Sulfur/Alkali/Calcium Oxide Sorbent Interaction in Pressurized Coal Combustors

Modeling and bench-scale experiments have been performed related to the capture of fuel-bound sulfur by calcium-based sorbents injected into pressurized coal combustors. Sorbent types tested include two limestones, a dolomite, a slaked lime, and a pressure-hydrated dolomite, with and without several sodium-based mineral promoters present. Sulfur capture data have been obtained at pressures up to 10 atm. These data have been incorporated into the porous sorbent model of Simons and Garman (6). Modeling of lean turbine combustors indicates that in-situ injection of pressure-hydrated sorbents should remove greater than 50 percent of the SO₂ at 10 atm and 0.5 sec residence time. Furthermore the presence of alkali minerals in the coal can enhance the intrinsic reactivity by a factor of two or more. Conveniently, the calcium sorbent can serve as a site for alkali condensation and removal.