2014 Volume 55 Issue 4 Pages 700-707
In order to recycle important rare metals (such as tantalum) in the print circuit boards of waste electronic equipment, the devices must first be delaminated from the board. The devices are then separated into each device type such as capacitors, resistors, thermistors and so on. In this study, the effect of orifices on spherical particles was clarified through numerical simulations of airflow and air–solid multiphase flow in a vertical single-column pneumatic separator. Airflow velocity profiles and particle trajectories were investigated for different numbers of orifices using spherical particles of identical size and different densities. By introducing multiple orifices, the eccentricity of the velocity profile in the vertical direction could be corrected. This eccentricity is caused by the presence of a mesh, which recovers heavy particles after they pass through the second orifice. When the distance between orifices ranged from 400 to 625 mm, it was expected that high-speed and high-efficiency separation between orifices would be possible. It implies that step-by-step separation could be conducted in a single separation column. However, under the calculation conditions of our study, the orifices did not affect the separation efficiency because this factor depends on the velocity profile around the feeding position. The separation rate was maximized when the orifices were separated by 625 mm.
