Oxygen carrier aided gasification of biomass at 1 MWth scale for biofuel production

Oxygen-steam circulating fluidized bed gasification of biogenic waste enables biofuel production with low feedstock pretreatment, and its efficiency can be improved by an active bed material. This study presents the first oxygen carrier aided gasification (OCAG) tests with ilmenite at 1 MW(th) pilot scale. The non-optimized, autothermal plant achieves cold gas efficiencies including C 2 H 4 up to 72 % and carbon conversion efficiencies of 86–97 % (gas-based) and 92 % (solids-based). A high oxidation degree in the bottom ash and a low one in the circulating material indicate oxygen transport to the upper reactor part. About 29 % of the measured carbon output (excluding CO 2 and CO) and 42 % of the feedstock energy input (excluding H 2 and CO) remain available for downstream conversion. Averaged over four balance points, ilmenite yields markedly lower heterocyclic and oxygenated aromatic hydrocarbons (0.3 g kg(feed) −1 ) and polycyclic aromatic hydrocarbons (3.3 g kg(feed) −1 ) than sand and olivine. Polycyclic aromatic hydrocarbon yields are similar to or lower than those from magnesite and dolomite, at higher monocyclic aromatic hydrocarbon yields (22.1 g kg(feed) −1 ). Differences in reactor type, pressure, residence time, and measuring setup exclude attribution to the bed material alone.