4. Conclusion
CO emission decreases with the excess oxygen ratio and the secondary gas flow rate, while NOx emissions show an inverse trend. The temperature profiles within the VFBC show a generally similar trend under various operating conditions. Higher secondary gas flow rate favors complete combustion of crushed peanut shell due to the stronger vortexing effect, resulting in higher combustion efficiency. To meet both minimum CO and NOx emission requirements of Taiwan EPA regulations, excess oxygen ratios ranging from 40% to 55% and the secondary gas flow rates ranging from 1.56 to 2 Nm3/min are optimal for crushed peanut shell combustion
in the VFBC.