RU2716554C1 - Steel melting method in converter - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, particularly, to processes of steel melting in converter. Metal stock is supplied in converter in the form of liquid cast iron and scrap metal, slag-forming materials, agglomerate, melt blowing with oxygen from above through the tuyere, change of the tuyere position above the melt level in the calm state and oxygen consumption during the blowdown. Additive of agglomerate is carried out prior to beginning of melt blowing with oxygen or / and during melt blowing by oxygen till the moment of intensive decarbonisation of melt; at that, agglomerate is used additionally containing oxides of zinc and titanium.

EFFECT: invention enables to develop a steelmaking technology in a converter which enables to recycle zinc-containing wastes, reduces the cost of producing steel and increases yield of the steel.

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Description

The invention relates to metallurgy, and more particularly, to steelmaking processes in a converter.

The formation of dusts from gas purifications with a high zinc content is a serious problem in the electric steel smelting process. This dust, being a hazardous waste of the third hazard class, cannot be used in the blast furnace process as a substitute for iron-containing materials. Disposal of this kind of waste consists in placement at specialized storage landfills, less often in quite costly processing in various ways, in order to extract iron and zinc oxides.

Closest to the proposed one is a method of steelmaking in a converter, which includes feeding a metal charge in the form of molten iron and scrap metal, slag-forming materials, blowing the melt with oxygen from above through an immersion lance, changing the position of the lance above the melt level in a calm state and oxygen consumption. The time of lowering the tuyeres from the initial position at the beginning of purging to the working position at the beginning of the decarburization period of the melt is set according to the given dependence. In the converter serves highly basic agglomerate with a basicity of mainly 2 to 5, which contains, by weight. %: SiO ₂ 3-6, CaO 10-30, MgO 2.0-6.5, Al ₂ O ₃ 0.5-1.5, MnO 1-4, FeO 12-18, Fe ₂ O ₃ 45- 55. The amount of scrap metal is set equal to 0.14-0.30 and highly basic sinter 0.007-0.07 of the amount of molten iron. The amount of highly basic agglomerate is determined depending on P1 — the phosphorus content in the molten iron and its P2 content in the metal on the converter felling, according to the dependence C = KZ ⋅ (P1 - P2) [Patent RU 2159289, IPC С21С 5/28, 2000].

The disadvantage of this method is that the heat balance of the smelting is not taken into account, which in the case of a high consumption of agglomerate leads to a shift in the heat balance from the side of subcooling, and, as a result, a decrease in the yield. The use of expensive initial raw materials for the production of sinter, with subsequent incomplete reduction of iron oxides of the sinter in the converter process, makes it inappropriate to use such material in the converter regarding its use in a blast furnace process with the complete extraction of iron.

The technical result of the invention is the development of steel smelting technology in a converter, which allows to utilize zinc-containing waste, reduce the cost of steel production and increase the yield of steel.

The specified technical result is achieved by the fact that in the method of steel smelting in a converter, which includes feeding a metal charge in the form of molten iron and scrap metal, slag-forming materials, agglomerate, blowing the melt with oxygen from above through a tuyere, changing along the course of blowing the position of the tuyere above the melt level in a steady state and oxygen consumption, according to the invention, the agglomerate additive is carried out before the melt is purged with oxygen and / or during the melt purge with oxygen until the end of the intensive about decarburization of the melt, while using agglomerate, additionally containing oxides of zinc and titanium with the following content of oxides in it, wt. %:

SiO ₂ - 3.0-12.0;

CaO - 10.0-35.0;

MgO - 0.5-10.0;

Al ₂ O ₃ - 0.5-10.0;

MnO - not more than 4.0;

FeO - 2.0-20.0;

Fe ₂ O ₃ - 45.0-70.0;

ZnO - not more than 14.0;

TiO ₂ - not more than 2.0.

Agglomerate, additionally contains oxides of Na ₂ O and Ka ₂ O, with the following content of wt. %:

Na ₂ O - not more than 2.0;

Ka ₂ O - not more than 1.0.

Before the melt is purged with oxygen, calcium and magnesium-containing slag-forming materials are added in the amount of 20-30 kg / t of steel, and during the melt purging with oxygen, calcium and magnesium-containing slag-forming materials are added in the amount of 30-40 kg / t of steel.

Along or after the melt is purged with oxygen, an aluminum-containing material is added in an amount of 0.2-5.0 kg / t of steel containing 3.0-20.0% aluminum metal and 35.0-65.0% aluminum oxide.

The essence of the proposed method is as follows.

It is known that agglomerate is made from iron ore concentrates, fluxing additives, solid fuels and metallurgical waste, with the exception of waste with a high content of zinc oxides (for example: zinc-containing dust, ZnO more than 2%). Zinc-containing wastes have a negative impact on the lining of the blast furnace, reducing its company. Therefore, the use of an agglomerate containing zinc oxides in the blast furnace process is unacceptable.

Exceeding the content of zinc oxide in dust by more than 2% leads to its accumulation in the pores of the blast furnace lining in metallic form, while the zinc is gradually oxidized to oxide, volume expansion occurs in the occupied volume, cracking and accelerated failure of the lining.

The main source of zinc-containing dust is mainly electric steelmaking. The content of zinc oxides in this dust is 10.0-30.0%. Due to the lack of the possibility of recycling this waste in blast furnace production, it is accumulated at the storage sites, which negatively affects the environment and constantly requires the commissioning of new storage sites. Dust processing by known pyrometallurgical and hydrometallurgical methods requires the creation of separate specialized industries, with high investment costs and with problematic payback of using iron-containing processed products in production.

The use of the inventive method of the agglomerate containing zinc oxides in the converter allows, on the one hand, to obtain relatively cheap agglomerate from production waste, while in the steelmaking process it is possible to quickly regulate the heat balance of the smelting, to increase the yield due to the partial reduction of iron oxides (the degree of reduction is 20.0-30.0%) contained in it, and also ensures the disposal of illiquid waste (zinc-containing dust).

The SiO ₂ content _of 3.0% is actually the minimum possible content based on the composition of any combination of agglomerate charge components. The excess of SiO ₂ more than 12.0% is not desirable due to the increased consumption of lime to maintain the basicity of the slag.

A CaO content of less than 10.0% in the agglomerate will require additional consumption of lime for smelting. Excess CaO of more than 35.0% leads to a significant increase in costs.

The MgO content of 0.5% is actually the minimum possible content based on the composition of any combination of components of the sintering mixture. An excess of MgO of more than 10.0% is not desirable due to an increase in the required concentration of magnesium in steelmaking slag and, as a consequence, a decrease in its liquid mobility, which negatively affects the metal dephosphorization process.

The content of Al ₂ O ₃ is actually the minimum possible content based on the composition of any combinations of the components of the charge of the sinter. Exceeding Al ₂ O ₃ above 10.0% negatively affects the durability of the converter lining, due to the increased slag mobility.

The MnO content of more than 4.0% in the agglomerate reduces the proportion of the main components of FeO and Fe ₂ O ₃ , which leads to a decrease in the overall efficiency of using the agglomerate in the smelting process.

The content of TiO ₂ more than 2.0% in the agglomerate reduces the proportion of the main components of FeO and Fe ₂ O ₃ , which leads to a decrease in the overall efficiency of using the agglomerate in the smelting process.

The ZnO content in the agglomerate of more than 14.0% corresponds to the fact that the ZnO content in the zinc-containing dust used for the production of agglomerate exceeds 30.0-40.0%, which allows it to be realized as a product, therefore, its use in the agglomerate becomes impractical.

The content of FeO 2.0-20.0% is actually the minimum possible content based on the composition of any combination of components of the sintering mixture.

A lower content of Fe ₂ O ₃ than 45.0% reduces the technical and economic efficiency of using the agglomerate as a cooler and source of iron instead of scrap metal. Obtaining the content of Fe ₂ O ₃ more than 70.0% is not economically feasible.

The content of Na ₂ O up to 2.0% and Ka ₂ O up to 1.0% - the maximum allowable content of these components in the sinter mixture, the excess of these margins negatively affects the condition of the lining of the steelmaking unit (leads to a decrease in durability and, accordingly, the unit company) . The source of Na ₂ O and Ka ₂ O in the sinter charge is zinc-containing steel smelting dust, therefore, these components are a limiting factor in the use of dust in the sinter charge.

The addition of calcium and magnesium-containing slag-forming materials in an amount of 20-30 kg / t of steel before the melt is blown is carried out with the aim of quickly slagging and a more complete process of liquid metal dephosphorization.

Along or after the melt is purged with oxygen, an aluminum-containing material (concentrate) is added in an amount of 0.2-5.0 kg / t of steel. An aluminum-containing material is used to precipitate a gas-slag emulsion (slag) during the smelting process in order to prevent slag spillage through the neck of the steelmaking unit. The consumption of aluminum-containing material is determined by the volume of slag and its oxidation. The use of aluminum for slag deposition is not economically feasible.

An example implementation of the method.

The proposed method of using zinc-containing agglomerate was implemented in a full-cycle steel production plant. Agglomerate was produced using zinc-containing dust from steelmaking in an amount of up to 30% of the sinter composition.

The use of zinc-containing agglomerate was carried out in the process of converter smelting and was carried out depending on the presence of excess heat in the heat balance of the smelting. Zinc-containing agglomerate was discharged along the bulk material supply path before the start of purging and / or from 5 minutes of purging of the melt until the end of intensive decarburization (14-16 minutes of purging). The end of intensive decarburization was determined by reducing the content of carbon monoxide in the exhaust gases and increasing the oxygen content in the exhaust gases. Sinter consumption varied from 1 to 5 tons for smelting. Calcium and magnesium-containing materials were added, as well as aluminum-containing material in the claimed ranges.

About 10,000 tons of zinc-containing agglomerate were used, which made it possible to utilize about 3,000 tons of zinc-containing dust from steelmaking, as well as replacing scrap metal with reduced iron from sinter oxides in an amount of 800 tons. A part of the lime that was previously used as a converter smelting cooler was also replaced. Steel yield increased by an average of 0.15%.

Thus, the use of the inventive method of steelmaking in the converter allowed to utilize zinc-containing waste, reduce the cost of steel production and increase the yield of steel.

Claims (6)

1. The method of steel smelting in the converter, including feeding the metal charge in the form of molten iron and scrap metal, slag-forming materials and sinter, blowing the melt with oxygen from above through the lance, changing along the course of blowing the position of the lance above the melt level in a quiet state and oxygen consumption, characterized in that the sinter additive is carried out before the melt is purged with oxygen and / or during the melt purge with oxygen until the end of intensive decarburization of the melt, using agl omerate containing oxides of zinc and titanium, with the following content of oxides in it, wt. %: SiO ₂ 3.0-12.0 CaO 10.0-35.0 MgO 0.5-10.0 Al ₂ O ₃ 0.5-10.0 MnO no more than 4.0 FeO 2.0-20.0 Fe ₂ O ₃ 5.0-70.0 Zno no more than 14,0 TiO ₂ no more than 2.0 2. The method according to p. 1, characterized in that the agglomerate further comprises oxides of Na ₂ O and Ka ₂ O, with the following content, wt. %: Na ₂ O no more than 2.0 Ka ₂ O no more than 1,0 3. The method according to p. 1, characterized in that before the melt is purged with oxygen, calcium and magnesium-containing slag-forming materials are added in an amount of 20-30 kg / t of steel, and during the melt purging with oxygen, calcium and magnesium-containing slag-forming materials are added to the amount of 30-40 kg / t of steel. 4. The method according to p. 1, characterized in that during or after the purge of the melt with oxygen, an aluminum-containing material is added in an amount of 0.2-5.0 kg / t of steel containing 3.0-20.0% metal aluminum and 35.0-65.0% alumina.