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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.

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At least 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
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

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↗
DOE OSTI2013

Phase transformation during mechano-synthesis of nanocrystalline/amorphous Fe–32Mn–6Si alloys

Mechano-synthesis of Fe–32Mn–6Si alloy by mechanical alloying of the elemental powder mixtures was evaluated by running the ball milling process under an inert argon gas atmosphere. In order to characterize the as-milled powders, powder sampling was performed at predetermined intervals from 0.5 to 192 h. X-ray florescence analyzer, X-ray diffraction, scanning electron microscope, and high resolution transmission electron microscope were utilized to investigate the chemical composition, structural evolution, morphological changes, and microstructure of the as-milled powders, respectively. According to the results, the nanocrystalline Fe–Mn–Si alloys were completely synthesized after 48 h of milling. Moreover, the formation of a considerable amount of amorphous phase during the milling process was indicated by quantitative X-ray diffraction analysis as well as high resolution transmission electron microscopy image and its selected area diffraction pattern. It was found that the α-to-γ and subsequently the amorphous-to-crystalline (especially martensite) phase transformation occurred by milling development. - Graphical abstract: Mechano-synthesis of nanocrystalline/amorphous Fe–32Mn–6Si shape memory alloys in the powder form: amorphous phase formation, α-to-γ phase transformation, mechano-crystallization of the amorphous, and martensite phase formation during the process. Highlights: • During MA, the α-to-γ phase transformation and amorphization occurred. • Mechano-crystallization of the amorphous phase occurred at sufficient milling time. • The formation of high amount of ε-martensite was evidenced at high milling times. • The platelet, spherical, and then irregular particle shapes was extended by MA. • By MA, the particles size was increased, then reduced, and afterward re-increased.

36 MATERIALS SCIENCE↗
DOE OSTI2023

2.2.3.106 - Lignin-First Biorefinery Development

The Lignin-First Biorefinery Development (LigFirst) project aims to develop a cost-effective, and scalable biomass fractionation strategy based on reductive catalytic fractionation (RCF). The RCF process uses a protic solvent, hydrogen gas or a hydrogen donor, and a metal catalyst in the presence of intact biomass to produce a stable, depolymerized lignin oil and a polysaccharide pulp, which can both be converted to value-added products in parallel processes. RCF is a promising strategy to enable the use of woody feedstocks in biochemical conversion processes and is also promising as a means to valorize lignin with equal emphasis to biomass carbohydrates. Guided by techno-economic analysis and life cycle assessment and in collaboration with industry partners, we are actively developing RCF methods to 1) avoid the need for exogenous hydrogen gas, 2) substantially reduce reactor pressure via use of low vapor pressure solvents, 3) separate the lignin solvolysis and catalytic processes through reaction engineering solutions, 4) reduce solvent loading below what can be achieved in typical batch reactors, and 5) avoid or minimize the use of organic solvents. The LigFirst project also collaborates closely with the Lignin Utilization and Lignin Conversion-to-SAF projects for critical substrate handoffs and analytics. Overall, the LigFirst project is enabling new approaches that ultimately can enable RCF to be a feedstock-agnostic method to valorize both polysaccharides and lignin.

BIOMASS FUELS↗
DOE OSTI2013

Description of the Process Model for the Technoeconomic Evaluation of MEA versus Mixed Amines for Carbon Dioxide Removal from Stack Gas

This model description is supplemental to the Lawrence Livermore National Laboratory (LLNL) report LLNL-TR-642494, Technoeconomic Evaluation of MEA versus Mixed Amines for CO2 Removal at Near- Commercial Scale at Duke Energy Gibson 3 Plant. We describe the assumptions and methodology used in the Laboratory’s simulation of its understanding of Huaneng’s novel amine solvent for CO2 capture with 35% mixed amine. The results of that simulation have been described in LLNL-TR-642494. The simulation was performed using ASPEN 7.0. The composition of the Huaneng’s novel amine solvent was estimated based on information gleaned from Huaneng patents. The chemistry of the process was described using nine equations, representing reactions within the absorber and stripper columns using the ELECTNRTL property method. As a rate-based ASPEN simulation model was not available to Lawrence Livermore at the time of writing, the height of a theoretical plate was estimated using open literature for similar processes. Composition of the flue gas was estimated based on information supplied by Duke Energy for Unit 3 of the Gibson plant. The simulation was scaled at one million short tons of CO2 absorbed per year. To aid stability of the model, convergence of the main solvent recycle loop was implemented manually, as described in the Blocks section below. Automatic convergence of this loop led to instability during the model iterations. Manual convergence of the loop enabled accurate representation and maintenance of model stability.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2020

A Collection of More than 900 Gas Mixture Adsorption Experiments in Porous Materials from Literature Meta-Analysis

Information on mixture adsorption equilibrium is vital in developing adsorption-based separation processes. Because measuring mixture adsorption is more difficult than measuring single-component adsorption, far more data of the latter kind are available. Previous efforts to compile experimental mixture adsorption data for gases have given data sets with at most a few dozen examples. Here, we report the results of systematic literature meta-analysis that produced a data set of more than 900 gas mixture adsorption experiments. This collection includes data from 125 different binary mixtures including 60 different molecular species and information from 333 different adsorbents. We refer to this data set as the Binary adsorption ISOtherm ExperimeNtal 2020 (BISON-20) Database. Because the BISON-20 data set enormously expands the number and variety of experimental results for binary gas adsorption that are readily available, it will be a useful resource for future efforts in developing new materials or processes for gas separations. As initial applications of the BISON-20 data set, we show how identifying replicate measurements can be used to assess the reliability of binary adsorption data, how the accuracy of Ideal Adsorbed Solution Theory (IAST) can be systematically tested using experimental data, and how trends in selectivity for gas separations across many materials can be examined.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Magnetic field influenced electron-impurity scattering and magnetotransport

We formulate a classical theory ($ω_cτ ≲ 1$ with $ω_c$ as the cyclotron frequency and $\tau$ as the relaxation time) to study the influence of perpendicular magnetic field on the electron-impurity scattering process in two-dimensional electron gas. To describe the curved incoming and outgoing trajectories, we introduce a general recipe based on an abstraction of the actual impurity scattering process to define the scattering parameters such as the incoming and outgoing momentum and coordinate jump. In this picture, we can conveniently describe the skew scattering and coordinate jump, which will eventually modify the Boltzmann equation. In this work, we find an anomalous Hall resistivity different from the conventional Boltzmann-Drude result and a negative magnetoresistivity as a parabolic function of magnetic field. The origin of these results is analyzed. The relevance between our theory and recent simulation and experimental works is also discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Design, Development, and Operation of an Integrated Fluidized Carbon Capture Unit Using Polyethylenimine Sorbents

In this paper, we present the design, development, and operation of a reactor system for CO 2 capture. Modifications were implemented to address differences in sorbent from 180 μm Geldart group B to 115 μm Geldart group A material; operational issues were discovered during experimental trials. The major obstacle in system operation was the ability to maintain a constant circulation of a solid sorbent stemming from this change in sorbent material. The system consisted of four fluid beds, through which a polyamine impregnated sorbent was circulated and adsorption, preheat, regeneration, and cooling processes occurred. Pressure transducers, thermocouples, gas flow meters, and gas composition instrumentation were used to characterize thermal, hydrodynamic, and gas adsorption performance in this integrated unit. A series of shakedown tests were performed and the configuration altered to meet the needs of the sorbent performance and achieve desired target capture efficiencies. Methods were identified, tested, and applied to continuously monitor critical operating parameters including solids circulation rate, adsorbed and desorbed CO 2 , solids inventories, and pressures. The working capacity and CO 2 capture efficiency were used to assess sorbent performance while CO 2 closure was used to define data quality and approach to steady-state. Testing demonstrated >90% capture efficiencies and identified the regenerator to be the process step limiting throughput. Sorbent performance was found to be related to the reactant stoichiometry. Finally, a stochastic model with an exponential dependence on the relative CO 2 /amine concentration was used to describe 90% of the variance in the data.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2012

SUB-ALFVENIC NON-IDEAL MAGNETOHYDRODYNAMIC TURBULENCE SIMULATIONS WITH AMBIPOLAR DIFFUSION. III. IMPLICATIONS FOR OBSERVATIONS AND TURBULENT ENHANCEMENT

Ambipolar diffusion (AD) is believed to be a crucial process for redistributing magnetic flux in the dense molecular gas that occurs in regions of star formation. We carry out numerical simulations of this process in regions of low ionization using the heavy-ion approximation. The simulations are for regions of strong field (plasma {beta} = 0.1) and mildly supersonic turbulence (M=3, corresponding to an Alfven Mach number of 0.67). The velocity power spectrum of the neutral gas changes from an Iroshnikov-Kraichnan spectrum in the case of ideal MHD to a Burgers spectrum in the case of a shock-dominated hydrodynamic system. The magnetic power spectrum shows a similar behavior. We use a one-dimensional radiative transfer code to post-process our simulation results; the simulated emission from the CS J = 2-1 and H{sup 13}CO{sup +} J = 1-0 lines shows that the effects of AD are observable in principle. Linewidths of ions are observed to be less than those of neutrals, and we confirm previous suggestions that this is due to AD. We show that AD is unlikely to affect the Chandrasekhar-Fermi method for inferring field strengths unless the AD is stronger than generally observed. Finally, we present a study of the enhancement of AD by turbulence, finding that AD is accelerated by factor 2-4.5 for non-self-gravitating systems with the level of turbulence we consider.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Effect of Through-Thickness Friction Stir Processing Parameters on Weld Repair and Modification of Fusion-Welded AA6061 Aluminum Alloy

Through-thickness friction stir processing was successfully carried out for microstructure modification and elimination of fusion defects of the gas metal arc welds by applying the process on as-welded joints. Variation in rotational speed from 750 to 1050 rpm and traveling speed from 50 to 200 mm/min resulted in minor changes (approximately 1 µm) in the grain size of nugget zone, while this variation in elongation result was up to 40%. The hardness profile, the width of softening zone, minimum hardness and fracture location also changed for different processing conditions. Furthermore, the defects were vanished efficiently across the welds profile by this method. The results also verified the geometric dynamic recrystallization phenomena as a dominant mechanism of microstructural modification.

36 MATERIALS SCIENCE↗