Valorization of Pine Needles by Thermal Conversion to Solid, Liquid and Gaseous Fuels in a Screw Reactor

PurposeThe purpose of this study was to optimize the pyrolysis conditions to obtain maximum bio-oil yield from pine needles using a screw pyrolyzer for utilizing this abundantly available ligno-cellulosic biomass from pine forest as an alternate source of fuel.MethodsPyrolysis was conducted in a pilot scale single screw reactor. Process parameters such as pyrolysis temperature, biomass particle size, solid residence time and gas flow rate were optimized by employing Taguchi's L-9 Orthogonal Array. Chemical characterization of bio-oil was conducted using gas chromatographic/mass spectroscopy (GC/MS) analysis. Fuel properties of bio-oil and biochar were determined using ASTM standard methods. Composition of product gas was determined by gas chromatography and higher heating value (HHV) was calculated theoretically.ResultsResults revealed that bio-oil yield was primarily influenced by pyrolysis temperature and biomass particle size. The optimum conditions for maximum bio-oil yield were-pyrolysis temperature of 500 degrees C, particle size of 1.25-2.0 mm, solid residence time of 15 min and N-2 gas flow rate of 30 l h(-1)(Gas flow velocity similar to 0.33 m min(-1)). A maximum bio-oil yield of 28.98% was achieved at optimum conditions.ConclusionsOptimized conditions found in this experiment can be employed to continuous pyrolysis of pine needles for production of higher grade energy products like bio-oil, biochar and product gas through screw reactor.Graphical Abstract