RU2588926C2 - Method for production of vanadium-bearing slag suitable for producing directly commercial ferrovanadium therefrom - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used in production of rich vanadium containing slag and commercial ferrovanadium. Method involves pouring of vanadium dry iron into an arc steel furnace and heating of dry iron to the temperature of hot metal devanadation - 1,421-1,470 °C; after that, according to the results of slag analysis, there is performed gradual feeding of dross in the amount of 4-8 % of the weight of dry iron, and of soda (Na₂ CO₃) in the amount of 7-10 % of the weight of slag; carbon is additionally introduced while maintaining 10-15 % FeO content in slag and the ratio of (Na₂O)/(V₂O₅) within 0.3-0.5; when the ratio of V/Fe=1.3-2.3 in slag is reached, the process of dry iron devanadation is finished and slag containing 27-32 % V₂O₅ is discharged; at that, during the devanadation process until the discharge there is performed a continuous deep stirring of the metal with argon or nitrogen through the bottom or through submersible tuyeres with specific intensity of 0.01-0.03 m³/(t·minutes).

EFFECT: invention allows, bypassing the stage of cheap and environmentally hazardous chemical processing in production of vanadium pentoxide, to produce rich in vanadium pentoxide slag suitable for direct production from it of commercial ferrovanadium.

1 cl, 3 dwg, 3 tbl, 2 ex

Description

The invention relates to ferrous metallurgy, in particular to a method for the production of rich vanadium-containing slag, suitable for producing directly commercial ferrovanadium.

Now all manufacturers receive vanadium-containing slag - the main raw material of the domestic ferroalloy industry for the production of vanadium pentoxide (by chemical processing of V-slag). The resulting technical vanadium pentoxide contains 87-90% V ₂ O ₅ , from which further silicotermic or aluminothermic reduction is obtained commodity ferrovanadium.

Chemical redistribution operations are extremely sensitive to the composition of V-slag. These requirements lead to the fact that the slag is obtained in the form of a viscous, porridge-like mass, which creates significant technological difficulties. The chemical redistribution of vanadium-containing slag is a very costly and environmentally harmful process.

A known method of production of vanadium-containing slag in a bucket on a vibrating stand, [1]. A bucket with a capacity of 77-80 tons is filled with vanadium-containing cast iron, having an average of 1.22% V.

Vanadium in cast iron is oxidized with gaseous oxygen. During purging, rolling mill scale and anthracite are added to reduce and / or control the process temperature, preventing the temperature from rising above 1400 ° C. Anthracite is added in an amount of 3000 kg to compensate for the loss of approximately 2% of carbon during its oxidation. To improve the averaging of temperature and chemical composition over the volume of cast iron, the bucket is subjected to vibration at a special stand. At the end of the process, the intermediate product is sent for processing in the converter, and the slag obtained by the thick consistency from the ladle is “dumped” into the slag (turning the ladle upside down) and sent for crushing and magnetization from metal inclusions. The produced slag is exported. A typical composition of the resulting vanadium slag is as follows,%:

The disadvantages of this method are:

- a high-cost three-stage process, which includes the production of V-containing pig iron by a complex two-stage introduced process, followed by devanadization of this cast iron in a ladle on a vibrating stand to produce vanadium slag;

- high viscosity of the resulting slag;

- a relatively low content of vanadium pentoxide in the slag;

- irretrievable loss of vanadium with slag from smelters containing 0.9% V ₂ O ₅ .

The closest in technical essence and the achieved effect to the proposed method is a method for the production of vanadium-containing slag during converter conversion of vanadium low-silicon cast iron to NTMK, obtained by processing vanadium-containing titanomagnetite ores [2], namely, that vanadium low-silicon cast iron converter 165 is cast into cast iron then an oxidizing agent-cooler — mill scale in the amount of 70-80 kg / ton of pig iron is planted in the converter for cooling and adjusting the oxidation of the final slag. After that, a water-cooled lance is lowered to 1-2 m above the metal level and the cast iron is blown with technical oxygen with a flow rate of 300-400 m ³ / min (10-14 m ³ / t of cast iron) for 7-9 minutes. Purging of cast iron with oxygen is accompanied by the oxidation of elements V, Si, Ti, Mn, Fe with almost the same speed and a very rapid increase in temperature.

The process of cast iron devanadation is carried out in the range from 1230-1260 to 1340-1420 ° C with an optimum of 1360-1380 ° C, with oxygen purging, as a rule, for 7-8 minutes; after lowering [C] to 3.5-3.8% and [V] less than 0.04-0.06%, the oxygen blast is switched off and through the same lance, one argon is blown from above (without immersion in metal) with a flow rate of up to 100 m ³ / min (100/165 = 0.6 m ³ / (t · min) for 1-2 minutes. The average chemical composition of the resulting commercial vanadium slag according to the prototype (manufactured by NTMK) is as follows,%:

Slag fully satisfies the conditions for chemical processing of higher grades of vanadium pentoxide (ШВд1 and ШВд2 according to TU 14-11-178-86).

The disadvantages of the method:

- the chemical composition of the slag determines the high viscosity and relatively low content of vanadium pentoxide and allows it to be used only for chemical processing into vanadium pentoxide, which is accompanied by a high cost and environmental problems during such a redistribution;

- the relatively low content of vanadium pentoxide in the resulting slag (according to the prototype) in combination with a high content of iron oxides and high viscosity do not allow to obtain commercial ferrovanadium directly from it.

So from the slag composition NTMK (composition see above) was obtained metal containing,%, [3]:

While in accordance with GOST 27130-94 the chemical composition of the commodity, the poorest, ferrovanadium FVd40U0.5-1 must meet the following,%:

Vanadium slag is a key product of vanadium redistribution, in which vanadium is in concentrated form.

The cost of vanadium in slag is much lower (25-30%) than in pentoxide and ferrovanadium.

The invention is directed to the production of V-slag, which makes it possible to directly produce commercial ferrovanadium (of the type ФВд40У0,5-ФВд40У1).

This problem is solved by the fact that in the method of producing vanadium-containing slag during the devanization of low-silicon cast iron, which includes casting iron into a steelmaking unit, heating the smelter in a given interval, doping, oxidizing impurities of cast iron and the formation of V-containing slag, mixing with argon, separate release of metal (semi-product ) and V-slag, according to the invention, the devanization of low-silicon cast iron is carried out in an arc furnace with heating and temperature control of the process by electric arcs, continuous g Ubin stirring melting purging with argon (through the bottom or through submerged tuyeres) having a specific intensity of 0.01-0.03 m ³ / (min · m), a gradual scale unit dose additive in an amount of 4-8% by weight of iron (metal) and soda in the amount of 7-10% by weight of the slag, providing during the oxidation period of the pig iron elements in the slag the content of FeO 10-17% and the ratio (Na ₂ O) / (V ₂ O ₅ ) in the range of 0.3-0.5; the devanadation process is completed when the ratio in the slag V / Fe = 1.3-2.3 and a temperature of from 1421 to 1470 ° C; at a temperature of 1421 to 1470 ° C, carbon is introduced into the slag volume in small-sized or powder form (coke, graphite, etc.) until the V / Fe ratio in the range of 1.3-2.3 is obtained in the slag, after which the process of pig iron devanation is completed ( turn off the current).

The input of thermal energy by electric arcs makes it possible to fully realize the endothermic processes of oxidation of iron elements only by iron oxides (FeO and Fe ₂ O ₃ ) of the forming slag phase. In this case, in contrast to the oxidation of iron elements by gaseous oxygen, Fig. 1, the process of vanadium oxidation by iron oxides of the slag phase takes precedence (the negative Gibbs energy in this case is greater for the vanadium oxidation reaction, Fig. 2, and an increased content of vanadium oxides in the slag is ensured due to less dilution by incoming Si, Ti, Mn oxides) .

The process is controlled by mass transfer in the slag phase. Therefore, it is necessary to mix both the metal and the slag in the process of devanation from the beginning to the end. At the same time, deep purging provides greater mixing energy, compared to surface, with equal gas flow rates or allows reducing gas consumption with equal mixing energy. When the gas flow rate is less than 0.01 m ³ / (t · min), the mixing energy is not enough. At a flow rate greater than 0.03 m ³ / (t · min), the resistance of the furnace lining deteriorates.

The control of the energy input by electric arcs ensures the process of devanadation with liquid slag. During the operation of electric arcs, the slag temperature is on average 100 ° C higher than that of metal. This helps to reduce the viscosity of V-slag.

The introduction of Na ₂ O into the V-slag within the range of Na ₂ O / V ₂ O ₅ = 0.3-0.5 provides an optimal technological viscosity of about 0.3 Pz. When Na ₂ O / V ₂ O ₅ <0.3, a further decrease in viscosity is insignificant; an increase in the ratio of Na ₂ O / V ₂ O ₅ > 0.5 produces excessively liquid slags that reduce the durability of the furnace lining.

Direct measurements of the viscosity of vanadium-containing slags show that soda additives (Na ₂ CO ₃ ) significantly reduce their viscosity at temperatures above 1420 ° C. Above 1470 ° C, a decrease in viscosity is less noticeable and the production of excessively liquid slags is also undesirable.

The temperature increase in the production of commercial V-slag to 1421-1470 ° C is more appropriate at the end of the process. This contributes to an increase in the content in the slag (V ₂ O ₅ ) due to improved mass transfer between cast iron and slag, providing a high average value Lv = ~ 270-300. The vanadium recovery ratio is increased to 98%. At this time, it is advisable to add carbon to the slag, as a result of which there is a selective reduction of iron oxides in the slag and it becomes possible to promptly influence the production of the required contents of vanadium and iron oxides in the slag. In this case, the ratio of V / Fe in it increases. It is desirable to produce carbon additives until V / Fe ratios in the range of 1.3 to 2.3 are obtained in the slag (see Fig. 3 below). Exceeding the specified limits of the ratio leads to a decrease in the content of V ₂ O ₅ in the slag.

For the process of devanation to proceed, the actual content of vanadium in the metal should be higher than the equilibrium [Vp]. We determined the values of [V] p in cast iron, depending on the temperature and composition of V-slags, table. one.

It can be seen that with an increase in the process temperature of 1470 ° C, content in the slag (V ₂ O ₅ ) and a decrease in activity (FeO), the vanadium content in the cast iron [V] p equilibrium with the slag increases to 530 · 10 ^-4 % (0.053%) . For the process of devanation to occur, it is necessary [V] f≥ [V] p. We take the most often obtained actual value [V] f = 600 · 10 ^-4 %> 530 · 10 ^-4 %. The actual distribution coefficient of vanadium between the metal and slag at optimal cast iron devanadation is known in the range Lv = (V) / [V] = 248-313, [2]; 270, [4]. With this in mind, the content of vanadium in the slag (V) should be in the range (V) = Lv · [% V] f = (248 · 0.06–313 · 0.06) = 14.9–18.8%, which corresponds to the content in the slag of 27-32% V ₂ O ₅ .

Empirically established, Fig. 3, that the content in the slag of 27-32% V ₂ O _{5 is} achieved when the ratio (V) / (Fe) in the range of 1.3-2.3 (Fig. 3).

It was also experimentally established that when using slag with (V ₂ O ₅ ) less than 27%, the production of ferrovanadium directly with the vanadium content required by the standard (35-48%) does not work even with the aluminothermic process in an electric furnace. More than 32% (V ₂ O ₅ ) in the slag is not achieved with the devaluation of V-containing cast irons.

Entering scale of less than 4% does not provide a content of (FeO) ≥10% and oxidation of vanadium in the process of cast iron devandation, which provides the necessary ratio of Na ₂ O / V ₂ O ₅ in the slag (taking into account the significant consumption of scale and the oxidation of carbon) . An increase in the amount of scale more than 8% by weight of the metal (cast iron) leads to an excessive content of iron oxides in the slag (FeO)> 15% and to a decrease in the ratio of Na ₂ O / V ₂ O ₅ .

The process of vanadium oxidation according to the prototype is accompanied by the formation of refractory (from _tmelt to 1750 ° C) thermodynamically stable vanadium-containing spinelids [2, p. 113].

The x-ray phase analysis of the slag obtained by the proposed method showed that the introduction of Na ₂ O into the slag (in practice in the form of soda ash Na ₂ CO ₃ ), ensuring the ratio of Na ₂ O / V ₂ O ₅ in the slag in a given range of contents and reduced in activity slag (FeO) leads to the formation of spinel without the participation of vanadium. Vanadium binds to compounds of magnesiopascolite type with the composition Ca ₂ Mg (V ₁₀ O ₂₈ ) that are thermodynamically lighter than vanadium reducible (which is essential when using slags to directly produce ferrovanadium by the metallothermic method). A change in the phase composition of the slag in this direction is also facilitated by an additional input of alumina (Al ₂ O ₃ ) to its composition up to 7-15%.

The method is as follows.

Example 1

V-containing cast iron at a temperature of 1250-1270 ° C is poured into an arc steel furnace. To facilitate and stabilize the ignition of the arc, a small amount of scale is planted at the beginning (it is possible together with oxidized pellets). Turn on the current and begin mixing the smelting with argon (or nitrogen) with an intensity of 0.01 m ³ (t · min) continuously until the release; regulate the melting temperature by the introduced electric power, gradually increase it at the end of the melting to 1421-1450 ° C; during the process, periodically (at intervals of 5-10 minutes), an express analysis of slag samples is performed on FeO, Na ₂ O and V ₂ O ₅ and, according to their results, gradually descaled using a system of storage, batching and automatic feeding of materials according to calculation in an amount of 8% by weight of metal and soda in an amount of 10% by weight of slag, the ratio of Na ₂ O to the resulting V ₂ O ₅ in the slag is maintained at 0.3 and the (FeO) content of 10-13%; at a temperature in the range of 1421-1450 ° C, carbon is introduced into the slag volume in the form of fine-lumped or powdery carbon (coke, graphite, etc.) in portions until the slag increases (V) / (Fe) = 1.3-1.7 ; when the ratio (V) / (Fe) = 1.3-1.7 is reached in the slag, the melting is completed (the current is turned off). Slag from the furnace is released (or downloaded) into a special slag. Metal is released separately into a bucket for further conversion to steel.

The composition of the resulting slag,%:

Example 2

Perform as well as in example 1, but with the following features: mixing with argon is carried out with an intensity of 0.03 m ³ / (t · min), the melting temperature is increased by electric arcs to 1421-1470 ° C, according to the results of slag analysis, gradually slag is planted in a total amount of 4% by weight of the metal and Na ₂ CO ₃ in an amount providing a ratio of Na ₂ O to the resulting V ₂ O ₅ in slag equal to 0.5; if necessary, to increase the V / Fe ratio in the slag in the range of 1421-1470 ° C, carbon is gradually added portionwise into it (for example, through the arch hole in the furnace arch (using an automated system of metered additives of materials) until the ratio in the slag V / Fe = 2.3; when the ratio V / Fe = 2.3 is reached, the smelting is completed (the current is turned off). Slag and metal are released separately.

The composition of the resulting slag,%:

Obtained by the proposed method, V-containing slag is used directly for the production of ferrovanadium. For comparison, slags of various compositions were used, table. 2.

The results of using slags of the known and proposed methods directly for the production of commercial ferrovanadium (by the method of metallothermal reduction in an electric furnace) are given in table. 3.

It is seen that in the V-alloy using slag obtained by the proposed method (slag No. 3), the content of vanadium is 1.5-2 times higher and meets the requirements for commercial ferrovanadium ([V] = 35-48%).

The technology for the production of ferrovanadium by the metallothermic method in an electric furnace provides, after the stage of reduction of vanadium from V-slag, the subsequent oxidation of [Si], [Mn] and [Al] in the same electric furnace with V-slag, learned by the proposed method (adding it to the metal surface after downloading the reduced slag). Therefore, ferrovanadium was obtained in all melts with contents not only [V], but also [% Si], [% Mn] and [Al] within the requirements of the standard.

Information sources:

1. Rohrmann J.S. Afr. Inst. Metall. V. 85, No. 5, 1985, S. 141-150.

2. Smirnov L.A., Deryabin Yu.A., Nosov S.K. and other Converter redistribution of vanadium cast iron. - Yekaterinburg: Sredneuralskoe Book Publishing House, 2000, p. 165-176.

3. Seregin A.N. g. Problems of ferrous metallurgy and materials science, 2010, No. 2, p. 1-9.

4. Seregin A.N., Mazurov E.F., Zaitsev A.I. g. Problems of ferrous metallurgy and materials science, 2009, No. 3, p. 33-38.

Claims (2)

1. A method for the production of vanadium slag suitable for directly producing commercial ferrovanadium from it, including pouring vanadium low-silicon cast iron into a steelmaking unit, additive oxidizing agents of scale, sinter, etc., the formation of oxidative slag and devanadation of cast iron in a given temperature range, stirring by blowing argon the release of metal (intermediate) and V-containing slag, characterized in that the devanization of low-silicon cast iron is carried out in an arc furnace with heating and regulation of t mperatury process arcs produce continuous stirring deep purge gases melting (argon, nitrogen through the bottom or through submerged tuyeres) having a specific intensity of 0.01-0.03 m ³ / (min • t), the additive produces a gradual scale unit dose in an amount of 4 -8% by weight of cast iron (metal) and soda in an amount of 7-10% by weight of slag; during the period of oxidation of the elements of cast iron, 10-15% FeO and the ratio (Na ₂ O) / (V ₂ O ₅ ) in the range of 0.3-0.5; when the ratio V / Fe = 1.3-2.3 and a temperature in the range of 1421-1470 ° C is reached in the slag, the process of cast iron devanadation is completed (the current is turned off). 2. The method according to p. 1, characterized in that at a temperature in the range from 1421 to 1470 ° C, carbon is introduced into the slag volume in small or powder form (coke, graphite) until a V / Fe ratio of 1.3 is obtained in the slag -2.3.

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