JP5962162B2 - Hot metal refining method - Google Patents

Description

  The present invention relates to a hot metal refining method for dephosphorization in an iron bath transporter.

In recent years, from the viewpoint of environmental protection, the amount of CO ₂ emission has become a problem. Therefore, a manufacturing process for molten steel has been taken in which the amount of scrap used is increased and the hot metal content is reduced.
In order to dissolve a large amount of scrap, a thermal margin is required, so a heat source such as a carbon source for heating is added to the hot metal during the dephosphorization process to compensate for the shortage of the heat source. (For example, Patent Document 1).
In addition, carbon monoxide (CO) generated in the converter and blown oxygen are combusted on the bath surface, so-called secondary combustion, and the combustion heat is applied to the molten iron (see FIG. Patent Document 2).
Further, for the purpose of improving the efficiency of the metallurgical reaction, in order to promote the hatching of slag, a method of adding a burner to the top blowing lance and heating and adding a dephosphorizing agent from the central hole of the burner is also performed (for example, Patent Documents 3, 4, and 5).

Japanese Patent Laid-Open No. 9-20913 JP 60-67610 A Japanese Patent Laid-Open No. 11-80825 JP-A-2005-336586 JP 2007-92158

In the method of charging the carbonaceous material of Patent Document 1, it becomes possible to secure a heat source. However, the melting cost increases, the sulfur contained in the carbonaceous material is mixed, and S in the blown steel There have been problems such as an increase in concentration and an increase in the amount of carbon dioxide (CO ₂ ) generated.
In the method of burning CO generated in the converter and blown oxygen on the bath surface in Patent Document 2, there is a problem that the furnace body refractory is worn.
In addition, in iron bath transporters such as pots and torpedo cars, the free board (space on the iron bath surface) in the container is narrow, so a large amount of hot metal spitting occurs, so a large amount of oxygen cannot be supplied. There is also.
Patent Documents 3, 4, and 5 relate to a heat application technique using a burner in a converter, but due to the structure of the burner part of the top blowing lance, the flame length of the burner is long, and the surface of the hot metal generally extends from the tip of the lance. However, iron bath transporters such as pots and torpedo cars cannot be blown at the lance height of a converter. Therefore, when a nozzle structure such as Patent Documents 3, 4, and 5 is used in an iron bath transporter, the fuel cannot be burned out within the lance height, and heat cannot be sufficiently applied to the molten iron. There is also.

  The present invention solves the above-mentioned problem, and in refining with an iron bath transporter in which the lance height cannot be sufficiently high, the combustion heat of the burner is efficiently applied to the molten iron, and the scrap blending amount is reduced. It aims at providing the refining method of the molten iron which can be increased.

(1) A method for refining molten iron according to the present invention includes a burner function for injecting oxidizing gas and fuel and a granular material for injecting granular auxiliary materials in an iron bath transporter such as a pan-type iron transporter and a torpedo car. A method for refining molten iron in which hot metal is dephosphorized using a burner lance having a blowing function,
The oxidizing gas ejected from the burner lance and / or the fuel gas jet is refined by applying a swirling flow.

(2) Further, in the above (1), the burner lance is formed by attaching a nozzle tip having one or more downward gas ejection holes to the end of a long cylindrical body, A swirl flow forming member that imparts a swirl flow to the gas jet is provided in one or a plurality of ejection holes.

(3) Further, in the above (1) or (2), as the fuel, one of gas fuel such as propane gas, LNG and C gas, liquid fuel such as heavy oil, or solid fuel such as plastic It is characterized by using seeds or two or more.

(4) Moreover, in the thing in any one of said (1) thru | or (3), granular auxiliary material is any one of iron oxide, a solvent, and a carbon containing substance, or two or more types It is a granular material.

  The method for refining molten iron according to the present invention includes a burner function for injecting an oxidizing gas and fuel and a granular material blowing function for blowing granular auxiliary materials in an iron bath transporter such as a pan-type iron transporter and a torpedo car. A method for refining molten iron using a burner lance having a degassing process, wherein a swirl flow is applied to the gas jet ejected from the burner lance so as to extend from the burner lance. The flame length can be shortened, and even when the lance height cannot be made sufficiently high as in the case of an iron bath transporter, heat can be reliably applied to the molten iron. As a result, the amount of heat applied to the molten iron is increased, the thermal margin is greatly improved, and the scrap blending amount can be increased as compared with the conventional case.

It is explanatory drawing of the nozzle tip of the burner lance used for the refining method of the molten iron which concerns on one embodiment of this invention, Fig.1 (a) is sectional drawing, FIG.1 (b) shows a nozzle tip in Fig.1 (a). It is the figure seen from the arrow AA direction. It is explanatory drawing of the refining equipment used for the refining method of the molten iron which concerns on one embodiment of this invention. 3A and 3B are explanatory views of a nozzle tip of a burner lance of a comparative example, FIG. 3A is a cross-sectional view, and FIG. 3B is a view of the nozzle tip viewed from the direction BB in FIG. . It is a graph which shows the comparison of the burner flame length at the time of using the nozzle tip shown in FIG. 1, and the case where the nozzle tip shown in FIG. 3 is used.

FIG. 2 is an explanatory diagram for explaining an outline of molten iron refining equipment for performing the molten iron refining method according to the present embodiment. First, the molten iron refining equipment will be described with reference to FIG.
The molten iron refining equipment 1 includes a pan-type iron bath transporter 5 containing a molten iron 3 produced by a hot metal production facility such as a blast furnace, a burner lance 7, and an injection lance 9.
The burner lance 7 according to the present embodiment has a burner function for injecting an oxidizing gas and fuel and a granular material blowing function for blowing powdery auxiliary materials.

1A and 1B are explanatory views for explaining a main part of the burner lance 7, in which FIG. 1A is an axial sectional view of a tip portion, and FIG. 1B is an AA view of FIG. is there.
As shown in FIG. 1, the burner lance 7 is directed from the center to the outer peripheral portion, a powder injection hole 11 for injecting powder, a fuel injection hole 13 for injecting gaseous fuel, and a fuel for burning the fuel. A combustion oxidizing gas injection hole 15 for injecting an oxidizing gas is formed by attaching a nozzle tip 17 concentrically arranged at the tip of a long cylindrical body 19. Since the arrangement of each injection hole is as described above, as shown in FIG. 1B, the cross-sectional shape of the granular material injection hole 11 is circular, the fuel injection hole 13 and the combustion oxidizing gas injection hole. The cross-sectional shape of 15 is an annular shape.
A spiral swirl vane 21 is provided on the inner wall of the combustion oxidizing gas injection hole 15 to impart a swirling flow to the combustion oxidizing gas to be injected.
In addition, a cooling water circulation path 23 through which cooling water is circulated and supplied is provided on the outer peripheral portion of the combustion oxidizing gas injection hole 15 to prevent the burner from being melted. The cooling water circulation path 23 is connected to a cooling water supply pipe and a cooling water drain pipe (not shown).

By imparting a swirl flow to the combustion oxidizing gas, mixing of the fuel and the combustion oxidizing gas is promoted, the fuel combustibility is improved, and the flame length is shortened.
The point that the flame length is shortened will be described in more detail. 3 is an explanatory diagram of the nozzle tip 25 that does not have the swirl vane 21. The nozzle tip 25 of FIG. 3 is different from that of FIG. 1 only in that it does not have the swirl vane 21. The configuration is the same. Therefore, in FIG. 3, the same parts as those in FIG.
FIG. 4 is a graph showing a comparison of burner flame length when the nozzle tip 17 shown in FIG. 1 is used and when the nozzle tip 25 shown in FIG. 3 is used, and the vertical axis indicates the burner flame length ( m), the horizontal axis indicates the flow rate of propane gas (Nm ³ / min) as fuel.
Both types of nozzle tips have longer burner flame lengths as the fuel and combustion oxygen flow rates increase.
However, in the case of using the nozzle tip 25 of FIG. 3, even when the fuel flow rate is small, the flame length is longer than the lance height equivalent (1 m) at the actual dephosphorization process. On the other hand, when the swirl flow is applied by the nozzle tip 17 of FIG. 1, the flame length is less affected by the fuel flow rate than that of FIG. 3, and is within the range corresponding to the lance height at the time of dephosphorization under any conditions. ing.
The reason why the flame length is shortened is that, as described above, the mixing of the fuel and the oxidizing gas for combustion is promoted to improve the combustibility of the fuel.
In this way, by shortening the flame length, even if the lance height cannot be sufficiently high, such as in iron bath transporters such as pan-type iron transporters and torpedo cars, heat is applied to the molten iron 3. Can be ensured. As a result, the amount of heat applied to the molten iron is increased, and the amount of scrap can be increased.

Next, a method for refining molten iron using the refining equipment 1 will be described.
In the method for refining molten iron according to an embodiment of the present invention, a burner function for injecting oxidizing gas and propane gas as fuel and lime as a granular auxiliary material are blown in the pan-type iron bath transporter 5. A method for refining molten iron using a burner lance 7 having a function of blowing particles, wherein the molten iron is dephosphorized by applying a swirl flow to the gas jet ejected from the burner lance 7. It is what.
In the present embodiment, as shown in FIG. 2, iron oxide is blown from the injection lance 9.

  According to the molten iron refining method of the present embodiment, the flame length can be shortened, and even when the lance height cannot be sufficiently high as in the pan-type iron bath transporter 5, the molten iron 3 It is possible to ensure heat buildup. As a result, the amount of heat applied to the molten iron 3 is increased, the thermal margin is greatly improved, and the scrap blending amount can be increased as compared with the prior art. As a result, it is possible to reduce the melting cost of dephosphorization, achieve resource saving and energy saving, and bring about an industrially beneficial effect.

In the above embodiment, propane gas is taken as an example of the fuel injected from the fuel injection hole 13, but in addition to this, gaseous fuel such as LNG and C gas, liquid fuel such as heavy oil, or solid fuel such as plastic 1 type (s) or 2 or more types can be used.
Moreover, in said embodiment, although the lime which is a solvent was injected from the granular material injection hole 11, and iron oxide was injected from the injection lance 9 different from the burner lance 7, the granular material injection hole As the powdery auxiliary material to be ejected from No. 11, any one of iron oxide, a solvent, and a carbon-containing substance, or two or more kinds thereof can be used.

In the above embodiment, the example in which the swirl vane 21 that imparts the swirl flow to the combustion oxidizing gas to be injected is provided on the inner wall of the combustion oxidizing gas injection hole 15 is shown. A swirl vane may be provided on the inner wall of the fuel injection hole 13. Further, swirl vanes may be provided in both the combustion oxidizing gas injection hole 15 and the fuel injection hole 13.
In the above embodiment, the swirl vane 21 is cited as an example of the swirl flow forming member of the present invention. However, the swirl flow forming member is not limited to this, and swirl to the gas injected from the burner lance. The shape of the swirl flow forming member is not particularly limited as long as it can impart a flow.
Further, as a method for imparting a swirl flow to the gas injected from the burner lance, in addition to providing a swirl flow forming member in the gas injection hole, for example, the gas discharge direction of the injection hole 15 is made to be a tangent method on the inner surface of the nozzle tip 17 outlet. Thus, a swirl flow may be formed.

  In the above embodiment, the pan-type iron bath transporter 5 is shown as an example of the iron bath transporter, but it goes without saying that the same result can be obtained even when the phosphorus removal treatment is performed with a torpedo car.

An experiment for confirming the effect of the present invention was conducted, which will be described below.
Hot metal was charged into a 2.5-ton pan-type iron transporter and dephosphorized and blown. In dephosphorization blowing, molten iron having a temperature of 1400 ° C. was charged, and then iron oxide was supplied from the injection lance 9.
Further, lime as powder, propane gas as fuel, and oxygen for fuel combustion were supplied from an upper blowing lance provided with a burner function and a powder blowing function.
The burner lances used were those having the nozzle tip 17 shown in FIG. 1 as an example of the invention and those having the nozzle tip 25 shown in FIG. 3 as a comparative example.
As another comparative example, an experiment was also conducted in the case where nitrogen (N2) gas was supplied instead of fuel and oxygen using the nozzle tip 17 of FIG. 1 and not used as a burner. Furthermore, the addition amount of lime was adjusted so that the basicity (mass% CaO / mass% SiO ₂ ) of the slag in the furnace was 2.5.
The temperature and chemical composition of the molten iron are shown in Table 1. In Table 1, each component is a value adjusted before the dephosphorization treatment.

  Table 2 shows the blowing conditions for the inventive examples and the comparative examples.

The difference between Invention Examples 1 to 3 is that the amount of propane gas and combustion oxygen gas blown from the top blowing lance is changed. Comparative Examples 1 to 3 correspond to Inventive Examples 1 to 3, respectively, and the difference from Inventive Examples 1 to 3 is only the nozzle tips used.
In Comparative Example 4, the nozzle tip 17 shown in FIG. 1 is used, but nitrogen (N 2) gas is supplied instead of fuel and oxygen and is not used as a burner.
Table 3 shows experimental results based on differences in the blowing conditions of Invention Examples 1 to 3 and Comparative Examples 1 to 4.

In any of Comparative Examples 1 to 4 and Invention Examples 1 to 3, the phosphorus (P) concentration and the carbon (C) concentration after the treatment vary slightly, but no significant difference is observed.
On the other hand, at the post-treatment temperature, in Comparative Examples 1 to 3 and Inventive Examples 1 to 3 using a burner, the temperature is higher than that of Comparative Example 4 using no burner.
Further, as can be seen from comparison between Invention Example 1 and Comparative Example 1, Invention Example 2 and Comparative Example 2, Invention Example 3 and Comparative Example 3, In Invention Examples 1 to 3, Comparative Example 1 under the same fuel flow rate condition. The post-treatment temperature is higher than ~ 3. As shown in FIG. 4, the nozzle tip 17 capable of imparting a swirling flow efficiently burns fuel within the lance height, whereas the nozzle tip 25 not capable of imparting a swirling flow has a long flame length. Therefore, the fuel cannot be combusted within the lance height, and the amount of heat applied to the hot metal with respect to the fuel flow rate becomes small.

  From the above, refining using a top blow lance with burner function and powder blowing function in dephosphorization processing in a refining vessel with a low lance height, such as iron bath transporters such as pot type iron transporters and torpedo cars. At that time, by applying a swirl flow to the gas jet ejected from the gas ejection hole and refining, the thermal margin is greatly improved compared to the conventional one, and more scrap can be melted than before. Proven.

DESCRIPTION OF SYMBOLS 1 Molten iron refining equipment 3 Molten iron 5 Pan type iron bath transport device 7 Burner lance 9 Injection lance 11 Granule injection hole 13 Fuel injection hole 15 Combustion oxidizing gas injection hole 17 Nozzle tip 19 Cylindrical body 21 Swirling blade 23 Cooling water circulation Road 25 Nozzle tip

Claims (4)

In iron bath transporters such as pot-type iron transporters and torpedo cars, the removal of hot metal using a burner lance that has a burner function for injecting oxidizing gas and fuel and a granular material blowing function for blowing granular auxiliary materials A method for refining molten iron for phosphorus treatment,
A method for refining molten iron, wherein a revolving flow is imparted to the oxidizing gas and / or the gas jet of the fuel ejected from the burner lance.   The burner lance is formed by attaching a nozzle tip having one or more downward gas ejection holes to the end of a long cylindrical body, and imparts a swirl flow to one or more of the gas ejection holes. The method for refining molten iron according to claim 1, wherein a swirl flow forming member is provided.   3. The fuel according to claim 1, wherein one or more of gaseous fuels such as propane gas, LNG and C gas, liquid fuels such as heavy oil, and solid fuels such as plastic are used as the fuel. The method for refining molten iron as described. 4. The powdery auxiliary material is any one of iron oxide, a solvent, and a carbon-containing substance, or two or more kinds of powder particles. 5. Method for refining molten iron.