. Circulation fan 3 generally uses a high-speed motor with an external, magnetically coupled connection. However, other types of motors that meet the requirements can also be used.

[0043] The inverter control system uses HMI visual monitoring to control the speed of circulating fan 3 to adjust the flow rate and display system status, operating data, and fault diagnosis information in real time. The inverter control system includes a touch screen, a PLC controller, and an inverter, equipped with an emergency stop button. The inverter control system is connected to the motor of circulating fan 3 and the fan's associated sensors, and communicates with the verification control system 10 via the Modbus protocol.

[0044] The heat exchanger 4 is a shell and tube heat exchanger, and other types of heat exchangers may also be used. The function of the heat exchanger 4 is to remove the heat generated by the circulation fan 3 in the loop device when the natural gas mixed with hydrogen or pure hydrogen gas is pressurized and worked on it.

[0045] The temperature control system 5 is an integrated unit, comprising a refrigeration unit, a water pump, a regulating valve, a flow meter, an electric heater, a cold water tank circulation system, and a supporting temperature control system. To maintain the required temperature stability of the gas flow medium within the loop during the calibration process, a heat exchanger is required to quickly and promptly cool the gas medium at the loop fan outlet. This is achieved through the temperature control system 5. The design of the temperature control system 5 directly affects the loop system's measurement uncertainty and flow meter calibration efficiency, making it a core and challenging aspect of loop design. The temperature control system 5 communicates with the calibration control system 10 via the Modbus protocol.

[0046] The bypass control device 6 includes a flow control valve, a mass flow meter, a temperature transmitter, and a pressure transmitter. Within the loop, the flow control method uses a frequency converter equipped with the circulating fan 3 for high-volume flow regulation. Due to the inherent limitations of the circulating fan 3's flow regulation ratio, bypass control is required to ensure stable operation at low flow rates. The bypass design is calculated based on 20% of the maximum flow rate of a single circulating fan 3. The bypass flow is controlled by a bypass flow control valve and metered by a mass flow meter to accurately regulate the flow of natural gas-blended hydrogen or pure hydrogen throughout the loop system's full range. The temperature transmitter and pressure transmitter are used to convert mass flow into volume flow for low-volume flow control.

[0047] The working-level standard device 7 includes at least two standard pipelines arranged in parallel; a gas manifold is connected at the inlet and outlet of each standard pipeline, and the standard pipeline is connected in series with an electric forced sealing ball valve, a pressure gauge, a rectifier, a verification mass flowmeter 70, a rectifier, a working-level standard flowmeter 71 and an electric forced sealing ball valve in the direction of gas flow from the inlet to the outlet. The verification mass flowmeter 70 uses a mass flowmeter, and other types of flowmeters can also be used. The working-level standard flowmeter 71 uses a turbine flowmeter. A temperature transmitter and a pressure transmitter are installed next to the verification mass flowmeter 70 and the working-level standard flowmeter 71 respectively.

[0048] The inspected device 8 includes at least two parallel pipelines. A gas manifold is connected to the inlet and outlet of each pipeline. Each pipeline, in the direction of gas flow from inlet to outlet, is connected in series with an electric forced-seal ball valve, a rectifier, a first inspected station, a rectifier, a second inspected station, an expansion joint, a pressure gauge, and an electric forced-seal ball valve. Flowmeters 80 are placed at the first and second inspected stations. Unused stations are replaced with straight pipe sections. A temperature transmitter and a pressure transmitter are installed next to each inspected station.

[0049] The transfer turbine assembly 9 comprises a bypass line and at least one transfer turbine line, connected in parallel. The bypass and transfer turbine lines' inlets and outlets are connected to a gas manifold, respectively. An electric forced-seal ball valve is installed in the bypass line. Each transfer turbine line is connected in series, in the order of gas flow from inlet to outlet, with an electric forced-seal ball valve, a pressure gauge, a rectifier, a transfer turbine flowmeter, a rectifier, a transfer turbine flowmeter, and an electric forced-seal ball valve. A temperature transmitter and a pressure transmitter are installed next to each transfer turbine flowmeter.

[0050] The calibration control system 10 includes two parts: a metrological calibration system workstation 103 and a process control system workstation 101. A single system or two separate systems can be used. The metrological calibration system workstation 103 collects and processes real-time detection data such as temperature, pressure, flow, and components during the metrological calibration process, calculates flow, calibrates the flowmeter 80 under test using a working-level standard flowmeter 71, calibrates the working-level standard flowmeter 71 using a transfer turbine flowmeter 90, and displays, outputs, saves, and prints calibration results. The process control system workstation 101 regulates and controls the pressure and flow of the gas medium, switches valves, collects, monitors, and displays state parameters. It interacts with the fan control system and temperature control system 5 to complete automatic calibration and other tasks.

[0051] A calibration method for a natural gas hydrogen-blended or pure hydrogen calibration loop comprises the following steps:

[0052] Step 1: The gas component x is obtained by mass spectrometry analysis i ;

[0053] Natural gas mixed with hydrogen is a mixture gas, which refers to the gas components of natural gas mixed with hydrogen. There are 21 types of gas components, including: N2, CO2, Ar, CH4, C2H6, C3H8, n-C4H 10 、i-C4H 10 、n-C5H 12 、iC5 H 12 、C6 H 14 、C7H 16 、C8H 18 、C9 H 20 、C 10 H 22 , H2, CO, H2S, He, O2 and H2O;

[0054] Step 2: Calculate the contrast density function and contrast temperature function Specifically,

[0055]

[0056] Where:

[0057] β v,ij is the molar binary parameter between components i and j at isochoric conditions;

[0058] γ v,ij is the binary location parameter of components i and j at equal volume, dimensionless;

[0059] ρ c,i is the critical density of component i, in kg / m 3 ;

[0060] ρ c,j is the critical density of component j, in kg / m 3 ;

[0061] x i is the mole fraction of component i in the gas mixture;

[0062] x j is the mole fraction of component j in the gas mixture;

[0063] N is the number of components in the gas mixture, i.e. 21;

[0064]

[0065] Where:

[0066] β T,ij is the molar binary parameter between components i and j at the isotherm, dimensionless;

[0067] γ T,ij is the binary localization parameter of components i and j at the isotherm, dimensionless;

[0068] T c,i is the temperature of component i, in K, obtained by the temperature transmitter next to the working-level standard flowmeter 71 or the temperature transmitter next to the flowmeter under test 80;

[0069] T c,j is the temperature of component i, in K, obtained by the temperature transmitter next to the working-level standard flowmeter 71 or the temperature transmitter next to the flowmeter under test 80;

[0070] N is the number of components in the gas mixture, i.e. 21;

[0071] Step 3: Assuming the molar density ρ of the gas mixture, obtain the relative density δ and the inverse of the relative temperature τ of the gas mixture;

[0072] Specifically,

[0073]

[0074] Where:

[0075] T is the temperature of the gas mixture, in K, collected by the temperature transmitter;

[0076] Step 4: Calculate the comparative Helmholtz free energy Binary contrast Helmholtz free energy and ideal Helmholtz free energy Specifically,

[0077]

[0078] Where:

[0079] K is the number of terms; Pol is the term of the polynomial; Exp is the exponential term;

[0080] n oi,k Comparison with Helmholtz free energy Parameters;

[0081] d oi,k , t oi,k and c oi,k is the exponential parameter of the interaction between components i and j, dimensionless;

[0082]

[0083] Where:

[0084] n ij,k is the interaction correlation factor between components i and j;

[0085] n oi,k To compare the Helmholtz free energy Parameters,

[0086] d ij,k , t ij,k ,η ij,k , ε ij,k and γ ij,k is the exponential parameter of the interaction between components i and j, dimensionless;

[0087]

[0088] Where:

[0089] R * is the ideal gas constant, 8.314510 J / mol·K;

[0090] R is the standard gas constant, 8.314472 J / mol·K;

[0091] T c,i is the critical temperature of component i, in K, obtained by the temperature transmitter next to the working-level standard flowmeter 71 or the temperature transmitter next to the flowmeter under test 80;

[0092] ρ c,i is the critical density of component i, in kg / m 3 ;

[0093] θ oi,k To compare the Helmholtz free energy Calculation factor of ;

[0094] Step 5: Calculate the ideal Helmholtz free energy α o and the residual Helmholtz free energy α r , substitute the dimensionless Helmholtz free energy α with respect to the inverse of the molar density ρ of the gas mixture and obtain P 计算 ;

[0095] Specifically,

[0096]

[0097] Where:

[0098] is the molar composition of the gas mixture;

[0099] ρ is the molar density of the gas mixture, kg / m 3 ;

[0100] N is the number of components in the gas mixture;

[0101]

[0102] Where:

[0103] F ij is a binary adjustment factor;

[0104]

[0105] in,

[0106]

[0107] Step 6: Check whether |P is satisfied 计算 -P 输入 |<10 -6 If it is satisfied, proceed to step 7. If it is not satisfied, return to step 3 and re-assume the molar density ρ value of the gas mixture; P 输入 It is directly obtained by the pressure transmitter next to the working-level standard flowmeter 71 or the pressure transmitter next to the flowmeter being tested 80.

[0108] Step 7: Calculate the compression factors of the working-level standard flow meter 71 and the flow meter under test 80 respectively; the specific calculation formula of the compression factor is:

[0109]

[0110] in,

[0111]

[0112] Step 8: Calculate the flow indication error between the flow meter under test 80 and the working-level standard flow meter 71 based on the compression factor, and calibrate the flow meter under test 80 based on the flow indication error.

[0113] Specifically:

[0114]

[0115] Where:

[0116] E ij is the relative indication error of the flow meter 80 under test during the j-th test at the i-th test point;

[0117] q ij The instantaneous flow rate value displayed by the flow meter 80 during the jth calibration at the i-th calibration point can be the average of the instantaneous flow rates read multiple times during a calibration process. The unit is m 3 / h;

[0118] (q h ) ij The instantaneous flow value of the working level standard flowmeter 71 converted to the state of the flowmeter 80 in the device 8 under test during the j-th test at the i-th test point, in m 3 / h.

[0119]

[0120] Where:

[0121] (q s ) ij The instantaneous flow rate value displayed by the flow meter 80 during the jth calibration at the i-th calibration point can be the average of the instantaneous flow rates read multiple times during a calibration process. The unit is m 3 / h;

[0122] T s , T m ——Thermodynamic temperatures of the gases at the working-level standard flowmeter 71 and the flowmeter under test 80 during the j-th calibration at the i-th calibration point, in K, obtained by the temperature transmitter;

[0123] P s , P m ——The absolute static pressure at the working level standard flowmeter 71 and the flowmeter under test 80 during the jth calibration at the i-th calibration point, in kPa, obtained by the pressure transmitter;

[0124] z s , z m —— are the compression factors of the working-level standard flowmeter 71 and the flowmeter under test 80 during the j-th calibration at the i-th calibration point, calculated in step 7.

[0125] like Figure 3 As shown, the various devices are connected by pipes to form a closed loop. Through the gas supply and exhaust device 1, and in accordance with the process flow sequence, the loop is slowly and steadily filled with high-pressure natural gas mixed with hydrogen or pure hydrogen, except for the device under test 8. The pressure is raised to, for example, 6.3 MPa. The flowmeters 80 to be tested are installed at the first and second test stations, respectively, according to their calibers. The temperature and pressure transmitters supporting the flowmeters 80 are also installed. The electrically driven, forced-seal ball valve at the inlet of the test pipeline is then opened, allowing the high-pressure natural gas mixed with hydrogen or pure hydrogen to enter the pipeline until the pressures before and after the valve are balanced.

[0126] When the working-level standard device 7 verifies the flow meter 80 to be tested, the verification control system 10 sets the verification flow point according to the flow range of the flow meter 80 to be tested, and configures the pipeline combination of the working-level standard flow meter 71. For example, the verification flow points of the flow meter 80 to be tested are 3000m 3 / h、1200m 3 / h、600m 3 / h、80m 3 / h, Figure 3 There are 4 DN100 (flow range: 20~400m 3 / h) working-level standard flowmeter 71, 6 DN200 (flow range: 80~1600m 3 / h) of the working-level standard flow meter 71, the working-level standard flow meter 71 combination can ultimately achieve 20 ~ 9600m 3 / h test flow range. When the test flow point is 3000m 3 / h, two DN200 working-level standard flow meters 71 are used for verification, and the verification control system 10 connects the pipelines of the two selected DN200 working-level standard flow meters 71; when the verification flow point is 1200m 3 / h, a DN200 working-level standard flow meter 71 is used for verification, and the verification control system 10 closes one of the two DN200 working-level standard flow meters 71 pipelines to ensure that only one DN200 working-level standard flow meter 71 pipeline is connected; when the verification flow point is 600m 3 / h, two DN100 working-level standard flow meters 71 are used for verification. The verification control system 10 first connects the pipelines of the two selected DN100 working-level standard flow meters 71, and then closes the pipeline of one DN200 working-level standard flow meter 71. The verification flow point is 80m 3When the flow rate is 1 / h, a DN100 working-grade standard flowmeter 71 is used for calibration. The calibration control system 10 shuts off one of the two DN100 working-grade standard flowmeters 71, ensuring that only one DN100 working-grade standard flowmeter 71 is open. Calibration is generally performed in descending order of flow rate. When the working-grade standard device 7 calibrates the device under test 8, the electrically driven forced-sealed ball valves at the inlet and outlet of the working-grade standard flowmeter 71 pipeline must be closed, and the electrically driven forced-sealed ball valve on the bypass line to the turbine device 9 must be opened.

[0127] During calibration, the flow at each calibration point in the loop is adjusted through the flow interlocking control of the circulating fan 3 + bypass flow control valve and the bypass mass flowmeter. At the same time, the circulating fan 3 + bypass flow regulation completes the pressure increase adjustment at this flow, so that at the calibration flow, the pressure increase of the circulating fan 3 is equal to the resistance loss along the loop. Since the work of the circulating fan 3 causes the gas medium in the loop to rise to varying degrees, the heat exchanger 4 connected in series with the circulating fan 3 is used to balance the temperature change of the medium. The temperature control system 5 is set to cool the heat exchanger 4. The outlet gas medium temperature of the heat exchanger 4 is interlocked with the cooling water volume to control the temperature of the gas medium in the closed process system. After the pressure, flow, and temperature of the loop system are stabilized within the calibration requirements, data collection is carried out to complete the calibration or calibration of the natural gas hydrogen-blended or pure hydrogen gas flow under specific operating conditions.

[0128] The process of transferring the value of the turbine device 9 to calibrate the working level standard device 7 is as follows: A. First, ensure that two DN100 (flow range: 20~400m 3 / h) The transfer turbine flowmeter 90 is sent to the authorized calibration agency for higher-precision standard device traceability, the bypass electric forced sealing ball valve of the inspected device 8 is opened, the electric forced sealing ball valves of the inlet and outlet of all inspected flowmeters 80 are closed, the electric forced sealing ball valves of the inlet and outlet of the transfer turbine flowmeter 90 are opened, and the bypass electric forced sealing ball valve of the transfer turbine device 9 is closed; B. The average value of these two DN100 transfer turbine flowmeters 90 is used as the measurement result, and the value transfer is performed on the four DN100 working-level standard flowmeters 71 of the same diameter in the working-level standard device 7 respectively; C. The four DN100 working-level standard flowmeters 71 in the working-level standard device 7 are used in parallel, and one DN200 (flow range: 80~1600m 3 / h) working-grade standard flowmeter 71 for measurement value transfer; D. This DN200 working-grade standard flowmeter 71 is then used to transfer measurement values to the other five DN200 working-grade standard flowmeters 71 in the working-grade standard device 7. Therefore, the working-grade standard flowmeter does not need to be disassembled for inspection. Instead, the smaller-caliber transfer turbine flowmeter only needs to be sent to an authorized calibration agency for traceability to the higher-precision standard device. This transfer turbine flowmeter is more convenient to disassemble, assemble, and transport. The traced transfer turbine flowmeter can then be used to transfer measurement values to the working-grade standard flowmeter, saving labor and financial costs.

[0129] The relative expanded uncertainty of the working-level standard device 7 after calibration with the transfer turbine flowmeter 90 is better than 0.16% (k=2), the repeatability is better than 0.05%, the stability is better than 0.05% / a, and the calibration accuracy is higher; domestic natural gas calibration stations can generally only calibrate flow meters with a level 1.0 accuracy. According to the requirements of the calibration regulations, the relative expanded uncertainty of the working-level standard device 7 should not be greater than 1 / 3 of the absolute value of the maximum allowable error of the flow meter 80 being tested. Therefore, the working-level standard device 7 after calibration with the transfer turbine flowmeter 90 can perform online real-flow calibration on flow meters with a level 0.5 accuracy.

[0130] The combustible gas detector 17 is used to monitor whether there is a leak of combustible gas such as methane or hydrogen in the environment, thereby preventing the occurrence of fire and explosion accidents.

[0131] The calibration control system 10 can realize automatic pipeline configuration, automatic arrangement of calibration flow points, calibration times and calibration time with one-button operation, automatic process flow, automatic pressure regulation and flow control, automatic switching of standard pipelines, and has safety protection logic (including differential pressure alarm logic of valves before and after the pipeline, standard meter overspeed protection logic, loop low pressure alarm and interlocking protection logic), automatically judges the stability of fluid temperature, pressure and flow, automatically starts calibration and automatically analyzes calibration results, automatically re-inspects if the calibration results are unqualified, automatically restores the initial process after the calibration task is completed, and automatically generates a calibration certificate and original data records after the calibration task is completed.

[0132] The above embodiments are merely some explanations of the concept and implementation of the present invention, and are not intended to limit the same. Under the concept of the present invention, technical solutions that have not been substantially changed are still within the scope of protection.

Claims

1. A natural gas hydrogen-blended or pure hydrogen calibration loop, characterized by: The device comprises a gas supply and exhaust device (1), a filter device (2), a circulating fan (3), a heat exchanger (4), a temperature control system (5), a bypass adjustment device (6), a working level standard device (7), a device to be tested (8), a transfer turbine device (9) and a verification control system (10) which are sequentially connected to form a loop according to the gas flow sequence; The air supply and exhaust device (1) is installed at the air inlet of the loop and is equipped with a pressure regulating valve, which is used to supply air and regulate the pressure or exhaust and release the pressure of the gas in the loop; the filtering device (2) is used to filter gas impurities; the circulating fan (3) is used to provide power for the loop and regulate the flow; the heat exchanger (4) is used to remove the heat in the loop; the temperature control system (5) is used to cool the gas in the loop; the bypass regulating device (6) is used to ensure the stable operation of the low flow rate in the loop; the working level standard device (7) is used to calibrate the device to be tested; the flow meter (80) to be tested is set at the device to be tested (8); the transfer turbine device (9) is used to calibrate the device to be tested; the verification control system (10) is installed in the control room to collect the instrument signals of the loop for measurement verification and process control.

2. The natural gas blended with hydrogen or pure hydrogen calibration loop according to claim 1, characterized in that: The filtering device (2) comprises a filter, a pressure transmitter, a temperature transmitter, a differential pressure transmitter (20), a pressure gauge and a thermometer; the filter is used to filter impurities in the gas, and the differential pressure transmitter (20) is used to detect the differential pressure at both ends of the filter.

3. The natural gas hydrogen-blended or pure hydrogen calibration loop according to claim 1, characterized in that: The bypass regulating device (6) comprises a flow regulating valve, a mass flow meter, a temperature transmitter and a pressure transmitter.

4. The natural gas hydrogen-blended or pure hydrogen calibration loop according to claim 1, characterized in that: The working-level standard device (7) comprises at least two standard pipelines arranged in parallel, an electric forced sealing ball valve is provided at both the inlet and outlet ends of the standard pipeline, the electric forced sealing ball valve, a pressure gauge, a verification mass flow meter (70) and a working-level standard flow meter (71) are sequentially connected in series in the direction of gas flow from the inlet to the outlet, and a rectifier is connected at both ends of the verification mass flow meter.

5. The natural gas blended with hydrogen or pure hydrogen calibration loop according to claim 1, characterized in that: The inspected device (8) comprises at least two inspected pipelines arranged in parallel, an electric forced sealing ball valve is provided at both the inlet and outlet ends of the inspected pipeline, the inspected pipeline is connected in series with a first inspected station, a second inspected station, an expansion joint and a pressure gauge in the direction of gas flow from the inlet to the outlet, a rectifier is connected at both ends of the first inspected station, and inspected flow meters (80) are placed at the first inspected station and the second inspected station.

6. The natural gas hydrogen-blended or pure hydrogen calibration loop according to claim 1, characterized in that: The transfer turbine device (9) comprises a bypass pipeline and at least one transfer turbine pipeline, the bypass pipeline and the transfer turbine pipeline are connected in parallel, and an electric forced sealing ball valve is provided at the inlet and outlet ends of the transfer turbine pipeline; the transfer turbine pipeline is sequentially connected in series with a pressure gauge and two transfer turbine flowmeters (90), and a rectifier is connected to the front end of each transfer turbine flowmeter (90).

7. The natural gas hydrogen-blended or pure hydrogen calibration loop according to claim 1, characterized in that: The verification control system (10) comprises a metrological verification system workstation (103) and a process control system workstation (101); the metrological verification system workstation (103) is used to complete flow calculation and calibrate the flow meter (80) being tested; the process control system workstation (101) includes regulation control of gas medium flow, valve switching, fan control system and temperature control system verification.

8. A calibration method for a natural gas hydrogen-blended or pure hydrogen calibration loop according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: The gas component x is obtained by mass spectrometry analysis (18) i ; Step 2: Calculate the contrast density function and contrast temperature function Step 3: Assuming the molar density ρ of the gas mixture, obtain the relative density δ and the inverse of the relative temperature τ of the gas mixture; Step 4: Calculate the comparative Helmholtz free energy Binary contrast Helmholtz free energy and ideal Helmholtz free energy Step 5: Calculate the ideal Helmholtz free energy α o and the residual Helmholtz free energy α r , substitute the dimensionless Helmholtz free energy α with respect to the inverse of the molar density ρ of the gas mixture and obtain P 计算 ; Step 6: Check whether |P is satisfied 计算 -P 输入 |<10 -6 If it is satisfied, proceed to step 7. If it is not satisfied, return to step 3 and re-assume the molar density ρ value of the gas mixture, where P 输入 Obtained by pressure transmitter; Step 7, respectively calculating the compression factors at the working-level standard flow meter and the flow meter under test (80); Step 8: Calculate the flow indication error between the flow meter under test (80) and the working-level standard flow meter based on the compression factor, and calibrate the flow meter under test (80) based on the flow indication error.

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