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Title: Tar removal in hot gas streams
Author: Odongo, Anthony
ISNI:       0000 0004 5989 7190
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2015
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Thermal conversion of organic materials through gasification yields gaseous fuel. The fuel gas often requires cleaning and upgrading ahead of combustion in advanced technologies such as gas engines, fuel cells and turbines. Tar is one of the major impurities found in streams, and can foul and block equipment. This study focuses on catalytic destruction of tar in a hot gas stream, at different operating conditions to improve the gas yield and quality. Steam gasification and reforming of tar involves thermal decomposition of tar and the reaction of tar with steam and fuel gases. These processes contribute to complex kinetics of the overall process involving a series of reactions, including: CO + H2O ͍ CO2 + H2, CO + 3H2 → CH4 + H2O, C + H2O → CO + H2, CH4 + 2H2O → CO2 + 4H2, CO2 + 4H2 → CH4 + 2H2O, C + 2H2O → 2H2 + CO2, CO + 2H2 → CH3OH, C + CO2 → 2CO, 2C + H2 → C2H2, & C + 2H2 → CH4. The concentration of each component affects the rate of reaction for each product. Introducing a catalyst to these processes increases the rate reactions and hence the number of successful reactions. The operating temperature, residence time and type of feedstock are other factors that can also affect the gas yield and quality. In this work, a continuous fixed bed-reactor was developed and assembled at Imperial College London, and used to investigate the activity of Pt-, Rh- and Ni-based catalysts, provided by Johnson Matthey. Experiments were performed at temperatures from 700 oC to up to 950 oC. The carrier gas flow rate, the steam-to-carbon ratio and feed gas composition were also varied to investigate the reaction kinetics and reaction pathways. Rh- and Pt-based catalysts had a better activity, thermal durability and corrosion resistance than the Ni-based catalyst. The Rh-catalyst results at considered conditions and above 800 oC were just about the same as the equilibrium results. Rh- had a better longevity and a tar conversion to syngas as high as 98% at 750 oC and S/C of 3. Ni deactivated within initial 30 minutes whereas the Rh- and Pt-catalyst activity remained steady.
Supervisor: Millan-Agorio, Marcos ; Hellgardt, Klaus Sponsor: Imperial College London ; Johnson Matthey plc
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available