Combustion of Agglomerates Formed by Carbon Slurry Fuels.

The reaction of carbon-black agglomerates, formed during the combustion of carbon slurry fuels, is considered. A monodisperse stream of agglomerates 10-75 micrometers initial diameter was observed in the post-flame region of a flat-flame burner yielding particle size, mass, temperature and velocity as a function of time in the burner gases. Test considered burner fuel equivalence ratios of 0.2-1.4, and gas temperatures of 1620-1960 K at atmospheric pressure. Several carbon-black formulations were considered monodisperse blacks having ultimate carbon black particle sizes of 70, 150 and 300 nm, and a blend involving 50 mass loadings each of carbon blacks having ultimate carbon particle sizes of 70 and 300 nm. The measurements were compared with a shrinking sphere model of the process using two alternative reaction mechanisms carbon reaction with O2 and OH or with O2, CO2 and H2O. Empirical transport enhancement and areareactivity parameters were defined to allow for gas motion and reaction in agglomerate pores. These parameters were determined form the data. Both reaction mechanisms satisfactorily correlated the data using empirical parameters which were relatively independent of ambient conditions, particle size and extent of reaction--aside from an initial transient period where the pore structure of the agglomerate developed. The rate of combustion of monodisperse blacks increased slightly as the ultimate carbon-black particle size was reduced. The burning rate of the carbon-black blend was lower than the other fuels considered during the investigation yielding residence times for reaction 10-50 longer than monodisperse blacks at comparable conditions. Author