This paper describes development of reduction technology of unburned carbon concentration in fly ash during blended combustion of sub-bituminous coal with bituminous coal using a pulverized coal combustion test facility of CRIEPI. In this investigation, blended ratio of sub-bituminous coal means 30%. Then, moisture content of sub-bituminous coal is about 20% and fuel ratio of bituminous coal is about 1.5. When both primary air velocity and swirl vane angle of secondary and tertiary air are reduced, oxygen consumption progressed efficiently around the burner outlet. And by adaptation of air injection point and ratio for multi staged air, both NO_x concentration at the exit of furnace and unburned carbon concentration in fly ash are able to be reduced. Furthermore, when pulverized coal is concentrated at the exit of burner, oxygen consumption is improved still more. As a result, it is cleared that unburned carbon concentration in fly ash is reduced to 3% at 100ppm of NO_x concentration at the exit of furnace by optimizing burner structure, operation condition and multi staged air injection condition.
