HCN and NH₃Released from Biomass and Soybean Cake under Rapid Pyrolysis

Abstract

HCN (hydrocyanic acid) and NH3 (ammonia) (including HNCO (isocyanic acid)) released during rapid pyrolysis of three biomass samples (rice straw, chinar leaves, pine sawdust) and a nitrogen rich material (soybean cake) were measured. The pyrolysis runs were conducted at 600−1200 °C using a high-frequency furnace. Much more HCN than NH3 was released in the biomass runs while the reverse was observed in the soybean cake runs. Because lignin was a common constituent of biomass cells and nearly absent in soybean, the effect of its content on HCN release from the biomass was determined. A strong correlation was established for each biomass sample suggesting that lignin may promote formation of heterocyclic nitrogenous compounds which then decompose to form HCN. HCN release and char/tar-N formation decreased at a higher pyrolysis temperature. Pyrolysis at >1000 °C is desirable since most nitrogen in the biomass will be converted to N2 with <7% released as HCN and NH3.