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Artykuły w czasopismach na temat "Cool Core Cycles"
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Prasad, Deovrat, Prateek Sharma, Arif Babul, Gerard M. Voit i Brian W. O’Shea. "Cool-core cycles and Phoenix". Monthly Notices of the Royal Astronomical Society 495, nr 1 (6.05.2020): 594–99. http://dx.doi.org/10.1093/mnras/staa1247.
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ABSTRACT Recent observations show that the star formation rate (SFR) in the Phoenix cluster’s central galaxy is ∼500 M⊙ yr−1. Even though Phoenix is a massive cluster (M200 ≈ 2.0 × 1015 M⊙; z ≈ 0.6) such a high central SFR is not expected in a scenario in which feedback from an active galactic nucleus (AGN) maintains the intracluster medium in a state of rough thermal balance. It has been argued that either AGN feedback saturates in very massive clusters or the central supermassive black hole is too small to produce enough kinetic feedback and hence is unable to quench the catastrophic cooling. In this work, we present an alternate scenario wherein intense short-lived cooling and star formation phases followed by strong AGN outbursts are part of the AGN feedback loop. Using results from a 3D hydrodynamic simulation of a standard cool-core cluster (M200 ∼ 7 × 1014 M⊙; z = 0), scaled to account for differences in mass and redshift, we argue that Phoenix is at the end of a cooling phase in which an AGN outburst has begun but has not yet arrested core cooling. This state of high cooling rate and star formation is expected to last for ≲100 Myr in Phoenix.
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Prasad, Deovrat, Prateek Sharma i Arif Babul. "COOL CORE CYCLES: COLD GAS AND AGN JET FEEDBACK IN CLUSTER CORES". Astrophysical Journal 811, nr 2 (28.09.2015): 108. http://dx.doi.org/10.1088/0004-637x/811/2/108.
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Ferland, Marie A., Peter S. Roy i Colin V. Murray-Wallace. "Glacial Lowstand Deposits on the Outer Continental Shelf of Southeastern Australia". Quaternary Research 44, nr 2 (wrzesień 1995): 294–99. http://dx.doi.org/10.1006/qres.1995.1074.
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AbstractVibracores collected from water depths of 130 to 150 m on the outer continental shelf of southeastern Australia contain evidence for several cycles of shallow marine deposition. One of these vibracores (112/VC/134; lat. 33°24′S, long, 151°58′ E) preserves evidence for the last three glacial lowstands, as inferred from radiocarbon dating, amino acid racemization, and fossil mollusc assemblages. The core contains the inner-shelf molluscs Pecten fumatus, Placamen placidium, and Tawera gallinula, which today live in water depths of 10 to 50 m, in the cool waters of southern Australia. Radiocarbon dating and amino acid racemization analyses on multiple valves of P. fumatus in the core indicate three distinct age groupings of fossil molluscs: (1) those younger than 20,000 yr B.P., (2) those with minimum ages of about 100,000 yr, and (3) those with minimum ages of about 200,000 yr. We assign these sediments to oxygen isotope stages 2, 6, and 8, respectively. The core contains the first shallow-marine lowstand deposits to be recovered from the shelf of eastern Australia. These deposits constrain the last three glacial lowstands on this margin to water depths <130 m below present sea level.
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Schellenberger, Gerrit, Ewan O’Sullivan, Simona Giacintucci, Jan Vrtilek, Laurence P. David, Francoise Combes, Laura Bîrzan, Hsi-An Pan i Lihwai Lin. "Feedback in the Extremely Violent Group Merger NGC 6338". Astrophysical Journal 948, nr 2 (1.05.2023): 101. http://dx.doi.org/10.3847/1538-4357/acc52e.
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Abstract The galaxy group NGC 6338 is one of the most violent group–group mergers known to date. While the central dominant galaxies rush at each other at 1400 km s−1 along the line of sight, with dramatic gas heating and shock fronts detected, the central gas in the BCGs remains cool. There are also indications of feedback from active galactic nuclei, and neither subcluster core has been disrupted. With our deep radio uGMRT data at 383 and 650 MHz, we clearly detect a set of large, old lobes in the southern BCG coinciding with the X-ray cavities, while the northern and smaller BCG appears slightly extended in the radio. The southern BCG also hosts a smaller younger set of lobes perpendicular to the larger lobes, but also coinciding with the inner X-ray cavities and matching the jet direction in the parsec-resolution VLBA image. Our spectral analysis confirms the history of two feedback cycles. The high radio frequency analysis classifies the compact source in the southern BCG with a power law, while ruling out a significant contribution from accretion. The radio lightcurve over three decades shows a change about 10 yr ago, which might be related to ongoing feedback in the core. The southern BCG in the NGC 6338 merger remains another prominent case where the direction of jet-mode feedback between two cycles changed dramatically.
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Cielo, S., A. Babul, V. Antonuccio-Delogu, J. Silk i M. Volonteri. "Feedback from reorienting AGN jets". Astronomy & Astrophysics 617 (wrzesień 2018): A58. http://dx.doi.org/10.1051/0004-6361/201832582.
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Aims. We test the effects of re-orienting jets from an active galactic nucleus (AGN) on the intracluster medium in a galaxy cluster environment with short central cooling time. We investigate both the appearance and the properties of the resulting cavities, and the efficiency of the jets in providing near-isotropic heating to the cooling cluster core. Methods. We use numerical simulations to explore four models of AGN jets over several active/inactive cycles. We keep the jet power and duration fixed across the models, varying only the jet re-orientation angle prescription. We track the total energy of the intracluster medium (ICM) in the cluster core over time, and the fraction of the jet energy transferred to the ICM. We pay particular attention to where the energy is deposited. We also generate synthetic X-ray images of the simulated cluster and compare them qualitatively to actual observations. Results. Jets whose re-orientation is minimal (≲20°) typically produce conical structures of interconnected cavities, with the opening angle of the cones being ~15–20°, extending to ~300 kpc from the cluster centre. Such jets transfer about 60% of their energy to the ICM, yet they are not very efficient at heating the cluster core, and even less efficient at heating it isotropically, because the jet energy is deposited further out. Jets that re-orientate by ≳20° generally produce multiple pairs of detached cavities. Although smaller, these cavities are inflated within the central 50 kpc and are more isotropically distributed, resulting in more effective heating of the core. Such jets, over hundreds of millions of years, can deposit up to 80% of their energy precisely where it is required. Consequently, these models come the closest in terms of approaching a heating/cooling balance and mitigating runaway cooling of the cluster core even though all models have identical jet power/duration profiles. Additionally, the corresponding synthetic X-ray images exhibit structures and features closely resembling those seen in real cool-core clusters.
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Donders, Timme, Konstantinos Panagiotopoulos, Andreas Koutsodendris, Adele Bertini, Anna Maria Mercuri, Alessia Masi, Nathalie Combourieu-Nebout i in. "1.36 million years of Mediterranean forest refugium dynamics in response to glacial–interglacial cycle strength". Proceedings of the National Academy of Sciences 118, nr 34 (16.08.2021): e2026111118. http://dx.doi.org/10.1073/pnas.2026111118.
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The sediment record from Lake Ohrid (Southwestern Balkans) represents the longest continuous lake archive in Europe, extending back to 1.36 Ma. We reconstruct the vegetation history based on pollen analysis of the DEEP core to reveal changes in vegetation cover and forest diversity during glacial–interglacial (G–IG) cycles and early basin development. The earliest lake phase saw a significantly different composition rich in relict tree taxa and few herbs. Subsequent establishment of a permanent steppic herb association around 1.2 Ma implies a threshold response to changes in moisture availability and temperature and gradual adjustment of the basin morphology. A change in the character of G–IG cycles during the Early–Middle Pleistocene Transition is reflected in the record by reorganization of the vegetation from obliquity- to eccentricity-paced cycles. Based on a quantitative analysis of tree taxa richness, the first large-scale decline in tree diversity occurred around 0.94 Ma. Subsequent variations in tree richness were largely driven by the amplitude and duration of G–IG cycles. Significant tree richness declines occurred in periods with abundant dry herb associations, pointing to aridity affecting tree population survival. Assessment of long-term legacy effects between global climate and regional vegetation change reveals a significant influence of cool interglacial conditions on subsequent glacial vegetation composition and diversity. This effect is contrary to observations at high latitudes, where glacial intensity is known to control subsequent interglacial vegetation, and the evidence demonstrates that the Lake Ohrid catchment functioned as a refugium for both thermophilous and temperate tree species.
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Irving, Zackery A., Steven H. Saar, Bradford J. Wargelin i José-Dias do Nascimento. "Stellar Cycles in Fully Convective Stars and a New Interpretation of Dynamo Evolution". Astrophysical Journal 949, nr 2 (1.06.2023): 51. http://dx.doi.org/10.3847/1538-4357/acc468.
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Abstract An αΩ dynamo, combining shear and cyclonic convection in the tachocline, is believed to generate the solar cycle. However, this model cannot explain cycles in fast rotators (with minimal shear) or in fully convective stars (no tachocline); an analysis of these stars could therefore provide key insights into how these cycles work. We reexamine ASAS data for 15 M dwarfs, 11 of which are presumed fully convective; the addition of newer ASAS-SN data confirms cycles in roughly 12 of them, while presenting new or revised rotation periods for 5 stars. The amplitudes and periods of these cycles follow A cyc ∝ P cyc 0.94 ± 0.11 , with P cyc/P rot ∝ Ro −1.02±0.06 (where Ro is the Rossby number), very similar to P cyc/P rot ∝ Ro −0.81±0.17 that we find for 40 previously studied FGK stars, although P cyc/P rot and α are a factor of ∼20 smaller in the M stars. The very different P cyc/P rot–Ro relation seen here compared to previous work suggests that two types of dynamo, with opposite Ro dependences, operate in cool stars. Initially, a (likely α 2 or α 2Ω) dynamo operates throughout the convective zone in mid- to late-M and fast-rotating FGK stars, but once magnetic breaking decouples the core and convective envelope, a tachocline αΩ dynamo begins and eventually dominates in older FGK stars. A change in α in the tachocline dynamo generates the fundamentally different P cyc/P rot–Ro relation.
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Walker, Anthony, Matthew Driller, Matt Brearley, Christos Argus i Ben Rattray. "Cold-water immersion and iced-slush ingestion are effective at cooling firefighters following a simulated search and rescue task in a hot environment". Applied Physiology, Nutrition, and Metabolism 39, nr 10 (październik 2014): 1159–66. http://dx.doi.org/10.1139/apnm-2014-0038.
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Firefighters are exposed to hot environments, which results in elevated core temperatures. Rapidly reducing core temperatures will likely increase safety as firefighters are redeployed to subsequent operational tasks. This study investigated the effectiveness of cold-water immersion (CWI) and iced-slush ingestion (SLUSH) to cool firefighters post-incident. Seventy-four Australian firefighters (mean ± SD age: 38.9 ± 9.0 years) undertook a simulated search and rescue task in a heat chamber (105 ± 5 °C). Testing involved two 20-min work cycles separated by a 10-min rest period. Ambient temperature during recovery periods was 19.3 ± 2.7 °C. Participants were randomly assigned one of three 15-min cooling protocols: (i) CWI, 15 °C to umbilicus; (ii) SLUSH, 7 g·kg−1 body weight; or (iii) seated rest (CONT). Core temperature and strength were measured pre- and postsimulation and directly after cooling. Mean temperatures for all groups reached 38.9 ± 0.9 °C at the conclusion of the second work task. Both CWI and SLUSH delivered cooling rates in excess of CONT (0.093 and 0.092 compared with 0.058 °C·min−1) and reduced temperatures to baseline measurements within the 15-min cooling period. Grip strength was not negatively impacted by either SLUSH or CONT. CWI and SLUSH provide evidence-based alternatives to passive recovery and forearm immersion protocols currently adopted by many fire services. To maximise the likelihood of adoption, we recommend SLUSH ingestion as a practical and effective cooling strategy for post-incident cooling of firefighters in temperate regions.
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Stevens, Lora R., Jeffery R. Stone, Josh Campbell i Sherilyn C. Fritz. "A 2200-yr record of hydrologic variability from Foy Lake, Montana, USA, inferred from diatom and geochemical data". Quaternary Research 65, nr 02 (marzec 2006): 264–74. http://dx.doi.org/10.1016/j.yqres.2005.08.024.
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AbstractA 2200-yr long, high-resolution (∼5 yr) record of drought variability in northwest Montana is inferred from diatoms and δ18O values of bio-induced carbonate preserved in a varved lacustrine core from Foy Lake. A previously developed model of the diatom response to lake-level fluctuations is used to constrain estimates of paleolake levels derived from the diatom data. High-frequency (decadal) fluctuations in the de-trended δ18O record mirror variations in wet/dry cycles inferred from Banff tree-rings, demonstrating the sensitivity of the oxygen-isotope values to changes in regional moisture balance. Low frequency (multi-centennial) isotopic changes may be associated with shifts in the seasonal distribution of precipitation. From 200 B.C. to A.D. 800, both diatom and isotope records indicate that climate was dry and lake level low, with poor diatom preservation and high organic carbon: nitrogen ratios. Subsequently, lake level rose slightly, although the climate was drier and more stable than modern conditions. At A.D. 1200, lake level increased to approximately 6 m below present elevation, after which the lake fluctuated between this elevation and full stage, with particularly cool and/or wetter conditions after 1700. The hydrologic balance of the lake shifted abruptly at 1894 because of the establishment of a lumber mill at the lake's outlet. Spectral analysis of the δ18O data indicates that severe droughts occurred with multi-decadal (50 to 70 yr) frequency.
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Desprat, S., M. F. Sánchez Goñi, J. F. McManus, J. Duprat i E. Cortijo. "Millennial-scale climatic variability between 340 000 and 270 000 years ago in SW Europe: evidence from a NW Iberian margin pollen sequence". Climate of the Past 5, nr 1 (6.03.2009): 53–72. http://dx.doi.org/10.5194/cp-5-53-2009.
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Abstract. We present a new high-resolution marine pollen record from NW Iberian margin sediments (core MD03-2697) covering the interval between 340 000 and 270 000 years ago, a time period centred on Marine Isotope Stage (MIS) 9 and characterized by particular baseline climate states. This study enables the documentation of vegetation changes in the north-western Iberian Peninsula and therefore the terrestrial climatic variability at orbital and in particular at millennial scales during MIS 9, directly on a marine stratigraphy. Suborbital vegetation changes in NW Iberia in response to cool/cold events are detected throughout the studied interval even during MIS 9e ice volume minimum. However, they appear more frequent and of higher amplitude during the 30 000 years following the MIS 9e interglacial period and during the MIS 9a-8 transition, which correspond to intervals of an intermediate to high ice volume and mainly periods of ice growth. Each suborbital cold event detected in NW Iberia has a counterpart in the Southern Iberian margin SST record. High to moderate amplitude cold episodes detected on land and in the ocean appear to be related to changes in deep water circulation and probably to iceberg discharges at least during MIS 9d, the mid-MIS 9c cold event and MIS 9b. This work provides therefore additional evidence of pervasive millennial-scale climatic variability in the North Atlantic borderlands throughout past climatic cycles of the Late Pleistocene, regardless of glacial state. However, ice volume might have an indirect influence on the amplitude of the millennial climatic changes in Southern Europe.
Części książek na temat "Cool Core Cycles"
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Vega-Coloma, Mabel, i Claudio Zaror. "The Life Cycle Sustainability Indicators for Electricity Generation in Chile: Challenges in the Use of Primary Information". W Towards a Sustainable Future - Life Cycle Management, 229–39. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-77127-0_21.
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AbstractThe need to get an appropriate quantification of the sustainability indicators involves the use of site-specific information that could come from several sources, affecting its quality. This study analyses the quality and sources to build eight environmental, seven social and four economic indicators for eight electricity generation technologies in 2005, 2009 and 2015 as reference years, following the ISO 14.040-44:2006 life cycle assessment approach. The results show for the three dimensions important differences among the periods, reaching over 400% of reduction in 2015 in case of acidification for coal power plants, thanks to environmental regulations. For levelized electricity cost and corruption index, the variations reach around 40% and 30%, mainly for fossil fuel-based power plants. These changes support the need to have a centralized, reliable and accurate data system of registration, in order to contribute to the sustainability of the electricity system in Chile.
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Garber, Michael G. "“Bill Bailey, Won’t You Please Come Home?”". W My Melancholy Baby, 41–69. University Press of Mississippi, 2021. http://dx.doi.org/10.14325/mississippi/9781496834294.003.0002.
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This chapter presents a history, reception study, and analysis of “Bill Bailey, Won’t You Please Come Home?” (Hughie Cannon, 1902). The discussion establishes the relationship of this comic rhythm song to a long line of previous and later coon songs, proto-blues, love ballads, and torch songs. It details the “Bill Bailey” song cycle, initiated by the collective innovation of the creative circle surrounding Cannon. Details are presented of the song’s popularity, folk traditions, revival as the quintessential Las Vegas number, and incorporation (including as a lullaby) in movies and in literature by George Bernard Shaw, Edith Nesbit, and Edgardo Vega Yunqué. The cheerful melody and bemoaning lyrics are analyzed. The survey of performances encompasses renditions by Bobby Darin, Ella Fitzgerald, Della Reese, Nellie Lutcher, Nancy Wilson, Ann-Margret, Patsy Cline, and many others, revealing intriguing performance traditions, such as that one-seventh shift blame from the woman to the man.
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Blaauw, Derick, Anmar Pretorius i Rinie Schenck. "Socio-economic Dynamics of the Informal Economy". W Coal and Energy in South Africa, 160–75. Edinburgh University Press, 2021. http://dx.doi.org/10.3366/edinburgh/9781474487054.003.0012.
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The well-being of Emalahleni’s residents is linked to the boom and bust cycles faced by the local economy. Many people who lose their jobs as a result of this are forced to seek income earning opportunities in the informal economy and day labouring is one of these employment seeking strategies. This chapter investigates the dynamics and changes in the day labour market to provide a micro-perspective of the impact of mine closures and shrinking businesses on the local economy. Two comparable surveys conducted in 2008 and 2018 reveal that the absolute number of day labourers and the proportion of foreigners increased significantly; unemployment is as high as 86% and real and reservation wages have decreased as result of the oversupply and limited demand. The increased supply in the day labour markets with limited demand will undoubtedly influence lives and livelihoods of the day labourers in Emalahleni in the years to come.
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Tchagnaou, Akimou. "Principes d’organisation scolaire : problématique de la répartition des effectifs d’élèves par classe dans des CEG de Lomé". W Langues, formations et pédagogies : le miroir africain, 105–24. Observatoire européen du plurilinguisme, 2018. http://dx.doi.org/10.3917/oep.agbef.2018.02.0105.
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La répartition des élèves par classe relève de l’organisation de l’école, du collège ou du lycée. Elle est soumise à des contraintes administratives qui, par principe, sont supposées être objectives et logiques. Mais s’agissant des CEG de Lomé, cette situation exige une réflexion puisqu’au fur et à mesure qu’on évolue dans le système partant des classes de sixième aux classes de troisième, il y a une réduction systématique du nombre de classes. L’importance des effectifs à l’entrée du premier cycle du secondaire n’impulse aucunement l’accroissement des infrastructures d’accueil.
Streszczenia konferencji na temat "Cool Core Cycles"
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Longinos, Sotirios, Lei Wang, Anna Loskutova, Dichuan Zhang i Randy Hazlett. "Cyclic LN2 Treatment of Coal Samples from Coal Basin in Kazakhstan". W SPE EuropEC - Europe Energy Conference featured at the 83rd EAGE Annual Conference & Exhibition. SPE, 2022. http://dx.doi.org/10.2118/209697-ms.
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Abstract In recent years liquid nitrogen (LN2) fracturing technology has been investigated as a promising stimulating technique in coalbed methane (CBM) development. Using the immersion method, this study experimentally examines and illustrates the efficacy of LN2 cryogenic fracturing for a CBM reservoir in the Karaganda Basin of East Kazakhstan. Coal core plugs were frozen with LN2 under different lab-controlled conditions like the length freezing time (FT) and the number of freezing thawing cycles (FTC). Then these treated core plugs were subjected to uniaxial compressive strength test and SEM analysis for comparisons. The results from SEM analysis showed that the LN2 freezing-thawing process can augment the cryogenic fracture and the fracture interconnectivity. Moreover, uniaxial compressive test indicated that compressive strength is kept decreasing with successively increasing the number of freezing-thawing cycles and the same decreasing trend was observed with freezing time experiments compared with the coal sample without liquid nitrogen case.
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Lu, Xijia, Brock Forrest, Scott Martin, Jeremy Fetvedt, Michael McGroddy i David Freed. "Integration and Optimization of Coal Gasification Systems With a Near-Zero Emissions Supercritical Carbon Dioxide Power Cycle". W ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-58066.
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The Allam Cycle is a semi-closed, recuperated, oxy-fuel, supercritical carbon dioxide (sCO2) Brayton power cycle, offering advantages over simple cycle and combined cycle arrangements. The Allam Cycle uniquely combines oxy-combustion with a substantially elevated operating pressure, high sCO2 recirculation flow, high gross turbine efficiency, and inventive low- and high-grade heat recuperation. As a result, the core Allam Cycle meets or exceeds the achievable net efficiencies of existing high efficiency combined cycle plants not equipped for carbon capture, while capturing substantially all CO2 emissions at purities and pressures necessary for downstream CO2 reuse and/or sequestration. Additionally, with minor alterations, the core cycle can operate with a variety of organic fuels. A 50MWt natural gas-fired demonstration of the core cycle is currently under development by 8 Rivers, NET Power, CB&I, Exelon, and Toshiba. This paper addresses the coal syngas-fired variant of the Allam Cycle system, extending beyond high-level feasibility analyses conducted in previous studies. The paper explores in detail the unique considerations, possible hurdles, and advantages of integrating a commercially-available coal gasifier with the Allam Cycle. In particular, the paper analyzes five (5) primary technical optimizations that drive the Allam Cycle’s advantages in efficiency and cost over conventional baselines. These include: (1) a simpler overall process, requiring fewer critical integration points while still providing for efficient high- and low-grade heat recuperation; (2) high efficiencies regardless of coal rank and type used — further, the efficiency drop when using low-rank coal in an Allam Cycle arrangement is smaller than IGCC arrangements; (3) high efficiencies regardless of syngas composition (such as H2:CO ratio), particularly when compared to gasification in the chemical industry and IGCC with carbon capture and sequestration; (4) the ability to utilize a singular, cost-effective post-combustion SOX/NOX removal mechanism; and (5) considerable water savings versus IGCC and SCPC baselines, with the ability to run substantially water free with only minor impacts to overall efficiency.
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Mahagaokar, Uday, i Egon L. Doering. "High Level Heat Recovery in Coal and Coke Gasification Combined Cycle Systems". W ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-259.
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Integrated coal gasification combined cycle systems offer a very efficient and environmentally superior method for converting coal or petroleum coke to electric power. The high efficiency is derived from effective utilization of high level energy in all parts of the IGCC system. Entrained flow gasification represents one of the cleanest and most efficient technologies for converting coal or coke to syngas, and also produces significant quantities of high level sensible heat in the raw syngas exiting the gasifier. This heat can be recovered as high pressure steam through the use of syngas coolers. Alternatively, the syngas cooler capital may be saved by using a water quench at the expense of heat recovery. This paper examines the economic benefits of heat recovery in a syngas cooler relative to water quench by determining the value of the recovered energy versus the cost of recovery. The results show that for power generation in a gasification combined cycle configuration, the cost of syngas cooling is justified by the value of the energy recovered — this applies not only to coal feeds but also to low-priced feeds like petroleum coke.
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Nihart, Raoul. "Dynamic Modelling of the Gasification Island of a Coal-Based IGCC". W ASME Turbo Expo 2000: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/2000-gt-0170.
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In developed countries, coal power plants are often used to work in part load and possibly to follow the demand. Consequently, the transient behaviour of these power plants is a very important issue. In integrated coal gasification combined cycles (IGCCs), the complex interactions between the different parts of the plant make the process behaviour difficult to predict. This paper describes a non-linear simulation model of the gasification island. It comprises mainly a module for the gasifier reactor with water walls, two different ones for the convective and radiant syngas coolers, a raw gas / clean gas heat exchanger and a simple module for the gas treatment. This latter is simplified because it has only a small influence on the transients of the plant given its low inertia. All these modules have been introduced into a dynamic computational tool previously designed to simulate the transients of gas combined cycles (Dechamps, 1995). The computational code, called CCDYN (Combined Cycle DYNamics), is a modular and flexible code, each module being a main component (like a gasifier, a gas turbine, a heat exchanger, …) solving a set of transient equations. This paper also presents some results and demonstrates the interest of such a modelling. As an example, the gasification island of a coal-based IGCC is modelled in the case of different coal feed properties and the influence on the syngas composition is illustrated. Another example is the evolution with time of the various temperatures in the system during a start-up procedure and a load variation. The thermochemical and physical properties used in the models are extracted from Barin (1989), from Perry and Green (1984) and from Dechamps (1995).
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Le Guevel, Thierry, i Philippe Thomas. "Fuel Flexibility and Petroleum Coke Combustion at Provence 250 MW CFB". W 17th International Conference on Fluidized Bed Combustion. ASMEDC, 2003. http://dx.doi.org/10.1115/fbc2003-094.
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The Provence 250 MWe CFB boiler was originally designed in 1992 for a local coal (Provence lignite) with a high sulfur and high ash content. This large CFB, features a pant leg bottom furnace, 4 cyclones and 4 fluid bed heat exchangers to provide the active temperature control of the furnace and reheated steam final temperature. After start up in 1995 with this local coal, several other fuel types were burnt. Mainly 3 fuels were tested over the last 5 years, on a long term basis, with various degrees of combination with the Gardanne coal up to full firing alone: • a lean coal (Gard, France), low volatile bituminous type, not far from semi anthracite type coals, • an imported coal, representative of low ash low sulfur content imported coal, • a petroleum coke, with a high sulfur content. This last test demonstrates the widest flexibility with regards to fuel reactivity range of a CFB plant with this architecture. The fuel, limestone and ash handling/injection systems were able to cope with this fuel diversity without equipment modifications. Since these tests were conclusive both on the pollutant emissions and on the operating concern, a permit to burn petroleum coke in commercial operation in a 250 MWe CFB boiler has been obtained in December 2001. This paper presents the main features and the results of the petroleum coke tests performed and compare them with the feedback on operating conditions of the boiler and emissions performances for Provence lignite and imported coal. These positive results demonstrate the wide fuel capability of large CFB boilers with this boiler architecture. First, they emphasize the critical role of advanced cyclones to accept fuels with very different reactivities and minimize limestone consumption. Second, these results show the role of the Fluid Bed Heat Exchangers system to control actively the furnace temperature, while controlling the reheated steam temperature without using spray.
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Schmitt, Joshua, Fernando Karg Bulnes i Anoop Mathur. "IDAES Platform for Evaluating Thermal Energy Storage for Coal-Fired Indirect sCO2 Power Cycles". W ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-83379.
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Abstract This paper demonstrates the modelling of a novel power cycle for coal-fired indirect supercritical carbon dioxide (sCO2). and thermal energy storage (TES). TES integrated with coal fired power plant can improve the efficiency, making the power generator responsive to ramp rate. The parallel models were developed in IDAES, an open-source code developed by the Department of Energy (DOE), and Aspen Plus V.10 by Aspen Technology, Inc., which is used in many industries to model and optimize a variety of chemical processes. The benefit of using Aspen Plus for coal combustion is its ability to model solids and multiphase fluids that will be present in the various coal and sCO2 power cycles. The property database and equations of state (EOS) available in the Aspen and IDAES software provide accurate results for the process conditions present in the cycles involved in this project. A baseline model was selected from DOE studies and compared against results from the system modelling. Current results from the model are close to those found using Aspen and those in the baseline model. The system model was also connected to a dual-media thermocline thermal energy storage system (DMTES) that uses a Python script to determine temperatures of molten salt provided by the DMTES. The code uses variables of heat flow, mass flow, and temperature to determine the performance of the sCO2 power block IDAES model. From this, the power block output is determined for steady state and quasi steady state conditions. The DMTES system is modeled for dynamic situations and is shown to have near-constant temperature during charge or discharge, depending on the position of the DMTES system thermal transition zone. The results show how temperature is maintained across a large range of state-of-charge.
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Ulizar, Inaki, i Pericles Pilidis. "A Semiclosed Cycle Gas Turbine With Carbon Dioxide-Argon as Working Fluid". W ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-345.
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This paper describes the performance analysis of a semi closed cycle gas turbine. The working fluid is carbon dioxide and the fuel is low heating value gas synthesised from coal. The objective of the machine is to produce clean electricity with the smallest efficiency penalty. Firstly the thermodynamic properties of the gases in the cycle were obtained as a function of temperature and pressure. Then two performance simulation codes were developed. These have the ability of simulating different configurations of open, closed and semi-closed cycles. The first code was used for cycle optimisation and the second for off-design studies. The design and off-design performance of the machine are predicted. The production of clean electricity will be at the expense of a lower efficiency compared with current equipment. Finally, some critical issues for the development of such a gas turbine are identified.
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Palestra, Nicola, Giovanna Barigozzi i Antonio Perdichizzi. "Inlet Air Cooling Applied to Combined Cycle Power Plants: Influence of Site Climate and Thermal Storage Systems". W ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27046.
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The paper presents the results of an investigation on inlet air cooling systems based on cool thermal storage, applied to combined cycle power plants. Such systems provide a significant increase of electric energy production in the peak hours; the charge of the cool thermal storage is performed instead during night time. The inlet air cooling system also allows the plant to reduce power output dependence on ambient conditions. A 127 MW combined cycle power plant operating in the Italian scenario is the object of this investigation. Two different technologies for cool thermal storage have been considered: ice harvester and stratified chilled water. To evaluate the performance of the combined cycle under different operating conditions, inlet cooling systems have been simulated with an in-house developed computational code. An economical analysis has been then performed. Different plant location sites have been considered, with the purpose to weigh up the influence of climatic conditions. Finally, a parametric analysis has been carried out in order to investigate how a variation of the thermal storage size affects the combined cycle performances and the investment profitability. It was found that both considered cool thermal storage technologies perform similarly in terms of gross extra-production of energy. Despite to that, ice harvester shows higher parasitic load due to chillers consumptions. Warmer climates of plant site resulted to increase more the amount of operational hours than power output augmentation; investment profitability is different as well. Results of parametric analysis showed how important may be, for economical results, the size of inlet cooling storage.
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Dechamps, P. J., i Ph Mathieu. "Phasing the Construction of an IGCC Plant for Fuel Flexibility". W ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-144.
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The Integrated Coal Gasification in Combined Cycle technique allows a come back to coal: starting with a Combined Cycle plant, it is possible to add gasification units several years later and hence to switch from natural gas to coal. However, the price to pay will be capital cost but also a loss of performances of the resulting plant compared to a genuine Integrated Coal Gasification in Combined Cycle. In this paper, we investigate the phasing option starting with a new Combined Cycle plant, optimized on natural gas operation, and ending with an Integrated Coal Gasification in Combined Cycle plant. We calculate the performances of the resulting plants with four types of gasifiers based on Texaco, Shell, Dow and British-Gas-Lurgi processes. We then compare the performances of these four plants with the performances of new Integrated Coal Gasification in Combined Cycle plants, optimized on coal operation and fully integrated, comprising the same four gasifiers. We finally compare the loss of performances in the four cases and recommend the selection of a gasifier type for such a phasing strategy.
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Zhang, Shengjun. "Performance Analysis of a Novel PXS With Organic Rankine Cycle (ORC) System". W 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-16178.
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With the increasing of core thermal power of the nuclear power plant, the decay heat of the core increases in the accident. Therefore, the heat removal capacity of the PXS should be enhanced to fulfill the requirement of core safety. A new scheme is put forward to improve the cooling capacity of PXS and provides long-term power for station blackout (SBO) accident or loss of normal feedwater. In this system, the Organic Rankine Cycle is incorporated between the hot leg and cold leg of PRHR. The decay heat of the core is the heat source and the cooling pool outside the containment is the cool source. The natural circulation of the primary loop is established due to the density difference. The primary fluid flows into the evaporator of the ORC system, where the working fluid of the ORC system is evaporated. Then the temperature of the primary fluid is decreased. The vaporized working fluid drives the expander, which is coaxially fixed with the fluid pump, to generate the power. Finally, the exhausted vapor flows into the condenser and the residual heat is discharged outside of the containment simultaneously. The working fluid in the condenser is pumped into the evaporator by the fluid pump for liquid supplement and the cycle keeps on working continuously. A steady state analysis is performed on a 1700MWe nuclear power plant with ORC as the heat removal system. The heat transfer area of the ORC evaporator is fixed as 487.7m2, which is the same as the area of PRHR HX. The efficiencies of fluid pump and expander of ORC system are assumed as 0.75 and 0.8, respectively. The decay heat of the core is about 67.62MWe, which is 1.38% of the core full power. The working fluids are screened and R141b offers excellent performance. The efficiency of fluid pump and expander are assumed as 0.75 and 0.8, respectively. The condensing temperature is assumed as 80°C and the evaporating temperature is 160°C. The results show that 7.83MWe will be generated by the ORC system and the heat transfer area of the condenser is about 994.5m2. The residual heat of 59.79MWe will be discharged to the water tank outside the containment.