Fast pyrolysis of radiata pine in a bench scale plant with a fluidized bed: Influence of a char separation system and reaction conditions on the production of bio-oil

Sawdust of radiata pine was pyrolyzed in a bench scale plant equipped mainly with a fluidized bed, a char separation system, and a series of quenching columns. In the experiments, the influence of reaction temperature and feed size on the yield of bio-oil was investigated. In addition, the efficiency of the char separation system, which was composed of a cyclone, as well as a hot filter, was examined by considering the content of alkali and alkali earth metals in the bio-oil. Chemical and physical analyses were also conducted with each pyrolysis product fraction. The maximum yield of bio-oil, 67 wt% of product, was obtained at 474 °C. A smaller particle size was found to be better for the production of bio-oil due to good heat transfer into the inner part of the feed. Bio-oils obtained with the char removal system contained about 0.01 wt% of ash. In particular, a sample of bio-oil had characteristics of being almost alkali and alkali earth metal free, and had less than 1 ppm of calcium, magnesium, and potassium. The char that was produced had a higher heating value of 26 MJ/kg. Therefore, it can be used as an energy-supplying source.