| Summary: | 碩士 === 國立中興大學 === 森林學系所 === 101 === Gasification can be defined as the conversion of carbon feedstock (e.g., biomass, waste, coal, etc.) to combustible gas by partial oxidation at elevated temperature. Torrefaction, on the other hand, is the conversion of biomass to combustible and easy storage product by thermal treatment at a lower temperature. Currently only few studies have investigated gasification of torrefied biomass. Therefore, in this study, Cryptomeria japonica, Bambusa stenostachya and rice husk pellet along with torrefied products at 250oC and 350oC respectively were gasified in a 30 kWth bubbling fluidized bed gasifier to investigate the effect of feedstock, torrefied condition and air equivalence ratio (ER) on syngas composition, lower heating value and tar content.
The results show that after gasifiication, the CO, CH4, H2 , and tar content, and lower heating value of syngas decrease with increasing the ER, but CO2 shows the contrary tendency. In addition, the higher temperature torrefaction is, the more CO and H2 content of syngas are, but the CH4 content in syngas shows decrease and the tar content presents obviously descendent. It can also be seen that the gasification of rice husk pellet, torrefied rice husk pellet and torrefied Bambusa stenostachya, all reveal sintering phenomenon. It is because higher ash contents in feedstock would agglomerate during gasification, and cause the de-fluidization to influence syngas composition and tar content.
Moreover, torrefaction as the pre-treatment for gasification with a lower ER is an effective method to increase H2 yield rate for further using in the fuel cell.
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