Characteristics of pulverized-coal combustion in the system of oxygen recycled flue gas combustion

Concerning to the system of oxygen/recycled flue gas combustion for the removal of carbon dioxide from pulverized-coal firing power plants, combustion characteristics of pulverized coal and the heat absorption performance of boiler furnace were studied. To determine the ignition characteristics in the CO2-rich atmosphere, the flame propagation speed of pulverized-coal cloud was measured in a microgravity combustion chamber. The results revealed that the flame propagation speed in an O-2/CO2 atmosphere was markedly low compared with that in O-2/N-2 and (O)2/Ar, and that it was improved by increasing the O-2 concentration. NOx and SO2 emissions from the system were investigated in the industrial-scale combustion test facilities. NOx emission was not so largely decreased by staging as air-blown combustion, while a considerable part of sulfur was absorbed in ash in the system. As for the heat absorption performance of the boiler furnace, a 3-dimensional numerical analysis was applied to a large utility boiler furnace. It was found that a furnace designed for normal air-blown combustion was just large enough for the oxygen/recycled flue gas combustion with a realizable ratio of flue gas recycling. (C) 1997 Elsevier Science Ltd.