RU2177039C1 - Method of blast-furnace smelting - Google Patents

Abstract

FIELD: ferrous metallurgy; applicable in smelting of pig iron with low content of sulfur. SUBSTANCE: method includes charging into blast furnace or iron ore burden containing pellets with basicity of 0.3-0.5 and sinter; introduction into burden of coke and fluxes. Charged into blast furnace are pellets in amount of 30-70% of total iron ore burden. Fluxes are used in the form of domolite, limestone and line in ratio of 1.0:(3.5-3.6):(0.5-0.6) and introduced into sinter. Total consumption of fluxes per ton of pig iron and sinter basicity by (CaO+MgO)/(SiO₂+Al₂O₃) are determined by definite expressions. EFFECT: low content of sulfur, reduced consumption of coke and increased productivity of blast furnace. 2 tbl, 1 ex

Description

 The invention relates to ferrous metallurgy and can be used in the smelting of cast iron in blast furnaces.

 There is a method of blast-furnace smelting on the main slag with high heating of the hearth and this ensures a decrease in sulfur content in pig iron (Ostroukhov M.Ya., Shparber L.Ya. Operation of blast furnaces. M: Metallurgy, 1975, p. 249).

 The disadvantage of this method is an increase in the demand for coke and a decrease in furnace productivity, since for every 0.01% reduction in the sulfur content in cast iron, an additional 1% of coke has to be produced, while the cast iron is smelted 1% less.

 The closest analogue to the claimed method is a method for blast-furnace melting of titanomagnetite raw materials, which includes loading an iron ore charge containing pellets with a basicity of 0.3-0.5 and sinter into the furnace, introducing coke and fluxes into the charge, and 30-70% of the pellets are loaded into the furnace iron ore charge and give additional raw carbonates of alkaline earth metals, and limestone, dolomite or mixtures thereof are introduced as such carbonates (see RF patent 2063443, C 21 B 5/00).

 The disadvantage of this method is the use of crude carbonates - their consumption reaches 78 kg / t of cast iron. According to the reference data, an increase in the consumption of ordinary limestone by 10 kg / t of cast iron is accompanied by an increase in the specific consumption of coke and a decrease in furnace productivity by 0.5%, and dolomitized - by 0.4%. Therefore, in the known method, the specific consumption of coke is relatively high and amounts to 458 kg / t of pig iron and more. (tab. 3 methods). The sulfur content in cast iron also turns out to be high and amounts to 0.028% and does not change from the use of the method (table. 2 of the method). The method is applicable only for the smelting of cast iron with a high titanium content of 0.28%.

 The technical task of this method is to reduce the sulfur content in cast iron while reducing the specific consumption of coke and increasing the productivity of the furnace.

где В_А - основность агломерата;
А и Ок - содержание агломерата и окатышей по массе в шихте доменной печи, %;
0,2 и 0,08 - коэффициенты, определенные эмпирически;
В - основность шлака по (CaO+Mg)/(SiO₂+Al₂O₃), устанавливаемая в пределах 1,03-1,07;
SiO₂ок, Al₂O₃ок, CaOок, MgOок - содержание соответствующих оксидов в окатышах, %;
в состав флюсов включают доломит, известняк и известь в соотношении 1,0: (3,5-3,6):(0,5-0,6) и вводят их в агломерационную шихту, определив суммарный расход на 1 т чугуна из выражения:

где Ф - суммарный расход доломита, известняка и извести, кг/т;
Р и K - расход руды и концентрата в составе агломерационной шихты, кг/т чугуна;
В_А - основность агломерата;
SiO₂р, Al₂O₃р, CaOр, MgOр - содержание по массе соответствующих оксидов в руде агломерационной шихты, %;
SiO₂к, Al₂O₃к, CaOк, MgOк - содержание по массе соответствующих оксидов в концентрате агломерационной шихты, %;
СаОф+MgOф - содержание по массе соответствующих оксидов в смеси доломита, известняка и извести, %.The problem is solved in that in the method of blast furnace smelting, which includes loading an iron ore charge into the furnace containing pellets with a basicity of 0.3-0.5 and agglomerate, introducing coke and fluxes into the charge, and 30-70% of the iron ore pellets are loaded into the furnace the mixture according to the invention in the mixture use an agglomerate with a basicity of (CaO + Mg) / (SiO ₂ + Al ₂ O ₃ ), determined by the expression

where In _And - the basicity of the agglomerate;
A and OK - the content of agglomerate and pellets by weight in the charge of the blast furnace,%;
0.2 and 0.08 are the coefficients determined empirically;
In - the basicity of the slag according to (CaO + Mg) / (SiO ₂ + Al ₂ O ₃ ), set in the range of 1.03-1.07;
SiO ₂ ok, Al ₂ O ₃ ok, CaOok, MgOok - the content of the corresponding oxides in the pellets,%;
the composition of the fluxes includes dolomite, limestone and lime in a ratio of 1.0: (3.5-3.6) :( 0.5-0.6) and they are introduced into the sinter mixture, determining the total consumption per 1 ton of cast iron from the expression :

where f is the total consumption of dolomite, limestone and lime, kg / t;
P and K are the consumption of ore and concentrate in the composition of the sinter mixture, kg / t of pig iron;
In _A - the basicity of the agglomerate;
SiO ₂ p, Al ₂ O ₃ p, CaOp, MgOp — content by weight of the corresponding oxides in the ore of the sinter charge,%;
SiO ₂ k, Al ₂ O ₃ k, CaOk, MgOk — content by weight of the corresponding oxides in the sinter concentrate,%;
CaOf + MgOf — content by weight of the corresponding oxides in the mixture of dolomite, limestone and lime,%.

The use of an agglomerate with a basicity value B _A less than calculated by the proposed expression leads to slag with a basicity B less than 1.03. A basicity of B below 1.03 causes an increase in the sulfur content of cast iron due to a decrease in the concentration of sulfur-absorbing components (CaO and MgO). The use of an agglomerate with a basicity of B _A greater than the value calculated by the proposed expression results in slag with a basicity of B greater than 1.07. Such slag worsens the sulfur content in pig iron, the specific consumption of coke, and furnace productivity due to an increase in slag viscosity.

The expenditure of flux (dolomite, limestone and lime) in a smaller amount than in the expression for the determination of Φ leads to an agglomerate with insufficient basicity compared to that required in accordance with the expression for the determination of B _A. The consumption of flux in a larger amount than in the expression for the determination of Φ leads to an agglomerate with excess basicity compared to that required in accordance with the expression for the determination of B _A.

The specified ratio between the costs of dolomite, limestone and lime, allows to obtain high-quality agglomerate. In this case, dolomite is a source of MgO, limestone and lime are sources of CaO. In addition, limestone and dolomite serve as gas-forming components of the sinter mixture, since CO ₂ is released from them during the sintering process. The evolution of gas during the agglomeration gives the resulting agglomerate high porosity and, accordingly, high reducibility. Lime serves as a binder of the components of the agglomeration charge and gives the produced agglomerate high strength. The use of dolomite, limestone and lime in the specified ratio allows you to optimally combine the various properties of the sinter - to obtain sinter with basicity, MgO content, strength and reducibility, providing a decrease in sulfur content in pig iron by 0.005-0.007% abs. (10-30% rel.) And specific consumption of coke by 1-3 kg / t of pig iron with an increase in furnace productivity by 0.2-1%. To realize the favorable properties of the agglomerate, the basicity of blast furnace slag is expressed by the ratio B = (CaO + MgO) / (SiO ₂ + Al ₂ O ₃ ) and is maintained within the range of 1.03-1.07. The above limits of the ratio of the costs of dolomite, limestone and lime are determined by the technical capabilities of ensuring average values between the extreme values.

Example
Melting on a blast furnace 4 OJSC MMK. The ore part of the charge consists of 60% sinter and 40% pellets. The content in the pellets: SiO ₂ = 7.63%; Al ₂ O ₃ = 0.34%; CaO = 2.95%; MgO = 0.26%. The basicity of blast furnace slag in (CaO + MgO) / (SiO ₂ + Al ₂ O ₃ ) is 1.05.

Расход руды в составе агломерационной шихты - 448 кг/т чугуна, концентрата - 572 кг/т чугуна. Содержание SiO₂, Al₂O₃, CaO, MgO в них и в смеси доломита, известняка и извести в соотношении 1,0:3,5:0,6 приведено в табл.А.Then, according to the application for the invention, an agglomerate with a basicity of B _A = (CaO + MgO) / (SiO ₂ + Al ₂ O ₃ ) of component

Ore consumption in the composition of the sinter charge is 448 kg / t of pig iron, concentrate - 572 kg / t of pig iron. The content of SiO ₂ , Al ₂ O ₃ , CaO, MgO in them and in a mixture of dolomite, limestone and lime in a ratio of 1.0: 3.5: 0.6 are given in Table A.

Показатели работы доменной печи с использованием предлагаемого способа доменной плавки и без него приведены в табл. 1.In the conditions of the example, in accordance with the claimed method, the total consumption of dolomite, limestone and lime (F) is

The performance of the blast furnace using the proposed method of blast furnace smelting and without it are given in table. 1.

 The results of blast furnace smelting, obtained by deviating from the proposed method, are presented in table. 2.

Claims (1)

A blast-furnace melting method, comprising loading an iron ore charge into the furnace containing pellets with a basicity of 0.3-0.5 and an agglomerate, introducing coke and fluxes into the charge, wherein 30-70% of the pellets from the weight of the iron ore charge are loaded into the furnace, characterized in that charge use agglomerate basicity of (CaO + MgO) / (SiO ₂ + Al ₂ O ₃ ), determined by the expression

where In _And - the basicity of the agglomerate;
A and OK - the content of agglomerate and pellets by weight in the charge of the blast furnace,%;
0.2 and 0.08 are the coefficients determined empirically;
In - the basicity of the slag according to (CaO + MgO) / (SiO ₂ + Al ₂ O ₃ ), set in the range of 1.03-1.07;
SiO ₂ ok, Al ₂ O ₃ ok, CaOok, MgOok - the content of the corresponding oxides in the pellets,%,
the composition of the fluxes include dolomite, limestone and lime in a ratio of 1.0: (3.5-3.6) :( 0.5-0.6) and enter them into an agglomerate, determining the total consumption per 1 ton of cast iron from the expression:

,
where f is the total consumption of dolomite, limestone and lime, kg / t;
P and K - the consumption of ore and concentrate in the sinter, kg / t of pig iron;
In _A - the basicity of the agglomerate;
SiO ₂ p, Al ₂ O ₃ p, CaOp, MgOp — content by weight of the corresponding oxides in the sinter ore,%;
SiO ₂ k, Al ₂ O ₃ k, CaOk, MgOk — content by weight of the corresponding oxides in the agglomerate concentrate,%;
CaOf + MgOf - content by weight of the corresponding oxides in the mixture of dolomite, limestone and lime,%.

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