Effects of particle size and agglomeration on flame propagation behavior in dust clouds

Abstract

Dust explosion occurs when ignition energy is given to a flammable particle clouds dispersed in air. During dust explosion, high speed flame propagation occurs and pressure rises significantly. Since the specific surface area increases as the particle size decreases, the risk of dust explosion increases. However, when the particle size is further decreases to several tens micro meters, agglomeration occurs easily, and dispersion condition changes. In order to appropriately evaluate the risk of dust explosion of fine particles, it is necessary to study the relationship between flame propagation behavior and particle characteristics, such as size and agglomeration. The purpose of this study is to investigate the effects of particle size and agglomeration on flame propagation behavior in dust clouds. The flame propagation behavior was examined changing the particle size of PMMA particles and the effect of particle agglomeration was investigated. On this account, PMMA particles with a very narrow particle size distribution were used. As a result, the minimum explosible concentration increased as the particle size decreased. On the other hand, the flame propagation velocity increased as the particle size decreased. In this way, the minimum explosible concentration and flame propagation velocity showed the opposite tendency to the particle size. It is considered that the inter-particle distance will be important for the minimum explosible concentration, meanwhile the specific surface area will be important for the flame propagation velocity. The severity of the explosion can be serious for the smaller particles, despite the minimum explosible concentration is large and the occurrence probability is low.