Recuperação de bio-óleo proveniente do resíduo do sisal em um sistema de leito fixo.

Abstract

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.