Performance and efficiency analysis of steam-methanol reforming processes in combined parallel plate heat exchanger-reactors
Authors: Chen Junjie 
Published: February 2023

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