Regenerator for radiant tube burner and method of manufacturing the same

Abstract

To provide a heat storage body in which a plurality of honeycomb structures are continuously provided in an axial direction in which cells extend, and an increase in pressure loss is suppressed in gas circulation due to the fact that the positions of the cells in each of the honeycomb structures are shifted between the adjacent honeycomb structures.SOLUTION: In a heat storage body 1 in which a plurality of ceramic honeycomb structures 10 including a plurality of cells partitioned by partition walls extending in a single direction and arranged in a row are continuously provided in an axial direction in which the cells extend with end surfaces where the cells are open facing each other, only a layer of silicic acid-based glass is interposed at a boundary between the honeycomb structures 10 adjacent to each other in the axial direction in which the cells extend.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a regenerator for a regenerative radiant tube burner and a method for manufacturing the regenerator. [Background technology]

[0002] A radiant tube burner is a device that indirectly heats the material to be treated by radiating heat from a burner inside a metal or ceramic tube. Radiant tube burners can increase the temperature of the furnace atmosphere without affecting the furnace atmosphere. Radiant tube burners have open tubes at both ends, supplying combustion air from one end and discharging exhaust gas from the other. Radiant tube burners include those with straight, U-shaped, and W-shaped tubes. On the other hand, there are also so-called single-ended radiant tube burners, in which one end of the tube is closed inside the furnace and both an air inlet for introducing combustion air and an exhaust port for discharging exhaust gas are located at the open end.

[0003] Radiant tube burners also include regenerative burners. In regenerative radiant tube burners, the direction of gas flow is switched at predetermined time intervals so that exhaust gas heated to a high temperature by burner combustion and newly supplied gas for burner combustion alternately come into contact with the heat storage body. The heat of the exhaust gas is recovered by the heat storage body, and the recovered heat is used to preheat the newly supplied gas.

[0004] Solid balls made of alumina or the like have traditionally been widely used as heat storage bodies for radiant tube burners. Meanwhile, the use of honeycomb structures made of ceramics such as alumina as heat storage bodies has also been proposed (see, for example, Patent Document 1). Honeycomb structures have a large number of cells separated by partition walls, and the cells extend in a single direction, which offers the advantage of low pressure loss associated with gas flow. Furthermore, honeycomb structures have a significantly larger surface area than solid balls, which offers the advantage of a larger area contributing to heat exchange.

[0005] Heat storage bodies with this honeycomb structure are arranged in the straight tube section (the section where the tube is straight) of the radiant tube. Conventionally, honeycomb structures that are long in the axial direction of the cells have been used as heat storage bodies with honeycomb structure arranged inside the radiant tube. Since being long in the axial direction of the cells means being long in the axial direction of the radiant tube, fewer honeycomb structures need to be installed inside the radiant tube, making installation easier.

[0006] However, the fact that the honeycomb structure is long in the axial direction of the cells also means that it is long in the direction of gas flow. Therefore, when storing heat from high-temperature gas and releasing it to low-temperature gas, a temperature difference (temperature distribution) is likely to occur between one side and the other side in the gas flow direction in the heat storage body having the honeycomb structure. As a result, damage such as cracks and fractures may occur in the heat storage body having the honeycomb structure due to thermal stress.

[0007] In addition, the heat generated by the burner can cause the straight tube sections of the radiant tube to bend. In this case, if the honeycomb structured heat storage body is long in the axial direction of the cells, the curved section of the deformed tube can interfere with the heat storage body when trying to remove it from the radiant tube for replacement, making it impossible to remove.

[0008] Therefore, it has been proposed to use multiple honeycomb structures, each short in the axial direction of the cells, as a heat storage medium in the straight tube section of a radiant tube, so that they are connected in the axial direction of the cells (see, for example, Patent Document 2). In this case, the honeycomb structures that are short in the axial direction of the cells correspond to multiple honeycomb structures that are long in the axial direction of the cells, divided into multiple pieces. Because the individual honeycomb structures are short in the gas flow direction, temperature differences are less likely to occur, and damage due to thermal stress is suppressed. Furthermore, even if the straight tube section of the radiant tube is deformed and curved due to heating by the burner, honeycomb structures that are short in the axial direction of the cells have the advantage of being easier to remove from the radiant tube than honeycomb structures that are long in the axial direction of the cells.

[0009] However, when a honeycomb structure is used as a heat storage body, the gas exchanging heat with the heat storage body flows inside the cells. Therefore, when multiple honeycomb structures are connected in the axial direction of the cells, if the cells are misaligned between adjacent honeycomb structures, pressure loss in the gas flow increases. If the pressure loss of the gas flowing through the cells increases, heat exchange is not performed efficiently. In addition, gas tends to stagnate near the boundaries of adjacent honeycomb structures, which causes a local increase in the temperature of the honeycomb structure and may cause damage due to thermal stress.

[0010] Furthermore, if gas tends to stagnate due to pressure loss, impurities contained in the exhaust gas tend to adhere to the inside of the cells, making the cells more susceptible to clogging. When cells become clogged, not only does the gas not flow properly and heat exchange cannot be performed, but the gas blocked in that area can locally increase the temperature of the honeycomb structure, which may cause damage due to thermal stress. Such problems become more severe as the number of honeycomb structures connected in the axial direction of the cells increases.

[0011] It would be sufficient if the cell positions of multiple honeycomb structures connected in the axial direction of the cells could be aligned, but radiant tubes are typically cylindrical, and the shape of honeycomb structures is often cylindrical to match the shape of the tube. Therefore, when inserting a honeycomb structure into a radiant tube, the honeycomb structure easily rotates inside the tube. Therefore, when inserting multiple honeycomb structures connected in the axial direction of the cells into a radiant tube one by one, it is very difficult to align the cell positions. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Publication number 2-23950 [Patent Document 2] Patent No. 3754507 Summary of the Invention [Problem to be solved by the invention]

[0013] In view of the above-mentioned circumstances, the present invention aims to provide a heat storage body in which a plurality of honeycomb structures are arranged in the axial direction of the extension of the cells, and in which the positions of the cells in each honeycomb structure are misaligned with those of adjacent honeycomb structures, thereby preventing an increase in pressure loss during gas flow, and a method for manufacturing such a heat storage body. [Means for solving the problem]

[0014] In order to solve the above problems, the heat storage body for a radiant tube burner according to the present invention (hereinafter sometimes simply referred to as "heat storage body") has the following features: "A heat storage body in which a plurality of ceramic honeycomb structures each having a plurality of cells separated by partition walls arranged in a row extending in a single direction are connected in an axial direction of the cells with the open end faces of the cells facing each other, A plurality of the honeycomb structures are integrated together with only a layer of silicate glass interposed between the boundaries of the honeycomb structures adjacent to each other in the axial direction of the cells.

[0015] The heat storage body of this configuration can be manufactured by the following heat storage body manufacturing method. "A method for manufacturing a heat storage body in which a plurality of ceramic honeycomb structures each having a plurality of cells partitioned by partition walls arranged in a row extending in a single direction are connected in an axial direction of the cells with the open end faces of the cells facing each other, In the honeycomb structure, the end face facing the other honeycomb structure is coated with a coating agent containing silicon dioxide, The end face coated with the coating is placed over the end face of another honeycomb structure, and the silicon dioxide contained in the coating agent is melted by heating, and then solidified by cooling to turn the coating agent into silicate glass, and multiple honeycomb structures are integrated together with only a layer of silicate glass interposed between the boundaries of adjacent honeycomb structures in the axial direction of the cell extension.

[0016] Hereinafter, the "axial direction in which the cells extend" will be referred to as the "axial direction of the cells." Conventionally, multiple honeycomb structures have been joined together to increase the cross-sectional area perpendicular to the axial direction of the cells. This is because, although honeycomb structures are generally formed by extrusion molding, it is difficult to form large molded bodies using extrusion molding. Therefore, in order to increase the amount of gas flowing through the honeycomb structure, multiple honeycomb structure segments are joined together so that the axial directions of the cells are parallel and the open end faces of the cells are flush with each other, thereby increasing the cross-sectional area perpendicular to the axial direction of the cells. In contrast, in the present invention, multiple honeycomb structures are joined together in the axial direction of the cells with the open end faces facing each other. Joining multiple honeycomb structures in this direction was not possible in the prior art.

[0017] In addition, it has been conventionally believed that a bonding agent (bonding material) with a composition similar to that of the ceramic material constituting the honeycomb structures is desirable for bonding multiple honeycomb structures. This approach is believed to result in similar thermal expansion coefficients between the honeycomb structures and the bonding agent layer (hereinafter referred to as the "bonding layer"), making it less likely for thermal stress and resulting damage to occur. Conventional bonding layers primarily composed of ceramic materials have high mechanical strength, making it easier to maintain the bonded, integrated state of multiple honeycomb structures for a long period of time. In contrast, in the present invention, a silicate glass layer is used as the bonding layer for integrating multiple honeycomb structures. Because silicate glass layers do not have high mechanical strength, using a silicate glass layer as the bonding layer for integrating multiple honeycomb structures is a technique not previously used in the prior art.

[0018] The inventors wanted to maintain a state in which multiple honeycomb structures are integrated during the installation of the heat storage body inside the radiant tube, but to weaken the bonds between the honeycomb structures and ultimately separate the honeycomb structures when the heat storage body is installed inside the radiant tube burner and is actually used. If multiple honeycomb structures were firmly joined in the axial direction of the cells, the multiple honeycomb structures would act like a single rigid body. This would result in the same problems as in the conventional case in which a honeycomb structure long in the axial direction of the cells was used as a heat storage body for a radiant tube burner, namely, a temperature difference easily occurs between one side and the other in the gas flow direction, causing damage to the heat storage body due to thermal stress, and a problem in which the heat storage body cannot be removed from the tube if the straight tube section of the radiant tube is deformed and curved by heating by the burner.

[0019] In contrast, in the present invention, when the heat storage body reaches a high temperature during actual use of the radiant tube burner, the bonding layer of silicate glass bonding the multiple honeycomb structures together softens, weakening the bond and eventually separating the honeycomb structures into multiple pieces. This makes it possible to achieve the effects of dividing the honeycomb structures that make up the heat storage body into multiple pieces, namely, making it difficult for temperature differences to occur in the direction of gas flow in the separated individual honeycomb structures, thereby suppressing damage caused by thermal stress, and also making it possible to remove the separated individual honeycomb structures from the tube even if the straight tube portion of the radiant tube is deformed and curved by heating by the burner.

[0020] In the present invention, prior to the installation of the heat storage body inside the radiant tube, the plurality of honeycomb structures are joined in the axial direction of the cells. In other words, the work of joining the plurality of honeycomb structures in the axial direction of the cells while aligning the cell positions of adjacent honeycomb structures in each of the plurality of honeycomb structures can be performed at a factory where the heat storage body is manufactured, rather than at the site where the radiant tube burner is used. Therefore, the work of aligning the cell positions is much easier than when aligning the cell positions while inserting the plurality of honeycomb structures one by one into the radiant tube at the site where the radiant tube burner is used.

[0021] Furthermore, since the heat storage body of the present invention is made up of multiple honeycomb structures integrated together, even if they are not firmly joined, at the site where the radiant tube burner is used, it is sufficient to simply insert the integrated heat storage body into the radiant tube, which makes the work of installing the heat storage body inside the radiant tube extremely easy.

[0022] The heat storage body for a radiant tube burner according to the present invention has the following features in addition to the above configuration: "The honeycomb structure is composed of a silicon carbide ceramic sintered body, In the plurality of honeycomb structures, the surfaces excluding the end faces facing the other honeycomb structures are coated with an anti-oxidation layer of silicate glass.

[0023] Silicon carbide is a ceramic material with high thermal conductivity. Specifically, the thermal conductivities of alumina, cordierite, and mullite are 9 to 30 W / m·K, 0.6 W / m·K, and 1.5 W / m·K, respectively, while silicon carbide has a high thermal conductivity of 75 to 130 W / m·K. Therefore, a heat storage medium consisting of multiple honeycomb structures made of sintered silicon carbide ceramics has high heat exchange efficiency.

[0024] In addition, the thermal expansion coefficient of silicon carbide is 4.0 to 4.5 (×10 -6 K). That is, silicon carbide has high thermal conductivity and a small coefficient of thermal expansion, and therefore has excellent thermal shock resistance. Therefore, a heat storage medium consisting of multiple honeycomb structures made of silicon carbide ceramic sintered bodies is suitable as a heat storage medium that is constantly subjected to temperature changes caused by repeated heat storage and heat release.

[0025] However, silicon carbide oxidizes when used at high temperatures in an oxygen-containing atmosphere. Therefore, in this configuration, the surface of a honeycomb structure made of a silicon carbide ceramic sintered body, excluding the end faces (end faces where the cells are open) facing other honeycomb structures, i.e., the surface excluding the end faces covered with the bonding layer, is coated with an anti-oxidation layer of silicate glass. The silicate glass layer prevents contact between the silicon carbide that makes up the honeycomb structure and oxygen, effectively suppressing oxidation of the silicon carbide.

[0026] Another feature of this configuration is that a silicate glass layer is used as both the bonding layer and the anti-oxidation layer.

[0027] The heat storage body for a radiant tube burner according to the present invention has the following features in addition to the above configuration: "The plurality of honeycomb structures have the same cell shape, the same cell density, and the same partition wall thickness, When the state in which the positions of the cells of adjacent honeycomb structures in the axial direction of the cells are aligned is defined as a cell misalignment angle of zero degrees, and when the angle obtained by rotating one honeycomb structure relative to the other honeycomb structure around an axis that is parallel to the axial direction of the cells and passes through the center of the honeycomb structure as the rotation center axis is referred to as the cell misalignment angle, the cell misalignment angle can be defined as being equal to or greater than zero degrees and equal to or less than 11 degrees.

[0028] As will be described in detail later, as a result of investigation, it was found that when the cell misalignment angle between honeycomb structures adjacent in the cell axial direction is 11 degrees or less, the pressure loss in gas flow does not increase significantly compared to when the cell misalignment angle is zero degrees. Therefore, by adopting this configuration, it is possible to provide a heat storage body in which a plurality of honeycomb structures are joined in the cell axial direction while suppressing an increase in pressure loss in gas flow. [Effects of the Invention]

[0029] As described above, according to the present invention, it is possible to provide a heat storage body in which a plurality of honeycomb structures are arranged in the axial direction of the extension of the cells, and in which the positions of the cells in each honeycomb structure are shifted between adjacent honeycomb structures, thereby suppressing an increase in pressure loss during gas flow, and a method for manufacturing the heat storage body. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1(a) is an exploded perspective view showing the components of a heat storage body according to one embodiment of the present invention, and FIG. 1(b) is a plan view of a honeycomb structure which is a component of the heat storage body. [Figure 2] FIG. 2 is a side view of a heat storage body according to an embodiment of the present invention. [Figure 3] FIG. 10 is an exploded perspective view showing components of a heat storage body according to another embodiment. [Figure 4]10 is a graph showing the relationship between the cell misalignment angle and the pressure loss change ratio. DETAILED DESCRIPTION OF THE INVENTION

[0031] A specific embodiment of the present invention, a heat storage body 1 for a regenerative radiant tube burner (simply referred to as "heat storage body 1"), and its manufacturing method will be described below with reference to Figures 1 and 2. The heat storage body 1 is composed of a plurality of honeycomb structures 10 of the same configuration. The honeycomb structure is a structure comprising a large number of cells 15 separated by partition walls 13 arranged in a row extending in a single direction.

[0032] The honeycomb structures 10 have the same shape in cross section (hereinafter referred to as "cross section") in a direction perpendicular to the axial direction (direction P in FIG. 1 and a direction parallel thereto) of the cells 15. Each of the honeycomb structures 10 has a circular outer shape in cross section, and a circular hole 10h concentric with the outer circle is formed through the center.

[0033] The plurality of honeycomb structures 10 are made of the same material, which is silicon carbide ceramics. The shape of the cells 15, the density of the cells 15, and the thickness of the partition walls 13 separating the cells 15 are all the same for each of the plurality of honeycomb structures 10. Such a honeycomb structure 10 can be manufactured by extruding a cylindrical honeycomb structure, firing the formed body in a non-oxidizing atmosphere, and then drilling circular holes 10h. The cells 15 are open on the inner circumferential surfaces of the circular holes 10h, but the open portions of the cells 15 may be closed by applying a silicon carbide-based coating material to the inner circumferential surfaces of the circular holes 10h.

[0034] Because the honeycomb structure 10 is made of silicon carbide ceramics, there is a problem that it will oxidize if it is placed in a radiant tube and used at high temperatures as the heat storage body 1. Therefore, the surfaces of each of the multiple honeycomb structures 10, i.e., both end faces S1 where the cells 15 are open, the side peripheral surface S2, and the inner surfaces of the cells 15, are coated with a first glass layer 21 made of silicate-based glass.

[0035] The first glass layer 21 is produced by a first coating step of coating the surface of the honeycomb structure 10, which is a silicon carbide ceramic sintered body, with a coating agent, and a first heat treatment step of converting the coating agent into silicate glass.

[0036] Specifically, the first coating process can be a process of immersing the honeycomb structure 10 in a coating agent, a process of impregnating the honeycomb structure 10 with the coating agent, or a process of applying or spraying the coating agent onto the surface of the honeycomb structure 10.

[0037] The coating agent is a slurry that becomes silicate glass upon heat treatment. It is composed of a silicon dioxide source mixed with a liquid medium such as water and a binder. The silicon dioxide source can be silica powder, glass powder (glass frit), or clay, either alone or in combination. In addition to the above components, the coating agent raw materials can also contain other components. The addition of boron oxide (B2O3) can adjust the viscosity (fluidity) and durability of the glass. Alkali metal oxides (e.g., Na2O, K2O, Li2O) reduce the viscosity and glass transition temperature of glass. Alkaline earth metal oxides (e.g., CaO, MgO, BaO, SrO) enhance the chemical durability of glass and affect its amorphization and crystallization. Aluminum oxide enhances the chemical durability of glass.

[0038] The first heat treatment step is a step of converting the coating agent into silicate glass. In the first heat treatment step, the honeycomb structure 10 coated with the coating agent is heated in an air atmosphere at a temperature of 100°C to 120°C to perform a drying process to remove the liquid medium in the coating agent, and then the temperature is raised to a temperature of 900°C to 1200°C, which is higher than the glass transition point, and heated for a predetermined time. This melts the silicon dioxide contained in the coating agent and spreads over the surface of the honeycomb structure 10. Thereafter, by cooling to a temperature lower than the glass transition point, the once-molten silicon dioxide solidifies and becomes silicate glass. As a result, a dense and airtight first glass layer 21 is formed in close contact with the surface of the honeycomb structure 10.

[0039] The presence of this dense and airtight first glass layer 21 prevents contact between the silicon carbide ceramic sintered body constituting the base and air, thereby effectively suppressing oxidation of silicon carbide when the honeycomb structure 10 is used at high temperatures as the heat storage body 1. The first glass layer 21 corresponds to the "antioxidation layer" of the present invention.

[0040] The heat storage body 1 of this embodiment is formed by bonding multiple honeycomb structures 10B, each coated with a first glass layer 21 as described above, in the axial direction of the cells 15 via a second glass layer 22 which is silicate-based glass.

[0041] The second glass layer 22 is formed through a second coating step and a second heat treatment step. The second coating step is a step of applying a coating agent to the end face S1 of each of the plurality of honeycomb structures 10B, the end face S1 of which faces the end face S1 of an adjacent honeycomb structure 10B. The coating agent may be applied to at least one of the two end faces S1 that face each other.

[0042] After the second coating step is completed, multiple honeycomb structures 10B are stacked so that the end face S1 coated with the coating agent faces the end face S1 of the adjacent honeycomb structure 10B, and a second heat treatment step is performed in this state. The second heat treatment step is similar to the first heat treatment step. In this second heat treatment step, the silicon dioxide contained in the coating agent melts and becomes adhesive, thereby adhering the honeycomb structures 10B whose end faces S1 are stacked together. Thereafter, the honeycomb structures are cooled to a temperature lower than the glass transition point, whereby the molten silicon dioxide solidifies and forms a second glass layer 22 of silicate-based glass. As a result, adjacent honeycomb structures 10B are bonded and integrated by the second glass layer 22. In other words, the coating agent used in the second coating step and the second heat treatment step is an adhesive, and the second glass layer 22 is a "bonding layer" that bonds adjacent honeycomb structures 10B together.

[0043] Therefore, after the second coating step, when the honeycomb structures 10B adjacent in the axial direction of the cells 15 are stacked together, the positions of the cells 15 in each honeycomb structure 10B can be aligned so that each of the many cells 15 belonging to each honeycomb structure 10B is connected to the cells 15 belonging to the other honeycomb structures 10B so as to be positioned on the same line, thereby obtaining a heat storage body 1 in which a plurality of honeycomb structures 10B are integrated. For example, by inserting a linear, long member such as a wire through the cells 15 belonging to each of the plurality of honeycomb structures 10B at the same position so as to penetrate the cells 15 at the same position, the plurality of honeycomb structures 10B can be stacked together in a state in which the cells are positioned.

[0044] The above manufacturing method produces a heat storage body 1 in which a plurality of honeycomb structures 10B are integrated via a second glass layer 22 made of silicate glass without misalignment of the cells 15. The heat storage body 1 has a circular outer cross section and has a circular hole 10h at the center of the cross section that is concentric with the outer circle. Such a heat storage body 1 is arranged in the straight tube section of a radiant tube. The straight tube section of the radiant tube has a double structure consisting of a cylindrical outer tube and a cylindrical inner tube that is concentric with the outer tube, and the heat storage body 1 is inserted into the space between the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube. The internal space of the inner tube is the space into which a burner is inserted.

[0045] If multiple honeycomb structures are not integrated, it would take time and effort to insert each honeycomb structure into the radiant tube one by one. Furthermore, when inserting multiple honeycomb structures into the radiant tube, it is necessary to align the cells so that each of the many cells belonging to each honeycomb structure is aligned on the same line as the cells belonging to other honeycomb structures. It is extremely difficult to align the cells while inserting the honeycomb structures into the radiant tube.

[0046] In contrast, the heat storage body 1 of this embodiment is formed by integrating a plurality of honeycomb structures 10B with the cells 15 aligned, so it is sufficient to simply insert the integrated heat storage body 1 into the internal space of the radiant tube. This makes it extremely easy to install the heat storage body 1 inside the radiant tube.

[0047] Here, if multiple honeycomb structures are firmly fixed together via a bonding layer, the integrated state is stable, but there is no point in constructing a heat storage body from multiple honeycomb structures. In other words, if multiple honeycomb structures are firmly integrated with a highly adhesive adhesive to form a heat storage body, the entire heat storage body becomes like a single rigid body elongated in the axial direction of the cells. This makes it easy for temperature differences to occur in the heat storage body in the gas flow direction, which may result in damage due to thermal stress. Furthermore, if the straight tube portion of the radiant tube is deformed and curved by heating with a burner, the heat storage body, which is joined together like a single rigid body elongated in the axial direction of the cells, cannot be removed from the radiant tube, making it impossible to replace.

[0048] In contrast, the heat storage body 1 of this embodiment is formed by bonding a plurality of honeycomb structures 10B in the axial direction of the cells 15 via the second glass layer 22 made of silicate glass. Therefore, when the heat storage body 1 becomes hot during operation of the radiant tube burner, the second glass layer 22 made of silicate glass softens, weakening the bonding and eventually separating into a plurality of honeycomb structures 10B. Therefore, in each honeycomb structure 10B, temperature differences in the gas flow direction are unlikely to occur, and damage due to thermal stress is suppressed.

[0049] Here, even if the heat storage body 1 separates into a plurality of honeycomb structures 10B as the second glass layer 22 of silicate glass softens, the honeycomb structures 10B already inserted inside the radiant tube do not naturally move in a rotating manner. Therefore, even if the heat storage body 1 separates into a plurality of honeycomb structures 10 after being inserted into the radiant tube, the cells 15 in the plurality of honeycomb structures 10 remain aligned.

[0050] After the heat storage body 1 is installed inside the radiant tube and the radiant tube burner has been in actual use for a certain period of time, the multiple honeycomb structures 10B that made up the heat storage body 1 are separated. Therefore, even if the straight tube portion of the radiant tube is deformed and curved due to heating by the burner, the separated honeycomb structures 10B can be individually removed from the radiant tube, making it easy to replace the heat storage body 1.

[0051] One of the features of the heat storage body 1 of this embodiment is that a silicate-based glass layer, which serves as an antioxidant layer for a silicon carbide ceramic sintered body, is also used as a bonding layer that "intentionally weakly bonds" a plurality of honeycomb structures 10B together in the axial direction of the cells 15. In addition, in the heat storage body 1 of this embodiment, both a silicate-based glass layer formed as the first glass layer 21 and a silicate-based glass layer formed as the second glass layer 22 are present at the boundary between the honeycomb structures 10 adjacent in the axial direction of the cells 15, but the two cannot be distinguished after the heat storage body 1 is completed. In other words, in the heat storage body 1, the "silicic acid-based glass layer" present at the boundary between the honeycomb structures 10 adjacent in the axial direction of the cells 15 is both a bonding layer and an antioxidant layer.

[0052] Next, we investigated the relationship between the degree of cell misalignment and the pressure loss of the gas flowing through the honeycomb structures when multiple honeycomb structures were connected in the axial direction of the cells. For multiple heat storage units, two honeycomb structures of the same configuration were joined together with different degrees of cell misalignment. The pressure of the gas flowing into the heat storage unit and the pressure of the gas exhausting from the heat storage unit were measured. The honeycomb structures had a circular cross-sectional shape and were perforated with a circular hole concentric with the outer circle. The rotation axis (corresponding to line P in Figure 1) was a line passing through the center of the circular hole and parallel to the axial direction of the cells. When two honeycomb structures were stacked so that the cell positions were perfectly aligned, this was defined as a "zero degree misalignment angle." The "misalignment angle" was the angle by which one honeycomb structure was rotated relative to the other honeycomb structure around the rotation axis. The misalignment angle was varied to 5, 8, 11, 22.5, and 45 degrees. The flow rate of the gas flowing into the heat storage body is 4.0 Nm 3 / min, 6.0Nm 3 / min, 9.0Nm 3 / min.

[0053] The pressure difference (pressure loss) between the gas flowing into the heat storage body and the gas being discharged from the heat storage body under each condition was calculated, and the results are shown in Table 1. Figure 4 also shows the pressure loss change ratio, assuming that the pressure loss when the cell misalignment angle is zero degrees is "1."

[0054] [Table 1]

[0055] As can be seen from Figure 4, regardless of the gas flow rate, when the cell misalignment angle is in the range of 0 to 11 degrees, the pressure loss change ratio remains below approximately 1.1, meaning that the pressure loss is not large. On the other hand, when the cell misalignment angle is 22.5 degrees or more, the pressure loss change ratio increases significantly to 1.3 or more. From this, it was considered desirable that when multiple honeycomb structures are joined in the axial direction of the cells to form a heat storage body, the cell misalignment angle between adjacent honeycomb structures should be in the range of 0 to 11 degrees.

[0056] The present invention has been described above by citing preferred embodiments, but the present invention is not limited to the above embodiments, and various improvements and design changes are possible as described below, without departing from the spirit of the present invention.

[0057] For example, in the above embodiment, a case has been exemplified in which a first glass layer 21 (solidified layer) of silicate glass acting as an antioxidant layer is formed by the first coating step and the first heat treatment step, and then a coating agent is applied to the end face S1 for bonding a plurality of honeycomb structures 10B. However, the present invention is not limited to this, and a configuration may be adopted in which the first glass layer 21 of silicate glass acting as an antioxidant layer and the second glass layer 22 of silicate glass for bonding a plurality of honeycomb structures 10 are formed simultaneously. In this case, for a certain honeycomb structure 10, the step of applying a coating agent to the end face S1 that will face the end face S1 of an adjacent honeycomb structure 10 in the first coating step also serves as the second coating step. Then, after stacking a plurality of honeycomb structures 10 having end faces S1 coated with a coating agent, a first heat treatment step in which the coating agent on the surface not in contact with other honeycomb structures 10 is heat treated to form a first glass layer 21 (antioxidation layer), and a second heat treatment step in which the coating agent between the end faces S1 of adjacent honeycomb structures 10 is heat treated to form a second glass layer 22 (bonding layer) are simultaneously performed. Also in this case, the "silica-based glass layer" present at the boundary between honeycomb structures 10 adjacent in the axial direction of the cells 15 is both a bonding layer and an antioxidation layer.

[0058] Furthermore, in the above embodiment, the case where the coating agent from which the first glass layer 21 and the second glass layer 22 are made are the same has been exemplified, but the compositions of the two coating agents may be different. For example, the coating agent from which the first glass layer 21 is made can be a coating agent having a higher glass transition point than the coating agent from which the second glass layer 22 is made. This makes it possible to prevent the first glass layer 21, which acts as an antioxidant layer, from softening significantly when the second glass layer 22, which serves as a bonding layer, softens due to heating during operation of the radiant tube burner.

[0059] In this way, when the coating agent that forms the first glass layer 21 and the coating agent that forms the second glass layer 22 have different compositions, a suitable manufacturing method is to form the first glass layer 21 through a first coating step and a first heat treatment step, and then form the second glass layer 22 through a second coating step and a second heat treatment step, as exemplified in the above embodiment.

[0060] 1 and 2 show an example in which the honeycomb structure 10 serving as a unit for connecting the cells 15 in the axial direction is an integrated honeycomb structure 10 obtained by firing an extrusion-molded molded body. However, the present invention is not limited to this. As shown in FIG. 3, a honeycomb structure 10C formed by joining a plurality of segments 10s having a honeycomb structure so that the axial directions of the cells 15 are parallel and the end faces S1 of the respective segments are flush with each other can also be used as a unit for connecting the cells 15 in the axial direction. Here, an example is shown in which the segments 10s are formed by firing molded bodies extruded into a cubic or rectangular parallelepiped shape, and the side peripheral faces of the segments 10s are joined together with an adhesive to form an integrated honeycomb structure. The honeycomb structure 10C has a circular cross-sectional shape and is processed so that circular holes 10h concentric with the outer circle penetrate the honeycomb structure in the axial direction. The adhesive is a mixture of ceramic powder with an organic binder and an inorganic binder, and the formed adhesive layer 30 is a layer that firmly bonds the segments 10s together, unlike a layer of silicate glass. Therefore, when a heat storage body in which a plurality of honeycomb structures 10C are bonded in the axial direction of the cells 15 with the second glass layer 22 is installed inside a radiant tube burner and actually used, and the heat storage body becomes hot, even if the bond by the second glass layer 22 weakens and the honeycomb structure 10C separates into multiple pieces, the bond by the adhesive layer 30 will not weaken and the segment 10s will not separate into multiple pieces. [Explanation of symbols]

[0061] 1 Heat storage body 13 Bulkhead 15 cells 21 First glass layer (anti-oxidation layer) 22 Second glass layer S1 end face S2 side surface

Claims

1. A heat storage body, comprising a plurality of ceramic honeycomb structures each having a plurality of cells partitioned by partition walls arranged in a row extending in a single direction, the plurality of honeycomb structures being arranged in an axial direction in which the cells extend, with open end faces of the cells facing each other, A plurality of honeycomb structures are integrated together with only a silicate glass layer interposed between the honeycomb structures adjacent to each other in the axial direction of the cells. A heat storage body for a radiant tube burner characterized by:

2. the honeycomb structure is made of a silicon carbide ceramic sintered body, In the plurality of honeycomb structures, the surfaces excluding the end faces facing the other honeycomb structures are coated with an oxidation prevention layer of silicate glass.

2. A heat storage body for a radiant tube burner according to claim 1.

3. The plurality of honeycomb structures have the same cell shape, the same cell density, and the same partition wall thickness, When the position of the cells of the adjacent honeycomb structures in the axial direction of the cells coincides, the cell misalignment angle is defined as zero degrees. When the cell misalignment angle is defined as the angle at which one honeycomb structure is rotated relative to the other honeycomb structure around an axis that is parallel to the axial direction of the cells and passes through the center of the honeycomb structure as the rotation center axis, the cell misalignment angle is equal to or greater than zero degrees and equal to or less than 11 degrees.

2. A heat storage body for a radiant tube burner according to claim 1.

4. A method for manufacturing a heat storage body, comprising: a plurality of ceramic honeycomb structures each having a plurality of cells partitioned by partition walls arranged in a row extending in a single direction; the plurality of ceramic honeycomb structures are connected in an axial direction of the cells with open end faces of the cells facing each other; In the honeycomb structure, the end face facing the other honeycomb structure is coated with a coating agent containing silicon dioxide, The end face coated with the coating is placed on the end face of another honeycomb structure, and the silicon dioxide contained in the coating agent is melted by heating, and then solidified by cooling to turn the coating agent into silicate glass. The honeycomb structures are integrated together in a state where only a layer of silicate glass is present at the boundary between the honeycomb structures adjacent to each other in the axial direction of the cell extension. A method for manufacturing a heat storage body for a radiant tube burner, characterized by the above-mentioned.

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