Note: Descriptions are shown in the official language in which they were submitted.
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SEPARATOR EMPLOYING AN ANNULAR V:E :RTICAL
FEEDWELL WITH ASSOCIATE~ CONCENTRIC
ANNU~R BAF~LE PLATE AND METHOD OF USING
SAME TO SEPARATE SOLIDS FROM LIQUI S
Back~r~be ~
There has long been an interest in apparatus
useful in the separation of solid materials from liquids
in which the solid materials are suspended. Such apparatus
have applications in diverse fields, such as the handling
of commercial and municipal wastes, beet sugar manufacture,
coal and uranium mining, phosphate rock processing and the
like.
U.S. Patent No. 3,523,889 describes one such
apparatus for rapidly and continuously separating suspended
solid materials from liquids. The apparatus described was
a marked departure rom the prior art in that i~ involved
the introduction of liquid in~luent feed containing freshly
agglomera~ing solids at a location near th~ bottom o~ the
separating tank or apparatus and below thel~el of previous-
ly aggiomerated solids. By means of this apparatus, a
dynamic sludge bed was created in which particles a~er being
dispersed radially outward collide with other agglomerated
particles to cause still ~urther agglomeration and settling.
This brought about substantial improvement in the throughput
of solid materials to be recovered.
In spite o the improved results obtained with the
apparatus of U.S. Patent 3,523,889, there is a theoretical
limit for a given unit or apparatus on the throughput and
recovery o~ solids. In order to increase throughput larger
and larger units ha~e been built. The erection and operation
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of large units have created problems in the realization of
expected increased throughput. Efforts have been made to
introduce the influent feed at more than one point within
the tank. These efforts led to various feedwell structures,
including annular feedwells, such as the one disclosed in
Australian Patent 421,865.
This patent describes a sedimentation apparatus
having an annular feedwell through which liquid feed con-
taining suspended solids is carried to an upper portion of
the tank above the level of previously settled solids. Upon
leaving the feedwell, influent feed strikes downwardly-angled
defl-ecting plates and is dispersed within the tank.
In the pxesent invention, it has been found that
by using an annular feedwell which deli~ers influent feed to
7'~ a position near the bottom of a settling tank, at which
posi~ion the influent feed is deflected radially outward and
inward by a substantially horizontal concentric annular
baffle, it is possible to maintain a substantially uniform
dynamic sludge bed in settling tanks of large diameter and
to achieve a high throughput of solids per unit area of
settling tank. It has also been found that by using an annular
feedwell with associate~ planar horizontal baffle plate it is
possible to effect a more even distribution of feed and solids
to be settled throughout the tank~
SummarY of the Invention
The present invention is directed to a sedimenta-
tion apparatus useful for rapidly and continuously separating
suspended solids from liquid at a predetermined and ~ontrolled
rate.
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According to the present invention, then, there is
provided a clarifier or thickener apparatus useful for separa-
ting solids from a liquid feed containing solids suspended
~: therein comprislng a tank for receiving the liquid feed, the
tank being provided with a top liquid outlet means and a bottom
solids outlet means, influent feed conduit means for supplying
- the liquid feed positioned closer to the top of the tank than
to the bottom of the tank, annular feedwell means in fluid
communication with the influent feed conduit means to receive
the liquid feed, the annular feedwell means being positioned
vertically within the tank such that the bottom of the annular
feedwell means is closer to the bottom of the tank than to the
-~ top thereof, the annular feedwell means being open at the
bottom thereof for the discharge into the tank of the liquid
feed supplied to the annular feedwell means via the influent
feed conduit means, the annular feedwell means having a larger
annular cross~section at the upper portion thereof than at the
lower portion thereof for the flow of the liquid feed intro-
duced thereinto, the annular feedwell means comprising an inner
shell or wall and an outer shell or wall, the bottom end of the
inner shell or wall being flanged radially inwardly with respect
to the tank and the bottom of the outer shell being flanged
radialy outwardly with respect to the tank, the bottom end of
the inner shell of the annular feedwell means extending below
the bottom end of the outer shell of the. annular feedwell means,
substantially horizontal baffle means positioned substantially
concentric with respect to the annular feedwell means and com-
mensurate with respect to the projected cross-sectional area
of the open bottom of the annular feedwell means the baffle
means being fixed and positioned so as to be spaced from but
directly opposed with respect to the open bottom of the annular
feedwell means for arresting and diverting the flow of the
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liquid feed leaving the bottom of the annular feedwell means
so that the liquid feed upon leaving the bottom of the annular
feedwell means moves radially inwardly past the bottom flanged
end of the inner shel.l of the annular feedwell means and radially
outwardly within the tank with respect to the bottom flanged
end of the outer shell of the annular feedwell means, the space
available for the radial outward flow from the bottom of the
annular feedwell means being greater than the space available
for the radial inward flow of the liquid feed, and adjustable
means for controlling the opening or distance between the open
bottom of the annular feedwell means and the baffle means
to control the discharge of the liquid feed from the open bottom
of the annular feedwell means, the adjustable means to control
the discharge of the liquid feed from the open bottom of the
feedwell means comprising at least one vertically slidable
flanged sleeve attached to the bottom of the feedwell means.
According to another aspect of the present invention,
there is also provided an annular feedwell structure suitable for
receiving and for radially inwardly and outwardly distributing
liquid containing suspended solids comprising a closed con-
tinuous outer wall structure, a closed continuous inner wall
structure, the upper ends of the outer and inner wall structures
being coterminous, the inner wall structure being positioned
substantially concentric with respect to an inwardly spaced
from the outer wall structure, the inner and outer wall
structures defining a top and bottom open-ended annular space
or annulus therebetween, the bottom end of the inner wall
structure extending below the bottom end of the outer wall
structure, each of the ends of the outer and inner wall struc-
tures being radially flanged, the bottom end of the outer wallstructure being radially outwardly flanged and the bottom
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end of the inner wall structure being inwardly flanged or in
the opposite direction from the flange at the bottom end of
the outer wall structure, and a substantially horizontal flat
baffle plate positioned directly beneath and spaced from the
bottom ends of the wall struc~ures, the baffle plate being com-
mensurate in size relative to the projected cross-sectional
area of the annular space or annulus defined by ,the bottom ends
of the wall structures and the upper portion of the annulus
defined by the inner and outer wall structures being greater
in cross-sectional area than the lower portion of the annulus
defined by the inner and outer wall structures, and adjustable
means for controlling the opening or distance between the open
bottom of the annular feedwell means and the baffle means to
control the discharge of the liquid feed from the open bottom
of the annular feedwell means, the adjustable means to control
the discharge of the liquid feed from the open bottom of the
feedwell means comprising at least one vertically slidable
flanged sleeve attached to the bottom of the feedwell means.
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The apparatus accordlng to an embodiment o~ this inven-
tion comprises a tank s-tructure, typically a cylindrical tank,
which has a top outlet means for removal of a clarified liquid
and a bottom outlet means from which settled solids can be with-
drawn. Influent liquid feed containing suspended solids is
introduced into the tank by a suitable influent means, such
as a pipe, which is connected to an annular feedwell. The feed-
well extends vertically downwardly within the tank to a position
substantially nearer the bottom than the top.
During passage of the influent liquid feed through
the feed pipe, agglomerating agent, e.g. an anionic polyelectro-
lyte, such as a polyacrylamide, is added to the influent liquid
feed. The net effect of the addition of the agglomerating agent
is to initiate the fresh formation of agglomerates of the solids
~n the influent liquid feed before the feed enters the annular
feedwell. If desired, however, agglomerating agent may be added
to the influent feed in the annular feedwell.
The influent liquid feed containing freshly agglomerating
solid materials is introduced into the annular feedwell through
the influent pipe and passes through the feedwell to a position
of entry or discharge within the tank structure. Closely adjacent
to the bottom discharge or opening of the annular feedwell a
substantiallyhorizontal planar annular baffle plate which is
concentric with the annular feedwell is positioned. The baffle
plate is dimensioned to substantially fit or to have the same
shape and size of the bottom discharge opening of the annular
feedwell. The baffle plate arrests and diverts the flow of
influent solids-containing liquid feed so that the feed is direct-
ed radially inward and outward within the tank through the open-
ing defined
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by the bottom of the annular feedwell and the matching baffleplate.
The clarifier or thickener apparatus of this embodiment
also includes means for controlling the rate of discharge of
solid materials through the bottom outlet means in order to
establish and maintain the level of previously settled solids
above the position of entry of influent feed. The apparatus
is also provided with means for withdrawing clarified liquid
through the top outlet means.
In accordance with another embodiment of the invention,
the influent feed means is positioned near the top of the appara-
tus and the annular feedwell extends concentrically vertically
downward within a cylindrical settling tank.
In accordance with yet another embodiment, the apparatus
is provided with vertically slidably adjustable sleeves, such
as right angles or flanges, attached to the bottom of the annular
feedwell at the position where the influent liquid feed enters
the tank. These adjustable sleeves function to define the open-
ing through which the feed passes radially inward and outward
into the tank before being dispersed so as to alter its velocity
and improve the likelihood that additional agglomeration will
occur within the tank. In this way the throughput and recovery
of solids can be increased.
The apparatus may be provided with a rotatable rake
or arm for collecting agglomerated and settled solids and conduct-
ing such settled solids to the bottom outlet means for discharge
and recovery. Desirably, the annular baffle plate is attached
or fixed to the top of the rotatable rake or raking means.
It is therefore a general object of the present invent-
ion to provide an improved apparatus for the settling and removal
of suspended solids from liquids, the apparatus enabling high
throughputs for a settling tank of large diameter.
It is also a general object of the present invention
to provide an improved process for the settling and removal
of suspended solids from liquids which process is highly ef-
ficient and permits high throughputs per unit area of settling
tank.
According to the present invention, then, there is
provided a process for separating solids from a liquid containing
solids suspended therein comprising adding an agglomerating
agent to the liquid to initiate the agglomeration of the solids
suspendedwithin the liquid, establishing and maintaing a rela-
tively dense fluid mass of suspended agglomerated solids within
a settling zone, the mass of suspended agglomerated solids oc-
cupying the lower portion of the settling zone, the upper portion
of the settling zone being occupied by clarified liquid derived
from the aforesaid solids-containing liquid such that there
is a defined interface between the clarified liquid and the
relatively dense mass of agglomerated solids, introducing the
liquidcontaining agglomerating agent and initially ~ormed agglome-
rates of solids into the relatively dense mass of agglomerated
solids, the liquid being introduced into the relatively dense
mass of agglomerated solids via an annular flowpath beneath the
interface and in the direction such that the liquid introduced
into the mass of agglomerated solids is introduced thereinto
concentrically or axially in directions radially inwardly and
outwardly relative to the settling zone, withdrawing agglomerated
solids from the bottom of the settling zone and withdrawing clari-
fied liquid from the top of the settling zone, the withdrawal of
clarified liquid and agglomerated solids from the settling
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æone and the introduction of liquid containing suspended solidsthereinto being conducted without additional agitation and so
as to maintain the interface at a predetermined level relative
to but above the introduction of the liquid into the relatively
dense mass of agglomerated solids such that only clarified liquor
is withdrawn from the top of the settling zone.
This invention will be better understood from the follow-
ing detailed description of a preferred embodiment thereof made
with reference to the accompanying drawings.
Fig. 1 is a topplan view of a thickener or clarifier
apparatus embodying this invention.
Fig. 2 is a partial sectional view along the line 2~
2 of Fig. 1.
Fig. 3 is a partial sectional view along the line 3-
3 of Fig. 1.
Fig. 4 is a sectional view along the line 4-4 of Fig.
2.
Fig. 5 is a schematic view of the apparatus.
Fig. 6 is a persp~ctive view of the annular feedwell
with associated concentric annular baffle plate and influent
pipe.
Referring to the drawings, Fig. 1 is a top plan view
of sedimentation apparatus 10. Apparatus 10 comprises a container
or tank structure 12 shown as cylindrical in design. Wall 14
of the tank structure serves to contain the liquid and suspended
solids undergoing treatment. Influent liquid feed containin~
suspended solids, e.g. aqueous liquids containingcoal, uranium
ore orother suspended solids, organic and/or inorganic, is intro-
duced into apparatus 10 through a suitable influent means, such
as pipe 16, shown here as positioned at or near the top of
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apparatus 10. During passage through the pipe, an agglomerating
agent, e.g. an anionic polyelectrolyte, such as a polyacrylamide,
is desirably added to the liquid influent feed by suitable means,
such as feedlines 18 positioned in fluid communication with
influent feed pipe 16. The purpose of the addition of the agglo-
merating agent is to initiate the formation of agglomerates
of the solids in the influent feed. The influent liquid feed,
now containin~ freshly agglomerating solid materials, is led
via feed pipe 16 into vertical annular feedwell 22. In the
10 embodiment shown, influent pipe 16 is Y-branched and has two
outlets 20a and 20b and annular feedwell 22 extends vertically
downward within tank 12. Alternatively, it is possible to add
agglomerating agent prior to passage of the liquid influent
feed through influent pipe 16 and/or after the influent feed
has entered feedwell 22.
As shown in Fig. 2, the influent feed, upon entry into
annular feedwell 22, passes to the bottom of feedwell 22 to
a position from which it enters the tank, namely, the open bottom
of feedwell 22. This position of entry of the influent feed
20 from the feedwell is substantially nearer the bottom of tank
12 than the top. At the open bottom of feedwell 22 there is
closely positioned annular baffle plate 24, concentric with
annular feedwell 22. Baffle plate 24 is planar and substantially
horizontally positioned parallel to and commensurate in size
to but spaced from the open bottom of feedwell 22. Baffle plate
24 serves to arrest and divert the flow of influent solids-
containing liquid feed so that the influent feed is directed
radially inward and outward within tank 12 but without signifi-
cant agitation of the dynamic mass of agglomerated solids at
30 about the bottom or lower portion of wall 14 of the tank
structure. As solid particles
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or agglomerates are deflected radially inward and outward they
collide with other particles and agglomerates in the mass of
agglomerated solids whereby further agglomeration is promoted.
- Because the radial movement of the particles is both inward
and outward, greater and more efficient utilization of the set-
tling tank is achieved and more uniform distribution of àgglome-
rated and/or settled solids result.
Referring now to Fig. 2, the apparatus is provided
with solids discharge means, such as valve 25 and discharge
pump 26, for controlling the rate of discharge of segregated
and collected solid materials through bottom outlet means 28,
such as the three-channeled pipe shown more particularly in
Fig. 4.
During operation of the apparatus it is essential that
the level of previously settled solids, i.e. interface 50, bet-
ween the clarified liquid and the relatively dense, dynamic
phase of agglomerated solids be maintained above the position
where influent feed enters tank 10 from annular feedwell 22.
In order to establish and maintain the desired level of previous-
ly settled solids, i.e. dense fluent mass of agglomerated solids,
apparatus 10 is provided with sensing means 30, such as mechanical
sensors or photoelectric sensors, for determining the level
of the settled, dense solids phase and for activating valve
25 and discharge pump 26 through suitable electric circuitry
(not shown). Settled agglomerated solids are removed at a rate
; such that the interface or top level of previously settled solids
is maintained above the position where the influent feed contain-
ing agglomerating a~ent enters tank 12 via feedwell 22 for agglo~
meration, settling and removal.
The clarifier or thickener apparatus 10 is shown provided
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with viewing window 32 to permit visual monitoring of the level
of the interface between settled solids and clarified liquid.
Viewing window 32 can also be used, as indicated hereinabove,
in connection with photoelectric sensors and an external light
source (not shown) to create a system for activating the valve
and discharge pump.
Also as shown in Fig. 2, annular feedwell 22 is larger
in cross-section at upper portion 22a closer to influent pipe
16 and smaller in cross-section at lower portion 22b closer
10 to the bottom of feedwell 22 and the point of entry of the solids-
containing influent feed into tank 12. At the location of entry
of the influent feed from annular feedwell 22 into tank 12,
annular feedwell 22 has attached to both its inner and outer
edges upwardly or downwardly slidably adjustable sleeves, angles
or flanges 34a and 34b which, in combination with baffle plate
24, define the opening or space between baffle plate 24 and
the bottom of feedwell 22
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and function to further increase or decrease and adjust
or alter the flow and velocity of influent feed into tank
12 as the influent feed is discharged from the bottom of
feedwell 22 radially inward and outward within the tank.
Control of solids agglomeration within tanX ~ is thereby
effected and increased throughput is achieved.
Annular feedwell 22 is conveniently attached to
bridge structure 36 which also supports central vertical
rotatable column 38 which is caused to rotate by an
appropriate driving means, such as motors and gears 40.
Attached at the lower portion of vertical rotatable column
38 are rotatable raking or stirring-moving mean~ 42, such
as rakes. On the bottom of means 42 blades 42a are fixed
and positioned to be closely adjacent to bottom 44 of tank
12, Rake blades 42a function to gather the settled solids
and conduct settled solids along bottom 44 of tank 12 ~o
outlet means 28. Bottom 44 of the tank is made of an
appropriate material, such as a metal, e.g. steel or concre~e
or asphalt. Settled solids are removed at a rate such that
the level of the relatively dense, dynamic settled solids
phase is maintained above the position where the influent feed
enters the tank. As illustrated, settled solids ar~ first
gathered and conducted along bottom 44 of tank 12 by rake 42
and rake blades 42a to a collector or sump 46, such as a
conical sump. Within sump 46 settled solids are directed
dow~ward to the outlet means 28 by scraper blades 48
attached to the lowermost portion of rotatable vertical
column 38. As shown more particularly in Fig. 4, the outlet
means 28 comprises a three-channeled pipe leading from
sump 46. Annular baffle plate 24 is conveniently attached to
the top of rake 42.
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The direction and movement of the suspended solids-
containing influent feed within apparatus lO is indicated in
Fig. 3. Feed enters apparatus lO through pipe 16 and is directed
to outlets 20a and 20b. The influent liquid feed then enters
annular feedwell 22 and passes vertically downward to a position
of entry into the tank below the upper level 50 of the relatively
dense settled solids phase. ~he flow of the influent liquid
feed is directed radially inward and outward by means of concen-
tric annular baffle plate 24 as the feed exits the bottom of
annular feedwell 22. Annular sleeves 34a and 34b which are
slidably adjustable up and down in combination with baffle plate
24 define the opening at the bottom of feedwell
~2
22 available for the feed to flow or move into tank ~1~ radially
outwardly and inwardly.
As the solids material in the influent feed agglomerates
and settles to the bottom of the tank to form the dynamic mass
of agglomerated solids clarified liquid effluent having a reduced
solids content, preferably substantially free of solids, moves
up through tank 12 within the mass of settled solids from the
point of entry of the influent feed into the tank and moves
above the level 50 of settled solids and overflows the top of
the tank 12 where it passes over either weir 51 located centrally
in the tank or annular weir 53 attached to the upper portion
of the inside of tank 12. Liquid effluent passes over weirs
51 and 53 and enters either inner annular overflow launderor
channel52 or outer annular overflow launder or channel 54 of
weirs 51 and 53, respectively. Channels 52 and 54 are intercon-
nected by connector pipe 56. Clarified liquid is then removed
from the apparatus by an appropriate outlet means, such as conduit
58,
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which receives the clarified liquid.
Fig. 5 is a schematic representation of the
operation of the appara~us of this invention and depicts
influent feed entering influent pipe 16, agglomerating agent
being added as the influent feed mo~es within pipe 16. The
influent feed, now containing agglomerating solids, is con-
dùcted to outlets 20a and 20b of pipe 16 and introduced into
the feedwell 22 for discharge into lower portion of the tank.
Within the tank influent feed-containin~-fr-eshly agglomerating
solid material is deflected radially outward and inward by
concentric annular baffle plate 24 and mixed with previously
agglomerating settled solids within the tank. Solids are
removed through outlet means 28 and clarified effluent
liquid is removed through outlet means 58. The settled solids
which are removed from the bottom of the tank can, if desired,
be reintroduced into influent pipe 16 to assist in solids
agglomeration and then into the solids agglomerating settling
zone within the tank to promote further agglomeration and
settlîng of solids.
Fig. 6 is a perspective view of the annular
feedwell 22 and an assQciatedY-branched influent pipe 16
to clearly show the manner in which influent feed enters ~he
feedwell at outlets 20a and 20b. Also shown is the associated
concentric annular baffle plate 24 and vertically slidably
adjustable right-angled concentric annular outer sleeve 34a.
As will be apparent to those skilled in the art in
the light of the foregoing disclosures, many modifications,
alterations and substitutions are possible in the practice of
this invention without departing from the spirit or scope
thereof.
