RU2385349C2 - Procedure for processing vanadium containing iron - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: procedure consists in charging coolers and slag forming materials, in casting vanadium containing iron into converter, in blasting with air enriched with oxygen, in tapping semi-product into ladle and in canting slag into slag pan. As cooler and slag forming material reverse high manganese agglomerate is introduced into converter to contents in melted slag MnO over 20 %, preferably, 25-27 %, and ratio Mn:V is maintained withing ranges 1.5:1.7. De-vanadisation of iron is completed at contents of carbon 2.0-2.8 in the semi-product at temperature above 1400°C, preferably 1450°C.

EFFECT: facilitating reduced contents of metal phase in converter slag, increased extraction of chromophore out of semi-product into slag and production of high homogeneous mixture of vanadium with reaction agent in slag.

1 dwg, 2 tbl, 1 ex

Description

The invention relates to ferrous metallurgy, in particular to a method for processing vanadium-containing cast irons to produce intermediate and vanadium-containing slags suitable for the production of vanadium oxide.

When converting vanadium-containing cast iron, vanadium-containing slag is produced using the upper oxygen blast or blowing from below with oxygen enriched air, with the addition of a coolant and an oxidizing agent, for example, scale. Due to a decrease in temperature (1350-1400 ° C) in the reaction zone of the converter, elements (Si, Ti, Cr, Mn, V) are oxidized (burned out). By controlling the temperature and duration of the conversion, the equilibrium of the oxidation reactions of the above elements can be shifted and converted to slag during carbon burnout.

A known method of processing vanadium-containing cast iron to produce vanadium slag by blowing oxygen in a converter and sitting as a cooler and oxidizing agent: dross 88-93% and flux 7-12%. The use of flux allows you to increase the extraction of vanadium from cast iron to slag and from slag to technical vanadium pentoxide (patent RU No. 2113497, publ. 1998.06.20).

In the method of processing vanadium cast iron by the duplex process, calcium and magnesium carbonates in the form of dolomite, magnesite, dunite, and lime are used as an additive for slag-forming materials (patent RU No. 1272705, publ. 2000.09.20).

The above methods do not allow to reduce the content of metal inclusions in the slag.

The closest in technical essence and the achieved result is a method of processing vanadium-containing cast irons in a converter, including loading a cooler and slag-forming materials (scale, pellets, pig iron, etc.), pouring vanadium-containing cast iron into a converter, purging with oxygen-enriched air, releasing semi-finished product and turning the slag into a slag bowl (RU 2105072 C1, C21B 5/28, 02.20.1998).

At the first stage of the existing converter redistribution of vanadium-containing cast iron, vanadium slag of the following chemical composition is obtained, wt.%: 12-18 V ₂ O ₅ , 1-3 CaO, 8-12 MnO, 4-7 Cr ₂ O ₃ , 8-10 TiO ₂ , 15-22 SiO ₂ , 28-30 Fe ₂ O ₃ , 1-3 Al ₂ O ₃ and 15-20 metal inclusions. The process of converting vanadium-containing pig iron is suspended when the content of carbon in the intermediate is 3.2-2.8%, and the temperature of the intermediate in the ladle after discharge from the converter should not exceed 1400 ° C. In the process of rolling out the converter, the vanadium-containing slag is in a viscous state with a high heterogeneity of the chemical composition of the spinel phase distributed in the volume of silicate components, while more than 15% of metal inclusions in the form of kings and dispersed iron are in the slag. Kings, the source of which is a high-carbon intermediate, in thick slags of the duplex process do not merge with the intermediate and freeze in the slag. Dispersed iron is the result of chemical decomposition of aluminate and iron chromate at high temperatures in the solid phase. It is known that wustite with corundum and chromium trioxide interact by reactions:

which are accompanied by a significant decrease in entropy (ΔS = -17 J (mol · K) ^-1 and ΔS = -12 J (mol K) ^-1, respectively.

However, these reactions are not reversible, since at high temperatures in the solid phase they dissociate with the formation of dispersed iron according to the equations:

The evolved gases in the viscous mass cause the formation of the porous structure of the slag. The physicochemical properties of converter slag both during its formation during melting and in the solid state are determined by the ratio between the spinel, silicate and metal phases.

In the technology for processing vanadium converter slag, a method for magnetic separation of metal inclusions is provided. However, stepwise grinding and double magnetization does not allow to obtain slag with a low content of metal inclusions. There are currently no techniques for mechanically separating the silicate from the spinel phase, so both phases are involved in further processing.

The existing technology has the following disadvantages:

- the introduction of a "cooler" and slag-forming material dilutes the vanadium slag to 12-18% V ₂ O ₅ and does not allow to achieve a uniform chemical composition of the spinel phase;

- low temperature (1350-1400 ° C) and high viscosity of vanadium slag do not allow to remove the kings of iron during the conversion process and, as a result, expensive intermediate grindings with double magnetic separation of metal inclusions are introduced at subsequent stages;

- the spinel-like vanadium-containing slag phase in the form of an inhomogeneous anisotropic product must be mixed with the reaction agent and, thereby, reduces the performance of the oxidative firing furnace of the charge;

- low temperatures of the intermediate result in a tense balance of heat at its redistribution into steel at the second stage of open-hearth or converter redistribution.

The objective of the invention is the development of a method for processing vanadium-containing cast irons to obtain marketable high-manganese vanadium slag with a homogeneous highly homogeneous spinel phase and a low content of metal inclusions, not higher than 8%.

The technical result of the invention is to reduce the content of the metal phase in the converter slag, increase the mass fraction of vanadium pentoxide and manganese oxide in the slag and obtain highly homogeneous mixing of vanadium with the reaction agent in the slag.

The technical solution of this problem is to remove the restrictions on the mass fraction of manganese oxide in the vanadium converter slag, maintaining the ratio of the mass fraction of manganese to vanadium in the range of 1.5-1.7. To increase the yield in the converter redistribution, pig iron devanadation is completed at a content of 2.8-2.0% carbon in the intermediate product at a temperature above 1400 ° C, maximally reducing the mass fraction of wustite (FeO) in the slag due to an increase in manganese oxide (MnO) in the slag more than 20%. To increase the temperature of the process of vanadium-containing cast iron demanding at the final stage, the supply of the cooler is not carried out, and the purge time is increased, providing the metal to overheat 100 ° C more above the Liquidus line.

The claimed parameters make it possible to obtain converter slag with desired properties, transfer wustite (FeO) to the metal phase, reduce slag viscosity and metal inclusion content, obtain a homogeneous highly homogeneous spinelide of manganese and vanadium, and increase the mass fraction of vanadium and manganese in the slag.

As a cooler, instead of the Bessemer agglomerate, a high-manganese agglomerate is used, which provides slag with a high content of vanadium and manganese in a liquid state. In such converter slags, the total content of iron and metallic inclusions sharply decreases.

An increase in temperature above 1400 ° C and an MnO content in the slag of more than 20% with a decrease in the carbon content in the intermediate to 2.8-2.0% leads to a maximum decrease in the mass fraction of wustite iron and metal inclusions in the slag and an increase in the concentration of vanadium and manganese oxides in it .

In preliminary experiments on the separation of iron and titanium from titanomagnetite in the reduction (blast furnace) and oxidation (converter) in the Tamman furnace, the distribution of the accompanying elements of vanadium, chromium, manganese and titanium between cast iron and slag was studied depending on the carbon content in the metal phase. The results are presented in the drawing, from which it can be seen that the minimum concentrations of these elements in the metal are in the range of carbon content of 2.8-2.0%. An increase in the carbon content in the metal phase leads to an increase in the residual concentrations of vanadium, chromium, manganese and titanium.

An example of the method

The experiments were carried out in a metallurgical complex equipped with converters with a capacity of 20 tons.

Before casting iron, a solid high manganese agglomerate was loaded into the converter. The sinter consumption was increased from smelting to smelting so that the concentration of manganese and vanadium increased.

In the converters, 6 melts were carried out during the devanadation of vanadium-containing cast iron, the composition of which according to Mn was regulated by an agglomerate containing, wt.%: Fe _total. 25.58; FeO 15.30; CaO 4.80; MgO 1.91; SiO ₂ 18.71; TiO ₂ 2.27; Al ₂ O ₃ 2.60; V ₂ O ₅ 0.83; Cr ₂ O ₃ 1.23; MnO 19.56; MnO ₂ 211.97; P ₂ O ₅ 0.42; SO ₃ 0.35; R ₂ O 0.42. Basicity 0.26.

As a result of purging the heats with an air flow rate of 30,000-32,000 m ³ / h, an intermediate was obtained with a temperature of 1385-1460 ° C, the chemical composition of which is given in Table 1.

At the same time, due to a decrease in the viscosity of vanadium-containing slag with an increase in the concentration of manganese oxides from 11.7 to 26.4% and a decrease in the concentration of wustite (FeO) from 32.1 to 5.8%, the content of metal inclusions in the slag decreased from 23.0 up to 3.2%, and the yield of intermediate was increased by 1.5-1.8% (Table 2).

High manganese vanadium containing slags in the converter were obtained in a liquid state. When draining into slag tanks, these slags practically do not react with the ingress intermediate and, after crystallization, contain less dispersed iron and metal inclusions.

After cooling, the slag was tipped onto a slag yard, crushed to a fraction of less than 200 mm, and a sample was taken.

The intermediate product was transferred to the open-hearth workshop for processing to steel.

Using the proposed technology in comparison with the known one, while maintaining all the advantages of processing vanadium-containing cast irons in converters, obtain commodity vanadium-containing slags with specified physicochemical properties for processing by various technologies, increase the yield and increase the concentration of vanadium and manganese oxides in the slag.

Table 1 Indices of swimming trunks during cast iron devanation using high manganese sinter Indicators Average heats of current production Numbers of experienced swimming trunks one 2 3 four 5 6 [C] cast. 4.60 4.60 4.65 4.64 4.68 4.70 4.82 [V] cast. 0.46 0.46 0.47 0.47 0.48 0.48 0.51 [Si] cast. 0.28 0.28 0.29 0.28 0.28 0.29 0.30 [Ti] cast. 0.23 0.23 0.24 0.23 0.23 0.24 0.25 [Mn] cast. 0.35 0.35 0.33 0.35 0.34 0.35 0.36 [Cr] cast iron. 0.22 0.22 0.24 0.23 0.23 0.24 0.26 [S] cast. 0,023 0,023 0.024 0,025 0.024 0,025 0,026 [P] cast. 0.056 0.056 0,055 0.056 0,055 0.056 0.058 Consumption is powerless. sinter., kg / smelting. 1000 0 0 0 0 0 0 Consumption marg. sinter, kg / smelting 0 500 600 800 900 1000 1400 Air consumption, m ³ / h 30000 30000 30500 31000 31500 32000 32000 Purge Duration, min 3.0 3.0 3.2 3.4 3.8 4.0 4.2 [C] half ex. 3.2 3.2 3.0 2,8 2.6 2,4 2.0 [V] sem. 0.04 0.04 0.05 0.06 0.08 0.10 0.09 [Si] half ex. 0.01 0.01 0.01 0.01 0.01 0.01 0.01 [Ti] half ex. 0.01 0.01 0.01 0.01 0.01 0.01 0.01 [Cr] half ex. 0.02 0.02 0,03 0.02 0.02 0.02 0.02 [Mn] half ex. 0.02 0.02 0.04 0,03 0,03 0.02 0.02 [S] half ex. 0,023 0.024 0,023 0.024 0,023 0,023 0,022 [P] half ex. 0,054 0,053 0,054 0,054 0,054 0,054 0,054 Half temperature, ° С 1360 1390 1400 1450 1450 1460 1460 FeO 32.1 28.3 25.7 19.3 15.4 10.3 5.8 V ₂ O ₅ 17,2 17.5 17.8 18.6 18.8 19.2 21,2 MnO 11.7 17.0 18.6 20.5 21.5 22.7 26,4 SiO ₂ 18,4 21.9 22.5 24.3 25,2 27.1 27,2 Cao 1,6 4.0 4.2 4.4 4.3 4.4 4.6 Cr ₂ O ₃ 6.3 4.1 4.6 5.1 6.1 6.1 6.2 TiO ₂ 10.0 7.1 7.8 8.5 9.6 10.5 10.6 Mn / v 0.68 1.32 1.45 1,52 1,58 1,64 1.72 Coeff. oslakov.% 95.2 96.7 94.2 91.6 86.1 82.1 78.3 Metal. incl.% 23.0 15.0 12.0 8.0 5.3 3.4 3.2

table 2 Dependence of yield (iron) in the intermediate and mass fraction of V ₂ O ₅ on the mass fraction of MnO in converter slag Options Indicators The content of MnO in the slag,% 11.7 17.0 18.6 20.5 21.5 22.7 26,4 Mn / V ratio 0.68 1.32 1.45 1,52 1,58 1,64 1.72 The increase in yield (Fe),% - 0.4 0.6 0.8 1,0 1,5 1.8 The increase in the mass fraction of V ₂ O ₅ in the slag, abs.% - 0.3 0.6 1.4 1,6 2.0 4.0

Claims (1)

A method of processing vanadium-containing cast irons in a converter, including loading coolers and slag-forming materials, pouring vanadium-containing cast iron into a converter, purging with oxygen-enriched air, discharging the intermediate into a ladle, and turning the slag into a slag bowl, characterized in that it is introduced as a cooler and a slag forming cooler reverse high-manganese agglomerate until the MnO content in the molten slag is more than 20%, preferably 25-27%, and the ratio of Mn: V is maintained in the range of 1.5-1.7, while the casting is completed at a carbon content of 2.0-2.8 in the intermediate product at a temperature above 1400 ° C, preferably 1450 ° C.

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