CHEMICAL HYDRIDE REACTOR DESIGNS FOR PORTABLE FUEL CELL DEVICES

This research addresses the issues of electrical energy storage that warfighters in the U.S. military face. A device is presented that combines an on-demand hydrogen reactor with a state of the art proton exchange membrane fuel cell. This thesis focuses on the design criteria and analysis of the chemical hydride reactor. On demand hydrogen release can occur by controlling the hydrolysis reaction of Ammonia Borane (AB). Maleic acid is used to promote rapid release of hydrogen and trap the ammonia released from AB. Reactor designs are categorized as either delivering liquid or solid ammonia borane into an acid filled reactor. In an effort to design as simple of a system as possible, the delivery mechanisms presented do not use electronically powered devices. The primary safety criterion is that the hydrogen does not overly pressurize and meets the consumption rate of the fuel cell. Two liquid delivery architectures are proposed and tested using the assumption that a pressure differential between two chambers will deliver ammonia borane solution into a reactor. Methods of controlling the exposure of solid ammonia borane to a promoter is also presented. Pressed AB pellets were experimentally analyzed in order to characterize the interaction of solid AB in acidic solution. Designs are ranked against each other using system parameters that are applicable to man portable device. Liquid delivery architectures provided a safe and robust method of hydrolysis control. A bag reactor system that met the hydrogen requirements of a fuel cell was developed and tested. When used to compliment a fuel cell and military grade batteries, such a reactor will save weight and volume for extended missions requiring electronic equipment.