Gasification of Olive Tree Pruning in Fluidized Bed: Experiments in a Laboratory-Scale Plant and Scale-up to Industrial Operation

Olive tree pruning was gasified with air in a laboratory fluidized bed (FB) reactor at 800, 850, and 900 degrees C and equivalence ratios (ERs) ranging from 0.12 to 0.35. A few additional tests were performed varying the fuel particle size, biomass feed rate, and oxygen enrichment in the air. The composition of the product gas was determined by measuring the light gas, water vapor, tar, and some inorganic contaminants. The solids produced were characterized by sampling from the cyclone and bed, providing approximate information about the char elutriation rate and residence time. The lower heating value of the gas, LHV (excluding benzene and tars), varied between 4.5 and 7.8 MJ/(Nm(3)) using air, whereas it increased to 9.3 MJ/(Nm(3)) using enriched air with 40% O-2. Carbon conversion increased with temperature (so did gasification efficiency), reaching 97% at 900 degrees C, indicating almost complete fuel conversion. Analysis of the results with the assistance of a previously developed FB gasification model indicated that most of the tests were, carried out under allothermal conditions (with significant heat added to or removed from the gasifier) and only a few tests were representative of autothermal conditions, i.e., the mode of operation of industrial air-blown FB gasifiers (without heat addition and with small heat losses). The model was also used to scale-up the laboratory-scale results to predict the gas composition of industrial-scale FB gasifiers.