JP2004250721A - Method for pretreating molten iron and lance for pretreatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for pretreating molten iron and a lance for pretreatment using this performance of this method with which the improvement of efficiency can be achieved at more than that of the conventional method by only applying a simple idea to a blowing means of powdery and granular refining agent. <P>SOLUTION: When the pretreatment is performed to the molten iron by blowing the powdery and granular refining agent 7 together with carrier gas 5 from the tip opening hole 13 in the horizontal part of the lance 2 for blowing the refining agent submerged by inclining into the molten iron held in a refining vessel, at the horizontal position except the tip opening hole, or on the upper half surface of the peripheral wall at bending position from the inclining part to the horizontal part, an another opening hole with the above opening hole, is arranged and mainly a part of the carrier gas is exhausted into the molten iron from the another opening hole 9 and the remaining carrier gas and the refining agent, are blown from the tip opening hole. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２３】
【表２】

【００２４】
操業の結果は、脱燐反応速度定数（下記（１）式で定義）で評価し、吹き込んだ酸化鉄の酸素を気体酸素に換算した酸素供給速度に対応させて図２に整理した。図２より、本発明によれば、脱燐反応速度定数が従来のランスを利用した場合に比べ１．４倍になり、脱燐が促進されることが明らかである。ちなみに、脱燐後の溶銑の組成を、従来ランスを使用した場合での組成と比較し、表３に示しておく。
【００２５】
【表３】

【００２６】
Ｋｐ＝ｌｎ（Ｐｉ／Ｐｆ）Ｗｏ_２ （１）
ここで、Ｋｐ：脱燐反応速度定数
Ｐｉ：処理前の溶銑中燐濃度（質量％）
Ｐｆ：処理後の溶銑中燐濃度（質量％）
Ｗｏ_２：脱珪外（脱珪時を除く）脱燐時に供給した酸素原単位（ｍ^３（標準状態）／ｔｏｎ）
【００２７】
【発明の効果】
以上述べたように、本発明により、高固気比での粉粒状精錬剤の吹き込みが安定して行えるばかりでなく、該精錬剤と溶銑との接触機会が増え、従来より脱燐効率や脱硫効率の向上が達成できるようになる。
【図面の簡単な説明】
【図１】本発明に係る溶銑の予備処理用ランスを示す模式図である。
【図２】本発明の実施効果を示す図である。
【図３】搬送用ガスの分離器を備えた溶銑の予備処理装置を示す横断面図である。
【図４】搬送用ガスの分離機能を備えた精錬剤吹き込みランスの継手を示す横断面図である。
【図５】精錬剤吹き込みランスの水平部の縦断面を示す図である。
【符号の説明】
１ 吹き込みタンク
２ ガス吹き込み用ランス
３ 中間経路
４ ガス分離器
５ 搬送ガス
６ 配管
７ 精錬剤
８ 混銑車（トピード・カー）
９ 別の開口
１０ ランス水平部の縦断面
１１ 上下の仕切り線
１２ 水平部
１３ 先端開口
１４ 溶銑
１５ 気泡[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pretreatment method and a lance for pretreatment of hot metal for dephosphorizing or desulfurizing hot metal, and in particular, blowing a powdery and granular refining agent through a lance immersed in hot metal held in a mixed iron wheel, The present invention relates to a technique for efficiently performing a preliminary treatment of a slab.
[0002]
[Prior art]
In recent years, in steelmaking, in order to reduce the refining load and operating cost in a converter, so-called “hot metal pretreatment” in which desiliconization, dephosphorization, and desulfurization are performed in advance of hot metal before charging the converter is widespread. As one of the pretreatments, a lance is immersed in hot metal held in a mixed iron wheel (also referred to as a topped car), which is a container for transporting hot metal, and a granular refining agent (eg, dephosphorization) is passed through the lance. There is a method of injecting iron oxide, quick lime or the like in the treatment, and a CaO-based desulfurizing agent in the desulfurization treatment using a carrier gas such as nitrogen to remove phosphorus or desulfurize (referred to as an injection method).
[0003]
In the pretreatment of the hot metal by the injection method, it is difficult to adjust the amount of the refining agent and the gas for transporting the same when the powdery and granular refining agent is actually blown into the hot metal, causing various problems. Therefore, studies have been made to solve these problems, and many techniques have been published.
[0004]
For example, prevention of blockage of the blowing lance, prevention of pulsation of the blowing agent, and the possibility of blowing with a low carrier gas amount and a high powder-particle ratio (high solid-gas ratio), so that the scattering of the melt is small and short. As shown in FIG. 3, a cyclone type gas separator 4 is provided in an intermediate path 3 between a blowing tank 1 and a lance 2 for blowing gas and a refining agent in order to efficiently perform refining in a time. Is disclosed outside the path to adjust the pressure and / or flow rate of the carrier gas 5 (see Patent Document 1).
[0005]
Although not shown, it has also been proposed to completely recover the fine powder of the refining agent contained in a part of the carrier gas discharged to the outside of the path and reuse it for blowing (see Patent Document 2).
[0006]
Furthermore, in order to solve the same problem as the above-mentioned technology, a lance 2 and a pipe 6 for supplying gas to the lance 2 are used to release a part of the carrier gas 5 as shown in FIG. There is also proposed a lance that elaborates the structure of the joint part (see Patent Document 3).
[0007]
However, in order to implement the techniques described in Patent Documents 1 to 3, a gas separator 4 or the like is provided in an intermediate path 3 between the blow tank 1 and the lance 2 or a rear end of the lance 2 is a double pipe. Then, it is necessary to use a lance processed into a special structure. Therefore, there is a problem that it is difficult to commercialize these technologies because the cost of equipment modification is high and economically disadvantageous. Further, the refining agent 7 is trapped in the bubbles 15 of the injected carrier gas 5, and there is a problem that the dephosphorization or desulfurization efficiency cannot be expected to be improved because of a low chance of contact with the hot metal 14 ( (See FIG. 1).
[0008]
[Patent Document 1]
JP-A-60-181218 (page 2, left column 12 lines to lower left column 8 lines)
[Patent Document 2]
JP-A-2000-53249 (paragraph [0008] on page 3 to paragraph [0012] on the lower left column)
[Patent Document 3]
JP-A-2-205615 (12 lines on the left column on page 2 to 8 lines on the lower left column)
[0009]
[Problems to be solved by the invention]
In view of such circumstances, the present invention is used for a pretreatment method of molten iron capable of achieving an improvement in dephosphorization or desulfurization efficiency and a method of performing the method by simply devising a simple means for blowing a granular refining agent. It aims to provide a lance for pretreatment.
[0010]
[Means for Solving the Problems]
The inventor conducted intensive research to achieve the above object, and realized the results in the present invention.
[0011]
That is, the present invention blows a granular refining agent together with a carrier gas from a leading end opening of a horizontal portion of a gas blowing lance that is inclined and immersed in hot metal held in a smelting vessel, and performs pretreatment of the hot metal. At this time, an opening different from the tip opening is provided at a horizontal portion position other than the tip opening, or on the upper half surface of the peripheral wall at a bending position from the inclined portion to the horizontal portion, and the transport gas is mainly provided from the other opening. A pretreatment method for hot metal, comprising discharging a part of the hot metal into the hot metal and blowing out the remaining carrier gas and the refining agent from the opening at the tip.
[0012]
Further, the present invention provides a method for simply dephosphorizing hot metal by immersing the hot metal in an inclined state in hot metal held in a smelting vessel and blowing a granular refining agent together with a carrier gas into the hot metal from a tip opening of a horizontal portion thereof. A lance for blowing gas having a pipe structure, wherein a hot hole characterized by being provided with an opening different from the tip opening on an upper half surface of a peripheral wall of a bent portion from the horizontal portion or the inclined portion to the horizontal portion. It is a lance for dephosphorization. In this case, it is preferable that a plurality of the other openings are provided, and the total area of the openings is 60 to 80% of the area of the tip opening.
[0013]
In the present invention, before the refining agent is blown into the hot metal, a part of the carrier gas is released into the hot metal, so that particles of the refining agent float in the hot metal surrounded by a large amount of the carrier gas. Can be suppressed. As a result, the opportunity for contact with the hot metal increases, and not only can the blowing of the granular refining agent at a high solid-gas ratio be performed stably, but also the opportunity for contact between the refining agent and the hot metal increases, and the dephosphorization or desulfurization is increased. Improvements in efficiency can be achieved.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described, taking into account the circumstances that led to the invention.
[0015]
First, the inventor did not make large-scale equipment remodeling in the hot metal pretreatment process, but simply injected the refining agent with a high solid-gas ratio by simply devising an existing gas injection lance made of steel and having a single pipe structure. Focusing on making it possible, he continued his research and experiments.
[0016]
Specifically, a container that holds water simulating hot metal, a lance that is immersed in the water at an angle, has a horizontal portion with an opening at the tip, and air that simulates a gas for transporting a refining agent. We conducted a model experiment to investigate the trajectory of an air jet in water. When performing a model experiment, if a hole is made at a different angle from the direction of travel of air in the horizontal portion from the front end opening of the lance to the rear end side, the phenomenon that a part of the air is released from the hole will occur. I found it. Therefore, if such a hole is provided in the lance used in the actual hot metal pretreatment process, before the refining agent is ejected into the hot metal from the tip opening, a part of the carrier gas is released first from the hole, We thought that the air bubbles trapping the refining agent ejected from the tip opening could be reduced.
[0017]
Therefore, the inventor manufactured a large number of lances having holes formed at an angle different from the traveling direction of the carrier gas on the upper half surface of the peripheral wall of the bent portion from the horizontal portion or the inclined portion to the horizontal portion, and performed a test operation. The present invention as described below has been completed.
[0018]
In the present invention, as shown in FIG. 1, a powdery refining agent is passed through a tip opening 13 of a horizontal portion 12 of a gas injection lance 2 sloping and immersed in hot metal 14 held in a refining vessel (not shown). 7 is blown together with the carrier gas 5 and the pretreatment of the hot metal 14 is performed at the position of the horizontal portion 12 other than the tip opening 13 or at the upper half surface of the peripheral wall at the bending position from the inclined portion to the horizontal portion. An opening 9 different from the opening 13 is provided, and a part of the carrier gas 5 is mainly discharged into the hot metal 14 from the other opening 9, and the remaining carrier gas 5 and the refining agent 7 are discharged from the tip opening 13. And blow it out. In the case of the dephosphorization treatment in the hot metal pretreatment, the refining agent is a mixture of two or more kinds selected from iron oxide and quick lime, and the carrier gas 5 is nitrogen, argon, air, and gaseous oxygen. This is because any substance that is effective for dephosphorization of the hot metal 14 may be used. In the desulfurization treatment, a CaO-based desulfurizing agent is used as the refining agent, and nitrogen and air are used as the carrier gas 5. As the smelting vessel, a mixed iron wheel 8 is preferable. Although a ladle may be used, it is most preferable if workability is considered. Further, the solid-gas ratio of the refining agent 7 and the carrier gas 5 to be passed through the gas blowing lance 2 is set to 30 to 100. The reason why the solid-gas ratio is set to 30 to 100 is that if the ratio is less than 30, the reaction speed is significantly reduced, and if it exceeds 100, it is inconvenient to carry.
[0019]
Next, the gas injection lance 2 used in the present invention is a so-called “single pipe structure” which has been used conventionally, has a horizontal portion with an open end, and is lined with a refractory on the surface of a steel pipe. In addition, it is a new simple twist. The idea is that, as shown in FIG. 1, an opening 9 different from the tip opening 13 is provided at an upper half position of the peripheral wall of the horizontal portion 12 or a bent portion from the inclined portion to the horizontal portion. . In this case, the opening in the upper half position of the lance peripheral wall is such that when the refining agent 7 is supplied to the inclined lance by the carrier gas 5, as shown in a vertical section in FIG. The refining agent is less in the upper half of the peripheral wall of the bent part, and segregates in the lower half to be conveyed. Therefore, it is preferable that the hole for discharging the carrier gas 5 before the refining agent 7 be provided in the upper half of the peripheral wall.
[0020]
Further, even if only one opening 9 is provided, it is effective to discharge the carrier gas 5 ahead of the refining agent 7, but if a plurality of openings 9 are provided at different positions, it is more effective. . However, the size of the openings 9 needs to be limited, and the total area of the openings 9 is preferably set to 60 to 80% of the area of the distal end opening 13. If it is less than 60%, blockage by the metal occurs, and if it is more than 80%, the strength of the lance itself is insufficient, causing a defect or the like, which causes inconvenience.
[0021]
【Example】
An example will be described with an example in which a phosphorus removal treatment is performed as a preliminary treatment. After the hot metal having the average composition shown in Table 1 was desiliconized from the blast furnace by the inclined casting gutter of the casting bed, it was received by the mixed iron wheel 8 having a transfer capacity of 320 tons. Charged many. At that time, as the lance 2 for blowing the refining agent 7, the one according to the present invention shown in FIG. 1 and the conventional lance (one having no separate opening 9) were used, and the operation was performed in each case. . Note that iron oxide and quick lime were used as the refining agent 7 and nitrogen gas was used as the carrier gas 5. Table 2 shows the usage amount, the opening position of the lance, the opening diameter, and the like.
[0022]
[Table 1]

[0023]
[Table 2]

[0024]
The results of the operation were evaluated by the dephosphorization reaction rate constant (defined by the following formula (1)), and are arranged in FIG. 2 corresponding to the oxygen supply rate obtained by converting the oxygen of the blown iron oxide into gaseous oxygen. From FIG. 2, it is clear that according to the present invention, the dephosphorization reaction rate constant is 1.4 times that in the case where a conventional lance is used, and the dephosphorization is promoted. Incidentally, the composition of the hot metal after dephosphorization is shown in Table 3 in comparison with the composition when a conventional lance is used.
[0025]
[Table 3]

[0026]
Kp = ln (Pi / Pf) Wo ₂ (1)
Here, Kp: Dephosphorization reaction rate constant Pi: Phosphorus concentration in hot metal before treatment (% by mass)
Pf: phosphorus concentration in hot metal after treatment (% by mass)
Wo ₂ : outside of desiliconization (except during desiliconization) Oxygen consumption unit supplied during dephosphorization (m ³ (standard state) / ton)
[0027]
【The invention's effect】
As described above, according to the present invention, not only can the blowing of the particulate refining agent at a high solid-gas ratio be performed stably, but also the opportunity of contact between the refining agent and the hot metal increases, and the dephosphorization efficiency and desulfurization are higher than before. Improvements in efficiency can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a lance for pretreatment of hot metal according to the present invention.
FIG. 2 is a diagram showing the effect of the present invention.
FIG. 3 is a cross-sectional view showing a pretreatment apparatus for hot metal provided with a carrier gas separator.
FIG. 4 is a cross-sectional view showing a joint of a lance for blowing a refining agent having a function of separating a carrier gas.
FIG. 5 is a view showing a vertical cross section of a horizontal portion of a refining agent blowing lance.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Injection tank 2 Gas injection lance 3 Intermediate route 4 Gas separator 5 Carrier gas 6 Piping 7 Refining agent 8 Mixed iron car (topido car)
9 Separate opening 10 Longitudinal section of lance horizontal part 11 Upper and lower partition lines 12 Horizontal part 13 Tip opening 14 Hot metal 15 Bubbles

Claims (3)

At the time of injecting a powdery refining agent together with a carrier gas from a front end opening of a horizontal portion of a gas injection lance that is inclined and immersed in hot metal held in a smelting vessel together with a carrier gas,
At the horizontal portion position other than the tip opening, or on the upper half surface of the peripheral wall at the bending position from the inclined portion to the horizontal portion, an opening different from the tip opening is provided, and a part of the carrier gas is mainly provided from the other opening. And discharging the remaining carrier gas and the refining agent from the opening at the end of the hot metal. It is immersed obliquely in the hot metal held in the smelting vessel, and blows a granular refining agent into the hot metal along with the carrier gas from the opening at the tip of the horizontal part to perform a pretreatment of the hot metal for gas injection of a single pipe structure. Lance,
A lance for pretreatment of hot metal, wherein an opening different from the tip opening is provided on an upper half surface of a peripheral wall of a bent portion from the horizontal portion or the inclined portion to the horizontal portion. 3. The lance for pretreatment of molten iron according to claim 2, wherein the plurality of other openings are formed in a plurality, and the total area of the openings is 60 to 80% of the opening area of the tip.

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