US2764398A - Stub tube refractory tile for recuperators - Google Patents

Description

p 1956 c. HERMAN 2,764,398

STUB TUBE REFRACTORY TILE FOR RECUFEIRATORS Filed April 10, 1953 IN V EN TOR. Car/ 1 5 6/7770.

United States Patent STUB TUBE REFRACTORY TILE FOR RECUPERATORS Carl L. Herman, Canonsburg, Pa., assignor to Amsler Morton Corporation, Pittsburgh, Pa., a corporation of Delaware Application April 10, 1953, Serial No. 347,870 5 Claims. (Cl. 263-51) back and forth across the recuperator chamber from the bottom to adjacent the top thereof for the purpose of absorbing heat from the waste gases and transferring it to the air flowing through the horizontal passages to the burners. These heat exchange tile structures are built inside an insulated wall of firebrick forming a chamber for the purpose of obtaining a heat exchange from the hot gases flowing from the furnace chamber down through the vertical flues to the stack. As the waste gases pass down through these flues, they impart their heat to the vertical flue tiles and flue blocks which is thereby transferred to the air or mixed air and gases traveling up through horizontal passes of the recuperator in a zigzag path transversely of the vertical flues.

The preferable method of operating the recuperator of this type is to cause hot furnace gases that are discharged from the furnace chamber to flow down through the vertical flues and to introduce the air or mixture of air in gases or gases to be heated at the bottom of the recuperator structure and causing them to flow through the several horizontal zigzag passes progressively toward the top of the structure, after which they are conducted to the burner for supplying the same with hot air for supporting the combustion of the fuel that is finally mixed at the burner and introduced into the combustion chamber. When operating recuperators in connection with heating or melting furnaces, it has been found that the hot waste gases from the furnace carry a material amount of finely divided dust and other foreign particles which become deposited on top of the recuperator structure and when this debris accumulates, it has a tendency to build up and clog the vertical flues and necessitate cleaning them out. In the structure as shown in U. S. Patent 2,574,738, a series of vertically extended stub flues were provided to catch the residue that is carried by the waste gases from the furnace chamber. When this deposit builds up around these stub tubes and the deposit is about to spill over and pass on through the tubes themselves, it must be removed or it will affect the operation of the recuperator. The stub tubes readily connect this deposit which fills up the area around them. The stub tubes, together with the top horizontal layer of tile that covers the top of the recuperator, should be removed and replaced before this deposit gets high enough to travel down the flues. However, structures fabricated by the use of the vertically heat from the upper end of the tube.

disposed stub tubes as illustrated in the aforementioned patent are frequently subjected to very hot gases issuing from the furnace chamber which are quite severe on these thin stub tubes. They are exposed completely and they extend above the top layer of the recuperator under which the air being heated passes. These thin stub tubes do not have any means of conducting heat from their outer surfaces. They have difficulty withstanding the intense heat caused by the gases flowing directly from the furnace. In view of the fact that these stub tubes do not have heat conducted away from their outer surfaces, they cannot cool sufficiently fast by conduction to permit it to cool during the operation of the furnace. This accumulation of heat causes the tubes to rise in temperature to such a degree that they become soft and collapse folding inwardly which increases the resistance to flow of the hot gases through their vertical flues and further builds up the temperature in the recuperator. They eventually stop up the vertical flues and make it necessary to remove some of the stub flues before it is necessary under ordinary circumstances to open up the recuperator to make normal repairs, resulting from normal service.

The principal object of this invention is to provide a stub tube or refractory tile for recuperators, which is provided with an increased cross section, to enable the tile to withstand the higher temperatures regardless of the heat concentration and cause the tile to conduct the heat to the top rows of the recuperator tile structure.

This feature of the invention is obtained by forming the tube integral with a base shaped like the flue block tile that is tubular and has its perimeter shaped to mate with the perimeter of adjacent tile structures. The tubular base of this stub block tile has formed integral therewith an upwardly tapering stub tube, which is not only formed integral with the base tile but functions as its tubular base, and also takes the shape of the base tile so that it presents a maximum amount of material in the tile structure that increases in cross section from the top of the stub tube section to the base tile so that it may more readily conduct a greater amount of heat from the upwardly extending portion of the stub tube. This character of stub tube tile block thus increases the efiiciency of the operation of the stub tubes and prevents them from being melted when subjected to such a great amount of heat that they would tend to collapse and close their vertical flues.

/ Again the tapering wallstructure of the upwardly proje'cting stub tube becomes uniformly thicker as it approaches the tubular base section of the tile. This provides an increased amount of tile material for conducting the heat from the outer upper end of the stub tube to the horizontal section of the recuperator structure where. the head may be dissipated by the heat exchange to. the air traveling through the horizontal paths and still-provide a material space to catch the cinders and foreign material passing with the hot gases out of the furnaces.

Tile blocks forming the tubular base of the stub tube structure, comprising this invention, have diiferent peri- [continued up the outer face of the stub tube which provides increased cross sectional area for transferring the The increasedcross sectional area is small, but it does provide for additional material for conducting heat away from upwardly projecting portions. 7 I

The stub tube refractory tile, comprisingthis invention, is rfitted with a series of* adjacent intermediate tile blocks to form a layer on top of the recuperator structure. Owing to the fact that the stub tube extends materially above the intermediate tile sections joining the same, the upwardly projecting stub tubes will catch a considerable amount of dirt, ash, and other foreign substance that would ordinarily pass down through the vertical tubes and accumulate therein causing them to become choked and finally prevent operation of the recuperator. The top layer or horizontal course of the recuperator tile structure, including the upwardly projecting stub tubes that are mounted in alignment with each vertical flue, is not cemented or otherwise secured to the next horizontal course on which it is supported. The top horizontal course on which the stub tubes are supported provides a smooth, plane surface, having a series of holes rep-resented by each of the vertical flues. Thus, the top horizontal course is uncemented to the top course of the recuperator tile structure defining the passages and is not attached. This permits this stub tube course to be removed along with the soot, dirt, and ash that is deposited in a crusted layer caught by the sides of the upwardly projecting stub tubes. When the space between the upwardly projecting stub tubes becomes completely filled and is no longer capable of catching any more dust or debris, then the whole layer is removed and replaced.

The specific structure of the stub tube as disclosed in this invention will not become soft or otherwise melt and cave in due to the high temperatures or pressure of the gases carrying foreign material that impinge against the sides of the tubes, because this tapered .construction provides sufiicient strength to withstand these pressures and also provides suflicient volume of ceramic tile material for conducting the heat away from the upwardly projecting portion of the tube. 7

Other objects and advantages appear hereinafter in the following description and claims.

The accompanying drawings show for the purpose of exemplirfication without limiting the invention or claims thereto certain practical embodiments of the invention wherein:

Fig. 1 is a View in vertical sec-tion of the stub tube comprising this invention.

Fig. 2 is a plan view of the structure shown in Fig. 1.

Fig. -3 is a view in vertical section of the recuperator tile structure assembled in a refractory chamber and embodying the principles of this invention.

Referring to the drawings, each of the tile members making up the recuperator structure is made of the refractory material capable of withstanding a high heat and a high degree of thermal shock. However, the type of tile in the lower courses of the recuperator, which are cooled by the flow of the air, may not be able to stand the extreme temperatures of the initial waste heat gases that the upper course is constructed to withstand and particularly the upwardly projecting stub tubes which are in the initial part of the recuperator and are required to assume a considerably higher amount of heat. Normal flue tile is slip cast.

The recuperator tile member or stub tube refractory tile member, as illustrated in Figs. 1 and 2, and pressformed from a high heat resistant super duty clay and comprises a tubular base section 1 which has a continuous open throat 2 and is formed with an outer perimetral surface which is provided with a groove 3. If the base '1 is cylindrical, the groove 6 becomes cylindrical. However, in most refractory structures of this kind, it is preferable to make them octagonal, and as illustrated in Fig. 2, the stub tube comprising this invention is made in this shape. This design provides better structural features as well as higher heat resisting material. Cement in the groove 3 holds the blocks together.

The perimetral surfaces of the upper and lower flanges -4 and 5 that are defined by the angular faces and the groove 3 therebetween is shaped in an octagonal form as illustrated in 'Fig. 2. The flanges 4 and 5 are substantially the same thickness. This tubular base member is constructed the same as the flue blocks that are employed in the lower portion of the recuperator tile structure.

Extending upwardly from the tubular base 1, the stub tube is provided with a tapered wall section as illustr-ated at '6, and the opening that extends therethrough is continuous and uniform. The upward projection 6 is approximately two and one half times or more in height relative to the tubular base and the outer wall surface tapers from the perimeter of the flange 4 to the upper end 7 of the stub tube 6.

Since the flanges of the tubular base are octagonal, the tapered faces of the upward extending stub tubes are likewise provided with octagonal faces such as illustrated at 8. The actual tapered surface is preferably formed following the curve of an arc '9 struck from the center 10 disposed outwardly from and above the upper end 7 as indicated by the construction line 11. This arcuate perimetral surface may be employed regardless of the shape of the perimetral surface of the base of the stub tube. It provides a heavier cross section adjacent the tubular base and a thinner intermediate section than if the structure were to follow the plane of the cord 12 which subtends the are formed by the are 9. Again the outer surface, as presented by the arc 9, is relatively steep adjacent the outer end of the stub tube which promotes the sliding of the debris more readily than that of a surface that would follow the subtended are '12.

A section of the recuperator chamber is shown in Fig. 3 wherein a recuperator refractory chamber 13 is enclosed by the refractory insulated walls 14 and 15, and the arched roof 16 which contains the passage 17 through which the gases pass that are drawn from the furnace chamber.

The bottom of the recuperator chamber 13 is provided with a bridge wall 18 designed to support the recuperator tile structure within the chamber 13, which is provided with a plurality of openings 20 that are aligned with the vertical fines of the recuperator tile structure for the purpose of conducting the waste gases from the recuperator through the passage 21 to the additional heat cxchangers or to the stack as the case may be.

The horizontal courses of the recuperator tile structure are formed by a plurality of different characters of tile members similar to those shown in Patent No. 2,092,402. The flue blocks 22, as shown, are similar to the base of the tubular member 1 of the stub tile section, and they are joined with the center blocks 23, together with the edge blocks 24, for completing the course of the tile structure.

Since the flue blocks 22 are octagonal in shape, the base structure of the stub tube refractory tile member must also be of similar shape so as to coincide with the same when positioned on the uppermost course of blocks as shown in Fig. 3. Each of the horizontal courses of the tile structure is connected by the tubular flue members 25 that are in turn cemented in recesses in the upper and lower flue blocks 22. Although all of the lower courses of the recuperator tile structure are cemented together, it is preferable that they not be cemented to the walls 14 and 15 to permit relative expansion and contraction of the same. However, they are sufficiently close fitting that the gases do not escape down past the outer perimeter of the horizontal courses, and the top is sealed Again the flue dust accumulates around the upwardly extending stub tubes and increases the seal of the horizontal courses at the upper end of the recuperator, and thus prevents any leakage of the waste gases other than through the vertical tubes through which they are intended to flow.

While for clarity of explanation, certain preferred embodiments of this invention have been shown and de' 5 scribed, it is to be understood that this invention is capable of many modifications. Changes in the construction and arrangement may be made therein, and certain parts may be employed Without the conjoint use of other parts without departing from the spirit and scope of this invention.

I claim:

1. A stub tube of compressed refractory material for recuperators com-prising a base section having a tubular passage, an upwardly extending flue section having a tubular passage and integral with said base section, the cross-sectional area of the flue section well being increasingly greater from the top of the flue section to where it joins the top of the base section to increase the thermal conductivity to the base section, and said tubular passage in said fiue section and said base section forming a continuous flue passage of uniform cross-section.

2. The structure of claim 1 characterized in that the lower outer perimetral surface of said tubular flue section joins the perimeter of said base section.

3. The structure of claim 2 characterized in that the perimeter of said base section is of polygonal shape.

4. The structure of claim 1 characterized in that said flue section wall is uniformly tapered from the top of the base section to the top of the flue section.

5. The structure of claim 1 characterized in that the shape of the outer perimetral face of said tubular flue section is tapered and conforms with the shape of the perimeter of said base section.

References Cited in the file of this patent UNITED STATES PATENTS 1,510,857 Munster Oct. 7, 1924 1,838,720 George Nov. 22, 1932 2,574,738 Graham et a1. Nov. 13, 1951

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