JP2006162103A - Heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchanger superior in heat resistance and anti-corrosiveness in a combustion exhaust gas flow passage of waste, having durability, and capable of improving the heat exchange effectiveness. <P>SOLUTION: A ceramic heat transfer tube 2 is constituted by connecting an upper heat transfer tube 2a and a lower heat transfer tube 2b by a coupling 4 of a nonmetallic fire resistant material. A flange f1 of an upper end part is locked on and penetratingly suspended by an upper wall 7a of the combustion exhaust gas flow passage for flowing combustion exhaust gas EG. A metallic inner pipe 5 is arranged with a clearance to an inner wall of the ceramic heat transfer tube 2. Low temperature gas La is supplied from one gas pipe 6a, and reaches up to a tip part of the ceramic heat transfer tube 2 via the clearance between the inner wall of the ceramic heat transfer tube 2 and the metallic inner pipe 5. High temperature gas Ha flowing in the metallic inner pipe 5 in the tip part and heated by heat exchange flows out to a gas pipe 6b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat exchanger, and more particularly to a heat exchanger that is excellent in heat resistance and corrosion resistance in a combustion exhaust gas passage such as waste and has durability, and that can improve a heat exchange rate.

  Today, in incinerators and gasification and melting furnaces that incinerate general waste and industrial waste, heat energy of the high-temperature combustion exhaust gas generated by incineration is recovered by heat exchange with low-temperature gas, and the recovered energy is discarded. Systems that are effectively used for thermal decomposition of materials and power generation have come to be adopted.

  The heat exchanger used for this heat exchange is, for example, a bayonet type with a double tube structure in which a heat transfer tube whose tip is closed is projected in the combustion exhaust gas flow path, and a metal inner tube is coaxially provided inside the heat transfer tube A heat exchanger is used.

  In this heat exchanger, heat is exchanged by flowing a low temperature gas into the heat transfer tube heated by the combustion exhaust gas through the metal inner tube, and the heated high temperature gas is passed through the gap between the inner wall of the heat transfer tube and the metal inner tube. It tries to collect. Alternatively, a low-temperature gas is introduced from a gap between the inner wall of the heat transfer tube and the metal inner tube, and the heat-exchanged high-temperature gas is recovered through the metal inner tube.

  By the way, the combustion exhaust gas contains highly corrosive gases such as chlorine, oxygen, water vapor, sulfur and alkali elements, and the heat transfer tubes are exposed to these gases, so that excellent corrosion resistance is required. Therefore, in the conventional heat exchanger, ceramics or the like is used for the heat transfer tube in addition to the heat-resistant metal (see, for example, Patent Documents 1 and 2).

  On the other hand, in order to improve the heat exchange rate, it is necessary to increase the projecting length to the flue gas passage to increase the contact area with the flue gas. However, there are restrictions on the length of manufacturing a ceramic heat transfer tube as a single piece with the current manufacturing technology, and it is difficult to manufacture a heat transfer tube with a length required to increase the heat exchange rate. In addition, there is a problem that enormous capital investment is required.

  Also, if multiple heat transfer tubes are connected using metal members, etc., cracks will occur due to the corrosion of the metal members or thermal stress due to the difference in thermal expansion at the connection portions, and local damage or dropping of the connection portions or heat transfer tubes will occur. Problems such as occur.

Furthermore, if the heat transfer tube is protruded laterally in the combustion exhaust gas flow path, the bending stress acting when the heat transfer tube is lengthened becomes large, which is disadvantageous in strength, and the heat transfer tube and the combustion exhaust gas flow path are caused by bending deflection. There is a problem that it is difficult to maintain airtightness.
JP 2000-297613 A JP 2001-108381 A

  An object of the present invention is to provide a heat exchanger that is excellent in heat resistance and corrosion resistance in a combustion exhaust gas passage for wastes and the like, is durable, and can improve the heat exchange rate.

  In order to achieve the above object, a heat exchanger according to the present invention includes a heat transfer tube formed of ceramic with a closed end, and an inner tube that is inserted into the heat transfer tube and provided with a gap between the inner wall of the heat transfer tube. In the heat exchanger installed in the combustion exhaust gas flow path from the combustion furnace, the heated tube is configured to be able to circulate a heated gas that is heated by heat exchange by communicating the gap and the inner tube. A plurality of connecting heat transfer tubes are connected to each other while maintaining airtightness, and have a locking portion protruding radially outward at an upper end portion, and the locking portion is an upper surface of the upper wall of the flue gas passage And is suspended while penetrating the upper wall of the flue gas passage.

  Here, the combustion furnace includes not only a combustion furnace for burning general waste and industrial waste but also a gasification melting furnace.

  According to the heat exchanger of the present invention, it is provided with a heat transfer tube formed of ceramics whose tip is closed, and an inner tube that is inserted into the heat transfer tube and arranged with a gap between the inner wall of the heat transfer tube, In the heat exchanger installed in the flue gas flow path from the combustion furnace, the heat transfer tube is connected to a plurality of connected heat transfer tubes so that the heated gas heated by heat exchange can be circulated through the gap and the inner tube. Since it is configured to be connected while maintaining airtightness, it can be a heat exchanger with improved durability of heat transfer tubes exposed to high corrosive gas at high temperature by ceramics with excellent heat resistance and corrosion resistance In the past, ceramic heat transfer tubes, which had a limited length that could be manufactured as a single unit from the viewpoint of manufacturing and cost, were connected to each other with a plurality of connected heat transfer tubes kept airtight, so that the heat exchange rate was reduced. Optimal It becomes possible to set the length becomes.

  Moreover, since the ceramic connection heat transfer tubes are connected to each other, it is possible to suppress the generation of thermal stress due to the difference in thermal expansion coefficient, and it is possible to prevent breakage or dropout due to cracks or the like caused by the thermal stress. .

    Further, the heat transfer tube has a locking portion projecting radially outward at the upper end portion, and this locking portion is locked to the upper surface of the upper wall of the flue gas passage so as to be airtight, and the upper wall of the flue gas passage. Therefore, even if the heat transfer tube is lengthened, bending stress does not act and the strength does not become insufficient, and the heat transfer tube has its own weight to improve the airtightness with the upper surface of the upper wall of the combustion exhaust gas flow path. It is easy to keep.

  Hereinafter, the heat exchanger of the present invention will be described based on the embodiments shown in the drawings. FIG. 8 illustrates an outline of the heat exchanger 1 of the present invention. The heat exchanger 1 is installed in a state where it passes through the upper wall 7a of the combustion exhaust gas passage through which the combustion exhaust gas EG from an incinerator, a melting furnace or the like circulates and protrudes and is suspended. The heat exchanger 1 includes a ceramic heat transfer tube 2 whose tip is closed and an inner metal tube 5 that is inserted into the ceramic heat transfer tube 2.

  The ceramic heat transfer tube 2 is configured by connecting an upper heat transfer tube 2a and a lower heat transfer tube 2b, which are connection heat transfer tubes, with a coupling 4 made of a non-metallic refractory material. The metal inner tube 5 is arranged to have a gap with the inner wall of the ceramic heat transfer tube 2, and the gap and the inside of the metal inner tube 5 communicate with each other.

  Upper end portions of the upper heat transfer tube 2a and the metal inner tube 5 are connected to gas pipes 6a and 6b, respectively, and a low-temperature gas La is supplied from one gas pipe 6a so that the inner wall and the metal inner tube 5 of the ceramic heat transfer tube 2 are supplied. It reaches the tip of the ceramic heat transfer tube 2 through the gap, flows into the metal inner tube 5 at the tip, and flows out to the gas pipe 6b.

  The ceramic heat transfer tube 2 is heated by the combustion exhaust gas EG flowing through the combustion exhaust gas channel 7, and the inflowing low temperature gas La becomes a high temperature gas Ha by heat exchange and flows out to the gas pipe 6b.

  Although only one ceramic heat transfer tube 2 is shown in FIG. 8, a plurality of ceramic heat transfer tubes 2 are installed in the combustion exhaust gas flow path 7, and a high-temperature gas Ha exchanged in heat with each ceramic heat transfer tube 2. Flows out to the gas pipe 6b.

  The high-temperature gas Ha that has flowed out to the gas pipe 6b is effectively used as energy for the thermal decomposition of waste or the generation of superheated steam for driving the power generation turbine.

  A low-temperature gas La is supplied from the gas pipe 6b through the metal inner pipe 5, and the heat-exchanged high-temperature gas Ha flows out to the gas pipe 6a through a gap between the metal inner pipe 5 and the inner wall of the ceramic heat transfer pipe 2. You may do it.

  Combustion exhaust gas EG contains very strong corrosive substances such as chlorine, oxygen, water vapor, sulfur and alkali elements, but does not easily react with the components of the incinerated ash in the ceramic heat transfer tube 2 and has excellent corrosion resistance and heat resistance. By forming from ceramics such as silicon carbide, titanium carbide, zirconium carbide and the like, even when exposed to such highly corrosive gas and adhering ash at high temperature, it is difficult to corrode and can be used for a long time.

  Moreover, these ceramics are excellent also in heat conductivity, and it becomes possible to improve a heat exchange rate.

  The inner metal pipe 5 is not exposed to highly corrosive gas, but uses SUS310S, Ni-base alloy, etc., which are excellent in corrosion resistance and heat resistance.

  Furthermore, in order to improve the heat exchange rate, it is effective to increase the area of the ceramic heat transfer tube 2 in contact with the combustion exhaust gas EG. However, in order to make the length of 3 to 4 m or more as an integrated object with the current manufacturing technology and equipment, in addition to difficulty in manufacturing, enormous capital investment is required.

  Therefore, in the present invention, the two ceramic heat transfer tubes 2a and 2b are connected to improve the heat exchange rate. For this connection, a coupling 4 integrally formed of a non-metallic refractory material is used. As the material, a ceramic refractory material such as silicon carbide, titanium carbide, zirconium carbide or the like is used in the same manner as the ceramic heat transfer tube 2, and a material having the same or similar thermal expansion coefficient as the ceramic forming the ceramic heat transfer tube 2 is used. It is used to suppress the generation of thermal stress and to prevent breakage or dropout caused by cracks in the ceramic heat transfer tube 2 and the coupling 4 caused by the thermal stress.

  The structure of the flange of the ceramic heat transfer tube 2 is illustrated in FIGS. FIG. 1 is a half vertical cross-sectional view of a ceramic heat transfer tube 2 connected by a coupling 4, and a line segment CL in the drawing indicates a central axis. FIG. 2 is a half vertical cross-sectional view of FIG. 1 rotated 90 ° around the central axis CL. Fig.3 (a) is AA sectional drawing in FIG. 1, and has shown the planar shape of the flange f1 of the upper end of the upper heat exchanger tube 2a. 3B is a cross-sectional view taken along the line B-B in FIG. 1, the planar shape of the flange f2 at the lower end of the upper heat transfer tube 2a, FIG. 3C is a cross-sectional view taken along the line CC in FIG. The planar shape of the flange f3 of the upper end of the lower heat exchanger tube 2b is shown.

  The flange f1 at the upper end of the upper heat transfer tube 2a is a general flange provided with a peripheral edge of uniform width protruding in the radial direction, and the flange f2 at the lower end is a straight line that cuts off part of the two peripheral edges. Part L is provided. The flange f3 at the upper end of the lower heat transfer tube 2b has the same shape as the above-described flange f2.

  The coupling 4 has a shape as shown in FIGS. 1 and 2 and FIG. 4A is a shape in the BB cross section of FIG. 1 and is connected to the flange f2 at the lower end of the upper heat transfer tube 2a. The planar shape of a connection part is shown. FIG. 4B shows the planar shape of the connecting portion with the flange f3 at the upper end of the lower heat transfer tube 2b in the shape of the DD section of FIG. Both of these connecting portions have engaging portions 4a and 4aa made of straight portions protruding toward the inner peripheral side so as to enlarge the peripheral width, and are substantially similar to the flanges f2 and f3 of the respective heat transfer tubes 2a and 2b. Thus, the flanges f2 and f3 can be inserted.

  In the middle of the coupling 4 in the height direction, an annular end contact portion 4b that protrudes to the inner peripheral side is provided, and a flange f2 at the lower end of the upper heat transfer tube 2a and a flange f3 at the upper end of the lower heat transfer tube 2b, respectively. Comes into contact with the end contact portion 4b through the sealing material S.

  In order to connect the heat transfer tubes 2a, 2b using the coupling 4, the straight portions L of the flanges f2, f3 of the heat transfer tubes 2a, 2b are shaped with the respective engaging portions 4a, 4aa of the coupling 4. It inserts after making a position match, It rotates after insertion, and the flanges f2 and f3 of the heat exchanger tubes 2a and 2b and each engaging part 4a and 4aa of the coupling 4 are engaged.

  Sealing materials S or gaskets G are interposed between the contact portions of the coupling 4 and the heat transfer tubes 2a and 2b so that the airtightness is maintained. The portion where the upper surface of the flange f2 at the lower end of the upper heat transfer tube 2a contacts the coupling 4 and the portion of the lower surface of the flange f3 at the upper end of the lower heat transfer tube 2b and the portion where the coupling 4 abuts depend on the suspension structure of the ceramic heat transfer tube 2 Since the compressive stress is generated, the gasket G having a pressure resistance is used.

  Examples of the material for forming the sealing material S and the gasket G include alumina, mullite, alumina-silica, and the like.

  A peripheral projection 3 protruding radially outward is provided on the outer periphery of the lower heat transfer tube 2b to prevent the sealing material S from moving downward and dropping.

  As illustrated in FIG. 5, the recesses F are provided in the engaging portions 4a and 4aa shown in FIGS. 4A and 4B, and the convex portions are provided in the flanges f2 and f3 of the heat transfer tubes 2a and 2b to be connected. Thus, a structure that fits into the recess F may be adopted.

  With this dent F, the heat transfer tubes 2a, 2b, and the coupling 4 are restricted from rotating even if the longitudinal direction is set as the rotation axis direction by slight vibrations, and it is possible to prevent disconnection from the coupling 4. Become.

  Such an engagement structure for restricting rotation is not limited to the illustrated example, and at least one of the coupling 4 and the heat transfer tubes 2a and 2b to be coupled may be provided with an engagement portion for restricting mutual rotation. That's fine.

  The shape of the connecting portion between the coupling 4 and the upper heat transfer tube 2a of the coupling 4 shown in FIG. 4A and the connecting portion with the lower heat transfer tube 2b of the coupling 4 shown in FIG. However, the present invention is not limited to this, and any rotation deviation angle may be used, and there may be no rotation deviation angle.

  FIG. 9 illustrates another structure for connecting the upper and lower heat transfer tubes 2a and 2b. The lower end portion of the upper heat transfer tube 2a has a tapered portion Ta that is reduced in diameter, and the upper end portion of the lower heat transfer tube 2b has a tapered portion Tb that is increased in diameter, and the taper angles thereof are substantially the same. ing.

  The inner diameter of the upper heat transfer tube 2a excluding the taper portion Ta is larger than the outer diameter of the taper portion Tb of the lower heat transfer tube 2b. The lower heat transfer tube 2b is inserted from the upper end portion of the upper heat transfer tube 2a, and the taper portions Ta, Tb is locked. A sealing material S is interposed between the taper portions Ta and Tb, and the heat transfer tubes 2a and 2b are connected to each other while maintaining airtightness by the weight of the lower heat transfer tube 2b.

  With this structure, since the connection is made of the same material, generation of thermal stress can be suppressed. Further, since there is no portion projecting radially outward with respect to the upper outer periphery on the outer periphery of the heat transfer tubes 2a and 2b, it is possible to prevent the incineration ash from accumulating, and the coupling 4 is not required and the structure is simplified. Can be achieved.

  FIG. 10 shows still another structure for connecting the upper and lower heat transfer tubes 2a and 2b. The lower end portion of the upper heat transfer tube 2a has a flange portion f2 that protrudes inward, and the upper end portion of the lower heat transfer tube 2b has a flange portion f3 that protrudes outward. . A sealing material S is interposed between the flange portions f2 and f3, and the heat transfer tubes 2a and 2b are connected while maintaining airtightness due to the weight of the lower heat transfer tube 2b.

  Even in this structure, since the connection is made of the same material, generation of thermal stress can be suppressed. Further, the coupling 4 is not necessary, and the structure can be simplified.

  The support structure for the upper wall 7a of the ceramic heat transfer tube 2 is illustrated in FIGS. In FIG. 6, the lower surface of the general flange f1 which consists of the periphery of the uniform width which protrudes to the radial direction outer side provided in the upper end of the ceramic heat exchanger tube 2 as shown to Fig.3 (a), and a combustion exhaust gas flow path upper wall A similar flange f4 provided on the upper surface of 7a faces through the sealing material S. The upper surface of the flange f1 at the upper end of the ceramic heat transfer tube 2 and the flange f5 of the gas pipe 6 are opposed to each other through the seal material S. For example, the flange f5 of the gas pipe 6 and the flange f4 of the upper wall 7a are not shown. Fastened with bolts and nuts, the gas pipe 6 and the ceramic heat transfer tube 2, and the ceramic heat transfer tube 2 and the upper wall 7a are connected in an airtight manner. The flange f1 at the upper end of the ceramic heat transfer tube 2 serves as a locking portion and is locked to the upper surface of the combustion exhaust gas flow channel upper wall 7a, so that the ceramic heat transfer tube 2 is suspended.

  In FIG. 7, the lower surface of the flange f1 at the upper end of the ceramic heat transfer tube 2 has a tapered portion that spreads to the outer peripheral side, and the flange f4 of the combustion exhaust gas flow channel upper wall 7a also has a tapered portion of substantially the same angle that receives this tapered portion. It is provided and faces through the sealing material S. In this state, the flange f5 of the gas pipe 6 and the flange f4 of the upper wall 7a are fastened by fastening bolts and nuts (not shown) and are connected in an airtight manner as in FIG.

  6 and 7, the ceramic heat transfer tube 2 can be stably suspended from the combustion exhaust gas flow channel upper wall 7a by its own weight. Further, since the fastening member can be fastened without being located at a place exposed to a corrosive gas at a high temperature, a general metal fastening member can be used.

  Further, by suspending the ceramic heat transfer tube 2 substantially vertically from the upper wall 7a of the flue gas flow path, a support structure for the above-described upper wall 7a becomes possible, and even if the ceramic heat transfer tube 2 becomes longer, it can be bent. It is advantageous in terms of strength without stress. In addition, the amount of combustion ash contained in the combustion exhaust gas EG deposited on the ceramic heat transfer tube 2 can be minimized, and the heat transfer coefficient can be prevented from being lowered and uneven, thereby further improving the heat exchange rate. It becomes possible and the maintainability is also improved.

  By suspending the tip of the ceramic heat transfer tube 2 without contacting the lower wall of the combustion exhaust gas flow path 7, the occurrence of thermal stress in the longitudinal direction of the ceramic heat transfer tube 2 can be prevented, and the structure is simple. Is possible.

  In order to suppress the accumulation amount of combustion ash, it is preferable to minimize the amount of protrusion of the coupling 4 in the radial direction from the ceramic heat transfer tube 2, and the upper end portion of the coupling 4 is chamfered to be tapered. By doing so, the amount of combustion ash deposited may be suppressed.

It is a semi-longitudinal sectional view which illustrates the ceramic heat exchanger tube concerning the present invention. FIG. 2 is a half longitudinal sectional view rotated by 90 ° around a central axis CL in FIG. 1. It is explanatory drawing which illustrates the whole flange of the ceramic heat exchanger tube which concerns on this invention. (A) is AA sectional drawing in FIG. 1, (b) is BB sectional drawing in FIG. 1, (c) is CC sectional drawing in FIG. It is explanatory drawing which illustrates the whole connection part of the coupling which concerns on this invention. (A) is BB sectional drawing in FIG. 1, (b) is DD sectional drawing in FIG. It is explanatory drawing which shows the other example of the connection part of the coupling shown to Fig.4 (a), (b). It is a longitudinal cross-sectional view which shows an example of the suspension structure of the heat exchanger of this invention. It is a longitudinal cross-sectional view which shows the other example of the hanging structure of the heat exchanger of this invention. It is explanatory drawing which shows the outline | summary of the heat exchanger of this invention. It is a half longitudinal cross-sectional view which shows the other example of the ceramic heat exchanger tube which concerns on this invention. It is a semi-longitudinal sectional view showing still another example of the ceramic heat transfer tube according to the present invention.

Explanation of symbols

1 Heat exchanger 2 Ceramic heat transfer tube
2a (Ceramic) Upper heat transfer tube
2b (Ceramic) Lower heat transfer tube
3 Circumferential protrusion 4 Coupling 4a, 4aa Engagement part 4b End contact part 5 Metal inner pipe 6, 6a, 6b Gas pipe
7 Combustion exhaust gas flow path 7a Upper wall
F Indentation of coupling
G Gasket S Seal material

Claims (3)

  A heat transfer tube formed of ceramics with a closed end, and an inner tube that is inserted into the heat transfer tube and arranged with a gap between the inner wall of the heat transfer tube and communicates the gap with the inner tube. In the heat exchanger installed in the combustion exhaust gas flow path from the combustion furnace, the heat transfer tube is connected with a plurality of connected heat transfer tubes being kept airtight. And has a locking portion protruding outward in the radial direction at the upper end portion, and the locking portion is locked to the upper surface of the upper wall of the flue gas flow path while maintaining airtightness, and the flue gas flow A heat exchanger characterized by being suspended through an upper wall of a road.   The heat exchanger according to claim 1, wherein the connection between the plurality of connection heat transfer tubes is through a coupling formed of a non-metallic refractory material.   The rotation regulation engagement part which regulates the mutual rotation which makes the longitudinal direction of the said heat exchanger tube the rotating shaft direction was provided in at least one of the coupling and the connection heat exchanger tube connected with the said coupling. Heat exchanger.

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