JP5874449B2 - Hot metal production method using vertical scrap melting furnace - Google Patents

Description

  The present invention uses a vertical scrap melting furnace having an upper tuyere above the main tuyere, and CO generated in the furnace is secondarily burned by blowing from the upper tuyere, and the heat is used as an iron source. The present invention relates to a hot metal manufacturing method for manufacturing hot metal while preheating iron-based scrap.

There is a cupola method as a scrap melting process in a vertical furnace. This cupola method is a method for producing hot metal by laminating or mixing scrap and coke from the upper part of the furnace. Before the tuyere, the combustion reaction shown in the following formula (1) proceeds, and the generated CO ₂ is changed to CO by the solution loss reaction shown in the following formula (2).
C + O ₂ → CO ₂ (1)
C + CO ₂ → 2CO (2)

  In vertical scrap melting furnaces, the higher the reaction rate of the solution loss reaction, which is an endothermic reaction, the higher the coke ratio. Conventionally, as a coke ratio reduction technology, there is an operation method in which the upper tuyere is provided above the main tuyere and the air is blown, so that CO generated by the solution loss reaction is secondarily burned and the scrap is preheated by the combustion heat. Known (for example, Patent Document 1). Further, in such secondary combustion operation, an operation method is also known in which the amount of air blown from the upper tuyere and the range of the distance in the furnace height direction of each tuyere are defined (for example, Patent Document 2).

Japanese Examined Patent Publication No. 7-23501 JP-A-10-204512

Patent Documents 1 and 2 show examples of small furnaces having an inner diameter of 0.9 m and an inner diameter of 0.6 m, respectively. It has been found that there is a problem that the coke ratio cannot be reduced sufficiently even if the technology for the conventional small furnace is applied to the furnace. In other words, in large furnaces, the air from the tuyere is difficult to reach the center of the furnace, so the exothermic reaction does not occur sufficiently on the furnace center side, and the degree of gas oxidation remains low. Insufficient heat supply. For this reason, it has been found that there is a problem that the scrap cannot be sufficiently melted in the center of the furnace and the coke ratio increases. FIG. 8 shows the result of examining the gas flow velocity at each position in the radial direction of the furnace from the furnace wall for the air blown from the main tuyere. Here, the gas flow rate is a measured value when air is blown at 140 Nm ³ / h from one tuyere with an inner diameter of 50 mm in the empty tower. According to FIG. 8, it can be seen that when the radial distance from the furnace wall is 0.75 m or more, the gas flow velocity is very slow.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and in a vertical scrap melting furnace having a main tuyere and an upper tuyere with an inner diameter of 1.5 m or more, from iron-based scrap to low coke. It is providing the hot metal manufacturing method which can manufacture hot metal by ratio.

As a result of repeated studies to solve the above problems, the present inventors have determined the installation position of the upper tuyere in the furnace height direction, the blowing rate from the upper tuyere, and the furnace center position flow rate of the upper tuyere blowing. It has been found that hot metal production at a low coke ratio can be realized by restricting to this range.
The present invention has been made on the basis of such findings and has the following gist.

[1] In a vertical scrap melting furnace with an inner diameter of 1.5 m or more, iron-based scrap and coke are charged from the top of the furnace, and a main tuyere provided in the lower part of the kiln and a position above the main tuyere A method for producing hot metal by blowing air from an upper tuyere provided in one or two upper and lower stages,
Upper tuyere position L _u / H (however, if the upper tuyere is provided in two upper and lower stages, the position of each upper tuyere in the upper and lower two stages), the air flow rate V _u / ( V _m + V _u ) (However, when the upper tuyere is provided in two upper and lower stages, the total blowing rate from the upper tuyere of the upper and lower two stages), at the furnace center position of the blowing from each upper tuyere method for producing a flow velocity V _c is the following (1) to (3) of the like satisfy either the primary tuyere and the molten iron using a vertical scrap melting furnace to the upper tuyeres, characterized in that air is blown .
(1) The following conditions are satisfied.
L _u /H=0.25 to 0.80
_{V u / (V m + V} u) = 0.21~0.37
V _c = 10 to 25
(2) Satisfies the following conditions.
L _u /H=0.35-0.70
_{V u / (V m + V} u) = 0.15~0.43
V _c = 10 to 25
(3) Satisfy the following conditions.
L _u /H=0.35-0.70
_{V u / (V m + V} u) = 0.21~0.37
V _c = 8~25
L _u : Distance in the furnace height direction from the main tuyere to the upper tuyere (m)
H: Furnace height direction distance from the main tuyere to the stock line (m)
V _m : Main tuyere air volume (Nm ³ / h)
V _u : Upper tuyere air volume (Nm ³ / h)
V _c : Flow velocity (Nm / s) at the furnace center position of the air blown from each upper tuyere

[2] In the manufacturing method of [1], the upper tuyere position L _u / H (however, when the upper tuyere is provided in two upper and lower stages, the position of each upper tuyere in the upper and lower two stages) , The blowing rate V _u / (V _m + V _u ) from the upper tuyere (however, when the upper tuyere is provided in two upper and lower stages, the total blowing rate from the upper and lower two tuyere) flow rate V _c at the furnace center position of the air from the upper tuyeres is, so as to satisfy the following condition, using a vertical scrap melting furnace, characterized in that air is blown from the primary tuyeres and the top tuyeres Hot metal production method.
L _u /H=0.35-0.70
_{V u / (V m + V} u) = 0.21~0.37
V _c = 10 to 25

  According to the method of the present invention, hot metal is produced from iron-based scrap at a low coke ratio in a vertical type scrap melting furnace having a main tuyere and an upper tuyere and having a furnace inner diameter of 1.5 m or more. Can do.

Drawing which shows typically one embodiment of a vertical scrap melting furnace used with the method of the present invention, and its basic operation form The flow velocity V _c at the furnace center position for blowing air from each upper tuyere is 8 Nm / s, the upper tuyere position (height) L _u / H and the blowing rate V _u / (V _m + V _u from the upper tuyere. ), The graph shows the relationship between the upper tuyere position L _u / H on the horizontal axis and the reduction in coke ratio compared to the case where no upper tuyere air is blown. The flow velocity V _c at the furnace center position for blowing air from each upper tuyere is 8 Nm / s, the upper tuyere position (height) L _u / H and the blowing rate V _u / (V _m + V _u from the upper tuyere. ) Is a graph showing the relationship between the reduction rate of coke ratio compared to the case where no upper tuyere air is blown, with the horizontal axis representing the air blowing rate V _u / (V _m + V _u ) from the upper tuyere. The flow velocity _{V c} at the furnace center position of the air from the upper tuyeres and 10 Nm / s, upper tuyeres position _{(height) L} blown rates from u / H and the upper tuyeres _{V u / (V m + V} u ), The graph shows the relationship between the upper tuyere position L _u / H on the horizontal axis and the reduction in coke ratio compared to the case where no upper tuyere air is blown. The flow velocity _{V c} at the furnace center position of the air from the upper tuyeres and 10 Nm / s, upper tuyeres position _{(height) L} blown rates from u / H and the upper tuyeres _{V u / (V m + V} u ) Is a graph showing the relationship between the reduction rate of coke ratio compared to the case where no upper tuyere air is blown, with the horizontal axis representing the air blowing rate V _u / (V _m + V _u ) from the upper tuyere. Graph showing the relationship between the flow velocity V _c at the furnace center position of the air blown from the upper tuyere and the coke ratio Graph showing the relationship between the shelves fishing occurrences of a flow rate V _c and furnace at a furnace center position of the air from the upper tuyeres Graph showing the gas flow velocity at each position in the furnace radial direction from the furnace wall for the air blown from the main tuyere in the vertical scrap melting furnace

The hot metal production method of the present invention is a vertical scrap melting furnace having a furnace inner diameter of 1.5 m or more, charged with iron-based scrap and coke from the top of the furnace, and a main tuyere provided at the bottom of the furnace, This is a method for producing hot metal by blowing air from the upper tuyere provided in one stage or two stages above and below the mouth (that is, performing a divided blowing operation by the main tuyere and the upper tuyere).
FIG. 1 schematically shows an embodiment of a vertical scrap melting furnace (hereinafter simply referred to as “vertical melting furnace”) used in the present invention and its basic operation mode.

  In the figure, 1 is a main tuyere provided at the lower part of the furnace, and 2 is an upper tuyere 2 provided above the main tuyere 1. Both the main tuyere 1 and the upper tuyere 2 are provided with a plurality (usually about 4 to 10) at appropriate intervals in the furnace body circumferential direction. In the present embodiment, only one upper tuyere 2 is provided, but it may be provided in two upper and lower stages. Further, 3 is a raw material charging portion provided at the furnace top, 4 is an exhaust gas outlet, and 5 is a tap outlet. This vertical melting furnace has no substantial limitation on the size and the like as long as the furnace inner diameter is 1.5 m or more. However, as a size that is substantially operable or advantageous in operation, The furnace inner diameter is about 2 to 4 m and the furnace height is about 6 to 10 m. Although there is no special upper limit for the position of the upper tuyere 2 in the furnace height direction, the furnace top temperature increases as the position becomes higher. Is preferred.

  In such a vertical melting furnace, iron scrap a and coke b are charged from the raw material charging portion 3 at the top of the furnace, and air or oxygen-enriched air is blown from the main tuyere 1 and the upper tuyere 2, respectively. The iron scrap a is melted with the heat of the combustion gas of coke b to form hot metal. At that time, CO generated by the air from the main tuyere 1 is secondarily combusted by the air from the upper tuyere 2, and the iron-based scrap a is preheated by this secondary combustion heat to increase energy efficiency. The generated hot metal c is taken out of the furnace through the outlet 5 at the bottom of the furnace. The temperature of air blown from the main tuyere 1 and the upper tuyere 2 is not particularly limited, but normally, air blown from the main tuyere 1 or oxygen-enriched air is hot air, and air blown from the upper tuyere 2 Or oxygen-enriched air is at room temperature.

When oxygen is enriched in the air blown from the main tuyere 1, there is no particular limitation on the oxygen enrichment rate, but if the oxygen enrichment rate is less than 15 vol%, the effect of oxygen enrichment is small, whereas it exceeds 35 vol%. Since the coke ratio increases due to an increase in solution loss due to the temperature rise before the tuyere, the oxygen enrichment rate is preferably 15 to 35 vol%.
In addition, when oxygen is enriched in the air blown from the upper tuyere 2, there is no special limitation on the oxygen enrichment rate, but if the oxygen enrichment rate exceeds 30 vol%, the solution loss due to the temperature rise before the tuyere As the coke ratio rises due to the increase in the amount of iron scrap and shelf hanging due to local overheating of the iron-based scrap is likely to occur, the oxygen enrichment rate is preferably 30 vol% or less.
The iron-based scrap a and coke b may be charged into the furnace at the same time or may be alternately charged. The main furnace charging materials are iron scrap a and coke b. In addition, for example, iron sources such as pig iron, reduced iron and iron ore, and charcoal materials such as charcoal and anthracite are charged. Also good.

In the hot metal production method of the present invention, the position L _u / H of the upper tuyere 2, the blowing rate V _u / (V _m + V _u ) from the upper tuyere 2, and the furnace center position of the blowing from each upper tuyere 2 flow rate V _c of, so as to satisfy any of the following (1) to (3), air is blown from the main tuyere 1 and the upper tuyeres 2.
(1) The following conditions are satisfied.
L _u /H=0.25 to 0.80
_{V u / (V m + V} u) = 0.21~0.37
V _c = 10 to 25
(2) Satisfies the following conditions.
L _u /H=0.35-0.70
_{V u / (V m + V} u) = 0.15~0.43
V _c = 10 to 25
(3) Satisfy the following conditions.
L _u /H=0.35-0.70
_{V u / (V m + V} u) = 0.21~0.37
V _c = 8~25
L _u : Distance in the furnace height direction from the main tuyere to the upper tuyere (m)
H: Furnace height direction distance from the main tuyere to the stock line (m)
V _m : Main tuyere air volume (Nm ³ / h)
V _u : Upper tuyere air volume (Nm ³ / h)
V _c : Flow velocity (Nm / s) at the furnace center position of the air blown from each upper tuyere

More preferably, air is blown from the main tuyere 1 and the upper tuyere 2 so as to satisfy the following conditions.
L _u /H=0.35-0.70
_{V u / (V m + V} u) = 0.21~0.37
V _c = 10 to 25

Ｖ_Ｃ：送風の炉中心位置での流速（ｍ／ｓ）
Ｖ_０：送風の羽口先での流速（ｍ／ｓ）
ａ：噴流の構造係数（−）
ｄ_０：羽口内径（ｍ）
Ｒ：羽口先から炉中心までの距離（ｍ） Here, when the upper tuyere 2 is provided in two upper and lower tiers, the “upper tuyere position L _u / H” is the position of each upper tuyere in the two upper and lower tiers. “Air blowing rate V _u / (V _m + V _u ) from the upper tuyere” is the total blowing rate from the upper tuyere of the upper and lower two stages. The stock line in the definition of H is the upper surface position of the in-furnace filler in the design of the furnace.
Moreover, the flow velocity V _c (flow velocity per tuyere) at the furnace center position of the air blown from each upper tuyere 2 is a calculated value in a free process in which the coke before the tuyere is not filled, (3) Formula (Reference: Φ.A. Abramov, “—Introduction to Fluid Mechanics for Resource Development Engineers”, Uchida Otsuru Farm, July 1983, p.197-p.203 ). In the following formula (3), a = 0.08, and d ₀ was calculated using the inner diameter of the tuyere used.

V _C : Flow velocity (m / s) at the center of the furnace for blowing air
V ₀ : Flow velocity (m / s) at the tip of the air blower
a: Structure coefficient of jet (-)
d ₀ : inner diameter of tuyere (m)
R: Distance from the tuyere to the furnace center (m)

Using a vertical melting furnace with an inner diameter of 3.4 m having the structure shown in FIG. 1, iron scrap and coke are charged from the top of the furnace and blown from the main tuyere 1 and the upper tuyere 2. In the process, the flow velocity V _c at the furnace center position for blowing air from the upper tuyere 2 is 8 Nm / s, the upper tuyere position (height) L _u / H and the blowing rate V _u / ( V _m + V _u ) was changed for operation, and the coke ratio was investigated. The results are shown in FIGS. 2 shows the relationship between the upper tuyere position L _u / H on the horizontal axis and the reduction in coke ratio compared to the case where no upper tuyere air is blown. FIG. The horizontal axis represents the air blowing rate V _u / (V _m + V _u ), and shows the relationship with the coke ratio reduction amount compared with the case where the upper tuyere air is not performed.

According to FIGS. 2 and 3, when the flow velocity _{V c} at the furnace center position of the air from the upper tuyere 2 was 8 Nm / s, the upper tuyeres position _L u / H _0.35~0. 70, in a range where the air blowing rate V _u / (V _m + V _u ) from the upper tuyere 2 is 0.21 to 0.37 (range (3) above), compared with the case where no upper tuyere air is blown It can be seen that the coke ratio can be reduced by 10 kg / t or more.
In this case, if the upper tuyere position L _u / H is less than the above lower limit value, the temperature of the gas in the furnace at the upper blowing position is high, so not only the secondary combustion reaction but also the coke combustion reaction and solution loss reaction occur, Therefore, it is considered that the coke ratio is not reduced. On the other hand, if the upper tuyere position L _u / H exceeds the above upper limit value, the heat generated in the secondary combustion is discharged from the furnace top without sufficiently reaching the iron-based scrap. Is considered not to decrease. Similar results were obtained when the upper tuyere 2 was provided in two upper and lower stages.

Further, if the blowing rate V _u / (V _m + V _u ) from the upper tuyere is less than the lower limit value, it is considered that the coke ratio is not reduced because the secondary combustion reaction amount is small and the generated heat amount is also small. Further, if the air blowing rate V _u / (V _m + V _u ) from the upper tuyere 2 exceeds the above upper limit, the amount of reaction due to secondary combustion increases and the furnace temperature rises, causing coke combustion reaction and solution loss. It is thought that the reaction also occurs and therefore the coke ratio does not decrease. Similar results were obtained when the upper tuyere 2 was provided in two upper and lower stages.

Further, the flow velocity V _c at the furnace center position of the air blown from the upper tuyere 2 is set to 10 Nm / s, the upper tuyere position (height) L _u / H and the air blowing rate V _u / (V _The operation was carried out by changing _m + V _u ), and the coke ratio was investigated. The results are shown in FIGS. 4 shows the relationship between the upper tuyere position L _u / H on the horizontal axis and the coke ratio reduction amount compared to the case where the upper tuyere air is not blown. FIG. The horizontal axis represents the air blowing rate V _u / (V _m + V _u ), and shows the relationship with the coke ratio reduction amount compared with the case where the upper tuyere air is not performed.

According to FIG 4 and FIG 5, when the flow velocity _{V c} at the furnace center position of the air from the upper tuyere 2 was 10 Nm / s, the upper tuyeres position _L u / H _0.25~0. 80, the air flow rate V _u / (V _m + V _u ) from the upper tuyere 2 is in the range of 0.21 to 0.37 (range (1) above), and the upper tuyere position L _u / H is 0. In the range of 35 to 0.70 and the air blowing rate V _u / (V _m + V _u ) from the upper tuyere 2 is in the range of 0.15 to 0.43 (the range of (2) above), the upper tuyere is not blown. It can be seen that the coke ratio can be reduced by 10 kg / t or more compared to the case.

Also in this case, if the upper tuyere position L _u / H is less than the above lower limit value, the temperature of the in-furnace gas at the upper blowing position is high, so not only the secondary combustion reaction but also the coke combustion reaction and solution loss reaction occur. Therefore, it is considered that the coke ratio is not reduced. On the other hand, if the upper tuyere position L _u / H exceeds the above upper limit value, the heat generated in the secondary combustion is discharged from the furnace top without sufficiently reaching the iron-based scrap. Is considered not to decrease. Similar results were obtained when the upper tuyere 2 was provided in two upper and lower stages.

Further, if the blowing rate V _u / (V _m + V _u ) from the upper tuyere is less than the lower limit value, it is considered that the coke ratio is not reduced because the secondary combustion reaction amount is small and the generated heat amount is also small. Further, if the air blowing rate V _u / (V _m + V _u ) from the upper tuyere 2 exceeds the above upper limit, the amount of reaction due to secondary combustion increases and the furnace temperature rises, causing coke combustion reaction and solution loss. It is thought that the reaction also occurs and therefore the coke ratio does not decrease. Similar results were obtained when the upper tuyere 2 was provided in two upper and lower stages.
Further, according to FIG. 4 and FIG. 5, when the flow velocity _{V c} at the furnace center position of the air from the upper tuyere 2 was 10 Nm / s, the upper tuyeres position _L u / H _0.35~0 .70, the coke ratio in the range of the blow rate V _u / (V _m + V _u ) from the upper tuyere 2 of 0.21 to 0.37 (the above preferred range) compared to the case where no upper tuyere blow is performed. Can be reduced by 15 kg / t or more.

Using a vertical melting furnace having a structure as shown in FIG. 1 and furnace inner diameters of 1.5 m, 2.5 m, and 3.4 m, respectively, iron scrap and coke are charged from the top of the furnace, and the main tuyere 1 In the hot metal manufacturing process for blowing air from the upper tuyere 2, the upper tuyere position L _u / H is 0.50, and the blowing rate V _u / (V _m + V _u ) from the upper tuyere 2 is 0.30, An operation test was conducted by changing the flow rate of the air blown from the upper tuyere 2, and the coke ratio was investigated. FIG. 6 shows the relationship between the flow velocity V _c at the furnace center position of the air blown from the upper tuyere 2 and the coke ratio. In addition, the same operation test was performed using a vertical melting furnace having an inner diameter of 3.4 m (upper tuyere position L _{u /} H: 0.50, air blowing rate V _u / (V _m + V _u ) from the upper tuyere. : 0.30), and the frequency of shelf hanging was examined. The relationship between the bridging occurrences of a flow rate V _c and furnace at a furnace center position of the air from the upper tuyeres 2 shown in FIG. In each operation test, 5-10 present the number of the upper tuyeres, by changing the inner diameter in the range of 60～180Mm, changing the flow rate V _c the total air volume certain conditions from the upper tuyeres 2 .

According to FIG. 6, even when a vertical melting furnace of any of the furnace inside diameter, is less than the flow velocity V _c is 8 Nm / s at the furnace center position of the air from the upper tuyeres 2, significantly higher coke ratio . This is because the air flow rate is slow, so the air does not reach the center of the furnace, and the exothermic reaction does not occur sufficiently on the furnace center side, so that iron-based scrap cannot be sufficiently melted in the same region. it is conceivable that. On the other hand, if the flow velocity _{V c} is 10 Nm / s or more, the effect of reducing the coke ratio is particularly noticeable.

In addition, according to FIG. 7, when the flow velocity V _c at the furnace center position of the air from the upper tuyeres 2 exceeds 25 Nm / s, hanging shelf due to local overheating of the iron-based scrap it occurs frequently. When shelf hanging occurs, it becomes difficult for the charge to descend, and the amount of output decreases, making it difficult to continue the operation. Therefore, operation cannot be performed under the blowing condition. A similar tendency was observed in tests using a vertical melting furnace having a furnace inner diameter of 1.5 m and 2.5 m.
For these reasons, the air blowing from the upper tuyeres 2, satisfies the lower limit, such as the flow velocity V _c is listed earlier in the furnace center position, and is preferably performed such that the following 25 Nm / s.

  Using a vertical melting furnace having a structure as shown in FIG. 1, iron scrap and coke were charged from the top of the furnace, and air was blown from the main tuyere 1 and the upper tuyere 2 to produce hot metal. The conventional example was carried out without blowing air from the upper tuyere 2. The vertical melting furnace used has a furnace inner diameter: 3.4 m, a furnace height direction distance H from the main tuyere 1 to the stock line: 8 m, the number of main tuyere: 10, and the main tuyere inner diameter: 150 mm.

  In this example, H2 was used as iron-based scrap, but similar results were obtained even when scraps other than H2 (HS, H1, H3, H4) were used. Note that H1 to H4 and HS are scrap types (heavy scraps) standardized by the Japan Iron Source Association and Iron Scrap Inspection Standard. Moreover, as coke which is a fuel, blast furnace coke adjusted to a particle size of 40 to 80 mm by sieving (average particle size in terms of mass: 48 mm) was used.

Table 1 shows the operation conditions of each example (conventional example, invention example and comparative example) and the operation results such as the coke ratio. The flow velocity V _c at the furnace center position of the air blown from the upper tuyere was calculated by using the equation (3) described above, a = 0.08, and d ₀ as the inner diameter of each tuyere.
The conventional example is an operation example in which the upper tuyere is not blown. Invention Example 1 has 10 upper tuyere with an inner diameter of 60 mm, Invention Example 2 has eight upper tuyere with an inner diameter of 130 mm, and Invention Example 3 has six upper tuyere with an inner diameter of 60 mm, both L _u / H = 0 This is an operation example in which the air is blown at V _u / (V _m + V _u ) = 0.30. While the coke ratio of the conventional example is 217 kg / t, the coke ratio of the invention example is 195 to 204 kg / t, and the coke ratio is reduced by 13 kg / t or more compared to the conventional example.
Inventive Example 4 is an operation example in which the air is blown at the furnace center position flow velocity V _c = 10 Nm / s and the upper tuyere position L _u /H=0.80 for the upper tuyere blow, and the inventive example 5 is the upper tuyere blow. This is an operation example in which ventilation is performed at a furnace center position flow velocity V _c = 10 Nm / s, blowing rate V _u / (V _m + V _u ) = 0.43 from the upper tuyere, and the coke ratio of these invention examples Is 205 to 206 kg / t, and the coke ratio is reduced by 11 kg / t or more compared to the conventional example.

In Comparative Examples 1 and 2, when the flow velocity V _c at the furnace center position of the air blowing from the upper tuyere 2 is 8 Nm / s, the blowing rate V _u / (V _m + V _u ) is 0.15 and the upper tuyere position, respectively. This is an operation example in which L _u / H is 0.25. The coke ratio of Comparative Example 1 is 209 kg / t, and the coke ratio of Comparative Example 2 is 210 kg / t, both of which reduce the coke ratio.
In Comparative Examples 3 and 4, the flow velocity V _c at the furnace center position of the air blown from the upper tuyere 2 is sufficiently high, but the air blowing rate V _u / (V _m + V _u ) is 0.50, respectively. This is an operation example in which the mouth position L _u / H is 0.20. The coke ratio of Comparative Example 3 is 211 kg / t, and the coke ratio of Comparative Example 4 is 212 kg / t, both of which reduce the coke ratio.

Comparative Example 5 is an operation example in which the flow velocity V _c at the furnace center position of the air from the upper tuyeres 2 and 6.4 nm / s. The coke ratio of this operation example is 213 kg / t, and the amount of coke ratio reduction is small.
Comparative Example 6 is an operation example in which the flow velocity V _c at the furnace center position of the air from the upper tuyeres 2 and 27.4Nm / s. In this operation example, shelf hanging due to local overheating of iron scrap occurred, making it difficult to continue the operation.

1 Main tuyere 2 Upper tuyere 3 Raw material charging part 4 Exhaust gas outlet 5 Outlet a Ferrous scrap b Coke c Hot metal

Claims (2)

In a vertical scrap melting furnace having an inner diameter of 1.5 m or more, iron-based scrap and coke are charged from the top of the furnace, and a main tuyere provided at the lower part of the furnace and one stage above the main tuyere A method of producing hot metal by blowing air from the upper tuyere provided in two upper and lower stages,
Upper tuyere position L _u / H (however, if the upper tuyere is provided in two upper and lower stages, the position of each upper tuyere in the upper and lower two stages), the air flow rate V _u / ( V _m + V _u ) (However, when the upper tuyere is provided in two upper and lower stages, the total blowing rate from the upper tuyere of the upper and lower two stages), at the furnace center position of the blowing from each upper tuyere method for producing a flow velocity V _c is the following (1) to (3) of the like satisfy either the primary tuyere and the molten iron using a vertical scrap melting furnace to the upper tuyeres, characterized in that air is blown .
(1) The following conditions are satisfied.
L _u /H=0.25 to 0.80
_{V u / (V m + V} u) = 0.21~0.37
V _c = 10 to 25
(2) Satisfies the following conditions.
L _u /H=0.35-0.70
_{V u / (V m + V} u) = 0.15~0.43
V _c = 10 to 25
(3) Satisfy the following conditions.
L _u /H=0.35-0.70
_{V u / (V m + V} u) = 0.21~0.37
V _c = 8~25
L _u : Distance in the furnace height direction from the main tuyere to the upper tuyere (m)
H: Furnace height direction distance from the main tuyere to the stock line (m)
V _m : Main tuyere air volume (Nm ³ / h)
V _u : Upper tuyere air volume (Nm ³ / h)
V _c : Flow velocity (Nm / s) at the furnace center position of the air blown from each upper tuyere Upper tuyere position L _u / H (however, if the upper tuyere is provided in two upper and lower stages, the position of each upper tuyere in the upper and lower two stages), the air flow rate V _u / ( V _m + V _u ) (However, when the upper tuyere is provided in two upper and lower stages, the total blowing rate from the upper tuyere of the upper and lower two stages), at the furnace center position of the blowing from each upper tuyere flow rate V _c is, so as to satisfy the following condition, molten iron manufacturing method using the vertical scrap melting furnace according to claim 1, characterized in that air is blown from the primary tuyeres and the top tuyere.
L _u /H=0.35-0.70
_{V u / (V m + V} u) = 0.21~0.37
V _c = 10 to 25

Images