2,316 research outputs found
Health consultation, W.R. Grace exfoliation facility : Phoenix, Maricopa County, Arizona
No full textabstract: The W.R. Grace facility in Phoenix, Arizona, received vermiculite concentrate from the Libby, Montana, vermiculite mine. W.R. Grace Company has owned and operated the Arizona site since 1964. In 1964 W.R. Grace purchased the company that had previously occupied the site and, following the relocation of its vermiculite exfoliation furnace from Glendale, Arizona, began processing vermiculite concentrate and marketing it under the Zonolite® brand. The objective of this health consultation is to evaluate exposure pathways and potential health effects in those persons who, between 1964 and 2002, may have been exposed to Libby asbestos as a result of vermiculite concentrate processing activities and waste materials from the W.R. Grace exfoliation facility in Phoenix.Under cooperative agreement with the Agency for Toxic Substances and Disease Registry.Includes bibliographical references (p. 22-24)
Simulation models for the minimum velocity for foam generation and propagation
No full textFoam injection is a promising means of reducing the relative mobility of gas, and hence improving the sweep efficiency of gas, in CO2 and H2 storage, soil-contaminant removal in aquifer remediation, enhanced oil recovery, and matrix-acid well stimulation. Theory (Rossen and Gauglitz, 1990; Ashoori et al., 2012) and experiments (Gauglitz et al., 2002; Yu et al., 2019, 2020) indicate that both foam generation and propagation in steady flow in porous media require the attainment of a sufficiently large superficial velocity or pressure gradient ∇P. Here we examine several foam-simulation models for their ability to represent a minimum velocity, or trigger, for foam generation. We define criteria for representation of such a trigger. For simplicity, we assume a homogeneous porous medium and absence of an oleic phase. We examine the Population-Balance (PB) models of Kam and Rossen (2003) and one of its variants (Kam, 2008), and the PB model of Chen et al. (2010); and the implicit-texture (IT) models in CMG-STARS (Computer Modeling Group, 2017) and of Lotfollahi et al. (2017). Our result show that the PB models of Kam and Rossen and its variant, and the IT models of CMG-STARS and of Lotfollahi et al. do represent a minimum velocity for foam generation. They achieve this by modeling an abrupt decrease in gas mobility with increasing pressure gradient over some range of ∇P. The model of Chen et al. (2010) is based on the model of Kovscek and Radke (1996), which was not intended to represent a trigger for foam generation (Kovscek and Radke, 1993). We cannot say categorically whether it could predict a trigger for any set of model parameter values. Instead, we derive criteria that must be satisfied by the choice of parameters to represent a trigger for foam generation. In simulations of radial foam propagation the STARS foam model predicts that foam propagation fails at the radius at which local ∇P cannot maintain strong foam, not at a greater velocity and ∇P as seen in experiments (Yu et al., 2020). In addition, we identify a fundamental challenge in representing foam generation at the large ∇P at the wellbore in a numerical simulation: conventional simulators do not represent ∇P at the wellbore. Foam generation at the very high superficial velocity at the well radius is not represented in the absence of truly exceptional grid refinement.Reservoir Engineerin
Analytical and Simulation Study of Sweep Efficiency in Gas-Injection EOR
No full textWAG (Water-Alternating-Gas injection) is a non-thermal EOR process, which was proposed to improve the volumetric sweep efficiency and consequently the oil recovery during a gas injection project. Though miscible gas injection gives fantastic displacement efficiency due to its miscibility with oil, it usually shows very poor volumetric sweep efficiency due to the high mobility of gas phase. Alternate injection of gas and water significantly reduces the gas relative mobility, and therefore leads to less gas fingering and/ or tonguing of gas. Aside from fingering and channeling, gravity segregation is another major effect that leads to the deterioration of sweep efficiency in gas-injection EOR processes. After the injected gas and water travels a certain distance in the reservoir, they completely segregate from each other under gravitational forces. Gas goes to the top of reservoir forming an override zone, and water goes to the bottom forming an under-ride zone. In Chapter one, fractional-flow theory is applied to provide insight into the advantages of HWAG. The fractional-flow method describes the flooding process in 1-D homogeneous reservoirs, which can be applied to a wide range of EOR processes. The method is accurate, when its assumptions are satisfied, in reflecting the saturation, front position and relative mobility of the agents injected, from which an optimal injection strategies can be determined. The main focus of Chapter two is the simulation study of gravity segregation in non-horizontal reservoirs. First, extensive simulations are done to examine the accuracy of Namani’s model for the segregation distance in dipping reservoirs. Second, it is equally important to understand all the dynamic processes during the process of gravity segregation.Petroleum EngineeringGeoscience & EngineeringCivil Engineering and Geoscience
Foam Propagation at Low Superficial Velocity: Implications for Long-Distance Foam Propagation
No full textSince the 1980s experimental and field studies have found anomalously slow propagation of foam that cannot be explained by surfactant adsorption. Friedmann et al. (1994) conducted foam-propagation experiments in a coneshaped sandpack and concluded that foam, once formed in the narrow inlet, was unable to propagate at all at lower superficial velocities towards the wider outlet. They hence concluded that long-distance foam propagation in radial flow from an injection well is in doubt. Ashoori et al. (2012) provide a theoretical explanation for slower or non-propagation of foam at decreasing superficial velocity. Their explanation connects foam propagation to the minimum velocity or pressure gradient required for foam generation in homogeneous porous media (Gauglitz et al., 2002). The conditions for propagation of foam are less demanding than those for creation of new foam. However, there still can be a minimum superficial velocity necessary for propagation of foam, except that it could be significantly smaller than the minimum velocity for foam generation from an initial state of no-foam. At even lower superficial velocity, theory (Kam and Rossen, 2003) predicts a collapse of foam. In this study, we extend the experimental approach of Friedmann et al. in the context of the theory of Ashoori et al. We use a cylindrical core with stepwise increasing diameters such that the superficial velocity in the outlet section is 1/16 of that in the inlet. N2 foam is created and stabilized by an alpha olefin sulfonate surfactant. Previously (Yu et al., 2019), we mapped the conditions for foam generation in a Bentheimer sandstone core as a function of total superficial velocity, surfactant concentration and injected gas fraction (foam quality). In this study, we extend the map to include the conditions for propagation of foam, after its creation in the narrow inlet section at greater superficial velocity. Thereafter, by reducing superficial velocity, we map the conditions for foam collapse. Our results suggest that the minimum superficial velocities for foam generation, propagation and maintenance increase with increasing foam quality and decreasing surfactant concentration, in agreement with theory. The minimum velocity for propagation of foam is much less than that for foam generation, and that for foam maintenance is less than that for propagation. The implications of our lab results for field application of foam are discussed.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Reservoir Engineerin
Electrochemical Impedance Spectroscopy And Potentiodynamic Polarization Studies Affected By The Microstructure Array Of A Monotectic Al-pb Alloy In A Nacl Solution
No full textFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)In this study, electrochemical impedance spectroscopy (EIS) plots and potentiodynamic polarization curves of tests carried out with monotectic Al-Pb alloy samples in a 0.5 Molar sodium chloride (NaCl) solution at 25°C are evaluated. It is shown that for a microstructure characterized by immiscible Pb droplets disseminated into an Al matrix, the microstructural array and segregation pattern are the corrosion driving forces. Microstructures characterized by Pb droplets of higher diameter and more homogeneously distributed into the Al-matrix, typical of positions close to the casting surface, have lower corrosion resistance. This has been attributed to a higher anode/ cathode area that characterizes such microstructures and that, as a consequence, induces a higher number of galvanic couples that are formed between the Pb droplets and the Al matrix.7010103110422013/15478-3; FAPESP; São Paulo Research Foundation; 2013/23396-7; FAPESP; São Paulo Research FoundationFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Liu, X., Zeng, M.Q., Ma, Y., Zhu, M., (2008) Wear, 265, pp. 1857-1863Lepper, K., James, M., Chashechkina, J., Rignry, D.A., (1997) Wear, 46, pp. 203-204An, J., Shen, X.X., Lu, Y., Liu, Y.B., (2006) Wear, 261, pp. 208-215An, J., Liu, Y.B., Lu, Y., Wang, J., Ma, B., (2002) J. Mater. Eng. Perform., 11, pp. 433-443Kaban, I., Kohler, M., Ratke, L., Hoyer, W., Mattern, N., Eckert, J., Greer, A.L., (2011) Acta Mater., 59, pp. 6880-6889Ratke, L., Muller, A., (2006) Scr. Mater., 54, pp. 1217-1220Yasuda, H., Ohnaka, I., Fujimoto, S., Takezawa, N., Tsuchiyama, A., Nakano, T., (2006) Scr. 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Description of the KNMI Operational Wave Forecast Model GONO
No full textThe purpose of this report is to give a description of the GONO computercode, which is operational at KNMI for many years now. The program was developed by J.W. Sanders, and its deep water version is based on a Norwegian wave prediction model. built by C. Haug in the sixties. Shallow water effects are however important in the southern part of the North Sea. giving a limitation of the wave growth and causing important swell dissipation. A discussion of the shallow water effects. as present in GONO, is given by Sanders in Ref. 3. The computer code GONO is written in ALGOL60 and operational on the Burroughs 6700 of KNMI. The program GONO calculates wind speed. wind direction and sea energy at every grid point of the GONO grid (cf. Appendix A) and swell energy at a limited number of points only (we call these points swell points). GONO runs every six hours and it gives a 12 and 24 hours forecast as well as results based on analyzed weather maps. In the winter of '79-'80 the output of GONO was compared with measurements and the operational wave model of Bracknell (United Kingdom). (The latter GONO version differs a little bit from the version here described). The preliminary results of this comparison are given in Ref. 4. A reasonable agreement of significant wave height and low-frequency energy, as given by GONO, with the observations was found. The present version of GONO, with small modifications compared to the previous version, is operational since the end of February 1980. Essentially, the GONO model is based on two steps. First. the sea energy at every grid point is determined. To this end advection of energy is treated by means of a finite difference scheme whereas the growth of the wave energy is calculated by means of an empirical growth curve (assuming that the wave spectrum has a fixed form). The second step is the calculation of the swell. Of course, in principle swell can be treated likewise, but then one has to store swell energy (and its direction) at every time, at every grid point for every frequency band. Also. this finite difference scheme is rather crude for swell propagation. whereas. because of stability reasons. there is an upper bound for the propagation speed (in the present case the upper bound is given by 13.87 m/s). If one is only interested in swell information at particular points (swell points), it is tempting to use a ray technique. The advantage of this technique is that it is very accurate. Swell is determined in this fashion in GONO.GON
Tungsten biochemistry of Pyrococcus furiosus
No full textTungsten is the heaviest element that exhibits biological activity (atomic number 74), when it is present in an enzyme. It is taken up by cells in the form of tungstate, and it is subsequently processed into an organic cofactor referred to as tungstopterin, which is found as active center in several enzymes. Pyrococcus furiosus is a hyperthermophilic archaeon that grows anaerobically at an optimal temperature of 100 ËšC, strictly dependent on the presence of tungstate. Over the last years, P. furiosus has become a model organism for hyperthermophiles, as many of its proteins have been the subject of research and its genome has been sequenced. Also regarding tungsten metabolism P. furiosus can be considered as a model: four tungsten containing aldehyde oxidoreductases were already characterized in some detail before the initiation of this study. In this thesis several aspects of tungsten metabolism in P. furiosus have been further explored: its tungstate transport system has been identified and characterized (WtpABC), studies on aspects of tungsten cofactor biosynthesis have been carried out and a new tungsten-containing aldehyde oxidoreductase (AOR), WOR5, has been purified and characterized.Applied Science
Biochemistry of Tungstoenzymes from Pyrococcus furiosus
No full textThe cell uses a variety of transition metals to provide greater catalytic diversity than could be achieved using only the functional groups of amino acids. The biochemistry of molybdenum and tungsten is unusual: they are the only 4d and 5d metal ions with established biological role(s). This thesis reports studies on the identification of tungstoenzymes using functional proteomics and on the physiological substrate, function and catalytic mechanism of one of the abundantly present tungstoenzymes of Pyrococcus furiosus; formaldehyde ferredoxin oxidoreductase (FOR). A new method of native-native two dimensional gel electrophoresis (2DGE) was developed in which no denaturants such as urea or SDS were applied (Chapter 2). Radioactively labeled tungsten (187WO42-) was added to the growth medium of P. furiosus to detect tungsten proteins for subsequent identification with mass spectrometry. The radiograms of gels containing radioactively labeled tungsten revealed six spots with tungsten-associated proteins. These spots were excised and analyzed by mass spectrometry. Two tungstoenzymes were identified as aldehyde ferredoxin oxidoreductase and formaldehyde ferredoxin oxidoreductase. No tungsten containing proteins could be identified from the other spots. A new tungsten containing oxidoreductase (WOR5) was discovered. It is the fifth and last member of the family of tungsten containing oxidoreductases from the hyperthermophilic archaeon P. furiosus. WOR5 was purified and characterized with EPR spectroscopy and electrochemistry (Chapter 3). It was found to be a homo-dimeric protein (subunit: 65 kDa) that contains one [4Fe-4S] cluster and one tungstobispterin cofactor per subunit. The enzyme has a broad substrate specificity with a high affinity for several substituted and non-substituted aliphatic and aromatic aldehydes with variable chain lengths, and it can use ferredoxin as electron acceptor in catalysis. The redox chemistry of the tungsten and iron-sulfur prosthetic groups in P. furiosus formaldehyde ferredoxin oxidoreductase (Chapter 4) and steady and pre-steady state kinetics (Chapter 5) for this enzyme were studied using formaldehyde as substrate and ferredoxin as electron acceptor. The intermediate, paramagnetic W(V) state could be trapped only by reduction of FOR with substrate, with consecutive one-electron intraprotein electron transfer to the single [4Fe-4S](2+;1+) cluster and partial comproportionation of the tungsten over W(IV, V, VI); this is a stable state in the absence of an external electron acceptor. Due to the very unfavorable hydratation equilibrium of the formaldehyde/methylene glycol couple no W(V) was found in dye mediated equilibrium redox titrations. The development of this intermediate was slow even at elevated temperatures and with a excess of substrate. The free formaldehyde, and not the methylene glycol, is the enzyme's substrate, implying that the KM for formaldehyde is three orders-of-magnitude less than the value previously reported in literature. The steady state kinetics of FOR is consistent with a substrate substituted-enzyme mechanism for three substrates (formaldehyde plus two ferredoxin molecules). The determined KM of ferredoxin (14 μM) was an order of magnitude less than previously reported values, due to the fact that at high concentrations of substrate the enzyme is inhibited and denatured. Pre-steady state difference spectra revealed peak shifts and a lack of isosbestic points, an indication that several out-of-phase processes happen simultaneously in the first seconds of the reaction. The binding and the oxidation of the substrate are both fast processes. The release of the product and the electron shuffling over the tungsten and iron-sulfur center in the absence of an external electron acceptor are slower. Based on these results, in combination with results from previous EPR studies two alternatives for a catalytic redox cycle are proposed.Applied Science
Press forming the double-dome benchmark geometry using a 0/90 uniaxial cross-ply advanced thermoplastic composite
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