Decomposition Characteristics and Kinetics of Microalgae in [N.sub.2] and C[O.sub.2] Atmospheres by a Thermogravimetry

The thermal degradation characteristics of microalgae were investigated in highly purified [N.sub.2] and C[O.sub.2] atmospheres by a thermogravimetric analysis (TGA) under different heating rates (10, 20, and 40[degrees]C/min). The results indicated that the total residual mass in C[O.sub.2] atmosphere (16.86%) was less than in [N.sub.2] atmosphere (23.12%); in addition, the kinetics of microalgae in [N.sub.2] and C[O.sub.2] atmospheres could be described by the pseudo bicomponent separated state model (PBSM) and pseudo-multi-component overall model (PMOM), respectively. The kinetic parameters calculated by Coats-Redfern method showed that, in C[O.sub.2] atmosphere, the apparent activation energy (E) of microalgae was between 9.863 and 309.381 kJ [mol.sup.-1] and the reaction order (n) was varied from 1.1 to 7. The kinetic parameters (E, n) of the second stage in C[O.sub.2] atmosphere were quite similar to those in [N.sub.2] atmosphere.