Thermal degradation kinetics and mechanisms of Posidonia Oceanica under inert and oxidative atmospheres

ABSTRACT

The thermal degradation characteristics of Posidonia Oceanica (PO), a marine biomass abundantly available on the coastal zone of the Mediterranean Basin, were investigated using thermogravimetric analysis under inert and oxidative atmospheres. The kinetic parameters of the both thermal degradations conditions were determined using n-reaction order model. Coats–Redfern and Phadnis–Deshpande methods were used to discuss the probable degradation mechanisms. Results showed that PO is an attractive alternative for energy production owing to its elevated heating value. Moreover, PO thermal degradation follows the usual shape of biomass decomposition. Hence, under inert atmosphere, its thermal degradation had two different stages after moisture release. The first stage corresponded to the volatiles release while the second stage corresponded to the char formation. The solid-state decomposition mechanisms followed by the devolatilization step of PO were two or three dimensional diffusion controlled reaction. However, the decomposition mechanism during PO char formation corresponded to a nucleation and growth mechanism. Under oxidative atmosphere, two stages were also observed corresponding to volatiles release and char combustion, respectively. The solid-state mechanism of volatiles release followed three dimensional diffusion controlled reaction while the char combustion mechanism corresponded to a contracting area phase boundary controlled reaction.

KEYWORDS:

• Decomposition mechanisms
• kinetic analysis
• Posidonia Oceanica
• thermal degradation