Particle-fluid dynamics in narrow slit settler driven by asymmetric feed

The asymmetric feed addition of a slurry consisting of water and ballotini particles (glass beads), 63-75 mu m in diameter, into a narrow slit settler was investigated. The vessel was 2.5 m long, 1.2 m high, and 0.015 m in ho rizontal depth. The presence of the solid particles in the feed caused a sh ift in the plume angle, from the vertical direction to a near horizontal di rection. The change in the angle increased sharply to an asymptotic value a s the solids loading was increased and more gradually as the position of th e feed entry was shifted farther from the position of symmetry Apart from p roducing an interesting phenomenon, this study demonstrated clearly that, i n modeling sedimentation it is sometimes necessary to consider the effect o f solids concentration gradients on convection of the suspension. Coupling of the hydrodynamic and particle transport equations may therefore become n ecessary. The shift in the feed plume angle was a consequence of a pressure gradient associated with having, effectively, a higher solids loading on o ne side of the feed position than on the other. The experimental results we re analyzed from the perspective of a simple energy balance, and using a co mputational fluid dynamics simulation, which considered simultaneous hydrod ynamics and particle transport.