Biomass gasification in fluidized bed: Where to locate the dolomite to improve gasification?

Calcined dolomites (OCa.OMg) are often used for hot gas cleanup in biomass gasification processes in a fluidized bed. Two locations are envisaged for such dolomite: in the same gasifier bed (mixed with silica sand) or in a secondary bed, downstream from the gasifier. Previous results obtained under very similar circumstances are here analyzed to determine which is the best location (regarding its chemical usefulness for tar elimination) of the dolomite. Gas and tar yields and gas compositions are here given for the two locations of the dolomite, and it is made both for gasification with air and with steam-O-2 mixtures. It is demonstrated how the effectiveness of the dolomite in the second reactor is only a little bit higher than for the in-bed location. This small increase in effectiveness is mainly found in gasification with H2O-O-2 mixtures, there no having noticeable chemical differences (between the two locations of the dolomite) in gasification with air.