Research Of Methane Concentration Detectiong System Based On Spectral Absorption

The coal industry has always been the pillar industry in our country.In recent years,with the wide use of natural gas,electricity and other clean energy,the coal industry is in transformation.Although its advanced mining equipment and automatic production,there has been many coal mine gas explosion accidents every year.Methane is the main component of coal gas,which is flammable and explosive and also can have an effect on the greenhouse.It is very important and significant to do the methane gas concentration of real-time monitoring for safety production and environmental protection.In this paper,it is based on the principle of the spectral absorption and the method of gas second harmonic detection to design the methane concentration detection system,which would analyze the theoretical principle and key technology to design the detection system and test its performance.The main work and achievements of this paper as follows:(1)To study the feasibility of methane detection scheme.This paper analyses the basic principle of spectrum absorption and second harmonic detection method to get the methane absorption lines and various parameters.The choice of methane wavelength measurement is in 1.66?m.Then it has done the simulation of the second harmonic signal based on MATLAB software to verify the feasibility and superiority of detection scheme.(2)The design of the detection module.The current technology is already relatively mature for the choice of light source and the design of chamber in the detection system,which is the good reference value.To pay more attention to the thorough analysis and research for detection module to get the smaller design error and better performance.The detection module would include the high frequency sinusoidal signal circuit based on the NE5532,temperature control circuit based on MAX1968,the preamplifier circuit based on AD8065,the filter circuit based on UAF42,the bipolar phase-locked amplifier circuit based on AD630 and the second harmonic amplitude calculation circuit based on the AD637.The module has the power supply circuit based on TPS65130,which can provide a stable voltage source and voltage range is-9V?+9V.Every circuit in detection module is designed based on the voltage range to ensure the stability of the overall detection performance.(3)The design of signal processing module.It has designed simple signal processing module based on the LabVIEW software,which is a combination of software and hardware.The DAQ data card can collect the data of second harmonic amplitude to send to computer to process and gas concentration directly is displayed in the graphical interface,which is more convenient and humanized.(4)System experiment measurement.It can connect with each module to do the experiments,including the experiment of second harmonic amplitude and methane concentration and so on.It would get a lot of test data,which be analyzed by mapping analysis and compared with the standard values.The detection system can be verified the feasibility of the system both in theory and experiment and its accuracy is better,the error is smaller.