WO2021077764A1

WO2021077764A1 - Composite heat conduction pipe containing low-melting-point metal, and production method therefor

Info

Publication number: WO2021077764A1
Application number: PCT/CN2020/095497
Authority: WO
Inventors: 李为冬
Original assignee: 德清金烨电力科技有限公司
Priority date: 2019-10-22
Filing date: 2020-06-11
Publication date: 2021-04-29
Also published as: CN110806135A

Abstract

The present invention relates to the field of heat exchange apparatus manufacturing, and in particular to a composite heat conduction pipe containing a low-melting-point metal, and a production method therefor. The present invention is implemented according to the following technical scheme: a composite heat conduction pipe containing a low-melting-point metal, comprising a rigid body inner layer and further comprising a rigid body outer layer and a flexible heat conduction layer located between the rigid body outer layer and the rigid body inner layer, wherein the flexible heat conduction layer contains a low-melting-point metal. The object of the present invention is to provide a composite heat conduction pipe containing a low-melting-point metal, and a production method therefor. The heat conduction performance of the composite heat conduction pipe is good, air in the pipe can be sufficiently and effectively preheated, structural rigidity problems are solved, the composite heat conduction pipe is not prone to being damaged in various links, such as installation, transportation and end welding, and the stability of a product is maintained.

Description

Composite heat conducting pipe containing low melting point metal and production method thereof

Technical field

The invention relates to the field of heat exchange equipment manufacturing, in particular to a composite heat conducting pipe containing a low melting point metal and a production method thereof.

Background technique

Heat exchange boxes and preheat boxes are common industrial components and are widely used in many industrial fields. Taking the power generation industry as an example, there will be multiple heat exchange tubes in the preheating tube box. The inside of the tube is ordinary air, and the inside and outside of the tube can be high-temperature gas generated in the previous process, such as flue gas. . These high-temperature gases conduct heat to the heat exchange tube, and the air in the heat exchange tube is preheated.

In the prior art, for example, the Chinese patent document with the authorization announcement number CN2901219Y discloses a new type of preheater for a thermal power boiler, which is equipped with multiple heat exchange tubes. The structure of this kind of heat exchange tube is a common double-layer structure, the inner ring is a steel pipe, and the outer ring is an enamel surface layer.

The enamel surface is provided on the outside of the steel pipe because the enamel has a certain effect of isolating corrosion and protecting the steel of the inner ring. This kind of double-layer structure heat exchange tube has been used in my country for more than 20 years, but there are many kinds of structures of this kind. defect.

First of all, with the further requirements of environmental protection in my country, the ammonia process is adopted for flue gas denitration. The sulfur trioxide in the flue gas reacts with ammonia to produce ammonium bisulfate, which becomes a viscous liquid after the temperature drops to 154 degrees. The flue gas contains a large number of particles, and this viscous liquid will adhere to the outer surface of the exchange tube, causing the blockage of the entire air preheater. In the prior art, only the cleaning device can be used to mechanically clean the outer surface of the exchange tube. However, due to the brittleness of the enamel layer, the cleaning process causes the enamel layer of the enamel tube to be damaged and the corrosion resistance is invalid.

Secondly, the thermal conductivity of enamel is not high, and the performance of heat conduction is not ideal, resulting in a flat preheating effect of the heat exchange tube on the air in the tube.

Third, during the installation process, the end of the heat exchange tube needs to be welded and connected to the tube sheet of the tube box. During the end welding process, the enamel layer cracks due to the difference in thermal expansion coefficient from steel.

Finally, the enamel layer on the outer layer of the heat exchange tube is relatively fragile and has poor impact resistance. This makes the heat exchange tube extremely prone to damage to the enamel layer during transportation and installation.

technical problem

The purpose of the present invention is to provide a composite heat conduction pipe containing low melting point metal and a production method thereof. The composite heat conduction pipe has good thermal conductivity, can fully and effectively preheat the air in the pipe, and solves the problem of structural rigidity. It is not easy to be damaged in each link of transportation and end welding, and the stability of the product is maintained.

Technical solutions

The above-mentioned technical purpose of the present invention is achieved by the following technical solutions: a composite heat conducting pipe containing low melting point metal, including a rigid inner layer, and also including an outer rigid layer and between the outer rigid layer and the inner rigid layer Between the flexible heat-conducting layer, the flexible heat-conducting layer contains a low melting point metal.

As a preference of the present invention, the material of the inner rigid layer is carbon steel, and the material of the outer rigid layer is stainless steel.

As a preference of the present invention, the melting point of the low melting point metal is 50°C-110°C.

As a preference of the present invention, the low melting point metal is a bismuth alloy.

As a preference of the present invention, the low melting point metal is a gallium alloy.

As a preference of the present invention, the low melting point metal is metallic sodium.

A method for producing a composite heat-conducting pipe containing a low melting point metal includes the following steps:

S01, the inner layer shot blasting step,

Subjecting the inner layer of the rigid body to shot blasting;

S02, three-layer composite step,

Compounding the inner layer of the rigid body with the sleeved flexible thermally conductive layer, and then sleeved into the outer layer of the rigid body, to obtain a composite pipe;

S03, drawing steps,

Put the composite tube into a stainless steel laminating machine for drawing processing, so that the outer rigid layer is reduced in diameter and tightly combined with other layers;

S04, cutting steps,

Cut to get the finished product.

Beneficial effect

In summary, the present invention has the following beneficial effects:

1. The outermost stainless steel has good corrosion resistance and can be reliably used in the flue gas anti-corrosion environment of wet desulfurization.

2. The low melting point metal is liquid under working conditions, which greatly enhances the heat conduction effect between the layers.

3. The outermost and innermost steel structure design makes this kind of composite heat-conducting stainless steel pipe have good structural strength and impact resistance, and will not be damaged or broken during transportation, installation, cleaning, and welding.

The best mode of the present invention

The present invention will be described in further detail below.

This specific embodiment is only an explanation of the present invention, and is not a limitation of the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contribution as needed, but as long as the rights of the present invention The scope of the requirements is protected by the patent law.

Embodiment 1. A composite heat conduction pipe, which has a three-layer structure, from the outside to the inside, respectively a rigid outer layer, a flexible heat conducting layer and a rigid inner layer. Among them, ordinary, non-corrosive air flows inside the heat pipe, and ordinary carbon steel can be used. The outer rigid outer layer is made of 316L stainless steel. Stainless steel is not easy to be corroded in the working environment in contact with various flue gases, and can be widely used in the flue gas anti-corrosion of wet desulfurization.

The material used in the middle layer, the flexible heat-conducting layer, is a low melting point metal. These low-melting-point metals are in a solid state in the normal non-working state, but in the working state, the temperature of the entire heat-conducting pipe rises, at this time these low-melting-point metals are liquid. In this implementation, a bismuth alloy is used.

The reason for this arrangement is that whether it is enamel in the prior art or other materials, although the layers of the composite pipe are closely attached, in a microscopic state, the layers are actually in point contact, that is, there is a gap. These gaps are filled with air, which greatly reduces the heat transfer effect. In this case, a flexible heat-conducting layer composed of a bismuth alloy material is especially arranged between the inner layer of the rigid body and the outer layer of the rigid body, which becomes liquid under working conditions, which greatly increases the contact area between the materials, and in the microscopic state It is also in contact with the inner surface of the rigid body and the outer surface of the rigid body, and has good thermal conductivity. According to the test data, in the traditional technical solution using enamel, the thermal conductivity is .9 w/(m•k), while the thermal conductivity of this embodiment reaches 16.2 w/(m•k).

The use of bismuth alloy is different from other ordinary materials. Even at high temperatures, the outer layer of stainless steel and the inner layer of stainless steel do not react chemically, and the workpiece is stable. And the bismuth alloy is non-flammable and explosive, also non-toxic, tasteless, and environmentally friendly. Its working state is liquid, but it is not volatile or oxidized.

Because the outer layer of stainless steel has strong structural rigidity, it is not easy to be damaged or broken during transportation and installation. In the process of welding and connecting the end of the composite heat conduction tube with the tube box plate, since the inner rigid layer and the outer rigid layer are both rigid materials, they can be welded to the tube box plate, and they are naturally welded during the welding process. As a whole, the end will not be broken due to the difference in the expansion coefficient of the material.

The manufacturing steps of this kind of composite heat conduction pipe are as follows: firstly, the outer surface of the rigid inner layer, that is, the carbon steel layer, is shot blasted. Subsequently, the flexible thermally conductive layer was put on. Then the two layers are sheathed together into the outer rigid layer, that is, the stainless steel layer. Finally, the composite layer is introduced into a stainless steel laminating machine for drawing processing, so that the outer rigid layer, that is, the stainless steel outer tube, is reduced in diameter and tightly combined with other layers. The finished product of this technical solution is obtained after the truncation is cut to length.

The second embodiment is different from the first embodiment in that the material used for the flexible thermal conductive layer is gallium alloy.

Embodiment 3 is different from Embodiment 1 in that the material used for the flexible heat-conducting layer is metallic sodium, and its melting point is 97.72 degrees Celsius.

In addition, alloys with different formulas and different proportions have different melting points. In this technical solution, it is required to be solid in the non-working state, and to become liquid at a temperature above the melting point in the working state. After the applicant’s test, the melting point is 50°C. -110°C is preferred, such as 70°C, 90°C, 100°C, etc.

Claims

A composite heat-conducting pipe containing a low-melting-point metal, comprising an inner rigid layer, characterized in that it further comprises an outer rigid layer and a flexible heat-conducting layer located between the outer rigid layer and the inner rigid layer, the flexible heat-conducting layer Contains low melting point metals.
The composite heat conducting pipe containing low melting point metal according to claim 1, wherein the material of the inner rigid layer is carbon steel, and the material of the outer rigid layer is stainless steel.
The composite heat conducting pipe containing low melting point metal according to claim 1, characterized in that: the melting point of the low melting point metal is 50°C-110°C.
The composite heat conducting pipe containing low melting point metal according to claim 1, characterized in that: the low melting point metal is a bismuth alloy.
The composite heat conduction pipe containing low melting point metal according to claim 2, characterized in that: the low melting point metal is a bismuth alloy.
The composite heat conducting pipe containing a low melting point metal according to claim 3, wherein: the low melting point metal is a bismuth alloy.
The composite heat conducting pipe containing low melting point metal according to claim 1, characterized in that: the low melting point metal is a gallium alloy.
The composite heat conducting pipe containing low melting point metal according to claim 2, characterized in that: the low melting point metal is a gallium alloy.
The composite heat conducting pipe containing low melting point metal according to claim 1, characterized in that: the low melting point metal is metallic sodium.
The composite heat conducting pipe containing low melting point metal according to claim 2, characterized in that: the low melting point metal is metallic sodium.
A method for producing a composite heat conducting pipe containing a low melting point metal according to claim 1, characterized in that it comprises the following steps: S01, the inner layer shot blasting step, subject the inner rigid layer to shot blasting; S02, the three-layer composite step, the inner rigid layer is compounded with the sleeved flexible thermally conductive layer, and then the outer rigid layer is sleeved to obtain Composite pipe; S03, drawing step, put the composite pipe into a stainless steel laminating machine for drawing processing, so that the outer rigid layer is reduced in diameter and tightly combined with other layers; S04, cutting step, cut to obtain Finished product.
A method for producing a composite heat conducting pipe containing a low melting point metal according to claim 2, characterized in that it comprises the following steps: S01, the inner layer shot blasting step, subject the inner rigid layer to shot blasting; S02, the three-layer composite step, the inner rigid layer is compounded with the sleeved flexible thermally conductive layer, and then the outer rigid layer is sleeved to obtain Composite pipe; S03, drawing step, put the composite pipe into a stainless steel laminating machine for drawing processing, so that the outer rigid layer is reduced in diameter and tightly combined with other layers; S04, cutting step, cut to obtain Finished product.
A method for producing a composite heat conducting pipe containing a low melting point metal according to claim 3, characterized in that it comprises the following steps: S01, the inner layer shot blasting step, subject the inner rigid layer to shot blasting; S02, the three-layer composite step, the inner rigid layer is compounded with the sleeved flexible thermally conductive layer, and then the outer rigid layer is sleeved to obtain Composite pipe; S03, drawing step, put the composite pipe into a stainless steel laminating machine for drawing processing, so that the outer rigid layer is reduced in diameter and tightly combined with other layers; S04, cutting step, cut to obtain Finished product.
A method for producing a composite heat conducting pipe containing a low melting point metal according to claim 4, characterized in that it comprises the following steps: S01, the inner layer shot blasting step, subject the inner rigid layer to shot blasting; S02, the three-layer composite step, the inner rigid layer is compounded with the sleeved flexible thermally conductive layer, and then the outer rigid layer is sleeved to obtain Composite pipe; S03, drawing step, put the composite pipe into a stainless steel laminating machine for drawing processing, so that the outer rigid layer is reduced in diameter and tightly combined with other layers; S04, cutting step, cut to obtain Finished product.
A method for producing a composite heat conducting pipe containing a low melting point metal according to claim 7, characterized in that it comprises the following steps: S01, the inner layer shot blasting step, subject the inner rigid layer to shot blasting; S02, the three-layer composite step, the inner rigid layer is compounded with the sleeved flexible thermally conductive layer, and then the outer rigid layer is sleeved to obtain Composite pipe; S03, drawing step, put the composite pipe into a stainless steel laminating machine for drawing processing, so that the outer rigid layer is reduced in diameter and tightly combined with other layers; S04, cutting step, cut to obtain Finished product.