Abstract
In pulverized coal fired power plants, it is important to reduce emissions of both NOx and unburned carbon. It is also desirable to use lower grade coal such as sub-bituminous coal with a moisture content higher than 20 %. In this study, the combustion technology for reducing the amount of unburned carbon without increasing NOx emission is investigated using the coal combustion test furnace. It was clarified that emissions of both NOx emission and unburned carbon were reduced by controlling conditions for air injection from a burner and by modifying the injection conditions for multistage air. Furthermore, NOx emission at the exit of the furnace decreased in the in-furnace blending method, which means that sub-bituminous coal is fired by the upper burner and bituminous coal is fired by the middle and lower burners, compared with that in the line blending method, which means that the blending ratios of sub-bituminous coal are equal for all burners. Then, the amount of unburned carbon in the in-furnace blending method was also lower than that in the line blending method.
