Defluidization phenomena during the pyrolysis of two plastic wastes

A couple of commercially available packaging-derived fuels, both obtained a s a result of mono-material recycling programs of polyethylene (PE) and pol yethylene terephthalate (PET), were fed in a laboratory scale bubbling flui dized-bed reactor, made of quartz. The effect of the main operating variabl es (bed solids hold-up, inert material size, fluidizing velocity, plastics feed rate) on the agglomeration and the defluidization phenomena was invest igated by means of experiments carried out in the bed temperature range of 450-650 degrees C. Different mechanisms of defluidization were identified a nd characterized. The time at which defluidization occurred was correlated to the ratio between the bed solids hold-up and the polymer feed rate by me ans of linear relationships. An increase of this ratio, as well as a decrea se of the bed temperature, led to a decrease of the defluidization time for both the recycled polymers. No substantial effects were found in the teste d range of fluidizing gas velocities. An operating criterion to avoid deflu idization was finally proposed. (C) 2000 Elsevier Science Ltd. All rights r eserved.