JP2001272180A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of a heat exchanger. SOLUTION: In the heat exchanger 15 effecting heat exchange between exhaust gas discharged out of a reducing furnace 19 and combustion air supplied into the reducing furnace 19, an exhaust gas discharging passage 33 is connected to heat storage furnaces 31, 32 through two sets of exhaust gas introducing passages 35, 36 switchably by a switching valve 34, while the ventilating passage 41 of a ventilation fan 30 is connected to the heat storage furnaces 31, 32 through two sets of combustion air introducing passages 43, 44 switchably by another switching valve 42 to supply the exhaust gas and air alternately into respective heat storage furnaces 31, 32 and effect heat exchange between both of them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger for exchanging heat between a combustion exhaust gas and a combustion gas, and more particularly to a pellet or briquette formed by granulating a mixed powder of an iron raw material and a reducing agent. It is suitable for use in a reduction furnace for producing reduced iron by reducing a product in a high-temperature atmosphere.

[0002]

2. Description of the Related Art FIG. 6 schematically shows a production process using a conventional reduced iron production apparatus.

In a conventional reduced iron production apparatus, as shown in FIG. 6, first, iron ore powder, coal powder, and a binder are mixed by a mixer (not shown), and the mixed powder is greened by a pelletizer 001. Granulated into balls (raw pellets) GB. Next, the green balls GB are put into a dryer 002 and dried by exhaust gas from a reduction furnace 004 described later. Then, the dried green balls GB are supplied to the reduction furnace 004 by the pellet supply device 003. On the other hand, the inside of the reduction furnace 004 is heated by a burner 005 and maintained in a high-temperature atmosphere, and the exhaust gas therein is exhausted by an exhaust duct 006.
Has been discharged from

[0004] Therefore, the green ball GB is supplied to the reduction furnace 00
Heated by the radiant heat from the furnace wall when moving inside 4, the coal reduces iron oxide in iron ore to produce pelleted reduced iron. Then, the reduced pellets are discharged by the pellet discharging device 007 and stored in the container 008. The exhaust gas discharged from the exhaust duct 006 is cooled by the primary cooler 009 and then sent to the heat exchanger 010, where the air that has undergone heat exchange and rises in temperature is reduced by the reduction furnace 004.
To be supplied to the furnace together with the fuel. On the other hand, the exhaust gas is cooled again by the secondary cooler 011 and part of the exhaust gas is used as drying air for the green balls GB as described above.
002, and then purified by the dust collector 012 and released to the atmosphere.

[0005]

As described above, in the conventional apparatus for producing reduced iron, the heat exchanger 010 controls the reduction furnace 004.
Heat is exchanged between the exhaust gas discharged from the furnace and the combustion air, and the heated combustion air is supplied to the reduction furnace 004. However, the temperature of the exhaust gas is as high as about 1300 ° C. and has large heat energy.
In the structure of No. 0, the heat-resistant temperature is about 900 ° C. or less, and the exhaust gas is cooled by the primary cooler 009 before being sent to the heat exchanger 010.

For this reason, the primary cooler 009 is required, and the exhaust gas processing system becomes large and complicated. In addition, the thermal energy held by the exhaust gas cannot be efficiently transmitted to the combustion air, and the combustion air required in the reduction furnace does not become hot, so that a large number of separate burners are required, and the apparatus is As the size increases, the fuel cost increases.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a heat exchanger in which heat exchange efficiency is improved.

[0008]

According to a first aspect of the present invention, there is provided a heat exchanger for performing heat exchange between a combustion exhaust gas and a combustion gas. A ceramic is used as a heat exchange member for temporarily storing heat of the combustion exhaust gas to heat the combustion gas.

The heat exchanger according to the second aspect of the present invention is characterized in that the temperature of the combustion exhaust gas is set to 1000 ° C. or higher.

Further, in the heat exchanger according to the third aspect of the present invention, the combustion exhaust gas is reduced in a high-temperature atmosphere by pellets or briquette agglomerates obtained by granulating a mixed powder of an iron raw material and a reducing agent. Exhaust gas discharged from a reduction furnace for producing reduced iron, and the combustion gas is used as combustion air supplied into the reduction furnace.

Further, in the heat exchanger according to a fourth aspect of the present invention, the heat exchange member is at least two regenerative furnaces, and the regenerative furnace is provided with an introduction path and an exhaust path for the combustion exhaust gas and the combustion gas. And a switching means for introducing the combustion exhaust gas only to the one regenerator and introducing the combustion gas only to the other regenerator in each of the introduction paths. Features.

The heat exchanger according to a fifth aspect of the present invention is characterized in that a soaking furnace is provided in a discharge path of the combustion gas discharged from the plurality of heat storage furnaces.

Further, in the heat exchanger according to the present invention, the heat exchanging member is made up of a large number of pebbles, and the pebbles are supplied to an upper heat storage section in the casing so as to be able to drop to a lower heat radiating section. The heat dissipating portion can be supplied again to the heat accumulating portion, and the heat accumulating portion communicates the introduction path and the exhaust passage of the combustion exhaust gas, and the heat dissipating portion communicates the introduction path and the exhaust passage of the combustion gas. It is characterized by.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration of a reduced iron manufacturing apparatus to which a heat exchanger according to a first embodiment of the present invention is applied, FIG. 2 is a graph showing a change in the inner wall temperature of a heat storage furnace, and FIG. And FIG. 4 is a graph showing the change in the heated air temperature in the soaking furnace.

In the apparatus for producing reduced iron according to the present embodiment,
As shown in FIG. 1, iron ore powder (iron raw material), coal powder (reducing agent), and limestone powder, which are raw materials for pellets, are supplied from hoppers 11, 12, and 13, respectively, and supplied from hopper 14. The mixture is mixed with the binder in the mixer 15. This mixed powder was pelletized with a pelletizer 16 to a diameter of 10
Green balls (raw pellets) GB having a size of about 20 mm are granulated, introduced into a dryer 17 and dried by exhaust gas from a reduction furnace 19 described later. Dry green ball GB
Is supplied to the reduction furnace 19 by the pellet supply device 20 via the conveyor 18.

A burner 21 is mounted on the reducing furnace 19, the inside of which is heated to maintain a high-temperature atmosphere, and exhaust gas can be discharged from an exhaust duct 22. Therefore, when the green ball GB moves inside the reduction furnace 19, it is heated to a high temperature inside, and the iron oxide in the iron ore is reduced by the coal, so that pellet-like reduced iron can be generated. Then, the reduced pellets are transferred to the pellet discharging device 2
By 3, it is carried out of the reduction furnace 19, stored in the container 24, and transported to the next step.

On the other hand, the exhaust gas discharged from the exhaust duct 22 is cooled to a predetermined temperature by the heat exchanger 25 and then circulated to the dryer 17 by the blower fan 26 to be used as a drying gas for the green balls GB. . afterwards,
The exhaust gas discharged from the dryer 17 is purified by a dust collector 27 and further sent to a chimney 29 by an exhaust fan 28.
Released to the atmosphere after desulfurization. On the other hand, the blower fan 3
The air sent to the heat exchanger 22 by 0 is heated here, sent to the reduction furnace 19, and supplied together with the fuel into the furnace.

In the heat exchanger 25, the two regenerative furnaces 31, 32 are made of ceramic refractory material, for example, are formed in a cylindrical shape, and the internal heat transfer area is set to have a predetermined area. As the ceramic refractory, for example, high alumina brick or silica brick may be used. A switching valve 34 is mounted at a downstream end of an exhaust gas exhaust passage 33 connected to the exhaust duct 22 of the reduction furnace 19, and the switching valve 34 is provided with two exhaust gas introduction passages 35 and 36. The ends are connected, and the ends are connected to one of the heat storage furnaces 31, 32, respectively. The other ends of the heat storage furnaces 31 and 32 are connected to the base ends of the exhaust gas discharge passages 37 and 38, and the front end is connected to the dryer 1 via a switching valve 39.
7 to the circulation path 40.

A switching valve 42 is mounted on the air passage 41 of the blower fan 30. The switching valve 42 is connected to the base ends of the two combustion air introduction paths 43 and 44, and the distal ends are respectively connected to the switching valves 42 and 44. It is connected to the other of the heat storage furnaces 31 and 32.
One of the heat storage furnaces 31 and 32 has a combustion air discharge passage 4.
The base ends of the tubes 5 and 46 are connected, and the front end is connected to a soaking furnace 49 via a switching valve 47 and a collecting passage 48, and further connected to a combustion air supply passage 50 to the reduction furnace 19. This soaking furnace 49 is desirably made of refractory bricks.

Therefore, the temperature of the exhaust gas immediately after being discharged from the exhaust duct 33 of the reduction furnace 19 is 1200 ° C. to 130 ° C.
0 ° C., and from the exhaust gas introduction path 35 (36) through the exhaust gas introduction path 35 (36) by the switching valve 34 through the exhaust gas discharge path 33.
2), and is sent from the circulation path 40 to the dryer 17 via the switching valve 39 through the exhaust gas discharge path 37 (38). Thus, the exhaust gas of 1200 ° C. to 1300 ° C.
1 (32), heat exchange is performed here, and the heat of the exhaust gas is temporarily stored in the heat storage furnace 31 (32).
And the exhaust gas can be cooled.

When the heat storage furnace 31 (32) is heated to a predetermined temperature or higher, air is blown by the blower fan 30 through the blower passage 41 and the combustion air introduction passage 43 is switched by the switching valve 42.
From (44), it is supplied into the regenerator 31 (32), passes through the combustion air discharge passage 45 (46), and is sent from the combustion air supply passage 50 to the reduction furnace 19 via the switching valve 47 and the collecting passage 48. By circulating the air in the heat storage furnace 31 (32) heated to a high temperature in this way, heat exchange is performed here, and the heat storage furnace 31 (32) is heated.
Air can be heated by the heat of (32) to be combustion air.

In the heat exchanger 25 of the present embodiment, the exhaust gas and the air are alternately supplied to the regenerators 31 and 32 so that the heat exchange between the two can be performed efficiently. That is,
First, the switching valve 34 connects the exhaust gas discharge path 33 and the exhaust gas introduction path 35, the switching valve 39 connects the exhaust gas discharge path 37 and the circulation path 40, and the switching valve 42
The communication between the blower passage 41 and the combustion air introduction passage 44 by means of
To communicate. In this state, the exhaust gas from the reduction furnace 19 is supplied into the regenerator 31 so that the heat of the exhaust gas is stored in the regenerator 31 while the exhaust gas is cooled. on the other hand,
The air from the blower fan 30 is supplied into the heat storage furnace 31 and is heated by the high-temperature heat storage furnace 31 to become combustion air.

When the temperature of the heat storage furnace 31 becomes lower than a predetermined temperature due to heating of the combustion air after a predetermined time elapses, and the temperature of the heat storage furnace 31 becomes higher than a predetermined temperature due to the heat of the exhaust gas, each of the switching valves 34, 39, 42, 47, and the exhaust gas exhaust path 3
3 and the exhaust gas introduction path 36, the exhaust gas exhaust path 38 and the circulation path 40, the ventilation path 41 and the combustion air introduction path 43, and the combustion air discharge path 45 and the collecting path 48. Then, the exhaust gas is supplied to the heat storage furnace 32 to be stored again, while the exhaust gas is cooled and the air is supplied to the heat storage furnace 31 to be heated.

By repeating this, heat exchange between the exhaust gas from the reduction furnace 19 and the combustion air sent to the reduction furnace 19 can be efficiently performed.

Here, with respect to the change in the inner wall temperature in the heat storage furnaces 31, 32, in the graph shown in FIG.
32 is heated to a predetermined temperature or higher, and each of the switching valves 34, 39,
Switching between 42 and 47, a (solid line) immediately after air was introduced into the heat storage furnaces 31 and 32, b (dotted line) after 20 minutes, 40
The minutes are indicated by c (two-dot chain line). Thus, it can be seen that the heat is stored at a high temperature on the outlet side of the combustion air, that is, on the inlet side of the exhaust gas, and does not decrease so much after an elapsed time of about 40 minutes. In the combustion air change at this time, in the graph shown in FIG.
A (solid line) immediately after the introduction into 32, b (dotted line) after 20 minutes, and c (two-dot chain line) after 40 minutes. As described above, the combustion air is heated to a high temperature by the heat storage of the heat storage furnaces 31 and 32 at the outlet side of the combustion air, and it can be seen that the heating energy has not decreased so much in the elapsed time of about 40 minutes.

Therefore, at the outlet side of the combustion air in the heat storage furnaces 31 and 32, the exhaust gas temperature of about 1300
It can be seen that the inner wall surface is heated (heat storage) to a temperature approximately equal to ° C, and the combustion air can be heated to a temperature approximately equal to approximately 1240 ° C. It can be seen that the heat exchanger 25 can be heated up to about 1130 ° C.), and the heat exchanger 25 with high heat exchange efficiency can be provided.

Further, in the heat exchanger 25, as can be seen from the graph of FIG. 3, the heating temperature of the combustion air discharged from the heat storage furnaces 31 and 32 decreases over time. After being introduced into the heating furnace 49, it is supplied to the reduction furnace 19. The graph shown in FIG.
It shows a change in temperature of the combustion air discharged from the furnaces 1 and 32. The one using the soaking furnace 49 is shown by a solid line, and the one without the soaking furnace 49 is shown by a dotted line. When the soaking furnace 49 is used as described above, the temperature change of the combustion air is reduced by 10%.
The temperature can be suppressed to 0 ° C. or less, and the variation in the temperature of the combustion air supplied to the reduction furnace 19 can be reduced, and the temperature control (combustion control of the burner 21) in the reduction furnace 19 can be facilitated.

As described above, in the heat exchanger 25 of the present embodiment, two heat storage furnaces 31 and 32 are provided, and heat exchange is performed by alternately supplying exhaust gas and air to the heat storage furnaces 31 and 32. Thereby, the heat exchange efficiency is improved. Therefore, reduction furnace 1
The temperature of the combustion air sent to the furnace 9 can be raised to a high temperature, and the amount of fuel in the reduction furnace 19 can be reduced to reduce the cost. In addition, the amount of exhaust gas from the reduction furnace 19 can be reduced by reducing the amount of fuel. And the exhaust gas treatment equipment can be made compact,
Operation costs can be reduced.

In the above embodiment, the heat storage furnace 3
Although two channels 1 and 32 are provided to switch the flow path of the exhaust gas and the air, the number of the heat storage furnaces may be three or more.

FIG. 5 shows a schematic configuration of a reduced iron production apparatus to which a heat exchanger according to a second embodiment of the present invention is applied. Note that members having the same functions as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description will be omitted.

In this embodiment, as shown in FIG. 5, in a heat exchanger 51 applied to an apparatus for producing reduced iron, a casing 52 has a vertical cylindrical shape, and a heat storage chamber 54 is formed by a bottom wall 53 at the top. Are formed, and a ceiling 55
Forms a heat radiation chamber 56. And the heat storage room 5
A supply chamber 58 is formed on the outer periphery of the fuel cell 4 through a communication hole 57.
Exhaust gas exhaust path (combustion exhaust gas introduction path) connected to
59 are connected. An exhaust gas outlet 60 is formed in the upper part of the heat storage chamber 54, and an exhaust gas outlet 61 is connected to the outlet 60. On the other hand, the heat radiating chamber 56
Is connected to the air passage 62 of the air blower fan 30,
Above 6, a discharge chamber 63 is defined by a bottom wall 53 and a ceiling 55, and a discharge port 64 of the discharge chamber 63 is connected to a combustion air supply path 65 to the reduction furnace 19.

Further, a large number of ceramic pebbles 66 as replacement members are filled in the heat storage chamber 54 and the heat radiation chamber 56 of the casing 52, and a pebble supply port 67 is formed in the upper part of the heat storage chamber 54. A pebble discharge port 68 is formed at a lower portion of the heat radiating chamber 56, and the heat storage chamber 54 and the heat radiating chamber 56 are connected by a communication passage 69, and a heat radiating chamber is provided between the pebble discharge port 68 and the pebble supply port 67. A circulation passage 70 is provided for returning the pebble 66 in 56 to the heat storage chamber 54.

Accordingly, the exhaust gas from the reduction furnace 19 is supplied to the supply chamber 58 of the casing 52 through the exhaust gas discharge path 59, and is supplied to the heat storage chamber 54 through the communication hole 57. In the heat storage chamber 54, the heat of the exhaust gas is stored in the pebble 66 filled in the heat storage chamber 54, and the high-temperature pebble 66 falls into the heat radiation chamber 56 through the communication passage 69, while the exhaust gas is cooled. Exhaust gas outlet 60
From the exhaust gas exhaust passage 61. On the other hand, when air is supplied from the blower fan 30 to the radiator chamber 56 through the blast passage 62, the air is heated by the pebble 66 heated to a high temperature in the radiator chamber 56, and the air becomes high temperature and the combustion air is discharged to the discharge chamber 63. To the reduction furnace 19 from the discharge port 64 through the combustion air supply path 65. The pebble 66 heated to a low temperature by heating the air in the heat radiating chamber 56 is returned to the heat storage chamber 54 through the circulation passage 70.

As described above, in the heat exchanger 51 of the present embodiment, the heat storage chamber 54 and the heat radiating chamber 56 are provided in the casing 51 and the pebble 66 is filled and circulates. By supplying the exhaust gas to store heat in the pebble 66 and supplying air to the heat radiating chamber 56 and performing heat exchange by heating with the pebble 66, the exhaust gas and the air are switched by the switching valve as in the above-described embodiment. It is not necessary to switch the flow path, the heat exchange processing can be performed continuously, and the heat exchange efficiency can be improved.

In each of the above-described embodiments, the heat exchanger of the present invention is applied to an apparatus for manufacturing reduced iron. However, the present invention is not limited to this, and may be applied to a heat exchanger such as a power plant.

[0037]

As described in detail in the above embodiment, according to the heat exchanger of the first aspect of the present invention, the heat exchanger for exchanging heat between the combustion exhaust gas and the combustion gas includes: Since ceramic is used as the heat exchange member for heating the combustion gas by temporarily storing the heat of the combustion exhaust gas, the combustion gas can be efficiently heated by the heat energy of the combustion exhaust gas, while the combustion exhaust gas can be efficiently heated. The gas can be cooled reliably, and the efficiency of heat exchange can be improved.

According to the heat exchanger of the second aspect of the present invention, the temperature of the combustion exhaust gas is set to 1000 ° C. or more.
By using a high temperature of the combustion exhaust gas, the heat exchange efficiency can be improved.

According to the heat exchanger of the present invention, the combustion exhaust gas is reduced in a high-temperature atmosphere by pellets or briquette-like agglomerates obtained by granulating a mixed powder of an iron raw material and a reducing agent. Since the exhaust gas discharged from the reduction furnace that produces reduced iron is used as the combustion gas supplied to the reduction furnace, the temperature of the combustion gas sent to the reduction furnace must be high. Can reduce the amount of fuel in the reduction furnace, thereby reducing costs. In addition, the reduction in the amount of fuel reduces the amount of exhaust gas from the reduction furnace, making the exhaust gas processing equipment compact. And operating costs can be reduced.

According to the heat exchanger of the fourth aspect of the present invention, the heat exchange member is at least two regenerators, and the regenerative furnace is provided with a combustion exhaust gas introduction path and a discharge path and introduces a combustion gas. And a discharge path, and switching means for introducing combustion exhaust gas into only one regenerator and introducing combustion gas only into the other regenerator in each of the introduction paths. By alternately introducing the combustion exhaust gas and the combustion gas into the fuel cell, the heat exchange efficiency between the two can be improved.

According to the heat exchanger of the present invention, since the soaking furnace is provided in the discharge path of the combustion gas discharged from the plurality of heat storage furnaces, the temperature change of the combustion air can be reduced. Therefore, temperature variation of the combustion air can be reduced to facilitate temperature control.

According to the heat exchanger of the present invention, the heat exchanging member is composed of a large number of pebbles, and the pebbles are supplied to the upper heat storage section in the casing so as to be able to drop to the lower heat radiating section. In addition, the heat release section can be supplied again to the heat storage section, and the heat storage section is connected to the combustion exhaust gas introduction path and discharge path, and the heat release section is connected to the combustion gas introduction path and discharge path. The heat exchange treatment with the combustion gas can be performed continuously, so that the working efficiency can be improved and the heat exchange efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for producing reduced iron to which a heat exchanger according to a first embodiment of the present invention is applied.

FIG. 2 is a graph showing a change in inner wall temperature of a heat storage furnace.

FIG. 3 is a graph showing a change in the temperature of heated air in a heat storage furnace.

FIG. 4 is a graph showing a change in heated air temperature in a soaking furnace.

FIG. 5 is a schematic configuration diagram of an apparatus for producing reduced iron to which a heat exchanger according to a second embodiment of the present invention is applied.

FIG. 6 is a schematic diagram illustrating a production process by a conventional reduced iron production apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 19 Reduction furnace 21 Burner 22 Exhaust duct 25 Heat exchanger 30 Blower fan 31 and 32 Heat storage furnace (heat exchange member) 33 Exhaust gas exhaust path 34, 39 Switching valve 35, 36 Exhaust gas introduction path 37, 38 Exhaust gas exhaust path 40 Circulation path 41 Blowing path 42,47 Switching valve 43,44 Combustion air introduction path 45,46 Combustion air discharge path 49 Soaking chamber 50 Combustion air supply path 51 Heat exchanger 52 Casing 54 Heat storage chamber 56 Heat radiation chamber 59 Exhaust gas discharge path (Introduction path of combustion exhaust gas) 61 Exhaust gas exhaust path 65 Combustion air supply path 66 Pebble (heat exchange member)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F27B 3/26 F27B 3/26 9/16 9/16 9/24 9/24 E F28D 17/02 F28D 17 / 02 19/02 19/02 // C22B 1/20 C22B 1/20 M (72) Inventor Koichi Hirata 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Invention Person Keiichi Sato 4-2-2 Kanon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Inside the Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd. F term (reference) 4K001 AA10 BA02 CA18 CA23 GA07 GB09 GB10 HA01 4K012 DE03 DE06 DE08 4K045 AA03 BA02 DA04 RB14 RB27 4K050 AA00 AA05 BA02 CA07 CD02 CD16 CE03 CF06 CG09 CG23 DA03 DA07 EA08 4K056 AA00 BA02 BB01 CA02 DA02 DA27 DA29 DA32 DB04 DB05 DB12 FA06

Claims (6)

[Claims] 1. A heat exchanger for exchanging heat between a combustion exhaust gas and a combustion gas, wherein the heat exchange member temporarily stores heat of the combustion exhaust gas to heat the combustion gas. A heat exchanger characterized by using ceramic as the material. 2. The heat exchanger according to claim 1, wherein the temperature of the combustion exhaust gas is 1000 ° C. or higher. 3. The heat exchanger according to claim 1, wherein the combustion exhaust gas is reduced in a high-temperature atmosphere by pellets or briquette-like agglomerates obtained by granulating a mixed powder of an iron raw material and a reducing agent. A heat exchanger comprising exhaust gas discharged from a reduction furnace for producing reduced iron and combustion air supplied to the inside of the reduction furnace. 4. The heat exchanger according to claim 1, wherein the heat exchange member is at least two regenerators, and the regenerator has an introduction path and an exhaust path for the combustion exhaust gas.
A switching means for providing an introduction path and an exhaust path for the combustion gas, and introducing the combustion exhaust gas to each of the introduction paths only to the one regenerator and introducing the combustion gas only to the other regenerator; A heat exchanger characterized by being provided. 5. The heat exchanger according to claim 4, wherein a soaking furnace is provided in a discharge path of the combustion gas discharged from the plurality of heat storage furnaces. 6. The heat exchanger according to claim 1, wherein the heat exchanging member is composed of a large number of pebbles, and the pebbles are supplied to an upper heat storage section in the casing so that the pebbles can be dropped to a lower heat radiating section. It is possible to supply the heat storage unit again from the heat radiating unit,
A heat exchanger, wherein the heat storage section communicates the introduction path and exhaust path of the combustion exhaust gas, and the heat radiation section communicates the introduction path and exhaust path of the combustion gas.