The effects of slow and fast pyrolysis on the yields and properties of produced bio-oils from macadamia nutshell

Abstract

The objective of this study is to investigate the effects of slow and fast pyrolysis on the yields and properties of bio-oils using Macadamia nutshell (MNS) as feedstock. A pilot scale auger pyrolysis reactor which had the facilities of conducting both slow and fast pyrolysis was utilized. The pyrolysis processes were carried out at a temperature of 500 ˚C, the heating rate of 5 ˚C/min, a residence time of 60 mins, and a feedstock particle size of 2 mm. The characterization of feedstock and the produced bio-oils was performed by different techniques like elemental analysis, Gas chromatography-mass spectrometry (GC–MS), and physicochemical properties analysis using appropriate ASTM standards. Proximate and ultimate analysis showed promising prospects of MNS as a feedstock for the pyrolysis process. In the case of slow pyrolysis, the bio-oil yield was found to be 39.7%, whereas the bio-oil yield was 49.5% for the fast pyrolysis process. Significant changes in the peak region of GC–MS were observed for bio-oils produced under two different pyrolysis conditions. It was found from the physicochemical properties analysis that calorific value is higher and water content is lower in the bio-oil produced through fast pyrolysis than the bio-oil produced through slow pyrolysis. Comparison with standard biodiesel properties revealed that produced bio-oils were not suitable for use in engines at this stage. Proper upgradation is required to make it suitable for engine application. Based on these results it can be concluded that the produced bio-oils can be used as fuel in other applications such as in boilers and as additives to produce valuable chemicals.