SPATIAL-DISTRIBUTION OF GAS AND SOLID-PHASES IN CONICAL SLURRY BUBBLE-COLUMNS

In this work we perform an experimental study of the spatial distribut ion of phases in slurry bubble columns with conical distributors that have a volume comparable to that of the cylindrical section. Three dif ferent distributors were used whose apex angles were 13 degrees, 22 de grees and 34 degrees. In gas-liquid operation, the gas holdups are axi ally uniform in the cylindrical section and decrease towards the wall, whereas in the conical section they increase towards the inlet. These trends are observed in the three cones for all the operating conditio ns explored. The solids distributions in the conical sections are qual itatively different depending on whether the operation is semibatch or continuous with respect to the flow of solid-liquid suspension: in se mibatch operation, the concentration monotonically increases towards t he bottom of the cone and exhibits a slight increase as the wall is ap proached; in continuous operation, an absolute maximum in solids conce ntration is obtained at a point located on the wall of the cone and in termediate height. The location of this maximum moves upwards as the t otal solids content in the column increases and as the apex angle decr eases. The maximum in solids concentration signals the most probable s ite for the onset of solids sedimentation and the presence of low mixi ng levels and reduced mass transfer rates in a slurry reactor. In the range of conditions explored in the present work, the lowest apex angl e (13 degrees) yields a more uniform solids distribution throughout th e system.