The high operating temperature of a SOFC (solid oxide fuel cell) has several consequences, from which the most important one is the possibility to feed the cell directly with unprocessed fuels. This eliminates the need for expensive external fuel reformers that hinder the cell from achieving a greater overall efficiency when coupled into a power generation system. Direct internal reforming (DIR) takes place directly on the anode of a SOFC by harnessing the available Nickel catalyst on its surface to process the incoming fuel. In this study a three dimensional steady state computational fluid dynamics model is implemented in a planar DIR SOFC to compare the overall cell performance operating on biogas, and coal syngas. Since chemical kinetics plays a significant role in the model accuracy, the present work also focuses on comparing three different chemical reaction mechanisms for the internal reforming process. These include a detailed heterogeneous mechanism consisting of 42 elementary reactions, a global homogeneous catalyzed mechanism, and a Langmuir-Hinshelwood based mechanism. The former includes autothermal reforming, steam reforming and water gas shift reaction effects, the latter two include steam reforming, and water gas shift reaction effects. The analysis yields detailed information about the cell, including polarization curves that help to assess the cell performance for each fuel. Meanwhile the chemical kinetics comparison amongst the analyzed mechanisms helps in establishing the best compromise between the accuracy of the model, and the computational resources devoted for the calculation.

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