Resolving inconsistencies in measurements of hydrogen cyanide in syngas

Syngas from biomass and coal gasification contains ammonia (NH3) and hydrogen cyanide (HCN) that originate from fuel bound nitrogen (FBN). Despite being minor constituents of the syngas, they are of great interest. They represent NOX precursors when the syngas is burned for process heating or IGCC applications and catalyst poison if the syngas is to be converted to fuels or chemicals. Measuring NH3 and HCN via wet chemical methods can be challenging and laborious, which may account for the relative paucity of NH3 and HCN measurements reported in the literature. Three frequently cited studies report HCN yields that are insignificant regardless of operating conditions and biomass feedstock types. These studies have been cited by other authors as justification for not measuring HCN in studies of nitrogen evolution during gasification. Other authors have reported much higher yields of HCN, on the order of a few tens of percent. Tellingly, sample collection methods are distinctive for these two ranges of HCN measurements. The present study investigated the analytical methods underlying these results, and found the lower numbers to be the result of flawed sampling methodologies. (C) 2014 Elsevier Ltd. All rights reserved.