For the re-use as a bed material of sulfated dolomite from fluidized bed combustion of residual oils, calcium sulfate was regenerated to calcium oxide. High temperature regeneration with CO was carried out in a fluidized bed of sulfated dolomite. As a result the use of higher temperature and lower CO concentration increased CaO regenera-tion under the conditions studied. 80-90% of CaO regeneration was obtained by use of 10 mol% CO at temperatures above 1050°C. The regeneration of CaSO4 was not influenced by the initial sulfated level of dolomite and the kind of reducing gas. In the preceding work CaS was not regenerated sufficiently, while in this study CaS was regenerated completely by two-step regeneration using air and CO. In the sulfided NiO-dolomite or sulfated Fe2O3-dolomite which was used as a catalyst in gasification or fluidized bed combustion of vaccum residue, regeneration was more difficult than that of sulfided or sulfated dolomite.
