SU798183A1 - Method of protecting lining of ore-thermal furnace - Google Patents

Description

(54) METHOD OF PROTECTION OF LINEING ORE-THERMAL (

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The invention relates to ferrous metallurgy, in particular, to smelting reduction in ore-smelting furnaces, in particular to: methods for lining a bath lining of a ore-smelting furnace during smelting of bauxite ores.

When smelting bauxite ore to produce electrocorundum and ferroalloy, the lining is destroyed by the penetration of ferroalloy into the lower layers of the refractory masonry.

There is a known method of protecting refractories in metallurgical aggregates by introducing cooling gaseous agents into the melt in the vicinity of places with local destruction of l3

However, with respect to the smelting of bauxite ores, the method has the following disadvantages:

with the introduction of cooling agents, the temperature of the slag melt decreases, which makes it difficult to release it from the furnace,

cooling agents introduced into the slag modify its chemical composition and saturate it with carbon and azo. Tom/

metal melt penetrates into the pores of the lining, and with cyclic OVEN

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temperature change occurs a change in the volume of the metal, and hence the increase in cracks. When the melt is reheated, the metal melts again and penetrates into the increasing cracks. As a result of this effect, the lining is destroyed and the metal penetrates to a greater depth;

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high consumption of gaseous agents, due to the need to cool the melt to a solid state.

The purpose of the invention is to reduce the depth of penetration of the liquid metal into the lining.

The goal is achieved by the fact that oxides of nitro-forming elements are introduced into the oxide, which provide

0 production of nitro-forming elements in the amount of 3.5-6% by weight of the melted mixture with metal overheating by 300-500 above its melting point, and pbd nitrogen by pressure

5 is fed into the lining of the furnace from the outside in the period of 0.5-0.8 duration of melting in the amount of 15200 for each percent of the nitro-forming element.

0 The method is carried out as follows. Agglomerated bauxite and anthracite are loaded into the ore-sintering furnace. The mixture prepared from these components contains 59-60%,. The melt of corundum and the metal melt of iron saturated with carbon are obtained by melting the charge in the furnace bath. For this purpose, a carbonaceous reducing agent is introduced into the composition, with an excess of 8–15%, exceeding the stomatometric ratio in the reduction of iron oxides by carbon, nitro-forming elements are introduced into the melt as oxides. Then the metal melt is overheated by 300-500 ° and the nitride-forming elements (Ti, A f) are reduced in the amount of 3.5-6% of the weight of the melted mixture. When the melt is reduced, 2–4% aluminum is obtained and. In view of the difference in specific gravity, the oxide melt of electrocorundum is above the molten metal. The temperature of the oxide melt reaches 2., which leads to overheating of the metal. Metalshl, in contact with magnesite masonry, penetrates into the cracks of the lining and fills them. In the period of 0.5-0.8 duration of melting in the lining serves nitrogen. The supply of gas under pressure of 0.5-4.0 atm is carried out through the main collector located on the furnace shell, through 8-10 nozzles, embedded in the masonry. 1/3 of the wall thickness. Nitrogen consumption is 157200 m3 / hour for each percent of the nitride-forming element. The accepted range of pressure and flow rates of nitrogen gas is due to the quality of the masonry of the furnace bath. When laying a bath with a calibrated brick, the pores in the furnace lining are minimal, on the order of 0.1-0.2 mm. For this quality of masonry, elevated pressures of nitrogen gas and minimum quantities are necessary, since the volume of molten metal penetrating into the masonry is negligible. When performing masonry with an unbroken brick, and when using masonry that was used in operation, the size of the pores and cracks in the masonry is 1-3 mm. In this case, an increased consumption of nitrogen gas (up to 200) is necessary, since the volume of the metal penetrating into the pores and cracks increases. During smelting in the period of 0.5-0.8 of the duration of smelting of the electrolytic corundum, the maximum amount of metal accumulates in the furnace, which at this time overheats to maximum temperatures. (1700ISOO c), since the electrocorundum melt has minimal electrical conductivity time, the maximum heat release in the molten metal layer. Gas is advisable to apply during this period of maximum heating of the lining. Passage through the cracks and pores of the magnesite masonry, the gas approaches the permeable lining zone. Nitrogen, reacting with nitride-forming elements AE and TI, forms refractory nitrides AEN, TiN with a melting point of 2200-3000 s, which form a solid phase and plug cracks. Penetration of molten metal into the masonry is prekrzhtsyaetsya. If the metal is overheated lower than 300, the melting temperature, the reduced nitride-forming elements are oxidized and transferred into the oxide melt, which reduces the effect of protecting the furnace lining. When the metal is overheated by more than 500 above the melting temperature, the lining is intensively destroyed, forming significant flaws. When reducing the amount of nitride-forming, less than 3.5% by weight of the melted mixture with nitride, an insufficient amount is formed, and the lining is not protected from further leakage of the metal. If the number of nitro-forming elements is more than 6.0%, then for their restoration an increased power consumption is required, which is accompanied by the destruction of the skull on the walls of the furnace. Example. In an electric furnace with a capacity of 10,500 kva, 35 tons of bauxite agglomerate containing 61% AE20 ,, 0.35% CaO, 0.2% MpO, 18%, 10% FeO, 0.1% HgO, 6% SlOg C — 0.5 were loaded % followed by sub-melting TIO at 3.5, 4.7 and 6.0% / and carried out the reduction of oxides with anthracite carbon. Received 22 tons. ; melt electrocorundum and V t ferroalloy. Release of ferroalloy produced through three releases of corundum. In the period of 0.5-0.8 of the duration of the smelting before releasing the ferroalloy, nitrogen gas was fed into the lining. The nitrogen supply was carried out through an annular manifold located on the furnace casing at a level of 1.5 m from the bottom sheet; on 10 branch pipes with a diameter of 16 mm located radially and recessed into the lining of 300 mm. Gas consumption 15-200. on the percentage of nitrile element. The passage of gas into the metal-corundum contact zone was carried out along the pores and cracks of the lining. The results of applying the proposed method are given in the table from which it follows that the service life

The magnesite brickwork of the furnace is increased to 4.2-4.5 years. Emergency breakthroughs melt is not bto.

When disassembling the bath furnace on; the feed repair turned out that the metal layer did not reach the external results of applying the proposed method of protecting the lining of the ore-smelting furnace

lining surface by 400 mm, i.e. to the depth of sealing of the supply pipes. In normal operation, the life of the lining is shortened due to the destruction of the brickwork by the overheated metal melt.

Claims (1)

1. French Patent 2262697, cl. C 21 C 5/48, 1974.