Experimental measurements of CO₂ adsorption on Indonesian low-rank coals under various conditions

In this study, the CO₂ adsorption capacity was measured on Indonesian low-rank coals in the raw and dry conditions in powder and block states using different coal sample preparation to estimate CO₂ sequestration and storage potential. Coal sample specimens were taken from three different areas in the South Sumatra Basin, Indonesia. The adsorption experiments were performed using the volumetric method at a temperature of 318.15 K and pressure up to 3 MPa. The CO₂ excess adsorption capacity of powder coal is always higher than block coal. Moreover, decreasing moisture content by the drying process increases CO₂ adsorption capacity on coal. Based on fitted CO₂ adsorption experimental data with the Langmuir and Freundlich isotherm model, the adsorption occurs on monolayer and multilayer at various conditions. Langmuir volume capacity and pressure show drying and crushing process increased adsorption capacity. However, the drying process affects more the capability of coal to adsorb CO₂ than the powdered sample, especially in low-rank coal. It was also observed adsorption capacity is directly proportional to huminite content in the coal. Due to lower moisture and higher huminite contents, the dried WB coal powder had the highest CO₂ adsorption capacity over the other coal samples in similar sample conditions. Altogether, this study may provide a better understanding in CO₂ adsorption on low-rank coal with different coal sample preparation resulting in different CO₂ adsorption capacity.