Catalytic Combustion and NO Formation of Natural Gas
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As the world energy demand increases and the utilization of non-traditional fossil fuels becomes more attractive, natural gas, from shale gas and in gaseous and liquefied forms, becomes one of the most promising alternative fuels nowadays. The natural gas offers lower fuel production and transportation costs, a lower carbon content, a higher combustion efficiency and a greater applicability to most of existing power plants and combustion engines. Challenges exist, especially in improving its ignition characteristics and to further reduce its greenhouse gas and particulate matter emissions. To overcome these restraints, hydrogen addition, catalyst modification and fuel lean combustion have been investigated recently. In this thesis, the ignition and emission properties of methane and its mixtures with hydrogen additive are first studied in the mini-channel reactor. Numerical investigations have been performed using the CHEMKIN PRO software for pure methane and the mixtures of methane and hydrogen in non-catalytic and catalytic combustion. These effects of the hydrogen fractions, Pt-catalyst, wall temperature and inlet conditions on the ignition delay and NO formation are investigated. Available gas phase kinetics and heterogeneous surface reaction mechanisms in the literature are implemented and analyzed. As the second part of this thesis, natural gas combustion on a counter-flow burner is investigated experimentally and numerically, with a focus on NO formation. The NO profiles, measured by the FT-IR spectroscopy, are compared with model results from CHEMIKIN and with the GRI-Mech 3.0 mechanism. The formation mechanism of NO and effects of the different fuel/oxidizer ratios on the NO formation are investigated.