Performance evaluation of a down draft double chamber pyrolysis reactor under field conditions

Sequestration of carbon through production of biochar has been recognized as a feasible approach to combat global warming. The application of biochar production technology in industrial scale is still new to developing countries due to high complexity and specificity of pyrolysis technology. Therefore, this study aimed to evaluate a small scale pyrolysis unit (Down Draft Double Chamber pyrolysis reactor – DDDC reactor) to be used in continuous biochar production with the use of paddy husk as the both feedstock and fuel material. The temperature variation, syngas composition and energy value, mass and energy balances of the DDDC reactor were evaluated through field trials. The average temperature varied from 330 °C to 560 °C from bottom to the top of the reactor fulfilling the temperature requirement for pyrolysis. However, fluctuations in temperature were observed during trials due to low energy supply through paddy husk as the fuel. This suggested a need of using a supplementary fuel source to operate the reactor. The biochar recovery of the reactor was 32% (dry matter basis) and the average biochar production rate was 1 kg/h for material input of 4.42 kg/h of paddy husk and 0.77 kg/h of coconut shell as fuel sources. The average raw syngas composition (v/v) was 20.78% CO, 13.3% CO2, 3.87% CH4, 0.3% CnHm, 6.91% H2, 0.68% O2, and 54.16% N2 with an average energy content of 5.34 MJ/m3. This study showed the potential for optimizing and upscaling a continuous mode paddy husk pyrolysis reactor for industrial applications.