The impact of fuel evaporation on the gas-phase kinetics in the mixing region of a diesel autothermal reformer

Autothermal reforming is a promising technology to produce syngas from diesel fuel. However, the mixing of liquid diesel fuel with high temperature streams of steam and oxygen presents a challenge: how to avoid formation of ethylene, a likely deposit precursor, in the region upstream of the catalyst bed. This work describes a coupled CFD-kinetics study in the mixing region of a diesel autothermal reformer that considers: (1) an atomizer model to explicitly account for fuel evaporation, (2) n-dodecane as a surrogate diesel fuel, (3) oxygen as the oxidant instead of air. The predictions indicate unacceptable levels of ethylene (>0.1 mol%) will be present at the mixer exit if the mixer gas temperature is greater than ∼350 °C. This temperature is likely to be too low for proper catalyst performance. Thus this analysis suggests that either improved mixer designs or a different choice of catalyst might be required to achieve suitable diesel autothermal reforming performance.