Abstract:
A spiral trough separator for treating a slurry of ore particles in water to separate heavier fines from other particles includes a helical trough making a plurality of revolutions around a vertical axis and having the surface of the trough modified with protuberances to agitate the ore particles to allow entrapped impurities to be liberated and grooves to provide enhanced flow of the finer heavier ore fines closer to such axis to increase the efficiency of the recovery.

Description:
BACKGROUND OF THE INVENTION 
     Vertical helical or spiral ore separators have been known for the use of concentrating heavy mineral particles and separating them from lighter rock particles. Typical of such separators are those shown in U.S. Pat. Nos. 629,595, 840,354 and 4,597,861; and in South African Patent Application No. 842,673 filed Nov. 4, 1984. None of these provides a high quality separation due principally to the failure to agitate the slurry and its particles sufficiently to cause good lateral movement across the width of the slurry conduit perpendicular to the direction of travel of the slurry. 
     It is an object of this invention to provide an improved helical ore separator. It is another object of this invention to provide an improved helical ore separator having a modified flow surface. Still other objects will become apparent from the more detailed description which follows. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention relates to a vertical axis helical trough separator having 3-10 revolutions about said axis, a feed end at the top of said separator and a discharge end at the bottom of the separator, the trough having an internal concave surface adapted to direct the flow of a slurry of solid particles in a liquid medium in a downward helical path, the surface containing a plurality of upwardly projecting spaced protuberances to agitate the ore particles thus permitting entrapped impurities interspersed with the heavier fines to be released. Preferably a plurality of downwardly projecting spaced grooves at selected locations between the feed end and the discharge end spacedly follows the protuberances. 
     In preferred embodiments of the invention the helical trough has 4-8 revolutions in its length with the middle revolutions being provided with a plurality of protuberances and spiral grooves in the flow path of the slurry, and the upper and lower revolutions having a smooth surface in the flow path of the slurry. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which: 
     FIG. 1 is a front elevational view of the separator of this invention; 
     FIG. 2 is a top plan view of the separator of this invention; 
     FIG. 3 is a perspective schematic view of a portion of the helical trough showing protuberances in the flow path of the slurry; and 
     FIG. 4 is a perspective schematic view of a portion of the helical trough showing spiral grooves in the flow path of the slurry. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention can best be understood by reference to the attached drawings. 
     The separator as seen in FIGS. 1-2 is a vertical helical trough 10 symmetrical about vertical axis 11 and including 4-8 revolutions around vertical axis 11 from the upper feed end 14 to the lower discharge end 15. In general this is used to concentrate the higher specific gravity mineral particles in an aqueous slurry of ore particles introduced at feed end 14 and allowed to flow downwardly by gravity to discharge end 15 where the heavier particles will concentrate closer to axis 11 and lighter particles will concentrate farther away from axis 11. Thus the product can be represented by a first stream at arrow 20 representing the heavier mineral particles and a second stream at arrow 21 representing the lighter weight gauge particles that may be discarded or recirculated. A splitter means 28 may also be employed to direct the streams to different outlets, as is common in the art. 
     The helical trough 10 may be supported in any manner appropriate for the purpose, such as that shown here of a column 12 and/or a plurality of supporting arms 13 extending radially outward from column 12 and attached at their distal ends to trough 10. Trough may be made in any size which will handle the separations required. Generally a size of between 4 and 12 feet vertical length and 2-3 feet in trough diameter with 4-8 revolutions in the total length is sufficient for most purposes. 
     The principal features of this invention lie in the surface modifications of the flow path of trough 10. The concave internal surface 27 of trough 10 which serves as the conduit for the slurry may be modified by a plurality of small upwardly projecting protuberances 23, such as hemispheres of 1/4 to 1/2 inch in diameter or by a plurality of spiral grooves 24 projecting downwardly in the internal surface 27, e.g., 0.01 to 0.05 inch wide and deep. Generally, the protuberances 23 extend laterally across the flow path of the slurry (radially with respect to axis 11), and if they are small, separate protuberances, are spaced apart in checkerboard arrangement (diamond formation) so as to prevent any unobstructed spiral channels in the direction of flow as indicated by arrow 22. Grooves 24 are arranged in a spiral direction so as to direct the flow of the slurry and its ore particles toward axis 11. Thus, the flow tends to be directed away from outer edge 25 of trough 10 and towards inner edge 26 of trough 10. The direction of grooves 24 is not parallel to outer edge 25 but is in a spiral cutting across flow direction 22 toward the inner edge 26. The surface modification of projecting protuberances tends to improve separation by agitating the ore particles and allowing entrapped impurities to be further liberated and the spiral grooves influence the flow of the finer heavier particles closer to vertical axis 11 improving recovery. 
     The pattern of individual protuberances 23 and grooves 24 may be varied to suit individual ore samples. 
     The vertical pattern of surface modifications can also be varied to suit particular conditions. Thus, a preferred arrangement is for upper portion 16 to be 1-3 revolutions of the helical trough 10, middle portion 17 to be 1-3 revolutions of the helical trough 10 and the lower portion 18 to be 1-3 revolutions of helical trough 10. Preferably, in middle portion 17 the surface modifications are protuberances 23 and grooves 24, with the upper portion 16 and lower portion 18 being smooth and free of any modifications. 
     In certain circumstances, it may be desirable, depending on many factors including the density of the slurry and the materials to be separated, also to provide protuberances and/or grooves in some parts of upper portion 16 and some parts of lower portion 18. For example, protuberances and/or grooves may be positioned in the lower parts of upper portion 16 and/or the upper parts of the lower portion 18 to obtain more efficient separation. In any event there always should be a beginning part of upper portion 16 and an ending part of lower portion 18 that is smooth and free of protuberances and/or grooves, In certain circumstances in any part of the spiral trough separator where protuberances and grooves are both used, the protuberances should be upstream and the grooves downstream, respectively, of each other. This can be maintained whether there is only one section of protuberances followed by a section of grooves, or whether there is a series of such protuberances followed by grooves; the section farthest downstream being grooves. 
     While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.