US 2738548 A
Description (OCR text may contain errors)
March 20, 1956 s. KASSEL METHOD AND APPARATUS FOR MANUFACTURE OF METALLIC PELLETS Filed April 19, 1952 F IE 1 MOLTEN. METAL RISING VAPORS QUENCHING AND RECEIVING CHAMBER DROPPING BOX STEAM COLLECTING ZONE WATER INLET DESCENDING ANNULAR COLUMN OF WATER! PELLET OUTLET INVENTOR: LOUIS S. KASSEL ATTORNEYS:
United States Patent METHOD AND APPARATUS FOR MANUFACTURE OF METALLIC PELLETS Application April 19, 1952, Serial No. 283,175
5 Claims. (Cl. 182.7)
This invention relates to an improved method and means for forming substantially spherical pellets from a desired molten metal or alloy.
Pellets in substantially spherical or shot form are useful for various purposes. For example, shotted lead is used in large quantities for fire arms, while aluminum shots or pellets may be used in deoxidizing steel, catalyst manufacture, and many other processes. Round shot and substantially spherical pellets may be formed, as they have been for many years, by dropping small metal globules through a considerable height in a shotting tower, where a molten metal stream is passed from a dropping box through a plurality of orifices, or through a screen, so that a multiplicity of molten globules fall through a high tower and into a suitable quench chamher; having water or other liquid medium or gaseous medium.
It is, however, undesirable in many instances to provide a high cooling tower permitting a long free fall of molten particles. Also, the dropping of molten globules directly into a liquid containing chamber is generally undesirable, particularly from the aspect of obtaining spherically shaped particles, since many metallic materials tend to flatten out when they hit the surface of water or other liquid. Particles which are not sufficiently cooled and which fall into a liquid receiving chamber may agglomerate as they pass downwardly therethrough and thus provide still another difficult'y in the collection of resulting pelleted particles.
It is, therefore, a principalobject of the present invention to provide an improved method and means for cooling and forming substantially spherical pellets from a molt'en'metal in a manner which precludes the need of an excessively long fall of the molten globules.
It is also an object of the present invention to provide for the fall of molten metal globules downwardly through an encompassing and closely confining ring-like stream so that particles may be cooled and take an initial set before passing into a receiving chamber.
Other objects and advantages of the present method of forming pellets will be apparent from succeeding portions of the description and upon reference to the accompanying drawing.
,Briefly, the method of manufacturing metallic pellets in accordance with the present invention, embodies passing moltenmetal downward through an orifice and forming discreet globules of the metal, dropping successive metallic globules from'the orifice downwardly through a closely confining tubular film of cooling fiuid, efiecting the cooling of the globules and discharging resulting cooling metal pellets from the confines of the lower end of the tubular fluid film.
In carrying out the present invention, water or other suitable liquid medium may be allowed to overflow circumferentially into the top end of a vertically disposed tubular member so that a liquid film covers the entire inner surface of the tubular member in a continuous downflowing tubular or ring-like stream. Molten metal- 2,738,548 Patented Mar. 20, 1956 lic globules are thus allowed to drop directly into the inside of the tubular film of liquid from a suitable orifice or dropping box, and then fall downwardly through the closely confining liquid film to obtain rapid cooling and at least an initial set into substantially spherical pellets. Preferably, the cross-sectional area or size of the shot inside of the tubular film of cooling fluid is correlated with respect to the size of the molten globules falling therethrough so that the free or open area inside of the fluid film is but slightly larger than the ultimate diameter of the metallic pellets being formed in the fall'through the elongated film. Thus, there is a fairly rapid cooling of the pellets and it is not necessary to have excessively long or high tubular members and tubular films to pro-v vide the desired cooling and forming of particles.
Also, the present method of forming pellets provides for the formation of steam within the vertical tubular film. The steam is formed as a result of the close proximity or by the contact of molten globules with the fluid medium as they fall successively downwardly through the tubular zone, and a resulting upward flow of this steam provides a cushioning effect and a slowing down of the fall of molten globules and pellets descending through the confining fluid film. This eifect permits the desired cooling within a lesser vertical height than might otherwise be necessary.
Thus, in a more specific embodiment, the present invention provides a method for forming substantially spherical metal pellets in a manner which comprises passing molten metal downwardly through an orifice and forming discreet globules of the metal, dropping successive metallic globules directly from the orifice through a closely confining and concurrentlyfalling tubularfilm of cooling fluid, effecting the cooling of the globules and the generation of vapor therebelow as they fall through the area bounded by the fluid film whereby the generated vapor cushions and slows the fall of said globules as they descend through the confining fluid film, and discharging resulting cooled substantially spheroidal metal pellets from the lower end of the tubular fluid film.
The method of manufacturing and forming desired substantially spheroidal metallic pellets may be more clearly described and explained by reference to the accompanying drawing and the following description thereof.
Figure 1 of the drawing indicates diagrammatically an apparatus arrangement providing for the dropping of a plurality of molten streams or globules from a dropping box through a plurality of tubular liquid films into a suitable quenching and receiving chamber, from which resulting spheroidal metal pellets may be withdrawn.
Figure 2 of the drawing shows an enlarged cross-sectional view of the dropping of molten globules through a portion of a forming tube and through a descending tubular film of cooling liquid.
Referring now to both Figures 1 and 2 of the drawing, there is shown a dropping box 1 suitable for receiving a molten metal by way of inlet line 2, which in turn may communicate directly with a suitable melting furnacev or the like, not shown. The bottom of the dropping box 1 has a plurality of orifices 3 providing for the formation of molten globules 4 which in turn drop successively from each of the orifices directly into the upper open ends of a plurality of vertically disposed forming tubes 5.
In accordance with the present improved invention;
' a ess a fil e up r ends at a h 9? the tabu a members 5 maybe serrated if desired so as to insure a substantially uniform distribution of the fluid circume enti l und e en i i ne wall surface a e ch ubu ar membe 5 a d P o i e a renta -wa t q nflo ing film 9. It is also preferable that the film 9 be made to flow in a manner providing a substantially thick film precluding the possibility of molten globules touching he s d surfa e of he ub l mem e 5- t i als within the scope of the improved method of operation to utilize a suitable wetting agent in the water or other fluid medium providing the downwardly flowing tubular lm f liquid 80 t a there is a ubsta ti l unif rm covering of the interior of the tubular members 5 and no dry spots therein to which the molten globules may t h tse The arrangement as indicated in Figure l of the drawing provides that the lower ends of each of the tubular members 5 terminate within the upper portion of a closed Dt fine-d quenching and receiving chamber 10. This chamber 10 has a suitable fluid inlet line 11, having control valve 12, and an overflow line 13 which regulates the upper surface of a liquid medium maintained in the chamber 10. Resulting formed pellets and water or other fluid medium are withdrawn from the lower end of chamber 10 by way of line 14 and valve 1 5. The pellets from line 14 may be passed to suitable screening and pellet recovery apparatus, not shown. The r pper end or top portion of chamber 10 is indicated as being closed and thus provides a steam collecting zone, so that steam which may result from the contact of the hot globules with the water in chamber 10 may collect and pass upwardly through each of the forming tubes 5 and within the confines of the tubular fluid film 9. The water or other fluid medium which is passed downwardly through the tubular member 5, as the fluid film 9, discharges from the lower end of each of the tubular members 5 as a circumferential film around each of the streams of dropping pellets and adds to the liquid medium maintained in chamber 10.
Referring now specifically to Figure 2 of the drawing, the molten globules 4 are indicated diagrammatically as falling successively through the ring-like or tubular fluid film 9 within tube 5 such that they are cooled relatively rapidly by the fluid medium comprising film 9. The lower and outer periphery of the globules 4, particularly while they are at a high temperature and in a molten state, will effect the rapid vaporization of a minor portion of the fluid film and will provide some steam or vapor directly below the leading edge or bottom portion of the peripheral surface of each globule. This steam in turn tends to provide a slowing of the rate of fall or descent of each of the particles whereby each of the globules and resulting pellets are maintained within the length of the tubular film 9 and tube member 5 for a longer period of time thanthey would if they were allowed to fall entirely freely with no steam cushioning effect or rising countercurrent flow of steam. The length of the tubular member 5 and the tubular fluid film 9 must of course be correlated with the type of molten metal being formed into pellets, and the melting point or other physical characteristics particularly efiecting the cooling and solidification of the pellets so that they will be permitted to be suifijcienly solidified prior to leaving the lower end of tube 5 and entering the quenching liquid in a suitable receiving chamber. 7 i
It is to, be understood that the present drawing is diagrammatic and that the apparatus shown is not to be considered limiting, and further, that various minor mod- 4 tisatipa may be made in the a pa atus 9! its arra s?- ment within the scope of the present invention. The tu' bular members 5 are preferably round so that the interior fluid film 9 is likewise ring-like or of a cylindrical form, however, in some instances it may be desirable to provide a tubular member having a corrugated surface and in turn provide a descending fluid film therein which has an irregular cross-section, rather than a true ring-like film with a circular inner area. Also, it is to be noted that the present drawing indicates a closed top receiving chamber 10 so that there is a steam collecting zone providing for the upward flow of such steam that may be formed in chamber 10 through the plurality of forming tubes 5 and countercurrent flow with respect to the descending molten globules and pellets. However, where sufficient vapor or steam is formed directly within the flow path of the pellets and within the confines of the descending fluid film 9 to provide the desired cushioning and slowing down of the free fall of the pellets, then it may be unnecessary to provide a closed top receiving chamber 10. i
I claim as my invention:
l. A method for producing metal pellets which comprises passing successive globules of molten metal down,- wardly through the open space within a closely confining, downwardly moving, vertically elongated tubular film of cooling liquid, cooling and solidifying the globules during their descent through said space and discharging the resultant metal pellets from the lower confines of said tubular film.
2. The method of claim 1 further characterized in that said liquid is vaporizable at the temperature of the molten metal globules whereby a vapor is formed in and rises through the space within the tubular film to cushion the fall of the globules as they descend through said space.
3. The method of claim 2 further characterized in that said liquid comprises water.
4. A method for producing substantially spherical aluminum pellets which comprises passing successive globules of molten aluminum downwardly through the open space within a closely confining, downwardly moving, vertically elongated tubular film of water, cooling and solidifying the globules during their descent through end of the tubular member, a collecting chamber at the lower end of said member, and means for maintaining a continuous, downwardly moving film of liquid over the inner walls of the tubular member in close proximity to the metal globules within said member.
References Cited in the file of this patent UNITED STATES PATENTS 251,092 Bragg Dec. 20. 1881 496,044 Deniston Apr. 25, 1893 1,393,383 Linebarger Oct, 11, 1921 1,837,869 Jewett et a1 t Dec. 22, 1931 0 Morris Ap 2, 19.40 2,209,519 Halbrock et al. July 30, 1 940 2,230,617 Hoar Feb. 4, 1941 2,394,727 Taylor Feb. 12, 1946