|
(11) | EP 0 192 792 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
||||||||||||||||||||||||
| (54) | Radiation panel |
| (57) The invention relates to a radiation panel suspended in a ,heating furnace, comprising
at least two suspending rod means (12) suspended from the upper wall (11) of said
furnace at a predetermined distance; a beam means (17) connected to the lower part
of said at least two suspending rod means (12); a plurality of longitudinal frames
(19) which are arranged in parallel with each other and have respective lower ends
supported by said beam means (17); a plurality of ceramic boards (20) which are vertically
arranged between adjacent said longitudinal frames (19); and a lateral frame (16)
connected to the upper part of said suspending rod means (12) to support the upper
ends of said longitudinal frames (19). |
[0002] In a heating furnace for heating material such as steel by a hot gas stream, radiation from the hot gas is dominant in heat transmission to the material. However, the efficiency of heat transmission in the furnace is not so high because gas is inherently poor in emissivity. In recent years, proposals have been made to increase efficiency of heat transmission by providing a radiation panel in a heating furnace. Further, use of gas-permeable ceramic boards in a radiation panel has also been proposed.
[0003] A conventional heating furnace provided with a radiation panel will be described with reference to Figure 1. In the Figure, a radiation panel 2 is placed in parallel to the ceiling 1 of the furnace and a hot gas is passed through the furnace as shown by arrow marks drawn by an outline thereby heating the material 4 which is supported by the supporting surface 3. The radiation panel 2 emits radiant heat as shown by solid arrow marks. In the conventional technique, although the radiant heat emitted from the lower surface of the radiation panel 2 hits the material 4, most of radiant heat emitted from the upper surface of the radiation panel 2 does not contribute to heat the material 4. Accordingly, that furnace showed poor efficiency in heating the material 4.
[0004] To eliminate such drawback, a proposal of a new heating furnace was made (Japanese Unexamined Patent Publication 17686/1985), in which a radiation panel 2 is placed substantially perpendicular to the hot gas stream as shown in Figure 2. In the heating furnace, a substantial part of the hot gas is passed through a gas-permeable radiation panel 2, whereby heat is effectively transmitted to the radiation panel 2. Some part of radiant heat emitted from the radiation panel 2 directly hits the material 4 and some part of radiant heat hits the material 4 after reflection from the ceiling 1 of the furnace; thus the material 4 can be effectively heated.
[0005] The radiation panel in this heating furnace is made of gas-permeable ceramic boards such as ceramic honeycomb boards, which are preferable. Although it is relatively easy to manufacture the ceramic honeycomb board having a cross-sectional area of, for instance, about 12 cm x 12 cm, it is difficult to manufacture a ceramic honeycomb board having a cross-sectional area several times as large as the former. The situation is nearly the same in case of other ceramic boards. Accordingly, it is necessary to assemble a large number of gas-permeable ceramic boards to fabricate a radiation panel having a large surface area of such as 0.5 m - several square meters in order to be used for a steel reheating furnace, for instance. In this case, almost all parts have to be made of ceramics to impart heat resistance properties. Accordingly, the assembly should have a construction difficult to breakdown. Further, the assembly is preferably of a construction as simple as possible in view of manufacturing cost and easiness of repairing at the time of breakdown.
[0006] The above-mentioned Japanese Unexamined'Patent Publication 17686/1985 has proposed a radiation panel of the construction as shown in Figure 3. The radiation panel comprises a plurality of ceramic honeycombs 81, two suspending rods 82, a plurality of lateral frames 84 and a single beam 83, all being made of ceramics. The beam 83 has its both ends suspended by the two suspending rods 82. On the beam 83, placed a plurality of ceramic honeycombs 81, on which the lateral frame 84 is placed. Another plurality of ceramic honeycombs 81 are placed on the lateral frame 84 and another lateral frame 84 is placed on that plurality of ceramic honeycombs 81; thus the radiation panel is fabricated by repetition of the above- mentioned operations. Both end portions of the lateral frame 84 are provided with through holes into which the suspending rods 82 are respectively inserted.
[0007] Although the radiation panel having the above-mentioned construction is useful to a certain extent, it still has several points to be improved. The points are as follows;
(1) The thickness of the cell wall of a ceramic honeycomb 81 is generally very thin. Accordingly, the ceramic honeycomb 81 is relatively weak to a compressing force applied from the longitudinal side even though the ceramic honeycomb 81 is light in weight. The strength of this radiation panel is therefore insufficient, because a ceramic honeycomb 81 must bear a load of other ceramic honeycombs 81 stacked thereon as well as a plurality of the lateral frames 84.
(2) A lateral frame 84 must bear a load of ceramic honeycombs 81 stacked thereon as well as other lateral frames 84. Accordingly, a considerable bending stress is exerted on a lateral ceramic frame 84, thereby easily causing breakdown of the lateral frame 84.
(3) It is difficult to produce a ceramic honeycomb 81 having the side surfaces with sufficient accuracy. Accordingly, a load is concentratedly exerted on a certain ceramic honeycomb 81 among a plurality of ceramic honeycombs 81 placed between adjacent lateral frames 84, thereby causing breakdown of the specified ceramic honeycomb 81.
[0008] An object of the present invention is, therefore, to provide a radiation panel suspended in a heating furnace, preferably a radiation panel suspended in a heating furnaced and placed substantially perpendicular to a hot gas stream, the radiation panel having a large area and a simple structure and not causing breakdown.
[0009] The radiation panel according to the present invention comprises at least two suspending rod means suspended from the upper wall of a heating furnace at a predetermined distance, a beam means connected to the lower part of the at least two suspending rod means, a plurality of longitudinal frames which are arranged in parallel with each other and have respective lower ends supported by the beam means, a plurality of ceramic boards which are vertically arranged between the adjacent longitudinal frames, and a lateral frame connected to the upper part of the suspending rod means to support the upper ends of the longitudinal frames.
[0010] Thus, the radiation panel is, as a whole, supported by the suspending rod means, whereby a substantial amount of load is born by the beam means connected to the lower parts of the suspending rods. The longitudinal frames are refrained from dropping from the assembly, because the upper and lower ends of the longitudinal frames are supported by the lateral frame and the beam means. The ceramic boards are vertically arranged between the adjacent longitudinal frames, whereby the weight of the longitudinal frames is not applied to the boards. Accordingly, the construction of the radiation panel is, as a whole, very simple; assembling operations for the panel is easy; and it is easy to fabricate the radiation panel having a large area. The longitudinal and lateral frames do not support nearly any load other than their own weight. The bending stress exerted to those frames is small because only wind pressure of the hot gas stream acts on them. Only tensile strength is exerted to the suspending rod means. The beam means must bear the almost all load. However, it is easy for the beam means to have a sufficient strength by suitably selecting material and dimensions of the beam means. A ceramic board bears only the weight of overlaid other ceramic boards. Accordingly, possibility of breakdown of the ceramic boards is small during long term use. Thus, the radiation panel of the present invention has, as a whole, a structure difficult of breakdown.
[0011] In the present invention, it is preferable that a plurality of ceramic boards, for instance, two ceramic boards are laterally arranged and their facing side surfaces are bonded together. With this construction, the distance between the longitudinal frames is widened and the number of longitudinal frames is reduced, whereby the structure can be simple, a load applied to the beam means and the suspending rod means can be small, and the total weight of the radiation panel can be small.
[0012] Preferred embodiments of the present invention will be described with reference to the accompanying drawings wherein:
Figure 1 is a diagram showing a conventional heating furnace;
Figure 2 is a diagram showing a heating furnace to which the present invention is applied;
Figure 3 is a front view of a conventional radiation panel;
Figure 4 is a front view of an embodiment of the radiation panel according to the present invention;
Figure 5 is an enlarged cross sectional view taken along a line X-X in Figure 4;
Figure 6 is a cross sectional view taken along a line Y-Y in Figure 4;
Figure 7 is a cross sectional view, similar to Figure 6, of another embodiment of the radiation panel of the present invention;
Figure 8 is a front view of still another embodiment of the radiation panel of the present-invention;
Figure 9 is a longitudinal cross sectional view showing an important part of a suspending rod assembly in Figure 8;
Figure 10 is a cross sectional view taken along a line Z-Z in Figure 9;
Figure 11 is a front view showing an end part of an upper suspending rod in Figure 8;
Figure 12 is a side view of the end portion of the upper suspending rod in Figure 11;
Figure 13 is a front view of a cotter in Figure 8;
Figure 14 is a side view of the cotter in Figure 13;
Figure 15 is a front view of a link plate in Figure 8;
Figure 16 is a side view of the link plate in Figure 15;
Figure 17 is a plan view of a tubular linkage member used for the radiation panel according to another embodiment of the present invention;
Figure 18 is a side view of the tubular linkage member in Figure 17: and
Figure 19 is a cross sectional view taken along a line W-W in Figure 17.
[0014] As shown in Figure 4, a pair of suspending rods 12, 12 as a suspending rod means passing through the upper wall 11 of a heating furnace are suspended in parallel with each other. A fixture member 13 is provided at the upper part of each of the suspending rods 12 and the length of the suspending rods extending downwardly can be adjusted by means of bolts 10 of the fixture members 13. After the suspending rods 12 are inserted into through holes 14 of the upper wall 11 and the length of the rods 12 extending downwardly is adjusted, material such as castable refractory, brick and so on is filled in the through holes 14 to firmly secure the suspending rods 12. The suspending rods 12 are preferably formed by ceramics of high strength such as a pressureless sintered body of silicon carbide, silicon nitride and so on.
[0015] First and second lateral frames 15 and 16 are previously inserted into the suspending rods 12, 12. Detailed description as to this construction will be described later.
[0016] At the lower part of the suspending rods 12, 12, a beam 17 as a beam means is fitted. The beam 17 is provided at the both ends with apertures 17a, through which the suspending rods 12, 12 are inserted, and a longitudinal groove 17b is formed in the upper surface of the beam 17 (Figure 5). As shown in Figure 6, after inserting the suspending rod 12 into the aperture 17a, a stopper pin 18 is inserted into an opening formed at the lower part of the suspending rod 12, whereby the beam 17 is engaged with the lower part of the suspending rod 12. The beam 17 is preferably formed by ceramics of high strength as similar to the suspending rod 12.
[0017] Then, a plurality of longitudinal frames 19 are supported by the beam 17 in such a manner that each lower end of the longitudinal frames 19 is fitted to the longitudinal groove 17b (Figures 5 and 6), and the longitudinal frames 19 are arranged at a substantially right angle to the beam 17 and in parallel with each other with predetermined intervals. In the inner side surface or surfaces of each of the longitudinal frames 19, guiding grooves 19a are formed as guides, whereby longitudinal frames 19 placed at both outermost sides have a cross section of a channel form or an H-form and the longitudinal frames 19 placed in the intermediate have a cross section of an H-form. The longitudinal frames 19 may be formed by extrusion-molding of material such as mullite, alumina, silicon carbide and so on.
[0018] Between the adjacent longitudinal frames 19, ceramic honeycombs 20 as ceramic boards are vertically arranged in a multi-stage. In this embodiment, a ceramic honeycombs 20 comprises two unit ceramic honeycombs whose side surfaces adjacent each other are bonded by an adhesive 21 of ceramics series. It is preferable that thermal expansion coefficient of the adhesive 21 is substantially the same as that of the unit ceramic board.
[0019] The unit ceramic honeycomb may be, for instance, in a square shape whose length of a side is 12 cm and may have a thickness of 1 to 3 cm in which a large number of square through cells of 5 mm x 5 mm are formed in the square surface with cell walls of 0.5 mm. Both lateral sides of the ceramic honeycomb 20 consisting of two bonded unit ceramic honeycombs is put in the guiding grooves 19a of each of the longitudinal frames 19 to be supported. Other ceramic honeycombs 20 are put one after another in the vertical direction, thus forming a panel surface. The ceramic honeycomb 20 is not necessarily bonded. It is preferable that the longitudinal frames 19 are vertically arranged at both lateral sides of the ceramic honeycomb 20.
[0020] The second lateral frame 16 has at its both ends through holes, in which the suspending rods 12, 12 are inserted and slidably connected to the upper part of the suspending rods 12. As shown in Figure 6, longitudinal grooves are formed in the upper and lower surfaces of the second lateral frame 16 to have a cross section of an H-form. The upper end of each of the longitudinal frames 19 is fitted to the lower longitudinal groove, whereby the upper parts of the longitudinal frames 19 are supported by the second lateral frame 16.
[0021] Similarly, the first lateral frame 15 has at its both ends through holes, in which the suspending rods 12, 12 are inserted, and has a lower surface with an longitudinal groove so that the cross section of the first lateral frame 15 is a channel shape. The first and second lateral frames 15, 16 may be of the same material as the longitudinal frame 19.
[0022] A plurality of partition walls 22 are arranged laterally between the first and second lateral frames 15 and 16 in such a manner that the upper and lower edges of the partition walls 22 are fitted in the longitudinal grooves of the lateral frames 15, 16. The partition walls 22 are used to save the number of ceramic honeycombs 20 when it is not necessary to provide a radiation panel in the entire distance between material to be heated (not shown) and the upper wall 11 of the furnace in case of the distance being too long. Accordingly, it is not always necessary to provide the first lateral frame 15 and the partition walls 22. A board material such as a molded board of ceramics fibers, a board of calcium silicate may be used for the partition wall 22.
[0023] In the construction as above-mentioned, both sides of ceramic honeycomb 20 are supported by the guiding grooves 19a of each of the longitudinal frames 19 and the ceramic honeycomb 20 is prevented from coming off, and in turn the upper and lower ends of the longitudinal frames 19 are supported by the lower groove of the second lateral frame 16 and the groove 17b of the beam 17 to be prevented from coming off. Both ends of the beam 17 and the lateral frames 15, 16 are connected to the suspending rods 12, 12. Accordingly, a plurality of ceramic honeycombs 20 are firmly held so that a radiation panel having a large area can be formed. The ceramic honeycomb 20 allows passing of hot gas thereby providing good heat transmission from the gas to the honeycomb and good heat radiation from the honeycomb. The beam 17 bears almost all burden of the ceramic honeycombs 20. The longitudinal frames 19 and lateral frames 15, 16 do not bear a substantial amount of the burden. Since the bending stress exerted to the frames is very slight, these frames do not easily break. When the radiation panel of the present invention is assembled, the ceramic honeycombs 20 are inserted between the longitudinal frames 19 and are put vertically one after another. Accordingly, the assembling is very easy and an excellent efficiency of working operations can be obtained. In addition, manufacturing cost is relatively low since the construction of the radiation panel is simple as a whole.
[0024] Figure 7 is a cross sectional view of another embodiment of the present invention. A beam means consisting of a grooved member 23 having a cross section of an H-form and a round pipe 24 is employed instead of the beam 17 shown in Figure 6. As similar to the beam 17, apertures through which the suspending rods 12 are inserted are formed at both end parts of the grooved member 23 and the round pipe 24.
[0025] Although the beam 17 has a function of bearing loads of the frames 16, 19 and the ceramic honeycombs 20 as well as another function of preventing from coming-off of the longitudinal frames by its groove 17b, the sectional shape of the beam 17 inevitably becomes complicated and large-sized. Accordingly, it is not easy to manufacture the beam 17 by extrusion-molding of ceramics having high strength.
[0026] Therefore, in the structure shown in Figure 7, the grooved member 23 having the latter function and the round pipe 24 having the former function are separately prepared. In this case, it is easy to produce the round pipe 24 of high strength ceramics by extrusion-molding. Since the grooved member 23 is supported by the round pipe 24 from the bottom, breaking-down of the grooved member seldom takes place. Even though the breaking-down occurs, it does not invite a serious problem. Accordingly, the grooved member 23 is not required to be made of high strength ceramics. It is therefore easy to produce the grooved member 23 by ceramics such as mullite, reaction-sintered silicon carbide and so on, which is inexpensive and allows molding of it into a complicate shape. A solid round bar may be used instead of the round pipe 24.
[0027] Figure 8 shows still another embodiment of the present invention. Namely, the first lateral frame 15 and the partition walls 22 as shown in Figure 4 are eliminated and suspending rod assemblies 30, 30 are employed instead of the suspending rods 12, 12. As apparent from Figures 9 and 10, each of the suspending rod assemblies 30 comprises an upper suspending rod 31, a lower suspending rod 32, cotters 33, 34 and link plates 35, 35, all being made of high strength ceramics.
[0028] As shown in Figures 11 and 12, an elongated through hole 41 having a width A is formed in the longitudinal direction in the lower end part of the upper suspending rod 31. The upper and lower ends of the through hole 41 are formed in a circular shape as apparent from Figure 12 showing the side of the upper suspending rod 31. A through hole 42 having the same shape as the through hole 41 is formed at upper end part of the lower suspending rod 32.
[0029] A cotter 33 is put in the through hole 41. As shown in Figures 13 and 14, the cotter 33 is formed of a plate like body having a thickness smaller than the width A of the through hole 41 and is provided with the top end portion 43 having a tapered round edge, a side 44 opposing the top end portion 43 with a distance C and a pair of projections 45 formed at both sides of the side 44. The top end portion 43 is shaped in an arch form in view from the side (Figure 14) and the arch has a radius of curvature same as or smaller than the arch formed at lower end of the through hole 41. Accordingly, application of excessive Heltz stress is prevented when the top end portion 43 comes to contact with the lower end of the through hole 41.
[0030] The link plates 35, 35 are respectively formed of a plate like body in which round openings 46, 47 are formed at both end portions as shown in Figures 15 and 16. The round openings 46, 46 of the link plates 35, 35 are respectively engaged with both sides of the side 44 of the cotter 33. In this case, the side 44 of the cotter 33 is made in an arch form in the cross sectional view, whereby the Helz stress at the contacting part between the inner circular portion of the round opening 46 and the side 44 can not be excessive. The projections 45 of the cotter 33 serve as detents when the link plate 35 is engaged with the cotter 33.
[0031] Similarly, the cotter 34 is put in the through hole 42 formed in the lower suspending rod 32 and both sides of the side of the cotter 34 are respectively engaged with the round openings 47, 47 of the link plates 35, 35.
[0032] The suspending rod assembly having the construction as above-mentioned provides the following advantage. Generally, in a large-sized heating furnace, the distance between the ceiling of the furnace and material to be heated is long. Particularly, in the radiation panel as shown in Figure 4, a suspending rod of 2 m long or more is required. It is not easy to produce such a long suspending rod made of high strength ceramics. Further, the long suspending rod makes fitting and removing operation for the radiation panel difficult. In addition, when the radiation panel having the long suspending rod is used, the radiation panel is subjected to the wind pressure of a hot gas stream, whereby a large bending stress is exerted on the suspending rod thereby resulting in breaking of the suspending rod.
[0033] On the other hand, in accordance with the suspending rod assembly as shown in Figures 8, 9 and 10, the length of the suspending rod is reduced so that production of the rod is easy. Further, when the radiation panel is installed in the heating furnace or when it is removed for repairing, efficiency of the operation is remarkably improved. In addition, with the suspending rod assembly, the lower suspending rod 32 can be inclined with respect to the upper suspending rod 31 in the vertical and parallel directions (accordingly in any direction) against the surface of the radiation panel. Accordingly, the radiation panel is inclinable or swingable against unexpected vibrations such as an earthquake as well as against the wind pressure of the hot gas stream, whereby the suspending rod is not subjected to an excessive bending stress.
[0034] For the cotters 33, 34, the length C is preferably made greater than the thickness B, because the cotter 33 can be small-sized and light in weight and have a sufficient strength for supporting. However, the above-mentioned relation is not essential from the viewpoint of design. The elongated through holes 41, 42 prevent the cotters 33, 34 from falling sideways. However, provision of the elongated through holes is not essential from the viewpoint of design. The projections 45 may be eliminated or may be replaced by another expedient of prevention of the link plate from coming off.
[0035] Openings formed in the link plate 35 may be in a desired shape other than the round openings 46, 47. Further, a single elongated opening may be formed instead of two round openings 46, 47. For the two link plates 35, 35, a single tubular linkage member 48 having two elongated round openings 49, 49 may be employed as shown in Figures 17, 18 and 19.
[0036] Three or more number of suspending rod means may be used if desired. A T-shaped guiding member or another guiding member may be used instead of the guiding groove. Use of a ceramic honeycomb is preferred from the standpoint of light weight and low gas flowing resistance. Particularly, the ceramic honeycomb made of material such as cordielite, mullite, silicon carbide, silicon nitride, alumina and so on, is preferably used because of high emissivity and/or high thermal resistance. However, other gas-permeable ceramic board (for instance, a board having gas-flowable holes of three-dimensional network) may be used. In addition, a gas-tight ceramic board may be used.
[0037] When the radiation panel according to the present invention is applied to a heating furnace, a plurality of the radiation panels may be placed in parallel with each other with a predetermined intervals in the flowing direction of hot gas. Further, in case that the width of the interior of the heating furnace is large, plural number of radiation panels may be laterally arranged in adjacent relation.
[0038] As described above, the radiation panel according the present invention is preferably suspended so that the panel is substantially perpendicular to a hot gas stream, although this invention is not restricted in this manner. Also, it may be so designed that the panel vertically suspended from the ceiling of the heating furnace is placed obliquely or in parallel to the hot gas stream.
[0039] As described above, in accordance with the present invention, a radiation panel having a large area can be formed by assembling a large number of ceramic boards. The ceramic boards are seldom broken because they only bear a compressive load of the own dead weight. Further, the radiation panel has a construction difficult to cause breakage since the weight of the ceramic boards is not substnatially applied to the lateral and longitudinal frames and a bending stress is not substantially effected. In addition; efficiency of assembling operations is improved and manufacturing cost is low because of relatively simple structure.
1. A radiation panel suspended in a heating furnace, characterized by comprising:
at least two suspending rod means suspended from the upper wall of said furnace at a predetermined distance,
a beam means connected to the lower part of said at least two suspending rod means,
a plurality of longitudinal frames which are arranged in parallel with each other and have respective lower ends supported by said beam means,
a plurality of ceramic boards which are vertically arranged between adjacent said longitudinal frames, and
a lateral frame connected to the upper part of said suspending rod means to support the upper ends of said longitudinal frames.
2. The radiation panel according to Claim 1, wherein said ceramic boards are gas-permeable
ceramic boards.
3. The radiation panel according to Claim 1 or 2, wherein said radiation panel is
placed substantially perpendicular to a hot gas stream.
4. The radiation panel according to any one of Claims 1 to 3, wherein guides are formed
in the side surfaces of said longitudinal frames except for the outer side surface
of the frames placed at the outermost sides and both lateral sides of said ceramic
boards are supported by said guides.
5. The radiation panel according to any one of Claims 1 to 4, wherein a groove is
formed in the upper surface of said beam means and the lower ends of said longitudinal
frames are fitted to said groove.
6. The radiation panel according to any one of Claims 2 to 5, wherein said gas-permeable
ceramic boards are ceramic honeycombs.
7. The radiation panel according to any one of Claims 1 to 6, wherein each of said
ceramic boards consists of a plurality of unit ceramic boards with their lateral side
surfaces bonded.
8. The radiation panel according to any one of Claims 1 to 7, wherein each of said
suspending rod means comprises a pair of suspending rods provided with a through hole
at their end portion to be connected, a pair of cotters each inserted in said through
hole, and a linkage means with its both ends engaged with projections which are formed
at both sides of said cotter.
9. The radiation panel according to Claim 8, wherein said linkage means is a pair
of link plate.
10. The radiation panel according to Claim 8 or 9, wherein said through hole is a
longitudinally elongated hole and said cotter is in a plate-like body having a dimension
in height greater than the width of said elongated hole.
ll. The radiation panel according to any one of Claims 1 to 10, wherein said beam
means comprises a round bar or round pipe of high strength and a grooved member mounted
on said round bar or round pipe.
12. The radiation panel according to any one of Claims 1 to 11, wherein said beam
means and/or said suspending rod means is made of ceramics of high strength.