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.

Thesis (Ph. D.)--Worcester Polytechnic Institute. / Keywords: deactivation; hysteresis; kinetics; structure sensitivity; methane oxidation on palladium. Includes bibliographical references (p. 150-158).

Catalytic combustion provides us an efficient approach for the utilization and mitigation of methane, the major component of natural gas as well as an important greenhouse gas in global warming. From the research of catalytic combustion of methane, better understandings as well as solutions to the current methane-related problems can be obtained. This study investigates lean methane combustion on palladium-based catalysts. Catalysts activities were tested through ignition and extinction experiments. Several pretreatments and their influence were studied. Instrumental neutron activation analysis (INAA) and x-ray diffraction (XRD) were used as characterization tools for the catalysts. It was found that after being reduced, catalysts had stable and excellent abilities for methane conversion. However, these abilities were strongly compromised by additional water in the feeds. XRD results, combined with other testing results, implied that reduction produced the most active samples, while INAA revealed the real Pd concentrations of these catalysts. / Chemical Engineering

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This work is devoted to generate knowledge and high quality experimental data of catalytic combustion at operational gas turbine conditions. The initial task of the thesis work was to design and construct a high pressure combustion test facility, where the catalytic combustion experiments can be performed at real gas turbine conditions. With this in mind, a highly advanced combustion test facility has been designed, constructed and tested. This test facility is capable of simulating combustion conditions relevant to a wide range of operating gas turbine conditions and different kinds of fuel gases. The shape of the combustor (test section) is similar to a “can” type gas turbine combustor, but with significant differences in its type of operation. The test combustor is expected to operate at near adiabatic combustion conditions and there will be no additions of cooling, dilution or secondary supply of air into the combustion process. The geometry of the combustor consists of three main zones such as air/fuel mixing zone, catalytic reaction zone and downstream gas phase reaction zone with no difference of the mass flow at inlet and exit. The maximum capacity of the test facility is 100 kW (fuel power) and the maximum air flow rate is 100g/s. The significant features of the test facility are counted as its operational pressure range (1 – 35 atm), air inlet temperatures (100 – 650 °C), fuel flexibility (LHV 4 - 40 MJ/m3) and air humidity (0 – 30% kg/kg of air). Given these features, combustion could be performed at any desired pressure up to 35 bars while controlling other parameters independently. Fuel flexibility of the applications was also taken into consideration in the design phase and proper measures have been taken in order to utilize two types of targeted fuels, methane and gasified biomass. Experimental results presented in this thesis are the operational performances of highly active precious metal catalysts (also called as ignition catalysts) and combinations of precious metal, perovskites and hexaaluminate catalysts (also called as fully catalytic configuration). Experiments were performed on different catalytic combustor configurations of various types of catalysts with methane and simulated gasified biomass over the full range of pressure. The types of catalysts considered on the combustor configurations are palladium on alumina (Pd/AL2O3), palladium lanthanum hexaaluminate (PdLaAl11O19), platinum on alumina (Pt/AL2O3),and palladium:platinum bi-metal on alumina (Pd:Pt/AL2O3). The influence of pressure, inlet temperature, flow velocity and air fuel ratio on the ignition, combustion stability and emission generation on the catalytic system were investigated and presented. Combustion catalysts were developed and provided mainly by the project partner, the Division of Chemical Technology, KTH. Division of Chemical Reaction Technology, KTH and Istituto di Ricerche sulla Combustione (CNR) Italy were also collaborated with some of the experimental investigations by providing specific types of catalysts developed by them for the specific conditions of gas turbine requirements. / <p>QC 20131125</p>

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Catalytic combustion is an efficient method to reduce pollutant emissions produced by a variety of fuels. In this thesis, the use of iron pentacarbonyl (Fe(CO)5) as a catalyst precursor in the combustion of natural gas is experimentally studied. The counter-flow diffusion flame burner is employed as the experimental apparatus. The products of combustion are analyzed by using a Gas Chromatograph (GC) to quantitate the effects of adding the catalyst. The experimental setup is such that a mixture of methane (CH4) and nitrogen (N2) is fed from the bottom burner while a mixture of oxygen (O2) and air is supplied from the top burner. The combustion of natural gas without catalyst is first characterized. The oxidizer and fuel flow parameters are set up so that a stable, flat blue flame is formed close to the centre plane between the two burners upon ignition. The experimental results agree with the literature data and the numerical predictions from CHEMKIN software. To investigate and evaluate the performance of iron-containing catalysts on emission reduction, a small amount of separated nitrogen flow is used to carry iron pentacarbonyl into the flame through the central port of the fuel-side burner. Catalytic combustion produces an orange flame. Compared with the non-catalytic combustion data, it is found that carbon monoxide (CO) and soot precursor acetylene (C2H2) are reduced by 80% to 95% when 7453ppm iron pentacarbonyl is added.

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Transportation sector CO2 emissions contribute to global warming. Methanol generated from clean energy sources has been proposed as a transportation fuel as an alternative to gasoline or diesel to reduce emissions. Catalytic methanol-steam reformers can be combined with high temperature polymer electrolyte membrane (HTPEM) fuel cell systems to create compact electrical power modules which run on liquid methanol. These modules combine the efficiency of a fuel cell system with the convenience of using a traditional, liquid hydrocarbon fuel. Catalytic methanol-steam reformers require a heat source as the methanol-steam reforming process is endothermic. The heat source for this system will initially be from the catalytic combustion of either pure methanol, during startup, or from HTPEM fuel cell anode waste gas during system operation. Efficient use of catalyst requires effective premixing of the fuel and air. This study will investigate parameters affecting premixing and their effect on temperature distributions and emissions.