Analysis of Trace Compounds Generated by Pressurized Oxygen Blown Entrained Flow Biomass Gasification

Trace compounds were measured in synthesis gas and waste water from a pilot scale pressurized entrained flow oxygen blown biomass gasifier. The feedstock used was milled soft stem wood powder. Gaseous trace compounds were analyzed by gas chromatography. Up to 20 ppm of hydrogen sulfide was observed in the cold synthesis gas and the concentration seemed to be independent of the oxygen equivalence ratio (ER). Benzene varied from 30 to 1100 ppm, strongly depended on the ER and correlated well with the methane concentration. The concentrations of acetylene and ethylene increased as the ER was reduced and could have acted as precursors for the observed soot particles which were characterized using thermogravimetric analysis, Xray diffraction, and scanning electron microscopy. Common polycyclic aromatic hydrocarbons from high temperature biomass gasification such as pyrene, phenanthrene, fluoranthene, and naphthalene were observed in low concentrations in the soot, in the cold synthesis gas and also in the waste water from the quench. Inorganic elements from the feedstock were observed in the waste water. Comparisons were also made with previous results from a black liquor gasifier. (C) 2014 American Institute of Chemical Engineers Environ Prog, 33: 699-705, 2014