Thermal Radiation Contribution to Metal Dust Explosions

Abstract

Despite the significant progress made towards the understanding of flame propagation mechanisms in dust-air mixtures, dust explosions still have a frequent occurrence and their danger presents a continuous threat to industries that produce, use and treat solid powders and dusts of combustible materials. In fact, many physical aspects are still needed to be clarified given the major difference existing between flame propagating in gaseous mixtures and in suspensions and many questions are still unanswered regarding the reasons behind the violence of fine metal dust explosions. Few experimental observations and theoretical considerations emphasized the potential role of radiation heat transfer in the behaviour of dust clouds’ flames in which acceleration in flame propagation speed and instabilities were observed. Unfortunately, only few information is available, so far, concerning the capacity of radiative transfers of taking part in the propagation process. While investigating radiation phenomenon in dust clouds, we are faced with a complicated problem difficult to model analytically. The development of numerical approach, based on discrete element method (DEM), in order to treat this problem, seems more convenient. MULTICOR code, developed at the LTI, has already succeeded at modelling heat transfer in a bed of particles. Under this work, radiative heat transfer exchanged between particles in suspension is successfully calculated and we propose an original method of calculating heat transfers between dust and gas in the preheat zone of the flame. We are currently working on adapting the radiation models implemented to the case of fine particles and taking into consideration light scattered. With the purpose of determining the flame propagation speed and improving the knowledge of the phenomena involved, it would be possible to contribute to the development of suitable means of prevention and mitigation of dust explosion hazard.