463 research outputs found

    Materials and Corrosion in Seawater Reverse Osmosis Plants: A Review

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    Desalination is emerging as one of the most promising solutions to extraction and increasing global demand for drinking water. A water purification process called reverse osmosis (RO), in which dissolved solids are separated from solutions by partially permeable membranes. Advances in membrane technology have resulted in the removal of up to 99% of salts in seawater. However, the process and system of seawater treatment RO are associated with many problems, such as scaling and fouling of the membranes, corrosion of the pumps, valves and piping system due to the highly concentrated salt solution and high chemical consumption. Nowadays, these problems have become very critical as they severely affect the desalination process and also massively deteriorate the performance and lifetime of the system components and materials. To ensure that the desalination process is always the best option for a low-maintenance, highly efficient and cost-effective system and process, a comprehensive study of these problems is essential. Therefore, this article addresses the characteristics of metallic materials and corrosion problems in the reverse osmosis process of seawater desalination, as well as the best solutions to focus on and evaluate for an optimal seawater desalination process, and the selection of the category of duplex stainless steels suitable for seawater desalination plants to reduce maintenance, avoid plant shutdown and ensure plant safety

    Essais de corrosion accélérée et évaluation de l’endommagement sur des conducteurs aluminium-acier de transport d’énergie électrique

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    La grande majorité des lignes électriques aériennes sont mises en service depuis plusieurs dizaines d’années et sont soumises à plusieurs phénomènes de dégradation. Les conducteurs de type ACSR (Aluminum Conductor Steel Reinforced) font partie des câbles les plus utilisés dans les lignes à haute tension, et sont soumis à plusieurs phénomènes climatiques impactant leurs propriétés électriques et mécaniques. L’un des phénomènes de dégradation très connu sur les structures métalliques est celui de dégradation par corrosion, dont les conséquences sont très peu étudiées sur les lignes électriques. L’objectif principal de ce manuscrit de thèse est de quantifier l’influence de la structure géométrique des fils et des câbles de type ACSR, ainsi que du graissage sur la corrosion de type NaCl. Le premier travail consistait à réaliser d’une part des essais en corrosion accélérée, dans lequel plusieurs échantillons de conducteurs électriques sont corrodés sui- vant des paramètres climatiques précis et contrôlés. Dans un second temps, une analyse microscopique et métallographique des échantillons corrodés est présentée dans ce ma- nuscrit de thèse, en étudiant l’impact de la corrosion subie par ces échantillons sur leurs paramètres mécaniques à l’aide de tests de traction, de torsion et de fatigue. Les résultats issus des tests mécaniques sont corrélés avec les observations métallographiques de façon à lier les mécanismes d’endommagement ayant lieu sur les fils avec les pertes des propriétés mécaniques relevées sur les fils. La corrosion des fils en acier (et de la couche de galvanisation) a un impact direct sur la tenue mécanique des conducteur ACSR de par la construction de ce type de câble. La corrosion se localise préférentiellement au niveau des contacts interfilaires avec les fils en aluminium pour les fils sans présence de graisse. La graisse présente dans les conducteurs graissés et les fils aluminium entourant le toron en acier permettent de réduire fortement la corrosion des fils en acier. Les essais de traction réalisés sur des fils corrodés confirment l’effet bénéfique de ces deux protections sur les propriétés mécaniques. En plus de la corrosion par piqûres, la couche interne de fils en aluminium est soumise à un mécanisme de corrosion galvanique des fils en aluminium au niveau des contacts interfilaires acier-aluminium. Pour ces fils en aluminium des conducteurs, la protection apportée par la graisse aux fils centraux d’acier est donc le facteur déterminant pour la durée de vie de ceux-ci. On retrouve pour la couche de fils interne en aluminium cette double dégradation par piqûres de corrosion et couplage galvanique avec des durées de vie en fatigue et torsion réduites. Cette diminution nette et importante uniquement observable sur les fils de couche interne non graissés confirme l’importance que prend le mécanisme de corrosion galvanique des fils aluminium lorsque la couche de galvanisation sur les fils acier est détruite ou proche de l’être.Abstract : The vast majority of overhead power lines have been inoperation for several decades and are subject to several degradation phenomena. The ACSR (Aluminum Conductor Steel Reinforced) type conductors are among the most used cables in high voltage lines, and are subjected to several climatic phenomena impacting their electrical and mechani- cal properties. One well-known degradation phenomena on metal structures is corrosion degradation, which the consequences have rarely been studied on powerlines. The main objective of this thesis manuscript is to quantify the influence of the geometric structure of ACSR wires and cables, as well as greasing on NaCl corrosion. The first task was to carry out tests in accelerated corrosion, in which several samples of electrical conductors are corroded according to precise and controlled climatic parameters. In a second step, a microscopic and metallographic analysis of the corroded samples is presented in this thesis manuscript, studying the impact of the corrosion suffered by these samples on their mechanical parameters using tensile, torsion and fatigue tests. The results of the mechanical tests are correlated with the metallographic observations in order to link the damage mechanisms occurring on the wires with the losses of the mechanical properties observed on the wires. Steel wires corrosion (and galvanized coating corrosion) has a direct impact on the ACSR conductors mechanical performance given by the construction of this type of cable. The corrosion is preferably localized at the interfilar contacts with aluminium wires without the presence of grease. Grease in the greased conductors and aluminum wires surrounding the steel strand greatly reduce the corrosion of steel wires. The tensile tests carried out on corroded wires confirm the beneficial effect of these two protections on the mechanical properties. In addition to pitting corrosion, the inner aluminum wires are subjected to galvanic corrosion in contact with steel-aluminium wires. For these inner aluminum wires, the grease protection provided to the central steel wires is therefore the determining factor for the lifetime of these wires. The double degradation by corrosion pitting and galvanic coupling is seen on the inner aluminum wires including reduced service lives in fatigue and torsion. This net and significant decrease, which can only be observed on the ungreased inner aluminum wires, confirms the galvanic corrosion mechanism importance on aluminium wires when the steel wires galvanized coating is destroyed or close to being destroyed

    Romantic Citation and the Receding Future

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    This dissertation reads citation in Romantic literature as an aporetic movement between present and past, whereby what is cited becomes the receding ground on which the present and future’s erosion is inscribed. Citation exceeds quotation in that it forwards a disastrous intertextuality that retroactively determines not only past texts but events, histories, objects, and genres as accelerants that overshadow and ghost the present with its own extinction. Against generative modes of intertextuality such as those of Kristeva and Bakhtin in which texts’ repetitions of other texts facilitates the open-ended overturning and transformation of prior writing, citation precipitates a no future. This no future of Romantic citation, inflected by the period’s geological insights into the earth’s history as layers of sedimented disasters and extinctions, registers anteriority as topographical depths whose pre-spent force attenuates futurity. Citation thus discloses the destructive feedback loop underlying the generation of “progress” or open-ended futures from the past. Chapter 1 examines how in Childe Harold’s Pilgrimage Byron’s re-collection of history’s ruins becomes a symptom of a post- and pre-post-Waterloo history entropically recycling itself and backdating its “end of history” further into the past and expansively across the globe. In chapter 2, Mary Shelley’s The Last Man cites literary texts as a form of déjà vu by which we discover ourselves as extinct proleptically in the literary past. Chapter 3 proposes that Percy Shelley’s re-cycled tropes and circular plots in the later poems encode the later poetry’s archaeological pull toward his corpus’s dark ground in the form of his early novel St. Irvyne and his other early Gothic texts that shadow his corpus with the specter of its exhaustion. And in chapter 4, Blake’s Jerusalem ends (Blake’s) history by re-citing his earlier works as if they were engines of apocalypse conspiratorially orientated toward Jerusalem’s abyssally predestined redemption, a volatile redemption that accelerates the burnout of Blake’s “System” rather than its survival into the future

    MECHANICAL PROPERTIES OF CLASS H CEMENT AT ROOM AND ELEVATED TEMPERATURES AND THE EFFECT OF GILSONITE AND MICROCELLULOSE ON ITS MECHANICAL PROPERTIES

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    With an increase in global energy demands, the importance of well integrity and the oilfield cements has become more important than ever as it guarantees the continuous supply of fossil fuel to fulfill the requirement of the world. Drilling operations in recent years have gone into much deeper depths to meet the global demands in hydrocarbons, geothermal, gas storage and carbon sequestration purposes. In well integrity, cement plays a crucial role as it seals/isolates the troublesome formation or thief zone meanwhile protect the casing from corrosion and giving structural support to it. Therefore, it is necessary that cement slurry characteristics should be designed according to the subsurface environment, thus a proper characterization of the mechanical properties of cement in the laboratory is mandatory get to know its behavior when exposed to downhole conditions, and cubes and cylinders are the most commonly used shapes to characterized the mechanical properties, nevertheless, American Petroleum Institute (API) does not have a recommendation for cylinders, moreover, a review of American Society for Testing and Materials (ASTM) and British standards (BS) for the UCS is given, hence a study to determine if a correlation between cubes and cylinders can be achieved is studied. Though there are many conventional additives in the market but unconventional additives like Gilsonite and Microcellulose is not extensively studied. Gilsonite is a naturally occurring additive that is derived from hydrocarbons classified as asphaltite. It has been used in water-based drilling fluid and sometimes with an oil base mud as a treatment for filtration and sloughing shale problems. Given the useful properties of Gilsonite such as impermeability, low specific gravity and its great corrosive and acidic resistance it has been used as a loss of circulation material in cement applications. Micro-cellulose (MC) has been reported as a great additive in geothermal well fluid loss curing solutions. Given the recent success of using Micro-Cellulose in curing loss circulation and providing Wellbore Strengthening, addition of some amount to the cement slurry could inevitably be an option for cement fluid loss cure. However, the Micro-Cellulose can change the hydration process on the cement due to its natural characteristics, decreasing the compressive strength of the cement at the early stages; this phenomenon will be further described in the paper This paper shows the results of more than 100 tests conducted on cement cubes and cylinders to determine if a correlation between cubes and cylinders can be obtained, cubes and cylinders samples of class H cement at room and elevated temperature were prepared, and an investigation of more than 500 test was performed to show the effect of age (up to 120 days) and temperature (23c and 75c) on class H neat, H + 4% Microcellulose and 4% Gilsonite to investigate the effect of those additives in the mechanical properties of the cement. It was observed that variation in the results existed in the UCS when cubes are compared with the cylinder, which raises the importance of the development of the new standard. The results showed the high compressive strength of the cube as much as 50% and 35% for the sample cured at high and room temperature respectively. Moreover, no correlation existed between the cylinder cured at high temperature and UCS or UPV. Whereas the cube sample was able to give a logarithmic or exponential correlation for all the testing scenarios. Hence a better understanding of the cylindrical sample is needed and the data from this research can help to compare the results from these two geometries. This research also focuses on the evaluation of mechanical properties of Gilsonite and Microcellulose (MC) cement composite and compared with neat Class H cement. The compressive strength of the cement is measured through a direct and indirect method. Samples were cured at high temperatures (75°C) and at ambient conditions for the period of 1, 3, 7, 14, 21, 28, 35, 60, 90 and 120 days. It was found that at high temperature (HT) the development of compressive strength in 4% Gilsonite cement composite was very rapid with the UCS going as high as 42MPa within three days of curing. Whereas 4% MC shows an identical behavior as Gilsonite at room temperature, but a decrease in strength at HT when compared to Gilsonite or neat class H cement

    Detection of benzotriazole and related analogues in surface samples collected near an Ohio airpark

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    Benzotriazoles are a class of contaminant of emerging concern which are commonly used as anticorrosive agents in aircraft deicer and anti-icing fluids (ADAFs). The analogues 1H-benzotriazole (BTZ), 4-methyl-1H-benzotrizole (4m-BTZ), and 5-methyl-1H-benzotriazole (5m-BTZ) are commonly found in environmental occurrence together. The two methylated isomers, collectively known as tolytriazole (TTZ), have different toxicity and stability. These contaminants are highly water soluble and resistant to biodegradation, making them persistent through water treatment. Benzotriazoles have been detected worldwide; this investigation focuses on monitoring three sites near a small airpark in Wilmington, Ohio. Two sites that receive runoff from the airpark, Lytle Creek and Indian Run, have been under investigation for decades due to documented poor water quality issues. This investigation adds to data from the two previous years documenting an increase in BTZ compounds that corresponds to an increase in activity at the airpark by an online retailer. Solid Phase Extraction (SPE) was used to isolate benzotriazoles from surface water samples. Liquid Chromatography/Mass Spectrometry (LC/MS) was used for separation and detection of analytes. Each consecutive monitoring season detected more BTZ and TTZ on average than previous seasons. The 2021 season detected TTZ from 0.346-1.785 µg/L at Indian Run. Lytle Creek yielded BTZ from 0.051-0.158 µg/L and TTZ from 1.700-51.87 µg/L. Other occurrences have detected BTZ compounds associated with airpark runoff ranging from ng/L to mg/L. Gas Chromatography/Mass Spectrometry (GC/MS) was employed to separate the two TTZ isomers that could not be separated by LC/MS. This method revealed a ratio of 41.29% 4m-BTZ and 58.71% 5m-BTZ in selected water samples, a ratio which is similar to findings in a Wisconsin study. Based on the ratios of each isomer, hazard quotients assessed most samples analyzed as low environmental risk with a few days presenting medium to high environmental risk. Sediment samples were also examined for presence of benzotriazoles, but the results were inconclusive

    Étude du vieillissement de pièces en matériaux composites à matrice organique de moteurs d’aéronefs et de ses conséquences sur leur réparation collée

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    Ce travail vise à étudier les conséquences du vieillissement hygrothermique sur la réparation collée de matériaux composites tissés 3D carbone/époxy, qui constituent les aubes fans du moteur CFM LEAP. Dans un contexte d’introduction massive de pièces en matériaux composites à matrice organique dans les moteurs d'avions, la maîtrise de leur réparation, notamment par collage, devient essentielle et prend de l'essor. L'optimisation de ces réparations collées est rendue possible par l'utilisation de traitements de surface, comme le traitement plasma atmosphérique dont l'intérêt a déjà été prouvé. Cependant, ces pièces en composite sont sensibles aux conditions climatiques dans lesquelles elles évoluent, notamment la chaleur et l'humidité, et subissent de ce fait des dégradations. La première étape de ce travail a permis de mettre en lumière les paramètres influençant la diffusion d'humidité via une étude statistique. Par la suite, l'analyse des effets vieillissement hygrothermique sur les matériaux composites tissés 3D a mis en évidence des altérations physico-chimiques, massiques et surfaciques, telles que la migration de particules, un lessivage de la matrice, ou l'apparition de fissures, ce qui va affecter l'efficacité des collages. L'utilisation du plasma atmosphérique sur le matériau vieilli a montré un effet désorbant sur les surfaces et des niveaux d'oxydation semblables à ceux des surfaces neuves traitées au plasma, ce qui pourrait permettre d'activer chimiquement la surface en vue d'un collage et de restaurer certaines de ses propriétés. La caractérisation mécanique via des tests d’adhérence des assemblages matériau composite vieilli/colle a montré une nette amélioration de la résistance mécanique suite à l’utilisation du traitement de surface par plasma

    Collage réversible au service de la démontabilité

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    L’objectif principal est de développer un système adhésif structural ou semi-structural interfacial stimulable thermiquement et permettant un démontage propre des films de peinture secs développés par Corso Magenta. La formulation proposée mettra en jeu deux systèmes thermosensibles pouvant conduire à la démontabilité de pièces collées. Ces systèmes associent des réactions thermoréversibles pour la réversibilité du collage, au moussage par voie chimique du matériau pour la séparabilité des pièces assemblées. Aujourd’hui la «démontabilité» des structures collées est recherchée pour diverses raisons tels la récupération des substrats pour faciliter la réutilisation et le recyclage de ces ressources. Les pratiques actuelles de démontage pour une structure collée font appel à des actions mécaniques de raclage souvent associées à la dégradation thermique de l’adhésif. Il en résulte une diminution des propriétés intrinsèques des substrats. De plus les méthodes de démontage recherchées doivent être faciles et peu coûteuses avec une séparation nette des substrats sans résidu adhésif laissant au moins une surface propre. Le collage structural implique une transmission quasi-totale de l’effort d’un substrat à l’autre sur la durée de service, effort très souvent élevé dans nombres d’application tels que les transports. Cette exigence impose d’emblée que le procédé de «démontabilité» n’altère pas les propriétés du système adhésif d’origine sur sa durée de fonctionnement
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