SU1560970A1 - Method of protecting graphite-containing elements of flux-melting furnace - Google Patents

Abstract

This invention relates to metallurgy, specifically to the operation of flux smelting furnaces. The purpose of the invention is to increase the durability of graphite lining and graphite electrodes. After the melted flux is drained from the melting tank, the electrodes are lowered to contact with the hearth, solid hydrocarbons are placed on the hearth along the perimeter of the lining and electrodes, and then the melting space of the flux furnace is closed, the arc is ignited between the hearth and electrodes and maintained for 3-5 seconds, with this amount of hydrocarbons placed on the hearth is 0.5-1 kg / m ^{2 of the} surface to be protected. Due to the organization of intensive and uniform washing of the protected surfaces with decomposition products, for example, naphthalene, they are evenly covered with a protective layer, which, in comparison with the known method, will increase the turnaround time from 37 to 78 heats and reduce the consumption of naphthalene several times. 1 tab.

Description

The invention relates to metallurgy, in particular, to protecting elements of electric smelting furnaces from destruction, and can be used for applying protective coatings on graphite lining, and gratirovannye electrodes of a flux melting furnace.

The purpose of the invention is to increase the durability of graphite lining and graphite electrodes.

The method is carried out as follows.

The essence of the method is to create optimal conditions for the pyrolysis of saturated solid hydrocarbons directly in the metallurgical unit, using its features for this. Carrying out the operation directly in the period after the flux is drained from the melting furnace, characterized by a temperature of the lining and electrodes of 1200-1400 C, promotes intensive pyrolysis of saturated hydrocarbons. Placing hydrocarbons on the bottom along the perimeter of the lining and electrodes provides the shortest way to deliver the protective material to the protected surface. An indispensable condition is the closure of the melting space of the furnace, ensuring the rational use of hydrocarbons

for its intended purpose and reducing their losses. The use of the arc provides the required temperature in the closed melting space, the presence of the predominant convective flows of gaseous hydrocarbons with pyrocarbon along the surface of the lining and the electrodes and the process of its deposition in the shortest possible time.

It has been established experimentally that the arc between the electrodes and the hearth must be maintained for 3-5 s. Less than 3 seconds, the arc maintenance time does not provide the necessary temperature gradient to obtain a uniform protective coating over the height of the melting tank and the electrodes.

Maintaining an arc for more than 5 seconds causes a danger of damage to the hearth of the fluo-smelting furnace.

It was experimentally determined that in order to achieve the optimum thickness of the protective layer (1-2 mm) on the surface of the lining and on the electrodes, the number of materials to be placed: hydrocarbons at the bottom should be 0.5-1.0 kg / m2 of the surface to be protected. With a consumption of hydrocarbons less than 0.5 kg / m2, their amount is insufficient for eapolation of voids and cracks, reaching a depth of 0.5 mm, and, therefore, for their healing. Consumption of more than 1 kg / m2 of hydrocarbons does not lead to the formation of a uniform protective layer, which causes the transition of pyrocarbon to the flux.

Example. A crucible-bucket type U503A with printed graphite lining was used to melt and heat the ANF-6 grade oxide fluoride flux on the OKB-1449 bifillary flux-melting furnace with graphite-coated electrodes 250 mm in diameter. The lining repair was carried out after the 20th from the start of the smelting campaign, the need for which was determined on the basis of a statistical analysis of crucible bucket lining wear. To do this, after the flux was drained, the electrodes were lowered to contact with the hearth and naphthalene (selected as a solid hydrocarbon) was placed evenly around the perimeter of the lining and electrodes in the amount of 1.9 and 3.8 kg at the rate of 0.5 and 1.0 kg / m2 of protection10

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My surface (the total surface of the lining and electrodes specified in the fluorescent furnace example is 3.8 m2). Then all the holes in the furnace were tightly closed with asbestos sheets, ignited the arc between the hearth and the electrodes and supported it for 2, 3, 4, 5 and 6s, respectively, for naphthalene consumption of 1.9 and 3.8 kg.

Two options were also tried for the exorbitant values of naphthalene consumption of 0.4 and 1.1 kg / m2 for the arc maintenance time of 5 s. At the same time, the total amount of naphthalene placed on the bottom was 1.52 and 4.18 kg. The number of experiments for transcendent hydrocarbon consumption was limited, since the lack of effectiveness for these values is obvious.

The table shows the technical and economic indicators of the state and service of the lining and electrodes.

For all the options after repair, the thickness of the applied protective layer was determined and the overall condition of the lining and electrodes was visually evaluated for the presence of surface defects (cracks, grooves, etc.).

A comparative analysis of the proposed and known methods was carried out on the basis of an assessment of technical and economic indicators given in the table.

The data in the table testify to the achievement of the optimal effect with regard to naphthalene consumption of 0.5-1.0 kg / m2 with a delay of the arc burning time of 3.4 and 5 s. Under these conditions, a necessary protective layer of the same thickness (1-2 mm) along the height of the melting vessel is provided. The resistance of the lining and electrodes increases by 1.6-1.8 times. With a naphthalene consumption of 0.4 kg / m2, despite the uniform thickness of the protective layer, its thickness was not ensured, which led to an insignificant increase in the durability of the lining (by 10%). The maintenance of arc burning for 2 s led to the formation of a non-uniform height of the melting capacity of the protective layer and, consequently, uneven wear of the lining and the electrodes. In addition, under these conditions, the application of the protective layer will

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Up to 20% of the area to be protected by the surface cracked.

Claims (1)

Invention Formula A method of protecting graphite-containing elements of a flux-smelting furnace, comprising applying carbon-containing material to the surface to be protected by precipitating it from a gaseous phase during the pyrolysis of hydrocarbons, different 1560970 In order to increase the resistance of the lining and electrodes, the pyrolysis of hydrocarbons is carried out in a melting furnace after the flux is drained, while lowering the electrodes until they come into contact with the bottom, on which solid hydrocarbons are placed in the perimeter of the lining and electrodes in an amount of 0.5-1, 0 kg / mg of the protected surface, after which the melting space is closed, ignite the arc and maintain it for 3–5 s. Protective material consumption specific, I od, kg / n I kg 0.9 / 0.3 0.9 / 0.4 t, 0 / 0.9 1.0 / 0.9 1.9 1.0 / 1.0 1.0 / 1.0 1.0 / 1.0 1.7 / 0.5 1.6 / 0.7 2.0 / 2.0 1.9 / 1.9 1.0 0.4 1and Known (prototype) , 9 / 0,4 , 0 / 0.9 , 0 / 1.0, 1 / 1.2, 2 / 1.3 , 6 / 0.7 , 9 / 1.9 40 58 59 60 60 43 78 72 73 72 42 73 1.2 0.5 0.5 0.5 0.5 U 0.4 0.4 0.4 0.4 1.1 0.4 15Z from the entire surface to be protected have the requirements of a depth of 0.3-0.5 mm Defects. On the lining on the electrodes are not detected Same s At the bottom, under the electrodes there are notches 15 km deep 20Z from the entire surface to be protected have trefoes with a depth of about 0.5 mm Defects on the Lining and electrodes are not detected. Same and On the bottom, under the electrodes, there are 25 km deep lines. 30Z from the entire protected surface have cracks up to 0.5 km deep. Defects on the lining and electrodes are not detected. 37 1.2