CHEMISTRY OF THE CO2-COAL INTERACTION

Geological storage of carbon dioxide in coal seams has emerged as a potential strategy for the mitigation of greenhouse gas emissions. Effective modeling of sequestration scenarios and accurate prediction of sequestration capacities rely on adsorption isotherms to provide relationships between pressure and adsorbed-amount at various temperatures. Investigations at NETL have attempted to provide information about the reliability of these measurements, insight into factors affecting the adsorption capacity, and information about the chemistry/mechanism of the adsorption phenomenon. These studies have included an inter-laboratory comparison of adsorption isotherm reproducibility; the derivation of an adsorption isotherm equation which accounts for the volume effects which may occur when an adsorbate alters the structure of an adsorbent such as is observed when the coal organic matrix swells in the presence of adsorbing gases; an examination of the effects of rank, moisture content, and temperature on the adsorption capacity; and spectroscopic investigations into the nature of the coal-CO₂ interaction(s).