JP5266700B2 - Hot metal dephosphorization method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently perform dephosphorizing treatment to molten iron by restricting the spouting of slag without adding CaF<SB>2</SB>-based flux in a vessel of small free-board, such as a molten iron ladle, a molten iron mixer car. <P>SOLUTION: The dephosphorizing treatment method for the molten iron related to this invention, is the one, in which the dephosphorizing treatment is applied to the molten iron by adding an oxygen source and a CaO-based dephosphorizing refining agent into the molten iron 2 held in the molten iron ladle 5 or the mixer car; and is characterized in that a gaseous oxygen source is supplied on the molten iron from one supplying system of a top-blowing lance 7 and also, at least a part of solidified oxygen source 4 from the other one supplying system of the top-blowing lance 7, is supplied with the top-blowing by using gas for carrying on the molten iron bath surface on the same position or the neighborhood of the position for supplying the above gaseous oxygen source, and the CaO-based dephosphorizing refining agent 3 is blown into the molten iron together with the gas for carrying through an injection lance 8. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  TECHNICAL FIELD The present invention relates to a hot metal dephosphorization method performed in a small freeboard container such as a hot metal ladle (also referred to as “blast furnace pan”) or a kneading car (also referred to as “torpedo car”). In addition, the present invention relates to a dephosphorization treatment method that can efficiently remove phosphorus without using a fluorine source for promoting the hatching of a dephosphorizing agent.

In recent years, the required quality for steel materials has become increasingly strict, and reduction of impurity elements typified by phosphorus and sulfur has been demanded. In order to meet such demands, in the steelmaking process, it is common to perform a dephosphorization process in the hot metal stage. In this dephosphorization treatment, an oxygen source such as oxygen gas (gaseous oxygen) or solid iron oxide is supplied to the hot metal as a dephosphorizing agent, and phosphorus in the hot metal is oxidized with oxygen in the dephosphorizing agent to form an oxide (P ₂ O ₅ ), and the produced phosphorus oxide is absorbed into the dephosphorization slag. As a dephosphorizing refining agent for forming a dephosphorizing refining slag, a CaO-based dephosphorizing refining agent is generally used.

  This hot metal dephosphorization process involves adding a dephosphorizing refining agent to the hot metal in the converter and blowing up oxygen gas, or dephosphorizing or dephosphorizing the hot metal in a kneading car or hot metal pan. And a method of blowing a dephosphorizing refining agent, etc., and processes are selected and implemented according to the facilities and environment of each steelworks. Of these, the method using a converter has the advantage that a low-phosphorus hot metal can be produced in a short time because the free board is large and oxygen gas can be sprayed onto the hot metal at a high flow rate. When there is no margin in the converter capacity and a new installation is required, high equipment costs are required. In addition to the dephosphorization reaction, the progress of the decarburization reaction is unavoidable, and the reduction of the heat margin in the subsequent process becomes a problem. On the other hand, the method using a kneading car or hot metal ladle has the advantage that the equipment cost is low due to the process using the existing hot metal transfer container, and the merit of hot metal dephosphorization can be enjoyed even if the converter capacity is not sufficient. And it is widely done.

However, the method using a kneading wheel or hot metal ladle has a problem that the dephosphorization reaction is not efficient compared to the case of using a converter because the free board is small and the stirring power of the hot metal cannot be increased. Therefore, in order to prevent this, by using a CaF ₂ -based solvent such as fluorite as a hatching accelerator for the CaO-based dephosphorizing refining agent, the meltability of the dephosphorizing refining slag is improved, A technique for improving the dephosphorization reactivity has been widely used (see, for example, Patent Document 1).

However, in recent years, the regulation standard of the amount of fluorine elution from slag has been strengthened from the viewpoint of environmental protection, and it has been necessary to reduce the fluorine content even in slag for dephosphorization, such as fluorite There has been a strong demand for the development of a method capable of highly efficient dephosphorization without using a CaF ₂ -based solvent.

  Therefore, in Patent Document 2, oxygen gas and at least a part of the CaO-based dephosphorizing refining agent are sprayed onto the hot metal bath surface through an upper blowing lance to the hot metal contained in a kneading wheel or hot metal ladle, and an injection lance or / and / or There has been proposed a method of dephosphorizing the molten iron by blowing a part of the CaO-based dephosphorizing refining agent into the molten iron together with a carrier gas through a blowing nozzle. In Patent Document 2, a solid oxygen source such as iron oxide (eg, sintered powder, mill scale) can be used in addition to oxygen gas as an oxygen source to be added to the refining vessel, that is, a dephosphorizing agent. It can be added by any method such as charging or blowing into the bath. Note that oxygen gas or oxygen-containing gas is referred to as gaseous oxygen source with respect to the solid oxygen source.

According to Patent Document 2, when oxygen gas is sprayed on the hot metal bath surface through the top blowing lance, a large amount of FeO is generated by the oxygen gas colliding with the bath surface, and CaO is generated in the region where this FeO is produced in large amounts through the top blowing lance. By directly supplying the system dephosphorization refining agent, the hatching of the CaO system dephosphorization refining agent is promoted without using a CaF ₂ system solvent, and an efficient dephosphorization process is possible.
JP-A-4-280909 Japanese Patent Laid-Open No. 2004-83989

According to Patent Document 2, the hatching of the CaO-based dephosphorization refining agent is promoted, and an efficient dephosphorization process is possible without using a CaF ₂ -based solvent. Forming (foaming) was severe, and a new problem of spout of slag for dephosphorization during dephosphorization occurred. This is because, during the dephosphorization process, the CaO-based dephosphorization refining agent is added from both the top blowing lance and the injection lance, so the hot metal bath surface is covered with the dephosphorization slag, and FeO and hot metal This was due to the fact that the place where the CO gas generated during the dephosphorization treatment was eliminated due to the reaction with carbon was lost.

  When slag blows out, the metal debris flows out together with the slag for dephosphorization and the iron yield is lowered, and the absolute amount of slag for dephosphorization and refining is insufficient, so that the phosphorus in the hot metal after the dephosphorization treatment There also arises a problem that the variation in density becomes large. Furthermore, when the amount of ejection is large, damage to peripheral equipment is caused. For this reason, when slag ejection occurs, the oxygen gas supply rate has to be reduced, and the treatment time has been extended and sedatives have been added.

The present invention has been made in view of the above circumstances, and its purpose is to suppress slag jetting while dephosphorizing hot metal using a small freeboard container such as a hot metal pan or a kneading car, It is an object of the present invention to provide a hot metal dephosphorization method capable of efficiently dephosphorizing hot metal without adding a CaF ₂ -based solvent.

  The hot metal dephosphorization processing method according to the first aspect of the present invention for solving the above-mentioned problem is to add an oxygen source and a CaO-based dephosphorization refining agent to hot metal contained in a hot metal ladle or a kneading car to dephosphorize the hot metal. A hot metal dephosphorization treatment method, wherein a gaseous oxygen source is blown from one supply system to the hot metal bath surface, and at least a part of the solid oxygen source is supplied from the other supply system. The hot gas is supplied to the hot metal bath surface near or in the vicinity of the place where the gaseous oxygen source is supplied using a carrier gas, and the CaO-based dephosphorizing refining agent is introduced into the hot metal together with the carrier gas through an injection lance. It is characterized by blowing.

  The hot metal dephosphorization method according to the second invention is characterized in that, in the first invention, the supply systems of the gaseous oxygen source and the solid oxygen source are arranged in the same lance. .

  The hot metal dephosphorization method according to the third invention is the first or second invention, wherein the solid oxygen source is one of sintered ore, mill scale, dust, and iron ore having a particle size of 1 mm or less. It is one type or two or more types.

  According to the present invention, when the molten oxygen is dephosphorized by blowing up the gaseous oxygen source, the CaO-based dephosphorizing refining agent is blown and added into the molten iron, and the same location as the location where the gaseous oxygen source is supplied Alternatively, since the solid oxygen source is added to the hot metal bath surface in the vicinity of the place where the gaseous oxygen source is supplied together with the carrier gas, the hot metal bath surface to which the solid oxygen source is added is formed from a CaO-based dephosphorizing refining agent. Since the dephosphorization slag is thin and the solid oxygen source is added to form a gas escape route, the gas escape route is secured in the region where the solid oxygen source is added and reacts with FeO. Since the generated CO gas is discharged out of the system through this escape route, the formation of dephosphorization slag is reduced, thereby suppressing the slag ejection.

  In addition, since the solid oxygen source is supplied together with the carrier gas to the hot metal bath surface near the location where the gaseous oxygen source is supplied or near the location where the gaseous oxygen source is supplied, the solid oxygen source is melted. As a result, the oxygen potential of the dephosphorization slag is rapidly increased and the dephosphorization ability of the slag is improved. By improving the dephosphorization ability of the dephosphorizing slag, even if the fluorine-containing material is not used as a medium solvent for promoting hatching, and even if the amount of CaO-based dephosphorizing agent used is small, It is possible to perform the dephosphorization process while maintaining the same dephosphorization rate as before.

  Hereinafter, the present invention will be specifically described.

  Hot metal dephosphorization treatment using a hot metal transport container such as a kneading wheel or hot metal ladle as a reaction container is generally a CaO-based dephosphorization refining agent, a gaseous oxygen source such as oxygen gas, and solid oxygen such as solid iron oxide. The source phosphorus is added to the hot metal, the phosphorus in the hot metal is oxidized by the gaseous oxygen source and the solid oxygen source, and the generated phosphorous oxide is converted into a dephosphorizing slag (hereinafter referred to as a slag for dephosphorization) formed from a CaO-based dephosphorizing agent. , Simply referred to as “slag”) and removing phosphorus in the hot metal. The gaseous oxygen source and the solid oxygen source are collectively referred to as the oxygen source.

In principle, solid oxygen sources are more efficient than gaseous oxygen sources for dephosphorization reactions. This is because the dephosphorization reaction is thermodynamically more advantageous at lower temperatures. When oxygen is added to the hot metal, decarburization and dephosphorization occur, but when a gaseous oxygen source is added, the temperature rise due to the exothermic heat of the oxidation reaction is dominant, whereas when a solid oxygen source is added, the solid oxygen source Since heat is absorbed during decomposition, temperature rise is suppressed. That is, by using a solid oxygen source, a temperature advantageous for the dephosphorization reaction is maintained. However, in order to promote the dephosphorization reaction, a temperature condition that can melt the solid oxygen source is necessary. Further, the solid oxygen source has a function of increasing the FeO component in the dephosphorization slag, which becomes FeO after melting and contributes to the dephosphorization reaction. Promotes the phosphorus reaction. In particular, in the dephosphorization process using the hot metal transfer container having an oxygen gas supply rate of 1 Nm ³ / min · T or less, the production rate of FeO by the oxygen gas is slow, which contributes to the formation of FeO components that contribute to the dephosphorization reaction. doing.

  Conventionally, the solid oxygen source has been generally dropped and introduced from a hopper installed above the reaction vessel during the dephosphorization process. In this case, in order to prevent the solid oxygen source from being sucked into the exhaust system, a granular or lump of several mm to several tens mm is used. The granular or lump solid oxygen source does not melt immediately when it is put into the reaction vessel, and may remain until the end of the dephosphorization treatment. In addition, FeO in the slag rises as the solid oxygen source melts, but the FeO in the slag reacts with the carbon in the hot metal and is reduced, so the melting rate of the solid oxygen source and the reduction rate of FeO Are equivalent, the FeO concentration in the slag does not increase. In other words, unless the melting rate of the solid oxygen source is set higher than the reduction rate of FeO in the slag, the oxygen potential in the slag does not increase and an improvement in the dephosphorization rate cannot be expected.

  In the present invention, a gaseous oxygen source is blown up and supplied from one supply system to the hot metal bath surface, and a solid oxygen source is supplied from another supply system to the hot metal bath surface at the same location where the gaseous oxygen source is supplied or The hot metal is blown and supplied onto the hot metal bath surface near the place where the gaseous oxygen source is supplied using a carrier gas.

  At the hot metal bath surface, the location where the gaseous oxygen source collides with the hot metal bath surface, that is, the hot point, is heated by the reaction between the gaseous oxygen source and the carbon in the hot metal, and the solid oxygen source supplied to the hot oxygen bath surface is quick. To increase the FeO component in the slag. Moreover, although the temperature of the peripheral part in the vicinity of the hot spot is lower than that of the hot spot, it is maintained at a relatively high temperature, so that the solid oxygen source supplied thereto is rapidly melted. As a result, the oxygen potential of the slag is increased, that is, the optimum slag for the dephosphorization reaction is quickly formed, and the dephosphorization process is possible even with a small amount of slag. The “hot metal bath surface in the vicinity of the place where the gaseous oxygen source is supplied” as used in the present invention means a portion near the fire point and having a temperature higher than the average temperature of the entire hot metal.

  As the gaseous oxygen source used in the present invention, oxygen gas (including industrial pure oxygen), air, oxygen-enriched air, a mixed gas of oxygen gas and inert gas, and the like can be used. In the case of normal dephosphorization treatment, it is preferable to use oxygen gas because the dephosphorization reaction rate is faster than when other gases are used. In the case of using a mixed gas, it is preferable to make the oxygen concentration higher than that of air in order to ensure the dephosphorization reaction rate.

  As a preferred embodiment of the present invention, as the gas for transporting the solid oxygen source, any one of air, a non-oxidizing gas, a rare gas, a reducing gas, and a carbon dioxide gas that is a weak oxidizing gas close to the non-oxidizing gas is used. One or more gases are used. Here, the reducing gas is a hydrocarbon gas such as propane gas and CO gas, the non-oxidizing gas is a gas having no oxidizing ability such as nitrogen gas, and the rare gas is Ar gas or He. An inert gas such as a gas. By using these gases, it is possible to suppress the temperature rise at or near the fire point, and in principle, conditions that are advantageous for dephosphorization can be created.

  In the present invention, the effect can be obtained even if the carrier gas of the solid oxygen source is a gas containing a certain amount of oxygen, such as air. However, from the above viewpoint of suppressing the temperature rise at or near the fire point, it is desirable that the concentration of oxygen contained in the carrier gas is lower than that of the gaseous oxygen source. For example, when the gaseous oxygen source is air, it is desirable to use a non-oxidizing gas, a rare gas, a reducing gas, a carbon dioxide gas, or the like as the carrier gas for the solid oxygen source. Further, when the gaseous oxygen source is pure oxygen or oxygen-enriched air, all of the above-described carrier gases can be used.

  Some solid oxygen sources contain a small amount of metallic iron, which may burn in a pure oxygen stream and damage equipment. Carrying the solid oxygen source with a carrier gas having a lower oxygen concentration than air is also effective from the industrial viewpoint of avoiding accidents.

  In the present invention, the CaO-based dephosphorizing refining agent is blown into the hot metal along with the carrier gas through the injection lance. The CaO-based dephosphorization refining agent is heated by being blown into the hot metal, and hatching is promoted. That is, the dephosphorization reaction is promoted. In addition, since the CaO-based dephosphorizing refining agent is not directly added to the fire point and the vicinity thereof, the thickness of the slag is reduced at the fire point and the vicinity thereof, and there is a gas escape route in the slag by the solid oxygen source added together with the carrier gas. Thus, the CO gas produced by the reaction between FeO in the slag and carbon in the hot metal is discharged out of the system through this escape route. Thereby, slag forming is reduced and slag ejection is suppressed. As the carrier gas for transporting the CaO-based dephosphorizing agent, as with the carrier gas of the solid oxygen source, weak oxidation close to air, non-oxidizing gas, rare gas, reducing gas, non-oxidizing gas Any one kind or two kinds or more of carbon dioxide which is a sex gas can be used.

  The CaO-based dephosphorizing refining agent used in the present invention is not particularly limited as long as it contains CaO and can be dephosphorized as intended in the present case. Usually, it consists of CaO alone, or contains 50 mass% or more of CaO, and contains other components as necessary.

  As other components, hatching accelerators are generally used. That is, although this case is a technique that enables the reduction or omission of hatching accelerators, it does not prohibit addition of hatching accelerators to further improve hatching efficiency. As the hatching accelerator, in particular, a substance containing titanium oxide or aluminum oxide having an action of promoting the hatching by lowering the melting point of CaO can be mentioned, and these are preferably used. Among these, addition of titanium oxide is preferable from the viewpoint of slag viscosity. Fluorine-containing materials such as fluorite can also be used as hatching accelerators. However, when the slag is disposed of or the like, it is preferable not to use the fluorine-containing substance as a hatching accelerator from the viewpoint of protecting the environment by suppressing the amount of fluorine eluted from the slag. A substance in which fluorine is inevitably mixed as an impurity component may be used.

  As a specific example of the CaO-based dephosphorization refining agent, it is preferable to use quick lime or limestone because it is inexpensive and has excellent dephosphorization ability. In addition, light-burning dolomite or converter slag (also referred to as “decarburized slag”) generated when decarburized and refined hot metal after dephosphorization treatment is used as a CaO-based dephosphorizing refining agent. It can also be used. The converter slag is mainly composed of CaO and has a low phosphorus content, so that it can be sufficiently used as a CaO-based dephosphorizing agent.

  In addition, as the solid oxygen source used in the present invention, iron ore sintered ore, mill scale, dust (= dust collection dust), iron sand, iron ore and the like can be used. Dust collection dust is dust containing iron that is recovered from exhaust gas in a blast furnace, converter, and sintering process. From the viewpoint of promoting melting of the solid oxygen source, the solid oxygen source is preferably a granular material having a particle size of 1 mm or less. When the particle size exceeds 1 mm, rapid melting is difficult, and it is difficult to increase the FeO component in the slag. Here, the particle size of 1 mm or less means that the particle size passes through a sieving machine with an opening size of 1 mm, and the spindle has a spindle shape with a major axis exceeding 1 mm as long as it passes through a sieving machine with an opening size of 1 mm. It doesn't matter. From the viewpoint of handling, the particle size is preferably 1 μm or more.

  In the dephosphorization process of the present invention, it is necessary to supply a solid oxygen source to the hot metal bath surface at or near the same location where the gaseous oxygen source is supplied. In this way, the gaseous oxygen source and the solid oxygen source are supplied. In order to supply, for example, at least two supply systems are installed in the upper blow lance for supplying these, a gaseous oxygen source is supplied from one of the supply systems, and solid oxygen is supplied from the other supply system. By supplying the source together with the above-described carrier gas, the above-described addition conditions can be achieved. In this case, whether the solid oxygen source is added in the same location as the location where the gaseous oxygen source is supplied or in the vicinity thereof is determined depending on the blowing condition (flow rate) Therefore, it cannot be defined simply from the shape of the top blowing lance alone. However, as long as an upper blowing lance having at least two supply systems is used, a gaseous oxygen source is supplied from one system, and a solid oxygen source is supplied from another system together with the carrier gas, it is within the scope of the present invention. Conditions can be set.

  As the above configuration having two supply systems, for example, the upper blowing lance has at least a double pipe structure, one is a flow path for oxygen gas, the other is a flow path for solid oxygen source and transport gas, and gas A method in which an oxygen source is supplied from a plurality of nozzle holes arranged concentrically around a lance center axis, while a solid oxygen source and a transport gas are supplied from nozzle holes arranged on a lance center axis Etc. can be adopted. Alternatively, a plurality of nozzle holes may be arranged on a concentric circle with the lance center axis as the center, and the gaseous oxygen source and the solid oxygen source may be supplied from alternate (alternate) holes.

In the present invention, it is not necessary to supply all of the solid oxygen source to be supplied to the hot metal bath surface at or near the same location where the gaseous oxygen source is supplied, and only a part of the solid oxygen source is gaseous oxygen. You may supply to the hot metal bath surface of the same place as the place where the source is supplied, or its vicinity. However, if there is a small amount of solid oxygen source to be supplied to the hot metal bath surface at or near the same location where the gaseous oxygen source is supplied, the increase in the FeO component in the slag is small, so to prevent this, The amount by which the FeO component in the slag is sufficiently increased may be set as the lower limit depending on the equipment specifications. Moreover, as an upper limit, what is necessary is just to suppress to the quantity which does not become excessive heat removal according to equipment specifications. For example, when dephosphorization is performed in a container of about 100 to 350 tons, the carrier gas is used for the pure oxygen gas content 1 Nm ³ (the pure oxygen gas content in the standard state) in the gaseous oxygen source supplied to the bath surface. It is preferable to add the solid oxygen source supplied in the range of 0.1 kg to 2 kg. If the amount is less than 0.1 kg, the effect expected in the present invention cannot be sufficiently obtained. On the other hand, if the amount exceeds 2 kg, the heat removal on the supply surface of the solid oxygen source is increased, and the slag is insufficiently hatched to remove phosphorus. Will be reduced. A more preferable supply amount is 0.3 kg or more and 2 kg or less.

  What is necessary is just to supply the solid oxygen source supplied to places other than the hot metal bath surface in the same place as the place where the gaseous oxygen source is supplied, or an appropriate method such as addition by blowing or blowing. In this case, in order to prevent the solid oxygen source from being sucked into the exhaust system, it is preferable to use a granular or lump of several mm to several tens mm.

  When a gaseous oxygen source is used, the hot metal temperature rises due to the oxidation reaction heat. On the other hand, when a solid oxygen source is used, the sensible heat, latent heat and decomposition heat of the solid oxygen source itself are oxidized reaction heat. Is larger than that, the hot metal temperature drops. Therefore, the use ratio of the gaseous oxygen source and the solid oxygen source is set according to the temperature before and after the hot metal treatment while maintaining the above range. In order to efficiently perform the dephosphorization reaction, it is preferable to stir the hot metal, and this stirring may be performed using a carrier gas blown from an injection lance for adding a CaO-based dephosphorizing agent.

  As the dephosphorizing slag, the FeO concentration in the slag is preferably in the range of 10% by mass or more and 50% by mass or less. Therefore, the supply amount of the solid oxygen source is maintained so that the FeO concentration in the slag can maintain this range. Is preferably adjusted. A more preferable range is 10% by mass or more and 30% by mass or less.

  By performing dephosphorization of the hot metal in this way, it is equivalent to the conventional one even if the fluorine-containing substance is not used as a medium solvent for promoting hatching while suppressing the slag for dephosphorization slag from being ejected from the container. Thus, it is possible to perform the dephosphorization treatment while maintaining the dephosphorization rate. As a result, by suppressing slag ejection, there is no need to reduce the supply rate of the gaseous oxygen source, it becomes possible to shorten the dephosphorization treatment time, and since the dephosphorization slag does not contain fluorine, The slag for dephosphorization refining can be reused without taking measures against fluorine leakage to the environment, and it is possible to avoid environmental burdens.

  An embodiment of the present invention in the dephosphorization processing facility shown in FIG. 1 will be described.

  In FIG. 1, a hot metal ladle 5 containing hot metal 2 is mounted on a carriage 6 and carried into a dephosphorization processing facility 1. The dephosphorization processing equipment 1 is provided with an upper blowing lance 7 and an injection lance 8 that can move up and down in the hot metal ladle 5. The upper blowing lance 7 accommodates oxygen gas and a storage tank 10. The solid oxygen source 4 is sprayed onto the hot metal 2, and the CaO-based dephosphorizing refining agent 3 contained in the storage tank 9 is sprayed onto the hot metal 2 from the injection lance 8. Although not shown, the upper blowing lance 7 has a quadruple tube structure, the outside and the inside thereof are a cooling water supply / drain passage, the inside thereof is an oxygen gas supply passage, and the inside is a central oxygen supply 4 supply. It is a road.

  The dephosphorization processing facility 1 is further provided with a raw material supply facility comprising a hopper 11, a raw material transfer device 12, and a chute 13, and the solid oxygen contained in the hopper 11 using this raw material supply facility. The source 4 can be added to the inside of the hot metal ladle 5 and added.

  The oxygen gas used is industrial pure oxygen, quick lime is used as the CaO-based dephosphorizing refining agent 3, dust collection dust in the sintering process is used as the solid oxygen source 4, and the CaO-based dephosphorizing refining agent 3 and Nitrogen gas was used as the carrier gas for the solid oxygen source 4. In the figure, reference numeral 14 denotes a dephosphorization slag formed from the CaO-based dephosphorization refining agent 3 and the like.

  The hot metal ladle 5 containing about 150 tons of hot metal 2 discharged from the blast furnace is transported to the dephosphorization treatment equipment 1 having the above-described configuration, and oxygen gas and a solid oxygen source 4 are sprayed onto the hot metal bath surface through the upper blowing lance 7. At the same time, the CaO-based dephosphorization refining agent 3 was blown into the hot metal via the injection lance 8, and further, the dephosphorization treatment was performed while the solid oxygen source 4 accommodated in the hopper 11 was added on top.

  For comparison, the dephosphorization treatment method according to Patent Document 2 described above, that is, oxygen gas and at least a part of the CaO-based dephosphorization refining agent 3 are sprayed onto the hot metal bath surface through the top blowing lance 7 and the injection lance. 8 through which a part of the CaO-based dephosphorization refining agent 3 is blown into the molten iron together with a carrier gas (nitrogen gas), and the dephosphorization treatment is performed while adding the solid oxygen source 4 over the chute 13 (comparative example) Was also implemented.

  FIG. 2 shows the phosphorus concentration in the hot metal after the dephosphorization treatment in comparison with the inventive example and the comparative example. In the figure, the oxygen free unit outside of Si removal on the horizontal axis is the unit of oxygen source obtained by subtracting the oxygen source spent for the desiliconization reaction from the total oxygen source supplied. As apparent from FIG. 2, when the de-Si external oxygen basic unit is the same, the phosphorous concentration in the hot metal after treatment is lower in the inventive example than in the comparative example, and the dephosphorization reaction is efficiently performed. I was able to confirm the progress. That is, it was confirmed that the present invention example has higher dephosphorization oxygen efficiency by about 1% than the comparative example. The numerical value in% in the figure is the dephosphorization oxygen efficiency obtained from the calculation.

Further, in the example of the present invention, even if the oxygen gas supply rate is increased to 2000 Nm ³ / hr, the dephosphorization slag 14 is not ejected and stable dephosphorization treatment is possible. As a result, as shown in FIG. Furthermore, the dephosphorization time was shortened by about 3 minutes compared to the comparative example. FIG. 3 is a diagram showing the dephosphorization processing time in comparison with the example of the present invention and the comparative example.

It is the schematic of the dephosphorization processing equipment which implemented this invention. It is a figure which compares and compares the phosphorus density | concentration in hot metal after a dephosphorization process with the example of this invention, and a comparative example. It is a figure which compares and shows the dephosphorization processing time by the example of this invention, and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dephosphorization processing equipment 2 Hot metal 3 CaO type | system | group dephosphorization refining agent 4 Solid oxygen source 5 Hot metal ladle 6 Carriage 7 Top blowing lance 8 Injection lance 9 Storage tank 10 Storage tank 11 Hopper 12 Raw material conveyance apparatus 13 Chute 14 Dephosphorization slag

Claims (1)

It was added and the hot metal pan or torpedo gaseous oxygen source into the contained molten iron in vehicles and the solid oxygen source and CaO-based dephosphorization refining agent subjected to dephosphorization treatment the hot metal, the a dephosphorization method of hot metal, the solid The oxygen source is one or more of sintered ore of iron ore having a particle size of 1 mm or less, mill scale, dust, iron sand and iron ore, and gaseous oxygen from one supply system of the top blowing lance the molten iron per 1 ton 0.222Nm ³ / min or less of the oxygen gas at a feed rate while top blowing supplied to the hot metal bath surface as a source, the solid oxygen source at least a portion from the other one supply line of the upper lance a blowing supplied above with carrier gas into the molten iron bath surface locations the same location or near the said gaseous source of oxygen is supplied, and, carrier gas of the CaO-based dephosphorization refining agent through injection lances With And wherein the blown into the molten iron, dephosphorization method hot metal.

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