Updraft gasification of juniper wood biomass using CO₂–O₂ and Air (N₂–O₂)

ABSTRACT

Biomass gasification is being considered as one of the most promising technologies for converting low-quality solid biomass fuel into gaseous fuel. Redberry juniper (Juniperus pinchotii), one of the woody species that dominate uncultivated lands in the southern great plains, USA, may have a great potential for bioenergy utilization. In this study, the results of gasification of juniper are presented. Juniper wood chips were gasified in an adiabatic fixed bed updraft gasifier using air and the mixture gas of carbon dioxide and oxygen (CO₂:O₂) as gasification medium. The effect of gasification parameters such as moisture contents, gasification mediums, and gasification temperature on produced gas properties and the tar yield were investigated. It was observed that oxy fuel gasification (the reaction of woody fuels with carbon dioxide) of juniper resulted in the increase of production of carbon monoxide, especially at higher peak gasification temperatures. As a result, the CO₂ gasification resulted in producing higher heating value gas (6264 kJ/nm³ with dilution of CO₂ and 19,750 kJ/nm³ inert free) compared to air gasification. For air gasification, it was observed that the updraft gasification produced large amount of the tar in the product gas (more than 100 g/nm³) for the fuels with moisture content between 6% and 11%. Generally, the tar yield increased with the increase of equivalence ratio (er) and moisture content. However, when the fuel moisture content reached 23.5%, the tar yield reduced significantly due low gasification temperature which reduced the less tar cracking.

KEYWORDS:

• bioenergy
• equivalence ratio
• gasification
• heating value
• wood fuels

Acknowledgments

We would like to thank the Department of Energy (DOE), Golden, Colorado, USA for the financial support under contract number OE-FG36-05G085003.

Nomenclature

CO	=	Carbon monoxide
CO2	=	Carbon dioxide
CH4	=	Methane
C2H6	=	Ethane
ER	=	Equivalence ratio
FB	=	Feedlot biomass
HHV	=	Higher heating value
MGT	=	Micro gas turbine
N2	=	Nitrogen
O2	=	Oxygen