Transport Phenomena in a Reformer with Micro-Power Applications.

Fuel cells are power sources which are efficient, have long life, are easily rechargeable and are cleaner than most traditional power sources such as batteries and internal combustion engines. Power density and safety issues make on-board generation of hydrogen by utilizing a reformer to provide the fuel for proton exchange membrane fuel cells (PEMFC) more desirable as compared to the direct supply of hydrogen. This research aims to develop an on board efficient small scale reformer to provide fuel (H2) for portable fuel cells. These can serve as power sources for personal mobile electronic devices with many promising applications; e.g. cell phones, personal digital assistants, notebooks etc. Understanding the transport in reformers is essential for improving both the efficiency of the reforming process and the quality of the processed fuel. Methanol-steam reforming is utilized as the fuel processing system in the present study. A packed-bed reformer is studied first. Then, a wall-coated reformer is studied; it has smaller power requirements for delivering fuel than does the packed catalytic bed reformer. Also, the wall coated catalytic layer has a smaller thermal resistance compared to the packed catalytic bed. This yields enhanced thermal management for the wall-coated reformer which improves reformer performance. In traditional reformers where heat is provided externally there are significant energy losses. To obtain efficient hydrogen conversion, a packed bed reformer with a novel heating configuration is studied where the heat for the reforming reaction is provided internally in the reformer. This transports heat directly and precisely to the catalytic layer (reaction sites) and thereby reduces energy losses in respect to both the heating of non-catalytic (no reaction) zones and also losses to the surroundings. To enhance the conversion of methanol to hydrogen the introduction of a nanoporous catalyst is also studied. The numerous surface of the nano/micro porous structure provides a high surface to volume ratio of the catalytic layer which increases the activity of the catalyst. A preliminary experiment was carried out to obtain an effective nanoporous catalyst by using pulsed laser ablation (PLA) technology. The properties of the nanoporous catalyst are directly related to the performance of the catalytic reaction and are analyzed. Experiments were carried out to evaluate the activity enhancement of the nanoporous catalyst in a novel reactor configuration. Photonic energy is used to provide the heat for the endothermic methanol reforming reaction which produces hydrogen. It is shown that photonic induced methanol reforming in a nanoporous catalyst reformer is feasible and promising.