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  • Articles  (1,631)
  • Wiley  (1,631)
  • Copernicus
  • Water Resources Research  (525)
  • Chemical Engineering and Technology  (285)
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  • 1
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    Effect of Cumulative Surface on Pore Development in Chalk (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract Pore development in natural porous media, as a result of mineral dissolution in flowing fluid, generates complex microstructures. Although the underlying dynamics of fluid flow and the kinetics of the dissolution reactions have been carefully analyzed in many scenarios, it remains interesting to ask if the preferentially developed flow paths share certain general petrophysical properties. Here we combine in situ X‐ray imaging with network modeling to study pore development in chalk driven by acidic fluid flow under ambient condition. We show that the trajectory of a growing pore correlates with the flow path that minimizes cumulative surface—the overall surface area available to fluid within the residence time—calculated along streamlines. This correlation is not a coincidence because cumulative surface determines conversion of reactant and thus defines the position of dissolution front. Model simulations show that, as fluid channelizes, the growth of the leading pore in the flow direction is guided by migration of the most far‐reaching dissolution front, even in an ever‐changing flow field. In addition, we present a complete tomographic time series of microstructure erosion and show a good accord between the in situ observation and the model simulation. Our results suggest that the microscopic pore development is a deterministic process while being sensitive to stochastic perturbations to the migrating dissolution front.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Nanocrystalline Zeolite Tetraethylammonium-Beta Membrane for Preferential Sorption and Transport of CO2 over N2 (2013)
    Wiley
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    Publication Date: 2013-06-07
    Description: CO 2 /N 2 gas separation was performed over a nanocrystalline zeolite tetraethylammonium (TEA)-beta membrane prepared on a stainless-steel porous disc by repeated hydrothermal crystallization. Two to three consecutive hydrothermal syntheses were required to form a membrane comprised of a continuous and compact layer of zeolite beta nanocrystals on the support. The membrane TEA-BEA3 obtained by three consecutive syntheses, in which the membrane from two consecutive syntheses was used as support, exhibited the highest structural order. When the separation experiment was performed over this membrane without applying any external applied pressure, 100 % selectivity of CO 2 over N 2 was observed. The separation was driven by differences in chemical potentials of the molecules generated only by the adsorption-desorption behavior of the gases into the membrane. The novel zeolite TEA-beta membrane provided promising results for the separation of small gas molecules due to the combined influence of diffusion and sorption selectivity. Nanocrystalline zeolite tetraethylammonium (TEA)-beta membranes were prepared by repeated coating of zeolite nanocrystals via hydrothermal crystallization from a colloidal solution over a porous stain-less-steel disc support. When the separation experiment was performed without applying any external pressure, a CO 2 selectivity over N 2 of 100 % could be achieved.
    Print ISSN: 0930-7516
    Electronic ISSN: 1521-4125
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 3
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    On parameterization of the inverse problem for estimating aquifer properties using tracer data (2012)
    Wiley
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    Publication Date: 2012-06-28
    Description: In developing a reliable approach for inferring hydrological properties through inverse modeling of tracer data, decisions made on how to parameterize heterogeneity (i.e., how to represent a heterogeneous distribution using a limited number of parameters that are amenable to estimation) are of paramount importance, as errors in the model structure are partly compensated for by estimating biased property values during the inversion. These biased estimates, while potentially providing an improved fit to the calibration data, may lead to wrong interpretations and conclusions and reduce the ability of the model to make reliable predictions. We consider the estimation of spatial variations in permeability and several other parameters through inverse modeling of tracer data, specifically synthetic and actual field data associated with the 2007 Winchester experiment from the Department of Energy Rifle site. Characterization is challenging due to the real-world complexities associated with field experiments in such a dynamic groundwater system. Our aim is to highlight and quantify the impact on inversion results of various decisions related to parameterization, such as the positioning of pilot points in a geostatistical parameterization; the handling of up-gradient regions; the inclusion of zonal information derived from geophysical data or core logs; extension from 2-D to 3-D; assumptions regarding the gradient direction, porosity, and the semivariogram function; and deteriorating experimental conditions. This work adds to the relatively limited number of studies that offer guidance on the use of pilot points in complex real-world experiments involving tracer data (as opposed to hydraulic head data).
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 4
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    Stochastic modeling of salt accumulation in the root zone due to capillary flux from brackish groundwater (2011)
    Wiley
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    Publication Date: 2011-09-07
    Description: Groundwater can be a source of both water and salts in semiarid areas, and therefore, capillary pressure–induced upward water flow may cause root zone salinization. To identify which conditions result in hazardous salt concentrations in the root zone, we combined the mass balance equations for salt and water, further assuming a Poisson-distributed daily rainfall and brackish groundwater quality. For the water fluxes (leaching, capillary upflow, and evapotranspiration), we account for osmotic effects of the dissolved salt mass using Van‘t Hoff's law. Root zone salinity depends on salt transport via capillary flux and on evapotranspiration, which concentrates salt in the root zone. Both a wet climate and shallow groundwater lead to wetter root zone conditions, which in combination with periodic rainfall enhances salt removal by leaching. For wet climates, root zone salinity (concentrations) increases as groundwater is more shallow (larger groundwater influence). For dry climates, salinity increases as groundwater is deeper because of a drier root zone and less leaching. For intermediate climates, opposing effects can push the salt balance either way. Root zone salinity increases almost linearly with groundwater salinity. With a simple analytical approximation, maximum concentrations can be related to the mean capillary flow rate, leaching rate, water saturation, and groundwater salinity for different soils, climates, and groundwater depths.
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    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 5
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    Effects of Aromatics on the Stability and Product Distribution of the Methanol to Olefin Process (2011)
    Wiley
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    Publication Date: 2011-09-28
    Description: Methanol to olefin process was investigated over a steam-treated Ca-ZSM-5 catalyst in a flow-type fixed bed reactor by adding aromatics to the methanol feed. As a comparison, the catalytic performance in the presence of nitrogen and water was also investigated. The experimental results exhibit that in the presence of aromatics, the total light olefin selectivity and the ethylene selectivity increased, while propylene selectivity increased with adding o- xylene and m -xylene to the methanol feed, but decreased with adding benzene, toluene, p -xylene and ethylbenzen to the methanol feed. The catalyst was characterized by temperature-programmed desorption of ammonia, N 2 adsorption, and scanning electron microscope. The adsorption of water and aromatics on the catalyst was also studied. Based on the results, it is concluded that aromatics may be responsible for the formation of light olefins and be more favorable for ethylene than propylene in methanol conversion. The methanol to olefin process was investigated over a steam-treated Ca-ZSM-5 catalyst in a flow-type fixed bed reactor by adding aromatics to the methanol feed. High light-olefin selectivity was gained. Further experimental data suggested that aromatics enhanced the formation of light olefins in methanol conversion.
    Print ISSN: 0930-7516
    Electronic ISSN: 1521-4125
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 6
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    Moisture Distribution in Fluidized Beds with Liquid Injection (2011)
    Wiley
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    Publication Date: 2011-06-08
    Description: Coupled discrete element method-computational fluid dynamics (DEM-CFD) simulations have been performed to study the fluid and particle dynamics in a fluidized-bed granulator on the scale of individual particles. Simulation of the gas and particle dynamics is combined with heat and mass transfer mechanisms, as the moisture distribution is a key parameter for the functionality of a fluidized-bed spray granulator. The model allows monitoring the moisture content and temperature of each individual particle as well as the temperature and humidity of the surrounding gas phase. A novel modeling approach is presented to describe the process dynamics of a fluidized bed in full detail for a reference time interval using coupled DEM-CFD simulations. The motion profile of gas and particles is extrapolated to larger time scales and used for the calculation of heat and mass transfer. Through this multiscale approach, a step forward is taken towards a physically based description of the microprocesses in granulation. Coupled discrete element method-computational fluid dynamics (DEM-CFD) simulations of the fluid and particle dynamics in a fluidized-bed granulator have been performed and combined with a model of heat and mass transfer. According to a novel multiscale modeling approach the process dynamics of a fluidized bed can be described in full detail for a reference time interval using DEM-CFD.
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 7
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    Indirect Synthesis of Bis(2-PhInd)ZrCl2 Metallocene Catalyst, Kinetic Study and Modeling of Ethylene Polymerization (2011)
    Wiley
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    Publication Date: 2011-01-25
    Description: Bis(2-phenylindenyl)zirconium dichloride (bis(2-PhInd)ZrCl 2 ) catalyst was synthesized via the preparation of bis(2-phenylindenyl)zirconium dimethyl (bis(2-PhInd)ZrMe 2 ) followed by chlorination to obtain the catalyst. Performance of the catalyst for ethylene polymerization and its kinetic behavior were investigated. Activity of the catalyst increased as the [Al]:[Zr] molar ratio increased to 2333:1, followed by reduction at higher ratios. The maximum activity of the catalyst was obtained at a polymerization temperature of 60 °C. The rate-time profile of the reaction was of a decay type under all conditions. A general kinetic scheme was modified by considering a reversible reaction of latent site formation, and used to predict dynamic polymerization rate and viscosity average molecular weight of the resulting polymer. Kinetic constants were estimated by the Nelder-Mead numerical optimization algorithm. It was shown that any deviation from the general kinetic behavior can be captured by the addition of the reversible reaction of latent site formation. Simulation results were in satisfactory agreement with experimental data. Bis(2-PhInd)ZrCl2 catalyst was synthesized using an indirect method which has the advantage of preparing the catalyst at room temperature. For better identification of the catalyst behavior, the kinetic constants were estimated and evaluated by quantitative modeling of the polymerization mechanism.
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 8
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    Semianalytical solutions for cocurrent and countercurrent imbibition and dispersion of solutes in immiscible two-phase flow (2011)
    Wiley
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    Publication Date: 2011-02-26
    Description: We derive a set of semianalytical solutions for the movement of solutes in immiscible two-phase flow. Our solutions are new in two ways: First, we fully account for the effects of capillary and viscous forces on the transport for arbitrary capillary-hydraulic properties. Second, we fully take hydrodynamic dispersion for the variable two-phase flow field into account. The understanding of immiscible two-phase flow and the simultaneous miscible displacement and mixing of components within a phase is important for many applications, including the location of nonaqueous phase liquids in the subsurface, the design of contaminant cleanup procedures, the sequestration of carbon dioxide, and enhanced oil-recovery techniques. For purely advective transport we combine a known exact solution for the description of immiscible two-phase flow with the method of characteristics for the advective transport equations to obtain solutions that describe cocurrent flow and countercurrent spontaneous imbibition and advective transport in one dimension. We show that for both cases the solute front can be located graphically by a modified Welge tangent. For the advective-dispersive solute transport, we derive approximate analytical solutions by the method of singular perturbation expansion. On the basis of this, we obtain analytical expressions for the growth of the dispersive zone for the case with and without the influence of capillary pressure. We show that for the case of spontaneous countercurrent imbibition the order of magnitude of the growth rate is far smaller than that for the viscous limit. We give some illustrative examples and compare the analytical expressions with numerical reference solutions.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 9
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    Coupled modeling of hydrogeochemical and electrical resistivity data for exploring the impact of recharge on subsurface contamination (2011)
    Wiley
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    Publication Date: 2011-02-09
    Description: The application of geophysical methods, in particular, electrical resistivity measurements, may be useful for monitoring subsurface contamination. However, interpreting geophysical data without additional data and without considering the associated hydrogeochemical processes is challenging since the geophysical response is sensitive to not only heterogeneity in rock properties but also to the saturation and chemical composition of pore fluids. We present an inverse modeling framework that incorporates the simulation of hydrogeochemical processes and time-lapse electrical resistivity data and apply it to various borehole and cross-borehole data sets collected in 2008 near the S-3 Ponds at the U.S. Department of Energy's Oak Ridge Integrated Field Research Challenge site, where efforts are underway to better understand freshwater recharge and associated contaminant dilution. Our goal is to show that the coupled hydrogeochemical-geophysical modeling framework can be used to (1) develop a model that honors all the available data sets, (2) help understand the response of the geophysical data to subsurface properties and processes at the site, and (3) allow for the estimation of petrophysical parameters needed for interpreting the geophysical data. We present a series of cases involving different data sets and increasingly complex models and find that the approach provides useful information about soil properties, recharge-related transport processes, and the geophysical response. Spatial heterogeneity of the petrophysical model can be described sufficiently with two layers, and its parameters can be estimated concurrently with the hydrogeochemical parameters. For successful application of the approach, the parameters of interest must be sensitive to the available data, and the experimental conditions must be carefully modeled.
    Print ISSN: 0043-1397
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    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 10
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    Atrazine Removal in Municipal Secondary Effluents by Fenton and Photo-Fenton Treatments (2013)
    Wiley
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    Publication Date: 2013-10-16
    Description: Alternative water sources, including effluents from municipal wastewater treatment plants (MWTP) are necessary to meet increasing water demand. Advanced oxidation processes based on the Fenton reaction were applied to remove atrazine from the secondary effluents of a MWTP that uses activated sludge. Fenton, UV-A photo-Fenton, and UV-C photo-Fenton treatments were tested. Atrazine removal percentages were around 20 % for Fenton, 60 % for UV-A photo-Fenton and 70 % for UV-C photo-Fenton treatments, respectively. Organic matter mineralization by Fenton treatment was monitored and no significant reduction was observed. However, organic matter oxidation in terms of COD reduction of around 30 and 40 % were achieved by Fenton and photo-Fenton processes, respectively. The photo-Fenton process with UV-C is a useful technique for atrazine degradation, leading to higher degradation than with UV-A while also being more attractive in an economic point of view. Wastewater treatment plant effluents are increasingly used as non-potable water sources to meet increasing water demands, and therefore, efficient removal of pollutants is needed. Atrazine is used as a probe molecule for the comparison of Fenton, UV-A photo-Fenton, and UV-C photo-Fenton treatment. The study includes economical evaluations of all options.
    Print ISSN: 0930-7516
    Electronic ISSN: 1521-4125
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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