A unique process for regenerating calcium-based sorbents which are in
the form of calcium sulfide was demonstrated by employing thermogravim
etric analysis (TGA). The process converts calcium sulfide to calcium
oxide by subjecting particles of the material to repeated cycles of ox
idation and reduction at temperatures between 950 and 1100 degrees C.
During each cycle a small portion of material is first converted to ca
lcium 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 sulf
idation and regeneration of typical calcium-based sorbents seems to en
hance 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.