PNEUMATIC CONVEYING OF SOLIDS THROUGH STRAIGHT PIPES

Abstract

The pneumatic transport of solid particles in both horizontal and vertical pipes was studied using glass beads, copper spheres, millet and grass seeds, having diameters ranging from 0.1 to 1.0mm. It was shown that the additional pressure drop and the particle velocity could be expressed by ΔP_s/L=0.057 (u_a/√gD)mρ_a, and u_s=u_a-u_t, respectively, in the case of vertical transport.
In vertical transport, the copper spheres and glass beads were found to be densely distributed toward the wall of the pipe whereas higher concentration near the axis was observed for, polystyrene particles.
The velocity profile of the air in the vertical pipe was symmetrical and was not appreciably affected by the addition of the particles. However, in the horizontal pipe, the velocity profile was asymmetric with respect to the pipe axis, and was found to be affected by the particle diameter, density, and the mass flow ratio of the air and the particles.
A simple impulsive model was used to explain the additional pressure drop in horizontal conduits, which was thought to be caused mainly by the collision between the particles and the surface of the pipe wall.