SU659645A1 - Method of preparing aluminium electrolyzer for electrolysis - Google Patents

Description

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The invention relates to the field of aluminum production by an electrolytic method and is aimed at improving the technological operation of preparing an electrolytic aluminum electrolyzer for start-up, equipped with a ready-made self-burning anode or pre-baked anodes.

A known method of thermal preparation for the start-up of an aluminum electrolysis cell for electrolysis includes the gradual heating of the cathode bottom with heat from burning a fuel-sprayed electrolyzer in the working space, pouring a lined bath of electrolyte into the mine, and further heating the cathode by burning fuel above the electrolyte surface. By a known method on a hearth place a layer in 2-3 cm of salt with m. Pl. 400-800 ° C and heat from combustion of the fuel is produced while melting the salt layer on the bottom 1.

The known method provides for the reduction of porosity and shrinkage of the interblock hemline seams, which increases the mechanical strength of the bottom and the service life of the cell.

However, low-melting components of the salt mixture poured into the hearth penetrate into the pores and cracks of the hearth, and when the molten aluminum is subsequently cast into the hearth, they are pushed out, passing into aluminum and lowering its grade.

The purpose of the invention is to increase the grade of aluminum.

This is achieved by first heating the hearth with heat from burning the fuel to a temperature not lower than 750 s, then pouring the electrolyte overheated to 970-1010C and heating the cathode and the lining to operating temperatures.

The method of preparation of the aluminum electrolysis cell for start-up for electrolysis is carried out in two stages as follows

& way.

In the first stage, the heating and burning of the coal lining is performed due to the heat from the organized combustion of the atomized fuel distributed evenly in the space between the inner surface of the shaft and the lower surface of the anode. In this case, the bottom surface of the anode is on a level with the side

0 of the cathode, and between the anode and the side of the mouth (.. 3, insulating caps are poured to reduce heat loss and create a condition for adjusting the excess air ratio. To protect against oxidation, the side lining surface is protected by known methods (for example, a layer of cryolite powder) and the atmosphere in the combustion zone support the reduction. The duration of the first stage of preparation depends on the design and power of the electrolyzer, as well as the technical characteristics of the used device for burning fuel. A chemically first stage of preparation for the start-up of a 150 kA electrolyzer with an upper conductor when using an installation with 10 gas burners with a total nominal capacity of 600 m3 / h lasts 12-15 hours. The temperature rise in the first stage is carried out according to a schedule in which three periods are provided : I period 40-50% of the time - smooth heating of the hearth up to 500 ° C °; C period 35-25% of the time - temperature exposure at the level of 500 ° C °; W period 25% of the time - heating the bottom below 750 ° C. The second stage begins with the moment of pouring overheated electrolyte. Before filling the electrolyte, heat insulating covers are removed, and the interelectrode distance is set at least 30-50 mm. In the final stage of preparation (before switching on the electric current), the cracks in the coal lining and the cathode shaft are filled with molten electrolyte, overheated to 970-1010 ° C, and the heating of the lining to the electrolysis process temperature of 940-965 ° C occurs under the electrolyte layer due to heat introduced by the electrolyte and heat from the continued incineration

Claims (1)

65E645 fuel over its open surface. Under the electrolyte layer due to thermal expansion of the cathode elements and impregnation of the upper layers of the bottom of the electrolyte components, such as sodium fluoride, carbonaceous materials will swell and the cracks filled with electrolyte will shrink. The carbon lining of the cathode of an electrolytic cell prepared in this way will be reliably protected from penetration of molten aluminum after starting the electrolysis and starting the process of isolating and accumulating the aluminum layer on the cathode, which will significantly increase the service life of the cathode device of the aluminum electrolysis cell and the grade of the resulting aluminum. Claims The method of preparing for the start-up of an aluminum electrolysis cell for electrolysis includes the gradual heating of the bottom-cathode with heat from burning a fuel-sprayed electrolyzer in the working space, pouring a lined electrolyte bath into the mine and further heating the cathode by burning fuel above the electrolyte surface, characterized in that in order to increase the grade of aluminum, first the hearth is heated with heat from burning fuel to a temperature not lower than it is then poured overheated to 970-. 1010 ° C electrolyte and continue heating the cathode and lining to operating temperatures. Sources of information taken into account in the examination 1. USSR author's certificate 549510, cl. C 25 C 3/06, -1974.