KR20160014688A - Method for removing phosphorus from hot metal - Google Patents

Abstract

When the molten iron in the converter-type refining furnace is subjected to the denitrification, the supply amount of the flux for dredging the extruded lance is adjusted appropriately in accordance with the amount of the oxygen gas supplied from the extruding lance, thereby performing the denitration reaction efficiently. An oxygen gas is blown into the molten iron 18 in the converter type refining furnace 2 from the ladle lance 5 and the CaO dredging flux 20 is blown into the impact surface against the molten oxygen gas, Which is produced by oxidizing phosphorus in the molten iron by a process for removing phosphorus in the molten iron by blowing the phosphorus produced in the molten iron into the CaO dredging flux, characterized in that, in the oxygen gas supplied into the furnace, (Kg / charcoal-ton) of the CaO-based degumming flux to be added to the charcoal bath surface from the ladle lance when the oxygen gas excluding the oxygen is excluded The addition amount of the CaO-based tin cyanide flux is adjusted in accordance with the amount of oxygen outside the silicon so that the ratio of the amount of CaO to the amount of oxygen outside the silicon-desiliconizer can be less than 0.90.

Description

METHOD FOR REMOVING PHOSPHORUS FROM HOT METAL [0002]

In the present invention, oxygen gas is blown from a lance into a furnace in a furnace-type refining furnace, and a gas containing mainly CaO as a main constituent And a cyanide flux is blown through the uploss lance.

In recent years, in a steelmaking integrated steelworks furnished with a blast furnace and a converter, it is advantageous in terms of cost and quality, and as a preliminary treatment for molten iron before decarburization refinement in a converter, Quot;), and a refining method for removing phosphorus in the charcoal line in advance is widely performed. This is due to the fact that the deoxidization reaction is likely to proceed as the refining temperature is lower, that is, the molten iron phase having a temperature lower than that of the molten steel phase is likely to proceed with the deoxidization reaction.

The deoxidizing treatment of the molten iron is carried out by adding a flux for dredging mainly containing CaO such as burnt lime and adding an oxygen source such as oxygen gas or iron oxide as a deinking agent and adding phosphorus as a deinking agent And the resulting phosphorus oxide (P ₂ O ₅ ) is converted into a slag formed by the slag formation of the flux for declining, which is made of 3CaO · P ₂ O ₅ (also referred to as "Ca ₃ (PO ₄ ) ₂ " And then fixed with a stable form of the compound. That is, it is a prerequisite that the dyed flux used contains CaO.

As described above, in the removal of the molten iron, the supply of an oxygen source such as oxygen gas and the CaO in the slag play an important role. Thus, in the deoxidation treatment of the molten iron, many methods for increasing the removal efficiency by specifying the ratio between the supply rate of the oxygen source and the supply rate of the CaO, and the method for increasing the removal efficiency by specifying the FeO concentration of the produced slag have been proposed have.

For example, Patent Document 1 discloses that when adding an oxygen source to a molten iron in the galvanizing process, the addition rate of the oxygen source is X (kg / min) and the addition rate of the dewaxing flux in terms of CaO is Y ( kg / min), a method is proposed in which a flux for CaO attributable to CaO is added to a molten iron and is subjected to molten iron processing under the condition that "0.50? X / Y? 2.0" is satisfied with respect to the addition rate X of the oxygen source . In this method, FeO is produced by the supplied oxygen source and the FeO concentration in the slag is increased, thereby improving the removal efficiency.

Further, Patent Document 2 discloses that, when a galvanizing line is subjected to a de-phosphorus treatment using a flux that does not substantially contain fluorine using a converter furnace, the mass concentration ratio of CaO and SiO _{2 in} the slag after the de- The slag basicity {(mass% CaO) / (mass% SiO ₂ )} is set to 2.5 or more and 3.5 or less, and the molten iron temperature after the removal treatment is set to 1320 ° C. or more and 1380 ° C. or less, ) The method of removing the bottom flue gas flow rate from the time before the elapse of 60% of the time until the completion of the finishing of the furnace at a rate of 0.18 Nm ³ / min or less per ton of the molten iron to a depth of 5% Has been proposed.

In Patent Document 3, in a method for producing an iron phosphorus charcoal which blows off gaseous oxygen and a CaO refining agent through an upturned lance and reduces the amount of slag after treatment to 30 kg / molten iron-ton or less, (Nm ³ / (min · charcoal-ton) and the supply rate of pure CaO (kg / (min · charcoal-ton)) in the scouring agent to the deionization process for 0.15 mass% Is set within a predetermined range.

Patent Document 4 discloses that when the CaO-containing powder is crushed together with the oxygen-containing gas in the lance without using the CaF ₂ -containing material by using a converter furnace, the silicon content [Si] before the treatment, (Kg / min) of the pure CaO in the CaO-containing powder to the mass flow rate (kg / min) of the oxygen gas is set to 0.56 + 0.5 x [Si] - 0.56 + 1.5 x [Si].

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

Patent Document 2: JP-A-2008-106296

Patent Document 3: JP-A-2004-83989

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

However, the above-mentioned prior art has the following problems.

That is, in Patent Document 1, since the range of the addition rate of the oxygen source to the addition rate of the dyneing flux in terms of CaO is wide (X / Y), under a condition of high silicon content of the molten iron, It may become impossible. That is, it is not influenced by the silicon content of the molten iron, and an efficient de-phosphorus treatment can not be stably carried out. Therefore, the technique of Patent Document 1 can not be applied in the operation of increasing the silicon content in the molten iron serving as the heat source for the purpose of promoting the dissolution of the cold iron source in the denitration treatment. The inventors of the present invention have confirmed that Patent Document 1 is suitable when the content of silicon in the molten iron is 0.10 mass% or less.

Patent Document 2 only specifies the basicity of the slag after the denitrification treatment and the basicity of the slag in the denitrification treatment is an important factor. However, even if the basicity of the slag after the denitrification treatment is secured as in Patent Document 2, do. Namely, as in Patent Document 2, it is not possible to stably perform efficient de-phosphorization only by defining the basicity of the slag after the denitration treatment.

Patent Document 3 discloses that a scouring agent as a CaO source and a feed rate and a feed rate of pure CaO are advantageous for removal of a charcoal in a specific range in a feed rate of gaseous oxygen and a feed rate of pure CaO, Lt; / RTI > However, this technique is premised on that the silicon content of the molten iron before the treatment is as low as, for example, 0.15 mass% or less, and the amount of slag after the treatment becomes 30 kg / molten iron-ton or less. In the case of the dephosphorization treatment, the phosphorus removal efficiency is low and the phosphorus content of the molten iron can not be sufficiently lowered.

Patent Document 4 discloses a method of treating a charcoal with a CaO-containing powder and a gaseous oxygen, wherein when the silicon content of the charcoal before the treatment is as high as 0.30 mass% or more, And the ratio of the mass flow rate (kg / min) of the oxygen gas to the value of the ratio. However, according to this method, the higher the silicon content of the molten iron before the treatment, the higher the appropriate range of the ratio between the rate of outgassing of the pure CaO-containing component and the flow rate of the oxygen gas mass, and at the same time, When the silicon content of the molten iron is large, the supply amount of the CaO-containing powder is excessive and the amount of slag is increased, making it difficult to perform the effective de-phosphorization treatment.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ozonization apparatus and an ozonization apparatus, It is possible to efficiently carry out the dephosphorization reaction by appropriately adjusting the supply amount of the flux for dredging from the outlet lance in accordance with the supply amount of the oxygen gas from the outlet lance at the time of drawing the molten iron by blowing the flux for dredging through the above- The method comprising the steps of:

The gist of the present invention to solve the above problems is as follows.

[1] While blowing oxygen gas from a ladle lance into a molten iron in a converter type refining furnace, a diesel flux containing CaO as a main component is blown into the impingement surface of the oxygen gas through the uprising lance, Wherein the phosphorus in the molten iron is oxidized and the generated phosphorous oxide is blown into the dredged flux so as to remove the phosphorus in the molten iron. In this method, a molten iron having a silicon content of not less than 0.20 mass% When the oxygen gas except for the amount used for the silicon removal reaction in the oxygen gas supplied into the furnace is defined as the amount of oxygen outside the silicon (kg / molten iron-ton), the molten iron is blown into the molten iron bath surface , The ratio of the amount of CaO (kg / molten iron-ton) and the amount of oxygen outside the silicon (CaO / Amount; dephosphorization treatment of the molten iron, which is in accordance with a de-silicon outer oxygen content is less than 0.90, adjusting the amount of the de-quoted flux is added by blowing from a lance sangchwi.

[2] The method for deodorizing a charcoal according to [1], wherein the ratio [CaO amount / amount of oxygen outside the silicon] is in the range of 0.80 or more and less than 0.90.

[3] In the deoxidizing treatment of the molten iron having a silicon content of not less than 0.30 mass% before the denitrification treatment, the CaO except for the CaO component used for producing CaO · SiO ₂ (calcium silicate) , When the ratio of the amount of CaO to the amount of oxygen outside the silicon desorbed is within the range of 0.80 or more and less than 0.90 and the deoxidizing treatment of the molten iron is carried out, the amount of the desiliconized CaO is in the range of 6 to 9 kg / , In the case where the additive amount of the drowning flux containing CaO as a main ingredient to be added by blowing in the ladle lances is adjusted and the molten iron is subjected to the dehulling treatment with the ratio [CaO amount / oxygen amount outside the silicon removal amount] being less than 0.80, The deoxidizing treatment of the molten iron according to the above [1], wherein the addition amount of the drowning flux containing CaO as a main component to be blown in the ladle lance is adjusted so that the CaO other than silicon is 8 kg / .

According to the present invention, the ratio of the amount of CaO to the amount of non-silicon outside oxygen [CaO amount / amount of oxygen outside the silicon] in CaO as a main component to be added from the ladle lance is adjusted so that CaO (P ₂ O ₅ ), in which the dewaxing flux containing CaO as a main component is generated, is efficiently absorbed by performing the removal treatment by controlling the removal efficiency within a high range, and as a result, It is realized to carry out the removal process.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an example of a converter type refining furnace suitable for practicing the present invention. FIG.
Fig. 2 is a graph showing the relationship between the ratio [CaO amount / oxygen amount outside the silicon removal amount] and the dehulled lime efficiency.
3 is a graph ^{showing the} relationship between the amount of oxygen outside the silicon and the molten iron before the deoxidizing treatment when the molten iron was subjected to deodorizing treatment with the oxygen amount of 11 to 13 Nm ³ / molten iron-ton and the ratio [CaO amount / And the phosphorus concentration in the molten iron after the phosphorus removal treatment.
Fig. 4 is a diagram showing the results of investigation of the relationship between de-siliconized CaO and deoxidation amount when the ratio [CaO amount / oxygen amount outside the silicon desiliconity] is less than 0.70.
5 is a diagram showing the results of investigation of the relationship between de-siliconized CaO and deoxidation amount when the ratio [CaO amount / amount of oxygen outside the silicon desiliconity] is 0.70 or more and less than 0.80.
6 is a diagram showing the results of investigation of the relationship between de-siliconized CaO and de-phosphorus content when the ratio [CaO amount / amount of oxygen outside the silicon desiliconity] is 0.80 or more and less than 0.90.
7 is a diagram showing the results of investigation of the relationship between de-siliconized CaO and de-phosphorus in the case where the ratio [CaO amount / amount of oxygen outside the silicon desiliconity] is 0.90 or more and less than 1.00.
8 is a graph showing the relationship between the carbon concentration in the molten iron after the denitrification treatment and the phosphorus concentration in the molten iron in comparison between Inventive Example 1 and Conventional Example 1. FIG.
9 is a graph showing the relationship between the silicon concentration in the molten iron before the denitration treatment and the amount of CaO used in the denitrification treatment in Comparative Example 2 and Comparative Example 2. FIG.
10 is a graph showing the relationship between the silicon concentration in the molten iron before the denitration treatment and the iron deinking amount in the denitration treatment in Examples 2 and 2 of the present invention.

Hereinafter, the present invention will be described in detail.

The charcoal used in the dephosphorization process of the present invention is a charcoal produced in a charcoal production facility such as a blast furnace and is used to convert a charcoal produced in a charcoal production facility into a charcoal carrier container such as charcoal ladle or torpedo car, And the returned iron wire is returned to a converter type refining furnace for removing the iron wire. If the silicon content of the molten iron exceeds 0.40% by mass, for example, in many cases, the denitration treatment is efficiently carried out with a small amount of flux used, so that silicon in the molten iron is removed beforehand (referred to as " ). However, the present invention does not require a silicon removal treatment because it is possible to efficiently perform the de-phosphorus treatment even in a molten iron having a silicon content of 0.20 mass% or more and a silicon content of at least 0.20 mass%.

Even in the case of performing the silicon removal treatment, it is not necessary to perform the silicon removal treatment until the silicon content becomes less than 0.20 mass%, and the silicon content of the silicon removal after the silicon removal is 0.20 mass% or more. However, the silicon content of the molten iron is preferably 0.40% by mass or less from the viewpoint of effectively performing the de-phosphorus treatment with a small amount of flux for dredging. That is, it is preferable to reduce the silicon content of the molten iron to 0.20 mass% or more and 0.40 mass% or less in the case of performing the silicon removal treatment, and to apply the dephosphorization method of the present invention.

As means for lowering the silicon content of the molten iron to the above range, an oxygen source such as oxygen gas or iron oxide is supplied to the molten iron, the silicon in the molten iron is oxidized by the oxygen source, and the silicon is forced to the oxide (SiO ₂ ) Can be used. When the molten iron is subjected to the silicon removal treatment, the produced slag is removed until the removal treatment.

The deodorization of the charcoal can be performed in a charcoal ladle or a charcoal transport container such as a toe-do-car. Since the charcoal refiners have larger freeboards than the charcoal transport containers, and the charcoal can be forcibly stirred, It is possible to quickly perform the removal treatment with the use amount of the flux for less denting. Therefore, in the present invention, a deoxidizing treatment is carried out using a converter-type refining furnace. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing an example of a transformer type refractory furnace system suitable for practicing the present invention; Fig.

1, the converter type refining furnace system 1 includes a converter type refining furnace 2 in which an outer periphery is made of a refractory 3 and a refractory 4 is installed inside the refractory 3, And an outlet lance 5 which is inserted into the interior of the converter type refining furnace 2 and is movable up and down. At the upper part of the converter type refining furnace 2 is provided a tapping hole 6 for tapping the molten iron after the treatment is finished and a bottom of the converter type refining furnace 2 is provided with a stirring gas And a bottom air hole 7 for blowing air. The bottom wind hole 7 is connected to a gas introduction pipe (not shown). A hood 8 for collecting the exhaust gas generated in the converter type refining furnace 2 is provided on the upper side of the converter type refining furnace 2 and various refining agents are put into the refining furnace 2 A raw material addition device 9 is provided. As the raw material adding device 9, for example, a hopper 10, a releasing device 11 provided at the lower part of the hopper 10, a chute 12 extending through the hood 8, ) Can be used. 1, only one hopper 10 containing iron oxide 21 such as iron ore is described, but actually, several hoppers are provided.

The outcoupling lance 5 is provided with an oxygen gas supply pipe 13 for supplying oxygen gas for industrial refining (pure oxygen gas for industrial use), a cooling water supply and drain pipe for supplying and discharging cooling water for cooling the upturn lance 5, (Not shown) are connected. The oxygen gas supply pipe 13 branches to the flux supply pipe 14 on the way and the flux supply pipe 14 passes through the dispenser 17 and then joins the oxygen gas supply pipe 13 again. The dispenser 17 contains a powdery dewaxing flux (hereinafter referred to as "CaO dewaxing flux 20") containing CaO as a main component such as quicklime, and the oxygen gas introduced into the dispenser 17 So that the CaO dredging flux 20 functions as a carrier gas for the CaO dredging flux 20 so that the flux 20 can be blown from the front end of the ladder lance 5 together with the oxygen gas toward the molten iron 18 in the furnace Consists of. In this case, the CaO-based drowning flux 20 is added to the collision position (referred to as "hot spot") between the oxygen gas and the hot water bath surface. A shutoff valve 15 is provided in the oxygen gas supply pipe 13 and a shutoff valve 16 is provided in the flux supply pipe 14. By opening and closing the shutoff valve 15 and the shutoff valve 16, So that it can be supplied only in the furnace.

A charcoal 18 is charged into the converter type refining furnace 2 and the air is supplied from the bottom air hole 7 to the Ar refining furnace 2, The CaO flux removing flux 20 is blown into the molten iron 18 from the extruded lance 5 together with the oxygen gas while blowing an inert gas such as gas or nitrogen gas as the agitating gas so that the molten iron 18 ) Is carried out. At this time, if necessary, the iron oxide 21 may be added to the surface of the molten iron bath in the raw material adding device 9 and added.

The phosphorus contained in the molten iron 18 is oxidized by the oxygen gas and is supplied to the slag 19 formed by the slagging of the CaO-based degassing flux 20 added to the phosphorus (P ₂ O ₅ ) to 3CaO · P ₂ O ₅ is fixed to a compound of a (also referred to as _{"Ca 3 (PO 4) 2} ") stable form, the dephosphorization reaction of the molten iron (18) advances. The iron oxide 21 not only functions as a commodity accelerator for the CaO dredging flux 20 but also has the function of increasing the oxygen potential of the slag 19 and enhancing the dehulling ability of the slag 19, ), The dephosphorylation reaction is promoted. However, since FeO is generated in the furnace by the oxygen gas supplied from the outlet lance 5, the addition of the iron oxide 21 is not a necessary condition in the present invention.

The inventors of the present invention have found out that the CaO-based degasser supplied from the dressing lance 5 can be used for the purpose of efficiently carrying out the de-phosphorus treatment even when the silicon content of the molten iron wire 18 is high in the de- (= Amount of CaO / amount of oxygen gas) between the amount of CaO emission in the cyanide flux and the amount of oxygen gas supplied from the upturning lance 5 on the elimination reaction. The oxygen gas supplied from the dressing lance 5 is also consumed in a silicon removal reaction (called a "silicon removal reaction") contained in the molten iron 18. The period during which the desiliconization reaction in the initial stage of refining takes place in the deoxidizing treatment of the molten iron is referred to as a "desiliconizing"

Here, in this investigation, in order to grasp the effect of only the oxygen gas amount on the denitration reaction, the oxygen gas excluding the amount used for the silicon removal reaction in the oxygen gas supplied into the furnace is defined as " did. The ratio of the amount of CaO (kg / charcoal-ton) and the amount of oxygen outside the silicon (kg / charcoal-ton) in the CaO dredging flux to be added to the charcoal bath surface from the ladle lance 5 / Amount of oxygen outside the silicon phase] were variously changed to investigate the effect of the ratio [CaO amount / oxygen amount outside the silicon removal amount] on the de-phosphorus reaction. Further, in the present invention, the ratio [CaO amount / amount of oxygen outside the silicon desiliconization] is also simply referred to as "CaO / O ".

The results of the investigation are shown in Fig. As shown in FIG. 2, when the ratio [CaO amount / amount of oxygen outside the silicon removed] is less than 0.90, the dehulled lime efficiency is maintained at 18 to 20% I found that the efficiency was low. Fig. 2 is a graph showing the relationship between the ratio [CaO amount / amount of oxygen outside the silicon removal] and dehulling lime efficiency. The dephosphorization lime efficiency is, and the CaO content in the CaO-based de-quoted flux in the same addition amount, the percentage of a mass ratio of CaO to form a compound of 3CaO · P ₂ O ₅ eseo the CaO is added when a dephosphorization process the molten iron 18 Respectively.

In the region where the ratio of deoxidizing lime having the ratio [CaO amount / amount of oxygen outside the silicon excluding silicon] of less than 0.90 hardly decreases, when the CaO drowning flux 20 is supplied into the furnace, the supplied CaO drowning flux 20, It can contribute to the de-ionization reaction at a certain rate. That is, the region where the ratio [CaO amount / oxygen amount outside the silicon removed by silicon] is less than 0.90 becomes a region where the deoxidation amount increases as the addition amount of the CaO-based drowning flux 20 is increased. On the other hand, even when a large amount of the CaO-based tin cyanide flux 20 is supplied in the region where the ratio [the amount of CaO / the amount of oxygen outside the silicon removed] exceeds 0.90 and the decolorization efficiency is lowered, Since the proportion contributing to the reaction is low, the CaO-based drowning-out flux 20 added in excess does not contribute to the dephosphorization reaction. Therefore, the region where the ratio [CaO amount / amount of oxygen outside the silicon desiliconity] exceeds 0.90 is simply the region where the CaO-based drowning flux 20 is excessively added.

That is, in order to prevent the excess addition of the CaO dredging flux 20, it is necessary to control the ratio [CaO amount / oxygen amount outside the silicon removal amount] to the extent that the CaO dredging flux 20 can effectively contribute to the elimination reaction And the specific value thereof was less than 0.90. In this range, the ratio [CaO amount / amount of oxygen outside the silicon] is preferably at least 0.6, more preferably at least 0.6, in view of the fact that the addition amount of the CaO- Preferably 0.80 or more.

The present invention is based on the above viewpoints. In the converter refining furnace (2) of the present invention, the deodorization method of the molten iron (18) The gas is blown and the CaO dredging flux 20 is blown into the impingement surface of the oxygen gas against the molten iron 18 through the outgassing lance 5 to oxidize the phosphorus in the molten iron by the oxygen gas And removing the phosphorus in the molten iron by blowing the generated phosphorous oxide into the CaO-based phosphorus removal flux, wherein the molten iron 18 having a silicon content of not less than 0.20 mass% , The ratio of the amount of CaO (kg / charcoal-ton) and the amount of oxygen outside the silicon (kg / charcoal-ton) in the CaO dredging flux to be added to the charcoal bath surface in the ladle lance 5, Deg.] Is less than 0.90, And the amount of the CaO-based drowning flux 20 to be added by blowing from the ladle lance 5 according to the amount of external oxygen is adjusted.

The amount of oxygen gas of ¹ Nm ³ / molten iron-ton corresponds to an addition amount of oxygen of 1.43 kg / molten iron-ton, and the amount of oxygen required to desilicon 1 kg of silicon is , And 1.142 kg (= 1 kg x (16 x 2) / 28). Therefore, when a molten iron having a silicon concentration of Z (mass%) is subjected to a deoxidizing treatment with the total amount of supplied oxygen gas set to F ₀ (Nm ³ / molten iron-ton), the amount of oxygen for deminning (kg / molten- (Kg / molten iron-ton) is represented by the following formula (2), and the amount of CaO supplied from the uprising lance 5 (kg / molten-ton-ton) ) ≪ / RTI >

(Kg / min-line-ton) = (Z / 100) x 1000 x 1.142 (One)

(Kg / charcoal-ton) = F ₀ × 1.43-amount of oxygen for desilicon (kg / charcoal-ton) (2)

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

Here, the total amount of oxygen gas or the amount of oxygen outside the denitration can be determined by determining the total amount of oxygen gas so as to satisfy the thermal condition in the molten iron temperature, the amount of scrap used, the silicon content in the molten iron before the treatment, The amount of oxygen outside the silicon that is required for the removal of the silicon is determined empirically from the content of phosphorus in the molten iron.

In addition, as in Patent Document 4, the ratio of the rate of outgassing (kg / min) of the pure CaO-containing component to the mass flow rate of oxygen gas (kg / min) Oxygen amount] is used as an index, the mass flow rate of the former oxygen gas also includes the oxygen consumed in the desiliconization reaction. Therefore, when the silicon content of the molten iron before the treatment becomes large, in the case of the former, The amount of CaO supplied to the reaction system tends to be excessive. On the other hand, in the present invention, even if the silicon content of the molten iron before the treatment is large, the CaO supply amount does not become excessive. That is, when the dephosphorization treatment method of the present invention is applied to the dephosphorization treatment of a molten iron having a large silicon content, the effect of increasing the dephosphorization efficiency is improved by reducing the amount of CaO used. Therefore, the dephosphorization method of the present invention is preferably applied to a deoxidization treatment of molten iron at a silicon content of not less than 0.20% by mass, more preferably not less than 0.25% by mass before the treatment.

As the CaO dredging flux 20 used in the present invention, any kind of material containing CaO in an amount of 50 mass% or more can be used, and for example, calcium oxide, calcium carbonate, and dolomite can be used. It is also possible to use iron oxide, fluorite, alumina, converter slag (slag produced in decarburization refining in the converter of molten iron), etc. as a fluxing flux 20 containing CaO as a main component. For example, the content of CaO in pure lime is about 90 to 96 mass%.

In the present invention, it is preferable that most of the CaO source used in the denitrification treatment is a powdery CaO dredging flux 20 supplied from the ladle lance 5, but in addition to this, ) Or a known CaO source such as crushed steelmaking slag may be used together at the beginning of the dephosphorization treatment (a period until 1/3 of the scheduled dephosphorization treatment time elapses). However, if the amount of CaO source other than the CaO-based dredging flux supplied from the ladle lance 5 is increased, it is necessary to secure the supply amount of the CaO-based dredging flux to the firing point for promoting the dephosphorization reaction, And the adjustment becomes difficult. Therefore, the amount of the CaO source other than the CaO-based decalcifying flux supplied from the outlet lance 5 is preferably about 1/4 or less, more preferably less than 1/5 of the total CaO source used in terms of CaO Do. The CaO source other than the CaO-based dredging flux supplied from the dressing lance 5 is supplied through the chute 12.

In the present invention, when the content of CaO is controlled to less than 0.90 and the charcoal 18 is subjected to a de-phosphorus treatment, if the silicon content of the charcoal 18 before the dephosphorization is 0.30 mass% or more, , The deinking amount decreased with the increase of the silicon content and the phosphorus concentration in the molten iron after the dephosphorization treatment tended to exceed 0.035 mass%. Fig. 3 is a graph ^{showing the results of the} measurement of the molten iron content of the steel sheet before and after the dephosphorization process, in which the phosphorus concentration was 0.100 to 0.120 mass% and the molten iron temperature was 1280 to 1300 deg. ] Is 0.80 or more and less than 0.90, and the molten iron temperature at the end of the de-phosphorization treatment is controlled to be 1350 to 1370 ° C. When the phosphorus concentration in the molten iron after the de-phosphorus treatment and the phosphorus concentration in the molten iron after the de- And the result of the investigation on the relationship. When the silicon content of the molten iron before the denitration treatment was less than 0.30 mass%, it was confirmed that the phosphorus concentration in the molten iron after the denitration treatment could be stably set to 0.035 mass% or less by applying the present invention.

It is considered that CaO in the CaO-based drowning flux produces a compound in the form of SiO ₂ and CaO · SiO ₂ (calcium silicate) produced by oxidation of silicon. So, when the silicon concentration process more than 0.30% by mass of hot metal dephosphorization, CaO · CaO amount dephosphorization of a low silicon concentration of the molten iron to be consumed for generation of SiO ₂ The reason that the silicon concentration of the de-phosphorus content decreased from more than 0.30 mass% of molten iron as much as compared to the case of CaO treatment is provided for the generation of 3CaO · P ₂ O ₅ the compounds of the stable form is that it is believed that due to the relatively Less.

Therefore, the inventors of the present invention have further studied that, when the charcoal 18 having a silicon concentration of 0.30 mass% or more is subjected to a de-phosphorus treatment, the CaO-based deoxidizing flux 20 is excessively or negatively added. In the examination, CaO except for the CaO-containing component used for producing CaO · SiO ₂ (calcium silicate) in the CaO supplied to the furnace as the CaO source such as the flux 20 for CaO dredging is referred to as "". CaO supplied to the furnace is the sum of CaO contained in the CaO-based dredging flux 20 supplied from the ladle lance 5 and CaO contained in the CaO source supplied from the chute 12. [ Further, CaO · SiO ₂ source to produce a SiO ₂ SiO ₂ is generated by the de-silicon reaction of the molten iron SiO ₂ contained in the additive material such as slag is also included.

As the CaO-containing component contributing to the elimination reaction is CaO other than silicon, it is presumed that the amount of deoxidization is increased by increasing the amount of CaO except desilicon in the conventional knowledge. However, as a result of experiments conducted by the inventors of the present invention, it has been found that the denitration behavior is changed by changing the ratio [CaO amount / oxygen content].

Fig. 4 to Fig. 7 show the results of investigation of the relationship between the desilicon content CaO and the deoxidation amount. Fig. 4 is a graph showing the relationship between the amount of CaO and the amount of oxygen removed from silicon in the case where the ratio [the amount of CaO / the amount of oxygen outside the silicon desorbed] is less than 0.70, External oxygen amount] is 0.80 or more and less than 0.90, FIG. 7 shows a result of investigation of the relationship between de-silicon content and deoxidation amount in the case where the ratio [CaO amount / amount of oxygen outside the silicon removed] is 0.90 or more and less than 1.00. "T.CaO" in FIG. 4 to FIG. 7 is the total amount of CaO in the added CaO-based tin cyanide flux.

As shown in FIG. 4 and FIG. 5, when the ratio [CaO amount / oxygen amount outside the silicon removal amount] was less than 0.80, the amount of deoxidation increased as the amount of CaO other than silicon was increased. That is, when the ratio [the amount of CaO / the amount of oxygen outside the silicon desiliconity] is less than 0.80, it is shown that the elimination reaction is efficiently performed by increasing CaO other than desilicon. On the other hand, when the ratio [the amount of CaO / the amount of oxygen outside the silicon excluding silicon] is 0.90 or more, it was found that the demineralization does not change even when CaO other than desilicon is increased as shown in Fig. When the ratio [CaO amount / amount of oxygen outside the silicon excluding silicon] is 0.90 or more, the efficiency is not good, but it is possible to perform the de-phosphorus treatment with an amount of CaO other than the minimum amount of silicon removed, I got it. The result of FIG. 7 is consistent with the result of FIG.

On the other hand, when the ratio [CaO amount / amount of oxygen outside the silicon removed] is in the range of 0.80 or more and less than 0.90, as shown in FIG. 6, The amount of deoxidation increases. However, when the amount of deasiloxane and CaO exceeds 9 kg / yttrium-ton, the increase of deoxidation is extremely small and the increase of deasiloxin CaO is not effective in increasing deoxidation. That is, even when the CaO-based drowning flux 20 is added so that the ratio of the CaO amount / the oxygen amount outside the silicon-removed silicon is in the range of 0.80 or more and less than 0.90, 9 km / / Tau-ton does not contribute to the dephosphorization reaction but is excessive, and conversely, it interferes with the reduction of the hot-wire temperature or the commodity of the CaO-based tin cyanide flux 20, I found out.

That is, when the molten iron 18 having a silicon concentration of 0.30 mass% or more is subjected to a dehydration treatment in a range of 0.80 or more and less than 0.90 in a ratio [CaO amount / oxygen amount outside the silicon removal amount], 6 to 9 kg / , More desirably, it is preferable to adjust the amount of desiliconized CaO to fall within a range of 6 to 8 kg / gallon-ton. By doing so, it is possible to add the CaO-based drowning-in-flux 20 to the surface without excess or deficiency, and the denitration treatment can be performed efficiently. However, even when a molten iron having a silicon concentration of 0.30 mass% or more is subjected to a deoxidizing treatment, when the ratio [CaO amount / amount of oxygen outside the silicon removed] is less than 0.80, the deoxidation amount due to the addition of desiliconizing CaO increases, It is preferable to increase the amount of CaO outside the denitration within a range where there is a sufficient allowance, and when it is 8 kg / min-line-ton or more, it is suitable to secure effective deoxidation.

As described above, according to the present invention, the ratio of the amount of CaO and the amount of oxygen outside the silicon contained in the CaO dredging flux added from the pickling lance 5 to the amount of CaO out-tearing flux In other words, as the CaO concentration in the slag is increased, the charcoal 18 is subjected to the de-phosphorus treatment under the operating conditions in which the de-phosphorus amount is increased, so that the added CaO- The cited flux 20 efficiently absorbs the generated phosphorous oxide (P ₂ O ₅ ), and as a result, the dephosphorization treatment is performed more efficiently than in the prior art.

[Example 1]

By using the converter type refining furnace system shown in Fig. 1, the present invention was applied to a charcoal which was drawn out from the blast furnace and subjected to a phosphorus removal treatment. The phosphorus concentration in the molten iron before the demineralization treatment is 0.100 to 0.120 mass%, the silicon concentration in the molten iron is 0.20 mass% or more and less than 0.30 mass%, and the molten iron temperature is 1280 to 1300 ° C. (11 to 12 Nm < ³ > / molten iron-ton) so that the molten steel becomes 1370 deg. The total amount of the CaO dredging flux is determined at a ratio of the ratio [CaO amount / amount of oxygen outside the silicon] to the range of 0.83 to 0.85, and the total use amount of the CaO dredging flux at the amount of oxygen outside the silicon is determined. And then subjected to a removal treatment (Example 1 of the present invention). The CaO source added in the furnace was only the CaO diesel flux blown from the ladle lance and the ratio [CaO amount / amount of oxygen outside the silicon removed] was adjusted so that the amount of CaO outside the denitration was 9 kg / molten iron-ton or less. As the flux for CaO dredging, quicklime (content of pure CaO content: 93 mass%) was used.

Fig. 8 shows the relationship between the carbon concentration in the molten iron after the denitration treatment and the phosphorus concentration in the molten iron, when the present invention is applied to the denitration treatment (Example 1 of the present invention). Fig. 8 shows the relationship between the carbon concentration in the molten iron after phosphorus removal treatment and the phosphorus concentration in the molten iron in the conventional denitration treatment as a prior art example 1. In this Conventional Example 1, the addition rate of the CaO-based drowning flux was set to 1.67 kg / (min · molten-ton) in the early stage of the dephosphorization treatment including the pure silica- (Min-char-ton) at the end of the treatment period was adjusted to about 1.4 kg / (min-char-ton) at the average of the treatment time as a whole, to be.

In the first and the first prior art examples, the oxygen supply rate was 1.94 to 2.50 Nm ³ / (min · char-ton) for desilicon groups and 1.33 Nm ³ / (min · char-ton) The blowing time was about 12 minutes. In addition, in Comparative Example 1, the ratio [CaO amount / oxygen amount outside the silicon removal amount] was all 1.00 or more, and the basicity (mass% CaO) / (mass% SiO ₂ ) of the slag after the removal treatment was in the range of 2.7 to 3.7. 8, the solid line represents the regression equation based on the cumulative square approximation value of the inventive example 1 obtained using the least squares method, and the broken line represents the regression equation by the cumulative square approximation value of the conventional example 1 obtained by using the least squares method .

In Example 1 of the present invention, since the ratio [CaO amount / oxygen amount outside the silicon removal amount] is less than 0.90, the dephosphorization efficiency is improved, and the CaO dross flux can be efficiently contributed to the de- , The concentration of phosphorus in the molten iron after the denitrification treatment was 0.030 mass% or less, and it was realized that the phosphorus concentration in the molten iron after the denitration treatment was stabilized lower than that of Conventional Example 1. On the contrary, in Conventional Example 1, the ratio [CaO amount / amount of oxygen outside the silicon removed] is 1.00 or more, the efficiency of dehulling lime is low, and the CaO dredging flux can not be efficiently contributed to the de-phosphorus reaction, It is considered that the phosphorus concentration in the charcoal is increased.

[Example 2]

In the case where the silicon concentration in the molten iron is higher than 0.30 mass% and less than 0.50 mass%, which is higher than that in the case of Inventive Example 1, the present invention is applied to the removal process. The conditions of the molten iron component other than silicon and the molten iron temperature were the same as those of the present invention. As the silicon content in the molten iron increased, the amount of oxygen outside the dense silicon was increased from 16.7 to 19.5 kg / molten iron-ton (11.7 to 13.7 Nm ³ / molten iron-ton).

When the ratio [CaO amount / amount of oxygen removed from silicon] is in the range of 0.75 or more and less than 0.90, and when the ratio [CaO amount / oxygen amount outside the silicon removal amount] is 0.80 or more and less than 0.90, , And when the ratio [CaO amount / amount of oxygen outside the silicon desorbed] is in the range of 0.75 or more and less than 0.80, the total amount of the CaO-based tin cyanide flux from the amount of oxygen outside the silicon so that the CaO other than silicon is 8 kg / (93 mass% of pure CaO content was blown as a CaO dredging flux from a ladle lance so that the addition rate was constant). The CaO source added in the furnace was only the CaO flux for dewaxing blown from the lance lance, and the amount of CaO outside the dense silicon was in the range of 8 to 9.6 kg / charcoal-ton.

As Conventional Example 2, a deodorizing method of a hot wire described in Patent Document 4 was applied to deodorize a molten iron having a silicon concentration of 0.30 mass% or more and less than 0.50 mass% in the hot wire. The CaO source added in the furnace was only the CaO diesel flux blown from the ladle lance and the value of the ratio between the rate of outgassing (kg / min) of the pure CaO-containing component and the mass flow rate of oxygen gas (kg / min) + 0.69 x [Si] to 0.56 + 0.83 x [Si] ", the content rate of the pure CaO content was determined. In this Conventional Example 2, the amount of oxygen outside the silicon is in the range of 18.2 to 22.5 kg / charcoal-ton. As a result, in the index of [CaO amount / oxygen amount outside the silicon removal amount] The basicity (mass% CaO) / (mass% SiO ₂ ) of the slag after the removal treatment was in the range of 2.4 to 2.6 in the range of 11 to 17 kg /

FIG. 9 shows the relationship between the silicon concentration in the molten iron before the denitration treatment and the amount of CaO used in the denitrification treatment in Comparative Examples 2 and 2. 10 shows the relationship between the silicon concentration in the molten iron before the denitration treatment and the deinking amount of the molten iron in the denitration treatment in Comparative Example 2 and Comparative Example 2. As shown in Fig.

9, it was found that, in Example 2 of the present invention, even if the silicon concentration in the molten iron is as high as 0.30 mass% or more, the amount of CaO used can be increased without increasing the amount as in Conventional Example 2. [

10, even if the amount of CaO to be used is drastically reduced compared with that of Conventional Example 2, there is no significant difference in demineralization amount. Therefore, in the method of the present invention, CaO / By controlling the addition amount, it can be seen that efficient deodorizing treatment is possible while greatly reducing the amount of CaO used.

Explanation of symbols

1: Furnace type refinery furnace

2: converter type refining furnace

3: Evil

4: Refractory

5:

6: Tapping area

7: bottom wind hole

8: Hood

9: Material addition device

10: Hopper

11: Release device

12: Suit

13: oxygen gas supply pipe

14: flux supply pipe

15: Isolation valve

16: Isolation valve

17: Dispenser

18: Charter

19: slag

20: Flux for CaO-based decaling

21: iron oxide

Claims (3)

An oxygen gas is blown into the molten iron in the converter type refining furnace from the ladle lance and the dyning flux containing CaO as a main component is blown into the impingement surface against the molten iron of the oxygen gas through the uprising lance, A method for removing phosphorus in a molten iron by oxidizing phosphorus in a molten iron and blowing the resulting phosphorus into a slag forming flux,
In the deoxidizing treatment of the molten iron having a silicon content of 0.20 mass% or more before the denitration treatment, the oxygen gas excluding the component used for the silicon removal reaction in the oxygen gas supplied to the furnace was defined as the amount of oxygen outside the silicon (kg / molten iron-ton) , The ratio of the amount of CaO (kg / charcoal-ton) in the flux for decalcification mainly containing CaO to the amount of oxygen outside the silicon (CaO amount / amount of oxygen outside the silicon denitration ] Is less than 0.90, the amount of the dyning flux to be added is adjusted by adjusting the amount of oxygen added outside the silicon lance in accordance with the amount of oxygen outside the denitration. The method according to claim 1,
And the ratio [CaO amount / amount of oxygen outside the silicon] is set in the range of 0.80 or more and less than 0.90. The method according to claim 1,
CaO, except for the CaO-containing component used for producing CaO · SiO ₂ (calcium silicate) in the CaO supplied to the furnace, is removed from the furnace at a rate of 0.30 mass% When defined,
In the case of performing the deoxidization of the molten iron within the range of the ratio [CaO amount / amount of oxygen outside the silicon] to 0.80 or more and less than 0.90, the molten iron is blown from the upturned lance so that the amount of the desiliconized CaO is in the range of 6 to 9 kg / The addition amount of the flux for decarburization mainly containing CaO to be added is adjusted,
In the case of performing the deoxidizing treatment of the molten iron in the ratio [the amount of CaO / the amount of oxygen outside the silicon excluding silicon] to the range of less than 0.80, CaO to be added by blowing from the ladle so that the amount of desiliconated CaO is 8 kg / A method for removing phosphorus from a molten iron to adjust an addition amount of a flux for dingning as a main component.

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