RECYCLING OF POLYMERS BY PYROLYSIS

The pyrolysis of plastic waste, scrap tires and other polymeric materials in a fluidized bed has been carried out based on a scale up program (laboratory plants 70 g/h, 500 g/h, 3000 g/h, and pilot plant 20-50 kg/h). The fluidized bed shows short residence times and high heat and mass transfers, and is heated indirectly up to 600 - 800 degrees C. In the case of poly(methylmethacrylate) (PMMA) or polystyrene as feedstock up to 97 wt. % of the monomer can be recovered. Other polymers give a more unspecific product spectrum. Depending on the process parameters between 30 and 60 % of the polymeric material could be recovered as oil which is comparable to that of a mixture of light benzene and bitumious coal tar if the pyrolysis gas is used as fluidizing gas. The other fractions are gas and a residue containing fillers and impurities (heavy metals). The gas fraction contains mainly methane, ethane, ethene, and propene, the oil fraction benzene, toluene, xylene, and naphthalene.