Milling and separation of the multi-component printed circuit board materials and the analysis of elutriation based on a single particle model

Abstract

Electronic waste, in the form of printed circuit boards (PCBs) or printed wiring boards (PWBs), represents a significant and growing fraction of the waste generated in many communities. It is necessary to identify schemes to manage and dispose this waste in an environmentally safe manner. The present work, examines the use of mechanical means to separate the metallic and non-metallic components present in PCBs. The unique characteristics of PCB construction pose challenges to the mechanical means of separation. In view of these unique characteristics of PCBs, an empirical approach is suggested to evaluate the effectiveness of the mechanical separation process. Two milling operations were used to obtain the feed for the separation using elutriation. Compositions of different size fractions from the milling operations are presented. Experimental data from the separation process is presented and the extent of use of mechanical means that results in optimum separation is identified. The separation efficiency is analyzed in terms of composition, particle size and operating condition of the elutriation flow rate. A probabilistic analysis based on single particle settling velocity shows that separation results with uniform particle size fraction can be described effectively. However, the probabilistic analysis captures only the qualitative features with mixed particle sizes and components.