JP4837536B2 - Hot metal desulfurization refining agent and desulfurization method - Google Patents
Hot metal desulfurization refining agent and desulfurization method Download PDFInfo
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本発明はCaF2を使用せずに溶銑の脱硫精錬を効果的に実施する技術に関するものである。 The present invention relates to a technique for effectively carrying out hot metal desulfurization refining without using CaF 2 .
鉄鋼業においては,粉体吹込み法や機械攪拌法(KR法)によって,溶銑を脱硫処理するにあたり,CaOを主成分とし,反応特性を向上させるために,特許文献1に開示のCaF2や,特許文献2に記載のAl2O3,特許文献3に提示のソーダ石灰硝子など,CaOを溶融させる効果の大きい物質を加えた精錬剤を用い、強還元性条件下で脱硫処理を実施している。特に、安価でCaO溶融効果の大きいCaF2は、各種溶銑の脱硫方法において汎くCaO系脱硫剤に添加されて用いられてきた。一方,地球環境保全・産業廃棄物の有効活用の観点から,これまで一般的に使用していたCaF2源としての蛍石の使用が制限され,脱硫方法として,精錬剤の使用裕度が広い機械攪拌法(KR法)が用いられつつある。 In the steel industry, when desulfurizing hot metal by a powder blowing method or a mechanical stirring method (KR method), CaO 2 disclosed in Patent Document 1 The desulfurization treatment was carried out under strongly reducing conditions using a refining agent to which a substance having a large effect of melting CaO such as Al 2 O 3 described in Patent Document 2 and soda-lime glass presented in Patent Document 3 was added. ing. In particular, CaF 2, which is inexpensive and has a large CaO melting effect, has been widely added to CaO-based desulfurizing agents in various hot metal desulfurization methods. On the other hand, from the viewpoint of global environmental protection and effective utilization of industrial waste, the use of fluorite as a CaF 2 source, which has been generally used so far, is limited, and the use of refining agents is wide as a desulfurization method. A mechanical stirring method (KR method) is being used.
しかし、機械攪拌法においては、前記開示のごとく脱硫能の高い精錬剤をただ漫然と使用しても、高い脱硫効率は実現できない。つまり、機械攪拌法において、精錬剤の具備すべき要件は、高い脱硫能の保持と、機械攪拌による精錬剤の溶銑への巻き込みの容易さが絶対条件となる.この観点で、脱硫剤の巻き込みに有利な回転羽根の形状(例えば特許文献4)や回転羽根と溶銑湯面との相対的位置関係の設定に関する技術(例えば特許文献5)が開示されている。 However, in the mechanical stirring method, high desulfurization efficiency cannot be realized even if a refining agent having a high desulfurization ability is simply used as described above. In other words, in the mechanical agitation method, the requirements for the refining agent are to maintain high desulfurization ability and to easily entrain the refining agent in the molten iron by mechanical agitation. From this viewpoint, a technique (for example, Patent Document 5) relating to the setting of the relative position relationship between the shape of the rotating blade (for example, Patent Document 4) and the rotating blade and the hot metal surface, which are advantageous for entrainment of the desulfurizing agent, is disclosed.
しかし、これらの技術は、脱硫スラグの巻き込みを有利にするための技術を開示しているに過ぎず、スラグの巻き込みの状況がスラグの組成あるいはスラグの性状によって大きく変化するという本発明者らが得ている実態を鑑みると、これらの技術単独では、高い脱硫能を得るための十分条件を与える技術とはなっていない。 However, these techniques merely disclose a technique for making desulfurization slag entrainment advantageous, and the inventors of the present invention that the entrainment situation of slag varies greatly depending on the composition of slag or the properties of slag. In view of the actual situation obtained, these technologies alone are not technologies that give sufficient conditions for obtaining high desulfurization ability.
本発明者らは、スラグが効率的に巻き込まれ、十分な脱硫反応が達成された処理後のスラグの性状や組成を調査し、処理後のスラグが球相当径で3mmφ以上かつ20mmφ以下の大きさである粒状を呈しており、かつ比重が3.5以上であることを見出し、このような条件を満たすために、スラグの液相率を処理温度で5%〜30%になるようにスラグ組成を調整する技術を開示している(特許文献6)。この開示技術は適正な液相率を持ったスラグ組成にすることによって、処理途中に溶鉄を巻き込みながらスラグが造粒(転動造粒)されていくことを利用し、機械攪拌において容易に溶銑に巻き込まれるスラグ粒を造ることを根幹とした技術であるが、逆に造粒までには一定の時間が必要であり、その間は、スラグの巻き込みが生じ難いために、脱硫反応が抑制されるというという欠点を持っていた。 The present inventors investigated the properties and composition of the slag after the treatment in which the slag was efficiently involved and sufficient desulfurization reaction was achieved, and the slag after the treatment had a sphere equivalent diameter of 3 mmφ or more and 20 mmφ or less. In order to satisfy these conditions, the slag has a liquid phase ratio of 5% to 30% at the treatment temperature. A technique for adjusting the composition is disclosed (Patent Document 6). This disclosed technology makes use of the fact that slag is granulated (rolling granulation) while entraining molten iron in the middle of processing by using a slag composition having an appropriate liquid phase ratio, and it is easy to use molten iron in mechanical stirring. This technology is based on the creation of slag grains that are caught in the slag, but on the contrary, a certain amount of time is required until granulation, and during that time, slag is less likely to be entrained, so the desulfurization reaction is suppressed. It had the disadvantage that.
さらに本発明者らは、上記適切な液相率を確保するための脱硫剤として、CaOにFeO源を添加する技術を開示している(特許文献7)。本開示技術については、従来酸素分圧を増加させるため脱硫材には極力含有させないことが必要と考えられていたFeOも、適切な添加量においては上記スラグ巻き込みに好適なスラグ組成を確保する安価な添加剤となることが見出されている。しかし、この技術も、スラグ組成のみの制御でスラグ巻き込みに好適なスラグ粒を処理中に形成させる前記技術に立脚したものであり、造粒までには一定の時間が必要であるという欠点は前記技術と共有している。 Furthermore, the present inventors have disclosed a technique of adding a FeO source to CaO as a desulfurization agent for ensuring the appropriate liquid phase ratio (Patent Document 7). With regard to the disclosed technology, FeO, which has conventionally been considered to be necessary to contain as little as possible in the desulfurization material in order to increase the oxygen partial pressure, is inexpensive enough to secure a slag composition suitable for the above slag entrainment in an appropriate addition amount. Has been found to be a good additive. However, this technique is also based on the technique of forming slag grains suitable for slag entrainment during processing by controlling only the slag composition, and the disadvantage that a certain time is required until granulation Share with technology.
本発明は、上記従来技術の課題を解決し、蛍石を使用せずに,かつ機械攪拌方式の脱硫処理の初期から脱硫反応を生じさせ、もって、溶銑の脱硫処理におけるより高い脱硫効率を実現し,且つ,再利用用途の少ない製鋼スラグ磁選粉を有効に利用できる技術を提示するものである。 The present invention solves the above-mentioned problems of the prior art, and produces a desulfurization reaction from the initial stage of the mechanical stirring type desulfurization process without using fluorite, thereby realizing higher desulfurization efficiency in the hot metal desulfurization process. However, the present invention presents a technology that can effectively use steelmaking slag magnetic powder selection with little reuse.
即ち、本発明の要旨とするところは,以下のとおりである。
(1)溶銑の機械攪拌式脱硫処理に用いる脱硫精錬剤であって、該脱硫精錬剤中の粒鉄量が1.5〜5.0質量%,FeO濃度が2.0〜7.0質量%、CaO濃度が80質量%以上であることを特徴とする溶銑の脱硫精錬剤。
ここでFeO濃度は、脱硫精錬剤中に含まれる酸化鉄がすべてFeOであるとして算定する。
(2)生石灰あるいは生石灰に製鋼スラグを配合したものを主原料とし、更に製鋼スラグ磁選粉を加えてなることを特徴とする上記(1)に記載の溶銑の脱硫精錬剤。
(3)更に該脱硫精錬剤中のAl2O3濃度が1.0〜5.0質量%以下であることを特徴とする上記(1)に記載の溶銑の脱硫精錬剤。
(4)生石灰あるいは生石灰に製鋼スラグを配合したものを主原料とし、更に製鋼スラグ磁選粉及びAl2O3源を加えてなることを特徴とする上記(3)に記載の溶銑の脱硫精錬剤。
(5)前記製鋼スラグ磁選粉の一部あるいは全部を2次精錬滓磁選粉としたことを特徴とする上記(2)又は(4)に記載の溶銑の脱硫精錬剤。
(6)上記(1)乃至(5)のいずれかに記載の脱硫精錬剤を用いて機械攪拌式脱硫処理を行うことを特徴とする溶銑の脱硫方法。
That is, the gist of the present invention is as follows.
(1) A desulfurization refining agent used in the mechanical stirring desulfurization treatment of hot metal, wherein the amount of granular iron in the desulfurization refining agent is 1.5 to 5.0 mass%, and the FeO concentration is 2.0 to 7.0 mass. %, And a CaO concentration of 80% by mass or more.
Here, the FeO concentration is calculated on the assumption that all of the iron oxide contained in the desulfurization refining agent is FeO.
(2) The hot metal desulfurization refining agent according to (1) above, wherein quick lime or a mixture of quick lime and steelmaking slag is used as a main raw material, and steelmaking slag magnetic powder is further added.
(3) The hot metal desulfurization refining agent as described in (1) above, wherein the concentration of Al 2 O 3 in the desulfurization refining agent is 1.0 to 5.0% by mass or less.
(4) The hot metal desulfurization refining agent as described in (3) above, wherein quick lime or a mixture of quick lime and steelmaking slag is used as a main raw material, and further steelmaking slag magnetic powder and an Al 2 O 3 source are added. .
(5) The desulfurization refining agent for hot metal as described in (2) or (4) above, wherein a part or all of the steelmaking slag magnetic powder separation is a secondary refining magnetic powder powder.
(6) A hot metal desulfurization method comprising performing a mechanical stirring type desulfurization treatment using the desulfurization refining agent according to any one of (1) to (5) above.
本発明の方法により、蛍石(CaF2)を使用せず、環境に調和した溶銑脱硫処理を高効率で行うことができ、且つ、利用価値の極めて少ない製鋼スラグ磁選粉が活用できる上に、磁選粉に多量に存在する鉄源の回収も併せて可能となった。 By the method of the present invention, hot metal desulfurization treatment harmonized with the environment can be performed with high efficiency without using fluorite (CaF 2 ), and steelmaking slag magnetic powder separation with extremely low utility value can be utilized. It was also possible to recover the iron source present in large quantities in the magnetic powder.
溶銑の機械攪拌式脱硫処理に用いる本発明の脱硫精錬剤は、脱硫精錬剤中の粒鉄量が1.5〜5.0質量%,FeO濃度が2.0〜7.0質量%、CaO濃度が80質量%以上であることを特徴とする。ここでFeO濃度は、脱硫精錬剤中に含まれる酸化鉄がすべてFeOであるとして算定する。以下同様である。 The desulfurization refining agent of the present invention used for the mechanical stirring type desulfurization treatment of hot metal has a granular iron content of 1.5 to 5.0% by mass, a FeO concentration of 2.0 to 7.0% by mass, and CaO. The concentration is 80% by mass or more. Here, the FeO concentration is calculated on the assumption that all of the iron oxide contained in the desulfurization refining agent is FeO. The same applies hereinafter.
本発明の脱硫精錬剤中のCaO濃度を80質量%以上とすることにより、CaOによる脱硫能力を十分に発揮することができる。また、脱硫精錬剤中のFeO濃度を2.0〜7.0質量%とすることにより、FeOによるCaOの滓化効果を発揮し、機械攪拌式脱硫処理においてスラグ巻き込みを促進することができる。 By making the CaO concentration in the desulfurization refining agent of the present invention 80% by mass or more, the desulfurization ability by CaO can be sufficiently exhibited. Moreover, the FeO density | concentration in a desulfurization refining agent shall be 2.0-7.0 mass%, the hatching effect of CaO by FeO can be exhibited, and slag entrainment can be accelerated | stimulated in a mechanical stirring type desulfurization process.
本発明は、脱硫精錬剤中の粒鉄量を1.5〜5.0質量%とする点が最大の特徴である。粒鉄は密度が高いので、粒鉄を含有する脱硫精錬剤の密度を高めることができ、機械攪拌式脱硫処理の初期から、溶銑に巻き込まれて脱硫反応に寄与するので、脱硫率を格段に高めることができる。そのため、脱硫精錬剤中に蛍石を含有することなく、蛍石を含有したときと同様の高い脱硫率を実現することができる。それに対し脱硫精錬剤中に粒鉄を含有しない従来の場合は、機械攪拌式脱硫処理を開始してしばらく経ってからでないと脱硫精錬剤が溶銑に巻き込まれず、十分に高い脱硫率を実現することができない。 The greatest feature of the present invention is that the amount of granular iron in the desulfurization refining agent is 1.5 to 5.0% by mass. Since the density of granular iron is high, the density of the desulfurization refining agent containing granular iron can be increased, and since it is involved in the desulfurization reaction by being involved in the hot metal from the beginning of the mechanical stirring desulfurization treatment, the desulfurization rate is markedly Can be increased. Therefore, a high desulfurization rate similar to that when fluorite is contained can be realized without containing fluorite in the desulfurization refining agent. On the other hand, in the conventional case where granular iron is not included in the desulfurization refining agent, the desulfurization refining agent is not involved in the hot metal until a while after the mechanical stirring type desulfurization treatment is started, and a sufficiently high desulfurization rate is realized I can't.
本発明において粒鉄とは、粒状の金属鉄を意味する。脱硫精錬剤を化学分析したときに金属鉄として検出される。 In the present invention, granular iron means granular metallic iron. It is detected as metallic iron when the desulfurization refining agent is chemically analyzed.
上記本発明の脱硫精錬剤において、生石灰あるいは生石灰に製鋼スラグを配合したものを主原料とし、更に製鋼スラグ磁選粉を加えてなることとすると好ましい。 In the desulfurization refining agent of the present invention, it is preferable to use quick lime or quick lime blended with steelmaking slag as a main raw material and further add steelmaking slag magnetic powder.
製鋼スラグ磁選粉とは、製鋼工程で排出されたスラグを冷却した後、該スラグをおよそ5.0mm以下に粉砕し,磁石により選別し,さらに2.0mm以下に粉砕したものであり,磁石につく粒鉄を含むスラグ粉である。表1に代表的な転炉滓磁選粉、表2に磁選粉を分離する前の代表的な転炉滓の化学組成を示す。表1の例は、およそ2000ガウスの磁力を持つ電磁石(磁化面積0.3m2)を用いて磁選したものである。なお、磁選粉中の酸化鉄には、FeOとFe2O3が含まれるが、表1のFeOの濃度は、スラグを化学分析した結果得られるT.Fe(質量%)から同じく化学分析から得られる金属Fe(質量%)を差し引いた酸化鉄中のFe濃度を全てFeOとして質量%に換算して得られた値である。本明細書中に記載している「FeO濃度」は全て、上記定義によるものである。 Steelmaking slag magnetic powder separation is a product in which the slag discharged in the steelmaking process is cooled, then slag is pulverized to approximately 5.0 mm or less, sorted with a magnet, and further pulverized to 2.0 mm or less. It is a slag powder containing fine grained iron. Table 1 shows the chemical composition of typical converter powder, and Table 2 shows the chemical composition of a typical converter powder before separating the magnetic powder. The example of Table 1 is magnetically selected using an electromagnet (magnetization area 0.3 m 2 ) having a magnetic force of approximately 2000 gauss. Note that the iron oxide in the magnetically segregated powder contains FeO and Fe 2 O 3, but the concentration of FeO in Table 1 is a T.C. obtained as a result of chemical analysis of slag. It is a value obtained by converting all Fe concentrations in iron oxide obtained by subtracting metal Fe (mass%) obtained from the same chemical analysis from Fe (mass%) into Fe mass% as FeO. All of the “FeO concentration” described in the present specification is as defined above.
製鋼過程で発生する製鋼スラグ磁選粉は,表1に示すように粒鉄を多量に含有するため,従来、製鋼精錬剤としての利用が困難とされ,転炉等の精錬炉に鉄源としてリサイクルする程度であった。本発明者らは、脱硫精錬剤として汎く使用される生石灰あるいは生石灰に製鋼スラグを配合したものを主原料とし、これに製鋼スラグ磁選粉を適量配合することにより、脱硫精錬剤中の粒鉄量が1.5〜5.0質量%,FeO濃度が2.0〜7.0質量%、CaO濃度が80質量%以上である本発明の脱硫精錬剤とすることができることを見出した。これにより、CaOに粒鉄を含まないFeO源のみを混合して同量のFeO濃度とした脱硫剤を用いて機械攪拌脱硫処理を行った場合と比較して、より高い脱硫能を得ることができる。 Steelmaking slag magnetic powder generated in the steelmaking process contains a large amount of granular iron as shown in Table 1, so that it has been difficult to use as a steelmaking refining agent in the past, and it is recycled as an iron source in a refining furnace such as a converter. It was about to do. The present inventors use quick lime widely used as a desulfurization refining agent or a mixture of quick lime and steelmaking slag as a main raw material, and by mixing an appropriate amount of steelmaking slag magnetically segregated powder, It was found that the desulfurization refining agent of the present invention having an amount of 1.5 to 5.0 mass%, an FeO concentration of 2.0 to 7.0 mass%, and a CaO concentration of 80 mass% or more can be obtained. As a result, higher desulfurization ability can be obtained as compared with the case where mechanical stirring desulfurization treatment is performed using a desulfurizing agent in which only FeO source not containing granular iron is mixed with CaO to obtain the same amount of FeO concentration. it can.
ここで、脱硫精錬剤の主原料として生石灰とともに製鋼スラグを配合する場合、製鋼スラグとして、脱硫に有効なCaO源としての製鋼スラグを用いると好ましい。脱硫に有効なCaO源としての製鋼スラグとは、転炉(脱炭)滓、溶銑予備処理滓、2次精錬滓等、CaO濃度が比較的高く、生石灰と混合して用いた場合に、生石灰単独使用の脱硫処理と比較してCaOの脱硫能を保持するか或いは向上させる製鋼スラグを言う。具体的には、脱硫精錬剤中のCaO成分として生石灰の代替となり、かつ脱硫精錬剤中のCaO含有量を80質量%以上に保持することのできる製鋼スラグであればよい。 Here, when steelmaking slag is blended with quick lime as the main raw material of the desulfurization refining agent, it is preferable to use steelmaking slag as a CaO source effective for desulfurization as the steelmaking slag. Steelmaking slag as an effective source of CaO for desulfurization means that converters (decarburization), hot metal pretreatment, secondary refining, etc. have a relatively high CaO concentration and are used when mixed with quicklime. This refers to steelmaking slag that retains or improves the desulfurization ability of CaO compared to a single-use desulfurization treatment. Specifically, any steelmaking slag may be used as long as it is a substitute for quick lime as a CaO component in the desulfurization refining agent and can maintain the CaO content in the desulfurization refining agent at 80% by mass or more.
表1からわかるように、転炉滓磁選粉には脱硫反応そのものに寄与するCaO分を多く含み、CaOの滓化を促進するFeO分が含まれていることの他に、粒鉄分もかなり多く含まれている。このうち、FeO分は非常に低融点のCaO−FeOX(X=1.0−1.5)相を生成し、CaOの早期滓化が生じ、KR機械攪拌法における転動造粒に必要な液相率を確保するのに有効であると考えられる。また、粒鉄を含む転炉滓磁選粉を脱硫精錬剤に含有させた場合、粒鉄を含まないFeO源を用いた場合よりも脱硫率が高くなっていたことから、転炉滓磁選粉内の粒鉄は、機械攪拌処理の初期から添加したCaOやスラグ液体成分と一体となり、密度の高いスラグ粒を形成して、処理の極初期から溶銑に巻き込まれて脱硫反応に寄与したため、脱硫率が格段に高くなったと考えられる。一方、粒鉄を含まないFeO源を用いた場合には、造粒されるスラグ粒に溶銑が取り込まれ、密度が高くなるのを待ってからでないとスラグ粒が溶銑に巻き込まれないために、脱硫反応が遅くなり、粒鉄を含んだ脱硫剤を用いた場合よりも脱硫能が劣ったと考えられる。従って、機械攪拌方式による溶銑の脱硫処理において、このような格段に高い脱硫能を得るためには、CaOをベースとした脱硫剤中に適量のFeO分と粒鉄が含まれていることが必要となってくる。 As can be seen from Table 1, the converter magnetic powder selection contains a large amount of CaO that contributes to the desulfurization reaction itself, and in addition to the content of FeO that promotes the hatching of CaO, there is also a considerable amount of granular iron. include. Among these, the FeO content generates a CaO-FeO x (X = 1.0-1.5) phase with a very low melting point, resulting in early hatching of CaO, which is necessary for rolling granulation in the KR mechanical stirring method. It is considered effective for securing a high liquid phase ratio. In addition, when the desulfurization refining agent contains a converter magnetic selection powder containing granular iron, the desulfurization rate is higher than when a FeO source not containing granular iron is used. Since the granular iron was integrated with the CaO and slag liquid components added from the beginning of the mechanical stirring process, and formed high-density slag grains and was involved in the hot metal from the very initial stage of the process, contributing to the desulfurization reaction. Is considered to be significantly higher. On the other hand, when using a FeO source that does not contain granular iron, hot metal is taken into the granulated slag grains, and the slag grains are not caught in the hot metal until the density is increased. It is considered that the desulfurization reaction was delayed and the desulfurization ability was inferior to that when a desulfurization agent containing granular iron was used. Therefore, in order to obtain such a remarkably high desulfurization ability in the hot metal desulfurization process by the mechanical stirring method, it is necessary that the CaO-based desulfurization agent contains an appropriate amount of FeO and granular iron. It becomes.
ここで、CaOの滓化効果を持つ成分としては、FeOの他にAl2O3やSiO2が考えられるが、CaO−Al2O3およびCaO−SiO2系の状態図からわかるように、これらの成分単独では、溶銑処理の温度(1300℃〜1450℃)では液体を生成せず、FeOと比べて液体の生成能力は劣る。本発明の目的は、機械攪拌による溶銑の脱硫処理の反応速度向上にあるのであり、よって本発明では、脱硫剤中のCaOの滓化促進剤としてCaO溶解能力の高いFeOの存在を必須とした。 Here, as components having a hatching effect of CaO, Al 2 O 3 and SiO 2 can be considered in addition to FeO, but as can be seen from the phase diagrams of CaO—Al 2 O 3 and CaO—SiO 2 systems, These components alone do not generate a liquid at the temperature of the hot metal treatment (1300 ° C. to 1450 ° C.), and the liquid generation ability is inferior to that of FeO. The object of the present invention is to improve the reaction rate of the hot metal desulfurization treatment by mechanical stirring. Therefore, in the present invention, the presence of FeO having a high CaO dissolving ability is essential as a CaO hatching accelerator in the desulfurization agent. .
脱炭吹錬や2次精錬等の精錬処理では、精錬反応を促進させるため、大きな攪拌力を付与するのが通例である。従って、精錬処理にて生成するスラグ中には、不可避的に粒鉄が混入する。よって、この粒鉄分を取り除く目的で行われる磁選処理で発生する磁選粉には、当然ながら粒鉄が多量に存在する。さらに、スラグの冷却、破砕、磁選処理においては、粒鉄の一部が酸化され、磁選粉内にFeOが生成する。また、転炉吹錬などの酸化精錬では、精錬直後のスラグ中にもFeOが存在し、そのスラグを磁選した磁選粉にもFeO分として残留する。従って、製鋼スラグの磁選粉は多量の粒鉄とFeOを同時に含んだものであり、本発明を達成するために必要な条件を具備した配合物である。 In refining processes such as decarburization blowing and secondary refining, it is usual to apply a large stirring force to promote the refining reaction. Accordingly, granular iron is inevitably mixed in the slag generated by the refining process. Therefore, naturally, a large amount of granular iron is present in the magnetically separated powder generated by the magnetic separation process performed for the purpose of removing the granular iron. Further, in the cooling, crushing, and magnetic separation processes of slag, a part of the granular iron is oxidized, and FeO is generated in the magnetic separation powder. Further, in oxidation refining such as converter blowing, FeO is also present in the slag immediately after refining, and it remains as a FeO content in magnetically selected powder obtained by magnetically selecting the slag. Therefore, the magnetically segregated powder of the steelmaking slag contains a large amount of granular iron and FeO at the same time, and is a compound having the conditions necessary for achieving the present invention.
なお、本発明において、脱硫精錬剤中の粒鉄量とFeO濃度には好適な範囲が存在する。すなわち、粒鉄量については、1.5質量%以上且つ5.0質量%以下、FeO濃度としては、2.0質量%以上且つ7.0質量%以下が好適な範囲である。ここで脱硫剤中の粒鉄量範囲を制限した理由は、粒鉄量が1.5質量%より少ない場合には、上述したようにスラグ中の密度が低く、脱硫処理の初期の巻き込みが抑制されて、本発明の効果を発揮することができないからであり、また粒鉄量が5.0質量%より多い場合は、機械攪拌に用いられる回転羽根に造粒された精錬剤が融着し精錬剤の巻き込み機能が低下する結果,脱硫反応の進行が妨げられるため、目的の高脱硫能は得られないからである。また、FeO濃度については、FeO濃度が2.0質量%より低い場合は、前述したFeOによるCaO滓化効果が十分には得られず、逆に7.0質量%より高いとスラグの脱硫能そのものが低下し目的の高脱硫能が得られないからである。 In the present invention, there are suitable ranges for the amount of granular iron and the FeO concentration in the desulfurization refining agent. That is, the preferred range for the amount of granular iron is 1.5% by mass to 5.0% by mass, and the FeO concentration is 2.0% by mass to 7.0% by mass. Here, the reason for limiting the amount of granular iron in the desulfurizing agent is that when the amount of granular iron is less than 1.5% by mass, the density in the slag is low as described above, and the initial entrainment of the desulfurization treatment is suppressed. This is because the effects of the present invention cannot be exhibited, and when the amount of granular iron is more than 5.0% by mass, the refining agent granulated on the rotary blade used for mechanical stirring is fused. This is because the desulfurization function of the refining agent is reduced and the progress of the desulfurization reaction is hindered, so that the desired high desulfurization ability cannot be obtained. As for the FeO concentration, when the FeO concentration is lower than 2.0% by mass, the above-described CaO hatching effect by FeO cannot be sufficiently obtained. Conversely, when the FeO concentration is higher than 7.0% by mass, the slag desulfurization ability is obtained. This is because the desired high desulfurization ability cannot be obtained.
本発明の脱硫精錬剤において、脱硫精錬剤中のCaO濃度を質量%で80%以上確保する必要がある。本発明者らの知見では、溶銑をKR機械攪拌方法で脱硫処理する場合に、処理後のスラグの塩基度((%CaO)/(%SiO2)比)を3.5以上に制御する必要がある。通常、脱硫処理をする容器に溶銑を装入する際に、高炉スラグをベースにした低塩基度のスラグが不可避的に混入する。脱硫精錬剤中のCaO濃度を質量%で80%以上に制限したのは、この条件においてのみ、脱硫精錬剤が上記低塩基度スラグと混合した場合でも、処理後のスラグ塩基度を3.5以上とすることができるからである。 In the desulfurizing and refining agent of the present invention, it is necessary to ensure the CaO concentration in the desulfurizing and refining agent by 80% by mass or more. The findings of the present inventors, in the case of desulfurization treatment the hot metal in KR mechanical stirring method, basicity of the slag after the treatment ((% CaO) / (% SiO 2) ratio) necessary to control more than 3.5 There is. Usually, when hot metal is charged into a vessel for desulfurization treatment, low basicity slag based on blast furnace slag is inevitably mixed. The reason why the CaO concentration in the desulfurization refining agent is limited to 80% or more by mass% is that only under this condition, even when the desulfurization refining agent is mixed with the low basicity slag, the slag basicity after the treatment is 3.5. This is because it can be as described above.
本発明者らは、粒鉄とFeOを含有する本発明に加えて、脱硫精錬剤中にAl2O3を含有することにより、さらに高い脱硫能が得られることを見出した。その理由は、FeOのCaO滓化効果に加えて、Al2O3の滓化効果が付加されるが、Al2O3の場合、FeOを増量する場合と異なって、スラグ酸素ポテンシャルを増加させないため、それによる脱硫阻害が生じ難く、磁選粉配合による脱硫率向上効果を促進したものと思われる。この効果は脱硫剤中のAl2O3含有量として2.0質量%以上で発揮される。しかし、Al2O3も多く配合されるとスラグの脱硫能を阻害するため、配合量は脱硫剤中のAl2O3含有量5.0%以下になるように制限される。 The present inventors have found that in addition to the present invention containing granular iron and FeO, a higher desulfurization ability can be obtained by including Al 2 O 3 in the desulfurization refining agent. The reason is that in addition to the CaO hatching effect of FeO, the hatching effect of Al 2 O 3 is added, but in the case of Al 2 O 3 , unlike the case of increasing FeO, the slag oxygen potential is not increased. Therefore, the desulfurization inhibition by that hardly occurs, and it seems that the effect of improving the desulfurization rate by the magnetically segregated powder blend was promoted. This effect is exhibited when the content of Al 2 O 3 in the desulfurizing agent is 2.0% by mass or more. However, if too much Al 2 O 3 is blended, the desulfurization ability of the slag is inhibited, so the blending amount is limited so that the Al 2 O 3 content in the desulfurizing agent is 5.0% or less.
脱硫精錬剤中にAl2O3を含有させるためのAl2O3源としては、任意の原料を用いることができる。特に、脱硫精錬剤に配合する製鋼スラグ磁選粉の一部又は全部を、適量のAl2O3が含有されている2次精錬滓磁選粉とすることにより、脱硫精錬剤のAl2O3源とすることができる。2次精錬滓磁選粉とは,RH処理や,脱酸処理,脱硫処理で生成するスラグと,不可避的に転炉から流出する脱炭滓とからなる高塩基度スラグを磁選処理して得られる磁選粉であり、その代表的な化学組成を表3に示した。2次精錬滓磁選粉の組成の特徴は、粒鉄およびFeOを含有していることに加えて、Al2O3が比較的高濃度で含有されていることである。2次精錬滓磁選粉を用いることにより、他の製鋼スラグ磁選粉を用いた場合よりさらに高い脱硫率が得られるが、その理由は上述のとおりである。なお、好適な量のFeOおよび粒鉄に加えて、好適な量のAl2O3を脱硫精錬剤に含有させることによって得られる格別に高い脱硫率は、Al2O3を少量しか含まない製鋼スラグ磁選粉と2次精錬スラグ磁選粉以外のAl2O3源の組み合わせでも同様に得られる。 Any raw material can be used as the Al 2 O 3 source for containing Al 2 O 3 in the desulfurization refining agent. In particular, a part of or all of the steelmaking slag magnetic powder blended in the desulfurization refining agent is made into a secondary refining magnetic separation powder containing an appropriate amount of Al 2 O 3 , thereby providing an Al 2 O 3 source of the desulfurization refining agent. It can be. Secondary refined magnetic separation is obtained by magnetic separation of high basicity slag composed of slag produced by RH treatment, deoxidation treatment and desulfurization treatment, and decarburized soot inevitably flowing out of the converter. Table 3 shows the typical chemical composition of magnetically selected powder. A characteristic of the composition of the secondary refined magnetically segregated powder is that, in addition to containing granular iron and FeO, Al 2 O 3 is contained at a relatively high concentration. By using secondary refined magnetic separation, a higher desulfurization rate can be obtained than in the case of using other steelmaking slag magnetic separation, and the reason is as described above. In addition to a suitable amount of FeO and granular iron, a particularly high desulfurization rate obtained by adding a suitable amount of Al 2 O 3 to the desulfurization refining agent is steelmaking containing only a small amount of Al 2 O 3. A combination of Al 2 O 3 sources other than slag magnetic powder separation and secondary refining slag magnetic powder separation is also obtained in the same manner.
本発明の溶銑の脱硫方法において、上記本発明の脱硫精錬剤を用いて機械攪拌式脱硫処理を行うことにより、脱硫精錬剤中に蛍石を含有しないにもかかわらず、格段に高い脱硫率で脱硫精錬を行うことが可能となる。 In the hot metal desulfurization method of the present invention, by performing the mechanical stirring type desulfurization treatment using the desulfurization refining agent of the present invention, the desulfurization refining agent has a remarkably high desulfurization rate even though it does not contain fluorite. It is possible to perform desulfurization refining.
[S]濃度が0.033〜0.040質量%,温度が1330℃〜1360℃の範囲の溶銑250tonを用いて溶銑の脱硫処理を機械攪拌脱硫設備(KR脱硫設備)で実施した。溶銑脱硫処理の条件は、精錬剤投入量:6.0〜7.0kg/ton、各原料の粒径:2.0mm以下、回転羽根回転数:100〜120rpm、回転羽根数:4枚、回転羽根外径:1.3〜1.5m、回転羽根浸漬深さ:0.7〜0.8m、処理時間:10〜13min、精錬後の(CaO/SiO2)の値は3.5以上である。残留高炉滓はその厚みで15mm以下の範囲になるよう排除した。 [S] Hot metal desulfurization treatment was performed in a mechanical stirring desulfurization facility (KR desulfurization facility) using 250 ton of hot metal having a concentration of 0.033 to 0.040 mass% and a temperature in the range of 1330 ° C to 1360 ° C. The conditions of the hot metal desulfurization treatment were: refining agent input: 6.0 to 7.0 kg / ton, particle size of each raw material: 2.0 mm or less, rotating blade rotation speed: 100 to 120 rpm, rotating blade number: 4 sheets, rotation Blade outer diameter: 1.3-1.5 m, rotary blade immersion depth: 0.7-0.8 m, treatment time: 10-13 min, (CaO / SiO 2 ) value after refining is 3.5 or more is there. Residual blast furnace slag was excluded so that its thickness was within 15 mm.
表4に本発明の脱硫精錬剤を用いた実施例を比較例とともに示した。表4には、本試験に用いた各種脱硫精錬剤を構成する原料の構成比を質量%で示している。原料は、生石灰、製鋼スラグとして転炉滓、製鋼スラグ磁選粉として転炉滓磁選粉を用い、その他に、場合によっては、FeO濃度およびAl2O3濃度を独立に調整することを狙って、それぞれ鉄鉱石、Al2O3レンガ屑および2次精錬滓磁選粉を用いている。表4には、これらの原料で構成される脱硫精錬剤の成分組成を試験で得られた脱硫率とともに示した。成分組成のうち、本発明範囲から外れる数値についてアンダーラインを付している。下記表6も同様である。転炉滓は、あらかじめサンプルを化学分析し、化学組成を把握していた同一ロットの転炉滓を統一して用いた。実施例に用いた転炉滓磁選粉および2次精錬滓磁選粉も同様である。Al2O3レンガ屑はAl2O3濃度で99質量%のものを用いた。ここで用いた転炉滓、転炉滓磁選粉および2次精錬滓磁選粉の化学組成を表5に示した。なお、表4に示す脱硫率:ηS(%)は(1)式で与えられる試験の結果から得られる脱硫の程度を示す値である。
ηS(%)=(SI−SF)/SI ・・・(1)
ここで、SIは処理前の溶銑中S濃度(質量%)、SFは処理後の溶銑中S濃度(質量%)である。
Table 4 shows examples using the desulfurization refining agent of the present invention together with comparative examples. Table 4 shows the composition ratio of raw materials constituting various desulfurization refining agents used in this test in mass%. The raw material uses quick lime, converter slag as steelmaking slag, converter slag magnetic separation as steelmaking slag magnetic powder, and in some cases, aiming to independently adjust FeO concentration and Al 2 O 3 concentration, Iron ore, Al 2 O 3 brick scrap and secondary refined magnetically selected powder are used respectively. Table 4 shows the component composition of the desulfurization refining agent composed of these raw materials together with the desulfurization rate obtained in the test. Among the component compositions, numerical values outside the scope of the present invention are underlined. The same applies to Table 6 below. The converter rod was used in a unified manner from the same lot that had previously been chemically analyzed and the chemical composition was known. The same applies to converter magnetic separation and secondary refining magnetic separation used in the examples. Al 2 O 3 brick scraps having an Al 2 O 3 concentration of 99% by mass were used. Table 5 shows the chemical compositions of the converter soot, the converter magnetizing powder, and the secondary refined magnetizing powder used here. Note that the desulfurization rate: η S (%) shown in Table 4 is a value indicating the degree of desulfurization obtained from the test result given by the equation (1).
η S (%) = (S I −S F ) / S I (1)
Here, S I is molten pig iron in S concentration (mass%) of the pretreatment, the S F is hot metal in S concentration after treatment (mass%).
比較例1は生石灰に蛍石を添加した場合であり、蛍石を用いると比較的高い脱硫率が得られている。一方で、生石灰に加え、FeOを比較的多量に含む転炉滓を添加した脱硫精錬剤を用いた場合の脱硫率を比較例3〜5に示し、蛍石と転炉滓を同時に添加した場合の脱硫率を比較例2に示した。転炉滓のみ添加のケースでは、FeO濃度を適当な範囲にすることによって蛍石添加のケースに匹敵するような脱硫能が得られているが、これは、特許文献7に開示されている技術を再現したものである。しかし、転炉滓単独の添加では、蛍石添加の脱硫率をさらに向上させることはできていない。一方、蛍石に加えて転炉滓を添加した比較例2では、蛍石単独添加よりもさらに高い脱硫率が得られている(比較例2)。これは、蛍石に加えて、転炉滓中のFeO分がCaO滓化を促進した効果が発揮されたものと考えられる。本発明では、蛍石無添加の制約条件において、蛍石単独添加よりも格段に高い脱硫率が得られる脱硫精錬剤を得ることを目標とし、具体的には脱硫率が比較例2(脱硫率=85%)以上となるような脱硫精錬剤を発明の範囲とした。 Comparative Example 1 is a case where fluorite is added to quicklime, and when fluorite is used, a relatively high desulfurization rate is obtained. On the other hand, in addition to quicklime, the desulfurization rate when using a desulfurization refining agent to which a converter soot containing a relatively large amount of FeO is used is shown in Comparative Examples 3 to 5, and when fluorite and a converter soot are added simultaneously The desulfurization rate was shown in Comparative Example 2. In the case of adding only the converter soot, desulfurization ability comparable to the case of adding fluorite is obtained by setting the FeO concentration in an appropriate range. This is the technology disclosed in Patent Document 7 Is reproduced. However, the addition of the converter soot alone cannot further improve the desulfurization rate of the addition of fluorite. On the other hand, in Comparative Example 2 in which a converter slag was added in addition to fluorite, a higher desulfurization rate was obtained than in the case of adding fluorite alone (Comparative Example 2). This is considered to be due to the fact that, in addition to fluorite, the FeO content in the converter slag accelerated CaO hatching. In the present invention, the goal is to obtain a desulfurization refining agent that can obtain a desulfurization rate much higher than the addition of fluorite alone under the constraint condition of no addition of fluorite. Specifically, the desulfurization rate is Comparative Example 2 (desulfurization rate). = 85%) A desulfurization refining agent that is greater than or equal to 85%) was included in the scope of the invention.
一方、試験No6〜12は、生石灰に粒鉄およびFeO分を多く含む転炉滓磁選粉を添加して得られる脱硫精錬剤を用いた場合の脱硫試験結果を示す。実施例7〜10に示すように、転炉滓磁選粉からFeOおよび粒鉄が供給され、脱硫精錬剤中のFeO濃度が2.0%〜7.0%、かつ、粒鉄の濃度が1.5%〜5.0%の範囲に入っているときに、85%以上の格段に高い脱硫能が得られた。さらに実施例7〜10では、同程度のFeOを精錬剤中に含む転炉滓単独添加の例(比較例3,4)では得られなかった高い脱硫率が得られており、これらの例は、本発明の特徴である「好適な量の粒鉄含有の効果」が端的に示されたものである。なお、比較例6は脱硫精錬剤中の粒鉄の濃度が低いために目的の脱硫率が得られなかった例であり、比較例11は転炉滓磁選粉の添加量が多すぎたためにFeOおよび粒鉄濃度が好適な範囲の上限を超えた場合の例であり、さらに、比較例12は、粒鉄は好適な範囲にあるが、FeO濃度が好適な範囲の上限を超えた場合の例である。いずれの例でも、目的とする格段に高い脱硫率は得られていない。 On the other hand, Test Nos. 6 to 12 show desulfurization test results in the case of using a desulfurization refining agent obtained by adding converter magnetic powder containing a large amount of granular iron and FeO to quick lime. As shown in Examples 7 to 10, FeO and granular iron are supplied from the converter magnetic separation powder, the FeO concentration in the desulfurization refining agent is 2.0% to 7.0%, and the concentration of granular iron is 1. When it was within the range of 5% to 5.0%, a remarkably high desulfurization ability of 85% or more was obtained. Furthermore, in Examples 7-10, the high desulfurization rate which was not obtained in the example (comparative example 3 and 4) of the converter iron single addition which contains the same degree FeO in a refining agent is obtained, These examples are The “effect of containing a suitable amount of granular iron”, which is a feature of the present invention, is simply shown. In addition, Comparative Example 6 is an example in which the target desulfurization rate was not obtained because the concentration of granular iron in the desulfurization refining agent was low, and Comparative Example 11 was FeO because the addition amount of the converter magnetic separation powder was too large. In addition, Comparative Example 12 is an example in which the granular iron is in a suitable range, but the FeO concentration exceeds the upper limit of the suitable range. It is. In any of the examples, the intended remarkably high desulfurization rate is not obtained.
No13〜20は生石灰に2次精錬滓磁選粉を添加した場合の例である。試験No18〜20では、脱硫精錬剤中のAl2O3濃度を単独で高めるためにAl2O3レンガ屑を追加して添加している。実施例14〜16および実施例18、19に示すように、2次精錬滓磁選粉から或いは一部Al2O3源としてAl2O3レンガ屑から、FeO、粒鉄およびAl2O3が供給され、脱硫精錬剤中のFeO濃度が2.0%〜7.0%、かつ、粒鉄の濃度が1.5%〜5.0%、さらに、Al2O3濃度が1.5%〜5.0%の範囲に入っているときに、格段に高い脱硫能が得られている。なお、比較例13は2次精錬滓磁選粉の添加量が過少であり、Al2O3濃度が好適な濃度より低くなった場合の例であり、比較例17は、粒鉄量が好適な量より高い場合の例、および、比較例20はAl2O3濃度が好適な濃度より高い場合の例を示すが、いずれの場合も、本発明の技術で目標とする85%以上の脱硫率に達していない。また、試験No21は、Al2O3を少量しか含まない製鋼スラグ磁選粉とAl2O3源としてレンガ屑を用いたときの請求項2に示した発明の実施例である。さらにAl2O3源としては、Al2O3を比較的多く含む2次精錬滓を用いても良く、実施例22は、塩基度2.9、FeO濃度=14.1質量%、粒鉄量=2.0質量%、Al2O3濃度=20.2質量%の2次精錬滓と脱炭滓磁選粉を生石灰に配合して脱硫精錬剤を構成した場合の実施例を示す。 No13-20 is an example at the time of adding a secondary refined magnetic selection powder to quicklime. In Test No18~20, it is added by adding Al 2 O 3 brick chips in order to increase the Al 2 O 3 concentration in the desulfurizing refining agent alone. As shown in Examples 14-16 and Examples 18 and 19, from the Al 2 O 3 brick scrap as a secondary refining slag magnetic separator powder or some Al 2 O 3 source, FeO, is granulated metallic iron and Al 2 O 3 The FeO concentration in the desulfurizing and refining agent is 2.0% to 7.0%, the concentration of granular iron is 1.5% to 5.0%, and the Al 2 O 3 concentration is 1.5%. When it is in the range of ˜5.0%, a remarkably high desulfurization ability is obtained. In addition, Comparative Example 13 is an example in which the amount of secondary refining magnetic separation powder is too small, and the Al 2 O 3 concentration is lower than a suitable concentration, and Comparative Example 17 has a suitable amount of granular iron. Example in which the amount is higher than the amount and Comparative Example 20 shows an example in which the Al 2 O 3 concentration is higher than a suitable concentration. In each case, the desulfurization rate of 85% or more targeted by the technology of the present invention Not reached. Moreover, test No21 is an Example of the invention shown in Claim 2 when using steelmaking slag magnetic powder containing only a small amount of Al 2 O 3 and brick scrap as an Al 2 O 3 source. Further, as the Al 2 O 3 source, secondary smelting iron containing a relatively large amount of Al 2 O 3 may be used. In Example 22, basicity is 2.9, FeO concentration = 14.1% by mass, granular iron An example in which a desulfurization refining agent is configured by blending a secondary smelting powder and an amount of Al 2 O 3 concentration of 20.2% by mass and a decarburized magnetically segregated powder into quicklime is shown.
表6には、生石灰の一部を製鋼スラグに置き換えてCaO源とした場合の本発明による実施例と比較例を示したものである。表6で示した脱硫試験の試験条件は実施例1と同じであるが、製鋼スラグおよび製鋼スラグ磁選粉はあらかじめ化学組成が判っているものを使用せず、保管場所の任意の部分から抜き取ったものを用い、脱硫精錬剤配合後に化学組成を分析により求めた。 Table 6 shows examples and comparative examples according to the present invention in which a portion of quicklime is replaced with steelmaking slag to form a CaO source. The test conditions of the desulfurization test shown in Table 6 are the same as those in Example 1. However, the steelmaking slag and the steelmaking slag magnetically segregated powder were not extracted from those having a known chemical composition, and were extracted from any part of the storage location. The chemical composition was determined by analysis after blending the desulfurization refining agent.
試験No23〜25は生石灰の一部を転炉滓で置き換え、さらに転炉滓磁選粉を配合した脱硫精錬剤を用いた場合の結果である。No23、No24の実施例に示すように、生石灰の一部を転炉滓で置き換えても、好適なCaO濃度、FeO濃度および粒鉄量が確保できている限り、請求項1に示す本発明の効果は得られた。生石灰の一部を製鋼スラグで置き換えた場合、必然的に脱硫精錬剤中のCaO濃度は低下するため、過多に製鋼スラグによる生石灰の置き換えを行うと脱硫精錬剤中のCaO濃度が80質量%を下回り、本発明の効果は得られない(比較例25)。 Test Nos. 23 to 25 are results when a desulfurization refining agent in which part of quick lime is replaced with a converter slag and further mixed with a converter magnetic separation powder is used. As shown in the examples of No. 23 and No. 24, even if a portion of quicklime is replaced with a converter slag, as long as a suitable CaO concentration, FeO concentration and amount of granular iron can be secured, the present invention shown in claim 1 can be used. The effect was obtained. When a portion of quicklime is replaced with steelmaking slag, the CaO concentration in the desulfurization and refining agent inevitably decreases. Therefore, if excessive replacement of quicklime with steelmaking slag is performed, the CaO concentration in the desulfurization and refining agent will be 80% by mass. The effect of the present invention is not obtained (Comparative Example 25).
一方、生石灰と置き換える製鋼スラグとして脱炭滓以外の製鋼スラグを用いても、好適なCaO濃度、FeO濃度および粒鉄量が確保されている限り、同様の効果が得られる。例えば、試験No26は生石灰と置き換える製鋼スラグとして塩基度2.9、FeO濃度=23質量%、粒鉄量=4質量%の転炉型溶銑脱りん処理後スラグを用いた場合の本発明の実施例を示す。 On the other hand, even if steelmaking slag other than decarburized slag is used as steelmaking slag to replace quicklime, the same effect can be obtained as long as a suitable CaO concentration, FeO concentration, and amount of granular iron are ensured. For example, test No. 26 is an implementation of the present invention when using slag after converter-type hot metal dephosphorization treatment with a basicity of 2.9, FeO concentration = 23 mass%, and iron content = 4 mass% as steelmaking slag to replace quicklime. An example is shown.
さらに脱硫精錬剤中にAl2O3を含有する本発明においても、実施例27に示すように、生石灰を一部脱炭滓に置き換えた場合でも格別に高い脱硫率が得られている。 Furthermore, even in the present invention in which Al 2 O 3 is contained in the desulfurization refining agent, as shown in Example 27, a particularly high desulfurization rate is obtained even when quick lime is partially replaced with decarburized soot.
Claims (6)
該脱硫精錬剤中の粒鉄量が1.5〜5.0質量%,FeO濃度が2.0〜7.0質量%、CaO濃度が80質量%以上であることを特徴とする溶銑の脱硫精錬剤。
ここでFeO濃度は、脱硫精錬剤中に含まれる酸化鉄がすべてFeOであるとして算定する。 A desulfurization refining agent used in the mechanical stirring desulfurization treatment of hot metal,
The amount of granular iron in the desulfurization refining agent is 1.5 to 5.0 mass%, the FeO concentration is 2.0 to 7.0 mass%, and the CaO concentration is 80 mass% or more. Refining agent.
Here, the FeO concentration is calculated on the assumption that all of the iron oxide contained in the desulfurization refining agent is FeO.
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