Many chemical processes utilize catalysts to enhance chemical conversion behavior. A catalyst promotes the rate of chemical conversion but does not affect the energy transformations which occur during the reaction. The present study is focused primarily upon the performance and efficiency analysis of steam-methanol reforming processes in combined parallel plate heat exchanger-reactors. The steady-state continuity, momentum, energy, and species conservation equations are solved in the fluid phase and the heat equation is solved in the solid phase using a finite volume approach. An adaptive meshing scheme is used for the discretization of the differential equations. Computational fluid dynamics simulations are carried out over a wide range of material conductivities. Continuity in temperature and heat flux is applied at the fluid-solid interfaces. Neither heat-transfer nor mass-transfer correlations are employed. Parallel processing employing a message passing interface is used to speed up the most demanding calculations. The present study aims to explore how to effectively enhance chemical conversion behavior by utilizing catalysts. Particular emphasis is placed upon the effect of wall thermal conductivity on the performance and efficiency of steam-methanol reforming processes in combined parallel plate heat exchanger-reactors. The results indicate that the arrangement leads to improved heat transfer and therefore chemical conversion. The honeycomb structure imparts strength to the overall system permitting the walls to be very thin and thereby being responsible for the low weight and rapid thermal response of the reactor configuration. The heat transfer from the process catalyst to the dividing wall is highly efficient, however, the uptake of the energy by the heat transfer fluid will suffer from all of the limitations of traditional heat transfer operations. The process provides more efficient utilization and uniform usage of the heat generated by the exothermic reaction, thus allowing the endothermic reaction to be carried out at a somewhat higher temperature. The temperature control possible with this system is extremely efficient because all the catalytic material in the reactor channels is on the surface of the walls that can transmit heat through the walls directly to the thermal control channels. Adiabatic conditions prevail in the autothermal reactor because the catalytic oxidation reaction is exothermic in nature and the heat generated in the course of such a reaction is usually sufficient to initiate and sustain the endothermic reforming reaction. The thickness of the catalyst coating depends upon the process proceeding within the catalyst matrix. The thin walls and small internal diameters of the channels result in an extremely difficult system for carrying out reactions and transferring heat by giving rise to a high ratio of wall surface area.

Keywords: Chemical processes; Autothermal reactors; Heat transfer; Reaction chambers; Heterogeneous oxidation; Transport phenomena