Fluidized bed testing of commercially prepared MgO-promoted hematite and CuO–Fe2O3 mixed metal oxide oxygen carriers for methane and coal chemical looping combustion

Abstract

Performance data of two commercially prepared oxygen carriers, MgO-promoted natural mineral hematite (Fe2O3) and synthetic mixed metal CuO–Fe2O3/alumina, are described in this paper. Large, 180-kg (400-pound) batches of both oxygen carriers were successfully prepared at a commercial catalyst preparation facility.These carriers have shown excellent reactivity and stable performance during cyclic chemical-looping combustion (CLC) tests conducted with methane/air at 700–850°C in an atmospheric fluid bed reactor. Attrition resistance of both oxygen carriers with particle size of 100–150μm, measured using the ASTM 5757D method, was better than that of standard fluidized bed cracking catalysts. The presence of MgO on the hematite oxygen carrier significantly improved the oxygen utilization of hematite for methane CLC. The CuO–Fe2O3/alumina oxygen carrier showed excellent performance during the 25-cycle fluidized bed CLC test conducted at 800°C with methane and air. Full combustion of methane to CO2 and stable oxygen transfer capacity were observed during all the cycles. The fluidization of this material was easy, with no particle agglomeration as is traditionally observed with CuO-containing materials. Fluidized bed temperature programmed reaction tests with coal were also conducted with both materials.