Release of Sulfur and Nitrogen during Co-pyrolysis of Coal and Biomass under Inert Atmosphere

Coal combustion is a major energy provider but also a serious pollutant emitter worldwide. Biomass has attracted increasing research attention due to its carbon neutral and other advantages during co-pyrolysis of coal. Therefore, pyrolysis of corn straw, lignite coal, and their mixed fuel was investigated using a horizontal tube furnace at a temperature range of 300–900 °C in this study by concentrating on emissions of nitrogen- and sulfur-bearing gases. Emissions of HCN, NH3, COS, and SO2 were monitored, and char yield was calculated during pyrolysis. Results showed that char yield decreases with increasing temperature due to the decomposition of heterocyclic aromatic hydrocarbon. Sulfur (42.45 wt %, 900 °C) and nitrogen (73.23 wt %, 600 °C) were released from the mixed fuel during pyrolysis. The synergistic effect between corn straw and coal was evaluated and their experimental and calculated values were compared. The synergistic effect on emissions was remarkable at a temperature range of 600–800 °C due to high biomass content and desynchronization of volatile matter emissions between the coal and biomass. Volatiles in the biomass, which are released before coal, stimulated the volatilization of coal. Several conventional gases, such as CH4 and C2H6, were also analyzed to investigate emission patterns at different temperatures.