US3039444A - Apparatus for and method of introducing tertiary air into furnaces - Google Patents

Description

F. M. BARTON APPARATUS FOR AND METHOD OF INTRODUCING TERTIARY AIR INTO FURNACES June 19, 1962 5 Sheets-Sheet 1 Filed Feb. 4, 1960 INVENTOR FRANK M 5/1 era/v A ORNEY June 19, 1962 F BARTON 3,039,444

APPARATUS FOR AND METHOD OF INTRODUCING TERTIARY AIR INTO FURNACES iNVENTOR fPA/VK f7 BARTON A'ITORNEY June 19, 1962 Filed Feb. 4, 1960 F. M. BARTON 3,039,444 APPARATUS FOR AND METHOD OF INTRODUCING TERTIARY AIR INTO FURNACES 5 Sheets-Sheet 3 INVENTOR FRANK M BA/ETO/V ATTORNEY June 19, 1962 F. M. BARTON APPARATUS FOR AND METHOD OF INTRODUCING TERTIARY AIR INTO FURNACES 5 Sheets-Sheet 4 Filed Feb. 4, 1960 7 M 3 RT Y 4 mm/ 8 alm 2 v. v 4 .A 3 k 7 NY/ 3 w a A v a F I 2 7 4 4e 3 J n 19, 1962 F. M. BARTON 3,039,444

APPARATUS FOR AND METHOD OF INTRQDUCING TERTIARY AIR INTO FURNACES Filed Feb. 4, 1960 5 Sheets-Sheet 5 I I I INVENTOR 44 i i igif Q39 F -12 ATTORNEY 3,039,444 APPARATUS FOR AND NETHOD OF INTRODUC- TNG TERTIARY AIR INTO FURNACES Francis M. Barton, St. Albans, N.Y., assignor to Foster Wheeler Corporation, New York, N.Y., a corporation of New York Filed Feb. 4, I960, Ser. No. 6,648 6 Claims. (Cl. 122-235) This invention relates to furnaces, and more particularly to apparatus for and method of selectively control ling the quantity and direction of the flow of secondary or tertiary air into a furnace.

In furnaces of vapor generators where a low volatile fuel, as for example, pulverized anthractite coal, silt or culmbank anthracite, is to be burned, either alone or in admixture with a relatively high volatile fuel, such as bituminous coal, or where a long flame path in the furnace is desired, regardless of the volatility of the fuel to be burned, the furnace must be constructed to provide means for supplying air at points along at least part of the proposed flame path to insure ignition and combustion of substantially all the fuel. It is, therefore, conventional practice to provide a furnace with an arch spaced a substantial distance from the furnace bottom and to dispose a plurality of burners in the arch arranged to direct the fuel downwardly into the furnace chamber adjacent a vertical wall of the furnace. A plurality of spaced air inlet ports are arranged in the vertical wall of the furnace, which air inlet ports are in communication with a windbox to receive and deliver air, through said ports, into the furnace chamber along the path of the fuel to supply the necessary oxygen for progressive combustion of the fuel. In the aforedescribed furnaces the quantity of air flowing into the furnace chamber is controlled by dampers positioned at the inlet end of the inlet ports and/ or by dampers disposed at the air inlet of the Windbox.

'l he problem encountered in the aforedescribed conventional furnace construction is that the distribution and quantity of air admitted through the tertiary air inlet ports cannot be predetermined with the degree of accuracy necessary to achieve proper flame position and shape within the furnace chamber, as well as provide for optimum fuel combustion. The proper position and shape of the burning fuel within a furnace chamber is important because improper flame position and/ or shape will cause hot spots on and/or flame impingement against at least some of the fluid conducting tubular members lining the furnace Walls which results in rapid tube failure and/or uneven distribution and transfer of heat to the fluid conducting tubular members and, in turn, adversely effects the efliciency of the vapor generator. A further disadvantage of the conventional furnace construction is the inability to control tertiary air entry into the furnace chamber so that incomplete or delayed combustion of the fuel is eliminated, which incomplete or delayed combustion results in increased carbon loss and/ or increased furnace exit gas temperatures. Even in furnaces constructed in accordance with the same furnace design as previously constructed furnaces, proper flame position and shape, as well as proper tertiary air distribution for optimum fuel combustion, cannot be predetermined. Consequently, proper flame position and shape within the furnace chamber can only be achieved after complete construction of the vapor generator and by a costly, time consuming trial and error test procedure. This test procedure consists of placing the furnace in operation and visually observing the flame within the furnace chamber, and thereafter, shutting down the furnace and, after allowing the furnace to cool sufliciently, sealing various air inlet ports and/or adjusting various dampers to control the amount of air I 3,039,444 Patented June 19, 1962 delivered to certain areas of the furnace chamber. After firing up the furnace, the flame position and shape is again observed. If the corrective measures did not provide the desired flame position and shape which is quite often the case, the aforedescribed procedure is repeated. This trial and error method is followed over and over again until the desired flame position and shape is observed. Another disadvantage of the aforedescribed test procedure, in addition to the cost and time involved, is that the proper flame position and shape achieved is only for a particular firin'g rate of the burners and for a particular fuel. If the firing rate deviates or a different fuel is used from that used during the test procedure, the flame shape and position changes so that the vapor generator would have to be removed from service (shut-down) to readjust the tertiary air flow pattern into the furnace and thereby provide the desired flame shape and position by the aforedescribed trial and error procedure.

It is therefore one of the objects of the present invention to provide apparatus for and method of introducing tertiary air into a furnace chamber whereby a desired flame position and shape is achieved without following the heretofore required costly, time consuming test procedure. It is another object of this invention to provide apparatus for and method of introducing tertiary air into a furnace chamber so that proper flame position and shape is obtained for a Wide range of firing rates of the burners. A further object of the present invention is to provide apparatus for and method of achieving optimum distribution of the tertiary air, within the furnace chamber for substantially complete combustion of fuel.

Accordingly, the present invention contemplates, in an arch fired furnace, a novel apparatus for and method of introducing tertiary air into a furnace chamber comprising a plurality of air inlet ports in at least one of the vertical walls of the furnace, each of the inlet ports being provided with adjustable means to control the amount of air flow therethrough and the direction of the air flow into the. furnace chamber while the furnace is in operation. The air inlet ports are arranged to provide the theoretically desired flame length, position and shape to provide for substantially complete combustion of the fuel and the desired furnace exit :gas temperatures. The quantity and direction of tertiary air flow through each inlet port is then regulated, while the furnace is in operation, to achieve the desired tertiary air distribution in the furnace chamber and provide proper flame position and shape and optimum fuel combustion over a relatively wide range of firing rates of the burners.

The invention will be more clearly understood from the following description when considered in connection with the accompanying drawings, in which:

FIG. 1 is a fragmentary elevational view in section of a vapor generator showing a portion of the furnace chamber, the arch and the upper portion of the tertiary air inlet apparatus according to this invention;

FIG. 1A is a fragmentary sectional view of the furnace chamber of the vapor generator of FIG. 1, joining FIG. 1 along line a-a, and showing the lower portion of the tertiary air inlet apparatus according to this invention;

FIG. 2 is a fragmentary view similar to FIGS. 1 and 1A, but on an enlarged scale, showing in section and in greater detail one of the air port inlet assemblies according to this invention;

FIG. 3 is a fragmentary sectional view, taken substantially along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary view in section on a still larger scale of the tertiary air inlet assembly shown in FIG. 2; and showing in detail the vane actuating assemblies.

FIG. 5 is a sectional view taken substantially along line.55 of FIG. 4.

Now referring to the drawings, and more particularly to FIGS. 1, 1A and 2, the reference'numeral generally designates an arch fired vapor generator which in part comprises a setting having a front wall '11, rear wall (not shown) side walls 12 (only one of which is shown in the drawings) and a floor and roof (not shown), the walls, floor and roof defining therebetween a furnace chamber 14. Front wall 11 is divided into an upper section 11A and a lower section 1113 which lies in a vertical plane horizontally ofiset to the right from the vertical plane of upper section 11A as viewed in FIG. 1. The upper section 11A and lower section 11B are connected by a substantially horizontally extending archroof 15. The interior surfaces of side walls 12 are lined by parallely arranged fluid cooled tubes 16, while the rear wall (not shown) is also lined by fluid cooled tubes. Lower front wall section 11B is lined by closely spaced parallel tubular members 18 which extend, from a header 19 (FIG. 1A) upwardly, to arch-roof (FIG. 1) thence inwardly and somewhat horizontally of the furnace combustion chamber 14 adjacent furnace arch 15. In the plane of upper wall section 11A, tubular members 18 extend vertically and terminate in a horizontal transfer header 21. The upper front wall section 11A is lined by fluid tubes 22 which are connected at their lower ends to header 21. A plurality of pulverized fuel burners 23 (only one of which is shown in FIG. 1) are disposed in and supported in the roof of a secondary air windbox 20. The burners 23 are arranged in horizontal spaced relationship with each other between side walls 12. Portions of the tubular members 18, at the arch 15, are suitably bent and offset from each other to form a plurality of burner ports 24 corresponding in number to the number of burners 23. Each of the burners 23 is positioned substantially vertically with the outlet of the burner nozzle 25 disposed adjacent a burner port 24 so as to discharge pulverized fuel downwardly, through burner port 24, into furnace chamber 14. To provide for the admission of tertiary air into furnace chamber 14 along the path of fuel flow down through furnace chamber 14, the lower section 11B of front wall 11 (FIGS. 1 and 1A) is provided with a tertiary air inlet port apparatus embodying the present invention and generally designated by the reference numeral 27.

Tertiary air inlet port apparatus 27, as herein illustrated, includes the provision of a windbox 23 which extends substantially the entire width of lower front wall section 11B. Windbox 28 comprises a top wall 29, a front wall 30, side walls 31 and 31A (FIG. 3) and a bottom wall 32 (FIG. 1A) which comprises two spaced horizontal wall portions connected together by an inclined wall portion. Windbox 28 is suitably supported and connected in a fluid tight manner along the edges of walls 30, 31, 31A and 32 to the lower section 11B of front wall 11 to form with the latter a plenum chamber 33. Air under pressure is delivered to windbox 28 by means of a motor driven fan 17 (FIG. 1A) through ducts 28A and 28B into plenum chamber 33 through an inlet 26 in one of the side walls 31 of the windbox (FIG. 1).

As shown and in accordance with the present invention, a plurality of novel air inlet port assemblies 34 are secured to the lower section 11B of front wall 11, as will be hereinafter described, within plenum chamber 33 of windbox 28. Air inlet port assemblies 34, as best shown in FIGS. 2 and 3, are arranged in two horizontal rows spaced one above the other with the air inlet port assemblies 34 of the lower row horizontally off-set from the air inlet port assemblies 34 of the upper row of the air inlet port assemblies. Although, for purposes of illustration air inlet port assemblies 34 are shown as arranged in two rows, it is contemplated that the air inlet port assemblies may be arranged in more than two rows or in any other pattern which may be deemed desirable for a particular vapor generator design without departing from the scope and spirit of this invention.

Since the construction of each of the air inlet port assemblies 34 and the manner of securing them to front wall 11 is the same, only one of the air inlet port assemblies shall be described in detail and the same reference characters will be applied to the like parts of the other air inlet port assemblies.

Each of the air inlet port assemblies 34 comprises two side plates 35 and 36 which are held in spaced, parallel relationship to each other by a top plate 37 and a bottom plate 38. Top plate 37 and bottom plate 38 are suitably secured in a fluid tight manner, as by welding, to the respective top and bottom edges of side walls 35 and 36 to form a substantially rectangular frame. As best shown in FIGS. 3 and 5, the spacing between side plates 35 and 36 is substantially the same as the center-to-center distance between three adjacent tubular'members 18. The length of side plates 35 and 36 or the spacing between top and bottom plates 37 and 38, is determined by the size air inlet port desired. A plurality of spaced vanes 39 are disposed within the frame formed by the side, top and bottom plates 35, 36, 37 and 38, respectively, and are pivotally supported between side plates 35 and 36 in spaced parallel relationship to each other. Each of the vanes 39 is suitably secured, as by welding, to a shaft 45 which extends, at opposite ends, through aligned openings in side plate 35 and 36. To prevent endwise movement of shaft 4% out of the opening in side plate 35, a washer 41 is tack welded to shaft 40, adjacent the exterior side of plate 35. Vanes 39 are dimensioned and spaced from each other so that when in a fully closed position, as shown in FIG. 2 the top portion of the vane below overlaps the lower portion of the vane 39 above and abuts the shaft of the vane above. The uppermost vane 39, when adjusted in a fully closed position, abuts a plate 42 which depends from top plate 37 and extends between side plates 35 and 36.

The above described frame and vane assembly is secured in its preselected position within plenum chamber 33 by welding side plates 35 and 36 along their respective vertical end edges to two tubular members 18. Top and bottom plates 37 and 38, respectively, are provided with arcuate cut-out portions, not shown, along their edges adjacent tubular members 18 so that portions of top and bottom plates 37 and 38 extend into the two spaces formed between the three adjacent tubular members 18. As best shown in FIG. 5, vanes 39 are also provided along one edge with three arcuate cut-out portions 44 to provide projecting portions 45 which extend into the spaces between the three adjacent tubular members 18.

To provide for conjoined pivotal movement of vanes 39 of an air inlet port assembly 34, a crank arm 46 is fixedly connected at one end to the end of each shaft 40. At the opposite end each of the crank arms 46 is pivotally connected to a bar or gang link 47. Two of the crank arms 46, hereinafter designated 46A, are longer in length than the other arms 46. Each of the crank arms 46A is fixedly connected at one end to a shaft 40 of a vane 39, pivotally connected to bar 47, and at the opposite end pivotally joined to an actuating assembly 48, hereinafter fully described. Although, two arms 46A are shown and described, the invention is not limited thereto. It is contemplated that one or more than two arms 46A, depending upon the size of the air inlet port assemblies 34, may be provided for connecting vanes 39 to the associated actuating assemblies 48 without departing from the scope of the invention.

To support the actuating assemblies 48 of the air inlet port assemblies 34, a supporting frame, comprising angle irons 49 and 50, a T-shaped beam 51 and bracing angle irons 52 and 53, is provided. Angle irons 49 and are secured to the top of plate 37 and extend horizontally in spaced relationship to each other in a plane normal to tubular members 18. The distal ends of angle irons 49 and 50 are connected together by T-shaped beam 51. Angle iron 52 is connected to side plate 35 on the air inlet port assembly 34 and extends at an angle upwardly to T-shaped beam 51 where it is connected to the latter. Angle iron 53 is disposed to extend diagonally between the opposite ends of angle irons 49 and 50, and is secured at its ends to angle irons 49 and 50.

As best shown in FIG. 4, each of the actuating assemblies 48 for the upper row of air inlet port assemblies 34 comprises a sleeve 54 which is secured to angle iron 53 and extends vertically through top wall 29 of windbox 28 to the exterior of vapor generator 10. Sleeve 54 is open at its lower end to receive axially therein a pipe 55. Pipe 55 extends from a point substantially below the open end of the sleeve to a point within sleeve 54 and in spaced relationship with the top of the latter. A threaded shaft 56 is secured at one end to the top of pipe 55 and projects coaxially through and beyond the top of the tubular sleeve 54. A handwheel 57 is turned upon threaded shaft 56 and is held at its hub by a bearing member 58 which is secured to the top of sleeve 54. Bearing member 58 is constructed so as to permit handwheel 57 to be rotated but prevents axial movement of the handwheel relative to sleeve 54. Pipe 55 is provided with a lug 59 which projects into a longitudinally extending slot 60 in sleeve 54. The cooperative relationship of lug 59 and slot 60 prevents rotation of pipe 55 and threaded shaft 56, but allows longitudinal movement of pipe 55 and threaded shaft 56 when handwheel 57 is rotated. A tab 13 is disposed to span slot 60 and is secured near the lower end of the sleeve 54 to prevent the spreading of slot 60 under the pressure exerted by lug 59 upon the sides of the slot when handwheel 57 is rotated. At the lower end of pipe 55 is secured, in coextensive relationship therewith, a connecting plate 61. A link 62, consisting of two spaced plates (see FIG. is pivotally connected to connecting plate 61 by means of a bolt 63 which projects through aligned holes in connecting plate 61 and both plates of link 62. The plates of link 62 are positioned on opposite sides of the connecting plate 61, with spacer members (not shown) disposed between the adjacent surfaces of the plates of link 62 and the opposite sides of the connecting plate 61 so that the plates of link 62 extend in spaced parallel relationship to each other, Link 62 extends downwardly parallel to air inlet port assembly 34 to a point adjacent the uppermost crank arm 46A. A second link 64, consisting of two spaced plates, is disposed in endwise alignment with link 62. The end portions of the plates of link 64 are disposed between the end portions of the plates of link 62 while the end portion of the upper longer crank arm 46A is disposed between the two plates of link 64. The end portions of the plates of links 62 and 64 of crank arm 46A are pivotally connected together by means of a bolt 65 which is passed through registered holes in the plates of links 62 and 64 and crank arm 46A. As best shown in FIG. 2, link 64 extends downwardly from its connection with link 62 to a point adjacent the lower longer crank arm 46A. The distal end portion of the lower longer crank arm 46A is disposed between the distal end portions of the plates of link 64 and is pivotally connected to the latter by means of a bolt 66 which extends through aligned holes in arm 46A and of the plates of link 64 (FIG. 2).

In operation of the actuating assembly 48, rotation of handwheel 57 upon threaded shaft 56 causes threaded shaft 56 to move longitudinally since it is restrained against rotation about its axis by reason of lug 59 which rides in slot 60 in tubular sleeve 54. With threaded shaft 56 fixedly connected to pipe 55, longitudinal movement of threaded shaft 56 is imparted to pipe 55, and pipe 55 moves longitudinally relative to sleeve 54 upon rotation of handwheel 57. Longitudinal movement of pipe 55 is transmitted to links 62 and 64 and, in turn, longitudinal movement of links 62 and 64 causes pivotal movement of crank arms 46A. Since crank arms 46A are connected to bar or gang link 47, gang link 47 will be moved longitudinally. Longitudinal movement of gang link 47 imparts pivotal movement to each crank arms 46 in an are about shafts 40, which in turn, efiects rotation of shafts 40 and the vanes 39 fixedly connected to the shafts.

As shown in FIGS. 1A and 2, actuating assemblies 48 for the air inlet port assemblies 34 of the lower row, are substantially of the same construction as the actuating assemblies 48 for the air inlet port assemblies 34 of the.

upper row. Therefore, the actuating assemblies 48 for the lower rows of the air inlet port assemblies will not be described in detail and like parts of the actuating assemblies 48 of the lower row of air inlet port assemblies will be identified by the same reference numerals as the corresponding parts of the actuating assemblies 48 for the upper row of air inlet port assemblies 34, except that the numerals will have the sufiix A added thereto. Each of the actuating assemblies 48 for the lower row of air inlet port assemblies 34 only differ from the aforedescribed actuating assemblies 48 as hereinafter set forth. Each of the sleeves 54A is secured to T-shaped beam 51, in a suitable manner, as by welding. The pipe 55A is considerably longer than pipe 55 of the actuating assemblies 48 for the upper row of air inlet port assemblies 34 and extends to a point adjacent the top of the lower air inlet port assembly. As best shown in FIG. 2, the lower end portion of pipe 55A is supported for longitudinal movement in a sleeve 67 which is secured to the end of an angle iron 68. The opposite end of angle iron 68 is fixedly connected to a horizontal tiebar 69 (see FIG. 2). As best shown in FIG. 1A, link 62A is pivotally connected to link 64A at a point below the upper end portion of link 64A rather than being connected at the end portion of the link as shown and described for the actuating assemblies for the upper row of air inlet port assemblies 34.

To prevent leakage of air from plenum chamber 33, of windbox 28, past the sleeves 54 and 54A of the actuating assemblies 47, where they pass through top wall 29 of windbox 28, tubular members 54 and 54A are seal welded around their peripheral surfaces to plate 74) of top wall 29.

As best shown in FIGS. 3 and 5 cooled tubular members 18 which line the lower section 11B of front wall 11 are provided with longitudinal fins 71. Each tubular member 18 is provided with a pair of fins 71 which extend diametrically opposite each other from the surface of the tubular member into the spaces between adjacent tubular members 13. The fins 71 on the side opposite the furnace chamber side thereof are covered by a layer of refractory material 72. The fins 71 and refractory layers 72 are not continuous for the entire length of tubular members 18, but terminate at points slightly beyond the planes of top plate 37 and bottom plate 38 of each of the air inlet port assemblies 34 so that the spaces between tubular members 18 in the area defined by side plates 35 and 36, top plate 37, and bottom plate 38 of each of the air inlet port assemblies 34 are open and unobstructed. With the spaces between tubular members 18 only open in the area defined by the air inlet port assemblies 34, tertiary air from the plenum chamber 33 of windbox 28 is free to flow into furnace chamber 14 only through each of the air inlet port assemblies 34.

As best shown in FIG. 2, side plates 35 and 36 of each of the air inlet port assemblies 34, are provided with a plurality of vertically spaced horizontally extending slots 75. Slots 75 are provided to allow differential linear expansion between side plates 35 and 36 and tubular members 18 and thereby prevent buckling of plates 35 and 36, which warpage or buckling would cause binding of vanes 39 and render the air inlet port assembly inoperative.

In operation of vapor generator 16 having the tertiary air inlet apparatus, hereinbefore described, fuel, as for example, a low volatile pulverized fuel, is delivered to burners 23 from a suitable source thereof (not shown). The fuel is discharged from nozzles 25 of burners 23,

75 through burner ports 24 formed in the arch 15, downwardly into furnace chamber 14 adjacent lower front wall section 11B. To provide the necessary combustion air for progressively burning the fuel in furnace chamber 14, tertiary air is delivered by fan 17 through ducts 28A and 28B and inlet 26 into plenum chamber 33 of windbox 28. The air passes from plenum chamber 33 into air inlet port assemblies 34 and thence, through the spaces between the tubular members 18, into furnace chamber 14. The air in furnace chamber 14 admixes with the downward flow of fuel and supplies the necessary oxygen to support the substantially complete combustion of the fuel.

While the vapor generator is in operation, the desired flame shape and position, as well as optimum combustion of the fuel, within the furnace chamber 14 can be obtained by controlling the amount and direction of tertiary air flow into the furnace chamber 14 through each of the air inlet port assemblies 34. Individual control of the amount and direction of the tertiary air flow through each of the air inlet port assemblies 34 is accomplished by turning handwheel 57 of the actuating assembly 48 which is associated with the air inlet port assembly 34 through which the amount and direction of the air is to be adjusted. Turning handwheel 57 effects longitudinal movement of threaded shaft 56 and pipe 55 in an upward or downward direction, depending upon the direction of rotation of handwheel 57. Longitudinal movement of pipe 55 causes longitudinal movement of links 62 and 64 which, in turn, is translated into arcuate movement of each of the vanes 39 through crank arms 46A and 46 and gang link 47. If it is desired to direct the air flow through a particular air inlet port assembly 34 at a greater angle downwardly into furnace chamber 14, handwheel 57 is turned to pivot vanes 39 to a more vertical position. To completely cut-off of air through a particular air inlet port assembly 48, handwheel 57 of that air inlet port assembly is turned to rotate the vanes 39 to a substantially vertical position, as shown in FIG. 2 and by the broken lines in FIG. 4, where the vane 39 below abuts the shaft 46 of the vane 39 above and the uppermost vane 39 abuts pendent plate 42. By relative adjustment of each of the air inlet port assemblies 34, the amount and direction of the entry of tertiary air into each part of a large area of the furnace chamber 14 is achieved to provide the desired flame shape and position for maximum fuel combustion and heat generation Without the creation of hot spots within the furnace. It is also feasible by relative adjustment of the direction and amount of air flow into furnace chamber 14, through the individual air inlet port assemblies 34, to provide a pattern of distribution of tertiary air whereby flame shapes and positions are provided for optimum fuel combustion over a relatively wide range of load upon the vapor generator 19 without development of hot spots within the furnace.

While but one embodiment of the present invention has been described as having application to a furnace wall lined with fluid cooled tubular members 18 arranged in spaced parallel relationship to each other, the application of the present invention to a furnace wall lined by tangentially disposed fluid cooled tubular members 18 is also contemplated. In this second embodiment, the space for communicating the windbox with the furnace chamber through the air inlet port assemblies would be provided for between the tubular members by bending and off-setting a portion of two or more tubular members out of the plane of the tubes in the manner as is well known to those skilled in the art. In addition, it is within the preview of the present invention to provide an inlet port assemblies 34 of such size that they would span one or more than three tubular members 18. It is also contemplated, without departing from the scope and spirit of the present invention, to have a metallic plate which would form a windbox wall adjacent tubular members 18 in the area between the air inlet port assemblies 34, in which event, the spaces between the tubular members need not be sealed with a refractory layer 72.

It is apparent from the foregoing description, that a novel tertiary air inlet method and apparatus for a furnace has been provided by which proper flame shape and position within the furnace chamber can be achieved readily and easily while the furnace is in operation. The tertiary air inlet method and apparatus according to this invention also provides a means for achieving a pattern of tertiary air flow into the furnace chamber which will produce over a wide range (.f firing rates flame shapes and positions which will achzve optimum fuel combustion Without development 0" lot spots within the furnace chamber and with furnace ,ds temperatures at relatively low values. It is also a tertiary air inlet method and apparatus which provides a quick and easy means of readjustment of the tertiary air flow pattern or distribution into the furnace chamber to provide the proper flame shape and position when the vapor generator employs a fuel having different combustability characteristics from the fuel previously used.

Although but one embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the arrangement of parts without departing from the spirit and scope of the invention, as the same will now be understood by those skilled in the art.

What is claimed is:

1. In a furnace having a plurality of contiguous walls forming therebetween a furnace chamber and wherein said walls are lined by a plurality of vertically extending spaced parallel fluid conducting tubular members, a system for introducing air into said furnace chamber through at least one of said furnace walls comprising, a relatively large opening in said one furnace wall communicating with the spaces between the tubular members of the furnace wall, a windbox overlying said opening and secured to said furnace wall at the periphery of the opening, a plurality of frame members each of which comprises spaced parallel side walls connected together by spaced parallel top and bottom walls, the distance between the side walls of the frame members being substantially equal to the center to center distance between at least three tubular members, said frame members being disposed within said wall opening in spaced relationship to each other, each of said frame members being connected at the side walls to two of said tubular members to thereby form an air port communicating the windbox with the furnace chamber through the two spaces between the three tubular members, a plurality of vanes disposed within each frame member and pivotally supported one above the other by the side walls of said frame members, linkage means for connecting the vanes within a frame member together for conjoined movement, each of the vanes within a frame member being constructed along one edge to at least partially extend into the spaces between the tubular members with which the air port formed by a frame member communicates, means for sealing the spaces between the tubular members surrounding the frame members, second means for supplying air from a source thereof to said windboX, and a vane actuating assembly for each frame member, said vane actuating assembly being connected at one end to said vanes within a frame member and at the other end extending exteriorly of the furnace, each of said vane actuating assemblies being operative to adjust the position of the vanes to which the associated vane actuating vane assembly is connected and thereby control the direction and quantity of air flowing through each of the frame members into the furnace chamber, each of the vanes along said one edge thereof is constructed with arcuate cutout portions dimensioned to partially encompass the tubular members within the air port formed by a frame member and to provide vane portions extending into the space between the tubular members.

2. In a furnace having a plurality of contiguous walls forming therebetween a furnace chamber and wherein said walls are lined by a plurality of vertically extending spaced parallel fluid conducting tubular members, a system for introducing air intosaid furnace chamber through at least one of said furnace walls comprising, a relatively large opening in said one furnace Wall communicating with the spaces between the tubular members of the furnace wall, a windbox overlying said opening and secured to said furnace wall at the periphery of the opening, a plurality of frame members each of which comprises spaced parallel side walls connected together by spaced parallel top and bottom walls, the distance between the side walls of the frame members being substantially equal to the center to center distance between at least three tubular members, said frame members being disposed within said wall opening in spaced relationship to each other, each of said frame members being connected at the side walls of two of said tubular members to thereby form an air port communicating the windbox with the furnace chamber through the two spaces between the three tubular members, a plurality of vanes disposed within each frame member and pivotally supported one above the other by the side walls of said frame members, linkage means for connecting the vanes within a frame member together for conjoined movement, each of the vanes within a frame member being constructed along one edge to at least partially extend into the spaces between the tubular members with which the air port formed by a frame member communicates, means for sealing the spaces between the tubular members surrounding the frame members, second means for supplying air from a source thereof to said windbox, and a vane actuating assembly for each frame member, said vane actuating assembly being connected at one end to said vanes within a frame member and at the other end extending exteriorly of the furnace, each of said vane actuating assemblies being operative to adjust the position of the vanes to which the associated vane actuating assembly is connected and thereby control the direction and quantity of air flowing through each of the frame members into the furnace chamber, said frame members are arranged in horizontal rows disposed one above the other with frame members of one row offset horizontally from the frame members of the other row.

3. A furnace having a bottom, an arch roof spaced a substantial distance from the bottom, a plurality of contiguous walls including a first wall, the walls defining therebetween a furnace chamber, the first wall lined by a plurality of spaced fluid conducting tubular members, at least one burner penetrating through the arch roof and arranged to direct fuel and air downward into the furnace chamber in proximity with the first wall, the first wall defining a plurality of spaced air ports communicating in flow series with spaces between the tubular members lining the first wall, each of the air ports being of quadrangular configuration, a vane assembly disposed in each of the air ports and comprising a plurality of pivotally mounted vanes connected to each other for conjoined movement, each vane having one edge thereof constructed to at least partially extend into at least one of the spaces between the tubular members adjacent the air ports, means for supplying air from a source thereof to said air ports, means connected to each vane assembly and extending externally of the furnace for pivotally moving the vanes to control the quantity and direction of the flow of air through each of the air ports into the furnace chamber.

4. A furnace having a bottom, an arch roof spaced a substantial distance from the bottom, a plurality of contiguous walls including a first wall, the walls defining therebetween a furnace chamber, the first wall lined by a plurality of spaced fluid conducting tubular members, at least one burner penetrating through the arch roof and arranged to direct fuel and air downward into the chamber in proximity with the first wall, a system for introducing air into the furnace chamber through the first wall and comprising a relatively large opening defined by the first wall and communicating in flow series with spaces between the tubular members lining the first wall, a windbox secured to said furnace wall at the periphery of said opening, a plurality of frame members, each frame member comprising spaced parallel side walls connected together by spaced parallel top and bottom walls, the frame members being disposed within the wall opening in spaced relationship to each other, each of the frame members being connected at the side walls of the frame members to two of the tubular members, means for sealing the spaces between the tubular members in the areas surrounding the frame members so that each of the frame members forms an air port communicating the windbox with the furnace chamber through at least one of the spaces" between the tubular members, a plurality of vanes pivotally mounted between the side walls of the frame members, second means for connecting the vanes within each frame member together for conjoined movement, each of the vanes being constructed along one edge to at least partially extend into at least one of the spaces between the tubular members adjacent the air ports, third means for supplying air from a source thereof to the windbox, and a vane actuating member for each frame member, the vane actuating member being connected to the vanes within the frame member for adjusting the position of the vanes within the frame member and thereby controlling the quantity and direction of the flow of air from each of the air ports formed by the frame members into the furnace chamber.

5. The system of claim 4 wherein each vane has a shaft about which it is pivoted and wherein the second means comprises an arm for each vane connected at one end to the shaft of a vane and at the other end to a main link, the main link being connected to the vane actuating member.

6. The system of claim 4 wherein the vane actuating member extends externally of the furnace whereby adjustment of the vanes for control of flow of quantity and direction of air through each frame member is effected while the furnace is in operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,866,404 Frisch et al. July 5, 1932 1,966,054 Wheeler July 10, 1934 2,011,026 Bailey et a1 Aug. 13, 1935 2,229,068 Frisch Jan. 21, 1941 2,759,460 Craig Aug. 21, 1956 FOREIGN PATENTS 759,462 Great Britain Oct. 17, 1956

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