Non-destructive quality control of carbon anodes using modal analysis, acousto-ultrasonic and latent variable methods

La performance des cuves d’électrolyse utilisées dans la production d’aluminium primaire par le procédé Hall-Héroult est fortement influencée par la qualité des anodes de carbone. Celles-ci sont de plus en plus variables en raison de la qualité décroissante des matières premières (coke et braie) et des changements de fournisseurs qui deviennent de plus en plus fréquents afin de réduire le coût d’achat et de rencontrer les spécifications des usines. En effet, les défauts des anodes, tels les fissures, les pores et les hétérogénéités, causés par cette variabilité, doivent être détectés le plus tôt possible afin d’éviter d’utiliser des anodes défectueuses dans les cuves et/ou d’apporter des ajustements au niveau du procédé de fabrication des anodes. Cependant, les fabricants d’anodes ne sont pas préparés pour réagir à cette situation afin de maintenir une qualité d'anode stable. Par conséquent, il devient prioritaire de développer des techniques permettant d’inspecter le volume complet de chaque anode individuelle afin d’améliorer le contrôle de la qualité des anodes et de compenser la variabilité provenant des matières premières. Un système d’inspection basé sur les techniques d’analyse modale et d’acousto-ultrasonique est proposé pour contrôler la qualité des anodes de manière rapide et non destructive. Les données massives (modes de vibration et signaux acoustiques) ont été analysées à l'aide de méthodes statistiques à variables latentes, telles que l'Analyse en Composantes Principales (ACP) et la Projection sur les Structures Latentes (PSL), afin de regrouper les anodes testées en fonction de leurs signatures vibratoires et acousto-ultrasoniques. Le système d'inspection a été premièrement investigué sur des tranches d'anodes industrielles et ensuite testé sur plusieurs anodes pleine grandeur produites sous différentes conditions à l’usine de Alcoa Deschambault au Québec (ADQ). La méthode proposée a permis de distinguer les anodes saines de celles contenant des défauts ainsi que d’identifier le type et la sévérité des défauts, et de les localiser. La méthode acousto-ultrasonique a été validée qualitativement par la tomographie à rayon-X, pour les analyses des tranches d’anodes. Pour les tests réalisés sur les blocs d’anode, la validation a été réalisée au moyen de photos recueillies après avoir coupé certaines anodes parmi celles testées.The performance of the Hall-Héroult electrolysis reduction process used for the industrial aluminium smelting is strongly influenced by the quality of carbon anodes, particularly by the presence of defects in their internal structure, such as cracks, pores and heterogeneities. This is partly due to the decreasing quality and increasing variability of the raw materials available on the market as well as the frequent suppliers changes made in order to meet the smelter’s specifications and to reduce purchasing costs. However, the anode producers are not prepared to cope with these variations and in order to maintain consistent anode quality. Consequently, it becomes a priority to develop alternative methods for inspecting each anode block to improve quality control and maintain consistent anode quality in spite of the variability of incoming raw materials.A rapid and non-destructive inspection system for anode quality control is proposed based on modal analysis and acousto-ultrasonic techniques. The large set of vibration and acousto-ultrasonic data collected from baked anode materials was analyzed using multivariate latent variable methods, such as Principal Component Analysis (PCA) and Partial Least Squares (PLS), in order to cluster the tested anodes based on vibration and their acousto-ultrasonic signatures. The inspection system was investigated first using slices collected from industrial anodes and then on several full size anodes produced under different conditions at the Alcoa Deschambault in Québec (ADQ). It is shown that the proposed method allows discriminating defect-free anodes from those containing various types of defects. In addition, the acousto-ultrasonic features obtained in different frequency ranges were found to be sensitive to the defects severities and were able to locate them in anode blocks. The acousto-ultrasonic method was validated qualitatively using X-ray computed tomography, when studying the anode slices. The results obtained on the full size anode blocks were validated by means of images collected after cutting some tested anodes

Challenges and Prospects of Steelmaking Towards the Year 2050

The world steel industry is strongly based on coal/coke in ironmaking, resulting in huge carbon dioxide emissions corresponding to approximately 7% of the total anthropogenic CO2 emissions. As the world is experiencing a period of imminent threat owing to climate change, the steel industry is also facing a tremendous challenge in next decades. This themed issue makes a survey on the current situation of steel production, energy consumption, and CO2 emissions, as well as cross-sections of the potential methods to decrease CO2 emissions in current processes via improved energy and materials efficiency, increasing recycling, utilizing alternative energy sources, and adopting CO2 capture and storage. The current state, problems and plans in the two biggest steel producing countries, China and India are introduced. Generally contemplating, incremental improvements in current processes play a key role in rapid mitigation of specific emissions, but finally they are insufficient when striving for carbon neutral production in the long run. Then hydrogen and electrification are the apparent solutions also to iron and steel production. The book gives a holistic overview of the current situation and challenges, and an inclusive compilation of the potential technologies and solutions for the global CO2 emissions problem

Book of abstracts of the 14th International Symposium of Croatian Metallurgical Society - SHMD \u272020, Materials and metallurgy

Book of abstracts of the 14th International Symposium of Croatian Metallurgical Society - SHMD \u272020, Materials and metallurgy held in Šibenik, Croatia, June 21-26, 2020. Abstracts are organized in four sections: Materials - section A; Process metallurgy - Section B; Plastic processing - Section C and Metallurgy and related topics - Section D

Chemistry: Space resources for teachers including suggestions for classroom activities and laboratory experiments

Curriculum supplement to assist general chemistry teachers in updating instruction materials with aerospace development

Future Energy: Opportunities & Challenges

Future Energy: Opportunities & Challenges was originally published in 2013 by the International Society of Automation. Rights for this work have been reverted to the authors by the original publisher. The author has chosen to license this work with a Creative Commons Attribution 4.0 International license (see https://creativecommons.org/licenses/by/4.0/). Click the blue Download button to download the full book PDF, or download individual chapters from the list.https://trace.tennessee.edu/openbooks/1000/thumbnail.jp

Mathematical Modeling Of Pre And Post Combustion Processes In Coal Power Plant

Coal is a brownish-black sedimentary rock with organic and inorganic constituents. It has been a vital energy resource for humans for millennia. Coal accounts for approximately one quarter of the world’s energy consumption, with 65% of this is energy utilized by residential consumers, and 35% by industrial consumers. Coal operated power stations provide 42% of U.S. electricity supply. The United States hold 96% of coal reserves in North America region, out of which 26% are known for commercial usage. The coal combusted in these power generating facilities requires certain pre-combustion processing, while by-products of coal combustion go through certain post-combustion processing. The application of hydrometallurgical extraction of Rare Earth Elements (REE) from North Dakota Lignite coal feedstock can assist coal value amplification. Extraction of REE from lignite coals liberates REEs and CMs that are vital to electronics, power storage, aviation, and magnets industries. The REE extraction process also reduces the sulfur content of ND lignite coal, along with ash components that foul heat exchange surfaces and can have benefits for post-combustion scrubbing units. When coal is combusted, the exhaust gasses contain carbon dioxide (CO2), sulfur dioxide (SO2), oxides of nitrogen (NOx), water (H2O) and nitrogen (N2). Carbon dioxide comprises approximately 8-10 vol% of the flue gas and is reported to contribute to the greenhouse effect, a primary reason for climate change. Carbon Capture and Storage (CCS) involves of CO2 by use of liquid or solid absorbents to separate CO2 from combustion flue gas. Little data is available on gas-liquid interfacial area correlations in the literature for use of second generation solvents, such as MonoEthanolAmine (MEA), in structured packing absorber columns consisting of thin corrugated metal plates or gauzes, designed to force fluids on complicated paths. While mathematical model development for existing post-combustion carbon capture (PCCC) technologies, such as carbon capture simulations using computational fluid dynamics (CFD) for prediction of mass transfer coefficients is well developed, models describing the behavior of third generation solvents is lacking. Two main research opportunities exist: (i) due to the complex chemistry of coal, there is a requirement for a modeling tool that can account for the coal composition and complex hydrometallurgical extraction processes to assist in designing and sizing pre-combustion REE extraction plants; and (ii) CFD models are required that can capture the mass transfer coefficients of third generation CO2 solvents using structured packing. Two primary hypotheses have been developed to address the research opportunities: (1.) Process modeling of hydrometallurgical extraction of REE provides some theory-based understanding that is complementary to experimental validation and, with the help of chemical kinetics and percentage carboxylation existing in feedstocks, can forecast the efficiency and leachability of other feedstocks, and (2.) A detailed Volume of Fluid (VOF) simulation of coupled mass and momentum transfer problems in small intricate regions of corrugated structured and packed panels placed at 45° angle can be used to predict mass transfer coefficients for third generation solvents by using open-source numerical C/C++ based framework called Open Fields-Operations-And-Manipulations (OpenFOAM). The hydrometallurgical process modeling is developed using METSIM, a leading hydrometallurgical process modeling software tool. The steady state process model provides an overview of REE production along with equipment inventory sizing. The model also has functions to define percentage of organic carboxylic acid bonds present in coal, since, the prior research has identified that the primary association of REE in lignite coal is as weakly-bonded complexes of carboxyl groups, which are targets of the extraction technology. The CFD modeling work is expected to determine critical mass transfer coefficients for CO2 capture using structured packing columns. Further, the developed CFD model and its validity will be tested against experimental data from various industrial and literature sources

Composition-structure-activity relations in Cu-Sn and Cu-S based electrocatalysts for CO2 conversion

The development of our society relying on utilization of raw materials from Earth has left unprecedented marks on our planet’s environment. A key issue is the climate change phenomenon caused by the continuous increase in the atmospheric concentration of the greenhouse gas CO2 due to combustion of fossil fuels as main energy source. The mitigation of the CO2 emissions via its capture and conversion, increase in the utilization of renewable energy and recycling technologies, and eliminating the dependence from fossil fuels is a strategy for building sustainable society. A promising concept for tackling the CO2 emission via its conversion into valuable products (hydrocarbons and alcohols etc.) is the electrochemical reduction of CO2 (CO2ER), that has many advantages over the other conversion concepts. Cu is unique in terms of material that can intrinsically catalyze CO2 reduction into hydrocarbons and alcohols. However, there are many Cu catalyst/experimental conditions/engineering - related challenges and other issues of various nature that affect the product selectivity and therefore still hinder the large-scale application of the CO2ER. Regarding the catalyst and experimental conditions challenges, possible alternative for overcoming the selectivity issues is step- wise CO2ER i.e., two-electron electrochemical reduction of CO2 into CO and subsequent conversion of CO into hydrocarbons, alcohols and other valuable products. Furthermore, another two-electron product, that is formic acid (HCOOH) or formate (HCOO–) that find various industrial applications and are also promising alternative as fuel in fuel cells, together with CO can be produced with high selectivity on various cheap and abundant electrocatalysts. Namely, the Cu rich Cu-Sn materials appear to be promising catalysts for CO2ER into CO, while Sn rich Cu-Sn and Cu-S for production of HCOO–, and therefore they are worth and inspiring to be more thoroughly studied in terms of their composition- structure relations with the catalytic activity for electrochemical conversion of CO2. Hence, the first main goal of this thesis is dedicated to study of the composition-structure-CO2ER activity relations in the Cu-Sn and Cu-S based electrocatalyst materials. On the other hand, the second main goal encompasses providing simple, cheap and fast synthesis methods for both Cu-Sn and Cu-S based materials, and moreover, including a successful proof-of-concept for recycling/repurposing waste for deriving CO selective Cu-Sn electrocatalyst, which are prerequisites toward possible application of these materials for large-scale conversion of CO2 and building a sustainable society based on recycling in order to mitigate and finally cease the extraction of natural resources. The thesis is divided into three studies, from which the first study represents determination of the composition and speciation of Cu and Sn in Cu-Sn electrocatalysts under CO2 electrolysis in order to reveal the relationship between these parameters and the CO2ER selectivity alteration between CO and HCOO– at various applied potentials. For the purpose of this study, SnO2 functionalized CuO nanowires with varying thickness of surface SnO2 layers (low and high Sn), were synthesized. The CO2ER product quantification was performed using chromatography, while the material characterization methods comprised of mainly spectroscopy-based techniques including ex-situ soft x-ray XAS, in-situ hard x-ray XAS and quasi in-situ XPS, supported by microscopy/electron diffraction (EF-TEM, HR-TEM and SAED) and computational modeling (DFT). The results show that thin layer of SnO2 (low Sn) functionalized CuO nanowires electrocatalysts that are selective for CO2ER into CO, reaching maximal FE of ~80% at –0.7 V, undergo surface transformation generating Cu0 and SnOx (Snd+) species under all examined potentials. The presence of Snd+ is supporting the Sn to Cu charge redistribution mechanism and therefore promoting desorption of the Cu bound *CO intermediate, leading to significantly higher CO evolution, compared to the activity of pristine Cu. On the other hand, the results show that the increase in the surface Sn content is beneficial for CO2ER into HCOO–, achieving the highest FE (80%) at –0.9 V for the catalyst with highest Sn content. Altering the potential toward more negative values is leading to increase in the surface fraction of metallic Sn specie that readily bind the *OCHO* intermediate following the HCOO– pathway, accompanied with significant suppression of the competitive hydrogen evolution reaction (HER) due to weak binding of the *H intermediate. Even though these Cu-Sn materials can reach very high selectivity for both CO and HCOO– in dependence of the surface Sn content, sophisticated, expensive and time-consuming approach, that includes atomic layer deposition (ALD) of SnO2, was used for their synthesis. An important requirement for future practical application of the CO2ER catalysts is definitely simple, cheap and fast synthesis. Therefore, in the scope of the second study, facile one-step electrochemical method was developed for deriving Cu-Sn foam with low Sn content from waste bronze. The bronze derived Cu-Sn foam reached 80% FE for CO at –0.8 V, competing with the best catalysts for this purpose, which makes it promising for future large-scale application. This study is showing that recycling/repurposing waste material for CO2ER catalyst synthesis is achievable, which is an important step towards sustainable supply of materials for this purpose. The third study is based on investigation of the composition-structure relations in Cu-S catalysts selective for CO2ER into HCOO–, and moreover presenting a facile method for synthesis of these materials based on direct reaction between elemental Cu and S dissolved in toluene, hence avoiding usage of expensive and extremely toxic precursors. The most important finding in this study, based on examination of the Cu-S catalysts with quasi in-situ XPS, reveals that under CO2 electrolysis the materials do not undergo complete reduction and Cu+ surface species persist at all examined potentials (–0.5 to –0.9 V), compared to pristine Cu which is completely reduced to metallic under identical conditions. The presence of residual surface sulfur species is most probably stabilizing the Cu+ with oxophilic nature on which the *OCHO* intermediate favorably binds and further converts into HCOO–. However, the HCOO– selectivity that can reach up to 70-75% is dependent on activation of the electrocatalyst that is related to the Cu:S surface composition and various electrode-electrolyte interface effects. Namely, besides the S2–, presence of unexpected SO42– specie is found on the surface of the electrocatalysts that are subjected to applied potential of –0.9 V, most probably due to local pH increase effects. These local effects are not fully understood from this study which is inspiring for further research that involve probing the electrode-electrolyte interface with other surface sensitive methods under in- situ conditions such as Raman and infrared spectroscopy. Finally, the future challenges include an adaptation of the facile synthesis methods developed in this work to prepare gas-diffusion electrodes loaded with Cu-Sn and Cu-S catalysts. Examining their CO2ER activity in gas-diffusion electrolyzers is important to achieve high current densities and, hence, industrial relevant conversion rates that are required for future large-scale applications