Abstract
Intermediate and fast pyrolysis (IFP) for the recovery of bio-oil from organic matter have gained the attention of researchers in their attempt to increase the contribution of renewables into the energy mix. Current research has focused on equipment configuration and variables for higher yields of the oils; methods of upgrading the oils for compatibility with existing fuel infrastructure and engines, and various tests to characterize the products or test their applicability as fuels. This paper reviews the progress in experimental work around intermediate- fast pyrolysis (hot vapour residence~1-20s; moderate to high liquid yields) in the past twelve years. The review focuses on the experimental scope, equipment used, preparation of raw materials, experimental design and characterization of bio-oils. Experimental work covering actual applications of the oils are not covered in this review paper. The feedstocks mostly researched on in IFP were rice husks, followed by pinewood, Jatropha curcas cake and rapeseed respectively. Most IFP studies have been done on woody biomass (over 100 different feedstocks) due to their consistency, followed by agricultural residues then herbaceous energy crops. Lignocellulosics proved to be the veteran organic feedstocks (~95% of IFP) ahead of non- lignocellulosic biomass (~5%). The most applied technologies in recent years, were fluidized bed followed by the free fall reactors. For the experimental design, most papers reviewed used the simple single parameter method, while a few used the central composite rotatable design and full factorial design methods. The characterization tests mostly conducted on the oils were the pH, viscosity, Karl Fischer titration and calorific value.