Effects of SO2 and ph concentration on CO2 adsorption capacity in coal seams for CO2 sequestration with considerations for flue gas from coal-fired power plants

Coal-fired power plants produce flue gas consisting mainly of nitrogen (around 79%), followed by CO₂ (around 10-15%), and small amounts of other gases such as HO₂, NO_x and SO₂. One of the promising methods for reducing CO₂ emission is CO₂ sequestration into deep, unminable coal seams. At present, flue gases exhausted from coal-fired plant must be separated to extract pure CO₂ before injecting it into coal seams. In order to enhance the efficiency of carbon capture and storage (CCS) from a coal-fired power plant, oxy-fuel combustion technology has been employed. This technology uses pure oxygen to burn the coal, and consequently CO₂ concentration in the flue gas is theoretically increased up to 95%. This study aims to simulate the CH₄ replacement mechanism in coal by using pure CO₂ and a synthesized flue gas (99% CO₂ and 1% SO₂) that is similar to the emission gas from the coalfired power plants. A measurement procedure for gas adsorption is employed which, after establishing methane adsorption equilibrium of the coal samples, injects pure CO₂ or the synthesized flue gas into an adsorption cell in order to investigate CH₄ replacement properties. Coal samples used for the present experiments were taken from the coal seams of Vietnam, Japan, Australia, China and Indonesia. The samples were crushed to particle sizes ranging from 250 urn to 5 mm. The concentration of gases was taken from the adsorption cell and analyzed by using a gas chromatograph. Adsorption isotherms of CH₄, CO₂ and SO₂ were measured by using the volumetric method apparatus. This paper discusses the characteristics of methane replacement by using pure CO₂, the synthesized flue gas and the effect of SO₂ on adsorption properties of coal.