Relevant bibliographies by topics / Reactor recirculation

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Academic literature on the topic 'Reactor recirculation'

Author: Grafiati
Published: 4 June 2021
Last updated: 4 February 2022

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Journal articles on the topic "Reactor recirculation"

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Núñez, L. A., and B. Martínez. "Evaluation of an anaerobic/aerobic system for carbon and nitrogen removal in slaughterhouse wastewater." Water Science and Technology 44, no. 4 (August 1, 2001): 271–77. http://dx.doi.org/10.2166/wst.2001.0233.

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In this work the performance of an anaerobic UASB reactor coupled with an activated sludge reactor for carbon and nitrogen removal in slaughterhouse wastewater is investigated. Periods with and without recirculation of aerobic effluent over 165 days are analysed. Working with a recirculation ratio of 2, removal efficiencies up to 90% and 65% are obtained for DQO and total nitrogen (TN), respectively. Higher recirculation ratios caused severe washout of active biomass in both reactors due to the high hydraulic loading rates applied. Denitrification in the UASB reactor was complete, with no nitrite accumulation and mainly to nitrogen gas. Significant decreases in COD removal efficiencies in the UASB reactor were observed at recirculation ratio of 2. Sudden decreases in total nitrogen efficiencies were related to inhibition process of nitrifying microorganisms, especially at high recirculation ratios.
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Vistanty, Hanny, and Rizal Awaluddin Malik. "ENHANCED PERFORMANCE OF MULTI-STAGE ANAEROBIC DIGESTION OF TOFU WASTEWATER: ROLE OF RECIRCULATION." Jurnal Riset Teknologi Pencegahan Pencemaran Industri 10, no. 1 (August 19, 2019): 29–37. http://dx.doi.org/10.21771/jrtppi.2019.v10.no1.p29-37.

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Continuous three-stage anaerobic reactors with recirculation system were employed to treat real tofu wastewater. The system consists of 3 reactors connected in series and effluent of the last reactor was partly returned as feed of the first reactor along with fresh wastewater. The recirculation system was conducted on four variations of recirculation ratio (RR)s of 0, 1.0, 1.3, and 1.5 to evaluate the influence of recirculation on stability and performance of anaerobic system. Results showed that recirculation improved the performance of anaerobic digestion. COD was fluctuated without recirculation and gradually decreased to 373 and 298 mg/L at RR 1.3 and 1.5, respectively. Likewise, pH value was dropped to 6.5 at RR 0, and started to increase to approximately 8.0 upon employing recirculation. In addition, the system also showed excellent toleration against rise in ammonia loading, with effluent ammonia approximately 4.678 mg/L. The findings showed that the system employed had excellent efficiency and stability in treating tofu wastewater.
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Lepistö, Raghida, and Jukka Rintala. "The Removal of Chlorinated Phenolic Compounds from Chlorine Bleaching Effluents Using Thermophilic Anaerobic Processes." Water Science and Technology 29, no. 5-6 (March 1, 1994): 373–80. http://dx.doi.org/10.2166/wst.1994.0730.

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Thermophilic (55°C) anaerobic removal of chlorinated phenolic compounds (CPC) from softwood bleaching effluents was studied using four different types of anaerobic processes: an upflow anaerobic sludge blanket (UASB) reactor (R1); a UASB reactor enriched with sulfate (R2); a UASB reactor with recirculation (R3); and a fixed bed reactor with recirculation (R4). The concentrations of 16 CPCs were analyzed by gas Chromatography. In all processes most of the chlorinated phenols, catechols, guaiacols, and hydroquinons detected in the bleached kraft mill effluent (BKME) were either eliminated or reduced by as much as 80-95%. However, 2,4-DCP, 2,6-DCP, 4,5-DCG, 3,4,5-TCC, and TeCC were accumulated or only partially removed in all reactors, except in R4 where at high concentrations they were significantly reduced. All the reactors removed 30-70% of the COD and 25-67% of the adsorbable organic halides (AOX). The reactors with recirculation had slightly higher removal efficiencies than the other reactors, while the addition of sulfate had no apparent effect. High concentrations of BKME reduced the COD removal efficiency but not the CPC removal.
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Lukitawesa, Rachma Wikandari, Ria Millati, Mohammad J. Taherzadeh, and Claes Niklasson. "Effect of Effluent Recirculation on Biogas Production Using Two-stage Anaerobic Digestion of Citrus Waste." Molecules 23, no. 12 (December 19, 2018): 3380. http://dx.doi.org/10.3390/molecules23123380.

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Citrus waste is a promising potential feedstock for anaerobic digestion, yet the presence of inhibitors such as d-limonene is known to limit the process. Effluent recirculation has been proven to increase methane yield in a semi-continuous process for recalcitrant material, but it has never been applied to toxic materials. This study was aimed to investigate the effect of recirculation on biogas production from citrus waste as toxic feedstock in two-stage anaerobic digestion. The first digestion was carried out in a stirred tank reactor (STR). The effluent from the first-stage was filtered using a rotary drum filter to separate the solid and the liquid phase. The solid phase, rich in hydrophobic D-limonene, was discarded, and the liquid phase containing less D-limonene was fed into the second digester in an up-flow anaerobic sludge bed (UASB) reactor. A high organic loading rate (OLR 5 g VS/(L·day)) of citrus waste was fed into the first-stage reactor every day. The effluent of the first-stage was then fed into the second-stage reactor. This experiment was run for 120 days. A reactor configuration without recirculation was used as control. The result shows that the reactor with effluent recirculation produced a higher methane yield (160–203 NmL/g·VS) compared to that without recirculation (66–113 NmL/g·VS). More stable performance was also observed in the reactor with recirculation as shown by the pH of 5–6, while without recirculation the pH dropped to the range of 3.7–4.7. The VS reduction for the reactor with recirculation was 33–35% higher than that of the control without recirculation. Recirculation might affect the hydrolysis-acidogenesis process by regulating pH in the first-stage and removing most of the D-limonene content from the substrate through filtration.
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Yaya Beas, Rosa Elena, Katarzyna Kujawa-Roeleveld, Jules B. van Lier, and Grietje Zeeman. "A downflow hanging sponge (DHS) reactor for faecal coliform removal from an upflow anaerobic sludge blanket (UASB) effluent." Water Science and Technology 72, no. 11 (August 11, 2015): 2034–44. http://dx.doi.org/10.2166/wst.2015.427.

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This research was conducted to study the faecal coliforms removal capacity of downflow hanging sponge (DHS) reactors as a post-treatment for an upflow anaerobic sludge blanket (UASB) reactor. Three long-term continuous laboratory-scale DHS reactors, i.e. a reactor with cube type sponges without recirculation, a similar one with recirculation and a reactor with curtain type sponges, were studied. The porosities of the applied medium were 91%, 87% and 47% respectively. The organic loading rates were 0.86 kgCOD m−3 d−1, 0.53 kgCOD m−3 d−1 and 0.24 kgCOD m−3 d−1 correspondingly at hydraulic loading rates of 1.92 m3 m−2 d−1, 2.97 m3 m−2 d−1 and 1.32 m3 m−2 d−1, respectively (COD: chemical oxygen demand). The corresponding averages for faecal coliform removal were 99.997%, 99.919% and 92.121% respectively. The 1989 WHO guidelines standards, in terms of faecal coliform content for unrestricted irrigation (category A), was achieved with the effluent of the cube type DHS (G1) without recirculation. Restricted irrigation, category B and C, is assigned to the effluent of the cube type with recirculation and the curtain type, respectively. Particularly for organic compounds, the effluent of evaluated DHS reactors complies with USEPA standards for irrigation of so called non-food crops like pasture for milking animals, fodder, fibre, and seed crops.
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Suna Erses, A., and T. T. Onay. "Accelerated landfill waste decomposition by external leachate recirculation from an old landfill cell." Water Science and Technology 47, no. 12 (June 1, 2003): 215–22. http://dx.doi.org/10.2166/wst.2003.0649.

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This research is focused on the management of moisture regime for a young landfill site in terms of leachate recirculation which entails the containment, collection and reinjection of leachate back into the landfill to promote in situ anaerobic biological treatment. Moreover, an innovative leachate management strategy was developed by using leachate recirculation from a mature landfill site into a young landfill site to provide accelerated waste stabilization. For this purpose, two reactors simulating young and old landfills were used in the laboratory. These reactors were loaded with shredded and compacted municipal solid waste with a typical composition determined for Istanbul Region. Both reactors were operated in a constant temperature room at 32°C to enhance the growth of anaerobic microorganisms. Moreover, water was added to the reactors in order to simulate the annual rainfall. The reactor having the properties of old landfills was used as a control reactor. The reactor which represented the characteristics of young landfill was operated under four operational stages to enhance the activity of methanogenic population and accelerate waste stabilization. Results of this study indicated that the utilization of leachate recirculation enhanced waste stabilization in the young landfill by increasing the uniformity, and providing additional substrate and nutrients. Additions of buffer solutions of KOH and Na2CO3 together with leachate recirculation enhanced further waste stabilization and prevented possible acid inhibition. The utilization of external leachate recycled from the old landfill having desired acclimated anaerobic microorganisms, low organic content and higher buffer capacity into a young landfill could be a promising leachate management strategy for faster and controlled waste stabilization.
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Bertolino, Sueli Moura, Lucas Antônio Melgaço, Nayara Carolina Quites, and Versiane Albis Leao. "Performance Evaluation of Two Anaerobic Reactors for Removing Sulphate from Industrial Effluents." Advanced Materials Research 825 (October 2013): 491–95. http://dx.doi.org/10.4028/www.scientific.net/amr.825.491.

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Reactors hydrodynamic condition and the choice of substrate are important factors for the optimization and implementation of this sulphate-reducing biological process. This study evaluated two continuous anaerobic reactors, UASB and fluidized bed. The maximum removal achieved by the UASB reactor when operated without recirculation was 65% for a substrate load applied to 3.55 kg/m3 d. When the mass transfer conditions of the reactor were improved by recirculating the biomass, the sulphate removal efficiency increased to 89%, representing a removal rate of 1.94 kg SO42-/m-3 .d-1. Glycerol was used with the carbon and electron source for SRB in the fluidized bed reactor and was compared to the performance with lactate. For the same sulphate load applied, a removal efficiency of 70%-90% was observed, resulting in a residual concentration average of 254 mg/L sulphate. Glycerol, which is a by-product from biodiesel production, is a potential choice as substrate for sulphate reduction.
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Dong, Chun Juan, Tian Tian Zhao, and Qing Ye Pan. "Treatment of Actual Coking Wastewater by Two-Stage EGSB System with Self-Recirculation and Crossed Recirculation." Advanced Materials Research 955-959 (June 2014): 2374–77. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.2374.

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To investigate the possibility of simultaneous high efficient removal of COD and NH3-N in the actual coking wastewater through micro-aerobic granular bio-film reactor, two-stage granular bio-film reactor system (EGSBI+ EGSBII) were continuously operated through two effluent recirculation ways for about 5 months: ERW1(24L.h-1 self-recirculation) and ERW2(15 L.h-1 self-recirculation +15 L.h-1 crossed recirculation). Compared with ERW1, through using ERW2, the two-stage EGSB reactor system could attain high COD and NH3-N removal efficiencies (86.7%-96.9% and 48.6%-80.4%) and low effluent NO2- and NO3- concentrations (0-25mg.L-1 and 7-71mg.L-1). Using ERW1, the two-stage EGSB reactor system melt with difficult of NO2- accumulation in the EGSBII (accompanied with low NH3-N removal of only 41.4%). Using ERW2, the difficult of accumulation in the EGSBII was solved and simultaneously high efficient removal of NH3-N and NO2- in the EGSBI was achieved.
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Hwang, Ping-Chih, and Sheng-Shung Cheng. "Treatment of p-Cresol with a Recirculating UASB Reactor Using the Concept of Kinetic Control." Water Science and Technology 24, no. 5 (September 1, 1991): 133–40. http://dx.doi.org/10.2166/wst.1991.0119.

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A series of batch Biochemical Methane Potential(BMP) tests and an Upflow Anaerobic Sludge Bed (UASB) bioreactor were conducted to investigate the biodegradability of p-cresol.The inhibition of microbes caused by substrate accumulation due to shock loading, recirculating pump turn-off and thermal shock were also studied. The results showed that the microbial activity was inhibited or even poisoned in the high concentration range(1000mg/L) of p-cresol. However, the volumetric loading of the reactor could be maintained relatively high at 8.0 kgCOD/m3·day, if the recirculation of effluent was used to maintain the substrate concentration in the reactor within a suitable range. The concept of so-called kinetic control was proved to be a critical strategy for the treatment of the inhibitory substrate. The results of shock loading, recirculation cessation and thermal shock tests all showed that the concentration control in the reactor would be of vital importance for the treatment of inhibitive compounds with biological processes, and the critical concentration of the highest degradation rate could be estimated with a modified Haldane equation derived from the batch BMP data.
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Donker, H. J. G. W., P. Opic, and H. P. de Vries. "P-Removal in Completely Mixed Systems." Water Science and Technology 17, no. 11-12 (November 1, 1985): 325–26. http://dx.doi.org/10.2166/wst.1985.0254.

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Ca. 60 % of the Dutch activated sludge plants consist of completely mixed systems, experiments have been carried out in completely mixed pilot plants to study the biological P-removal. The research was carried out in two pilot plants. The pilot plants consisted of: anaerobic reactor, anoxic reactor, aerobic reactor and a clarifier. All the reactors were completely mixed. Both plants were fed with settled domestic waste water at a sludge loading of 400 and 250 g COD/kg sludge.day respectively. The results are given below:sludge loading (g COD/kg sludge.day)400400250ratio Anaerobic : Anoxic : Aerobic1: 1:2,71:1:4,11:1:2,7P-removal (%)802875N-removal (%)505065COD-removal (%)858585 It has been shown that there is no significant difference between the results at the two different sludge loadings. Remarkable is the difference between the ratio 1:1:2,7 in combination with the internal recirculation flow anoxic-anaerobic of 160 % and the ratio 1:1:4,1 with a recirculation flow of 30 %. During the start-up at a sludge loading of 250 g COD/kg sludge.day and an internal recirculation flow of 30 %, bulking sludge developed almost immediately. The Premoval was completely disturbed. Increasing the internal recirculation flow to 160% had a positive effect on settling properties and P-removal. This investigation has pointed out that a completely mixed system is suitable for biological P-removal, without negatively affecting the nitrification. Important factors in the process are the ratio anaerobic:anoxic:aerobic and the recirculation flows.
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Dissertations / Theses on the topic "Reactor recirculation"

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Mosquera, Luis G. "Wastewater Disinfection in Enclosed Recirculation Systems with Electromagnetic Waves." ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1752.

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Finding the most cost-effective and environmental friendly way to treat and disinfect wastewater has been raising concerns around the world. Failure in performing disinfection of wastewater before returning it to the environment could have terrible consequences to human health and the ecosystem. The risks associated to continue with current practices have led to the creation of stringent regulations. In this research the HYDROPATH technology is tested while attaching a HydroFlow 60i unit to a reactor that works as a closed recirculation system. To determine the feasibility of the HydroFlow 60i unit as an alternative method to chlorine, the EPA method 1306 is used being Escherichia coli the unit of quantification. After performing several experiments modifying parameters such as conductivity and detention time, it was concluded that the HydroFlow 60i unit by itself would not able to replace current disinfection technologies, to meet EPA standards of E. coli removal.
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Hinks, John William. "The prediction of flow rates in a high recirculation airlift reactor." Thesis, University of Portsmouth, 1996. https://researchportal.port.ac.uk/portal/en/theses/the-prediction-of-flow-rates-in-a-high-recirculation-airlift-reactor(66637c38-034c-4772-801e-738f91f5d405).html.

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Dhaouadi, Hatem. "Étude d'un réacteur à gazosiphon à recirculation externe." Vandoeuvre-les-Nancy, INPL, 1997. http://www.theses.fr/1997INPL030N.

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Deux réacteurs à gazosiphon à recirculation externe sont utilisés pour effectuer une étude hydrodynamique et de transfert de matière. Le premier à 6 m de haut et 0,15 m de diamètre, le second à 2,5 m de haut et 0,1 m de diamètre. Les résultats ont été obtenus avec différents systèmes ; air-eau, air+solutions aqueuses de glycérol et air-eau-billes de verre. Deux types de séparateurs gaz-liquide et de jonction descente-montée ont été étudiés. L’influence du diamètre de la descente à lui aussi été étudié. Les principaux paramètres hydrodynamiques sont estimés en utilisant divers techniques de mesures. Ainsi la rétention de gaz dans la montée a été mesurée en utilisant trois techniques indépendantes ; la méthode volumétrique, la méthode manométrique et la méthode optique. La vitesse de liquide dans la montée est estimée en utilisant des techniques de traçage (thermique et salin). Un modèle hydrodynamique est proposé et la résolution des équations de bilan de matière se fait dans le domaine de temps en utilisant un logiciel de résolution de systèmes d'équation différentielles assez puissant (MODEST). Les paramètres du modèle sont évalués en comparant la courbe expérimentale à la courbe théorique. Le modèle développé pour l'étude hydrodynamique est étendu au transfert de matière et montre une bonne concordance entre les résultats expérimentaux (réponses des sondes mesurant l'oxygène dissout dans le liquide) et le modèle théorique proposé
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de, Souza Althea Caroline. "The use of computational fluid dynamics to simulate the flow in a high recirculation airlift reactor." Thesis, University of Portsmouth, 2000. https://researchportal.port.ac.uk/portal/en/theses/the-use-of-computational-fluid-dynamics-to-simulate-the-flow-in-a-high-recirculation-airlift-reactor(2dd55384-1826-4ef9-8f01-3b6f8e86aaee).html.

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Bosch, Timo [Verfasser], and Angelika [Akademischer Betreuer] Heinzel. "Characterization of a novel radial reactor for a solid oxide fuel cell system with anode off-gas recirculation / Timo Bosch ; Betreuer: Angelika Heinzel." Duisburg, 2018. http://d-nb.info/1174543752/34.

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Stimpson, Curtis K. "The Composition and Morphology of Coal Ash Deposits Collected in an Oxy-Fuel, Pulverized Coal Reactor." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3225.

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Coal ash deposits were collected in a 160 kWth, down-fired oxy-coal reactor under staged and unstaged conditions for four different coals (PRB, Gatling, Illinois #6, and Mahoning). Concentration measurements of carbon, oxygen, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, potassium, calcium, titanium, chromium, manganese, iron, nickel, strontium, and barium were gathered from each deposit sample using scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). Backscattered electron micrographs for each deposit sample were analyzed to gather morphological data. Particle size and shape were studied for each deposit collected. The average particle sizes of the particles in upstream deposits were much larger than the average particle sizes of the downstream deposits. The downstream deposits consisted primarily of spherical particles while the upstream deposits consisted of round, irregular polygonal, and porous particles. Deposit particles are believed to have deposited at all stages of burnout; those depositing early during pyrolysis may have continued to react after deposition. Element maps for the aforementioned elements were collected with SEM-EDS and analyzed to quantify both average composition and composition of individual particles. These values were compared to ASTM ash analyses performed for each coal and ash collected from the flue gas stream with a cyclonic particle separator. It was found that sulfur concentrations of deposits do not correlate with corresponding sulfur concentrations of the coal. Comparison of similar experiments performed with air-combustion show that oxy-combustion deposits contain about twice as much sulfur as air-combustion deposits when burning the same coal. Deposition propensity of each coal was also examined, and the PRB and Gatling coals were found to have a moderately high deposition propensity whereas the deposition propensity of the Mahoning and Illinois #6 coals was fairly low.
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Santana, Roberta Silva de Souza. "Influência da velocidade ascensional e do regime de alimentação em ASBBR para tratamento de águas residuárias de laticínios." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/74/74132/tde-18032013-111649/.

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O presente trabalho teve como objetivo avaliar a influência da velocidade ascensional de recirculação e da estratégia de alimentação na eficiência de um reator anaeróbio com biomassa imobilizada operado em bateladas seqüenciais tratando efluentes provenientes de um laticínio de pequeno porte. Avaliaram-se três condições operacionais com valores de velocidade de 0,2 m.h-1, 3,8 m.h-1 e 6,4 m.h-1, com tempo de ciclo de 48 horas. Finda esta etapa, avaliou-se a influência do volume tratado na eficiência do sistema. Nesta avaliação, o tempo de ciclo foi de 24 horas e estudaram-se duas condições experimentais, nas quais diariamente o reator era alimentado com 50% e 67% de seu volume. O reator, com volume total de 1000 L, foi instalado em área próxima ao laticínio. O suporte (\"biobob\") utilizado para imobilização da biomassa foi um enchimento plástico preenchido com espuma de poliuretano. A alimentação foi feita com efluentes oriundos do laticínio escola da Prefeitura do Campus USP Pirassununga - PUSP-P com carga orgânica variável, de acordo com suas atividades. O monitoramento do reator foi realizado através de análises de demanda química de oxigênio (DQO) em amostras filtradas em membrana de poro 1,2 µm e brutas, nitrogênio total Kjedahl e amoniacal, alcalinidade a bicarbonat o e ácidos voláteis totais. Verificada a estabilidade do sistema, realizaram-se amostragens temporais para medida de concentração de substratos e metabólitos intermediários. A biomassa oriunda do inóculo e do reator nas três primeiras condições experimentais foi analisada através de exames de microscopia de contraste de luz e fluorescência, análises de biologia molecular e atividade metanogênica específica. O período total de monitoramento no estudo da influência da velocidade ascensional de recirculação fo i de 570 dias. As eficiências médias de remoção de matéria orgânica em amostras brutas foram 82 ± 11 %; 84 ± 9%; 87 ± 9 %, quando as velocidades foram de 0,2 m.h-1, 3,8 m.h-1 e 6,4 m.h-1, respectivamente. As eficiências médias de remoção de matéria orgânica em amostras filtradas foram 82 ± 9%; 83 ± 13 %; 87 ± 9 %, quando as velocidades foram de 0,2 m.h-1, 3,8 m.h-1 e 6,4 m.h-1, respectivamente. Não foram verificadas diferenças significativas entre as eficiências de remoção de matéria orgânica à medida que a velocidade ascensional aumentou, todavia percebeu-se diminuição no desvio padrão de tal parâmetro, favorecimento no processo de geração e consumo de ácidos e aumento na velocidade de conversão da matéria orgânica. Os resultados das análises de biologia molecular demonstraram que a biomassa se modificou adaptando-se ao efluente, mas apresentando pouca variação entre as duas últimas condições operacionais. Quando o tempo de ciclo foi diminuído para 24 horas, e o sistema alimentado com 50% e 67% de seu volum e reacional, também não se verificou diferenças significativas em relação à eficiência de remoção de matéria orgânica, todavia a última condição operacional a que proporcionou maior volume de efluente tratado por dia. Conclui-se que o ASBBR foi eficiente, robusto e confiável para o tratamento de efluentes de laticínios nas condições de operações testadas.
The aim of the present study was to evaluate the influence of the recirculation rate and feed strategy on the efficiency of an Anaerobic Sequencing Batch Biofilm Reactor - ASBBR -treating effluents from a small dairy industry. Three operational conditions were studied in which the recirculation rate was 0.2 m.h-1, 3.8 m.h-1 e 6.4 m.h-1 and the cycle time was 48 h. When this assay was finished, the cycle time was decreased to 24 hours and two operational conditions were studied, in which the reactor was fed with 50% and 67% of its reaction volume, respectively. The reactor with total volume of 1000L was assembled in an area closed to the dairy. The biomass was immobilized in plastic supports containing polyurethane foam. The reactor was fed by effluents from the dairy school ( Prefeitura do Campus USP Pirassununga - PUSP-P) with organic loading rate variable according to the operations occurred in the plant. The system was monitored through chemical oxygen demand (COD) analyses, and measurements of nitrogen, alkalinity and volatile acids concentrations. When stability was verified, temporal profiles of substrate and metabolites concentrations were obtained. The biomass from the inoculum and from the reactor (operational conditions 1, 2 and 3) was analyzed through microscopic exams, molecular biology analyses and specific methanogenic activity assays. The monitoring period for the study of the influence of the recirculation rate lasted 570 days. The average efficiencies of organic matter removal were 82 ± 11 %; 84 ± 9%; 87 ± 9 %, when the velocities were 0.2 m.h-1, 3.8 m.h-1 e 6.4 m.h-1, respectively. The average efficiencies of organic matter removal in filtrated samples were 82 ± 9%; 83 ± 13 %; 87 ± 9 % when the velocities were 0.2 m.h-1, 3.8 m.h-1 e 6.4 m.h-1, respectively. Statistic differences were not verified; nevertheless it was possible to observe that the values of standard errors decreased, the production and consumption of the volatile acids improved and the rate of organic matter removal increased when the velocity was rose. The results from the molecular biology analyses showed that the biomass changed and adapted to the treatment conditions, presenting low variation along the last condition. When the cycle time was decreased to 24 hours, and the system was fed with 50% and 67%, statistic difference among the efficiencies were again not observed, nevertheless, the latter condition resulted in the highest daily treated volume. It was possible to conclude that the ASBBR was efficient, robust and reliable in treating dairy effluents at the practiced conditions.
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Sánchez, Ortiz Iván Andrés. "Remoção de nitrogênio de água residuária de produção intensiva de tilápias com recirculação utilizando reator de leito fluidizado com circulação em tubos concêntricos /." Ilha Solteira : [s.n.], 2009. http://hdl.handle.net/11449/98076.

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Orientador: Tsunao Matsumoto
Banca: Francisco Javier Cuba Teran
Banca: Rejane Helena Ribeiro Costa
Resumo: O presente projeto de pesquisa avaliou o desempenho de remoção de nitrogênio num sistema de tratamento biológico das águas residuárias de produção intensiva de Tilápia Nilótica com recirculação utilizando decantador horizontal e um reator aeróbio de leito fluidizado com circulação em tubos concêntricos. Utilizou-se como material suporte carvão ativado granular com densidade aparente de 1,64g/cm3 e tamanho efetivo de 0,34mm numa concentração de 80g/L. Foram avaliadas as velocidades de circulação e as expansões de quatro configurações de reatores com diâmetro externo constante de 250mm e diâmetros internos variáveis de 100, 125, 150 e 200mm. O reator utilizado no sistema de tratamento possui um volume efetivo de 113L e diâmetro interno de 100mm. O sistema foi inoculado durante três semanas com água do Lago do Ipê do município de Ilha Solteira SP e foi feita a avaliação ao longo de oito semanas com reposição semanal de 55% do volume total de água do sistema; o período de detenção hidráulica no reator foi de 11,9 minutos. Durante o projeto foram monitorados os seguintes parâmetros: sólidos totais, suspensos voláteis e fixos, cor aparente, OD, pH, condutividade, temperatura, potencial redox, amônia, amônio, turbidez, DQO, DBO, nitrogênio total, fósforo total. Os resultados mostraram que as remoções médias de nitrogênio amoniacal total, DBO, DQO, fósforo e nitrogênio total foram de 27%, 47%, 75%, 38% e 24% respectivamente. O sistema de tratamento avaliado mostrou-se como uma alternativa efetiva para o reuso da água no sistema de recirculação capaz de manter as características de qualidade da água dentro dos valores recomendáveis para criação das Tilápias e dos valores permitidos pela legislação brasileira para lançamento de efluentes com exceção do fósforo.
Abstract: This research project evaluated the nitrogen removal efficiency in a biological treatment system of an intensive Nile Tilapia laboratory facility with recirculation by a rectangular sedimentation tank and a three phase aerobic fluidized bed internal-loop airlift reactor. Granular activated carbon was used as support particles with density of 1,64g/cm3 and effective size of 0,34mm in a concentration of 80g/L. Liquid circulation velocities and gas holdup were evaluated in four different reactor configurations with a 250mm constant external diameter and internal variable diameters of 100, 125, 150 and 200mm. On the evaluated reactor the effective volume was 113L and the internal diameter 100mm. The system was inoculated during three weeks with natural water from Ipê Lake localized in Ilha Solteira's SP municipality and was evaluated in an eigth week period with a 55% weekly total water exchange rate; reactor's hydraulic detention time was 11,9 minutes. During the study were measured the next parameters: total, suspended, volatile and fixed solids, apparent color, DO, pH, conductivity, temperature, oxidation reduction potential, ammonia, turbidity, COD, BOD, total nitrogen, total phosphorous. Results showed that average removal rates of total ammonia nitrogen, BOD, COD, phosphorus and total nitrogen were 27%, 47%, 75%, 38% and 24% respectively. Evaluated treatment system showed as an effective alternative for water reuse in the recirculation system capable of maintain water quality characteristics within the recommended values for fish farming and meeting the Brazilian standards for final effluent discharges with exception of phosphorous values.
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9

Lima, Daniel Moureira Fontes. "Influência da razão de recirculação na produção de hidrogênio em reator anaeróbio de leito fixo." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-11052011-091202/.

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A presente pesquisa avaliou diferentes razões de recirculação do meio líquido com a finalidade de identificar a melhor condição de mistura para uma produção elevada e contínua de hidrogênio em um reator anaeróbio de leito fixo com fluxo ascendente alimentado com um meio contendo sacarose como fonte de carbono e uréia como fonte de nitrogênio. Foi utilizado polietileno de baixa densidade como meio suporte para imobilização da biomassa. O experimento foi iniciado com ensaios hidrodinâmicos (pulso, utilizando dextran blue como traçador) que determinaram as seguintes razões de recirculação em relação à vazão de alimentação utilizadas: R = 0,25, 0,5, 1,0 e 2,0. O experimento foi realizado em duas etapas, nas quais foram operados dois reatores idênticos simultaneamente, testando-se duas razões de recirculação diferentes. A DQO da água residuária foi de 2000 mg/L. O tempo de detenção hidráulica teórico foi de 2 horas e a temperatura foi mantida em 25 graus Celsius. A remoção de sacarose apresentou valores médios de 67%, 79%, 71% e 70% para R = 0,25, 0,5, 1,0 e 2,0, respectivamente. Os valores médios de rendimento de hidrogênio foram 1,14 mol \'H IND.2\'/mol sac, 1,43 mol \'H IND.2\'/mol sac, 1,34 mol \'H IND.2\'/mol sac e 0,86 mol \'H IND.2\'/.mol sac e de produção volumétrica de hidrogênio foram 74,34 mL \'H IND.2\'/(h.L), 124,78 mL \'H IND.2\'/(h.L), 96,57 mL \'H IND.2\'/(h.L) e 73,49 mL \'H IND.2\'/(h.L) para as vazões de recirculação de 0,25, 0,5, 1,0 e 2,0, respectivamente. O biogás produzido foi composto de \'H IND.2\', e \'CO IND.2\', com valores percentuais médios para \'H IND.2\', de 50%, 56%, 56% e 46% para R = 0,25, 0,5, 1,0 e 2,0, respectivamente. Não houve presença de metano em nenhuma fase de operação. Os principais produtos intermediários produzidos durante a produção de \'H IND.2\', foram ácido acético, ácido butírico e etanol, de forma similar para todas as fases de recirculação. Analisando todos os parâmetros de operação, foi possível notar que a melhor vazão de recirculação obtida foi de R = 0,5. Ajustando os dados obtidos a uma função polinomial, porém, chegou-se a um ponto de ótimo em R = 0,6. Durante os experimentos observou-se uma queda na produção do biogás, provavelmente por atuação de microrganismos consumidores deste.
The present research evaluated different recirculation rates of the liquid medium for the purpose of identify the best mixture condition for a high and continuous hydrogen production in an anaerobic upflow fixed-bed reactor fed with a medium containing sucrose as carbon source and urea as nitrogen source. Low density polyethylene was used as medium for biomass immobilization. The experiment began with hydrodynamic tests (pulse, using dextran blue as tracer) which led to the following recirculation rates related with the feed flow rate used in this work: R = 0,25, 0,5, 1,0 and 2,0. The experiment was conducted in two stages, where two identical reactors were operated simultaneously, by testing two different recirculation rates. COD from wastewater was 2000 mg/L. The theoretical hydraulic retention time was 2 hours and the temperature was maintained at 25 Celsius degrees. The average values of sucrose consumption were 67%, 79%, 71% and 70% for R = 0,25, 0,5, 1,0 and 2,0, respectively. The average values of hydrogen yield were 1,14 mol \'H IND.2\'/mol sac, 1,43 mol \'H IND.2\'/mol sac, 1,34 mol \'H IND.2\'/mol sac and 0,86 mol \'H IND.2\'/mol sac and of hydrogen production rate were 74.34 mL \'H IND.2\'/(h.L), 124.78 mL \'H IND.2\'/(h.L), 96.57 mL \'H IND.2\'/(h.L) and 73.49 mL \'H IND.2\'/(h.L) for recirculation rates of 0.25, 0.5, 1.0 and 2.0, respectively. The biogas produced was composed by \'H IND.2\', and \'CO IND.2\', with average values for \'H IND.2\', of 50%, 56%, 56% and 46% for R = 0,25, 0,5, 1,0 and 2,0, respectively. Methane was not detected. The main intermediate products produced during the hydrogen production were acetic acid, butyric acid and ethanol, similar in all stages of recirculation. Analyzing all operating parameters, it was identified that the better recirculation rate obtained during the experiments was R = 0.5. Adjusting all data obtained with a polynomial function, it was found an optimal recirculation rate of R = 0.6. During the experiments there was a drop in biogas production, probably by the activity of microrganisms consumers of this biogas.
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Vuitik, Guilherme Araujo. "Efeitos da recirculação em reatores anaeróbios compartimentados no tratamento de vinhaça." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-10102017-160442/.

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A digestão anaeróbia é uma potencial solução para a destinação dos grandes volumes de vinhaça gerada em biorrefinarias de cana-de-açúcar. A alta concentração de matéria orgânica presente na vinhaça é uma questão importante a ser considerada, uma vez que as populações microbianas anaeróbias, principalmente metanogênicas, são sensíveis a sobrecargas orgânicas. Uma série de configurações de reatores, bem como diferentes estratégias de partida e operação tem sido aplicadas ao tratamento de vinhaça, como a recirculação do efluente tratado, a qual é usualmente empregada para prevenir eventos de sobrecarga orgânica. O objetivo deste estudo foi determinar a influência da recirculação de efluentes em reatores anaeróbios compartimentados (RAC) tratando águas residuárias concentradas, uma vez que a literatura não é conclusiva sobre os efeitos da recirculação neste tipo de reator. Para atingir esse objetivo, foi utilizada uma abordagem dupla: experimental e modelagem matemática. Um RAC com 4 compartimentos em série em escala de bancada foi alimentado com vinhaça de cana-de-açúcar (DQO = 18,0 g/L) e monitorado durante 273 dias. Os parâmetros cinéticos e de transferência de massa do reator foram obtidos e utilizados para criar um modelo matemático para a conversão da matéria orgânica no software Matlab®. Tanto os dados operacionais como os parâmetros cinéticos mostraram que a elevada concentração de DQO fez com que o RAC não se comportasse como um sistema de duas fases, bem como a recirculação não resultasse em melhorias relevantes de desempenho. O modelo matemático concordou com os dados operacionais e mostrou que, em termos de capacidade de conversão, o uso de elevadas taxas de recirculação não é necessário para um adequado desempenho do RAC, uma vez que a cinética bioquímica observada não foi expressivamente limitada pela concentração de substrato.
Anaerobic digestion is a potential approach to handle the large volume of vinasse generated in sugarcane biorefineries. The high concentration of organic matter present in vinasse is an important issue to be considered, since anaerobic microbial populations, mainly methanogens, are sensitive to organic overloads. A serie of reactors configurations, as well as different startup and operating strategies, have been applied to the treatment of vinasse, so that the recirculation of the treated effluent is usually used to prevent organic overloading events. The aim of this study was to determine the influence of effluent recirculation in anaerobic baffled reactors (ABR) treating high concentrated wastewater, since literature is not conclusive about its effects. To achieve this aim an experimental and mathematical modeling dual approach was employed. A bench-scale ABR with four serial baffleds was fed with sugarcane vinasse (COD = 18,0 g/L) and monitored for 273 days. Kinetic and mass transfer parameters were obtained and used to create a mathematical model for the organic matter conversion in Matlab®. Both the operating data and the kinetic parameters showed that at high COD concentrations the ABR does not behave as a two-stage system, as well as recirculation did not result in relevant performance improvements. The mathematical model agreed with the operational data and showed that, in terms of conversion capacity, the use of high recirculation ratios is not necessary for suitable ABR performance, since the observed biochemical kinetics were not high limited by the concentration of substrate.
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Books on the topic "Reactor recirculation"

1

Duce, S. W. Radionuclide buildup in BWR reactor coolant recirculation piping. Washington, D.C: Division of Engineering, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1989.

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Hinks, John William. The prediction of flow rates in a high recirculation airlift reactor. Portsmouth: University of Portsmouth, 1996.

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Souza, Althea Caroline De. The use of computational fluid dynamicsto simulate the flow in a high recirculation airlift reactor. Portsmouth: University of Portsmouth, 1999.

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Holman, Garry S. Application of reliability techniques to prioritize BWR recirculation loop welds for in-service inspection. Washington, DC: Division of Engineering, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1989.

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U.S. Nuclear Regulatory Commission. Office of Nuclear Regulatory Research., ed. Draft regulatory guide DG-1038: Water sources for long-term recirculation cooling following a loss-of-coolant accident. 2nd ed. [Washington, D.C.]: U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, 1995.

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J, García García, López Montero J. V, U.S. Nuclear Regulatory Commission. Office of Nuclear Regulatory Research., and NUCLENOR S. A, eds. Assessment of single recirculation pump trip transient in Santa Maria de Garona Nuclear Power Plant with TRAC-BF1/MOD1, version 0.4. Washington, DC: Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 2001.

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Assessment of single recirculation pump trip transient in Santa Maria de Garona Nuclear Power Plant with TRAC-BF1/MOD1, version 0.4. Washington, DC: Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 2001.

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Assessment of single recirculation pump trip transient in Santa Maria de Garona Nuclear Power Plant with TRAC-BF1/MOD1, version 0.4. Washington, DC: Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 2001.

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Draft regulatory guide DG-1107: Water sources for long-term recirculation cooling following a loss-of-coolant accident : (proposed revision 3 to Regulatory Guide 1.82). [Washington, D.C.]: U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, 2003.

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Draft regulatory guide DG-1107: Water sources for long-term recirculation cooling following a loss-of-coolant accident : (proposed revision 3 to Regulatory Guide 1.82). [Washington, D.C.]: U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, 2003.

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Book chapters on the topic "Reactor recirculation"

1

Saiki, K., T. Iikura, K. Matsumoto, H. Komita, M. Kobayashi, T. Saito, and H. Tanaka. "Performance Comparison of Nuclear Reactor Recirculation Pumps Tested under Large Reynolds Number Difference." In Hydraulic Machinery and Cavitation, 1083–92. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-010-9385-9_110.

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Brereton, C., J. R. Grace, C. J. Lim, and J. Zhu. "Engineering Aspects of Recirculating Fluidised Bed Combustion." In Chemical Reactor Technology for Environmentally Safe Reactors and Products, 507–36. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2747-9_21.

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Korf, S. J., J. A. Roos, P. T. Coolen, J. G. van Ommen, and J. R. H. Ross. "The Oxidative Coupling of Methane in a Recirculating Fast Fluid Bed Reactor." In The European Oil and Gas Conference, 537–43. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-010-9844-1_79.

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"Chapter 5. Research on Recirculation Cooling under Accident Conditions." In Current state of research on pressurized water reactor safety, 35–46. EDP Sciences, 2020. http://dx.doi.org/10.1051/978-2-7598-2165-5-009.

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Contractor, R. M., H. E. Bergna, H. S. Horowitz, C. M. Blackstone, U. Chowdhry, and A. W. Sleight. "Butane Oxidation to Maleic Anhydride in A Recirculating Solids Reactor." In Studies in Surface Science and Catalysis, 645–54. Elsevier, 1988. http://dx.doi.org/10.1016/s0167-2991(09)60694-7.

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CONTRACTOR, R. M. "BUTANE OXIDATION TO MALEIC ANHYDRIDE IN A RECIRCULATING SOLIDS RISER REACTOR." In Circulating Fluidized Bed Technology, 467–74. Elsevier, 1988. http://dx.doi.org/10.1016/b978-0-08-036225-0.50050-2.

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Berezowski, Marek, and Daniel Dubaj. "Chaotic oscillations in a system of two parallel reactors with recirculation of mass." In Computer Aided Chemical Engineering, 377–82. Elsevier, 2003. http://dx.doi.org/10.1016/s1570-7946(03)80144-x.

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"Fenton-like oxidation of phenol with a Cu-chitosan/Al2O3 catalyst in a recirculating batch reactor." In Advanced Oxidation Technologies, 119–36. CRC Press, 2014. http://dx.doi.org/10.1201/b16657-12.

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Machocki, A., and A. Denis. "Oxidative coupling of methane to ethylene in a reaction system with products separation and gas recirculation." In Natural Gas Conversion V, Proceedings ofthe 5th International Natural Gas Conversion Symposium,, 313–18. Elsevier, 1998. http://dx.doi.org/10.1016/s0167-2991(98)80450-3.

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Ali Mergheni, Mohamed, Mohamed Mahdi Belhajbrahim, Toufik Boushaki, and Jean-Charles Sautet. "A New Combustion Method in a Burner with Three Separate Jets." In Numerical and Experimental Studies on Combustion Engines and Vehicles. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.90571.

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Oxy-flames from burners with separated jets present attractive perspectives because the separation of reactants generates a better thermal efficiency and reduction of pollutant emissions. The principal idea is to confine the fuel jet by oxygen jets to favor the mixing in order to improve the flame stability. This chapter concerns the effect of equivalence ratio on characteristics of a non-premixed oxy-methane flame from a burner with separated jets. The burner of 25 kW power is composed with three aligned jets, one central methane jet surrounded by two oxygen jets. The numerical simulation is carried out using Reynolds Average Navier-Stokes (RANS) technique with k-ε as a turbulence closure model. The eddy dissipation model is applied to take into account the turbulence-reaction interactions. The study is performed with different global equivalence ratios (0.7, 0.8 and 1). The validation of the numerical tools is done by comparison with experimental data of the stoichiometric regime (Ф = 1). The two lean regimes of Ф = 0.7 and 0.8 are investigated only by calculations. The velocity fields with different equivalence ratio are presented. It yields to increase of longitudinal and transverse velocity, promotes the fluctuation in interaction zone between fuel and oxygen also a better mixing quality and a decrease of the size of the recirculation zone.
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Conference papers on the topic "Reactor recirculation"

1

Engel, Robert, André Fibier, Jens Heldt, and Andreas Ronecker. "Hydro-Abrasive Wear Damage at Reactor Recirculation Pump Bearing Journals." In ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78489.

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During the refueling and maintenance outage in August 2011 at Leibstadt Nuclear Power Plant in Switzerland, the inspection of the hydrostatic bearings of the two identical recirculation pumps revealed a deep circumferential erosion groove on the inside surface of each of the bearing journals. The bearing journals are made of austenitic stainless steel. The cylindrical journal is welded to the back shroud of the impeller and surrounds the internal stationary heat exchanger of the pump by forming a narrow fluid filled annulus. The location of material removal was the same as in the year 2004 when similar wear damage was fixed by build-up welding. The plant decided to repair the damage during the subsequent outage in 2012. However, the Swiss Federal Nuclear Safety Inspectorate in return required the plant to identify the precise erosion mechanism, to ensure the structural integrity of the journals by taking into account the rate of material removal from 2004 up to the 2012 outage, and to include provisions for the early detection of a journal failure. This paper summarizes the previous as well as the latest results of different inspections, investigations, evaluations, and analyses done to meet the requirements of the Swiss regulatory authority. The results show that, from a safety-related and an operational availability perspective, it is acceptable not to repair the damaged bearing journals prior to the 2012 outage.
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KARCHES, TAMAS. "EFFECT OF INTERNAL RECIRCULATION ON REACTOR MODELS IN WASTEWATER TREATMENT." In WATER POLLUTION 2018. Southampton UK: WIT Press, 2018. http://dx.doi.org/10.2495/wp180151.

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Sommerville, Daniel. "Boiling Water Reactor Recirculation Line Break Acoustic Loads: A Bounding Approach." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97728.

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Recent industry communications have identified issues pertaining to incorrectly calculated recirculation line break acoustic loads or structural evaluations that need to include, but have previously excluded, the recirculation line break acoustic loads. Various organizations have studied the recirculation line break event and have developed methodologies to calculate the decompression loads caused by this event on various boiling water reactor internal components. In general, loads are calculated in a plant specific and operating condition specific manner. Once these loads are available then the necessary structural evaluations can be performed. With the various flexibility options that an operating boiling water reactor can be licensed for it can become difficult to know when the recirculation line break acoustic loads must be updated and subsequently, which structural evaluations must be updated as well. In this paper a simple extension of an existing, benchmarked, acoustic loads methodology is suggested in which a bounding set of input parameters is evaluated in order to predict acoustic loads that will bound all flexibility options that are currently implemented at operating plants. The objective of this approach is to save the utilities time and money by enabling a single iteration of loads calculation and structural analysis. This approach is shown to produce loads that are approximately a factor of 1.5 larger than those predicted using typical operating parameters.
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Molyneux, John, Raju Ananth, and Jay Gillis. "Decompression Pressure Wave Loads in a Boiling Water Reactor (BWR) Due to Recirculation Pipe Break." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77781.

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This paper presents a theoretical and numerical investigation of one of the postulated accidents for Boiling Water Reactors (BWRs), namely, a double-ended guillotine break of recirculation outlet line that leads to a sudden depressurization locally at the recirculation outlet nozzle. The depressurization wave front thus formed will propagate inside the reactor leading to transient loads on the internals. The paper discusses the solution to this wave propagation problem.
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Morgan, James W. "Recirculation Pump Speed Control System Upgrades in Nuclear Boiling Water Reactors." In 16th International Conference on Nuclear Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/icone16-48411.

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The nuclear power industry is faced with determining what to do with equipment and instrumentation reaching obsolescence and selecting the appropriate approach for upgrading the affected equipment. One of the systems in a nuclear power plant that has been a source of poor reliability in terms of replacement parts and control performance is the reactor recirculation pump speed/ flow control system for boiling water reactors (BWR). All of the operating BWR-3 and BWR-4’s use motor-generator sets, with a fluid coupled speed changer, to control the speed of the recirculation water pumps over the entire speed range of the pumps. These systems historically have had high maintenance costs, relative low efficiency, and relatively inaccurate speed control creating unwanted unit de-rates. BWR-5 and BWR-6 recirculation flow control schemes, which use flow control valves in conjunction with two-speed pumps, are also subject to upgrades for improved performance and reliability. These systems can be improved by installing solid-state adjustable speed drives (ASD), also known as variable frequency drives (VFD), in place of the motor-generator sets and the flow control valves. Several system configurations and ASD designs have been considered for optimal reliability and return on investment. This paper will discuss a highly reliable system and ASD design that is being developed for nuclear power plant reactor recirculation water pump controls. Design considerations discussed include ASD topology, controls architecture, accident, transient and hydraulic analyses, potential reactor internals modifications, installation, demolition and economic benefits.
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6

TANEJA, RAJESH, MANISH KUMAR, A. K. RAGHAV, and ATUL K. MITTAL. "ON SITE INTEGRATED LANDFILL LEACHATE TREATMENT: RECIRCULATION AND UPFLOW ANAEROBIC SLUDGE BLANKET REACTOR (UASBR)." In Proceedings of the International Conference on CBEE 2009. WORLD SCIENTIFIC, 2009. http://dx.doi.org/10.1142/9789814295048_0033.

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Cogliati, Joshua J., and Abderrafi M. Ougouag. "Pebble Bed Reactor Dust Production Model." In Fourth International Topical Meeting on High Temperature Reactor Technology. ASMEDC, 2008. http://dx.doi.org/10.1115/htr2008-58289.

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The operation of pebble bed reactors, including fuel circulation, can generate graphite dust, which in turn could be a concern for internal components; and to the near field in the remote event of a break in the coolant circuits. The design of the reactor system must, therefore, take the dust into account and the operation must include contingencies for dust removal and for mitigation of potential releases. Such planning requires a proper assessment of the dust inventory. This paper presents a predictive model of dust generation in an operating pebble bed with recirculating fuel. In this preliminary work the production model is based on the use of the assumption of proportionality between the dust production and the normal force and distance traveled. The model developed in this work uses the slip distances and the inter-pebble forces computed by the authors’ PEBBLES. The code, based on the discrete element method, simulates the relevant static and kinetic friction interactions between the pebbles as well as the recirculation of the pebbles through the reactor vessel. The interaction between pebbles and walls of the reactor vat is treated using the same approach. The amount of dust produced is proportional to the wear coefficient for adhesive wear (taken from literature) and to the slip volume, the product of the contact area and the slip distance. The paper will compare the predicted volume with the measured production rates. The simulation tallies the dust production based on the location of creation. Two peak production zones from intra pebble forces are predicted within the bed. The first zone is located near the pebble inlet chute due to the speed of the dropping pebbles. The second peak zone occurs lower in the reactor with increased pebble contact force due to the weight of supported pebbles. This paper presents the first use of a Discrete Element Method simulation of pebble bed dust production.
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8

Prakash, V., J. Steimes, D. J. E. M. Roekaerts, and S. A. Klein. "Modelling the Effect of External Flue Gas Recirculation on NOx and CO Emissions in a Premixed Gas Turbine Combustor With Chemical Reactor Networks." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76548.

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The increasing amount of renewable energy and emission norms challenge gas turbine power plants to operate at part-load with high efficiency, while reducing NOx and CO emissions. A novel solution to this dilemma is external Flue Gas Recirculation (FGR), in which flue gases are recirculated to the gas turbine inlet, increasing compressor inlet temperature and enabling higher part load efficiencies. FGR also alters the oxidizer composition, potentially leading to reduced NOx levels. This paper presents a kinetic model using chemical reactor networks in a lean premixed combustor to study the impact of FGR on emissions. The flame zone is split in two perfectly stirred reactors modelling the flame front and the recirculation zone. The flame reactor is determined based on a chemical time scale approach, accounting for different reaction kinetics due to FGR oxidizers. The recirculation zone is determined through empirical correlations. It is followed by a plug flow reactor. This method requires less details of the flow field, has been validated with literature data and is generally applicable for modelling premixed flames. Results show that due to less O2 concentration, NOx formation is inhibited down to 10–40% and CO levels are escalated up to 50%, for identical flame temperatures. Increasing combustor pressure leads to a rise in NOx due to thermal effects beyond 1800 K, and a drop in CO levels, due to the reduced chemical dissociation of CO2. Wet FGR reduces NOx by 5–10% and increases CO by 10–20%.
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9

Shiraki, Keisuke, Akira Taniguchi, Takushi Fujino, Shouhei Nakama, Osamu Suzuki, and Hiroyuki Kobayashi. "Experience of Work for Replacing Reactor Recirculation Piping in Narrow Space of MARK-I Containment Vessel." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28367.

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Tsuruga unit-1, the first Japanese commercial BWR (BWR-II, 357MWe) started its operation in 1970, has a Mark-I type containment vessel and 3-loop reactor recirculation piping. In the 33rd planned outage of 2011, most parts of the reactor recirculation piping were replaced to improve corrosion resistance and inspectability. This replacement work dealing with long pipe pieces had to be conducted in limiting condition and severe environment such as the narrow work space, only one small entrance hatch, and high dose rate. In addition, other maintenance works by four contractors were concurrently being carried out in the same area. Therefore, these work processes in the containment vessel were controlled carefully through close coordination with contractors and using advanced construction technique. As a result, it was achieved that efficient process which contributed to shortening work period and injury-free work in this challenging environment and condition. Regarding radiation management, radiation dose rate was reduced substantially by applying chemical decontamination using ozone as chemical agent. Experience obtained from this work is valuable in the current situation that many operators are trying to operate their aging nuclear plants continuously as long as economically viable.
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10

Beerer, David, Vincent McDonell, Scott Samuelsen, and Leonard Angello. "Interpretation of Flow Reactor Based Ignition Delay Measurements." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-60268.

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Compositional variation of global gas supplies is becoming a growing concern. Both the range and rate-of-change of this variation is expected to increase as global markets for Liquefied Natural Gas (LNG) continue to expand. Greater fuel composition variation poses increased operational risk to gas turbine engines employing lean premixed combustion systems. Information on ignition delay at high pressure and intermediate temperatures is valuable for lean premixed gas turbine design. In order to avoid autoignition of the fuel/air mixture within the premixer, the ignition delay time must be greater than the residence time. Evaluating the residence time is not a straight forward task because of the complex aerodynamics due to recirculation zones, separation regions, and boundary layers effects which may create regions where the local residence times may be longer than the bulk or average residence time. Additionally, reliable experiments on ignition delay at gas turbine conditions are difficult to conduct. Devices for testing include shock tubes, rapid compression machine and flow reactors. In a flow reactor ignition delay data are commonly determined by measuring the distance from the fuel injector to the reaction front (L) and dividing it by the bulk or average flow velocity (U) under steady flow conditions to obtain a bulk residence time which is assumed to be equal to the ignition delay time. However this method is susceptible to the same boundary layer effects or recirculation zones found in premixers. An alternative method for obtaining ignition delay data in a flow reactor is presented herein, where ignition delay times are obtained by measuring the time difference between fuel injection and ignition using high speed instrumentation. Ignition delay times for methane, ethane and propane at gas turbine conditions were in the range of 40–500 ms. The results obtained show excellent agreement with recently proposed chemical mechanisms for hydrocarbons at low temperature/high pressure conditions.
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Reports on the topic "Reactor recirculation"

1

Holman, G. Application of reliability techniques to prioritize BWR (boiling water reactor) recirculation loop welds for in-service inspection. Office of Scientific and Technical Information (OSTI), December 1989. http://dx.doi.org/10.2172/5193479.

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