Testing of a highly reactive impregnated Fe2O3/Al2O3 oxygen carrier for a SR-CLC system in a continuous CLC unit

A Fe-based oxygen carrier was evaluated for H2 production with CO2 capture by coupling steam reforming of methane and chemical–looping combustion processes (SRCLC). In this process hydrogen is obtained by conventional steam reforming of methane (SR), and the heat necessary to carry out the endothermic reformed reactions is supplied by a chemical-looping combustion (CLC) system with inherent CO2 capture The tail gas from the PSA unit, a mixture of CH4, H2, CO and CO2, is used as fuel in the CLC system. The Fe-based oxygen carrier was made by incipient hot impregnation using Al2O3 as support and was first characterized by TGA and batch fluidized bed reactor in order to determine the reactivity for CH4, CO and H2 and the fluidization behaviour. The oxygen carrier behaviour with respect to gas combustion was evaluated in a continuous CLC unit using a simulated PSA off-gas stream as fuel. Methane was also used as fuel for comparison purposes. During 46 h of continuous operation, the OC never showed agglomeration problems or carbon deposition, and the loss of fines due to attrition was moderate. It was found that the fuel composition has low effect on the combustion efficiency and full conversion can be obtained at 880ºC with an oxygen carrier-to-fuel ratio > 1.5. The solids inventory needed to fully convert methane or PSA-offgas was found to be lower than those found with other Fe-based materials, both natural and synthetic. These results were due to the important positive effect of using alumina as support for impregnated Fe-based OC on the oxygen carrier reactivity. Therefore, the Fe2O3/Al2O3 oxygen carrier prepared by impregnation is suitable for burning a PSA tail gas for the H2 production with CO2 capture in the SR-CLC process.