Recycling Mixed Plastics Waste as Reductant in Ironmaking

Abstract

One of the major obstacles to the implementation of an appropriate plastics recycling scheme is the inhomogeneity of many plastics waste. Accordingly, most of the existing recycling schemes require a feedstock that is reasonably pure and contains only items made from a single polymer type. However, in reality, waste plastics contain a mixture of plastic types, and are often contaminated with non-plastic items. This demands sorting out, which is expensive and highly labour intensive. In this work, the reduction of reagent grade iron oxide by mixed plastic waste (MPW) has been investigated through experiments conducted in a laboratory scale horizontal tube furnace. Composite pellets of reagent grade iron oxide (97 % Fe₂O₃) with MPW [consisting of 50 wt % high density polyethylene (HDPE), 30% polypropylene (PP), 10% low density polyethylene (LDPE) and 10% polyethylene terephthalate (PET)] were rapidly heated at 1520°C under high purity argon gas and the off gas was continuously analysed for CO, CO₂ and CH₄ using an online infrared gas analyser (IR). The extent of reduction after ten minutes was determined for each carbonaceous reductant and the results were compared with the extent of reduction by conventional metallurgical coke under the same experimental conditions. The results show that iron oxide can be effectively reduced to produce metallic iron using MPW as reductant. An improvement in extent of reduction was observed over metallurgical coke and the individual polymers when MPW was used as reductant. This eliminates the need to sort out individual plastics from municipal solid waste for their effective utilisation as reductants in ironmaking.

Keywords: Reduction, Metallurgical coke, Mixed plastics waste, Extent of reduction