US3749533A

US3749533A - Pelletizing apparatus

Info

Publication number: US3749533A
Application number: US00198687A
Authority: US
Inventors: R Lombardi
Original assignee: Dravo Corp
Current assignee: Dravo Corp
Priority date: 1971-11-15
Filing date: 1971-11-15
Publication date: 1973-07-31
Anticipated expiration: 1990-07-31

Abstract

A pelletizing disk supplied with feed material falling by gravity through a duct has a hood over a portion of the disk over the area from which the dust arises with a suction opening at the periphery of the disk arranged to collect only that dust that tends to escape from under the hood at a distance remote from the place where the feed material falls onto the disk. The hood is formed of spaced upper and lower cones with the suction opening being formed between the upper and lower cones. A suction pipe leads from the space between the two cones. Part of the suction opening nearest the feed pipe may be blocked off.

Description

Umted States Patent 11 1 Lombardi 1451 July 31, 1973 I 1 PELLETIZING APPARATUS 2,914,797 12/1959 Cavanagh 425/222 3,210,772 1965 Sti l' 425 [751 lnvcnm" Lmnhardl, Cram", 3 241,521 3/1966 ki h r dsonu 14 1 /95 [731 Assignee: Dravo Corp ration, Pittsburgh, Pa. :32; 3:32;

233 5 [22] Filed: Nov. 15, 1971 3:463:098 8/1969 Gyde 264/117 x [21] Appl. No.: 198,687 Primary Examiner Assistant Examiner-John S. Brown [52] US. Cl. 425/73, l4l/93, 209/136, Attorney william H, Par-melee 425/8, 425/222 [51] Int. Cl B2811 17/00 57 R CT [58] g '5" 555322 g A pelletizing disk supplied with feed material falling by 222 264/l0i 102 17 f gravity through a duct has a hood over a portlon of the 26l/l06 n] 1 1 ll0/1l9 disk over the area from which the dust arises with a suc- 209/l36 tion opening at the periphery of the disk arranged to 222/132 2 6 collect only that dust that tends to escape from under the hood at a distance remote from the place where the 5 6] References Cited feed material falls onto the disk. The hood is formed of spaced upper and lower cones with the suction opening UNITED STATES PATENTS being formed between the upper and lower cones. A 2,939,172 6/1960 Vonreppert 264/117 suction pipe leads from the space between the two 141/1 cones. Part of the suction opening nearest the feed pipe arres1.... 1,951,790 5/1930 Curran 425 6 may be blocked 2,795,329 6/1957 Schaub 209/139 R 8 Claims, 2 Drawing Figures l I6 I I l I4 I a 12 i l :l I5 I 4 4 ,4,

Patented July 31, 1973 INVENTOR. Rag mond R Lombardt Mf -@24 1 m Attorneys PELLETIZING APPARATUS This invention relates to an apparatus for and method of forming fines into pellets, and is for a pelletizing disk with means so arranged as to substantially reduce the dust and attendant loss of mineral values in the operation of such apparatus.

In various industries finely-divided minerals or ore concentrate with or without added powdered chemicals or fuel are discharged by gravity from an elevated source of supply onto the surface of a large rotating inclined disk by which the dry feed material is carried beneath a spray of water in such manner that tiny pellets first form and then increase in size as they roll over the dry material on the disk and upon reaching a desired size range they are discharged over the edge of the disk, all in a manner well understood and extensively practiced in industry.

As the fine material falls onto the disk, dust is generated by the impact of the finely-divided and powdered material onto the disk. This dust which tends to drift away, is both a valuable ingredient and is a fine material important to the rolling of strong green pellets. Perhaps, more important, is the need'to have clean air in the pelletizing area so that workers attending the apparatus are not required to wear breathing masks and healthful conditions are maintained around the plant, as well as in the nearby vicinity.

Attempts have heretofore been made to suppress the dust by completely covering the disk with a hood with a pipe leading from under the hood to a suction fan and some kind of air cleaner to collect the dust. The feed material is discharged onto the disk through a duct or closed chute that passes through the cover. In other instances a smaller hood, also connected with a suction fan, but of a size to cover only a portion of the disk around the feed pipe or duct has been used, thus enabling the operator to observe the operation of the disk and possibly make some adjustment required from time to time to keep the pellets within a selected size range or correct for some other condition.

Both of these hood arrangements produce a suction under the entire area of the hood and much dust is immediately entrained in a current of air leading to the suction fan which might otherwise not leave the surface of the disk or would fall back onto the disk. The drawing off of fines in this way is referred to in the art as leaching.

The present invention provides a hood and method wherein this leaching of fines is substantially reduced and practically only those fines which would otherwise drift into the ambient air are drawn by vacuum to a dust collector. To this end there is provided a hood of less area than the disk so as not to obstruct an adequate view of what is happening on the disk, but which has a suction opening only at its periphery while providing beneath the hood above the immediate area of discharge of material onto the disk a relatively quiescent pocket of air where particles may fall back onto the disk. The preferred manner of constructing the hood is to provide two hood-like members, an upper one spaced from but enveloping the lower one, the space between the two leading to a suction pipe while the opening between the peripheral edges of the two is an inlet port. In its simplest form these two hood-like members are in the form of truncated cones, one above the other, the lower one being attached at its top to the feed inlet pipe and the upper one being attached at its top to a suction pipe concentric about the inlet pipe. Desirably also the cones are non-symmetrical and eccentrically positioned about the feed pipe so that the entire hood structure is positioned above only part of the area of the inclined disk which is below its center of rotation. Also, the hood spreads further out over the disk from the feed supply pipe toward the periphery of the disk on the down side and to each side of the supply pipe than it spreads up from the supply pipe toward the center of rotation of the disk. In fact in this upside area of the double cone arrangement, part of the opening at the periphery of the two cones nearest the feed pipe may be blocked off so that the peripheral opening between the two cones is less than 360.

My invention may be more fully understood by reference to the accompanying drawings showing a preferred embodiment of the invention, and in which:

FIG. I is a vertical section showing somewhat schematically the lower portion of an inclined pelletizing disk over which the hood of the present invention is located; and

FIG. 2 is a somewhat schematic front view of the disk and hood on a smaller scale and indicating in addition a water spray above the upper portion of the disk.

In the drawing, 2 represents more or less schematically a typical pelletizing disk carried on a motordriven shaft 3 by which the disk is rotated. The axis of the shaft is inclined, the angle of inclination usually being adjustable. Typically the disk is at an angle of about 45. The diameter of the disks may vary, but they are commonly of the order of fourteen inches to twenty feet or so in diameter.

There is usually a beam structure 4 supported at each end on stanchions or end frames 5, the beam being spaced above the disk substantially over the side-toside or horizontal diameter. Among other things it may support a spray nozzle 6 and water supply pipe leading thereto. The disk, its manner of support and the drive for rotating it and various water spray arrangements are well known in the art and form no part per se of the present invention.

Positioned over that quadrant of the disk between its center of rotation and the lower edge of the disk is a feed conduit or duct 10 through which the finely divided feed material falls by gravity from a conveyor or other source of supply to the disk at a controlled rate, as is also commonly understood in the art. The lower end of the feed pipe 10 is cut off at an angle so that it is generally, but not necessarily parallel with the surface of the disk, the terminal end of said pipe being designated 11.

'Supported by and suspended from the feed pipe is a hood structure designated generally as 12. The hood is comprised of a lower hood element 13 and an upper or outer hood element 14. The element 13 is preferably in the form of a truncated cone of irregular shape, which, as seen in FIG. 1, extends downwardly and outwardly on the lower side of the feed pipe 10 a considerably longer distance and at a less steep incline than the opposite side of the cone which extends over the up-slope of the disk toward the center of rotation of the disk. Not only is this cone eccentric to the axis of the pipe, but it is not coaxial so that the upper peripheral edge of the cone is closer to the disk than its lower edge.

There is a collar 13a about the top of the element 13 by which it is attached to the feed pipe.

The upper or outer element 14 of the hood duplicates the shape and disposition with respect to the feed pipe of the lower or inner one, but is larger so that there is a space 15 between the two. A collar 14a at the top of the upper cone is attached to a suction pipe 16 concentrically positioned about and spaced from the feed pipe 10. it has an elbow or angular extension 17 at its top that leads to a suction pump or fan and dust separator (not shown).

In operation the feed material falls through the feed pipe 10 onto the disk where some of the powdered fines rise as dust. Much of this dust wili rise into the rather quiescent or dead area under the impervious lower cone around the feed pipe and settle back onto the rotating disk, but some of it will tend to drift toward the periphery of the double cone hood and be drawn by suction up into the space between the hoods and carried out by the current of air which is being drawn through the pipe 16-17.

Preferably, but not necessarily, the opening between the peripheries of the two cones does not extend around the feed pipe a full 360, but as indicated, is closed by plate 18 around the upper side of the feed pipe through an arc of the order of 120 to 160 preferably, and less than 180, that is around that portion of the hood which is closest to the feed pipe. This results in very little suction close to the feed pipe directly above the disk, but there will be some gentle drift of air toward the more remote periphery of the hood to carry suspended dust particles into the suction passage. This area of the peripheral opening that is blocked off is that portion which is not only closest to the feed pipe but also closest to the surface of the disk and is on the up-side of the feed pipe while the greatest dustgenerating turbulence of the feed material is at the down-side. For both of these reasons it is unnecessary and undesirable to have any strong direct up-sweep of air into the suction opening in this region.

The overall area of the hood is less than the radius of the disk since at its furthest distance down from the feed pipe it extends only to a position above the outer edge of the flat circular area of the disk, that is, the hood need not extend over the edge of the flange around the disk. From the lowest point on the hood, as viewed in FIG. 1, the radius of the hood does not decrease for 90 or slightly more to each side of this point. Expressed another way, the lower edge of the hood describes a true semi-circle and perhaps a few degrees more, but then the radius of the hood decreases rapidly to the point where at best it extends only a short distance beyond the feed pipe. As thus proportioned and shaped, the operator of the disk can observe at a glance conditions over the greater portion of the area of the disk; certainly enough of the surface can be readily seen to enable the operator to make such changes in operating conditions as may be required from time to time.

While the structure is simple and inexpensive and does not cover an excessively large area of the disk, it does serve to capture all or most all of the dust that would otherwise drift out into the area around the apparatus without however leaching away or drawing off much material that, in a quiescent atmosphere, does not drift away and which falls back onto the disk. This is important not only to the economy of the operation and the size of the air-cleaning equipment required, but also fines which are required in the feed mix to cause good balling" of the mix and the production of strong pellets, are not removed or leached away to any appreciable extent.

I claim:

1. The combination with an inclined rotatable pelletizing disk and a feed pipe having a discharge terminal positioned above the disk between its lower edge and its axis of rotation through which the finely-divided feed material falls by gravity onto the disk, of a hood structure extending radially from the feed pipe over the disk toward its lower edge the greater portion of the distance from the feed pipe to said edge and extending in a semicircle over the disk around the feed pipe, and means at the periphery of the hood providing a suction opening only about the periphery thereof, the area of hood between said means at the periphery of the feed pipe being impervious to the passage of air upwardly therethrough whereby dust generated by the discharge of powdered material from the pipe onto the disk can be sucked away from the disk only when it tends to escape from under the hood.

2. The combination defined in claim 1 in which the hood structure diminishes in radius over that portion of the disk that slopes upwardly between the feed pipe and the center of rotation of the disk.

3. The combination defined in claim 2 in which there is no suction opening around the periphery of that portion of the hood structure of diminishing radius through an arc of about to but is provided around the remainder of the periphery of the hood structure.

4. The combination defined in claim 1 wherein the hood structure comprises spaced upper and lower hood elements of substantially the same shape with the spacing of the elements forming the suction opening around the periphery of the lower hood element and between peripheries of the inner and outer hood elements and also a suction space between the two elements, and a suction pipe opening into and leading from said suction space.

S. The combination defined in claim 1 wherein the hood structure is eccentrically positioned about the feed pipe in such manner that the most its area extends over the surface of the disk down-slope from the feed pipe and wherein most of that portion of the hood structure up-slope from the feed pipe has no peripheral suction opening.

6. The combination defined in claim 4 wherein the peripheral edges of said hood elements terminate in a common plane which intersects the plane of the disk above the feed pipe so that the edge of the hood upslope of the feed pipe is closer to the surface of the disk than the down-slope edge.

7. For use with an inclined pelletizing disk having a feed pipe arranged to discharge fines to be pelletized by gravity onto the disk, the invention comprising:

a. a hood structure arranged to be supported above a portion of the disk by said feed pipe, the hood structure comprising,

l. spaced upper and lower hood elements of truncated irregular cone shape eccentrically positioned about the feed pipe and with a first portion of the hood structure which extends furthest from the feed pipe having a less steep slope than a second portion at the opposite side of the feed P p 2. the first portion having an opening around its periphery into the space between the two elements 6 and the periphery of the second portion being terminal of the feed pipev closed, 8. The invention defined in claim 7 wherein the out- 3. an outlet duct at the top of the upper element for let duct at the top of the upper element is concentric connection with a suction pump, about the feed pipe and the top of the upper element 4 the interior of the lower element providing a rel- 5 is attached to and suspended from said outlet duct atively quiescent zone over the disk around the

Claims

2. the first portion having an opening around its periphery into the space between the two elements and the periphery of the second portion being closed,

3. an outlet duct at the top of the upper element for connection with a suction pump,

3. The combination defined in claim 2 in which there is no suction opening around the periphery of that portion of the hood structure of diminishing radius through an arc of about 120* to 160* but is provided around the remainder of the periphery of the hood structure.

4. the interior of the lower element providing a relatively quiescent zone over the disk around the terminal of the feed pipe.

5. The combination defined in claim 1 wherein the hood structure is eccentrically positioned about the feed pipe in such manner that the most its area extends over the surface of the disk down-slope from the feed pipe and wherein most of that portion of the hood structure up-slope from the feed pipe has no peripheral suction opening.

6. The combination defined in claim 4 wherein the peripheral edges of said hood elements terminate in a common plane which intersects the plane of the disk above the feed pipe so that the edge of the hood up-slope of the feed pipe is closer to the surface of the disk than the down-slope edge.

7. For use with an inclined pelletizing disk having a feed pipe arranged to discharge fines to be pelletized by gravity onto the disk, the invention comprising: a. a hood structure arranged to be supported above a portion of the disk by said feed pipe, the hood structure comprising,

8. The invention defined in claim 7 wherein the outlet duct at the top of the upper element is concentric about the feed pipe and the top of the upper element is attached to and suspended from said outlet duct.