Characteristics of co-combustion of anthracite with bituminous coal in a 200-MWe circulating fluidized bed boiler

The effect of co-combustion of Vietnamese anthracite with Australian bituminous coal on the performance of a commercial circulating fluidized bed boiler was observed in the Tonghae thermal power plant.The temperature in the cyclone exit of the boiler increased slightly, which caused a decrease in the desulfurization efficiency as the co-combustion ratio of the bituminous coal increased from 40 to 100%. The unburned carbon fraction also increased. Consequently, the fine particles of the bituminous coal had lower combustion reactivity than those of the anthracite.NOx emissions decreased as the bituminous coal ratio increased, although the fraction of nitrogen in the bituminous coal was higher than that in the anthracite. However, the emission of dust was found to increase due to an increase in the amount of CaO and MgO in the fly ash, which could lower the efficiency of the electrostatic precipitator.From these results, we concluded that the complete switch from the anthracite to Australian bituminous coal was possible, although the efficiency and the operation stability became lower than before. Additionally, as a future study, it is necessary to monitor the instability of the temperature increase and its effect on the prolonged clinker formation in the boiler.

► Co-combustion of different grade coals was carried out in the commercial CFB boiler.
► The reactivity of fine particles of coals affected the performance of the CFB boiler.
► Cyclone temperature increase caused the decrease of the desulfurization efficiency.
► NOx emission decreased despite higher fraction of N in co-combustion condition.
► Dust emission was affected by CaO and MgO fractions in the fly ash.