Search NASA⌕ Search

SEARCH · Search NASA

Results for “Gas processing”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Aerosol Deposition: Room Temperature Solid-State Deposition of Ceramics

The ability to integrate ceramics with other materials has been limited by the high temperature s (>800C) associated with ceramic processing. A novel process, known as aerosol deposition (AD), capable of preparing ceramic films at room temperature (RT) has been the subject of recent interest in the thermal spray and microelectronics communities. In this process, ceramic particles are accelerated using pressurized gas, impacted on a substrate and form a dense film under vacuum. This revolutionary process eliminates high temperature processing, enabling new coatings and microelectronic device integration as a back end of line process, in which ceramics can be deposited on metals, plastics, and glasses . Future impact s of this technology on Sandia's mission could include improved ceramic integration, miniaturized magnetic circulators in radar applications, new RF communication products, modification of commercial - off - the - shelf electronics, fabrication of conformal capacitors, thin batteries, glass - to - metal seals, and transparent electronics. Currently, optimization for RT solid - state deposition of ceramics is achieved empirically and fundamental mechanisms for ceramic particle - particle bonding are not well understood. Obtaining this knowledge will allow process - microstructure - property relation ship realization and will enable a differentiating ceramic integration capability. This LDRD leveraged Sandias existing equipment and capabilities in simulation, experimentation, and materials characterization to discover the fundamental mechanisms for ceramic particle deformation, particle - substrate bonding, and particle - particle bonding in RT consolidated films. RT deformation of individual Al 2 O 3 particles was examined computationally and experimentally as a model system for understanding the complex dynamics associated with in vacuo RT deposition conditions associated with AD. Subsequently, particle - substrate bonding and particle - particle bonding in AD Al 2 O 3 consolidated films were examined computationally and experimentally. Fundamental mechanisms behind the AD process were proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Galaxy cluster baryon fractions revisited

We measure the baryons contained in both the stellar and hot-gas components for 12 galaxy clusters and groups at z ∼ 0.1 with M = 1-5 × 10{sup 14} M {sub ☉}. This paper improves upon our previous work through the addition of XMM-Newton X-ray data, enabling measurements of the total mass and masses of each major baryonic component—intracluster medium, intracluster stars, and stars in galaxies—for each system. We recover a mean relation for the stellar mass versus halo mass, M{sub ⋆}∝M{sub 500}{sup −0.52±0.04}, that is 1σ shallower than in our previous result. We confirm that the partitioning of baryons between the stellar and hot-gas components is a strong function of M {sub 500}; the fractions of total mass in stars and X-ray gas within a sphere of radius r {sub 500} scale as f{sub ⋆}∝M{sub 500}{sup −0.45±0.04} and f{sub gas}∝M{sub 500}{sup 0.26±0.03}, respectively. We also confirm that the combination of the brightest cluster galaxy and intracluster stars is an increasingly important contributor to the stellar baryon budget in lower halo masses. Studies that fail to fully account for intracluster stars typically underestimate the normalization of the stellar baryon fraction versus M {sub 500} relation by ∼25%. Our derived stellar baryon fractions are also higher, and the trend with halo mass weaker, than those derived from recent halo occupation distribution and abundance matching analyses. One difference from our previous work is the weak, but statistically significant, dependence here of the total baryon fraction upon halo mass: f{sub bary}∝M{sub 500}{sup 0.16±0.04}. For M {sub 500} ≳ 2 × 10{sup 14}, the total baryon fractions within r {sub 500} are on average 18% below the universal value from the seven year Wilkinson Microwave Anisotropy Probe (WMAP) analysis, or 7% below for the cosmological parameters from the Planck analysis. In the latter case, the difference between the universal value and cluster baryon fractions is less than the systematic uncertainties associated with the M {sub 500} determinations. The total baryon fractions exhibit significant scatter, particularly at M {sub 500} < 2 × 10{sup 14} M {sub ☉} where they range from 60%-90%, or 65%-100%, of the universal value for WMAP7 and Planck, respectively. The ratio of the stellar-to-gas mass within r {sub 500} (M {sub *}/M {sub gas}), a measure of integrated star-formation efficiency, strongly decreases with increasing M {sub 500}. This relation is tight, with an implied intrinsic scatter of 12%. The fact that this relation remains tight at low mass implies that the larger scatter in the total baryon fractions at these masses arises from either true scatter in the total baryon content or observational scatter in M {sub 500} rather than late-time physical processes such as redistribution of gas to beyond r {sub 500}. If the scatter in the baryon content at low mass is physical, then our results imply that in this mass range, the integrated star-formation efficiency rather than the baryon fraction that is constant at fixed halo mass.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Design and Cooling Performance of Additively Manufactured Ceramic Turbine Vanes

Ceramic materials are of significant interest in aviation and power generation gas turbine engines due to their low density and ability to withstand high temperatures. Increased cycle thermal efficiency and higher specific power output is possible by incorporating ceramic components that enable high turbine inlet temperatures and lower required cooling airflow levels. However, ceramics can be difficult and costly to form into the complex shapes used in gas turbine components, often requiring specialized multi-step processes. Furthermore, ceramic components in the hottest areas of a gas turbine, such as vanes or blade shroud seals, will still likely require cooling which is challenging to implement in conventional ceramic manufacturing approaches. Therefore, this study presents a multidisciplinary approach that investigates the design, fabrication, and overall cooling effectiveness evaluation of additively manufactured (AM), polymer derived ceramic (PDC) turbine vanes. A thermo-mechanically optimized vane design was generated, ceramic additive manufacturing of the complex cooling configuration was developed, and quantification of the increase in overall cooling effectiveness was performed in a 1X scale, high-speed facility using infrared thermography. This study produced a PDC AM process, capable of printing complex internal cooling schemes in 1X scale turbine vanes. Furthermore, it was found that the optimized vane more than doubled the overall cooling effectiveness observed in the baseline design, which reasonably agreed with thermomechanical optimization model predictions. Additionally, the optimized ceramic vane outperformed an identical metal vane, in terms of area averaged cooling effectiveness, suggesting that the ceramic vane could operate at reduced coolant flowrates to achieve comparable levels of cooling performance.

Reynolds number↗
DOE OSTI2023

Design and Cooling Performance of Additively Manufactured Ceramic Turbine Vanes

Ceramic materials are of significant interest in aviation and power generation gas turbine engines due to their low density and ability to withstand high temperatures. Increased cycle thermal efficiency and higher specific power output is possible by incorporating ceramic components that enable high turbine inlet temperatures and lower required cooling airflow levels. However, ceramics can be difficult and costly to form into the complex shapes used in gas turbine components, often requiring specialized multi-step processes. Furthermore, ceramic components in the hottest areas of a gas turbine, such as vanes or blade shroud seals, will still likely require cooling which is challenging to implement in conventional ceramic manufacturing approaches. Therefore, this study presents a multidisciplinary approach that investigates the design, fabrication and overall cooling effectiveness evaluation of additively manufactured (AM), polymer derived ceramic (PDC) turbine vanes. A thermo-mechanically optimized vane design was generated, ceramic additive manufacturing of the complex cooling configuration was developed, and quantification of the increase in overall cooling effectiveness was performed in a 1X scale, high-speed facility using infrared thermography. This study produced a PDC AM process, capable of printing complex internal cooling schemes in 1X scale turbine vanes. It was found that the optimized vane more than doubled the overall cooling effectiveness observed in the baseline design, which reasonably agreed with thermomechanical optimization model predictions. Additionally, the optimized ceramic vane outperformed an identical metal vane, in terms of area averaged cooling effectiveness, suggesting that the ceramic vane could operate at reduced coolant flow rates to achieve comparable levels of cooling performance.

Fox, Andrew↗
DOE OSTI2020

A Method for Obtaining Liquid–Solid Adsorption Rates from Molecular Dynamics Simulations: Applied to Methanol on Pt(111) in H 2 O

Adsorption is an important step in heterogeneous catalysis as it predetermines how many reactant molecules can participate in a surface reaction per unit time. While the rate of adsorption processes is well studied in gas–solid adsorption in both theory and experiment, such rates are still not well studied for liquid–solid adsorption. This is partly because the ever-changing configurations of liquid-phase solvent molecules impede the ability to study a molecule approaching a surface from a liquid phase by either experiment or theory. In this work, we develop a method using molecular dynamics (MD) simulations to study the rate of adsorption in liquid–solid adsorption processes. Specifically, we use MD to model the diffusion of a methanol molecule in aqueous solvent and its adsorption to a Pt(111) surface. We find that by approximating the solute motion as following the same displacement rates as a random walk model, the adsorbed and non-adsorbed states of the methanol molecule near the Pt(111) surface can be discerned and quantified. In particular, this methodology enables extracting a sticking coefficient and a macroscopically relatable adsorption rate. This method can be applied to arbitrary types of reactants and surfaces, as well as different liquid environments, thus providing a general tool for predicting quantitative adsorption rates of liquid–solid adsorption systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Development of an Open Global Oil and Gas Infrastructure Inventory and Geodatabase

This submission contains a technical report describing the development process and visual graphics for the Global Oil and Gas Infrastructure database. Access the GOGI database using the following link: https://edx.netl.doe.gov/dataset/global-oil-gas-features-database There is a web-mapping tool that allows you to visualize and interact with this data also available here: https://edxspatial.arcgis.netl.doe.gov/maps/edxspatial-gogi-index.html Acknowledgement: This work was performed under a CRADA between NETL and EDF, and was funded under the Climate and Clean Air Coalition (CCAC) Oil and Gas Methane Science Studies. The studies are managed by United Nations Environment in collaboration with the Office of the Chief Scientist, Steven Hamburg of the Environmental Defense Fund. Funding was provided by the Environmental Defense Fund, OGCI Companies (Shell, BP, ENI, Petrobras, Repsol, Total, Equinor, CNPC, Saudi Aramco, Exxon, Oxy, Chevron, Pemex) and CCAC.

GOGI↗
DOE OSTI2013

Increasing Gas Hydrate Formation Temperature for Desalination of High Salinity Produced Water with Secondary Guests

We suggest a new gas hydrate-based desalination process using water-immiscible hydrate formers; cyclopentane (CP) and cyclohexane (CH) as secondary hydrate guests to alleviate temperature requirements for hydrate formation. The hydrate formation reactions were carried out in an isobaric condition of 3.1 MPa to find the upper temperature limit of CO2 hydrate formation. Simulated produced water (8.95 wt % salinity) mixed with the hydrate formers shows an increased upper temperature limit from -2 °C for simple CO2 hydrate to 16 and 7 °C for double (CO2 + CP) and (CO2 + CH) hydrates, respectively. The resulting conversion rate to double hydrate turned out to be similar to that with simple CO2 hydrate at the upper temperature limit. Hydrate formation rates (Rf) for the double hydrates with CP and CH are shown to be 22 and 16 times higher, respectively, than that of the simple CO2 hydrate at the upper temperature limit. Such mild hydrate formation temperature and fast formation kinetics indicate increased energy efficiency of the double hydrate system for the desalination process. Dissociated water from the hydrates shows greater than 90% salt removal efficiency for the hydrates with the secondary guests, which is also improved from about 70% salt removal efficiency for the simple hydrates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Hybrid Ceramic-CMC Vane with EBC for Future Coal Derived Syngas Fired 65% Efficient Turbine Combined Cycle

The efficiency of both simple cycle and combined cycle power generation systems scale with the peak temperature at which the gas exits the combustor to drive the turbine. In conventional systems, a substantial fraction of the total turbine core flow exiting the compressor is diverted downstream to cool metallic turbine hardware rather than power the turbine, much of which is used to cool the first-stage turbine vane. The use of coal derived syngas fuels provides an additional challenge to the lifetime of materials utilized in the turbine, as particulate byproducts created in the coal gasification process melt in the combustion gas, and can subsequently deposit and interact with the turbine hardware. The development of durable hot-section materials capable of operating at temperature well above that of single crystal superalloy airfoil/zirconia based thermal barrier coatings is critical to realizing 65% efficient coal derived syngas fired gas turbine based power systems. To enable higher turbine inlet temperatures while lowering cooling air requirements, United Technologies Research Center (UTRC), the central R&D laboratory supporting UT Pratt & Whitney, led the conceptual design of a new type of ceramic composite turbine hot section materials system. The design focused on a novel hybrid monolithic ceramic-fiber reinforced ceramic matrix composite (CMC) first stage turbine vane having an environmental barrier coating. By utilizing ceramic construction in the turbine hot-section, the core flow normally used to cool metallic components will be substantially reduced, increasing efficiency and reducing emissions. To provide the framework for future demonstration testing, UTRC partnered with University of North Dakota Energy and Environmental Research Center (UNDEERC) to provide a conceptual design for a gasified coal fed high-pressure turbine combustor system designed to mimic the conditions expected in a future 65% fuel to busbar efficient syngas fueled gas turbine based combined cycle. The UNDEERC and UTRC collaborated on characterizing dusts from coal gasifier filtration systems.

10 SYNTHETIC FUELS↗
DOE OSTI2017

Preliminary analysis of species partitioning in the DWPF melter. Sludge batch 7A

The work described in this report is preliminary in nature since its goal was to demonstrate the feasibility of estimating the off-gas carryover from the Defense Waste Processing Facility (DWPF) melter based on a simple mass balance using measured feed and glass pour stream (PS) compositions and time-averaged melter operating data over the duration of one canister-filling cycle. The DWPF has been in radioactive operation for over 20 years processing a wide range of high-level waste (HLW) feed compositions under varying conditions such as bubbled vs. non-bubbled and feeding vs. idling. So it is desirable to find out how the varying feed compositions and operating parameters would have impacted the off-gas entrainment. However, the DWPF melter is not equipped with off-gas sampling or monitoring capabilities, so it is not feasible to measure off-gas entrainment rates directly. The proposed method provides an indirect way of doing so.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2011

Thermalization of atomic particles in gases

A model of the atomic particle thermalization process due to scattering in various gases with application of the Born-Mayer potential is presented. The thermalization process of atomic particles using the statistical modeling method is considered. Our thermalization model is adapted to a wide class of atomic collision partners, takes into account the real energy and angular distributions of atomic particle sources, and makes it possible to calculate the parameters of the spatial zone of their thermalization and transfer into the diffusion motion mode. The energy range of applicability for the atomic particle thermalization model is interesting for many applied problems in plasma physics, gas discharge, and ion plating processes.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Elemental Fluorine-18 Gas: Enhanced Production and Availability

The overall objective of this project was to develop an efficient, reproducible and reliable process for the preparation of fluorine-18 labeled fluorine gas ([¹⁸F]F₂) from readily available cyclotron-produced [¹⁸F]fluoride ion. The two step process entailed the production of [¹⁸F]fluoromethane with subsequent conversion to [¹⁸F]F₂ by electric discharge of [¹⁸F]fluoromethane in the presence of carrier nonradioactive F₂ gas. The specific goals of this project were i) to optimize the preparation of [¹⁸F]fluoromethane from [¹⁸F]fluoride ion; ii) to develop a prototype automated system for the production of [¹⁸F]F₂ from [¹⁸F]fluoride ion and iii) develop a compact user friendly automated system for the preparation of [¹⁸F]F₂ with initial synthesis of fluorine-18 labeled radiotracers. Over the last decade there has been an increased interest in the production of "non-standard" positron-emitting isotopes for the preparation of new radiotracers for a variety of applications including medical imaging and therapy. The increased availability of these isotopes from small biomedical cyclotrons has prompted their use in labeling radiotracers. In much the same way the production of [¹⁸F]F₂ gas has been known for several decades. However, access to [¹⁸F]F₂ gas has been limited to those laboratories with the means (e.g. F₂ targetry for the cyclotron) and the project-based need to work with [¹⁸F]F₂ gas. Relatively few laboratories, compared to those that produce [¹⁸F]fluoride ion on a daily basis, possess the capability to produce and use [¹⁸F]F₂ gas. A simplified, reliable system employing [¹⁸F]fluoride ion from cyclotron targetry systems that are already in place coupled with on-demand production of the [¹⁸F]F₂ gas would greatly enhance its availability. This would improve the availability of [¹⁸F]F₂ gas and promote further work with a valuable precursor. The major goals of the project were accomplished over the funding period. The preparation of ¹⁸F]fluoromethane has been automated with reproducible yields greater than 90% conversion from [¹⁸F]fluoride ion. A trap and release system was established for the [¹⁸F]fluoride ion concentration and direct elution of the [¹⁸F]fluoride ion into the reaction vial with the appropriate base and precursor in DMSO. Other solvents were also investigated. The production time for [¹⁸F]fluoromethane is less than 10 minutes. An automated system for the [¹⁸F]F₂ gas production from the [18F]fluoromethane has been developed. The unit coupled to the [¹⁸F]fluoromethane system permits the on demand production of [¹⁸F]F₂ gas. In less than 30 minutes, mCi quantities of [¹⁸F]F₂ gas were produced. Several variables for the [¹⁸F]F₂ gas production were investigated and a set of parameters for reproducible operation were determined. These parameters included discharge chamber size, carrier gas (He, Ne, Ar), discharge time, discharge current, mass of F₂ gas added to the chamber. FDOPA and EF5 were used to test the reactivity of the [¹⁸F]F₂ gas. Both products were produced in low to modest yield. The ready availability of [¹⁸F]F₂ gas has potential impact to advance both DOE mission-driven initiatives and nuclear medicine initiatives through other federally funded agencies such as NIH and DoD. New reactions involving the use of [¹⁸F]F₂ gas will lead to direct labeling of new radiotracers and intermediates as well as new fluorine-18 labeled synthons that may be further reacted with other reagents to provide useful fluorine-18 labeled compounds. New tracers to understand and follow plant and microbial metabolism as well as new tracers for nuclear medicine applications, that have been either difficult to obtain or never produced due to the limited availability of [¹⁸F]F₂ gas, may be prepared using the techniques developed .

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2017

Minimize Solvent Oxidation with NO X Pre-Scrubbing

A novel method to remove nitrogen dioxide (NO 2 ) from the flue gas of coal-fired power plants with CO 2 capture was further developed for commercial implementation. The technology leverages the equipment and chemistry in an existing (sulfur dioxide) SO 2 polishing scrubber upstream of the main CO 2 capture unit to remove the NO 2 , preventing degradation of the CO 2 capture solvent and formation of nitrosamines (environmental hazards). The research in this report focuses on further evaluation of the chemical additives and operating conditions associated with the NO 2 removal process to define conditions for commercial scale testing and deployment. Experimental work systematically evaluated a series of potential additives to minimize the oxidation of sulfite in a representative SO 2 pre-scrubber solution (sulfite, in turn, absorbs NO 2 ). The additive combinations and concentrations were varied alongside important process conditions such as temperature, oxygen concentration, and metals present in solution to mimic the conditions expected in a commercial system. Important results of the parametric experimental work include identifying a new, potent sulfite oxidation inhibitor, revealing the importance of combining inhibitors with metal chelating agents, validation of a low-cost additive process, and development of a new semi-empirical model to represent mechanisms associated with sulfite oxidation. In addition, the experimental work reveled the impact of operating at higher temperatures (representative of a field test unit), which will guide the selection and concertation of additives as well. Engineering analysis found that waste solutions from the pre-scrubber with NO 2 additives may potentially be integrated with existing processes on site (e.g., flue gas desulfurization unit). In addition, techno-economic analysis identified potential net savings as large as $1.30/tonne CO 2 captured and quantified the potential benefit of low cost additive options actively being pursued by the development team. Finally, the experimental results and engineering analysis supported the development of a detailed field testing plan and protocol to evaluate the technology at near-commercial scale. The field test preparation included development of procedures to introduce chemical additives to an existing SO 2 polishing unit and identification of representative flue gas conditions based on a review of existing plants. These activities will have direct bearing on operation and design of commercial units.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2012

THE RELATION BETWEEN COOL CLUSTER CORES AND HERSCHEL-DETECTED STAR FORMATION IN BRIGHTEST CLUSTER GALAXIES

We present far-infrared (FIR) analysis of 68 brightest cluster galaxies (BCGs) at 0.08 < z < 1.0. Deriving total infrared luminosities directly from Spitzer and Herschel photometry spanning the peak of the dust component (24-500 {mu}m), we calculate the obscured star formation rate (SFR). 22{sup +6.2}{sub -5.3}% of the BCGs are detected in the far-infrared, with SFR = 1-150 M{sub Sun} yr{sup -1}. The infrared luminosity is highly correlated with cluster X-ray gas cooling times for cool-core clusters (gas cooling time <1 Gyr), strongly suggesting that the star formation in these BCGs is influenced by the cluster-scale cooling process. The occurrence of the molecular gas tracing H{alpha} emission is also correlated with obscured star formation. For all but the most luminous BCGs (L{sub TIR} > 2 Multiplication-Sign 10{sup 11} L{sub Sun }), only a small ({approx}<0.4 mag) reddening correction is required for SFR(H{alpha}) to agree with SFR{sub FIR}. The relatively low H{alpha} extinction (dust obscuration), compared to values reported for the general star-forming population, lends further weight to an alternate (external) origin for the cold gas. Finally, we use a stacking analysis of non-cool-core clusters to show that the majority of the fuel for star formation in the FIR-bright BCGs is unlikely to originate from normal stellar mass loss.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Carbonate-Catalyzed CO 2 Insertion into Hydrocarbon C-H Bonds (Final Technical Report)

The development of methods to utilize CO 2 as a feedstock for chemical and fuel synthesis is critical for creating renewable alternatives to fossil fuel-based products. This project investigated a class of catalyst materials known as "dispersed carbonates", which are composed of alkali carbonate salts (e.g. potassium carbonate) dispersed in porous support materials. These catalysts react with CO 2 and organic molecules to form chemicals known as carboxylates that have wide applications in the chemical industry. The project used a combination of spectroscopic and reactivity studies to provide fundamental insight into the structure and mechanism of dispersed carbonates in these reactions, leading to variants with greater reactivity. In addition, dispersed carbonates were investigated for CO 2 hydrogenation catalysis, which is critical for processes under development for making sustainable fuels. The dispersed carbonates proved to be highly active and selective catalysts for the reverse water gas shift reaction in which CO 2 is hydrogenated to CO. The dispersed carbonates provide a compelling alternative to conventional metal-based catalysts for reverse water gas shift that could enable new process designs with higher efficiency and lower complexity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Nanocrystalline silicon: Lattice dynamics and enhanced thermoelectric properties

In this study, silicon has several advantages when compared to other thermoelectric materials, but until recently it was not used for thermoelectric applications due to its high thermal conductivity, 156 W K -1 m -1 at room temperature. Nanostructuration as means to decrease thermal transport through enhanced phonon scattering has been a subject of many studies. In this work we have evaluated the effects of nanostructuration on the lattice dynamics of bulk nanocrystalline doped silicon. The samples were prepared by gas phase synthesis, followed by current and pressure assisted sintering. The heat capacity, density of phonons states, and elastic constants were measured, which all reveal a significant, ≈25%, reduction in the speed of sound. The samples present a significantly decreased lattice thermal conductivity, ≈25 W K -1 m -1 , which, combined with a very high carrier mobility, results in a dimensionless figure of merit with a competitive value that peaks at ZT ≈ 0.57 at 973 °C. Due to its easily scalable and extremely low-cost production process, nanocrystalline Si prepared by gas phase synthesis followed by sintering could become the material of choice for high temperature thermoelectric generators.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

THE RAPID DECLINE IN METALLICITY OF DAMPED Lyα SYSTEMS AT z ∼ 5

We present evidence that the cosmological mean metallicity of neutral atomic hydrogen gas shows a sudden decrease at z > 4.7 down to 〈Z〉=−2.03{sub −0.11}{sup +0.09}, which is 6σ deviant from that predicted by a linear fit to the data at lower redshifts. This measurement is made possible by the chemical abundance measurements of eight new damped Lyα (DLA) systems at z > 4.7 observed with the Echellette Spectrograph and Imager on the Keck II Telescope, doubling the number of measurements at z > 4.7 to 16. Possible explanations for this sudden decrease in metallicity include a change in the physical processes that enrich the neutral gas within disks, or an increase of the covering factor of neutral gas outside disks due to a lower ultraviolet radiation field and higher density at high redshift. The later possibility would result in a new population of presumably lower metallicity DLAs, with an increased contribution to the DLA population at higher redshifts resulting in a reduced mean metallicity. Furthermore, we provide evidence of a possible decrease at z > 4.7 in the comoving metal mass density of DLAs, ρ{sub metals}(z){sub DLA}, which is flat out to z ∼ 4.3. Such a decrease is expected, as otherwise most of the metals from star-forming galaxies would reside in DLAs by z ∼ 6. While the metallicity is decreasing at high redshift, the contribution of DLAs to the total metal budget of the universe increases with redshift, with DLAs at z ∼ 4.3 accounting for ∼20% as many metals as produced by Lyman break galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

AGN ACTIVITY AND THE MISALIGNED HOT ISM IN THE COMPACT RADIO ELLIPTICAL NGC 4278

The analysis of a deep (579 ks) Chandra ACIS pointing of the elliptical galaxy NGC 4278, which hosts a low-luminosity active galactic nucleus (AGN) and compact radio emission, allowed us to detect extended emission from hot gas out to a radius of {approx}5 kpc, with 0.5-8 keV luminosity of 2.4 Multiplication-Sign 10{sup 39} erg s{sup -1}. The emission is elongated in the NE-SW direction, misaligned with respect to the stellar body, and aligned with the ionized gas and with the Spitzer IRAC 8 {mu}m non-stellar emission. The nuclear X-ray luminosity decreased by a factor of {approx}18 since the first Chandra observation in 2005, a dimming that enabled the detection of hot gas even at the position of the nucleus. The gas shows a significantly larger temperature (kT = 0.75 keV) in both the projected and deprojected profiles in the inner {approx}300 pc than in the surrounding region, where it stays at {approx}0.3 keV, a value lower than expected from standard gas heating assumptions. The nuclear X-ray emission is consistent with that of a low radiative efficiency accretion flow, accreting mass at a rate close to the Bondi rate; estimates of the power of the nuclear jets require that the accretion rate is not largely reduced with respect to the Bondi rate. Among possible origins for the central large hot gas temperature, such as gravitational heating from the central massive black hole and a recent AGN outburst, interaction with the nuclear jets seems more likely, especially if the latter remain confined, and heat the nuclear region frequently. The unusual hot gas distribution on the galactic scale could be due to the accreting cold gas triggering the cooling of the hot phase, a process also contributing to the observed line emission from ionized gas, and to the hot gas temperature being lower than expected; alternatively, the latter could be due to the efficiency of the Type Ia supernova heating that is lower than usually adopted.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Front-End Engineering Design Study for Retrofit Post-Combustion Carbon Capture on a Natural Gas Combined Cycle Power Plant

The objective of the project is to conduct a Front-End Engineering Design (FEED) study to determine the technical and economic feasibility of installing a retrofit, post-combustion, carbon capture facility on a commercially operating, natural gas-fired, combined cycle (NGCC) power plant. The Electric Power Research Institute (EPRI), California Resources Corporation (CRC), and Fluor Corporation used Fluor's Econamine FG Plus SM (EFG+) conducted the FEED study for capturing CO 2 produced by CRC's 550 MWe Elk Hills Power Plant (EHPP), located in the Elk Hills Oil Field near Tupman, Kern County, California. The EHPP was commissioned in 2003 and is powered by two General Electric 7FA gas turbines, with two heat recovery steam generators (HRSGs) providing steam to a General Electric D11 steam turbine. The target capture amount is 4,000 tonnes CO 2 /day for use in either enhanced oil recovery or dedicated geological saline storage located on CRC property at or nearby EHPP. This CO 2 is captured from a combination of the CO 2 emitted from the flue gas from EHPP and the flue gas generated from a natural gas-fired auxiliary boiler that supplies steam to the EFG+ process.

03 NATURAL GAS↗