Catalytic Fluidized-Bed Combustion. Enhancement of Sulfation of Calcium Oxide by Iron Oxide

A small amount of iron oxide coated on the surface of dolomite particles substantially increases both the reaction rate and the ultimate capacity for sulfur dioxide sorption. Although the iron oxide coating catalyzes the sulfation of Tymochtee dolomite, it has an inhibiting effect on Greer limestone. The interplay of two opposing effects, increase in the chemical rate and a decrease In pore diffusion rate due to pore plugging, has been demonstrated by experiments with pellets made from pulverized Greer limestone. All kinetic data were fitted with a pore closing model with a varying porosity in the product layer. For Tymochtee dolomite with 1.08% (by weight based on CaO) Fe₂O₃ coated on uncalcined stone, it has been shown, through a model, that for 90% sulfur retention a 40% reduction of the sorbent requirement can be achieved over the uncatalyzed case. FlukJization tests at 900°C showed that no additional attrition of the sorbent particles was caused by the coated iron oxide.