WO2024203847A1 - Heat insulating material for combustion chamber, water heater, and boiler - Google Patents

Abstract

This heat insulation material for a combustion chamber is a plate-like molding including inorganic fibers, the heat insulation material being characterized in that when the bulk densities of a first main surface part, a second main surface part, and a central part between the first main surface part and the second main surface part in the thickness direction are compared, at least the bulk density of the first main surface part is smaller than the bulk density of the central part, and the first main surface part is arranged toward the inner wall surface of the combustion chamber.

Description

Combustion chamber insulation, water heaters and boilers

The present invention relates to insulation for combustion chambers, water heaters and boilers.

Boilers and water heaters are used as devices that supply steam and hot water using fuels such as petroleum.

Boilers and water heaters burn fuel in a combustion chamber and transfer the heat of combustion to water through water pipes placed inside the combustion chamber, thereby generating steam and hot water from water.

Since the combustion chamber becomes very hot, it is usually protected by refractories and insulation to protect the surrounding equipment from heat damage and to reduce energy loss (see, for example, Patent Documents 1 and 2).

In particular, in combustion chambers where the temperature rises due to combustion gases, refractories and insulation materials are generally made by pouring a fluid containing heat-resistant materials onto the surface of the object to be installed and solidifying it. Such materials are also called castable materials. Although castable materials can conform to surfaces of any shape and provide a certain degree of insulation, they have problems such as insufficient insulation, being heavy, taking a long time to dry, and being difficult to work with during construction.

Patent No. 4946594 Patent No. 4640705

The use of insulating materials containing inorganic fibers instead of castable materials is being considered, but insulating materials installed inside combustion chambers must have improved insulating properties, be stable and easy to install and maintain, be durable, and be able to be supplied at low cost.

The present invention was made to solve the above problems, and the object of the present invention is to provide a combustion chamber insulation material that has a greater insulating effect, can be stably and easily installed and maintained, is durable, and can be supplied at low cost.

In other words, the combustion chamber insulation material of the present invention is a plate-shaped molded body containing inorganic fibers, and is characterized in that when comparing the bulk densities of a first main surface portion, a second main surface portion, and a central portion located between the first main surface portion and the second main surface portion in the thickness direction, the bulk density of at least the first main surface portion is smaller than the bulk density of the central portion, and the first main surface portion is positioned toward the inner wall surface of the combustion chamber.
The combustion chamber insulation material of the present invention has a low bulk density of the first main surface portion and is positioned toward the inner wall surface of the combustion chamber, thereby creating an air layer on the inner wall surface side of the combustion chamber, thereby enhancing the insulating effect.

It is preferable that the bulk density of the second main surface portion is (i) greater than the bulk density of the central portion, or (ii) less than the bulk density of the central portion.

The combustion chamber insulating material of the present invention is preferably formed by a papermaking method.
By forming the material using a papermaking method and drying it, the bulk density of the combustion chamber insulating material in the thickness direction can be easily adjusted.

The combustion chamber insulating material of the present invention preferably has a flat or curved shape.
When the combustion chamber insulating material of the present invention has the above-mentioned shape, it can be disposed at various locations inside the combustion chamber.

The combustion chamber insulating material of the present invention preferably has an overall bulk density of 0.20 to 0.35 g/cm ³ .
When the overall bulk density is within the above range, the strength required for the heat insulating material is ensured, while the weight can be reduced in comparison with a fireproof material using an amorphous material.

It is preferable that the bulk density of the first main surface portion is 3% or more smaller than the larger of the bulk density of the second main surface portion and the bulk density of the central portion.
When the bulk density of the first main surface portion is within the above range, an air layer is formed on the inner wall surface side of the combustion chamber, thereby enhancing the heat insulating effect. In addition, by making the larger of the bulk density of the second main surface portion and the bulk density of the central portion 3% or more higher than the bulk density of the first main surface portion, the wind erosion resistance against contact with combustion gas is enhanced, and the strength as a heat insulating material is ensured, allowing the heat insulating material of the present invention to be used stably for a long period of time.

The water heater of the present invention comprises a combustion chamber, a heat exchanger installed in the combustion chamber, and the combustion chamber insulation material of the present invention, and is characterized in that the first main surface portion of the combustion chamber insulation material is arranged facing the inner wall surface of the combustion chamber.

The water heater of the present invention is equipped with the combustion chamber insulation material of the present invention, and since the bulk density of the first main surface portion is small, an air layer can be created on the inner wall surface side of the combustion chamber, thereby enhancing the insulation effect, and providing excellent _CO2 emission suppression effect.

The boiler of the present invention is characterized in that it comprises a combustion chamber and the combustion chamber insulation material of the present invention, and the first main surface portion of the combustion chamber insulation material is arranged facing the inner wall surface of the combustion chamber.

The boiler of the present invention is equipped with the combustion chamber insulation material of the present invention, and since the bulk density of the first main surface portion is small, an air layer can be created on the inner wall surface side of the combustion chamber to enhance the insulation effect, and the boiler has an excellent effect of suppressing _CO2 emissions.

FIG. 1 is a perspective view showing a typical example of a combustion chamber insulating material of the present invention. FIG. 2 is a cross-sectional view taken along line AA of FIG. 1, showing a schematic example of the internal structure of the combustion chamber insulating material. FIG. 3 is a cross-sectional view taken along line AA of FIG. 1, showing a schematic diagram of another example of the internal structure of the combustion chamber insulating material. FIG. 4 is a cross-sectional view showing an example of a process for producing the combustion chamber insulating material of the present invention. FIG. 5 is a cross-sectional view showing a schematic example of another process for producing a combustion chamber insulating material of the present invention. FIG. 6 is a cross-sectional view illustrating an example of a water heater according to the present invention. FIG. 7 is a cross-sectional view showing a schematic example of a boiler according to the present invention.

Detailed Description of the Invention
[Insulation material for combustion chamber]
First, the combustion chamber insulating material of the present invention will be described.
The combustion chamber insulating material of the present invention is a plate-shaped molded body containing inorganic fibers, and is characterized in that when comparing the bulk densities of a first main surface portion, a second main surface portion, and a central portion located between the first main surface portion and the second main surface portion in the thickness direction, the bulk density of at least the first main surface portion is smaller than the bulk density of the central portion, and the first main surface portion is arranged toward the inner wall surface of the combustion chamber.

In this specification, a plate shape refers to a shape having two opposing main surfaces with a relatively large area and side surfaces connecting the two main surfaces. The direction in which the two main surfaces extend is also called the surface direction, and the direction connecting the two main surfaces is also called the thickness direction. At least one of the two opposing main surfaces may be curved.

FIG. 1 is a perspective view showing a typical example of a combustion chamber insulating material of the present invention.
The combustion chamber insulating material 1 shown in FIG. 1 is composed of a plate-like molded body 10 containing inorganic fibers.
The plate-like molded body 10 has a plate-like shape having opposing first and second main surfaces 10a, 10b, each having a relatively large area, and a side surface 10c connecting the first and second main surfaces 10a, 10b.

When viewed from the thickness direction, the shapes of the first main surface 10a and the second main surface 10b are approximately circular. Therefore, the external shape of the plate-shaped molded body 10 and the combustion chamber insulation material 1 can be said to be a disk shape having a predetermined thickness.

The combustion chamber insulation material of the present invention preferably has a flat or curved shape. With the above-mentioned shape, the combustion chamber insulation material of the present invention can be placed in various locations inside the combustion chamber. The shape of the combustion chamber insulation material is the shape of a plate-shaped molded body.

Since the combustion chamber insulating material 1 is composed only of the plate-shaped molded body 10, the plate-shaped molded body 10 can be said to be the combustion chamber insulating material 1.
That is, in the combustion chamber insulating material of the present invention, the plate-like molded body itself may be the combustion chamber insulating material.

The plate-like molded body contains inorganic fibers.
The inorganic fibers preferably include at least one selected from the group consisting of biosoluble fibers, alumina fibers, rock wool, and glass fibers.
As the biosoluble fiber, for example, alkaline earth silicate fiber (AES fiber) can be used. Also, shot components of non-fibrous particles may be contained.
When the inorganic fibers contain the above-mentioned material, a plate-shaped molded product having excellent heat resistance can be obtained.

The combustion chamber insulation material 1 is made of a plate-shaped molded body 10 containing inorganic fibers, so it has a smaller weight per volume and is easier to work with than castable materials. The plate-shaped molded body 10 has properties such that the inorganic fibers have little localized bias and are less likely to deform, making it suitable as an insulation material to be placed inside a combustion chamber.

The plate-shaped molded body may be a paper molded body or a needle body. A paper molded body is a molded body obtained by pouring a slurry containing inorganic fibers into a mold and then performing paper molding by suction dehydration and drying (papermaking method). A plate-shaped molded body obtained by the papermaking method is also called a plate-shaped paper molded body. A needle body is a molded body obtained by subjecting an inorganic fiber aggregate to a needling process, and a plate-shaped molded body obtained by the needling process is also called a plate-shaped needle body.

The plate-shaped molded body is preferably formed by a papermaking method. Papermaking bodies have the property of having little localized bias in the inorganic fibers and being resistant to deformation, making them suitable as insulating materials to be placed inside the combustion chamber.

The average fiber diameter of the inorganic fibers is not particularly limited, but if the plate-shaped molded product is a paper product, it is preferably 2.0 to 15.0 μm. If the average fiber diameter of the inorganic fibers is within the above range, a dense plate-shaped molded product with little local deviation in bulk density can be obtained.

The average fiber length of the inorganic fibers is not particularly limited, but when the plate-shaped molded product is a paper product, it is preferably 0.05 to 3.0 mm. When the average fiber length of the inorganic fibers is within the above range, a laminated plate-shaped molded product is obtained with little localized bias of the inorganic fibers, and the bulk density and heat insulation properties are stable.

The combustion chamber insulation material of the present invention has a different bulk density in the thickness direction of the plate-shaped molded body. Specifically, when comparing the bulk densities of the first main surface portion, the second main surface portion, and the central portion between the first main surface portion and the second main surface portion in the thickness direction of the plate-shaped molded body, the bulk density of at least the first main surface portion is smaller than the bulk density of the central portion.

The internal structure of a combustion chamber insulating material 1A, which is a first embodiment of the combustion chamber insulating material 1, will be described below with reference to FIG.
Fig. 2 is a cross-sectional view taken along line A-A, which is a schematic diagram showing an example of the internal structure of the combustion chamber insulation material in Fig. 1. The combustion chamber insulation material 1A is composed of a plate-shaped molded body 10A. When comparing the bulk densities of the first main surface portion 11, the second main surface portion 12, and the central portion 13 between the first main surface portion 11 and the second main surface portion 12 in the thickness direction of the plate-shaped molded body 10A, the bulk density of the first main surface portion 11 is the smallest, followed by the central portion 13 and the second main surface portion 12 in that order.
The first main surface portion 11 includes a first main surface 10Aa, and the second main surface portion 12 includes a second main surface 10Ab.

Next, the internal structure of a combustion chamber insulating material 1B, which is a second embodiment of the combustion chamber insulating material 1, will be described below with reference to Fig. 3. Only the differences from the combustion chamber insulating material 1A, which is the first embodiment, will be described here, and descriptions of common parts will be omitted.
FIG. 3 is a cross-sectional view taken along line AA of FIG. 1, showing a schematic diagram of another example of the internal structure of the combustion chamber insulating material.
In the plate-shaped molded body 10B constituting the combustion chamber insulating material 1B, the first main surface portion 11 and the second main surface portion 12 have low bulk density, and the central portion 13 has high bulk density. The bulk density of the second main surface portion 12 may be intermediate between the bulk density of the first main surface portion 11 and the bulk density of the central portion 13.
The first main surface portion 11 includes a first main surface 10Ba, and the second main surface portion 12 includes a second main surface 10Bb.

In Figures 2 and 3, the first main surface portion 11, the second main surface portion 12, and the central portion 13 are divided into three equal parts in the thickness direction, but the thicknesses of the first main surface portion 11, the second main surface portion 12, and the central portion 13 do not have to be the same.

The bulk density of the second main surface portion is preferably (i) greater than the bulk density of the central portion, or (ii) less than the bulk density of the central portion. The bulk density of the second main surface portion may be approximately the same as the bulk density of the central portion.

In the combustion chamber insulation material of the present invention, the bulk density of the first main surface portion of the plate-shaped molded body is preferably at least 3% smaller than the larger of the bulk density of the second main surface portion and the bulk density of the central portion, and more preferably at least 5% smaller.

The combustion chamber insulation material of the present invention is arranged so that the first main surface faces the inner wall surface of the combustion chamber. By arranging the first main surface, which has a low bulk density, facing the inner wall surface of the combustion chamber, a large insulating effect can be obtained.

The combustion chamber insulation material of the present invention is a plate-shaped molded body formed as an integral unit, and is not an assembly of multiple plate-shaped molded bodies with different bulk densities stacked in the thickness direction.

The bulk density of the combustion chamber insulation material as a whole is preferably 0.20 to 0.35 g/cm ³ .
When the bulk density of the plate-shaped molded body is within the above range, the strength (bending strength) and insulating properties required for a combustion chamber insulation material can be maintained, while the weight increase of the combustion chamber can be suppressed compared to fireproof materials and insulation materials made of amorphous materials.

The bulk density can be adjusted, for example, by adjusting the fiber length of the inorganic fibers and the aggregate floc size, or by adjusting the compression conditions during slurry dewatering and drying.

Incidentally, the bulk density of fireproof materials and heat insulating materials made of amorphous materials is usually about 0.7 to 1.5 g/cm ³ , which does not satisfy the preferable bulk density of the above-mentioned combustion chamber insulating material.

The thickness of the plate-shaped molded body is preferably 1 to 10 cm. If the thickness of the plate-shaped molded body is within the above range, it can exhibit sufficient insulating properties as an insulating material.

The area of the plate-like molded body as viewed in the thickness direction (area in plan view) is preferably 350 to 15,000 ^cm2 .

The volume of the plate-shaped molded body is preferably 700 to 150,000 cm ^3. When the volume of the plate-shaped molded body is within the above range, damage due to thermal shrinkage is particularly unlikely to occur.

The plate-shaped molded body may have holes penetrating in the thickness direction. By forming such holes, it becomes easier to cover the inner wall surface of the combustion chamber in which piping such as water pipes and smoke pipes are arranged.

The plate-shaped molded body may contain components other than inorganic fibers. Examples of components other than inorganic fibers include inorganic particles, inorganic binders, organic binders, coagulants, etc.

Examples of inorganic particles include silica particles, alumina particles, titania particles, zirconia particles, and natural mineral particles.
Examples of the inorganic binder include silica sol, alumina sol, titania sol, zirconia sol, and fumed silica.
Examples of the organic binder include polyvinyl alcohol, starch, acrylic resin, and polyacrylamide.

The weight ratio of inorganic fibers in the plate-shaped molded body is preferably 30 to 97% by weight.

The method for producing the combustion chamber insulating material of the present invention is not particularly limited, but it can be produced, for example, by the following procedure.
A method for producing the combustion chamber insulating material 1A will be described below with reference to FIG.
FIG. 4 is a cross-sectional view showing an example of a process for producing the combustion chamber insulating material of the present invention.
Step (1) A slurry containing water, inorganic fibers, an inorganic binder, an organic binder and a flocculant is prepared, and a base sheet 50 of the heat insulating material is obtained by a papermaking method (FIG. 4A).
Step (2) After papermaking, a SUS plate HP heated to 150° C. is placed on the first main surface 50a of the original sheet containing moisture, and dried for 30 minutes (FIG. 4B).
Step (3): Next, the original sheet 50 of (2) is sandwiched between two SUS plates HP heated to 150° C. from the first main surface 50a side and the second main surface 50b side, and dried for one hour while compressing the original sheet 50 to a desired thickness (FIG. 4C). In this way, a combustion chamber insulating material 1A can be obtained (FIG. 4D).

In the above method, the organic binder solidifies on the first main surface 50a side of the original sheet 50 where drying has progressed, and even when compressed, the original sheet 50 does not collapse and the bulk density does not change. When the original sheet 50 is sandwiched between two SUS plates HP, the undried parts are compressed, and the bulk density of the inorganic fibers in the central portion 13 and second main surface portion 12 of the obtained plate-shaped molded body 10A increases. In the plate-shaped molded body 10A, the second main surface portion 12 has a higher bulk density than the central portion 13, which is thought to be because the central portion of the original sheet 50 was slightly dried in the above step (2).

Next, a method for producing the combustion chamber insulating material 1B will be described with reference to FIG.
FIG. 5 is a cross-sectional view showing a schematic example of another process for producing a combustion chamber insulating material of the present invention.
(1) A slurry containing water, inorganic fibers, an inorganic binder, an organic binder and a flocculant is prepared, and a base sheet 50 of the heat insulating material is obtained by a papermaking method (FIG. 5A).
(2) After the papermaking process, a SUS plate HP heated to 150° C. is placed on the second main surface 50b of the original sheet containing moisture, and then dried for 30 minutes (FIG. 5B).
(3) After that, the original sheet 50 is turned upside down, and a SUS plate HP heated to 150° C. is placed on the first main surface 50a, and dried for 30 minutes (FIG. 5C).
(4) Next, the original sheet 50 of (3) is sandwiched between two SUS plates HP heated to 150° C. from the first main surface 50 a side and the second main surface 50 b side, and dried for one hour while compressing the original sheet 50 to a desired thickness (D in FIG. 5). In this way, a combustion chamber insulating material 1B can be obtained (E in FIG. 5).

In the above method, the organic binder solidifies on the first main surface 50a and second main surface 50b of the original sheet 50, where drying has progressed, and the original sheet 50 does not collapse even when compressed, and the bulk density does not change. When the original sheet 50 is sandwiched between two SUS plates HP, only the undried central portion is compressed, and the bulk density of the central portion 13 of the resulting plate-like molded body 10B increases.

The combustion chamber insulation material of the present invention has a greater insulating effect because the surface with the lower bulk density is arranged facing the inner wall surface of the combustion chamber. Since the combustion chamber insulation material of the present invention is a plate-shaped molded body containing inorganic fibers, it is lighter in weight than a castable molded body of the same volume and can be stably and easily attached and maintained on the inner wall surface of the combustion chamber. Furthermore, since the combustion chamber insulation material of the present invention contains inorganic fibers, it is durable and can be supplied at low cost.

The combustion chamber insulation material of the present invention can be used, for example, in devices equipped with a combustion chamber. Examples of devices equipped with a combustion chamber include water heaters and boilers.

[Water heater]
The water heater of the present invention comprises a combustion chamber, a heat exchanger installed within the combustion chamber, and a combustion chamber insulation material of the present invention, and is characterized in that a first main surface portion of the combustion chamber insulation material is arranged facing the inner wall surface of the combustion chamber.
The water heater of the present invention is equipped with the combustion chamber insulation material of the present invention, and since the bulk density of the first main surface portion is small, an air layer can be created on the inner wall surface side of the combustion chamber, thereby enhancing the insulation effect, and providing excellent _CO2 emission suppression effect.

An example of a water heater according to the present invention will be described below.
FIG. 6 is a cross-sectional view illustrating an example of a water heater according to the present invention.
The water heater 500 has a combustion chamber 540 and a heat exchanger 170 disposed within the combustion chamber 540 .
The combustion chamber 540 has a metal container 150 and two combustion chamber insulation materials 1 arranged on a top surface 150a and a bottom surface 150b of the metal container 150. The combustion chamber insulation material 1 is arranged such that a first main surface 10a faces the inner wall surface of the combustion chamber.
Water flows through heat exchanger 170 , and the water within heat exchanger 170 is heated in combustion chamber 540 to become hot water (hot water), which is then supplied outside water heater 500 .

The temperature of the hot water supplied can be adjusted as needed by adjusting the amount of fuel burned in the combustion chamber and the amount of water passing through the heat exchanger per unit time.

[boiler]
The boiler of the present invention comprises a combustion chamber and the combustion chamber insulation material of the present invention, and is characterized in that a first main surface portion of the combustion chamber insulation material is arranged facing the inner wall surface of the combustion chamber.
The boiler of the present invention is equipped with the combustion chamber insulation material of the present invention, and since the bulk density of the first main surface portion is small, an air layer can be created on the inner wall surface side of the combustion chamber to enhance the insulation effect, and the boiler has an excellent effect of suppressing _CO2 emissions.

An example of a boiler according to the present invention will now be described.
FIG. 7 is a cross-sectional view showing a schematic example of a boiler according to the present invention.
The boiler 600 has a combustion chamber 550 and a water tube 180 disposed within the combustion chamber 550 .
The combustion chamber 550 has a metal container 160 and two combustion chamber insulation materials 1 arranged on a top surface 160a and a bottom surface 160b of the metal container 160. The combustion chamber insulation material 1 is arranged such that a first main surface 10a faces the inner wall surface of the combustion chamber.
Water is supplied into the water pipe 180 from the lower part of the combustion chamber 550 , and the water passing through the water pipe 180 is heated in the combustion chamber 550 to become steam, which is discharged from the upper part of the combustion chamber 550 .
The discharged water vapor is used for power generation, heating, cleaning, cooking, drying, disinfection, sterilization, etc. after separating the liquid water or superheating as necessary.

The method for placing the combustion chamber insulation material on the inner wall surface of the combustion chamber is not particularly limited, and it can be fixed with bolts and nuts, for example. The first main surface portion of the combustion chamber insulation material may be placed on the inner wall surface of the combustion chamber via an inorganic adhesive.

The following items are disclosed in this specification:

The present disclosure (1) is a plate-shaped molded body containing inorganic fibers, characterized in that, when comparing the bulk densities of a first main surface portion, a second main surface portion, and a central portion located between the first main surface portion and the second main surface portion in the thickness direction, the bulk density of at least the first main surface portion is smaller than the bulk density of the central portion, and the first main surface portion is disposed toward the inner wall surface of the combustion chamber.

The present disclosure (2) is a combustion chamber insulation material as described in the present disclosure (1), in which the bulk density of the second main surface portion is (i) greater than the bulk density of the central portion, or (ii) less than the bulk density of the central portion.

The present disclosure (3) is a combustion chamber insulation material described in the present disclosure (1) or (2), which is molded by a papermaking method.

The present disclosure (4) is a combustion chamber insulating material described in any one of the present disclosures (1) to (3) having a flat or curved shape.

The present disclosure (5) is a combustion chamber insulating material according to any one of the present disclosures (1) to (4), having an overall bulk density of 0.20 to 0.35 g/cm ³ .

The present disclosure (6) is a combustion chamber insulating material according to any one of the present disclosures (1) to (5), in which the bulk density of the first main surface portion is 3% or more smaller than the larger of the bulk density of the second main surface portion and the bulk density of the central portion.

The present disclosure (7) is a water heater comprising a combustion chamber, a heat exchanger installed in the combustion chamber, and a combustion chamber insulation material described in any one of the present disclosures (1) to (6), characterized in that a first main surface portion of the combustion chamber insulation material is arranged facing the inner wall surface of the combustion chamber.

The present disclosure (8) is a boiler comprising a combustion chamber and a combustion chamber insulation material described in any one of the present disclosures (1) to (6), characterized in that a first main surface portion of the combustion chamber insulation material is arranged facing the inner wall surface of the combustion chamber.

(Example)
Examples that more specifically disclose the present invention are shown below. Note that the present invention is not limited to these examples. In the following examples, the upper layer of the plate-shaped molded body corresponds to the first main surface portion, the middle layer corresponds to the center portion, and the lower layer corresponds to the second main surface portion.

Example 1
Water, AES fiber, inorganic binder (silica sol), organic binder (acrylate-based latex) and coagulant (aluminum sulfate) were added to a commercially available pulper and dispersed to prepare a slurry liquid. The prepared slurry liquid was poured into a mold, dehydrated, and a prototype sheet was obtained by a papermaking method. The thickness of the prototype sheet was 38 mm. A Teflon (registered trademark)-coated SUS metal plate was placed on the first main surface of the obtained prototype sheet and dried at 150 ° C for 30 minutes. Thereafter, the prototype sheet was sandwiched between two of the same SUS metal plates from the first main surface side and the second main surface side, and the thickness of the prototype sheet was adjusted to 30 mm, and dried at 150 ° C for 1 hour to obtain a plate-shaped molded body. The bulk density of the upper layer of the obtained plate-shaped molded body was 0.294 g / cm ³ , the bulk density of the middle layer was 0.316 g / cm ³ , and the bulk density of the lower layer was 0.338 g / cm ³ .

Example 2
Water, AES fiber, inorganic binder (silica sol), organic binder (acrylate-based latex) and coagulant (aluminum sulfate) were added to a commercially available pulper and dispersed to prepare a slurry liquid according to Example 2. The prepared slurry liquid was poured into a mold, dehydrated, and a prototype sheet was obtained by a papermaking method. The thickness of the prototype sheet was 35 mm. A Teflon (registered trademark)-coated SUS metal plate was placed on the second main surface of the obtained prototype sheet and dried at 150 ° C for 30 minutes. Next, the prototype sheet was turned over, and the same SUS metal plate was placed on the first main surface and dried at 150 ° C for 30 minutes. Thereafter, the prototype sheet was sandwiched from the first main surface side and the second main surface side using two of the same SUS metal plates, the thickness of the prototype sheet was adjusted to 30 mm, and it was dried at 150 ° C for 1 hour to obtain a plate-shaped molded body. The bulk density of the upper layer of the obtained plate-like molded product was 0.221 g/cm ³ , the bulk density of the middle layer was 0.239 g/cm ³ , and the bulk density of the lower layer was 0.226 g/cm ³ .

Example 3
Using the slurry prepared in Example 1, a prototype sheet was made and dried in the same manner as in Example 2 to obtain a plate-like molded product having a thickness of 30 mm. The bulk density of the upper layer of the obtained plate-like molded product was 0.291 g/ ^cm3 , the bulk density of the middle layer was 0.320 g/ ^cm3 , and the bulk density of the lower layer was 0.293 g/ ^cm3 .

Comparative Example 1
A 30 mm thick original sheet was obtained in the same manner as in Example 1. The obtained original sheet was placed on a plate-shaped shelf in a dryer and dried at 150° C. for 3 hours to obtain a 30 mm thick plate-shaped molded product. The bulk density of the obtained plate-shaped molded product was uniform and was 0.300 g/cm ³ .

Comparative Example 2
A 30 mm thick original sheet was obtained in the same manner as in Example 2. The obtained original sheet was placed on a plate-shaped shelf in a dryer and dried at 150° C. for 3 hours to obtain a 30 mm thick plate-shaped molded product. The bulk density of the obtained plate-shaped molded product was uniform and was 0.220 g/cm ³ .

Comparative Example 3
Water, AES fiber, inorganic binder (silica sol), organic binder (acrylate-based latex), and coagulant (aluminum sulfate) were charged into a commercially available pulper and dispersed to prepare a slurry liquid according to Comparative Example 3. The prepared slurry liquid was poured into a mold, dehydrated, and a master sheet having a thickness of 15 mm was obtained by a papermaking method. The master sheet obtained was placed on a plate-shaped shelf in a dryer and dried at 150°C for 3 hours to obtain a plate-shaped molded body S. The bulk density of the obtained plate-shaped molded body was uniform and was 0.350 g/ ^cm3 .
A plate-like molded product T having a thickness of 15 mm and a bulk density of 0.220 g/cm ³ was obtained in the same manner as in Comparative Example 2.
The plate-like molded body T was placed on the plate-like molded body S to obtain a plate-like molded body having a thickness of 30 mm.

Comparative Example 4
The castable refractory material was impregnated with an appropriate amount of water, molded, and dried to obtain a plate-shaped molded product having a diameter of 70 mm and a thickness of 30 mm. The bulk density was 0.760 g/ ^cm3 .

(Measurement of bulk density)
For the plate-shaped bodies of Examples 1 to 3, the plate-shaped bodies were punched out into squares with sides of 50 mm each, and cut into three equal parts in the thickness direction. Next, the weight and thickness of each of the plate-shaped bodies cut into three parts were measured. The thickness was measured with a vernier caliper.
Then, the bulk density of the first main surface portion, the bulk density of the second main surface portion, and the bulk density of the central portion were each calculated from the surface specific gravity (weight/area) calculated from the weight and the thickness, as shown in the formula below.
(weight/area)/thickness=bulk density [g/cm ³ ]

The bulk density of the plate-shaped molded bodies of Comparative Examples 1 and 2 and the castable molded body of Comparative Example 4 was calculated using the above formula by measuring the weight and thickness without cutting.

The weight and thickness of each of the plate-shaped molded bodies S and T in Comparative Example 3 were measured, and the bulk density was calculated using the above formula.

(Insulation rating)
The heat insulating properties of the plate-like molded articles of Examples 1 to 3 and Comparative Examples 1 to 3, and the castable molded article of Comparative Example 4 were evaluated by the following method.
A heating plate (Inconel: registered trademark) with a heater embedded therein to reproduce the temperature state in the combustion chamber and a stainless steel plate were prepared, and the plate-shaped molded body or castable molded body was sandwiched and fixed between these two plates. The plate-shaped molded bodies of Examples 1 to 3 and Comparative Example 3 were arranged so that the main surface of the upper layer side or the side with a low bulk density was in contact with the stainless steel plate. In Comparative Example 5, the main surface of the plate-shaped molded body of Example 1 on the side with a high bulk density was arranged so that it was in contact with the stainless steel plate. The heating plate was heated to 1000°C and maintained for 10 minutes. Thereafter, the temperature of the stainless steel plate on the surface in contact with the plate-shaped molded body or castable molded body was measured. The results are shown in Table 1. The lower the temperature, the better the thermal insulation.

(Evaluation of bending strength)
The bending strength of the plate-like molded product in the present invention was measured by preparing a sample of the plate-like molded product having a width of 40 mm, a length of 200 mm, and a thickness of 30 mm, using a universal material testing machine (model number: 5567, manufactured by Instron). The measurement method was in accordance with JIS R2619 (test method for bending strength of fireproof insulating bricks), and the maximum load was determined with the above-mentioned sample dimensions, a pressure speed of 10 mm/min, and a distance between supporting rolls of 150 mm, and the bending strength was calculated.
A bending strength of 0.28 MPa or more was evaluated as ◯, and a bending strength of less than 0.28 MPa was evaluated as Δ.
The results are shown in Table 1.

 

 

As shown in Table 1, the insulation materials of Examples 1 to 3, in which the upper layer (metal surface side) of the plate-shaped molded body has a lower bulk density than the middle layer, had better insulation properties than the insulation material of Comparative Example 1, which used a plate-shaped molded body with a uniform bulk density, and Comparative Example 4, which used a castable molded body. Comparative Example 3 had a low bulk density of the plate-shaped molded body on the metal surface side, and the insulation properties were equivalent to those of Examples 1 to 3, but since multiple plate-shaped molded bodies were stacked, the bending strength was lower than that of the insulation materials of Examples 1 to 3, which are integrated plate-shaped molded bodies, resulting in a high risk of damage to the low-density parts during handling. Comparative Example 2 had the same insulation properties as Examples 1 to 3, but since the bulk density was too low, the bending strength was insufficient, resulting in a high risk of damage during handling. Comparative Example 5 used the same plate-shaped molded body as Example 1, but since the bulk density on the metal surface side was high, the insulation properties were inferior to those of Example 1.

1, 1A, 1B Combustion chamber insulation material 10, 10A, 10B Plate-shaped molded body 10a, 10Aa, 10Ba First main surface 10b, 10Ab, 10Bb of plate-shaped molded body Second main surface 10c of plate-shaped molded body Side surface 11 of plate-shaped molded body First main surface portion 12 Second main surface portion 13 Central portion 50 Original sheet 50a First main surface 50b of original sheet Second main surface HP of original sheet SUS plate 150, 160 Metal container 150a, 160a Top surface 150b, 160b of metal container Bottom surface 170 of metal container Heat exchanger 180 Water tube 540, 550 Combustion chamber 500 Water heater 600 Boiler

Claims (8)

A plate-like molded body containing inorganic fibers,
When comparing the bulk densities of the first main surface portion, the second main surface portion, and the central portion between the first main surface portion and the second main surface portion in the thickness direction, the bulk density of at least the first main surface portion is smaller than the bulk density of the central portion;
13. A combustion chamber insulating material, comprising: a first main surface portion disposed facing an inner wall surface of the combustion chamber. The combustion chamber insulation material according to claim 1, wherein the bulk density of the second main surface portion is (i) greater than the bulk density of the central portion, or (ii) less than the bulk density of the central portion. The combustion chamber insulation material according to claim 1 or 2, which is formed by a papermaking method. The combustion chamber insulation material according to any one of claims 1 to 3, which has a flat or curved shape. The combustion chamber insulating material according to any one of claims 1 to 4, having an overall bulk density of 0.20 to 0.35 g/ ^cm3 . The combustion chamber insulation material according to any one of claims 1 to 5, wherein the bulk density of the first main surface portion is 3% or more smaller than the larger of the bulk density of the second main surface portion and the bulk density of the central portion. A combustion chamber;
A heat exchanger installed in the combustion chamber;
The combustion chamber insulating material according to any one of claims 1 to 6,
A water heater characterized in that a first main surface portion of the combustion chamber insulation material is arranged facing an inner wall surface of the combustion chamber. A combustion chamber;
The combustion chamber insulating material according to any one of claims 1 to 6,
A boiler characterized in that a first main surface portion of the combustion chamber insulation material is arranged facing the inner wall surface of the combustion chamber.

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