An overview of current micro-structured fuel processing activities from fundamental studies to early markets application

摘要

For both mobile and stationary applications, high and low temperature fuel cell systems, there is a pressing need for compact(er) hydrogen production systems [1]. For completely integrated fuel processing systems then size is a crucial issue. The advantages of microstructured technology are many. However, the enhanced heat and mass transfer that is achieved together with the ease of system integration via integrated heat exchanger reactor designs leads to highly intensified systems. Generally speaking, a fuel processor consists of a reformer and various CO-cleanup reactors depending on whether the target fuel cell is SOFC or PEM based, all of which fall within the product portfolio of IMM. This contribution is focused on the continuing development of all reformer types i.e. those based on steam reforming, autothermal (ATR) and partial oxidation (POx), from W to kW scale. Primarily, if the final objective is increased compactness of the finished system(s) then POx of light hydrocarbons such as propane and LPG is particularly interesting. Major challenges here are (a) coke formation as lifetimes of up to at least 10,000 hours must be achieved and (b) hot spot formation caused by the large exotherm which can be solved by operating in the integrated reactor/heat exchanger mode. This requires improvements in catalytic efficiency and application which for the most part is achieved through the enhancement of the heat and mass transfer characteristics. Catalyst development work performed by IMM has shown that carbon formation was neither observed at the reactor inlet or over the noble metal based catalysts applied but rather at the reactor outlet, i.e. by the product. It could be suppressed by coatings inactive for the Boudouard reaction [2]. All parts of the development chain will be addressed from fundamental studies, catalyst screening, reactor design and fabrication to final integration of various systems. A complete fuel processor, integrated to a HT-PEM system, which has been operated for up to 3500 hours will be briefly discussed together with ongoing measures that are being adopted to address issues related to mass production of such systems. These include the obstacles that must be surpassed with respect to (a) continuous catalyst coating techniques e.g. by screen printing, (b) sealing techniques e.g. by high powered continuous wave laser welding and (c) structuring for the cost effective introduction of such units to a more widespread utilisation.