WO2007055404A1

WO2007055404A1 - Method of hot metal dephosphorization treatment

Info

Publication number: WO2007055404A1
Application number: PCT/JP2006/322792
Authority: WO
Inventors: Yuichi Uchida; Masaru Washio; Akihiko Inoue; Yasunori Muraki; Yasuo Kishimoto; Shotaro Fujiki
Original assignee: Jfe Steel Corporation
Priority date: 2005-11-09
Filing date: 2006-11-09
Publication date: 2007-05-18
Also published as: CN101305105A; KR20080059226A; CN101305105B; KR101001078B1; TW200730636A; TWI310053B

Abstract

A method of hot metal dephosphorization treatment, comprising adding a dephosphorization refining agent composed mainly of CaO and reducing the added dephosphorization refining agent composed mainly of CaO to slags to thereby accomplish dephosphorization of the hot metal, wherein a gaseous oxygen source is fed from one supply system to a surface of hot metal bath and a solid oxygen source is fed from another supply system to a surface of hot metal bath in the vicinity of the site where the gaseous oxygen source is fed by the use of carrier gas. Thus, without the use of any medium solvent containing fluorine, there can be accomplished dephosphorization treatment with dephosphorization efficiency and iron yield equal to or higher than those of the prior art.

Description

Technical field of hot metal dephosphorization process

The present invention relates to a hot metal dephosphorization method, and more particularly, to a method for efficiently dephosphorizing hot metal with a high iron yield without using a fluorine source as a solvent. . Light

Fine

Background art

In the steelmaking process using blast furnace hot metal, before the decarburization blowing in the converter, most of the Si and P contained in the hot metal is oxidized and removed using oxygen gas or solid iron oxide. So-called hot metal pretreatment such as phosphorus treatment or hot metal desulfurization treatment in which S contained in the hot metal is removed under a reducing atmosphere with a desulfurizing agent is generally performed.

In recent years, the quality requirements for steel products have become more stringent than ever, and there is an increasing demand for lower phosphorus concentrations. In order to meet this quality requirement, it is necessary to increase the amount of hot metal to be dephosphorized in the hot metal pretreatment more than before and to stably reduce the phosphorus concentration after dephosphorization. On the other hand, it is essential to reduce slag emissions in the steelmaking process in order to respond to the environmental impacts represented by recent global warming. In order to reduce the amount of slag discharged during the dephosphorization of hot metal, the introduction of a dephosphorizing agent that melts and functions as a dephosphorizing refinery (“slag for dephosphorizing refinement”) It is necessary to reduce the amount. In hot metal dephosphorization, the main dephosphorizing agent is lime. In order to meet the above quality requirements and reduce slag discharge, the amount of dephosphorization required while reducing the amount of lime used. That is, a technology that efficiently removes phosphorous with a small amount of lime is required.

In the dephosphorization process, lime that does not fl ux ing does not contribute to the dephosphorization reaction, so to reduce the amount of lime used, the hatching of the added lime is promoted. Is important. Conventionally, fluorite (ore containing calcium fluoride as a main component) is known as a fluxing agent with excellent hatching ability of slag including lime. Fluorite has also been used in processing. However, in recent years, with the tightening of environmental regulations, the use of a solvent containing fluorine has been restricted. Therefore, means for promoting the dephosphorization reaction with lime without using fluorite have been studied. Many proposals have been made. As one of the means, a technique using another solvent (a hatching accelerator) as a substitute for fluorite has been proposed. For example, in Japanese Patent Application Laid-Open No. 2 02 _ 3 0 9 3 1 2, a medium solvent containing aluminum oxide is used as a substitute for fluorite in decarburization or dephosphorization of hot metal. A method has been proposed. However, the aluminum oxide proposed as a substitute for fluorite in Japanese Patent Laid-Open No. 2 0 0 2-3 0 9 3 1 2 promotes slag hatching but has the effect of increasing the viscosity of the slag. ing. For this reason, if the amount of aluminum oxide used is large, when slag is discharged from the reaction vessel after dephosphorization, slag may adhere to the furnace and remain. As a result, the so-called “re-phospho ₀ sphorizati _0n ” is generated, in which the phosphorus in the residual slag returns to the hot metal when dephosphorization is performed in the next charge (hot metal filling). There was a problem of adversely affecting the dephosphorization treatment of the next charge. Furthermore, due to the high viscosity of the slag, many iron particles (metal droplets) are trapped in the slag, and these iron particles are taken out of the furnace when the slag is discharged to increase the iron yield. There was also a problem of lowering. On the other hand, as a method of promoting the hatching of lime without depending on the hatching accelerator, JP-A 2 0 0 0-1 4 4 2 2 6 discloses quick lime, iron oxide and Z or oxygen gas. Technology that consists of supplying a treatment agent with a specified CaO / O ratio to the same location of the molten iron at the same time, that is, quick lime is applied to the collision part (called "fire point") between the oxygen gas and the molten metal surface. The technology to be introduced is disclosed.

On the other hand, also in Japanese Patent Laid-Open No. 2 0 3-3 2 8 0 2 1, when oxygen gas is used as a carrier gas and a lime-containing refinement agent is blown, the collision between the oxygen gas and the molten metal surface occurs. It has been introduced that the protrusions, that is, the hot spots, become hot and the lime hatches. In Japanese Patent Laid-Open No. 20 0 3-3 2 8 0 2 1, in addition, in order to avoid a slowing of the progress of the dephosphorization reaction due to a high hot point, a nematic agent containing an endothermic substance is It has been proposed to improve the dephosphorization efficiency at the hot spot.

However, the decarburization reaction by oxygen gas is dominant at the fire point, and the temperature is higher than 2100 due to heat generation such as the decarburization reaction. For this reason, the burden of cooling this to an appropriate temperature is great, and a means for improving the dephosphorization efficiency more effectively has been demanded. Disclosure of the invention

[Problems to be solved by the invention]

The present invention has been made in view of the above circumstances, and the object of the present invention is to use a small amount of lime without using a fluorine-containing medium solvent for dephosphorizing molten iron. It is an object of the present invention to provide a hot metal dephosphorization method that can dephosphorize at a dephosphorization efficiency and iron yield equivalent to those of conventional methods, which is more advantageous than previously proposed.

[Means for solving the problems]

The method for dephosphorizing hot metal according to the first aspect of the invention for solving the above problem comprises adding a dephosphorizing agent mainly composed of CaO to the hot metal and degassing mainly composed of added CaO. In the molten iron dephosphorization method, a gaseous oxygen source is supplied from one supply system to the molten iron bath surface, and the other one It is characterized by supplying the solid oxygen source from the supply system to the hot metal bath surface near the place where the gaseous oxygen source is supplied, using a carrier gas.

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

According to a third aspect of the present invention, there is provided a hot metal dephosphorization method according to the first or second aspect, wherein a dephosphorizing agent mainly composed of CaO is added through the gas oxygen source supply system. The gaseous oxygen source is supplied to the hot metal bath surface. According to a fourth aspect of the present invention, there is provided a hot metal dephosphorization method according to any one of the first to third aspects, wherein the transport gas for the solid oxygen source is air, reducing gas, carbon dioxide gas, non-oxidizing gas. It is one or two or more gases of gas and rare gas, and has an oxygen concentration lower than that of the gaseous oxygen source.

According to a fifth aspect of the present invention, there is provided a hot metal dephosphorization method according to any one of the first to fourth aspects, wherein the solid oxygen source is a sintered ore, a mill scale, a dust collecting dust having a particle size of 1 mm or less. It is characterized by being one or more of iron, iron sand and iron ore.

According to a sixth aspect of the present invention, there is provided a dephosphorization method for hot metal according to a sixth aspect of the invention, wherein a dephosphorizing agent mainly composed of CaO is added to a hot metal together with an oxygen source in a converter, and the added CaO is added. In the hot metal dephosphorization process, the main dephosphorizing fertilizer is hatched to form slag, and the hot metal dephosphorization process is used. From one of these supply systems, a dephosphorizing agent composed mainly of CaO is supplied to the molten iron bath together with gaseous oxygen, and a solid oxygen source and gaseous oxygen are supplied from the other supply system. One or more of air, reducing gas, carbon dioxide gas, non-oxidizing gas, and noble gas is transferred to the hot metal bath surface near the same location as the carrier gas. It is characterized by being supplied as a product.

According to a _{seventh aspect} of the present invention, there is provided a hot metal dephosphorization method according to any one of the first to sixth aspects, wherein a solid is disposed at a position surrounded by a plurality of hot spots formed by supplying a gaseous oxygen source. It is characterized by supplying an oxygen source. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be specifically described.

Hot metal dephosphorization is performed using a hot metal transfer container such as a torpedo car or hot metal pan, or a refinery furnace such as a converter as a reaction vessel. Then, a decontaminating agent mainly composed of C a 0, a gaseous oxygen source such as oxygen gas, and a solid oxygen source such as solid iron oxide are added to the hot metal, and phosphorus in the hot metal is added to the gaseous oxygen source and Phosphorus oxide that is oxidized by a solid oxygen source is composed of a dephosphorizing agent mainly composed of CaO. It is carried out by removing the phosphorus in the hot metal by taking it into the slag for dephosphorization. Gaseous oxygen sources and solid oxygen sources are collectively referred to as oxygen sources. '

In principle, solid oxygen sources are more efficient than gaseous oxygen sources for degassing 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 input, the temperature rise due to decarburization heat is dominant, whereas when a solid oxygen source is input, the solid oxygen source Since heat is absorbed during decomposition, temperature rise is suppressed. In other words, 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. In addition, the solid oxygen source becomes Fe 0 after melting, and contributes to the dephosphorylation reaction, and has a function of increasing the FeO component in the dephosphorization slag. This promotes the dephosphorization reaction. Conventionally, the solid oxygen source is generally dropped 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 to several tens of millimeters is used. The granular or massive solid oxygen source does not melt immediately even if it is put into the reaction vessel, and may remain until the end of the dephosphorization treatment. In addition, F e O in the slag rises as the solid oxygen source melts, but the F e O in the slag reacts with the carbon in the hot metal and is reduced, so the melting rate of the solid oxygen source If the reduction rate of FeO is equivalent to that of FeO, the concentration of FeO in the slag will 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 will not increase and the dephosphorization rate cannot be improved. In the present invention, a gaseous oxygen source is 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 near the location where the gaseous oxygen source is supplied. To supply.

On the hot metal bath surface, the location where the gaseous oxygen source collides with the hot metal bath surface, that is, the fire point, is excessively high gh oxy gen n by the gaseous oxygen source. pot ent ialfield) is formed, but the temperature is high due to the reaction between the gaseous oxygen source and the carbon in the hot metal. Therefore, supplying a solid oxygen source directly to the fire point does not provide a significant effect in terms of oxygen potential and cooling. On the other hand, the peripheral part near the hot spot is maintained at a relatively high temperature, although the temperature is lower than the hot spot, so that the solid oxygen source supplied thereto can be quickly melted. Moreover, an excessive high oxygen potential field such as a fire point is not formed, and the solid oxygen source can contribute to the reaction efficiently. This increases the oxygen potential of the slag, that is, the optimal slag for dephosphorization reaction is quickly formed, and the dephosphorization process can be performed even at low slag and at high temperatures. Become. In the present invention, the “hot metal bath surface in the vicinity of the place where the gaseous oxygen source is supplied” refers to the vicinity of the surface where the supplied gaseous oxygen source first contacts the hot metal. For example, when supplying a gaseous oxygen source from an upper blowing lance, the gaseous oxygen source injected from the upper blowing lance is in the vicinity of a position where it collides with the hot metal bath surface, and the gaseous oxygen source is injected into the injection lance or When using a tuyere to inject (blow) into the hot metal, the surface where the gaseous oxygen source enters the hot metal at the exit of the injection lance or tuyere (also defined as “fire point”) ). However, in a normal dephosphorization process, the bath surface temperature is maintained at a relatively high temperature even if the bath surface of the hot metal to which the gaseous oxygen source is supplied is kept at a relatively high temperature. A portion higher than the average temperature is preferable.

It should be noted that the centers of the supply positions on the bath surfaces from both systems must not coincide with each other, and it is preferable that the center of the supply position of the solid oxygen source does not cover the hot spot region. However, there is no problem that the supply areas themselves overlap. In addition, since different gases are sprayed onto the bath surface from both systems, even if the centers of the supply positions on the bath surface are very close to each other, a difference in area is ensured if they do not substantially match. There is no problem.

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, oxygen gas is used because the dephosphorization reaction rate is faster than when other gases are used. In the case of a mixed gas, it is preferable to make the oxygen concentration higher than that of air in order to ensure the dephosphorization reaction rate. Les. As a preferred embodiment of the present invention, as the gas for transporting the solid oxygen source, air, non-oxidizing gas, rare gas, reducing gas, carbon dioxide gas which is a weak oxidizing gas close to non-oxidizing gas is used. Use one or more of these gases. Here, the reducing gas is a hydrocarbon gas such as propane gas and CO gas, and the non-oxidizing gas is a gas having no oxidizing ability such as nitrogen gas, and the rare gas is an Ar gas. And inert gas such as He gas. By using these gases, the temperature rise near the fire point can be suppressed, and in principle conditions favorable for dephosphorization can be created.

In the present invention, the effect can be obtained even if the carrier gas for the solid oxygen source is a gas containing a certain amount of oxygen, such as air. However, from the above viewpoint, it is desirable that the concentration of oxygen contained in the carrier gas be 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, etc. as the transport gas for the solid oxygen source. Further, when the gaseous oxygen source is pure oxygen or oxygen-enriched air, all of the above-mentioned transport gases can be used.

Some solid oxygen sources contain a small amount of metallic iron, which may burn in a pure oxygen stream and cause damage to equipment. Transporting a solid oxygen source with a transport gas having a lower oxygen concentration than air is also effective from an industrial point of view to avoid accidents. In the present invention, the dephosphorizing agent containing mainly CaO may be added separately from the gaseous oxygen source from a hopper or the like. However, in a more preferred embodiment of the present invention, a dephosphorizing agent mainly composed of CaO is supplied to the hot metal bath surface together with a gaseous oxygen source. As a result, the dephosphorizing agent itself mainly composed of CaO is also heated in a high-temperature atmosphere, so that the slag can be made even faster. That is, the dephosphorization reaction can be further promoted.

The dephosphorizing agent mainly composed of C a O used in the present invention contains C a O, and is particularly limited to the content of C a O as long as it can perform the intended dephosphorization treatment. There is no about. Usually, it is composed of C a O alone or contains 50% by mass or more of C a O, and other components as necessary.

As other components, hatching accelerators are generally mentioned. In other words, although this application is a technology that enables the reduction or omission of hatching accelerators, it does not prohibit addition of hatching accelerators to further improve hatching efficiency. Examples of hatching promoters include substances containing titanium oxide and aluminum oxide (A 1 ₂ 0 ₃ ), which act to lower the melting point of CaO and promote hatching; It is preferable to use them as part of the solvent. 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 disposing of slag, etc., it is preferable not to use a fluorine-containing substance as a solvent from the viewpoint of protecting the environment by suppressing the amount of fluorine eluted from the slag. Substances in which fluorine is inevitably mixed as an impurity component may be used. Of course, when using a material containing titanium oxide or a material containing aluminum oxide, it is preferable that the material does not contain fluorine from this viewpoint.

As a specific example of a dephosphorizing agent composed mainly of CaO, it is preferable to use quick lime or limestone because it is inexpensive and has excellent dephosphorization ability. It is also known as slag (“BOF slag” or “de carbu lizati on slag”) that is generated when decarburized and refined hot metal after light-burning dolomite or dephosphorization treatment is used in the next converter. ) Can also be used as a dephosphorizing agent mainly composed of C a O. The decarburized soot is mainly composed of C a 0 and has a low phosphorus content, so that it can be sufficiently used as a dephosphorizing fertilizer mainly composed of C a 0. Further, as the solid oxygen source used in the present invention, iron ore sintered ore, mill scale, dust collecting dust (dust), iron sand, iron ore and the like can be used. A dust collection dust is a dust containing iron that is recovered from exhaust gas in a blast furnace, converter, or sintering process. From the viewpoint of promoting the melting of the solid oxygen source, the solid oxygen source is preferably a powder 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 Fe 0 component of the slag. Here, a particle size of 1 mm or less means that a sieve with a mesh size of 1 mm is passed. As long as it passes through a sieve with an opening size of 1 mm, it may have a spindle shape with a major axis exceeding 1 mm. From the viewpoint of handling, the particle size is preferably 1 μm or more.

Among the above-mentioned solid oxygen sources, iron sand and fine iron ore are particularly suitable because they are fine powders of 1 mm or less in the form of generation and do not require powdering. Of these, iron sand not only functions as a solid oxygen source, but also contains about 7 to 10% of titanium oxide, which promotes the incubation of dephosphorizing fertilizers mainly composed of CaO. It also has a function as an agent and is particularly suitable.

Titanium oxide acts as an acidic oxide in the slag composition at the time of dephosphorization, and has an excellent effect of hatching CaO, which is the main dephosphorizing agent for dephosphorization. Addition of iron sand containing selenium promotes the hatching of a dephosphorizing agent composed mainly of C o and promotes the dephosphorization reaction. In addition, titanium oxide has the effect of reducing the viscosity of slag composed of dephosphorizing spirits mainly composed of C a 0, which makes it easy to discharge slag from the reaction vessel after dephosphorization. It has the effect of becoming. For this reason, the amount of residual slag in the reaction vessel after slag discharge becomes negligibly small, and in the dephosphorization treatment of the next charge, the dephosphorization reaction is not hindered by dephosphorization, etc. Phosphorus treatment is possible.

The amount of titanium oxide in the slag is preferably 10% by mass or less in terms of Ti ₂ O ₂ . If it exceeds 10% by mass, the ratio of C a O, which is the main component, decreases, so the effect of improving the dephosphorization ability is offset and the effect of addition is reduced. On the other hand, the amount of titanium oxide is preferably 1% by mass or more in terms of T i O ₂ in order to surely enjoy the above-mentioned effects such as a decrease in slag viscosity. Here, T i refers to O ₂ conversion is, T i 〇 is titanium oxide, has the form of a T i 〇 _2, T i ₂ 〇 _3, T i ₃ 〇 _5, the T i min of these T This means that i 0 ₂ is converted and displayed. The reaction vessel used for the dephosphorization treatment is not particularly limited, and a ladle type vessel such as a hot metal ladle or a charging ladle, a torpedo car, a converter, etc. can be used. In the dephosphorization treatment of the present invention, both a gaseous oxygen source and a solid oxygen source are supplied as an oxygen source in order to promote the dephosphorization reaction. Of these, the gaseous oxygen source is the top blow lance. It can be supplied by any method such as top blowing, injection into the molten iron by an injection or tuyere, or bottom blowing. A solid oxygen source must also be supplied to the hot metal bath near the location where the gaseous oxygen source is supplied. For example, when a gaseous oxygen source is being blown up, it is preferable to supply the solid oxygen source from above to the vicinity of the collision surface at the hot metal bath surface of the gaseous oxygen source. Alternatively, a solid oxygen source may be supplied in the vicinity of the collision surface at the hot metal bath surface of the gaseous oxygen source using a carrier gas from the bottom blowing tuyere. If a gaseous oxygen source is being injected through an injection lance or tuyere, the ability to provide a system to supply a solid oxygen source to the same injection lance or tuyere. By providing a clearance or tuyere, a solid oxygen source can be supplied near the surface where the gaseous oxygen source enters the gun at the exit of the junction lance or tuyere. Further, in the dephosphorization treatment of the present invention, it is preferable to supply a dephosphorizing agent mainly composed of CaO to the hot metal bath surface at the same place as the place where the gaseous oxygen source is supplied. In this way, in order to supply a gaseous oxygen source and a solid oxygen source as well as a dephosphorizing agent mainly composed of CaO, for example, a lance for supplying them (an upper lance, an injection lance, etc.) ) At least two supply systems are installed at the tuyere, and a dephosphorizing agent mainly composed of CaO is supplied from one of the supply systems together with the gaseous oxygen source, and the other. By supplying a solid oxygen source together with the above-described carrier gas from one supply system, the above addition condition can be achieved. The supply means may be any means such as a top blow lance, injection lance, tuyere, etc., but it is supplied from the top blow lance because it has a small thermal load and is highly durable and easy to operate. It is preferable to do.

The size of the dephosphorizing agent composed mainly of C a 0 supplied with the gaseous oxygen source is preferably 1 mm or less from the viewpoint of promoting hatching. The bath surface to which the gaseous oxygen source is supplied, that is, the fire point, is superior in the decarburization reaction with oxygen gas. Due to the heat generated by the decarburization reaction, for example, the dephosphorization of the converter has a high temperature exceeding 200. On the other hand, the dephosphorization reaction is thermodynamically accelerated at lower temperatures. Therefore, the dephosphorization reaction takes place substantially in the peripheral part of the temperature of approximately 1800 ° C. or less, slightly away from the fire point.

The top blow lance has at least two supply systems, one of which supplies the gaseous oxygen source and the other one directs the solid oxygen source with the carrier gas to the vicinity of the fire point. As a result, the solid oxygen source is supplied to a portion near the fire point where the dephosphorization reaction is substantially promoted. Since the solid oxygen source is supplied by a carrier gas having a lower oxygen concentration than oxygen gas, the temperature of the portion does not rise excessively, and the good reactivity of the solid oxygen source prevents dephosphorization. Further promoted. For example, the dephosphorization capacity at 1800 ° C is approximately double the dephosphorization capacity at 2 0 0 0 by thermodynamic estimation.

The above-described configuration having two supply systems is, for example, a double-pipe structure with at least a top blowing lance, one with an oxygen gas flow path, the other with a solid oxygen source and a carrier gas. A gaseous oxygen source was supplied from a nozzle hole arranged on a concentric circle centered on the lance center axis, while a solid oxygen source and a carrier gas were arranged on the lance center axis. A method of supplying from the nozzle hole can be adopted. This method creates a state of supplying a solid oxygen source at a position surrounded by a plurality of fire spots formed by supplying a gaseous oxygen source, so that a solid oxygen source supply surrounded by a fire spot is generated. The part is particularly suitable because the high temperature state below the fire point is stably maintained. Alternatively, a plurality of nozzle holes may be arranged on a concentric circle centered on the lance central axis, and a gaseous oxygen source and a solid oxygen source may be supplied from alternate (alternate) holes. It is not necessary to supply all of the solid oxygen source to be supplied to the hot metal bath surface in the vicinity of the place where the gaseous oxygen source is supplied, but a place where only a part of the solid oxygen source is supplied with the gaseous oxygen source It may be supplied to the hot metal bath surface in the vicinity of. However, if the amount of solid oxygen supplied to the hot metal bath near the location where the gaseous oxygen source is supplied is small, the increase in the Fe ◦ component in the slag will be small. In addition, depending on the equipment specifications, the lower limit should be the amount by which the increase in the FeO component in the slag is sufficient. Also, the upper limit may be limited to an amount that does not cause excessive heat removal according to the equipment specifications. For example, when dephosphorization is performed in a container of about 100 to 3500 tons, it is transported to a gaseous oxygen source 1 N m ³ (pure oxygen gas in the standard state) that is supplied to the bath surface. The solid oxygen source supplied by the working gas is preferably added in the range of 0.1 kg to 2 kg. ◦ Less than 1 kg, the effect expected by the present invention cannot be obtained sufficiently. On the other hand, if it exceeds 2 kg, heat removal on the supply surface of the solid oxygen source increases, resulting in insufficient slag hatching. It will reduce your phosphorus capacity. A more preferred supply is 0.3 kg or more. The solid oxygen source to be supplied to a place other than the vicinity of the hot metal bath surface to which the gaseous oxygen source is supplied may be supplied by an appropriate method such as top addition or injection addition. Similarly, when supplying at least a part of a degassing fertilizer mainly composed of CaO to a place other than the bath surface of the hot metal to which a gaseous oxygen source is supplied, the top addition and the injection are performed. It may be supplied by an appropriate method such as addition of water.

When a gaseous oxygen source is used, the hot metal temperature rises due to the oxidation reaction heat. When a solid oxygen source is used, the sensible heat, latent heat, and decomposition heat of the solid oxygen source itself are higher than the oxidation reaction heat. Is too large, the hot metal temperature drops. Therefore, the usage ratio between 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. Further, in order to efficiently perform the dephosphorization reaction, it is preferable to stir the hot metal. For this stirring, generally, gas stirring using a nozzle or the like embedded in the bottom of the furnace is performed. Good. As the dephosphorization slag, the F e O concentration in the slag is preferably in the range of 10% by mass to 50% by mass, so that the F e O concentration in the slag can maintain this range. Thus, it is preferable to adjust the supply amount of the solid oxygen source. A more preferable range is 30% by mass or less.

By performing the dephosphorization treatment of the molten iron in this way, the dephosphorization treatment can be carried out while maintaining the same dephosphorization rate as before without using a fluorine-containing substance as a solvent. Is possible. As a result, the slag can be reused without taking measures against fluorine leakage to the remote area, and the environmental load can be avoided. In addition, even if the dephosphorization temperature is increased, it is possible to maintain the same amount of dephosphorization as in the past. In this case, the iron yield in the dephosphorization process can be increased, which is an industrially beneficial effect. Is brought about.

〔Example〕

(Example 1)

The molten iron discharged from the blast furnace is desiliconized in a blast furnace casthouse and then transported to a 300 ton capacity converter, where a total of four dephosphorization processes are carried out (this Invention Examples 1 to 4). The phosphorus concentration in the hot metal before dephosphorization was unified to 0.1 2 mass%, and the phosphorus concentration in the hot metal after dephosphorization was 0.020 mass. /. Below, the iron yield was targeted at 98% or more. The iron yield (7?) Is the rolling mass; the final mass (W. tens W _s ) of the mass of molten iron (W ₀ ) and the mass of the scrap (W _s ) The mass (W) of the hot metal discharged after dephosphorization was expressed as a percentage (7? = 100 W / (W. + W _s )).

In addition to the cooling water supply and drainage system, the dephosphorization process has two separate supply systems, supplying oxygen gas and quicklime powder (average particle size of 1 mm or less) from one supply system, and other supply systems. Then, an upper blowing lance was used to supply a solid oxygen source in the form of nitrogen gas as a carrier gas. The structure of the top blow lance is a double pipe structure for the supply system of oxygen gas and solid oxygen source, one of which is a flow path for oxygen gas and the other is a flow path for solid oxygen source and transport gas. The source is supplied from a plurality of nozzle holes arranged concentrically around the center axis of the lance, while the solid oxygen source and the transport gas are supplied from a single nozzle hole arranged on the center axis of the lance. It was made to supply from. The solid oxygen source was supplied so that the center of the supply position did not reach the hot spot area. It processed without adding fluorine-containing substances such as fluorite. From the tuyeres at the bottom of the converter furnace, nitrogen is used as the stirring gas, 0.03 to 0.3 per ton of hot metal. Blowing in at a flow rate of 0 N m ³ / min.

As solid oxygen sources, powdered iron ore (average particle size 50 m), iron sand (average particle size 100 m), mill scale (average particle size 500 m), iron ore sintered ore ( One of the average particle size of 100 m) was used and sprayed onto the hot metal bath surface. The oxygen gas sending condition was set at 0.6 2.5 N m ³ / min per ton of hot metal. The oxygen intensity was 1 2 Nm ³ t excluding oxygen necessary for desiliconization.

In addition, as a comparative example, dephosphorization treatment was performed in which granular iron ore (average particle size of about 2 O mm) was placed on top of the furnace on top. Other dephosphorization treatment conditions in the comparative example were performed in accordance with the examples of the present invention. Table 1 shows the hot metal components and operating conditions before and after the dephosphorization treatment in the present invention example and the comparative example. The basic unit and the amount of solid oxygen used are shown in amounts equivalent to 1 ton of hot metal.

The amount of titanium oxide in the slag in the case of the sand and solid oxygen source became 4 mass% in T i 〇 ₂ equivalent.

*) Ratio of solid oxygen source supplied by carrier gas to 02 force supplied from top blowing lance

As shown in Table 1, in all examples of the present invention in which a solid oxygen source was supplied to the blowing surface of the oxygen gas from the top blowing lance, the phosphorus concentration in the hot metal after dephosphorization was 0.02% by mass. And the iron yield reached 98% or more. In contrast, in the comparative example, the phosphorus concentration in the hot metal after the dephosphorization treatment was 0.020 mass. /. Higher, When we tried to reduce this, the iron yield dropped to below 98%, confirming that the two were not both.

(Example 2)

After desiliconizing the hot metal discharged from the blast furnace in the blast furnace bed, it was transported to a 300t capacity converter, and dephosphorization treatment was performed a total of 15 times in this converter (Invention Example 1 1-25). . The deaeration treatment was carried out in the same manner as in Example 1. The hot metal concentration after the deaeration treatment was set to 0.020 mass ¾ or less and the iron yield was set to 98 ¾ or more.

As iron oxide, iron sand having an average particle size of 100 m was used. Iron oxide was used in combination with a supply gas from the top blow lance and a top hopper from the furnace hopper.

The dephosphorizing agent consists of quick lime powder (average particle size of 1 mm or less) supplied from the gaseous oxygen source supply system and massive lime (average diameter of about 1 O mm) that is placed on top of the furnace hopper. In combination, the basicity of the slag (weight ratio of C a O component and S i O 2 component in the slag) was adjusted. In Invention Example 18, quick lime powder was not supplied from the supply system of the gaseous oxygen source, and only massive lime was put on top from the furnace on the top. Further, for Invention Example 22, the limestone powder (average particle size of 1 mm or less) was supplied in addition to the quick lime powder from the supply system of the gaseous oxygen source.

Further, as Comparative Examples 1 1 to 14, dephosphorization treatment was also performed when iron oxide was not projected from the top blowing lance. Further, as Comparative Examples 15 to 17, dephosphorization treatment was also performed when a part of iron oxide was supplied from a supply system of a gaseous oxygen source. Other dephosphorization treatment conditions in the comparative example were performed in accordance with the examples of the present invention.

Table 2 shows the hot metal components before and after the dephosphorization treatment and the operating conditions in the inventive examples and comparative examples. Table 2

As shown in Table 2, even when a part of the oxygen source is put on top, in the present invention example, the phosphorus concentration in the hot metal after the dephosphorization treatment becomes 0.020% by mass or less, and The iron yield was over 98%. On the other hand, in the comparative example, it was not possible to achieve both a phosphorus concentration in the hot metal after dephosphorization treatment of 0.020% by mass or less and an iron yield of 98% or more.

(Example 3)

The hot metal discharged from the blast furnace was desiliconized in the blast furnace bed, and then transferred to a 300-ton capacity converter, and dephosphorization treatment was carried out twice in total (Invention Examples 31 to 32). As the bottom blowing gas, oxygen gas was blown from the inner tube of the tuyeres of the double tube structure at the bottom of the converter furnace at a flow rate of about 0. S Nm SZmin per ton of hot metal. Outer tube The dephosphorization treatment was performed in the same manner as in Example 1 except that propane gas for cooling the tuyere was blown. As the iron oxide, a mill scale having an average particle size of 500 / m was used. The target concentration of hot metal after dephosphorization was 0.020% by mass or less and iron yield was 98% or more.

Table 3 shows the hot metal components and operating conditions before and after the dephosphorization treatment in the examples of the present invention.

Three

Industrial applicability

According to the present invention, during the dephosphorization of the hot metal, a dephosphorizing agent mainly composed of CaO is added to the hot metal, and a gaseous oxygen source is supplied from one supply system to the hot metal bath surface. Supply a solid oxygen source from another supply system to the hot metal bath surface near the place where the gaseous oxygen source is supplied. As a result, the melting of the solid oxygen source is accelerated, the oxygen potential of the degassing / slagging slag is rapidly increased, and the dephosphorization ability of the slag is improved. By improving the dephosphorization capacity of slag, the basicity of slag for dephosphorization and refinement (C a OZS i) 0 ₂₎ the or lowered than the conventional, even a molten iron temperature after dephosphorization or raised as compared with the conventional dephosphorization reaction is not inhibited, efficiently molten iron can be dephosphorization process . In addition, as the gas for transporting the solid oxygen source, a gas having a lower oxygen concentration than the gaseous oxygen source such as air, reducing gas, carbon dioxide gas, non-oxidizing gas, and rare gas is used. It does not form an excessively high oxygen potential field like the hot spot, and can suppress the decarburization reaction and promote the dephosphorization reaction more efficiently.

Claims

The scope of the claims

1. Add a dephosphorizing fertilizer mainly composed of C a 0 to the molten iron, and then add the dephosphorized fermented agent mainly composed of C a 0 to form a slag. In the hot metal dephosphorization method,

A gaseous oxygen source is supplied from one supply system to the hot metal bath surface, a solid oxygen source is supplied from the other supply system, and a transport gas is used on the hot metal bath surface near the location where the gaseous oxygen source is supplied. A hot metal degassing method, characterized in that the hot metal is supplied.

2. The hot metal dephosphorization method according to claim 1, wherein the supply systems of the gaseous oxygen source and the solid oxygen source are arranged in the same lance.

3. A dephosphorizing agent mainly composed of CaO is supplied to the hot metal bath surface together with the gaseous oxygen source through the gaseous oxygen source supply system. The method for removing phosphorus from hot metal as described in 1.

4. The dephosphorizing agent mainly composed of CaO is supplied to the hot metal bath surface together with the gaseous oxygen source through the gaseous oxygen source supply system. Of hot metal dephosphorization.

5. The gas for transporting the solid oxygen source is one or more gases selected from the group consisting of air, reducing gas, carbon dioxide gas, non-oxidizing gas, and noble gas, and the gaseous oxygen source. 5. The hot metal dephosphorization method according to any one of claims 1 to 4, wherein the oxygen concentration is lower than that of the hot metal.

6. The solid oxygen source may be one or more of sintered ore having a particle size of 1 mm or less, mill scale, dust collection dust, iron sand, or iron ore, The method for dephosphorizing hot metal according to any one of claims 1 to 4.

7. In the converter, a dephosphorizing agent mainly composed of C a O is used together with the oxygen source. At least in the dephosphorization method for hot metal, which is added to the hot metal, and the dephosphorizing agent mainly composed of added CaO is hatched to form a slag, and the hot metal is dephosphorized. Using a top-blow lance with two supply channels, one of these supply systems supplies a degassing fertilizer composed mainly of CaO to the hot metal bath surface along with gaseous oxygen, and the other one Solid oxygen source from the supply system, one of air, reducing gas, carbon dioxide gas, non-oxidizing gas, and noble gas on the hot metal bath surface near the same location where gaseous oxygen is supplied Alternatively, the hot metal dephosphorization method, wherein two or more gases are supplied as a carrier gas.

8. The solid oxygen source 'is supplied to a position surrounded by a plurality of fire points formed by supplying the gaseous oxygen source, either 1, 2, 3, 4, or 7 The method for dephosphorizing hot metal as described in 1.