RU2048669C1 - Lining of electric arc furnace bath for smelting foundry ferrochrome - Google Patents

Abstract

FIELD: metallurgy; smelting foundry ferrochrome. SUBSTANCE: hearth units of furnace are provided with protective coating which consists of carbon-containing and current-carrying layers. Carbon-containing layer is made in form of carbon- containing energy concentrator mounted in center of hearth. Carbon-containing layer has varying section in form of bevels from base of carbon-containing energy concentrator to side walls; these bevels reduce from center to periphery. Units forming the hearth are made of magnesite. Outer surfaces of carbon- containing layer and energy concentrator are filled with mixture of crushed ferromanganese and chrome ore in ratio of 2:1. EFFECT: enhanced reliability. 3 cl, 4 dwg

Description

 The invention relates to the field of metallurgy, in particular to furnaces for the production of ferroalloys, in particular to a lining of a bath of an electric arc furnace for smelting ferrochrome.

Known lining of the furnace bath for the smelting of ferrochrome (Edneral F.P. Electrometallurgy of steel and ferroalloy. M. Metallurgy, 1977, p. 366 367). It includes two rows of magnesite bricks "on the die" and 10 11 rows "on the edge", each of which is deployed relative to the previous one by 45 90 ^about . The walls of the furnace are made of magnesite brick "on the edge."

 A significant drawback of this lining is that the magnesite brick has a high electrical resistance, which significantly increases the start-up time of the furnace after overhaul, the heating of the hearth and the conditions of normal operation of the tap hole are worsened.

Known lining the bottom of the bathtub of the furnace for smelting pig iron ferrochrome, adopted as a prototype (Lining of the bathtub of the furnace N 19 in the shop N 2 for smelting pig iron ferrochrome. TI 139-F-26-92. Chelyabinsk: CHEMK, 1992, S. 2 3). According to this prototype, the lining includes one row of magnesite brick "on the die", nine rows of magnesite brick "on the edge". Moreover, each subsequent row of bricks is located at an angle of 45 ^about the previous one. The last row of the hearth is made of magnesite brick "on the end". The lining also contains a side part made of magnesite brick.

 A significant drawback of the design of the lining of the prototype is the significant start-up time of the furnace after major repairs, poor heating of the hearth, as well as abnormal working conditions of the notch. All this is due to the high electrical resistance of the lining of the furnace bathtub, made of magnesite brick. The conditions for heating and starting up the furnace are even worse when operating on a closed furnace of high power.

 The developed lining of the furnace bath can significantly reduce its heating time after overhaul, to ensure high-quality heating of the bath and the normal operation of the tap hole.

 The essence of the developed lining is that it is made of magnesite brick. In addition to the known, the developed lining includes an energy concentrator made of a carbon-containing material in the form of a cone and mounted in the center of the furnace bath on the surface of the last row of a magnesite brick bottom mounted on the end. The developed lining includes a carbon-containing layer on top of the last row of the bottom of the bathtub of the furnace made of magnesite brick, installed "on the end". This carbon-containing layer is made in the form of a hearth mass of variable cross section and covers magnesite bricks from the base of the energy concentrator to the side of the furnace. The surfaces of the energy concentrator and the carbon-containing layer after their installation and execution are filled with a conductive layer.

 A feature of the installed energy concentrator and carbon-containing layer is that they are necessary only for the period of the start-up of the furnace after overhaul and at the first time of its operation. In the future, these additional elements of the lining are destroyed, but it is their presence that allows during the start-up of the furnace to increase the electrical conductivity of the bottom of the bathtub, to ensure the concentration of electric and thermal energy in its center, due to which the bottom warms up qualitatively, the notch functions normally, the start-up time of the furnace is significantly reduced and its output at rated performance.

In FIG. 1 is an equivalent circuit diagram of an electric arc furnace for smelting a conversion ferrochrome made taking into account the installation of an energy concentrator and the implementation of a carbon-containing layer. Here: Z _e ', Z _e '', Z _e ''' the total electrical resistance of the electrodes of phases A, B, C; Z _W ', Z _W '', Z _W ''' the total electrical resistance of the mixture in phases; Z _d ', Z _d '', Z _d ''' total electric resistance of the arc in phases; Z _p ', Z _p '', Z _p ''' phase electrical resistance of the melt; Z _k ', Z _k '', Z _k ''' the total electrical resistance of the energy concentrator in phases; Z _y ', Z _y '', Z _y ''' the total electrical resistance of the carbon-containing layer in phases.

 As can be seen from FIG. 1, in order to reduce the electrical resistance of the hearth of the furnace bath during the production of ferrochrome during the start-up after major repairs, it was proposed to introduce constant electrical resistances included in parallel with the total melt electrical resistance in the equivalent electrical equivalent circuit. The electrical resistances of the energy concentrator and the carbon-containing layer are shunting relative to the electrical resistance of the melt. Due to the presence of these resistances, in accordance with the well-known laws of electrical engineering, the electrical resistance of the melt is significantly reduced, due to which the flowing currents increase, which leads to an intensification of the heating of the hearth of the furnace bath, as well as a significant reduction in its start-up time.

 In FIG. 2 shows a developed device, a cross section; in FIG. 3 plan of the furnace with lining; in FIG. 4 basic geometric parameters of the lining.

 The developed lining includes the last row of magnesite bricks 1 installed “on the end”, the side part made of magnesite bricks 2, an energy concentrator 3, a carbon-containing layer 4, a conductive backfill 5, a letka 6.

The lining of the bath is as follows. All operations for its manufacture prior to the installation of an energy concentrator from a carbon-containing material are performed according to known technology. After installing the last row of the hearth of magnesite brick “on the end”, a cylindrical core of the energy concentrator 3 made of carbon-containing material is installed on it in the center of the hearth. Then a cone is formed around this core by the hearth. The diameter of the base of the energy concentrator, made in the form of a cone, should not exceed the difference between the diameters of the decay of the electrodes and the diameter of the electrode, i.e. d _to ≅ d _re d _e where: d _{to the} diameter of the base of the energy concentrator 3; d _{pe the} diameter of the decay of the electrodes; d _{e the} diameter of the electrode. The height of the energy concentrator 3 is 0.5 0.8 of the diameter of the electrode, i.e. h _to 0.5 0.8 d _e , where h _{to the} height of the energy concentrator.

After installing the energy concentrator 3 from its base to the side part 2 of the lining of the bottom of the furnace bath, the last row of magnesite bricks installed "on the end" is covered with a carbon-containing layer, which is made from a hearth mass. The carbon-containing layer is of variable cross section. So, the thickness of this layer at the base of energy concentrator 3 does not exceed the height of removal of the base of the notch 6 from the bottom of the furnace bath, and the height of the carbon-containing layer at the side part 2 does not exceed half the height of the removal of the base of the notch from the bottom of the furnace bath. In FIG. 4 shows some geometric parameters of the lining. Here: d _{to the} diameter of the base of the energy concentrator 3, d _{to the} diameter of the furnace bath.

 After installing the energy concentrator 3, and performing the carbon-containing layer 4, refueling of their outer surfaces with conductive material is performed. A mixture of crushed ferromanganese and chromium ore in a ratio of 2 1 is used as a conductive material, while the thickness of this mixture on the bottom of the furnace bath is at least 400 mm, and at its side part at least 300 mm.

 When starting an electric arc furnace after overhaul due to the use of an energy concentrator and a carbon-containing layer on the bottom of the furnace bath, the transient electric resistance in the "melt electrical resistance" section is significantly reduced, which leads to an increase in electric current and also the concentration of electric and thermal energies in the center of the furnace bath . Due to this, the heating time of the furnace is significantly reduced, i.e. its start-up is accelerated, high-quality heating of the hearth of the furnace occurs and the normal operation of the tap hole is ensured.

 The energy concentrator and carbon-containing layer in a month or two after the start-up of the furnace will be destroyed. However, the presence of these elements makes it possible to provide satisfactory conditions for heating and starting the furnace, which is especially important for closed electric arc furnaces of high power. In other words, the proposed lining is intended only for the start-up period of the furnace during the smelting of ferrochrome.

 The developed lining can significantly reduce the time the furnace reaches its rated output. Due to this, the output of conversion ferrochrome in the first months of operation of the furnace after major repairs is increased, the specific norms of energy consumption are reduced.

Studies have shown that the implementation of the proposed device can reduce the start-up time of the furnace after overhaul by 15 17% and also reduce the specific energy consumption during smelting of ferrochrome by at least 3%
The use of the developed lining will extend the life of the main lining made of magnesite brick.

Claims (3)

 1. LATER OF THE BATH OF THE ELECTRIC ARC FURNACE FOR Smelting the FRAME FERROCHROME, containing a metal casing, a lining of thermal insulation, brickwork, side walls and a hearth made of blocks mounted on the end, covered with a two-layer protective coating over the hearth made of a carbon-containing layer and current the fact that the carbon-containing layer is made in the form of a carbon-containing energy concentrator installed in the center of the hearth, while the carbon-containing layer from the base of the carbon-containing con entratora energy to the side walls has a variable cross-section in the form of bevels which decrease from the center towards the periphery, and the blocks that form the hearth, made of magnesite, wherein the outer surface layer and a carbonaceous energy concentrator are filled with a mixture of crushed ferromanganese ore and chromium in a ratio of 1 February.  2. The lining according to claim 1, characterized in that the energy concentrator is made in the form of a cone, while the diameter of the base does not exceed the difference between the diameters of the decay of the electrodes and the diameter of the electrode, and the height of the energy concentrator is 0.5 to 0.8 of the diameter of the electrode.  3. The lining according to claim 1, characterized in that the carbon-containing layer is made of a hearth mass, while the height of this layer at the base of the energy concentrator does not exceed the height of removal of the notch base from the bottom of the furnace bath, and the height of the carbon-containing layer at the side wall does not exceed half the height removing the base of the tap hole from the bottom of the furnace bath.

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