Study on Tar Generation from Downdraft Gasification of Oil Palm Fronds

One of the most challenging issues concerning the gasification of oil palm fronds (OPF) is the presence of tar and particulates formed during the process considering its high volatile matter content. In this study, a tar sampling train custom built based on standard tar sampling protocols was used to quantify the gravimetric concentration of tar (g/Nm³) in syngas produced from downdraft gasification of OPF. The amount of char, ash and solid tar produced from the gasification process was measured in order to account for the mass and carbon conversion efficiency for downdraft gasification of OPF. Elemental analysis of the char and solid tar samples was done using ultimate analysis machine, while the relative concentration of the different compounds in the liquid tar was determined making use of a liquid gas chromatography (GC) unit. In addition, the cleaning efficiency of a proposed syngas cleaning system was determined by comparing the tar concentration in raw gas and cleaned gas samples. Average tar concentration of 4.928 g/Nm³ and 1.923 g/Nm³ was obtained for raw gas and cleaned gas samples respectively. Tar concentration in the raw gas sample obtained from downdraft gasification of OPF was found to be higher compared to results for other biomass materials, which could be attributed to its higher volatile matter percentage. Average cleaning efficiency of 61% which is comparable to that of sand bed filter and venturi scrubber cleaning systems reported in literature was obtained for the cleaning system proposed in the current study.