Control of Reaction Rate in Dust Flames

Abstract

EVER since Nusselt¹ introduced the boundary layer concept, about forty years ago, for calculating rates of heat and mass transfer to a spherical particle, it has been universally accepted (without proof) by subsequent theoretical work (see ref. 2) that the reaction-rate of particles in a dust flame is determined by the rate of supply of oxygen through a diffusional boundary layer surrounding the particles. That this might not in fact be so was first suggested³ about five years ago, the alternative proposition being that the rate control was chemical, not physical ; the source of the implied error is attributed to the mis-interpretation of reaction data in terms of diffusion instead of chemisorption which, according to Brunauer⁴, has been a common mistake in the past. Support for the alternative hypothesis, however, has now been provided by analysis of experimental results obtained recently from an anthracite flame.