Gasification of waste tires in a circulating fixed-bed reactor within the scope of waste to energy

Abstract

Thermochemical decomposition of waste tires was evaluated in order to produce solid and gaseous products within the aim of waste-to-energy concept. Pyrolysis and gasification occur in an “oxygen-starved” environment to “thermally degrade” organic wastes. Waste tires form a large volume of a landfill space that may lead to serious environmental issues and management complexities. Proximate and ultimate analyses reported that approximately 80% carbon in waste tire can be converted to different solid, liquid and gaseous forms for energy gain. Pyrolysis and gasification experiments were carried out in a circulating fixed-bed reactor with cyclone separator at varying temperatures between 600 and 800 °C. Dried air (0.05–0.5 L/min) and pure oxygen (0.01–0.015 L/min) were fed to gasification reactor as partially oxidizing agents. Pyrolysis gasification (PyroGasification—PG) was conducted to produce “syngas” which mainly contains carbon monoxide and hydrogen. One and 4 h of cooking time for the first-step pyrolysis were applied in a nitrogen-rich medium before gasification to enrich carbon amount in fuel. A syngas rich in H2, CH4 and CO with a high calorific value of almost 4900 kcal/m3 was obtained in gasification experiments performed with 0.05 L/min of dried air. Volumetric percentages of hydrogen and methane in syngas were around 35% and 40%, respectively. More than 65% mass and 80% volume reductions which are very important for waste management hierarchy and minimization were achieved by gasification of waste tires.