A. Orio et al., PERFORMANCE OF DIFFERENT DOLOMITES ON HOT RAW GAS CLEANING FROM BIOMASS GASIFICATION WITH AIR, Industrial & engineering chemistry research, 36(9), 1997, pp. 3800-3808
Calcined dolomites (CaO-MgO) from four different quarries have been te
sted for the upgrading of the hot raw gas from a fluidized bed gasifie
r of biomass with air. These calcined dolomites have big macropores (9
00-4000 Angstrom) and low (3.8-12 m(2)/g) BET surface areas. They have
been tested in a fixed bed of 6 cm i.d. downstream from the air-blown
biomass gasifier. The change in gas composition (contents in H-2, CO,
CO2, CH4,...), tar content, gas heating value, etc., has been studied
at different temperatures (780-920 degrees C) as well as space-times
for the gas in the bed (0.03-0.10 kg.h/m(3)) and the type of dolomite.
Increasing the equivalence ratio used in the gasifier and decreasing
the WC ratio of the gas increases the refractoriness of the tars to be
eliminated by the calcined dolomite. Activation energies (100 +/- 20
kJ/mol) and preexponential factors for the overall tar elimination rea
ction have been calculated for the different dolomites under realistic
conditions. The activity of the dolomite for tar elimination can incr
ease by 20% on increasing its pore diameter or its Fe2O3 content. Comp
arison of results with similar ones obtained in biomass gasification w
ith steam is also presented.