Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02241598 1998-09-08
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BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus For feedin~~ and
removing
mufti-phase fluids from a tluid treatment apparatus. It is particularly
useful, but not limited
to, methods for feeding and removing dual phase liquids such as slurries or
suspensions to
flotation apparatus such as lameson cells.
BACKGROUND ART
When feeding non-homogeneous fluids to a treatment apparatus eg feeding
slurries
or suspensions to settlers, mixers, flotation apparatus etc, the treatment
apparatus is usually
preceded by a vessel or pump box into which the fluid is fed. Most fluid
treatment vessels
operate best when they have a constant feed rate. The fluid dynamics and
separation
efficiency of flotation cells in particular can be disturbed even by small
variations in the
feed rate. Generally therefore a fixed speed pump is connected to this pump
box for
maintaining a consistent flow rate to the fluid treatment apparatus.
There are several difficulties with this system, however. It is vital that the
level of
~ 5 fluid in the pump box does not exceed certain minimum or maximum levels.
Since the
flow rate provided by the fixed speed pump is constant, the level in the pump
box will rise
and fall according to the feed rate into the pump box. If the feed flow rate
is higher than
the flow rate of the fixed speed pump, the pump box will overfill and some of
the feed may
be lost or will short circuit the treatment vessel. Equally if the feed of the
flow rate is
2o below the fixed speed pump, the level in the pump box will drop. If the
pump box level is
very (ow or indeed the pump box runs dry, the fixed speed pump may be damaged.
Some of these difficulties can be overcome by partial recycle mechanisms. This
however requires additional pumping equipment with associated additional
expense.
CA 02241598 1998-09-08
Alternatively, this may be achieved by the use of a tailin~~ recycle chamber
attached
to the pump box.
Another disadvantage of conventional systems is the expense associated with
the
separate construction. Take for example a flotation cell as defined by
Australian patent
application number 45592/96 (hereinafter referred to as the "Jameson cell").
To separate
particulate matter from a slurry or suspension as shown in Figure l, cells 100
are placed
above pump box 200 and pump 300 transfers the slurry from pump box 200 on the
ground
upwardly to the bank of Jameson cells. The tailings then fall downwardly under
force of
gravity, rather than a separate recycle pumping circuit, for partial recycle
back to the pump
box. Situating a bank of Jameson cells above the pump box, however, is
expensive both in
terms of capital construction costs and operational costs since pump 300 must
force the
slurry upwards for between 5 and 10 metres to reach the Jameson cells.
In an effort to overcome at least some of the disadvantages of the prior art
or
alternatively provide an alternative to the prior art it is proposed to
provide a method and
I 5 apparatus for providing and removing non-homogeneous fluids to a treatment
vessel which
is cheaper to construct and provides cheaper and more consistent operation
than
conventional methods.
DISCLOSURE OF THE INVENTION
Accordingly in a first aspect, the present invention provides a feed
arrangement for a
2o vessel for treating non-homogeneous fluids comprising a pump box to receive
the fluid
from a fluid feed and provide the fluid to an inlet side of the treatment
vessel via a
pumping means wherein a fluid transfer port extends between the pump box and
treatment
vessel for two way fluid communication therebetween to equalise the respective
hydrostatic pressures in the treatment vessel and pump box.
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In another aspect, the present invention provides a treatment vessel for
treating non-
homogeneous fluids, said vessel bein~~ divided into a treatment chamber. a
pump chamber
and one or more outlet chambers for one or more components of the non-
homogeneous
Fluid, and a pumping means transferring fluid from said pump chamber to said
treatment
chamber, wherein a transfer port extends between an outlet side of the
treatment vessel to
the pump chamber to permit two-way fluid communication therebetween for
equalising the
respective hydrostatic pressures in the treatment vessel and pump box.
In a first embodiment, the pump box and treatment vessel are side by side.
By positioning the pump chamber box next to the treatment vessel there is a
substantial saving both in capital construction costs but also in operating
costs as it is now
unnecessary for the pump which transfers fluid from the pump chamber into the
treatment
chamber to overcome the substantial head of liquid in conventional apparatus
(see figure
In another preferred embodiment, the transfer port comprises a recycle
chamber. The
~ 5 fluid leaving the treatment vessel enters the recycle chamber. One or more
control means
such as valves then allows this fluid to leave the recycle chamber and pass to
the outlets.
The recycle chamber is separated from the pump chamber preferably by means of
a wall.
The recycle means comprises an orifice through the wall separating the recycle
chamber
from the pump chamber. Preferably, this orifice comprises one or more slits
extending
2o along the floor of the recycle and pump chambers. This orifice allows fluid
to flow in both
directions. The arrangement provides that the pump chamber is in fluid
communication
with the treatment chamber via the recycle chamber. In this way the levels of
fluid
between the treatment chamber and pump chamber may equalise by flow through
the
orifice.
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In a particularly preferred embodiment, the recycle means is arranged to
agitate the
fluid enterin~l the pump chamber via the transfer port. In this way the fluid
is thoroughly
mixed prior to being pumped from the pump chamber into the treatment chamber
or vessel.
In a particularly preferred embodiment, the treatment chamber comprises one or
more Jameson cells.
In another embodiment, the transfer port is configured to provide fluid to the
pump
box which is essentially representative of the bulk content of the fluid in
the recycle
chamber. To explain, as will be appreciated by persons skilled in the art,
when dealing
with solid/liquid or sold/gas fluids if the fluid is not continually mixed,
the solid particles
tend to settle out. If one then removes or recycles some of the fluid at an
upper portion of
the vessel eg by an overflow, the fluid has little or no solids content. It is
important to
recycle fluid back to the pump box which is representative of the fluid
entering the recycle
chamber. For this reason, it is preferred that any orifice between the recycle
chamber and
the pump box is positioned at a maximum height that the fluid entering the
pump box is
~ 5 substantially representative of the bulk content of the fluid in the
recycle chamber. In
another embodiment, the transfer orifice and/or port may be positioned at a
lowermost
portion of the pump box. This ensures that a substantial portion of the solids
as well as the
liquid is recycled back to the pump box.
In a further aspect, the present invention provides a method of feeding a
fluid to a
2o treatment vessel comprising feeding a fluid to a pump box upstream of the
treatment
vessel, pumping the fluid from the pump box to the treatment vessel and
providing a
transfer port between the pump box and treatment vessel for equalising their
respective
hydrostatic pressures.
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(n still a further aspect, the present invention provides a method of
controllin~T the
head of tluid in the pump box and/or a treatment vessel in which fluid is
transferred from
said pump box to the treatment vessel by a pump, said method comprising
providing a
transfer port between the pump box and treatment vessel to maintain direct two-
wav fluid
s communication between the treatment vessel and the pump box for equalising
their
respective hydrostatic pressures.
It is preferred that the hydrostatic head in the treatment vessel and recycle
chamber is
greater than the pump box. This provides continuous recycling of fluid from
the recycle
chamber to the pump box. This continuous partial recycle of fluids can be
obtained by
appropriate sizing of the treatment chamber, recycle chamber, pump chamber and
transfer
port.
Unless the context clearly requires otherwise, throughout the description and
the
claims, the words 'comprise', 'comprising', and the like are to be construed
in an inclusive
as opposed to an exclusive or exhaustive sense; that is to say, in the sense
of "including.
~ 5 but not limited to".
Non-homogeneous fluids can include, but are not limited to, slurries.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described by way of example only with
reference
to the accompanying drawings in which:
2o Figure 1 is a conventional Jameson cell flotation plant,
Figure 2 is an external perspective view of an apparatus according to a first
embodiment of the present invention,
Figure 3 is a perspective view of the interior of the apparatus of figure l,
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Figures 4 and 5 are perspective and interior views oFan apparatus according to
a
second embodiment of the present invention,
Figures 6 and 7 are perspective and internal views of an apparatus according
to a
third embodiment of the present invention, and
a Figures 8 and 9 are perspective and plan views of an apparatus according to
a fourth
embodiment of the present invention.
Figure 10 is a perspective view of an apparatus according to a fifth
embodiment of
the present invention.
MODES) FOR CARRYING OUT THE INVENTION
Referring firstly to figures 2 and 3, the present invention comprises a
structure 10
which houses a pump box or chamber 20, an outlet chamber 40 and treatment
chamber or
vessel 60. Each of these chambers 20, 40 and vessel 60 are in fluid
communication with
each other. The pump box chamber 20 comprises feed inlet 21 and pump outlet
22. The
pump is not shown in the drawings but will be discussed below. As shown more
clearly in
~ 5 figure 3, the outlet chamber 40 comprises outlet 41. The outlet flow rate
is controlled by
valves 42 as will be discussed further below.
A transfer port which comprises recycle chamber 55 extends from treatment
vessel
60 to pump box 20. This recycle chamber 55 is in fluid communication with the
pump box
20 via orifice 70. This orifice may be of any particular shape but for reasons
that will be
2o discussed below a slit on the lowermost edge of wall 45 dividing the pump
box 20 from
recycle chamber 55 is preferred.
As discussed above, the treatment vessel 60 may be of any desired
construction. For
the sake of illustration in the following description, treatment vessel 60 is
a tlotation cell,
however, it could equally be a settler, a mixer etc.
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The inventive apparatus operates as follows. A slurry or suspension
comprisin~T a
liquid and particulate material is fed into pump box ?0 via inlet ? 1. A pump
(not shown) is
connected to outlet 22 positioned at a lower portion of the pump box ?0. This
pump
transfers the slurry from pump box 20 into treatment vessel 60 via external
pipin~l. Once
the treatment or separation occurs in vessel 60, the valuable floated material
is separated as
a froth in a known manner and exits through outlet 61. The tailings or gangue
material
flows downwardly along the sloping tank floor 62 towards transfer port ~0 and
into recycle
chamber 5~. If valves 42 are open, once recycle chamber 55 is full the
tailings/gangue will
flow upwardly through valves 42 and exit through outlet 41. Valves 42 may for
example
I o be dart valves.
As will be clear to persons skilled in the art, pump box 20 remains in fluid
communication with the treatment vessel 60 via transfer port 50, the recycle
chamber
and orifice 70. This in turn will ensure that the level in pump box 20 remains
fairly
constant since the relative heads of liquid in the pump box 20 and treatment
vessel 60 will
I 5 alter the quantity of tailings recycled back to pump box 20 through
transfer port 50 and
orifice 70. In the embodiments shown, the orifice 70 is adjacent the lowermost
portion of
the pump box. As will be explained later, however, transfer port 50 and
orifice 70 are
configured to provide liquid to the pump box which is representative of the
bulk content of
the fluid in the recycle chamber 55.
2o To explain, there are several modes of operation of the present
application. In a first
or constant flow mode of operation, the feed rate through inlet 21 should be
equal to the
tlow rate of the fixed speed pump transferring the slurry from pump box 20 to
treatment
vessel 60. In this instance, the level in the pump box 20 will remain constant
as will the
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flow rate into the tlotation cells) 60. This is an ideal situation which only
rarely occurs in
practice.
If. however. the feed rate through inlet 21 is lower than the capacity of the
fined
speed pump, the level in pump box 20 will drop below the level of liquid in
the treatment
s vessel 60. Then the inventive arrangement operates in recycle mode. In this
instance, due
to the higher head of liquid in treatment vessel 60, the tailings/gangue will
flow through
transfer port 50 and recycle chamber 55 and a portion will be recycled through
orifice 70
back into pump box 20 until the levels of fluid in the treatment vessel 60 and
pump box 20
equalise. This ensures that the level of fluid in the pump box 20 will not
fall below the
level of the liquid in the treatment vessel thereby guaranteeing constant flow
rate to the
treatment vessel which as discussed above is particularly important for
flotation or similar
separation operations.
The third or overflow mode of operation is where the incoming feed rate 21 is
higher
than the capacity of the fixed speed pump. In this instance, the level in pump
box 20 will
~5 slowly rise until it is above the level of liquid in the treatment vessel.
Since the head of
liquid in the pump box 20 is greater than the head of liquid of treatment
vessel 60, some of
the incoming slurry will be forced through the orifice 70 from the pump box 20
into
recycle chamber 55 until the level of the fluid in the pump box 20 equalises
with the level
in treatment vessel 60. Even if some of the valuable particulate material
enters recycle
2o chamber 55 this material is not lost. Once the feed rate drops below the
capacity of fixed
speed pump, the apparatus will revert to its "recycle" mode of operation where
the fluid
level in treatment vessel 60 is higher than in pump box 20 and fluid will be
forced from
recycle chamber 55 through the oritice 70 back into the pump box 20 from where
it is
transferred to the treatment apparatus 60. Accordingly, any particulate
material remaining
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in recycle chamber » will be transferred back to pump box 20 from where it is
forwarded
to the treatment vessel 60. This ensures that none of the slurry "short
circuits" the
treatment vessel and escapes through outlet 41.
The wall 4~ separating pump box 20 from outlet chamber 40 preferably has an
overflow weir 46 at its uppermost portion. This overflow weir 46 is set at a
distance
slightly below the upper point of treatment vessel 60 such that if the level
in pump box 20
continues to rise due to an increased feed rate, some of the slurry will
overflow to outlet
chamber 40 and escape through outlet 41. This is the only instance where some
of the
incoming slurry will short circuit the treatment apparatus.
Accordingly it can be seen that the inventive apparatus may be dimensioned
such that
the pump box 20 is essentially self regulating. The fluid communication
between the
pump box 20 and vessel 60 via orifice 70, recycle chamber 55 and outlet
chamber 40
ensures that the fluid in the pump box is maintained between appropriate
minimum and
maximum levels without the need for expensive and complicated recycling
componentry.
~ 5 In the embodiment shown in figures 2 and 3, orifice 70 is positioned
adjacent the
lowermost portion of the pump box 20. This ensures that the solids in the
slurry entering
recycle chamber 55 are recycled back to pump box 20. The orifice may be
positioned at
any point on the pump box 20 provided that the fluid entering the pump box
from the
recycle chamber is representative of the bulk content of fluids in the recycle
chamber. In
2o the prior art, fluid is generally recycled from the upper portion of the
recycle chamber.
Unless the fluid in the recycle chamber is continuously mixed, such a
configuration will
recycle mainly liquid and the solids in the slurry will settle out to the
bottom of the recycle
chamber and not be returned to the pump box.
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Figures 4 and 5 show the inventive apparatus when used in conjunction with the
Jameson cell and its downcomers. As mentioned above, in the prior art these
Jameson
cells are positioned directly above the pump box (see figure 1 ) to allow for
recycling of
the tailing by gravity back to the pump box. Of course, this not only requires
a larger
s pump to transfer the fluid from the pump box vertically upwards by 5-10
metres to the
Jameson cells but requires substantial supporting structures to be constructed
for the
Jameson cells. With the inventive apparatus, a much smaller pump may be used
to
transfer the incoming slurry in pump box 20 to the inlet of the Jameson cell
10.
It will therefore be clear to persons skilled in the art that by providing the
pump
1o box 20 at the same level as the treatment apparatus 60, and preferably the
same level as
the outlet chamber 40, there is a substantial saving in terms of construction
cost. It is not
necessary to provide separate supporting structures for each of the process
components
nor is it necessary to provide extensive piping to transfer the various fluids
from the
pump box to the treatment apparatus to the outlet apparatus. It is also clear
to persons
Is skilled in the art that by providing the pump box 20 next to and at the
same level as the
treatment apparatus 60 the pump to transfer the fluid from the pump box to the
treatment
apparatus may be much smaller than conventional apparatus. The operating costs
for
such a pump will also be reduced it is estimated by about 20% as compared to a
conventional arrangement since the pump is not required to overcome the
substantial
2o head of liquid from the pump box to the treatment vessel above.
The applicant has also found that the inventive arrangement has significant
advantages in terms of the quality of the fluid entering the treatment vessel.
To explain,
in the circumstances where the head of liquid in the treatment vessel is
higher than that in
the pump box 20, liquid will be forced through recycle chamber 55 and orifice
70 into the
CA 02241598 1998-09-08
pump box 20. The velocity ofthis recycled tailings portion can be quite high
and serves to
a~~itate the liquid in the pump box 20. In this regard it is preferred that
orifice 70 is
provided by a slit extending substantially across the entire width of recycle
chamber >j and
pump box 20. With this configuration the fluid travelling from recycle chamber
~~ to
pump box 20 serves to sweep any particulate material resting on the floor of
pump box 20
for subsequent removal by the pump through outlet 22. Other configurations of
orifice 70
have also been envisaged and in fact there may be several orifices between
pump box 20
and recycle chamber 55.
This agitation of the fluid in pump box 20 is a distinct advantage over
conventional
recycle mechanisms which may, in some instances, require additional agitation
apparatus
for example an impeller.
A further embodiment of the inventive apparatus is shown in figures 6 and 7.
In this
embodiment a section of the floor 25 of the pump box 20 between the outlet 22
and inlet
21 is sloped. This provides that any particulate material settling on this
portion of the
~ 5 pump box floor 20 will slide downwardly toward the outlet 22 and be taken
up by the
pump and fed to settlement vessel 60.
A still further advantage of the present application is that it provides a
complete
package to an end user without the necessity for building a separate pump box.
Generally
the construction and installation of fluid treatment vessels is a specialised
business. A
2o plant operator will order a treatment vessel which will be installed by a
contractor. The
pump box is then generally built by the plant owner/operator and connected to
the
treatment vessel. This causes some difficulties as the pump box is not always
tailored to
suit the particular liquid treatment vessels. Generally a plant owner/operator
will have a
standard pump box which they will use for virtually every treatment vessel. As
mentioned
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above, the maintenance of consistent flow to treatment vessels such as
flotation cells is
vital to efficient operation. A poorly constructed pump box may cause the
treatment
vessel to operate at less than optimum level. This is not because of any
inherent problem
in the treatment vessel but rather that the pump box is not tailored to
maintain the
required flow rate to the treatment vessel.
With the inventive apparatus, there is no need to build a separate pump box as
it is
already included in the apparatus and tailored specifically to match the
treatment vessel
60. This is a significant advantage over the prior art. Not only is the
capital cost less, the
plant owner/operator will not have to delay operation of the treatment vessel
until the
to pump box can be constructed since the pump box/treatment vessel comes as a
single unit.
It will also help manufacturers of specialised treatment vessels since they
can ensure that
the pump box 20 is of the correct dimensions to maintain optimal operation of
the
treatment vessel 60.
A still further embodiment of the inventive apparatus is shown in figures 8
and 9.
In this embodiment, the treatment vessel is provided by a circular or conical
tank 160.
The pump box 120, outlet chamber 140, control valves 142, exit 141, and
recycle
chamber 150 are provided on one side of the treatment tank 160. The fluid
communication between treatment vessel 160 and the pump box 120 is via orifice
170.
This modification of the treatment vessel reduces the costs of material and
manufacture.
The modification allows for the use of thinner steel plates and less
structural side and
bottom supports.
It also allows for an innovative multiple treatment tank layout as shown in
figure 9.
As it will be seen in this embodiment, the outlet chamber 140 of one treatment
apparatus
100 may be easily connected to the pump box 120 of an adjacent vessel and so
on and so
on by pipeline 200. Indeed, it may be possible to place the feed box of an
adjacent vessel
CA 02241598 1998-09-08
_ I :1 _
at a slightly lower level such that the tailings from a first outlet chamber
140 are ~~ravitv
fed to the pump box I 20 of the next treatment apparatus.
A further embodiment of the inventive apparatus is shown in figure 10. Similar
to
figure 8, the treatment vessel 260 comprises a circular tank with a conical
bottom. Again
this embodiment has the advantage of reduced cost of construction material and
manufacture. The figure shows an alternative location arrangement of the pump
box 220,
the recycle chamber 255 and the outlet chamber 240 with respect to the
treatment vessel
260. Compared to the embodiment shown in figure 8 only the outlet chamber
shares a wall
246 with the treatment vessel. The unfloated portion of the fluid in the
treatment chamber
260 enters the recycle chamber. A part of the fluid in the recycle chamber
recycles back to
the pump box 220 through the orifice 270 and the remaining exits through
control valves
242 to the exit 241 via the outlet chamber 240.
These configurations also provides a very small footprint for the plant layout
as
compared to conventional structures.
It will be clear to persons skilled in the art that the present invention may
be
embodied in forms other than those shown in the preferred embodiments without
departing
from the spirit or scope of the invention as described.
