Estimating the limiting absolute sorption of carbon dioxide by coal for coal-bed storage of carbon dioxide

This paper estimates the limiting absolute sorption of carbon dioxide by five coals using the isotherm space transformation (IST) method. Estimating the maximum number of moles that can accumulate in a unit mass of sorbent, regardless of pressure and temperature is useful for estimation of the carbon dioxide storage capacity of an underground coal reservoir. The IST method captured the behaviour of the coal-carbon dioxide system for representative ranges of pressure and temperature and generated sorption isotherms for any temperature within the range. For the investigated pressure and temperature range, a good fit was found between the experimental points and the regression curve. It is reasonable to assume, therefore, that the equation well captured the behaviour of the coal-CO2 systems studied. The value of limiting absolute sorption was found to be inversely proportional to the mineral matter content. No relationship was established between the petrography of the investigated samples and the sorption (or storage) capacity of the coal. The results suggest that in the subcritical pressure range, the sorption capacity is not directly correlated with the limiting absolute sorption values.