621 / 2019-01-20 13:41:08

Predominance area diagrams of CuO, CaSO4 and Fe2O3 reacted with sulfur gas at different temperatures

Chemical Looping Combustion; CaSO4 oxygen carrier; Fe2O3 oxygen carrier; CuO oxygen carrier; SO2; sulfur.

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The chemical stabilities of CaSO4, CuO and Fe2O3 oxygen carriers reductions by sulfur were studied. CaSO4 was reduced to CaS as well as CaO, with SO2 release. While CuO and Fe2O3 oxygen carriers may reduce to Cu2O, Cu and Fe3O4, FeO, Fe, and metal sulfides CuS, CuS2, FeS, FeS2. For CaSO4 oxygen carrier, at the lower partial pressure of SO2, there is an intermediate range, where CaO is the stable species. The range for CaO stability is increasing with reaction temperature, and decreasing with the sulfur partial pressure. For Fe2O3 oxygen carrier, with the increasing temperature, the stabilities of Fe, FeO as well as FeS were enlarging, while those of Fe3O4 and FeS2 are decreasing. For CuO oxygen carrier, higher reaction temperatures are favorable for Cu, Cu2O and Cu2S formations, and unfavorable for CuS formation. In addition, with the increasing of sulfur partial pressure, the solid products are mainly shifted from Fe3O4 →(FeO) →(Fe) →FeS →FeS2 for Fe2O3-S reaction system, and for CuO-S system, the solid products are shifted mainly from Cu2O →(Cu)→Cu2S→CuS. In a real system, when the values of real partials of sulfur, sulfur dioxide and reaction temperature T are controlled in a range, the finial products should be CaS, or Fe3O4, or FeO, or Fe or Cu, or Cu2O, without the formations of CaO or metal sulfides of iron and copper.