US3401922A - Linear grate for shaft kilns - Google Patents

Description

Sept. 17, 1968 J. B. JONES, JR

LINEAR GRATE FOR SHAFT KILNS 2 SheetsSheet 1 Filed Oct. 24, 1966 INVENTOR.

JOHN B. JONES Jr. A Q i A 7'TORNE) Sept. 17, 1968 J. B. JONES, JR

LINEAR GRATE FOR SHAFT KILNS 2 Sheets-Sheet 2 Filed Oct. 24, 1966 FIG. 8

INVENTOR. JOHN B. JQNES Jr.

ATTORNEY United States ABSTRACT OF THE DISCLOSURE A discharge grate for circular shaft kilns has at least one generally rectangular opening with a retarder plate juxtaposed below the opening therein, and a linear pusher bar is mounted in the space above the retarder plate so that on reciprocating motion it moves material off the edges of the retarder plate. The bar configuration is such that material discharged from the kiln is uniform across the lateral extent of the kiln.

Specification This application is a continuation-in-part of copending application Ser. No. 498,892, filed Oct. 20, 1965, for Linear Grate for Shaft Kilns, by the present applicant, but now abandoned.

This invention relates to improvements in shaft kilns, and particularly to the discharge grate for such units.

One type of process equipment commonly found in diverse kinds of industry is a gravity flow vessel having an upper feed and a lower discharge. Such vessels may have a longer vertical extent than their cross-sectional dimensions. Commonly such vessels are called shaft or vertical kilns, shaft furnaces, shaft generators, and the like, depending on the type of treatment and the material being treated. Such devices are useful for burning or calcining lime, coking coal, burning magnesite, dolomite, retorting oil shalt, etc. The equipment is generally the type well known for various treatments, and commonly they include the vertical vessel having means for uniformly feeding granular or pulverulent material across the lateral extent of the vessel, a lower discharge means for providing a uniform discharge across the lateral extent of the kiln, and some means for introducing a stream of treating fluid through the pulverulent material. The majority of known installations have been rectangular kilns of relatively small cross-sectional dimensions. Also, some circular shaft kilns have been tried, but due to their limited diameters and lack of control of uniform movement of the particulate material through the kiln, they have not been received with favor in the industry. A major problem occurs with such equipment on increasing the cross-sectional dimensions, and that is to provide a uniform downward movement of material throughout the cross-sectional extent of the kiln from the top to a lower section adjacent the discharge end so as to aid uniform treatment of all of the material as it passes through the kiln.

It is, therefore, an object of the invention to provide an apparatus to uniformly remove solids from the bottoms of shaft furnaces or kilns and to provide for uniform downward movement of solids throughout the cross-sectional extent of some such kilns from the top to adjacent the bottom thereof.

Another object of the invention is to provide a discharge apparatus for shaft kilns so as to distribute treatment fluids uniformly throughout the material moving through the kiln.

These and other objects and advantages of the invention may be readily ascertained by referring to the following description and appended illustrations in which:

FIG. 1 is a perspective view, partly cut away, of a discharge grate mounted in a vertical kiln according to the invention;

FIG. 2 is a cross-sectional view of the discharge grate illustrated in FIG. 1;

FIG. 3 is a top plan view of the grate section of the device of FIG. 1;

FIG. 4 is an enlarged detailed view of a material pusher bar arrangement of the grate illustrated in FIG. 1;

FIG. 5 is a top plan view, illustrating schematically another embodiment of a grate according to the invention;

FIG. 6 is an enlarged detailed view of a portion of the grate, taken along section line 66 of FIG. 5;

FIG. 7 is a diagrammatic plan view of a portion of a kiln grate segregated into discharge zones, illustrating a determination of the configuration of a pusher bar;

FIG. 8 is a vertical section through a portion of the kiln, illustrating the same discharge areas of FIG. 7; and

FIG. 9 is an enlarged detailed view of a pusher bar section showing the configuration of a segment of the bar of a portion of the discharge area illustrated in FIGS. 7 and 8.

In general, the apparatus of the invention provides grate or discharge means for removal of material from a vertical shaft kiln, and the grate means includes flow diverters mounted adjacent the bottom of a shaft kiln. The flow diverters are arranged in a linear pattern, producing generally linear outlets in a symmetrical pattern about the center or axis of the vessel. The flow diverters are arranged to form one or more generally rectangular discharge openings in the bottom of the kiln, each of which extends linearly from one side to the other side across the bottom of a kiln. The flow diverters provide openings through which the solids may flow freely without bridging between adjacent diverter plates. The diverter plates may be composed of flat plates, generally horizontally arranged in relation to the axis of a kiln, or they may be two plates joined together as an angle with an angle of less than therebetween. The angle of each plate is preferably arranged at an angle to the horizontal which is at least as great, and preferably greater, than the angle of repose of the material being treated. Material flow retarders are mounted below and in juxtaposition with the openings, but the retarders are spaced far enough below the opening so as to retard direct flow of solids through the opening and the pulverulent material is retained in the kiln. Pusher means are mounted in the space between the retarder plates and the diverter plates for mechanically releasing the solids resting on the retarder plates and thereby provide movement of the material through the kiln. The pusher means extend completely across the retarder plates, and are arranged to be activated in a generally reciprocating action across the plates to provide a controlled release of material from the kiln. The geometry of the pusher means is arranged to provide a discharge of material such that downward movement of the column of material supported above the discharge openings and the adjacent diverter plates is uniform across the lateral extent of the kiln.

The design of the grate is arranged as a volumetric discharge mechanism, and the pushers control the flow of solids to provide the uniform downward movement of the contained materials across the lateral extent of the vessel. This provides a uniform movement of the solids in relation of their mass to the cross-sectional dimensions of the vessel. To provide a uniform flow of solids across the lateral extent of the vessel, the configuration of the pusher means i arranged so that the ratio of the distance of the supported column of material passing through the discharge opening at any point divided by the height of the pusher at that point is a constant.

The device illustrated in FIGS. l-4 demonstrates a grate with four openings in a circular vessel. The invention, however, is applicable to grates having one or more openings, the number of openings in the grate being determined by numerou considerations, including particle size and kind, the size of the kiln, etc. As illustrated in FIGS. 1-4, a shaft kiln with upright walls 10, which is preferably circular but may be elliptical or similar configurations, is provided with a grate structure shown in general by numeral 12. The kiln wall extends upwardly to a predetermined height, as determined by the treatment desired, only a portion of which is shown for purposes of the present invention. The kiln may be provided with a conical or equivalent configuration bottom 14 providing a single central outlet 16 for the release of solid material which passes the grate 12. In instances where it is desired to pass a treatment fluid upwardly through the mass of material in the kiln, an inlet conduit 18 is provided through the wall of the bottom 14 for injecting fluid into the space therein, for subsequent movement up through the grate and through the material in the kiln. Where a fluid is injected into the conical bottom 14, some means must be provided for the discharge of solid material through the single opening with sealing means to prevent discharge of fluids. A star feeder, or the like, may be used for such purposes. In many instances, kilns are arranged for the treatment of material at elevated temperatures, and such kilns have a wall which is lined with a refractory, etc.

The four-opening grate illustrated includes five deflector or diverter plates 20, 21, 22, 23 and 24, providing the four generally linear or rectangular openings between the diverter plates. The end diverter plates 20 and 24 are mounted adjacent the wall of the kiln and each must have an arcuate configuration on its outside edge where it intersects the wall to conform with the geometry of the wall. These two diverter plates are, also, provided with a straight inside edge, the chord of a circle, for forming a side for the linear opening. Angularly shaped diverter plates 21, 22 and 23 are spaced across the remaining distance of the kiln to provide the four openings. Each of the diverter plates 21, 22 and 23 extends completely across the kiln and the space between each pair of adjacent diverter plates has linear sides and curved ends coincident with the wall of the kiln. The diverter plates are two planar members welded together and angle shaped, and the angle between the two plates should be substantially less than 180. The angle between the two plates is normally determined by the angle of repose of the material treated, that is, that angle of the plate from the horizontal on which the pulverulent material will not rest but will slide off the plate. Where a flat plate is used as a diverter plate, a triangular shaped static bed of material will remain above the plate, and the cross-sectional area of the 4 static bed is equal to one-half the width of the diverter plate times its height. The height of material is determined by the angle of repose of the pulverulent material in itself and this may exceed the 60 angle. The preferred form is the angular diverter plates to provide a smooth flow of material into the opening.

The grate is arranged to discharge a column of material of greater cross-sectional dimensions than the dimensions of the discharge openings. Each opening discharges from a column which is bounded by the wall at each end and imaginary planes which extend vertically from the peak of the diverter plates. To provide a uniform flow of the material in the column which is bounded by the planes from the peaks of the two diverter plates and the wall between the points of intersection of the Peaks of the two diverter plates and the wall, all of the material across the lateral extent must move downwardly of the column at a uniform rate. Thus, the opening 26, for example, must discharge all the material in the column bounded by the planes from the peaks of diverter plates 21 and 22 and the wall at each end thereof. In a similar manner, the openings 25, 27 and 28 between the other deflector plates must discharge all the material in the column thereabove. The material in the column is prevented from flowing out the openings 25-28, inclusive, by means of a retainer plate spaced below each of the openings. A plate 30 is mounted below the opening 25 and prevents the material from passing therethrough. The distance at which the plate is placed below the opening is generally determined by the size of material in the column to prevent bridging of the material between the bottom edge of the deflector plate and the retarder plate. Additionally, the retarder plate edges must extend underneath the deflector plates to prevent a free flow of material over its edge into the conical bottom 14. The distance of the edge of the retarder plate under the deflector plate is determined by the angle of repose of the material on itself. Retarder plate 31 is mounted below the opening 26, retarder plate 32 is mounted below the opening 27, and retarder plate 33 is mounted below the opening 28.

To obtain a flow of material downwardly through the kiln, pusher bars are provided at each opening for the controlled movement of material resting on the retarder plates at a rate so that the column above each point on the pusher bar moves downwardly uniformly across the extent of the kiln. As shown in FIG. 3, a column of material supported by the retarder plate 31 between the diverter plates 21 and 22 is discharged over the edges of the plate 31 by means of a pusher bar 41. The material supported between the imaginary planes passing axially of the kiln from the peaks of the two diverter plates 21 and 22 must pass through the openings over the edges of plate 31. In the mid-section of the column, the distance b between the peaks of the two diverter plates is uniform until the peak of diverter plate 21 intersects the wall of the kiln and the height of the pusher is uniform. At the point of the intersection of the peak with the wall, the width of the column of material decreases around to the intersection of the peak of diverter 22 and the wall. Where the width of the column i uniform, the height of the pusher bar is uniform. Where the width of the column decreases, as for example at point a, the height of the pusher bar must decrease to maintain constant the ratio of the width of the column divided by the height of the pusher bar. Furthermore, since the wall is arcuate 0n the ends and the pusher bar must extend to the wall at all positions of movement to provide for movement of the material adjacent the wall, the pusher bar is extended into a notch 63 at one end and a notch 64 at the opposite end, FIG. 4. Thus, by having the ends of the pusher bars in the notch, the pusher is in close proximity to the wall at all positions of movement and the material along and adjacent to the wall is moved through the opening in the manner of the material in the center of the pusher bars.

Thus, as the width of the column of material above any point on the bar changes, the height of the bar is changed to compensate for the difference in volume of material to be moved.

The pusher bars reciprocate in the opening between the deflector plates on the retarder plates. In the four-opening grate as shown in FIGS. 1-4, pusher bar 41, for example, is interconnected to pusher bar 40 by means of piston rods 42 and 43. The piston rods are actuated by motors 44 and 45 for movement of the pusher bars in the openings. On the opposite side of the kiln pusher bars 46 and 47 are interconnected by means of rods 51 and 52 which are activated by motors 48 and 49. In one embodiment the motors may be hydraulic motors to prvide a reciprocating movement of the pusher bars. In other embodiments air motors may be used for movement of the rods for reciprocating the bars. Also, rotary motors with eccentrics may likewise be used. A reciprocating motor is preferred, however, as it easily gives a measure of control and a change of the stroke of the bars for changing the movement of flow of the material through a kiln. The actuating motors may, of course, be positioned in the kiln where desired. The height of the pusher bar at a particular point multiplied by the area on the retarder plate across which it moves is the volume of material moved at that point. Since the area over which the bar 41 moves is uniform across its extent, the change of height of the bar provides for the change in volume of material moved.

Minor adjustments may be made in the height of the pusher from point to point to compensate for the character of the solids being discharged, by means of structural braces or the like which may, also, be required to give the moving mechanism adequate strength. The retarder plates may be mounted to provide adjustable distances from the divider plates so that adjustments of the grate may be made in the field by changing the position of the retarder plates. As shown, the pushers rest on the plates and for economical reasons, they should have hardened guides that slide on the retarder plates; however, the pushers may be mounted on rollers or the like to aid the movement of the same across the retarder plates.

The four-opening grate shown in FIGS. 1-4 is useful for large diameter kilns. The two center pushers have a long, uniform height, middle section with tapering ends. The two outermost pushers, however, must be tapered from the center to the ends because of the curvature of the wall, which changes the width of the supported column, and which starts curving from the midpoint of the opening. Thus the distance between the peak of the inner diverter 21 or 23 and the wall from the midpoint around to the intersection of the peak with the wall is progressively decreasing. Thus, the top edge of the pusher bar is generally arcuate, following the formula representing that distance between the wall and the peak of the inner diverter divided by the height of the pusher is a constant ratio. As more grate openings are added, the configuration of the additional pushers generally follow the configurations of those shown for the two inside openings of the grate. Thus, a five-opening grate would utilize a center pusher having a uniform height substantially completely across its extent with only minor tapered ends. As the number of openings is reduced, however, the configuration of the pusher bars or blades is considerably changed.

As illustrated in FIGS. -9, a two-opening grate is provided for a kiln and the height of the pusher bar must vary from the center to the ends in accordance with the formula. In the schematic diagram of FIG. 5 a kiln 70 is provided with a grate having two openings 71 and 72 in which a pusher bar is mounted. A deflector plate, shown in general by numeral 73, is mounted centerwise of the kiln and two opposed side deflector plates 74L and 74R are mounted on each side thereof. The shape of the deflector plate 73 is angular; however, a top piece or a bonnet is provided to permit the injection of a fluid, such as a gas, into the granular material. In this instance the deflector includes plates 75 and 76 which are joined t0- gether at an angle forming a peak. The peak is covered by plates 78 and 79 which are joined together to form angular plates of approximately the configuration of the plates 75 and 76 having a peak 77. A plurality of spacer plates 80 and 81, spacedly positioned along the top of plates 75 and 76, support the upper plates. The angle between both sets of plates, i.e., 7576 and 78-79, is such that the angle of each plate from the horizontal is at least as great, and preferably greater, than the angle of repose of the material so that there will be no hangs of material in the kiln due to the deflector plates. The side deflector plates 74L and 74R are secured in position and supported by supports 82 in accordance with conventional structural practice. A retarder plate 85 is mounted below the opening 72 (between edges 74a and 76a of the two diverter plates 74L and 74R) and a retarder plate 86 is mounted below the other discharge opening 71. Pusher bars 88 and 89 are respectively mounted in the openings 72 and 71 to move material reposed on the retarder plates into the bottom of the kiln, in accordance with that explained above. The diagrams of FIGS. 7, 8 and 9 illustrate the change in shape of the pusher bar in relation to the amount of material which must be moved to provide a uniform flow of material in the column extending above and beyond the discharge opening. As shown in FIG. 7, imaginary columns of equal width are set off in a portion of the kiln to illustrate the changing dimensions which must be accounted for by the configuration of the pusher bar. For example, the column marked G has its one end along the wall 70 and the other on the peak 77 of the diverter plate 73. This area is larger than the adjacent area H due to the wall curvature, and H is larger than I, etc., down to the area marked R. The decrease in area, and consequently the volume of the column extending upwardly along planes at right angles to the boundaries of the area, is decreasing along the curvature of the wall 70*. Thus, the amount of material in each column is decreasing (but the grate opening remains constant until area 0) and the amount of material which must be moved by the pusher bar from the column, likewise, decreases from the center to the edge. The formula given above, where the width of the column at any one position along the pusher rod divided by the height of the pusher bar at that position, is a constant is used to determine the configuration of the pusher. The maximum width of the largest column (at the lateral center of the kiln) determines the constant, and since the distance of the width of the column at any point is known, the height of the pusher bar at that point may be readily determined. In FIG. 9 the point M represents the effective midpoint of the area of a column of material acted on by the pusher and the height H the effective height at the center of the area, representing the average between the edges, is determined from the constant, and the average width of the area W of FIG. 9. The width W- of each area is uniform in the diagrams, for purposes of calculation. In the case of pusher bars adjacent a deflector plate mounted on the kiln wall, the configuration is generally arcuate from end to end, and for the two-opening grate shown in FIG. 5, both pusher bars have arcuate tops. For a grate having a single opening, the pusher bar is, likewise, arcuate from the high point in the center to low points in the ends. As shown in FIGS. 1-4, for more than two openings the pusher has a uniform height central portion and tapered ends. In all cases, the pusher ends extend into a notch in the kiln wall, providing material movement adjacent the wall.

The deflector plate shown in FIG. 6, including the bonnet, is provided with a series of openings 90 and 91 spaced across the extent of the lower angled plate, which permits fluid to pass upwardly into the bonnet, around its lower edges and into the bed of material in the kiln. This,

of course, provides a convenient means for injecting fluid into the material bed at its bottom portion rather than having the fluid come through the openings in the grate. Fluid may be injected beneath the diverter plate by means of conduits passing through the wall to the underside of the diverter plates. Where fiat plates are used as diverter plates in place of the angles and it is desired to inject fluids into the beds, perforated pipes or the like placed under the plates will provide means for injecting the fluid into the bed. Also, the height of the adjacent diverters may be varied and the diverters and retainer plates may be staggered in the kiln to meet certain operating conditions.

While the invention has been illustrated by reference to a particular embodiment, there is no intent to limit the spirit or the scope of the invention to the precise details so set forth except as defined in the following claims.

I claim:

1. Grate means for a hollow cylindrical member having its axis upright, comprising a series of spaced-apart deflector plates extending from one side to the opposed side of the wall of the cylindrical member providing at least one essentially rectangular opening across a lower end of said member, said rectangular opening being defined by the straight edges of said deflector plates extending generally along the chords of said cylindrical member and the wall of said member; a material support plate mounted below and spaced from each said at least one opening and having its edges extending under the edge of each deflector plate to prevent a space therebetween along vertical lines; pusher means mounted in the space between said deflector plates and said support plate, said pusher means intersecting said wall at both ends and at positions of movement in said rectangular opening, said pusher means being arranged to sweep a uniform amount of material incrementally along its length in relation to the volume of material in said member at each incremental position on said pusher means; and means for reciprocally moving said pusher means across each said support plate.

2. Grate means according to claim 1 wherein the ends of said pusher means extend into recesses in the wall of said member.

3. Grate means for the lower end of a hollow circular member having an upright wall and its axis generally upright comprising a series of spaced-apart deflector plates extending from one side to the opposed side of the wall of said tubular member, said deflector plates defining a series of essentially rectangular parallel openings between the plates with the edges of each opening being a chord of said tubular member and said openings extending across the extent of said tubular member; a material support plate mounted below and spaced from each said opening and each having its edges extending under the edge of the adjacent deflector plate to prevent a space therebetween along vertical lines, there being a recess in the wall of said tubular member at the ends of each said rectangular opening; pusher bar means mounted in the space between adjacent deflector plates and each support plate, the ends of said pusher bar means being of a progressively reducing height and extending into said recesses so as to be in full contact with supported material in said tubular member on reciprocating movement of said pusher bar means and to discharge a uniform incremental amount of material along said pusher bar means in relation to the amount of supported material for discharge at each increment of length of said pusher bar means; and means for reciprocally moving each said pusher bar means across each said support plate.

4. Grate means according to claim 3 wherein five deflector plates provide four openings therebetween.

5. Grate means according to claim 3 wherein three deflector plates provide for two openings therebetween.

6. Grate means according to claim 4 wherein the pusher bar means for two openings are joined together and the other two pusher bars are joined together.

7. In a tubular circular member having an upright axis and grate means adjacent the lower edge thereof inclusive of at least one generally rectangular opening and a retarder plate adjacent to and below said opening over the edges of which material is pushed for discharge of the same from said tubular member, comprising substantially linear pusher bar means mounted in said at least one opening in said grate and above said retarder plate, said bar having a vertical configuration any point on which is determined by the constant ratio of material in the column which is discharged at that point divided by the height of the pusher bar means; and means for reciprocating said pusher bar means in said opening toward and from opposed edges of said rectangular opening.

8. The improvement of claim 7 wherein at least a portion of each of the ends of said pusher bar means is of decreasing height from centerwise to the end.

9. The improvement of claim 7 wherein at least a portion of each of the ends of said pusher bar means is arcuate curing to ends of a lesser height than the middle of said bar.

10. The improvement of claim 7 wherein said pusher bar means is arcuate along its top edge from the middle thereof to its ends, and said ends are of a lesser height than said middle.

11. In a cylindrical, vertical shaft apparatus for treating particulate material having a grate positioned in said shaft apparatus adjacent its lower end, the improvement in said grate comprising:

(a) transversely disposed, spaced-apart, substantially parallel, material diverter members providing at least one substantially rectangular material discharge opening between said material diverter members;

(b) a material support member mounted in spacedapart relation to and below each one of said material discharge openings, said support member extending on each side of each opening beyond a vertical downward projection of the edges of said diverter members;

(c) pusher means mounted in each said discharge opening and extending lengthwise thereof; and

(d) means to reciprocate each said pusher means transversely of said discharge opening to sweep from said support member a quantity of said material that is equal to summation of the incremental volumes of material swept by said pusher means during each stroke, each said incremental volume being equal to the length of the transverse stroke of said pusher means times an incremental length along said pusher means times the mean height of said pusher means at each incremental length, where the height of said pusher means bears a constant ratio to the width of the column of material, measured transversely of said discharge opening, that is supported for discharge through said opening.

12. In a cylindrical, vertical shaft apparatus for treating particulate material having a grate positioned in said shaft apparatus adjacent its lower end, the improvement in said grate comprising:

(a) transversely disposed, spaced-apart, substantially parallel, material diverter members providing at least one substantially rectangular material discharge opening between said material diverter members;

(b) a material support member mounted in spacedapart relation to and below each one of said material discharge openings, said support member extending on each side of each opening beyond a vertical downward projection of the edges of said diverter members;

(c) pusher means mounted in each said discharge opening above said support member for discharging material from said support member, each said pusher means comprising a bar of at least the maximum width of the opening in which it is mounted and disposed lengthwise of said discharge opening and movable transversely of said opening, the height of said pusher bar at any point along its length bears a constant ratio to the width of the unit column of material at said location, measured transversely of said opening, that is supported by said diverter members for discharge through said opening; and

(d) means to reciprocate said pusher means transversely of said discharge opening.

13. Grate means according to claim 3 wherein each said pusher bar means is reciprocably movable across each said support plate parallel to the edges of said deflector plates.

References Cited UNITED STATES PATENTS Hubmann et a1. 34167 X Ellerbeck 263-29 Bland 26329 X Jonsson 21417.8 X Brakel et a1. 26329 Stanley 263--29 10 JOHN J. CAMBY, Acting Primary Examiner.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, D.C. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,401 ,922 September 17 1968 John B. Jones, Jr.

It is certified that error apyears in the above identified patent and that said Letters Patent are hereby corrected as shovm below:

Column 8, line 20, "curing" should read curving Signed and sealed this 17th day of February 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer WILLIAM E. SCHUYLER, JR.

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