CH_4分子光谱分析在井下瓦斯浓度监测中的研究

Research on Concentration Detection in Mine Based on Spectra Analysis of CH_4 Molecular

根据CH4中C-H键特殊的光谱振动吸收特性,设计了基于特征光谱吸收的CH4浓度光谱分析方法,用于矿井下低浓度CH4的高精度实时监测。在分析CH4分子键所对应的特殊光谱吸收波长的条件下,选择傅里叶变换干涉仪作为干涉工具,结合CCD探测器采集干涉条纹,最终经光谱分析算法得到各波长上光强衰减量度,从而反演CH4气体浓度。利用比尔朗伯定理及浓度程长积公式,可以得到CH4的理论最小探测浓度可达到0.1%,实际受环境等影响会有小幅波动,但不影响0.1%的探测精度,完全满足瓦斯浓度为0～5%的井下实时探测要求。计算实验显示,在采用傅里叶变换光谱分析法探测CH4浓度时,数据显示:在长度为10cm的气室中,对浓度介于0～5%的CH4进行探测时,满足探测精度0.1%的实时探测要求。

According to the special spectra vibration absorption characteristics about C--H bond of CH4,the spectra detection system was designed to get CH4 concentration and would be used to monitor CH4 concentration in mine re- al time. By analyzing the special spectra absorption wavelength corresponding to CH4 molecular, Fourier transforma- tion interferometer was chosen and used with CCD detector for gathering interference fringes. The intensity attenua- tion of laser could be analyzed by spectra analysis algorithm, and CH4 concentration could be inferred by Lambert- Beer theorem with the least detection precision of 0.1%. The detection precision could be reduced by environment, but it still kept to 0.1%. The computation experiment demonstrated that the system was satisfied with the real-time detection precision of 0.1% in the air chamber with 10 cm length for detecting CH4 concentration from 0 to 5%, when using Fourier transformation spectrophotometric method.