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Now showing 1 - 10 of 321
  • Publication
    NGL/LPG Extraction from Marcellus Shale Gas
    (2015-05-04) Champagne, Jocelyn; Ordonez, Freddy; Zhang, Zhiyi
    This process describes a design in which 6 million metric tons per annum of Marcellus Shale Gas is separated into its components through heat exchangers, pressure drops, and, finally, flowing through distillation columns. The goal was essentially to remove all of the methane gas as the overhead product of the heavy removal column and use the subsequent columns to fraction off heavier hydrocarbons. Heat exchangers could not remove sufficient heat from the feed prior to entering the columns and as a result, the overhead product for the heavy removal column consists of 84% by mole of methane and 15% by mole of ethane. Essentially all of the methane is being removed with the overhead product of the HRC but 85% of ethane is being removed here as well. By selling the major product (ethane) and the byproducts (propane and butane), our process design solution yields a net present value of $166.0 million, with an internal rate of return of 32.3%. The high profitability is secured in a sensitivity analysis on the ethane selling price, the total permanent investment, and the total fixed cost.
  • Publication
    An Examination of SOFC Anode Functional Layers Based on Ceria in YSZ
    (2007-08-21) Gross, Michael D; Vohs, John M; Gorte, Raymond J
    The properties of solid oxide fuel cell (SOFC) anode functional layers prepared by impregnation of ceria and catalytic metals into porous yttria-stabilized zirconia (YSZ) have been examined for operation at 973 K. By varying the thickness of the functional layer, the conductivity of the ceria-YSZ composite was determined to be only 0.015–0.02 S/cm. The initial performance of anodes made with ceria loadings of 40 or 60 wt % were similar but the anodes with lower loadings lost conductivity above 1073 K due to sintering of the ceria. The addition of dopant levels of catalytic metals was found to be critical. The addition of 1 wt % Pd or Ni decreased the anode impedances in humidified H2 dramatically, while the improvement with 5 wt % Cu was significant but more modest. Pd doping also decreased the anode impedance in dry CH4 much more than did Cu doping; however, addition of either Pd or Cu led to similar improvements for operation in n-butane. Based on these results, suggestions are made for ways to improve SOFC anode functional layers.
  • Publication
    Detailed Microscopic Analysis of Self-interstitial Aggregation in Silicon. II. Thermodynamic Analysis of Single Clusters
    (2010-07-19) Kapur, Sumeet; Nieves, Alex M; Sinno, Talid
    We analyze results generated by large-scale molecular-dynamics simulations of self-interstitial clusters in crystalline silicon using a recently developed computational method for probing the thermodynamics of defects in solids. In this approach, the potential-energy landscape is sampled with lengthy molecular-dynamics simulations and repeated energy minimizations in order to build distribution functions that quantitatively describe the formation thermodynamics of a particular defect cluster. Using this method, a comprehensive picture for interstitial aggregation is proposed. In particular, we find that both vibrational and configuration entropic factors play important roles in determining self-interstitial cluster morphology. In addition to the expected role of temperature, we also find that applied (hydrostatic) pressure and the commensurate lattice strain greatly influence the resulting aggregation pathways. Interestingly, the effect of pressure appears to manifest not by altering the thermodynamics of individual defect configurations but rather by changing the overall energy landscape associated with the defect. These effects appear to be general and are predicted using multiple, well-tested, empirical interatomic potentials for silicon. Our results suggest that internal stress environments within a silicon wafer (e.g., created by ion implantation) could have profound effects on the observed selfinterstitial cluster morphology.
  • Publication
    Engineering Composite Oxide SOFC Anodes for Efficient Oxidation of Methane
    (2008-02-14) Kim, Guntae; Corre, G.; Irvine, J. T. S.; Vohs, John M; Gorte, Raymond J
    Ceramic anodes for solid oxide fuel cells SOFCs were prepared by aqueous impregnation of nitrate salts to produce composites with 45 wt % La0.8Sr0.2Cr0.5Mn0.5O3 (LCSM)in a 65% porous yttria-stabilized zirconia (YSZ) scaffold. Scanning electron micrographs indicate that the LSCM coats the YSZ pores following calcination at 1473 K. Composites produced in this manner exhibit conductivities at 1073 K of approximately 1 S/cm in air and 0.1 S/cm in humidified H2. A SOFC with a composite anode composed of 45 wt % LSCM, 0.5 wt % Pd, and 5 wt % ceria exhibited maximum power densities at 1073 K of 1.1 and 0.71 W cm−2 in humidified (3% H2O) H2 and methane, respectively.
  • Publication
    Analysis of the Performance of the Electrodes in a Natural Gas Assisted Steam Electrolysis Cell
    (2008-02-01) Wang, Wensheng; Gorte, Raymond J; Vohs, John M
    The performance of solid oxide electrolysis (SOE) cells while operating in the natural gas assisted steam electrolysis (NGASE) mode was evaluated. The SOE cells used yttria-stabilized-zirconia (YSZ) as the oxygen ion conducting electrolyte, Co–CeO2–YSZ as the H2–H2O electrode, and Pd-doped CeO2 YSZ source as the CH4-oxidation electrode. The cell electrochemical performance was evaluated as a function of the H2O/H2 ratio and the extent of conversion of CH4. The results of this study provide insight into the factors that control electrode performance and further demonstrate the viability of an NGASE cell for the production of H2.
  • Publication
    An Efficient and Safe Cooking Stove for Las Delicias, El Salvador
    (2017-04-18) Castaner, Maria; Li, Daniel; Minor, Nicolas
    The primary objective of this project was to design an efficient and safe cooking stove based on the resources available in El Salvador while ensuring it could be inexpensive to produce. The stove is a cuboid, 18"×18"×12" in dimension, and weighs 75 lbs. It has a top cover to cook on, and a unique three-chamber design: a chamber for combustion, a chamber to pump hot air into the combustion chamber with a bellows, and a third chamber to add insulation material. A ventilation tube connects the inner chamber with the exterior to safely vent flue gas to the outside. The stove is made out of stainless steel, and uses sand as an insulator. The product’s overall energy efficiency was calculated to be about 33%, and it requires approximately 19-20 minutes to boil 5 liters of water assuming a pot diameter of 14”. The estimated manufacturing cost of producing the first 200 stoves is $51.77 per unit, without including capital equipment costs. A unit can be priced at $65, which would give the manufacturer a 25% margin while maintaining competitiveness in the market against stoves such as Turbococina and Ecocina. The stove is estimated to cost a family $15 per month to operate, which corresponds to 50% in charcoal fuel savings compared to using an open flame. The stove can be manufactured using local labor and would take on average 6 to 7 hours to construct one unit.
  • Publication
    Heat Recovery from Natural Gas Liquefaction Process
    (2012-04-01) Calabrese, Michelle; Douglas, Kaitlin; Orinstein, Brendan; Vasansiri, Kritithy; Wang, Marisa
    This project recommends several possible processes which expand and improve upon an existing section of a natural gas liquefaction plant. The section in question involves the combustion of the effluent fuel from the liquefaction process to produce usable work that drives the overall process. The existing process involves a simple gas turbine, which utilizes a Brayton cycle to convert combustion heat to shaft work. While the existing platform successfully provides power to the overall liquefaction process, the gaseous exhaust from this process leaves the system at elevated temperatures. The processes presented in this project seek to recover the heat that is lost through the exhaust and therefore, improve the thermodynamic efficiency of this system. Additionally, these processes more rigorously meet environmental standards concerning flue gas compositions and temperatures. Seven such processes are presented in this report. Each of these provides a net of 40MW, the required power to drive the liquefaction process, while performing at higher thermodynamic efficiencies than the simple gas turbine process. Rigorous economic analyses were performed for each of the presented processes. One recovery system has a lower net present value (NPV) than that of the simple gas turbine, four have approximately equal NPVs, and two systems have significantly better NPVs than that of the simple gas turbine. The optimal system has an NPV of $22 million and an internal rate of return (IRR) of 28.2% versus the simple gas turbine with an NPV of $12.3 million and an IRR of 20.3%. Further analyses of the economic and pricing assumptions may be required before final project approval.
  • Publication
    Surface probe measurements of the elasticity of sectioned tissue, thin gels and polyelectrolyte multilayer films : correlations between substrate stiffness and cell adhesion
    (2004-10-10) Engler, Adam J; Richert, Ludovic; Wong, Joyce; Picart, Catherine; Discher, Dennis E
    Surface probe measurements of the elasticity of thin-film matrices as well as biological samples prove generally important to understanding cell attachment across such systems. To illustrate this, sectioned arteries were probed by Atomic Force Microscopy (AFM) within the smooth muscle cell (SMC)-rich medial layer, yielding an apparent Young’s modulus Emedia ~ 5-8 kPa. Polyacrylamide gels with Egel spanning several-fold above and below this range were then cast 5-70 μm thick and coated with collagen: SMC spreading shows a hyperbolic dependence in projected cell area versus Egel. The modulus that gives half-max spreading is E1/2-spread ~ 8-10 kPa, proving remarkably close to Emedia. More complex, layer-by-layer micro-films of poly(L-lysine)/hyaluronic acid were also tested and show equivalent trends of increased SMC spreading with increased stiffness. Adhesive spreading of cells thus seems to correlate broadly with the effective stiffness of synthetic materials and tissues.
  • Publication
    Green Glycol: A Novel 2-Step Process
    (2019-05-14) Falcones, Ingemar; Golden, Sarah; Kowalchuk, Maria
    Ethylene glycol demand is growing rapidly, particularly in the global polyethylene terephthalate markets.¹ Traditional production of non-renewable ethylene glycol involves steam cracking of ethane or the methanol-to-olefin process to obtain ethylene.6 In response to environmental movements, Coca-Cola® began creating ethylene glycol from renewably sourced ethanol, by producing the ethylene oxide intermediate in a two-step reaction process.² Novel research at Leiden University, entitled Direct conversion of ethanol into ethylene oxide on gold based catalysts, explores a catalyst which produces ethylene oxide in one step, showing potential for a more efficient renewable process.³ This project explores the scaling of the Leiden research to an industrial level. The makeup raw material flows accounting for the recycle streams in the process are 237,000 MT fuel-grade ethanol per year, 81,000 MT oxygen per year, and 26,000 MT carbon dioxide diluent per year. The design first reacts ethanol and low concentration oxygen feeds to form an ethylene oxide intermediate, as well as undesired byproducts. A series of separations isolate ethylene oxide for further reaction, while recycling unconverted feeds and diluents. EO is then hydrolyzed to form mono-, di-, tri-, and higher order glycols. The following separation series removes water for recycle, then isolates fiber grade (99.9 wt%) monoethylene glycol as the main product. The bottoms of this separation results in an ethylene glycol mixture that is sold as a slurry for additional revenue. A financial analysis of the process over a 15 year period shows that the process does not directly compete with the existing monoethylene glycol market. However, a 14.5% green premium on the selling price of monoethylene glycol would reach a 15% IRR and achieve profitability. Future work should be focused on investigating catalyst performance and reproducing similar reaction behavior in industrial-scale conditions.
  • Publication
    Cellular Agriculture
    (2022-04-19) Kim, Christina; Kishun, Amanda; Lubna, Fahmida
    Cellular agriculture is a field of biotechnology focused on the production of animal products using cells grown in vitro . Traditional meat production consumes vast amounts of water, arable land, and feed crops, as well as driving deforestation, emitting large amounts of greenhouse gases, and creating large potential reservoirs for zoonotic diseases. As the global demand for meat increases, continuing to scale up the industry for slaughtered meat could have disastrous consequences for the environment. Growing cells in bioreactors creates the potential to drastically decrease land requirements, feed requirements, and other environmental impacts. For example, hindgut fermentation of feed, the main source of methane emissions from cattle farming, can be eliminated entirely by supplying the cells with pure glucose. This report proposes a process to produce 35 million pounds per year of a cultured ground beef product. The process starts with a starter colony of bovine muscle satellite cells, which are proliferated, differentiated to bovine muscle fiber, and then dewetted, mixed with plant-based fat, and extruded to the final product. Bubble column bioreactors are used for the seed train, final proliferation, and differentiation steps in order to adequately oxygenate large process volumes without threatening cell viability. The process shows profitability at a price of $100 per pound of product. The plant has a return on investment of 217%, an investor’s rate of return of 223%, and a cumulative net present value of about $2 billion over the plant’s lifespan.