JP2014189894A - Induction heating method for reduced iron and induction heating device for reduced iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the metallization of reduced iron while suppressing reduction in a production amount (ton/hour).SOLUTION: While rotating a storing body 501 whose inside is stored with reduced irons, AC power is fed to a coil 502 fitted to the outer circumference of the storing body 501. When the storing body 501 is rotated in this way, by the mutual contact among the three or more reduced irons, a closed circuit by the three or more reduced irons is formed, and also, the contact positions of the respective three or more reduced irons with the other reduced irons are made to move.

Description

  The present invention relates to an induction heating method for reduced iron and an induction heating apparatus for reduced iron, and is particularly suitable for heating reduced iron to increase the metallization rate of reduced iron.

Conventionally, reduced iron (DRI) is obtained by heat-treating an agglomerate obtained by mixing powdered iron oxide and powdered carbonaceous material using, for example, a rotary hearth furnace (RHF). : (Direct Reduced Iron)) is manufactured (see Patent Document 1).
When the metallization rate of the reduced iron produced in this way is increased, the melting time for producing the hot metal in the melting furnace in the subsequent process can be shortened. Thereby, the manufacturing amount [ton / hour] of hot metal can be increased, and hot metal can be manufactured cheaply.
Here, the metallization rate is expressed by the following equation (1).
Metallization rate [%] = {(metallic iron content in reduced iron) / (total iron content in reduced iron)} × 100 (1)
In the formula (1), the unit of metallic iron in the reduced iron and the total iron in the reduced iron may be any of [mass], [weight], and [volume] as long as they are the same.
Therefore, in order to increase the metallization rate of reduced iron, it is conceivable to increase the heating time in the rotary hearth furnace.

JP 2007-298202 A

However, if it does in this way, the processing time in a rotary hearth furnace will become long. For this reason, there exists a possibility that the manufacturing amount (ton / hour) of the reduced iron which raised the metallization rate may fall.
This invention is made | formed in view of such a problem, and it aims at enabling it to improve the metalization rate of reduced iron, suppressing the fall of a manufacturing amount (ton / hour).

  The induction heating method of reduced iron according to the present invention is an induction heating method of reduced iron that induction-heats reduced iron, and is provided on at least one of an outer peripheral surface and an inside of a housing portion that houses a plurality of the reduced irons inside When three or more reduced irons are brought into contact with each other when induction heating of a plurality of reduced irons housed in the housing part by applying alternating current power to the coils arranged on the coil, the three irons are brought into contact with each other. The plurality of reduced irons housed in the housing portion so that a closed circuit is formed by the reduced irons and the contact positions of the three or more reduced irons with the other reduced irons move. The position of the inside of the container is changed.

  An induction heating apparatus for reduced iron according to the present invention is an induction heating apparatus for reduced iron that induction-heats reduced iron, and includes a storage section that stores a plurality of the reduced irons, an outer peripheral surface of the storage section, and an A coil disposed for at least one of the coils, and a drive unit that drives the housing unit to change the position of the plurality of reduced irons in the housing body, and AC power is supplied to the coil. When the reduced iron is inductively heated, the three or more reduced irons contact each other to form a closed circuit with the three or more reduced irons, and the three or more reduced irons The position of the plurality of reduced iron accommodated in the accommodating portion is changed by the operation of the driving portion so that the contact position with each other reduced iron is in a moving state. .

  According to the present invention, when induction heating of a plurality of reduced irons, a closed circuit is formed by the three or more reduced irons when the three or more reduced irons come into contact with each other, and the three or more reduced irons are formed. The contact position of each iron with the other reduced iron was moved. Accordingly, the reduced iron can be induction-heated to a temperature equal to or higher than the temperature at which the reduction reaction occurs without welding the reduced iron. Therefore, the metallization rate of reduced iron can be improved while suppressing a decrease in production amount (ton / hour).

It is a figure (photograph) which shows an example of the mode of the cross section of reduced iron. It is a figure which shows notionally an example of the penetration depth of the eddy current which flows into one reduced iron. It is a figure which shows notionally an example of a mode that reduced iron welds. It is a figure which illustrates notionally that the metallization rate of reduced iron can be raised. It is a figure which shows an example of a structure of the induction heating apparatus of reduced iron. It is a figure which shows the 1st modification of a structure of the induction heating apparatus of reduced iron. It is a figure (plan view) showing the composition of the 1st modification of a coil. It is a figure which shows the 2nd modification of a structure of the induction heating apparatus of reduced iron. It is a figure which shows the analysis result of distribution of the magnetic field which generate | occur | produces in the induction heating apparatus of reduced iron when the coil shown in FIG. 5 is used. It is a figure which shows the analysis result of distribution of the magnetic field which generate | occur | produces in the induction heating apparatus of reduced iron when the coil shown to Fig.7 (a) is used. It is a figure which shows the analysis result of distribution of the magnetic field which generate | occur | produces in the induction heating apparatus of reduced iron when the coil shown in FIG.7 (b) is used. It is a figure which shows the analysis result of distribution of the magnetic field which generate | occur | produces in the induction heating apparatus of reduced iron when the coil shown in FIG. 8 is used.

(Knowledge obtained by the present inventors)
Prior to describing the embodiments of the present invention, the knowledge obtained by the present inventors will be described.
FIG. 1 is a diagram (photograph) showing an example of a cross section of reduced iron.
Shrinkage occurs during the process in which the agglomerates are heat treated in a rotary hearth furnace. As a result, pores are generated in the reduced iron as shown in FIG. In the rotary hearth furnace described above, the agglomerated material is generally heated using radiant heating by a burner. That is, in the rotary hearth furnace, the agglomerates and reduced iron are heated by heat transfer from the outside. Therefore, in a heating method using heat transfer such as a rotary hearth furnace, heat transfer is inhibited by the pores inside the reduced iron. For this reason, in the method of increasing the heating time in the rotary hearth furnace, the reduced iron cannot be heated efficiently, and it is easy to increase the production amount of reduced iron [ton / hour] with an increased metallization rate. is not.

  Therefore, the present inventors have examined a method for directly heating the reduced iron itself, rather than heating the reduced iron using external heat transfer. As such a method, a method by induction heating can be considered. Induction heating is to heat an object by an eddy current flowing through the object by applying a magnetic field generated by supplying AC power to the coil to the object (magnetic material).

FIG. 2 is a diagram conceptually illustrating an example of the penetration depth of eddy current flowing in one reduced iron.
In FIG. 2, when the temperature is equal to or lower than the Curie temperature (about 770 [° C.]), the reduced iron is a ferromagnetic substance, so that the eddy current penetration depth δ is small. Therefore, if the temperature is equal to or lower than the Curie temperature, the eddy current 201 can flow through the reduced iron.

On the other hand, when the temperature is equal to or higher than the Curie temperature, the reduced iron is a paramagnetic substance, so that the penetration depth δ of the eddy current increases. For this reason, in the reduced iron with a small magnitude | size, an eddy current cannot be sent through the inside and it cannot heat to temperature higher than Curie temperature.
Here, the temperature at which the reduction reaction occurs is about 950 [° C.], which is higher than the Curie temperature of the reduced iron. Therefore, for reduced iron with a small size, simply performing induction heating cannot increase the temperature of reduced iron to the temperature at which the reduction reaction occurs, and the metallization rate of reduced iron cannot be improved. .

The present inventors tried induction heating of reduced iron produced in a rotary hearth furnace based on the above knowledge.
Here, induction heating was attempted by filling a plurality of reduced irons manufactured in a rotary hearth furnace into a hollow cylindrical housing portion having a solenoid wound around the outer periphery. As a result, among the plurality of reduced irons after the test, there was one in which the reduced irons were welded together.
FIG. 3 is a diagram conceptually showing an example of a state in which reduced irons are welded together. A phenomenon in which such reduced iron is welded will be described with reference to FIG.
As described above, when reduced iron having a small size exists alone, the reduced iron cannot be heated to a temperature higher than the temperature at which the reduction reaction occurs by induction heating. On the other hand, as shown in FIG. 3, when three or more reduced irons 301a to 301f are in contact with each other so that a closed circuit is formed with the reduced irons in contact with each other, the magnetic field 302 generated in the gap between them An eddy current 303 flows through the reduced irons 301a to 301f and can be heated to a temperature higher than the temperature at which the reduction reaction occurs. However, since the electrical resistance of the contact portions 304a to 304f of the reduced irons 301a to 301f is large, if the contact position of the three or more reduced irons 301a to 301f does not change, the contact portion of the reduced irons 301a to 301f is caused by the eddy current 303. The calorific value in 304a-304f becomes large, and welding of reduced iron occurs.

As described above, in the reduced iron having a small size, the present inventors are in a state where three or more reduced irons are in contact with each other so that a closed circuit is formed by the reduced irons in contact with each other. It was found that when the iron contact position is maintained unchanged, the reduced iron can be heated to a temperature higher than the temperature at which the reduction reaction occurs by induction heating, but the reduced iron is welded.
From such knowledge, the present inventors reduced the reduced iron when the contact position of the reduced iron with other reduced iron moves and three or more reduced irons contact each other to form a closed circuit. The inventors have conceived the technical idea that reduced iron can be heated to a temperature higher than the temperature at which the reduction reaction occurs by induction heating without causing iron welding.

FIG. 4 shows that three or more reduced irons come into contact with each other to form a closed circuit with the three or more reduced irons, and each of the three or more reduced irons is in contact with another reduced iron. It is a figure which illustrates notionally that the metallization rate of the said reduced iron can be raised when it is set as the state which moves. In the following description, “three or more reduced irons in contact with each other so as to form a closed circuit” will be referred to as a “reduced iron group” as necessary.
FIG. 4A is a diagram conceptually illustrating an example of a reduced iron group. A double arrow line shown in FIG. 4A indicates that the reduced iron moves.

In FIG. 4A, as described with reference to FIG. 3, when induction heating is performed, an eddy current 402 flows inside the reduced iron group 401.
FIG. 4B and FIG. 4C are diagrams conceptually illustrating an example of a state before and after metallization of one reduced iron 401 a constituting the reduced iron group 401.
In the reduced iron 401a manufactured in the rotary hearth furnace, the surface side is a reduced portion 403 having a high metallization rate, whereas the central side is an unreduced portion 404 having a low metallization rate (see FIG. 4 (b)). According to the knowledge of the present inventors, the metallization rate of the reducing part 403 is about 90 [%], whereas the metallization rate of the unreduced part 404 is about 30 to 40 [%].

  Since the unreduced portion 404 has a larger electric resistance than the reducing portion 403, as shown in FIG. 4B, the eddy current 402 having a high current density flows through the reducing portion 403 (that is, around the unreduced portion 404). Thereby, the temperature of the unreduced part 404 rises, and the unreduced part 404 is metallized by a reduction reaction. Thereby, as shown in FIG.4 (c), the area | region of the unreduced part 404 reduces and the area | region of the reduction | restoration part 404 increases.

Here, the reduced iron group is difficult to be formed when the reduced iron is too small. Moreover, even if the reduced iron group is formed, it is difficult to form an eddy current having a high current density. Therefore, it is not easy to heat reduced iron whose size is too small to a temperature at which a reduction reaction occurs by induction heating.
On the other hand, in the case of reduced iron that is too large, as described above, eddy current flows inside the eddy current penetration depth δ even if it increases, so even if it exists alone (the aforementioned closed circuit is formed). If not, it can be heated to a temperature at which the reduction reaction takes place by induction heating.
From the above viewpoint, in the embodiment described below, the range of the diameter of reduced iron that is a target for improving the metallization rate (target of induction heating) is 5 [mm] to 100 [mm]. Here, the diameter of reduced iron means the maximum value of the distance between two points on the surface of reduced iron that face each other with the center of gravity of reduced iron.

  In addition, if the metallization rate of reduced iron before induction heating is too small, it is difficult to form eddy currents with a high current density, so that reduced iron is heated to a temperature at which a reduction reaction occurs by induction heating. Is not easy. From such a viewpoint, in the embodiment shown below, the metallization rate of reduced iron before performing induction heating is set to 40 [%] or more.

(Embodiment)
Based on the above findings, the present inventors have come up with an embodiment of the present invention. Hereinafter, an embodiment of the present invention will be described. In each figure, the x, y, and z coordinates represent the correspondence between the directions in each figure, and the origin of the x, y, and z coordinates is not limited to the position shown in each figure.
FIG. 5 is a diagram illustrating an example of a configuration of an induction heating apparatus for reduced iron. FIG. 5A is a diagram of the reduced iron induction heating device 500 viewed along a horizontal direction (x-axis direction) orthogonal to a direction (y-axis direction) in which reduced iron is conveyed. FIG. 5B is a view of the reduced iron induction heating apparatus 500 as viewed along the direction (y-axis direction) in which the reduced iron is conveyed.

In FIG. 5, the reduced iron induction heating device 500 includes an accommodating portion 501, a coil 502, a rotating portion 503, a supporting portion 504, a motor 505, and a gear 506.
Reduced iron is accommodated inside the accommodating portion 501.
The accommodating part 501 of this embodiment is demonstrated below.
The shape of the accommodating portion 501 is a hollow cylindrical shape. In addition, a heat insulating material is attached to the inner wall surface of the accommodating portion 501. Reduced iron produced in a rotary hearth furnace is conveyed from one end 501a of the opening portion of the accommodating portion 501 to the inside of the accommodating portion 501, and is induction-heated from the other end portion 501b of the opening portion of the accommodating portion 501. Reduced iron with an increased metallization rate is conveyed to a compression molding machine. HBI (Hot Briquetted Iron) is manufactured by a compression molding machine. In addition, you may remove the powder adhering to reduced iron, before conveying to a compression molding machine.

  As shown in FIG. 5A, the accommodating portion 501 is disposed such that its axis substantially coincides with the horizontal direction (y-axis direction). In order to facilitate the transport of the reduced iron, the axis of the accommodating part 501 is in the horizontal direction so that the one end 501a of the opening part of the accommodating part 501 is higher than the other end 501b. It may be inclined. If the angle formed between the axis of the housing part 501 and the horizontal direction is too large (too close to 90 °), the contact positions of the reduced irons that are in contact with each other inside the housing part 501 cannot be moved. It becomes easy to cause welding of reduced iron. From such a viewpoint, the angle formed by the axis of the accommodating portion 501 and the horizontal direction can be determined as appropriate.

  The coil 502 of the present embodiment is a solenoid wound around the outer peripheral surface of the housing portion 501. An AC power source is connected to both ends of the coil 502, and AC power is supplied from the AC power source to the coil. As a result, an AC magnetic field is generated inside the accommodating portion 501, and an eddy current can be caused to flow inside the reduced iron as described above. The coil 502 is attached to the outer peripheral surface of the housing portion 501 while being insulated from the housing portion 501. The number of turns of the coil 502 can be determined as appropriate according to the installation space of the coil 502, the target temperature of reduced iron, and the like.

  In the present embodiment, there are four rotating parts 503. One rotating portion 503 is disposed at each of the four corner positions of the bottom of the accommodating portion 501. The rotation shafts 511a to 511c of the rotation units 503a to 503c are in a direction (y-axis direction) substantially parallel to the axial direction of the storage units 501a to 503c. In FIG. 5, only three rotating parts 503a to 503c are shown, but rotating parts having the same configuration as the rotating parts 503a to 503c are also arranged in the remaining corners of the accommodating part 501 not shown in FIG. The

The rotating part 503 and the container 501 are in contact with each other, and the container 501 also rotates with its axial direction as the rotation axis as the rotating part 503 rotates.
A motor 505 is installed inside the support portion 504. The power from the motor 505 is transmitted to the rotating unit 503 via the gear 506, and all the rotating units 503a to 503c rotate in one direction (same direction). By rotating the rotating part 503 in this way, the accommodating part 501 also rotates in one direction with the axis as a rotation axis. As described above, in the present embodiment, the driving unit of the housing unit 501 is configured by using the rotating unit 503, the motor 505, and the gear 506. Further, the rotation direction of the housing portion 501 is determined by the rotation direction of the motor 505, and the rotation speed (rotational speed) of the storage portion 501 is determined by the rotation speed of the motor 505.

In the present embodiment, the movement of the reduced iron inside the storage unit 501 is determined according to the space factor of the reduced iron in the storage unit 501 and the rotation speed of the storage unit 501.
First, as the space factor of reduced iron in the accommodating portion 501 decreases, it becomes more difficult for three or more reduced irons to contact each other so as to form a closed circuit. On the other hand, as the space factor of the reduced iron in the housing portion 501 increases, it becomes easier to maintain a state where the contact position of the reduced iron with other reduced iron does not change. Moreover, when the space factor of the reduced iron in the accommodating part 501 becomes large, the accommodating part 501 may not be able to be rotated depending on the ability of the drive part such as the motor 505.

Further, as the rotational speed of the accommodating portion 501 increases, it becomes more difficult for three or more reduced irons to contact each other so as to form a closed circuit. On the other hand, the slower the rotational speed of the accommodating portion 501, the easier it is to maintain a state where the contact position of the reduced iron with other reduced iron does not change.
In the present embodiment, from the above viewpoint, three or more reduced irons contact each other to form a closed circuit by the three or more reduced irons, and each of the three or more reduced irons. The range (upper and lower limits) of the reduced iron space factor in the housing part 501 and the rotational speed range (upper and lower limits) of the housing part 501 are appropriately determined so that the position of contact with the other reduced iron is moved. Is done.

Next, the result of induction heating of reduced iron using the reduced iron induction heating apparatus 500 of the present embodiment will be described.
Here, reduced iron induction heating apparatus 500 was configured and operated as follows.
Length in the axial direction L1 = 300 [mm] of the area where the reduced iron is accommodated
The axial length L2 of the area around which the coil 502 is wound L2 = 250 [mm]
Number of turns of coil 502 = 8 [Turn]
Electric power applied to the coil 502 = 6 kW [W], 26.5 [kHz]
Inner diameter D of housing portion 501 = 100 [mm]
Space factor of reduced iron in the housing unit 501 = 100 [%]
Reduced iron diameter = 10 [mm] to 30 [mm]
Number of rotations of motor 505 = 6 [rpm]
Heating time = 30 [min]

In addition, the accommodating part 501 was arrange | positioned so that an axial direction might correspond substantially with a horizontal direction. In addition, the coil 502 is attached to the outer peripheral surface of the housing portion 501 so that the axial center of the coil 502 and the axial center of the housing portion 501 substantially coincide with each other. Further, a heat insulating material was arranged in the region so that the reduced iron would not move to a region inside the container 501 and outside the both ends of the length L1 shown in FIG.
Table 1 shows the components and metallization ratio of the reduced iron stored in the storage unit 501 before heating.

Numbers 1 to 4 in Table 1 show results obtained by sampling and measuring reduced iron having a diameter of about 20 [mm] to 30 [mm] from reduced iron manufactured in a rotary hearth furnace. 10 shows the result of having sampled and measured the reduced iron which has a diameter of about 10 [mm]-20 [mm] from the reduced iron similarly manufactured with the rotary hearth furnace.
“T-Fe”, “M-Fe”, “FeO”, “Fe ₂ O ₃ ”, and “C” in Table 1 represent components contained in reduced iron, and are shown in these columns. The numbers represent mass% [wt%]. “M / T” represents a metallization rate [%]. “Ave” is the arithmetic average value [%] of the metallization rate shown in the column of “M / T”. The metalization rate of the reduced iron before heating is determined by the value shown in the “ave” column and the weight ratio of each reduced iron. Specifically, the weight ratio of the reduced irons of Nos. 1 to 4 was 41 [%], and the weight ratio of the reduced irons of Nos. 5 to 10 was 59 [%]. The rate was about 75.5 [%] (≈0.41 × 72 + 0.59 × 78).

  Table 2 is a figure which shows the result of having heated the above reduced iron on the conditions mentioned above. Table 2 shows the results of sampling and measuring reduced iron after heating from the three regions inside the ends of the length L2 shown in FIG. Each item in Table 2 is the same as the item shown in Table 1.

  From Tables 1 and 2, by using the reduced iron induction heating apparatus 500 of this embodiment, the metallization rate can be improved by 10 [%] or more by heat treatment of about 30 [min]. It can be seen that the metalization rate on the center side of the reduced iron, which is difficult to heat in a short time by the heat method, can be increased. As described above, the reduced iron before heating has a low metalization rate on the center side and a high metalization rate on the surface side. Therefore, the metallization rate shown in Table 1 and Table 2 shows the average metallization rate in the whole inside of reduced iron.

  As described above, in the present embodiment, AC power is supplied to the coil 502 attached to the outer peripheral surface of the container 501 while rotating the container 501 in which reduced iron is accommodated. Thus, when rotating the container 501, three or more reduced irons come into contact with each other to form a closed circuit by the three or more reduced irons, and each of the three or more reduced irons Make the contact position with other reduced iron move. Thereby, an eddy current can be generated in reduced iron and induction iron can be induction-heated to the temperature more than the temperature which raise | generates a reductive reaction. In induction heating, such reduced iron is directly heated, so that reduced iron can be heated more efficiently than when reduced iron is heated by heat transfer from the outside. Therefore, the metallization rate of reduced iron can be improved, suppressing the fall of manufacturing amount (ton / hour).

  In addition, if it moves so that the contact position with the other reduced irons of three or more reduced irons which comprise a reduced iron group may change, reduced iron will contact any reduced iron before and after a movement. Good. That is, in FIG. 4 (a), in order to simplify the explanation, the case where the positional relationship of three or more reduced irons constituting the reduced iron group does not change is shown as an example. The positional relationship between three or more reduced irons constituting the iron group may change. Thus, if it moves so that the contact position with the other reduced iron of three or more reduced irons which comprise a reduced iron group may change, three or more reduced irons which comprise a reduced iron group with progress of time. The positional relationship of may or may not change.

  Further, when three or more reduced irons come into contact with each other, a closed circuit is formed by the three or more reduced irons, and the contact position of each of the three or more reduced irons with each other reduced iron moves. Most preferably, the state is formed of all reduced iron inside the container 501. However, such a state does not necessarily need to be formed of all reduced iron inside the container 501. For example, the arithmetic average value of the metallization rate after heating of the plurality of reduced irons is 5% or more larger than the arithmetic average value of the metallization rate before heating of the plurality of reduced irons, and the storage unit 501 When the volume ratio of the reduced iron being welded among all the reduced iron accommodated is 5 [volume%] or less, such a state is generally formed inside the container 501. Can be considered. Therefore, what is necessary is just to determine the space factor of the reduced iron in a container, the rotation speed of the container 501 etc. so that such conditions may be satisfy | filled.

(Modification)
<Modification 1>
In the present embodiment, the case where the coil 502 is a solenoid has been described as an example. However, the coil 502 is not limited to a solenoid.
[Modification 1-1]
FIG. 6 is a diagram illustrating a first modification of the configuration of the induction heating apparatus for reduced iron. FIG. 6A is a view of the reduced iron induction heating device 600 viewed along a horizontal direction (x-axis direction) orthogonal to a direction (y-axis direction) in which reduced iron is conveyed. It is a figure corresponding to a). FIG. 6B is a view of the reduced iron induction heating device 600 viewed along the direction (y-axis direction) in which the reduced iron is conveyed, and corresponds to FIG.

The reduced iron induction heating apparatus 600 of this modification is obtained by replacing the coil 502 of the reduced iron induction heating apparatus 500 shown in FIG. 5 with coils 602a and 602b. The rest of the configuration of the reduced iron induction heating apparatus 600 of this modification is the same as that of the reduced iron induction heating apparatus 500 shown in FIG.
FIG. 7 is a diagram (plan view) showing a configuration of a first modification of the coils 602a and 602b. Fig.7 (a) is a figure which shows the 1st example of the shape of coil 602a, 602b, and FIG.7 (b) is a figure which shows the 2nd example of the shape of coil 602a, 602b.

  In FIG. 6, the two coils 602 a and 602 b are the same and are arranged in the same direction along the axial direction (y-axis direction) of the container 501. As shown in FIG. 6A, the coil surfaces of the coils 602 a and 602 b are curved so as to be substantially parallel to the lower half area of the outer peripheral surface of the container 501. In the example shown in FIG. 7, the coils 602 a and 602 b are curved along the outer peripheral surface of the container 501 so that the broken line portion shown in FIG. Such coils 602 a and 602 b are arranged with respect to the lower half region of the outer peripheral surface of the container 501.

  In the example shown in FIG. 7A, the winding directions of the coils 602a and 602b are the same direction. Specifically, in the example shown in FIG. 7A, the winding direction of the coils 602a and 602b is clockwise toward the paper surface. On the other hand, in the example shown in FIG. 7B, the winding direction of the coils 602a and 602b is different between the outermost part and the other part. Specifically, in the example shown in FIG. 7B, the coils 602a and 602b are folded back at the outermost periphery, and the winding direction of the outermost periphery of the coils 602a and 602b is clockwise toward the paper surface. On the other hand, the winding direction of the other portions is counterclockwise toward the paper surface. The arrow lines shown in FIGS. 7A and 7B indicate the direction of current flow at a certain timing. Thus, the directions of the currents flowing through the coils 602a and 602b are reversed so that the magnetic fields generated from the coils 602a and 602b mutually intensify.

[Modification 1-2]
FIG. 8 is a diagram showing a second modification of the configuration of the induction heating apparatus for reduced iron. FIG. 8A is a view of the reduced iron induction heating device 800 viewed along a horizontal direction (x-axis direction) orthogonal to the direction (y-axis direction) in which reduced iron is conveyed. It is a figure corresponding to a). FIG. 8B is a view of the reduced iron induction heating apparatus 800 as viewed along the direction (y-axis direction) in which the reduced iron is conveyed, and corresponds to FIG.
In the induction heating apparatus 500 for reduced iron shown in FIG. 5, the case where the coil 502 is arranged on the outer peripheral surface of the container 501 has been described as an example. On the other hand, in this modification, as shown in FIG. 8, a coil 802 is disposed inside the container 501. Specifically, in a state in which the coil 802 is insulated from the winding shaft portion 801 with respect to the cylindrical winding shaft portion 801 disposed inside the housing 501 so as to be substantially coaxial with the axis of the housing 501. It is wound and becomes a solenoid. The winding shaft portion 801 is preferably made of a ferromagnetic material. In addition, the coil 802 is provided with an insulating coating on the surface thereof so as not to be damaged by contact with the reduced iron. Other configurations of the reduced iron induction heating device 800 of this modification are the same as those of the reduced iron induction heating device 500 shown in FIG.

[Results of magnetic field analysis when each coil is used]
9 to 12 show the analysis results of the distribution of the magnetic field generated in the induction heating apparatus for reduced iron when the coils shown in FIGS. 5, 7 (a), 7 (b), and 8 are used, respectively. FIG. More specifically, FIG. 9 shows the distribution of the magnetic field when viewed from the AA direction in FIG. 10A and 11A show the distribution of the magnetic field when viewed from the AA direction in FIG. 6A, and FIGS. 10B and 11B show the distribution of FIG. The distribution of the magnetic field when seen from the BB direction of b) is represented. FIG. 12 shows the distribution of the magnetic field when viewed from the BB direction of 鵜 8 (b).
Here, electromagnetic field analysis was performed under the same conditions except for the coil.

  First, from the results of FIGS. 8 and 12, the lower half of the interior of the container 501 in which reduced iron exists, regardless of whether the coil is disposed outside the container 501 or inside the container 501. The magnetic flux density does not change significantly. Therefore, by adjusting the number of turns of the coil, it can be understood that the same effect can be obtained regardless of whether the coil is disposed on the outer peripheral surface of the housing portion 501 or the inside of the housing portion 501. . Note that, for example, both the coils 502 and 802 may be used to arrange the coils on both the outer peripheral surface and the inside of the housing portion 501.

  Further, from the results of FIGS. 9, 10B and 11B, the coil surface is the outer peripheral surface of the lower half of the housing portion 501 rather than the coil being a solenoid (see FIGS. 5 and 9). The magnetic flux in the lower half region inside the container 501 where reduced iron is present is configured such that the coil is configured so as to face the coil (see FIGS. 7, 10B, and 11B). It can be seen that the density can be increased.

  Further, as shown in FIG. 7 (b), by making the winding direction of the relatively outer peripheral portion relatively opposite to the winding direction of the inner peripheral portion, as shown in FIG. In particular, the magnetic field generated from the outer peripheral portion can push back the magnetic field generated relatively from the inner peripheral portion in the direction of the coil surface. Thus, from the results of FIGS. 10 and 11, when the coil is configured and arranged so that the coil surface faces the outer peripheral surface of the lower half of the housing portion 501, the winding of the portion on the outer peripheral side is relatively performed. When the direction is relatively opposite to the winding direction of the inner peripheral portion (see FIGS. 7B and 11), the winding direction is the same (FIGS. 7A and 10). It can be seen that the magnetic flux density in the lower half region inside the container 501 where the reduced iron is present can be further increased.

<Modification 2>
In the present embodiment, the case where the container 501 is rotated in the same direction by 360 ° has been described as an example. However, when three or more reduced irons come into contact with each other, a closed circuit is formed by the three or more reduced irons, and the contact position of each of the three or more reduced irons with each other reduced iron moves. This is not always necessary as long as it is in a state.
For example, the angle at which the container 501 is rotated may be less than 360 °, and the direction of rotation / rotation may be changed over time. Further, the container 501 may be swung. Furthermore, the container 501 has a screw-like stirring bar that rotates coaxially with the axis of the container 501 inside the container 501, and the stirring bar is rotated (driven) by a motor without moving the main body of the container 501. You may make it make it.

<Modification 3>
In the present embodiment, the case where reduced iron manufactured in a rotary hearth furnace is induction-heated and the reduced iron subjected to induction heating is compression-molded by a compression molding machine is described as an example. However, this is not necessarily required if reduced iron having the above-described conditions is to be heated.

  It should be noted that the embodiments of the present invention described above are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. Is. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

401 Reduced iron group 402 Eddy current 403 Reduced part 404 Unreduced part 500, 600, 800 Reduced iron induction heating device 501 Housing part 502, 602, 802 Coil 503 Rotating part 504 Supporting part 505 Motor 506 Gear

Claims (4)

A method for induction heating of reduced iron by induction heating of reduced iron,
A plurality of reduced irons housed in the housing part by applying AC power to the coil disposed on at least one of the outer peripheral surface and the inside of the housing part that houses the plurality of reduced irons When the three or more reduced irons come into contact with each other, a closed circuit is formed by the three or more reduced irons, and each of the three or more reduced irons A method for induction heating of reduced iron, wherein the positions of the plurality of reduced irons housed in the housing part are changed so that the contact position of the iron is moved. The reduced iron has a diameter in the range of 5 [mm] to 100 [mm],
The method for induction heating of reduced iron according to claim 1, wherein a metallization rate of the reduced iron before the induction heating is 40% or more. An induction heating apparatus for reduced iron for induction heating of reduced iron,
An accommodating portion for accommodating a plurality of the reduced irons therein;
A coil disposed with respect to at least one of the outer peripheral surface and the inside of the housing portion;
A drive unit that drives the housing unit to change the position of the plurality of reduced irons inside the housing body,
When the reduced iron is inductively heated by applying AC power to the coil, the three or more reduced irons contact each other to form a closed circuit with the three or more reduced irons, and the 3 The position of the plurality of reduced iron accommodated in the accommodating portion in the container so that the contact position of each of the two or more reduced irons with the other reduced iron is in a state of moving, An induction heating apparatus for reduced iron, which is changed by driving the housing. The reduced iron has a diameter in the range of 5 [mm] to 100 [mm],
4. The reduced iron induction heating apparatus according to claim 3, wherein a metallization ratio of the reduced iron before the induction heating is 40% or more. 5.

Images