A simple and low-cost integrative sensor system for methane and hydrogen measurement
Résumé
Energy production by methanization or gasification of biomass is dependant on the chemical composition of the gas generated. The resistive sensors based on semiconductor metal oxides, like the MQ series sensors, are inex-pensive and frequently used in gas detection. These sensors, initially dedicated to detecting gas leaks in safetysystems, have relatively small measurement ranges (i.e. limited to concentrations below 10,000 ppm). It istherefore necessary tofind solutions to adapt these categories of sensors for gas measurements in the energysector where the gas concentration is much more significant. In this article, we propose a protocol using anadaptable capsule for MQ-4 and MQ-8 sensors to measure high concentrations of CH4and H2respectively. Thetechnique consists of diluting the gas to be studied in a known volume of air. Three methods are proposed andcompared regarding the linearity and the repeatability of the measurements. Thefirst method was done in anairtight enclosed chamber, the second method consists of directly injecting the gas on the sensor placed in an openenvironment, and thefinal method was accomplished by direct injection of the gas on the sensor placed in apartially closed capsule. Comparisons show that thefirst technique provides the best repeatability, with amaximum standard deviation of 13.88% for CH4measurement and 5.1% for H2. However, its linearity is weak(i.e. R2¼0.8637 for CH4and R2¼0.5756 for H2). The second technique has better linearity but bad repeatability.The third technique presents the best results with R2values of 0.9973 for the CH4measurement and 0.9472 forH2. The use of the partially closed capsule resulted in an acceptable linear response of the sensors by up to 20%concentration of CH4and until 13.33% concentration of H2in the studied gas. The use of this simple and low-cost technique facilitates the characterization of combustible gases in isolated areas. It allows local operators ofbiomass valorization systems to control and improve their installations while avoiding the high costs of con-ventional measurement devices. This study, hence, contributes to the development of rural electrification projectsin remote area
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