Smelting lance, method for smelting molten iron, and smelting equipment

Abstract

To provide a refining lance or the like that can improve the phosphorus removal capacity. [Solution] The smelting lance has a lance tip section having a central hole formed in the center and a plurality of main holes formed around the central hole and along the central hole, and a gas supply section for supplying gas to the lance tip section. The smelting lance has a first flow path for supplying a first gas, a second flow path formed along the first flow path and for supplying a second gas, and a mixing section connected to both the end of the first flow path and the second flow path. The end of the first flow path or the second flow path is formed to widen toward the mixing section.

Description

Technical Field

[0001] The present invention relates to a refining lance, a method for refining molten iron, and refining equipment.

Background Art

[0002] Lime is used for dephosphorization of molten iron in converters. The melting point of lime is higher than the temperature of molten iron. For this reason, by blowing lime into molten iron together with refining gas, the heat generated when oxygen reacts with carbon contained in molten iron on the surface of molten iron is utilized to promote the melting of lime.

[0003] As such a refining lance, for example, Patent Document 1 discloses a refining lance that blows dephosphorization refining agent powder from a central hole provided at a tip end portion.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] In Patent Document 1, dephosphorization refining agent powder, which is a refining flux, is blown into molten iron together with carrier gas. Further, the refining gas is blown out from an outlet different from that for the carrier gas in the refining lance. For this reason, the refining gas reacts with molten iron at a location different from that of the carrier gas. That is, there is a problem that the refining flux is locally supplied at a position away from the position where the refining gas is supplied.

[0006] Such problems can arise when supplying granular materials, such as smelting flux, as well as oxygen gas, to molten iron. For example, when using lime-containing smelting flux as granular material, the advantage of using the high temperature generated during the reaction between oxygen and molten iron to melt the lime is not fully utilized, resulting in a problem where sufficient dephosphorization capacity cannot be obtained.

[0007] This invention has been made in view of the above-mentioned problems, and aims to provide a refining lance, etc., that can suppress the discharge of granular material from an uneven position. [Means for solving the problem]

[0008] To solve the above problems, the present invention has the following features. [1] A smelting lance having a central hole formed in the center and a lance tip portion having a plurality of main holes formed around the central hole and along the central hole, and a gas supply portion for supplying gas to the lance tip portion, It comprises a first flow path for supplying a first gas, a second flow path formed along the first flow path and for supplying a second gas, and a mixing section connected to both the first flow path and the second flow path at their ends. A refining lance, wherein the end of the first or second flow path is formed to widen toward the mixing section. [2] The first gas contains particulate matter, The axis of the first flow path is provided in a direction along the axis of the central hole, The mixing portion is formed such that the length from the central hole of the lance tip portion to the first flow path is in accordance with the average particle size of the granular material, as described in [1]. [3] The surface extending from the opening of the central hole to the opening of the main hole is formed at an acute or obtuse angle with respect to the axial direction of the central hole, as described in [1] or [2]. [4] The second flow path of the gas supply unit is formed to cover the first flow path, The central hole of the lance tip portion opens on the end side of the first flow path, The refining lance according to [3], wherein the surface extending from the opening of the central hole to the opening of the main hole is formed at an obtuse angle with respect to the axial direction of the central hole. [5] The first flow path of the gas supply unit is formed to cover the second flow path, The main hole of the lance tip portion opens on the end side of the first flow path, The surface extending from the opening of the central hole to the opening of the main hole is formed at an acute angle with respect to the axial direction of the central hole, as described in [3]. [6] It has a flow velocity adjustment unit that adjusts the flow velocity of the gas in the first flow path and the flow velocity of the gas in the second flow path, The smelting lance according to any one of [1] to [5], wherein the flow velocity adjustment unit adjusts the flow velocity of either the first flow path or the second flow path to be faster than the other. [7] The first channel is connected to an oxygen-containing gas supply unit that supplies oxygen-containing gas, as described in [1] to [6], for refining. [8] A method for refining molten iron, comprising refining molten iron using a refining lance described in any of [1] to [7], The charging process involves charging molten iron into the converter, An oxidation refining step is performed by blowing a refining gas into the molten iron using the refining lance to carry out oxidation refining. A method for smelting molten iron, including [a specific substance]. [9] A converter into which molten iron is charged, A refining apparatus including a refining lance as described in any of [1] to [7]. [Effects of the Invention]

[0009] According to the refining lance and the like of the present invention, the refining lance comprises: a first flow path for supplying a first gas; a second flow path for supplying a second gas; and a mixing section connected to both the first flow path and an end of the second flow path. Further, an end of the first flow path or the second flow path is formed to expand toward the mixing section. Accordingly, the gas and particulate matter discharged from the end formed to expand toward the mixing section are supplied so as to diffuse in the mixing section. This can suppress discharge of the particulate matter from a deviated position among the central hole and the main hole. [BRIEF DESCRIPTION OF THE DRAWINGS]

[0010] [Figure 1] It is an explanatory diagram showing an outline of refining equipment. [Figure 2] It is an explanatory diagram showing an outline of a refining lance. [Figure 3] It is an explanatory diagram showing the formation mode of a central hole and a main hole in a lance tip portion. [Figure 4] It is an explanatory diagram showing an outline of a mixing section. [Figure 5] It is a flow diagram showing a method for refining molten iron. [Figure 6] It is an explanatory diagram showing an outline of a mixing section according to Modification 1. [Figure 7] It is an explanatory diagram showing an outline of a mixing section according to Example 2. [Figure 8] It is an explanatory diagram showing a mode in which refining flux supplied from the first flow path moves to the main hole. [Figure 9] It is an explanatory diagram showing an outline of a mixing section according to Modification 2. [Figure 10] It is a simulation result obtained by visualizing the trajectory of refining flux in a refining lance. [Figure 11] It is a graph showing the relationship between the average particle diameter of refining flux and the length that satisfies the condition for sufficiently mixing the refining flux and refining gas. [Figure 12] It is a graph showing phosphorus distribution for both the example of the present invention and the comparative example. [MODE FOR CARRYING OUT THE INVENTION]

[0011] (First Embodiment) Embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows an overview of the refining equipment 100. As shown in Figure 1, the refining equipment 100 has a converter 10.

[0012] The converter 10 is formed in the shape of a container with an open top. The converter 10 has an iron shell 11 on its outer shell, and a refractory material 12 is provided inside the iron shell 11. An outlet 13 for discharging the molten metal after refining is provided at the top of the converter 10.

[0013] The bottom of the converter 10 is provided with a bottom-blowing tuyere 14 for blowing stirring gas into the molten iron 20 inside the furnace. The bottom-blowing tuyere 14 is connected to a gas inlet pipe 15.

[0014] A smelting lance 30 is inserted into the opening of the converter 10. The smelting lance 30 is designed to be movable vertically, in other words, its insertion position in the converter 10 can be changed. A gas supply system 40 is connected to the smelting lance 30 to supply gas.

[0015] The gas supply system 40 has an oxygen gas piping 41 for supplying oxygen gas. The oxygen gas piping 41 branches into a first pipe 42, a second pipe 43, and a third pipe 44. The first pipe 42 is connected to the refining lance 30. The second pipe 43 and the third pipe are connected to a fourth pipe 46. The fourth pipe 46 is connected to the refining lance 30.

[0016] Each of the first pipe 42, second pipe 43, and third pipe 44 is provided with a flow control valve 45. By adjusting each of the flow control valves 45, the flow rate of the fluid flowing through the first pipe 42, second pipe 43, and third pipe 44 can be adjusted.

[0017] A dispenser 47 for containing granular material is connected to the third pipe 44. The dispenser 47 is equipped with a control valve 48 for adjusting the supply of granular material. Examples of granular material include smelting flux.

[0018] Examples of fluxes used for smelting include CaO dephosphorizing agents (quicklime (CaO), limestone (CaCO3), dolomite (CaCO3·MgCO3), decarburized slag, secondary smelting slag), as well as iron oxide powder such as iron ore and mill scale, raw materials for slag (e.g., silica (SiO2), brick scraps containing magnesium oxide, etc.), and slag accelerators (containing fluorite (CaF2), titanium dioxide (TiO2), aluminum oxide (Al2O3), etc.).

[0019] Furthermore, the refining flux may be a mixture of multiple materials. For example, the CaO dephosphorizing refining agent may be a mixture of quicklime, limestone, dolomite, and fluorite or aluminum oxide, provided that the CaO content is 50% by mass or more.

[0020] As described above, the smelting lance 30 is connected to the first pipe 42, which is connected to the oxygen gas pipe 41. Therefore, the smelting lance 30 can blow oxygen gas, which is used as a smelting gas, onto the surface of the molten iron 20 contained in the converter 10.

[0021] Furthermore, a fourth pipe 46 is connected to the refining lance 30. The fourth pipe 46 is connected to the oxygen gas pipe 41 via the second pipe 43 and the third pipe 44. Therefore, the oxygen gas also functions as a conveying gas to transport the refining flux to the refining lance 30.

[0022] The smelting flux is supplied from the fourth pipe 46 to the smelting lance 30 and sprayed onto the surface of the molten iron 20 contained in the converter 10. The spraying of the smelting flux onto the surface of the molten iron 20 is also called projection.

[0023] Furthermore, a shut-off valve 49 for blocking the flow of fluid is provided downstream of the flow control valve 45 of the second pipe 43 and upstream of the connection point of the fourth pipe 46. Also, a shut-off valve 49 for blocking the flow of fluid is provided downstream of the flow control valve 45 of the third pipe 44 and upstream of the dispenser 47. Furthermore, a shut-off valve 49 for blocking the flow of fluid is provided downstream of the dispenser 47 of the third pipe 44 and upstream of the connection point of the fourth pipe 46.

[0024] By closing the shut-off valve 49 of the second pipe 43 and the two shut-off valves 49 of the third pipe 44, it is also possible to supply only oxygen gas from the first pipe 42 to the refining lance 30.

[0025] Figure 2 shows an overview of the refining lance 30. As shown in Figure 2, the refining lance 30 is formed in a cylindrical shape and has a lance tip portion 31 formed at the tip end and a gas supply portion 32 that supplies gas to the lance tip portion 31. The lance tip portion 31 and the gas supply portion 32 are connected, for example, by welding.

[0026] The lance tip portion 31 has a central hole 31a formed in the center, and multiple main holes 31b formed around the central hole 31a and along the central hole 31a. The central hole 31a is formed along the axial direction of the refining lance 30. Each of the main holes 31b is formed at an angle to the axis of the refining lance 30, and its tip is formed away from the central hole 31a.

[0027] Furthermore, the main bore 31b may be formed in a so-called Laval nozzle shape, where the diameter widens towards the opening at the tip, or it may be formed in a so-called straight shape, where the diameter is constant. In addition, the number of holes and the diameter of the main bore 31b can be determined, for example, according to the gas pressure supplied to the refining lance 30.

[0028] The gas supply unit 32 is not particularly limited, but for example, it is formed in a cylindrical shape. In this embodiment, the gas supply unit 32 is formed having a first cylindrical unit 33, a second cylindrical unit 34 provided to cover the circumferential surface of the first cylindrical unit 33, a third cylindrical unit 35 formed to cover the circumferential surface of the second cylindrical unit 34, and a fourth cylindrical unit 36 ​​formed to cover the circumferential surface of the third cylindrical unit 35. Each of the first to fourth cylindrical units 33 to 36 is formed in a hollow cylindrical shape, for example.

[0029] The first cylinder 33 functions as a first flow path 37 for supplying the first gas. A second flow path 38 for supplying the second gas is formed between the outer wall of the first cylinder 33 and the inner wall of the second cylinder 34. In other words, the second flow path 38 is formed along the first flow path 37.

[0030] The first gas is not particularly limited, but in this embodiment, a conveying gas containing a refining flux is used. In other words, the first flow path 37 is connected to a fourth pipe 46 which serves as an oxygen-containing gas supply unit that supplies oxygen and an oxygen-containing gas containing a refining flux. The second gas is not particularly limited, but in this embodiment, a refining gas is used.

[0031] Furthermore, the gas flow velocity in the first channel 37 is adjusted by a flow control valve 45 that adjusts the flow rate of the fluid flowing through the second pipe 43 and the third pipe 44, as described in Figure 1. The gas flow velocity in the second channel 38 is adjusted by a flow control valve 45 that adjusts the flow rate of the fluid flowing through the first pipe 42, as described in Figure 1. Therefore, each flow control valve 45 functions as a flow velocity adjustment unit.

[0032] The first cylinder 33 is formed to be shorter than the second cylinder 34. The second cylinders 34 to the fourth cylinder 36 are connected to the lance tip portion 31. In other words, the smelting lance 30 has a mixing portion 39 that is connected to both the first flow path 37 and the second flow path 38 at their ends. The mixing portion 39 is connected to the central hole 31a and the main hole 31b of the lance tip portion 31, respectively.

[0033] Therefore, the first gas and the second gas are mixed in the mixing section 39, and the mixed gas of the first gas and the second gas is blown out from the central hole 31a and the main hole 31b of the lance tip section 31, respectively.

[0034] Furthermore, an introduction channel P1 for introducing cooling water into the refining lance 30 is formed between the outer wall of the second cylinder 34 and the inner wall of the third cylinder 35. The introduction channel P1 is connected to a water supply pipe (not shown).

[0035] Furthermore, a discharge channel P2 for discharging cooling water from the refining lance 30 is formed between the outer wall of the third cylinder 35 and the inner wall of the fourth cylinder 36. The discharge channel P2 is connected to a drain pipe (not shown).

[0036] In this embodiment, the flow path formed between the outer wall of the second cylinder 34 and the inner wall of the third cylinder 35 is designated as the inlet passage P1, and the flow path formed between the outer wall of the third cylinder 35 and the inner wall of the fourth cylinder 36 is designated as the discharge passage P2. However, the flow path formed between the outer wall of the third cylinder 35 and the inner wall of the fourth cylinder 36 may be designated as the inlet passage, and the flow path formed between the outer wall of the second cylinder 34 and the inner wall of the third cylinder 35 may be designated as the discharge passage.

[0037] Figure 3 shows the formation of the central hole 31a and main holes 31b of the lance tip portion 31. As shown in Figure 3, the lance tip portion 31 is formed in a circular shape when viewed from above. The central hole 31a is formed in the center of the lance tip portion 31. Each of the main holes 31b is formed to surround the central hole 31a. In other words, each of the main holes 31b is formed radially from the central hole 31a.

[0038] Figure 4 shows an overview of the mixing section 39. As shown in Figure 4, the end of the first flow path 37 facing the mixing section 39 is formed to widen toward the mixing section 39. In this embodiment, the end of the first flow path 37 facing the mixing section 39 is tapered so that its diameter widens toward the mixing section 39.

[0039] Because the end of the first channel 37 facing the mixing section 39 is formed in this manner, the conveying gas is supplied from the first channel 37 to the mixing section 39 so as to spread and diffuse radially across the refining lance 30, as shown by the dashed line in Figure 4. Therefore, the refining flux F is also supplied from the first channel 37 to the mixing section 39 so as to spread and diffuse radially across the refining lance 30, similar to the conveying gas. As a result, the refining flux F can be supplied uniformly to the central hole 31a and the multiple main holes 31b.

[0040] The taper formed at the end of the first flow path 37 facing the mixing section 39 should have an angle of 5° to 45°. By setting the taper angle to 5° or more, sufficient radial spreading of the refining flux F can be easily obtained. Alternatively, by setting the taper angle to 45° or less, the influence on the movement of the refining flux F can be appropriately controlled, making it easier to obtain sufficient radial spreading of the refining flux F.

[0041] By uniformly supplying the refining flux F to the central hole 31a and the multiple main holes 31b, the high temperature generated during the reaction between oxygen and molten iron can be used to melt the lime-containing refining flux F into the molten iron, thereby improving the dephosphorization capacity. Furthermore, if a granular material other than the refining flux F is used, the effect of adding the granular material to the molten iron can be obtained in a dispersed manner rather than locally.

[0042] Preferably, the axis AX1 of the first flow path 37 is provided in a direction along the axis AX2 of the central hole 31a. Furthermore, preferably, the length h of the mixing section 39 from the central hole 31a of the lance tip section 31 to the first flow path 37 is formed according to the average particle size d of the refining flux F.

[0043] For example, as the average particle size d of the refining flux F decreases, the length h from the central hole 31a of the lance tip portion 31 to the first flow path 37 should be increased. The average particle size d of the refining flux F can be measured, for example, by sieving. It is preferable to increase the length h as the average particle size d decreases. The length h should satisfy the following formula. h≧-0.137d+55.8 In the formula, "h" is the length (cm) and "d" is the average particle size (μm).

[0044] The length h from the central hole 31a of the lance tip portion 31 to the first flow path 37 can be changed, for example, by adjusting the position of the lower end of the first cylinder 33 in the direction of the axis AX1.

[0045] Regardless of the average particle size d of the refining flux F, if the length h from the central hole 31a of the lance tip section 31 to the first flow path 37 is short, the mixing region of the refining gas and the conveying gas becomes narrower. As a result, the difference in gas pressure between the first flow path 37 and the second flow path 38 is maintained in the mixing section 39, so the flow velocity (m / s) of the refining flux F increases.

[0046] Therefore, the smelting flux F is mainly ejected from the central hole 31a. As a result, the smelting flux F is supplied locally to the surface of the molten iron bath. Consequently, it becomes difficult to promote smelting reactions such as dephosphorization reactions by the smelting flux F.

[0047] Furthermore, by forming the end of the first flow path 37 facing the mixing section 39 in a tapered shape, the length h from the central hole 31a of the lance tip section 31 to the first flow path 37 can be made shorter for an appropriate average particle size d of the refining flux F.

[0048] Furthermore, if the lance tip portion 31 does not have a central hole 31a, and the length h from the central hole 31a to the first flow path 37 is short, the refining gas and the refining flux F may not mix smoothly, and the refining flux F may not be ejected. Also, even if the refining gas and the refining flux F are mixed, there is a risk that the refining flux F may be ejected unevenly from some of the main holes 31b. In either case, there is room for improvement in promoting refining reactions such as the dephosphorization reaction by the refining flux F.

[0049] Furthermore, if the average particle size d of the refining flux F is small relative to the length h from the central hole 31a of the lance tip portion 31 to the first flow path 37, the influence of the conveying gas becomes greater than the inertial force of the refining flux F. As a result, the radial spread of the refining flux F ejected from the first cylinder 33 becomes smaller.

[0050] Therefore, by appropriately adjusting the average particle size d with respect to the length h from the central hole 31a of the lance tip portion 31 to the first flow path 37, refining reactions such as the dephosphorization reaction by the refining flux F can be promoted.

[0051] By setting the length h from the central hole 31a to the first flow path 37 according to the average particle size d of the refining flux F, it is possible to ensure the radial spread of the refining flux F ejected from the first cylinder 33. As a result, it is possible to suppress the discharge of the refining flux F from an uneven position among the central hole 31a and the main hole 31b.

[0052] The molten iron refining method using the refining lance 30 described above will now be explained. Figure 5 shows a flowchart illustrating the molten iron refining method. In the molten iron refining method shown in Figure 5, oxidative refining is performed by blowing refining gas and refining flux F from the refining lance 30 onto the molten iron contained in the converter.

[0053] Examples of oxidative refining include desiliconization, dephosphorization, and decarburization of molten iron. In this embodiment, an example in which dephosphorization is performed as part of oxidative refining will be described.

[0054] As shown in Figure 5, the charging process is first carried out by charging molten iron into the converter 10 through the opening (step S01).

[0055] The molten iron used in the charging process of step S01 includes molten pig iron produced in a blast furnace (not shown) and molten cold iron. This molten iron is transported in molten iron transport containers such as torpedo cars and blast furnace ladles.

[0056] The molten iron used in the charging process of step S01 may be one that has already undergone desiliconization treatment as a preliminary treatment, or it may be one that has not undergone desiliconization treatment.

[0057] Next, an oxidation refining process is carried out in which refining gas is blown into the molten iron using the refining lance 30 described above to perform oxidation refining (step S02). Through this oxidation refining process, the molten iron is adjusted to the desired composition.

[0058] In the oxidation refining process of step S02, the refining gas reacts with some of the carbon in the molten iron, and a decarburization reaction (C + O → CO) occurs at the fire point, which is the point where the refining gas collides with the molten iron bath surface. If the molten iron contains silicon, a desilicate reaction (Si + 2O → SiO2) also occurs. In addition, an oxidation reaction of iron (Fe + O → FeO) occurs at the fire point.

[0059] In the oxidation refining step S02, it is preferable that the flow rate of either the first flow path 37 or the second flow path 38 is adjusted to be faster than the other by the respective flow rate control valves 45. In this embodiment, it is preferable that the flow rate of the first flow path 37 is adjusted to be faster than the flow rate of the second flow path 38. By adjusting in this way, the refining flux F can be diffused in the mixing section 39.

[0060] Furthermore, it is preferable to set the gas pressure in the first channel 37 higher than the gas pressure in the second channel 38. Generally, much larger quantities of refining gas are used compared to the conveying gas. If the gas pressure in the second channel 38 is higher than the gas pressure in the first channel 37, the gas ejection from the first channel 37 may be inhibited, that is, the ejection of the refining flux F from the first channel 37 may be inhibited. Therefore, by adjusting the gas pressure in this way, it is possible to make it easier to eject the refining flux F from the central hole 31a and the main hole 31b.

[0061] The refining flux containing the CaO dephosphorizing agent ejected from the main hole 31b and the central hole 31a is blown onto the fire point along with the refining gas. Since the fire point is at a high temperature and is where FeO is generated, the refining flux is heated and reacts with FeO to form slag.

[0062] Furthermore, if a desiliconization reaction occurs, the refining flux reacts with the SiO2 produced by the desiliconization reaction and becomes slag. The slag-formed refining flux forms slag inside the furnace.

[0063] As decarburization and desiliconization reactions occur and the carbon and silicon concentrations of the molten iron begin to decrease, the phosphorus in the molten iron is oxidized by the supplied oxygen gas and the generated FeO to produce phosphorus oxide (P2O5). This phosphorus oxide (P2O5) is absorbed into the slag, which mainly consists of the slag-forming CaO dephosphorization agent, and the dephosphorization reaction shown in equation (1) below proceeds.

[0064] 2[P]+5(FeO)+3(CaO)= (3CaO P2O5)+5[Fe] (1) Here, in equation (1), [P] and [Fe] represent the components in molten iron, and (FeO), (CaO), and (3CaO·P2O5) represent the components in the slag.

[0065] The higher the basicity of the slag in the furnace ((mass % CaO) / (mass % SiO2)), the more the dephosphorization reaction in equation (1) proceeds; therefore, the basicity of the slag should be controlled to 1.5 or higher. For example, if the refining flux is supplied only from the refining lance, it may not be possible to raise the basicity of the slag to 1.5 or higher, or to ensure a basicity of 1.5 or higher. In such cases, for example, at the beginning of refining, a portion of the planned amount of refining flux may be added from above via a chute from a hopper located above the converter 10.

[0066] When the dephosphorization reaction progresses and the phosphorus concentration of the molten iron decreases to a predetermined value, the supply of oxygen gas from the smelting lance 30 is stopped to terminate the dephosphorization process. The addition of the smelting flux may be terminated during the dephosphorization process or upon completion of the dephosphorization process.

[0067] As described above, it is possible to suppress the discharge of the refining flux F from an off-center position among the central hole 31a and the main hole 31b. As a result, the refining flux F is blown onto the firing point of the refining gas. The firing point has a high temperature and a high concentration of iron oxide, which reacts with the refining flux F to promote the slag formation of the refining flux F. Therefore, the slag formation of the refining flux F is promoted, and the dephosphorization reaction of molten iron is promoted.

[0068] Furthermore, in the above-described embodiment, oxygen gas was used as the transport gas. The transport gas is not limited to oxygen gas; for example, an inert gas such as nitrogen gas or argon gas may be used.

[0069] Since the dephosphorization and decarburization refining of molten iron in a converter are almost identical in their refining methods, the decarburization refining of molten iron can be carried out in accordance with the dephosphorization process described above.

[0070] In the decarburization and refining of molten iron, it is acceptable to use either molten iron that has already undergone desiliconization or dephosphorization as a preliminary treatment, or molten iron that has not undergone desiliconization or dephosphorization.

[0071] (Variation 1) In the above-described embodiment, an example was given in which a conveying gas containing the refining flux is supplied from the first flow path 37. The conveying gas containing the refining flux may also be supplied from the second flow path.

[0072] Figure 6 shows an overview of the mixing section 39 according to Modification 1. As shown in Figure 6, the end of the second flow path 38 facing the mixing section 39 is formed to widen toward the mixing section 39. In this embodiment, the wall portion of the first cylinder 33 at the end of the second flow path 38 facing the mixing section 39 is tapered so that its diameter widens toward the mixing section 39.

[0073] Because the end of the second flow path 38 facing the mixing section 39 is formed in this manner, the transport gas is supplied from the second flow path 38 to the mixing section 39 in a diffuse manner, as shown by the dashed line in Figure 6. Therefore, the refining flux F is also supplied from the second flow path 38 to the mixing section 39 in a diffuse manner, similar to the transport gas. As a result, the refining flux F can be supplied uniformly to the central hole 31a and the multiple main holes 31b.

[0074] Therefore, the advantage of using the high temperature generated during the reaction between oxygen and molten iron to melt the lime-containing smelting flux F into the molten iron can be fully utilized, thereby improving the dephosphorization capacity.

[0075] (Second Embodiment) In the above-described embodiment, an example was given in which the surface extending from the opening of the central hole 31a to the opening of the main hole 31b is formed flat. This surface may be formed at an angle with respect to the axis AX2 direction of the central hole 31a.

[0076] Figure 7 shows an overview of the mixing section 39 according to Example 2. As shown in Figure 7, when a conveying gas containing the refining flux F is supplied from the first flow path 37, the surface 31c extending from the opening of the central hole 31a to the opening of the main hole 31b is preferably formed at an obtuse angle θ1 with respect to the axis AX2 direction of the central hole 31a. If the surface 31c is formed in a curved shape, the angle θ1 between the tangent to the surface 31c at the edge of the central hole 31a and the axis AX2 is preferably formed at an obtuse angle.

[0077] The central hole 31a of the lance tip portion 31 opens closer to the end of the first flow path 37 than the main hole 31b. That is, the distance of the central hole 31a from the central hole 31a to the end of the first flow path 37 in the axial direction AX2 is shorter than the distance from the main hole 31b to the end of the first flow path 37.

[0078] The inclination angle θ1 is preferably greater than 90°, and it is preferable that 90° < θ1 ≤ 135°. By making the inclination angle greater than 90°, it is easier to make the direction in which the refining flux F that collides with the surface 31c moves radially. Also, by making the inclination angle 135° or less, the lance tip portion 31 can be cooled appropriately, and refining can be performed stably. Furthermore, if the inclination angle θ1 exceeds 135°, the space between the main hole 31b and the central hole 31a becomes narrower. As a result, the flow path of the cooling water in between becomes narrower, and there is a risk that the cooling effect will decrease.

[0079] Figure 8 shows how the refining flux F supplied from the first channel moves into the main hole 31b. As shown in Figure 8, the surface 31c is formed to have a gentle slope from the opening of the central hole 31a located at a higher position to the main hole 31b located at a lower position.

[0080] The refining flux F supplied from the first flow path bounces back in accordance with the inclination direction of the surface 31c upon contact with the surface 31c. The refining flux F that has come into contact with the surface 31c is then guided by the influence of the refining gas into the main hole 31b formed near the surface 31c that it came into contact with.

[0081] Thus, when the refining flux F diffused in the mixing section 39 comes into contact with the surface 31c, it is guided not only to the central hole 31a but also to the main hole 31b. Therefore, uneven distribution of the refining flux F discharged from the central hole 31a and the main hole 31b can be suppressed.

[0082] In other words, by making the surface 31c slope downward from the central hole 31a to the main hole 31b, the refining flux F ejected from the first cylinder 33 can more easily move towards the main hole 31b after colliding with the inner surface of the lance tip portion 31. As a result, the radial spread of the refining flux F ejected from the first cylinder 33 is increased.

[0083] (Modification 2) In the above-described embodiment, an example was given in which a conveying gas containing the refining flux is supplied from the first flow path 37. The conveying gas containing the refining flux may also be supplied from the second flow path.

[0084] Figure 9 shows an overview of the mixing section 39 according to Modification 2. As shown in Figure 9, as explained in Modification 1, the wall portion of the first cylinder 33 at the end of the second flow path 38 facing the mixing section 39 is tapered so that its diameter increases toward the mixing section 39. In this case, it is preferable that a conveying gas containing the refining flux F is supplied from the second flow path 38.

[0085] Furthermore, as shown in Figure 9, the surface 31c extending from the opening of the central hole 31a to the opening of the main hole 31b is preferably formed at an acute angle θ2 with respect to the axis AX2 of the central hole 31a. If the surface 31c is formed in a curved shape, it is preferable that the angle θ2 between the tangent to the surface 31c at the edge of the central hole 31a and the axis AX2 is formed at an acute angle.

[0086] The inclination angle θ2 is preferably greater than 0°, and it is preferable that 0° < θ2 ≤ 45°. By making the inclination angle greater than 0°, it is easier to make the direction in which the refining flux F that collides with the surface 31c moves radially. Furthermore, by making the inclination angle 45° or less, the lance tip portion 31 can be cooled appropriately, and refining can be performed stably.

[0087] The main hole 31b of the lance tip portion 31 opens closer to the end of the first flow path 37 than the central hole 31a. That is, the distance of the central hole 31a from the central hole 31a to the end of the second flow path 38 in the axial direction AX2 is formed to be longer than the distance from the main hole 31b to the end of the second flow path 38.

[0088] Even when the lance tip portion 31 is formed in this manner, similar to the embodiment described above, the refining flux F diffused in the mixing portion 39 is guided not only to the main hole 31b but also to the central hole 31a when it comes into contact with the surface 31c. Therefore, it is possible to suppress uneven distribution of the refining flux F discharged from the central hole 31a and the main hole 31b. [Examples]

[0089] Figure 10 shows the simulation results visualizing the trajectory of the refining flux in the refining lance. In the simulation, the average particle size d of the refining flux F was set to 200 μm. In addition, oxygen gas at a predetermined flow rate was supplied from the first pipe 42 and the fourth pipe 46 of the gas supply system 40.

[0090] Figure 10(a) shows the simulation results when the length h from the central hole 31a to the first channel 37 is set to 6 cm. Figure 10(b) shows the simulation results when the length h from the central hole 31a to the first channel 37 is set to 40 cm. Figure 10(c) shows the simulation results when the length h from the central hole 31a to the first channel 37 is set to 100 cm.

[0091] In Figures 10(a) to (c), the trajectory of the refining flux F is shown by a solid line. As shown in Figures 10(a) to (c), as the length h increases, the proportion of the refining flux F passing through the main hole 31b increases.

[0092] Figure 11 shows the relationship between the average particle size d of the smelting flux F and the length h required for sufficient mixing of the smelting flux F and the smelting gas. As shown in Figure 11, the length h increases as the average particle size d decreases.

[0093] Using the smelting lance described in the above embodiment and a conventional smelting lance, dephosphorization treatment of molten iron was performed, and the phosphorus distribution, which is the ratio of phosphorus concentration in the molten iron to phosphorus concentration in the slag after dephosphorization treatment for both, was verified.

[0094] The smelting lance used as an example of the invention, as shown in Figure 11, had the end of the first channel 37 tapered at a 10-degree angle. In contrast, the smelting lance used as a comparative example was a conventional type with no tapered processing at the end of the first channel 37. In both the example of the invention and the comparative example, the length h from the central hole 31a to the first channel 37 was set to 40 cm.

[0095] For the verification, a 330-ton capacity converter was used. Quicklime powder with an average particle size of 100 μm was used as the refining flux. Oxygen gas was used as the conveying gas. Argon gas was used as the stirring gas blown in from the bottom tuyeres.

[0096] Before dephosphorization, the molten iron was standardized to have a carbon concentration of 4.5-4.7 mass%, a phosphorus concentration of 0.11-0.12 mass%, and a molten iron temperature of 1300-1320°C. The target phosphorus concentration of the molten iron after dephosphorization was 0.050 mass% or less.

[0097] Figure 12 is a graph showing the phosphorus distribution for both the present invention example and the comparative example. The phosphorus distribution is shown in a normalized state, and the temperature at the end of refining was 1660°C. As shown in Figure 12, the present invention example showed an improvement of approximately 3% in phosphorus distribution compared to the comparative example.

[0098] In other words, it was confirmed that the dephosphorization reaction of molten iron was accelerated by using the smelting lance of the present invention. This is thought to be because, in the example of the present invention, quicklime powder was uniformly added to the firing point of the smelting gas, which accelerated the slag formation of the quicklime powder. [Explanation of Symbols]

[0099] 100 Refining Equipment 10 Converter 20 Molten iron 30 Refining Lance 31 Lance tip section 31a Center hole 31b Main hole 31c The surface from the opening of the central hole to the opening of the main hole 32 Gas Supply Department 37 First channel 38 Second channel 39 Mixing section 45 Flow rate adjustment section F Refining flux AX1 Axis of the first flow path AX2 Axis of the central hole

Claims

1. A smelting lance having a central hole formed in the center and a lance tip portion having a plurality of main holes formed around the central hole and along the central hole, and a gas supply portion for supplying gas to the lance tip portion, It comprises a first flow path for supplying a first gas, a second flow path formed along the first flow path and for supplying a second gas, and a mixing section connected to both the first flow path and the second flow path at their ends. A refining lance, wherein the end of the first or second flow path is formed to widen toward the mixing section.

2. The first gas contains particulate matter, The axis of the first flow path is provided in a direction along the axis of the central hole, The refining lance according to claim 1, wherein the length of the mixing section from the central hole of the lance tip section to the first flow path is formed according to the average particle size of the granular material.

3. The refining lance according to claim 1, wherein the surface extending from the opening of the central hole to the opening of the main hole is formed at an acute or obtuse angle with respect to the axial direction of the central hole.

4. The refining lance according to claim 2, wherein the surface extending from the opening of the central hole to the opening of the main hole is formed at an acute or obtuse angle with respect to the axial direction of the central hole.

5. The second flow path of the gas supply unit is formed to cover the first flow path, The central hole of the lance tip portion opens on the end side of the first flow path, The refining lance according to claim 3, wherein the surface extending from the opening of the central hole to the opening of the main hole is formed at an obtuse angle with respect to the axial direction of the central hole.

6. The second flow path of the gas supply unit is formed to cover the first flow path, The central hole of the lance tip portion opens on the end side of the first flow path, The refining lance according to claim 4, wherein the surface extending from the opening of the central hole to the opening of the main hole is formed at an obtuse angle with respect to the axial direction of the central hole.

7. The first flow path of the gas supply unit is formed to cover the second flow path, The main hole of the lance tip portion opens on the end side of the first flow path, The refining lance according to claim 3, wherein the surface extending from the opening of the central hole to the opening of the main hole is formed at an acute angle with respect to the axial direction of the central hole.

8. The first flow path of the gas supply unit is formed to cover the second flow path, The main hole of the lance tip portion opens on the end side of the first flow path, The refining lance according to claim 4, wherein the surface extending from the opening of the central hole to the opening of the main hole is formed at an acute angle with respect to the axial direction of the central hole.

9. It has a flow velocity adjustment unit that adjusts the flow velocity of the gas in the first flow path and the flow velocity of the gas in the second flow path, The smelting lance according to claim 1, wherein the flow velocity adjustment unit adjusts the flow velocity of either the first flow path or the second flow path to be faster than the other.

10. The smelting lance according to any one of claims 1 to 9, wherein the first flow path is connected to an oxygen-containing gas supply unit that supplies an oxygen-containing gas containing oxygen.

11. A method for refining molten iron, comprising refining molten iron using a refining lance according to any one of claims 1 to 9, The charging process involves charging molten iron into the converter, An oxidation refining step is performed by blowing a refining gas into the molten iron using the refining lance to carry out oxidation refining. A method for smelting molten iron, including [a specific substance].

12. A method for refining molten iron, comprising refining molten iron using the refining lance described in claim 10, The charging process involves charging molten iron into the converter, An oxidation refining step is performed by blowing a refining gas into the molten iron using the refining lance to carry out oxidation refining. A method for smelting molten iron, including [a specific substance].

13. A converter into which molten iron is charged, A refining apparatus comprising a refining lance according to any one of claims 1 to 9.

14. A converter into which molten iron is charged, A refining apparatus comprising a refining lance as described in claim 10.

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