JPH10121120A - Steelmaking method using iron scrap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a steel, by which high calory gas usable firstly to molten iron from iron scrap and power generation in a cupola, is obtd. and the steel is produced by using the molten iron as raw material in an electric furnace and the high calory gas is used to fuel for power generation to generate the electric power and as a result, the production of the steel with the electric furnace is executed remarkably more economic than the conventional method. SOLUTION: The steelmaking method using the iron scrap is provided with the following processes. (A) The iron scrap (a) and coke (b) are charged into the cupola 3 from the upper part thereof, and gaseous oxygen (e) or the gaseous oxygen and the air (f) and carbonaceous material (d) of >=150kg/ton of produced molten iron are injected from tuyeres at the lower part of the cupola to burn the carbonaceous material, and the iron scrap is made to the molten iron (g), and exhaust gas (m) having >=1500kcal/Nm<3> calory is recovered from the top part of the cupola. (B) The steel (k) is produced in the electric furnace 13 by using the molten iron as a part of the iron raw material. (C) The exhaust gas is used as the fuel of a boiler 20 for power generation to generate the electric power. As the carbonaceous material, pulverized fine coal is desirable to use and as the coke, the coke for blast furnace is desirable to use.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hot metal (C: 3 wt%) obtained by using cupola to obtain hot metal from iron scrap (including reduced iron) and a high calorie gas usable for power generation.
Using the above-mentioned Fe-C alloy) as a raw material, steel is produced by an electric furnace, particularly an arc furnace, and power is generated by using the high-calorie gas as a fuel for power generation. And a method for producing steel that is significantly more economical.

[0002]

2. Description of the Related Art Today, a large amount of iron scrap is generated, and it is required to produce steel using this iron scrap from the viewpoint of resource recycling. Conventionally, steel is produced by melting iron scrap at room temperature as it is in an electric furnace, mainly an electric arc furnace. However, this method consumes expensive electric power of about 350 to 400 kwh per ton of steel, and therefore, a more economical method for producing steel is required.

[0003] Thus, a method of melting steel scrap in a cupola in advance and producing steel in an electric furnace using the obtained hot metal as a raw material has already been disclosed. JP-A-6-2876
No. 21 discloses a method in which a vertical furnace such as a cupola is used in combination with a converter or an arc furnace.

FIG. 10 shows an outline of this method. Iron scrap 31a and coke 31b as cupper 31
The molten iron is heated and melted, and the manufactured hot metal is placed in a ladle 34, mixed with the iron scrap 36a, charged into an electric furnace 40, and refined to produce steel. Since hot metal has a lot of sensible heat, energy costs can be reduced.

[0005]

Industrial-scale cupolas use expensive massive coke as a heat source. This is because, due to the characteristics of the cupola which is a vertical furnace, a coke bed is formed at the bottom of the furnace, hot air is blown from the tuyere at the bottom of the furnace, and the large amount of coke is oxidized and heated to melt the iron scrap.

The latent heat of the exhaust gas of the conventional cupola is:
It is low calorie at about 1000 kcal / Nm ³ and cannot be used as a fuel for a boiler for thermal power generation due to its low so-called theoretical combustion temperature (for example, Iron and Steel Handbook II, 3rd edition, 1979, p. 317). It is only used for preheating of blast air. Hot metal produced by cupola is used as cast iron with high added value.However, as hot iron for high power consumption type arc furnace steelmaking that produces general steel materials, the electric power of the arc furnace is generated by the sensible heat and latent heat of the hot metal. Even if you reduce the basic unit,
The cost of fuel in Cupola is high, and the exhaust gas cannot be used effectively, so that it is not an economical process as a whole.

[0007] From the viewpoint of the operation of arc furnace steelmaking, the arc furnace is generally operated only during the night on weekdays when the electricity rate is low, and is operated all day on holidays because the electricity rate is low. Therefore, the operating rate of cupola is also reduced during the daytime on weekdays. As a result, the operation of cupolas has a high heat loss due to the start-up and shutdown due to intermittent operation, which not only deteriorates the thermal efficiency but also makes it impossible to supply a stable hot metal to the arc furnace. The molten iron composition is not constant, which worsens the productivity of the electric furnace and does not reduce the electric power consumption of the electric furnace much.

[0008] In order to solve the above problems, hot metal is manufactured at a lower fuel cost, the method of blending hot metal into an electric furnace, particularly an arc furnace, is optimized, and the method is adapted to the irregular operation of steel making of the arc furnace. There is a need to establish a hot metal production process and an appropriate operation method.

[0009]

Means for Solving the Problems The inventors have conducted various studies to solve the above-mentioned problems on the following assumptions. Although a cupola with good thermal efficiency is used as an iron scrap melting furnace, inexpensive carbon materials, especially pulverized coal, are used as fuels other than coke in order to produce hot metal at low cost. This is because the pulverized coal injection technology in the blast furnace has been established and can be applied to cupola. In addition, high calorie, which uses a large amount of pulverized coal and can use gas obtained from cupola as a fuel for power generation,
The process is capable of recovering exhaust gas of 0 kcal / Nm ³ or more. Coke is mainly used to ensure air permeability in the furnace, but instead of expensive large lump coke used in industrial-scale cupolas, coke for blast furnaces, which is about 1/3 the cost, is mainly used. .

Under the above premise, the following invention has been made. A first invention is a steelmaking method using iron scrap, comprising the following steps. (A) Iron scrap and coke are charged into the cupola from the upper portion of the cupola, and oxygen gas and air, and 1 ton per ton of hot metal from which the carbon material is produced, from the tuyere at the lower portion of the cupola.
The carbon material is burned by injecting 50 kg or more, and the iron scrap is turned into hot metal.
collecting exhaust gas having a calorific value of 1 / Nm ³ or more,
(B) using the hot metal as part or all of an iron raw material,
Steel is melted in an electric furnace, and (c) the exhaust gas is used as fuel for a power generation boiler.

In the present invention, iron scrap and coke are charged into the cupola, and oxygen gas and air and inexpensive carbon material are supplied from the lower tuyere of the cupola at a rate of 15 tons of molten iron per ton.
0 kg or more is blown to burn the carbon material to produce hot metal, and an exhaust gas having a calorific value of 1500 kcal / Nm ³ or more is recovered from the upper part of the cupola, and this is used for power generation. Hot metal can be manufactured.

In a second aspect of the present invention, the amount of air blown together with the oxygen gas blown from the tuyere is an amount of air in which the nitrogen gas concentration in the exhaust gas is 10 vol% to 40 vol%. Is a steel making method.

The calorific value of the exhaust gas is adjusted to a desired range, that is, about 150 by blowing air from the tuyere at which the nitrogen gas concentration in the exhaust gas becomes 10 vol% or more and 40 vol% or less.
Can be 2500kcal / Nm ³ from 0kcal / Nm ^3. When the nitrogen gas concentration exceeds 40 vol%, the calorific value of the exhaust gas is about 1500 kcal / Nm.
^{It is} less than ³ , which is not desirable as exhaust gas for power generation.
In the case of exhaust gas having a nitrogen gas concentration of less than 10 vol%,
Although the calorific value exceeds 2500 kcal / Nm ³ , such operation is not desirable because a large amount of oxygen gas is used and the temperature at the tuyere exceeds 2200 ° C.

A third invention is a steel making method using iron scrap, wherein the carbon material is pulverized coal. Coke powder, plastics and the like can be used as the carbon material, but pulverized coal is inexpensive as a carbon material and its use has been established, so that it can be used as a desirable carbon material.

A fourth invention is a steelmaking method using iron scrap, wherein the coke is blast furnace coke. In cupolas, usually expensive massive coke is used, so it is desirable to use relatively inexpensive blast furnace coke.

According to a fifth aspect of the present invention, there is provided a steelmaking method using an iron scrap in the electric furnace, wherein a mixing ratio of the hot metal is 40 to 60%. When the composition of the hot metal in the electric furnace is less than 40%, the heat input from the hot metal is small and the steel making time is prolonged. This is because the time becomes longer.

In a sixth aspect of the present invention, the operating rate of the cupola is 40 to 60% on weekdays, hot metal produced during the day is received and stored in a hot metal pot, and the hot metal is used as an iron source in an electric furnace operation at night. It is a method of melting scrap iron. Steelmaking work is performed only at night due to high electricity rates on weekdays, but the operation of cupola is a continuous operation, so the operation rate on weekdays is almost constant in the range of 40 to 60%, and the hot metal produced is received in a hot metal pot. The hot metal is used as an iron source for electric furnace operation at night.

A seventh invention is characterized in that the operating rate of the cupola is 80% or more on holidays (including Saturdays, Sundays and public holidays), and the produced hot metal is directly used as an iron source for electric furnace operation. This is a steel making method using iron scraper. Since electricity rates on holidays are low, both the cupola and the electric furnace will operate at 80% or more.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the basic configuration of the present invention will be described with reference to FIG. Cupola 3 with good thermal efficiency and operation technology is used as an iron scrap melting furnace. In order to recover high calorie which can use the exhaust gas (m) obtained from cupola as a fuel for power generation, that is, exhaust gas (m) of 1500 kcal / Nm ³ or more, 150 kg / ton ( ton: per ton of hot metal to be produced) or more. At this time, as the carbon material, an inexpensive carbon material, particularly, pulverized coal is desirable. Pulverized coal injection technology in blast furnaces has been established. This is because it can be applied to cupolas.

As the coke (b), blast furnace coke whose cost is preferably about 1/3 that of expensive large coke used in cupola is used. Furthermore, in order to reduce the amount of blast furnace coke used as little as possible, a heat source for melting the iron scrap (a) is supplied by burning the carbon material (d), and the coke is mainly air-permeable in the furnace. Use to hold.

The exhaust gas (m) generated by operating the cupola as described above is 1500 kcal / Nm.
^{Since it has three} or more latent heats, it can be used as fuel in power generation boilers, and if the generated electric power (o) is used on its own for oxygen production equipment, etc. or sold, the production cost of hot metal (g) can be greatly reduced Can be. The produced hot metal is refined by adding iron scrap (i) as needed in the arc furnace 13 to produce molten steel (k) at low cost.

FIG. 2 shows more specific equipment of the steel making method according to the present invention. The equipment for carrying out the present invention includes (A) hot metal production equipment, (B) hot metal storage equipment, (C) steelmaking equipment for an arc furnace, and (D) power generation equipment.

The hot metal production facility (A) is basically a cupola 3
However, the point different from the conventional cupola is that a large amount of carbon material, for example, pulverized coal is blown from the tuyere, and this pulverized coal is burned with oxygen gas and air to dissolve iron scrap,
Coke charged from the upper part of the cupola is mainly used to ensure air permeability in the furnace. Other equipment contents are not different from conventional cupola.

The hot metal yard facility (B) for holding hot metal produced during the daytime on weekdays until night is provided with a hot metal pot with a lid 11 for preventing a temperature drop. Hold until operation. The daytime and nighttime may be arbitrarily determined. For example, 7:00 to 19:00 in the morning may be the daytime, and the others may be the nighttime. In order to keep the number of hot metal pots at a reasonable level, the operation on weekdays is kept constant in the range of 40 to 60%. The operation rate on holidays (Saturday, Sunday, and public holidays) is at least 80% or more.

The arc furnace steelmaking facility (C) for producing steel from hot metal produced by cupola and iron scrap added as required does not differ from the conventional one. The arc furnace may be an AC arc furnace or a DC arc furnace.

The power generation facility (D) for generating power by using exhaust gas having high calories from the cupola as a fuel is a normal power generation facility. Since the electricity generated here is usually not large in capacity, it is difficult to directly use it as electric power for an arc furnace requiring a large electric power capacity.Therefore, for example, electric power for rolling equipment or external power It is desirable to sell to a power company.

Hereinafter, the steel making method and apparatus using the iron scrap shown in FIG. 2 as an iron source will be described in detail. In FIG. 2, iron scrap (a), coke (b), and auxiliary material (c), which are iron sources, are charged into a material bucket 1 in layers, and the material bucket is hoisted by a hoisting machine 2, and iron scrap (a) And coke (b) and auxiliary material (c) are charged into cupola 3. Further, carbon material (d), oxygen (e) and air (f) are blown into the cupola 3 from the tuyere 4 at the lower part of the furnace body to heat and dissolve the iron scrap (a).

The produced hot metal (g) and slag (h)
After tapping from the tap hole 6 and separating the slag (h), the hot metal (g) is charged into the hot metal pot 8 through the inclined gutter 7, transported to the hot metal yard 10 by the bogie 9, and the lid 11 is removed. The hot metal (g) is kept warm and stored. Next, the hot metal (g)
Is charged into the arc furnace 13, iron scrap (i) is further charged into the arc furnace 13, and the sensible heat and latent heat of the hot metal (g) and the arc heat and oxygen (j) generated at the electrode 14 are used to remove iron. The scrap (i) is melted and refined to produce molten steel (k), and the molten steel (k) is conveyed to the secondary refining process in the ladle 15.

The exhaust gas (m) of the cupola is supplied to the dust collector 16
After removing dust at 17 and 17, boiler 18 with auxiliary fuel (n)
The steam is recovered by the boiler 18, the steam turbine 19 is driven by the steam, and the power is converted into electric power (o) by the generator 20.

Next, since the arc furnace steelmaking operates irregularly as described above, in order to adapt to this, the cupola is intermittently operated to some extent as described above. On the other hand, since a vertical furnace such as a cupola is a packed bed, continuous operation is desirable from the viewpoint of heat loss. Therefore, a method was studied in which the cupola furnace was operated continuously to secure a required amount of hot metal and to supply a stable hot metal to steelmaking of the arc furnace.

In general, arc furnace steelmaking is a combination of weekly night operation at a low power rate and continuous operation on all days of a holiday at a low power rate. For this irregular operation, continuous operation with a low tapping rate of an average operation degree of 40 to 60% on weekdays, and during the daytime when the arc furnace is shut down, so that a constant amount of hot metal can be mixed into the arc furnace at all times. The hot metal is stored and stored in the hot metal yard, and the hot metal is mixed into the iron source of the arc furnace during the weekday and night when the arc furnace operates.

The cupola on the holiday is a continuous operation with a high tapping rate of 80% or more in operation, and the amount of hot metal required for the continuous operation of the arc furnace on the holiday is ensured. Therefore, by providing a hot metal storage area and keeping the hot metal heat-stored, continuous operation of the cupola becomes possible, and there is no heat loss due to startup and shutdown, and stable hot metal can be supplied to steelmaking in an arc furnace.

Due to the low tapping operation and high tapping operation of the cupola furnace, the generated exhaust gas, ie, the amount of by-product gas fluctuates, and the electric power becomes unstable. Therefore, a stable amount of electric power is generated by using gas, liquid, or solid auxiliary fuel with the amount of heat corresponding to the exhaust gas shortage.

Next, an embodiment of a method for producing hot metal using iron scrap in the present invention will be described. In the present invention, iron scrap and coke, which are iron raw materials, are charged into the cupola from the upper part of the cupola, and oxygen gas, air, and carbon material are supplied from the lower tuyere of the cupola to 150 kg or more per ton of hot metal. And the carbon material is burned to convert the iron raw material into hot metal.
An exhaust gas having a calorific value of cal / Nm ³ or more is collected.

This cupola is basically not much different from conventional cupola equipment. However, the above process smoothly produces hot metal having a carbon content of 3 to 4% by weight, and the exhaust gas is reduced to 15%.
In order to secure a calorific value of 00 kcal / Nm ³ or more, the carbon material is 150 kg
Inject more than / ton. In order to sufficiently burn the carbon material at the tuyere tip, it is desirable to blow oxygen gas.

Oxygen gas is blown in addition to the air blown from the tuyere, and the nitrogen gas concentration in the exhaust gas is reduced to 40 vol% or less. Further, the N ₂ gas concentration of the exhaust gas is 40 vol%.
When it is less than 1, the exhaust gas has a calorific value of 1500 kcal / Nm ³ or more, and the N ₂ gas concentration is 10 vol.
%, The exhaust gas has a calorific value of 2500 kcal / Nm ³ or more.

As the carbon material, pulverized coal, powdered coke, powdered waste plastic, and the like can be used. However, waste plastic containing chlorine is not desirable because it does not damage the cupola furnace wall. Of these, pulverized coal and pulverized waste plastic containing no chlorine are particularly inexpensive, and since their use has been established in blast furnaces, it is desirable to blow them.

The blowing speed of oxygen gas and air is determined by the total blowing speed of oxygen gas, oxygen gas in air, and oxygen contained in the carbon material to be blown (hereinafter referred to as total oxygen blowing speed). Is desirably 0.5 or more in an excess oxygen ratio defined by Excess oxygen ratio = total oxygen amount blowing rate (Nm ³ / hr) /
(C (kg / hr) in carbon material × 1.87 + H (kg / hr) in carbon material × 5.6) Here, C (kg / hr) of carbon material: blowing of C in carbon material Velocity H in carbon material (kg / hr): H blowing rate in carbon material If the excess oxygen ratio is less than 0.5, the carbon material blown from the tuyere does not completely burn and the operation is unstable. It is because it becomes.

Further, it is desirable that the coke is blast furnace coke. This is because coke for blast furnace is extremely inexpensive as compared with coke for conventional cupola, and greatly contributes to reduction of hot metal production cost. As described above, by using blast furnace coke and pulverized coal, cupola using plastic waste, etc. as a heat source, hot metal can be produced at low fuel cost and electric power can be obtained with by-product gas and auxiliary fuel. As a result, it is possible to sell electricity and consume it in-house.

[0040]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. Example 1 According to the steel making process using iron scrap shown in FIG. 2, the annual output of molten steel of the arc furnace was increased to about 900,000 t.
The design example of this process with the scale is shown below. (A) Hot metal production equipment 1) Capacity: 2,000 [t / d] 2) Tapping amount Weekday all day: 38 [t / h] (Daytime (10 hours) Holiday (Saturday, Sunday, holiday): 80 [t / h] 3) Operating hours: 24 (h / d) per day 4) Annual operating days: 351 (d / year) 5) Basic units of raw materials and the like (unit: THM = per ton of hot metal) are shown in FIG. 6) Properties of raw material used for cupola Iron scrap: bulk specific gravity 0.65 coke: coke for blast furnace, particle size 25-60 [mm] Pulverized coal: low calorific value 6900 [kcal / kg] 7) Hot metal: component composition is shown in FIG. . Temperature: 1500 [° C.] 8) Slag CaO / SiO ₂ : 1.25 [−] Temperature: 1550 [° C.] 9) Exhaust gas (by-product gas): The gas composition is shown in FIG. Low calorific value: 1967 [kcal / Nm ³ ] Temperature: 150 [° C] (B) Hot metal ladle yard Scale: 90 [ton] Pot x 10 [units] (C) Arc furnace steelmaking equipment 1) Steel output: 150 [ t / tap] → 165 [t / h] 3960 ton / 24h 2) Annual working days: 351 [d / year] 3) Operating hours: 10 hours during the daytime on weekdays, 24 hours on holidays (Saturday, Sunday and public holidays) 4) Yield yield: 92 [%] 5) Hot metal mixing ratio: 50 [%] (remaining iron scrap) 6) 1 heat time: 55 [min] 7) Heat cycle: shown in FIG. (D) Power generation facilities 1) Electricity generation (use only cupola exhaust gas (by-product gas)) Full day on weekdays: 26,686 [kw] All day on Saturdays and Sundays: 56, 180 [kw] 2) Contracted power generation with electric power company: 60,000 [kw] 3) Auxiliary fuel for power generation Maximum deficient capacity: 33,314 [kw] (difference between weekday power generation and power company contracted volume) Auxiliary fuel: Fuel oil C (lower heating value: 9,800 [kc] al / kg]) Maximum required fuel amount: 7,693 [kg / h]

Under the above premise, by constantly mixing a fixed amount of 50% hot metal in the arc furnace, the electric power consumption of the arc furnace is set to about 120 to 170 [kwh] as shown in FIG.
/ Per ton of molten steel]. In addition, a trial calculation of investment recovery in the case of adding hot metal manufacturing equipment, hot metal storage facilities, and power generation equipment to existing arc furnace steelmaking was made. However, due to the reduction in electric power consumption of the arc furnace and the power generation profits from cupola exhaust gas (by-product gas), It was also revealed that it could be recovered in a short period of time.

Example 2 Internal volume as shown in FIG.
The operation was performed using a 5 m ³ , 10-ton Nissan cupola while changing the amount of pulverized coal used, the amount of oxygen gas, the amount of coke charged, and the like. The results are shown in the table shown in FIG. In FIG. 7, 26 is an iron scrap loading bucket, 21 is a cupola, 24 is a furnace wall, and 22 is a tuyere. FIG. 8 shows an example of the structure of the tuyere. The pulverized coal PC was blown from the center of the tuyere, and oxygen gas was blown from the outside of the tuyere, air was blown from the outside thereof, and steam (H ₂ O) for cooling the tip of the tuyere was blown as needed. A combustion zone 29 and a raceway 25 were formed at the tuyere tip.

Case 1 in the table of FIG. 9 is a case where the operation was performed using only blast furnace coke and oxygen gas without using pulverized coal.
Unless a lot of steam is blown from the tuyere, the tuyere
It cannot be lower than 00 ° C. In Case 2, pulverized coal was blown at 198 kg / t, oxygen gas and air were used together, and an exhaust gas of about 2360 kcal / Nm ³ was obtained. Case 3 blows 140 kg / t of pulverized coal,
About 2489 kcal / N using both oxygen gas and air
m ³ of exhaust gas were obtained.

The case 4 blows 140 kg / t of pulverized coal, uses both oxygen gas and air, and
An exhaust gas of al / Nm ³ was obtained. In Case 5, pulverized coal was blown at a rate of 150 kg / t and both oxygen gas and air were used. In this case, since the amount of air was large, the amount of nitrogen gas in the exhaust gas was about 37.2 vol%. An exhaust gas having a calorific value of about 1774 kcal / Nm ³ was obtained.

[0045]

As described above, according to the present invention, inexpensive large lump coke is produced by using inexpensive blast furnace coke and carbon material, particularly pulverized coal, to produce hot metal with cupola capable of melting iron scrap. Hot metal can be produced at a significantly lower cost than the conventional cupola used. Furthermore, when this hot metal is used, the sensible heat and latent heat can further reduce the electric power consumption of the arc furnace.

In addition, in order to adapt to arc furnace steelmaking, which is an irregular operation, a hot metal yard for temporarily storing and storing the hot metal produced has been installed, so that the cupola can be operated continuously and the cupola can be started up. Not only the heat loss due to the shutdown is eliminated, but also the hot metal can be stably supplied to the arc furnace, and the electric power consumption of the arc furnace can be stably and easily reduced.

The exhaust gas (by-product gas) obtained from the conventional cupola operation has a low utility value because of its low calorie. However, in the present invention, there is an advantage that a large amount of high caloric exhaust gas can be obtained. Since it can be used as a fuel for power generation, it is possible to generate power in-house, and it is possible to realize wholesale power and private consumption of power. Therefore, it is more economical from the viewpoint of energy cost than a power generation method in which fossil fuel is simply burnt and converted to electric power instead of steam, and leads to effective use of resources from the viewpoint of energy consumption.

As described above, by implementing the optimal hot metal blending process integrated with the steelmaking of the arc furnace, the investment recovery of the present process can be achieved at an early stage from the profit of reducing the electric power consumption of the arc furnace and the power generation profit by the exhaust gas of the cupola. . Therefore, it is possible to provide an electric power generation type arc furnace steelmaking process from an electric power consumption type arc furnace steelmaking, which can greatly contribute to industry.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention.

FIG. 2 is a diagram showing specific equipment of the present invention.

FIG. 3 is a diagram showing a substance balance in an example of the present invention.

FIG. 4 is a diagram showing the composition of hot metal and exhaust gas in an example of the present invention.

FIG. 5 is a diagram showing a steel production cycle in an example of the present invention.

FIG. 6 is a diagram showing a power consumption unit of steel in an example of the present invention.

FIG. 7 is a diagram illustrating a structure of a cupola according to an embodiment of the present invention.

FIG. 8 is a diagram showing a pulverized coal injection method according to an embodiment of the present invention.

FIG. 9 is a view showing a substance balance in examples in which the present invention is carried out under various conditions.

FIG. 10 is a diagram showing an example of a conventional technique.

[Explanation of symbols]

 3,21 cupola 4,22 tuyere 8 hot metal pot 13 electric furnace 28 charging port above cupola

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshimichi Maki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Masayuki Watanabe 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor Tatsuro Ariyama 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (7)

[Claims] 1. A steel making method using iron scrap, comprising the following steps. (A) Iron scrap and coke are charged into the cupola from the upper portion of the cupola, and oxygen gas and air, and 1 ton per ton of hot metal from which the carbon material is produced, from the tuyere at the lower portion of the cupola.
50 kg or more is blown to burn the carbon material, the iron scrap is turned into hot metal, and 1500 kc from the upper part of the cupola.
collecting exhaust gas having a calorific value of at least al / Nm ³ ,
(B) using the hot metal as part or all of an iron raw material,
In an electric furnace, steel is melted, and (c) the exhaust gas is used as a fuel for power generation to generate power. 2. The amount of air blown together with the oxygen gas blown from the tuyere is adjusted to a nitrogen gas concentration of 10% in the exhaust gas.
The steel making method using iron scrap according to claim 1, wherein the amount of air is set to be not less than vol% and not more than 40vol%. 3. The steel making method according to claim 1, wherein the carbon material is pulverized coal. 4. The steel making method using iron scrap according to claim 1, wherein the coke is blast furnace coke. 5. The steel making method according to claim 1, wherein the mixing ratio of the hot metal in the electric furnace is 40% to 60%. 6. The operation rate of the cupola is 40% to 60% on weekdays, and the produced hot metal is received and stored in a hot metal pot, and the hot metal is used as an iron source in an electric furnace operation at night. A steel making method using the iron scrap according to claim 1. 7. The iron scrap according to claim 1, wherein the operation rate of the cupola is set to 80% or more on holidays, and the produced hot metal is used directly as an iron source for the operation of the electric furnace. The steelmaking method to do.