Non-traditional domestic refractory materials for aluminum metallurgy

Abstract

The promising and most accessible natural and technogenic raw materials are considered for lining metallurgical units for producing primary and secondary aluminum. A potential form of natural raw material for use as a dry barrier mix in aluminum electrolyzers is quartz pyrophyllite rock. For lining melting and casting units of the aluminum industry with the greatest technical and economic efficiency it is desirable to use aluminothermal slags and fuzed materials of OAO Klyuchevsk Ferroalloy Plant.The material sciences laboratories of OAP VOSTIO and NTTS Nonferrous Metals are carrying out a systematic search for new varieties of natural and technogenic refractory raw material suitable for preparing the linings of aluminum industry units; determination of its properties. The aim of this work is a reduction in the specific cost of refractories with sufficient wear resistance. Here a marked reduction in the cost of metal preparation is achieved by excluding expensive production conversion, i.e. high-temperature treatment of raw material and articles.A purposeful search for highly effective mineral raw material has been carried out taking account of the following main facts: melt resistance to reagents of metallurgical units, i.e. aluminum, cryolite, fluorite and mixtures of them; thermal stability under service conditions, i.e. absence of shrinkage, melting, corrosion, loss of strength, thermal spalling; economic capacity, i.e. possibilities for use without firing or fuzing raw material; ecological potential, i.e. absence of toxic and carcinogenic impurities in the raw material; accessibility, i.e. presence of reserves in mineral resources and dumps. A study was made of more than 40 varieties of natural and technogenic mineral raw materials of the Ural for their conformity with the suitability criteria listed above for the refractories of aluminum electrolyzers and melting and casting units. On the basis of comprehensive studies some promising raw materials were selected relating to the systems Al 2 O 3 -SiO 2 , CaO-Al 2 O 3 , CaO-MgO-Al 2 O 3 . Then from them pyrophyllite and aluminothermal slag were considered.Pyrophyllite. Among the numerous natural materials forming commercial deposits, there is most interest for producing aluminosilicate refractories in pyrophyllite Al 2 O 3 ·4SiO 2 ·H 2 O having refractoriness of 1710°C. The theoretical composition of the mineral is, wt.%: Al 2 O 3 28.3, SiO 2 66.7, H 2 O 5.0. The melting temperature is~1750°C.In view of the similar crystalline structure of pyrophyllite and talc many of their physicochemical properties are identical. Pyrophyllite has perfect jointing over plane (001), low hardness (about 1.0 of Moh's scale), a lamellar form of individual minerals, and a true density (specific gravity) of 2.8 -2.9 g/cm 3 . On heating, constitutional water is removed entirely in the range 600 -1000°C. The total dehydration product it metapyrophyllite Al 2 O 3 ·4SiO 2 . At 1150°C metapyrophyllite decomposes with formation of mullite and cristobalite. The overall sequence of phase ...

Pyrophyllite: An Economic Mineral for Different Industrial Applications

“…Despite the presence of large quantities of low-grade pyrophyllite ores, the impurities in these ores limit their use. Thus, there is an imperative need for techniques to improve the purity of these low-grade ores [28]. Several techniques have been tested to remove impurities from industrial minerals, such as removing iron from dolomite [29], talc [30], and kaolin [31,32].…”

“…Several techniques have been tested to remove impurities from industrial minerals, such as removing iron from dolomite [29], talc [30], and kaolin [31,32]. Moreover, several studies have used electrolysis, flotation, and electrification to remove sulfur, chlorine, iron, and titanium from non-metallic minerals [20,28,33]. For pyrophyllite, gravity separation techniques, flotation, magnetic separation, and leaching by ammonia and oxalic acid have been explored [1,8,18,28,34,35].…”

“…Moreover, several studies have used electrolysis, flotation, and electrification to remove sulfur, chlorine, iron, and titanium from non-metallic minerals [20,28,33]. For pyrophyllite, gravity separation techniques, flotation, magnetic separation, and leaching by ammonia and oxalic acid have been explored [1,8,18,28,34,35]. Furthermore, microwaves combined with sequential magnetic separation treatment have been used and considered as a promising method for upgrading low-grade pyrophyllite ore [19,36].…”

Chemical and Mineralogical Characterization of Saudi-Pyrophyllite ore and its Potential Applications

“…While grade B, due to its high iron content, its industrial applications are limited, therefore needs treatment to remove iron because of its adverse effect on the final products. AGJSR Kim et al, 2019;Perepelitsyn et al, 2008). However, it can be used as a carrier for insecticides and as a dusting agent for the roofing and rubber industry where high purity is not required (Table 2).…”

Pyrophyllitic raw materials from the Kul’-Yurt-Tau deposit as a base for ceramic composites

“…Studies of such properties will make it possible to replace expensive conventional raw materials in mixes used for ceramic and refractory materials with pyrophyllitic material or to use it as an autonomous component for producing ceramics and refractories as well as other products [1,2].…”