JP3501621B2 - Industrial furnace and method for constructing thermal insulation layer of industrial furnace - Google Patents

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, and this heat insulating layer blocks heat conduction to protect the furnace and melt steel in the furnace. Is designed to prevent cooling. The heat insulating layer applied in a furnace such as the industrial furnace described above is generally formed by molding refractory castables or plastic refractories in a block shape and sticking these blocks in the furnace with mortar. Further, in recent years, lining with ceramic fibers is becoming popular, and a method of attaching block-shaped ceramic fibers into a furnace with mortar or ceramic pins is adopted, which is called a veneering method.

[0003]

By the way, in order to more firmly adhere the block-shaped ceramic fibers to the refractory wall surface of the furnace with the mortar, the scale adhered to the refractory wall surface in advance, so-called It is necessary to completely remove the kimono. Further, when the refractory wall surface 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 fiber is forcibly adhered with the mortar, there is a technical problem that the block-shaped ceramic fiber is immediately dropped by remelting during the operation. For this reason, conventionally, it is necessary to perform a so-called keren operation to remove the scale and the molten layer before the block-shaped ceramic fiber is attached, which requires considerable labor and time.

Generally, the typical shape of the refractory castable or plastic refractory or the insulating block of ceramic fiber is a square of 200 mm and a thickness of about 30 to 50 mm. It is constructed by connecting it to the refractory wall with mortar. For this reason, the efficiency of construction is extremely low, and it takes a great deal of time to construct the heat insulating layer.

Further, since the heat insulating blocks are bonded together, the block bodies often contract due to the influence of heat received during operation, external alkali components, etc., resulting in a gap between the joined blocks. Therefore, there is a technical problem that the flame goes around the boundary portion of the refractory and reduces the adhesive strength of the mortar. If the adhesive strength of this mortar deteriorates, the heat insulating block in the furnace naturally falls off, forcing the operation of the furnace to be stopped.

The present invention has been made in view of the above-mentioned technical problems of the conventional ones, and an industrial furnace provided with a heat insulating layer having excellent adhesiveness on the wall surface of the refractory material, and an adhesive property on the wall surface of the refractory material. It is an object of the present invention to provide a method for constructing a heat insulating layer for an industrial furnace, which enables the excellent heat insulating layer to be easily and quickly constructed.

[0007]

The industrial furnace according to the present invention, which has been made to solve the above problems, has a gas-hardness property which is constructed on a refractory wall with a thickness of 1 to 10 mm along the shape of the wall. The heat insulating layer comprises a mortar and a castable layer having a predetermined thickness along the upper surface of the air-hardening mortar, and the castable layer is a dry layer.
Bulk specific gravity after drying is 0.7 to 1.2, thermal conductivity is 0.1
To 0.4 W / (mK) lightweight caster
It is characterized by being bullish.

In order to solve the above-mentioned problems, the method for applying a heat insulating layer for an industrial furnace according to the present invention comprises applying a gas-hardening mortar on a refractory wall with a thickness of 1 to 10 mm along the shape of the wall. 1 step, the bulk specific gravity after drying on the upper surface of the air-hardening mortar is 0.7 to 1.2, heat conduction
Light with characteristics of 0.1 to 0.4 W / (m · K)
A heat insulating layer is formed on the refractory wall surface by a second step of constructing the quantity castable with a predetermined thickness. Further , it is preferable that the air-hardening mortar is applied on the refractory wall surface by spraying means or trowel application means, and the castable is applied on the air-hardening mortar by spraying means or trowel application means.

According to the present invention, as described above, the air-hardening mortar is used as the first layer on the fire-resistant wall surface, and the heat-insulating layer is formed by applying the castable in the amorphous state as the second layer on the air-hardening mortar. Each of the first layer and the second layer is applied by spraying means or troweling means. Thereby, the heat insulating layer can be easily formed in a short time. The present invention, in particular, by using the air-hardening mortar as the adhesive layer, the scale adhered to the refractory wall surface of the furnace, and the molten layer formed by the reaction of the fuel gas component and the powder component during continuous casting with the refractory wall surface. Castables can be installed 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 not only excellent durability but also excellent heat insulating property. Castables with a bulk specific gravity of less than 0.7 lack strength in terms of strength, and have a thermal conductivity of more than 0.4 W / (mK) and a bulk specific gravity of more than 1.2. In addition, the heat insulating effect is reduced, and the heat insulating material easily falls off due to its own weight.

Further, since the air-hardening mortar is applied on the refractory wall with a thickness of 1 to 10 mm, the castable can be firmly adhered. Further, even when the castable is damaged or corroded, the initial construction thickness can be obtained by a light work such as blowing the castable onto 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 applying a heat insulating layer to the industrial furnace according to the present invention will be described based on the embodiments. FIG. 1 is a sectional view showing a state in which a heat insulating layer according to the present invention is formed on the inner wall surface of an industrial furnace, for example. That is, reference numeral 1 denotes a part of a refractory wall of an industrial furnace or the like, and as a first step, a gas-hardening mortar 2 having a predetermined thickness is applied to the inner surface of the refractory wall 1 along the shape of the inner surface. It

This air-hardening mortar 2 is a mortar using an inorganic binder such as sodium silicate, sodium phosphate, aluminum phosphate, etc., and has the characteristic that it is superior in adhesive strength to thermosetting mortar by clay bonding. Have Particularly, a preferable material is a high alumina material, and a binder using sodium silicate is the most suitable. Table 1 exemplifies the formulation example (No. 1 to No. 3).

[0014]

[Table 1]

The air-hardening mortar 2 is applied to the inner surface of the fireproof wall 1 with a substantially uniform thickness by either spraying means or troweling means. In this case, the coating amount of the air-hardening mortar 2 on the fireproof wall 1 is 1 to 10.
It is desirable to set the thickness 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 will be poor, and it will be difficult to hold a lightweight castable to be described later with sufficient adhesive force. Further, if the coating amount of the air-curable mortar 2 on the wall 1 exceeds 10 mm, the binder in the air-curable mortar is re-melted by the water when the lightweight castable is sprayed, so that the construction body may droop down. This is 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-hardening mortar 2. This lightweight castable requires considerable heat insulation, heat resistance, and corrosion resistance to be used as a heat insulation layer of an industrial furnace, and has a dry bulk density in the range of 0.7 to 1.2 after construction, Thermal conductivity is 0.1-0.4
Those in the range of W / (m · K) are desired.

The lightweight castable used here contains 5 to 50 wt% of gypsum, and the rest is a refractory raw material.
Ceramic fiber and porous raw material (However, refractory raw material,
Ceramic fibers and porous raw materials do not contain clay, bentonite and ultrafine silica powder. 1) or 2 or more thereof, or 5 to 50 wt% of calcined gypsum, 1 or 2 or more of clay, bentonite and ultrafine silica powder 0.5 to 15
1 wt% or more of refractory raw materials, ceramic fibers and porous raw materials (including clay, bentonite and silica fine powder are not included in the refractory raw materials, ceramic fibers and porous raw materials) with the balance being wt%. It is composed of.

Here, the refractory raw material is alumina,
One or more of alumina-silica and chamotte are preferable, and the addition amount thereof is 15 to 94.5.
It is preferably wt%. The ceramic fiber is preferably alumina or alumina-silica, and the addition amount thereof is preferably 1 to 50 wt%. Furthermore, the porous raw material is preferably one or more of alumina hollow aggregate, chamotte, barlite, vermiculite and artificial lightweight aggregate,
The bulk specific gravity of the porous raw material is preferably 0.03 to 1.5. The amount of the porous raw material added is 10 to 10.
It is preferably 50 wt%.

In addition, calcined gypsum (CaSO ₄ 1 / 2H ₂
O) is a fast-curing binder and also exhibits good water retention and adhesiveness. 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). In addition, since curing failure does not occur at low temperatures and the mechanical strength increases at lower temperatures, it is also a feature that curing failures at low temperatures of about 5 ° C. are prevented and mechanical strength characteristics are improved.

When the amount of calcined gypsum added is less than 5 wt%, not only the mechanical strength characteristics of the heat insulating layer as a construction product are lacking, but also the curing time of the construction product is significantly lengthened. The characteristics and workability are reduced. Meanwhile, 5
If it exceeds 0 wt%, the set expansion characteristic, which is one of the characteristics of calcined gypsum, is damaged and warpage and cracks due to expansion are induced.
The preferable addition amount of calcined gypsum is 8 to 25 wt%.

The refractory raw materials are alumina and silica (S
It is 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 are used. Here, the alumina is 80 wt% or more of Al ₂ O ₃ , and the alumina-silica is less than 80 wt% of Al ₂ O ₃ and 50 wt%.
More raw materials are used, and chamotte is a raw material containing less than 50 wt% of Al ₂ O _{3 and} more than 10 wt%. As the raw material such as alumina, it is desirable to use an artificial raw material for 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 the ceramic fiber or the porous raw material, it 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 when it is less than 15 wt%, the heat resistance becomes low. On the other hand, when it exceeds 94.5 wt%, the heat resistance is improved,
Adhesion is reduced.

The ceramic fiber is added to reduce the weight and improve the heat insulating property. As this ceramic fiber, an alumina material or an alumina-silica material containing less than 80 wt% and more than 40 wt% of Al ₂ O ₃ is used. Further, the ceramic fiber can be used either amorphous or crystalline, and can be used regardless of any shape of granular (curled) or bulk, and is usually commercially available. The existing one is used. The addition amount of the ceramic fiber is preferably in the range of 1 to 50 wt%, and when it is less than 1 wt%, the heat insulating property is deteriorated. on the other hand,
When it exceeds 50 wt%, 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 and improve the heat insulating property of the castable refractory like the ceramic fiber. As the porous raw material, alumina hollow aggregate having a bulk density of 0.03 to 1.5, chamotte,
One or more kinds of perlite, vermiculite and artificial lightweight aggregate are used. The porous raw material may have any particle size, but in order to impart heat insulating properties and workability, the maximum particle size is preferably 7 mm or less, more preferably 5 mm.
mm or less. The amount of porous raw material added 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, if it exceeds 50 wt%, the heat insulating property is improved, but the workability, that is, the fluidity and the adhesive property are deteriorated, and the strength of the construction body (heat insulating layer) is decreased. still,
The refractory raw material, the ceramic fiber and the porous raw material described above do not contain clay, bentonite and ultrafine silica powder described later.

In the case of troweling and spraying, although there is a limit to the amount of clay, bentonite, etc. added, good workability (adhesiveness or adhesion, finish of the surface of the construction body) Properties, etc.) tends to be easily obtained.

Clay, bentonite and silica ultrafine powder 1
If the amount of one kind or two or more kinds added is less than 0.5 wt%, the effect of imparting adhesiveness or adhesiveness is reduced. On the other hand, if it exceeds 15% by weight, the heat resistance of the product decreases,
Further, the shrinkage at the time of solidification becomes large, and cracks and fractures occur in the construction body. Considering the spraying workability and the coating workability, preferably clay and / or bentonite is the main component, and a small amount of ultrafine silica powder is added. The mixing ratio is
Clay and / or bentonite 5 to 8 and silica ultrafine powder 2 to 5 (when the total mixing amount is 10).

The castable material 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 that the castable be lightweight and have a characteristic of W / (m · K). The castable has excellent durability and heat insulation. The thermal conductivity is 0.1 W /
Castables having a bulk specific gravity of less than (m · K) of less than 0.7 tend to lack durability in terms of strength. Further, when the thermal conductivity exceeds 0.4 W / (m · K) and the bulk specific gravity exceeds 1.2, the heat insulating effect is deteriorated and it is easily dropped off by its own weight.

In constructing this lightweight castable, the above-mentioned irregular-shaped lightweight castable 3 is sprayed as a second layer onto the air-hardening mortar 2 formed as a first layer, and a heat insulating layer composed of two layers is formed. It is formed. The spraying of the lightweight castable 3 can be performed by any means of dry spraying in which powder is sprayed with the nozzle mix and wet spraying in which water is added beforehand to make it wet. It is also possible to use a trowel coating means instead of spraying.

As shown in FIG. 1, by forming a heat insulating layer consisting of two layers, the first layer of the air-hardening mortar 2 is
Insulation protection is provided by the lightweight castable 3 formed as a second layer. At the same time, the air-hardening mortar 2 serves to firmly adhere the second-layer lightweight castable 3 to the wall body 1 by the binder in the mortar. Further, unlike the conventional castable construction in the form of a block, the lightweight castable 3 is of an irregular shape and is constructed by spraying means or troweling means.

Therefore, it is possible to avoid the problem that the joints between the blocks do not appear and the flame goes around the boundary of the refractory, which reduces the adhesive strength of the mortar, unlike the prior art. When the lightweight castable is damaged or eroded, it can be easily repaired by spraying or troweling the lightweight castable again on the damaged or eroded portion.

[0031]

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

[0032]

[Table 2] Then, the state of the lightweight castable was observed immediately after construction and after 6 months of operation. The results are shown in Table 4, "Status after construction"
And "state after 6 months of operation".

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

Further, No. 1 shown in Table 1 was added to the ceiling of the heating furnace. The air-hardening mortar 3 was applied by a spraying means so as to have a thickness of 5 mm, and the same lightweight castable as that of Example a was applied by a spraying means so as to have a thickness of 100 mm to form a heat insulating layer. This was designated as Example d. Also in these Examples b to d, the situation of lightweight castables immediately after construction and after 6 months of operation was observed as in Example a, and the results are also shown in Table 4.

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

(Comparative Example b) As Comparative Example b, No. 1 in Table 3 was displayed on the ceiling of the heating furnace. The thermosetting 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 by a spraying means so as to have a thickness of 50 mm to form a heat insulating layer. Then, as in Example a, the situation of the lightweight castable immediately after the construction and after the operation for 6 months was observed, and the results are shown in Table 4. The thermosetting mortar is a mortar that contains refractory clay as a binder in alumina fine powder or mullite fine powder, and in order to obtain strength, it is fired at a temperature at which a ceramic bond is formed by the added refractory clay. It is something that must be done. Table 3 exemplifies the compounding examples (No. 1 to No. 3) of the thermosetting mortar.

[0037]

[Table 3]

Comparative Example c As Comparative Example c, No. 1 shown in Table 1 was displayed on the ceiling of the heating furnace. 20 mm of 1 air-hardening mortar
Was applied by a spraying means so that the thickness of the castable light-weight castable was 100 mm by a spraying means to form a heat insulating layer. Then, as in Example a, the situation of the lightweight castable immediately after the construction and after the operation for 6 months was observed, and the results are shown in Table 4.

[0039]

[Table 4]

From the above verification results, the following can be derived. First, as is clear from comparison between Example a and Comparative Example a, even when the thickness of the lightweight castable is the same, it plays a role of an adhesive between the castable and the ceiling of the heating furnace. If mortar is not used, no problem will occur immediately after construction, but after 6 months of operation, the castable will peel off and fall off. Further, as shown in Example b, not only the spraying means but also the trowel applying means can be used as the construction means of the air-hardening mortar and the lightweight castable, and the same result can be obtained.

Further, as is clear from comparison between Example c and Comparative Example b, in the case where the thickness of the light castable was the same and the thickness of the mortar was also the same, a case of using a hard mortar as the mortar However, when thermosetting mortar is used, the castable peels off and falls after 6 months of operation.

Further, as is clear 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 made excessively large, immediately after construction. Part of the castable peels off, and after 6 months of operation, the castable peels off and falls off. The inventors have confirmed that the thickness of the air-hardening mortar is preferably 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 are shown in Example ef,
It was 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 surface of 50 mm is applied on the surface.
And the thickness was applied by a spraying means to form a heat insulating layer. At this time, as shown in Tables 5 and 6, lightweight castables having different bulk specific gravities and thermal conductivity after drying (Example e)
Using f and 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 this result, the bulk specific gravity after drying is 0.7.
To 1.2, thermal conductivity of 0.1 to 0.4 W / (m ·
It was confirmed that the lightweight castable having the characteristics of K) has excellent durability and excellent heat insulating properties. It should be noted that castables having a bulk specific gravity of less than 0.7 are found to have poor durability in terms of strength. Further, when the thermal conductivity exceeds 0.4 W / (m · K) and the bulk specific gravity exceeds 1.2, it is confirmed that the heat insulating effect is deteriorated and the particles are peeled off by their own weight.

[0047]

As is apparent from the above description and verification results, the industrial furnace and the method for constructing the heat insulating layer of the industrial furnace according to the present invention are constructed by applying a gas-hardening mortar on a refractory wall of the industrial furnace,
By constructing a castable on the upper surface of this air-hardening mortar, a heat insulating layer is formed on the refractory wall surface, and it is possible to obtain an industrial furnace provided with a heat insulating layer in which castables do not fall off. The heat insulation layer can be applied easily and in a short time. Further, since it is possible to firmly construct a lightweight castable without removing the scale adhered to the refractory wall surface of the industrial furnace or the molten layer formed on the refractory wall surface, the labor and time required for the work can be reduced. The cost of molten steel can be reduced as a result.

Furthermore, in the castable obtained by the construction method of the present invention, the castable having a predetermined thickness is formed substantially uniformly, and no joints are generated due to the joining of the block bodies as in the conventional case, and the joints are not formed in the joints. There is no reduction in the adhesive strength of the mortar due to the rotation of the flame. Furthermore, in repairing, since the initial construction thickness can be obtained only by blowing a light castable onto the damaged or corroded portion, maintenance work can be reduced.

[Brief description of drawings]

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

[Explanation of symbols]

1 fire wall 2 mortar (hardening mortar) 3 lightweight castable

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-54-161503 (JP, A) JP-A-8-245271 (JP, A) JP-A-9-301779 (JP, A) 72964 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) F27D 1/16

Claims (3)

(57) [Claims] 1. A fire-resistant wall surface having a shape of 1 along the shape of the wall surface.
A heat insulating layer composed of a gas-hardening mortar having a thickness of 10 mm and a castable having a predetermined thickness along the upper surface of the gas- hardening mortar is provided , and the castable has a dry bulk. Specific gravity is 0.7 to
1.2, thermal conductivity of 0.1 to 0.4 W / (mK)
An industrial furnace characterized by being a lightweight castable with characteristics. 2. A first method for constructing a gas-hardening mortar on a refractory wall with a thickness of 1 to 10 mm along the shape of the wall.
Process and the bulk ratio after drying on the upper surface of the air-hardening mortar
Weight 0.7 to 1.2, thermal conductivity 0.1 to 0.4W
Insulation layer construction for an industrial furnace, characterized in that a heat insulation layer is formed on the refractory wall surface by a second step of constructing a lightweight castable having a characteristic of / (m · K) with a predetermined thickness. Method. 3. The air-hardening mortar is applied on the refractory wall surface by spraying means or trowel application means, and the castable is applied on the air-hardening mortar by spraying means or trowel application means. The method for constructing a heat insulating layer for an industrial furnace according to claim 2 , wherein