Dynamic Modeling of Fixed-Bed Fischer-Tropsch Reactors with Phase Change Material Diluents

A simplified transient model for fixed-bed reactors was extended to account for the heat sink effect of the phase change material diluent in the Fischer-Tropsch reactor energy balance. The resulting model was found to accurately approximate the more rigorous two-dimensional model with significantly less computational requirements even at the hotspot, where the reactor enthalpy balance is most sensitive. As anticipated, the presence of the encapsulated phase change material in the reactor induced thermal inertia, thereby restricting the temperature ramp rate in the reactor to acceptably safe operational limits for the catalyst. Although there was a reduction in both the CH4 and C5+ productivity, the reduction in CH4 production was up to four times that of the C5+ at the same coolant temperature.