JP2001056197A - Heat transfer tube for heat exchange - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat transfer tube for heat exchange, whose metallic surface will not be corroded even when the tube is exposed to high-temperature corrosive environment for a long period of time and which is capable of recovering more high-temperature heat compared with a conventional heat transfer tube. SOLUTION: A tube 1, through which fluid to be heated flows, is constituted of a heat resistant alloy and the outside of the heat resistant alloy tube 1 is coated with a cover material 3, consisting of a ceramics alloy composite material, through a thermal expansion cushioning material 2 while the thermal expansion cushioning material 2 is provided with a non-adhesive structure with respect to the heat resistant alloy tube 1 or the cover material 3 made of the ceramics alloy composite material. Further, the heat transfer tube for heat exchange is provided with a three-layered structure, in which at least a part of the thermal expansion cushioning material 2 is contacted with the heat resistant alloy tube 1 and at least a part of the cover material 3, made of the ceramics alloy composite material, is contacted with the thermal expansion cushioning material 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to municipal solid waste, coal,
The present invention relates to an electric heat exchanger tube for heat exchange in a heat recovery / utilization system that recovers thermal energy from high temperature combustion exhaust gas of sewage treatment, papermaking sludge, and other industrial wastes through a fluid such as steam or air to generate power.

[0002]

2. Description of the Related Art Exhaust gas generated when municipal solid waste or industrial waste is incinerated contains hydrogen chloride gas, NaCl containing sodium, potassium, etc., KCl, Na ₂ SO _{4 and} other basic salts. The corrosiveness of hydrogen chloride and basic salts increases as the temperature increases. Therefore, in a waste heat boiler that recovers heat from the combustion exhaust gas of municipal solid waste and industrial waste, the steam flowing through the heat exchange tube is generally used to reduce the damage of corrosion damage due to hydrogen chloride and basic salts. It is kept below 300 ° C.

Therefore, in order to recover higher-temperature heat energy from this corrosive environment, as disclosed in JP-A-10-274401, the outer surface of a boiler tube made of a heat-resistant metal is sprayed by a thermal spraying method. A method has been devised in which a heat exchange tube is coated with a ceramic film by a chemical vapor deposition method or a chemical vapor deposition method to improve the high-temperature corrosion resistance. Since the boiler tube is based on metal, it has the toughness necessary for the heat exchange tube, and the surface has
In general, high corrosion resistance in high-temperature exhaust gas was ensured by using ceramics that have excellent high-temperature strength and low wettability with salts and exhibit excellent high-temperature corrosion performance.

[0004]

However, in the above-described conventional heat exchange tubes, since the ceramics and the metal are bonded by a thermal spraying method or a vapor deposition method, if they are exposed to a high-temperature corrosive atmosphere for a long time. Under the influence of the difference in the coefficient of thermal expansion between the ceramic and the metal, the ceramic is easily separated from the metal surface. Then, the metal part where the ceramic has been peeled off starts to corrode. For this reason, there is a problem that this method is insufficient as a method for reliably preventing corrosion of the heat exchange tube.

Accordingly, the present invention has been made to solve the problem of the separation of ceramics and metal due to the difference in thermal expansion without lowering the thermal conductivity. An object of the present invention is to provide a heat exchanger tube for heat exchange that can recover heat at a higher temperature than conventional ones without corrosion of the surface.

[0006]

A heat exchange tube for heat exchange according to the present invention is provided in a high temperature gas atmosphere, and performs heat exchange from the high temperature gas to a fluid to be heated in the heat transfer tube. The pipe through which the fluid to be heated flows is made of a heat-resistant alloy,
The outside of the heat-resistant alloy pipe is covered with a cover material made of a ceramic alloy composite material via a thermal expansion buffer material, and the thermal expansion buffer material is provided on the cover material made of the ceramic alloy composite material and / or the heat-resistant alloy pipe. In a non-adhesive structure, at least a part of the heat-resistant alloy tube and the thermal expansion buffer material are in contact with each other, and further, from the three-layer structure in which the thermal expansion buffer material and at least a part of the ceramic alloy composite material cover material are in contact. (Claim 1).

[0007] With this configuration, the heat-resistant alloy pipe and the cover material made of the ceramic alloy composite material are exposed to a high-temperature atmosphere and are not adhered to each other even if they are thermally expanded in the pipe axis direction. The alloy pipe and the cover material made of the ceramic alloy composite material are not damaged by mutual shearing force. Also, even if the heat-resistant alloy tube expands in the radial direction,
The expansion in the radial direction is absorbed by the thermal expansion buffer material of the intermediate layer, and the cover material made of the ceramic alloy composite material is not damaged. In addition, the thermal expansion buffer and the cover material made of ceramic alloy composite material, or the thermal expansion buffer and the heat-resistant alloy tube are in contact but not adhered to each other. It has a structure that is strong against thermal shocks. Therefore, with this three-layer structure, the heat energy of the high-temperature fluid existing outside the ceramic alloy composite material cover material can be stably transferred to the heated fluid flowing inside the heat-resistant alloy tube for a long time. .

With regard to the heat transfer coefficient, the structure of the present invention is such that at least a portion of the heat-resistant alloy tube and the thermal expansion buffer material come into contact with each other, and further, at least a portion of the ceramic alloy composite material cover material comes into contact with the thermal expansion buffer material. Because of the three-layer structure, the thermal conductivity between the ceramic alloy composite material cover material and the heat-resistant alloy tube is prevented from lowering. Almost the entire inner surface of the ceramic alloy composite cover material, and
It is more preferable that almost the entire outer surface of the heat-resistant alloy tube comes into contact with the thermal expansion buffer material serving as the intermediate layer in terms of improving the thermal conductivity. If there is no thermal expansion buffer and the cover material made of the ceramic alloy composite material and the heat-resistant alloy pipe are completely separated without contact, that is, if there is a gap, a gas heat insulating layer is formed there. This is not preferable because the thermal conductivity sharply decreases.

Here, the heat-resistant alloy which is the material of the tube through which the fluid to be heated flows is, for example, carbon steel / alloy steel for boilers,
Alternatively, stainless steel, heat-resistant steel, Ni-based / Co-based heat-resistant alloys (Inconel, Hastelloy, stellite, etc.) and the like, and chromium, which is a high melting point metal, are also suitable.
Furthermore, the ceramic alloy composite material constituting the cover material can be selected from a wide range of oxides, carbides, nitrides, borides, silicides, carbon, and the like, and mixtures thereof. For example, Al ₂ O ₃ or Sialon (SiAlNO) is used as an oxide, and SiC or B is used as a carbide.
₄ C, AlN as nitride, Si ₃ N _4, T as borides
iB ₂ and MoSi are suitable as silicide.

In the present invention, the thermal expansion buffer is made of a material such as fibers, powders, films and tapes containing boron, carbon or aluminum as a main component.
It is characterized by comprising a thermal expansion absorption layer having voids formed on the outer surface of the heat-resistant alloy tube or the inner surface of the ceramic alloy composite material cover material (claim 2).

According to this configuration, the volume ratio of the voids in the absorption layer changes with respect to the thermal expansion in the tube axis direction and the radial direction of the heat-resistant alloy tube, so that the thermal expansion buffer is made of the heat-resistant alloy tube and the ceramic alloy composite material. The difference in thermal expansion of the cover material is absorbed, and damage to the ceramic alloy composite material cover material due to thermal shock can be prevented. The thermal expansion absorbing layer having voids may be formed on either the outer surface of the heat-resistant alloy tube or the inner surface of the ceramic alloy composite material cover material. Such a thermal expansion absorbing layer can be formed by using a material such as a fiber, a powder, a film, and a tape mainly containing boron, carbon, or aluminum.

Further, the ceramic alloy composite material constituting the cover material in the present invention contains Al and AlN,
AlN of 1 wt% or more and 90 wt% or less, (Al + AlN + A
(ON) is a total ratio of 50 wt% or more and 100 wt% or less (claim 3).

AlN, which is aluminum nitride, is a material having excellent corrosion resistance to air oxidation and corrosion resistance to various molten metals such as molten steel among ceramic materials. In an inert atmosphere, it is also excellent in corrosion resistance to various molten slags such as blast furnace slag. Are better. In addition, it has relatively high hardness, so that it has excellent wear resistance. Further, it has an extremely high thermal conductivity, a low coefficient of thermal expansion, and a relatively low elastic modulus, so that it has a feature that is relatively resistant to thermal shock. As described above, AlN is a material having both excellent corrosion resistance and wear resistance and relatively excellent thermal shock resistance.

[0014] Along with AlN, metallic aluminum A
1 is also a material having extremely good heat conduction, is a metal that is advantageous for reducing thermal shock, and is suitable as a component of a heat transfer tube. In the manufacturing process of ceramic alloy composite material cover material, changes to AlN reacts with N ₂ atmosphere Many Al, become configuration Al is dispersed unreacted during AlN, A
1N enhances the bonding force between the particles.

With this configuration, even if the sintered body receives a thermal shock, AlN has a function of preventing shape deformation, and Al surrounded by AlN has a function of reducing the thermal shock. Therefore, in order to maintain this function, AlN must be contained at least 1 wt% or more. If the content of AlN is less than 1 wt%, the bonding force between the particles is small and insufficient, and 90 wt%.
Exceeding the ratio is undesirable because the properties of the ceramic alloy composite material become closer to ceramics and become brittle. Therefore, the content ratio of AlN is set to 1 wt% or more and 90 wt% or less.

In the ceramic alloy composite material, Al and AlON are dispersed in AlN. (Al
When the content weight ratio of (+ AlN + AlON) is 50 wt% or more and 100 wt% or less, the ceramic alloy composite material cover material can maintain high thermal shock resistance while having thermal deformation characteristics. In addition, since nitrides containing aluminum have poor wettability to oxide dust contained in high-temperature exhaust gas, dusts are unlikely to adhere to the ceramic alloy composite material cover material if contained in a considerable amount. It has the characteristic of becoming. Therefore, (A
If the content ratio of (l + AlN + AlON) is 50 wt% or more, the property of preventing dust adhesion can be effectively exhibited. In the production of the heat transfer tube, AlO
Eliminate N, and the weight ratio of Al and AlN alone is 50wt
% Or more and 100% by weight or less.

Here, AlON means Al, O, N
Is a general term for solid liquids such as Al ₁₁ O ₁₅ N, AlO
N, Al ₁₉₈ O ₂₈₈ N ₄ , Al ₂₇ O ₃₉ N, Al ₁₀ N ₈ O ₃ ,
Al ₉ O ₃ N ₇ , SiAl ₇ O ₂ N ₇ and Si ₃ Al ₃ O _4.5 N ₅ are mentioned.

Further, in the present invention, a release agent comprising a compound containing boron or carbon is applied to the outer surface of the heat-resistant alloy tube (claim 4).

By applying the release agent, the slip between the heat-resistant alloy tube and the cover material made of the ceramic alloy composite material is improved, and the elongation due to the difference in thermal expansion between the two members becomes smoother.

Further, the present invention is characterized in that the porosity of the ceramic alloy composite material is 2% or more and 60% or less (claim 5).

In the production of a cover material made of a ceramic alloy composite material, in order to reduce the porosity to less than 2%, a high-temperature and high-pressure atmosphere is required in the production process, and the production cost rises sharply. Pores in the ceramic alloy composite material are not simple circular holes but have irregular shapes.
Their sizes range from sub-micron or less to several hundred microns in line-to-line distance. In a ceramic alloy composite material having such pores, if the porosity is larger than 60%, dust containing a basic salt easily penetrates into the ceramic alloy composite material, and the corrosion effect reaches even the heat-resistant alloy pipe. Therefore, the lower limit of the porosity is preferably 2%, and the upper limit is preferably 60%.

[0022]

FIG. 1 shows a cross section of a heat exchanger tube for heat exchange according to an embodiment of the present invention (a partially enlarged cross-sectional view is also shown). The outside of a tubular body 1 made of a heat-resistant alloy is covered with a cover material 3 made of a ceramic alloy composite material via a thermal expansion buffer material 2, and these three members 1, 2, and 3 form a three-layer structure. The material 2 has a non-adhesive structure to the cover material 3 made of a ceramic alloy composite material and / or the heat-resistant alloy tube 1.

A high-temperature gas flows outside the outer surface of the cover material 3 made of a ceramic alloy composite material, and a fluid to be heated passes inside the heat-resistant alloy tube 1. The temperature of the hot gas is 400 ° C ~ 1
At 200 ° C., a ceramic alloy composite material forming the cover material 3 is selected depending on the gas atmosphere conditions.

The high-temperature exhaust gas contains HCl and / or SOx. When a high-temperature dust collecting device having an exhaust gas temperature of 300 ° C. or higher is installed in an exhaust gas treatment line, the heat exchange tube for heat exchange of the present invention can be used for high-temperature exhaust gas after dust removal. The fluid to be heated flowing in the heat exchange tube for heat exchange of the present invention represents a combustion exhaust gas containing air, water vapor, and ₂ to 25 vol% (wet basis) of CO _2. The steam can be heated to about 550 ° C. Also, the fluid to be heated can be up to 100
It was confirmed that pressurization up to ata was possible. The thickness of the heat-resistant alloy tube 1 is 3 to 10 mm, and the thickness of the thermal expansion buffer 2 is 0.1 to 8 mm.
Preferably, the thickness of the ceramic alloy composite material cover material 3 is 3 to 20 mm. Heat-resistant alloy tube 1, thermal expansion buffer 2, cover material 3 made of ceramic alloy composite material
If the thickness of each of the heat exchangers is larger than the upper limit value, it becomes impossible to obtain a heat transfer coefficient having a practically significant design as a heat exchanger.
On the other hand, when the heat transfer tubes are smaller than the respective lower limit values, the heat transfer tubes cannot withstand thermal shock and are easily damaged.

Cover material 3 made of ceramic alloy composite material
As shown in FIG. 1, the thermal expansion buffer 2 covers the outside of the heat-resistant alloy tube 1 wrapped in the thermal expansion buffer 2, and the thermal expansion buffer 2 is provided between the ceramic alloy composite cover material 3 and the heat-resistant alloy tube 1. It has an intervening structure. The heat exchange tube for heat exchange of the present invention does not use a method in which ceramics or a corrosion-resistant alloy is bonded to the outer surface of the heat-resistant alloy tube 1 by spraying or vapor deposition or other methods. Since it has a covered shape, even if it is exposed to a high temperature and the heat-resistant alloy pipe 1 expands in the pipe axis direction and the radial direction, it is absorbed by the thermal expansion buffer 2 and the ceramic alloy composite material cover 3 It does not damage the structure. The cover material 3 made of the ceramic alloy composite material and the heat-resistant alloy tube 1 do not need to be a perfect circle, but an eccentric circle,
It may be oval, square or distorted. Also,
Heat-resistant alloy tube 1 and ceramic alloy composite material cover material 3
However, they need not be concentric. Further, the outer surface roughness of the heat-resistant alloy tube 1 may be rough or smooth.

The larger the contact area between the outer surface of the heat-resistant alloy tube 1 and the inner surface of the thermal expansion buffer 2 and the inner surface of the ceramic alloy composite cover material 3 and the outer surface of the thermal expansion buffer 2, Heat transfer from the high-temperature exhaust gas flowing outside to the fluid to be heated in the heat-resistant alloy tube 1 increases.

As the thermal expansion buffer 2, a material containing boron, carbon, or aluminum as a main component is used. Using these materials, a thermal expansion absorbing layer having a void is formed on the outer surface of the heat-resistant alloy tube 1 or the inner surface of the ceramic alloy composite material cover material 3. As a material for forming the thermal expansion absorbing layer, for example, a film containing carbon fiber, boron, or carbon, or an aluminum foil is preferable. In addition, a fine powder of plastic is sprayed on the heat-resistant alloy pipe 1 or
Alternatively, a tape containing carbon is wrapped around the heat-resistant alloy tube 1, and a low-boiling-point medium is volatilized from these components in a heat process for manufacturing the heat transfer tube of the present invention, and the carbon-based material also functions as a thermal expansion buffer. It doesn't matter. Since the thermal expansion buffer 2 is used to absorb the difference in thermal expansion between the heat-resistant alloy tube 1 and the cover material 2 made of the ceramic alloy composite material, the thermal expansion buffer 2 has voids, and the volume ratio changes. Performs this function.

Among ceramic alloy composite materials, a material composed of AIN + Al + AlON mainly containing aluminum element is most preferable for the heat transfer tube of the present invention in terms of performance. Because, in the present invention, the ceramic alloy composite material is desired to have high-temperature corrosion resistance of ceramic properties and ductility of alloy properties, but in this regard, the aluminum element is compared with the main elements forming other ceramic alloy composite materials. Optimum in ductility. Also, the contact surface between the heat-resistant alloy and the ceramic alloy composite material has the advantage that the rate of damage during expansion and contraction is smaller than that of other ceramic alloy composite materials by using an aluminum-based ceramic alloy composite material with excellent ductility. I have.

The ceramic alloy composite material mainly containing aluminum element is obtained by, for example, pressing a mixed powder of a low-purity Al source powder and a high-purity Al source powder and sintering the compact. Can be The low-purity Al source powder includes, for example, Si, M without metal Al or Al alloy powder.
It may contain an alloying element such as g. The high-purity Al source powder contains, for example, 90 wt% or more of Al. The filling obtained by molding these mixed powders is heated in a nitrogen atmosphere. Al in the powder melts (pure Al has a melting point of 660
Is a ° C., Al-Mg alloy has a melting point lowered to a maximum 450 ° C., in the Al-Si alloy melting point is lowered to a maximum 577 ° C.), is reached 680 ° C., Al a certain amount of atmosphere of N ₂ And AIN is converted to AIN, and a small amount of unreacted Al is dispersed in AIN. Since AlN having ceramic properties forms a film around Al, the commercialized AIN + Al + AlON ceramic alloy composite material cover material 3 does not melt and break its shape even when exposed to a high temperature higher than the melting point of Al. Absent. Further, since the degree of nitriding can be controlled by setting the temperature and pressure during molding and during heating, the AIN concentration that enhances the ceramic properties can be adjusted according to the conditions of the high-temperature exhaust gas and the amount of heat recovered. If the AIN or Al concentration cannot be set to the set value during molding and heating, AI
N or Al may be supplied between the ceramic alloy composite material and the heat-resistant alloy.

Ceramics mainly composed of aluminum element
In addition to AlN and Al, heat resistant alloys
May be blended as long as the substance is not suitable. That is, Ti
O_Two, ZrO_Two, Cr_TwoO_Three, Al_TwoO_Three, SiO_Two, Y
_TwoO_Three, CeO_Two, Sc_TwoO_ThreeOne selected from
Is more than one oxide and also less of these oxides
A composite oxide containing at least one may be contained. Also, B
N, MgB_Two, CaB₆, TiB _Two, ZrB_Two, AlB_Twoof
Even if one or more borides selected from among them enter
Good. Also, B_FourC, TiC, ZrC, Cr_ThreeC_Two, Al_Four
C_ThreeOne or more carbonizations selected from, SiC
Things may enter. Also, TiN, ZrN, Cr _TwoN,
Si_ThreeN_FourOne or more nitrides selected from
You may enter. Si_TwoN_TwoContains oxynitride represented by O
You may. Regarding the composition, in this invention, any composition
There may be. Also, part of Al in AlON is replaced with Si.
It may be exchanged. However, the molar ratio of Si / Al is 1.0
The following is preferred from the viewpoint of corrosion resistance.

When exposed to a high temperature, the outer surface of the heat-resistant alloy tube 1 is coated with BN or the like to improve the mutual slip between the outer surface of the heat-resistant alloy tube 1 and the inner surface of the ceramic alloy composite cover material 2. A compound containing boron or carbon such as B ₄ C is applied. This functions as a release agent that more effectively prevents the adhesion between the ceramic material and the metal and improves the slip of each. The coating thickness is preferably 1 to 60 microns.

The high-temperature exhaust gas contains H as a corrosive substance.
There is a condensate composed of a gaseous substance such as Cl or SOx and a basic salt such as NaCl or KC1. This condensate forms submicrons on the small scale and forms aggregates on the large scale.
It has a size of about 0 microns. In order to reduce the cost of the heat exchange tube for heat exchange of the present invention, it is effective to increase the porosity of the ceramic alloy composite material to 2% or more. Is likely to erode into ceramic alloy composites, empirically 60
%, The effect of the present invention cannot be exhibited.

FIG. 2 shows a side view and a cross section of the heat exchanger tube for heat exchange according to the present invention. A heat transfer tube for heat exchange is set in an atmosphere in which a high-temperature gas flows, and a fluid to be heated enters the inside of the heat-resistant alloy tube 1 from one end and escapes to the other end. Basically, the outer periphery of the heat-resistant alloy tube 1 exposed to the high-temperature gas is covered by a ceramic alloy composite material cover material 3 via a thermal expansion buffer material 2. As described above, the thermal expansion buffer 2 has a non-adhesive structure with respect to the ceramic alloy composite cover material 3 and / or the heat-resistant alloy tube 1.

The flow velocity of the fluid to be heated in the pipe is in accordance with the waste combustion or coal combustion boiler, but the flow velocity may be changed to a lower speed or a higher speed depending on the purpose. Heat-resistant alloy tube 1 through which the fluid to be heated of the heat transfer tube for heat exchange flows 1
The pipe diameter of the pipe may be any number as long as the fluid to be heated flows.
It is preferable to make it 0 A in terms of manufacturing. The length of the heat exchange tube is preferably 1 m to 6 m. When the heat exchange tube for heat exchange becomes long, the amount of deflection of the heat-resistant alloy tube 1 increases, and there is a fear that the ceramic alloy composite material of the cover material 3 is cracked.
In this case, the problem can be solved by providing a column for supporting the cover material 3 made of a ceramic alloy material from the outside and reducing the amount of deflection of the heat-resistant alloy tube 1. In addition, as can be seen from FIG. 2, a long heat transfer tube can be made by welding both ends of the heat-resistant alloy tube 1 that is not covered with the ceramic alloy composite material of the short heat transfer tube.

FIGS. 3 and 4 show another example of the configuration of the heat exchanger tube for heat exchange obtained from the present invention. FIG. 3 shows a state in which one end of the heat exchange heat transfer tube is closed, and the fluid to be heated is caused to flow through the heat resistant tube 4 provided in the heat resistant alloy tube 1. In the structure in which the fluid to be heated is heated, all portions exposed to a high-temperature gas that applies heat to the fluid to be heated are covered with a cover material 3 made of a ceramic alloy composite material. In the case of this type, the outer diameter of the heat exchange tube for heat exchange is preferably φ30 to 200 mm.

FIG. 4 shows a heat-resistant alloy tube 1 through which a fluid to be heated flows.
Is formed in a U-shape, and the outer portion including the bent portion is covered with a cover material 3 made of a ceramic alloy composite material. The U-shaped bent portion requires more voids 5 because the thermal expansion deformation of the heat-resistant alloy and the ceramic alloy composite material is more complicated than that of the heat exchange tube for heat exchange having a straight tube shape.

[0037]

[Examples] (1) In a garbage incineration pilot plant for treating municipal waste and industrial waste, about 95
The following several types of heat exchange tubes for heat exchange were inserted into a high-temperature exhaust gas at 0 ° C. to about 650 ° C. Heat-resistant alloy pipe: SUS304-15A Thermal expansion buffer: Layer mainly composed of Al foil, thickness 1 to 1
2mm ceramic alloy composite material cover material: Al + AlN +
AlON-90 wt% or more, wall thickness -4 to 10 mm, porosity 4
0% heat-resistant alloy tube: SUS304-20A Thermal expansion buffer: Carbon fiber equivalent, thickness 0.2 to 2 mm Ceramic alloy composite material cover material: Al + AlN +
AlON-90 wt% or more, wall thickness-3 to 8 mm, porosity 20
% Heat-resistant alloy tube: SUS304-20A, outer surface is coated with BN Thermal expansion buffer: Carbon fiber equivalent, 0.2 to 2 mm thick Cover material made of ceramic alloy composite material: Al10AlN +
AlON-90 wt% or more, wall thickness-3 to 8 mm, porosity 20
% Heat-resistant alloy tube: SUS304-20A Thermal expansion buffer material: Carbon fiber equivalent, thickness 1-2 mm Ceramic alloy composite material cover material: Al ₂ O ₃ -80
wt% or more, the thickness -2～4Mm, the main component of the non-N ₂ of porosity 30% flue _{gas, O 2: 2~16 (vol,} dr
y)%, HCl: 200 to 600 (vol, dry) ppm, SO
x: max 300 (vol, dry) ppm, CO ₂ : 4 to 19 (vol, dry)
dry)%, which is a general exhaust gas atmosphere generated when municipal waste and industrial waste are burned.

As a result of the exposure test, no crack occurred in the ceramic alloy composite material cover material under any conditions. After the exposure test for 1200 hours, each heat transfer tube was taken out and its cross section was observed.
The cross section of the heat transfer tube coated with
It was found that the slip of the N-coat and the cover material made of the ceramic alloy composite material was smoother than that of the heat transfer tube. Inlet temperature 280 ° C to 400 ° C as fluid to be heated
When steam is used, at all the conditions (1) to (5), at the outlet of the heat exchange tube group, 540 ° C. or higher, 100
I found the possibility of ata. When air or waste combustion exhaust gas is used as the fluid to be heated, 1000 to 400
It was confirmed that 0 mmAq of air and 50 to 400 mmAq of waste flue gas could be heated up to 800 ° C.
However, since the cover material made of the ceramic alloy composite material of the heat transfer tube is mainly composed of Al ₂ O ₃ having relatively low thermal conductivity,
The heat transfer coefficient was lower than that of the heat transfer tube.

(2) Municipal waste is partially oxidized to about 1000
Heat-resistant alloy tube: heat-resistant tube for boiler STBA28-20A Thermal expansion buffer: carbon fiber of 80 wt% or more, thickness 0.5 to
3mm ceramic alloy composite cover material: Al + AIN-
86 wt%, Al ₂ O ₃ -6 wt%, wall thickness -4 to 5 mm, porosity 25% Heat-resistant alloy tube: Heat-resistant tube for boiler STBA28-20A Thermal expansion buffer: 80% by weight or more carbon fiber, 1-3 mm thick ceramics Alloy composite cover material: SiC-95wt
%, A heat exchange tube having a wall thickness of -4 to 5 mm and a porosity of 2% was inserted. The fluid to be heated is steam and air.

As a result of conducting a heat exchange test in a reducing atmosphere having a CO concentration of 5 to 15 (vol, dry)%, since the high-temperature gas was a reducing gas, SiC and AIN were almost oxidized and deteriorated. No good heat exchange could be performed.

(3) Two types of heat-resistant alloy tubes: heat-resistant tubes for boilers STBA28-40A and 65A in the flue gas of coal, sewage sludge dewatering cake, and dry sludge incinerator Thermal expansion support material: 80% by weight or more of carbon Fine powder / fiber mixed layer,
0.2-4mm thick ceramic alloy composite material cover material: SiC-95wt% or more, wall thickness-about 7mm, coaxial tube shape (equivalent to Fig. 3) Heat-resistant alloy tube: Two types of heat-resistant tubes for boilers STBA28-20A and 50A Thermal expansion buffer material: Fine powder layer of boron 80wt% or more, thickness 0.3
~ 2mm Ceramic alloy composite cover material: Al ₂ O ₃ -95
wt% or more, wall thickness-about 4mm, coaxial tube shape (equivalent to Fig. 3), heat-resistant alloy tube: heat-resistant tube for boiler STBA28-15A and 20A, thermal expansion buffer material: carbon fiber of 80wt% or more, thickness 0 .4 ~
1mm ceramic alloy composite material cover material: Al + AIN-
A U-tube (equivalent to FIG. 4) heat exchange tube for heat exchange having a thickness of -6 to 8 mm and 90% or more was inserted.

As a result of the test, the combustion exhaust gas of coal and sewage sludge contains several hundred (vol, dry) ppm of SOx. Even under these conditions, the heat transfer tube is not corroded and the power generation efficiency is 30% or more. It has been found that it is possible to recover high-temperature and high-pressure steam and to recover high-temperature air and high-temperature combustion exhaust gas.

[0043]

As described above, the heat exchanger tube for heat exchange of the present invention has excellent toughness of a tube made of a heat-resistant alloy and the properties of both ceramics and metal constituting a cover material covering its outer surface. The ceramic alloy composite material has an excellent high-temperature corrosion resistance, and a thermal expansion buffer material is provided between both members to absorb a difference in thermal expansion, and the thermal expansion buffer material is a ceramic alloy composite material cover material and / or Since it has a non-adhesive structure to the heat-resistant alloy pipe, it is possible to prevent damage to the ceramic alloy composite material cover material due to thermal shock, and as a result, waste combustion exhaust gas, coal combustion exhaust gas, sewage sludge combustion exhaust gas Another object of the present invention is to recover high-temperature heat that has not been used before from a high-temperature corrosive environment in combustion exhaust gas from industrial waste.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a heat exchanger tube for heat exchange according to an embodiment of the present invention.

FIG. 2 is a side view and a cross-sectional view of the heat exchange tube for heat exchange of the present invention.

FIG. 3 is a cross-sectional view showing another embodiment of the present invention.

FIG. 4 is a sectional view showing still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat-resistant alloy pipe 2 Thermal expansion buffer 3 Ceramic alloy composite material cover material 4 Heat-resistant tube 5 Void

Claims (5)

[Claims] 1. A heat exchange tube for heat exchange provided in a high temperature gas atmosphere and exchanging heat from the high temperature gas to a fluid to be heated in a heat transfer tube, wherein the tube through which the fluid to be heated flows is made of a heat resistant alloy, The outside of the pipe is covered with a cover material made of a ceramic alloy composite material via a thermal expansion buffer material, and the thermal expansion buffer material has a non-adhesive structure to the cover material made of the ceramic alloy composite material and / or the heat-resistant alloy pipe. The heat-resistant alloy pipe and at least a part of the thermal expansion buffer material are in contact with each other, and the thermal expansion buffer material and at least a part of the ceramic alloy composite material cover material have a three-layer structure. Heat transfer tubes for heat exchange. 2. The thermal expansion buffer material is made of a material such as a fiber, powder, film, or tape mainly containing boron, carbon, or aluminum, and is formed on the outer surface of the heat-resistant alloy tube or the ceramic alloy composite. The heat exchanger tube for heat exchange according to claim 1, comprising a thermal expansion absorbing layer having a void formed on an inner surface of the cover material made of a material. 3. The ceramic alloy composite material constituting the cover material includes Al and AlN, wherein AlN is 1 wt% or more and 90 wt% or less, and the total ratio of (A1 + AlN + AlON) is 50 wt% or more and 100 wt% or less. The heat exchanger tube for heat exchange according to claim 1 or 2, wherein 4. The heat exchange transfer according to claim 1, wherein a release agent made of a compound containing boron or carbon is applied to an outer surface of the heat-resistant alloy tube. Heat tube. 5. The porosity of the ceramic alloy composite material is 2% or more and 60% or less.
The heat exchange tube for heat exchange according to any one of claims 1 to 4.