Thermal conversion of elephant grass (Pennisetum purpureum Schum) to bio-gas, bio-oil and charcoal.
Elephant grass is an abundant, fast growing plant with significant potential as a renewable energy source and for conversion to higher calorific value fuels. This work investigates thermal conversion of elephant grass to bio-gas, bio-oil and charcoal under two heating rates of 10 and 50 degrees C/min. The energy required to pyrolyse elephant grass was evaluated using computer aided thermal analysis technique, while composition of the resultant bio-gas and bio-oil products were monitored with gas chromatographic and mass spectroscopic techniques. At 500 degrees C, the bio-gas compounds consisted primarily of CO2 and CO with small amounts of methane and higher hydrocarbon compounds. The heat of combustion of the bio-gas compounds was estimated to be 3.7-7.4 times higher than the heat required to pyrolyse elephant grass under both heating rates, which confirms that the pyrolysis process can be self-maintained. Faster heating rate was found to increase the amount of liquid products by 10%, while charcoal yields remained almost the same at 30%. The bio-oil mainly consisted of organic acids, phthalate esters, benzene compounds and amides. The amount of organic acids and benzene compounds were significantly reduced at 50 degrees C/min, while the yields of phthalate esters and naphthalene compounds increased. The difference in bio-oil composition with increased heating rate is believed to be associated with the reduction of the secondary reactions of pyrolysis, which are more pronounced under lower heating rate.
Strezov
Vladimir
V
Graduate School of the Environment, Macquarie University, Sydney, NSW 2109, Australia. vstrezov@gse.mq.edu.au
Evans
Tim J
TJ
Hayman
Chris
C
D001674:Bioelectric Energy Sources; D002606:Charcoal / Q000138:chemical synthesis*; D008903:Minerals / Q000032:analysis; D008970:Molecular Weight; D031782:Pennisetum / Q000378:metabolism*; D010938:Plant Oils / Q000138:chemical synthesis* / Q000737:chemistry; D013696:Temperature; D014835:Volatilization
D008903:Minerals; D010938:Plant Oils; D002606:Charcoal