Effects of Metal Cations Present Naturally in Coal on the Fate of Coal-Bound Nitrogen in the Fixed-Bed Pyrolysis of 25 Coals with Different Ranks: Correlation between Inherent Fe Cations and N2Formation from Low-Rank Coals†

The fate of coal-N in the fixed-bed pyrolysis of 25 coals with 62−81 wt % (daf) C has been studied with a quartz reactor at 1000 °C under ambient pressure to examine the effects of metal cations present naturally in these coals on the partitioning of coal-N into N2, NH3, HCN, tar-N, and char-N. Nitrogen mass balances for all runs fall within the reasonable range of 100 ± 5%, and N2 is the predominant product for all of the coals. As the N2 yield increases, the sum of NH3, HCN, and tar-N is unchanged significantly, whereas the char-N yield decreases almost linearly, showing that most of N2 originates from char-N. When eight kinds of inherent metals, such as Na, Mg, Al, Si, K, Ca, Fe, and Ti, are determined by the conventional method and related with the N2 yield, there exists a strong, direct correlation between the Fe content and N2 formation for low-rank coals with less than 75 wt % (daf) C. Transmission electron microscopy coupled with an energy-dispersive analysis of X-rays (TEM−EDAX) measurements afte...