HYDROGEN-SULFIDE CAPTURE BY LIMESTONE AND DOLOMITE AT ELEVATED PRESSURE .1. SORBENT PERFORMANCE

Sulfur emission control in fossil fuel gasification plants implies the removal of H2S from the product gas either inside the furnace or in t he gas clean-up system. In a fluidized-bed gasifier, in-bed sulfur cap ture can be accomplished by adding a calcium-based sorbent such as lim estone or dolomite to the bed and removing the sulfur from the system with the bottom ash in the form of CaS. This work describes the H2S up take by a set of physically and chemically different limestones and do lomites under pressurized conditions, typically for those in a pressur ized fluidized-bed gasifier (2 MPa, 950 degrees C). The tests were don e with a pressurized thermobalance at two p(CO2) levels. Thus, the sul fidation of both calcined and uncalcined sorbents could be analyzed. T he effect of p(H2S) was also investigated for uncalcined limestones an d half-calcined dolomites. The results are presented as conversion of CaCO3 or CaO to CaS vs time plots. The results are also compared with the sulfur capture performance of the same sorbents under pressurized combustion conditions.