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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Effect of bimetallic modification on blast furnace slag and its application in low‐temperature selective catalytic reduction

Abstract Objective In order to control NO x in low‐temperature flue gases emitted from non‐power industries and to reduce the preparation cost of denitration catalysts, this study uses inexpensive blast furnace slag as raw material to prepare denitration catalysts. Methods After cooling, drying and grinding, the blast furnace slag becomes a powder with considerable fineness and meets the requirements of activity index, which is called GGBS (ground granulated blast furnace slag). Using GGBS as denitration catalyst carrier, the active components M (M = Fe, Co, Ni, Cu and Ce) are loaded on Mn‐based GGBS catalyst using an impregnation method. Conclusions The effect of different active components on the denitration performance and sulfur resistance of Mn‐based GGBS catalysts is investigated. The results show that the Mn‐Ce/GGBS catalyst has better denitration performance and sulfur resistance. The Mn‐Ce/GGBS catalyst has a significant denitration performance when load ratio is 2:1. The active component Ce improves the denitration performance of the catalyst, reduces sulfur poisoning and extends the life of the catalyst. The SO 2 in the flue gas increases the acid sites on the catalyst surface and improves catalyst activity. The larger the ratios of Mn 4+ /Mn 3+ , Ce 4+ /Ce 3+ and O α /O β , the stronger the catalyst activity and the better the denitration performance. © 2022 Society of Chemical Industry (SCI).

Zhang, Lei↗
DOE OSTI2018

Transient Interaction Between Reduction and Slagging Reactions of Wustite in Simulated Cohesive Zone of Blast Furnace

The blast furnace cohesive zone plays an important role in the gas flow distribution and heat-transfer efficiency. Previous work mainly employed temperature-based indices to evaluate and predict the shape and thickness of the cohesive zone, whereas the internal reactions and related effects on the softening and melting properties of a complex burden are ignored. In this study, an innovative index, namely, shrinkage rate (SR), is first proposed to directly estimate the shrinkage behavior of wustite (FeO)-packed bed inside a simulated cohesive zone. The index is applied as the temperature increases to elucidate the transient interaction between reduction and slagging reactions. Results show that the thermally induced slagging reaction causes the packed bed to shrink at lower temperature, and the SR doubles when compounds with low melting temperature are generated by adding a reasonable concentration of CaO or SiO{sub 2}. The reduction reaction becomes the driving force during the shrinkage of the packed bed between 1173 K and 1273 K when CO is introduced in the mixture gas. Then, the dominating factors for further shrinkage include slagging, reduction, or both factors. These factors vary with respect to the added compounds or temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The Melting Behavior of Hydrogen Direct Reduced Iron in Molten Steel and Slag: An Integrated Computational and Experimental Study

Direct reduced iron (DRI) and hot briquetted iron (HBI) are essential feedstocks for tramp element control in the electric arc furnace (EAF). Due to greenhouse gas (GHG) concerns related to CO2 emissions, hydrogen as a substitute for natural gas and a reductant in DRI production is being widely explored to reduce GHG emissions in ironmaking. This study examines the melting behavior of hydrogen DRI (H-DRI) pellets in the EAF containing low-carbon (0.1 wt.%) molten steel and molten slag. A computational heat transfer model was developed to predict the melting behavior of H-DRI pellets. To validate the model, a set of experimental laboratory simulations was conducted by immersing H-DRI in a molten steel bath and slag. The temperature history at the center of the pellet during melting and the shell thickness at different melting stages were utilized to validate the model. The simulation results agree with the experimental measurements of steel balls and H-DRI in different metallic molten steel and slag baths.

Materials Science↗
NASA NTRS1991

Optical Measurements on Solid Specimens of Solid Rocket Motor Exhaust and Solid Rocket Motor Slag

Samples of aluminum slag were investigated to aid the Earth Science and Applications Division at the Marshall Space Flight Center (MSFC). Alumina from space motor propellant exhaust and space motor propellant slag was examined as a component of space refuse. Thermal emittance and solar absorptivity measurements were taken to support their comparison with reflectance measurements derived from actual debris. To determine the similarity between the samples and space motor exhaust or space motor slag, emittance and absorbance results were correlated with an examination of specimen morphology.

Roberts, F. E., III↗
NASA NTRS2007

An Analysis of the Orbital Distribution of Solid Rocket Motor Slag

The contribution made by orbiting solid rocket motors (SRMs) to the orbital debris environment is both potentially significant and insufficiently studied. A combination of rocket motor design and the mechanisms of the combustion process can lead to the emission of sufficiently large and numerous by-products to warrant assessment of their contribution to the orbital debris environment. These particles are formed during SRM tail-off, or the termination of burn, by the rapid expansion, dissemination, and solidification of the molten Al2O3 slag pool accumulated during the main burn phase of SRMs utilizing immersion-type nozzles. Though the usage of SRMs is low compared to the usage of liquid fueled motors, the propensity of SRMs to generate particles in the 100 m and larger size regime has caused concern regarding their contributing to the debris environment. Particle sizes as large as 1 cm have been witnessed in ground tests conducted under vacuum conditions and comparable sizes have been estimated via ground-based telescopic and in-situ observations of sub-orbital SRM tail-off events. Using sub-orbital and post recovery observations, a simplistic number-size-velocity distribution of slag from on-orbit SRM firings was postulated. In this paper we have developed more elaborate distributions and emission scenarios and modeled the resultant orbital population and its time evolution by incorporating a historical database of SRM launches, propellant masses, and likely location and time of particulate deposition. From this analysis a more comprehensive understanding has been obtained of the role of SRM ejecta in the orbital debris environment, indicating that SRM slag is a significant component of the current and future population.

Horstman, Matthew F.↗
NASA NTRS2008

The Solid Rocket Motor Slag Population: Results of a Radar-Based Regressive Statistical Evaluation

Solid rocket motor (SRM) slag has been identified as a potential source of man-made orbital debris. The possibility that SRMs (in addition to generating dust particles in the sub-millimeter range) may generate particles up to centimeters in size has caused concern regarding their contribution to the debris environment. Returned surfaces from space do not have sufficient area or exposure time to provide a clear picture of the SRM millimeter and centimeter debris population. Currently, radar observation is probably the only way to collect data showing the debris contribution from SRMs. Such observation is used to sample the debris environment, but it is difficult to obtain accurate orbital elements for the detected debris objects. NASA has developed several models to describe the different orbital debris populations, based on assumed debris production mechanisms to create clouds of debris objects that can be propagated in time. The NASA model, LEGEND (LEO-to-GEO Environment Debris), functions as a time-tested debris model for most debris sources. However, the current LEGEND model does not include contributions from the SRM population. An SRM model has recently been developed by NASA, based on purely theoretical details of SRM production and known SRM launches, but verification with hard data is needed. Because the detections of individual SRM objects cannot be deterministically separated from the total debris observed by radar, the validation of the SRM model can only be done by combining it with the LEGEND breakup model and comparing it with data. By applying observational constraints, the degree of SRM slag contribution to the environment may be estimated. This serves as an observationally sound method from which to calibrate a purely theoretical model into something more realistic. For this study, we use the populations observed by the Haystack radar from 1996 to present. For the SRM debris, we use a historical database of SRM launches, propellant masses, and estimated locations and times of tailoff to produce and propagate the SRM debris clouds. Comparisons with radar data from the ensuing years were made, and the SRM model was altered with respect to size and mass production of slag particles to reflect the populations estimated from the data. The result is a model SRM population that fits within the bounds of the observed environment and estimates of the production and contribution of SRM debris to the environment.

Horstman, Matthew F.↗
NASA NTRS2012

One-Dimensional, Two-Phase Flow Modeling Toward Interpreting Motor Slag Expulsion Phenomena

Aluminum oxide slag accumulation and expulsion was previously shown to be a player in various solid rocket motor phenomena, including the Space Shuttle's Reusable Solid Rocket Motor (RSRM) pressure perturbation, or "blip," and phantom moment. In the latter case, such un ]commanded side accelerations near the end of burn have also been identified in several other motor systems. However, efforts to estimate the mass expelled during a given event have come up short. Either bulk calculations are performed without enough physics present, or multiphase, multidimensional Computational Fluid Dynamic analyses are performed that give a snapshot in time and space but do not always aid in grasping the general principle. One ]dimensional, two ]phase compressible flow calculations yield an analytical result for nozzle flow under certain assumptions. This can be carried further to relate the bulk motor parameters of pressure, thrust, and mass flow rate under the different exhaust conditions driven by the addition of condensed phase mass flow. An unknown parameter is correlated to airflow testing with water injection where mass flow rates and pressure are known. Comparison is also made to full ]scale static test motor data where thrust and pressure changes are known and similar behavior is shown. The end goal is to be able to include the accumulation and flow of slag in internal ballistics predictions. This will allow better prediction of the tailoff when much slag is ejected and of mass retained versus time, believed to be a contributor to the widely-observed "flight knockdown" parameter.

Kibbey, Timothy P.↗
DOE OSTI2017

Experimental Study on Electrical Conductivity of MnO-CaO-SiO{sub 2} Slags at 1723 K to 1823 K (1450 °C to 1550 °C) and Various Oxygen Potentials

The electrical conductivity of molten slag has many important and practical effects in modeling and operating the electric smelting furnace. In the present study, the electrical conductivities (total and electronic/ionic properties) of MnO-CaO-SiO{sub 2} slags were measured by a four-electrode method at different oxygen potentials and temperatures. Experimental results show that the effects of temperature on the total, electronic, and ionic conductivities obey the Arrhenius law, and all conductivities increase when increasing the temperature. The stepped potential chronoamperometry method was used to measure the electronic transference number, which is affected strongly by oxygen potential but is unaffected by temperature. The total electrical, electronic, and ionic conductivities present similar increasing trends when increasing the CO/CO{sub 2} ratio, which resulted from increasing Mn{sup 2+}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Calcium Treatment for FeSi-killed Fe-13 Pct Cr Stainless Steel with Various Top Slag Compositions

Calcium treatment of Fe-13 pct Cr stainless steel, with inclusion modification as its main purpose, was evaluated on a laboratory scale. The stability diagram of Ca-Al was obtained using the FactSage software and could be divided into three parts based on the [Al] content: the ultra-low-Al region, the low-Al region, and the medium-high-Al region. Each of these regions required different amounts of calcium for inclusion modification. The ferrosilicon deoxidation product could be modified into low melting temperature inclusions by a CaO-SiO{sub 2} top slag in the ultra-low-Al region ([Al] content less than 40 ppm). Calcium treatment was necessary to modify the ferrosilicon deoxidation product into low melting temperature inclusions in the low-Al region ([Al] content from 40 to 100 ppm) for the CaO-SiO{sub 2}-Al{sub 2}O{sub 3} top slag. Calcium addition has a “liquid window” where adding calcium can accelerate inclusion modification. Adding calcium for 15 and 30 minutes resulted in complete modification times of 45 and 60 minutes, respectively, which indicates that early calcium treatment can produce plastic inclusions sooner. The relationship between the steel and inclusion content was determined by fitting the experimental data in the low-Al region. An appropriate range of T.Ca/T.O (total calcium content/total oxygen content) for inclusion modification is 0.99 to 1.44.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Manganese Recovery by Silicothermic Reduction of MnO in BaO-MnO-MgO-CaF{sub 2} (-SiO{sub 2}) Slags

The effects of reducing agent, CaF{sub 2} content, and reaction temperature upon the silicothermic reduction of MnO in the BaO-MnO-MgO-CaF{sub 2} (-SiO{sub 2}) slags were investigated. Mn recovery was proportional to Si activity in the molten alloy. Moreover, 90 pct yield of Mn recovery was obtained under 5 mass pct CaF{sub 2} content and 1873 K (1600 °C) reaction temperature. Increasing CaF{sub 2} content above 5 pct yielded little or no further increase in Mn recovery, because it was accompanied by increased slag viscosity owing to the precipitation of high melting point compounds such as Ba{sub 2}SiO{sub 4}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Electrochemical Transfer of S Between Molten Steel and Molten Slag

S transfer between molten steel and molten slag was investigated in view of the electrochemical character of S transfer. C-saturated molten steel containing S was allowed to react with CaO-SiO{sub 2}-Al{sub 2}O{sub 3}-MgO slag at 1673 K (1400 °C) until the two phases arrive at a chemical equilibrium. The application of an electric field of constant current through graphite electrodes lowered the S content in the molten steel below its chemical equilibrium level, and the system arrived at a new equilibrium level (electrochemical equilibrium). However, subsequent shutting off of the electric field did not lead to the system reverting to the original chemical equilibrium: reversion of S was observed but to a limited extent. The application of an electric field of opposite direction or flowing of CO gas allowed significant reversion of S. Side reactions (decomposition of oxide components) were observed, and these were considered to be coupled to the transfer of S. An electrochemical reaction mechanism was proposed based on the experimental observations found in the present study.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of Reoxidation of Liquid Steel and Slag Composition on the Chemistry Evolution of Inclusions During Electroslag Remelting

Electroslag remelting (ESR) is increasingly used to produce some varieties of special steels and alloys, mainly because of its ability to provide extreme cleanliness and an excellent solidification structure simultaneously. In the present study, the combined effects of varying SiO{sub 2} contents in slag and reoxidation of liquid steel on the chemistry evolution of inclusions and the alloying element content in steel during ESR were investigated. The inclusions in the steel before ESR refining were found to be oxysulfides of patch-type (Ca,Mn)S adhering to a CaO-Al{sub 2}O{sub 3}-SiO{sub 2}-MgO inclusion. The oxide inclusions in both the liquid metal pool and remelted ingots are CaO-Al{sub 2}O{sub 3}-MgO and MgAl{sub 2}O{sub 4} together with CaO-Al{sub 2}O{sub 3}-SiO{sub 2}-MgO inclusions (slightly less than 30 pct of the total inclusions), which were confirmed to originate from the reduction of SiO{sub 2} from the original oxide inclusions by dissolved Al in liquid steel during ESR. CaO-Al{sub 2}O{sub 3}-MgO and MgAl{sub 2}O{sub 4} are newly formed inclusions resulting from the reactions taking place inside liquid steel in the liquid metal pool caused by reoxidation of liquid steel during ESR. Increasing the SiO{sub 2} content in slag not only considerably reduced aluminum pickup in parallel with silicon loss during ESR, but also suppressed the decrease in SiO{sub 2} content in oxide inclusions. (Ca,Mn)S inclusions were fully removed before liquid metal droplets collected in the liquid metal pool.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Numerical Simulation of Recirculating Flow and Physical Model of Slag–Metal Behavior in an RH Reactor: Application to Desulfurization

Computational fluid dynamics (CFD) techniques and a 1:7.5 physical model of an RH degasser have been used to evaluate the flow of gas and metal inside an RH reactor for vacuum degassing of liquid steel. The effect of gas injection on the gas spatial distribution, steel circulation rate and flow field inside the ladle, snorkels and vacuum chamber have been assessed. N-pentane oil was employed to evaluate the average residence time as well as the slag droplet size distribution. The predicted radial gas distribution and liquid circulation rate have been validated against experimental data from a physical model. The results with incorporation of the virtual mass force coefficient of 0.25 and the turbulence dispersion force showed better predictions of gas distribution in the up-snorkel as well as circulation rate. Full-scale simulations were performed, and the predicted circulation rate was significantly affected by the argon bubble expansion. Data from these simulations were used to analyze the degree of desulfurization performed by the addition of desulfurizing agents inside the vacuum chamber. A model of the kinetics of desulfurization based on the results from the physical model and CFD simulation and on slag dispersion inside liquid steel yields degrees of desulfurization similar to the industrial trials reported in the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Inclusion Characterization in Aluminum-Deoxidized Special Steel with Certain Sulfur Content Under Combined Influences of Slag Refining, Calcium Treatment, and Reoxidation

Inclusions in Al-killed steel with [S] of about 0.0060 to 0.0070 mass pct were characterized and discussed, evaluating the combined effects of basic slag refining and Ca treatment in ladle, together with reoxidation of liquid steel in casting tundish. Inclusions were changed from Al{sub 2}O{sub 3} to MgO-Al{sub 2}O{sub 3} spinel and then to MgO-Al{sub 2}O{sub 3}-CaO during basic slag refining. After Ca treatment, many (MgO-Al{sub 2}O{sub 3}) + CaS inclusions were formed, featuring the coexistence of MgO-Al{sub 2}O{sub 3} and CaS to form a dual-phased structure. In the following Ar blowing, the number density of (MgO-Al{sub 2}O{sub 3}) + CaS inclusions and pure CaS increased obviously, which implied that [Ca] preferentially reacted with [S] rather than [O] in steel. Reoxidation in casting tundish caused the pickup of oxygen in steel, and the rise of total oxygen (T.O) was 0.0002 mass pct; even 55t steel has been poured. As a result, the content of CaO in inclusions increased and MgO-Al{sub 2}O{sub 3}-CaO inclusions were formed again. Thermodynamic calculations revealed that the driving force was strong for the formation of CaS-based inclusions. Higher carbon content in steel would help to reduce oxygen content while enhancing the activity of [S] in steel, which further stabilized the existence of CaS-based inclusions. Therefore, inclusions were mostly the solid (MgO-Al{sub 2}O{sub 3}) + CaS dual-phase ones, without the formation of liquid calcium aluminates. Contents of CaS and CaO in inclusions were affected by the [mass pct S]/[mass pct O] ratio, which was calculated as about 4.58 K and 5.34 K at 1873 K and 1823 K, respectively. This finding implied that lower oxygen was not favorable to prevent the solid inclusions in the calcium treatment of high carbon special steel.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Control of Slag Carryover from the BOF Vessel During Tapping: BOF Cold Model Studies

In a modern integrated steel plant, slag-free tapping during transfer of liquid steel from the BOF vessel to the ladle is prerequisite to produce ultraclean steel for high-end critical applications. The present investigation aims to examine the drain vortices during the liquid steel tapping process. The tapping experiments were conducted in a geometrical down-scaled Perspex BOF cold model, which was more akin to the industrial practice than the other geometries previously reported in the literature. The study highlights the influence of the complex BOF shape on drain vortices during the tapping process. It is observed that vorticity behavior during liquid steel tapping from the BOF vessel is different from the earlier observations reported for the teeming process. The parametric study of the tapping process and its analysis confirmed that the threshold height for drain vortices is strongly influenced by the nozzle diameter (ND) and marginally influenced by the residual inertia of the liquid. The carryover ratio (COR) for the water-oil experiments is in agreement with the values obtained in industrial practice. Yield loss tends to increase with the increase in ND. The onset of drain vortices in the presence of overlying phase (oil/slag) during the BOF tapping process could be principally controlled by the vessel design. The physical properties of the overlying phase had negligible influence on the drain vortices. The critical times for vortex and drain sink formation were predicted based on dimensional analysis coupled with the mathematical formulation for the tapping process. A strategy to control the slag carryover during the tapping process in industry is also discussed and postulated based on the understanding developed from water modeling experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Nozzle Port Angle on Transient Flow and Surface Slag Behavior During Continuous Steel-Slab Casting

Undesirable flow variations can cause severe instabilities at the interface between liquid mold flux and molten steel across the mold top-region during continuous steel casting, resulting in surface defects in the final products. A three-dimensional Large Eddy Simulation (LES) model using the volume of fluid method for the slag and molten steel phases is validated with plant measurements, and applied to gain new insights into the effects of nozzle port angle on transient flow, top slag/steel interface movement, and slag behavior during continuous slab casting under nominally steady conditions. Upward-angled ports produce a single-roll flow pattern with lower surface velocity, due to rapid momentum dissipation of the spreading jet. However, strong jet wobbling from the port leads to greater interface variations. Severe level drops allow easy entrapment of liquid flux by the solidifying steel shell at the meniscus. Sudden level rises may also be detrimental, leading to overflow of the solidified meniscus region. Downward-angled ports produce a classic double-roll pattern with less jet turbulence and a more stable interface everywhere except near the narrow faces. Finally, the flow patterns, surface velocity, and level predicted from the validated LES model are compared with steady-state standard k-ε model predictions.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Reaction Mechanism and Kinetics of Boron Removal from Molten Silicon via CaO-SiO{sub 2}-CaCl{sub 2} Slag Treatment and Ammonia Injection

To improve the boron-removal efficiency of metallurgical-grade silicon by increasing the reaction rate, a combined method with the 30 mol pct CaO-23.3 mol pct SiO{sub 2}-46.7 mol pct CaCl{sub 2} slag treatment and ammonia injection at 1723 K to 1823 K was proposed. For 1 hour and at 1823 K, the maximum removal efficiency of boron was 98 pct, and the final boron concentration in silicon decreased to 1.5 ppmw by the present method without the introduction of the iron catalyst. A kinetic model was also established to clarify the reaction mechanism and rate-limiting steps of this complicated boron-removal process. In this model, the rate-limiting step is the mass transfer of boron oxide at the interface between the slag and silicon phase.

36 MATERIALS SCIENCE↗
DOE OSTI2019

A Kinetic Study Investigating the Carbothermic Recovery of Chromium from a Stainless-Steel Slag

In 2018, the stainless-steel industry produced > 10 million tons of slag, which for the most part was landfilled because of chromium oxide contamination. Long-term studies indicate a possible formation of soluble hexavalent chromium, which is classified as carcinogenic. Recent research focuses on the development of a treatment technology to recover chromium from the slag into a ferroalloy, producing an oxidic material that can be utilized in the construction industry. To date, there has been no literature dealing with the kinetics of a carbothermic treatment process to result in a model to predict the necessary treatment time. The present article fills this gap by investigating the reduction kinetics of chromium oxide of a process close to practical applications. Based on experimental measurements, a model has been developed to predict the necessary treatment time to reach a specific final chromium concentration as a function of the starting concentration and required process temperature in the range between 1600 °C and 1700 °C. Finally, presented findings can serve as a guideline to develop kinetic models in similar pyrometallurgical recovery processes.

36 MATERIALS SCIENCE↗