Aspects of Catalytic Combustion

Catalytic combustion or total oxidation is frequently applied in fuel processor systems. The motivations are two-fold  

A large variety of conventional burners is commercially available and some of them may well be suited to supplying heat to fuel processors especially during start-up. However, these devices will not be discussed as they are notwithin the scopeofthis book. 

Combustion of hydrogen contained in gas mixtures such as anode off-gas is a critical issue, because the explosion limits of the reaction range from 4 to 75% for hydrogen in air. 

Veser and Schmidt studied the catalytic and homogeneous ignition and the homogeneous extinction behaviour of lower alkanes and alkenes ]428]. Platinum foil was used as the catalyst The surface ignition temperature decreased with increasing number of carbon atoms in the fuel and with increasing modified equivalence ratio 0, which was derived from the equivalence ratio. The latter is defined as the ratio of vol.% air to vol.% fuel in the feed normalised by the ratio required for total combustion  

Raimondeau et al. modelled the homogeneous high temperature combustion of a pre-heated stoichiometric mixture of methane and air at 2 m s flow rate and a 1000 °C reference temperature, which corresponded to the methane ignition 

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This section briefly discusses some aspects of catalytic combustion mechanisms, i.e., surface reaction kinetics and heterogeneous-homogeneous reactions. Based on this discussion and the previous section, the extreme demands on combustion catalysts are presented. Finally, the role of mathematical modeling of this complex catalytic system is examined. 

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