Heat insulating device

Abstract

To provide a heat insulation plate preventing burning of a cable due to radiant heat generated by leaked melted metal.SOLUTION: A heat insulating device 10 preventing burning of a cable group C due to radiant heat of melted metal M leaked from an apparatus such as a self-fluxing furnace and a converter is formed of two or more iron-based plate materials 11 and 12 having corrosion resistance. A plate thickness of each of the iron-based plate materials 11 and 12 is 0.5 mm or more and 3.0 mm or less, and adjacent plate materials are in parallel with each other and are separated from each other by a distance of 150 mm or more, and provided so as to face a residence region between a laying position of the cable group C and the residence region of the leaked melted metal M.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heat shielding device for shielding radiant heat of a high-temperature heating element, and particularly to a heat shielding device for preventing the surrounding cables from being burned by the radiant heat of molten metal leaked from equipment such as a blast furnace or a converter in a copper smelting plant made of copper.

Background Art

[0002] In dry copper smelting, copper concentrate with a copper grade of about 20 to 30% obtained by beneficiating sulfide ore mainly composed of chalcopyrite is used as a raw material. This copper concentrate is charged into a blast furnace together with silica and subjected to oxidation treatment, so that iron is phase-separated as slag, and matte with a copper grade of about 60% is produced. This matte is charged into a converter and further oxidized to produce blister copper with a copper grade of about 98%. The blister copper is charged into a refining furnace in the subsequent stage to remove oxygen, thereby producing refined blister copper with a copper grade of 99% or more. By casting this refined blister copper, an anode formed is subjected to electrolytic smelting to produce electrolytic copper with a copper grade of 99.99% or more.

[0003] In the above blast furnace, converter, and refining furnace, in order to handle molten metal in an extremely high-temperature molten state (hereinafter referred to as molten metal or melt) that exceeds at least 1000°C and may reach about 1250°C in some cases, if molten metal leaks from the above furnace due to some operation troubles and is exposed to the atmosphere, various cables such as the power cable for operating the furnace and the communication cable of electronic equipment around it may be burned by the extremely strong radiant heat emitted from the leaked molten metal.

[0004] When leakage of the molten metal described above occurs, damage to equipment and buildings can be minimized by immediately taking measures such as extinguishing fires of surrounding combustibles and repairing the leakage points of the equipment. However, if the cable that supplies electricity to the equipment malfunctions and burns out, it often takes a long time to restore it, and depending on the degree of burnout, the operation of the equipment may be stopped for several days or more. In copper smelting, when the operation is stopped for several days or more, the shipment of electrolytic copper stops, which will cause serious problems to the downstream industries that use electrolytic copper as a raw material. Therefore, when molten metal leaks from equipment that handles molten metal such as a reverberatory furnace or a converter, it is desirable that the adverse effects of its radiant heat do not reach the surrounding cables.

[0005] Therefore, various technologies for protecting cables from radiant heat emitted from a high-temperature heating element have been proposed. For example, Patent Document 1 discloses a technique for preventing burnout of a group of cables laid in a cable rack by providing a shielding plate equipped with a heat insulating material below the cable rack. The technique of this Patent Document 1 describes that by providing the heat insulating material on the upper surface side of the shielding plate via a spacer, an air layer is formed between these heat insulating materials and the shielding plate, so that an excellent heat insulating effect can be obtained.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, it is difficult to protect the cable from the radiant heat emitted by the molten metal exceeding 1000°C handled in copper smelting by simply providing one heat shield. That is, according to the Stefan-Boltzmann law, the radiant energy emitted from a heat source is proportional to the fourth power of the temperature of the heat source. Therefore, when the temperature of the heat source exceeds about 700°C, the influence of the radiant heat on the surrounding equipment becomes particularly significant, and there is a risk of burning out the insulators such as PVC (polyvinyl chloride), PE (polyethylene), and fluororesin, which are generally used as the coating materials for cables such as power cables, control cables, coaxial cables, ethernet cables, and optical cables.

[0008] Furthermore, when burning occurs in the cable, this cable may act like a fuse wire and cause the fire to spread, potentially affecting the equipment in the instrument room and electrical room. Also, in copper smelting, sulfur dioxide gas is produced as a by-product during the formation of matte, and corrosion by sulfurous acid becomes a problem with iron materials and heat insulation materials commonly used as heat shields. The present invention has been made in view of the above circumstances, and an object thereof is to provide a heat shield that prevents the cable from burning due to the radiant heat emitted from the leaked molten metal.

Means for Solving the Problems

[0009] To achieve the above object, a heat shielding device according to the present invention is a heat shielding device for preventing the cables from burning due to the radiant heat of the molten metal leaked from the equipment, and is composed of two or more iron-based plate materials having corrosion resistance. The thickness of each of these iron-based plate materials is 0.5 mm or more and 3.0 mm or less, and adjacent ones are parallel to each other and spaced 150 mm or more apart, and it is provided so as to face the retention region between the laying position of the cable group and the retention region of the leaked molten metal.

Effects of the Invention

[0010] According to the present invention, it is possible to simply and relatively inexpensively prevent the cable from burning due to the radiant heat emitted from the leaked molten metal.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0012] Hereinafter, a heat insulation device according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the heat insulation device according to this embodiment of the present invention is a heat insulation device 10 that prevents a cable group C from being burned by radiant heat indicated by white arrows emitted from molten metal M leaked from a furnace such as a blast furnace or a converter in a copper smelting factory (not shown). Specifically, this heat insulation device 10 includes two iron-based plate materials 11 and 12 having corrosion resistance, a plurality of metal rods 13 for suspending these iron-based plate materials 11 and 12, and a nut group 14 screwed to each of these metal rods 13.

[0013] The above iron-based plate materials 11 and 12 are suspended from structures such as a framework or a ceiling beam so as to be positioned in the air in a horizontal posture spaced apart in the vertical direction from each other by the above plurality of metal rods 13 and the nut group 14 screwed to each of these metal rods 13. Thereby, between the cable rack 1 where the cable group C is laid and the retention area where it is assumed that the molten metal M leaked from the above furnace stays in the building of the copper smelting factory, the iron-based plate materials 11 and 12 can be arranged so as to face this retention area. Note that the number of iron-based plate materials is not limited to the above two, and three or more may be used. Further, the retention area of the above molten metal M can be defined by providing a weir with a refractory material such as bricks.

[0014] By providing the heat insulation device 10 with the above structure, with respect to the radiant heat emitted from the molten metal leaked from a furnace such as a blast furnace or a converter, the power transmission cables, control cables, ladle crane cables, and converter / refining furnace tilting motor power transmission cables of equipment such as blast furnaces, converters, and refining furnaces laid on the cable rack 1 provided above the retention area of the leaked molten metal M, etc., represented by the cable group C, can be protected at a lower cost compared to conventional cable protection means.

[0015] That is, when protecting a cable from a heating element that reaches a high temperature where radiant heat becomes a problem, conventionally, a water-cooled jacket was sometimes provided along the cable or a fire-resistant heat insulating material was provided. However, these conventional cable protection means are not economical because it is necessary to protect the cable over a wide range that is not normally exposed to a high-temperature heating element when assuming protection from molten metal that occurs only during troubles such as equipment leakage. Also, most heat insulating materials do not have durability in a sulfurous acid gas atmosphere or an atmospheric atmosphere exceeding 1000°C.

[0016] Also, it is conceivable to prevent the cable from being exposed to the radiant heat of the molten metal leaked from the equipment by bypassing the place where the leaked molten metal can stay in the cable laying route. However, in this case as well, it is extremely inefficient and costly because it is necessary to avoid a place that does not normally become a high-temperature atmosphere and lay the cable in a roundabout route when the shortest route is possible. Also, due to restrictions on the equipment layout of the factory building, etc., it may be difficult to relocate existing cables.

[0017] Furthermore, by wrapping a heat-resistant sheet material such as a glass cloth (heat-resistant cloth / tape) around a cable, it is conceivable to improve the heat resistance of a coated cable, which generally has a heat resistance of about 60°C, up to about 600°C. However, there are extremely many cables that require protection from molten metal leaking in a copper smelting plant, and it is unrealistic to take the above measures for each of them. In addition, to prevent the cable from burning out, it is desirable to ensure that the temperature at the cable laying location does not exceed about 50°C.

[0018] On the other hand, by providing the heat insulation device 10 with the above structure below the cable rack and operating the equipment that handles molten metal using electricity supplied through the cable group C protected by this heat insulation device 10, it is possible to simply and relatively inexpensively prevent the trouble that the cable burns due to the radiant heat emitted from the molten metal leaking from the equipment, and as a result, the equipment stops operating for a long period.

[0019] In addition, although not limited, the following cases are assumed as the situation where molten metal leaks (flows out) from the above equipment. (1) The iron skin of the converter during blowing is melted and the internal molten metal leaks. (2) During converter operation, molten metal in the form of fume or droplets blows out from the furnace mouth together with high-temperature gas. (3) During operation, the iron skin of the reverberatory furnace is melted and the internal molten metal leaks. (4) During operation, the level of molten metal in the reverberatory furnace rises and molten metal leaks from the inspection port. (5) When lifting a ladle containing molten metal with a crane via a hook, the ladle is toppled due to insufficient engagement at the engaging part of the hook, and the internal molten metal flows out onto the floor surface. (6) During operation, the iron skin of the refining furnace is melted and the internal molten metal leaks.

[0020] The materials of the above iron-based plates 11 and 12 are not particularly limited as long as they have corrosion resistance against sulfurous acid gas by-produced in copper smelting. However, stainless steel, weathering steel plate, or coated iron material is preferable. Among these, stainless steel typified by SUS304, SUS316, and SUS430 is more preferable from the viewpoint of having excellent corrosion resistance and a smaller heat emissivity compared to other metals, thus obtaining a higher heat insulation effect. Note that examples of the above weathering steel plate include an alloy obtained by adding copper and chromium to iron. Further, examples of the coated iron material include those coated with so-called corrosion-resistant coatings such as epoxy resin-based paints and polyurethane resin paints on the surface of the iron material.

[0021] For each of the above iron-based plates 11 and 12, those with a plate thickness of 0.5 mm or more and 3.0 mm or less are used. This plate thickness is preferably 1.0 mm or more and 2.0 mm or less, and more preferably 1.0 mm. If this plate thickness is less than 0.5 mm, there is a high risk of being greatly deformed by the radiant heat from the molten metal or having holes opened by the fumes and droplets of the molten metal scattered from the equipment, so it is not preferable. Conversely, if this plate thickness is more than 3.0 mm, the workability deteriorates, and the self-weight becomes too heavy, so there is a risk that the engagement portion with the metal rod 13 may be deformed and fall off due to the radiant heat, so it is not preferable. The reason why a plate thickness of 1.0 mm is most preferable is that it has excellent workability and a large throughput, so a great cost merit can be obtained when purchasing a large quantity for installation in the factory.

[0022] The separation distance D1 between the scene in the area where the leaked molten metal M can stay in the building and the lower iron-based plate 11, the separation distance D2 between the iron-based plates 11 and 12, and the separation distance D3 between the upper iron-based plate 12 and the lower end of the cable rack 1 may be appropriately designed according to various conditions such as the temperature of the leaked molten metal M, the area spread on the scene (floor surface) at the time of leakage, the length and position of the cable to be protected, and the heat-resistant temperature of the coating material of the cable. For this design, it is preferable to design based on the calculation of radiant energy according to Stefan-Boltzmann's law.

[0023] According to the above radiant energy calculation, since the maximum temperature of the molten metal handled in copper smelting is about 1250°C, if the separation distance D1 between the area where the leaked molten metal M can stay in the building and the lower iron-based plate 11 is preferably 1200 mm or more, more preferably 1500 mm or more, by setting the distance D2 between the iron-based plates 11 and 12 to 150 mm or more, preferably 200 mm or more, the temperature of the laying location of the cable group C can be made not to exceed about 50°C as described above. The separation distance D3 between the upper iron-based plate 12 and the lower end of the cable rack 1 is not particularly limited as long as they are separated via an air layer, but considering workability during installation, etc., 100 mm or more is preferable, and 150 mm or more is more preferable. Also, in order to sufficiently exhibit the heat insulation effect, it is preferable that the distance D4 from the end in the width direction of the iron-based plates 11 and 12 to the end in the width direction of the cable rack 1 is ensured to be 200 mm or more.

[0024] Specifically explaining the calculation of radiant energy, the heat flux q [kW / m 2 of the radiant energy from a high-temperature heat source to the member facing it can be obtained using the following formula 1. [Formula 1] q = Q / A = σF A F E (T1 4 -T2 4 ) Here, Q is the radiant heat quantity [W] of the heat source, A is the area [m 2 of the heated member receiving the radiant heat, σ is the Stefan-Boltzmann constant (5.67·10 -8 [W / (m 2 ·K 4 )]), F A is the form factor between two surfaces obtained from Figure 3, F E is the blackbody related value (the product of the emissivity ε1 of the heat source and the emissivity ε2 of the heated member, and when the heat source is molten metal, 0.15 can be used for ε1, and when the heated member is an iron-based plate, 0.61 can be used for ε2), and T1 and T2 are the temperatures [K] of the heat source and the heated member, respectively.

[0025] According to separately conducted experiments, due to the radiant heat from molten metal at a temperature of approximately 1250°C handled at a copper smelting plant, an iron plate of a predetermined size installed at a position 1.5 m away from the melt surface of the molten metal was heated to 245°C. By substituting these conditions into the above formula 1, the heat flux q due to the radiant heat from the molten metal handled at the copper smelting plant to the iron plate is approximately 4200 kW / m 2 It was found that this is the case. Substitute the value of this heat flux q into the above formula 1 again, set the separation distance D1 between the scene of the area where the leaked molten metal M at a temperature of 1250°C can stay indoors and the lower iron-based plate 11 to 1200 mm, and further determine F A and F E By substituting the values respectively, when the temperature of the iron-based plate 11 was obtained, it was about 570°C, and it was found that the heat insulation effect was insufficient with only one iron-based plate 11

[0026] Therefore, assuming this iron-based plate 11 at 570°C as a high-temperature heat source, the radiant heat quantity Q from the iron-based plate 11 to the iron-based plate 12 was calculated using the above formula 1. At that time, when the calculation was repeated with the separation distance D2 between these iron-based plates 11 and 12 as a parameter, the temperature of the iron-based plate 12 became 126°C when the separation distance D2 was 200 mm. Although convective heat transfer and conductive heat transfer can be considered in the heat transfer from the lower iron-based plate 11 to the upper iron-based plate 12 in addition to radiant heat transfer, the air existing between these iron-based plates 11 and 12 functions as a heat insulation material with an extremely low thermal conductivity k of 0.0317 W / (m·K) at 1 atmosphere and 100°C, so convective heat transfer can be substantially ignored. Also, since the iron-based plates 11 and 12 are only connected by a plurality of metal rods 13, conductive heat transfer can also be substantially ignored

[0027] As described above, if the temperature of the iron-based plate 12 indirectly heated through the iron-based plate 11 is a low temperature below 200°C, the radiant heat from this iron-based plate 12 to the cable rack 1 can be substantially ignored. Also, if the separation distance D3 between the upper iron-based plate 12 and the lower end of the cable rack 1 is ensured to be 100 mm or more, the air existing between them functions as a heat insulator as described above, so that the temperature at the laying location of the cable group C can be made not to exceed about 50°C described above. Incidentally, even when the separation distance D2 between the iron-based plates 11 and 12 is 150 mm, since the temperature of the iron-based plate 12 can be suppressed below 200°C, the temperature at the laying location of the cable group C can be made not to exceed about 50°C. The upper limit value of the separation distance D2 between the iron-based plates 11 and 12 is not particularly limited, but is generally preferably about 350 mm or less, more preferably 300 mm or less, due to the limitation of the equipment configuration in the building.

[0028] It is preferable to use split bolts (also referred to as long screws or full screws) for the plurality of metal rods 13 that suspend the above-mentioned iron-based plates 11 and 12. By using split bolts, the height of the iron-based plates 11 and 12 can be easily changed only by adjusting the position of the nut screwed onto them up and down. Specifically, a plurality of through holes are provided at positions that coincide with each other in the vertical direction in the iron-based plates 11 and 12 at regular intervals in the longitudinal direction, and the plurality of metal rods 13 are respectively inserted through these through holes, and the iron-based plates 11 and 12 are each sandwiched and fixed from above and below with nuts 14. Incidentally, the above-mentioned through holes are preferably long holes extending in the longitudinal direction of the iron-based plates 11 and 12, whereby stress can be relieved when the iron-based plates 11 and 12 thermally expand.

[0029] The upper ends of the plurality of metal rods 13 described above may be welded to an existing structure, or a through hole may be formed in the beam portion of the structure and the upper end portion of the split bolt may be inserted therethrough and fixed with a nut. Alternatively, as shown in FIG. 2, when the cable rack 1 is suspended from the ceiling I-shaped steel 5 using the L-shaped steel 2 that supports it, the metal rod 3 and the mounting bracket 4, the upper ends of the plurality of metal rods 13 may also be suspended from the I-shaped steel 5 using the mounting bracket 15 in the same manner.

Explanation of reference numerals

[0030] 1 Cable rack 2 L-shaped steel 3, 13 Metal rod 4, 15 Mounting bracket 10 Heat insulation device 11, 12 Iron-based sheet 14 Nut C Cable group M Molten metal

Claims

Claim 1 A heat shield device for preventing the burning of a cable group due to the radiant heat of molten metal leaked from a machine, comprising two or more iron-based plate materials having corrosion resistance, each of the iron-based plate materials having a thickness of 0.5 mm or more and 3.0 mm or less, adjacent ones being parallel to each other and separated by 150 mm or more, and being provided so as to face the retention area between the laying position of the cable group and the retention area of the leaked molten metal. A heat shield device characterized by that. Claim 2 The heat shield device according to claim 1, wherein the cable group is laid on a cable rack, and the two or more iron-based plate materials are suspended by a plurality of metal bars at a position separated directly below the cable rack. Claim 3 A copper refining method characterized by operating a device for handling molten metal using electricity supplied through a cable protected by the heat shield device according to claim 1 or 2.

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