JP3860050B2 - Medium heat exchanger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a medium heat exchanger that recovers waste heat from high-temperature exhaust gas such as a melting furnace using a granular heat medium.
[0002]
[Prior art]
The medium heat exchanger that recovers waste heat from high-temperature exhaust gas such as a melting furnace has a small cross-section communicating part in which the bottom of the upper heat exchange chamber through which the high-temperature exhaust gas circulates is reduced to a cone shape such as a cone or a pyramid. There is a type in which the granular heat medium is communicated with the lower heat exchange chamber through which the low-temperature gas circulates, and the granular heat medium is passed from the upper heat exchange chamber to the lower heat exchange chamber through the communication portion to exchange heat in each heat exchange chamber. Note that the heat exchanged heat medium is conveyed back from the bottom of the lower heat exchange chamber to the upper portion of the upper heat exchange chamber for circulation.
[0003]
In the granular heat medium, in order to increase the ratio of the total heat transfer area to the total volume to ensure high heat exchange efficiency, alumina having a small particle diameter of about 1 to 2 mm (specific gravity ρ = 3.65). ) Particles are often used. The reason for using a lot of alumina particles is that the particles themselves are inexpensive and the specific gravity is relatively small, so that the cost of returning and conveying them to the upper upper heat exchange chamber is also low.
[0004]
Gasified metal chloride is contained in the high-temperature exhaust gas from the melting furnace or the like, and this gasified metal chloride liquefies around 600 to 700 ° C. and has high tackiness when the temperature is lowered. Adheres to the surface of the granular heat medium. The adhesion of the metal chloride to the surface of the heat medium often occurs in the vicinity of the communicating portion between the upper heat exchange chamber and the lower heat exchange chamber, which is just about 600 to 700 ° C.
[0005]
For this reason, when the metal chloride adheres to the surface of the heat medium in such a narrow cross-sectional area, the above-mentioned small mass granular heat medium adheres to the cone-shaped bottom of the upper heat exchange chamber, and this adhesion There is a problem that the entrance of the communication portion having a narrow cross-sectional area is blocked. When such a clogged state occurs, it is necessary to stop the operation of the heat exchanger and remove these attached heat medium.
[0006]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to prevent the communication portion entrance of the upper heat exchange chamber and the lower heat exchange chamber from being blocked without lowering the heat exchange efficiency.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is configured such that the bottom of the upper heat exchange chamber through which the high-temperature exhaust gas flows is reduced in a cone shape, and communicates with the lower heat exchange chamber through which the low-temperature gas flows through the communication section having a small cross section. The granular heat medium is passed from the upper heat exchange chamber to the lower heat exchange chamber through the communication section, and heat exchange is performed with the gas flowing through each of the heat exchange chambers. In a medium heat exchanger that is returned from the bottom of the exchange chamber to the top of the upper heat exchange chamber and circulated, the heat medium is divided into small mass standard particles that have a mass that is four times or more that of the standard particles. A configuration was adopted in which the particles were mixed, and the mixing ratio of the heavy particles was 5% by mass or more.
[0008]
In other words, the granular heat medium is a mixture of small mass standard particles and 5 mass% or more of heavy particles having a mass 4 times or more that of the standard particles. The standard particles to be attached to the cone-shaped bottom of the chamber are drawn into the movement of heavy particles with a large mass and smoothly flow into the communication section, and the heat medium is transferred to the lower heat exchange chamber without blocking the inlet of the communication section. It was made to fall to.
[0009]
The reason why the mass of the heavy particles is 4 times or more that of the standard particles and the mixing ratio thereof is 5 mass% or more is that when the mass of each heavy particle is less than 4 times and the mixing ratio is less than 5 mass%, This is because the inclusion of the standard particles due to the movement of the particles becomes insufficient. The mixing ratio of the heavy particles is desirably 20% by mass or less in order to ensure high heat exchange efficiency and return conveyance efficiency for circulation use.
[0010]
As a means for making the mass of the heavy particles 4 times or more that of the standard particles, a means for increasing the specific gravity or particle diameter of the heavy particles larger than that of the standard particles can be employed. Of course, both the specific gravity and the particle size may be increased.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3. 1 and 2 are the first embodiment. As shown in FIG. 1, the medium heat exchanger includes an upper heat exchange chamber 2 through which a high-temperature exhaust gas 1 from a melting furnace (not shown) flows, and a lower heat exchange chamber 4 through which a low-temperature gas 3 such as the atmosphere flows. Are arranged in a vertical direction, the bottom of the upper heat exchange chamber 2 is reduced in a cone shape, and communicated with the lower heat exchange chamber 4 through a communication section 5 having a small cross section. Each heat exchange chamber 2, 4 is provided with a plurality of trays 6, 7, and the granular heat medium 10 charged into the upper part of the upper heat exchange chamber 2 from the inlet 9 of the hopper 8 is an upper heat Contact with the hot exhaust gas 1 that sequentially falls to each tray 6 in the exchange chamber 2, the communication portion 5, and each tray 7 in the lower heat exchange chamber 4 and circulates from the vent 11 to the exhaust 12 in the upper heat exchange chamber 2. Then, the sensible heat is recovered, and the recovered sensible heat is discharged to the low temperature gas 3 flowing from the vent 13 to the exhaust port 14 in the lower heat exchange chamber 4 to exchange heat. A flow rate adjusting plate 15 that adjusts the flow rate of the heat medium 10 falling into the lower heat exchange chamber 4 is provided below the communication portion 5.
[0012]
The heat medium 10 collected at the bottom of the lower heat exchange chamber 4 through the heat exchange is conveyed from the discharge port 16 through the return path 17 to the upper hopper 8 by the air lifter 18 and circulated for use.
[0013]
This heat medium 10 is a mixture of 5 mass% of heavy particles 10b of chromium-based alloy steel having an average particle size of 1.5 mm and a specific gravity of 7.8 to standard alumina particles 10a having an average particle size of 1.2 mm and a specific gravity of 3.65. It is a thing. Incidentally, the mass of the heavy particle 10b is about 4.2 times that of the standard particle 10a.
[0014]
As shown in FIG. 2, the heat transfer medium 10 in which standard particles 10 a and heavy particles 10 b are mixed is filled in the reduced diameter bottom portion of the upper heat exchange chamber 2 and the communication portion 5 having a small cross section. The filled heat medium 10 also serves as a material seal for the upper heat exchange chamber 2 and the lower heat exchange chamber 4, and gradually moves downward to escape from the lower end of the communication portion 5. The heat medium 10 that has escaped from the communication portion 5 is dispersed to the surroundings by the Jinkasa flow rate adjusting plate 15 and falls into the lower heat exchange chamber 4.
[0015]
As described above, the temperature in the vicinity of the communication portion 5 is around 600 to 700 ° C., and the metal chloride contained in the high temperature exhaust gas 1 is liquefied and sticky, and adheres to the surface of the heat medium 10. For this reason, among the heat medium 10 that moves down the bottom of the upper heat exchange chamber 2, the standard particles 10a having a small mass try to adhere to the cone-shaped bottom because the adhesion of the metal chloride is greater than the gravity. To do. However, in this embodiment, the heavy particles 10b having a large mass entrain the standard particles 10a to be attached to the bottom portion and smoothly flow into the communication portion 5, so that each heat medium 10 adheres to the bottom portion or the communication portion. It falls from the communication part 5 to the lower heat exchange chamber 4 without closing the inlet of 5.
[0016]
The metal chloride adhered to the heat medium 10 solidifies and loses its adhesiveness when the temperature is further lowered. Therefore, as shown in FIG. 1, heat accumulated in the bottom of the lower heat exchange chamber 4 after heat exchange. The medium 10 loses the adhesiveness of the metal chloride adhering to its surface. In this embodiment, since there is a large mass difference between the standard particles 10a and the heavy particles 10b, a speed difference occurs between these particles when moving to the discharge port 16, and the rubbing effect between the particles The action of peeling off the metal chloride adhered and solidified on the surface also occurs. The peeled metal chloride is transported along the return path 17 by the air lifter 18 together with the heat medium 10 and enters the upper heat exchange chamber 2 from the hopper 8. The gas is discharged from the exhaust port 12 and collected by a bag filter (not shown) provided in the exhaust path.
[0017]
FIG. 3 shows a second embodiment. The structure of this medium heat exchanger is the same as that of the first embodiment shown in FIG. 1, and only the structure of the heat medium 10 is different. The heat medium 10 of this embodiment is a mixture of alumina standard particles 10a having an average particle diameter of 1.2 mm and specific gravity of 3.65, and 10% by mass of the same alumina weight particles 10b having an average particle diameter of 3.0 mm. The mass of the heavy particle 10b is about 15.6 times that of the standard particle 10a.
[0018]
Also in this embodiment, the heavy particles 10b having a large mass entrain the standard particles 10a having a small mass to be attached to the cone-shaped bottom portion of the upper heat exchange chamber 2 and smoothly flow into the communicating portion 5. 10 falls to the lower heat exchange chamber 4 from the communication part 5 without adhering to the bottom part or closing the inlet of the communication part 5.
[0019]
Further, in this embodiment, since there is a large particle size difference between the standard particles 10a and the heavy particles 10b, when the heat medium 10 accumulated at the bottom of the lower heat exchange chamber 4 is moved to the discharge port 16, these particles are moved. Not only does the mass difference cause a speed difference between the particles, but also the peripheral speed difference due to the rotation during the movement increases, and the effect of rubbing between the particles further increases, and the metal chloride adhered and solidified on the surface is reduced. More peeling.
[0020]
In each of the above-described embodiments, alumina is used as the standard particle of the heat medium. However, the standard particle is not limited to alumina as long as it has a relatively small specific gravity. Further, the heavy particles in the case of increasing the mass due to the difference in specific gravity are not limited to the chromium-based alloy steel used in the first embodiment.
[0021]
【The invention's effect】
As described above, in the medium heat exchanger according to the present invention, a granular heat medium is prepared by mixing 5 mass% or more of a weight particle having a mass of four times or more of this standard particle with a small mass of standard particles. Therefore, the standard particles that are going to adhere to the cone-shaped bottom of the upper heat exchange chamber due to the adhesive force of the metal chloride are drawn into the movement of heavy particles with a large mass and smoothly flow into the communication part. The heat medium can be dropped into the lower heat exchange chamber without being blocked, and the heat exchanger can be stably operated for a long time.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a medium heat exchanger according to a first embodiment. FIG. 2 is an enlarged longitudinal sectional view of a main part of FIG. 1. FIG. 3 is an essential part of a medium heat exchanger according to a second embodiment. Expanded longitudinal section [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 High temperature exhaust gas 2 Upper heat exchange chamber 3 Low temperature gas 4 Lower heat exchange chamber 5 Communication part 6, 7 Tray 8 Hopper 9 Inlet 10 Heat medium 10a Standard particle 10b Weight particle 11 Vent 12 Exhaust 13 13 Vent 14 Exhaust 15 Flow control plate 16 Discharge port 17 Return path 18 Air lifter

Claims (3)

The bottom of the upper heat exchange chamber through which the high-temperature exhaust gas flows is reduced in a cone shape, communicated with the lower heat exchange chamber through which the low-temperature gas flows through a small cross-section communicating portion, and the granular heat medium is transferred from the upper heat exchange chamber to the above-mentioned It is passed through the lower heat exchange chamber at the communication section to exchange heat with the gas flowing through each of the heat exchange chambers, and the heat exchanged heat medium is returned from the bottom of the lower heat exchange chamber to the upper portion of the upper heat exchange chamber. In a medium type heat exchanger that is transported and circulated, the heat medium is a mixture of heavy particles having a mass that is four times or more of the standard particles mixed with small standard particles, and the mixing ratio of the heavy particles Is a medium type heat exchanger characterized in that the content is 5% by mass or more. The medium heat exchanger according to claim 1, wherein the heavy particles have a specific gravity larger than that of the standard particles. The medium heat exchanger according to claim 1 or 2, wherein the heavy particles have a larger particle size than the standard particles.

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