RESEARCH METHOD OF RELATIVE CONTRIBUTION OF VOLATILE-N AND CHAR-N TO N0 FORMATION BASED ON COAL / CHAR RESPECTIVE COMBUSTION EXPERIMENT: DISCUSSION ON EXPERIMENT AND CALCULATION

Abstract

During fluidized-bed combustion of coal, nitrogen in coal ( coal-N ) is divided into volatile nitrogen (volatile-N) and char nitrogen (char-N). which both make a contribution to N₂O formation. "Coal / char respective combustion experiment" is one of methods researching the relative contribution of volatile-N and char-N. Its main points are that two combustion experiments for coal and char prepared from the same coal are respectively performed to determine the contribution of coal-N and char-N, and the difference in contribution between both of them is taken as that of volatile-N, then the relative contribution is calculated. In this paper, the method is discussed in experimental technique and calculation of relative contribution. The char's properties and the distribution of coal-N between volatile-N and char-N can strongly be influenced by devolatilization temperature. The percentage of coal-N retained in char can decrease with increasing devolatilization temperature. Therefore, the char prepared at one given temperature is different from those prepared at other ones which are lower or higher than the given one. So the former char cannot take the place of the latter chars to be used in combustion experiment at other temperatures, and the temperature for char preparation should be the same as that for coal / char combustion experiment. The equipment for char preparation has notable influence on char's characteristics. Hence, the equipment for coal / char combustion should exactly be the same one as that for char preparation. It is demonstrated that the difference between percent conversion of coal-N and that of char-N could not be regarded as that of volatile-N. For the cases in which more than 90% of N in coal remains in char, the converted amount and percent conversion of N in char formed during coal combustion are larger than those of N in char prepared by coal pyrolysis and the latter char cannot be representative of the former one.

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