JPH10252974A - Seal structure of ceramic pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the breakage of a ceramic pipe, and secure the sealing performance in the ceramic pipe such as a ceramic filter in which the hot gas is handled. SOLUTION: A metallic pipe 3 having approximately same diameter of the section is placed on a ceramic pipe 1 through a sheet packing 3b-1, and ceramic fibers 5b-1, 5b-2 and a metallic ring 5b-3 are arranged between the outer circumference of the metallic pipe 3 and the ceramic pipe 1 to perform the sealing. A lower end part of the ceramic pipe is placed on a receiving member, and a fiber filling layer is provided on the outer circumference of the lower end part of the ceramic pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic pipe sealing structure suitable for relieving thermal stress generated when a ceramic pipe having a small thermal expansion and being fragile is attached to a metal container having a large thermal expansion. For example, the present invention relates to a sealing structure of a long porous ceramic filter for collecting high-temperature gas.

[0002]

2. Description of the Related Art In recent years, a pressurized fluidized bed boiler using coal as fuel has been developed, and a system for operating a gas turbine using this combustion gas has been studied. On this occasion,
In order to remove the combustion gas, a ceramic filter that functions at high temperature is required. The gas temperature is 850
° C or higher, and conventional devices such as a bag filter cannot be used. For this purpose, ceramic filters have been developed.

The most problematic problem with ceramic filters is breakage. Ceramics, unlike conventional metals and bag filter materials, are not flexible and do not elongate, and thus break immediately upon exceeding a critical stress. In particular, in the case of ceramics, the most problematic is a connection portion with a metal having a different coefficient of thermal expansion. When the element size of the ceramics filter device is long, the amount of expansion due to the difference in thermal expansion to be absorbed by the seal portion reaches several tens of mm.

As a method of sealing a ceramic heat transfer tube for a ceramic heat exchanger having a structure substantially similar to that of a ceramic filter, Japanese Patent Publication No. 44954/94 discloses a method in which a ceramic tube is penetrated through a metal tube plate and a metal ring is arranged around the tube. A method of sand-sealing the gap has been proposed.

[0005]

However, the method described in Japanese Patent Publication No. 44954/94 is not applicable to the case where a ceramic filter or the like of a pressurized fluidized bed boiler using coal as fuel is subjected to high temperatures. Can not. The biggest problem is that the ceramic tube is directly constrained to the tube sheet though through a sand seal.

In the case of a ceramic filter device, a large number of tubular porous ceramic elements are provided on a large metal tube sheet. The metal tube sheet is already distorted at the time of manufacturing, and even if a metal plate sheet that is perfectly manufactured without any distortion can be manufactured, a large deformation occurs due to the temperature difference of the tube sheet itself when the boiler is started. Also, during normal operation, backwashing is periodically performed to remove dust attached to the surface, and even when the rigidity is increased, the metal tube sheet is deformed by several mm. Due to this tube sheet deformation, a large stress is generated in the ceramic element inserted through the metal tube sheet, and the ceramic element is easily broken. In order to avoid this, it is effective to loosen the powder seal and reduce the stress load. However, as described in Japanese Patent Publication No. 1-49544, it is effective to loosen the powder seal. The powder is scattered and the sealing property is reduced. In particular, since the ceramic filter is backwashed, the powder is instantly scattered.

[0007] To solve this problem, Japanese Patent Laid-Open No. 7-873 has been proposed.
No. 0 proposes a method of indirectly sealing a porous ceramic tube via a metal tube. This method
In this method, a metal ring is placed around a metal tube, and this gap is sand-sealed. In this method, unlike the method of directly constraining the ceramic tube, the ceramic tube is indirectly constrained, so that no stress is applied to the ceramic tube and the ceramic tube is not broken. However, this method has a problem caused by using a sand seal. First, it is difficult to seal many elements uniformly. Since the powder is packed into narrow gaps, the sealing property changes depending on the degree of leakage or filling during the filling operation. Next, there is a problem of vibration of the device. The only thing that stops the powder is the powder retaining ring placed on top and bottom. Due to vibrations caused by backwashing during operation, the holding power of the filled powder changes, and although the ceramic tube does not break, it restrains the metal tube,
The sealing property between the metal pipe and the ceramic pipe is reduced, and the most important dust sealing property as a function is reduced.

In order to prevent this, it has been necessary to reexamine the sealing method drastically. Further, the ceramics filter has a structure in which the elements of the ceramics tube are simply placed on the lower tube sheet without being restrained. Therefore, since there is no difference in elongation at the lower part, the conventional ceramic filter has a structure in which ceramic fibers are simply placed on the fitting portion of the metal tube plate and the ceramic tube is placed. However, in the lower part, dust from the refractory and heat insulating materials used in the container generated during long-term operation tended to collect, and these tended to enter the fitting portion and restrain the ceramic tube. . In the worst case, there is a possibility that the ceramic pipe may be restrained and cracked.

An object of the present invention is to provide a sealing structure for a ceramic tube which can solve the above problems.

[0010]

[Means for Solving the Problems]

(1) In the sealing structure for a ceramic tube of the present invention, a metal tube having substantially the same cross-sectional diameter as the ceramic tube is placed on the upper surface of the ceramic tube via a sealing member. A filler layer made of ceramic fibers and a metal ring is arranged and sealed between them.

(2) The sealing structure for a ceramic pipe according to the present invention is characterized in that the lower end of the ceramic pipe is placed on a receiving member, and a fiber filling layer is provided on the outer periphery of the lower end of the ceramic pipe. I do.

According to the present invention (1), the ceramic tube receives only the load of the metal tube placed thereon in the compression direction and is not joined to the metal tube. Completely separated and disconnected. Therefore,
Even if an unexpectedly high stress such as an earthquake occurs in the upper partition pipe, the sealing performance between the unconnected metal pipe and the ceramic pipe will be reduced, and this part will act as a safety valve to prevent dust leakage. It does not cause stress directly on the ceramic tube. In addition, a filling layer made of a metal ring and ceramic fibers is arranged between the outer periphery of the metal tube and the upper partition tube plate. The ceramic fibers forming the filling layer are flexible and can maintain uniform sealing properties in the circumferential direction. However, there is a drawback that the metal ring forming the filling layer is strong, unlike ceramic fibers, although it has a disadvantage that it is easily deformed by dynamic pressure such as backwashing, so that the sealing property can be ensured.

If the metal ring is too thick, if the axis of the upper partition tube plate is displaced due to tilting or the like, the metal ring bites into the metal tube placed on the upper surface of the ceramics tube and has a sealing property. Not only is it not maintained, but there is a risk of the ceramic tube falling. Therefore, it is desirable that the thickness of the metal ring be kept to a minimum thickness for suppressing deformation of the ceramic fiber.

In the present invention (2), the lower end of the ceramic tube is placed on the receiving member, and the lower end of the ceramic tube is not restrained. Therefore, there is no problem of the position shifting (sliding) due to the difference in extension between the ceramic tube and the receiving member. Further, since there is no movement of the position due to the difference in elongation between the ceramic tube and the receiving member, the sealing property can be ensured by the fiber filling layer provided on the outer periphery of the lower end portion of the ceramic tube.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. Porous ceramic tube 1
Is placed on a sheet packing 3b-2 formed by knitting ceramic fibers placed on a receiving ring 2a of a fitting portion where the lower tube sheet 2 as a receiving member rises.

On the upper surface of the ceramic tube 1, a metal tube 3 having a cross-sectional diameter substantially equal to that of the ceramic tube 1 and a thickness larger than the ceramic tube 1 is placed via a sheet packing 3b-1 as a sealing member. This metal tube 3 is connected to a seal portion 5 provided on an upper tube plate 4 as an upper partition tube plate.

FIG. 2 shows the seal portion 5 in detail. The metal tube 3 is simply placed on the upper surface of the ceramic tube 1 via a sheet packing 3b-1 in which ceramic fibers are knitted and sewn in a ring shape. Around the outer periphery of the metal tube 3, there is arranged a metal ring 5 a to which a horizontal flange portion 5 a ′ is fixed to the upper tube sheet 4. In the gap between the metal ring 5a and the metal tube 3, FIG.
As shown in the figure, the ceramic fibrous filler 5b-1,
5b-2 and a metal ring 5b-3 made of a thin metal plate are combined and filled.

In the present embodiment, the combination of the ceramic fibrous fillers 5b-1 and 5b-2 and the metal ring (ring) 5b-3 made of a thin metal plate is shown in FIGS. The one shown in b) is used.

In FIG. 3 (a), a seamless felt 5b-1 formed by compressing ceramic fibers as a filler of ceramic fibers into a ring shape is placed at the center in the vertical direction, and metal is placed above and below it. Metal ring 5b made of thin plate
-3 is arranged. Further, a plurality of ropes 5b-2 as ceramic fiber fillers formed by sewing and knitting ceramic fibers were arranged on the upper and lower sides. In order to compress these seal portions 5 to make them elastic, a metal tube 5c is placed on the upper surface of the metal tube 5c in an unconstrained state, and the metal tube 5c is mounted on the flange portion of the upper tube sheet 4 by the flange portion of the metal ring 5a. It was fixed with bolts via a metal plate 5d placed on 5a '. In this state, the sealing portion 5 can always obtain high sealing performance.

In FIG. 3 (b), not only the upper and lower portions of a seamless felt 5b-1 formed by compressing ceramic fibers into a ring shape, but also a knitted upper and lower ceramic fibers are sewn to form a ring shape. Rope 5b-2
A structure in which a metal ring 5b-3 made of a thin metal plate is interposed therebetween is employed. This provides a seal structure that can withstand an environment where backwashing is performed at higher pressure.

A description will be given below of the results of a seal test conducted for adopting the seal structure above the ceramic tube 1. FIG. 5 is a vertical sectional side view showing the test apparatus. Place the test body 11 in the electric furnace 12,
Heated to a temperature of 850 ° C. The test section is sealed,
Air was supplied through the air supply pipe 13, and a back pressure of 4500 mmAq was set up by the backwash pipe 14 from the back side. Also, the blow-by caused by the consolidation due to the lateral movement most affects the sealing performance. In order to reproduce this movement, a lateral push bar 15 having a movement of 2 mm in the lateral direction is attached to a shaft at the lower part of the test piece by a shaker and an eccentric cam. In this state, the differential pressure gauge 1
In 6, the internal pressure was measured to evaluate the sealing property.

FIG. 6 shows the configuration of the seal portion and the test results. No. 2 is a conventional method that does not include a metal ring made of a sheet metal,
No. No. 4 is a comparative method in which a metal thick metal ring having a thickness of 10 t was mounted. No. Reference numeral 5 includes a metal ring (thickness 2t) made of a thin metal plate according to the embodiment of the present invention. The test results were organized by the number of lateral movements until the pressure loss on the differential pressure gauge did not rise. As is clear from the results shown in FIG. 6, in the conventional method, the felt was scattered tens of thousands of times, and the pressure loss was reduced. In the comparative method, excellent results were obtained in the first test, but biting occurred in the second test, and there was a problem in reliability. On the other hand, in the embodiment of the present invention, reproducible and stable results were obtained.

Next, the sealing structure at the lower end of the ceramic tube 1 in the present embodiment will be described. As shown in FIG. 4, a two-part bolted metal ring 6 is disposed above the lower tube sheet 2 and around a receiving ring 2a projecting further obliquely upward, and ceramic fibers are placed above and below the gap between the two. 7a and 7b are packed to form a packed layer, which is compressed by tightening the metal ring 6 with bolts and packing the ceramic fibers 7a and 7b. As a result, it is possible to reliably prevent dust from entering this portion.

[0024]

As is apparent from the above description, the seal structure of the present invention is relatively low in strength compared to metal in a large and long member such as a high-temperature dust removal gas filter. Since the sealing property can be ensured without restraining the ceramic pipe, a great effect of reducing the risk of breakage, which is the most problematic in the ceramic pipe, can be obtained.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view of an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a portion A in FIG.

FIGS. 3 (a) and 3 (b) show examples of combinations of a ceramic filler and a metal ring made of a thin metal plate in an upper seal portion of a ceramic tube according to the embodiment of the present invention, respectively. FIG.

FIG. 4 is an enlarged sectional view of a portion B in FIG.

FIG. 5 is a vertical sectional side view of a test device used for a seal test according to one embodiment of the present invention.

FIG. 6 is a diagram showing test results using the test apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic tube 2 Lower tube sheet 2a Receiving ring 3 Metal tube 3b-1 Sheet packing 3b-2 Sheet packing 4 Upper tube sheet 5 Seal part 5a Metal ring 5c Metal tube 5d Metal plate 5b-1, 5b-2 Ceramic fiber Filler 5b-3 Metal ring made of sheet metal 6 Metal ring 7a, 7b Ceramic fiber

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Hashimoto 1-1-1, Akunoura-cho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Toshio Koyanagi 1-1, Akunoura-cho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. Inside

Claims (2)

[Claims] 1. A metal tube having substantially the same cross-sectional diameter as the ceramic tube is placed on the upper surface of the ceramic tube via a sealing member, and ceramic fibers and a metal ring are placed between the outer periphery of the metal tube and an upper partition tube plate. A sealing structure for a ceramic tube, wherein a sealing layer is formed and sealed. 2. A sealing structure for a ceramic pipe, wherein a lower end of the ceramic pipe is placed on a receiving member, and a fiber filling layer is provided on an outer periphery of the lower end of the ceramic pipe.