In order to provide a theoretical basis for methane sensor placement in the vertical direction of a tunnel,the software Fluent was used to simulate methane distribution. A geometric roadway model was established and d...In order to provide a theoretical basis for methane sensor placement in the vertical direction of a tunnel,the software Fluent was used to simulate methane distribution. A geometric roadway model was established and divided by grids. Methane distribution in both level and vertical sections was simulated using a realizable k-ε model with the Fluent software according to a conservation equation in a turbulent state,a turbulent kinetic energy equation and a turbulent dissipation rate equation. The realizable k-ε model and the Fluent software were used to simulate methane distribution according to the principle of the conservation equation in a state of turbulent flow. The results show that after overflow-ing,a methane level with a certain thickness is formed. Methane density curves at three specific levels were internally consistent and methane density at higher levels is denser than that at lower levels. Methane distribution becomes thinner in the direction of wind and methane in the vertical direction becomes uniform if wind speed is high. The distance be-tween sensors and roof should be less than 300 mm which is in agreement with mine safety regulations.展开更多
Methane is an explosive gas in coalmines and needs to be monitored by methane sensors.Conductivetype methane sensors are small,simple and stable,and they are very promising for mining safety or home safety application...Methane is an explosive gas in coalmines and needs to be monitored by methane sensors.Conductivetype methane sensors are small,simple and stable,and they are very promising for mining safety or home safety applications.They can even be employed in mining Internet of things if the power consumption can be lowered down to few milliwatts.Many researches of nanomaterialsbased conductive-type methane sensors have been reported recently.This review intends to present a comprehensive and critical summary on the recent progresses in the nanomaterials-based conductive-type methane sensors field.Many excellent methane-sensitive nanomaterials will be present,such as SnO2,ZnO,TiO2,WO3,carbon nanotubes,graphene,rare earth metal-based perovskite oxides and their hybrids.Particular attention is given to the synthetic methods of the nanomaterials,sensing mechanisms of the nanomaterials and the relationship between the sensing performance and the structures and components of the nanomaterials.Finally,the future trends and perspectives of nanomaterials-based conductive-type methane sensors are proposed.展开更多
To improve the reliability of coal mine safety monitoring systems we have analyzed the characteristics of a methane sensor, an important component of the monitoring system of production safety in a coal mine and studi...To improve the reliability of coal mine safety monitoring systems we have analyzed the characteristics of a methane sensor, an important component of the monitoring system of production safety in a coal mine and studied the main type and mode of faults when the sensor was used on-line. We introduced a new method based on artificial neural network to detect faults of methane sensors. In addition, using the output information of a single methane sensor, we established a sensor output model of a dynamic non-linear neural network for on-line fault detection. Finally, the fault of the heating wire of the sensor was simulated, indicating that, when the methane sensor had a fault, the predicted output of the neural network clearly deviated from the actual output, exceeding the pre-set threshold and showing that a fault had occurred in the methane sensor. The result shows that the model has good convergence and stability, and is quite capable of meeting the requirements for on-line fault detection of methane sensors.展开更多
Based on the deficiency of catalytic elements in methane sensors such as sintering,activity decrease and surface area reduction at high temperature, three differentnano vectors Ce-Zr-Al_2O_3, Ce-Al_2O_3, and Zr-Al_2O_...Based on the deficiency of catalytic elements in methane sensors such as sintering,activity decrease and surface area reduction at high temperature, three differentnano vectors Ce-Zr-Al_2O_3, Ce-Al_2O_3, and Zr-Al_2O_3 were prepared via sol-gel technique inthe experiment.BET surface area, catalytic activity and thermal stability were tested andcompared.It is found from the experiment that the Ce-doped Al_2O_3 vector possesseshigher catalytic activity than pure Al_2O_3 vector.Zr-doped Al_2O_3 vector can enhance thethermal stability of methane sensors.Ce-Zr-Al solid solution can be obtained by the presenceof Ce and Zr doped with Al_2O_3.The reaction activity and thermal stability of catalyticsensors were improved because of the unique synergy effect from Ce-Zr-O.Among themixed cocatalysts, Ce-Zr-O was reported to be an excellent cocatalyst material.The performanceof methane sensors can be improved significantly via the modification ofCe-Zr-Al_2O_3 vector.展开更多
Based on spectrum principle and analyzing the infrared absorption spectrum ofmethane, a kind of optical fiber methane gas sensor and its system are developed. DFBLD(Distributedfeedback laser diode) in 1 300 nm waveban...Based on spectrum principle and analyzing the infrared absorption spectrum ofmethane, a kind of optical fiber methane gas sensor and its system are developed. DFBLD(Distributedfeedback laser diode) in 1 300 nm waveband is used as illuminant and phase-detecting technology isused to carry out harmonic wave detecting the concentration of methane. The sensitivity can arriveat 10^(-5). Experiments results show that the performance targets of the sensor such as sensitivitycan basically satisfy the requests of methane detection.展开更多
This report presents the results of experiments to evaluate a prototype fiber optic methane monitor exposed to smoke using a smoke chamber to simulate atmospheric conditions in an underground coal mine after a fire or...This report presents the results of experiments to evaluate a prototype fiber optic methane monitor exposed to smoke using a smoke chamber to simulate atmospheric conditions in an underground coal mine after a fire or explosion. The experiments were conducted using test fires of different combustible sources commonly found in mines —douglas-fir wood, SBR belt, and Pittsburgh seam coal. The experiments were designed to assess the response of the fiber optic methane sensor to different contaminants,different contaminant levels and different contaminant durations produced from the test fires. Since the prototype methane monitor detects methane by measuring absorption at a specific wavelength, optical power at the absorption wavelength(1650 nm) was measured as a function of smoke concentration and duration. The other sensor response parameter-methane response times-were measured between smoke tests to assess the impact of soot accumulation on the sensor. Results indicate that the sensor screen effectively prevented smoke from obscuring the optical beam within the sensor head, with minimal impact on the system optical power budget. Methane response times increased with smoke exposure duration, attributed to soot loading on the protective screen.展开更多
Methane gas sensor was fabricated based on electrocatalytic properties of the Pd/MWNT nanocomposites on indium tin oxide （ITO） glass substrates. A linear response for methane was obtained in the range of 0-16% （v/v...Methane gas sensor was fabricated based on electrocatalytic properties of the Pd/MWNT nanocomposites on indium tin oxide （ITO） glass substrates. A linear response for methane was obtained in the range of 0-16% （v/v） with a detection limit of 0.167% （v/ v） and R.S.D. of 4.1%. After 100 times sensing or stable stored more than 12 months in atmosphere, unconspicuous measurable decrease was observed. The response time was less than 60 s at room temperature and ambient pressure. Some common potential interferents in samples such as N2, CO, CO2, ethane, propane, pentane, methanol, ethanol, H2 and NH3 were investigated and all the effects were less than 5% on the response for 3.0% （v/v） methane. The sensor was applied to methane determinations in man-made gas samples, the results are satisfied.展开更多
Continental margins in world oceans contain large amounts of marine gas hydrates. Changes in the temperature and pressure of sediment may destabilize the methane hydrate, leading to its release and seepage into the se...Continental margins in world oceans contain large amounts of marine gas hydrates. Changes in the temperature and pressure of sediment may destabilize the methane hydrate, leading to its release and seepage into the sea. This process would increase the dissolved methane in the ambient seawater. In this study, a methane sensor was used to detect methane anomalies in the water column in southwestern Dongsha and Shenhu, northern slope of the South China Sea. Methane plumes were detected at stations SCS001 and T001 in the southwestern Dongsha area, and station SCS002 in the Shenhu area, respectively. The maximum methane concentrations were 8.8 nmol/L in southwestern Dongsha and 10.1 nmol/L in Shenhu, which are about 4–5 times higher than the background methane concentration. This indicates that there are active methane seepages present in both the southwestern Dongsha and Shenhu areas, which are likely related to a methane hydrate reservoir beneath the seafloor. A methane sensor with a low detection limit is a practical instrument with which to detect methane plumes in oceanic environments and to monitor methane leakage from the seafloor.展开更多
Development of metal oxide semiconductors-based methane sensors with good response and low power consumption is one of the major challenges to realize the real-time monitoring of methane leakage.In this work,a self-as...Development of metal oxide semiconductors-based methane sensors with good response and low power consumption is one of the major challenges to realize the real-time monitoring of methane leakage.In this work,a self-assembled mulberry-like ZnO/SnO_(2)hierarchical structure is constructed by a two-step hydrothermal method.The resultant sensor works at room temperature with excellent response of~56.1%to 2000 ppm CH_(4)at 55%relative humidity.It is found that the strain induced at the ZnO/SnO_(2)interface greatly enhances the piezoelectric polarization on the ZnO surface and that the band bending results in the accumulation of chemically adsorbed O_(2)^(-)ions close to the interface,leading to significant improvement in the sensing performance of the methane gas sensor at room temperature.展开更多
Oil and gas pipeline transportation,as a relatively safe way of oil and gas transportation,undertakes most of the transportation tasks of crude oil and natural gas.Oil and gas pipeline accidents affect a wide range of...Oil and gas pipeline transportation,as a relatively safe way of oil and gas transportation,undertakes most of the transportation tasks of crude oil and natural gas.Oil and gas pipeline accidents affect a wide range of consequences.Therefore,the oil and gas pipeline leakage detection is paid more and more attention.In this paper,ultra-low power methane gas sensor is selected to collect methane gas concentration in the air,and wireless network technology is used to build a wireless network sensor system with 4G function.Through the sensor distribution along the pipeline,it can intuitively and accurately judge whether there is a micro-leakage in the pipeline,and understand the diffusion situation after the leakage.The sensor system has high reliability and stability,and has high value of popularization and application.展开更多
<span style="font-family:;" "=""><span style="font-family:Verdana;">Methane is released from waste disposal areas as a result from anaerobic decay of food. Methane causes...<span style="font-family:;" "=""><span style="font-family:Verdana;">Methane is released from waste disposal areas as a result from anaerobic decay of food. Methane causes more greenhouse effects than carbon dioxide so a methane monitoring system is required to warn its release from gas emitting environments. The low explosive limit of methane is 5% in ambient air, so gas leakage is dangerous and can produce explosions. An entire head monitoring system was built around a MQ-4 methane gas sensor as it is cheap and reliable. The design proves to be flexible enough as it can measure CH</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> emissions in ducts, CH</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> in landfills at different depths and even in cattle barns. The measuring system head consists of a suction pump, solenoids, and a methane sensor. Measurements are taken 13 seconds after methane gas sucking. </span><span style="font-family:Verdana;">A timing of 100 seconds is required for purging the chamber before the</span><span style="font-family:Verdana;"> second solenoid is turned-on. Devices temperature during operation was sampled with a thermal Flir-One camera and solenoid coil temperature was of 24.9</span></span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="white-space:nowrap;">˚</span>C </span><span style="font-family:Verdana;">after a continuous operation of 30 seconds. As hoses for emission sampling</span><span style="font-family:Verdana;"> become larger time for sampling increases as well as energy consumption.</span></span>展开更多
基金Projects 2005AA133070 supported by the National High Technology Research and Development Program of China[2005]688 and [2005]555 by the Devel-opment Fund for Electronic and Information Industry
文摘In order to provide a theoretical basis for methane sensor placement in the vertical direction of a tunnel,the software Fluent was used to simulate methane distribution. A geometric roadway model was established and divided by grids. Methane distribution in both level and vertical sections was simulated using a realizable k-ε model with the Fluent software according to a conservation equation in a turbulent state,a turbulent kinetic energy equation and a turbulent dissipation rate equation. The realizable k-ε model and the Fluent software were used to simulate methane distribution according to the principle of the conservation equation in a state of turbulent flow. The results show that after overflow-ing,a methane level with a certain thickness is formed. Methane density curves at three specific levels were internally consistent and methane density at higher levels is denser than that at lower levels. Methane distribution becomes thinner in the direction of wind and methane in the vertical direction becomes uniform if wind speed is high. The distance be-tween sensors and roof should be less than 300 mm which is in agreement with mine safety regulations.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.2020QN69)。
文摘Methane is an explosive gas in coalmines and needs to be monitored by methane sensors.Conductivetype methane sensors are small,simple and stable,and they are very promising for mining safety or home safety applications.They can even be employed in mining Internet of things if the power consumption can be lowered down to few milliwatts.Many researches of nanomaterialsbased conductive-type methane sensors have been reported recently.This review intends to present a comprehensive and critical summary on the recent progresses in the nanomaterials-based conductive-type methane sensors field.Many excellent methane-sensitive nanomaterials will be present,such as SnO2,ZnO,TiO2,WO3,carbon nanotubes,graphene,rare earth metal-based perovskite oxides and their hybrids.Particular attention is given to the synthetic methods of the nanomaterials,sensing mechanisms of the nanomaterials and the relationship between the sensing performance and the structures and components of the nanomaterials.Finally,the future trends and perspectives of nanomaterials-based conductive-type methane sensors are proposed.
基金Projects 50534080 supported by the National Natural Science Foundation of ChinaNCET-05-0602 by the Program for New Century Excellent Talents in Universities of China2006KJ019B by the National Natural Science Foundation of Anhui Province Education Office
文摘To improve the reliability of coal mine safety monitoring systems we have analyzed the characteristics of a methane sensor, an important component of the monitoring system of production safety in a coal mine and studied the main type and mode of faults when the sensor was used on-line. We introduced a new method based on artificial neural network to detect faults of methane sensors. In addition, using the output information of a single methane sensor, we established a sensor output model of a dynamic non-linear neural network for on-line fault detection. Finally, the fault of the heating wire of the sensor was simulated, indicating that, when the methane sensor had a fault, the predicted output of the neural network clearly deviated from the actual output, exceeding the pre-set threshold and showing that a fault had occurred in the methane sensor. The result shows that the model has good convergence and stability, and is quite capable of meeting the requirements for on-line fault detection of methane sensors.
基金Supported by the National Natural Science Foundation of China(60910005)
文摘Based on the deficiency of catalytic elements in methane sensors such as sintering,activity decrease and surface area reduction at high temperature, three differentnano vectors Ce-Zr-Al_2O_3, Ce-Al_2O_3, and Zr-Al_2O_3 were prepared via sol-gel technique inthe experiment.BET surface area, catalytic activity and thermal stability were tested andcompared.It is found from the experiment that the Ce-doped Al_2O_3 vector possesseshigher catalytic activity than pure Al_2O_3 vector.Zr-doped Al_2O_3 vector can enhance thethermal stability of methane sensors.Ce-Zr-Al solid solution can be obtained by the presenceof Ce and Zr doped with Al_2O_3.The reaction activity and thermal stability of catalyticsensors were improved because of the unique synergy effect from Ce-Zr-O.Among themixed cocatalysts, Ce-Zr-O was reported to be an excellent cocatalyst material.The performanceof methane sensors can be improved significantly via the modification ofCe-Zr-Al_2O_3 vector.
文摘Based on spectrum principle and analyzing the infrared absorption spectrum ofmethane, a kind of optical fiber methane gas sensor and its system are developed. DFBLD(Distributedfeedback laser diode) in 1 300 nm waveband is used as illuminant and phase-detecting technology isused to carry out harmonic wave detecting the concentration of methane. The sensitivity can arriveat 10^(-5). Experiments results show that the performance targets of the sensor such as sensitivitycan basically satisfy the requests of methane detection.
文摘This report presents the results of experiments to evaluate a prototype fiber optic methane monitor exposed to smoke using a smoke chamber to simulate atmospheric conditions in an underground coal mine after a fire or explosion. The experiments were conducted using test fires of different combustible sources commonly found in mines —douglas-fir wood, SBR belt, and Pittsburgh seam coal. The experiments were designed to assess the response of the fiber optic methane sensor to different contaminants,different contaminant levels and different contaminant durations produced from the test fires. Since the prototype methane monitor detects methane by measuring absorption at a specific wavelength, optical power at the absorption wavelength(1650 nm) was measured as a function of smoke concentration and duration. The other sensor response parameter-methane response times-were measured between smoke tests to assess the impact of soot accumulation on the sensor. Results indicate that the sensor screen effectively prevented smoke from obscuring the optical beam within the sensor head, with minimal impact on the system optical power budget. Methane response times increased with smoke exposure duration, attributed to soot loading on the protective screen.
基金supported by grants from the Key Project of National Natural Science Foundation of China(No.50534100)2008 Undergraduate Creative Foundation of Taiyuan City(No.08122055).
文摘Methane gas sensor was fabricated based on electrocatalytic properties of the Pd/MWNT nanocomposites on indium tin oxide （ITO） glass substrates. A linear response for methane was obtained in the range of 0-16% （v/v） with a detection limit of 0.167% （v/ v） and R.S.D. of 4.1%. After 100 times sensing or stable stored more than 12 months in atmosphere, unconspicuous measurable decrease was observed. The response time was less than 60 s at room temperature and ambient pressure. Some common potential interferents in samples such as N2, CO, CO2, ethane, propane, pentane, methanol, ethanol, H2 and NH3 were investigated and all the effects were less than 5% on the response for 3.0% （v/v） methane. The sensor was applied to methane determinations in man-made gas samples, the results are satisfied.
基金Supported by the National Key R&D Program of China(No.2017YFC0306701)the National Natural Science Foundation of China(No.41106052)the Fundamental Research Funds for National Nonprofit Institute Grant(No.JG1511)
文摘Continental margins in world oceans contain large amounts of marine gas hydrates. Changes in the temperature and pressure of sediment may destabilize the methane hydrate, leading to its release and seepage into the sea. This process would increase the dissolved methane in the ambient seawater. In this study, a methane sensor was used to detect methane anomalies in the water column in southwestern Dongsha and Shenhu, northern slope of the South China Sea. Methane plumes were detected at stations SCS001 and T001 in the southwestern Dongsha area, and station SCS002 in the Shenhu area, respectively. The maximum methane concentrations were 8.8 nmol/L in southwestern Dongsha and 10.1 nmol/L in Shenhu, which are about 4–5 times higher than the background methane concentration. This indicates that there are active methane seepages present in both the southwestern Dongsha and Shenhu areas, which are likely related to a methane hydrate reservoir beneath the seafloor. A methane sensor with a low detection limit is a practical instrument with which to detect methane plumes in oceanic environments and to monitor methane leakage from the seafloor.
基金financially supported by the National Natural Science Foundation of China(No.12174092,21902046,U21A20500)Overseas Expertise Introduction Center for Discipline Innovation(D18025)+1 种基金Hubei Provincial Department of Science and Technology(No.2019CFA079)Wuhan Science and Technology Bureau(2020010601012163)
文摘Development of metal oxide semiconductors-based methane sensors with good response and low power consumption is one of the major challenges to realize the real-time monitoring of methane leakage.In this work,a self-assembled mulberry-like ZnO/SnO_(2)hierarchical structure is constructed by a two-step hydrothermal method.The resultant sensor works at room temperature with excellent response of~56.1%to 2000 ppm CH_(4)at 55%relative humidity.It is found that the strain induced at the ZnO/SnO_(2)interface greatly enhances the piezoelectric polarization on the ZnO surface and that the band bending results in the accumulation of chemically adsorbed O_(2)^(-)ions close to the interface,leading to significant improvement in the sensing performance of the methane gas sensor at room temperature.
基金The 2019 Ministry of Education industry-university cooperation collaborative education project“Research on the Construction of Economics and Management Professional Data Analysis Laboratory”(Project number:201902077020)。
文摘Oil and gas pipeline transportation,as a relatively safe way of oil and gas transportation,undertakes most of the transportation tasks of crude oil and natural gas.Oil and gas pipeline accidents affect a wide range of consequences.Therefore,the oil and gas pipeline leakage detection is paid more and more attention.In this paper,ultra-low power methane gas sensor is selected to collect methane gas concentration in the air,and wireless network technology is used to build a wireless network sensor system with 4G function.Through the sensor distribution along the pipeline,it can intuitively and accurately judge whether there is a micro-leakage in the pipeline,and understand the diffusion situation after the leakage.The sensor system has high reliability and stability,and has high value of popularization and application.
文摘<span style="font-family:;" "=""><span style="font-family:Verdana;">Methane is released from waste disposal areas as a result from anaerobic decay of food. Methane causes more greenhouse effects than carbon dioxide so a methane monitoring system is required to warn its release from gas emitting environments. The low explosive limit of methane is 5% in ambient air, so gas leakage is dangerous and can produce explosions. An entire head monitoring system was built around a MQ-4 methane gas sensor as it is cheap and reliable. The design proves to be flexible enough as it can measure CH</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> emissions in ducts, CH</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> in landfills at different depths and even in cattle barns. The measuring system head consists of a suction pump, solenoids, and a methane sensor. Measurements are taken 13 seconds after methane gas sucking. </span><span style="font-family:Verdana;">A timing of 100 seconds is required for purging the chamber before the</span><span style="font-family:Verdana;"> second solenoid is turned-on. Devices temperature during operation was sampled with a thermal Flir-One camera and solenoid coil temperature was of 24.9</span></span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="white-space:nowrap;">˚</span>C </span><span style="font-family:Verdana;">after a continuous operation of 30 seconds. As hoses for emission sampling</span><span style="font-family:Verdana;"> become larger time for sampling increases as well as energy consumption.</span></span>
