RU2342439C1 - Method of blast-furnace melting - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention concerns ferrous metallurgy. Particularly it concerns technique of blast-furnace melting. Method includes introduction into furnace charge pellet, agglomerate, coke, metallic additions and flux, electro steel-smelting slag of oxidising period of fraction 10-80 mm with content 25-44% FeO, 5-23% of buckshot and basicity 1.8-3.6 at following ration of materials, wt %: agglomerate 40-74; pellet 5-25; ore not more than 3.5; metallic additions not more than 10; coke 15-26; coal 1-6; electro steel-smelting slag of oxidising period 0.1-18, at that ratio CaO/SiO₂ of furnace charge is kept up 0.80-1.10.

EFFECT: reduction of cast iron cost price, improving of blast furnace productivity, refining of melted cast iron.

Description

The invention relates to ferrous metallurgy, and in particular to a method of blast-furnace smelting using electric furnace steelmaking slag of the oxidizing period.

Known charge for a blast furnace, consisting of pellets with a basicity of 0.2-0.9 and fluxed sinter with a basicity of 2.0-3.5, in which, in order to ensure smooth flow of slag formation along the height of the furnace, an additional fluxed sinter with basicity 0.7-1.1 in the amount of 10-40% of the weight of the iron ore part of the charge [1].

Significant disadvantages of this mixture for blast furnaces are:

- additional costs associated with the production of damper agglomerate and its high cost;

- reduced productivity of blast furnaces due to the use of a significant amount of fluxed agglomerate in the charge, leading to an increase in the slag ratio;

- high consumption of coke for recovery due to the lack of cheap carbon-containing substitutes for coke.

There is also a known method of blast-furnace smelting, including the introduction of pellets, sinter, metal additives and fluxes into the charge, in which specially prepared metal flux with a basicity of 1.1-1.6 in pieces of 10-60 mm in size is introduced into the mixture as metal additives and flux and loaded into the furnace is mixed with unfluxed pellets with a basicity of 0.05-0.5 in a ratio of 1: 2 to 1:50 [2].

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.

There is also a known method of blast-furnace smelting, which includes loading iron ore materials, coke and metal additives into the furnace with a fraction of 10-120 mm, in which the magnetic part of steelmaking slag with a basicity of 0.9-1.4 with a fraction of 10-40 mm more than 80% is used as metal additive. , while the loading of metal additives is carried out in the Central zone of the furnace with a flow rate of 11-80 kg / t of pig iron [3].

Significant disadvantages of this method of blast furnace smelting are:

- additional costs for the production of a product of processing metallurgical slag due to the need to isolate its magnetic component and additional sorting;

- decrease in the productivity of the blast furnace due to disturbances in the course of the furnace occurring after a certain period of time in connection with a short-term decrease in coke consumption when loading material into the central zone of the blast furnace and the further development of the peripheral gas flow.

Also known is selected as a prototype [4] the method of blast furnace smelting, including the loading of iron ore materials (sinter, pellets, ore, metal additives), coke, fluxes, their supply to the blast furnace through the top, in which part of the metal additives are loaded in the form of a mixture of metal concentrate obtained by enrichment methods from metallurgical waste products with a fraction of 10-50 mm and 50-250 mm in a ratio of 1: (0.2-5.0), respectively, in an amount of (10-70)% of the total weight of metal additives.

Significant disadvantages of this method of blast furnace smelting are:

- increased consumption of coke due to the uneven distribution of pieces of the fraction of more than 100 mm along the radius of the top of the blast furnace;

- irrational use of metal concentrate with a high iron content in connection with the possibility of using this type of product in steelmaking with the exception of blast furnace redistribution.

The desired technical results of the invention are:

- reduction in the cost of cast iron;

- increase the productivity of the blast furnace;

- improving the quality of cast iron.

For this purpose, a blast furnace smelting method is proposed, which includes loading into the furnace a batch containing pellets, sinter, coke, metal additives, in which ore, coal and electric furnace smelting slag of an oxidizing period of a fraction of 10-80 mm with a content of 25-44% FeO are added to the batch; 5-23% of the kings of iron and a basicity of 1.8-3.6 in the following ratio of materials, wt.%:

Agglomerate 40-74 Pellets 5-25 Ore no more than 3,5 Metal Additives no more than 10 Coke 15-26 Coal 1-6 Electric Steel Slag oxidative period 0,1-18

while the ratio of CaO / SiO ₂ charge support 0.80-1.10.

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 amount of charge loaded, it is impossible to maintain an even course of the blast furnace, and when loading sinter more than 74% it will cause cooling of the blast furnace 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 blast furnace productivity due to the increased iron content in this material, and when loading pellets of more than 25%, there is a sharp deterioration in the quality of cast iron, which is not further redistributed allows to obtain rail steel with a low concentration of titanium-containing 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 waste products, are introduced into the composition of the charge to maintain the total iron content in the charge, but when loading metal additives of more than 10%, there is a need for additional heat costs, leading to a decrease in furnace productivity.

The amount of coke is taken based on the fact that when the coke is loaded less than 15%, the blast furnace goes cold, and when the coke is loaded more than 26%, the sulfur content in cast iron increases, overheating and loss of productivity of the blast furnace.

The amount of coal is taken on the assumption that when loading coal less than 1%, the cost of cast iron increases, and when loading coal more than 6%, blast furnace disruptions occur due to its low strength, leading to a loss in furnace productivity.

The amount of electric furnace smelting slag of the oxidizing period is based on the fact that when loading the electric furnace smelting slag of the oxidizing period of less than 0.1%, it is not possible to achieve the desired effect of reducing the cost of smelted pig iron and increasing the productivity of the blast furnace due to the insufficient amount of this material, and when loading the electric furnace smelting slag of the oxidative period more 18% there is an instability of the blast furnace and a decrease in its productivity.

The content of the fraction of the electric furnace smelting slag of the oxidizing period of less than 10 mm leads to an increase in the amount of dust removal, a decrease in the gas permeability of the charge column, which causes a loss in the productivity of the blast furnace, and when the fraction increases more than 80 mm, situations arise in the clogging of the funnels of the furnace loading systems, leading to emergency situations.

When the FeO content in the slag is less than 25%, the degree of direct reduction of iron decreases and thereby the “garbage” of the hearth occurs, and with an increase of more than 44% there is a cooling in the furnace hearth and emergency situations occur.

The content of iron kings is taken from the fact that when the content is less than 5%, the productivity of the blast furnace decreases, and with an increase in their content of more than 23%, the cost of cast iron increases, due to the additional costs of their extraction.

The basicity was adopted on the assumption that with a decrease in basicity of less than 1.8, there is a decrease in the quality of cast iron, and with an increase of more than 3.6, a decrease in the productivity of the blast furnace due to the need for periodic “washing” of the furnace.

The inventive method of blast furnace smelting was implemented on a blast furnace with a useful volume of 1719 m ³ when blowing in the amount of 3000 m ³ / h with a temperature of 1080 ° C, natural gas and oxygen. In the experiments used charge materials in the range specified in the claims while maintaining the ratio of CaO / SiO ₂ mixture of 0.80-1.10 of the following chemical composition:

Agglomerate: 51-59% Fe _total ; 7-12% CaO; 1.5-4.5% MgO; 6.5-10.5% SiO ₂ ; 1.75-2.75% Al ₂ O ₃ ; 0.01-0.02% S.

Pellets: 57-67% Fe _total ; 0.8-2.6% CaO; 3.0-6.0% SiO ₂ ; 0.30-0.75% V ₂ O ₅ ; 2.0-3.5% TiO ₂ .

Ore: 45-54% Fe _total ; 5.2-8.3% CaO; 0.40-1.80% MgO; 9.70-14.5% SiO ₂ ; 2.7-4.8% Al ₂ O ₃ .

Metal additives: 25-79% Fe _total ; 25.4-44.8% CaO; 4.4-10.8% MgO; 12.2-22.5% SiO ₂ ; 2.0-3.8% Al ₂ About ₃ .

Coke: 83-88% C; ash 10.2-14.5%; moisture 1.5-5.1%; sulfur 0.3-0.5%; the yield of volatiles is 0.8-1.4%.

Coal: 75-83% C; ash 4.2-15.5%; moisture 2.5-7.1%; sulfur 0.1-0.45%; the yield of volatiles is 14.5-21.4%.

Electro-steelmaking slag of the oxidizing period: 25-79% Fe _total ; 30.2-54.3% CaO; 7.4-12.8% MgO; 14.1-21.5% SiO ₂ ; 2.0-3.8% Al ₂ About ₃ .

The loading was carried out through a two-cone loading device with a separate, second ore skip according to the KKKK 6RRRKK loading system.

Conducting blast furnace smelting according to the present method allowed to reduce the cost of pig iron by 7.2 rubles / t due to a decrease in coke consumption from 415 kg / t of pig iron to 412 kg / t of pig iron, to increase the productivity of the furnace by 0.8 t / h due to the washing effect of the furnace blast furnace, to improve the quality of cast iron due to a decrease in the concentration of phosphorus from 0.09 to 0.08%, sulfur from 0.029 to 0.026%.

Information sources

1. RF patent No. 502941 C21B 5/00.

2. RF patent No. 94016296 C21B 5/00.

3. RF patent No. 02115739 C21B 5/00.

4. Application No. 94001238 С21В 5/00.

Claims (1)

A blast furnace smelting process comprising loading a charge into the furnace containing pellets, sinter, coke, metal additives, characterized in that the composition of the charge is additionally injected with ore, coal and electric furnace slag of the oxidative period of a fraction of 10-80 mm with a content of 25-44% FeO, 5 -23% of the kings of iron and a basicity of 1.8-3.6, in the following ratio of materials, wt.%: Agglomerate 40-74 Pellets 5-25 Ore no more than 3,5 Metal Additives no more than 10 Coke 15-26 Coal 1-6 Electric Steel Slag oxidative period 0,1-18, while the ratio of CaO / SiO ₂ charge support 0.80-1.10.