Utilization and recycling of end of life plastics for sustainable and clean industrial processes including the iron and steel industry

Abstract

About 400 million tonnes of plastics are produced per annum worldwide. End-of-life of plastics disposal contaminates the waterways, aquifers and limits the landfill areas. Options for recycling plastic wastes include, feedstock recycling, mechanical /material recycling, industrial energy recovery, municipal solid waste incineration. Incineration of plastics containing E-Wastes releases noxious odours, harmful gases, dioxins, HBr, polybrominated diphenylethers and other hydrocarbons. This study focusses on recycling options, in particular, feedstock recycling of plastics in high-temperature materials processing, for a sustainable solution to the plastic wastes not suitable for recycling. Of the 7% CO2 emissions attributed to the iron and steel industry worldwide, ∼30% of the carbon footprint is reduced using the waste plastics compared to other carbon sources, in addition to energy savings. Plastics have higher H2 content, than the coal. Hydrogen evolved from the plastics acts as the reductant alongside the carbon monoxide. Hydrogen reduction of iron ore in presence of plastics increases the reaction rates due to higher diffusion of H2 compared to CO. Plastic replacement reduces the process temperature by at least 100–200 °C due to the reducing gases (hydrogen) which enhance the energy efficiency of the process. Similarly, plastics greatly reduce the emissions in other high carbon footprint process such as magnesia production while contributing to energy. Keywords: Waste plastics, Thermo and thermoset plastics, Iron and steel industry, Feedstock recycling, Carbon sequestration, Energy and emissions savings