Dissertations / Theses on the topic 'Filter clogging'

Since the introduction of the Ballast Water Management Convention, ballast water treatment systems are required to be used on ships for processing the ballast water to avoid spreading bacteria or other microbes which can destroy foreign ecosystems. One way of pre-processing the water for treatment is by straining the water through a filtration unit. When the filter mesh retains particles, it begins to clog and could potentially clog rapidly if the concentration of particles in the water is high. The clog jeopardises the system. The thesis aims at investigating if machine learning through neural networks can be implemented with the system to predictively determine filter clogging by investigating two popular network structures for time series analysis. The problem came down to initially determine different grades of clogging for the filter element based on sampled sensor data from the ballast water treatment system. The data were then put through regression analysis through two neural networks for parameter prediction, one LSTM and one CNN. The LSTM predicted values of variable and clogging labels for the next 5 seconds and the CNN predicted values of variable and clogging labels for the next 30 seconds. The predicted data were then verified through classification analysis by an LSTM network and a CNN. The LSTM regression network achieved an r 2 -score of 0.981 and the LSTM classification network achieved a classification accuracy of 99.5%. The CNN regression network achieved an r 2 -score of 0.876 and the CNN classification network achieved a classification accuracy of 93.3%. The results conclude that ML can be used for identifying different grades of clogging but that further research is required to determine if all clogging states can be classified.
Sedan Ballast Water Management-konventionen introducerades har fartyg behövt använda barlastvattensystem för att behandla barlastvattnet i ett försök att hämma spridningen av bakterier och andra mikrober som kan vara farliga för främmande ecosystem. Ett sätt att förbehandla vattnet innan behandling är genom att låta det passera genom ett filter. När filtret samlar på sig partiklar börjar det att klogga och kan potentiellt klogga igen snabbt när koncentrationen av partiklar i vattnet är hög. Kloggning kan äventyra systemets säkerhet. Det här examensarbetet ämnar att undersöka om maskininlärning genom neurala nätvärk kan implementeras i systemet för att prediktivt bestämma filtrets kloggningsgrad genom att undersöka lämpligheten hos två populära nätverksstrukturer för tidsserieanalys. Problemet handlade initialt om att bedömma olika kloggningsgrader för filterelementet baserat på samplade sensordata från barlastvattensystemet. Datan kördes sedan för regressionsanalys genom två neurala nätverk, ett av typen LSTM och ett av typen CNN för att prediktivt bestämma paramterarna. LSTM-nätvärket uppskattade variabelvärden och kloggningsgrad för de kommande 5 sekundrarna medan CNN:et uppskattade variabelvärden och kloggningsgrad för de kommande 30 sekunderna. Den uppskattade datan verifierades sedan genom klassificering av ett LSTM nätverk och två CNN. LSTM nätverket för regression uppnådde ett r 2 -resultat på 0.981 och LSTM nätverket för klassificering uppnådde en klassificeringsgrad på 99.5%. CNN:et för regression uppn˚adde ett r 2 -resultat på 0.876 och CNN:et för klassificering uppnådde en klassificeringsgrad på 93.3%. Resultatet visar att ML kan användas för att identifiera olika kloggningsgrad men ytterligare forskning krävs för att bestämma om alla kloggningsstadier kan klassificeras.

Östby waterworks in the community of Kramfors has since 2003 had problems of fast clogging of the slow sand filters. As the clogging appears more often, they must be cleaned more frequently which has made the drinking water preparation difficult. Wintertime it has sometimes been impossible to clean the filters which has led to their closing and this has influenced the water quality negatively.

The waterworks is a surface waterworks which takes its raw water from the lake Sjöbysjön. The water is flocculated and filtered in a contact filter with the flocculent EKOFLOCK 91. Thereafter it is alkalinized before it reaches the outdoors placed slow sand filters. After the filters the water is alkalinized and disinfected before it reaches the customers.

This thesis work has looked into which factors influence the clogging and trials have been made in order to optimize the waterworks and thereby reduce the clogging. The raw water has been studied with aspect to biology and chemistry, the filtered water has been studied with aspect to chemistry and also the pressures in the slow sand filters have been studied.

The colour of the raw water from Sjöbysjön and its catchment area has increased since the beginning of the 90-ies and also the bio volume has increased in the lake.

The contents of aluminium before the slow sand filters are far higher than the contents after, which leads to the conclusion that aluminium is accumulated in the filters. The differential pressure over the sand bed increases with time after a cleaning. This indicates an accumulation of particles which increases with the load. Observations of the filter surface before cleaning showed that it was covered by a brown, jelly-like film. The internal resistance in the filter beds increases successively after a cleaning and one month after cleaning it is highest in the upper part of the sand bed. All this points to that flocculated aluminium is gathered in the slow sand filters, on the surface, causing clogging.

While the thesis work has been going on a process of alkalinizing before the contact filters has been reengaged and this has influenced the flocking of organic materials. When raising the pH the dose of flocculent was increased and this combined increased the amount of flocculated material. The contact filters could not bear this increased amount of flock load but showed instead a breakthrough.

In a few lab scale trials the flocking pH was varied as well as the dose flocculent to the raw water and after this the water was filtrated. A tendency was seen that the separation of aluminium, colour and turbidity increased with increasing pH and dose flocculent. At the pH 6.2 and the chemical dose of 60 g/m3 the content of aluminium, the colour and the turbidity showed the lowest values in the filtrate.

Vattenverket i Östby, Kramfors kommun, har sedan 2003 haft problem med för snabba igensättningar i långsamfiltren. Ju oftare de sätter igen desto mer frekvent måste de rensas vilket har försvårat dricksvattenberedningen. Vintertid har rensningar ibland inte kunnat utföras och långsamfiltren har därför stängts av vilket har påverkat vattenkvaliteten negativt.

Verket är ett ytvattenverk som tar sitt råvatten från Sjöbysjön. Vattnet flockas och filtreras i kontaktfilter med fällningskemikalien EKOFLOCK 91. Därefter mellanalkaliniseras det innan det går till de utomhus placerade långsamfiltren. Efter långsamfiltren efteralkaliniseras och desinficeras det innan det når konsumenterna.

I detta examensarbete har faktorer som påverkar igensättningarna undersökts och försök har också gjorts för att optimera driften och därmed minska igensättningarna. Råvattnet har undersökts avseende dess biologi och kemi, filtraten i verken har undersökts med avseende på deras kemi och tryckbildningar i långsamfiltren har studerats.

Färgtalet i råvattentäkten Sjöbysjön och dess tillrinningsområde har ökat sedan början av 90- talet och dessutom har biovolymen i sjön ökat.

Halterna aluminium före långsamfiltren är mycket högre än halterna efter, vilket antyder att aluminium ansamlas i filtren. Differentialtrycket över sandbädden ökar med tiden efter en rensning. Detta tyder på en ansamling av partiklar som ökar med belastningen. Observationer av filterytan innan rensning visade att den täcktes av en brun geléaktig hinna. Motståndet i filtren ökar successivt efter en rensning och är en månad efter rensning störst i den övre delen av sandbädden. Allt detta pekar på att aluminiumflock ansamlas i långsamfiltren, på ytan, och orsakar igensättningarna.

Under examensarbetets gång har en föralkalinisering återinförts i vattenverkets process och den har påverkat fällningen av det organiska materialet. Då pH höjts har också dosen fällningskemikalie ökats vilket har ökat mängden flock. Denna ökade flockmängd har kontaktfiltren inte kunnat bära utan istället släppt igenom.

I några försök i labbskala varierades fällnings-pH och dos fällningskemikalie till råvatten med en efterföljande filtrering. Tendenser som kunde ses var att avskiljningen av aluminium, färg och turbiditet ökade med ökat pH och ökad dos fällningskemikalie. Vid pH 6,2 och kemikaliedos på 60 g/m3 var aluminiumhalterna, färgen och turbiditeten som minst i filtratet.

Approximately 1500 km (43%) of the strategic Scottish trunk road network drainage asset takes the form of Highway Filter Drains (HFDs). However, despite their popularity, they are prone to clogging, therefore they have an estimated operational life-cycle of ten-years. This research was undertaken to investigate the complex inter-relationship between catchment characteristics, road dynamics and the physical characteristics of the road to establish the key factors that govern the generation and spatial variability of Road-Deposited-Sediment (RDS). The aim being to establish the impact RDS Particle Size Distribution (PSD) has on clogging and the operational life-cycle of HFDs. The research adopted an integrated approach, incorporating: (i) a Field Study to investigate RDS PSD grading envelopes across the Scottish trunk road network, (ii) a HFD Field Survey (HFD-FS) to investigate the current condition of HFDs across a range of catchments, (iii) a HFD Field Study to establish whether, or not, graded stone PSD envelopes comply with specification requirements when first placed in the trench, (iv) 3 HFD Field Studies to assess the level of risk of system failure through evaluating the causes and quantifying the individual, cumulative and influencing factors which contribute to the evolution of clogging in HFDs, and (v) a Field Study utilising Ground Penetrating Radar data to explore why stratified (clogged) layers evolve within some HFDs. Based on the results of this research, design and maintenance procedures were then identified to improve the performance of HFDs. Results established that Scottish trunk roads operate under variable catchment characteristics and road dynamics, with the condition and specification of the road surface, volume of traffic, road geometry, number of running lanes and adjacent land use governing the generation and spatial variability of RDS. Five of the nine trunk road RDS PSD profiles shared a peak particle diameter of 425 μm, two had a peak of 600 μm, one had a peak of 1180 μm and one resulted in a peak of 2120 μm. Particles >1000 μm were mostly mineral or asphalt and it was shown that there is a direct link between the factors that govern the generation and spatial variability of RDS and those that govern the evolution of clogging and actual operational life-cycle of HFDs. The HFD-FS revealed that 69% were assigned Filter Drain Condition Index ratings of 3 or below, which identifies these as having exceeded the ten-year estimated operational life-cycle. 94% of those deemed to have reached the end of their operational life-cycle were over-the-edge (OTE) HFDs, which supports the assertion that pre-treatment would increase their operational life-cycle. Results also established that introducing a kerb-line and gully-pots or grass-strip between the road and the HFD significantly reduced the indices of particle size composition d50 and d90 and percentage of RDS retained at depths spanning 0 - 400 mm, compared to OTE HFDs with comparable catchment characteristics and road dynamics. Based on these results, the operational life-cycle of HFDs with a kerb-line and gully-pots and OTE HFDs with a grass-strip can be expected to exceed twenty-years, if catchment characteristics and road dynamics are representative of those in this study. This research also identified that compacting Type B graded stone with ‘heavy vibrating machinery’ during construction could potentially contribute to clogging. It was also established that HFD harrowing may exacerbate clogging because the process of disintegrating the cake-layer mobilises an otherwise rigid and compacted RDS mass and this is more likely to penetrate deeper into the HFD and inundate the HFD during a storm event. These findings indicate that current HFD construction and maintenance practice could have a detrimental impact on the effective operational life-cycle of HFDs. Overall, this research study has demonstrated that there are considerable uncertainties related to PSD grading envelopes and percentage of RDS migrating from roads to HFDs. It is clear therefore that one of the most notable findings of this research is that given the scale of strategic trunk road networks, assuming a single HFD operational life-cycle profile, for a trunk road or trunk road network, is highly unlikely to be representative of a HFD at the local level. It follows then that the widely accepted estimated ten-year operational life-cycle for HFDs, does not reflect the actual operational life-cycle of HFDs.

A obstrução de emissores tem sido um entrave para a microirrigação. Porém, tem-se notado poucos estudos relativos ao desenvolvimento de equipamentos que auxiliam na prevenção da obstrução de emissores nos últimos anos. Os estudos realizados nesta linha estão geralmente ligados à caracterização dos sistemas em uso. O objetivo deste trabalho foi desenvolver um sistema de filtragem com reversão automática de fluxo, de alta frequência. O sistema foi concebido para operar com água de baixa qualidade, com inversão de fluxo e limpezas automáticas e com volume mínimo de água para realização das limpezas. As decisões do controlador do sistema de filtragem têm como base a perda de carga, obtida por meio de transdutores de pressão instalados na entrada e na saída do sistema. O protótipo final é composto, basicamente, por três filtros de tela e onze válvulas solenoides controladas eletronicamente. Determinou-se a curva de perda de carga em função da vazão, a eficiência de retenção e o volume mínimo de água para limpeza dos filtros. A eficiência de retenção de partículas foi determinada em delineamento experimental inteiramente aleatorizado em esquema fatorial, sendo testados três fatores: tempo de reversão (15 e 30 s); incremento da perda de carga (25 e 50%) e concentração de sólidos (500 e 1000 mg L-1). A eficiência de retenção de sólidos totais foi de 71,7 e 78,3% para as concentrações de 500 e 1000 mg L-1, respectivamente, tendo apresentado diferença significativa a 1% de probabilidade. Entretanto, a eficiência retenção de sólidos maiores que 50 ?m (Ed > 50) foi de 98,6 ± 0,7%, não sendo significante para nenhum dos tratamentos ao nível de significância de 1%. O volume médio de água despendido durante as limpezas foi de 5,39 L por limpeza, que representou um volume de água de limpeza por volume de água filtrada de 8,0 e 12,6 L m-3, para as concentrações de 500 e 1000 mg L-1, respectivamente. Os valores de eficiência energética do sistema de filtragem variaram de 80 a 90% para a vazão de 2 m3 h-1 com pressão de entrada entre 15 a 40 mca. As limpezas do sistema de filtragem não foram totalmente eficazes na retomada da perda de carga, com tendência de aumento com o tempo. A inversão de fluxo com frequências de 11,11 e 22,22 mHz influenciou na evolução da perda de carga do sistema de filtragem, tornando-a mais lenta que a evolução para o sistema funcionando sem inversão de fluxo. Considerou-se que o sistema de filtragem desenvolvido apresentou potencial para filtragem da água de irrigação com baixa qualidade, porém necessita de manutenções periódicas para limpeza do elemento filtrante. A perda de carga admissível do sistema de filtragem deve ser o valor mais restritivo entre o critério de desempenho de retenção de partículas e o de variação de vazão do sistema de irrigação.
Emitters clogging have been a barrier to trickle irrigation. Just a few studies have been performed concerning equipments which assist in preventing emitters clogging in recent years, especially regarding to development equipment. Studies carried out on this issue are usually linked to the characterization of systems in use. The aim of this study was to develop a filtering system with automatic flow reversal of high frequency. The system is designed to operate with low quality water, with reverse flow and automatic cleanings and with minimum volume of water to perform the cleaning. Decisions by the controller of the filtration system are based on head loss, obtained by pressure transducers installed at the upstream and downstream of the system. The final prototype consists of three screen filters and eleven electronically controlled solenoid valves. The curve of head loss was determined as a function of water flow, retention efficiency and minimum volume of water required for cleaning the filters. The efficiency in particle retention was determined following a completely randomized experimental design in a factorial scheme in which three factors were tested: reversal time (15 and 30 s) increase in head loss (25 and 50%) and solids concentration (500 and 1000 mg L-1). The total solids retention efficiency was 71.7 and 78.3% for concentrations of 500 and 1000 mg L-1, respectively, presenting a significant difference at 1%. However, when analyzing the retention efficiency of solids larger than 50 ?m (Ed> 50), none of the treatments was significant at 1%, whose efficiency was 98.6 ± 0.7%. The mean volume of water expended during the cleaning was 5.39 L. It represented a volume of water for cleaning per volume of filtered water from 8.0 and 12.6 L m-3, to concentrations of 500 and 1000 mg L-1, respectively. The energy efficiency values of filtering system ranged from 80 to 90% considering flow rate of 2 m3 h-1 and inlet pressure ranging from 15 to 40 mca. The filtering system cleaning was not totally effective in reestablishing the head loss, with an upward trend over time. The reverse flow with frequency of 11.11 and 22.22 mHz influenced the head loss evolution of the filtration system, making it slower than the trend for the system running without flow reversal. The developed filtration system has potential for filtering low quality irrigation water, but it requires periodic maintenance to clean the filter element. The allowable head loss of the filter system should be the most restrictive value between the criterion of particle retention performance and the flow variation of the irrigation system because of the increase in head loss in the filters.

Les performances de filtration d’un filtre à manche vis-à-vis de particules submicroniques et nanométriques ont été évaluées à l’échelle du laboratoire durant plusieurs cycles de colmatage/décolmatage. La distribution granulométrique des particules (aérosol de combustion) était représentative de celle rencontrée en incinération de nano-déchets en sortie de chambre de combustion à l’échelle du laboratoire. Le filtre à manche opérait en conditions réalistes, représentatives de celles rencontrées dans les lignes de traitement des fumées d’incinération de déchets en termes de température, humidité, vitesse de filtration, présence de réactifs et conditions de décolmatage. Le flux d’air et le filtre à manche étaient chauffés à 150°C, la teneur en eau était de 10-12% (soit 3% d’humidité relative HR), et la vitesse de filtration était fixée à 1,9 cm.s⁻¹. Un mélange de particules de taille submicronique de charbon actif et de bicarbonate de sodium, utilisées dans les lignes de traitement des fumées d’incinération pour l’abattement des dioxines/furanes et des gaz acides, était généré simultanément avec l’aérosol de combustion. L’étude s’est centrée sur les performances de filtration au début de la durée de vie du filtre à manche, avant stabilisation de la perte de charge résiduelle du filtre résultant des précédents cycles de filtration. La perte de charge maximale du filtre était fixée à 150 Pa pour tous les cycles de filtration avant décolmatage par rétro-soufflage à air comprimé. Les performances du filtre à manche ont été évaluées en termes d’évolution de sa perte de charge et de son efficacité de collecte (totale et fractionnelle) au cours des cycles de colmatage/décolmatage. De plus, des études expérimentales et théoriques ont été menées afin d’étudier l’influence de divers paramètres sur les performances de filtration du filtre en configuration manche ou plane, tels que l’humidité de l’air (3% HR versus 0% HR à 150°C), la température (150°C versus 24°C), la vitesse de filtration (1,9 cm.s⁻¹ versus 1,4 cm.s⁻¹) et l’influence de l’injection de réactifs. Les principaux résultats de cette étude sont : (i) importante efficacité de capture des particules du filtre à manche en conditions représentatives des lignes de traitement des fumées d’incinération : efficacité minimale de collecte de 98,5% mesurée pour des particules de taille 74 ± 15 nm (diamètre de mobilité électrique), (ii) influence du gâteau résiduel de particules au début de chaque cycle de filtration sur les performances de traitement, (iii) influence significative de l’humidité de l’air sur la structure du gâteau de particules probablement due à l’augmentation des forces d’adhésion entre les particules en présence d’humidité (150°C – 3% HR soit environ 100 g d’eau par kg d’air sec) ; augmentation plus rapide de la perte de charge du filtre à manche en présence d’humidité (150°C – 3% HR) qu’en conditions d’air sec (150°C – 0% HR)
Filtration performance of a pulse-jet bag filter was evaluated at the laboratory-scale regarding submicronic particles with a nanosized fraction during clogging/unclogging cycles. The particle size distribution was representative to those encountered at the outlet of a nano-waste incineration device at laboratory-scale. The bag filter was operated in conditions as similar as possible to those found in flue gas treatment of waste incineration plants, in terms of temperature, humidity, filtration velocity, injection of sorbent reagents and unclogging conditions. The air flow and the bag filter were heated to 150°C, the water content was maintained in the air flow in the range of 10-12% (3% of relative humidity RH), and filtration velocity throughout the bag filter was fixed at 1.9 cm.s⁻¹. A mixture of submicronic suspended particles of activated carbon and sodium bicarbonate, both used in flue gas treatment systems mainly for the removal of dioxins/furans and acid gases, was generated simultaneously with the aerosol representative of combustion emissions.The study focused on the filtration performance at the beginning of the bag filter’s lifetime filter for the 11 first clogging-unclogging cycles before stabilizing the residual pressure drop reached after pulse-jet unclogging. The maximum pressure drop was set at 150 Pa for all filtration cycles. Once the maximum pressure drop was reached, the filter was unclogged using the pulse-jet system. The performance of the bag filter was evaluated in terms of the evolution of pressure drop, fractional and total particle collection efficiencies, during the clogging/unclogging cycles.Moreover, an experimental and theoretical study was carried out on the influence of different parameters on the filtration performance of bag filter and flat filter, such as influence of humidity (3% RH versus 0% RH at 150°C), temperature (150°C versus 24°C), filtration velocity (1.9 cm.s⁻¹ versus 1.4 cm.s⁻¹) and the influence of the injection of sorbent reagents.The main results of this study are: (i) high collection efficiency of the bag filter in representative conditions of flue gas treatment of waste incineration: minimun particle collection efficiency of 98.5% for particle diameter of 74 ± 15 nm (electrical mobility diameter), (ii) influence of residual particle cake at the beginning of the filtration cycles on the bag filter performance, (iii) significant influence of humidity on the porosity of the particle cake due to the capillary condensation of water between the particles in presence of humidity (150°C - 3% RH i.e. almost 100 g of water per kg of dry air). Faster increase of bag filter pressure drop in presence of humidiy (150°C - 3% RH) as compared to the dry conditions (150°C - 0% RH)

L'utilisation de filtres plissés dans le domaine du traitement de l'air est extrêmement fréquente en raison de leur simplicité d'utilisation et de maintenance. Néanmoins, au cours du colmatage, la perte de charge augmente considérablement avec le dépôt de particules. Par conséquent le débit de filtration n'est plus maintenu et une détérioration des médias peut se produire. Il est essentiel de caractériser cette évolution en fonction des conditions opératoires pour mieux concevoir ces équipements. Les travaux ont consisté en une étude expérimentale de l'influence des conditions opératoires sur la géométrie du dépôt par des observations en Tomographie d'Émission MonoPhotonique. Une approche numérique a consisté, dans un premier temps, en une étude de la perméabilité de médias bien caractérisés afin de valider le code GeoDict. Dans un deuxième temps, une étude de la vitesse de l'air a été entreprise sur les médias plissés. La confrontation des résultats numériques avec les données expérimentales nous a permis une validation du code dans les gammes de propriétés des médias et de vitesses typiques. Concernant les médias bimodaux, l'acquisition rapide de données a permis de tester différentes corrélations analytiques afin de classifier les modèles existants d'une manière qui facilite leur utilisation. Si les résultats expérimentaux obtenus sur la localisation du dépôt préférentiel initial dans les filtres plissés sont encourageants, notamment vis-à-vis des simulations d'écoulement réalisées avec GeoDict, ceux issus des acquisitions sur les filtres précolmatés sont à prendre avec prudence et suggèrent d'apporter un certain nombre d'amélioration à notre technique
Pleated filters are widely used in air treatments because of the advantageous effective surface to overall dimension ratio they offer. Their major drawback though resides in their reduced lifetime which still needs to be controlled. Indeed, when clogging, the pressure drop considerably increases, the filtration flow is then no longer maintained which might lead to the deterioration of the media. It is then crucial to characterize the evolution of the pressure drop under operating conditions in order to best design these equipments. Part of our work consisted in studying how the operating conditions influence the geometry of the deposit. To do so, we used Single-Photon Emission Computed Tomography (SPECT), a non-destructive imaging technique that keeps intact the particle structuring. The visualization of aerosol deposit at the beginning of the filtration process allows observing preferential particle deposition on the whole height of the pleat. A numerical approach was used to study the permeability of bimodal fibrous media and we experimentally studied the local velocity as well as the biphasic flow inside pleated filter media. Comparison between experiments and simulations allowed us to validate the Geodict code for a wide range of media properties and velocities. Regarding bimodal fibrous media, the fast data acquisition has allowed testing several existing models which resulted in classifying them in a unique way. If the experimental results on the initial deposition in pleated filters are encouraging, those related to beforehand clogging point to several improvements regarding the technique we used

The clogging of fibrous air filters by solid aerosol particles in the inertial interception capture range was experimentally and theoretically investigated. Flat filters were loaded to particle filter cake formation at 0.10 m/s filter face velocity with monodisperse aerosols. An evaporator-condenser aerosol generator capable of producing a stable 0.6 kg/hr product of monodisperse, solid aerosols in the range 1 to 5 micrometers aerodynamic diameter was designed, fabricated, and optimized. The output aerosol was introduced into a vertical challenge duct, where the mass concentrations upstream and downstream of the filter sample, and thus the filter penetration, were measured using continuous flow sampling through two light scattering photometers. Simultaneous measurements were made of the filter flow resistance during the particle loading process. A discussion of the possible definitions of clogging is given from descriptions of the plots of the experimental filtration responses with mass challenge. The relationship between the clogging point and effective filter pore diameter for different aerosol challenges is given for medium efficiency fibreglass papers and for filters made with 15.5 micrometer diameter monodisperse fibres.

Lors d'un accident de type APRP (Accident de Perte du Réfrigérant Primaire) survenant dans réacteur nucléaire à eau pressurisé (REP), des débris sont générés et ils peuvent être partiellement transportés jusqu'aux filtres des systèmes de secours RIS-EAS des puisards situés dans le fond de l'enceinte de confinement du réacteur. Ces débris peuvent contribuer au colmatage « physique » des filtres. Un autre effet dit « effet chimique » correspond à l'apport de cations en solution de par la corrosion des débris (fibres d'isolant) et la possible corrosion de surfaces métalliques présentes dans le bâtiment réacteur. Ces cations métalliques peuvent former des précipités au sein du lit fibreux formés et accentuer le colmatage physique. En cas d'accident grave avec fusion du cœur, des charges additionnelles de débris sont à considérer comme la présence de particules formées de matériaux de structure, des barres de commande et de produits de fission et des particules de béton résultant d'un interaction corium-béton. Il a été clairement identifié dans la littérature que ces effets chimiques sont à prendre en compte pour s'assurer de la fonction recirculation sur une longue période. La question de recherche est d'être en mesure de comprendre la nature de ces effets chimiques, les paramètres les conditionnant et leurs ampleurs. Le sujet de thèse porte sur l'étude de ces effets chimiques, pour cela une approche paramétrique sera suivie en couplant plusieurs mesures chimiques et en corrélant ces mesures à une perte de charge. Les mesures chimiques en solution se feront principalement par ICP et la caractérisation des précipités potentiellement formés pourra se faire par des analyses type MEB-EDX, DRX et XPS. La boucle de filtration est à concevoir
During a LOCA accident (Loss Of Coolant Accident) occurring to a nuclear Pressurized Water Reactor (PWR), debris are generated and can be partially transported to the RIS-EAS filter in the sumps located in the bottom of the nuclear reactor containment. These debris can contribute to the « physical » clogging of the filters. Another effect called « chemical effects » corresponds to the presence of cations in solution resulting from the debris' corrosion and the possible corrosion of the metal surface present in the reactor containment vessel. In the case of a severe accident with core fuel meltdown, additional loads debris are to be considered as presence of particles formed of structural materials, control rod material, fission products and concrete particles resulting from corium-concrete interaction. To ensure the long term liquid recirculation functionality, the chemical effect have to be understood: nature of these chemical effects, conditioning parameters and potential effect on the clogging. The thesis aims at studying the chemical effects after designing a dedicated experimental loop: a parametric approach , coupled with several chemical and pressure drop measurements. Chemical speciation in solution and precipitate characterizations will/can be respectively performed by ICP and MEB-EDX, DRX and XPS techniques

Cette étude porte sur la filtration des particules métalliques contenues dans les fumées de métallisation. Des retours d'expériences spécifiques aux dépoussiéreurs filtrants les fumées de métallisation témoignent d'un colmatage des filtres très rapide ainsi que de l'inefficacité des techniques de décolmatage pneumatique habituellement utilisées. Il en résulte une durée de vie des éléments filtrants très réduite. L'objectif de cette étude est de caractériser le colmatage puis le décolmatage afin d'améliorer les performances des dépoussiéreurs à cartouches filtrantes vis-à-vis des fumées de métallisation. Trois axes de recherches ont été exploré sur un banc pilote spécialement équipé : - la caractérisation des fumées de métallisation. Elle a permis de qualifier la structure spatiale de la particule par la dimension fractale et le facteur de forme dynamique grâce au couplage série DMA-ELPI et à une méthodologie originale d'analyse des données validée sur différents aérosols. Les caractéristiques obtenues expliquent les propriétés colmatantes des fumées de métallisation. - La caractérisation du dépôt engendré au cours de la phase de filtration (ou de colmatage). Elle montre une structure incompressible dans la gamme de filtration habituellement pratiquée en industrie. Ces travaux ont permis d'estimer la porosité expérimentale du dépôt formé par les fumées de métallisation. - L'étude sur le décolmatage. Elle décrit et explique l'inefficacité des décolmatages utilisés en industrie. Il ressort que seule une très faible surface du média plissé est décolmatée. L'alternative du precoating se révèle très efficace mais seulement en mode off-line
This study deals with the filtration of metallic particles contained in the metallization fumes. Experience feedback specific to the filtration of metallization fumes by dust collectors report a rapid clogging of filters and the inefficiency of pneumatic cleaning techniques commonly used. This leads to a high reduction in filters lifetime. The objective of this study is characterize clogging then unclogging in order to improve the performance of dust cartridge filter against metallization fumes. Three research axes were explored on a dedicated bench : - Metallization fumes characterization. It allows describing the spatial structure of the particle by the fractal dimension and the dynamic shape factor with the DMA-ELPI serial coupling and thanks to an original data analysis methodology validated on various aerosols. The characteristics obtained explain the clogging properties of metallization fumes. - Characterization of the cake generated during the filtration phase (or clogging). It shows a incompressible structure in the velocities filtration range of industry. The experimental porosity of the cake formed by filtering metallization fumes is estimated thanks to these studies. - Study on cleaning. It describes and explains the inefficiency of pneumatic cleaning techniques employed in industry. It appears that only a very small surface of the pleated media is unclogged. The precoating alternative is shown to be very efficient provided that it is combined with off-line cleaning procedures

This thesis presents a novel hybrid prognostic methodology, integrating physics-based and data-driven prognostic models, to enhance the prognostic accuracy, robustness, and applicability. The presented prognostic methodology integrates the short-term predictions of a physics-based model with the longer term projection of a similarity-based data-driven model, to obtain remaining useful life estimations. The hybrid prognostic methodology has been applied on specific components of two different engineering systems, one which represents accelerated, and the other a nominal degradation process. Clogged filter and fatigue crack propagation failure cases are selected as case studies. An experimental rig has been developed to investigate the accelerated clogging phenomena whereas the publicly available Virkler fatigue crack propagation dataset is chosen after an extensive literature search and dataset analysis. The filter clogging experimental rig is designed to obtain reproducible filter clogging data under different operational profiles. This data is thought to be a good benchmark dataset for prognostic models. The performance of the presented methodology has been evaluated by comparing remaining useful life estimations obtained from both hybrid and individual prognostic models. This comparison has been based on the most recent prognostic evaluation metrics. The results show that the presented methodology improves accuracy, robustness and applicability. The work contained herein is therefore expected to contribute to scientific knowledge as well as industrial technology development.

Mathematical Modeling of Fines Migration and Clogging in Porous Media Guido Kampel 87 Pages Directed by Dr. Guillermo H. Goldsztein A porous medium is a material that contains regions filled with fluid embedded in a solid matrix. These fluid filled regions are called pores or voids. Suspensions are fluids with small particles called fines. As a suspension flows through a porous material, some fines are trapped within the material while others that were trapped may be released. Filters are an example of porous media. We model filters as networks of channels. As a suspension flows across the filter, particles clog channels. We assume that there is no flow through clogged channels. In the first part of this thesis, we compute a sharp upper bound on the number of channels that can clog before fluid can no longer flow through the filter. Soil mass is another example of porous media. Fluid in porous media flows through tortuous paths. This tortuosity and inertial effects cause fines to collide with pore walls. After each collision, a particle looses momentum and needs to be accelerated again by hydrodynamic forces. As a result, the average velocity of fines is smaller than that of the fluid. This retardation of the fines with respect to the fluid may lead to an increase of the concentration of fines in certain regions which may eventually result in the plugging of the porous medium. This effect is of importance in flows near wells where the flow has circular symmetry and thus, it is not macroscopically homogeneous. In the second part of this thesis we develop and analyze a mathematical model to study the physical effect described above. In the third and last part of this thesis we study particle migration and clogging as suspension flows through filters by means of numerical simulations and elementary analysis. We explore the effect that network geometry, probability distribution of the width of the channels and probability distribution of the diameter of the particles have on the performance of filters.

Thesis (Ph.D)--Mathematics, Georgia Institute of Technology, 2008.
Committee Chair: Goldsztein, Guillermo; Committee Member: Dieci, Luca; Committee Member: McCuan, John; Committee Member: Santamarina, Juan; Committee Member: Zhou, Haomin.

Cette étude concerne la filtration par un filtre à fibres d'un gaz contaminé soit par des particules solides submicroniques soit par un aérosol liquide submicronique. Après une synthèse de l'ensemble des travaux réalisés antérieurement, nous nous intéressons dans un premier temps à caractériser les différents filtres (très haute efficacité et moyenne efficacité) mis à notre disposition. Les résultats expérimentaux relatifs à la filtration de particules solides nous ont permis de détailler le processus de colmatage et de décrire en particulier l'évolution de la perte de charge, de l'efficacité, du profil de pénétration de l'aérosol au sein du medium. Des observations au microscope montrent que dans une première étape du colmatage, des dendrites sont formées sur les fibres dans la profondeur du filtre et que dans une seconde étape un gâteau se construit sur la surface du filtre. L’originalité de la partie expérimentale réside dans la caractérisation du gâteau et la détermination du point de transition entre les deux phases de la filtration. Un nouveau modèle théorique a été développé et permet de rendre compte de l'ensemble des résultats expérimentaux. La filtration d'un aérosol liquide a été décrite et a mis en évidence l'existence d'une masse seuil pour laquelle on observe une brutale augmentation de la perte de charge du filtre, correspondant à la présence d'un film liquide forme sur la surface du filtre. L’influence de certains paramètres opératoires a été étudiée ainsi que la nature de l'aérosol, en particulier la tension superficielle du liquide. Enfin, diverses approches ont permis de décrire théoriquement les phénomènes observés et d'ouvrir différentes perspectives de modélisation plus fines.

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The use of fresh water available in the world needs to be more efficient, and localized irrigation systems such as drip irrigation show high efficiency for water use in crop irrigation. In the city of Salto do Lontra, state of Paraná, Brazil, several producers use drip irrigation in fruit growing and horticulture, accompanied by a family farming project developed in the region.One major problem of this system is the clogging in drip emitters, which can be caused by chemical, physical or biological agents, reducing the uniformity of water and fertilizer application, diminishing the system s effectiveness and usability. Reviews of uniformity were made to monitor the clogging over the treatments, whereas, according to the change of flow, with little variation in pressure, clogged emitters were found. Each system received a treatment for unclogging the emitters, composed of phosphoric acid and of calcium hypochlorite, which were subsequently analyzed by Tukey's comparison test and statistical control charts. The filters used (disc filter and screen filter) were analyzed by weighing the impurities contained therein, in an interval of six reviews. The uniformity was better assessed by CUD and CV, as the CUC presented data above 90% even with high variation in flow and pressure. With the help of control charts, it can be seen that the calcium hypochlorite showed better performance than the phosphoric acid to clean the system for returning the initial flow rating. The disc filter was more efficient for waste retention when compared to the screen filter, which showed blockage in the system where it was installed
O uso da água doce disponível no mundo necessita ser mais eficiente, e sistemas de irrigação localizada, como o gotejamento, apresentam alta eficiência em aplicação de água para as culturas. No município de Salto do Lontra PR, vários produtores fazem uso do gotejamento em fruticultura e horticultura, acompanhados pelo projeto de agricultura familiar desenvolvido na região. Um grande problema do uso de gotejamento é o entupimento dos emissores, que pode ser causado por agentes químicos, físicos ou biológicos, reduzindo a uniformidade de aplicação de água e fertilizante, tornando menor a vida útil do sistema e ineficaz. Avaliações de uniformidade foram feitas para monitorar o entupimento ao longo dos tratamentos, sendo que, conforme a alteração da vazão, com pouca variação de pressão, foram constatados os emissores obstruídos. Cada sistema recebeu um tratamento para desobstrução dos emissores, que foram à base de ácido fosfórico e de hipoclorito de cálcio, que, posteriormente, foram analisados por comparações de média ao teste Tukey e por gráficos de controle estatístico. Os filtros utilizados (filtro de discos e filtro de tela) foram analisados por meio de pesagem das impurezas contidas neles, a cada seis avaliações. A uniformidade foi melhor avaliada pelo CUD e CV, já que o CUC apresentou dados acima de 90%, mesmo com alta variação de vazão e pressão. Com auxílio dos gráficos de controle, pode-se ver que o hipoclorito de cálcio apresentou melhor desempenho que o ácido fosfórico na limpeza do sistema, por retornar a vazão inicial das avaliações. O filtro de discos foi mais eficiente quanto à retenção de resíduos quando comparado ao filtro de tela, que apresentou entupimento no sistema em que estava instalado.

At present, agriculture is the human activity which requires more volume of water. Given the importance and scarcity of this resource, the efficient use of water has become a priority. On one hand, if possible, it is necessary to use irrigation systems such as microirrigation that use water more efficiently. On the other hand, treated wastewater reuse by agriculture helps to have the necessary water at the same time that it allows to release water of higher quality for other uses. In this sense, microirrigation is the safest system to apply reclaimed effluents. However, its main problem is emitter clogging, which can negatively affect crop yields and system maintenance. In order to avoid emitter clogging, the use of filters is compulsory. Those filters that work better with effluents are sand filters, although, due to their pressure requirements, concentrate most of the energy demand of drip irrigation systems. This thesis determines the effect of three types of sand filters with different drainage designs (arm collector, inserted domes and porous media), two media height (0.2 and 0.3 m) and two filtration velocities (30 and 60 m/h) in the quality of filtered water, the pressure loss in the filters, the energy consumption of the system and emitter clogging
En l’actualitat, l’agricultura és l’activitat humana que requereix més quantitat d’aigua. Davant la importància i escassetat d’aquest recurs, l’ús eficient de l’aigua s’ha convertit en una prioritat. D’una banda i si és possible, es fa necessària la utilització de sistemes de reg com el reg per degoteig que empren de forma més eficient l’aigua. D’altra banda, la reutilització d’aigües residuals tractades per l’ús agrícola ajuda a disposar de l’aigua necessària per a reg al mateix temps que permet alliberar aigües de major qualitat per a altres usos. En aquest sentit, el reg per degoteig és el sistema més segur per aplicar aigües regenerades. No obstant això, el seu principal problema és l’obturació dels degoters, que pot afectar negativament al rendiment dels cultius i al maneig de la instal·lació. Per intentar evitar les obturacions, resulta imprescindible instal·lar filtres. Els que millor funcionen amb aquest tipus d’aigües són els filtres de sorra, encara que, degut a la pressió que requereixen, concentren la major part de demanda d’energia dels sistemes de reg per degoteig. En la present tesi es determina l’efecte de tres tipus de filtres de sorra amb diferents dissenys de drenatge (de braços col·lectors, de crepines inserides i de medi porós), l’alçada del medi filtrant (0.2 i 0.3 m) i la velocitat de filtració (30 i 60 m/h) en la qualitat de l’aigua filtrada, la caiguda de pressió en els filtres, el consum energètic del sistema i l’obturació dels degoters

[Truncated abstract] Self-filtration is here defined as particle detachment and re-deposition causing re-arrangement of the particles and therefore pore space which affects water flow in soil by decreasing hydraulic conductivity. This is of particular important in soils which are susceptible to structural breakdown. The objective of this thesis was to examine the dynamics of the self-filtration process in sodic sandy soils as affected by ionic strength and soil solution composition. The temporal changes of hydraulic conductivity and the elution of fine particles from soil columns were used as the main criteria to assess selffiltration. Two porous media exhibiting significantly different structural cohesion were examined, one a loamy sand (Balkuling soil) from agricultural land use and the second a mining residue from mineral sands operations . . . The effects of the composition of mixed calcium (Ca) and sodium (Na) ions in solution (sodium adsorption ratio (SAR)) on the exchange behaviour and saturated hydraulic conductivity were examined by carrying out batch binary exchange and saturated column transport experiments. A strong preference for Ca2+ ions in the exchange complex was observed for both soils. Generally K/Ko was found to decrease with increasing sodium adsorption ratio with the more structured Balkuling soil maintaining K/Ko for SARs 3 and 5 at an electrolyte concentration of 100 mmol/L. However measurements at the critical threshold and turbidity concentrations at a SAR of 15 revealed structural breakdown of the pore matrix system attributed to various extents of slaking, swelling, dispersion and decreases of pore radii as a result of selffiltration during leaching. These experiments illustrate the wide range of complex interactions involving clay mineralogy, solution composition and structural factors which can influence the extent of mobilization, transport and re-deposition of colloidal particles during the leaching process in soil profiles.

博士
國立臺灣大學
化學工程學系
86
As a first step to study the mechanism of filtration of deformable particles, the compression and deformation behaviors of calcium-alginate gel particles bed under mechanical loading and hydraulic drag in a particles bed were conducted in the first part of this study. Experimental results show that progressive decreases in the bed height, volume, and porosity of the bed took place gradually as the pressure on the bed was increased, with the particles being deformed into flattened dodecahedrons. Cake filtration and crossflow filtration experiments of Saccharomyces cerevisiae and PMMA were conducted to examine the structure of flux limiting layer formed by deformable particles. Effect of particle deformation due to friction drag and mass of cake on the reduction of porosity was studied to examine how this variation led to the increase in filtration resistance. Results showed that as the cake formed by deformable gel particles exhibits a rapid increase in flow resistance or decrease in porosity due to area contact between particles, a flux limiting layer, resistant material is formed next to the filter medium during filtration. A dynamic analysis proposed by Lu and Hwang (1993) was modified to investigate cake formation in both cake filtration and crossflow filtration of deformable particles by taking the transient effect of cake compression and the effect of area contact between particles into consideration. The simulated results agreed well with the experimental data. In the second part of this study, three-dimensional particles deposition on four basic woven structures was studied numerically by analyzing forces acting on the depositing particles and was applied to estimate the change of clarity of filtrate at the initial stage of filtration. The effects of woven structures, feed concentration and particle/pore size ratio on the transient behavior of cake filtration and the variation of medium resistances at the beginning stage of cake filtration were analyzed quantitatively. The simulated results showed that the filtration period at the initial stage can be divided into the three modes of standard pore blocking, intermediate blocking and cake formation in accordance with the law of blocking for all types of pores. Furthermore, the critical concentration proposed by previous investigators is also confirmed quantitatively in this study.

碩士
國立中興大學
環境工程學系所
99
Although the average rainfall in Taiwan is higher than lots of country, water resources in Taiwan are still significantly insufficient because of the landform and climate. To solve this problem, our government built reservoirs to supply sufficient water resource. Human activity caused serious eutrophication in our reservoirs and lots of algae growth rapidly in short-term, Algae were impacted the water treatment processes and reduced the quality of drinking water. Recently a large amount of algae has been found at specific periods (2008.11~12、2009.03)was set up in Li Yu Tan reservoir. Serious algae bloom accompanied rapid sand filter of water supply plant has been clogged. So water company has to raise the backwash frequency to assured the quality of effluent in water treatment processes. In this study, two rapid sand filter modules to simulate different operation conditions were constructed. The large module in Li Yu Tan water supply plant in order to simulate the operation of filtration processes. The small module was set up in laboratory and used to simulate the situation when influent contains large number of algae. In this investigation (2010.04~2011.04),The maximum concentration of algae was observed in October. The diatom was the predominant species in the reservoir. In different season, algae species change significantly with weather and temperature. In large rapid sand filter module, experiments were conducted under five operating conditions. The average removal efficiency of turbidity was higher than 80% in each case. Raising media diameter can reduce the head lost in the operational term. Other experiments determined that decreasing packed depth may reduce the turbidity removal rate. Isolation of predominant species in the reservoir is difficult because diatom growth slower than other green algae. In this study, four kind of algae were isolated. There were Cycotella sp.、Chlorella sp.、Oscillatoria sp. and Scenedesmus sp.. In small rapid sand filter module, The Oscillatoria sp. formed serious clogging in surface of filters and accumulated highest head lost about 53 cm in 8 hr. The Chlorella sp. accumulated lowest head lost about 40 cm in 8 hr and it is most easiest to breakthrough the filters into filtrate.

碩士
國立中央大學
環境工程研究所
100
Due to extreme high turbidity during typhoons or heavy rains, which resulted in difficulties in potable water treatment, the water intake well to draw water from upper levels of the reservoir was built in the Shihmen reservoir. After drawing water from the intake well, it was found that the rapid sand filter was severely clogged, the head loss increased dramatically, and the filtration run-time was seriously shortened. The objectives of this study were first to investigate filter clogging in Ping-Jan Water Treatment Plant while intake water from the water intake well by water quality analysis of different water intake locations, filter-bed analysis, and pilot study. It was shown that the water qualities from different water intake locations were similar; thus, the water quality was not the cause for the clogging. From the floc retention analysis, scanning microscopy, and energy-dispersive X-ray spectroscopy of filter media, it was found that the particles only deposited on the surface of filter while intake water from the water intake well. Bubbles observed in coagulation tanks on-site and in coagulation, sedimentation, and filtration units of the pilot, it was determined that the air-binding is responsible of the filter clogging.

Infiltration facilities are source control mechanisms that are implemented in urban developments with reduced natural permeable surfaces. Despite the development of design criteria for infiltration facilities, these systems continue to fail due to headloss development, overflow, or chemical breakthrough. The limited research on the long-term performance of these systems has emphasized the role of physical filtration mechanisms within porous media filters to address concerns surrounding system failure, namely filter clogging. A continuous macroscopic depth filtration model was developed to investigate the clogging potential of the underlying sand filter. This continuous model furthers the understanding of temporal and spatial changes in system performance for the development of more appropriate design criteria and more suitable maintenance regimes. The characterization of long-term system performance by defining three different failure modes and a probabilistic approach comprises a comprehensive methodology by considering several performance criteria rather than assuming that one criterion dictates the overall system performance.