(71q) Effect of Size Constraints on Integration Potential in Logistical Fuels Processing

The theoretical energy efficiency of a fuel cell system is approximately three times higher than a combustion engine based generator, thus it would provide substantial savings if alternative means of power production could be developed. Recent efforts have been focused on reforming existing logistical fuels, e.g. diesel or JP-8 for use in fuel cell systems. This is particularly important for military applications, as it would allow for the US armed forces to move towards using one single logistical fuel. To meet these ends the Center for Microfibrous Materials Manufacturing (CM3) at Auburn University has developed a bench scale test bed for investigating running a portable radar system of a PEM fuel cell stack by producing high purity hydrogen from steam reforming (SR) of JP-8. In principle, a PEM fuel cell system consists of the fuel processing section and the fuel cell itself, with the former being the reformer and post-combustion cleanup steps. Such systems inherently possess tremendous integration potential, not just limited to recycling unused material, but also in terms of energy recovery. Process integration techniques can be employed to realize this potential by providing global process insights and identifying overall process performance targets. Current methods for resource management such as thermal and mass pinch analyses are aimed at processing facilities, i.e. stationary plants, where the overall goal is to balance reductions in operating cost against increased capital investments to maximize profitability. For a certain class of problems however, conventional pinch analyses fail to adequately address the resource management problems. For compact and/or mobile applications the deciding factor is not simply the resource utilization level or cost of equipment, but is often a trade-off between the achievable resource utilization and the weight and/or volume of the equipment. In this contribution we study thermal management and resource conservation strategies in logistical fuels processing for mobile applications. Based on performance data obtained from the test bed, models have been developed for three reformation strategies, i.e. steam reforming (SR), partial oxidation (POX) and auto-thermal reforming (ATR). A comprehensive efficiency analysis of hydrogen production from logistical fuels also requires an evaluation of effects of changing the fuel itself. Therefore the fuel processing system for each reformation strategy has been modeled for a variety of fuels. This contribution will illustrate the results of a process integration analysis of different reforming strategies of various fuels. To further increase the integration potential, the use of heat pipe technology has been investigated. A simple, systematic method for targeting of optimum heat pipe usage in heat exchange networks has been developed to augment existing thermal pinch analysis methods.