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 ofthese materials is still practiced causing potential risk to our ecosystem through gas emissions (essentially CH4) and groundwater leaching. Co-Gasification within the existing infrastructure of pulverized coal utility gasifiers is considered a practicalnear-term solution for these rich hydrocarbon waste materials while minimizing capital requirements and maintaining thehigh efficiency of pulverized coal reactors. Systematic and numerical modeling of coal/tire shred fuel blend gasification ispresented in this study. Co-combustion and gasification of tire shred and coal is a complex problem that involves gas andparticle phases, along with the effect of turbulence on the chemical reactions. Coal/tire shred gasification modeling involvesthe prediction of volatile evolution and char burnout from the co-pulverized coal/biomass particles along with simulation ofthe gasification chemistry occurring in the gas phase. The mathematical models used for co-pulverized coal/tire shredparticle gasification consist of models for turbulent flow (RNG k-ε model); gas phase gasification (Species Transportmodel); particles dispersion by turbulent flow (Cloud Tracking model); coal/biomass particles devolatilization (ConstantRate model); heterogeneous char reaction (Multiple surface reactions model); and radiation (Discrete Ordinates model). Thecoal was blended with 5, 10, and 20% tire shred (mass basis) for co-gasification. The effect of the percentage of tire shredblended with coal on the temperature distribution, products distribution, particle burnout rate, and pollutant emissions at theexit of the furnace will be presented.