Letteratura scientifica selezionata sul tema "Silica fouling"
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Articoli di riviste sul tema "Silica fouling"
1
Koo, Chai Hoon, Abdul Wahab Mohammad, Fatihah Suja', and Meor Zainal Meor Talib. "Comparative Assessment of Membrane Fouling Propensity Using Colloidal Silica as Foulant." Applied Mechanics and Materials 209-211 (October 2012): 1995–98. http://dx.doi.org/10.4028/www.scientific.net/amm.209-211.1995.
Testo completoAbstract (sommario):
Other than silt density index (SDI), modified fouling index (MFI) is claimed as one of most useful fouling predictive tools in the practice of reverse osmosis. In this study, the effect of colloidal silica particles on the MFI value with the presence of crossflow sampler (CFS) cell at the upstream of MFI setup was systematically investigated. Colloidal silica with the particle size ranging from 70-100 nm was used as the model foulant in this experiment. The feed silica suspension was 0, 50, and 200 mg/L. The effect of membrane pore size as the test membrane in the dead-end cell on the fouling indices was also studied. Polyvinylidene fluoride (PVDF) membranes with molecular weight cut-offs of 150 and 100 kDa were employed. As predicted, the experiment results demonstrated that the fouling indices increased significantly as the feed silica concentration increased. The CFS-MFI values were always lower than the MFI in all the fouling index tests due to the shear force effect generated under the crossflow filtration mode. The fouling index generated from PVDF100 was higher than that of PVDF150 due to the retention of smaller particles. For this reason, PVDF100 membrane was preferred to be used as the test membrane for fouling index tests using colloidal silica over the PVDF150.
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Freeman, Scott D. N., and Randall J. Majerle. "Silica fouling revisited." Desalination 103, no. 1-2 (November 1995): 113–15. http://dx.doi.org/10.1016/0011-9164(95)00092-5.
Testo completo
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Chan, S. H., Z. J. Chen, and P. He. "Effect of Ferric Chloride on Silica Fouling." Journal of Heat Transfer 117, no. 2 (May 1, 1995): 323–28. http://dx.doi.org/10.1115/1.2822524.
Testo completoAbstract (sommario):
This study presents the results of an experimental investigation of the effects of Fe3+ ion in aqueous solution on silica fouling of heat exchanger and assesses the relative effect of Fe3+, Na+, and K+ ions on silica fouling. Experiments were conducted at 165–125°C, 1.58 MPa, and under turbulent flow conditions. It was shown that adding a few ppm of Fe3+ into silica solution was sufficient to formulate chemical coagulation and deposition of silica colloidal particles, which in turn caused a significant increase in the fouling rate. It was also observed that when Fe3+ was added to the silica solutions containing either Na+ or K+ ions, the fouling behaviors were found to be similar. Thus Fe3+ was found to be dominant over Na+ and K+ ions in its effects on silica fouling.
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Chan, S. H., Z. J. Chen, and P. He. "Effects of Sodium and Potassium Chlorides on Silica Fouling." Journal of Heat Transfer 115, no. 1 (February 1, 1993): 82–90. http://dx.doi.org/10.1115/1.2910674.
Testo completoAbstract (sommario):
The effects of NaCl and KCl salts in aqueous solutions on silica fouling of heat exchangers under turbulent flow conditions were examined experimentally over a range of pH, velocity, and salt concentration levels. The fundamental attachment process of silica fouling from those aqueous solutions was described. The silica fouling rate in NaCl solutions was found to be greater than that in KCl solutions. In all cases, the fouling rate increased with the salt concentration. When both salts were present simultaneously, the fouling rate found to be closer to that of the KCl system than that of the NaCl system. Effects of salinity on equilibrium solubility of silica at 165° C were also reported. Finally, the plausible theory of polymerization and the fundamental ion-cloud theory were used to describe the silica scale attachment process and the possible causes of salt effects on silica fouling of heat transfer surfaces.
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Nghiem, Long Duc, Christiane Espendiller, and Gerd Braun. "Influence of organic and colloidal fouling on the removal of sulphamethoxazole by nanofiltration membranes." Water Science and Technology 58, no. 1 (July 1, 2008): 163–69. http://dx.doi.org/10.2166/wst.2008.647.
Testo completoAbstract (sommario):
This study investigated the effects of organic and colloidal fouling on the removal of a representative micropollutant sulphamethoxazole by two commercially available NF membranes. Alginate, bovine serum albumin and colloidal silica were selected as model foulants to simulate hydrophilic and hydrophobic organic fractions, and colloidal matter that are often found in treated effluent and surface water. Membrane fouling was related to the membrane and foulant characteristics and subsequently the separation behaviour of the micropollutant sulphamethoxazole under different solution pH. On the basis of these results, it was confirmed that membrane fouling is strongly dependent on both the foulant and membrane characteristics. The complex relationship among retention mechanisms, fouling mechanisms and the effects of fouling on retention was systematically delineated. Of the three model foulants selected for this study, colloidal fouling resulted in the most significant reduction in retention of sulphamethoxazole as well as inorganic salts, while flux decline as a result of colloidal fouling was quite moderate. Reduction in retention caused by fouling was attributed to a phenomenon known as cake-enhance concentration polarisation, which was a predominant mechanism of colloidal fouling. In addition, the reported results suggested that the effect of fouling on retention is also membrane pore size dependent.
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Chan, S. H., H. Rau, C. DeBellis, and K. F. Neusen. "Silica Fouling of Heat Transfer Equipment—Experiments and Model." Journal of Heat Transfer 110, no. 4a (November 1, 1988): 841–49. http://dx.doi.org/10.1115/1.3250583.
Testo completoAbstract (sommario):
Silica fouling of heat transfer equipment in geothermal energy systems is studied. The effects of temperature, pH, and salinity on silica solubility and silica polymerization are reviewed. Experimental fouling data are presented for geothermal brines with different pH values, chemical compositions, and thermal-hydraulic conditions. The effects of supersaturation, pH, Reynolds number, and the concentration of ions in the brine solution on the formation of silica scale in the heat exchanger tube are discussed. A silica deposition model is proposed that accounts for supersaturation, pH factor, salinity, and thermal-hydraulic effects. Results based on the analytical model are compared with silica fouling data obtained in the laboratory as well as from two geothermal fields.
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Lunevich, L., P. Sanciolo, L. F. Dumée, and S. R. Gray. "Silica fouling in high salinity waters in reverse osmosis desalination (sodium–silica system)." Environmental Science: Water Research & Technology 2, no. 3 (2016): 539–48. http://dx.doi.org/10.1039/c6ew00065g.
Testo completo
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Park, Yong-Min, Kyung-Min Yeon, and Chul-hwi Park. "Silica treatment technologies in reverse osmosis for industrial desalination: A review." Environmental Engineering Research 25, no. 6 (January 3, 2020): 819–29. http://dx.doi.org/10.4491/eer.2019.353.
Testo completoAbstract (sommario):
Reverse osmosis (RO) is the main process of current industrial desalination, and its performance is affected by the quality of water source. Natural water contains a certain level of silica, which is originated from metal silicate in the earth crust. Due to its complexity, silica fouling is difficult to control, which often causes less efficient design of RO system for safe operation. In the present work, we review the current state of silica treatment technology in RO desalination. Silica chemistry is investigated in standpoint of the scale formation mechanism among multiple forms of silica species and its synergistic interaction with other foulants such as organic matter. Then, pretreatment methods to remove silica in the RO feed water are outlined. They include softening/coagulation, seed precipitation/aggregation, tight ultrafiltration, ion exchange, adsorbents media, and electro coagulation. We finally highlight the mitigation of RO fouling under silica rich conditions, whose concept can be implemented in different ways of antiscalant dosing, high/low pH operation, and intermediate softening of the RO concentrate, respectively. This review will provide comprehensive information and insight about the optimal operation of industrial RO susceptible to silica fouling.
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Gilron, Jack, Yitzhak Ladizansky, and Eli Korin. "Silica Fouling in Direct Contact Membrane Distillation." Industrial & Engineering Chemistry Research 52, no. 31 (June 21, 2013): 10521–29. http://dx.doi.org/10.1021/ie400265b.
Testo completo
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Sugama, Toshifumi, and Keith Gawlik. "Anti-silica fouling coatings in geothermal environments." Materials Letters 57, no. 3 (December 2002): 666–73. http://dx.doi.org/10.1016/s0167-577x(02)00851-0.
Testo completoTesi sul tema "Silica fouling"
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Chen, Dong. "Ultrasonic Control of Ceramic Membrane Fouling Caused by Silica Particles and Dissolved Organic Matter." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1109363214.
Testo completo
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Beltran, Osuna Angela Aurora. "Evaluation of Antifouling Materials Based on Silica Gels." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1323359814.
Testo completo
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Yu, Hong School of Chemical Engineering & Industrial Chemistry UNSW. "The mechanisms of composite fouling in Australian sugar mill evaporators by calcium oxalate and amorphous silica." Awarded by:University of New South Wales. School of Chemical Engineering and Industrial Chemistry, 2004. http://handle.unsw.edu.au/1959.4/20527.
Testo completoAbstract (sommario):
Deposition of amorphous silica (SiO2) and calcium oxalate (CaOx) on the calandria tubes of juice evaporators cause serious processing problems in Australian cane sugar mills. The removal of these deposits by mechanical and chemical means is a timeconsuming and costly experience. The cost of downtime and chemical cleaning can be several million dollars per year for the Australian sugar industry. The interactions between CaOx and SiO2 have not been investigated previously because conventional studies only address fouling by individual components. The present work evaluates their interactions using two experimental approaches: batch tests for assessing kinetic and thermodynamic behaviour, and fouling-loop experiments for examining composite fouling behaviour under different operating conditions. The above two approaches were employed both in the absence and in the presence of sugar to elucidate the effect of sugar on composite fouling mechanisms and to determine the controlling species responsible for composite fouling. The composite fouling experiments were performed in a novel closed-loop circulation system simulating the effect of feed composition of successive stages of evaporation cycle in a single run. In addition, the fouling-loop system was operated in a constant composition mode to study the effects of thermal hydraulic conditions on composite fouling. The combined information obtained from both the batch and fouling-loop tests in this study offer a unique insight into the mechanisms of composite fouling of CaOx and SiO2. Some of the highlights of the obtained results are as follows: ??? Identification of a complex interactive process in calcium oxalate monohydrate ??? silica (COM-SiO2) systems by investigation of the kinetics and thermodynamics of COM-SiO2 coprecipitation in water and sugar solutions, and an understanding of the mechanisms of these interactions; ??? Development of a novel fouling-loop system, which is simple, efficient and cost effective for the study of the effect of juice composition on scale formation in various stages of juice evaporation; ??? Elucidation of composite fouling mechanisms, e.g., a feed composition dependent fouling mechanism is proposed; ??? Isolation and verification of the existence of certain species in composite deposits, which is known to be thermodynamically unstable. In other words, it is established that calcium oxalate trihydrate is stable under certain conditions; ??? Evaluation of the role of thermal hydraulic operating parameters in determining the characteristics of subcooled flow boiling heat transfer and in determining the strength of the composite deposit; ??? Development and validation of an empirical model to predict the subcooled flow boiling heat transfer coefficients in water and sugar solutions; ??? Development of an analytical model incorporating the effects of operating parameters for COM and SiO2 composite fouling in sugar solutions. This model predicted the experimental data better than available models. Results of this work are significant, not only because they have made a valuable contribution to advance the fundamental understanding of heat exchanger fouling, but also because they may play a key role in the development of scale control and removal strategies to minimize the composite fouling in Australian sugar mill evaporators. For example it was found that, in order to effectively minimize the rate of composite fouling and reduce the scale tenacity, it would be necessary to control thermal hydraulic operating conditions, especially the fluid velocity, and to adjust the initial CaOx/SiO2 supersaturation ratio to the optimum value. To achieve the optimal CaOx/SiO2 ratio, certain device can be developed to sequentially measure oxalic acid and SiO2 concentrations in juice so that the correct proportions of chemicals can be added. Model simulations of the composite fouling rate may also effectively and economically provide comparative and relevant information essential for process optimisation and evaporator design
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El, Fouhaili Bandar. "Development of hydrophobic/superhydrophobic anti-fouling photopolymer coatings for PVC reactor." Thesis, Mulhouse, 2014. http://www.theses.fr/2014MULH6191.
Testo completoAbstract (sommario):
Lors de la polymérisation en suspension du chlorure de vinyle, il se forme sur les parois un dépôt de polychlorure de vinyle (PVC). Ce phénomène, nommé encroûtement, génère des problèmes car il limite la production de PVC et affecte la qualité du produit final. Dans ce contexte, un projet FUI (Fond Unique Interministériel) intitulé «Ecoating», a été financé dans le cadre d’une collaboration entre plusieurs partenaires industriels et universitaires (INEOS ChlorVinyls, Mäder Research, Avenir Group, LPIM, ESPCI-ParisTech). Deux thèses ont vu le jour au LPIM, avec pour but de développer un revêtement (photo)polymère aux propriétés anti-encroûtement durables qui permettrait d’améliorer la qualité du PVC produit, d’augmenter les quantités produites et ainsi d’améliorer la compétitivité des usines de PVC. Cette thèse s’inscrit dans le développement d’un vernis photopolymère répondant au cahier des charges. Pour éviter l’encroûtement des réacteurs, il est nécessaire de stopper une étape du mécanisme d’encroûtement comme l'adsorption sur les parois du réacteur d’un copolymère nommé Acvagen Graft Copolymer (AGC). Ce copolymère est très actif dans le phénomène d’encroûtement (site de nucléation) et se trouve principalement dans la phase aqueuse du milieu réactionnel. La stratégie de recherche élaborée dans ce projet a été basée sur le développement d'un revêtement photopolymère présentant une faible affinité pour l'eau et devant adhérer à la surface des réacteurs pour éviter la formation de croûte. Les polymères à base de fluoroacrylates ont été les premiers candidats choisis dans cette étude du fait que leurs propriétés exceptionnelles (faible énergie de surface, stabilité chimique et haute hydrophobicité...) pouvaient éviter l'adsorption de l'AGC sur les parois du réacteur, et par conséquent le développement de la croûte. Une recherche bibliographique a été réalisée pour comprendre le comportement particulier de ces molécules qui migrent vers la surface du film et s’organisent en surface pour donner des surfaces hydrophobes. Des mélanges de résines fluoroacryliques modèles ont été testés pour évaluer le caractère hydrophobe du revêtement, comprendre la migration des molécules de fluor vers l’interface en fonction de la nature de substrat et aussi déterminer l’influence de l’ajout d’additifs fluorés au mélange sur les propriétés globales du film. Cette étude nous a permis de comprendre l’influence de l’additif fluoré sur les propriétés chimiques et physiques du film. À l’échelle du laboratoire des tests d’immersion de ces revêtements déposés sur l’acier inoxydable ont étés réalisés dans l’eau chaude (80°C) afin de caractériser leur caractère hydrophobe en fonction du vieillissement dans l’eau chaude ainsi que l’adhésion du film au substrat. Nous avons observé une diminution de l'hydrophobicité de la surface du film au cours du temps lors d’une immersion. [...]<br>Our scientific approach has explored different strategies to develop a durable UV-cured coating with antifouling properties to prevent the crust formation. Firstly, the potential of fluoroacrylate photocurable coatings was exhaustively investigated. Indeed, their outstanding properties (low surface energy, chemical stability and high hydrophobicity...) could limit the adsorption of the AGC on the reactor walls and further encrusting. A bibliographic research highlighted the behavior of fluorinated monomers on film surface and the parameters affecting the hydrophobic properties. Different fluorinated monomers were selected. At low concentration, they provide hydrophobic surfaces on 316L stainless steel, the reference substrate. However, a decrease of the films surface hydrophobicity in hot water was observed with time, and was attributed to a disorganization of the fluorinated chains on the coating surface. An optimization of the amount of fluoroacrylate monomer was performed by confocal Raman microscopy (CRM) to promote the fluorinated chains stability on the surface before and after immersion in hot water at 80°C. The beneficial effect was found maximal at a concentration ranging from 1 to 1.8 wt%. However, even after this optimization, a decrease of the film surface hydrophobicity was observed for increased immersion time in hot water. Therefore, optimized fluoroacrylate monomer concentration was combined with alternated thermal/immersion post-treatment and has conducted to more stable photocured films. This result was attributed to a rigidification of the fluorinated chains on the film surface limiting thus, the extent of their disorganization. After this study realized at a laboratory scale, we tested the photocured coating in the VCM pilot reactor. A surface cleaning, an increase of the stainless steel roughness by shot blasting and the use of alkoxysilanes as coupling agents were implemented in order to enhance the adhesion properties of the photopolymer film on stainless steel. In addition, the use of a fluorinated monomer containing a heteroatom improved the rigidification when associated with the alternated thermal/immersion post-treatment. The crust formation was limited during four successive polymerizations in the VCM pilot reactor. A durable anti-fouling UV-coating could be not obtained due to some swelling phenomena resulting from the lack of coating adhesion or some abrasion occurring from small PVC pellets during the PVC polymerization.A second part of this project was dedicated to superhydrophobic coatings. Indeed, reducing interaction with water should lead to a better protection of the substrate. A literature review on the superhydrophobic surfaces has shown that the contact with hot water generally strongly affects their antiwetting properties and induces a large contact angle decrease. [...]
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Perry, Jeffrey L. "Fouling in silicon microchannel designs used for IC chip cooling and its mitigation /." Online version of thesis, 2008. http://hdl.handle.net/1850/6211.
Testo completo
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Boyd, Christopher. "Assessment, Optimization, and Enhancement of Ultrafiltration (UF) Membrane Processes in Potable Water Treatment." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5909.
Testo completoAbstract (sommario):
This dissertation reports on research related to ultrafiltration (UF) membranes in drinking water applications. A pilot-scale investigation identified seasonal surface water quality impacts on UF performance and resulted in the development of a dynamic chemically enhanced backwash protocol for fouling management. Subsequent analysis of UF process data revealed limitations with the use of specific flux, transmembrane pressure (TMP), and other normalization techniques for assessing UF process fouling. A new TMP balance approach is presented that identifies the pressure contribution of membrane fouling and structural changes, enables direct process performance comparisons at different operating fluxes, and distinguishes between physically and chemically unresolved fouling. In addition to the TMP balance, a five component optimization approach is presented for the systematic improvement of UF processes on the basis of TMP variations. Terms are defined for assessing process event performance, a new process utilization term is presented to benchmark UF productivity, and new measures for evaluating maintenance procedures are discussed. Using these tools, a correlation between process utilization and operating pressures was established and a sustainable process utilization of 93.5% was achieved.
UF process capabilities may be further enhanced by pre-coating media onto the membrane surface. Silicon dioxide (SiO2) and powdered activated carbon (PAC) are evaluated as pre-coating materials, and the applicability of the TMP balance for assessing pre-coated membrane performance is demonstrated. The first use of SiO2 as a support layer for PAC in a membrane pre-coating application is presented at the laboratory-scale. SiO2-PAC pre-coatings successfully reduced physically unresolved fouling and enhanced UF membrane organics removal capabilities.<br>Ph.D.<br>Doctorate<br>Civil, Environmental, and Construction Engineering<br>Engineering and Computer Science<br>Environmental Engineering
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Li, Cheng-Cho, and 李正周. "Cleaning strategies for the silica fouling on ultrafiltration membrane." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/98641110434628260222.
Testo completoAbstract (sommario):
碩士<br>國立交通大學<br>工學院碩士在職專班永續環境科技組<br>97<br>In recent years, the recycle of wastewater has increasing gained the traction in the industry of Semiconductor and Photonics. The value of wafer recycling is not only supported by government regulations but also the fashion of environmental friendly industry. The recycle techniques for the high turbidity and complex-compositon CMP wastewater continue to improve; however, the recycle efficiency is low due to the nature of sewage that easy to cause fouling and scaling during the recycling process. The dissolved silica will enhance fouling and scaling on the membrane unit due to it is not easy to be removed from the wastewater via the coagulation precipitation because of the small molecular weight and stable chemical property.
This study investigated the cleaning strategies for the Silica fouling on ultrafiltration membrane by taking into account variables of time, pH of chemical solutions and temperature for cleaning. The cleaning efficiency was evaluated by the recovery rate of the flux as well as the surface condition of the membrane under electron microscope. The experimental data showed that the best cleaning efficiency can be received under the condition of 60 minutes cleaning time and the temperature of 50℃ with pH11 alkali solution. Among the three variables in this experiment, the elevation of temperature resulted the most positive effect to the cleaning efficiency. The experiment was virtually designed to meet the condition in a real fab; with minor modifications, the data is applicable on-the-spot to the fab. The experiment also observed membrane pore enlargement that maybe incurred by fouling pile-up or over cleaning. Ways to avoid the degrading filter efficiency of the membrane include shortening clean cycle to eliminate fouling pile-up and adjusting cleaning conditions.
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Lee, Sooi Li. "Role of surfactants in filtration and fouling of colloidal silica." Master's thesis, 2014. http://hdl.handle.net/10362/13290.
Testo completoAbstract (sommario):
The EM3E Master is an Education Programme supported by the European Commission, the
European Membrane Society (EMS), the European Membrane House (EMH), and a large international network of industrial companies, research centres and universities<br>The objective of this study is to investigate the influence of three different types of surfactants (i) anionic sodium dodecyl sulphate (SDS), (ii) cationic (hexadecyltrimethylammonium bromide (CTAB), and (iii) non-ionic: Triton X-100 (Polyethylene glycol tert-octylphenyl ether)
and the effect of surfactant concentration on ultrafiltration of colloidal silica nanoparticles. Due to the high surface area to volume ratio of nanoparticles, the role of surface interactions on the stability of silica suspensions is enhanced. The effects of adsorption of surfactants are studied by means of static light scattering and zeta potential measurements. The strongest
particle-surfactant interaction is observed between oppositely charged CTAB with silica,
followed by TX-100 and SDS.
An ultrafiltration hollow-fibre membrane is used in a semi-dead end configuration to perform filtration of silica suspension with varying surfactant concentration to critical micelle concentration (CMC) ratio, csurfactant/ccmc in a flux-step mode. The effect of surfactants and process conditions (flux) on filtration process have been compared by evaluating the critical flux and total fouling rate. The occurrence of critical flux and evolution of fouling rates are also strongly affected by the surfactant concentration. This difference in filtration performance is attributed to various competing and complementary mechanisms: electrostatic and hydrophobic interactions between surfactant-membrane surface, electrostatic and hydrophobic interactions between particles as well as the hydrodynamic effect of fluid motion
towards the membrane. A comparison of the overall fouling potential for surfactant-silica systems showed that SDS-silica systems showed fouling rates of an order of magnitude higher than those of CTAB-silica and TX100-silica systems at the same csurf/cCMC ratio. This was an unexpected finding, as we would expect stable colloidal systems such as SDS-silica systems would exhibit lower fouling than unstable colloidal systems (e.g. CTAB-silica systems).<br>European Commission
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Yu, Hong. "The mechanisms of composite fouling in Australian sugar mill evaporators by calcium oxalate and amorphous silica." 2004. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20050324.110406/index.html.
Testo completo
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Mustafa, Ghulam Mohammad Chemical Sciences & Engineering Faculty of Engineering UNSW. "The study of pretreatment options for composite fouling of reverse osmosis membranes used in water treatment and production." 2007. http://handle.unsw.edu.au/1959.4/40882.
Testo completoAbstract (sommario):
Most common inorganic foulants in RO processes operating on brackish water are calcium carbonate, calcium sulphate and silica. However, silica fouling is the recovery limiting factor in RO system. Silica chemistry is complex and its degree of fouling strongly depends on the silica solubility and its polymerization under different operating conditions of RO process. In several studies carried out in batch and dynamic tests, the presence of polyvalent cations and supersaturation of silica in solutions were found to be the important factors (apart from pH and temperature) that affected the rate of silica polymerization and its induction period. Agitation did increased silica solubility; however, its effect was negligible in presence of polyvalent cations. Alkalization of water solution by coagulants particularly sodium hydroxide was found suitable for silica removal during pretreatment. The presence of magnesium in solution played a key role in silica removal mostly by the mechanism of adsorption to the metal hydroxide. The options of inline mixing (high agitation) for 5 to 10 minutes and microfiltration before RO were found suitable for silica pretreatment. During dynamic tests, the most dominant mechanism for salt deposition (mostly CaSO4) was particulate type in high concentration water solution; while crystallization fouling was the prevailing mechanism of deposition (mostly CaCO3 and silica) in low concentration solution. Silica showed significant effect on size and shape of inorganic salt crystals during coprecipitation. Moreover, the presence of common antiscalants promoted silica fouling. This important finding recommends an extra caution while using antiscalants in case feed water contains silica to a level that can attain saturation near membrane during RO process. A model was developed to predict the silica fouling index (SFI) based on the experimental data for induction period of silica polymerization. The model takes into account the effect of polyvalent cations and concentration polarization near membrane during RO process. It provides a conservative basis for predicting the maximum silica deposition in RO process at the normal operating conditions. A generalised correlation, which was developed for determination of the mass transfer coefficient in RO process, incorporated the effect of temperature change that is usually not considered in previous correlations. A correlation for reduction of silica content in feed water, down to a safe limit of 15 ppm for RO process, was also formulated and validated by the experimental results.
Capitoli di libri sul tema "Silica fouling"
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Kroupa, Martin, Michal Vonka, Miroslav Soos, and Juraj Kosek. "Probing Coagulation and Fouling in Colloidal Dispersions with Viscosity Measurements: In Silico Proof of Concept." In Polymer Reaction Engineering of Dispersed Systems, 161–82. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/12_2017_17.
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Mahmoud Waheeb, Omar. "Connect Two Crude Oil Distillation Units with One Crude Oil De-Salter in Dewania Refinery." In Crude Oil - New Technologies and Recent Approaches [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98182.
Testo completoAbstract (sommario):
Crude oil, which exported to refineries, already contains salt, water, and fouling crude oil received with salt content not less than 50 ppm. Dewania refinery with a capacity of 20,000 BPSD, which serves with two crude distillation units, each unit with a capacity of 10,000 BPSD, which operate without crude desalter. In an aim to reduce the effects of salts, water and, fouling associated with crude oil, two crude distillation units connected with one crude oil desalter with a capacity of 20,000 BPSD (one desalter). crude oil desalter transferred from (Daura Refinery) to Dewania refinery, in aim to reduce salt content from 50ppm to 5 ppm and mitigate water and other fouling. Crude oil desalter installed in the middle distance between two crude distillations units (90 m from each unit isometric piping). Crude oil, which is pumped by a charge pump to preheated in crude oil distillation unit with a train of heat exchangers. When the pipeline size increased from 4″ to 6″, which reduces the pressure dropped from 0.946 to 0.15 bar for each transfer pipeline and in consequence, the total pressure drop reduces from 11.011 to 10.215 bar for the whole unit. In an aim to reduce the heat dissipated from surface of transfer pipeline. Each transfer pipeline insulated with calcium silicate insulator, the thickness of insulator increased from 38mm to 50mm in an aim to reduce heat loss from −101.56 watts/m to −84.282 watts/m, which reduced temperature difference between the surface pipeline and environment from 13 to 10°C.
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Holberg, Stefan. "Non-Hydrolyzed Resins for Organic-Inorganic Hybrid Coatings." In Research Perspectives on Functional Micro- and Nanoscale Coatings, 105–35. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-5225-0066-7.ch005.
Testo completoAbstract (sommario):
This chapter focuses on resins based on non-hydrolyzed, monomeric and polymeric alkoxysilanes. As alternative to classical sol-gel processing, the resins are applied to a surface without a preceding hydrolysis step. Only after application, hydrolysis and condensation of the alkoxysilyl groups occur by means of atmospheric moisture to result cross-linked organic-inorganic hybrid coatings. While the use of non-hydrolyzed silanes is well established, for example by applying polyethyl silicate as binder for zinc-rich anti-corrosive primers, this chapter describes the chemical structures of various novel organic-inorganic hybrid precursors that have significantly extended the area of application to adhesives and scratch-resistant, repellent, or anti-fouling coatings. At present, individual resins are produced and applied at industrial scale in the fields of protective coatings and automotive topcoats.
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Holberg, Stefan. "Non-Hydrolyzed Resins for Organic-Inorganic Hybrid Coatings." In Materials Science and Engineering, 771–801. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-1798-6.ch030.
Testo completoAbstract (sommario):
This chapter focuses on resins based on non-hydrolyzed, monomeric and polymeric alkoxysilanes. As alternative to classical sol-gel processing, the resins are applied to a surface without a preceding hydrolysis step. Only after application, hydrolysis and condensation of the alkoxysilyl groups occur by means of atmospheric moisture to result cross-linked organic-inorganic hybrid coatings. While the use of non-hydrolyzed silanes is well established, for example by applying polyethyl silicate as binder for zinc-rich anti-corrosive primers, this chapter describes the chemical structures of various novel organic-inorganic hybrid precursors that have significantly extended the area of application to adhesives and scratch-resistant, repellent, or anti-fouling coatings. At present, individual resins are produced and applied at industrial scale in the fields of protective coatings and automotive topcoats.
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Brindha Devi, Parthiban, and Ridhanya Jeyaseelan. "Natural Medicinal Compounds from Marine Fungi towards Drug Discovery: A Review." In Drug Design - Novel Advances in the Omics Field and Applications [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94137.
Testo completoAbstract (sommario):
Marine fungi are species of fungi which live in estuaries environment and marine environment. These species are found in common habitat. Marine fungi are rich in antimicrobial compounds such as anthrones, cephalosporins, peptides, steroids. These compounds which are derived mainly focused in the area of anti-inflammatory, anti-oxidant, anti-fungal, anti-microbial, anti-fouling activity. Bioactive terpene compounds are produced by marine fungi and marine derived fungi can produce sclerotides, trichoderins. Marine fungi have become the richest sources of biologically active metabolites and structurally novel in the marine environment. In a recent study the marine derived fungi dichotomomyces cejpii exhibits activity towards cannabinoid which is used to treat alzheimer dementia. Aspergillus unguis showed significant acetyl cholinesterase besides its anti-oxidant activity. These acts as a promising intent for discovery of pharmaceutically important metabolites like alkaloids, peptides. Computational (in silico) strategies have been developed and broadly applied to pharmacology advancement and testing. This review summarizes the bioactive compounds derived from marine fungi in accordance with the sources and their biological activities.
Atti di convegni sul tema "Silica fouling"
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Perry, Jeffrey L., and Satish G. Kandlikar. "Investigation of Fouling in Microchannels." In ASME 4th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2006. http://dx.doi.org/10.1115/icnmm2006-96248.
Testo completoAbstract (sommario):
Particulate fouling in microchannels is a subject that is largely unexplored. It does, however, have significant implications for all microchannel flows since the hydraulic diameters are very small and consequently are susceptible to excessively large pressure drops. The significant forces for dilute solutions of silica particles ranging from 3 to 10 μm are studied in rectangular microchannels made in silicon with a hydraulic diameter of 106 μm. The effects of zeta potential which is pH driven, lift force on the particulates and their fouling characteristics are evaluated by measuring the pressure drop across the microchannel test section.
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Perry, Jeffrey L., and Satish G. Kandlikar. "Investigation of Fouling and Its Mitigation in Silicon Microchannels." In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62038.
Testo completoAbstract (sommario):
Particulate fouling studies with 4.0-μm silica and 1.25-μm alumina dispersions in water were performed in rectangular, silicon microchannels having a hydraulic diameter of 225 μm with a Reynolds number of 17. Data show the absence of particle deposition within the microchannels. The primary reason for this is the relatively high wall shear stress at the microchannel walls of 2.3 Pa compared to conventional size passageways. In contrast, the headers for the microchannels are quite susceptible to particulate fouling under the same conditions. This is because the shear stress in the header region is lower. Moreover, there is a secondary effect in particulate fouling when fibrous elements exist within the particle dispersion. The fouling behavior due to fibrous material is quite different. In fact, the presence of fibers is extremely detrimental to pressure drops within a microchannel device.
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Harun, Z., Muhamad Zaini Yunos, Mohd Riduan Jamalludin, Muhamad Fikri Shohur, Hatijah Basri, and Ahmad Fauzi Ismail. "Effect of operating condition on polysulfone/PEG/silica membrane fouling in wastewater separation." In 2013 International Conference on Advanced Materials and Information Technology Processing. Southampton, UK: WIT Press, 2014. http://dx.doi.org/10.2495/amitp130121.
Testo completo
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Degereji, Mohammed U. "Numerical Assessment of the Slagging Potential of Nigerian Coal for Possible Co-Firing." In ASME 2015 9th International Conference on Energy Sustainability collocated with the ASME 2015 Power Conference, the ASME 2015 13th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2015 Nuclear Forum. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/es2015-49781.
Testo completoAbstract (sommario):
Co-firing coal and biomass offers a sustainable renewable energy option. However, slagging and fouling have been identified as some of the major operational challenges associated with co-firing. The chemistry of individual fuels can be used to determine the slagging potential of the blend. Previously, we have developed a numerical slagging index (NSI) based on the ash content in coal and the chemical properties of the coal ash. The NSI has been tested on a wide range of coals, and very good prediction results were obtained. In this paper, the slagging potential of Nigerian coal and other coals from Australia, Colombia and South Africa have been numerically evaluated. The predicted results using the NSI indicate that the Nigerian coal has relatively low slagging propensity when compared with other coals tested in this paper. One of the Australian coals seems to have lower slagging potential, and this may be attributed to the extraordinary low ash content for the coal, as reported. It has been observed that the silica-rich coal ash composition can be used to select suitable coals that could be co-fired with the alkali-rich biomass, with low operational risk. However, detail information on the chemical properties of blend and the particle-particle interaction can improve the performance of the assessment tool.
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Guinn, John E., and Debjyoti Banerjee. "Experimental Study of Nanofluids for Droplet Cooling Applications Using Temperature Microsensors." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-14101.
Testo completoAbstract (sommario):
The use of nano-fluids in droplet cooling (boiling) was explored parametrically in this experimental study. The experimental parameters are: nanofluid composition, superheat, liquid subcooling, and spray parameters (nozzle diameter, injection distance, size of droplets, injection pressure, mass flow rate, etc.). Two test fluids were used in the experiments: de-ionized (DI) water and nanofluid. The nano-fluid consists of silica nano-particles with a nominal diameter of 10nm dissolved in water at 2% concentration by weight. An experimental apparatus was fabricated to measure the surface temperature fluctuations during spray cooling of a heated surface. An array of microthermocouples (Thin Film Thermocouples or "TFT") was micro-fabricated on a heated surface to measure the surface temperature fluctuations during spray cooling. The TFT are capable of measuring temperature fluctuations up to a speed of 100 MHz. In the experiments, the exit of the single droplet spray was set a distance of 10 mm away from the surface and was aligned with the location of the TFT array. The spray was produced by pumping test fluid using a syringe pump into a traversing spray head. Silicon wafers with surface micromachined TFT array were clamped on the top of the heater apparatus for measuring temperature changes on the surface of the heater. Wire bead K-Type thermocouples were embedded in the heater apparatus and were used to measure heat flux. The transient temperature data from the TFT were recorded by a data acquisition system connected to a computer. The nano-fluid spray was found to cause fouling of the heater surface due to precipitation of the constituent nano-particles during boiling. This caused the overall heat flux to decrease drastically when compared to spray cooling using water. The nano-fluid spray was found to enhance heat flux by 300% compared to the base heat flux without the spray.
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Smith, Karl J. P., Joshua Winans, and James McGrath. "Ultrathin Membrane Fouling Mechanism Transitions in Dead-End Filtration of Protein." In ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icnmm2016-7989.
Testo completoAbstract (sommario):
Ultrathin membranes will likely see great utility in future membrane-based separations, but key aspects of the performance of these membranes, especially when they are used to filter protein, remain poorly understood. In this work we perform protein filtrations using new nanoporous silicon nitride (NPN) membranes. Several concentrations of protein are filtered using dead end filtration in a benchtop centrifuge, and we track fouling based on the amount of filtrate passed over time. A modification of the classic fouling model that includes the effects of using a centrifuge and allow for the visualization of a transition between pore constriction and cake filtration demonstrate that for a range of protein concentrations, cake filtration supersedes pore constriction after ∼30 seconds at 690 g.
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May Estebaranz, Alan, Simon Hogg, Michael Hilfer, and Phil Dyer. "A Static Test Facility for the Study of Deposit Fouling on Steam Turbine Blades." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25517.
Testo completoAbstract (sommario):
For several decades it has been recognised that deposition on the surfaces of steam turbine blades during operation can result in significant loss in thermal performance and, in some cases, a large reduction in the steam swallowing capacity. One principal cause of deposit fouling on HP turbines is copper, although other elements, for example silicon, can also be problematic. Copper is initially corroded from condenser and feedheater tubes by the water which then contaminates the inner surfaces of the boiler as the water is evaporated. The steam from the boiler becomes contaminated with copper oxides as a result of the copper fouling inside the boiler. The solubility of copper compounds in steam is a strong function of pressure. As the steam expands through the turbine and pressure reduces, the copper oxides deposit out onto the blade surfaces, roughening them and resulting in loss of performance [1]. A test facility is being developed by Durham University to allow copper deposition under real steam conditions to be investigated in a laboratory environment. The facility consists of a non-flow ‘box test’ type arrangement. The initial experimental arrangement consisted of a single reactor vessel. Superheated steam at typical boiler conditions was created in the reactor vessel and held at these conditions for several 10’s of hours. The reactor vessel also contains a copper sample and a sample of target blade material. During this first stage of the test, copper dissolves into the steam, contaminating it with copper metal and its oxides. In the second stage of the test the steam conditions are quickly reduced to lower pressure values that are representative of the latter stages of a typical HP turbine cylinder from a large fossil-fired unit. The reduced solubility of copper in steam at the lower pressure results in copper depositing out onto the sample of blade material. Conditions are held constant again for 10’s of hours during this second stage of the test, to allow sufficient time for a reasonable amount of deposition to occur. The reactor vessel is then cooled and the sample of blade material removed for analysis. Results from some initial testing using the single reactor vessel arrangement are described in this paper. The results demonstrate that it is possible to create a copper transport and deposition process under representative steam conditions using a test facility of this type. It was found to be difficult to control, accurately, the single reactor vessel tests, particularly during the second phase when the steam conditions were reduced. A revised test set-up is proposed consisting of two reactor vessels, in order to improve the operability of the facility. The ultimate aim of the work is to use this facility to investigate, systematically, deposition under different steam conditions and to produce a physically based model of the process. The facility will be validated by comparing test results with deposit samples taken from real turbines that experience copper fouling during operation.
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Lukas, Malte. "Comparison of Spectrometric Techniques for the Analysis of Liquid Gas Turbine Fuels." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-202.
Testo completoAbstract (sommario):
High temperature corrosion and fuel system fouling are major concerns that confront gas turbine users. Fuel treatment is a critical requirement for gas turbine operators burning alternative fuels and even so called “clean fuels”. Spectrometric fuel analysis is used to determine the amount of treatment required as well as the efficiency of the treatment. In most cases, analytical techniques developed by chemists for use in laboratory environments have been adopted for field use. This paper describes the various spectrometric techniques available to the gas turbine user to analyze fuels for contaminants such as sodium, potassium, vanadium, lead, calcium, silicon etc. and additives such as magnesium compounds. Atomic absorption spectroscopy (AAS) and various atomic emission spectroscopy (AES) techniques will be discussed and compared.
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Stalder, Jean-Pierre, and Peter A. Huber. "Use of Chromium Containing Fuel Additive to Reduce High Temperature Corrosion of Hot Section Parts." In ASME Turbo Expo 2000: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/2000-gt-0138.
Testo completoAbstract (sommario):
The use of “clean” fuel is a prerequisite at today’s elevated gas turbine firing temperature, modern engines are more sensitive to high temperature corrosion if there are impurities present in the fuel and/or in the combustion air. It is a common belief that distillate grade fuels are contaminant-free, which is often not true. Frequently operators burning distillates ignore the fuel quality as a possible source of difficulties. This matter being also of concern in plants mainly operated on natural gas and where distillate fuel oil is the back-up fuel. Distillates may contain water, dirt and often trace metals such as sodium, vanadium and lead which can cause severe damages to the gas turbines. Sodium being very often introduced through contamination with seawater during the fuel storage and delivery chain to the plant, and in combination, or with air borne salt ingested by the combustion air. Excursions of sodium in treated crude or heavy fuel oil can occur during unnoticed malfunctions of the fuel treatment plant, when changing the heavy fuel provenience without centrifuge adjustment, or by inadequate fuel handling. For burning heavy fuel, treatment with oil-soluble magnesium fuel additive is state of the art to inhibit hot corrosion caused by vanadium. Air borne salts, sodium, potassium and lead contaminated distillates, gaseous fuels, washed and unwashed crude and residual oil can not be handled by simple magnesium based additives. The addition of elements like silicon and/or chromium is highly effective in reducing turbine blade hot corrosion and hot section fouling. This paper describes field experience with the use of chromium containing fuel additive to reduce high temperature corrosion of hot section parts, as well as the interaction of oil-soluble chromium and magnesium-chromium additives on material behaviour of blades and vanes, and their economical and environmental aspects.
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Tuckerman, David B., R. Fabian W. Pease, Zihong Guo, Jenny E. Hu, Ozgur Yildirim, Geoff Deane, and Lowell Wood. "Microchannel Heat Transfer: Early History, Commercial Applications, and Emerging Opportunities." In ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2011. http://dx.doi.org/10.1115/icnmm2011-58308.
Testo completoAbstract (sommario):
In 1980, high-performance computing was becoming limited by the heat dissipated in semiconductor chips. IBM was introducing a new chip packaging technology that featured a specific thermal conductance of about 5000 W/m2·°C and occupied approximately 1 liter of space in order to cool 300 W. IBM was also developing a superconducting computer technology to circumvent the thermal problem posed by continued scaling of semiconductor chips. The following year, two of us (DBT and RFWP) showed theoretically and experimentally that by scaling down the dimensions of a conventional plate-fin liquid-cooled heat sink to a channel width of ∼50 μm, operating in the laminar flow regime, and integrated within the silicon chip, we could achieve in a laboratory demonstration at least a 20-fold improvement in specific thermal conductance, and more than 1000-fold greater volumetric heat removal. The reception of this advance was mixed, but what really stalled its adoption was the emergence of high-speed low-power CMOS semiconductor circuitry. Two decades later even scaled CMOS circuitry was getting too hot, and various commercialization attempts were then undertaken; some were successful, others not. New commercialization opportunities are now appearing including ones that enable society’s more efficient use of energy. A specific example of one such opportunity will be described, i.e., the use of microchannels in a novel, highly efficient regenerative heat-exchanger configuration, intended for heat-treating low-viscosity liquids for purposes such as pasteurization. Water was successfully heat-treated in continuous-flow tests of an experimental scaled-down prototype ultrahigh-temperature (UHT) pasteurizer incorporating a linear counterflow microchannel (50 μm parallel-plate channel separation) heat exchanger having an integrated electric heater at the hot end. The use of an integral electric heater permitted a unique manifold-less arrangement for reversing the flow directions at the hot end, wherein perfect local mass balance was enforced locally (i.e., between every pair of adjacent counter-flowing microchannels), eliminating a major potential source of flow maldistribution that would have otherwise reduced heat-exchanger effectiveness. Water entered the device at room temperature, steadily heated to 135°C in about 2.5 s, was maintained at 135°C for ∼2.5 s, and then cooled in ∼2.5 s, exiting at no more than 2°C above its original temperature, indicative of high heat-exchanger effectiveness. Heat leaks to ambient air required an excess of heater power, but those could be mostly eliminated in a scaled-up design and with proper attention to exterior insulation. Subsequent tests with milk flowing in heated microchannels revealed that fouling can be a severe problem (perhaps exacerbated by the long-tailed residence-time distribution characteristic of laminar flow), limiting continuous use to less than 2 hours for UHT pasteurization conditions. Conventional high-temperature short-time (HTST) milk pasteurization employs much lower peak temperatures and it is more likely that a practical microchannel system could be constructed for that application.