CHARACTERISTICS OF PRODUCER GAS AND ASH DURING BIOMASS (DIRECT) GASIFICATION IN AN AUTOTHERMAL PILOT-SCALE BUBBLING FLUIDIZED BED REACTOR

摘要

Results from direct biomass gasification with air in an autothermal pilot-scale bubbling fluidized bedrnreactor are presented. The fluidized bed was operated with temperatures in the range 790℃ to 870℃. For thernoperating conditions used, namely equivalence ratio in the range 0.21 to 0.35, the dry gas composition was 11.3 torn17.2%v CO, 2.8 to 5.0%v CH_4, 1.0 to 2.2%v C_2H_4 and 5.8 to 12.7%v H_2. The higher concentration of combustiblerngases, in particular H2, was observed during gasification of wood pellets, and for an equivalence ratio of 0.24. Thernlower heating value of the dry gas was in range 3.8 MJ/Nm~3 to 6.1 MJ/Nm~3, with the higher values observed forrnwood pellets and lower equivalence ratios. The bottom bed particles showed to have catalytic effect to improvernproducer gas quality, namely in terms of H2. The bottom bed ash show a composition that reflects the original sandrnbed (silica sand) properties, showing small concentration of inorganic chemical elements typical of the biomass (Ca,rnK, Na). The fly ash also show Si as the most abundant element, although the chemical elements typical of thernbiomass are present in relative higher amount when compared to bottom ash, being Ca or K the second mostrnabundant.