RU2095485C1 - Cathode unit of aluminum electrolyzer - Google Patents

Abstract

FIELD: aluminum production. SUBSTANCE: in cathode unit of aluminum electrolyzer, gap between cathode rod, opening in cathode housing, and brick masonry is filled with free running finely dispersed oxide-based refractory materials, mainly silicon and/or aluminum oxides. Refractory brick of socle periphery is placed on cathode rod with 0.1-5.0-mm gap. EFFECT: improved construction. 3 cl, 1 dwg, 1 tbl

Description

 The invention relates to the electrolytic production of aluminum, in particular to the improvement of the cathode device of an aluminum electrolyzer.

 Known cathodic device of an aluminum electrolyzer containing a base of brickwork in a metal casing with holes (windows) in the side walls for the cathode rods, a damping layer (pillow) and hearth sections installed on it with cathode rods forming a gap around the perimeter of the holes of the cathode casing, increased the height of the brickwork on the periphery of the socle (edge), and in places of contact with the cathode rods, the bricks must be ground to them, the gap between the rod and the brick should not be more than 1 mm, and the gap p between the cathode rod and the hole in the casing is covered with mastic, consisting of asbestos and liquid glass.

 During firing and subsequent start-up of the electrolyzer with a known cathode device, when the temperature rises in the cathode, the liquid part of the bonding mastic is distilled off in the gaps of the windows of the cathode casing. The second part of the mastic - asbestos, becomes even more porous. Containment gases containing volatile hydrocarbons and tarry substances freely penetrate through the loosened asbestos layer into the atmosphere. This opens up the access of air oxygen through the gap in the "windows" of the cathode casing to the carbon materials of the "cushion", hearth sections and interblock seams. With increasing temperature, firstly, tarry and volatile hydrocarbons are distilled from the cathode to the atmosphere through gaps in the “windows” of the casing, secondly, carbon is oxidized by the “cushion”, hearth sections and interblock sections, and interblock seams, and they burn out. In practice, when firing and especially starting the electrolyzer, one can observe the knocking out of gas flares and the release of resinous substances from the “windows” of the cathode casing with the subsequent leakage of liquid aluminum. As a result, all this leads to a decrease in the grade of the obtained aluminum and the service life of the electrolyzer.

 The need to rub chamotte bricks of the masonry of the edge to the cathode rods, according to the well-known technical solution, does not exclude the filtration of gaseous substances. In addition, during the operation of the cathode, when the arrow of the cathode rod sags and changes, the hard fit of the “edge” brick on the cathode rod can lead to deformation of the entire masonry, the appearance of torques and the raising of the hearth blocks in the plane of the central interblock seam. This also leads to the metallization of the hearth, reducing the service life of the electrolyzer, the grade of aluminum obtained.

 The purpose of the proposed technical solution is to increase the grade of the obtained aluminum, the service life of the cell.

 This goal is achieved by the fact that in the cathode device of an aluminum electrolyzer containing a base of brickwork in a metal casing with holes in the side walls for the cathode rods (windows), a damping layer (pillow) on the base and the hearth sections installed on it with cathode rods forming the gap around the perimeter of the holes of the cathode casing, the increased height of the brickwork (edge) along the periphery of the base, the gap between the cathode rod, the hole in the cathode casing and the brickwork is made of loose finely ispersnyh refractory materials based on oxides, preferably oxides of silicon and / or aluminum. Refractory brick of the periphery of the base is mounted on the cathode rod with a gap of 0.1-5.0 mm.

 Loose fine oxides in the gap between the cathode rod and the window in the cathode casing seal the gap. They prevent mutual filtering of coking gases and atmospheric oxygen, compensate for the thermal deformations of the cathode rod that occur during this process, thereby preventing the rod from tearing off the hearth block and raising (swelling) the hearth, which leads to an improvement in the grade of aluminum and an increase in the service life of the cell.

 The presence of a gap between the “brow” brick and the cathode rod filled with bulk oxides complements the sealing of carbon materials from the atmosphere, reduces the influence of thermal deformation of the cathode rod on the refractory lining, and contributes to an increase in the grade of aluminum and the service life of the cell. The gap between the brick "brow" and the cathode rod less than 0.1 mm requires grinding the brick to the rod and surface treatment of the rod. In addition, a particle size of less than 0.1 mm is difficult to obtain. A gap of more than 5 mm is undesirable, since in this case it is necessary to install any spacers to realize such a gap.

 The drawing shows a cathode device (fragment) containing a steel cathode casing 1 with windows 2 for cathode rods 3 installed with a gap 4 in the windows 2. The gap 4 is filled with finely dispersed materials based on silicon oxides (screening of quartzite, sand) and / or aluminum ( alumina dust collection). The cathode rods 3 are sealed in the hearth sections 5 and mounted on the “cushion” 6 made on the refractory base 7. The refractory brow 8 is made with a gap 9. The side blocks 10 are installed on the brow 8 and an interblock seam 11. Outside, the gap 4 can be closed by the refractory putty 12 to prevent leakage of bulk material. In this case, the installation of a flange 13 mounted movably on the cap screws is desirable outside the putty 12.

 Implementation example.

 The cathode devices of four S-8B electrolyzers are mounted for a current of 155 kA according to the proposed technical solution. The first two experimental electrolyzers (A, B) implement point 1 of the proposed technical solution, moreover, finely dispersed quartzite (screenings for preparing the charge in silicon production) is used on the electrolyzer "A", fine alumina (dust from the electrolysis cells). At the same time, there is no gap 9 and the bricks were ground. On the other two experimental electrolyzers (C, D), p. 1, 2 of the proposed device is implemented, moreover, a mixture of quartzite and alumina in the gap 4 and alumina in the gap 9 are used on the electrolyzer "C", and a mixture of quartzite and alumina in the electrolyzer "D" Gaps 4 and 9.

 As witness electrolysers, 4 S-8B electrolyzers mounted in the same building were adopted. The cathodes of witnesses are mounted according to the prototype. Firing and starting the electrolytic cells using metal and pouring the electrolyte according to known methods.

 The results of comparative observations, parameter measurements of experimental electrolyzers and witnesses are shown in the table.

 As follows from the test results obtained, during the operation of the experimental electrolytic cells there are no gaseous emissions of resinous substances, a liquid binder in the windows of the cathode rods, torches are absent during firing and when starting up for electrolysis, while the listed factors take place on witness electrolysis cells. This indicates the absence of binder loss and intense carbon oxidation reactions of the cathode device. In addition, there are no liquid metal proteins in the “windows” of the cathode rods in the experimental electrolyzers, which confirms the absence of metallization of the hearth due to the improvement of its monolithicity. This is also indicated by the smaller temperature difference of the outer ends of the cathode rods, the difference in the current load across the cathode rods and a smaller voltage drop in the hearth on the experimental electrolyzers compared to the witnesses. Moreover, after start-up on experimental electrolyzers, a decrease in the voltage drop in the hearth occurred, and on witnesses an increase.

 As a result, the content of Fe and Si impurities in the cathode metal on experimental electrolyzers is much lower, and the operating voltage is 10–20% lower than on witnesses.

 Thus, the expected increase in the service life of the cathode device due to the lack of metallization of the cathode when using the proposed technical solution is 3-4 months along with an increase in the grade of the obtained metal.

 An additional objective of the invention can be considered energy saving.

Claims (3)

 1. The cathode device of an aluminum electrolyzer containing a base of brickwork in a metal casing with holes in the side walls for the cathode rods, a damping layer and hearth sections installed on it with cathode rods forming a gap around the perimeter of the holes of the cathode casing, an increased height of the brickwork around the periphery socle, characterized in that the gap between the cathode rod, the hole in the cathode casing and the brickwork is made of bulk fine refractory materials based on oxide in.  2. The device according to p. 1, characterized in that the gap is made on the basis of oxides of silicon or aluminum.  3. The device according to claims 1 and 2, characterized in that the refractory brick is installed on the cathode rod with a gap of 0.1 to 5.0 m.

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