Improving particle flow in liquid-solid countercurrent extraction tower by insert structure optimization: A combined study on experiments and DEM simulations

The particle velocity distributions in the liquid-solid countercurrent nylon 6 extraction tower equipped with different types of inserts were investigated by both cold-model experiments and 2D-DEM simulations. The cold-model experiment results near the insert were well interpreted by the distribution of the particle contact force acquired from the DEM simulation. Compared with the disordered particle flow caused by a conventional single-funnel insert, the uniform particle flow could be realized by a special combination of single-funnel inserts with 53 degrees and 35 degrees dip angles of the upper and lower parts, respectively. In addition, a new type of insert, the multi funnel insert, was found to be more beneficial in improving the uniformity of the particle velocity distribution because it made the particle contact force near the insert uniform. Furthermore, the mass flow state could be maintained in a wider range of discharge rate, which implied an enhancement of the operating flexibility of the tower equipped with the multi-funnel insert. These developed inserts have the potential to be applied in large-scale liquid-solid countercurrent extraction processes. (C) 2018 Elsevier B.V. All rights reserved.