WO2023039725A1

WO2023039725A1 - Radiant tube heating system

Info

Publication number: WO2023039725A1
Application number: PCT/CN2021/118325
Authority: WO
Inventors: 梅磊; 李璟涛; 沈峰; 范霁红; 门凤臣
Original assignee: 国家电投集团电站运营技术（北京）有限公司; 国家电投集团科学技术研究院有限公司
Priority date: 2021-09-14
Filing date: 2021-09-14
Publication date: 2023-03-23

Abstract

Provided is a radiant tube heating system, comprising: a radiant tube (1), a heating body (2), and molten salt (3), wherein the heating body (2) runs through the radiant tube (1); the molten salt (3) is filled inside the radiant tube (1) and covers the heating body (2); the heating body (2) is used to heat the molten salt (3) to keep the molten salt (3) at a first preset temperature; the molten salt (3) absorbs the heat of the heating body (2) and uses the heat to heat the radiant tube (1), keeping the radiant tube (1) at a second preset temperature. The structure of the radiant tube heating system is simplified, the cost is reduced, the heat transfer efficiency is improved, and the service life of the radiant tube is prolonged.

Description

Radiant Tube Heating System

technical field

The present application relates to the technical field of industrial heating, in particular to a radiant tube heating system.

Background technique

With the development of modern technology, people have higher and higher requirements for the energy saving, efficiency and service life of heating parts of heating furnaces. Radiant tubes are the main heating elements widely used in furnaces. The radiant tubes currently used are mainly divided into two categories: gas radiant tubes and electric radiant tubes.

The traditional gas radiant tube is mainly composed of three parts: burner, heat exchanger, and radiant tube body. The gas radiant tube heats the tube wall through the combustion of gas in the tube, and then the tube wall heats the material in the form of heat radiation. The specific working principle of the gas radiant tube is: the burner is installed at the gas input end of the radiant tube, and a heat exchanger is installed at the exhaust gas outlet end. The form heats the tube wall, and finally the combustion exhaust gas flows to the outlet end, and the exhaust gas passes through the heat exchanger to heat the newly entering cold air to save resources. The most important part of the radiant tube is the radiant tube body. Since the heating is carried out through the radiation of the tube body, the radiant tube body is in a high-temperature working environment for a long time, so the radiant tube body is prone to failure. The main reasons for the failure of the radiant tube body are: 1) Local long-term burning and oxidation; 2) There is a relatively large temperature drop in the length direction of the tube body, which will cause the tube body to be subject to greater thermal stress; 3) In the combustion The explosion of air flow generated during the chemical reaction makes the radiant tube vibrate continuously.

The traditional electric radiant tube is a high temperature resistant stainless steel tube. The heating element inside the radiant tube is a heating element composed of multiple resistance wires. The resistance wire heating element is composed of multiple resistance wires and their insulators for series insertion and isolation. , the heat of the resistance wire heating element radiates to the outside through the radiant tube first, which consumes the heat energy of the heating component; secondly, the heat is concentrated inside the radiant tube, which affects the service life of the entire radiant tube. At the same time, the traditional electric radiant tube is mostly hollow inside, and the heat capacity of the gas is small, so the heating element component needs to switch the heating state frequently, making the electric radiant tube easy to heat and fail.

Contents of the invention

The purpose of this application is to solve one of the above-mentioned technical problems at least to a certain extent.

Therefore, the first purpose of the present application is to propose a radiant tube heating system, which can prolong the service life of the radiant tube, improve the heat transfer efficiency of the radiant tube, and reduce the equipment investment cost.

In order to achieve the above purpose, the embodiment of the first aspect of the present application proposes a radiant tube heating system, including:

Radiant tubes, heating bodies and molten salts,

Wherein, the heating body runs through the radiant tube;

The molten salt is filled inside the radiant tube and wraps the heating body;

The heating body is used to heat the molten salt to keep the molten salt at a first preset temperature;

The molten salt absorbs the heat of the heating body, and uses the heat to heat the radiant tube to keep the radiant tube at a second preset temperature.

Optionally, the system also includes a temperature monitoring device,

The temperature monitoring device includes a temperature transmitter, a temperature controller and a current transmitter,

The temperature transmitter, the temperature controller, and the current transmitter are sequentially connected in series and arranged outside the radiant tube;

One end of the temperature transmitter is placed inside the radiant tube, and the temperature transmitter is used to monitor the temperature of the molten salt;

One end of the current transmitter is connected to the heating body, and the current transmitter is used to adjust the current of the heating body according to the instruction of the temperature controller, so as to realize the adjustment of the temperature of the molten salt.

Optionally, the system also includes a pressure monitoring device,

The pressure monitoring device includes a pressure transmitter, a pressure display and a valve,

The pressure transmitter, the pressure display and the valve are sequentially connected in series;

When the valve is opened, the pressure transmitter detects the pressure inside the radiation tube, and the pressure display displays the pressure detected by the pressure transmitter.

Optionally, the system also includes a safety release device,

The safety release device includes a breathing valve and/or a safety valve, and the breathing valve and/or the safety valve are arranged on the casing of the radiation tube.

Optionally, the breathing valve is used to balance the pressure inside the radiant tube and keep it within a preset range.

Optionally, the safety valve is used to keep the pressure inside the radiation tube not higher than the upper limit value of the radiation tube.

Optionally, when the temperature of the molten salt exceeds the first preset temperature, the current transmitter stops supplying power to the heating body;

When the temperature of the molten salt is lower than the first preset temperature, the current transducer continues to supply power to the heating body.

Optionally, the radiant tube includes a plurality of radiating segments, and two adjacent radiating segments are connected by an insulator.

Optionally, the insulator includes at least one insulator passage hole,

The at least one insulator flow hole is used to communicate with two adjacent radiating sections, so that the molten salts inside the two adjacent radiating sections flow mutually.

Optionally, the shape of the cross-section of the at least one insulator passage hole is one of square, circular, rectangular and fan-shaped.

Optionally, the shape of the radiant tube is one of I-shape, U-shape, P-shape and W-shape.

The radiant tube heating system of the embodiment of the present application uses molten salt heat exchange to replace the existing gas heating, which can reduce the use of gas and prolong the service life of the radiant tube; the molten salt is filled into the radiant tube to improve the heat transfer efficiency of the radiant tube; The structure of the heating system is simplified, and the burner, heat exchanger, induced draft fan, blower and other related equipment of the gas radiant tube are omitted, which reduces the equipment investment cost.

Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application, and do not constitute improper limitations to the present application. In the attached picture:

Fig. 1 is the structural representation of the radiant tube heating system of an embodiment of the present application;

Fig. 2 is the structural representation of the radiant tube heating system of another embodiment of the present application;

Fig. 3 is a schematic structural view of a radiant tube heating system according to yet another embodiment of the present application;

Fig. 4 is a schematic structural view of a radiant tube heating system according to another embodiment of the present application;

Fig. 5 is the structural representation of the radiant tube heating system of a specific embodiment of the present application;

Fig. 6 is a schematic diagram of the first structure of a radiant tube heating system having multiple radiant sections according to an embodiment of the present application;

Fig. 7 is a second structural schematic diagram of a radiant tube heating system having a plurality of radiant sections according to an embodiment of the present application;

Fig. 8 is a third structural schematic diagram of a radiant tube heating system having multiple radiant sections according to an embodiment of the present application;

Fig. 9 is a fourth structural schematic diagram of a radiant tube heating system having multiple radiant sections according to an embodiment of the present application;

Fig. 10 is a fifth structural schematic diagram of a radiant tube heating system having multiple radiant sections according to an embodiment of the present application;

11 is a first cross-sectional view of an insulator according to an embodiment of the present application;

12 is a second cross-sectional view of an insulator according to one embodiment of the present application.

Detailed ways

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and embodiments.

The present application will be described in further detail below in conjunction with specific examples, and these examples should not be construed as limiting the scope of protection claimed in the present application.

The radiant tube heating system of the embodiment of the present application will be described below with reference to the accompanying drawings.

Fig. 1 is a schematic structural diagram of a radiant tube heating system according to an embodiment of the present application.

As shown in FIG. 1 , the radiant tube heating system includes a radiant tube 1 , a heating body 2 and a molten salt 3 .

Wherein, the heating body 2 runs through the radiant tube 1 . It can be seen from FIG. 1 that the middle section of the heating body 2 is located inside the radiant tube 1 , and its two ends extend out of the radiant tube 1 .

Molten salt 3 is filled inside the radiant tube 1 and wraps the heating body 2 . The heating body 2 heats the molten salt 3 to keep the molten salt 3 at a first preset temperature. After the molten salt 3 absorbs the heat of the heating body 2, it uses the heat to heat the radiant tube 1 to keep the radiant tube 1 at a second preset temperature. That is to say, filling the molten salt 3 into the inside of the radiant tube 1 is used to absorb the heat of the heating body 2 on the one hand, and on the other hand, the absorbed heat is radiated and conducted (mainly in the form of conduction) Transfer to the body of the radiant tube 1, so that the radiant tube 1 can be kept at a proper temperature.

The type of molten salt can be selected according to factors such as the heating load of the radiant tube 1 , the physical and chemical properties of the molten salt 3 itself, and the material of the radiant tube 1 body. Specifically, a single molten salt or a composite molten salt with strong corrosion resistance, good thermal stability, low vapor pressure, and wide operating temperature range can be selected. Molten salt 3 can be divided into two categories according to whether it is heated above the melting point: the first type is molten salt of covalent compounds that can be heated above the melting point, and representative ones include BeCl2, AlCl3, HgCl2, ZnCl2, etc. The second category is molten salt that can meet the requirements of heat storage without heating above the melting point. Representative examples are SiO2, Al2O3, etc., which only meet the requirements of heat storage and heat conduction.

The specifications of the radiant tube 1 can be selected according to the size of the heating load and the temperature to be reached. For example, standard radiant tubes with different diameters from DN100 to DN250 can be selected, and the material of the tubes is high-temperature-resistant alloy steel. The highest temperature that the radiant tube 1 can withstand is selected according to the temperature that the radiant tube 1 needs to reach. The temperature that the radiant tube 1 needs to reach can be higher than the melting point of the molten salt 3 or lower than the melting point of the molten salt 3 . The material is selected according to the required temperature of the radiant tube 1 and the maximum tolerable temperature, such as ZG35Cr24Ni7SiNRe, ZG30Cr25Ni12Si2NRe, ZG40Cr25Ni20Si2 and other materials. The shape of the radiation tube 1 can be selected from different forms such as I-type, U-type, P-type, W-type, etc.

In an embodiment of the present application, the heating body 2 may be a single resistance wire, may also be a plurality of resistance wires, or may be a combination of other conductors. Shown in Figure 1 is the case of using a single resistance wire. The resistance wire or other conductors need to be cold-tightened during installation (that is, tightened at room temperature to prevent the resistance wire from loosening and touching the radiation tube at high temperature), and the resistance temperature of the resistance wire or other conductors is selected according to the temperature required by the radiation tube 1 .

The radiant tube using molten salt heat exchange can realize a wide range of temperature operation according to the requirements of working temperature and workload, and the operating temperature range is 200-1200 ℃, or even higher. It is only limited by the radiant tube itself, such as the melting point of HTS is 142°C, the melting point of NaBF4-NaF is 384°C, the melting point of FLiNaK is 454°C, the melting point of SiO2 is 1723°C, and the melting point of Al2O3 is 2050°C, which can meet various industrial heating needs.

Since molten salt has greater specific heat and thermal conductivity than the same volume of flue gas and air, the working curve of the radiant tube based on molten salt heat exchange is smoother and more volatile than the working curve of the gas radiant tube and the electric radiant tube. Smaller, the heating body does not need to be started and stopped frequently. At the same time, the thermal conductivity is high and the efficiency is high. In addition, compared with gas-fired radiant tubes, the operating cost is lower, and equipment such as blowers, induced draft fans, and chimneys are not required, and equipment investment costs are low.

In another embodiment of the present application, as shown in FIG. 2 , the radiant tube heating system further includes a temperature monitoring device 4 .

Wherein, the temperature monitoring device 4 further includes a temperature transmitter 41 , a temperature controller 42 and a current transmitter 43 .

The temperature transmitter 41 , the temperature controller 42 , and the current transmitter 43 are serially connected in sequence, and are arranged outside the radiant tube 1 .

One end of the temperature transmitter 41 is placed inside the radiant tube 1 , and the temperature transmitter 41 is used to monitor the temperature of the molten salt 3 . One end of the current transducer 43 is connected to the heating body 2, and the current transducer 43 is used to adjust the current of the heating body 2 according to the instruction of the temperature controller 42, so as to realize the melting Salt 3 temperature regulation.

Specifically, the temperature transmitter 41 monitors the temperature of the molten salt 3 in real time to ensure that the heating requirement is met and at the same time ensure that the molten salt 3 does not overheat. If the temperature that the temperature transmitter 41 monitors is lower than the first preset temperature, the temperature controller 42 controls the current transmitter 43 to keep supplying power to the heating body 2, so that the heating body 2 keeps working; if the temperature transmitter 41 monitors When the temperature reached is higher than the first preset temperature, the temperature controller 42 controls the current transmitter 43 to stop supplying power to the heating body 2, so that the heating body 2 is no longer heated.

In yet another embodiment of the present application, as shown in FIG. 3 , the radiant tube heating system further includes a pressure monitoring device 5 .

Wherein, the pressure monitoring device 5 further includes a pressure transmitter 51 , a pressure display 52 and a valve 53 .

The pressure transmitter 51 , the pressure display 52 and the valve 53 are connected in series in sequence.

When the valve 53 is opened, the pressure transmitter 51 detects the pressure inside the radiant tube 1 , and the pressure display 52 displays the pressure detected by the pressure transmitter 51 . The setting of the pressure monitoring device 5 can be selected according to the physical and chemical properties of the molten salt 3, which can prevent the saturated vapor pressure from rising due to the heating of the molten salt 3, causing the radiant tube 1 to bear excessive compressive stress.

In yet another embodiment of the present application, as shown in FIG. 4 or FIG. 5 , the radiant tube heating system further includes a safety release device 6 .

The safety release device 6 may include a breathing valve 61 and/or a safety valve 62 , and the breathing valve 61 and/or the safety valve 62 are arranged on the casing of the radiation tube 1 . Specifically, it can be arranged on the upper part or the end of the radiant tube 1 .

The breathing valve 61 is used to balance the pressure inside the radiant tube and keep it within a preset range.

The safety valve 62 is used to keep the pressure inside the radiation tube 1 not higher than the upper limit value of the radiation tube 1 .

The breathing valve 61 and the safety valve 62 can be separately arranged on the shell of the radiation tube 1 , or both can be set on the shell of the radiation tube 1 at the same time as shown in FIG. 4 or FIG. 5 .

In an embodiment of the present application, as shown in FIGS. 6-10 , the radiant tube 1 may include a plurality of radiating segments 11 , and two adjacent radiating segments 11 are connected by an insulator 12 .

As shown in FIG. 11 , the insulator 12 further includes at least one insulator passage hole 121 .

The at least one insulator flow hole 121 is used to communicate with two adjacent radiating sections 11 , so that the molten salt 3 inside the two adjacent radiating sections 11 can flow mutually. The shape of at least one insulator passage hole 121 may be any one of square, circular, rectangular, and fan-shaped. For example, the cross-section of the insulator passage holes 121 in FIG. 11 is rectangular, and the number is four; the cross-section of the insulator passage holes 121 in FIG. 12 is fan-shaped, and the number is three.

Specifically, the heating body 2 is inserted on the insulator 12, and it should be ensured that the heating body 2 is arranged symmetrically to ensure the uniformity of heating. If the heating is not uniform, the molten salt in the radiant section with high temperature will flow into the radiant section with low temperature through the insulator flow hole 121 . In addition, the insulator passage hole 121 should also meet the requirements for supporting the heating body 2 .

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or order between them. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

It should be understood that each part of the present application may be realized by hardware, software, firmware or a combination thereof. In the embodiments described above, various steps or methods may be implemented by software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or combination of the following techniques known in the art: Discrete logic circuits, ASICs with suitable combinational logic gates, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

It should be noted that, in the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the embodiments or EXAMPLES A specific feature, structure, material, or characteristic described is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Claims

A radiant tube heating system, characterized in that it comprises: a radiant tube, a heating body and molten salt,

Wherein, the heating body runs through the radiant tube;

The molten salt is filled inside the radiant tube and wraps the heating body;

The heating body is used to heat the molten salt to keep the molten salt at a first preset temperature;

The molten salt absorbs the heat of the heating body, and uses the heat to heat the radiant tube to keep the radiant tube at a second preset temperature.
The radiant tube heating system according to claim 1, wherein said system further comprises a temperature monitoring device,

The temperature monitoring device includes a temperature transmitter, a temperature controller and a current transmitter,

The temperature transmitter, the temperature controller, and the current transmitter are sequentially connected in series and arranged outside the radiant tube;

One end of the temperature transmitter is placed inside the radiant tube, and the temperature transmitter is used to monitor the temperature of the molten salt;

One end of the current transmitter is connected to the heating body, and the current transmitter is used to adjust the current of the heating body according to the instruction of the temperature controller, so as to realize the adjustment of the temperature of the molten salt.
The radiant tube heating system according to claim 1 or 2, wherein the system further comprises a pressure monitoring device,

The pressure monitoring device includes a pressure transmitter, a pressure display and a valve,

The pressure transmitter, the pressure display and the valve are sequentially connected in series;

When the valve is open, the pressure transmitter detects the pressure inside the radiant tube.
The radiant tube heating system according to any one of claims 1-3, wherein the system further comprises a safety release device,

The safety release device includes a breathing valve and/or a safety valve, and the breathing valve and/or the safety valve are arranged on the casing of the radiation tube.
The radiant tube heating system of claim 4, comprising:

The breathing valve is used to balance the pressure inside the radiant tube to keep it within a preset range.
The radiant tube heating system of claim 4, comprising:

The safety valve is used to keep the pressure inside the radiation tube not higher than the upper limit value of the radiation tube.
The radiant tube heating system of claim 2, comprising:

When the temperature of the molten salt exceeds the first preset temperature, the current transmitter stops supplying power to the heating body;

When the temperature of the molten salt is lower than the first preset temperature, the current transducer continues to supply power to the heating body.
The radiant tube heating system according to claim 1, wherein the radiant tube comprises a plurality of radiant sections, and two adjacent radiant sections are connected by an insulator.
The radiant tube heating system of claim 8 wherein said insulator includes at least one insulator flow hole,

The at least one insulator flow hole is used to communicate with two adjacent radiating sections, so that the molten salts inside the two adjacent radiating sections flow mutually.
The radiant tube heating system according to claim 9, wherein the shape of the section of the at least one insulator flow hole is one of square, circular, rectangular and fan-shaped.
The radiant tube heating system according to any one of claims 1-10, characterized in that, the shape of the radiant tube is one of I-shape, U-shape, P-shape and W-shape.