JP3787960B2 - Smelting reduction smelting method - Google Patents

Description

【００１７】
【表２】

【００１８】
次に、上記の回収ダスト６は、粉状の鉱石１１と混合する。この混合には、公知のミキサ４を使用すれば良いので、説明を省略する。なお、本発明は、ダストと鉱石との混合率（重量比）を特に限定するものではないが、具体的にＣｒ鉱石を使用するに当たっては、ダスト：Ｃｒ鉱石＝２：５程度が好ましい。その理由は、ダストの嵩比重は、Ｃｒ鉱石の嵩比重が２．５程度であるのに対して、０．８〜１．０と低く、ダストの配合比率を高くすると、混合物２０の比重が小さくなる。それと同時に、該混合物２０を、添加ランス５を介して転炉１内に吹込んでも、その飛散率が高くなる。発明者の調査によれば、以下の（１）式で定まるダストと鉱石の混合率αが０．５以上となると、飛散率が５％以上と大きくなった。
【００１９】
α＝ダスト重量／（鉱石重量＋ダスト重量） …（１）
この時のダストの比重は、約１．５であり、飛散率低下の観点からは、該ダストの比重を１．５以上となる配合割合で操業することが望まれる。
なお、混合時の比重は、（２）式で表わされるので、混合する鉱石（Ａ）とダスト（Ｂ）の比重により操業に適する混合比率が決まることになる。
【００２０】
【数１】

【００２１】
ここで、ρ_A ，ρ_B ； 粉体Ａ，Ｂの比重
α，β； 粉体Ａ，Ｂの重量混合比
従って、本発明では、この飛散率に基づき、上記ダストの混合率（重量比）αを０．５以下とするのが望ましい。
【００２２】
また、本発明では、転炉１の上方に送酸用とは別に設けた添加ランス５を介して転炉１内の溶湯に添加するが、発明者は、その際に混合後の粉体の水分をある範囲に維持する必要があることを見い出した。
すなわち、水分含有率を０．５％以下とすれば、ダスト粒径に関わらず、詰まりの問題が少ない状態で吹込み可能となる。しかし、雨天では原料の水分は高くなるので、水分０．５重量％未満となるまで乾燥するのは困難となる。また、乾燥に要するエネルギー・コストも大きくなる。従って、１００μｍ以下の粒度を２０重量％以下とすると同時に、水分を２重量％以下となるまで乾燥を行うようにするのである。
【００２３】
ここで、水分２重量％以下で詰まりがなくなる理由について、詰りに関係すると考えられる混合物の特性を各種試験方法（説明省略）で調べてみたところ、図５に示すように、混合物の安息角、圧縮度、凝集性、流動性が水分による影響を受けており、その特性がいずれも大略２水分重量％を境に変化することが明らかになった。本発明では、この調査結果に基づき、水分を２重量％以下に定めたのである。水分がその値を超えて多くなると、添加ランス５からの吹き込み特性が悪化するのは、ダスト中に金属鉄分が含有されており、水分と該金属鉄分との間で酸化反応が生じ、酸化物が該ランス壁に固着するためと考えられる。なお、乾燥する手段は、特に限定しないが、例えばロータリーキルンが適する手段の一つである。該キルンに、鉱石とダストを投入することにより、乾燥と同時に混合が促進されるからである。
【００２４】
さらに、本発明では、溶融還元精錬以外の脱炭精錬で発生したダストも使用するようにした。上記本発明の実施で得たステンレス鋼母溶湯は、上底吹転炉に装入され、通常の方法で脱炭精錬されてステンレス鋼とされるが、その際、該転炉の排ガスから、量的には少ないが、表１及び２に示したものと同様のダストが回収されるからである。そこで、このダストも前記と同様の方法で回収、鉱石との混合、乾燥を行い、リサイクル使用するようにしたのである。
【００２５】
加えて、本発明でダストと鉱石の混合物２０をその添加ランス５から溶湯１４に添加する方法は、該混合物２０の自重で落下させても、あるいはキャリア・ガスを用いて溶湯面に吹き付けても良い。実際に添加するに当っては、あらかじめ実験やモデル計算によって炉内発生ガスの上昇流速の比較的に小さい場所を見出しておき、そこに添加ランス５の先端の位置をさせて混合物２０を供給する。図３は、このことを説明する図である。転炉１内に溶湯１４が保持され、酸素上吹用ランス１５から酸素ガス１３を吹込むと共に、前記混合物２０の添加ランス５から該混合物２０を添加する。この時、炉内発生ガスの上昇気流１９は、図３に模式的に示すような分布となっており、上昇気流１９の流速の小さい位置に該混合物２０を供給すると良い。このことにより、塊状に成形して炉上シュートから投入する場合と比べて遜色のない添加歩留を達成することができる。また、添加ランス５の使用により、精錬中の投入量を制御することができるため、ダスト投入による炉内反応への外乱も少くなく、安定した操業が可能である。また、本発明では特定成分の制約を受けないため、発生ダストの全量をリサイクルすることができるのである。
【００２６】
なお、ここで溶融還元炉にて用いる炭材は、特に限定するものではないが、無煙炭が還元促進を進める上で溶融還元に適すること、および無煙炭はスラグ中で微細化し、スラグ中より排ガスにダストとなって飛散するので、特にダスト中のＣが多いことから、本発明に適する炭材である。
【００２７】
【実施例】
転炉１からの排ガスに含まれるダストを、図１の集塵装置１２で回収し、該ダストにＣｒ鉱石１８を混合して、前記（１）式で定まるダストと鉱石の混合率αが０．５以下の溶融還元精錬を行った。
まず、原料ヤードにて、予め粉状のＣｒ鉱石および集塵装置１２より回収したダストをショベルにて交互にパレットにα＝０．３〜０．４の比率となるように積み込んだ。使用したダストは、表１に示した粗粒物である。この混合物を載せたパレットを原料ヤードより地下の打ち込みバンカーへ運搬し、該混合物をロータリー・キルンへ投入、乾燥した。該キルン内に約２０分滞留させた後、取り出した混合物（粉体）の水分を測定したところ、乾燥後の水分は、晴天時には０．３〜０．７重量％、雨天時には１〜１．９重量％程度であった。
【００２８】
次に、上記乾燥で水分が２重量％以下になった混合物を、下記条件で溶融還元精錬に利用した。
溶融還元炉は、ガスを上底吹き可能な転炉型反応容器であり、かつ前記混合物のための添加ランス５を有している。その際、上吹き酸素ガスの流量は、５５０Ｎｍ³ ／分とし、底吹きガスは、炉底羽口より酸素：５０Ｎｍ³ ／ｍｉｎ、窒素：２０Ｎｍ³ ／ｍｉｎの混合ガスとした。鉄源は、ＳＵＳ３０４の溶製時には、２００ｋｇ／ｔ、ＳＵＳ４３０の溶製時には、４０ｋｇ／ｔのスクラップを予め炉内へ装入した後、溶銑を１２０〜１５０ｔ装入している。また、吹錬中に、サブ・ランスで溶鉄温度が１５５０〜１５７０℃になったことを確認した後、前記添加ランス５を介して混合物を１０００〜１５００ｋｇ／ｍｉｎの割合で供給した。同時に、炭材として無煙炭（ベトナム産、ＶＭ５．８％、ＨＧＩ３５）を７００〜１０００ｋｇ／分の割合で炉内へ投入した。ランスの高さとしては、Ｏ₂ 供給ランスが溶鉄面より３．５〜４ｍ、混合物の添加ランス５が溶鉄面より３．５〜５ｍである。
【００２９】
このような精錬を多数チャージ行い、操業成績をＣｒ成分の添加歩留で代表させて、図４に一括示した。図４に黒丸で示したデータは、上記本発明の実施例であり、一方、白丸で示したデータは、Ｃｒ鉱石１８のみを１００％添加する従来例での歩留りである。図４より、本発明の実施例（黒丸）と、従来より工程的に実施されているＣｒ鉱石単体（１００％）で投入した場合の歩留（白丸）とでは、ほとんど差がなく良好な歩留が得られた。また、ダスト中の炭材（Ｃ成分３０％）の歩留についても、同様に調査したところ、工程的に投入している炭材と同等の歩留であることが分かった。
【００３０】
引き続き、上記した本発明に係る溶融還元精錬方法で得た母溶湯を、別の転炉を用いて、ＳＵＳ ３０４を始めとして、多くのステンレス鋼の製造に利用した。その結果、従来は、未使用であったダストをリサイクルでき、該ダスト中の金属分の回収で、溶融還元炉でのＣｒ及びＦｅの歩留がそれぞれ４％及び５％向上した。さらに、Ｃｒ鉱石の還元歩留りについても３〜４％向上した。この理由は、明確ではないが、Ｃｒ鉱石と共にダストを吹込むことで、ダスト中のＣがＣｒ鉱石の還元促進に好影響を与えたものと考えられる。なお、既に述べたように、従来は、ダストをリサイクルする際には、ダスト還元用の炭材を必要としたが、本発明によってこの炭材が不要になった。
【００３１】
前記と同じ操業方法を用いてα＝０．６〜０．７の溶融還元操業も行い、その操業成績を、同じくＣｒ成分の添加歩留で図４に整理した。その結果、従来のＣｒ鉱石と比べて良好な結果ではあるものの、α＝０．３〜０．４の場合と比べると、歩留が若干低下している。また、ダスト中への飛散量が同時に増加しており、αの増加で飛散率が高くなったものと思われる。
【００３２】
続いて、α＝０．３〜０．４の条件で、大雨時に混合物をロータリ・キルンで乾燥させつつ操業した。乾燥後の水分は、１．５〜２．５ｗｔ％と投入前の原料水分の変動により大きく変動する。この操業成績については、これまでに述べた成績と変わらなかったが、ランスでの詰り及びコンベア前ホッパ内での詰りが、２日に１回程度発生した。そこで、４〜５チャージ分の操業で、混合物の吹込みを行った後、Ｃｒ鉱石のみを吹込み、ランス等での詰りを解消する操業を１〜２チャージ行った。このようなことを繰り返して操業を続けることができたが、通算でのダストの混合比率は必然的に低くなった。
【００３３】
また、ダスト・リサイクル量をさらに拡大すべく、リサイクルするダストの粒度を変更する操業も行った。具体的には、図１中粗粒分離機３での水量を低下させることにより滞留時間を延長し、全ダストに対する細粒ダストの比率を増加させた。この時の粗粒ダストの粒度例を表３に示す。
【００３４】
【表３】

【００３５】
表３に示すように、１００μｍ以下のダストの比率は約３０ｗｔ％である。この際、従来の知見より詰りが大きくなることが予想されたので、ロータリ・キルンでの熱風量を増加させ乾燥を強化した。その結果、乾燥出側の水分は、０．６〜１．０ｗｔ％であった。また、天候が雨天となり、乾燥機出側水分が高くなりそうな場合は、ダストの混合を中止した。Ｃｒ歩留については、図４の中に示すが、上記実施例と同等で良好であった。但し、飛散量が若干増加し、ダストの発生が増加する傾向が見られた。
【００３６】
なお、上記実施例は、ステンレス鋼を製造する前の母溶鋼を製造する溶融還元精錬の場合であるが、本発明は、それに限らず、例えば高Ｍｎ鋼の精錬においても使用できる。
【００３７】
【発明の効果】
以上述べたように、本発明により、溶融還元製錬において発生したＣ及びＣｒ等の含有量が高いダストをリサイクル使用できるようになった。その結果、従来に比べて安価に、溶融還元精錬が実施可能となり、この方法を利用して製造したステンレス鋼の価格が低下できるようになった。
【図面の簡単な説明】
【図１】本発明に係る溶融還元製錬法を実施した設備の一例を示す図である
【図２】ダスト、鉱石混合物の水分と、その添加ランスの詰りとの関係を示す図である。
【図３】転炉内での添加ランスの適切位置を説明する図である。
【図４】溶融還元精錬でのＣｒの添加歩留を示す図である。
【図５】粉体混合物の各種特性に及ぼす水分の影響を示す図であり、（ａ）は粉体混合物の安息角、（ｂ）は圧縮度、（ｃ）は凝集性、（ｄ）は流動性への影響を示すものである。
【符号の説明】
１ 転炉（冶金反応容器）
２ ダストの回収システム
３ 粗粒分離機
４ 混合機（ミキサ）
５ 添加ランス
６ 粗粒ダスト
７ 微粒ダスト
８ シックナ
９ 排ガスの回収システム
１０ 水槽
１１ 濃縮槽
１２ 集塵装置
１３ 酸素ガス（酸素）
１４ 溶融金属（金属溶湯）
１５ 上吹ランス
１６ 配管
１７ 排水
１８ 鉱石（Ｃｒ鉱石）
１９ 上昇気流
２０ 混合粉（混合物）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a molten metal by a smelting reduction smelting method using a converter reactor, and in particular, dust generated during smelting of a stainless steel mother metal is again used for refining a carbon material and a metal. It is a technology that uses it as a source and melts or reduces Cr ore, Mn ore, etc. at low cost.
[0002]
[Prior art]
In order to produce stainless steel, conventionally, an electric furnace-AOD (argon-oxygen decarburization) combined process or a process using a converter has been adopted. Recently, however, a technology has been developed to directly use inexpensive Cr ore without using expensive Cr sources such as Fe-Cr alloy and pre-reduced Cr pellets when melting stainless steel in the converter process. It was done. It is called a smelting reduction smelting method. Cr ore and a carbon-containing substance that is a reducing agent are added to a molten metal in a metallurgical reaction vessel (hereinafter referred to as a reaction vessel), and the resulting Cr ore. Is melt-reduced and melted in a molten metal to produce a stainless steel mother bath. This process is now in practical use after much research on specific implementation.
[0003]
Introducing one of the studies, for example, Japanese Patent Application Laid-Open No. 7-3006009 discloses a method of adding powdered Cr ore to a molten metal from an upper opening (furnace port) of a converter, which is a long cylinder. (Hereinafter referred to as Lance). The advantage of this method is that the dropping rate of powdered Cr ore is increased by introducing it through a long lance, and before the Cr ore particles reach the molten metal due to the upward flow of exhaust gas generated during smelting. In addition, it is prevented from being scattered and taken away by the exhaust gas, and a high addition yield of Cr can be secured.
[0004]
However, this method also has the following problems.
(1) In order to reduce Cr ore, coke or anthracite is generally used as a carbon-containing material, but in order to effectively reduce the carbon ore, these carbons are always present in the slag present on the molten metal. It is necessary to retain the contained material. In other words, a large amount of carbon material is required, and the cost is enormous.
(2) The carbonaceous material powder staying in the slag is scattered while staying in the slag, escapes from the converter together with the exhaust gas, and is collected by the dust collector, but has a high C content ( (Usually 30-50% by weight) dust is generated in large quantities.
[0005]
As a method for reusing dust having a high C content, a smelting reduction smelting method using a reduction furnace such as an electric furnace or a rotary kiln (Japanese Patent Laid-Open No. 61-37727), or agglomeration by briquetting Processing (for example, see Japanese Patent Application Laid-Open No. 59-215414) and the like are conceivable, but none of these methods has been put into practical use because of high processing costs.
[0006]
Incidentally, the mother water produced by the smelting reduction smelting process is then smelting decarburization rectification in a conventional converter, it is stainless steel. In addition, the recovered unused dust is 200 kg / t or more per charge.
[0007]
[Problems to be solved by the invention]
In view of such circumstances, an object of the present invention is to provide a smelting reduction smelting method in which the smelting cost is significantly reduced compared to the conventional method when producing a stainless steel mother bath by a so-called smelting reduction smelting method.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the inventor has focused on the recycling use of the collected dust. However, at the stage of actual execution, dust was clogged with hoppers, lances, etc., and smooth operation was impossible. As a result of earnest research on the cause, it was found that dust was oxidized by moisture during transportation, and adhered to and solidified on various devices, and we worked hard to realize it, including countermeasures, and completed the following invention. It was.
[0009]
That is, the present invention adds a carbon-containing substance and ore to a molten metal held in a converter-type metallurgical reaction vessel, and blows oxygen gas onto the surface of the molten metal to contain the main component metal of the ore. the method wrought steel smelting reduction to obtain the dust that occurred during the smelting, the exhaust gas from the converter type metallurgical reaction vessel was slurried in water treatment, the 100μm or less by rectifying separated from the slurry The smelting reduction smelting, characterized in that after being recovered as 20% by weight or less , mixed with the ore, the mixture is dried to a moisture content of 2% by weight or less , and then added again to the molten metal through a lance. Is the method.
[0010]
In addition, the present invention, when the metal melt obtained by the smelting reduction smelting is subsequently decarburized and refined in another converter-type metallurgical reaction vessel, the recovered dust is also generated by the smelting reduction smelting, It is a smelting reduction smelting method characterized in that it is mixed with ore together with recovered dust.
Furthermore, the present invention is a smelting reduction refining method characterized in that the mixing rate determined by the following formula (1) of the dust and ore is 0.5 or less.
[0011]
α = Dust weight / (Ore weight + Dust weight) (1 )
[0012]
In addition, the present invention is also a smelting reduction smelting method characterized in that the ore is Cr ore or the carbon-containing material is mainly anthracite. According to the present invention, since the dust having a high C content generated mainly during smelting reduction smelting is recycled, the dust can be recycled without increasing the carbon material cost, and the smelting cost is reduced. It will be cheaper. That is, since the ore containing the metal oxide can be reduced by recycling the dust, the metal yield in the entire system of the smelting reduction apparatus is improved. Conventionally, when dust is recycled, measures such as agglomeration with a carbonaceous material have been performed. However, in the present invention, the dust can be recycled. Moreover, since the apparatus for that purpose is simple and not large-scale, the equipment cost can be reduced.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of equipment for carrying out the smelting reduction smelting method according to the present invention. For example, in the case of stainless steel smelting, the reactor 1 is used as a reaction vessel, and in the case of stainless steel smelting, the hot metal and scrap dephosphorized in the pretreatment are charged in advance and put into the molten metal surface from above the converter. The molten metal 14 is held in a state of being raised to a predetermined temperature by blowing the carbonaceous material and oxygen 13. The acid feeding is performed by blowing an oxygen gas 13 from the so-called upper blowing lance 15 disposed above the converter 1 onto the surface of the molten metal 14 at a high speed. In the present invention, dust generated during smelting reduction smelting with such an apparatus is recovered by a dust recovery system shown in the lower right of FIG. 1 and recycled for the same or subsequent smelting reduction smelting. . Hereinafter, embodiments will be described in more detail.
[0014]
First, the dust collection system of FIG. 1 collects dust contained in the exhaust gas by spraying water in the dust collector 12 to the exhaust gas from the converter 1. At that time, the water in which the dust is collected (hereinafter referred to as dust collection water) flows through the pipe 16 as slurry. In particular, among the dusts generated by smelting reduction smelting, those in which the staying carbon material in the slag is scattered are relatively coarse particles, and thus are recovered as coarse dust 6 via the coarse separator 3. . Here, the coarse grain separator 3 is an apparatus that retains dust collection water and sediments dust by gravity. On the other hand, the fine dust is put into the thickener 8 together with the drainage 17 of the coarse separator 3, concentrated, extracted from the lower part of the thickener 8, further concentrated in the concentration tank 11, and then extracted from the lower part. It is made into fine dust 7. Tables 1 and 2 show examples of the particle sizes and chemical components of the coarse dust 6 and the fine dust 7. Of these recovered coarse particle dust 6 and fine particle dust 7, particularly coarse particle dust 6 is suitable for the object to be treated in the present invention. The particle size distribution of the dust 6 is a rectifying separation of the thickener 8, it shall be the a 100μm or less than 20% by weight. The reason for this is that, as shown in FIG. 2, dust having a size of 100 μm or less has a high iron content, and agglomeration occurs when water is contained, and clogs with a hopper or the like. Therefore, it is desirable to reduce the content of dust of 100 μm or less as much as possible. However, since the coarse grain separator 3 is intended to settle a part of the dust by gravity based on the specific gravity and particle size of the dust and to sort the dust, the iron-containing dust of 100 μm or less is generated at all. Otherwise, coarse dust having a light specific gravity also flows into the thickener at the same time, and the amount of dust 6 suitable for recycling into the furnace via the lance according to the present invention is greatly reduced.
[0015]
Therefore, when conditions for causing clogging with a dust hopper or the like were examined in detail, the content of dust of 100 μm or less was reduced to 20% by weight or less under the drying conditions of moisture of 2% by weight or less, as will be described later. It was found that the problem of clogging could be avoided.
[0016]
[Table 1]

[0017]
[Table 2]

[0018]
Next, the recovered dust 6 is mixed with the powdered ore 11. Since this mixing may be performed using a known mixer 4, description thereof is omitted. In the present invention, the mixing ratio (weight ratio) of dust and ore is not particularly limited, but when using Cr ore specifically, it is preferably about dust: Cr ore = 2: 5. The reason is that the bulk specific gravity of the dust is as low as 0.8 to 1.0 while the bulk specific gravity of the Cr ore is about 2.5, and when the mixing ratio of the dust is increased, the specific gravity of the mixture 20 is increased. Get smaller. At the same time, even when the mixture 20 is blown into the converter 1 through the addition lance 5, the scattering rate is increased. According to the inventor's investigation, when the mixing ratio α of dust and ore determined by the following formula (1) is 0.5 or more, the scattering rate is as large as 5% or more.
[0019]
α = dust weight / (ore weight + dust weight) (1)
The specific gravity of the dust at this time is about 1.5, and from the viewpoint of reducing the scattering rate, it is desirable to operate at a blending ratio at which the specific gravity of the dust is 1.5 or more.
In addition, since the specific gravity at the time of mixing is represented by (2) Formula, the mixing ratio suitable for operation is decided by the specific gravity of the ore (A) and dust (B) to mix.
[0020]
[Expression 1]

[0021]
Here, ρ _A , ρ _B ; specific gravity α, β of powders A and B; weight mixing ratio of powders A and B. Therefore, in the present invention, the mixing ratio (weight ratio) of the dust based on this scattering rate. α is preferably 0.5 or less.
[0022]
Moreover, in this invention, although adding to the molten metal in the converter 1 via the addition lance 5 provided separately from the object for acid feeding above the converter 1, the inventor of the powder after mixing in that case It has been found that the moisture needs to be maintained in a certain range.
That is, if the moisture content is 0.5% or less, it is possible to blow in a state where there are few clogging problems regardless of the particle size of the dust. However, since the moisture content of the raw material is high in rainy weather, it is difficult to dry until the moisture content is less than 0.5% by weight. In addition, the energy cost required for drying increases. Therefore, the particle size of 100 μm or less is set to 20% by weight or less, and at the same time, drying is performed until the water content becomes 2% by weight or less.
[0023]
Here, when the characteristics of the mixture considered to be related to clogging were investigated by various test methods (explanation omitted) for the reason why clogging disappears at a moisture content of 2% by weight or less, the repose angle of the mixture as shown in FIG. It has been clarified that the compressibility, cohesiveness, and fluidity are affected by moisture, and all of the properties change at a boundary of approximately 2% by weight of moisture. In the present invention, the water content is set to 2% by weight or less based on the results of this investigation. When the moisture exceeds that value, the blowing characteristics from the addition lance 5 deteriorates because the metal iron is contained in the dust, and an oxidation reaction occurs between the water and the metal iron. This is thought to be due to adhering to the lance wall. In addition, although the means to dry is not specifically limited, For example, a rotary kiln is one of the suitable means. This is because by adding ore and dust into the kiln, mixing is accelerated simultaneously with drying.
[0024]
Furthermore, in the present invention, dust generated by decarburization refining other than smelting reduction refining is also used. The molten stainless steel mother obtained in the implementation of the present invention is charged into the top-bottom blow converter, and decarburized and refined into a stainless steel by a normal method, but at that time, from the exhaust gas of the converter, This is because the same dust as that shown in Tables 1 and 2 is recovered, although the amount is small. Therefore, this dust was recovered, mixed with ore, dried by the same method as described above, and recycled.
[0025]
In addition, in the present invention, the method of adding the mixture 20 of dust and ore from the addition lance 5 to the molten metal 14 can be performed by dropping the mixture 20 by its own weight or by spraying the molten metal surface using a carrier gas. good. For the actual addition, a place where the rising velocity of the gas generated in the furnace is relatively small is found in advance by experiments and model calculations, and the position of the tip of the addition lance 5 is set there to supply the mixture 20. . FIG. 3 is a diagram for explaining this. The molten metal 14 is held in the converter 1, and oxygen gas 13 is blown from the oxygen up-blowing lance 15, and the mixture 20 is added from the addition lance 5 of the mixture 20. At this time, the ascending airflow 19 of the gas generated in the furnace has a distribution as schematically shown in FIG. 3, and the mixture 20 may be supplied to a position where the flow velocity of the ascending airflow 19 is small. This makes it possible to achieve an additive yield that is inferior to that in the case of being formed into a lump shape and fed from the furnace chute. In addition, since the amount of charge during refining can be controlled by using the addition lance 5, there is little disturbance to the reaction in the furnace due to dust input, and stable operation is possible. In addition, since the present invention is not restricted by specific components, the total amount of generated dust can be recycled.
[0026]
The carbonaceous material used in the smelting reduction furnace here is not particularly limited, but the anthracite coal is suitable for smelting reduction in promoting reduction promotion, and the anthracite coal is refined in the slag and converted into the exhaust gas from the slag. Since it is scattered as dust, there is a large amount of C in the dust, so it is a carbon material suitable for the present invention.
[0027]
【Example】
The dust contained in the exhaust gas from the converter 1 is recovered by the dust collector 12 of FIG. 1, and the Cr ore 18 is mixed with the dust, and the mixing ratio α of the dust and ore determined by the equation (1) is 0. Smelting reduction refining of .5 or less was performed.
First, in the raw material yard, powdery Cr ore and dust collected from the dust collector 12 were alternately loaded on a pallet so as to have a ratio of α = 0.3 to 0.4 with a shovel. The dust used is a coarse product shown in Table 1. The pallet on which this mixture was placed was transported from the raw material yard to an underground bunker, and the mixture was placed in a rotary kiln and dried. After the water in the kiln was retained for about 20 minutes, the water content of the extracted mixture (powder) was measured. The water content after drying was 0.3 to 0.7% by weight when it was fine and 1-1. It was about 9% by weight.
[0028]
Next, the mixture whose water content became 2% by weight or less by the above drying was used for smelting reduction refining under the following conditions.
The smelting reduction furnace is a converter type reaction vessel capable of blowing gas at the bottom, and has an addition lance 5 for the mixture. At that time, the top-blown oxygen gas flow rate to 550Nm ³ / min, a bottom-blown gas, oxygen from the furnace bottom tuyeres: 50 Nm ³ / min, nitrogen: and a mixed gas of 20 Nm ³ / min. As for the iron source, 200 kg / t of SUS304 is melted, and 40 kg / t of scrap is charged into the furnace in advance when SUS430 is melted, and then hot metal is charged 120 to 150 t. Moreover, after confirming that the molten iron temperature became 1550-1570 degreeC with the sub lance during blowing, the mixture was supplied at the rate of 1000-1500 kg / min via the said addition lance 5. FIG. At the same time, anthracite (Vietnam, VM 5.8%, HGI 35) was charged into the furnace as a carbon material at a rate of 700 to 1000 kg / min. As for the height of the lance, the O ₂ supply lance is 3.5 to 4 m from the molten iron surface, and the addition lance 5 of the mixture is 3.5 to 5 m from the molten iron surface.
[0029]
A large number of such refining operations were carried out, and the operation results were represented by the Cr component addition yield as shown in FIG. The data indicated by black circles in FIG. 4 is an example of the present invention, while the data indicated by white circles is the yield in the conventional example in which only 100% of the Cr ore 18 is added. From FIG. 4, there is almost no difference between the embodiment of the present invention (black circle) and the yield (white circle) when introduced with the Cr ore simple substance (100%) that has been implemented in a conventional manner (white circle), and good steps. A distillate was obtained. Further, the yield of the carbonaceous material in the dust (C component 30%) was investigated in the same manner, and it was found that the yield was equivalent to the carbonaceous material that was being introduced in the process.
[0030]
Subsequently, the mother molten metal obtained by the smelting reduction refining method according to the present invention described above was used for the production of many stainless steels including SUS 304 using another converter. As a result, it was possible to recycle unused dust, and the yield of Cr and Fe in the smelting reduction furnace was improved by 4% and 5%, respectively, by recovering the metal content in the dust. Furthermore, the reduction yield of Cr ore was improved by 3 to 4%. The reason for this is not clear, but it is considered that C in the dust had a positive effect on the promotion of reduction of the Cr ore by injecting the dust with the Cr ore. In addition, as already stated, conventionally, when recycling dust, a carbon material for dust reduction was required. However, according to the present invention, this carbon material is no longer necessary.
[0031]
Using the same operation method as described above, a smelting reduction operation of α = 0.6 to 0.7 was also performed, and the operation results were arranged in FIG. As a result, although it is a favorable result compared with the conventional Cr ore, compared with the case of (alpha) = 0.3-0.4, the yield has fallen a little. In addition, the amount of scattering into the dust increased at the same time, and it is considered that the scattering rate increased with the increase of α.
[0032]
Subsequently, the mixture was operated under conditions of α = 0.3 to 0.4 while drying the mixture in a rotary kiln during heavy rain. The moisture after drying varies greatly by 1.5 to 2.5 wt% due to the fluctuation of the raw material moisture before the addition. Although this operation result was not different from the results described so far, clogging at the lance and clogging in the hopper before the conveyor occurred about once every two days. Therefore, after the mixture was blown in the operation for 4 to 5 charges, only the Cr ore was blown and the operation for eliminating clogging with a lance or the like was performed for 1 to 2 charges. Although it was possible to continue the operation by repeating this, the total dust mixing ratio was inevitably low.
[0033]
In addition, in order to further expand the amount of dust recycling, operations were performed to change the particle size of the dust to be recycled. Specifically, the residence time was extended by reducing the amount of water in the coarse grain separator 3 in FIG. 1, and the ratio of fine dust to total dust was increased. Table 3 shows an example of the particle size of the coarse dust at this time.
[0034]
[Table 3]

[0035]
As shown in Table 3, the ratio of dust of 100 μm or less is about 30 wt%. At this time, since clogging was expected to be larger than the conventional knowledge, the amount of hot air in the rotary kiln was increased to enhance drying. As a result, the moisture on the dry exit side was 0.6 to 1.0 wt%. Also, when the weather was raining and the moisture on the dryer exit side would be high, mixing of dust was stopped. The Cr yield is shown in FIG. 4, which is the same as that of the above example and good. However, there was a tendency that the amount of scattering increased slightly and the generation of dust increased.
[0036]
In addition, although the said Example is the case of the smelting reduction refining which manufactures the mother molten steel before manufacturing stainless steel, this invention is not restricted to this, For example, it can be used also in refining of high Mn steel.
[0037]
【The invention's effect】
As described above, according to the present invention, dust having a high content such as C and Cr generated in smelting reduction smelting can be recycled. As a result, smelting reduction refining can be carried out at a lower cost than before, and the price of stainless steel produced using this method can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of equipment in which a smelting reduction smelting method according to the present invention is performed. FIG. 2 is a diagram showing the relationship between the moisture of dust and ore mixture and the clogging of the added lance.
FIG. 3 is a diagram illustrating an appropriate position of an addition lance in the converter.
FIG. 4 is a view showing an addition yield of Cr in smelting reduction refining.
FIG. 5 is a diagram showing the influence of moisture on various properties of the powder mixture, (a) is the angle of repose of the powder mixture, (b) is the degree of compression, (c) is cohesive, (d) is It shows the effect on liquidity.
[Explanation of symbols]
1 Converter (metallurgical reactor)
2 Dust collection system 3 Coarse grain separator 4 Mixer
5 Addition lance 6 Coarse dust 7 Fine dust 8 Thickener 9 Exhaust gas recovery system 10 Water tank 11 Concentration tank 12 Dust collector 13 Oxygen gas (oxygen)
14 Molten metal (metal melt)
15 Top blow lance 16 Piping 17 Drainage 18 Ore (Cr ore)
19 Updraft 20 Mixed powder (mixture)

Claims (5)

The molten metal held in the converter type metallurgical reaction vessel, with the addition of carbon-containing material and ore, blowing oxygen gas to the molten metal surface, smelting smelting reduction made to obtain a molten metal comprising a main component metal of the ore In the method
The dust that occurred during the smelting, after the exhaust gas from the converter type metallurgical reaction vessel was slurried in water treatment, by rectifying separated from the slurry to recover 100μm or less as 20 wt% or less, A smelting reduction smelting method comprising mixing with the ore, drying the mixture to 2% by weight or less , and then adding the mixture again to the molten metal through a lance.   The molten metal obtained by the smelting reduction smelting is subsequently generated and recovered when decarburizing and refining in another converter-type metallurgical reaction vessel. The smelting reduction smelting method according to claim 1, wherein mixing is performed. The smelting reduction smelting method according to claim 1 or 2, wherein a mixing ratio determined by the following formula (1) of the dust and the ore is 0.5 or less.
α = dust weight / (ore weight + dust weight) (1) The smelting reduction smelting method according to any one of claims 1 to 3, wherein the ore is Cr ore. The carbon-containing material is mainly anthracite
The smelting reduction refining method in any one of Claims 1-4 characterized by the above-mentioned.

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