In this work, a mathematical model is developed for simulating the behavior of a direct reduction moving bed reactor for the production of sponge iron. The pellet scale model is based on a grain model with product layer resistance. The reactor is modeled through a nonisothermal, steady state, heterogeneous model. Model predictions show good agreement with the data of Foolad Mobarake plant (Isfahan, Iran). Finally, the effects of reducing gas parameters and pellet characteristics on the reduction extent have been investigated. (C) 2010 Elsevier B.V. All rights reserved.