Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “PRODUCTIVITY”

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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Multifunctional landscapes: Site characterization and field-scale design to incorporate biomass production into an agricultural system

Current and future demand for food, feed, fiber, and energy require novel approaches to land management, which demands that multifunctional landscapes are created to integrate various ecosystem functions into a sustainable land use. We developed an approach to design such landscapes at a field scale to minimize concerns of land use change, water quality, and greenhouse gas emissions associated with production of food and bioenergy. This study leverages concepts of nutrient recovery and phytoremediation to place bioenergy crops on the landscape to recover nutrients released to watersheds by commodity crops. Crop placement is determined by evaluating spatial variability of: 1) soils, 2) surface flow pathways, 3) shallow groundwater flow gradients, 4) subsurface nitrate concentrations, and 5) primary crop yield. A 0.8 ha bioenergy buffer was designed within a 6.5 ha field to intercept concentrated surface flow, capture and use nitrate leachate, and minimize use of productive areas. Denitrification-Decomposition (DNDC) simulations show that on average, a switchgrass (Panicum Virgatum L.) or willow (Salix spp.) buffer within this catchment according to this design could reduce annual leached NO3 by 61 or 59% and N2O emission by 5.5 or 10.8%, respectively, produce 8.7 or 9.7 Mg ha-1 of biomass respectively, and displace 6.7 Mg ha-1 of corn (Zea mays L.) grain. Therefore, placement of bioenergy crops has the potential to increase environmental sustainability when the pairing of location and crop type result in minimal disruption of current food production systems and provides additional environmental benefits.

09 BIOMASS FUELS↗
DOE OSTI2019

From Lignin to Valuable Products–Strategies, Challenges, and Prospects

The exploration of effective approaches for the valorization of lignin to valuable products attracts broad interests of a growing scientific community. By fully unlocking the potential of the world’s most abundant resource of bio-aromatics, it could improve the profitability and carbon efficiency of the entire biorefinery process, thus accelerate the replacement of fossil resources with bioresources in our society. This review summaries the latest cutting-edge innovations of lignin chemical valorization with the focus on the aforementioned three key aspects.

lignin, biofuels↗
DOE OSTI2014

Fission product release and survivability of UN-kernel LWR TRISO fuel

A thermomechanical assessment of the LWR application of TRISO fuel with UN kernels was performed. Fission product release under operational and transient temperature conditions was determined by extrapolation from fission product recoil calculations and limited data from irradiated UN pellets. Both fission recoil and diffusive release were considered and internal particle pressures computed for both 650 and 800 um diameter kernels as a function of buffer layer thickness. These pressures were used in conjunction with a finite element program to compute the radial and tangential stresses generated within a TRISO particle undergoing burnup. Creep and swelling of the inner and outer pyrolytic carbon layers were included in the analyses. A measure of reliability of the TRISO particle was obtained by computing the probability of survival of the SiC barrier layer and the maximum tensile stress generated in the pyrolytic carbon layers from internal pressure and thermomechanics of the layers. These reliability estimates were obtained as functions of the kernel diameter, buffer layer thickness, and pyrolytic carbon layer thickness. The value of the probability of survival at the end of irradiation was inversely proportional to the maximum pressure.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2018

Trace element migration during UF4 bomb reduction: Implications to metal fuel production, worker health and safety, and nuclear forensics

Understanding the migration of trace contaminants during the production of U metal is vital for fabricating advanced nuclear fuels, for managing worker health and safety at foundry and processing facilities, and for advancing nuclear forensic science. A common method used to produce actinide metals is the bomb reduction of suitable U precursors. Here, we report the results of a series of experiments designed to quantitatively track the trace contaminants Th, Ca, and, Mg through a bomb reduction of UF4 using a vacuum induction furnace. In this series, UF4 charges were doped with increasing levels of elemental Th from 0-1000 ppm Th/U. Following reduction, the metal ingot products and the associated slag and crucibles were individually digested and analyzed using inductively coupled plasma-mass spectrometry. The results show that Th fractionation occurred at all concentrations but was most significant, and near quantitative, in samples starting with Th concentrations below 100 ppm. Thorium was found to incorporate into the slag and crucible in roughly equal proportions. A significant amount of U and Ca migrated into the crucible walls, each correlated with Mg migration from the MgO crucible to the U metal product.

Reilly, Dallas D.↗
DOE OSTI2019

Enhanced Catalyst Durability for Bio-Based Adipic Acid Production by Atomic Layer Deposition

Harsh reaction environments challenge the lifetime productivity of conventional catalysts and impede emerging biobased chemical processes. Condensed-phase processing of muconic acid, a biobased platform chemical, leads to problematic levels of catalyst leaching and fouling. Atomic layer deposition (ALD) can improve catalyst durability using protective metal oxide coatings; however, a targeted coating strategy and cost models thereof are needed for application-specific deactivation challenges that can surmount these challenges while accounting for process implications. Herein, we utilize thin (<5 wt% Al) Al2O3 ALD coatings to increase the lifetime productivity of Pd/TiO2 during muconic acid hydrogenation to adipic acid. The ALD coating decreases Pd leaching by >3x and markedly improves the thermal stability of Pd and TiO2. Economic analysis for an adipic acid biorefinery supports that increased material costs and reduced catalyst productivity can be justified through lifetime extension. Broadly, this work lays the foundation for reducing the cost of biobased chemical processes through catalyst stability.

Settle, Amy↗
DOE OSTI2016

Measurement of D*±, D± and D s ± meson production cross sections in pp collisions at s = 7 TeV with the ATLAS detector

The production of D *± , D ± and D $±\atop{s}$charmed mesons has been measured with the ATLAS detector in pp collisions at √s = 7 TeV at the LHC, using data corresponding to an integrated luminosity of 280 nb -1 . The charmed mesons have been reconstructed in the range of transverse momentum 3.5 T (D)<100 GeV and pseudorapidity |η(D)|<2.1. The differential cross sections as a function of transverse momentum and pseudorapidity were measured for D *± and D ± production. The next-to-leading-order QCD predictions are consistent with the data in the visible kinematic region within the large theoretical uncertainties. Using the visible D cross sections and an extrapolation to the full kinematic phase space, the strangeness-suppression factor in charm fragmentation, the fraction of charged non-strange D mesons produced in a vector state, and the total cross section of charm production at √s = 7 TeV were derived.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Production of lipid and carbohydrate from microalgae without compromising biomass productivities: Role of Ca and Mg

We report the cultivation of Chlorella sorokiniana str. SLA-04 in media containing trace amounts of Ca and Mg. The differences in productivities of biomass, lipids and carbohydrates were assessed relative to cultures grown in standard media (BG-11) that contain approximately 8 × higher concentration of Ca and 30 × higher concentration of Mg. Culture performance in N-limited standard media was also investigated. In addition to growth and accumulation of storage products (lipid and carbohydrate), we measured the utilization of N, Ca and Mg and monitored changes in cell size and photosynthetic activity. Our results showed that limitation of Ca or Mg did not inhibit cell replication and culture growth. On the contrary, Ca-limited (Ca L ) cultures had ~30% higher biomass productivity relative to the control with excessive nutrients possibly due to improvement in cell wall flexibility and cell division. We also observed that Ca L and Mg-limited (Mg L ) cultures had nearly 3-fold higher lipid concentration (measured as fatty acid methyl ester) and 50% higher carbohydrate concentration than the nutrient excess control cultures. Simultaneous culture growth and lipid accumulation in Ca L and Mg L cultures suggest that de novo synthesis was the primary mechanism for lipid accumulation in Ca/Mg-limited media. Overall, our study demonstrates that micronutrient optimization, in addition to optimization of macronutrients, could significantly improve microalgal biorefinery yields.

09 BIOMASS FUELS↗
DOE OSTI2015

Cement As a Waste Form for Nuclear Fission Products: The Case of 90 Sr and Its Daughters [Cement As a Container for Nuclear Fission Products: The Case of 90 Sr and Its Daughters]

One of the main challenges faced by the nuclear industry is the long-term confinement of nuclear waste. Because it is inexpensive and easy to manufacture, cement is the material of choice to store large volumes of radioactive materials, in particular the low-level medium-lived fission products. It is therefore of utmost importance to assess the chemical and structural stability of cement containing radioactive species. Here, we use ab initio calculations based on density functional theory (DFT) to study the effects of 90 Sr insertion and decay in C–S–H (calcium-silicate-hydrate) in order to test the ability of cement to trap and hold this radioactive fission product and to investigate the consequences of its β-decay on the cement paste structure. We show that 90 Sr is stable when it substitutes the Ca 2+ ions in C–S–H, and so is its daughter nucleus 90 Y after β-decay. Interestingly, 90 Zr, daughter of 90 Y and final product in the decay sequence, is found to be unstable compared to the bulk phase of the element at zero K but stable when compared to the solvated ion in water. Furthermore, cement appears as a suitable waste form for 90 Sr storage.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Acceleration and Stabilization of Electron Transfer Products with Improved Quantum Yields upon Cation Binding to a Fused Bis-Zinc Porphyrin-Quinone Donor–Acceptor Conjugate

The role of metal ions in promoting electron transfer processes in biological coenzymes is of great significance not only to understand their mechanistic details but also due to their direct utilization in a number of chemical and biochemical processes. Here, we demonstrate an increased rate of forward electron transfer with improved reaction quantum yield, and an enhanced lifetime of electron transfer products upon cation binding to the acceptor entity in a donor-acceptor conjugate. Selective binding of cations such as Mg 2+ or Sc 3+ to the electron acceptor, quinone, in a fused, bis-zinc porphyrin-quinone donor-acceptor conjugate leads to facile reduction of the quinone making the electron transfer process thermodynamically highly feasible. Furthermore, the binding of metal ions to the electron transfer product, quinone anion, decelerates the reverse electron transfer process due to ion-pairing interactions, resulting in improving both the lifetime and quantum yields of the electron transfer products. Furthermore, systematic studies including spectral, electrochemical, computational, spectroelectrochemical, and transient absorption techniques, coupled with data analysis by Global Target Analysis (GloTarAn), are performed to demonstrate these novel findings that are relevant to further our understanding of electron transfer processes occurring in biological coenzymes and pertinent energy harvesting schemes.

Charge transfer↗
DOE OSTI2020

CeTi 2 O 6 —A Promising Oxide for Solar Thermochemical Hydrogen Production

A large entropy of reduction is crucial in achieving materials capable of high-efficiency solar thermochemical hydrogen (STCH) production through two-step thermochemical water splitting cycles. We have recently demonstrated that the onsite electronic entropy of reduction attains an extreme value of 4.26 kB at 1500 K in Ce 4+ → Ce 3+ redox reactions, which explains the high performance and uniqueness of CeO 2 as an archetypal STCH material. However, ceria requires high temperatures (T > 1500 °C) to achieve a reasonable reduction extent because of its large reduction enthalpy, which is a major obstacle in practical applications. Therefore, new materials with a large entropy of reduction and lower reduction enthalpy are required. Here, we perform a systematic screening to search for Ce 4+ -based oxides which possess thermodynamics superior to CeO 2 for STCH production. We first search the Inorganic Crystal Structure Database (ICSD) and literature for Ce 4+ -based oxides and subsequently use density functional theory to compute their reduction enthalpies (i.e., oxygen vacancy formation energies). Here, we find that CeTi 2 O 6 with the brannerite structure is the most promising candidate for STCH because it possesses three essential characteristics of an STCH material: (i) a smaller reduction enthalpy compared to ceria yet large enough to split water, (ii) a high thermal stability, as reported experimentally, and (iii) a large entropy of reduction associated with Ce 4+ → Ce 3+ redox. Our proposed design strategy suggests that further exploration of Ce 4+ oxides for STCH production is warranted.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Production and distillative recovery of valuable lignin-derived products from biocrude

Value-added chemicals present in liquid products from direct liquefaction of biomass can be recovered as bioproducts in an integrated biorefinery to enhance the economic viability of biomass-to-liquid fuel technologies and afford a higher return on investment. In recent efforts, RTI International is exploring and developing processes that could be used to produce bioproducts in addition to liquid fuel from biocrude intermediates. The present study focused on the production and recovery of high-value lignin-derived compounds from biocrude. Catalytic pyrolysis with a nonzeolite, alumina-based catalyst was used to produce the biocrude from loblolly pine in RTI's 1-tonne per day pilot-scale plant. Distillation was evaluated as a potential separation method given that the biocrude is relatively thermally stable and distillable compared to raw pyrolysis oils. The distillation studies were performed with a laboratory distillation unit (PETRODIST 300 CC) and the biocrude was fractionated into four distillate cuts: cut 1 (IBP-110 °C), cut 2 (110–200 °C), cut 3 (200–300 °C), and cut 4 (300–400 °C). In a case study, cut 3 was distilled further to concentrate the lignin-derived chemicals boiling between 200 and 270 °C. The results showed that a biocrude containing about 10 wt% guaiacols could be concentrated to about 35 wt% of guaiacols (representing 75% recovery) in the first distillation step. The second distillation step increased the concentration of guaiacols to about 53 wt% (representing 80% recovery). Furthermore, these findings suggest that it is possible to isolate and concentrate the lignin-derived products using a distillation column with a number of plates/trays. The yields, physicochemical properties, and chemical composition of the fractions, as well as the overall distillation separation efficiency, are reported.

09 BIOMASS FUELS↗
DOE OSTI2020

Life cycle energy use and greenhouse gas emissions of ammonia production from renewable resources and industrial by-products

Conventionally, ammonia is produced from natural gas via steam methane reforming (SMR), water-gas shift reaction, and the Haber–Bosch process. The process uses fossil natural gas, which leads to 2.6 metric tons of life cycle greenhouse gas (GHG) emissions per metric ton of ammonia produced. With ammonia being the second most produced chemical in the world, its production accounts for approximately 2% of worldwide fossil energy use and generates over 420 million tons of CO 2 annually. To reduce its carbon intensity, ammonia synthesis relying on renewable energy or utilizing by-products from industrial processes is of interest. In this work, we conduct a life cycle analysis of conventional and alternative ammonia production pathways by tracking energy use and emissions in all conversion stages, from the primary material and energy resources to the ammonia plant gates. Of all the alternative pathways, obtaining N 2 from cryogenic distillation and H 2 from low-temperature electrolysis using renewable electricity has the lowest cradle-to-plant-gate GHG emissions, representing a 91% decrease from the conventional SMR pathway.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Engineering Escherichia coli coculture systems for the production of biochemical products

Significance Production of industrial compounds by using engineered microorganisms is a robust method to reduce our reliance on nonrenewable petroleum resources and increase the utility of renewable resources, such as lignocellulose. Because there are major limitations for engineering a single microbial cell to achieve high-yield production, we developed microbial coculture systems consisting of two different microbial cell types to use sugar mixtures that can be derived from lignocellulose efficiently. We demonstrate that this approach is successful for achieving high-level production of two important value-added molecules, cis , cis -muconic acid and 4-hydroxybenzoic acid. This accomplishment establishes a previously unidentified technology for advancing future research in metabolic engineering and synthetic biology.

4-hydroxybenzoic acid↗