In thermochemical biomass conversion processes, especially gasification, the tar content, and composition is a major subject. Because of the various processes examined at VUT, this work picks up the opportunity to compare the different tar amounts and its composition at different temperatures and process parameters. Gasification of biomass was carried out at the 100‐kW steam‐blown dual fluidized bed gasifier pilot plant III (800–870°C) and the 70‐kW air‐blown pressurized research unit (800–900°C; 1–5 bar) at VUT. Olivine is a catalyst for tar conversion; hence it was used as bed material in steam gasification and also in pressurized air gasification. For better understanding of tar formation during thermochemical conversion of biomass, the tar content and composition in the producer gas were analyzed with a gas chromatograph coupled with a mass spectrometer.Basic differences between the two thermochemical conversion processes occurred especially at higher temperatures or higher pressures. The tar composition was shifted to higher molecular tars such as polyaromatic hydrocarbons. Decreasing tar amounts were found at higher temperatures or higher pressures. Therefore, in future, an optimization of gasification processes should be easier to accomplish, which means lower tar content in the producer gas, which results in a better utilization of the biomass. © 2009 American Institute of Chemical Engineers Environ Prog, 2009

A steam blown dual fluidized bed gasification plant was used to yield a nitrogen (N2) free product gas (synthesis gas) from various biomass fuels. In addition to the variation of process parameters like temperature, steam to carbon ratio, fluidization rate, and the influence of different bed materials, various feedstock inputs affected the generation of the product gas. This study focuses on the gasification of different biomass feedstock. The variation of biomass implies wood chips, wood pellets, sewage sludge pellets, and straw pellets. The chosen evaluated experimental results are all gained from the uniformly operated “classical” 100 kW “DUAL FLUID” gasifier at Vienna University of Technology at constant gasification temperatures between 800°C and 810°C. In the “classical” design, the gasification reactor is a bubbling fluidized bed. The composition and ash melting behavior of each feedstock is displayed, as well as the ranges of the product gas compositions generated. Beside the main gaseous product gas components, typical content ranges of dust and char are highlighted. The content and composition of tar in the product gas is discussed. Further it is possible to present gravimetrical and gas chromatography coupled with mass spectrometry measured tar values. Not less than five significant component‐groups of tar will also be outlined for each feedstock. © 2012 American Institute of Chemical Engineers Environ Prog, 2012