To study the effects of flue gas recirculation ratio on combustion and heat transfer characteristics in oxy-coal combustion

numerical investigation on air combustion and oxy-fuel combustion of pulverized coal was carried out in a 500 kW combustion test facility. Moreover

the chemical permeation devolatilization(CPD) model was used to describe the devolatilization behavior of pulverized coal. The volatile components are considered as a variety of light gases. The detailed reaction mechanism was applied for volatiles combustion

and the radiative property models were modified for oxy-fuel combustion. The results show that

although the momentum ratio of the secondary air to the primary air is reduced by more than 50% in oxy-fuel combustion

employing the same swirl burner can still obtain the in-furnace flow characteristics which is similar to the air combustion. Both the combustion temperature and the ignition position of the pulverized coal are affected by the circulation rate. In oxy-fuel combustion with recirculation ratio of 72%

the distribution of the average temperature in the furnace and the ignition position are similar to those in air combustion. As the increase of recirculation ratio

the radiative heat transfer decreases.