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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Effect of Two Advanced Noise Reduction Technologies on the Aerodynamic Performance of an Ultra High Bypass Ratio Fan

A wind tunnel experiment was conducted in the NASA Glenn Research Center anechoic 9- by 15-Foot Low-Speed Wind Tunnel to investigate two new advanced noise reduction technologies in support of the NASA Fundamental Aeronautics Program Subsonic Fixed Wing Project. The goal of the experiment was to demonstrate the noise reduction potential and effect on fan model performance of the two noise reduction technologies in a scale model Ultra-High Bypass turbofan at simulated takeoff and approach aircraft flight speeds. The two novel noise reduction technologies are called Over-the-Rotor acoustic treatment and Soft Vanes. Both technologies were aimed at modifying the local noise source mechanisms of the fan tip vortex/fan case interaction and the rotor wake-stator interaction. For the Over-the-Rotor acoustic treatment, two noise reduction configurations were investigated. The results showed that the two noise reduction technologies, Over-the-Rotor and Soft Vanes, were able to reduce the noise level of the fan model, but the Over-the-Rotor configurations had a significant negative impact on the fan aerodynamic performance; the loss in fan aerodynamic efficiency was between 2.75 to 8.75 percent, depending on configuration, compared to the conventional solid baseline fan case rubstrip also tested. Performance results with the Soft Vanes showed that there was no measurable change in the corrected fan thrust and a 1.8 percent loss in corrected stator vane thrust, which resulted in a total net thrust loss of approximately 0.5 percent compared with the baseline reference stator vane set.

Hughes, Christoper E.↗
NASA NTRS2016

Innovative Flow Control Concepts for Drag Reduction

This paper highlights the technology development of two flow control concepts for aircraft drag reduction. The NASA Environmentally Responsible Aviation (ERA) project worked with Boeing to demonstrate these two concepts on a specially outfitted Boeing 757 ecoDemonstrator during the spring of 2015. The first flow control concept used Active Flow Control (AFC) to delay flow separation on a highly deflected rudder and increase the side force that it generates. This may enable a smaller vertical tail to provide the control authority needed in the event of an engine failure during takeoff and landing, while still operating in a conventional manner over the rest of the flight envelope. Thirty-one sweeping jet AFC actuators were installed and successfully flight-tested on the vertical tail of the 757 ecoDemonstrator. Pilot feedback, flow cone visualization, and analysis of the flight test data confirmed that the AFC is effective, as a smoother flight and enhanced rudder control authority were reported. The second flow control concept is the Insect Accretion Mitigation (IAM) innovation where surfaces were engineered to mitigate insect residue adhesion on a wing's leading edge. This is necessary because something as small as an insect residue on the leading edge of a laminar flow wing design can cause turbulent wedges that interrupt laminar flow, resulting in an increase in drag and fuel use. Several non-stick coatings were developed by NASA and applied to panels that were mounted on the leading edge of the wing of the 757 ecoDemonstrator. The performance of the coated surfaces was measured and validated by the reduction in the number of bug adhesions relative to uncoated control panels flown simultaneously. Both flow control concepts (i.e., sweeping jet actuators and non-stick coatings) for drag reduction were the culmination of several years of development, from wind tunnel tests to flight tests, and produced valuable data for the advancement of modern aircraft designs. The ERA systems analysis studies performed by NASA indicated that AFC-enhanced vertical tail could produce approximately 0.9% drag reduction for a large twin aisle aircraft and IAM coatings could enable approximately 1.2% drag reduction recovery for a potential total drag reduction of approximately 3.3% for a single aisle aircraft with a natural laminar flow (NLF) wing design.

Lin, John C.↗
NASA NTRS2015

Reduction of Subjective and Objective System Complexity

Occam's razor is often used in science to define the minimum criteria to establish a physical or philosophical idea or relationship. Albert Einstein is attributed the saying "everything should be made as simple as possible, but not simpler". These heuristic ideas are based on a belief that there is a minimum state or set of states for a given system or phenomena. In looking at system complexity, these heuristics point us to an idea that complexity can be reduced to a minimum. How then, do we approach a reduction in complexity? Complexity has been described as a subjective concept and an objective measure of a system. Subjective complexity is based on human cognitive comprehension of the functions and inter relationships of a system. Subjective complexity is defined by the ability to fully comprehend the system. Simplifying complexity, in a subjective sense, is thus gaining a deeper understanding of the system. As Apple's Jonathon Ive has stated," It's not just minimalism or the absence of clutter. It involves digging through the depth of complexity. To be truly simple, you have to go really deep". Simplicity is not the absence of complexity but a deeper understanding of complexity. Subjective complexity, based on this human comprehension, cannot then be discerned from the sociological concept of ignorance. The inability to comprehend a system can be either a lack of knowledge, an inability to understand the intricacies of a system, or both. Reduction in this sense is based purely on a cognitive ability to understand the system and no system then may be truly complex. From this view, education and experience seem to be the keys to reduction or eliminating complexity. Objective complexity, is the measure of the systems functions and interrelationships which exist independent of human comprehension. Jonathon Ive's statement does not say that complexity is removed, only that the complexity is understood. From this standpoint, reduction of complexity can be approached in finding the optimal or 'best balance' of the system functions and interrelationships. This is achievable following von Bertalanffy's approach of describing systems as a set of equations representing both the system functions and the system interrelationships. Reduction is found based on an objective function defining the system output given variations in the system inputs and the system operating environment. By minimizing the objective function with respect to these inputs and environments, a reduced system can be found. Thus, a reduction of the system complexity is feasible.

Watson, Michael D.↗
NASA NTRS2018

Measurement of Noise Reduction from Acoustic Casing Treatments Installed over a Subscale High Bypass Ratio Turbofan Rotor

NASA is continuing to develop over-the-rotor acoustic liners for turbofan applications. A series of low Technology Readiness Level experiments were conducted to better understand the acoustic and aerodynamic effects of these acoustic liners. The final experiment included the evaluation of four acoustic casing treatment concepts and two baseline configurations in an internal flow axial compressor facility with a 1.5 pressure-ratio high-bypass turbofan rotor. An inlet in-duct array was utilized to extract sound power levels propagating forward from the turbofan rotor. The effect of a circumferentially grooved relative to a hardwall fan case was found to reduce the in-duct sound power level by about 1.5dB for frequencies less than 2kHz while increasing noise from 4 to 8kHz by as much as 7.5dB at low fan speeds. The four acoustic treatment concepts were incorporated into the bottoms of the circumferential grooves and found to provide an additional 1 to 2dB sound power level reduction under 2kHz. The sound power level reduction was found to be even greater, 2.5 to 3.5dB, when evaluating the reduction on rotor alone duct modes (co-rotating modes). The acoustic treatments also appeared to reduce multiple pure tone noise at transonic fan speeds. Depending on the acoustic treatment concept, the high-frequency noise created by the circumferential grooves was reduced by 1.5 to 5 dB. The total noise reduction from acoustic treatments embedded into the bottoms of circumferential grooves relative to a hardwall baseline was found to be 2.5 to 3.5dB sound power level. The sound power level reduction for rotor alone (co-rotating) modes was found to be 3.5 to 4.5dB. These results show the potential for significant turbofan noise reduction by incorporating acoustic treatments over-the-rotor.

Noise↗
NASA NTRS2018

Measurement of Noise Reduction from Acoustic Casing Treatments Installed Over a Subscale High Bypass Ratio Turbofan Rotor

NASA is continuing to develop over-the-rotor acoustic liners for turbofan applications. A series of low Technology Readiness Level experiments were conducted to better understand the acoustic and aerodynamic effects of these acoustic liners. The final experiment included the evaluation of four acoustic casing treatment concepts and two baseline configurations in an internal flow axial compressor facility with a 1.5 pressure-ratio high-bypass turbofan rotor. An inlet in-duct array was utilized to extract sound power levels propagating forward from the turbofan rotor. The effect of a circumferentially grooved relative to a hardwall fan case was found to reduce the in-duct sound power level by about 1.5dB for frequencies less than 2kHz while increasing noise from 4 to 8kHz by as much as 7.5dB at low fan speeds. The four acoustic treatment concepts were incorporated into the bottoms of the circumferential grooves and found to provide an additional 1 to 2dB sound power level reduction under 2kHz. The sound power level reduction was found to be even greater, 2.5 to 3.5dB, when evaluating the reduction on rotor alone duct modes (co-rotating modes). The acoustic treatments also appeared to reduce multiple pure tone noise at transonic fan speeds. Depending on the acoustic treatment concept, the high-frequency noise created by the circumferential grooves was reduced by 1.5 to 5 dB. The total noise reduction from acoustic treatments embedded into the bottoms of circumferential grooves relative to a hardwall baseline was found to be 2.5 to 3.5dB sound power level. The sound power level reduction for rotor alone (co-rotating) modes was found to be 3.5 to 4.5dB. These results show the potential for significant turbofan noise reduction by incorporating acoustic treatments over-the-rotor.

Aeroacoustics↗
DOE OSTI2017

Space-time least-squares Petrov-Galerkin projection in nonlinear model reduction.

Our work proposes a space-time least-squares Petrov-Galerkin (ST-LSPG) projection method for model reduction of nonlinear dynamical systems. In contrast to typical nonlinear model-reduction methods that first apply Petrov-Galerkin projection in the spatial dimension and subsequently apply time integration to numerically resolve the resulting low-dimensional dynamical system, the proposed method applies projection in space and time simultaneously. To accomplish this, the method first introduces a low-dimensional space-time trial subspace, which can be obtained by computing tensor decompositions of state-snapshot data. The method then computes discrete-optimal approximations in this space-time trial subspace by minimizing the residual arising after time discretization over all space and time in a weighted ℓ 2 -norm. This norm can be de ned to enable complexity reduction (i.e., hyper-reduction) in time, which leads to space-time collocation and space-time GNAT variants of the ST-LSPG method. Advantages of the approach relative to typical spatial-projection-based nonlinear model reduction methods such as Galerkin projection and least-squares Petrov-Galerkin projection include: (1) a reduction of both the spatial and temporal dimensions of the dynamical system, (2) the removal of spurious temporal modes (e.g., unstable growth) from the state space, and (3) error bounds that exhibit slower growth in time. Numerical examples performed on model problems in fluid dynamics demonstrate the ability of the method to generate orders-of-magnitude computational savings relative to spatial-projection-based reduced-order models without sacrificing accuracy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Chemical-Biological Cyclic Process for Hexavalent Chromium Reduction to Trivalent Chromium in Aqueous Medium - 20224

Conventional treatment of chromium contamination focuses on immobilization of the highly toxic and water-soluble form Cr(VI), by reducing it to the relatively less toxic and less mobile trivalent form, Cr(III), using reducing compounds like ferrous sulfate or ferrous iron, Fe(II). The Cr(VI) also respond to biodegradation and subsequent reduction. During the reduction reaction, Fe(II) is oxidized to ferric, Fe(III), which, being at the highest oxidation state, has no ability to reduce Cr(VI), and therefore remediation process terminates. The good news is that metal-reducing bacteria, S. oneidensis MR-1, can regenerate Fe(II) from Fe(III) with the help of an organic electron donor in an appropriate bacterial media. Thus, in the Cr(VI) chemical remediation process, Fe(II) to Fe(III) conversion is reversed by the biological process, regenerating Fe(II) and the Cr(VI) chemical reduction process continues in a cyclic fashion. This study presents the results of regeneration of Fe(II) from fresh Fe(III) as well as from the reaction products of Cr(VI) and Fe(II). Both fresh Fe(III) and reaction product Fe(III) exhibited the same reduction behavior. Fe(II) production increased with the increase of initial concentration of Fe(III), resulting in 87.5% Fe(II) regeneration. The extent of Fe(III) reduction (Fe(II)t/Fe(III)0.hour) was 21 times higher than the extent of Cr(VI) reduction (Cr(VI)t/Cr(VI)0.hour) by S. oneidensis MR-1. In a cyclic process of sequential Cr(VI) addition, the amount of Fe(II) regeneration decreased with the increase in cycle number, a fixed quantity of starting S. oneidensis MR-1 could regenerate Fe(II) at least five times in a ten-hour period. More importantly, regenerated Fe(II) instantly reduced Cr(VI) to Cr(III). So, Fe(II) regeneration with metal-reducing bacteria has a good potential for application in groundwater and wastewater remediation in reducing Cr(VI) to Cr(III). As a comparison of chemical to biological transformation, chemical transformation of Cr(VI) by Fe(II) was almost 600 times greater than that of biological transformation. Therefore a chemical-biological cyclic process offers potential applications for remediation of groundwater and hexavalent chromium contaminated waste sites. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Sum Reduction with OpenMP Offload on NVIDIA Grace-Hopper System

We evaluate the performance of the baseline and optimized reductions in OpenMP on an NVIDIA Grace-Hopper system. We explore the impacts of the number of teams, the number of elements to sum per loop iteration, and simultaneous execution on the central-processing unit (CPU) and the GPU in the unified memory (UM) mode upon the reduction performance. The experimental results show that the optimized reductions are 6.120X to 20.906X faster than the baselines on the GPU, and their efficiency ranges from 89% to 95% of the theoretical GPU memory bandwidth. Depending on where an input array is allocated in the program when co-running the reduction on the CPU and GPU in the UM mode, the average speedup over the GPU-only execution is approximately 2.484 or 1.067, and the speedup of the optimized reductions over the baseline reductions ranges from 0.996 to 10.654 or from 0.998 to 6.729.

Jin, Zheming↗
DOE OSTI2026

Elucidating key reducing species beyond ions in hydrogen plasma smelting reduction of iron ore

Hydrogen plasma smelting reduction (HPSR) of iron ore has attracted significant attention over the past decade due to its high-temperature operation, rapid plasma mediated reduction kinetics, and simpler density-based separation of molten iron product, compared to H2-based solid-state reduction. All of these attributes enable processing of low-grade ores for downstream use in electric-arc furnaces, as virgin iron with low gangue content is required for high quality steel and improved furnace operation. While positive ions exist within the plasma arc, this work demonstrates that near the anodic ore surface, hydrogen radicals and vibrationally excited hydrogen species dominate and their densities correlate well with observed reduction rates. Species concentrations in the transferred plasma arc and at the plasma-ore interface are evaluated using coupled thermal plasma and near-wall non-equilibrium plasma models. The thermal plasma model is validated against experimental voltage data and spectroscopic measurements of plasma temperature and density for varying current inputs. Modeling of the near surface thermochemical non-equilibrium and micrometer scale anode sheath layer reveals, in addition to the expected H + , significant concentrations of ArH + and H$^+_3$ ions, typically not observed in thermal plasmas under thermodynamic equilibrium. Our results show that the inverted sheath structure at the anodic ore surface strongly suppresses reactive positive ion fluxes, while non-equilibrium electron-impact processes generate abundant hydrogen radicals and vibrationally excited species. These findings highlight the critical role of non-equilibrium effects in hydrogen arc-driven iron ore reduction and advance understanding beyond prevailing hypotheses centered on hydrogen ion-driven mechanisms.

08 HYDROGEN↗
DOE OSTI2019

Multilevel Techniques for Compression and Reduction of Scientific Data---The Multivariate Case

We develop a technique for multigrid adaptive reduction of data (MGARD). Special attention is given to the case of tensor product grids, where our approach permits the use of nonuniformly spaced grids in each direction, which can prove problematic for many types of data reduction methods. An important feature of our approach is the provision of guaranteed, computable bounds on the loss incurred by the reduction of the data. Many users are leery of lossy algorithms and will only consider using them provided that numerical bounds on the pointwise difference between the original and the reduced datasets are given. Accordingly, we develop techniques for bounding the loss measured in the $L^{\infty}(\Omega)$ norm, and we show that these bounds are realistic in the sense that they do not significantly overestimate the actual loss. Here, the resulting loss indicators are used to guide the adaptive reduction of the data so that the reduced dataset meets a user-prescribed tolerance or memory constraint. Illustrative numerical examples, including the reduction of data arising from the simulation of a nonlinear reaction-diffusion problem, a turbulent channel flow, and a climate simulation, are provided.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

The DREAM approach to demand-side emissions reductions in Indonesia, 2020–2060

Indonesia’s current energy system modeling is heavily focused on the supply side, but emissions reductions in the demand sector have a significant impact on advancing Indonesia’s ambitious emissions reductions goals. To address the gap, we develop a new modeling tool DREAM Indonesia based on a bottom-up, technology-rich demand side framework and formulate projections of demand-side emissions reductions in Indonesia in 2020–2060. We find that demand-side energy efficiency and electrification can halve the growth rate of final energy demand to 1.4% annually over 2020–2060 and reverse the growing trend of emissions. The feasibility of full electrification by 2060, coupled with rapid adoption of existing technologies, positions the building sector as a model for achievable decarbonization and a cornerstone of Indonesia’s emissions reductions ambitions. In the industrial sector, extensive emissions reductions of 87% by 2060 (compared to business-as-usual) are achievable through energy efficiency improvements, alongside enhanced material efficiency measures including optimized material usage, low-carbon substitutions, innovative technologies, and increased circularity. In the transportation sector, balancing final energy demand by incorporating energy efficiency improvements across all transport modes, along with electrification particularly in road transportation, could decrease the emissions by up to 82% in 2060 compared to business-as-usual. This study provides insights and modeling approaches for rapidly growing Asian economies as well as other developing countries facing combined development and decarbonization challenges.

DREAM Indonesia↗
DOE OSTI2018

Electrochemical behavior of Nd and its co-reduction with Bi in molten LiCl-KCl salts - 18360

A molten salt phase is used as the solvent in pyrochemical reprocessing. The molten salt waste generated in pyro-processes contains the residual lanthanides and actinides as various compounds. Various methods have been proposed for recovering and recycling these useful elements. The separation of actinides from lanthanides is performed by electrolysis or reductive extraction. Herein we have studied PyroRedSox-based co-reduction of Nd and Bi via electrolysis in a molten chloride salt. The redox behavior of Nd and the formation potential of intermetallic compounds of Nd and Bi were determined using cyclic voltammetry (CV). Electrorefining was performed under a constant reductive potential at 773 K in LiCl-KCl eutectic mixture; the co-reduction potential was -1.37 V. Lastly, the co-reduction potential of the intermetallic compound was applied to reduce the amount of Nd and Bi. Scanning electron microscopy (SEM) revealed that various kinds of intermetallic compounds were formed in Bi and Nd, and were deposed in the lower part of the molten salt, allowing purification of the contaminated molten salt. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Electrochemical CO 2 Reduction with Atomic Iron-Dispersed on Nitrogen-Doped Graphene

Electrochemical reduction of CO 2 provides an opportunity to reach a carbon-neutral energy recycling regime, in which CO 2 emissions from fuel use are collected and converted back to fuels. The reduction of CO 2 to CO is the first step toward the synthesis of more complex carbon-based fuels and chemicals. Therefore, understanding this step is crucial for the development of high-performance electrocatalyst for CO 2 conversion to higher order products such as hydrocarbons. In this paper, atomic iron dispersed on nitrogen-doped graphene (Fe/NG) is synthesized as an efficient electrocatalyst for CO 2 reduction to CO. Fe/NG has a low reduction overpotential with high Faradic efficiency up to 80%. The existence of nitrogen-confined atomic Fe moieties on the nitrogen-doped graphene layer is confirmed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure analysis. The Fe/NG catalysts provide an ideal platform for comparative studies of the effect of the catalytic center on the electrocatalytic performance. Finally, the CO 2 reduction reaction mechanism on atomic Fe surrounded by four N atoms (Fe–N 4 ) embedded in nitrogen-doped graphene is further investigated through density functional theory calculations, revealing a possible promotional effect of nitrogen doping on graphene.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Surface-Plasmon-Assisted Photoelectrochemical Reduction of CO 2 and NO 3 – on Nanostructured Silver Electrodes

Electrochemical reduction of carbon dioxide (CO 2 ) typically suffers from low selectivity and poor reaction rates that necessitate high overpotentials, which impede its possible application for CO 2 capture, sequestration, or carbon-based fuel production. New strategies to address these issues include the utilization of photoexcited charge carriers to overcome activation barriers for reactions that produce desirable products. Here, this study demonstrates surface-plasmon-enhanced photoelectrochemical reduction of CO 2 and nitrate (NO 3 - ) on silver nanostructured electrodes. The observed photocurrent likely originates from a resonant charge transfer between the photogenerated plasmonic hot electrons and the lowest unoccupied molecular orbital (MO) acceptor energy levels of adsorbed CO 2 , NO 3 - , or their reductive intermediates. The observed differences in the resonant effects at the Ag electrode with respect to electrode potential and photon energy for CO 2 versus NO 3 - reduction suggest that plasmonic hot-carriers interact selectively with specific MO acceptor energy levels of adsorbed surface species such as CO 2 , NO 3 - , or their reductive intermediates. This unique plasmon-assisted charge generation and transfer mechanism can be used to increase yield, efficiency, and selectivity of various photoelectrochemical processes.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Perovskite Photocatalytic CO 2 Reduction or Photoredox Organic Transformation?

Abstract Metal‐halide perovskites have been explored as photocatalysts for CO 2 reduction. We report that perovskite photocatalytic CO 2 reduction in organic solvents is likely problematic. Instead, the detected products (i.e., CO) likely result from a photoredox organic transformation involving the solvent. Our observations have been validated using isotopic labeling experiments, band energy analysis, and new control experiments. We designed a typical perovskite photocatalytic setup in organic solvents that led to CO production of up to ≈1000 μmol g −1 h −1 . CO 2 reduction in organic solvents must be studied with extra care because photoredox organic transformations can produce orders of magnitude higher rate of CO or CH 4 than is typical for CO 2 reduction routes. Though CO 2 reduction is not likely to occur, in situ CO generation is extremely fast. Hence a suitable system can be established for challenging organic reactions that use CO as a feedstock but exploit the solvent as a CO surrogate.

14 SOLAR ENERGY↗
DOE OSTI2018

Reduction Enhancement Mechanisms of a Low-Grade Iron Ore–Coal Composite by NaCl

The reduction behavior of a low iron grade with high SiO{sub 2} content ore–coal composite was investigated in the temperature range of 1143 K to 1263 K (870 °C to 990 °C). Sodium chloride was chosen as an additive to promote this reduction process. The effect of the sodium chloride addition and its mechanism was also investigated. Results showed that the added sodium chloride could enhance the reduction of wustite to iron due to the decrease of fayalite, and a higher metallization ratio of reduced sample was obtained. Thermogravimetric–differential scanning calorimeter analysis showed that sodium chloride could greatly facilitate the gasification process of coal and, thus, provide sufficient carbon monoxide to the reduction process of iron oxides. Meanwhile, sodium chloride promoted the reduction process of iron ore pellets directly as the coal gasification effect was excluded. Microstructures of reduced sample revealed that sodium chloride broke the structure of ore and enhanced the growth of newly formed iron particles. As the ore–coal composite with mol (C/Fe = 1.4) and 3 mass pct sodium chloride addition was roasted at 1233 K (960 °C) for 55 minutes, a reduced sample with metallization ration of 74.45 pct could be obtained.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of Low-temperature Pre-oxidation on the Titanomagnetite Ore Structure and Reduction Behaviors in a Fluidized Bed

With respect to high efficient utilization of low-grade iron ore resource, the behavior of low-temperature “973 K to 1123 K (700 °C to 850 °C)” oxidation, on the phase transition of SA TTM ore (South African titanomagnetite), and its effect on subsequent reduction was investigated. The results showed that hematite and rutile are the oxidation product below 1048 K (775 °C), while pseudobrookite is the stable phase above 1073 K (800 °C). With the increase in temperature and oxidation time, there is a competitive relationship between the amount of hematite and pseudobrookite generated. The reduction efficiency of SA TTM was significantly improved by oxidation pretreatment, primarily due to the dissociation of titania-ferrous oxides to more easily reducible hematite. But the generation of pseudobrookite phase decreases the amount of free hematite available for reduction, which weakens the improvement effect of pre-oxidation. The equilibrium relationship between the metallization degree and the gas reduction potential for TTM ore with pre-oxidation treatment has been built. Finally, the reduction metallization degree for the first and second step can be improved averagely by 16.67 and 3.45 pct, respectively, for sample pre-oxidized at 1098 K (825 °C) for 15 and 90 minutes, while 26.96 and 7.4 pct, improvement is achieved for sample pre-oxidized at a lower temperature of 1048 K (775 °C) for 120 minutes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Carbothermic Reduction Kinetics of Phosphorous Vaporization from Tri-calcium Phosphate (TCP) Under Microwave Rapid Heating With/Without the Presence of Fe{sub 3}O{sub 4}

The kinetics of vapor phase dephosphorization from tri-calcium phosphate (TCP) by carbothermic reduction was studied with and without the presence of Fe{sub 3}O{sub 4}. Microwave heating was utilized to obtain large variations in the heating rate (HR). In the reduction of TCP alone, the phosphorous removal fraction (RF; equal to ∆P{sub 2}O{sub 5}/P{sub 2}O{sub 5}{sup 0}, where ∆P{sub 2}O{sub 5} is the weight change and P{sub 2}O{sub 5}{sup 0} is the P{sub 2}O{sub 5} weight before heating) decreased as the HR increased. In other words, a shorter residence time at a high temperature resulted in a smaller reduction fraction of TCP. An apparently third-order reaction was postulated to account for the kinetics using a fitting simulation based on the additive law of the reaction progress. On the other hand, the phosphorous removal (dephosphorization) rate (RR; equal to ∆P{sub 2}O{sub 3}/t{sub MW}, where t{sub MW} is the microwave heating time period) increased as the HR increased above 1200 °C. The reduction ratio of Fe{sub 3}O{sub 4} above 1100 °C is higher than 97 pct regardless of the heating rate. The reduction of TCP in the presence of Fe{sub 3}O{sub 4} showed that RF increased slightly with increasing HR despite a shorter residence time at a high temperature. The RR also increased with the HR even though RF decreased to half of the values observed in the cases without Fe{sub 3}O{sub 4} for temperatures above 1200 °C. The practicality and optimal operation conditions of phosphorus vapor removal were discussed.

36 MATERIALS SCIENCE↗