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 the gas clean-up system. In a fluidized-bed gasifier, in-bed sulfur capture can be accomplished by adding a calcium-based sorbent such as limestone 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 uptake by a set of physically and chemically different limestones and dolomites under pressurized conditions, typically for those in a pressurized fluidized-bed gasifier (2 MPa, 950 °C). The tests were done with a pressurized thermobalance at two pco₂ levels. Thus, the sulfidation of both calcined and uncalcined sorbents could be analyzed. The effect of pH₂s was also investigated for uncalcined limestones and 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.