JP6079677B2

JP6079677B2 - Blast furnace blowing pulverized coal, blast furnace blowing pulverized coal manufacturing method and blast furnace operating method

Info

Publication number: JP6079677B2
Application number: JP2014064908A
Authority: JP
Inventors: 祐輔田中; 泰之森川; 竹下　将功; 将功竹下
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2014-03-27
Filing date: 2014-03-27
Publication date: 2017-02-15
Anticipated expiration: 2034-03-27
Also published as: JP2015187294A

Description

本発明は、高炉吹込み用微粉炭、及び、粒径分布が異なる２種類以上の微粉炭を混合して、高炉吹込み用微粉炭を製造する方法、並びに、高炉吹込み用微粉炭、または、前記方法により製造された微粉炭を用いる高炉操業方法に関する。 The present invention relates to a method for producing pulverized coal for blast furnace injection by mixing pulverized coal for blast furnace injection and two or more types of pulverized coal having different particle size distributions, and pulverized coal for blast furnace injection, or The present invention relates to a blast furnace operating method using pulverized coal produced by the above method.

高炉操業において、高炉炉頂から高炉内へ、鉄源である鉱石を投入するとともに、還元材であるコークスを投入している。さらに近年の高炉操業では、還元材の機能を果たす微粉炭を羽口から高炉に供給し、羽口前で燃焼させることでＣＯガスを発生させ、鉱石の還元に前記微粉炭を利用している。微粉炭は、石炭を乾留して製造されるコークスに比べて安価であるので、コークスの使用量を減らし代わりに微粉炭の供給量を増やすことによって、コストを大きく低減することができる上にコークスを製造するコークス炉の負荷を軽減することができ、コークス炉を延命することにもなる。 In blast furnace operation, iron ore as an iron source and coke as a reducing material are introduced from the top of the blast furnace into the blast furnace. Furthermore, in recent blast furnace operations, pulverized coal that functions as a reducing material is supplied from the tuyere to the blast furnace and burned before the tuyere to generate CO gas, and the pulverized coal is used for ore reduction. . Since pulverized coal is cheaper than coke produced by carbonizing coal, the cost can be greatly reduced by reducing the amount of coke used and increasing the supply of pulverized coal instead. Can reduce the load on the coke oven, and also prolong the life of the coke oven.

コークスの使用量を減らすために、高炉での燃焼性を確保した上で微粉炭の高炉への供給量を多くすることが望ましい。しかしながら、燃焼性を確保するために、微粉炭を細かくし過ぎると、微粉炭を輸送する輸送配管内部に微粉炭が付着する現象が発生しやすくなる。この現象が発生すると微粉炭の輸送量が減少するし、付着した状況を放置しておくと、いずれは輸送配管が閉塞してしまい、高炉操業を安定して行うことができなくなるという問題がある。この問題に対しては、粗く砕いた微粉炭を輸送配管で高炉に供給して、微粉炭の配管の内面に微粉炭が付着することを防ぐことが考えられる。しかしながら、粗く砕いた微粉炭は羽口前での燃焼性を確保しにくく、そのような微粉炭を高炉に供給し続けると、羽口前で燃え残った微粉炭に起因する微細なチャーなどが、高炉の通気性を悪化させてしまい、高炉の炉況が不安定となり、出銑量の低下の原因となるという問題が生じる。 In order to reduce the amount of coke used, it is desirable to increase the amount of pulverized coal supplied to the blast furnace while ensuring flammability in the blast furnace. However, if the pulverized coal is made too fine in order to ensure combustibility, a phenomenon in which the pulverized coal adheres to the inside of the transport pipe that transports the pulverized coal tends to occur. If this phenomenon occurs, the amount of pulverized coal transported will decrease, and if the state of adhesion is left unattended, there will be a problem that the transport piping will eventually be blocked, making it impossible to stably operate the blast furnace. . In order to solve this problem, it is conceivable to supply coarsely crushed pulverized coal to the blast furnace through a transportation pipe to prevent the pulverized coal from adhering to the inner surface of the pulverized coal pipe. However, coarsely pulverized pulverized coal is difficult to ensure flammability before the tuyere, and if such pulverized coal continues to be supplied to the blast furnace, fine char caused by the pulverized coal remaining unburned in front of the tuyere This causes a problem that the air permeability of the blast furnace is deteriorated, the furnace condition of the blast furnace becomes unstable, and the output amount is reduced.

この問題を解決すべく、特許文献１及び２の技術が提案されている。特許文献１には、微粉炭が輸送配管に付着しないように粒径分布の下限を定め、微粉炭の燃焼性を維持するように粒径分布の上限を定めることが提案されている。特許文献２には、複数銘柄の石炭を同時に粉砕する際に、事前に十分混合し、平均ＨＧＩに対応した粉砕力で粉砕することによって、目的とする粒径分布の微粉炭を得ることが記載されている。 In order to solve this problem, techniques of Patent Documents 1 and 2 have been proposed. Patent Document 1 proposes that the lower limit of the particle size distribution is set so that the pulverized coal does not adhere to the transport pipe, and the upper limit of the particle size distribution is set so as to maintain the combustibility of the pulverized coal. Patent Document 2 describes that when pulverizing multiple brands of coal at the same time, the pulverized coal having a desired particle size distribution is obtained by sufficiently mixing in advance and pulverizing with a pulverization force corresponding to the average HGI. Has been.

特開２００２−１９４４０８号公報JP 2002-194408 A 特開２００７−１７５５６１号公報JP 2007-175561 A

高炉での微粉炭の燃焼性を向上させつつ微粉炭が輸送配管に付着しないように、特許文献１及び２に記載の方法に従って、微粉炭を調製して輸送配管に供給しても、長時間経過すると、輸送配管のうち、特に比較的径の小さい枝管中の、曲率が大きいベンド部で微粉炭が閉塞してしまう場合がある。特許文献１及び２のいずれの方法であっても、輸送配管が閉塞してしまう可能性が依然として存在するというのが実情である。 Even if the pulverized coal is prepared and supplied to the transport pipe according to the methods described in Patent Documents 1 and 2 so that the pulverized coal does not adhere to the transport pipe while improving the combustibility of the pulverized coal in the blast furnace, the After the passage, the pulverized coal may be blocked at the bend portion having a large curvature, particularly in the branch pipe having a relatively small diameter. In either method of Patent Documents 1 and 2, there is still a possibility that the transportation pipe may be blocked.

本発明は上記実情に鑑みてなされたもので、その目的とするところは、高炉での燃焼性を高位に保つとともに、輸送配管のうち、微粉炭による閉塞が生じ易いベンド部であっても詰まりにくい高炉吹込み用微粉炭、及び、その高炉吹込み用微粉炭を製造する方法、並びに、その方法で製造された微粉炭を用いる高炉操業方法を提供することである。 The present invention has been made in view of the above circumstances, and the object thereof is to keep the flammability in the blast furnace at a high level and to clog even a bend portion that is likely to be blocked by pulverized coal in the transport pipe. It is an object of the present invention to provide a pulverized coal for blast furnace injection, a method for producing the pulverized coal for blast furnace injection, and a blast furnace operating method using the pulverized coal produced by the method.

上記課題を解決するための本発明の要旨は以下の通りである。
（１）質量基準の粒径分布で、粒径が４５μｍ以下となる粒子の質量割合が４５質量％以上となり、粒径が３２５μｍ以上となる粒子の質量割合が１．５質量％以上となる粒径分布を有することを特徴とする高炉吹込み用微粉炭。
（２）高炉吹込み用微粉炭を製造する方法であって、質量基準の粒径分布で、粒径が４５μｍ以下となる粒子の質量割合が４５質量％以上となり、粒径が３２５μｍ以上となる粒子の質量割合が１．５質量％以上となる粒径分布を有するように、高炉吹込み用微粉炭を調製することを特徴とする高炉吹込み用微粉炭の製造方法。
（３）それぞれ異なる粉砕条件で粉砕され、質量平均粒径が異なる２種類以上の微粉炭を混合して、前記高炉吹込み用微粉炭を調製することを特徴とする上記（２）に記載の高炉吹込み用微粉炭の製造方法。
（４）上記（１）に記載の高炉吹込み用微粉炭を用いて、あるいは、上記（２）または上記（３）に記載の高炉吹込み用微粉炭の製造方法によって製造された高炉吹込み用微粉炭を用いて、高炉を操業する高炉操業方法であって、前記高炉吹込み用微粉炭を、前記高炉に接続する配管を通じて１５０ｋｇ／トン−溶銑以上で前記高炉に吹き込むことを特徴とする高炉操業方法。 The gist of the present invention for solving the above problems is as follows.
(1) Particles having a mass-based particle size distribution in which the mass ratio of particles having a particle diameter of 45 μm or less is 45 mass% or more, and the mass ratio of particles having a particle diameter of 325 μm or more is 1.5 mass% or more. A pulverized coal for blast furnace injection characterized by having a diameter distribution.
(2) A method for producing pulverized coal for blast furnace injection, in which the mass ratio of particles having a particle size of 45 μm or less is 45% by mass or more and the particle size is 325 μm or more in a mass-based particle size distribution. A method for producing pulverized coal for blast furnace injection, comprising preparing pulverized coal for blast furnace injection so as to have a particle size distribution in which a mass ratio of particles is 1.5 mass% or more.
(3) The pulverized coal for blast furnace blowing is prepared by mixing two or more types of pulverized coal that are pulverized under different pulverization conditions and have different mass average particle diameters. A method for producing pulverized coal for blast furnace injection.
(4) Blast furnace injection produced using the pulverized coal for blast furnace injection described in (1) above or by the method for producing pulverized coal for blast furnace injection described in (2) or (3) above. A blast furnace operating method for operating a blast furnace using pulverized coal, wherein the blast furnace blowing pulverized coal is blown into the blast furnace at 150 kg / ton-molten or more through a pipe connected to the blast furnace. Blast furnace operation method.

本発明によって、高炉内での微粉炭の燃焼性を向上させ、還元材比を低減させることを可能とする上に、輸送配管のうち特にベンド部が微粉炭で閉塞することを防止し、安定して高炉操業を可能とする。 According to the present invention, it is possible to improve the combustibility of pulverized coal in the blast furnace and reduce the reducing material ratio, and in addition, it is possible to prevent the bend portion of the transport piping from being blocked with pulverized coal, and to be stable. Thus, blast furnace operation is possible.

微粉炭供給設備を示す説明図である。It is explanatory drawing which shows pulverized coal supply equipment. 図１に示すベンド部に付着する微粉炭の機構を示す説明図である。It is explanatory drawing which shows the mechanism of the pulverized coal adhering to the bend part shown in FIG. 図１に示すベンド部を容易に通過可能とする微粉炭の機構を示す説明図である。It is explanatory drawing which shows the mechanism of the pulverized coal which can pass the bend part shown in FIG. 1 easily. 本発明の高炉吹込み用微粉炭について、質量基準で表した粒径分布の一例を示すグラフである。It is a graph which shows an example of the particle size distribution represented on the mass basis about the pulverized coal for blast furnace injection of this invention. 図４に示す粒径分布を累積分布で表し、粒子径の大きい部分を示すグラフである。It is a graph which shows the particle size distribution shown in FIG. 4 by cumulative distribution, and shows the part with a large particle diameter.

以下、添付図面を参照して本発明を具体的に説明する。図１は、高炉へ微粉炭を供給する微粉炭供給設備を示す説明図である。高炉１００の炉下部側壁には、羽口１０１が高炉の周方向に沿って複数設けられ、各羽口１０１には、熱風を送風するためのブローパイプ２１が接続されている。図１では、簡略化のためにブローパイプ２１が１つのみ羽口１０１に接続されている形態を示している。ブローパイプ２１には熱風炉２２が接続され、ブローパイプ２１への高温送風が可能となっており、ブローパイプ２１には、高炉吹込み用微粉炭７を吹き込むランス１５が挿入され設置されている。微粉炭７がランス１５を通じてブローパイプ２１に供給されるとともに、熱風炉２２からブローパイプ２１を通じて羽口１０１へ熱風が供給され、熱風とともに、微粉炭７が高炉１００へ吹き込まれる。 Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing a pulverized coal supply facility for supplying pulverized coal to a blast furnace. A plurality of tuyere 101 are provided on the furnace lower side wall of the blast furnace 100 along the circumferential direction of the blast furnace, and a blow pipe 21 for blowing hot air is connected to each tuyere 101. FIG. 1 shows a form in which only one blow pipe 21 is connected to the tuyere 101 for simplification. A hot stove 22 is connected to the blow pipe 21 so that high-temperature air can be blown into the blow pipe 21, and a lance 15 for blowing blast furnace pulverized coal 7 is inserted and installed in the blow pipe 21. . While the pulverized coal 7 is supplied to the blow pipe 21 through the lance 15, hot air is supplied from the hot blast furnace 22 to the tuyere 101 through the blow pipe 21, and the pulverized coal 7 is blown into the blast furnace 100 together with the hot air.

微粉炭供給設備１は、ランス１５と、該ランス１５に接続される輸送配管１０と、該輸送配管１０が接続され、粒径分布が相互に異なる２種の微粉炭２ａ，２ｂを混合して所定の粒径分布を有する微粉炭７を調製する微粉炭混合吹込装置６と、石炭２を前記微粉炭２ａ，２ｂに粉砕する粉砕機３と、微粉炭２ａ，２ｂを保管するホッパ４と、を有する。 The pulverized coal supply facility 1 includes a lance 15, a transport pipe 10 connected to the lance 15, and two pulverized coals 2a and 2b to which the transport pipe 10 is connected and the particle size distributions are different from each other. A pulverized coal mixing blowing device 6 for preparing pulverized coal 7 having a predetermined particle size distribution, a pulverizer 3 for pulverizing the coal 2 into the pulverized coal 2a, 2b, a hopper 4 for storing the pulverized coal 2a, 2b, Have

まず、石炭２を粉砕機３に供給する。この石炭２は、通常、複数銘柄（石炭種）からなり、ヤードなどに保管されている。本実施形態では、粉砕機３を２台用い、粉砕機（粗粉砕機）３ａで石炭２を砕いて粗粉炭２ａを作製し、粉砕機（微粉砕機）３ｂで石炭２を砕いて、粗粉炭２ａより粒径が細かい細粉炭２ｂを作製する。粉砕機３としては、ハンマーミルやボールミルなどの公知の機構を有する粉砕装置を採用することができる。 First, the coal 2 is supplied to the pulverizer 3. The coal 2 is usually composed of a plurality of brands (coal species) and stored in a yard or the like. In the present embodiment, two pulverizers 3 are used, the coal 2 is crushed by a pulverizer (coarse pulverizer) 3a to produce coarse pulverized coal 2a, and the coal 2 is crushed by a pulverizer (fine pulverizer) 3b. Fine pulverized coal 2b having a smaller particle diameter than pulverized coal 2a is produced. As the pulverizer 3, a pulverizer having a known mechanism such as a hammer mill or a ball mill can be employed.

次いで、粗粉炭２ａ及び細粉炭２ｂをそれぞれ保管するホッパ４（４ａ，４ｂ）に供給し貯留する。該ホッパ４ａ，４ｂの底部に設けられたフィーダ５で、貯留された粗粉炭２ａ及び細粉炭２ｂをそれぞれ適量切出して微粉炭混合吹込装置６に供給する。該微粉炭混合吹込装置６で、所定の質量基準の粒径分布を有するように、粗粉炭２ａ及び細粉炭２ｂを混合して、高炉吹込み用微粉炭７を調製（製造）する。 Next, the coarse pulverized coal 2a and the fine pulverized coal 2b are supplied to and stored in the hopper 4 (4a, 4b) for storing them. The feeders 5 provided at the bottoms of the hoppers 4a and 4b cut out appropriate amounts of the stored coarse pulverized coal 2a and fine pulverized coal 2b, respectively, and supply them to the pulverized coal mixing and blowing device 6. The pulverized coal mixing and blowing device 6 prepares (manufactures) blast furnace blowing pulverized coal 7 by mixing the coarse pulverized coal 2a and fine pulverized coal 2b so as to have a predetermined mass-based particle size distribution.

微粉炭混合吹込装置６には、輸送配管１０が接続され、該輸送配管１０はランス１５に接続していて、微粉炭混合吹込装置６からランス１５に向けて、キャリアガスで微粉炭７を輸送し、羽口１０１を通じて高炉１００へ吹き込む。輸送配管１０は、主管１０ａと、複数の羽口１０１に対応する本数の枝管１０ｂと、からなる。主管１０ａは、一端が微粉炭混合吹込装置６に接続され、別の一端が分配器１４に接続され、該分配器１４で枝分かれして複数の枝管１０ｂに繋がる。複数の枝管１０ｂは、１個の分配器１４から、それぞれ異なる位置の複数の羽口１０１に配置される複数のランス１５に接続するように構成されている。枝管１０ｂは直線状であることが好ましいが、ランス１５の位置によっては、複数のうち幾つかの枝管１０ｂを屈曲させて、該枝管１０ｂに、ある程度の曲率を有するベンド部１０ｃを設ける必要が生じてくる。 A transportation pipe 10 is connected to the pulverized coal mixing blowing device 6, and the transportation piping 10 is connected to a lance 15. The pulverized coal 7 is transported from the pulverized coal mixing blowing device 6 to the lance 15 with a carrier gas. Then, it blows into the blast furnace 100 through the tuyere 101. The transport pipe 10 includes a main pipe 10 a and a number of branch pipes 10 b corresponding to the plurality of tuyere 101. One end of the main pipe 10a is connected to the pulverized coal mixing blow-in device 6, and the other end is connected to the distributor 14. The distributor 14 branches off and connects to a plurality of branch pipes 10b. The plurality of branch pipes 10b are configured to be connected from one distributor 14 to a plurality of lances 15 arranged at a plurality of tuyere 101 at different positions. The branch pipe 10b is preferably straight, but depending on the position of the lance 15, some of the plurality of branch pipes 10b are bent, and the branch pipe 10b is provided with a bend portion 10c having a certain degree of curvature. The need arises.

高炉吹込み用微粉炭７は、燃焼性が高いことが望ましく、かつ、輸送配管１０に付着せずに輸送配管１０を容易に通過することが望ましい。高炉１００の内部には、熱風によってレースウエイと呼ばれる空間が羽口１０１の部分から形成され、該空間で微粉炭７の燃焼が行われ、燃焼しきれなかった炭素と灰分との集合体は未燃チャーとなり、該未燃チャーが多いと高炉の通気性が悪化する。この通気性の悪化は、吹き込まれる微粉炭７が容易に燃焼することで解消する。また、微粉炭７が、羽口１０１に供給される際に輸送配管１０に付着して堆積してしまうと、輸送配管１０で微粉炭７の輸送可能な量が減ってしまう上に、輸送配管１０で微粉炭７が堆積した状態を放置しておくと、堆積した微粉炭７が成長してしまい、微粉炭７で輸送配管１０が閉塞してしまう可能性があり、微粉炭７の吹き込み量が安定せず、高炉操業を安定して行うことができなくなる。例えば、微粉炭混合吹込装置６から分配器１４までの間で主管１０ａが閉塞した場合には、全羽口１０１からの微粉炭７の吹込みが不可能となり、高炉炉頂からのオールコークス装入操業に切り替えなければならず、炉内状況を安定化させるためには長時間を要する。また、枝管１０ｂのいずれかが閉塞すれば、炉内周方向で微粉炭吹込み量にバラツキが発生し、溶銑の成分変動や炉況不調の原因となる。特に、微粉炭吹込み量が多い高炉操業の場合には、減風や休風を余儀なくされて、減産その他大きな問題となる。微粉炭７が、輸送配管１０を容易に通過可能であれば、これらの問題は生じない。 It is desirable that the blast furnace blowing pulverized coal 7 has high combustibility and easily passes through the transport pipe 10 without adhering to the transport pipe 10. Inside the blast furnace 100, a space called a raceway is formed from the tuyere 101 by hot air, and the pulverized coal 7 is burned in the space, and an aggregate of carbon and ash that could not be burned is not yet formed. If it becomes a burning char and there is much this unburned char, the air permeability of a blast furnace will deteriorate. This deterioration in air permeability is solved by the easy combustion of the pulverized coal 7 to be blown. Further, if the pulverized coal 7 adheres to and accumulates on the transport pipe 10 when being supplied to the tuyere 101, the amount of the pulverized coal 7 that can be transported by the transport pipe 10 decreases, and the transport pipe. If the state in which the pulverized coal 7 is accumulated at 10 is left as it is, the accumulated pulverized coal 7 may grow, and the transportation pipe 10 may be blocked by the pulverized coal 7. However, the blast furnace operation cannot be performed stably. For example, when the main pipe 10a is blocked between the pulverized coal mixing blowing device 6 and the distributor 14, the pulverized coal 7 cannot be blown from all the tuyere 101, and all coke charging from the top of the blast furnace is not possible. It is necessary to switch to entry operation, and it takes a long time to stabilize the in-furnace situation. Moreover, if any of the branch pipes 10b is blocked, the amount of pulverized coal injection varies in the inner circumferential direction of the furnace, causing hot metal component fluctuations and furnace condition malfunction. In particular, in the case of blast furnace operation with a large amount of pulverized coal injection, it is forced to reduce the wind and pause, which causes a reduction in production and other major problems. If the pulverized coal 7 can easily pass through the transport pipe 10, these problems do not occur.

燃焼性を高めるためには、高炉吹込み用微粉炭を細かくすることが有効である。しかしながら、微粉炭は、細かくなるほど付着力は強くなり、輸送配管１０に付着しやすくなる。図２は、輸送配管１０のうち、特にベンド部１０ｃに付着する従来技術の高炉吹込み用微粉炭７’の機構を示す説明図である。ベンド部１０ｃを通過する際に、微粉炭７’は、ベンド部１０ｃの内壁、特に、曲率の大きい側に衝突してしまう。衝突が繰り返されると、始めのうちは内壁に微粉炭７’が付着するだけで済むが、そのうちに、付着した微粉炭７’に、更に微粉炭が付着し堆積していき、微粉炭７’が成長してしまう。ひいては、輸送配管１０が、成長した微粉炭７’で閉塞するおそれがある。ベンド部１０ｃへの微粉炭７’の付着のし易さは、微粉炭７’の粒径や銘柄、あるいは輸送配管１０の内壁の状態により異なっており、わずかな曲率のベンド部１０ｃであっても付着した微粉炭７’が成長する場合もあり、輸送配管１０の中心軸で曲率が０．１以上のベンド部１０ｃでも、微粉炭７’の付着による閉塞が生じる場合がある。なお、枝管１０ｂは直線状であることが好ましいので、ベント部１０ｃの曲率は、最大でも５（１／ｍ）としてある。 In order to improve combustibility, it is effective to make pulverized coal for blast furnace injection fine. However, the finer the pulverized coal, the stronger the adhesion, and the easier it is to adhere to the transport pipe 10. FIG. 2 is an explanatory diagram showing a mechanism of blast furnace blowing pulverized coal 7 ′ of the prior art adhering to the bend portion 10 c in the transport pipe 10. When passing through the bend portion 10c, the pulverized coal 7 'collides with the inner wall of the bend portion 10c, in particular, on the side with a large curvature. When the collision is repeated, the pulverized coal 7 'only needs to be attached to the inner wall at the beginning. However, pulverized coal further adheres and accumulates on the attached pulverized coal 7', and the pulverized coal 7 ' Will grow. As a result, there is a possibility that the transport pipe 10 may be clogged with the grown pulverized coal 7 '. The ease of attachment of the pulverized coal 7 'to the bend portion 10c differs depending on the particle size and brand of the pulverized coal 7' or the state of the inner wall of the transport pipe 10, and the bend portion 10c has a slight curvature. The adhering pulverized coal 7 ′ may grow, and even the bend portion 10 c having a curvature of 0.1 or more on the central axis of the transport pipe 10 may be clogged due to the adhering pulverized coal 7 ′. In addition, since it is preferable that the branch pipe 10b is linear, the curvature of the vent part 10c is 5 (1 / m) at the maximum.

そこで、本発明者らは、特にベンド部１０ｃにおける高炉吹込み用微粉炭７’の成長を阻害する方法を検討するとともに実験を繰り返し、本発明の完成に至った。本発明者らは、微粉炭７のうち、細粉炭２ｂの質量割合を多くしつつも、細粉炭２ｂよりも粒径が大きい粗粉炭２ａを加えておくことに想到した。図３は、ベンド部１０ｃを容易に通過可能とする微粉炭７の機構を示す説明図である。微粉炭７がベンド部１０ｃの内壁に衝突し、その衝突が繰り返されると、内壁に細粉炭２ｂが付着することになるが、そのうちに、粗粉炭２ａが、内壁に付着した細粉炭２ｂに衝突して、細粉炭２ｂの成長を阻害する。微粉炭７の粒子のエネルギーは粒径に比例し、粒子は直線的に流れるので、細粉炭２ｂが堆積する部分に衝突し、その部分が剥がれるので、細粉炭２ｂの成長が防止される。粒径が大きいほどエネルギーが大きく、細粉炭２ｂの成長を防止する効果が高い。 Therefore, the present inventors examined a method for inhibiting the growth of blast furnace blowing pulverized coal 7 'particularly in the bend portion 10c, and repeated the experiment, thereby completing the present invention. The inventors of the present invention have conceived of adding pulverized coal 2a having a larger particle size than pulverized coal 2b while increasing the mass ratio of pulverized coal 2b in pulverized coal 7. FIG. 3 is an explanatory view showing a mechanism of the pulverized coal 7 that can easily pass through the bend portion 10c. When the pulverized coal 7 collides with the inner wall of the bend portion 10c and the collision is repeated, the pulverized coal 2b adheres to the inner wall, but the pulverized coal 2a collides with the pulverized coal 2b attached to the inner wall. Then, the growth of the fine coal 2b is inhibited. The energy of the particles of the pulverized coal 7 is proportional to the particle size, and the particles flow linearly. Therefore, the particles collide with the portion where the pulverized coal 2b is deposited, and the portion is peeled off, so that the growth of the pulverized coal 2b is prevented. The larger the particle size, the larger the energy and the higher the effect of preventing the growth of the fine coal 2b.

本発明の微粉炭７は、質量基準の粒径分布で、粒径が４５μｍ以下となる粒子の質量割合が４５質量％以上となり、粒子径が３２５μｍ以上となる粒子の質量割合が１．５質量％以上となる粒径分布を有する。図４は、高炉吹込み用微粉炭７の粒径分布の一例を示すグラフであり、図５は、図４に示す粒径分布を累積分布で表し、粒子径の大きい部分を示すグラフである。図４及び図５のグラフには、従来技術の高炉吹込み用微粉炭７’の粒径分布も示してある。図４のグラフによれば、微粉炭７’に比べて、微粉炭７は、粒径が１００μｍ以上３２５μｍ未満となる微粉炭の質量割合が小さく、粒径が３２５μｍ以上となる微粉炭の質量割合が大きい。また、図５のグラフによれば、微粉炭７は、粒径が３２５μｍ以上となる微粉炭の質量割合は２％以上あるが、微粉炭７’では、粒径が３２５μｍ以上となる微粉炭の質量割合が１．５％未満である。すなわち、微粉炭７は、微粉炭７’よりも、細粉炭２ｂの成長防止に効果的な粗粉炭２ａ（粒径が３２５μｍ以上）の質量割合が大きい。 The pulverized coal 7 of the present invention has a mass-based particle size distribution, the mass ratio of particles having a particle diameter of 45 μm or less is 45 mass% or more, and the mass ratio of particles having a particle diameter of 325 μm or more is 1.5 mass. % Particle size distribution. FIG. 4 is a graph showing an example of the particle size distribution of the blast furnace-injecting pulverized coal 7, and FIG. 5 is a graph showing the particle size distribution shown in FIG. . The graphs of FIGS. 4 and 5 also show the particle size distribution of pulverized coal 7 'for blast furnace injection according to the prior art. According to the graph of FIG. 4, the pulverized coal 7 has a smaller mass ratio of the pulverized coal having a particle size of 100 μm or more and less than 325 μm and a mass ratio of the pulverized coal having a particle size of 325 μm or more, compared to the pulverized coal 7 ′. Is big. Moreover, according to the graph of FIG. 5, although the pulverized coal 7 has a mass ratio of 2% or more of the pulverized coal having a particle size of 325 μm or more, the pulverized coal 7 ′ has a particle size of 325 μm or more. The mass ratio is less than 1.5%. That is, the pulverized coal 7 has a larger mass ratio of the coarse pulverized coal 2a (particle diameter of 325 μm or more) effective in preventing the growth of the fine pulverized coal 2b than the pulverized coal 7 '.

微粉炭７は、粒子径が４５μｍ以下となる粒子の質量割合が４５質量％以上であれば、細粉炭２ｂの割合が大きいので、高炉１００内での微粉炭７の燃焼性を向上させて、高炉の通気性の悪化を防ぐことができる。しかしながら、特に、輸送配管１０のベンド部１０ｃに付着しやすくなってしまう。そこで、更に、微粉炭７を、粒径が３２５μｍ以上の質量割合を１．５質量％以上とする粒度分布とする。粒径が３２５μｍ以上の質量割合を１．５質量％以上とするためには、粒子径が４５μｍ以下となる粒子の質量割合が９８．５質量％未満である必要がある。また、微粉炭７は、粒径が３２５μｍ以上の質量割合が１．５質量％未満となってしまうと、粒子径が４５μｍ以下となる粒子の質量割合が４５質量％以上であっても、輸送配管１０への微粉炭７の付着を防止しにくくなってしまう。 The pulverized coal 7 has a large proportion of fine pulverized coal 2b if the mass ratio of the particles having a particle diameter of 45 μm or less is 45% by mass or more, thereby improving the combustibility of the pulverized coal 7 in the blast furnace 100, Deterioration of air permeability of the blast furnace can be prevented. However, in particular, it tends to adhere to the bend portion 10 c of the transport pipe 10. Therefore, the pulverized coal 7 is further set to a particle size distribution in which the mass ratio of the particle size of 325 μm or more is 1.5 mass% or more. In order to set the mass ratio of the particle diameter of 325 μm or more to 1.5 mass% or more, the mass ratio of the particles having a particle diameter of 45 μm or less needs to be less than 98.5 mass%. The pulverized coal 7 is transported when the mass ratio of the particle size is 325 μm or more is less than 1.5 mass%, even if the mass ratio of the particles having a particle diameter of 45 μm or less is 45 mass% or more. It becomes difficult to prevent the pulverized coal 7 from adhering to the pipe 10.

また、微粉炭７は、粒径が３２５μｍ以上の粒子の質量割合が５．０質量％以下であることが好ましい。微粉炭７は、粒径が３２５μｍ以上の質量割合が５．０質量％以下であれば、高炉１００内での微粉炭７の燃焼性を悪化させることなく、輸送配管１０への微粉炭７の付着を防止する効果を奏する。特に、近年の高炉操業においては、１５０ｋｇ／トン−溶銑以上のように、微粉炭７を多量に高炉１００に吹込んでおり、そのような場合に、本発明は特に有効である。なぜならば、微粉炭７を多量に吹き込むので、燃焼性を向上させる必要があり微粉炭７を細かくする必要があるが、そうすると、微粉炭７の付着力はより強くなってしまう。しかしながら、そういう場合であっても、輸送配管１０に付着した微粉炭７が成長することを効果的に防止し得る。なお、粒径３２５μｍ以上の微粉炭といえども、粗粉砕機で粉砕されるので、あまり大きな粒径となることはなく、特段粒径の上限を設定する必要はない。しかしながら、微粉炭混合吹込装置６から羽口１０１まで気流輸送することとなるため、１ｍｍ以下とすることが好ましい。 Moreover, as for the pulverized coal 7, it is preferable that the mass ratio of the particle | grains whose particle size is 325 micrometers or more is 5.0 mass% or less. If pulverized coal 7 has a particle size of 325 μm or more and a mass ratio of 5.0% by mass or less, pulverized coal 7 in transportation pipe 10 is not deteriorated in combustibility of pulverized coal 7 in blast furnace 100. There is an effect of preventing adhesion. In particular, in recent blast furnace operations, a large amount of pulverized coal 7 is blown into the blast furnace 100 such as 150 kg / ton-molten iron or more. In such a case, the present invention is particularly effective. This is because, since a large amount of pulverized coal 7 is blown, it is necessary to improve combustibility and to make the pulverized coal 7 finer, but in that case, the adhesion of the pulverized coal 7 becomes stronger. However, even in such a case, it is possible to effectively prevent the pulverized coal 7 attached to the transport pipe 10 from growing. Note that even pulverized coal having a particle size of 325 μm or more is pulverized by a coarse pulverizer, so that the particle size does not become too large, and there is no need to set an upper limit of the special particle size. However, since the air is transported from the pulverized coal mixing blower 6 to the tuyere 101, it is preferable to set it to 1 mm or less.

質量基準の粒径分布で、粒径が４５μｍ以下となる粒子の質量割合が４５質量％以上となり、粒子径が３２５μｍ以上となる粒子の質量割合が１．５質量％以上となる粒径分布を有する微粉炭７を調整するためには、石炭２の硬さと粉砕機３の粉砕力などを適宜選択する。原料とする石炭２として多様な銘柄のものを使用できることが望ましく、微粉炭７の粒径分布は、粉砕機３の粉砕力を調整して、粗粉炭２ａ及び細粉炭２ｂの粒径分布を調整し、この粗粉炭２ａ及び細粉炭２ｂの混合割合を適宜調整することで、微粉炭７を上記の粒径分布と調製することが可能である。粗粉炭２ａは、ハードグローブ指数ＨＧＩが５０未満の比較的硬い石炭を砕くことで作製することが好ましい。これにより、粗粉砕機３ａの動力の低減を図ることができる。 In a particle size distribution based on mass, a particle size distribution in which the mass ratio of particles having a particle diameter of 45 μm or less is 45 mass% or more, and the mass ratio of particles having a particle diameter of 325 μm or more is 1.5 mass% or more. In order to adjust the pulverized coal 7 having, the hardness of the coal 2 and the pulverizing force of the pulverizer 3 are appropriately selected. It is desirable that various brands of coal 2 can be used as the raw material, and the particle size distribution of the pulverized coal 7 is adjusted by adjusting the pulverization force of the pulverizer 3 to adjust the particle size distribution of the coarse coal 2a and the fine coal 2b. The pulverized coal 7 can be prepared with the above particle size distribution by appropriately adjusting the mixing ratio of the coarse coal 2a and the fine coal 2b. Coarse coal 2a is preferably produced by crushing relatively hard coal having a hard glove index HGI of less than 50. As a result, the power of the coarse pulverizer 3a can be reduced.

粗粉炭２ａと微粉炭２ｂとは、質量平均粒径が異なるように２種類以上の粉砕条件で粉砕されることが好ましい。質量平均粒径とは、例えば、図４に示す、横軸を粒径、縦軸を質量割合とした、質量基準の粒径分布の曲線を、粒径の最小値から最大値まで積分し、１００で除算した値を意味する。 Coarse coal 2a and pulverized coal 2b are preferably pulverized under two or more types of pulverization conditions so that the mass average particle diameter is different. The mass average particle size is, for example, shown in FIG. 4, integrating a mass-based particle size distribution curve with the horizontal axis as the particle size and the vertical axis as the mass ratio, from the minimum value to the maximum value of the particle size, It means the value divided by 100.

本発明における微粉炭の粒径とは、ふるい分け法によって測定した試験用ふるいの目開きで表したものを使用している。粉粒体の粒径には、沈降法によるストークス相当径で表したもの、顕微鏡法による円相当径で表したもの及び光散乱法による球相当、並びに電気抵抗試験方法による球相当値で表したもの、レーザー回折式粒度分布測定装置を用いて計測したものなどの、様々な計測装置・方法がある。計測装置・測定方法により粒径の値は必ずしも一致しないが、これら多様な粒径測定を工程的に行いながら本発明を実施する場合には、ふるい分け法による粒径とそれらの工程的に行う粒径測定法により求まる粒径との間の相関を予め把握しておき、ふるい分け法における粒径として３２５μｍ、４５μｍに相当する値で管理すればよい。 The particle size of the pulverized coal in the present invention is the one represented by the mesh size of the test sieve measured by the sieving method. The particle size of the granular material is represented by the equivalent Stokes diameter by the sedimentation method, the equivalent circle diameter by the microscopic method, the equivalent sphere by the light scattering method, and the equivalent sphere value by the electrical resistance test method. There are various measuring devices and methods such as those measured using a laser diffraction type particle size distribution measuring device. The particle size values do not necessarily match depending on the measuring device / measurement method, but when carrying out the present invention while performing these various particle size measurements step by step, the particle sizes obtained by the screening method and the particles to be processed step by step What is necessary is just to grasp | ascertain beforehand the correlation between the particle size calculated | required by the diameter measuring method, and to manage by the value equivalent to 325 micrometers and 45 micrometers as a particle size in a sieving method.

本実施形態では、高炉吹込み用微粉炭７の基となる微粉炭は、粗粉炭２ａ及び細粉炭２ｂの２種類からなることとしたが、本発明はこの形態に限られるものではない。微粉炭７が、質量基準の粒径分布で、粒子径が４５μｍ以下となる粒子の質量割合が４５質量％以上となり、粒子径が３２５μｍ以上となる粒子の質量割合が１．５質量％以上となる粒径分布を有すれば、高炉での燃焼性を確保し得る上に、ベンド部１０ｃでの閉塞を防ぐことができるので、高炉吹込み用微粉炭７の基となる微粉炭は１種類からなるようにしてもよく、３種類以上からなるようにしてもよい。微粉炭７が１種類からなれば、微粉炭混合吹込装置６は不要となる上に、粉砕機３及びホッパ４が１台で足りるので、設備のメンテナンス作業を省き得る点が有利である。また、上記実施形態では、２種類の微粉炭２ａ，２ｂをそれぞれ粉砕しまたは保管する粉砕機及びホッパを、２台ずつ設けてあるが、高炉吹込み用微粉炭７を３種類以上の微粉炭を混合して調製するならば、微粉炭７の粒径分布の微調整はより容易になる。その場合には、高炉吹き込み用微粉炭７の基となる微粉炭の種類数に適宜合わせた台数の粉砕機及びホッパを微粉炭供給設備１に設ければよい。 In this embodiment, although the pulverized coal used as the basis of the blast furnace blowing pulverized coal 7 is composed of two types of coarse pulverized coal 2a and fine pulverized coal 2b, the present invention is not limited to this embodiment. The pulverized coal 7 has a mass-based particle size distribution, the mass ratio of particles having a particle diameter of 45 μm or less is 45 mass% or more, and the mass ratio of particles having a particle diameter of 325 μm or more is 1.5 mass% or more. If the particle size distribution is such that flammability in the blast furnace can be ensured and blockage at the bend portion 10c can be prevented, one kind of pulverized coal that serves as the basis for the blast furnace blowing pulverized coal 7 is used. It may be made up of three or more kinds. If the pulverized coal 7 is composed of one type, the pulverized coal mixing blow-in device 6 is not necessary, and the pulverizer 3 and the hopper 4 are sufficient, so that it is advantageous in that the maintenance work of the facilities can be omitted. In the above embodiment, two pulverizers and two hoppers for pulverizing or storing the two types of pulverized coal 2a and 2b are provided, respectively. However, the blast furnace blowing pulverized coal 7 includes three or more types of pulverized coal. If the mixture is prepared, fine adjustment of the particle size distribution of the pulverized coal 7 becomes easier. In that case, the pulverized coal supply facility 1 may be provided with a number of pulverizers and hoppers appropriately matched to the number of types of pulverized coal used as the basis of the blast furnace blowing pulverized coal 7.

以上のように、本発明によって、高炉内での微粉炭の燃焼性を向上させ、還元材比を低減させることを可能とする上に、微粉炭輸送配管のうち、特にベンド部が微粉炭で閉塞することを防止し、安定した高炉操業を可能とする。 As described above, according to the present invention, it is possible to improve the combustibility of pulverized coal in the blast furnace and reduce the reducing material ratio, and in addition, the bend portion of the pulverized coal transport pipe is particularly pulverized coal. Prevents clogging and enables stable blast furnace operation.

図１に示す微粉炭供給設備１を用いて、高炉１００に微粉炭７を吹き込みつつ、高炉１００に焼結鉱及びコークスを投入して溶銑を得る高炉操業を行った（本発明例１）。粉砕機３ａ，３ｂはローラーミルを用いた。粉砕機３ａ，３ｂで砕く粗粉炭２ａ及び細粉炭２ｂの粒度分布、及び、微粉炭混合吹込装置６でのこれらの混合割合を適宜調製して、粒子径が４５μｍ以下となる粒子の質量割合が５０質量％、粒子径が３２５μｍ以上となる粒子の質量割合が１．８質量％となる粒径分布を有するように、微粉炭７を調製した。この高炉操業においては、出銑比が２．２［トン−溶銑／（日・ｍ^３）］となるように、高炉１００に、焼結鉱及びコークスを投入し、微粉炭７を、１６０ｋｇ／トン−溶銑で高炉１００に吹き込んだ（本発明例１）。 Using the pulverized coal supply facility 1 shown in FIG. 1, blast furnace operation was performed in which sinter and coke were introduced into the blast furnace 100 and molten iron was obtained while blowing the pulverized coal 7 into the blast furnace 100 (Invention Example 1). The crushers 3a and 3b used roller mills. The particle size distribution of the coarse coal 2a and the fine coal 2b to be crushed by the pulverizers 3a and 3b, and the mixing ratio thereof in the pulverized coal mixing and blowing device 6 are appropriately prepared so that the mass ratio of the particles having a particle diameter of 45 μm or less is obtained. Pulverized coal 7 was prepared so as to have a particle size distribution in which the mass ratio of particles with a particle size of 50% by mass and 325 μm or more was 1.8% by mass. In this blast furnace operation, sinter and coke are charged into the blast furnace 100 so that the output ratio is 2.2 [tons-molten metal / (day · m ³ )], and pulverized coal 7 is added at 160 kg / Ton-hot metal was blown into the blast furnace 100 (Invention Example 1).

また、粗粉炭２ａ及び細粉炭２ｂの粒度分布及び混合割合を適宜変更し、高炉１００へ吹き込まれる微粉炭での、粒径が４５μｍ以下となる粒子の質量割合、及び、粒径が３２５μｍ以上となる粒子の質量割合を、変更した以外は本発明例１と同様にして、複数の高炉操業を行った（本発明例２，３及び比較例１〜３）。高炉１００には羽口１０１が４０個設けられており、この個数に対応して、枝管１０ｂが４０本存在している。全高炉操業において、この枝管１０ｂのうち、曲率が５（１／ｍ）以下となるベンド部１０ｃが２０箇所ある。この２０箇所が閉塞するか否かも評価した。変更した粒子の質量割合、高操業の結果、及び、閉塞評価を、表１に示す。 In addition, the particle size distribution and mixing ratio of the coarse coal 2a and the fine coal 2b are appropriately changed, and the mass proportion of particles with a particle size of 45 μm or less in the pulverized coal blown into the blast furnace 100, and the particle size is 325 μm or more. A plurality of blast furnace operations were performed in the same manner as Example 1 except that the mass ratio of the particles to be changed was changed (Invention Examples 2 and 3 and Comparative Examples 1 to 3). The blast furnace 100 is provided with 40 tuyere 101, and there are 40 branch pipes 10b corresponding to this number. In the entire blast furnace operation, there are 20 bend portions 10c having a curvature of 5 (1 / m) or less in the branch pipe 10b. It was also evaluated whether or not these 20 places were blocked. Table 1 shows the mass ratio of the changed particles, the results of the high operation, and the blockage evaluation.

表１における「項目（Ａ）」は、粒径が４５μｍ以下となる粒子の質量割合を表し、「項目（Ｂ）は、粒径が３２５μｍ以上となる粒子の質量割合を表す。 “Item (A)” in Table 1 represents a mass ratio of particles having a particle diameter of 45 μm or less, and “Item (B) represents a mass ratio of particles having a particle diameter of 325 μm or more.

表１における「通気抵抗指数」は、Ｋ＝（Ｐ_Ｂ ^２−Ｐ_Ｔ ^２）／Ｖ^１．７×１００で表される。
ここで、Ｐ_Ｂ：送風圧（ｋＰａ）、
Ｐ_Ｔ：炉頂圧（ｋＰａ）、
Ｖ：送風量（Ｎｍ^３／分）である。
この通気抵抗指数が高いと、微粉炭の燃焼性が悪化し、未燃チャーが多くなったせいで、通気性が悪化したものと推測される。 The “ventilation resistance index” in Table 1 is represented by K = (P _B ² −P _T ² ) / V ^1.7 × 100.
Here, P _B : blowing pressure (kPa),
P _T : furnace top pressure (kPa),
V: Air flow rate (Nm ³ / min).
When this ventilation resistance index is high, it is presumed that the flammability of pulverized coal deteriorated and the breathability deteriorated due to an increase in unburned char.

また、表１における「閉塞評価」は、輸送配管１０の閉塞評価を意味し、次の基準で評価した。
◎：６時間の間、輸送配管１０に閉塞が一切発生しなかった。
○：６時間のうちに、１箇所のベンド部１０ｃに閉塞が確認された。
×：６時間のうちに、２箇所以上のベンド部１０ｃに閉塞が確認された。
１日の高炉操業において、複数回出銑を行うが、各出銑を開始する時間間隔は概ね６時間であり、６時間、輸送配管１０が閉塞しなければ、問題は発生しなかったとみなす。 Moreover, “clogging evaluation” in Table 1 means clogging evaluation of the transport pipe 10 and was evaluated according to the following criteria.
A: No blockage occurred in the transport pipe 10 for 6 hours.
A: Blocking was confirmed in one bend portion 10c within 6 hours.
X: Blocking was confirmed in two or more bend portions 10c within 6 hours.
In the daily blast furnace operation, brewing is performed a plurality of times, and the time interval for starting each brewing is approximately 6 hours. If the transportation pipe 10 is not blocked for 6 hours, it is considered that no problem has occurred.

本発明例１〜３は、微粉炭７は、粒子径が４５μｍ以下となる粒子の質量割合が４５質量％以上となり、粒子径が３２５μｍ以上となる粒子の質量割合が１．５質量％以上となる粒径分布を有し、本発明の要件を満たす。一方で、比較例１〜３は、高炉１００に吹き込まれる微粉炭は、粒子径が４５μｍ以下となる粒子の質量割合が４５質量％未満、及び／または、粒子径が３２５μｍ以上となる粒子の質量割合が１．５質量％未満、となる粒径分布を有する。 In Invention Examples 1 to 3, the pulverized coal 7 has a mass ratio of particles with a particle diameter of 45 μm or less of 45 mass% or more, and a mass ratio of particles with a particle diameter of 325 μm or more is 1.5 mass% or more. Satisfying the requirements of the present invention. On the other hand, in Comparative Examples 1 to 3, the pulverized coal blown into the blast furnace 100 has a mass ratio of particles with a particle diameter of 45 μm or less and / or a particle diameter of 325 μm or more. The particle size distribution is such that the ratio is less than 1.5% by mass.

本発明例１では、微粉炭７は、粒子径が４５μｍ以下となる粒子の質量割合が４５質量％以上となり、粒子径が３２５μｍ以上となる粒子の質量割合が１．５質量％以上となる粒径分布を有する一方で、比較例１では、微粉炭７は、粒子径が４５μｍ以下となる粒子の質量割合が４５質量％未満、及び、粒子径が３２５μｍ以上となる粒子の質量割合が１．５質量％未満、である。本発明例１では、通気抵抗指数は０．９２と低く抑えられ、閉塞評価も◎と良好であった。一方で、比較例１では、通気抵抗指数も本発明例１の場合よりも高い上に、閉塞評価も×となった。この比較例１では微粉炭の配管閉塞に伴い微粉炭吹き込み量が低下してしまうので、本発明例１の場合と比べて、炉頂から投入するコークス量を多めにしておく必要があり、還元材比も高めに推移した。 In Invention Example 1, the pulverized coal 7 is a particle having a mass ratio of particles with a particle diameter of 45 μm or less and 45 mass% or more, and a mass ratio of particles with a particle diameter of 325 μm or more is 1.5 mass% or more. While having a diameter distribution, in Comparative Example 1, the pulverized coal 7 has a mass ratio of particles having a particle diameter of 45 μm or less of less than 45 mass% and a mass ratio of particles having a particle diameter of 325 μm or more of 1. Less than 5% by weight. In Example 1 of the present invention, the airflow resistance index was kept low at 0.92, and the blockage evaluation was also good as ◎. On the other hand, in Comparative Example 1, the airflow resistance index was higher than that of Example 1 of the present invention, and the blockage evaluation was x. In Comparative Example 1, since the amount of pulverized coal injection decreases as the pulverized coal is blocked, it is necessary to increase the amount of coke introduced from the top of the furnace as compared with Example 1 of the present invention. The ratio of materials was also high.

本発明例２及び比較例２ではともに、微粉炭は、粒子径が３２５μｍ以上となる粒子の質量割合が１．５質量％以上となっており、閉塞評価はともに良好である。しかしながら、比較例２では、粒子径が４５μｍ以下となる粒子の質量割合が４５質量％未満である一方で、本発明例２では、その粒子の割合が４５質量％以上である。比較例２では、通気抵抗指数は１．０に達してしまう一方で、本発明例２では、通気抵抗指数は１．０未満を確保できた。通気抵抗指数が上がった理由は、細粒の微粉炭の割合が低下した分、粗粒の微粉炭の割合を増加させた結果、微粉炭の燃焼性が悪化し未燃チャーが比較的多くなったからと推察される。比較例２では、このような通気性悪化による送風圧力の増加や不安定が生じるため、本発明例２に比べて還元材比がやや増加した。 In both Invention Example 2 and Comparative Example 2, the pulverized coal has a mass ratio of particles with a particle diameter of 325 μm or more of 1.5% by mass or more, and both evaluations of blockage are good. However, in Comparative Example 2, the mass ratio of particles having a particle diameter of 45 μm or less is less than 45 mass%, while in Inventive Example 2, the ratio of the particles is 45 mass% or more. In Comparative Example 2, the airflow resistance index reached 1.0, while in Example 2 of the present invention, the airflow resistance index was less than 1.0. The reason why the airflow resistance index has increased is that the proportion of fine pulverized coal has been increased and the proportion of coarse pulverized coal has been increased. As a result, the combustibility of pulverized coal has deteriorated and unburned char has become relatively large. It is presumed that In Comparative Example 2, since the increase in air pressure and instability due to such deterioration in air permeability occurred, the ratio of the reducing material slightly increased compared to Example 2 of the present invention.

本発明例３及び比較例３ではともに、微粉炭は、粒子径が４５μｍ以下となる粒子の質量割合が４５質量％以上となっている。本発明例３では、更に、微粉炭は、粒子径が３２５μｍ以上となる粒子の質量割合が１．５質量％以上であるので、閉塞評価は○となった上に、通気抵抗指数は１．０未満を確保できている。一方で、比較例３では、その粒子の質量割合が１．５質量％未満であり、閉塞評価は×となり、輸送配管１０のベンド部１０ｃの幾らかが閉塞してしまったことがわかるし、通気抵抗指数は１．０以上となってしまった。本発明例３及び比較例３を比較すればわかるように、閉塞評価が×であると、粒子径が４５μｍ以下となる粒子の質量割合が同じであっても、通気抵抗指数は大きく変わる。輸送配管の一部に閉塞が生じて、羽口の全てに同じように微粉炭を供給できない場合、高炉１００内における、円周方向でのコークスの燃焼状態が不均一になるので、炉内の通気が不安定となり、ひいては、通気抵抗指数が高くなってしまったものと推察される。なお、本発明例では、１５０ｋｇ／トン−溶銑を超えた１６０ｋｇ／トン−溶銑で、微粉炭７を高炉１００に多量に吹き込んでいるにも拘らず、閉塞評価を良好とした上に、通気抵抗指数を抑え、還元材比も低くすることができたことがわかる。 In both Invention Example 3 and Comparative Example 3, the pulverized coal has a mass ratio of particles with a particle diameter of 45 μm or less of 45% by mass or more. In Invention Example 3, since the pulverized coal has a mass ratio of particles having a particle diameter of 325 μm or more of 1.5% by mass or more, the blockage evaluation is ○, and the ventilation resistance index is 1. Less than 0 can be secured. On the other hand, in Comparative Example 3, the mass ratio of the particles is less than 1.5% by mass, the blockage evaluation is x, and it can be seen that some of the bend portions 10c of the transport pipe 10 have been blocked, The ventilation resistance index was 1.0 or more. As can be seen from a comparison between Invention Example 3 and Comparative Example 3, when the occlusion evaluation is x, the airflow resistance index greatly changes even if the mass ratio of the particles having a particle diameter of 45 μm or less is the same. When clogging occurs in a part of the transport pipe and pulverized coal cannot be supplied to all of the tuyers in the same manner, the combustion state of the coke in the circumferential direction in the blast furnace 100 becomes uneven. It is presumed that the ventilation became unstable, and as a result, the ventilation resistance index increased. In the example of the present invention, although the blast furnace 100 was blown in a large amount of pulverized coal 7 at 160 kg / tonne hot metal exceeding 150 kg / tonne hot metal, the airflow resistance was improved. It can be seen that the index could be reduced and the reducing material ratio could be lowered.

上記の評価結果から、本発明の微粉炭を高炉に吹き込めば、高炉内での微粉炭の燃焼性を向上させ、通気抵抗指数を抑え還元材比を低減させることを可能とする上に、微粉炭輸送配管のうち、特にベンド部が微粉炭で閉塞することを防止し、安定した高炉操業を可能であることがわかる。 From the above evaluation results, if the pulverized coal of the present invention is blown into the blast furnace, it is possible to improve the flammability of the pulverized coal in the blast furnace, reduce the air flow resistance index, and reduce the reducing material ratio. It can be seen that, among the charcoal transport pipes, the bend portion is prevented from being blocked with pulverized coal, and stable blast furnace operation is possible.

１微粉炭供給設備
２石炭
２ａ微粉炭（粗粉炭）
２ｂ微粉炭（細粉炭）
３粉砕機
３ａ粉砕機（粗粉砕機）
３ｂ粉砕機（微粉砕機）
４ａホッパ
４ｂホッパ
５フィーダ
６微粉炭混合吹込装置
７高炉吹込み用微粉炭（本発明）
７’ 高炉吹込み用微粉炭（従来技術）
１０輸送配管
１０ａ主管
１０ｂ枝管
１０ｃベンド部
１４分配器
１５ランス
２１ブローパイプ
２２熱風炉
１００高炉
１０１羽口 1 Pulverized coal supply equipment 2 Coal 2a Pulverized coal (Coarse coal)
2b pulverized coal (fine pulverized coal)
3 Crusher 3a Crusher (Coarse Crusher)
3b Crusher (fine crusher)
4a hopper 4b hopper 5 feeder 6 pulverized coal mixing blowing device 7 pulverized coal for blast furnace blowing (present invention)
7 'Pulverized coal for blast furnace injection (prior art)
DESCRIPTION OF SYMBOLS 10 Transport piping 10a Main pipe 10b Branch pipe 10c Bend part 14 Distributor 15 Lance 21 Blow pipe 22 Hot stove 100 Blast furnace 101 tuyere

Claims

In the mass-based particle size distribution, the mass ratio of particles having a particle diameter of 45 μm or less is 45 mass% or more, and the mass ratio of particles having a particle diameter of 325 μm or more and 1 mm or less is 1.5 mass% or more and 5.0 mass A pulverized coal for blast furnace injection, characterized by having a particle size distribution of not more than% .

A method for producing pulverized coal for blast furnace injection,
In the mass-based particle size distribution, the mass ratio of particles having a particle diameter of 45 μm or less is 45 mass% or more, and the mass ratio of particles having a particle diameter of 325 μm or more and 1 mm or less is 1.5 mass% or more and 5.0 mass A method for producing pulverized coal for blast furnace injection, characterized in that pulverized coal for blast furnace injection is prepared so as to have a particle size distribution of not more than% .

The pulverized coal for blast furnace injection according to claim 2, wherein the pulverized coal for blast furnace injection is prepared by mixing two or more types of pulverized coal that are pulverized under different pulverization conditions and different in mass average particle diameter. A method for producing pulverized coal.

Using the pulverized coal for blast furnace injection according to claim 1, or using the pulverized coal for blast furnace injection manufactured by the method for producing pulverized coal for blast furnace injection according to claim 2 or claim 3. A blast furnace operating method for operating a blast furnace,
A blast furnace operating method, wherein the pulverized coal for blowing blast furnace is blown into the blast furnace at a rate of 150 kg / ton-molten or more through a pipe connected to the blast furnace.