Abstract:
A separator includes a vessel having feed means for feeding liquid containing suspended solids into the vessel, a liquid outlet, a sludge outlet, and at least one settling member located above the sludge outlet, the settling member having an inner settling surface and outer settling surface, with the inner settling surface surrounding an aperture extending through settling member.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a separator for separating solids suspended in a liquid from the liquid. 
     Separators have been provided with settling members which have settling surfaces onto which solids can settle. The settling members have been provided in the form of cones, spirals or inclined angle-iron sections. 
     SUMMARY OF THE INVENTION 
     According to the invention a separator includes a vessel having; 
     feed means for feeding liquid containing suspended solids into the vessel; 
     a liquid outlet; 
     a sludge outlet; and 
     at least one settling member located above the sludge outlet, the settling member having inner and outer settling surfaces, with the inner settling surface surrounding an aperture extending through the settling member. 
     The settling member may be endless and the inner and outer settling surfaces may be connected together at an apex. Preferably the inner and outer settling surfaces diverge away from one another from the apex. In one form of the invention the apex is circular in plan view. In another form of the invention the apex is polygonal in plan view. 
     The feed means preferably includes a downwardly extending feed conduit. 
     A recycle conduit may be provided for recycling liquid into the feed conduit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional side view of a separator according to the invention; 
     FIG. 2 is a side view on line II—II of FIG. 1; 
     FIG. 3 is a plan view of FIG. 1; 
     FIG. 4 is a plan view of settling member according to the invention; 
     FIG. 5 is a cross-sectional side view on line V—V of FIG. 4; 
     FIG. 6 is a cross-sectional side view of a separator according to another embodiment of the invention; and 
     FIG. 7 is a partly cut-away perspective view of the separator of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring firstly to FIGS. 1 to  3 , a separator  10  includes a vessel  12  having a feed conduit  14  with a diverging feed section  15 , a liquid outlet  16  from a launder  18 , a sludge outlet  20 , three endless settling members  22  and a recycle conduit  24  having a collector  25 . 
     Referring now to FIGS. 4 and 5, each endless settling member  22  has a substantially horizontally extending apex  26 , an aperture or bore  28 , an endless inner settling surface  30  and an endless outer settling surface  32 . The settling surfaces  30  and  32  diverge downwardly and outwardly from the apex  26  towards their respective lower ends  34  and  36 . 
     Each settling member  22  is moulded from glass reinforced plastic or fibre reinforced plastic or is fabricated from suitable material. The inner and outer settling surfaces are coated with a 3 mm thick, high density polyethylene coating to facilitate the flow of particles over the surfaces. 
     The settling member  22  is hollow and is filled with particulate material. Although the settling member has a base  38 , it will be appreciated that the settling member may not have a base, in which case water would occupy the space between the settling surfaces  30  and  32 . 
     In use, liquid containing suspended solids and a flocculant is introduced into the feed conduit  14  below the launder  18 . As the suspension moves downwardly, its velocity decreases in the diverging feed section  15 . The suspension is directed peripherally outwardly as it flows between the annular gap between the diverging feed section  15  and the collector  25 . Smaller solid particles rise upwardly through the annular gap between the sidewalls of the vessel  12  and the feed conduit  14 . A floc bed (not shown) is formed between the diverging feed section  15  and the sidewalls of the vessel  12 . The smaller solid particles agglomerate within the floc bed and settle downwardly towards the settling members  22 . The downwardly settling agglomerated solid particles from the floc bed, and the downwardly settling larger solid particles from the feed conduit, settle on the inclined endless settling surfaces  30  and  32 . The solids slide downwardly along and off the settling surfaces  30  and  32  to collect in the form of a sludge below the settling members  22 . That is, the lower end  36  of the outer settling surface  32  is spaced from an inner surface of the vessel  12  and forms a drop-off edge permitting solids to side downwardly therefrom. The sludge is discharged from the vessel  12  through the sludge outlet  20 . 
     Relatively clean water flows upwardly. Some of the upwardly flowing relatively clean water is collected in the collector  25 , whereupon it rises upwardly through the recycle conduit  24  to be discharged into the feed conduit  14  to dilute the feed. The diameter of the bottom of the collector  25  is substantially the same as the diameter of the apex  26  of the settling members  22 . The remaining relatively clean water, not collected in the collector  25 , flows upwardly through the annular gap between the sidewalls of the vessel  12  and the feed conduit  14  into the launder  18 , from whence it is discharged via the liquid outlet  16 . 
     The total surface area of the inner and outer settling surfaces on one of the settling members is more than double the total settling surface area of two cones of the same height and inclination as one of the settling members. The applicant believes that this increased settling area will result in a more efficient separation process. In addition, the outer settling surface  32  is located more directly in the pathway of the downwardly settling solid particles than the settling surface  30 . The applicant believes that this will also result in a more efficient separation process. 
     Referring now to FIGS. 6 and 7 a separator  10 . 1  is shown which is similar to the separator  10 . The suffix . 1  is used to denote parts in the separator  10 . 1  corresponding to parts in the separator  10 . The separator  10 . 1  operates in the same manner as the separator  10 , and fresh feed is fed into the top of the feed conduit  14 . 1 . 
     It will be appreciated that many modifications or improvements of the invention are possible without departing from the spirit or scope of the invention.