PhD Theses

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Browsing PhD Theses by Subject "Air Gasification"

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    Investigation of the influence of moisture content on biomass conversion in high temperature air/steam gasification (HTAG) process
    (University of Dar es Salaam, 2013) Wilson, Lugano
    Though they are sustainable, biomass energy technologies are challenged by the varied biomass characteristics. This study invoked Gibbs equilibrium modelling and laboratory techniques to investigate characteristics of 15 types of Tanzania biomasses for application in the high temperature air/steam gasification (HTAG) process. The laboratory investigation findings showthat the biomasses’ elemental composition of oxygen ranged from 27.40-42.70% whereas that of carbon and hydrogen ranged from 35.60-56.90% and 4.50-7.50%, respectively. Akinetic study showed that with the exception of sunflower stalks, jatropha husks and sisal bole that exhibited zero order reaction mechanism, all other biomasses obeyed the first order. Biomasses with highest activation energy values were rice husks (935.33 kJ/mole), rice bran (1,023.45 kJ/mole), and palm shells (1,070.84 kJ/mole). The combined laboratory and modelling investigations revealed that moisture content above 20% degraded cold gasification efficiency of the HTAG process, which resulted in lowsyngas heating value, below 6 MJ/nm3. However, hydrogen content of the syngas increased with moisture (up to 40%) and steam injection. The positive effect of high temperature, above 900°C was to enhance syngas evolution ateach moisture level. Based on the findings of this study, the analyzed biomasses exhibited suitable elemental composition and performance characteristics for use in thermochemical processes like the HTAG. For an efficient biomass conversion in the gasification process, its proper harvesting, handling and storage of the biomass is recommended. A wider application of the gasification technology for converting the abundant tropical biomass to the needy energyis therefore envisaged.