(7b) High Energy Efficiency Micro Channel Raector for the Intermediate Temperature Fuel Cell Systems

Toyota introduced the world's first Fuel Cell Hybrid Vehicle, the FCHV, into the market in 2002. Although fuel cell vehicles have great potential as future vehicles, it is also realized that further breakthrough technologies to solve essential problems, such as cost, energy efficiency and cruising range, are needed for Fuel Cell vehicles to be competitive with Internal combustion engine, the ICE vehicles. As a means of solution to the problems, Toyota proposed the high efficiency fuel cell system consisted of a combination of intermediate temperature (300-400 degrees-C) hydrogen membrane fuel cell, HMFC, with a heat exchanged hydrogen generator in 2004.The use of an on-board reformer with a Fuel Cell system is a very attractive option for FC vehicles because of its long cruising range and no need for a new hydrogen infrastructure. Two characteristics are essential for an on-board Fuel Cell used with a reformer, a high power density and an intermediate operating temperature. However, the on-board reformer for HMFC system requires the processing of a liquid hydrocarbon fuel to produce a hydrogen-rich gas stream suitable for consumption by the fuel cell. Conventional technology for hydrocarbon steam reforming experiences heat transfer limitations resulting in long residence times and large equipment. As a result, most automotive on-board reforming efforts have targeted partial oxidation (POX) and autothermal (ATR) reforming approaches that the heat by injecting air along with the reactants as opposed to heat exchanged reactor. However, heat exchanged reforming offers several potential advantages over the POX or ATR approaches, including the fact that steam reforming can combust waste anode gas as fuel to provide the necessary heat input, allowing it to be more efficient. POX and ATR, which are thermally neutral or exothermic, cannot use the waste anode gas in this way. Several methods have been proposed to achieve this system. However both conversion rate and reformer efficiency are not adequate. In this paper, we introduce a compact and high energy efficiency heat exchanged micro channel reactor which generates a supply of hydrogen-rich gas to an intermediate temperature hydrogen membrane fuel cell, which we call HMFC. In addition, we introduce the catalyst coating technique appropriate to the metallic substrate of a micro channel reactor. One of the main problems in the use of microreactors for heterogeneous catalytic reactions is the development of catalytically active microporous support materials. Several solutions have been proposed to overcome this problem, such as filling the channels with the catalyst, or scale down of industrial reactors, or anodic oxidation of microstructured aluminium foils. However all solutions are not adequate from the viewpoint of trade-off between adhesive and film thickness. In this paper, we will introduce the catalyst coating technique appropriate to the metallic substrate of micro channel reactors. In this paper, we will introduce two new leads for future FC vehicles. The first is a compact and high energy efficiency heat exchanged micro channel reactor. The second is a catalyst coating technique. As a result of the two techniques, the overall core volume of the reactor is 33.7 cc to generate 4.5 kW LHV hydrogen. While reforming iso-octane at a space velocity 50,000 h-1, the reformer efficiency achieved more than 80% by recovery of heat and steam after integration with an intermediate temperature fuel cell. In the catalyst coating technique, immobilization of nano particles prepared from a colloid solution and metal salt solution produces good adhesion of catalyst metal substrate to the micro channel reactor. The catalyst coats were best suited to coat micro channel reactor due to ultra-thin layers ranging in thickness from 0.1 to 50 micrometers. The present reformer system has successfully demonstrated that the high efficiency reactor can achieve a long cruising range. Furthermore, the current demonstration is a major step towards the goal of future FC vehicles.