JP2003105421A - Method for removing vanadium in molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing vanadium in molten iron by which the vanadium concentration in the molten iron can sufficiently be reduced by effectively promoting the removal of the vanadium from the molten iron when a refining is performed in a pretreating process to the molten iron, or when blowing in a converter is performed. SOLUTION: (1) This method for removing the vanadium in the molten iron is peculiarly controlled to <=35 of CVO value=(WOR)<2> /(WCa O×WV) in the pretreating process to the molten iron, wherein, WCa O: CaO adding quantity (kg) when the refining is performed, WOR: oxygen amount (kg) except the oxygen consumed n an oxidized reaction with Si in the oxygen added amount when the refining is performed, and WV: V quantity (kg) at an initial stage in the molten iron. (2) The method for removing the vanadium in the molten iron is peculiarly performed by blowing in the converter under the condition satisfying 3.0<slag basicity (CaO/SiO2 ) in the furnace<5.0, 10%<(T.Fe) in the slag in the furnace <25%, 15 kg<slag quantity in the furnace (per 1 ton of the molten iron)<80 kg and 1600 deg.C<blowing-out temperature<1680 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field relating to a method for removing vanadium from molten iron, and more particularly, to devanadium from molten iron during refining in a hot metal pretreatment step or during blowing in a converter. , And belongs to the technical field of a method for reducing the vanadium concentration of molten iron.

[0002]

2. Description of the Related Art A hot metal pretreatment process for performing a dephosphorization process, a desulfurization process, etc. in a steelmaking process reduces the S concentration and P concentration of the hot metal and facilitates the C concentration and temperature adjustment in a converter. It is a thing. Valuable elements such as vanadium contained in the hot metal tapped from the blast furnace move into the slag in the hot metal pretreatment step, and also in the converter together with the dephosphorization process into the slag.

The vanadium removed from the hot metal in the hot metal pretreatment process and the converter process is processed as steelmaking slag. Conventionally, various methods have been proposed for recovering vanadium in hot metal or molten steel containing vanadium. Has been done. That is, a method of recovering vanadium is proposed by producing a vanadium compound by reacting hot metal containing vanadium under oxygen conditions, or by reacting with soda ash, and transferring the vanadium compound thus obtained into slag. Has been done.

For example, Japanese Patent Laid-Open No. 62-185821 discloses that
"To oxidize vanadium by subjecting molten steel containing vanadium and phosphorus to oxidizing conditions at 1650 ° C"
Furthermore, "the formation of the oxidizing condition is performed by blowing oxygen gas or adding Fe ₂ O ₃ " is described. Further, JP-A-55-94453 discloses that "adding an alkali metal compound to vanadium-containing hot metal and controlling oxidation at 1250 to 1500 ° C to migrate vanadium oxide into slag". ing. Furthermore, Japanese Patent Publication No. 58-38485 discloses a method for recovering vanadium from hot metal before charging a converter with the highest possible efficiency, "Phosphorus concentration of hot metal is dephosphorized by desiliconizing treatment. It is set to 0.080% or less, and vanadium in the hot metal is efficiently transferred to the slag produced by secondary dephosphorization, and vanadium is recovered from this slag. "

[0005]

However, in the above-mentioned conventional vanadium recovery technique, there is almost no mention of effectively reducing the vanadium concentration in the hot metal. For example, when the vanadium concentration of the hot metal to be used exceeds the upper limit of the intended product standard, no explicit condition has been proposed for reducing the vanadium concentration of the hot metal, and nothing is shown. Absent. In recent years, the concentration of vanadium contained in the hot metal may increase due to changes in the circumstances of raw materials such as ores supplied to the blast furnace or sintering. At that time, in the conventional hot metal pretreatment technology and converter blowing technology, the vanadium concentration of the molten steel after converter blowing may exceed the upper limit of the product specification.

The present invention has been made in view of such circumstances, and its purpose is to remove the molten iron from the molten iron during refining in the hot metal pretreatment step or during blowing in a converter. It is intended to provide a method for removing vanadium from molten iron, which can effectively promote vanadium and sufficiently reduce the vanadium concentration of molten iron.

[0007]

A method for removing vanadium from molten iron according to the present invention, which has been able to achieve the above object, is a method for removing vanadium from molten iron according to claims 1 to 6 (first invention to first invention).
A method for removing vanadium from molten iron according to a sixth aspect of the invention, which has the following configuration.

That is, the method for removing vanadium from molten iron according to claim 1 is as follows when refining in the hot metal pretreatment step.
It is a method for removing vanadium from molten iron, characterized in that the CVO value represented by (1) is controlled to 35 or less (first invention).
However, in the following formula (1), W _CaO : mass of CaO added during refining (kg), W _OR : mass of oxygen added during refining (: W _O ) in the oxidation reaction of Si in the hot metal Mass (kg) of oxygen other than consumed oxygen, W _V : initial mass (kg) of vanadium in the hot metal.

CVO value = (W _OR ) ² / (W _CaO × W _V ) --------- Equation (1)

In the method for removing vanadium from molten iron according to a second aspect of the present invention, the W _CaO and the W _CaO are _added depending on the initial concentration of Si in the hot metal.
_The method for removing vanadium from molten iron according to claim 1, wherein the ratio with _V is controlled to a value that satisfies the following formula (2) (second invention). However, in the following formula (2), [Si] is the initial concentration (mass%) of Si in the hot metal.

15 ≦ (W _CaO / W _V ) / [Si] ≦ 200 -------- Equation (2)

The method for removing vanadium from molten iron according to claim 3 is characterized in that the temperature of the hot metal after the completion of refining is controlled to 1200 to 1400 ° C (devanadium method for molten iron according to claim 1 or 2. 3 invention).

The method for removing vanadium from molten iron according to claim 4 is characterized in that blowing is carried out in a converter under conditions satisfying the following formulas (3), (4), (5) and (6). (4th invention). However, in the following formula (3), the basicity is the basicity [: CaO (%) /
SiO ₂ (%)]. In the formula (4) below, T.Fe is T.Fe (: total iron) in the slag in the furnace. In formula (5) below, the amount of slag in the furnace is 1 ton (t ・ s) of molten iron in the furnace.
The amount of slag (kg).

3.0 <Basicity (CaO / SiO ₂ ) <5.0 ------------ Formula (3) 10% <(T.Fe) <25% ---- -------------------- Formula (4) 15kg / t ・ s <In-furnace slag amount <80kg / t ・ s ------ Formula (5) 1600 ° C <blown-out temperature <1680 ° C ---------------- Formula (6)

In the method for removing vanadium from molten iron according to claim 5, when the required V removal rate represented by the following formula (7) is 50 to 80%, the following formulas (8), (9), (10) ) And (11) are blown, and the required V removal rate is 80 to 95%, conditions (12), (13), (14) and (15) below are satisfied. If the required V removal rate is 95 to 100%, blow it under the conditions that satisfy the following equations (16), (17), (18) and (19). A method for removing vanadium from molten iron according to claim 4 (5th invention). However, in the following formula (7), C _V0 is the concentration (%) of V before refining, which is the value of C _V0 shown in the following formula (20), and C _V1 is in the molten iron after the refining is completed. Is the target concentration (%) of V. In the following formulas (8) to (19), the basicity is the basicity in the furnace slag [: CaO (%) / SiO ₂ (%)], and T.Fe is the T.
Fe (: total iron) and the amount of slag in the furnace are the amount of slag (kg) per ton (t · s) of molten iron in the furnace.

Required V removal rate = [(C _V0 −C _V1 ) / C _V0 ] × 100 (%) ---- Formula (7)

When the required V removal rate = 50 to 80% 3.0 <Basicity (CaO / SiO ₂ ) <5.0 ------------ Formula (8) 10% <( T.Fe) <25% ------------------------ Equation (9) 15 kg / t ・ s <Slag amount in furnace <80 kg / t ・s ------ Formula (10) 1600 ° C <blown temperature <1680 ° C ---------------- Formula (11)

When the required V removal rate = 80 to 95% 3.4 <basicity (CaO / SiO ₂ ) <4.5 ------------ Formula (12) 12% <( T.Fe) <25% ------------------------ Formula (13) 20kg / t ・ s <Slag amount in furnace <80kg / t ・s ------ Formula (14) 1600 ° C <blowing temperature <1680 ° C ---------------- Formula (15)

When the required V removal rate = 95 to 100%, 3.8 <basicity (CaO / SiO ₂ ) <4.2 ------------ Equation (16) 15% <( T.Fe) <25% ------------------------ Equation (17) 25kg / t ・ s <Slag amount in furnace <80kg / t ・s ------ Formula (18) 1600 ° C <blown temperature <1680 ° C ---------------- Formula (19)

C _V0 = [total amount of V contained in the material charged in the converter (before refining) / amount of molten iron after refining] × 100 (%) ----------- ----- Formula (20)

In the method for removing vanadium from molten iron according to claim 6, the molten iron to be blown is desiliconized before the blowing.
The method for removing vanadium from molten iron according to claim 4 or 5, characterized in that molten iron subjected to dephosphorization treatment is used.
invention).

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is implemented, for example, in the following modes (modes 1 and 2).

[Mode 1] After the hot metal (containing vanadium) tapped from the blast furnace is charged into a hot metal pretreatment container, oxygen is blown into the hot metal, and an auxiliary material containing CaO is added to the hot metal. Pretreatment (desiliconization / phosphorus removal treatment).
At this time, the CVO value represented by the above equation (1) is controlled to be 35 or less. Alternatively, a condition that satisfies the above-mentioned expression (2) is set. By doing so, it is possible to carry out desiliconization and dephosphorization of the hot metal as well as devanadium that sufficiently reduces the vanadium concentration of the hot metal.

[Mode 2] After the hot metal (containing vanadium) tapped from the blast furnace is charged into a converter, oxygen is blown into the hot metal and an auxiliary material containing CaO and iron ore is added and blown. I do. At this time, the above equations (3), (4), (5)
And blowing is performed under the condition that (6) is satisfied. Alternatively, the conditions (8), (9), (10) and (11) above, or the conditions (12), (13), (14) and (15), or the expression ( The conditions satisfy 16), (17), (18) and (19).
Then, vanadium removal for sufficiently reducing the vanadium concentration of the hot metal can also be performed.

The present invention is implemented in such a form.

In order to develop a method for removing vanadium of molten iron in a hot metal pretreatment step and a method for removing vanadium of molten iron in a converter, the present invention carries out experiments under various conditions and analyzes the obtained data. It was completed based on the knowledge obtained as a result. That is, the inventors of the present invention, as a result of earnest studies, by adjusting the conditions in the hot metal pretreatment step to specific conditions, or by blowing in the converter to specific conditions, from molten iron It has been found that the vanadium deoxidization of can be effectively promoted and the vanadium concentration of molten iron can be sufficiently reduced, and the present invention has been completed based on this finding. The present invention thus completed relates to a method for removing vanadium from molten iron, which is the method for removing vanadium from molten iron according to claims 1 to 6 (the method for removing vanadium from molten iron according to the first invention to the sixth invention).

According to the method for removing vanadium from molten iron according to the first aspect of the present invention (claim 1), the CVO value represented by the above formula (1) is controlled to 35 or less during refining in the hot metal pretreatment step. As a result, vanadium removal from molten pig iron (molten iron) can be effectively promoted in the molten pig iron pretreatment step, and the vanadium concentration of molten iron can be sufficiently reduced. It should be noted that if the CVO value is controlled to 20 or less, the vanadium removal can be promoted more effectively, and if the CVO value is controlled to 10 or less, the vanadium removal can be promoted more effectively.

In the method for removing vanadium from molten iron according to the second aspect of the invention (claim 2), in addition to the requirements of the first aspect of the invention, the above equation (2) must be satisfied according to the initial concentration of Si in the hot metal. As a requirement, the oxygen amount necessary for the oxidation reaction of Si in the hot metal and the oxygen amount necessary for vanadium removal can be secured. That is, the vanadium removal can be controlled more effectively by controlling the optimum vanadium removal conditions according to the initial Si concentration. When (W _CaO / W _V ) / [Si] in the above formula (2) is set to 15 to 130, vanadium desorption can be promoted more effectively.

In the method for removing vanadium from molten iron according to the third invention (claim 3), in addition to the requirements of the first invention or the second invention, the hot metal temperature after refining is 1200 to 1400.
It is also a requirement to control the temperature at 0 ° C, which promotes the oxidation reaction equilibrium of vanadium. That is, by improving the efficiency of the devanadium reaction, the vanadium removal can be promoted more effectively. In addition, if the hot metal temperature after completion of the refining is controlled to 1250 to 1320 ° C., vanadium removal can be promoted more effectively.

According to the method for vanadium removal of molten iron according to the fourth aspect of the present invention (claim 4), the above-mentioned formula is used in the converter.
Blowing is carried out under the conditions that satisfy (3), (4), (5) and (6), which effectively promotes devanadium removal from molten iron in the converter and the vanadium concentration of molten iron. Can be sufficiently reduced.

In the method for vanadium removal of molten iron according to the fifth aspect of the present invention (claim 5), the required vanadium removal rate (de-V removal rate) is obtained under the conditions within the requirements of the fourth invention. Therefore, it is possible to perform vanadium removal without incurring an increase in the amount of auxiliary raw materials used and a decrease in iron yield. Can be obtained.

That is, since the vanadium removal reaction is an oxidation reaction, if the basicity (CaO / SiO ₂ ) of the slag in the furnace is too low, the V removal rate decreases, while the basicity (CaO / Si ₂ ) of the slag in the furnace decreases.
If the content of O ₂ ) is too high, poor slag formation occurs, the V removal rate decreases, the amount of auxiliary raw materials used increases, and the cost increases.

Regarding the total iron content (T.Fe) in the in-furnace slag, the higher it is, the more advantageous it is in terms of the V removal rate, but if it is too high, the iron yield decreases, the Mn yield decreases, and the converter furnace refractory This will shorten the life of the product. In operation, if (T.Fe) is raised too much to cause peroxide, sloping will occur.

A larger amount of in-furnace slag is naturally advantageous for vanadium removal, and there is a necessary amount depending on the conditions. However, if this amount is too large, the amount of auxiliary raw material used increases and the cost rises. The iron yield is also reduced. Therefore, it is desirable to reduce the amount of in-furnace slag as much as possible within a range where the V concentration in molten iron at the time of blowing is satisfied. However, if the amount of slag in the furnace is reduced too much, the cover slag that covers the molten steel surface disappears, leading to a decrease in the life of the refractory of the converter. In addition to the above problems, the yield of iron decreases.

A lower blowout temperature is more advantageous in terms of vanadium removal, but this is determined in consideration of the type of steel and the temperature drop in the steps after the converter and cannot be largely controlled.

The method for removing vanadium from molten iron according to the fifth aspect of the invention (claim 5) takes the above into consideration, and conditions are set according to the required V removal rate so as not to cause the above-mentioned negative side. Is defined. Therefore, vanadium can be removed and the required V removal rate can be obtained without causing negative effects such as an increase in the amount of the auxiliary raw material used and a decrease in iron yield.

In the method for removing vanadium from molten iron according to the sixth aspect of the present invention (claim 6), in addition to the requirements of the fourth or fifth aspect of the invention, desiliconization before the blowing is performed as molten iron for blowing. It is also a requirement to use molten iron that has been dephosphorized,
This makes it possible to easily adjust the C concentration and temperature during blowing in the converter. Further, in converter blowing using molten iron that has been subjected to desiliconization / dephosphorization treatment, there is almost no need to perform desiliconization / dephosphorization treatment, so normally, in order to pursue cost merit, reduction of slag amount and ( T.Fe) is reduced. This is disadvantageous for vanadium removal, and the conventional conventional method often causes the target concentration of V to deviate from the upper limit. Therefore, if the control is performed within the range of the present invention, it is possible to obtain a necessary V-elimination ratio and prevent V deviation.

In the present invention, the mass of oxygen added during refining in the hot metal pretreatment step, that is, W _O , means the amount of oxygen (so-called solid acid) in oxides such as iron oxide added as a refining agent, Oxygen blown in (so-called vapor acid)
And the total amount of oxygen. The former solid acid is consumed by participating in dephosphorization reaction and vanadium reaction, and the latter gas acid is consumed by participating in oxidation reaction of Si in hot metal.

As described above, W _OR is the mass of oxygen other than oxygen consumed in the oxidation reaction of Si in the hot metal in the mass of oxygen added during refining (: W _O ). That is, W
_OR = W _O - a [mass of oxygen consumed in the oxidation reaction (hexane + Katasan) of Si], in other words, W _OR is not contribute to the oxidation reaction of Si among oxygen addition during refining It is the mass of solid acid + gas acid.

Molten iron naturally includes molten iron, but in the present invention, molten steel is also included. That is, the molten iron is charged into the converter, and the components are usually adjusted in the converter to form molten steel. However, this molten steel is also the molten iron at the time of charging the converter, so it is expressed as molten iron in the present invention. Therefore, the devanadium removal method according to the present invention may be called a devanadium removal method for hot metal and molten steel in a strict sense, but it is expressed as a vanadium removal method for hot metal.

In the above formula (20), the material charged in the converter means the molten iron charged in the converter and the other materials. The materials other than the molten iron include scraps, auxiliary materials, slag, etc., depending on the case. That is,
Molten iron is always charged to the converter, and in addition to this, scrap, auxiliary materials, slag, etc. are charged, but not all of the latter ones are charged. Depends on the case. V contained in the material charged in the converter
The total amount (before refining) of is the total amount of V contained in the material charged in the converter. For example, when each of the materials charged in the converter contains V, it means the total amount of V.

[0042]

EXAMPLES Examples and comparative examples of the present invention will be described below.
The present invention is not limited to this embodiment.

[Example 1] Table 1 shows the components and temperatures of the hot metal tapped from the blast furnace. After loading 90 t (tons) of this hot metal into a converter-type hot metal pretreatment container, auxiliary materials such as lime and scale are charged from above, and further oxygen is blown into the hot metal using an oxygen lance while further adding lime. And scale mixed powder (lime: 56.0% by mass, scale (Fe ₂ O ₃ ): 4
4.0 mass%] was blown into the hot metal from the injection lance to perform a pretreatment (desiliconization / dephosphorization treatment) of the hot metal. The initial mass W _V of vanadium in the hot metal is 27 kg.

At this time, the amount of lime charged from above is 95
0kg, the amount of powder blown from the injection lance is 1250kg, the amount of oxygen blown from the oxygen lance is 4
It was set to 03 Nm ³ . That is, the amount of oxygen used for desiliconizing the hot metal is 403 Nm ³ . The total amount of this gaseous acid and the solid acid from the scale (Fe ₂ O ₃ ) is 651 Nm ³ . The sum of the amount of lime charged from above and the amount of lime in the powder is 1650 kg in total. That is,
W _CaO : 1650 kg, W _O : 160 kg, W _OR : 770 kg
And As a result, the CVO value represented by the above equation (1) was controlled to 13. Note that (W _CaO /
The value of W _V ) / [Si] is 191.

Table 2 shows the components and temperatures of the hot metal after the hot metal pretreatment. As can be seen from Tables 1 and 2, the amounts of Si, P and V are greatly reduced by the hot metal pretreatment, and vanadium is effectively removed together with desiliconization and dephosphorization. High phosphorus rate and V removal rate.

[Comparative Example 1] Table 3 shows the components and temperature of the hot metal tapped from the blast furnace. After loading 90 tons of this hot metal into a converter-type hot metal pretreatment container, lime and auxiliary materials such as scales were charged from above, and oxygen was blown into the hot metal using an oxygen lance to further add lime and scale. The mixed powder [lime: 56.0% by mass, scale (Fe ₂ O ₃ ): 44.0% by mass] was blown into the hot metal from the injection lance to carry out a pretreatment (desiliconization / dephosphorization treatment) of the hot metal. The initial mass W _V of vanadium in the hot metal is 27 kg.

At this time, the amount of lime charged from above is 58
0kg, the amount of powder blown from the injection lance is 1180kg, the amount of oxygen blown from the oxygen lance is 4
It was set to 18 Nm ³ . That is, the amount of oxygen used for desiliconizing the hot metal is 418 Nm ³ . This gas acid and the solid acid from the scale (Fe ₂ O ₃ ) are combined to give a total of 880 Nm ³ . The sum of the amount of lime charged from above and the amount of lime in the powder gives a total of 1218 kg. That is,
W _CaO : 1218 kg, W _O : 137 kg, W _OR : 1120
It was set to kg. As a result, the CVO expressed by the above equation (1) is obtained.
The value is 38, which is the CVO in the case of the first embodiment.
CVO value larger than the above value and defined by the present invention: 3
It does not satisfy 5 or less. In addition, (W in the above equation (2)
The value of _{CaO / W V) / [Si} ] has become a 129.

Table 4 shows the components and temperatures of the hot metal after the hot metal pretreatment. As can be seen from Tables 3 and 4, desiliconization and dephosphorization are effectively performed by the above-described hot metal pretreatment as in the case of Example 1, but devanadium is removed in the case of Example 1 above. It is inferior to the above, the degree of decrease in the amount of V is small, and the V removal rate is small.

[Experimental Example 1] CV represented by the above equation (1)
FIG. 1 shows an example of the relationship between the O value and the V removal rate ΔV obtained by the experiment. This V removal rate (ΔV) is ΔV
(% × 10 ³ ) = 100 × 10 ³ × [(V concentration in hot metal before treatment)-(V concentration in hot metal after treatment)] / (V concentration in hot metal before treatment). Although this data has some variations, it can be seen that the V removal rate (ΔV) can be adjusted by the CVO value. Especially when the CVO value is 10 or less,
It can be seen that the rate is large and the V removal is effectively promoted.

In FIG. 1, the data of the example shows the result in the case of the above-mentioned example 1, and the data of the comparative example shows the result in the case of the above-mentioned comparative example 1. It can be seen from FIG. 1 that the CVO value in the case of Example 1 is smaller than that in Comparative Example 1 and the resulting deV removal rate is excellent.

Example 2 and Comparative Example 2 After the hot metal tapped from the blast furnace was charged into the converter, oxygen was blown into the hot metal, and by-products containing quick lime, fluorite, iron ore and light dross were added. Raw materials were added and blowing was performed.

At this time, as the converter, a top-bottom blow type 24
A 0t converter was used. The V content of the molten pig iron charged to the converter, that is, the initial concentration of V (C _V0 ) is 0.005 to 0.060 mass%. The temperature of the molten iron charged into the converter is 1250 to 14
It is 00 ° C. Regarding blowing conditions, the basic unit of top-blown oxygen: 42 to 52 Nm ³ / t, the upper-blown oxygen supply rate: 2.0
~ 4.0 Nm ³ / t ・ s, basicity in furnace slag (CaO (%)
/ SiO ₂ (%): 2.0 to 6.0, total iron content (T.Fe) in the furnace slag: 5 to 35%, furnace slag content: 0 to 100
kg / t · s, blowing stop temperature: 1580 to 1720 ° C.

As for the basic unit of the auxiliary raw material, quick lime: 0
30kg / t, fluorite: 0-4kg / t, iron ore: 7-25kg
/ T, light drop: 0 to 20 kg / t.

The results of the above blowing will be described below. In addition, the following vanadium removal rate (V removal rate) is the V removal rate (%) shown by the following formula (22).

V removal rate = [(C _V0 −C _VX ) / C _V0 ] × 100 (%) ---- Formula (22)

However, in the above formula (22), C _V0 is the concentration (%) of V before refining, and C represented by the following formula (23)
It is the value of _V0 , and C _VX is the concentration (%) of V in the molten iron after the completion of refining.

C _V0 = [total amount of V contained in the material charged in the converter (before refining) / amount of molten iron after refining] × 100 (%) ----------- ----- Formula (23)

As a result of the above-mentioned blowing, first, the relationship between the basicity (CaO (%) / SiO ₂ (%)) (hereinafter also referred to as C / S) of the in-furnace slag and the vanadium removal rate is shown in FIG. . When C / S is low, the vanadium removal rate (V removal rate) is small, and when C / S is high, the V removal rate is large, but when C / S is too high, the V removal rate is small, and C / S: It can be seen that in the case of 3.0 to 5.0, the V removal rate is high and a good V removal rate can be obtained.

FIG. 3 shows the relationship between the (T.Fe) of the in-furnace slag and the vanadium removal rate. When (T.Fe) is low, the V removal rate is low, and when (T.Fe) is high, the V removal rate is high, and (TF
e): A good V removal rate is obtained at 10% or more. However, if (T.Fe) exceeds 25%, the yield of iron decreases. Therefore, it is understood that (T.Fe) should be 10 to 25%.

FIG. 4 shows the relationship between the amount of slag in the furnace and the vanadium removal rate. If the amount of slag in the furnace is small, the V removal rate is small,
When the amount of slag in the furnace increases, the V removal rate increases, and when the amount of slag in the furnace: 15 kg / t · s or more, a good V removal rate is obtained. However, if the amount of slag in the furnace exceeds 80 kg / t · s, the amount of auxiliary raw materials used increases and the iron yield decreases. Therefore, it is understood that the amount of slag in the furnace should be 15 to 80 kg / t · s.

FIG. 5 shows the relationship between the blowout temperature and the vanadium removal rate.
Shown in. It can be seen that the blowout temperature does not significantly affect the V removal rate, but the V removal rate decreases when the blowout temperature exceeds 1680 ° C. Further, if the blowing stop temperature exceeds 1680 ° C., the life of the refractory material is shortened. On the other hand, set the blowout temperature to 1
If the temperature is 600 ° C. or lower, there are problems such as restrictions on the steel types to which converter blowing can be applied. Therefore, the blowout temperature is 1
It is understood that the temperature is preferably 600 to 1680 ° C.

Among the results of the above blowing, the case of the example of the present invention (the method of the present invention) in which the conditions of the present invention are satisfied and the conditions of the example in which the conditions of the present invention are not satisfied are used. In the case of the smelted comparative example (prior art), the V content at the time of charging the hot metal into the converter (the V concentration before refining, that is, the above formula (2
The V concentration shown in 3): C _V0 ) and the V concentration after blowing off the converter (concentration of V in molten iron after the end of refining: C _VX ) are shown in FIG. In the case of the embodiment of the present invention, the V concentration before refining (C _V0 ) is higher than in the case of the comparative example, but the rate of decrease of the V concentration with the elapsed time of blowing is large, and the V removal rate is high. And the V concentration (C _VX ) at the time of blowing off the converter is extremely low. In the case of the comparative example, the standard upper limit value of V concentration: 0.006
However, in the case of the examples of the present invention, the V concentration (C _VX ) at the time of blowing off the converter is extremely lower than the standard upper limit value: 0.006 mass%, and the V concentration standard is sufficiently satisfied. Meet

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

[Table 3]

[0066]

[Table 4]

[0067]

INDUSTRIAL APPLICABILITY According to the method for vanadium removal of molten iron according to the present invention, the vanadium concentration of molten iron can be sufficiently reduced by effectively promoting the removal of vanadium from molten iron during refining in the hot metal pretreatment process. become able to. Further, it becomes possible to effectively promote vanadium removal from molten iron at the time of blowing in the converter, and to sufficiently reduce the vanadium concentration of molten iron.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a CVO value and a ΔV value of a V removal rate according to Experimental Example 1.

FIG. 2 is a diagram showing a relationship between C / S of basicity of slag and a vanadium removal rate according to Example 2 and Comparative Example 2.

FIG. 3 shows (TF of slag according to Example 2 and Comparative Example 2).
It is a figure which shows the relationship between e) and a vanadium removal rate.

FIG. 4 is a diagram showing a relationship between an in-reactor slag amount and a vanadium removal rate according to Example 2 and Comparative Example 2.

FIG. 5 is a graph showing a relationship between a converter blowing temperature and a vanadium removal rate according to Example 2 and Comparative Example 2.

FIG. 6 at the time of hot metal charging and at the time of blowing stop according to the method of the invention and according to the prior art
It is a figure which shows [V] (namely, V density).

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Claims (6)

[Claims] 1. A method for removing vanadium from molten iron, wherein the CVO value represented by the following formula (1) is controlled to 35 or less during refining in the hot metal pretreatment step. CVO value = (W _OR ) ² / (W _CaO × W _V ) -------- Formula (1) However, in the above formula (1), W _CaO : Mass of CaO added during refining (kg) , W _OR : Mass of oxygen other than oxygen consumed for oxidation reaction of Si in hot metal in mass of oxygen added during refining (: W _O ), W _V : Initial vanadium content in hot metal Mass (kg). 2. The W according to the initial concentration of Si in the hot metal
2. The vanadium removal method for molten iron according to claim 1, wherein the ratio of _CaO and W _V is controlled to a value that satisfies the following formula (2). 15 ≦ (W _CaO / W _V ) / [Si] ≦ 200 -------- Equation (2) However, in the above equation (2), [Si]: initial concentration of Si in the hot metal (mass%) Is. 3. The hot metal temperature after the refining is 1200 to 14
The method for removing vanadium from molten iron according to claim 1 or 2, wherein the temperature is controlled to 00 ° C. 4. A method for removing vanadium from molten iron, which comprises performing blowing in a converter under conditions satisfying the following formulas (3), (4), (5) and (6). 3.0 <basicity _{(CaO / SiO 2) <5.0} ------------ formula (3) 10% <(T.Fe ) <25% ------- ----------------- Equation (4) 15 kg / t · s <In-furnace slag amount <80 kg / t · s ------ Equation (5) 1600 ° C < Blown temperature <1680 ° C ---------------- Formula (6) However, in the above formula (3), the basicity is the basicity [: CaO (% ) / SiO ₂ (%)]. Equation (4)
At, T.Fe is T.Fe in the furnace slag (: total iron)
Is. In the above formula (5), the amount of slag in the furnace is the amount of slag (kg) per ton (t · s) of molten iron in the furnace. 5. The required V removal rate represented by the following formula (7) is 50:
In the case of 80%, the following formulas (8), (9), (10) and
Blowing under conditions that satisfy (11), the required V removal rate is 80-
In the case of 95%, the following formulas (12), (13), (14) and (1
Blowing is performed under the conditions that satisfy 5), and the required V removal rate is 95-1.
When it is 00%, the following formulas (16), (17), (18) and (1
The method for removing vanadium from molten iron according to claim 4, wherein the blowing is performed under a condition that satisfies 9). Required de-V ratio = [(C _V0 −C _V1 ) / C _V0 ] × 100 (%) ---- Formula (7) When required de-V ratio = 50 to 80% 3.0 <basicity (CaO / SiO ₂ ) <5.0 ------------ Formula (8) 10% <(T.Fe) <25% ---------------- -------- Formula (9) 15kg / t ・ s <Furnace slag amount <80kg / t ・ s ------ Formula (10) 1600 ℃ <Blowout temperature <1680 ℃ --- ------------- case of formula (11) requires removal V rate = 80% to 95% 3.4 <basicity _{(CaO / SiO 2) <4.5} ------ ------ Formula (12) 12% <(T.Fe) <25% ------------------------ Formula (13) 20kg / T ・ s <amount of slag in the furnace <80 kg / t ・ s ------ Formula (14) 1600 ° C <blowing temperature <1680 ° C ---------------- Formula (15) When the required V removal rate = 95 to 100% 3.8 <Basicity (CaO / SiO ₂ ) <4.2 ------------ Formula (16) 15% < (T.Fe) <25% ------------------------ Equation (17) 25kg / t ・ s <amount of slag in the furnace < 80 kg / t · s ------ Formula (18) 1600 ° C <blown-out temperature <1680 ° C ---------------- Formula (19) However, the above formula (7 ), C _V0 is the concentration (%) of V before refining and is the value of C _{V0 represented by} the following formula (20), and C _V1 is the target concentration of V in molten iron after the refining is finished ( %)
Is. In the above formulas (8) to (19), the basicity is the basicity in the furnace slag [: CaO (%) / SiO ₂ (%)], and T.Fe is the T.Fe (: total in the furnace slag. Iron) and the amount of slag in the furnace are the amount of slag (kg) per ton (t · s) of molten iron in the furnace. C _V0 = [total amount of V contained in the material charged in the converter (before refining) / amount of molten iron after finishing refining] × 100 (%) -------------- -Formula (20) 6. The method for removing vanadium from molten iron according to claim 4, wherein the molten iron to be blown is a molten iron which has been subjected to desiliconization / phosphorus removal treatment before the blowing.