Resumo:
Several designs for bio-oil recovery systems from rapid pyrolysis are found in the
literature, most of which involve heat exchangers and/or electrostatic precipitators.
However, there are bio-oils that have a high incrustation rate, which makes their
collection difficult by conventional methods. This is the case of sisal solid residue bio
oil, which has one of the highest viscosities and pour point ever studied. The objective
of this work is to evaluate a new bio-oil recovery process from sisal solid waste, based
on a series of fixed beds, coupled to shell and tube heat exchangers. The new recovery
system minimized incrustations from the reduction of sharp curves and connections,
which are mainly responsible for this event. This system has two heat exchangers,
followed by five vessels in series, which contain the beds, and accompanied by two
more heat exchangers. The first type of experiment was carried out with glass spheres
fixed-beds, whose recovery of the bio-oil in the beds was obtained by flow of previously
heated fluid; the second type of experiment was conducted in water columns, whose
accumulated bio-oil was conducted outside the plant together with water. A series of
operations were carried out in a pilot plant for rapid pyrolysis based on central
composite factorial designs, seeking to verify the its efficiency at different temperatures
and biomass flow rates. In addition, analyses of infrared spectroscopy (FTIR), gas
chromatography coupled with mass spectrometry (GC-MS), and nuclear magnetic
resonance (NMR) were performed on samples of sisal residue bio-oil and water
obtained, in order to study the separation capacity of each system. The results of this
work showed that the recovery method based on fixed beds of glass spheres obtained
the best bio-oil yield (15.08% at 550 oC and 1.556 kg/h), without presenting any types
of operational instabilities due to incrustations. On the other hand, there were no
significant chemical differences in the composition of bio-oils between the beds. With
the water bed, the yield was low (6.8%) and, despite recovering hydrophilic species in
the aqueous phase, it generated a significant amount of liquid effluents. The method
of recovery through sphere beds proved to be promising, especially with regard to
efficiency, drastic reduction of incrustations and absence of liquid effluents, when
compared to the water column system.
