Microwave-Assisted Pyrolysis of Pine Wood Sawdust Mixed with Activated Carbon for Bio-Oil and Bio-Char Production

Anissa Khelfa,Eugène Vorobiev,Mohamed Koubaa,Filipe Augusto Rodrigues

doi:10.3390/pr8111437

Abstract

Pyrolysis of pine wood sawdust was carried out using microwave-heating technology in the presence of activated carbon (AC). Experimental conditions were of 20 min processing time, 10 wt.% of AC, and a microwave power varying from 100 to 800 W. The results obtained showed that the microwave absorber allowed increasing the bio-oil yield up to 2 folds by reducing the charcoal fraction. The maximum temperature reached was 505 °C at 800 W. The higher heating values (HHV) of the solid residues ranged from 17.6 to 30.3 MJ/kg. The highest HHV was obtained for the sample heated at 800 W with 10 wt.% of AC, which was 33% higher than the non-charged sample heated at the same power. Furthermore, the addition of AC allowed showing the probable catalytic effect of the AC in the charged sample pyrolysis bio-oils.

Highlights

Fossil fuels are the most widely used energy sources nowadays and comprise over 80% of the world’s energy supply
High moisture content is a desirable characteristic in microwave biomass pyrolysis as it plays a role in the initial microwave absorption and allows increasing the raw material temperature to the water boiling point [23]
For the 2nd category of samples, pyrolysis temperatures were reached at 505 ± 2 ◦ C. These results show that the desired pyrolysis temperature could be obtained using 10 wt.% of MW absorber with a MW

Summary

Introduction

Fossil fuels are the most widely used energy sources nowadays and comprise over 80% of the world’s energy supply. Lignocellulosic biomass (e.g., wood, crops, agricultural and forestry residues, etc.) would be preferable due to its high density (i.e., high energy content per volume), its low amount of ash, and its very low amount of nitrogen. It consists of 35–50 wt.% cellulose, 25–30 wt.% hemicelluloses, 15–20 wt.%. One of the main thermochemical conversion routes for the conversion of biomass resources into value-added products is pyrolysis This process consists of heating the biomass in the absence of air. It allows the production of three valuable fractions: a bio-oil fraction called “condensable liquid”, a volatile fraction, and a carbon-rich solid residue (biochar). Gas fraction, as the light molecular weight gases, has shown great potential in fuel application [14], electricity generation [15], and as feedstock for H2 production [16]

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Conclusion