Technoeconomic feasibility of producing clean fuels from waste plastics: A novel process model

Plastic waste is a problematic issue impacting the environment and human health. A proper recycling of plastics to valuable products is highly needed to meet the increase in energy demand. Plastics have high heating value; therefore, the thermochemical recycling of plastic waste is a valid and feasible approach. Recently, ethanol has attracted wide applications such as the conversion of ethanol to olefins, and hydrocarbons. It burns completely and cleanly, where it reduces the emissions of greenhouses compared to the usual fuels. Hydrogen and other higher hydrocarbons are also crucial in meeting the energy demand. In this study, the plastic waste, mainly polyethylene and polypropylene (due to their availability) were gasified using steam gasification process to produce syngas which then was further processed to hydrogen, ethanol, and other valuable liquid hydrocarbons. An alternative design is constructed integrating steam methane reforming (SMR) with plastic gasification to utilize the heat at the outlet of the gasifier and to enhance the syngas heating value. The two models were compared in terms of syngas heating value, energy analysis and economic analysis. The main parameters that have been evaluated are the production rate of fuel per total feedstock, total required heat, overall process efficiency, and fuel levelized production cost. The results indicated that Case 2 generates syngas with a higher heating value of 55 %, produces four times more H₂, and comparable amount of ethanol and other fuels than Case 1. The analysis also revealed that Case 2 has a process efficiency that is 3 % better and a 37.5 % lower fuel production cost than Case 1. Overall, the design of Case 2 was found to be more efficient and cost-effective than the Case 1 design.