Pinched Sluices and Cones and Spirals
Pinched Sluices and Cones and SpiralsPinched SluicesPinched
sluices of various forms have been used for heavy minerals
separations for centuries;An inclined trough made of wood,
aluminum, steel and fiberglass, about 1 m long, narrowing from
about 200 mm in width at the feed to about 25 mm at the
discharge;
Conceptual Diagram of Basic Principle of Pinched Sluice
ConcentratorPulp of between 50-60% solids enters gently and
stratifies as it descends; The materials squeeze into the narrow
discharge area. The piling causes the bed to dilate and allows
heavy minerals to migrate and move along the bottom. The lighter
particles are forced to the top. The resulting strata are separated
by a splitter at the discharge end.
Reichert ConeA wet gravity concentrating device designed for
high-capacity applications;Its principle of operation is similar to
that of a pinched sluice, but the pulp flow is not restricted or
influenced by side-wall effect, which is somewhat detrimental to
pinched-sluice operation;High capacity and low operating costs;A
single unit comprises several cone sections stacked vertically, so
as to permit several stages of upgrading;The cones are made of
fiberglass and are mounted in circular frames over 6 m high; each
cone is 2 m diameter and there are no moving parts in the unit
The system shown is one of the many possible systems using
double and single cones, together with trays, which direct heavy
minerals fractions from the center draw-off areas of the cones to
external collection boxes
The feed pulp of between 55-70% solids by weight is distributed
evenly around the periphery of the cone;As it flows towards the
center of the cone the heavy particles separated to the bottom of
the film;This concentrate is removed by an annular slot at the
bottom of the concentrating cone; the part of the film flowing over
the slot is the tailing
SpiralsMany varied applications in mineral processing; their
most extensive usage has been in the treatment of heavy mineral san
deposits, such as those carrying ilmenite, rutile, zircon, and
monazite;In recent years, in the recovery of fine coal
Humphreys spiral first commercial application being on
chrome-bearing sands; it is composed of a helical conduit of
modified semicircular cross-section
Feed pulp, of between 15-45% solids by weight and in the size
range 3 mm to 75 m, is introduces at the top of the spiral and, as
it flows spirally downwards, the particles stratify due to the
combined effect of centrifugal, the differential settling rates of
the particles, and the effect of interstitial trickling through the
flowing particle bed;Ports for the removal of the higher
specific-gravity particles are located at the lowest points in the
cross-section;The grade of concentrate taken from descending ports
progressively decreases, tailings being discharged from the lower
end of the spiral conduit.
The main separation effect is due to hindered settling, with the
largest, densest particles reporting preferentially to the
concentrate, which forms in a band along the inner edge of the
stream (Mills, 1978)
Spirals are made with slopes of varying steepness, the angle
affecting the specific gravity of separation, but having little
effect on the concentrate grade and recover;Shallow angles are used
to separate coal from shale, while steeper angles are used for
normal heavy mineral-silica separations;The steepest angles are
used to separate heavy minerals from heavy waste minerals Example:
zircon (SG = 4.7) from kyanite and staurolite (SG = 3.6)
