Experimental investigation on tar produced from palm shells derived syngas using zeolite HZSM-5 catalyst

The efficiency of the gas cleaning step is one of the fundamental steps to the successful operation of biomass gasification technologies for power generation. In the present study, catalytic cracking is selected as the hot gas cleaning technology using zeolite HZSM-5 catalyst in order to reduce tar produced from palm shells gasification in the laboratory scale fixed bed reactor. The experimental conditions for average biomass particle size, nitrogen flow rate and percentage of zeolite HZSM-5 catalyst are in the range of 1.18-7.13 mm, 3-7 L/min, and 2-10 wt% respectively with constant air flow rate of 5 L/min to the inlet of the reactor. From the gas chromatographic analysis of the tar produced from the gasification process, it is found that the phenol in the tar is in the range of 5-8 vol% when the oxygen to nitrogen flow rate ratio is varied from 0.10 to 0.15. A decreasing trend in the phenol concentration is observed when oxygen to nitrogen ratio is increased. The overall oxygenated aromatic compounds in the tar content are comparable when operating with oxygen to nitrogen ratio of 0.12 and 0.15. The lowest concentration of phenol is achieved when 5 wt% of zeolite HZSM-5 catalyst is used with a reduction of 99% and 79% for oxygen to nitrogen ratio of 0.10 or 0.15 respectively when compared to the phenol concentration with the absence of the catalyst. Furthermore, higher percentage of the catalyst results in less chemical compounds found in tar. Tar content increased as lower concentration of oxygen content in gas mixture or larger palm shells particle size is used.