RU2547379C1 - Metallurgical flux and method of its manufacturing - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, in particular to compositions and method of manufacturing of fluxes for high temperature machines. The metallurgy flux is manufactured as granules of bi-ceramic composition, contains in wt %: magnesium oxide is base, calcium oxide 12-30, silicon carbide 2-10, iron oxides 3-10, aluminium oxide 2-7. The method includes loading and baking in the rotary kiln of the mixture of flux constituents with creation of the rolled pellets of bi-ceramic composition with outside enclosure and core, at that mixture of the flux constituents contains in wt %: dolomite 45-65, caustic magnesite and/or calcinated magnesite 25-45, iron containing material 3-7, aluminium containing material 3-7.

EFFECT: invention increases hydration stability of the metallurgy flux, and ensures quality of autocrucible coating of the lining of the high temperature machine due to formation of slag with high fluidity.

2 cl, 2 tbl

Description

The invention relates to the field of metallurgy, in particular to compositions and methods for producing fluxes used in various high-temperature units.

Known flux containing magnesium oxide, calcium oxide, iron oxide, silicon oxide, aluminum oxide, organic and / or mineral compounds and carbon, oxides and / or chlorides, and / or fluorides of alkali metals and hydrocarbonate forms of magnesium. Known flux is obtained by mixing the calcined magnesia-containing material and a binder, aluminum-containing waste, carbon-containing materials, natural magnesite and / or brucite, then briquetted (RU 2374327 from 02.26.2007, C21C 5/36).

The main disadvantage of the known flux is the presence in it of chlorides and / or fluorides of alkali metals, which makes the production and use of flux of this composition is not environmentally friendly, polluting the environment. The low content of calcium oxide (0.5-10%) does not significantly improve the refining properties of flux in the steelmaking process. The flux has large values of the indicator "weight loss during calcination", which leads to a decrease in the temperature of the slag with the introduction of flux, increases the viscosity of the slag, so increased energy costs to reduce the viscosity of slag in the steelmaking unit. The deterioration of slag formation and a decrease in the heat content of the smelting does not allow increasing the content of MgO oxides in the slag to the extent of its saturation, which negatively affects the durability of the lining of thermal units.

Known flux, including magnesia flux with a content of magnesium oxide of at least 20% and red clay in an amount of 10-40%. Red clay is used as a component for slag guidance and contains a mixture of aluminum oxides (12-27%), iron (2.5-15%), silicon (43-74%), magnesium (0.7-7.3 %), calcium (0.5-7.7%), alkali metal oxides (1.4-8.7%). RU 2345143 dated March 19, 2007

The disadvantage of this flux is the reduction in basicity (CaO to SiO ₂ ratio) of slag with the introduction of red clay, which has a very high content of silicon oxide (43-74%). The decrease in basicity negatively affects the refining ability of slag; increases its aggressive effect on the lining of the steelmaking unit; Refractory wear occurs. This requires more frequent repairs and, as a result, the technical and economic performance of metallurgical units is deteriorating.

Known flux containing, in wt.%: Magnesium oxides - base, calcium oxides - 15-30, silicon oxides - 2-7, iron oxides - 4-10. Moreover, the flux granules consist of a bicerramic material - shell and core (RU 2363737 from 02.27.2008). Also known is a flux containing, in wt.%: Dolomite - 45-65, caustic magnesite and / or calcined magnesite - 25-50, iron-containing material - 5-10, which is obtained by firing a mixture of slag-forming components in a rotary kiln (RU 2381279 from 14.04 .2008).

Known flux has the form of granules, which are characterized by a bicerramic structure; the phase composition of the outer part of the flux granules contains calcium ferrites with a melting point of 1435 ° C. Thermogranulation starts not earlier than this temperature, which requires an increased temperature of the process of formation of granules when passing through the furnace, otherwise the components of the calcined material are not fully involved. It takes a long residence time of the forming granules in the furnace, the unit's performance is lost, and due to the low strength of the granules during the firing process, granule fragments are present up to 25%, which further reduces the furnace productivity by granular flux. The content of calcium oxide in the shell and core of the granule limits the grain size of the used initial dolomite, violation of the ratio of calcium and magnesium oxides in the shell and core causes the destruction of the granules during their storage and transportation.

The technical result from the use of the invention is to increase the hydration stability and yield of the finished product, as well as ensuring the quality of the skull coating of the lining of the high-temperature unit (due to the formation of slag, increased fluidity).

The specified technical result is achieved due to the fact that the metallurgical flux containing oxides of magnesium, calcium, silicon and iron, made in the form of granules of a bicerramic composition, according to the invention additionally contains aluminum oxide, in the following ratio, wt.%:

magnesium oxide - the base;

calcium oxide - 12-30;

silicon dioxide - 2-10;

iron oxides - 3-10;

aluminum oxide - 2-7.

The specified technical result is also achieved as a result of the fact that according to the invention, the mixture further comprises an aluminum-containing material, according to the invention, the mixture further comprises an aluminum-containing material, according to the invention, the mixture further comprises an aluminum-containing material, according to the invention, the mixture contains a component of dolomite, caustic magnesite and / or calcined magnesite, an iron-containing material in a rotary kiln; , wt.%:

dolomite - 45-65;

caustic magnesite and / or calcined magnesite - 25-45;

iron-containing material - 3-7;

aluminum-containing material - 3-7.

The metallurgical flux in accordance with the claimed invention has the form of rolled strong granules of bicerramic material, with a certain phase and chemical composition gradient, which increases the flux assimilation rate by the slag melt during steelmaking in metallurgical units, thereby providing the best quality of the skull coating of the lining of steelmaking units. The bioceramic composition of the flux is presented as follows: the flux granules have a dolomite origin (dolomite grain), onto which the magnesian component of the raw material charge (sintered periclase particles) adheres. The silicate component in the core of the granules is represented by calcium silicates: alite, in the lining of the granules - larnite. The phase composition of the granules of metallurgical flux obtained in accordance with the present invention, are presented in table 1.

A feature of the inventive metallurgical flux is the introduction into the mixture of calcined components, an aluminum-containing material, which contributes to the formation of granules with a strong shell and core due to the formation of brownmillerite films (4CaOAl ₂ O ₃ Fe ₂ O ₃ ) in them. Moreover, the fraction of brownmillerite in the shell and core is in the range from ~ 2 to ~ 7%. The presence of reinforcing films of brownmillerite increases the strength of the flux granules, better protects its core (calcined dolomite). Brownmillerite is formed at a temperature (not higher than 1395 ° C), this contributes to an earlier start of the formation of thermogranules, thereby providing almost complete granulation of the calcined materials; the yield of product (fr. 40-4 mm) reaches 95-100%. This increases the productivity of the furnace, reduces the specific consumption of gas and raw materials, as a result - reduces the cost of flux.

Brownmillerite is not subject to hydration and its films protect the grain of calcined dolomite, thereby increasing the hydration stability of the finished product. In addition, due to the presence of brownmillerite in the flux, the components of the flux will dissolve earlier and faster in the slag. The fast absorption of MgO by slag promotes the formation of a skull with a high MgO content, which reduces the destructive effect of slag on the lining of the aggregate, and the dissolution of CaO accelerates the phosphorus and sulfur absorption capacity of the slag.

In accordance with the present invention, the flux contains calcium oxides in the range of 12-30%. An increase in calcium oxide in a metallurgical flux of more than 30% leads to a significant increase in the melting temperature of this material, which impairs its performance. The content of calcium oxides of less than 12% in the flux impairs slag formation and the refining ability of slag. The basicity of the slag also decreases, and, as a result, the reactivity to oxidize the masonry refractories increases, and the lining resistance of high-temperature aggregates decreases.

The content of silicon dioxide (SiO ₂ ) of at least 2% in the flux is due to the use of materials of the reduced charge. A SiO ₂ content _of not more than 10% is necessary in order to prevent a decrease in the basicity of slag in metallurgical aggregates as a result of the introduction of such a flux. The limitation on this oxide will not contribute to the formation in the flux (upon receipt) of refractory silicates of magnesium and calcium, the presence of which increases the melting point of this product and reduces its dissolution rate in the slag.

An increase in the content of iron oxides in the flux of more than 10% leads to an increase in the oxidation of slag of metallurgical units, which negatively affects the stability of the lining of the units, while a decrease in the content of iron oxides in the flux of less than 3% increases the melting point of the flux, which leads to an extension of the melting period of the material, so and to additional heat losses during metal melting.

In the production of flux, a raw mix is used, consisting of dolomite in an amount of 45-65%, caustic and / or calcined magnesite in an amount of 25-45%, iron-containing material in an amount of 3-7%, aluminum-containing material in an amount of 3-7%. The declared values (limits) of the starting components are selected experimentally.

Dolomite with a grain size of 3-35 mm, or 5-30 mm, or 5-25 mm is used as the main raw material component. Grains with a particle size of less than 3 mm can provoke excessive formation of a skull layer (fat) in the furnace, which will lead to a halt of the high-temperature unit. From dolomite larger than 35 mm, the flux is too large -> 40 mm, which will be slowly absorbed by the slag. The selected classes of dolomite fineness and thermogranulation processes due to physicochemical transformations of the remaining components of the charge ensure the production of flux of the optimal size.

Caustic magnesite is obtained by collecting dust in the production of periclase powder in rotary kilns and / or shaft furnaces operating on the firing of natural magnesia materials (magnesite, brucite, dolomite, dolomitic magnesite) and / or on the firing of a mixture of natural and calcined or caustic magnesia materials / or from furnaces operating for firing the mixture according to the claimed method.

Calcined magnesite is obtained by low-temperature firing of magnesia materials in rotary and / or shaft furnaces. In addition, as calcined magnesite, dust collectors from smelting furnaces obtained by collecting dispersed dust in the manufacture of fused periclase can be used.

As the starting iron-containing material, iron oxides in the form of siderite ore (FeCO ₃ ), siderite agglomerate, as well as iron-containing waste from metallurgical production (for example, suction dust from steelmaking, iron oxide) are used.

As an aluminum-containing material for the purposes of the present invention, high-alumina clay, bauxite, alumina are used. Achieving the result of the proposed method is ensured by the introduction of aluminum-containing material in the range of 3-7%. The claimed limits are obtained experimentally and are optimal, providing the necessary liquid mobility of the slag, improving its distribution when applying the skull coating. Its presence in an amount of less than 3% leads to insufficient thermal granulation of the calcined materials, not allowing to significantly increase the furnace productivity of the finished product due to the insufficient amount of alumina to form a low-temperature brownmillerite compound during the firing of raw materials and, as a result, does not provide complete protection of the calcined grain dolomite. The introduction of more than 7% alumina-containing material into the charge promotes the formation of a low-level skull layer on the furnace lining due to the excessive formation of fusible compounds.

The components of the raw material mixture within the specified limits using continuous weighing batchers are loaded into a rotary kiln. In the materials of the initial charge when moving through the furnace certain physical and physico-chemical processes occur. First, in the heating zone, physical moisture is removed from the starting materials; the components of the mixture are mixed and heated. In the decarbonization zone of the furnace, CO _{2 is} removed from dolomite and siderite ore grains, organic impurities are burned out, and dehydration and interaction of the aluminum-containing material with other oxides begins. At the same time, dolomite grains become more porous, but due to their structure they retain a rather high mechanical strength, and siderite grains disintegrate and iron oxides are released. Already in this zone and, further, with increasing temperature, the interaction of calcium oxide and oxides Al ₂ O ₃ , Fe ₂ O ₃ , SiO ₂ begins with the formation of calcium silicates and brownmillerite, which has the lowest melting point (formation) of these compounds (1395 ° C). Moreover, brownmillerite is mainly concentrated in the outer shell of the grain of calcined dolomite. When passing through the furnace, dispersed periclase material is wound on dolomite grain with the formation of a thermogranule.

The specified composition of the charge provides the claimed result for this method of production of calcined flux. The chemical composition of such a flux meets the requirements for this product when it is used to adjust the composition of slag melts in metallurgical units (Table 2).

The proposed method for the production of flux allows you to get the product in the form of rounded granules, which due to the formation on their surface of the outer shell of a certain phase composition have high strength and optimal size, the ability to be stored for a long time and not be destroyed.

When using a flux of this composition, its absorption by slag will occur faster, thereby accelerating the formation of slag and regulating the degree of basicity. The addition of aluminum-containing material increases the slag's fluid mobility, which increases the area of the formation of the skull on the lining of the metallurgical unit when applied and better protects the refractory materials of the lining from the aggressive effects of oxidized slag. Thus, the claimed technical result is achieved by the invention.

Table 1 The phase composition of the granules of metallurgical flux The phase composition of the granules,% inner zone outer zone Periclase 43-50 72-74 Calcium oxide 27-35 no Alit 16-22 no Larnit no 14-19 Brownmillerite 3-6 9-14

table 2 The chemical composition of the raw materials and flux materials Chemical composition, wt.d% MgO Al ₂ O ₃ Cao SiO ₂ Fe ₂ O ₃ Δm Flux 1 55.0 4,5 28.8 5,4 5.5 0.30 Dolomite 22.0 0.60 30.1 1.90 0.68 44.5 Calcined Magnesite 87.3 0.15 4,5 3,5 1.65 2,5 Siderite ore 12.5 3.2 5,0 6.0 42.3 29.5 High alumina clay 1.30 40.6 0.50 22.7 18.3 12.3 Flux 2 66.0 2,8 20.3 2.7 7.8 0.15 Dolomite 22.8 0.50 29.8 1,2 0.56 45.0 Caustic Magnesite 84.2 0.10 3.60 1.7 1.95 8.0 Siderite ore 11.10 2,8 6.2 7.1 47.9 24.4 Bauxite 1.12 58.0 0.23 7.0 21.5 12.7 Flux 3 54.0 4.8 29.5 5.3 5,4 0.55 Dolomite 24.0 0.58 28.0 3.4 0.50 43.0 Calcined Magnesite 80.1 0.25 8.2 4.0 2.0 5,0 Steel smelting dust 14.1 1,0 5.1 7.2 58.0 12,2 Alumina - 97.0 - - - 1,5

Claims (2)

1. A method of manufacturing a metallurgical flux, comprising loading and firing in a rotary kiln a mixture of slag-forming components containing dolomite, caustic magnesite and / or calcined magnesite, an iron-containing material, with the formation of rounded granules of biceric composition with an outer shell and core, characterized in that the mixture is slag-forming components additionally contains aluminum-containing material in the following components, wt.%:
Dolomite 45-65 Caustic magnesite and / or calcined magnesite 25-45 Iron material 3-7 Aluminum-containing material 3-7 2. Metallurgical flux containing oxides of magnesium, calcium, silicon and iron, characterized in that it is made by the method according to claim 1 in the form of granules of a bicerramic composition and additionally contains aluminum oxide in the following ratio, wt.%:
Magnesium oxide The basis Calcium oxide 12-30 Silica 2-10 Iron oxides 3-10 Aluminium oxide 2-7