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

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.

COMSOL Simulation for Design of Induction Heating System in VULCAN Facility

The experimental facility VULCAN was setup to study the fuel-coolant interaction (FCI) phenomena in a postulated severe accident of light water reactors. The heating system is important for the facility to prepare molten material in a crucible. This article is concerned with the design of the heating system, which applies electromagnetic induction heating method. The COMSOL code was employed to simulate the induction heating characteristics of a graphite crucible under different current and frequency of the work coil (inductor). Given a frequency, the relationship between the crucible’s average temperature and the inductor’s current is obtained, which is instrumental to select the power supply of the induction heating system. Meanwhile, the skin effect of induction heating is analyzed to guide the choice of frequency and inductor of the heating system. According to the simulation results, the induction heating system of frequency 47 kHz is suitable for the experiment, with a good agreement in temperature between the measured and the predicted.

Alloying Elements Effects on Electrical Conductivity and Mechanical Properties of Newly Fabricated Al Based Alloys Produced by Conventional Casting Process

The present investigation deals with a comprehensive study on the production of aluminum based alloys with the incorporation of different alloying elements and their effect on its electrical conductivity and mechanical properties. Casting of pure aluminum with different concentration and combinations of alloying additives such as cupper (Cu), magnesium (Mg) and silver (Ag) were carried out using a graphite crucible. The as-cast microstructure was modified by hot rolling followed by different heat-treated conditions viz., annealing, normalizing, quenching, and age hardening. The mechanical properties and electrical conductivity of the produced heat-treated alloys sheets under various processing conditions were carried out using tensile testing, hardness, and electrical resistivity measurements. It was found that by increasing the alloying elements content, yield strength results increased significantly by more than 250% and 500% for the as rolled and 8 h aged Al-Cu-Mg alloy, respectively. On the other hand, the electrical conductivity reduces slightly with −14.6% and −16.57% for the as rolled and 8 h aged of the same Al-Cu-Mg alloy, respectively.

Microstructure and Properties of TiAl-Based Alloys Melted in Graphite Crucible

This paper presents the chemical and phase composition, microstructure, and selected properties both at room temperature and at the temperature corresponding to the expected operating conditions of three successive generations of TiAl-based alloys (Ti-47Al-2W-0.5Si, Ti-45Al-8Nb-0.5(B,C), and Ti-45Al-5Nb-2Cr-1Mo-0.5(B,C)-0.2Si) melted in a vacuum induction furnace with high-density isostatic pressed graphite crucibles. The obtained results of mechanical and physical properties of the produced alloys were compared to the properties of reference alloys with similar chemical composition and melted in a cold copper crucible furnace. The effect of increased carbon content in the produced alloys due to the degradation of the graphite crucible during melting is higher strength properties, lower plastic properties, higher coefficient of thermal expansion, and improved creep resistance. It was shown that the proposed technology could be successfully used in the production of different generation TiAl-based intermetallic alloys.

Hydrolysis-Based Hydrogen Generation Investigation of Aluminum System Adding Low-Melting Metals

In this age of human civilization, there is a need for more efficient, cleaner, and renewable energy as opposed to that provided by nonrenewable sources such as coal and oil. In this sense, hydrogen energy has been proven to be a better choice. In this paper, a portable graphite crucible metal smelting furnace was used to prepare ten multi-element aluminum alloy ingots with different components. The microstructure and phase composition of the ingots and reaction products were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The reaction was carried out in a constant temperature water bath furnace at 60 °C, and the hydrogen production performance of the multi-element aluminum alloys in different proportions was compared by the drainage gas collection method. The experimental results show that the as-cast microstructure of Al–Ga–In–Sn aluminum alloy is composed of a solid solution of Al and part of Ga, and a second phase of In3Sn. After the hydrolysis reaction, the products were dried at 150 °C and then analyzed by XRD. The products were mainly composed of AlOOH and In3Sn. Alloys with different compositions react at the same hydrolysis temperature, and the hydrogen production performance is related to the ratio of low-melting-point metal elements. By comparing two different ratios of Ga–In–Sn (GIS), the hydrogen production capacity and production rate when the ratio is 6:3:1 are generally higher than those when the ratio is 7:2:1. The second phase content affects the hydrogen production performance.

On the industrial symbiosis of alumina and iron/steel production: Suitability of ferroalumina as raw material in iron and steel making

The biggest challenge for our society, in order to foster the sustainable circular economy, is the efficient recycling of wastes from industrial, commercial, domestic and other streams. The transition to a circular economy is the goal of the European Commission’s Circular Economy Action, which was first launched in 2015. In 2020 the above action plan announced initiatives along the entire life cycle of the product, with the aim to make sustainable products the norm in the EU. Therefore, it is anticipated that the above action will result in an increase in Europe’s economic competitiveness, sustainability, resource efficiency and resource security. Within this context, the suitability of ferroalumina as a raw material in the blast furnace is investigated. Ferroalumina is the product of the high-pressure filter press dewatering process of the Greek red mud generated during the production of alumina by means of the Bayer cycle. Ferroalumina is a low-cost raw material and its possible charging in the blast furnace and/or steelmaking aggregates is a step towards industrial symbiosis, where the wastes, namely by-products, of an industry or an industrial process, become the raw materials for another. In the present work the effect of ferroalumina addition as a raw material was examined by smelting ferroalumina, blast furnace-slag, lime and scrap at 1550°C in a graphite crucible and a constant slag basicity. The increase of the alumina content in the slag improves the desulfurization capacity. Moreover, the silicon exchange between slag and metal was examined. The results indicate that the alkalis’ capacity of the slag increases with the addition of ferroalumina. The analysis of the finally obtained slag suggests that it could be suitable for utilization in slag-cement production.

Separation of titanium and silicon oxides during plasma-arc melting of quartz-leucoxene concentrate

The aim of the work was investigation of separation of titanium’s and silicon’s oxides during plasma-arc melting of quartz-leucoxene concentrate from Yarega deposit. The melting was proceeded in laboratory plasma-arc furnace in graphite crucible at 16 – 40 kW of arc power. The microstructure and R-x phase analysis of solidified melt were investigated after arc melting. The melt separated on two layers. The upper layer consisted mainly of SiO2 in the form of glass, the lower layer — mainly of cemented titanium oxide particles ≈ 100 μm in dimension. TiO2, Ti8O15, Ti6O11, Fe3TiO3O10, Ti3O5 were observed. These particles formed during melting and moved throw liquid glass to the bottom of crucible with the speed of V ≈ 10–4 m/s. The separation of TiO2 and SiO2 required energy W ≈ 100 GJ/t of concentrate in laboratory plasma arc furnace. The possibility of industrial employment of the arc melting separation was discussed. The estimated energy requirement was about 5 GJ/t in 20-t arc furnace.