Investigation of Co-gasification Characteristics of Wood-coconut Fibers Pellet and Rice Husk Mixtures in a Downdraft Fixed Bed Gasifier

Increasing energy demand, in line with the rate of population growth, is always followed by the pace of the waste dump. Where the largest percentage comes from organic waste, it is potentially utilized as raw material of biomass mixture for emission reduction efforts in fuel conversion from waste energy. The main objective of this paper is to study the characteristics of co-gasification, especially gasification temperature, lower heating value and gas emission, on the performance of the biomass gasification process in a downdraft fixed bed gasifier. In this study, organic waste used twigs, coconut fibers and rice husks in the pelletization as raw materials on the combustion technology Downdraft Gasifier. Methods were carried out by co-gasification techniques between WCF (wood-coconut fibers) pellet and rice husk on 100% pellet composition, 75:25, 50:50, 25:75 and 100% rice husk. Syngas testing is done with direct measurement on the burner with TCD type Shimadzu 8A gas chromatography. The highest reactor temperature in the pyrolysis zone was 400^oC to 850^oC and the temperature in the oxidation zone was 1000^oC to 1200^oC. The result of the synthetic gas testing obtained the highest lower heating value (LHV) in WCF 100% pellet composition at 4.07 MJ/Nm³ with 85% efficiency. The lower heating value of the lowest syngas in a 100% pellet composition was 2.99 MJ/Nm³, where the increase of WCF pellets will increase the LHV syngas value. This resulted in visually low tar content and low ash particles in all compositions of approximately 30 to 35% of the initial mass of each composition, with the lowest ash in 100% rice husk composition at 0.29 g.

Biomas; Co-gasification; Downdraft gasifier; Pelletization; Synthetic gas

The added volume ratio of the pellets result in an encroachment on syngas heating value (lower heating value) and increase the value of the gas composition of CO and H₂. The comparison of pellets 100% shows the most optimal LHV value and composition of CO and H₂ gas greatest was 4.07 MJ/Nm³. The more WCF pellets increase, the larger the LHV value and the resulting combustible gas levels will be.

The equivalence ratio (ER) in optimal conditions of WCF gasification is 0.25 and the efficiency of gasification (cold gas efficiency) is 85%. The specific gasification rate (SGR) in optimal conditions the test is 0.0088 kg/m².s. and the gas specific production rate (SGPR) in is 0.0287 m³ m².s. These conditions show that variating WCF pellets ratio will optimize the gasification performance.

Thank you to the Tropical Renewable Energy Center of Universitas Indonesia, who provided start-up research grants to carry out this research.

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