Control of Operative Conditions in CRTs Glass Recycling Process

Dismantled CRTs are generally used in the production of new CRTs in close-circuit recycling scheme, but CRT technology is becoming obsolete, clue to the technological changes towards flat panels so new applications must be found. On the other hand, new legislation, such as the European Directive on Waste Electric and Electronic Equipment (WEEE), will require increased recycling and recovery rate, while landfilling should be more and more a residual option. CRTs contain mainly two types of glass (funnel and panel), welded together with a lead frit. In colour equipments, the funnel contains a significant quantity of PbO (18% similar to 20% in weight), and present a carbon coating on the inside surface. The panel, instead, is characterized by high levels of BaO (9% similar to 11% in weight) and SrO (8% similar to 10% in weight). In this study, the whole process for CRT glass recycling has been tested to obtain a product able to meet the required market standard. A mechanical process at industrial scale has been tested, consisting of an attrition operation controlled by a screening unit. It has been monitored in order to set up the best working conditions in terms of fine particles production and quality control. The products (input, oversize and undersize) have been characterized by image and chemical analysis to determine morphologic, morphometric and compositional properties. The analysis on under-size product allowed individuating the suitable rotational speed and water content to control fine particle production and decontamination. The obtained glass cutlets, thus, have been utilised in a thermal process at laboratory scale to produce a porous glass suitable for structural and insulating applications in building constructions, using calcium carbonate as foaming agent. Different operative conditions have been tested, varying process temperature and concentration of the foaming agent. The properties of porous glass obtained have been investigated by physical analysis, in order to set up the proper conditions.