Abstract

One of the main challenges for plastic waste conversion plants is low profitability due to variations in feedstock conditions and the small percentage of valuable components in the product. In this study, we designed the pyrolytic oil and gas upgrading process based on the innovative microwave-assisted pyrolysis method. The process is designed to recover energy and chemicals from 17.5 tonnes of oil feed per day, produced from the pyrolysis of 25 tonnes of pre-treated electronic waste plastic. A continuous distillation train with five columns is designed to recover toluene, ethylbenzene, and styrene at chemical grade purity with recovery rates between 70% and 90%. While considering no price for the feed oil, the configuration had a net present value of $2.24 million. When the feed oil price was increased to $262 per tonne, the net present value dropped to -5.80 million, requiring an external credit of $90.80 per tonne of waste to reach the break-even point. This highlights how the economic performance of upstream pyrolysis and metal recovery affects overall feasibility. Life cycle assessment showed that chemical recovery through pyrolysis outperformed conventional incineration when the electricity mix emitted less than 0.582 kg CO2-eq per kWh. In Quebec, replacing incineration with pyrolysis reduced the global warming impact by 145% from 40,545 to -16,155 kg CO2-eq per day for the treatment of 25 tonnes of e-waste. Due to uncertainties in the composition and flow rate of the waste stream, and to lower the capital cost of the plant, we designed the alternative semi-continuous upgrading process with only one column. Overall, more than 320 different scenarios were designed and analyzed. Results showed that the proposed system can achieve recoveries between 66-90% and 90% and requires the external credit as low as $18.89 per tonne of waste. Furthermore, adding a second column to the semi-continuous plant produced a profitable design with a net present value of $0.99 million, with no external financial support.