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Use of zeolite-based micro-porous materials in enhancing methane combustion performance

Authors Hui, Kwan San
Issue Date 2008
Summary Use of zeolite in enhancing methane combustion performance was studied. Both experimental and analytical studies were carried out. This work focused on two parts. The first part was about methane combustion at low concentration condition aiming at air cleaning usage. The second part focused on methane combustion at high concentration condition aiming at energy generation. In low methane concentration condition, performance of multi-metal-(Cu, Cr, Ni, Co and Zn)-ion-exchanged zeolites on methane combustion was evaluated under various parameters including the amount of metal loading, reaction temperature, space velocity and methane concentration. The results showed that the amount of metal loading in zeolite played an important role in affecting the apparent activation energy for methane combustion, the active sites, and the BET surface area of the catalyst. An optimized amount of metal loading at which the highest catalytic activity was observed due to the combined effects of the various factors was determined. Further experiments were designed to investigate the effect of ozone on low-temperature combustion of methane over the zeolite material. The presence of ozone to the zeolite catalyst enhanced methane combustion efficiency by 24-56%, giving overall performance of 93% in 295-435 °C. Mechanisms of methane combustion with the catalyst with and without ozone were proposed. Recycled zeolite materials from coal fly ash were also used in the work demonstrating good performance. In high methane concentration condition, the influence of preheat temperature on flame propagation and extinction was analytically and experimentally investigated under various parameters including tube diameter, equivalence ratio (fuel concentration) and mixture flow rate. The analytical model provides insights into sustaining propagating flame in small channels. Experimental results confirm the analytical results that the flame speed increases and the flammability limit shifts toward the fuel lean direction through increasing preheat temperature. Zeolite catalyst was applied to increase the propagating flame speed in small channels. Keywords: Natural gas; Methane; Zeolite; Transition metal ions; Palladium; Catalytic combustion; Mechanisms; Activation energy; Narrow channels; Flammability limits; Flame speed; Asymptotic analysis; Recycling; Environment; Economy
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008
Language English
Format Thesis
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