Experimental Investigation of Gasification of Densified Agricultural Biomass in a Downdraft Gasifier

Abstract

Biomass has increasingly become one of the most popular renewable sources of energy in Thailand, especially, agricultural wastes from economic crops. These wastes can be converted to fuel gas with gasification technology and used for firing processes in various industries and electric power production. This work was to investigate producer gas production from densified agro-residues in the form of briquette (50-55 mm in diameter, 20-35 mm thick) and pellet (5-6 mm in diameter, 20-30 mm long) of corncobs, rice husks, wood chips, and oil palm fronds in a 50 kWth throatless downdraft gasifier. Producer gas generated from this system contained H2, CO, and CH4 which were combustible. From the results, the gasifier was found to work satisfactorily and seemed to prefer pellets to briquettes. The main composition in products gas were in the range of 18-20% of carbon monoxide, 1-6% of hydrogen, and 0.9-l.9% of methane. Maximum gasification efficiencies in the range of 69-73% were obtained for biomass pellets from wood chips, corncobs, oil palm fronds, and rice husks with the calorific value of producer gas in the range of 12-16 MJ/Nm3. The fuel consumption rates were in the range of 15-16 kg/h and specific gas production of 2-3 m3/kg. The gravimetric concentration of biomass tar in the raw product gas was found around 18-45 g/Nm3, in which pelletized fuel appeared to show slightly lower tar than briquette fuel.