Evaluation of NOx formation in pulverized coal firing by use of nitrogen isotope ratios

摘要

In order to estiamte the amount of the thermal NOx emission from large coal-fired utility boilers, studies were conducted to evalaute the mechanisms of NOx formation by use of nitrogen isotope ratios in a drop tube furnace and a 700MW coal-fired utility boiler. NOx was trapped chemically as salts from gas samples at the sites, and the salts were converted to nitrogen in the laboratory for isotopic mass spectroscopy. As resutls, the changes of nitrogen isotope ratios during formation of thermal NOx and fuel NOx and during decomposition of NOx were found to be large enough to evalaute the reaction mechanisms in the boiler furnace. Using these characteristics and data obtained at the power plant, NOx formation in pulverized-coal-fired boiler was evalauted reasonably.