Continuous flow cracking of waste plastics

Abstract

Experiments of waste polymers cracking in a continuous flow tube reactor were carried out. The main components of the reactor unit were a screw extruder as a waste plastics feeder and a tube cracking reactor equipped with an internal screw mixer. Cracking process was realized at the temperature range 420–480 °C and raw material feeding rate from 0.3 up to 2.4 kg/h. The principal process products, gaseous and liquid hydrocarbon fractions, are similar to the refinery cracking products. They are unstable due to the high olefins content (especially from polystyrene cracking) and their chemical composition and properties strongly depend on the applied feed composition, i.e. shares of polyethylene, polypropylene and polystyrene. The material balance experiments showed that the main products, liquid or solid materials in ambient temperature, contain typically 20–40% of gasoline fractions (range of boiling point 35–180 °C) and 60–80% of light gas oil fractions (initial boiling point>180 °C). The solid carbon residues are similar to coal cokes and contain even of 50% mineral components. Their calorific values attain 20 MJ/kg and they are solid fuels of quality similar to brown coals.