JP2012052731A - Furnace building structure of furnace side wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a furnace building structure of a furnace side wall capable of preventing extrusion of refractories to the inside of a furnace and elongating a service life of the refractories.SOLUTION: This furnace building structure of the furnace side wall is constituted so that an inclined face (30) is formed on a top face of a lowermost refractory (1), a thickness of an intermediate refractory (2) is gradually increased from the inside (21a) of the furnace to the outside (21b) of the furnace, the uppermost refractory (3) is disposed in a state of being pressed by a top end shell (4) of a shell (20), and the refractories (1, 2, 3) are disposed in a state of not extruded to the inside (21a) of the furnace.

Description

  The present invention relates to a furnace building structure on a side wall of a kiln, and more particularly, to an improvement of the furnace building structure at a portion that protrudes inside an electric furnace.

Conventionally, in a kiln, a refractory is lined on the inside of the iron skin, but a general kiln has a round or rectangular shape when viewed from directly above, and the iron skin structure is straight or inside. It has a structure that is concave and convex outward. Therefore, the refractory applied on the inside is also straight or concave on the inside. In this case, when the inside of the kiln becomes high temperature, the refractories are pressed against each other by thermal expansion, and a force is exerted so that the refractories are pressed against the iron skin side.
However, exceptionally, there are kilns that are concave in many parts, but only partially convex. In such a case, at the tip of this convex part, when the inside of the kiln becomes high temperature, the refractories come into contact with each other by thermal expansion, and the refractory in this convex part is separated from the iron skin and pushed out into the furnace. Power works. In this case, there is a problem that the refractory at the tip is pushed into the furnace and is damaged, and further, the refractory at that portion is lost, so that the damage is enlarged.

Several improvements have been proposed for this problem.
That is, in patent document 1, while showing the structure which connects the refractory of the same part in the tundish used for continuous casting of steel with the metal on the back side and an anchor, and making a convex part and a crevice on the upper and lower surfaces of the stacked brick, A brick structure to be fitted is proposed.
Moreover, when constructing an irregular refractory, Patent Document 2 introduces an attempt to suppress the protrusion of the refractory to the inside of the furnace by an anchor block attached to the iron shell.

JP-A-8-117975 JP 2009-45654 A

Since the conventional refractory structure on the side wall of the kiln is configured as described above, the following problems exist.
That is, in the configuration of Patent Document 1, there is a problem that if this is applied to an electric furnace, the refractory is broken from the anchor portion or the brick is broken from the fitting portion, resulting in damage. The electric furnace uses a large refractory compared to the tundish, and it is presumed that a large stress concentration occurred due to the high temperature in the furnace.

Moreover, in the structure of patent document 2, when it applied to a large sized shape like an electric furnace, there existed a problem that an anchor block broke by the stress concentration to an anchor block.
The present invention intends to provide a furnace construction structure for suppressing the protrusion of the refractory constituting the convex side wall to the inside of the furnace at a portion that is convex inside the electric furnace. is there. In other words, the present applicant uses a large refractory to reduce the number of joints themselves to suppress joint damage, and converts the force with which the refractories are pressed against each other by thermal expansion into a force toward the iron skin side of the convex part. Such a structure has been studied and the present invention has been achieved.

  A furnace construction of a furnace side wall according to the present invention has a convex furnace wall projecting inside the iron skin of the furnace, and the lowermost refractory and the intermediate stage in which the convex furnace wall is laminated in the height direction. In the furnace construction of the furnace side wall composed of the refractory and the uppermost refractory, the lowermost refractory is constrained not to be pushed into the furnace, and is formed on the upper surface of the furnace refractory so that the inside of the furnace is high. An inclined surface that is lower than the inside of the furnace on the side wall side of the iron skin, a thickness in the vertical direction of the intermediate-stage refractory, and a first thickness located inside the furnace, and the intermediate A second thickness which is formed on the side wall side of the step refractory and is thicker than the first thickness, and the uppermost refractory is restrained from being pushed into the furnace, and the uppermost refractory And a top end iron skin arranged to press downward. The bottom refractory is constrained not to be pushed into the furnace by a furnace bottom brick provided in the furnace, or fixed by an anchor, or fixed by a furnace bottom brick and an anchor, or fixed by a hardware, Alternatively, the structure is fixed by an anchor and a hardware, and the uppermost refractory is fixed so as not to be pushed into the furnace by an anchor or a fixing pin, and the lowermost refractory The key brick is provided between the object and the intermediate-stage refractory, and the inclination angle between the upper surface of the lowermost refractory and the horizontal direction is in the range of 5 to 35 degrees. Further, the intermediate stage refractory is composed of any one to six pieces, and the surface angle difference between the upper surface direction and the lower surface direction of the intermediate stage refractory is 1 degree to Configuration that is in the range of 10 degrees There, also, said between the crest steel shell and top refractory, a configuration in which compressible filler is provided as an expansion margin.

Since the construction of the furnace side wall according to the present invention is configured as described above, the following effects can be obtained.
That is, it has a convex furnace wall that protrudes inside the iron skin of the kiln, and the convex furnace wall is composed of a lowermost refractory, an intermediate refractory, and an uppermost refractory laminated in the height direction. The bottom refractory is constrained so as not to be pushed into the furnace, and is formed on the upper surface of the furnace refractory so that the inner side of the furnace is high on the side of the iron side. An inclined surface that is lower than the inside of the furnace, a thickness in the vertical direction of the intermediate stage refractory, and a first thickness located inside the furnace, and the side wall side of the intermediate refractory The uppermost refractory is constrained not to be pushed into the furnace, and is arranged to press the uppermost refractory downward. A large kiln such as an electric furnace because it is composed of In can suppress damage to the refractory at the portion that is convex to the furnace interior, it becomes possible to dramatically extend the life of the kiln.
In addition, the lowermost refractory is restrained so as not to be pushed into the furnace by a furnace bottom brick provided in the furnace, or fixed by an anchor, or fixed by a furnace bottom brick and an anchor, or fixed by a hardware. Alternatively, the bottom refractory can be securely fixed by being fixed by the anchor and the hardware.
In addition, since the key brick is provided between the lowermost refractory and the intermediate refractory, the extrusion of each refractory into the furnace can be reliably prevented.
Moreover, the inclination angle which the upper surface of the said lowermost stage refractory makes with a horizontal direction is the range of 5-35 degree, Therefore The extrusion to the furnace inner side of a lowermost stage refractory can be prevented.
Further, the intermediate stage refractory is composed of any one of 1 to 6, so that the manufacture is easy and the furnace building operation is also easy.
The surface angle difference between the upper surface direction and the lower surface direction of the intermediate refractory is in the range of 1 degree to 10 degrees, so that the thickness can be reduced inside the furnace and increased outside the furnace, A force toward the outside of the furnace can be exerted by the pressing force due to expansion.
Between the uppermost refractory and the top end iron skin, a contractible filler is provided as an expansion allowance to absorb the thermal expansion in the vertical direction of each refractory, Damage and the like can be prevented.

It is a vertical direction sectional view showing an example of a furnace construction of the present invention. It is horizontal direction sectional drawing which shows an example of the furnace construction of this invention. It is a figure which shows an example of the vertical direction cross section of the refractory of the lowest stage of this invention. It is a figure which shows an example of the vertical direction cross section of the refractory of the intermediate | middle stage of this invention. 5 is a vertical sectional view showing a furnace construction of Comparative Example 1. FIG. 6 is a vertical sectional view showing a furnace construction of Comparative Example 2. FIG.

  The present invention provides a furnace construction that improves the layered structure of the refractory that protrudes inside the electric furnace, prevents the refractory from being pushed into the furnace, and extends the life of the refractory. The purpose is to do.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a furnace building structure for a furnace side wall according to the present invention will be described with reference to the drawings.
In FIG. 1, what is indicated by reference numeral 100 is a kiln, and a part of the iron skin 20 is bent in a convex furnace wall 101 formed to project inward from a part of the kiln 100. A top iron skin 9, a top iron skin 4, a side wall iron skin 7, and a bottom iron skin 8 are formed.

  A permanent refractory 10 and the furnace wall wear refractory shown in FIG. 2 are laminated along the side wall side skin 7 on the bottom iron skin 8, and a furnace in the furnace 21 is partly attached to the permanent refractory 10. A laminated refractory 22 is provided in a state where a part thereof is in contact with the furnace bottom brick 12 on the bottom backing stamp 11.

The molten metal 14 </ b> A located on the furnace bottom brick 12 is in contact with a part of the laminated refractory 22.
The laminated refractory 22 is composed of a bottom refractory 1, an intermediate refractory 2, and a top refractory 3 from the bottom side, and each refractory 1, 2 is interposed between the refractories 1, 2. The key brick 5 is provided so as not to be pushed out into the furnace 21 side.
The fixing pin 6 provided on the top end iron skin 4 passes through the compressible filler 13 provided between the uppermost refractory 3 and the upper end refractory 3 and is screwed to the uppermost refractory 3. By being inserted, the uppermost refractory 3 is prevented from being pushed out to the furnace inner side 21a.
The contractible filler 13 has an absorbing action as an expansion allowance of the refractories 1, 2, and 3.

Next, FIGS. 1 to 4 will be described more specifically.
In the first aspect of the present invention, in the convex furnace wall 101 portion in which the kiln 100 is convex on the inside,
The lowermost refractory 1 (shown in FIG. 3) constrained so as not to be pushed out into the furnace 21, and the upper surface of the lower refractory 1 is higher at the furnace inner side 21 a and lower at the side wall side iron skin 7 side. The bottom refractory 1 with
One or a plurality of intermediate stage refractories 2 (shown in FIG. 4), and the vertical thickness of each intermediate stage refractory is thin at the furnace inner side 21a and thick at the furnace outer side 21b. Refractory 2 and
An uppermost refractory 3 which is constrained not to be pushed into the furnace 21;
The top iron skin 4 installed so as to press the uppermost refractory 3 downward,
It is a refractory furnace construction consisting of

The second is that the lowermost refractory 1 of the invention 1 is restrained from being pushed out to the furnace inner side 21a by the furnace bottom brick 12 installed on the furnace inner side 21a and / or fixed by an anchor (not shown). And / or a refractory furnace construction structure fixed by hardware (not shown).
The third is a refractory building structure in which the uppermost refractory 3 is fixed by an anchor (not shown) or fixed by a fixing pin 6 in the first and second aspects.
The fourth is a refractory building structure in which the key brick 5 is inserted between each refractory 1, 2, 2, 2 in the first to third aspects.

When constructing a refractory member that protrudes toward the furnace inner side 21a, it is necessary to use a large-sized refractory. Damage occurs. In order to suppress this, it is necessary to reduce the joint itself. As a countermeasure for this, it is preferable to use a large refractory structure and to have about 1 to 3 blocks in the horizontal direction. More preferably, it is 1 to 2. In the case of dividing into two or three, it is not preferable to use a through joint in the vertical direction, and it is preferable to use a so-called staggered joint in which the joint is shifted so that the vertical joint does not become a through joint.
It is necessary to prevent the lowermost refractory 1 from being pushed into the furnace 21 by some method. Several measures can be taken to prevent extrusion into the furnace 21. One example is to construct the bottom brick 12 on the front side of the furnace inner side 21a of the lowermost refractory 1. Another means is that the lowermost refractory 1 is coupled to the iron skin 20 by an anchor or a hardware (not shown) and receives a force acting to push it out to the furnace inner side 21a. Unless measures are taken to prevent the lowermost refractory 1 from being pushed out, the lowermost refractory 1 is pushed out into the furnace inner side 21a by the thermal expansion of the adjacent refractory.

It is necessary to provide an inclination so that the upper surface 30 of the lowermost refractory 1 is high at the furnace inner side 21a and lower at the furnace outer side 21b. An example thereof is shown in FIG.
That is, an inclined surface 30 is formed so as to descend from the furnace inner inner surface 16 to the side wall side outer surface 17 of the lowermost refractory 1. By this inclination, a plurality of refractories to be installed thereon are held, and a force toward the furnace outer side 21b is given to these blocks by a binding force with the ceiling iron shell 4 described later.
It is preferable that an inclination angle A formed by the upper surface of the lowermost refractory 1, that is, the inclined surface 30, with the horizontal direction H is in the range of 5 degrees to 35 degrees. If the angle is less than 5 degrees, it is not preferable because the intermediate stage refractory 2 cannot be prevented from being pushed into the furnace inner side 21a. On the other hand, when the angle exceeds 35 degrees, the pressing force applied from the intermediate refractory 2 to the lowermost refractory 1 becomes too large as a force acting on the furnace inner side 21a, and the stepped refractory 1 is pushed out to the furnace inner side 21a. The potential increases. The angle is more preferably in the range of 8 degrees to 25 degrees.

The intermediate stage refractory 2 is formed of one or a plurality of refractories in which the vertical thickness of each stage refractory is thin at the furnace inner side 21a and thick at the furnace outer side 21b. An example thereof is shown in FIG. That is, the first thickness T ₁ which is the vertical height of the inner surface 18 inside the furnace inside the intermediate refractory 2 is the second thickness T ₂ which is the vertical height of the outer side wall 19 on the outer side wall. It is configured to be smaller.
By making the vertical thickness of each refractory thin at the furnace inner side 21a and thicker at the furnace outer side 21b and restraining them from above and below in the vertical direction, a vertical squeezing force is generated by thermal expansion, And it becomes possible to work the force which goes to the furnace outer side 21b with the urging force. Making the vertical thickness of the refractory thin at the furnace inner side 21a and thicker at the furnace outer side 21b can be defined by a surface angle difference B formed by the upper surface direction M and the lower surface direction N, which are two surfaces in the vertical direction of the refractory. . The surface angle difference B is preferably 1 to 10 degrees. If the surface angle difference B is smaller than 1 degree, the pressing force does not work sufficiently, and the intermediate refractory 2 is pushed out into the furnace. On the other hand, if the surface angle difference B is larger than 10 degrees, it becomes difficult to configure the in-furnace refractory with a plurality of refractories for the lowermost refractory 1. More preferably, it is 3 to 8 degrees. The surface angle difference B of a plurality of refractories is not necessarily the same, and the surface angle difference B may be changed depending on the step.

  The number of the intermediate refractories 2 in the height direction is 1 to 6. When the number is small, the refractory becomes large and manufacturing and building work are difficult. On the other hand, when the number of refractories is large, manufacturing becomes easy, but problems such as increased joints and poor corrosion resistance at those portions occur. A more preferable number is 2 to 4.

The method of connecting the intermediate refractory 2 with the hardware and the anchor introduced in Patent Document 1, the method of forming irregularities on the upper and lower surfaces of the refractory, and the method of suppressing with the anchor block of Patent Document 2 Attempts were made on the convex part of the furnace, but none of them was effective because the intermediate refractory 2 cracked. This is presumed that when a large structure such as an electric furnace is required, a greater force is applied to the refractory and the refractory is destroyed.
Via the uppermost refractory 3, the force generated in the lowermost refractory 1 and the intermediate refractory 2 is transmitted to the top end iron shell 4, and the force acting vertically downward from the iron skin 4 is transmitted to the intermediate refractory. Tell 2 Further, like the lowermost refractory 1 and the intermediate refractory 2, the uppermost refractory 3 has a force that is pushed out to the inside of the furnace due to the thermal expansion in the horizontal direction.

  In the exemplary view of the present invention shown in FIG. 1, an example is shown in which the upper and lower surfaces of the uppermost refractory 3 are parallel in shape. The upper and lower refractories 3 are parallel to each other because the uppermost refractory 3 is finally inserted between the top iron shell 4 and the intermediate refractory 2 for the convenience of building. However, the present invention is not limited to this. For example, in the structure in which the top end iron skin 4 is attached later, it may be inclined so as to be thin at the furnace inner side 21a and thick at the furnace outer side 21b like the intermediate refractory 2. When such an inclination is applied, a force is exerted so that the uppermost refractory 3 is pushed out to the furnace outer side 21b by the above-described vertical pressing force.

On the other hand, in the case of being parallel as shown in FIG. 1, the force that pushes out to the furnace outer side 21b does not work due to the pressing force, and only the force that pushes out to the furnace inner side 21a is applied. In this case, it is necessary to connect to the top iron core 4 side with an anchor or a hardware (not shown) so as not to be pushed out to the furnace inner side 21a by this force. Since the uppermost refractory 3 is located higher than the surface of the electric furnace, the heat load is lower than that of the lowermost refractory 1 and the intermediate refractory 2, and even if an anchor or a hardware (not shown) or a fixing pin 6 is attached. Refractories will crack and will not be destroyed. Further, in order to absorb the thermal expansion in the vertical direction of the lowermost refractory 1, the intermediate refractory 2, and the uppermost refractory 3, there is an expansion allowance between the uppermost refractory 3 and the top end iron skin 4. As shown, a retractable filler 13 is provided. As the compressible filler 13, a stamp material, a fiber board, a fire-resistant blanket, a plastic refractory, or the like can be used. The fixing pin 6 may be made of a known material such as metal, refractory, or ceramic. The furnace bottom brick 12 may be an irregular refractory such as a regular brick or a stamp material. When the bottom brick 12 melts down and the remaining size is reduced, it may be appropriately repaired with a refractory for repair.
In addition to the above, it is possible to provide the key brick 5 between the refractories so as to prevent the refractories from sliding out and moving in the joint direction. The size, shape, and number of key bricks can be those normally used.

The refractory and key brick 5 used in the present invention may be a general material used for a furnace wall of an electric furnace, and is not particularly limited. For example, magnesia-carbonaceous, magnesia-based Dolomite, dolomite / carbon, magnesia / dolomite, magnesia / dolomite / carbon, magnesia / lime / carbon, magnesia / chrome. Precast blocks of irregular refractories can also be used, but have the disadvantage of being somewhat inferior in terms of corrosion resistance. More preferably, a refractory material of a fixed shape is used.
The construction method is not particularly limited, and a general construction method can be used. Although it is preferable to use joint mortar, it is applicable also to construction which does not use joint mortar.

Example FIG. 1 and FIG. 2 show a vertical sectional view and a horizontal sectional view when the furnace construction structure according to the present invention is applied to a refractory construction part that protrudes toward the furnace inner side 21a of a 140-ton electric furnace. Show. The lowermost refractory 1 supported the force of pushing out into the furnace inner side 21a by constructing a small brick in the furnace inner side 21a. The upper surface inclination angle A of the lowermost refractory 1 was 12 degrees. The intermediate-stage refractory 2 is formed of three regular refractories in the vertical direction, and the surface angle difference B formed between the upper surface direction M and the lower surface direction N of each refractory is 4 degrees. The uppermost refractory 3 has parallel upper and lower surfaces, and the upper surface thereof is fixed to the top end iron skin 4 with a fixing pin 6. Above the uppermost refractory 3, there is a top end skin 4, which has a structure that suppresses the pushing-up force from the lower side. A key brick 5 was installed between the lowest refractory 1 and the intermediate refractory 2 and between the plurality of intermediate refractories 2. The shape of the key brick 5 was a cylindrical shape, the size was φ70 mm, and the height was 50 mm. A stamp material having a thickness of 100 mm was applied as the compressible filler 13 between the uppermost refractory 3 and the top end iron skin 4. The thickness of the large refractory from the furnace inner side 21a to the furnace outer side 21b, so-called construction thickness, was set to 700 mm. Further, the thickness in the vertical direction of the five refractories 1 to 3 from the lowermost stage to the uppermost stage was 1500 mm. Moreover, the total width of the large refractory in the horizontal direction was 1720 mm, and was divided into two in the horizontal direction. In addition, both large refractories and key bricks were made of magnesia and carbon.
The electric furnace having a built-in structure according to the present invention constructed as described above can be operated for one year or more and has a life of 2556 charges. When the refractory using the damaged state was collected and analyzed, the large refractory according to the present invention has no major damage such as cracking and peeling, the joint is solid, and the refractory is pushed into the furnace. There was no evidence of this. The main cause of damage was melting, confirming the superiority of the present invention.

Comparative Example FIG. 5 shows a cross-sectional view of Comparative Example 1 in the vertical direction. The construction pressure, construction height, and width in the horizontal direction of the refractory were the same as in the previous examples, and the refractory material was also the same.
When viewed in the height direction, refractories 1, 2, and 3 in which the lowermost, intermediate, uppermost and all upper and lower surfaces are parallel are constructed, and the lowermost refractory 1 is divided into the inside of the furnace as in the embodiment. This is the construction of the bricks. With such a structure, the force of pushing out to the furnace inner side 21a was supported. The uppermost refractory 3 from the lower second refractory was connected to the iron skin 4 by a fixing pin 6 extending from the top iron skin 4. The construction body according to the comparative example 1 was used in the same electric furnace as the example, and the basic operation conditions were used without change.
In Comparative Example 1, the service life was about 5 months, and the number of uses was 1051 charges. When the refractory using the damaged state was collected and analyzed, the intermediate refractory 2 was fixed with the fixing pin 6, but the force to push it into the furnace was strong, and from the hole through which the fixing pin 6 passes. It was found that a crack occurred and eventually pushed inside the furnace.

Next, FIG. 6 shows a sectional view of Comparative Example 2 in the vertical direction. When viewed in the height direction, refractories 1, 2 and 3 are constructed with the bottom, middle and top tiers all parallel to the top and bottom surfaces, and the bottom refractory 1 is constructed with a small brick inside the furnace. The same as in Comparative Example 1, but between the lowermost refractory 1 and the lower second refractory, between the lower third refractory and the lower fourth refractory It differs from the comparative example 1 in that the key bricks are sandwiched between them, and the fixing pin 6 extending from the top end iron skin 4 is connected only to the uppermost refractory 3.
In Comparative Example 2, the service life was about 7 months, and the number of uses was 1210 charges. As in Comparative Example 1, the used refractory was collected and analyzed. As a result, the uppermost refractory 3 was not particularly damaged, but the intermediate refractory 2 was approaching the inside of the furnace.

  The furnace construction of the furnace side wall according to the present invention can be applied not only to an electric furnace but also to other molten metal containers.

DESCRIPTION OF SYMBOLS 1 Bottom refractory 2 Intermediate refractory 3 Top refractory 4 Top end skin 5 Key brick 6 Fixing pin 7 Side wall side skin 8 Bottom iron skin 9 Upper iron skin 10 Perm refractory 11 Furnace bottom stamp material 12 Furnace bottom brick 13 Retractable filler 14 Molten metal surface 14A Molten metal 15 Furnace wall wear refractory 16 Furnace inner surface 17 Side wall side outer surface 18 Furnace inner surface 19 Side wall side outer surface 20 Iron skin 21 Furnace 21a Furnace 21b Outer furnace side 100 Furnace furnace 101 Convex furnace wall

Claims (8)

The bottom refractory (1) having a convex furnace wall (101) protruding inside the iron skin (20) of the kiln (100), the convex furnace wall (101) being stacked in the height direction. In the furnace construction of the furnace side wall composed of the middle refractory (2) and the uppermost refractory (3),
The lowermost refractory (1) is constrained not to be pushed out into the furnace (21), and is formed on the upper surface of the furnace refractory (21a) so that the inner side (21a) is high and the side wall side iron skin of the iron skin (20). An inclined surface (30) that is lower than the furnace inner side (21a) on the (7) side,
A first thickness (T ₁ ) formed as a vertical thickness of the intermediate refractory (2) and located inside the furnace (21a), and the side iron on the side wall of the intermediate refractory (2) A second thickness (T ₂ ) formed on the skin (20) side and thicker than the first thickness (T ₁ );
The uppermost refractory (3) is constrained not to be pushed out into the furnace (21), and the top iron provided to press the uppermost refractory (3) downward. Leather (4),
A furnace construction on the side wall of a kiln characterized by comprising   The lowermost refractory (1) is restrained so as not to be pushed out into the furnace inside (21a) by the furnace bottom brick (12) provided in the furnace (21), or fixed by an anchor, or the furnace bottom 2. A furnace construction structure for a furnace furnace side wall according to claim 1, wherein the structure is fixed by a brick (12) and an anchor, or by a hardware, or by an anchor and a hardware.   3. The construction of a furnace furnace side wall according to claim 1 or 2, wherein the uppermost refractory (3) is fixed so as not to be pushed out into the furnace inside (21a) by an anchor or a fixing pin (6). Furnace structure.   The kiln according to any one of claims 1 to 3, wherein a key brick (5) is provided between the lowermost refractory (1) and the intermediate refractory (2). Side wall furnace construction.   The inclination angle (A) formed by the upper surface of the lowermost refractory (1) with the horizontal direction (H) is in the range of 5 degrees to 35 degrees, according to any one of claims 1 to 4. A furnace construction on the furnace side wall.   6. The furnace erection structure of a furnace furnace side wall according to any one of claims 1 to 5, wherein the intermediate refractory (2) comprises any one of 1 to 6.   The surface angle difference (B) formed by the upper surface direction (M) and the lower surface direction (N) of the intermediate-stage refractory (2) is in the range of 1 to 10 degrees. The furnace construction on the side wall of the kiln.   The contractible filler (13) is provided as an expansion allowance between the uppermost refractory (3) and the top end iron skin (4). A furnace construction on a side wall of a furnace according to any one of the above.

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