TWI568856B - Dephosphorizing treatment method for molten iron - Google Patents

Description

Dephosphorization treatment method of molten iron

The invention relates to a dephosphorization treatment method for molten iron, wherein the dephosphorization treatment method of the molten iron is to blow oxygen from the molten iron in the converter type refining furnace from the top blowing spray gun, and through the top blowing spray gun The collision surface of the oxygen and the molten iron bath surface is blown with a solvent for dephosphorization containing CaO as a main component.

In recent years, in the iron and steel plants with blast furnaces and converters, the iron and steel plants have been operating in a steel plant. Because of their advantages in terms of cost and quantity, the following refining methods are widely carried out, that is, the molten iron is removed before decarburization and refining in the converter. Phosphorus treatment (also referred to as "pre-dephosphorization treatment") is used as a pretreatment to remove phosphorus from the molten iron in advance. It is based on the principle that, thermodynamically, the lower the refining temperature, the easier the dephosphorization reaction is, that is, the dephosphorization reaction is easily carried out in the molten iron stage where the temperature is lower than the molten steel stage, so that a small amount of refining agent can be utilized. Dephosphorization refining is carried out.

The dephosphorization treatment of the molten iron is carried out by adding a solvent for dephosphorization containing CaO as a main component such as quicklime, and adding an oxygen source such as oxygen or iron oxide as a dephosphorization agent, and using a dephosphorization agent (oxygen) The source of the phosphorus in the molten iron, the resulting phosphorus oxide (P ₂ O ₅ ) as a stable form of the compound 3CaO. P ₂ O ₅ (also referred to as "Ca ₃ (PO ₄ ) ₂ ") is fixed in slag formed by slagging of a solvent for dephosphorization. That is, the solvent for dephosphorization used contains CaO as a necessary condition.

As described above, in the dephosphorization treatment of the molten iron, the supply of the oxygen source such as oxygen and the CaO in the slag play an important role. Therefore, in the dephosphorization treatment of molten iron, a plurality of methods have been proposed: a method of increasing the ratio of the supply rate of the oxygen source to the supply rate of CaO, and improving the dephosphorization efficiency, or FeO for the generated slag. A method in which the concentration is specified to increase the dephosphorization efficiency.

For example, in Patent Document 1, a method is proposed in which a dephosphorization solvent is used when an oxygen source is added to the molten iron in the dephosphorization treatment of the molten iron, and the oxygen source is added at a rate of X (kg/min). When the addition rate of the CaO conversion is Y (kg/min), the solvent for dephosphorization as a CaO source is added to the condition that the addition rate X of the oxygen source satisfies "0.50 ≦ X / Y ≦ 2.0". The molten iron is processed by molten iron. The method is a method in which FeO is produced by a supplied oxygen source to increase the FeO concentration in the slag, thereby improving the dephosphorization efficiency.

Further, Patent Document 2 proposes a method of using a furnace in the form of a converter to dephosphorize molten iron using a solvent for dephosphorization which does not substantially contain fluorine, and CaO in the slag after dephosphorization treatment slag basicity ((mass% CaO) / (mass% SiO ₂₎₎ SiO ₂ mass ratio of the concentration that is defined at 2.5 or more and 3.5 or less, and that the temperature of the molten iron after the dephosphorization at least 1380 and 1320 ℃ Below °C, and from the 60% of the total blowing time to the end of the blowing, the bottom blowing gas flow rate is maintained at 0.18 Nm ³ /min or less per ton of molten iron, thereby melting after the dephosphorization treatment. The dephosphorization treatment is carried out in the slag in which the T.Fe concentration is 5% by mass or more.

Further, in Patent Document 3, a method for producing a low-phosphorus molten iron in which gaseous oxygen is blown by a top-blowing lance and a refining agent as a source of CaO, and the amount of slag after treatment is 30 kg/ton or less is used. The following method is proposed: a method of dephosphorizing molten iron having a niobium content of 0.15% by mass or less, or a supply rate of gaseous oxygen (Nm ³ /(min. molten iron-ton)) and a simple CaO component in a refining agent A method in which the ratio of the supply speed (kg/(min. molten iron-ton) is within a predetermined range.

Further, Patent Document 4 proposes a method for dephosphorizing a molten iron by using a furnace in the form of a converter, and blowing a powder containing CaO from a spray gun and an oxygen-containing gas without using a substance containing CaF ₂ In the dephosphorization treatment, the top blowing speed (kg/min) of the CaO component in the CaO-containing powder and the mass of oxygen are obtained for the molten iron having a niobium content [Si] (% by mass) before the treatment of 0.30 or more. The ratio of the flow rate (kg/min) is in the range of 0.56 + 0.5 × [Si] - 0.56 + 1.5 × [Si].

Prior art literature

Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2007-92181

Patent Document 2: Japanese Patent Laid-Open Publication No. 2008-106296

Patent Document 3: Japanese Patent Laid-Open Publication No. 2004-83989

Patent Document 4: Japanese Patent Laid-Open No. 2011-12286

However, the following problems exist in the prior art.

That is, in Patent Document 1, the rate of addition of the oxygen source and the dissolution of dephosphorization Since the ratio of the CaO conversion rate (X/Y) of the agent is wide, the high dephosphorization amount cannot be maintained under the condition that the ruthenium content of the molten iron is high. That is, it is not possible to stably carry out an efficient dephosphorization treatment without being affected by the niobium content of the molten iron. Therefore, in the operation of increasing the content of ruthenium in the molten iron which is a heat source to promote the melting of the cold iron source in the dephosphorization treatment, the technique of Patent Document 1 cannot be applied. The inventors of the present invention have confirmed that Patent Document 1 is suitable for the case where the cerium content of the molten iron is 0.10% by mass or less.

In the patent document 2, the basicity of the slag after the dephosphorization treatment is defined, and although the alkalinity of the slag is an important factor in the dephosphorization treatment, the slag after the dephosphorization treatment is ensured as in Patent Document 2. Alkalinity also causes insufficient dephosphorization. In other words, as in Patent Document 2, only the alkalinity of the slag after the dephosphorization treatment is regulated, and efficient dephosphorization treatment cannot be stably performed.

Patent Document 3 teaches that in the dephosphorization treatment method in which the refining agent as the CaO source and the molten iron of the gaseous oxygen are blown out, the ratio of the supply rate of the gaseous oxygen to the supply rate of the pure CaO component contributes to the molten iron in a specific range. Dephosphorization. However, the premise of the above technology is that the ruthenium content of the molten iron before the treatment is as small as, for example, 0.15% by mass or less, and the amount of slag after the treatment reaches 30 kg/ton or less of molten iron, when the melting of the ruthenium content is not sufficiently lowered. When the iron is subjected to dephosphorization treatment, there is a case where the dephosphorization efficiency is low and the phosphorus content of the molten iron cannot be sufficiently lowered.

In the dephosphorization treatment method of the molten iron containing the CaO powder and the gaseous oxygen in the top of the patent document 4, when the niobium content of the molten iron before the treatment is as high as 0.30% by mass or more, the top blowing speed for the simple CaO component ( Kg/min) and mass flow of oxygen The ratio of (kg/min) has given the criteria for operation. However, according to the method, the higher the niobium content of the molten iron before the treatment, the more appropriate the ratio of the ratio of the top blowing speed to the oxygen mass flow rate of the pure CaO component is on the high value side, and the total supply of oxygen is also increased. It is large. Therefore, when the content of bismuth in the molten iron is large, the supply amount of the powder containing CaO is excessive and the amount of slag is increased, so that it is difficult to carry out efficient dephosphorization treatment.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a dephosphorization treatment method for molten iron, in which a molten iron in a converter type refining furnace is blown with oxygen from a top blowing lance, and is passed through the top blowing lance When the collision surface of the oxygen and the molten iron bath surface is blown with a solvent for dephosphorization containing CaO as a main component, and the molten iron is subjected to dephosphorization treatment, the supply amount of oxygen from the top blowing spray gun is applied to the top blowing spray gun. The supply amount of the solvent for dephosphorization is appropriately adjusted, whereby the dephosphorization reaction can be efficiently performed.

The gist of the present invention for solving the above problems is as follows.

[1] A dephosphorization treatment method for molten iron, in which a molten iron in a converter type refining furnace is blown with oxygen from a top-blowing lance, and a collision surface of the oxygen and molten iron is blown to CaO via the top-blowing lance. a solvent for dephosphorization of a main component, wherein the phosphorus in the molten iron is oxidized by the oxygen, and the generated phosphorus oxide is introduced into the solvent for dephosphorization of the slag, thereby removing the molten iron Phosphorus, in the dephosphorization treatment method, when dephosphorization treatment is performed on the molten iron having a niobium content of 0.20% by mass or more before the dephosphorization treatment, when the oxygen supplied to the furnace is removed for the depurination reaction The amount of CaO in the dephosphorization solvent containing CaO as a main component added to the molten iron bath surface by blowing from the top-blowing lance is defined as the amount of oxygen in the deoxidized external oxygen (kilogram/ton of molten iron). (kg / ton of molten iron) The ratio of the amount of oxygen outside the deuterium [the amount of CaO/the amount of oxygen outside the deuterium] is less than 0.90, and the solvent for dephosphorization added to the top-blowing lance is blown according to the amount of oxygen outside the deodorization. The amount of addition is adjusted.

[2] The method for dephosphorization treatment of molten iron according to [1], wherein the ratio [CaO amount / deuterium outside oxygen amount] is in a range of 0.80 or more and less than 0.90.

[3] The method for dephosphorization of molten iron according to [1], wherein when the molten iron having a niobium content of 0.30% by mass or more before the dephosphorization treatment is subjected to dephosphorization treatment, it is supplied to the furnace. CaO has been removed to form CaO. When CaO of the CaO portion of SiO ₂ (calcium silicate) is defined as CaO outside the deuterium, the molten iron is subjected to the ratio of [CaO amount / deuterium outside oxygen amount] in the range of 0.80 or more and less than 0.90. In the case of dephosphorization treatment, CaO is mainly added to the top-blown spray gun by means of the above-mentioned deodorization CaO being in the range of 6 kg/ton of molten iron to 9 kg/ton of molten iron. When the amount of the solvent for dephosphorization of the component is adjusted, and the ratio of [the amount of CaO / the amount of oxygen outside the deuterium] is less than 0.80, the molten iron is subjected to dephosphorization treatment, and the dislocation is performed. The amount of addition of the solvent for dephosphorization containing CaO as a main component added to the top-blowing lance is adjusted in such a manner that the external CaO reaches 8 kg/ton or more.

According to the present invention, the ratio of the amount of CaO in the solvent for dephosphorization using CaO as a main component added from the top-blowing lance to the amount of oxygen released from the outside (the amount of CaO/the amount of oxygen outside the deuterium) is controlled by CaO as a main component. The dephosphorization treatment is carried out in a range in which the dephosphorization efficiency of CaO in the solvent for dephosphorization is high. Therefore, the added dephosphorization solvent containing CaO as a main component absorbs the generated phosphorus oxide efficiently (P _{2 ).} O ₅ ), as a result, it is possible to carry out dephosphorization treatment more efficiently than in the prior art.

1‧‧‧ Converter type refining furnace equipment

2‧‧‧ Converter type refining furnace

3‧‧‧ 铁皮

4‧‧‧Refractory materials

5‧‧‧ top blow gun

6‧‧‧Outlet

7‧‧‧ bottom blowing vent

8‧‧‧Exhaust hood

9‧‧‧Material addition device

10‧‧‧ funnel

11‧‧‧cut out device

12‧‧‧Chute

13‧‧‧Oxygen supply tube

14‧‧‧Solvent supply tube

15‧‧‧Isolation valve

16‧‧‧Isolation valve

17‧‧‧Distributor

18‧‧‧ molten iron

19‧‧‧ slag

20‧‧‧CaO desolvent solvent

21‧‧‧ Iron Oxide

Fig. 1 is a schematic view showing an example of a converter type refining furnace apparatus suitable for carrying out the present invention.

Fig. 2 is a graph showing the relationship between the ratio [CaO amount/outer oxygen amount] and dephosphorization lime efficiency.

Figure 3 is a graph showing that the amount of deuterium outside the oxygen is 11 Nm ³ / molten iron - ton ~ 13 Nm ³ / molten iron - ton, so that the ratio [CaO amount / deuterium outside oxygen amount] is above 0.80 and not up to 0.90. A graph showing the relationship between the concentration of ruthenium in the molten iron before the dephosphorization treatment and the phosphorus concentration in the molten iron after the dephosphorization treatment.

4 is a graph showing the results of investigations on the relationship between the amount of CaO and the amount of dephosphorization when the ratio of [CaO amount/outer oxygen content] is less than 0.70.

FIG. 5 is a graph showing the results of investigations on the relationship between the amount of CaO and the amount of dephosphorization when the ratio of [CaO amount/outer oxygen content] is 0.70 or more and less than 0.80.

FIG. 6 is a view showing the results of investigations on the relationship between the amount of CaO and the amount of dephosphorization when the ratio of [CaO amount/outer oxygen content] is 0.80 or more and less than 0.90.

FIG. 7 is a view showing the results of investigations on the relationship between the amount of CaO and the amount of dephosphorization when the ratio of [CaO amount/outer oxygen content] is 0.90 or more and less than 1.00.

Fig. 8 is a graph showing the relationship between the carbon concentration in the molten iron after the dephosphorization treatment and the phosphorus concentration in the molten iron in Comparative Example 1 and Conventional Example 1.

Figure 9 is a comparative view showing the dephosphorization treatment in Example 2 of the present invention and Conventional Example 2 A graph showing the relationship between the concentration of rhodium in molten iron and the amount of CaO used in dephosphorization treatment.

Fig. 10 is a view showing, in contrast, the relationship between the concentration of bismuth in the molten iron before the dephosphorization treatment and the amount of dephosphorization of the molten iron in the dephosphorization treatment in the examples 2 and 2 in the present invention.

Hereinafter, the present invention will be specifically described.

The molten iron used in the dephosphorization treatment of the present invention is a molten iron produced by using a molten iron manufacturing facility such as a blast furnace, and uses a molten iron transfer container such as a molten iron drum or a mixed iron car to receive a molten iron manufactured by using a molten iron manufacturing facility. The molten iron received is transferred to a converter type refining furnace apparatus that performs dephosphorization treatment. When the cerium content of the molten iron is as high as, for example, more than 0.40% by mass, in order to efficiently perform the dephosphorization treatment using a small amount of the solvent for dephosphorization, the bismuth in the molten iron may be removed before the dephosphorization treatment (referred to as "melting". Iron dislocation treatment"). However, in the present invention, even if the molten iron having a high niobium content of 0.20% by mass or more of niobium content can be efficiently dephosphorized, it is not necessary to carry out the deodorization treatment.

In the case where the deodorization treatment is carried out, it is not necessary to carry out the deodorization treatment until the niobium content is less than 0.20% by mass, and the niobium content of the molten iron after the deodorization treatment may be 0.20% by mass or more. However, from the viewpoint of efficiently performing dephosphorization treatment using a small amount of solvent for dephosphorization, the niobium content of the molten iron is desirably 0.40% by mass or less. In other words, in the case of performing the deodorization treatment, it is preferred to apply the dephosphorization treatment method of the present invention after the niobium content of the molten iron is reduced to a range of 0.20% by mass or more and 0.40% by mass or less.

As means for lowering the niobium content of the molten iron to the above range, a method of supplying an oxygen source such as oxygen or iron oxide to the molten iron, and oxidizing the niobium in the molten iron to the oxide by the oxygen source may be used. The form of (SiO ₂ ) is forcibly removed. When the molten iron has been subjected to the deodorization treatment, the generated slag is discharged before the dephosphorization treatment.

The dephosphorization treatment of the molten iron can also be carried out in a molten iron transfer container such as a molten iron drum or a mixed iron car, but the converter type refining furnace is larger in free space than the molten iron transfer container, and can be used for the molten iron. By vigorously stirring, the dephosphorization treatment can be rapidly performed using a small amount of solvent for dephosphorization. Therefore, in the present invention, the dephosphorization treatment is carried out using a converter type refining furnace. Fig. 1 is a schematic view showing an example of a converter type refining furnace apparatus suitable for carrying out the present invention.

As shown in Fig. 1, the converter type refining furnace apparatus 1 includes a converter type refining furnace 2, which is formed of a metal shell 3, and is coated with a refractory material 4 on the inner side of the iron sheet 3, and a top blowing lance 5 inserted into the The inside of the converter type refining furnace 2 is movable in the vertical direction. In the upper portion of the converter type refining furnace 2, a discharge port 6 for discharging the treated molten iron 18 after the dephosphorization treatment is completed is provided, and in the bottom of the converter type refining furnace 2, it is provided to be used for blowing and stirring. The twyer 7 is blown with the bottom of the gas. The bottom blowing tuyere 7 is connected to a gas introduction pipe (not shown). Further, above the converter type refining furnace 2, a hood 8 for collecting the exhaust gas generated by the converter type refining furnace 2 is provided, and is provided to supply various refining agents to the converter type refining furnace 2. Internal material addition device 9. As the material adding device 9, for example, a hopper 10, a cutting device 11 provided at a lower portion of the hopper 10, a chute connected to the cutting device 11 and penetrating the hood 8 can be used. 12 raw material supply device. In Fig. 1, only one funnel 10 for accommodating iron oxide 21 such as iron ore is described. However, a plurality of funnels are actually provided.

On the top-blowing lance 5, an oxygen supply pipe 13 for supplying oxygen for dephosphorization refining (industrial pure oxygen), and a cooling water supply pipe for supplying or discharging cooling water for cooling the top-blowing lance 5 are connected (not Graphic). The oxygen supply pipe 13 branches out of the solvent supply pipe 14 in the middle, and the solvent supply pipe 14 passes through the dispenser 17, and then merges with the oxygen supply pipe 13 again. In the dispenser 17, a powdery dephosphorization solvent (hereinafter referred to as "CaO-based dephosphorization solvent 20") containing CaO as a main component such as quicklime is contained, and oxygen introduced into the distributor 17 is used as a CaO-based dephosphorization. The carrier gas for the solvent 20 is used, and the CaO-based dephosphorization solvent 20 is blown from the tip end of the top-blowing lance 5 to the molten iron 18 in the furnace together with oxygen. At this time, the CaO-based dephosphorization solvent 20 is added to the collision position of the oxygen and the molten iron bath surface (referred to as "ignition point"). The oxygen supply pipe 13 is provided with an isolation valve 15, and the solvent supply pipe 14 is provided with an isolation valve 16, and is configured to supply only oxygen to the furnace by opening and closing the isolation valve 15 and the isolation valve 16.

After the cold iron source such as iron scrap is placed in the converter type refining furnace 2, the molten iron 18 is placed in the converter type refining furnace 2, and Ar gas or nitrogen gas is blown from the bottom blowing blast opening 7 and the like. The inert gas is used as a stirring gas, and the CaO-based dephosphorization solvent 20 is added to the molten iron 18 together with the oxygen gas from the top blowing lance 5, and the molten iron 18 in the furnace is subjected to dephosphorization treatment. At this time, the iron oxide 21 may be added to the molten iron bath surface from the raw material adding device 9 as needed.

The phosphorus contained in the molten iron 18 is oxidized by oxygen to become phosphorus oxide (P ₂ O ₅ ), and is a stable form of the compound 3CaO. P ₂ O ₅ (also referred to as "Ca ₃ (PO ₄ ) ₂ ") is fixed to the slag 19 formed by the slagging of the CaO-based dephosphorization solvent 20 added to the furnace to carry out the molten iron 18 Dephosphorization reaction. The iron oxide 21 functions not only as a slag-promoting agent for the CaO-based dephosphorization solvent 20 but also as a function of increasing the oxygen potential of the slag 19 and improving the dephosphorization ability of the slag 19, so that the iron oxide 21 can be added. And promote the dephosphorization reaction. However, since FeO is generated in the furnace by the oxygen supplied from the top blowing lance 5, the addition of the iron oxide 21 is not an essential condition in the present invention.

In the dephosphorization treatment of the molten iron 18 which is carried out as described above, the inventors of the present invention have investigated the self-priming blow gun 5 for the purpose of efficiently performing dephosphorization treatment even when the niobium content of the molten iron 18 is high. The ratio of the amount of CaO in the solvent for dephosphorization of the supplied CaO to the amount of oxygen supplied from the top-blowing lance 5 (= CaO amount/oxygen amount) affects the dephosphorization reaction. The oxygen supplied from the top blowing lance 5 is also consumed in the removal reaction of ruthenium contained in the molten iron 18 (referred to as "depuration reaction"). In the dephosphorization treatment of the molten iron, a period in which the deodorization reaction in the initial stage of refining is preferentially generated may be referred to as a "disintegration period", and the difference thereafter may be referred to as a "dephosphorization period".

Therefore, at the time of the investigation, in order to grasp the influence of the amount of oxygen only on the dephosphorization reaction, the oxygen which has been removed from the portion of the oxygen supplied to the furnace for the depurination reaction is defined as "the amount of oxygen released from the deuterium". "." In the investigation, the amount of CaO (kg/ton of molten iron) in the CaO-based dephosphorization solvent added to the surface of the molten iron from the top blowing spray gun 5 and the amount of oxygen released per kilometer (kg/min The ratio of iron (the amount of CaO / the amount of oxygen outside the deuterium) was varied, and the ratio of [CaO amount / amount of oxygen outside the decarburization] to the dephosphorization reaction was investigated. ring. Further, in the present invention, the ratio [CaO amount / deuterium outside oxygen amount] is also simply referred to as "CaO/O".

The survey results are shown in Figure 2. As shown in Fig. 2, if the ratio [CaO amount / deuterium outside oxygen amount] is less than 0.90, the dephosphorization lime efficiency is maintained at 18% to 20%, but if the ratio [CaO amount / deuterium outside oxygen amount] reaches 0.90 Above, the dephosphorization lime efficiency is lowered. Fig. 2 is a graph showing the relationship between the ratio [CaO amount/outer oxygen amount] and dephosphorization lime efficiency. Here, the dephosphorization lime efficiency means that 3CaO is formed among the added CaO when the molten iron 18 is subjected to dephosphorization treatment by setting the CaO amount in the CaO-based dephosphorization solvent to the same addition amount in percentage. . The mass ratio of the CaO portion of the compound of P ₂ O ₅ .

When the CaO-based dephosphorization solvent 20 is supplied to the furnace in a region where the dephosphorization lime efficiency of the [CaO amount/decarburization outside oxygen amount] is less than 0.90, the supplied CaO-based dephosphorization is used. The solvent 20 can contribute to the dephosphorization reaction in a fixed ratio. In other words, the region where the amount of the CaO-based dephosphorization solvent 20 is increased and the dephosphorization amount is increased as the region where the amount of the CaO-based deuterium is less than 0.90 is increased. On the other hand, in a region where the efficiency of the dephosphorization lime which exceeds [CaO amount/outer oxygen content] exceeds 0.90, even if a large amount of the CaO-based dephosphorization solvent 20 is supplied, it contributes to the CaO-based dephosphorization solvent 20 The proportion of the dephosphorization reaction is also low, so the excessively added CaO-based dephosphorization solvent 20 does not contribute to the dephosphorization reaction. Therefore, the region in which the ratio of [CaO amount/exhaled oxygen amount] exceeds 0.90 is only a region in which the CaO-based dephosphorization solvent 20 is excessively added.

In other words, in order to prevent excessive addition of the CaO-based dephosphorization solvent 20, it is necessary to control the ratio of [CaO amount/exhaled external oxygen amount] to the range in which the CaO-based dephosphorization solvent 20 can effectively assist the dephosphorization reaction. Its specific value is less than 0.90. In the range In addition, when the amount of the solvent 20 for dephosphorization of CaO is large, the amount of dephosphorization is increased, and the phosphorus content of the molten iron is lowered. Therefore, the ratio of [the amount of CaO / the amount of oxygen outside the decarburization] is preferably 0.6 or more. It is desirable to set it to 0.80 or more.

The present invention is based on the above, and the dephosphorization treatment method of the molten iron 18 in the converter type refining furnace 2 of the present invention is that the molten iron 18 in the converter type refining furnace is blown with oxygen from the top blowing lance 5, and The top blowing lance 5 blows the CaO-based dephosphorization solvent 20 to the collision surface of the oxygen and the molten iron 18, and the phosphorus in the molten iron is oxidized by the oxygen to introduce the generated phosphorus oxide into the surface. The slag-forming CaO-based dephosphorization solvent removes phosphorus in the molten iron, and the dephosphorization treatment method of the molten iron 18 is characterized in that the cerium content before the dephosphorization treatment is 0.20% by mass or more When the molten iron 18 is subjected to the dephosphorization treatment, the amount of CaO (kilogram per ton of molten iron) in the CaO-based dephosphorization solvent added to the surface of the molten iron bath is blown from the top blowing lance 5, and the amount of oxygen outside the enthalpy ( The ratio [CaO amount / deuterium outside oxygen amount] of kilograms per ton of molten iron is less than 0.90, and the CaO-based dephosphorization solvent added to the top-blowing lance 5 is blown according to the amount of oxygen released from the top. The amount of addition is adjusted.

When the ratio [CaO amount / deuterium outside oxygen amount] is obtained, the amount of oxygen of 1 Nm ³ / molten iron-ton is equivalent to the oxygen addition amount of 1.43 kg / ton of molten iron, in order to remove 1 kg of hydrazine. The amount of oxygen was 1.142 kg (=1 kg × (16 × 2) / 28). Therefore, when the total amount of supplied oxygen is F ₀ (Nm ³ / molten iron-ton) and the molten iron having a cerium concentration of Z (% by mass) is subjected to dephosphorization treatment, the amount of oxygen for deodorization (kg / Each ton of molten iron is expressed by the following formula (1), and the amount of oxygen released per kilogram (kg/min of molten iron) is expressed by the following formula (2), and the amount of CaO supplied from the top-blowing lance 5 (kg/ton of molten iron) ) can be obtained by the following formula (3).

Oxygen consumption for desorption (kg / ton of molten iron) = (Z / 100) × 1000 × 1.142... (1)

Exhaled outside oxygen (kg / ton of molten iron) = F ₀ × 1.43 - Oxygen for deodorization (kg / ton of molten iron) ... (2)

The amount of CaO (kg / ton of molten iron) = the amount of oxygen outside the dew (Nm ³ / molten iron - ton) × (the value of [CaO / O]) ... (3)

Here, the total amount of oxygen or the amount of oxygen outside the deuterium is set in such a manner that the total amount of oxygen is determined in accordance with the condition of the molten iron temperature, the amount of iron filings, the amount of antimony in the molten iron before the treatment, and the like to satisfy the heat condition. Or, according to the phosphorus content in the molten iron before the treatment, the phosphorus content in the molten iron required, etc., the amount of external oxygen required for dephosphorization is determined empirically.

In addition, as in the case of Patent Document 4, the ratio of the top blowing speed (kg/min) of the simple CaO component to the mass flow rate (kg/min) of oxygen is used as an index, and the [CaO amount/desorption of the present invention. When the amount of oxygen outside the sputum is compared with the index, the oxygen flow rate of the former also includes the oxygen consumed in the devolatilization reaction. Therefore, if the ruthenium content of the molten iron before the treatment increases, in the former case, There is a tendency that the amount of CaO supplied in the entire dephosphorization treatment is excessive. On the other hand, in the present invention, even if the niobium content of the molten iron before the treatment is increased, the CaO supply amount is not excessive. That is, in the dephosphorization treatment of the molten iron having a large amount of antimony, the dephosphorization treatment method of the present invention has an effect of reducing the amount of CaO used and improving the efficiency of dephosphorization lime. Therefore, the dephosphorization treatment of the present invention The method is preferably applied to dephosphorization treatment of molten iron having a niobium content of 0.20% by mass or more before the treatment, and more preferably to dephosphorization treatment of molten iron having a niobium content of 0.25 mass% or more before the treatment.

The solvent 20 for dephosphorization of the CaO used in the present invention may be used in any type as long as it contains 50% by mass or more of CaO. For example, quicklime, calcium carbonate, dolomite or the like can be used. Among these, a substance such as iron oxide, fluorite, alumina, or converter slag (melt produced by decarburization refining in a converter) may be used as a component containing CaO as a main component. Solvent 20 for phosphorus. Further, the simple CaO component of the quicklime is about 90% by mass to 96% by mass.

In the present invention, it is preferable that most of the CaO source used in the dephosphorization treatment is the powdery CaO-based dephosphorization solvent 20 supplied from the top-blowing lance 5, but other than this, for example, At the initial stage of the phosphorus treatment (a period of 1/3 of the predetermined dephosphorization treatment time), a known CaO source such as small or granular quicklime or broken steel slag is used. However, when the amount of CaO source other than the solvent for dephosphorization of CaO supplied from the top-blowing lance 5 is increased, it is difficult to simultaneously supply the amount of CaO-based dephosphorization solvent for the ignition point to promote the dephosphorization reaction. Ensure the adjustment of the composition and amount of slag in the furnace. Therefore, the amount of CaO source other than the solvent for dephosphorization of CaO supplied from the top-blowing lance 5 is preferably limited to about 1/4 of the amount of use of all CaO sources in terms of CaO, and more preferably, it is limited. It is less than 1/5 of the amount of use of all CaO sources. The CaO source other than the CaO-based dephosphorization solvent supplied from the top blowing lance 5 is supplied through the chute 12.

In the present invention, the ratio of [CaO amount/outer oxygen content] is controlled to less than 0.90, and the molten iron 18 is subjected to dephosphorization treatment. However, when the cerium content of the molten iron 18 before the dephosphorization treatment is 0.30% by mass or more, As shown in Fig. 3, the following tendency was observed: as the content of cerium increased, the amount of dephosphorization decreased, and the concentration of phosphorus in the molten iron after dephosphorization treatment exceeded 0.035 mass%. Fig. 3 is a view showing a molten iron having a phosphorus concentration of 0.100% by mass to 0.120% by mass and a molten iron temperature of 1280 ° C to 1300 ° C before the dephosphorization treatment, and the amount of deuterium outside the oxygen reaches 11 Nm ³ / molten iron - ton ~ 13 Nm ³ / molten iron - ton, the ratio of [CaO amount / deuterium outside oxygen amount] is 0.80 or more and less than 0.90, and the molten iron temperature at the end of dephosphorization treatment is controlled to 1350 ° C to 1370 ° C, and the present invention is applied. A graph showing the results of investigations on the relationship between the concentration of ruthenium in the molten iron before the dephosphorization treatment and the phosphorus concentration in the molten iron after the dephosphorization treatment. In addition, when the cerium content of the molten iron before the dephosphorization treatment is less than 0.30% by mass, the phosphorus concentration in the molten iron after the dephosphorization treatment can be stably maintained at 0.035 mass% or less by applying the present invention.

CaO in the solvent for dephosphorization of CaO can be considered to form SiO ₂ and CaO formed by oxidation of ruthenium. A compound of the form of SiO ₂ (calcium citrate). Therefore, the reason why the amount of dephosphorization in the molten iron having a cerium concentration of 0.30% by mass or more is lowered is considered to be as follows: If the molten iron having a cerium concentration of 0.30% by mass or more is subjected to dephosphorization treatment, CaO. The amount of CaO consumed in the formation of SiO ₂ is increased in the case of dephosphorization of molten iron having a lower concentration of cerium, and is used to form a stable form of the compound 3CaO. The CaO of P ₂ O ₅ is relatively reduced.

Therefore, the present inventors have further studied that when the molten iron 18 having a cerium concentration of 0.30% by mass or more is subjected to dephosphorization treatment, the CaO-based dephosphorization solvent 20 is just added, and the dephosphorization treatment is efficiently performed. In the discussion, CaO, which is supplied to the furnace as a CaO source such as a solvent for dephosphorization of CaO, has been removed to form CaO. The CaO of the CaO portion of SiO ₂ (calcium silicate) is defined as "out of CaO". Here, the CaO supplied to the furnace is a combination of CaO contained in the CaO-based dephosphorization solvent 20 supplied from the top-blowing lance 5 and CaO contained in the CaO source supplied from the chute 12. By. Also, used to generate CaO. A source of SiO _2, SiO _2, SiO ₂ in addition to the removal of silicon by reaction of molten iron and generated slag also include other additive materials contained in the SiO _2.

Since the CaO portion contributing to the dephosphorization reaction is CaO outside the deuterium, it is presumed that, according to the conventional findings, the more the CaO is removed, the more the dephosphorization amount is increased. However, the results of experiments by the inventors of the present invention have revealed that even if the amount of CaO is the same even if the amount of CaO is the same, the dephosphorization behavior is also changed by changing the ratio [CaO amount / amount of oxygen outside the deuterium].

Fig. 4 to Fig. 7 show the results of investigations on the relationship between CaO and the amount of dephosphorization. Fig. 4 shows the results of a survey on the relationship between the amount of CaO and the amount of dephosphorization when the ratio of [CaO amount/outer oxygen content] is less than 0.70, and Fig. 5 shows that the ratio [CaO amount/outer oxygen content] is 0.70 or more. The results of the investigation on the relationship between CaO and dephosphorization in the absence of 0.80, Fig. 6 shows the relationship between the CaO content and the dephosphorization amount when the ratio of CaO/outer oxygen is 0.80 or more and less than 0.90. As a result of the investigation, FIG. 7 shows the results of investigations on the relationship between the CaO content and the dephosphorization amount when the ratio of [CaO amount/outer oxygen content] is 0.90 or more and less than 1.00. The "T.CaO" in FIGS. 4 to 7 is the total amount of CaO in the solvent for dephosphorization of the added CaO system.

As shown in FIG. 4 and FIG. 5, when the ratio [CaO amount/exhaled oxygen amount] is less than 0.80, the amount of dephosphorization increases as the CaO increases. That is, it can be known that when the ratio is [CaO When the amount of oxygen outside the deuterium is less than 0.80, the dephosphorization reaction can be efficiently carried out by increasing the CaO outside the deuterium. On the other hand, when the ratio [CaO amount / deuterium outside oxygen amount] is 0.90 or more, as shown in FIG. 7, even if CaO is removed from the deuterium, the dephosphorization amount does not change. When the ratio [CaO amount / deuterium outside oxygen amount] is 0.90 or more, although the efficiency is not good, the dephosphorization treatment can be performed with a minimum amount of deodorized CaO, and even if the dislocation is increased, CaO is only excessively added. . The results of Figure 7 are consistent with the results of Figure 2.

On the other hand, when the ratio of [CaO amount / deuterium outside oxygen amount] is 0.80 or more and less than 0.90, as shown in Fig. 6, the amount of dephosphorization increases with the increase of CaO due to depuration until dislocation. The external CaO reaches 9 kg / ton of molten iron, and if the CaO exceeds 9 kg / ton of molten iron, the increase of dephosphorization is very small, and the increase of CaO outside the dehydration is invalid for the increase of dephosphorization. . In other words, when the ratio of [CaO amount/outer oxygen content] is 0.80 or more and less than 0.90, the CaO-based dephosphorization solvent 20 is added even if the CaO exceeds 9 kg/ton of molten iron. The portion of the CaO added with more than 9 kg/ton of molten iron does not contribute to the dephosphorization reaction and is an excessive portion, and conversely hinders the decrease in the temperature of the molten iron or the slagging of the solvent 20 for dephosphorization of CaO. On the contrary, there are cases where the dephosphorization reaction is hindered.

In other words, when the molten iron 18 having a cerium concentration of 0.30% by mass or more is subjected to a dephosphorization treatment in a range of 0.80 or more and less than 0.90, and it is preferable to remove the molten iron 18 having a cerium concentration of 0.30% by mass or more. The extra-CaO is adjusted to be in the range of 6 kg/ton of molten iron ~9 kg/ton of molten iron, and it is more desirable to adjust the dislocation outside CaO to be 6 kg/ton of molten iron ~8 kg/ton Within the range of molten iron. By the operation as described above, the CaO-based dephosphorization solvent 20 can be added just right, so that it can be efficiently Dephosphorization treatment. However, even when the molten iron having a cerium concentration of 0.30% by mass or more is subjected to dephosphorization treatment, when the ratio [CaO amount / deuterium outside oxygen amount] is less than 0.80, dephosphorization is accompanied by addition of CaO other than deodorization. Since the amount is increased, it is preferable to increase the amount of de-extracted CaO in a range having a margin in temperature, and it is preferable to set it to 8 kg/ton or more of molten iron in order to secure an effective amount of dephosphorization.

As described above, according to the present invention, the ratio of the CaO amount in the CaO-based dephosphorization solvent added to the top-blowing lance 5 to the amount of the extra-deuterium oxygen [CaO amount/out-of-twisting oxygen amount] is controlled in the CaO system. Dephosphorization treatment is carried out in a range in which the dephosphorization efficiency of CaO in the solvent for phosphorus is high, in other words, the molten iron 18 is dephosphorized under operating conditions in which the CaO concentration in the slag is increased and the dephosphorization amount is increased. Therefore, the added CaO-based dephosphorization solvent 20 efficiently absorbs the generated phosphorus oxide (P ₂ O ₅ ), and as a result, the dephosphorization treatment can be performed more efficiently than in the prior art.

Example

[Example 1]

The dephosphorization treatment is carried out by applying the present invention to the molten iron produced from the blast furnace using the converter type refining furnace apparatus shown in Fig. 1. The phosphorus concentration in the molten iron before the dephosphorization treatment is 0.100% by mass to 0.120% by mass, the bismuth concentration in the molten iron is 0.20% by mass or more and less than 0.30% by mass, and the molten iron temperature is 1280 ° C to 1300 ° C for the melting Iron, at the end of the dephosphorization treatment, the molten iron temperature reaches 1350 ° C ~ 1370 ° C, and the deuterium outside oxygen is at 15.7 kg / ton of molten iron ~ 17.2 kg / ton of molten iron (11 Nm ³ / molten iron -ton~12Nm ³ / molten iron-ton). The ratio [CaO amount / deuterium outside oxygen amount] is in the range of 0.83 to 0.85, and the total amount of the CaO-based dephosphorization solvent is determined according to the amount of oxygen removed from the deuterium, so that the addition rate is fixed and the top-blowing gun is used. Dephosphorization treatment (Inventive Example 1) was carried out by blowing a solvent for dephosphorization of CaO. The CaO source added to the furnace is only the CaO-based dephosphorization solvent blown from the top-blowing lance, and the CaO amount is less than 9 kg/min. Quantity] to adjust. As a solvent for dephosphorization of CaO, quicklime (93% by mass of the CaO component alone) was used.

Fig. 8 is a graph showing the relationship between the carbon concentration in the molten iron and the phosphorus concentration in the molten iron after the dephosphorization treatment in the dephosphorization treatment (Inventive Example 1) by applying the present invention. In Fig. 8, as a conventional example 1, the relationship between the carbon concentration in the molten iron after the dephosphorization treatment in the conventional dephosphorization treatment and the phosphorus concentration in the molten iron is shown. The conventional example 1 is a dephosphorization treatment performed under the same conditions as in the first example of the present invention except for the following conditions: the addition rate of the CaO-based dephosphorization solvent is also included in the self-contained CaO component. The dephosphorization treatment in the first to the middle of the dephosphorization treatment was set to 1.67 kg / (min. molten iron - ton), and was set to 0.84 kg / (min. molten iron - ton) from the middle to the end of the dephosphorization treatment. It was adjusted to an average of about 1.4 kg/(min. molten iron-ton) over the entire processing time.

In the present invention example 1 and the prior art 1, the oxygen supply rate is set to 1.94 Nm ³ /(min. molten iron-ton) to 2.50 Nm ³ /(min. molten iron-ton) during the desorption period, during the dephosphorization period. Set to 1.33 Nm ³ / (min. molten iron - ton), the blowing time is about 12 minutes. Further, in the conventional example 1, the ratio [CaO amount/exhaled oxygen amount] is 1.00 or more, and the alkalinity ((mass% CaO) / (mass % SiO ₂ )) of the slag after the dephosphorization treatment is 2.7~ The scope of 3.7. In addition, in FIG. 8, the solid line shows the regression equation of the power approximation of the example 1 of the invention obtained by the least squares method, and the broken line shows the regression equation of the power approximation of the conventional example 1 obtained by the least squares method.

In the first example of the present invention, the dephosphorization treatment is carried out by setting the ratio [CaO amount/exhalation outside oxygen amount] to less than 0.90, so that the dephosphorization lime efficiency is improved, and the CaO-based dephosphorization solvent can efficiently help dephosphorization. As shown in FIG. 8, the phosphorus concentration in the molten iron after the dephosphorization treatment is 0.030% by mass or less, and the phosphorus concentration in the molten iron after the dephosphorization treatment is stabilized lower than that of the conventional example 1. On the other hand, in the conventional example 1, the ratio [CaO amount/exhaled oxygen amount] is 1.00 or more, and the dephosphorization lime efficiency is low, so that the CaO-based dephosphorization solvent cannot efficiently assist the dephosphorization reaction, and thus it is considered that The phosphorus concentration in the molten iron after the dephosphorization treatment is increased.

[Embodiment 2]

When the cerium concentration in the molten iron is 0.30% by mass or more and less than 0.50% by mass higher than that of the present invention 1, the dephosphorization treatment is carried out by applying the present invention. The conditions of the molten iron component and the molten iron temperature other than the crucible were the same as in the inventive example 1. With the increase of the content of antimony in the molten iron, the amount of deuterium outside the oxygen increased to 16.7 kg / ton of molten iron ~ 19.5 kg / ton of molten iron (11.7Nm ³ / molten iron - ton ~ 13.7Nm ³ / molten iron -ton).

When the ratio of [CaO amount/outer oxygen content] is in the range of 0.75 or more and less than 0.90, in the case where the ratio [CaO amount/outer oxygen content] is 0.80 or more and less than 0.90, the dislocation is performed. The external CaO is in the range of 6 kg / ton of molten iron ~ 9 kg / ton of molten iron, and when the ratio of [CaO amount / deuterium outside oxygen] is 0.75 or more and less than 0.80, The method of CaO dephosphorization is determined according to the amount of CaO dephosphorization solvent, and the total amount of CaO dephosphorization solvent is determined according to the amount of oxygen removed from the crucible, and is blown from the top blowing gun in such a manner that the addition speed is fixed. Quicklime (93% by mass of the CaO component alone) is subjected to dephosphorization treatment as a solvent for dephosphorization of CaO (Example of the present invention) 2). The CaO source added to the furnace is only the CaO-based dephosphorization solvent blown from the top-blowing gun, and the CaO outside the decarburization is in the range of 8 kg/ton of molten iron to 9.6 kg/ton of molten iron.

In the conventional example 2, the dephosphorization treatment of the molten iron in the molten iron is carried out by applying the dephosphorization treatment method of the molten iron described in Patent Document 4 to 0.30% by mass or more and less than 0.50% by mass. The CaO source added to the furnace is only the CaO-based dephosphorization solvent blown from the top blowing lance, and the ratio of the top blowing speed (kg/min) of the pure CaO component to the mass flow rate (kg/min) of oxygen is added. The top blowing speed of the simple CaO component was determined in the range of "0.56 + 0.69 × [Si] - 0.56 + 0.83 × [Si]". In the prior art example 2, the amount of deuterium outside oxygen is in the range of 18.2 kg/ton of molten iron to 22.5 kg/ton of molten iron, and as a result, the index of [CaO amount/exhaled oxygen amount] is at 0.96. In the range of ~1.19, the CaO outside the decarburization is in the range of 11 kg / ton of molten iron ~ 17 kg / ton of molten iron, and the alkalinity of the slag after dephosphorization treatment ((% by mass CaO) / (% by mass) SiO ₂ )) is in the range of 2.4 to 2.6.

Fig. 9 is a view showing, in a comparative manner, the relationship between the concentration of ruthenium in the molten iron before the dephosphorization treatment and the amount of CaO used in the dephosphorization treatment in the examples 2 and 2 in the present invention. Further, Fig. 10 shows, in contrast, the relationship between the concentration of ruthenium in the molten iron before the dephosphorization treatment and the amount of dephosphorization of the molten iron in the dephosphorization treatment in the examples 2 and 2 in the present invention.

According to the ninth aspect of the invention, in the second embodiment, even if the cerium concentration in the molten iron is as high as 0.30% by mass or more, the dephosphorization treatment can be carried out without significantly increasing the amount of CaO used as in the conventional example 2.

Further, according to Fig. 10, even if the amount of CaO used is larger than that of the conventional example 2 The amount of reduction is not large, and no significant difference is observed in the amount of dephosphorization. Therefore, in the method of the present invention, the amount of CaO added can be controlled by setting the amount of CaO/the amount of oxygen outside the deuterium to 0.9 or less. On the one hand, the amount of CaO used is greatly reduced, and on the one hand, dephosphorization treatment is efficiently performed.

1‧‧‧ Converter type refining furnace equipment

2‧‧‧ Converter type refining furnace

3‧‧‧ 铁皮

4‧‧‧Refractory materials

5‧‧‧ top blow gun

6‧‧‧Outlet

7‧‧‧ bottom blowing vent

8‧‧‧Exhaust hood

9‧‧‧Material addition device

10‧‧‧ funnel

11‧‧‧cut out device

12‧‧‧Chute

13‧‧‧Oxygen supply tube

14‧‧‧Solvent supply tube

15‧‧‧Isolation valve

16‧‧‧Isolation valve

17‧‧‧Distributor

18‧‧‧ molten iron

19‧‧‧ slag

20‧‧‧CaO desolvent solvent

21‧‧‧ Iron Oxide

Claims (1)

A dephosphorization treatment method for molten iron, in which a molten iron in a converter-type refining furnace is blown with oxygen from a top-blowing lance, and a collision surface of the oxygen and molten iron is blown by the top-blowing lance with CaO as a main component Dephosphorization solvent, the phosphorus in the molten iron is oxidized by the oxygen, and the generated phosphorus oxide is introduced into the slag-removing solvent for dephosphorization, thereby removing phosphorus in the molten iron, The method for dephosphorization treatment of the molten iron is characterized in that, when dephosphorization treatment is performed on the molten iron having a niobium content of 0.30% by mass or more before the dephosphorization treatment, the oxygen supplied to the furnace is removed for use in the dephosphorization treatment. The oxygen in the enthalpy of the reaction is defined as the amount of oxygen removed (kg/ton of molten iron), and the CaO supplied to the furnace has been removed to form CaO. When CaO of the CaO portion of SiO ₂ (calcium silicate) is defined as CaO outside the crucible, the amount of CaO in the solvent for dephosphorization containing CaO as a main component added to the molten iron bath surface is blown by a top blowing lance ( When the ratio of the kilograms per ton of molten iron to the amount of the deuterium outside the oxygen is in the range of 0.80 or more and less than 0.90, and the molten iron is dephosphorized, the CaO outside the decarburization reaches 6 kg/ Adjusting the amount of the dephosphorization solvent added from the top blowing spray gun according to the amount of molten iron outside the range of ~9 kg/ton of molten iron per ton of molten iron; When the ratio of the CaO amount to the amount of the deuterium outside oxygen is in the range of less than 0.80 and the molten iron is dephosphorized, the CaO outside the decarburization reaches 8 kg/ton or more of molten iron. In the manner, the amount of the solvent for dephosphorization added by the top blowing spray gun is adjusted.