Effect of particle size distribution on mixing and segregation in a gas-solid fluidized bed with binary system

Abstract

The mixing and segregation characteristics were investigated in gas-solid fluidized beds with binary solid mixture. Bed materials were constituted with binary solids, having different size and density. To investigate the effect of particle size distribution on the mixing characteristics, two other binary solid mixtures were used, which have similar mean particle size and particle density, but their particle size distribution was different to each other. Bed column has ID=0.14 m and H=2.14m. Bed aspect ratio was 3.0. Bed materials were two sets: one of bed materials was the mixture of ilmenite (dp=153 mm, ρs=3,860 kg/m3) and coke (dp =582 mm, ρs =1,762 kg/m3), which has wide size distribution. The other bed materials was the mixture of ceramic beads (dp =122 mm, ρs =3,800 kg/m3) and plastic beads (dp =813 mm, ρs =1,500 kg/m3), which has narrow size distribution. Bed composition of ilmenite-coke mixture was determined to 0.7:0.3 by mass ratio. And, bed composition of ceramic beads-plastic beads was 0.75:0.25 by mass ratio. Axial bed pressure drop was measured according to gas velocity. Bed composition was measured according to axial bed height by sampling. Bed pressure drop of ilmenite-coke mixture was maximized above Uo=0.15 m/s, and fully fluidization was occurred. However, criterion of mixing to segregation was not found in the axial bed composition according to gas velocity. In the case of ceramicbeads-plastic beads mixture, bed pressure drop was maximized at Uo=0.05 m/s, and the criterion of mixing to segregation was found at the same gas velocity.