RU2131487C1 - Facing of cathode casing of aluminium cell - Google Patents

Abstract

FIELD: equipment for aluminium production. SUBSTANCE: facing includes carbon blocks, heat insulation, refractory layers and upper protective layer of mixed alumina and aluminium fluoride or fresh cryolite taken in relation 2:(0.75-0.9). Lower protective layer is in the form of two steel sheets laid one over another with gap equal to 1-3 mm and filled with alumina or it is ceramic material layer. Refractory material layer is placed between lower and upper protective layers. Red brick is used as ceramic material. Facing prevents fluoride penetration into heat insulation layer. EFFECT: increased service life period of facing, enhanced operational parameters of cell. 5 cl, 2 dwg

Description

 The invention relates to the field of non-ferrous metallurgy, in particular to the design of an electrolytic cell for producing aluminum.

 Known lining of the cathode casing of an aluminum electrolyzer containing coal blocks, refractory and heat-insulating layers with a layer of crevice red brick between them, while the cracks in the bricks form vertical channels (USSR copyright certificate N 1571104).

 The disadvantage of this lining is the possibility of penetration of aluminum and electrolyte through cracks in the brick, which leads to a decrease in the life of the lining.

 Known lining of the cathode casing of an aluminum electrolyzer containing carbon blocks, refractory and heat-insulating layers and a protective layer made of a metal sheet (Japanese application N 58-161789).

 The disadvantage of this lining is that the protective layer cannot provide reliable protection of the thermal insulation from impregnation with fluorine salts throughout the campaign.

 Known lining of the cathode casing of an aluminum electrolyzer containing carbon blocks, refractory and heat-insulating layers and a layer located between them, made of nepheline (USSR author's certificate N 918335), which we take as the closest analogue.

 This solution increases the service life of the cell, but does not provide complete protection of the lining from the penetration of aluminum and fluorine salts into the insulating material, which degrades its quality and reduces the performance of the cell.

 An object of the invention is the elimination of fluorine salts in the insulating lining, increasing the service life of the lining of the cathode casing and improving the performance of the cell.

 The problem is solved as follows.

 In a lining having carbon blocks and a heat-insulating layer, the upper protective layer consists of a mixture of alumina with aluminum fluoride or fresh cryolite, taken in the ratio 2: (0.75-0.9). The lower protective layer consists of two steel sheets laid horizontally one above the other with a gap of 1-3 mm filled with alumina or a layer of ceramic material, while a layer of refractory material is placed between the first and second protective layers.

 As a ceramic material, red brick can be used.

 An example of a lining is shown in the drawings, where in FIG. 1 shows an example of lining of the cathode casing of an aluminum electrolyzer with metal sheets in the lower protective layer; in FIG. 2 shows an example of lining the cathode casing of an aluminum electrolyzer with ceramic material in the lower protective layer.

 The lining consists of a side lining 1 of the hearth, consisting of carbon blocks 2, laid on the upper protective layer 3, consisting of a mixture of alumina (70%) and fresh cryolite or aluminum fluoride (30%). Under the protective layer 3 is a layer of refractory material 4 made of fireclay brick. After layer 4, a lower protective layer is laid, consisting of two steel sheets 5 and 6, between which a layer of alumina 7 is 1-3 mm thick. The same alumina layers are located above sheet 5 and below sheet 6. The thickness of the alumina layer is selected from the condition for compensating for possible irregularities in the steel sheets.

 The lower protective layer may consist of a layer of ceramic material 8. When performing the lower protective layer of ceramic material, such as red brick, the layer thickness is 65 mm.

 Below the second protective layer is a heat-insulating material 9 made of foam diatomite brick. The space between the side lining 1 and the coal blocks is filled with a hearth mass 10.

 The protective layer 3, consisting of a mixture of alumina with cryolite, has a thickness of 40 mm and is compacted by a roller or other method.

 The thickness of the steel sheets 5 and 6 is 3-5 mm. The sheet of one horizon can be continuous or consist of separate sheets laid in horizons with a dressing of joints of 200-400 mm.

 Steel sheets can be made of heat-resistant steel, for example, grade 09G2S or steel art. 3. When using sheets of steel Art. 3, the thickness of the refractory material 4 should be doubled.

 The ratio of alumina and fluoride salts in the first protective layer is taken from the condition of providing optimal conditions for the protection of the underlying layers of the lining.

Claims (5)

 1. The lining of the cathode casing of an aluminum electrolyzer, containing carbon blocks heat-insulating, refractory layers and a protective layer located between them, characterized in that the lining is additionally provided with an upper protective layer made of a mixture of alumina and fluorine salts, on which the carbon blocks are laid, and the lower protective layer made of two horizontal rows of steel sheets or a layer of ceramic material, while a layer of refractory material is placed between the lower and upper protective layers.  2. The lining according to claim 1, characterized in that between the steel sheets placed a layer of alumina with a thickness of 1-3 mm.  3. Lining according to claim 1, characterized in that red brick is used as a ceramic material.  4. The lining according to claim 1, characterized in that the mixture of alumina with fluorine salts is taken in a ratio of 2: (0.75 - 0.9).  5. Lining according to claim 1, characterized in that fresh cryolite is used as the fluorine salt.

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