Behavior of heavy metals in steam fluidized bed gasification of contaminated biomass

Heavy metal phytoextraction by growing energy crops such as flax could be a promising approach for remediation of brownfields with energy benefits. The present paper deals with flax (40 wt %) and hardwood (60 wt %) cogasification with particular focus on the distribution of heavy metals to both solid and gaseous gasification products. The blended fuel was gasified by steam in a fluidized bed gasifier at about 850 °C and steam to biomass ratio of 1.01 kg kg^-1. Concentrations of selected heavy metals (Cd, Cu, Ni, Pb, and Zn) were determined in bed ash, cyclone ash, and in downstream producer gas. From the analysis, it follows that under the given experimental conditions the subsequent order of heavy metals volatility can be found: Cd (mostly in producer gas) < Pb < Zn < Cu < Ni. Heavy metals concentrations in the producer gas (nitrogen free, dry gas) were determined in the range of 0.37-4.2 mg m^-3.