The syngas chemical looping process co-produces hydrogen and electricity from syngas through the cyclic reduction and regeneration of an iron oxide based oxygen carrier, hi this article, the reducer, which reduces the oxygen carrier with syngas, is investigated through thermodynamic analysis, experiments, and ASPEN Plus simulation. The thermodynamic analysis indicates that the countercurrent moving-bed reducer offers better gas and solids conversions when compared to the fluidized-bed reducer. The reducer is continuously operated for 15 h in a bench scale moving-bed reactor. A syngas conversion in excess of 99.5% and an oxygen carrier conversion of nearly 50% are obtained. An ASPEN Plus (R) model is developed which simulates the reducer performance. The results of simulation are consistent with those obtained from both the thermodynamic analysis and experiments. Both the experiments and simulation indicate that the proposed SCL reducer concept is feasible. (C) 2009 American Institute of Chemical Engineers AIChE J, 56: 2186-2199, 2010