Thermal degradation kinetics of calcium-enriched bio-oil

The thermal decomposition of calcium-enriched bio-oil (CEB) was studied in air by thermogravimetric experiments. The characteristics, to a great extent, are quite similar to that of calcium acetate (CA). The decomposition processes can be divided into four stages: the loss of volatile materials, devolatilization and degradation of pyrolytic lignin, decomposition of organic calcium salts and residual carbon, decomposition of CaCO3 to CaO. The activation energy values are lower than that of CA at the corresponding decomposition stages. The CaCO3 from amorphous CEBs exhibits the higher calcination rate than that from CA. The actual mechanisms of the second and the third stages obey the nucleation and growth model (A1), with integral form of F(alpha) = -ln(1 - alpha). The high-porosity of calcined CEBs should be the further evidence of the mechanism. Correspondingly, the mechanism c the fourth stage obeys three-dimensional (3-D) phase boundary reaction (R3) mechanism with integral form of F(alpha) = 1-(1 - alpha)(1/3). (C) 2008 American Institute of Chemical Engineers.