Yonmo Sung

Experimental study on interaction and excess heat release under oxy-fuel combustion of blended coals

The combustion behavior and excess heat release during the oxy-fuel combustion of blended coals were investigated experimentally using a non-isothermal thermogravimetric analyzer. The atmospheres were set to 10%O2/90%CO2, 21%O2/79%N2, 30%O2/70%CO2, and 50%O2/50%CO2, and Arthur coal (bituminous coal, BA) and KPU (sub-bituminous coal, SK) were selected as fuel with blending ratios of BA25%/SK75%, BA50%/SK50%, and BA75%/SK25%. The purpose of this study is to investigate the interaction between the blended coals and the effects of blending ratio and oxygen concentration on the excess heat release under oxy-fuel combustion. The results showed that as the oxygen concentration and proportion of sub-bituminous coal increased, the peak value in the differential thermal analysis curve increased by the enhanced reaction rate. A higher oxygen concentration led to excess heat release. The ignition temperatures depended on the volatile matter content of the sub-bituminous coal, whereas the burnout temperature was largely affected by the fixed carbon content of the bituminous coal. For interaction behaviors on characteristic temperatures, the volatile release temperature shows an additive behavior; however, ignition and burnout temperatures show non-additive behaviors for blended coals.

Influence of Surrounding Gas and Coal Characteristics on Flame Propagation in Oxy-Fuel Combustion of Pulverized Coal

Oxy-fuel combustion of pulverized coal is one of the promising new technologies to reduce CO2 and NOx from coal combustion. However, the stability of pulverized coal flame is reduced in the oxy-fuel combustion. This flame stability is concerned with the flame propagation that is affected by surrounding gas and coal characteristics, such as gas temperature, gas composition, coal volatile, coal activation energy and coal size. In this paper, a study on the influence of surrounding gas and coal characteristics on the flame propagation velocity in oxy-fuel combustion of pulverized coal was preformed. One dimensional model was used to calculate the flame propagation velocity of pulverized coal clouds. In this model, the radiation is considered to be the main source of heat exchange, and Monte Carlo method was adopted for accurate calculation of radiation heat flux. It was found that the flame propagation velocity become higher with the decrease of coal activation energy and the increase of coal volatile. Also, according to the increase of gas temperature and O2 concentration, flame propagation velocity increased.