Effect of coalbed methane airflow with optimum action concentration on coal oxidation under low temperatures

Abstract

To explore the effect of coalbed methane (CBM) airflow on coal oxidation under low temperatures, an experimental apparatus was developed and applied to simulate coal oxidation under different oxidizing atmospheres. The formation of carbon monoxide CO, the index gas, in CBM airflow was analyzed to obtain the optimum concentration of CH4 that exerted the strongest influence on coal oxidation. Then, a comparison experiment was performed on coal oxidation in dry air and in CH4 at the optimum concentration by using electron spin resonance (ESR) and Fourier transform infrared (FTIR) technology. The results suggest that 25% of CH4 has the strongest effect on coal oxidation at low temperatures. The free radical concentration (Ng) in coal increases with temperature in both dry air and 25% CH4. At this concentration, CH4 can inhibit the reactivity of coal substantially while raising the excitation temperature. The oxidation of aliphatic hydrocarbons is severely inhibited by 25% CH4, which reduces its consumption rate and abates its decrement in the initial phase. Although 25% CH4 restricts the consumption of –OH and –COOH in oxidation, it promotes the formation of –C–O.