Browsing by Subject "Syngas"
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Item Conversion of liquid heptane to syngas through combustion in porous media(2007-05) Dixon, Michael James, 1982-; Ellzey, Janet L.Liquid heptane is converted to syngas in a porous inert media reactor consisting of a packed bed of alumina oxide pellets. The exhaust gases are analyzed for hydrogen, carbon monoxide, carbon dioxide, methane, and higher hydrocarbon concentrations over equivalence ratios ranging from 1.4 to 3.8 and a range of mixture inlet velocities. Other parameters of interest are the hydrogen and energy conversion efficiencies, carbon monoxide conversion efficiency, energy conversion efficiency, temperature measurements, reaction front propagation characteristics, soot production during burner operation, and limitations of the material properties. Various experimental values are compared to numerical results obtained from a porous media computational model. Hydrogen production increases with increasing equivalence ratio and mixture inlet velocity. However, hydrogen conversion efficiency reaches its peak value of 77% at an equivalence ratio of 3.0. Conversion efficiency increases with the mixture inlet velocity reaching peak values of 81% at a velocity of 80 cm/s for an equivalence ratio of 2.5. CO conversion efficiency peaks leaner than hydrogen conversion, and reaches values in excess of 90%.Item Development of a New Flame Speed Vessel to Measure the Effect of Steam Dilution on Laminar Flame Speeds of Syngas Fuel Blends at Elevated Pressures and Temperatures(2012-07-16) Krejci, MichaelSynthetic gas, syngas, is a popular alternative fuel for the gas turbine industry, but the composition of syngas can contain different types and amounts of contaminants, such as carbon dioxide, methane, moisture, and nitrogen, depending on the industrial process involved in its manufacturing. The presence of steam in syngas blends is of particular interest from a thermo-chemical perspective as there is limited information available in the literature. This study investigates the effect of moisture content (0 ? 15% by volume), temperature (323 ? 423 K), and pressure (1 ? 10 atm) on syngas mixtures by measuring the laminar flame speed in a newly developed constant-volume, heated experimental facility. This heated vessel also broadens the experimental field of study in the authors? laboratory to low vapor pressure fuels and other vaporized liquids. The new facility is capable of performing flame speed experiments at an initial pressure as high as 30 atm and an initial temperature up to 600 K. Several validation experiments were performed to demonstrate the complete functionality of the flame speed facility. Additionally, a design-of-experiments methodology was used to study the mentioned syngas conditions that are relevant to the gas turbine industry. The design-of-experiments methodology provided the capability to identify the most influential factor on the laminar flame speed of the conditions studied. The experimental flame speed data are compared to the most up-to-date C4 mechanism developed through collaboration between Texas A&M and the National University of Ireland Galway. Along with good model agreement shown with all presented data, a rigorous uncertainty analysis of the flame speed has been performed showing an extensive range of values from 4.0 cm/s to 16.7 cm/s. The amount of carbon monoxide dilution in the fuel was shown to be the most influential factor on the laminar flame speed from fuel lean to fuel rich. This is verified by comparing the laminar flame speed of the atmospheric mixtures. Also, the measured Markstein lengths of the atmospheric mixtures are compared and do not demonstrate a strong impact from any one factor but the ratio of hydrogen and carbon monoxide plays a key role. Mixtures with high levels of CO appear to stabilize the flame structure of thermal-diffusive instability. The increase of steam dilution has only a small effect on the laminar flame speed of high-CO mixtures, while more hydrogen-dominated mixtures demonstrate a much larger and negative effect of increasing water content on the laminar flame speed.Item Glow Discharge Enhanced Chemical Reaction: Application in Ammonia Synthesis and Hydrocarbon Gas Cleanup(2014-06-05) Ming, PingjiaTwo different plasma enhanced processing technologies were investigated in this study: ammonia synthesis from steam and nitrogen, and hydrocarbon gas clean up. Ammonia is a common sanitizer in swimming pool and fish tank, changing the pH of the water, which does not benefit bacteria. Also ammonia is used in various NOx reduction technologies, for example, selective catalytic reduction (SCR) methods have been studied for the cleaning of diesel engine exhaust. A small compact glow discharge was applied to investigate ammonia synthesis from steam and nitrogen. Ammonia was successfully detected via UV-VIS absorbance and through increasing pH value of treated water by product gas. Heavier hydrocarbon C3 to C5 are produced with natural gas, but cannot be used in sensitive energy conversion systems, like solid oxide fuel cell (SOFC). Utilizing small amount of energy to clean up and reform heavier hydrocarbon into synthesis gas is necessary when using hydrocarbon sources which contain heavier hydrocarbons mixture such as EPE (74.8% methane, 8% ethane, 8% ethylene, 2.1% propane and 1.1% Propene). Non-thermal plasmas, due to their unique non-equilibrium characteristics, offer advantages as method of reforming at lower temperature (100-150 ?C) and atmospheric pressure. For an EPE gas mixture, a high conversion and low specific energy cost is desirable. Variation in discharge power density, air and, water addition were tested, in order to find conditions which were energetically feasibility, efficiency and sufficiently reduced the higher hydrocarbon. High conversion efficiency was achieved, in propane and propene, which was more than 90%, without carbon deposition through air addition. For a 1 J/ml power density and 1.08 O2/C ratio condition, a process efficiency of 74% and 54% available output energy was achieved. At the same time, the concentration of ethane, ethylene, propane, propylene, and acetylene were cleaned-up to value of 1.01%, 1.67%, 0.08%, 0.00%, and 0.50%, respectively, less than 20% of their original input amount. Higher power density produced cleaner (less high hydrocarbons) in the products, and were still energetically feasible, but less efficient.Item Studies of rich and ultra-rich combustion for syngas production(2012-12) Smith, Colin Healey; Ellzey, Janet L.; Ezekoye, Ofodike A; Hidrovo, Carlos H; Berberoglu, Halil; Raja, Laxminarayan LSyngas is a mixture of hydrogen (H2), carbon monoxide (CO) and other species including nitrogen (N2), water (H2O), methane (CH4) and higher hydrocarbons. Syngas is a highly desired product because it is very versatile. It can be used for combustion in turbines or engines, converted to H2 for use in fuel cells, turned into diesel or other high-molecular weight fuels by the Fischer-Tropsch process and used as a chemical feedstock. Syngas can be derived from hydrocarbons in the presence of oxidizer or water as in steam reforming. There are many demonstrated methods to produce syngas with or without water addition including catalytic methods, plasma reforming and combustion. The goal of this study is to add to the understanding of non-catalytic conversion of hydrocarbon fuels to syngas, and this was accomplished through two investigations: the first on fuel conversion potential and the second on the effect of preheat temperature. A primarily experimental investigation of the conversion of jet fuel and butanol to syngas was undertaken to understand the potential of these fuels for conversion. With these new data and previously-published experimental data, a comparison amongst a larger set of fuels for conversion was also conducted. Significant soot formation was observed in experiments with both fuels, but soot formation was so significant in the jet fuel experiments that it limited the range of experimental operating conditions. The comparison amongst fuels indicated that higher conversion rates are observed with smaller molecular weight fuels, generally. However, equilibrium calculations, which are often used to determine trends in fuel conversion, showed the opposite trend. In order to investigate preheat temperature, which is one important aspect of non-catalytic conversion, experiments were undertaken with burner-stabilized flames that are effectively 1-D and steady-state. An extensive set of model calculations were compared to the obtained experimental data and was used to investigate the effect of preheat temperatures that were beyond what was achievable experimentally. Throughout the range of operating conditions that were tested experimentally, the computational model was excellent in its predictions. Experiments where the reactants were preheated showed a significant expansion of the stable operating range of the burner (increasing the equivalence ratio at which the flame blew off). However, increasing preheat temperature beyond what is required for stabilization did not improve syngas yields.Item Superadiabatic combustion in counter-flow heat exchangers(2009-05) Schoegl, Ingmar Michael; Ellzey, Janet L.Syngas, a combustible gaseous mixture of hydrogen, carbon monoxide, and other species, is a promising fuel for efficient energy conversion technologies. Syngas is produced by breaking down a primary fuel into a hydrogen-rich mixture in a process called fuel reforming. The motivation for the utilization of syngas rather than the primary fuel is that syngas can be used in energy conversion technologies that offer higher conversion efficiencies, e.g. gas turbines and fuel cells. One approach for syngas production is partial oxidation, which is an oxygen starved combustion process that does not require a catalyst. Efficient conversion to syngas occurs at high levels of oxygen depletion, resulting in mixtures that are not flammable in conventional combustion applications. In non-catalytic partial oxidation, internal heat recirculation is used to increase the local reaction temperatures by transferring heat from the product stream to pre-heat the fuel/air mixture before reactions occur, thus increasing reaction rates and allowing for combustion outside the conventional flammability limits. As peak temperatures lie above the adiabatic equilibrium temperature predicted by thermodynamic calculations, the combustion regime used for non-catalytic fuel reforming is referred to as 'superadiabatic'. Counter-flow heat exchange is an effective way to transfer heat between adjacent channels and is used for a novel, heat-recirculating fuel reformer design. An analytical study predicts that combustion zone locations inside adjacent flow channels adjust to operating conditions, thus stabilizing the process for independent variations of flow velocities and mixture compositions. In experiments, a reactor prototype with four channels with alternating flow directions is developed and investigated. Tests with methane/air and propane/air mixtures validate the operating principle, and measurements of the resulting syngas compositions verify the feasibility of the concept for practical fuel-reformer applications. Results from a two-dimensional numerical study with detailed reaction chemistry are consistent with experimental observations. Details of the reaction zone reveal that reactions are initiated in the vicinity of the channel walls, resulting in "tulip"-shaped reaction layers. Overall, results confirm the viability of the non-catalytic reactor design for fuel reforming applications.