Nitrogen release during fixed-bed gasification of several coals with CO2:: factors controlling formation of N2

Nitrogen release from several coals with different ranks during CO2 gasification at 0.1 MPa and 1000 degrees C has been studied with a fixed-bed quartz reactor. Among HCN, NH3, N-2, and tar-N analyzed, N-2 is the main product for all the samples in the whole range of coal conversion. As the gasification of every char after devolatilization proceeds, N-2 increases with a corresponding decrease in the nitrogen in each residue. This shows that the N-2 formed originates mostly from solid-gas reactions. When N2 yield is evaluated on the basis of char-N remaining just after devolatilization, it is almost independent of type of parent coal and demineralization with HCl washing. Only the extent of char gasification can determine the yield, which reaches about 658 after complete gasification. The rate of N-2 formation is always lower than that of CO production. It is thus suggested that accumulation of N-containing surface species is necessary for the start of N-2 formation. (C) 1999 Elsevier Science Ltd. All rights reserved.