Bed defluidisation during the fluidised bed pyrolysis of plastic waste mixtures

The risk of occurrence of phenomena inducing worsening of fluidisation quality and eventually leading to bed defluidisation is one of the major constraints to an easier utilisation of fluidised beds for the low-temperature pyrolysis of plastic wastes. In order to investigate these phenomena, different mixtures of plastic wastes, obtained by combination of three commercially-available recycled polymers, were fed to a laboratory-scale bubbling fluidised bed reactor. Two mechanisms of defluidisation were identified and the time at which defluidisation occurred was measured and correlated to a key variable of the process. The observed phenomenology was also simulated by means of room-temperature experiments carried out with a selected mineral oil. The results allow us to demonstrate the existence of a synergistic effect between the observed mechanisms of defluidisation. © 2004 Elsevier Ltd. All rights reserved.