Aluminium is a vital component of the world's economy, thanks to its versatile applications. However, the environmental impacts of primary production result in a growing desire and societal pressure to develop more efficient recycling techniques. Secondary aluminium is produced at 5% of the energy consumption used to produce primary aluminium. Unfortunately, many recycling techniques suffer from an undesired loss in quality and material due to the complex particle shapes, variety of alloys, and contaminants. This research focuses on a state-of-the-art scrap sorting technique that aims to overcome the problems associated with the singulation of particles with sizes up to 500mm (max. diameter). Singulation is the process where a random particle flow is regularized into an individually spaced 1D file of particles. Subsequent particle identification and sorting into multiple categories increases scrap quality to allow for more efficient up-cycling. A combination of literature study, model simulations and setup experiments is used to study the effects of particle- and equipment properties on obstructing processes. Firstly, this study focuses on three particle properties: Length-to-Width (LW) ratio, density, and complexity of shape. Four different samples are studied: Base case, high LW, high density, high complexity of shape. Obtained results show the adverse effects of increased LW-ratio on the singulation performance. An average LW-ratio increase from 2 to 6 decreases the singulation performance by 10-15%. Surprisingly, the expected frequent entanglement of complexly shaped particles was seldom observed. In addition, the flow of complexly shaped particles showed similar singulation rates compared to low LW particles. High density particles were only linked to minor obstructing events. Secondly, this study focuses on obstructing processes by studying the particle flow over and between setup equipment. Two processes are the most important: 1) transition behaviour (single particle flow) and 2) merging mechanisms (multiple particle flow). Video analysis has shown the adverse effects of unpredictable particle flow upon transitioning between setup stages. This results in an entirely random process, thereby deteriorating performance and rapidly wearing the chute surface. Unpredictable flow on the chute is primarily related to specific yet frequent circumstances. The amount of correction in flow a particle requires to align into a single file seems the best indicator. Centre-fed, parallel orientated particles require the least correction. Edge-fed, perpendicularly orientated particles require most. The latter is associated with the highest degree of unpredictable rolling. This observed phenomenon increases with particle size. The chute is designed to merge particles with crossing trajectories. Merging particles rotate around their point of contact as a whole until the combined bounding box is orientated parallel to the direction of flow. This explains the poor performance of high LW particles and surprisingly good performance of complex-shaped particles. The bounding box of merging high LW particles is already orientated parallel to the direction of flow. Limited rotational force is therefore exerted on the particles. In addition, the higher moment of inertia and chute design further restrict rotation towards sequential flow. Consequently, the current singulation process functions below its potential. The passive singulation process benefits from a reject of high LW particles towards the coarse faction (to be re-shredded) and smooth transition designs to reduce unpredictable flow.