Mobile hearth furnace and heating method

Abstract

To provide a mobile hearth furnace that can heat a larger quantity of material to be heated. [Solution] The mobile hearth furnace 1 comprises a mobile hearth 10 on which an object to be heated 3 is placed and moves, a furnace body 20 arranged along the mobile hearth 10 and having a heating space 5 on which the object to be heated 3 placed on the mobile hearth 10 is heated, and a microwave introduction space 6 which is a space along the heating space 5 into which microwaves generated by a microwave generator 40 are introduced, and a partition member 30 that separates the heating space 5 and the microwave introduction space 6 and has microwave transparency.

Description

Technical Field

[0001] The present invention relates to a moving hearth furnace and a method for heating an object to be heated in the moving hearth furnace.

Background Art

[0002] Conventionally, a rotary kiln has been used to uniformly bake an object to be heated, such as ore, while stirring it. When baking an object to be heated while stirring it, there is a problem that a large amount of dust is generated. In order to suppress the generation of such dust, in a moving hearth furnace such as a rotary hearth furnace, baking of an object to be heated using a burner is also performed.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, in a moving hearth furnace using a burner, only the surface can be heated, and it is necessary to thinly spread the object to be heated for heating, and there is a problem that it is difficult to heat a large amount of the object to be heated.

[0004] The present invention has been made in view of such problems, and an object thereof is to provide a moving hearth furnace and a heating method for enabling heating of a larger amount of an object to be heated.

Means for Solving the Problems

[0005] In order to achieve the above object, a moving hearth furnace according to an aspect of the present invention includes a moving hearth that moves with an object to be heated placed thereon, and a furnace body disposed along the moving hearth, the furnace body having an internal heating space in which the object to be heated placed on the moving hearth is heated, and a microwave introduction space that is a space along the heating space and into which microwaves generated by a microwave generator are introduced, and a partition member that partitions the heating space and the microwave introduction space and has microwave permeability.

[0006] Furthermore, in a mobile hearth furnace according to one aspect of the present invention, the partition member may partially absorb microwaves and partially transmit them to the heating space.

[0007] Furthermore, in a mobile hearth furnace according to one aspect of the present invention, a heat insulating material may be provided on the side of the partition member facing the microwave introduction space.

[0008] Furthermore, in a mobile hearth furnace according to one aspect of the present invention, the furnace body is divided into a plurality of zones along the direction of movement of the object to be heated, and at least one of the plurality of zones may further include a discharge mechanism located on the downstream side in the direction of movement of the object to be heated, for discharging gas generated in the heated space of the zone.

[0009] Furthermore, in a mobile hearth furnace according to one aspect of the present invention, the microwave introduction space is located above the heating space, and the horizontal length of the heating space may be longer than the vertical length of the heating space in a plane perpendicular to the direction of movement of the object to be heated.

[0010] Furthermore, in a mobile hearth furnace according to one aspect of the present invention, the mobile hearth may be a rotating hearth.

[0011] Furthermore, a mobile hearth furnace according to one aspect of the present invention may further include one or more microwave generators that generate microwaves to be introduced into the microwave introduction space.

[0012] Furthermore, a mobile hearth furnace according to one aspect of the present invention comprises a mobile hearth on which an object to be heated is placed and moves, a furnace body arranged along the mobile hearth, into which microwaves generated by a microwave generator are introduced and the object to be heated placed on the mobile hearth is heated, and a pincushion circuit arranged in the gap between the mobile hearth and the furnace body.

[0013] Furthermore, in a movable hearth furnace according to one aspect of the present invention, the pincushion circuit has a plurality of needle-shaped members, and each needle-shaped member of the pincushion circuit may be arranged so that its longitudinal direction is perpendicular to the surface facing it.

[0014] Furthermore, a heating method according to one aspect of the present invention is a method for heating an object to be heated in a mobile hearth furnace, wherein, within the furnace body of the mobile hearth furnace, a heating space in which the object to be heated is heated and a microwave introduction space, which is a space along the heating space in which microwaves are introduced, are separated by a microwave-transparent partition member, and the method includes the steps of moving a mobile hearth on which the object to be heated is placed in the heating space, and heating the object to be heated by introducing microwaves into the microwave introduction space and irradiating it with microwaves. [Effects of the Invention]

[0015] According to one aspect of the present invention, a mobile hearth furnace and heating method can be used to heat an object using microwaves in the mobile hearth furnace, enabling the heating of a larger quantity of the object. [Brief explanation of the drawing]

[0016] [Figure 1] A schematic diagram showing the external appearance of a mobile hearth furnace according to an embodiment of the present invention. [Figure 2] A schematic vertical cross-sectional view showing the internal structure of a mobile hearth furnace according to the same embodiment. [Figure 3] A schematic vertical cross-sectional view showing the internal structure of a mobile hearth furnace according to the same embodiment. [Figure 4] Figure showing the discharge mechanism in the same embodiment. [Figure 5] A diagram showing the air supply mechanism in the same embodiment. [Figure 6] A schematic cross-sectional view showing another example of the internal structure of a movable hearth furnace according to the same embodiment. [Figure 7] A schematic cross-sectional view showing another example of the internal structure of a movable hearth furnace according to the same embodiment. [Figure 8] A schematic cross-sectional view showing another example of the internal structure of a movable hearth furnace according to the same embodiment. [Figure 9] A schematic cross-sectional view showing another example of the internal structure of a movable hearth furnace according to the same embodiment. [Figure 10] Vertical cross-sectional schematic view showing another example of the internal structure of the moving hearth furnace according to the embodiment [Figure 11] Vertical cross-sectional schematic view showing another example of the internal structure of the moving hearth furnace according to the embodiment

Embodiment for Implementing the Invention

[0017] Hereinafter, the moving hearth furnace and heating method according to the present invention will be described using embodiments. In the following embodiments, components denoted by the same reference numerals are identical or corresponding, and repeated descriptions may be omitted. The moving hearth furnace according to the present embodiment has, inside the furnace body, a heating space where the object to be heated is heated and a microwave introduction space where microwaves are introduced, which are partitioned by a partition member having microwave permeability. The object to be heated on the moving hearth that is moved in the heating space is heated by the microwaves propagated from the microwave introduction space through the partition member into the heating space.

[0018] FIG. 1 is a schematic view showing the appearance of the moving hearth furnace 1 according to the present embodiment, and FIGS. 2 and 3 are vertical cross-sectional schematic views showing the internal structure of the moving hearth furnace 1. In FIG. 2, a vertical cross-section perpendicular to the moving direction of the object to be heated 3 in the moving hearth furnace 1 is shown, and in FIG. 3, a vertical cross-section along the moving direction of the object to be heated 3 in the moving hearth 10 is shown. In FIGS. 1 and 3, the microwave generator 40 and the waveguide 41 are omitted. In the present embodiment, the case where the moving hearth furnace 1 is a rotary hearth furnace in which the moving hearth 10 moves annularly in a horizontal plane will be mainly described. When the moving hearth furnace 1 is a rotary hearth furnace, the circumferential direction of the annular rotary hearth furnace may be simply referred to as the circumferential direction, and its radial direction may be simply referred to as the radial direction.

[0019] The moving hearth furnace 1 includes a moving hearth 10 that moves with the object to be heated 3 placed thereon, a furnace body 20 arranged along the moving hearth 10, and a partition member 30 that divides the interior of the furnace body 20 into a heating space 5 and a microwave introduction space 6. As required, there are a heat insulating material 24 and a refractory material 25 arranged on the inner surface of the furnace body 20 surrounding the heating space 5, a heat insulating material 31 arranged on the microwave introduction space 6 side of the partition member 30, one or more microwave generators 40 that generate microwaves introduced into the microwave introduction space 6, one or more waveguide pipes 41 for introducing the microwaves generated by the one or more microwave generators 40 into the furnace body 20, a partition wall 50 that divides the interior of the furnace body 20 into a plurality of zones Z1 to Z6 along the moving direction of the object to be heated 3, an introduction part 51 for introducing the object to be heated 3 into the furnace body 20, a leveler 52 for flattening the object to be heated 3 placed on the moving hearth 10, an exhaust mechanism 53 for discharging the gas generated in the furnace body 20, an air supply mechanism 54 for supplying air into the furnace body 20, a needle mountain circuit 55 for preventing the propagation of microwaves between adjacent zones, and a lead-out part 56 for leading out the object to be heated 3 from the furnace body 20. In this embodiment, as an example, the case where the moving hearth 10 moves in the direction indicated by the arrow in FIG. 1 inside the furnace body 20 will be described, but the moving direction of the moving hearth 10 may be the reverse. Regarding the plurality of zones Z1 to Z6, the upstream side in the moving direction of the object to be heated 3 may be referred to as the front stage, and the downstream side may be referred to as the rear stage.

[0020] The object to be heated 3 is not particularly limited as long as it is an object to be heated by microwave irradiation. For example, it may be ore, ceramics, etc. The ore may be, for example, ore such as iron, nickel, or manganese. Also, the heating of the object to be heated 3 may be performed, for example, to bake the object to be heated 3. Further, the object to be heated 3 may contain a reducing agent such as coal or coke, for example. The heating temperature of the object to be heated 3 is not particularly limited. For example, the object to be heated 3 may be heated to a temperature of about 500°C to 1200°C by microwave irradiation.

[0021] The movable hearth 10 may also be a rotating hearth. This embodiment will mainly describe this case. The movable hearth 10, which is a rotating hearth, may have, for example, an annular hearth 11, running wheels 12 fixed to the lower surface of the hearth 11, and a driving means (not shown) for rotating the hearth 11. This embodiment will mainly describe the case in which the movable hearth 10 rotates as the running wheels 12 travel on rails arranged in an annular shape, but the mechanism for supporting the movable hearth 10 so that it can rotate is not limited to this. For example, the rail may be fixed to the lower surface of the movable hearth 10, and the movable hearth 10 may rotate as the rail moves on rollers. The driving means may rotate the movable hearth 10 by, for example, rotating a rotating roller that is in contact with the movable hearth 10.

[0022] As an example, the hearth 11 may have a base 111, an insulating material 112 placed on the base 111, and a refractory material 113 placed on the insulating material 112, as shown in Figure 2.

[0023] The base 111 may be, for example, a plate-shaped member extending in the circumferential direction. More specifically, the base 111 may be an annular shape of a disc with a predetermined thickness, with the center hollowed out in a concentric manner. The radial width of the base 111 may be, for example, about the same as the radial width of the opening on the lower side of the furnace body 20. In order to prevent microwaves from leaking to the outside of the furnace body 20 through the hearth 11, the base 111 may, for example, be non-transparent to microwaves. In this case, the base 111 may, for example, be microwave reflective. The microwave reflective material is not particularly limited, but may be a metal such as stainless steel, carbon steel, nickel, nickel alloy, copper, or copper alloy.

[0024] The thermal insulation material 112 has thermal insulation properties. The thermal insulation material 112 may also have microwave permeability. For example, the thermal insulation material 112 may have the same shape as the base 111 in a plan view. The thermal insulation material 112 may be, for example, a member arranged in an annular shape with a predetermined thickness on the upper surface of the base 111. The thermal insulation material 112 having thermal insulation properties and microwave permeability may be, for example, thermal insulation bricks, or a member made of a material containing alumina. By having the thermal insulation material 112 in the hearth 11, heat transfer from the inside to the outside of the furnace body 20 through the hearth 11 can be suppressed, and the heating efficiency in the heating space 5 can be improved.

[0025] The refractory material 113 has heat resistance. Preferably, the refractory material 113 has heat resistance that can withstand the temperature of the heated object 3 heated by microwave irradiation, for example. The refractory material 113 may, for example, have microwave transparency, or it may partially absorb and partially transmit microwaves. For example, the refractory material 113 may have the same shape as the base 111 in a plan view. For example, the refractory material 113 may be a member arranged in an annular shape with a predetermined thickness on the upper surface of the heat insulating material 112. For example, the refractory material 113 may be a refractory brick, or it may be a member made of a material containing silicon nitride. For example, the material containing silicon nitride may be silicon nitride-containing SiAlON. Since there are refractory bricks and silicon nitride-containing members that have microwave transparency, or that partially absorb and partially transmit microwaves, it is preferable to use a refractory material 113 that has the desired microwave transmission characteristics. If the refractory material 113 partially absorbs and partially transmits microwaves, for example, the temperature difference between the object to be heated 3 and the refractory material 113 can be reduced, and the heating of the object to be heated 3 by microwave irradiation can be further promoted. Therefore, it is preferable that the refractory material 113, which has microwave absorption properties, has microwave absorption properties to the extent that the temperature difference between the object to be heated 3 and the refractory material 113 can be reduced.

[0026] The furnace body 20 is positioned along the movable hearth 10. Therefore, if the movable hearth 10 is a rotating hearth, the furnace body 20 is also positioned in a concentric ring shape with the movable hearth 10. The furnace body 20 may have, for example, an inner side wall 21, an outer side wall 22, and a ceiling 23 connecting the upper ends of the side walls 21 and 22, which are positioned to surround the movable hearth 10. To prevent microwaves from leaking from inside the furnace body 20 through the side walls 21, 22 and the ceiling 23, it is preferable that the side walls 21, 22 and the ceiling 23 are not permeable to microwaves. In this case, the side walls 21, 22 and the ceiling 23 may, for example, have microwave reflectivity. Microwave reflectivity materials may be, for example, those described above.

[0027] The furnace body 20 has a heating space 5 in which the object to be heated 3, placed on the movable hearth 10, is heated, and a microwave introduction space 6 along the heating space 5. The microwave introduction space 6 is the space into which microwaves generated by the microwave generator 40 are introduced. The heating space 5 and the microwave introduction space 6 are separated by a partition member 30. In this embodiment, the case in which the microwave introduction space 6 is located above the heating space 5 will be mainly described, and the case in which it is not located will be described later. When the microwave introduction space 6 is located above the heating space 5, for example, as shown in Figure 2, the horizontal length W1 of the heating space 5 in a plane perpendicular to the direction of movement of the object to be heated 3 may be longer than the vertical length H1 of the heating space 5. With this configuration, microwaves can be propagated more easily from the microwave introduction space 6 to the heating space 5, and the volume of the heating space 5 can be reduced by suppressing the height of the heating space 5, making it possible to heat the object to be heated 3 more efficiently. When the object to be heated 3 is heated, the heating space 5 is normally at atmospheric pressure.

[0028] In the furnace body 20, the heating space 5 may be surrounded, for example, by side walls 21 and 22, a partition member 30, and a hearth 11. If insulating material 24 and refractory material 25 are placed on the inner surface of the furnace body 20, the heating space 5 may be further narrowed in accordance with the insulating material 24 and refractory material 25. In addition, to prevent atmospheric gas or heat in the heating space 5 from leaking to the outside, water seal troughs (not shown) may be provided in the gaps between the movable hearth 10 and the side walls 21 and 22. In addition, to prevent microwaves from leaking to the outside of the furnace body 20, microwave leakage prevention mechanisms may be provided in these gaps. The microwave leakage prevention mechanism may be, for example, a pincushion circuit. In addition, in the furnace body 20, the microwave introduction space 6 may be surrounded, for example, by side walls 21 and 22, a ceiling 23, and a partition member 30.

[0029] At least one of, for example, an insulating material 24 and a refractory material 25 may be attached to the inner surface of the furnace body 20 surrounding the heating space 5. For example, the insulating material 24 and the refractory material 25 may each have properties similar to those of the insulating material 112 and the refractory material 113. By placing the insulating material 24 on the inner surface of the furnace body 20, heat transfer from the heating space 5 to the outside of the furnace body 20 can be suppressed. In addition, for example, insulating material may also be attached to the outer surface of the furnace body 20.

[0030] Within the furnace body 20, microwaves reside in the region enclosed by the furnace body 20 and the hearth 11. Therefore, it is preferable to determine the size of the inside of the furnace body 20 using simulations or other methods to prevent localized concentration of microwaves. Furthermore, while a smaller volume of the heating space 5 allows for more efficient heating of the object to be heated 3, if the volume is too small, dust and other particles may be more easily generated from the object to be heated 3 in response to gas exhaust by the exhaust mechanism 53 and air supply by the air supply mechanism 54. For this reason, the size of the heating space 5 may be determined to have a volume large enough to suppress the generation of such dust and other particles.

[0031] The partition member 30 is a member that separates the heating space 5 and the microwave introduction space 6. Since the partition member 30 faces the heating space 5 where the object to be heated 3 is heated, it is preferable that it also has heat resistance. The heat resistance is preferably such that it can withstand the temperature of the object to be heated 3 heated by microwave irradiation. The partition member 30 has microwave permeability. The partition member 30 may, for example, partially absorb microwaves and partially transmit them to the heating space 5 side. The partition member 30 may be, for example, a plate-shaped member extending in the circumferential direction. If the inside of the furnace body 20 is divided into a plurality of zones Z1 to Z6 by partition walls 50, a partition member 30 may be placed in each zone. In this case, the shape of a single partition member 30 may be a circular annular shape with a predetermined thickness, where the center is hollowed out in a concentric circle, and the annular shape is divided into a plurality of parts in the circumferential direction. The partition member 30 may be supported, for example, by protrusions 21a and 22a that protrude from the inner surfaces of the side walls 21 and 22, respectively, within the furnace body 20. The partition member 30 is preferably positioned between the heating space 5 and the microwave introduction space 6 so that gas cannot move between them. The heat-resistant partition member 30 may have properties similar to those of the refractory material 113 described above.

[0032] The thermal insulation material 31 may be placed on the side of the partition member 30 facing the microwave introduction space 6. The thermal insulation material 31 has thermal insulation properties. Preferably, the thermal insulation material 31 has microwave permeability. The thermal insulation material 31 may be placed over the entire upper surface of the partition member 30, for example. That is, the thermal insulation material 31 may, for example, have the same shape as the partition member 30 in a plan view. The thermal insulation material 31 may have the same properties as the thermal insulation material 112 described above.

[0033] The microwave generator 40 generates microwaves to be introduced into the microwave introduction space 6. The microwave generator 40 may generate microwaves using, for example, a magnetron, klystron, gyrotron, or semiconductor element. Generating microwaves using a semiconductor element may, for example, involve oscillating microwaves using the semiconductor element, or amplifying microwaves using the semiconductor element. The frequency band of the microwaves may be, for example, around 433.92 MHz, 915 MHz, 2.45 GHz, 5.8 GHz, or other frequency bands within the range of 300 MHz to 300 GHz. For example, one or more microwave generators 40 that generate microwaves to be introduced into the microwave introduction space 6 may be provided for each zone Z1 to Z6 of the furnace body 20. Also, for example, microwaves may not be introduced into some of the zones Z1 to Z6.

[0034] Waveguide 41 transmits microwaves generated by microwave generator 40 to microwave introduction space 6 within furnace body 20. Waveguide 41 may be, for example, a rectangular waveguide, a circular waveguide, etc. Waveguide 41 may also be, for example, a hollow waveguide. In Figure 2, microwaves are introduced from above into microwave introduction space 6, that is, when waveguide 41 is connected to the ceiling 23 of furnace body 20, but instead of this, or together with this, waveguide 41 may be connected to at least one of the side walls 21, 22. Thus, microwaves may be introduced into microwave introduction space 6 from above, from the side, or both. Also, instead of waveguide 41, microwaves may be transmitted into microwave introduction space 6 by microwave transmission means such as a coaxial cable. Alternatively, for example, microwaves generated by the microwave generator 40 may be directly irradiated into the microwave introduction space 6 inside the furnace body 20. In this case, for example, the mobile hearth furnace 1 does not need to have a waveguide 41, and an antenna for emitting microwaves may be provided inside the microwave introduction space 6. Microwave irradiation inside the furnace body 20 is usually performed in multimode.

[0035] Furthermore, in zones Z1 to Z6, microwave irradiation may be performed such that the temperature of the object to be heated 3 in the heating space 5 gradually increases from zone Z1 to zone Z6. In this case, for example, the output (i.e., power) of the multiple microwave generators 40 may gradually increase from the microwave generator 40 that generates microwaves introduced into the microwave introduction space 6 of zone Z1 to the microwave generator 40 that generates microwaves introduced into the microwave introduction space 6 of zone Z6.

[0036] The microwave generator 40 may be controlled by, for example, a control unit (not shown). The control unit may, for example, use the temperature of the heating space 5 in each zone, acquired by a temperature sensor, to control the microwave generator 40 that generates microwaves to be introduced into the microwave introduction space 6 of each zone so that each heating space 5 reaches a desired temperature. The temperature of each zone may, for example, be the temperature of the object to be heated 3 moving through each zone. The temperature sensor may, for example, be a radiation thermometer that measures the temperature of the outer surface of the object to be heated 3. The control by the control unit may, for example, be feedback control.

[0037] The partition walls 50 divide the interior of the furnace body 20 into multiple zones Z1 to Z6 along the direction of movement of the object to be heated 3. Therefore, it is preferable to provide partition walls 50 at the boundaries of each zone Z1 to Z6. The partition walls 50 may, for example, divide the microwave introduction space 6 into zones Z1 to Z6 and also divide the upper side of the heating space 5 into zones Z1 to Z6. In order to allow the object to be heated 3 on the movable hearth 10 to move from the introduction section 51 to the discharge section 56, it is preferable that the heating spaces 5 divided into zones Z1 to Z6 are connected so that the object to be heated 3 can move. That is, as shown in Figure 3, it is preferable that there are no partition walls 50 on the lower side of the heating space 5, and that adjacent heating spaces 5 are connected on the lower side of the heating space 5. In order to allow independent microwave irradiation for each zone Z1 to Z6, the partition walls 50 may, for example, be made of a material that does not transmit microwaves. In this case, the two adjacent microwave introduction spaces 6, separated by zones Z1 to Z6, may not be connected and may be completely separated by a partition wall 50. The partition wall 50, which does not transmit microwaves, may, for example, have microwave reflectivity. The microwave reflectivity material may be, for example, one of the materials described above. In this embodiment, the case in which the furnace body 20 is divided into six zones Z1 to Z6 will be mainly described, but the number of zones in the furnace body 20 is not particularly limited and may be, for example, five or fewer, or seven or more. Also, the furnace body 20 may not be divided into multiple zones.

[0038] The object to be heated 3 is introduced onto the movable hearth 10 of the heating space 5 via the introduction section 51. The introduction section 51 is preferably positioned upstream of the direction of movement of the object to be heated 3 in the foremost zone Z1, as shown in Figure 3. The introduction section 51 may, for example, have one or more tubular members for introducing the object to be heated 3 from outside the furnace body 20 into the heating space 5 inside the furnace body 20. If the introduction section 51 has two or more tubular members, for example, two or more tubular members whose longitudinal direction extends vertically may be arranged parallel to a direction perpendicular to the direction of movement of the object to be heated 3. In this case, the diameter and length of the tubular members may be determined so that microwaves do not leak through the tubular members. For example, the diameter of the tubular members may be 1 / 2 or less of the wavelength of microwaves irradiated inside the furnace body 20. The tubular members may also have microwave reflectivity, for example. Microwave reflectivity materials may be, for example, those described above.

[0039] The leveler 52 levels the object to be heated 3 introduced onto the movable hearth 10. The leveler 52 may have, for example, a roller and a driving means for rotating the roller. The leveler 52 preferably levels the object to be heated 3 in the foremost zone Z1, downstream from the position where the object to be heated 3 is introduced, and in the vicinity of that position.

[0040] The discharge mechanism 53 discharges gas generated in the heating space 5 of at least one of the multiple zones Z1 to Z6. This gas may be, for example, a tar-containing gas. By discharging the tar-containing gas to the outside of the furnace body 20, the absorption of microwaves by tar in the heating space 5 can be suppressed, and the generation of sparks by tar can be suppressed. The discharge mechanism 53 may be provided in each of the multiple zones Z1 to Z6, or in some of the zones. The discharge mechanism 53 may be positioned downstream in the direction of movement of the heated object 3 in each zone. As an example, as shown in Figure 3, the discharge mechanism 53 may be positioned near the boundary between each of the zones Z2 to Z6 and the adjacent downstream zones Z3 to Z1. As an example, as shown in Figure 3, the discharge mechanism 53 may be positioned so that the opening 53a faces upstream in the direction of movement of the heated object 3, or it may be positioned so that it faces vertically downward. The discharge mechanism 53 may include, for example, a blower for discharging the gas generated in the heating space 5 to the outside of the furnace body 20.

[0041] Figure 4 is a view of the discharge mechanism 53 from the side of the opening 53a. As shown in Figure 4, the discharge mechanism 53 may, for example, have a rectangular box-shaped portion 53b having an opening 53a on one side, a tubular portion 53c having a tubular shape, and a tapered portion 53d connecting the inside of the box-shaped portion 53b and the inside of the tubular portion 53c. The discharge mechanism 53 may be arranged such that, for example, the box-shaped portion 53b is located in the heating space 5, and the tubular portion 53c extends vertically to the outside of the furnace body 20, penetrating the partition member 30, the heat insulating material 31, and the ceiling 23 of the furnace body 20. The box-shaped portion 53b, the tubular portion 53c, and the tapered portion 53d may, for example, not transmit microwaves. In this case, the box-shaped portion 53b, the tubular portion 53c, and the tapered portion 53d may, for example, have microwave reflectivity. The microwave-reflective material may be, for example, one of the materials described above. Furthermore, to prevent microwave leakage through the discharge mechanism 53, a perforated board or mesh member may be provided at the opening 53a. The perforated board or mesh member is preferably made of metal with an aperture ratio that prevents microwaves of the frequency introduced into the furnace body 20 from passing through. The metal may be, for example, one of the materials described above.

[0042] The air supply mechanism 54 is for supplying an atmospheric gas or air from outside the furnace body 20 to the heating space 5 in at least one of the multiple zones Z1 to Z6. The air supply mechanism 54 may be provided in each of the multiple zones Z1 to Z6, or in some of the zones. The air supply mechanism 54 may be located, for example, upstream in the direction of movement of the object to be heated 3 in the zone where the discharge mechanism 53 is located. As an example, in each of the zones Z2 to Z6, the air supply mechanism 54 may be located near the boundary with the adjacent upstream zones Z1 to Z5. As an example, the air supply mechanism 54 may be located such that its opening 54a faces downstream in the direction of movement of the object to be heated 3, as shown in Figure 3. The air supply mechanism 54 may have a blower for introducing an atmospheric gas, such as air, nitrogen gas, or a rare gas, into the heating space 5 within the furnace body 20. For example, if a discharge mechanism 53 and an air supply mechanism 54 are arranged in a certain zone, the volume per unit time of gas discharged from the heated space 5 by the discharge mechanism 53 may be the same as the volume per unit time of atmospheric gas supplied to the heated space 5 by the air supply mechanism 54.

[0043] Figure 5 is a view of the air supply mechanism 54 from the side of the opening 54a. As shown in Figure 5, the air supply mechanism 54 may, for example, have a rectangular parallelepiped box-shaped portion 54b having an opening 54a on one side, and a tubular portion 54c that communicates with the inside of the box-shaped portion 54b and has a tubular shape. The air supply mechanism 54 may be arranged such that, for example, the box-shaped portion 54b is located in the heating space 5, and the tubular portion 54c extends horizontally through the side wall 21 or side wall 22 of the furnace body 20 to the outside of the furnace body 20. The box-shaped portion 54b and the tubular portion 54c may, for example, be materials that do not transmit microwaves. In this case, the box-shaped portion 54b and the tubular portion 54c may, for example, have microwave reflectivity. Microwave reflectivity materials may be, for example, those described above. In addition, to prevent microwave leakage through the air supply mechanism 54, a perforated board or mesh member may be provided at the opening 54a. This perforated board or mesh member may be the same as the perforated board or mesh member provided in the opening 53a.

[0044] The pincushion circuit 55 has a plurality of parallel-arranged needle-shaped members and is intended to prevent microwave propagation. The pincushion circuit 55 may be located on the lower end side of the partition wall 50 to prevent microwave propagation through the gap between the lower end of the partition wall 50 and the object to be heated 3. The pincushion circuit 55 may be located on the lower end side of all partition walls 50, or on the lower end side of some partition walls 50. When microwaves are introduced into at least one of two adjacent zones, it is preferable to place the pincushion circuit 55 on the lower end side of the partition wall 50 separating the two zones. On the other hand, when microwaves are not introduced into either of the two adjacent zones, the pincushion circuit 55 does not need to be located on the lower end side of the partition wall 50 separating the two zones. For example, when microwaves are not introduced into zones Z1 and Z6, the pincushion circuit 55 does not need to be located on the lower end side of the partition wall 50 separating zones Z1 and Z6, as shown in Figure 3. The pincushion circuit 55 is sometimes called a pincushion structure. The longitudinal length of the needle-shaped members may be, for example, 1 / 4 of the wavelength of the microwaves irradiated inside the furnace body 20. The needle-shaped members are preferably conductive. The conductive material may be, for example, a metal. The metal may be, for example, one of the above. The pincushion circuit 55 is preferably arranged below the partition wall 50 so as not to obstruct the movement of the object to be heated 3 and to prevent the propagation of microwaves.

[0045] The object to be heated 3 on the moving hearth 10 in the heating space 5 is led out of the furnace body 20 via the outlet section 56. The outlet section 56 is preferably positioned downstream in the direction of movement of the object to be heated 3 in the last zone Z6. The outlet section 56 may be, for example, a screw conveyor that moves the object to be heated 3 in the horizontal direction. In this case, for example, a microwave leakage prevention mechanism such as a choke structure is preferably provided in the gap between the rotating shaft of the motor that drives the screw conveyor and the tubular member through which the rotating shaft passes, in order to prevent microwave leakage. Also, for example, if the screw conveyor has an outlet which is a tubular member, the diameter and length of the tubular member may be determined so as not to allow microwave leakage through the tubular member. For example, the diameter of the tubular member may be 1 / 2 or less of the wavelength of the microwaves irradiated inside the furnace body 20.

[0046] Next, a method for heating the object to be heated 3 using the movable hearth furnace 1 according to this embodiment will be described. First, the object to be heated 3, such as ore, is introduced onto the movable hearth 10 in the heating space 5 of zone Z1 of the furnace body 20 via the introduction section 51. The object to be heated 3 introduced into the furnace body 20 is leveled flat on the movable hearth 10 by the leveler 52 and moves within the heating space 5 from zone Z1 to zone Z6 in accordance with the rotation of the movable hearth 10.

[0047] Furthermore, microwaves generated by the microwave generator 40 are introduced into the microwave introduction space 6 via the waveguide 41 and irradiated from the microwave introduction space 6 onto the object to be heated 3 as it moves through the heating space 5 via the insulating material 31 and the partition member 30. The object to be heated 3 is heated by this microwave irradiation. Since heating by microwave irradiation is internal heating, compared to external heating using a burner, the object to be heated 3 on the moving hearth 10 can be heated to the desired temperature even if its thickness is greater, and a larger amount of object to be heated 3 can be heated. The object to be heated 3 may be heated by microwaves so that the temperature gradually increases from zone Z1 to zone Z6. In addition, gases containing tar generated in each zone are discharged to the furnace body 20 by the discharge mechanism 53. In addition, an atmosphere gas or air of a volume similar to that of the discharged gas is supplied to the heating space 5 by the air supply mechanism 54. After being heated in the moving hearth furnace 1, the object to be heated 3 is discharged to the outside of the furnace body 20 from the outlet section 56.

[0048] As described above, with the mobile hearth furnace 1 according to this embodiment, since the object to be heated 3 is heated by irradiating it with microwaves, it is not necessary to spread the object to be heated 3 thinly on the mobile hearth 10 as in conventional heating using a burner, and a larger amount of object to be heated 3 can be heated, thereby improving heating efficiency.

[0049] Furthermore, tar, dust, or water vapor generated in the heating space 5 can cause microwave sparks, but because the inside of the furnace body 20 is divided into the heating space 5 and the microwave introduction space 6, these can be prevented from flowing into the microwave introduction space 6, thereby suppressing the generation of sparks inside the microwave introduction space 6 or the waveguide 41. In addition, by separating the heating space 5 and the microwave introduction space 6, the volume of the heating space 5 can be made smaller, and the heating efficiency can be improved accordingly. Also, because the heating space 5 and the microwave introduction space 6 are separated, the heating space 5 and the space inside the furnace body 20 that is irradiated with microwaves can be designed independently, making it possible to make both of them the size and shape suitable for heating the object to be heated 3 and for microwave irradiation, respectively.

[0050] Furthermore, the presence of the discharge mechanism 53 allows for the discharge of tar-containing gases generated in the heating space 5 of each zone to the outside of the furnace body 20, thereby suppressing, for example, the reduction in microwave irradiation efficiency due to tar. In addition, in accordance with the discharge of the gas, the atmospheric gas of the heating space 5 can be introduced into the heating space 5 via the air supply mechanism 54.

[0051] Furthermore, if the partition member 30 partially absorbs and partially transmits microwaves, the partition member 30 will also be heated in accordance with the partial absorption of microwaves, thereby reducing the temperature difference between the object to be heated 3 and the partition member 30. As a result, for example, tar generated by heating the object to be heated 3 in the heating space 5 will not condense on the surface of the partition member 30, thereby suppressing the generation of sparks in the heating space 5 and preventing a decrease in microwave irradiation efficiency due to condensed tar.

[0052] Furthermore, by arranging the insulating material 31 on the microwave introduction space 6 side of the partition member 30, heat transfer from the heating space 5 to the microwave introduction space 6 can be reduced, thereby improving the heating efficiency in the heating space 5. It is also possible to prevent the temperature of the microwave introduction space 6 from rising. For this reason, the mobile hearth furnace 1 does not necessarily have to be equipped with a cooling mechanism to cool, for example, the waveguide 41.

[0053] Furthermore, if the microwave introduction space 6 is located above the heating space 5, and the horizontal length W1 of the heating space 5 is longer than the vertical length H1 of the heating space 5 in a plane perpendicular to the direction of movement of the object to be heated 3, the area of ​​the boundary between the heating space 5 and the microwave introduction space 6 can be made wider. As a result, the object to be heated 3 can be efficiently heated by microwave irradiation from the microwave introduction space 6 to the heating space 5 via the partition member 30.

[0054] Furthermore, if the interior of the furnace body 20 is divided into multiple zones Z1 to Z6, and a pincushion circuit 55 is provided at the boundary of these zones, microwave propagation can be prevented at the location where the pincushion circuit 55 is provided. Therefore, the control content related to microwave irradiation, such as the microwave output or irradiation time, can be changed for each zone.

[0055] In this embodiment, the case where the microwave introduction space 6 is located above the heating space 5 has been mainly described, but this is not required. For example, the microwave introduction space 6 may be located to the side of the heating space 5. More specifically, in a mobile hearth furnace 1, which is a rotary hearth furnace, the microwave introduction space 6 may be located on the inner or outer circumference side of the heating space 5. Figure 6 is a schematic longitudinal cross-sectional view showing the internal structure of a mobile hearth furnace 1 in which the microwave introduction space 6 is located on the inner circumference side of the heating space 5. In Figure 6, a cross-section is shown in a direction perpendicular to the direction of movement of the object to be heated 3 in the mobile hearth furnace 1.

[0056] As shown in Figure 6, the microwave introduction space 6 may be located on the inner circumference side of the heating space 5. In this case, as shown in Figure 6, it is preferable that the furnace body 20, along with the side walls 21, 22 and ceiling 23, also has a floor 26 located at the bottom of the microwave introduction space 6. It is preferable that this floor 26 is also impermeable to microwaves. The floor 26 may, for example, have microwave reflectivity. Microwave reflectivity materials may be, for example, those described above.

[0057] In this case, the heating space 5 in the furnace body 20 may be enclosed by, for example, a side wall 22, a ceiling 23, a partition member 30, and a hearth 11. If an insulating material 24 and a refractory material 25 are placed on the inner surface of the furnace body 20, the heating space 5 may become even narrower in accordance with the insulating material 24 and the refractory material 25. In addition, a water seal trough and a microwave leakage prevention mechanism may be provided in the gap between the movable hearth 10 and the side wall 22, and in the gap between the movable hearth 10 and the floor 26. Furthermore, in the furnace body 20, the microwave introduction space 6 may be enclosed by, for example, a side wall 21, a ceiling 23, a partition member 30, and a floor 26.

[0058] In this case as well, the heating space 5 and the microwave introduction space 6 are separated by a partition member 30, and the insulating material 31 may be placed on the microwave introduction space 6 side of the partition member 30. In addition, insulating material 24 and refractory material 25 may be attached to the inner surface of the furnace body 20 surrounding the heating space 5. As an example, as shown in Figure 6, insulating material 24 and refractory material 25 may be attached to the inner surface of the side wall 22 and the inner surface of the ceiling 23.

[0059] As shown in Figure 6, even in a mobile hearth furnace 1 where the microwave introduction space 6 is located to the side of the heating space 5, the microwaves introduced into the microwave introduction space 6 can heat the object to be heated 3 on the mobile hearth 10 in the heating space 5, and the same effect as in a mobile hearth furnace 1 where the microwave introduction space 6 is located above the heating space 5 can be obtained.

[0060] The mobile hearth furnace 1 according to this embodiment may further include a pincushion circuit 65, which is a microwave leakage prevention mechanism, positioned in the gap between the mobile hearth 10 and the furnace body 20. Figure 7 is a schematic longitudinal cross-sectional view showing an example of a mobile hearth furnace 1 having a pincushion circuit 65. The pincushion circuit 65 has a plurality of needle-shaped members, and as an example, it may be arranged between parallel microwave-reflective wall members 61, 62 or between wall members 63, 64. The microwave-reflective material may be, for example, one of the above. Each needle-shaped member of the pincushion circuit 65 may be provided such that its longitudinal direction is perpendicular to the surface facing it, i.e., the upper surface of the wall members 61, 63.

[0061] The wall member 61 may be, for example, a ring-shaped member in plan view that is continuously provided at the inner end of the base 111. The wall member 62 may be, for example, a ring-shaped member in plan view that is continuously provided at the lower end of the side wall 21. The wall member 63 may be, for example, a ring-shaped member in plan view that is continuously provided at the outer end of the base 111. The wall member 64 may be, for example, a ring-shaped member in plan view that is continuously provided at the lower end of the side wall 22.

[0062] The length and material of the needle-shaped members of the needle-pin circuit 65 may be the same as those of the needle-pin circuit 55 described above. Furthermore, it is preferable that the multiple needle-shaped members of the needle-pin circuit 65 be arranged radially and circumferentially so as to prevent microwaves from leaking from the heating space 5 to the outside of the furnace body 20 through the gap between the movable hearth 10 and the furnace body 20. By providing the needle-pin circuit 65 in the gap between the movable hearth 10 and the furnace body 20, it is possible to prevent microwave leakage to the outside of the furnace body 20 while allowing the movement of the movable hearth 10.

[0063] Figure 7 shows the case where the needle-shaped members of the pincushion circuit 65 are attached to the wall members 62 and 64, i.e., the furnace body 20 side, but this is not required. As shown in Figure 8, the needle-shaped members of the pincushion circuit 65 may also be attached to the wall members 61 and 63, i.e., the movable hearth 10 side.

[0064] As an example, as shown in Figure 9, a pincushion circuit 65 and a water seal trough 66 may be provided in the gap between the movable hearth 10 and the furnace body 20. In this case, as shown in Figure 9, it is preferable that the pincushion circuit 65 be positioned closer to the heating space 5 than the water seal trough 66. This prevents microwaves from propagating to the water seal trough 66, and prevents the water in the water seal trough 66 from being heated by microwaves and evaporating. When a water seal trough 66 is provided in the gap between the movable hearth 10 and the furnace body 20, the wall members 61 to 64 may be provided such that the ends of the gaps between wall members 61 and 62, and the gaps between wall members 63 and 64, that are farther from the heating space 5, extend vertically downward, as shown in Figure 9.

[0065] As another example, as shown in Figure 10, the needle-shaped members of the needle-shaped circuit 65 may be attached to each of the wall members 61 to 64. That is, the needle-shaped members may be attached to both the movable hearth 10 side and the furnace body 20 side. In this case, as an example, the needle-shaped members may be arranged so that, when viewed from the longitudinal direction of the needle-shaped members, the needle-shaped member on the movable hearth 10 side and the needle-shaped member on the furnace body 20 side overlap.

[0066] Furthermore, while Figures 7 to 10 describe the case where each needle-shaped member of the pincushion circuit 65 is provided with its longitudinal direction aligned with the vertical direction, this is not required. For example, as shown in Figure 11, each needle-shaped member may be provided with its longitudinal direction aligned with the radial direction. Also, as shown in Figure 11, the pincushion circuit 65 may be positioned, for example, in the gap between the lower part of the side wall 21 and the inner surface of the base 111, and in the gap between the lower part of the side wall 22 and the outer surface of the base 111. Thus, when the surface facing the needle-shaped member is a curved surface, the provision that each needle-shaped member of the pincushion circuit 65 is provided with its longitudinal direction perpendicular to the surface facing it may mean, for example, that each needle-shaped member of the pincushion circuit 65 is provided with its longitudinal direction perpendicular to the tangent plane at the intersection of the inner or outer surface of the base 111 facing the needle-shaped member and a straight line extending in the longitudinal direction of the needle-shaped member.

[0067] Furthermore, although this embodiment mainly describes the case in which the inside of the furnace body 20 is divided into a heating space 5 and a microwave introduction space 6 by a partition member 30, this is not required. The entire inside of the furnace body 20 may be a heating space, and microwaves may be directly introduced into that heating space. In this case, the mobile hearth furnace 1 may, for example, consist of a mobile hearth 10 that moves with the object to be heated 3 placed on it, a furnace body 20 arranged along the mobile hearth 10, into which microwaves generated by a microwave generator 40 are introduced to heat the object to be heated 3 placed on the mobile hearth 10, and a pincushion circuit 65 arranged in the gap between the mobile hearth 10 and the furnace body 20.

[0068] Furthermore, in this embodiment, the case in which the movable hearth 10 is a rotary hearth, that is, the case in which the movable hearth furnace 1 is a rotary hearth furnace, has been mainly described as a preferred example, but this is not the case. For example, the movable hearth furnace 1 may be a movable hearth furnace equipped with a movable hearth that moves linearly in a horizontal plane.

[0069] Furthermore, the embodiments described above are illustrative examples for specifically carrying out the present invention and do not limit the technical scope of the present invention. The technical scope of the present invention is indicated by the claims rather than by the description of the embodiments, and modifications within the literal scope and equivalent meaning of the claims are intended. [Explanation of Symbols]

[0070] 1. Mobile hearth furnace 3 Object to be heated 5 Heating space 6. Microwave introduction space 10 Mobile hearth 20 Furnace body 30 Partition Members 31 Insulation 40 Microwave Generator 53 Ejection mechanism 55, 65 Needle circuit

Claims

1. A movable hearth with the object to be heated placed on it, A furnace body arranged along the movable hearth, having inside a heating space in which an object to be heated placed on the movable hearth is heated, and a microwave introduction space which is a space along the heating space into which microwaves generated by a microwave generator are introduced, A partition member that separates the heating space and the microwave introduction space, wherein the partition member has microwave permeability. A mobile hearth furnace that can be driven around.

2. A movable hearth furnace according to claim 1, The partition member partially absorbs microwaves and partially transmits them to the heating space.

3. A movable hearth furnace according to claim 1, The furnace body is divided into multiple zones along the direction of movement of the object to be heated. In at least one of the aforementioned multiple zones, a discharge mechanism is located downstream in the direction of movement of the object to be heated, and further comprises a discharge mechanism for discharging gas generated in the heated space of that zone.

4. A movable hearth furnace according to any one of claims 1 to 3, The microwave introduction space is located above the heating space, In a plane perpendicular to the direction of movement of the object to be heated, the horizontal length of the heating space is longer than the vertical length of the heating space.

5. A movable hearth furnace according to any one of claims 1 to 3, The aforementioned movable hearth is a rotating hearth.

6. A movable hearth furnace according to any one of claims 1 to 3, The system further includes one or more microwave generators that generate microwaves to be introduced into the microwave introduction space.

7. A movable hearth with the object to be heated placed on it, A furnace body arranged along the aforementioned movable hearth, wherein microwaves generated by a microwave generator are introduced into the furnace body, and an object to be heated placed on the movable hearth is heated; A pincushion circuit is positioned in the gap between the movable hearth and the furnace body. A mobile hearth furnace that can be driven around.

8. A movable hearth furnace according to claim 7, The aforementioned pincushion circuit has a plurality of needle-shaped members, Each needle-shaped member of the aforementioned pincushion circuit is positioned so that its longitudinal direction is perpendicular to the surface facing it.

9. A method for heating an object to be heated in a mobile hearth furnace, Within the furnace body of the aforementioned mobile hearth furnace, the heating space in which the object to be heated is heated and the microwave introduction space, which is a space along the heating space in which microwaves are introduced, are separated by a partition member having microwave-penetrating properties. The process of moving the movable hearth on which the object to be heated is placed in the heating space, The process includes the step of introducing microwaves into the microwave introduction space to heat the object to be heated by irradiating it with microwaves.

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