Energy- and economic-balance estimation of pyrolysis plant for fuel-gas production from plastic waste based on bench-scale plant operations

Abstract

Several pyrolysis plants have been developed and commercially operated to produce fuel oil from plastic waste. By contrast, only a few examples of fuel-gas production plants have been reported. This study investigates the feasibility of fuel-gas production from plastic waste using a bench-scale pyrolysis plant by analyzing the material and energy balances of the plant. As part of a waste-to-fuel-gas project for substituting natural gas used in cogeneration equipment, this study examines the material and energy balances during operation of an externally heated rotary kiln reactor.The scale-up simulation of a 200-kg/h plant was performed based on the operation results obtained for a 2-kg/h plant using polypropylene and laminates of polypropylene with polyethylene terephthalate as feedstock. Based on the 200-kg/h plant estimates, the amount of fuel generated as fuel gas, fuel-gas consumed, and excess fuel gas used for supplying electricity to a factory using a cogeneration system equaled 3.86 × 107, 1.49 × 107, and 2.42 × 107 MJ/year, respectively, in terms of the lower heating value. The excess fuel could be used as a natural-gas substitute in cogeneration systems. In cases where a fuel-gas production system with 200-kg/h capacity costs less than USD 2,467,000, the pyrolysis-based fuel production is considered economically beneficial compared to the current treatment methods owing to the associated cost savings of up to approximately USD 177,000/year realized by ensuring substitution of 2.42 × 107 MJ/year of natural gas.

Keywords

• Fuel gas
• Plastic waste
• Pyrolysis
• Energy balance
• Economic balance