JP2588099B2 - Corrosion and wear resistant double pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion-resistant and abrasion-resistant double tube used as a furnace wall tube of a commercial or industrial boiler.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of effective use of energy, power generation methods with higher thermal efficiency, such as ultra-supercritical steam conditions and combined power generation with a pressurized fluidized-bed boiler, have been used in power generation boilers. In addition, municipal solid waste and industrial waste, which had been simply incinerated, have been reviewed as new fuels. In addition, Orinoco tar and low-grade coal will have to be used as fuel in the future due to resource depletion.

[0003] In accordance with such a movement, steel tubes for boilers have been used in increasingly severe environments. For example, steel pipes are required to have high high-temperature strength for super-supercritical pressure in steam conditions, high high-temperature erosion resistance for fluidized-bed boilers, and high high-temperature corrosion resistance for waste power generation and low-grade fuel. However, materials that can achieve both high-temperature strength and corrosion resistance are limited, and even very expensive. Double pipes can solve this problem.In fact, the inner pipe is made of a material with excellent high-temperature strength, and the outer pipe is made of a material with excellent resistance to high-temperature erosion and corrosion. It is used as

In particular, in the furnace wall tube, stainless steel cannot be used because water passes through the inner surface and high temperature water stress corrosion cracking becomes a problem, and carbon steel or low alloy steel containing Cr and Mo is used. When the outer surface of the pipe is exposed to a severe corrosive environment, a protector and a build-up are indispensable, and a double pipe has been promoted as an alternative.

As a method for manufacturing a double pipe, for example,
JP-A-190007 and JP-A-61-190008 disclose that a capsule formed by a thick-walled malleable metal cylinder and a thin-walled metal cylinder having a different diameter from the cylinder is filled with powder and hermetically sealed. A method of compressing the powder by cold isostatic pressing to form a billet and hot-extruding the billet, and a container of rubber or similar material having concentric cylindrical inner and outer double walls. Inside, while accommodating the cylindrical material of the malleable metal in close contact with one container wall,
A method is proposed in which a powder material is filled and sealed between the other container wall and the cylindrical material, and this is pressurized by cold isostatic pressure, and the material taken out of the container is hot-extruded as a billet. Have been.

[0006] However, when a half is embedded in a wall side such as a furnace wall tube, corrosion is a problem on the flame side, and the wall side has a milder corrosive environment than the flame side. The outer layer on the wall side does not need to be as thick as the outer layer on the flame side. However, in the conventional double pipe, since the thickness of the outer layer portion is uniform, more waste is generated by the outer layer material on the wall side. Materials with excellent erosion and corrosion resistance, such as those used as outer layer materials, are usually very expensive, so using a conventional double tube for a furnace wall tube is very uneconomical and requires limited resources. Immediate improvement is required from the standpoint of effective use of.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a double pipe used as a furnace wall pipe of a boiler for business use, industrial use, etc.
It is an object of the present invention to provide a shape that can be provided at a lower cost than conventional ones.

[0008]

The present inventors have conducted various experiments and studies in order to achieve the above object, and as a result, have found that the thickness of the outer layer material on the wall side is smaller than the thickness of the outer layer material on the flame side. if,
It has been found that the amount of expensive corrosion-resistant material used as an outer layer material can be reduced. Furthermore, in order to manufacture a double pipe in which the thickness of the outer layer material on the wall side is smaller than the thickness of the outer layer material on the flame side, the center of the inner layer of the double pipe does not coincide with the center of the double pipe body. I found out what to do.

The present invention has been made based on the above findings, and the gist of the present invention is that the center of a circle forming a boundary between an outer layer and an inner layer in a cross section perpendicular to the pipe axis is: A corrosion-resistant and abrasion-resistant double pipe characterized in that it does not coincide with the axis of the double pipe. Here, the types of the metal material to be the inner layer and the metal material to be the outer layer are not particularly limited. For example, as the inner layer material, carbon steel, low alloy steel, stainless steel, nickel and nickel alloy, cobalt and cobalt alloy , Titanium and titanium alloys. On the other hand, as the outer layer material, among the functions such as corrosion resistance, high-temperature corrosion resistance, oxidation resistance, and wear resistance, it may be selected according to the required function, for example, Hastelloy, stellite, Ni-Cr alloy, stainless steel, Fe-based superalloys, nickel and nickel alloys, cobalt and cobalt alloys,
Titanium and titanium alloys can be mentioned.

[0010]

The present invention will be described below in detail. First, the cross-sectional shape of the double pipe of the present invention is shown in FIG. In this case, the outer layer of the double pipe becomes a corrosion resistant material. As shown in FIG. 1, the thickness of the outer layer portion of the double pipe can be gradually changed depending on the location by slightly shifting the center of the double pipe main body and the center of the circle forming the boundary between the outer layer and the inner layer. . In addition, the portion where the outer layer has the maximum thickness and the portion where the outer layer has the minimum thickness are located on opposite sides of the center of the tube. Therefore, if the part where the outer layer thickness is maximum is directed to the flame side where corrosion resistance is most required, the part where the outer layer thickness is minimum will necessarily be directed to the wall side where corrosion resistance is not so problematic. Compared with the case of a normal double pipe having a constant thickness at any part, the amount of the outer layer material which is generally expensive can be reduced.

The double pipe according to the present invention can be used in any steel pipe environment in which a portion where corrosion resistance is a problem and a portion where corrosion resistance is not a problem are located on opposite sides of the center of the pipe. For example, superheater tubes,
It can be used as an evaporator tube depending on the corrosive environment.
In particular, it is not limited only to the use as a furnace wall tube.

Further, it is the inner surface of the pipe that is required to have corrosion resistance, and the part where corrosion resistance is a problem and the part where corrosion resistance is not a problem are located at positions opposite to each other with respect to the center of the pipe. In such a case, for example, in the case of a fluidized sand transport pipe in a fluidized bed boiler, the inner layer may have a cross-sectional shape as shown in FIG. 2 so that the inner layer is made of a corrosion-resistant material. This is no different from the case where the part to be wrapped is the outer surface of the tube.

An embodiment of the present invention will be described below.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in Table 1, the outer diameter, the diameter of the circle forming the boundary between the outer layer and the inner layer, the inner diameter, and the distance between the center of the circle forming the boundary between the outer layer and the inner layer and the center of the double pipe are shown. HIP heavy pipe
-Manufactured by a hot pressing process. Table 1 also shows the maximum thickness and minimum thickness of the corrosion resistant material obtained at that time, and the saving rate of the corrosion resistant material.
Are also shown. Here, No. Nos. 1 to 3 are examples of the present invention in which the outer layer is made of a corrosion-resistant material. Nos. 4 to 6 are examples of the present invention in which the inner layer is made of a corrosion-resistant material. Reference numerals 7 and 8 denote conventional double tubes which are comparative examples. In addition, the saving rate of the corrosion-resistant material means that the amount of the corrosion-resistant material required for any double pipe of the present invention has the same outer diameter and inner diameter as that of the double pipe of the present invention, and the thickness of the corrosion-resistant material extends over the entire circumference. It is shown what percentage was reduced with respect to the amount of the corrosion-resistant material required for the conventional double-pipe which is equal to the maximum corrosion-resistant material thickness of the double-pipe of the present invention.

As is apparent from Table 1, the double pipe according to the present invention can save 25 to 40% of the corrosion-resistant material as compared with the conventional double pipe.

[0016]

[Table 1]

[0017]

As described above, according to the present invention, it is possible to manufacture a double pipe having the same corrosion resistance as the conventional one at a much lower cost than before, and to contribute to the development of industry. It is very large to do.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a double pipe of the present invention when a corrosion-resistant material is used as an outer layer.

FIG. 2 is a cross-sectional view of the double pipe of the present invention when a corrosion-resistant material is used as an inner layer.

[Explanation of symbols]

 Reference Signs List 1 outer layer material (corrosion resistant material) 2 inner layer material 3 outer layer material 4 inner layer material (corrosion resistant material) 5 center of double pipe 6 center of circle forming boundary between outer layer and inner layer

Claims (1)

(57) [Claims] 1. A double pipe, wherein the center of a circle forming a boundary between an outer layer and an inner layer in a cross section perpendicular to the pipe axis does not coincide with the axis of the double pipe. Abrasive double tube.