Title:
GRATE STRUCTURE FOR INCINERATOR
United States Patent 3783802


Abstract:
In a hollow pyrometric incinerator grate structure are groups of axially spaced grate support means such as rings. Elongated grate bars are disposed on the support means circumferentially in rows about the interior of the hollow body. Each grate bar is engaged at its center with an intermediate support and the opposite ends of each grate bar bear freely on opposite axially spaced supports to enable biaxial stress relief.



Inventors:
SCHRAGE D
Application Number:
05/247579
Publication Date:
01/08/1974
Filing Date:
04/26/1972
Assignee:
AQUA CHEM INC,US
Primary Class:
Other Classes:
110/240
International Classes:
F23G5/22; F23H9/00; (IPC1-7): F23G5/06
Field of Search:
110/14,15,35 126
View Patent Images:
US Patent References:
3577941INCINERATOR1971-05-11Schoppe
3487793DRUM-SHAPED GRID FOR A REFUSE INCINERATOR1970-01-06Lerner et al.
2496156Rotary-type burner for solid fuels1950-01-31Fulton
2426348Rotary-grate burner1947-08-26Fulton et al.
2116024Furnace grate1938-05-03Helmick
1910985Grate bar fastener1933-05-23Clawson
1575350Method of burning fuel and apparatus therefor1926-03-02McEwen



Primary Examiner:
Sprague, Kenneth W.
Attorney, Agent or Firm:
Ralph, Hohenfeldt Et Al G.
Claims:
I claim

1. In a pyrometric incinerator for disposing of combustible waste and the like, grate structure comprising:

2. The invention set forth in claim 1 wherein:

3. The invention set forth in claim 1 wherein:

4. The invention set forth in claim 3 including:

5. The invention set forth in claim 1 wherein:

6. The invention set forth in claim 1 wherein:

7. The invention set forth in claim 6 wherein:

8. The invention set forth in claim 6 wherein:

9. For use in an incinerator, a hollow grate support body comprising:

10. The invention set forth in claim 9 including:

11. The invention set forth in claim 9 wherein:

12. The invention set forth in claim 11 wherein:

13. The invention set forth in claim 10 including:

14. The invention set forth in claim 13 wherein:

Description:
BACKGROUND OF THE INVENTION

This invention relates to incinerators, and, in particular, to improvements in the rotating pyrometric cone or grate structure used in incinerators for combustible waste materials such as garbage.

A known type of incinerator has an open-ended hollow body or grate support structure which is sometimes conically shaped and is mounted within an enclosure on an inclined axis of rotation. Disposed circularly around the interior of the hollow body are rows of grate bars on which the combustible materials are deposited. The combustible materials are ignited initially with a gas flame or the like while the body is rotating slowly. Ignition is sustained by forcing air for combustion from the outside to the inside of the body through the grates. The prevailing combustion temperatures are sufficient to cause the grates and the hollow supporting body to become more than red hot. Alternate heating and cooling and uneven thermal distribution in the body and grates causes internal stresses, distortion and other forms of deterioration which have necessitated premature replacement or rebuilding of the grate structure.

Fastening the grate bars in the hollow conical body has presented problems. It has been the custom to hold the grates within the hollow grate support body by means of several slots in the edge of each grate bar which hook onto axially spaced apart rings within the body. When the grate bars are alternately subjected to cooling and heating, expansive and contractive thermal stresses are developed in them. These stresses often result in the grate bars fracturing in the vicinity of their support engaging slots in which case some of the bars may break away completely with obvious undesirable consequences. Moreover, when one or more grate bars break away, the self-supporting effect of adjacent bars is removed in which case there is a greater tendency for the remaining bars to twist, fracture and shear off.

The hollow supporting body for the grates has also presented problems. The body is desirably supported in cantilever fashion to allow an open end for charging its interior with burnable materials, but this makes the conical grate structure particularly vulnerable to distortion and fracture due to cyclical and uneven thermal distribution.

SUMMARY OF THE INVENTION

An object of the present invention is to overcome the abovenoted disadvantages by providing a grate structure which is capable of adapting to varying thermal stresses without distorting or fracturing.

Another important object of this invention is to provide means for supporting the grates within the structure in such manner that the grates are not subjected to undue tensil, compressive, shearing or torsional stresses.

Another object is to have only a central region of each grate engaged with an intermediate support in the support structure and to have the end portion of the grates merely bearing on their supports so that they are free to expand and contract without developing high internal stresses.

A further object is to provide a conical grate support structure which is constructed as a lattice so as to accommodate thermal changes without fracturing.

How the foregoing and other more specific objects of the invention are achieved will appear throughout the course of a more detailed description of a preferred embodiment of the invention which will be set forth hereinafter.

In general terms, one embodiment of the new grate structure comprises a hollow cone which is formed of generally axially directed struts that engage with axially spaced apart flange rings. The struts are interconnected with each other to form what may be termed a lattice structure. This structure accommodates axially and circumferentially imposed thermal stresses.

The axially adjacent rows of grates which are disposed about the interior of the support structure each have a central slot on one edge or some other suitable means for relatively loosely engaging the grates with sets of intermediate rings that encircle the interior of the hollow body. Axially spaced apart in opposite directions from each intermediate ring are supporting rings on which the opposite end portions of each grate bear. There is no positive engagement between the end portions of the grates and their supporting rings.

An embodiment of the invention will now be described in reference to the drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial vertical sectional view of an incinerator which employs the new grate structure;

FIG. 2 is a partial sectional view taken on an axial plane through the grate structure;

FIG. 3 is a side elevation view of the grate structure with one half showing the exterior thereof and the other half showing the interior with the grates removed;

FIG. 4 is a semi-plan view looking at the plane 4--4 in FIG. 3, one quadrant showing the circularly disposed grate supporting ring means and the other having the same omitted to show the outside struts of the grate supporting body;

FIG. 5 is a fragmentary elevation view of the joints between the struts and other members of the hollow body;

FIG. 6 is a side elevation view of one form of elongated gate which may be used in the new incinerator grate structure;

FIG. 7 is a bottom-edge view of the grate in FIG. 6;

FIG. 8 is a side elevation view of another form of elongated grate that may be used in the new grate structure; and

FIG. 9 is a plan view of the grate shown in the preceding figure.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 shows an incinerator with a portion of its housing 10 broken away to expose the inclined conical pyrometric cone or grate structure 11 constituting the subject of the present invention. More information on an incinerator of this type may be obtained from U.S. Pat. No. 3,577,941 which is assigned to the assignee of the present invention.

The invention is directed to improving the hollow generally conical body 11 and the means for supporting a multiplicity of interiorly arranged rows of grates 12 therein. Body 11 is supported for rotation on a turntable 13 about an axis that is inclined from horizontal. The structural details of the body 11 will be discussed later. For present purposes it is sufficient to observe that the body 11 has an open end 14 through which combustible material can be fed to the interior for being burned. The feed end 14 is provided with a beveled annular metal shroud 15. The shourd 15 helps to retain combustible materials in body 11 when it is being rotated during combustion.

Hollow body 11 has a flange ring 16 at its lower end. Although it is not evident in FIG. 1, flange ring 16 has an aperture which is in alignment with an aperture in turntable 13 so that large unburnable residues may be discharged from the hollow body 11 periodically. Also not visible in the drawing but exemplified in the cited patent is a convex valve member which is adapted to be selectively positioned in the aperture of turntable 13 to close it when the incinerator is in use. A lead screw, not shown, which is driven by a shaft 17 on whose end there is a handwheel 18 may be used to advance and retract the convex valve member into and out of the aperture in turntable 13. There is a turntable base structure 19 which is surrounded by several circumferentially spaced rollers 20. Behind or below base structure 19 is a housing 21 in which there is a suitable shaft for supporting the hollow body 11 for rotation and a reduction gear train which, like the shaft, is not shown. On top of housing 21 there is a speed reducer 22 which is connected to a prime mover such as a motor that is located behind the speed reducer and not visible in FIG. 1. A shaft 23 extends from speed reducer 22 into a gear housing 24. There is a pinion on the end of shaft 23 which engages with a large gear within housing 24, the pinion and gear not being shown, but it will be understood that they constitute part of the known mechanism for rotating the hollow body 11 at rotational speeds under one revolution per minute.

Hollow body 11 and its supporting and driving structure which was just described are all mounted on a carriage which is marked with the numeral 25. The carriage 25 has four wheels two of which, 26 and 27, are visible in FIG. 1. The wheels run on parallel tracks such as the one marked 28. These tracks lay on opposite sides of the incinerator enclosure 10 so that the sides of carriage 25 remain on the outside of the enclosure when the hollow body 11 is in place within it.

The roof 29, front wall 30 and rear wall 31 together with the side walls which are not shown, are all refractory lined to cope with the intense heat that develops in enclosure 10 during incineration. Rear wall 31 has a vertical portion as shown and a refractory lined inclined portion 32 which connects with and is supported on base 19 and carriage 25. Thus, the construction is such that when carriage 25 is rolled to the right on tracks 28 as in FIG. 1, the body 11 and its associated parts will be exposed for maintenance and there will also be access to the interior of enclosure 10 for maintenance purposes.

When the interior of hollow body 11 is charged with wastes, the wastes must be ignited initially by external means. Thus, a gas jet 33 is provided for directing a flame into hollow body 11 to effect ignition. The flame may also be continued during regular operation of the incinerator to assist combustion of evolved gases and solid materials. When combustion of waste has commenced in hollow body 11, the combustion process is promoted and sustained by blowing air from the outside of the inside of body 11 through suitable grooves in the sides of grates 12. The combustion air injection means is symbolized by a header 34 which may have several jet openings or nozzles in its top for projecting air at relatively high velocity through the grate openings and into hollow body 11. There may be several air jet headers 34 adjacent each other and they may each be connected to a blower, not shown, by means of pipes such as the one marked 35. Fine ashes which are produced by combustion of the wastes fall through the spaces or grooves between grates 12 and settle into an ash hopper, not shown.

The gaseous products of combustion which may be incompletely oxidized in hollow body 11 are withdrawn upwardly through the inlet of an afterburner 36, a fragment of which is shown in FIG. 1. The duct which extends into enclosure 10 for directing gases to the afterburner is omitted from the drawing. There is also a conduit or chute 37 for delivering combustible material to the feed opening 14 of body 11 to charge the same. A chute extension for directing flow of the waste materials through enclosure 10 to feed opening 14 is also omitted from the drawing.

Attention is now invited to FIGS. 2-8 for a more detailed discussion of the construction of hollow body 11, its grates and grate supporting means therein. Referring to the right half of FIG. 3, one may see that the conical portion of hollow body 11 is comprised of a plurality of offset struts illustrative ones of which are marked 45-52. As is the case with all the struts, the upper ends 53 and 54 of typical struts 48 and 49 are welded to a flange ring 55 as are the corresponding upper ends of adjacent struts. The lower ends 56 and 57, for example, of struts 48 and 49 are welded to a relatively smaller diameter flat ring or apertured flange 16. As can be seen in FIG. 4, flange 16 has several circumferentially spaced holes 58 for bolting the flange and housing 12 to turntable 13 as shown in FIG. 1. The various struts, which are disposed in a circular pattern, are offset in their central region and abut each other as indicated in the vicinity of reference numeral 59. These butt joints are preferably welded. Thus, one may see that four quadrants formed of struts such as 45-52 will define a conical hollow body portion wherein the inside edges of all of the struts define a cone of revolution. Viewed from the outside, the struts present the appearance of a lattice structure.

One portion of hollow body 11 is substantially cylindrical as designated generally by the reference numeral 60. The axial boundaries of cylindrical portion 60 are defined by intermediate flange 55 and an end flange 61 to which shroud 15 is attached by any suitable means. Another lattice structure defining cylindrical portion 60 of hollow body 11 is formed with struts such as 62-67 which are arranged in triangular relationship and have their opposed ends welded respectively to flanges 55 and 61. The manner of welding struts such as 65 and 66 in the cylindrical portion of the body and struts 53 and 54 in the conical portion with flange 55 is exhibited in FIG. 5.

It will be evident to those skilled in the art that the offsets or bends in the central regions of the juxtaposed struts which form the conical portion of body 11 being in abutment with each other at points such as 59 result in a rigid, lightweight lattice structure which is adapted to expand or extend axially and radially to a limited degree for accommodating thermal and other physical stresses exerted in any direction. The triangularly disposed struts such as 62-67 impart similar properties to the cylindrical portion 60 of hollow body 11.

One may see in the left portion of FIG. 3 that triangularly arranged struts such as 62-67 present straight edges to the interior of hollow body 11 to define an interior cylinder of revolution. The inside surface of this cylinder is marked with the numeral 68 in FIGS. 2 and 3. Similarly, offset struts such as 45-52 present straight edges to the interior of hollow body 11 which define a cone of revolution that is marked with the numeral 69. This can also be clearly seen in FIGS. 2 and 3.

FIGS. 2 and 3 show that within cylindrical portion 60 of body 11 are circumferentially spaced clips such as intermediate clip 70 and axially spaced apart clips 71 and 72 which are welded to the individual triangularly arranged struts. Intermediate clip 70 is provided with a slot 73, as are other corresponding clips, for accommodating grate support ring 74. Similarly, clips 71 and 72 are slotted for receiving grate support rings 75 and 76, respectively.

One type of grate which may be supported on the set of rings 74-76 is depicted in FIGS. 6 and 7. The grates 12 are shown in phantom in FIG. 2. These grates are disposed adjacent each other around the interior of cylindrical body portion 60 as can be seen particularly well in FIG. 1.

In the type of the grate shown in FIGS. 6 and 7, one edge has an L-shaped slot 77 which constitutes a hook so that the center of the elongated grate 12 may be engaged with an intermediate grate support ring such as 74. Note that the edges of the grates at their end portions 78 and 79 are planar and that their sides have a plurality of grooves 80 so that when the grates are side-by-side there will be radial openings for air to pass into hollow body 11 and for fine ashes to fall out. From inspection of FIG. 2, it will be evident that the juxtaposed grates 12 are hooked on intermediate support ring 74 and that their opposed planar end portions 78 and 79 merely bear on axially spaced apart support rings 75 and 76. Thus there is only one point of engagement between each grate 12 and an intermediate support ring 74 while the end portions of the grates are free to expand and contract and have no restraints.

The conical part of hollow body 11 has three rows of grates 12 encircling the interior of the body as can be seen in FIGS. 1-3. The grates 12 in the top row within the conical portion are all supported on an intermediate support ring 90 and their opposed ends bear freely on opposite axially spaced apart support rings 91 and 92. Support rings 90-92 are retained by clips 93-95, respectively, which are welded to the lattice struts. Axially displaced rows of grates 12 are similarly releasably supported on intermediate rings 96 and 97. There are a pair of axially spaced apart grate end supporting rings 98 and 99 cooperating to support a row of grates with intermediate ring 96 and there are another pair of spaced apart support rings 100 and 101 cooperating with intermediate ring 97 to support the lowermost row of grate bars 12 which encircles the interior of the conical portion of hollow body 11. All of the support rings are captured in slotted retaining clips such as 94 and 95. The rows of grates 12 encircling the interior of hollow body 11 define a combustion space for materials fed in through feed opening 14 of hollow body 11. As the hollow body rotates in the assembly depicted in FIG. 1, ash and other fine particles sift through the opening defined by grooves 80 in the grates, and these fine materials accumulate in the bottom of enclosure 10 from which they are periodically removed by opening a door in the ash hopper, not shown. Large non-combustible pieces which are inevitably found in waste materials are periodically removed from the combustion chamber in hollow body 11 through an opening 105 in bottom flange 16, as can be seen in FIG. 2. As mentioned earlier, the means for closing opening 105 during operation of the incinerator may be a convexly shaped valve, not shown, which is advanced and retracted by handwheel 18 outside of the incinerator mechanism as can be seen in FIG. 1.

Another type of grate bar 12' is depicted in the side and plan views of FIGS. 8 and 9 respectively. Grate bars of the 12' type may be considered a preferred form. They are so shaped that when they are arranged in rows in the conical support there is more space for ashes and small particles which are usually completely burned to drop into the ash hopper. These bars also allow anchoring them to the intermediate supporting rings positively with a pin without inhibiting thermal expansion and contraction.

In FIGS. 8 and 9 a typical grate bar 12' comprises an elongate or axially extending body or web 110 whose sides 111 and 112 are slightly beveled or converging toward each other. Integral with opposite ends of body 110 are substantially T-shaped heads 113 and 114, the latter being narrower than the former in a direction transverse to the elongated body 110. A foot 115 extends down from heat 113 and a foot 116 extends from head 114. The bottom surfaces 118 and 119 respectively of the feet are flat and adapted to rest on the axially spaced apart support rings such as rings 98 and 99 of cone 11 in FIG. 3.

Extending downwardly from body 110, as can be seen clearly in FIG. 8, are a pair of tongues 120 and 121 which define a slot 122 by which the grate bar 12' may be engaged with a support ring 96, in FIG. 3, which ring is axially intermediate rings 98 and 99 in this figure. A cross section of a typical intermediate support ring is shown in phantom in FIG. 8. The tongues have aligned holes 123 for receiving a pin, not shown, for loosely but positively securing each grate bar 12' to its intermediate supporting ring. Ribs 124 and 125 between the heads 113 and 114 and tongues 120 and 121 serve as reinforcement for the tongues.

The overall longitudinally beveled or tapered shape of the grate bars 12' permits them to be positioned next to each other with the sides of their T-heads 113 and 114 abutting regardless of the fact that the axially spaced supporting rings have different diameters due to the conical shape of part of the support structure 11.

The invention is not limited to the embodiments shown in the drawings. For instance, hollow body 11 of the grate structure may have other shapes such as a basket, bulb or sphere. However, the partially conical and partially cylindrical type described has the advantage of inducing constant agitation and demixing in the combustion chamber and so promotes more complete combustion of the wastes.

In summary, a new rotating grate structure for an incinerator or other type of furnace has been described. The grate structure is distinguished by using a hollow supporting frame which has a cylindrical portion and an axially contiguous conical portion which are both comprised of struts that form a lattice. The internal rows of grates are releasably engaged with concentric and axially spaced apart intermediate support means. The ends of the grates merely rest on support ring means which are on opposite sides of each of the intermediate rings. The lack of axial restraint on the end portions of the grates permit them to expand and contract and otherwise yield so that they do not develop internal stresses or torsional forces that might cause the grates to fracture as in prior art designs.

Although a preferred embodiment of the invention has been described in detail, such description is to be considered illustrative rather than limiting, for the invention may be variously embodied and is to be limited only by interpretation of the claims which follow.