Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a claxifier Eor separatincl
suspended solids from a liquicl.
The clarifier can be used in a variety of systems,
including but not limi-ted to wastewater t~eatmen-t sys-tems. In
~eneral, clarifiers for removing suspended solids from liquids
-tend to be somewhat complica-ted and consequen-tly expensive to
produce and maintain. Examples of pa-tented clarifiers are
found in ~ni-ted States Patents Nos. 3,237,767, issued to M.J.
Fowle et al on March 1, 1CJ66; ~,64~,129 issued to P.F.
McDaniel et al on February 15, 1972; 4,357,242, issued to
C.R. Chandler on Novemher ~, 1982; 4,592,845, issuecl-to P.
Lejeune et al on June 3, 19S6 and 4,663,054, issued to R.T.
O'Connell et al on May 5, 1987.
The object of the presen-t inven-tion is to ;~
15 provide a clarifier, which is relatlvely simple in -terms of -~
both structure and operation, and which is adapted to separate ~-
solids from a licluid in an efficient manner. ?
Accordingly, the present incention relates to a ;~
liquid clarifier comprising tank means, said tank means
~0 including side wall means and downwardly tapering bottom wall
means ~losing the bo-ttom end of the slde wall means; tube
means ex-tending downwardly in said tank beyond the middle
thereof; inle-t pipe means in the top wall means for
introducing a solids-containing liquid into said tube means, ,`
25 said tube means being considerably larger in area than said ~
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inlet pipe means, whereby the velocity of liquid enterincl the
tank means is substantially recl-uced upon entering sai~ tube
means; deflector means in saicl-tank means beneath -the bottom
end of said tube means for cleflecting -the liquicl en-tering the
5 tank -towards said side wall means and said bottom w~ll means;
first outle-t pipe means in -the ]ower end of said bottom wall
means for dischargin~ solids from the tank and; second outlet.
pipe means in said side wall means promi~a-te saicl top wall
means for recirculating solids from the tank means. `~
The inven-tion will be described in greater detail
with reference to t~le accompanying drawings, which illustra-te
a preferred embodiment of the invention, and wherein:
Figure 1 is a longitudinal seGtional view of the
clarifier of Fig. l;
; 15 Figure 2 is a longitudinal sec-tional view of -the `;
clarifier of Fig. li
Figure 3 is a perspective view from above of a
diffuser used in the apparatus of Fic~s. l and 2, and
Fi~ure ~ is a perspective view of an al-terna-tive form ~~-
of deflector for use in the apparatus of Figs. 1 and 2.
With reference to Figs. l and 2, the clarifier of the
present invention includes an elongated tank l, which is
defined by a cylindrical side wall 2, a circular top wall 3
and a frusto-conical hottom wall S. A mi~ture of liquid and
solids, i.e. a solids-containing liquid is introduced into the
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-top end of the tank 1 via an inlet pipe 6. Fluicl is
discharged from the tank 1 via an outlet pipe 7 near the top
end of the tank side wall 2, and solids are discharged a-t -the
narrow bottom end of the tank 1 via an outle-t pipe 9. Solids
can ~e recircula-ted to the top inlet encl of the tank via a
return pipe 10 connecting the frusto-conical bottom end of the
tank to the pipe 6. Flow through the pipe 10 is controlled by
a pump 11.
The liquid en-ters -the tank 1 via the no-t closed top
end 13 of a central down flow well or tube 14r i.e~ the pipe h
e~tends downwardly through the end 13 into the tube 14. Liquid
' entering the tube 14 is evenly distributed in the tube by a
;I diffuser 16. As best shown in FicJ. 3, the cliffuser L6
i~ includes a cylindrical side wall 17, and a circular bottom
wall 18 containing holes 20 permitting the passage of liquid
and some solids therethrough. There is sufficient clearance
between the side wall 17 and the tube 14 to permit -the free
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! flow of overflow from -the diffuser downwardly in the tube 14,
~ The leng-th of the tube 14 is more than one-half the leng-th of
,~ 20 the tank 1, liquid being discharged pro~imate the junction~
'~ between the side and bottom walls 2 and 5, respectively.
a-terial discharged from the bottom end 21 of -the
tube 14 is deflec-ted outwardly by a conical deflector 22. As
shown in ~ig. 4, the side 24 of the deflector 2~ car be
concave in the longi-tudinal direction. Alternatively, the
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deElector can be a flat plate ~not shown) inclined wi-th
respect -to the clirec-tion of flow oE the influent for
deflec~-tirlg the influerlt towards one side of the tarlk 1. 'I`he
deflector 22 clirects the liquicl raclially outwardly towarcls -the
5 side wall 2 and the bo-t-tom wall 5 oE the tank 1. With
sufficient velocity, the liquid is deflected baek towards the
center of the tank, creating a zone of radially opposed flow.
Solids settle to the bottom of the tank 1, while liquid rises
until it overflows the side wall 26 of an annlllar overflow
weir or tray 27 loca-ted proximate the top end of the -tank 1,
or is decanted to the water-out pipe. ~s shown in Fig. 2, the
weir 27 is at the same level as the fluicl ou-tlet pipe 7.
A few design considerations wor-t:hy of note are
discussecl in what follows. The pipeline velocity, i.e. the
flow velocity ~n the inlet pipe 6 should be equal -to or
greater than the velocity required to maintain any solids in
suspension and great enough to yield a flow rate ~Q):pipe
diameter ratio which will result in turbulen-t flow. The type
and construction of each static mi~er will have i-ts own
Reynolds number indicative of when laminar flow changes to
turbulent flow. The Reynolds number for pipe flow can be
calculated using the equation:
Re = 3157QS
uD
when re is the Reynolds number, Q is the flow rate in g/m,
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S is the specific gravity, u is the viscos:ity in centipoise
and D is -the pipe cliameter in inches. For ]cnown values of Q,
s and u, a value or ~ is selected and the Reynolds number
tRe) is calculated. The Re is compared with the Re recluired
for the static to achieve turblllen-t flow. :[f the vallle is
unsatisfactory, a different pipe diameter D is selected and Re
is again calculated.
The diame-ter oF -the cen-tral well or tube 1~ is
selected using the equation ~=AV, where Q is -the flow rate in
cubic feet per minu-te, A is a the cross-sec-tional area of -the
tube 14 in square feet and V is the fluid veloci-ty in Eeet per
minute. For a given flow rate and a selec-ted velocity, the
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- cross-sectional area and hence -the diame-ter can readily be
calcula-ted. The velocity should be selectecl with goQd flow
formation in mind.
The diameter of the tank 1 can also be selected using
the equation Q=AV, where Q is upward flow rate in cubic feet
per minute, A is the cross-sectional area of the -tank 1, and V
is the upward veloci-ty in fee-t per minute. Given Q, the
upward velocity or rise rate should be equal to or less -than
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the particulate matter se-ttling ra-te. The settling rate is a
characteristic of the influent, the specific gravity of the
particula-te ma-terial and the viscosity of the liquid carrLer.
If Q is known, for a selected upward velocity V, A can be
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~25 calculated. The cross-sectional value ~-,f A for the -tank to
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obtain the required cross-sectional area of the -tank.
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In or~ler to calculate the distance between -the bot,tom end of
the tube 14 and the hottom eclge of deflec-to~ 22, the first
step is to calculate the surface area of cylincler formecl by
ex-tencling the tube 14 downwardly to such bo-ttom edge of t,he
deflector 2, and make such area equal to the cross-sectional
area of the central tube 14 using -the equation 2 rh~= ~r2 ,
where h is less than or equal to r/2. The deflector 22 can be
suspended from the tube 14 using a sleeve (not, shown). The
diame-ter of -the sleeve can be greater than the diameter of -tlle
tube 14, whereby eddies are formed to improve mixing.
Tt will be noted that -the followincJ descrip-tion of
~` the operation of the apparatus refers to elemen-ts or hardware
- which do not form part of the invention, and which are no-t
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shown in the drawings.
In operation, a solids-containing liquic1 is fed via
-the inlet pipe 6 to the tank, from a sump or other source.
Level control devices start and stop a delivery pump which is
sized -to the system requirements. The pump delivers influent
-through pipes, which may include one or more s-tatic mi~ers
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l~ 20 t~7here chemicals, e.g. flocculants can be added to neutrali2e
', chargecd particles and to aid in flocculation.
The influent enters the -tank via the pipe 6 and the
tube 14. The velocity of the liquicl en-tering the tube 14 is
reduced substantially, because the diame-ter of the tube 14 is
substantially greater than that of the inle-t pipe 6. Fluid
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veloci-ty is inversely propc)rtional -to the s~uare of the
diameter of a pipe or tube. Thus, the flow velocity in the
tube 14 is substantially less than -that in the pipe 6. The
long, large diame-ter central well or tube 14 maintains
influent separate from clarif:ied or partially clarified
effluent liquid in -the tank 1. Influent flows downwardly ou-t
of the tube 14 into contact wi-th the deflector 22 which
creates a cross flow, i.e. radial flow of influent towards -the
side wall 2 of the casing 1 or 5. The influent hits the side
wall 2 and is deflectecl back towards -the center of the tank
with a downward component in -the direction of flow. Thus, a
quiet or quiescen-t zone is created by radially opposed meeting
and thus facilitating clarification, i.e. se-ttling of solids.
Moreover, mi~ing of the incoming liquid with liquid already in
the tank l is promoted. Par-tially clarified liquid rises -to
the top of the tan]c, while solids se-ttle -towards the conical
; bottom wall 5 and the outlet pipe 9. As mentioned above,
liquid, with much or all of the solids removed therefrom,
overflows the weir 27 or is decanted and is removed via the
outlet pipe 7.
By controlling the flow velocities into and out of
the tank 1, a zone of concentrated solids is maintained which,
in effect, clarifies incoming liquid by contact and
filtration. Because incoming solids are introduced by cross
flow into an area which (e~cept during start-up) already has a
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concentra-tion of solids, goocl contac-t of incomincl solids with
solicls alL-eacly in -the tanlc is effec-ted. The solicls conten-t of
the liquid in the tank is effectecl. The solicls con-tent of the
liquicl in the -tank can be incre,-secl by rec~ircuk~ting some of
the solids th~ou~h the E)iE'e 10 and the pump ll. The loc~ation
and shape oE the deflector 22 results in a quiescent zone 28
(Fig. 2) in the area beneath -the declector where the
separation settling of solids occurs most readily.
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