Assessing the exergy sustainability of a paddy drying system driven by a biomass gasifier

Paddy parboiling in rice industries is an energy-intensive process that requires huge attention for energy conservation, fuel economy, and sustainability. Thus, several research initiatives have been undertaken to adopt a suitable energy conversion system in such industries to improve thermal efficiency and reduce environmental impact. In this study, exergy performance and exergy-based sustainability indicators have been investigated on a reversible bed paddy dryer coupled with a rice husk-fuelled downdraft gasifier. The experiment was conducted at the optimum operating conditions such as an equivalence ratio of 0.2 in the gasifier and a drying air temperature of 80℃ in the dryer. The exergy efficiency of the reversible bed dryer and the gasifier were 65.53% and 70.92% respectively. The lowest exergy efficiency of 35.29% was seen in the combustion chamber since a huge exergy destruction of 2.75 kW occurred. Therefore, the combustion chamber has a high potential improvement of about 1.66 kW. Due to less exergy destruction, the gas cooler and air duct showed high exergy efficiency of 62.36% and 76.2% respectively and the lowest values in exergy-based sustainability indicators. The assessment of environmental and sustainability factors on each component showed that the combustion chamber has a high waste exergy ratio of 0.688, environment effect factor of 1.95, exergy destruction coefficient of 0.69, and exergy sustainability index of 0.51.