JP5915568B2 - Method of refining hot metal in converter type refining furnace - Google Patents

Description

  The present invention supplies a refining oxygen gas and a secondary combustion oxygen gas from a top blowing lance into a converter type refining furnace, and a reaction between the refining oxygen gas and carbon in the molten iron in the converter type refining furnace. The present invention relates to a method for oxidizing and refining hot metal contained in a converter type refining furnace while performing secondary combustion of the generated CO gas with secondary combustion oxygen gas, and more specifically, the hot metal in the converter type refining furnace. The present invention relates to a hot metal refining method in a converter-type refining furnace, which can efficiently apply secondary combustion heat to the furnace.

  In recent years, the reduction of slag generation in hot metal decarburization and refining (also called “decarburization treatment”) in converter-type refining furnaces, reduction of the amount of solvent used for dephosphorization, mainly CaO, and the yield of Mn ore For the purpose of improvement, a dephosphorization treatment (also referred to as “preliminary dephosphorization treatment”) is widely performed as a pretreatment for hot metal before decarburization refining in a converter type refining furnace. This hot metal dephosphorization process is characterized by being performed on hot metal in a relatively low temperature range of about 1300 to 1400 ° C., which is advantageous for dephosphorization equilibrium. In the dephosphorization process, the hot metal temperature is relatively low. During the dephosphorization process, the hot metal adheres to and solidifies on the inner wall and furnace opening of the converter-type smelting furnace and deposits the metal, leading to a decrease in the yield of hot metal. There was a point.

Also, in situations where the price of hot metal raw material is soaring and the amount of CO ₂ gas generated is required to be reduced, a large amount of iron scrap is charged into the converter-type refining furnace together with hot metal in the dephosphorization of hot metal. There is a need to dissolve scrap during the dephosphorization process. However, hot metal dephosphorization using a converter-type smelting furnace may cause heat loss due to charging of the hot metal into the converter-type smelting furnace and the hot metal discharged from the converter-type smelting furnace after smelting. Therefore, it is basically disadvantageous for melting iron scrap. Therefore, in order to ensure the heat for melting iron scrap in the hot metal, the advantages of the hot metal dephosphorization process described above are abandoned, and the converter type is performed without dephosphorizing the hot metal using a converter type refining furnace. In some cases, decarburization and refining of hot metal was performed in a refining furnace. In this case, problems such as an increase in the amount of slag generated and an increase in manufacturing cost occur.

In order to solve these problems, various means have been proposed. As a method of applying heat to the hot metal during the dephosphorization process in order to promote the melting of iron scrap, for example, Patent Document 1 discloses a process in which a hot metal dephosphorization process using a converter-type smelting furnace is used. A method has been proposed in which the secondary combustion rate is in the range of 12% or more. Patent Document 1 says that an increase in the iron scrap blending ratio can be obtained by using the secondary combustion heat, but it does not disclose how to heat the secondary combustion heat to the hot metal, which is efficient for hot metal. It is hard to say that secondary combustion heat is applied. The secondary combustion means that CO gas generated by the reaction between carbon in the hot metal and the oxygen source for dephosphorization is burned into CO ₂ gas in the furnace by the oxygen source during the dephosphorization process.

  In Patent Document 2, when hot metal is dephosphorized, hot metal having a silicon content of 0.2% by mass or less is used, and from the center hole, powder CaO-based dephosphorizing refining agent, oxygen gas, and surrounding holes are used. A powdered CaO-based dephosphorization agent that uses a top lance with a quadruple tube structure to supply fuel such as propane gas, forms a flame at the tip of the top lance, and is heated, heated, or melted with this flame. There has been proposed a method of dephosphorizing by spraying hot metal on the hot metal together with oxygen gas. This method is an effective method for raising the hot metal temperature, but it is necessary to modify the structure of the top blowing lance so that powder can be blown, and it can be applied to equipment with a general top blowing lance installed. Can not do it.

In addition, as a method for preventing the adhesion of the metal to the inner wall and the furnace port of the converter type refining furnace and the method for melting the adhered metal, for example, in Patent Document 3, at the tip of the top blowing lance, on the circumference An inner nozzle having an outward inclination angle θ _{1 and} an outer nozzle having an outward inclination angle θ _{2 in} the same direction as the inner nozzle are provided so that θ ₂ is larger than θ _1. A refining method is disclosed in which the overlapping area of the cavity (injection surface to the molten metal) due to the oxygen jet of the outer nozzle is controlled to be 50% or less of the area of the cavity due to the oxygen jet of the inner nozzle. Patent Document 3 is a technique that reduces the collision force of the oxygen jet to the hot metal surface by reducing the overlap of oxygen jets from the nozzles provided at the tip of the lance, thereby reducing spitting (scattering of metal). is there. However, this method seems to have an effect of reducing spitting, but as long as an oxygen jet is blown onto the hot metal surface, it is difficult to make spitting zero, and in the furnace and the furnace mouth. If a bullion has adhered, it is impossible to remove the bullion.

  In Patent Document 4, a main nozzle composed of a refining laval nozzle and a straight sub-nozzle for promoting secondary combustion are alternately arranged at the tip of the top lance, and an upper position having a predetermined interval from the tip of the lance. An upper blowing lance having an auxiliary nozzle for melting a metal bar having a diameter of 1 to 15 mm at an angle of −45 ° to + 70 ° with respect to the horizontal is disclosed. Patent Document 4 states that by using this top blowing lance, the metal that has adhered to the entire area of the converter-type refining furnace can be removed. However, a refining laval nozzle and a secondary combustion accelerating nozzle are provided at the tip of the lance. Since the sub nozzle is arranged, the oxygen jet from the secondary nozzle for accelerating secondary combustion may affect the oxygen jet from the refining laval nozzle, and there is a concern that the refining ability is lowered. Moreover, when there are few ingots adhering to the inner wall of the smelting furnace, there is a concern that the refractory melting may be accelerated by the oxygen gas blown from the auxiliary nozzle toward the inner wall.

JP 2002-167614 A JP 2005-336586 A Japanese Patent Laid-Open No. 11-36009 JP-A-10-219329

  As described above, conventionally proposed technology for applying heat to the hot metal to promote melting of iron scrap in the dephosphorization process, as well as technology for preventing adhesion of metal to the inner wall of a converter-type refining furnace, and dissolution of metal The technology is still not fully effective, and there are many points that need to be improved.

  The present invention has been made in view of the above circumstances. The purpose of the present invention is to supply oxygen gas from an upper blowing lance and oxidize and refine hot metal contained in a converter type refining furnace. It is to provide a method for refining hot metal in a converter smelting furnace that can apply heat to the hot metal at the same time. Furthermore, at the same time as applying heat to the hot metal, the ground attached to the inner wall of the converter smelting furnace is provided. It is an object of the present invention to provide a hot metal refining method in a converter type refining furnace that can efficiently dissolve gold.

The gist of the present invention for solving the above problems is as follows.
[1] A refining main hole nozzle in a vertically downward direction or an obliquely downward direction is disposed at the tip of the upper blowing lance, and horizontally or obliquely on the side of the upper blowing lance at an upper position spaced from the tip of the upper blowing lance. Using an upper blowing lance in which a sub-hole nozzle in a downward direction is disposed, oxygen gas is supplied from the refining main hole nozzle and the sub-hole nozzle into the converter refining furnace, and the furnace of the converter refining furnace The control index (A) for the secondary combustion rate in the furnace is shown below when the hot metal contained in the converter refining furnace is oxidatively refined by blowing the stirring gas from the bottom blowing tuyeres installed at the bottom to the hot metal. When the control index (B) of the heat rate of the secondary combustion heat to the hot metal is defined by the following formula (2), the secondary combustion rate in the furnace is controlled. The product of the index (A) and the control index (B) of the heat rate of secondary combustion heat to the hot metal A × B) satisfies the relationship of the following formula (3): the ratio of the oxygen gas flow rate supplied from the sub-hole nozzle to the oxygen gas flow rate supplied from the refining main hole nozzle, and the slag present in the furnace One or more of the basicity ((mass% CaO) / (mass% SiO ₂ )) and the stirring gas flow rate per ton of hot metal blown from the bottom blowing tuyere are adjusted. A method for refining hot metal in a converter-type refining furnace.
A = (30 + R ₁ × 150−6 × S _ba ) (1)
B = (400 × F _b −20) (2)
A × B ≧ 650 (3)
However, in the formulas (1) to (3), A is a control index of the secondary combustion rate in the furnace, B is a control index of the heat rate of secondary combustion heat to the hot metal, and R ₁ is Ratio (F _s / F) of the oxygen gas flow rate (F _s , unit: Nm ³ / min) supplied from the sub-hole nozzle to the oxygen gas flow rate (F _m , unit: Nm ³ / min) supplied from the refining main hole nozzle _m ), S _ba is the basicity of the slag present in the furnace, F _b is the stirring gas flow rate (Nm ³ / (min · t)) per ton of hot metal blown from the bottom blowing tuyere, and F _b Is in the range of 0.07 to 0.25 Nm ³ / (min · t).
[2] The control index (B ′) for the rate of heat application of the secondary combustion heat to the hot metal other than the hot metal is represented by the following formula (4) based on the control index (B) for the heat rate of secondary combustion heat to the hot metal: The product (A × B ′) of the control index (A) of the secondary combustion rate in the furnace and the control index (B ′) of the heat rate of the secondary combustion heat other than the hot metal is as follows: Further, the ratio of the oxygen gas flow rate supplied from the sub-hole nozzle to the oxygen gas flow rate supplied from the main hole nozzle for refining, the basicity of the slag present in the furnace ((mass% The above [1], wherein any one or more of the stirring gas flow rate per ton of hot metal blown from the bottom blowing tuyere is adjusted (CaO) / (mass% SiO ₂ )) The method for refining hot metal in the converter type refining furnace described in 1.
B ′ = (100−B) = (120−400 × F _b ) (4)
A × B ′ ≧ 1000 (5)
However, in the formulas (4) and (5), B ′ is a control index for the rate of heat deposition of the secondary combustion heat other than the hot metal.
[3] The product (A × B ′) of the control index (A) of the secondary combustion rate in the furnace and the control index (B ′) of the heat rate of the secondary combustion heat other than the hot metal is In order to satisfy the equation (6), the ratio of the oxygen gas flow rate supplied from the sub-hole nozzle to the oxygen gas flow rate supplied from the refining main hole nozzle, the basicity of the slag present in the furnace ((mass% CaO ) / (Mass% SiO ₂ )), wherein any one or more of the stirring gas flow rate per ton of hot metal blown from the bottom blowing tuyere is adjusted. The hot metal refining method in the converter type refining furnace as described.
3000 ≧ A × B ′ (6)
[4] In the converter-type refining furnace according to any one of [1] to [3] above, the oxidation refining is a dephosphorization treatment performed on hot metal as a preliminary treatment. Hot metal refining method.
[5] The product (A × B ′) of the control index (A) of the secondary combustion rate in the furnace and the control index (B ′) of the heat rate of the secondary combustion heat other than the hot metal is In order to satisfy the formula (7), the ratio of the oxygen gas flow rate supplied from the sub-hole nozzle to the oxygen gas flow rate supplied from the refining main hole nozzle, the basicity of the slag present in the furnace ((mass% CaO ) / (Mass% SiO ₂ )), wherein any one or two or more of the stirring gas flow rate per ton of hot metal blown from the bottom blowing tuyere is adjusted. The hot metal refining method in the converter type refining furnace as described.
2500 ≧ A × B ′ (7)

  According to the present invention, the control of the secondary combustion rate is performed so that the product (A × B) of the control index of the secondary combustion rate and the control index of the heat rate of the secondary combustion heat to the hot metal becomes 650 or more. Since at least one of the operating conditions directly affecting the index and the control index of the heat rate of secondary combustion heat to the hot metal is adjusted, a predetermined amount or more of the secondary combustion heat is always applied to the hot metal and converted. In hot metal oxidative refining such as dephosphorization using a furnace-type refining furnace, it is possible to efficiently apply heat to the hot metal for melting a cold iron source such as iron scrap. Furthermore, when the product (A × B ′) of the control index of the secondary combustion rate and the control index of the heat rate of the secondary combustion heat other than the hot metal is controlled to 1000 or more, the converter type refining furnace It is possible to efficiently dissolve the metal attached to the inner wall.

  That is, in the present invention, since the secondary combustion heat is actively used as a heat source for melting a cold iron source such as iron scrap, and as a heat source for removing metal attached to the inner wall of the converter type refining furnace, Even when adding cold iron sources such as iron scrap, it is not necessary to use expensive heat sources such as ferrosilicon and metal Al, and the work of removing the furnace body ingots outside the refining time is reduced. As a result, industrially beneficial effects such as an improvement in the productivity of the converter-type smelting furnace and an improvement in the yield of hot metal are brought about.

It is a schematic sectional drawing which shows one example of the converter type refining equipment used when implementing this invention. It is a general | schematic expanded longitudinal cross-sectional view of the upper blowing lance shown in FIG. It is a cross-sectional conceptual diagram of the converter type refining furnace at the time of the dephosphorization process performed in the state which stopped oxygen gas supply from a subhole nozzle. It is a cross-sectional conceptual diagram of the converter type refining furnace at the time of the dephosphorization process performed in the state which supplied oxygen gas from the subhole nozzle. Is a diagram showing the relationship between the ratio R ₁ and the secondary combustion rate. It is a figure which shows the relationship between slag basicity and a secondary combustion rate. It is a figure which shows the relationship between the gas flow rate for stirring, and the heat rate of the secondary combustion heat to the hot metal. It is a figure which shows the relationship between a product (AxB) and hot metal temperature rise amount ((DELTA) T).

  Hereinafter, the present invention will be described in detail.

  As a heat source for melting a cold iron source such as iron scrap, the present inventors steadily heat the secondary combustion heat to the hot metal, and further, the secondary combustion heat is applied to the inner wall of the converter type refining furnace. In order to efficiently dissolve the adhered metal, tests were conducted under variously changed operating conditions in the dephosphorization treatment of hot metal in a converter type refining furnace. The converter-type refining furnace used has a refining main hole nozzle arranged vertically or obliquely downward at the tip of the upper blow lance, and the upper blow lance at an upper position spaced from the tip of the upper blow lance. It is a converter type refining furnace provided with an upper blowing lance in which a side hole nozzle in a horizontal direction or a diagonally downward direction is arranged on a side surface. Using this converter-type refining furnace, oxygen gas is supplied from the refining main hole nozzle to the hot metal, and the hot metal is dephosphorized while supplying oxygen gas mainly responsible for secondary combustion from the subhole nozzle. At that time, we investigated the secondary combustion rate, the rate of heat of secondary combustion heat to the hot metal, the amount of heat of secondary combustion heat to the hot metal, the amount of heat of secondary combustion heat to other than hot metal, etc. .

  First, the converter type refining equipment used in the present invention will be described. FIG. 1 is a schematic cross-sectional view showing an example of a converter-type refining facility used in carrying out the present invention, and FIG. 2 is a schematic enlarged vertical cross-sectional view of the upper blowing lance 3 shown in FIG.

As shown in FIG. 1, a converter-type smelting furnace 1 used in the present invention has an outer shell composed of an iron shell 4, and a converter-type smelting furnace 2 in which a refractory 5 is applied inside the iron shell 4. And an upper blowing lance 3 which is inserted into the converter type refining furnace 2 and is movable in the vertical direction. A top 6 of the converter type refining furnace 2 is provided with a hot water outlet 6 for discharging the hot metal 21 after the dephosphorization process, and a stirring gas 23 is provided at the bottom of the converter type refining furnace 2. A plurality of bottom blowing tuyere 7 for blowing are provided. The bottom blowing tuyere 7 is connected to a gas introduction pipe 8. Further, a flue 11 for collecting exhaust gas generated from the converter refining furnace 2 is provided above the converter refining furnace 2, and the CO gas concentration in the exhaust gas is disposed in the middle of the flue 11. An exhaust gas analyzer 12 for analyzing (volume%) and CO ₂ gas concentration (volume%) is installed. The secondary combustion rate is obtained from the CO gas concentration and CO ₂ gas concentration in the analyzed exhaust gas. The secondary combustion rate is defined by the following equation (8).
A _PC = V _CO2 × 100 / (V _CO2 + V _CO ) (8)
However, in the equation (8), _APC is the secondary combustion rate (%), V _CO2 is the CO ₂ gas concentration (volume%) in the exhaust gas, and V _CO is the CO gas concentration (volume%) in the exhaust gas.

  A refining oxygen gas supply pipe 9 for supplying refining oxygen gas injected from the refining main hole nozzle and a sub hole for supplying oxygen gas injected from the sub hole nozzle to the top blowing lance 3. An oxygen gas supply pipe 10 is connected to a cooling water supply pipe (not shown) and a drain pipe (not shown) for supplying and discharging cooling water for cooling the top blowing lance 3. .

  As shown in FIG. 2, the upper blow lance 3 is composed of a cylindrical lance main body 13 and a copper cast lance tip 14 connected to the lower end of the lance main body 13 by welding or the like. 13 is composed of four types of steel pipes that are concentric, that is, an outer pipe 15, an intermediate pipe 16, an inner pipe 17, and a partition pipe 18, that is, a quadruple pipe. However, the partition pipe 18 is not arranged up to the position of the lance tip 14, and is closed just below the installation position of the sub-hole nozzle 20.

  The refining oxygen gas supply pipe 9 communicates with the partition pipe 18, the sub-hole oxygen gas supply pipe 10 communicates with the inner pipe 17, and a cooling water supply pipe and a drain pipe (not shown) are respectively provided in the outer pipe 15. Alternatively, it communicates with either one of the intermediate tubes 16. That is, the refining oxygen gas injected from the refining main hole nozzle 19 passes through the inside of the partition pipe 18, and the oxygen gas injected from the subhole nozzle 20 passes through the gap between the inner pipe 17 and the partition pipe 18, A gap between the pipe 15 and the middle pipe 16 and a gap between the middle pipe 16 and the inner pipe 17 serve as a cooling water supply channel or a drain channel. One of the gap between the outer pipe 15 and the middle pipe 16 and the gap between the middle pipe 16 and the inner pipe 17 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 14. After the partition pipe 18 is interrupted, the refining oxygen gas supplied from the refining oxygen gas supply pipe 9 is configured to pass through the inside of the inner pipe 17.

  At the tip of the lance tip 14, a plurality of refining main hole nozzles 19 are arranged at substantially equal intervals in the circumferential direction of the tip surface, pass through the inside of the partition pipe 18, and after the partition pipe 18 is interrupted, Oxygen gas that has passed through the inside of the pipe 17 is jetted from the refining main hole nozzle 19 as an oxygen gas jet. The refining main hole nozzle 19 takes the shape of a Laval nozzle composed of two conical bodies, the portion of which the cross section is reduced and the portion of the enlarged portion, and the refining oxygen gas is sonic from the refining main hole nozzle 19. Injected at supersonic or subsonic speed. In FIG. 2, the refining main hole nozzle 19 faces obliquely downward, but it may be vertically downward, and it is not essential to install a plurality of them, and only one may be arranged. .

  In addition, the lance body 13 is provided with an obliquely downward sub-hole nozzle 20 that opens in the side surface of the lance body 13 at an upper position spaced from the tip of the upper blowing lance 3 in the circumferential direction of the lance body 13. A plurality of oxygen gas is provided at equal intervals, and oxygen gas that has passed through the gap between the inner pipe 17 and the partition pipe 18 is jetted from the sub-hole nozzle 20. The number of sub-hole nozzles 20 installed in the circumferential direction is set to 4 or more, preferably 6 or more, from the viewpoint of evenly injecting oxygen gas into the furnace. The distance from the tip of the upper blowing lance 3 to the installation position of the sub-hole nozzle 20 (the lower end of the opening of the sub-hole nozzle 20) does not need to be specified in particular, and is an arbitrary distance in the range of 0.5 to 5.0 m. do it. The sub-hole nozzle 20 is a straight nozzle having a circular cross section and a constant cross-sectional area in the nozzle axial direction.

The upper blowing lance 3 shown in FIGS. 1 and 2 is configured so that the oxygen gas flow rate can be independently controlled by the refining main hole nozzle 19 and the sub-hole nozzle 20. Installation may be omitted and oxygen gas may be supplied through one flow path. However, in this case, the ratio R ₁ (= F _s / F) between the oxygen gas flow rate (F _m ) supplied from the refining main hole nozzle 19 and the oxygen gas flow rate (F _s ) supplied from the sub hole nozzle 20. F _m ) is a constant value corresponding to the sectional area of each nozzle, and the ratio R ₁ cannot be arbitrarily changed during refining. In the present invention, as described later, changing the ratio R ₁ during refining is one effective means. From the viewpoint of easily achieving the present invention, as shown in FIG. It is preferable that the hole nozzle 19 and the sub-hole nozzle 20 are configured so that the oxygen gas flow rate can be controlled independently. In FIG. 2, the sub-hole nozzle 20 is diagonally downward, but the direction may be horizontal.

In the converter-type refining facility 1 having this configuration, the hot metal 21 is charged into the converter-type refining furnace 2, and further, quick lime is charged as a CaO-based dephosphorization refining agent, and nitrogen gas or While blowing Ar gas as a stirring gas, oxygen gas was blown as a dephosphorizing agent from the refining main hole nozzle 19 of the upper blowing lance 3 toward the hot metal 21, and inside the furnace from the sub-hole nozzle 20 of the upper blowing lance 3. Oxygen gas for secondary combustion is injected into the space, and the hot metal 21 is dephosphorized. The quick lime added to the furnace reacts with iron oxide (FeO) produced by oxidizing the hot metal 21 by the oxygen gas supplied from the refining main hole nozzle 19 to hatch, and slag 22 having excellent dephosphorization ability. Is formed. Phosphorus (P) in the hot metal is oxidized by oxygen gas supplied from the top blowing lance 3 or iron oxide formed in the slag to become phosphor oxide (P ₂ O ₅ ), and this phosphor oxide is absorbed by the slag 22. As a result, the dephosphorization reaction of the hot metal 21 proceeds. The dephosphorization reaction of the hot metal 21 is represented by the following formula (9).

2P + 5FeO + 3CaO → 3CaO · P ₂ O ₅ + Fe (9)
Along with this dephosphorization reaction, a decarburization reaction (C + O → CO) in which the oxygen gas supplied from the refining main hole nozzle 19 reacts with the carbon in the hot metal also occurs, and CO gas is generated in the furnace. Part of this CO gas is oxidized (combusted) by oxygen gas injected from the sub-hole nozzle 20 or oxygen gas supplied from the refining main hole nozzle 19 to become CO ₂ gas. The phenomenon in which this CO gas is oxidized to CO ₂ gas is referred to as “secondary combustion”. As described above, the secondary combustion rate is defined by the equation (8).

The present inventors studied to give secondary combustion heat to the hot metal 21 in this dephosphorization treatment. As a result, the ratio of the oxygen gas flow rate (F _s , unit: Nm ³ / min) supplied from the sub-hole nozzle 20 to the oxygen gas flow rate (F _m , unit: Nm ³ / min) supplied from the refining main hole nozzle 19 By changing R ₁ (= F _s / F _m ) and changing the basicity of slag 22 ((mass% CaO) / (mass% SiO ₂ )), the secondary combustion rate in the furnace is changed. I found out that it can be controlled.

That is, the oxygen gas supplied from the sub-hole nozzle 20 mainly causes a secondary combustion reaction between the oxygen gas supplied from the refining main hole nozzle 19 and the CO gas generated by the reaction of the carbon in the hot metal. , Producing CO ₂ gas. Therefore, when the ratio R ₁ (= F _s / F _m ) is increased, the amount of CO gas combusted with respect to the amount of CO gas generated increases, so the secondary combustion rate increases.

  The relationship between the basicity of the slag 22 and the secondary combustion rate is as follows.

  In the case of a general top blowing lance that does not include the sub-hole nozzle 20, the secondary combustion rate by the oxygen gas supplied from the refining main hole nozzle 19 decreases as the basicity of the slag 22 decreases. It is known to be a trend. This is because the secondary combustion by the oxygen gas supplied from the refining main hole nozzle 19 is performed by the oxygen gas jet 24 from the refining main hole nozzle 19 as shown in the conceptual cross-sectional view of the converter type refining furnace of FIG. It is thought that this occurs when the CO gas in the furnace is entrained in the furnace. For this reason, when the basicity of the slag 22 is low, the viscosity of the slag 22 in the furnace is high, as shown in FIG. As described above, a large amount of CO gas bubbles are held in the slag 22 so that the slag 22 is formed (foamed state), and the CO gas in the furnace is entrained from the refining main hole nozzle 19 into the oxygen gas jet 24. Therefore, it is considered that the secondary combustion rate decreases as the basicity of the slag 22 decreases. 3 indicates the entrainment of the CO gas in the furnace into the oxygen gas jet 24.

  On the other hand, when the basicity of the slag 22 is high, the viscosity of the slag 22 is low, and as shown in FIG. 3B, the forming of the slag 22 is suppressed, and the oxygen gas jet 24 from the refining main hole nozzle 19 is suppressed. It is considered that the entrainment of the CO gas in the furnace is not hindered and the secondary combustion by the oxygen gas jet 24 proceeds. FIG. 3 is a conceptual cross-sectional view of a converter-type refining furnace at the time of dephosphorization performed in a state where the supply of oxygen gas from the sub-hole nozzle 20 is stopped, and FIG. 3 (A) shows relative slag basicity. FIG. 3B shows a case where the basicity of the slag is relatively high and the forming is slight.

  However, when oxygen gas is supplied from the sub-hole nozzle 20 using the top blowing lance 3 in which the sub-hole nozzle 20 is arranged, the oxygen gas supplied from the sub-hole nozzle 20 causes the hot metal 21 and When the secondary combustion reaction is considered to have occurred inside the slag 22 and the slag 22 is strongly formed due to a decrease in the basicity of the slag 22, as shown in FIG. The flow rate of the oxygen gas jet 25 from the sub-hole nozzle 20 is attenuated, and the secondary combustion reaction zone 26 is formed at a position away from the hot metal surface, and the oxygen gas supplied from the sub-hole nozzle 20 and the particles in the slag It is considered that the decarburization reaction caused by the direct reaction with iron 27 is reduced, thereby increasing the secondary combustion rate.

  On the other hand, when the basicity of the slag 22 is relatively high, as shown in FIG. 4B, the formation of the slag 22 is suppressed, the secondary combustion reaction zone 26 approaches the hot metal surface, and the sub-hole nozzle It is considered that the decarburization reaction caused by the direct reaction between the oxygen gas supplied from 20 and the granular iron 27 in the slag increases, thereby reducing the secondary combustion rate. FIG. 4 is a conceptual cross-sectional view of a converter-type refining furnace at the time of dephosphorization performed in a state where oxygen gas is supplied from the sub-hole nozzle 20, and FIG. FIG. 4B shows a case where the basicity of the slag is relatively high and the forming is slight.

The oxygen gas flow rate (F _s , also referred to as “sub-hole oxygen flow rate”) supplied from the sub-hole nozzle 20 relative to the oxygen gas flow rate (F _m , also referred to as “main-hole oxygen flow rate”) supplied from the refining main hole nozzle 19 In order to quantitatively grasp the influence of the ratio R ₁ (= F _s / F _m ) on the secondary combustion rate and the influence of the basicity of the slag 22 on the secondary combustion rate, the hot metal conditions and the blowing conditions are set. It was investigated by changing only the ratio R ₁ or the slag basicity. As a result, the dependency between the ratio R ₁ and the secondary combustion rate was observed as shown in FIG. 5, and the relationship between the slag basicity and the secondary combustion rate was as shown in FIG. From these results, it was found that the secondary combustion rate can be approximated by the following formula (1 ′) with respect to the basicity of the ratio R ₁ and the slag basicity.
A _PC ≈ (30 + R ₁ × 150−6 × S _ba ) (1 ′)
However, in the formula (1 ′), A _PC is the secondary combustion rate (%) in the furnace, and S _ba is the basicity of the slag 22 existing in the furnace ((mass% CaO) / (mass% SiO _2). )).

From this result, it was found that the right side of the equation (1 ′) can be used as a control index for the secondary combustion rate in the furnace. If the control index of the secondary combustion rate in the furnace is A, the control index (A) of the secondary combustion rate in the furnace is expressed by the following equation (1).
A = (30 + R ₁ × 150−6 × S _ba ) (1)
It has also been found that the secondary combustion rate in the furnace may be controlled by adjusting this value.

In addition, the inventors of the present invention applied heat of the secondary combustion heat to the hot metal 21 in contact between the hot metal 21 and the hot gas after the secondary combustion, and in contact with the slag 22 and the furnace wall heated by the hot gas. Considered to be affected, the relationship between the flow rate of the stirring gas from the bottom blowing tuyere 7 responsible for stirring the hot metal 21 and the heat rate of the secondary combustion heat to the hot metal 21 was investigated. As a result, as shown in FIG. 7, the secondary combustion heat is obtained when the stirring gas flow rate per ton of hot metal blown from the bottom blowing tuyere 7 is in the range of 0.07 to 0.25 Nm ³ / (min · t). It was found that the heat rate of the molten iron to the hot metal 21 can be approximated by the following equation (2 ′) using the stirring gas flow rate per ton of hot metal blown from the bottom blowing tuyere.
B _PC ≈ (400 × F _b −20) (2 ′)
However, in the equation (2 ′), B _PC is the heat rate (%) of secondary combustion heat to the hot metal, and F _b is the stirring gas flow rate (Nm ³⁾ per ton of hot metal blown from the bottom blowing tuyere. / (Min · t)).

From this result, it was found that the right side of the equation (2 ′) can be used as a control index of the heat rate of secondary combustion heat to the hot metal. Assuming that the control index of the heat rate of the secondary combustion heat to the hot metal is B, the control index (B) of the heat rate of the secondary combustion heat to the hot metal is expressed by the following equation (2).
B = (400 × F _b −20) (2)
It has also been found that by adjusting this value, it is possible to control the heat rate of secondary combustion heat to the hot metal.

The change range of the heat rate of the secondary combustion heat by changing the stirring gas flow rate F _b blown from the bottom blowing tuyere 7 is about 10 to 80% as shown in FIG. This range cannot be exceeded by the operation of _b alone. Therefore, the application range of the formula (2) is such that the above F _b is in the range of 0.07 to 0.25 Nm ³ / (min · t), and the control index of the heat rate of secondary combustion heat to the hot metal The application range of (B) is in the range of 8-80.

  Furthermore, the present inventors have examined how much secondary combustion heat is required to be applied to the hot metal 21 in order to enable melting of a cold iron source such as iron scrap.

The amount of heat given to the hot metal 21 by the secondary combustion is the product of the secondary combustion rate (A _PC ) in the furnace and the heat rate of the secondary combustion heat to the hot metal (B _PC ) (A _PC × B _PC The product (A x B) of the control index (A) of the secondary combustion rate in the furnace and the control index (B) of the heat rate of secondary combustion heat to the molten iron is changed. Then, the influence of the product (A × B) on the temperature of the hot metal 21 after the dephosphorization treatment was investigated. The hot metal temperature after the dephosphorization treatment is based on the hot metal temperature in the dephosphorization treatment of the hot metal using a general top blowing lance not provided with the sub-hole nozzle 20, and the hot metal temperature using the general top blowing lance. Evaluation was made based on the difference from the hot metal temperature after dephosphorization treatment.

  The survey results are shown in FIG. As shown in FIG. 8, a correlation of “A × B = 27 × ΔT + 575” is recognized between the product (A × B) and the hot metal temperature increase (ΔT), and the product (A × B) is 575. Under the conditions, the hot metal temperature is equivalent to the conventional dephosphorization treatment using a general top blowing lance, and when the product (A × B) exceeds 575, the hot metal temperature rises compared to the conventional dephosphorization treatment. On the contrary, when the product (A × B) is smaller than 575, it has been found that the hot metal temperature is lower than that of the conventional dephosphorization treatment.

  In order to enable melting of cold iron sources such as iron scrap, it is desirable to raise the hot metal temperature by at least 3 ° C. or more than the conventional dephosphorization process using a general top blowing lance. In order to enable melting of cold iron sources such as scrap, the product of the control index (A) of the secondary combustion rate in the furnace and the control index (B) of the heat rate of secondary combustion heat to the hot metal It was found that (A × B) needs to be controlled within the range of the following formula (3).

A × B ≧ 650 (3)
The control index (A) of the secondary combustion rate is a function of the ratio R ₁ and the slag basicity S _ba (see the formula (1)), and the control index of the heat rate of the secondary combustion heat to the molten iron (B) is a function of the stirring gas flow rate F _b from the bottom blowing tuyere 7 (see equation (2)), and therefore the sub-hole nozzle 20 with respect to the oxygen gas flow rate supplied from the refining main hole nozzle 19. The ratio R ₁ of the oxygen gas flow rate supplied from the furnace, the basicity S _ba of the slag 22 existing in the furnace ((mass% CaO) / (mass% SiO ₂ )), per ton of hot metal blown from the bottom blowing tuyere 7 By adjusting any one or more of the stirring gas flow rate F _b , a control index for secondary combustion rate (A) and a control index for heat rate of secondary combustion heat to molten iron (B) When the product (A × B) is 650 or more, a sufficient amount of heat to enable melting of the cold iron source is obtained by secondary combustion. It was found that 21 could heat up.

That is, according to the present invention, the product (A × B) of the control index (A) of the secondary combustion rate in the furnace and the control index (B) of the heat rate of the secondary combustion heat to the molten iron 21 is as described above. The ratio R _{1 of} the oxygen gas flow rate supplied from the sub-hole nozzle 20 to the oxygen gas flow rate supplied from the refining main hole nozzle 19 and the basicity S of the slag present in the furnace so as to satisfy the relationship of the expression (3) _ba, is mandatory to adjust one kind or two or more kinds of the stirring gas flow rate F _b of the molten iron per ton blown from the bottom tuyeres.

However, the basicity S _ba of the slag 22 also affects the dephosphorization behavior. For the dephosphorization reaction, the basicity S _ba should be secured to 1.5 or more, preferably 2.0 or more. Therefore, when heat compensation of the hot metal 21 is performed by secondary combustion, the ratio R ₁ or the stirring gas flow rate F _b is adjusted with the basicity S _ba being 1.5 or more, or these It is preferable to control so that the product (A × B) satisfies the expression (3) by adjusting both of the above. Since the application range of the control index (A) for the rate of heat application of the secondary combustion heat to the molten iron 21 is up to 80, the product (A × B) is 8000 at the maximum.

  Furthermore, the present inventors have studied to efficiently dissolve the metal that has adhered to the inner wall of the converter refining furnace 2 with the secondary combustion heat.

The heat rate of the secondary combustion heat that contributes to the increase in the temperature of the slag 22, the exhaust gas temperature, and the temperature of the refractory 5 can be approximated by the following equation (4 ′).
B _PC ′ = (100−B _PC ) ≈ (120−400 × F _b ) (4 ′)
However, in the equation (4 ′), B _PC ′ is a heat deposition rate (%) of the secondary combustion heat to the hot metal other than the hot metal.

Therefore, it has been found that the right side of (4 ′) can be used as a control index for the rate of heat deposition of the secondary combustion heat other than the hot metal. Assuming that the control index of the heat rate of the secondary combustion heat other than the molten iron is B ′, the control index (B ′) of the heat rate of the secondary combustion heat other than the molten iron is expressed by the following equation (4). .
B ′ = (100−B) = (120−400 × F _b ) (4)
It has also been found that by adjusting this value, it is possible to control the heat deposition rate of the secondary combustion heat to other than the hot metal.

The melting of the metal that has adhered to the inner wall of the converter-type refining furnace 2 takes place between the secondary combustion rate (A _PC ) in the furnace and the heat rate of the secondary combustion heat other than the hot metal (B _PC '). Since the product (A _PC × B _PC ') is considered to have an effect, the control index (A) of the secondary combustion rate in the furnace and the rate of heat absorption of the secondary combustion heat other than the hot metal (B') It was investigated how much the value of the product (A × B ′) would dissolve the bullion. As a result, when the product (A × B ′) satisfies the following formula (5), that is, when the product (A × B ′) is 1000 or more, the ground attached to the inner wall of the converter type refining furnace It was confirmed that gold was dissolved (see Examples described later).

A × B ′ ≧ 1000 (5)
As described above, the secondary combustion rate control index (A) is a function of the ratio R ₁ and the slag basicity S _ba , and the secondary combustion heat control index (B) ') Is a function of the stirring gas flow rate F _b from the bottom blowing tuyere 7, and therefore the ratio R of the oxygen gas flow rate supplied from the sub-hole nozzle 20 to the oxygen gas flow rate supplied from the refining main hole nozzle 19 is R. ₁ of the basicity S _ba ((mass% CaO) / (mass% SiO ₂ )) of the slag 22 existing in the furnace, and the stirring gas flow rate F _b per ton of hot metal blown from the bottom blowing tuyere 7 The product (A × B) of the control index (A) of the secondary combustion rate and the control index (B ′) of the heat rate of the secondary combustion heat other than the hot metal by adjusting any one or two or more By setting ') to 1000 or more, it is possible to dissolve the metal that has adhered to the inner wall of the converter refining furnace 2 by the secondary combustion heat. It was found that In this case, the ratio R ₁ , the slag basicity S _ba , and the stirring gas flow rate F _b are adjusted within a range where the product (A × B) is 650 or more.

  When the product (A × B ′) is less than 1000, the amount of heat for melting the bullion adhering to the inner wall of the converter-type refining furnace 2 decreases, and the bullion adheres to the furnace, affecting the productivity. Will give.

On the other hand, if the product (A × B ′) is excessive, the refractory 5 may be damaged. When the product (A × B ′) exceeds 3000 from the test in which the product (A × B ′) is changed, not only the melting of the metal adhering to the inner wall of the converter refining furnace 2 but also the refractory 5 There was a tendency for accelerated erosion to be somewhat worse. Therefore, when the product (A × B ′) satisfies the following formula (6), that is, if the product (A × B ′) is 3000 or less, it is confirmed that the refractory 5 can be prevented from being promoted to melt. (See examples below).
3000 ≧ A × B ′ (6)
In particular, when there is a portion of the inner wall of the converter-type refining furnace 2 where there is little local metal adhesion, in order to avoid the erosion of the refractory 5 and to avoid adverse effects on productivity, It is preferable to adjust so that (A × B ′) does not exceed 3000.

  In addition, in the hot metal dephosphorization process in the converter-type refining furnace 2, the product (A × B ′) also affects the dephosphorization efficiency.

From the test in which the product (A × B ′) was changed, when the product (A × B ′) was 1000 or more, the CaO-based dephosphorization refining agent charged in the converter-type refining furnace 2 was rapidly dissolved, 9) It contributes to the dephosphorization reaction shown in the formula. However, when the product (A × B ′) exceeds 2500, the slag 22 existing in the furnace becomes higher than the improvement in the dephosphorization efficiency due to the increase in the melting amount of the CaO-based dephosphorization refining agent. Thus, the dephosphorization reaction shown in the formula (9), which is an exothermic reaction, is greatly affected, and the dephosphorization efficiency is lowered. Therefore, it was confirmed that when the product (A × B ′) satisfies the following formula (7), the dephosphorization efficiency can be maintained at a high level (see Examples described later).
2500 ≧ A × B ′ (7)
That is, for efficient dephosphorization reaction, the product (A × B ′) is preferably 2500 or less.

As described above, according to the present invention, the product (A × B) of the control index (A) of the secondary combustion rate and the control index (B) of the heat rate of the secondary combustion heat to the molten iron is 650. As described above, since at least one of the ratio R ₁ , the slag basicity S _ba , and the stirring gas flow rate F _b is controlled, a predetermined amount or more of secondary combustion heat is always applied to the hot metal 21, In the oxidative refining of the hot metal 21 such as dephosphorization using the converter type refining furnace 2, it is possible to efficiently apply heat to the hot metal 21 for melting a cold iron source such as iron scrap. . Further, when the product (A × B ′) of the control index of the secondary combustion rate and the control index of the heat rate of the secondary combustion heat other than the molten iron is controlled to 1000 or more, the converter type refining furnace 2 It is possible to efficiently dissolve the metal attached to the inner wall of the steel.

  In the above description, the present invention is applied to the hot metal dephosphorization treatment in the converter refining furnace 2, but the hot metal decarburization refining process in the converter refining furnace 2 also follows the above. The present invention can be applied by oxidizing and refining.

  When the hot metal was dephosphorized using the 300 ton / heat converter type refining furnace shown in FIG. 1, the present invention was applied to a dephosphorization test (invention example) and the present invention was applied. An example (comparative example) in which a dephosphorization test was conducted without doing so will be described.

  The hot metal used is a hot metal that has been subjected to desulfurization treatment so that the test results can be easily understood. Hot metal temperature: 1300 ° C., hot metal Si concentration: 0.25 mass%, hot metal Mn concentration: Although hot metal having the same temperature and the same composition of 0.40% by mass was used, the present invention can be applied to any hot metal composition to be used.

  After the hot metal is charged into the converter-type refining furnace, a CaO-based dephosphorizing refining agent consisting of a predetermined amount of quicklime is further charged, and nitrogen gas at various flow rates is blown as a stirring gas from the bottom blowing tuyere. However, oxygen gas was supplied from the top blowing lance. The distance between the tip of the lance and the hot metal stationary hot water surface (referred to as “lance height”) and the amount of oxygen gas for refining from the main hole nozzle for refining were the same in all tests. The oxygen gas supplied from the refining main hole nozzle at the tip of the top blowing lance causes dephosphorization reaction and decarburization reaction of the hot metal. This decarburization reaction generates CO gas, and the generated CO gas rises in the furnace. In the process, it reacted with the oxygen gas supplied from the sub-hole nozzle, and a secondary combustion reaction occurred.

Table 1 shows a list of experimental conditions and results obtained as examples of the present invention and comparative examples. In the table, “A × B actual value” and “A × B ′ actual value” indicate results calculated from the heat balance, carbon balance, and oxygen balance before and after the dephosphorization treatment, respectively. That is, it is an actual measurement value of the amount of heat (second product (A _PC × B _PC )) of the secondary combustion heat to the molten iron and the amount of heat other than the second combustion heat (product (A _PC × B _PC ′)). . The amount of hot metal temperature rise is determined by using the hot metal temperature at the end of the dephosphorization process using a general upper blowing lance that does not have a sub-hole nozzle and the upper blowing lance having a sub-hole nozzle. The temperature difference with the hot metal temperature at the time of completion | finish of the process in the dephosphorization process performed by supplying oxygen gas from a nozzle is shown. It shows that the larger the amount of hot metal temperature rise, the larger the amount of secondary combustion heat that is deposited on the hot metal, that is, the greater the heat compensation by the secondary combustion heat.

In tests No. 1 to 14, the ratio R ₁ (= F _s / F _m ) of the oxygen gas flow rate (F _s ) from the sub-hole nozzle to the oxygen gas flow rate (F _m ) from the refining main hole nozzle, slag base The dephosphorization treatment was performed by changing the degree S _ba and the bottom blowing stirring gas flow rate F _b .

  As shown in Test Nos. 8, 11, and 14, when the value of the product (A × B) is less than 650, it is compared with a general dephosphorization treatment with a general top blowing lance having no sub-hole nozzle. It was found that the hot metal temperature decreased. That is, it was found that the heat compensation effect cannot be obtained. In Test No. 11, the product (A × B ′) value was more than 3000, and the melting loss of the furnace refractory was slightly increased.

  On the other hand, in the tests No. 1 to 7, 9, 10, 12, and 13 in which the product (A × B) is 650 or more, the hot metal temperature after the dephosphorization treatment is generally not provided with a sub-hole nozzle. It was found to be higher than the dephosphorization treatment with a large top blowing lance, and that the heat compensation effect by the secondary combustion heat was developed.

  However, in the test Nos. 9, 10, and 12 where the value of the product (A × B ′) is less than 1000, the amount of bullion to the inner wall of the converter type refining furnace is increased. In the test No. 13 in which the value of A × B ′) exceeds 3000, although the metal was melted, the melting loss of the furnace refractory was slightly increased. In tests No. 1 to 7 in which the value of the product (A × B) is 650 or more and the value of the product (A × B ′) is 1000 or more and 3000 or less, While melting of the ingot, melting of the furnace refractory was not observed.

  A test in which the hot metal dephosphorization process was performed by applying the present invention using the 300 ton / heat converter type refining furnace shown in FIG. 1 will be described.

  The hot metal used is a hot metal that has been subjected to desulfurization treatment so that the test results can be easily understood. Hot metal temperature: 1300 ° C., hot metal Si concentration: 0.25 mass%, hot metal Mn concentration: Hot metal having the same temperature and the same composition of 0.40% by mass was used.

After the hot metal is charged into the converter-type refining furnace, a CaO dephosphorization refining agent consisting of 4 tons of quicklime is charged, and nitrogen gas at various flow rates is blown in as a stirring gas from the bottom blowing tuyere. However, oxygen gas was supplied from the top blowing lance. The distance between the tip of the lance and the hot metal stationary hot water surface (referred to as “lance height”) and the amount of oxygen gas for refining from the main hole nozzle for refining were the same in all tests. The addition of the four tons of lime, calculated basicity of the slag (mass ratio of the amount of CaO and SiO ₂ amount of silicon occurs by combustion of the hot metal in the quicklime) is 2.5.

  In addition, iron ore is used as a cooling material so that the hot metal temperature at the end of the treatment is equivalent to the hot metal temperature at the end of the treatment in the dephosphorization process using a general top blowing lance that does not have a sub-hole nozzle. A predetermined amount was charged.

Table 2 shows a list of experimental conditions and results of each test. Note that the slag formation rates shown in Table 2 (%) is the ratio of the actual slag basicity S _ba and calculated basicity (2.5 in all tests of this example), larger the value Thus, the CaO-based dephosphorization refining agent is an indicator that there is a large CaO source that can contribute to the dephosphorization reaction.

Further, the phosphorus distribution Lp increase rate (%) shown in Table 2 means that a general top blowing lance having no sub-hole nozzle is used, and operating conditions other than the oxygen gas blowing ratio are set for each test No. A sub-hole nozzle is provided for the average phosphorus distribution (= Lp (1): phosphorus concentration in slag (mass%) / phosphorus concentration in molten iron (mass%)) when dephosphorization is performed under the same operating conditions. This is the rate of increase of phosphorus distribution (= Lp (2)) in the dephosphorization process using the top blowing lance. It shows that dephosphorization processing is performed efficiently, so that the value of phosphorus distribution Lp increase rate is large. The following formula (10) shows the phosphorus distribution Lp increase rate (%).
Phosphorus partitioning Lp increase rate (%) = [(Lp (2) −Lp (1)) / Lp (1)] × 100 (10)

In tests No. 15 to 24, the ratio R ₁ (= F _s / F _m ) of the oxygen gas flow rate (F _s ) from the sub-hole nozzle to the oxygen gas flow rate (F _m ) from the refining main hole nozzle, and bottom-blown agitation gas flow rate F _b change respectively subjected to dephosphorization. As described above, the amount of quicklime charged in all tests is constant.

  As shown in Test Nos. 15-17 and 21-24, in a test where the value of the product (A × B ′) exceeds 1000 and falls below 2500, a general top blowing lance without a sub-hole nozzle is used. Compared with the dephosphorization treatment, the phosphorus distribution Lp increase rate was a positive value, indicating that the dephosphorization reaction was promoted.

  On the other hand, as shown in Test Nos. 18 to 20, in the test where the product (A × B ′) is less than 1000, the effect of promoting the dephosphorization reaction cannot be obtained, and the product (A In the test in the range where the value of × B ′) exceeds 2500, the phosphorus distribution Lp increase rate is a negative value as compared with the dephosphorization treatment with a general top blowing lance without a sub-hole nozzle, It was found that the dephosphorization reaction was inhibited.

  When the hatching rate was evaluated, it was found that the hatching rate increased until the product (A × B ′) value reached 1800, and did not change at 1800 or higher. From this result, in the range where the value of the product (A × B ′) is less than 1000, the slag temperature cannot be sufficiently increased, and the amount of CaO that remains undissolved and does not contribute to the dephosphorization reaction increases. It is considered that the effect of promoting the dephosphorization reaction was not obtained.

  On the other hand, when the product (A × B ′) is 1800 or more, the amount of CaO contributing to the dephosphorization reaction is almost the same, but when the product (A × B ′) is 2500 or more, the dephosphorization is performed. It was found that the reaction promoting effect could not be obtained. This is because when the product (A × B ′) value is 2500 or more, the dephosphorization reaction inhibition effect due to the increase in the slag temperature is greater than the dephosphorization reaction promotion effect due to the increase in the hatching rate, and the phosphorus distribution is increased. It is considered that the Lp increase rate decreases.

DESCRIPTION OF SYMBOLS 1 Converter type refining equipment 2 Converter type refining furnace 3 Top blowing lance 4 Iron skin 5 Refractory 6 Outlet 7 Bottom blowing tuyere 8 Gas introduction pipe 9 Refining oxygen gas supply pipe 10 Sub-hole oxygen gas supply pipe 11 Flue 12 Exhaust gas analyzer 13 Lance body 14 Lance tip 15 Outer pipe 16 Middle pipe 17 Inner pipe 18 Partition pipe 19 Refining main hole nozzle 20 Sub-hole nozzle 21 Hot metal 22 Slag 23 Stirring gas 24 Oxygen gas jet 25 Oxygen gas jet 26 Secondary combustion reaction zone 27 Grain iron

Claims (4)

A refining main hole nozzle in the vertically downward direction or diagonally downward direction is arranged at the tip of the top blowing lance, and in the horizontal direction or diagonally downward direction on the side of the top blowing lance that is spaced from the tip of the top blowing lance. Using an upper blow lance with a sub-hole nozzle, oxygen gas is supplied from the refining main hole nozzle and the sub-hole nozzle into the converter refining furnace, and installed at the bottom of the converter refining furnace. When the hot metal contained in the converter-type refining furnace is oxidatively refined by blowing the stirring gas from the bottom blowing tuyere into the hot metal,
The oxidative refining is a dephosphorization treatment performed on hot metal as a preliminary treatment,
The control index (A) of the secondary combustion rate in the furnace is defined by the following equation (1), and the control index (B) of the heat rate of secondary combustion heat to the molten iron is (2) When defined by the equation, the product (A × B) of the control index (A) of the secondary combustion rate in the furnace and the control index (B) of the heat rate of the secondary combustion heat to the hot metal is ( 3) The ratio of the oxygen gas flow rate supplied from the sub-hole nozzle to the oxygen gas flow rate supplied from the refining main hole nozzle, the basicity of the slag present in the furnace ((mass% CaO) so as to satisfy the relationship of the formula 3) / (Mass% SiO ₂ )), in a converter type smelting furnace, characterized by adjusting one or more of the stirring gas flow rate per ton of hot metal blown from the bottom blowing tuyere Hot metal refining method.
A = (30 + R ₁ × 150−6 × S _ba ) (1)
B = (400 × F _b −20) (2)
A × B ≧ 650 (3)
However, in the formulas (1) to (3), A is a control index of the secondary combustion rate in the furnace, B is a control index of the heat rate of the secondary combustion heat to the hot metal, and R ₁ is Ratio (F _s / F) of the oxygen gas flow rate (F _s , unit: Nm ³ / min) supplied from the sub-hole nozzle to the oxygen gas flow rate (F _m , unit: Nm ³ / min) supplied from the refining main hole nozzle _{m), S ba} the basicity of slag present in the furnace, _{F b} is the stirring gas flow rate of molten iron per ton blown from the bottom tuyeres ^{(Nm 3 / (min · t} )), F b Is in the range of 0.07 to 0.25 Nm ³ / (min · t). The control index (B ′) for the rate of heat applied to other than the hot metal of the secondary combustion heat is defined by the following formula (4) based on the control index (B) for the heat rate of the secondary combustion heat to the hot metal: Then, the product (A × B ′) of the control index (A) of the secondary combustion rate in the furnace and the control index (B ′) of the heat rate other than the molten iron of the secondary combustion heat is (5 × 5) ), The ratio of the oxygen gas flow rate supplied from the sub-hole nozzle to the oxygen gas flow rate supplied from the refining main hole nozzle, the basicity of the slag present in the furnace ((mass% CaO) / (Mass% SiO ₂ )), or any one or more of the stirring gas flow rate per ton of hot metal blown from the bottom blowing tuyere is adjusted. A method for refining hot metal in a furnace-type refining furnace.
B ′ = (100−B) = (120−400 × F _b ) (4)
A × B ′ ≧ 1000 (5)
However, in the formulas (4) and (5), B ′ is a control index for the rate of heat deposition of the secondary combustion heat other than the hot metal. The product (A × B ′) of the control index (A) of the secondary combustion rate in the furnace and the control index (B ′) of the heat rate of the secondary combustion heat other than the hot metal is the following (6) Further, in order to satisfy the formula, the ratio of the oxygen gas flow rate supplied from the sub-hole nozzle to the oxygen gas flow rate supplied from the refining main hole nozzle, the basicity of the slag present in the furnace ((mass% CaO) / ( wt% SiO _2)), and adjusting one kind or two or more kinds of the stirring gas flow rate of molten iron per ton blown from the bottom tuyeres, converter according to claim 2 Method of refining hot metal in a type refining furnace
3000 ≧ A × B ′ (6) The product (A × B ′) of the control index (A) of the secondary combustion rate in the furnace and the control index (B ′) of the heat rate of the secondary combustion heat other than the hot metal is the following (7) Further, in order to satisfy the formula, the ratio of the oxygen gas flow rate supplied from the sub-hole nozzle to the oxygen gas flow rate supplied from the refining main hole nozzle, the basicity of the slag present in the furnace ((mass% CaO) / ( wt% SiO _2)), and adjusting one kind or two or more kinds of the stirring gas flow rate of molten iron per ton blown from the bottom tuyeres, converter according to claim 2 Method of refining hot metal in a type refining furnace
2500 ≧ A × B ′ (7)

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