RU2359041C1 - Method of blast-furnace melting - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to ferrous metallurgy field, particularly to methods of blast-furnace melting implementation. Method includes introduction into stock in the capacity of flux and carbon-bearing material of crushed electrodes of fraction 30-120 mm with carbon content - 50-70%, content of fluorides of sodium, aluminium, calcium and magnesium - 25-35%, content of admixtures - 5-15%, ratio of elements in composition of beneficial components without admixtures: sodium, aluminium, calcium, magnesium - (5-15):(1-4):(5-20):(0.1-1.0), after-reactionary strength (CSR) - 60-70%, reactivity of carbon (CRI) - 0% at temperature up to 950°C, 40-50% at temperature 1100°C. Additionally part of carbon-bearing materials is introduced in the form of schungite, and part of iron-ore and carbon-bearing materials - in the for of iron-carbon-bering briquetts with ratio CaO:SiO₂ - 0.4:1.4.

EFFECT: productivity improvement of blast furnace and reduction of coke consumption.

Description

The invention relates to the field of ferrous metallurgy, and in particular to methods of blast furnace smelting.

A known method of blast-furnace smelting, selected as a prototype, is known [1], which includes introducing pellets, sinter, metal additives and fluxes into the mixture, in which specially prepared metal flux with a basicity of 1.1-1.6 in pieces of 10- particle size is introduced into the mixture as metal additives and flux 60 mm and load it into the furnace in a mixture with unfluxed pellets with a basicity of 0.05-0.5 in a ratio of 1: 2 to 1:50.

Significant disadvantages of this method of blast furnace smelting are:

- the high cost of the resulting cast iron in connection with the additional costs of special preparation of metal flux;

- high consumption of carbon-containing coke material;

- reduced productivity of the blast furnace.

There is also a known method of blast furnace smelting, which includes loading iron ore materials, a slag-forming component and solid fuel into a blast furnace, in which calcium ferrite-calcium flux is used as a slag-forming component, in which the ratio CaO / Fe ₂ O ₃ is 0.15-0.55 with a SiO ₂ content _of 1-7% and Fe _total more than 50% [2].

Significant disadvantages of this method of blast furnace smelting are:

- the formation of insufficiently fluid slag, which leads to an insufficient degree of desulfurization of pig iron and a decrease in its quality;

- increased consumption of coke due to the additional cost of heat for the melting of ferrite-calcium flux.

There is also a known method of blast-furnace smelting, which includes loading iron ore materials, coke, blowing air and fuel additives into air lances, loading a solid carbon-containing additive into a given furnace top, in which lump shungite is used as a solid carbon-containing additive, mixing it when loaded into a furnace with coke and loading into the annular zone of the top, located within the radius of 0.1 and 0.95 of the radius of the top, and the basicity of iron materials modulo (CaO + MgO) / (SiO ₂ + Al ₂ About ₃ ) when loading shung ita is increased by 0.001-0.004 for each kg of schungite loaded into the furnace per 1 ton of cast iron [3].

Significant disadvantages of this method of blast furnace smelting are:

- reduced productivity of the blast furnace due to a decrease in the fluid mobility of the blast furnace slag;

- high consumption of coke associated with the maintenance of increased basicity of slag in a blast furnace.

The desired technical results of the invention are:

- improving the quality of cast iron;

- reduction in coke consumption.

For this purpose, a blast-furnace smelting method is proposed, which includes introducing iron ore materials (pellets, sinter, metal additives), carbon-containing materials and fluxes into the charge, in which the electrode fraction is introduced into the charge as a flux and carbon-containing material

30-120 mm with a carbon content of 50-70%, a content of sodium, aluminum, calcium and magnesium fluorides - 25-35%, an impurity content (oxides of calcium, silicon, aluminum, magnesium, iron) - 5-15%, the ratio of elements as a part of useful components (without impurities): sodium: aluminum: calcium: magnesium -

(5-15) :( 1-4) :( 5-20) :( 0.1-1.0), post-reaction strength (CSR) - 60-70%, carbon reactivity (CRT) - 0% at temperature up to 950 ° С, 40-50% at a temperature of 1100 ° С; instead, part of the carbon-containing materials use shungite, and as iron ore material and carbon-containing materials, iron-carbon briquettes with a CaO: SiO ₂ ratio of 0.4: 1.4 are used in the following ratio of materials in the charge, wt.%:

Agglomerate 40-74 Pellets 5-25 Ore no more than 3,5 Metal Additives no more than 10 Iron-carbon briquettes 0.1-15 Coke 12-26 Coal 1-6 Shungite 0.1-5 Electrode battle 0.1-5

The claimed limits are selected experimentally.

The amount of sinter is taken based on the fact that when loading sinter less than 40% of the total charge charge, it is impossible to maintain an even course of the blast furnace, and when loading sinter more than 74%, cooling of the blast furnace is observed due to a decrease in coke consumption.

The number of pellets is based on the fact that when loading pellets of less than 5%, it is not possible to achieve the required productivity of the blast furnace due to the total iron content in this charge, and when loading pellets of more than 25%, a noticeable increase in the titanium content in cast iron occurs, which does not allow to obtain rail steel with a low content of titanium oxide inclusions.

Ore is introduced into the blast furnace to adjust the slag regime of the furnace, but when it is loaded more than 3.5%, the productivity of the blast furnace decreases due to a decrease in the total iron content and a sharp decrease in the basicity of slag.

Metal additives, which are metal production wastes, are introduced into the composition of the mixture to maintain the total iron content in the mixture, however, when loading metal additives more than 10%, the cost of cast iron is increased.

The amount of coke is taken based on the fact that when the coke is loaded less than 12%, the sulfur content in cast iron increases due to reduced heating, and when the coke is loaded more than 26%, the blast furnace overheats, leading to unproductive coke overuse and loss of blast furnace productivity.

The amount of coal is taken based on the fact that when loading coal less than 1%, the cost of cast iron increases due to the increased consumption of other carbon-containing materials, and when loading coal more than 6% there are disturbances in the course of the blast furnace due to its low strength, leading to a loss in furnace productivity.

The loading of schungite in the furnace in an amount of 0.1-5% leads to the most optimal mode of using shungite carbon: on the one hand, as a substitute for coke, on the other hand, increasing the service life of the blast furnace due to the formation of hard-to-recover silicon carbide compounds deposited on the walls of the blast furnace furnace and leading to the formation of a skull preventing the erosion of the refractory masonry, and when loading schungite less than 0.1% there is an increase in the cost of cast iron due to the increased consumption of other carbon-containing mate ialov, and when loading more than 5% blast furnace disorders arise stroke and consequently decrease iron quality.

Iron-carbon briquettes, which are pressed cement-based products from iron-containing and carbon-containing production wastes, are introduced into the blast furnace mixture to reduce coke consumption and reduce the cost of cast iron, and when loading briquettes less than 0.1% it is not possible to obtain the required reduction in coke consumption, and when loading briquettes more than 5% there is a sharp decrease in the productivity of the blast furnace due to insufficient iron content in the briquette. The CaO: SiO ₂ ratio of 0.4: 1.4 is based on the fact that, with a CaO: SiO ₂ ratio _of less than 0.4, a sharp decrease in the quality of cast iron occurs due to a general decrease in the basicity of the blast furnace charge, and with a CaO: SiO ₂ ratio _of more than 1 , 4, the productivity of the blast furnace is sharply reduced due to the opposite effect - the “garbage” of the hearth.

The electrode battle, which is crushed and sorted pieces of high-strength carbon material (carbon base), impregnated with fluoride salts of the electrolyte of aluminum electrolysis cells and treated with lime suspension, is introduced into the composition of the charge to ensure normal slag mode of blast furnace smelting and as a substitute for coke, and with a decrease in the consumption of electrode battle less than 0.1% in the composition of the charge decreases the fluidity of the blast furnace slag and decreases the productivity of the furnace, and increase its consumption e is 5%, the charge leads to an increased sodium arrival of the blast furnace, which causes destruction of the refractory lining and increased coke consumption.

The specified ratio of the components determines the optimal heat balance, self-supply of heat to the melting processes of the fluoride compounds of sodium, aluminum, calcium and magnesium contained in the electrode battle, maximum fluidity and refining ability of the slag with a sufficiently high additional effect to reduce coke consumption. The specified ratio of elements in the composition of the useful components of the battle (without impurities) ensures maximum activity of the physical and chemical processes of interaction of the electrode battle with the components of the blast furnace charge and the greatest refining ability of slags.

Reducing the minimum size of pieces of electrode battle less than 30 mm can lead to a violation of the gas dynamics of the process due to an increase in the pressure difference between the blast pressures in the column of charge materials. Increasing the maximum size of pieces over 120 mm leads to the fact that he does not have time to completely react before entering the blast furnace in the forge. This leads to clutter of the hearth and, as a result, to a decrease in furnace productivity.

When the carbon content in the electrode battle is below 50%, a sufficient heat supply to the near-tuyere zone of the blast furnace is not ensured, which reduces the effect of ensuring the fluidity of the slag, the desulphurization of cast iron and the reduction of coke consumption. When the carbon content is more than 70%, heat losses with gaseous products of its oxidation increase, the intensity of gas evolution in the tuyere zone increases, the gas-dynamic melting mode is violated, and the battle activity decreases due to a decrease in the content of low-melting fluorine compounds in it.

When the content of sodium, aluminum, calcium and magnesium fluorides is less than 25%, the electrode battle does not provide sufficient fluidity and refining ability of blast furnace slag. When the content of sodium, aluminum, calcium and magnesium fluorides is more than 35%, the activity of the electrode battle decreases due to a decrease in the carbon content and insufficient heat supply to the process of melting fluoride compounds, while the supply of sodium to the blast furnace increases significantly, which leads to a decrease in the lining resistance and an increase in coke consumption.

The content of impurities (oxides of calcium, silicon, aluminum, magnesium, iron) less than 5% leads to a rise in the cost of electrode battle due to the need for its additional enrichment. When the content of impurities exceeds 15%, the activity of the battle decreases and the assimilating and refining ability of metallurgical slags deteriorates.

Exit of the ratio of elements in the composition of the useful components of the electrode battle (without impurities) sodium: aluminum: calcium: magnesium beyond these limits leads to an increase in the melting temperature of the battle and a deterioration in its assimilating and refining ability.

A decrease in post-reaction strength of less than 60% leads to the destruction of pieces of electrode battle to the tuyere zone and a violation of the gas permeability of the charge column. An increase in the postreaction strength of more than 70% leads to an increase in the time it takes to realize its function as an additional fuel due to the high duration of burning of the carbon part of large pieces that were not destroyed in the tuyere zone.

Electrode battle should be characterized by zero reactivity of carbon at temperatures up to 950 ° C, which ensures the safety of the pieces until reaching the near-tuber zone and the beginning of the burning of the carbon base in the lower part of the blast furnace. A decrease in the reactivity of carbon in an electrode battle at a temperature of 1100 ° C below 40% causes insufficient heat input from its oxidation in the near-tuber zone, which leads to an increase in coke consumption. An increase in the reactivity of carbon of the electrode battle at a temperature of 1100 ° C over 50% leads to intense carbon burnout to the tuyere zone, melting of the contained fluorides and violation of the gas-dynamic melting mode.

The inventive method of blast furnace smelting was used on blast furnaces with a volume of 1310 m ³ and 1719 m ³ for melting refractory titanium-containing pellets, the content of which in the metallized blast furnace charge was 20%. Electrode battle made of crushed and sorted spent carbon lining of electrolytic cells with the content of: sodium fluoride NaF - 19.0%; aluminum fluoride AlF ₃ - 9.1%; CaF ₂ - 2.5%; MgF ₂ - 1.5%; CaO - 10%, C - 55%, impurities - 2.9%, including Fe ₂ O ₃ - 1.1%; Al ₂ O ₃ - 1.6%; SiO ₂ - 0.1%, S - 0.1%. The ratio of elements in the composition of useful components (without impurities): sodium: aluminum: calcium: magnesium - 10.5: 2.9: 8.4: 0.6. The size of the electrode battle is 30-120 mm. The battle consumption amounted to 5 kg / t of molten iron. This material was loaded instead of the iron ore part of the charge and coke. Iron-carbon briquettes with a content of: Fe 35-60%; With 1-20% and a CaO: SiO ₂ ratio of 0.4: 1.4, and schungite were loaded into a blast furnace in the same way.

Maintaining blast furnace smelting by the present method allowed to increase the productivity of the blast furnace by 0.8% due to improved fluid mobility of blast furnace slag, as well as to reduce the consumption of coke by 3.2 kg / t of cast iron.

Information sources

1. RF patent No. 94016296, C21B 5/00.

2. RF patent No. 2087538, C21B 5/00.

3. RF patent No. 2186854, C21B 5/00.

Claims (1)

A blast-furnace melting method, including introducing iron ore materials into the charge in the form of ore, pellets, sinter, metal additives, carbon-containing materials and fluxes, characterized in that, as a flux and carbon-containing material, an electrode battle of a fraction of 30-120 mm with a carbon content is introduced into the charge - 50-70%, the content of sodium, aluminum, calcium and magnesium fluorides - 25-35%, the content of impurities in the form of oxides of calcium, silicon, aluminum, magnesium, iron - 5-15%, the ratio of elements in the composition of useful components without impurities: sodium , alu minium, calcium, magnesium - (5-15) :( 1-4) :( 5-20) :( 0.1-1.0), post-reaction strength (CSR) - 60-70%, carbon reactivity (CRI ) - 0% at a temperature of up to 950 ° C, 40-50% at a temperature of 1100 ° C, while part of the carbon-containing materials are introduced in the form of coal, coke and shungite, part of the iron ore material and carbon-containing materials are in the form of iron-carbon briquettes with the CaO ratio: SiO ₂ - 0.4: 1.4 in the following ratio of materials in the mixture, wt.%:
agglomerate 40-74 pellets 5-25 ore no more than 3,5 metal additives no more than 10 carbon-containing briquettes 0.1-15 coke 12-26 coal 1-6 shungite 0.1-5 electrode battle 0.1-5