American Journal of Applied Sciences, 10 (4): 395-402, 2013 ISSN: 1546-9239 ©2013 Science Publication doi:10.3844/ajassp.2013.395.402 Published Online 10 (4) 2013 (http://www.thescipub.com/ajas.toc) Corresponding Author: Kittichai Triratanasirichai, Department of Mechanical Engineering, Faculty of Engineering, KhonKaen University, 123 Mittraparb Road, Muang, Khon Kaen 40002, Thailand 395 Science Publications AJAS QUALITY ENHANCEMENT OF PRODUCER GAS FROM CASSAVA RHIZOME USING HIGH TEMPERATURE AIR- STEAM DOWNDRAFT GASIFICATION Worapot Ngamchompoo and Kittichai Triratanasirichai Department of Mechanical Engineering, Faculty of Engineering, Khon Kaen University,123 Mittraparb Road, Muang, Khon Kaen 40002, Thailand Received 2012-11-28, Revised 2013-03-06; Accepted 2013-05-08 ABSTRACT High Temperature Air-Steam Gasification (HTAG) was performed on a bench-scale downdraft gasifier. A cassava rhizome was used as feedstock for the gasification. Air and steam were utilized as the gasifying agents. The objectives in this study were to study the potential of HTAG technology applied with a downdraft gasifier to improve producer gas quality in terms of Higher Heating Value (HHV) and lower tar content. The results were compared with conventional air-steam gasification (without preheating). The results were that the HHV of the producer gas from the HTAG process at 900°C improved by as much as 5.1 MJ/Nm 3 (at S/B ratio = 0.3), while the air-steam gasification, HTAG at 300°C and HTAG at 600°C couldonly obtain a HHV of 3.8 MJ/Nm 3 (at S/B = 0.4), 4.2 MJ/Nm 3 (at S/B = 0.1) and4.8 MJ/Nm 3 (at S/B = 0.2), respectively. In addition, tar content in the producer gas of the HTAG process at 900°C had the lowest value (95 mg/m 3 ) which could be used as fuel in an internal combustion engine. While the minimum tar content of the air-steam gasification was 320 mg/m 3 . In the HTAG process at 900°C, the maximum Cold Gas Efficiency (CGE) was 65%, which was slightly lower than the CGE of air-steam gasification (69%). However, in the HTAG process at 300, 600 and 900°C the maximum Hot Gas Efficiency (HGE) increased 33% (from 72 to 96%), 25 (from 72 to 90%) and 7 (from 72 to 77%), respectively; when compared with air-steam gasification. Keywords: Downdraft Gasifier, Cassava Rhizome, High Temperature Air-Steam Gasification (HTAG) 1. INTRODUCTION The cassava rhizome is located between the stalk and root of the cassava plant (Fig. 1). It becomes a residue left from the cassava plant when it is burnt in preparation for next seasons planting. Burning the crop residue from a field or from part of a field can cause smoke and impact the environment; moreover, there is no benefit from the potential use of agriculture wastes. Researchers have reported that cassava production in Thailand is about 25 million tons per year (Atong et al., 2011) and about 8-10 million tons are made up of the rhizome. Therefore, the potential conversion of the cassava rhizome into renewable energy could be substantial. Biomass gasification is a series of thermo- chemical processes which can convert solid biomass into combustible gases called syn gas or producer gas. The main compositions of producer gas are H 2 , CO, CH 4 and CO 2 . High quality producer gas can be used as fuel in the Internal Combustion Engine (ICE) for producing electricity. High Temperature Air-steam Gasification (HTAG) technology has previously been developed (Lucas et al., 2004; Tsuji et al., 2002), this technology was discovered that using air and mixtures of air and steam preheated to high temperature (300-1000°C) as gasifying agent for biomass gasification process can increase the quality of producer gas. This is because sensible heat from preheating can be utilized to replace partial heat which is produced by biomass combustion and can support the endothermic gasification reaction.