Pyrolysis and gasification characteristics of Pongamia residue (de-oiled cake) using thermogravimetry and downdraft gasifier

• Thermal decomposition of the Pongamia de-oiled cake occurs in three stages.
• At low heating rate (10 °C/min), the higher mass loss rate was achieved.
• The minimum activation energy of 162 kJ/mol is required for complete gasification.
• Gasification efficiency of the de-oiled cake pellets was 65% as compared to the wood (84%).
• Pongamia de-oiled cake pellets of 17 mm and 11.5 mm diameter are not suitable for efficient and problem free gasification.

General research in the area of gasification of biomass includes either study of kinetics of pyrolysis or gasification of selected bios mass. A combined kinetic investigation of the pyrolysis of the de-oiled cake at various heating rates along with gasification of pelletized biomass was carried out in the present work. It is found that the thermal decomposition of de-oiled cake occurs in three stages. Most of the material decomposed (∼60%) in stage-II between 166 °C and 480 °C. Kinetic parameters were obtained by differential and FWO methods. The activation energies are obtained in the range of 68.8–177.9 kJ/mol and 41.3–161.8 kJ/mol by differential method and FWO methods respectively. These results were consistent with those obtained in the literature. The TGA results show that a minimum heating rate (10 °C/min) and minimum activation energy (162 kJ/mol) is required for pyrolysis and gasification of de-oiled cake. The results of TGA were used to select the suitable size of pellets. De-oiled cake pellets of 17 mm and 11.5 mm diameter and length in the range of 10–68 mm were prepared and gasified in a 20 kWe downdraft wood gasifier. The complete gasification of pellets could not be achieved because of less porosity and more elasticity and presence of larger thermal gradient within the pellets. Pongamia de-oiled cake pellets of 17 mm and 11.5 mm diameters are not suitable for gasification.