Application of electric field to a fluidized bed for recovering residual metals from fine particles of the non-metallic fraction of waste printed circuit boards

摘要

In this study, the strengthening of the density segregation in a gas-solid fluidized bed is evaluated by applying an external electric field to recover residual metals from fine particles of the non-metallic fraction of waste printed circuit boards. The results demonstrate that large amounts of metals remain in the fine non-metallic fraction of the waste printed circuit boards and account for 21.93 wt%. The main residual metals are Fe, Cu, Sn, Zn, Mg, and Pb, and their contents are 6.06 wt%, 535 wt%, 2.92 wt%, 1.99 wt %, 1.36 wt%, and 1,31 wt%, respectively. The external electric field apparently influences the fluidization characteristics by changing the hydrodynamics and the bubble motions in the gas-solid fluidized bed. The minimum fluidized air flow velocity is larger in a fluidized bed with an electric field than in a common fluidized bed. After applying the electric field, the bed expansion increases from 1.15 to 1.21, the gas is well-distributed, and the interaction between the gas and the solid is enhanced. The horizontal motion of the particles can break the agglomeration of glass fibers and loosen the gas-solid bed, which results in an increase in the metal recovery from 67.61% to 76.61%. Based on this research, a novel recycling flowchart of fine waste printed circuit boards is proposed. (C) 2018 Elsevier Ltd. All rights reserved.