Quality Enhancement of Producer Gas From Cassava Rhizome Using High Temperature Air-Steam Downdraft Gasification

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/Nm³ (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/Nm³ (at S/B = 0.4), 4.2 MJ/Nm₃ (at S/B = 0.1) and4.8 MJ/Nm³ (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/m³) which could be used as fuel in an internal combustion engine. While the minimum tar content of the air-steam gasification was 320 mg/m³. 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.