(239f) Techno-Economic and Life Cycle Analysis of Polypropylene Plastic Waste Recycling through Fast Pyrolysis

Plastic disposal has been generating several environmental problems in the past decades. Currently, only 9% of plastic waste is mechanically recycled in the United States. Chemical recycling breaks down the plastics waste into its constituents, therefore complements mechanical recycling, reducing the environmental impacts and resource depletion. The pyrolysis process can handle hard-to-recycle plastics, while producing a wide range of valuable products including oil, waxes, and aromatics. Therefore, pyrolysis provides opportunities to reduce oil usage, carbon dioxide emissions, and the quantities of waste for disposal. On the other hand, the economic potential and environmental impacts are not well studied for particular feedstocks.

Polypropylene (PP) is one of the most abundantly used plastic types, and it constitutes 16% of the global plastic production. For this study, we focus on the design, synthesis, and simulation of an open-loop recycling process of waste PP through fast pyrolysis, and exam the environmental and economic performances. The reactor was designed to operate at 510 ℃. Operating at this temperature had a synergistic effect on the plant by optimizing the production of paraffin waxes while suppressing the formation of liquid petroleum gas (LPG) and aromatics The subsequent produced waxes were further cracked using a fluid catalytic cracking (FCC) reactor in a second fluidized bed reactor. In addition, a total of three distillation columns were utilized to separate product streams and produce 99 % purity gasoline and diesel. Techno-economic analysis and life-cycle assessment were conducted to characterize the economic feasibility and environmental implications of the proposed technology. The initial dried plastic throughput of the plant was set at 2500 kg/hr, while sensitivity analysis on important process parameters such as plant capacity, and volatility of gasoline, diesel, and plastic prices was done to obtain the optimum plant design conditions for both profitability as well as the environment. Results of this research indicate that a fine-tuned fast pyrolysis process integrated with downstream upgrading and separation units presents a potential opportunity to feasibly convert plastic wastes into liquid fuels such as gasoline and diesel to achieve circular economy.