Sulphur Dioxide Abetment Using Synthesized South African Limestone/Siliceous Sorbents

This study presents experimental findings on the preparation and characterization of locally available fly ash, CaO obtained from calcination of limestone in a laboratory kiln at a temperature of 900oC and CaO/ siliceous sorbent prepared using an atmospheric hydration process. The sorbent was prepared under different hydration conditions: CaO/ fly ash weight ratio, hydration temperature (55 - 75oC) and hydration period (4-10 hours). The sorbents were then tested in a fixed bed reactor for the removal of SO2 at 87 oC and relative humidity of 50 %. The chemical composition of both the fly ash and calcined limestone had relatively high Fe2O3 and oxides of other transitional elements which provided catalytic ability during the sorbent sorption process. All the three hydration variables had both individual and interactive effects on SO2 sorption capacity. Generally the sorbents had higher SO2 absorption capacity compared to calcined limestone or fly ash alone. The sorbents had mesoporous structure larger pore volume and BET specific surface area than both calcined limestone and fly ash, the starting materials. The X-ray diffraction (XRD) analysis showed the presence of complex compounds containing calcium silicate hydrate in the synthesized sorbents.