Combustion experiments of coke granules were conducted using a sintering simulator in order to examine fundamentally a way to reduce NOx emission from the iron are sintering process. Existing state of coke and kind of adhering materials were variously changed in the experiment.
For any coke granules, conversion ratio of N in coke into NO in outlet gas was high in the early stage of combustion because of relatively low temperature of the coke surface. Therefore, depression of combustion rate in the early stage can be a key to suppress overall NO emission. In the case of the coke granulated with fine materials which would not become to be melt, however, not only the conversion ratio but also combustion rate of coke decreased comparing with coke particles without adhering fine materials. On the other hand, in the case of the coke granulated with fine materials having the composition of calciumferrite, CF, combustion rate did not decrease much because melt formed in the early stage of combustion removed quickly from coke surface and the conversion ratio was vanishingly small.
On the basis of these results, sintering tests was carried out with a laboratory-scale sinter pot using pregranulated coke with fine mixtures of iron ores, limestone and burnt lime. Reduction of the conversion ratio into NOx in outlet gas was obtained by about 30% for P type coke and more than 40% for S type.
