Fast pyrolysis of stem wood was performed in a pilot-scale cyclone reactor with a reactor wall temperature of ∼750°C. Wood powder was introduced to the pyrolyzer at 20 kg/h during the experiments. Stable operation of the pyrolyzer was easily achieved, and the resulting yields of the products were 54.6 wt % of pyrolysis oil, 15.2 wt % of solid residue, and 20.1 wt % of gases. From the ingoing raw material, 3.4 wt % of the mass could be recovered as deposits, mainly on the walls of the reactor and in the oil condensing part of the plant. The mass and energy balance closures were approximately 93% and 89%, respectively. The physicochemical properties of the pyrolysis oil, solid residue, and noncondensable gas were measured and compared to values in the literature. The results also show that it is possible to produce an oil with a very low concentration of ash-forming elements because particle separation has already occurred in the cyclone reactor.

Soot concentration measurements were performed using diode-laser extinction in an atmospheric air-blown entrained flow gasifier at two vertical levels. The gasifier was operated at different air-fuel equivalence ratios and with variations in fuel and burner configurations. Two fuels were investigated: wood powder and peat powder. These were burned using two burner configurations, one giving a rotating flow inside the gasifier (swirl), and one where the fuel and air were injected parallel with the gasifier axis (jet). The diode-laser measurements were performed at the wavelength 808 nm from which the soot concentrations were estimated, and additionally at 450 nm in order to gain insight into the spectral dependence of the extinction to estimate measurement quality. Additional diagnostic techniques were used, such as an electrical low-pressure impactor (ELPI) for soot size distributions and gas chromatography for species concentration measurements. The results show that wood powder produces higher soot concentrations than peat powder, especially at lower air-fuel equivalence ratios. Furthermore, the burner configuration had in general much less impact than the choice of fuel on the soot concentration.

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