JP2014189859A - Hot pig iron refining method in converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restore to molten iron or molten steel with high yield, a manganese oxide supplied to the inside of a furnace as a manganese source for component adjustment when dephosphorization treatment or decarbonization refining of the molten iron in a converter is performed.SOLUTION: By using a top-blown lance 3 including a fine particle supply flow passage for refining, a fuel gas supply flow passage, an oxidizing gas supply flow passage for fuel gas burning, and an oxidizing gas supply flow passage for refining which are provided separately, fuel gas is supplied from the fuel gas supply flow passage, and at the same time, oxidizing gas for burning is supplied from the oxidizing gas supply flow passage for burning, and while flame is formed at a tip lower side of the top-blown lance, a fine particle for refining including manganese oxide is added from the fine particle supply flow passage for refining toward a molten iron bath surface, and oxidizing gas for refining is supplied from the oxidizing gas supply flow passage for refining, thereby molten iron 26 in a converter 2 is subjected to oxidation refining. In this case, when a heat generation amount of the fuel gas is denoted by Q (MJ/minute) and the fine particle for refining an addition speed is denoted by S (kg/minute), a heat generation amount Q and/or an addition speed S is adjusted so that a value of a ratio Q/S may become 1.0 MJ/kg or more.

Description

  The present invention relates to a method of spraying a refining oxidizing gas from a top blowing lance to hot metal in a converter, and dephosphorizing or decarburizing the hot metal, specifically, forming a flame at the tip of the top blowing lance, The present invention relates to a refining method capable of heating manganese oxide supplied as a manganese source for component adjustment with this flame, thereby increasing the reduction yield of molten manganese oxide to molten iron or molten steel.

  In order to produce steel products from hot metal produced in a blast furnace, it is necessary to go through a steelmaking refining process. In this steelmaking refining process, after removing the impurity components contained in the hot metal, the components are adjusted to a composition corresponding to the material characteristics of the steel product. Impurity components contained in the hot metal include phosphorus and sulfur in addition to carbon contained in 4% by mass or more. On the other hand, components required from the material characteristics of steel products are components that increase strength and toughness. There are some manganese and silicon.

  In the steelmaking refining process, in order to remove carbon and phosphorus, a large amount of oxygen is added to the hot metal to cause an oxidation reaction, or slag having excellent dephosphorization ability and hot metal are reacted. In particular, in recent years, instead of the conventional molten steel refining method that simultaneously removed carbon and phosphorus in the hot metal using a converter, refining mainly using dephosphorization as a preliminary treatment in the hot metal stage ("dephosphorization treatment") , "Preliminary dephosphorization treatment", etc., followed by refining mainly using decarburization in a converter to produce molten steel from hot metal.

  By dephosphorizing the hot metal as a preliminary treatment, the decarburization and refining in the converter in the subsequent process eliminates the need to add a solvent for dephosphorization and reduce the amount of slag in the furnace. Thus, it became possible to reduce the manganese oxide with carbon in the hot metal by introducing manganese ore into the furnace. Thereby, the operation which reduced the usage-amount of manganese-type alloy iron used for the manganese component adjustment of molten steel came to be performed.

  However, a part of the manganese in the added manganese ore remains in the slag in the converter decarburization refining, and the yield of manganese to the molten steel is about 60 to 70% by mass, and the manganese yield is further increased. It was difficult to increase. In order to increase the manganese yield, it is necessary to promote the reduction of manganese in the slag to molten iron (molten iron or molten steel) and lower the manganese distribution ratio between slag and metal. It is extremely difficult to lower the value. This is because at the end of converter decarburization refining, the carbon concentration in the molten steel decreases and the degree of oxidation of slag increases, so manganese tends to become manganese oxide, and the reduction of manganese from slag is suppressed. This is because manganese moves from molten steel to slag.

  In order not only to improve manganese yield but also to suppress iron oxidation, the oxygen gas supply flow rate (also referred to as “acid feed rate”) is usually reduced at the end of decarburization and slag oxidation is increased. I am trying not to. However, if the acid feed rate is lowered, the stirring effect of the molten iron and slag by the oxygen jet is reduced, so even if the acid feed rate is lowered, the slag oxidation degree does not fall as expected, and the slag oxidation degree There is a limit to the effect of lowering. Further, when the acid feed rate is lowered, there arises a problem that reduction of exhaust gas recovery rate and extension of refining time are inevitable.

Moreover, in order to lower the manganese distribution ratio, it is necessary to control the slag composition or reduce the amount of slag from the balance of manganese to slag and metal. Therefore, a method of controlling the basicity of slag ((mass% CaO) / (mass% SiO ₂ )) to be higher is used. However, when the phosphorus removal in the dephosphorization treatment performed as a preliminary treatment is insufficient and the phosphorus concentration in the hot metal is high, a CaO source for the dephosphorization reaction is required. Further, the manganese ore contains silicon oxide ( Since gangue mainly composed of SiO ₂ ) is contained, it is necessary to increase the amount of CaO source added such as quicklime in order to secure a highly basic slag. That is, although the basicity of slag can be increased, the amount of slag increases and there is a limit to reducing the amount of slag. In this case, even if the concentration of manganese oxide in the slag decreases, the amount of slag increases, so the amount of manganese oxide remaining in the slag does not decrease so much.

  Furthermore, as a means of actively reducing the oxidation degree of slag, adding a carbonaceous material such as graphite during decarburization refining in a converter is also performed, but nitrogen and sulfur contained in the carbonaceous material are reduced. Since it adversely affects steel products, the amount of carbonaceous material added is limited to a very small range, specifically, it is only used for slag forming control, and the amount of manganese oxide in the slag is reduced. Cannot be added.

  Therefore, in view of these problems, Patent Document 1 states that the phosphorus concentration in the hot metal is a steel material in the preliminary dephosphorization treatment for the purpose of lowering the manganese distribution ratio without adjusting the acid feed rate and slag composition. In converter decarburization and refining, the manganese-containing plastic molding formed from manganese ore and plastic is added in the latter half of decarburization and manganese is oxidized by carbon and hydrogen contained in the plastic. A refining method for reducing things has been proposed. According to this method, manganese oxide can be reduced by carbon and hydrogen contained in the plastic, so that the manganese yield can be improved.

  However, in patent document 1, the process which manufactures a manganese containing plastic molding is required, and the manufacturing cost of molten steel is increased. Moreover, when the plastic containing chlorine is used, the problem that the lifetime of a furnace refractory shortens also generate | occur | produces.

  By the way, recent steel products are required to adjust the component composition to an extremely narrow range. Therefore, molten steel produced from a converter is refined in a secondary smelting furnace such as an RH vacuum degasser. In this secondary refining, the composition of the molten steel is adjusted. In secondary refining performed under reduced pressure, gas components such as nitrogen and hydrogen are also removed. In secondary refining, the manganese component of molten steel is adjusted, and electrolytic manganese or manganese-based alloy iron is usually used for this component adjustment. Since raw material costs are reduced by using inexpensive manganese ore instead of these expensive alloys, it is desired to use manganese ore as a manganese source in the secondary smelting furnace.

  However, when manganese ore is used as a manganese source in secondary refining, the molten steel is removed by reduction of the manganese ore, so a heating agent such as a carbonaceous material is required. When a carbon material is added as a heat-up agent, nitrogen and sulfur contained in the carbon material dissolve in the molten steel, and the concentration thereof increases. Since it is virtually impossible to remove these components in the process after the secondary refining, the amount of addition is limited. Moreover, although the method of raising the temperature at the time of completion | finish of converter decarburization refining can also be taken, there exists a problem that the lifetime of a converter refractory becomes short. Furthermore, although it is possible to use metallic aluminum as a heat raising agent, aluminum is more expensive than manganese, and the use of metallic aluminum as a heat raising agent for manganese ore reduction is manufactured on the contrary. Cost increases.

  For the purpose of increasing the amount of manganese ore by secondary refining under reduced pressure without causing such problems, Patent Document 2 discloses that the molten steel is heated on the surface of the molten steel bath under reduced pressure while being heated with a burner. Furthermore, a vacuum refining method has been proposed in which oxide powder such as silicon, manganese or iron oxide powder is projected and added. According to this method, since the molten steel is heated by the burner, a decrease in the molten steel temperature is suppressed, and it becomes possible to compensate for heat removal during oxide reduction.

  However, in Patent Document 2, carbon contained in molten steel is used as a reducing agent for oxide powder, and the carbon concentration in the molten steel before secondary refining under reduced pressure is usually 0.02. It is about 0.10% by mass, and there is a limit to the amount of oxide that can be reduced with a high yield.

JP 2003-253317 A JP 7-41827 A

  The present invention has been made in view of the above circumstances, and the object is to spray a refining oxidizing gas from the top blowing lance to the hot metal in the converter and dephosphorize or decarburize the hot metal. Without reducing the amount of manganese oxide supplied into the furnace as a manganese source for component adjustment to hot metal or molten steel at a high yield without processing the manganese oxide into a molded body such as a manganese-containing plastic molded body. It is to provide a hot metal refining method.

The gist of the present invention for solving the above problems is as follows.
[1] An upper blowing lance having a refining powder supply channel, a fuel gas supply channel, an oxidizing gas supply channel for combustion of fuel gas, and an oxidizing gas supply channel for refining separately. And at the same time as supplying the fuel gas from the fuel gas supply flow path, supplying the combustion oxidizing gas from the combustion oxidizing gas supply flow path, and blowing the upper gas with the combustion oxidizing gas and the fuel gas. While forming a flame below the tip of the lance, the refining powder containing manganese oxide is added together with an inert gas from the refining powder supply channel toward the hot metal bath surface in the converter, and A method for refining hot metal in a converter, wherein the refining oxidizing gas is supplied from the refining oxidizing gas supply channel toward the hot metal bath surface in the converter and the hot metal in the converter is oxidized and refined. , The calorific value of the fuel gas is Q (MJ / min), the refining powder When the addition rate is S (kg / min), the calorific value Q and / or the addition rate S so that the ratio Q / S between the calorific value Q and the addition rate S is 1.0 MJ / kg or more. A method for refining hot metal in a converter, characterized by adjusting the temperature.
[2] Furthermore, when the average particle diameter of the powder for refining is R (μm), the relationship among the calorific value Q, the addition rate S, and the average particle diameter R is as follows: The hot metal in the converter according to the above [1], wherein at least one of the calorific value Q, the addition rate S, and the average particle size R is adjusted so as to be within the range of the formula. Refining method.
Q / S ≧ 0.4 × R ^0.2 (1)

According to the present invention, the ratio Q / S between the calorific value Q of the fuel gas and the addition rate S of the refining powder is controlled to 1.0 MJ / kg or more, and the refining powder containing manganese oxide Since the body is heated, the refining powder containing manganese oxide is heated to a high temperature (about 2000 ° C.) when passing through the formed flame, whereby the manganese oxide in the refining powder Can be thermally dissociated from MnO ₂ which is a stable form at normal temperature to MnO which is a stable form at high temperature, and manganese oxide can be sufficiently reduced with a small amount of reducing agent. That is, it becomes possible to reduce manganese oxide efficiently. As a result, it is possible to reduce manganese oxide to hot metal or molten steel with a high yield.

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. It is a figure which shows the relationship between the value of ratio Q / S in test No.1-9, and manganese yield. It is a figure which shows the relationship between the value of ratio Q / S in test No. 21-45, and a manganese yield, using the average particle diameter R of the powder for refinement | purification as a parameter | index. It is a figure which shows the relationship between the critical point of ratio Q / S, and the average particle diameter R of the powder for refining.

  Hereinafter, the present invention will be specifically described.

  The present invention is directed to oxidation refining performed by supplying oxidizing gas for refining from a top blow lance to hot metal contained in a converter, and this oxidation refining is currently performed before decarburization refining. Hot metal dephosphorization treatment and hot metal decarburization refining are performed as treatments. The present invention can be applied to both hot metal dephosphorization and hot metal decarburization. In this case, in hot metal decarburization refining, either hot metal that has been subjected to dephosphorization treatment or hot metal that has not been subjected to dephosphorization treatment may be used. The present invention can be applied to the case where the present invention is applied to hot metal dephosphorization treatment and the hot metal refined by the dephosphorization treatment is decarburized and refined in a converter. As the oxidizing gas for refining, oxygen gas (industrial pure oxygen), oxygen-enriched air, or a mixed gas of oxygen gas and rare gas is used, but oxygen gas is generally used.

  The hot metal used in the present invention is a hot metal produced in a blast furnace, and this hot metal is received in a hot metal transfer container such as a hot metal ladle or a topped car and transferred to a converter for performing dephosphorization treatment or decarburization refining. To do. When performing the dephosphorization process by applying the present invention, it is possible to efficiently perform the dephosphorization process with a small amount of lime-based solvent, so that the silicon in the hot metal is previously removed before the dephosphorization process. It is preferable to remove (referred to as “hot metal desiliconization treatment”) and to reduce the silicon content of the hot metal to 0.20 mass% or less, desirably 0.10 mass% or less. When the desiliconization process is performed, the slag generated during the desiliconization process is discharged before the dephosphorization process. Naturally, even hot metal that has not been subjected to desiliconization treatment can be dephosphorized by applying the present invention.

Hereinafter, the present invention will be described by taking as an example the case where the present invention is applied to decarburization refining of hot metal that has not been dephosphorized. In decarburization and refining of hot metal that has not been dephosphorized, a dephosphorization reaction (2P + 5O → P ₂ O ₅ ) occurs simultaneously with a decarburization reaction (C + O → CO), and carbon and phosphorus in the hot metal are removed. Naturally, in hot metal decarburization refining, silicon having a higher affinity for oxygen than carbon and phosphorus is also removed from the hot metal.

  FIG. 1 is a schematic cross-sectional view showing an example of a converter facility used when carrying out the present invention, and FIG. 2 is a schematic enlarged vertical cross-sectional view of an upper blowing lance 3 shown in FIG. FIG. 2 shows an upper blowing lance 3 having a six-pipe structure as an example of the upper blowing lance.

  As shown in FIG. 1, a converter facility 1 used in decarburization and refining according to the present invention includes a furnace body 2 in which an outer shell is formed of an iron shell 4 and a refractory 5 is constructed inside the iron shell 4. And an upper blowing lance 3 which is inserted into the furnace body 2 and is movable in the vertical direction. In the upper part of the furnace main body 2, a hot water outlet 6 for pouring molten steel produced from the molten iron 26 by decarburization refining is provided, and a stirring gas 28 is blown into the furnace bottom part of the furnace main body 2. A plurality of bottom blowing tuyere 7 are provided. The bottom blowing tuyere 7 is connected to a gas introduction pipe 8.

  A refining powder supply pipe 9 for supplying a refining powder 29 containing manganese oxide together with a carrier gas, a fuel gas supply pipe 10 for supplying a fuel gas, and a fuel gas to the top blowing lance 3 A combustion oxidizing gas supply pipe 11 that supplies a combustion oxidizing gas to be used and a refining oxidizing gas supply pipe 12 that supplies a refining oxidizing gas are connected to each other. Also, a cooling water supply pipe (not shown) and a cooling water drain pipe (not shown) for supplying and discharging cooling water for cooling the upper blowing lance 3 are connected to the upper blowing lance 3. Yes.

  Here, the refining powder 29 may be a single element of manganese oxide. In addition to the manganese oxide, a lime-based solvent (quick lime, limestone, etc.), iron oxide (iron ore, mill scale, steel) Recovered dust, etc.) and flammable substances (aluminum ash, coke, coal, etc.) may be contained. As the manganese oxide, manganese ore is generally used, but it can be used as long as it contains manganese oxide. As the transfer gas for transferring the refining powder 29, an inert gas such as nitrogen gas or argon gas is used. As the fuel gas supplied from the fuel gas supply pipe 10, propane gas, liquefied natural gas, coke oven gas, or the like is used. Further, oxygen gas, oxygen-enriched air, air, or the like is used as the combustion oxidizing gas supplied from the combustion oxidizing gas supply pipe 11 for burning the fuel gas. FIG. 1 shows an example in which the oxidizing gas for combustion and the oxidizing gas for refining are oxygen gases.

  In addition, it is possible to use hydrocarbon-based liquid fuel such as heavy oil and kerosene instead of fuel gas, but there is a risk of clogging at the nozzle at the outlet of the flow path. Use fuel gas (gaseous fuel). If gaseous fuel is used, not only can clogging of nozzles and the like be prevented, but also the supply speed can be easily adjusted, and furthermore, since ignition is easy, misfire can be prevented.

  The other end of the refining powder supply pipe 9 is connected to a dispenser 13 that contains the refining powder 29, and the dispenser 13 is connected to a refining powder carrying gas supply pipe 9 </ b> A. An inert gas is supplied to the gas supply pipe 9A for powder refining for refining. That is, the inert gas supplied to the dispenser 13 through the gas supply pipe 9 </ b> A for refining powder transport functions as a transport gas for the refining powder 29 stored in the dispenser 13 and is stored in the dispenser 13. The refining powder 29 is supplied to the upper blowing lance 3 through the refining powder supply pipe 9 and can be sprayed from the tip of the upper blowing lance 3 toward the hot metal 26.

  The refining powder transfer gas supply pipe 9A is directly connected to the refining powder supply pipe 9. By opening and closing the shut-off valve 34, the refining powder 29 is not transferred and the inert gas is directly transferred. It is configured so that it can be supplied to the upper blowing lance 3. When the refining powder 29 is conveyed, the shutoff valve 34 is closed.

  As an example of the top blow lance used in the present invention, a top blow lance 3 having a six-pipe structure shown in FIG. 2 is a copper lance body 14 and a copper casting connected to the lower end of the lance body 14 by welding or the like. The lance body 14 is composed of six types of concentric steel pipes including 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. That is, it is composed of a six-fold pipe. The refining powder supply pipe 9 communicates with the innermost pipe 20, the fuel gas supply pipe 10 communicates with the partition pipe 21, the combustion oxidizing gas supply pipe 11 communicates with the inner pipe 22, and the refining oxidizing gas. The supply pipe 12 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. That is, the refining powder 29 passes through the innermost pipe 20 together with the carrier gas, the fuel gas such as propane gas passes through the gap between the innermost pipe 20 and the partition pipe 21, and the combustion oxidizing gas passes through the partition pipe. The refining oxidizing gas passes through the gap between the inner pipe 22 and the inner pipe 23 through the gap between the inner pipe 22 and the inner pipe 22. 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 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 15.

  The inside of the innermost pipe 20 communicates with a refining powder injection hole 16 disposed substantially at the axial center of the lance tip 15, and the gap between the innermost pipe 20 and the partition pipe 21 is a refining powder injection hole. A fuel gas injection hole 17 that opens as an annular nozzle or a plurality of concentric nozzle holes around 16 is communicated. The gap between the partition tube 21 and the inner tube 22 communicates with the combustion oxidizing gas injection hole 18 that opens as an annular nozzle or a plurality of concentric nozzle holes around the fuel gas injection hole 17. A gap between the inner tube 22 and the intermediate tube 23 communicates with a plurality of refining oxidizing gas injection holes 19 provided around the combustion oxidizing gas injection hole 18. The refining powder injection hole 16 is a nozzle for spraying the refining powder 29 together with the carrier gas, the fuel gas injection hole 17 is a nozzle for injecting fuel gas, and the combustion oxidizing gas injection hole 18 is The nozzle for injecting combustion oxidizing gas for burning the fuel gas and the refining oxidizing gas injection hole 19 are nozzles for spraying the refining oxidizing gas.

  That is, the inside of the innermost pipe 20 becomes the refining powder supply flow path 30, the gap between the innermost pipe 20 and the partition pipe 21 becomes the fuel gas supply flow path 31, and the gap between the partition pipe 21 and the inner pipe 22 becomes A combustion oxidizing gas supply flow path 32 is formed, and a gap between the inner pipe 22 and the intermediate pipe 23 is a refining oxidizing gas supply flow path 33. In FIG. 2, the refining powder injection hole 16 is a straight nozzle, while the refining oxidizing gas injection hole 19 is composed of two conical bodies, a portion whose cross section is reduced and a portion where the cross section is enlarged. However, the refining powder injection hole 16 may also have a Laval nozzle shape. The fuel gas injection holes 17 and the combustion oxidizing gas injection holes 18 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.

  The decarburization and refining according to the present invention for reducing manganese oxide contained in the refining powder 29 to molten steel produced from the molten iron 26 with a high yield using the converter equipment 1 having this configuration. This is performed on the hot metal 26 as shown below.

First, a cold iron source is charged into the furnace body 2. Cold iron sources used include 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 and direct reduced iron. Can be used. 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. The blending ratio of the cold iron source is defined by the following formula (2).
Cold iron source blending ratio (% by mass) = Cold iron source blending amount × 100 / (molten iron blending amount + cold iron source blending amount) (2)
This is because when the blending ratio of the cold iron source is 4.0% by mass or more, an effect of improving productivity appears and at the same time, an effect of reducing the amount of CO ₂ gas generated can be obtained. The upper limit of the blending ratio of the cold iron source does not need to be particularly determined, and the molten steel temperature at the end of decarburization refining can be added up to an upper limit that can maintain the target range. Before and after the charging of the cold iron source is completed, the stirring gas 28 starts to be blown from the bottom blowing tuyere 7.

  After charging the cold iron source into the furnace body 2, the hot metal 26 is charged into the furnace body 2. The hot metal 26 to be used is subjected to a desulfurization treatment in advance as required based on the component standard of the steel product to be manufactured. Incidentally, the main chemical components of the hot metal 26 not subjected to the dephosphorization treatment are carbon: 3.8 to 5.0% by mass, silicon: 0.2 to 0.5% by mass, phosphorus: 0.08 to 0%. .2% by mass, sulfur: about 0.05% by mass or less.

However, in the decarburization refining of the hot metal 26 which has not been subjected to the dephosphorization treatment, it is necessary to cause a dephosphorization reaction. For that purpose, the basicity ((mass% CaO) / (Mass% SiO ₂ )) needs to be secured to 2.0 or more. As the amount of slag 27 in the furnace increases, the reduction efficiency of manganese oxide decreases, so in order to reduce the amount of slag generation in the furnace and increase the reduction efficiency of manganese oxide, the hot metal 26 is desiliconized beforehand. It is preferable to reduce the silicon concentration in the hot metal to 0.20 mass% or less, desirably 0.10 mass% or less. By reducing the silicon concentration in the hot metal in advance, the amount of slag 27 generated can be suppressed even if the basicity of the slag 27 is secured to 2.0 or more. Moreover, if the hot metal temperature is in the range of 1200 to 1400 ° C., decarburization and refining can be performed without any problem.

  Next, the refining oxidizing gas is sprayed from the refining oxidizing gas injection hole 19 of the top blowing lance 3 toward the bath surface of the hot metal 26 and the inert gas is supplied to the dispenser 13 to refining the top blowing lance 3. The refining powder 29 is sprayed from the powder injection hole 16 toward the bath surface of the hot metal 26 using an inert gas as a carrier gas. Before and after the refining powder 29 is sprayed, the fuel gas is injected from the fuel gas injection hole 17 of the upper blowing lance 3 and the oxidizing gas for combustion from the combustion oxidizing gas injection hole 18 of the upper blowing lance 3. And a flame is generated below the upper blowing lance 3.

  The fuel gas supplied from the fuel gas injection hole 17 and the combustion oxidizing gas supplied from the combustion oxidizing gas injection hole 18 are close to each other in all directions in the upper blowing lance radial direction, and therefore interfere with each other. However, because the ambient temperature is high, even when there is no ignition device, combustion occurs when the gas concentration reaches the combustion limit range, and a flame is formed below the upper blowing lance 3. At that time, the supply flow rate of the fuel gas supplied to the upper blow lance 3 and the supply flow rate of the combustion oxidizing gas are adjusted, and the fuel gas is completely burned by the combustion oxidizing gas. In this case, the supply flow rates of the fuel gas and the oxidizing gas for combustion are controlled so that complete combustion occurs inside the furnace body 2.

  When the hot metal 26 is decarburized and refined in this way, in the present invention, the calorific value of the fuel gas supplied from the fuel gas injection hole 17 is supplied from the refining powder injection hole 16 to Q (MJ / min). When the addition rate of the refined powder 29 is S (kg / min), the calorific value is such that the ratio Q / S between the calorific value Q and the addition rate S is 1.0 MJ / kg or more. Adjust Q and / or addition rate S.

  By controlling the value of the ratio Q / S to be 1.0 MJ / kg or more, the refining powder 29 containing manganese oxide is sufficiently heated by the flame formed, and has a temperature of 2000 ° C. or higher. The hot metal is supplied to the hot metal 26 in a heated state. The temperature of the refining powder 29 increases as the value of the ratio Q / S increases, but the fuel gas efficiency decreases. Therefore, the value of the ratio Q / S is preferably 5.0 MJ / kg or less.

Manganese oxide contained in the refining powder 29 undergoes thermal dissociation shown in the following formulas (3), (4), and (5) in the process of being heated to a temperature of 2000 ° C. or higher, and at room temperature. Manganese oxide in the form of MnO ₂ is supplied to the hot metal 26 in the form of MnO, which is a stable form at high temperature.

MnO ₂ (s) = 1/2 Mn ₂ O ₃ (s) + 1 / 4O ₂ (g) (3)
Mn ₂ O ₃ (s) = 2/3 Mn ₃ O ₄ (s) + 1 / 6O ₂ (g) (4)
Mn ₃ O ₄ (s) = 3MnO (s) + 1 / 2O ₂ (g) (5)
The reaction of the formula (3) occurs at about 400 ° C. or higher, the reaction of the formula (4) occurs at about 1000 ° C. or higher, and the reaction of the formula (5) occurs at about 1700 ° C. or higher. In the formulas (3) to (5), (s) represents a solid, and (g) represents a gas.

That is, the manganese oxide is heated to 2000 ° C. or more to reduce the oxygen content in the same manner as reduced, and as a result, the amount of the reducing agent is smaller than that in the case of reducing the normal temperature manganese oxide. It becomes possible to reduce with. The hot metal 26 contains carbon, and this carbon functions as a reducing agent for manganese oxide. However, when the manganese oxide to be reduced is changed from MnO ₂ to MnO, heat as a reducing agent for carbon in hot metal is reduced. The mechanical function is greatly increased, and the reduction reaction of manganese oxide shown in the following formula (6) is promoted. Further, the equation (6) is an endothermic reaction, and the reaction of the equation (6) is promoted by heating the manganese oxide itself.

MnO (s) + [C] = [Mn] + CO (g) (6)
That is, it is possible to reduce manganese oxide into hot metal with a high yield. In the formula (6), [C] represents carbon in the hot metal, and [Mn] represents manganese in the hot metal.

  In the present invention, when the average particle diameter of the refining powder 29 supplied from the refining powder injection hole 16 is R (μm), the calorific value Q, the addition rate S, and the average particle It is preferable to adjust at least one of the calorific value Q, the addition rate S, and the average particle size R so that the relationship with the diameter R falls within the range of the following formula (1).

Q / S ≧ 0.4 × R ^0.2 (1)
By controlling so as to satisfy the expression (1), it is possible to reduce the manganese oxide into the hot metal with a higher yield.

  Of the refining powder 29 injected together with the conveying gas from the refining powder injection hole 16, the nonflammable lime-based medium solvent and iron oxide are heated or heated by the heat of the flame formed. It is heated and melted and sprayed onto the bath surface of the hot metal 26 in a heated or molten state. As a result, the heat of the heated refining powder 29 reaches the molten iron 26, the temperature of the molten iron 26 rises, and the melting of the added cold iron source is promoted. The combustible substance in the refining powder 29 injected together with the carrier gas from the refining powder injection hole 16 is burned by the flame, and the combustion heat of the combustible substance is added to the combustion heat of the fuel gas. This contributes to the heating of the hot metal 26, and the temperature of the hot metal 26 rises to promote the dissolution of the added cold iron source.

In the dephosphorization reaction of the hot metal 26, phosphorus in the hot metal reacts with an oxidizing gas or iron oxide to form phosphor oxide (P ₂ O ₅ ), and this phosphor oxide is formed by the incubation of the lime-based solvent. It progresses by being absorbed by the slag 27 in the form of 3CaO · P ₂ O ₅ . In addition, the rate of dephosphorization increases as the hatching of the lime-based medium solvent is promoted. Therefore, it is particularly preferable to add a lime-based solvent such as quick lime (CaO), limestone (CaCO ₃ ), slaked lime (Ca (OH) ₂ ) to the refining powder 29. When the lime-based medium solvent is not blended with the refining powder 29 or when the addition amount is insufficient even when blended with the refining powder 29, the lime-based medium solvent is charged into the furnace.

  When the decarburization reaction of the hot metal 26 proceeds and the molten steel having the target carbon concentration is produced, all the supply from the top blowing lance 3 into the furnace is stopped and the decarburization refining is finished. After decarburization and refining, the molten steel melted by tilting the furnace body 2 is discharged into a molten steel holding container such as a ladle through the outlet 6 and the discharged molten steel is conveyed to the next step.

As described above, according to the present invention, the value of the ratio Q / S between the calorific value Q of the fuel gas and the addition rate S of the refining powder 29 is controlled to 1.0 MJ / kg or more, and manganese oxidation Since the refining powder 29 containing the product is heated, the refining powder 29 containing the manganese oxide is heated to a high temperature (about 2000 ° C.) when passing through the formed flame. Manganese oxide in the powder for refining is thermally dissociated from MnO ₂ which is a stable form at normal temperature to MnO which is a stable form at high temperature, and manganese oxide can be sufficiently reduced with a small amount of reducing agent. As a result, reduction of manganese oxide to hot metal or molten steel with high yield is realized.

  In addition, although the said description was performed as an example when the hot metal which has not been dephosphorized is decarburized and refined in a converter, even when the hot metal subjected to dephosphorization is decarburized and refined in a converter, The present invention can be applied by decarburizing and refining along the above. Further, the present invention can also be applied to the dephosphorization of hot metal in a converter, which is performed as a preliminary treatment, by oxidative refining in accordance with the above.

  Using a small converter with a furnace capacity of 2.5 tons, which has the same structure as the converter shown in FIG. 1, a refining powder containing manganese oxide is formed below the tip of the top blowing lance. The amount of heat Q of the fuel gas supplied from the top blowing lance and the powder for refining supplied from the top blowing lance when decarburizing and refining the hot metal that has not been dephosphorized by adding the top blowing while heating with a flame. The ratio Q / S value with the addition rate S of the steel was changed, and a test was conducted to investigate the effect of the ratio Q / S value on the yield of manganese in the manganese oxide to the molten steel (Test No. 1 9). In addition, although a flame was formed at the tip of the top blowing lance, a test was also conducted in which the fine powder for refining was charged and added from above the converter without supplying the fine powder for refining from the top blowing lance (Test No. 10). ).

  As the powder for refining, a mixture having an average particle diameter of 100 μm, in which manganese ore, quicklime and iron ore were mixed at a ratio of 4: 5: 3, was used. However, in Test No. 10, the manganese ore, quicklime and iron ore were granular (particle size 10 to 50 mm), and a mixture thereof was added from above the converter. Propane gas was used as the fuel gas.

  The top blowing lance used in these tests is of a six-pipe structure, similarly to the top blowing lance shown in FIG. It is comprised in order of the path, the oxidizing gas supply flow path for combustion, the oxidizing gas supply flow path for refining, the water supply flow path for cooling water, and the water discharge flow path for cooling water.

  Refining powder is from a circular straight type refining powder injection hole at the center of the lance, fuel gas is from an annular (ring-shaped) fuel gas injection hole, and combustion oxygen gas to burn the fuel gas is annular ( The oxygen gas for refining was supplied into the furnace through three Laval nozzle type refining oxidizing gas injection holes arranged concentrically from the ring-shaped combustion oxidizing gas injection holes. The fine powder injection hole has an inner diameter of 11.5 mm, the fuel gas injection hole has an annular slit gap of 1.0 mm, and the combustion oxidizing gas injection hole has an annular slit gap of 1.85 mm. The refining oxidizing gas injection hole is a Laval nozzle having a throat diameter of 9.1 mm, and has a discharge angle of 15 ° (referred to as “tilt angle”) with respect to the lance center axis.

  In the test, first, iron scrap was charged into the converter main body, and then hot metal having a temperature of 1350 ° C. was charged. Then, argon gas was blown into the hot metal as a stirring gas from the bottom blowing tuyeres while oxygen gas for refining was blown toward the hot metal bath surface. A flame was formed below the top blowing lance with propane gas and oxygen gas for combustion. The pure manganese metal content in the manganese ore used was 48% by mass, and Table 1 shows the temperature and chemical composition of the hot metal used in these tests.

Nitrogen gas was used as the carrier gas for the refining powder, and the flow rate was 0.70 Nm ³ / min. The supply flow rate of oxygen gas for combustion was set to an amount necessary for complete combustion of propane gas. The flow rate of oxygen gas for refining, the range up to 15 minutes elapsed from the time of blowing start 8.0 nm ³ / min, from after 15 minutes elapsed until the end decarburization refining was 5.5 Nm ³ / min. The bottom blowing stirring gas blowing flow rate was set to 0.25 Nm ³ / min in the entire range from the start of blowing to the end of decarburization refining. The amount of iron scrap charged was adjusted so that the molten steel temperature at the end of decarburization refining was 1650 ° C. The refining powder was added for 10 minutes in all tests. The calorific value of propane gas was converted to 99.1 MJ / Nm ³ . In Test No. 10, the supply amount of propane gas was 0.30 Nm ³ / min. Other conditions were the same as those in Test Nos. 1-9.

  Table 2 shows the operation conditions and operation results in Test Nos. 1 to 10. In the remarks column of Table 2, tests within the scope of the present invention are indicated as “examples of the present invention”, and tests outside the scope of the present invention are indicated as “comparative examples”.

  As shown in Table 2, when the manganese yield (also referred to as “Mn yield”) is compared between test No. 6 and test No. 10, it is possible to operate with an increased manganese yield by applying the present invention. Was confirmed. 3 shows the relationship between the ratio Q / S value and the manganese yield in Test Nos. 1 to 9. As is clear from FIG. 3, it was confirmed that the manganese yield was remarkably increased under the condition that the value of the ratio Q / S was 1.0 MJ / kg or more.

  Fuel gas supplied from the top blowing lance when performing decarburization refining of the hot metal that has not been dephosphorized using the small converter equipment used in Example 1 and the top blowing lance used in Example 1. The ratio Q / S between the calorific value Q of the refining powder and the addition rate S of the refining powder supplied from the top blowing lance is changed, and the average particle diameter R of the refining powder used is changed, and the ratio Q A test was conducted to investigate the influence of manganese in the manganese oxide having a value of / S and an average particle size R on the yield of the molten steel (Test Nos. 21 to 45).

  As the powder for refining, a mixture in which manganese ore, quicklime and iron ore are mixed at a ratio of 4: 5: 3 is used. The average particle size R of the powder for refining is 1000 μm, 250 μm, 100 μm, 50 μm. , And changed to 5 levels of 25 μm. Propane gas was used as the fuel gas.

  In the test, first, iron scrap was charged into the converter main body, and then hot metal having a temperature of 1350 ° C. was charged, and then from the top blowing lance, powder for smelting, propane gas, and oxygen gas for combustion Then, argon gas was blown into the hot metal as a stirring gas from the bottom blowing tuyeres while oxygen gas for refining was blown toward the hot metal bath surface. A flame was formed below the top blowing lance with propane gas and oxygen gas for combustion. The pure manganese metal content in the manganese ore used was 48% by mass. The chemical composition of the hot metal used is the same as in Example 1.

Nitrogen gas was used as the carrier gas for the refining powder, and the flow rate was 0.70 Nm ³ / min. The supply flow rate of oxygen gas for combustion was set to an amount necessary for complete combustion of propane gas. The flow rate of oxygen gas for refining, the range up to 15 minutes elapsed from the time of blowing start 8.0 nm ³ / min, from after 15 minutes elapsed until the end decarburization refining was 5.5 Nm ³ / min. The bottom blowing stirring gas blowing flow rate was set to 0.25 Nm ³ / min in the entire range from the start of blowing to the end of decarburization refining. The amount of iron scrap charged was adjusted so that the molten steel temperature at the end of decarburization refining was 1650 ° C. The refining powder was added for 10 minutes in all tests. The calorific value of propane gas was converted to 99.1 MJ / Nm ³ .

  Table 3 shows the operation conditions and operation results in Test Nos. 21 to 45. In the remarks column of Table 3, tests within the scope of the present invention are displayed as “examples of the present invention”, and tests outside the scope of the present invention are displayed as “comparative examples”.

  4 shows the relationship between the value of the ratio Q / S in Test Nos. 21 to 45 and the manganese yield, using the average particle size R of the powder for refining as an index. As shown in FIG. 4, although the manganese yield increases as the value of the ratio Q / S increases, the manganese yield when the ratio Q / S is the same as the average particle size R of the refining powder increases. Was found to decrease. Here, in FIG. 4, the value of the ratio Q / S at which the manganese yield rapidly increases (hereinafter referred to as “the critical point of the ratio Q / S”) was determined for each average particle size R of the powder for refining. For example, in a refining powder having an average particle size R of 1000 μm, the critical point of the ratio Q / S is when the ratio Q / S is about 1.57 MJ / kg.

With the critical point of the ratio Q / S thus determined as the vertical axis and the average particle diameter R of the refining powder as the horizontal axis, the critical point of the ratio Q / S and the average particle diameter R of the refining powder as The relationship is shown in FIG. When the high manganese yield range is approximated by the relationship between the critical point of the ratio Q / S and the average particle size R based on FIG. 5, the high manganese yield range may be within the range of the following formula (1). all right.
Q / S ≧ 0.4 × R ^0.2 (1)
However, in the formula (1), Q is the calorific value of the fuel gas (MJ / min), S is the addition rate (kg / min) of the refining powder, and R is the average particle size (μm) of the refining powder. is there. In FIG. 5, the horizontal axis is displayed on a logarithmic scale. The critical point of the ratio Q / S varies depending on the average particle size R of the refining powder as shown in the equation (1), but the upper limit of the ratio Q / S is the average particle of the refining powder. The diameter R is not affected and is preferably 5.0 MJ / kg or less regardless of the average particle diameter R of the refining powder.

  That is, by adjusting at least one of the calorific value Q of the fuel gas, the addition rate S of the refining powder, and the average particle size R of the refining powder, the relationship of formula (1) is satisfied, It was confirmed that the yield can be improved.

DESCRIPTION OF SYMBOLS 1 Converter equipment 2 Furnace main body 3 Top blowing lance 4 Iron skin 5 Refractory 6 Outlet 7 Bottom blowing tuyere 8 Gas introduction pipe 9 Refining powder supply pipe 10 Fuel gas supply pipe 11 Combustion oxidizing gas supply pipe 12 Refining oxidizing gas supply pipe 13 Dispenser 14 Lance body 15 Lance tip 16 Refining powder injection hole 17 Fuel gas injection hole 18 Combustion oxidizing gas injection hole 19 Refining oxidizing gas injection hole 20 Innermost pipe 21 Partition pipe 22 inner pipe 23 middle pipe 24 outer pipe 25 outermost pipe 26 hot metal 27 slag 28 gas for stirring 29 powder for refining 30 powder supply path for refining 31 fuel gas supply flow path 32 oxidizing gas supply flow path for combustion 33 Refining oxidizing gas supply flow path 34 Shut-off valve

Claims (2)

Refining powder supply flow path, fuel gas supply flow path, fuel gas combustion oxidizing gas supply flow path, and refining oxidizing gas supply flow path, each using an upper blowing lance, The fuel gas is supplied from the fuel gas supply flow path, and at the same time, the combustion oxidizing gas is supplied from the combustion oxidizing gas supply flow path, and the tip of the upper blowing lance is formed by the combustion oxidizing gas and the fuel gas. While forming a flame below, the refining powder containing manganese oxide is added together with an inert gas toward the hot metal bath surface in the converter from the refining powder supply channel, and the refining A method for refining hot metal in a converter, wherein the oxidizing gas for refining is supplied toward the hot metal bath surface in the converter from the oxidizing gas supply flow path, and the hot metal in the converter is oxidized and refined.
When the calorific value of the fuel gas is Q (MJ / min) and the addition rate of the refining powder is S (kg / min), the ratio Q / S between the calorific value Q and the addition rate S is 1. A method for refining hot metal in a converter, wherein the calorific value Q and / or the addition rate S is adjusted so as to be 0.0 MJ / kg or more. Furthermore, when the average particle size of the refining powder is R (μm), the relationship between the calorific value Q, the addition rate S, and the average particle size R is within the range of the following formula (1). 2. The method for refining hot metal in a converter according to claim 1, wherein at least one of the calorific value Q, the addition rate S, and the average particle size R is adjusted so as to be within.
Q / S ≧ 0.4 × R ^0.2 (1)

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