JPH07278635A - Shifting layer type scrap melting furnace and production of molten iron - Google Patents

Abstract

PURPOSE:To provide a scrap melting furnace, in which a large quantity of scrap can be used and further, the quality of molten iron can be controlled, by using coke and fine coal for blast furnace which is inexpensive in comparison with coke for casting. CONSTITUTION:This scrap melting furnace is composed of a vertical furnace I and a furnace hearth part II having the large inner diameter of 1.0-3.0 times of the inner diameter of the vertical furnace I and plural steps of the tuyeres 3, 4 at the upper and the lower parts, and the furnace type having carbonaceous material and/or flux blowing nozzle 5 and blasting air and/or oxygen blowing nozzle 6 in the roof part of the furnace hearth part II or the furnace type having the blasting air and oxygen blowing tuyere in the side wall part of the furnace hearth part. This melting furnace uses the inexpensive coke for blast furnace in comparison with the coke for casting, further, a large quantity of scrap can be used and the quality of the molten iron can be controlled and the scrap can be melted in a low coke ratio and a high heat efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scrap melting furnace, and relates to a method for manufacturing a melt, characterized in that the quality of the melt is controlled and the scrap is melted at a low coke ratio with high thermal efficiency.

[0002]

2. Description of the Related Art As a scrap melting process in a vertical furnace, there is a cupola method. In the cupola method, scrap and coke are charged in layers or mixed from the upper part of the furnace, and there are hot-air cupola with one-stage tuyere with a blast temperature of around 500 ° C and cold-air cupola with two-stage tuyere by normal temperature blasting. At the same time, high-quality coke for casting having a coke quality of C92%, an ash content of about 8%, and a grain size of 150 mm or more is required.

When a casting scrap / mold pig charging ratio of 30 to 60% (scrap 70 to 40%) is used and a casting coke is used, the fuel ratio is about 120 to 140 kg / t, and the secondary combustion rate η _CO ^(TOP) (= CO ₂ ^(TOP) / (CO ^(TOP) + CO
₂ ^(TOP) )) is about 40% with hot air cupola, two-tier tuyeres
In case of cold air cupola, it is operated at around 50%. This secondary combustion rate is affected by the degree of progress of equation (2) following the C combustion reaction of equation (1).

C + O ₂ → CO ₂ +97,000 kcal / (kmol · C) (1) C + CO ₂ → 2CO-38200 kcal / (kmol · C) (2) When using blast furnace coke having a particle size of 60 mm or less, an endothermic reaction occurs. Since the reaction progress of a certain equation (2) is fast, the secondary combustion rate η _CO surely decreases, and the solubility of scrap deteriorates. Therefore, in the prior art, for the purpose of slowing down the reaction rate of the equation (2), a high-cost foundry coke having a particle size of 150 mm or more was required.

Two-stage tuyeres aiming to improve the secondary combustion rate
In the case of a room temperature blast cupola, the purpose is to promote the reaction of the formula (3) by the secondary blast, but because the operation at room temperature blast has an oxygen enrichment rate of 3% or less, the tuyere at the primary tuyere The pre-temperature is low, and in normal operation, it is unavoidable to use C-containing low melting point casting scraps and mold pigs in an amount of 40 to 60% (scrap use ratio of 60 to 40%).

CO + 1 / 2O ₂ → CO ₂ +67590 kcal / (kmolt · CO) (3) As described above, in the case of the present cupola, the use of blast furnace coke and the operation of using the entire amount of scrap are severe.

For the purpose of using blast furnace coke, Japanese Patent Application Laid-Open No. 3-111505 proposes a method for improving the blowing method of the secondary blowing tuyere in a cupola type melting furnace having a secondary tuyere. There is. This is an inert carrier gas instead of the combustion-supporting gas in order to suppress the carbon solution reaction due to the overheating of the coke for the next melting, which is charged above the secondary tuyere level surface,
For example, N ₂ is used to blow powdery limestone and / or iron ore, respectively. Judging from the examples, the fluctuation of the secondary combustion rate is small and contributes to the reduction of the solution loss reaction, but the value is about 45%, which is almost within the operating range of the current cupola when the coke for casting is used. equal. In terms of operation, there is the complexity of adjusting the secondary air flow rate according to the time or scrap layer drop.

Further, for the purpose of reducing the coke ratio, a scrap melting method using pulverized coal is disclosed in JP-A-1-19522.
5 and JP-A-2-157590.

In both cases, since raceway is not generated in the furnace, in order to secure the pulverized coal combustion space,
Combustion towers or combustion chambers are specially installed, and heat loss generated during combustion and life of refractories are problems.

In the EOF method using a vertical furnace having a water cooling wall member as a refining furnace, oxygen is supplied from a nozzle arranged on the lower side of the bath surface to the upper surface of the bath in the vertical furnace. Oil / pulverized coal is blown together with oxygen through the burner, and the exhaust gas completely burned by the hot air enriched by the blowing nozzle placed above preheats the scrap iron placed on the furnace . The preheating temperature is about 800 ° C at the maximum, and the structure is such that the preheating furnace is discontinuously charged.

The problem is that the waste gas temperature fluctuates due to the complicated structure of the scrap iron preheating device and the discontinuous charging method.

Japanese Unexamined Patent Publication (Kokai) No. 1-501401 discloses a hot metal producing apparatus comprising a blast furnace having tuyere and a furnace floor having a diameter larger than that of the blast furnace and having a tuyere portion. In this furnace, the ore is not charged from the top of the furnace and only the ore is charged, and the fuel is added directly onto the fuel bed at the joint between the blast furnace and the hearth. The tuyere position is such that the primary tuyere is located in the area where fuel exists, and the upper tuyere is located in the area where ore that does not contain fuel exists. When this furnace is used for scrap melting, the solution layer does not contain fuel in the blast furnace part, so the solution loss reaction does not proceed and the exhaust gas η _CO
Highly efficient ^(TOP) operation can be expected. But,
The coke charging part is a region that comes into contact with high-temperature gas, and since the charging amount is large, the coke charging part has a large cross-sectional area,
Therefore, there are problems in facilities such as ensuring heat resistance and sealing property against gas leakage. In addition, there are concerns about damage to the side wall bricks and hanging on the shelf in the blast furnace due to deposits. In addition, since the coke charging part is a fixed type, the coke charging area is specified, and if the coke ratio changes, the coke consumption rate and scrap melting rate will differ, resulting in a coke charging cycle and a scrap charging cycle. It can be considered complicated due to different items. In addition, there is a coke packed layer in front of the tuyere of the hearth, and when carbonaceous material is blown from the tuyere under normal temperature blowing, there is a problem with the combustibility of the carbonaceous material. However, it is also possible that the breathability deteriorates. According to the operation example that seems to have been applied to scrap melting, the usage ratio of the carbon-containing casting waste is about 60%, and it is unclear whether or not the operation is possible when all scrap is used.

As a scrap melting method capable of avoiding the above-mentioned drawbacks of the prior art and using a large amount of fine coke for a blast furnace having a fine grain of 60 mm or less and a large amount of scrap, coke is provided in the peripheral portion of the furnace and in the central portion of the furnace. Japanese Patent Application No. 05-239272, Japanese Patent Application No. 05-
Presented at 248515. This is a shaft-type scrap melting that can reduce the fuel consumption by suppressing the carbon solution loss reaction of the equation (2) in the furnace while increasing the thermal efficiency while considering the simple furnace structure that can enlarge the equipment. It is about the furnace.

[0014]

In the prior art, it is difficult to operate using blast furnace coke and using a large amount of scrap, and in the scrap melting method using carbon material, the carbon material is directly scraped or coke filled. There is a dedicated combustion tower or chamber that secures a combustion space rather than blowing into the layer. In this case, heat loss and life of refractory materials are problems.

Regarding the quality of the molten metal, it is also a problem that S in the molten metal is at a high level.

On the other hand, in the case of a hot metal production apparatus comprising a blast furnace having tuyere and a hearth having a diameter larger than that of the blast furnace,
Since there is a fuel supply unit in the hearth, there are problems in terms of equipment structure such as heat resistance of the fuel supply unit that comes into contact with high temperature gas and sealing performance against gas leakage. Further, regarding the blowing of carbonaceous material under normal temperature blowing, its combustibility is a problem.

The coke peripheral charging method is characterized in that it can be operated efficiently, but it is difficult to control the quality of the molten metal promptly, and if pulverized coal is blown from the tuyere even with carbonaceous material, it will be at room temperature. Under the blast, it was necessary to preheat the temperature of the pulverized coal blowing part such as the pre-combustion of natural gas to 600 ° C. or higher in the tuyere.

The present invention does not install a coke charging site exposed to high-temperature gas, which causes a problem of gas sealability, in the hearth, eliminates the formation of deposits in the furnace, and smoothly descends the charge. To reduce the cost by using blast furnace coke and steam coal, improve secondary combustion rate to improve scrap preheating and solubility, and maintain high productivity under high thermal efficiency. The purpose of the present invention is to provide a scrap melting method capable of controlling the quality of molten metal.

[0019]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems. In terms of equipment, since the coke charging site is on the low temperature side, scrap and coke are charged from the top of the furnace for use in blast furnaces. In order to enable the use of coke, aim for low coke ratio operation and consider injecting a large amount of carbonaceous material from the tuyere or nozzle of the hearth. In addition to the conventional method of mixing scrap and coke and charging them in a layered manner, the charging method of the peripheral portion of the coke is considered as a charging method of the charging material. Combustion rate C at the tuyere by charging coke into the furnace periphery and scrap from the center to the middle
O ₂ / (CO + CO ₂ ) is increased, and in the scrap preheating region, the solution loss reaction amount of the equation (2) in the coke layer having a smaller grain size and a larger air flow resistance than the scrap is suppressed to suppress the scrap preheating. It is characterized by being able to operate with high thermal efficiency by performing it efficiently.

Regarding the control of the quality of the molten metal, considering the use of a large amount of the carbonaceous material as a carburizing accelerator and the blowing of the carbonaceous material flux from the nozzle installed in the upper part of the hearth, for example, the acceleration of carburizing and the decrease of the S I was able to control.

That is, the gist of the present invention is that a vertical furnace having an upper tuyere or a multi-stage tuyere and a diameter 1.0 to 3.0 times larger than the diameter of the vertical furnace are provided, and a side wall is provided. A moving bed type scrap melting furnace consisting of a hearth having a primary tuyere and / or a blowing air and / or oxygen blowing nozzle at the upper part and a carbonaceous material and / or flux blowing nozzle at the upper part if necessary is presented. Further, in the moving bed type scrap melting furnace, there is provided a method for producing hot metal, characterized in that coke is charged from the upper portion of the vertical furnace to the peripheral portion of the furnace and scrap is charged from the central portion to the intermediate portion.

Here, the central part is defined as a region within 1/3 of the radius of the furnace, and the peripheral part of the furnace is a region sandwiched between the radial position R _S calculated by the equation (4) and the furnace wall. The middle part is defined as a region sandwiched between the central part and the peripheral part.

When the boundary radius position between scrap and the peripheral charging coke is R _S and the radius of the furnace opening is R _O , R _S / R _O
Is defined by equation (4).

[0024] _{R S / R O = {1} / (A + 1)} 1/2 ... (4) _{However, A = (W CR / ρ} CR) / (W S / ρ S) where, W _CR: coke ratio (kg / t) W _S: scrap ratio (kg / t) ρ _CR: coke bulk density (kg / m ³⁾ [rho _S: bulk density (kg / m ³⁾ of the scrap addition, and the side wall portion of the hearth Indicates the vertical portion with respect to the ground, and the upper part of the hearth is defined as the region between the vertical furnace and the side wall.

[0025]

The present invention will be described in detail below.

FIG. 1 is a diagram showing a conceptual diagram of a scrap melting furnace according to the present invention.

Coke 7 is charged in the peripheral portion of the furnace, and scrap 8 is charged in the middle portion from the central portion. One or a plurality of tuyere are installed in the vertical direction (in FIG. 1, two locations, a primary tuyere 3 and an upper tuyere 4 are shown). The upper tuyere 4 installed in the vertical furnace 1 is set so that its protruding position is at the boundary position between the scrap 8 and the coke 7 obtained by the equation (4).

In the hearth II, the inner diameter of the hearth was set to be 1.0 to 3.0 times larger than the inner diameter of the upper vertical furnace. Also, the hearth
Carbon material and / or flux injection nozzle 5 on top of II,
The primary tuyere 3 was provided in the blown air and / or oxygen blowing nozzle 6 or the side wall. Scrap and coke are charged from the top of the vertical furnace. Therefore, although it has a hearth II having a larger inner diameter than the upper vertical furnace I, the problem of gas sealability in the hearth II is solved.

First, the necessity of making the inner diameter of the hearth larger than the inner diameter of the upper vertical furnace and the size thereof will be described.

When the peripheral coke charged in the upper vertical furnace falls to the hearth, the coke deposit shape is defined by the angle of repose of the coke. Therefore, the inner diameter of the hearth is set to the inner diameter of the upper vertical furnace. By setting the ratio to 1.4 times or more, it is possible to secure a space where a large amount of pulverized coal can be burned in the upper part of the coke. Securing the space enables combustion of pulverized coal without preheating in the tuyere even under normal temperature blowing. In the conventional type in which the carbonaceous material is blown into the coke packed bed, there are restrictions on the blowing conditions, tuyere structure, and coke particle size necessary for providing the raceway space, but the present invention eliminates this restriction. Further, when the combustibility of the carbonaceous material deteriorates, in the conventional type, the air permeability in the coke-filled layer may deteriorate, which may hinder the operation, but the method of the present invention does not cause the air permeability to deteriorate. Therefore, it became easy to use the carbonaceous material, and it became possible to inject a large amount of carbonaceous material. In addition, as one of the conventional techniques, carbon material combustion in a dedicated combustion furnace of carbon material or outside the furnace was considered, but in that case, heat loss does not need to be considered in the case of this device. . Further, even if unburned materials are generated when a large amount of carbon materials are burned, the unburned materials are utilized as a carburizing material for molten metal. The combustion space should be as wide as possible, but if the inner diameter of the hearth is more than 3.0 as compared with the inner diameter of the upper vertical furnace, the heat dissipated in the furnace body will increase and the overall combustion efficiency will decrease. Therefore, when considering the large-scale combustion of carbonaceous material, the inner diameter of the hearth is preferably 1.4 to 3.0 times that of the upper vertical furnace. On the other hand, when it is not necessary to blow a large amount of carbonaceous material, it is not necessary to secure a wide combustion space in the hearth, so the inner diameter of the hearth is 1.0 to 1.4 times the inner diameter of the upper vertical furnace. About twice is enough.

Next, the installation positions of various nozzles installed in the hearth and the reasons for the installation will be described. The carbonaceous materials such as pulverized coal and carbonaceous materials are directly injected into the space inside the furnace from the nozzle installed in the upper part of the hearth, and oxygen and / or air is injected into the nozzle and / or oxygen from the primary tuyere. And burned. It is preferable that the blown air and / or the oxygen blowing part is located above the hearth part because the combustion time of the carbonaceous material is made as long as possible. When the large-scale combustion of carbonaceous material is not taken into consideration, the blowing air and / or oxygen burns the coke, and therefore the primary tuyere is used for blowing air. In this case, in order to minimize the reaction time of the coke and suppress the reaction of the formula (2) as much as possible, it is preferable to install the primary tuyere on the side wall of the hearth.
The carbonaceous material and / or flux injection nozzle, which is installed on the upper part of the hearth as needed, is used to inject a large amount of carbonaceous material or to control the quality of the molten metal.
It is installed to inject flux for reduction. When separating coke and scrap and charging coke into the surrounding area, a portion of the pulverized coal blown from the hearth is used as a carburizing material because the amount of carburizing when melting scrap is small.
Regarding the control of S in the molten metal, carbonaceous materials and //
Alternatively, by injecting lime powder from the flux injecting nozzle so as to have a predetermined basicity, it is possible to control the quality of the molten metal with the aim of reducing the molten metal S.

Next, the presence of the furnace body structure of the present invention having an upper vertical furnace and a hearth, that is, the presence of a space in the hearth, not only controls the quality of the molten metals C and S, but also burns the hearth. Rate η _CO ⁽¹⁾ (=
Explain that it can be used to control CO ₂ ⁽¹⁾ / (CO ⁽¹⁾ + CO ₂ ⁽¹⁾ )) to a high level.

The coke descending from the upper vertical furnace to the hearth part spreads to the peripheral part according to the angle of repose (36 °) of the coke, and a space is formed in the upper part. Securing the combustion space in the hearth is utilized to improve the combustibility of pulverized coal and to secure the conditions for blowing air or oxygen into the slag bath. In the combustion space in the hearth, a large amount of carbonaceous material can be burned, and the ventilation conditions for complete combustion (reaction of equation (1)) can be set, and the combustion rate η _CO ^{( 1)} can be improved. Even when the carbonaceous material is not blown, the air and / or oxygen is blown to the slag layer of the hearth from the blown air and / or oxygen blowing nozzle set at the upper part of the hearth, so that the hearth is blown. It is possible to improve the combustion rate η _CO ⁽¹⁾ in some parts. In the latter case, coke existing in the slag layer mixed with air and / or oxygen reacts in the slag layer to generate an exothermic reaction of the formula (1). Is to suppress. In this way, by utilizing the existence of the space in the hearth, the combustion rate η in the hearth
_CO ⁽¹⁾ can be controlled high. This high burning rate η _CO
^{If (1)} can be secured, the amount of coke charged in the furnace top can be reduced, and thus the amount of coke involved in the reaction of equation (2) can be reduced. Therefore, the amount of solution loss reaction decreases, and 2
It is possible to suppress a decrease in the secondary combustion rate η _CO ^(TOP) .

Also, as a means for controlling the secondary combustion rate η _CO ^(TOP) of the exhaust gas, it is effective to employ the upper tuyere. The upper tuyere is used to burn the gas burned in the hearth η _CO ⁽¹⁾ (=
CO ₂ ⁽¹⁾ / (CO ⁽¹⁾ + CO ₂ ⁽¹⁾ )) was installed in order to raise it further, by the air blow from the upper tuyere,
The reaction of equation (3) is promoted, and the secondary combustion rate η of the furnace top exhaust gas
It is possible to raise _CO ^(TOP) .

Next, a method of using fine coke having an average particle size of 60 mm or less will be described. The refinement of coke not only increases the solution loss reaction rate of Eq. (2) with the combustion gas in the space of the hearth or the combustion gas in the primary tuyere, but also in the upper vertical furnace (2 Since the solution loss reaction amount in the equation) also increases, the exhaust gas secondary combustion rate η _CO ^(TOP) decreases, and as a result, operation with a high coke ratio is forced. In order to suppress this, it is necessary to shorten the contact time with the highly reactive fine grain coke and prevent the combustion gas from flowing in the fine grain coke layer. Coke peripheral charging is adopted as this measure.

In the upper vertical furnace, the blast furnace coke having a grain size of 60 mm or less is charged in the peripheral portion in the coke layer having a low porosity in the upper vertical furnace. By increasing the ventilation resistance of, by flowing the main flow of gas burned in the hearth to the scrap layer charged from the center of the furnace to the middle part,
The purpose is to suppress the solution loss reaction amount in the equation (2). Also in the hearth, when the coke charged in the periphery falls to the hearth, the thickness of the coke layer becomes thin, and the scrap layer charged from the center to the middle part enters the hearth. As compared with the conventional method, there is no coke packed bed (coke bed), or the coke packed bed becomes shorter, and the time involved in the solution loss reaction of equation (2) is extremely shortened. As a result, the amount of solution loss reaction in equation (2) in the furnace hearth is small, and operation with a high combustion rate η _CO ⁽¹⁾ can be maintained.

As described above, by adopting the peripheral coke charging method, the solution loss reaction amount of the equation (2) can be reduced,
Secondary combustion rate η _CO ^(TOP) = CO
₂ ^(TOP) / (CO ^(TOP) + CO ₂ ^(TOP) ) is high, and operation with high thermal efficiency is possible. This also contributes to the reduction of the coke ratio. In this way, the coke peripheral charging is a method that enables the use of blast furnace coke having a smaller grain size than the normally used casting coke.

Further, in the peripheral coke charging method, a method of utilizing the upper tuyere for more efficient operation will be described.

As a method for controlling the secondary combustion rate η _CO ^(TOP) higher, there is use of the upper tuyere, but when peripheral coke charging is adopted, the protruding position of the upper tuyere is set as the boundary between scrap and coke. It is more effective to project into a position or scrap layer. This is because the direct reaction between the blown air and blown oxygen from the upper tuyere and the coke can be suppressed, so that the reaction of the formula (3) can be efficiently performed. When aiming for the most heat-efficient operation,
With the upper tuyere protruding into the scrap layer, air and / or oxygen that can completely burn the CO gas amount after the primary tuyere combustion can be blown according to the equation (3), and η _CO ^(TOP) ≧
A burning rate of 65% can be achieved. Thereby, the reaction efficiency becomes good and the coke ratio can be reduced.

Regarding the coke peripheral charging method, a conventional charging device such as Bell + MA (movable armor) is used.
It can be controlled by a die or bellless charging device.

Further, by adopting the charging around the coke, it becomes possible to suppress the formation of deposits in the lower portion of the upper vertical furnace.
This is because, in the normal charging method, the scrap layer is in contact with the furnace wall, so when a low-melting slag in a semi-molten state is generated,
It adheres to the brick of the furnace wall and solidifies to form an adhered substance. The formation of the adhered matter worsens the unloading of the load, and in some cases, hanging of the shelves occurs and the operation becomes impossible. On the other hand, when the coke layer is present in the peripheral portion, the low melting point slag in the semi-molten state is trapped in the coke layer and does not contact the furnace wall portion. Therefore, it is difficult to generate the deposit.

Next, a technique for using a large amount of scrap will be described.

According to the experiments so far, the particle size is 1500 m.
Regarding the solubility of scrap containing m, a high temperature gas is required, and the theoretical combustion gas temperature Tf before the primary tuyere and the scrap usage ratio have the relationship shown in FIG. This is because the melting point of metal increases as the amount of C in the metal decreases.

According to FIG. 3, it is possible to operate even if the Tf is low as the die pig ratio and the cast iron scrap ratio increase, but the Tf is 265 in order to achieve the melting of all scrap.
0 ° C or higher is required. Since the combustion rate η _CO ⁽¹⁾ at the primary tuyere changes depending on the coke particle size, it is necessary to change the blowing conditions depending on the coke particle size during operation.

The oxygen enrichment rate for maintaining Tf ≧ 2650 ° C. differs depending on the burning rate burning rate η _CO ⁽¹⁾ in the hearth. When using coke with a large grain size,
η _CO ⁽¹⁾ is high, and as shown in Fig. 4, T without _CO enrichment
f ≧ 2650 ° C. can be achieved, and the entire scrap can be used. On the other hand, when using blast furnace coke with a particle size of 60 mm or less, compared to η _CO ⁽¹⁾ ≤ 30% in conventional cupola operation,
The peripheral coke charging method enables highly efficient operation with η _CO ⁽¹⁾ > 40%, but an oxygen enrichment rate of about 5% is required to achieve Tf ≧ 2650 ° C. under normal temperature blowing. is there.

As described above, in order to use a large amount of scrap, it is necessary to change the blowing condition depending on the coke grain size, but it is possible to use the entire scrap by achieving Tf ≧ 2650 ° C.

[0047]

EXAMPLES The features of the present invention will be specifically described with reference to the following examples.

A melting furnace (A type) of the type shown in FIG.
Is a vertical furnace with an effective height of 4.6 m and a furnace diameter of 2 m and four upper tuyeres at equal intervals in the circumferential direction at a height of 0.5 m from the boundary between the vertical furnace and the hearth. Hearth diameter 2.8m, height 2m
And has eight primary tuyere at equal intervals in the circumferential direction on the side wall of the hearth. The melting furnace of this structure is called an A-type scrap melting furnace. In addition, the melting furnace (B type) of the type shown in FIG. 1 (b) has a furnace diameter of 2 m and upper tuyeres 4 at equal intervals in the circumferential direction at a height of 0.5 m from the boundary between the vertical furnace and the hearth. 3. Vertical furnace with an effective height of 4.6 m and a hearth diameter of 4.
It has a hearth with a height of 0 m and a height of 2 m.
Four blast air and / or oxygen blowing nozzles and two carbonaceous material and / or flux blowing nozzles are installed at a position of 5 m at equal intervals in the circumferential direction and at symmetrical positions in the circumferential direction. The melting furnace of this structure is called a B-type scrap melting furnace.

Charging of scrap was controlled by a bellow bubble armor. Of the operating specifications, the blast humidity is 15g
/ Nm3, limestone basic unit charged from the furnace top is 40 kg /
t.

The comparative example is an operation example of a cupola using only a normal vertical furnace, and the comparative example 1 is an operation example of a one-stage tuyere and a hot-air blowing cupola of 500 ° C. Operation using casting coke and blast furnace coke. Examples and Comparative Example 2 are examples of operation of a room temperature blow cupola with a two-stage tuyere, and the mold pig ratio or the cast iron scrap ratio is 30% and 60%, respectively.

Example 1 This is a case using an A-type scrap melting furnace, and the air blown from the tuyere of the hearth was hot air blow (500 ° C.). The ratio of cast iron scrap was set to 30% and only the primary tuyere was blown, and the same conditions as in Comparative Example 1 were used. As the charging method, charging around the coke was adopted. The coke charging area was finely adjusted during the operation, but at the final steady state, the coke was charged in the area of the furnace opening dimensionless radial position of 0.75 to 1.0, and the scrap was charged therein.

When a coke for casting having a particle diameter of 150 mm is used, the exhaust gas η _CO ^(TOP) is higher than that of Comparative Example 1 by about 20%. Even when blast furnace coke having a particle diameter of 60 mm is used, exhaust gas η _CO ^(TOP) = 28%
On the other hand, the improvement effect with efficiency improvement is large. In the embodiment, the heat surplus and the fuel ratio can be reduced.

Example 2 In the case of using a type A scrap melting furnace, the air blown from the hearth tuyere was room temperature air blow (25 ° C.), and the upper tuyere was used for the two-stage tuyere. The coke used has a particle size of 60 m
m was used as the blast furnace coke, and the scrap iron ratio was 0%. Regarding the charging method of the charging material, coke was charged in the region of the non-dimensional radius position 0.74 to 1.0 of the furnace opening, and the scrap was inserted from the center to the middle portion. In the operation, start blowing air at the primary tuyere, obtain the hearth combustion rate η _CO ⁽¹⁾ ,
After that, we switched to a two-stage blast. Burning rate in the hearth η _CO
^{In (1)} , about 60% was achieved, and the oxygen enrichment rate was set to 6.3% so that the theoretical gas combustion temperature Tf ≧ 2650 ° C. at the tip of the hearth of the hearth was satisfied. As a result, the solubility is good, stable operation is possible, and the air flow rate of the upper tuyeres is different, but the use of the upper tuyeres causes the exhaust gas η _CO ^(TOP) ≧ 7.
Achieved 0%. Despite the severe conditions of using all scrap and using blast furnace coke, compared to Comparative Example 2,
It has become possible to operate efficiently.

Example 3 This is a case where a B-type scrap melting furnace is used. The air blown from the ceiling of the hearth floor was blown at room temperature (25 ° C). The coke used was a blast furnace coke having a particle size of 60 mm, and the scrap iron ratio was 0%.

As a result of blowing blast air and / or oxygen from the blast air and / or oxygen blowing nozzle into the slag bath, when the upper tuyere is not used and when scrap and blast furnace coke are mixed and charged, exhaust gas η _CO ^(TOP) was about 45%. Exhaust gas η _CO ^(TOP) when using blast furnace coke in a conventional cupola is about 28%, but the improvement effect with efficiency improvement is large. When blast furnace coke is charged into the area of approximately 0.74 to 1.0 at the dimensionless radial position of the furnace mouth, and scrap is charged from the center to the middle in the peripheral area, the exhaust gas η _CO
^(TOP) rises, and when combined with upper tuyere ventilation, exhaust gas η
_CO ^(TOP) ≥ 70% or more of the operation could be continued. Compared to the cupola operation of Comparative Example 2 in which the coke for casting having a large particle diameter with room temperature air blowing and two-stage tuyeres was used, efficient operation was possible.

Example 4 This is a case in which 80 kg / t of pulverized coal was blown from the carbonaceous material and / or the flux blowing nozzle in the operation without using the upper tuyere of Example 3 in which the peripheral coke was charged. . In this case, exhaust gas η _CO compared to before pulverized coal injection
^(TOP) was reduced by about 5-10%, but exhaust gas η _CO ^(TOP) ≧ 70 due to the combined use of air blow from the upper tuyere
% Or more of operations became possible. In this way, it became possible to operate at a charging coke ratio from the furnace top of 50 kg / t or less. In this way, it was confirmed that stable operation is possible even under the injection of pulverized coal.

Example 5 In Example 4, since S in the molten metal was 0.1% when the slag basicity was 0.8, aiming at a decrease in S in the molten metal, a carbonaceous material and / or a flux blowing nozzle was used. By blowing in 14 kg / t of lime powder, the slag basicity could be increased to about 1.3 and S in the molten metal could be reduced to 0.06%.

[0058]

[Table 1]

[0059]

As described above, in the present invention, blast furnace coke and pulverized coal, which are cheaper than casting coke, are used, and a large amount of scrap can be used, and the quality of molten metal can be controlled. A melting furnace is provided, and the effect of the invention is extremely large.

[Brief description of drawings]

1A and 1B are conceptual views of a scrap melting furnace according to the method of the present invention.

FIG. 2 is a diagram showing a relationship between slag basicity and S in molten metal.

FIG. 3 is a diagram showing a relationship between a theoretical combustion temperature Tf before tuyere and a scrap ratio (scrap usage ratio).

[Fig. 4] Tf ≧ 26 for the combustion rate η _CO ⁽¹⁾ in the hearth
The figure which shows the oxygen enrichment rate required in order to guarantee 50 degreeC.

[Explanation of symbols]

 I ... Vertical furnace II ... Hearth part 3 ... Primary tuyere 4 ... Upper tuyere 5 ... Carbonaceous material and / or flux blowing nozzle 6 ... Blower air and / or oxygen blowing nozzle 7 ... Coke 8 ... Scrap

Claims (5)

[Claims] 1. A vertical furnace having an upper tuyere and a diameter 1.0 to 3.0 times larger than the diameter of the vertical furnace, and a primary tuyere and one of blown air and / or oxygen blowing nozzles. Seed or 2
A moving bed type scrap melting furnace consisting of a hearth with seeds. 2. The moving bed type scrap melting furnace according to claim 1, wherein the vertical furnace has 1 to 2 stages of upper tuyeres in the vertical direction. 3. The moving bed type according to claim 1 or 2, wherein the hearth has a primary tuyere in the side wall and a carbonaceous material and / or flux blowing nozzle in the upper part. Scrap melting furnace. 4. The hearth part has a carbonaceous material and / or flux blowing nozzle and a blast air and / or oxygen blowing nozzle in the upper part, according to any one of claims 1 to 3. The moving bed type scrap melting furnace described. 5. A method for producing hot metal in a moving bed type scrap melting furnace according to claim 1,
A method for producing hot metal, characterized in that coke is charged from the upper part of the vertical furnace to the peripheral part of the furnace and scrap is charged from the central part to the intermediate part.