Emission Characteristics of NO_x and Unburned Carbon in Fly Ash of Sub-bituminous Coal Combustion(Special Issue on International Conference on Power and Energy System)

Sub-bituminous coal is considered to be one substitute fuel for bituminous coal. Since sub-bituminous coal contains more than 20% moisture, there are some problems with its utilization, such as a decrease in combustibility, high NO_x emission and so on. This report describes the emission characteristics of NO_x and unburned carbon in fly ash of sub-bituminous coal combustion through the use of a pulverized coal combustion test furnace. On the sub-bituminous coal combustion, ignition at the burner exit worsened and the combustion flame became diffused. Then, both NO_x emission and the unburned carbon concentration in fly ash became high. In order to keep stable combustion and to form an effective NO_x reduction flame, the swirl vane angle of secondary air was reduced and the Air/Coal ratio was lowered. As a result, the combustion flame became moderate, and both NO_x emission and unburned carbon concentration in fly ash could be reduced.