Axial Particle Concentration Distribution in Two-Phase and Three-Phase Fluidized Beds with Binary Solid Mixtures

The axial particle concentrations before and after layer inversion were measured in two-phase (liquid-solid) and three-phase (gas-liquid-solid) fluidized beds. The experiments were carried out in a using a half-tube acrylic column (210-mm diameter) having a height of 1.8 m. 3.2-mm polymer beads (1,280 kg/m3) and 0.385-mm glass beads (2,500 kg/m3) were selected as a binary solid mixture of lighter/larger particles and denser/smaller particles, respectively. Water was the continuous phase in both cases, whereas air is the dispersed phase for the three-phase system. The axial particle concentration distribution was determined by measuring the axial pressure gradient and sampling the denser/smaller particles along the bed height. In three-phase fluidized beds of the particle mixture, the total solid phase holdup decreased with increasing liquid velocity, but the gas phase holdup remained the same at a given superficial gas velocity. After air injection into the two-phase fluidized bed of the binary mixtures, there were initial contractions of the upper layer of the bed above the liquid velocity corresponding to the inversion point.