Fluidised bed pyrolysis of low density polyethylene to produce petrochemical feedstock

Pyrolysis of plastic waste has been proposed as a tertiary or feedstock rec ycling route where the plastic waste materials are processed back to produc e basic petrochemicals that can be used as feedstock to make virgin plastic or refined fuels. The detailed analysis of the derived products from the p yrolysis of plastics provides data on the suitability of the process and th e influence of process conditions on the compatibility of the feedstock pro duced with the conventional petroleum feedstock. Low density polyethylene ( LDPE) is a major component of municipal solid waste and this paper describe s the influence of pyrolysis temperature from 500 to 700 degrees C on the y ield and composition of the derived products. The main gases produced from the pyrolysis of LDPE were hydrogen, methane, ethane, ethene, propane, prop ene, butane and butene. There was a dramatic increase in gas yield with inc reasing temperature of pyrolysis. Analysis of the derived oils and waxes sh owed that the pyrolysis of LDPE gave a mainly aliphatic composition consist ing of a series of alkanes, alkenes and alkadienes which showed a decrease in concentration as the pyrolysis temperature was increased. The oil showed an increase in aromatic composition with increasing temperature of pyrolys is and at 700 degrees C significant concentrations of single ring aromatic compounds and polycyclic aromatic hydrocarbons were detected. The derived o il and wax have great potential to be recycled back into the petrochemicals industry as a feedstock for the production of new plastics or the producti on of refined fuels. (C) 1999 Elsevier Science B.V. All rights reserved.