The Effect of Air Fuel Ratio and Temperature on Syngas Composition and Calorific Value Produced from Downdraft Gasifier of Rubber Wood-Coal Mixture

Rubber wood (Ficus elastica) is one the biomass waste that can be used as raw material for a gasification process and has a calorific value of 4,069 cal/gram. Gasification is a process to convert a solid fuel to syngas (CO, CH4, and H2) through a combustion process using limited air between 20% to 40% of air stoichiometry. Depending on the direction of airflow, the gasifiers are classified as updraft, downdraft, and cross-flow. The downdraft type of gasifier produces a lower tar content than updraft type. The gasification of rubber wood and rubber wood-coal mixture were carried out in this research. The purpose of the research is to determine the effect of Air Fuel Ratio (AFR) and temperature on calorific value and composition of syngas by using a downdraft gasifier. The variations of AFR were 0.64, 0.95, and 1.26. The temperature of gasification was varied between 600ºC-1000ºC. The result showed that the percentage of CO, H2, and CH4 decreased with increasing of AFR, so decreasing the calorific value. The calorific value of syngas increased along with the temperature. The use of coal in the gasification process can maintain stable combustion the temperatures and increase the syngas produced. The best-operating conditions in the research occurred at AFR of 0.64, the temperature of 800ºC and use of coal as a stabilizer. At this condition, the percentage of syngas of 35.95% of CO, 15.95% of H2, 9.38% of CH4, and caloric value of 9,420 MJ/m3 was obtained.