JP5493737B2 - Hot metal desulfurization method - Google Patents
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Description
本発明は、溶銑の脱硫方法に関する。 The present invention relates to a hot metal desulfurization method.
溶鋼を製造する際の脱硫処理は溶銑予備処理工程で行うのが一般的である。インジェクション脱硫においては、粉体の脱硫材を搬送ガスとともに溶銑中に吹き込むことで脱硫を行っており、溶銑温度（１３５０〜１４５０℃）で分解あるいは蒸発を起こしにくいＣａＯ系脱硫材が使用される。ＣａＯは融点が２５００℃超であるため溶銑温度においては固体である。固体ＣａＯによる脱硫反応はＣａＯ内のＳ拡散律速で進行するが、この反応は非常に遅いことが一般に知られている。 The desulfurization treatment when producing molten steel is generally performed in a hot metal pretreatment process. In injection desulfurization, desulfurization is performed by blowing a powder desulfurization material into a hot metal together with a carrier gas, and a CaO-based desulfurization material that does not easily decompose or evaporate at a hot metal temperature (1350 to 1450 ° C.) is used. CaO is a solid at the hot metal temperature because it has a melting point of over 2500 ° C. Although the desulfurization reaction with solid CaO proceeds at the rate of S diffusion in CaO, it is generally known that this reaction is very slow.
そこで、Ｍｇ、ＣａＣ2のようなＳと反応しやすい物質とＣａＯを混合した脱硫材を使用して脱硫速度を向上させ、低硫域まで短時間で脱硫することが従来から行われているが、脱硫材コストが高くなるのに加えて、Ｍｇの気化あるいはＣａＣ2の熱分解による温度低下が起こるので、復硫が生じる場合がある。 Therefore, it has been conventionally performed to improve the desulfurization rate using a desulfurization material in which CaO is mixed with a substance that easily reacts with S, such as Mg and CaC 2 , and to desulfurize in a short time to a low sulfur region. In addition to an increase in the cost of the desulfurization material, a temperature decrease due to vaporization of Mg or thermal decomposition of CaC 2 may occur, so that resulfurization may occur.
これに替わる方法としては、金属Ａｌを使用することが挙げられる。例えば、特許文献１では、溶銑のＡｌ濃度を調整した後に粒度０．４ｍｍ以下のＣａＯを溶銑中に吹き込む脱硫方法が開示されている。 An alternative method is to use metallic Al. For example, Patent Document 1 discloses a desulfurization method in which CaO having a particle size of 0.4 mm or less is blown into hot metal after adjusting the Al concentration of the hot metal.
また別の方法としては、脱硫材粒径を細かくすることが挙げられる。これは、単位質量あたりの表面積を増大させて溶銑に接触する面積を多くし、脱硫速度を向上させる方法である。例えば、特許文献２では、ＣａＯ粉体の粒径を４５μｍが８０質量％以上とし、吹き込み速度を４０〜６０ｋｇ／ｍｉｎとする溶融金属の脱硫方法が開示されている。特許文献３では、粒径３０μｍ以上６０μｍ未満の粉体構成率が５０％以上である溶銑の脱硫材が開示されている。
Another method includes reducing the particle size of the desulfurized material. This is a method of increasing the surface area per unit mass to increase the area in contact with the hot metal and improving the desulfurization rate. For example,
脱硫速度はＳ濃度に比例するので、脱硫反応はＳ濃度が低下するほど起こりにくくなる。よって低硫域まで脱硫するには、脱硫材をより長時間吹き込む必要がある。低硫域の一般的な定義はないが、本発明においては、０．００３質量％以下のＳ濃度域を低硫域と定義する。下限には０質量％を含む。 Since the desulfurization rate is proportional to the S concentration, the desulfurization reaction is less likely to occur as the S concentration decreases. Therefore, it is necessary to blow the desulfurization material for a longer time in order to desulfurize to the low sulfur region. Although there is no general definition of a low sulfur region, in the present invention, an S concentration region of 0.003% by mass or less is defined as a low sulfur region. The lower limit includes 0% by mass.
特許文献１は、後述するように脱硫反応によりＣａＯから放出されたＯとＡｌおよび溶銑中のＳｉが反応して一部のＣａＯ粒子が液相となり、そこにＳが浸透することで反応速度を向上させる方法であるが、低硫域では液相が生成しにくくなるので、効果が小さくなりやすい。 In Patent Document 1, as described later, O released from CaO by a desulfurization reaction, Al, and Si in the hot metal react to form a part of CaO particles in a liquid phase, and S permeates there to increase the reaction rate. Although it is a method to improve, since it becomes difficult to produce | generate a liquid phase in a low sulfur area, an effect tends to become small.
特許文献２および３は、Ｓ濃度が高い領域では単位質量あたりの表面積増大による脱硫速度向上効果は得られやすいが、低硫域では脱硫材粒子とＳが反応する機会そのものが少ないため、効果は得られにくくなる。
In
近年では、脱硫速度向上のために脱硫材粉体の吹き込み速度（単位時間あたり脱硫剤吹き込み供給量）を速くすることも行われる。これは、より多くの脱硫材粒子を連続的に溶銑中に供給することで、単位時間あたりに脱硫材粒子と溶銑が接触する面積を増大させることを指向した方法である。しかし、吹き込み速度を高くすると脱硫ＣａＯ効率が低下するという問題がある。これは、溶銑内に侵入せずＳと反応しないまま浮上してしまう脱硫材粉体が多くなるためとされている。 In recent years, in order to improve the desulfurization rate, the blowing rate of the desulfurizing material powder (desulfurizing agent blowing supply amount per unit time) is also increased. This is a method aimed at increasing the area of contact between the desulfurized material particles and the hot metal per unit time by continuously supplying more desulfurized material particles into the hot metal. However, there is a problem that desulfurization CaO efficiency decreases when the blowing speed is increased. This is because the amount of desulfurized material powder that does not enter the hot metal and floats without reacting with S increases.
ここで、脱硫ＣａＯ効率とは、脱硫材に含まれるＣａＯ質量に対する、Ｓと反応したＣａＯ質量の割合であり、式（１）で定義する。
脱硫ＣａＯ効率（％）＝（Ｓ0−Ｓ）×（56/32）／（Ｗ×ＸCaO）×100000 （１）
Ｓ0：処理前Ｓ濃度（質量％）
Ｓ：処理後Ｓ濃度（質量％）
Ｗ：脱硫材原単位（ｋｇ／ｔ）
ＸCaO：脱硫材のＣａＯ濃度（質量％）
Here, desulfurization CaO efficiency is the ratio of the mass of CaO reacted with S to the mass of CaO contained in the desulfurization material, and is defined by the formula (1).
Desulfurization CaO efficiency (%) = (S 0 −S) × (56/32) / (W × X CaO ) × 100000 (1)
S 0 : S concentration before treatment (mass%)
S: S concentration after treatment (mass%)
W: Desulfurization material basic unit (kg / t)
X CaO : CaO concentration of desulfurized material (% by mass)
脱硫ＣａＯ効率が低下すると、目標とするＳ濃度まで脱硫するのにより多量の脱硫材を使用する必要があるので、これは精錬コストおよびスラグ排出量の増加を招く。 If the desulfurization CaO efficiency is reduced, it is necessary to use a larger amount of desulfurization material to desulfurize to the target S concentration, which leads to an increase in refining costs and slag emissions.
このような問題に鑑み、本発明は、ＣａＯ系脱硫材の高速吹き込み処理において脱硫ＣａＯ効率が低下しない溶銑の脱硫方法を提供することを目的とする。 In view of such a problem, an object of the present invention is to provide a hot metal desulfurization method in which the desulfurization CaO efficiency does not decrease in the high-speed blowing treatment of the CaO-based desulfurization material.
本発明は上記課題を解決するためになされたものであり、その手段は、以下の通りである。
（１）溶銑へ金属Ａｌを上方より添加して溶銑中Ａｌ濃度を０．００５質量％以上０．０２質量％以下とし、ＣａＯ濃度が９０質量％以上であり、粒径５μｍ以上３０μｍ未満の粉体構成率が５０％以上である脱硫材を、インジェクション方式で該溶銑中に吹き込むことを特徴とする、溶銑の脱硫方法。
（２）溶銑への脱硫材の吹き込み速度が１００〜３００ｋｇ／ｍｉｎであることを特徴とする、（１）に記載の溶銑の脱硫方法。
The present invention has been made to solve the above-mentioned problems, and the means thereof is as follows.
(1) Metal Al is added to the hot metal from above to make the Al concentration in the hot metal 0.005 mass% or more and 0.02 mass% or less, the CaO concentration is 90 mass% or more, and the particle size is 5 μm or more and less than 30 μm. A desulfurization method for hot metal, which comprises blowing a desulfurization material having a body composition ratio of 50% or more into the hot metal by an injection method.
(2) The hot metal desulfurization method according to (1), wherein the blowing speed of the desulfurization material into the hot metal is 100 to 300 kg / min.
本発明によれば、溶銑にＡｌを添加し、特定範囲の粒径をある一定比率以上有するＣａＯ系脱硫材を高速でインジェクションすることで、高い脱硫ＣａＯ効率を維持したまま短時間で低硫域まで脱硫することができる。これにより脱硫処理時間の短縮、精練コストの削減、スラグ排出量の削減といった効果を享受することができる。 According to the present invention, by adding Al to hot metal and injecting a CaO-based desulfurization material having a specific range of particle sizes of a certain ratio or more at a high speed, a low sulfur content is maintained in a short time while maintaining high desulfurization CaO efficiency. Can be desulfurized. As a result, it is possible to enjoy the effects of shortening the desulfurization time, reducing the scouring cost, and reducing the amount of slag discharged.
以下に、本発明の実施の形態について詳細に説明する。まず、金属Ａｌが脱硫速度を向上させる機構について説明する。ＣａＯによる脱硫反応は式（２）で表される。
ＣａＯ＋Ｓ＝ＣａＳ＋Ｏ （２）
Hereinafter, embodiments of the present invention will be described in detail. First, the mechanism by which metal Al improves the desulfurization rate will be described. The desulfurization reaction with CaO is represented by the formula (2).
CaO + S = CaS + O (2)
すなわち、ＣａＯはＳと反応してＣａＳになる際にＯを放出する。金属Ａｌを添加しない場合は、ＣａＯの脱硫反応で放出されたＯと溶銑中のＳｉが反応してＣａＯ粒子表層にＣａＯ−ＳｉＯ2相が生成する。この相は溶銑温度において固体なので、ＳはＣａＯ内部に浸透できず、脱硫反応が停滞する。一方、溶銑に金属Ａｌを添加した場合は、このＯとＡｌ、溶銑中のＳｉが反応してＣａＯ粒子表層にＣａＯ−Ａｌ2Ｏ3−ＳｉＯ2相が生成する。この相は溶銑温度において液相を含むので、ＳはＣａＯ内部に浸透でき、脱硫反応が継続する。金属Ａｌを添加する際の溶銑温度は１３５０℃以上が好ましく、１４００℃以上であればより好ましい。 That is, CaO releases O when it reacts with S to become CaS. When metal Al is not added, O released in the desulfurization reaction of CaO reacts with Si in the hot metal to form a CaO—SiO 2 phase on the surface layer of CaO particles. Since this phase is solid at the hot metal temperature, S cannot penetrate into CaO, and the desulfurization reaction stagnates. On the other hand, when metal Al is added to the hot metal, this O, Al, and Si in the hot metal react to produce a CaO—Al 2 O 3 —SiO 2 phase on the CaO particle surface layer. Since this phase contains the liquid phase at the hot metal temperature, S can penetrate into the CaO and the desulfurization reaction continues. The hot metal temperature when adding metal Al is preferably 1350 ° C. or higher, and more preferably 1400 ° C. or higher.
溶銑のＳｉ濃度は０．２質量％以上０．８質量％以下であることが好ましい。０．２質量％未満では脱硫反応で放出されたＯと溶銑Ｓｉの反応量が極めて少なくなり、ＣａＯ粒子表層にはＣａＯ−Ａｌ2Ｏ3−ＳｉＯ2相よりも融点の高いＣａＯ−Ａｌ2Ｏ3相が生成するため、ＳがＣａＯ内部に浸透しにくくなる。また、０．８質量％超では脱硫反応で放出されたＯと溶銑Ｓｉの反応が主になってＣａＯ−ＳｉＯ2相がＣａＯ粒子表層に生成するため、ＳがＣａＯ内部に浸透しにくくなる。 It is preferable that the Si concentration of the hot metal is 0.2% by mass or more and 0.8% by mass or less. Extremely small amount of reaction released O and hot metal Si desulfurization reaction is less than 0.2 wt%, having a melting point higher than the CaO particle surface layer CaO-Al 2 O 3 -SiO 2-phase CaO-Al 2 O Since three phases are generated, it becomes difficult for S to penetrate into CaO. On the other hand, if it exceeds 0.8% by mass, the reaction between O released by the desulfurization reaction and molten iron Si mainly forms a CaO—SiO 2 phase in the surface layer of CaO particles, so that S hardly penetrates into CaO.
Ａｌは、溶銑中Ａｌ濃度が０．００５質量％以上０．０２質量％以下となるように添加する。Ａｌ濃度が０．００５質量％未満では、脱硫反応で放出されたＯと溶銑Ｓｉの反応が主になってＣａＯ−ＳｉＯ2相がＣａＯ粒子表層に生成するため、ＳがＣａＯ内部に浸透しにくくなる。 Al is added so that the Al concentration in the hot metal is 0.005 mass% or more and 0.02 mass% or less. When the Al concentration is less than 0.005% by mass, the reaction between O released by the desulfurization reaction and hot metal Si mainly forms a CaO-SiO 2 phase in the surface layer of CaO particles, so that S hardly penetrates into CaO. Become.
一方、Ａｌ濃度が０．０２質量％超ではＡｌ添加の効果はほぼ飽和するので、これより金属Ａｌ添加量を増やすと温度ロスおよびコストが増加するデメリットの方が大きくなる。 On the other hand, when the Al concentration exceeds 0.02% by mass, the effect of Al addition is almost saturated. Therefore, when the amount of metal Al addition is increased, the disadvantage of increased temperature loss and cost becomes greater.
脱硫反応でＣａＯより放出されるＯは、溶銑Ｓが高いほど多くなる。よって金属Ａｌは脱硫材吹き込み前あるいは脱硫材吹き込み開始後の数分間の、Ｓ濃度が高い時期に添加するのが好ましい。また、後述するように、溶銑へ吹き込まれた脱硫材粒子は、溶銑表面に浮上した後に溶銑と接触して脱硫する。よって溶銑より比重の軽い金属Ａｌを、溶銑表面の上方より添加すれば、溶解した金属Ａｌは脱硫の主反応サイトである溶銑表面にある程度濃化するので、前記した脱硫促進効果を得られやすくなる。 The amount of O released from CaO in the desulfurization reaction increases as the hot metal S increases. Therefore, it is preferable to add metal Al at a time when the S concentration is high for several minutes before blowing the desulfurizing material or after starting blowing the desulfurizing material. Further, as will be described later, the desulfurized material particles blown into the hot metal float on the hot metal surface and then desulfurize in contact with the hot metal. Therefore, if a metal Al having a lighter specific gravity than the hot metal is added from above the hot metal surface, the dissolved metal Al will be concentrated to some extent on the hot metal surface, which is the main reaction site for desulfurization. .
次に、本発明で使用する脱硫材について説明する。脱硫材の組成はＣａＯ濃度が９０質量％以上である。ＣａＯ系脱硫材にはその原料である石灰石（ＣａＣＯ3）に含まれるＳｉＯ2、Ａｌ2Ｏ3、ＦｅＯ、Ｆｅ2Ｏ3などが不純物として存在している。これら不純物が合計で１０質量％超含有されるようになるとＣａＯと化合物を生成しやすくなり、Ｓと反応するＣａＯが減ってしまうので、脱硫ＣａＯ効率が低下しやすくなる。 Next, the desulfurization material used in the present invention will be described. The composition of the desulfurization material has a CaO concentration of 90% by mass or more. In the CaO-based desulfurization material, SiO 2 , Al 2 O 3 , FeO, Fe 2 O 3 and the like contained in the raw material limestone (CaCO 3 ) exist as impurities. When these impurities are contained in a total of more than 10% by mass, CaO and a compound are likely to be generated, and CaO reacting with S is reduced, so that the desulfurization CaO efficiency is easily lowered.
ＣａＯ濃度については、例えばＸ線回折法とＩＣＰ発光分光分析法を組み合わせることによって測定できる。まず、Ｘ線回折法により、Ｃａ含有化合物についてＣａＯ、ＣａＣ2、ＣａＣＯ3などの相対比率を算出する。次にＩＣＰ発光分光分析法でトータルＣａ濃度を求め、上記Ｘ線回折法で測定した比率を用いて按分することにより、試料中のＣａＯ濃度を求めることができる。 The CaO concentration can be measured, for example, by combining an X-ray diffraction method and an ICP emission spectroscopic analysis method. First, relative ratios of CaO, CaC 2 , CaCO 3 and the like are calculated for the Ca-containing compound by X-ray diffraction. Next, the CaO concentration in the sample can be obtained by obtaining the total Ca concentration by ICP emission spectroscopic analysis and apportioning it using the ratio measured by the X-ray diffraction method.
次に本発明を完成するに至った実験について説明する。 Next, the experiment that led to the completion of the present invention will be described.
混銑車において、溶銑５００ｔへ脱硫材粉体（ＣａＯ濃度：９５質量％）２ｔを、吹き込み速度１００〜３００ｋｇ／ｍｉｎでインジェクションする脱硫実験を行い、インジェクション前、インジェクション中、インジェクション後にそれぞれ溶銑をサンプリングした。インジェクション中およびインジェクション後のサンプル断面を走査型電子顕微鏡で調査したが、いずれもＣａＯ粒子は発見されなかった。さらに、サンプルのＣａ濃度を化学分析したが、インジェクション前からインジェクション後にかけてほとんど変動していなかった。 In a kneading vehicle, a desulfurization experiment was performed by injecting 2t of desulfurized material powder (CaO concentration: 95% by mass) into hot metal 500t at a blowing speed of 100 to 300 kg / min, and the hot metal was sampled before, during, and after the injection. . The cross section of the sample during and after the injection was examined with a scanning electron microscope, but no CaO particles were found. Furthermore, although the Ca concentration of the sample was chemically analyzed, it hardly changed from before injection to after injection.
これらの結果から、吹き込んだ脱硫材粉体はガス気泡内に留まったまま溶銑表面に浮上していると推定された。即ち、インジェクション方式における脱硫機構は、従来いわれているような吹き込んだ脱硫材粒子が吹き込みガスから溶鉄内に侵入し溶銑に接触した状態で浮上しながらＳと反応するのではなく、吹き込まれた脱硫材粒子は気泡内にそのほとんどが滞留し、溶銑表面に浮上した後に溶銑と接触して脱硫反応が進むという機構である。 From these results, it was estimated that the blown desulfurized powder powder floated on the hot metal surface while remaining in the gas bubbles. In other words, the desulfurization mechanism in the injection method is such that the blown desulfurization material particles enter the molten iron from the blown gas and float with the molten iron in contact with the molten iron, but do not react with S, but blown desulfurization. The material particles have a mechanism that most of the particles stay in the bubbles and float on the surface of the hot metal, and then contact with the hot metal to proceed with the desulfurization reaction.
従来は脱硫材粉体が細かすぎると溶銑中に吹き込まれたガスが溶銑表面に浮上するまでの間に、ガス気泡から脱硫材粒子が脱出できないままで終わる確率が増大し、脱硫効率が低下すると考えられていたが、発明者らが新たに見出した脱硫機構であれば、従来言われているよりも細かい脱硫材でも脱硫効率が低下しない可能性がある。 Conventionally, if the powder of desulfurized material is too fine, the probability that the desulfurized particles will not escape from the gas bubbles increases until the gas blown into the hot metal surface rises to the hot metal surface, and the desulfurization efficiency decreases. However, if the desulfurization mechanism was newly found by the inventors, there is a possibility that the desulfurization efficiency will not be reduced even with a finer desulfurization material than conventionally known.
そこで次に発明者らは、ＣａＯ含有率が９５質量％の脱硫材粉末を、目開き５μｍ、１０μｍ、２０μｍ、３０μｍ、４０μｍ、５０μｍ、６０μｍ、７０μｍ、８０μｍ、９０μｍ、１００μｍのメッシュクロスを用いて選別した。そして鍋方式のインジェクション設備において、溶銑へ金属Ａｌを上方より添加して溶銑中にＡｌを０．０１質量％含有させ、目標粒径別に選別を行った脱硫材を、吹き込み速度１００〜３００ｋｇ／ｍｉｎで吹き込む試験を行った。 Therefore, the inventors next used a desulfurized material powder having a CaO content of 95% by mass using mesh cloth having openings of 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, and 100 μm. Selected. And in the pan-type injection equipment, the desulfurized material which added metal Al to hot metal from the upper side and contained 0.01 mass% of Al in the hot metal and selected according to the target particle size was blown at a rate of 100 to 300 kg / min. The test which blows in was done.
図１にその結果を示す。脱硫材粒径が５μｍ以上５０μｍ未満の範囲ではいずれもＳ濃度＝０．００１質量％まで、前記（１）式で定義する脱硫ＣａＯ効率で１０％以上まで脱硫でき、脱硫ＣａＯ効率は良好であった。脱硫試験後に採取したスラグの断面を走査型電子顕微鏡で調査したところ、粒径の半分以上あるいは内部まで全てＣａＯ−Ａｌ2Ｏ3−ＳｉＯ2相となった脱硫材粒子が多数検出された。ＣａＯ−Ａｌ2Ｏ3−ＳｉＯ2相はＳを含有しており、この相の厚みは概ね５μｍ以上５０μｍ未満であり、特に５μｍ以上３０μｍ未満のものが多かった。ＣａＯ−Ａｌ2Ｏ3−ＳｉＯ2相の厚みは、溶銑Ｓ濃度が高い段階で生成した場合は厚くなり、低硫域で生成した場合は薄くなると考えられる。すなわち、脱硫材粒径が５μｍ以上５０μｍ未満の範囲で良好な脱硫ＣａＯ効率が得られた理由は、溶銑Ｓ濃度の低下に伴って変化するＣａＯ−Ａｌ2Ｏ3−ＳｉＯ2相の厚みとほぼ同じであるために、低硫域においても内部まで脱硫に有効利用されたからであると考えられる。 The result is shown in FIG. In the range where the particle size of the desulfurization material is 5 μm or more and less than 50 μm, the desulfurization CaO efficiency defined by the above formula (1) can be desulfurized to an S concentration = 0.001 mass%, and the desulfurization CaO efficiency is good. It was. When a cross-section of the slag collected after the desulfurization test was examined with a scanning electron microscope, a large number of desulfurization material particles that became CaO—Al 2 O 3 —SiO 2 phase more than half of the particle size or even inside were detected. The CaO—Al 2 O 3 —SiO 2 phase contains S, and the thickness of this phase is generally not less than 5 μm and less than 50 μm, and in particular, there are many that are not less than 5 μm and less than 30 μm. The thickness of the CaO—Al 2 O 3 —SiO 2 phase is considered to be thick when it is formed at a stage where the hot metal S concentration is high, and thin when it is formed in a low sulfur region. That is, the reason why a good desulfurized CaO efficiency was obtained when the particle size of the desulfurized material was 5 μm or more and less than 50 μm was almost the same as the thickness of the CaO—Al 2 O 3 —SiO 2 phase that changed as the hot metal S concentration decreased. Because it is the same, it is considered that it was effectively utilized for desulfurization even in the low sulfur region.
脱硫材粒径が大きいと単位質量あたりの表面積が小さくなるのに加え、低硫域では表層のみにしかＣａＯ−Ａｌ2Ｏ3−ＳｉＯ2相が生成しないので、５０μｍ超の粒子について脱硫ＣａＯ効率の低下が起こったものと考えられる。 When the particle size of the desulfurized material is large, the surface area per unit mass is reduced, and in the low sulfur region, the CaO—Al 2 O 3 —SiO 2 phase is formed only on the surface layer. It is probable that the decline occurred.
一方、脱硫材粒径が小さくなり過ぎると溶銑上に浮上した後も溶銑と接触しない割合が増え、それらは脱硫に寄与しないため、５μｍ未満でも脱硫ＣａＯ効率の低下が起こったものと考えられる。この結果から、本発明における脱硫材粒径は５μｍ以上５０μｍ未満、より好ましくは５μｍ以上３０μｍ未満と規定した。脱硫材粒径分布の測定については、目開き５０μｍと５μｍのメッシュクロスを用いて選定し、５０μｍの篩下かつ５μｍの篩上の比率（質量％）をもって粒径５μｍ以上５０μｍ未満の粉体構成率とすることができる。 On the other hand, if the particle size of the desulfurized material becomes too small, the proportion not coming into contact with the hot metal even after floating on the hot metal increases, and they do not contribute to desulfurization. From this result, the particle size of the desulfurized material in the present invention is defined as 5 μm or more and less than 50 μm, more preferably 5 μm or more and less than 30 μm. For the measurement of the particle size distribution of the desulfurized material, it is selected using a mesh cloth having openings of 50 μm and 5 μm. Rate.
次に、粒径５μｍ以上５０μｍ未満の構成比率を種々変えて、それぞれについて脱硫効率の評価を行った。脱硫処理条件は上記の実験を同様とした。その結果を図２に示す。図２から明らかなように、粒径５μｍ以上５０μｍ未満の粉体構成比率が５０％以上であれば脱硫効率が良好な値を示すことが明らかとなった。同様に粒径５μｍ以上３０μｍ未満の構成比率を種々変えて、脱硫効率の評価を行った結果を図３に示す。粒径５μｍ以上３０μｍ未満の粉体構成比率が５０％以上であれば脱硫効率がさらに良好となることが明らかとなった。 Next, the desulfurization efficiency was evaluated for each of the various composition ratios of particle sizes of 5 μm or more and less than 50 μm. The desulfurization treatment conditions were the same as in the above experiment. The result is shown in FIG. As is clear from FIG. 2, it has been clarified that the desulfurization efficiency shows a good value when the powder composition ratio having a particle size of 5 μm or more and less than 50 μm is 50% or more. Similarly, FIG. 3 shows the result of evaluating the desulfurization efficiency by changing the composition ratio of particle diameters of 5 μm or more and less than 30 μm in various ways. It has been clarified that the desulfurization efficiency is further improved when the composition ratio of the powder having a particle size of 5 μm or more and less than 30 μm is 50% or more.
脱硫材の吹き込み速度を高くすると溶銑と脱硫材粒子の接触時間が短くなるので、ＣａＯ内部までＳが浸透しにくくなるが、粒径５μｍ以上５０μｍ未満の粉体構成比率が５０％以上とすれば、吹き込み速度が高くなっても溶銑との接触時間内にＳはＣａＯ内部の浸透でき、高い脱硫ＣａＯ効率を得ることができる。 When the blowing speed of the desulfurization material is increased, the contact time between the hot metal and the desulfurization material particles is shortened, so that it is difficult for S to penetrate into the CaO. However, if the powder composition ratio with a particle size of 5 μm or more and less than 50 μm is 50% or more. Even if the blowing speed increases, S can penetrate into the CaO within the contact time with the hot metal, and high desulfurized CaO efficiency can be obtained.
なお、吹き込み速度の上限を３００ｋｇ／ｍｉｎとするのは、過度に高くすると溶銑の揺動が激しくなり、浮上した脱硫材および溶銑が処理容器の外に飛散しやすくなるためである。また、吹き込み速度の下限を１００ｋｇ／ｍｉｎとするのは、脱硫材は粒径が細かいほどランス内部あるいはランス孔周辺に付着・堆積しやすく、過度に低い速度で吹き込むと、吹き込みが安定しなくなったりランス孔が閉塞したりしやすくなるためである。 Note that the upper limit of the blowing speed is set to 300 kg / min because if the temperature is excessively high, the hot metal swings vigorously, and the desulfurized material and hot metal that have floated are likely to be scattered outside the processing vessel. The lower limit of the blowing speed is set to 100 kg / min because the finer the desulfurized material, the easier it is to adhere and deposit inside the lance or around the lance hole, and if blown at an excessively low speed, the blowing may become unstable. This is because the lance hole is easily blocked.
以上に説明した本発明の脱硫方法により、脱硫ＣａＯ効率の向上を図ることができる。なお、搬送ガスは不活性ガス（Ｎ2、Ａｒ）を使用すれば良い。 By the desulfurization method of the present invention described above, the efficiency of desulfurization CaO can be improved. Note that an inert gas (N 2 , Ar) may be used as the carrier gas.
以下に表１を基にして本発明の実施例を具体的に説明する。 Examples of the present invention will be specifically described below based on Table 1.
溶銑４００ｔを混銑車から溶銑鍋に装入し、温度が１３５５〜１４１０℃、Ｓｉ濃度が０．４〜０．６％の溶銑へ塊状あるいは線状の金属Ａｌを上方から添加して溶銑中Ａｌ濃度を０．００３〜０．０１２質量％とし、ランスを溶銑に浸漬し、Ｎ2を搬送ガスとして脱硫材粉体を吹き込んだ。その結果を表１に示す。本発明範囲から外れる数値にアンダーラインを付している。 400t of hot metal is charged into the hot metal ladle from the kneading car and molten or linear metal Al is added from above to the hot metal having a temperature of 1355 to 1410 ° C and an Si concentration of 0.4 to 0.6%. The concentration was 0.003 to 0.012% by mass, the lance was immersed in the hot metal, and desulfurized powder was blown in using N 2 as a carrier gas. The results are shown in Table 1. Numerical values that fall outside the scope of the present invention are underlined.
実施例１〜４、６、７は発明例である。実施例１〜４では、いずれも脱硫材吹き込み速度：１９０〜２９０ｋｇ／ｍｉｎの高速吹き込み条件下において、本発明の条件を満足たす脱硫材を使用したので、脱硫ＣａＯ効率を１０％超としながら１０分未満でＳ＝０．００１％まで脱硫することができた。
Examples 1 to 4, 6, and 7 are invention examples. In Examples 1 to 4 , since the desulfurizing material satisfying the conditions of the present invention was used under the high-speed blowing condition of 190 to 290 kg / min, the desulfurizing CaO efficiency exceeded 10%. In less than 10 minutes, it was possible to desulfurize to S = 0.001%.
実施例６では、脱硫材吹き込み速度が９５ｋｇ／ｍｉｎと低く、吹き込み速度：１００〜３００ｋｇ／ｍｉｎの時と比較して、吹き込みが安定しにくかった。また、所要時間が１５．２分に増加した。 In Example 6, the desulfurization material blowing rate was as low as 95 kg / min, and the blowing rate was less stable as compared with the blowing rate of 100 to 300 kg / min. Also, the required time increased to 15.2 minutes.
また実施例７では、脱硫材吹き込み速度が３０５ｋｇ／ｍｉｎと高く、吹き込み中の溶銑の揺動が激しく、吹き込んで浮上した脱硫材の一部が溶銑鍋の外に飛散した。 Further, in Example 7, the desulfurization material blowing speed was as high as 305 kg / min, and the hot metal rocking during the blowing was intense, and a part of the desulfurized material blown and floated scattered outside the hot metal pan.
一方、実施例８では脱硫材のＣａＯ濃度が８５％と低かったため、Ｓ＝０．００３％までしか脱硫できず、脱硫ＣａＯ効率が８．８％に低下した。 On the other hand, in Example 8, since the CaO concentration of the desulfurization material was as low as 85%, desulfurization was possible only up to S = 0.003%, and the desulfurization CaO efficiency was reduced to 8.8%.
実施例９では脱硫材の５μｍ以上５０μｍ未満の粉体構成率が４０％と低かったため、Ｓ＝０．００２％までしか脱硫できず、脱硫ＣａＯ効率が７．８％に低下した。 In Example 9, since the powder composition ratio of the desulfurization material of 5 μm or more and less than 50 μm was as low as 40%, desulfurization was possible only up to S = 0.002%, and the desulfurization CaO efficiency was reduced to 7.8%.
実施例１０では脱硫材の５μｍ以上５０μｍ未満の粉体構成率が４１％と低かったため、脱硫ＣａＯ効率は６．９％に低下し、実施例１〜５と同等のＳ濃度域まで脱硫するのに１２分超の時間を必要とした。 In Example 10, since the powder composition ratio of the desulfurization material of 5 μm or more and less than 50 μm was as low as 41%, the desulfurization CaO efficiency was reduced to 6.9%, and desulfurization was performed up to the S concentration range equivalent to Examples 1-5. Took more than 12 minutes.
実施例１１では脱硫材のＣａＯ濃度が８５％と低いため、脱硫ＣａＯ効率が８．８％に低下した。また、脱硫材吹き込み速度が９５ｋｇ／ｍｉｎと低く、吹き込み速度：１００〜３００ｋｇ／ｍｉｎの時と比較して、吹き込みが安定しにくかった。また、所要時間が１７．７分に増加した。 In Example 11, since the CaO concentration of the desulfurization material was as low as 85%, the desulfurization CaO efficiency was lowered to 8.8%. Moreover, compared with the time of desulfurization material blowing speed | velocity being as low as 95 kg / min and blowing speed: 100-300 kg / min, blowing was hard to be stable. The required time increased to 17.7 minutes.
実施例１２では脱硫材のＣａＯ濃度が８５％と低いため、脱硫ＣａＯ効率が８．０％に低下した。また、脱硫材吹き込み速度が３０５ｋｇ／ｍｉｎと高く、吹き込み中の溶銑の揺動が激しく、吹き込んで浮上した脱硫材の一部が溶銑鍋の外に飛散した。 In Example 12, since the CaO concentration of the desulfurized material was as low as 85%, the desulfurized CaO efficiency was reduced to 8.0%. Moreover, the desulfurization material blowing speed was as high as 305 kg / min, and the hot metal rocking during blowing was intense, and a part of the desulfurized material blown and floated was scattered outside the hot metal pan.
実施例１３では溶銑のＡｌ濃度が０．００３％と低いため、Ｓ＝０．００９％までしか脱硫できず、脱硫ＣａＯ効率が６．０％に低下した。 In Example 13, since the Al concentration of the hot metal was as low as 0.003%, desulfurization was possible only up to S = 0.000%, and the desulfurization CaO efficiency was reduced to 6.0%.
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