AU9462998A

AU9462998A - Structure of metallurgical furnace and operating method using the same metallurgical furnace

Info

Publication number: AU9462998A
Application number: AU94629/98A
Authority: AU
Inventors: Shinichi Isozaki; Katsuhiro Iwasaki; Masahiro Kawakami; Akishi Kimura; Terutoshi Sawada; Takeshi Sekiguchi; Norihiko Taguchi; Masayuki Watanabe; Mitsuhiro Yamanaka
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 1997-10-20
Filing date: 1998-10-19
Publication date: 1999-05-10
Anticipated expiration: 2018-10-19
Also published as: KR100339261B1; WO1999020966A1; CN1276862A; CA2307090A1; AU751764B2; KR20010024276A; CA2307090C

Description

STRUCTURE OF METALLURGICAL FURNACE AND OPERATION METHOD USING THE SAME 5 FIELD OF THE INVENTION The present invention relates to a structure of a metallurgical furnace and an operation method using the metallurgical furnace. BACKGROUND OF THE INVENTION 10 In various types of metallurgical furnaces such as converters, electric furnaces, and smelting reduction furnaces, inside surface of furnace wall is generally structured by a refractory. The furnace wall made of refractory, however, is significantly damaged particularly at sections contacting with molten slag and sections exposed to high temperature gases, though sections immersed in molten metal such as molten 15 steel are damaged to a relatively small degree. Consequently, the furnace walls are required to be replaced in a short period. As a countermeasures to the phenomenon, there is a proposal that the sections not immersed in molten metal are structured by a water-cooled metallic panel inside of which cooling water passes through. 20 For example, Japanese Unexamined Patent Publication No. 4-316983 discloses the following furnace wall structure of a metallurgical furnace. (A) A refractory furnace wall which is used inside ofthe furnace comprises a refractory lining and a water-cooled panel. (B) A partition member is inserted between the water-cooled panel and the adjacent 25 refractory lining. (C) A castable refractory layer is arranged between the water-cooled panel and a furnace body shell. 1 ~j) 1 (D) The partition member becomes a mold form of the castable refractory which is cast between the water-cooled panel and the funace body shell. (E) The water-cooled panel prevents over heat of the refractory lining, which improves the durability of the furnace wall. 5 Japanese Unexamined Patent Publication No. 4-316984 discloses an attachment structure ofthe water-cooled panel ofthe metallurgical furnace as shown below. (a) A water-cooled panel is partially arranged at inside wall ofthe metallurgical furnace. 10 (b) A refractory material is filled in the space between the water-cooled panel and a furnace body shell. (c) An upper surface, a lower surface, all or partial side surfaces of the space between the water-cooled panel and the furnace body shell is surrounded by the thin steel sheets. 15 (d) Even if water leaks from the water-cooled panel, the leaked water does not enter the metallic bath since the water-cooled panel is surrounded by the thin steel sheets. Japanese Unexamined Patent Publication No. 6-50669 discloses a refining vessel wherein a molten metal is accommodated and refining is performed. A funace wall 20 section which is immersed in molten metal during refining is covered with a refractory material. A portion or all ofthe furnace wall over the furnace wall section comprises a cooling structure having a cooling system. The water-cooled panel in prior arts described above comprises a water-supply 25 opening, a water-discharge opening, plurality of water passages and turn portions. The water-supply opening is located at bottom section of the water-cooled panel. The water-discharge opening is located at top section ofthe water-cooled panel. The plurality of water passages are arranged horizontally between the water-supply 2 opening and the water-discharge opening. The turn portions connect the plurality of water passages. The cooling water goes up through the water-passage running horizontally while turning the flow direction thereof by 180 degrees, then the cooling water leaves the passage from a water-discharge opening located at top section of the 5 water-cooled panel. Since the water-passage of cooling water in a water-cooled panel in prior art has 180 degrees of the turn, the pressure drop of cooling water increases, which requires the increase in discharge pressure of a pump for circulating the cooling water. Thus, there induces a problem of increase in investment and operation cost 10 Japanese Unexamined Patent Publication No. 4-316983 and No. 4-316984 disclose that a single water-cooled panel is mounted to a part of furnace walls. However, when water-cooled panels are mounted on the whole inner periphery of a furnace, plurality of water-cooled panels are required to be arranged in rows. But, Japanese Unexamined Patent Publication No. 4-316983 and No. 4-316984 do not 15 disclose the arrangement of water-cooled panels. Regarding stationary iron scrap melting furnace and iron ore smelting reduction furnace, which continuously hold and manufacture pig iron, the temperature of pig iron and slag held in the furnace is high compared with that in blast furnace, and the 20 operation is conduced under vigorous agitation of pig iron and slag to accelerate the reactions. Accordingly, the lining bricks severely wear, and the life is in a range of from several weeks to several months. Therefore, for that type of furnace, to grasp the residual thickness of bricks at an accurate order during operation is extremely important to increase the operation stability and to reduce the refractory cost. 25 With that type of stationary iron scrap melting furnaces and stationary iron ore smelting reduction furnaces, when the residual thickness of lining bricks is determined using the above-described methods, there induce problems described below. 3 According to the method using thermocouples, the range of estimation of the residual thickness with a single thermocouple is limited, and lots of thermocouples are necessary to cover the whole furnace body area. In addition, the degree of contact between thermocouple and brick induces change in temperature determined by 5 thermocouple, which fails to give sufficient accuracy of estimation. According to the method using coaxial cables, the residual thickness of bricks is determined at a good accuracy. The obtained information is, however, only that on the point of buried coaxial cable. As a result, the necessary number of probes is far more than that of thermocouples to cover the whole furnace area. 10 According to the method using a radioactive substance, continuous determination of the wear rate of bricks cannot be done because the determination is based on the presence/absence of the radioactive substance. In addition, there is a need of burying a large number of particles of radioactive substance to cover the whole furnace depth. Furthermore, handling of radioactive substance requires safe and hygienic limitations, 15 thus the method is not a practical one. Therefore, if the conventional methods for estimating residual thickness of bricks are applied to a stationary iron scrap melting furnace and an iron ore smelting reduction furmace, which funaces have far short life compared with that of blast furnace, to determine the residual thickness of bricks at a high accuracy over the whole 20 furnace area, the cost of instruments and the cost to mount the instruments to fumace extremely increase the total cost, which is uneconomical. For iron smelting in smelting reduction, those two types of smelting furaces are proposed. For example, Japanese Unexamined Patent Publication No. 1-198414 25 discloses a converter smelting reduction furmace in which the center part of the fumace is supported by trunnion bearings, and Japanese Unexamined Patent Publication No. 4-80311 discloses a shaft type stationary smelting reduction fumace in which a tap hole is located at bottom of the furnace.

Smelting reduction of iron is a continuous smelting process, and there is no necessity of applying a tilting smelting furmace such as converter smelting reduction furnace. In the furnace holding both high temperature molten iron and high temperature molten slag, the refractory in the lower vessel at the bottom section of the 5 furnace is severely damaged, which results in the damage of shell in the lower vessel caused by thermal deformation. Therefore, the tilting smelting furnaces which are possible to replace the lower vessel, as seen in the converters for steel making, are advantageous as the smelting reduction furnaces. Conventional type of tilting smelting furnaces which are able to replace the lower 10 vessel thereof, however, increases the supporting weight of the support section for tilting the furnace such as trunnion bearings when the furnace shell becomes large, thus increasing the size of facilities to secure the mechanical strength of the support sections, which results in increased investment. -Furthermore, size increase induces difficulty in locating auxiliary equipment around the furnace. 15 Degree of increase in investment of stationary smelting furnaces with the size increase in furnace shell is small compared with that of tilting smelting furnaces. Conventional type of stationary smelting furnaces, however, cannot replace the whole lower vessel, though a part ofthe furace bottom section such as the portion of bottom blowing nozzle attachment is replaceable, as disclosed in Japanese Unexamined Patent 20 Publication No. 4-80311. According to a known method to charge a seed melt to that type of smelting reduction furnace, cool iron source such as scrap and pig is melted in the smelting reduction furnace using oxygen jet, which melt is used as the seed melt. The method 25 has, however, a possibility to damage the lining refractory because FeO which is severely corrosive to the refractory is generated. To cope with the phenomenon, there is a proposed method in which an opening is located at top of the stationary furnace for charging the melt, as in the case of a tilting furnace body. Inside of the furnace, however, there are water-cooled panels arranged over the whole periphery thereof, so these water-cooled panels might be damaged. In addition, since the smelting reduction furnace is operated under high pressures of 0.2 MPa or more, an opening thereon requires to assure the sealing performance. It is 5 very difficult to perform the work described below within a few hours: that is, the opening is plugged to prevent the solidification of molten iron after the charge thereof, and the operation of the furnace is resumed after confirming the air-tightness. The smelting reduction process of iron ores in the presence of an iron bath is a 10 method for discharging continuously or intermittently the molten iron and the molten slag which are yielded by melting the iron ores and flux such as calcium oxide charged onto the iron bath using the combustion heat generated from oxygen of carbon materials such as coal and coke, and by reducing thus melted iron ores by carbon materials. According to the method, a stining gas is blown into the furnace from 15 bottom thereof to enhance the reactions in the furnace. Since the iron bath is necessary to be held in the furnace, the discharge operation leaves a specified quantity of the iron bath in the fumace. Consequently, a tap hole is generally located at a side wall of the furnace, and the molten iron is left below the level of the tap hole to secure the specified quantity thereof 20 Smelting reduction fumaces adopt either a tilting furnace body which is able to rotate by itself, as seen in converters for steel making, and a stationary furnace body as seen in blast furnace. For a tilting furnace body, if the work bricks wore to come to the end of their life, the residual melt consisting of molten iron and molten slag can be discharged by tilting the furnace body to let the melt flow through the tap hole located 25 at top or side ofthe furnace body. For a stationary furnace body, however, the discharge ofthe residual melt has to be done by allowing the furnace body to cool to solidify the melt, then by pulverizing or cutting thus solidified melt to pieces before discharging thereof. The period of allowing to stand for cooling the melt takes a long 6 time, and the funace repair time is extended to result in a low operation efficiency. In addition, the requirement of facilities and personnel for discharging work increases the production cost. There introduced several methods to solve the problem. For example, 5 Japanese Unexamined Patent Publication No. 2-66110 and Japanese Patent Unexamined Publication No. 3-253508 disclose a method to discharge the residual melt through a tap hole located at bottom of the furmace. Japanese Unexamined Patent Publication No. 2-66110 discloses a tap hole open/close device in which the tap hole which is opened and closed by a gate is located 10 at bottom ofthe furnace, and a plugging sand is charged into the tap hole through a top oxygen blowing lance which ascends and descends in the furnace to conduct opening and closing ofthe tap hole. Japanese Patent Unexamined Publication No. 3-253508 discloses a tap hole structure in which a sliding nozzle is placed at outlet of the tap hole at bottom ofthe furnace, a brick body provided with a passage for tapping inside 15 thereof while connecting the passage with the tap hole, and the tap hole is positioned above the furnace floor level to leave a specified quantity of the molten iron in the furnace. Since Japanese Unexamined Patent Publication No. 2-66110 allows to discharge the melt from bottom ofthe funace, the residual melt can be discharged from the tap 20 hole when the furace ends its life. During normal tapping operation, however, it is extremely difficult to plug the tap hole while leaving a specified quantity of molten iron in the furnace because the tap hole is necessary to be plugged with a force that resists the weight of the iron bath remained in the furnace. Furthennore, there is a problem that the charge of plugging sand into the tap hole is not possible. 25 Japanese Patent Unexamined Publication No. 3-253508 allows the charge of plugging sand into the tap hole. However, there are brick bodies standing in the furnace, so a certain quantity of the iron bath is unavoidably left in the furnace. If the standing brick bodies are broken, the residual melt can be discharged. In that case, 7 however, the standing brick bodies are necessary to be fabricated by a material and a structure which are readily broken, which may induce wear ofthe brick bodies to fail in securing the specified quantity of iron bath in the furnace during normal operation. As described above, even when a tap hole is located at bottom of the stationary furnace 5 body, it is extremely difficult to attain both the functions of leaving a specified quantity of iron bath in the furnace during normal operation and of letting readily discharge the residual melt at the end of furnace life. SUMMARY OF THE INVENTION 10 It is an object of the present inventioP to provide a metallurgical furnace and an operation method using the metallurgical furnace, wherein a cost of equipment and an operating cost can be reduced. First, to attain the object, the present invention provides a metallurgical furnace 15 comprising: a furnace body shell; a bottom wall comprising a lining brick, said lining brick being arranged inside of the furnace body shell; and a side wall comprising a water-cooled metallic panel, said water-cooled metallic 20 panel being arranged inside of the fumace body shell. It is preferable that said water-cooled metallic panel includes a water passage having a structure of a swirl figure. Secondly, the present invention provides a water-cooled panel arranged on a side 25 wall of a metallurgical furnace, the water-cooled panel comprising: a water-cooled metallic panel; a water passage having a structure of a swirl figure, said water passage being arranged in the water-cooled metallic panel. 8 Thirdly, the present invention provides a metallurgical furnace comprising: a furnace body shell; a fumace wall comprising water cooled panels, said furnace wall being arranged 5 inside of the funace body shell; metallic partition members which are arranged between water cooled panels and are fixed on the furace body shell; and a castable refractory layer which is formed in a portion surrounded by the water cooled panels, the partition members, and the furnace body shell. 10 It is preferable that said metallic partition member has a wedge shape and a cross section ofthe metallic partition member becomes narrower from the side ofthe furnace body shell to the inside of furmace. Fourthly, the present invention provides a metallurgical furnace comprising: 15 a furnace body for producing a molten metal containing iron and a slag therein and for accommodating the molten metal and the slag; a furnace body shell for forming an outer shell of the furnace body; an inner periphery brick which is arranged at an inner periphery of the furnace body that contacts the molten metal and a molten slag, said inner periphery brick 20 consisting essentially of at least one selected from the group consisting of MgO, A1 2 0 3 , graphite, SiC, and SiO 2 ; and a detection brick which is arranged on outside ofthe inner periphery brick, said detection brick containing a detection substance in an amount of 10 wt.% or more, said detection brick inducing no operational problem when the substance elutes into the 25 molten metal and the molten slag and that is readily detectable. It is desirable that the detection substance is at least one selected from the group consisting of Cr oxide, Sr oxide, and Zr oxide. It is desirable that the detection brick has a thickness of at least 30 mm. 9 Fifthly, the present invention provides a metallurgical furnace comprising: a furnace body comprising an upper vessel and a lower vessel, the furmace body being separable into the upper vessel and the lower vessel; 5 a support base which is located beneath the furnace body and is connected to the lower vessel, said support base supporting the furnace body when the upper vessel is connected with the lower vessel; lift means for raising the support base to contact the upper vessel and the lower vessel to each other and for lowering the support base to separate the lower vessel from 10 the upper vessel; position adjusting means for adjusting a vertical position of the support base which was raised by the lift means and holding the position ofthe support base; fixing means for fixing the support base, the vertical position thereof being adjusted by the position adjusting means; and 15 upper vessel support means for supporting the upper vessel at a specified lifted position when the furnace body is separated into the upper vessel and the lower vessel by the lift means. Sixthly, the present invention provides a method for replacing a lower vessel of a 20 metallurgical furmace, the method comprising the steps of: (a) providing a furnace body and a support base, the furnace body comprising an upper vessel and a lower vessel and being separable into the upper vessel and the lower vessel, the support base being located beneath the furnace body and being connected to the lower vessel; 25 (b) releasing a connection between the upper vessel and the lower vessel while supporting the furnace body by using the support base; (c) lowering the support base after the connection was released; 10 (d) separating the upper vessel from the lower vessel by supporting the upper vessel at a specified position using an upper vessel supporting means in the step (c) of lowering the support base; (e) transferring the separated lower vessel from directly beneath the upper vessel; 5 (f) bringing a new lower vessel connected to the support base to directly beneath the upper vessel; and (g) connecting the new lower vessel with the upper vessel by raising the support base. 10 Seventhly, the present invention provides a sealing device which is used in a metallurgical furnace, the sealing device comprising: a pair of flanges; a seal surface member which is attached to at least one seal surface of the pair of flanges; and 15 at least two seal members which are arranged between the seal surface member and the confronting seal surface or the confronting seal surface member and along a radius direction of the flange to seal therebetween. It is preferable that said seal member is a tube seal. Though the present sealing device is arranged at the flange portion, the portion is not limited to the flange portion. 20 The sealing device may be arranged at the welding portion of the seal members. Eighthly, the present invention provides a metallurgical furnace comprising: a furnace body; a tap hole which is arranged at a lower portion of the furnace body; a pan for receiving a prepared molten iron from a casting ladle; and 25 a passage to lead the molten iron from the pan to the tap hole for introducing the molten iron as a seed melt into the metallurgical furmace through the tap hole. 11 Ninthly, the present invention provides a method for operating a metallurgical furnace comprising the steps of: blowing a stirring gas from at least one bottom blowing nozzle at a bottom ofthe metallurgical furnace into an iron bath; 5 discharging an iron melt from a tap hole arranged at a side wall; and blowing an oxygen containing gas from said at least one bottom blowing nozzle by changing the stirring gas into the oxygen containing gas, thereby melting a refractory in the peripheral area ofthe at least one bottom blowing nozzle, enlarging a hole diameter ofthe at least one bottom blowing nozzle ; and discharging a residual 10 melt through the enlarged hole. The stirring gas may be blown from a side blowing nozzle near the bottom ofthe metallurgical furnace into the iron bath. The stirring gas may be blown from at least one bottom blowing nozzle at a bottom ofthe metallurgical furnace and a side blowing nozzle near the bottom of the metallurgical furnace into the iron bath. 15 It is preferable that the above method for operating the metallurgical furnace further comprises the steps of detecting a residual length of the bottom blowing nozzle by a sensor. BRIEF DESCRIPTION OF THE DRAWINGS 20 FIG. 1 is a cross sectional view of a water-cooled panel of Embodiment 1 according to the present invention. FIG. 2 is another cross sectional view of another water-cooled panel of Embodiment 1 according to the present invention. FIG. 3 is another cross sectional view of another water-cooled panel of 25 Embodiment 1 according to the present invention. FIG. 4 is another cross sectional view of another water-cooled panel of Embodiment 1 according to the present invention. 12 FIG. 5 is another cross sectional view of another water-cooled panel of Embodiment 1 according to the present invention. FIG. 6 is a schematic cross sectional view of a smelting reduction furnace provided with water-cooled panels according to Embodiment 1 of the present 5 invention. FIG. 7 is a cross sectional view of a structure of water passage in a conventional water-cooled panel. FIG. 8 is a schematic cross sectional view of a smelting reduction furnace provided with the water-cooled panels according to Embodiment 2 of the present 10 invention. FIG. 9 is a schematic view of the water-cooled panel of FIG. 8 seen from inside of the furnace. FIG. 10 is a schematic longitudinal cross section view of the water-cooled panel of FIG. 8. 15 FIG. 11 shows a state immediately before removing the water-cooled panel according to Embodiment 2 of the present invention. FIG. 12 shows a state after removing the water-cooled panel according to Embodiment 2 of the present invention. FIG. 13 shows a state of newly mounting the water-cooled panel according to 20 Embodiment 2 the present invention. FIG. 14 is a schematic cross sectional side view of a stationary furnace according to Embodiment 3 of the present invention. FIG. 15 is a schematic cross sectional plan view illustrating the brick laying structure at the side wall section of the furnace body according to Example 1 of 25 Embodiment 3. FIG. 16 is a schematic cross sectional plan view illustrating the brick laying structure at the side wall section of the furnace body according to Example 2 of Embodiment3. 13 FIG. 17 is a schematic plan view of a stationary smelting furnace according to Embodiment 4 of the present invention. FIG. 18 is a schematic cross sectional view ofthe smelting furnace of FIG. 17 viewed along X-X plane, illustrating the state that the upper vessel and the lower vessel 5 are joined together. FIG. 19 is a schematic cross sectional view ofthe smelting furnace of FIG. 17 viewed along X-X plane, illustrating the state that the lower vessel is removed. FIG. 20 is a schematic longitudinal cross sectional view ofthe smelting furace of FIG. 17 viewed along Y-Y plane. 10 FIG. 21 is a schematic longitudinal cross sectional view ofthe smelting fumace of FIG. 17 viewed along Z-Z plane. FIG. 22 is a cross sectional view illustrating a seal device of Embodiment 5 of the present invention. FIG. 23 is an explanation view illustrating a deformed state of the flange 15 according to Embodiment 5 of the present invention. FIG. 24 is an explanation view illustrating the replacement of compensation member after the deformation occurred on a flange according to Embodiment 5 ofthe present invention.. FIG. 25 is an explanation view illustrating a smelting reduction furnace according 20 to Embodiment 6 of the present invention. FIG. 26 is a cross sectional view along A-A line in FIG. 25, illustrating the structure of the passage to introduce molten iron according to Embodiment 6 of the present invention. FIG. 27 is a perspective view illustrating a structure of tap hole according to 25 Embodiment 6 of the present invention. FIG. 28 is a perspective view illustrating an example of structure of the tap hole to prevent spalling according to Embodiment 6 of the present invention. 14 FIG. 29 is another perspective view illustrating another example of structure of the tap hole to prevent spalling according to Embodiment 6 of the present invention. FIG. 30 is a schematic cross sectional side view of a stationary furnace body according to Embodiment 7 of the present invention. 5 FIG. 31 is an enlarged view of a bottom blowing nozzle of FIG. 30. FIG. 32 a graph of observed values of bottom blowing nozzle temperature, decreased length of bottom blowing nozzle, and backpressure of introduced oxygen, with time, according to Embodiment 7 ofthe present invention. 10 15 DESCRIPTION OF THE PREFERRED EMBODIMENT Embodiment 1 According to Embodiment 1 of the present invention, the structure of water 5 passage in a water-cooled panel which is made of metal and is mounted on a side wall of a metallurgical furmace, through which water passage a cooling water passes, wherein the water passage is in a swirl figure. The pressure drop across the water passage in the water-cooled panel ranging from the water-supply opening to the water-discharge opening is expressed by 10 equation (1). AP=[(C + k x L/D) x y x V 2 ]/(2 x g x 10000) (1) where: AP is the pressure drop across the water passage, (kgf/cm 2 ); c is the pressureloss factor at the turn of the water passage, (-); k is the friction factor on a straight section ofthe water passage, (-); L is the total length of the straight sections of 15 the water passage, (m); D is the equivalent diameter of the water passage, (in); y is the density ofthe cooling water, (kgf/cm 3 ); V is the flow speed ofthe cooling water, (m/sec); and g is the acceleration of gravity, (m/sec 2 ). The pressure loss factor C at the turn of the water passage referred herein designates the sum of the pressure loss factor (i at each turn. The pressure loss factor 20 C1 at the tum by 180 degrees is 2.42 on each turn, and the pressure loss factor (2 at the turn by 90 degrees is 0.965 on each turn. Thus, the pressure drop at the turn of 180 degrees becomes larger than that at the turn of 90 degrees by about 2.5 fold. When the number of turns increases, the pressure drop AP of the water passage becomes significantly depending on the pressure drop at the turns. 25 Since the water passage in a water-cooled panel according to Embodiment 1 adopts a swirl figure directing from the outer peripheral part to the center part of the water-cooled panel, most of the turns have 90 degrees of turn angle which gives less pressure loss factor, and reducing the number of 180 degree turns, though the number 16 of turns increases across the water passage. The total length of straight section L is unchanged from that in the prior art water passage. Therefore, the total pressure drop AP across the water passage decreases from that of the prior art water passage. 5 Embodiment 1 is described below referring to the drawings. FIGs. 1 through 5 show schematic cross sectional views of Embodiment 1. In these figures, the metallic water-cooled panel 1 has a width of W and a height of H. The water-cooled panels 1 shown in FIGs. 1 through 5 have the same size to each other. The water-cooled panel 1 is preferably made of copper cast which has 10 good thermal conductivity. The water-cooled panel 1 is provided with a water supply opening 3 and a water-discharge opening 4. Inside ofthe water-cooled panel 1, there formed a water passage 2 in a swirl figure. Thus, the cooling water supplied from the water-supply opening 3 passes through the water passage 2, and goes out from the water-discharge opening 4. The water passage 2 has a constant width d. 15 According to the water-cooled panel 1 shown in FIG. 1, both the water-supply opening 3 and the water-discharge opening 4 are located at center part of the water cooled panel 1. Consequently, the cooling water flows from the center part of the water-cooled panel 1 toward the outer peripheral part thereof through the water passage 2 in a swirled flow pattern, then turns the flow direction thereof at the outer 20 peripheral part to go back toward the center part through the water passage 2 in a swirled flow pattern. The turns in the water-cooled panel 1 consist of two 180 degree turns and fourteen 90 degree turns. According to the water-cooled panel 1 shown in FIG. 2, both the water-supply opening 3 and the water-discharge opening 4 are located at bottom section of outer 25 peripheral part of the water-cooled panel 1 in adjacent flow passes to each other. Consequently, the cooling water flows from the outer peripheral part toward the center part of the water-cooled panel 1, then turns the flow direction thereof at the center part 17 to go back toward the outer peripheral part. The turns in the water-cooled panel consist of two 180 degree turns and sixteen 90 degree turns. According to the water-cooled panel 1 shown in FIG. 3, the water-supply opening 3 is located at bottom section of the outer peripheral part of the water-cooled panel 1, 5 and the water-discharge opening is located at center part thereof Consequently, the cooling water flows from the outer peripheral part to the center part of the water-cooled panel 1 in a swirled flow pattern. The turns in the water-cooled panel 1 consist of one 180 degree turn and seventeen 90 degree turns. According to the water-cooled panel 1 shown in FIG. 4, the water-supply opening 10 3 is located at bottom section of outer periphery of the water-cooled panel 1, and the water-discharge opening 4 is located at top section of outer peripheral part thereof Consequently, the cooling water flows from the outer peripheral part of the water cooled panel 1 toward the center part thereof in a swirled flow pattern, then tums the flow direction thereof at the center part to return toward the outer peripheral part of the 15 water-cooled panel 1 in a swirled flow pattern. The turns in the water-cooled panel consist of two 180 degree turns and fifteen 90 degree turns. According to the water-cooled panel 1 shown in FIG. 5, the water-supply opening 3 and the water-discharge opening 4 are located at each end of bottom section of the outer peripheral part of the water-cooled panel 1. The turns consist of two 180 degree 20 turns and fifteen 90 degree turns. In these water-cooled panels 1 described above, the water-supply opening 3 and the water-discharge opening 4 may be inversely used to each other to guide the cooling water in reverse direction from the direction of flow shown in these figures, or the water-cooled panel 1 may be rotated by 180 degrees around the center axis of the 25 water-cooled panel 1, or the water-cooled panel 1 may be rotated to a mirror-synnetry position. To keep the pressure drop across the water passage 2 to a low level, it is preferable that the number of 180 degree turns is not more than two in a single water cooled panel 1. 18 Since the water passage 2 according to Embodiment 1 is in a swirl figure, both the width W and the height H ofthe water-cooled panel 1 are necessary to be a value of multiple of integral numbers to the width d ofthe water passage. However, optimum values ofthe width W and the height H ofthe water-cooled panel 1 may be 5 preliminarily determined based on the size of the target metallurgical furnace and the area for mounting the water-cooled panel 1. FIG. 6 illustrates a cross section of a smelting reduction furnace of iron ores provided with water-cooled panels 1 according to the present invention. The smelting reduction furnace 5 which is structured with lining bricks 7 and water-cooled 10 panels 1 on the inner surface ofthe furnace body shell 6 holds a molten iron 9 and a molten slag 10 inside thereof Oxygen is introduced through the top blowing lance 8 to reduce the iron ores. As shown in Fig. 6, the water-cooled panels 1 are arranged along the whole inner periphery ofthe fumace at the places where the molten slag 10 exists. Each ofthe water-cooled panels 1 is fixed to the furnace body shell 6 using 15 bolts (not shown). As described above, the water passage 2 of the water-cooled panel 1 according to Embodiment 1 has a swirl figure, the pressure drop AP across the water passage 2 is kept to a low level, thus reducing both the investment and the operating cost. In addition, the sections contacting with high temperature molten stag 10 are formed by 20 water-cooled panels 1, so the durability of the smelting reduction furnace 5 is significantly extended. Not limited to smelting reduction furnace 5, metallurgical furnaces such as electric furnaces and converters can be equipped with the water-cooled panels 1 according to the invention, and furthermore, the structure of the water passage 2 is not 25 limited to that above-described but may be in any shape if only the water passage is in a swirl figure. The following-given example applies the water-cooled panel shown in FIG. 1 to a smelting reduction furnace shown in FIG. 6. The water-cooled panel was made of 19 copper cast. The size of a single water-cooled panel 1 was 1,050 mm in width W, 1,200 mm in height H, and 90 mm in thickness. The water passage had a rectangular cross section having a size of 54 mm in width d and 40 mm in depth, with 12.69 m of the total length L ofthe straight sections, giving 0.0456 mm of equivalent diameter D. 5 The flow speed V of cooling water within the water passage was 7 m/sec giving 54 m 3 /hr of flow rate. To evaluate the pressure drop across the water-cooled panel according to the present invention, a water-cooled panel having the conventional water passage structure shown in FIG. 7 was separately used to let the cooling water flow therethrough under the same condition as above. The tums of water-cooled panel of 10 the conventional type consist of eleven 180 degree turns. The pressure drop AP across the water-cooled panel according to the present invention and that across the conventional water-cooled panel were computed on the equation (1) using the values of: the pressure drop factor (i per single 180 degree turn as 2.42; the pressure drop factor 2 per single 90 degree turn as 0.965; the friction 15 factor X at straight section of the water passage as 0.023 86; the density y of cooling water as 1000 kgf/m 3 ; and the acceleration of gravity g as 9,8 m/sec 2 . The computation formula for the water-cooled panel according to the present invention is given in equation (2), and that for the conventional water-cooled panel is given in equation (3). 20 AP = [(2.42 x 2 + 0.965 x 14 + 0.02386 x 12.69/0.0456) x 1000 x 72]/(2 x 9.8 x 10000) = 6.24 (kgf/cm 2 ) (2) AP = [(2.42 x 11 + 0.02386 x 12.69/0.0456) x 1000 x 72]/(2 x 9.8 x 10000) = 8.31 (kgf/cm 2 ) (3) Thus, the pressure drop AP across the water-cooled panel according to the present 25 invention was 6.24 kgf/cm 2 , and that of the conventional water-cooled panel was 8.31 kgf/cm 2 . Therefore, the power of a pump for circulating cooling water decreased by 7 kW per single water-cooled panel. The durability of water-cooled panel showed no 20 difference between the one according to the present invention and the conventional one. The water passage ofthe water-cooled panel according to Embodiment 1 to be mounted on walls of various types of metallurgical furnaces has a swirl figure, so the 5 pressure drop across the water passage is reduced to a low level, thus reducing both the investment and the operating cost. 21 Embodiment 2 An attachment structure of water-cooled panels in a metallurgical furnace comprises plurality of water-cooled panels arranged in rows on walls ofthe metallurgical fumace, metallic partition members fixed on the furnace body shell, and 5 a castable refractory layer formed in a range surrounded by the water-cooled panels, the partition members, and the fumace body shell. It is preferable that said metallic partition member has a wedge shape and a cross section of the metallic partition member becomes narrower from the side ofthe fumace body shell to the inside of furace. 10 Each of the water-cooled panels is separated from adjacent one by metallic partition members mounted on the furnace body shell. Also the castable refractory layer packed in the space between the water-cooled panel and the furnace body shell is separated from adjacent one by the partition members. Accordingly, only the target water-cooled panel is allowed to be replaced without damaging both the adjacent 15 water-cooled panels and the adjacent castable refractory layers packed in a space between other water-cooled panels and the furnace body shell. In addition, since the partition members are made of metal, replacement work does not damage them. Furthermore, the partition member is formed in a wedge shape narrowing from the furnace body shell side toward the inside furmace, so the removal of castable 20 refractory layer is easily done, thus prompt replacement of water-cooled panel is assured. Embodiment 2 of the present invention is described in detail referring to the drawings. FIG. 8 shows a schematic cross sectional view of a smelting reduction 25 fumace for iron ores in operating mode, which furnace is provided with the water cooled panels according to the present invention. FIG. 9 shows the rows of water cooled panels ofFIG. 8 viewed from inside ofthe furnace. FIG. 10 shows a longitudinal cross sectional view of the water-cooled panels of FIG. 8. 22 Regarding FIGs. 8 through 10, the smelting reduction furnace 101 of which the inside surface of the fumace body shell 102 is covered with lining bricks 103 and water-cooled panels 104 made of copper holds a molten iron 106 and a molten slag 107 inside thereof, and oxygen is supplied through a top blowing lance 105 to reduce 5 the iron ores. The water-cooled panels 104 are arranged in rows over the whole inner periphery ofthe furmace at the positions where the molten slag 107 exists while avoiding the water-cooled panels 4 from direct contact with the molten iron 106. The number of rows ofthe water-cooled panels 104 is four in vertical direction giving a staggered 10 arrangement, or giving displacements of a pitch of half width (W) of a water-cooled panel in each row. The water-cooled panel 104 is fixed to a position surrounded by the metallic partition members 8 that are attached by welding or other means onto the inside surface ofthe furnace body shell 102. The fixation of the water-cooled panel 104 is 15 done by bolts 110, 110 penetrating the fumace body shell 102 and by nuts 111, 111. In a space surrounded by the water-cooled panel 104, the partition members 108, and the furmace body shell 102, a castable refractory layer 109 of an castable refractory is packed. The water-cooled panel 104 is provided with a water-supply pipe 112 which penetrates the furnace body shell 102, and a water-discharge pipe 113 which also 20 penetrates the furnace body shell 102, through which cooling water passes across the water-cooled panel 104 for cooling thereof The castable refractory layer 109 is formed by pouring an castable refractory through a charge opening 114 after removing the plug 115 on charge opening 114. With the attachment procedure, the water cooled panel 104 is separated from above and beneath the water-cooled panels 104a, 25 104b, respectively, and the castable refractory layer 109 is also separated from above and beneath the castable refractory layers 109a, 109b, respectively. The partition members 108 are made of steel or stainless steel, and the cross section thereof is a wedge shape narrowing from the furnace body shell 102 side 23 toward inside ofthe furnace. FIG. 10 shows the partition member 108 formed by combining two flat steel sheets into a wedge shape. The partition member may be formed by bending a single piece of steel sheet or may be a wedge shape steel piece. The projection length (L) of the partition member 108 from the furnace body shell 102 5 is set to above the position of the surface of water-cooled panel 104 facing the furnace body shell 102 to prevent the castable refractory layer 109 from connecting other castable refractory layers at four adjacent sides thereof The projection length (L) is, however, not required to set to above the position of the surface of water-cooled panel 104 facing the inside of funace, and the projection length (L) may be at or lower than 10 the level ofthe water-cooled panel 104 facing inside of the furnace. The partition members 108 are not required to weld to the furnace body shell 102 but may be attached by other means such as bolts. Partition members 108 are also placed at boundary of the lining bricks 103 and the water-cooled panel 104. The partition member 108, however, has slope only on 15 the side facing the water-cooled panel 104 while keeping the side contacting the lining bricks 103 to flat to support the lining bricks 103. The procedure for replacing the water-cooled panel 104 is described below referring to Figs. 11 through 13. Fig. 11 shows a state immediately before the removal ofthe water-cooled panel 104. As shown in Fig. 11, firstly the water-supply 20 pipe 112 and the water-discharge pipe 113 are cut at outside of the fumace body shell 102. Then the nuts 111, 111 and the plugs 115, 115 of charge openings are removed. And a tool 116 attached to an air hammer or the like is inserted through the charge opening 114 to crush the castable refractory layer 109 to remove. After that, the water-cooled panel 104 is taken off to inside of the furmace. 25 Fig. 12 shows a state after removing the water-cooled panel 104. As shown in Fig. 12, the castable refractory layer 109 is removed from the partition members 108 and the furnace body shell 102 to minimize the residual amount ofthe castable 24 refractory layer 109. If excess amount of castable refractory layer 109 is left, the succeedingly- filled castable refractory layer 109 becomes fragile. Fig. 13 illustrates the state to newly mount the water-cooled panel 104. As shown in Fig. 13, the water-cooled panel 104 is attached by penetrating the bolts 110, 5 110, the water-supply pipe 112, and the water-discharge pipe 113 through the furnace body shell 102 from inside thereof Then, the water-cooled panel 104 is fixed using the nuts 111, 111. The castable refractory is charged from the charge opening 114 to form the castable refractory layer 109. After that, the plugs 115, 115 of charge openings are attached, and the water-supply pipe 112 and the water-discharge pipe 113 10 are connected to complete the replacement procedure. Owing to the procedure of replacement of water-cooled panel 104, only the target water-cooled panel 104 is able to be replaced while avoiding the damage on other water-cooled panels 104a, 104b and other castable refractory layers 109a, 109b. The above-described procedure deals with the case that the water-cooled panel 15 104 is attached to a smelting reduction furnace 101. The present invention, however, can be applied by the method described above also to an electric furnace or a converter. Although the arrangement of water-cooled panels 104 in the above-given description is staggered arrangement, it may be other arrangement such as squares to perform the effect of the present invention. In addition, the shape of water-cooled 20 panel 104 and the method to connect the water-cooled panel 104 with the furnace body shell 102 is not limited to the one described above but may be other one for applying the present invention if only the function is the same. According to Embodiment 102 ofthe present invention, a metallic partition member attached to the furnace body shell is located between water-cooled panels. 25 Therefore, replacement of only the target water-cooled panel can be done without damaging other water-cooled panels and other castable refractory layers, thus assuring repair of a water-cooled panel in a short time at a low cost. 25 Embodiment 3 According to Embodiment 3 ofthe present invention, the brick laying structure in a fumace body of a stationary furnace which continuously holds and manufactures a molten metal containing iron, comprises: bricks being arranged at innermost periphery 5 ofthe furnace wall that contacts the molten metal and a molten slag and being made of one or more kinds of bricks selected from the group ofthe bricks consisting mainly of MgO, A1 2 0 3 , graphite, SiC, or SiO 2 ; bricks being arranged outside of the innermost bricks, which contains a substance that induces no operational problem even when the substance elutes into the molten metal and the molten slag and that is readily detectable 10 as a detection material to concentrations of 10 wt.% or more. It is preferable that the detection material is one or more ofthe substances selected from the orniin enRi-tin, nfn Cr hnse nyide s Sr hae nwide qnd 7r he oyide It iq desirable that he bricks containing the detection material are arranged to a thickness of 30 mm or more. Also, it is desirable that the bricks arranged at innermost periphery of 15 the furnace is a single layer, the bricks containing the detection material are arranged in a single layer, and a single layer of bricks is inserted between the layer of bricks containing the detection material and a fumace body shell, thus forming a structure of three layers of bricks. According to Embodiment 3, a stationary furnace is used as the furnace body that 20 continuously holds and manufactures molten metal containing iron. The use of stationary fumace body allows to keep the investment to a low level compared with that of tilting furnace such as converter, thus contributing to the reduction in fixed cost in the production cost. In addition, that type of fumace allows to apply a water cooled metallic panel which has higher durability than refractory to the furnace walls at 25 sections contacting with slag and at upper wall sections therefrom, which contributes to the reduction of refractory cost. The furnace body has a structure of brick laying of at least two layers. The bricks 26 being arranged at innermost periphery of the furnace contacting the molten metal and molten slag which are held in the furnace, (hereinafter referred to simply as "the innermost periphery bricks"), are the bricks consisting mainly of MgO, A1 2 0 3 , graphite, SiC, or SiO2, which bricks are generally used when the furnace holds a 5 molten metal containing iron. Depending on the position in the furnace body, the innermost periphery bricks may be different one at each position, for example, bricks consisting mainly of MgO and bricks consisting mainly of SiC. To the outer side of the innermost periphery bricks, or to the furnace body shell side, the bricks that contain a substance which induces no operational problem even when the substance elutes into 10 the molten metal and into the molten slag, and which is readily detectable, (hereinafter referred to simply as "the detection bricks"), are arranged. The substance that is readily detectable according to the present invention means a substance that is contained very little in the raw materials to manufacture the metal containing iron and that is contained very little in the innermost periphery bricks. 15 During the operation of a furnace body having the above-described brick laying structure, the innermost periphery bricks wear caused by molten metal or molten slag, and finally the outer side of the detection bricks are exposed. The exposed detection bricks then wear, similar with the innermost periphery bricks, caused by the molten metal or the molten slag, and the detection substance elutes into the molten metal and 20 the molten slag. When samples are collected from the molten metal and the molten slag to analyze the content of the detection substance in the molten metal or the molten slag, the detection substance is detected as a result of exposure and wear of the detection bricks, which detection substance is not found during the period that the innermost periphery bricks hold the molten metal and the molten slag. In this way, at 25 the point that the detection substance is detected in the molten metal or the molten slag, the state that the innermost periphery bricks are lost by wear at somewhere in the fumace is informed. 27 The contents of detection substance in the detection brick are 10 wt.% or more, preferably 20 wt.% or more. Since the analysis limit of a metal containing iron and of a slag generated during the manufacture of metal is generally 10-3 wt.%, the detection substance cannot be detected unless it elutes into the molten metal or into the molten 5 slag to above the analysis limit. By including the detection substance to a level of 10 wt.% or more in the detection bricks, the detection of the detection substance becomes possible, thus preventing the accident of melt leak. When the content of the detection substance is 20 wt.% or more, the detection becomes more easily. A preferable detection substance is Cr base oxide, Sr base oxide, or Zr base oxide. 10 These oxides such as Cr 2 0 3 , SrO, and ZrO 2 do not induce operational problem even when they elute into the molten metal and into the molten slag containing iron. The raw materials to manufacture the molten metal containing iron contain very little amount of these oxides, and the above-described innermost periphery bricks contain very little amount of these oxides. Accordingly, detection of these elements in the 15 molten metal or the molten slag indicates that the innermost periphery bricks surely wore to expose the detection bricks. In addition, these oxides are stable compounds which have far higher melting point than the processing temperatures of from 1200 to 1800 'C of molten metal containing iron. The Cr 2 0 3 and ZrO 2 compounds have already been practically used 20 as the brick materials. The SrO compound is an oxide of alkali earth group metals which behave almost the same as MgO, CaO, and BaO, while having no toxicity which is seen in BaO, and cheap one. Even when these oxides are contained to 10 wt.% or more in bricks, the anti-erosion property of the bricks is high, giving no less anti-erosion property than that of the innermost periphery bricks applied to the present 25 invention. Thus, these oxides are most suitable ones as the detection substance. The detection bricks are preferably arranged to thicknesses of 30 mm or more. Even if the detection bricks are exposed, the anti-erosion property of the detection bricks is not significantly inferior to that of the innermost periphery bricks, so the 28 durability of the furnace body does not extremely degrade. Since, however, the analysis limit is 10'3 wt.% as described above, the detection substance cannot be detected unless the detection bricks are exposed to some area. As a margin of erosion ofthe detection bricks until the detection becomes possible, the detection bricks are 5 arranged to thicknesses of30 mm or more, preferably 50 mm or more. It is preferable that each of the innermost periphery bricks and the detection bricks is a single layer, and that a further layer of bricks is inserted between the detection bricks and the furnace body shell, thus forming total three layers of brick laying structure. Since each of the innermost periphery bricks and the detection bricks is a 10 single layer, even when the thickness of these bricks becomes thin caused by wear, they do not separate nor drop, and function their inherent durability, so the life of furnace body is not extremely shortened. The metal containing iron according to the present invention means pig iron, steel, iron alloy, and alloyed iron. 15 Embodiment 3 is described below referring to the drawings. Fig. 14 is a schematic cross sectional side view of a stationary furnace body for iron ore smelting reduction, illustrating a mode to carry out Embodiment 3. In the figure, the smelting reduction furnace 1 comprises an outer shell of the furnace body shell 202, and three layers of brick laying in a sequent order from the 20 inside ofthe furnace toward the furnace body shell 202 at the bottom section of the furnace body shell 202, the innermost periphery bricks 203, the indication bricks 204, and permanent bricks 205. The furnace 201 is fixed to the foundation 216 by the support frame 215. The molten iron 206 and the molten slag 207 are held at the position of the three-layered brick laying structure. At the upper section of the 25 furnace body shell 202 forming the side walls ofthe smelting reduction furnace 201, there provided a duct 213 which connects a dust collector (not shown) and a preliminary reduction furnace (not shown), and a raw material charge opening 214 to charge the raw materials to the furnace. A top blowing lance 208 penetrates through 29 the furnace body shell 202 at ceiling thereof in a movable mode in vertical direction, through which oxygen is blown into the furnace. At the bottom of the smelting reduction furace 201, there provided gas-blowing tuyeres 210 through which an inert gas and exhaust gas from the smelting reduction 5 furnace 201 are blown into the molten iron 206 as the stirring gas, is connected to a gas supply pipe 211, and also provided a tap hole 212 filled with mud agent 217 at a position of three layers brick laying structure on side walls of the furnace. Furthermore, at above the three layers brick laying structure on side walls of the smelting reduction furnace 201, water-cooled metallic panels 209 made of copper, 10 copper alloy, etc. are mounted on the inner periphery of the furace body shell 202. The water-cooled metallic panels 209 have high durability to the molten slag 207 so that the panels 209 are used as substitute for refractory. The innermost periphery bricks 203 contacting with the molten iron 6 and the molten slag 7 are the bricks consisting mainly of MgO, A1 2 0 3 , graphite, SiC, or SiO 2 . 15 In concrete terms, the materials for the bricks are selected from the group of MgO dolomite base bricks, MgO-graphite base bricks, A1 2 0 3 -graphite base bricks, high A1 2 0 3 base bricks, A1 2 0 3 -SiC-graphite base bricks, graphite base bricks, SiC base bricks, agalmatolite base bricks, clay base bricks, silica base bricks, etc. depending on each application. In that case, more than one kind of these bricks may be arranged in 20 separate sections of the same furnace, or a single type of the bricks may be lined over the whole wall surface ofthe furnace. As for a smelting reduction furnace 1 for iron ores, MgO-dolomite base bricks and MgO-graphite base bricks are preferred from the viewpoint of durability. The detection bricks 204 are the ones which contain a substance as the detection 25 substance that induces no operational problem even when the substance elutes into the molten metal 6 and into the molten slag 207 and that is contained to a very little amount in the innermost periphery bricks 203 and in the raw material to manufacture the molten iron 6, to a level of 10 wt.% or more. The phrase of "containing very little 30 amount in the innermost periphery bricks 203 and in the raw materials" means that the substance is allowed to exist to a slight amount as an impurity in the innermost periphery bricks 203 and in the raw materials to manufacture. Even if the innermost periphery bricks 203 and the raw materials to manufacture contain the substance to a 5 slight amount, the wear of the detection bricks 204 gives a change in the analyzed values, thus the loss of the detection bricks 204 can be identified. A preferable detection substance is a Cr base oxide, a Sr base oxide, or a Zr base oxide. The bricks containing these oxides may be MgO-Cr 2

O

3 base bricks, SrO Cr 2

O

3 base bricks, SrO-graphite base bricks, ZrO 2 base bricks, ZrO 2 -Cr 2

O

3 base bricks, 10 etc. If these bricks containing Cr base oxide, Sr base oxide, and Zr base oxide are arranged in separate sections respectively within a funace, the kinds of detection substances differ with the damaged section of the innermost periphery bricks 203, so the damaged position of the innermost periphery bricks 203 is identified. Since the permanent bricks 205 do not directly contact with the molten iron 206 15 and the molten slag 207, they may be made of a material having inferior anti-erosion property to that of the innermost periphery bricks 203. In concrete terms, MgO base bricks and clay base bricks may be used, and they are reused on replacement of bricks. To the smelting reduction furnace 201, iron ores, coal, calcium oxide, and lightly burned dolomite are charged through the raw material charge opening 214, oxygen is 20 blown through the top blowing lance 208, and an inert gas such as nitrogen gas is blown through the gas blowing tuyeres 210 to perform the smelting reduction ofthe iron ores to manufacture the molten iron 206. After the molten iron 206 is held to a specified amount and before the molten iron 206 reaches the level of the water-cooled metallic panels 209, the tap hole 212 is opened to tap the molten iron 206 and the 25 molten slag 20 7 into a molten iron holding vessel (not shown). After tapped the molten iron, the tap hole 212 is again filled with the mud agent 217 to stop the tapping, then resume the operation. 31 Samples are collected from thus tapped molten iron 6 and molten slag 207, and the detection substance in the molten iron or the molten slag is analyzed. The analytical method may be chemical analysis or instrumental analysis of fluorescent X ray analysis, ICP, etc. When the detection substance is detected in the molten iron 5 206 or in the molten slag 207, the detection indicates that the innermost periphery bricks 203 are lost by wear at some place within the smelting reduction fumace 201 and that the detection bricks 204 are exposed. Once the detection substance is detected, the operation of the smelting reduction fumace 201 is stopped, and the replacement of bricks is conducted. 10 With that procedure, the wear to lose the innermost periphery bricks 203 is surely identified without using special sensors. In addition, when any position of the innermost periphery bricks 203 wore, the phenomenon is detected. The above-given description deals with the iron ore smelting reduction fumace 201 as the stationary fumace body. The stationary furnace body is, however, not 15 limited to the smelting reduction furnace 201, and the fumace body may be applied to an iron scrap melting funace to which oxygen is blown to continuously melt the iron scrap and to a smelting funace to which oxygen is blown to reduce Ni ores and Cr ores by coke to manufacture molten Fe-Ni alloy and Fe-Cr alloy. To manufacture Fe Cr alloy, Cr base oxide cannot be used as the detection substance, so either Sr base 20 oxide or Zr base oxide is used. The above-given description deals with a three layer brick laying structure. The present invention structure is also carried out with a double layer brick laying structure consisting of the innermost periphery bricks 203 and the detection bricks 204, or with a three or more layers of brick laying structure. 25 Example 1 In a smelting reduction fumace 201 illustrated in Fig. 14, the innermost periphery bricks 203 were made ofMgO-graphite base bricks arranged to a thickness of 900 mm, and the detection bricks 204 were laid to three equally divided peripheral zones of 32 the furmace, bricks of each of which zones were made of MgO-Cr 2

O

3 base bricks 204a, SrO-graphite base bricks 204b, and SrO-Cr 2

O

3 base bricks 204c, as the detection bricks 204 to a thickness of 150 mm. Outside of the detection bricks 204, there arranged MgO base bricks as the permanent bricks 205 to a thickness of 150 mm. 5 The diameter ofthe furnace body shell 202 was 10 m. Fig. 15 shows a schematic sectional plan view ofthe side wall section ofthe furnace body having the above described brick laying structure. The oxygen supply rate through the top blowing lance 208 was 75,000 Nm 3 /Hr, the iron ore charge rate was 190 ton/Hr, the coal charge rate was 100 ton/Hr, the 10 calcium oxide charge rate was 204 ton/Hr, the lightly burned dolomite charge rate was 4 ton/Hr to conduct the smelting reduction of iron ores. The result was the manufacture of molten iron 6 at a rate of 125 ton/Hr while tapping the yielded molten iron 6 and the molten slag 207 at every two hours through the tap hole 212 into a molten iron holding vessel. The operation was continued while analyzing the content 15 of Cr and Sr in the tapped molten iron 206 and in the molten slag 207. After 70 days of operation, the Cr content in the molten iron 206 increased to a level of 0.02 wt.%, and the operation was stopped. There was no change in Sr content in both the molten iron 206 and the molten slag 207. Then, the furnace was disassembled and the damage in the furnace was observed. Fig. 15 shows the 20 observed result of damage by broken line. As shown by broken line in Fig. 15, the innermost periphery bricks 203 was lost at the side wall section to expose the MgO-Cr 2

O

3 base bricks 204a, giving a wear of about 20 mm. In other sections, however, the innermost periphery bricks 203 are left undamaged, and the SrO-graphite base bricks 204b and the SrO-Cr 2

O

3 base bricks 25 204c were left undamaged. Example 2 In a smelting reduction furnace 1 illustrated in Fig. 14, the innermost periphery bricks 203 were made of MgO-graphite base bricks arranged to a thickness of 900 mm, and 33 the detection bricks 204 were laid to two equally divided peripheral zones of the furnace, bricks of each of which zones were made of Zr0 2 base bricks 204d and Zr0 2 Cr 2

O

3 base bricks 204e, as the detection bricks 204 to a thickness of 150 mm. At outside of the detection bricks 204, there arranged MgO base bricks as the permanent 5 bricks 205 to a thickness of 150 mm. The diameter ofthe furnace body shell 202 was 10 m. Fig. 16 shows a schematic sectional plan view of the side wall section of the fumace body having the above-described brick laying structure. The oxygen supply rate through the top blowing lance 208 was 75,000 Nm 3 /Hr, the iron ore charge rate was 190 ton/Hr, the coal charge rate was 100 ton/-fr, the 10 calcium oxide charge rate was 4 ton/Ir, the lightly burned dolomite charge rate was 4 ton/Hr to conduct the smelting reduction of the iron ores. The result was the manufacture of molten iron 206 at a rate of 125 ton/Hr while tapping the yielded molten iron 6 and the molten slag 207 at every two hours through the tap hole 212 into a molten iron holding vessel. The operation was continued while analyzing the 15 content of Zr and Cr in the tapped molten iron 206 and molten slag 207. After 70 days of operation, the Zr content in the molten slag 207 increased to a level of 0.02 wt.% as ZrO2, and the operation was stopped. There was no change in Cr content in both the molten iron 6 and the molten slag 207. Then, the furnace was disassembled and the damage in the furnace was observed. Fig. 16 shows the 20 observed result of damage by broken line. As shown by broken line in Fig. 16, the innermost periphery bricks 203 was lost at the side wall section to expose the ZrO 2 base bricks 204d to about 10 m 2 of area, giving a wear of about 15 mm. In other sections, however, the innermost periphery bricks 203 are left undamaged, and the ZrO 2 -Cr 2

O

3 base bricks 204e were left 25 undamaged. According to Embodiment 3, in a stationary furnace body which continuously holds and manufactures molten metal containing iron, the worn state ofthe bricks lined over the whole area of inside surface of the furnace can be correctly and readily 34 identified at a low cost without using any special sensor, thus providing very large effect to the industries related. 35 Embodiment 4 The stationary smelting furnace allowing replacement of a lower vessel according to Embodiment 4 of the present invention comprises: a fumace body separable to at least an upper vessel and a lower vessel; 5 a support base located beneath the furnace body and being connected to the lower vessel, thus supporting the total furnace body during operation under the state of connecting the upper vessel with the lower vessel; a lift means to raise and lower the support base, thus separating and attaching the upper vessel and the lower vessel from and to each other; a position adjusting means to 10 adjust and hold the vertical position of the support base which was raised by the lift means; a fixing means to fix the support base, the vertical position thereof being adjusted by the position adjusting means; and an upper vessel support means to support the upper vessel at a specified lifted position in a state that the furnace body is separated to 15 two sections by the lift means. A method for replacing a lower vessel of a stationary smelting furnace including a furnace body separable to at least an upper vessel and a lower vessel, and a support base located beneath the furnace body and being connected to the lower vessel, thus supporting the total furnace body during operation under the state of connecting the 20 upper vessel with the lower vessel, the method comprises the steps of: releasing the connection between the upper vessel and the lower vessel while supporting the furnace body using the support base; lowering the support base; separating the upper vessel from the lower vessel in lowering passage of the 25 support base while supporting the upper vessel at a specified lifted position using an upper vessel supporting means; transferring thus separated lower vessel from directly beneath the upper vessel; 36 bringing a new lower vessel connected to the support base to directly beneath the upper vessel; then connecting the new lower vessel with the upper vessel by raising the support base. According to Embodiment 4, the furnace body is separable to at least two 5 sections, or the upper vessel and the lower vessel. During smelting when the upper vessel and the lower vessel are connected to each other, the support base located beneath the lower vessel supports the weight of the furnace body consisting of the upper vessel and the lower vessel and the weight of the raw materials and the reaction products in the furnace body, and functions as a stationary smelting furnace. 10 Consequently, the furnace according to the present invention becomes superior in mechanical strength to the tilting smelting furnaces, thus suppresses the increase in investment even in a large furnace. Furthermore, according to Embodiment 4, the replacement of lower vessel is conducted by releasing the connection between the upper vessel and the lower vessel 15 followed by supporting the upper vessel at a specified position at a lift not interfering the replacement of the lower vessel using a means to support the upper vessel, then by lowering only the lower vessel to separate thereof from the upper vessel. Therefore, the replacement of the lower vessel is easily done while avoiding the interference of the upper vessel. The load applied to the means to support the upper vessel is solely 20 the weight of the upper vessel, so the required mechanical strength of the means to support the upper vessel is significantly less than that of the support of tilting smelting furnace, and the increase in investment is suppressed. Embodiment 4 is described in detail referring to the drawings. Fig. 17 shows a schematic drawing of plan view of a stationary smelting furnace according to a mode 25 of present invention. Figs. 18 and 19 show schematic drawings of cross section of the smelting furnace of Fig. 17 viewed along X-X plane. Fig. 18 illustrates the state that the upper vessel and the lower vessel are joined together. Fig. 19 illustrates the state that the lower vessel is removed. Fig. 20 shows a schematic longitudinal cross 37 section ofthe smelting furnace of Fig. 17 viewed along Y-Y plane. Fig. 21 shows a schematic longitudinal cross section ofthe smelting fumace of Fig. 17 viewed along Z Zplane. In these figures, the furnace body 302 comprises an upper vessel 303 and a lower 5 vessel 304, inside wall of both of which is structured by a refractory. The upper vessel 303 and the lower vessel 304 are separably connected together using a flange 316 located at lower end of the upper vessel 303 and a flange 317 located at upper end of the lower vessel 304. A support base 305 is provided beneath the furnace body 302. Thus, the lower vessel 304 and the support base 305 are separably connected to 10 each other via a support bed 306 located on the support base 305 using bolts (not shown) or the like. Beneath the support base 305, there positioned total eight moving cotters 308 which are able to be inserted into a gap between the support bed 305 and the foundation 326. According to the mode herein described to carry out the present 15 invention, these moving cotters 308 are adopted as a means to adjust and hold the vertical position of the support base 305. The moving cotter 308 has a wedge shape cross section. Thus the adjustment of insertion depth of the moving cotters 308 into the gap between the support base 305 and the foundation 326 allows the adjustment of vertical position of the support base 305, or the position between an intermediate frame 20 312 and a support arm 313, (detailed description about the intermediate frame 312 and the support arm 313 is not given). The support base 305 is fixed to the foundation 326 using stud-anchor bolts 310 projecting onto the foundation 326. According to the mode herein described to carry out the present invention, these anchor bolts 310 are used as the fixing mechanism to 25 fix the support base 305 which was adjusted the vertical position thereof by the moving cotters 308. The anchor bolts 310 accounting total six of them are located within a pit 319 for accepting the anchor bolts, and a pin 325 is placed at a center part of each of the anchor bolt 310 to make the anchor bolt 310 possible to flex at the pin 38 position, thus avoiding the anchor bolt from interfering the movement ofthe support base 5. At each of the four corners of the foundation 326 corresponding to the support base 305, a pit 320 for installing jack is provided, and ajack 307 is installed in the pit 5 320. With the extension and retraction of the jacks 307, the support base 305 raises and lowers while supporting both the upper vessel 303 and the lower vessel 304, or supporting the lower vessel 304. According to the mode herein described to carry out the present invention, the jacks 307 are adopted as a lift means that raises and lowers the support base 305 to separate and attach the upper vessel 303 and the lower vessel 10 304 from and to each other. The jacks 307 are retracted into the pits 320 for installing jacks to avoid interfering the movement of the support base 305. There is a pit 308 beneath the furnace body 302. A vehicle 314 moves in the pit 308 along rails 315. The vehicle 314 loads the support base 305 in a state of supporting the lower vessel 304 to transfer. According to the mode herein described 15 to carry out the present invention, the vehicle 314 is adopted as the transfer means to bring out the lower vessel 304 from directly beneath the upper vessel 303. A support arm 313 is located at each of two sides of the upper vessel 303, and an intermediate frame 312 is located directly beneath the support arm 313. When the furnace body 302 is lowered by the jacks 307, the intermediate arm 313 is supported 20 by the intermediate frame 312 in the lowering course ofjacks 307, thus stopping further lowering of the upper vessel 303. Therefore, the lower vessel 304 loaded onto the vehicle 14 can be moved without interference of the upper vessel 303. According to the mode herein described to carry out the present invention, the intermediate frame 312 is adopted as the means to support the upper vessel to support the upper vessel 303 25 at a specified lifted position. The upper vessel 303 is provided with a top blowing lance 321 which penetrates the ceiling plate thereof, and a duct 324 which acts as the exhaust gas flow passage and also as the raw material charge opening. The lower vessel 304 is provided with a tap 39 hole 322 and a bottom blowing tuyeres 323. Thus the smelting furnace 1 is structured. The smelting furnace 301 is the one for smelting reduction process, and a flexible duct (not shown) is provided to the upper part of the duct 324 to seal the exhaust gas flowing through the duct 324 even while the upper vessel 303 is raising or 5 lowering. The procedure for replacing the lower vessel 304 in a smelting funace 1 described above is as follows. First, the vehicle 314 is prepared directly beneath the support base 305 which is 10 fixed by anchor bolts 310. And the connection between the flange 316 and the flange 317 is released, and the nuts 311 and the anchor bolts 310 are removed. Then, the jacks 307 are raised to bring them contact with the bottom face of the support base 305. After contacting the jacks 307 with the bottom face of the support base 305, further the jacks 307 are raised to let the jacks 307 support the upper vessel 303, the lower vessel 15 304, and the support base 305, thus forming a gap between the support base 305 and the moving cotters 308. In that state, the moving cotters 308 are withdrawn from the gap between the support base 305 and the foundation 326. After withdrawing the moving cotters 308, the jacks 307 are applied to gradually lower the upper vessel 303, the lower vessel 304, and the support base 305. 20 In the course of lowering, the support arm 313 is supported by the intermediate frame 312, and the upper vessel 303 stops lowering. The jacks 307, however, continue their lowering motion to load the support base 305 in a state that the support base 305 supports the lower vessel 304. The vehicle 314 that loads the lower vessel 304 and the support base 305 moves from directly beneath the upper vessel 303 to a 25 position for replacing the lower vessel (not shown). At the position for replacing the lower vessel, a support base 305 that mounts a prepared lower vessel 304 is loaded to the vehicle 314 using a crane (not shown) or the like. Alternatively, the used lower 40 vessel 304 may be removed from the support base 305 and a prepared lower vessel 304 may be loaded to the vehicle 314. Next, the vehicle 314 is moved to bring the prepared lower vessel 304 directly beneath the upper vessel 303. The support base 305 in a state of supporting the 5 prepared lower vessel 304 is raised using the jacks 307, thus bringing the flange 317 of the lower vessel 304 contact with the flange 316 of the upper vessel 303. After connecting the flange 316 with the flange 317, thejacks 307 are further raised to a position that the upper vessel 303 is pushed up by the lower vessel 304. Then the jacks 307 are stopped raising. In that state, the moving cotters 308 are inserted into a 10 gap between the support base 305 and the foundation 326, and the jacks 307 are lowered to place the support base 305 onto the moving cotters 308. To avoid applying the load of the furnace body 302 to the intermediate frame 312, the adjustment of vertical position of the support base 305 by the moving cotters 308 may be done on the basis of forming a gap of about 10 mm between the intermediate frame 15 312 and the support arm 313. The support base 305 is then fixed using the anchor bolts 310 and nuts 311, thus completing the replacement ofthe lower vessel 304. After attaching the lower vessel 304, the intermediate frame 312 and the support arm 313 may be in contact to each other. When, however, the smelting begins in the smelting furnace 301, both the 20 upper vessel 303 and the lower vessel 304 thermally expand, and the intermediate frame 312 and the support arm 313 are separated from each other, thus the support base 305 bears the whole weight. In this way, the smelting furnace 1 according to Embodiment 4 is able to replace the lower vessel 304 even for a stationary smelting fumace. In particular, for a 25 smelting furnace such as smelting reduction furnace that requires the replacement of the lower vessel 304, the furmace according to the present invention is able to be applied as a low cost smelting furnace without inducing increase in investment. 41 The above-given description deals with a smelting furnace 301 in which the furnace body is separated into two parts. The application of the present invention is not limited to that type of two pieces of furnace, and the upper vessel 303 may further be divided into two or more pieces, the internal walls ofthe upper vessel 303 may not 5 be structured by refractory. The lift means to let the upper vessel 303 and the lower vessel 304 separate and contact from and to each other, the position adjusting means that adjusts and holds the vertical position of the support base 305, the fixing mechanism to fix the support base 305, the upper vessel support means to support the upper vessel 303, and the moving means to transfer the support base 305 in a state that 10 supports the lower vessel 304 may not be limited to the above-described ones but may be conventional ones having individual functions thereof Since the smelting furnace according to the present invention is a stationary type and is able to replace the lower vessel at the bottom section thereof, the investment is significantly reduced compared with a tilting smelting furnace which can replace the 15 lower vessel. Conventional stationary smelting furnaces cannot replace the lower vessel thereof, and the life of the smelting furnace is determined by the damage of the lower vessel, so there is necessity of repair of whole furnace on every damage accident of the lower vessel. To this point, the present invention makes possible to repair the smelting furnace by replacing only the lower vessel, and the effect is remarkable. 20 42 Embodiment 5 A sealing device which is used in a metallurgical fumace, the sealing device comprises: a pair of flanges; 5 a seal surface member which is attached to at least one seal surface of the pair of flanges; and at least two seal members which are arranged between the seal surface member and the confronting seal surface or the confronting seal surface member and along a radius direction of the flange to seal therebetween. 10 It is preferable that said seal member is a tube seal and said tube seal is connected with a gas passage to introduce a seal-expansion gas. Further, the flange sealing device further comprises restriction members to fix the seal member to a specified position on the seal face; and a gas passage to introduce a purge gas into a space formed between the two seal members and a pair of flanges. 15 Fig. 22 illustrates a mode of sealing device according to Embodiment 5 applied to, for example, large size flange sealing of a furnace body with an internal pressure of 2 kgf/cm 2 . The sealing device seals between the lower flange 1 ( for example, 12,000 mm in outer diameter) and the upper flange 402. A seal face member 405 (for example, a cross sectional size of 300 x 30 mm) is attached to the seal face of the upper 20 flange 402. The seal face member 405 is mounted to the upper flange in a replaceable manner using bolts 411, 411. A packing is inserted between the rear face of the seal face member and the upper flange to assure the air-tightness between the seal face member and the upper flange. Between the seal face of the upper flange, or the seal face member 405, and the seal face of the lower flange 401, expansion seals 25 403, 403 ( for example, a cross sectional size of 40 x 40 mm) are inserted at inner side and outer side of the furnace with a specified distance therebetween. Each of the expansion seals 403, 403 has a tube shape which is able to introduce a gas thereinto, and is connected with each of passages of seal-expansion gas 407, 407. These gas 43 passages are connected with a gas (usually air) supply source (not shown), through which an expansion air is supplied while adjusting the supply pressure to maintain the air-tightness between the seal faces. At far sides of these expansion seals, there located restriction members 404, 404 (for example, a cross sectional size of 40 x 40 5 mm) being fixed to the lower flange, thus restricting the displacement of the expansion seals in flange radial direction. In the lower flange, a passage of purge gas 408 is formed, and the passage of purge gas 408 is connected to an inert gas (usually nitrogen gas) supply source (not shown). The end ofthe passage of purge gas 408 passes through a restriction member located between the expansion seals and opens the space 10 formed by the above-described expansion seals 403, 403 and the upper and lower seal faces. The purge nitrogen gas is introduced to the space. At the inner side (furmace side) of the lower flange, a shield plate 410 is attached to enclose the above-described seal structure to protect thereof from the heat inside of fumace. To each of the upper and lower flanges 401, 402, respectively, a passage 412 of cooling water for cooling 15 the flanges runs therethrough. Each of the flanges has holes 406 for bolts ( for example, seventy two M80 bolts). According to the device, the upper face of the restriction member 404 and the seal face member 405 are attached to each other, and the lower flange 401 and the upper flange 402 are connected together by the tightening bolts. Then, the expansion air of 20 3 kgftcm 2 is introduced to the two NBR expansion seals 403 through the two passages 407 of seal expansion gas, thus establishing the sealing by expanding the purge gas expansion gas seal to press thereof against the seal face member 405. Also the contact face of the restriction member which is fixed to the lower flange 1 is sealed by the expansion force of the expansion seal 403. Nitrogen gas of 2.5 kgf/cm 2 is 25 introduced to the space between the two expansion seals 403 through the two passages 408 of purge gas. With the introduced purge gas, toxic gases such as CO in the furnace does not come out from the furnace even when the expansion seal 403 at inner side facing the furnace fails to maintain the sealing perfonnance, resulting only 44 entering the purge gas (nitrogen gas) to the furnace. Thus the safety of the outside environment of the furmace is secured. Even when the furnace has a high temperature environment inside thereof, the shield plate 410 cuts off the direct radiation of heat to the expansion seal 403, and the passage 412 of cooling water for cooling flange 5 reduces the metal temperature near the expansion seal 403 to maintain the temperature ofthe expansion seal 403 to a heat-resistive level (for example, 80 0 C ) or less. According to the structure, if the gap between the lower flange 401 and the upper flange 402, as shown in Fig. 23, is about 10 mm or less, then the seal is established by the expansion force of the expansion seal 403. Even if, however, in the course of 10 repeated cycles of tightening and releasing the flanges, a flange is deformed to exceed the gap between the flanges 10 mm, the sealing performance can be maintained by inserting a seal 409 between the upper flange 402 and the seal face member 405, or, as illustrated in Fig. 24, by replacing the seal face member 405 by a new one which follows the deformed surface ofthe flange. Even when a seal face gathered flaws in 15 the course of tightening and releasing of flanges, only the seal face member 405 is required to be replaced. As described above, according to the present invention, the seal face on a flange is designed in a replaceable form, so the repair of the flange becomes easy, the compensation to deformation of flange face becomes possible, thus the sealing 20 performance is easily maintained. In addition, the application of plurality of expansion seals as the seal members on the flange improves the sealing performance. Furthermore, the introduction of a purge gas between the seal members prevents occurrence of gas leak even when the air-tightness degrades, thus increasing the safety. Those are significant effects of the present invention. 25 45 Embodiment 6 A metallurgical furmace comprises: a fumace body; a tap hole which is arranged at a lower portion of the fumace body; a pan for receiving a prepared molten iron from a casting ladle; and a passage to lead the molten iron from the pan to the tap hole for 5 introducing the molten iron as a seed melt into the metallurgical furmace through the tap hole. It is preferable that the metallurgical fumace further comprises a heat insulating sleeve which is arranged inside of the tap hole to prevent spalling when the molten iron is introduced. The heat insulating sleeve is one selected from the group consisting of a 10 pipe formed by chamotte brick and a pipe formed by chamotte castable. Also, it is desirable that the metallurgical furmace further comprises a heat insulating fiber or sheet which is arranged inside ofthe tap hole to prevent spalling; and a refractory pipe member being arranged inside of the fiber or sheet. The heat insulating fiber or sheet is made of a material selected from the group of a 15 rockwool material, a glass material, and a porous material. The refractory pipe member is formed by a material selected from the group consisting of a fired refractory or precast caster of A1 2 0 3 , MgO-C, and A1 2 0 3 -SiC-C. The following is the description of a mode of the apparatus to charge a seed melt 20 according to Embodiment 6 referring to Fig. 25. The apparatus is the one to charge the seed melt to a smelting reduction fumace. The apparatus comprises a pan 530 which receives a prepared molten iron 520 from a casting ladle 510, a smelting reduction furnace 550 provided with a tap hole 540, and a passage to introduce the molten iron from the pan 530 to the tap hole 540 ofthe smelting reduction furmace, 25 thus charging the molten iron in the pan as the seed melt from the tap hole of the smelting reduction fumace. If a blast furnace is available in steel works, the molten iron produced in the iron making process may be used as the seed melt. If an electric fumace is available in the steel making process, the molten iron produced by melting 46 pig iron in the steel making process may be used as the seed melt. Alternatively, a molten iron produced by melting and carburizing scrap may be used as the seed melt. The passage 560 to introduce molten iron guiding the molten iron in the pan is provided with, as shown in Fig. 26, a refractory pipe 562 through which the molten 5 iron passes, within the box 561. A sand 563 is packed between the box and the refractory pipe. The refractory pipe is requested to have durability only during the introduction period ofthe seed melt, so an inexpensive material such as SK34 may be used. According to the present invention, the structure of the refractory of the tap hole 10 is, as shown in Fig. 27, set bricks 544 having a rectangular outer figure and a circular inner cross section. The structure of the tap hole of a smelting reduction furnace is basically the same with that of blast furnace. Since molten iron and molten slag flow inside ofthe smelting reduction furnace, there occurs no mud precipitation in front of the tap hole to 15 a thickness over that of the refractory of tap hole, which is seen in blast furnace. Accordingly, an operation to recover the depth of the tap hole, which is applied in blast furnace, is not possible. Since the life of tap hole determines the life of the smelting reduction furnace body, care should be paid not to damage the refractory of tap hole by spalling during the charge of molten iron. 20 To prevent spalling of the refractory of tap hole during the charge of molten iron, there applied a method to preheat the refractory of tap hole by gas burners or the like. The seed melt temperature during the charge period is necessary at levels of 1400 'C or more to secure the time for preparing for operation after the charge of molten iron and to have a margin of temperature reduction during the preparation time. So the 25 prevention of spalling of refractory only by the preheating is difficult. Consequently, it is preferable, as shown in Fig. 28, that an insulation sleeve 541 to prevent spalling is placed inside of the above-described sleeve inside ofthe set bricks to prevent damage of the refractory during the charge of molten iron. The sleeve 541 is 47 structured by, for example, a pipe fabricated by chamotte base bricks or a pipe formed by chamotte base castable. According to a mode of the present invention illustrated in Fig. 29, an insulation fiber or sheet 542 to prevent spalling is placed at inner side of the set bricks 544 to 5 prevent the damage of tap hole during the charge of molten iron, and further a pipe member 543 made of refractory is located at inside of the fiber or sheet. The insulation fiber or sheet 542 is made of; for example, rockwool base material, glass base material, or porous material. The pipe member 543 made of refractory is stmctured by a fired refractory or a precast caster made of, for example, A1 2 0 3 , MgO 10 C, or A1 2 0 3 -SiO-C. The arrangement gives the inner diameter ofthe tap hole to a range of approximately from 50 to 100 mm. As described above, the present invention uses the tap hole of the smelting reduction furnace as the charge opening of the seed melt, so there is no need of mechanical seal means. That is, since a smelting reduction furnace is a facility 15 operated under high pressures of 0.2 MPa or more, if a charge opening for seed melt is separately provided, the seal of the opening is required to be maintained. To this point, when the tap hole is used also as the charge opening for the seed melt, as in the case of the present invention, the operation of the fumace can be resumed by plugging the opening using a mud gun after the charge, in accordance with common operation 20 procedure. Therefore, no mechanical seal means is necessary. In addition, the insulation performance of the tap hole increases, thus allowing to receive the seed melt while protecting the refractory of tap hole. Example The apparatus to charge seed melt, which is shown in Fig. 25 was operated under 25 the conditions given below. [Pan] Height: 2,000 mm Quantity of molten iron: 40 tons x 4 batches 48 [Passage to introduce molten iron (Pipe member made of refractory)] Height at pan side: 1,150 mm Length of pipe member made of refractory: 13 m Material ofrefractory pipe: SK34 5 [Tap hole] Height: 800 mm [Insulation sleeve to prevent spalling] Pipe fabricated by chamotte base bricks [Insulation fiber to prevent spalling] 10 Rockwool base material [Pipe made of refractory] Fired refractory made of A1 2 0 3 No damage was observed at the tap hole during the charge of molten iron. After 15 the charge of molten iron, the tap hole was plugged using a mud gun, thus operation was resumed in a short time. As described above, the present invention uses the tap hole also as the charge opening of seed melt, so the operation of the furmace can be resumed promptly after 20 plugging the tap hole. In addition, since the present invention adopts a structure to prevent spalling of the refractory of tap hole, a remarkable effect to give no damage of the refractory of tap hole is provided. 25 49 Embodiment 7 A method for operating a metallurgical furnace comprises the steps of: blowing a stirring gas from at least one bottom blowing nozzle at a bottom ofthe metallurgical furnace into an iron bath; 5 discharging an iron melt from a tap hole arranged at a side wall; and blowing an oxygen containing gas from said at least one bottom blowing nozzle by changing the stirring gas into the oxygen containing gas, thereby melting a refractory in the peripheral area ofthe at least one bottom blowing nozzle , enlarging a hole diameter of the at least one bottom blowing nozzle ; and discharging a residual 10 melt through the enlarged hole. It is preferable that the method for operating the metallurgical furnace further comprises the step of detecting a residual length of the bottom blowing nozzle by a sensor. The changing of the stirring gas into the oxygen containing gas is carried out when the residual length ofthe bottom blowing nozzle becomes equal to a reference 15 length. According to Embodiment 7, a stationary furnace body is applied as the furnace body for operating with a residual quantity of iron bath. By using a stationary furmace body, investment is maintained at a low level compared with that of tilting furnace body such as converter, thus contributing to the reduction of fixed cost in the 20 production cost. Furthermore, use of the stationary furnace body allows to mount water-cooled metallic panels instead of refractory at sections of furnace walls contacting the slag, which also contributes to the reduction of the cost of refractory of the furnace body. A tap hole is located at a side wall of the stationary furnace body, and the pig iron 25 and the molten slag yielded in the furnace are discharged through the tap hole continuously or intermittently, thus a specified quantity of iron bath is secured below the level of the tap hole throughout the operating period. An stirring gas is blown 50 through a bottom blowing nozzle located at bottom of the furnace to agitate the iron bath, thus enhancing the intrafumace reactions such as reduction. When the furnace ends its life resulted from wear of lining bricks ofthe stationary furnace body or from wear of bottom blowing nozzles, at least one ofthe bottom 5 blowing nozzles is switched from introducing the stining gas to introducing a gas containing oxygen to blow the gas containing oxygen into the furnace. Then, the oxygen in the gas containing oxygen reacts with the iron bath to yield FeO while generating heat. The generated heat and the yielded FeO melt the refractory of the bottom blowing nozzle and the refractory in the peripheral area of the bottom blowing 10 nozzle. As a result, a hole widened centering around the position that the bottom blowing nozzle existed is formed from inside of the furnace toward the outside thereof Then the widened hole penetrates the furnace bottom, thus allowing the residual quantity of melt in the furnace to discharge to outside thereof through the widened hole. 15 If the residual length of the bottom blowing nozzle is determined during operation by a sensor, then the discharge of residual quantity of melt can be conducted at the time that the residual length of the bottom blowing nozzle becomes equal to a reference length that is specified based on the life ofthe refractory. Accordingly, the refractory ofthe furnace is able to be used to a critical state, which further reduces the cost of 20 refractory of the furmace body. The term "iron bath"referred herein designates molten iron, molten steel, and a melt of molten iron alloy. The term "stirring gas" referred herein designates an inert gas such as nitrogen and Ar, and an exhaust gas generated from the stationary furnace body. The term "gas containing oxygen" referred herein designates air, oxygen, and 25 a gas mixture of air and oxygen. The present invention is described in the following referring to the drawings. Fig. 30 is a schematic drawing of cross sectional side view of a stationary furnace body 51 for iron ore smelting reduction illustrating a mode according to the present invention. Fig. 31 shows an enlarged view ofthe bottom blowing nozzle section of Fig. 30. In these figures, the outer shell is formed by a furnace body shell 602, and inside of which, a smelting reduction furnace 601 structured by work bricks 603 and 5 permanent bricks 604 in a sequent order from inside to outside of the furnace body, thus forming a two layer brick laying structure, is fixed on a foundation 623 using a support frame 622. The molten iron 606 and the molten slag 607 are held at the section of the two-layered brick laying structure. Above the furnace body shell 602 which forms the side walls ofthe smelting 10 reduction furnace 601, there positioned a duct 620 connecting to a dust collector (not shown) and to an auxiliary reduction furnace (not shown), and a raw material charge opening 621 through which the raw materials are charged into the furnace. A top blowing lance 618 is located at the ceiling of the furnace penetrating the furnace body shell 602 in a movable manner in vertical direction, and oxygen is blown therethrough 15 into the furnace. At the bottom of the smelting reduction furnace 601, a plurality of bottom blowing nozzles 608, 608a, 608b are located to blow an inert gas such as nitrogen and Ar, or an exhaust gas of the smelting reduction furnace 601 as the stirring gas into the molten iron 606. The number of the bottom blowing nozzles 608 is in a range of 20 approximately from 6 to 20, though it depends on the volume of the smelting reduction furnace 601. Each of the bottom blowing nozzles 608, 608a, 608b is a stainless steel pipe with inner diameters of from 10 to 30 mm, being surrounded by a sleeve brick 610 to prevent erosion ofthe bottom blowing nozzles 608, 608a, 608b made of stainless steel by the molten iron 606. 25 The method to mount the bottom blowing nozzles 608, 608a, 608b to the bottom of furnace may be, for example, done by forming an integral set of each ofthe bottom blowing nozzles 608, 608a, 608b with a sleeve brick 610 and a holding bracket 611, then by inserting them into the work brick 603 to fit them together, and by fix the 52 holding bracket 611 to the furnace body shell 602 by welding, bolting, or other adequate means. After that, the bottom blowing nozzles 608, 608a, 608b are connected with the gas supply pipe 612, through which pipe the stirring gas is introduced. The mode of the present invention described here uses nitrogen gas as an 5 example ofthe stirring gas. According to the mode of present invention described here, the gas supply pipe 612 connected to the bottom blowing nozzle 608 located at bottom center ofthe furnace is divided into the supply pipe 612a of stirring gas and the supply pipe 612b of gas containing oxygen. The gas blown through the bottom blowing nozzle 608 is 10 able to be switched between the stirring gas and the gas containing oxygen using a valve 613 located on the supply pipe 612a of stirring gas and a valve 614 located on the supply pipe 612b of gas containing oxygen. Inside ofthe bottom blowing nozzle 608, an inner pipe 609 made of stainless steel is placed, and the tip of the inner pipe 609 reaches the inside surface of the furnace. 15 An optical fiber 617 is inserted into the inner pipe 609 to fit thereto along with a mortar (not shown). The tip of the optical fiber 617 at outer side of the furnace is connected to a sensing device 616. The sensing device 616 and the optical fiber 617 structure a sensor 615 which determines the residual length of the bottom blowing nozzle 608. The determination of the residual length ofthe bottom blowing nozzle 608 using the 20 sensor 615 is done by the procedure given below. The sensing device 616 is a device that has functions of transmitting and receiving optical pulse signals and of processing and computing the signals. The optical pulse signals transmitted from the sensing device 616 pass through the optical fiber 617, and reflect at the tip of the optical fiber at inner side of the furnace 25 to return to the sensing device 616. The sensing device 616 determines the time between the optical pulse signal transmission and reception, and computes the length of the optical fiber 617 to the tip thereof at inner side ofthe furnace. With the wear of the bottom blowing nozzle 608, the optical fiber 617 also wears, so the length of the 53 optical fiber 617 to the tip at inner side ofthe furnace agrees with the length of the bottom blowing nozzle 608 to the tip at inner side of the furnace. Thus the residual length ofthe bottom blowing nozzle 608 is determined. At a section of two layered brick laying structure on the side walls ofthe funace, 5 a tap hole 605 filled with a mud agent 624 is located. At above the brick laying structure on the side walls of the smelting reduction furnace 601, the water-cooled metallic panels 619 made of copper and copper alloy are attached along the inner periphery of the furnace body shell 602. The water-cooled metallic panels 619 have higher durability to the molten slag 607 than refractory, so they are used as a substitute 10 for refractory. To the smelting reduction furnace 1 with the above-described structure, iron ores, coal, calcium oxide, and lightly burned dolomite are charged through the raw material charge opening 621, oxygen is blown through the top blowing lance 618, and nitrogen is blown through the bottom blowing nozzles 608, 608a, 608b to conduct smelting 15 reduction of the iron ores to manufacture the molten iron 606. After the molten iron 606 is produced to a specified quantity and before reaching the level thereof to the level of the water-cooled metallic panels 619, the tap hole 605 is opened to discharge the molten iron 606 and the molten slag 607 into a molten iron holding vessel (not shown). After discharged the molten iron, the tap hole 605 is filled with the mud 20 agent 624 to stop discharge, then resume the operation of the furnace. During operation, if the sensor 615 determines that the residual length of the bottom blowing nozzle 608 becomes equal to the reference length, or if visual observation or thermocouple observation detects that the residual thickness of the work bricks 603 becomes the reference thickness, then the gas blown through the bottom 25 blowing nozzle 608 is switched to the gas containing oxygen. In that case, the blowing of stirring gas through the bottom blowing nozzles 608a, 608b is not required, and it may be stopped. The gas containing oxygen is selected from air, oxygen, and a mixed gas of air and oxygen. 54 The reference value of residual thickness of the work bricks is in a range of approximately from 40 to 80 mm, and the reference value of residual length of the bottom blowing nozzle 8 is the one that the length fitting the work bricks 603 becomes 40 to 80 mm. Since, however, the wearing rate of the work bricks 603 and of the 5 bottom blowing nozzle 608 differs with individual use objects, the reference values of residual length and residual thickness are not limited to the above-described ones, and optimum values may be set on each use object of the funace. When the gas containing oxygen is blown through the bottom blowing nozzle 608, the molten iron 606 is oxidized to yield FeO while generating heat. The 10 generated heat firstly melts the bottom blowing nozzle 608 made of stainless steel, then the FeO and the oxidation heat melt the sleeve brick 610 in the peripheral area of the bottom blowing nozzle 608, thus forming a widened concavity at tip ofthe bottom blowing nozzle 608. Continuous blowing ofthe gas containing oxygen develops the concavity from inner side ofthe furnace toward the furnace body shell 602 side, and a 15 widened hole is formed inside of the sleeve brick 610 extending from the inner side of the furnace to the funace body shell 602 side. Fig. 31 shows the widened hole by a broken line in the sleeve brick 610, and the inside diameter of the widened hole is designated by a symbol D. When the widened hole reaches the position ofthe holding bracket 611, the holding bracket 611 melts, then the molten iron 606 and the 20 molten slag 607 in the furnace drop to flow into a molten iron holding vessel (not shown) located beneath the furnace bottom in advance, thus the molten iron and the molten slag are discharged from the furnace. Part of the optical fiber 617 and ofthe gas supply pipe 612 simultaneously melt. Flow rate ofthe gas containing oxygen which is blown through the bottom 25 blowing nozzle 8 having inner diameters of from 10 to 30 mm is preferably in a range of from 100 to 1,000 Nm 3 /1r. Less than 1,000 Nm 3 /Hr of flow rate results in slow melting rate, which takes too long time until discharge. Over 1,000 Nm 3 /Hr of flow 55 rate induces a cooling effect caused by the blown-in gas, thus slowing the melting of sleeve brick 10, which also takes too long time until discharge. Under the conditions described above, the inner diameter D ofthe widened hole becomes to a range of from 100 to 200 mm. Thus, the molten iron 6 left in the 5 furnace is promptly discharged, for example, within a few minutes for a quantity of about 500 tons. Since the inner diameter D ofthe widened hole is in a range of from 100 to 200 mm, the recovery of operation is possible with a work similar to that for a common replacement work of bottom blowing nozzle 608. The common replacement work of bottom blowing nozzle 608 means a work that the holding 10 bracket 611 is separated from the furnace body shell 602, that both the bottom blowing nozzle 608 and the sleeve brick 610 are taken out together, and that a bottom blowing nozzle 8 which was newly assembled integrally by a sleeve brick 610 and a holding bracket 611 is inserted to fit in the work brick 603, thus conducting the replacement work. Consequently, the inner diameter D ofthe hole is not necessary to widen to 15 over 200 mm. For example, if the hole is widened to 400 mm, the recovery work takes too long time, which is not preferable. As described above, the molten iron 606 and the molten slag 607 are discharged from the fumace using the bottom blowing nozzle 608, and the residual melt is safely discharged at a low cost without using no special device. 20 The description given above deals with an iron ore smelting reduction furnace 601 as the stationary furnace body. The stationary fumace body is, however, not limited to the smelting reduction furnace 601, and the present invention is able to be applied also to an iron scrap melting furnace which continuously melts iron scrap while blowing oxygen into the furmace, or to a smelting furnace which produces 25 molten Fe-Ni alloy and Fe-Cr alloy by reducing Ni ore and Cr ore by coke under oxygen blowing. The number and the positions of the bottom blowing nozzles that blow a gas containing oxygen into the furnace are not limited to those described above, and the gas containing oxygen may be blown through a plurality of bottom blowing 56 nozzles. The sensor 615 is also not limited to that described above, and it may have a structure to bury an optical fiber 617 into the sleeve brick 610, or alternatively, a coaxial cable or two electrically conductive wires insulated from each other may be used instead ofthe optical fiber 617 to sense the flowing electromagnetic pulse signals. 5 In addition, the application of the present invention is not affected by adopting the bottom blowing nozzle 608 made of a refractory instead of stainless steel. Example The embodiment is described in the following using the smelting reduction 10 furnace 601 shown in Fig. 30. To inside surface ofthe furnace body shell ofthe furnace having a diameter of 10 m, the work bricks made ofMgO-graphite base bricks were laid to a thickness of 900 mm, and MgO-base bricks as the permanent bricks were laid to a thickness of 150 mm to outside ofthe work brick layer. The bottom blowing nozzle was made of a stainless steel pipe having 29 mm in outer diameter and 15 25 mm in inner diameter. An optical fiber having a diameter of 0.2 mm was inserted into a stainless steel pipe having 17 mm in outer diameter and 12 mm in inner diameter along with mortar. The total number of the bottom blowing nozzles was ten, among which, one located at center of the furmace was used to introduce the gas containing oxygen. 20 The smelting reduction of iron ores was conducted under the conditions given below. The total rate of nitrogen gas supply through the bottom blowing nozzles was in a range of from 8,000 to 12,000 Nm 3 /Hr. The rate of oxygen supply through the top blowing lance was 75,000 Nm 3 /Hr. The rate of iron ore charge was 19 ton/Hr. The rate of coal charge was 100 ton/Hr. The rate of calcium oxide charge was 4 25 ton/Hr. The rate of lightly burned dolomite charge was 4 ton/Hr. The resulted production rate of the molten iron was 125 ton/Hr. The operation was continued while discharging the yielded molten iron and molten slag through the tap hole into a molten iron holding vessel at every two hours. 57 After 75 days of operation, the length of the bottom blowing nozzle inserted into the work bricks was determined to 50 mm by the sensor, the operation was stopped. Oxygen was blown into the furnace through the bottom blowing nozzle at a rate of 300 Nm 3 /Hr. The discharge of molten iron began on 33 minutes had passed after blowing 5 the oxygen, and the discharged molten iron gave a quite uniform straight flow. Within 3 minutes, all the quantity was discharged accounting for 520 tons of molten iron into the molten iron holding vessel. After completing the discharge of molten iron, the discharge of molten slag began. The tapping rate decreased with the discharge of molten slag, and finally the widened hole was plugged with the slag and 10 the chips of worn bricks, thus ended the discharge. Fig. 3 gives a graph of observed values. They include: the temperatures of bottom blowing nozzle determined by thermocouples buried in the sleeve bricks at outer peripheral area in the vicinity of boundary between the work bricks and the permanent bricks; the reduction in length ofthe bottom blowing nozzle determined by 15 sensors; and the backpressure of blown oxygen. These values were observed with time after the beginning of oxygen introduction. As seen in Fig. 32, the temperatures of bottom blowing nozzle ranged from 400 to 600 *C, and these values are no problem in view of temperature. The backpressure gradually decreased with time, and lowered to 4 kg/cm 2 at discharge time. At the beginning of oxygen introduction, 20 the length of the bottom blowing nozzle between the tip of inner side of the furnace and the holding bracket was about 100 cm. The decreased length of the bottom blowing nozzle determined by sensors also gave about 100 cm. So the accuracy of sensors was proved. After the intralmace area was cooled, visual observation was given to outside 25 and inside ofthe furnace, and to the hole widened for discharging the melt. The result was that the fumace held only 3 to 4 tons of residue consisting mainly of carbon materials, which suggested an extremely good discharge state. The discharge hole was widened to diameters of from 100 to 150 mm, and the hole area stayed within the 58 sleeve bricks. The visual observation confirmed that no damage occurred on the devices around the fumace bottom area. According to the present invention, the stationary fumace body adopts blowing of a gas containing oxygen into the furnace through a bottom blowing nozzle which is 5 normally used to introduce stirring gas, thus widening the hole to mount the bottom blowing nozzle to discharge the residual melt, so the residual melt is surely discharged at a low cost. As a result, the operating efficiency of the furmace body significantly increases, while remarkably reducing the cost to discharge the residue in the fumace. Therefore, the industrial effect is significant. 10 59

Claims

1. A metallurgical furnace comprising: 5 a furnace body shell; a bottom wall comprising a lining brick, said lining brick being arranged inside of the furnace body shell; and a side wall comprising a water-cooled metallic panel, said water-cooled metallic panel being arranged inside ofthe furnace body shell. 10

2. The metallurgical furnace of claim 1, wherein said water-cooled metallic panel includes a water passage having a structure of a swirl figure.

3. A water-cooled panel arranged on a side wall of a metallurgical furnace, the water 15 cooled panel comprising: a water-cooled metallic panel; a water passage having a structure of a swirl figure, said water passage being arranged in the water-cooled metallic panel. 20

4. A metallurgical furnace comprising: a furnace body shell; a furnace wall comprising water cooled panels, said furnace wall being arranged inside of the furnace body shell; metallic partition members which are arranged between water cooled panels and 25 are fixed on the furnace body shell; and a castable refractory layer which is formed in a portion surrounded by the water cooled panels, the partition members, and the furnace body shell. 60

5. The metallurgical furnace of claim 4, wherein said metallic partition member has a wedge shape, a cross section of the metallic partition member becoming narrower from the side of the furnace body shell to the inside of furnace. 5

6. A metallurgical furnace comprising: a furnace body for producing a molten metal containing iron and a slag therein and for accommodating the molten metal and the slag; a furnace body shell for forming an outer shell ofthe furnace body; 10 an inner periphery brick which is arranged at an inner periphery ofthe furnace body that contacts the molten metal and a molten slag, said inner periphery brick consisting essentially of at least one selected from the group consisting of MgO, A1 2 0 3 , graphite, SiC, and SiO 2 ; and a detection brick which is arranged on outside of the inner periphery brick, said 15 detection brick containing a detection substance in an amount of 10 wt.% or more, said detection brick inducing no operational problem when the substance elutes into the molten metal and the molten slag and that is readily detectable.

7. The metallurgical furnace of claim 6, wherein the detection substance is at least 20 one selected from the group consisting of Cr oxide, Sr oxide, and Zr oxide.

8. The metallurgical furnace of claim 6, wherein the detection brick has a thickness of at least 30 mm. 25

9. The metallurgical furnace of claim 6, further comprising a single brick layer which is arranged between the detection brick and the furnace body shell. 61

10. A metallurgical furnace comprising: a furnace body comprising an upper vessel and a lower vessel, the furnace body being separable into the upper vessel and the lower vessel; 5 a support base which is located beneath the furnace body and is connected to the lower vessel, said support base supporting the furnace body when the upper vessel is connected With the lower vessel; lift means for raising the support base to contact the upper vessel and the lower vessel to each other and for lowering the support base to separate the lower vessel from 10 the upper vessel; position adjusting means for adjusting a vertical position of the support base which was raised by the lift means and holding the position of the support base; fixing means for fixing the support base, the vertical position thereof being adjusted by the position adjusting means; and 15 upper vessel support means for supporting the upper vessel at a specified lifted position when the furnace body is separated into the upper vessel and the lower vessel by the lift means.

11. A method for replacing a lower vessel of a metallurgical furnace, the method 20 comprising the steps of: (a) providing a furnace body and a support base, the furnace body comprising an upper vessel and a lower vessel and being separable into the upper vessel and the lower vessel, the support base being located beneath the furnace body and being connected to the lower vessel; 25 (b) releasing a connection between the upper vessel and the lower vessel while supporting the furnace body by using the support base; (c) lowering the support base after the connection was released; 62 (d) separating the upper vessel from the lower vessel by supporting the upper vessel at a specified position using an upper vessel supporting means in the step (c) of lowering the support base; (e) transferring the separated lower vessel from directly beneath the upper vessel; 5 (f) bringing a new lower vessel connected to the support base to directly beneath the upper vessel; and (g) connecting the new lower vessel with the upper vessel by raising the support base. 10

12. A sealing device which is used in a metallurgical furnace, the sealing device comprising: a pair of flanges; a seal surface member which is attached to at least one seal surface of the pair of flanges; and 15 at least two seal members which are arranged between the seal surface member and the confronting seal surface or the confronting seal surface member and along a radius direction of the flange to seal therebetween.

13. The sealing device of claim 12, wherein said seal member is a tube seal. 20

14. The sealing device of claim 13, wherein the tube seal has a gas passage to introduce a seal-expansion gas.

15. The sealing device of claim 12, further comprising: 25 restriction members to fix the seal member to a specified position on the seal surface; and a gas passage to introduce a purge gas into a space formed between the at least two seal members and the pair of flanges. 63

16. A metallurgical fumace comprising: a fumace body; a tap hole which is arranged at a lower portion of the fumace body; 5 a pan for receiving a prepared molten iron from a casting ladle; and a passage to lead the molten iron from the pan to the tap hole for introducing the molten iron as a seed melt into the metallurgical fumace through the tap hole.

17. The metallurgical fumace of claim 16, further comprising a heat insulating sleeve 10 which is arranged inside of the tap hole to prevent spalling when the molten iron is introduced.

18. The metallurgical fumace of claim 17, wherein the heat insulating sleeve is one selected from the group consisting of a pipe formed by chamotte brick and a pipe 15 formed by chamotte castable.

19. The metallurgical furmace of claim 16, further comprising: a heat insulating fiber or sheet which is arranged inside of the tap hole to prevent spalling; and 20 a refractory pipe member being arranged inside of the fiber or sheet.

20. The metallurgical furnace of claim 19, wherein the heat insulating fiber or sheet is made of a material selected from the group of a rockwool material, a glass material, and a porous material. 25

21. The metallurgical furnace of claim 19, wherein the refractory pipe member is formed by a material selected from the group consisting of a fired refractory or precast caster of Al 2 0 3 , MgO-C, and A1 2 0 3 -SiC-C. 64

22. A method for operating a metallurgical furnace comprising the steps of: blowing a stirring gas from at least one bottom blowing nozzle at a bottom of the metallurgical furnace into an iron bath; 5 discharging an iron melt from a tap hole arranged at a side wall; and blowing an oxygen containing gas from said at least one bottom blowing nozzle by changing the stirring gas into the oxygen containing gas, thereby melting a refractory in the peripheral area of the at least one bottom blowing nozzle , enlarging a hole diameter of the at least one bottom blowing nozzle ; and discharging a residual 10 melt through the enlarged hole.

23. The method of claim 22, further comprising the step of detecting a residual length of the bottom blowing nozzle by a sensor. 15

24. The method of claim 23, wherein the changing of the stirring gas into the oxygen containing gas is carried out when the residual length of the bottom blowing nozzle becomes equal to a reference length.

25. The method of claim 22, wherein the step of blowing a stirring gas comprises 20 blowing a stirring gas from at least one bottom blowing nozzle at a bottom of the metallurgical furnace and a side blowing nozzle near the bottom of the metallurgical furnace into the iron bath. 25 65