JP3785356B2 - Highly reactive coke for blast furnace and method for producing the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、高炉の燃料比を低減させ、生産性を向上させる高炉操業を可能とするための、高炉用高反応性コークスおよびその製造方法に関する。
【０００２】
【従来の技術】
通常の高炉においては、炉頂から鉄鉱石（焼結鉱）および高炉用コークスを層状に装入し、この鉄鉱石を炉内で還元した後、溶融状態にある銑鉄を製造している。
【０００３】
ところで、高炉には、熱保存帯と呼ばれる温度が１０００℃程度でほぼ一定の領域があり、この温度は通常高炉用コークスのガス化開始温度に相当する。すなわち、高炉内でＣ＋ＣＯ2＝２ＣＯで表されるコークスのガス化反応が起るためには、約１０００℃以上の温度が必要となる。鉄鉱石の還元は、その約７０％が熱保存帯より高温領域で生じるが、温度が高くなるに伴い、還元平衡ガス組成が高ＣＯ濃度側になり、還元反応を進めるためには、より高いＣＯ濃度組成のガスが必要となる。さらに、約１１００℃以上で、鉄鉱石からの融液生成が見られ、その結果として鉄鉱石（焼結鉱）中への還元ガスの浸透が抑制されてしまう。このため、熱保存帯温度が高いと、ＣＯガスによる鉄鉱石の間接還元を有効に活用できず、還元効率もある値以上に向上しない。
【０００４】
一方高炉用高反応性コークスは、反応性が高いことから、高炉内のＣＯ2がコークス表面に接した際、Ｃ＋ＣＯ2＝２ＣＯの反応がより低温から活発に行われる。また、その結果として、炉内に生じたＣＯガスが鉄鉱石と有効に反応して、還元反応が促進される。
【０００５】
Ｃ＋ＣＯ2＝２ＣＯの反応は吸熱反応であり、高炉における熱保存帯温度を低下させる効果がある。すなわち、通常高炉用コークス使用時は、１０００℃程度の熱保存帯が生成し、その温度がほとんど変化しないのに対し、高炉用高反応性コークスを使用することによって、熱保存帯温度を９００〜９５０℃に低下させることが可能となる。その結果、還元平衡ガス組成が低ＣＯ濃度側になり、還元平衡到達点に余裕ができるため、還元がより進行することになり、還元効率が向上する。このため、高炉用高反応性コークスを通常高炉用コークスの一部、あるいは全量と置換して使用することができれば、高炉の還元効率が向上し、コークス比を低下できる。
【０００６】
従来行われてきた高炉用高反応性コークス製造法は、高炉用コークスの製造に適さない、コークス化した際に反応性が高くなる非微粘結炭や一般炭を原料炭に配合する方法であった。
【０００７】
【発明が解決しようとする課題】
しかし、非微粘結炭や一般炭の配合による方法は、配合量が少ないと反応性が向上せず、配合量を多くするとコークス強度を維持することが困難であった。コークス強度が低いと、高炉の炉頂から装入する時に粉化してしまい、高炉の通気性を悪化させることになる。
【０００８】
以上のように、高炉での使用に適した高炉用高反応性コークスの製造方法が確立されていなかったため、高炉の還元効率向上には限界があった。
【０００９】
そこで本発明においては、コークス強度を確保して高炉の通気性を維持することができ、かつ、高炉寿命、高炉安定操業の面で問題がない、高炉用高反応性コークスおよびこれを製造する方法を提供することを目的とする。
【００１０】
【課題を解決するための手段】
本発明の要旨は、
（１） 鋼板洗浄工程または、めっき工程において排出される廃液とコークスを接触させてなる高炉用高反応性コークス、
（２） 鋼板洗浄工程または、めっき工程において排出される廃液とコークスを接触させることを特徴とする高炉用高反応性コークスの製造方法、
（３） 鋼板洗浄工程または、めっき工程において排出される含クロム廃液を、ｐＨ４．５以上８以下に調整し、析出物を除去後、析出物除去廃液をコークスと接触させることを特徴とする高炉用高反応性コークスの製造方法、
である。
【００１１】
【発明の実施の形態】
本発明者らは、反応性が高く、かつ強度の高いコークスを製造する方法について検討し、コークス炉で製造したコークスの表面に酸洗廃液またはメッキ廃液を接触させることにより、コークスの強度を維持したまま反応性を向上させる方法を発明した。
【００１２】
通常酸洗前の鋼板の表面には酸化物、油脂その他の汚れが存在しているので、その上に電気メッキなどの表面処理を行う場合の妨げとなる。そこでこれらの表面層に付着している酸化物、油脂等を剥離するために脱脂、酸洗などの前処理を行う。鋼板を酸で洗浄することにより鋼板の酸化被膜やスケール（金属酸化物）を取り除く。この時、鋼板の金属成分も同時に酸中に溶出する。溶出成分は、鉄が主成分であるが、鋼板の種類により溶出成分が異なる。例えば、普通鋼の溶出液の場合は、鉄が主成分（５０〜１００ｇ／ｌ程度）で、続いてマンガン（鉄１００質量％に対して約１質量％以下）、微量成分としてクロム、ニッケル、マグネシウム、銅など（鉄１００質量％に対して約０．１質量％以下）が含まれる場合もある。ステンレス鋼の溶出液の場合も、鉄が主成分（５０〜１００ｇ／ｌ程度）であるが、これ以外にクロムが多量（鉄１００質量％に対して１０〜４０質量％）に含まれている。以上の様に鋼板の酸洗浄実施後の溶液（以降、酸洗廃液と呼ぶ）に溶解している金属成分は、遷移金属を主成分として、種々の成分が混合している。
【００１３】
また、電気メッキ等で使用されるメッキ浴は、一般にニッケル、錫、亜鉛等の金属塩を水に溶解させたものを使用する。例えば、ニッケルメッキの場合は、硫酸ニッケル、塩化ニッケル等の水溶液を使用する。これらのメッキ浴は、メッキ作業における被メッキ金属の溶解やスラッジの蓄積によりメッキ浴の純度が低下する。これを防止するために一部の溶液を廃液として抜き出し、新しいメッキ溶液を補充する。このため、メッキ廃液にはメッキ液の金属成分（ニッケル、錫、亜鉛等）と被メッキ金属から溶出した金属成分（鉄、ニッケル、クロム、マグネシウム、銅等）が混在している。
【００１４】
本発明者は、酸洗廃液またはメッキ廃液がそれぞれの工程から排出される状態で使用できる点と、溶解成分として遷移金属をはじめとした上記金属を含有している点に着目し、コークスのＣ＋ＣＯ2＝２ＣＯの反応を活性化させる触媒としての可能性を探索し、本発明に至った。
【００１５】
具体的には、種々の鋼板の酸洗廃液をコークスに接触させ、溶解している金属成分をコークスに担持し、Ｃ＋ＣＯ2＝２ＣＯの反応性を調べた結果、鋼板洗浄工程において排出される酸洗廃液をコークスと接触させることにより、得られたコークスのＣ＋ＣＯ2＝２ＣＯの反応性を飛躍的に向上させることができることがわかった。ここで使用される酸洗浄液は、硫酸、硝酸、塩酸、リン酸、シュウ酸、フッ酸または、それらの２種以上の混合物である。酸洗廃液の溶解主成分である鉄が触媒として作用していると考えられる。
【００１６】
また、メッキ廃液の場合も同様に、メッキ工程において排出されるメッキ廃液をコークスと接触させることにより、得られたコークスのＣ＋ＣＯ2＝２ＣＯの反応性を飛躍的に向上させることができることがわかった。メッキ廃液中の主成分であるニッケルと、鋼板から溶出した微量の鉄が、上記反応の促進に寄与しているものと考えられる。
【００１７】
一方、クロムはコークスに担持された金属成分、特に鉄の触媒活性を抑制することを確認している。これはクロムが鉄と複合酸化物を形成し安定化するものと考えられる。具体的には、クロムが鉄１００質量％に対して約１質量％以上１０質量％以下のクロム含有廃液では、鉄の触媒活性の抑制作用が発現する。クロムが鉄１００質量％に対して約１０質量％以上１００質量％以下のクロム含有廃液では、鉄の触媒活性はあるものの、クロム含有量の増加に伴い、触媒活性抑制作用がおおきくなる。クロムが鉄１００質量％に対して１００質量％以上の場合は、反応活性が著しく低下する。
【００１８】
すなわち、全くクロムを含有しない廃液が最も好ましいが、クロムが鉄１００質量％に対して約１質量％未満のクロム含有廃液であれば鉄の触媒活性の抑制作用がほとんど発現しないため使用可能であり、鉄１００質量％に対して約０．１質量％未満の微量のクロム含有廃液であればより好ましい。
【００１９】
ここで、クロムを除く廃液中金属のコークスへの添加量としては、添加量が多いほど触媒としての効果が大きいので、特に上限と下限を定めるものではないが、一般的に、コークス中の炭素１００ｍｏｌ％に対して０．０１ｍｏｌ％以上の担持量であることが望ましい。この量は、たとえば鉄（Ｆｅ）およびニッケル（Ｎｉ）の場合、コークス中の炭素１００質量％に対して、それぞれ０．０４７質量％以上および０．０４９質量％以上の担持量に相当する。また、コークス中には約１０質量％の灰分が含まれるので、鉄（Ｆｅ）およびニッケル（Ｎｉ）の場合、コークス１００質量％に対してそれぞれ、０．０４２質量％以上および０．０４４質量％以上の担持量に相当する。
【００２０】
次に、上述の様に、廃液中のクロムが鉄の触媒活性を抑制するため、クロムを事前に除去することに着目した。
【００２１】
ステンレス鋼板の酸洗廃液は、クロムを多量に含有しているが、触媒として有効な金属成分、特に鉄が存在するので、３価クロムイオンと２価鉄イオンの溶解度積の違いを利用し、クロムを水酸化物として沈殿させ、溶液から分離した。具体的にはｐＨ４．５以上で３価クロムは、水酸化物でほとんど沈殿し、２価鉄は、ｐＨ８前後で沈殿しはじめｐＨ９でほぼ完全に沈殿するため、アルカリによりｐＨを４．５以上８以下、好ましくは４．５以上７以下に調整することにより、廃液から、クロムを分離することができる。アルカリとしてアルカリ金属またはアルカリ土類金属の水酸化物、炭酸塩、もしくはアンモニア水等、アルカリ性を示す水溶液が利用できる。クロムは水酸化物として沈殿するので、一般に濾過によりクロム沈殿物と濾液が分離される。クロムを分離した廃液をコークスと接触させ、クロムを除く金属成分を担持させたコークスのＣ＋ＣＯ2＝２ＣＯの反応性を調べたところ、クロム除去を行っていない廃液に対して、反応性は、大幅に向上した。
【００２２】
酸洗廃液は、原液のままコークスと接触させることも可能であるが、希釈により金属の担持量を調整して担持することも可能である。また、容器および配管の酸腐食を考慮する場合、中和処理を行った後、コークスと接触させることもできる。
【００２３】
酸洗廃液とコークスを接触させる方法としては、液体をコークス上部から噴霧する方法、液体中にコークスを浸す方法などが考えられるが、コークス中の水分が上昇することは高炉操業上必ずしも好ましいことではないので、噴霧が望ましい。
【００２４】
一般的に、高炉に近い場所で酸洗廃液を噴霧した方が、コークス表面における触媒保持率は高いので、設備制約条件やコストなどを総合的に判断して噴霧場所を決定すればよい。
【００２５】
また、めっき廃液の場合、クロム含有量は微量であるが、酸洗廃液と同様にクロムを除去しても良い。
【００２６】
【実施例】
以下、実施例に基づき、本発明を具体的に説明する。
【００２７】
炉幅４２５ｍｍ、炉高４００ｍｍ、炉長６００ｍｍの試験コークス炉を用い、粘結炭６５質量％、非微粘結炭３５質量％の配合炭を装入密度０．８３ｄｒｙ−ｔ／ｍ3の装入密度で装入し、炉温１２５０℃、乾留時間１８．５時間の条件で乾留した。焼成後のコークスについては、窒素で冷却した後、コークスを粉砕し、１５０〜３００μｍに整粒した。整粒したコークスに実施例および比較例に基づき、酸洗廃液をスプレーにより接触させ、廃液中の金属成分をコークスに担持させた。担持しているＦｅ濃度の分析方法は、試料を一部取り出し、誘導結合プラズマ発光分析法（ＩＣＰ）により測定したが、原子吸光法や吸光光度法により分析をおこなってもかまわない。
【００２８】
実施例１は、普通鋼の酸洗工程より採取した酸洗廃液をコークスと接触させ、鉄の担持量がコークス１００質量％に対して１質量％になるように調整した。廃液中のクロム濃度は鉄１００質量％に対して０．０２質量％であった。
【００２９】
実施例２は、ステンレス鋼の酸洗工程より採取した酸洗廃液をコークスと接触させ、鉄の担持量がコークス１００質量％に対して１質量％になるように調整した。廃液中のクロム濃度は鉄１００質量％に対して３０質量％であった。
【００３０】
実施例３は、ステンレス鋼の酸洗工程より採取した酸洗廃液をアンモニア水でｐＨ６に調整し、生成した沈殿物を濾過した濾液をコークスと接触させ、鉄の担持量がコークス１００質量％に対して１質量％になるように調整した。廃液中のクロム濃度は鉄１００質量％に対して０．３質量％であった。
【００３１】
実施例４は、普通鋼のニッケルメッキ工程より採取したメッキ廃液をコークスと接触させ、ニッケルの担持量がコークス１００質量％に対して１質量％になるように調整した。
【００３２】
比較例１は、コークス単独である。
【００３３】
酸洗廃液と接触させたコークスを乾燥後、熱天秤を用いて、ＣＯ／ＣＯ2＝５０／５０（ｖｏｌ／ｖｏｌ）の雰囲気で１０℃／ｍｉｎで１０００℃まで昇温し、質量減少開始温度と１０００℃質量減少率を求めた。ここで、質量減少開始温度は、１０秒間の質量減少率（％）（（質量減少量／初期質量）×１００）が常に０．００４％を上回る最低の温度とした。１０００℃質量減少率（％）は、（（１０００℃における質量減少量／初期質量）×１００）である。実施例１は、比較例１に対して、大幅に質量減少開始温度が低下し、質量減少率も大きくなり、普通鋼の酸洗廃液を用いることでコークスのＣ＋ＣＯ2＝２ＣＯ反応の反応性を向上できることを示している。実施例２のステンレス鋼酸洗廃液では、質量減少はわずかであったが、比較例１に対して約４０℃の反応開始温度低下が見られた。ｐＨ調整後、沈殿物を除去した溶液では、実施例３のようにＣ＋ＣＯ2＝２ＣＯ反応の反応性を向上することができる。
【００３４】
実施例４のニッケルメッキ廃液では、比較例１と比較すると質量減少開始温度が低下し、１０００℃質量減少率が増加している。特に、質量減少開始温度の低下は、他の実施例と比較しても著しい。
【００３５】
【表１】
以上より、本発明により、反応性が高い、高炉用高反応性コークスが製造可能であることがわかる。
【００３７】
【発明の効果】
本発明により、極めて簡易な方法で、高炉用高反応性コークスが製造可能となった。本発明により、高炉での使用に適した高炉用高反応性コークスの製造方法が確立され、高炉の還元効率向上が期待できる点で、その工業的価値は大きい。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a highly reactive coke for a blast furnace and a method for producing the same for reducing the fuel ratio of the blast furnace and enabling blast furnace operation to improve productivity.
[0002]
[Prior art]
In a normal blast furnace, iron ore (sintered ore) and blast furnace coke are charged in layers from the top of the furnace, and the iron ore is reduced in the furnace, and then molten pig iron is produced.
[0003]
By the way, in the blast furnace, there is a region where the temperature called a heat preservation zone is approximately constant at about 1000 ° C., and this temperature usually corresponds to the gasification start temperature of coke for blast furnace. That is, in order for the coke gasification reaction represented by C + CO 2 = 2CO to occur in the blast furnace, a temperature of about 1000 ° C. or higher is required. About 70% of the reduction of iron ore occurs in a higher temperature region than the heat preservation zone, but as the temperature increases, the reduction equilibrium gas composition becomes higher in CO concentration side and is higher in order to advance the reduction reaction. A gas having a CO concentration composition is required. Furthermore, melt generation from iron ore is observed at about 1100 ° C. or higher, and as a result, permeation of reducing gas into iron ore (sintered ore) is suppressed. For this reason, if the heat preservation zone temperature is high, indirect reduction of iron ore with CO gas cannot be effectively utilized, and the reduction efficiency is not improved beyond a certain value.
[0004]
On the other hand, since highly reactive coke for blast furnace has high reactivity, when CO 2 in the blast furnace comes into contact with the coke surface, the reaction of C + CO 2 = 2CO is actively performed from a lower temperature. As a result, the CO gas generated in the furnace effectively reacts with the iron ore to promote the reduction reaction.
[0005]
The reaction of C + CO 2 = 2CO is an endothermic reaction, and has the effect of reducing the temperature of the heat preservation zone in the blast furnace. That is, when a coke for a blast furnace is used, a heat storage zone of about 1000 ° C. is generated, and the temperature hardly changes. On the other hand, by using a highly reactive coke for a blast furnace, a heat storage zone temperature of 900 to It can be lowered to 950 ° C. As a result, the reduction equilibrium gas composition is on the low CO concentration side and there is a margin at the reduction equilibrium arrival point, so that the reduction proceeds further and the reduction efficiency is improved. For this reason, if the highly reactive coke for blast furnace can be used by replacing a part or all of the normal blast furnace coke, the reduction efficiency of the blast furnace can be improved and the coke ratio can be lowered.
[0006]
The conventional highly reactive coke production method for blast furnace is a method that is not suitable for the production of coke for blast furnace. there were.
[0007]
[Problems to be solved by the invention]
However, the method of blending non-slightly caking coal or steam coal does not improve the reactivity when the blending amount is small, and it is difficult to maintain the coke strength when the blending amount is large. If the coke strength is low, it is pulverized when charged from the top of the blast furnace, and the air permeability of the blast furnace is deteriorated.
[0008]
As described above, since a method for producing highly reactive coke for blast furnaces suitable for use in blast furnaces has not been established, there has been a limit to improving the reduction efficiency of blast furnaces.
[0009]
Therefore, in the present invention, coke strength can be ensured to maintain the blast furnace air permeability, and there is no problem in terms of blast furnace life and stable blast furnace operation, and a highly reactive coke for blast furnace and a method for producing the same The purpose is to provide.
[0010]
[Means for Solving the Problems]
The gist of the present invention is as follows.
(1) High-reactivity coke for blast furnace made by bringing waste liquid discharged in the steel plate cleaning process or plating process into contact with coke,
(2) A method for producing a highly reactive coke for a blast furnace, wherein the waste liquid discharged in the steel plate washing step or the plating step is brought into contact with coke.
(3) A blast furnace characterized in that the chromium-containing waste liquid discharged in the steel plate cleaning process or the plating process is adjusted to pH 4.5 or more and 8 or less, and after removing the precipitate, the precipitate removing waste liquid is brought into contact with coke. A method for producing highly reactive coke,
It is.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present inventors examined a method for producing coke having high reactivity and high strength, and maintaining the strength of the coke by bringing the pickling waste liquid or the plating waste liquid into contact with the surface of the coke produced in the coke oven. The present inventors have invented a method for improving the reactivity.
[0012]
Usually, the surface of the steel sheet before pickling contains oxides, fats and other dirt, which hinders surface treatment such as electroplating. Therefore, pretreatment such as degreasing and pickling is performed in order to remove oxides, fats and oils adhering to these surface layers. The steel sheet is washed with acid to remove the oxide film and scale (metal oxide) on the steel sheet. At this time, the metal component of the steel sheet is also eluted in the acid. The elution component is mainly composed of iron, but the elution component varies depending on the type of steel sheet. For example, in the case of an eluate of ordinary steel, iron is the main component (about 50 to 100 g / l), followed by manganese (about 1% by mass or less with respect to 100% by mass of iron), and trace components such as chromium, nickel, Magnesium, copper, etc. (about 0.1 mass% or less with respect to 100 mass% of iron) may be contained. In the case of the eluate of stainless steel, iron is the main component (about 50 to 100 g / l), but besides this, chromium is contained in a large amount (10 to 40% by mass with respect to 100% by mass of iron). . As described above, the metal component dissolved in the solution after the acid cleaning of the steel sheet (hereinafter referred to as the pickling waste liquid) is composed mainly of transition metal and mixed with various components.
[0013]
A plating bath used for electroplating or the like generally uses a metal salt such as nickel, tin or zinc dissolved in water. For example, in the case of nickel plating, an aqueous solution of nickel sulfate, nickel chloride or the like is used. In these plating baths, the purity of the plating bath decreases due to dissolution of metal to be plated and accumulation of sludge in the plating operation. In order to prevent this, a part of the solution is taken out as a waste solution and replenished with a new plating solution. For this reason, the plating waste liquid contains a metal component (nickel, tin, zinc, etc.) of the plating solution and a metal component (iron, nickel, chromium, magnesium, copper, etc.) eluted from the metal to be plated.
[0014]
The inventor pays attention to the fact that the pickling waste liquid or the plating waste liquid can be used in a state where it is discharged from each process, and that it contains the above-mentioned metals including transition metals as dissolved components. The possibility of a catalyst for activating the reaction of 2 = 2CO was searched and the present invention was reached.
[0015]
Specifically, the pickling waste liquid of various steel plates is brought into contact with coke, the dissolved metal component is supported on the coke, and the reactivity of C + CO 2 = 2CO is examined. As a result, the acid discharged in the steel plate cleaning process It was found that the reactivity of C + CO 2 = 2CO of the obtained coke can be drastically improved by bringing the washing waste liquid into contact with coke. The acid cleaning solution used here is sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, oxalic acid, hydrofluoric acid, or a mixture of two or more thereof. It is thought that iron, which is the main component of the pickling waste liquid, acts as a catalyst.
[0016]
Similarly, in the case of the plating waste liquid, it was found that the reactivity of C + CO 2 = 2CO of the obtained coke can be dramatically improved by bringing the plating waste liquid discharged in the plating step into contact with coke. . It is considered that nickel, which is the main component in the plating waste liquid, and a small amount of iron eluted from the steel plate contribute to the promotion of the reaction.
[0017]
On the other hand, it has been confirmed that chromium suppresses the catalytic activity of metal components supported on coke, particularly iron. This is thought to be because chromium forms a complex oxide with iron and stabilizes. Specifically, in a chromium-containing waste liquid in which chromium is about 1% by mass or more and 10% by mass or less with respect to 100% by mass of iron, an inhibitory action on iron catalytic activity is exhibited. In the chromium-containing waste liquid in which chromium is about 10% by mass or more and 100% by mass or less with respect to 100% by mass of iron, although there is catalytic activity of iron, the activity of suppressing the catalyst activity increases greatly as the chromium content increases. When chromium is 100% by mass or more with respect to 100% by mass of iron, the reaction activity is remarkably lowered.
[0018]
That is, a waste liquid containing no chromium is most preferable, but if the chromium-containing waste liquid contains less than about 1% by mass of chromium with respect to 100% by mass of iron, it can be used because it hardly exhibits an inhibitory effect on iron catalytic activity. More preferably, it is a trace amount chromium-containing waste liquid of less than about 0.1% by mass with respect to 100% by mass of iron.
[0019]
Here, as the addition amount of the metal in the waste liquid excluding chromium to the coke, the larger the addition amount, the greater the effect as a catalyst, so there is no particular upper limit and lower limit. The supported amount is preferably 0.01 mol% or more with respect to 100 mol%. For example, in the case of iron (Fe) and nickel (Ni), this amount corresponds to a supported amount of 0.047% by mass or more and 0.049% by mass or more with respect to 100% by mass of carbon in coke, respectively. Further, since about 10% by mass of ash is contained in the coke, in the case of iron (Fe) and nickel (Ni), 0.042% by mass or more and 0.044% by mass with respect to 100% by mass of coke, respectively. It corresponds to the above loading amount.
[0020]
Next, attention was paid to the removal of chromium in advance because the chromium in the waste liquid suppresses the catalytic activity of iron as described above.
[0021]
The pickling waste liquid of the stainless steel sheet contains a large amount of chromium, but since there is an effective metal component as a catalyst, particularly iron, the difference in solubility product between trivalent chromium ions and divalent iron ions is utilized. Chromium was precipitated as a hydroxide and separated from the solution. Specifically, at pH 4.5 or higher, trivalent chromium is almost precipitated as hydroxide, and divalent iron begins to precipitate around pH 8 and almost completely precipitates at pH 9, so the pH is 4.5 or higher with alkali. By adjusting to 8 or less, preferably 4.5 or more and 7 or less, chromium can be separated from the waste liquid. An alkaline aqueous solution such as an alkali metal or alkaline earth metal hydroxide, carbonate, or aqueous ammonia can be used as the alkali. Since chromium precipitates as a hydroxide, the chromium precipitate and the filtrate are generally separated by filtration. The waste liquid from which chromium was separated was brought into contact with coke, and the reactivity of C + CO 2 = 2CO in the coke loaded with metal components excluding chromium was investigated. Improved.
[0022]
The pickling waste liquid can be brought into contact with coke as it is, but can also be supported by adjusting the amount of metal supported by dilution. Moreover, when acid corrosion of a container and piping is considered, it can also be made to contact with coke after performing a neutralization process.
[0023]
As a method of bringing the pickling waste liquid and coke into contact with each other, a method of spraying a liquid from the upper part of the coke, a method of immersing the coke in the liquid, and the like can be considered. Spraying is desirable because there is not.
[0024]
In general, the catalyst retention on the coke surface is higher when the pickling waste liquid is sprayed in a place close to the blast furnace. Therefore, the spraying place may be determined by comprehensively judging equipment constraint conditions and costs.
[0025]
In the case of the plating waste liquid, the chromium content is very small, but chromium may be removed in the same manner as the pickling waste liquid.
[0026]
【Example】
Hereinafter, based on an Example, this invention is demonstrated concretely.
[0027]
Using a test coke oven with a furnace width of 425 mm, a furnace height of 400 mm, and a furnace length of 600 mm, a blended coal of caking coal 65% by mass and non-minor caking coal 35% by mass was charged with a charging density of 0.83 dry-t / m 3 . The reactor was charged at a charging density and subjected to dry distillation under conditions of a furnace temperature of 1250 ° C. and a dry distillation time of 18.5 hours. About the coke after baking, after cooling with nitrogen, the coke was grind | pulverized and it sized to 150-300 micrometers. Based on Examples and Comparative Examples, the pickled waste liquid was brought into contact with the sized coke by spraying, and the metal components in the waste liquid were supported on the coke. As a method for analyzing the concentration of Fe supported, a part of the sample was taken and measured by inductively coupled plasma atomic emission spectrometry (ICP), but it may be analyzed by atomic absorption spectrometry or absorptiometry.
[0028]
In Example 1, the pickling waste liquid collected from the pickling process of ordinary steel was brought into contact with coke, and the iron loading was adjusted to 1% by mass with respect to 100% by mass of coke. The chromium concentration in the waste liquid was 0.02% by mass with respect to 100% by mass of iron.
[0029]
In Example 2, the pickling waste liquid collected from the pickling process of stainless steel was brought into contact with coke, and the iron loading was adjusted to 1% by mass with respect to 100% by mass of coke. The chromium concentration in the waste liquid was 30% by mass with respect to 100% by mass of iron.
[0030]
In Example 3, the pickling waste liquid collected from the pickling process of stainless steel was adjusted to pH 6 with ammonia water, the filtrate obtained by filtering the produced precipitate was brought into contact with coke, and the iron loading was 100% by mass of coke. It adjusted so that it might become 1 mass% with respect to it. The chromium concentration in the waste liquid was 0.3% by mass with respect to 100% by mass of iron.
[0031]
In Example 4, the plating waste liquid collected from the nickel plating step of plain steel was brought into contact with coke, and the amount of nickel supported was adjusted to 1% by mass with respect to 100% by mass of coke.
[0032]
Comparative Example 1 is coke alone.
[0033]
After drying the coke brought into contact with the pickling waste liquid, the temperature is increased to 1000 ° C. at 10 ° C./min in an atmosphere of CO / CO 2 = 50/50 (vol / vol) using a thermobalance, and the mass reduction start temperature And 1000 ° C. mass reduction rate. Here, the mass decrease start temperature was set to the lowest temperature at which the mass decrease rate (%) for 10 seconds ((mass decrease amount / initial mass) × 100) always exceeded 0.004%. The 1000 ° C. mass decrease rate (%) is ((mass decrease amount at 1000 ° C./initial mass) × 100). In Example 1, compared with Comparative Example 1, the mass reduction start temperature is greatly reduced and the mass reduction rate is also increased. By using the pickling waste liquid of ordinary steel, the reactivity of C + CO 2 = 2CO reaction of coke is increased. It shows that it can be improved. In the stainless steel pickling waste liquid of Example 2, the mass decrease was slight, but a reaction start temperature drop of about 40 ° C. was observed with respect to Comparative Example 1. In the solution from which the precipitate is removed after the pH adjustment, the reactivity of the C + CO 2 = 2CO reaction can be improved as in Example 3.
[0034]
In the nickel plating waste liquid of Example 4, compared with Comparative Example 1, the mass decrease start temperature is decreased and the mass decrease rate of 1000 ° C. is increased. In particular, the decrease in the mass decrease start temperature is significant even when compared with other examples.
[0035]
[Table 1]
From the above, it can be seen that according to the present invention, highly reactive coke for blast furnace having high reactivity can be produced.
[0037]
【The invention's effect】
According to the present invention, a highly reactive coke for a blast furnace can be produced by an extremely simple method. The present invention establishes a method for producing highly reactive coke for blast furnaces suitable for use in a blast furnace, and its industrial value is great in that it can be expected to improve the reduction efficiency of the blast furnace.
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