Regeneration of Sulfided Calcium-Based Sorbents by a Cyclic Process

A unique process for regenerating calcium-based sorbents which are in the form of calcium sulfide was demonstrated by employing thermogravimetric analysis (TGA). The process converts calcium sulfide to calcium oxide by subjecting particles of the material to repeated cycles of oxidation and reduction at temperatures between 950 and 1100 °C. During each cycle a small portion of material is first converted to calcium sulfate by oxidation and then to calcium oxide by reduction. Air can be used for oxidation and any of the following gases can be used for reduction: 30 mol % CO, 5 mol % CH4, or 2 mol % C3H8. Repeated sulfidation and regeneration of typical calcium-based sorbents seems to enhance the reactivity of the materials. However, incorporation of iron oxide or flyash containing an appreciable concentration of iron oxide in the sorbent has a deleterious effect.