Relevance and challenges of plant control in the pre-processing stage for enhanced sorting performance

Abstract

To increase recycling rates many technological improvements can be made within sorting (processing and sorting on article basis) and recycling (processing and sorting on particle basis) of waste. This paper discusses such technological improvements, focussing on the potential of pre-processing (pre-shredding, screening, air and ballistic separation) in sorting plants. For this purpose, the general structure of state-of-the-art sorting plants is briefly introduced. Material flow characteristics such as input material composition or volume flow, have high impact on the performance of such sorting plants and are discussed accordingly. By adjusting parameters such as shredder speeds or screen cuts, these characteristics can be set to adjust the plant in accordance with variations in the input material. Such adaptions can only be made if the material flow data is reliable and available in nearly real-time (e.g., through built-in sensors). The related challenges in data acquisition, data analysis, and plant control are discussed. Finally, a case study is presented to demonstrate the potential of adaptive plant control: Through data derived from near-infrared sensors the load of two processing lines could be adjusted, resulting in significantly increased plant performance: Yield of product fractions from 3D-/heavy processing lines could be increased by 3-15 wt%.