Development of a single stage heat integrated water–gas shift reactor for fuel processing

Compacting of the water–gas shift (WGS) section within a fuel processor for fuel cell based power generation by means of heat integration is presented. The concept of isothermal adiabatic operation is demonstrated. Isothermal adiabatic operation is achieved by dissipating the reaction heat throughout the catalyst support structure by means of thermal conduction. Thus the reactor overall behaves adiabatically, while the catalyst bed is nearly isothermal, while no active heat exchange with a second medium is applied. The concept allows for a much lower feed temperature. Accordingly, the conventional double staged WGS reactors with intermediate heat exchange can be replaced with a single WGS reactor. Two reactor designs, based on aluminum metal foam and aluminum metal monolith were evaluated. For the design of the isothermal adiabatic reactor, the intrinsic kinetics for a noble-metal WGS catalyst was measured and a power law rate equation was obtained. Isothermal adiabatic operation was approached for the foam, mainly hampered by a troublesome catalyst coating. The monolith allows for a simpler reactor design and its performance agreed well with model predictions. Simulations of the process dynamics further indicate superior performance of the isothermal adiabatic concept compared to the adiabatic concept. This would allow a much simpler control philosophy for the WGS section in a fuel processor.