Environmentally informed modelling and optimisation of shredding performance for recycling waste tyres

Abstract

The shredding process is a crucial and foundational step in most waste tyre recycling processes, designed to reduce tyre size into smaller fragments. However, a comprehensive quantitative analysis is required to determine the optimal shredding performance with minimum energy consumption and maximum productivity. Moreover, there is a need to investigate the environmental impacts of the shredding process for sustainable waste tyre management. To address these challenges, this paper aims to optimise both shredding performance and environmental impact by using Finite Element Methods (FEM) and Life Cycle Assessment (LCA). A FEM simulation model is developed and thoroughly validated against performance criteria, including particle size & distribution and energy consumption. We establish a cradle-to-grave structure, covering material acquisition, de-beading, shredding, classifying, and embankment application. The FEM model aligns the significant inputs and the outcomes of the shredding simulation with the scope and inventory of LCA. The FEM-LCA model is employed to investigate the effects of key design and operational variables on shredding performance and environmental indicators, including particle characteristics, throughput, energy consumption, and CO₂ emissions. By constructing an input-output correlation coefficient matrix, we identify parameters that have strong correlations with both shredding performance and environmental outcomes. Shredding process with reduced shaft clearance and cutter clearance can generate 80 % and 50 % more (<100 mm) shreds but consume 57 % and 100 % more energy for recycling waste tyres. However, increasing the clearances by 40 mm results in a reduction of CO₂ emissions in the shredding process by 25 % and 50 %, respectively. With a cutter clearance of 60 mm and a shaft clearance of 400 mm, these optimised settings improve shredding performance while enhancing environmental sustainability.