Fuel micro

The French Nuclear Research Center CEA announced the successful fabrication of high performances prototypes fuelled by H2 and based on thin films type structures on Si substrate obtained by micro-electronics fabrication techniques (RIE for fuel micro-channels, PVD for anode collector, CVD, serigraphy, inkjet for Pt catalyst, lithography) with a Nafion membrane [15]. An impressive power density of 300 mW cm with a stabilisation around 150 mW cm" during hundred hours was reported. 

The alternative fuel cycle option is a once-through cycle with cermet fuel (micro-particles of fuel in a metallic matrix). 

Post-irradiation examination from the MSRE showed no interactions (erosion or corrosion) between the salt and the graphite. The original machining marks were still clearly visible. Out of reactor tests were conducted to 1400°C with no interactions between the salt and graphite. Experiments show the non-wetting behaviour of the fluoride salts of interest and demonstrate that liquid fluoride salts will not penetrate small cracks in the graphite. For the AHTR, this has the practical implication that the clean coolant will not contact the fuel micro spheres that are embedded in a carbon matrix. 

Combining informativeness and accuracy with readability, Stephanie Yanchinski explores the hopes, fears and, more importantly, the realities of biotechnology - the science of using micro-organisms to manufacture chemicals, drugs, fuel and food. 

For jet fuels, the elimination of free water using filters and coalescers by purging during storage, and the limit of 5 ppm dissolved water are sufficient to avoid incidents potentially attributable to water contamination formation of micro-crystals of ice at low temperature, increased risk of corrosion, growth of micro-organisms. 

Water-in-od emulsion explosives have been made as typified by a formulation containing 20% water, 12% oil, 2% microspheres, 1% emulsifier, and 65% ammonium nitrate. The micro droplets of an emulsion explosive offer the advantage of intimate contact between fuel and oxidizer, and tend to equal or outperform conventional water-based slurries. 

Technology Comparison Diesel Engine Gas Engine Simple Cycle Gas Turbine Micro Turbine Fuel Cell Solar Energy Photovoltic Cell Wind Bio Mass River Hydro... 

Different approaches utilizing multidimensional EC or SEC systems have been reported for the analysis of middle distillates in diesel fuel. A method, based on the EC separation of paraffins and naphthenes by means of a micro-particulate, organic gel column has been described (23, 24). The complete system contained up to four different EC columns, a number of column-switching valves and a dielectric constant detector. However, the EC column for the separation of paraffins and naphthenes, which is an essential part of the system, is no longer commercially available. 

Sol-gel techniques have been successfidly applied to form fuel cell components with enhanced microstructures for high-temperature fuel cells. The apphcations were recently extended to synthesis of hybrid electrolyte for PEMFC. Although die results look promising, the sol-gel processing needs further development to deposit micro-structured materials in a selective area such as the triple-phase boundary of a fuel cell. That is, in the case of PEMFC, the sol-gel techniques need to be expanded to form membrane-electrode-assembly with improved microstructures in addition to the synthesis of hybrid membranes to get higher fuel cell performance. 

Computational study on the micro-channel fuel processors... 

The catalytic combustor provides heat for the endothermic reforming reaction and the vaporization of liquid fuel. The endothermic reforming reaction is carried out in a parallel flow-type micro-channel of the reformer unit. It is well known that the methanol steam reforming reaction for hydrogen production over the Cu/ZnO/AbOs catalyst involves the following reactions [10]. Eq. (1) is the algebraic summation of Eqs. (2) and (3). 

Nature as model for micro-reactor development general advantages of micro flow onset of industrial interest micro heat exchanger vision of mefhanol-fuel reforming costs stiU too prohibitive [231],... 

Many authors mention the use of micro reactors for fuel processing as one of the most promising fields [1,104]. Wegeng et al. point at using this micro-fuel processing for transportation [Ij. The placement of reformers imder the hood of an automobile for converting liquid hydrocarbons to hydrogen is explicitly mentioned. 

Accordingly, serious commercially oriented attempts are currently being made to develop special gas-phase micro and mini reactors for reformer technology [91, 247-259], This is a complex task since the reaction step itself, hydrogen formation, covers several individual processes. Additionally, heat exchangers are required to optimize the energy balance and the use of liquid reactants demands micro evaporators [254, 260, 261], Moreover, further systems are required to reduce the CO content to a level that is no longer poisonous for a fuel cell. Overall, three to six micro-reactor components are typically needed to construct a complete, ready-to-use micro-reformer system. 

A growing number of research groups are active in the field. The activity of reforming catalysts has been improved and a number of test reactors for fuel partial oxidation, reforming, water-gas shift, and selective oxidation reactions were described however, hardly any commercial micro-channel reformers have been reported. Obviously, the developments are still inhibited by a multitude of technical problems, before coming to commercialization. Concerning reformer developments with small-scale, but not micro-channel-based reformers, the first companies have been formed in the meantime (see, e.g., ) and reformers of large capacity for non-stationary household applications are on the market. 

ISPP imits are not the only micro device imits of interest for space applications micro fuel cells, compact cleanup units for water treatment, portable heating and cooling units and devices for chemical processing and mining are considered [91]. 

ScHOUTEN, J. C., Rebrov, E., de Croon, M. H. J. M., Challenging prospects for microstructured reaction architectures in high-throughput catalyst screening, small scale fuel processing, and sustainable fine chemical synthesis, in Proceedings of the Micro Chemical Plant - International Workshop, pp. L5 (25-32) (4 Eebruary 2003), Kyoto, Japan. 

Hermann, I., Lindner, M., Winkel-MANN, H., DuSTERWALD, H. G., Microreaction technology in fuel processing for fuel cell vehicles, in Proceedings of the VDE World Microtechnologies Congress, MICRO.tec 2000,... 

Comings, V., Hardt, S., Hessel, V., Kolb, G., Lowe, H., Wichert, M., Zape, R., a methanol steam micro-reformer for low power fuel cell applications, Chem. Eng. Commun. (2003) accepted for publication. 

Such bimetallic alloys display higher tolerance to the presence of methanol, as shown in Fig. 11.12, where Pt-Cr/C is compared with Pt/C. However, an increase in alcohol concentration leads to a decrease in the tolerance of the catalyst [Koffi et al., 2005 Coutanceau et ah, 2006]. Low power densities are currently obtained in DMFCs working at low temperature [Hogarth and Ralph, 2002] because it is difficult to activate the oxidation reaction of the alcohol and the reduction reaction of molecular oxygen at room temperature. To counterbalance the loss of performance of the cell due to low reaction rates, the membrane thickness can be reduced in order to increase its conductance [Shen et al., 2004]. As a result, methanol crossover is strongly increased. This could be detrimental to the fuel cell s electrical performance, as methanol acts as a poison for conventional Pt-based catalysts present in fuel cell cathodes, especially in the case of mini or micro fuel cell applications, where high methanol concentrations are required (5-10 M). 

Lu GQ, Wang CY, Yen TJ, Zhang X. 2004. Development and characterization of a silicon-based micro direct methanol fuel cell. Electrochim Acta 49 821-828. 

Yamazaki Y. 2004. Application of MEMS technology to micro fuel cells. Electrochim Acta 50 663 -666. 

The hnding of very substantial amounts of incomplete oxidation products for methanol and formaldehyde oxidation can have considerable consequences for technical applications, such as in DMFCs. In that case, the release of formaldehyde at the fuel cell exhaust has to be avoided not only from efficiency and energetic reasons, but in particular because of the toxicity of formaldehyde. While in standard DMFC applications the catalyst loading is sufficiently high that this is not a problem, i.e., only CO2 is detected [Arico et al., 1998], the trend to reducing the catalyst loading or applications in micro fuel cells may lead to situations where the formation of incomplete oxidation products could indeed become problematic (see also Wasmus et al. [1995]). For such purposes, one could dehne a maximum space velocity above which formation of incomplete oxidation products may become critical. 

Micro-hydro systems use the natural flow of water to yield up to 100 kW output of electrical energy [22]. Simplicity, efficiency, longevity, reliability, and low maintenance costs make these systems attractive for mral development [23]. Like solar and wind, the fuel source for microhydro power is free, and the use of hydro-powered turbines to generate electricity produces no on-site air pollution. 

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