Computer modelling methodology for shredding of end of life consumer electronic devices

Increased environmental concerns in recent years as well as potential economic benefits and, in some cases, mandatory regulations have placed more challenges on the recycling of end of he electronic products. The first step of the recycling system is to disassemble the pre-collected end of life electronic products either by hand or to shred by machine in preparation for the following recycling steps. Since the volume of the end of life electronic products for recycling is huge, a great deal of manual labor is required for hand disassembly. Because of the high cost of labor, shredding is often a more economical choice than manual operation.;Quality control of the intermediate recycling products is of critical importance to reach recycling targets determined by economic and environmental considerations. Thus the shredding operation plays an important role in the whole recycling system since it affects the characteristics (size, composition, etc.) of the intermediate recycling streams and thus the ultimate material recovery and the recycling rate. Accurate knowledge of the shredder output is needed to optimise the mutual compatibility of the successive processes in the recycling system. To optimise material recovery and to minimize waste generation in recycling end of life electronic products, and to get better understanding of the shredding process and thus better quality control of the intermediate products created during shredding, a computer simulation model for shredder is developed and presented in this thesis. This is of critical importance to reach recycling targets. Results from the simulation model may also provide suggestions for the designer of electronic products in the view of the relationship between product design and recycling rate.;The computer simulation model presented in this dissertation is developed based on advanced mathematical matrix operations and manipulation. The model simulates the size reduction and material liberation during the shredding process for end of life electronic products.;Based on the simulation of the transition of size distribution and liberation distribution of end of life electronic products during the shredding process, we can investigate the interrelationship between product design and its recycling rate at its life cycle closure.;To evaluate the validity of the computer model, an image-analysis based procedure is proposed which measures the size distribution and liberation distribution data and uses those data to construct size distribution and liberation distribution matrices for inputs to and outputs from the shredder. The image analysis procedure and the accompanying algorithm to transform the collected 2-D data to 3-D data can be used to evaluate the computer simulation model.;The computer model assumes that all materials constituting end of life electronic products defined in the shredder model break according to the same shredding transformation matrix. This is obviously a simplification since various materials will break differently due to their specific mechanical properties, joint methods, designs, and complexities. How to take those differences in the shredder simulation model into consideration is a subject of future work.