JPH09178377A - Honeycomb-like thermal storage unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb-like thermal storage unit which make it possible to efficiently heat exchange without damaging for high temperature and corrosive exhaust gas. SOLUTION: This honeycomb-like thermal storage unit 1 comprises a plurality of honeycomb structures 2 stacked recover the waste heat of the exhaust gas by alternately passing the exhaust gas and gas to be heated to a channel formed of a through hole 3. The structure 2 made at the high temperature part of the unit in contact with the high temperature exhaust of aluminum titanate as a main crystal phase or the structure made of aluminum titanate and mullite. The thermal storage part becoming the temperature of at least 1,200 deg.C or higher at the time of normal operation of a baking furnace is constituted by the structure 2 of the alumina of a main crystal state, the unit of the lower temperature side than the structure 2 of the alumina as the main crystal phase is constituted by at least one combination selected from among the structure 2 of cordierite as the main crystal phase, the structure 2 of mullite as the main crystal phase and the structure 2 of corrosion resistant porcelain material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a stack of a plurality of honeycomb structures, and exhaust gas and heated gas are alternately passed through a flow path constituted by through holes to recover waste heat in the exhaust gas. The present invention relates to a honeycomb heat storage body, and particularly to a honeycomb heat storage body that can be suitably used for exhaust gas in a corrosive atmosphere at high temperature.

[0002]

2. Description of the Related Art Conventionally, in a combustion heating furnace used for general industries such as a steel furnace, an aluminum melting furnace, and a glass melting furnace, waste heat of a combustion gas is used to preheat combustion air to increase thermal efficiency. As a heat storage element used for this purpose, one using ceramic spheres as described in JP-A-58-26036 or one using a honeycomb-shaped structure as described in JP-A-4-251190 Etc. were known.

In the above conventional heat storage body, first, the high temperature combustion exhaust gas and the spherical or honeycomb heat storage body are brought into contact with each other to store the heat of the combustion exhaust gas in the heat storage body, and then the low temperature heated gas and the heat storage body. The waste heat of the combustion exhaust gas is efficiently used by heating the gas to be heated by bringing it into contact with the heat storage body.

[0004]

However, when ceramic spheres are used among the above-mentioned heat accumulators, the ceramic spheres have a large airflow resistance and a small contact area between the ceramic spheres and the gaseous gas. However, there has been a problem that heat exchange cannot be performed, and the heat storage body needs to have a large configuration.

[0005] On the other hand, when the heat storage body is formed into a honeycomb shape, the geometric specific surface area is larger than the volume, so that the heat can be effectively exchanged with a compact size. However, among the combustion heating furnaces for general industry, glass melting furnaces,
Regarding a ceramic firing furnace that is operated at a high temperature of 1400 ° C. or higher, a honeycomb heat storage body using a cordierite honeycomb structure, which is disclosed in a conventional example and is most often used, is a cordier. Since the softening temperature of the light is around 1400 ° C., the cordierite honeycomb structure is softened and destroyed in an extreme case, and there is a problem that the honeycomb heat storage body cannot be used as it is.

[0006] Among the examples in which the heat storage body is formed in a honeycomb shape, there is an example in which a corrosion resistant honeycomb structure and a cordierite honeycomb structure are combined for use in a corrosive atmosphere. Had a problem that it did not reach a satisfactory level at a high temperature of around 1300 ° C. and because iron scales and the like came flying. For example, when an alumina honeycomb structure is used as the corrosion-resistant honeycomb structure, although there is no problem in reactivity with the iron scale, even when a steady operation at 1300 ° C. is performed, sometimes an operation involving a sudden temperature change is performed. However, since alumina has a high coefficient of thermal expansion and a low thermal shock resistance, there is a problem of causing thermal shock cracking. Other mullite and SiC also have a problem of thermal shock cracking, similar to alumina, because they have high thermal expansion coefficients. Honeycomb subdivision can be considered as a means for improving the thermal shock resistance, but there is a problem that handling is troublesome.

Further, when the cordierite honeycomb structure is used, when the fuel of the combustion burner is heavy oil, SOx is generated due to the sulfur content in the heavy oil,
Below the acid dew point, there was a problem that dilute sulfuric acid was generated by reaction with water, and the cordierite honeycomb structure was corroded.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a honeycomb-shaped heat storage body capable of efficiently exchanging heat without destroying corrosive exhaust gas at high temperature.

[0009]

The honeycomb heat storage body of the present invention is formed by stacking a plurality of honeycomb structures, and the exhaust gas and the gas to be heated are alternately passed through a flow path formed of through holes to form the exhaust gas. In a honeycomb heat storage body for recovering waste heat therein, a high temperature portion of the heat storage body in contact with high temperature exhaust gas is composed of a honeycomb structure having aluminum-titanate as a main crystal phase or a honeycomb structure including aluminum-titanate and mullite. In the steady-state operation of the firing furnace, the heat storage part that has a temperature of at least 1200 ° C. or higher is formed of a honeycomb structure having alumina as a main crystal phase, and the temperature is lower than that of the honeycomb structure having alumina as a main crystal phase. The heat storage material is a honeycomb structure having cordierite as a main crystal phase, a honeycomb structure having mullite as a main crystal phase, and a corrosion-resistant porcelain honeycomb. And it is characterized in that comprising a combination of at least one selected from among concrete body.

In the above-mentioned structure, in the honeycomb heat storage body of the present invention, from the upstream side to the downstream side of the high temperature exhaust gas, (1) a honeycomb structure having aluminum-titanate as a main crystal phase or aluminum-titanate and mullite is used. Of the honeycomb structure, (2) a honeycomb structure containing alumina as a main crystal phase, (3) a honeycomb structure containing cordierite as a main crystal phase, a honeycomb structure containing mullite as a main crystal phase, and a corrosion-resistant porcelain honeycomb. By configuring the honeycomb heat storage body with at least one honeycomb structure selected from the above, a honeycomb heat storage body capable of efficiently exchanging heat without corroding exhaust gas that is corrosive at high temperature is obtained. be able to.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the structure of an example of a honeycomb heat storage body of the present invention. In FIG. 1, the honeycomb heat storage body 1 is formed by stacking a plurality of rectangular parallelepiped honeycomb structures 2 so that the flow paths formed by the through holes 3 are aligned in one direction. In the example shown in FIG. 1, the upper part in the figure is the surface in contact with the high temperature gas, and the part (a) in contact with the high temperature exhaust gas during the steady operation of the firing furnace is a honeycomb structure or aluminum-containing titanium-titanate as the main crystal phase. It is composed of a honeycomb structure composed of titanate and mullite. The part (b), which has a temperature of at least 1200 ° C. or higher in the high temperature part, is composed of a honeycomb structure having alumina as a main crystal phase. The (c) part on the lower temperature side than the honeycomb structure containing alumina as a main crystal phase is at least one selected from a honeycomb structure containing cordierite and mullite as a main crystal phase, or a corrosion-resistant porcelain honeycomb structure. The two are combined and stacked so that the flow paths formed by the through holes 3 are aligned in one direction.

In addition, in the example shown in FIG. 1, all the honeycomb structures 2 have the same shape, but at least the shape of the honeycomb structure at the outer peripheral portion of the surface in contact with the high temperature exhaust gas is at least the central structure. It can also be made smaller than the body shape.

Of the materials constituting the honeycomb heat storage body 2 shown in FIG. 1, aluminum-titanate is known as a heat resistant and low thermal expansion material, and is excellent in compatibility with iron even at a high temperature of about 1300 ° C. Since it is stable against iron and has high thermal shock resistance, it does not crack even when the temperature changes suddenly. Also, aluminum
It is known that titanate decomposes into alumina and titania with a peak around 1100 ° C. and has high thermal expansion. When it is expected that the furnace is used for a long time at a temperature of 1250 ° C. or lower, the thermal decomposition can be suppressed by solid-dissolving MgO and Fe ₂ O ₃ .

Although the solid solution of MgO in aluminum-titanate can suppress the thermal decomposition having a peak around 1100 ° C. to some extent, MgO alone is not sufficient, and it is desirable to simultaneously form a solid solution with Fe ₂ O ₃ . Also,
In the present invention, it has been found that not only the conventionally known effect of suppressing the thermal decomposition as the effect of the solid solution of MgO but also the effect of improving the corrosion resistance, particularly the alkali resistance is improved. Mg
The reason why the addition amount of O is preferably 4% by weight or more is that the alkali resistance is remarkably improved when it is 4% by weight or more, as will be apparent from the examples described later, and is 10% by weight or less. It is preferable that if MgO is added in excess of 10% by weight, MgO cannot completely form a solid solution and spinel or magnesium titanate having a high coefficient of thermal expansion is produced, and the coefficient of thermal expansion of the honeycomb structure is high. Because it will be.

When Fe ₂ O ₃ is solid-dissolved in aluminum-titanate, Fe ions are completely replaced with Al ions,
Suppresses the thermal decomposition of aluminum-titanate. Fe ₂
It is preferable that the addition amount of O ₃ is 2% by weight or more.
If it is less than 10% by weight, thermal decomposition cannot be completely suppressed, and if it is 10% by weight or less, 10% by weight is preferable.
This is because the coefficient of thermal expansion becomes high when the value exceeds.

The reason for using the honeycomb structure containing alumina as the main crystal phase at a temperature lower than the use range of the honeycomb structure containing aluminum-titanate as the main crystal phase is that aluminum-titanate is expensive, so that at least direct It is sufficient to use it in the part that comes into contact with high-temperature exhaust gas, and even with a honeycomb structure whose main crystal phase is alumina, which has a high coefficient of thermal expansion, if it does not come into direct contact with high-temperature exhaust gas, the thermal shock will be mitigated and it will be sufficient This is to endure. In addition, since the corrosion of iron and sometimes alkali components becomes a problem at least at a temperature of 1200 ° C. or higher during steady operation of the firing furnace, it is necessary to use a honeycomb structure having alumina as a main crystal phase having excellent corrosion resistance. Become.

Further, in the present invention, it is necessary to use at least one of a honeycomb structure having cordierite and mullite as a main crystal phase or a corrosion-resistant porcelain honeycomb structure in combination in the low temperature portion. If the temperature is 1200 ° C. or lower, corrosion by iron or alkali proceeds only moderately, and a cordierite honeycomb structure having a low thermal expansion coefficient and excellent thermal shock resistance can be used. Therefore, there is an advantage that the honeycomb structure can be made large and the handling becomes easy. Further, when the amount of iron and alkali discharged from the firing furnace is large, it is possible to use a honeycomb structure having mullite as a main crystal phase, which has a higher coefficient of thermal expansion than cordierite, but has excellent heat resistance and corrosion resistance. Preferably, it is possible to use a honeycomb structure having cordierite as a main crystal phase only in a portion having a lower temperature.

Further, when heavy oil is used as the fuel, SOx is generated by the sulfur content in the heavy oil, and the portion of the heat storage body having a temperature below the dew point is corroded and cannot be used for a long time. In such a case, it is desirable to use a corrosion-resistant porcelain honeycomb structure. Corrosion-resistant porcelain includes feldspar porcelain, alumina-based porcelain, etc., all of which have an open porosity close to zero and are particularly excellent in acid resistance. In such an industrial furnace, the operating temperature, the exhaust gas atmosphere, etc. are different depending on the furnace, and it is necessary to have an optimal heat storage structure according to the conditions.

FIG. 2 is a view showing an example in which a heat exchanger using the honeycomb heat storage body of the present invention is installed in a combustion chamber of a combustion heating furnace. In the example shown in FIG.
Reference numerals 1 and 12-2 denote a honeycomb-shaped regenerator having the structure shown in FIG.
3-1 and 13-2 are honeycomb-shaped regenerators 12-1 and 12-
The heat exchangers 14-1, 14-2 are fuel inlets provided in the heat exchangers 13-1, 13-2. In the example shown in FIG. 2, two heat exchangers 13-1, 13-
The reason why 2 is provided is that, when one is storing heat by flowing high-temperature exhaust gas, the other can simultaneously heat the low-temperature gas to be heated, so that heat exchange can be performed efficiently.

In the example shown in FIG. 2, first, as indicated by an arrow in the figure, air as a gas to be heated is supplied to the heat exchange element 13-1 which has previously stored heat in the honeycomb heat storage element 12-1, and at the same time fuel is supplied. While injecting fuel from the inlet 14-1,
The high temperature exhaust gas in the combustion chamber 11 is passed through the heat exchanger 13-2. In this state, the air is preheated and supplied to the combustion chamber 11 together with the fuel, and the honeycomb-shaped regenerator 12-2 of the heat exchanger 13-2 is stored.

Next, by switching the flow of gas so that the gas flows in the direction opposite to the arrow in the figure, the heat exchanger 13-
Air, which is the gas to be heated, is caused to flow through 2 to feed the fuel from the fuel inlet 14-2, and the high temperature exhaust gas in the combustion chamber 11 is passed through the heat exchanger 13-2. By repeating the above steps continuously, heat exchange can be performed.

[0022]

An actual example will be described below. Example 1 A honeycomb structure of various materials used in the present invention is prepared,
Melting point, 40-80, for each honeycomb structure
The thermal expansion coefficient at 0 ° C., electric furnace spalling breakdown temperature, alkali resistance and acid resistance were examined. Here, the electric furnace spalling breakdown temperature is 75 mm × 75 mm × 50 mm
The honeycomb structure having the above shape was held in an electric furnace at each temperature for 1 hour and then taken out and air-cooled to investigate whether cracks occurred, and the maximum temperature at which no cracks occurred was determined. In addition, regarding the alkali resistance and the acid resistance, the relative evaluation of each example is described in the order of ⊚>○>Δ> x from the better. The results are shown in Table 1 below.

[0023]

[Table 1]

From the results shown in Table 1, the honeycomb structure made of aluminum-titanate used in the present invention has a high melting point of 1800 ° C., a low thermal expansion coefficient, and a high electric furnace spalling breakdown temperature. It was found to form a strong honeycomb structure. In addition, regarding the evaluation of alkali resistance and acid resistance, it was found that the aluminum-titanate used in the present invention can obtain preferable results equal to or higher than those of other materials.
On the other hand, in the porcelain honeycomb structure used in the low temperature portion of the honeycomb-shaped heat storage body in the present invention, although the thermal expansion coefficient is high and not excellent against thermal shock, it is superior to other materials in the evaluation of acid resistance. I found out.

Example 2 Next, with respect to the honeycomb-shaped heat storage body having several different configurations as examples of the present invention and comparative examples, the usage conditions when actually used as the heat storage body were observed. First, in the example of the present invention and the comparative example, the honeycomb structures were stacked so that the flow paths thereof were aligned, and as shown in Table 2 below, the high temperature part (a), the middle temperature part (b), and the low temperature part (c) were formed. The honeycomb heat storage bodies of the present invention example and the comparative example having the structure shown in FIG. 3 were prepared by changing the material (some of the materials are the same in the comparative examples). All the honeycomb structures had the same size of 75 mm × 75 mm × 50 mm. The atmosphere in the furnace used for the test was under severe conditions in which alkali and iron were often scattered. The burner used here includes natural gas and heavy oil, and when heavy oil is used as a fuel, generation of sulfuric acid was confirmed at a temperature below the acid dew point.

The prepared honeycomb-shaped heat storage bodies of the present invention and comparative examples were repeatedly subjected to heat absorption and waste heat according to the schedule shown in FIG. Here, the temperature difference between when the high temperature exhaust gas where the temperature of the entire heat storage body is the highest and when the cooling air where the temperature is the lowest is passed is about 150 ° C. Table 2 below
The configuration and usage of each honeycomb heat storage body is shown in Fig.
The heat storage body temperature measured here is the highest in the whole heat storage body at the point where the temperature is highest on the plane of the heat storage body at each measurement point of the temperature measurement positions (1) to (4) shown in FIG. It is a measurement of the temperature during time, that is, during passage of high-temperature exhaust gas. The honeycomb-shaped heat storage body used here has a length (L) of the entire heat storage body depending on the operating temperature so that the temperature on the intake side (temperature measurement position (4)) is always 300 ° C. or lower.
Dimension) was changed. This is to protect equipment such as piping and valves.

[0027]

[Table 2]

From the results shown in Table 2, the following was found. Comparative Example Test No. In No. 1, since the honeycomb structure made of cordierite was used in all of the high, medium and low temperature parts of the heat storage body,
The honeycomb structure is melted in a high temperature portion where the temperature exceeds the melting point of cordierite, and the cordierite honeycomb structure used in the medium temperature portion exceeding 1200 ° C. is also softened and damaged due to rapid progress of corrosion of alkali, iron and the like. Has occurred. Therefore, it was found that it is not suitable as a honeycomb heat storage body. In addition, the comparative test No. In 2,
An alumina honeycomb structure was used to prevent melting damage in the high temperature portion, but the alumina honeycomb structure was damaged due to its high thermal expansion coefficient and poor thermal shock resistance. At the same time, for the cordierite honeycomb structure in the middle temperature part, the comparative example test No. As in No. 1, it was unusable because of damage due to corrosion.

Furthermore, the thermal expansion coefficient is higher than that of alumina in the high temperature portion.
A mullite honeycomb structure with a small number is used to
Comparative Example Test No. Using Lumina Honeycomb Structure At three
Is not damaged by corrosion in the medium temperature part, and
Alumina honeycomb structure because the thermal shock is weaker than the
The body was not damaged by thermal shock. But high temperature
In the part, the mullite honeycomb structure was damaged due to thermal shock.
I did Therefore, the present invention example test No. 6, 7, 8, 9, 1
At 0, thermal shock and corrosion due to alkali, iron, etc. are large.
On the high temperature side, consists of pure aluminum-titanate
Honeycomb structure, aluminum-titanate 5% by weight
MgO and 5 wt% Fe_Two O _Three Honeycomb structure with addition of
Made of aluminium-titanate and mullite
Using a honeycomb structure that has the highest temperature
Alumina hani
Uses a cam structure and results in temperatures below 1200 ° C
Cordierite, mullite and cordierite in the low temperature area
Evaluation was performed using each mullite honeycomb structure.
Was.

As a result, the aluminum-titanate of the present invention is excellent in alkali resistance and resistance to iron, has a small coefficient of thermal expansion, is also resistant to thermal shock, and can be used without problems as a honeycomb structure in a high temperature portion where corrosion is severe at high temperatures. I was able to. It was also found that it can be used without problems in an alumina honeycomb structure in the middle temperature part and various honeycomb structures in the low temperature part, and heat exchange can be performed with good heat efficiency without destruction as a honeycomb heat storage body. However, the comparative test No. In No. 4, since the alumina honeycomb structure used in the medium temperature part was used at 1200 ° C. or higher, no abnormality was observed in the honeycomb structure in the high temperature part and the medium temperature part, but the cordierite honeycomb in the low temperature part. It became unusable due to melting damage. The invention example test No. 6,
The alumina honeycomb structure used in the medium temperature part in 7, 8 and 9 has no problem even if it is used in the low temperature part, that is, in the low temperature region from the temperature measurement position (3).

Natural gas was used as the fuel for the burner of the firing furnace used in the tests so far, and no corrosion by sulfuric acid was observed in the low temperature part during cooling. However, the comparative test No. In Example 5, since heavy oil was used as the fuel for the burner, sulfuric acid was generated due to the condensation of SOx in the low temperature portion during cooling, and the cordierite honeycomb structure in the low temperature portion was corroded by the sulfuric acid. Therefore, in the present invention, when using heavy oil as the fuel for the burner, by using a porcelain honeycomb structure in a portion where acid resistance is required by combining a cordierite honeycomb structure and a porcelain honeycomb structure in the low temperature part, Even in the low temperature part, there was no problem as the honeycomb-shaped heat storage body did not break or melt.

Example 3 Mg for Aluminum-Titanate Honeycomb Structure
The effect of the addition of O and Fe ₂ O ₃ was investigated. First, FIG. 5 shows a change in characteristics due to MgO contained in the aluminum-titanate used in the present invention. here,
The coefficient of thermal expansion is 4 in the flow direction of the honeycomb structure after firing.
The coefficient of thermal expansion of 0-800 degreeC is shown. The weight reduction rate, which is an index of alkali resistance, is a measurement of the weight reduction rate when the honeycomb structure is immersed in a 10 wt% NaOH aqueous solution at 150 ° C. for 20 hours. The smaller the weight loss rate, the better the alkali resistance. The addition amount of Fe ₂ O ₃ was 5% by weight in each case.

From the results shown in FIG. 5, it can be seen that the characteristics of the thermal expansion coefficient and the body alkalinity of the aluminum-titanate honeycomb structure change depending on the addition amount of MgO. MgO
The coefficient of thermal expansion tends to decrease temporarily with the addition of, but when it exceeds a certain addition amount, it gradually increases. Further, the alkali resistance has a lower weight reduction rate due to the addition of MgO, and when it reaches a certain level, it does not further decrease. From FIG. 4, it is understood that the addition amount of MgO is preferably 4 to 10% by weight within a range satisfying both the characteristics of the thermal expansion coefficient and the alkali resistance required for the honeycomb heat storage body.

Next, FIG. 6 shows the thermal expansion coefficients of the honeycomb structures having various compositions after firing, which were held in an electric furnace at a temperature of 1100 ° C. for each time. Aluminum −
The honeycomb structure (AT) containing only titanate and no addition of MgO and Fe ₂ O ₃ has a thermal expansion coefficient immediately increased after a short time heat treatment. Further, in the honeycomb structure (MAT) in which 10% by weight of MgO is added to aluminum-titanate, the thermal expansion coefficient is gradually increased by the heat treatment for a long time. Therefore, when a honeycomb structure having this composition is used at a high temperature for a long time, the coefficient of thermal expansion increases and the probability of destruction due to thermal shock increases.

Then, Mg is added to aluminum titanate.
Honeycomb structure (M and O ₂ and Fe ₂ O ₃ added simultaneously)
In ATF), the coefficient of thermal expansion was measured after the heat treatment for a long time, but it was found that the coefficient of thermal expansion increased in the honeycomb structure (MATF-1) containing 1% by weight of Fe ₂ O _3. 2% by weight added honeycomb structure (M
ATF-2), 5% by weight added honeycomb structure (MA
TF-5) and 10 wt% added honeycomb structure (M
Regarding ATF-10), it was possible to obtain a honeycomb structure which has a low thermal expansion and maintains a stable low thermal expansion even during a heat treatment at a high temperature for a long time. However, Fe ₂
In the honeycomb structure (MATF-15) in which the amount of O ₃ added was increased to 15% by weight, the coefficient of thermal expansion did not increase due to the long-time heat treatment, but the coefficient of thermal expansion of the unheated honeycomb structure was extremely high. It rises and cannot be used. In addition,
The amount of the above-mentioned MATF-based MgO added was uniformly 5% by weight. From the above, it is understood that the addition amount of Fe ₂ O ₃ is preferably 2 to 10% by weight.

Therefore, it is understood that the aluminum-titanate honeycomb structure used in the present invention preferably contains MgO in an amount of 4 to 10% by weight and Fe ₂ O _{3 in an amount} of 2 to 10% by weight.

In the above embodiment, the high temperature part,
As raw materials such as cordierite, mullite, and aluminum-titanate, which form each honeycomb structure of the middle temperature portion and the low temperature portion, generally used raw materials, chamotte and the like can be used alone or in combination.

[0038]

As is apparent from the above description, according to the present invention, from the upstream side to the downstream side of high temperature exhaust gas, (1) a honeycomb structure or an aluminum-titanate having aluminum-titanate as a main crystal phase is formed. And mullite honeycomb structure, (2) honeycomb structure containing alumina as a main crystal phase, (3) honeycomb structure containing cordierite as a main crystal phase, honeycomb structure containing mullite as a main crystal phase, and corrosion-resistant porcelain Since at least one honeycomb structure selected from the quality honeycombs constitutes the honeycomb heat storage body, it is possible to efficiently perform heat exchange without destroying corrosive exhaust gas even at high temperatures. A heat storage body can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an example of a honeycomb heat storage body of the present invention.

FIG. 2 is a diagram showing an example in which a heat exchanger using the honeycomb-shaped regenerator of the present invention is installed in a combustion chamber of a combustion heating furnace.

[Fig. 3] Fig. 3 is a diagram showing a configuration of a honeycomb heat storage body used in an example.

FIG. 4 is a graph showing a temperature curve during operation of the honeycomb heat storage body in the example.

FIG. 5: M of aluminum-titanate honeycomb structure
5 is a graph showing changes in alkali resistance and thermal expansion coefficient due to addition of gO.

FIG. 6 shows an aluminum-titanate honeycomb structure with M
6 is a graph showing the relationship between the aging time and the coefficient of thermal expansion when gO and Fe ₂ O ₃ are added.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 honeycomb heat storage body, 2 honeycomb structure, 3 through holes, 11 combustion chambers, 12-1, 12-2 heat exchange body, 1
3-1, 13-2 Honeycomb-shaped heat storage body, 14-1, 14
-2 fuel inlet

Claims (5)

[Claims] 1. A stack of a plurality of honeycomb structures,
In a honeycomb heat storage body for recovering the waste heat in the exhaust gas by alternately passing the exhaust gas and the heated gas through the flow path constituted by the through hole, the high temperature part of the heat storage body in contact with the high temperature exhaust gas is aluminum-titanate. A honeycomb structure as a main crystal phase or aluminum-composed of a honeycomb structure composed of titanate and mullite, during steady operation of the firing furnace,
A portion of the heat storage body having a temperature of at least 1200 ° C. or higher is constituted by a honeycomb structure having an alumina main crystal phase, and the heat storage body at a temperature lower than the honeycomb structure having an alumina main crystal phase is mainly cordierite. A honeycomb heat storage body, which is formed by combining at least one selected from a honeycomb structure having a crystal phase, a honeycomb structure having mullite as a main crystal phase, and a corrosion-resistant porcelain honeycomb structure. 2. The high temperature portion is a honeycomb structure having aluminum-titanate as a main crystal phase, the medium temperature portion is a honeycomb structure having alumina as a main crystal phase, and the low temperature portion is mainly composed of cordierite. The honeycomb heat storage body according to claim 1, which is a honeycomb structure. 3. The aluminum-titanate portion of the honeycomb structure containing aluminum-titanate as a main crystal phase or the honeycomb structure containing aluminum-titanate and mullite contains 4 to 10% by weight of MgO and Fe ₂ O _3.
2 to 10% by weight of the honeycomb-shaped heat storage body according to claim 1. 4. The coefficient of thermal expansion of the honeycomb structure containing aluminum-titanate as a main crystal phase or the honeycomb structure containing aluminum-titanate and mullite at 40 to 800 ° C. of 1.0 × 10 ⁻⁶ / ° C. The honeycomb heat storage body according to claim 3, wherein: 5. The honeycomb structure according to claim 1, wherein a portion of the heat storage body at a temperature lower than that of the honeycomb structure having alumina as a main crystal phase has a temperature at least below an acid dew point as the corrosion-resistant honeycomb structure. Heat storage body.