Dynamics and control of autothermal reactors for the production of hydrogen

Autothermal reactors, coupling endothermic and exothermic reactions in parallel channels, represent one of the most promising technologies for hydrogen production. The bulk of existing research work concerning their operation refers, however, to steady state conditions. In the present work, the dynamic behavior of autothermal reactors is analyzed. It is demonstrated that such systems are modeled by systems of equations that are stiff, their dynamics consequently featuring two time scales. Within the framework of singular perturbations, reduced-order, nonstiff models are derived for the transient evolution in each time scale. Furthermore, the challenges posed by the transient operation of autothermal reactors are identified, along with demonstrating the implementation of feedback control in order to improve transient performance and to avoid severe issues (such as reactor extinction) that can arise in the course of operating the reactor. All theoretical concepts are illustrated with numerical simulations performed using the model of a hydrogen production reactor.