Prospects for using aluminosilicate refractories for aluminum electrolyzers. Part 1. Features of the structure of aluminosilicate refractories intended for aluminum electrolyzers

Abstract

Comparative analysis is provided for the structure and properties of aluminosilicate refractories grade ShPD. It is established that refractory ShPD M -45, produced with the use of an addition of mullite-corundum chamotte surpasses in all characteristics refractories prepared by the normal technology. Refractory ShPD M -45 may be recommended for use in aluminum electrolyzers.The service life of the lining of the cathode assembly of an aluminum electrolyzer is an important engineering parameter. In order to avoid penetration of subsidiary products of an electrolyzer into the lining a refractory layer is laid down under hearth blocks of the electrolyzer. Sodium vapor and fluorine compounds, diffusing into the refractory layer, lead to a change in its chemical-mineral and phase compositions and destruction of the refractory itself, as for the cathode lining of the aluminum electrolyzer as a whole, and therefore the question of selecting the grade of refractory remains important.There is currently use of aluminosilicate refractories for the refractory layer. The chemical and phase composition of chamotte refractories is determined by the raw material composition and properties. In turn the properties of the aluminosilicate articles depend not only on the Al 2 O 3 content within them, but also on the overall total sum of fluxes and often on their chemical nature [1]. The degree of mullitization, the composition of mullite, and the glassy phase in chamotte refractories, depend on the properties of the original raw material, firing temperature and duration.Properties are provided in the present communication for the characteristics and phase composition of chamotte dense articles of ShPD produced by traditional technology (ShPD-43), and with the use of addition of mullite-corundum chamotte (ShPD M -45). Studies were carried out petrographically in reflected and transmitted light in microscopes MBI-6 and MN-8 respectively. Articles made of ShPD M -45 with addition of mullite-corundum chamotte in production properties and phase composition somewhat exceed those for articles made of ShPD-43 prepared by normal technology. The physicochemical indices of ShPD, prepared by both production methods, are provided in Table 1.The average apparent density of specimens of the corresponding type of refractory was determined by hydrostatic weighing. Open porosity of ShPD M -45 articles was lower by a factor of 1.5, and the average density was higher by a factor of 1.1 than for articles without mullite-corundum chamotte. Since open porosity is connected with the nature of pores,

Prospects of the use of aluminosilicate refractories for aluminum electrolyzers. Part 3. The role of the glass phase formed in the operation of aluminum electrolyzers

“…The authors of [10] have established that an iron-and-titanium-bearing glass consists of a silica skeleton and regions enriched with compounds of impurity cations. We have detected similar glasses in ShPDm-45 articles, the characteristic of which is given in Part 1 of the present paper [11].…”

Study of the mineral and phase composition of aluminosilicate refractory ShPDM-45 after service in an aluminum electrolyzer of OAO Zaporozh’e aluminum combine

“…It is apparent that the service life of electrolyzers with use of ShPD M -45 material as a refractory-barrier will be significantly higher and longer than with use of unmolded aluminosilicate materials. This is also confirmed by data in [6], that one of the requirements for aluminosilicate refractory, intended for aluminum electrolyzers, is preparation of a macrostructure with pores with a predominant diameter of less than 5 mm [22].…”

“…The presence of metal beads based on Fe, Si-Al in a sample after service indicates that a reducing atmosphere is observed in the refractory layer [16], and this is confirmed by data of previous studies [3,6]. Silicon, aluminum, iron-containing phases are reduced preferentially and also partly calcium-and titanium-containing compounds.…”

Prospects for using aluminosilicate refractories for aluminum electrolyzers. Part 2. Resistance of aluminosilicate refractories to the action of commercial electrolyte

“…Data from laboratory studies are provided in this article for the resistance of aluminosilicate refractories ShA-5, ShPD-43 and ShPD M -45 [3] to the action of a commercial electrolyte with a cryolite ratio (c.r.) of 2.4.…”