US2788753A - Furnace wall construction - Google Patents

Description

April 16, 1957 O. NYGAARD FURNACE WALL CONSTRUCTIQN Filed NOV. 50, 1950 7 Sheets-Sheet 1 April 16, 1957 o. NYGAARD FURNACE WALL couswsucnou 7 Sheets-Sheet 2 Filed Nov. 50. 1950 April 16, 1957 o. NYGAARD FURNACE WALL CONSTRUCTION 7 Shets-Sheet 3 Filed Nov. 50, 1950 Fig.6

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FURNACE WALL CONSTRUCTION Filed Nov. 30, 1950 '7 Sheets-Sheet 7 United States Patent FURNACE WALL CONSTRUCTION Oscar Nygaard, Saugus, Mass, assignor to Bernitz Furnace Appliance Company, Boston, Mass, a corporation of Massachusetts Application November 30, 1950, Serial No. 198,318

13 filaims. (Cl. 110-1) This invention relates to improvements in furnace wall construction and especially to an improved front wall refractory structure for a furnace of the spreader stoker traveling grate continuous and discharge type in which there is provided a rotor mechanism for feeding fuel, together with one or more feed openings in the front Wall for receiving and guiding fuel from the rotor mechanism into the combustion chamber of the furnace.

Installation of stoker equipment of this type introduces problems in connection with providing a satisfactory refractory structure at the inner side of the front wall of the furnace. The exceedingly high temperatures generated in the spreader stoker furnace of this type produces a very great amount of wear and rapid break-down of refractory materials such as conventional fire clay bricks and similar products. Use of more heat resistant and durable refractories of the silicon carbide type, for example, has not been feasible due, in a large measure, to the fact that the fabrication process of silicon carbide is entirely difierent from the process of making fire clay refractory shapes, and involves very costly moulds which wear out rapidly due to the very high abrasive nature of silicon carbide. Since the size, shape, and lateral spacing of the feed openings and, hence, the refractory materials which are to fit around these openings, vary widely in accordance with the differing specifications of various spreader stokers manufactured and sold, the expense of making silicon carbide moulds in a range of sizes is prohibitive. The result has been that less resistant refractories have been made use of and have been built up on the job to fit the varying dimensional requirements, and these refractories are subject to frequent break-down and repair. This causes interruption of operation materially detracting from the efiiciency of the furnace operation.

The present invention deals with the problems indicated and aims to devise a more efiicient and economical refractory construction for use at the inner side of the front wall of a furnace of the continuous ash discharge traveling grate spreader stoker type. It is a further object of the invention to provide a composite refractory body wherein the shape and construction of the constituent parts are so designed as to make possible, from an economic standpoint, the use of more heat and abrasion resistant refractories of the silicon carbide type. Still another object of the invention is to devise a novel form of silicon carbide type refractory unit which, in one standard size, can readily be adapted to fit a wide range of dimensional requirements.

These and other objects and novel features will be more fully understood and appreciated from the following description of a preferred embodiment of the invention selected for purposes of illustration and shown in the accompanying drawings, in which Fig. l is a vertical, cross-sectional view taken through a typical fuel inlet opening of the front Wall of a furnace of the continuous ash discharge traveling grate spreader stoker type, showing certain operating parts of the spread- 2,788,753 Patented Apr. 16, 1957 ice er stoker mechanism, and more particularly indicating portions of the refractory elements of the invention mounted at the inner furnace side of the furnace front wall plate;

Fig. 2 is a fragmentary front elevation of the furnace wall shown in Fig. l viewed from the inner furnace side thereof and illustrating one of the stoker feed openings, together with hanger members of the invention located in an operative position with respect to the feed openings;

Fig. 3 is a plan cross-sectional view taken transversely along the line 33 of Fig. 2 through a hanger member shown between the feed openings in Fig. 2, and illustrating hanger brackets in one position of adjustment thereon;

Fig. 4 is another cross-sectional view similar to Fig. 3 showing the hanger brackets in an alternative position of adjustment;

Fig. 5 is an isometric view of a clay refractory block employed with the pier hangers of the invention;

Fig. 6 is a top plan view of another form of refractory block employed with the sill hangers of the invention;

Fig. 7 is a side elevational view of the refractory block shown in top plan view Fig. 6;

Fig. 8 is a top plan view of another form of a clay refractory block employed with the sill hangers of the invention;

Fig. 9 is an elevational view of the refractory block shown in Fig. 8;

Fig. 10 is a top plan view of a clay refractory block similar to the block shown in Figs. 8 and 9 but located on the opposite side of the sill assembly;

Fig. 11 is a fragmentary inside of the furnace elevational View of the silicon carbide refractory tile members of the invention installed over the clay refractory blocks in proper relation to the stoker feed openings;

Fig. 12 is a top plan view, taken on line 1212 of Fig. 11, with the top cap of plastic material removed, and illustrating upper refractory pier forming tile members of the invention arranged in one desired position of adjustment with respect to the inner side of the furnace front wall plate;

Fig. 13 is a similar plan view,.to the view shown in Fig. 12, but showing an intermediate position of adjustment of the pier forming tile members in relation to the furnace front wall plate;

Fig. 14 is a view similar to Figs. 12 and 13 further illustrating the pier forming members in a third position of adjustment with relation to the furnace front wall plate;

Fig. 15 is a vertical, cross-sectional view taken on the line 1515 of Fig. 13;

Fig. 16 is another vertical, cross-sectional view taken on the line 16-16 of Fig. 11; r v

Fig. 17 is an isometric view of one of the pier forming itile members of the invention;

Fig. 18 is a cross-section taken on the line :18-18 of Fig. 11 further illustrating the refractory sill forming tile members located on the inner side of the furnace front wall plate;

Fig. 19 is an isometric view illustrating the under side construction of the central sill forming tile members of the invention;

Fig. 20 is another isometric view illustrating the under side construction of one of the end sill forming tile members.

In the structure shown in Fig. l of the drawings there has been illustrated a spreader stoker front wall of a furnace equipped with a mechanism of the conventional type including a hopper 10 for holding fuel, such as comparatively fine coal. The latter is delivered to a feeding table 12 where it is continuously advanced by a pusher member 14 across the feed table and caused to fall downwardly into the path of movement of a rotor 16 provided with vanes or blades 18 for propelling the fuel into 3 the furnace. The stoker platform .19 forms the roof over the stoker vestibule 21. Located below in spaced relation to the roof 19 and, protruding partly within the vestibule 21, is a traveling grate 24 of conventional construction indicated diagrammatically. Supported upon the roof 19 of the vestibule 21 is a transversely of the stoker vertically positioned metal plate 26 of substantial thickness which forms the exterior surface of the furnace front wall and comprises a part of the stoker structure. This front plate is provided with laterally spaced rectangular openings 28 further identified by inwardly extending lips 30 and located so as to register with the Stoker fuel feeding mechanism.

. The above brief description of the typical spreader stoker mechanism as shown in the drawings: of this application has been made merely to clarify its functional relationship to the improved refractory wall structure presently robe described.

accordance with the invention 1. provide an inner refractory wall section which is designed to withstand the high. temperatures inherent with this. type of sicker. This inner, wall section is made up of spaced-apart piers which project inwardly at either side of the fuel inlet openings 28, together with intervening sills which project inwardly at points below the fuel inlet openings 28. A source of air supply for cooling the piers and sills, which are hollow structuressealed tight against air leaks at either sides, top and bottom, is provided by conduits 22 and 23, which communicate with a main air supply duct 20,, shown clearly in Fig. l, with duet 23 containing damper means 17 for con-trolling the air pressure to the piers and sills. In my improved refractory wall section I employ very highly heat conductive and heat and abrasion resistant refractory material of the silicon carbide type, for example, for all surfaces exposed to the fire, and I have devised novel silicon carbide shapes and cooperating. metal hangers the latter being solidly anchored to the. inner side of the furnace front wall plate 26. These hangers function to locate the silicon carbide shapes in spaced relation to said front wall plate 26 to constitute 'a protective apron of air cooled super-refrao t-ory material. I also combine refractory material ofa less heat-resistant. and less heat-conductive nature with the silicon carbide shapes andmetal hanger members in order to obtain a composite construction. having exceedingly high. heat-resistance and protective characteristics, as will appear hereinafter.

Considering first the hanger members of the invention utilized to support the refractory materials, and referring in particular to Fig. 2, numeral 32 denotes a hanger member preferably constructed of high heat resistant alloy steel, orother suitable material, which is solidly bolted to the inner side of the furnace wall plate 26 by means of bolts 34 extending through elongated slots 36. The hanger 32- shown in Fig. 2 is intended to be representative of a plurality of such members located at the opposide sides of fuel inlet openings 23, and may conveniently be referred to as" pier hangers. Each of these hanger members comprises a flat body portion which bears against the furnace wall and extends vertically upward, asshown. Integral with this flat body portion is a central vertical web 38, and intersecting this web at the bottom thereof is a horizontal flange or supporting shelf 40. Inspaced relation toand above the shelf 40 is a second larger flange or supporting shelf 42, and still a third-supporting shelfv 44 is locatedin spaced relation above the-shelf 42, as shown in Fig. 2. At its upper end the hanger 32 is alsoprovided with a top fimge 46 which forms. abase and support for the cap 45 of preferablyplastic refractory material Figs. 1 and 11. It will be observedthat the. bot-tom shelf 40 occurs in-spaced relation'ahove the chain grate member 24 and in an elevated positionz with respect to the lowermost edge of the refractories, vas is more clearly shown in Fig. ll.

a supporting shelf 44 has been further indicated in Figs. 3 and 4 whereurrt will .be observed that at one side of the web portion 38 there is provided a pair of concentric bracket slots 50 and 52 which occur in spaced relation to one another and which have their arcs of curvature generated from a center taken outside of the shelf 44. Similarly, a second pair of concentric spaced slots 51 and 53 are provided at the other side of the shelf 44. Adjustably supported on the shelf 44 at either side of the web 33 are two bracket members 54 and 56 being secured by means of bolts, as 58 and 6! which pass through the slots described and hold the bracket members in a desired position of adjustment. The bracket members include fan-shaped base portions integral with which are vertical sides 62 and 64. These sides extend inwardly in an angular direction with respect to the furnace front wall plate 26 and to one another and support at their upper edge rails 66 and 68, as shown in Figs. 2 and 3. It will be observed that by moving the brackets and their holding bolts along the curved slots it is possible to readily rotate the brackets about a ventical. axis, with the result that the position of the sides 62 and as with their respective rails 66 and 68 may be varied to a very considerable extent, both with respect to the angle at which the sides are directed toward the furnace front wall plate, as well as the actual spacing of the rail members from the hanger web portion 33. A second set of brackets 47 and 49 may, in a similar mam ner, be mounted on the hanger shelf 42.

In conjunction. with the pier hangers secured at the sides of. the fuel inlet opening 28,v I provide a plurality of sill hangers which are located along that portion of the furnace wall occurring immediately below the fuel inlet opening 28. These sill hangers have been indicated in Fig. 2 and are denoted by numerals '70, 72 and 74, each of which is similar in shape. The hangers are formed with vertical body portions which are bolted to the furnace front wall plate as shown in Fig. 2 and which have integrally formed therewith respective portions 82, 84 and 86. Transversely disposed'onrespective shelf portions 82, 84 and 86, and integral with them, are vertical sides bearing rails 88, 90 and 92. The rails-are located in a fixed position substantially parallel with the furnace front wall plate and in spaced relation to it, as may be more clearly seen in Fig. 18. Vertical webs 94, 96 and 98 divide their respective shelf portions 76, 78 and into two separate supporting surfaces.

Areas of the furnace front wall plate 26 occuriug between the several sill hangers, as well as the pier hangers and the fuel inlet opening 28 may, for some installations, be made more heat-resistant by covering these surfaces with a layer or sheet of insulating material of conventional character, as denoted by numeral 100, Figs. 1 and 3.. This-insulating material may be applied during the installation of they hangers and is not essential in all cases. 7

An important feature in the cons-truction andarrangement of the pier and sill hanger members. above described, in. addition to their primary function of supporting refractory shapes, resides in the fact that the refractory shapes are. of such construction, and are so arranged on the hangers thatthey may be installed, removed and replaced by similarshapes in a highly selective manner, independently of one another, and with a minimum amount of labor and time required.

Considering first the refractory shapes for the pier hangers, attention is directed to Figs. 5, l5 and 16, where'- in there is shown a refractory pier block 102 which is adapted to be mounted on the bottom shelf 40 of the pier hanger 32. As noted in Fig. 5 the pier block has a fiat top'and bottom andis'formed with twofrcnt stir faces 162a and 10212 which meet at an angle at a point centrally of the block. In-tersecting the respective sides 102a.and 102?) are two additionaloblique sides 1820 and 102d; A vertical slot 194 extends centrally along the upper portion of the block, as noted in Fig. 5, and intersects a second horizontally extending slot 106 which passes all the way through the block. By means of these two slots 104 and 106 it will readily be seen that the block 102 may be engaged about the web 38 which passes between the sides of the block defined by the slot 104 and simultaneously the shelf portion 40 is received in the slot 106, thus allowing the block to be firmly located on the supporting shelf portion 40 of the hanger.

The block 102 is preferably composed of a refractory material, such as fire clay, or the like, and when mounted about the base of the hanger 32 serves to provide a heat insulating layer around the lower portion of the hanger and, in addition, provides a substantial mass of insulation at the bottom or under side of the hanger to shield this member from heat directed upwardly from the chain grate 24. It is also pointed out that the block 102 closes the space between the vestibule roof 19 and the fire face apron blocks 120 and serves to seal off the internal air space within the pier in the manner shown in Fig. 16.

While the clay material block 102 is arranged and designed to protect against overheating the metallic pier hanger, the block 102 is in turn protected against direct exposure to the fire by a further novel structure forming a protective apron of a silicon carbide type of refractory having a much higher heat resisting value than the block 102. This protective apron or skirt comprises a series of pier tiles arranged in opposed pairs and with respective pairs being superimposed, one above another, in overlapping relation in the manner illustrated in Figs. 11, 12 and 16 to accommodate expansion, wherein numeral 120 refers to tiles of a lowermost pair and numeral 122 refers to tiles of an uppermost pair.

Each tile element of a respective pair is of angular shape which combine to make two fire side surfaces 122:: and 12217 separated only by plastic joint material 127, and which meet at an obtuse angle with two other surfaces 122a and 122d, as seen in Figs. 1-1, 12, 13 and 14.

The upper edges of the tile elements 120 and the lower edges of the tile elements 122 are formed with complementary shouldered or flanged portions which allow the edges of the respective tiles to lie in overlapping relation with respect to one another and with vertical sides of these portions actually being in contact with one another, while the horizontally extending parts of the shouldered or flanged portions are disposed in slightly spaced-apart relation, as shown at 129 in Figs. 15 and 16 of the drawings.

The slight amount of clearance resulting from this relative arrangement of the upper and lower tile elements permits these members to remain in sealed contact with one another and yet they may expand or contract in the course of their exposure to intense heat without producing excessive strains and stresses in the material.

In order to support the tile elements in the desired overlapping position described, the internal pier surfaces of these members are constructed in the manner illustrated in Fig. 17, as well as Figs. 15 and 16. Attention is directed to Fig. 17 where it will be seen that there is provided 2. lug extension 124 formed integrally with the tile body and extending between the two obliquely posh tioned faces of the tile body.

At its under side the extension 124 is recessed to provide an elongated slot or groove 128 shaped to fit over the rail member 68, Fig. 15, from which the element 122 is suspended to form a shield against the fire. It is also pointed out that by means of this arrangement the tile member is only contacting the supporting rail along narrow lines which serve to retard transfer of heat through the refractory into the bracket and hanger structure. In this connection I may also form the rail members with serrations or narrow grooves 130 to provide a passageway along which cooling air may pass.

Figs; 12, 13 and 14 show the high temperature resistant tile elements 122 supported and suspended on the companion brackets 54 and 56, at a multiplicity of varying angles with respect to the furnace front wall plate.

It will be observed that the end of the tile elements 122 nearest the hanger web portion 38 can be moved outward from the position shown in Fig. 12 to that of the position in Fig. 14, to widen the pier at the furnace front plate and thus bridge any length of the space between the lips or frame portions 30 within the limits shown in Figs. 12 and 14, While the distance between the obtuse corner of the fire face surfaces 122a and 122k remain constant. It will also be observed that the meeting edges of the right and left-hand tile elements 122 are so constructed that a joint contact will always be had irrespective of the angular position of the tile elements.

Between the outer ends of the apron tile elements and 122 and the furnace front wall plate, a filling of high heat resistant plastic refractory material 123 is applied to complete the fire face surfaces 122a and 122d, and to form a seal against air leaks from the pier interior. In connection therewith it will be observed that the end surface 121 of the lowermost skirt or apron block 120 is provided with a slot 125 to form an anchorage for the plastic filling material to prevent it from slipping downward into the space between the grate surface 24 and the lower edge of the refractory front wall.

It will thus be seen that with a single combination of a right-hand and left-hand angular refractory shape, such as is constituted by either tiles 120 or 122, it is possible to encompass a relatively wide range of dimensional variations between the feed openings in the furnace front wall plate and with respect to the size and angularity of the pier.

Since it is an expensive process to mold the refractory tile elements, particularly when these are of highly abrasive silicon carbide materials, this adjustability feature is an extremely important one inasmuch as only one mould will be required for any shape shown, yet being able to fit any pier Width and angularity with respect to the furnace front wall plate. The resultant reduced fabrication cost is a major factor in permitting the silicon carbide refractory members of the invention to be successfully employed with a great many types of spreader stoker installations. The importance of this advantage is, of course, more fully appreciated when it is realized that the service life and reliability of refractory materials of the silicon carbide type is much greater than the ordinary fire clay type of refractory shapes. Hence, very costly shutdowns and idling of large boiler units are prevented.

A generally similar type of composite refractory structure is provided for mounting on the sill hangers which occur below the feed openings. Attention is directed to Figs. 6 to 10, inclusive, which illustrate suitable refractory blocks of clay brick material 138, as shown in Fig. 6, adapted to be engaged over, and to be supported by, the sill hangers 70, 72 and 74. These blocks are formed with fiat top and bottom surfaces 139 and 141 respectively. At the forward or inner end, the upper portion of the block is tapered back in conformity with the sill angle. A notch 149 is made in the tapered surface to provide an air space after assembly in the wall. At the center of the block the transverse notch is joined by a recess 143 to the same depth made in the top surface 139, to provide access of cooling air to the notched out space 140. Along the two opposite side edges 145 of the blocks 138 are formed slots 142 which are adapted to receive therein shelf portions 76, 78 and 80 of the respective brackets 70, 72 and 74, as has been more clearly shown in Figs. 1 and 18.

Although I do not wish to limit myself to any particular arrangement of refractory block construction, a preferred arrangement is one in which blocks similar to the block 138 are supported between hangers 70 and 72 and also between hangers 72 and 74. With this arrangement the same desirable protective features described with respect to the bottom of the pier hanger 38 is achieved in the case of each of the sill hangers and adjacent furnace wall areas.

In the. space occurring between the pier block 128 and the adjacent sill hanger 7i), 1 mount a specially formed refractory block of clay brick material, such as that illustrated in Figs. 8 and 9, and denoted by numeral 148 in the case of a left-hand block and by the numeral 150 Fig. in the case of a right-hand block, as viewed from-a point within the furnace. As will be seen from an inspection of Fig. 8, the block 148 is formed with an angularly extending side surface 152 which is designed to extend along a plane substantially parallel to the adjacent oblique face 126a of the pier block 120. These two latter members may be fitted fairly closely together and a groove 154 may be provided in the angularly extended surface 152 of the block 148 in order to receive bonding material therein.

At its opposite side the block 148 is formed with a slot or groove 156 in which may be received the left side edge of the sill flange 76. Similarly, the block 150 Fig. 10 will be arranged on the right side flange of the opposite sill bracket 80, as shown in Fig. 11, to fill the intervening space between the bracket 80 and the adjacent pier member.

Overlying the clay refractory sill blocks in much the same manner as described in connection with the pier blocks, is provided a protective sill apron made up of overlapping sill tile elements of silicon carbide refractory which are more fully disclosed in Figs. 18, 19 and 20. The sill' tile elements preferably comprise a central tile element 160 and two side tile elements 162 and 164 Fig. 11. The central tile member 160 has been shown as viewed from its under side in Fig. 19, while one of the side tile elements 164 has been shown as viewed from its under side in Fig. 20.

Referring first to the central tile 16!), shown in Figs.

I of the invention. The conduits 180 and 19.0 are preferably connected through the furnace front wall plate at several different points therealong, and in Fig.2 I have shown one 7 suitable arrangement consisting of an air passageway 182 18 and 19, it will be seen that the tile member is formed with a fire side inclined sill surface 166 which extends from the edge of the feed opening inwardly and downwardly to define a diverging guideway for directing fuel into the furnace.

' As noted in Fig. 19, the tile 160 has its under surface formed with an elongated slot 168 adapted to engage over the rail 96 of the hanger member 78. Preferably the length of the elongated slot 168 may exceed the length of the rail 90 so that some adjustment in directions transversely of the hanger may be carried out.

At points immediately below the elongated slot 168 the sill tile may be formed with a recessed surface 167 which permits the tile member to fit snugly down about the sill block 138, as shown in Fig. 18. At its upper inner section the sill tile may be formed with a recess 170 and a transverse rib 172. The latter member is shaped to permit the sill tile to bear against the layer of insulation 100, as shown in Fig; 18, to form a seal over the recessed air providing a greater clearance and a free air flow between the sill tile and the adjacent portions of the hanger and furnace wall, as is also evident from an inspection of Fig. 18.

Similarly, the right-hand and left-hand side sill tiles 164 and 162 are formed with rail-engaging slots and ribs, as is shown in Fig. 20, and the mounting of these members is the same as that already described with the further addition, however, that these side sill members have overlapping'edges 174 adapted to engage with and overlie corresponding recessed edges 176 of the central sill tile 160. As was the case with respect to the pier tile, it will be seen that when assembled Fig. 11 the adjacent sill tiles will be spaced apart slightly to form a clearance 161 at their meeting edges and may slide upon one another and expand and contract without developing internal stresses, and yet a substantial sealed relationship is obtained with respect to the adjacent sill tile members.

In order further to protect the furnace wall against high located between the two sill hangers 72 .and 74, and a second air passageway 184 located at one side of the pier hanger 32. Air may thus be conducted through the openin gs 182 into the space occurring between the furnace wall and the sill blocks, finally passing out through the sill tile members through especially provided openings 186 as shown in Fig. 11. i I

Similarly, air is conducted through the passageways 134 into the space between the'pier tile and the furnace front wall plate and from this point air is circulated around all the surfaces interior of the pier and then out from the pier through air passageways 188 formed in the front sides of the pier tile members, as is clearly shown in Fig. 11.

I have found that by thus combining a composite refractory in both the pier and sill structures employing materials of widely different characteristics andwith air circulating means and air venting means located through the various tile members, a very desirable cooling eifect can be realized which aids materially in the success of the tile elements in withstanding the intense heat to which they are subjected. Moreover, by thus utilizing the combined effect of a composite refractory arrangement and cooling air circulated internally of the composite refractory structure, I have found it is practical to mold both the sill and the pier apron tile shapes of relatively thin cross-sectional size, thus greatly reducing the cost of the material for building the inner refractory wall.

I am also enabled to realize another important advantage stemming from the fact that the cooling air as it is circulated about the refractory elements which is capable of very high heat transfer becomes highly preheated and at its point of discharge into the combustion furnace is capable of producing increased combustion efliciency.

Another very important result that has been noted during operation with the construction described herein, is that the fire face surfaces of both sills and piers remain relatively clean and free from accumulations of fly ash and slag. Hence, the proper distribution of the coal is maintained over the complete grate surface, and bare spots, that would permit the combustion air to, by-pass the fuel bed and thus lower the efiiciency, are definitely eliminated.

From the foregoing description of my invention it will I be appreciated that I have disclosed -a novel refractory wall of unique composite structural aspects wherein a high degree of durability is realized with .a minimum cost. When it is understood that the maximum front'to rear dimension for the piers is only about 10 inches and even less for the sill sections, it will be clear that the employment of silicon carbide refractories in the fire face tile to make a more durable construction presented a very ditlicult problem. Since first quality silicon carbide refractories have a heat transfer coefiicient of 108 B. t. u.s per square foot per inch thickness per hour as against 10 B. t. u.s for fire clay brick materials, and inasmuch' as all the refractories employed necessarily must be anchored and fully supported upon metal brackets and also in view of the proximity of the metal furnace front plate due to the limited wall thickness, it will be understood how readily the intense heat of the furnace could be transferred to the brackets and the furnace front plate so that these parts would warp and burn out in'a very short time. This problem has been definitely solved by the design presented in the drawings of this application.

It will be observed that the siliconcarbide shapes, which when assembled form the fire face of the wall, are supported on, and anchored to, the metal brackets or hangers in such a manner that only point or line contacts are made, thus efiectively reducing the heat transfer to the metal support to a minimum and eliminating the danger of overheating these parts, as well as the furnace front plate.

This factor is also augmented in value by reason of the unique apron or skirt-like design and arrangement of the silicon carbide face tile, which provide a very economical use of an exceedingly costly refractory material without any loss of structural strength and stability. In addition thereto, since these apron members are made of comparatively thin cross section, permitting a much more efficient air cooling and a larger internal air space within the pier and sill structures with correspondingly larger intrenal surfaces in contact with the cooling air, they also act as a very efiective heat screening means for the other component parts of the piers and sills.

An important feature of this invention is that the sills and piers disclosed herein are separate structures, having no interdependent support or anchorage, and each structure is of a construction which permits renewals of any of its component parts without interfering with or disturbing any adjacent structure. The facility provided by this construction for replacing any of the members exposed to the fire should be noted. All such members are independently and detachably supported on a companion metal bracket-thus, repairs or renewals can be made quickly to any part of the furnace wall at the minimum labor cost and boiler outage. When the sill tile is to be renewed, it is merely necessary to lift the old one off its bracket, and replace it with a new one, each tile being separately renewable, and the center tile can be renewed by merely lifting the two side tiles to clear the overlapping flanges of the center tile, an operation which requires only a minute or two of time.

If one of the apron tiles of a pier is to be renewed, the refractory cement cap at the top is quickly broken up, which leaves access to the tile. The upper one at either side can then be lifted off its respective supports, and the lower tile in turn lifted off its support and renewed if necessary; but the upper one can be changed without disturbing the lower ones, if desired. Of further outstanding importance is the adjustability feature of the silicon carbide pier tile and its supporting hangers whereby one standard pier tile shape may be employed with a relatively wide range of required furnace specifications. Without this feature the utilization of silicon carbide refractories for pier construction would be hopeless due to the prohibitive cost for making a separate mould for each variation in shape and size that will be required because of the multitude of varying angles around the fuel feeding openings, the multitude of different sizes of fuel feeding openings, and their spacings from each other.

While I have shown a preferred embodiment of the invention, it should be understood that various changes and modifications may be practiced in keeping with the scope of the appended claims.

I claim:

I. In a furnace of the spreader stoker continuous ash discharge type including an exterior furnace front wall plate having a fuel inlet opening therethrough, the combination with' said front wall plate, of refractory piers mounted at either side of the feed opening, hanger means secured to the inner side of the front wall plate below the feed opening, each of said hanger means having a base provided with shelf portions, refractory sill blocks of comparatively low heat conductivity formed with slotted sections which are detachably engaged over the shelf portions, sill members inclined inwardly and downwardly of the furnace front wall and comprising refractory tile elements of comparatively high heat conductivity and of angular shape located above the sill blocks, the under side of said tile elements being shaped with elongated grooves, and said hanger means presenting elongated rail portions adapted to engage in the elongated grooves of the tile elements and detachably support the latter members in protective relationship with respect to the hangers and sill blocks, said refractory sill tiles cooperating with the refractory piers to form a diverging guideway for the fuel.

2. In a furnace of the spreader stoker continuous ash discharge type, including an outer wall section having a fuel inlet opening therethrough, refractory sills mounted on the inner side of the front wall at points below the fuel inlet opening, refractory supporting metal hangers secured to the outer front wall section and extending upwardly at either side of the fuel inlet opening, said hangers having a base provided with shelf portions, refractory pier blocks formed with slotted portions which are detachably engaged over the shelf portion, pier members comprising refractory tile elements of angular shape, said tile elements being located around the refractory pier blocks and hangers and having a grooved interior supporting surface, and bracket means movable on the hangers to rotate some of the tile elements about a vertical axis into varying positions of angularity with respect to the outer wall section.

3. In a furnace of the type described herein, the combination with an exterior furnace front wall plate formed with a fuel inlet opening therethrough, of hangers secured at the inner surface of the front wall plate at points below and at either side of the fuel inlet opening, a refractory wall section supported on the hangers in protective relationship to the inner surface of the said furnace front plate, said refractory wall section including a plurality of overlapping tile members arranged in edge to edge relationship to one another and located on those hangers occurring below the fuel inlet opening to form a sill inclined downwardly and inwardly of the furnace front wall plate, overlapping angle tile members supported on hangers at either side of the fuel inlet opening to provide piers, said piers presenting obliquely disposed faces with respect to said front wall plate, said faces converging inwardly toward each other toward the interior of the furnace and which cooperate with the sill to guide the fuel toward the interior of the furnace, and means on the respective hangers to adjust the angle tile members of the piers about a vertical axis into varying positions of angularity with relation to the fuel inlet opening and said front wall plate.

4. A structure as described in claim 3, in which the refractory tile members are located in spaced relationship to the front wall plate, to form an inner refractory wall section for cooperatively enclosing an interior air space between the refractory wall section and the front wall plate of the furnace, this air space being closed at the top and bottom thereof by other refractory members, means for circulating air between the refractory wall section and the front wall plate, and said angle tile members being formed with air passageways which open into the furnace interior for conducting heated air into the combustion chamber of the furnace.

5. A device as described in claim 3, in which the base of the refractory wall section includes refractory blocks forming the bottom of the pier and sill structure, and said blocks supported at the lower ends of respective hanger members.

6. A structure as defined in claim 3, in which the hanger means for the pier tile members are formed with companion brackets having rail portions secured at the upper sides thereof, and each of said tiles has inner grooved surfaces cooperating with the said rail portion of the companion brackets to hold the tiles in a substantially locked position.

7. A device as described in claim 3, in which the hanger members present vertically spaced shelf portions and integral vertical web portions extending therebetween in a centrally located position, a plurality of tire brick members formed with slotted portions adapted to engage about the vertical web portions of the hangers and rest upon the said shelf portions.

8. A device as described in claim 3, in which the hanger members include companion brackets having horizontal rails of elongated shape and said tile members are formed with grooved sections adapted to'engage on the rails of the companion brackets to provide a substantially narrow line of contact, thereby to retard heat transmission.

9. In a furnace of the spreader stoker continuous ash discharge type, including an exterior furnace front wall plate having a fuel inlet opening therethrough, the combination with said front wall plate of refractory sills mounted on the inner side of the front Wall plate at points below the fuel inlet opening therethrough, re-

fractory supporting metal hangers secured to the front wall plate and extending upwardly at either side of the fuel inlet opening, each of said hangers having a base provided with shelf portions, refractory pier blocks formed with slotted portions which are detachably engaged over the shelf portions, pier members comprising refractory tile elements of angular shape, said tile elements being located about the refractory pier blocks and hangers and having grooved inner surfaces, each of said pier hangers further including other shelf portions located above said base shelf portions for supporting sets of opposed horizontally spaced brackets, said other shelf portions having means therein which permits locking said brackets thereto at a plurality of angular positions in relation to said front wall plate, each of the sets of brackets being supported on a shelf of the hanger in vertically spaced position to one another, and each bracket of a respective set, at its upper side, being constructed with elongated tile supporting rails adapted to engage in the grooved inner surface of a tile element and detachably support the tile in protective relationship to the refractory pier blocks and in an angularly disposed position with respect to the fuel inlet opening and said front wall plate, and said refractory tile elements cooperating with the refractory sill to form a guideway for the fuel inwardly flared toward the interior of the furnace.

10. A device as described in claim 9, in which said other shelf portions are formed with slots, and means for adjustably securing said brackets in the slotted portions of the shelves.

11. A structure as described in claim 9, in which the pier tile elements are formed with air passageways communicating with the furnace interior, and means for circulating a current of air between the said front wall plate and said tile elements, thereby to provide a cooling effect upon said tile elements.

12. In a furnace enclosure comprising a traveling grate forming the floor thereof, a wall structure, including an exterior metal plate of substantial thickness, having its lower edge elevated-above said door to form a continuous elongated space therebetween to provide an egress for the continuous disposal of the furnace refuse, a plurality of fuel inlet openings to the furnace exterior through said wall structure, through which fuel may be fed to the furnace by a spreader stoker, said fuel inlet openings being laterally spaced apart in substantially level relationship and elevated above the lower edge of said wall; brackets rigidly attached to said exterior plate at a level below each said fuel inlet opening and above said lower edge of the wall structure, said brackets each comprising a pair of vertically spaced integral shelves, the uppermost shelf having an upwardly extending elongated rail portion spaced some distance inwardly from said plate, a prefabricated refractory block, having the characteristics of comparatively high heat conductivity and high heat resistance supported and anchored on said rail portion, a refractory block of comparatively lesser heat conductivity and heat resistance having a body portion forming a part of the lower edge of the wall structure and underlying and totally enclosing the lowermost shelf of said bracket and shielding it from the furnace heat, while the refractory block of high heat resistance, which forms a part of the lower boundary of said fuel inlet opening, overlies and shields from the furnace fire both the said lower heat resistant block and its supporting bracket. i

13. In a furnace of the spreader stoker continuous ash discharge type, including an exterior furnace front wall plate having a fuel inlet opening formed therethrou'g h, refractory sills mounted on the inner side of the front wall plate at points below the fuel inlet opening, refractory supporting metal hangers secured to the front wall plate and extending upwardly at either side of the fuel inlet opening; said hangers having bases provided with shelf portions, refractory pier blocks of comparatively low heat conductivity formed with slotted portions which are detachably engaged and supported over the shelf portions, pier face members comprising refractory tile elements of relatively high heat conductivity, said tile elements being supported in an upright position to form a protective shield about the refractory pier blocks and hangers and having a grooved interior supporting surface, upwardly extending companion bracket means forming a part of the hanger, said companion bracket means being adjustable in horizontally extending slots and being interposed between some of the tile elements of high heat conductive quality and their respective hangers, said bracket means being formed with rail-like edges to provide for suspending the tile elements on relatively narrow lines of contact thereby to retard heat transmission from the tile elements to the hanger.

References Cited in the file of this patent V UNITED STATES PATENTS 787,432

Brett et al. Apr. 18, 1905 1,084,853 Gallagher Jan. 20, 1914 1,281,902 Bone Oct. 15, 1918 1,331,774 Kitchen. Feb. 24, 1920 1,410,729 Balz Mar. 28,. 1922 1,489,683 Allen -4.-- Apr. 3, 1924 1,539,275 Saathoff May 26', 1925 1,665,555 Liptak .Apr. 10, 1928 1,712,849 Sharp May 14, 1929 1,719,475 lacobus July 2,v 1929 1,766,175 Hosbein June 24, 15930 1,957,098 Denny May 1,. 1934 2,065,555 Beers Dec. 29,, 1936 2,100,252 Hotfman Nov. 23, 1937 2,192,682 Anderson u Mar. 5, 1940 2,418,042 Mosshart -2 Mar. 25, 1947 2,431,422 Rehm Nov. 25, 1.947 2,491,547 Bennett et al. Dec. 20, I949 2,501,734 Miller Mar. 28, 1950 2,557,456 Nichol June 19, 1951 I FOREIGN PATENTS 448,663 Great Britain June 1-2, 1936 we. W

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