The conversion of a gaseous reformable fuel and/or a liquid reformable fuel to a hydrogen-rich carbon monoxide-containing gas mixture, a product commonly referred to as “synthesis gas” or “syngas,” can be carried out in accordance with any of such well known fuel reforming operations such as steam reforming, dry reforming, autothermal reforming, and catalytic partial oxidation reforming.
The development of improved fuel reformers, fuel reformer components, and reforming processes continues to be the focus of considerable research due to the potential of fuel cell systems or simply, “fuel cells,” i.e., devices for the electrochemical conversion of electrochemically oxidizable fuels such as hydrogen, mixtures of hydrogen and carbon monoxide, for example, syngas, and the like, to electricity, to play a greatly expanded role for general applications including main power units (MPUs) and auxiliary power units (APUs). Fuel cells also can be used for specialized applications, for example, as on-board electrical generating devices for electric vehicles, backup and primary power sources for residential-use devices, main power sources for leisure-use, outdoor and other power-consuming devices in out-of-grid locations, and lighter weight, higher power density, ambient temperature-independent replacements for portable battery packs.
Because large scale, economic production of hydrogen, infrastructure required for its distribution, and practical means for its storage (especially as a transportation fuel) are widely believed to be a long way off, much current research and development has been directed to improving both fuel reformers as sources of electrochemically oxidizable fuels, notably mixtures of hydrogen and carbon monoxide, and fuel cell assemblies, commonly referred to as fuel cell “stacks,” as convertors of such fuels to electricity, and the integration of fuel reformers and fuel cells into more compact, reliable and efficient devices for the production of electrical energy.
With these considerations in mind, the efficient delivery of a mixture of a reformable fuel and an oxygen-containing gas and/or steam to a fuel reformer and/or a fuel cell stack is another area where development is needed. For example, a reformable fuel is usually mixed with air using a static mixer, where the reformable fuel typically is added to the air stream just prior to the static mixer and the resulting mixed reformable fuel and air stream delivered to a fuel reformer. However, such mixers typically cannot adequately mix the constituents before delivery to the reformer for example, due to the pressure drop. An injector nozzle system also can be used to mix a reformable fuel and air; however these systems do not typically provide a continuous fluid flow which can be measured accurately.
In addition, although gaseous reformable fuels can be pressurized and mixed with air somewhat efficiently, the vaporization of liquid reformable fuel followed by mixing with air is more challenging. The mixing should provide a fairly uniform composition, i.e., a homogenous mixture, of the reformable fuel and air to the reformer so that the temperature of reaction can be monitored and controlled appropriately and the flow rates of the air stream and reformable fuel addition adjusted to maintain an efficient reforming process while minimizing coking, which can be deleterious to reforming catalysts as well as fuel cell stacks. Thus, there is a need to improve apparatus for and methods of delivery of a mixed stream of a reformable fuel and an oxygen-containing gas to a reformer of a fuel cell unit.