Experimental and CPFD study of axial and radial liquid mixing in water-fluidized beds of two solids exhibiting layer inversion

Abstract

Time-responses of concentration of a saline tracer were determined during fluidization by water at 15°C in a column of 191mm diameter. Mono-component beds contained 1.85mm glass beads (density 2500kg/m3) or 0.550mm ceramic spheres (density 3800kg/m3). A binary fluidized bed, containing equal volumes of these two solids, displayed layer-inversion at superficial liquid velocities of 40.5 and 43.5mm/s at 10 and 20°C, respectively. Saline tracer pulses were injected just above the distributor, at the column centre. The salt concentration at the bed surface was measured at three radial positions for superficial water velocities up to 127mm/s. Concentration profiles, simulated by computational particle-fluid dynamics (CPFD) with Eulerian–Lagrangian methodology, showed reasonable agreement with the experimental data. An axial/radial dispersion model was also applied for the mono-component and binary fluidized beds.. The axial dispersion coefficients for the glass beads exceed those for the ceramic spheres. Those for the binary bed are less than expected based on the mono-component data, though a maximum appears at the inversion velocity when closed–closed boundary conditions are employed.