Natural gas energy metering method and natural gas energy metering device

Abstract

The invention discloses a natural gas energy metering method and a natural gas energy metering device. The metering method comprises the following steps: detecting TCO2 and TCnHm by adopting a non-dispersive infrared gas sensor; a laser sensor is adopted for detection to obtain TCH4, and the TCnHm is corrected based on the TCH4 to obtain T 'CnHm except CH4; tH2 is detected through a thermal conductivity gas sensor, and TH2 is corrected based on TCH4, TCO2 and T 'CnHm to obtain T' H2; an ultrasonic flowmeter is adopted to detect the measured flow velocity of gas in the natural gas pipeline, the measured flow velocity is corrected to obtain the actual flow velocity of the gas in combination with TCH4, TCO2, T 'CnHm, T' H2 and the pressure and temperature, obtained by the ultrasonic flowmeter, in the natural gas pipeline, and the actual flow q of the gas in the natural gas pipeline is calculated based on the actual flow velocity; energy is calculated by selecting a fixed infrared absorption wavelength of the CnHm to convert the CnHm into one of fixed components of C1-C6, and natural gas energy Q is calculated according to an energy calculation formula # imgabs0 #; therefore, operation is simple, cost is low, and calculation results are accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas energy metering, and in particular to a natural gas energy metering method and a natural gas energy metering device. Background Art

[0002] As a high-quality, clean, and efficient energy source and an important chemical raw material, natural gas has been widely valued by countries around the world, and its share in the world's energy structure has been increasing. At present, the proven reserves far exceed those of oil. With the rapid development of the natural gas industry, the International Energy Agency predicts that around 2030 to 2040, natural gas will replace oil and become the world's largest energy source. my country has abundant natural gas reserves and a complex geographical distribution environment. With the improvement of gas pipelines such as the West-East Gas Transmission Line, Zhongwu Line, and Se-Ning-Lan Line, natural gas consumption will grow rapidly. Natural gas is a mixture of hydrocarbons dominated by methane and other "impurities" (such as nitrogen, carbon dioxide, and hydrogen sulfide) that cannot contribute to calorific value. The calorific value of natural gas of different qualities sometimes varies greatly, and the value of natural gas is essentially the calorific value of these "hydrocarbon" substances. The previous volume measurement cannot fully reflect the fair trading principle of "price according to quality, high quality and high price", while energy measurement is a direct reflection of value. The total energy of natural gas trade is defined as: the total flow of natural gas multiplied by the unit calorific value. The implementation of energy measurement is an inevitable trend to optimize market trade, solve the contradiction between supply and demand, and align with international practices.

[0003] Nowadays, flow metering technology is relatively mature, so determining the calorific value is the key to improving the accuracy of analysis, including direct method and indirect method. Among them, the direct method is to use a calorimeter for direct combustion measurement. Its equipment installation, debugging and operation are complicated, and the environmental requirements are high. It cannot be used in measurement and handover. The indirect method is currently widely used. Usually, a gas chromatograph is used to analyze the composition data of natural gas, and then the calorific value is calculated according to the formula. However, this method has the disadvantages of intermittent sampling, long analysis cycle, inability to perform real-time online detection, and the chromatograph is expensive due to its dependence on imports.

[0004] In order to achieve fast and real-time detection, the prior art RUHRGAS AG's patent EP1181531A1 discloses a method and device for measuring the calorific value of natural gas, which uses ultrasound to measure the natural gas sound velocity / flow rate, and a multi-channel infrared sensor to measure the various components of natural gas, and finally obtains the total calorific value. However, due to the large mutual interference between the main component of natural gas, CH4, and other hydrocarbons, and the flow performance of the ultrasonic flowmeter in actual use, due to the working environment (temperature, pressure, oil and dust) factors, it will cause performance degradation, and the accuracy of natural gas calorific value measurement will deteriorate.

[0005] In addition, Mizi Technology's patent CN102269695B discloses a method for measuring the calorific value of a mixed gas. Multiple TDLAS sensors are used to measure the content of light hydrocarbons such as methane and ethane, and heavy hydrocarbons (C3~C4) and then calculate the calorific value. However, the use of multiple TDLAS sensors is costly, which seriously restricts market promotion and application. Summary of the invention

[0006] The main purpose of the present invention is to provide a natural gas energy metering method and a natural gas energy metering device that can perform rapid and accurate analysis and have low cost.

[0007] To achieve the above object, the present invention proposes a natural gas energy metering method, which comprises the following steps: Step S1: Use a non-spectral infrared gas sensor to detect the volume concentration T of CO2 in the natural gas pipeline. CO2 and C n H m Volume concentration T CnHm , where C n H m For hydrocarbons; Step S2: Using a laser sensor to detect the volume concentration T of CH4 in the natural gas pipeline CH4 , and based on T CH4 To T CnHm Correction is performed to obtain the actual volume concentration T' of hydrocarbons other than CH4 CnHm ; Step S3: Use a thermal conductivity gas sensor to detect the volume concentration T of H2 in the natural gas pipeline. H2 , and based on T CH4 , T CO2 and T' CnHm To T H2 Correction is made to obtain the actual volume concentration T' of H2 H2 ; Step S4: Use an ultrasonic flowmeter to detect the flow rate of the gas in the natural gas pipeline to obtain the measured gas flow rate. CH4 , T CO2 , T' CnHm , T' H2 The ultrasonic flow meter obtains the pressure and temperature in the natural gas pipeline, corrects the measured flow rate to obtain the actual flow rate of the gas, and calculates the actual flow rate q of the gas in the natural gas pipeline based on the actual flow rate; Step S5, by selecting C n H m The fixed infrared absorption wavelength will be C n H mConvert it into one of the fixed components of C1~C6 to calculate the energy, and calculate the natural gas energy Q according to the energy calculation formula. The energy calculation formula is: , where is the calorific value constant of methane, The fixed components of hydrocarbons to be converted, is the calorific value constant of hydrogen.

[0008] Furthermore, the infrared absorption wavelength of the CO2 is 4.26 μm, and the C n H m The fixed infrared absorption wavelength is λ1, and the one fixed component is C3H8.

[0009] Furthermore, the step S2 specifically includes: Step S21: Use the laser sensor to emit light with a wavelength of λ2 to detect the volume concentration T of CH4 in the natural gas pipeline. CH4 ; Step S22, using CH4 of different known volume concentrations to calibrate the non-dispersive infrared gas sensor, and obtaining a function ABS=f(T) between the absorption rate of CH4 of different concentrations and the concentration, wherein ABS is the absorption rate of CH4, and T is the volume concentration of CH4; Step S23, using C with different known volume concentrations n H m The non-spectral infrared gas sensor is calibrated to obtain different concentrations C n H m The function between absorbance and concentration is ABS'=f'(T'), where ABS' is C n H m Absorption rate, T' is C n H m Volume concentration; Step S24: The volume concentration of CH4 in the natural gas pipeline is T CH4 Substituting into ABS=f(T), we can get the actual absorption rate of CH4 ABS(CH4), and the C n H m Volume concentration T CnHm Substituting into ABS'=f'(T'), we get C n H m The actual absorption rate ABS' (C n H m ); Step S25, calculate ABS' (C n H m ) and ABS (CH4), and obtain the C n H mThe actual absorption rate ΔABS' (C n H m ); Step S26: ΔABS' (C n H m ) into ABS'=f'(T'), we get T' CnHm .

[0010] Furthermore, the step S3 specifically includes: Step S31: Use the thermal conductivity gas sensor to detect and obtain the volume concentration T of H2 in the natural gas pipeline. H2 ; Step S32, calibrating the concentration of H2 with different known concentrations to obtain a calibration function AD=f(T1), where AD is the response voltage value and T1 is the corresponding H2 concentration; Step S33: calibrate the interference gases of different known concentrations to obtain the interference concentration function T1=f(T 干扰气 ), wherein the interfering gas includes CH4, CO2 and hydrocarbons other than CH4; Step S34: Calculate T according to the first correction compensation formula H2 The difference in the concentration of H2 interfered by the interfering gas is T' H2 , the first correction compensation formula is:

[0011] Where a1, b1, c1 are the interference coefficients of CH4 to H2, a2, b2, c2 are the n H m a3, b3, and c3 are the interference coefficients of CO2 on H2.

[0012] Furthermore, the step S4 specifically includes: Step S41, using the ultrasonic flowmeter to detect the gas flow rate in the natural gas pipeline, obtaining the gas measurement flow rate v, and obtaining the sound channel angle φ of the ultrasonic flowmeter, the time and actual propagation speed of the ultrasonic wave in the gas in the forward and reverse flow during the detection process, and the cross-sectional area S of the natural gas pipeline; Step S42: Calculate the predicted length L of the acoustic channel of the ultrasonic flowmeter according to the acoustic channel length calculation formula. The acoustic channel length calculation formula is: , where is the time it takes for the ultrasonic wave to propagate downstream in the gas, is the time for ultrasonic wave to propagate in the gas in the countercurrent direction; Step S43, combining T CH4 , T CO2 , T' CnHm , T'H2 The ultrasonic flow meter obtains the pressure and temperature in the pipeline to obtain the theoretical propagation speed of the ultrasonic wave in the gas, and based on the theoretical propagation speed, corrects and compensates the predicted length of the sound channel to obtain the actual length of the sound channel; Step S44: Based on the actual length of the sound channel, the actual gas flow rate is calculated according to the gas flow rate calculation formula, and the gas flow rate calculation formula is: , where v' is the actual gas flow rate, and L' is the actual length of the sound channel; Step S45: Based on the actual gas flow rate and the cross-sectional area of ​​the natural gas pipeline, the actual gas flow rate is calculated according to the gas flow calculation formula. The gas flow calculation formula is: , where S is the cross-sectional area of ​​the natural gas pipeline.

[0013] Furthermore, the step S43 specifically includes: Step S431: Obtain the pressure and temperature in the natural gas pipeline, and combine the pressure and temperature of the natural gas pipeline with the pressure and temperature of the natural gas pipeline. CH4 , T CO2 , T' CnHm and T' H2 Get the theoretical propagation speed C of ultrasonic wave in gas; Step S432: Based on the theoretical propagation velocity and actual propagation velocity of ultrasonic waves in the gas, the actual length L' of the sound channel of the ultrasonic flowmeter is calculated according to the second correction compensation formula. The second correction compensation formula is: , where C f is the actual propagation speed of ultrasound in gas.

[0014] The present invention also provides a natural gas energy metering device, which is applicable to the natural gas energy metering method. The natural gas energy metering device comprises: The gas concentration detection component is used to be installed on the natural gas pipeline, including a non-spectral infrared gas sensor, a laser sensor and a thermal conductivity gas sensor. The non-spectral infrared gas sensor is used to detect the volume concentration T of CO2 in the natural gas pipeline. CO2 and C n H m Volume concentration T CnHm The laser sensor is used to detect the volume concentration T of CH4 in the natural gas pipeline. CH4 The thermal conductivity gas sensor is used to detect the volume concentration T of H2 in the natural gas pipeline. H2 ; An ultrasonic flow meter, which is arranged on the natural gas pipeline to detect the flow rate of the gas in the natural gas pipeline and obtain the measured flow rate of the gas; The microprocessor is connected in communication with the gas concentration detection component and the ultrasonic flow meter to obtain and calculate the natural gas energy according to the volume concentration data transmitted by the gas concentration detection component and the gas measurement flow rate data transmitted by the ultrasonic flow meter.

[0015] Furthermore, the gas concentration detection assembly further comprises a shell, an air chamber is provided in the shell, a first side wall of the shell in the first direction is provided with an air vent, one end of the air vent is connected to the air chamber, and the other end is connected to the natural gas pipeline; The non-spectral infrared gas sensor comprises an infrared light source and a detector, wherein the infrared light source and the detector are respectively arranged at two ends of the gas chamber in the second direction, the infrared light source is used to emit infrared light into the gas chamber, and the detector is used to receive the infrared light; The thermal conductivity gas sensor is arranged on a side of the gas chamber away from the first side wall in the first direction, and includes a detection chamber and a reference chamber sequentially distributed along the second direction, and the detection chamber is communicated with the gas chamber; The first direction and the second direction are perpendicular to each other in a plane.

[0016] Furthermore, an air pipe is inserted into the air vent to connect the air chamber and the natural gas pipeline, and the air pipe includes an air inlet cavity and an air outlet cavity, and the air inlet cavity and the air outlet cavity are distributed in sequence along the second direction and are respectively extended along the first direction.

[0017] In the technical solution of the present invention, the volume concentration of each component of natural gas in the natural gas pipeline is measured by the non-dispersive infrared gas sensor, the laser sensor and the thermal conductivity gas sensor, and the actual volume concentration is obtained by correction and compensation, and the flow rate of the gas in the natural gas pipeline is measured by the ultrasonic flowmeter, and the actual flow rate of the gas is obtained by correction and compensation in combination with the actual volume concentration of each component of the natural gas, and then the actual flow rate of the gas in the natural gas pipeline is calculated, and then the actual volume concentration data of each component of the natural gas and the actual flow data of the gas are combined to calculate the natural gas energy value according to the energy calculation formula; in this way, the operation is simple, and the cost is lower than that of measuring with multiple TDLAS sensors, and in the analysis process, not only the volume concentration data of hydrocarbons and the volume concentration data of hydrogen are corrected and compensated to obtain accurate volume concentration data, but also the gas flow data measured by the ultrasonic flowmeter is corrected and compensated according to the volume concentration data of each component in the natural gas and the pressure and temperature in the natural gas pipeline to obtain accurate flow data, which greatly improves the accuracy of subsequent natural gas energy calculation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0019] Figure 1 A flow chart of the natural gas energy metering method provided by the present invention; Figure 2 for Figure 1 Flow chart of step S2; Figure 3 for Figure 1 Flow chart of step S3; Figure 4 for Figure 1 Flow chart of step S4; Figure 5 for Figure 4 Flow chart of step S43; Figure 6 This is the infrared absorption comparison diagram of CnHm (C1~C6); Figure 7 is a linear relationship diagram between CH4 concentration and C3H8 absorption rate in one embodiment of the present invention; Figure 8 Graph showing the linear relationship between C3H8 concentration and absorbance in one embodiment of the present invention; Fig. 9 A linear relationship diagram of CO2 concentration and H2 interference concentration in one embodiment of the present invention; Fig.10 is a linear relationship diagram of CH4 concentration and H2 interference concentration in one embodiment of the present invention; Fig.11 A linear relationship diagram of C3H8 concentration and H2 interference concentration in one embodiment of the present invention; Fig.12 A schematic structural diagram of an embodiment of a natural gas energy metering device provided by the present invention; Fig.13 for Fig.12 Schematic diagram of some structures of natural gas energy metering device; Fig.14 for Fig.13 A cross-sectional view of Fig.15 for Fig.12 Schematic diagram of part of the structure of the natural gas energy metering device.

[0020] Description of Figure Numbers: 100. Natural gas energy metering device 1. Gas concentration detection component; 11. non-spectral infrared gas sensor; 111. infrared light source; 112. detector; 113. first window; plate; 114. second window plate; 12. Laser sensor; 13. Thermal conductivity gas sensor; 131. Detection chamber; 132. Reference chamber; 133. Filter element; 14. Shell; 141. Air chamber; 15, trachea; 151, air inlet cavity; 152, air outlet cavity; 16. A first circuit board; 17. A second circuit board; 18. Cable waterproof connector; 2. Ultrasonic flow meter; 3. Display; 4. Connect the pipeline; 200. Natural gas pipeline.

[0021] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0022] 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.

[0023] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0024] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0025] Nowadays, flow metering technology is relatively mature, so determining the calorific value is the key to improving the accuracy of analysis, including direct method and indirect method. Among them, the direct method is to use a calorimeter for direct combustion measurement. Its equipment installation, debugging and operation are complicated, and the environmental requirements are high. It cannot be used in measurement and handover. The indirect method is currently widely used. Usually, a gas chromatograph is used to analyze the composition data of natural gas, and then the calorific value is calculated according to the formula. However, this method has the disadvantages of intermittent sampling, long analysis cycle, inability to perform real-time online detection, and the chromatograph is expensive due to its dependence on imports.

[0026] In order to achieve fast and real-time detection, the prior art RUHRGAS AG's patent EP1181531A1 discloses a method and device for measuring the calorific value of natural gas, which uses ultrasound to measure the natural gas sound velocity / flow rate, and a multi-channel infrared sensor to measure the various components of natural gas, and finally obtains the total calorific value. However, due to the large mutual interference between the main component of natural gas, CH4, and other hydrocarbons, and the flow performance of the ultrasonic flowmeter in actual use, due to the working environment (temperature, pressure, oil and dust) factors, it will cause performance degradation, and the accuracy of natural gas calorific value measurement will deteriorate.

[0027] In addition, Mizi Technology's patent CN102269695B discloses a method for measuring the calorific value of a mixed gas. Multiple TDLAS sensors are used to measure the content of light hydrocarbons such as methane and ethane, and heavy hydrocarbons (C3~C4) and then calculate the calorific value. However, the use of multiple TDLAS sensors is costly, which seriously restricts market promotion and application.

[0028] In view of this, the present invention provides a natural gas energy metering method. Figures 1 to 5 The present invention provides a flow chart of the natural gas energy metering method.

[0029] See also Figure 1 , the natural gas energy metering method comprises the following steps: Step S1: Use a non-spectral infrared gas sensor to detect the volume concentration T of CO2 (carbon dioxide) in the natural gas pipeline. CO2 and C n H m Volume concentration T CnHm , where C n H m For hydrocarbons.

[0030] In this step, according to C n H m The infrared absorption spectrum of Figure 6 As shown, between 3.3~3.5μm C n H m All have absorption peaks.

[0031] It should be noted that n is a positive integer not greater than 6, that is, n=1, 2, 3, 4, 5, 6.

[0032] It should also be noted that, in one embodiment of the present invention, the infrared absorption wavelength of CO2 is 4.26 μm. n H m The fixed infrared absorption wavelength is 3.46 μm, while C n H m (n=1~6) There is absorption at λ1=3.46μm.

[0033] The impact data of C1~C6 on the infrared test of 3.46μm channel is shown in Table 1.

[0034] Table 1

[0035] Table 2

[0036] Step S2: Using a laser sensor to detect and obtain the volume concentration T of CH4 (methane) in the natural gas pipeline CH4 , and based on T CH4 To T CnHm Correction is performed to obtain the actual volume concentration T' of hydrocarbons other than CH4 CnHm .

[0037] In this step, the measured T CH4 To T CnHm Correction compensation is performed to obtain accurate volume concentration data of hydrocarbons other than CH4, thereby improving the accuracy of subsequent calculation results.

[0038] Step S3: Use a thermal conductivity gas sensor to detect and obtain the volume concentration T of H2 (hydrogen) in the natural gas pipeline. H2, and based on T CH4 , T CO2 and T' CnHm To T H2 Correction is made to obtain the actual volume concentration T' of H2 H2 .

[0039] In this step, the measured T CH4 , T CO2 and T' CnHm The measured volume concentration of hydrogen is corrected and compensated to obtain accurate volume concentration data of H2, thereby improving the accuracy of subsequent calculation results.

[0040] Step S4: Use an ultrasonic flowmeter to detect the flow rate of the gas in the natural gas pipeline to obtain the measured gas flow rate. CH4 , T CO2 , T' CnHm , T' H2 The ultrasonic flowmeter obtains the pressure and temperature in the natural gas pipeline, corrects the measured flow rate to obtain the actual flow rate of the gas, and calculates the actual flow rate q of the gas in the natural gas pipeline based on the actual flow rate.

[0041] In this step, according to T CH4 , T CO2 , T' CnHm , T' H2 The ultrasonic flowmeter obtains the pressure and temperature in the natural gas pipeline to correct and compensate the gas measurement flow detected by the ultrasonic flowmeter to obtain more accurate gas flow data, namely, the actual gas flow.

[0042] Step S5: Calculate the natural gas energy Q according to the energy calculation formula. The energy calculation formula is: ; (1) In formula (1), is the calorific value constant of methane; is the fixed component calorific value constant of the converted hydrocarbon; is the calorific value constant of hydrogen.

[0043] In this step, by comparing Table 1 and Table 2, it can be seen that C n H m The volume concentration ratio coefficient measured by the sensor made of a detector with a 3.46um narrowband filter is very close to the calorific value coefficient, so C3H8 can be used to represent C n H m To calculate the calorific value.

[0044] In the technical solution of the present invention, the volume concentration of each component of natural gas in the natural gas pipeline is measured by the non-dispersive infrared gas sensor, laser sensor and thermal conductivity gas sensor, and correction and compensation are performed to obtain the actual volume concentration, and the flow rate of the gas in the natural gas pipeline is measured by the ultrasonic flowmeter, and correction and compensation are performed in combination with the actual volume concentration of each component of natural gas to obtain the actual flow rate of the gas, and then the actual flow rate of the gas in the natural gas pipeline is calculated, and then the actual volume concentration data of each component of natural gas and the actual flow data of gas are combined to calculate the natural gas energy value according to the energy calculation formula; in this way, the operation is simple, and the cost is lower than that of measuring with multiple TDLAS sensors, and in the analysis process, not only the volume concentration data of hydrocarbons and the volume concentration data of hydrogen are corrected and compensated to obtain accurate volume concentration data, but also the gas flow data measured by the ultrasonic flowmeter is corrected and compensated according to the volume concentration data of each component in the natural gas and the pressure and temperature in the natural gas pipeline to obtain accurate flow data, which greatly improves the accuracy of subsequent natural gas energy calculation results.

[0045] For further information, see Figure 2 , the step S2 specifically includes: Step S21: Use the laser sensor to emit light with a wavelength of λ2=1653.7nm to detect the volume concentration T of CH4 in the natural gas pipeline. CH4 .

[0046] In this step, the laser sensor uses light of a certain wavelength to detect the volume concentration of CH4 so as not to be affected by C n H m and CO2 interference to improve detection accuracy.

[0047] Step S22, using CH4 of different known volume concentrations to calibrate the non-dispersive infrared gas sensor to obtain a cubic function ABS=f(T) between the absorbance of CH4 of different concentrations and the concentration, wherein ABS is the absorbance of CH4 and T is the volume concentration of CH4.

[0048] In this step, according to the reference signal REF and the measurement signal TST measured by the non-dispersive infrared gas sensor when different concentrations of CH4 are respectively introduced into the non-dispersive infrared gas sensor during calibration, its absorbance ABS and the linear relationship between the volume concentration of CH4 and the absorbance are obtained.

[0049] Step S23, using C with different known volume concentrations n H m The non-spectral infrared gas sensor is calibrated to obtain different concentrations C n H mThe cubic function between absorbance and concentration is ABS'=f'(T'), where ABS' is C n H m Absorption rate, T' is C n H m volume concentration.

[0050] In this step, different concentrations of C are introduced into the non-dispersive infrared gas sensor according to the calibration process. n H m The reference signal REF and the measurement signal TST measured by the non-spectral infrared gas sensor are used to obtain the absorption rate ABS' and C n H m The linear relationship between volume concentration and absorbance (as shown in Table 3 and Figure 8 as shown).

[0051] Table 3

[0052] Step S24: The volume concentration of CH4 in the natural gas pipeline is T CH4 Substituting into ABS=f(T), we can get the actual absorption rate of CH4 ABS(CH4), and the C n H m Volume concentration T CnHm Substituting into ABS'=f'(T'), we get C n H m The actual absorption rate ABS' (C n H m ).

[0053] It should be noted that the effects of different CH4 concentrations on C3H8 absorption are shown in Table 4 and Figure 7 shown.

[0054] Table 4

[0055] Step S25, calculate ABS' (C n H m ) and ABS (CH4), and obtain the C n H m The actual absorption rate ΔABS' (C n H m ); Step S26: ΔABS' (C n H m ) into ABS'=f'(T'), we get T' CnHm .

[0056] For details, please refer to Figure 3 , the step S3 specifically includes: Step S31: Use the thermal conductivity gas sensor to detect the volume concentration T of H2 in the natural gas pipeline. H2 .

[0057] Step S32, calibrate the concentration of H2 with different known concentrations to obtain a calibration function AD=f(T1), wherein AD is the response voltage value and T1 is the corresponding H2 concentration.

[0058] Step S33: calibrate the interference gases of different known concentrations to obtain the interference concentration function T1=f(T 干扰气 ), wherein the interfering gas includes CH4, CO2 and hydrocarbons other than CH4.

[0059] Step S34: Calculate T according to the first correction compensation formula H2 The difference in the concentration of H2 interfered by the interfering gas is T' H2 , the first correction compensation formula is: ; (2) In formula (2), a1, b1, c1 are the interference coefficients of CH4 to H2; a2, b2, c2 is C n H m Interference coefficient for H2; a3, b3, c3 are the interference coefficients of CO2 on H2.

[0060] It should be noted that T CH4 , T CO2 and T' CnHm The linear relationships of the H2 interference concentration are shown in Table 5 and Figures 9 to 11 As shown: Table 5

[0061] In addition, in some cost-insensitive application scenarios, it is also possible to use TDLAS laser sensors to accurately and quickly measure H2 concentration.

[0062] For details, please refer to Figure 4 , the step S4 specifically includes: Step S41, using the ultrasonic flowmeter to detect the gas flow rate in the natural gas pipeline, obtain the gas measurement flow rate v, and obtain the sound channel angle φ of the ultrasonic flowmeter, the time and actual propagation speed of the ultrasonic wave in the gas during the detection process, and the cross-sectional area S of the natural gas pipeline.

[0063] Step S42: Calculate the predicted length L of the acoustic channel of the ultrasonic flowmeter according to the acoustic channel length calculation formula. The acoustic channel length calculation formula is: ; (3) In formula (3), It is the time for the ultrasonic wave to propagate downstream in the gas, in seconds; It is the time for ultrasonic wave to propagate in the gas in the countercurrent direction, in seconds.

[0064] Please note that Fig.15 , the calculation formula for the time of ultrasonic wave propagation downstream in gas is: ; (4) The calculation formula for the time of ultrasonic wave propagation in the gas is: ; (5) Thus, according to equations (4) and (5), the above-mentioned vocal tract length calculation formula (3) is obtained.

[0065] Step S43, combining TCH4, TCO2, T'CnHm, T'H2 and the ultrasonic flowmeter to obtain the pressure and temperature in the pipeline, obtain the theoretical propagation speed of ultrasound in the gas, and based on the theoretical propagation speed, correct and compensate the predicted length of the sound channel to obtain the actual length of the sound channel.

[0066] Step S44: Based on the actual length of the sound channel, the actual gas flow rate is calculated according to the gas flow rate calculation formula, and the gas flow rate calculation formula is: ; (6) Where, v' is the actual gas flow rate, unit is m / s; L' is the actual length of the vocal tract, in meters.

[0067] It should be noted that the gas flow rate calculation formula (6) is also obtained based on the above formulas (4) and (5).

[0068] Step S45: Based on the actual gas flow rate and the cross-sectional area of ​​the natural gas pipeline, the actual gas flow rate is calculated according to a gas flow calculation formula, and the gas flow calculation formula is: ; (7) In formula (7), S is the cross-sectional area of ​​the natural gas pipeline.

[0069] In this way, the time difference method is used to obtain the actual gas flow rate data, and the gas flow rate is corrected and compensated to obtain the actual gas flow rate data.

[0070] For further information, see Figure 5 , the step S43 specifically includes: Step S431: Obtain the pressure and temperature in the natural gas pipeline, and combine the pressure and temperature of the natural gas pipeline with the pressure and temperature of the natural gas pipeline. CH4 , T CO2 , T' CnHm and T' H2 Obtain the theoretical propagation velocity C of ultrasound in gas.

[0071] In this step, the ultrasonic flow meter is provided with a pressure sensor and a temperature sensor, and the pressure and temperature in the natural gas pipeline can be measured by the ultrasonic flow meter. CH4 , T CO2 , T' CnHm and T' H2 According to the calculation method provided in AGA report NO 10 (American Gas Association Transportation Measurement Committee Report No. 10), the theoretical propagation speed of ultrasound in gas can be calculated. The specific calculation process will not be described here one by one.

[0072] Step S432: Based on the theoretical propagation velocity and the actual propagation velocity of the ultrasonic wave in the gas, the actual length L' of the sound channel of the ultrasonic flow meter is calculated according to the second correction compensation formula. The second correction compensation formula is: ; (8) In formula (8), C f is the actual propagation speed of ultrasound in gas.

[0073] In this way, the sound path of the sound channel is corrected and compensated by the theoretical propagation speed and actual propagation speed of ultrasonic waves in the gas, and then substituted into the above formula (3) for calculation to obtain accurate gas flow rate data.

[0074] It should be noted that, in the present invention, the ultrasonic flowmeter can be a single-channel flowmeter or a multi-channel flowmeter, which can detect multiple gas profiles at the same time to eliminate the influence of vortex and asymmetric flow on the measurement results.

[0075] More specifically, when a multi-channel flow meter is used for detection, it is necessary to detect and obtain the measured flow velocity of the gas in each channel, and then, based on the theoretical propagation velocity and actual propagation velocity of ultrasonic waves in the gas in each channel, the length of each channel is corrected and compensated to obtain the actual length of each channel, and then the measured flow velocity of the gas in each channel is corrected and compensated based on the actual length of each channel to obtain the actual flow velocity of the gas in each channel, and the average flow velocity is calculated to obtain the average flow velocity, and finally, according to the gas flow calculation formula, the average flow velocity is multiplied by the cross-sectional area of ​​the natural gas pipeline to obtain the actual gas flow, thereby improving accuracy.

[0076] The present invention further provides a natural gas energy metering device 100, which is applicable to the natural gas energy metering method described above.

[0077] See also Fig.12 The natural gas energy metering device 100 includes a gas concentration detection component 1, an ultrasonic flowmeter 2 and a microprocessor. The gas concentration detection component 1 is used to be arranged on a natural gas pipeline 200, and includes a non-spectral infrared gas sensor 11, a laser sensor 12 and a thermal conductivity gas sensor 13. The non-spectral infrared gas sensor 11 is used to detect and obtain the volume concentration T of CO2 in the natural gas pipeline 200. CO2 and C n H m Volume concentration T CnHm The laser sensor 12 is used to detect the volume concentration T of CH4 in the natural gas pipeline 200. CH4 The thermal conductivity gas sensor 13 is used to detect the volume concentration T of H2 in the natural gas pipeline. H2 ; The ultrasonic flowmeter 2 is used to be installed on the natural gas pipeline 200 to detect the flow rate of the gas in the natural gas pipeline 200 and obtain the gas measurement flow rate; the microprocessor is communicated with the gas concentration detection component 1 and the ultrasonic flowmeter 2 to obtain and calculate the natural gas energy based on the volume concentration data transmitted by the gas concentration detection component 1 and the gas measurement flow rate data transmitted by the ultrasonic flowmeter 2.

[0078] For further information, see Figure 12 to Figure 14 The gas concentration detection component 1 also includes a shell 14, in which an air chamber 141 is provided, and a vent is opened on the first side wall of the shell 14 in the first direction, one end of the vent is connected to the air chamber 141, and the other end is connected to the natural gas pipeline 200; the non-spectral infrared gas sensor 11 includes an infrared light source 111 and a detector 112, and the infrared light source 111 and the detector 112 are respectively arranged at the two ends of the air chamber 141 in the second direction, the infrared light source 111 is used to emit infrared light into the air chamber 141, and the detector 112 is used to receive the infrared light; the thermal conductivity gas sensor is arranged on the side of the air chamber 141 away from the first side wall in the first direction, and includes a detection chamber 131 and a reference chamber 132 distributed in sequence along the second direction, and the detection chamber 131 is connected to the air chamber 141; wherein, the first direction and the second direction are perpendicular to each other in the plane.

[0079] In this way, the non-dispersive infrared gas sensor 11 and the thermal conductivity gas sensor are integrated. Compared with the separate settings of the non-dispersive infrared gas sensor 11 and the thermal conductivity gas sensor, the integrated design makes the structure compact and the appearance small, which is conducive to the miniaturization of the natural gas energy metering device 100 and convenient carrying.

[0080] For further information, see Fig.14 The detection chamber 131 and the reference chamber 132 of the thermal conductivity gas sensor have equal volumes. A filter element 133 is provided between the detection chamber 131 and the gas chamber 141. The filter element 133 is made of sintered 316L stainless steel and has the characteristics of high strength, high precision, high temperature resistance and easy cleaning.

[0081] For details, please refer to Fig.13 and Fig.14 The gas concentration detection component 1 also includes a power module, a first circuit board 16 and a second circuit board 17. The power module is electrically connected to the first circuit board 16 and the second circuit board 17. The first circuit board 16 is electrically connected to the infrared light source 111 and the detector 112 of the non-spectral infrared gas sensor 11. The second circuit board 17 is electrically connected to the thermal conductivity gas sensor. Furthermore, a cable waterproof connector 18 is provided on the second side wall of the housing 14 in the first direction. The wires on the first circuit board 16 and the second circuit board 17 are all gathered at the cable waterproof connector 18. The cable waterproof connector 18 has a protection level of IP68 to improve safety.

[0082] Specifically, the distance between the infrared light source 111 and the detector 112 is adjustable to achieve measurements of different ranges.

[0083] For details, please refer to Fig.14 A first window piece 113 is provided on the side of the infrared light source 111 facing the detector 112, and a second window piece 114 is provided on the side of the detector 112 facing the infrared light source 111. The materials of the first window piece 113 and the second window piece 114 are both calcium fluoride, which is suitable for the transmission wavelength of infrared light.

[0084] Specifically, a filter is provided on the side of the detector 112 facing the infrared light source 111. Furthermore, the filter is a narrow-band filter of 3.46 μm, which can filter ethane (C2H6), propane (C3H8), and n-butane (C4H 10 ) and other major alkane components are equivalent to hydrocarbons (C n H m ) for measurement.

[0085] For details, please refer to Fig.13 and Fig.14The vent is provided with an air pipe 15 to connect the air chamber 141 and the natural gas pipeline 200. The air pipe 15 includes an air inlet cavity 151 and an air outlet cavity 152. The air inlet cavity 151 and the air outlet cavity 152 are sequentially distributed along the second direction and are respectively extended along the first direction. In this way, a pressure difference is generated between the air inlet cavity 151 and the air outlet cavity 152 to achieve gas replacement in the air chamber 141.

[0086] Specifically, the laser sensor 12 includes an optical head, a collimating lens, a light detector, a laser emitter, a sample chamber and a reflector. The circuit generates a periodic driving signal to light up the laser emitter, so that the laser emitter emits light of a specific wavelength (1653.7nm), which is received by the detector after passing through the sample chamber to generate a detection signal. The circuit demodulates the detection signal to obtain an absorption signal, compares the absorption signal with the reference channel in real time, performs correction, outputs methane measurement volume concentration data, and transmits it to the microprocessor for processing.

[0087] For details, please refer to Fig.12 The natural gas energy metering device 100 also includes a display 3, which is electrically connected to the microprocessor and is used to at least display the volume concentration data of each component of the natural gas, the gas flow rate data and the natural gas energy calculation result transmitted by the microprocessor for viewing by the staff.

[0088] Specifically, in one embodiment of the present invention, the natural gas energy metering device 100 may be directly connected to the natural gas pipeline 200 .

[0089] Of course, see Figure 12 to Figure 14 In another embodiment of the present invention, the natural gas energy metering device 100 also includes a connecting pipe 4, which is used to communicate with the natural gas pipeline 200 to accommodate the natural gas flowing in from the natural gas pipeline 200, and the gas concentration detection component 1 and the ultrasonic flowmeter 2 are both arranged in the connecting pipe 4.

[0090] Furthermore, the connecting pipeline 4 is flange-connected to the natural gas pipeline 200 .

[0091] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A natural gas energy metering method, characterized in that: The natural gas energy metering method comprises the following steps: Step S1: Use a non-spectral infrared gas sensor to detect the volume concentration T of CO2 in the natural gas pipeline. CO2 and C n H m Volume concentration T CnHm , where C n H m For hydrocarbons; Step S2: Using a laser sensor to detect the volume concentration T of CH4 in the natural gas pipeline CH4 , and based on T CH4 To T CnHm Correction is performed to obtain the actual volume concentration T' of hydrocarbons other than CH4 CnHm ; Step S3: Use a thermal conductivity gas sensor to detect the volume concentration T of H2 in the natural gas pipeline. H2 , and based on T CH4 , T CO2 and T' CnHm To T H2 Correction is made to obtain the actual volume concentration T' of H2 H2 ; Step S4: Use an ultrasonic flowmeter to detect the flow rate of the gas in the natural gas pipeline to obtain the measured gas flow rate. CH4 , T CO2 , T' CnHm , T' H2 The ultrasonic flow meter obtains the pressure and temperature in the natural gas pipeline, corrects the measured flow rate to obtain the actual flow rate of the gas, and calculates the actual flow rate q of the gas in the natural gas pipeline based on the actual flow rate; Step S5, by selecting C n H m The fixed infrared absorption wavelength will be C n H m Convert it into one of the fixed components of C1~C6 to calculate the energy, and calculate the natural gas energy Q according to the energy calculation formula. The energy calculation formula is: , where is the calorific value constant of methane, is the fixed component calorific value constant of the converted hydrocarbon, is the calorific value constant of hydrogen.

2. The natural gas energy metering method according to claim 1, characterized in that: The infrared absorption wavelength of CO2 is 4.26 μm. n H m The fixed infrared absorption wavelength is λ1, and the one fixed component is C3H8.

3. The natural gas energy metering method according to claim 1, characterized in that: The step S2 specifically includes: Step S21: Use the laser sensor to emit light with a wavelength of λ2 to detect the volume concentration T of CH4 in the natural gas pipeline. CH4 ; Step S22, using CH4 of different known volume concentrations to calibrate the non-dispersive infrared gas sensor, and obtaining a cubic function ABS=f(T) between the absorption rate of CH4 of different concentrations and the concentration, wherein ABS is the absorption rate of CH4, and T is the volume concentration of CH4; Step S23, using C with different known volume concentrations n H m The non-spectral infrared gas sensor is calibrated to obtain different concentrations C n H m The function between absorbance and concentration is ABS'=f'(T'), where ABS' is C n H m Absorption rate, T' is C n H m Volume concentration; Step S24: The volume concentration of CH4 in the natural gas pipeline is T CH4 Substituting into ABS=f(T), we can get the actual absorption rate of CH4 ABS(CH4), and the C n H m Volume concentration T CnHm Substituting into ABS'=f'(T'), we get C n H m The actual absorption rate ABS' (C n H m ); Step S25, calculate ABS' (C n H m ) and ABS (CH4), and obtain the C n H m The actual absorption rate ΔABS' (C n H m ); Step S26: ΔABS' (C n H m ) into ABS'=f'(T'), we get T' CnHm .

4. The natural gas energy metering method according to claim 1, characterized in that: The step S3 specifically includes: Step S31: Use the thermal conductivity gas sensor to detect and obtain the volume concentration T of H2 in the natural gas pipeline. H2 ; Step S32, calibrating the concentration of H2 with different known concentrations to obtain a calibration function AD=f(T1), where AD is the response voltage value and T1 is the corresponding H2 concentration; Step S33: calibrate the interference gases of different known concentrations to obtain the interference concentration function T1=f(T 干扰气 ), wherein the interfering gas includes CH4, CO2 and hydrocarbons other than CH4; Step S34: Calculate T according to the first correction compensation formula H2 The difference in the concentration of H2 interfered by the interfering gas is T' H2 , the first correction compensation formula is: Where a1, b1, c1 are the interference coefficients of CH4 to H2, a2, b2, c2 are the n H m a3, b3, and c3 are the interference coefficients of CO2 on H2.

5. The natural gas energy metering method according to claim 1, characterized in that: The step S4 specifically includes: Step S41, using the ultrasonic flowmeter to detect the gas flow rate in the natural gas pipeline, obtaining the gas measurement flow rate v, and obtaining the sound channel angle φ of the ultrasonic flowmeter, the time and actual propagation speed of the ultrasonic wave in the gas in the forward and reverse flow during the detection process, and the cross-sectional area S of the natural gas pipeline; Step S42: Calculate the predicted length L of the acoustic channel of the ultrasonic flowmeter according to the acoustic channel length calculation formula. The acoustic channel length calculation formula is: , where is the time it takes for the ultrasonic wave to propagate downstream in the gas, is the time for ultrasonic wave to propagate in the gas in the countercurrent direction; Step S43: Combine T CH4 , T CO2 , T' CnHm , T' H2 The ultrasonic flow meter obtains the pressure and temperature in the pipeline to obtain the theoretical propagation speed of the ultrasonic wave in the gas, and based on the theoretical propagation speed, corrects and compensates the predicted length of the sound channel to obtain the actual length of the sound channel; Step S44: Based on the actual length of the sound channel, the actual gas flow rate is calculated according to the gas flow rate calculation formula, and the gas flow rate calculation formula is: , where v' is the actual gas flow rate, and L' is the actual length of the sound channel; Step S45: Based on the actual gas flow rate and the cross-sectional area of ​​the natural gas pipeline, the actual gas flow rate is calculated according to the gas flow calculation formula. The gas flow calculation formula is: , where S is the cross-sectional area of ​​the natural gas pipeline.

6. The natural gas energy metering method according to claim 5, characterized in that: The step S43 specifically includes: Step S431: Obtain the pressure and temperature in the natural gas pipeline, and combine the pressure and temperature of the natural gas pipeline with the pressure and temperature of the natural gas pipeline. CH4 , T CO2 , T' CnHm and T' H2 Get the theoretical propagation speed C of ultrasonic wave in gas; Step S432: Based on the theoretical propagation velocity and actual propagation velocity of ultrasonic waves in the gas, the actual length L' of the sound channel of the ultrasonic flowmeter is calculated according to the second correction compensation formula. The second correction compensation formula is: , where C f is the actual propagation speed of ultrasound in gas.

7. A natural gas energy metering device, applicable to the natural gas energy metering method according to any one of claims 1 to 6, characterized in that: The natural gas energy metering device comprises: The gas concentration detection component is used to be installed on the natural gas pipeline, including a non-spectral infrared gas sensor, a laser sensor and a thermal conductivity gas sensor. The non-spectral infrared gas sensor is used to detect the volume concentration T of CO2 in the natural gas pipeline. CO2 and C n H m Volume concentration T CnHm The laser sensor is used to detect the volume concentration T of CH4 in the natural gas pipeline. CH4 The thermal conductivity gas sensor is used to detect the volume concentration T of H2 in the natural gas pipeline. H2 ; An ultrasonic flow meter, which is arranged on the natural gas pipeline to detect the flow rate of the gas in the natural gas pipeline and obtain the measured flow rate of the gas; The microprocessor is connected in communication with the gas concentration detection component and the ultrasonic flow meter to obtain and calculate the natural gas energy according to the volume concentration data transmitted by the gas concentration detection component and the gas measurement flow rate data transmitted by the ultrasonic flow meter.

8. The natural gas energy metering device according to claim 7, characterized in that: The gas concentration detection assembly further comprises a shell, an air chamber is arranged in the shell, a first side wall of the shell in the first direction is provided with an air vent, one end of the air vent is connected to the air chamber, and the other end is connected to the natural gas pipeline; The non-spectral infrared gas sensor comprises an infrared light source and a detector, wherein the infrared light source and the detector are respectively arranged at two ends of the gas chamber in the second direction, the infrared light source is used to emit infrared light into the gas chamber, and the detector is used to receive the infrared light; The thermal conductivity gas sensor is arranged on a side of the gas chamber away from the first side wall in the first direction, and includes a detection chamber and a reference chamber sequentially distributed along the second direction, and the detection chamber is communicated with the gas chamber; The first direction and the second direction are perpendicular to each other in a plane.

9. The natural gas energy metering device according to claim 8, characterized in that: An air pipe is inserted into the air vent to connect the air chamber and the natural gas pipeline. The air pipe includes an air inlet cavity and an air outlet cavity. The air inlet cavity and the air outlet cavity are distributed in sequence along the second direction and are respectively extended along the first direction.

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