Coal, Adsorption

Adsorption refers to the phenomenon by which gas molecules are aligned and arranged in layered form along the internal surface of the micropores under the influence of pressure. After methane gas is generated at the time of coalification, it reaches to the coal matrix full of micropores following the drainage path formed by macropore system and migrates into it through diffusion passing from one pore to the other where adsorption takes place in the micropores.

In context to coal bed methane (CBM), adsorption refers to the mechanism of gas storage within coal bed. The methane gas generated during coalification is stored in the coal bed mainly in three different ways – (a) as adsorbed molecules in the micropores, (b) as free gas in the meso- to macropores (cleat, fracture, cell lumens, etc.), and (c) as gas dissolved in groundwater. Out of these three, the first category is the most significant one as it is mainly responsible for storage of huge quantity of thermogenic methane gas in...