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 microporous heat insulation material layer laminated on the outside of the at least one refractory layer; and an iron shell 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 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, a microporous insulation layer laminated on the outside of the at least one refractory layer, and a steel shell formed on the outside of the microporous insulation layer. [2] The high-temperature gas pipe according to [1], wherein the materials and thicknesses of the at least one refractory layer and the microporous insulation layer are designed so that the temperature at the interface between the microporous insulation layer and the steel shell is equal to or higher than the dew point temperature of the high-temperature gas. [3] The high-temperature gas pipe according to [1], wherein the materials and thicknesses of the at least one refractory layer and the microporous insulation layer are designed so that the temperature at the interface between the microporous insulation layer and the steel shell is equal to or higher than 100°C. [4] The high-temperature gas pipe according to any one of [1] to [3], wherein the at least one refractory layer includes, in order from the working surface side, a wear refractory layer, a heat insulating brick layer, and a castable refractory layer. [5] The high-temperature gas pipe according to any one of [1] to [3], wherein the microporous heat insulating material layer is formed of WDS (registered trademark).

[0008] According to the above configuration, by placing the microporous insulation layer as the outermost layer of the insulation material in contact with the steel shell, the amount of water vapor reaching the microporous insulation layer is reduced, thereby suppressing hydration reactions to a certain extent. Furthermore, by designing the materials and thicknesses of the refractory layer and the microporous insulation layer so that the temperature at the interface between the microporous insulation layer and the steel shell is equal to or higher than the dew point temperature of the high-temperature gas, it is possible to more reliably prevent deterioration of the insulation performance of the microporous insulation due to hydration reactions. By using microporous insulation with excellent insulation performance and further preventing deterioration of that insulation performance, it is possible to reduce the size and weight of the piping.

[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, a castable refractory layer 13, and a microporous insulating material layer 14 are layered, with a steel shell 15 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 alumina refractory preferably has an alumina content of 90% or more, and preferably has few through-pores and a porosity of 20% or less to prevent the penetration of the carrier gas. The insulating brick layer 12 is formed of an insulating material that prevents heat from escaping from the working surface, while 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, it is preferable to use a mullite refractory for the insulating brick layer 12. The castable refractory layer 13 is an insulating layer formed of a castable refractory for dimensional adjustment. The castable refractory is a mixture of refractory aggregate and a binder such as alumina cement.

[0012] The microporous insulation layer 14 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 14 is not limited to those made from silica-based raw materials, and may also be made from other raw materials, such as alumina-based raw materials. Specific examples include mullite, a crystalline mixture of alumina and silica. The steel shell 15 is disposed on the outside of the microporous insulation layer 14 to maintain the structure of the high-temperature gas pipe 10.

[0013] In the high-temperature gas pipe 10 including the microporous insulation layer 14 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.

[0014] Materials such as WDS (registered trademark) that constitute the microporous insulation layer 14 have a maximum operating temperature of 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 the piping using the microporous insulation layer 14, it is preferable to arrange the microporous insulation layer 14 in a layer that is outside the other refractory layers and in a lower temperature range. In this embodiment, the microporous insulation layer 14 is arranged as the outermost insulating material layer that contacts the steel shell 15. Note that the refractory layers inside the microporous insulation layer 14 are not limited to the three-layer structure of the wear refractory layer 11, the insulating brick layer 12, and the castable refractory layer 13 described above, as long as at least one refractory layer that constitutes the working surface inside the pipe is arranged. For example, the tube may have a structure in which the wear refractory layer 11, the insulating brick layer 12, and the microporous insulating layer 14 are laminated in this order from the working surface side inside the tube, with the steel shell 15 formed on the outside. Also, the order in which the insulating brick layer 12 and the castable refractory layer 13 are formed from the working surface side may be reversed. Note that the castable refractory layer 13 has both fire resistance and insulating properties, and therefore may be an example of either a refractory layer or an insulating layer.

[0015] From the viewpoint of miniaturizing and lightening the piping, 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 upper limit of the thickness of the microporous insulation layer may be 20.0 mm or less or 12.5 mm or less. The lower limit of the thickness of the microporous insulation layer is also not particularly limited, but 5.0 mm is generally the manufacturing limit.

[0016] 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), water vapor that penetrates the porous refractory structure of the wear refractory layer 11, the insulating brick layer 12, and the castable refractory layer 13 from the inside of the pipe may condense into water, which may then come into contact with the microporous insulation layer 14, potentially causing a hydration reaction. This hydration reaction damages the closed microspace structure of the microporous insulation, resulting in a decrease in insulation performance. This problem is not limited to silica-based materials; similar problems occur with insulation materials with a microstructure made from other materials, such as alumina-based materials. By placing the microporous insulation layer 14 as the outermost layer of insulation material in contact with the steel shell 15, the amount of water vapor reaching the microporous insulation layer 14 is reduced, thereby suppressing hydration to some extent, regardless of whether or not the design described below is used.

[0017] Furthermore, in this embodiment, the materials and thicknesses of the wear refractory layer 11, the insulating brick layer 12, the castable refractory layer 13, and the microporous insulation layer 14 are set so that the temperature at the interface between the microporous insulation layer 14 and the steel shell 15 is equal to or higher than the dew point temperature of the high-temperature gas. This prevents condensation of water vapor that reaches the microporous insulation layer 14, more reliably preventing degradation of the insulation performance due to hydration reactions in the microporous insulation. The temperature at the interface between the microporous insulation layer 14 and the steel shell 15 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 of each layer, and the 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 steel shell 15. Because the shell 15 has a higher thermal conductivity than the thermal insulator and the temperature difference between its outer and inner surfaces is small, the temperature of the outer surface of the shell 15 may be considered to be the temperature at the interface between the microporous insulation layer 14 and the shell 15. The dew point temperature of high-temperature gas varies depending on the pressure and the amount of water vapor, but for simplicity, 100°C, the condensation temperature of water vapor at atmospheric pressure, can be used as the standard. The heat-resistant temperature of a typical shell 15 is 600°C, and depending on the material, it is approximately 250°C. Therefore, it is possible to design the temperature at the interface between the microporous insulation layer 14 and the shell 15 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, the thinning of the refractory layer allows for further miniaturization and weight reduction of the high-temperature gas piping.

[0018] The following describes the results of heat conduction calculations performed on design examples of high-temperature gas pipes that satisfy the above-described requirements for the embodiments 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. Starting from the working surface, 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 microporous insulation material (WDS®) layer was set to 0.03 W / m·K, and the thermal conductivity of the steel shell was set to 40 W / m·K. The temperature of the gas transported through the high-temperature gas pipe was set to 1000°C, and the atmospheric temperature was set to 25°C. Table 1 shows examples of the layer configuration of the high-temperature gas pipe 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 pipe. 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 calculation.

[0019]

[0020] In Table 1, Example 1-1 is an example in which a microporous insulation layer was formed with a layer thickness of 5.0 mm. In Example 1-2, the castable refractory layer was thickened so that the heat dissipation amount was approximately the same (5621.2 kcal / m h) as in Example 1 (5625.5 kcal / m h) without forming a microporous insulation layer. As a result, the outer diameter of the high-temperature gas pipe was increased by 170.0 mm compared to Example 1. Similarly, in Example 2-2, in which the castable refractory layer was thickened so that the heat dissipation amount was approximately the same as in Example 2-1, in which a microporous insulation layer was formed with a layer thickness of 10.0 mm, the outer diameter of the high-temperature gas pipe was increased by 360.0 mm. In Example 3-2, in which the castable refractory layer was thickened so that the heat dissipation amount was approximately the same as in Example 3-1, in which a microporous insulation layer was formed with a layer thickness of 12.5 mm, the outer diameter of the high-temperature gas pipe was increased by 460.0 mm. Thus, the more one wishes to improve the insulating performance of high-temperature gas piping and reduce the amount of heat dissipated to the outside, the greater the effect of reducing the size and weight of the piping by forming a microporous insulating material layer.

[0021] On the other hand, in Examples 1-1, 2-1, and 3-1, the interface temperature between the microporous insulation layer and the steel shell is 100°C or higher, so if the pressure at the interface is about normal pressure, condensation of water vapor that reaches the microporous insulation layer does not occur. Therefore, in these examples, the hydration reaction of the microporous insulation material can be suppressed, and the insulation performance can be maintained.

[0022] On the other hand, in Examples 4 and 5, in which the microporous insulation layer was made even thicker, the amount of heat dissipation was further reduced and the insulation performance was improved, but the interface temperature between the microporous insulation layer and the steel shell was below 100°C. In these examples, condensation of water vapor that reached the microporous insulation layer may occur, and the insulation performance may be reduced due to a hydration reaction of the microporous insulation. However, if it is possible to predict that the dew point temperature of the high-temperature gas will be below 100°C based on the pressure at the interface and the amount of water vapor contained in the gas, designs such as those in Examples 4 and 5 may also be possible.

[0023] 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 1-1 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 it is not necessary to omit the castable refractory layer when thinning the refractory layer; any layer may be thinned.

[0024] In the case of high-temperature gas piping, the ratio of pipe thickness to outer diameter is high, so providing a microporous insulation layer is highly effective in reducing the size by thinning the refractory layer while maintaining thermal insulation performance. For example, in Examples 1-2, 2-2, and 3-2, where a microporous insulation layer is not provided, the ratio of the outer diameter to the inner diameter d of the piping exceeds 2.0, whereas in Examples 1-1, 2-1, and 3-1, where a microporous insulation layer is provided, the ratio of the outer diameter to the inner diameter d of the piping can be reduced to 2.0 or less while maintaining equivalent thermal insulation performance. The ratio of the outer diameter to the inner diameter d of the piping is 1.5 or less in Examples 7 to 10, 1.4 or less in Examples 8 to 10, and 1.1 or less in Example 10.

[0025] The above results demonstrate that by disposing a microporous insulation layer between the refractory layer constituting the inner working surface of a high-temperature gas pipe and the outermost steel shell, it is possible to reduce the outer diameter and weight of the pipe. Furthermore, it was demonstrated that in a high-temperature gas pipe designed as described above, the temperature at the interface between the microporous insulation layer and the steel shell can be set to a temperature above the dew point of the high-temperature gas, more specifically, for example, 100°C or higher, thereby suppressing the hydration reaction of the microporous insulation layer. When the temperature of the gas being transported is set to 1000°C as in the above example, a suitable interface temperature can be achieved by setting the thickness of the microporous insulation layer to 12.5 mm or less. While there is no lower limit to the thickness of the microporous insulation layer, the 5.0 mm shown in Example 1-1 is generally the manufacturing limit.

[0026] 10...High-temperature gas piping, 11...Weir refractory layer, 12...Insulating brick layer, 13...Castable refractory layer, 14...Microporous insulating material layer, 15...Iron shell.

Claims

1. A high-temperature gas pipe for transporting high-temperature gas containing steam, comprising: at least one refractory layer constituting a working surface inside the pipe; a microporous insulation layer laminated on the outside of the at least one refractory layer; and a steel shell formed on the outside of the microporous insulation layer.

2. The high-temperature gas piping according to claim 1, wherein the materials and thicknesses of the at least one refractory layer and the microporous insulation layer are designed so that the temperature at the interface between the microporous insulation layer and the steel shell is equal to or higher than the dew point temperature of the high-temperature gas.

3. The high-temperature gas piping according to claim 1, wherein the materials and thicknesses of the at least one refractory layer and the microporous insulation layer are designed so that the temperature at the interface between the microporous insulation layer and the steel shell is 100°C or higher.

4. A high-temperature gas piping according to any one of claims 1 to 3, wherein the at least one refractory layer includes, in order from the working surface side, a wear refractory layer, a heat insulating brick layer, and a castable refractory layer.

5. A high-temperature gas pipe according to any one of claims 1 to 3, wherein the microporous insulation layer is formed of WDS (registered trademark).

Images