Morphological and Morphometrical Characteristics of Particulate Solids To Recycle Resulting from Electric Cables Crio-comminution.

Abstract

Waste disposal is nowadays a well-known critical problem for environmental protection. For this reason, in the last years, the research in the field of waste recycling increased more and more with the specific target to find solutions oriented to reduce the environmental impact of waste and to recover precious metals and other useful materials. In this perspective it assumes great importance the possibility to recover waste products resulting from material goods dismantling, or from products at the end of their "life cycle", or simply from "common" household or industrial waste [1]. Electric cables represent a great family belonging to such a class of products.The possibility to recover metals from electric cables has been investigated in this work. Electric cables are usually constituted by various components, different for chemical-physical attributes, that is: i) conductors (i.e. copper or aluminum), ii) shield materials, usually metallic, iii) insulating materials (i.e. PVC, PE, rubber) and iv) coating materials (i.e plastic or metals). The study was particularly addressed to verify the effect of the comminution of such products when performed at different temperatures, ranging from room up to criogenic conditions, utilizing different cooling media as CO 2 (-20°C) and nitrogen (-100°C). More specifically the parameters investigated have been particles morphological and morphometrical attributes and their degree of liberation, being these parameters of primarily importance in respect of the further electrostatic separation processes (particle surface charge and flow modalities) and final reuse (mixture properties).A systematic imaging based procedure [2] was applied on the particle products [3] resulting from the different criogenic comminution tests. Results envisaged as particles present a different shape (Figure 1) according to the different comminution temperature applied ( Figure 2). Particle profile roughness seems to be particularly influenced by temperature ( Figure 3). More specifically the results obtained through criogenic comminution show, in average, a lower size class distribution for the products in comparison with those obtainable at room temperature. Moving from room temperature to CO 2 and nitrogen environmetal controlled comminution, particles show a decreasing value of fractal dimension [4], of Feret diameter and of the area/perimeter ratio. Such results have to be economically analyzed and compared in respect of the different level of energy required for the two approaches.