RU2768432C2 - Method for production of fluxed iron ore agglomerate - Google Patents

Abstract

FIELD: metallurgy of ferrous metals.

SUBSTANCE: invention relates to production of raw material for blast-furnace smelting — fluxed iron-ore agglomerate from multicomponent mixtures containing raw materials of various deposits. Method includes adjusting the composition of the components of the charge, which includes iron-ore materials, a fluxing additive and solid fuel, feeding the components of the charge for mixing, agglomerate pelletizing and sintering. Fluxing additive is supplied for mixing in form of lime, limestone and hematite-lime mixture with particle size less than 3 mm, including hematite-containing material and lime-containing material in amount providing ratio CaO_(c)/Fe₂O_3(c) equal to 0.175–0.700, where CaO_(c) is content of calcium oxide in mixture, wt. %; Fe₂O_3(c) is the content of hematite in the mixture, wt. %. It is expedient to use hematite agglomeration ore, or steel smelting sludge, or aspiration dust of steel production as a hematite-containing material.

EFFECT: invention enables to obtain agglomerate with basicity higher than 2,2 to 5,0 with low content of undigested lime inclusions, high strength characteristics and low content of fines.

1 cl, 2 tbl

Description

The invention relates to the metallurgy of ferrous metals, in particular to the production of raw materials for blast-furnace smelting - fluxed iron ore sinter from multicomponent charges containing raw materials from various deposits.

A known method for the manufacture of sinter from oxidized ores and concentrates, which consists in the fact that part of the ore with an iron content of at least 50% and ferrous oxide (FeO) of not more than 10% is mixed and / or jointly crushed with lime, forming micropellets with a diameter of 1, 6 mm to 5.0 mm with a basicity (CaO/SiO ₂ ) of no more than 3 units, which are dried and fed into the stream of pre-mixed coke, return and the rest of the ore, after which they are pelletized, loaded onto a sintering machine and sintered (RU, No. 2608046 C1, IPC C22B 1/16 (2006.01), published 01/12/2017).

Used in the known method, the sinter mixture contains several iron ore materials with different chemical composition of the silicate component. Since the implementation of the known method does not take into account the chemical composition of the silicate component of the iron ore components of the sinter charge, which determines the direction of mineral formation reactions and the final phase composition of the sinter, there is a possibility that the region of crystallization of the binders will be in the field of dicalcium silicate, self-destructive upon cooling. This leads to the output of the finished agglomerate with low strength characteristics and a significant content of fines.

The closest analogue of the invention is a method for the production of fluxed iron ore agglomerate, including adjusting the composition of particles less than 3 mm in the pelletized charge, including iron ore materials, solid fuel and fluxing additive, according to the sum of the modules-ratios CaO/SiO ₂ ; FeO/ _Fetot ; Al ₂ O ₃ /SiO ₂ ; and MgO/SiO ₂ , which is maintained within 1.0-1.9 and 2.2-3.1 to obtain olivine binders and ferrite, respectively, the supply of charge components for mixing, pelletizing and sintering, while sintering the agglomerate on olivine binders are carried out at a temperature of 1270-1320°C in a reducing atmosphere created by an increased consumption of solid fuel of at least 4 wt. % with particle sizes equal to or less than 2.5 mm, and when obtaining an agglomerate on ferrite binders, sintering is carried out at a temperature of 1220-1260 ° C in an oxidizing atmosphere, achieved by lowering the consumption of solid fuel to 2.5-3.0 wt . % with a particle size of 2.5-4.0 mm. (RU, No. 2048548 C1, IPC C22B 1/16 (2006.01), publ. 11/20/1995).

This method does not provide the production of sinter with a basicity of more than 2.2 to 5.0 with high strength characteristics and a low content of fines, which is advisable to use to reduce flux additives in the charge of blast furnaces, where the main iron ore component is unfluxed pellets.

Obtaining a sinter with a high basicity over 2.2 to 5.0 requires the introduction of an additional amount of fluxing additives (limestone, lime, etc.) into the sintering mixture, which must be completely assimilated by the iron silicate melt at the stage of liquid-phase hardening in order to ensure the stable formation of ferrite bonds in the finished product. agglomerate. However, during the sintering of the agglomerate at the stage of solid-phase interaction, the amount of low-melting ferrite compounds is not enough to intensify the formation of an iron-silicate melt at the stage of liquid-phase hardening, which assimilates fluxing additives.

Thus, upon receipt of an agglomerate with a basicity of more than 2.2 to 5.0, a large amount of fluxing additives in the sinter charge leads to the formation of undigested lime inclusions in the finished agglomerate. This, in turn, is accompanied by a deterioration in the strength characteristics of the agglomerate and an increase in fines in its composition.

The invention is based on the task of improving the method for the production of fluxed iron ore sinter, in which, due to technological features, during the sintering of the agglomerate at the stage of solid-phase interaction, the formation of the required amount of low-melting ferrite compounds is ensured, which intensifies the formation of an iron-silicate melt assimilating fluxing additives at the stage of liquid-phase hardening, which leads to obtaining an agglomerate with a basicity of over 2.2 to 5.0 with a low content of inclusions of undigested lime, high strength characteristics and a low content of fines.

The problem is solved by the fact that in the method for the production of fluxed iron ore sinter, which includes adjusting the composition of the charge components, including iron ore materials, fluxing additive and solid fuel, supplying the charge components for mixing, pelletizing and sintering the sinter, according to the invention, the fluxing additive for mixing is served in the form lime, limestone and hematite-lime mixture with a particle size of less than 3 mm, including hematite-containing material and lime-containing material in an amount that provides the CaO _(c) /Fe ₂ O _{3 (c)} ratio equal to 0.175-0.700, where CaO _(c) is the oxide content calcium in the mixture, wt. %; Fe ₂ O _3(c) - the content of hematite in the mixture, wt. %.

It is advisable to use hematite sintering ore, or steel-smelting sludge, or aspiration dust from steel production as a hematite-containing material.

The essence of the proposed method is to ensure the maximum assimilation of fluxing additives by the iron silicate melt at the stage of liquid-phase hardening and, thus, to minimize the presence of undigested lime inclusions in the final structure of the agglomerate with a basicity of more than 2.2 to 5.0 due to the use of lime as a fluxing additive. , limestone and hematite-lime mixture.

Submission for mixing of a fluxing additive in the form of lime, limestone and hematite-lime mixture with a particle size of less than 3 mm, including hematite-containing material and lime-containing material, in an amount that provides the CaO _(c) /Fe ₂ O _{3 (c)} ratio equal to 0.175-0.700, where CaO _(c) is the content of calcium oxide in the mixture, wt. %; Fe ₂ O _3(c) - the content of hematite in the mixture, wt. %, ensures the presence in the charge of a material that has a significant amount of contacts of hematite with calcium oxides, which leads to the formation of low-melting ferrite compounds at the stage of solid-phase interaction.

One of the most fusible compounds formed in a fluxed sinter charge at the stage of solid-phase interaction are calcium ferrites. In the CaO - Fe ₂ O ₃ system, there are three low-melting ferrite compounds: dicalcium ferrite Ca ₂ Fe ₂ O ₃ ; single-calcium ferrite CaFe ₂ O ₄ and semi-calcium ferrite CaFe ₄ O ₇ . Calcium ferrites are formed at the stage of solid-phase interaction during the interaction of CaO-containing compounds with hematite at the points of their contact. The temperature of the beginning of the formation of calcium ferrites is up to 600°C, when redox reactions in the charge are difficult. Therefore, at temperatures up to 600°C, hematite cannot be formed due to the oxidation of other iron oxides (wustite, magnetite) present in the sintering charge. The use of lime, limestone and hematite-lime mixture as a fluxing additive, according to the proposed method, provides at the stage of solid-phase interaction the formation of the required amount of low-melting ferrite compounds, the melting of which at temperatures of 1216-1226°C intensifies the formation of an iron silicate melt that assimilates fluxing additives. As a result, the finished sinter with a basicity of more than 2.2 to 5.0 has a low content of undigested lime inclusions, high strength characteristics and a low content of fines.

The stoichiometric ratio CaO/Fe ₂ O ₃ corresponding to the formula of semi-calcium, single-calcium and dicalcium ferrites, which is, respectively, 0.175, 0.35 and 0.7. is in the claimed range of the ratio CaO _(c) /Fe ₂ O _3(c.). , which ensures the formation of the required amount of low-melting ferrite compounds at the stage of solid-phase interaction, depending on the number of contacts of hematite with calcium oxides. The melting of low-melting ferritic compounds at the stage of liquid-phase hardening intensifies the formation of an iron-silicate melt, assimilating fluxing additives in the sintering charge, which ensures the production of sinter with a basicity of over 2.2 to 5.0 with a low content of undigested lime inclusions, high strength characteristics and a low content of fines.

The CaO _(c) /Fe ₂ O _{3 (c)} ratio of 0.175 corresponds to the stoichiometric ratio corresponding to the formula of semi-calcium ferrite. A decrease in the value of this ratio leads to the fact that at the stage of solid-phase interaction an insufficient amount of low-melting ferrite compounds is formed, which reduces at the stage of liquid-phase hardening the intensity of the formation of an iron silicate melt that assimilates fluxing additives in the sintering charge.

The CaO _(c) /Fe ₂ O _{3 (c)} ratio of 0.7 corresponds to the stoichiometric ratio corresponding to the formula of dicalcium ferrite. If this value is exceeded by increasing the amount of lime-containing material in the hematite-lime mixture, the amount of fusible ferrite compounds formed remains at the same level, which does not affect the intensity of the formation of the iron silicate melt. As a result, a large number of inclusions of undigested lime remain in the finished sinter.

With an increase in the particle size of the hematite-lime mixture of more than 3 mm, the number of contacts between hematite and calcium oxides decreases. As a result, at the stage of solid-phase interaction, an insufficient amount of low-melting ferrite compounds is formed, reducing the intensity of the formation of an iron silicate melt at the stage of liquid-phase hardening. The amount of iron silicate melt is not enough to assimilate fluxing additives, as a result, inclusions of undigested lime remain in the finished sinter.

The production method of fluxed iron ore sinter used for blast furnace smelting is carried out as follows.

As the main components of the charge, iron ore materials are used in the form of sinter ore, iron ore concentrate, etc., solid fuel in the form of, for example, coke breeze, a fluxing additive in the form of lime and limestone to achieve a basicity of the sinter up to 2.2, as well as a fluxing additive in in the form of a hematite-lime mixture, including hematite-containing and lime-containing materials, to achieve a basicity of more than 2.2 to 5.0. As a hematite-containing material in the hematite-lime mixture, oxidized sintering ores with a low silica content can be used, for example, from the Yakovlevsky mine (RF), the Caradjas deposit (Brazil), etc. Metallurgical production wastes, for example, steel-smelting slurry, or aspiration dust from steelmaking can also be used. high in hematite and low in silica. Prepared lime or limestone is used as the lime-containing material in the hematite-lime mixture. Hematite-containing and lime-containing materials are used with a particle size of less than 3 mm.

The hematite-lime mixture is preliminarily prepared on a special site using floor equipment to homogenize its composition. Hematite-containing and lime-containing materials included in the hematite-lime mixture are taken in an amount that provides the CaO _(c) /Fe ₂ O _{3 (c)} ratio of 0.175-0.700, where CaO is the content of calcium oxide in the mixture, wt. %; Fe ₂ O ₃ - the content of hematite in the mixture, wt. %.

Next, batch components are dosed in a given amount, mixed, pelletized and sintered on a sintering machine.

Example.

Method for the production of fluxed iron ore sinter according to the proposed method was carried out as follows.

As a hematite-containing material for the preparation of a hematite-lime mixture with a ratio of CaO _(c) /Fe ₂ O _{3 (c)} equal to 0.175, a size class of 0-3 mm sintering ore from the Yakovlevsky mine was used, separated on a screen, and as a lime-containing material - screenings of lime of a size class 0-3 mm.

Petrographic studies of the Yakovlevskaya agglomeration ore showed that iron oxides in it are in the form of hematite and magnetite. Therefore, the amount of hematite in the sinter ore was determined based on its chemical composition according to the formula:

Fe ₂ O ₃ -FeO⋅69/31,

where: Fe ₂ O ₃ - the amount of ferric oxide in the sintering ore, wt. %;

FeO - the amount of ferrous oxide in the sintering ore, wt. %;

69 - the amount of ferric oxide in magnetite, wt. %;

31 - the amount of ferrous oxide in magnetite, wt. %.

As a hematite-containing material in a hematite-lime mixture with a CaO _(c) /Fe ₂ O _{3 (c)} ratio of 0.4 and 0.7, converter sludge dehydrated in storage tanks to a moisture content of 15.0% was used, and as a lime-containing material - screening of lime with a fineness class of 0-3 mm.

Petrographic studies of converter sludge showed that iron oxides in it are predominantly in the form of hematite. In addition to hematite, iron oxides are found in equal proportions in the form of magnetite and wustite. Therefore, the amount of hematite in the converter sludge was determined based on its chemical composition according to the formula:

Fe ₂ O ₃ -0.5⋅FeO⋅69/31,

where: 0.5 - distribution coefficient of ferrous iron between magnetite and wustite, units.

The chemical composition of the resulting hematite-lime mixture is presented in Table 1.

The following were used as the main components of the sinter charge: sinter ore, iron ore concentrate, coke breeze, lime, waste from metallurgical production. To achieve a basicity of more than 2.2, a hematite-lime mixture was supplied as a fluxing additive to the sintering mixture in the required amount.

The agglomerate was produced with a basicity of 2.3; 3.5 and 5.0, for which a hematite-lime mixture was used with a ratio of CaO _(c) /Fe ₂ O _{3 (c)} equal to 0.175; 0.4 and 0.7 respectively.

In all cases, the particle size of the hematite-lime mixture was less than 3 mm, as evidenced by the absence of an overlattice product when it was screened on a sieve with a mesh diameter of 3 mm.

The quality of the sinter was assessed according to GOST 15137-77 according to the output of the size class 0-5 mm on the screens of the blast-furnace shop sinter per day.

Obtained according to the proposed method, the agglomerate, according to visual assessment, did not contain inclusions of undigested lime, had high strength characteristics and a low content of fines.

In a sinter with a basicity of 2.3; 3.5 and 5.0 after testing in a drum according to GOST 15137-77, the yield of size class +5 mm (strength) was 67.5%, the yield of size class -0.5 mm (abrasion) was 5.1%, and the yield size class 0-5 mm on the sinter screens of the blast-furnace shop per day amounted to 15.0%.

Technological parameters of the proposed method for the production of sinter and the results are presented in table 2, experiments 1-3.

Also carried out the production of fluxed iron ore sinter by a known method (the closest analogue), the technological parameters and the results of which are presented in table. 2, experience 4.

As charge materials used materials similar to those used in the proposed method.

To obtain an agglomerate with a basicity of 3.5, limestone with a particle size of less than 3 mm was supplied as a fluxing additive, as evidenced by the absence of an overlattice product when it was screened on a sieve with a cell diameter of 3 mm. The sinter charge was mixed, pelletized, fed to a sintering machine and sintered.

According to visual assessment, the resulting agglomerate contained inclusions of undigested lime. After tests in a drum according to GOST 15137-77, the strength of the agglomerate was lower in comparison with the proposed method and amounted to 65.0%, and the wear resistance was higher and amounted to 6.0%. The output of the size class 0-5 mm on the screens of the blast furnace shop sinter per day was 18.0%. Thus, the strength characteristics of the agglomerate are lower, and the fines content is higher compared to the proposed method.

In the sinter produced according to the proposed method for the production of fluxed iron ore sinter, the strength characteristics are higher, and the fines content is lower than in the sinter produced according to the known method - the closest analogue.

Thus, the use of the proposed method leads to the production of an agglomerate with a basicity of more than 2.2 to 5.0 with a low content of undigested lime inclusions, high strength characteristics and a low content of fines.

Claims (2)

1. A method for the production of a fluxed iron ore sinter, including adjusting the composition of the charge components, including iron ore materials, a fluxing additive and solid fuel, supplying the charge components for mixing, pelletizing and sintering the sinter, characterized in that the fluxing additive for mixing is served in the form of lime, limestone and hematite-lime mixture with a particle size of less than 3 mm, including hematite-containing material and lime-containing material in an amount that provides the CaO _(c) /Fe ₂ O _{3 (c)} ratio of 0.175-0.700, where CaO _(c) is the content of calcium oxide in the mixture, wt. %; Fe ₂ O _3(c) - the content of hematite in the mixture, wt. %. 2. The method according to claim 1, characterized in that hematite-containing sintering ore, or steel-smelting sludge, or aspiration dust from steelmaking is used as the hematite-containing material.