The design of gasifiers and their operation has conventionally been an experience based enterprise. Gasification models developed over the years and reported in the literature have not been robust enough to apply to a wide range of operating conditions, gasifier geometries and feedstocks. The primary reason behind this shortcoming is the failure to incorporate submodels that describe the underlying physical and chemical processes with sufficient fidelity. Moreover, in a multiphysics problem like gasification modeling, the researcher is invariably required to balance the effort expended in any submodel with the returns offered in terms of effects on key output parameters.