Development of molten bath gasification processes has been proposed for their potential to overcome the disadvantages of conventional gas-solid reaction systems. Coal particles, injected into the molten slag tend to disintegrate, due to high temperatures required to maintain the bath in the molten state, which also favours high reaction rates. Sulphur and nitrogen, which exist in the raw coal and could form polluting compounds, should be retained in the slag. A model of coal gasification in a molten bath gasifier is developed here. The model assumes that overall gasification can be decomposed into three distinct processes: volatile release and combustion (gas-phase combustion), coal-char combustion (solid phase combustion) and coal-char gasification. The polluting elements, ie S and N, present in raw coals, are also included in the reaction scheme. The reaction of S with species contained in the molten slag (mainly in the form of CaO), and the water gas-shift reaction were also considered. This model describes the gasification process regardless of the flow patterns of reactants and products inside the molten slag. However, the residence time of gases in the slag zone, and sulphur retention, are highly dependent on the developed flow field. To account for the fluid dynamic effects, a Fluent CFD code was used to visualise the flow patters of reactants and products. In conjunction with the gasification process, the bubbles were tracked inside the slag reactor based on a Lagrangian approach. For the model, special User Defined Subroutines (UDS) were written in FORTRAN language in order to be compiled and linked with the commercial Computational Fluid Dynamics (CFD) code FLUENT4, which was used for the calculations. The model was initially applied to a 2-D configuration and subsequently to the 3-D one. The 3D calculations, due to plane symmetry, were performed only for one half of the cylindrical reactor, along with the numerical mesh at the outer surfaces and the boundary conditions. Simulation results based on the assumed reactions and the model predicted transport fields show that coal gasification is completed very fast due to the high temperatures prevailing in the molten bath. Initially, solid conversion is due to devolatilisation reactions. Subsequently, coal-char combustion and gasification reactions proceed in parallel, resulting in almost complete solid conversion. The oxygen mass fraction decreases rapidly, since it is consumed due to coal-char and gas phase combustion. CO and H2 mass fractions increase with time as char-CO2 and char-H2O gasification reactions proceed. The obtained results are in good agreement with experimental data, indicating the validity of the established model.