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Патент USA US3080119

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March 5, 1963
Filed Nov. 13, 1958
5 Sheets-Sheet 1
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March 5, 1963
Filed Nov. 15, 1958
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March 5, 1963
Filed Nov. 13, 1958
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United States Patent 0 "ice
Patented Mar. 5, 1963
There are no teachings in the prior art, however, which
disclose any method whereby some of the kinetic energy
of the discharging over?ow fraction can be utilized.
Possibly such devices have never been attempted as it
was thought that the energy which could be recovered
from the over?ow material was negligible in comparison
This invention relates to continuous centrifugal devices,
to the energy that can be recovered at the point of under
?ow. This, as noted above, is due to the fact that the
over?ow material is discharged much closer to the axis
of rotation than the under?ow material. Another fac
Ralph H. Halbach, San Leandro, Calrf., assignor to _Dorr
Oliver Incorporated, Stamford, Conn., a corporation of
Filed Nov. 13, 1958, Ser. No. 773,788
7 Claims. (Cl. 233-28)
generally of the rotary bowl disc type. More. particu
larly, this invention relates to means for utilizing the
kinetic energy of the discharging clari?ed effluent to
tor which undoubtedly has prevented people from de
veloping means for so recovering power from the clari
?ed over?ow is that the physical embodiment and dispo~
sition of the over?ow lip are such that mechanical adapta
15 tions to position jets there present a most di?icult and
so far unsolved engineering problem.
been utilized as an effective tool to obtain a separation
It has been discovered that the available energy which
of lighter fractions from heavier fractions contalned III
may be recovered from the discharging over?ow is un
a given feed material. Commonly, these separations are
expectedly quite considerable and, in fact, may account
made between liquids and solids but may, in some in
effect savings in the power required to drive such cen
Continuous rotary bowl disc type centrifuges have long
for as much as 10 to 20% of the power required to drive
stances, be a separation between two immiscible liquids 20 the centrifuge. It has further been discovered that sim
of differing densities. In machines of this general type,
feed material containing the two fractions to be sepa
rated is introduced into a rotor through a conduit co
axially disposed with relation to the rotor shaft. Due to
the centrifugal forces developed through rotation of the
rotor, the heavier constituents of the feed material are
thrown toward the outer diameter of the rotor bowl and
the lighter constituents are accordingly displaced in
wardly. The separated heavier fraction is discharged
from the periphery of the rotor through a plurality of
nozzles while the lighter fraction over?ows an annular
lip of the centrifuge located at a point closer to the axis
of rotation than the discharge point of the heavier ma
terial. By such means a slurry material may be fed to
the centrifuge and two products recovered: a clari?ed
over?ow and a denser under?ow comprised of solids.
The kinetic energy of the discharging over?ow and
under?ow is quite high in centrifugal machines. This
results from the fact that at the moment of discharge
the material is traveling at substantially the same high
velocity as the rotor. An energy gradient of the mate
rial within the rotor bowl exists between the axis of ro
tation and the outermost point of the rotor bowl. In
theory, the kinetic energy of a particle located at the
ple and effective apparatus for recovering available power
from this discharging over?ow can be constructed in a
practical and inexpensive manner without necessitating
25 extensive modi?cation of existing centrifuges of the ro
tary bowl disc type.
It is therefore an object of this invention to provide
means whereby a portion of the kinetic energy of the
clari?ed e?luent discharging from continuous rotary bowl
centrifuges can be utilized. A corollary object of this
invention is to provide means whereby the horsepower
consumption of continuous rotary bowl disc type centri
fuges can be effectively reduced.
A further object of this invention is to provide means
whereby foaming or excessive aeration of the clari?ed
ef?uent discharging from continuous rotary bowl centri
fuges is materially reduced.
Quite brie?y, the objects of this invention are achieved
by the use of an annular ring which is positioned adja
cent the over?ow lip of continuous rotary bowl centrifu
gal machines. This annular ring is provided with closed
channel sections which enforce a change in direction of
the clari?ed e?iuent liquid. By these means the velocity
of the e?iuent relative to the rotor housing is substan
tially reduced thereby enabling a reduction in the loss of
center of rotation of the rotor will be zero and the same 45
krnetic energy from the system. Utilization of this de
particle will reach a maximum kinetic energy at the outer
periphery of the rotor. In this latter case the kinetic
energy will be a function of the velocity of the rotor at
that outermost point. Ideally, then, if both the over?ow
and under?ow fractions could be discharged at the cen
ter of rotation, no power would be required to drive such
a centrifuge except to account for necessary losses due to
vice also tends to minimize foaming of the clari?ed .e?lu
ent as such e?luent is channeled to discharge substantially
as a solid stream. This is in distinction to the continuous
50 thin curtain of liquid which is discharged over the con
ventional over?ow lip, which, due to aspiration, may
cause considerable foaming in the clari?ed over?ow
friction and heat. This ideal means of discharge is im
In the drawings:
possible as, by necessity, the under?ow material must be
1 is a view in side elevation, partially cut away,
discharged at a point remote from the axis of rotation 55
showing the apparatus of this invention positioned within
if the bene?ts of centrifugal forces are to be utilized.
a rotor bowl, disc type centrifuge including additional
Also, for practical considerations, it is not possible to
reaction nozzle means.
discharge over?ow material at the center of rotation as,
FIG. 2 is a view in plan, partially cut away, of a pre
‘by necessity, provision must be made for the rotor shaft,
feed passages and other mechanical devices which im 60 ferred embodiment of the apparatus of this invention.
FIG. 3 is a view in section taken through line 3—3 of
pose physical limitations on the location of the over?ow
FIG. 2.
FIG. 4 is a detail view taken on line 4-4 of FIG. 2,
It is well known in the prior art that a substantial
showing an arrangement of the inlet openings of the ad
reduction in the power requirements for driving centri
ditlonal reaction nozzle means.
fuges may be achieved by utilizing nozzles that discharge 65 FIG. 5 is a graph in which horsepower requirements
backwardly with respect to the rotation of the rotor.
versus feeding rates are plotted.
These under?ow nozzles work on a jet reaction prin
Referring to FIG. 1, there is generally illustrated a
ciple whereby the discharging under?ow is caused to de
centrifuge having a housing 11, a rotor 12, a stationary
liver a thrust which acts in the direction of rotation and
feed passage 13 comprising concentric tubular members
enables substantial reduction in the horsepower required 70 13a and 13b, an over?ow passage 14 and an under?ow
to drive the centrifuge.
discharge passage '16. The interior of the rotor and more
particularly the rotor bowl contains a series of stacked
discs 17. These discs surround a feedwell structure 17a
nular ring and is not impinged against the trailing edge
extending from a hub portion 17b and constituting there
with feed duct means'l7c extending radially to provide
42a of recess 42.
A detailed view of the cross section of the discharge
ring 29 is shown in FIG. 3. Also FIG. 4 shows a pre
a feed connection between said feedwell structure and
the interior or separating chamber of the rotor bowl.
In operation feed material containing material to be
ferred shape given to the entrance to channel section 38.
As previously mentioned, the object of the annular
ring is to enforce a change in direction in the discharging
separated enters via conduit 18 and passes through feed
e?luent. Unlike a jetting action which is obtained by
passage 13 into the interior of the rotor bowl section
means of the nozzles 23 used for discharging the heavier
19. The shaft 21 connected to the hub portion 17b is 10 under?ow, the passageways of the annular ring depend
driven by a motor, not shown and the rotor is caused
not upon a jet action but rather upon an enforced
to spin at high velocities. The denser fraction of ma
change in the direction of the ?uid. For example, when
terial in the feed is thrown toward the periphery in the
operating a machine discharging at 200 gallons per minute
separating chamber of the rotor bowl as at 22‘ while the
while rotating the centrifuge at about 3000 rpm, one
lighter constituents of the feed are displaced upwardly 15 standard design of 30 inch rotor will provide a velocity
and inwardly through the discs 17 to discharge via pass
at the point of discharge of the clari?ed e?iuent of ap
age 14. Under?ow material is discharged via nozzles
proximately 185 feet per second. (This being, of course,
23 .into a volute section 24; conduit 26 conducts the
the velocity of the over?ow lip.) If an annular ring
under?ow material from the volute section. While not
as herein shown is installed utilizing 10 backwardly di—
illustrated herein, underflow material may be recycled 20 rected channel sections, the speed of the discharging
from conduit 26 to the lower part of the rotor 28 Where
liquid relative to the moving rotor can be changed from
by such material is recycled via return tubes 27 to a
zero to approximately 85 feet per second. Alternatively,
point near the under?ow nozzles. Over?ow material is
as stated with respect to a point ?xed in space, the dis
discharged from annular ring 29 which contains a plu
charging clari?ed ef?uent from an over?ow lip will be
rality of closed channel sections or passageways 38. 25 ?ung from the lip of the rotor tangentially at a velocity
These closed channel sections direct the over?ow ma
of approximately 185 feet per second in the direction of
terial backwardly with respect to the rotation of the
rotation and by utilizing the backwardly discharging
rotor and into volute section 31 as a substantially solid
channel sections, the e?iuent will be discharged tangen
stream. Conduit 32 communicates with volute 31 and
tially at a velocity of only about 100 feet per second
leads the clari?ed e?luent from the centrifuge.
30 (185 ft./sec.—-85 ft./sec.) in the direction of rotation.
With speci?c reference to FIG. 2, details of the pre~
Such utilization of the kinetic energy of the effluent will
ferred embodiment of this invention are shown. Annular
effect a considerable reduction of the overall power re
ring 29 is provided with holes 33 in order that the ring
quirements for operating the centrifuge.
may be securely bolted onto the normal over?ow lip
The graph of FIG. 5 is illustrative of the power sav
34 of the centrifuge. A plurality of passageways 38 are 35 ings made possible by the discharge ring. As can be
provided which force the clari?ed e?iuent of change di
observed, power requirements for driving centrifuges are
rection and discharge backwardly with respect to the ro~
plotted along the ordinant in horsepower and the feed
tation of the rotor bowl. This material discharges as at
rates to the centrifuge are plotted along the abscissa in
opening 36 of passageway 38. As can be seen, an over
hang 37 is provided on ring 29 to provide a reservoir for
the accumulation or" liquid in the event that the dis
charge passages 38 are temporarily unable to discharge
the established quantity of clari?ed e?luent. Addition
ally, if the reservoir becomes entirely ?lled, liquid can
gallons per minute.
The upper curve is a plot of test
data obtained using the normal over?ow lip while the
lower curve is a plot of test data obtained using the dis
charge ring herein disclosed. In each case, this data was
obtained when the centrifuge was operated at 3000 r.p.m.
Inspection of these curves dramatically illustrates the
power savings made possible through the use of the dis
charge ring. For example, at a feed rate of 200 g.p.m.,
about 100 HP. is required to drive a standard centri
fuge while only about 83 HP. is required to drive the
ditions within the rotor.
same centrifuge with the herein described discharge ring
As previously noted, use of this over?ow discharge 50 installed, representing a savings of 17% in overall power
ring is advantageous not only in reducing the power
consumption of the centrifuge, but also it is extremely use
I claim:
ful in preventing the formation of foam and froth which
1. In a centrifugal machine for separating a liquid
normally attends the discharge of certain liquids. By
solids suspension into a heavy slurry fraction discharg
con?ning the discharge of the clari?ed ef?uent to com 55 ing as underflow from the discharge nozzles of the rotor
paratively solid streams, aspiration and aeration of this
bowl and a light \fraction discharging as over?ow from
e?luent can be greatly reduced.
the bowl, and having means for feeding the suspension
> In the design of the annular ring it is essential that
into the 'bowl, and means for continuously recirculating
discharge over lip 41 into the discharge volute. Thus, 45
under conditions of overload, clari?ed e?luent will be
discharged over the over?ow lip 41 insuring adequate
discharge and preventing an unbalance of operating con—v
a sufficient clearance or passageway or recess 42 be
under?ow rrnaterial into the bowl at a controlled rate; a
provided to enable the backwardly discharging effluent 60 rotor structure which comprises a rotor bowl having a
to escape from the ring.
Ideally, all of the available
energy of the e?luent could be recovered if it were dis
?rst trunco-conical section provided with an over?ow neck
portion at the constricted end, a second trunco-conical
charged at zero velocity or, in other words, discharged
section, an intermediate section interconnecting the wide
backwardly at the same velocity at which the discharge
ends of said trunco-conical sections and provided with
lip of the rotor is traveling forward. If this condition
discharge nozzles spaced from one another along the
prevails, however, the effluent will have zero velocity
periphery thereof for discharging said under?ow and
with respect to the housing and fall straight downward.
providing substantial recovery of power input required
In this instance, the ef?uent would not get out of the
for the rotation of the bowl, and a hub portion closing
way of the rotating ring and thus would be impinged
the narrow end of said second trunco-conical section and
against the trailing edge of recess 42. This, of course, 70 de?ning with said trunco-conical sections an annular
would‘ destroy much of the power saving made possible
separating chamber, a. rotor shaft extending from said
by use of this invention. Accordingly, the discharging
hub portion centrally through the area de?ned by said
velocity of the e?°luent and the shape of recess 42 must
overflow neck, and an auxiliary power recovery arrange
cooperate to enable the effluent to discharge from open
ment comprising an annular energy recovery means lo
ing 36 in such a manner that the effluent clears the an 75 cated on the end of said neck portion concentrically there
with and having an inner cylindrical face de?ning the
area of the over?ow, and formed at the outer periphery
with outwardly facing recesses spaced from one another
along said periphery, each of which recesses is de?ned
by a substantially radial face located substantially in a
plane containing the rotor axis and by an associated face
extending substantially at right angles from said radial
therewith, and a second stationary tubular member sur
rounding said ?rst member in concentrically spaced rela
tionship therewith to constitute therewith an annular
stationary feed inlet passage extending into the interior
of said feedwell structure.
3. The machine according to claim 1, wherein said in
let opening of the passageways is oval, and said straight
discharge end portion of the passageways is of tubular
face and substantially parallel to the rotor axis, said an
nular means further having over?ow reaction discharge
4. The arrangement according to claim 1, wherein said
passageways communicating with respective recesses and 10
neck of the bowl has a terminal face and said
extending in a plane transversal of the rotor axis and
annular power recovery means is a ring member fastened
curved rearwardly with respect to the direction of rota
to said terminal face.
tion of the bowl and in said transverse plane de?ned in
5. The machine according to claim 1, wherein said
plan view by an inner wall shaped as a sharply bent
curve and by an outer Wall spaced horizontally from 15 over?ow neck of the bowl has a terminal face and said
annular power recovery means is a ring member fastened
said inner wall and shaped as a shallow curve converging
said terminal face, with fastening bolt members extend
towards said sharply bent curve, an elongated inlet open
ing located in said inner cylindrical face and extending
in the peripheral direction thereof, an outlet opening in
said radial face, said outlet opening in said radial face
being signi?cantly smaller than said inlet opening, said
inner and said outer walls connecting said inlet opening
with said outlet opening, whereby the ?ow cross-sections
of each passageway diminish gradually and smoothly
from said elongated inlet opening located in said inner 25
ing through said ring member in the space between re
spective reaction passageways, securing said ring mem
ber to said neck.
6. The machine according to claim 5, wherein said
bolt members are located in the respective areas extending
straight discharge end portion directed substantially at
between said inner cylindrical face of the ring member
and said sharply bent curve of the respective above de
?ned passageways.
7. The machine according to claim 4, wherein said
inner cylindrical face of the ring member provides the
effective over?ow diameter, and wherein said ring mem
normal to said radial face at a velocity great enough to
?owing through said passageways.
cylindrical face to said signi?cantly smaller outlet open
ing in said radial face, each passageway comprising a
ber has a transverse annular shelf portion located at the
right angles to said radial face and having said outlet
outer end thereof and extending inwardly from said in
opening thereof spaced from said associated face at a
cylindrical face to provide an annular inwardly over
mnimum radial distance from said cylindrical inner face,
hanging dam against spillage of over?ow liquid over
whereby the over?owing liquid discharges in a direction
avoid impingement upon said associated face, thereby
providing recovery of a substantial portion of the energy 35
expended for maintaining said recirculation of under
?ow, in addition to the power being recovered through
the reaction nozzles discharging the under?ow.
2. The machine according to claim 1, wherein there is
provided a longitudinal feedwell structure extending from 40
the hub portion concentric with the shaft and having
feed duct means extending radially therefrom to provide
a feed connection between said feedwell structure and
said separating chamber, and wherein said means for
feeding the suspension comprise a ?rst stationary tubular
member surrounding said shaft in spaced relationship‘
References Cited in the ?le of this patent
Jahn _______________ __ July 9, 1912
Leitch et al. _________ __ Feb. 19, 1918
Hall ________________ __ Jan. 14, 1919
Ruda _______________ __ June 18, 1929
Svensson ____________ __ Aug. 15, 1939
Glasson _____________ __ Jan. 13, 1953
Millard ____________ __ Nov. 30, 1954
Caddell _____________ __ May 29, 1956
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