Design and experimental evaluation of a pilot-scale screw pyrolysis unit with producer gas based heating

This study presents the design, development, and experimental evaluation of a pilot-scale screw pyrolysis unit utilizing producer gas-based heating for the thermochemical conversion of biomass into biochar, bio-oil, and producer gas. The system was evaluated using grinded rice straw as feedstock, with varying biomass feed rates (8, 12, and 16 kg/h) and residence times (5, 10, and 15 minutes) to investigate the impact of these parameters on product yields and energy efficiency. The results indicated that increasing the feed rate led to a significant rise in biochar and producer gas yields, while bio-oil recovery reached a saturation point at higher feed rates. The producer gas generated during pyrolysis was able to replace 77% thermal energy required for heating the reactor, reducing reliance on external fuel sources and enhancing the system’s overall energy efficiency. Mass and energy balance analyses revealed that while higher feed rates improved energy recovery, energy losses also increased, highlighting the need for optimization in reactor design and heat management. The average energy efficiency of the reactor was found to be 65% at 16 kg/h feeding rate. This study provides key insights into the optimization of screw pyrolysis systems and demonstrates its potential for scalable, energy-efficient biomass conversion, contributing to renewable energy production and sustainable waste management solutions.