Note: Descriptions are shown in the official language in which they were submitted.
C I F 3: C A T I O N
TI~
~9iAPPARATUS ~ND MET~OD FOR G.~3 AB~30RP~IO~ :IN ;~ LIQUID~
BACRGRO~JND OF :ir~E INVENT:I:ON
5_ield ~:1~ tha :r~7~ti~n
The present invention relates generally to an
apparatus and method for adding a gas or liguid to a
liquid, and more particularly/ for effec~ing absorption
of a gas in a liguid.
~0~ ri~ n o~ ~h@ ~
Water treatment ~or potable water supplies
frequently involves the addi~ion of chlorine to maintain
water quality. However, the use of chlorine leaves
carcinogenic residuals in the water in quantities wh.ich
15are unacceptable. It has been ~ound ~hat ~reatment by
ozone enables smaller amounts of chlorine to b~ used to
maintain the purity o~ the ~ater in a water supply
system.
De.vices are known for injecting ozone or other
20gases into water for purification. In these devicei~, the
gas is ~ubblf~d into a liquid stream for absorptlon at
~' atmospheric pressure and siubmergence.
I~VE~T~0~
An ob7ect of the present invention isi to proYide
25increased absorption of a gas into a liquid.
Another ohject o~ the invention is to provide
effective water treaitment using reduced levels of
chlorine in a water supply system.
Arlother object of the invention is to provide means
30or ozone treatmfant of watPr for a water supply system.
~1~ A further object of the invention is to provide for
', nearly complete absorption of a gais in~o a liquid at
increased absorption rates.
I Yet another object is to effectively add a gas or
j~ 35liquid to a lifquid with a~ increased dwell time and
~' efficient mixing. These and other objec~s of the
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invention are pro~ided .in a method and apparatus for
injecting gas or li~uid at a low pressure into a liquid
and then directing th~ mixture into a pump. When a gas
is injected into the li~uid, the gas and liquid mixture
5 is caused to flow downward prior to rPaching the pump to
increase the dwell time of the gas bubbles in the liquid.
Because oî the increasirlg dep~h of liquid, the pressure
of the ga~ and 1 iquid mix~ure increases during the
downward flow, ~hereby reducing ~he si~e of ~he bubbles
10 and increasing the absorption rate of the gas into the
liquid. The rate of downward flow of the liquid and gas
mixture is slightly greater ~han ~he upward mo~ion of the
gas bubbles os that a higher conce~tration of the gas
bubbles is drawn into the pump. The li~uid and gas
mixture is then discharged under pressure from the
apparatus into a reservisr of the li~uid.
The apparatus o~ thQ invention is generally eithPr
supported or suspended within a tank and has a liquid
inlet below the liquid level in the tank. Within the
inlet, the gas or a second liquid is injected into the
li~uid. In one development, the in-flowing liquid
creates a luw pressure zone which draws in the gas or
second liquid, such as by flowing over air foils having
feed openings on low pressure surfaces, so ~hat a
25 pressurized f~ed is not required. In another
developm~nt, the liquid inlet is maintained at a constant
level below the liquid surface. This en5ures that the
~apparatus can operate regardless of the liquid level.
.~A generally vertically oriented tube extends frQm
the liquid inlet to an inlet of the pump so ~ha~ the
liquid and gas mixture are drawn downwardly opposite the
~,~direction of the gas bubbles, which increases the dwell
time of the gas in the liquid. The liquid and gas
~:mixture is agitated and mixed by the pump and is then
forced out a pump outlet. At least one~ and preferrably
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a plurality of nozzles are provided at the outlet of the
pump for directing i;he liqu.id and gas mixture back into
the li~uid reservoir.
Thus, the gas is in contact with the li~uid for an
increased length o~ tlme, the dwell time of the gas
bubbles in the liquid being controlled by the flow rate
: in the vertically dispos0d tube. Furthermo~e, the
abs~rption of the gas into the liquid is increased by the
increasing pressures present as the liquid and gas
lo mixture flows downward through the tube. Once in the
pump, the pump impeller imparts energy to the mixture
which further reduces the bubble size and mixes the gas
- and liquid~ after which the liquid and gas mixture is
subjected to a back pressure created by the nozzles at
the outlets of the pump. The back pres~ure increases the
: gas absorption rate as taught by Stearns in his U.S.
~ Patent No. 3,~77,5~1.
; Once discharged from the apparatus, ~he gas bubbles
have a still further opportunity for absorption while
, 20 rising to the surfa~e of the liquid within the resevoir.
,~, The absorption of the gas into the liquid is even further
enhanced by directing the nozzles of the device somewhat
~,1 downwardly so that the travel time of the bubbles through
1~ ~he liquid is increased. The no~zles also disperse the
;3~ 25 liquid and gas mixture throughout the container or
:`1 reservoir.
-, The method and apparatus of ~he present in~enti~n
are particularly useful in effecting ozone, oxygen or air
absortion during potable water treatment, and, when ozone
is used, a reduced amount of chlorine is required while
maintaining the quality of the water. It is expected
that absorption of the ozone or other gas into the water
will be such that little, if any, of the gas bubbles
leave the liquid. It is also contempla~ed that the
.l~ 35 present apparatus can be used for carbonation of
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beverages and the like, as well as for other gas/liquid
or liguid/liquid m;ixing operations, and may even be
useful in ga~/gas mixing. In these instances, the two
fluids being mixed preferrably have different specific
5gr~vities to enable the dwell time ~o be ~ontrolled and
increased.
B:P~IE:F DESCRIPl~ION OF 5r~IE DR~WIN(:S
Figure 1 is a vertical cross section of an
apparatus a~cording to the principles of the present
10invention in us~ in a liquid reservoir;
Figure 2 is a cross section along line II-II of
Figure 1 showing a pump outlek arrangement for the
apparatus;
Figure 3 is an enlarged detail of an airfoil
15arrangement at the liquid inlet o~ the apparatus o~
Figure 1:
Figure 4 is a side elevational view of an airfoi~
of Figure 3;
Figure 5 is a cross section of Figure 4 showing the
20airfoil arrange~ent of khe present invention;
Figure 6 is a vertical cross section of a s~cond
embodiment of the invention; and
Figure 7 is a cross ~ection along line VII-VII of
Figure 6 showiny a venturi air inlet.
- 25D~TAILED DESCRIPTION OF T~E
~ PRES~N~LY PREF~RR~D ~MBODIMEN~5
i In Figure 1, is shown an apparatus 10 within a tank
12 filled with liquid 14. For example, th2 liquid 14 can
be water in a water treatment system to which oæone or
30oxygen is to be added, although it can also be a liquid
into which gas, such as carbon dioxide or the like, is
to ~2 mixed ox any two fluids preferrably of differing
pecific ~ravities. The apparatus ~0 has an inlet
opening 16 in~o which ~he liquid 14 is drawn ~or passage
35through a vertical tube 18~ ~lthough a vertical tube 18
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i~ preferred, it is of cour~e possible for the tube 18
to be inclined as well, howe~er, not at a~ angle
exceeding 45 degrees. In the illustrated example, the
inlet 16 is of a larger diameter than the tube 18. The
enlarged inlet 16 is formed by a frusto-conical wall 20
connecting the tube 18 to a larger diameter wall 22.
Within the tube 18, are one or more airfoils 24
which inject a gas or liquid, such as ozone, in-~o the
liquid 14. After injection og ~h~ gas or liquid, ~he
mixture flows downward through the tube 18 at a flow rate
such that gas bubbles 26 will not rise to the surfaceO
The tube 18 is connected at its lower end to a pump 28
which draws the liquid 14 downward along the vertisal
extent of the tube 18. ~he kube 1~ can be as short as
one foot or as long as 40 or more feet. The pump 28
includes an impeller 30 mounted therewithin on a shaft
- 32 which is driven by a drive motor 34. The drive motor
34 is suspended ~elow the device 10 and is of a
submersible de~ign, including liquid tight seals and the
like. A power cable 36 connects the dri~e mctor 34 to
a control box 38 which can include a power switch and/or
a speed control.
~ At an outlet of the pump 78 is mounted a nozzle
`~ hou~ing 40 which includes a plurality of noz~le openings
42 for directing the liquid 14 back into the tank 12.
` The nozæles 42 of the illustrated example are directed
., somewhat downwardly in a mutually opposed radial
;i: direction to provide increased dispersion of the gas-
treated liquid.
,~ 30 The device 1~ is shown mountPd vn a base 44 resting
on a ~loor of the tank 12. It is also possible to
suspend the unit 10 from a structure over the tank 12 or
~ ~ even to provide a floating support (not shown).
,~ Referring now to Figure ~, the nozzle housing 40
! 35 includes eight of the nozzles 42 directed radially
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outward in the nozzl~ hou~ing ~o ~t equally spaced
intervals. each of the nozzles 42 includes a feed
channel 46 which transmi~s the gas-treated liquid 14 from
the pump 28 to the individual nozæles ~2. Although other
nozzle arrangements are possi~le~ the illustrated nozzle
design disperses the gas treated liquid throughout the
tank 12. The outlet opening of each nozzle 42 is
somewhat smaller tha~ ~e respec~ive ~eed channel 46 50
that a back pressure is genera~ed at ~he nozæles ~2 by
the pump 28. A nozzle outlet pressure for the present
device of 10 psi has been found to be ideal for ozone or
13~ while an outlet pressure ol 20 psi is better for
oxygen or 2
In Figure 3, two of the airfoil members 24 are
positioned within the vertical tube 18, each of th~
airfoils 24 including a forward high pr~ssure surface 50
and a low pressure surface 52 rel~tive to the 10w of ~he
liquid 14 as indicated ~y arrows F. The forward surfaces
50 of the airfoils 24 create high pressure regions in the
liquid 14 during the flow of the liquid, while a low
pressure is created at the low pressure surfaces 52~
Openings 54 are provided in th~ low pressure surfaces 52
extending through to the interior of the airfoils ~4.
Internally of each of the airfoils 24, a divider wall 56
is provided to divide each airfoil into two chambers 58
and 60. The openings 54 are in communica~ion with ~he
~irst chamber 58 from which a fluid i5 fed~ The low
pressure at th~ openings 54 draws the fluid through ~he
openings so that the fluid feed need not be pressurized.
The bubbles 26 of gas which have been drawn from
: the openings 54 have an upward velocity shown
schematically at ~0 The flow rate of the liquid has a
downward velocity as indicated at ~. In a preferred ;.
example, the liquid flow rate B is greater by a small
amount than the upward velocity ~ of the bubbles 26.
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Referring now to Figure 4, the airfoil 24 extends
across the extent of the tu~e 18 and includes one ~ more
of the gas outlet openings 54 along the low pressure
surface 520 The first chamber 58 in which the openings
54 are provided i5 supplied with a gas or other fluid
through a conduit line 62. The airfoil unit 24 has been
mounted within the tube 18 through an opening 64 cut in
the side of ~e tube 18, ~he opening 64 being sealed with
a sealant 66 proYided around the interface of the airfoil
24 with the tube 180
In Fi~ure 5 can be seen a preferred ~mbodiment
including two of the air~oils 2~ moun~.ed within the
cylindrical tube 1~ and conneGted to a single gas supply
source 68 which, for example, contains ozone *or use in
waker purification. Since the op~nings 54 on the low
pressure surface 52 draw the gas of other fluid from the
source 6~, the source 68 need ~ot be under pressure,
although it certai.nly mayO The source 68 can even be an
open tube f~r aspirating air or enriched air.
The devic4 of the first embodimen-t op~rates by
drawing in the liquid 14 at the inlet 16 so thak it flows
past the airfoils 240 The flowing liquid 14 creates low
pressure regions adjacent the gas outlet openings 54,
which in turn causes bubbles of the gas to be drawn
~5 through the openings 54 and into the liquid. The gas can
either be induced by the velocity ov~r the airfoil
section or can be supplied undPr pressur2 for a greater
flow rate. Since the liquid flow ra~e ~ is greater ~han
the gas bubble rise rate ~, the gas bubbles are carried
down the tube 18 at a relatively slow rate to result in
a co~centraked mixture o~ yas and liquid, The
. counteracting ~lows o~ liquid and gas thereby increase
¦ the dwell time of the bubbles 26 in the liquid. As the
mixture descends down the tube 18, ~he increasing static
pressure reduces the size o the bubbles 26 and increases
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the ab~orption rat~ of the gas into the liquid 14. The
compressed mixt.ure then enters the pump 28 whi~h mi~es
the liquid and gas and f~rther reduces the si~e of the
bubbles 26. The mixture is then discharged through th~
nozzles 42. The nozzle outlet pressure of one
emhodiment, for example, is between 10 to 20 pounds per
squar~ inch 50 that a back pressure is provided at the
nozzles for further gas absorption. Since the nozzles
42 are directed downwardly, any gas bubbles which have
yet to be absorbed will traverse a greaker path to rise
to the surface of the liquid and thereby fac.ilitate even
further gas absorption by the liquid.
A second embodiment is shown in Figure 6, which
differs from the first embodiment in several aspectsO
Where like elements are c~mmon between the first and
second embodiments, the same reference sharacters have
been used. A float 70 rides on the surface 14 of the
liquid and supports the inlet 16 at a fixed distance
below the surface 14. Although other shapes are
possible, a ring shaped floa~ 70 is shown, ~ith the inlet
16 being susp nded kherebelow on cables 72.
The tube 18 is flexible to accomodate vertical
movement of the inlet 16 as the liquid level 1~ changes.
A telescoping connection 74 is provided, having an inner
~, 25 sleeve 76 and an outer sleeve 78 in sliding relation,
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ï preferrably with a gasket 80 or other sealing means
therebetweenO It is also possible for the tube 18 to
simply be 1exible, such as of a flexible corrigated
;~ tube.
The gas feed arrangement of this embodimen~ differs
`I from that of the first embodiment in that a venturi inlet
., housing 82 is mounted adjacent the inlet 16. The venturi
:.l inlet housing 82 includes an annular constriction 84
which reduces the diameter of the ~low path, behind which
l 35 is an annular gas feed opening 86 which is connected to
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a chamber 88. A gas or other fluid is fed into the
: chamber B8 by a supply hose 90 which extends to a source
of fluid to be mixed into the liquid. As shown, the
supply hose 90 can simply draw tha gas from the
environment since there is no need to pressurize the gas.
The environmental gas can be air or 9 when t.he process
occurs in a sealed vessel, any other gas.
In Figure 7~ ~he ven~uri inlet housing 82 and the
chamber ~8 extends around the tube 1~. Referring again
to Figure 6, the liquid and gas bubble mixture ~lows down
the tube 18 at a rate slightly greater than the rise rate
; of the bubbles and into a pump 92. The pump 92 is a
centri~ugal pump. The pump 92 has a 'cangentially
directed outlet 94 from which the mixture is ejected back
into the liq~id. It is conte~plated to connect a conduit
(not shown) to the outlet 94 to feed the liquid and gas
. mixture to a separate reservoir.
The second embodiment, and in particular the gas
`, feed arrangement of the second embodiment, are useful for
injecting gas not only into a liquid, but also for
injecting a gas or other fluid into a slurry. The gas
feed arrangement shown in Fiyures 6 and 7 is less likely
to become blocked or otherwise impeded than an embodiment
having airfoils extending across the intake opening,
~. 25 although this depends on the consistancy of the slurry.
,i Thus, there has been described and shown a methodand apparatus for increasing gas absorption in a liquid.
The invention is particularly useful in increasing ozone
or air absorption in water treatment facilities. It is
also possible to use the present invention to inject
carbon dioxide into beverages, and the like, or to mix
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two liquid~ or two gases together.
: It should be understood that various changes and
modificatlons to the presently preferred embodiments
described herein will be apparent to those skilled in the
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art. Such changes and modifications can be made without
departing from the spirit and scope of the present
invention and without dimin.ishing its attendant
advantages. It is therefore intended that such changes
5 and modifications be covered by the appended claims.
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