Fuels by pyrolysis of waste plastics from agricultural and packaging sectors in a pilot scale reactor

The pyrolysis of waste plastics (so called chemical recycling) is one perspective way of their utilizations, but the end product properties are a key point of the industrial leading of processes. In this paper a pilot scale pyrolysis process has been investigated. Waste plastics were decomposed in a tube reactor at 520 °C, using hourly feed rate of 9.0 kg. Raw materials were selectively collected wastes from agricultural and packaging industry. For supporting the more intensive cracking of CC bonds of main polymer structure a commercial ZSM-5 catalyst was tested in concentration of 5.0%. Products were separated into gases, gasoline, light and heavy oil by distillation. Plastic wastes could be converted into gasoline and light oil with yields of 20–48% and 17–36% depending on the used parameters. The gas and liquid products had significant content of unsaturated hydrocarbons, principally olefins. In the presence of ZSM-5 catalyst the yields of lighter fractions (especially gasoline) could be considerably increased and the average molecular weight of each fraction has decreased. Gasoline had C5–C15 hydrocarbons, while light oil had C12–C28. The used catalyst has promoted the formation of i-butane in gases and affected the composition of both gasoline and light oil. Properties of products are advantageous for fuel-like applications, and they are able to increase the productivity of refinery. On the other hand the possibility for further utilization of products from pyrolysis basically was affected by the source and the properties of raw materials. Waste polyethylene from agricultural consisted of some elements from fertilizers (N, S, P and Ca), which could not be removed from the surfaces of raw materials by pre-treatment (e.g. washing). In that case significant concentration of N, S, P and Ca can be measured in all products, but the catalyst has decreased the concentration of impurities. Gasoline, light oil and heavy oil were nitrogen free and sulphur content was below 12 mg/kg in hydrocarbons obtained by the pyrolysis of polypropylene waste from packaging.