JP4599744B2

JP4599744B2 - Method for producing hot metal pretreatment agent using dust collection dust containing iron oxide

Info

Publication number: JP4599744B2
Application number: JP2001102862A
Authority: JP
Inventors: 守須田; 伸和北川
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2001-04-02
Filing date: 2001-04-02
Publication date: 2010-12-15
Anticipated expiration: 2021-04-02
Also published as: JP2002294320A

Description

【０００１】
【発明の属する技術分野】
本発明は、製鉄関連設備から排出される酸化鉄含有集塵ダストを利用した溶銑予備処理剤の製造方法に関するものである。
【０００２】
【従来の技術】
一般に、溶銑予備処理では、高炉鋳床に設置された出銑樋内の溶銑に酸化鉄を主体とする脱珪剤を散布し、その流下する過程で脱珪を図る特開昭58-56723号公報に開示されている散布方式と、出銑樋端に近接して設けられた傾注樋内の溶銑に対して酸化鉄を主とする脱珪剤を投射添加する特開昭59-143010 号公報等に開示されている投射方式が知られている。また、取鍋やトピードカー等の溶銑容器内に収容された溶銑中に酸化鉄、生石灰、炭酸カルシウム等を混合した脱珪脱燐剤を空気、窒素等の搬送気体によって輸送管路内を浮遊状態で輸送し、浸漬ランスの先端から吹き込むインジェクション方式が知られている。
【０００３】
従来の散布方式、投射方式およびインジェクション方式による溶銑予備処理には、粒径１mm以下の脱珪剤、脱珪脱燐剤が一般的に用いられている。これら予備処理剤は粉砕処理によって粒度が調整されているため、粒度分布として100 μm 以下の比率が少なくなっている。従来の溶銑予備処理剤は粒径が比較的大きいため溶銑予備処理を実施する際、溶銑との反応速度が遅いので溶銑容器内のスラグ中に未反応の酸化鉄が増加して反応効率が低下すると共にスラグフォーミングが著しくなる。
【０００４】
フォーミング防止剤を添加しても溶銑容器への溶銑充填量低下が避けられなかった。溶銑を脱珪、脱燐処理するための酸化鉄源として、焼結鉱粉や破砕ミルスケールが使用されているが、これらの粉粒体は貯蔵ホッパからディスペンサを経由して気体輸送配管内を高速高圧で搬送される。これら粉粒体は硬いため高速高圧で搬送する際に、気体輸送配管が著しく磨耗する。
【０００５】
管体の磨耗を低減するため微粉鉄鉱石で薄めて機械的衝撃を緩和することが知られている。例えば、特公平4-38809 号公報には、製鉄関連設備から排出される酸化鉄含有集塵ダストを、下記粉体特性を満たすという条件の下で、粉粒状のスケールおよび／または鉄鉱石と混合したものであることを特徴とする溶銑予備処理剤が開示されている。粒度構成：150 μm 以下で、かつ105 μm 以下のものが全体の80〜90重量％を占める流動性指数:35 〜40、噴流性指数:79 〜90。
【０００６】
【発明が解決しようとする課題】
しかるに、前記特公平4-38809 号公報に開示されている従来技術は、酸化鉄含有集塵ダストの粒度構成が：150 μm 以下で、かつ105 μm 以下のものが全体の80〜90重量％を占めることを要件の一つとしており、微粉ダストと粒度の大きい他のダストとの混合組み合わせに大きな制限があり、製鉄関連設備から排出される酸化鉄含有集塵ダストの全てに適用できるものとなっていない。すなわち、酸化鉄含有集塵ダストには、電気炉から発生するダストのように粒径分布で50μm 以下が50質量％以上を占めるものがあるが、前記公報の従来技術はこのような超微粉ダストに適用することができない。
【０００７】
本発明は、酸化鉄含有集塵ダストのうち粒径分布で50μm 以下が50質量％以上を占める凝集性の大きな超微粉ダストを、ホッパ内に堆積した状態から棚吊りを生じることなく安定して切り出すことを可能にした溶銑予備処理剤の製造方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
前記目的を達成するための請求項１記載の本発明は、製鉄関連設備から排出される酸化鉄含有集塵ダストを、溶銑脱珪、脱燐処理する酸化剤として利用する溶銑予備処理剤の製造に際し、前記酸化鉄含有集塵ダストが粒径分布で50μm 以下の割合が50質量％以上かつ凝集度が70を超える高い凝集性を有する超微粉集塵ダストであり、該超微粉集塵ダストを貯蔵ホッパに受け入れる前の段階で前記溶銑予備処理剤の５〜50質量％の割合として、残部の酸化鉄および脱珪脱燐助剤を包含する粒径分布で50μm 超〜1000μm の割合が50質量％以上かつ凝集度が70以下の低い凝集性を有する粉粒体と混合させてなることを特徴とする酸化鉄含有集塵ダストを利用した溶銑予備処理剤の製造方法である。
【０００９】
請求項２記載の本発明は、前記超微粉集塵ダストを前記溶銑予備処理剤の10〜30質量％の割合とすることを特徴とする請求項１記載の酸化鉄含有集塵ダストを利用した溶銑予備処理剤の製造方法である。
請求項３記載の本発明は、製鉄関連設備から排出される酸化鉄含有集塵ダストを、溶銑脱珪、脱燐処理する酸化剤として利用する溶銑予備処理剤の使用に際し、前記酸化鉄含有集塵ダストが粒径分布で50μm 以下の割合が50質量％以上かつ凝集度が70を超える高い凝集性を有する超微粉集塵ダストであり、該超微粉集塵ダストを前記溶銑予備処理剤の５〜50質量％の割合として、残部の酸化鉄および脱珪脱燐助剤を包含する粒径分布で50μm 超〜1000μm の割合が50質量％以上かつ凝集度が70以下の低い凝集性を有する粉粒体と混合させた前記溶銑予備処理剤を、ホッパあるいはディスペンサから排出する気送過程で超微粉集塵ダストを分散させることを特徴とする酸化鉄含有集塵ダストを利用した溶銑予備処理剤の使用方法である。
【００１０】
【発明の実施の形態】
本発明らは、酸化鉄含有集塵ダストのうち粒径分布で50μm 以下が50質量％以上を占める超微粉の電気炉ダストを脱珪、脱燐処理するための溶銑予備処理剤として利用することに着目し種々検討を重ねた。
溶銑処理センタでトピードカー内の溶銑に超微粉の電気炉ダスト単体を吹き込む実験を試みたが、その際には、電気炉ダストが超微粉のため搬送時に輸送用タンクローリに60％が残留し、またホッパ内で電気炉ダストの棚吊りを起こし、吹き込み用ランスから電気炉ダストを安定して吹き込むことができなかった。
【００１１】
そこで、超微粉の電気炉ダストに、50μm 超が50質量％以上の粒径分布を有する比較的粗粒の焼結ダスト並びに石灰粉（CaO ）とを混合してトピードカー内の溶銑に吹き込む実験を行った。
表１に、焼結機から発生する焼結ダストおよび電気炉から発生する電気炉ダストの粒度分布およびその他の性状を示す。表１に示すように、焼結ダストは50μm 以下が１質量％の粒度分布で凝集度が70であるのに比較して、電気炉ダストは50μm 以下が70質量％の粒度分布であり超微粉であるために凝集度が79と高い値を示している。
【００１２】
なお、凝集度とは、振幅１mm、振動時間（sec ）＝20＋(1.6−W)/0.06 の条件で振動させた粉体を、60、100 、200 メッシュの３段階で篩分けし、（60メッシュオーバ）＋（100 メッシュオーバ）×0.6 ＋（200 メッシュオーバ）×0.2 の式で算出される粉体重量比率で表したものである。
ここで、Ｗ＝(P−A)×C/100 ＋A (g/cm³) であり、Ｃ：圧縮度（＝ 100×(P-A) ）、Ｐ：緩み見掛け比重、Ａ：固め見掛け比重である。
【００１３】
【表１】

【００１４】
図２に焼結ダストと電気炉ダストとを混合した溶銑予備処理剤における電気炉ダストの混合比率（質量％）と安息角との関係を、また図３に石灰粉と電気炉ダストとを混合した溶銑予備処理剤における電気炉ダストの混合比率（質量％）と安息角との関係を示す。
図２から凝集度が70を超える電気炉ダストと凝集度が70以下である焼結ダストと混合する場合、電気炉ダストの混合比率が40質量％まではホッパ内に棚吊りを起こすことなく浸漬ランスからトピードカー内の溶銑中に吹き込み可能であるが、40質量％を超えると安息角が55度を超えるためホッパ内に棚吊りが発生し、吹き込み不可能となる。
【００１５】
また、図３から凝集度が70以下の石灰粉と混合する場合、電気炉ダストの混合比率が50質量％まではホッパ内に棚吊りを起こすことなく吹き込み可能である。50質量％を超えると安息角が55度を超えるためホッパ内に棚吊りが発生し、吹き込み不可能となる。
このように原料の種類により若干の差はあるが電気炉ダストが50質量％を超えると間違いなくホッパ内に棚吊りが発生して切り出し困難となりトピードカーへの吹き込みができなくなることが分かった。さらに電気炉ダストのホッパ内での棚吊り防止には、これと混合する焼結ダスト、石灰粉の粒径分布を50μm 超〜1000μm の割合が50質量％以上とする必要のあることが分かった。
【００１６】
図２および図３から焼結ダストや石灰粉に混合可能な凝集度が70を超える電気炉ダストの混合比率は、安息角を55度以下のレベルに確保できる50質量％が上限となる。一方、電気炉ダストの混合比率の下限は、利用量を勘案して５質量％とする。電気炉ダストの利用量並びに吹き込みの安定性を考慮すると電気炉ダストの混合比率は、10〜30質量％の範囲が好適となる。
【００１７】
以下、本発明の実施の形態を図面に基づいて説明する。
図１に示すように、鉄スクラップの溶解、精錬を行う電気炉１から発生する排ガスは、CO、H₂等の可燃性ガスを含有しているので、これを燃焼塔２に導いて燃焼させ、1000〜1200℃の燃焼ガスとする。その燃焼ガスでスクラップ原料を予熱すると共に空気予熱器（図示せず）へ供給して燃焼用空気を予熱し、これを燃焼塔２に供給することにより熱回収している。このようにして低温とした排ガスは、集塵機３に導かれ排ガス中のダストが集塵される。
【００１８】
集塵機３内に溜まった電気炉ダストは、専用コンテナ４に収納してトラックにより搬送されてミキサー５に供給されると共に、焼結ダストホッパ６からミキサー５に切り出された焼結ダストと混合して溶銑予備処理剤とする。
電気炉ダストおよび焼結ダストの粒度分布およびその他の性状は、表１に示した通りである。電気炉ダストは、粒径分布で50μm 以下の割合が50質量％以上の超微粉で、かつ凝集度が70を超える高い凝集性を有するので、凝集度が70以下で凝集性が低い焼結ダストと混合して電気炉ダストの混合比率を５〜50質量％、好ましくは10〜30質量％の割合とする。例えば、溶銑予備処理剤中の電気炉ダストの混合比率を20質量％、焼結ダストの混合比率を80質量％とする。
【００１９】
ミキサー５により混合された溶銑予備処理剤は、タンクローリ７により搬送され、貯蔵ホッパ８に貯蔵される。貯蔵ホッパ８に貯蔵された溶銑予備処理剤は電気炉ダストの混合比率が20質量％であるため、貯蔵ホッパ８内に溶銑予備処理剤が堆積した状態から排出口へ棚吊りを生じることなくスムーズな流れを形成しつつ開状態の開閉弁９を通過し、下方に配置されたディスペンサ10に安定して供給される。
【００２０】
ディスペンサ10は加圧気体供給ライン（図示省略）により空気等の気体で所定の圧力に加圧された後に開閉弁11を開き、ディスペンサ10内の溶銑予備処理剤が、堆積した状態から排出口へ棚吊りを生じることなくスムーズな流れを形成しつつロータリフィーダ17による切り出し量の制御により所定速度で輸送管路12に供給される。
【００２１】
輸送管路12には、溶銑予備処理剤を輸送するのに必要な空気等の搬送気体13が供給されており、したがって、溶銑予備処理剤は浮遊状態で輸送管路13内を流れ、トピードカー14内に挿入した浸漬ランス15から溶銑16中に吹き込まれて溶銑16の脱珪、脱燐処理が行われる。このとき、ディスペンサ10内の溶銑予備処理剤は、気体圧力により浮遊状態で排出口から切り出され、引き続き浮遊状態で輸送管路13内を流れる間に電気炉ダストの分散が促進される。このため微粉同士の凝集が抑制され、各部への付着による閉塞等のトラブルが防止できるのである。
【００２２】
溶銑予備処理剤中の電気炉ダストの混合比率を20質量％、焼結ダストの混合比率を80質量％とした本発明例（貯蔵ホッパ８→ディスペンサ10→輸送管路12→浸漬ランス15→トピードカー14という一連の吹込工程）における吹込時間（min )と粉体吹込速度（kg/min）との関係を図４に示した。図４から明らかなように、本発明によれば溶銑予備処理剤の吹込開始から約30分の吹込終了まで550kg/min程度の粉体吹込速度で安定した状態で吹き込みを実施することができる。
【００２３】
一方、図５に溶銑予備処理剤中の電気炉ダストの混合比率を60質量％、焼結ダストの混合比率を40質量％とする比較例における吹込時間（min ）と粉体吹込速度（kg/min）との関係を示した。比較例の場合、電気炉ダストの比率が高く、吹込時間５分経過頃からディスペンサ10内に棚吊りが生じたため急激に吹込速度が低下し、約10分で吹き込みが不可能となった。
【００２４】
前記実施の形態では、焼結ダストと電気炉ダストとを混合した溶銑予備処理剤の場合について説明したが、本発明では電気炉ダスト以外の粒径分布で50μm 以下の割合が50質量％以上かつ凝集度が70を超える高い凝集性を有する製鉄関連設備から排出される超微粉の各種酸化鉄含有集塵ダストにも適用できる。超微粉ダストと混合する原料としては、粒径分布で50μm 超〜1000μm の割合が50質量％以上かつ凝集度が70以下の低い凝集性を有するものであれば一般的に使用されている酸化鉄および脱珪脱燐助剤を包含する各種原料（石灰粉、溶銑予備処理で発生した集塵ダスト、粉砕鉱石、粉砕ダスト、螢石粉等）が利用できるのはいうまでもない。
【００２５】
【発明の効果】
本発明によって製造された溶銑予備処理剤は、ホッパ等の貯留槽や容器内での堆積状態から排出口方向への流れが促され、棚吊りを生じることなくスムーズに切り出すことができ、このため凝集性の大きい超微粉の酸化鉄含有集塵ダストを溶銑予備処理剤として有効に利用できる。
【図面の簡単な説明】
【図１】本発明での溶銑予備処理剤の調合、吹き込み例を示すフロー図である。
【図２】焼結ダストと電気炉ダストとを混合した溶銑予備処理剤における電気炉ダスト混合比率と安息角との関係を示すグラフである。
【図３】石灰粉と電気炉ダストとを混合した溶銑予備処理剤における電気炉ダスト混合比率と安息角との関係を示すグラフである。
【図４】本発明例における溶銑予備処理剤の粉体吹込速度の経時変化を示すグラフである。
【図５】比較例における溶銑予備処理剤の粉体吹込速度の経時変化を示すグラフである。
【符号の説明】
１電気炉
２燃焼塔
３集塵機
４専用コンテナ
５ミキサー
６焼結ダストホッパ
７タンクローリ
８貯蔵ホッパ
９、11 開閉弁
10 ディスペンサ
12 輸送管路
13 搬送気体
14 トピードカー
15 浸漬ランス
16 溶銑
17 ロータリフィーダ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a hot metal pretreatment agent that uses iron oxide-containing dust collection dust discharged from iron-related equipment.
[0002]
[Prior art]
Generally, in the hot metal preliminary treatment, a desiliconizing agent mainly composed of iron oxide is sprayed on the hot metal in the slag installed on the blast furnace casting floor, and desiliconization is performed in the process of flowing down. Japanese Patent Application Laid-Open No. 59-143010, etc., in which a desiliconizing agent mainly composed of iron oxide is projected and added to the spraying method disclosed in the official gazette and the hot metal in the tilting iron provided close to the tap end Is known. In addition, desiliconization and dephosphorization agents mixed with iron oxide, quicklime, calcium carbonate, etc. in hot metal contained in hot metal containers such as ladle and topped car are floated in the transportation pipeline by carrier gas such as air and nitrogen. An injection method is known in which the product is transported by a nozzle and blown from the tip of an immersion lance.
[0003]
In the hot metal pretreatment by the conventional spraying method, projection method and injection method, a desiliconizing agent and a desiliconizing dephosphorizing agent having a particle size of 1 mm or less are generally used. Since the particle size of these pretreatment agents is adjusted by pulverization, the particle size distribution has a ratio of 100 μm or less. Since the conventional hot metal pretreatment agent has a relatively large particle size, when the hot metal pretreatment is performed, the reaction rate with the hot metal is slow, so unreacted iron oxide increases in the slag in the hot metal vessel and the reaction efficiency decreases. In addition, slag forming becomes remarkable.
[0004]
Even when the antifoaming agent was added, the hot metal filling amount in the hot metal container was inevitably lowered. Sintered ore powder and crushing mill scale are used as iron oxide sources for desiliconization and dephosphorization of hot metal, but these granular materials are transferred from the storage hopper through the dispenser into the gas transport pipe. Transported at high speed and high pressure. Since these powders are hard, the gas transport piping is significantly worn when transported at high speed and pressure.
[0005]
It is known to reduce mechanical impact by diluting with fine iron ore to reduce tube wear. For example, in Japanese Patent Publication No. 4-38809, iron oxide-containing dust collection dust discharged from iron-related equipment is mixed with granular scale and / or iron ore under the condition that the following powder characteristics are satisfied. A hot metal pretreatment agent characterized by the above is disclosed. Particle size composition: Fluidity index: 35 to 40, and jetness index: 79 to 90 with 80 to 90% by weight of the total particle size of 150 μm or less and 105 μm or less.
[0006]
[Problems to be solved by the invention]
However, in the prior art disclosed in the above Japanese Patent Publication No. 4-38809, the particle size composition of the iron oxide-containing dust collection dust is 150 μm or less and 105 μm or less accounts for 80 to 90% by weight of the total. One of the requirements is to occupy, and there is a great restriction on the combination of fine dust and other dust with large particle size, and it can be applied to all the iron oxide-containing dust collection dust discharged from iron-related equipment. Not. That is, some iron oxide-containing dust collection dusts, such as dust generated from an electric furnace, have a particle size distribution of 50 μm or less accounting for 50% by mass or more. Cannot be applied to.
[0007]
The present invention stably collects ultrafine dust particles having a high cohesiveness in which the particle size distribution is 50% by mass or more in the iron oxide-containing dust collecting dust from the state in which the dust particles are accumulated in the hopper without causing shelf hanging. It aims at providing the manufacturing method of the hot metal pretreatment agent which enabled cutting out.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention according to claim 1 is the production of a hot metal pretreatment agent that uses iron oxide-containing dust-collected dust discharged from iron-related equipment as an oxidizing agent for hot metal desiliconization and dephosphorization. In this case, the iron oxide-containing dust collection dust is an ultrafine dust collection dust having a high cohesiveness in which the ratio of particle size distribution of 50 μm or less is 50 mass% or more and the cohesion degree exceeds 70, and the ultrafine dust collection dust is As a ratio of 5 to 50% by mass of the hot metal pretreatment agent in the stage before being received in the storage hopper, a ratio of more than 50 μm to 1000 μm in the particle size distribution including the remaining iron oxide and desiliconization and dephosphorization aid is 50% by mass. It is a method for producing a hot metal pretreatment agent using iron oxide-containing dust collecting dust, characterized by being mixed with a powder having a low cohesiveness of not less than% and an aggregation degree of not more than 70.
[0009]
The present invention according to claim 2 utilizes the iron oxide-containing dust collection dust according to claim 1, wherein the ultrafine dust collection dust is set to a ratio of 10 to 30% by mass of the hot metal pretreatment agent. It is a manufacturing method of a hot metal pretreatment agent.
The present invention described in claim 3 is directed to use of the iron oxide-containing dust collection dust used in the hot metal pretreatment agent, which utilizes the iron oxide-containing dust collection dust discharged from the iron-related equipment as an oxidizing agent for hot metal desiliconization and dephosphorization. Dust dust is an ultrafine dust collection dust having a high cohesiveness with a particle size distribution with a ratio of 50 μm or less of 50% by mass or more and an agglomeration degree exceeding 70. The ultrafine dust collection dust is treated as 5% of the hot metal pretreatment agent. As a proportion of ~ 50% by mass, a powder having a low cohesiveness with a particle size distribution including the remaining iron oxide and dephosphorization and phosphorus removal aid, with a proportion of more than 50 µm to 1000 µm of 50% by mass or more and an aggregation degree of 70 or less The hot metal pretreatment agent using iron oxide-containing dust collection dust is characterized by dispersing ultrafine dust collection dust in the air-feeding process of discharging the hot metal pretreatment agent mixed with the granular material from a hopper or dispenser. How to use.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention uses iron oxide-containing dust collection dust as a hot metal pretreatment agent for desiliconization and dephosphorization of ultrafine electric furnace dust whose particle size distribution is 50 μm or less and whose particle size distribution is 50% by mass or more. Various studies were repeated focusing on
Attempts were made to blow electric furnace dust alone into the hot metal in the topped car at the hot metal treatment center. At that time, 60% of the electric furnace dust remained in the transport tank lorry during transportation due to the ultrafine powder. The electric furnace dust was suspended in the hopper, and the electric furnace dust could not be stably blown from the blowing lance.
[0011]
Therefore, an experiment in which ultra-fine electric furnace dust was mixed with relatively coarse sintered dust and lime powder (CaO) having a particle size distribution of more than 50% by mass over 50μm and blown into the hot metal in the topped car. went.
Table 1 shows the particle size distribution and other properties of the sintered dust generated from the sintering machine and the electric furnace dust generated from the electric furnace. As shown in Table 1, the sintered dust has a particle size distribution of 1% by mass with a particle size of 50 μm or less and an agglomeration degree of 70, whereas the dust of the electric furnace dust has a particle size distribution of 70% by mass or less with an ultrafine powder. Therefore, the degree of aggregation is as high as 79.
[0012]
The agglomeration degree means that the powder vibrated under the conditions of amplitude 1 mm, vibration time (sec) = 20 + (1.6−W) /0.06 is sieved in three stages of 60, 100 and 200 mesh (60 This is expressed as a powder weight ratio calculated by the following formula: mesh over) + (100 mesh over) × 0.6 + (200 mesh over) × 0.2.
Here, W = (P−A) × C / 100 + A (g / cm ³ ), C: degree of compression (= 100 × (PA)), P: loose apparent specific gravity, A: firm apparent specific gravity .
[0013]
[Table 1]

[0014]
Fig. 2 shows the relationship between the mixing ratio (mass%) of the electric furnace dust and the angle of repose in the hot metal pretreatment agent mixed with sintered dust and electric furnace dust, and Fig. 3 shows the mixture of lime powder and electric furnace dust. The relationship between the mixing ratio (mass%) of the electric furnace dust and the angle of repose in the molten iron pretreatment agent is shown.
Fig. 2 shows that when electric furnace dust with a cohesion degree exceeding 70 and sintered dust with an aggregation degree of 70 or less are mixed, up to 40% by mass of the electric furnace dust is immersed without suspending in the hopper. It can be blown from the lance into the hot metal in the topped car, but if it exceeds 40% by mass, the angle of repose exceeds 55 degrees, so that shelves are generated in the hopper and cannot be blown.
[0015]
Moreover, when mixing with the lime powder whose aggregation degree is 70 or less from FIG. 3, it can blow in without raising a shelf in a hopper until the mixing ratio of electric furnace dust is 50 mass%. If it exceeds 50 mass%, the angle of repose exceeds 55 degrees, so that shelves are generated in the hopper and cannot be blown.
As described above, it was found that although there is a slight difference depending on the type of raw material, if the electric furnace dust exceeds 50% by mass, shelves are definitely generated in the hopper, making it difficult to cut out and blowing into the topped car becomes impossible. Furthermore, in order to prevent shelves of electric furnace dust in the hopper, it was found that the particle size distribution of sintered dust and lime powder to be mixed with it must be more than 50% by mass of more than 50μm to 1000μm. .
[0016]
From FIG. 2 and FIG. 3, the upper limit of the mixing ratio of the electric furnace dust having a cohesion degree exceeding 70 that can be mixed with the sintered dust or lime powder is 50 mass% at which the angle of repose can be secured at a level of 55 degrees or less. On the other hand, the lower limit of the mixing ratio of the electric furnace dust is 5% by mass in consideration of the usage amount. Considering the utilization amount of electric furnace dust and the stability of blowing, the mixing ratio of electric furnace dust is preferably in the range of 10 to 30% by mass.
[0017]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, since the exhaust gas generated from the electric furnace 1 for melting and refining iron scrap contains a combustible gas such as CO and H ₂ , it is guided to the combustion tower 2 and burned. The combustion gas is 1000 to 1200 ° C. The scrap raw material is preheated with the combustion gas and supplied to an air preheater (not shown) to preheat the combustion air and supplied to the combustion tower 2 for heat recovery. The exhaust gas having a low temperature is guided to the dust collector 3 to collect dust in the exhaust gas.
[0018]
The electric furnace dust accumulated in the dust collector 3 is stored in a dedicated container 4 and transported by a truck and supplied to the mixer 5, and mixed with the sintered dust cut out from the sintered dust hopper 6 to the mixer 5. A pretreatment agent is used.
The particle size distribution and other properties of the electric furnace dust and sintered dust are as shown in Table 1. Electric furnace dust is an ultrafine powder with a particle size distribution of 50 μm or less and 50% by mass or more, and has a high agglomeration degree exceeding 70. Therefore, a sintered dust having a low agglomeration degree and a low agglomeration degree. The mixing ratio of the electric furnace dust is 5 to 50% by mass, preferably 10 to 30% by mass. For example, the mixing ratio of the electric furnace dust in the hot metal pretreatment agent is 20 mass%, and the mixing ratio of the sintered dust is 80 mass%.
[0019]
The hot metal pretreatment agent mixed by the mixer 5 is conveyed by the tank lorry 7 and stored in the storage hopper 8. Since the hot metal pretreatment agent stored in the storage hopper 8 has a mixing ratio of electric furnace dust of 20% by mass, the hot metal pretreatment agent can be smoothly suspended from the state where the hot metal pretreatment agent is accumulated in the storage hopper 8 without suspending the shelf from the discharge port. It passes through the open on-off valve 9 while forming a simple flow, and is stably supplied to the dispenser 10 disposed below.
[0020]
After the dispenser 10 is pressurized to a predetermined pressure with a gas such as air by a pressurized gas supply line (not shown), the on-off valve 11 is opened, and the hot metal pretreatment agent in the dispenser 10 is deposited from the accumulated state to the discharge port. It is supplied to the transport pipeline 12 at a predetermined speed by controlling the cut-out amount by the rotary feeder 17 while forming a smooth flow without causing shelf hanging.
[0021]
The transport pipeline 12 is supplied with a carrier gas 13 such as air necessary for transporting the hot metal pretreatment agent. Therefore, the hot metal pretreatment agent flows in the transport pipeline 13 in a floating state, and the topped car 14 The immersion lance 15 inserted into the hot metal 16 is blown into the hot metal 16 to perform desiliconization and dephosphorization of the hot metal 16. At this time, the hot metal pretreatment agent in the dispenser 10 is cut out from the discharge port in a floating state by the gas pressure, and the dispersion of the electric furnace dust is promoted while flowing in the transport pipe 13 in the floating state. For this reason, aggregation of fine powder is suppressed and troubles, such as obstruction | occlusion by adhesion to each part, can be prevented.
[0022]
Example of the present invention in which the mixing ratio of the electric furnace dust in the hot metal pretreatment agent is 20% by mass and the mixing ratio of the sintered dust is 80% by mass (storage hopper 8 → dispenser 10 → transport line 12 → dipping lance 15 → tope car FIG. 4 shows the relationship between the blowing time (min) and the powder blowing speed (kg / min) in a series of blowing steps 14. As is apparent from FIG. 4, according to the present invention, it is possible to carry out the blowing in a stable state at a powder blowing speed of about 550 kg / min from the start of blowing the hot metal pretreatment agent to the end of blowing for about 30 minutes.
[0023]
On the other hand, FIG. 5 shows the blowing time (min) and powder blowing speed (kg / kg) in the comparative example in which the mixing ratio of the electric furnace dust in the hot metal pretreatment agent is 60 mass% and the mixing ratio of the sintered dust is 40 mass%. min). In the case of the comparative example, the ratio of the electric furnace dust was high, and since the shelf hang was generated in the dispenser 10 from about 5 minutes after the blowing time, the blowing speed rapidly decreased, and the blowing became impossible in about 10 minutes.
[0024]
In the above embodiment, the hot metal pretreatment agent in which sintered dust and electric furnace dust are mixed has been described. In the present invention, the particle size distribution other than electric furnace dust has a ratio of 50 μm or less and 50 mass% or more and The present invention can also be applied to various dust collection dusts containing various types of ultra-fine powder discharged from iron-related equipment with high cohesiveness exceeding 70. As a raw material to be mixed with ultrafine dust, generally used iron oxide is used as long as it has a low cohesiveness with a particle size distribution of a ratio of more than 50 μm to 1000 μm of 50 mass% or more and an aggregation degree of 70 or less. Needless to say, various raw materials including desiliconization and dephosphorization aids (lime powder, dust collection dust generated by hot metal pretreatment, crushed ore, pulverized dust, fluorite powder, etc.) can be used.
[0025]
【The invention's effect】
The hot metal pretreatment agent produced according to the present invention is facilitated to flow from the accumulation state in a storage tank or container such as a hopper to the discharge port direction, and can be cut out smoothly without causing shelf hanging. It is possible to effectively use the ultrafine powdered iron oxide-containing dust collection dust having high cohesiveness as a hot metal pretreatment agent.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an example of preparation and blowing of hot metal pretreatment agent in the present invention.
FIG. 2 is a graph showing a relationship between an electric furnace dust mixing ratio and an angle of repose in a hot metal pretreatment agent in which sintered dust and electric furnace dust are mixed.
FIG. 3 is a graph showing a relationship between an electric furnace dust mixing ratio and an angle of repose in a hot metal pretreatment agent in which lime powder and electric furnace dust are mixed.
FIG. 4 is a graph showing the change over time in the powder blowing rate of the hot metal pretreatment agent in the inventive example.
FIG. 5 is a graph showing the change over time in the powder blowing rate of the hot metal pretreatment agent in a comparative example.
[Explanation of symbols]
1 Electric furnace 2 Combustion tower 3 Dust collector 4 Dedicated container 5 Mixer 6 Sintered dust hopper 7 Tank lorry 8

Storage hopper

9, 11 Open / close valve
10 Dispenser
12 Transport pipeline
13 Carrier gas
14 Toped Car
15 Immersion lance
16 Hot metal
17 Rotary feeder

Claims

In the production of hot metal pretreatment agent that uses iron oxide-containing dust collection dust discharged from iron-related facilities as an oxidizing agent for hot metal desiliconization and dephosphorization, the iron oxide-containing dust collection dust has a particle size distribution of 50 μm or less. Is an ultrafine dust collection dust having a high cohesiveness with a ratio of 50% by mass or more and an agglomeration degree exceeding 70, and at the stage before receiving the ultrafine dust collection dust in the storage hopper, As a proportion of 50% by mass, particles having a low cohesiveness with a particle size distribution including the remaining iron oxide and desiliconization and dephosphorization assistant, a proportion of more than 50 μm to 1000 μm being 50% by mass or more and an agglomeration degree of 70 or less A method for producing a hot metal pretreatment agent using iron oxide-containing dust collection dust, characterized by being mixed with a body.

The method for producing a hot metal pretreatment agent using iron oxide-containing dust collection dust according to claim 1, wherein the ultrafine dust collection dust is contained in a ratio of 10 to 30% by mass of the hot metal pretreatment agent.

When using a hot metal pretreatment agent that uses iron oxide-containing dust collection dust discharged from iron-related equipment as an oxidizing agent for hot metal desiliconization and dephosphorization, the iron oxide-containing dust collection dust has a particle size distribution of 50 μm or less. Is an ultrafine dust collection dust having a high cohesiveness with a proportion of 50% by mass or more and an agglomeration degree exceeding 70, and the ultrafine dust collection dust is used as a proportion of 5 to 50% by mass of the hot metal pretreatment agent. The hot metal reserve mixed with a granular material having a low cohesiveness with a particle size distribution including the iron oxide and the dephosphorization dephosphorization agent in a ratio of more than 50 μm to 1000 μm of 50 mass% or more and an aggregation degree of 70 or less A method of using a hot metal pretreatment agent using iron oxide-containing dust collection dust, characterized in that ultrafine dust collection dust is dispersed in the air-feeding process of discharging the treatment agent from a hopper or dispenser.