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

Abstract

The 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. Pyrolysis 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 L9 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. Results 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 °C, particle size of 1.25–2.0 mm, solid residence time of 15 min and N2 gas flow rate of 30 l h− 1(Gas flow velocity ∼ 0.33 m min−1). A maximum bio-oil yield of 28.98% was achieved at optimum conditions. Optimized 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.