Research on CH4 Gas Detection and Temperature Correction Based on TDLAS Technology
MA Li1, 2, FAN Xin-li1, 2, ZHANG Shuo1, 2, WANG Wei-feng1, 2, WEI Gao-ming1, 2
1. School of Safety Science and Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
2. Shaanxi Provincial Key of Coal Fire Hazard Prevention and Control, Xi’an University of Science and Technology, Xi’an 710054, China
Abstract：Accurate detection of CH4 is essential to prevent gas explosion and ensure safe production. However, the gas detection technology based on tunable diode laser absorption spectroscopy (TDLAS) has a large error due to temperature change. This paper explored the CH4 detection based on TDLAS technology and the temperature compensation method, analyzed the impact of temperature on CH4 absorption line, and finally eliminated the impact of environmental temperature on the CH4 detection through algorithm compensation model. This study used TDLAS technology’s principle and theory to design the transmitter unit, absorption cell, signal receiver unit and data processing unit. A CH4 detection system based on TDLAS technology was established, the concentration of CH4 at different ambient temperatures (10~50 ℃) was measured, and the effect of temperature change on the intensity and half width at half-maximum of CH4 absorption line at 1.653 μm was analyzed. In order to eliminate the influence of temperature on CH4 detection and improve the compensation effect, the particle swarm optimization (PSO) was employed to optimize the optimal weight and the threshold of back propagation neural network (BPNN). The PSO-BP temperature compensation model of CH4 was established, which overcame the characteristics of slow convergence rate and easy to fall into local optimum of the BPNN The result indicated that: (1) Based on TDLAS technology, the CH4 detection concentration dropped with the increasement of ambient temperature, the relative error range within the whole experimental temperature was 4.25%~12.13%. The relationship between CH4 detection concentration and temperature under different ambient temperatures can be expressed as a cubic polynomial; (2) The absorption intensity and half width at half-maximum of CH4 gas decrease with the increase of temperature relationship between it and temperature was a monotonous decreasing function. The relative change rate of temperature on the absorption line intensity of CH4 gas was greater than the half width. The absorption line intensity of CH4 gas was more susceptible to the temperature change; (3) The absolute mean error (MAE) of the BPNN and PSO-BP model test samples were 12.88% and 1.81%, the mean absolute percentage error (MAPE) were 2.3% and 0.3%, the root mean square (RMSE) were 15.96% and 2.69%, and the correlation coefficient R2 were 0.980 6 and 0.999 6, respectively. By establishing the PSO-BP temperature compensation model, the compensation effect was mostly distributed within the error range of ±1.0%, and MAE, MAPE, RMSE, R2 and another evaluation indexes were greatly improved. It has a certain reference significance to improve the accurate detection of CH4 in the mine with TDLAS technology.
Key words：Tunable diode laser absorption spectroscopy; CH4 gas concentration; Accurate detection; Neural networks; Particle swarm optimization; Temperature compensation
马 砺，范新丽，张 朔，王伟峰，魏高明. 基于TDLAS技术的CH4气体检测与温度补偿方法[J]. 光谱学与光谱分析, 2021, 41(11): 3632-3638.
MA Li, FAN Xin-li, ZHANG Shuo, WANG Wei-feng, WEI Gao-ming. Research on CH4 Gas Detection and Temperature Correction Based on TDLAS Technology. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(11): 3632-3638.
