The development of alternative technologies for the removal of gas pollutants is an important aspect for the environmental friendliness of energy production. During coal gasification, N2 contained in coal is converted to NH3 and, as much as 50% of the ammonia in the fuel gas can be converted to nitrogen oxides (??x). At these conditions, decomposition seems to be the only applicable solution for the removal of NH3. The application of a high temperature catalytic membrane reactor process appears to offer an efficient and cost effective method of removing the NH3 from coal gasification gas streams.The present work examines the operation of such a selective membrane, used for the decomposition of NH3, under a 2-D axissymetric CFD approach where the flow field, the chemical reactions and the selective porous membrane behavior are being modeled and computed. The main target of this effort was to obtain a more detailed view of the flow field and to investigate the decomposition of ammonia in comparison with a simpler 1-D modeling approach and, thus, to evaluate the advantages and disadvantages of each method.