Pyro-gasification of rice husk to bio-fuel an optimization study of process parameters

Abstract

Rice husk is a promising candidate of sustainable biomass-based renewable energy source with a gross caloric content of around 19.73 MJ/kg. As an efficient thermo-conversion process, pyro-gasification has the potential to convert biomass into oil and gas fuels. However, the bio-oil and gas yields are strongly dependent on the pyro-gasification operating parameters. This study employed response surface methodology (RSM) based on central composite design (CCD) experiment to determine the optimum conditions for pyro-gasification of rice-husk. Three selected most influencing operating parameters, namely feed mass (g), nitrogen flow (mL/min), and reactor temperature (°C) were optimized through 16 individual experimental runs for their possible synergistic effects. The results show excellent model fitting criteria (R2 > 0.9 and R2-adj > 0.85) for bio-oil and gas product responses that proves the suitability of RSM based on CCD experiment for rice-husk pyro-gasification study. The optimized optimum condition for rice-husk pyro-gasification process was at 897 g of feed mass, 1.97 mL/min of N2 gas flowrate, and 593 °C of reaction temperature. These conditions allow the achievement of estimated bio-oil and gas product yield of 47.78% and 11.41%, respectively. The composition analysis revealed that the main component of bio-oil was C15 (unsaturated), whereas the gas products were C3–C4. This study suggests that rice-husk pyro-gasification is capable to achieve maximum yield of bio-oil and gas products with low char generation.