Graduate Program

Technology

Degree Name

Master of Science (MS)

Semester of Degree Completion

2013

Thesis Director

Jerry Cloward

Thesis Committee Member

Peter Ping Liu

Thesis Committee Member

Jonathan P. Blitz

Thesis Committee Member

Isaac Slaven

Abstract

The threat of energy depletion and greenhouse gas effect prove that fossil fuels are no longer sustainable for wide use. Thus, looking for alternative energy resources that are sustainable for use, environmentally friendly as well as regionally available is a challenge for current researchers. Biomass gasification is a process that turns solid biomass into combustible syn-gas. The identification of appropriate fuel sources for biomass gasification facilities in a particular region is significant from both energy and economic efficiency perspective.

This research developed three methods to calculate thermal conversion efficiency for biomass gasification using a downdraft laboratory scale gasification system. These three methods incorporated equivalence ratio, stoichiometric ratio, and elemental balance methodology, which calculate the thermal conversion efficiency in relation to the syn-gas composition measured experimentally by using a gas chromatography (GC) instrument. All three methods are able to relate the gasification chamber pressure (P_reac) (therefore air flow) to the syn-gas output, which overcomes a major weakness of previous models published in the literature. All three models produce consistent results in terms of thermal conversion efficiency of different biomass feedstock.

This research investigated gasification and corresponding thermal conversion efficiency of three biomass fuels including 100% woodchips, a mix of 50wt% woodchips and 50wt% Arundo donax, as well as 100% Arundo donax. Different biomass feedstock requires different reactor pressure to maintain its optimum and stable condition for gasification. In this study, the nominal pressure for woodchips was 35 (3.5 inch of water) while the pressure of 100% Arundo donax was around 20 (2.0 inch of water) and 30 (3.0 inch of water) for 50/50 mix of woodchips and Arundo donax. Consequently, it was found that the thermal conversion efficiency for woodchips was around 80%, whereas that of Arundo donax was around 42-48%. The efficiency for 50/50 mix of woodchips and Arundo donax was 67-69% depending upon the methods used for its calculation. The results from this research could be combined with other tools to determine the most energy and economic efficient biomass fuel for a local biomass power plant.

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