U.S. patent number 3,623,656 [Application Number 05/007,285] was granted by the patent office on 1971-11-30 for three-phase centrifuge.
This patent grant is currently assigned to Pennwalt Corporation. Invention is credited to Andre C. Lavanchy.
United States Patent |
3,623,656 |
Lavanchy |
November 30, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
THREE-PHASE CENTRIFUGE
Abstract
Solids and two liquids, each having different specific
gravities, are separated in a centrifuge having a helical screw
conveyor mounted within an elongated bowl tapered at one end. A
group of solids discharge openings is disposed at the tapered end,
and two groups of concentrically arranged liquid discharge
openings, one for each separated liquid, are disposed at the other
end of the bowl. One group of liquid discharge openings has an
annular ring dam mounted adjacent thereto to serve as a weir; the
second group of liquid discharge openings has an annular channel
disposed adjacent thereto for receiving the separated liquid
discharged therethrough, and a skimmer passage disposed within the
channel for receiving the liquid within the channel. Optionally,
the centrifuge contains a plurality of radially extending ribs
mounted adjacent to the two groups of liquid discharge openings for
controlling the rotational speed of the separated liquids with
respect to the bowl immediately prior to discharge of the liquids.
Also, a scraper member is mounted on the screw conveyor for the
removal of solids which have accumulated on the inner annular
surface of the bowl, and a vane is rigidly mounted between adjacent
flights of the conveyor to exclude the lighter of the two separated
liquids from the space adjacent to the solids discharge
openings.
Inventors: |
Lavanchy; Andre C. (Devon,
PA) |
Assignee: |
Pennwalt Corporation
(Philadelphia, PA)
|
Family
ID: |
21725276 |
Appl.
No.: |
05/007,285 |
Filed: |
January 30, 1970 |
Current U.S.
Class: |
494/53; 494/57;
494/52 |
Current CPC
Class: |
B04B
1/20 (20130101); B04B 11/02 (20130101); B04B
2001/2083 (20130101) |
Current International
Class: |
B04B
1/00 (20060101); B04B 11/00 (20060101); B04B
1/20 (20060101); B04B 11/02 (20060101); B04b
001/00 (); B04b 007/00 (); B04b 011/00 () |
Field of
Search: |
;233/7,19,20,21,3,27,4,39,41,46,47 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Franklin; Jordan
Assistant Examiner: Krizmanich; George H.
Claims
What is claimed is:
1. A three-phase centrifuge for separating solids, a first liquid,
and a second liquid, each having different specific gravities, from
feed comprising a liquids-solids mixture, said centrifuge
comprising:
a. an elongated hollow bowl of circular cross section mounted for
rotation about an axis, said bowl having an inner annular surface
with a portion thereof decreasing in diameter approaching one end
of said bowl, said bowl having a solids discharge opening disposed
at said one end, the other end of said bowl having disposed therein
a first group of liquid discharge openings for discharge of the
first liquid, and a second group of liquid discharge openings for
discharge of the second liquid, said second group of liquid
discharge openings opening into the interior of said bowl at said
other end at a lesser distance from the axis of rotation than said
first group of liquid discharge openings;
b. annular ring dam means mounted adjacent said second group of
liquid discharge openings, said ring dam means serving as a weir
over which said second liquid flows upon being discharged;
c. a screw conveyor disposed within said bowl and mounted for
coaxial rotation therein, said conveyor including an axially
elongated hub radially spaced from said bowl to define therewith an
annular separating chamber, flights mounted on said hub for
movement therewith, said flights having their distal edges
generally complementing the inside contour of said bowl;
d. feed means having an outlet, said outlet being positioned
between said one end and said other end of said bowl, said outlet
being adapted to introduce said feed into said separating
chamber;
e. and vane means mounted on said hub and extending between
adjacent flights, said vane means being located adjacent said
portion of said inner annular surface which is decreasing in
diameter, said vane means being adapted to exclude said second
liquid from that portion of the separation chamber in which said
vane means is positioned.
2. A three-phase centrifuge for separating solids, a first liquid,
and a second liquid, each having different specific gravities, from
feed comprising a liquids-solids mixture, said centrifuge
comprising;
a. an elongated hollow bowl of circular cross section mounted for
rotation about an axis, said bowl having an inner annular surface
with a portion thereof decreasing in diameter approaching one end
of said bowl, said bowl having a solids discharge opening disposed
at said one end, the other end of said bowl having disposed therein
a first group of liquid discharge openings for discharge of the
first liquid, and a second group of liquid discharge openings for
discharge of the second liquid, said second group of liquid
discharge openings opening into the interior of said bowl at said
other end at a lesser distance from the axis of rotation than said
first group of liquid discharge openings;
b. annular ring dam means mounted adjacent said second group of
liquid discharge openings, said ring dam means serving as a weir
over which said second liquid flows upon being discharged;
c. a screw conveyor disposed within said bowl and mounted for
coaxial rotation therein, said conveyor including an axially
elongated hub radially spaced from said bowl to define therewith an
annular separating chamber, flights mounted on said hub for
movement therewith, said flights having their distal edges
generally complementing the inside contour of said bowl;
d. feed means having an outlet, said outlet being positioned
between said one end and said other end of said bowl, said outlet
being adapted to introduce said feed into said separating
chamber;
e. radically extending rib means mounted adjacent to said other
end, said radially extending rib means being adapted to control the
rotational velocity of one of said liquids with respect to said
bowl;
f. and screen means mounted adjacent said plurality of radially
extending ribs, said screen means being adapted to reduce the
turbulence of said first liquid and said second liquid being
discharged through said first and said second groups of liquid
discharge openings.
3. A three-phase centrifuge for separating solids, a first liquid,
and a second liquid, each having different specific gravities, from
feed comprising a liquids-solids mixture, said centrifuge
comprising:
a. an elongated hollow bowl of circular cross section mounted for
rotation about an axis, said bowl having an inner annular surface
with a portion thereof decreasing in diameter approaching one end
of said bowl, said bowl having a solids discharge opening disposed
at said one end, the other end of said bowl having disposed therein
a first group of liquid discharge openings for discharge of the
first liquid, and a second group of liquid discharge openings for
discharge of the second liquid, said second group of liquid
discharge openings opening into the interior of said bowl at said
other end at a lesser distance from the axis of rotation than said
first group of liquid discharge openings;
b. annular ring dam means mounted adjacent said second group of
liquid discharge openings, said ring dam means serving as a weir
over which said second liquid flows upon being discharged;
c. a screw conveyor disposed within said bowl and mounted for
coaxial rotation therein, said conveyor including an axially
elongated hub radially spaced from said bowl to define therewith an
annular separating chamber, flights mounted on said hub for
movement therewith, said flights having their distal edges
generally complementing the inside contour of said bowl;
d. feed means having an outlet, said outlet being positioned
between said one end and said other end of said bowl, said outlet
being adapted to introduce said feed into said separating
chamber;
e. and means defining an annular channel on the exterior of said
other end adjacent to said first group of liquid discharge
openings, said annular channel opening in an inward direction and
being adapted to receive said first liquid discharged through said
first group of liquid discharge openings, and further including a
skimmer tube having an inlet for receiving said first liquid from
said channel, said inlet being disposed within said channel, said
first group of liquid discharge openings extending from the
interior to the exterior of said bowl in a radially inward
direction, and said second group of liquid discharge openings
extending from the interior to the exterior of said bowl in a
radially outward direction, said first group of liquid discharge
openings terminating adjacent said annular channel, said second
group of liquid discharge openings terminating at the outer annular
surface of said bowl.
4. A three-phase centrifuge for separating solids, a first liquid,
and a second liquid, each having different specific gravities, from
feed comprising a liquids-solids mixture, said centrifuge
comprising:
a. an elongated hollow bowl of circular cross section mounted for
rotation about an axis, said bowl having an inner annular surface
with a portion thereof decreasing in diameter approaching one end
of said bowl, said bowl having a solids discharge opening disposed
at said one end, the other end of said bowl having disposed therein
a first group of liquid discharge openings for discharge of the
first liquid, and a second group of liquid discharge openings for
discharge of the second liquid, said second group of liquid
discharge openings opening into the interior of said bowl at said
other end at a lesser distance from the axis of rotation than said
first group of liquid discharge openings, said first group of
openings extending from the interior to the exterior of said bowl
in a radially inward direction, said second group of openings
extending from the interior to the exterior of said bowl in a
radially outward direction, said second group of liquid discharge
openings terminating at the outer annular surface of said bowl;
b. annular ring dam means mounted adjacent to said second group of
liquid discharge openings, said ring dam means serving as a weir
over which said second liquid flows upon being discharged;
c. a screw conveyor disposed within said bowl and mounted for
coaxial rotation therein, said conveyor including an axially
elongated hub radially spaced from said bowl to define therewith an
annular separating chamber, flights mounted on said hub for
movement therewith, said flights having their distal edges
generally complementing the inside contour of said bowl;
d. feed means having an outlet, said outlet being positioned
between said one end and said other end of said bowl, said outlet
being adapted to introduce said feed into said separating
chamber.
5. A three-phase centrifuge according to claim 4 including an
annular cup-shaped member, said cup-shaped member comprising a base
portion and an annular flange portion extending from said base
portion, said flange portion having an inner annular surface which
increases in diameter in a direction away from said base portion,
said base portion mounted to the exterior of said other end and
said flange portion extending in a direction toward said one end of
said bowl, the inner annular surface of said flange portion and the
outer annular surface of said bowl defining an annular zone, the
outer annular surface of said flange portion having a plurality of
annular grooves disposed therein, means surrounding said flange
portion and cooperating with said annular grooves to define a first
space and a second space on either side of said means, said annular
cup-shaped member and said means being adapted to rotate with
respect to each other, said annular zone communicating with said
second space, said first group of liquid discharge openings
extending from the interior of said bowl to said first space, and
said second group of liquid discharge openings extending from the
interior of said bowl to said annular zone.
6. A three-phase centrifuge according to claim 5 in which said base
portion includes a radially inwardly extending rim defining an
annular channel between said base portion and said other end, said
annular channel being disposed adjacent said first group of liquid
discharge openings.
7. A three-phase centrifuge for separating solids, a first liquid,
and a second liquid, each having different specific gravities, from
feed comprising a liquids-solids mixture, said centrifuge
comprising:
a. an elongated hollow bowl of circular cross section mounted for
rotation about an axis, said bowl having an inner annular surface
with a portion thereof decreasing in diameter approaching one end
of said bowl, said bowl having a solids discharge opening disposed
at said one end, the other end of said bowl having disposed therein
a first group of liquid discharge openings for discharge of the
first liquid, and a second group of liquid discharge openings for
discharge of the second liquid, said second group of liquid
discharge openings opening into the interior of said bowl at said
other end at a lesser distance from the axis of rotation than said
first group of liquid discharge openings;
b. annular ring dam means mounted adjacent said second group of
liquid discharge openings, said ring dam means serving as a weir
over which said second liquid flows upon being discharged;
c. a screw conveyor disposed within said bowl and mounted for
coaxial rotation therein, said conveyor including an axially
elongated hub radially spaced from said bowl to define therewith an
annular separating chamber, flights mounted on said hub for
movement therewith, said flights having their distal edges
generally complementing the inside contour of said bowl;
d. feed means having an outlet, said outlet being positioned
between said one end and said other end of said bowl, said outlet
being adapted to introduce said feed into said separating
chamber;
e. and means defining an annular channel on the exterior of said
other end adjacent to said first group of liquid discharge
openings, said annular channel opening in an inward direction and
being adapted to receive said first liquid discharged through said
first group of liquid discharge openings, and further including a
skimmer tube having an inlet for receiving said first liquid from
said channel, said inlet being disposed within said channel.
8. A three-phase centrifuge according to claim 7, including annular
underdam ring means mounted adjacent said group of liquid discharge
openings, said annular underdam ring means being adapted to prevent
discharge of said second liquid through said first group of liquid
discharge openings.
9. A three-phase centrifuge according to claim 7 including a
radially extending rib means mounted on the interior of said bowl
adjacent said other end, said radially extending rib means being
adapted to control the rotational velocity of one of said liquids
with respect to said bowl and annular underdam ring means mounted
adjacent said first group of liquid discharge openings, said
annular underdam ring means being adapted to prevent discharge of
said second liquid through said first group of liquid discharge
openings.
10. A three-phase centrifuge for separating solids, a first liquid
and a second liquid, each having different specific gravities, from
feed comprising a liquids-solids mixture, said centrifuge
comprising:
a. an elongated hollow bowl of circular cross section mounted for
rotation about an axis, said bowl having an inner annular surface
with a portion thereof decreasing in diameter approaching one end
of said bowl, said bowl having a solids discharge opening disposed
at said one end, the other end of said bowl having disposed therein
a first group of liquid discharge openings for discharge of the
first liquid, and a second group of liquid discharge openings for
discharge of the second liquid, said second group of liquid
discharge openings opening into the interior of said bowl at said
other end at a lesser distance from the axis of rotation than said
first group of liquid discharge openings;
b. means defining an annular channel on the exterior of said other
end adjacent said first group of liquid discharge openings, said
annular channel being adapted to receive said first liquid
discharged through said first group of liquid discharge openings
and further including a skimmer tube having an inlet for receiving
said first liquid from said annular channel, said inlet being
disposed within said channel;
c. a screw conveyor disposed within said bowl and mounted for
coaxial rotation therein, said conveyor including an axially
elongated hub radially spaced from said bowl to define therewith an
annular separating chamber, flights mounted on said hub for
movement therewith, said flights having their distal edges
generally complementing the inside contour of said bowl;
d. feed means having an outlet, said outlet being positioned
between said one end and said other end of said bowl, said outlet
being adapted to introduce said feed into said separating
chamber.
11. A three-phase centrifuge for separating solids, a first liquid,
and a second liquid, each having different specific gravities, from
feed comprising a liquids-solids mixture, said centrifuge
comprising:
a. an elongated hollow bowl of circular cross section mounted for
rotation about an axis, said bowl having an inner annular surface
with a portion thereof decreasing in diameter approaching one end
of said bowl, said bowl having a solids discharge opening disposed
at said one end, the other end of said bowl having disposed therein
a first group of liquid discharge openings for discharge of the
first liquid, and a second group of liquid discharge openings for
discharge of the second liquid, said second group of liquid
discharge openings opening into the interior of said bowl at said
other end at a lesser distance from the axis of rotation than said
first group of liquid discharge openings;
b. annular ring dam means mounted adjacent said second group of
liquid discharge openings, said ring dam means serving as a weir
over which said second liquid flows upon being discharged;
c. a screw conveyor disposed within said bowl and mounted for
coaxial rotation therein, said conveyor including an axially
elongated hub radially spaced from said bowl to define therewith an
annular separating chamber, flights mounted on said hub for
movement therewith, said flights having their distal edges
generally complementing the inside contour of said bowl;
d. feed means having an outlet, said outlet being positioned
between said one end and said other end of said bowl, said outlet
being adapted to introduce said feed into said separating
chamber;
e. annular underdam ring means mounted adjacent said first group of
liquid discharge openings, said annular underdam ring means being
adapted to prevent discharge of said second liquid through said
first group of liquid discharge openings.
12. A three-phase centrifuge for separating solids, a first liquid,
and a second liquid, each having different specific gravities, from
feed comprising a liquids-solids mixture, said centrifuge
comprising:
a. an elongated hollow bowl of circular cross section mounted for
rotation about an axis, said bowl having an inner annular surface
with a portion thereof decreasing in diameter approaching one end
of said bowl, said bowl having a solids discharge opening disposed
at said one end, the other end of said bowl having disposed therein
a first group of liquid discharge openings for discharge of the
first liquid, and a second group of liquid discharge openings for
discharge of the second liquid, said second group of liquid
discharge openings opening into the interior of said bowl at said
other end at a lesser distance from the axis of rotation than said
first group of liquid discharge openings;
b. annular ring dam means mounted adjacent said second group of
liquid discharge openings, said ring dam means serving as a weir
over which said second liquid flows upon being discharged;
c. a screw conveyor disposed within said bowl and mounted for
coaxial rotation therein, said conveyor including an axially
elongated hub radially spaced from said bowl to define therewith an
annular separating chamber, flights mounted on said hub for
movement therewith, said flights having their distal edges
generally complementing the inside contour of said bowl;
d. feed means having an outlet, said outlet being positioned
between said one end and said other end of said bowl, said outlet
being adapted to introduce said feed into said separating
chamber;
e. radially extending rib means mounted adjacent to said other end,
said radially extending rib means being adapted to control the
rotational velocity of one of said liquids with respect to said
bowl.
13. A three-phase centrifuge for separating solids, a first liquid,
and a second liquid, each having different specific gravities, from
feed comprising a liquids-solids mixture, said centrifuge
comprising:
a. an elongated hollow bowl of circular cross section mounted for
rotation about an axis, said bowl having an inner annular surface
with a portion thereof decreasing in diameter approaching one end
of said bowl, said bowl having a solids discharge opening disposed
at said one end, the other end of said bowl having disposed therein
a first group of liquid discharge openings for discharge of the
first liquid, and a second group of liquid discharge openings for
discharge of the second liquid, said second group of liquid
discharge openings opening into the interior of said bowl at said
other end at a lesser distance from the axis of rotation than said
first group of liquid discharge openings;
b. annular ring dam means mounted adjacent said second group of
liquid discharge openings, said ring dam means serving as a weir
over which said second liquid flows upon being discharged;
c. a screw conveyor disposed within said bowl and mounted for
coaxial rotation therein, said conveyor including an axially
elongated hub radially spaced from said bowl to define therewith an
annular separating chamber, flights mounted on said hub for
movement therewith, said flights having their distal edges
generally complementing the inside contour of said bowl;
d. feed means having an outlet, said outlet being positioned
between said one end and said other end of said bowl, said outlet
being adapted to introduce said feed into said separating
chamber;
e. a scraper member mounted adjacent the distal edges of one of
said flights, said scraper member being disposed adjacent said
inner annular surface, and adjacent said other end of said bowl,
and adapted to rotate about said axis upon rotation of said screw
conveyor to remove accumulations of solids on said inner annular
surface.
Description
This invention relates to centrifugal separators, but more
particularly to a three-phase solid bowl centrifugal separator for
separating liquids from finely divided solids, i.e., a centrifuge
for separating solids, a first liquid, and a second liquid, each
having different specific gravities, from feed comprising a
liquids-solids mixture.
Conventionally, such a centrifuge comprises an elongated bowl,
tapered at one end, and mounted for rotation about an axis.
Coaxially mounted within the bowl is a helical screw conveyor which
is adapted to rotate at a speed slightly different than the speed
of the bowl.
Feed is introduced into the bowl, and due to centrifugal force
effected by the rotation of the bowl, the feed separates into its
component parts. Due to the slight difference in the rotational
speed between the bowl and the helical screw conveyor, the solids
sedimented against the wall are conveyed along the inner annular
surface of the bowl to solids discharge openings located at the
tapered end of the bowl, while two separated liquids simultaneously
exit through separate liquid discharge openings.
Various means exist for discharging separated liquids from the
centrifuge bowl. Some centrifuges utilize two liquid discharge
conduits, one for each separated liquid. These liquid discharge
conduits are supported deep within the central portion of the
centrifuge bowl, and although normally stationary, are mounted so
as to be radially adjustable. This allows the radial position of
the conduits to be changed during rotation of the centrifuge bowl
to skim off desired amounts of each of the separated liquids. One
difficulty presented with this arrangement is the problem of
supporting such conduits deep within a centrifuge bowl which is
rotating at an extremely high speed. Another is the necessarily
complex arrangements needed to seal against leakage, and to vary
the radial positions of the conduits during operation of the
centrifuge bowl.
Other centrifuges of the prior art have groups of liquid discharge
openings, one group for each separated liquid, disposed in the
centrifuge bowl. The openings are arranged and the centrifuge is
operated such that during discharge of the separated liquids, each
opening is normally completely filled with the liquid being
discharged. An individual plate is adjustably mounted adjacent to
each opening to vary the size of the opening to control the
discharge of the separated liquid. This has the disadvantage of not
only being time consuming, but necessitates stopping the centrifuge
to make necessary adjustments. Also, varying the size of each
opening in this manner has the effect of choking the system which
lowers the overall efficienty of the centrifuge. For example, fluid
flow through an ordinary conduit is choked when the area of the
conduit through which the fluid is flowing is reduced. Greater
pressure is required to achieve the same rate of flow through the
reduced area. This required increment in pressure is translated in
the centrifuge by an inward shift of the liquid level, thereby
creating an unbalanced condition. As a result, the line of
separation between the separated liquids in the centrifuge bowl
also shifts, thereby varying the recovery of the separated
materials from that desired. Consequently a three-phase centrifuge
is needed which is of relatively simple construction, can be
adjusted during the operation thereof, and maximizes the efficiency
of the separation process.
Accordingly, one of the principal objects of the present invention
is to provide a three-phase centrifuge of relatively simple
construction which optimizes the efficiency of the separation
process.
Another object of the present invention is to provide a three-phase
centrifuge which minimizes the loss of one of the separated liquids
through the solids discharge openings.
Another object of the present invention is to provide a centrifuge
which prevents the accumulation of solids along the inner annular
wall of the centrifuge bowl.
Another object of the present invention is to provide a three-phase
centrifuge which prevents relative rotation between the separated
liquids and the centrifuge bowl immediately prior to discharge of
the liquids.
Another object of the present invention is to provide a three-phase
centrifuge in which the line of separation between two separated
liquids is adjustable during the operation of the centrifuge.
Another object of the present invention is to provide a three-phase
centrifuge having a wider range of potential adjustment of the line
of separation between two separated liquids.
Another object of the present invention is to provide a three-phase
centrifuge in which major adjustments for the separation process
can be made before the centrifuge is put into operation, and minor
adjustments can be made during the operation of the centrifuge.
Another object of the present invention is to provide a three-phase
centrifuge which prevents discharge of any interfacial emulsion
layer along with one of the desired separated liquids.
Briefly, the present invention seeks to accomplish such objects by
providing a countercurrent three-phase centrifuge having an annular
ring dam disposed adjacent to a first group of liquid discharge
openings for initial and major adjustment of the E-line, i.e., the
line of separation between two liquid phases within a centrifuge
bowl. Further provided is a skimming means mounted adjacent to a
second group of liquid discharge openings for fine adjustment of
the E-line during the operation of the centrifuge, each group of
liquid discharge openings being disposed in the same end of the
centrifuge bowl. The centrifuge is also provided with means for
preventing loss of one of the separated liquids through the solids
discharge openings, and with means for preventing the accumulation
of solids on the inner annular surface of the bowl. Also provided
is a series or plurality of radially extending ribs mounted
adjacent to the first and second groups of liquid discharge
openings for preventing relative rotation between the separated
liquids and bowl immediately prior to discharge of the liquids.
In the drawings:
FIG. 1 is an elevational view of a three-phase centrifuge embodying
the invention with a portion broken away to show the interior
thereof in section;
FIG. 2 is an enlarged sectional view, showing the liquid discharge
end of the centrifuge in detail;
FIG. 3 is an enlarged view, taken along line 3--3 of FIG. 2 showing
the plurality of radially extending ribs mounted adjacent to the
liquid discharge outlets;
FIG. 4 is an enlarged view, taken along line 4--4 of FIG. 1,
showing a vane mounted on the hub of the helical conveyor;
FIG. 5 is an enlarged view showing a mechanical linkage for
controlling a skimmer passage as embodied in the present
invention.
Referring to FIG. 1 of the drawings, there is illustrated a
three-phase centrifuge, designated generally by the numeral 10,
having an imperforate centrifuge bowl 12, journaled at the ends
thereof in main bearings 13 and 15. The bowl 12 is disposed within
a cover 14, and adapted to be belt driven by a motor (not shown),
the belt extending around a pulley 16. The centrifuge bowl 12 is
capable of being rotated, about an axis through the center thereof,
at speeds which will generate a centrifugal force equal to several
thousand times the force of gravity. Disposed within the bowl 12 is
a helical screw conveyor 18 adapted to rotate at a speed that is
slightly different than that of the bowl 12. The helical conveyor
18 includes coiled screw flights 20, the distal edges of the screw
flights 20 generally complementing the inside contour of the bowl
12. The bowl 12 and the conveyor 18 are mounted in coaxial
relationship.
It is to be noted that the axially elongated bowl 12 is mainly of
imperforate cylindrical construction. However, the end portion 22
of the bowl adjacent to end wall 24 is of convergent or
truncoconical form, its inner annular surface gradually decreasing
in diameter toward the end wall 24.
Disposed within the end portion 22, and adjacent to end wall 24, is
a group of solids discharge openings 26 symmetrically arranged
about the rotational axis. Disposed at the other end of bowl 12 is
an end member 28. Integral with end member 28 is a front hub 29
which is supported within main bearing 13. A first group of liquid
discharge openings 30 is symmetrically disposed with respect to the
axis of rotation within end member 28 adjacent to the inner annular
face of bowl 12. A second group of liquid discharge openings 32 is
symmetrically disposed within end member 28 at a lesser radial
distance from the axis of rotation than openings 30. As can be seen
in FIG. 2, and which will be more fully explained later, during
rotation of the bowl 12 the liquids separate into two concentric
pools, heavy liquid phase discharging through openings 30, while
light liquid phase is discharging through openings 32.
The helical screw conveyor 18, being hollow, has a feed chamber 34
disposed therein. The process feed stream, or liquids-solids
mixture to be separated, is introduced into feed chamber 34 through
an axially extending feedpipe 36. This mixture is then delivered
from feed chamber 34, through a plurality of radially extending
passages 38 disposed within the helical conveyor 18, into a
separation chamber 40. As illustrated in FIG. 1, the separation
chamber 40 is defined by the inner surface of the bowl 12 and the
helical conveyor 18.
Mounted within the bowl 12, and adjacent to liquid discharge
openings 32, is an annular ring dam 42. This ring dam 42 acts as a
weir, over which light liquid phase flows on being discharged
through liquid discharge openings 32. Ring dam 42 is available in
various sizes depending on the relative specific gravities of the
two liquid phases to be separated. Thus, by knowing the
concentration of a mixture, and the relative specific gravities of
each phase of the mixture, a proper size ring dam can be selected
which will provide a self-regulating centrifugal separation system.
Using the selected ring dam, and assuming the concentration and the
relative specific gravities of the phases remain constant, the
position of the E-line, i.e., the line of separation between the
two liquid phases, is fixed within the centrifuge bowl during the
rotation thereof. Thus, by fixing the exact location of the E-line,
the purity of the recovered phases can be controlled, i.e., there
will be no intermingling of the two liquid phases being discharged.
It is to be noted that openings 32 are disposed and the centrifuge
operated in a manner such that light liquid phase discharging
through the openings 32 does not completely fill the openings, and
the ring dam 42 acts only as a weir and does not reduce the flow
area of the discharge passage actually used for conducting liquid
since the latter is generously oversized. This is to be
distinguished from arrangements having flow passages which are
choked to control the rate at which liquid discharges from the
centrifuge bowl. Arrangements which choke the discharge parts have
the undesirable effect of shifting the position of the E-line
within the centrifuge bowl, thus preventing recovery of the desired
separated materials and reducing the overall efficiency of the
separation process.
Mounted within bowl 12, and adjacent to ring dam 42, is an underdam
ring 44, which partially extends over liquid discharge openings 30,
as shown in FIG. 3. This underdam ring 44 is provided to compensate
for a possible emulsion layer between the two liquid phases and to
increase the range of potential E-line adjustment. By partially
extending over openings 30, underdam ring 44 prevents the discharge
therethrough of any emulsion which might form as a layer between
the two liquid phases. The ring 44 also blocks light liquid phase
from discharging through the liquid discharge openings 30.
As best shown in FIG. 3, a plurality of radially extending ribs 46
is mounted to the face of underdam ring 44. These ribs 46 are
symmetrically disposed around the circumference of the face of
underdam ring 44, and extend over openings 30 and 32. In order to
reduce the turbulence of the liquids being discharged through
openings 30 and 32, an annular screen member 48 is removably
mounted to the faces of the ribs 46, the screen member extending in
a radial direction to the same extent as the ribs 46. The screen
member 48, with its flow-directing apertures, is an optional
accessory which can be removed when not needed.
The ribs 46 serve to maintain zero relative rotational velocity
between the liquids and bowl 12 by acting as abutting means for
liquid particles tending to increase or decrease in rotational
velocity with respect to the bowl. For example, if a liquid
particle rotating at the same velocity as the bowl moves inwardly
toward the axis of rotation, it will tend to increase in velocity.
However, any liquid particle doing the same as it moves between
adjacent ribs will immediately contact the edge of one of the ribs
46 which will thus halt movement of the liquid particle with
respect to the bowl 12. Maintaining zero relative rotational
velocity between the separated liquids and the bowl 12 is necessary
to prevent shifting the position of the E-line during the
separation process. An undesired change in the position of the
E-line prevents achievement of the desired separation results.
As shown in FIGS. 1 and 4, a vane member 68 is mounted on helical
screw conveyor 18. The latter extends between adjacent flights of
the conveyor 18 at the right hand or solids discharge end of
separation chamber 40. This vane 68 is axially located on screw
conveyor 18 immediately adjacent to the plurality of radially
extending passages 38 (See FIG. 1). As can be seen, the upper edge
of vane 68 extends above the E-line or line of separation between
the two liquid phases, and acts as a rotating dam which allows only
heavy liquid phase to flow to this converging portion of separation
chamber 40.
Also mounted on helical screw conveyor 18 is a scraper member 70.
Scraper member 70 is positioned on the periphery of the flight
adjacent to end member 28. Upon rotation of the helical screw
conveyor 18, scraper member 70 removes any accumulations of solids
on the inner annular surface of the centrifuge bowl adjacent to
liquid discharge openings 30. This prevents clogging of the
openings 30, and allows these accumulations of solids to be
loosened, and conveyed toward the solids discharge openings 26 by
the helical screw conveyor 18.
Referring to FIG. 2, it can be seen that an annular generally
cup-shaped member 50 is mounted to the exterior side of end member
28. This cup-shaped member 50 is comprised of a base portion 51 and
an annular flange portion 53. It is noted that the inner annular
surface of the flange portion 53 increases in diameter in a
direction extending away from the base portion 51. An annular zone
55 is thus defined by the outer surface of the bowl 12 and the
inner annular surface of the flange portion 55. Integral with the
base portion 51 is a radially extending rim 52. Thus, as can be
seen, an annular channel 54 is defined by the annular cup-shaped 50
and end member 28, the channel 54 being disposed adjacent to liquid
discharge openings 30. Thus, heavy liquid phase is discharged into
the annular channel 54 during rotation of the centrifuge bowl
12.
As shown in FIG. 2, disposed within the annular channel 54 is a
skimmer tube 56. This skimmer tube 56 has a liquid inlet 58 (See
FIG. 5) disposed therein for receiving the heavy liquid phase from
the annular channel 54, and a liquid outlet 59 for discharging the
heavy liquid phase.
The skimmer tube 56 is mounted so that it can be radially moved
into or out of channel 54 to receive more or less of the heavy
liquid phase within the channel. A suitable mechanism for radially
moving the skimmer tube into or out of channel 54 is illustrated in
FIG. 5. The skimmer tube 56 is actuated through a crank 82, a
threaded bolt 84, a slide member 89, a lever rod 85, and an
eccentrically mounted skimmer ring 80, the threaded bolt 84 being
threadably connected to the slide member 89. As can be seen, upon
rotating the crank 82 the slide member 89 will slide into or out of
the cover 14 and thus vary the radial position of the skimmer tube
56. The adjustment range of the bolt 84 is limited by practical
space considerations. Increased travel of skimmer tube 56 is
obtained by changing the position of the connection between the
slide member 89 and lever rod 85. As can be seen in FIG. 5, slide
member 89 and lever rod 85 are held together by a removable pin at
one of three positions, i.e., 86, 87, or 88. It is to be noted that
the skimmer tube 56 is welded to the skimmer ring 80 so that liquid
passes through the skimmer tube 56, outlet 59, and into a generally
tangentially extending channel 81 formed in the skimmer ring 80.
The present arrangement for radially moving the skimmer tube 56 is
only one means for doing so. Other means, many of which are well
known in the art, are equally satisfactory for moving the tube.
As best shown in FIG. 2, disposed on the outer periphery of the
annular cup-shaped member 50 are two annular grooves 60 and 61. As
can be seen, these grooves cooperate with two annular partitions 62
and 63 respectively to define two annular spaces 65 and 67 between
the centrifugal bowl 12 and the cover 14. Because the member 50
rotates with centrifuge bowl 12, and the partitions 62 and 63 are
stationary, this construction effectively seals the annular space
65 from the annular space 67 during operation of the centrifuge. It
can be seen that light liquid phase will be discharged into annular
space 65 via openings 32 and annular zone 55, while heavy liquid
phase is discharged into annular space 67 via openings 30, annular
channel 54, skimmer tube 56, and channel 81. The separated liquids
are recovered from annular spaces 65 and 67 through appropriate
discharge outlets (not shown).
Referring to FIGS. 2 and 3, the particular arrangement of liquid
discharge openings 30 and 32 will be described in greater detail.
It is first noted that openings 30 and 32 are not angularly
aligned, but that openings 32 are located between adjacent openings
30. This allows for the crossover arrangement, i.e., openings 30
extend from the interior to the exterior of bowl 12 in a radially
inward direction, while openings 32 extend from the interior to the
exterior of the bowl in a radially outward direction. It can also
be seen that each of the openings 30 forms a single extended
passageway extending from separation chamber 40 to annular channel
54, while each of the openings 32 includes a distinct passageway 33
extending the openings 32 to the outer annular surface of end
member 28. Thus, heavy liquid phase and light liquid phase are
discharged in opposite directions, i.e., heavy liquid phase is
discharged radially inward from separation chamber 40, via openings
30, and into annular channel 54, while light liquid phase is
discharged radially outward from separation chamber 40, via
openings 32, passageways 33, and into annular zone 55.
In operation, the process feed stream, or liquids-solids mixture to
be separated, is delivered through feed tube 36 into feed chamber
34, through radial passages 38, and into the separation chamber 40.
Under the influence of centrifugal force, the mixture forms a layer
against the inner annular surface of bowl 12, the solid particles
being urged by reason of their high specific gravity to form a
layer immediately next to the inner annular surface of the bowl,
while the lighter liquid tends to rise toward the center of the
bowl. The liquid will separate into two concentric pools toward the
center of the bowl, the heavy liquid phase being that pool nearest
the inner annular surface of the bowl.
As aforesaid, because the bowl 12 and the helical screw conveyor 18
are operating at slightly different speeds, solids are moved
axially to the right, along the inner annular surface of bowl 12,
up the inner annular surface of the end portion 22, and are
discharged through solids discharge openings 26. Ordinarily, as the
solids are moving along the inner annular surface of the end
portion 22, they would pass through both liquid phases. Thus, a
portion of each of the liquid phases would be washed out through
the solids discharge openings 26 with the solids. However, vane 68
on the helical conveyor 18 acts as a rotating dam. As previously
stated, the upper edge of vane 68 extends above the E-line, or the
line of separation between the two liquid phases. Thus, the lighter
of the two phases or that pool nearest the axis of rotation is
effectively dammed off from this portion of the separation chamber.
Therefore, vane 68 serves to allow recovery of more of the light
liquid phase because it is not carried out the solids discharge
openings 26 with the discharged solids.
Simultaneously, the two liquid phases are being discharged through
openings 30 and 32. Light liquid phase is discharged through
openings 32, while heavy liquid phase is discharged through
openings 30. As previously stated, ring dam 42 is available in
various sizes depending on the relative specific gravities of the
two liquid phases. Thus, by knowing the concentration of the
mixture, and the relative specific gravities of the phases to be
separated, a proper size ring dam can be selected before operation
of the centrifuge is begun which predetermines the position of the
E-line or line of separation between the two liquid phases.
Therefore, the major adjustment of the E-line is made before the
separation process is begun by selecting the proper size ring dam
42. As previously stated, the underdam ring 44 is provided to
increase the range of potential E-line adjustment, and compensate
for a possible emulsion layer. As can be seen in FIG. 2, underdam
ring 44 extends partially over liquid discharge openings 30.
Therefore, only the desired heavy liquid phase is discharged
through openings 30, the underdam ring preventing the discharge of
any interfacial emulsion, or light liquid phase.
Thus, heavy liquid phase is discharged through openings 30, into
annular channel 54, into skimmer tube 56 and into the annular space
67. As previously stated, the skimmer tube 56 is radially movable
so that its liquid inlet 58 can be moved into or out of the channel
54 to recover more or less heavy liquid phase therefrom. When the
liquid inlet 58 is moved into the annular channel 54 to contact the
liquid therein, the dynamic pressure of the rotating liquid coming
into contact with the inlet 58 promotes the flow of liquid through
the skimmer tube 56, and thus reduces the depth of the heavy liquid
phase pool, and consequently the E-line position is changed. This
serves to optimize performance either under static conditions, or
in response to slight variations in the relative specific gravities
of the two liquid phases, or to variations in the relative
concentration of the two liquid phases. Thus, skimmer tube 56
provides for the fine adjustment of the E-line position without
stopping the centrifuge. Also, location of skimmer tube 56 on the
exterior of bowl 12 allows for a more simplified construction, and
eliminates the problem of supporting and sealing a skimmer tube
extending deep into the central portion of the centrifuge bowl.
Thus, the present invention optimizes the efficiency of the
separation process by providing means to prevent, or compensate
for, various conditions which may occur during the operation of the
centrifuge, which conditions would normally prevent obtaining the
desired separation results .
* * * * *