The gas in a coal produced during the coalification process, that is the process of organic material change into peat, lignit, subbituminous, bituminous, till antrachite, as the influenced of pressure and temperature. | The gas in a coal produced during the coalification process, that is the process of organic material change into peat, lignit, subbituminous, bituminous, till antrachite, as the influenced of pressure and temperature. |