Fig. 5B and C show the CO and NOx concentrations profiles within the combustor at various secondary gas flow rates, respectively. In Fig. 5B, at the location of 2.03 m above the distributor, the CO concentration values increase with secondary gas flow rate. At the highest secondary gas flow rate (2.56 Nm3/min), the CO concentration reaches the peak value. This can be attributed to the fact that more un-burned particles are carried back to the splashing zone. The stoichiometric oxygen ratio in the bed is 90%; therefore, as more particles carried back to the bed and splashing zones, the CO concentration goes higher. In Fig. 5C, at the location of 2.03 m
above the distributor, NOx concentrations increase with the secondary gas flow rate which is due to the fact the higher secondary