Transformation of nitrogen during pyrolysis of Na-loaded Shengli brown coal

The impact of Na content on nitrogen transformation during the pyrolysis of Shengli raw coal and the Na-loaded coal in a fixed-bed/fluidized-bed quartz reactor was investigated. The quantification of NH₃ and HCN in gas product was carried out using an ultraviolet-visible spectrophotometer while the occurrence modes of nitrogen in the solid chars were detected by X-ray photoelectron spectroscopy (XPS). The results indicate that the transformation of coal-N to NH₃ can be catalytically enhanced by certain amount of Na at low temperature. When the final pyrolysis temperature is relatively high, the presence of Na appears to inhibit the formation of NH₃. Meanwhile, for any given pyrolysis temperature, the production of HCN will be suppressed by Na. When the pyrolysis temperature is high, the increase of Na content in coal causes the reduction of nitrogen remaining in char and promotes quaternary nitrogen formation, whereas, the effect is negligible at low temperature.