US3154806A - Pelletizing apparatus - Google Patents

Description

Nov. 3, 1964 P. STEFFENSEN PELLETIZING APPARATUS 4 Sheets-Sheet 1 Filed Yov. 29, 1956 INVENTOR Percy L. sleffcnsen ATTORNEY Nov. 3, 1964 P. STEFFENSEN PELLETIZINGAPPARATUS 4 Sheets-Sheet 2 Filed Nov. 29, 1956 INVENTOR Percy L. Sfcffensen wil M.

ATTORNEY 1964 P. L. STEFFENSEN 3,

PELLETIZING APPARATUS Filed Nov. 29, 1956 4 Sheets-Sheet 3 INVENTOR Percy L. Sfcf/ensen BY W.

ATTORNEY Nov. 3, 1964 P. L. STEFFENSEN PELLETIZING APPARATUS 4 Sheets-Sheet 4 Filed Nov. 29, 1956 m n m m B 0 V "U N n I! n S L V Y B 9% km n E @Q 5% mm United States Patent 3,154,806 PELLETIZENG APPAPATUS Percy Lea Estefiensen, Cornwall, in, asslgnor to Eethlehern Steel. Qornpany, a corporation of Pennsylvania Nov. 29, 1956, Ser. No. 625,159

7 Claims. (Cl. 18-4) This invention relates to pelletization of ores and the like, and more particularly to apparatus for balling or pelletizing fine ores or concentrates in preparation for further treatment.

Concentrates from low grade iron ores are conventionally produced by processes which include fine grinding, followed by flotation and/or magnetic separation. iaterids of the resultant small grain size, however, can not be economically utilized in a blast furnace, so they are preferably formed into wet balls or pellets of convenient size, and then heated until suthciently dry and hard to withstand considerable handling.

A conventional way of making such pellets has been to pass the powdered material through a revolving inclined cylindrical drum. The material may be sufficiently wet from previous treatment, but if not it is sprayed with water, and gradually collects into balls in the rotating drum. Since these pellets are not of any uniform size, the, discharge from the cylindrical drum must be screened, and as much as 75% to 80% may have to be recycled through the drum as being still undersize, which is obviously expensive and wasteful practice.

It is an object of this invention, therefore, to provide an apparatus which will make, segregate and discharge pellets of substantially uniform size and quality at a high production rate.

Another object is to eliminate any need for screening and recycling undersize pellets, and to prevent breakage of pellets todue to screening.

An additional object is to provide efiicient cutter and scraper mechanisms for a cone-shaped pelletizer.

Still other purposes, and advantages of the invention will appear hereinafter in the specification, claims, and drawings.

In the annexed four sheets of drawings:

FIG. 1 is a side elevation of the invention, illustrating somewhat diagrammatically the relationship between the feeder belt, slinger, reciprocating scraper means, balling cone, receiving belt, and driving and mounting means;

FIG. 2 is a top plan View of the invention, pellet receiving belt being additionally shown;

FIG. 3 is a transverse detail section taken on the line 3-3 of FIG. 4;

FIG. 4 is a vertical section taken through the upper half of the cone, illustrating the reciprocating scraper and the spindle around which the cone rotates;

FIG. 5" is a detail end view showing the feeder belt, slinger, splash shield, and curtain;

FIG. 6 is a vertical section generally similar to FIG. 4 but showing the stationary cutters; and

FIG, 7 is a transverse section taken on the line 77 of FIG. 6, and showing in particular the arrangement of the rear cutters.

Referring to the drawings, the reference numeral 1 designates a conventional fioor underlying a pair of parallel I- beams 2 and 3, the former of which has a pair of supports 4 upon which one end of a rectangular base 5. is pivoted by pins 6, with the other end of said base 5 being adjustably held by bolts 7 movable in elongated slots 8 in standards on the second l-beam 3. Mounted on said base 5 is an inclined frame it} in which the bearings 11 and. 11 support a forwardly and upwardly extending extra-heavy pipe 12 rotatable concentrically ith the s s lass ice about an elongated fiXed spindle 13 terminally attached at its lower end to said frame it).

A pelletizing drum 14 formed of welded steel plates in the shape of a frustum of a cone has a reinforced discharge rim 15 at its large open end and a bottom end closure 16 having a central opening 17 through which extends the fixed spindle 13. A large ring gear 18 is mounted concentrically behind said end closure 16 on a spider 19 of radial I-beam members secured on pipe 12 and rotatable therewith on bearings 29 about the spindle 13. The bottom end closure ls) is removably bolted onto said spider 19.

Also mounted on the frame In is the base 21 of a drive motor 22 connected by the sheave 23, belt 24 and sheave 25 to a gear reducer 25 having an output shaft 27 driving a pinion 28 meshing with the ring gear 18.

Mounted on a separate frame 29 or" conventional structural members adjacent to but slightly higher than the top of the pelletizing drum 14 is a motor base 3% which supports a scraper motor 31 equipped with a sheave 32 connecting by belt 33 to sheave 34 on gear reducer 35.

Referring particularly to FIGS. 3 and 4, the forward end of the upwardly tilted spindle 13 has positioned thereon a pair of longitudinally spaced split rings 36 and 327 on which a longitudinally slotted large pipe 33 is tightly clamped by pairs of lugs 39 drawn together by bolts 4% and nuts 41. Conventional sealing devices 41a, 41b and 410 about said pipe 3% guard the central opening 17 against entry of any erosive matter. Welded at right angles to said pipe 38 inside the drum 14 are a pair of spaced parallel upright arms 42 and 43 of unequal lengths. Said arms 42 and 43 are connected by a gusset plate 79 and surmounted by a large pipe '71 inclined in substantially parallel spaced relation to the upper inside surface of the drum. For maximum rigidity, the upper end of said pipe '71 may be tied to external structure by a thrust bar (not shown). Welded longitudinally atop said pipe 73 and tilted oppositely to the direction of rotation of the drum 14 is a cutter adapter plate '72, braced by side bars 73, upon which plate is bolted a series of cutters 74 having wedge shaped upper cutting edges of tungsten carbide or other hard alloy.

Positioned rearwardly of the arm 43 in spaced parallel relation to the bottom end closure 16 and braced against said arm 43 by side bars 75 and '75 is the an ularly bent rear cutter adapter 76, to which is bolted a series of wedge-shaped cutters 74' having tungsten carbide inserts 7d" as previously described.

In offset parallel relation to the pipe 71 on the upright arms 42. and 43 are horizontal angles 44 and as supporting pairs of small upright parallel plate members as and as each with a short interposed pipe 47. Scraper support arms 43 and 58 each provided with pairs of lower bearing blocks 49 are pivotally mounted by means of a stud so or the like extending through said pipe 47 and secured by end nuts 51. Upper bearing blocks 52 on said support arms and 48' are adapted for pivoted attachment to the elongated hollow box-shaped member 53 of edge-welded angles and angularly welded similar extension member 54 by through bolts 55 secured by nut 55. Angles 57 and 58 welded atop said members 53 and 5 have bolted to their upright flanges a series of regularly spaced short bars 59 each having a plurality of spaced scraper teeth 63 of tungsten carbide.

Reciprocating motion is imparted to the scraper arms 53 and 54- by means of a pivot bolt 61, clamp 62, connecting arm as, and adjustable extension arm pivotally connected to crank arm 65 on the gear reducer 35.

The action of the scraper teeth so assists the stationary cutters and 74' to prevent the moist ore from accumulating on the interior of the cone to such a degree that it would hamper the operation of the cone. The teeth 6t) also continually loosen and roughen the surface of the material on the interior of the cone, which facilitates the pick-up of moist ore by the revolving partlyformed pellets.

The quality of the pellets is considerably adected by a number of factors, including the character, distribution and rate of delivery of the feed, the size, shape and tilt of the cone, the kind and thickness of the inner surface, and the rotational speed of the cone. For example, in order to ball moist iron ore concentrates properly, they should contain about 9 /2 to l /2% moisture. Small amounts of additives such as bentonite and soda ash will assist balling and increase the crushing strength of the pellets. Particle size of ore feed is determined by the previous concentrating steps.

In pelletizing fine iron ore concentrates, I have found that very satisfactory pellets up to about 1% in. in diameter may be formed in cone-shaped drums of the type described ranging from about 3 feet to 11 feet in maximum diameters, with depths varying from about twothirds to one-half their maximum diameters. For a truncated cone 11 feet in greatest diameter and 6 feet deep, the included angle of the upper portion of the cone, formed by imaginary extensions of the side lines of the cone from the discharge rim to about 60% of the depth of the drum, may be from about 40 to 54, with 48 being generally satisfactory as an intermediate figure. In about the inner 40 percent of the depth of the cone,

where initial pelletizing takes place, the included angle a of the cone may if desired be somewhat greater, for example about 60, to fiush out any small crumbs of ore and to provide better control over the formation of the seed pellets. A wedge shaped inner liner or cone of concrete '77, as shown in FIG. 4, is perhaps the simplest way of providing two diiferent slopes in a large metal cone. It is, of course, necessary to reserve proper clearance for the cutting and scraping devices.

The incoming feed passes over a belt conveyor d7 having a supporting frame '73 beneath which is suspended a motor 75 having a pulley 89 connected by belt 81 driving jack pulleys 82 and 33 which in turn through a belt 84 will drive pulley S5 rotating horizontal shaft 36 journaled in bearings 87 on said frame 78 beneath the head pulley 88 of the belt conveyor. Said shaft carries a pair of horizontally spaced parallel flat bars 39 having interposed slinger rods 9% which will divide and distribute the fa ling feed material. A metal splash shield 91 and depending rubber curtain 92 will prevent undesired waste of feed and annoyance to operating personnel.

As above described, the pulverulent material 66 to be pelletized is fed from the belt conveyor 67 into the rotating drum 14. There the material, if not already sufficiently wet, may be sprayed with water through any conventional nozzle means (not shown), and quickly balls into pellets 68 of suitable size. The pellets are automatically classified according to size by the rotating cone. The smaller pellets stay close to the center or beneath the larger pellets until the desired size is reached. Pellets of proper size are discharged over the discharge lip onto the conveyor 69 to the furnace or sintering machine (not shown) where the pellets are fired to hardness.

The agglomerating action of the material during rotation of the cone is such that a pellet will not be discharged from the cone until it has reached a desired minimum size, which size may be regulated by varying the angular position of the lower side of the cone with respect to the horizontal. The smaller sized crumbs and pellets, as they are carried farther up the wall in the direction of rotation of the cone, constantly tend to fall backward on the bed of material until they have attained an individual size or mass great enough to cause them to move toward the discharge lip of the cone. By tilting the cone upwardly and so increasing the angle between the axis of rotation of the cone and the horizontal, the

size of the pellets leaving the cone will be increased, and by decreasing said angle, the size of pellets will be reduced.

The angle of tilt controls the rate of passage of the material through the cone. In order to adjust the machine, the base 5 may be tilted slightly upward or downward, as required, by means of hydraulic jacks or the like (not shown), preferably beg nning with the bottom side of the cone being approximately horizontal. I have found that the size of iron ore pellets can be varied from as small as A inch diameter to 1% inch or more merely by changing the angle between the axis of rotation and the horizontal. As this angle is increased, the size of pellet increases, and to decrease the size of pellets, the angle is decreased. With a 48 outer included-angle cone, 1 have found that maximum output capacity of uniformly sized and regularly formed pellets of iron ore concentrate is obtained when the lower side of the cone is tilted slightly downward, or approximately 2 below horizontal, thus causing the axis of rotation of the cone to be about 22 above horizontal. A range of about 4 above or 4 below the horizontal, however, will give good results.

The size of pellet can also be varied considerably by changing the point at which the feed enters the drum. The closer to the discharge lip the feed is introduced, the larger the pellets will become; and conversely, the closer to the base of the drum, the smaller the pellets. In general, I prefer to distribute the. feed evenly over the rear half of the lower side of the cone, which is very efficiently accomplished by the rotating slinger rods 90. The build-up of fines in the drum will then be substantially as shown in FIG. 1 in dotted lines.

The peripheral speed should be such that the ore rolls and cascades to a limited extent but does not slide. If the speed is too low, the mass in the drum slides and no pellets are formed. Excessive speeds may cause pellet breakage. Furthermore, for any given product size, there is a rather limited and critical range of speeds for the machine. For iron ore pellets about A; inch diameter, on an 11 ft. cone, satisfactory peripheral speeds may be approximately 450 to 585 ft. per minute, equivalent to 13 to 17 revolutions per minute. Very small pellets such as the bird seed used in traveling grate sintering, may permit as much as to r.p.m. on the sazne machine. Smaller drums, of course, will require higher rotational speeds for equivalent peripheral speeds.

The inside surface of the drum must be in proper condition or balls will not form satisfactorily. Fine materials such as iron ore concentrates will adhere in a sufficiently compact layer to provide a proper inside surface. Creation of this layer may be assisted by providing a full inner lining 93 of expanded metal tack-welded in place, or by using other suitable means to provide a roughened surface which will promote adhesion. Where a concrete lining 77 is used, it will bond effectively to such expanded metal.

When the machine is first started and moist fine material such as ore concentrate is fed to it, a progressively thickening lining of the material is built up inside the cone until it reaches a specified thickness, perhaps an inch or more, as determined by the clearance of the fixed cutters 74 and 74' from the inner surface of the cone. As the cone is rotated relative to these fixed cutters 74 and 74', excess concentrate is trimmed away and a level and uniform thickness of the concentrate lining is maintained. The smoothness of this inner surface adjacent the discharge rim 15 is useful in making the finished pellets uniformly smooth and round. The frictional effect of a. rough surface is preferred for the beginning and intermediate stages of pelletizing, which occur in approximately the lower two-thirds of the cone, and the raspiug action of the oscillating scraper teeth will create a suitably rough surface on this lower area of the concentrate lining. It will be noted that the Wear from the cutters and scraper is on the concentrate lining, which is self-renewing, and not on the metal cone.

Although the invention has been shown and described hereinabove in considerable detail, it is not intended to have it narrowly limited thereby, but there may also be used all such modifications, substitutions or equivalents thereof as are embraced within the scope and spirit of the invention or as are pointed out in the appended claims.

I claim:

1. A pelletizing apparatus for moist pulverulent material comprising a frusto-conical drum, said drum being open at its Wide end and closed at its narrow end, the depth of the drum from its wide end to its narrow end being approximately one-half to two-thirds of its diameter at its wide end, the included angle of the drum being approximately 4054 adjacent its open end and approximately 60 adjacent its closed end, and the axis of rotation of the drum bein inclined upwardly approximately 16 to 31 from horizontal.

2. A pelletizing apparatus for moist pulverulent material comprising a frusto-conical drum, said drum being open at its wide end and closed at its narrow end, the depth of the drum from its wide end to its narrow end being approximately one-half to two-thirds of its diameter at its wide end, and the included angle of the drum being not less than approximately 40, reciprocable scraper means for forming adjacent the closed end of the drum a lining of moist, pulverulent material having a continuously roughened surface, and a stationary scraper for forming adjacent the open end of the drum a lining of said material having a smooth surface, the axis of rotation of the drum having an upward tilt relative to horizontal equal to approximately one-half said included angle.

3. The combination, with a pelletizing drum having a fixed central shaft and means for rotating the drum about said shaft, upright arms mounted on said shaft, stationary cutters on said upright arms close to the inner surface of the drum, lateral support arms on said upright arms, a reciprocable member pivotally mounted on said support arms parallel to the cutters on said upright arms, a series of short bars each having a plurality of spaced scraper teeth mounted on said member, and means for reciprocating said member to roughen the lining of adherent pulverulent material in the pelletizing drum.

4. A peiletizing apparatus comprising a frusto-conical drurn rotatably supported by a fixed central shaft, means for rotating the drum about the shaft, and a scraper mounted on said shaft adjacent the inner surface of the drum.

5. A pelletizing apparatus comprising a base, a trustoconical drum rotatabiy mounted on said base, said drum being open at its larger end and closer at its smaller end, said drum being rotatably mounted on a fixed central shaft extending through the closed end of said drum, means for rotating the drum about the shaft, and a scraper mounted on said shaft adjacent the inner surface of the drum.

6. A pelletizing apparatus as defined in claim 5 in winch the frusto-conical drum has a or greater included angle and depth equal to one-half to two-thirds of its maximum diameter.

7. A pelletizing apparatus as defined in claim 6, in which the included angle of the frusto-conical drum does not exceed 54 at its larger end.

References Cited in the file of this patent UNITED STATES PATENTS 1,239,221 Rodman Sept. 4, 1917 2,638,625 Studebaker et a1 May 19, 1953 2,662,641 Clarke et al Dec. 15, 1953 2,709,833 V/ilkund June 7, 1955 2,726,959 Lushsbough et al Dec. 13, 1955 2,778,056 Wynne Jan. 22, 1957 2,831,210 De Vaney Apr. 22, 1958 2,947,016 De Vaney Aug. 2, 1960 FOREIGN PATENTS 181,807 Austria Apr. 25, 1955 21,840 Finland Aug. 8, 1947 915,072 Germany July 15, 1954 OTHER REFERENCES Agglomeration, pp. 161-174, October 1951; Chemical Engineering, pp. and 171 of particular interest.

Claims (1)

1. A PELLETIZING APPARATUS FOR MOIST PULVERULENT MATERIAL COMPRISING A FRUSTO-CONICAL DRUM, SAID DRUM BEING OPEN AT ITS WIDE END AND CLOSED AT ITS NARROW END, THE DEPTH OF THE DRUM FROM ITS WIDE END TO ITS NARROW END BEING APPROXIMATELY ONE-HALF TO TWO-THIRDS OF ITS DIAMETER AT ITS WIDE END, THE INCLUDED ANGLE OF THE DRUM BEING APPROXIMATELY 40*-54* ADJACENT ITS OPEN END AND APPROXIMATELY 60* ADJACENT ITS CLOSED END, AND THE AXIS OF ROTATION OF THE DRUM BEING INCLINED UPWARDLY APPROXIMATELY 16* TO 31* FROM HORIZONTAL.

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