Fast pyrolysis of microalgae to produce renewable fuels

In the present study, fast pyrolysis tests of microalgae were performed in the fluid bed reactor. The experiments were completed at temperature of 500 degreesC with a heating rate of 600 degreesC s(-1) and a sweep gas (N-2) flow rate of 0.4 m(3) h(-1) and a vapour residence time of 2-3 s. In comparison with the previous studies on slow pyrolysis from microalgae in an autoclave, a greater amount of high quality bio-oil can be directly produced from continuously processing microalgae feeds at a rate of 4 g min(-1) in the present work, which has a potential for commercial application of large-scale production of liquid fuels. The liquid product yields of 18 and 24% from fast pyrolysis of Chllorella protothecoides and Microcystis aeruginosa were obtained. The saturated and polar fractions account for 1.14 and 31.17% of the bio-oils of microalgae on average, which are higher than those of bio-oil from wood. The H/C and O/C molar ratios of microalgae bio-oil are 1.7 and 0.3, respectively. The gas chromatograph analyses showed that the distribution of straight-chain alkanes of the saturated fractions from microalgae bio-oils were similar to diesel fuel. Bio-oil product from fast pyrolysis microalgae is characterized by low oxygen content with a higher heating value of 29 MJ/kg, a density of 1.16 kg l(-1) and a viscosity of 0.10 Pa s. These properties of bio-oil of microalgae make it more suitable for fuel oil use than fast pyrolysis oils from lignocellulosic materials. (C) 2003 Elsevier B.V. All rights reserved.