Environmental Engineering Reference
In-Depth Information
11.3 A FIRST LOOK AT FAST PYROLYSIS OIL
Figure 11.2 shows graduated cylinders containing pyrolysis oil, which is the com-
mon name of the liquid produced by the fast pyrolysis process, and the wood chips
from which it is produced. The oil in the picture is produced from pinewood chips
of
1 mm, which are converted in a fluidized bed operated at 500
C, typical fast
pyrolysis conditions. Both cylinders contain the same amount of energy, showing
that during pyrolysis the volumetric energy content increased considerably. Pyrol-
ysis oil is a brown, free-flowing liquid typically containing significant amounts
of water.
The elemental composition and some properties of bio-oils are given in Table 11.1.
Clearly, the elemental composition of pyrolysis oil resembles that of wood, showing
that this bio-oil is liquefied biomass. Depending on the feedstock, its moisture content,
and the applied condensation method, water is present in this liquid in concentrations
ranging from 5 to 35 wt%. Higher concentrations of water cause phase separation,
leading to the formation of an aqueous phase and an oil phase. Hydrothermal lique-
faction tends to produce liquids that contain less oxygen compared to the feedstock
(see Table 11.1). In Table 11.1, also, properties of heavy fuel oil (fossil origin) are
given for comparison.
FIGURE 11.2
Pyrolysis oil (left) and pinewood from which it originates (right).
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