Traveling hearth furnace and heating method

Abstract

To provide a moving hearth furnace capable of heating a larger amount of objects to be heated. [Solution] The mobile hearth furnace 1 comprises a mobile hearth 10 that moves with an object to be heated 3 placed on it, a furnace body 20 arranged along the mobile hearth 10, the furnace body 20 having inside it a heating space 5 in which the object to be heated 3 placed on the mobile hearth 10 is heated, and a microwave introduction space 6 that is a space along the heating space 5 and 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, the partition member 30 being microwave transparent.

Description

[Technical Field]

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

[0002] Conventionally, rotary kilns have been used to stir and uniformly burn materials such as ores. When materials are fired while being stirred, a large amount of dust is generated. To prevent this, materials are fired using a burner in a moving hearth furnace such as a rotary hearth furnace. Summary of the Invention [Problem to be solved by the invention]

[0003] However, a moving hearth furnace using a burner can only heat the surface, and the material to be heated must be thinly spread out, making it difficult to heat a large amount of material.

[0004] The present invention has been made in view of the above problems, and its object is to provide a moving hearth furnace and a heating method that enable a larger amount of objects to be heated to be heated. [Means for solving the problem]

[0005] In order to achieve the above-mentioned object, a movable hearth furnace according to one aspect of the present invention comprises a movable hearth that moves with an object to be heated placed on it, a furnace body arranged along the movable hearth, the furnace body having inside it a heating space in which the object to be heated placed on the movable 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 separates the heating space from the microwave introduction space and is microwave-transparent.

[0006] In the moving 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 side.

[0007] Furthermore, the movable hearth furnace according to one aspect of the present invention may further include a heat insulating material disposed on the surface of the partition member facing the microwave introduction space.

[0008] In addition, in a moving hearth furnace according to one embodiment of the present invention, the interior of the furnace body is divided into multiple zones along the direction of movement of the heated material, and at least one of the multiple zones may further include an exhaust mechanism located downstream in the direction of movement of the heated material, for exhausting gas generated in the heating space of the zone.

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

[0010] In the moving hearth furnace according to one aspect of the present invention, the moving hearth may be a rotary hearth.

[0011] Furthermore, the traveling 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] In addition, a movable hearth furnace according to one aspect of the present invention comprises a movable hearth that moves with an object to be heated placed on it, a furnace body arranged along the movable hearth, into which microwaves generated by a microwave generator are introduced to heat the object to be heated placed on the movable hearth, and a pincushion circuit arranged in the gap between the movable hearth and the furnace body.

[0013] In addition, in a moving hearth furnace according to one aspect of the present invention, the pincushion circuit may have 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 movable hearth furnace, in which, inside the furnace body of the movable 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 and into which microwaves are introduced, are separated by a microwave-transparent partition member, and the method includes the steps of moving the movable hearth on which the object to be heated is placed in the heating space, and introducing microwaves into the microwave introduction space to irradiate and heat the object to be heated. [Effects of the Invention]

[0015] According to the mobile hearth furnace and heating method of one aspect of the present invention, the object to be heated can be heated by microwaves in the mobile hearth furnace, making it possible to heat a larger amount of the object to be heated. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing the appearance of a moving hearth furnace according to an embodiment of the present invention; [Figure 2] FIG. 10 is a schematic vertical cross-sectional view showing the internal structure of the moving hearth furnace according to the embodiment. [Figure 3] FIG. 10 is a schematic vertical cross-sectional view showing the internal structure of the moving hearth furnace according to the embodiment. [Figure 4] FIG. 10 is a diagram showing a discharge mechanism in the same embodiment. [Figure 5] FIG. 10 shows an air supply mechanism in the same embodiment. [Figure 6] FIG. 10 is a schematic vertical cross-sectional view showing another example of the internal structure of the moving hearth furnace according to the embodiment. [Figure 7] FIG. 10 is a schematic vertical cross-sectional view showing another example of the internal structure of the moving hearth furnace according to the embodiment. [Figure 8] FIG. 10 is a schematic vertical cross-sectional view showing another example of the internal structure of the moving hearth furnace according to the embodiment. [Figure 9] FIG. 10 is a schematic vertical cross-sectional view showing another example of the internal structure of the moving hearth furnace according to the embodiment. [Figure 10] FIG. 10 is a schematic vertical cross-sectional view showing another example of the internal structure of the moving hearth furnace according to the embodiment. [Figure 11] FIG. 10 is a schematic vertical cross-sectional view showing another example of the internal structure of the moving hearth furnace according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] The mobile hearth furnace and heating method according to the present invention will be described below using embodiments. In the following embodiments, components with the same reference numerals are the same or equivalent, and repeated description may be omitted. In the mobile hearth furnace according to this embodiment, a heating space in which the object to be heated is heated and a microwave introduction space into which microwaves are introduced are separated by a microwave-transparent partition member within the furnace body, and the object to be heated on a mobile hearth that is moved in the heating space is heated by microwaves that propagate from the microwave introduction space through the partition member to the heating space.

[0018] FIG. 1 is a schematic diagram showing the appearance of a mobile hearth furnace 1 according to this embodiment, and FIGS. 2 and 3 are schematic longitudinal cross-sectional views showing the internal structure of the mobile hearth furnace 1. FIG. 2 shows a longitudinal cross-section perpendicular to the direction of movement of the object 3 to be heated in the mobile hearth furnace 1, and FIG. 3 shows a longitudinal cross-section along the direction of movement of the object 3 to be heated in the mobile hearth 10. Note that the microwave generator 40 and the waveguide 41 are omitted from FIGS. 1 and 3. In this embodiment, the mobile hearth furnace 1 will be mainly described as a rotary hearth furnace in which the mobile hearth 10 moves in a circular shape within a horizontal plane. Note that when the mobile 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 the radial direction thereof may be simply referred to as the radial direction.

[0019] The movable hearth furnace 1 comprises a movable hearth 10 that moves with an object to be heated 3 placed thereon, a furnace body 20 arranged along the movable 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. If necessary, the movable hearth furnace 1 comprises a heat insulating material 24 and a refractory material 25 arranged on the inner surface of the furnace body 20 that surrounds 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 to be introduced into the microwave introduction space 6, and a microwave generator 31 that generates microwaves to be introduced into the microwave introduction space 6. The furnace body 20 may further include one or more waveguides 41 for introducing the microwaves into the furnace body 20, partition walls 50 for dividing the interior of the furnace body 20 into multiple zones Z1 to Z6 along the direction of movement of the object 3, an introduction section 51 for introducing the object 3 into the furnace body 20, a leveler 52 for leveling the object 3 placed on the movable hearth 10, an exhaust mechanism 53 for discharging gas generated within the furnace body 20, an air supply mechanism 54 for supplying air into the furnace body 20, a pincushion circuit 55 for preventing microwave propagation between adjacent zones, and an outlet section 56 for guiding the object 3 out of the furnace body 20. In this embodiment, as an example, a case in which the movable hearth 10 moves within the furnace body 20 in the direction indicated by the arrow in FIG. 1 is described, but the movement direction of the movable hearth 10 may be reversed. Note that with respect to the multiple zones Z1 to Z6, the upstream side in the direction of movement of the object 3 may be referred to as the front stage, and the downstream side in the direction of movement of the object 3 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, and may be, for example, ore, ceramics, etc. The ore may be, for example, iron, nickel, manganese, ore, etc. Furthermore, the object to be heated 3 may be heated, for example, for the purpose of firing the object to be heated 3. Furthermore, the object to be heated 3 may contain a reducing agent, for example, coal or coke. The heating temperature of the object to be heated 3 is not particularly limited, and 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 be a rotary hearth. This embodiment will mainly describe this case. The movable hearth 10, which is a rotary hearth, may have, for example, an annular hearth 11, traveling wheels 12 fixed to the underside of the hearth 11, and a drive means (not shown) for rotating the hearth 11. This embodiment will mainly describe a case in which the movable hearth 10 rotates by the traveling wheels 12 running on annularly arranged rails, but the mechanism for rotatably supporting the movable hearth 10 is not limited to this. For example, rails may be fixed to the underside of the movable hearth 10, and the movable hearth 10 may rotate by the rails moving on rollers. The drive means may rotate the movable hearth 10, for example, by rotating and driving rotating rollers in contact with the movable hearth 10.

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

[0023] The base 111 may be, for example, a plate-like member extending in the circumferential direction. More specifically, the base 111 may be in the shape of a circular ring having a predetermined thickness and a concentric hollow at the center. The radial width of the base 111 may be, for example, approximately the same as the radial width of the opening at the lower side of the furnace body 20. For example, the base 111 may be opaque to microwaves so as to prevent microwaves from leaking outside the furnace body 20 through the hearth 11. In this case, the base 111 may be, for example, microwave-reflective. The microwave-reflective material is not particularly limited, but may be, for example, a metal such as stainless steel, carbon steel, nickel, a nickel alloy, copper, or a copper alloy.

[0024] The heat insulating material 112 has thermal insulation properties. The heat insulating material 112 may further have microwave transparency. For example, the heat insulating material 112 may have the same shape as the base 111 in a plan view. The heat insulating material 112 may be, for example, a ring-shaped member with a predetermined thickness arranged on the upper surface of the base 111. The heat insulating material 112 having thermal insulation properties and microwave transparency may be, for example, an insulating brick or a member made of a material containing alumina. When the hearth 11 has the heat insulating material 112, heat transfer from the inside to the outside of the furnace body 20 via 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. It is preferable that the refractory material 113 has heat resistance sufficient to withstand the temperature of the object 3 heated by microwave irradiation, for example. The refractory material 113 may be, for example, microwave-transparent, or 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 with a predetermined thickness arranged in an annular shape on the upper surface of the heat insulating material 112. The refractory material 113 may be, for example, a firebrick, or a member made of a material containing silicon nitride. For example, the material containing silicon nitride may be sialon (SiAlON) containing silicon nitride. Among refractory bricks or members containing silicon nitride, there are, for example, those that are microwave-transparent, or those that partially absorb and partially transmit microwaves. Therefore, it is preferable to use a refractory material 113 having desired microwave transmission characteristics. For example, if the refractory material 113 partially absorbs microwaves and partially transmits them, the temperature difference between the object to be heated 3 and the refractory material 113 can be further reduced, and heating of the object to be heated 3 by microwave irradiation can be further promoted. Therefore, it is preferable that the refractory material 113 having 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 further reduced.

[0026] The furnace body 20 is arranged along the movable hearth 10. Therefore, when the movable hearth 10 is a rotary hearth, the furnace body 20 is also arranged in a ring shape concentric with the movable hearth 10. The furnace body 20 may have, for example, an inner peripheral side wall 21, an outer peripheral side wall 22, and a ceiling 23 connecting the upper ends of the side walls 21 and 22, which are arranged to surround the movable hearth 10. In order to prevent microwaves from leaking from the inside of the furnace body 20 through the side walls 21 and 22 and the ceiling 23, it is preferable that the side walls 21 and 22 and the ceiling 23 are not transparent to microwaves. In this case, the side walls 21 and 22 and the ceiling 23 may be, for example, microwave-reflective. The microwave-reflective material may be, for example, one of those described above.

[0027] The furnace body 20 has therein a heating space 5 in which the object 3 placed on the movable hearth 10 is heated, and a microwave introduction space 6 aligned with the heating space 5. The microwave introduction space 6 is a space into which microwaves generated by a 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 other cases will be described later. When the microwave introduction space 6 is located above the heating space 5, for example, as shown in FIG. 2 , the horizontal length W1 of the heating space 5 in a plane perpendicular to the direction of movement of the object 3 may be longer than the vertical length H1 of the heating space 5. This configuration facilitates microwave propagation from the microwave introduction space 6 to the heating space 5, and by reducing the height of the heating space 5, the volume of the heating space 5 can be reduced, resulting in more efficient heating of the object 3. When the object 3 to be heated is heated, the heating space 5 is usually at normal pressure.

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

[0029] At least one of a heat insulating material 24 and a fireproof material 25 may be attached to the inner surface of the furnace body 20 surrounding the heating space 5. For example, the heat insulating material 24 and the fireproof material 25 may have the same properties as the heat insulating material 112 and the fireproof material 113, respectively. By disposing the heat insulating material 24 on the inner surface of the furnace body 20, it is possible to suppress heat transfer from the heating space 5 to the outside of the furnace body 20. Furthermore, for example, a heat insulating material may also be attached to the outer surface of the furnace body 20.

[0030] Inside the furnace body 20, microwaves are present in an area surrounded by the furnace body 20 and the hearth 11. Therefore, it is preferable to determine the size of the interior of the furnace body 20 using simulations or the like so that the microwaves do not concentrate locally. Furthermore, the smaller the volume of the heating space 5, the more efficiently the object 3 can be heated. However, if the volume is too small, dust and the like may be more likely to be generated from the object 3 due to, for example, the exhaust of gas by the exhaust mechanism 53 and the supply of air by the air supply mechanism 54. Therefore, the size of the heating space 5 may be determined to have a volume large enough to suppress the generation of such dust and the like.

[0031] The partition member 30 is a member that separates the heating space 5 from the microwave introduction space 6. The partition member 30 faces the heating space 5 where the object to be heated 3 is heated, so it is preferable that the partition member 30 also has heat resistance. The heat resistance is preferably such that the partition member can withstand the temperature of the object to be heated 3 heated by microwave irradiation, for example. The partition member 30 is microwave transparent. For example, the partition member 30 may partially absorb microwaves and partially transmit them to the heating space 5 side. The partition member 30 may be, for example, a plate-like member extending in the circumferential direction. Note that if the interior of the furnace body 20 is divided into multiple zones Z1 to Z6 by partition walls 50, a partition member 30 may be disposed in each zone. In this case, the shape of one partition member 30 may be a ring-shaped disk having a predetermined thickness and concentrically hollowed out at the center, which is divided into multiple sections in the circumferential direction. The partition member 30 may be supported, for example, by protrusions 21a and 22a protruding from the inner surfaces of the side walls 21 and 22, respectively, within the furnace body 20. The partition member 30 is preferably disposed 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 heat insulating material 31 may be arranged on the surface of the partition member 30 facing the microwave introduction space 6. The heat insulating material 31 has thermal insulation properties. It is preferable that the heat insulating material 31 is microwave transparent. The heat insulating material 31 may be arranged, for example, over the entire upper surface of the partition member 30. That is, the heat insulating material 31 may have the same shape as the partition member 30 in a plan view, for example. The heat insulating material 31 may have properties similar to those of the heat insulating 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, a klystron, a gyrotron, or a semiconductor element. Generating microwaves using a semiconductor element may, for example, involve oscillating microwaves using a semiconductor element, or amplifying microwaves using a semiconductor element. The microwave frequency band may be, for example, around 433.92 MHz, 915 MHz, 2.45 GHz, or 5.8 GHz, or may be any other frequency band 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 of zones Z1 to Z6 of the furnace body 20. Furthermore, for example, microwaves may not be introduced into some of zones Z1 to Z6.

[0034] The waveguide 41 transmits microwaves generated by the microwave generator 40 to the microwave introduction space 6 in the furnace body 20. The waveguide 41 may be, for example, a rectangular waveguide or a circular waveguide. The waveguide 41 may also be, for example, a hollow waveguide. While FIG. 2 illustrates a case in which microwaves are introduced into the microwave introduction space 6 from above, i.e., a case in which the waveguide 41 is connected to the ceiling 23 of the furnace body 20, the waveguide 41 may alternatively or additionally be connected to at least one of the side walls 21, 22. Thus, microwaves may be introduced into the microwave introduction space 6 from above, from the side, or both. Instead of the waveguide 41, microwaves may be transmitted into the microwave introduction space 6 by microwave transmission means such as a coaxial cable. Furthermore, for example, microwaves generated by the microwave generator 40 may be directly irradiated into the microwave introduction space 6 in the furnace body 20. In this case, for example, the traveling hearth furnace 1 does not need to have a waveguide 41, and an antenna for emitting microwaves may be provided in the microwave introduction space 6. Note that microwave irradiation inside the furnace body 20 is usually performed in multimode.

[0035] In zones Z1 to Z6, microwaves may be irradiated so 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 to be introduced into the microwave introduction space 6 in zone Z1 toward the microwave generator 40 that generates microwaves to be introduced into the microwave introduction space 6 in zone Z6.

[0036] The microwave generator 40 may be controlled by, for example, a control unit (not shown). For example, the control unit may 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 be, for example, the temperature of the object 3 to be heated moving through each zone. For example, the temperature sensor may be a radiation thermometer that measures the temperature of the outer peripheral surface of the object 3 to be heated. The control by the control unit may be, for example, feedback control.

[0037] The partition walls 50 are used to divide the interior of the furnace body 20 into multiple zones Z1 to Z6 along the movement direction of the object 3. Therefore, it is preferable that a partition wall 50 be provided at each boundary between the zones Z1 to Z6. For example, the partition walls 50 may divide the microwave introduction space 6 into the zones Z1 to Z6 and also divide the upper side of the heating space 5 into the zones Z1 to Z6. Note that, in order to allow the object 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 the zones Z1 to Z6 are connected to allow the object 3 to move. That is, as shown in FIG. 3 , it is preferable that no partition wall 50 is present below the heating space 5, and that adjacent heating spaces 5 are connected below the heating space 5. In order to allow independent microwave irradiation for each of the zones Z1 to Z6, the partition walls 50 may be, for example, opaque to microwaves. In this case, two adjacent microwave introduction spaces 6 partitioned into zones Z1 to Z6 may not be connected, but may be completely separated by a partition wall 50. The partition wall 50, which is not microwave-transmitting, may be, for example, microwave-reflective. The microwave-reflective material may be, for example, one of those described above. Note that in this embodiment, a case where the interior of the furnace body 20 is partitioned 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 less, or seven or more. Furthermore, the interior of the furnace body 20 does not have to be partitioned into, for example, multiple zones.

[0038] The object 3 is introduced onto the moving hearth 10 in the heating space 5 through the introduction section 51. As shown in FIG. 3 , the introduction section 51 is preferably disposed in the front-most zone Z1, at a position upstream in the direction of movement of the object 3. For example, the introduction section 51 may have one or more tubular members for introducing the object 3 from outside the furnace body 20 into the heating space 5 in the furnace body 20. When the introduction section 51 has two or more tubular members, for example, two or more tubular members whose longitudinal directions extend vertically may be arranged parallel to each other in a direction perpendicular to the direction of movement of the object 3. In this case, the diameter and length of the tubular members may be determined so as to prevent microwave leakage through the tubular members. For example, the diameter of the tubular member may be equal to or less than half the wavelength of the microwaves irradiated in the furnace body 20. Furthermore, the tubular member may have microwave reflectivity, for example. The microwave-reflective material may be, for example, one of those described above.

[0039] The leveler 52 flattens the object 3 that has been introduced onto the movable hearth 10. The leveler 52 may have, for example, a roller and a drive means for rotating the roller. The leveler 52 is preferably located in the front-most zone Z1 downstream of the position where the object 3 is introduced and flattens the object 3 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 gas containing tar. By discharging the tar-containing gas to the outside of the furnace body 20, it is possible to suppress absorption of microwaves by the tar in the heating space 5 and also suppress generation of sparks due to the tar. The discharge mechanism 53 may be provided, for example, in each of the multiple zones Z1 to Z6, or in some of the zones. The discharge mechanism 53 may be disposed downstream in the direction of movement of the object 3 in each zone. For example, as shown in FIG. 3, the discharge mechanism 53 may be disposed near the boundary between each of the zones Z2 to Z6 and the adjacent subsequent zones Z3 to Z1. For example, as shown in FIG. 3, the discharge mechanism 53 may be disposed so that the opening 53a faces upstream in the direction of movement of the object 3, or so that the opening 53a faces vertically downward. The exhaust mechanism 53 may have, for example, a blower for exhausting the gas generated in the heating space 5 to the outside of the furnace body 20.

[0041] FIG. 4 is a view of the discharge mechanism 53 as viewed from the opening 53a side. As shown in FIG. 4, the discharge mechanism 53 may, for example, have a rectangular parallelepiped 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 interior of the box-shaped portion 53b to the interior of the tubular portion 53c. The discharge mechanism 53 may, for example, be arranged such that the box-shaped portion 53b is present in the heating space 5 and the tubular portion 53c penetrates the partition member 30, the heat insulating material 31, and the ceiling 23 of the furnace body 20 and extends vertically to the outside of the furnace body 20. For example, the box-shaped portion 53b, the tubular portion 53c, and the tapered portion 53d may be opaque to microwaves. In this case, the box-shaped portion 53b, the tubular portion 53c, and the tapered portion 53d may, for example, be microwave reflective. The microwave-reflective material may be, for example, any of those described above. Furthermore, a punching board or a mesh member may be provided in the opening 53a to prevent microwaves from leaking through the exhaust mechanism 53. The punching board or mesh member is preferably made of a metal having an opening ratio that prevents microwaves of the frequency to be introduced into the furnace body 20 from passing through. The metal may be, for example, any of those described above.

[0042] The air supply mechanism 54 supplies 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, for example, or in some of the zones. The air supply mechanism 54 may be located upstream in the direction of movement of the object 3 in the zone where the discharge mechanism 53 is located. As an example, the air supply mechanism 54 may be located near the boundary between each of the zones Z2 to Z6 and the adjacent upstream zone Z1 to Z5. As an example, as shown in FIG. 3, the air supply mechanism 54 may be located so that the opening 54a faces downstream in the direction of movement of the object 3. The air supply mechanism 54 may have a blower for introducing atmospheric gas such as air, nitrogen gas, or rare gas into the heating space 5 in the furnace body 20. For example, when an exhaust mechanism 53 and an air supply mechanism 54 are arranged in a certain zone, the volume per unit time of gas exhausted from the heating space 5 by the exhaust mechanism 53 may be the same as the volume per unit time of the ambient gas supplied to the heating space 5 by the air supply mechanism 54.

[0043] FIG. 5 is a view of the air supply mechanism 54 as viewed from the opening 54a side. As shown in FIG. 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 communicating with the interior of the box-shaped portion 54b and having a tubular shape. The air supply mechanism 54 may, for example, be arranged such that the box-shaped portion 54b is present in the heating space 5 and the tubular portion 54c penetrates the side wall 21 or 22 of the furnace body 20 and extends horizontally to the outside of the furnace body 20. For example, the box-shaped portion 54b and the tubular portion 54c may be opaque to microwaves. In this case, the box-shaped portion 54b and the tubular portion 54c may be, for example, microwave-reflective. The microwave-reflective material may be, for example, one of those described above. Furthermore, a punching board or a mesh member may be provided at the opening 54a to prevent microwaves from leaking through the air supply mechanism 54. This punching board or mesh member may be the same as the punching board or mesh member provided in the opening 53a.

[0044] The pincushion circuit 55 has multiple needle-shaped members arranged in parallel and is intended to prevent microwave propagation. The pincushion circuit 55 may be arranged 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 arranged on the lower end side of all or some of the partition walls 50, for example. When microwaves are introduced into at least one of two adjacent zones, it is preferable that the pincushion circuit 55 be arranged 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 arranged 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 arranged on the lower end side of the partition wall 50 separating zones Z1 and Z6, as shown in FIG. 3. The pincushion circuit 55 is sometimes called a pincushion structure. The longitudinal length of the needle-shaped member may be, for example, ¼ of the wavelength of the microwaves irradiated in the furnace body 20. The needle-shaped member is preferably, for example, electrically conductive. The electrically conductive material may be, for example, a metal. The metal may be, for example, one of those described above. The pincushion circuit 55 is preferably arranged below the partition wall 50 so as not to interfere with the movement of the object 3 to be heated and so as to prevent the propagation of microwaves.

[0045] The object 3 on the moving hearth 10 in the heating space 5 is discharged to the outside of the furnace body 20 via the discharge section 56. The discharge section 56 is preferably located downstream in the direction of movement of the object 3 in the final zone Z6. For example, the discharge section 56 may be a screw conveyor that moves the object 3 horizontally. In this case, a microwave leakage prevention mechanism such as a choke structure is preferably provided in the gap between the rotating shaft of the motor driving the screw conveyor and the tubular member through which the rotating shaft passes to prevent microwave leakage. Furthermore, for example, if the screw conveyor has a tubular outlet, the diameter and length of the tubular member may be determined to prevent microwave leakage through the tubular member. For example, the diameter of the tubular member may be equal to or less than half the wavelength of the microwaves irradiated within the furnace body 20.

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

[0047] Microwaves generated by the microwave generator 40 are introduced into the microwave introduction space 6 via a waveguide 41 and irradiated onto the object 3 moving through the heating space 5 via the insulating material 31 and the partition member 30. The object 3 is heated by this microwave irradiation. Because microwave irradiation is internal heating, the object 3 can be heated to a desired temperature even if the thickness of the object 3 on the movable hearth 10 is larger, compared to external heating using a burner. This allows for the heating of a larger amount of object 3. The object 3 may be heated by microwaves so that its temperature gradually increases from zone Z1 to zone Z6. Gases containing tar generated in each zone are discharged into the furnace body 20 by an exhaust mechanism 53. An atmospheric gas or air with a volume approximately equal to the discharged gas is delivered to the heating space 5 by an air delivery mechanism 54. After being heat-treated in the movable hearth furnace 1, the object 3 is discharged to the outside of the furnace body 20 through an outlet 56.

[0048] As described above, according to the movable hearth furnace 1 of this embodiment, the object to be heated 3 is heated by irradiating it with microwaves, so there is no need to spread the object to be heated 3 thinly on the movable 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, although tar, dust, or water vapor generated in the heating space 5 can cause microwave sparks, separating the interior of the furnace body 20 into the heating space 5 and the microwave introduction space 6 prevents these from flowing into the microwave introduction space 6, thereby suppressing the generation of sparks inside the microwave introduction space 6 or the waveguide 41. Separating the heating space 5 from the microwave introduction space 6 also reduces the volume of the heating space 5, thereby improving heating efficiency. Separating the heating space 5 from the microwave introduction space 6 also allows the heating space 5 and the space within the furnace body 20 to be irradiated with microwaves to be designed independently, allowing both to be sized and shaped appropriately for heating the object 3 and irradiating microwaves, respectively.

[0050] Furthermore, by providing the exhaust mechanism 53, gases containing tar generated in the heating space 5 of each zone can be exhausted to the outside of the furnace body 20, thereby making it possible to suppress a decrease in microwave irradiation efficiency due to tar, for example. In addition, in response to the exhaust 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 microwaves and partially transmits them, the partition member 30 will also be heated in response to the partial absorption of the microwaves, thereby making it possible to further reduce the temperature difference between the object to be heated 3 and the partition member 30. Therefore, for example, it is possible to prevent tar and the like generated by heating the object to be heated 3 in the heating space 5 from condensing 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 heat insulating material 31 on the microwave introduction space 6 side of the partition member 30, it is possible to reduce the transfer of heat from the heating space 5 to the microwave introduction space 6, 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. Therefore, the traveling hearth furnace 1 does not necessarily have to be equipped with a cooling mechanism for cooling the waveguide 41, etc.

[0053] Furthermore, when 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, it is possible to increase the area of ​​the boundary between the heating space 5 and the microwave introduction space 6. This makes it possible to efficiently heat the object to be heated 3 by irradiating microwaves 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 pincushion circuits 55 are provided at the boundaries of these zones, it is possible to prevent microwave propagation at the locations where the pincushion circuits 55 are provided. Therefore, the control details related to microwave irradiation, such as microwave output or irradiation time, can be changed for each zone.

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

[0056] As shown in Fig. 6, the microwave introduction space 6 may be located on the inner periphery of the heating space 5. In this case, as shown in Fig. 6, the furnace body 20 preferably has side walls 21, 22, and a ceiling 23, as well as a floor 26 located at the bottom of the microwave introduction space 6. This floor 26 is also preferably made of a material that is not transparent to microwaves. The floor 26 may, for example, be microwave reflective. The microwave reflective material may be, for example, one of those described above.

[0057] In this case, in the furnace body 20, the heating space 5 may be surrounded by, for example, the sidewalls 22, the ceiling 23, the partition member 30, and the hearth 11. Note that, if a heat insulating material 24 and a refractory material 25 are arranged on the inner surface of the furnace body 20, the heating space 5 may be further narrowed in accordance with the heat insulating material 24 and the refractory material 25. Furthermore, for example, a water seal trough and a microwave leakage prevention mechanism may be provided in the gap between the movable hearth 10 and the sidewall 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 surrounded by, for example, the sidewalls 21, the ceiling 23, the partition member 30, and the 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 a heat insulating material 31 may be arranged on the microwave introduction space 6 side of the partition member 30. Furthermore, for example, a heat insulating material 24 and a fireproof 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 Fig. 6, a heat insulating material 24 and a fireproof 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 the case of a mobile hearth furnace 1 in which 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 3 on the mobile hearth 10 in the heating space 5, thereby achieving the same effect as in the case of a mobile hearth furnace 1 in which the microwave introduction space 6 is located above the heating space 5.

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

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

[0062] The length and material of the needle-shaped members of the pincushion circuit 65 may be the same as those of the pincushion circuit 55. Preferably, the multiple needle-shaped members of the pincushion circuit 65 are arranged radially and circumferentially 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 pincushion circuit 65 in the gap between the movable hearth 10 and the furnace body 20, it is possible to prevent microwaves from leaking to the outside of the furnace body 20 while allowing the movable hearth 10 to move.

[0063] 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 necessarily the case. As shown in FIG. 8, the needle-shaped members of the pincushion circuit 65 may be attached to the wall members 61 and 63, i.e., the movable hearth 10 side.

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

[0065] 10, the needle-shaped members of the pincushion 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 the needle-shaped members on the movable hearth 10 side and the needle-shaped members on the furnace body 20 side overlap when viewed in the longitudinal direction of the needle-shaped members.

[0066] 7 to 10 illustrate the case where each needle-shaped member of the pincushion circuit 65 is arranged so that its longitudinal direction is aligned with the vertical direction, but this is not necessarily the case. For example, as shown in FIG. 11 , each needle-shaped member may be arranged so that its longitudinal direction is aligned with the radial direction. Also, as shown in FIG. 11 , the pincushion circuit 65 may be disposed, for example, in the gap between the lower portion of the side wall 21 and the inner surface of the base 111, and in the gap between the lower portion of the side wall 22 and the outer surface of the base 111. In this way, when the surface facing the needle-shaped member is curved, "the needle-shaped members of the pincushion circuit 65 are arranged so that their longitudinal direction is perpendicular to the opposing surface" may mean, for example, that each needle-shaped member of the pincushion circuit 65 is arranged so that its longitudinal direction is 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 line extending in the longitudinal direction of the needle-shaped member.

[0067] Furthermore, in this embodiment, the case where the interior of the furnace body 20 is divided into the heating space 5 and the microwave introduction space 6 by the partition member 30 has been mainly described, but this is not necessarily the case. The entire interior of the furnace body 20 may be the heating space, and microwaves may be introduced directly into this heating space. In this case, the movable hearth furnace 1 may include, for example, a movable hearth 10 that moves with the object to be heated 3 placed thereon, a furnace body 20 arranged along the movable hearth 10, into which microwaves generated by a microwave generator 40 are introduced to heat the object to be heated 3 placed on the movable hearth 10, and a pincushion circuit 65 arranged in the gap between the movable hearth 10 and the furnace body 20.

[0068] In addition, in this embodiment, a preferred example has been described in which the mobile hearth 10 is a rotary hearth, i.e., the mobile hearth furnace 1 is a rotary hearth furnace, but this is not necessarily the case. For example, the mobile hearth furnace 1 may be a mobile hearth furnace having a mobile hearth that moves linearly within a horizontal plane.

[0069] Furthermore, the above-described embodiments are merely examples for specifically implementing the present invention, and are not intended to limit the technical scope of the present invention. The technical scope of the present invention is defined by the claims, not by the description of the embodiments, and is intended to include modifications within the literal scope of the claims and within the scope of equivalent meanings. [Explanation of symbols]

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

Claims

1. a moving hearth that moves with an object to be heated placed on it; A furnace body is arranged along the movable hearth, and has inside thereof 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 and into which microwaves generated by a microwave generator are introduced; a microwave-transparent member that separates the heating space from the microwave introduction space; Equipped with The inside of the furnace body is divided into a plurality of zones along the direction of movement of the object to be heated, The moving hearth furnace further comprises an exhaust mechanism disposed in each of at least two of the plurality of zones for exhausting gas generated in the heating space of the corresponding zone.

2. 2. The moving hearth furnace of claim 1, The member partially absorbs microwaves and partially transmits them to the heating space.

3. 3. The moving hearth furnace according to claim 1 or 2, 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.

4. 3. The moving hearth furnace according to claim 1 or 2, The moving hearth is a rotary hearth.

5. 3. The moving hearth furnace according to claim 1 or 2, The microwave introduction space further includes one or more microwave generators that generate microwaves to be introduced into the microwave introduction space.

6. A method for heating an object to be heated in a moving hearth furnace, comprising: In the interior of the furnace body of the moving 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 and into which microwaves are introduced are separated by a microwave-transparent member, The inside of the furnace body is divided into a plurality of zones along the direction of movement of the object to be heated, a step of moving a movable hearth on which the object to be heated is placed in the heating space; a step of introducing microwaves into the microwave introduction space to irradiate the object to be heated with microwaves and heat it; a step of discharging gas generated in the heating space of each of the plurality of zones by a discharge mechanism disposed in each of the plurality of zones; Includes.

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