JP2003138311A - Gas top-blowing lance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas top-blowing lance provided with a turning means for giving the turning flow to the spouted oxygen gas jet at the side surface of a through hole only by modifying the lance without needing large capital investment. SOLUTION: The volume of gas flowing through in a main flowing course 8 and that of gas flowing through the turning flow course 6 are divided by the ratio of the cross sectional area of an orifice 11 for main gas to that of an orifice 12 for turning gas arranged in the lance.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for refining molten iron in a converter, especially a decarburizing furnace, an iron bath type smelting reduction furnace, a converter type scrap melting furnace, and the like. The present invention relates to the structure of a gas blowing lance. In the field of steelmaking, ore raw materials such as chromium ore and iron ore and carbonaceous materials such as coke have recently been added to hot metal in a converter, and the ore is directly melted and reduced. Techniques for recovering valuable metals in ore have become widespread.
In carrying out such smelting reduction of ore, a large amount of heating / reducing energy is usually required. Also,
Not only in the smelting reduction, but also in the converter operation in which general steelmaking using blast furnace molten iron as a raw material, a large amount of ore and scrap are supplied into the converter, and heating, reduction, and melting may be performed. Furthermore, in the decarburization blowing of stainless steel in a converter, the temperature must be raised to a high temperature in the initial stage of blowing to reduce the oxidation loss of Cr in the metal. Therefore, in order to perform such an operation while maintaining the productivity at a high level, it is necessary to supply a carbon material as an energy source and oxygen gas for burning the carbon material as quickly as possible. [0003] Usually, the supply of oxygen gas to hot metal or molten steel (hereinafter, referred to as molten metal) held in a converter is performed by using an upper-blowing lance for most of the supply of oxygen gas. Increasing the supply speed causes a problem that dust generation increases. This increase in the generation rate of dust causes a decrease in the yield of molten steel to be manufactured and an increase in the cost of subsequent dust treatment. In particular, in order to perform smelting reduction at high productivity, it is important to suppress the dust generation rate. ing. [0004] Further, when the top-blown oxygen is supplied at a high speed, there is also a problem that the secondary combustion rate is reduced and the heat-up efficiency of the molten metal is reduced. [0005] By the way, it is considered that such dust is mainly caused by bursting of CO gas bubbles generated by the decarburization reaction of the molten metal, or caused by direct evaporation of metal components from the molten metal. Both
It increases as the degree of collision between the oxygen gas jet blown upward and the molten metal and the supply speed of the oxygen gas increase. As a countermeasure for suppressing the generation of dust, it is effective to block the top-blown oxygen gas jet from the surface of the molten metal in the molten slag layer existing on the molten metal. For this purpose, it is necessary to reduce the depth of the depression in the slag layer caused by the collision of the top-blown oxygen gas jet so that the depression does not reach the surface of the molten metal. In other words, the above-described conditions such as the suppression of the dust generation speed are achieved by making the upper blown oxygen gas jet a so-called soft blow. At the same time, it is known that soft blowing of the top-blown oxygen gas jet results in an improvement in the secondary combustion rate, and as a method for increasing the rate of supplying thermal energy to the molten metal while reducing the rate of dust generation. Extremely effective. [0007] The secondary combustion means that CO gas generated in the furnace by oxygen refining of molten metal is converted into CO ₂ in the upper space in the furnace.
And the secondary combustion rate is calculated as [(vol% CO ₂ ) / ｛(vol% CO) +
(Vol% CO ₂ )}] × 100. In addition, the heat transfer efficiency refers to an efficiency at which heat generated in the secondary combustion becomes sensible heat of the molten iron and the slag. [0008] Conventionally, in converter refining, in order to increase the secondary combustion rate in the furnace, that is, to improve the heat supply capacity, the soft blow of the top-blown oxygen gas jet is performed as follows. Method is taken. (1) The tip position of the upper blowing lance (hereinafter referred to as the lance height) is raised. (2) The nozzle of the top blowing lance is made porous to disperse the top blowing oxygen gas jet. (3) The nozzle shape of the upper blowing lance is made non-circular to promote the attenuation of the flow velocity of the upper blowing oxygen gas jet. (4) The main flow of the gas from the upper blowing lance is turned into a swirling flow to promote the attenuation of the flow velocity of the upper blowing oxygen gas jet. Regarding the above (3), the following technology is disclosed. JP-A-61-143507 discloses that CO
In order to obtain the effect of increasing the secondary combustion, the ratio of the major axis to the minor axis is a non-circular opening having a ratio of 1.2 or more, and the secondary combustion promoting lance of a converter having at least two or more nozzles of the same shape is provided. Disclosed is also shown that, when the nozzle has three or four holes, each nozzle has a major axis on the radial line of the lance. This nozzle hole is a uniform hole whose cross section does not change. In Japanese Patent Application Laid-Open No. 62-44517, a subsonic sub-nozzle having a band-shaped cross-section surrounding the main nozzle is disposed to recover the secondary combustion heat of CO. In Japanese Patent Application Laid-Open No. H8-60219, two or more nozzles for ejecting an upper blowing gas are provided,
A converter refining technique using a nozzle having a rectangular shape, an elliptical shape, an arc shape, or a combination thereof is disclosed. This technology is related to decarburization refining with high heat transfer efficiency, high secondary combustion rate, low dust and high iron yield, and the ratio of long side to short side is large. It is described that the gas flow velocity is greatly attenuated immediately after the gas is ejected as compared with the gas emitted from the gas. And as an example, the arrangement of the nozzle openings is in the shape of a “2”, the shape in which the majority circle and the small semicircle face each other, the shape in which the “C” is arranged below the small semicircle, the periphery of the “2” shape 2 illustrates a nozzle having a shape surrounded by an intermittent arc. Also in this technique, the nozzle hole has a uniform shape whose cross section does not change. Regarding the above (4), the following technology is disclosed. In Japanese Patent Application Laid-Open No. H11-58528, the oxygen gas is introduced horizontally at the top of a single-hole downwardly extending truncated conical through-hole such that the oxygen gas has a tangential component having a circular cross section of the through-hole. Disclosed is a nozzle tip provided with an opening. This technology is related to decarburization refining with high heat transfer efficiency, high secondary combustion rate, low dust and high iron yield. By turning the main gas flow, the flow velocity to the molten steel surface can be greatly reduced. . [0017] However, the increase in the lance height in the above (1) causes a low heat transfer efficiency of heat generated in the secondary combustion, resulting in a rise in exhaust gas temperature and lining in the furnace. This leads to an increase in erosion of the refractory, which is not preferable.
In addition, in the case of making the nozzle porous in the above (2), unless the inclination angle of the hole with respect to the vertical (hereinafter referred to as the nozzle inclination angle) is increased to some extent, the oxygen gas jet dispersed and supplied from the multi-hole nozzle is reassembled. As a result, a sufficient soft blow effect cannot be obtained. On the other hand, if the nozzle inclination angle is increased, the oxygen gas jet directly collides with the furnace wall, causing a problem that the furnace wall is damaged. Regarding the non-circularization of the nozzle in (3), the effect of attenuating the flow velocity of the gas jet due to the mere non-circularization is smaller than that of the present invention. In addition, the lance structure becomes complicated and the durability deteriorates. With respect to the swirling flow (4), the gas jet flow velocity has a large damping effect, and has a great effect on dust reduction and high secondary combustion. However, since the gas flow spreads greatly only with the swirling flow, when the lance height is high, oxygen directly hits the refractory and the refractory erosion increases. Also,
In the vicinity immediately below the nozzle, a strong upward gas flow is generated at the center of the swirling flow, and when the lance height is low, the metal or dust jumps into the lance hole, resulting in a problem of a short life of the nozzle. The inventors of the present invention have proposed Japanese Patent Application No. 11-339.
In No. 314, the oxygen gas spouted on the side of the through hole
A lance for blowing gas upward provided with a swirling means for imparting a swirling flow to the jet is provided. However, the above-mentioned gas blowing lance has to control two types of gas flows, that is, an axial flow and a swirling flow, and requires a large investment in remodeling the lance body and peripheral equipment. . In view of the above circumstances, it is an object of the present invention to provide a swirl means for imparting a swirl flow to an ejected oxygen gas jet on a side surface of a through-hole without requiring a large capital investment only by remodeling the lance. To develop and provide a lance for gas blowing. Means for Solving the Problems In order to achieve the above object, the inventor has made extensive studies and experiments and completed the results as the present invention. That is, the present invention relates to a lance for blowing an oxygen gas jet from above onto a molten metal held in a converter type refining furnace, and a lance is provided at the tip of a long cylindrical body.
A gas tip blowing lance having a nozzle tip having one or a plurality of through holes, and a swirling flow path provided on a side surface of the through hole for imparting a swirling flow to an oxygen gas jet ejected from the through hole; A gas blowing lance characterized in that an orifice plate is provided in a lance for branching a gas flowing through a through hole and a gas flowing through the swirling flow path. The perforated orifice plate is arranged at a right angle to the gas flow path.
The orifice plate has an opening formed with an orifice for restricting gas flowing in the swirling flow path and / or gas flowing in the through hole. ADVANTAGE OF THE INVENTION According to this invention, soft blow of the gas flow velocity injected from the lance can be achieved only by remodeling in a lance, without requiring large capital investment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below on the basis of the circumstances leading to the invention. First, the inventor measured the flow velocity distribution of the top-blown gas jet in a cold model experiment in order to confirm the effect of soft blowing using the top-blown gas lance. FIGS. 1 to 3 show the nozzle tip of the upper blowing lance used in the embodiment used here. FIG. 1 is a longitudinal sectional view of a nozzle 1 according to an embodiment of the present invention, and FIG.
FIG. 3 is a view along arrow A, and FIG. 3 is a view along arrow BB in FIG. The nozzle 1 according to the embodiment includes a main flow path 8 for ejecting an upwardly blown jet gas jet (downward flow) 9 downward from the upstream flow path 2 and a swirling flow path 6 for imparting a swirling motion to the main flow path 8. And In this embodiment, there is one main flow path 8, which is a frustoconical hole. The main stream 4 descends through a main gas orifice 11 provided at the center of the orifice plate 3 as shown in FIG. The branch flow 5 entering the swirl flow path 6 is formed by a swirl gas orifice 12 shown in FIG.
And enters a swirl flow path 6, as shown in FIG. 3, as a swirl flow 7, flows into a main flow path 8, and imparts a swirl component 10 to the jet gas jet (downflow) 9. The nozzle of this embodiment has four swirl flow paths 6 in one main flow path 8.
Are connected. Since the flow rates of the main flow 4 and the branch flow 5 are roughly divided in proportion to the opening areas of the orifices 11 and 12, it is possible to determine the size and ratio of the opening areas of the orifices 11 and 12 according to the appropriate amounts. it can. The gas flows into the main flow 4 and the branch flow 5 by the orifices 11 and 12 provided upstream of the holes. As a conventional example, a comparison was made with the embodiment using a nozzle tip 1 provided with six through-holes of a type in which the cross-sectional area of the flow path of the ejection hole 13 rapidly increased as shown in FIG. FIG.
FIG. 4A is a transverse sectional view, and FIG. 4B is a longitudinal sectional view. The gas used was nitrogen, and the gas jet was jetted in the axial direction of the lance (vertically downward). The gas flow rate was 9.0 m ³ (standard state) / min, and the radial distribution of the vertical component of the gas jet flow velocity was measured at a position 600 mm below the tip of the nozzle. FIG. 5 shows the gas flow velocity distribution at a position 600 mm below the tip of the nozzle when each of the nozzle tips shown in FIGS. 1 and 4 is used at each position. Curve 21 shown in FIG.
1 shows the jet flow velocity distribution of the nozzle of the embodiment shown in FIG. In addition, the conventional nozzle shown in FIG.
As shown by the curve 22, the jet flow velocity was large and hard blow occurred. Since the nozzle of the embodiment has a small jet flow velocity and is soft-blowed, it is effective in reducing dust generation and improving secondary combustion. EXAMPLE Heating and blowing of molten metal and smelting and reducing blowing of Cr ore were performed in a 5-ton scale top and bottom blown converter, and the heating rate and dust generation rate during smelting reduction were investigated. The operation was carried out according to the following procedure. After the molten iron having the chemical composition shown in Table 1 was charged into the converter, first, nitrogen gas was introduced at 5.0 m ³ (standard state) / min through the bottom-blowing tuyere. While blowing pure oxygen gas through the top blowing lance at a rate of 20 m ³ (standard condition) / min, lump coke and quick lime and silica as slag-making materials were charged into the furnace from a shooter provided on the furnace and raised. Heat and slag were made. The cross-sectional area ratio between the orifice 12 for swirling gas and the orifice 11 for main gas in the embodiment was set to 0.1. After heating, decarburization blowing was performed. During operation, the temperature of the molten metal was measured using a so-called sub-lance, and the rate of heating was measured based on the measured value. In the smelting reduction blowing, the Cr ore and the carbonaceous material were continuously charged as appropriate, and the flue gas was appropriately sampled from the flue to investigate the dust concentration in the flue gas. In the embodiment using the lance shown in FIG. 1 according to the present invention and the comparative example using the conventional lance in which the cross section of the flow path suddenly expands as shown in FIG. Table 2 shows the speed index and the dust generation speed index. The lance height shown in Table 2 is the distance from the surface of the molten metal to the tip of the upper blowing lance. The heat-up rate index is a relative comparison with the heat-up rate of Comparative Example 1 being 100. Also,
The dust generation rate index is a relative comparison with the value of Comparative Example 1 being 1.0. A comparison between the example of Table 2 and the comparative example confirmed that the rate of heat rise was significantly improved in the example, and that the decarboxylation efficiency during decarburization blowing was equivalent to that of the comparative example. . Although the above Examples and Comparative Examples relate to heat-up and smelting reduction blowing of Cr ore in converter refining, the technology of the present invention relates to iron ore, manganese ore, nickel ore, and other carbon ore. The present invention can also be effectively applied to reducible ores, or aggregated ores thereof, preliminary reduced ores, and the like. Needless to say, it is also effective in increasing the usage of cold iron sources such as scrap in converter refining. [Table 1] [Table 2] As described above, according to the present invention, in the furnace at the time of heating, scrap melting, or smelting reduction, the secondary combustion rate and the heating efficiency are maintained at a high level, and the dust emission is reduced. The generation speed can be greatly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a nozzle tip of an embodiment. FIG. 2 is a view as viewed in the direction of arrows AA in FIG. 1; FIG. 3 is a view taken in the direction of arrows BB in FIG. 1; 4A and 4B show a nozzle tip of a comparative example, in which FIG. 4A is a cross-sectional view, and FIG. FIG. 5 is a graph showing a radial distribution of a vertical component of a gas jet flow velocity at a position 600 mm below a nozzle tip, obtained by a cold model experiment using various lances. [Description of Signs] 1 Nozzle tip 2 Upstream channel 3 Orifice plate 4 Main flow 5 Branch flow 6 Swirl flow path 7 Swirl flow 8 Main flow path (frustoconical hole) 9 Injected gas jet (downward flow) 10 Swirl Component 11 Orifice 12 for main gas Orifice 13 for swirling gas Orifices 21 and 22 Curve

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Hideji Takeuchi             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba             Iron Research Institute F term (reference) 4K070 CF02

Claims (1)

Claims: 1. A lance for blowing an oxygen gas jet from above onto a molten metal held in a converter type refining furnace, wherein one or more through holes are provided at the tip of a long cylindrical body. A nozzle tip having a swirl flow path for providing a swirl flow to the oxygen gas jet ejected from the through-hole at a side surface of the through-hole. An upper gas blowing lance, wherein an orifice plate for branching a gas flowing in a swirling flow path is provided in the lance.