JPH09157725A - Method for melting ferrous scrap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scrap melting method having low wearing speed of refractory-made furnace wall by using a metallurgical furnace of a top and bottom combination-blown converter, etc. SOLUTION: At the time of melting ferrous scrap by using the metallurgical furnace of the top and bottom combination-blown converter, etc., and utilizing the heat generated by combustion of carbonaceous material together with oxygen-containing gas, a top gas blown lance 1 having a lance hole group A3 having 1-4 holes in the range of 0-12 deg. jetting angle θ for each hole and a lance hole group B2 having 3-6 holes in the range of 15-20 deg. jetting angle βfor each hole and arranged so as to surround the lance hole group A3, is used. At the scrap melting stage, flowing speed reaching a bath surface of the oxygen-containing gas jetted from the lance hole group A3 is made to be 5-20m/s and that from the lance hole group B2 is made to be 20-80m/s. At the slag spattering stage, flowing speed reaching the bath surface of gas of nitrogen, etc., jetted from the lance hole group A3 is made to be 50-300m/s and that from the lance hole group B2 is made to be 5-20m/s.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for melting iron-based scrap.

[0002]

2. Description of the Related Art In recent years, it has become a technical subject to efficiently produce molten metal by recycling solid metal raw materials such as scrap due to resource and environmental problems. Conventionally, most electric furnaces have been used for scrap melting, but in the case of electric furnaces, a large amount of electric power is consumed for melting and refining scrap, so in countries such as Japan, where electricity prices are extremely high. It is not preferable because the cost increases. Therefore, as a method of economically melting and refining scrap without relying on an electric furnace, it is possible to melt scrap using inexpensive carbonaceous materials by utilizing the surplus production capacity of a converter with a high acid transfer capacity.
Refining methods have come to be considered.

Under such circumstances, generally, the existing upper-bottom blowing composite blowing converter is used to suppress the increase in equipment and to ignite the fire species charged in the furnace together with scrap. After that, a method of melting and refining while charging carbonaceous material as a heat source from above the furnace at the time of top-bottom blowing is proposed.

On the other hand, in Japanese Patent Laid-Open No. 2-141511, a reaction vessel capable of gas stirring a melt is used.
The amount of free fixed carbon present in the reaction vessel was set at 17 kg per ton of molten slag by using molten slag of 350 kg or more per ton of hot metal and using coal having a sulfur content of 0.4% or more.
A method for melting steel scrap, which is sprayed with acid while maintaining the pressure of at least kg, is disclosed.

In this technique, the carbonaceous material existing in the molten slag phase is oxidatively burned (= exothermic reaction) with top-blown oxygen,
The slag phase is strongly stirred and the generated heat is transferred to the molten metal phase to dissolve the scrap, but the CO ₂ produced by the reaction of the carbonaceous material and oxygen is scattered outside the slag phase. It is easy to cause the so-called solution loss reaction (equation), which is a reaction of contacting the carbonaceous material and reducing it to CO.

CO ₂ + C = 2CO-Q (endothermic reaction) Formula Q: heat quantity (J / mol) A means for reducing the manufacturing cost by minimizing the amount of energy required for melting scrap unit weight (= The means for maximizing the dissolution energy efficiency is the ratio of CO _{2 in} the exhaust gas (= C
O ₂ % / [CO% + CO ₂ %]), that is, the so-called secondary combustion rate is preferably increased.

For that purpose, CO gas regenerated by the solution loss reaction is converted into CO gas by O _{2 in} the upper space.
Need to be reoxidized to ₂ . Since the heat transfer direction obtained by this oxidation reaction is the same as the exhaust gas transfer direction (= from the slag phase or the molten metal phase to the top of the melting furnace),
It is difficult to transfer heat to the slag phase. Therefore, the heat deposition efficiency represented by the formula is poor, and the temperature of the exhaust gas in the upper space is raised, and at the same time, the temperature of the refractory furnace wall surface is raised,
Caused significant wear and tear.

[0008]

(Equation 1)

On the other hand, in Japanese Patent Laid-Open No. 61-67708, molten iron, agglomerates of pre-reduced ore, carbonaceous material and oxygen are supplied to a reaction vessel capable of blowing an oxygen-containing gas into the molten metal at the top and bottom. In the smelting reduction process in which oxides are reduced and melted by the above method, the method of cooling the furnace wall part above the slag level or its vicinity, and the cooling of the furnace wall part above the slag level or its vicinity are controlled by the upper blowing lance ( By injecting one or more of CO ₂ , N ₂ , hydrocarbon-containing fluid, powdered carbonaceous material, water mist and water vapor into the furnace wall portion from a system independent of the oxygen-containing gas supply system in the composite lance). And / or a method of water-cooling the iron skin of the furnace wall portion, and a method of ejecting from the wall surface of the furnace wall portion through a pipe or a porous refractory.

This is not a method of melting iron-based scrap but a method of smelting reduction of ore, but it can be applied as a countermeasure against wear of a refractory furnace wall. However, if a cooling gas or coolant is sprayed onto a part of the refractory furnace wall, that part will be overcooled more than necessary or below the temperature of the molten metal phase, and the temperature will be locally uneven. Occurs. In particular, in the method of ejecting the coolant from the lance, heating / cooling is repeated when tapping or slag or when the lance height is changed.

On the other hand, the method of jetting the coolant from the tuyere fixed to the refractory furnace wall cannot cope with the fluctuation of the slag level due to the increase or decrease of the amount of slag or molten metal during the operation. The degree of wear of the furnace wall is mainly proportional to the time of exposure to high temperature, but if there is local temperature nonuniformity or repeated heating / cooling as described above, stress / strain will be generated and wear will occur. Amplify. Therefore, the method of cooling by cooling a specific part of the refractory furnace wall is to increase the amount of slag and molten metal in the furnace, such as scrap melting, or to change the lance height. On the other hand, it is not a fundamental solution.

On the other hand, a method of protecting the refractory furnace wall surface and prolonging the life of the furnace wall by coating the slag generated in the furnace on the refractory furnace wall surface in advance has been conventionally performed. For example, Japanese Patent Laid-Open No. 61-5622
No. 3 gazette discloses, as a converter slag coating method, a method in which air or a slow reactive gas is blown from a top blowing lance to a decarburizing slag remaining in the furnace, and slag is splashed onto a furnace wall for coating. There is.

However, is this method efficient in a short time?
One slag splash to evenly coat the slag
There is no detailed description about raising conditions, so it is easy to implement
I couldn't do that. Also, when using this method,
Specific gravity 1-2 g / cm generated in normal converter operation ^ThreeDegree
Blow from the top blowing lance to repel the rug
Specific gravity 0.01g / cm^ThreeSome degree of air or slow reactive gas injection
The flow velocity is large depending on the density difference (hereinafter, hard flow).
Slag coat
To efficiently dissolve scrap after finishing
If you want to increase the secondary combustion rate, on the contrary
The flow velocity of the oxygen jet is low (hereinafter referred to as soft blow).
Must be done. Therefore, based on the traditional design
Slag coating using only one top blowing lance
Both scrap smelting was difficult to carry out.

As a soft blow-oriented nozzle, Japanese Patent Publication No. 47-4770 has an actuating mechanism which can move up and down in a pipe between a tip outlet and a throat of a circular oxygen nozzle of an upper blowing lance. A lance with a spindle is disclosed. In this case, oxygen flows through the slit formed in the gap between the circular nozzle and the spindle, but the jet flow after passing through the gap merges immediately after the outlet and becomes a hard blow, so the secondary combustion rate does not improve.

[0015]

SUMMARY OF THE INVENTION The present invention relates to a method disclosed in
When the technique disclosed in Japanese Patent No. 1415111 is carried out, the heat of the slag phase and the molten metal phase is badly caused, which causes significant wear of the reaction vessel refractory, and in Japanese Patent Laid-Open No. 61-67708. By repeating overcooling and recuperation in the case of implementing the technology
In addition, there is a problem that the life of the refractory does not extend so much, and a problem that the lance for obtaining a high secondary combustion rate cannot efficiently perform slag coating in JP-A-61-56223, and JP-B-47-4770. An object of the disclosed technology is to solve the problem that the secondary combustion rate is not improved.

[0016]

DISCLOSURE OF THE INVENTION The inventors of the present invention use two gas passages independent of each other and an upper blowing lance having a lance hole connected to each of the gas passages and eject the gas through the two passages. It was found that by appropriately adjusting the gas flow rate, a large amount of oxygen can be soft blown during scrap melting, and a small amount of gas can be hard blown during slag coating.

The present invention was made based on this finding, and the gist thereof is as follows. (1) When using a metallurgical furnace such as a top-and-bottom blow converter to melt the iron-based scrap by the heat generated when the carbonaceous material is burned by the oxygen-containing gas, the number of holes is 1 to 4 and each hole is Of the lance hole group A having a jet angle θ of 0 to 12 degrees, and the lance hole group A surrounding the lance hole group A, the number of holes is 3 to 6, and the jet angle β of each hole is 15 A lance hole group B in the range of up to 20 degrees, and a lance hole group A and a lance hole group B using an upper blowing lance for gas injection having the lower end surface thereof.
And a slag for supplying molten oxygen to the refractory wall surface inside the metallurgical furnace by supplying a gas such as nitrogen from the lance hole group A and the lance hole group B to supply the oxygen-containing gas from the scrap melting stage. In the method of melting iron-based scrap, which comprises a scattering period, in the scrap melting period, the oxygen-containing gas ejected from the lance hole group A has a bath surface arrival velocity of 5 to 20 m / s and is ejected from the lance hole group B. The flow velocity of the oxygen-containing gas to reach the bath surface is 20 to 80 m / s, and the flow velocity of the gas to be ejected from the lance hole group A is 50 to 300 m / s during the slag scattering period, and the gas is ejected from the lance hole group B. A method for melting iron-based scrap, characterized in that the flow velocity of the gas to reach the bath surface is set to 5 to 20 m / s.

Here, the scrap melting period and the slag scattering period are the slag scattering period, immediately after the scrap melting period is completed, without discharging slag and molten iron, or after discharging a part of them. It is also possible to discharge all of the molten iron and transfer the slag in a state where it remains. Bath surface arrival velocity u
(M / s) is a value calculated by the following method.

[0019]

(Equation 2)

LG: Distance between the tip of the lance and the surface of the molten iron still (mm) P _O : Absolute secondary pressure of the nozzle (kgf / cm ² ) P _Op : Absolute secondary pressure of the nozzle proper expansion (kgf / cm ² ) M _Op : Discharge Mach number at proper expansion (-) d: Nozzle throat diameter (mm) The absolute secondary pressure P _o of the lance nozzle is the absolute pressure of the stagnation part of the lance nozzle before the throat. Further, the proper expansion absolute secondary pressure P _Op of the lance nozzle is calculated by the following formula.

S _e / S _t = 0.259 (P _e / P _Op ) ^-5/7 {1- (P _e / P _Op ) ^2/7 } ^-1/2 S _e : Area of lance nozzle outlet (mm ² ) _St : Lance nozzle throat area (mm ² ) P _e : Lance nozzle outlet atmosphere absolute pressure (kgf / c
m ² ) P _Op ： Lance nozzle proper expansion absolute secondary pressure (kgf / cm
² )

(2) A pair of concentric circles or concentric 3 to 16-sided slits on the lower end face of the lance, and partition walls fixed to the lance lower end face at 3 to 6 circumferential positions and fixed to both long sides of the slit. In the method for melting iron-based scrap as described in (1) above, 3 to 6 slit holes are formed by using a lance which is a lance hole group B.

In this case, 3 to 6 partition walls are arranged in a part of the slit, and the long side length L1 (mm) and the short side length L2 (mm) of each of the slit holes separated by the partition wall. Ratio of
It is preferable that 1 / L2 is 10 to 225 and (L1 × L2) / R is 0.4 to 4 when the lance diameter is R (mm). The bath surface arrival flow velocity u (m / s) is a value calculated by the following method.

[0024]

(Equation 3)

(3) To spray powder containing at least one of magnesium oxide and calcium oxide in the range of 0.3 to ³ kg / Nm ³ from at least one of the lance hole groups A and B during the slag scattering period. The method for melting iron-based scrap according to (1) or (2) above, which is characterized in that.

In a metallurgical furnace such as a top-bottom blowing converter, two elemental techniques are required to economically establish a method for melting scrap by heat generated when carbonaceous material is burned by using oxygen-containing gas. Is. One is a high secondary combustion technology with good heat deposition to enable melting at a low energy cost, and the other is to reduce melting loss of refractory.

On the other hand, the inventors of the present invention use two gas passages independent of each other and an upper blowing lance having a lance hole connected to each of the gas passages, and the gas jetted through the two passages. It was found that by appropriately adjusting the flow rate, soft blowing can be performed with a large flow rate of oxygen during scrap melting, and hard blowing can be performed with a small flow rate of gas during slag coating.

FIG. 1 is a schematic diagram showing an embodiment of the present invention. The present invention is a lance hole group A for supplying a small flow rate of gas.
(Reference numeral 3 in FIG. 1) and a lance hole group B (reference numeral 2 in FIG. 1) for supplying a large amount of gas are used to appropriately control the flow velocity of each gas to be ejected. The point is that both slag scattering by hard blow that makes use of the jet characteristics of group A and high secondary combustion blown acid by soft blow that makes use of the jet characteristics of lance hole group B are compatible.

According to a detailed study by the present inventors, in order to achieve the soft blow by the lance hole group B, the flow velocity of oxygen discharged from the lance hole group A to reach the bath surface is 5 to 20 m / s in the scrap melting period. The flow velocity of oxygen discharged from the lance hole group B to reach the bath surface may be set to 20 to 80 m / s.

Here, when the flow velocity of oxygen discharged from the lance hole group A to the bath surface is higher than 20 m / s, the gas discharged from the lance hole group A and the lance hole group B are too strong because the jet flow is too strong. Even if the gas discharged from the nozzles interferes with and coalesces, and the gas discharged from the lance hole group B is a soft blow, it becomes a single strong jet flow and the secondary combustion rate is greatly reduced. On the contrary, when the flow velocity of the oxygen discharged from the lance hole group A to the bath surface is smaller than 5 m / s, the jet flow is too weak and the lance hole group A contains scattered particles of slag and molten iron, and There is a risk of blockage. The results of this experiment are shown in FIG. Further, when the flow velocity of oxygen discharged from the lance hole group B to the bath surface is higher than 80 m / s, the secondary combustion rate is lowered because the jet flow is too strong, and when it is lower than 20 m / s, CO is CO ₂ because the jet is too weak
The heat burning efficiency is lowered because the burning area becomes higher than the bath surface.

On the other hand, in the slag scattering period, it is necessary to effectively scatter and adhere the slag to the road wall surface with a small amount of gas. The condition is that the gas discharged from the lance hole group A reaches the bath surface at a flow velocity of 50. ˜300 m / s, and the flow velocity of gas discharged from the lance hole group B reaching the bath surface is 5 to 20 m / s. When the velocity of the gas discharged from the lance hole group A reaching the bath surface is smaller than 50 m / s, the slag does not scatter to the upper part of the furnace wall because the jet strength is small, and it is 300 m.
When it is larger than / s, the jet flow is too strong, so that the slag scatters even over the furnace mouth, and the ratio of scattering loss outside the furnace without adhering to the furnace wall increases. FIG. 3 shows the results of this experiment.

Further, in order to achieve effective slag scattering, it is necessary to set the flow velocity of gas discharged from the lance hole group B to reach the bath surface of 5 to 20 m / s. That is, it is important that the gas in the lance hole group B is entrained in the strong jet discharged from the lance hole group A to form one stronger jet, and when this flow velocity is less than 5 m / s, The gas from the lance hole group B does not show any effect because the jet flow is too weak, and when it is higher than 20 m / s, a part of the gas from the lance hole group B is discharged from the lance hole group A. Efficiency is reduced because it does not get caught in the gas flow and exhibits its own behavior.

Here, the lance hole group A has 1 to 4 holes and has a jet angle γ of 0 to 12 degrees, and the lance hole group B has 3 to 6 holes and 15 to It must have a jet angle γ of 20 degrees. When the number of holes in the lance hole group A is more than 4, the jet flow cannot be hard blown because the gas flow rate discharged from one hole is small, the slag scattering is small, and the jet angle is greater than 12 degrees. Since it interferes with the gas from the lance hole group B, soft blow cannot be performed during the scrap melting period, and the secondary combustion rate decreases. If the number of holes in the lance hole group B is smaller than 3, the jet flow cannot be soft blown because the flow rate of gas discharged from one hole is large, and the secondary combustion rate is reduced. If the number is too large, the distance between the adjacent nozzles becomes small, so that the gas discharged from the adjacent nozzles cannot be combined into a soft blow and the secondary combustion rate decreases. Further, if the ejection angle is smaller than 15 degrees, it cannot interfere with the gas from the lance hole group A to be a soft blow, and if it is larger than 20 degrees, the oxygen gas jet flows too close to the furnace wall. As a result, melting of the refractory becomes severe.

The gas supplied during the slag scattering period may be one or more gases such as nitrogen, Ar, CO, which is an inert gas, or CO ₂ which is a weakly oxidizing gas. It should be done over ~ 5 minutes. If it is shorter than 1 minute, the slag will not scatter enough,
Even if the time is longer than 5 minutes, no further effect is obtained, and rather the productivity of the converter is lowered.

Furthermore, a pair of concentric circles or concentric 3 to 16-sided slits are provided on the lower end surface of the lance, and partition walls fixed to the lance lower end surface at 3 to 6 circumferential positions thereof and fixed to both long sides of the slit. By forming 3 to 6 slit holes and using these lances as the lance hole group B, higher secondary combustion rate and higher heat deposition efficiency can be obtained, and even during the slag scattering period, The same slag scattering situation as in the case of the circular nozzle is obtained.

Here, the number of partition walls is 3 to 6, and the long side length L1 of each of the slit holes separated by the partition walls.
(Mm) and short side length L2 (mm) ratio L1 / L2 is 10
225, and the lance diameter is R (mm) (L1
By setting the shape such that xL2) / R is 0.4 to 4, a further effect is exhibited. As shown in FIG. 4, this is the long side (L1) of each slit hole separated by the partition wall.
It is shown that it is preferable to use a so-called elongated ejection hole in which the ratio of the short side (L2) is large. The reason for this is that the circumference of the jet cross section becomes longer than that of the gas emitted from the circular hole,
This is because a large secondary combustion rate is obtained because it is greatly affected by the interaction with the gas outside the jet flow and has a large damping effect immediately after the jet flow leaves the nozzle. This effect can be obtained if L1 / L2 is 10 or more, but if L1 / L2 is larger than 225, piping of the lance cooling water becomes difficult, which is not realistic.

Further, the gas emitted from such an elongated nozzle has a characteristic that it is greatly attenuated immediately after being ejected, but after that, it is attenuated only at the 1/2 power of the distance from the nozzle tip. On the other hand, the gas emitted from the circular nozzle has a small attenuation immediately after being ejected, but thereafter, it attenuates at the first power of the distance from the nozzle tip. Therefore, it is necessary to convert the jet flow from the elongated shape to the circular cross-sectional shape after exiting from the nozzle in order to increase the subsequent attenuation while taking advantage of the characteristic that it is greatly attenuated immediately after the ejection. This condition is (L1 ×
L2) / R is set to 4 or less, and thereby high heat-transfer efficiency can be obtained. Also, (L1 × L2) /
When R is smaller than 0.4, it is difficult to maintain the machining accuracy of the nozzle.

The lance hole group B is a concentric polygon or a slit hole surrounded by a concentric circle and a partition, and the concentric polygon is in the range of 3 to 16 polygons. This is because there is no digon as a polygon, and when the number of angles is larger than that of a hexagon, it becomes difficult to process the degree of its effect, which is uneconomical.

The number of partition walls is more than three.
If less, from individual slits separated by bulkheads
Soft blow cannot be performed because the flow velocity of the released gas is high,
If there are more than six, adjacent spaces separated by a partition
Because the gas emitted from the rit interferes and becomes easier to combine,
This is because it becomes difficult to softly blow the beam. Of the present invention
To further enhance the effect, the lance hole group during the slag scattering period
From at least one of A and B, 0.3 to 3 kg / Nm^Three
With less magnesium oxide and calcium oxide
It is also necessary to spray powder containing one kind
You. The higher the melting point and viscosity of the scattered slag, the stronger the furnace wall.
It adheres firmly and has excellent durability after adhesion. But this
When slag like that is generated during the scrap melting period,
Since the fluidity is poor, a large amount of granular iron is mixed in the slag and the yield is increased.
Cause a significant decrease in Therefore, run during the slag scattering period.
Control the slag composition from at least one of the spore groups A and B
It is necessary to mix powders for this purpose. As powder
Is at least one of magnesium oxide and calcium oxide
Must include type. This is the melting point of slag
And has the effect of increasing viscosity, MgO, CaO, MgC
O_Three, CaCO _ThreeThat has a chemical composition of
No. The amount is 0.3 to 3 kg / Nm.^ThreeThe range of
It is appropriate. 0.3 kg / Nm^ThreeLess than
As the slag composition hardly changes, the effect of powder mixing is
Without 3kg / Nm^ThreeIf more than
Cooling due to too much, adheres to refractory surface
There is a problem that the temperature drops.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION

[0041]

EXAMPLES In the examples, an 8 ton top-bottom blowing converter was used. As the bottom blowing gas, a mixed gas of oxygen and a tuyere cooling gas was used, and oxygen gas was supplied from a top blowing lance. The top blowing lance had the shape shown in FIG. 1, and the number of holes of the lance hole groups A and B, the ejection angle of the holes, and the gas flow rate were changed.

In the experiment, when about 3 tons of hot metal, slag, and carbonaceous material were added, the carbonaceous material was continuously added while oxygen was being blown upward to raise the temperature, and when the temperature reached about 1350 ° C. Then, the scrap was charged, and the carbonaceous material was continuously added while the oxygen was blown upward to melt the scrap. The carbonaceous material was added in excess of the amount burned by top-blown oxygen so that the carbonaceous material was always present in the slag. Coke and anthracite were used as the carbonaceous material, the oxygen supply rate was 1500 Nm ³ / Hr, the exhaust gas temperature was measured with a two-color thermometer, and the state of wear of the converter refractory was evaluated by observing the inside of the furnace after the test.

Table 1 summarizes the experimental results for the scrap melting period. Under the conditions of the present invention shown in Test Nos. 1 to 9, a high secondary combustion rate and a high heat deposition efficiency can be achieved without clogging of the lance holes and melting of the refractory. Table 2 shows the results of the slag scattering test conducted subsequently for 2 to 4 minutes. Under the conditions of the present invention shown in Test Nos. 18 to 28, a very good slag scattering condition was obtained.

Table 3 shows the experimental results when the lance hole group B has a shape as shown in FIG. The angle was 17 degrees, a lance having a single lance hole group A was used, and the oxygen gas reaching the bath surface from the lance hole group B had a flow rate of 30 during the scrap melting period.
~ 60 m / s, the flow velocity of oxygen gas reaching the bath surface from the lance hole group A is 8 to 15 m / s, and the lance hole group B is in the slag scattering period.
The flow velocity of nitrogen gas reaching the bath surface from 8 to 15 m / s, and the flow velocity of nitrogen gas from the lance hole group A reaching the bath surface from 100 to 20
0 m / s. As a result, good results have been obtained in all cases.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

In a slag scattering test carried out under the same conditions as Experiment No. 18, 1 kg / Nm ^{3 of} light-burnt dolomite powder was sprayed from the lance hole group B. As a result, the scattering condition was about the same as that of Experiment No. 18, but the durability of the adhered slag was improved.

[0049]

EFFECTS OF THE INVENTION By using the present invention, efficient scrap melting is possible without causing significant wear of refractory materials.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an upper blowing lance used in the present invention.

FIG. 2 is a diagram illustrating a flow rate of oxygen discharged from the lance hole group A and a flow rate of oxygen discharged from the lance hole group A when the flow rate of oxygen discharged from the lance hole group B is 50 m / s in the scrap melting period.
It is a figure which shows the relationship with the next combustion rate.

FIG. 3 shows the flow rate of nitrogen discharged from the lance hole group A and the slag scattering state when the flow rate of nitrogen discharged from the lance hole group B is 10 m / s in the slag scattering period. It is a figure which shows a relationship.

FIG. 4 is a diagram showing an example (concentric type) of an upper blowing lance based on the present invention.

FIG. 5 is a diagram showing an example (concentric type) of an upper blowing lance based on the present invention.

[Explanation of symbols]

 1 Lance 2 Lance hole group B 3 Lance hole group A 11 Lance 12 Lance hole group B 13 Lance hole group A 14 Partition L1 Long side length L2 Short side length

Claims (3)

[Claims] 1. When a ferrous scrap is melted by heat generated during combustion of carbonaceous material by an oxygen-containing gas using a metallurgical furnace such as a top-bottom blowing converter, the number of holes is 1 to 4 Lance hole group A in which the ejection angle θ of each hole is in the range of 0 to 12 degrees
And a lance hole group B arranged so as to surround the lance hole group A, the number of holes is 3 to 6, and the ejection angle β of each hole is in the range of 15 to 20 degrees. Using a top blowing lance for blowing gas inside, a scrap melting period in which an oxygen-containing gas is supplied from the lance hole group A and the lance hole group B, and a gas such as nitrogen from the lance hole group A and the lance hole group B And a molten slag is scattered toward the wall surface of the refractory inside the metallurgical furnace. In the method for melting iron-based scrap, a lance hole group A is ejected during the scrap melting period. The flow rate of the oxygen-containing gas reaching the bath surface is 5 to 20 m / s, and the flow rate of the oxygen-containing gas ejected from the lance hole group B is 20 to 80 m / s.
In the slag scattering period, the flow velocity of gas ejected from the lance hole group A is 50 to 300 m / s, and the flow velocity of gas ejected from the lance hole group B is 5 to 20 m.
/ S is a melting method of iron-based scrap, characterized in that. 2. A slit formed of a pair of concentric circles or concentric 3 to 16 polygons on the lower end surface of the lance, and a circumferential direction 3 to 3 of the slits.
It is characterized in that three to six slit holes are formed by the partition walls provided near the lower end surface of the lance at six positions and fixed to both long sides of the slit, and this is performed using a lance that is a lance hole group B. The method for melting iron-based scrap according to claim 1. 3. A powder containing at least one of magnesium oxide and calcium oxide in the range of 0.3 to ³ kg / Nm ³ is sprayed from at least one of the lance hole groups A and B during the slag scattering period. The method for melting iron-based scrap according to claim 1 or 2.