JP6608598B2 - Manufacturing method of honeycomb structure - Google Patents

Description

The present invention relates to a method for manufacturing a honeycomb structure.

In general, the performance of a heat exchanger in an air preheating device largely depends on the area of the heat transfer surface in contact with the gas to be heat exchanged. The larger the area of the heat transfer surface, the better the heat exchange performance of the heat exchanger, The preheated air can be obtained. Therefore, the heat exchange element of the heat exchanger is required to have a fine structure and be excellent in heat resistance.
Patent Document 1 describes an air preheating device using a ceramic honeycomb structure having a fine structure and excellent heat resistance as a heat exchange element of a heat exchanger. Patent Document 2 describes a filter using as a substrate a ceramic honeycomb structure having a fine structure and having an outer peripheral surface coated with an outer peripheral coating agent. Furthermore, Patent Document 3 describes a heating element using a ceramic honeycomb structure having a fine structure and having a surface coated with a catalyst coating layer as a resistor.

  However, although the ceramic honeycomb structures described in Patent Documents 1 to 3 have a fine structure and can be used at high temperatures, the ceramic honeycomb structures are generally made of a porous ceramic. There was a risk that gas could permeate through the partition walls defining the cells of the ceramic honeycomb structure. Therefore, when the ceramic honeycomb structure described in Patent Documents 1 to 3 is used as a heat exchange element of a heat exchanger that performs heat exchange between two types of gases, the two types of gases permeate the partition walls and mix. Therefore, the function as a heat exchanger may be deteriorated.

  Patent Documents 2 and 3 disclose a technique for coating the surface of the partition walls of a ceramic honeycomb structure made of a porous ceramic. However, in Patent Document 2, this occurs when used at high temperatures. In order to relieve thermal stress, the outer periphery coating agent is coated, and in Patent Document 3, the catalyst coating layer is coated for the purpose of preventing oxidation when used under high temperature. The function to prevent was insufficient.

JP 2012-193946 A JP 2011-84448 A JP-A-9-306644

The present invention solves the problems of the prior art as described above, and its object is to provide a method for producing transmission hardly occurs honeycomb structure of the gas.

  In order to solve the above problems, a honeycomb structure according to one embodiment of the present invention includes a substrate in which a plurality of cells partitioned in a polygonal column by ceramic partition walls are arranged in a honeycomb shape, and the plurality of cells A honeycomb structure used in a heat exchange element that introduces a high-temperature gas in a part and introduces a low-temperature gas in another part and continuously exchanges heat between the high-temperature gas and the low-temperature gas. And a glass layer coated on the surface of the partition wall, wherein the mass of the glass layer is 20% by mass or more of the mass of the substrate.

In this honeycomb structure, the thickness of the glass layer may be 10% or less of the minimum side length of the polygonal opening that opens at the axial end of the cell.
Further, the glass layer is formed by a surface treatment in which a surface treatment liquid containing ceramic powder is disposed on the surface of the partition wall and then subjected to a heat treatment, and the viscosity of the surface treatment liquid is 60 mPa · s or less. May be. And the temperature of the said heat processing is good also as 1000 to 1300 degreeC.
Furthermore, in this honeycomb structure, the glass layer may be composed of at least one of silica and alumina. Furthermore, in this honeycomb structure, the ceramic constituting the partition may be silicon carbide.

  In the honeycomb structure according to the present invention, since the glass layer is coated on the surface of the partition walls of the substrate, and the mass of the glass layer is 20% by mass or more of the mass of the substrate, gas permeation hardly occurs.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment of the honeycomb structure which concerns on this invention, (a) is a whole perspective view, (b) is a partial enlarged view (enlarged view of the part enclosed with the circle of (a)). It is an enlarged view explaining a glass layer. It is a graph which shows the relationship between the mass of a glass layer, and the ventilation resistance value of a honeycomb structure. It is a graph which shows the relationship between the mass of a glass layer, and the gas permeability of a honeycomb structure. It is a graph which shows the relationship between the viscosity of a surface treatment liquid, the bulk specific gravity of a honeycomb structure, and the thickness of a glass layer. It is the elements on larger scale which expand and show the detail of the honeycomb structure used as a heat exchange element.

Embodiments of the present invention will be described below in detail with reference to the drawings.
A honeycomb structure 1 shown in FIG. 1 includes a substrate 2 in which a plurality of cells 10 (the length of one side is, for example, 1 mm or more and 10 mm or less) partitioned in a rectangular column shape by partition walls 2a made of a porous ceramic. I have. More specifically, the substrate 2 has a structure in which a plurality of cells 10 are arranged in the vertical direction and the horizontal direction without gaps to form a lattice shape.
Note that the shape of the cell 10 is not limited to a quadrangular prism shape, and any shape can be applied as long as it is a shape that can be arranged in a space without gaps. For example, a triangular prism shape or a hexagonal prism shape may be used. Even in the case of a quadrangular prism, the cross-sectional shape of the cell 10 is not limited to a square as shown in FIG. 1, and a shape such as a rectangle or a parallelogram is also applicable.

Further, the type of ceramic constituting the partition 2a (that is, the ceramic constituting the substrate 2) is not particularly limited, and silicon carbide, silica, glass, alumina, silicon nitride, boron nitride, magnesia, zirconia, titania, Among ceramics such as hafnia, yttria, and lantana, one kind can be used alone, or two or more kinds can be used in combination. In these, since it is excellent in heat resistance, silicon carbide is preferable.
The honeycomb structure 1 includes a glass layer 3 coated on the surface of the substrate 2 (the surface of the partition walls 2a) by performing the following treatment on the substrate 2 (see FIG. 2). That is, the glass layer 3 is formed on the surface of the partition wall 2a of the base body 2 by performing a surface treatment in which a surface treatment liquid containing ceramic powder is disposed on the surface of the partition wall 2a of the base body 2 in the form of a film and then heat-treated. ing. The method for disposing the surface treatment liquid on the surface of the substrate 2 is not particularly limited, and examples include dipping, spraying, and coating.

When the surface treatment is performed on the porous ceramic constituting the substrate 2, the ceramic powder in the surface treatment liquid is vitrified and fluidized, penetrates into the pores of the porous ceramic and hardens to close the pores, and the surface of the partition wall 2 a The glass layer 3 is cured by covering. And this glass layer 3 is formed so that the mass of the glass layer 3 may be 20 mass% or more of the mass of the base 2.
As described above, since the pores are closed by the glass layer 3 and the surface of the partition wall 2a is covered, the gas permeability of the honeycomb structure 1 is lowered, and the gas in the cell 10 passes through the partition wall 2a and is adjacent. Leaking into the cell 10 is suppressed. If the mass of the glass layer 3 is 20% by mass or more of the mass of the substrate 2, a sufficient amount of the glass layer 3 is coated on the surface of the partition wall 2a, so that the gas in the cell 10 passes through the partition wall 2a. Leakage to adjacent cells 10 is prevented.

  However, if the glass layer 3 has too much mass, the cell 10 may be clogged. That is, the glass-shaped layer 3 may block the square opening 10 a that opens at the end of the cell 10 in the axial direction. In order to prevent clogging of the cell 10, the thickness T of the glass layer 3 is set to the minimum side length L of each side of the opening 10 a of the cell 10 (in this embodiment, the opening Since the shape of 10a is a square and the lengths of all sides are the same, it is preferably 10% or less of the length of one side), more preferably 5% or less (see FIG. 2). .

  When the thickness T of the glass layer 3 is in the above range, the honeycomb structure 1 having a low gas permeability can be obtained while preventing the cells 10 from being clogged. Further, the glass layer 3 is less likely to be uneven in thickness, and the glass layer 3 having a uniform thickness can be formed. For example, when the thickness T of the glass layer 3 is 15% or more of the minimum side length L of the opening 10a, the cell 10 is clogged due to the uneven thickness of the glass layer 30, and all the cells are blocked. About 20% of the obstruction occurs. If the thickness T of the glass layer 3 is 10% or less of the minimum side length L of the opening 10a, the cell 10 is hardly blocked.

If such a honeycomb structure 1 is used as a heat exchange element of a heat exchanger, air and exhaust gas can be evenly vented to each cell 10, and pressure when air and exhaust gas are vented to the cell 10. Loss can be reduced.
The mass and thickness T of the glass layer 3 can be controlled by the number of times of surface treatment and the viscosity of the surface treatment liquid used for the surface treatment. For example, the viscosity of the surface treatment liquid is preferably 60 mPa · s or less. Then, since the surface treatment liquid easily penetrates into the pores of the porous ceramic, the mass of the glass layer 3 formed on the surface of the partition wall 2a tends to be large, and the mass is 20% by mass or more of the mass of the base 2 The glass layer 3 can be easily formed. Further, since the thickness of the glass layer 3 formed on the surface of the partition wall 2a can be reduced, the honeycomb structure 1 having a low gas permeability can be obtained while preventing the cells 10 from being clogged.

Note that the temperature of the heat treatment is preferably 1000 ° C. or higher and 1300 ° C. or lower. If it is 1000 degreeC or more, since the fluidity | liquidity of the vitrified ceramic powder will become high, it will become easy to osmose | permeate in a pore. Moreover, if it is 1300 degrees C or less, since foaming of the vitrified ceramic powder can be suppressed, the clogging of the cell 10 by foaming is suppressed.
The composition of the surface treatment liquid is ceramic powder and a solvent, and additives such as thickeners, surfactants (dispersing agents), peptizers and pour point depressants may be added as necessary. . Although the kind of solvent is not specifically limited, Organic solvents, such as water, isopropyl alcohol, and ethanol, are mention | raise | lifted.

Furthermore, although the density | concentration of the ceramic powder in a surface treatment liquid is not specifically limited, It is preferable to set it as 20 to 60 mass%.
Furthermore, the average particle diameter of the ceramic powder is not particularly limited, but is preferably 0.1 μm or more and 200 μm or less.
Furthermore, the kind of ceramic powder contained in the surface treatment liquid is not particularly limited, and ceramics such as silica, glass, alumina, silicon carbide, silicon nitride, boron nitride, magnesia, zirconia, titania, hafnia, yttria, lantana, etc. Of these, one can be used alone, or two or more can be used in combination. Among these, it is preferable to use at least one of silica and alumina, and it is more preferable to use silica. If silica is used as the ceramic powder, the glass layer 3 becomes a silicate glass layer composed of silica.

Here, the relationship between the mass of the glass layer, the ventilation resistance value and the gas permeability of the honeycomb structure is shown in the graphs of FIGS. The type of ceramic constituting the honeycomb structure is silicon carbide, and the type of ceramic constituting the glass layer is silica (the type of ceramic powder included in the surface treatment liquid is silica).
The gas permeability is the ratio of the amount of gas that passes through the partition walls of the cells of the honeycomb structure and goes out of the cells. This gas permeability is introduced by pressurizing gas into the cells of the honeycomb structure (introducing gas at a pressure when the honeycomb structure is used as a heat exchange element of the heat exchanger), It can be obtained by measuring the amount of gas that has permeated and exited the cell.

Further, the ventilation resistance value is a numerical value indicating the ease of gas permeation, and in the graph of FIG. 3, the gas permeation of the honeycomb structure in which the mass of the glass layer is 5% by mass or less of the mass of the substrate is shown. It is shown as a relative value when the ease is 1. This ventilation resistance value can be obtained by introducing a high-pressure gas into the cells of the honeycomb structure and measuring the amount of gas that has permeated the partition walls of the cells and exited from the cells.
From the graph of FIG. 3, when the mass of the glass layer increases, the ventilation resistance value increases. When the mass of the glass layer is 20% by mass or more of the mass of the substrate, the ventilation resistance value is extremely high, and the gas acts as a cell partition. It can be seen that it is very difficult to transmit. Further, the graph of FIG. 4 shows that the gas permeability decreases as the mass of the glass layer increases, and if the mass of the glass layer is 20% by mass or more of the mass of the substrate, the gas does not permeate the partition walls of the cell. .

Next, the relationship between the viscosity of the surface treatment liquid used for the surface treatment, the bulk specific gravity of the honeycomb structure, and the thickness of the glass layer is shown in the graph of FIG. In addition, the numerical value of the bulk specific gravity of the honeycomb structure in the graph of FIG. 5 is shown as a relative value when the bulk specific gravity of the honeycomb structure in which the glass layer is not formed is 1. In addition, the numerical value of the glass layer thickness in the graph of FIG. 5 is the sum of the partition wall thickness and the glass layer thickness. When the partition wall thickness of the honeycomb structure in which the glass layer is not formed is 1, The relative value of is shown.
Furthermore, the mass of the glass layer formed in the honeycomb structure is 20% by mass of the mass of the substrate in which the glass layer is formed. Further, the type of ceramic constituting the honeycomb structure is silicon carbide, and the type of ceramic constituting the glass layer is silica (the type of ceramic powder contained in the surface treatment liquid is silica).

From the graph of FIG. 5, when the viscosity of the surface treatment liquid is 60 mPa · s or less, the bulk specific gravity of the honeycomb structure increases and the thickness of the glass layer is small, whereas the viscosity of the surface treatment liquid is small. Is over 60 mPa · s, the bulk specific gravity of the honeycomb structure is hardly increased and the thickness of the glass layer is large.
This is because when the viscosity of the surface treatment liquid is 60 mPa · s or less, the surface treatment liquid easily penetrates into the pores, and the glass layer is formed even inside the pores. It is considered that a glass layer having a sufficient mass can be formed while maintaining the bulk specific gravity.

Such a honeycomb structure 1 of the present embodiment is suitable as a heat exchange element of a heat exchanger that exchanges heat between two kinds of gases because gas hardly permeates. Hereinafter, an example in which the honeycomb structure 1 of the present embodiment is used as a heat exchange element of a heat exchanger will be described with reference to FIGS.
The heat exchanger of this embodiment is provided in an exhaust heat recovery type air preheating device applied to a burner such as a heat treatment furnace. This heat exchanger exchanges heat between the high-temperature exhaust gas after using combustion air from a burner (not shown) for burning fuel by air and the low-temperature air supplied to the burner. To recover the heat of the exhaust gas. A high temperature gas, that is, exhaust gas, is introduced into a part of the cells 10 of the honeycomb structure 1 used as a heat exchange element, and a low temperature is introduced into the other part. Gas, ie air, is introduced. Since the exhaust cell 10A into which the high-temperature exhaust gas is introduced and the air cell 10B into which the low-temperature air is introduced are adjacent to each other, heat is continuously exchanged via the partition wall 2a, so that the air is preheated. This will be described in more detail below.

As shown in FIGS. 1 and 6, the honeycomb structure 1 used as a heat exchange element of a heat exchanger has a plurality of cells 10 partitioned in a rectangular column shape by partition walls 2 a made of porous ceramics arranged in a honeycomb shape. A substrate 2 is provided. More specifically, the substrate 2 has a structure in which a plurality of cells 10 are arranged in the vertical direction and the horizontal direction without gaps to form a lattice shape. And the surface of the partition 2a of the base | substrate 2 is coat | covered with the glass layer 3 formed by the said surface treatment.
Exhaust cells 10A into which exhaust gas is introduced are arranged in a row in the horizontal direction to form an exhaust cell row (see FIG. 6A, which is a cross-sectional view taken along the line AA in FIG. 1). Moreover, the air cells 10B into which air is introduced are arranged in a row in the lateral direction to form an air cell row (see FIG. 6B, which is a cross-sectional view taken along the line BB in FIG. 1). The exhaust cell rows and the air cell rows are alternately arranged in the vertical direction.

Further, both ends of the exhaust cell row are open, and the exhaust gas discharged from the burner is sent from the opening 11 on one end side of the heat exchange element (the opening 11 on the lower end side in the example of FIG. 6) to the exhaust cell 10A. It is introduced and discharged from the opening 12 on the other end side of the heat exchange element (the opening 12 on the upper end side in the example of FIG. 6 and hereinafter referred to as “exhaust gas discharge port”).
Since the upper end of the exhaust cell row is cut in an oblique direction so as to cross the longitudinal direction of the exhaust cell 10A, the exhaust gas discharge ports 12 of the exhaust cells 10A in the exhaust cell row are aligned with the exhaust cells 10A. The exhaust cells 10A are sequentially arranged at different positions in the longitudinal direction according to the order (see (a) of FIG. 6). The upper end surface of the heat exchange element is sealed with a sealing material 13. Thereby, the exhaust gas discharged from the exhaust gas outlet 12 of each exhaust cell 10 </ b> A merges, and between the upper end surface (sealing material 13) of the sealed heat exchange element and each exhaust gas outlet 12. The exhaust gas flow path 14 is formed through a common exhaust port 15 provided on the side surface of the exhaust cell row.

On the other hand, both ends of the air cell row are also open, and air is introduced into the air cell 10B from the opening 21 on the other end side of the heat exchange element (opening 21 on the upper end side in the example of FIG. 6) and preheated. The heat exchanging element is discharged from an opening 22 on one end side (the opening 22 on the lower end side in the example of FIG. 6 and hereinafter referred to as “air discharge port”) and supplied to the burner.
In addition, since the lower end of the air cell row is cut in an oblique direction so as to cross the longitudinal direction of the air cell 10B, the air discharge ports 22 of the air cells 10B in the air cell row are arranged in the order of the air cells 10B. Accordingly, the air cells 10B are sequentially arranged at different positions in the longitudinal direction (see FIG. 6B). The lower end surface of the heat exchange element is sealed with a sealing material 23. Thereby, the air discharged from the air discharge port 22 of each air cell 10B merges and is formed between the lower end surface (sealing material 23) of the sealed heat exchange element and each air discharge port 22. Then, the air is discharged from a common discharge port 25 provided on the side surface of the air cell row through the air combination channel 24.

  With such a configuration, the exhaust gas and the air flow through separate flow paths. Since the minute cells 10A and 10B constituting the flow path are adjacent to each other and there is almost no gas permeation in the partition wall between the cells 10A and 10B, it is possible to perform countercurrent heat exchange with high efficiency. Yes, preheated air can be obtained. In addition, since the amount of air does not become insufficient when air is mixed into the exhaust gas, it is difficult for the burner to burn fuel. Furthermore, since the heat exchange element is made of ceramic, it has excellent heat resistance and can be used even at high temperatures.

DESCRIPTION OF SYMBOLS 1 Honeycomb structure 2 Base | substrate 2a Partition 3 Glass layer 10 Cell 10a Opening part

Claims (2)

A plurality of cells divided into polygonal columns by ceramic partition walls have a substrate arranged in a honeycomb shape. A high temperature gas is introduced into a part of the plurality of cells, and a low temperature gas is introduced into the other part. A method for manufacturing a honeycomb structure used in a heat exchange element that performs heat exchange continuously between the high temperature gas and the low temperature gas,
The ceramic constituting the partition wall is silicon carbide,
A surface treatment liquid containing a ceramic powder and having a viscosity of 60 mPa · s or less is disposed on the surface of the partition wall, and then subjected to a heat treatment, so that the mass is 20% by mass or more of the mass of the base body and A method for manufacturing a honeycomb structure, comprising forming a glass layer covering a surface. The method for manufacturing a honeycomb structured body according to claim 1 , wherein the glass layer is composed of at least one of silica and alumina.

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