Conclusion
The investigation of combustion behavior and pollutant emissions
has been conducted in a pilot scale VFBC for sawdust and RDF.
Experiments were conducted to investigate the effects of various
operating conditions, such as fuel property, bed temperature,
excess oxygen ratio, and in-bed stoichiometric oxygen ratio on the
CO and NOx emissions. The results show that due to their different
particle structures, sawdust combusts primarily in the splashing
zone, while RDF combusts primarily in the bed zone. RDF combustion
has lower temperature levels compared with sawdust, and
its in-bed temperature distribution is nearly uniform. The CO
emissions of both fuels decrease with the bed temperature, excess
oxygen ratio, and in-bed stoichiometric oxygen ratio. The combustion
of sawdust cannot meet the CO emission requirement of
Taiwan’s EPA. However, using RDF as the fuel, the peak CO emissions
of this study are lower than 50 ppm under all operating
conditions. In this study, flue gas recirculation combustion mode
was employed to decrease the NOx emission. The NOx emissions
show an inverse trend with that of CO emission, and NOx emissions
from the combustion of both fuels are within 100 ppm.