Abstract
It is very important to use low-rank coals for Japanese coal-fired power stations from the view points of energy security and fuel cost. Three kinds of Upgraded Brown Coal (UBC) were fired in a pulverized coal combustion test furnace (thermal input of fuel: 760kW) in this study. Gas compositions at the furnace outlet and unburned carbon in fly ash were measured. The results were compared with those of coal combustion tests. The relationship between two-stage combustion ratio and NOX concentrations on combustion of UBCs are different from that of a bituminous coal combustion, because NOX concentrations on non-staged combustion of UBCs are lower than that of the bituminous coal combustion. The unburned carbon concentration in fly ash on the bituminous coal combustion increases with increase in two-stage combustion ratio. Those on combustion of UBCs are, on the other hand, almost constant, when two-stage combustion ratio is changed. The NOX conversion ratios (NOX concentration at the furnace outlet / NOX concentration when all the nitrogen in the fuel converts into NOX) of UBCs are lower than those of coals. The combustion efficiencies of UBCs are almost same with those of coals.
