Comparative study on the effect of fragmentation type on components liberation during recycling of printed wiring boards

摘要

The use of selective comminution is an essential requirement for pre-concentration processes, as early upstream separation has proved to be most efficient. Comparative comminution tests involving Electro Dynamic Fragmentation (EDF) and shredding in cutting mill have been carried out with the aim to evaluate the liberation degree of printed wiring boards (PWB). A fragmentation protocol has been elaborated enabling a rigorous comparison between identical PWBs treated with the both equipment. In the case of EDF, employing various energy inputs and successive treatment stages has resulted in different fragmentation degrees starting from entire removal of components to structure delamination and size reduction. Second stage communition by hammer mill preceded by EDF has secured better copper liberation in comparison with two-stage EDF. Evaluation of copper liberation degree was carried out through following particle size evolution of the fragmented fractions as well as by dedicated copper leaching protocol. Although tendency towards liberation along material boundaries is well pronounced when EDF was applied, this has not led to an improved liberation in the case of the tested PWB's.