Characteristics of NO‐reduction by tar‐included syngas from an updraft gasifier

Experiments of nitric oxide reduction by the tar‐included syngas from a small biomass updraft gasifier have been carried out on a tubular reactor under a temperature range of 900 to 1200°C. The initial mole fraction of NO was 1000 ppm and that of the oxygen and gasification syngas were varied. Comparison of the reburning results of the present syngas with other fuels clarified the influence of tar. Under the conditions of this work, the participation of tar compounds in NO reduction mainly begins with cracking into light hydrocarbons which is sensitive to both the oxygen concentration and the temperature. Tar leads to a satisfactory NO‐reduction improvement under relative oxygen‐rich conditions, supplying extra hydrocarbon radicals and creating a more appropriate atmosphere for reburning reactions. As for a reductive environment, little benefit was gained from the presence of tar. The rise of temperature brings a clear promotion only to NO reduction with a high oxygen flow rate, while polymerization should be concerned for a low oxygen flow rate. It is believed that a substantial portion of tar converts to acetylene through cracking under suitable reburning conditions, resulting in an active NO‐reduction reaction pathway. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 602–608, 2014