2014 Volume 55 Issue 6 Pages 952-957
To recycle important rare metals (such as tantalum) from the printed circuit boards of waste electronic equipment, devices must first be delaminated from the boards. The devices are then separated into individual device types. For the practical use of the separation process, the authors previously developed a double-tube pneumatic separator. One of the features of this equipment is the introduction of orifices in a pneumatic separation column; an air–solid multiphase flow simulation was conducted to clarify its effect. The effects of the orifices on the floating characteristics and floating rates of cuboid particles and spherical particles with the same solid volume and mass as the cuboid particles were investigated for cases in which the number of orifices and the volumetric airflow rate in the separation column were varied. The results showed that the floating characteristics of cuboid particles were much different from those of spherical particles. It was estimated that the volumetric airflow rate could be decreased by 14% with the cuboid particles and the same particle recovery could still be achieved. When the volumetric airflow rate was identical, the treatment throughput for the cuboid particles was expected to increase by 20–30%. These results were caused by the difference in the cross-sectional areas of the particles, which indicates that taking the particle shape into account is extremely important for the numerical simulation of pneumatic separation. To thoroughly recover the cuboid particles, it is ideal to use a volumetric airflow rate greater than 0.129 m3·s−1 or less than 0.0615 m3·s−1, regardless of the orifice introduction. The number of orifices had no effect on either the separation efficiency or floating rate in the range of 0.118–0.129 m3·s−1. On the other hand, it was shown that the floating rate clearly changed depending on whether the orifices were introduced or not for the 0.103 m3·s−1 case.