High-temperature gas piping

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

Technical Field

[0001] The present invention relates to a high-temperature gas pipe.

Background Art

[0002] Various refractory structures used for pipes for transporting high-temperature fluids have been proposed. For example, in Patent Document 1, in order to provide an inner wall surface of a pipe, a container, etc. that is resistant to thermal shock by an internal fluid with a large temperature change, in a heat insulation structure of an inner wall surface of a pipe, a container, etc. that receives a thermal cycle by an internal fluid, a technique in which a titanium layer and a mullite layer are coated on the inner wall surface is described. Further, in Patent Document 2, in order to prevent voids in the radial direction of the pipe and voids at connection points, a heat insulation structure in which the low-temperature side inside the pipe is a felt-like material mainly composed of ceramic fibers and the high-temperature side is a tubular rigid molded body mainly composed of ceramic fibers is formed, and an inorganic foaming amorphous material that expands and cures at room temperature is interposed between the felt-like material and the inner wall of the pipe, and a tubular heat insulation wall in which the heat insulation structure is pressure-bonded to the inner wall of the pipe is described.

[0003] On the other hand, a fine porous heat insulation material having heat insulation performance superior to conventional heat insulation materials such as calcium silicate and ceramic fibers is known. Specifically, the fine porous heat insulation material is, for example, a material in which a closed fine space with a diameter of 100 nm or less is formed using a spherical hollow structure material having a particle size of 5 nm or more and 30 nm or less as a main raw material, and for example, WDS (registered trademark), a nano heat insulation material using fumed silica as a raw material, is known. Other fine porous heat insulation materials include aerogels such as silica aerogel described in Patent Document 3 and Patent Document 4, and nanoporous silica. In the fine porous heat insulation material, heat transfer due to internal air convection is suppressed, so high heat insulation performance is achieved. By using a fine porous heat insulation material with high heat insulation performance, miniaturization and weight reduction of devices and equipment become possible.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] Even with the pipe insulation structures described in Patent Documents 1 and 2 above, the use of microporous insulation materials makes it possible to miniaturize and lighten the pipes. However, in the case of high-temperature gas piping that transports high-temperature gas containing water vapor, there is a problem that water vapor that permeates through the porous refractory structure from inside the pipe condenses into water, and when the water comes into contact with the microporous insulation material, the structure of the closed microspace is damaged by a hydration reaction, reducing the insulation performance.

[0006] Therefore, the present invention aims to provide a high-temperature gas piping system for transporting high-temperature gases containing water vapor that can achieve miniaturization and weight reduction of the piping by using a fine porous insulation material while suppressing the deterioration of thermal insulation performance due to hydration reactions. [Means for solving the problem]

[0007] [1] A high-temperature gas piping for transporting a high-temperature gas containing water vapor, comprising: at least one refractory layer constituting the working surface inside the piping; an impermeable layer laminated on the outside of the at least one refractory layer; a fine porous insulation layer laminated on the outside of the impermeable layer; and an outer shell layer formed on the outside of the fine porous insulation layer. [2] The high-temperature gas piping according to [1], wherein at least one refractory layer or insulating layer is laminated between the impermeable layer and the fine porous insulating layer. [3] The high-temperature gas piping according to [2], wherein a wearable refractory layer, an insulating brick layer, a castable refractory layer, and the fine porous insulating material layer are laminated in order from the working surface side, and the impermeable layer is laminated between the insulating brick layer and the castable refractory layer. [4] The high-temperature gas piping according to [1], wherein the impermeable layer and the fine porous insulation layer are adjacent to each other. [5] The high-temperature gas piping according to [4], wherein a wearable refractory layer, an insulating brick layer, a castable refractory layer, and the fine porous insulating material layer are laminated in order from the working surface side, and the impermeable layer is laminated between the castable refractory layer and the fine porous insulating material layer. [6] The above-mentioned fine porous insulation layer is formed of WDS®, the high-temperature gas piping according to any one of items [1] to [5].

[0008] According to the above configuration, in high-temperature gas piping, an impermeable layer is laminated between the refractory layer and the microporous insulation layer that constitute the working surface inside the pipe. As a result, water vapor does not reach the microporous insulation layer, and the piping can be made smaller and lighter while suppressing the hydration reaction of the microporous insulation. Because water vapor does not reach the microporous insulation layer, the insulation performance can be increased to such a low temperature that, for example, the temperature of the microporous insulation layer falls below the dew point temperature of the gas. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of a high-temperature gas piping according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. In this specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted.

[0011] Figure 1 is a cross-sectional view of a high-temperature gas piping according to one embodiment of the present invention. In the illustrated example, the high-temperature gas piping 10 has a structure in which a wear refractory layer 11, an insulating brick layer 12, an impermeable layer 13, a castable refractory layer 14, and a fine porous insulating material layer 15 are laminated in order from the working surface (innermost surface) side inside the pipe, 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 temperature at which high-temperature gas can be transported. Specifically, it is preferable to use an alumina refractory material as 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 inside of the layer is formed of a refractory material that has strength to withstand temperatures equivalent to those of the wear refractory layer. Specifically, it is preferable to use a mullite refractory material as the insulating brick layer 12. The alumina refractory material described above preferably has an alumina content of 90% or more, and preferably has few through-pores and a porosity of 20% or less in order to obstruct the entry of the transport gas. The high-temperature gas piping according to the embodiment of the present invention is a refractory structure that transports high-temperature gas containing water vapor. Therefore, when used as high-temperature gas piping, there is no decrease in melting point or wear due to high-temperature reaction between the refractory material on the internal working surface and the high-temperature gas. In molten metal containers such as converters used in steel refining, wear occurs on the working surface of the wear refractory material due to melting, but in the high-temperature gas piping application of the present invention, wear does not occur on the working surface of the wear refractory material due to melting.

[0012] The impermeable layer 13 is a layer that prevents 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 that has condensed from water vapor, from passing through. 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 amorphous (castable) refractory material for dimensional adjustment. The castable refractory layer 14 is also a refractory layer that does not suffer wear due to melting in the high-temperature gas piping application of the present invention. The castable refractory material is a mixture of refractory aggregate and a binder such as alumina cement.

[0013] Furthermore, the refractory layer in the high-temperature gas piping 10 of the present invention is not limited to a three-layer structure consisting of a wearable refractory layer 11, an insulating brick layer 12, and a castable refractory layer 14; it only needs to have at least one refractory layer. For example, without a castable refractory layer, the pipe may have a structure in which a wearable refractory layer 11, an insulating brick layer 12, an impermeable layer 13, and a fine porous insulating material layer 15 are stacked in order from the working surface side inside the pipe, with an outer shell layer 16 formed on the outside. Also, the formation order of the insulating brick layer 12 and the castable refractory layer 14 from the working surface side may be reversed. Furthermore, from the viewpoint of miniaturizing and lightening the piping, it is preferable that the thickness of each layer be as small as possible. 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. Also, 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. Also, for example, the thickness of the impermeable layer may be 0.1 mm or more, or 0.5 mm or less.

[0014] The microporous thermal insulation layer 15 is a layer formed from the microporous thermal insulation material described above. More specifically, the microporous thermal insulation material is formed by creating closed microspaces using spherical hollow structural material as the main raw material. Examples of main raw materials include fumed silica, aerogels such as silica aerogel, and nanoporous silica. The particle size of the spherical hollow structural 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-thermal insulation material made from fumed silica, is also an example of a microporous thermal insulation material. The microporous thermal insulation layer 15 is not limited to being composed of silica-based raw materials, but may also be composed of alumina-based raw materials, for example. Specifically, mullite, a mixed crystal of alumina and silica, is an example. The outer shell layer 16 is a layer that is placed outside the microporous thermal insulation layer 15 to maintain the structure of the high-temperature gas piping 10 and protect the microporous thermal insulation layer 15. Specifically, the outer shell layer 16 is formed from a metal pipe such as iron, or a resin pipe. Iron pipes are preferred from the viewpoint of strength and cost.

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

[0016] In a high-temperature gas pipe 10 including the fine porous insulation layer 15 described above, the insulation performance of the fine porous insulation layer is higher than that of the other layers formed by the refractory materials, insulating bricks, and castable refractory materials. Therefore, sufficient insulation can be achieved with a thinner layer thickness, making the pipe smaller and lighter. Specifically, for example, if the inner diameter is determined by the gas flow rate, the outer diameter of the pipe can be made smaller. Alternatively, if the outer diameter of the pipe is determined by spatial constraints, the inner diameter can be made larger to increase the gas flow rate.

[0017] On the other hand, as already mentioned, when transporting high-temperature gases containing water vapor, such as COG (Coke Oven Gas), through the high-temperature gas piping 10, water vapor that permeates the porous refractory structure from inside the pipe may condense into water, and a hydration reaction may occur when the water comes into contact with the microporous insulation layer 15. When a hydration reaction occurs, the structure of the closed microspaces in the microporous insulation is damaged, and the insulation performance deteriorates. This is not limited to cases where the raw material is silica-based; similar problems occur with microstructured insulation materials made from other raw materials such as alumina.

[0018] Therefore, in the present embodiment, by disposing the impervious layer 13 between the ware refractory layer 11 and the heat insulating brick layer 12, which are refractory layers constituting the operating surface inside the pipe, and the fine porous heat insulating material layer 15, water vapor is prevented from reaching the fine porous heat insulating material layer 15, and a decrease in the heat insulating performance due to the hydration reaction in the fine porous heat insulating material layer 15 is prevented. As a result, even when the high-temperature gas pipe 10 conveys high-temperature gas containing water vapor, miniaturization and weight reduction of the pipe can be achieved while maintaining the heat insulating performance by the fine porous heat insulating material layer 15. Since water vapor does not reach the fine porous heat insulating material layer 15, for example, the heat insulating performance can be enhanced to such an extent that the temperature of the fine porous heat insulating material layer 15 becomes lower than the dew point temperature of the gas. Alternatively, since the heat resistant temperature of the iron skin constituting the outer shell layer 16 is generally 600°C and about 250°C depending on the material, for example, in the range of 600°C or less, it is also possible to design such that the temperature at the interface between the fine porous heat insulating material layer 15 and the outer shell layer 16 greatly exceeds 100°C, such as 250°C or more. In this case, the high-temperature gas pipe can be further miniaturized and weight-reduced by making the refractory layer thinner. The temperature at the interface between the fine porous heat insulating material layer 15 and the outer shell layer 16 can be calculated by heat conduction calculation based on the temperature of the gas conveyed in the high-temperature gas pipe, the atmospheric temperature, the layer thickness and the thermal conductivity of each layer. Alternatively, the temperature may be measured by arranging a thermocouple or the like. Further, the temperature may be calculated by measuring the emissivity of the outer surface of the outer shell layer 16. Since the outer shell layer 16 has a higher thermal conductivity than the heat insulating material and the temperature difference between the outer surface and the inner surface is small, the temperature of the outer surface of the outer shell layer 16 may be regarded as the temperature at the interface between the fine porous heat insulating material layer 15 and the outer shell layer 16.

[0019] Note that the refractory layer laminated inside the impervious layer 13 is not limited to the two-layer structure of the wear refractory layer 11 and the heat-insulating brick layer 12, and at least one refractory layer constituting the operating surface inside the pipe may be arranged. In the above example, at least one refractory layer or heat-insulating material layer, specifically the castable refractory layer 14, is laminated between the impervious layer 13 and the fine porous heat-insulating material layer 15, and the impervious layer 13 is laminated between the heat-insulating brick layer 12 and the castable refractory layer 14. However, this is not limited to this example, and the impervious layer 13 and the fine porous heat-insulating material layer 15 may be adjacent to each other. Specifically, for example, the wear refractory layer 11, the heat-insulating brick layer 12, the castable refractory layer 14, and the fine porous heat-insulating material layer 15 are laminated in order from the operating surface side, and the impervious layer 13 may be laminated between the castable refractory layer 14 and the fine porous heat-insulating material layer 15. Alternatively, two or more refractory layers or heat-insulating material layers may be laminated between the impervious layer 13 and the fine porous heat-insulating material layer 15. Note that since the castable refractory layer 14 has both fire resistance and heat insulation properties, it can be an example of either the refractory layer or the heat-insulating material layer.

[0020] Also, the fine porous heat-insulating material layer 15 does not necessarily have to contact the outer shell layer 16, and another heat-insulating material layer may be laminated between them. However, materials such as WDS (registered trademark) constituting the fine porous heat-insulating material layer 15 have a maximum use temperature of less than 1000°C, and the lower the temperature, the smaller the thermal conductivity. Therefore, from the perspective of downsizing and weight reduction of the pipe by the fine porous heat-insulating material layer 15, it is preferable to arrange the fine porous heat-insulating material layer 15 in a layer in a lower temperature zone outside the other refractory layers.

[0021] The following describes the results of a thermal conductivity calculation for a design example of a high-temperature gas piping that satisfies the conditions of the embodiment of the present invention described above. In the thermal conductivity calculation, the inner diameter d at the working surface of the high-temperature gas piping was set to 1000 mm, and the thermal conductivity of the wear refractory layer was set to 1.5 W / m·K, the thermal conductivity of the insulating brick layer to 0.8 W / m·K, the thermal conductivity of the castable refractory layer to 0.5 W / m·K, the thermal conductivity of the impermeable layer to 40 W / m·K, the thermal conductivity of the microporous insulation material (WDS®) layer to 0.03 W / m·K, and the thermal conductivity of the outer shell layer (steel shell) to 40 W / m·K. In the following example, unlike the example in Figure 1 above, an impermeable layer is laminated between the castable refractory layer and the microporous insulation material layer. The temperature of the gas transported in the high-temperature gas piping was set to 1000°C, and the ambient temperature 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 amount of heat dissipated to the outside calculated in each example, the higher the thermal insulation performance of the high-temperature gas piping. The interface temperature shown in Table 1 represents the temperature at the interface between the microporous insulation layer and the steel shell, as calculated by the heat conduction calculation.

[0023] [Table 1]

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

[0025] Even when the microporous insulation layer was formed with the thinnest thickness of 5.0 mm in Example 1, the amount of heat dissipation was significantly reduced compared to the comparative example, indicating 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., miniaturization and weight reduction of the pipe is possible. Further increasing the thickness of the microporous insulation layer, as in Examples 2 to 5, further improves insulation performance. In Examples 4 and 5, as a result of the improved insulation performance, the interface temperature between the microporous insulation layer and the steel shell falls below 100°C. In these cases, if water vapor reaches the microporous insulation layer, water may be generated by the condensation of water vapor, potentially causing a hydration reaction in the microporous insulation. However, in these examples, the presence of an 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 of further miniaturization and weight reduction of piping by making the refractory layer thinner compared to the layer configuration of Example 1 above. In Examples 6 to 10, the castable refractory layer is omitted, in Examples 7 to 10 the insulating brick layer is gradually thinned, and in Example 10 the wearable refractory layer is also thinned. In these examples, the interface temperature between the microporous insulating material layer and the steel shell is well above 100°C, but 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, so designs like these examples are possible if 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, and any layer may be thinned.

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

[0028] The results described above demonstrate that by laminating an impermeable layer between the refractory layer and the microporous insulation layer that constitute the working surface inside the high-temperature gas piping, it is possible to miniaturize and lighten the piping while suppressing the hydration reaction of the microporous insulation material. For example, when it is desirable to lower the surface temperature of the piping for reasons such as the outside of the piping being exposed to the working space, even if the insulation performance is increased to such an extent that the interface temperature between the microporous insulation layer and the outer shell layer falls below 100°C, water vapor condensation does not occur, and the hydration reaction in the microporous insulation material can be suppressed, thus maintaining the insulation performance. The thickness of the microporous insulation layer is not limited, but the range of 5.0 mm to 20.0 mm in the above example can be cited as an example. [Explanation of Symbols]

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

Claims

1. A high-temperature gas piping system for transporting high-temperature gas containing water vapor, The refractory structure of the aforementioned piping comprises at least one refractory layer forming the internal working surface, An impermeable layer laminated on the outside of the aforementioned at least one refractory layer, A layer of finely porous insulating material is laminated on the outside of the aforementioned impermeable layer, An outer shell layer formed on the outside of the aforementioned microporous thermal insulation layer and High-temperature gas piping equipped with a piping system.

2. The high-temperature gas piping according to claim 1, wherein at least one refractory layer or insulating layer is laminated between the impermeable layer and the fine porous insulating layer.

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

4. The high-temperature gas piping according to claim 1, wherein the impermeable layer and the fine porous insulation layer are adjacent to each other.

5. The high-temperature gas piping according to claim 4, wherein a wearable refractory layer, an insulating brick layer, a castable refractory layer, and the fine porous insulating material layer are laminated in that order from the working surface side, and the impermeable layer is laminated between the castable refractory layer and the fine porous insulating material layer.

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

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