Perpustakaan Digital ITB

The use of biomass as a co-firing fuel in coal-fired power plants has become an important strategy to reduce fossil-fuel consumption and pollutant emissions. Sawdust is a potential biomass resource because it is widely available as a wood-processing residue. However, raw sawdust has high moisture content and different combustion characteristics from coal, while torrefied sawdust has improved fuel properties and more coal-like behaviour. Therefore, this study investigates the effect of co-firing coal with raw and torrefied sawdust on temperature distribution, flue-gas composition, and emission characteristics in a 350 MWe pulverized-coal boiler. The analysis was conducted using computational fluid dynamics (CFD). The 100% coal case was first validated against reference operating data and showed acceptable agreement, with errors of 0.55% for economizer outlet temperature, 2.88% for furnace exit gas temperature, and 1.13% for excess oxygen. The simulation cases consisted of 100% coal, 10% and 20% rawsawdust co-firing, 10%, 20%, and 50% torrefied-sawdust co-firing, and 100% torrefiedsawdust firing. The evaluated parameters included temperature distribution, furnace exit gas temperature, outlet temperature, O?, CO?, H?O, SO?, and predicted pollutant NO. The results show that biomass substitution generally reduced the peak furnace temperature. Raw sawdust slightly decreased the temperature intensity while maintaining a similar combustion-zone location to coal. Higher torrefied-sawdust ratios produced a more uniform temperature field but caused a larger reduction in furnace temperature. Co-firing also reduced SO? and predicted NO emissions compared with the 100% coal case. Among the investigated cases, 20% torrefied-sawdust co-firing was selected as the recommended ratio because it produced the furnace exit gas temperature closest to coal, maintained a similar temperature distribution, and reduced pollutant emissions. Therefore, 20% torrefied sawdust provides the ratio because it produced the furnace exit gas temperature closest to coal, maintained best balance between thermal performance and emission reduction under the assumptions of this numerical study.