Boiler heat pipe air preheater

Abstract

The utility model discloses a boiler heat pipe air preheater, and belongs to the field of air preheaters. The heat pipe air preheater comprises a heat pipe, a plurality of through holes are formed in the pipe wall of the left half section of the heat pipe, flexible metal bumps protruding towards the interior of the heat pipe are arranged at the positions of the through holes, and liquid heat transfer media are contained in the heat pipe. During use, the heat pipe is obliquely or vertically arranged, and the left half section of the heat pipe is located at the lower end. According to the heat pipe air preheater, the flexible metal bumps are arranged on the pipe wall of the heat pipe, so that the pits are formed in the pipe wall of the heat pipe, a liquid heat transfer medium is easier to form a vaporization core at the pits, gas generated by boiling of the liquid heat transfer medium can be increased at the same time, and therefore the working efficiency of the heat pipe air preheater is improved.

Description

Technical Field

[0001] The utility model belongs to the field of air preheaters and relates to a boiler heat pipe air preheater. Background Art

[0002] A heat pipe air preheater is a device that utilizes the heat energy carried by the flue gas at the boiler outlet and transfers heat super-conductively through heat pipes to preheat the combustion-supporting air of the boiler or for other drying purposes. The temperature of the flue gas at the boiler outlet is relatively high, which heats the liquid heat transfer medium in the heat pipes located in the boiler flue gas passage. After the liquid boils and vaporizes, it flows towards the boiler combustion-supporting air passage. When the gas formed after the liquid boils and vaporizes reaches the heat pipes located in the boiler combustion-supporting air passage, the gas heats the air, thus achieving the purpose of recovering the heat of the boiler flue gas to preheat the combustion-supporting air of the boiler. Usually, the flow direction of the flue gas in the boiler flue gas passage is opposite to the air flow direction in the boiler combustion-supporting air passage. Therefore, through the heat pipe air preheater, reverse-flow gas-gas heat exchange can be achieved.

[0003] In the actual working state of the heat pipe air preheater, the liquid heat transfer medium continuously boils and vaporizes, and the gas continuously flows into the boiler combustion-supporting air passage to heat the air. Then, after heating the air, it condenses and liquefies and flows back into the boiler flue gas passage. During this process, the boiling state of the liquid heat transfer medium directly affects the working state of the heat pipe air preheater. The boiling process of the liquid is the formation of bubbles, i.e., vaporization nuclei, at certain points on the heating surface. After the bubbles are formed, they grow, float, and finally escape from the liquid surface. That is to say, during the boiling process of the liquid, the easier it is to form vaporization nuclei, the more vaporization gas will be generated and flow into the boiler combustion-supporting air passage for heat exchange within the same time, thereby enabling the heat pipe air preheater to have a higher heat exchange efficiency.

[0004] Therefore, it is necessary to provide a boiler heat pipe air preheater that makes it easier for the liquid to form vaporization nuclei when boiling, so as to achieve more vaporization gas escaping from the liquid surface and flowing into the boiler combustion-supporting air passage within the same time, and improve the heat exchange efficiency of the heat pipe air preheater. Content of the Utility Model

[0005] In order to overcome the problems in the background art, the utility model provides a flexible metal bulge protruding towards the inside of the heat pipe on the heat pipe wall of the heat pipe air preheater. The heat pipe wall is the heating surface, and a flexible metal bulge protruding towards the inside of the heat pipe is provided. Since the liquid heat transfer medium is contained inside the heat pipe, for the liquid heat transfer medium, there are multiple flexible metal bulges protruding inwards on the heat pipe wall, which is equivalent to the heat pipe wall between the flexible metal bulges forming pits. When there are pits on the heating surface, it is easier to form vaporization nuclei at the pits. Therefore, when flexible metal bulges are provided on the heat pipe wall, it is more conducive to the formation of vaporization nuclei, so that when the liquid boils, it is easier to form bubbles, achieving the purpose that more vaporized gas escapes from the liquid surface and flows into the boiler combustion-supporting air channel at the same time, and improving the heat exchange efficiency of the heat pipe air preheater.

[0006] In order to achieve the above object, the utility model is realized through the following technical solutions:

[0007] The heat pipe air preheater includes a heat pipe 1. A plurality of through holes are opened on the left half section of the heat pipe wall of the heat pipe 1, and a flexible metal bulge 2 protruding towards the inside of the heat pipe 1 is provided at the position of the through holes. A liquid heat transfer medium 3 is contained inside the heat pipe 1.

[0008] During use, the heat pipe 1 is arranged obliquely or vertically, and the left half section of the heat pipe 1 is located at the lower end.

[0009] Preferably, the flexible metal bulge 2 is spherical crown-shaped.

[0010] Preferably, the liquid heat transfer medium 3 submerges all the flexible metal bulges 2.

[0011] Preferably, the heat pipe air preheater further includes fins 4. The fins 4 are located outside the heat pipe 1, and the fins 4 are fixedly arranged on the heat pipe wall of the heat pipe 1.

[0012] The beneficial effects of the utility model:

[0013] 1. By providing flexible metal bulges on the heat pipe wall, the utility model provides pits that are more conducive to the formation of vaporization nuclei for the boiling of the liquid heat transfer medium, making it easier to form vaporization nuclei when the liquid heat transfer medium boils, thereby increasing the amount of gas generated by the boiling and vaporization of the liquid heat transfer medium in the same time and improving the working efficiency of the heat pipe air preheater.

[0014] 2. The flexible metal bulges of the utility model can deform under the action of external forces. If the liquid heat transfer medium freezes into a solid and expands in volume, the flexible metal bulges will deform and will not be crushed due to the volume expansion caused by the freezing of the liquid. After the flexible metal bulges deform, pits can still be provided on the heat pipe wall. Description of the Drawings

[0015] Figure 1 This is a schematic diagram of the working state of the present utility model.

[0016] In the figure, 1 - heat pipe, 2 - flexible metal bulge, 3 - liquid heat transfer medium, 4 - fin. Specific embodiments

[0017] The present utility model will be further described in detail below in conjunction with specific embodiments.

[0018] As Figure 1 shown, the heat pipe air preheater includes a heat pipe 1. A plurality of through holes are provided on the left half section of the pipe wall of the heat pipe 1. At the position of the through holes, a flexible metal bulge 2 protruding into the heat pipe 1 is provided. The heat pipe 1 is filled with a liquid heat transfer medium 3.

[0019] During use, the heat pipe 1 is arranged obliquely or vertically, and the left half section of the heat pipe 1 is located at the lower end.

[0020] As Figure 1As shown in the figure, during actual use, the heat pipe 1 is fixedly installed on the partition between the boiler flue gas passage and the boiler combustion-supporting air passage. Taking the partition as the boundary, the left half of the heat pipe 1 is on the left side of the partition, and the right half of the heat pipe 1 is on the right side of the partition. The left half of the heat pipe 1 (i.e., the section provided with the flexible metal bulge 2) is located in the boiler flue gas passage, and the right half of the heat pipe 1 is located in the boiler combustion-supporting air passage. At the same time, the left half located in the boiler flue gas passage is lower in height than the right half located in the boiler combustion-supporting air passage. During normal operation, high-temperature flue gas enters the boiler flue gas passage. At this time, the temperature of the liquid heat transfer medium 3 in the heat pipe 1 is relatively low and has not reached the boiling state. There is a temperature difference between the flue gas and the liquid heat transfer medium 3, so the flue gas will heat the liquid heat transfer medium 3. When the flue gas heats the liquid heat transfer medium 3 to the boiling point of the liquid heat transfer medium 3, the liquid heat transfer medium 3 begins to boil. Since the liquid heat transfer medium 3 is contained in the heat pipe 1, for the liquid heat transfer medium 3, the flexible metal bulge 2 protruding inward is provided on the wall of the heat pipe 1, which is equivalent to providing pits between the flexible metal bulges 2 on the heating surface. And because the boiling of the liquid heat transfer medium 3 in the heat pipe 1 belongs to the boiling heat transfer phenomenon, the boiling property of the liquid heat transfer medium 3 conforms to the property of the boiling heat transfer phenomenon. When there are pits on the heating surface, the liquid is more likely to form vaporization nuclei at the pits. Therefore, compared with the flat wall of the heat pipe 1, the heat pipe air preheater of the present invention can make the liquid heat transfer medium 3 more likely to form vaporization nuclei at the pits between the flexible metal bulges 2, so as to increase the probability of the liquid forming vaporization nuclei in the same time. The liquid is more likely to form vaporization nuclei, which means that in the same time, more bubbles will be formed in the liquid. A larger number of bubbles grow, float, and escape from the liquid surface, then more vaporization gas will be generated. In the same time, more vaporization gas flows into the boiler combustion-supporting air passage to heat the combustion-supporting air, and the working efficiency of the heat pipe air preheater is improved. After the gas heats the combustion-supporting air, the temperature decreases and condenses back into the liquid and flows back into the boiler flue gas passage, and so on, to carry out normal operation in a cycle.

[0021] Since the water content in boiler flue gas is usually high and the temperature of the boiler flue gas itself is high, water dew point will be generated in the flue gas. Sulfur and nitrogen elements are usually contained in the coal used in the boiler. After combustion of these two elements, acid anhydrides will be generated. When the acid anhydrides contact with water vapor in the flue gas, acidic steam will be formed, thus generating acid dew point. Before the heat pipe air preheater starts to work, the temperature of the liquid heat transfer medium 3 in the heat pipe 1 is usually lower than the dew point temperature, so the temperature of the heat pipe 1 wall is also lower than the dew point temperature, resulting in the condensation of steam (including acidic steam) on the surface of the heat pipe 1 wall to form a liquid film, which corrodes the heat pipe 1 and causes the failure of the heat pipe air preheater. Therefore, it is necessary to solve the corrosion problem of the heat pipe air preheater through the constant temperature heat pipe technology. The constant temperature heat pipe realizes that the heat pipe air preheater does not work at a certain set temperature and starts to work only above the set temperature by selecting liquid heat transfer media 3 with different boiling points. Thus, during the working process of the heat pipe air preheater, the wall temperature of the heat pipe 1 is controlled above the dew point temperature through the constant temperature heat pipe technology to solve the corrosion problem. Since it is necessary to select the liquid heat transfer medium 3 according to the actual situation, that is, it is possible to use a liquid heat transfer medium 3 with relatively special properties. When the boiler does not work, no flue gas is generated, so the heat pipe air preheater does not work either, and its own temperature is relatively low. At the same time, the ambient temperature where it is located is also relatively low. Some liquid heat transfer media 3 may solidify into solids. Also, because some liquid heat transfer media 3 have relatively special properties, such as water, after it solidifies into a solid, its volume will expand. When the liquid heat transfer medium 3 solidifies into a solid in the heat pipe 1 and expands in volume, it will generate pressure on the inwardly convex flexible metal bulge 2. At this time, since the bulge is made of flexible metal material, when the flexible metal is subjected to the pressure generated by the liquid condensation, it will deform to avoid being crushed by the flexible metal bulge 2. The flexible metal can usually return to its original shape after deformation. When the heat pipe air preheater works next time, the liquid heat transfer medium 3 becomes liquid after being heated, and the force on the flexible metal bulge 2 disappears, so it can return to its original shape. Even if the flexible metal bulge 2 is under force for a long time and cannot return to its original shape, it can also prevent the heat pipe wall from being flat and cause pits on the heat pipe wall.

[0022] The flexible metal bulge 2 is spherical crown-shaped.

[0023] The shape of the flexible metal bulge 2 is relatively regular, which helps to further increase the probability of forming a vaporization core of the liquid heat transfer medium 3 at the flexible metal bulge 2.

[0024] The liquid heat transfer medium 3 submerges all the flexible metal bulges 2.

[0025] When the liquid heat transfer medium 3 boils and submerges more flexible metal bulges 2, more pits will be submerged, and more sites will be available for the formation of vaporization nuclei more easily. Thus, when the liquid heat transfer medium 3 submerges all the flexible metal bulges 2, the utilization rate of the pits formed between the flexible metal bulges 2 can be higher, providing more sites for the formation of vaporization nuclei for the liquid heat transfer medium.

[0026] The heat pipe air preheater further includes fins 4, which are located outside the heat pipe 1 and are fixedly arranged on the pipe wall of the heat pipe 1.

[0027] By providing the fins 4, the heat transfer area of the heat pipe 1 can be expanded to a certain extent, enhancing the heat transfer effect of the heat pipe air preheater, effectively reducing the volume and weight of the heat pipe air preheater, saving consumables, and helping to reduce the cost of the heat pipe air preheater.

[0028] The working process of the present utility model: The high-temperature flue gas generated during the operation of the boiler enters the boiler flue gas passage through the flue gas outlet. The high-temperature flue gas heats the heat pipes located in the boiler flue gas passage. After the temperature of the heat pipes rises, it forms a heating effect on the liquid heat transfer medium 3 inside the heat pipes, which is equivalent to the flue gas heating the liquid heat transfer medium 3. When the liquid heat transfer medium 3 is heated and reaches the boiling point, it begins to boil and vaporize. The vapor formed will flow along the heat pipes into the boiler combustion-supporting air passage. The gas itself has a relatively high temperature. After it enters the boiler combustion-supporting air passage, it heats the air in the boiler combustion-supporting air passage. The temperature of the gas itself decreases and it condenses back into a liquid. The liquid flows back along the heat pipes into the boiler flue gas passage under the action of its own gravity and continues to be heated and boiled to form gas. In this way, the cycle continues, and the heat of the boiler flue gas is recovered to heat the combustion-supporting air.

[0029] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present utility model and are not restrictive. Although the present utility model has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in terms of form and details without departing from the scope defined by the claims of the present utility model.

Claims

1. A boiler heat pipe air preheater, characterized in that: The heat pipe air preheater includes a heat pipe (1). A plurality of through holes are formed in the left half section of the pipe wall of the heat pipe (1), and a flexible metal bulge (2) protruding into the interior of the heat pipe (1) is arranged at the positions of the through holes. A liquid heat transfer medium (3) is contained inside the heat pipe (1). During use, the heat pipe (1) is arranged obliquely or vertically, and the left half section of the heat pipe (1) is located at the lower end.

2. The boiler heat pipe air preheater according to claim 1, characterized in that: The flexible metal bulge (2) is in a spherical crown shape.

3. A boiler heat pipe air preheater according to any one of claims 1 or 2, characterized in that: The liquid heat transfer medium (3) submerges all the flexible metal bulges (2).

4. A boiler heat pipe air preheater according to claim 1, characterized in that: The heat pipe air preheater further includes fins (4). The fins (4) are located outside the heat pipe (1), and the fins (4) are fixedly arranged on the pipe wall of the heat pipe (1).

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