2 - Particle behavior

Abstract

This chapter focuses on the motion of a single particle which is the basis for understanding the behavior of particles in groups. The motion of a single particle in the two cases, most essential and most practically applicable, include: horizontal and vertical co-axial impinging streams. The concept of impinging streams (IS) was originally presented for gas–solid systems. Processing solid-in-gas suspensions is an important area where impinging streams may be applicable. To carry out an IS process, it is necessary to accelerate particles by gas flow, i.e., accelerating tubes are needed in a gas–solid impinging stream device. To a considerable extent, the feature of impinging streams enhancing transfer between phases is related to the behavior of particles, especially to their motion. The most important phenomenon in gas–solid suspension impinging streams is that, by inertia, particles can penetrate to and fro between the opposing streams and thus behave as oscillation movement. This results in lengthened residence time and increased concentration of the particles in the active region, yielding a positive effect on heat and mass transfer between phases. Horizontal co-axial impinging streams are obviously important to have certain experimental evidences. Some experimental data obtained by several researchers and a comparison of the data with their theoretical results are presented.