CFD modeling of devolatilization and combustion of shredded tires and pine wood in rotary cement kilns

摘要

Computational fluid dynamics (CFD) has been used to study the devolatilization and combustion of large particles of shredded scrap tire "rubber" and pulverized pine wood "biomass" in a rotary cement kilns. The CFD model constitutes of modeling the hydrodynamics within the rotary kiln, heat transfer, devolatilization and co-combustion of rubber and biomass blends. Equivalent particle diameters of 1 mm and 2 mm for biomass and rubber, respectively, were used to simulate the process conditions and co-combustion in cement rotary kilns. The ratios of biomass substitution were varied from 5% to 20% on mass basis. The effect of the percentage of biomass content on the temperature distribution and devolatilization rate as well as wall heat transfer rate are presented. Results indicate that up to 20% biomass blend provides improved combustion characteristics compared with combustion of scrap tire alone. Further, the devolatilization rate was found to improve remarkably when scrap tire is blended with biomass. Most importantly, the biomass blend was found to increase the flame spreading and penetration, consequently improving the wall heat transfer rate, therefore providing favorable conditions for heat transfer to the cement clinker. The present study provides additional knowledge for future investigations on the use of biomass residues and some industrial wastes as alternative fuels for rotary cement kilns. That is, the use of alternative fuels in rotary cement kilns has a potential for economic improvement and environmental sustainability.