Macro and micro-mechanism of effect of EMF on CBM adsorption in coal

Coal bed methane (CBM) exploitation can solve problems of gas catastrophe and "greenhouse effect" caused by its release and it can also be utilized as a clean energy resource. In China reserves of CBM are very high, but seventy percent of this exist in low permeability coal seams. So CBM exploitation is very difficult. This paper describes the experimental results of effect of electromagnetic field (EMF) on CBM adsorption in coal and analyzes the macro- and micro-mechanism. The experiments show that alternating electromagnetic filed can enhance the desorption rate of methane and increase the initial desorption quality. The following mechanism can be obtained according to theory of dielectric physics and surface physical chemistry. In macrocosm EMF can cause rise in coal body temperature because of dielectric loss and cause decrease in quantity of methane absorption in coal. In microcosm adsorption of methane on coal surfaces is due to the results of electric interaction of methane and coal surfaces molecules. Therefore, EMF can change these attractions, decrease the adsorption potential energy barrier and quantity of methane absorption in coal. So CBM exploitation with EMF is a very promising method.