On the pyrolysis of different microalgae species in a conical spouted bed reactor: Bio-fuel yields and characterization

[Display omitted] •Spouted beds are suitable for fast pyrolysis of microalgae with high bio-oil yield.•Algal bio-oil contains lower water content compared to lignocellulosic biomass.•Algal bio-gas holds the potential to be used as fuel and syngas.•Bio-char can be used as soil amender and renewable solid fuel. The aim of this work was to study fast pyrolysis of three microalgae species in a continuous bench-scale conical spouted bed reactor at 500 °C. Bio-gas, bio-oil and bio-char yields have been determined and characterized by using GC, GC/MS, elemental analyzer and SEM. Bio-oil was the main product obtained through pyrolysis of microalgae. The non-condensable gaseous stream is made up of mainly hydrogen, carbon monoxide and carbon dioxide, apart from other light hydrocarbons detected in lower concentration, as are methane, ethane, ethylene, propane and propylene. The compounds identified in the bio-oil have been categorized into hydrocarbons, nitrogen containing compounds, ketones, alcohols, acids, lactones, phenols and aldehydes. The nitrogen and carbon contents of the microalgae bio-chars are higher than those for bio-chars derived from other biomasses. Pyrolysis improved the morphology and porous structure of microalgae. Finally, the mechanism involving microalgae pyrolysis has been approached and the main reaction pathways have been proposed.