CA1082461A - Method and apparatus for agglomerating finely divided agglomerative materials in a rotating drum - Google Patents
Method and apparatus for agglomerating finely divided agglomerative materials in a rotating drumInfo
- Publication number
- CA1082461A CA1082461A CA225,768A CA225768A CA1082461A CA 1082461 A CA1082461 A CA 1082461A CA 225768 A CA225768 A CA 225768A CA 1082461 A CA1082461 A CA 1082461A
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- Canada
- Prior art keywords
- drum
- scraper
- finely divided
- ridges
- agglomerative
- Prior art date
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
- B01J2/12—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic in rotating drums
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Mixers Of The Rotary Stirring Type (AREA)
- Muffle Furnaces And Rotary Kilns (AREA)
- Processing Of Solid Wastes (AREA)
- Glanulating (AREA)
- Solid Fuels And Fuel-Associated Substances (AREA)
Abstract
TITLE
METHOD AND APPARATUS FOR AGGLOMERATING
FINELY DIVIDED AGGLOMERATIVE
MATERIALS IN A ROTATING DRUM
ABSTRACT OF THE DISCLOSURE
A rotary drum assembly includes separate agglomerating and hardening drums that are rotated independently of each other.
The agglomerating drum has a generally cylindrical configuration with an inner cylindrical wall. A scraper is rotatably position-ed within the agglomerating drum in spaced relation to the inner cylindrical wall with its axis spaced from the axis of the drum.
The scraper has a tubular body portion with a plurality of parallel rows of blades extending radially therefrom. Each of the rows extends lengthwise along substantially the entire length of the scraper body portion and follow a helical path having a angle turn about the axis of the tubular body portion.
The rows of blades thus make a single convolution about the scraper body portion. Drive means are provided to synchronously rotate the agglomerating drum and scraper with the scraper arranged to rotate in a direction opposite to the direction of rotation of the drum. The scraper is also arranged to rotate at a preselected and different speed relative to the speed of the drum. Agglomerative material is introduced into the rotating agglomerating drum and forms a layer of agglomerative material on the drum inner cylindrical wall. The scraper is rotated in a direction opposite to the direction of rotation of the agglomerat-ing drum and at a preselected synchronous speed with the agglom-erating drum. The parallel rows of blades on the scraper form a plurality of spaced elongated generally longitudinal ridges and valleys in the layer of agglomerative material on the drum cylindrical wall. The ridges have a slight arucate configuration and form less than a single convolution throughout the entire length of the agglomerating drum. The spaced elongated ridges in the layer of agglomerative material extend lengthwise in the drum substantially parallel to the axis of the drum and serve as longitudinally extending lifters to mix and agitate other particulate agglomerative materials introduced into the drum by lifting portions of the other particulate agglomerative material from the underside of the bed and depositing the material on the upper surface of the bed. This type of mixing promotes the formation of agglomerates having a preselected relatively narrow size consist. The synchronous rotation of the scraper removes agglomerative material deposited on the surface of the elongated ridges and valleys formed in the layer of agglomerative material so that the desired ridge and valley configuration is maintained in the layer of agglomerative material.
METHOD AND APPARATUS FOR AGGLOMERATING
FINELY DIVIDED AGGLOMERATIVE
MATERIALS IN A ROTATING DRUM
ABSTRACT OF THE DISCLOSURE
A rotary drum assembly includes separate agglomerating and hardening drums that are rotated independently of each other.
The agglomerating drum has a generally cylindrical configuration with an inner cylindrical wall. A scraper is rotatably position-ed within the agglomerating drum in spaced relation to the inner cylindrical wall with its axis spaced from the axis of the drum.
The scraper has a tubular body portion with a plurality of parallel rows of blades extending radially therefrom. Each of the rows extends lengthwise along substantially the entire length of the scraper body portion and follow a helical path having a angle turn about the axis of the tubular body portion.
The rows of blades thus make a single convolution about the scraper body portion. Drive means are provided to synchronously rotate the agglomerating drum and scraper with the scraper arranged to rotate in a direction opposite to the direction of rotation of the drum. The scraper is also arranged to rotate at a preselected and different speed relative to the speed of the drum. Agglomerative material is introduced into the rotating agglomerating drum and forms a layer of agglomerative material on the drum inner cylindrical wall. The scraper is rotated in a direction opposite to the direction of rotation of the agglomerat-ing drum and at a preselected synchronous speed with the agglom-erating drum. The parallel rows of blades on the scraper form a plurality of spaced elongated generally longitudinal ridges and valleys in the layer of agglomerative material on the drum cylindrical wall. The ridges have a slight arucate configuration and form less than a single convolution throughout the entire length of the agglomerating drum. The spaced elongated ridges in the layer of agglomerative material extend lengthwise in the drum substantially parallel to the axis of the drum and serve as longitudinally extending lifters to mix and agitate other particulate agglomerative materials introduced into the drum by lifting portions of the other particulate agglomerative material from the underside of the bed and depositing the material on the upper surface of the bed. This type of mixing promotes the formation of agglomerates having a preselected relatively narrow size consist. The synchronous rotation of the scraper removes agglomerative material deposited on the surface of the elongated ridges and valleys formed in the layer of agglomerative material so that the desired ridge and valley configuration is maintained in the layer of agglomerative material.
Description
4~;1 BACKGROUND OF THE IN~IENTION
1. Field of the Invention This invention relates to a method and an apparatus for agglomerating finely divided agglomerative materials in a rotating drum and more particularly to a method and an apparatus for agglomerating finely divided coal particles and finely divided particles of carbonaceous residue in a rotating drum to form carbonaceous agglomerates.
1. Field of the Invention This invention relates to a method and an apparatus for agglomerating finely divided agglomerative materials in a rotating drum and more particularly to a method and an apparatus for agglomerating finely divided coal particles and finely divided particles of carbonaceous residue in a rotating drum to form carbonaceous agglomerates.
2. Description of the Prior Art The procesq for making formcoke, as described in United States Patents 3,073,751; 3,401,089 and 3,562,783, in-cludes introducing particulate bituminous coal and finely divided char (the solid carbonaceous residue of coal which has been distilled at a temperature of between 800F. and 1400F.) in a rotary retort. Depending on the type of coal employed and the ratio of coal to char, pitch may also be added as a binder to increase the strength of the agglomerates formed in this process.
Preferably, the particulate coal and finely divided char are heated to an elevated temperature before they are introduced into the rota~y retort so that the constituents supply as sensible heat substantially all of the heat required to achieve the desired temperature for agglomerating the carbonaceous materials.
During the agglomeration process the retort is rotated to effect intimate mixing of the constituents and tumbling of the agglomerates as they are formed. As the constituents are mixed in the retort the coal particles are further heated to such extent that partial distillation of the coal particles occurs, e~olving tar and forming a loosely coherent plastic sticky mass in the retort. ~ere a pitch binder is employed it further con-tributes to the agglomeration of the particulate material within ~4~1 the retort.
It is believed that the loosely coherent plastic mass formed in the rotary retort breaks up during tumbling into relatively fine plastic particles. Growth of the plastic particles is attained by a snowballing type of tumbling or rolling action on the upper inclined exposed surface of the plastic mass of particulate material in the retort. Repeated tumbling or rolling of the particles causes the continued growth of the plastic particles into agglomerates. The agglomerates continue to grow until the binder evolved by the coal particles and the pitch binder, if employed, loses its plasticity. There-after, the agglomerates rigidify and the growth process is stopped.
The agglomerates recovered from the agglomerating retort are thereafter calcined at an elevated temperature between 1500F.
and 1800F. and formcoke is obtained that has strength and abrasion resi~tance that is equal or superior to that of conven-tional blast furnace coke. One of the objectives of the above described formcoke process is to form clo~ely sized agglomerates having a suitable size range as, for example, a size range of between 3/4" x 2" or a size range of between l" x 3". Oversized agglomerates, i.e. agglomerates having a size greater than the desired size, and undersizad agglomerates, i.e. agglomerates having a size less than the desired size, may not be suitable for use in a conventional blast furnace or other conventional metallurgical processes.
It has been discovered that, in conventional sized retorts, agglomerates of a suitable size range can be obtained in shallow beds where the ratio of the absolute bed depth of the particulate material to the diameter of the retort is maintained below a critical value. The absolute bed depth designates the true dimensional depth of the bed occupied by the carbonaceous ~VI~
material within the rotary retort~ It has been found where the ratio of absolute bed depth to retort diameter is maintained below the critical ratio (shallow bed) substantially all of the agglomerates have a size less than 4" and a substantial portion of the agglomerates have a suitable size range. Where, however, the ratio of absolute bed depth to retort diameter is increased above the critical ratio to form a deep bed the agglomerate product formed has a substantial quantity of agglomerates with a size greater than 4" and a reduced quantity of agglomerates with a suitable size range.
From an economic standpoint it is desirable to use retorts having as large a diameter as possible and to maintain as deep a bed of carbonaceous material as possible in the rotat-ing retort. With these conditions, however, it is also essential that the size range of the agglomerate product formed is within the suitable size range.
In United States Patents 3,368,012 and 3,460,195 there i~ disclosed a rotary retort for agglomerating carbonaceous material in a deep bed in which the ratio of absolute bed depth to retort diameter may be increased above the aforementioned critical ratio and a substantial yield of agglomerates of suitable size range is obtained. In accordance with the teaching of these patents, preheated particulate bituminous coal and finely divided char are agglomerated in a rotary retort that has a plurality of longitudinally extending rakes secured to the rotary retort inner cylindrical wall. Each of the ra~es has a plurality of tines extending inwardly toward the center of the rotary retort and the tines have a length between l/~ and l/3 fhe diameter of the rotary retort. The tines on the ra~es are ~0 spaced from each other at a preselected distance to relieve the compaction pressure exerted on the bed of carbonaceous material ~8;~46~
and to control the size of the agglomerates formed in the retort.
An agglomerate product having a suitable size range is obtained even when the ratio of absolute bed depth to retort diameter is increased substantially above the ratio previously considered the critical ratio to obtain an acceptable yield of agglomerates having a suitable size range.
During the agglomeration process the carbonaceous materials have a tendency to adhere as a sticky plastic mass to the inner wall of the rotary retort and to the rake tines.
Separate apparatus is required to remove the accumulation of agglomerated carbonaceous materials adhering to the retort wall and to the rake tines. Because of the tine spacing, difficulty i8 encountered in removing the deposits of carbonaceous material on the retort wall and on the rake tines. Further, a substantial amount of energy is required to rotate the retort while the apparatus, such as a fixed scraper device, removes the carbonaceous deposits from the retort inner wall and rake tines.
It i8 also known in the agglomeration of agglomerative materials that a smooth inner cylindrical wall of the rotary drum or retort is not the optimum surface for forming agglomerates.
Various types of metallic lifters for the agglomerative material within the rotary drum have been proposed as, for example, the lifter6 disclosed in United States Patents 3,124,338; 2,695,221;
2,926,079; 2,213,~56 and 3,68g,044. These lifters are not suitable, however, where the agglomerative material has a tendency to adhere to the inner wall of the drum. After a short period of time a layer of the agglomerative material is formed on the wall of the drum to a depth that i9 equal ~o or greater than the height of the metallic lifters. This layer of agglo-merative material reduces and soon eliminates the effect of the metallic lifters.
~38;~;~
United States Patent 3,348,262 discloses a fixed scraper for controlling the thickness of the layer or coating of agglomerative material deposited on the inner surface of the rotating drum. The layer has a uniform thickness and a gener-ally relatively smooth surface. United States Patents 2,697,068 and 3,316,585 disclose rotary scrapers positioned within the rotary drum that are arranged to continuously remove agglomera-tive material from the inner wall of the drum and maintain a layer of the agglomerative material of a preselected uniform thickness on the wall of the drum. It is stated the layer of agglomerative material provides a surface that is superior to a smooth cylindrical wall.
United States Patent 2,831,210 discloses a cutter bar positioned within the rotary drum adjacent the inner wall of the drum. The cutter bar has spaced teeth extending toward the drum inner wall. The cutter bar is arranged to reciprocate longitudinally relative to the drum wall and cut a series of allochiral left and right hand helical grooves in the layer of agglomerative material deposited on the drum inner wall. The rate of reciprocation of the cutter bar and the speed of rota-tion of the retort are controlled so that the helical grooves do not track each other on successive strokes of the cutter bar and thus provide a controlled roughness to the surface o~ the layer of agglomerative material on the drum inner wall. It is stated the roughened surface of the layer is superior to a smooth surface.
United States Patent 2,778,056 discloses an agglomerat-ing drum with a scraper positioned therein. The drum and scraper are arranged to rotate at preselected synchronous speeds with the scraper rotating in a direction opposite to the direction of drum rotation. The scraper disclosed is in the form of a l'ribbon"
flight" conveyor and forms multiple convolutions of helical grooves in material adhering to the inner surface of the drum.
1~8'~4~;1 The convolutions of the main portion of the scraper have the direction of a right handed thread ~o that the multiple convolutions foxmed in the surface of the material adhering to the inner surface of the drum are 80 inclined that loose material in the groves tends to move back toward the inlet of the drum. Adjacent the end~ of the drum the direction of thread rotation of the scraper i~ rever~ed to minimize 8pil-lage of the material fed ~nto the drum and also accelerate the discharge of the agglomerates formed. The helical groves formed in the material adhering to the inner surface of the drum extend generally circumferentially around the drum 80 that the material w~thin the drum tends to roll or slide downwardly wlthin the groove~ and be carried back towards the entrance of the drum. ~he rldge~ formed between the grooves, because of thelr generally circumferential arrangement around the inner ~ur~ace of the drum, do not functlon a~ lifter~ to mlx the matorial wtthin the drum.
There t~ a neod for method and apparatus to control the ~urface configuration of the layer of agglomerat~ve mater-i~l depo~ted on the drum ~nnex wall and provide elongatedr~dge~ and ~a}leys that ~erve a~ generally longitudinal l~fters ~--~ --8--~38;~46~
~o that other agglomerative material fed into the drum i~ lifted by the ridges formed in the deposited material and adequately mixed and agglomerates of a preselected size range are formed.
SUMMARY OF THE INVENTION
This invention relates to a method and an apparatu~
for agglomerating finely divided agqlomerating material in a rotating drum. The method includes feeding finely divided agglomerative material into a substantially horizontal rotating drum having an inner wall. The drum ha~ a longitudinal axis and i8 arranged to rotate about the longitudinal axi~. A layer of ~inely divlded agglomeratlve material i8 deposited on the drwm inner wall. A longitudinally extending scraper i~ rotated ~n tho drum in a diroction oppo~ite to the dlrectlon of rota-tlon of the drum and in ~ixed timed relation to the rotation ot the drum to form a preselected number of alternating longi-tudinally extondin~ ridge~ and valley~ according to the following for~ul~s N - b U2 Ul wheres N ~ a who~e number ~nd number of ridge~ formed b ~ number o~ ~craper blades Ul ~ drum ~peed, rpm U2 ~ ~craper spped, rpm.
'~ ,1~;
~08'~
A Plurality of elongated alternating and longitudinally extending ridge~ and valleys are formed in the làyer. The ridges and valleys extend substantially lengthwi~e along the drum inner wall and ~ubstantially parallel to the drum longitudinal axi9. The 80 formed same ridges and valleys are maintained in the layer depo~$ted on the drum inner wall while rotating the drum and formlng agglomerates from other material ~ntroduced into the rotary drum.
The apparatus for agglamerating the finely divided agglomorative material includes a cylindrical rotary drum having a longitudinal axis and an inner wall. Mean~ are provided to rotate the drum about $t~ longitudinal axi~ at a pre~elected ~p--d and dopo~$t a layer of the f$nely divided agglomeratl~e ~ater~al on the drum inner wall. An elongated rotary ~craper ha~ a body portion and a longitudinal axls. The rotary scraper i~ po~ition~d ~n the cyllndrical drum in ~paced relation to the cyl~ndrtcal drum lnner wall wlth the ~craper body portion longitudinal ax~s spaced from the longitudinal axis of the rotary drum. Blade mean~ extend rad~ally outwardly from the ~craper r` ~ - 9A -4~;~
and extend lengthwise thereon. Means are provided to rotate the rotary scraper in a direction opposite to the direction of rotation of the drum in timed relation to the rotation of the drum and provide relative movement between the rotary drum inner wall and the scraper blade means to form a plurality of elongated alternating and longitudinally extending ridges and valleys in the layer of agglomerative material deposited on the drum inner wall. The rotary scraper is further arranged to remove other finely divided agglomerative material deposited on the surface of the ridges and valleys formed in the layer of agglomerative material.
The above method and apparatus are particularly suit-able for agglomerating finely divided carbonaceous materials at an elevated temperature and forming a substantial ~uantity of agglomerates having a preselected size range. The carbonaceous materials at an elevated temperature are introduced into a rotating drum which serveg as a retort and a layer of carbo-naceous material is deposited on the retort inner cylindrical wall. A plurality of longitudinally extending spaced ridges and valleys are formed in the layer of carbonaceous material with the ridges and valleys extending substantially parallel to the retort longitudinal axis. After the binder in the carbo-naceous particles is evolved the layer of carbonaceous material loses its plasticity and rigidifies to form a relatively rigid layer with ridges and valleys formed therein.
As other finely divided carbonaceous material is introduced into the rotating retort the car~onaceous material forms a bed in the retor_ with an upper surface extending up-wardly in the direction of rotation of the retort. The longitudinally extending ridges of carbonaceous material formed on the inner wall serve as lifters to convey or lift a portion ~8Z4ti~
of the finely divided carbonaceous material adjacent the retort inner wall in the direction of retort rotation and deposit at least a portion of this carbonaceous material on the upper surface of the bed to both intimately mix the finely divided carbonaceous material in the retort and deposit particles on the upper inclined surface of the bed. Repeated tumbling of the particles and partially formed agglomerates on the upper surface of the bed causes continued growth to form agglomerates of a preselected size. ~ny finely divided carbonaceous material deposited on the exposed surface of the ridges and valleys is continually removed therefrom so that the ridges and valleys of a preselected configuration are maintained during the agglomeration process. Where desired metallic lifters, such as elongated metallic members of proper dimension, may be secured to the retort inner wall to provide support for the longitud-inally extending ridges of carbonaceous material and also serve a~ an integral portion of the lifters.
With the above arrangement a plurality of spaced elongated ridges are formed on the inner wall of the rotating retort to serve as lifting or mixing devices for the finely div~ded carbonaceous material. The scraper posit~oned in the retort that initially shaped the elongated longitudinally extendlng ridges and valleys in the layer of carbonaceous material further removes other agglomerative carbonaceous material that may be deposited on the surface of the ridges and valleys ~o that the layer of carbonaceous material retains its ridge and valley configuration during the agglomeration process.
Accordingly, the principal object of this invention is to provide a method and an apparatus for forming elongated longitudinally extending ridges and valleys in a layer of agglomerative material deposited on the inner wall of a rotary drum, 4~i1 Another object of this invention is to provide a method and an apparatus for maintaining a plurality of spaced longitudinally extending lifters formed of agglomerative material on the inner wall of a rotary drum.
These and othex objects and advantages of this invention will be more completely disclosed and described in the following specification, the accompanying drawings and the appended claims.
BR~EF DESCRIPTION OF THE DRAWINGS
Figure 1 is a top plan view of a rotary drum assembly having separate balling and hardening drums.
Figure 2 is a view in side elevation of the rotary drum assembly, illustrating the rotary scraper rotatably supported in the balling drum.
Figure 3 is an enlarged view of the balling drum in side elevation and section, illustrating the support and drive for the rotary scraper and schematically the longitudinally extending rows of scraper blades.
Figure 4 is a view in section taken along the line IV-IV of Figure 3, illustrating in detail the rotary scraper with two rows of scraper blades extending radially therefrom.
Figure 5 is a fragmentary view in section taken along the line V-V of Figure 4, illustrating a scraper blade element of a row of scraper blades adjustably secured to the blade support.
Figure 6 is a view in end elevation of the balling drum feed and illustrating the relative position of the rotary scraper in the balling drum.
Figure 7 is a diagrammatic view in section and in elevation of the balling drum, illustrating schematically the 4~
rotary scraper having two rows of ~lades within the balling drum rotating in a direction opposite to the direction of drum rotation and the manner in which elongated generally longitud-inally extending ridges and valleys are formed in a layer of agglomerative material on the inner wall of the drum with the ridges serving as generally longitudinal lifters for the particulate agglomerative material within the balling drum.
Figure 8 is a graphical representation of the height of the ridges attainable at various ratios of scraper speed to drum speed with a drum having an effective diameter of 141" and a scraper having a diameter of 46.1".
INTRODUCTION
Throughout the specification the rotary cylindrical drum will also be referred to as a rotary retort or kiln. The terms rotary retort or kiln are intended to designate a cylindrical drum in which partial distillation of one or more of the constituents takes place during the agglomeration process.
Although the preferred method includes the partial distillation of coal during the agglomeration process, it should be under-stood that it is not intended to limit the invention to such aprocess and the invention may be practiced with materials that agglomerate at ambient temperature. It is not intended by illustrating and describing the rotary cylindrical drum assembly herein as including a separate agglomerating drum and a separate hardening drum to be limited to such an assembly. The invention may also be practiced in a single cylindrical drum assembly.
~he agglomerating drum in this specification is also referred to as a balling drum.
Referring to the drawings and particularly Figures 1 and 2 there is illustrated a rotary drum assembly generally 1, _ ~4~
designated by the numeral 10 that includes separate balling and hardening drums designated by the numerals 12 and 14, respectively. The balling drum 12 has a generally cylindrical configuration with a front feed or inlet opening 16, a rear discharge opening 18 and a longitudinal axis 15 about which the balling drum 12 rotates. The discharge opening 18 of drum 12 extends into a stationary housing 20. The hardening drum 14 also has a generally cylindrical configuration with an inlet opening 22 that extends into the fixed stationary housing 20 and a discharge opening 24 with a trommel screen 26 connected thereto. The trommel screen 26 is enclosed by a housing 28 that has outlets 30 and 32 for agglomerates separated according to size by the trommel screen 26. As shown in Figure 3, the dis-charge opening 18 of balling drum 12 extends into the inlet opening 22 of hardening drum 14 so that agglomerates formed in the balling drum 12 are discharged directly into the hardening drum 14. The balling drum outlet opening 18 has an annular dam 34 that controls the inventory of agglomerative material and agglomerates in the balling drum 12. A sealed housing 36 surrounds the balling drum inlet opening 16 and, as illus~rated in Figure 6, suitable inlets 38 and 40 are provided in the housing 36 for introducing agglomerative material, such as coal and char, into the balling drum 12.
As illustrated in Figures 1 and 2, the balling drum 12 has an annular gear 42 secured thereto that meshes with a drive gear 44 connected to a suitable drive means designated by the numeral 46. The ~allinq drum 12 has a pair of annular metallic tires 48 and 50 that rotatably support the drum 12 on roller assemblies 52 and 54 and limit axial movement of balling drum 12.
The roller as~emblies 52 and 54 and the front housing 36 are supported on a platform 58 that is movable vertically to change - ~ ~4t;i the angle of inclination of the balling drum 12. The balling drum longitudinal axis 15, i.e. the axis of rotation, is substantially horizontal and where desired the platform 58 may be utilized to incline the balling drum 12 axis of rotation to control the residence time of the material therein. The hardening drum 14 has a similar annular gear 60 secured thereto that meshes with a drive gear 62. A separate drive means 64 rotates the hardening drum 14 at a preselected speed that is independent of the speed of rotation of the balling drum 12.
Annular metallic tires 66 and 68 support the hardening drum 14 on roller assemblies 70 and 72 to permit rotation of the hard-ening drum 14 by the drive means 64 and prevent axial movement of the hardening drum 14 during rotation thereof.
Referring to Figures 3 and 6, a scraper generally designated by the numeral 74 has a longitudinal axis 75 and is rotatably positioned within the balling drum 12 in spaced relation to the drum ~nner wall 76. The rotary scraper 74 is located above a horizontal plane extending through the longi-tudinal axis 15 of the drum 12 and, as viewed in Figure 6, on the left side of a vertical plane extending through the longitudinal axis of drum 12. With this arrangement, the rotary scraper 74 is positioned in the upper left quadrant of the cylindrical ope~ing in the balling drum 12 as defined by the inner ~rum wall 76 and is arranged to rotate about its longi-tudinal axis 75. As later explained, the position of the rotary scraper is determined by the direction o~ drum rotation. For example, as viewed in Figures 6 and 7, drum rotation is in a counter-clockwise direction as indicated by the directional arrow 78 and the rotary scraper 74 is positioned in the upper quadrant opposite from the inclined bed of agglomerative material formed within balling drum 12.
J~4~1 The rotary scraper 74 has a tubular body portion 80 with a front end shaft 82 and a rear end shaft 84 secured thereto and extending therefrom. It should be understood that the body portion 80 may also be solid and of a configuration other than a cylinder. The body portion 80 may have a smaller transverse dimension than illustrated as long as the body por-tion has sufficient strength to rotatably support the blades.
The front end shaft 82 extends through a suitable seal 86 in the housing 36 and is rotatably supported in a bearing 88 mounted on the housing 36. The front end shaft 82 has a sprocket 90 nonrotatably secured thereto and the front end shaft is supported in another bearing 94 which, in turn, is supported on a fixed beam 92. The rear end shaft 84 is rotatably supported in a bearing 96 which is supported on a fixed support beam 98.
The beam 98 is secured to a portion of the fixed housing 20 en-closing the balling drum outlet opening 18 and the hardening drum inlet opening 22. With this arrangement the scraper 74 is rotatably supported wlthin the balling drum 12 and is supported at its end portions in bearings.
The drive for rotating the scraper 74 includes a drive motor 100, illustrated in Figures 3 and 6, connected through a suitable speed reducer 102 to a drive sprocket 104. An endless chain 106 i8 reeved about the sproekets 90 and 104 and is arranged to rotate the scraper 74 in a direction opposite to the direction of rotation of the drum 12 as indicated in Figures 3, 6 and 7 by the directiona} arrow 56. Suitable control means are provided to rotate the ~craper 74 in synchronous relation with the balling drum 12 so that the scraper 74 rotates at a pre-~elected speed ratio with the balling drum 12. Where desired the control means can be arranged to change the relative speeds of the scraper or the drum to obtain other speed ratios between 4~i~
the scraper and the drum so that, as later discussed, other ridge and valley configurations may be obtained.
The scraper 74 has two rows of scraper blades gener-ally designated by the numerals 108 and 110 secured to the outer surface of the tube 80. The rows of blades include separate blade assemblies that have a blade support member 116 rigidly secured to the surface of the tube 80 as by welding or the like. Separate blades or blade segments are secured to the blade support members 116 by means of bolts 120. The blade segments 118 have elongated slotted portions 122 that permit radial adjustment of blade segments 118 on the blade support members 116.
The rows of blades 108 and 110 extend parallel and lengthwise along the tube 80 to form elongated continuous cut-ting surfaces along substantially the entire length of the scraper 74. In Figure 3 only the end portions of the rows of blades 10~ and 110 are illustrated. The rows of blades provide a continuous cutting surface that preferably follows an arcuate helical path in which the helix has less than a single turn about the axis 75 of the tube 80 throughout the length of the scraper 74 as diagrammatically illustrated by the --~-- line 124 in Figure 3.
The scraper 74 thus has two separate rows of blades extending lengthwise throughout substantially the entire length of the scraper 74. The rows of blades follow a helical path and pre~erably form a helix not exceeding a single turn about the tube axis in which the rows of blades 108 are displaced to the left about the axis 75 as viewed in Figure 3 between the front and rear end of the scraper 74. It should be understood that other blade configurations may be employed that have the rows of blades arranged parallel to the longitudinal axis of the scraper 4~;1 tube 80 or form a helix with more than one turn about the tube axis. The blade arrangement should be such, however, that the ridges formed ~n the material adhering to the drum inner wall extend longitudinally along the drum inner surface and are substantially parallel to the axis of the drum. With this arrangement the ridges formed by the blades serve as longitud-inally extending lifters to lift and mix the material in the drum.
It should also be understood that the number of rows of blades secured to the outer surface of the tube 80 can be increased or decreased as, for example, the scraper 74 can have one, three or four rows of blades rather than two opposed rows as illustrated. It is desirable, however, that the rows of blades be equidistantly positioned on the periphery of the scraper tube 80 to provide symmetrical ridges and valleys in the layer of agglomerative material deposited on the balling drum inner wall 76.
Referring to Figure 7, there is illustrated diagrammatically the manner in which the rotary scraper 74 forms ridges and valleys in a layer of agglomerative material deposited on the inner wall 76 of balling drum 12 and the manner in which the ridges serve as lifters to admix the agglomerative constituent~sand aid in forming agglomerates of a preselected size range from the agglomerative material.
To form a corrugated or scalloped surface with longitudinally extending ridges and valleys on the wall of the balling drum, agglomerative material is first introduced into the balling drum. Where particulate ~ituminous coal, finely divided char and pitch are the agglomerative cvnstituents, the coal may be preheated to a temperature of between 400DF. and 625~F. which is below the temperature at which the surface of `~8~
the coal particles becomes plastic and sticky. The char is preheated to a temperature between 1000F. and 1200F. to supply the sensible heat required for the agglomeration process.
The coal, char and pitch at the above elevated temperatures are introduced into the balling drum 12 as the balling drum 12 is rotating in a counter-clockwise direction as illustrated in Figure 7.
The agglomerative constituents are mixed by the rotation of the drum 12 and heat is transferred from the char to the coal particles and pitch and the agglomerative con-stituents form a sticky plastic mass. A layer of the sticky plastic mass is deposited on the inner surface 76 of balling drum 12. The rotary scraper 74 is synchronously rotated in a direction opposite to the direction of rotation of balling drum 12 and at ~wice the speed of the balling drum 12. At this synchronous speed the rows of scraper blades 108 and 110 periodically move toward and away from the wall of the drum 12.
Because the rotation of the scraper is synbhronous with the rotation of the drum at a ratio of 2 to 1, four elongated ridges 130, 132, 134 ana 136 are formed in the layer of agglomerative material 126. The rows of scraper blades are so spaced from the drum wall 76 that the layer of agglomerative material deposited on the drum inner wall 76 i8 continuous and elongated valleys 138, 140, 142 and 144 are formed in the agglomerative material between the ridges 130 - 136. While the layer of agglomerative material is being deposited on the drum wall 76 and is being shaped by the scraper 7~ the agglomerative material in the layer is plastic and flexible. When the binder associated with the coal and pitch loses its plasticity due to the pyrolysis that takes place at the elevated temperature with-in the drum the layer hardens and rigidifies to retain the longitudinally extending ridge and valley configuration above discussed.
The material to be formed into agglomerates, pref-erably the same material employed in forming the corrugated or scalloped layer on the drum wall, may be introduced into the drum while the layer is hardening or after the layer has hardened. The agglomerative material is introduced on a continuous basis into the rotating drum at a preselected rate to form a bed of agglomerative material within the drum. The bed is designated by the numeral 146 in Figure 7. Rotation of the drum in the direction indicated by arrow 78 moves the bed of agglomerative material upwardly along one side of the retort to an extent that the top surface of the bed 146 has, for example, an angle of repose of about 70. The angle of repose is dependent on the speed of rotation of the drum 12. As the drum 12 rotates the longitudinally extending ridges 130 - 136 in the layer 126 move under the bed of agglomerative material and promote agitation of the bed. ~he agitation of the bed includes top to bottom mixing whereby a portion of the agglom-erative material in the bed adjacent the drum wall 76 is con-veyed upwardly through the bed. The longitudinally extending ridges further turn a substantial portion of this agglomerative material in the portion conveyed by the longitudinally extending ridges and valleys over and onto the bed top surface 14a.
Moving a portion of the agglomerative material up-ward~y through the bed and turning a portion of the agglomerative material over thoroughly admixes the agglomerative material and also continuously deposits partially agglomerated agglom-erates 152 on the bed upper surface 148 at the top portion 150 of bed 146. The partially agglomerated agglomerates 152 roll down the bed upper surface 14 a and the partially agglomerated agglomerates grow in size by picking up additional plastic particles from the upper surface of the bed. In order to ob-tain the above described bottom mixing of the agglomerative material it is essenti~l that the ridges 130 extend longitud-inally along the inner surface of the drum to be effective as lifters. The angle of inclination of balling drum 12 conveys the partially agglomerated agglomerates as they grow toward the balling drum discharge opening 18. The partially agglom-erated agglomerates continue to grow until the binder loses its plasticity and full size agglomerates then harden and rigidify. After the agglomerates harden no further growth takes place. The agglomerates so formed are introduced into the hardening drum where rotation of the hardening drum permits -substantial completion of the pyrolysis of the agglomerative constituents and relatively rigid hard agglomerates are with-drawn from the hardening drum.
The agglomerative material in bed 146 because of its pla~ticity has a tendency to adhere to the interior surface of the layer of rigid agglomerative material deposited on the drum inner wall 76. The scraper assembly 74, because of its continued rotation at a preselected synchronous speed, continuously removes the fresh deposit of agglomerative material on the outer surface of the ridges and valleys while the newly deppsited agglomerative material is in a relatively plastic state to thereby maintain the configuration of ridges and va}leys as illustrated in Figure 7. Where desired, metallic support members may be secured to the drum inner wall and the ridge portions 13~ - 136 formed therein. The metallic support members provide structural support for the ridges and the synchronous rotation of the scraper 74 prevents interference between the metallic support members and the scraper blades.
~8;~4f~1 It may be desirable for certain agglomerative conditions to vary the number and height of the ridges and valleys around the periphery of the drum wall. Figure 8 illustrates the enlarged ridge height and the number of ridges where two rows of blades are positioned on the scraper 74.
Thus, where it is desirable to obtain maximum ridge height with the scraper rotating in a direction opposite to the direction of rotation of the drum the ratio of scraper speed to drum speed is about 2 to 1. Where a maximum of ridges are desired the ratio of scraper speed to drum speed is increased.
Where the number of ridges or lifters is increased, the height of the ridges or lifters decreases. For example, where the ratio of scraper speed to drum speed is 6 to 1, twelve ridges are formed around the periphery of the drum wall. The ridge height is substantially reduced as compared with the height of the ridges where only four ridges are formed on the drum wall 76.
Where more than two rows of blades are secured to the tube 80 the ridge height is reduced for the came ratio of scraper speed to drum spe~d as is indicated in Figure 8 for three rows of blades and four rows of blades.
With the previously described method, in order to have the scraper blades form and maintain the same and the d0sired number of longitudinally extending ridges and valleys, it is essential that the product of the number of rows of blades on the scraper multiplied by the ratio of scraper revo}utions to drum revolutions per unit time is a whole number.
b U2 N =
wherein N = number of ridges formed b = number of scraper blades Ul = drum speed, rpm U2 = scraper speed, rpm ` ~8'~
For example, with a scraper having two rows of blades and the scraper rotating 2 times faster than the drum, four longitudinally extending ridges and valleys are formed and the rows of blades will sequentially move in timed relation through the longitudinally spaced valleys without disturbing the adjacent ridges.
Where twelve peaks are desired and the rotary scraper has two rows of blades, the ratio of scraper speed to drum speed must be 6, as exemplified by the following calculation.
N = 2 x 6 N = 12 It should be noted that it is also possible with the above method and apparatus to control the thickness of the layer and form ridges and valleys in the layer so deposited on the drum inner wall. The blades on the scraper as they rotate relative to the drum follow arcuate overlapping paths through the layer and thu~ form the ridges and valleys above d~scus~ed~
With the above method and apparatus it is now possible to form lifters on the inner surface of the drum from the same or substantially the ~ame material that is agglomerated in the drum. After the lifters in the form of ridges are formed in the layer of material deposited on the wall of the drum the blades of the rotary scraper 74 remove the material that is deposited on the surface of the ridges and valleys in the layer.
Preferably, the particulate coal and finely divided char are heated to an elevated temperature before they are introduced into the rota~y retort so that the constituents supply as sensible heat substantially all of the heat required to achieve the desired temperature for agglomerating the carbonaceous materials.
During the agglomeration process the retort is rotated to effect intimate mixing of the constituents and tumbling of the agglomerates as they are formed. As the constituents are mixed in the retort the coal particles are further heated to such extent that partial distillation of the coal particles occurs, e~olving tar and forming a loosely coherent plastic sticky mass in the retort. ~ere a pitch binder is employed it further con-tributes to the agglomeration of the particulate material within ~4~1 the retort.
It is believed that the loosely coherent plastic mass formed in the rotary retort breaks up during tumbling into relatively fine plastic particles. Growth of the plastic particles is attained by a snowballing type of tumbling or rolling action on the upper inclined exposed surface of the plastic mass of particulate material in the retort. Repeated tumbling or rolling of the particles causes the continued growth of the plastic particles into agglomerates. The agglomerates continue to grow until the binder evolved by the coal particles and the pitch binder, if employed, loses its plasticity. There-after, the agglomerates rigidify and the growth process is stopped.
The agglomerates recovered from the agglomerating retort are thereafter calcined at an elevated temperature between 1500F.
and 1800F. and formcoke is obtained that has strength and abrasion resi~tance that is equal or superior to that of conven-tional blast furnace coke. One of the objectives of the above described formcoke process is to form clo~ely sized agglomerates having a suitable size range as, for example, a size range of between 3/4" x 2" or a size range of between l" x 3". Oversized agglomerates, i.e. agglomerates having a size greater than the desired size, and undersizad agglomerates, i.e. agglomerates having a size less than the desired size, may not be suitable for use in a conventional blast furnace or other conventional metallurgical processes.
It has been discovered that, in conventional sized retorts, agglomerates of a suitable size range can be obtained in shallow beds where the ratio of the absolute bed depth of the particulate material to the diameter of the retort is maintained below a critical value. The absolute bed depth designates the true dimensional depth of the bed occupied by the carbonaceous ~VI~
material within the rotary retort~ It has been found where the ratio of absolute bed depth to retort diameter is maintained below the critical ratio (shallow bed) substantially all of the agglomerates have a size less than 4" and a substantial portion of the agglomerates have a suitable size range. Where, however, the ratio of absolute bed depth to retort diameter is increased above the critical ratio to form a deep bed the agglomerate product formed has a substantial quantity of agglomerates with a size greater than 4" and a reduced quantity of agglomerates with a suitable size range.
From an economic standpoint it is desirable to use retorts having as large a diameter as possible and to maintain as deep a bed of carbonaceous material as possible in the rotat-ing retort. With these conditions, however, it is also essential that the size range of the agglomerate product formed is within the suitable size range.
In United States Patents 3,368,012 and 3,460,195 there i~ disclosed a rotary retort for agglomerating carbonaceous material in a deep bed in which the ratio of absolute bed depth to retort diameter may be increased above the aforementioned critical ratio and a substantial yield of agglomerates of suitable size range is obtained. In accordance with the teaching of these patents, preheated particulate bituminous coal and finely divided char are agglomerated in a rotary retort that has a plurality of longitudinally extending rakes secured to the rotary retort inner cylindrical wall. Each of the ra~es has a plurality of tines extending inwardly toward the center of the rotary retort and the tines have a length between l/~ and l/3 fhe diameter of the rotary retort. The tines on the ra~es are ~0 spaced from each other at a preselected distance to relieve the compaction pressure exerted on the bed of carbonaceous material ~8;~46~
and to control the size of the agglomerates formed in the retort.
An agglomerate product having a suitable size range is obtained even when the ratio of absolute bed depth to retort diameter is increased substantially above the ratio previously considered the critical ratio to obtain an acceptable yield of agglomerates having a suitable size range.
During the agglomeration process the carbonaceous materials have a tendency to adhere as a sticky plastic mass to the inner wall of the rotary retort and to the rake tines.
Separate apparatus is required to remove the accumulation of agglomerated carbonaceous materials adhering to the retort wall and to the rake tines. Because of the tine spacing, difficulty i8 encountered in removing the deposits of carbonaceous material on the retort wall and on the rake tines. Further, a substantial amount of energy is required to rotate the retort while the apparatus, such as a fixed scraper device, removes the carbonaceous deposits from the retort inner wall and rake tines.
It i8 also known in the agglomeration of agglomerative materials that a smooth inner cylindrical wall of the rotary drum or retort is not the optimum surface for forming agglomerates.
Various types of metallic lifters for the agglomerative material within the rotary drum have been proposed as, for example, the lifter6 disclosed in United States Patents 3,124,338; 2,695,221;
2,926,079; 2,213,~56 and 3,68g,044. These lifters are not suitable, however, where the agglomerative material has a tendency to adhere to the inner wall of the drum. After a short period of time a layer of the agglomerative material is formed on the wall of the drum to a depth that i9 equal ~o or greater than the height of the metallic lifters. This layer of agglo-merative material reduces and soon eliminates the effect of the metallic lifters.
~38;~;~
United States Patent 3,348,262 discloses a fixed scraper for controlling the thickness of the layer or coating of agglomerative material deposited on the inner surface of the rotating drum. The layer has a uniform thickness and a gener-ally relatively smooth surface. United States Patents 2,697,068 and 3,316,585 disclose rotary scrapers positioned within the rotary drum that are arranged to continuously remove agglomera-tive material from the inner wall of the drum and maintain a layer of the agglomerative material of a preselected uniform thickness on the wall of the drum. It is stated the layer of agglomerative material provides a surface that is superior to a smooth cylindrical wall.
United States Patent 2,831,210 discloses a cutter bar positioned within the rotary drum adjacent the inner wall of the drum. The cutter bar has spaced teeth extending toward the drum inner wall. The cutter bar is arranged to reciprocate longitudinally relative to the drum wall and cut a series of allochiral left and right hand helical grooves in the layer of agglomerative material deposited on the drum inner wall. The rate of reciprocation of the cutter bar and the speed of rota-tion of the retort are controlled so that the helical grooves do not track each other on successive strokes of the cutter bar and thus provide a controlled roughness to the surface o~ the layer of agglomerative material on the drum inner wall. It is stated the roughened surface of the layer is superior to a smooth surface.
United States Patent 2,778,056 discloses an agglomerat-ing drum with a scraper positioned therein. The drum and scraper are arranged to rotate at preselected synchronous speeds with the scraper rotating in a direction opposite to the direction of drum rotation. The scraper disclosed is in the form of a l'ribbon"
flight" conveyor and forms multiple convolutions of helical grooves in material adhering to the inner surface of the drum.
1~8'~4~;1 The convolutions of the main portion of the scraper have the direction of a right handed thread ~o that the multiple convolutions foxmed in the surface of the material adhering to the inner surface of the drum are 80 inclined that loose material in the groves tends to move back toward the inlet of the drum. Adjacent the end~ of the drum the direction of thread rotation of the scraper i~ rever~ed to minimize 8pil-lage of the material fed ~nto the drum and also accelerate the discharge of the agglomerates formed. The helical groves formed in the material adhering to the inner surface of the drum extend generally circumferentially around the drum 80 that the material w~thin the drum tends to roll or slide downwardly wlthin the groove~ and be carried back towards the entrance of the drum. ~he rldge~ formed between the grooves, because of thelr generally circumferential arrangement around the inner ~ur~ace of the drum, do not functlon a~ lifter~ to mlx the matorial wtthin the drum.
There t~ a neod for method and apparatus to control the ~urface configuration of the layer of agglomerat~ve mater-i~l depo~ted on the drum ~nnex wall and provide elongatedr~dge~ and ~a}leys that ~erve a~ generally longitudinal l~fters ~--~ --8--~38;~46~
~o that other agglomerative material fed into the drum i~ lifted by the ridges formed in the deposited material and adequately mixed and agglomerates of a preselected size range are formed.
SUMMARY OF THE INVENTION
This invention relates to a method and an apparatu~
for agglomerating finely divided agqlomerating material in a rotating drum. The method includes feeding finely divided agglomerative material into a substantially horizontal rotating drum having an inner wall. The drum ha~ a longitudinal axis and i8 arranged to rotate about the longitudinal axi~. A layer of ~inely divlded agglomeratlve material i8 deposited on the drwm inner wall. A longitudinally extending scraper i~ rotated ~n tho drum in a diroction oppo~ite to the dlrectlon of rota-tlon of the drum and in ~ixed timed relation to the rotation ot the drum to form a preselected number of alternating longi-tudinally extondin~ ridge~ and valley~ according to the following for~ul~s N - b U2 Ul wheres N ~ a who~e number ~nd number of ridge~ formed b ~ number o~ ~craper blades Ul ~ drum ~peed, rpm U2 ~ ~craper spped, rpm.
'~ ,1~;
~08'~
A Plurality of elongated alternating and longitudinally extending ridge~ and valleys are formed in the làyer. The ridges and valleys extend substantially lengthwi~e along the drum inner wall and ~ubstantially parallel to the drum longitudinal axi9. The 80 formed same ridges and valleys are maintained in the layer depo~$ted on the drum inner wall while rotating the drum and formlng agglomerates from other material ~ntroduced into the rotary drum.
The apparatus for agglamerating the finely divided agglomorative material includes a cylindrical rotary drum having a longitudinal axis and an inner wall. Mean~ are provided to rotate the drum about $t~ longitudinal axi~ at a pre~elected ~p--d and dopo~$t a layer of the f$nely divided agglomeratl~e ~ater~al on the drum inner wall. An elongated rotary ~craper ha~ a body portion and a longitudinal axls. The rotary scraper i~ po~ition~d ~n the cyllndrical drum in ~paced relation to the cyl~ndrtcal drum lnner wall wlth the ~craper body portion longitudinal ax~s spaced from the longitudinal axis of the rotary drum. Blade mean~ extend rad~ally outwardly from the ~craper r` ~ - 9A -4~;~
and extend lengthwise thereon. Means are provided to rotate the rotary scraper in a direction opposite to the direction of rotation of the drum in timed relation to the rotation of the drum and provide relative movement between the rotary drum inner wall and the scraper blade means to form a plurality of elongated alternating and longitudinally extending ridges and valleys in the layer of agglomerative material deposited on the drum inner wall. The rotary scraper is further arranged to remove other finely divided agglomerative material deposited on the surface of the ridges and valleys formed in the layer of agglomerative material.
The above method and apparatus are particularly suit-able for agglomerating finely divided carbonaceous materials at an elevated temperature and forming a substantial ~uantity of agglomerates having a preselected size range. The carbonaceous materials at an elevated temperature are introduced into a rotating drum which serveg as a retort and a layer of carbo-naceous material is deposited on the retort inner cylindrical wall. A plurality of longitudinally extending spaced ridges and valleys are formed in the layer of carbonaceous material with the ridges and valleys extending substantially parallel to the retort longitudinal axis. After the binder in the carbo-naceous particles is evolved the layer of carbonaceous material loses its plasticity and rigidifies to form a relatively rigid layer with ridges and valleys formed therein.
As other finely divided carbonaceous material is introduced into the rotating retort the car~onaceous material forms a bed in the retor_ with an upper surface extending up-wardly in the direction of rotation of the retort. The longitudinally extending ridges of carbonaceous material formed on the inner wall serve as lifters to convey or lift a portion ~8Z4ti~
of the finely divided carbonaceous material adjacent the retort inner wall in the direction of retort rotation and deposit at least a portion of this carbonaceous material on the upper surface of the bed to both intimately mix the finely divided carbonaceous material in the retort and deposit particles on the upper inclined surface of the bed. Repeated tumbling of the particles and partially formed agglomerates on the upper surface of the bed causes continued growth to form agglomerates of a preselected size. ~ny finely divided carbonaceous material deposited on the exposed surface of the ridges and valleys is continually removed therefrom so that the ridges and valleys of a preselected configuration are maintained during the agglomeration process. Where desired metallic lifters, such as elongated metallic members of proper dimension, may be secured to the retort inner wall to provide support for the longitud-inally extending ridges of carbonaceous material and also serve a~ an integral portion of the lifters.
With the above arrangement a plurality of spaced elongated ridges are formed on the inner wall of the rotating retort to serve as lifting or mixing devices for the finely div~ded carbonaceous material. The scraper posit~oned in the retort that initially shaped the elongated longitudinally extendlng ridges and valleys in the layer of carbonaceous material further removes other agglomerative carbonaceous material that may be deposited on the surface of the ridges and valleys ~o that the layer of carbonaceous material retains its ridge and valley configuration during the agglomeration process.
Accordingly, the principal object of this invention is to provide a method and an apparatus for forming elongated longitudinally extending ridges and valleys in a layer of agglomerative material deposited on the inner wall of a rotary drum, 4~i1 Another object of this invention is to provide a method and an apparatus for maintaining a plurality of spaced longitudinally extending lifters formed of agglomerative material on the inner wall of a rotary drum.
These and othex objects and advantages of this invention will be more completely disclosed and described in the following specification, the accompanying drawings and the appended claims.
BR~EF DESCRIPTION OF THE DRAWINGS
Figure 1 is a top plan view of a rotary drum assembly having separate balling and hardening drums.
Figure 2 is a view in side elevation of the rotary drum assembly, illustrating the rotary scraper rotatably supported in the balling drum.
Figure 3 is an enlarged view of the balling drum in side elevation and section, illustrating the support and drive for the rotary scraper and schematically the longitudinally extending rows of scraper blades.
Figure 4 is a view in section taken along the line IV-IV of Figure 3, illustrating in detail the rotary scraper with two rows of scraper blades extending radially therefrom.
Figure 5 is a fragmentary view in section taken along the line V-V of Figure 4, illustrating a scraper blade element of a row of scraper blades adjustably secured to the blade support.
Figure 6 is a view in end elevation of the balling drum feed and illustrating the relative position of the rotary scraper in the balling drum.
Figure 7 is a diagrammatic view in section and in elevation of the balling drum, illustrating schematically the 4~
rotary scraper having two rows of ~lades within the balling drum rotating in a direction opposite to the direction of drum rotation and the manner in which elongated generally longitud-inally extending ridges and valleys are formed in a layer of agglomerative material on the inner wall of the drum with the ridges serving as generally longitudinal lifters for the particulate agglomerative material within the balling drum.
Figure 8 is a graphical representation of the height of the ridges attainable at various ratios of scraper speed to drum speed with a drum having an effective diameter of 141" and a scraper having a diameter of 46.1".
INTRODUCTION
Throughout the specification the rotary cylindrical drum will also be referred to as a rotary retort or kiln. The terms rotary retort or kiln are intended to designate a cylindrical drum in which partial distillation of one or more of the constituents takes place during the agglomeration process.
Although the preferred method includes the partial distillation of coal during the agglomeration process, it should be under-stood that it is not intended to limit the invention to such aprocess and the invention may be practiced with materials that agglomerate at ambient temperature. It is not intended by illustrating and describing the rotary cylindrical drum assembly herein as including a separate agglomerating drum and a separate hardening drum to be limited to such an assembly. The invention may also be practiced in a single cylindrical drum assembly.
~he agglomerating drum in this specification is also referred to as a balling drum.
Referring to the drawings and particularly Figures 1 and 2 there is illustrated a rotary drum assembly generally 1, _ ~4~
designated by the numeral 10 that includes separate balling and hardening drums designated by the numerals 12 and 14, respectively. The balling drum 12 has a generally cylindrical configuration with a front feed or inlet opening 16, a rear discharge opening 18 and a longitudinal axis 15 about which the balling drum 12 rotates. The discharge opening 18 of drum 12 extends into a stationary housing 20. The hardening drum 14 also has a generally cylindrical configuration with an inlet opening 22 that extends into the fixed stationary housing 20 and a discharge opening 24 with a trommel screen 26 connected thereto. The trommel screen 26 is enclosed by a housing 28 that has outlets 30 and 32 for agglomerates separated according to size by the trommel screen 26. As shown in Figure 3, the dis-charge opening 18 of balling drum 12 extends into the inlet opening 22 of hardening drum 14 so that agglomerates formed in the balling drum 12 are discharged directly into the hardening drum 14. The balling drum outlet opening 18 has an annular dam 34 that controls the inventory of agglomerative material and agglomerates in the balling drum 12. A sealed housing 36 surrounds the balling drum inlet opening 16 and, as illus~rated in Figure 6, suitable inlets 38 and 40 are provided in the housing 36 for introducing agglomerative material, such as coal and char, into the balling drum 12.
As illustrated in Figures 1 and 2, the balling drum 12 has an annular gear 42 secured thereto that meshes with a drive gear 44 connected to a suitable drive means designated by the numeral 46. The ~allinq drum 12 has a pair of annular metallic tires 48 and 50 that rotatably support the drum 12 on roller assemblies 52 and 54 and limit axial movement of balling drum 12.
The roller as~emblies 52 and 54 and the front housing 36 are supported on a platform 58 that is movable vertically to change - ~ ~4t;i the angle of inclination of the balling drum 12. The balling drum longitudinal axis 15, i.e. the axis of rotation, is substantially horizontal and where desired the platform 58 may be utilized to incline the balling drum 12 axis of rotation to control the residence time of the material therein. The hardening drum 14 has a similar annular gear 60 secured thereto that meshes with a drive gear 62. A separate drive means 64 rotates the hardening drum 14 at a preselected speed that is independent of the speed of rotation of the balling drum 12.
Annular metallic tires 66 and 68 support the hardening drum 14 on roller assemblies 70 and 72 to permit rotation of the hard-ening drum 14 by the drive means 64 and prevent axial movement of the hardening drum 14 during rotation thereof.
Referring to Figures 3 and 6, a scraper generally designated by the numeral 74 has a longitudinal axis 75 and is rotatably positioned within the balling drum 12 in spaced relation to the drum ~nner wall 76. The rotary scraper 74 is located above a horizontal plane extending through the longi-tudinal axis 15 of the drum 12 and, as viewed in Figure 6, on the left side of a vertical plane extending through the longitudinal axis of drum 12. With this arrangement, the rotary scraper 74 is positioned in the upper left quadrant of the cylindrical ope~ing in the balling drum 12 as defined by the inner ~rum wall 76 and is arranged to rotate about its longi-tudinal axis 75. As later explained, the position of the rotary scraper is determined by the direction o~ drum rotation. For example, as viewed in Figures 6 and 7, drum rotation is in a counter-clockwise direction as indicated by the directional arrow 78 and the rotary scraper 74 is positioned in the upper quadrant opposite from the inclined bed of agglomerative material formed within balling drum 12.
J~4~1 The rotary scraper 74 has a tubular body portion 80 with a front end shaft 82 and a rear end shaft 84 secured thereto and extending therefrom. It should be understood that the body portion 80 may also be solid and of a configuration other than a cylinder. The body portion 80 may have a smaller transverse dimension than illustrated as long as the body por-tion has sufficient strength to rotatably support the blades.
The front end shaft 82 extends through a suitable seal 86 in the housing 36 and is rotatably supported in a bearing 88 mounted on the housing 36. The front end shaft 82 has a sprocket 90 nonrotatably secured thereto and the front end shaft is supported in another bearing 94 which, in turn, is supported on a fixed beam 92. The rear end shaft 84 is rotatably supported in a bearing 96 which is supported on a fixed support beam 98.
The beam 98 is secured to a portion of the fixed housing 20 en-closing the balling drum outlet opening 18 and the hardening drum inlet opening 22. With this arrangement the scraper 74 is rotatably supported wlthin the balling drum 12 and is supported at its end portions in bearings.
The drive for rotating the scraper 74 includes a drive motor 100, illustrated in Figures 3 and 6, connected through a suitable speed reducer 102 to a drive sprocket 104. An endless chain 106 i8 reeved about the sproekets 90 and 104 and is arranged to rotate the scraper 74 in a direction opposite to the direction of rotation of the drum 12 as indicated in Figures 3, 6 and 7 by the directiona} arrow 56. Suitable control means are provided to rotate the ~craper 74 in synchronous relation with the balling drum 12 so that the scraper 74 rotates at a pre-~elected speed ratio with the balling drum 12. Where desired the control means can be arranged to change the relative speeds of the scraper or the drum to obtain other speed ratios between 4~i~
the scraper and the drum so that, as later discussed, other ridge and valley configurations may be obtained.
The scraper 74 has two rows of scraper blades gener-ally designated by the numerals 108 and 110 secured to the outer surface of the tube 80. The rows of blades include separate blade assemblies that have a blade support member 116 rigidly secured to the surface of the tube 80 as by welding or the like. Separate blades or blade segments are secured to the blade support members 116 by means of bolts 120. The blade segments 118 have elongated slotted portions 122 that permit radial adjustment of blade segments 118 on the blade support members 116.
The rows of blades 108 and 110 extend parallel and lengthwise along the tube 80 to form elongated continuous cut-ting surfaces along substantially the entire length of the scraper 74. In Figure 3 only the end portions of the rows of blades 10~ and 110 are illustrated. The rows of blades provide a continuous cutting surface that preferably follows an arcuate helical path in which the helix has less than a single turn about the axis 75 of the tube 80 throughout the length of the scraper 74 as diagrammatically illustrated by the --~-- line 124 in Figure 3.
The scraper 74 thus has two separate rows of blades extending lengthwise throughout substantially the entire length of the scraper 74. The rows of blades follow a helical path and pre~erably form a helix not exceeding a single turn about the tube axis in which the rows of blades 108 are displaced to the left about the axis 75 as viewed in Figure 3 between the front and rear end of the scraper 74. It should be understood that other blade configurations may be employed that have the rows of blades arranged parallel to the longitudinal axis of the scraper 4~;1 tube 80 or form a helix with more than one turn about the tube axis. The blade arrangement should be such, however, that the ridges formed ~n the material adhering to the drum inner wall extend longitudinally along the drum inner surface and are substantially parallel to the axis of the drum. With this arrangement the ridges formed by the blades serve as longitud-inally extending lifters to lift and mix the material in the drum.
It should also be understood that the number of rows of blades secured to the outer surface of the tube 80 can be increased or decreased as, for example, the scraper 74 can have one, three or four rows of blades rather than two opposed rows as illustrated. It is desirable, however, that the rows of blades be equidistantly positioned on the periphery of the scraper tube 80 to provide symmetrical ridges and valleys in the layer of agglomerative material deposited on the balling drum inner wall 76.
Referring to Figure 7, there is illustrated diagrammatically the manner in which the rotary scraper 74 forms ridges and valleys in a layer of agglomerative material deposited on the inner wall 76 of balling drum 12 and the manner in which the ridges serve as lifters to admix the agglomerative constituent~sand aid in forming agglomerates of a preselected size range from the agglomerative material.
To form a corrugated or scalloped surface with longitudinally extending ridges and valleys on the wall of the balling drum, agglomerative material is first introduced into the balling drum. Where particulate ~ituminous coal, finely divided char and pitch are the agglomerative cvnstituents, the coal may be preheated to a temperature of between 400DF. and 625~F. which is below the temperature at which the surface of `~8~
the coal particles becomes plastic and sticky. The char is preheated to a temperature between 1000F. and 1200F. to supply the sensible heat required for the agglomeration process.
The coal, char and pitch at the above elevated temperatures are introduced into the balling drum 12 as the balling drum 12 is rotating in a counter-clockwise direction as illustrated in Figure 7.
The agglomerative constituents are mixed by the rotation of the drum 12 and heat is transferred from the char to the coal particles and pitch and the agglomerative con-stituents form a sticky plastic mass. A layer of the sticky plastic mass is deposited on the inner surface 76 of balling drum 12. The rotary scraper 74 is synchronously rotated in a direction opposite to the direction of rotation of balling drum 12 and at ~wice the speed of the balling drum 12. At this synchronous speed the rows of scraper blades 108 and 110 periodically move toward and away from the wall of the drum 12.
Because the rotation of the scraper is synbhronous with the rotation of the drum at a ratio of 2 to 1, four elongated ridges 130, 132, 134 ana 136 are formed in the layer of agglomerative material 126. The rows of scraper blades are so spaced from the drum wall 76 that the layer of agglomerative material deposited on the drum inner wall 76 i8 continuous and elongated valleys 138, 140, 142 and 144 are formed in the agglomerative material between the ridges 130 - 136. While the layer of agglomerative material is being deposited on the drum wall 76 and is being shaped by the scraper 7~ the agglomerative material in the layer is plastic and flexible. When the binder associated with the coal and pitch loses its plasticity due to the pyrolysis that takes place at the elevated temperature with-in the drum the layer hardens and rigidifies to retain the longitudinally extending ridge and valley configuration above discussed.
The material to be formed into agglomerates, pref-erably the same material employed in forming the corrugated or scalloped layer on the drum wall, may be introduced into the drum while the layer is hardening or after the layer has hardened. The agglomerative material is introduced on a continuous basis into the rotating drum at a preselected rate to form a bed of agglomerative material within the drum. The bed is designated by the numeral 146 in Figure 7. Rotation of the drum in the direction indicated by arrow 78 moves the bed of agglomerative material upwardly along one side of the retort to an extent that the top surface of the bed 146 has, for example, an angle of repose of about 70. The angle of repose is dependent on the speed of rotation of the drum 12. As the drum 12 rotates the longitudinally extending ridges 130 - 136 in the layer 126 move under the bed of agglomerative material and promote agitation of the bed. ~he agitation of the bed includes top to bottom mixing whereby a portion of the agglom-erative material in the bed adjacent the drum wall 76 is con-veyed upwardly through the bed. The longitudinally extending ridges further turn a substantial portion of this agglomerative material in the portion conveyed by the longitudinally extending ridges and valleys over and onto the bed top surface 14a.
Moving a portion of the agglomerative material up-ward~y through the bed and turning a portion of the agglomerative material over thoroughly admixes the agglomerative material and also continuously deposits partially agglomerated agglom-erates 152 on the bed upper surface 148 at the top portion 150 of bed 146. The partially agglomerated agglomerates 152 roll down the bed upper surface 14 a and the partially agglomerated agglomerates grow in size by picking up additional plastic particles from the upper surface of the bed. In order to ob-tain the above described bottom mixing of the agglomerative material it is essenti~l that the ridges 130 extend longitud-inally along the inner surface of the drum to be effective as lifters. The angle of inclination of balling drum 12 conveys the partially agglomerated agglomerates as they grow toward the balling drum discharge opening 18. The partially agglom-erated agglomerates continue to grow until the binder loses its plasticity and full size agglomerates then harden and rigidify. After the agglomerates harden no further growth takes place. The agglomerates so formed are introduced into the hardening drum where rotation of the hardening drum permits -substantial completion of the pyrolysis of the agglomerative constituents and relatively rigid hard agglomerates are with-drawn from the hardening drum.
The agglomerative material in bed 146 because of its pla~ticity has a tendency to adhere to the interior surface of the layer of rigid agglomerative material deposited on the drum inner wall 76. The scraper assembly 74, because of its continued rotation at a preselected synchronous speed, continuously removes the fresh deposit of agglomerative material on the outer surface of the ridges and valleys while the newly deppsited agglomerative material is in a relatively plastic state to thereby maintain the configuration of ridges and va}leys as illustrated in Figure 7. Where desired, metallic support members may be secured to the drum inner wall and the ridge portions 13~ - 136 formed therein. The metallic support members provide structural support for the ridges and the synchronous rotation of the scraper 74 prevents interference between the metallic support members and the scraper blades.
~8;~4f~1 It may be desirable for certain agglomerative conditions to vary the number and height of the ridges and valleys around the periphery of the drum wall. Figure 8 illustrates the enlarged ridge height and the number of ridges where two rows of blades are positioned on the scraper 74.
Thus, where it is desirable to obtain maximum ridge height with the scraper rotating in a direction opposite to the direction of rotation of the drum the ratio of scraper speed to drum speed is about 2 to 1. Where a maximum of ridges are desired the ratio of scraper speed to drum speed is increased.
Where the number of ridges or lifters is increased, the height of the ridges or lifters decreases. For example, where the ratio of scraper speed to drum speed is 6 to 1, twelve ridges are formed around the periphery of the drum wall. The ridge height is substantially reduced as compared with the height of the ridges where only four ridges are formed on the drum wall 76.
Where more than two rows of blades are secured to the tube 80 the ridge height is reduced for the came ratio of scraper speed to drum spe~d as is indicated in Figure 8 for three rows of blades and four rows of blades.
With the previously described method, in order to have the scraper blades form and maintain the same and the d0sired number of longitudinally extending ridges and valleys, it is essential that the product of the number of rows of blades on the scraper multiplied by the ratio of scraper revo}utions to drum revolutions per unit time is a whole number.
b U2 N =
wherein N = number of ridges formed b = number of scraper blades Ul = drum speed, rpm U2 = scraper speed, rpm ` ~8'~
For example, with a scraper having two rows of blades and the scraper rotating 2 times faster than the drum, four longitudinally extending ridges and valleys are formed and the rows of blades will sequentially move in timed relation through the longitudinally spaced valleys without disturbing the adjacent ridges.
Where twelve peaks are desired and the rotary scraper has two rows of blades, the ratio of scraper speed to drum speed must be 6, as exemplified by the following calculation.
N = 2 x 6 N = 12 It should be noted that it is also possible with the above method and apparatus to control the thickness of the layer and form ridges and valleys in the layer so deposited on the drum inner wall. The blades on the scraper as they rotate relative to the drum follow arcuate overlapping paths through the layer and thu~ form the ridges and valleys above d~scus~ed~
With the above method and apparatus it is now possible to form lifters on the inner surface of the drum from the same or substantially the ~ame material that is agglomerated in the drum. After the lifters in the form of ridges are formed in the layer of material deposited on the wall of the drum the blades of the rotary scraper 74 remove the material that is deposited on the surface of the ridges and valleys in the layer.
Claims (14)
1. A method for agglomerating finely divided agglomerative material comprising, feeding finely divided agglomerative material into a substantially horizontal rotating drum having an inner wall, said drum having a longitudinal axis and said drum arranged to rotate about said longitudinal axis, depositing a layer of said finely divided agglomerative material on said drum inner wall, rotating a longitudinally extending scraper in said drum in a direction opposite to the direction of rotation of said drum and in fixed timed relation to the rotation of said drum to form a preselected number of alternating longitudinally extending ridges and valleys in said layer according to the following formulas where: N = a whole number and number of ridges formed b = number of scraper blades U1 = drum speed, rpm U2 = scraper speed, rpm forming a plurality of elongated alternating and longitudinally extending ridges and valleys in said layer, said ridges and val-leys extending substantially lengthwise along said drum inner wall and substantially parallel to said drum longitudinal axis, and maintaining said same ridges and same valleys so formed in said layer deposited on the drum inner wall while rotating said drum and forming agglomerated from other finely divided agglom-erative material introduced into said rotary drum.
2. A method for agglomerating finely divided agglomerative material as set forth in claim 1 which includes, forming a bed of other finely divided material in said drum, rotating said drum and forming an upper inclined surface on said bed, moving said longitudinally extending ridges and valleys under said bed and lifting a portion of said other agglomerative material adjacent said drum inner wall with said longitudinally extending ridges and valleys and thereafter depositing the lifted portion of said other agglomerative material on the upper inclined surface of said bed.
3. A method for agglomerating finely divided agglomerative material as set forth in claim 1 which includes, maintaining the rotation of said scraper in said drum at said fixed timed rela-tion to the rotation of said drum to maintain the pattern of ridges and valleys in said layer while forming agglomerates from other finely divided material.
4. A method for agglomerating finely divided agglomerative material as set forth in claim 1 which includes, controlling the ratio of speeds of said rotating drum and said rotating scraper to control the height and number of ridges and valleys formed in said layer.
5. A method for agglomerating finely divided agglomerative material as set forth in claim 4 in which, the scraper is rotated at a speed twice the speed of the rotating drum to thereby form four ridges and four valleys in said layer.
6. A method for agglomerating finely divided agglomerative material as set forth in claim 1 in which, said elongated ridges and valleys have a lengthwise arcuate configuration in the form of a helix having less than one convolution throughout the length of the drum.
7. A method for agglomerating finely divided agglomerative material as set forth in claim 1 in which, said finely divided agglomerative material includes bituminous coal and char heated to an elevated temperature before being introduced into said rotating drum.
8. Apparatus for agglomerating finely divided agglomerative material comprising, a cylindrical rotary drum having a longitud-inal axis and an inner wall, means to rotate said cylindrical drum about said drum longitudinal axis at a preselected speed and deposit a layer of finely divided agglomerative material on said drum inner wall, an elongated rotary scraper having a body portion with a longitudinal axis, said rotary scraper positioned
8. Apparatus for agglomerating finely divided agglomerative material comprising, a cylindrical rotary drum having a longitud-inal axis and an inner wall, means to rotate said cylindrical drum about said drum longitudinal axis at a preselected speed and deposit a layer of finely divided agglomerative material on said drum inner wall, an elongated rotary scraper having a body portion with a longitudinal axis, said rotary scraper positioned
Claim 8 - continued in said cylindrical drum in spaced relation to said cylindrical drum inner wall with said scraper body portion longitudinal axis spaced from said drum longitudinal axis, blade means extending radially outwardly from said scraper and extending lengthwise thereon, and means to rotate said rotary scraper in a direction opposite to the direction of rotation of the drum in timed rota-lion to the rotation of the drum and provide relative movement between said rotary drum inner wall and said scraper blade means to form a plurality of elongated alternating and longitudinally extending ridges and valleys in said layer of agglomerative mater-ial deposited on said drum inner wall, said rotary scraper arranged to remove other finely divided agglomerative material deposited on the surface of said ridges and valleys formed in said layer of agglomerative material.
9. Apparatus for agglomerating finely divided agglomerative material as set forth in claim 8 which includes, means to provide synchronous rotation between said cylindrical rotary drum and said rotary scraper.
10. Apparatus for agglomerating finely divided agglomerative material as set forth in claim 8 in which, said blade means includes a plurality of parallel rows of blades spaced around the periphery of said rotary scraper.
11. Apparatus for agglomerating finely divided agglomerative material as set forth in claim 10 in which, said plurality of parallel rows of blades includes two rows of blades positioned in opposed relation to each other on said rotary scraper, said means to rotate said rotary scraper arranged to rotate said rotary scraper at twice the speed of rotation of the cylindrical rotary drum to thereby form four ridges and four valleys in said layer of agglomerative material deposited on said drum inner wall.
12. Apparatus for agglomerating finely divided agglomerative material as set forth in claim 11 in which, said parallel rows of blades having an arcuate configuration in the form of a helix having a single turn about the axis of said scraper body portion to thereby form arcuate parallel longitudinally extending ridges and valleys in said layer of finely divided agglomerative material.
13. Apparatus for agglomerating finely divided agglomerative material as set forth in claim 8 in which, said layer of agglom-erative material is a relatively rigid layer of carbonaceous material formed from the agglomeration of finely divided coal and finely divided char.
14. Apparatus for agglomerating finely divided agglomerative material as set forth in claim 8 which includes, positioning said rotary scraper within said rotary drum at a location in a quadrant of said drum diametrically opposite from the quadrant of said drum occupied by said agglomerative material during rotation of said drum.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US46683374A | 1974-05-03 | 1974-05-03 | |
| US466,833 | 1974-05-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1082461A true CA1082461A (en) | 1980-07-29 |
Family
ID=23853275
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA225,768A Expired CA1082461A (en) | 1974-05-03 | 1975-04-29 | Method and apparatus for agglomerating finely divided agglomerative materials in a rotating drum |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5129382A (en) |
| BE (1) | BE828575A (en) |
| CA (1) | CA1082461A (en) |
| DE (1) | DE2519206A1 (en) |
| FR (1) | FR2269370A1 (en) |
| GB (1) | GB1455234A (en) |
| ZA (1) | ZA752631B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1099901A (en) * | 1976-03-31 | 1981-04-28 | Earl W. Bennethum | Agglomerating process and apparatus |
| DE2843216C2 (en) * | 1978-10-04 | 1980-08-14 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Device for data input with an optically scannable data carrier |
| JP3577503B2 (en) * | 1992-09-28 | 2004-10-13 | 大日本インキ化学工業株式会社 | Color code |
-
1975
- 1975-04-23 ZA ZA00752631A patent/ZA752631B/en unknown
- 1975-04-23 GB GB1687375A patent/GB1455234A/en not_active Expired
- 1975-04-29 CA CA225,768A patent/CA1082461A/en not_active Expired
- 1975-04-30 FR FR7513677A patent/FR2269370A1/fr not_active Withdrawn
- 1975-04-30 BE BE2054318A patent/BE828575A/en unknown
- 1975-04-30 DE DE19752519206 patent/DE2519206A1/en active Pending
- 1975-05-02 JP JP50053808A patent/JPS5129382A/ja active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| FR2269370A1 (en) | 1975-11-28 |
| GB1455234A (en) | 1976-11-10 |
| BE828575A (en) | 1975-10-30 |
| JPS5129382A (en) | 1976-03-12 |
| DE2519206A1 (en) | 1975-11-13 |
| ZA752631B (en) | 1976-06-30 |
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