Experiments on soot formation from propane under partial oxidation conditions in a turbulent plug-flow reactor

Abstract

Soot formation from propane was investigated in a turbulent plug-flow reactor at temperatures around 1200°C. Propane was mixed into a hot flue gas flow with residual oxygen contents between 2.3% and 5.2%, corresponding to initial propane concentrations of up to 3%. About 60% of the carbon originating from propane is oxidized mainly to CO, the remainder is pyrolized to C 2 H 2 , CH 4 and traces of C 2 H 4 . Up to 2% of the carbon is converted finally to soot. The oxygen bound in CO 2 turned out to be not available for propane oxidation. The soot formation rates were time-independent at least for residence times below 40 ms. Both, the fuel concentration and the stoichiometric ratio of the partial oxidation of injected propane with the residual oxygen in the flue gas had an influence on the soot formation threshold and on the soot growth rate. Their combined influence is described by one parameter, the “propane surplus”. Measurement of the size distribution of soot allowed the determination of the soot surface area. The observed growth rates can tentatively be explained by reactions of the pyrolysis products C 2 H 2 , CH 4 and C 2 H 4 with the available soot surface area.