JP2000193221A - Heat-resistant and corrosion-resistant protecting tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a defective ceramic protecting tube and a heater immediately exchangeable by providing a bar near the opened mouth of the protecting tube, and exchanging a broken or corroded tube causing the breakage of the heater by using a crane with hook even during operation. SOLUTION: A protective tube 1 is formed in a tubular body having a closed front end, and a bar 6 is installed to the opening section of the tube 1. Therefore, when a through hole occurs in the bottom section of the tube 1 which is relatively largely corrosive and a heater or sensor is damaged, the tube 1 can be removed by using the bar 6 for exchanging the heater or sensor and tube 1 with new ones. Namely, after a broken heater 2 and internal insulation 5a, 5b, and 5c insulating and holding the heater 2 are removed, the corroded or broken tube 2 is pulled out by putting the hook of a crane etc. on the bar 6 of the tube 1 and a new protective tube, heater, etc., are set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection tube for protecting a heater, a sensor and the like in a melting furnace such as a refuse incineration ash melting furnace.

[0002]

2. Description of the Related Art Garbage discarded from homes and companies is burned in incinerators of local governments, and the incinerated ash and fly ash contained in the smoke (elements contained: Si, Al, Fe, Ca,
Mg, K, Mn, Cl, Na, and S) contain heavy metal components and toxic contaminants such as dioxin and furan.

Until now, unburned incineration ash after being burned in local government incinerators has been buried as it is in the final disposal site. However, location conditions have become severe, making it difficult to secure a place. In addition, detoxification of harmful pollutants such as dioxin and furan is being regulated strictly by laws and regulations, so incineration ash and fly ash are collected and re-melted to detoxify harmful pollutants. The need for melting furnaces is growing year by year.

[0004] The incinerated ash after being burned in an incinerator, which is turned into slag by high-temperature heat treatment, can be reduced to 1/2 of the incinerated ash.
The high-temperature heat treatment method in this melting furnace is considered promising because its volume can be reduced to about 1/10 and harmful pollutants such as dioxin can be decomposed and detoxified by high heat. .

FIG. 2 shows a typical example of a heat treatment in a melting furnace. First, the incineration ash 11 is put into the melting furnace 12 and heated to 1300 to 1600 ° C. by the heater 2 as an electric heat source.
The metal element 13 contained by melting the incineration ash 11 evaporates. The metal element 13 is taken out, rapidly cooled by a cooling device (not shown), and condensed into fine particles, which are collected by a filter or the like 15 to collect a metal concentrate 16. On the other hand, toxic pollutants such as dioxin and furan are thermally destroyed, and the detoxified gas 17 is released into the atmosphere via a gas treatment device. Further, the residue in the melting furnace 12 is slag (glass)
It is taken out as a granular granule 18 for effective use or final disposal.

This melting furnace 12 requires a heater 2 and a thermocouple 3 for temperature control.
Since 1 exists in the melting furnace 12 as molten slag, molten salt, or a vapor component thereof, it is necessary to protect the heater 2 and the thermocouple 3 from these substances.

Therefore, a heating tube 2 and a thermocouple 3 are covered with a protective tube 1 made of ceramics having excellent heat resistance and corrosion resistance. As the material of the protective tube 1,
For example, as shown in JP 51-71312 discloses composite ceramics of MgO-ZrSiO ₂ -Al ₂ O ₃ is used. The present inventors have also found that MgO-Al
₂ 0 ₃ of the composite ceramics are coming proposed so far. As shown in this publication,
A shape in which the tip of a protection tube is sealed on one side is generally widely used.

[0008]

By the way, when heat-treating ash generated by garbage incineration, Cd contained in the ash,
In order to decompose metal elements such as Pd and Zn and harmful pollutants such as dioxin and furan, 1300-1
Detoxification is performed by heating and melting at 600 ° C.
The protective tube 1 used in 2 is exposed to molten salt, molten slag, steam, or the like formed by melting the incineration ash 11. Therefore, Si, Al, Fe, C
a, Na gradually penetrates and erodes into the ceramics and the furnace material forming the protective tube 1 and gradually deteriorates the ceramics and the furnace material and causes a deterioration in strength, so that cracks or breakage are likely to occur. Melting, etc.
It could not be used for a long time. Further, when the furnace material (for example, 4a in FIG. 3) holding the protection tube is deformed due to corrosion or thermal influence, a large stress is applied to the protection tube holding portion, and the protection tube holding portion may be deformed or cracked. Was. If the protection tube is cracked or damaged, corrosive gas enters into the protection tube and corrodes the heater. The heater is made of a conductive metal component such as molybdenum disilicide, but is more easily eroded by corrosive gases than the ceramic material used for the protective tube,
The heater material deteriorates and breaks. Normally, multiple heaters are installed in an electrothermal heating and melting furnace.However, if more than half of the total number of heaters breaks, the amount of heat required for ash melting cannot be generated, so the melting furnace is temporarily stopped. After stopping, the only option is to replace the heater and protection tube with new ones and restart the operation. Once the melting furnace is stopped, the surrounding furnace materials other than the heater protection tube often need to be replaced with new products in many cases, and it is necessary to rebuild the furnace after dismantling the furnace, resulting in a large repair cost.

[0009]

In view of the above, the present invention provides
It is an object of the present invention to provide a means for immediately replacing a protective tube and a heater in which a failure has occurred and realizing a melting furnace operation for a long period of time.

According to the present invention, a bar is provided near the opening of a ceramic protective tube, and a crane with a hook is used even during operation to replace the protective tube at a location where the protective tube is broken or melted and the heater is broken. A structure that can be used. As a method of attaching the bar to the protective tube, first, a through hole for attachment is made in the protective tube side, the bar is inserted therein, and the gap is filled with an inorganic adhesive.

Further, if the both ends of the bar are slightly protruded from the outer surface of the protection tube, the strength of the protection tube holding portion in the radial direction is improved, so that the deformation and cracking of the protection tube when the furnace material holding the protection tube is deformed. It becomes prevention. In addition, when pulling out the protective tube from the furnace material, the end face of the bar contacts the furnace material, and the outer surface of the protective tube does not directly contact the furnace material. can do.

Further, the material of the bar must substantially match the material of the protective tube with the coefficient of thermal expansion, and must be kept within a range of about ± 10%. If this coefficient of thermal expansion is not matched, cracks will occur in the bar and the mounting part, and a gap will occur between the protection tube mounting hole and the bar, corrosive gas will enter the inside of the protection tube, and heater corrosion and breakage will occur. sell. Further, the material strength of the bar material must be a high-strength material because replacement requires a weight of the protection tube and a contact resistance force between the furnace material and the side surface of the protection tube.
It is preferable that the bending strength at 300 ° C. is 250 MPa or more.

Further, it is preferable that the surface of the bar is a baked skin. This is because, as a result of examining the relationship with the corrosion resistance by changing the surface state of the material used as the bar in various ways, the corrosion resistance is better when the burnt surface is used as the bar surface without processing than the ground surface or lapping surface We discovered that it was excellent and adopted a baked surface on the bar surface. The reason why the burnt surface has better corrosion resistance than the processed surface is as follows.

A. The voids on the ceramic surface are smaller than those inside. In other words, if a void exists, the corrosive component penetrates into the ceramic porcelain through the void. be able to. When the burnt surface is removed by processing, voids in the ceramic porcelain are exposed on the surface, and the corrosion resistance deteriorates.

B. Corrosion resistance improves as the ceramic crystal grain size increases. In oxide ceramics, the particle size is larger on the surface of the ceramic porcelain, and the particle size inside is relatively smaller than that on the surface. In other words, if the ceramic surface is the outer surface of the protective tube, the surface having the largest crystal grain size becomes the slag or slag evaporative gas contact surface, which is advantageous for corrosion resistance.

C. When grinding or lapping is applied to ceramics, the surface of the ceramic porcelain is damaged, and very fine microcracks are generated. When the processing surface is used as the slag or the slag evaporating gas contact surface, the corrosive component can easily penetrate into the ceramic porcelain more easily than the micro crack.

If the burnt surface is adopted as the surface of the bar, conventional machining such as grinding and lapping can be omitted, and the machining process can be simplified, so that there is an advantage that the production can be performed at lower cost. In addition, on the surface that becomes the baked skin surface,
In order to develop a larger crystal more largely and expose it to the surface of the protective tube, it is better to fire at a temperature higher than the complete densification temperature of the ceramic material, preferably 50 ° C. to less than the complete densification temperature of the ceramic material. It is desirable that the firing be performed while maintaining the temperature at 100 ° C. or higher for 2 hours or longer. The outer surface of the corrosion-resistant and heat-resistant protective tube of the present invention thus obtained is composed of a large crystal of 10 to 20 μm or more, and has a no-void surface state.

Further, the material of the bar according to the present invention is characterized in that it is formed of alumina. That is, it is characterized by being formed of ceramics having a crystal phase of Al ₂ O ₃ .

That is, according to the present invention, as a ceramics constituting a heat-resistant and corrosion-resistant protective tube, various investigations were made, and as a result, Al ₂ O
We found that ₃ should be used. For example, SiC, S
In non-oxide ceramics mainly composed of i ₃ N _{4 and the} like,
When exposed to a temperature of 1500 ° C. or higher in an oxidizing atmosphere (atmosphere), sintering aid components such as Si and Ca components and rare earth elements are vitrified and start to be decomposed. It is also unsuitable as a bar material. On the other hand, in the case of oxide ceramics containing ZrO ₂ as a main component, even when high-purity
Exposure to a high temperature of 0 ° C. or more causes phase transformation and deterioration of strength, which is unsuitable as described above. MgO
Has excellent heat resistance and corrosion resistance under specific conditions, but when there is a trace amount of water in the atmosphere or ash, it reacts violently with this and forms magnesium hydroxide, and the corrosion resistance is significantly deteriorated Therefore, it is unsuitable as a bar material in a melting furnace in which water is substantially present. MgO spinel has no problem in heat resistance and corrosion resistance, but has low strength and is not suitable as a bar material. On the other hand, Al ₂ O ₃
Has an extremely high melting point of 2000 ° C. or higher,
It has stable heat resistance and corrosion resistance even at a high temperature of 600 ° C, and has high strength at high temperatures, making it an optimal material as a bar material.

In the melting furnace, Si, Al,
Erosive elements such as Fe, Ca, and Na erode into the grain boundaries in the ceramics constituting the bar material and corrode and alter the ceramics. For that purpose, it is necessary that the purity of Al ₂ O _{3 is} 99.9% by weight or more, and SiO ₂ , CaO, Na ₂
It is preferable to keep impurity components such as O and Fe ₂ O ₃ at 0.1% by weight or less. In order to make the impurity component 0.1% by weight or less, it is only necessary to use a high-purity primary material of Al ₂ O _{3 in} advance and prevent impurities from being mixed in the manufacturing process.

[0021]

Embodiments of the present invention will be described below.

As shown in FIG. 1, the protection tube 1 of the present invention comprises:
It is a tubular body with a closed end, and has a structure in which a bar 6 is installed at the opening of the protective tube. As shown in FIG. 2, this protective tube 1 is installed in a melting furnace 12 of a refuse incineration ash melting furnace so as to cover a sensor 2 such as a heater 2 or a thermocouple, and is used to remove gas from the furnace which contains many corrosive components. It can protect heaters and thermocouples. When using this protective tube 1,
As shown in FIG. 3, the heaters 2
Are arranged, and are further covered with the furnace materials 5a to 5c.

In particular, the protection tube 1 of the present invention can be replaced with a new heater, sensor, and protection tube 1 when a through hole is formed at the bottom of the protection tube having a relatively high degree of corrosion and the heater or sensor is damaged. Using the bar 6, the protective tube 1 in which the through hole has been generated can be removed and replaced with a new one.

Further, the provision of the bar 6 deforms the furnace material 4a of the protection tube mounting portion, and serves as resistance when stress is applied to the protection tube 1 side, thereby contributing to prevention of deformation of the protection tube 1 or crack generation. . Further, if the end face of the bar 6 is slightly protruded from the outer surface of the protection tube 1 to be in a convex state, the end surface of the bar 6 comes into contact with the furnace material 4a, and when the protection tube 1 is pulled out and inserted at the time of replacement. , The contact area can be reduced,
Work can be facilitated because the frictional resistance can be reduced.

The shape of the bar 6 is a columnar shape as shown in FIG. 1, but the present invention is not limited to this, and a bar 6 having a polygonal cross section such as a triangular prism or a quadrangular prism or an elliptical cross section may be used. Further, the bar 6 of the present invention may be used alone, or two or more bars may be used in various combinations. The bar 6 is not limited to support at both ends, and may be cantilever support in some cases.

The aspect ratio of the bar 6 is 0.03 to 0.03.
It is preferable that the end of the bar 6 protrudes from the outer surface of the protective tube 1 by 0.3 to 10 mm.

However, the shape of the bar that can be manufactured is φ10 × 2
It is preferably 60 L or less. This is because, when a bar having a diameter of 10 or more and exceeding 260 L is manufactured, it is difficult to manufacture the bar and mass production is difficult.

It is assumed that the bar is installed so as not to come into contact with a heater or the like in the protection tube 1.

A specific method of replacing the protection tube 1 is shown in FIG.
, The heating heater 2 at the location where the heater breakage has occurred and the furnace materials 5a, 5b,
5c is removed first, and then the bar 6
A hook such as a crane may be hooked on the tube, the protective tube that has been damaged or damaged may be pulled out, and then a new protective tube, a heater and its insulation / holding furnace material may be set, and necessary electrical wiring is performed thereafter.

The protection tube 1 of the present invention is not limited to the above-described refuse incineration ash melting furnace 12, but may be used to protect heaters and various sensors in various melting furnaces such as a metal melting furnace and a blast furnace. Can be used as a tube. Also,
Appropriate adjustment of the average crystal grain size and porosity of the ceramic porcelain other than the protective tube can be used for various parts requiring heat resistance and corrosion resistance, such as various furnace wall materials and holder materials.

[0031]

EXAMPLE 1 Assuming the environment inside a refuse incineration ash melting furnace, various ceramic materials were manufactured, and a reaction test with the refuse incineration ash was performed.

First, as the incineration ash, the components are Al and C.
Ash made of a, Mg, Na, K, Zn, Pb, Si, Fe, Cl and the like was collected from an incinerator, and a tablet having a diameter of 12 mm × 1 mm and a weight of 0.3 g was produced by a dry press machine.

Next, tablet test pieces having a diameter of 30 mm × 10 mm were formed from various ceramics shown in Table 1 by dry press molding, and then fired at a temperature of 1500 ° C. or more in an appropriate atmosphere. A counterbore (diameter 13 mm × depth 1 mm) for accommodating the incinerated ash tablet was formed in advance on each test piece. The characteristic values of various ceramics were measured by the following methods.

For the crystal phase, an X-ray diffractometer was used.
u with a voltage of 50 kV and a current of 200 mA,
The measurement range is 2θ = 10 ° ~ 90 ° and full scale 3 × 1
0 and analyzed as ^{4 ~10} × 10 ⁴ cps. The impurity is I
According to CP analysis, SiO ₂ , CaO, Na ₂ O, Fe ₂
Quantitative analysis was performed on the O ₃ component.

The crystal grain size was measured by taking a SEM photograph of the fractured surface at a magnification of about 500 to 1000 times and using the photograph by a cord method. The bulk specific gravity, porosity, and bending strength were tested and measured based on the JIS method.

In the reaction test, an ash tablet was placed in a counterbore of each ceramic test piece, and 1550 in air.
A heat treatment at 50 ° C. for 50 hours was applied.

Thereafter, the appearance of each test piece was visually observed to check for melting or cracks. The cross section of each test piece was cut and polished, and the presence or absence of cracks was examined by SEM (about 50 to 200 times), and the wavelength dispersion type EPMA analyzer was used to accelerate the voltage of 15 kV and probe current of 2.0 × 10 ^−7. In A, each element of Si, Ca, and Na was detected and output in a mapping format, and then the diffusion depth (reaction layer) of these elements was examined.

The results are as shown in Table 1.
In the table, those with cracks, melting, and reaction layers are indicated by x, and those without cracks are indicated by o. The strength is 250MPa
Those that did not meet the criteria were also marked as ×.

[0039]

[Table 1]

From the results in the above table, it can be seen that SiC, Si ₃ N ₄ ,
Since ZrO ₂ was melted or cracked, it was confirmed that ZrO ₂ was unsuitable as a bar material.

Although MgO spinel does not cause any problem in a crack and a reaction layer, it is unsuitable because of its low strength. On the other hand, Al ₂ O ₃ has no melting or cracking, has no reaction layer with the ash component, and has no problem in strength, indicating that it can be used as a bar material without any problem.

Example 2 As an example of the present invention, No. 1 in Table 1 was used. For the ceramics of No. 2, the surface condition of the ceramic test piece that comes into contact with the ash tablet was prepared for each of three types: burnt skin, ground surface, and lapping surface. The test piece was heat-treated in the same manner as in Example 1, and cracks, melting, and diffusion depth of Ca element (reaction layer) were examined. Table 2 shows the results.

In the table, the absence of the processing column means that there is no mechanical processing after firing, and the grinding means grinding and grinding of about 0.3 mm from the burnt surface with a # 140 diamond grindstone. After the above-mentioned grinding, after rough lapping using GC abrasive grains having an average particle diameter of 10 μm on an alumina platen, an average particle diameter of 1 μm was used as a finishing lap on a tin platen.
Shows that a total of about 50 μm lapping was performed using the diamond abrasive grains of No. 1. The shape was the same as in Example 1. Regarding the method of determining the reaction layer, those in which Ca element diffusion of 0.3 mm or more was recognized from the ceramic surface were indicated by x, and those of 0.3 mm or less were indicated by ○.

As shown in Table 2, it was found that the surface of the ceramics had no corrosion (burnt surface) having the highest corrosion resistance.

[0045]

[Table 2]

Example 3 A bar was made of an alumina material, which was attached to a protective tube, and a protective tube replacement operation was performed during operation with a test device.
We checked the availability of the bar. As for the type of bar, several materials with different purity, high temperature strength and creep property
180L, this has an outer diameter of φ180 × φ160 × 8
It was attached to the open end side of the 00L protective tube. For mounting, a bar mounting hole was made in the protective tube, a bar was inserted into the hole, and the bar was fixed with an alumina-based adhesive. The melting furnace is a heater heating method, and the temperature in the furnace is 1300 ° C.

For the high temperature strength in the table, a test piece having a shape of 3 × 4 × 45 was manufactured, and three-point bending was evaluated at 1300 ° C. The amount of strain is 1.5 kg at the center of the test piece of the same shape at 1300 ° C.
When a load of f / mm ² was applied and the strain was maintained for 100 hours, the strain amount was 100 μm or more, and x was less than 100 μm. Further, in the replacement work item, “○” indicates that the replacement work is OK, and “x” means that the replacement work was not performed because the bar was broken or deformed during the replacement work.

It was confirmed that when alumina having a purity of 99.9% or more was used as a bar material, a high-temperature strength of 260 MPa or more at 1300 ° C. could be secured, and replacement work could be performed without any problem.

[0049]

[Table 3]

Example 4 As an example of the present invention, No. 1 in Table 2 was used in which the surface of the bar was baked. Those manufactured according to the specifications of 3-1 and set in the vicinity of the opening of the protection tube were assembled in an actual furnace, and a comparative test was performed with an actual machine. Protection tube body material is Al ₂ O ₃ , outer diameter 100 ~
250 mm, inner diameter 80 to 230 mm, thickness t is 10 m
A protective tube with a bar having a length of 800 mm and a length of 800 mm as shown in FIG. 1 was produced. At this time, the length of the bar was adjusted to 100 to 260 mm so as to protrude from the outer surface of the protective tube to 0 to 11 mm, and the bar was attached.

In addition, in the evaluation items, "O" indicates that the replacement work was OK, and "X" indicates that the bar was broken or deformed during the replacement work.
This means that the replacement work could not be performed. The actual machine test was performed in the refuse incineration ash melting furnace 12 shown in FIG. The results are shown in Tables 4 and 5.

As shown in Table 4, Nos. 1, 2, and 4 to 9 had an aspect ratio of 0.03 to 0.15, so the resistance to the radial stress of the protection tube itself increased, and the furnace holding the protection tube was used. When stress was applied to the protective tube due to material deformation, deformation and cracks of the protective tube could be prevented, and replacement of the protective tube was facilitated. No3 has an aspect ratio of 0.02
Therefore, stress was concentrated on the bar when it was pulled out, and the bar was broken.

As shown in Table 5, Nos. 2 to 5 are 0.3 to 10 mm.
Because the furnace material (Fig. 34a) and the protective tube are not in close contact with each other, the contact area between the outer surface of the protective tube and the furnace material is reduced, the frictional resistance can be reduced, and the replacement operation can be performed easily. Was. In No. 1, since the furnace material and the protective tube were in close contact with each other, the contact area between the outer surface of the protective tube and the furnace material was increased, the frictional resistance was increased, and replacement work was difficult.

[0054]

[Table 4]

[0055]

[Table 5]

[0056]

As described above, if a protective tube having a bar is used, the protective tube has both heat and corrosion resistance and a large resistance to the radial stress of the protective tube itself. When stress is applied to the tube, deformation and cracking of the protection tube can be prevented.

Further, since the replacement operation during the operation can be performed, the furnace can be continuously operated while replacing with a new protective tube, so that the furnace can be favorably used for a long time. Also, if the bar is slightly protruded from the outer surface of the protection tube,
Since the contact area between the outer surface of the protection tube and the furnace material is reduced and the frictional force is reduced, the replacement operation can be performed easily.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a heat and corrosion resistant protective tube of the present invention.

FIG. 2 is a schematic view showing a refuse incineration ash melting furnace using the heat-resistant and corrosion-resistant protective tube of the present invention.

FIG. 3 is a cross-sectional view showing the installation state of the heat and corrosion resistant protective tube of the present invention.

[Explanation of symbols]

 1. Protection tube 2. Heater 3. Thermocouple 4. Furnace material 5. Furnace material 6. Bar 11. Incineration ash 12. Melting furnace 13. Metal element 14. Filter 15. ..Metal concentrate 16..Gas 17..Slag-like granules

Claims (5)

[Claims] 1. A heat-resistant and corrosion-resistant protective tube comprising a ceramic protective tube sealed on one side for protecting a heater, a sensor and the like, wherein the protective tube is provided with a bar inside the vicinity of an opening. 2. The bar has an aspect ratio of 0.03 to 0.3.
2. The heat-resistant and corrosion-resistant protective tube according to claim 1, wherein the protective tube protrudes from the outer surface of the protective tube by 0.3 to 10 mm. 3. The bar according to claim 1, wherein said bar has a thermal expansion coefficient of ± 10.
% And a strength of 1300 in air.
2. The temperature is 250 MPa or more at a temperature of 1.degree.
Heat and corrosion resistant protective tube as described. 4. The heat-resistant and corrosion-resistant protective tube according to claim 1, wherein the surface of the bar is a baked surface. 5. The heat-resistant and corrosion-resistant protective tube according to claim 1, wherein said bar is made of a ceramic having an Al ₂ O ₃ content of 99.9% by weight or more.