Investigation of Mullitization in Fused Materials Based on Kaolinite Clay and Production Waste
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INVESTIGATION OF MULLITIZATION IN FUSED MATERIALS BASED ON KAOLINITE CLAY AND PRODUCTION WASTE M. Kh. Rumi,1, 2 Sh. K. Irmatova,1 Sh. A. Faiziev,1 M. A. Zufarov,1 E. P. Mansurova,1 E. M. Urazaeva,1 and G. M. Arushanov1 Translated from Steklo i Keramika, No. 7, pp. 8 – 12, July, 2020.
The results of studies on using a concentrated radiation flux to obtain fused materials based on kaolinite clay and high-alumina waste are reported. The phase composition, microstructure, and elemental composition of the synthesized materials were determined. It was found that the additive content 10 – 20% by weight and melt cooling rate about 103 K/sec are preferable for the formation of the optimal microstructure in the form of mullite needles with different orientations. Key words: mullite, glass phase, needle-shaped, fusion, Claus catalyst.
vcool ~ 103 K/sec) and slow cooling on a water-cooled metal substrate on which the melting was performed (rate of cooling vcool ~ 102 K/sec) [2, 3]. The maximum amount of additive introduced is determined on the basis of calculated data on full binding of the free-silica component into mullite. Theoretically, when kaolin is heated its aluminate component fully enters into the primary-mullite formation reaction via the scheme [4]
It is well-known that one of the quality metrics of fireclay refractories is the chemical composition, specifically, the content of aluminum oxide present in them. Conventionally, to increase its content and, correspondingly, to increase the mullite yield, additional alumina is added into fireclay made from kaolinite clays. However, this method is very energy-intensive, additional high-temperature firing is required in order for the reaction forming secondary mullite to go to completion [1]. For this reason it is of interest to obtain fillers for aluminosilicate and specifically, fireclay, light-weight refractories by fusion of native materials with added high-alumina production wastes.
3(A2O3 × 2SiO2 × 2H2O) (600 – 1200°C) = 3A2O3 × 2SiO2 (primary mullite) + 4SiO2 + 6H2O.
To bind the formed free-silica and obtain secondary mullite the temperature must be increased to 1600 – 1650°C and alumina must be added in order for the following reaction to occur
MATERIALS, METHODS Samples of black, carbonaceous, additive-free kaolinite clay (black clay, in what follows) as well as samples with a two-component composition — black clay + high-alumina production waste (spent Claus catalyst (SCC)), weight content of the waste varying in the range 10 – 40%, were fused in the Large Solar Furnace (LSF). For purposes of purification, prior to use the spent wastes were subjected to heat-treatment by heating in the LSF at temperature (1300°C) below their melting temperature. The melted material was cooled by two methods — discharging a stream of the melt into water (cooling rate 1 2
(1)
4SiO2 + 6A2O3 (1200 – 1650°C) = 2(3A2O3 × 2SiO2 ) secondary mullite.
(2)
Therefore, to ensure complete binding of the silica component of kaolin and to obtain the stoichiometric mul
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