Rice husk fixed bed gasification for circular economy in compact rice mills

Abstract

ABSTRACT Considering the physicochemical properties of residual rice husk, which is suitable for gasification and its vast availability in Colombia, an experimental analysis of the energy potential of rice husk for small-scale fixed bed gasification processes was conducted, thereby facilitating the implementation of the circular economy model in compact rice mills. Because of the impact of air flow on the process equivalence ratio (ER), gas calorific value, and gasifier thermal power, the optimum air superficial velocity (VSair) considering the end use of the producer gas for both internal combustion engines (ICEs) and atmospheric burners (AB), is examined. According to the results, biomass consumption rate, cold gas efficiency (CGE), and process temperature increased in the ranges 1–1.55 kg/h and 45–65% and 825–950°C, respectively, when ER goes from 0.23 to 0.3. To obtain the highest process performance, the process should be conducted at a VSair ~ 5.1 m/min and ER ~ 0.3. Under these parameters, a gas with thermal power and lower heating value (LHV) of 3.6 kWth and 4.78 MJ/Nm3, respectively, was obtained. These properties allow for an engine fuel quality (EFQ) of 1817 kJ/kg. For comparison, an ICE designed to be fueled with natural gas (EFQ of natural gas approx. 2650 kJ/kg) would have a ~ 30% drop in its maximum power when fed with the producer gas obtained through rice husk gasification.