Energy Recovery from Waste Tires Via Thermochemical Pathways

Abstract

AbstractDemand for automotive tires has been increasing at a significant rate to reach production rate of 2.9 billion in 2017 that contributed to the generation of almost 1 billion waste tires. The pathways for handling of these waste tires have been limited to aggregate construction applications and direct incineration as fuel. The rate of recycling feasibility was limited by the availability of waste tires with structure intact for their upgrading and reuse in the economy. In the USA, although 40% of the waste tires are disposed by combustion for energy recovery in cement kilns, pulp and paper mills, and electricity generation, the presence of sulfur from vulcanized rubber, the production of hazardous pollutants, and low temperatures caused due to slow heterogenous combustion leads to significant energy and resource losses. Additionally, this pathway is limited to thermal energy production and thus lacks versatility. Alternative thermochemical pathways such as pyrolysis and gasification offer better pathways for the utilization of these wastes as they provide uniform products such as synthetic gas, bio-oil and char. Versatility is also achieved via syngas production as it is a precursor to liquid fuels and various other essential petrochemicals. These pathways provide improved energy efficiency, feasibility, and scalability for increased waste tire utilization and value outcome compared to the current application pathways. Results are reported from the investigations on high-temperature pyrolysis and CO2-assisted gasification of waste tires with focus on the evolutionary behavior of syngas production, its constituents, and energy yield in lab-scale fixed-bed reactor. The impact of CO2 addition, temperature, and the addition of biomass feedstock to the waste tire was investigated to understand the feasibility of waste tire disposal via this pathway while also utilizing the CO2 pollutant and maintaining high energy efficiency. Lack of inhibitive effects observed when tire was co-processed with biomass, makes the disposal of waste tires along with other wastes easier along with established feasibility regime for efficient and economical disposal of waste tires while recovering energy and utilizing CO2.KeywordsWaste tiresSyngasGasificationPyrolysisRecyclingEnergy recovery