Modeling and optimization of the mixed reforming of methane: Maximizing CO2 utilization for non-equilibrated reaction

In the present study, a reactor model for mixed reforming over Ni-based catalyst was developed to investigate non-equilibrium behavior and reactions. Kinetic parameters were estimated by fitting experimental data for CH4 and CO2 conversions and H2/CO ratios under a variety of conditions, and the CO2 consumption rate was shown to be significantly affected by operating conditions due to the different characteristics of each reaction: dry reforming (DRM), steam reforming for the production of CO (SRM1) and CO2 (SRM2), and the water-gas shift (WGS) reaction. For optimization study, a reactor composed of three sections with different inert fractions and wall temperatures was considered, and optimization was conducted using various weighting factors on the CO productivity and the CO2 consumption per unit CO productivity; when maximum CO2 consumption per CO productivity was achieved, inert fraction of the first part of the reactor was lowered and wall temperature for the third part of the reactor was decreased, compared to maximum CO productivity case. Further analysis of instantaneous reaction rates showed that, in the case of maximum CO2 consumption, one third of the later part of the reactor could be obviated, resulting in an increase in CO productivity per unit volume, that is, the efficiency of the reactor. As a result, the strategy in the present study was successfully applied in the design of a mixed reforming reaction process providing maximum CO2 conversion as well as minimum CO2 emissions while reducing energy costs.