Detailed Analysis of Gas, Char and Bio-oil Products of Oak Wood Pyrolysis at Different Operating Conditions

Numerous processes convert biomass into bio-oil and syngas namely: pyrolysis and gasification. Pyrolysis allows the simultaneous production of biochar, bio-oil (or tar) and syngas (mixture of CO2, CH4, H-2 and CO molecules). The concentrations and compositions of these products highly depend on the operating conditions and biomass feedstock. This work presents a complete and detailed study of the chemical composition of the syngas, bio-oil and char derived from oak wood chips pyrolysis, in function of temperature, heating rate and vapor residence time. Gas chromatography-mass spectrometry was used to determine the concentrations of ten gases and several bio-oil compounds. Elemental analysis was applied to analyze the char produced. We show that as the temperature increased from 400 to 800 degrees C, char and bio-oil yields decreased while gases yield increased. The concentrations of H-2, CO and CH4 increased while that of CO2 dropped with the temperature. The heating rate had a smaller impact on the products distribution in contrast to the temperature. The residence time significantly influenced the gases repartition. The composition of the bio-oil included: benzene, toluene, ethylbenzene, xylene, naphthalene and phenol among others. The char elemental analysis showed a drop in the hydrogen and oxygen content and an increase in the carbon content as result of the volatilization process in comparison to the biomass contents. This study helps identifying the adequate parameters required for the pyrolysis post-processes applications (combustion, gasification, or catalytic pyrolysis) and those needed to favor the formation of desired products (char, bio-oil, syngas) with relevant compositions and concentrations. [GRAPHICS] .