Adsorption of carbon dioxide by different coal components

South Africa is a signatory to the Kyoto Protocol as a developing country, and in time may be required to meet certain CO₂ emission reduction targets. Due to the country's reliance on coal as a major energy source and the large petrochemical industries, South Africa is amongst the world's high CO ₂ emitters. Carbon dioxide sequestration into uneconomical coal seams has been proposed as a strategy for carbon dioxide emission reduction as coals have a high gas storage capacity. However, there is a lack of fundamental understanding as to the actual CO₂ uptake and retention mechanisms by the various components in South African coals. Coal is a complex mixture of organic and inorganic components, and varies in composition across the country. Adsorption properties could be enhanced by understanding the CO₂ uptake behaviour of different individual coal macerals, as porosity is related to maceral composition. Typically, vitrinite predominately contains micropores, and inertinite contains mesopores and macropores. Therefore the maceral and microlithotype composition plays a significant role in the porosity and gas transport properties related to CO₂ sequestration. South African coals are typically rich in inertinite, differing from Northern Hemisphere coals, and consequently research results conducted on non-South African coals may not be applicable. The objective of the project is to determine the uptake of CO₂ in a variety of South African coals with varying rank (bituminous coal versus semi-anthracite) and varying maceral composition (vitrinite-rich coal versus inertinite-rich coal, versus mineral-rich coal). Adsorption rate and amount of gas adsorbed will be determined, as well as any CMB release. As CO₂ sequestration is likely to occur in deep coal seams, temperature and pressure could be additional variables.