US1732514A - Furnace water wall and wall element - Google Patents

Description

Oct. 22, 1-929. H E 1,732,514

FURNACE WATER WALL AND WALL ELEMENT Filed D80. 16, 1926 2 $h$t$-$h$$t 1 INVL'NTOR Mm J m 6 BY @arguw I Oct. 22, 1929. v T HUNTER 1,732,514

FURNACE WATER WALL AND WALL ELEMENT Filed Dec. 16, 1926 2 Sheets-Sheet 2 m/ VE/V 70)? WT W A TTOHNEYS Patented Oct. 22, 1929 NITED STATES PATT' ARTHUR TEMPLETON HUNTER, OF WEBSTER GROVES, MISSOURI, ASSIGNOB "I'O INTER- NATIONAL COMBUSTION ENGINEERING CORPORATION, OF NEW YORK, N. Y., A. COR- PORKTION OF DELAWARE,

FURNACE WATER WALL AND WALL ELEMENT Application filed December 16, 1926. Serial Ito-155,197.

This invention comprises a novel furnace Water wall, and wall element, and has more particular reference to water or similar fluid circulation walls .for boiler furnaces, although available for other furnaces, the Water wall being adapted to function'for the generation of steam or for the superheating of steam or for purposes of keeping relatively ments willpresent an eflective face toward the combustion space and possess such structure as to bring about the transfer or flow of heat at a high rate from all parts of the wall face inwardly to the tubular portion of the element and the water or other medium circulating therein. A further object is to afford a structure or cross section of water wall element which can be practically and economically manufactured, and. to afford a method of manufacture thereof. Other and further object and advantages of the presentinvention will be elucidated in the hereinafter following description of one ormore embodiments thereof or will be understood to those skilled in the subject.

In referring to a furnace wall or water wall herein the word wall is intended to include any boundin surface of the furnace or combustion cham ber, including a bottom wall or floor. Inusing the word water in connection with the water wall or boiler, it is intended to include water either in liquid form or vapor, since steam .possesses the capacity to absorb and carry away heat through the passages of the wall elements. B a water wall element it is intended to re er' toany elongated tubular element enclosing a circulation passage and provided with the characteristic features of this invention. The tube portion'hereof is preferably cylindrical, with a circular interior passage, but may be of other shape.

- The furnace water wall element hereof may be broadly described as comprising the tube portion and an exterior extension which'constitutes a facing and which has such ample cross section as to afford a high rate of heat transfer from all parts of the front face of the extension inwardly to the tube portion of the element and the water or other medium.

circulating therein.

The term facing is intended to include a front or inward enlargement of the tube constituting an extension or appendage which faces toward the combustion or flames within the furnace, while the .face of the element is the front surface of such facing or extension, facing the flames.

A system or bankof wall elements such as referred to may be assembled to form a furnace water wall which itself is novel and const tutes a portion of the present invention. Prior to the present invention, I have 'known of no practical method of manufacturing such a wall element or water wall as herein described and the method as hereinafter explained constitutes another portion, of the present invention, the method however having been divided out and made the subject of divisional application Serial No. 307,984, filed September 24, 1928, for Method of forming an extension upon a tube.

In the accompanyingdrawings Fig. 1 is a transverse section of a water wall element or tube constituting an illustrative embodiment of the present invention. v v

Fig. 2 is a similar view showingone of many possible variations of form and structure of the wall element hereof.

F ig. 3 is a perspective view showing th preferred longitudinal structure of a water wall element having a cross section such as Fig. 1.

t Fig. 4 is a front or face view of a water wall built up of wall elements such as shown in Fig. 3. f

A Fig. 5 is a transverse section taken on the line 55 of Fi 4 indicating how the furnace wall may be closed and completed by means of suitable refractory packing and exterior shell.

Fig. 6' shows a cross section of a method and apparatus for manufacturing the novel wall element of this invention.

. Water passage 12 and the exterior extension or facing 13. The latter may be described as consistin of a central part or body 14 and preferably symmetrical opposite w ngs 15 rendering the facing substantially wider than the diameter of the tube 11, and the front face or surface 16 extending over the whole width of the body and wings.

- As will be described, the metal constituting the tube 11 is preferably integral with that constituting the extension or facing 13, but as the two consist preferably of different or united metals the drawing indicates a theoretical division line, or line of union 17 between the two. .In structure the described element is preferably made from a preformed steel tube 11 and an integrally united or fuse welded cast iron extenslon 13. The tube may be a seamless wrought steel tube of standard type used for'boiler tubes, while the extension may consist of gray cast iron cast directly and integrally upon the steel tube as Wlll be subsequently described. I

It will be noticed that the extenslon or facing 13 has ample cross section so as to afford a high and rapid rate of heat transfer from 'all parts of the face inwardly to the tube portion and the water flowing therein. This is due to the indicated shape and .arrangement including a cross section of extension wnich is not merely thick enough to present a wide avenue of heat travel, but is of gradually widening character fromthe most remote point or the tips of the wings 15 to the place of heat conduction through the original tube line to the circulating water. Units of heat entering at various parts of the face are not impeded by congestion at any point .of small cross section, so that at each point of the face the heat is able to travel inwardly or from the face, with substantially separate paths of travel of the heat entering at each unit of face area. Thls allows for practically unrestricted heat travel from the furnace wall face exposed to the the in an inward direction towards the circulating medium While the design might ter is, able to take up and carry away the heat. The described wall element is therefor self protecting from destruction by con- 165 gestion and overheating at any point there iar. The tube portion is protected from de- 'terioration, while its capacity to receive heat is increased by the large exposure of the extension; and the extension is protected by the rapid conduction of received heat to the tube and its removal by circulation.

The desired conduction and results would not to be attainable for extreme conditions of boiler service unless the tube portion and facing extension are unitarily connected as stated. The line or union 17 therefore preferably indicates a line of intimate and absolute contact between the two portions, with molecules or crystals interlocked continuously along the contiguous portions of the tube and facing. All the drawbacks of clamping or bolting devices are obviated, and the improvement is superior to a shrunk attachment in that the latter has but poor conduction to the tube, and by growth gradually loosens, overheats and burns away.

Some of the preferable features of the illustrated wall element are as follows. The face or front surface 16 is preferably plane and flat so as to lie in the plane of the water wall, and with adjacent wall elements afford a substantially flush, flat wall. Preferably also the middle portion 14 of the extension is of substantial thickness so that the original tube periphery does not directly contact the flames, although in some cases the thickness of the facing extension might be reduced to leave the tube portion substantially centrally exposed. The entire extension 13 preferably spans a substantial extent of periphcry of the tube, more than 90 but less than 180, as shown. One factor is to avoid excessive weight and this is well accomplished by the particular curved contour at the outer sides of the wings 15 as shown in Fig. l. The facing extension also is preferably bilateral and symmetrical, thus minimizing the distance of travel of the heat from the extreme wing tips to the circulating tube for any given spacing of the tubes in the wall. The design shown minimizes any tendency to bend or warp the tube by expansion or growth.

The advantageous heat conduction of the invention is approximately indicated by the heat travel arrows 18 shown at the left side of Fig. 1, showing that at each point in the facing theheat received from the flames travels inwardly and not along or parallel contour and having embedded in the face lit) thereof plates or blocks 21 of some highly refractory material having high heat conducting qualities, such as carboglaze, a form of silicon carbide, al undum, or the like. This structure increases the life of the wall due to the v greater resistance to heat of the refractory as compared with cast iron.

Rather thanapply the extension facing continuously to the tube portion it ispreferably applied in relatively short sections as shown at 13, 13 in Fig. 3, with spaces or grooves 23 between each two sect-ions. These spaces facilitate the manufacture of the wall element and in use they allow expansion of till the hot sect-ions without causing curving of the element and swelling of the wall. The arrangement also allows for the gradual growth which occurs with repeated heatings of ferrous metals. While a mild steel, low in carbon, is preferable for the preformed tube, cast iron is superior for the facing. for example a gray iron high in carbon, and the rapid transfer of heat enables the iron to be kept form excessive temperatures, and if kept below 900 F. this may preclude the growth occuring at higher temperatures.

Taking a specific instance, namely, with a #9 seamless boiler tube, having a diameter of about 3 inches, the spaces between the sect- ions 13, 13 may be inch. Each section may be about 6 inches long and of a width slightly less than the. spacing between the tubes. Fig. 4 shows a furnace wall constructed in this manner from elements such as shown in Fig. 3. The center lines of the elements having a 6 inch spacing, each section 13 may be 5 inch wide, thus allow ing a separating space 25 of inch between the successive elements for expansion.

It will be understood that the wall tubes may have their ends expanded into headers as is usual with circulation tubes in boilers and furnaces. The tubes, for example, may be vertically arranged and of 20 foot length, in which case the facing extensions may be omitted above the highest level of the com bustion flames in the furnace. If needed to conform to the arrangement of the boiler or furnace the wall elements of this inven-' tion may have a curved or bent shape, pref erably applied to the tubes before the addition of the extensions.

The illustrated wall structure with the by an outer sheet metal casingor shell 28.

A mode of interconnection for spacing the water wall from the exterior shell is indi cated in the form of clamps or braces 29 shown extending more than half way around the tube portion 11 of some of the wall elements, where the same are. suitably tightened, while the outer extension or stem of each clamp device is secured by nuts or otherwise in proper relation to the enclosing shell 28. Fig. 5 therefore indicates a completed water wall embodying the present invention.

Another advantage of the water wall of this invention is that fuel of a flowing nature maybe injected into the furnace between the sections of the wall. Thus in Figs. 4 and 5 is indicated a tube or'burner 30 projecting through the furnace wall and directin a stream of fuel, which may be pulverized uel mixed with air, or oil, the edges of the wall sections at the injecting point being broken away to accommodate the burner. A furnace so constructed is very eflective for pulverized coal combustion.

Indeed, the wall may be open for the through passage of products of combustion or settling of ashes,'in which case'the spaces between the tube elements of the wall will be unpacked, and may be enlarged by reducing the lateral width or dimension of each facing or extension, so long as it faces the fire, protects the tube and carries the radiant heat effectively to the circulating water. with ample section to avoid congestion of heat; an example being the lower tier of tubes of a. water tube boiler, which may carry facing extensions at their lower sides or facing the flames, in which case the gaps or grooves 23 are not necessary as there is no continuous flush surface to be distorted by swelling.

The water wall element, hereinabove described, may be manufactured on an economical basis by the following method. Starting with a standard seamless steel tube of the desired shape and length this should first be thoroughly cleaned prior to the casting operations. It should first be dipped in pickling acid to loosen the scale, for at least half of the circumference of the tube, and this should be followed by sand blasting until the surfaceis bright and clean.

A portion of the length of the tube may then be inserted in a special mold such as is indicated in Fig. 6. This comprises a lower mold section 32 and above it a remo-vable upper section or cope 33. The casting space 34 corresponds with the cross section shape of the facing extension 13 as seen in Fig. 1, and is to be formed by a suitable pattern positioned against the side of the tube 11 during the molding of thesand. A sheet ducting the molten iron to the lower part of the casting recess 34, and a pouring spout gate or wide channel 35 is indicated for con-- 36 is arranged to connect with the gate. The sand in the cope 33 may be supported and held by gagets 37 or other devices known to the molding art. For reasons that will appear it is preferable to arrange an exit or riser 38 for the molten iron, so that it can be poured into the mold in excess and run out through the riser and thence overflow through a gutter 39. The molten metal will 1 be able to fill the casting space 34 to the highest point thereof due to the porosity of the sand, and the riser 38 preferably takes off from the recess 34 at a point as close as possible to the upper side of the preformed tube 11. In some cases a permanent mold might be used in lieu of the sand mold described.

Thearrangement thus described may be employed for casting a single extension section 13 upon the steel tube, or by the arrangement shown in Fig. 8 may be employed for simultaneous formation of a number of such sections. The order of production of extension sections may be varied. Thus alternate 5 sections may be cast upon the tube and subsequently others between them; or a series of sections may be cast and after the casting is cooled-the tube may be shifted along for the production of another series and so on until the full desired number of-sections is cast. in Fig. 4 the pouring spout 36 is shown as having multiple or divided channels 41 entering the respective sheet gates for. the several sections; and likewise the several 35- risers 38 are shown delivering through separate overflow channels 42 to a common overflow point. The several casting recesses 34 .may be originally formed as a single recess and spaced before casting by a series of baked cores 43 arranged between the successive sections and representing the spaces 23 shown in Fig. 3.

According to the present method the preformed tube is preferably preheated to a fairly high degree for example 800 to 900 F. soas to soften the metal or prepare it for the fuse welding operation by which the other end of the tube so as to bring the tube temperature as high and as uniformly as ossible over the entire lengthv or portion to e treated.

r The casting, it will be observed,'is performed directly upon the surface of the preheated tube 11. The molten cast iron may be at a temperature of about 2900 F. According to this invention the preferred operation is to allow the molten iron to fill the casting recesspand then, while part of the iron flows out through the riser, keeping up a continuous flow through the gate 35, recess 34 and the riser 38, for a substantial period in order to elevate further the temperature of the steel tube, bringing it nearer to the fusion point and insuring integral uniting of the tube and extension, with molecular interlocking of the two portions of the finished product.

The diagram Fig. 7 indicates substantially the operation. The casting space 34 is full of molten iron. The sheet gate 35 brings the iron into the recess across the whole Width thereof, while the sheet riser 38 is also of the full width, this arrangement insuring the continuous passage of a full width stream of molten iron through the recess 34 from the entrance to the exit, this stream represented by arrows 47 on the diagram. It will be noticed that the natural path of the'molten iron stream is toward the surface of the steel tube and thence around such surface to the riser 38. The molten iron will be at its hottest temperature near the lower part of the tube but will maintain a substantially uniform heating effect because the arrangement causes the stream to travel in more intimate contact with the tube as it pro- 'gress and while it is cooling.

The result is that the entire exposed and preheated surface of the tube is elevated to a fairly even temperature for integral uniting or fuse welding with the cast iron extension formed upon it. It is estimated that the tube steel, at its exposed surface, will in this process be raised nearly to, but not over 1250 to 1300 F., at which it will soften enough for welding or fusion to the cast metal, without actually melting or running.

The preferred manipulation is substantially as follows. The molten iron is poured from a ladle into the spout 36 first at a fast rate of flow in order to fill the mold quickly. As soon as the mold is filled and overflow at the riser commences. the pouring should be slowed down to as slow rate as practicable. By this plan the maximum heating, 11p of the tube by the iron is secured with the minimum of erosion of the steel-by the stream of iron. The pouring may be continued for about one minute more or less. The extent of pouring is best determined by the weight of metal, and preferably several times the weight of the casting itself should be flowed through the mold. For example, in casting four facing sections, as in Fig. 8, and assuming that these will contain about 25 pounds of metal, a ladle may be employed which when filled to a certain point will hold 100 pounds of molten iron. The pouring will then be continued until all of the iron from the ladle has passed into or from the mold.

lll

The spout 36 being at a higher level than the discharge channel-39 gravity will maining the hot iron along the steel surface must be carefully determined. Excessive operation will cause the iron to wash away portions of the heated steel and so impair the strength of the tube. If the pouring is insuificiently continued the steel will not be brought to the welding temperature and there will be no real bond or effective fusion established between the metal of the tube and the extension. The result will be greatly impaired conductivity so that one of the main objects of the invention would be affected; and moreover the inadequately united portions are liable subsequently to separate. culated as to bring the steel tube to a welding temperature, the iron thereby becoming welded and fused to the tube with a thorough union involving an intercrystalline struc ture. The formation of bubbles at the line of union is precluded by the described operation, since the bubbles tend to rise without having access to the surface of the steeltube, as indicated at 48 in Fig. 7

Many variations. suggest themselves.

Thus by a suitable elongated mold an entire till twenty foot tube can be treated in one operation. The tube may be of any nature suitable to its purpose, and the facing or extension is not necessarily of cast iron but may be cast steel. Other modes of effecting fusion, welding or uniting of the two por tions can in some cases be substituted, for example, autogenous welding of preformed tube and extension, but it is believed that effective water walls for high temperature furnaces can be best manufactured on a practical basis by the preferred system described.

The described molding and casting method may be improved and quickened as follows. The mold portions containingthe gates and risers may consist of previously prepared hard-baked dry sand cores, and the runnerand pouring spout may likew'isebe composed of baked sand and located directly on top of the baked core members. After the tube is placed in the mold the baked cores defining the facing extension are placed against the tube, and then green sand is placed to surround the tube and cores and tamped tightly, before the pouring of the measured amount of moltenv iron as already described. This system reduceserror's and losses, and makes all castings uniform; and accidental entry of dirt into the mold is prevented. The molding time is shortened, and the molding requires less skill. The output from each moldis in- The operation should be so calcreased, since. one set of men may be employed in making the separate baked cores, while another set is applying cores and forming the molds. The larger out ut is therefore accompanied by lower cost 0 production. The small cores separating the casting into longitudinal sections may advantageously be composed of cast iron, and they may be pasted and covered with sand before being applied at the mold; this givingv a cleaner separation between sections, and giving a more uniform result as the cast iron core is not subject to crushing; and it is readily knocked out after.

the cooling and removal of the product.

There have thus been described a furnace water wall and a wall element and a method of making the same embodying the principles and attaining the objects of the present invention. Many matters of operation, combi nation, arrangement, structure and design may be variously modified without departing from the principles and therefore it'is not intended to limit the invention to such matters except to the extent set forth in the appended claims. v A What is claimed is:

. 1. In or for the wall or lining of a furnace,

of metal along the paths of heat conductionfrom the exposed face to the tube as to aflord high conduction rate from allexposed portions to the medium circulating in the tube :and thus to avoid destructive congestion of cat.

2. In or for the wall or lining of a furnace,

a unitary metallic element adapted to absorb radiant heat and to b'e cooled by interior circulation, the same comprising a preformed tube portion, and an added facing extension integrally fused thereon and surrounding and covering the'inner side only of the tubeand facing the fire "but terminatin to leave uncovered the outer side of the tu e, and having ample thickness of metal along the avenue of heat conduction from the exposed face to the tube. 3. A furnace element as in claim 2 and wherein the tube portion is a preformed steel tube, and the extension is of cast iron fused on to the tube.

4. In or for the wall or lining of a furnace, a unitary metallic element adapted to absorb radiant heat and to be. cooled by interior circulation, the same comprising a tube portion,

and an integral facing extension thereon surrounding and covering the inner side only of the tube and facing the fire but terminating to lea e n overed. the o t r i e f the tube,

' said extension having a sectional thickness increasing from its most remote portion-to the tube to afford an enlarging avenue for co gduction from the face to the median in the tu e.

5. A furnace element as in claim 4 and wherein the extension has a thickness suflicient to span between 45 and 90 of the tube circumference at each side of a center line taken symmetricallg to the surface of the extension facing the re. 6

6. In or for the wall or lining of a furnace, a unitary metallic element adapted to absorb radiant heat and to be cooled by interior circu= lation, the same comprising a tube portion, and an integral facing extension thereon surrounding and covering the inner side only of the tube and facing the fire but terminating to leave uncovered the outer side ofthe tube, said extension having a cross sectional thickness near the tube at least several times that of the tube wall.

7. In or for the circulation-cooled wall or lining of a furnace, a tubular metallic element adapted to be exposed to radiant heat, the same comprising a tube portion, and, arranged along the length of the tube portion, a slightly separated series of facing extension sections, each surrounding and covering the inner side of the tube but terminating to leave uncovered the outer side of the tube.

In testimony whereof, I have aflixed my I I signature hereto.

ARTHUR TEMPLETON HUNTER.

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