JP5870868B2 - Method of refining hot metal in converter - Google Patents

Description

  The present invention uses an upper blowing lance having a burner function and heats the powdered smelting agent together with an inert gas in the converter while heating with a burner flame formed below the tip of the upper blowing lance. The present invention relates to a method of spraying molten iron to which a cold iron source has been added, applying a heat of a powdery refining agent to the molten iron, and subjecting the molten iron to oxidation refining such as dephosphorization or decarburization while melting the cold iron source.

From the viewpoint of environmental protection, it is an urgent task to reduce CO ₂ emissions in the steel manufacturing process. In the steelmaking process, the amount of cold iron such as iron scrap used as the iron source is increased to lower the hot metal content rate. Actions such as making it happen are being studied and implemented. This is because when manufacturing steel products, hot metal production in a blast furnace requires a large amount of energy for reducing and melting iron ore, and at the same time emits a large amount of CO ₂ while This is because the iron source only needs heat of melting, and when the cold iron source is used in the steel making process, the amount of energy used and the amount of CO ₂ generated can be reduced.

  However, in the steel manufacturing process consisting of a combination of a blast furnace and a converter, the heat source for melting a cold iron source such as iron scrap mainly consists of sensible heat of hot metal, combustion heat of carbon and silicon in the hot metal, A large amount of cold iron source cannot be dissolved. In addition, dephosphorization treatment (also referred to as “preliminary dephosphorization treatment”) is carried out as a pretreatment for hot metal, and not only a reduction in hot metal temperature due to the addition of the treatment process but also carbon and silicon in the hot metal. Is oxidized by dephosphorization treatment, and its concentration decreases, which is disadvantageous for the dissolution of the cold iron source. The hot metal dephosphorization process is a process in which dephosphorization process is performed in advance in the hot metal stage before decarburization and refining in the converter to remove a certain amount of phosphorus in the hot metal.

  Thus, many methods have been proposed for increasing the thermal margin of hot metal and molten steel in dephosphorization processing and converter decarburization refining. For example, Patent Document 1 discloses a method in which a carbon source is added to generated slag during dephosphorization treatment, an oxygen source is blown into the slag to burn the carbon source, and the combustion heat is applied to the hot metal. Proposed.

  In Patent Document 2, a powder heating burner having a five-pipe structure is used, and a raw material granular material injected from the center of the powder heating burner is heated by a burner flame formed around the converter. A method is proposed in which the raw material granular material is melted and reduced in a converter.

JP-A-9-20913 JP 2010-215983 A

  However, the above prior art has the following problems.

That is, in patent document 1, although a hot metal temperature rises by adding a carbon source in production | generation slag, mixing of the sulfur contained in a carbon source is caused, and the sulfur concentration in steel becomes high. In addition, there is a problem that the refining time becomes long to ensure the combustion time of the carbon source, and the manufacturing cost increases. Furthermore, since the carbon source is burned, there is a problem that the amount of CO ₂ generated naturally increases.

  In Patent Document 2, an operation in which the flow rates of the fuel and the combustion oxygen gas are defined is described in the embodiment, but the ejection speed of the fuel and the combustion oxygen gas from the lance is not described. When the ejection speed of the fuel gas reaches a certain value or more, the flame blows off and a stable flame cannot be formed. That is, in order to stably ignite the burner flame, it is necessary to limit the input heat amount per unit cross-sectional area of the flow path outlet, but Patent Document 2 does not describe anything. Further, when the ejection speed of the combustion oxygen gas is out of a certain range, the temperature in the flame is lowered, and this makes it impossible to obtain an effective heat receiving efficiency. Not listed.

  The present invention has been made in view of the above circumstances, and its object is to use an upper blowing lance having a burner function, and to inactivate the powdery smelting agent with a burner flame via the upper blowing lance. It is possible to stably form a burner flame when spraying molten iron with a cold iron source in the converter together with gas and subjecting the molten iron to oxidation refining such as dephosphorization and decarburization. An object of the present invention is to provide a method for refining hot metal in a converter that can stably increase the blending ratio of a cold iron source such as scrap.

The gist of the present invention for solving the above problems is as follows.
[1] Top having a powdery refining agent supply channel, a fuel gas supply channel, an oxidizing gas supply channel for combustion of the fuel gas, and an oxidizing gas supply channel for refining disposed above the converter Using a blow lance, the input heat amount per unit cross-sectional area at the outlet of the fuel gas supply channel from the fuel gas supply channel is 250 kJ / (mm ² · min) or more and 800 kJ / (mm ² · min) or less. At the same time as supplying the fuel gas, the oxidizing gas is supplied from the combustion oxidizing gas supply channel to form a flame below the tip of the top blowing lance, As a refining agent, one or more of iron oxide, lime-based medium solvent, and combustible substance are supplied together with an inert gas toward the hot metal bath surface in the converter, and from the refining oxidizing gas supply flow path. Supply the oxidizing gas for refining toward the hot metal bath surface, and cool the converter inside Wherein the oxidizing smelting of added hot metal source, hot metal process for refining in the converter.
[2] The converter according to [1], wherein a jetting speed of the combustion oxidizing gas at an outlet of the combustion oxidizing gas supply channel is controlled to 75 Nm / sec or more and 315 Nm / sec or less. Of refining hot metal in Japan.
[3] The above [1] or [2], wherein propane gas is used as the fuel gas, and the propane gas ejection speed at the outlet of the fuel gas supply flow path is controlled to 133 Nm / sec or less. The method for refining hot metal in the converter described in 1.
[4] The liquefied natural gas is used as the fuel gas, and the ejection speed of the liquefied natural gas at the outlet of the fuel gas supply flow path is controlled to 290 Nm / sec or less. [2] A method for refining hot metal in a converter according to [2].
[5] The upper blowing lance has a powdery refining agent supply channel, a fuel gas supply channel, an oxidizing gas supply channel for combustion of the fuel gas, and an oxidizing gas supply for refining from the center side in the cross-sectional structure. In the converter according to any one of [1] to [4] above, which has a six-pipe structure that forms two cooling water flow paths, a flow path, cooling water supply water, and drainage. Hot metal refining method.
[6] The method for refining hot metal in a converter according to any one of [1] to [5] above, wherein the oxidation refining is dephosphorization of hot metal.

According to the present invention, the amount of heat input per unit cross-sectional area at the outlet of the fuel gas supply channel of the fuel gas for forming the burner flame below the top blowing lance tip is controlled, so that the fuel gas is stably ignited. As a result, the flame is stably formed, and as a result, it is possible to stably heat the powder refining agent supplied into the furnace through the top blowing lance, and the heat of the powder refining agent is ensured to the hot metal. Therefore, the heat margin of the hot metal is improved, and the mixing ratio of the cold iron source such as iron scrap can be greatly increased in the oxidation refining of the hot metal in the converter. In addition, since the heat receiving efficiency to the hot metal is stably maintained high, the carbonized material for carburizing can be reduced, and there is an effect of reducing CO ₂ emission.

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 investigation result of the relationship between the heat input per unit cross-sectional area in a fuel gas supply flow path exit, and stable ignition. It is a figure which shows the relationship between the ejection speed of the oxidizing gas for combustion, and the heating temperature of a powdery refining agent.

  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, and the present invention can be applied to any of them. In this case, in hot metal decarburization refining, either hot metal that has been previously dephosphorized or hot metal that has not been dephosphorized may be used. The present invention can also be applied to the case where the present invention is applied to a dephosphorization process and the hot metal refined by the dephosphorization process 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 and decarburization refining. To do. When performing the dephosphorization process, in order to efficiently perform the dephosphorization process with a small amount of the lime-based medium solvent, the silicon in the hot metal is removed in advance before the dephosphorization process (referred to as “hot metal desiliconization process”). In addition, it is preferable to reduce the silicon content of the hot metal to 0.20% by mass or less, desirably 0.10% by mass or less. When the desiliconization process is performed, the slag generated during the desiliconization process is discharged before the dephosphorization process.

  Hereinafter, the present invention will be described by taking hot metal dephosphorization treatment in a converter as an example. The hot metal dephosphorization treatment can also be performed in a hot metal transport container such as a hot metal pan or a topped car, but the free board is larger than these hot metal transport containers and the hot metal can be vigorously stirred. In addition, in the present invention, the dephosphorization process is performed using a converter because not only the melting capacity of the cold iron source is high but also the dephosphorization process can be performed quickly with a small amount of lime-based solvent. To do.

  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.

  As shown in FIG. 1, the converter equipment 1 used for the dephosphorization process in the present invention has a furnace body 2 in which an outer shell is constituted by an iron skin 4 and a refractory 5 is enforced inside the iron skin 4; An upper blowing lance 3 that is inserted into the furnace body 2 and is movable in the vertical direction is provided. A top 6 of the furnace body 2 is provided with a hot water outlet 6 for pouring hot metal 26 after the dephosphorization process, and a plurality of bottoms for injecting a stirring gas 28 into the furnace bottom of the furnace body 2. A blowing tuyere 7 is provided. The bottom blowing tuyere 7 is connected to a gas introduction pipe 8.

  The top blow lance 3 is supplied with a powdery refining agent 29 composed of at least one of iron oxide, lime-based solvent, and combustible substance together with an inert gas such as nitrogen gas and Ar gas. A refining agent supply pipe 9, a fuel gas supply pipe 10 for supplying gas fuel such as propane gas, liquefied natural gas, coke oven gas, etc., and an oxidizing property such as oxygen gas and air for burning the supplied fuel gas Combustion oxidizing gas supply pipe 11 for supplying a gas, refining oxidizing gas supply pipe 12 for supplying a refining oxidizing gas such as oxygen gas, and cooling for cooling the top blowing lance 3 A cooling water supply pipe and a drain pipe (not shown) for supplying and discharging water are connected. FIG. 1 shows an example in which the oxidizing gas for combustion and the oxidizing gas for refining are oxygen gases.

  Instead of the fuel gas, it is possible to use a hydrocarbon-based liquid fuel such as heavy oil or kerosene. However, in the present invention, there is a risk of clogging at the nozzle at the outlet of the flow path. (Gaseous fuel) is used. If gaseous fuel is used, not only can clogging of nozzles and the like be prevented, but there are advantages such as easy adjustment of the supply flow rate and easy ignition to prevent misfire.

  The other end of the powdery refining agent supply pipe 9 is connected to a dispenser 13 containing a powdery refining agent 29, and the dispenser 13 is connected to a powdery refining agent conveying gas supply pipe 9A. The inert gas supplied to the dispenser 13 through the agent conveying gas supply pipe 9A functions as a conveying gas for the powdery refining agent 29 accommodated in the dispenser 13, and the powdery refining agent accommodated in the dispenser 13 29 is supplied to the upper blowing lance 3 through the powdery refining agent supply pipe 9 and can be sprayed toward the hot metal 26 from the tip of the upper blowing lance 3. FIG. 1 shows an example of nitrogen gas as the carrier gas for the powdery refining agent 29.

  As shown in FIG. 2, the upper blow lance 3 is composed of a cylindrical lance main body 14 and a copper cast lance tip 15 connected to the lower end of the lance main body 14 by welding or the like. Reference numeral 14 denotes an innermost tube 20, a partition tube 21, an inner tube 22, an intermediate tube 23, an outer tube 24, and an outermost tube 25, which are six types of concentric steel tubes, that is, six-fold tubes. The powdery refining agent 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. Through the inside of the innermost pipe 20, fuel gas such as propane gas passes through the gap between the innermost pipe 20 and the partition pipe 21, and the oxidizing gas for fuel combustion passes through the gap between the partition pipe 21 and the inner pipe 22, The refining oxidizing gas passes through the gap between the inner pipe 22 and the middle pipe 23, and 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 are the water supply flow path of the cooling water or It is a drainage 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 tube 20 communicates with the center hole 16 disposed substantially at the axial center position of the lance tip 15, and the gap between the innermost tube 20 and the partition tube 21 is an annular nozzle around the center hole 16. Alternatively, the gap between the partition pipe 21 and the inner pipe 22 communicates with the fuel gas injection holes 17 that are opened as a plurality of concentric nozzle holes, and an annular nozzle or a plurality of concentric circles are formed around the fuel gas injection holes 17. The combustion oxidizing gas injection holes 18 opened as individual nozzle holes communicate with each other, and a plurality of gaps between the inner tube 22 and the intermediate tube 23 are provided around the combustion oxidizing gas injection holes 18. It communicates with the hole 19. The center hole 16 is a nozzle for spraying the powdery refining agent 29 together with the carrier gas, the fuel gas injection hole 17 is a nozzle for injecting the fuel gas, and the combustion oxidizing gas injection hole 18 is for burning the fuel gas. The nozzle for injecting the oxidizing gas and the peripheral hole 19 are nozzles for spraying the oxidizing gas for refining.

  That is, the inside of the innermost pipe 20 is a powdery refining agent supply flow path, the gap between the innermost pipe 20 and the partition pipe 21 is a fuel gas supply flow path, and the gap between the partition pipe 21 and the inner pipe 22 is for combustion. An oxidizing gas supply flow path is formed, and a gap between the inner pipe 22 and the intermediate pipe 23 is a refining oxidizing gas supply flow path. In FIG. 2, the center hole 16 is a straight nozzle, and the peripheral hole 19 is in the shape of a Laval nozzle composed of two cones, a portion whose cross section is reduced and a portion where the cross section is enlarged. The 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.

  Using the converter equipment 1 having this configuration, the dephosphorization treatment according to the present invention for the purpose of increasing the blending ratio of the cold iron source is performed on the hot metal 26 as follows.

First, a cold iron source is charged into the furnace body 2. The cold iron source used is iron scrap such as slabs and steel plate crops and city scraps generated at steelworks, bullion recovered from slag by magnetic sorting, and cold iron, reduced iron, etc. can do. The blending ratio of the cold iron source is preferably 5% by mass or more based on the total iron source to be charged (mixing ratio of the cold iron source (mass%) = cold iron source blending amount × 100 / (molten iron blending amount). + Cold iron source blending amount)). This is because when the blending ratio of the cold iron source is less than 5% by mass, not only the effect of improving the productivity is small but also the effect of reducing the amount of CO ₂ generation is small. The upper limit of the blending ratio of the cold iron source does not need to be particularly determined, and the hot metal temperature after the dephosphorization treatment can be added up to an upper limit that can maintain the target range. Before and after the cold iron source is charged, 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 can be treated with any composition, and may be subjected to desulfurization treatment or desiliconization treatment before the dephosphorization treatment. Incidentally, the main chemical components of the hot metal 26 before the dephosphorization treatment are carbon: 3.8 to 5.0% by mass, silicon: 0.3% by mass or less, phosphorus: 0.08 to 0.2% by mass, sulfur : About 0.05% by mass or less. However, if the amount of slag 27 produced in the furnace body during the dephosphorization process increases, the dephosphorization efficiency decreases. As described above, in order to increase the dephosphorization efficiency by reducing the amount of slag generated in the furnace. In addition, it is preferable to reduce the silicon concentration in the hot metal to 0.20% by mass or less, preferably 0.10% by mass or less in advance by desiliconization treatment. Moreover, if the hot metal temperature is in the range of 1200 to 1400 ° C., dephosphorization can be performed without any problem.

  Next, an inert gas is supplied to the dispenser 13, and a powdery refining agent 29 composed of one or more of iron oxide, lime-based medium solvent, and combustible substance is supplied from the center hole 16 of the top blowing lance 3 to the inert gas. At the same time, spray toward the bath surface of hot metal 26. Before and after the spraying of the powdery refining agent 29, fuel gas is injected from the fuel gas injection hole 17 of the upper blowing lance 3, and oxidizing gas such as oxygen gas is injected from the combustion oxidizing gas injection hole 18, A flame is generated below the upper blowing lance 3.

In generating a flame at the tip of the upper blowing lance 3, the fuel gas supply amount and the oxygen gas supply amount supplied to the upper blowing lance 3 are adjusted to completely burn the fuel gas. At that time, in order to stably ignite the burner flame, the input heat amount per unit cross-sectional area at the outlet of the fuel gas supply flow path is controlled to 800 kJ / (mm ² · min) or less.

  Here, the amount of heat input per unit cross-sectional area at the fuel gas supply channel outlet is defined by the following equation (1), and the ejection speed in the equation (1) is defined by the following equation (2). .

Heat input per unit cross-sectional area at the channel outlet (kJ / (mm ² · min)) = Fuel heating value (kJ / Nm ³ ) x Injection speed (Nm / min) ÷ 10 ⁶ (1)
Blowing speed (Nm / min) = gas flow rate (Nm ³ / min) / the channel outlet cross-sectional area (m ²⁾ ... ⁽²⁾
The fuel heating value “Nm ³ ” and the ejection speed “Nm / min” are the flow rate and speed converted to the standard state (0 ° C., 1 atm).

That is, the amount of heat input per unit cross-sectional area at the fuel gas supply channel outlet depends on the fuel gas ejection speed, so the cross-sectional area of the fuel gas supply channel outlet, that is, the cross-sectional area of the fuel gas injection hole 17 is calculated. By adjusting, it becomes possible to adjust the amount of input heat per unit cross-sectional area at the outlet of the flow path. Even if the gas flow rate (Nm ³ / min) of the fuel gas is changed, the input heat amount per unit cross-sectional area changes. However, even if the gas flow rate of the fuel gas is constant, the cross-sectional area of the fuel gas injection hole 17 is changed. By adjusting, the amount of input heat per unit cross-sectional area can be changed. Note that the heat generation amount of the fuel becomes a constant value according to the fuel gas used.

On the other hand, if the input heat amount per unit cross-sectional area in the fuel gas injection hole 17 is too small, the heating amount of the hot metal decreases, so the input heat amount per unit cross-sectional area in the fuel gas injection hole 17 is 250 kJ / (mm ² · Minutes).

  Furthermore, it is preferable to control the ejection speed of the combustion oxidizing gas at the outlet of the combustion oxidizing gas supply flow path, that is, the combustion oxidizing gas injection hole 18 to 75 Nm / sec or more and 315 Nm / sec or less. This is because when the ejection speed of the oxidizing gas for combustion exceeds 315 Nm / sec, the amount of heat transfer to the powdery refining agent 29 is rapidly reduced. On the other hand, when the ejection speed of the oxidizing gas for combustion is less than 75 Nm / second, the fuel gas ejection speed may be too low in some cases, and in that case, the flame is not stable. The ejection speed of the combustion oxidizing gas can also be controlled by adjusting the cross-sectional area of the combustion oxidizing gas injection hole 18.

  By supplying the fuel gas and the oxidizing gas for combustion under this condition, the fuel supplied from the fuel gas injection hole 17 and the oxidizing gas supplied from the combustion oxidizing gas injection hole 18 are Because they are close to each other in the radial direction, they interfere with each other and the ambient temperature is high. Even if there is no ignition device, combustion occurs when the gas concentration reaches the combustion limit range, and the top blow lance A flame is formed below 3.

  The powdery refining agent 29 injected together with the inert gas from the center hole 16 is heated or heated / melted by the heat of the formed flame, and is sprayed on the bath surface of the hot metal 26 in a heated or molten state. Thereby, the heat of the powdery refining agent 29 is applied to the molten iron 26, the temperature of the molten iron 26 rises, and the dissolution of the added cold iron source is promoted.

  At that time, refining oxidizing gas such as oxygen gas is blown toward the bath surface of the hot metal 26 from the peripheral hole 19 of the upper blowing lance 3.

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 addition, the rate of dephosphorization increases as the hatching of the lime-based medium solvent is promoted. Therefore, as the powdery refining agent 29, it is preferable to use a lime-based medium solvent such as quick lime (CaO), limestone (CaCO ₃ ), and slaked lime (Ca (OH) ₂ ). A mixture of quicklime with fluorite (CaF ₂ ) or alumina (Al ₂ O ₃ ) as a hatching accelerator can also be used as the lime-based solvent. It is also possible to use converter slag produced in the decarburization blowing process of the molten iron 26 (CaO-SiO ₂ slag) as all or part of the lime-based medium solvent.

  The lime-based medium solvent sprayed on the hot metal bath surface as the powdery refining agent 29 immediately hatches to form slag 27, and the supplied oxidizing gas for refining reacts with phosphorus in the hot metal to produce phosphor oxide. Is formed. Combined with the strong stirring of the hot metal 26 and the slag 27 by the stirring gas 28, the formed phosphorous oxide is rapidly absorbed by the hatched slag 27, and the dephosphorization reaction of the hot metal 26 proceeds promptly. When the lime-based medium solvent is not used as the powdery refining agent 29, the lime-based medium solvent is separately put on top from the furnace hopper.

  When iron oxide such as iron ore or mill scale is used as the powdery refining agent 29, the iron oxide functions as an oxygen source and reacts with phosphorus in the molten steel to advance a dephosphorization reaction. Further, the iron oxide reacts with the lime-based medium solvent to form a FeO-CaO compound on the surface of the lime-based medium solvent, which promotes the hatching of the lime-based medium solvent and promotes the dephosphorization reaction. When iron oxide containing combustible material such as blast furnace dust or converter dust is used, the combustible material is burned by the flame, and in addition to the above, the combustion heat of the combustible material is used to heat the hot metal 26. Contribute.

  Further, as the powdery refining agent 29, aluminum ash (30 to 50% by mass of metal Al produced by reaction of Al and oxygen in the air when Al ingot or scrap is melted in a melting furnace) is contained. When a flammable substance such as (Al oxide) or coke is used, the flammable substance is burned by the flame, and the combustion heat of the flammable substance contributes to the heating of the hot metal 26 in addition to the combustion heat of the fuel. In the case where a mixture of a lime-based solvent, iron oxide and a combustible substance is used as the powdery refining agent 29, the respective effects can be obtained in parallel.

  Further, the powdery refining agent 29 is heated or heated / melted, and the heat is transmitted to the hot metal 26, and further, the combustion heat of the flame at the tip of the upper blowing lance existing above the hot metal 26 is supplied to the hot metal 26. Since it is transmitted, the hot iron 26 is vigorously stirred, and the melting of the cold iron source in the hot metal is promoted. That is, the melting of the charged cold iron source is completed during the dephosphorization process.

  Thereafter, when the phosphorus concentration in the hot metal 26 becomes the target value or less, all the supply from the top blowing lance 3 to the hot metal 26 is stopped, and the dephosphorization process is ended. After the dephosphorization treatment, the hot metal 26 that has been subjected to the dephosphorization treatment by tilting the furnace body 2 is discharged into a hot metal holding container such as a ladle or a converter charging pan through the hot water outlet 6, and the molten hot metal is discharged. 26 is transferred to the next process.

  As described above, according to the present invention, the amount of heat input per unit sectional area of the fuel gas injection hole 17 of the fuel gas for forming the burner flame below the top blowing lance tip is controlled. It is possible to stably ignite and form a flame stably. As a result, it is possible to stably heat the powdery refining agent 29 supplied into the furnace via the top blowing lance 3, and the powdery refining agent is realized. Since the heat of 29 is surely applied to the hot metal 26, the thermal margin of the hot metal 26 is improved, and the mixing ratio of the cold iron source such as iron scrap is greatly increased in the oxidation refining of the hot metal 26 in the converter facility 1. Is realized.

  In addition, also in decarburization refining of hot metal in a converter, the present invention can be applied by oxidizing refining along the above.

  Using a small furnace, the heat deposition behavior of the powdered smelting agent was investigated. The top blowing lance used in the small furnace is of a six-pipe structure, similarly to the top blowing lance shown in FIG. 2, and from the center in the cross section thereof, the powdery refining agent supply flow path, the fuel gas supply flow It is composed of two cooling water passages, a passage, an oxidizing gas supply passage for combustion of the fuel gas, an oxidizing gas supply passage for refining, a coolant supply water and a drainage. The powdered refining agent is from the center hole of the circular straight type at the center of the lance, the fuel gas is from the annular (ring-shaped) fuel gas injection hole, and the oxygen gas for fuel gas combustion is the annular (ring-shaped) combustion oxidation The oxygen gas for refining was supplied into the furnace through the peripheral holes of a plurality of Laval nozzle types arranged concentrically from the chemical gas injection hole. In addition, as long as it is the top blowing lance which has the flow path shown above, it does not interfere even if it is a 7-pipe structure or more.

  The center hole has an inner diameter of 11.5 mm, the fuel gas injection hole has an annular slit gap of 0.5 mm to 2 mm, and the combustion oxidizing gas injection hole has an annular slit gap of 0.75 mm to 1.85 mm. The peripheral hole is a three-hole Laval nozzle having a throat diameter of 7 mm and has an angle of 15 ° with respect to the lance center axis. By changing the gap of the annular slit of the fuel gas injection hole and the gap of the annular slit of the oxidizing gas injection hole for combustion, the ejection speed can be changed even at the same flow rate.

Chromium ore was used as the powder refining agent. Also, propane gas (calorific value: 100.5 MJ / Nm ³ ) and liquefied natural gas (calorific value: 45.9 MJ / Nm ³ ) are used as the fuel gas, and the fuel gas supply flow rate is 0.16 Nm for propane gas. ³ / min, liquefied natural gas was 0.35 Nm ³ / min. The supply amount of oxygen gas for fuel gas combustion was 0.8 Nm ³ / min, the supply amount of refining oxygen gas was 5 Nm ³ / min, and the supply amount of chromium ore as a powder refining agent was 5 kg / min.

  We investigated the stable ignition region of the flame using an upper blowing lance with various changes in the annular slit width of the fuel gas injection hole. As a result, the burner flame is stably ignited under the condition that the ejection speed of the propane gas from the fuel gas injection hole is 133 Nm / sec or less, whereas in the case of liquefied natural gas, the fuel gas injection hole of liquefied natural gas It was found that the burner flame was stably ignited under the condition that the jet velocity from the gas was 290 Nm / sec or less.

Based on these results, the amount of heat input per unit cross-sectional area at the outlet of the channel (kJ) determined by the equation (1) based on the fuel heating value (kJ / Nm ³ ) of propane gas and liquefied natural gas and the jet velocity at that time / (mm ² · min)), and the relationship between this input heat amount and stable ignition was determined. The relationship between the calculated input heat amount and stable ignition is shown in FIG. In FIG. 3, “circle” indicates the result of propane gas, “triangle” indicates the result of liquefied natural gas, and “black” indicates misfire.

As shown in FIG. 3, since the probability of misfire increases when the input heat amount exceeds 800 kJ / (mm ² · min), in order to ignite the burner flame stably, the unit cross-sectional area in the fuel gas injection hole It was found that the amount of heat input must be 800 kJ / (mm ² · min) or less. On the other hand, if the amount of heat input per unit cross-sectional area in the fuel gas injection hole is too small, the amount of heating of the hot metal decreases, so the amount of heat input per unit cross-sectional area in the fuel gas injection hole is 250 kJ / (mm ² · min) It is necessary to secure

  In addition, using an upper blowing lance in which the annular slit width of the combustion oxidizing gas injection hole is variously changed, a fuel flame and a combustion oxygen gas are blown from the upper blowing lance to form a stable flame. Chromium ore was blown together with inert gas (nitrogen gas) from the powder smelting agent supply channel of the blowing lance, and the temperature of the chromium ore immediately after passing through the flame was measured with a two-color thermometer. The measurement results are shown in FIG.

  As shown in FIG. 4, it has been found that when the ejection speed of the combustion oxygen gas changes, the amount of heat that is applied from the flame to the powdery refining agent changes. That is, when the ejection speed of the combustion oxygen gas exceeds 315 Nm / sec, the amount of heat transferred to the powdered smelting agent is rapidly reduced, so the ejection speed of the combustion oxygen gas is suppressed to 315 Nm / sec or less. It has been found that this is preferable.

  In the converter equipment shown in FIG. 1, the present invention was applied to perform a dephosphorization treatment test of hot metal to which iron scrap was added (Invention Example 11 and Invention Example 12). The top blowing lance used has a six-pipe structure, similar to the top blowing lance shown in FIG. Further, for comparison, Comparative Example 11 in which the fuel gas ejection speed is changed and the amount of heat input per unit cross-sectional area at the outlet (fuel gas injection hole) of the fuel gas supply channel is outside the scope of the present invention is compared. The test operation which does not form a flame under Example 12 and an upper blowing lance tip was also performed (Comparative Example 13). Quick lime was used as a refining agent supplied from the top blowing lance. Table 1 shows the operating conditions of the present invention and comparative examples.

  In the test, a plurality of lance bodies 14 having the same dimensions were prepared, and a plurality of lance tips 15 each having a design change were prepared. The plurality of lance tips 15 has a center hole 16 having an inner diameter of 55 mm, and the peripheral hole 19 is a five-hole Laval nozzle having a throat diameter of 50 mm, and is arranged at an inclination angle of 15 ° with respect to the lance center axis. In addition, each of the plurality of lance tips 15 has a design change with respect to the fuel gas injection holes 17 and the combustion oxidizing gas injection holes 18. Specifically, the fuel gas injection hole 17 and the combustion oxidizing gas injection hole 18 are annular slit nozzles, and the width of the annular slit gap is 5.5 mm to 20.0 mm in the fuel gas injection hole 17. In the range, and the combustion oxidizing gas injection hole 18 has a different arbitrary dimension in the range of 8.3 mm to 25.4 mm.

The plurality of lance tips 15 and the plurality of lance main bodies 14 are welded to prepare a plurality of upper blowing lances 3 having different gaps between the fuel gas injection holes 17 and the combustion oxidizing gas injection holes 18. By using the top blow lance set in this way, the fuel gas and the oxidizing gas for combustion are ejected at the same flow rate (m ³ / sec) when forming the flame. It was possible to change (discharge speed (Nm / sec)).

As the fuel gas, liquefied natural gas (calorific value: 45.9 MJ / Nm ³ ) was used. The supply flow rate (supply rate) of liquefied natural gas was 25 Nm ³ / min. In this case, the fuel gas ejection speed is 87 Nm / sec to 331 Nm / sec. In addition, oxygen gas was used as the oxidizing gas for combustion, and the supply flow rate (supply rate) was set to 57 Nm ³ / min in order to completely burn the liquefied natural gas. The ejection speed of oxygen gas was 242 Nm / sec to 331 Nm / sec.

  In Invention Examples 11 and 12, and Comparative Examples 11 and 12, after 40 tons of iron scrap was charged into the furnace body, 300 tons of hot metal was charged into the furnace body, and oxygen gas was blown up to about 13 The dephosphorization process for a minute was performed. At the same time, liquefied natural gas was supplied as a fuel gas, a flame was formed below the tip of the upper blowing lance, and quick lime was blown into the flame as a powdery refining agent together with nitrogen gas from the powdery refining agent supply channel. After completion of the dephosphorization treatment, the hot metal was poured out into a hot metal holding container.

  In Invention Examples 11 and 12, no undissolved iron scrap was found inside the furnace body after pouring, and it was confirmed that the added 40 ton of iron scrap was completely dissolved during the dephosphorization process. On the other hand, Comparative Examples 11 and 12 are dephosphorization treatments under conditions where the fuel gas ejection speed is changed and the input heat amount per unit cross-sectional area at the outlet of the fuel gas supply channel is outside the scope of the present invention. As a result of unloading the hot metal after completion of the dephosphorization treatment, undissolved iron scrap remained inside the furnace main body and could not be completely dissolved during the dephosphorization treatment.

  Further, in Comparative Example 13, the hot metal was dephosphorized under the same conditions as in Examples 11 and 12 of the present invention except that no flame was formed below the top blowing lance tip. As a result, undissolved iron scrap remained inside the furnace body, and 40 tons of iron scrap could not be completely dissolved during the dephosphorization process.

  As described above, by applying the present invention, it was possible to perform a stable operation without generating undissolved iron scrap. Further, in Table 1, the dephosphorization characteristics in the examples of the present invention are the same as those in the comparative example so that the amount of auxiliary raw material used, the amount of oxygen blown up, the composition of the hot metal before and after the dephosphorization treatment, and the hot metal temperature are also shown. It was confirmed that there was no increase in the amount of raw materials and oxygen used.

  Using the converter and top blowing lance used in Example 2, the dephosphorization treatment was performed under the condition that the fuel gas was propane gas (Examples 21 and 22 of the present invention). Further, for comparison, the fuel gas ejection speed is changed, and the amount of heat input per unit cross-sectional area at the outlet of the fuel gas supply channel is outside the scope of the present invention. A test operation in which no flame was formed below the tip of the blowing lance was also performed (Comparative Example 23). Table 2 shows the operating conditions of the inventive examples and comparative examples. The conditions are the same as in Example 2 except that the fuel gas is changed.

Propane gas (calorific value: 100.5 MJ / Nm ³ ) was used as the fuel gas, and the supply flow rate (supply rate) of propane gas was 12 Nm ³ / min. The ejection speed of the fuel gas was 42 Nm / sec to 172 Nm / sec. In addition, oxygen gas was used as the oxidizing gas for combustion, and the supply flow rate (supply rate) was set to 57 Nm ³ / min in order to completely burn the liquefied natural gas. The oxygen gas ejection speed was 242 Nm / sec to 331 Nm / sec.

  In Invention Examples 21 and 22 and Comparative Examples 21 and 22, after 40 tons of iron scrap was charged into the furnace body, 300 tons of hot metal was charged into the furnace body and oxygen gas was blown up for about 13 minutes. The dephosphorization process was performed. At the same time, propane gas was supplied as a fuel gas, a flame was formed below the tip of the upper blowing lance, and quick lime was blown into the flame as a powdery refining agent together with nitrogen gas from the powdery refining agent supply channel. After completion of the dephosphorization treatment, the hot metal was poured out into a hot metal holding container.

  In Invention Examples 21 and 22, no undissolved iron scrap was found inside the furnace main body after pouring, and it was confirmed that the added 40 ton of iron scrap was completely dissolved during the dephosphorization process. On the other hand, Comparative Examples 21 and 22 are dephosphorization treatments under conditions where the fuel gas ejection speed is changed and the input heat amount per unit cross-sectional area at the outlet of the fuel gas supply channel is outside the scope of the present invention. As a result of unloading the hot metal after completion of the dephosphorization treatment, undissolved iron scrap remained inside the furnace main body and could not be completely dissolved during the dephosphorization treatment.

  Further, in Comparative Example 23, the hot metal was dephosphorized under the same conditions as in Examples 21 and 22 of the present invention except that no flame was formed below the top blowing lance tip. As a result, a large amount of undissolved iron scrap remained inside the furnace body, and 40 tons of iron scrap could not be completely dissolved during the dephosphorization process.

  As described above, by applying the present invention, it was possible to perform a stable operation without generating undissolved iron scrap.

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 Powder refiner 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 Center hole 17 Fuel gas injection hole 18 Combustion oxidizing gas injection hole 19 Perimeter 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 refining agent

Claims (6)

An upper blowing lance having a powdery refining agent supply channel, a fuel gas supply channel, an oxidizing gas supply channel for combustion of the fuel gas, and an oxidizing gas supply channel for refining disposed above the converter Use
When a fuel gas is supplied from the fuel gas supply channel so that the amount of heat input per unit cross-sectional area at the outlet of the fuel gas supply channel is 250 kJ / (mm ² · min) or more and 800 kJ / (mm ² · min) or less At the same time, supplying an oxidizing gas from the combustion oxidizing gas supply flow path, forming a flame below the tip of the upper blowing lance,
From the powdery refining agent supply flow path, as a powdery refining agent, supply one or more of iron oxide, lime-based solvent, and combustible substance together with an inert gas toward the hot metal bath surface in the converter, And supplying the refining oxidizing gas from the refining oxidizing gas supply channel toward the hot metal bath surface,
A method for refining hot metal in a converter, comprising oxidizing and refining hot metal to which a cold iron source is added in the converter.   2. The refining of hot metal in the converter according to claim 1, wherein a jetting speed of the combustion oxidizing gas at the outlet of the combustion oxidizing gas supply flow path is controlled to 75 Nm / sec or more and 315 Nm / sec or less. Method.   3. The converter according to claim 1, wherein propane gas is used as the fuel gas, and a propane gas injection speed at an outlet of the fuel gas supply flow path is controlled to 133 Nm / sec or less. Of refining hot metal in Japan.   The liquefied natural gas is used as the fuel gas, and the jet speed of the liquefied natural gas at the outlet of the fuel gas supply channel is controlled to 290 Nm / sec or less. A method for refining hot metal in a converter.   The upper blow lance is, from the center side in the cross-sectional structure, a powdery refining agent supply channel, a fuel gas supply channel, an oxidizing gas supply channel for combustion of the fuel gas, an oxidizing gas supply channel for refining, The method for refining hot metal in a converter according to any one of claims 1 to 4, characterized in that it has a six-pipe structure constituting two cooling water flow paths for cooling water supply and drainage.   The method for refining hot metal in a converter according to any one of claims 1 to 5, wherein the oxidative refining is dephosphorization of hot metal.

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