US2687804A - Process and apparatus for the specific gravity classification of bulk substances utilizing finely granulated separating media - Google Patents

Description

W. VOG EL ATUS Aug. 31, 1954 2,687

PROCESS AND APPAR FOR THE SPECIFIC GRAVITY CLASSIFICATION OF BULK SUBSTANCES UTILIZING FINELY GRANULATED SEPARATING MEDIA Ongmal Flled July 23, 1947 2 Sheets-Sheet l Aug. 31, 1954 w. VOGEL PROCESS AND APPARATUS CLASSIFICATION OF B 2,687,804 FOR THE SPECIFIC GRAVITY ULK SUBSTANCES UTILIZING FINELY GRANULATED SEPARATING MEDIA Original Filed July 23, 1947 2 Sheets-Sheet 2 Patented Aug. 31, 1954 PROCESS AND APPARATUS FOR THE SPE- CIFIC GRAVITY CLASSIFICATION OF BULK SUBSTANCES UTILIZING FINELY GRANU- LATED SEPARATING MEDIA Walter Vogel, Santiago, Chile Original application July 23, 1947, Serial No.

763,121. Divided and this" application August Claims priority, application Switzerland September 11, 1946 11 Claims. 1 I The present invention relates to the process and apparatus for the specific gravity classificationof bulk substances utilizing finely granulated separating media. This application is a divisional of my prior application Serial No.

763,121gfiled July 23,1947, now patented under No. 2,612,269, dated September 30, 1952, and entitled Process and Apparatus for Specific Gravity Classificationof Bulk Substances.

As indicated in'said application, the separating media may be'sand, gravelor other material reduced to suitable size inconjunction with apparatuseffective to carryout the process.

More specifically the present invention relates to a process and apparatus for specific gravity classification of bulk substances in which the finely granulated media in the material to be separated flow in strata in an inclined stream greater than the natural angle ofrepose of the media. and includesfthe discharge of the media and the material after first changing the directionof flow thereof at different relative velocities.

More particularly the invention relates to a dryprocess for separating solid materials in accordance with theirspecific gr'avities' in a continuously moving stream of finely divideddry separating medium including feeding the material tobe separated andthemedium at one'end of the zone disposed at an angle at least greater than thematerialangle or repose; changingthe movement of thestream from a straight line flow to an arcuate flow tangentially to the straight line now thereby imparting different relativevelocities. to the strata, separating the strata in accordance with the velocity thereof and removingthe separated materials from the respective strata.

From GermanPatent740,005and a's'set forth in my above identified prior application, it is knownto separate in a stream of finely granulated separatingmedium flowing in atrough means withthevelocity of thediiferent layers increasingfrom thejlower to the upper layers. In such instances the stream with separating medium flows inthe manner of a liquid in which, inaccorda'nce with the Archimedean principle, the heaver particles" gradually sink to'the bottom of theseparating meduim and. the lighter particles' are carried to thetop. With'such'arrangeinents the diirerentvelocities of the advafice movement of the finely'granulated separating medium is-"achieved by thechcice of an gle of-slope' of the trough within which process is effected, as well as by adjiistinent'ofthe blade orthe like which dividesthe stream'of separat- 2 ing medium and which blade is located at the discharge end of the trough. As pointed out in my prior application, such known processes do not accomplish satisfactory separation since the different velocities upon which principle the process is predicated, do not remain constant throughout the separating medium until the same reaches the discharge end Therefore, and consistent with the statement of the invention, it is an object of the present invention to provide a process and an apparatus that eliminates such drawbacks in the prior art in a manner diiferent from that embodied in my prior application Serial No. 763,121 now Patent No. 2,612,269 and which will permit adequate separation, the intensity of which can be regulated at will since the invention, provides for the discharge of the difierent layers of separating medium at different velocities.

Specifically the present invention has for an object to provide an improved process and apparatus for effecting specific gravitybulk classification in which separating media flows through a trough sloping at an angle at least greater than the natural angle of repose and by discharging the media in the from of a nappe so that the layers more distant from the center of the arc traverse a greater distance in a given period of time compared with the layers closer to the center of the nappe.

In the accomplishment of the invention as hereinabove set forth, increased velocity is imparted to the advance movement of the upper layers of the separating medium. However the a present invention has for an object to provide for an inversion of this principle by increasing the velocity of the lower layers by the provision of a conveyor trough sloping upwardly at an angle greater than the angle, of repose in which the rate of feed of the lower layers is greater thanthe rate of feed of the upper layers.

The specific gravity classification of more than two substances can very conveniently be accomplished by means of this invention and for this purpose two or more superimposed layers of separating media diminishing in specific gravity fromthe bottom to the top, are used simultaneously. If for example it is desired to obtain three products, two finely granulated separating media ofdiverse specific gravity are used, thatis,an upper layer of lesser specific, gravity over a lower layer of greater specific gravity. These" layers advance in the trough simultaneously. At the discharge end of the trough the light weight substance will be in the uppermost layer, the middle weight substance will be in the intermediate layer, and the heavy weight substance will be in the lowermost layer, and. same may be removed therefrom by screening each layer individually so as to recover the separating media for re-use in the trough aforementioned.

It is advantageous to use separating media having similar angles of repose. In some cases, in order to avoid intermingling of the layers, it may be expedient that the granulations of the separating medium of greater specific gravity be smaller than the granulations of the separating medium of lesser specific gravity. It may also be advantageous to have between the two layers of separating media of diverse specific gravities, an intermediate layer composed of a mixture of the adjoining layers, which mixture generally forms spontaneously during operation of the apparatus covered by this invention.

In order to maintain a constant separative in tensity, the specific gravities as well as the angles of repose of the granulates of separating media should be maintained without variation. For this purpose the invention may be complemented with means for the continuous elimination of residues accumulating during the separating process, as well as for elimination of the secondary granuiations that gradually accumulate in the separating media through screening thereof after the division of the diverse layers, which diminishes the purity thereof as a result of the inclusion of extraneous material.

For greater convenience it is possible to pass through a cleaning device, a partial stream of the separating medium used in any closed circuit. The method used may be, for example, either hydromechanical separation in a decantation machine, or pneumatic cleaning by means of air currents. If the hydromechanical method is used, the cleaned separating medium must be dried before being re-used in the separating process.

Many advantages are derived by using as a separating medium a material capable of being magnetized, the cleaning of which may subsequently be accomplished by magnetic separation, by merely passing a partial stream of the separating medium over an adequate magnetic field.

The purpose of this invention may also be achieved by using as a separating medium, hollow iron balls, in sizes and wall thicknesses proportionate to the specific gravity desired. It is likewise possible to use cast materials such as metallic alloys or glass, slag and ceramic materials, such as porcelain or materials held together by means of resins or other binding agents, including ferrous aggregates, in any given size required, and also, if necessary, spherical in structure. The use of such materials is particularly applicable in the separation of large bulk substances, inasmuch as in such cases it is thereby possible to select the most adequate proportion of the size of granulation of the separating media.

Finally, advantages may be derived by selecting as a separating medium a material whose hardness is greater than the hardest residue of the substance to be separated, so that during continuous contact thereof with the substance being separated in the trough, the residue as well as the secondary granulations will continue to disintegrate as a result of friction with the harder separating medium, and can then be separated therefrom by a simple screening operation. For this purpose the size of granulation chosen for the separating medium must be larger than the size of the perforation or mesh of the screen used therefor. For example, in the separation of stock-piled bulk coal, the separating media used may be hollow cast steel or basalt balls, or solid glass balls 8 to 10 in diameter. Thus a 12 mm. mesh screen may be used to recover the substance to be separated, and an 8 mm. mesh screen may be used to recover the separating medium from the residue, and if the screen be combined with a conveyor, it will be possible to return in a continuous manner, the screened separating medium to the principal circuit of the process effected by this invention.

The invention will now be described with reference to particular apparatus illustrated in the accompanying drawings, in which:

Figure l is a diagrammatic view in vertical cross-section of one form of the apparatus;

Figure 2 is a diagrammatic View in vertical cross-section of another form of the apparatus,

and

Figure 3 is a diagrammatic view partially in vertical cross section illustrating the form of apparatus of Figure 1 embodiedin a circuit including the return of the separating media to the troughs and the cleaning and drying of a partial stream thereof.

As illustrated in the drawing, the apparatus comprises a downwardly sloping covered trough i including a bottom i which trough is sloped at an angle greater than the angle of repose of the separating media. At the upper or head end of the trough is a feed hopper which includes funnels 2 and 3 for receiving the separating media and between these funnels there is provided a duct 3 through which is introduced the substance to be separated. The discharge end of the trough i terminates over roller 5 rotatably mounted on horizontal shaft 6 and driven by suitable transmission means including motor M. The bottom i of the trough is disposed in tangential relation with respect to the surface of the roller ii. The roller includes side extensions l of a height or radial distance from the center of shaft ii such that they approximate the height of the side walls of the trough i. These side extensions i move very close, during rotation, to the side walls of the trough and as illustrated the same are partly covered by a conveyor belt 8 passing over rollers 9 and ii constituting guide rollers, one of which is driven from the motor. As indicated this belt bearing on and moving with the rim or periphery of the side extensions ll diverts the flow of medium and materials passing over the rotating roller 5. The action is such that the flow through the space defined by the surface of the roller, the inner surface of the side extensions and the conveyor belt is such that the superimposed layers of separating medium furthest removed from the surface of the roller advances at increased velocity. As the separating medium discharged by the belt passes over the lower pulley is it is divided into partial streams by one or more dividing blades l i from which partial streams the diverse fractions of the substance to be separated are recovered individually. It is believed clearthat the surface of the roller 5 impells the separating medium and additionally the conveyor belt t impells the medium so that in the flowing arcuate stream between the discharge end of the trough i and the guide roller it the action of the belt imparts increased velocity to the layer of medium furthest removed from the center of the roller 5 and closest the surface of the belt.

In connection with separation effected by the I aforedes'cribecl apparatus, the relative movement downward from each strata tothat below renowing the angle of reposa fluidiaes the sand-ymediurn; I

In connection withthearrangement shown in Figure 2 the apparatus embodiedtherein con stitutes a kinematic inversion of the relationship shown inFigure 1. In Figure 2 the conveyor trough I2 is again a coveredtrough andslopes upwardly toward its 'dischargeend at an angle greater than' the angle of repose ofthe separat ingmedium. At the lower end ofthe trough, that is at that portion-preceding the rectilinear section, there is provided an a-rcuate platel3 which in effect constitutes a feed hopper; This arcuate plate is spaced above the bottom I4 Ofllh trough which is similarly arcuateatitsiower end and between the plate and the bottom of the trough and upwa-rdly along thetroughmoves the conveyor I 5; 'Iliecdnveyor passes over spaced rollers IB'and II; the roller I I being at the bottom of the trough; Separating media: isied through inlet funnels I8 and I9 and the material to beseparated is introducedthrough a duct: 20 disposed between thefunnels. This feedhopper relationship including the funnels, duct and the arcuate plateis such that the separating media aresupplied at difierent rates ofintensity"to the rectilinearsefction of the trough in which section separation is effected. A .conveyorbelt I5 maybe composed of segments travelling along the bottom of the trough and this belt advances'the separating media containing the substance to be separated. If desired the belt may "be eliminated and the material may be advanced upthe trough by f orcefeeding utilizing suitable pumps in conjunction with the funnels I8, I9 and the inlet duct 210. As indicated in thedrawing the belt after passing over the upper pulley IE on its return run passes over pulley I I whose perimeteris above the arcuate portion of thebottom I4 and belt enters thefeed hopper or arcuate portion between the plate I3 and bottom I4. The movement of the beltadvances the lower layer of the separating medium in the trough at a higher velocity than the upper layer thus" creating lrela tive movements betweenadjacent layers and producing the same separating eifect as is efiected in the preceding arrangement with the result that the lightweight particlesare carried to the top of the trough thereby effecting desiredseparation. After the strata of medium and the materials entrained therein pass over upper pulley IBthe stream is divided into partial streams by one or more adjustable blades 12I and from which partial streams the different fractions of the substances to be separated are recovered by individually screening these partial streams. a

The arrangement of Figure Zis of particular importance with regard to the classification of substances composed oflarge size granulations such as bulk coal Generally speaking, bulk coal is classified by methods including hand picking which involve high costs and great loss of time when cons ide ring the output factor; With the present invention as disclosed in Figure 2; including the upwardly sloping trough, the' structural relationship is provided1which permits housing the entire plant in a rather 'low volume of space since there is sufiicient vertical difference between the front feed and the upper dischargeend to permit of installation of screens and other complementary equipment operable onthe'material forseparating media andreturnin'g thesame to the feed hopper. Withthis differencein elevation" such equipmentcanbeinstalled in a suhstantially horizontal position. The means for returning the media to the troughs ihcludes a hopper or bin 29 which receives media after it 'has passed through screen S. The discharge from-this hopper isdeposited on'aconveyorbelt which deliversthe media to another conveyor such as a bu'cketelevator 31. This elevator feeds the media toa conveyor 32 which is provided with blades, not shown,

to 'di'vertthe mediafro'm the conveyor belt to fall into the'funnelsIfl and I9.- Atrough 33 feeds the substance to be separ'atedinto the ducts 20.

In view of this lows'pac'eiactor and the fact that the process involved is a dry process that is very simple to operate, the present invention-is particularly suitable for underground installation. In other words the apparatus of Figure 2 can be installed rightin the mine in connection with the grading of coal thereby providing an trated in Figure 3 in which cleaning devices in clude receptacles whichreceive the fractions of the substances being separatedfrom the partial streams. In other wordsthe blade-22 divides the discharge into partial streamswhich flow over suitable screens denoted at S andthe fractions of material to be separated pass ofi of these screens into "suitable troughs or hoppers H for conveyance to their final destinations The granulatedmedium that passesthrough j the screen S contains the residue and secondary granulations and this granulated medium is discharged into a-bin or hopper 23 from whieh it passes to a conveyor belt which carries it to asuitable elevator such as abucket elevator 25 which carries it to another conveyor 26 arranged over the funnels'2 and 3. The conveyor that is above the feed funnels is providedwith suitable scrapers, notfshown, which divert medium into the respective hoppers and further divert a'partial stream PS into a decantation machine 27 which removes residue and secondary granulations from the 1 separating medium. The clean separating medium CS M passes through a drying drum 28 after it leavesthe decantation machine and is returned to the conveyorbeltj 2Aearrying the screened medium from adjacent thedischargeend of the trough. The justprevibusly described arrangement cleans only a partial stream of the medium. However it -"is obvious that the entire stream of separating medium passing through the screen at thedischarge end offthetrough may pass directly to thedecantation machine thence through the drum and thence to a conveyor belt "arranged above the feed hoppers from which it is diverted into the respective hoppers. Obviouslyinstead of a wet process theseparatingmedium from ad- .jacentthe discharge end canbecleanedby air current.

It is therefore clear that l have provided a process and apparatus-for separating in a specific gravity classification of bullc substances utilizing finely granulated separating medium advancing in an inclined troueh'the f ed of the m t r through the trou h. being such that the velocity of different layers of media in the trough is different and the stream flowing in a straight line through the trough is diverted to an arcuate fiow tangentially to the base of the trough in which different strata of the stream have different relative velocities.

What. I claim is:

l. A dry process for separating solid material in accordance with their specific gravities in a continuously moving stream of finely divided dry separating media including feeding the material to be separated and the media at one end of a zone disposed at. an angle sloping downwardly at least slightly greater than the natural angle of repose, changing the movement of said stream from a straight line flow to an arcuate flow tans ntially to the straight line of fiow, thereby imparting different relative velocities to the strata, separating the strata in accordance with the velocity thereof and removing the separated materials from the respective; strata. I

2. Aprocess as described in claim 1 in which the stream is confined during its change of movement and the. areuatefiow is of sufficient extent to divert the stream back toward its point of feed and discharging the stream in an arcuate flow prior to separation of the strata.

3. A dry process for separating solid materials in accordance with their specific gravities in a continuously moving stream of finely divided dry separating media including feeding materials to be separated and the media to one end of a separating zone, confining the material and media into a flowing stream of sufficient length and depth and at an angle greater than the natural angle of slope of the media permitting relative vertical components of movement in the strata in the streain following. the angle of repose of the media to provide a fiuidizing flow, imparting an arcuate movement to the stream in a tangential direction with respect to the straight line fiow while simultaneously imparting increased velocity to one strata so that the strata with the materials to be separated entrained therein move at different relative. velocities, discharging the strata while moving at different relative velocities, separating the strata into partial streams each con taining material of different specific gravities and separating the material from the partial stream.

i. The process as defined in and by claim 3 in which the straight line flow is directed downwardly and the increased velocity is imparted to the upper strata.

5. The process as defined in and by claim 3 in which the major component of straight line fiow is directed upwardly and the increased velocity is imparted to the lower strata.

6. The process as defined in and by claim 3 and including the return of separating media and reintroducing thereof into the feed end of the zone.

'7. An apparatus for dry media separation of solid materials in accordance with their specific gravities including a trough disposed at an angle at least slightly greater than the natural angle of repose of the media and materials, vertically extending and longitudinally aligned feeding means at the upper end of the trough including means for feeding a mass of finely granulated separating medium to form a lower stratum, means for feeding finely granulated separating medium to form'an upper stratum and means for feeding the materials to be separated interme' diate said strata, the relative movement downward from each strata to that below following the angle of repose fiuidizing the medium to entrain particles of material of different specific gravity in the diiierent strata of medium, a member having a surface supported for movement in an arcuate path tangentially to the bottom, of the trough so that the member receives strata from the trough and impells the same in an arouate path imparting greater velocity to at least one strata, said strata discharging with difierent relative velocities, and means for separating the strata into partial streams in accordance with their specific gravities.

8. An apparatus as defined in and by claim '7 in which the trough slopes downwardly and the member imparts increased velocity to the upper strata.

9. An apparatus as defined in and by claim 7 in which the trough further includes a major portion being inclined upwardly at an angle greater than the natural angle of repose, said member comprises aconveyor belt, the trough includes a downwardly sloping portion preceding the upwardly sloping portion, and means supporting and guiding the conveyor belt so that a portion thereof follows an arcuate path disposed tangentially with respect to the bottom of both said trough portions, said belt moving through out said upwardly sloping trough portion to impart greater relative velocities to the strata flowing upwardly with the lowermost strata having higher velocity.

10. In an apparatus for separating materials according to specific gravities, the combination of an inclined trough having upper and lower ends, said trough confining a flowing stream of finely granulated stratified separating medium and material to be separated therein and said trough being at least slightly more inclined than the natural angle of repose of said medium so that the mass of medium and materials flows downwardly, means at the upper end of the trough for feeding the materials to be separated and the medium to the trough, rotatable conveying means at the lower end of the trough rotating in such direction as to continue the fiow of said stream in an arcuate path, said conveying means receiving and carrying strata of said stream at different velocities corresponding to the radius of the circle they have to follow, said conveying means comprising a roller so disposed that the bottom of the trough is tangent thereto, disc means at the sides of said roller confining the how, and a moving belt transverse to and adjacent said disc means and following an arcuate path receiving and conveying the medium therein around the roller axis.

11. In an apparatus for separating materials according to their specific gravities, a combination of certain means including separate longitudinally aligned channels including a central channel to receive and feed materials to be separated and additional channels adjacent thereto respectively receiving masses of finely granulated separating media, an inclined trough extending downwardly from said channels at an angle greater than the natural angle of repose of the media so that the materials and media flow therethrough superimposed strata, said trough including an arcuate portion disposed tangentially with respect to the bottom thereof changing the direction or" flow of the strata, said arcuate portion terminating in an upward inclination re ter han the angle of slope and said trough continuing said upward flow a substantial dis? 9 tance, means for conveying the strata through said upwardly sloping portion and for imparting increased velocity to the lowermost strata, and means for discharging the strata at the upper end of the upwardly sloping portion in partial streams in accordance with their specific gravities and means for removing the media from said streams.

References Cited in the file of this patent UNITED STATES PATENTS Number Name 1 Date 119,757 Griscom Oct. 10, 1871 163,298 Buechley May 18, 1875 239,994 Truax Apr. 12, 1881 463,305 Hofiman Nov. 17, 1891 800,293 Hauge Sept. 26, 1905 1,028,797 Stromborg June 4, 1912 Number Number

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