Impact of Inert Mass Fraction on Explosible Dusts

Abstract

<abstract><title><italic>Abstract. </italic></title> Dust characteristics, such as ash content (inert mass fraction), energy content, particle size distribution (PSD), and particle density, affect the minimum explosible concentration (MEC) of a dust. The hypothesis tested in this study is that, at a specific dust concentration, the combustible particles must be closer than a certain maximum separation distance for a flame to propagate from one burning particle to another. The particle distance was determined using mass median diameter (MMD) and particle density, assuming uniform dispersion and that all the particles were of the same size as MMD. Explosible dusts were mixed with fuller’s earth, an inert dust, to determine the percentage of inert dust required to prevent a deflagration in the Center for Agricultural Air Quality Engineering and Science (CAAQES) chamber. It was assumed that the addition of an inert dust to an explosible dust increases the distance between the volatile particles, inhibiting flame propagation. Explosibility tests were also conducted using the CAAQES chamber to demonstrate that the inert mass fraction (ash content) affects the MECs of corn starch and sugar. Additionally, a theoretical approach was developed to determine the percentage of inert dust required to prevent a deflagration based on particle distances. It was concluded that dust containing a minimum inert mass fraction of approximately 50% will not be capable of a deflagration, and a higher inert mass fraction will increase the MEC of a dust by inhibiting flame propagation.