Dynamics and control of a parallel-plates reactor for ethanol steam reforming thermally coupled with catalytic ethanol combustion

Abstract

This paper analyzes the design and open-loop and closed-loop dynamics of a compact heat-integrated milli-reactor feedback control system for hydrogen production through ethanol steam reforming. The steam reforming is thermally integrated with ethanol combustion in a parallel-plates reactor. The catalysts are washcoated on metal structures separated by metal sheets. The non-steady state is studied using a rigorous modeling of the reactor to characterize the dynamics and identify variables of interest for a control system. Disturbances are caused in temperatures and flowrates, and the outlet temperature, molar composition and hydrogen yield are analyzed. The response, in terms of mass, is almost instantaneous. However, the thermal response is about 300 s until it reaches a new steady state. Flowrate to the reforming section appears as the variable to modify to satisfy changes in H₂ demand. The ethanol feed to combustion section is identified as the most feasible option to be manipulated in a control system of the temperature and composition of the generated syn-gas. The closed-loop study shows the dynamics of the reactor to set-point changes and disturbances by implementing four different control modes. The control shows satisfactory performance when changes in the set-point are applied and in none of the cases the system becomes unstable.