Fundamental Factors in the Design of a Fast-Responding Methanol-to-Hydrogen Steam Reformer for Transportation Applications

Abstract

Improving the dynamic response of the steam reformer in a fuel cell power plant designed for transportation applications will enable the power plant to operate in a transient manner with a reduced need for supplementary batteries and their associated cost, weight, and life cycle limitations. As a method of seeking improvements to the dynamic response, a sixth-order dynamic model of a steam reformer is used with a design optimization process to determine the values of the steam reformer design parameters which will yield the fastest response time to a step input in hydrogen demand under a variety of initial conditions. Results of this analysis suggest that a steam reformer designed to have a maximum output of approximately 12,600 mol/h of hydrogen and optimized for fast response could have response times on the order of 15–20 s. A sensitivity analysis suggests that this response can be achieved primarily by reducing the thermal capacity of the reformer and improving the rate of heat transfer to the gaseous constituents within the reformer. With a steam reformer response time on the order of 15–20 s, supplementary energy storage devices, such as the ultracapacitor and flywheel, become more feasible. These devices are attractive because they have superior life cycle and power density characteristics when compared with traditional chemical batteries.