JPH10318682A - Industrial furnace and construction for heat insulating layer of industrial furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrial furnace having a heat insulating layer in which a castable refractory hardly drops on the refractory wall surface of the industrial furnace or the like and a construction method for the heat insulating layer of the industrial furnace which can be easily constructed for a short time. SOLUTION: An air setting mortar 2 with a prescribed thickness is applied substantially uniformly on the inner side surface of the refractory wall 1 of an industrial furnace or the like. A light castable refractory 3 is further applied substantially uniformly with a prescribed thickness to the upper surface of the air setting mortar 2. Thus, a heat insulating layer is formed on the inner side surface of the refractory wall 1. The air setting mortar 2 is desirably formed so as to have the thickness of 1 to 10 mm on the surface of the refractory wall 1. Further, the air setting mortar and the castable refractory are applied by a spray means or a lever coating means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial furnace such as a steel heating furnace and a soaking furnace, and a method for constructing a heat insulating layer lined in the furnace.

[0002]

2. Description of the Related Art In an industrial furnace such as a steel heating furnace or a soaking furnace, a heat insulating layer is formed in the furnace. This heat insulating layer blocks heat conduction, protects the furnace, and melts the steel in the furnace. To prevent cooling. The heat insulating layer constructed in a furnace such as the above-mentioned industrial furnace is generally formed by forming a refractory castable or plastic refractory into a block shape, and attaching these blocks to the furnace with mortar. In recent years, lining using ceramic fibers has become popular, and a method of attaching block-shaped ceramic fibers to a furnace using mortar or ceramic pins has been adopted as a veneering method.

[0003]

In order to adhere the block-shaped ceramic fiber more firmly to the refractory wall of the furnace by using a mortar, it is necessary to use a scale previously attached to the refractory wall, that is, a so-called attachment. Kimono needs to be completely removed. When the refractory wall of the furnace reacts with the fuel gas component or the powder component and is melted, it is impossible to bond the block-shaped ceramic fibers with mortar. Even if the block-shaped ceramic fibers were forcibly bonded with a mortar, there was a technical problem that the block-shaped ceramic fibers were immediately dropped off due to re-melting during operation. For this reason, a so-called Keren operation for removing the scale and the molten layer before attaching the block-shaped ceramic fiber has conventionally been required, and considerable labor and time have been spent.

In general, a typical shape of the above-mentioned refractory castable, plastic refractory, or ceramic fiber insulation block is a square of 200 mm and a thickness of about 30 to 50 mm. It is constructed by connecting the mortar to the refractory wall. For this reason, the efficiency of the construction is extremely poor, and a large amount of time is spent on the construction of the heat insulating layer.

[0005] In addition, due to the heat-insulating blocks bonded together, the blocks often shrink under the influence of heat received during operation or an external alkali component and the like, and a gap is generated between the joined blocks. For this reason, there is a technical problem that the flame goes around the boundary of the refractory and lowers the adhesive strength of the mortar. If the adhesive strength of the mortar is reduced, the heat insulating block in the furnace was naturally dropped, and the operation of the furnace had to be stopped.

The present invention has been made in view of the above-mentioned technical problems of the prior art, and has an industrial furnace provided with a heat insulating layer having excellent adhesion on a refractory wall surface, and an adhesive on an refractory wall surface. It is an object of the present invention to provide a method for constructing a heat insulating layer of an industrial furnace, which can easily form a heat insulating layer having excellent quality in a short time.

[0007]

An industrial furnace according to the present invention, which has been made to solve the above-mentioned problems, comprises an air-hardening mortar constructed on a refractory wall with a predetermined thickness along the shape of the wall. And a castable that is constructed along the upper surface of the air-hardened mortar and has a predetermined thickness. Preferably, the castable is a lightweight castable having characteristics of a bulk specific gravity after drying of 0.7 to 1.2 and a thermal conductivity of 0.1 to 0.4 W / (m · K). The air-hardening mortar is desirably formed on the refractory wall to a thickness of 1 to 10 mm.

[0008] In order to solve the above-mentioned problems, a method for applying a heat insulating layer of an industrial furnace according to the present invention is a first step of applying an air-hardening mortar on a refractory wall with a predetermined thickness along the shape of the wall. And a second step of applying a castable to the upper surface of the air-hardened mortar with a predetermined thickness to form a heat insulating layer on the refractory wall surface. Preferably, the castable is a lightweight castable having characteristics of a bulk specific gravity after drying of 0.7 to 1.2 and a thermal conductivity of 0.1 to 0.4 W / (m · K). It is desirable to apply the air-hardening mortar on the refractory wall with a thickness of 1 to 10 mm. Further, it is preferable that the air-hardening mortar is applied to the refractory wall surface by spraying or troweling means, and the castable is applied to the air-hardening mortar by spraying or troweling means.

According to the present invention, as described above, an air-hardening mortar is used as a first layer on a fire-resistant wall, and a castable in an amorphous state is formed as a second layer on the air-hardening mortar to form a heat insulating layer. Each of the first and second layers is applied by spraying means or troweling means. Thus, the heat insulating layer can be easily formed in a short time. In particular, the present invention uses a gas-hardened mortar as an adhesive layer, so that a scale adhered to the refractory wall of the furnace or a molten layer formed by reacting a fuel gas component or a powder component during continuous casting with the refractory wall surface. Castables can be constructed without removing them.

The castable has a bulk specific gravity after drying of 0.7 to 1.2 and a thermal conductivity of 0.1 to 0.4.
Since it is a lightweight castable having the characteristic of W / (m · K), it has excellent durability and excellent heat insulation. Note that castables having a bulk specific gravity of less than 0.7 lack durability because of their strength, and if the thermal conductivity exceeds 0.4 W / (m · K) and the bulk specific gravity exceeds 1.2. In addition, the heat insulating effect is reduced, and it is easy to fall off by its own weight.

The castable mortar is applied on the refractory wall with a thickness of 1 to 10 mm, so that the castable can be firmly bonded. Further, even when the castable is damaged or corroded, the initial work thickness can be obtained by light work such as blowing the castable over the damaged or corroded portion, and the repair work can be easily performed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an industrial furnace and a method for constructing a heat insulating layer of the industrial furnace according to the present invention will be described based on embodiments. FIG. 1 is a sectional view showing, for example, a state in which a heat insulating layer according to the present invention is formed on the inner wall surface of an industrial furnace. That is, reference numeral 1 denotes a part of a refractory wall of an industrial furnace or the like, and as a first step, an air-hardened mortar 2 having a predetermined thickness is applied to the inner surface of the refractory wall 1 along the shape of the inner surface. You.

The air-hardening mortar 2 is a mortar using an inorganic binder such as sodium silicate, sodium phosphate, or aluminum phosphate, and has a characteristic that it has a higher adhesive strength than a thermosetting mortar formed by clay bonding. Have. In particular, a preferable material is high alumina, and a binder using sodium silicate is most suitable. Table 1 exemplifies the composition examples (No. 1 to No. 3).

[0014]

[Table 1]

The air-hardening mortar 2 is applied to the inner surface of the refractory wall 1 with a substantially uniform thickness by either spraying means or troweling means. In this case, the amount of the air-hardening mortar 2 applied to the fire-resistant wall 1 is 1 to 10
It is desirable that the thickness be in the range of mm. If the amount of the air-hardening mortar 2 applied to the wall 1 is less than 1 mm, the adhesiveness is poor, and it becomes difficult to hold a lightweight castable described later with a sufficient adhesive force. If the amount of the air-hardened mortar 2 applied to the wall 1 exceeds 10 mm, the binder in the air-hardened mortar is re-melted due to the water at the time of spraying of the lightweight castable, and there is an inconvenience that the construction body drips. Because it occurs.

Next, as a second step, a lightweight castable 2 having a substantially uniform thickness is applied to the upper surface of the air-hardened mortar 2. This lightweight castable requires considerable heat insulation, heat resistance, and corrosion resistance in order to be used as a heat insulation layer of an industrial furnace, and has a dry bulk density of 0.7 to 1.2 after construction, and Thermal conductivity is 0.1-0.4
A range of W / (m · K) is desired.

The lightweight castable used here contains 5 to 50% by weight of calcined gypsum, the remainder being a refractory raw material,
Ceramic fiber and porous material (however, fire-resistant material,
Ceramic fibers and porous raw materials do not include clay, bentonite and silica ultrafines. ), Or one or more of clay, bentonite and ultrafine silica powder 0.5 to 15%
wt%, with the balance being one or more of refractory raw materials, ceramic fibers and porous raw materials (however, the refractory raw materials, ceramic fibers and porous raw materials do not include clay, bentonite and silica fine powder). It is composed of

Here, the refractory raw material is alumina,
It is preferable to use one or more of alumina-siliceous material and chamotte, and the addition amount thereof is 15 to 94.5.
It is preferably wt%. The ceramic fibers are preferably made of alumina or alumina-silica, and the amount of the ceramic fibers is preferably 1 to 50 wt%. Further, the porous raw material is preferably one or two or more of alumina hollow aggregate, chamotte, burlite, vermiculite and artificial lightweight aggregate,
The bulk specific gravity of the porous raw material is preferably from 0.03 to 1.5. The amount of the porous raw material to be added is 10 to
Preferably, it is 50 wt%.

Further, calcined gypsum (CaSO ₄ .1 / 2H ₂₎
O) is a fast-curing binder that also exhibits good water retention and adhesion. Since it has a Mohs hardness of 2 and is soft, it functions as a lubricant and improves the surface finish of the construction body (heat insulating layer). Further, since poor mechanical strength does not occur at low temperatures, and mechanical strength increases at a very low temperature, poor curing at low temperatures of about 5 ° C. is prevented and mechanical strength characteristics are also improved.

If the amount of calcined gypsum is less than 5 wt%, not only does the construction of the heat insulating layer lack mechanical strength characteristics, but also the curing time of the construction becomes extremely long, which results in: Characteristics and workability deteriorate. 5
If the amount exceeds 0 wt%, one of the characteristics of calcined gypsum is the setting and expanding property, which causes warpage and cracks due to expansion.
The preferred addition amount of calcined gypsum is 8 to 25 wt%.

The refractory raw materials are alumina and silica (S
It refers to a raw material mainly composed of iO ₂ ) and is added to improve the fire resistance and heat resistance of castable refractories. This refractory raw material has an Al ₂ O ₃ content of 10
% Or more of one or more of alumina, alumina-silica and chamotte. Here, alumina refers to Al ₂ O ₃ of 80 wt% or more, and alumina-silica refers to Al ₂ O ₃ smaller than 80 wt% and 50 wt%.
Chamotte refers to a material with less than 50 wt% Al ₂ O _{3 and} greater than 10 wt%. As the raw material such as alumina, it is desirable to use an artificial raw material of sintering or electrofusion, but it is also possible to use a natural raw material such as bauxite or chamotte.

The maximum particle size of the refractory raw material is preferably 7 mm or less. However, when used in combination with a ceramic fiber or a porous raw material, the thickness is 60 mesh or less, more preferably 100 mesh or less, from the viewpoint of workability. The addition amount of the refractory raw material is preferably in the range of 15 to 94.5 wt%, and if it is less than 15 wt%, the heat resistance will be low. On the other hand, if it exceeds 94.5% by weight, heat resistance is improved,
Adhesion decreases.

The ceramic fiber is added to reduce weight and improve heat insulation. As the ceramic fiber, alumina or alumina-silica containing less than 80 wt% and more than 40 wt% of Al ₂ O ₃ is used. In addition, the ceramic fiber can be any of amorphous and crystalline, and can be used irrespective of granular (curl) or bulk shape. Is used. The amount of the ceramic fiber added is preferably in the range of 1 to 50% by weight, and if it is less than 1% by weight, the heat insulating property decreases. on the other hand,
If it exceeds 50% by weight, the dispersibility of the raw material is deteriorated, and the strength of the construction body (heat insulating layer) is reduced.

The porous raw material is added in order to reduce the weight of the castable refractory and to improve the heat insulation as in the case of the ceramic fiber. As the porous raw material, alumina hollow aggregate having a bulk specific gravity of 0.03 to 1.5, chamotte,
One or more of perlite, vermiculite and artificial lightweight aggregate are used. The porous raw material may have any particle size, but it is preferable that the maximum particle size is 7 mm or less, more preferably 5 mm or less, in order to provide heat insulation and workability.
mm or less. The addition amount of the porous raw material is 10 to 50 w
The range of t% is preferable, and if it is less than 10 wt%, the heat insulating effect is small. On the other hand, when the content exceeds 50 wt%, the heat insulating property is improved, but the workability, that is, the flowability and the adhesiveness are lowered, and the strength of the construction body (heat insulating layer) is lowered. still,
The above-mentioned refractory raw materials, ceramic fibers and porous raw materials do not contain clay, bentonite and ultrafine silica powder described later.

In the case of troweling and spraying, although the amount of clay, bentonite, etc. is limited, the better the workability (adhesiveness or adhesion, finish of the surface of the construction body) as the amount is increased. ) Tend to be easily obtained.

Clay, bentonite and ultrafine silica powder 1
When the amount of the seed or two or more kinds is less than 0.5 wt%, the effect of imparting adhesiveness or adhesion is reduced. On the other hand, if it exceeds 15 wt%, the heat resistance of the product will decrease,
In addition, the shrinkage at the time of consolidation increases, and cracks and cracks occur in the construction body. Considering the spraying workability and the coating workability, it is preferable to mainly use clay and / or bentonite, and a small amount of silica ultrafine powder is added. The mixing ratio is
With respect to clay and / or bentonite 5 to 8, ultrafine silica powder 2 to 5 is used (when the total mixing amount is 10).

The castable has a bulk specific gravity after drying of 0.7 to 1.2 and a thermal conductivity of 0.1 to 0.4.
It is desirable to be a lightweight castable having a characteristic of W / (m · K). The castable is excellent in durability and heat insulation. The thermal conductivity is 0.1 W /
Castables having a bulk density of less than (m · K) and a specific gravity of less than 0.7 tend to lack durability in terms of strength. When the thermal conductivity exceeds 0.4 W / (m · K) and the bulk specific gravity exceeds 1.2, the heat insulating effect is reduced, and the material tends to fall off due to its own weight.

When the lightweight castable is constructed, the irregular lightweight castable 3 is sprayed as a second layer on the air-hardened mortar 2 formed as a first layer, and a two-layer heat insulating layer is formed. It is formed. The spraying of the lightweight castable 3 can be performed by either a dry spraying method in which powder is sprayed by a nozzle mix or a wet spraying method in which water is added in advance and wetted. It is also possible to use a troweling means instead of spraying.

As shown in FIG. 1, by forming the heat insulating layer of two layers, the first layer of the air-hardening mortar 2
It receives thermal insulation protection by the lightweight castable 3 formed as a second layer. At the same time, the air-hardened mortar 2 functions to firmly adhere the lightweight castable 3 of the second layer to the wall 1 by the binder in the mortar. The lightweight castable 3 is different from the conventional castable in the form of a block, which is constructed by spraying or troweling an irregular-shaped castable.

Therefore, unlike the related art, the joint between the blocks does not appear, and the problem that the bonding strength of the mortar is reduced by the flame circling at the boundary of the refractory can be avoided. When the lightweight castable is damaged or eroded, it can be easily repaired by spraying the damaged castable on the damaged or eroded portion again or applying troweling.

[0031]

EXAMPLE A heat insulating layer was formed on the ceiling portion of a heating furnace in which a refractory wall was melted by a gas component and a powder component by a construction method as shown in Examples a to d below. (Example a) No. shown in Table 1 above. The air-hardening mortar No. 1 was applied to the ceiling of the heating furnace so as to have a thickness of 1 mm by spraying means, and a light-weight castable was applied to the surface thereof by spraying means to have a thickness of 30 mm to form a heat insulating layer. Table 2 shows the composition of the lightweight castable used at this time.

[0032]

[Table 2] Then, the state of the lightweight castable immediately after the construction and after the operation for 6 months was observed. Table 4 shows the results.
And "Situation after 6 months operation".

(Examples b to d) Nos. Shown in Table 1 above were placed on the ceiling of the heating furnace. 2 air-hardening mortar is 10mm
And the same lightweight castable as in Example a was applied to the surface thereof to a thickness of 30 m.
Example b was obtained by applying a trowel coating means to form a heat insulating layer so as to obtain m. In addition, No. shown in Table 1 above was placed on the ceiling of the heating furnace. The air-hardening mortar No. 1 was applied by a spraying means so as to have a thickness of 5 mm, and the same lightweight castable as in Example a was applied to the surface thereof by the spraying means so as to have a thickness of 50 mm to form a heat insulating layer. This was designated as Example c.

Further, No. 1 described in Table 1 was placed on the ceiling of the heating furnace. 3 was applied by a spraying means so as to have a thickness of 5 mm, and the same lightweight castable as in Example a was applied by a spraying means so as to have a thickness of 100 mm on the surface thereof to form a heat insulating layer. This was designated as Example d. Then, in these examples b to d, the conditions of the lightweight castable immediately after the construction and after the operation for 6 months were observed in the same manner as in the example a. The results are also shown in Table 4.

(Comparative Example a) As Comparative Example a, the same lightweight castable as in Example a was directly applied to the ceiling of the heating furnace by a spraying means so as to have a thickness of 30 mm without using any mortar. A heat insulating layer was formed. Then, the condition of the lightweight castable immediately after the construction and after the operation for 6 months was observed in the same manner as in Example a, and the results are shown in Table 4.

(Comparative Example b) As Comparative Example b, No. 3 of Table 3 was placed on the ceiling of the heating furnace. The thermosetting mortar No. 1 was applied by spraying means so as to have a thickness of 5 mm, and the same lightweight castable as in Example a was applied by spraying means so as to have a thickness of 50 mm on the surface thereof to form a heat insulating layer. Then, the condition of the lightweight castable immediately after the construction and after the operation for 6 months was observed in the same manner as in Example a, and the results are shown in Table 4. The thermosetting mortar is a mortar containing refractory clay as a binder in alumina fine powder or mullite fine powder, and is fired at a temperature at which a ceramic bond is formed by the added refractory clay in order to obtain strength. What you have to do. Table 3 shows examples of blending of the thermosetting mortar (No. 1 to No. 3).

[0037]

[Table 3]

(Comparative Example c) As Comparative Example c, No. 1 shown in Table 1 was placed on the ceiling of the heating furnace. 1 settable mortar is 20mm
Was applied by a spraying means so as to have a thickness of 100 mm, and the light-weight castable was applied to the surface by a spraying means so as to have a thickness of 100 mm to form a heat insulating layer. Then, the condition of the lightweight castable immediately after the construction and after the operation for 6 months was observed in the same manner as in Example a, and the results are shown in Table 4.

[0039]

[Table 4]

From the above verification results, the following can be derived. First, as apparent from a comparison between Example a and Comparative Example a, even when the thickness of the lightweight castable is the same, a role of an adhesive is provided between the castable and the ceiling of the heating furnace. If no mortar is used, no problems occur immediately after the construction, but the castables peel off and fall off after 6 months of operation. Further, as shown in Example b, not only the spraying means but also the troweling means can be used for applying the air-hardening mortar and the light-weight castable.

Further, as is apparent from a comparison between Example c and Comparative Example b, when the thickness of the light-weight castable is the same and the thickness of the mortar is the same, the case where an air-hardened mortar is used as the mortar Although no problem occurs, the castable peels off and falls off after 6 months of operation when the thermosetting mortar is used.

As is apparent from comparison between Example d and Comparative Example c, even if the thickness of the lightweight castable is the same, if the thickness of the air-hardening mortar is excessively large, The castables partially peel off, and after 6 months of operation, the entire castables peel off and fall off. The inventors have confirmed that the thickness of the air-hardening mortar is desirably in the range of 1 to 10 mm, including other verifications, and it can be said that Comparative Example c supports this.

Next, the condition after construction and the condition after 6 months of operation due to the difference in the characteristics of the lightweight castable will be described in Example ef.
Observed as Comparative Example de. First, air-hardening mortar is applied to the ceiling of the heating furnace by a spraying means so as to have a thickness of 5 mm, and a lightweight castable is applied to the surface by 50 mm.
To form a heat insulating layer. At this time, as shown in Tables 5 and 6, a light-weight castable having a changed bulk specific gravity and thermal conductivity after drying (Example e)
f, Using Comparative Example de), the situation after construction and the situation after 6 months of operation were observed. The results are shown in Tables 5 and 6.

[0044]

[Table 5]

[0045]

[Table 6]

From these results, it is found that the bulk specific gravity after drying is 0.7
To 1.2, thermal conductivity of 0.1 to 0.4 W / (m ·
The light castable having the characteristic of K) was found to have excellent durability and excellent heat insulation. In addition, it is recognized that castables having a bulk specific gravity of less than 0.7 affect durability from the viewpoint of strength. When the thermal conductivity exceeded 0.4 W / (m · K) and the bulk specific gravity exceeded 1.2, it was recognized that the heat insulating effect was reduced and that the material was peeled off by its own weight.

[0047]

As is apparent from the above description and the results of the verification, the industrial furnace and the method for constructing a heat insulating layer of an industrial furnace according to the present invention construct an air-hardening mortar on a refractory wall of an industrial furnace or the like.
By applying a castable on the upper surface of the air-hardened mortar, a heat insulating layer is formed on the fire-resistant wall surface, and an industrial furnace having a heat insulating layer with less castable dropout can be obtained. The heat insulation layer can be applied easily and in a short time. Further, without performing the work of removing the scale attached to the refractory wall of the industrial furnace or the molten layer formed on the refractory wall, it is possible to strongly construct a lightweight castable, so that the labor and time required for the work are reduced. As a result, the cost of molten steel can be reduced.

Further, the castable obtained by the construction method of the present invention is such that castables of a predetermined thickness are formed substantially uniformly, and no joints are generated due to the joining of the blocks as in the prior art. There is no decrease in the adhesive strength of the mortar due to the rotation of the flame. Furthermore, in the repair, the initial work thickness can be obtained only by blowing the lightweight castable over the damaged or corroded portion, so that the maintenance work can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which a heat insulating layer is formed on a refractory wall based on a construction method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fire-resistant wall 2 Mortar (air-hardening mortar) 3 Lightweight castable

Claims (7)

[Claims] 1. An air-hardened mortar formed on a refractory wall with a predetermined thickness along the shape of the wall, and a castable formed on the refractory wall with a predetermined thickness along an upper surface of the air-hardened mortar. An industrial furnace comprising a heat insulating layer configured. 2. The castable has a bulk specific gravity after drying of 0.7 to 1.2 and a thermal conductivity of 0.1 to 0.4 W /
The industrial furnace according to claim 1, which is a lightweight castable having a characteristic of (mK). 3. The air-hardening mortar is provided on a refractory wall.
The industrial furnace according to claim 1 or 2, wherein the industrial furnace is formed to a thickness of 10 to 10 mm. 4. A first step of applying an air-hardening mortar on a refractory wall with a predetermined thickness along the shape of the wall.
A second step of applying a castable to the upper surface of the air-hardened mortar with a predetermined thickness, thereby forming a heat insulating layer on the refractory wall surface. 5. The castable has a bulk specific gravity after drying of 0.7 to 1.2 and a thermal conductivity of 0.1 to 0.4 W /.
The method of claim 4, wherein the method is a lightweight castable having characteristics of (m · K). 6. The air-hardening mortar is provided on a refractory wall.
The method according to claim 4, wherein the method is performed with a thickness of 10 to 10 mm. 7. The air-hardening mortar is applied to the refractory wall by spraying or troweling means, and the castable is applied to air-hardening mortar by spraying or troweling means. The method for constructing a heat insulating layer of an industrial furnace according to any one of claims 4 to 6.