Прегледај по Аутор "Smiljanic, Slavko"

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    Influence of Process Parameters in Three-Stage Purification of Aluminate Solution and Aluminum Hydroxide
    (MDPI, 2023) Damjanovic, Vladimir; Filipovic, Radislav; Obrenovic, Zoran; Perusic, Mitar; Kostic, Dusko; Smiljanic, Slavko; Stopic, Srecko
    The influence of process parameters in the three-stage purification of aluminate solution from the Bayer process and aluminum hydroxide was considered in this paper. One of the ways of purification is treating the aluminate solution in order to reduce the concentrations in the starting raw material (solution) and then treating the aluminum hydroxide at a certain temperature and time in order to obtain an alumina precursor of adequate quality. The purification process itself is divided into three phases. The first phase involves the treatment of sodium aluminate with lime in order to primarily remove Ca2+ and (SiO3)2􀀀 impurities. Phase II aims to remove impurities of Zn2+, Fe2+, and Cu2+ by treatment with controlled precipitation using specially prepared crystallization centers. In Phase III, Na+ is removed by the process of hydrothermal washing of Al2O3 3H2O. In this work, parameters such as temperature (T), reaction time (t), and concentration of lime (c) were studied in order to remove the mentioned impurities and obtain the purest possible product that would be an adequate precursor for special types of alumina.
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    Quantification of Modifiers Fading during Melt Holding in the Aluminum Casting Furnace
    (MDPI, 2023) Djurdjevic, Mile; Manasijevic, Srecko; Smiljanic, Slavko; Ristic, Marko
    Strontium (Sr) and sodium (Na) are the most used modifiers in the aluminum casting industry. Both lose their concentration (fade) during holding in the melting furnace. Three types of chemical reactions in the melt may cause modifier fading: vaporizing, oxidizing, or reacting with some other elements from the melt. Due to Na and Sr’s very low vapor pressure, their vaporization from the aluminum melt was excluded as a reason for the modifiers’ fading. Oxidation looks like the major chemical reaction that causes the fading of Na and Sr from an aluminum melt. The present paper aimed to quantify the fading of Na and Sr in an Al–Si–Cu–Mg alloy. The loss of modifiers (Na and Sr) during melt holding in a furnace can be analytically quantified using equations taken from the literature. The calculated surface reaction rate constant (ks) can estimate the modifier’s loss during melt holding in industrial and laboratory furnaces.