The Control of Separation Processes in Mechanical Recycling of Waste Refrigerators by Partition Function

The recycling of e-waste in general allows the recovery of valuable materials, which can be reused as secondary raw materials. However this implies, to adopt reliable treatment processes to achieve specific standard characteristics. Actually, the market standards are very strict and strongly affect the economic value of recovered materials.

In particular, waste refrigerators recycling allows the recovery of different plastic materials and metallic fractions (ferrous and non ferrous), whose economic value has considerably increased in the last years. Only in Italy, in 2010, approximately 66,000 tons of waste refrigerators were collected for recycling. An efficient recycling treatment could assure about 85% of recovery rate.

In this paper, a model to control and characterize the materials recovered from mechanical recycling of carcasses dismantled from waste refrigerators is proposed. The treatment flow sheet consists of various separation and comminution operations. A mathematical model was implemented to determine a partition function, utilizing data obtained from the treatment of 100 waste refrigerator carcasses, carrying out mass balance of recovered materials. The partition function was used to determine control parameters and assess the quality of the recovered products, and, therefore, of the applied technologies. The results have shown that for waste refrigerator carcasses it has been possible to reach for ferrous metals a recovery rate of 97.5% with purity of more than 98%. Other metals also reached a good quality (about 87% for non-ferrous metals, 92% for mixed recyclable plastics), but with lower recovery rates.

Keywords: Material control and characterization, Mechanical recycling, Waste refrigerators.