Gas-producing characteristics of cemented gangue-fly ash backfill and its influence on false alarm of CO monitoring in coal mines

Abstract

The filling mining practice in coal mines shows that the gases produced by the reaction within the cemented gangue-fly ash backfill slurry causes CO monitoring errors. In this study, two slurries with the coarse aggregate and fine aggregate schemes in the filling mining are used to investigate the gas-producing characteristics and mechanism, and the effect of gas composition on the electrochemical CO sensor for mining is also studied. Results indicate as the reaction of the slurry continues, the concentrations of O₂ and CO₂ decrease, while the concentrations of CO, CH_4, and H₂ increase, and the mechanisms of gases consumption and production are obtained by comparing the crystal structure of CGFB slurry before and after reaction. Furthermore, H₂ is the primary factor causing the false alarm of the electrochemical CO sensor and has a positive cross-interference, which is quantified by interference factor Q. Q value is mainly affected by H₂ or CO concentration when H₂ concentration is lower or higher than 30 ppm, respectively. Meanwhile, an effective method is proposed to solve the false alarm of the electrochemical CO sensor by correcting the measurements using dynamic Q and the on-site H₂ concentration, and the absolute error of the corrected value is less than 1 ppm.