A COMPARATIVE-STUDY OF CARBON-BLACK AND DIESEL SOOT REACTIVITY IN THE TEMPERATURE-RANGE 500-600-DEGREES-C - EFFECT OF ADDITIVES

The oxidation reactivities of some soots generated in a small diesel engine were measured by thermogravimetry at 500 degrees C and 600 degrees C. The materials tested included carbon black as a reference carbon and some soots that contained iron and copper resulting from the use of diesel fuel additives. In all cases, mass transfer effects were present and the true reactivities had to be evaluated by their elimination. This was achieved by means of a one-dimensional model of oxygen transfer and by extrapolation of data from different bed sizes. Agreement between the two methods was good. Reliable values of the effective diffusion coefficients within particle beds are essential for successful modelling. The relative reaction rates between samples change markedly when mass transfer effects are eliminated. The presence of the metals increases the reactivity of soots, with copper producing an enhancement of 470% at 600 degrees C.