Thermal behaviour and kinetics of alga Polysiphonia elongata biomass during pyrolysis

The pyrolysis characteristics and kinetics of Polysiphonia elongata were investigated using a thermogravimetric analyzer. The main decomposition of samples occurred between 225 °C and 485 °C at heating rates of 5–40 °C/min; owing to release of 78–82% of total volatiles. The heating rate effected pyrolysis characteristics such as maximum devolatilization rate and decomposition temperature. However, total volatile matter yield was not significantly affected by heating rate. The activation energy of pyrolysis reaction was calculated by model free Friedman and Kissenger–Akahira–Sunose methods and mean values were 116.23 kJ/mol and 126.48 kJ/mol, respectively. A variance in the activation energy with the proceeding conversions was observed for the models applied, which shows that the pyrolysis process was composed of multi-step kinetics. The Coats–Redfern method was used to determine pre-exponential factor and reaction order. The obtained parameters were used in simulation of pyrolysis process and results were in a good agreement with experimental data.