JP2018070975A - Refining method for molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refining method for a molten iron in which a heat-receiving efficiency is enhanced considering a thermal characteristic of a powder in refining a molten iron to make it possible to improve a blending ratio of a cold iron source such as iron scraps.SOLUTION: In a refining method for a molten iron in which a top-blown lance having a powder supply passage, a fuel gas supply passage and an oxidizing gas supply passage is used to carry out dephosphorization treatment or decarbonization treatment, the dephosphorization treatment or decarbonization treatment described above is carried out on a condition satisfying the following mathematical formula (1) shown by Number 7, wherein S represents a feed rate per 1 t of a total amount of a molten iron of a powder supplied from the powder supply passage and a cold iron source; R represents a volume average particle diameter; Crepresents a specific heat at 298 K; λ represents a heat conductivity at 298 K; and Q represents a fuel gas heating value which is a product of a lower heating value) of a fuel gas supplied from the fuel gas supply passage and a fuel gas flow amount per 1 t of a total amount of the molten iron of a powder and the cold iron source.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hot metal refining method in which hot metal discharged from a blast furnace is subjected to preliminary dephosphorization treatment or decarburization treatment in a hot metal vessel.

Reduction of CO ₂ emissions is an important issue in the steelmaking process. In order to solve the problem, it has been attempted to increase the blending ratio of a cold iron source such as iron scrap as an iron source to be used in the steel making process. The reason why this attempt is made is that in the manufacture of steel products, the production of hot metal in a blast furnace requires a great deal of energy to reduce and melt iron ore, whereas the cold iron source only needs heat of melting. This is because, when a cold iron source is used in the steelmaking process, the amount of energy used for reducing heat of iron ore can be reduced, and the amount of CO ₂ generated can be greatly reduced.

  However, in the molten steel manufacturing process using a combination of blast furnace and converter, the melting heat source of the cold iron source is the sensible heat of the hot metal and the combustion heat due to the oxidation of carbon and silicon in the hot metal, and the melting amount of the cold iron source Has its own limits. Therefore, various means have been proposed in order to increase the blending ratio of the cold iron source in the steelmaking refining process.

  For example, in Patent Document 1, when the hot metal is subjected to preliminary dephosphorization treatment, a carbon source is added to the generated slag during the preliminary dephosphorization treatment, and an oxygen source is blown into the slag to burn the carbon source, A method has been proposed in which the combustion heat is applied to the hot metal.

  Patent Document 2 discloses a method in which carbonaceous materials such as coal, coke, pitch, and heavy oil are blown together with oxygen into a molten iron bath for gasification, and at the same time, iron scrap is melted and refined. A gasifying agent blowing nozzle outside the nozzle, and an oxidation for secondary combustion of the in-furnace generated gas whose nozzle central axis is inclined at an angle of 20 to 60 ° outward from the lance axis There has been proposed a method of melting and refining iron scrap while performing gasification of a carbonaceous material and simultaneously performing secondary combustion of the in-furnace generated gas using an upper blowing lance having an agent blowing nozzle.

  In Patent Document 3, when decarburizing and refining hot metal in a converter, it is independent of the main hole for oxygen ejection and the supply flow path of oxygen gas ejected from the main hole, and is used for fuel gas, oxygen gas and refining. Using an upper blowing lance having a flux supply sub-hole capable of jetting flux simultaneously, the oxygen gas jets ejected from the oxygen jet main holes are kept separated from each other and independently of the oxygen gas jets There has been proposed a converter decarburization refining method in which a flame is formed at the tip of the sub-hole and a refining flux is allowed to pass through the flame to promote hatching of the refining flux.

  In Patent Document 4, when an oxygen source is supplied and the hot metal is preliminarily dephosphorized, a hot metal having a silicon content of 0.2% by mass or less is used and heated or heated to the bath surface of the hot metal. A method of performing preliminary dephosphorization treatment by adding a powdered dephosphorization medium solvent mainly composed of molten CaO together with a gaseous oxygen source through an upper blowing lance has been proposed.

In Patent Document 5, a powdered dephosphorization medium solvent mainly composed of CaO, SiO ₂ and iron oxide is used as a carrier gas with an oxygen-containing gas as a carrier gas from a central hole arranged in the axial center of the top lance. At the same time, a flame is formed by supplying one or more of hydrocarbon-based gas fuel or liquid fuel from a first peripheral hole arranged around the central hole, and the flame is used for the dephosphorization. There has been proposed a method of heating and melting the solvent and preliminarily dephosphorizing the hot metal by spraying a refining oxygen-containing gas onto the hot metal from the second peripheral hole arranged outside the first peripheral hole.

  In Patent Document 6, as a method of compensating heat for reducing oxides in a smelting reduction furnace, when heating a powdered oxide in a flame formed by burning a fuel gas with an oxidizing gas, There has been proposed a method of adjusting the supply ratio of the powdered oxide and the calorific value of the fuel in an appropriate ratio for carrying out appropriate heat compensation in accordance with the particle size of the powder to be heated.

  In Patent Document 7, as a method for compensating heat in a smelting reduction furnace or the like, heating is performed when a granular material containing a carbonaceous material is heated in a flame formed by burning a fuel gas with an oxidizing gas. There has been proposed a method of adjusting the temperature of the carbonaceous material in the granular material to 800 ° C. or less by appropriately controlling the ratio between the heat capacity of the granular material and the calorific value of the fuel gas.

Japanese Patent No. 3577365 JP 60-67610 A Japanese Patent Laid-Open No. 11-80825 Japanese Patent No. 5031977 Japanese Patent No. 4735169 Japanese Patent No. 5087955 JP 2013-133541 A

However, the above prior art has the following problems.
That is, in Patent Document 1, the hot metal temperature is increased by adding the carbon source to the generated slag, but the sulfur contained in the carbon source is mixed into the hot metal and the sulfur concentration in the steel is increased. . Moreover, since it is necessary to ensure the combustion time of a carbon source, there exists a problem that refining time becomes long, productivity falls, and manufacturing cost rises.

  In Patent Document 2, iron scrap is melted while the secondary combustion heat is applied to the iron bath. However, the efficiency of heat application to the iron bath of the secondary combustion heat is low, and much secondary combustion heat is received. If the secondary combustion rate is increased as much as possible, the heat damage of the refractory of the smelting furnace body becomes severe, which causes a problem that the furnace life is shortened.

  In Patent Documents 3 to 5, the hot metal is refined using the combustion heat of the burner lance. The burner lance used has a quadruple pipe structure in Patent Document 4 and a five-pipe structure in Patent Documents 3 and 5. In both methods, a powder refining agent is supplied using oxygen gas as a carrier gas, and at the same time, this refining agent is heated by a burner flame. However, it cannot be said that any method is optimized with respect to the heating efficiency to the refining agent and the influence on the refractory.

  Patent Document 6 proposes an equation that gives an appropriate ratio of the powder oxide supply rate and the calorific value of the fuel by paying attention to the particle diameter of the powdered oxide, and Patent Document 7 also applies to the specific heat of the granular material. While paying attention, we have proposed a relational expression that gives an appropriate ratio between the powder supply rate and the calorific value of the fuel. However, in addition to the particle size and specific heat of the powder, the heating behavior of the powder includes the transfer of the powder. The thermal characteristics are expected to have a great influence, and it cannot be said that Patent Document 6 and Patent Document 7 are optimized in consideration of the thermal characteristics of the powder.

  The present invention has been made in view of the above circumstances. The purpose of the present invention is to improve the heat receiving efficiency in consideration of the thermal characteristics of powder when refining hot metal, It is to provide a hot metal refining method capable of increasing the blending ratio.

  As a result of intensive investigations on the problems of the prior art described above, the inventors have found that the hot metal of powder supplied from the powder supply channel and the source of cold iron in blowing using a burner lance that also serves as an acid feed Of the fuel gas supplied from the fuel gas supply flow path Q (MJ / (min · t)) S / Focusing on Q, by controlling the S / Q in consideration of the heat transfer characteristics of the powder in addition to the particle size and specific heat of the powder, the effect on the refractory damage rate is suppressed, and high heat receiving efficiency is achieved. The present invention was developed by finding out what can be obtained.

The present invention uses an upper blowing lance having at least a powder supply channel, a fuel gas supply channel, and an oxidizing gas supply channel to supply hot gas in the hot metal container from the fuel gas supply channel. An oxidizing gas is supplied from one of the oxidizing gas supply channels to form a flame below the tip of the upper blowing lance, and a lime-based medium is supplied from the powder supply channel. One or more powders of a powdery refining agent, a powdery oxide, and a powdery combustible substance containing a solvent are supplied toward the hot metal bath surface in the hot metal container, and the oxidizing gas supply channel In the hot metal refining method for dephosphorization or decarburization by supplying oxygen-containing gas from the other flow path to the hot metal in the hot metal container,
The supply rate per 1 ton of the total amount of hot metal powder and cold iron source supplied from the powder supply channel is S (kg / (min · t)), and the volume average particle diameter of the powder is R (μm). ), The specific heat at 298K is C _p (kJ / (kg · K)), the thermal conductivity at 298K is λ (W / (m · K)), and the fuel gas supplied from the fuel gas supply channel The fuel gas calorific value, which is the product of the lower heating value (MJ / Nm ³ ) and the fuel gas flow rate (Nm ³ / (min · t)) per 1 ton of hot metal and cold iron source, is expressed as Q (MJ / (min T)) is a hot metal refining method, characterized in that the dephosphorization treatment or the decarburization treatment is performed under conditions satisfying the following mathematical formula (1).

但し、Ｍ_ｉは粉体中に占める粉体ｉの質量比率であり、Ｃ_ｐ，ｊ（ｋＪ／（ｋｇ・Ｋ））は粉体中に含まれる粉体ｉの２９８Ｋにおける比熱、Ｒ_ｉ（μｍ）は粉体中に含まれる粉体ｉの体積平均平均粒径、λ_ｉ（Ｗ／（ｍ・Ｋ））は粉体中に含まれる粉体ｉの２９８Ｋにおける熱伝導率、ｉは粉体の種類を示す整数である、
（３）前記酸化性ガス供給流路は、燃料燃焼用酸化性ガス噴射孔と精錬用酸化性ガス噴射孔とからなること、
がより好ましい解決手段となるものと考えられる。 In the hot metal refining method according to the present invention configured as described above,
(1) The ratio (S / Q) of the supply rate S per 1 ton of the total amount of hot metal of the powder and cold iron source and the calorific value Q of the fuel gas is 1.2 or more,
(2) When the powder is constituted by mixing different kinds of powder, the S / Q is subjected to the dephosphorization treatment or the decarburization treatment under the condition satisfying the following mathematical formula (3):

However, M _i is the mass ratio of the powder i in the powder, and C _{p, j} (kJ / (kg · K)) is the specific heat of the powder i contained in the powder at 298 K, R _i ( μm) is the volume average average particle size of the powder i contained in the powder, λ _i (W / (m · K)) is the thermal conductivity of the powder i contained in the powder at 298K, and i is the powder An integer indicating the type of body,
(3) The oxidizing gas supply flow path includes an oxidizing gas injection hole for fuel combustion and an oxidizing gas injection hole for refining;
Is considered to be a more preferable solution.

  According to the present invention, in hot metal refining, at least one powder of a powder refining agent, a powdered oxide, and a powder heat source containing a lime-based medium solvent from an upper blowing lance is used as a hot metal bath in a hot metal container. When adding powder to the hot metal while being heated by a flame formed below the tip of the top blowing lance when supplying to the surface, in consideration of the thermal conductivity in addition to the particle size and specific heat of the powder In order to optimize the ratio between the supply speed and the fuel heating value, the heat of the flame can be efficiently applied to the hot metal via the powder. Thereby, in the preliminary dephosphorization treatment and decarburization treatment of hot metal, it is realized to increase the blending ratio of cold iron sources such as iron scrap and to suppress the heating temperature while suppressing the refractory melting. .

It is a schematic sectional drawing which shows an example of the converter equipment used when implementing this invention. It is a general | schematic expanded longitudinal cross-sectional view of the upper blowing lance shown in FIG. Is a graph showing the relationship between the S / Q value and Chakunetsu efficiency index in the case of using Al ₂ O ₃ city gas, as a powder as a fuel. It is a graph which shows the relationship between S / Q value and a thermal efficiency index at the time of using propane gas as a fuel and MgO as a powder. It is a graph which shows the relationship between S / Q value and a thermal efficiency index at the time of using propane gas as a fuel and silicon carbide as a powder. It is a graph which shows the relationship between the particle size of each powder, and the S / Q value from which a thermal efficiency index becomes 2 or more.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments suitable for carrying out the present invention will be described with reference to the accompanying drawings.
In practicing the present invention, it is preferable to use a converter as shown in FIG. FIG. 1 shows an example of a top-bottom blow converter used for carrying out the present invention. FIG. 2 is an enlarged partial vertical sectional view of the upper blow lance 3 shown in FIG. 1 (only the lance tip is shown in cross section). The example shown here is a six-pipe lance.

  As shown in FIG. 1, an upper bottom blown converter (hereinafter also simply referred to as “converter”) 1 used for dephosphorization or decarburization in the present invention has an outer shell composed of an iron shell 2, and this iron Inside the skin 2, there are provided a furnace body 4 on which a refractory 3 is applied, and an upper blowing lance 5 inserted into the furnace body 4 and movable in the vertical direction. An upper part of the furnace body 4 is provided with a hot water outlet 7 for pouring hot metal 6 after the dephosphorization process or decarburization process is completed, and a stirring gas 8 is provided at the bottom of the furnace body 4. Are provided with a plurality of bottom blowing tuyere 9. The bottom blowing tuyere 9 is connected to a gas introduction pipe 10.

  The top blow lance 5 includes a carrier gas composed of an inert gas such as nitrogen gas or Ar gas, and any one of a powder refining agent containing a lime-based solvent, a powder oxide, and a powder combustible substance. Powder supply pipe 12 for supplying powder 11 including the above, fuel gas supply pipe 13 for supplying gas fuel such as propane gas, liquefied natural gas, coke oven gas, city gas, and the supplied fuel Oxygen gas for burning gas, oxidizing gas supply pipe 14 for fuel combustion for supplying oxidizing gas for fuel combustion such as air, and refining for supplying oxidizing gas for refining such as oxygen gas An oxidizing gas supply pipe 15 and a cooling water supply pipe and a drain pipe for supplying and discharging cooling water for cooling the upper blowing lance 5 are provided. FIG. 1 shows an example in which the oxidizing gas for combustion and the oxidizing gas for refining are oxygen gases.

  It is possible to use hydrocarbon-based liquid fuel such as heavy oil or kerosene instead of the fuel gas supplied to the fuel gas supply pipe 13, but there is a risk of clogging at the nozzle at the outlet of the flow path. Therefore, in the present invention, fuel gas (gaseous fuel) is used. If it is gaseous fuel, it not only can prevent clogging of a nozzle etc., but there is an advantage that adjustment of a supply speed is easy or misfiring can be prevented because ignition is easy.

  The other end of the powder supply pipe 12 is connected to a dispenser 16 containing the powder 11, and the dispenser 16 is connected to a powder transfer gas supply pipe 17. The inert gas supplied to the dispenser 16 functions as a conveying gas for the powder 11 accommodated in the dispenser 16, and the powder 11 accommodated in the dispenser 16 blows up through the powder supply pipe 12. It is supplied to the lance 5 and can be sprayed toward the hot metal 6 from the tip of the upper blowing lance 5.

  As an example of the upper blowing lance 5, an upper blowing lance having a six-pipe structure shown in FIG. 2 includes a cylindrical lance body 18 and a lance tip made of copper casting connected to the lower end of the lance body 18 by welding or the like. 19. The lance body 18 has six types of concentric steel pipes, that is, a six-fold concentric multiple pipe structure, that is, an innermost pipe 20, a partition pipe 21, an inner pipe 22, an intermediate pipe 23, an outer pipe 24, and an outermost pipe 25. The powder supply pipe 12 communicates with the innermost pipe 20, the fuel gas supply pipe 13 communicates with the partition pipe 21, the fuel combustion oxidizing gas supply pipe 14 communicates with the inner pipe 22, and the refining oxidizing gas supply. The pipe 15 communicates with the middle pipe 23, and the cooling water supply pipe and the drain pipe communicate with either the outer pipe 24 or the outermost pipe 25, respectively. Therefore, the powder 11 to be blown passes through the inside of the innermost pipe 20 together with the carrier gas, and the fuel gas such as propane gas and city gas passes through the gap between the innermost pipe 20 and the partition pipe 21 and is an oxidizing gas for fuel combustion. Passes through the gap between the partition pipe 21 and the inner pipe 22, and the oxidizing gas for refining passes through the gap between the inner pipe 22 and the middle pipe. The gap between the middle tube 23 and the outer tube 24 and the gap between the outer tube 24 and the outermost tube 25 serve as a cooling water supply channel or a drain channel. One of the gap between the middle pipe 23 and the outer pipe 24 and the gap between the outer pipe 24 and the outermost pipe 25 is a water supply flow path, and the other is a drainage flow path. The cooling water is configured to reverse at the position of the lance tip 19.

  The inside of the innermost tube 20 communicates with the powder injection hole 26 disposed substantially at the axial center of the lance tip 19, and the gap between the innermost tube 20 and the partition tube 21 is around the powder injection hole 26. An annular nozzle or a fuel gas injection hole 27 that opens as a plurality of nozzle holes on a concentric circle communicates with the gap between the partition pipe 21 and the inner pipe 22. The fuel combustion oxidizing gas injection holes 28 that open as a plurality of concentric nozzle holes communicate with each other, and the gap between the inner tube 22 and the intermediate tube 23 is formed around the fuel combustion oxidizing gas injection holes 28. A plurality of refining oxidizing gas injection holes 29 communicate with each other. The powder injection hole 26 is a nozzle for spraying the powder 11 together with the carrier gas, the fuel gas injection hole 27 is a nozzle for injecting the fuel gas, and the oxidizing gas injection hole 28 for fuel combustion is the fuel gas. The nozzle for injecting the burning oxidizing gas and the refining oxidizing gas injection hole 29 are nozzles for spraying the refining oxidizing gas.

  That is, the inside of the innermost pipe 20 is a powder supply flow path, the gap between the innermost pipe 20 and the partition pipe 21 is a fuel gas supply flow path, and the gap between the partition pipe 21 and the inner pipe 22 is an oxidizing property for combustion. A gas supply flow path is formed, and a gap between the inner pipe 22 and the intermediate pipe 23 is a refining oxidizing gas supply flow path. In FIG. 2, the powder injection hole 26 is a straight nozzle, and the oxidizing gas injection hole 29 for refining is the shape of a Laval nozzle composed of two cones, a portion whose cross section is reduced and a portion where the cross section is enlarged. However, the powder injection hole 26 may also have a Laval nozzle shape. The fuel gas injection hole 27 and the fuel combustion oxidizing gas injection hole 28 are straight nozzles that open in the shape of an annular slit, or straight nozzles that have a circular cross section. In the Laval nozzle, the position where the cross section is the narrowest, which is the boundary between the two cones of the reduced portion and the enlarged portion, is called a throat.

  Hereinafter, a method for performing the dephosphorization process or the decarburization process using the converter 1 including the above-described top blowing lance 5 will be described.

First, a cold iron source is charged into the furnace body 4. The cold iron source used is iron scrap such as slabs and steel plate crops and city scraps generated at steelworks, bullion recovered from slag by magnetic sorting, and cold iron, reduced iron, etc. can do. The blending ratio of the cold iron source is 4.0% by mass or more, preferably 5.0% by mass or more with respect to the total iron source to be charged (mixing ratio of the cold iron source (mass%) = cold). Iron source blending amount × 100 / (molten iron blending amount + cold iron source blending amount)). This is because when the blending ratio of the cold iron source is less than 4.0% by mass, not only the effect of improving productivity is small but also the effect of reducing the amount of CO ₂ generation is small. The upper limit of the blending ratio of the cold iron source need not be particularly determined, and the iron bath temperature after the dephosphorization treatment or after the decarburization treatment can be added up to an upper limit capable of maintaining the target range. Before and after the cold iron source is charged, the stirring gas 8 starts to be blown from the bottom blowing tuyere 9.

  After charging the cold iron source into the furnace body 4, the hot metal 6 is charged into the furnace body 4. As the hot metal 6, for example, a desulfurization process or a desiliconization process may be performed before the dephosphorization process, or a dephosphorization process may be performed before the decarburization process. Incidentally, the main chemical components of the hot metal 6 before dephosphorization are: C: 3.8 to 5.0 mass%, Si: 0.6 mass% or less, P: 0.08 to 0.2 mass%, S : About 0.05% by mass or less. Moreover, if the hot metal temperature is in the range of 1200 to 1400 ° C., dephosphorization or decarburization can be performed without any problem.

  Next, a refining oxidizing gas such as oxygen gas is sprayed from the refining oxidizing gas injection hole 29 of the upper blowing lance 5 toward the bath surface of the hot metal 6 and an inert gas is supplied to the dispenser 16 as a conveying gas. The powder 11 is sprayed from the powder injection hole 26 of the upper blowing lance 5 toward the bath surface of the hot metal 6 together with the transfer gas. Before and after the powder 11 is sprayed, fuel gas is injected from the fuel gas injection hole 27 of the upper blowing lance 5 and fuel combustion oxidizing gas such as oxygen gas is injected from the fuel combustion oxidizing gas injection hole 28. A flame is generated below the upper blowing lance 5.

  The burner-type top blow lance 5 for refining hot metal by the above method supplies the heat of the flame by supplying iron oxide, lime-based solvent, flammable substance, etc. into the flame formed by burning the fuel gas. It is known that the heat can be transmitted efficiently, thereby improving the efficiency of heat application to the hot metal.

Next, an outline of a refining method for a converter according to an embodiment of the present invention will be described. In dephosphorization blowing, a solid oxygen source such as an oxygen-containing gas, iron ore, and scale is supplied to the bath surface of the hot metal 6 for the purpose of de-P or de-Si and de-P. Further, as a refining agent for the purpose of removing P, lump or powdery quick lime, limestone, decarburization furnace lees, ladle lees, and the like are added. As a slag basicity at the time of dephosphorization, the range of 1.5-3.5 is suitable, and when it remove | deviates from this range, dephosphorization efficiency will deteriorate. Specifically, when the slag basicity is less than 1.5, the dephosphorization ability of slag is low, and when the slag basicity exceeds 3.5, hatching of the refining agent is inhibited, resulting in poor dephosphorization. There is a concern that invites. On the other hand, in decarburization blowing, a solid oxygen source such as an oxygen-containing gas, iron ore, and scale is supplied to the bath surface of the hot metal 6 mainly for the purpose of de-C, and also for de-P and de-C. As the slag basicity of decarburization blowing, a range of 2.5 to 5.5 is suitable, and if it is outside this range, problems such as operational inhibition such as slag jetting during blowing and deterioration of dephosphorization efficiency occur. End up. Specifically, when the slag basicity is less than 2.5, the viscosity of the slag is high, and there is a concern that the slag in the furnace may be ejected from the furnace port during blowing, leading to operational inhibition, and the slag basicity is 5 If it exceeds .5, hatching of the refining agent is hindered, and as a result, there is a concern of dephosphorization failure.
As other refining agents, a refining agent containing an oxide such as Al ₂ O ₃ for promoting the hatching of a dephosphorizing refining agent, a refining agent containing an oxide such as MgO for protecting a refractory A refining agent containing a silicon source such as SiC for reacting with oxygen and supplying combustion heat as a heat source for refining is used according to the purpose.

  In the present invention, a part or all of the refining agent to be charged is powder 11 and is supplied while being heated through a flame formed below the upper blowing lance 5. As shown in the examples described later, in the dephosphorization blowing and decarburization blowing, the operating conditions of the burner lance are changed, and the heat receiving efficiency from the burner lance to the molten metal (= molten heat input amount / total calorific value due to fuel combustion) As a result of the evaluation, it has been found that it is possible to increase the heat receiving efficiency by performing the operation within a range satisfying the following mathematical formulas (1) and (2).

ここで、Ｓ（ｋｇ／（ｍｉｎ・ｔ））は、粉体１１の供給速度、Ｑ（ＭＪ／（ｍｉｎ・ｔ））は、燃料ガスの低位発熱量Ｑ_Ｌ（ＭＪ／Ｎｍ³）と溶銑および冷鉄源の合計量１ｔあたりの燃料ガス流量Ｆ（Ｎｍ³／（ｍｉｎ・ｔ））との積、Ｃ_ｐ（ｋＪ／（ｋｇ・Ｋ））は、粉体１１の２９８Ｋにおける比熱、Ｒ（μｍ）は粉体１１の体積平均平均粒径、λ（Ｗ／（ｍ・Ｋ））は、粉体１１の２９８Ｋにおける熱伝導率である。なお、ここで粉体１１の２９８Ｋにおける熱伝導率は、レーザーフラッシュ法や温度傾斜法で測定することが一般的である。測定試料として、粉体１１を５０μｍ以下に微粉砕した粉末を加圧成形したものを使用するが、この際、加圧成形後の嵩比重が、粉砕前の粉体１１の粒子密度の９０％以上になるように加圧成形して作製した試料で測定する。粉砕前の粉体１１の粒子密度の測定方法としては、液浸法などで実施することができる。

Here, S (kg / (min · t)) is the supply rate of the powder 11, Q (MJ / (min · t)) is the lower heating value Q _L (MJ / Nm ³ ) of the fuel gas and hot metal And the product of the fuel gas flow rate F (Nm ³ / (min · t)) per 1 ton of the cold iron source, C _p (kJ / (kg · K)) is the specific heat of the powder 11 at 298 K, R (Μm) is the volume average average particle size of the powder 11, and λ (W / (m · K)) is the thermal conductivity of the powder 11 at 298K. Here, the thermal conductivity of the powder 11 at 298K is generally measured by a laser flash method or a temperature gradient method. As a measurement sample, a powder obtained by pressure-molding a powder obtained by finely pulverizing the powder 11 to 50 μm or less is used. At this time, the bulk specific gravity after the pressure-molding is 90% of the particle density of the powder 11 before pulverization. Measurement is performed on a sample prepared by pressure molding so as to achieve the above. As a method for measuring the particle density of the powder 11 before pulverization, an immersion method or the like can be used.

The volume average particle size R of the powder 11 is weighted with a volume average particle size (so-called MV value, volume) measured by dispersing the powder with compressed air using, for example, a laser diffraction particle size distribution measuring device. Average sphere equivalent diameter). The lower heating value Q _L (MJ / Nm ³ ) is the standard combustion heat of the fuel gas based on 25 ° C and 1 atm, minus the latent heat of water vapor generated from hydrogen in the fuel gas and water originally contained in the fuel gas. This value is practically equivalent to the amount of heat available for heating the powder.

  When different types of powders having different particle size distributions are mixed, as shown in the following formula (3), the sum of the right side of the formula (1) multiplied by the mass ratio of each powder to be mixed is calculated. Is possible.

ここで、Ｍ_ｉは、粉体１１中に占める粉体ｉの質量比率であり、Ｃ_ｐ，ｉ（ｋＪ／（ｋｇ・Ｋ））は、粉体１１中に含まれる粉体ｉの２９８Ｋにおける比熱、Ｒ_ｉ（μｍ）は、粉体１１中に含まれる粉体ｉの体積平均平均粒径、λ_ｉ（Ｗ／（ｍ・Ｋ））は、粉体１１中に含まれる粉体ｉの２９８Ｋにおける熱伝導率、ｉは粉体の種類を示す整数であり、Σは整数ｉに関する総和、即ち全粉体種類についての合計を意味する。

Here, M _i is the mass ratio of the powder i in the powder 11, and C _{p, i} (kJ / (kg · K)) is 298 K of the powder i contained in the powder 11. Specific heat, R _i (μm) is the volume average average particle diameter of the powder i contained in the powder 11, and λ _i (W / (m · K)) is the powder i contained in the powder 11. The thermal conductivity at 298K, i is an integer indicating the type of powder, and Σ means the sum for the integer i, that is, the sum for all powder types.

  When the value of S / Q is smaller than the range of the above formula, the supply rate of the powder 11 is too small with respect to the heat supply rate of the burner lance, so that the combustion heat of the fuel gas does not sufficiently transfer to the powder 11, The heat transfer efficiency of the molten metal is reduced, and the advantage of the heat-up cost with heat-up agents generally used in dephosphorization blowing and decarburization blowing (for example, ferrosilicon, carbonaceous material, silicon carbide, etc.) In addition, the combustion heat of the fuel gas causes a temperature rise other than the molten metal (for example, an increase in the temperature of the atmosphere in the furnace, etc.), which may cause problems such as promoting the wear of the refractory. At this time, if the thermal conductivity of the powder 11 is relatively high, heat transfer to the powder or molten metal is efficiently achieved up to a condition where the supply rate of the powder 11 is relatively small with respect to the heat supply rate. An increase in exhaust gas temperature can be suppressed.

  Further, when S / Q is larger than 1.2, the total amount of powder 11 is limited, but the total heat supply amount is reduced, and the thermal compensation effect is reduced. Therefore, it is preferable that S / Q is 1.2 or less. The appropriate amount of the powder 11 to be used is determined by the refining purpose and the refining effect of the substance of the powder, and adding more powder 11 than the appropriate amount will waste resources and increase heat loss. There is a risk of inviting. On the other hand, the period for supplying the powder 11 and the fuel gas is not particularly limited as long as it is within a period suitable for the refining purpose to be added. However, the supply speed of the powder 11 and the fuel gas is generally limited by facilities. In consideration of these factors, conditions such as powder particle size, specific heat of powder, thermal conductivity of powder, and calorific value of fuel gas are set so that S / Q is within the above range. The supply speed and supply period of the powder 11 and fuel gas are adjusted accordingly.

<Example 1>
In this example, an upper bottom blowing converter shown in FIG. 1 was used, and a cold iron source 30t and hot metal 270t were charged into the furnace, and dephosphorization blowing was performed. The hot metal used was adjusted in advance to C: 4.5 mass%, Si: 0.4 mass%, and a temperature of 1320 ° C.

Powdered Al ₂ O ₃ was supplied as an auxiliary material via a flame formed below the upper blowing lance 5. Al ₂ O ₃ is added for the purpose of improving the dephosphorization efficiency by increasing the slag liquid phase rate. The total amount of the sum of, Al ₂ O _3, based on the on and Al ₂ O ₃ of the top-blown with powdery from auxiliary raw material charging chutes each test levels were the same. The specific heat Cp at 298 K of the powdered Al ₂ O ₃ used was 0.87 (kJ / (kg · K)), and the thermal conductivity λ at 298 K was 46.1 (W / (m · K)). In addition, powdery Al ₂ O ₃ having a volume average particle size of 10 μm, 30 μm, 100 μm, and 300 μm was used.

Table 1 shows conditions at each level when powdered Al ₂ O ₃ is heated and projected with a burner lance. Level 1 is a level in which powder is not projected and a flame is formed by city gas and city gas combustion oxygen, and the amount of heat received is calculated from the comparison with the case where city gas is not supplied. The heat receiving efficiency was determined in comparison with the amount. Under other dephosphorization blowing test conditions, the heat receiving efficiency at level 1 was set to 1, and the heat receiving efficiency obtained in the same manner was evaluated. In each example, the S / Q value is equal to or greater than the value calculated by (0.08 / C _p ) × R ^0.2 × (λ / 16 ^{) −0.3.} On the other hand, in the comparative example in which the value of S / Q is smaller than the value calculated by (0.08 / C _p ) × R ^0.2 × (λ / 16 ^{) −0.3} , the heat absorption efficiency index is less than 2. I understand that.

FIG. 3 shows the relationship between the heat application efficiency index and the S / Q value when heat-projecting powdered Al ₂ O ₃ . As the S / Q value increased, the heat absorption efficiency index gradually increased and showed a behavior of being saturated at almost the same heat input efficiency index regardless of the particle diameter. In addition, the smaller the particle size, the quicker the heat absorption efficiency index increases, so that the S / Q value where the heat absorption efficiency index exceeds 2 tends to decrease.

<Example 2>
In this example, an upper bottom blowing converter shown in FIG. 1 was used, a cold iron source 30 t and a hot metal 270 t were charged, and decarburization blowing was performed. The hot metal used was adjusted in advance to C: 4.5 mass%, Si: 0.4 mass%, and a temperature of 1320 ° C.

Powdered MgO or powdered silicon carbide (SiC) was supplied as a powder to be heated through a flame formed below the upper blowing lance 5. MgO is added for the purpose of suppressing refractory melting, and silicon carbide is added for the purpose of heating. In each test level, the total addition amount of the total additive of powdered MgO or silicon carbide blown up and MgO and / or silicon carbide added from the auxiliary material charging chute was the same. The specific heat Cp at 298 K of the powdered MgO used was 0.98 (kJ / (kg · K)), and the thermal conductivity λ at 298 K was 59.9 (W / (m · K)). The specific heat Cp at 298K of the powdered SiC used was 1.0 (kJ / (kg · K)), and the thermal conductivity λ at 298K was 18.0 (W / (m · K)). Propane gas (low heating value Q _L = 91.2 MJ / Nm ³ ) was used as the fuel gas. In addition, powdery MgO and powdery SiC each having a volume average particle size of 10 μm, 30 μm, 100 μm, and 300 μm were used.

Table 2 shows conditions at each level when powdered MgO is heated and projected with a burner lance. Level 50 is a level in which no powder is projected and a flame is formed by propane gas and propane gas combustion oxygen, and the amount of heat received is obtained by comparison with the case where propane gas is not supplied, and the total heat generation of the supplied propane gas. The heat receiving efficiency was determined in comparison with the amount. Under other decarburization blow smelting test conditions, the heat receiving efficiency at level 50 was set to 1, and the heat receiving efficiency obtained in the same manner was evaluated. At each level, in the present invention example in which the value of S / Q is equal to or greater than the value calculated by (0.08 / C _p ) × R ^0.2 × (λ / 16) ^−0.3 , the heat absorption efficiency index is 2 or more. On the other hand, in the comparative example in which the value of S / Q is smaller than the value calculated by (0.08 / C _p ) × R ^0.2 × (λ / 16) ^−0.3 , the heat absorption efficiency index is less than 2. I understand that.

  FIG. 4 shows the relationship between the heat receiving efficiency index and the S / Q value when heat-projecting powdered MgO. As in the case of dephosphorization blowing, as the S / Q value increased, the heat absorption efficiency index gradually increased and showed a behavior of being saturated at almost the same heat absorption efficiency index regardless of the particle diameter. In addition, since the heat absorption efficiency index increases rapidly as the particle size decreases, the S / Q value in which the heat absorption efficiency index exceeds 2 also tends to decrease.

Table 3 shows the conditions at each level when powdered SiC is similarly heat-projected with a burner lance. At each level, in the present invention example in which the value of S / Q is equal to or greater than the value calculated by (0.08 / C _p ) × R ^0.2 × (λ / 16) ^−0.3 , the heat absorption efficiency index is 2 or more. On the other hand, in the comparative example in which the value of S / Q is smaller than the value calculated by (0.08 / C _p ) × R ^0.2 × (λ / 16) ^−0.3 , the heat absorption efficiency index is less than 2. I understand that.

  FIG. 5 shows the relationship between the heat absorption efficiency index and the S / Q value when powdered SiC is heated and projected. Similar to the case where powdered MgO was heat-projected, the heat absorption efficiency index gradually increased as the S / Q value increased, and showed a behavior of being saturated at almost the same heat input efficiency index regardless of the particle diameter. In addition, the smaller the particle size, the quicker the heat absorption efficiency index increases. Therefore, there was a tendency for the S / Q value of the heat absorption efficiency index to exceed 2, but the powdered MgO having the same particle diameter was heated. It was found that the thermal efficiency index exceeded 2 with a larger S / Q value as compared with the case of projecting.

Here, from FIGS. 3 to 5, the S / Q value at which the heat absorption efficiency index is 2 or more is estimated for each powder and each particle size, and the S / Q value and the powder particle at which the heat absorption efficiency index is 2 or more. The relationship of the diameter is shown in FIG. As is clear from FIG. 6, if the S / Q value is (0.08 / C _p ) × R ^0.2 × (λ / 16) ^−0.3 or more, the thermal efficiency index becomes 2 or more, and the refractory melts down. And the heat of combustion of the fuel can be efficiently applied to the molten metal.

DESCRIPTION OF SYMBOLS 1 Top bottom blowing converter 2 Iron skin 3 Refractory 4 Furnace main body 5 Top blowing lance 6 Hot metal 7 Outlet 8 Stirring gas 9 Bottom blowing tuyere 10 Gas introduction pipe 11 Powder 12 Powder supply pipe 13 Fuel gas supply pipe 14 Oxidizing gas supply pipe for fuel combustion 15 Oxidizing gas supply pipe for refining 16 Dispenser 17 Powder supply gas supply pipe 18 Lance body 19 Lance tip 20 Innermost pipe 21 Partition pipe 22 Inner pipe 23 Middle pipe 24 Outer pipe 25 Outermost pipe 26 Powder injection hole 27 Fuel gas injection hole 28 Oxidizing gas injection hole for fuel combustion 29 Oxidizing gas injection hole for refining

Claims (4)

The hot metal in the hot metal container uses an upper blowing lance having at least a powder supply channel, a fuel gas supply channel, and an oxidizing gas supply channel. The fuel gas is supplied from the fuel gas supply channel, and the oxidation An oxidizing gas is supplied from one of the reactive gas supply channels to form a flame below the tip of the upper blowing lance, and a powder containing a lime-based solvent is supplied from the powder supply channel. One or more powders of powdery refining agent, powdered oxide, and powdery combustible substance are supplied toward the hot metal bath surface in the hot metal container, and the other oxidizing gas supply flow path is provided. In the hot metal refining method for dephosphorization or decarburization by supplying an oxygen-containing gas from the flow path to the hot metal in the hot metal vessel,
The supply rate per 1 ton of the total amount of hot metal powder and cold iron source supplied from the powder supply channel is S (kg / (min · t)), and the volume average particle diameter of the powder is R (μm). ), The specific heat at 298K is C _p (kJ / (kg · K)), the thermal conductivity at 298K is λ (W / (m · K)), and the fuel gas supplied from the fuel gas supply channel The fuel gas calorific value, which is the product of the lower heating value (MJ / Nm ³ ) and the fuel gas flow rate (Nm ³ / (min · t)) per 1 ton of hot metal and cold iron source, is expressed as Q (MJ / (min T)), the hot metal refining method, wherein the dephosphorization treatment or the decarburization treatment is performed under a condition satisfying the following mathematical formula (1).

  The ratio (S / Q) of the supply rate S per 1 ton of the total amount of hot metal and cold iron source of the powder to the fuel gas heating value Q (S / Q) is 1.2 or more. Refining hot metal. 2. The dephosphorization treatment or the decarburization treatment is performed on the S / Q under a condition satisfying the following mathematical formula (3) when the powder is configured by mixing different kinds of powders. Or the hot metal refining method of 2.

Here, M _i is the mass ratio of the powder i in the powder, and C _{p, i} (kJ / (kg · K)) is the specific heat at 298 K of the powder i contained in the powder, R _i (μm) is the volume average average particle size of the powder i contained in the powder, and λ _i (W / (m · K)) is the heat conduction of the powder i contained in the powder at 298K. Rate, i is an integer indicating the type of powder.   The hot metal refining method according to any one of claims 1 to 3, wherein the oxidizing gas supply channel includes an oxidizing gas injection hole for fuel combustion and an oxidizing gas injection hole for refining. .

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