Sand-filled sealing structure between at least one tube and a tube support plate

#The present invention relates to a sealing structure between at least one tube and a tube support plate, e.g. in a tubular heat exchanger.

#For the convenience of description, a reference is made to a heat exchanger comprising a gas channel through which a heating gas such as a high temperature combustion gas flows and a plurality of transversely extending heat exchanger tubes through which a gas to be heated, flows. In such a heat exchanger, holes are provided on the channel wall constituting a tube support plate, and the heat exchanger tubes extend through the holes and project with their open ends located outside the channel wall. It has been known to provide a header to enclose the projected portions and the open ends of the tubes. After being assembled, the heat exchanger of this type is heated and used at a high temperature. Thus, there is a considerable temperature difference between at the time of the assembling and at the time of its use. Further, even during the use, there will be a substantial temperature difference and temperature distribution between the heat exchanger tubes in which a gas to be heated flows and the tube support plate along which the heating gas flows and accordingly which is substantially affected by the temperature of the heating gas. Furthermore, both the gas to be heated and the heating gas undergo temperature changes as time passes. Due to such temperature differences, temperature distribution and temperature changes, there will be a difference in the thermal expansion degrees between the heat exchanger tubes and the tube support plate, whereby a thermal stress will be created. Further, in many cases, such a heat exchanger takes a form of a heavy large size structural installation, whereby a mechanical stress will be created by the weight of the installation itself, by the load caused by the manufacturing error or by other external forces.

#In order to prevent a deformation or breakage of the parts of the heat exchanger due to such thermal stress or mechanical stress, it is desired to enlarge the holes provided on the tube support plate so that their diameter is larger than the outer diameter of the heat exchanger tubes and thereby provide a structure which permits relative displacement of the heat exchanger tubes and the tube support plate. However, such a structure permits leakage of gases through the clearances between the holes and the heat exchanger tubes, whereby the heating gas and the gas to be heated will be mingled, such being undesirable.

#Now, the present invention will be described in detail with reference to the preferred embodiments.

#In the accompanying drawings, FIG. 1 is a cross sectional view of a heat-exchanger to which the present invention is applied.

#FIG. 2 is an enlarged cross sectional view of portion A of FIG. 1 illustrating an embodiment of the present invention.

#Referring to FIG. 1, a heat exchanger 1 is disposed across a gas channel 2 made of e.g. a refractory material. This heat exchanger 1 comprises a plurality of ceramic heat exchanger tubes 3, tube support plates 4 and 5, an inlet side header 6 for a gas to be heated and an outlet side header 7, as main components. In the gas channel 2, a combustion waste gas having a high temperature of e.g. 1,000.degree. C. flows as a heating gas in a vertical direction between the tube support plates 4 and 5, while a gas to be heated, flowing in from the inlet side header 6 and having a temperature of e.g. room temperature, is heated to a tempeature of e.g. 600.degree. C. during its travel through the heat exchanger tubes 3 and flows out of the outlet side header 7. Between the gas channel 2 and the heat exchanger 1, a stopper 8 secured to the heat exchanger 1, a heat resistant sealing member 9, and a pressing means 10 are disposed as illustrated, whereby the heat resistant sealing member 9 is pressed by the pressing means 10 towards the stopper 8 to establish a sealing to prevent leakage of the heating gas.

#The heating gas sides of the tube support plates 4 and 5 made of a metal, are lined, respectively, with a refractory materials 11, and the side of the tube support plate 5 facing the inlet for the gas to be heated, is lined with a heat insulating plate 12. On the other hand, the side of the tube support plate 4 facing the outlet for the heated gas is exposed directly to the heated gas. Further, the outlet side header 7 is also lined with a heat insulating material 41. In FIG. 1 and FIG. 4, the structures of the joint portions between the tube support plates 4 and 5 and the heat exchanger tubes 3 are all alike. Therefore, only one joint structure is shown in cross section, the rest being shown by their contours.

#As shown in FIG. 2 as an embodiment of the present invention, the tube support plate 4 is provided with a hole 13 having a diameter slightly larger than the outer diameter of the heat exchanger tube 3, and the refractory material 11 is likewise provided with a through-hole 14. The heat exchanger tube 3 extends through the hole 13 and the through-hole 14. An internally threaded ring member 15 is secured to the side of the tube support plate 4 facing the gas to be heated. This ring member 15 encloses the heat exchanger tube 3 with a space of e.g. from 5 to 30 mm therefrom. In the space between the ring member 15 and the heat exchanger tube 3, a heat resistant inorganic sand 16 is filled to form a sand layer having air-tightness. As the sand 16, there may be employed any optional particulate material having a proper particle size depending upon the temperature condition or the anti-corrosive condition under which the sealing structure of the present invention is used. It is usually preferred to employ an inorganic particulate material having a particle size of at most 0.3 mm, more preferably at most 0.05 mm, with a view to securing the air-tightness. For instance, there may be mentioned diatomaceous earth, silica sand, silica powder, cordierite powder, graphite powder or boron nitride powder. At each axial end of the sand layer, a flexible inorganic rope member 17 or 18 such as an asbestos rope or a synthetic inorganic fiber rope is provided as a means for preventing leakage of the sand 16 from the sand layer. Further, the rope member 18 is pressed towards the rope member 17 by a pressing ring 19 having an outer male screw thread corresponding to the inner female screw thread of the ring member 15.