Solid distribution and mixing time in stirred tanks: The case of floating particles

This work concerns floating particle distribution and liquid mixing dynamics in a solid-liquid stirred tank. Measurements of local solids concentration distribution at steady-state conditions and of liquid homogenization in the presence of dispersed particles at transient conditions are collected with up-pumping and down-pumping pitched blade turbines. Electrical resistance tomography is the selected experimental technique for the data acquisition in the opaque solid-liquid mixture. For the time dependent conductivity data processing, the same method commonly applied to the mixing time determination from planar laser induced fluorescence measurements is considered. The method is successfully extended to the characterization of liquid mixing with floating particles. The local data obtained by the ERT technique over the whole vessel volume are fully exploited. The robustness of the method for tackling conductivity variations close to the liquid free surface and due to the particles movement is assessed.