High temperature gas pipe

Abstract

The present invention provides a high temperature gas pipe for conveying high temperature gas containing steam, wherein miniaturization and weight reduction of the pipe are achieved by using a microporous heat insulation material while suppressing deterioration of heat insulation performance due to hydration reaction. Provided is a high temperature gas pipe for conveying high temperature gas containing steam, the high temperature gas pipe comprising: at least one refractory layer constituting a working surface inside the pipe; a water-impermeable layer laminated on the outside of the at least one refractory layer; a microporous heat insulation material layer laminated on the outside of the water-impermeable layer; and an outer shell layer formed on the outside of the microporous heat insulation material layer.

Description

High-temperature gas piping

[0001] The present invention relates to hot gas piping.

[0002] Various refractory structures for use in piping for transporting high-temperature fluids have been proposed. For example, Patent Document 1 describes a technology in which a titanium layer and a mullite layer are coated on the inner wall surface of a pipe or container that is subjected to a thermal cycle by an internal fluid in order to provide an inner wall of the pipe or container that is resistant to thermal shock caused by an internal fluid with large temperature changes. Patent Document 2 also describes a tubular insulation wall in which, to prevent voids in the radial direction of the pipe or at joints, an insulation structure is formed on the low-temperature side of the pipe, consisting of a blanket-like material mainly composed of ceramic fiber, and on the high-temperature side, consisting of a tubular hard molded body mainly composed of ceramic fiber, and an inorganic foamable amorphous material that expands and hardens at room temperature is interposed between the blanket-like material and the inner wall of the pipe, and the insulation structure is pressure-bonded to the inner wall of the pipe.

[0003] On the other hand, microporous insulation materials are known that have superior thermal insulation performance to conventional insulation materials such as calcium silicate and ceramic fiber. Specifically, microporous insulation materials are made primarily from spherical hollow structure materials with particle sizes of 5 nm to 30 nm, forming closed microspaces with diameters of 100 nm or less. For example, WDS (registered trademark), a nano-insulation material made from fumed silica, is known. Other known microporous insulation materials include aerogels such as silica aerogels described in Patent Documents 3 and 4, and nanoporous silica. Microporous insulation materials achieve high thermal insulation performance by suppressing heat transfer due to internal air convection. The use of microporous insulation materials with high thermal insulation performance enables the miniaturization and weight reduction of devices and equipment.

[0004] Japanese Patent Application Laid-Open No. 05-287553 Japanese Patent Application Laid-Open No. 59-162187 Japanese Patent Application Laid-Open No. 2022-082299 International Publication No. 2017 / 038646

[0005] The use of a microporous thermal insulation material also enables the pipe to be made smaller and lighter in weight in the thermal insulation structures of pipes such as those described in Patent Documents 1 and 2. However, in the case of high-temperature gas pipes that transport high-temperature gas containing water vapor, there is a problem in that water vapor that permeates the porous refractory structure from the inside of the pipe condenses into water, and when the water comes into contact with the microporous thermal insulation material, a hydration reaction damages the structure of the closed microspace, resulting in a decrease in thermal insulation performance.

[0006] Therefore, the present invention aims to provide a high-temperature gas piping that transports high-temperature gas containing water vapor, which can achieve miniaturization and weight reduction of the piping by using a microporous insulation material while suppressing the deterioration of insulation performance due to hydration reactions.

[0007] [1] A high-temperature gas pipe for transporting high-temperature gas containing water vapor, the high-temperature gas pipe comprising at least one refractory layer constituting an internal working surface of the pipe, an impermeable layer laminated on the outside of the at least one refractory layer, a microporous insulation layer laminated on the outside of the impermeable layer, and an outer shell layer formed on the outside of the microporous insulation layer. [2] The high-temperature gas pipe according to [1], in which at least one refractory layer or insulation layer is laminated between the impermeable layer and the microporous insulation layer. [3] The high-temperature gas pipe according to [2], in which, from the working surface side, a wear refractory layer, an insulating brick layer, a castable refractory layer, and the microporous insulation layer are laminated, with the impermeable layer laminated between the insulating brick layer and the castable refractory layer. [4] The high-temperature gas pipe according to [1], in which the impermeable layer and the microporous insulation layer are adjacent to each other. [5] The high-temperature gas pipe according to [4], wherein a wear refractory layer, a heat insulating brick layer, a castable refractory layer, and the microporous heat insulating layer are laminated in this order from the working surface side, and the water impermeable layer is laminated between the castable refractory layer and the microporous heat insulating layer. [6] The high-temperature gas pipe according to any one of [1] to [5], wherein the microporous heat insulating layer is formed of WDS (registered trademark).

[0008] According to the above configuration, since the water-impermeable layer is laminated between the refractory layer constituting the working surface inside the high-temperature gas pipe and the microporous insulation layer, water vapor does not reach the microporous insulation layer, and the hydration reaction of the microporous insulation is suppressed while the pipe can be made smaller and lighter. Because water vapor does not reach the microporous insulation layer, the insulation performance can be improved to such an extent that the temperature of the microporous insulation layer becomes lower, for example, below the dew point temperature of the gas.

[0009] 1 is a cross-sectional view of a high-temperature gas pipe according to an embodiment of the present invention.

[0010] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0011] FIG. 1 is a cross-sectional view of a high-temperature gas pipe according to one embodiment of the present invention. In the illustrated example, the high-temperature gas pipe 10 has a structure in which, from the working surface (innermost surface) of the pipe interior, a wear refractory layer 11, an insulating brick layer 12, an impermeable layer 13, a castable refractory layer 14, and a microporous insulating material layer 15 are layered, with an outer shell layer 16 formed on the outside. The wear refractory layer 11 is a refractory material with excellent hot strength that can withstand the working surface temperatures required to transport high-temperature gas. Specifically, an alumina refractory is preferably used for the wear refractory layer 11. The insulating brick layer 12 is formed of an insulating material that prevents heat from escaping from the working surface, but the interior of the layer is formed of a refractory material with strength sufficient to withstand temperatures equivalent to those of the wear refractory. Specifically, a mullite refractory is preferably used for the insulating brick layer 12. The alumina refractory desirably has an alumina content of 90% or more, and desirably has few through-pores and a porosity of 20% or less to inhibit the penetration of carrier gas. Since the high-temperature gas pipe according to the embodiment of the present invention is a refractory structure for transporting high-temperature gas containing water vapor, when used as a high-temperature gas pipe, the internal working surface does not suffer from a lower melting point or wear due to a high-temperature reaction between the refractory and the high-temperature gas. In molten metal vessels such as converters used in steel refining, the working surface of the wear refractory suffers wear due to melting, but in the high-temperature gas pipe application of the present invention, the working surface of the wear refractory does not suffer from wear due to melting.

[0012] The impermeable layer 13 is a layer that does not allow the passage of water vapor that has permeated the porous refractory structure of the wear refractory layer 11 and the insulating brick layer 12 from the inside of the pipe, or water condensed from the water vapor. Specifically, it is made of a metal material such as iron, stainless steel, or aluminum formed into a tubular or foil shape. The castable refractory layer 14 is an insulating layer formed of an unshaped (castable) refractory for dimensional adjustment. In the high-temperature gas piping application of the present invention, the castable refractory layer 14 is also a refractory layer that does not suffer wear due to melting. The castable refractory is a mixture of refractory aggregate and a binder such as alumina cement.

[0013] The refractory layer in the high-temperature gas pipe 10 of the present invention is not limited to a three-layer structure consisting of the wear refractory layer 11, the insulating brick layer 12, and the castable refractory layer 14, but may include at least one refractory layer. For example, the castable refractory layer may be omitted, and the pipe may have a structure in which the wear refractory layer 11, the insulating brick layer 12, the impermeable layer 13, and the microporous insulation layer 15 are stacked in this order from the working surface side of the pipe, with the outer shell layer 16 formed on the outside. Furthermore, the order in which the insulating brick layer 12 and the castable refractory layer 14 are formed from the working surface side may be reversed. From the viewpoint of reducing the size and weight of the pipe, the smaller the thickness of each layer, the more preferable. The thickness of each layer is not particularly limited, but for example, the thickness of the wear refractory layer may be 120.0 mm or less or 10.0 mm or more. For example, the thickness of the castable refractory layer may be 150.0 mm or less or 130.0 mm or more. The thickness of the insulating brick layer may be 200.0 mm or less or 50.0 mm or more. For example, the thickness of the impermeable layer may be 0.1 mm or more and 0.5 mm or less.

[0014] The microporous insulation layer 15 is a layer formed of the microporous insulation material described above. More specifically, the microporous insulation material is formed by forming closed microspaces using a spherical hollow structure material as the main raw material. Examples of the main raw material include fumed silica, aerogels such as silica aerogel, and nanoporous silica. The particle size of the spherical hollow structure material is, for example, 5 nm to 30 nm, and the diameter of the closed microspace is, for example, 100 nm or less. WDS (registered trademark), a nano-insulation material made from fumed silica, is also an example of a microporous insulation material. The microporous insulation layer 15 is not limited to those made from silica-based raw materials and may also be made from other materials, such as alumina-based raw materials. Specific examples include mullite, a crystalline mixture of alumina and silica. The outer shell layer 16 is disposed outside the microporous insulation layer 15 to maintain the structure of the high-temperature gas pipe 10 and protect the microporous insulation layer 15. Specifically, the outer shell layer 16 is formed of a metal pipe such as iron or a resin pipe, with an iron pipe being preferred from the viewpoints of strength and cost.

[0015] The thickness of the microporous thermal insulation layer is not particularly limited, but for example, the upper limit of the thickness of the microporous thermal insulation layer may be 20.0 mm or less. The lower limit of the thickness of the microporous thermal insulation layer is also not particularly limited, but 5.0 mm is generally the manufacturing limit.

[0016] In the high-temperature gas pipe 10 including the microporous insulation layer 15 described above, the insulating performance of the microporous insulation layer is higher than that of the wear refractory, insulating brick, or castable refractory that forms the other layers, so sufficient insulation can be achieved with a thinner layer thickness, allowing the pipe to be made smaller and lighter. Specifically, for example, when the inner diameter is determined based on the gas flow rate, the outer diameter of the pipe can be made smaller. Alternatively, when the outer diameter of the pipe is determined based on spatial constraints, the inner diameter can be made larger to increase the gas flow rate.

[0017] On the other hand, as already mentioned, when the high-temperature gas pipe 10 transports high-temperature gas containing water vapor, such as COG (Coke Oven Gas), the water vapor that permeates the porous refractory structure from inside the pipe condenses into water, and when the water comes into contact with the microporous insulation layer 15, a hydration reaction may occur. If a hydration reaction occurs, the structure of the closed microspaces of the microporous insulation will be damaged, and the insulation performance will be reduced. This problem is not limited to silica-based raw materials; similar problems occur with microstructured insulation materials made from other raw materials, such as alumina-based materials.

[0018] Therefore, in this embodiment, an impermeable layer 13 is disposed between the microporous insulation layer 15 and the wear refractory layer 11 and insulating brick layer 12, which are refractory layers constituting the working surface inside the pipe, thereby preventing water vapor from reaching the microporous insulation layer 15 and preventing a decrease in insulation performance due to hydration reactions in the microporous insulation layer 15. This makes it possible to achieve a reduction in the size and weight of the pipe while maintaining the insulation performance of the microporous insulation layer 15, even when the high-temperature gas pipe 10 transports high-temperature gas containing water vapor. Because water vapor does not reach the microporous insulation layer 15, the insulation performance can be improved to the extent that the temperature of the microporous insulation layer 15 becomes lower, for example, below the dew point temperature of the gas. Alternatively, since the heat resistance temperature of the steel shell constituting the outer shell layer 16 is generally 600°C, or approximately 250°C depending on the material, it is possible to design the temperature at the interface between the microporous insulation layer 15 and the outer shell layer 16 to be significantly higher than 100°C, for example, 250°C or higher, within a range of, for example, 600°C or less. In this case, by thinning the refractory layer, the high-temperature gas pipe can be further reduced in size and weight. The temperature at the interface between the microporous insulation layer 15 and the outer shell layer 16 can be calculated by heat conduction calculation based on the temperature of the gas transported in the high-temperature gas pipe, the atmospheric temperature, the thickness and thermal conductivity of each layer. Alternatively, the temperature can be measured using a thermocouple or the like. The temperature can also be calculated by measuring the emissivity of the outer surface of the outer shell layer 16. Because the outer shell layer 16 has a higher thermal conductivity than the insulation material and the temperature difference between the outer and inner surfaces is small, the temperature at the outer surface of the outer shell layer 16 can be considered the temperature at the interface between the microporous insulation layer 15 and the outer shell layer 16.

[0019] The refractory layer laminated inside the impermeable layer 13 is not limited to a two-layer structure consisting of the wear refractory layer 11 and the insulating brick layer 12, as long as at least one refractory layer constituting the working surface inside the pipe is disposed. In the above example, at least one refractory layer or insulating layer, specifically the castable refractory layer 14, is laminated between the impermeable layer 13 and the microporous insulation layer 15, and the impermeable layer 13 is laminated between the insulating brick layer 12 and the castable refractory layer 14. However, this example is not limited thereto, and the impermeable layer 13 and the microporous insulation layer 15 may be adjacent to each other. Specifically, for example, the wear refractory layer 11, the insulating brick layer 12, the castable refractory layer 14, and the microporous insulation layer 15 may be laminated in this order from the working surface side, and the impermeable layer 13 may be laminated between the castable refractory layer 14 and the microporous insulation layer 15. Alternatively, two or more refractory layers or heat insulating layers may be laminated between the impermeable layer 13 and the microporous heat insulating layer 15. Note that the castable refractory layer 14 has both fire resistance and heat insulating properties, and therefore may be an example of either a refractory layer or a heat insulating layer.

[0020] Furthermore, the microporous insulation layer 15 does not necessarily have to be in contact with the outer shell layer 16, and another insulation layer may be laminated between them. However, the maximum use temperature of materials such as WDS (registered trademark) that constitute the microporous insulation layer 15 is less than 1000°C, and the lower the temperature, the lower the thermal conductivity. Therefore, from the perspective of reducing the size and weight of piping by using the microporous insulation layer 15, it is preferable to place the microporous insulation layer 15 on the outer side of the other refractory layers, in a layer in a lower temperature zone.

[0021] The following describes the results of heat conduction calculations performed on a design example of a high-temperature gas pipe that satisfies the requirements of the embodiment of the present invention. In the heat conduction calculations, the inner diameter d of the working surface of the high-temperature gas pipe was set to 1000 mm. The thermal conductivity of the wear refractory layer was set to 1.5 W / m·K, the thermal conductivity of the insulating brick layer was set to 0.8 W / m·K, the thermal conductivity of the castable refractory layer was set to 0.5 W / m·K, the thermal conductivity of the impermeable layer was set to 40 W / m·K, the thermal conductivity of the microporous thermal insulation (WDS®) layer was set to 0.03 W / m·K, and the thermal conductivity of the outer shell layer (steel shell) was set to 40 W / m·K, respectively, from the working surface side. Note that in the following example, unlike the example shown in FIG. 1 , an impermeable layer is layered between the castable refractory layer and the microporous thermal insulation layer. The temperature of the gas transported by the high-temperature gas pipe was set to 1000°C, and the atmospheric temperature was set to 25°C.

[0022] Table 1 shows examples of layer configurations for high-temperature gas piping and the results of heat conduction calculations for each case. The smaller the calculated amount of heat dissipated to the outside in each example, the higher the insulation performance of the high-temperature gas piping. The interface temperatures shown in Table 1 indicate the temperatures at the interface between the microporous insulation layer and the steel shell, calculated by heat conduction calculations.

[0023]

[0024] In Table 1, the comparative example and each example are designed with approximately the same pipe outer diameter. In the comparative example, a microporous insulation layer and an impermeable layer are not stacked, and the insulation layer is formed only by a wear refractory layer, an insulating brick layer, and a castable refractory layer. In examples 1 to 5, a part of the castable refractory layer in the comparative example is replaced with a microporous insulation layer, and an impermeable layer is stacked between the castable refractory layer and the microporous insulation layer.

[0025] Even when the microporous insulation layer in Example 1 was formed with the thinnest layer thickness of 5.0 mm, the amount of heat dissipation was significantly reduced compared to the comparative example, demonstrating improved insulation performance even with the same pipe outer diameter. This means that the pipe outer diameter can be made smaller while maintaining the same insulation performance, i.e., the pipe can be made smaller and lighter. Increasing the thickness of the microporous insulation layer as in Examples 2 to 5 further improved insulation performance. In Examples 4 and 5, improved insulation performance resulted in the interface temperature between the microporous insulation layer and the steel shell falling below 100°C. In these cases, if water vapor reached the microporous insulation layer, condensation of the water vapor would generate water, potentially causing a hydration reaction in the microporous insulation. However, in the Examples, the impermeable layer prevents water vapor from reaching the microporous insulation layer, suppressing the hydration reaction in the microporous insulation and maintaining insulation performance.

[0026] Examples 6 to 10 are examples in which the piping is further reduced in size and weight by thinning the refractory layer compared to the layer configuration of Example 1 above. In Examples 6 to 10, the castable refractory layer is omitted, while in Examples 7 to 10, the insulating brick layer is gradually thinned, and in Example 10, the wear refractory layer is also thinned. In these examples, the interface temperature between the microporous insulation layer and the steel shell significantly exceeds 100°C. However, as mentioned above, if the interface temperature is 600°C or less (Examples 6 to 10) or 250°C or less (Examples 6 to 9), there is no problem in terms of the heat resistance temperature of the steel shell. Therefore, designs such as these examples are also possible as long as the amount of heat dissipated to the outside is acceptable. Note that thinning the refractory layer does not necessarily require omitting the castable refractory layer; any layer may be thinned.

[0027] In the case of high-temperature gas piping, the ratio of the pipe thickness to the outer diameter is high, so providing a microporous insulation layer is effective in reducing the size by thinning the refractory layer while maintaining the insulation performance. For example, in the comparative example, the ratio of the outer diameter to the inner diameter d of the piping exceeds 1.9, while in Example 6, the ratio of the outer diameter to the inner diameter d of the piping is 1.7 or less, and similarly in Example 7, it is 1.5 or less, in Examples 8 and 9, it is 1.4 or less, and in Example 10, it is 1.1 or less.

[0028] The above results show that by laminating an impermeable layer between the refractory layer constituting the inner working surface of a high-temperature gas pipe and the microporous insulation layer, it is possible to reduce the size and weight of the pipe while suppressing the hydration reaction of the microporous insulation. For example, when it is necessary to lower the surface temperature of the pipe because the outside of the pipe is exposed to the work space, even if the insulation performance is increased to a level where the interface temperature between the microporous insulation layer and the outer shell layer is below 100°C, water vapor condensation does not occur, and the hydration reaction in the microporous insulation can be suppressed and the insulation performance can be maintained. The thickness of the microporous insulation layer is not limited, but can be in the range of 5.0 mm to 20.0 mm in the above examples.

[0029] 10...High-temperature gas piping, 11...Weir refractory layer, 12...Insulating brick layer, 13...Impermeable layer, 14...Castable refractory layer, 15...Microporous insulating material layer, 16...Outer shell layer.

Claims

1. A high-temperature gas pipe for transporting high-temperature gas containing water vapor, comprising: at least one refractory layer constituting the internal working surface of the refractory structure of the pipe; an impermeable layer laminated on the outside of the at least one refractory layer; a microporous insulation layer laminated on the outside of the impermeable layer; and an outer shell layer formed on the outside of the microporous insulation layer.

2. The hot gas piping according to claim 1, wherein at least one refractory or insulating layer is laminated between said impermeable layer and said microporous insulating layer.

3. The high-temperature gas piping according to claim 2, wherein a wear refractory layer, an insulating brick layer, a castable refractory layer, and the microporous insulating material layer are laminated in this order from the working surface side, and the impermeable layer is laminated between the insulating brick layer and the castable refractory layer.

4. The hot gas piping according to claim 1, wherein said impermeable layer and said microporous insulation layer are adjacent to each other.

5. A high-temperature gas piping as described in claim 4, wherein a wear refractory layer, an insulating brick layer, a castable refractory layer, and the microporous insulation layer are laminated in this order from the working surface side, and the impermeable layer is laminated between the castable refractory layer and the microporous insulation layer.

6. A high-temperature gas pipe according to any one of claims 1 to 5, wherein the microporous insulation layer is formed of WDS (registered trademark).

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