JPH0770625A - Method for charging raw material to moving bed type scrap melting furnace - Google Patents

Abstract

PURPOSE:To make stable operation at a low coke ratio and low mold pig ratio (casting pig ratio) and to inexpensively produce molten iron by improving the waste gas etaco<(>TOP<)> (=CO2<(>TOP<)>/(CO<(>TOP<)>+CO2<(>TOP<)>)) of a moving bed type scrap melting furnace and further enabling the use of fine grained coke. CONSTITUTION:The boundary radius of scrap/coke or the sectional area for coke charging is calculated according to the coke ratio. The coke 2 is then charged to the periphery of the wall of parts 4 where primary tuyeres exist and the scrap 1 is charged into the center to middle parts or the center to the peripheral parts. The projecting positions of upper tuyeres 5 are set at the scrap/coke boundary region or the upper tuyeres are installed to the parts where the coke does not exist and further, the air permeation resistance within the coke layers is increased by using the fine-grained coke, by which the operation to maintain the high waste gas etaco<(>TOP<)> (=CO2<(>TOP<)>/(CO<(>TOP<)>+CO2<(>TOP<)>)) is made possible in the case of using the multistage tuyeres.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing pig iron using scrap as an iron source by using a vertical furnace having a tuyere and having a relatively simple structure, and in particular, scrap and coke charged from the top of the furnace. The present invention relates to a method for producing pig iron, which is characterized in that by improving the charging method of (1), the pig iron is continuously melted with good thermal efficiency and a low fuel ratio, and productivity and economy are improved.

[0002]

Most of pig iron is manufactured by a blast furnace. The blast furnace ironmaking method uses a sintered ore and a beret as the main raw materials to produce a large amount of hot metal extremely efficiently, and uses this as the main raw material to produce high quality cast products that match the product quality of many types in the steelmaking process. As a main raw material for steelmaking, it is usually operated at a so-called return balance hot metal ratio, which balances with hot metal and scrap generated during rolling and product refining processes. However, due to the increase in the amount of steel accumulated with the development of society, the market supply scale of scrap is inevitably expanded, and the need for effective utilization of recycled scrap is increasing. Regarding the use of circulating scrap in a blast furnace, various problems such as damage to the charging belt due to scrap shape and the problem of deposit formation due to the presence of impurities such as Zn, as well as the impact on the charging method and distribution of charges, etc. However, it is difficult to use a large amount of scrap at present.

As a scrap melting process using a vertical furnace other than the blast 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 a single-stage tuyere with a blast temperature of around 500 ° C and cold-air cupola with two-stage tuyere due to room-temperature air blowing.
Both cupolas require high-cost coke for castings with a coke quality of C92%, an ash content of about 8%, and a grain size of 150 mm or more. Regarding the fuel ratio, when the charging ratio of casting waste or pig iron is 30 to 60% and the rest is scrap, it is about 120 to 140 kg / t, and the exhaust gas composition η _CO
^(TOP) (= CO ₂ ^(TOP) / (CO ^(TOP) + CO ₂
^(TOP) ) is operated at around 40% in the case of hot air cupola and around 50% in the case of two-stage tuyere cold air cupola. This exhaust gas composition is influenced by the degree of progress of the reaction amount of the equation (4), which is an endothermic reaction, following the exothermic reaction of the following equation (3) that occurs before the primary tuyere. C + O ₂ → CO ₂ +97,000 kcal / kmol · C (3) C + CO ₂ → 2CO-38200 kcal / kmol · C (4)

When a blast furnace coke having a particle size of 60 mm or less is used, not only the reaction of formula (4) progresses rapidly and the coke ratio becomes high, but also the scrap melting is hindered by the temperature decrease and the particle size is small. There was a problem that the breathability deteriorates and stable operation becomes difficult. for that reason,
For the purpose of slowing down the reaction rate of the equation (4), a high-cost foundry coke having a grain size of 150 mm or more was required. Further, in the case of a cupola having a two-stage tuyere, CO gas produced in the primary tuyere is converted into C by the equation (5) which is an exothermic reaction.
It is burned with O ₂ and the heat of reaction is used for heating and melting scrap, coke and the like. CO + 1 / 2O ₂ → CO ₂ +67590 kcal / kmol CO ... (5)

However, even with this method, the coke temperature is 7
When the temperature rises to 00 ° C. or higher, the CO ₂ gas generated in the secondary combustion reacts with the coke and starts to generate CO by the so-called carbon solution reaction shown in the above formula (4). Here, the generated CO gas is exhausted to the outside of the furnace in an unburned state, resulting in wasteful consumption of coke. Furthermore, since the equation (4) is an endothermic reaction, not only coke but also scrap and the like are generated. Inhibits heating and melting. At present, in the cupola operation, the carbon solution reaction by the formula (4) is inevitable, the thermal efficiency and the productivity are lowered, and the fuel consumption rate is increasing. Further, in order to improve the melting property, it is unavoidable to use C-containing low melting point casting scraps and mold pigs in an amount of about 30 to 60%. As described above, in the present cupola operation, even if an expensive foundry coke having a large particle size is used, only the operation with the exhaust gas composition η _CO ^(TOP) ≦ 55% can be achieved.

As a method for improving this, Japanese Patent Laid-Open No. 3-1
Japanese Patent No. 11505 proposes a method for improving the secondary tuyere blowing method. In order to suppress the carbon solution reaction due to the overheating of the coke for the next melting that is charged above the secondary tuyere level surface, an inert carrier gas such as N ₂ is used instead of the flammable gas. It is characterized in that it is used to blow powdery limestone and / or iron ore, respectively. However, even in this method, scrap and coke are charged in a mixed or layered manner, and η _CO ^(TOP) is about 45%, which is within the range of the current cupola operation level, so that it is still considerably (Equation 4). It suggests that a solution loss reaction is present. In this way, scrap and coke from the furnace top,
When charged in layers or mixed, it is difficult to suppress the solution loss reaction of formula (4).

Further, Japanese Patent Application Laid-Open No. 1-501401 discloses a hot metal production apparatus comprising a blast furnace having tuyere and a hearth 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. 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 efficient operation with high exhaust gas η _CO ^(TOP) can be expected. However, in order to emphasize efficiency, it was necessary to set the hearth part with a large diameter for the blast furnace. However, the fuel charging section and the joint section between the blast furnace and the hearth are areas that come into contact with high-temperature gas, and there are various problems due to the complicated furnace body structure, such as ensuring heat resistance and problems with equipment. . In particular, in addition to ensuring the heat resistance of the coke charging part, the sealing property against gas leakage is a problem.
Due to the structure of the furnace body, it is difficult to increase the size of the equipment, and it is difficult to apply it to the melting of a large amount of scrap. Also,
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 different charging cycles for coke charging and scrap charging. It is also possible to consider the complexity of charging such as.

[0008]

SUMMARY OF THE INVENTION The present invention avoids equipment restrictions such as gas sealability of the coke charging portion exposed to high temperature gas as much as possible, and sets the coke charging area according to the coke ratio. Controlling the layer structure so that it is not disturbed, and considering the simple furnace body structure that can enlarge the equipment, suppress the carbon solution loss reaction of formula (4) in the furnace to improve the thermal efficiency, An object of the present invention is to provide a raw material charging method capable of reducing consumption and increasing productivity.

[0009]

Means for Solving the Problems 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 furnace top, The body structure is as simple as a normal cupola-type moving layer, allowing for large-scale equipment.
By adjusting the coke charging area according to the coke ratio, the surface level of scrap and coke can be kept constant, and proper raw material descent can be achieved.Furthermore, in operation, coke is charged around the furnace wall. By loading the scrap from the center to the periphery, the burning rate CO ₂ at the tuyere
/ (CO + CO ₂ ) is increased, and in the scrap preheating region, the solution loss reaction amount of the equation (4) in the coke layer having a smaller particle size and larger ventilation resistance than the scrap is suppressed to efficiently preheat the scrap. By doing
It is characterized in that it is possible to operate with high thermal efficiency.

[0010]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a conceptual diagram of a moving bed type scrap melting furnace by the method of the present invention, and FIG. 2 is a diagram showing a method of inserting scrap and coke and a state at the time of charging. Coke 2 is charged around the furnace wall, and scrap 1 is charged from the central portion to the intermediate portion or from the central portion to the peripheral portion. The method of charging coke around the furnace wall is the method of charging coke around the entire circumference (Fig. 2 (a)), and the coke exists at least at the tuyere installation part, not around the entire circumference. There is a charging method (FIG. 2 (b1 to b4)). It should be noted that the center portion to the peripheral portion here differ depending on the coke charging method shown in FIG. 2, and when the coke is continuously charged in the circumferential direction (FIG. 2 (a)), R
It is the area up to _S (the boundary position between scrap and coke), and when the coke is charged discontinuously in the circumferential direction (Fig. 2
In (b1 to b4)), scrap is also charged near the wall, and therefore the area from the center to the furnace wall is included. That is, the furnace wall portion includes a region having a radius of 1/2 to the wall. In the case of a moving bed having multi-stage tuyere, the upper-stage tuyere 5 is used in the charging method of FIG.
Is movable inside the furnace, and the tuyere protrusion position is defined by equation (1).
It is set so as to be at or inside the boundary position between the scrap 1 and the coke 2 obtained in step 2. When the target exhaust gas composition is on the low η _CO ^(TOP) side, the protruding position of the upper tuyeres 5 may be set in the coke layer. On the other hand, when adopting the charging method of FIG. 2 (b1 to b4), the upper tuyere 5 part is not at least directly above the primary tuyere 4 but at a portion between primary tuyere or where peripheral charging coke does not exist. To install.

Next, the reason why the solution loss reaction amount of the equation (4) can be reduced by the present invention will be explained. In the charging method of the present invention, coke exists around the furnace wall. Since the coke grain size is smaller than the scrap grain size, the porosity in the coke layer is lower than the porosity in the scrap layer, and most of the gas flows in the scrap layer. In order to reduce the gas flow in the coke layer as much as possible, the coke particle size can be refined or the particle size composition can be expanded and adjusted. The effect is remarkable when the coke grain size is 60 mm or less, as shown in FIG. As a result, the mainstream gas flows in the scrap layer without coke, so that the solution loss reaction of the equation (4) does not occur in the scrap layer. In the coke layer, a part of the solution loss reaction of the equation (4) occurs, but it is extremely reduced as compared with the conventional method. Thus, according to the charging method of the present invention, even if the coke particle size is about the same,
Operation with higher thermal efficiency (exhaust gas η _CO ^(TOP) = CO ₂ ^)
(TOP) / (High operation of CO ₂ ^(TOP) + CO ₂ ^(TOP) ))
Is possible. The improvement effect is large compared to the conventional method,
This is the case where the coke grain size is reduced, as shown in FIG. The effect becomes larger as the porosity in the coke layer is reduced by adding the grain size constitution. In addition, in the conventional charging method, as a result of the mixed charging of scrap and coke, the mainstream gas comes into contact with the coke, so the finer the particles become (4)
The reaction rate of the equation increased, and the amount of solution loss increased. As described above, in the conventional method, the refinement of coke tends to make the operation difficult, but in the coke charging method according to the present invention, even if the fine coke is used, it is possible to operate with high thermal efficiency. Yes, there is no problem in operation.

In the case of a moving layer having a multi-stage tuyere, as shown in FIG. 2, by arranging the upper tuyere 5 in a staggered manner rather than immediately above the site where the primary tuyere 4 exists, the primary tuyere portion Η _CO ⁽¹⁾ (= CO ₂ ⁽¹⁾ / (CO ₂ ⁽¹⁾ + CO ₂
^{According to (1)} )), the air flow rate of the upper tuyere can be set so as to obtain a predetermined exhaust gas composition. When aiming at the operation with the highest thermal efficiency, it is sufficient to blow air or oxygen that can completely burn the CO gas amount after the primary tuyere combustion according to the equation (5), and η _CO ^(TOP) ≧ 90% Burning rate can be achieved.

Next, a method of charging scrap and coke will be described. The charging method of FIG. 2A is a charging method using a conventional charging device, for example, Bell + MA.
(Movable armor) type charging device, there is a method of charging the peripheral coke, there is a method of charging the coke to the periphery with a bellless charging device. Further, as a new charging method, there is a method using a charging device, an example of which is shown in FIG. Front 2
There is a case where a mixed area of scrap and coke is formed in the middle part to the peripheral part. However, in the case of the charging system of FIG. 4, the scrap charging hopper 7 and the coke charging for charging the outer peripheral part are formed. Since the hopper 8 is provided separately,
The scrap 1 and the coke 2 can be reliably separated. As shown in the equation (1), the boundary portion between scrap and coke changes depending on the coke ratio. Therefore, a tiltable partition plate 11 is provided as a method of suppressing the boundary position between scrap and coke. The tilt angle of the partition plate 11 is adjusted to the scrap / coke boundary radius position corresponding to the coke ratio, and the coke is controlled so that the coke can be charged at a predetermined position.

As an example of the charging method of FIG. 2 (b), in addition to the charging method of FIG. 4, the peripheral charging portion is further divided into a coke 2 charging portion and a fine grain scrap 1a charging portion, At the boundary, a tiltable partition plate 11 is installed (FIG. 5). The tilt angle is determined by calculating the coke charging cross-sectional area shown in equation (2) according to the coke ratio. As another charging method, FIG. 6 shows an example of a charging device. Feeder 1 for charging coke on the furnace wall at the tuyere installation site
Set 0. In the case of a multi-stage tuyere cupola, the above-mentioned feeder 10 for charging coke is installed at the primary tuyere present portion. A partition plate 11 is provided in order to make the charging surfaces of the tops of the scrap 1 and the coke 2 constant, and the cross-sectional area of the coke charging portion can be adjusted according to the coke ratio.

Next, the charging state of the coke charged in the furnace by the charging method of FIG. 2 (a) will be described. The bulk density of coke and scrap is 500 kg / m ³ , respectively.
120kg / t, 80k when 3000kg / m ³
When a coke of g / t is charged into the furnace, the boundary radius between the scrap and the coke is obtained from the equation (1), and the dimensionless radii are about 0.75 to 1.0 (peripheral part) and 0.
The coke is charged in the area of 81 to 1.0 (peripheral portion). In the case of a cupola having a furnace diameter of 2 m, coke exists in regions of about 250 mm and 190 mm from the furnace wall portion, and scrap is charged inside and inside the center. When the coke ratio is 80 kg / t, the average particle size is 1
When using coke for casting of about 50 mm, 1 from the furnace wall
~ 2 pieces, when using coke with a particle size of about 60 mm,
When using fine coke having 3 to 5 pieces from the furnace wall and an average grain size of about 20 mm, this corresponds to a distance of about 9 to 10 pieces arranged from the furnace wall. For each coke ratio (CR), the dimensionless boundary radius of scrap and coke (R _S / R _t ) and furnace diameter 2 m
Width of coke from the furnace wall (Δr)
Is shown in Table 1.

[0016]

[Table 1]

The charging state of coke when the charging hopper shown in FIG. 6 is used in the charging system of FIG. 2 (b) will be described. The amount of coke charged into each hopper is determined based on the equation (2) from the number of charging hoppers and the coke ratio. For example, a moving bed with a furnace diameter of 2 m and 6 hoppers
In the case of individual pieces, when coke with a coke ratio of 120 kg / t and 80 kg / t is charged into the furnace, the coke charging area charged into each hopper is 0.22 from the formula (2).
It becomes 5m ² , 0.175m ² . When the charging surface is a semi-circular type, the tilting partition plate is adjusted so as to form a semi-circular charging part having a radius of 0.38 m and a radius of 0.33 m, respectively. In the case of a one-step tuyere moving bed, when the coke particle size charged in the peripheral area is large, the contact area between the gas and the coke is small and the reaction speed decreases, so only the peripheral charged coke of formula (3) The reaction does not end, and bed coke also participates in the reaction of formula (3). Therefore, the upper end position of the bed coke needs to be above the tuyere level. On the other hand, regarding the coke charged in the peripheral portion, when the fine grain coke is used, the combustion reaction of the equation (3) can be sufficiently dealt with by the fine grain coke in the peripheral portion. In this case, in order to reduce the reaction amount of the equation (4) and obtain high combustion efficiency, it is better to minimize the contact area between the gas and the bed coke.
If the reaction of equation (4) can be suppressed, it is desirable that the upper end of the coke bed be near the tuyere level. On the other hand, in the case of a moving bed with multi-stage tuyere, the exhaust gas combustion rate can be controlled in the upper tuyere, so the upper end position of the bed coke can be handled more flexibly than in the case with only one-stage tuyere. it can.

[0018]

EXAMPLES The features of the present invention will be specifically described with reference to the examples of Table 2 below. Hearth diameter 2m, 8 tuyeres, effective height 4.
A moving bed type melting furnace having a scale of 6 m and 20 t / h was used. This device has a two-stage tuyere structure with eight primary tuyere and four secondary tuyere. The charging device is a charging device of the type shown in FIG. 2A (hereinafter referred to as A charging device).
In the case of orienting the mold (b), the charging method shown in FIG. 5 is adopted, and four tiltable partition plates are installed in the circumferential direction, and the coke is 4
The coke was charged from one charging port to the primary tuyere (hereinafter referred to as B charging device). The B charging device has a structure in which the dimensionless radius R _S at the boundary between the large-sized scrap and the coke is set to 0.60 and the coke charging area is adjusted by the tiltable partition plate. The composition of the furnace top exhaust gas is η _CO ^(TOP) = (CO ₂ ^(TOP) / (CO ^(TOP)
+ CO ₂ ^(TOP) )). Further, in the case of the air blowing experiment with only the first stage tuyeres, the air blowing of the upper stage tuyeres was cut. Among the operational specifications, the blast humidity was 15 g / Nm ³ , and the limestone unit charged from the furnace top was 40 kg / t.

The comparative example is an ordinary cupola operation example, the comparative example 1 is a one-stage tuyere, a hot air blowing cupola of 500 ° C. is an operation example, and the comparative example 2 is a two-stage tuyere, a room temperature blowing cupola is an operating example. Yes, the die pig ratio or casting scrap iron ratio is 30
%, 60% operating specifications.

Example 1 is a one-stage tuyere of hot air blowing (500 ° C.), and the charging method is A type. When a coke for casting having a particle diameter of 150 mm is used, exhaust gas η _CO
^(TOP) can operate at a high level of 10 to 15%. In addition, even when using blast furnace coke having a particle size of 60 mm,
Exhaust gas η _CO ^(TOP) can be maintained at about 50%, and the improvement effect associated with efficiency improvement is large compared to η _CO ^(TOP) = 28% in the conventional operation. In the embodiment, the heat surplus and the fuel ratio can be reduced. Example 2 is an operation example in which a coke for casting having a particle diameter of 150 mm is used with a single-stage tuyere of normal temperature air blowing (25 ° C.). The charging method is B type. In the conventional charging method, in the case of normal temperature air blowing, the heat of melting was insufficient and operation was difficult.
In this operation, the type pig iron ratio was 0%, and when the steady state was reached, the coke ratio was 136 kg / t. From the formula (2), the partition plate was adjusted so that each of the four coke charging parts had a cross-sectional area of 0.363 m ² .
As a result, the exhaust gas η _CO ^(TOP) was maintained at 60% and stable operation was achieved, and the possibility of operation with a single-stage tuyere and room-temperature air blowing was confirmed.

Example 3 is an example in which room temperature air is blown, two-stage tuyeres are used, and an A type charging device is used. Coke grain size is 150m
Coke having m and an average particle size of 50 mm was used. Regarding the operation, the boundary position between scrap and coke is finely adjusted by the tilting of the partition plate by the exhaust gas η _CO , and the protruding position of the secondary tuyere is projected here so as to be as close as possible to the scrap and coke boundary part. 20 cm from the surroundings
Set to the position. Exhaust gas η depends on the air flow from the upper tuyeres
_CO was controllable, and in the example, it was possible to operate in the range of η _CO 65 to 90%. Η _CO in the normal two-stage tuyere operation shown in Comparative Example 2
In contrast to about 54%, in the embodiment, high η _CO ^(TOP) is possible, and the reduction of the die / pig ratio and the fuel ratio can be achieved. Example 4 is an example in which a room temperature blower, a two-stage tuyere, and a charging device of type B are used. This is an example of using blast furnace coke having a coke grain size of 60 mm. In this operation example, the operation was carried out at a mold pig ratio of 20% and the exhaust gas η _CO was 85%. Coke ratio is 109
The partition plate is adjusted so that the cross-sectional area of each of the four coke charging portions is 0.320 m ² from the formula (2). Compared to Comparative Example 2, despite the use of fine coke, a reduction in the pig iron ratio and a reduction in the fuel ratio were achieved.

[0022]

[Table 2]

[0023]

As described above, in the present invention, the use of fine coke, which has been difficult to use until now, has been improved by improving the method of charging raw materials such as scrap and coke into the moving bed type scrap melting furnace. In addition, it is possible to achieve high heat efficiency, a low fuel ratio, and a reduction in the mold pig ratio (cast iron ratio).

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a moving bed type scrap melting furnace according to the method of the present invention.

[Fig. 2] Schematic diagram showing scrap and coke charging method and tuyere installation site

[Fig. 3] Diagram showing the relationship between the peripheral coke particle size and the furnace top η _CO ^(TOP)

FIG. 4 is a diagram showing an example of a concept of a peripheral coke charging device.

FIG. 5 is a diagram showing an example of a concept of a peripheral coke charging device.

FIG. 6 is a diagram showing an example of a concept of a peripheral coke charging device.

[Explanation of symbols]

 1 Scrap 1a Fine grained scrap 2 Coke 3 Bed coke 4 Primary tuyere (lower stage tuyere) (installation site) 5 Secondary tuyere (upper stage tuyere) (installation site) 6 Tap hole 7 Scrap charging hopper 8 Coke Charge hopper 9 Fine grain scrap charge hopper 10 Coke charge feeder 11 Partition plate 12 Exhaust gas pipe

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[Procedure amendment]

[Submission date] January 17, 1994

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

[0016]

[Table 1]

Claims (6)

[Claims] 1. A method for charging a raw material into a moving bed type scrap melting furnace, characterized in that coke is charged into a peripheral portion of a furnace wall and scrap is charged into a central portion to an intermediate portion or from a central portion to a peripheral portion. . 2. When charging scrap and coke into a moving bed type scrap melting furnace with a radius of the furnace opening R _t , the radius R _s of the boundary between the two is determined based on the equation (1), and the center To R _s for charging scrap, and R _s to R _t for charging coke, and a method for charging raw materials into a moving bed type scrap melting furnace. R _s / R _t = {1 / (A + 1)} ^1/2 (1) where 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 ) ρ _S : scrap bulk density (kg / m ³ ) 3. A method of operating a moving bed type scrap melting furnace having multi-stage tuyere in the height direction, when the raw material charging method according to claim 1 or 2 is carried out, the tuyere located above is projected. A moving layer type scrap melting furnace operating method characterized in that the position is set closer to the center side than R _s (including the boundary) and air is blown. 4. When the raw material is charged into a moving bed type scrap melting furnace with a radius of the furnace mouth portion of R _t , coke is generated around the furnace wall where the primary tuyere exists based on the equation (2). A moving bed type scrap melting furnace characterized by determining the charging area, charging W _CR / n coke in the circumferential direction discontinuously at each coke charging port, and charging scrap to other parts. Method of charging raw materials to. S _CR = (A · πR _t ² ) / {(1 + A) * n} (2) where A = (W _CR / ρ _CR ) / (W _S / ρ _S ), where S _CR : coke Coke charging area per charging port (m ² ) n: Number of coke charging ports W _CR : Coke ratio (kg / t) W _S : Scrap ratio (kg / t) ρ _CR : Bulk density of coke (kg / m ³ ) ρ _S : Bulk density of scrap (kg / m ³ ) 5. A moving bed type scrap melting furnace having a multi-tiered tuyere in the height direction designed so that the upper tuyere position is not directly above the primary tuyere installation portion. For each coke charging hopper around the furnace wall, the coke charging area determined based on the coke charging method according to claim 4 is charged with a coke amount of W _CR / n, and scrapes are added to the other parts. The method of charging a raw material into a moving bed type scrap melting furnace according to claim 1, wherein the charging is performed. 6. The method for charging a raw material into a moving bed type scrap melting furnace according to claim 1, wherein the coke having an average particle diameter of 60 mm or less is charged.