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## Improvement of the recycle technologies for C5/C6 isomerization by layered PSA

Bárcia, Patrick da Silva; Silva, José A.C.; Rodrigues, A.E.
Tipo: Parte de Livro
ENG
Relevância na Pesquisa
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The objective of this work consists in studying the separation mono/dibranched paraffins by cyclic adsorption process using a layered bed of zeolites 5A and Beta (Figure 1). Aspen ADSIM 2006.5 (AspenTech Inc.) was used for numerically solving an adiabatic dynamic model incorporating mass, energy and momentum balance. Model parameters were taken from experimental data reported in the literature 1, 2. Parametric studies were simulated to determine how process performance is affected by purge quantity, 5A-to-Beta ratio, repressurization/blowdown schemes and operating temperature. Figure 2 shows that a combination of zeolites 5A and Beta can produce an octane gain of 1 RON comparatively to the conventional TIP 3 by reducing the monobranched C6 fraction in the product. Another advantage of this configuration is the possibility to increase the penetration distance because zeolite Beta acts like a “barrier” to the linear alkanes desorbed from zeolite 5A during the co-current depressurization step. It was also demonstrated that a slight increase in temperature (20 K) results in a RON benefit of 0.2 points. Several alternatives are provided to improve the performance of the existing TIP processes with this combination of adsorbents.

## Octane Upgrading of TIP Processes by Recycling in a Layered Zeolite 5A/BETA PSA

Silva, José A.C.; Rodrigues, A.E.; Bárcia, Patrick da Silva
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
154.65039%
The objective of this work consists in studying the separation mono/dibranched paraffins by cyclic adsorption process using a layered bed of zeolites 5A and Beta (Figure 1). Aspen ADSIM 2006.5 (AspenTech Inc.) was used for numerically solving an adiabatic dynamic model incorporating mass, energy and momentum balance. Model parameters were taken from experimental data reported in the literature 1, 2. Parametric studies were simulated to determine how process performance is affected by purge quantity, 5A-to-Beta ratio, repressurization/blowdown schemes and operating temperature. Figure 2 shows that a combination of zeolites 5A and Beta can produce an octane gain of 1 RON at 523 K comparatively to the conventional TIP3 by reducing the monobranched C6 fraction in the product. Another advantage of this configuration is the possibility to increase the penetration distance because zeolite Beta acts like a “barrier” to the linear alkanes desorbed from zeolite 5A during the cocurrent depressurization step. It was also demonstrated that a slight increase in temperature (20 K) results in a RON benefit of 0.2 points. Several alternatives are provided to improve the performance of the existing TIP processes with this combination of adsorbents.

## Separation of light naptha by adsorption processes

Bárcia, Patrick da Silva; Rodrigues, A.E.; Silva, José A.C.
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
154.65039%
In this work we studied the separation linear/mono/di-branched paraffins in a cyclic Pressure Swing Adsorption process using a layered bed of zeolites 5A and Beta (Figure 1). Zeolite Beta proved to be an efficient separator of mono-branched from di-branched paraffins [3]. Aspen ADSIM (AspenTech Inc.) was used for numerically solve an adiabatic dynamic model incorporating mass, energy and momentum balances. Model parameters were taken from experimental data obtained in our lab. The studies were performed with the objective to determine how process performance is affected by purge quantity, 5A-to-Beta ratio, repressurization/blowdown schemes and operating temperature which are typical operating parameters of PSA processes. Figure 2 shows the product average RON as a function of the zeolite 5A layer length and purge-to-feed ratio at T = 523 K, where it can be seen that RON is above 90 when the ratio of the layered bed is nearly 0.6. It was also demonstrated that a slight increase in temperature (20 K) results in a RON benefit of 0.2 points. Several alternatives are also provided to improve the performance of the existing TIP processes with this combination of adsorbents [4].

## Avaliação do pré-tratamento de uma corrente de purga para um sistema de filtração com membranas de osmose inversa descartadas

Frick, Julia Menegotto
Tipo: Dissertação Formato: application/pdf
POR
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## Modelo dinâmico de um túnel de vento de sopro

Oliveira, Generoso Niederauer de
Tipo: Tese de Doutorado Formato: 135 p. : il.
POR
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## Extraction of agar from Gelidium corneum using an alternative heating technology

Rocha, Cristina M. R.; Sousa, A. M.; Esparinha, A. S.; Cardoso, B. I.; Vicente, A. A.; Gonçalves, M. P.
Tipo: Conferência ou Objeto de Conferência
Relevância na Pesquisa
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Traditional polysaccharides extraction processes are often performed under heating which makes them time-, energy- and solvent-consuming. The aim of this work was to assess the possibility of using ohmic heating to replace conventional heating in the extraction of seaweed hydrocolloids. This technology is able to heat almost instantaneously the whole volume to be treated, using the ability that most materials have to dissipate energy as heat. As a result, it is energetically much more efficient, with efficiencies well above 95%. In traditional boilers, energetic efficiency is usually around 70-80%. This implies that the energetic efficiency of traditional extraction is below these values, as we have also to account for energy losses in the pipelines and in the extractor. The extraction of agar from Gelidium corneum (sesquipedale) was chosen as a model process due to the high temperatures and energy input needed. All traditional and ohmic extractions were made with a ratio of 50 g of water: 1 g of seaweed at 95 °C, for 2 hours on seaweeds pre-treated with NaOH and neutralized with diluted acetic acid. For the ohmic system, the voltage was set at 600 V and the distance between electrodes was 10 cm. The yields achieved (around 15-20%) were similar in both traditional and ohmic extractions. Gelling ability...

## Initial Effects of the Mount St. Helens Eruption on Nitrogen Cycle and Related Chemical Processes in Ryan Lake

Dahm, Clifford N.; Baross, John A.; Ward, Amelia K.; Lilley, Marvin D.; Sedell, James R.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
154.65039%
Ryan Lake, a 1.6-hectare basin lake near the periphery of the tree blowdown area in the blast zone 19 km north of Mount St. Helens, was studied from August to October 1980 to determine the microbial and chemical response of the lake to the eruption. Nutrient enrichment through the addition of fresh volcanic material and the organic debris from the surrounding conifer forest stimulated intense microbial activity. Concentrations of such nutrients as phosphorus, sulfur, manganese, iron, and dissolved organic carbon were markedly elevated. Nitrogen cycle activity was especially important to the lake ecosystem in regulating biogeochemical cycling owing to the limiting abundance of nitrogen compounds. Nitrogen fixation, both aerobic and anaerobic, was active from aerobic benthic and planktonic cyanobacteria with rates up to 210 nmol of N2 cm−1 h−1 and 667 nmol of N2 liter−1 h−1, respectively, and from anaerobic bacteria with rates reaching 220 nmol of N2 liter−1 h−1. Nitrification was limited to the aerobic epilimnion and littoral zones where rates were 43 and 261 nmol of NO2 liter−1 day−1, respectively. Potential denitrification rates were as high as 30 μmol of N2O liter−1 day−1 in the anaerobic hypolimnion. Total bacterial numbers ranged from 1 × 106 to 3 × 108 ml−1 with the number of viable sulfur-metal-oxidizing bacteria reaching 2 × 106 ml−1 in the hypolimnion. A general scenario for the microbial cycling of nitrogen...

## Large-Scale Wind Disturbances Promote Tree Diversity in a Central Amazon Forest

Marra, Daniel Magnabosco; Chambers, Jeffrey Q.; Higuchi, Niro; Trumbore, Susan E.; Ribeiro, Gabriel H. P. M.; dos Santos, Joaquim; Negrón-Juárez, Robinson I.; Reu, Björn; Wirth, Christian
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
196.96037%
Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m2) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 to 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583±46 trees ha−1) (mean±99% Confidence Interval) and basal area (26.7±2.4 m2 ha−1). Highly impacted areas had tree density and basal area as low as 120 trees ha−1 and 14.9 m2 ha−1, respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters...

## Aerodynamic performance measurements of a film-cooled turbine stage

Keogh, Rory (Rory Colm), 1968-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 168 p.; 10029960 bytes; 10029716 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
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The goal of this research is to measure the aerodynamic performance of a film-cooled turbine stage and to quantify the loss caused by film-cooling. A secondary goal of the research is to provide a detailed breakdown of the losses associated with film-cooling for the turbine stage being tested. The experimental work was carried out at the MIT Blowdown Turbine Facility using a highly loaded turbine stage. The Blowdown Turbine Facility is a short duration test facility capable of testing turbine stages under fully scaled conditions for a test duration of 0.5 seconds. The facility was modified to enable the measurement of the turbine mass flow and shaft torque. These newly developed measurement techniques, along with previously developed total pressure and temperature instruments, have enabled the measure- ment of the stage isentropic efficiency. A highly loaded turbine stage (without film-cooling) was designed, fabricated, and tested using the newly developed measurement techniques. The turbine stage was then modified to incorporate vane, blade and rotor casing coolant manifolds using precision electrical discharge machining. The film-cooling hole geometry was created using a laser drilling process to produce the required 43,000 cooling holes. The film-cooled stage was then tested over a range of operating conditions (pressure ratios and corrected speeds) and over a range of coolant-to-mainstream mass flow and temperature ratios.; (cont.) The loss due to film-cooling is defined as the difference in performance between the film-cooled turbine and an ideal turbine with the same velocity triangles and airfoil Mach number distributions. However...

## Design and operation of a counter-rotating aspirated compressor blowdown test facility; Counter-rotating aspirated compressor blowdown test facility

Parker, David V. (David Vickery)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 141 p.; 7485237 bytes; 7492657 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
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A unique counter-rotating aspirated compressor was tested in a blowdown facility at the Gas Turbine Laboratory at MIT. The facility expanded on experience from previous blowdown turbine and blowdown compressor experiments. Advances in thermocouple and facility designs enabled efficiency estimates through total temperature and total pressure measurements. The facility was designed to provide at least 100 ms of available test time, approximately a factor of five greater than previous blowdown compressor facilities. The adiabatic core efficiency of the compressor was estimated with an uncertainty of 0.8% and the corrected flow was estimated with an uncertainty of 1.0%. The compressor was tested at several operating conditions and two speed lines were partially mapped. The maximum measured total pressure ratio across the two stages was 3.02 to 1. The measured adiabatic efficiency for that point was 0.885. The span-wise total pressure, total temperature, and efficiency profiles were compared to the predicted profiles for runs with the corrected speeds of the two rotors at 90% of design and 100% design. There appears to be reasonable agreement between the predictions and the measurements.; by David V. Parker.; Thesis (S.M.)--Massachusetts Institute of Technology...

## Reservoir simulation studies of formation damage for improved recovery on oil-gas reservoirs.

Nguyen, Thi Kim Phuong
Relevância na Pesquisa
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This thesis is dedicated to the development of new technologies for sweep improvement due to plugging of highly permeable channels and layers by injected or lifted or mobilized fines particles. The following methods of improved waterflood have been proposed in the thesis: • Injection of raw or poorly treated water with consequent homogenization of the injectivity profile due to distributed along the well skin factor. • Injection of low salinity or fresh water resulting in lifting of reservoir fines, their migration and further capture by the rock with permeability reduction and redirection of the injected water into unswept area. • Injection of sweet water into watered-up abandoned wells during pressure blowdown in oil and gas reservoirs with strong water support. In the above three cases, the proposal of the new technologies was backed by detailed reservoir simulations. In all cases, the application of the proposed improved oil recovery technology, as forecasted by reservoir simulation, leads to 3-15% of incremental recovery and 2-3 times decrease of the amount of produced and injected water. The technology of raw water injection was developed using Eclipse waterflood BlackOil simulator with modelling of injectivity decline along the well due to plugging of porous media by injected particles. A new numerical procedure describing skin growth with time in each section of long horizontal wells have been developed and implemented into BlackOil Eclipse model. Different configurations of horizontal injectors and producers have been modelled resulting in production forecast with raw waterflooding. The technology of low salinity water injection have been developed using Eclipse reservoir modelling with polymer injection option...

## Supersonic flow field visualization studies of the MÅ = 6 price waverider planform

Garcia, Karl
Relevância na Pesquisa
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Supersonic tests of the conical flow derived MÅ Ê» = 6 (design) Price waverider planform were conducted using the Naval Postgraduate School wind tunnel. These tests are part of a continuing effort to study the characteristics of waverider configured vehicles. Two sting-mounted, flat-plate stainless-steel Price waverider planform models were utilized for testing in the NPS 4-inch by 4-inch cross section supersonic blowdown wind tunnel. Tests at Mach numbers of MÅ Ê» = 1.7, 2.8 and 4 were attempted but flowfield studies were only completed at MÅ Ê» = 4. Sting mount flow blockage (choked flow) prevented test section starting at freestream test Mach numbers of MÅ Ê» = 1.7 and 2.8. Horizontal (side-view) and vertical (top-view) mounted shadowgraph pictures and pressure sensitive paint images were taken at pitch angles of â ­Â¿ = 0Å Êº, 2Å Êº and 4Å Êº. The Mach 4 shadowgraph and pressure sensitive paint results correlate well with previous CFD results using the three-dimensional Price waverider model. The choked flow tests at MÅ Ê» = 1.7 and 2.8 are discussed in detail; suggestions are given for future work in this Mach number test spectrum.

## Core design and reactor physics of a breed and burn gas-cooled fast reactor

Yarsky, Peter
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 248 p.; 15635316 bytes; 15646642 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
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In order to fulfill the goals set forth by the Generation IV International Forum, the current NERI funded research has focused on the design of a Gas-cooled Fast Reactor (GFR) operating in a Breed and Burnm (B&B) fuel cycle mode. B&B refers to a once-through fuel cycle where low enriched uranium (less than 5 w/o 235U in U) subcritical assemblies are loaded into the core in equilibrium, yet in-situ plutonium breeding carries the fuel through a discharge burnup on the order of 150 MWD/kgHM. The B&B fuel cycle meets the GenIV goals of sustainability, economics, and proliferation resistance by increasing fuel burnup without the need for spent fuel reprocessing, recycle, or reuse of any kind. The neutronic requirements for B&B are strict and require an ultra-hard neutron spectrum. Therefore, the GFR is ideally suited for this fuel cycle. In the present work the B&B GFR concept evolved into two practical reactor designs, both of which build on extensive previous gas-cooled reactor design experience. The first version is the "demonstration" concept using highly neutronically reactive U15N fuel in a hexagonal pin fuel array that is nearly 50 v/o fuel. The core is helium cooled, with an outlet temperature of 570 °C.; The helium primary circuit is coupled to a steam Rankine power conversion system essentially identical to that for the British Advanced Gas-cooled Reactors. One advantage of the low coolant temperature compared to other GenIV GFR concepts is that it allows for the use of oxide dispersion strengthened stainless steels (ODS) in core. The fuel is manufactured using advanced vibration compaction techniques...

## Blowdown of hydrocarbons pressure vessel with partial phase separation

Speranza, Alessandro; Terenzi, Alessandro
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We propose a model for the simulation of the blowdown of vessels containing two-phase (gas-liquid) hydrocarbon fluids, considering non equilibrium between phases. Two phases may be present either already at the beginning of the blowdown process (for instance in gas-liquid separators) or as the liquid is formed from flashing of the vapor due to the cooling induced by pressure decrease. There is experimental evidence that the assumption of thermodynamic equilibrium is not appropriate, since the two phases show an independent temperature evolution. Thus, due to the greater heat transfer between the liquid phase with the wall, the wall in contact with the liquid experiences a stronger cooling than the wall in contact with the gas, during the blowdown. As a consequence, the vessel should be designed for a lower temperature than if it was supposed to contain vapor only. Our model is based on a compositional approach, and it takes into account internal heat and mass transfer processes, as well as heat transfer with the vessel wall and the external environment. Numerical simulations show a generally good agreement with experimental measurements.; Comment: 10 pages, 3 figures

## Small exotic rational surfaces without 1- and 3-handles

Yasui, Kouichi
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
175.1443%
We give new rational blowdown constructions of exotic CP^2#n(-CP^2) (5\leq n\leq 9) without using elliptic fibrations. We also show that our 4-manifolds admit handle decompositions without 1- and 3-handles, for 7\leq n\leq 9. A strategy for rational blowdown constructions of exotic CP^2#n(-CP^2) (1\leq n\leq 4) is also proposed.; Comment: 14 pages, 17 figures, minor changes

## Circulation in Blowdown Flows

Katz, J. I.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
285.87918%
The blowdown of high pressure gas in a pressure vessel produces rapid adiabatic cooling of the gas remaining in the vessel. The gas near the wall is warmed by conduction from the wall, producing radial temperature and density gradients that affect the flow, the mass efflux rate and the thermodynamic states of both the outflowing and the contained gas. The resulting buoyancy-driven flow circulates gas through the vessel and reduces, but does not eliminate, these gradients. The purpose of this note is to estimate when blowdown cooling is rapid enough that the gas in the pressure vessel is neither isothermal nor isopycnic, though it remains isobaric. I define a dimensionless number, the buoyancy circulation number BC, that parametrizes these effects.; Comment: 5 pp., no figures

## Exhaust of Underexpanded Jets from Finite Reservoirs

Orescanin, M. M.; Austin, J. M.
Tipo: Article; PeerReviewed Formato: application/pdf
Relevância na Pesquisa
175.1443%
The response of an underexpanded jet to a depleting finite reservoir is examined with experiments and simulations. An open-ended shock-tube facility with a variable reservoir length is used to obtain images of nitrogen- and helium-jet structures at successive instances during the blowdown from initial pressure ratios of up to 250. The reservoir and ambient pressures are simultaneously measured to obtain the instantaneous pressure ratio. We estimate the time scales for jet formation and reservoir depletion as a function of the specific heat ratio of the gas and the initial pressure ratio. The jet structure formation time scale is found to become approximately independent of the pressure ratio for ratios greater than 50. In the present work, no evidence of time dependence in the Mach disk shock location is observed for rates of pressure decrease associated with isentropic blowdown of a finite reservoir while the pressure ratio is greater than 15. The shock location in the finite-reservoir jet can be calculated from an existing empirical fit to infinite-reservoir jet data evaluated at the instantaneous reservoir pressure. For pressure ratios below 15, however, the present data deviate from a compilation of data for infinite-reservoir jets. A new fit is obtained to data in the lower-pressure regime. The self-similarity of the jet structure is quantified...

## Exhaust of Underexpanded Jets from Finite Reservoirs

Orescanin, M. M.; Prisco, D.; Austin, J. M.
Tipo: Book Section; PeerReviewed Formato: application/pdf
Relevância na Pesquisa
175.1443%
We examine the response of an underexpanded jet to a depleting, finite reservoir with experiments and simulations. An open-ended shock tube facility with variable reservoir length is used to obtain images of nitrogen and helium jet structures at successive instances during the blowdown from initial pressure ratios of up to 250. The reservoir and ambient pressures are simultaneously measured to obtain the instantaneous pressure ratio. We estimate the time-scales for jet formation and reservoir depletion as a function of the specific heat ratio of the gas and the initial pressure ratio. The jet structure formation time-scale is found to become approximately independent of pressure ratio for ratios greater than 50. In the present work, no evidence of time-dependence in the Mach disk shock location is observed for rates of pressure decrease associated with isentropic blowdown of a finite reservoir while the pressure ratio is greater than 15. The shock location in the finite- reservoir jet can be calculated from an existing empirical fit to infinite-reservoir jet data evaluated at the instantaneous reservoir pressure. For pressure ratios below 15, however, the present data deviate from a compilation of data for infinite-reservoir jets. A new fit is obtained to data in the lower pressure regime. The self-similarity of the jet structure is quantified and departure from similarity is noted to begin at pressure ratios lower than about 15...

## Composition of Fourier integral operators with fold and blowdown singularities

Felea, Raluca
Fonte: Taylor and Francis Publicador: Taylor and Francis
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
275.1443%
The purpose of this work is to present results about the composition of Fourier integral operators with certain singularities, for which the composition is not again a Fourier integral operator. The singularities considered here are folds and blowdowns. We prove that for such operators, the Schwartz kernel of F*F belongs to a class of distributions associated to two cleanly intersection Lagrangians. Such Fourier integral operators appear in integral geometry, inverse acoustic scattering theory and Synthetic Aperture Radar imaging, where the composition calculus can be used as a tool for finding approximate inversion formulas and for recovering images.

## Electrocoagulation to Remove Silica from Cooling Towers Water

Villegas-Mendoza,Iván Emmanuel; Martín-Domínguez,Alejandra; Pérez-Castrejón,Sara; Gelover-Santiago,Silvia Lucila
Fonte: Instituto Mexicano de Tecnología del Agua, Coordinación de Comunicación, Participación e Información Publicador: Instituto Mexicano de Tecnología del Agua, Coordinación de Comunicación, Participación e Información
Tipo: Artigo de Revista Científica Formato: text/html
This paper presents the results of a study carried out about the effect of water quality on the removal of dissolved silica using an electrocoagulation process with aluminum electrodes. Silica is found in replacement water (RW), usually known as make up water, and in cooling tower blowdown water (CTBW). Tests were conducted on a small pilot scale (~2 lmin-1) with a continuous flow device. The treatment train consisted of electrocoagulation (EC), flocculation, sedimentation and sand filtration. Two distinct RW and two CTBW with different physicochemical characteristics were studied. The response variables analyzed were: efficiency of aluminum to remove silica (ratio mgl-1 of dosed Al3+/mgl-1 SiO2 removed), removal efficiency of dosed Al3+, hydraulic head loss throughout the electrochemical reactor and voltage. The cost of the treatment for the four types of water is discussed. The ratio mgl-1 Al3+ dosed /mgl-1 silica removed ranged from 1.09 ± 0.06 to 1.33 ± 0.05 when treating RW and 0.85 ± 0.1 when treating CTBW. The consumption costs of energy, chemicals and electrodes for RW treatment ranged from US$0.52 to 0.74 m-3, and was approximately US$0.53 m-3 for CTBW.