Micro combustor

Micro-combustor matrices for hydrogen. Activity leader FIAT Research Centre (CRF). Estimated activity cost 8.7 million. 

Figure 2.42 Exploded view of the micro combustor test rig. The silicon parts are fitted between two Invar plates [76]...

Figure 2.43 Wall temperatures of the micro combustor increase with the equivalence ratio of fuel to air up to 1000 K [76] (by courtesy of SAGE Publications).

Figure 2.44 Design principle of a two-dimensional micro combustor [77] (by courtesy of IOP Publishing Ltd.).

Li, J.-F., Esashi, M., Silicon nitride ceramic-based two-dimensional micro-combustor,/. Micromech. Microeng. 2003, 13, 502-508. 

Spadaccini, C.M. Zhang, X. Cadou, C.P. Miki, N. Waitz, LA. Preliminary development of a hydrocarbon-fueled catalytic micro-combustor. Sensors Acutators A. Phys. 2003, 103, 219-224. 

Tadbir M A and Akbari M H (2011), Methanol steam reforming in a planar wash coated microreactor integrated with a micro-combustor , Int J Hydrogen Energy, 36,12822-12832. 

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). 

Mehra and Ayon [76] developed the first micro structured hydrogen combustor made of silicon. The device was developed to power a micro gas turbine. However, it could also be applied for fuel processing and is therefore included in this chapter. 

Dudfield et al. [88] presented results generated in the scope of the Mercatox program funded by the European Community aimed at a combined methanol steam reformer/combustor with consecutive CO clean-up by PrOx. First, various catalysts were tested for the reaction as micro spheres in a test reactor which was similar to a macroscopic shell-and-tube heat exchanger (Figure 2.57). 

To avoid high-pressure drop and clogging problems in randomly packed micro-structured reactors, multichannel reactors with catalytically active walls were proposed. The main problem is how to deposit a uniform catalyst layer in the microchannels. The thickness and porosity of the catalyst layer should also be enough to guarantee an adequate surface area. It is also possible to use methods of in situ growth of an oxide layer (e.g., by anodic oxidation of a metal substrate [169]) to form a washcoat of sufficient thickness to deposit an active component (metal particles). Suzuki et al. [170] have used this method to prepare Pt supported on nanoporous alumina obtained by anodic oxidation and integrate it into a microcatalytic combustor. Zeolite-coated microchannel reactors could be also prepared and they demonstrate higher productivity per mass of catalyst than conventional packed beds [171]. Also, a MSR where the microchannels are coated by a carbon layer, could be prepared [172]. 

Y. Choi, K. Tajima, W. Shin, N. Izu, I. Matsubara, N. Murayama, Combustor of ceramic Pt/alumina catalyst and its application for micro-thermoelectric hydrogen sensor, Appl. Catal. A-Gen. 287 (2005) 19. 

In a fluidized bed combustor, the rapid dispersion of injected combustible matter amongst the inert ash particles (the micro-mixing) affects crucially the combustion efficiency, whilst the overall solids circulation rate within the bed strongly influences the vertical and radial temperature profiles. 

Many micro energy conversion systems require a host of auxiliary components along with the core elements mentioned above. These can include micro heat exchangers and combustors to provide heat valves and flow regulators to control the flow of fuel or coolant temperature, pressure, or speed sensors along with electronics to control the device operation as well as power electronics and electrical energy storage. 

M. Esashi, A micro fuel reformer intergrated with a combustor and a microcharmd evaporator, J. Micromech. Microeng. 2006, 16, 191-197. 

K. Schubert, Micro-structured Methane Steam Reformer with Integrated Catalytic Combustor, Fuel Cells 2007, 2,... 

Casio Computer has developed a 2.4 We integrated micro fuel processor comprising a methanol steam reformer, a PrOx reactor and a catalytic combustor (Figures 27.10... 

Kim, T. (2009) Micro methanol reformer combined with a catalytic combustor for a PEM fuel cell. Int.J. Hydrogen Energy, 34 (16), 6790-6798. 

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. 

Yoshida, K., Tanaka, S., Hiraki, H., and Esashi, M. (2006) A micro fuel reformer integrated with a combustor and a microchannel evaporator. 

Pacific Northwest National Laboratory s (USA) microchannel reactor unit consisting, in part, of a combustor/evaporator made of stainless steel with an overall size of 41 x 60 x 20mm, with micro-machined combustor channels of 300 p x 500 p x 35 mm, is used to perform methane partial oxidation reaction at 900°C to produce carbon monoxide and hydrogen. Methane conversion efficiencies were more than 85% and 100% with 11 and 25ms residence times, respectively. 

Nishibori M, Shin W, Tajima K, Houlet LF, Izu N, Itoh T, Matsubara I (2008) Long-term stability of Pt/alumina catalyst combustors for micro-gas sensor application. J Eur Ceram Soc 28 2183-2190 Nowotny J (1988) Surface segregation of defects in oxide ceramic materials. Solid State Ion 28-30 1235-1243 Oudet F, Vejux A, Courtine P (1989) Evolution during thermal treatment of pure and lanthanum-doped Pt/Al O, and Pt-Rh/AljO, automotive exhaust catalysts transmission electron microscopy studies on model samples. Appl Catal 50 79-86... 

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