The increase in the ore throughput with increasing feed
concentration during spray and semi-rope discharges
(Fig. 6) is the same as that shown in Fig. 3 (for the spigot
loading). While the ore throughput increase during roping
(Fig. 6) is a reflection of the increase in the ore flow-rate
through the overflow; the ore flow-rate through the underflow
remains constant with further increase in the feed concentration
once roping commences (Fig. 3).
During the transition to roping the medium flow-rate at
the underflow dropped abruptly, and this coincided with a
drastic rise in the medium flow-rate at the overflow; indicating
that the collapse of the air core at the spigot resulted
in a transfer of medium from the underflow to the overflow.
The steady drop in medium flow-rate at the overflow
during roping is a consequence of increased quantities of
silica particles that have been displaced to the overflow as
shown in Fig. 3.
Furthermore, there was a transfer of medium from the
overflow to the underflow with increasing feed ore concentration
before roping commenced (Fig. 7). This is thought
to be a consequence of the interaction between the silica
particles and medium, resulting in the ‘dragging’ of medium
to the spigot.
The above-mentioned transfer of medium from the
overflow to the underflow with increased addition of silica
particles into the cyclone was further confirmed by the
behaviour of the density differential parameter (Fig. 8).
Density differential refers to the difference between the
underflow and overflow medium densities. The decrease
in the differential is a consequence of the dilution of the
high-density medium at the underflow by the low-density
medium from the overflow that was carried over to the spigot
by the ore particles. The actual values of the density
differentials shown in Fig. 8 might change in the presence
of low-density ore particles or floats (that would normally
exit at the overflow), due to the consequent interaction
between the floats particles and medium. The trend of the
curve in Fig. 8 is, however, not expected to change, thus,
spigot overloading should always be associated with
The increase in the ore throughput with increasing feedconcentration during spray and semi-rope discharges(Fig. 6) is the same as that shown in Fig. 3 (for the spigotloading). While the ore throughput increase during roping(Fig. 6) is a reflection of the increase in the ore flow-ratethrough the overflow; the ore flow-rate through the underflowremains constant with further increase in the feed concentrationonce roping commences (Fig. 3).During the transition to roping the medium flow-rate atthe underflow dropped abruptly, and this coincided with adrastic rise in the medium flow-rate at the overflow; indicatingthat the collapse of the air core at the spigot resultedin a transfer of medium from the underflow to the overflow.The steady drop in medium flow-rate at the overflowduring roping is a consequence of increased quantities ofsilica particles that have been displaced to the overflow asshown in Fig. 3.Furthermore, there was a transfer of medium from theoverflow to the underflow with increasing feed ore concentrationbefore roping commenced (Fig. 7). This is thoughtto be a consequence of the interaction between the silicaparticles and medium, resulting in the ‘dragging’ of mediumto the spigot.The above-mentioned transfer of medium from theoverflow to the underflow with increased addition of silicaparticles into the cyclone was further confirmed by thebehaviour of the density differential parameter (Fig. 8).Density differential refers to the difference between theunderflow and overflow medium densities. The decreasein the differential is a consequence of the dilution of thehigh-density medium at the underflow by the low-densitymedium from the overflow that was carried over to the spigotby the ore particles. The actual values of the densitydifferentials shown in Fig. 8 might change in the presenceof low-density ore particles or floats (that would normallyexit at the overflow), due to the consequent interactionbetween the floats particles and medium. The trend of thecurve in Fig. 8 is, however, not expected to change, thus,spigot overloading should always be associated with
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