scholarly journals Evaluation of Calcium Aluminate Slags and Pig Irons Produced from the Smelting-Reduction of Diasporic Bauxite

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7740
Author(s):  
Adamantia Lazou ◽  
Leiv Kolbeinsen ◽  
Jafar Safarian
Keyword(s):  
Calcium Aluminate ◽  
Analytical Techniques ◽  
Graphite Crucible ◽  
Low Grade ◽  
Atmospheric Conditions ◽  
Smelting Reduction ◽  
Alumina Crucible ◽  
Process Framework ◽  
Bauxite Ore ◽  
Lime Addition

This work evaluates the characteristics of calcium aluminate slag and pig iron samples obtained from the smelting of calcined and reduced diasporic bauxite ore. The study is conducted in the Pedersen process framework, which is a method to produce alumina from low-grade resources. Parameters such as the effect of crucible type, lime addition, and atmospheric conditions are studied considering the characteristics of the product pig irons and calcium aluminate slags for further uses. The behavior of the bauxite and distribution of the species between slag and metal was assessed based on the applied analytical techniques and thermodynamic calculations. Iron was reduced and separated from the slags in the presence of carbon (graphite crucible) for both the reduced and calcined bauxite. Si and Ti were mainly concentrated in the slags. Iron was separated from the slag in the absence of carbon (alumina crucible) for the H2-reduced bauxite. The results show that slags with increased lime additions are composed mainly of 5CaO.Al2O3 and CaO.Al2O3, that are considered highly leachable compounds. An optimum CaO/Al2O3 mass ratio of 1.12 was suggested. The presence of O2 and/or OH- in the furnace atmosphere will result in the formation of 12CaO.7Al2O3.

scholarly journals The Utilization of Bauxite Residue with a Calcite-Rich Bauxite Ore in the Pedersen Process for Iron and Alumina Extraction

2021 ◽  
Author(s):  
Adamantia Lazou ◽  
Casper Van Der Eijk ◽  
Kai Tang ◽  
Efthymios Balomenos ◽  
Leiv Kolbeinsen ◽  
...  
Keyword(s):  
Calcium Aluminate ◽  
Bauxite Residue ◽  
Reduction Process ◽  
Analytical Techniques ◽  
Pig Iron ◽  
Mass Ratio ◽  
Smelting Reduction ◽  
Bauxite Ore ◽  
Metal Phases ◽  
Alumina Recovery

AbstractMetallurgical grade alumina is produced worldwide through the well-known Bayer process, which unavoidably generates bauxite residue (BR, also known as red mud) in almost equal amounts to alumina. This study aims the valorization of BR through a smelting-reduction process to obtain calcium aluminate slags that can be a proper feed for alumina recovery via the Pedersen process. It investigates the thermodynamics and characteristics of the slags and pig iron produced from mixtures of BR, a bauxite beneficiation byproduct, and lime. In this context, the evolution of the different phases in the slags is studied with advanced analytical techniques and thermodynamic calculations. According to the results, a CaO/Al2O3 mass ratio within 1.3 to 1.4 in the slags can yield more Al2O3-containing leachable phases, such as CaO·Al2O3 and 12CaO·7Al2O3. The cooling dictates the amount and the characteristics of these phases, and the slower cooling rate yields improved slag characteristics. The distribution of the elements between the slag and metal phases shows that iron is separated, and the majority of the P, Cr, Ni, and V are distributed in the produced pig iron, while S, Ti, and Si are mostly concentrated in the slags.

Electron Microscopy/Diffraction Study of the Ternary Mn-Er-S System

1990 ◽  
Vol 48 (1) ◽  
pp. 76-77
Author(s):  
A. R. Landa Canovas ◽  
L.C. Otero Diaz ◽  
T. White ◽  
B.G. Hyde
Keyword(s):  
Electron Microscopy ◽  
Gas Flow ◽  
Graphite Crucible ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Alumina Crucible ◽  
X Ray ◽  
Intermediate Phases ◽  
Twin Band ◽  
Ar Gas

X-Ray diffraction revealed two intermediate phases in the system MnS+Er2S3,:MnEr2S4= MnS.Er2S3, and MnEr4S7= MnS.2Er2S3. Their structures may be described as NaCl type, chemically twinned at the unit cell level, and isostructural with CaTi2O4, and Y5S7 respectively; i.e. {l13} NaCl twin band widths are (4,4) and (4,3).The present study was to search for structurally-related (twinned B.) structures and or possible disorder, using the more sensitive and appropiate technigue of electron microscopy/diffraction.A sample with nominal composition MnEr2S4 was made by heating Mn3O4 and Er2O3 in a graphite crucible and a 5% H2S in Ar gas flow at 1500°C for 4 hours. A small amount of this material was thenannealed, in an alumina crucible, contained in sealed evacuated silica tube, for 24 days at 1100°C. Both samples were studied by X-ray powder diffraction, and in JEOL 2000 FX and 4000 EX microscopes.

scholarly journals The Influence of Environment in the Alteration of the Stained-Glass Windows in Portuguese Monuments

Heritage ◽  
2018 ◽  
Vol 1 (2) ◽  
pp. 365-376 ◽  
Author(s):  
Teresa Palomar ◽  
Pedro Redol ◽  
Isabel Cruz Almeida ◽  
Eduardo Pereira da Silva ◽  
Marcia Vilarigues
Keyword(s):  
Analytical Techniques ◽  
Soda Lime ◽  
Silicate Glasses ◽  
High Humidity ◽  
Atmospheric Conditions ◽  
Stained Glass ◽  
Mixed Alkali ◽  
Alkali Silicate ◽  
High Humidity Environment ◽  
Humidity Environment

This work presents the results of the exposure of soda-lime, potash-lime and mixed-alkali silicate glasses during ten and twenty months in different Portuguese monuments with historical stained-glass windows to characterize the influence of local environmental conditions. The glass samples were exposed in the Monastery of Batalha (Batalha), the Monastery of Jerónimos (Lisbon), and the Cathedral of Évora (Évora). A set of analytical techniques to assess the physicochemical effects were used, including optical microscopy and Fourier transform infrared spectroscopy. All the samples presented crystalline deposits on their surface; however, their quantity and nature depended on the atmospheric conditions during the days before the collection. Potash-lime silicate glass was the most altered glass in comparison with soda-lime and mixed-alkali silicate glasses. The samples from the Cathedral of Évora showed a high content of dust and salts on their surface but without severe chemical pathologies; however, those samples exposed in the Monastery of Jerónimos and the Monastery of Batalha presented alteration layers due to a high humidity environment.

scholarly journals Evaluation of the SOA Formation in the Reaction of Furfural with Atmospheric Oxidants

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 927
Author(s):  
Inmaculada Colmenar ◽  
Pilar Martín ◽  
Beatriz Cabañas ◽  
Sagrario Salgado ◽  
Florentina Villanueva ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ultrafine Particles ◽  
Analytical Techniques ◽  
Organic Aerosol ◽  
Nitrate Radical ◽  
Atmospheric Conditions ◽  
Severe Damage ◽  
Infrared Spectrophotometer ◽  
Cl Atoms ◽  
Product Study

An experimental product study of the reactions of furfural with the main tropospheric oxidants (Cl, OH and NO3) has been carried out using a Fourier Transform Infrared spectrophotometer (FTIR) and a gas chromatograph–mass spectrometer with a time of flight detector (GC–TOFMS). The main gas-phase products detected were 5-chloro-2(5H)-furanone, maleic anhydride, 2-nitrofuran and CO. Molar yields were quantified for the detected products in these reactions, thus suggesting the existence of nongaseous products that could not be observed with the analytical techniques employed. The formation of Secondary Organic Aerosol (SOA) from the oxidation of furfural with Cl atoms, OH, NO3 and ozone was investigated in a smog chamber in the absence of inorganic seed aerosols. The experimental results show the formation of ultrafine particles (less than 1 µm in diameter) for all of the studied reactions except for the nitrate radical. Given their small size, these ultrafine particles (<1 µm) can easily penetrate into the respiratory tract and reach the alveolar region. These particles, therefore, have the potential to cause severe damage to the respiratory system. The aerosol yield obtained, Y, was low (<0.04) in all cases, which means that the aerosols generated from furfural, under atmospheric conditions, could have little impact.

scholarly journals Study of Nickel Leaching Using Sulfuric Acid and Phosphoric Acid on The Selectivity Nickel Ore

2021 ◽  
Vol 16 (3) ◽  
pp. 393
Author(s):  
Syamsul Hidayat ◽  
Sri Yulianti ◽  
Dian Anggreini ◽  
Syamsul Bahtiar
Keyword(s):  
Sulfuric Acid ◽  
Phosphoric Acid ◽  
Nickel Content ◽  
Operating Time ◽  
Solution Concentration ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Low Grade ◽  
Atmospheric Conditions ◽  
Nickel Leaching

Study of nickel leaching using sulfuric acid and phosphoric acid on the selectivity of low-grade laterite nickel ore under atmospheric conditions has been successfully carried out. In this study, the laterite nickel leaching process was carried out by varying the solution concentration and operating time. The concentrations of sulfuric acid and phosphoric acid solutions were varied at 5 M and 6 M concentrations, while the operating time was varied at 4 hours and 6 hours. For other operating conditions, it is kept constant with an operating temperature of 90 ℃, pulp density 15% w / v, particle size ≤ 200 mesh. After that, the analysis stage was carried out using an atomic absorption spectroscopy (AAS) tool to determine the nickel content in the sample. The results showed that the highest nickel recovery was obtained at the concentration of 5 M sulfuric acid solution of 2.60% and 5 M phosphoric acid of 2.59% with the optimum operating time at 4 hours of operating time.

scholarly journals The leachability of a ternary CaO-Al2O3-SiO2 slag produced from smelting-reduction of low-grade bauxite for alumina recovery

2020 ◽  
Vol 191 ◽  
pp. 105184 ◽  
Author(s):  
Fabian Imanasa Azof ◽  
Michail Vafeias ◽  
Dimitrios Panias ◽  
Jafar Safarian
Keyword(s):  
Low Grade ◽  
Smelting Reduction ◽  
Alumina Recovery

Environmentally sustainable and cost-effective bioleaching of aluminum from low-grade bauxite ore using marine-derived Aspergillus niger

2020 ◽  
Vol 195 ◽  
pp. 105368 ◽  
Author(s):  
Syed Sikandar Shah ◽  
Mauricio Cesar Palmieri ◽  
Sandra Regina Pombeiro Sponchiado ◽  
Denise Bevilaqua
Keyword(s):  
Aspergillus Niger ◽  
Cost Effective ◽  
Low Grade ◽  
Environmentally Sustainable ◽  
Bauxite Ore
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