Mathematical Modeling of Particle Suspension in Pachuca Tanks

The efficient performance of Pachuca tanks is strongly linked to the suspension of mineral particles, which results from the motion of the liquid caused by injected gas rising, in general, through a central draft tube. This study reports a computational investigation on the effect of operating and design parameters on the suspension of particles. By extending the classical 2-phase drift-flux model to compute the gas hold-up, the three-phase (water-air-particles) system was simulated as consisting of a variable-density liquid plus the solid particles. These two phases were treated as interpenetrated continua using an Eulerian approach to set a turbulent recirculating flow model in 2-D and transient state. The model predicted adequately the measured critical superficial air velocity, uc, needed for maintaining particle suspensions, in pulps with 10-50 wt% solids. Additionally, the model was used to investigate the operation of industrial size reactors, obtaining results that agree well with the general trends reported in the literature, and highlighting important differences with respect to laboratory-scale reactors.