Numerical Modeling of Coal Tire-Shred Co-Gasification

Tires, plastics, cellulosic materials, i.e., papers and cardboards are rich in hydrocarbon yet land filling of the waste of these materials is still practiced causing potential risk to our ecosystem through gas emissions (essentially CH 4) and ground water leaching. Co-Gasification within the existing infrastructure of pulverized coal utility gasifiers is considered a practical near-term solution for these rich hydrocarbon waste materials while minimizing capital requirements and maintaining the high efficiency of pulverized coal reactors. Systematic and numerical modeling of coal/tire shred fuel blend gasification is presented in this study. Co-combustion and gasification of tire shred and coal is a complex problem that involves gas and particle phases, along with the effect of turbulence on the chemical reactions. Coal/tire shred gasification modeling involves the prediction of volatile evolution and char burnout from the co-pulverized coal/biomass particles along with simulation of the gasification chemistry occurring in the gas phase. The mathematical models used for co-pulverized coal/tire shred particle gasification consist of models for turbulent flow (RNG k-e model); gas phase gasification (Species Transport model); particles dispersion by turbulent flow (Cloud Tracking model); coal/biomass particles devolatilization (Constant Rate model); heterogeneous char reaction (Multiple surface reactions model); and radiation (Discrete Ordinates model). The coal was blended with 5, 10, and 20% tire shred (mass basis) for co-gasification. The effect of the percentage of tire shred blended with coal on the temperature distribution, products distribution, particle burnout rate, and pollutant emissions at the exit of the furnace will be presented.