Emission Characteristics of NOx and Unburned Carbon in Fly Ash of Sub-bituminous Coal Combustion.

Abstract

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 NOx emission and so on. This report describes the emission characteristics of NOx 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 NOx emission and the unburned carbon concentration in fly ash became high. In order to keep stable combustion and to form an effective NOx 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 NOx emission and unburned carbon concentration in fly ash could be reduced.