AN653 – Methane adsorption into coal measured by PCTPro-E&E


Coalbed methane is an important source of energy in many countries. In contrast to a conventional gas reservoir, methane is stored by adsorption into pores of the coal. In underground coal mining, it presents a serious safety risk and is one of the leading causes of coal mine accidents. Thus characterization of methane uptake is essential to development of new technologies to harness energy while mitigating environmental and underground mining risks. This application note shows the results of methane adsorption into a coal sample at room temperature and up to 150 bar. AN-653


CH4 adsorption into a bituminous coal sample was measured at 25 °C using a PCTPro E&E Sievert’s apparatus which was developed to study sorption of a variety of gases from vacuum up to 200 bar and from liquid He to 500 °C. Gas density temperature correction was done by measuring the apparent free gas volume at temperature. The density of the entire sample was assumed to be 1.4 kg/m3


The PCT isotherms of CH4 adsorption and desorption for Illinois bituminous coal are shown in Figure 1. The methane uptake is twice lower than that of CO2 reported for the same sample in AN654. Methane physisorbs into coal, thus its uptake depends on pore volume available in coal. The methane uptake 20 ml gas STP/ml sample at 40 bar is consistent with literature values for similar coal samples (4-25 ml gas STP/ml sample at 40 bar). The methane (or CO2) uptake variations are due largely to geological history and preparation of the sample. The PCTPro E&E is well-suited for the detailed characterization of coal used in the study.