Effect of SO₂ Co-Feeding on CO₂ adsorption capacity of south african coals during CO₂ sequestration

The effect of SO₂ in feed stream on CO₂ sorption capacity of unmineable South African coal seams during CO₂ sequestration was studied. Laboratory studies were carried out using a synthetic flue gas (99.5% CO₂/ 0.5% SO and 98.5% CO₂/1.5% SO₂) in a high pressure volumetric experimental setup connected with an on-line gas-chromatograph was used. The experiments were performed in dry and moisture-equilibrated (1.5 - 4.5 %) state at 35 °C and pressured up to 90 bars. The adsorption experimental data was fitted on existing adsorption models to understand the adsorption behaviour of the coal seams. The results showed that the presence of SO₂ and moisture of the coal significantly reduce the sorption capacity of CO₂. However, pressure increase from sub-critical to super-critical positively enhanced the CO₂ adsorption capacity of the coal samples studied. These results support the need for desulphurization of the flue gas before compression and storage in unmineable coal seams. In addition, the type of coal (properties), injection pressure and coal seam moisture play a vital role in the sequestration process.