Experimental Study of Biomass Gasification in a Downdraft Gasifier Using Different Feedstocks
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Date
2012-02-19
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Addis Ababa University
Abstract
The primary interest of this research work is to study the gasification properties of different
biomass feedstock materials which are easily available in Ethiopia. An overview of biomass is
discussed in this paper so as to have a clue what chemical composition does a biomass material
can have and its implication of energy conversion. The different types of conversion processes
are also covered in order to show the possible ways that energy can be extracted from biomass
and to compare their merits and demerits relative to gasification. A precise theoretical overview
of gasification is dealt which has laid a very starting ground for what is done in the simulation
and experimental works.
Experimental investigation is an irreplaceable tool to get a very meaningful finding in this
research even though simulation can give a good guidance and a pre insight. Simulation work
alone can be misleading since many simplifying assumptions were taken in order to make it
possible to simulate the very complicated thermo-chemical process inside the gasifier and also
the still unclearly phenomenon of tar formation. Both simulation and experimental work are
undertaken in this research. A Matlab program is used to simulate the effects of moisture content
and equivalence ratio on the constituent gas composition of the produced gas. An algorithm
based on a thermodynamic model with certain simplifying assumptions is used so that the Matlab
program will not miss the physical outlook of the modeled gasification process. Tables and
figures are generated which are suitable to see the effects of different parameters on the final
output of the gasification process.
An experimental investigation is undertaken using different feedstock materials. The
experiments are being carried out for some selected biomass materials which are charcoal,
sawdust, coffee husk and a mixture of sawdust and coffee husk. The effects of moisture content
and equivalence ratio on the final syngas composition are studied. The amount and nature of tar
produced while gasifying the different feedstock is also examined. A comparison of the
simulation and experimental works is done and it was reasoned out what effects the deviation of
the experimental result from that of the simulation work. It was also attempted to compare the
simulation and experimental results with those in literatures. At the end recommendations and
suggestion of future works are presented concerning the work of this research.
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Keywords
Biomass gasification, Downdraft Gasifier