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Abstract Although several works on rice husk gasification have been reported, none of those works investigated and discussed the propagation front. In present work, rice husk gasification is conducted in a small-scale throat-less downdraft gasifier. The aim of the work is to investigate the effect of tuyer distance above the grate on the propagation front and performance of the gasifier. Rice husk gasification is performed at an equivalence ratio of 0.20 with variations in tuyer position above the grate of 120 mm, 190 mm, 260 mm, 330 mm, and 400 mm. The result shows that tuyer distance above the grate affects the propagation rate and the performance of the gasifier. The flame and bed propagation rates are nearly similar for the tuyer 400 mm above the grate. Meanwhile, a volume fraction of combustible gases CO, H 2 , and CH 4 improve as tuyer distance above the grate increases. Maximum values of 15.18% CO, 6.99% H 2 , and 0.99% CH 4 are obtained for the tuyer 400 mm above the grate. Maximum HHV of 3.21 MJ/Nm3 and thermal efficiency of 76.90% are also achieved for the tuyer 400 mm above the grate. Highlights • Rice husk gasification in small-scale downdraft gasifier with equivalence ratio of 0.2 • Investigation effect of tuyer distance above the grate on propagation and performance. • Tuyer distance above grate are 120 mm, 190 mm, 260 mm, 330 mm, and 400 mm. • Flame and bed propagation rates are nearly similar at tuyer 400 mm. • Maximum HHV and thermal efficiency are achieved at tuyer 400 mm above the grate. [ABSTRACT FROM AUTHOR]

Downdraft gasifier is very attractive for biomass gasification due to its easy fabrication and operation, and also due to low tar content in producer gas. However, drawbacks such as grate blocking, channeling, and bridging are found in the downdraft gasifiers, typically for feedstock with low bulk density. Another disadvantage is the downdraft gasifiers only suitable for feedstock with low moisture content. The design of the gasifiers is an important parameter that affects their performance. Various works on design improvements have been done for enhancing the performance of the gasifiers. This paper aims to review small-scale downdraft gasifiers for biomass gasification which is focused on design improvements and their effect on the performance of the gasifiers. Many works from previous researchers have been studied and cited. The result shows that the design of the gasifiers is an important parameter in gasification, besides biomass feedstock characteristics and process parameters. [ABSTRACT FROM AUTHOR]