Brazilian refractory grade bauxite: a new alternative to refractories makers and users

Abstract

After two centuries of the discovery, we now know that there are several types of bauxites, in which mineralogy points to the most appropriate application. In the non-metallurgical industry, bauxites with refractory grades have been applied as raw materials in the production of high-alumina refractories for both shaped and unshaped. The increase in the cost of other sources of high-alumina raw materials has encouraged the refractory producers to find a more cost-effective substitute, such as refractory-grade calcined bauxites (RGB). Nowadays, concerns rise regarding the availability of RGB due to the continuous restrictions taking place in China, which has a 95% market share. This work presents a new RGB of high-alumina content (~85%) from a Brazilian source in which process enabled a technology with high refractoriness.

Refractory Grade Bauxite: An Overview about the Effects of different Bauxite Sources and Forming Processes on the Quality of the Material

“…According to the same source, Guyana was responsible for 6.6% of world´s RGB supply in 2015, while China takes the remainder. These numbers are close to the ones published by other sources, showing China While bauxite ore from Brazil, Guyana and other areas with tropical climate tends to be gibbsitic (Al(OH) 3 ) whose aluminum hydroxide is trihydrate, Chinese one is general, bauxite ores from these countries exhibit different mineralogy and physicochemical characteristics that promote different properties on the RGBs manufactured [12]. Traditionally, the mineralogy of RGB is composed by a combination among three or or more phases, hereinafter referred: corundum st phase), mullite (2 nd phase), tialite, rutile and/or hematite.…”

“…Traditionally, the mineralogy of RGB is composed by a combination among three or or more phases, hereinafter referred: corundum st phase), mullite (2 nd phase), tialite, rutile and/or hematite. Table 2 shows some properties of each phase mentioned [13] Considering thermal process, the diaspore from raw bauxite is straightly converted to α-alumina during assuring the crystal growth and inhibiting the reaction with silica in the liquid phase to form mullite [12]. Furthermore, the higher grade of titanium oxide in Chinese bauxite favors the tialite formation (β-Al 2 O 3 .TiO 2 ) above 1350ºC which can be an issue considering the mechanical strength due to its highly anisotropic thermal expansion ( Table 2) and an eutectoid transformation during the cooling, decomposing it into its precursors, temperature (750ºC -1300°C) [14].…”

Chemical Interaction between the Sr4Al6O12SO4 Ceramic Substrate and Al–Si Alloys

“…This relevance is largely due to the wide availability, ease of processing, and mechanical properties that allow it to have a wide range of applications, in some cases even comparable to steel [1][2][3][4][5][6]. For its production on an industrial scale, melting furnaces are used, which are mainly made up of refractory ceramics based on aluminosilicates (CRAS) due to their low cost, high availability, good mechanical properties, and resistance to corrosion and thermal shock [7][8][9][10][11][12]. However, this type of substrate presents a high corrosion rate in contact with liquid aluminum alloys (up to 6 mmh −1 ) due to the strong reducing effect of aluminum on silicon, leading to the critical task of selecting refractories for melting furnaces [13][14][15][16][17].…”

Leaching for iron removal from low-grade bauxite ore to access refractory instruction

“…Bauxite reserves contain high amounts of aluminum and are one of the most important aluminum ores (Donaldson and Raahauge, 2017). So far, more than 100 minerals have been identified for bauxites, of which only a few, including gibbsite Al(OH) 3 , boehmite (γ-AlO(OH)), and diaspore (α-AlO(OH)) are important reserves of aluminum (Pereira et al, 2019). More than 95% of the world's bauxite reserves are used in the alumina industry and metal production; the remaining 5% is used in abrasive, refractory, cement, chemical, and metal industries.…”