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 degrees C min(-1), pyrolysis temperature of 500 degrees 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 degrees 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.