In this paper we develop a distributed parameter model for a fixed bed vapor recovery reactor (VRR) in a carbothermic aluminum process. The model we develop for the reaction mechanism is based on the mass transfer limited (shrinking core) reaction scheme. This model is combined with the partial differential equations (PDEs) describing the component mass and energy balances. The system of PDEs is converted to a large system of differential algebraic equations (DAEs) using the method of lines. The large scale system of DAEs is solved using a DAE solver. The theoretical results have been compared to experiments, showing that the model predicts the reactor's behavior. Sensitivity analysis has been applied to the model using two important variables, gas superficial velocity and gas composition. (C) 2004 Elsevier Ltd. All rights reserved.