Note: Descriptions are shown in the official language in which they were submitted.
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"HYDRO-CYCLONE UNDERFLOW MONITOR"
FIELD OF THE INVENTION
This invention relates to a hydro-cyclone underflow
monitor and, more particularly, to a monitar which
is arranged to measure a variable feature
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associated with the shape of the stream of slurry
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emanating from an underflow outlet, with a view to
acquiring information as to density, flow rate, or
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other variable dependant on the performance of the
hydro-cyclone, or a combination of one or more of
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/these for
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these for the purposes of controlling the operation
of the hydro-cyclone or its associated circu~t.
BACKGROUND TO THE INVENTION
Hydro-cyclones are widely used in the metallurgical
industry for the separation of particles in a
slurry according to their size and/or density.
Common on-line measurements used in connection with
the operation of hydro-cyclones are the flow rate
and density of the slurry being fed to the
hydro-cyclone and the inlet pressure of such slurry.
The efficient operation of a hydro-cyclone requires
it to have a core of air along its axis with an
open discharge at the underflow and an overflow
containing bubbles of air. The measurement of the
flow or density of either discharge stream is
15 therefore difficult.
Because a hydro-cyclone reacts differently to
different compositions of the feed slurry, its
response to changes can be used to infer
information about material in its feed or discharge
/streams.
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streams. Some information can be obtained by the
measurement of the lnlet pressure, but this is so
highly correlated with the feed flow and density
measurements as to be of little practical use in
this regard. On the other hand, applicant
believes that the shape of the cyclone underflow is
a rich source of useful information concerning the
circuit in which the cyclone is installed.
It is, accordingly, the object of this invention to
provide a method of controlling the operation of a
hydro-cyclone, or, alternatively, a circuit of
which a hydro-cyclone is a component part, in which
the shape, or a variable associated with the shape
of the underflow slurry from the hydro-cyclone is
employed as a measured control variable.
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SUMMARY OF THE INVENTION
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In accordance with this invention there is provided
a method of controlling the operation of a
hydro-cyclone, or, alternati~ely, a circuit
embodying a hydro-cyclone, the method of control
including the measurement of a variable associated
/with the
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with the shape of the slurry underflow e~anating
from a hydro-cyclone underflow outlet, and relating
the value of the measured variable to a re~uired
value thereof.
S Further features of the invention provide for the
variable associated with the shape of the slurry
underflow emanating from the hydro-cyclone
underflow outlet to be the radius or diameter of
the generally roughly conical configuration
described by the underflow slurry at a position a
predetermined distance from the underflow outlet
(in effect the cone-angle); and for such radius,
diameter or angle to be detected by employing a
substantially abrasion resistant element carried at
the end of a downwardly extending, and generally
pivotally mounted arm, or arms, in which case the
value of the radius or diameter is detected by
determinaing the angle at which the arm or arms
extend.
In the case of the use of an abrasion resistant
element carried on a downwardly extending arm, the
arm is preferably urged towards the underflow at
/the required
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thP required position by means of a counterweight
or, alternatively, a suitable spring.
However, it is also acknowledged that such
measurement can be made by contactless methods, for
example using the ultrasound based echo technique.
It is envisaged that variations in a variable
feature of the shape of the underflow of a
hydro-cyclone could be used in a number of
: different ways as follows :-
10 (i) The measurement of such a variable
property of the underflow of the
hydro-cyclone could be used in a scheme
which constrains one or more control
actions so as to allow operation of the
cyclone over a range bounded by, but not
including, an undesirable form of
underflow. In this regard it is to ~e
noted that undesirable forms of underflow
have been employed in the past through
observation by plant operators but not
with any degree of accuracy or finesse in
/view of
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view of the fact that visual observation
only results in excessive or large
changes being noted.
(il) The use of such an underflow measurement
could be employed as a control variable
in a milling circuit to aid the
optimisation of its operation. In this
regard it could, it is believed,
beneficially replace the measurement of
the primary cyclone feed flow rate in,
for example, a multi-variable control
scheme.
(iii) The monitoring of the underflow in the
manner envisaged could be employed in
such a way as to provide a high-density
recycled feed to a mill. This may be
employed to facilitate a better control
of the total inflow of feed water ko a
mill in conjunction with the a controlled
addition of dilution water. It may be
that such a monitoring of the underflow
/shape could
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shape could enable a controlled roping of
the underflow to be employed.
(iv~ The proposed underflow measurement could
be employed to infer size characteristics
of overflow material, possibly in
conjunction with the cyclone feed
measurement and optionally some other
related measurements.
(v) The measured property associated with the
shape of the underflow could, either
alone, or in conjunction with cyclone
feed measurements, be employed to infer
density, viscosity, or flow rate of the
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underflow for the purposes of control.
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In order that the invention may be more fully
understood, two different embodiments thereof will
now be described with reference to the accompanying
drawings.
/BRIEF DESCRIPTION
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BRIEF DESCRIPTIO~ OF Tl~ DRAWI~GS
In the accompanying drawings each o~ Figs. l, 2 and
3 is a schematic illustration of a detector for
detecting the diameter or cone angle of the slurry
body emanating from a hydro-cyclone underflow
outlet.
DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS
As illustrated in Fig. l there is associated with
the underflow outlet l of a hydro-cyclone 2, a
dapending arm 3 mounted towards its upper end on a
pivot 4, with which is associated an angle detector
5.
A counterweight 6 is carried on an outwardly
projecting intermediate lateral arm 7 and the
lowermost end of the downwardly extending arm 3 is
provided with an abrasion resistant tip 8.
The tip 8, and counterweight as well as the other
design variables of the arm arrangement are such
that the abrasion resistant tip rides on the
/outermost surface
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outermoRt surface o~ the generally conical shaped
outlet stream 9 of slurry at a pozition spaced
downwardly from the underflow outlet 1 such that
the angle of the arm 3 will provide a measure of
the diameter of the underflow stream 9 at said
position below the outlet.
Accordingly, the angle detected by the angle
detector 5 can be employed as the measured variable
in the manner outlined above.
Turning now to Fig. 2, there is provided an
alternative arrangement in which a pair of parallel
arms 10 are held in a freely hinged parallelogram
configuration by two transverse parallel arms 11
spaced apart, and the uppermost o~ which is
pivotally supported at a position 12 such that, as
described above in relation to Fig. 1, the arms
depend.
Each of the parallel arms 10 has lower extended end
regions 13 each of which carry at their lowermost
ends abrasion resistant pads 14 of the nature
described above.
/Once again,
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Once agaln, in use, an angle detector 15 is used to
detect the angle o~ inclination o~ the uppermost
transverse arm 11 and the pads 14 of abrasion
re~istant material are supported on the conical
flowing stream 16 of under~low slurry, in use.
In the case of the embodiment of the invention
illustrated In Fig. 3, th~ arm 17 is carried at one
end of a carrier 18 extending about the outer æone
of the underflow (and out of contact therewith) for
10 90D of arc around the axis of the cyclone. The
carrier terminates at its other end in a pivot 19
extending radially outwardly with respect to the
cyclone axis. In this case the pivot's rotation
or angular position is a direct measure of the
change in radius of the underflow or cone angle
thereof.
It will be appreciated that numerous different
methods of determining characteristics of the shape
of the underflow stream of slurry can be employed
and these include the use of electromagnetic
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radiation, for example light and laser beams, in
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conjunction with shadowing, attentuation,
/reflection, or
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reflsction, or any form of im~ging process, as well
i as any positlon detection utilising ultrasonics.
It will accordingly be appreciated that the
invention provides an extremely simple method and
means of monitoring the shape of the underflow
stream of slurry material emanating from a
hydro-cyclone which can be employed for the
purposes of controlling a cyclone operation or a
circuit in which a cyclone is located, such control
generally being effected in combination with other
required measurements.
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