Nobuyuki Hidaka

Entrainment of fine particles with upward gas flow in a packed bed of coarse particles

Abstract A vertical column packed with glass spheres or pulverized coke was used as a cold model for a blast furnace, and the behavior of fine particles entrained by the ascending gas flow in the bed was investigated. The fines were sieved glass beads and FCC catalyst particles. Feed rates of the gas and fines, as well as the size and surface roughness of the fines and packing particles, were varied, and the effects of these on the dynamic and static holdups of the fines were determined. The pressure drop across the bed for the gas—solid flow was slightly larger than that for the gas flow. The dynamic and static holdups of the fines were correlated with empirical equations.

Axial mixing and segregation of multicomponent coarse particles fluidized by concurrent gas-liquid flow

Abstract Multicomponent solid particles were fluidized by upward concurrent flows of air and water in vertical columns of 7 cm diameter and 4.85 m height, and of 15 cm diameter and 2.7 m height. Solid particles used were sieved glass beads (2.2, 3.1 and 4.65 mm) and mixtures thereof. Axial changes in holdups of gas and solids were determined by sectioning the whole column simultaneously with horizontal plates. The solid holdup of coarse particles was more strongly affected by the liquid velocity than was that of fine particles. A one-dimensional sedimentation-dispersion model was applied to describe the axial holdup profile of each solids component. Calculated results were in agreement with experimental ones over an entire column consisting of dense and dilute regions. Parameters used in the calculation were correlated as experimental equations.

Segregation of solid particles of two sizes in bubble columns

Abstract Binary mixtures of solid particles were fluidized by a two-phase flow of gas and liquid. The changes in holdup of the two components with axial position in the column were determined. The experiments were conducted with three combinations of sieved glass beads (118 and 243 μm; 118 and 465 μm; and 243 and 465 μm diameter) in vertical columns of 7 cm diameter × 4.85 m height and 15 cm diameter × 2.7 m height under batch operation with respect to the solid phase. A sedimentation—dispersion model developed on the basis of the experiments gives a semi-empirical description of the axial distributions of segregation and solid holdup over the whole range of the column.

Effect of Surface Morphology on the Flow of Entrained Fine Particles by Ascending Gas through Packed Beds

Coarse particles of glass or cokes were packed in vertical columns, 1- and 2-m in height, and fine particles of glass or coke were entrained through the columns by the ascending gas flow. These systems were used as a model to investigate the flow of fine coal particles introduced into a blast furnace. The effects of properties of packed particles, as well as fines, on the static and dynamic holdups of fines were then investigated. The static holdup of fines was strongly affected by the surface roughness of the packed particles, while the dynamic holdup of fines was not. These results suggest that the fine particles are trapped in the form of static holdup in the isolated narrow spaces bounded with packed particles, and that they remain on the surface of the packed particles which are exposed to the gas flow for only a short period of time.

Axial mixing and segregation in a gas-liquid-solid three-phase fluidized bed of solid particles of different sizes and densities

Abstract Sieved silica-alumina particles (diameter = 481 μm; density = 1990 kg/m 3 ), glass beads (diameter = 516 μm; density = 2500 kg/m 3 ) or mixtures thereof were fluidized in a vertical bubble column of 7 cm in diameter and 4.50 m in height. The bed was operated batchwise or continuously with respect to the feed of solid particles. Axial changes in gas and solid holdups in the bed were measured by simultaneously sectioning the column with 20 horizontal plates. The measured solid holdup of each component in the column was compared with the analytical results calculated by a one-dimensional sedimentation-dispersion model. Both experimental and calculated results were in satisfactory agreement over the entire column, which consisted of dense and dilute regions, as well as circulating quantities of liquid and solid particles.

Inverted segregation of binary particles in gas-liquid-solid fluidized bed

Abstract Two-component mixtures of sieved glass beads (2.2, 3.1 and 4.65 mm) were fluidized by upward concurrent flows of air and water in two vertical columns, one of 7 cm diameter and 4.85 m height, and the other of 15 cm diameter and 2.7 m height. After steady-state operation, axial distributions of gas and solid holdups were measured by sectioning the whole column simultaneously with horizontal plates. When solid particles were fluidized at low liquid velocity and high gas velocity, an inverted segregation whereby small particles became concentrated below large particles was observed at a region where the total solid holdup was larger than 0.4. The axial holdup profile of each component of solid particles was described with a one-dimensional sedimentation-dispersion model. Inverted and normal segregation patterns calculated from the model were in agreement with experimental ones over an entire column consisting of dense and dilute regions.

Flow Behavior of a Gas−Liquid−Solid Fluidized Bed in a Self-Circulating Operation through an External Conduit

Flow behavior of liquid and multicomponent mixtures of solid particles in fluidizing columns with an external conduit was investigated for a self-circulating operation by an airlift effect. Experimental and analytical results are presented for circulating rates of liquid and particles and for axial changes in holdups of gas and solid in the column. From good agreement between both results, it was found that a one-dimensional sedimentation-dispersion model and mechanical energy balance equation were successfully applied to predict the axial change in gas and solid holdups as well as the circulating rates of liquid and solid particles in the columns.