Micro reforming

In this work, the MeOH kinetic model of Lee et al. [9] is adopted for the micro-channel fluid dynamics analysis. Pressure and concentration distributions are investigated and represented to provide the physico-chemical insight on the transport phenomena in the microscale flow chamber. The mass, momentum, and species equations were employed with kinetic equations that describe the chemical reaction characteristics to solve flow-field, methanol conversion rate, and species concentration variations along the micro-reformer channel. 

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. 

Also a simulation of the flow field in the methanol-reforming reactor of Figure 2.21 by means of the finite-volume method shows that recirculation zones are formed in the flow distribution chamber (see Figure 2.22). One of the goals of the work focused on the development of a micro reformer was to design the flow manifold in such a way that the volume flows in the different reaction channels are approximately the same [113]. In spite of the recirculation zones found, for the chosen design a flow variation of about 2% between different channels was predicted from the CFD simulations. In the application under study a washcoat cata-... 

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. 

In Canada, hydrogen production from natural gas via a fluidised bed reactor with hydrogen purification via a selective membrane is under investigation. Also, a methanol micro-reformer which includes an integrated metal membrane purification unit is being developed. 

Figure 2.4 (a) Schematic exploded view of an electrically heated micro reformer and (b) a photograph of the mounted and welded device [13] (by courtesy of Springer VDI Verlag). 

Kolb, G., Lowe, H., Wichert, M., Zapf, R., A methanol steam micro-reformer for... 

H. Yu, H. Chen, M. Pan, Y. Tang, K. Zeng, F. Peng, H. Wang, Effect of the metal foam materials on the performance of methanol steam micro-reformer for fuel cells, Appl. Catal. A Gen. 327 (2007) 106. 

Another integration study has been carried out by Kim and co-workers who prepared an integrated catalytic structured mini-channel network covered by a Pd-based membrane for hydrogen recovery. This first step work led to an hydrogen separator made of defect-free Pd layer. However, this is a step further towards the use of such a system as integrated micro-reformer and separator. 

Z Hsueh, C.-Y., Chu, H.-S., Yan, W.-M., and Chen, C.-H. (2010) Numerical study of heat and mass transfer in a plate methanol steam micro reformer with methanol catalytic combustor. Int. 

Metal foam (see, for example. Figure 3.5) has already been discussed in the context of heat exchangers. Micro-reactors, highly relevant to the subject of small fuel cells, have also been introduced in earlier chapters. The construction of metal foam based methanol steam micro-reformers to generate hydrogen for polymer electrolyte membrane fuel cells (PEMFCs) has been reported and in Guangzhou, Chinese researchers have looked at laminated micro-reactors in which copper-based catalysts have been supported by metal foams (see Figure 11.11 Yu et al., 2007). 

Kundu and colleagues, working at Samsung Electromechanics in Korea, developed the silicon-based micro-channel reactor shown in Figure 11.13. Here a Cu/Zn0/Al203 Johnson Matthey catalyst was used. In the experiments a serpentine patterned micro-reformer proved superior in tenns of activity to a parallel-patterned unit. Nevertheless, dates for commercialisation, conclude the authors in the review, remain uncertain. 

Micro-vaporizer plus packed bed micro-reformer... 

Heaters on the back side Cross-sectional view of channel Figure i i. i 3 The micro-reformer developed at Samsung. 

Typically, micro fuel cells use methanol as fuel alfhough hydrogen-fed micro fuel cells have also been developed. The choice of the type of fuel cell to use in portable devices may be limited to low-temperature fuel cells such as PEMFC (proton exchange membrane fuel cell/polymer electrolyte membrane fuel cell) and DMFC. However, micro reformed methanol fuel cells and miniature SOFCs have also been developed. 

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