Rapid Pyrolysis of Olive Residue. 1. Effect of Heat and Mass Transfer Limitations on Product Yields and Bio-oil Compositions

Abstract

In this study, the aim was to obtain high bio-oil yields in a fixed bed tubular reactor at various pyrolysis temperatures, reaction times, sweeping gas velocities, particle sizes, and heating rates. In order to improve heat and mass transfer, a stainless steel basket was used. The raw material, olive residue, was placed into the reactor in two different ways: directly and with a stainless steel mesh basket. It was proved that employment of the basket provided an effective heat transfer between the sample and reactor wall. As a consequence, higher volatile yields were observed. The maximum oil yield was achieved as 46.72% with a particle size of 0.85 < D p < 0.45 mm, heating rate of 500 °C min -1 , pyrolysis temperature of 500 °C, and sweeping gas flow rate of 400 cm 3 min -1 . It was concluded that reducing the residence time of evolved volatiles, minimizing the particle size, increasing the heating rate at a pyrolysis temperature of 500 °C, and improving the contact surface of raw material with the reactor wall caused enhancement of mass and heat transfer through the system. Compositions of bio-oils were determined in detail with various chromatographic and spectroscopic methods. These results show that the composition of bio-oil is quite similar to that of crude oil.

Pyrolysis of Napier Grass in a Fixed Bed Reactor: Effect of Operating Conditions on Product Yields and Characteristics

“…Decline in the bio-oil yield was observed with nitrogen flow between 40 to 60 mL/min. This could be as a result of short vapor residence time in the condenser coil which has contributed to yield more non-condensable gas (Uzun et al 2007;Pütün 2010;Keles et al 2011;Soetardji et al 2014). Generally, an increase in the yield of non-condensable gas was observed with increasing nitrogen flow, while bio-char yield decreased due to the rapid removal of pyrolysis vapor from the reaction zone.…”

Catalytic pyrolysis of biomass: Effects of pyrolysis temperature, sweeping gas flow rate and MgO catalyst

“…Since increasing the pyrolysis temperature decreases char yields, the char yield decreased up to 20% at 700 C. While the oil yield was 41% at the pyrolysis temperature of 400 C, it reached a maximum of 46% at the pyrolysis temperature of 550 C and at the final temperature of 700 C, the oil yield was decreased to 43%. It may be concluded that secondary reactions of the liquid fraction of volatiles and further decomposition of the char is proceeded in the reactor with increasing temperature and resulted with high gas, and low both oil and char yields at high temperatures (>600 C) [9,10,13].…”

“…The gas yield increased with increasing nitrogen flow rate; whereas the char yield decreases since uncondensed volatiles are removed from the reaction zone by the nitrogen stream. The effect of residence time on gas yield can be examined by changing the flow rate of the sweeping gas while pyrolysis temperature is kept constant [10,13]. The optimum oil yield reached its maximum value as 48.30% at the sweeping gas flow rate of 200 mL min À1 .…”

“…Increasing the sweeping gas flow rate from 100 to 200 mL min À1 caused a small increase of oil yield than expected because of insufficient quenching of pyrolysis vapors during the experiments. As it can be seen from literature, removing the evolved pyrolysis vapors instantly with high sweeping gas flow rates (or lower pyrolysis vapour residence times) with the proper quenching (using dry CO 2 ), the liquid yields should be high [13].…”

Pyrolysis: A Theoretical and Experimental Study on the Conversion of Softwood Sawmill Residues to Biooil

“…Again, this result has been demonstrated in other studies. 11,24 Increasing the gas flow rate decreases the residence time of volatile gases, and subsequently, the secondary reactions are reduced. Primary reactions are proposed as first order where biooil and gas are favored over biochar.…”