CHE.11 – Plastic to Petrol: Pyrolysis of Plastic Waste

• Yoon Chung
• Mark Hurley
• Ramcin Shakro
• Marek Smirnow

Global plastic production and accumulation continues to increase exponentially, with the world producing over 380 million tons of plastic per year. Plastic production is found in almost every industry typically producing single use plastics. Most of these plastics end up in landfills and incineration plants. These practices negatively affect the environment, polluting the air, the oceans, and the ground impacting humans, animals, plants, and Earth alike. Less than 10% of all plastic produced have been recycled. Something must be done to solve this recurring issue because conventional methods of dealing with plastic are not an effective long-term solution to the global plastic waste management issue.   The goal of this project is to investigate a chemical recycling method to deal with the accumulating plastic waste. This process utilizes pyrolysis of plastic waste, specifically polypropylene and polyethylene, to produce hydrocarbons blends that can be processed further to make diesel, gasoline, and heating oil used in homes. The plant design consists of a solids handling section, a pyrolysis-combustion section, a fractionating condenser, a gas concentration unit, and blending and storage section. The plastic waste feedstock first enters the solids handling section, where it is granulated, dried, and passed through an auger. From the auger the plastic waste enters a fluidized bed reactor along with sand and fluidizing gas. The waste plastic is pyrolyzed into hydrocarbon vapors and char. The sand and char are sent to the combustor unit where char is combusted to heat the sand and recirculate to the reactor. The hydrocarbon vapors from the reactor are sent to a condensing fractionator where cuts of heavy oil, light cycle oil, naphtha, and non-condensable gasses are separated. Heavy oil, light cycle oil, and naphtha is sent downstream to blending and storage. The non-condensable gas stream is split to be used as fluidization gas for the reactor and the remaining gas is sent to a gas concentration unit. The design processes 220,000 tons per year of plastic waste and generates 150, 1450, and 280 barrels per day of heavy oil, light cycle oil, and naphtha. In addition to plant design this report investigates competing processes, market analysis, process control schemes, HAZOP analysis, and an economic analysis. Economics of this design has shown heavy dependency on feedstock and product pricing. Plant economics would benefit from government incentives such as RIN pathways which are currently not available for plastic waste. Once economic issues are overcome, this technology has the potential to develop a feasible circular economy. Cracking technology is already well developed by the petroleum industry and the adjustment to a plastic feedstock would require minor additional equipment and slight adjustment to processing conditions. The petroleum industry has a sizeable advantage in developing and scaling these processes.