CA1042569A - Method of and apparatus for the dissolution of gaseous oxygen into a liquid - Google Patents
Method of and apparatus for the dissolution of gaseous oxygen into a liquidInfo
- Publication number
- CA1042569A CA1042569A CA224,228A CA224228A CA1042569A CA 1042569 A CA1042569 A CA 1042569A CA 224228 A CA224228 A CA 224228A CA 1042569 A CA1042569 A CA 1042569A
- Authority
- CA
- Canada
- Prior art keywords
- liquid
- oxygen
- gaseous oxygen
- confined
- pump
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/02—Aerobic processes
- C02F3/12—Activated sludge processes
- C02F3/1278—Provisions for mixing or aeration of the mixed liquor
- C02F3/1294—"Venturi" aeration means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/20—Mixing gases with liquids
- B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
- B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
- B01F23/2331—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the introduction of the gas along the axis of the stirrer or along the stirrer elements
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/40—Mixing liquids with liquids; Emulsifying
- B01F23/45—Mixing liquids with liquids; Emulsifying using flow mixing
- B01F23/454—Mixing liquids with liquids; Emulsifying using flow mixing by injecting a mixture of liquid and gas
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/20—Jet mixers, i.e. mixers using high-speed fluid streams
- B01F25/21—Jet mixers, i.e. mixers using high-speed fluid streams with submerged injectors, e.g. nozzles, for injecting high-pressure jets into a large volume or into mixing chambers
- B01F25/211—Jet mixers, i.e. mixers using high-speed fluid streams with submerged injectors, e.g. nozzles, for injecting high-pressure jets into a large volume or into mixing chambers the injectors being surrounded by guiding tubes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/20—Mixing gases with liquids
- B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/50—Circulation mixers, e.g. wherein at least part of the mixture is discharged from and reintroduced into a receptacle
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F33/00—Other mixers; Mixing plants; Combinations of mixers
- B01F33/80—Mixing plants; Combinations of mixers
- B01F33/81—Combinations of similar mixers, e.g. with rotary stirring devices in two or more receptacles
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
Abstract
ABSTRACT
Method of dissolving gaseous oxygen in a body of liquid by producing a pressurized stream of the liquid, in-troducing gaseous oxygen into the pressurized liquid stream and discharging the liquid stream through a nozzle, in the form of a high velocity jet, into the body of liquid.
Apparatus for carrying out the foregoing method.
Method of dissolving gaseous oxygen in a body of liquid by producing a pressurized stream of the liquid, in-troducing gaseous oxygen into the pressurized liquid stream and discharging the liquid stream through a nozzle, in the form of a high velocity jet, into the body of liquid.
Apparatus for carrying out the foregoing method.
Description
1~4~5~;9 The present invention relates broadly to the field of gas-liquid transfer and more particularly to a method of and apparatus for the dissolution of gaseous oxygen in a liquid.
It is well known that oxygen is soluble in a var-iety of liquids and that relatively pure oxygen can be util-ized in gas-liquid contacting systems for dissolving oxygen into liquids, including water. It is also well known that a .. . ..
variety of processes require the dissolution of oxygen in a --liquid and consequently efforts are being made continually to 10 improve upon existing methods and means for doing so. ~ -Although oxygen is not generally considered-to be a rare gas it is nevertheless an expensive gas, and therefore in processes in which the dissolution of oxygen in a liquid is - necessary or aesirable the overall costs involved in the oper- -ation of the process may depend in substantial measure on the absorption efficiency involved in the dissolution of the oxygen in the liquid as well as the efficiency of the oxygen generating process.
For example, many systems and processes which are 20 presently being utilized in the field of waste treatment re- `
- quire the dissolution of oxygen in the liquid undergoing treat- -ment. In activated sludge systems it is well known that the dissolution of oxygen is necessary to the reduction of the bio-, chemical oxygen demand of the waste liquid and the purification thereof.
Some activated sludge waste treatment systems which are found in the prior art depend upon air as a source of oxygen in the aeration or oxygenation of the waste liquid.
Other systems use gaseous oxygen or gas which has a high oxygen content, that is, an oxygen content in excess of that of air.
Regardless of whether air or gaseous oxygen is used for aeration purposes the overall operating costs of the waste ,. : .
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treatment system depend in part upon the absorption efficiency of the oxygen, that is, the amount of oxygen dissolved into the waste liquid relative to the total amount of oxygen brought into contact with the liquid. If a large amount of oxygen is brought into contact with the liquid but only a very small per-centage thereof is dissolved in the liquid then the absorption efficiency is very low and correspondingly the operating costs associated with the aeration stage of the purification process will be correspondingly high. On the other hand, if a very high percentage of the oxygen which is brought into contact -~ith the liquid is actually dissolved in the liquid then the absorption efficiency is high and correspondingly the operat-ing costs with respect to aeration are relatively low.
Although the principles of the present invention find -utility in any system or process in which gaseous oxygen is dissolved in liquid, the present invention finds particular utility in the field of activated sludge waste treatment sys-tems and will generally be aescribed hereinafter in the con-text of the aeration stage of an activated sludge waste treat-ment system.
In the field of activated sludge waste treatmentsystems a variety of systems and apparatus have been employed to dissolve oxygen in the waste liquid in the aeration stage . . .
of the process for reducing the B.O.D. For example, surface aerators which are located at the surface of the waste liquid and which agitate the liquid in the presence of air or an oxygen containing gas have long been used. Spargers for bubbling up air or oxygen from below the surface of the waste liquid have also been used in a number of installations. More ; 30 recently eductors or jet aerators utilizing ejector principles have been employed for the purpose of dissolving oxygen in the waste liquid by introducing a high velocity stream of liquid as 5~;9 well as a stream of air in the mixing chamber of an eductor or jet aerator and discharging the same in the form of a high velocity jet into the waste liquid below the surface thereof.
Other recent developments relate to the utilization of pure gaseous oxygen or gas which includes primarily oxygen, or at least a gas having a percentage of gaseous oxygen substan- -tially in excess of the percentage of oxygen found in atmos-- .
pheric air.
All of these various approaches, processes and tech-niques are intended to reduce to the extent possible the costof dissolving oxygen in the waste liquid and, as noted, the costs involved bear some not insubstantial relationship to the absorption efficiency of the system as well as the energy required to obtain such absorption efficiency. Most of the known systems which utilize high purity oxygen or at least a high oxygen content gas for the purpose of oxygenating a liquid, particularly in the field of activated sludge waste treatment systems, involve the employment of closed aeration - -~
tanks as well as seriatim staging of contacting cells to reach a sufficiently high level of oxygen utilization. A high util-ization factor is necessary in high purity oxygen systems to render such systems economical and it is generally understood that only a minor loss of oxygen can be tolerated in such sys-tems. Transfer efficiencies of up to 90% are generally con-sidered desirable and are presently being attributed to someclosed tank, series staged high oxygen content systems.
Apparently presently known high purity oxygen sys-tems are not sufficiently efficient to accomplish an acceptable absorption efficiency in a single tank or cell, and it is apparently that fact which necessitates the staging of closed tanks or cells in a manner so that the excess or off-gas of the first cell is collected and introduced into a subsequent s~9 cell for additional gas transfer and increased absorptlon eff-iciency. Three to five stages are generally utilized in an apparent effort to reach a desired absorption efficiency of 90% or more.
No system is believed to be known that can transfer a high percentage of pure oxygen in an open tank, one-pass contacting system and yet achieve a commercially acceptable -rate of oxygen transfer at a commercially acceptable power requirement. Systems are known which can transfer a high per-centage of pure oxygen in an open tank, one-pass contacting system, but these systems are extremely energy intensive and require the use of small orifices for introducing the oxygen which are subject to plugging, fouling, and the like. In addition to the mechanical problems associated with these 15 systems, the capacity of the devices are limited and therefore, ~ - -avery equipment intensive system is required to give any appreciable transfer rate.
In addiiton, many of the existing systems which uti- -lize either relatively pure oxygen or at least a gas having a high oxygen content also involve moving mechanical parts and apparatus within the aeration tank both above and below the surface of the waste liquid. These mechanical parts are exposed to relatively high concentrations of oxygen and are subject to problems of corrosion and the like. Furthermore, the existence of such mechanical equipment above the surface of the liquid requires a relatively high tank freeboard, generally in the range of about 3 to 5 feet, and thus far less than the entire volume of the tank is available for the confinement of the waste liquid. ~ ~ -In addition, such known so-called oxygen systems which utilize serially arranged closed systems and which are primarily biological in nature, such as activated sludge waste .
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l~Z5~;9 treatment systems, involve the existence of CO2 in the aera-tion tank between the surface of the waste liquid and the cover of the tank by virtue of the evolution or generation of C2 in the biological process. The existence of CO2, of course, has a tendency to reduce the concentration o~ oxygen and thus the absorption efficiency of the system, and tends to increase the dissolved CO2 level in the mixed liquor solu-tion which in turn effects pH, chemical composition and build-up of biological waste products which can potentially adver-10 sely affect the biological kenetics of the system. In the ~;
final stage of presently known oxygen systems concentrations f C2 of 50% by volume quite commonly exist in the off-gas.
Although jet aerators and similar high velocity jet -;
producing devices utilizing eductor principles have been used to accomplish oxygenation in many installations, it is believed that none have been successfully used in systems involving gaseous oxygen rather than air for providing the requisite oxygenation. Jet aeration systems, as studies indicate, com-pare extremely favorably with other oxygenation systems and in many respect have advantages which, it is believed, other oxygenation systems do not possess.
The present invention involves the utilization of -~ pure oxygen or at least a substantially high oxygen content gas for oxygenation purposes by producing at least one or more high velocity jets comprising liquid and oxygen, which jets are introduced into the waste liquid in a manner which differs considerably from that of previously known air jet aeration systems. In accordance with the information and data which has been developed, the absorption efficiencies which are available from this invention far exceed those which could have been anticipated in light of the present state of the art of jet aeration. Indeed the absorption efficiencies avail-~. . .
11~4ZS~9able from the practice of this invention compare favorably with other so-called "oxygen" systems but additionally this in-vention does not require closed or covered aeration tanks, arranged in series, and thus eliminates the difficulties which are inherent in such known systems.
Furthermore, this invention does not involve any mov-ing parts whatsoever within the liquid in the aeration tank or in an atmosphere having a high oxvgen content. Initial costs in the construction of a system embodying the principles of this invention, relative to other "oxygen" systems, are re-duced. Maintenance costs are also reduced by virtue of the absence of moving parts not only within the liquid but in the high oxygen containing atmosphere above the liquid. A greater -portion of the aeration tanks is-utiliæed for the confinement of waste liquid by virtuP of thé reduction of the tank free-board to about one foot. Since the present invention does not involve a cover for the aeration tank, the problems involved in CO2 buildup, both within and above the liquid, are elim-inated. In addition, since a system constructed in accordance 20 with the principles of this invention does not require any -mechanical mixer for mixing the liquid within the aeration tank, the potential problems relating to maintenance and down-time are eliminated.
In accordance with the foregoing, it is an object of this invention to increase the absorption efficiency of oxygen dissolution systems while avoiding the necessity of closed aeration tanks, multiple cells, mechanical liquid stirrers or mixers, excessive tank freeboard, CO2 buildup, and moving parts within the liquid or in a high oxygen content environment above the liquid.
Another object of the invention is to reduce the costs involved in dissolving oxygen into liquid, particularly , : . :.
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lI3~Z5~;9 in the aeration stage of activated sludge waste treatment sys-tems, thereby improving the efficiency of such systems and reducing the operating costs and energy requirements.
Another object of the invention is to provide a system for increasing the oxygen content of a liquid, which system is capable of extremely high dissolution rates at ex-tremely high absorption efficiencies without the necessity of utilizing enclosed oxygen pressurized serially arranged liquid tanks or reservoirs.
Another object of the invention is to provide high absorption efficiencies in a system which utilizes no moving ~-parts for dissolving the oxygen in the liquid except for a liquid pump, and the pump, instead of being located in a high oxygen content atmosphere, is exposed only to ambient air.
Another object of the invention is to increase the capacity of activated sludge waste treatment systems which rely on pure or relatively pure oxygen rather than air for oxygenation purposes in reducing the B.O.D. of the waste liquid.
The present invention involves a method of and appa-ratus for increasing the oxygen content of a body of liquid by producing a stream of liquid, pressurizing the stream, creating turbulence in the stream, introducing gaseous oxygen into the stream and then discharging the stream through a liquid nozzle into the body of liquid. Based upon conducted tests, the prèsent invention has many advantages over known methods and systems in terms of absorption ef~ioiency, ori ginal costs, operating costs and simplicity of design, con-struction and maintenance. All of these advantages are be-lieved to be obtained without introducing any disadvantageswith respect to previously known oxygenation systems.
The method and the system which are involved in the . . .
present lnvention lorld themselv~s to contlnuou~ operatlon l)y ~ich subs~ntial ~mounts of oxygen may be dlssolvod ln the .,~,, body of liquld nt extr~mely high absorptlon efficlencles in comparison to other well known ~o~called "oxygen" systems of water treatment and purlflcation.
In the preferred embodiment an In~ector, which is completely void of moving parts, is utilized as the instru-mentality by which the oxygen ls introduced into the liquid. A
pump is used to circulate liquid from the body to be oxygenated, through a conduit arrangement and back to the body of liquid, -;
As the liquid is circulated through the conduit the oxygen is introduced into the liquid by means of the injector in the form of a stream. Preferably the oxygen stream is introduced into the liquid stream on the inlet or upstream side or low pressure side of the pump, merely to utilize the pump as a mixer, but -tests indicate that the oxygen may be introduced on the dis-charge side of the pump without losing any of the enhanced characteristics of the system and without suffering any significant reduction in absorption efficiency.
The method and system of the present invention lend themselves not only to new construction but to modifications ~ - -of existing waste treatment and water purification facilities, The absorption efficiencies and total reductions in energy requirements which inure to the present invention do not depend upon the size of the aeration system, as a consequence of which the principles of the present invention find utility in very small oxygenation systems and activated sludge waste treatment systems as well as in very large systems that are employed, for example, ln the maJor metropolitan areas. `
In one particular aspect the present inventi;on provides a method of dissolving gaseous oxygen into liquid oomprising the steps of; confining a body of liquid into which ~a~eous oxygen iB to be discolved, continually removing a portion Jl/~ 8_ A;~ ., , . ~ . ,~ , . . .
5~i9 o the llquid rrom sald con~incd body, prcssuri7ing ~hc llquld ~emoved from 9aid confincd body, lnJectln~ gn8eoUS oxygcn -~nto ~ald pressurl7.ed llguld to oxygenate said liquid, causing said oxyeenated ].lquid to reside ln a pressurized state for at least about five second while removed from said conflned body, and returning said oxygenated liquid to said confined body and causing it to be discharged into said confined body through a discharge nozzle while undergoing a pressure drop in the range of approximately 5 to 12 psia, -In another aspect the present invention provides ~--apparatus for dissolving gaseous oxygen in a liquid comprising in combination, reservoir means for confining a body of liquid into which gaseous oxygen is to be dlssolved, circulating means comprising hydraulic circuitry connected to said reservoir means and including fluid conduit means externally of said reservoir means, fluid flow and pressure producing means connected in -~
said fluid conduit means externally of said liquid confining means for circulating and pressurizing liquid from said confined ~ :
liquid body through said fluid conduit means and returning said removed fluid back to said reservoir means, injector means ~ :
connected in said fluid conduit means for in~ecting gaseous oxygen into the liquid in said fluid conduit means to oxygenate said liquid, said circulating means further including nozzle discharge means disposed within said reservoir means for dis-charging the oxygenated liquid from said hydraulic circuitry into said confined liquid body, said fluid flow means and hydraulic circuitry being operative to maintain said oxygenated liquid within said circuitry for a minimum period of approx~
lmstely five seconds prior to discharge through said nozzle discharge means, said nozzle discharge means being adapted to effect a pressure drop of between approximately 5 to 12 psia as sald oxygenated liquid ls discharged into said confined liquid body, _8a-~ ~ , ` - `
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Z5¢9 ^~ Many feattlles~ advnntages and obJects of the resent inven~ion in addltion to the foregoing will become manlfest to those versed in the art by making reference to the detailed ~ ' _8b- ~
~ ~ t ~ . .
~ , 1~4ZS~;9 description which follows and the accompanying sheets of draw-ings, in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example only.
FIG. 1 is a graph which discloses the absorption efficiency of a typical prior art aeration system using conven-tional jet aeration equipment, at various levels of submergence.
FIG. 2 is a graph which illustrates the absorption efficiency of a conventional prior art jet aeration system, at a constant submergence, both when air and when high purity oxygen are used as the source of oxygen.
FIG. 3 is a graph which illustrates the absorption efficiency of a conventional prior art jet aeration system and of a system which embodies the principles of the present inven-tion, when high purity oxygen i8 used in systems as the source of oxygen, the submergence levels of both systems being the same.
FIG. 4, which appears on the sheet of drawings bearing FIG. 1, is a schematic or diagrammatic illustration of a conven-tional prior art ~et aeration system.
; FIG. 5 is an enlsrged sectional view of the jet aerator utilized in the ~et aeration sy3tem shown in FIG. 4.
FIG. 6 is a schematic or diagrammatic illustrationof a ~et aeration system constructed in accordance with the prlnciples of the present invention. `
FIG. 7 is an enlarged sectional view of the eductor utilized in the system shown in PIG. 6.
FIG. 8 is a graph which discloses the manner in which the absorption efficiency of the present invention varies 3~ in accordance with variations in jet submer~ence levels.
FIG. 9 is a curve which discloses the absorption efficiency of a system embodying the principles of the pres-jb/~,~
, . . . ................................. : . .
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5~9 ent invention operated over a range of jet pressure drops.
FIG. 10 is a graph which discloses the effect of var-iations in liquid residence time on the absorption efficiency of a system constructed in accordance with the principles of the present invention.
FIG. 11 is a graph which discloses the absorption efficiency of a system embodying the present invention operated both with and without shrouds to produce secondary delivery jets from the liquid jet nozzles submerged within the body of 10 liquid being oxygenated.
FIG. 12 is a graph which compares the oxygenation capacity of a conventional prior art jet aeration system using both air and high purity oxygen as the source of oxygen and a system constructed and operated in accordance with the 15 principles of the present invention, all at various oxygen-to-liquid flow ratios. ~.-As noted, aeration systems which utilize eductors or jet aerators embodying eductor principles have long been known in the prior art. Generally, waste liquid is pumped 20 from an aeration tank, through hydraulic conduits, to the liquid nozzle of a jet aerator or eductor. The jet aerator is furnished with a mixing chamber into which the waste liquid from the liquid nozzle issues and connected to which is a ~
source of pressurized or aspirated air. The admixture of ~ -25 waste liquid and air is then discharged from the jet aerator or eductor in the form of a high velocity jet into the aera- ;
tion tank below the surface of the liquid.
- The curves shown in FIG. 1 were developed from test data relating to a previously known aeration system utilizing 30 conventional jet aeration equipment. FIG. 1 illustrates that - such systems are capable of achieving a relatively high absorp-~ "...~ ~ ... .
tion or transfer efficiency when air (as contrasted with high , 1~4~S~;9 purity oxygen) is utilized in the gas-liquid contacting process. As a matter of fact the curves shown in FIG. 1 ill-ustrate that the absorption efficiencies of jet aeration sys-tems compare favorably with those available from any other aeration system, that is, one which utilizes air rather than oxygen in the oxygen transfer process.
On the other hand, the curves shown in FIG. 1 dis-close absorption efficiencies which would not be commercially feasible or acceptable, from an operating cost standpoint, in identical systems in which high purity oxygen were substituted for air as the source of oxygen.
The curves shown in FIG. 1 suggest, however, that if high purity oxygen is substituted for air and if, in addi-tion, experimentation were conducted to optimize the percent ransfer of the high purity oxygen, acceptable absorption efficiencies could possibly be attained. The fact that a substantially pure oxygen bubble will have a higher partial pressure of oxygen than will an air bubble and will not be subject to dilution of the percent oxygen content as oxygen is transferred into solution may well suggest to those skilled in the art a higher transfer efficiency than that which has been obtained with air, even without optimization.
In the course of the investigations which resulted in the present invention, the inventor experimented with the - 25 utilization of high purity oxygen instead of air in conven-tional prior art jet aeration systems. In the course of the investigations and experiments, the parameters whioh effect absorption efficiency were varied in an effort to maximize absorption efficiency.
The most favorable results obtained from this exper-imentation are shown in FIG. 2. The two curves shown therein were derived from test data concerning the same prior art jet .
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~4;~ 9 aeration system, but the curve entitled "Jet Aeration" re-sulted from the use of air as the source of oxygen, whereas the curve entitled "Jet Oxygenation" resulted from the use of high purity oxy~en. A comparison of the curves shown in FIG. 2 illustrates quite clearly that conventional jet aera-tion systems previously known in the prior art are probably not commercially feasible when high purity oxygen is substi-tuted for air, since the absorption efficiencies of such sys-tems do not increase substantially as a consequence of such 10 substitution. - ~
In the course of these investigations, experimenta- - -;
tion was conducted with numerous modifications in conventional jet aeration equipment. In each case the improvements in ab- ~-sorption efficiency using high purity oxygen instead of air were only marginal, resulting in most instances in not more than a two to three percent increase in transfer or absorp-tion efficiency. Even when the gaseous oxygen application ~ -rates were reduced or backed off to such an extent that the oxygen which went into solution was not even sufficient to saturate the motive liquid stream, absorption efficiency did not improve in any substantial degree.
It was as a consequence of the foregoing experimen-tation and the failure of conventional jet aeration equipment to produce high absorption efficiencies when utilizing high purity oxygen that consideration was given to alternative sys-tems. One possible system considered involved the pre-injec-tion of gaseous oxygen into a pressurized liquid motive stream. However, based upon information which is presently known to those skilled in the art of gas-liquid contactors and - 30 gas-liquid trans~er, such a system should not produce favorable absorption efficienceis since (1) the benefits which are known to derive from gas-liquid contacting at the nozzle of the jet ..,. . . ~ .: .. :
~4ZS~;9 aerator would be completed eliminated, (2) the amount of oxygen that could be transferred into the motive liquid stream would be limited by the motive stream flow rate and its saturation value, and (3) any gaseous oxygen that carries through the motive stream cycle may exit in a state of dispersion which is unfavorable for mass transfer.
Notwithstanding the foregoing it was decided to develop a prototype and conduct tests of such a system. The results were completely and unexpectedly favorable. FIG. 3 illustrates the substantial increase in absorption efficiency of an aeration system embodying the principles of the present invention and utilizing high purity oxygen as contrasted with a conventional jet aeration system also using high purity oxygen. The curve entitled "Jet Oxygenation" corresponds to the similarly entitled curve shown in FIG. 2. On the other hand, the curve entitled "Pre-injection Jet Oxygenation" dis- -closes the much higher absorption efficiencies available from a jet aeration system constructed in accordance with the prin-ciples of the present invention. Both curves illustrate the variation in absorption efficiency which results from varia-tions in the mass-flow ratio of gaseous oxygen and waste liquid.
FIG. 4 illustrates a conventional prior art jet aeration system and corresponds to the system which was used in developing the curves shown in FIG. 1, the curve entitled "Prior Art Jet Aeration"shown in FIG~ 2 and the aurve entitled "~et Oxygenation" shown in FIG. 3. The system includes a large aeration tank or reservoir indicated generally at ref-erence numeral 10 which contains a body of liquid 11 being oxygenated. The surface of the liquid 11 is shown at refer-ence character lla and it is noted that the surface of the liquid may very closely approach an open upper end 12 of the , ': ' ' ' ': ' . .. . .
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1342S~9 aeration tank 10. A side wall 13 of the tank 10 is, in the illustrated embodiment, cylindrically shaped, but it will be appreciated that the particular configuration of the tank 10 is not critical to the present invention. Unlike presently known high purity oxygen systems, however, the top 12 of the tank 10 is not closed or covered but instead is fully open to the atmosphere surrounding the tank 10.
A jet aerator 14 is located within the aeration tank 10 below the surface of the liquid 11. In the system which was actually used in the course of these investigations and experiments, the jet aerator 14 comprised a single unit (which may be referred to as a jet cluster) having a plur- ~ :
ality-of liquid nozzles 15 arranged radially about a verti--al axis and communicating with a common manifold 16 to which --is connected a conduit 17 which extends through the side wall 13 of the tank 10 and to a discharge side 18 of a liquid pump 19. Another condu.t 20 is connected at one end 21 there^f to the suction or inlet side of the pump 19, whereas an opposite end 22 communicates with the interior of the tank 10.
valve 23 is mounted in the high pressure liquid conduit 17 whereas a similar valve 24 is mounted in the low pressure liquid conduit 20.
Re~erring again to the jet aerator 14, a series of gas-liquid nozzles 26, corresponding in number and location to the liquid no~zles 15, communicate with an air manifold 27 to which is connected an air conduit 28 which extends through the side wall 13 of the aeration tank 10 to an air blower ( not shown).
In the operation of the conventional jet aeration - 30 system shown in FIG. 4, liquid 11 from the aeration tank 10 - is pumped through the conduit 20 by the liquid pump 19 and conducted through the conduit 17 to the liquid nozzles 15 of .
.:
.:
~Z569 the jet aerator 14. Liquid ~rom the nozzles 15 issues in the form of high velocity liquid jets and mixes with air being con-ducted through the conduit 28 to the manifold 27 surrounding the liquid nozzles 15. The admixture of liquid and air then issues in the form of high velocity jets from the air-liquid nozzles 26 extending radially about the axis of the jet aera-tor 14.
While the illustrated embodiment of the jet aerator 14 includes a plurality of liquid and air-liauid nozzles, the principles of the conventional jet aeration do not require a multi-nozzle jet aerator or cluster and in 'act many systems utilize one or more jet aerators, each of which comprises only a single liquid nozzle surrounded by an air-liquid nozzle.
FIG. 6 illustrates an aeration system embodying the principles of the present invention and a comparison of FIGS.
~ and 6 illustrates .he essential similari ~i25 O' an~ distinc-tions between the two systems. Those parts or components of the system shown in FIG. 6 which correspond to those shown in FIG. 4 are identified with the similar reference characters, and it is noted that the system shown in FIG. 6 does not utilize an air conduit 28. As a consequence the jet aerator chamber 27, which previously served as an air manifold, is now in direct communication with the liquid 11, and the air-liquid nozzles 26 merely serve to produce secondary liquidjets surrounding the jets which issue from the liquid nozzles lS.
In the system shown in FIG. 6 a conduit 30 has been added to interconnect the high pressure liquid conduit 17 and the low pressure conduit liquid 20. In the illustrated em-bodiment the diameter of the conduit 30 is significantly less than the diameter of either the conduit 17 or the conduit 20, ' ` . '" `', ' : `
.
, .: .
1~25~9 and mounted in the conduit 30 is an eductor 31, as well as a pair of valves 32 and 33 mounted on the opposite sides of the eductor 31. Another conduit indicated at reference numeral 34 is connected to the eductor 31 and has mounted therein a valve 36. The conduit 34 is connected to a source of high purity oxygen (not shown) although the principles of the present invention are applicable even though the percent of oxygen in the gas is substantially less than 100%.
Referring to FIG. 7, the eductor 31 comprises a liquid nozzle section 37, a mixing chamber 38 and a diffuser section 39. The precise embodiment of the eductor 31 is not critical to the present invention, however, and indeed it is not necessary that an eductor be used for the purpose of -.
introducing the oxygen into the liquid. What is important --. --is that the oxygen be introduced into the liquid in the form of fine bubbles, and for that purpose an eductor 31 is par- `- ~.
ticularly well suited. - ~`
.
In operation of the system disclosed in FIG. 6, the liquid pump 19, which is connected to an electric motor l9a, draws liquid from the tank 10 through the low pressure con-:-: duit 20 and discharges the liquid back into the tank 10 through the high pressure liquid conduit 17 and the liquid nozzles 15. A small poriton of the liquid being circulated : through the pump 19 and being discharged back into the tank 10 through the high pressure liquid conduit 17 is by-passed thorugh the conduit 30 back to the low pressure liquid con-duit 20. As this small portion of the liquid stream is con-ducted through the conduit 30, relatively high purity oxygen ~
is introduced into the liquid by virtue of the eductor 31. : - -30 Thus in the embodiment shown in FIG. 6, the oxygen is added . .
to the liquid stream on the suction side rather than the dis-charge side of the liquid pump 19.
, ~ .
i~42S~9 In the test facilities in which the investigations and experimentations were undertaken, the eductor or injector 31 produced oxygen bubbles in the order of about 2 millimeters or less in diameter, resulting in a specific interfacial area of about 30,000 cm /liter of gas. Based upon these investigations, it is believed that the very high absorption efficiencies resul-ting from the present invention may be obtained regardless of whether the oxygen is introduced into the low pressure liquid conduit 20 on the suction side of the pump 19 or in the high pressure liquid conduit 17 on the discharge side of the pump 19, and it is also believed that absorption efficiencies in the same order of magnitude as those achieved in the specific test fac-ility utilized can be obtained regardless of the manner in which the oxygen is introduced into the conduits 17 and 20, provided the specific interfacial area of the oxygen to the liquid is about 30,000 cm2/liter or gas, or greater.
That hydraulic circuitry, including the liquid nozzles 15, the high pressure liquid conduit 17, the liquid pump 19 and .the low pressure liquid conduit 20, by which the liquid 11 is circulated from the tank 10, through the circuitry and then back to the tank 10, is indicated generally at reference num-eral 36. -It is apparent that the principles of the present invention do not require any specific geometry or configura-tive relationships with respect to the hydraulic circuitry36. Nor is it required that the oxygen be introduced at any particular point in the hydraulic circuitry 36 as long as it is subjected to a minimum residence time therein. What is apparent, however, is that the liquid stream in the hydraulic circuitry 36 must be in a state of turbulence upstream of the liquid nozzles 15 to provide mixing of the oxygen bubbles in the liquid stream. By turbulence is meant a state of distur-bance of the liquid stream to produce relatively violent agi-. . . . .
. . . . . . . . .
-. . ~ .
,. ~
.
. .
.. . . .
, 1~4ZS69 tation or perturbation of the liquid.
It has been estimated that the Reynolds number of - the hydraulic circuitry 36 in the test facility was probably between 200,000 and 400,000. In the course of these inves-tigations, however, a considerable effort was made to varythe Reynolds number, and upon observation it was noted that there was no appreciable variation in absorption efficiency as a consequence of variation in Reynolds number. As noted, it is only necessary that the liquid stream be maintained in ` -a state of turbulence upstream of the liquid nozzles 15, but it is anticipated that, ~ith respect to any particular system, and depending upon the diameter of the pipes, the number of elbows and other fittings and the like, some adjustment with respect to the valves 23 and 24 and other experimentation may be required in order to obtain the maximum absorption efficiency.
The curve snown in FIG. 8 illustrates variation in absorption efficiency of the system shown in FI~.6 as the level of submergence of the jet aerator 14 is varied. The ~ -tests in connection with which this curve was developed were conducted at a fixed gas flow rate of 5 lbs. per hour per liquid iet nozzle 15. Actually, the jet aerator indicated at reference numeral 14 which was used in the test facility .
diagrammatically indicated in FIG. 6 comprised a total of 12 - 25 liquid nozzles 15 extending radially outwardly from a single casing. Experimentation indicates, however, that the absorp-tion efficiencies available from the invention do not depend upon the numbex of liquid jet nozzles involved, although it is apparent that the total rate of dissolution of oxygen in the liquid will vary in accordance with the number of liquid jet~.
FIG. 8 indicates that the absorption effiaiency of , . . . ~ , .
: .,.. ,...... , . . ~ . . , ~ .
1¢~4;~
the invention approaches almost 50~ even when the liquid jet approaches the very surface lla of the liquid 11 in the tank 10. Absorption efficiency increases upon an increase in li~uid jet submergence level and very nearly 100~ absorption efficiency was obtained when the liquid jets were located approximately 20 feet below the surface lla of the liquid 11.
In the course of the tests the liquid 11 in the tank 10 was tap water at standard conditions, but based upon com-parative test data the greatly increased absorption effic-iencies which the invention is capable of producing are alsoobtainable in the waste liquid introduced into the aeration tanks of activated sludge waste treatment systems. Beyond that, however, it would,appear as though the principles of the invention are applicable in any situation in which it is desirable to dissolve a gas into a liquid at greatly enhanced absorption efficiencies.
Based upon the results of these investigations, var-iations in the pressure drop across the liquid nozzles 15 ~'~
shown in FIG. 6 have a definite effect on the absorption ' 20, efficiency of the system. As illustrated in the curve shownin FIG. 9, the absorption efficiency of a system constructed in accordance with the principles of the invention probably requires a liquid nozzle pressuredrop of about 5 psia in order ' to provide a viable or practically commercial system, and the ', ~ , pressure may be advantageously increased to about 10-12 psia.
Further pressure drop, however, does not appear to enhance absorption efficiency to any significant degree and, on the other hand, requires the expenditure of additional energy.
Tests were conducted in an effort to determine whether the residence time of the liquid within that hydraulic circuitry bears some significant relationship to absorption efficiency. FIG. 10 discloses a curve which indicates varia- -.,;' ~, . ,, , ' .
1~4Z5~9 tions in absorption efficiency with variations in liquid res-idence time, that is, the time which elapses from the time that the liquid in the hydraluic circuitry 36 is first in-troduced to the gaseous oxygen until the liquid is discharged from the liquid nozzles 15 into the body of liquid 11. This curve indicates that, within limits, an increase in residence time produces an increase in absorption efficiency, but it -~
also indicates that a residence time of at least about five seconds is required to produce a co~mercially acceptable ab-sorption efficiency.
It will be understood, of course, that with respect to any given system it may be desirable to adjust flow rates of the gaseous oxygen and-of the recirculated liquid to pro-vide maximum absorption efficiency for that system in accor-dance with the principles of the invention described herein,but these adjustments fall within the purview of one having ordinary skill in the art. --Tests were also conducted in which the liquid nozzles 15 discharged directly into the liquid 11 both with and with- -out the benefit o the gas-liquid nozzles 26 surrounding the liquid nozzles 15. FIG. 11 illustrates that absorption efficiency is somewhat enhanced when the high velocity jets issuing from the liquid nozzles 15 are surrounded by the noz-zles 26 which, in the embodiment shown in FIG. 6, merely serve as shrouds to produce secondary liquid streams surrounding the jets issuing from the nozzles 15. Since the cost involved in providing the shrouds of nozzles 26 is quite nominal, the preferred embodiment should include the nozzles 26 to in-crease the absorption efficiency as the curve shown in FIG.
11 would indicate.
In the tests, the mean velocity of the liquid stream in the hydraulic circuitry 36 was between the range of about , .; . . : .
. .
~42S69 4 to 8 feet per second. It would appear that variations in liquid mean velocity may produce some variations in absorp-tion efficiency, but once again it is apparent that the only requirement relating to velocity is that it be sufficient to produce a state of turbulence of the liquid within the hydrau-lic circuitry so that the gaseous oxygen is mixed with the liquid.
It will be understood by those skilled in the art that any aeration system which can be considered commercially acceptable and economical must, in addition to providing acceptable absorption efficiencies at acceptable gas trans-fer rates, also be capable of producing such absorption effi-ciencies and gas transfer rates at acceptable energy require-ments. . ;
FIG. 3 discloses that the present invention is cap-able of producing extremely high absorption efficiencies at -~-economically acceptable sas .rar,sfer rates. FIG. 12 discloses that these high absorption efficiencies and rates are obtain- -- able at relatively low and entirely acceptable energy require-ments. Indeed FIG. 12 discloses that the present invention requires much less energy for dissolution of the oxygen in the liquid than does the conventional jet aeration system, regardless of whether air or high purity oxygen is utilized as the oxygenation medium.
In comparing the absorption efficiencies of systems constructed and operated in accordance with the principles of this invention with the absorption efficiencies a pre-viousl~ known "oxygeD~' s~stems which require a succession of completely enclosed tanks or cells, it is apparent that the 30 present invention compares favorably in terms of efficiencies, -but in addition attains such efficiencies in an open tank, one-pass contacting system.
In FIG. 5 the details of the jet aerator 14 are shown in greater detail. The air conduit 28 is shown con-nected to jet aerator 14 in the manner illustrated in FIG. 4, but in the system shown in FIG. 6 the conduit 28 is elimin-ated, as mentioned hereinabove. Again it should be empha-sized that while the embodiment of the jet aerator 14 illus-trated herein comprises a plurality of liquid jet nozzles arranged in a "cluster" form, the principles of the invention are equally applicable to systems in which individual and dis-tinct liquid jet nozzles are used for producing the.high velo-city jets in the aeration tank 10.
Although minor modifications might be suggested by . ~
those versed in the art, it should be understood that in- ~. ; . .
cluded within the scope of the patent warranted hereon all such modifications as reasonably come within the scope of t.he present contribution to the art.
..
~ , -
It is well known that oxygen is soluble in a var-iety of liquids and that relatively pure oxygen can be util-ized in gas-liquid contacting systems for dissolving oxygen into liquids, including water. It is also well known that a .. . ..
variety of processes require the dissolution of oxygen in a --liquid and consequently efforts are being made continually to 10 improve upon existing methods and means for doing so. ~ -Although oxygen is not generally considered-to be a rare gas it is nevertheless an expensive gas, and therefore in processes in which the dissolution of oxygen in a liquid is - necessary or aesirable the overall costs involved in the oper- -ation of the process may depend in substantial measure on the absorption efficiency involved in the dissolution of the oxygen in the liquid as well as the efficiency of the oxygen generating process.
For example, many systems and processes which are 20 presently being utilized in the field of waste treatment re- `
- quire the dissolution of oxygen in the liquid undergoing treat- -ment. In activated sludge systems it is well known that the dissolution of oxygen is necessary to the reduction of the bio-, chemical oxygen demand of the waste liquid and the purification thereof.
Some activated sludge waste treatment systems which are found in the prior art depend upon air as a source of oxygen in the aeration or oxygenation of the waste liquid.
Other systems use gaseous oxygen or gas which has a high oxygen content, that is, an oxygen content in excess of that of air.
Regardless of whether air or gaseous oxygen is used for aeration purposes the overall operating costs of the waste ,. : .
.' ' , ' ;. .
. . ~ `
treatment system depend in part upon the absorption efficiency of the oxygen, that is, the amount of oxygen dissolved into the waste liquid relative to the total amount of oxygen brought into contact with the liquid. If a large amount of oxygen is brought into contact with the liquid but only a very small per-centage thereof is dissolved in the liquid then the absorption efficiency is very low and correspondingly the operating costs associated with the aeration stage of the purification process will be correspondingly high. On the other hand, if a very high percentage of the oxygen which is brought into contact -~ith the liquid is actually dissolved in the liquid then the absorption efficiency is high and correspondingly the operat-ing costs with respect to aeration are relatively low.
Although the principles of the present invention find -utility in any system or process in which gaseous oxygen is dissolved in liquid, the present invention finds particular utility in the field of activated sludge waste treatment sys-tems and will generally be aescribed hereinafter in the con-text of the aeration stage of an activated sludge waste treat-ment system.
In the field of activated sludge waste treatmentsystems a variety of systems and apparatus have been employed to dissolve oxygen in the waste liquid in the aeration stage . . .
of the process for reducing the B.O.D. For example, surface aerators which are located at the surface of the waste liquid and which agitate the liquid in the presence of air or an oxygen containing gas have long been used. Spargers for bubbling up air or oxygen from below the surface of the waste liquid have also been used in a number of installations. More ; 30 recently eductors or jet aerators utilizing ejector principles have been employed for the purpose of dissolving oxygen in the waste liquid by introducing a high velocity stream of liquid as 5~;9 well as a stream of air in the mixing chamber of an eductor or jet aerator and discharging the same in the form of a high velocity jet into the waste liquid below the surface thereof.
Other recent developments relate to the utilization of pure gaseous oxygen or gas which includes primarily oxygen, or at least a gas having a percentage of gaseous oxygen substan- -tially in excess of the percentage of oxygen found in atmos-- .
pheric air.
All of these various approaches, processes and tech-niques are intended to reduce to the extent possible the costof dissolving oxygen in the waste liquid and, as noted, the costs involved bear some not insubstantial relationship to the absorption efficiency of the system as well as the energy required to obtain such absorption efficiency. Most of the known systems which utilize high purity oxygen or at least a high oxygen content gas for the purpose of oxygenating a liquid, particularly in the field of activated sludge waste treatment systems, involve the employment of closed aeration - -~
tanks as well as seriatim staging of contacting cells to reach a sufficiently high level of oxygen utilization. A high util-ization factor is necessary in high purity oxygen systems to render such systems economical and it is generally understood that only a minor loss of oxygen can be tolerated in such sys-tems. Transfer efficiencies of up to 90% are generally con-sidered desirable and are presently being attributed to someclosed tank, series staged high oxygen content systems.
Apparently presently known high purity oxygen sys-tems are not sufficiently efficient to accomplish an acceptable absorption efficiency in a single tank or cell, and it is apparently that fact which necessitates the staging of closed tanks or cells in a manner so that the excess or off-gas of the first cell is collected and introduced into a subsequent s~9 cell for additional gas transfer and increased absorptlon eff-iciency. Three to five stages are generally utilized in an apparent effort to reach a desired absorption efficiency of 90% or more.
No system is believed to be known that can transfer a high percentage of pure oxygen in an open tank, one-pass contacting system and yet achieve a commercially acceptable -rate of oxygen transfer at a commercially acceptable power requirement. Systems are known which can transfer a high per-centage of pure oxygen in an open tank, one-pass contacting system, but these systems are extremely energy intensive and require the use of small orifices for introducing the oxygen which are subject to plugging, fouling, and the like. In addition to the mechanical problems associated with these 15 systems, the capacity of the devices are limited and therefore, ~ - -avery equipment intensive system is required to give any appreciable transfer rate.
In addiiton, many of the existing systems which uti- -lize either relatively pure oxygen or at least a gas having a high oxygen content also involve moving mechanical parts and apparatus within the aeration tank both above and below the surface of the waste liquid. These mechanical parts are exposed to relatively high concentrations of oxygen and are subject to problems of corrosion and the like. Furthermore, the existence of such mechanical equipment above the surface of the liquid requires a relatively high tank freeboard, generally in the range of about 3 to 5 feet, and thus far less than the entire volume of the tank is available for the confinement of the waste liquid. ~ ~ -In addition, such known so-called oxygen systems which utilize serially arranged closed systems and which are primarily biological in nature, such as activated sludge waste .
.
.
. ... ..
l~Z5~;9 treatment systems, involve the existence of CO2 in the aera-tion tank between the surface of the waste liquid and the cover of the tank by virtue of the evolution or generation of C2 in the biological process. The existence of CO2, of course, has a tendency to reduce the concentration o~ oxygen and thus the absorption efficiency of the system, and tends to increase the dissolved CO2 level in the mixed liquor solu-tion which in turn effects pH, chemical composition and build-up of biological waste products which can potentially adver-10 sely affect the biological kenetics of the system. In the ~;
final stage of presently known oxygen systems concentrations f C2 of 50% by volume quite commonly exist in the off-gas.
Although jet aerators and similar high velocity jet -;
producing devices utilizing eductor principles have been used to accomplish oxygenation in many installations, it is believed that none have been successfully used in systems involving gaseous oxygen rather than air for providing the requisite oxygenation. Jet aeration systems, as studies indicate, com-pare extremely favorably with other oxygenation systems and in many respect have advantages which, it is believed, other oxygenation systems do not possess.
The present invention involves the utilization of -~ pure oxygen or at least a substantially high oxygen content gas for oxygenation purposes by producing at least one or more high velocity jets comprising liquid and oxygen, which jets are introduced into the waste liquid in a manner which differs considerably from that of previously known air jet aeration systems. In accordance with the information and data which has been developed, the absorption efficiencies which are available from this invention far exceed those which could have been anticipated in light of the present state of the art of jet aeration. Indeed the absorption efficiencies avail-~. . .
11~4ZS~9able from the practice of this invention compare favorably with other so-called "oxygen" systems but additionally this in-vention does not require closed or covered aeration tanks, arranged in series, and thus eliminates the difficulties which are inherent in such known systems.
Furthermore, this invention does not involve any mov-ing parts whatsoever within the liquid in the aeration tank or in an atmosphere having a high oxvgen content. Initial costs in the construction of a system embodying the principles of this invention, relative to other "oxygen" systems, are re-duced. Maintenance costs are also reduced by virtue of the absence of moving parts not only within the liquid but in the high oxygen containing atmosphere above the liquid. A greater -portion of the aeration tanks is-utiliæed for the confinement of waste liquid by virtuP of thé reduction of the tank free-board to about one foot. Since the present invention does not involve a cover for the aeration tank, the problems involved in CO2 buildup, both within and above the liquid, are elim-inated. In addition, since a system constructed in accordance 20 with the principles of this invention does not require any -mechanical mixer for mixing the liquid within the aeration tank, the potential problems relating to maintenance and down-time are eliminated.
In accordance with the foregoing, it is an object of this invention to increase the absorption efficiency of oxygen dissolution systems while avoiding the necessity of closed aeration tanks, multiple cells, mechanical liquid stirrers or mixers, excessive tank freeboard, CO2 buildup, and moving parts within the liquid or in a high oxygen content environment above the liquid.
Another object of the invention is to reduce the costs involved in dissolving oxygen into liquid, particularly , : . :.
., , . , . , , , ., ~ ., :: . . ~ .
lI3~Z5~;9 in the aeration stage of activated sludge waste treatment sys-tems, thereby improving the efficiency of such systems and reducing the operating costs and energy requirements.
Another object of the invention is to provide a system for increasing the oxygen content of a liquid, which system is capable of extremely high dissolution rates at ex-tremely high absorption efficiencies without the necessity of utilizing enclosed oxygen pressurized serially arranged liquid tanks or reservoirs.
Another object of the invention is to provide high absorption efficiencies in a system which utilizes no moving ~-parts for dissolving the oxygen in the liquid except for a liquid pump, and the pump, instead of being located in a high oxygen content atmosphere, is exposed only to ambient air.
Another object of the invention is to increase the capacity of activated sludge waste treatment systems which rely on pure or relatively pure oxygen rather than air for oxygenation purposes in reducing the B.O.D. of the waste liquid.
The present invention involves a method of and appa-ratus for increasing the oxygen content of a body of liquid by producing a stream of liquid, pressurizing the stream, creating turbulence in the stream, introducing gaseous oxygen into the stream and then discharging the stream through a liquid nozzle into the body of liquid. Based upon conducted tests, the prèsent invention has many advantages over known methods and systems in terms of absorption ef~ioiency, ori ginal costs, operating costs and simplicity of design, con-struction and maintenance. All of these advantages are be-lieved to be obtained without introducing any disadvantageswith respect to previously known oxygenation systems.
The method and the system which are involved in the . . .
present lnvention lorld themselv~s to contlnuou~ operatlon l)y ~ich subs~ntial ~mounts of oxygen may be dlssolvod ln the .,~,, body of liquld nt extr~mely high absorptlon efficlencles in comparison to other well known ~o~called "oxygen" systems of water treatment and purlflcation.
In the preferred embodiment an In~ector, which is completely void of moving parts, is utilized as the instru-mentality by which the oxygen ls introduced into the liquid. A
pump is used to circulate liquid from the body to be oxygenated, through a conduit arrangement and back to the body of liquid, -;
As the liquid is circulated through the conduit the oxygen is introduced into the liquid by means of the injector in the form of a stream. Preferably the oxygen stream is introduced into the liquid stream on the inlet or upstream side or low pressure side of the pump, merely to utilize the pump as a mixer, but -tests indicate that the oxygen may be introduced on the dis-charge side of the pump without losing any of the enhanced characteristics of the system and without suffering any significant reduction in absorption efficiency.
The method and system of the present invention lend themselves not only to new construction but to modifications ~ - -of existing waste treatment and water purification facilities, The absorption efficiencies and total reductions in energy requirements which inure to the present invention do not depend upon the size of the aeration system, as a consequence of which the principles of the present invention find utility in very small oxygenation systems and activated sludge waste treatment systems as well as in very large systems that are employed, for example, ln the maJor metropolitan areas. `
In one particular aspect the present inventi;on provides a method of dissolving gaseous oxygen into liquid oomprising the steps of; confining a body of liquid into which ~a~eous oxygen iB to be discolved, continually removing a portion Jl/~ 8_ A;~ ., , . ~ . ,~ , . . .
5~i9 o the llquid rrom sald con~incd body, prcssuri7ing ~hc llquld ~emoved from 9aid confincd body, lnJectln~ gn8eoUS oxygcn -~nto ~ald pressurl7.ed llguld to oxygenate said liquid, causing said oxyeenated ].lquid to reside ln a pressurized state for at least about five second while removed from said conflned body, and returning said oxygenated liquid to said confined body and causing it to be discharged into said confined body through a discharge nozzle while undergoing a pressure drop in the range of approximately 5 to 12 psia, -In another aspect the present invention provides ~--apparatus for dissolving gaseous oxygen in a liquid comprising in combination, reservoir means for confining a body of liquid into which gaseous oxygen is to be dlssolved, circulating means comprising hydraulic circuitry connected to said reservoir means and including fluid conduit means externally of said reservoir means, fluid flow and pressure producing means connected in -~
said fluid conduit means externally of said liquid confining means for circulating and pressurizing liquid from said confined ~ :
liquid body through said fluid conduit means and returning said removed fluid back to said reservoir means, injector means ~ :
connected in said fluid conduit means for in~ecting gaseous oxygen into the liquid in said fluid conduit means to oxygenate said liquid, said circulating means further including nozzle discharge means disposed within said reservoir means for dis-charging the oxygenated liquid from said hydraulic circuitry into said confined liquid body, said fluid flow means and hydraulic circuitry being operative to maintain said oxygenated liquid within said circuitry for a minimum period of approx~
lmstely five seconds prior to discharge through said nozzle discharge means, said nozzle discharge means being adapted to effect a pressure drop of between approximately 5 to 12 psia as sald oxygenated liquid ls discharged into said confined liquid body, _8a-~ ~ , ` - `
. :, .,, :. . ..
: . ~ . ' ~ . " : ' :
Z5¢9 ^~ Many feattlles~ advnntages and obJects of the resent inven~ion in addltion to the foregoing will become manlfest to those versed in the art by making reference to the detailed ~ ' _8b- ~
~ ~ t ~ . .
~ , 1~4ZS~;9 description which follows and the accompanying sheets of draw-ings, in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example only.
FIG. 1 is a graph which discloses the absorption efficiency of a typical prior art aeration system using conven-tional jet aeration equipment, at various levels of submergence.
FIG. 2 is a graph which illustrates the absorption efficiency of a conventional prior art jet aeration system, at a constant submergence, both when air and when high purity oxygen are used as the source of oxygen.
FIG. 3 is a graph which illustrates the absorption efficiency of a conventional prior art jet aeration system and of a system which embodies the principles of the present inven-tion, when high purity oxygen i8 used in systems as the source of oxygen, the submergence levels of both systems being the same.
FIG. 4, which appears on the sheet of drawings bearing FIG. 1, is a schematic or diagrammatic illustration of a conven-tional prior art ~et aeration system.
; FIG. 5 is an enlsrged sectional view of the jet aerator utilized in the ~et aeration sy3tem shown in FIG. 4.
FIG. 6 is a schematic or diagrammatic illustrationof a ~et aeration system constructed in accordance with the prlnciples of the present invention. `
FIG. 7 is an enlarged sectional view of the eductor utilized in the system shown in PIG. 6.
FIG. 8 is a graph which discloses the manner in which the absorption efficiency of the present invention varies 3~ in accordance with variations in jet submer~ence levels.
FIG. 9 is a curve which discloses the absorption efficiency of a system embodying the principles of the pres-jb/~,~
, . . . ................................. : . .
. .
5~9 ent invention operated over a range of jet pressure drops.
FIG. 10 is a graph which discloses the effect of var-iations in liquid residence time on the absorption efficiency of a system constructed in accordance with the principles of the present invention.
FIG. 11 is a graph which discloses the absorption efficiency of a system embodying the present invention operated both with and without shrouds to produce secondary delivery jets from the liquid jet nozzles submerged within the body of 10 liquid being oxygenated.
FIG. 12 is a graph which compares the oxygenation capacity of a conventional prior art jet aeration system using both air and high purity oxygen as the source of oxygen and a system constructed and operated in accordance with the 15 principles of the present invention, all at various oxygen-to-liquid flow ratios. ~.-As noted, aeration systems which utilize eductors or jet aerators embodying eductor principles have long been known in the prior art. Generally, waste liquid is pumped 20 from an aeration tank, through hydraulic conduits, to the liquid nozzle of a jet aerator or eductor. The jet aerator is furnished with a mixing chamber into which the waste liquid from the liquid nozzle issues and connected to which is a ~
source of pressurized or aspirated air. The admixture of ~ -25 waste liquid and air is then discharged from the jet aerator or eductor in the form of a high velocity jet into the aera- ;
tion tank below the surface of the liquid.
- The curves shown in FIG. 1 were developed from test data relating to a previously known aeration system utilizing 30 conventional jet aeration equipment. FIG. 1 illustrates that - such systems are capable of achieving a relatively high absorp-~ "...~ ~ ... .
tion or transfer efficiency when air (as contrasted with high , 1~4~S~;9 purity oxygen) is utilized in the gas-liquid contacting process. As a matter of fact the curves shown in FIG. 1 ill-ustrate that the absorption efficiencies of jet aeration sys-tems compare favorably with those available from any other aeration system, that is, one which utilizes air rather than oxygen in the oxygen transfer process.
On the other hand, the curves shown in FIG. 1 dis-close absorption efficiencies which would not be commercially feasible or acceptable, from an operating cost standpoint, in identical systems in which high purity oxygen were substituted for air as the source of oxygen.
The curves shown in FIG. 1 suggest, however, that if high purity oxygen is substituted for air and if, in addi-tion, experimentation were conducted to optimize the percent ransfer of the high purity oxygen, acceptable absorption efficiencies could possibly be attained. The fact that a substantially pure oxygen bubble will have a higher partial pressure of oxygen than will an air bubble and will not be subject to dilution of the percent oxygen content as oxygen is transferred into solution may well suggest to those skilled in the art a higher transfer efficiency than that which has been obtained with air, even without optimization.
In the course of the investigations which resulted in the present invention, the inventor experimented with the - 25 utilization of high purity oxygen instead of air in conven-tional prior art jet aeration systems. In the course of the investigations and experiments, the parameters whioh effect absorption efficiency were varied in an effort to maximize absorption efficiency.
The most favorable results obtained from this exper-imentation are shown in FIG. 2. The two curves shown therein were derived from test data concerning the same prior art jet .
.
~4;~ 9 aeration system, but the curve entitled "Jet Aeration" re-sulted from the use of air as the source of oxygen, whereas the curve entitled "Jet Oxygenation" resulted from the use of high purity oxy~en. A comparison of the curves shown in FIG. 2 illustrates quite clearly that conventional jet aera-tion systems previously known in the prior art are probably not commercially feasible when high purity oxygen is substi-tuted for air, since the absorption efficiencies of such sys-tems do not increase substantially as a consequence of such 10 substitution. - ~
In the course of these investigations, experimenta- - -;
tion was conducted with numerous modifications in conventional jet aeration equipment. In each case the improvements in ab- ~-sorption efficiency using high purity oxygen instead of air were only marginal, resulting in most instances in not more than a two to three percent increase in transfer or absorp-tion efficiency. Even when the gaseous oxygen application ~ -rates were reduced or backed off to such an extent that the oxygen which went into solution was not even sufficient to saturate the motive liquid stream, absorption efficiency did not improve in any substantial degree.
It was as a consequence of the foregoing experimen-tation and the failure of conventional jet aeration equipment to produce high absorption efficiencies when utilizing high purity oxygen that consideration was given to alternative sys-tems. One possible system considered involved the pre-injec-tion of gaseous oxygen into a pressurized liquid motive stream. However, based upon information which is presently known to those skilled in the art of gas-liquid contactors and - 30 gas-liquid trans~er, such a system should not produce favorable absorption efficienceis since (1) the benefits which are known to derive from gas-liquid contacting at the nozzle of the jet ..,. . . ~ .: .. :
~4ZS~;9 aerator would be completed eliminated, (2) the amount of oxygen that could be transferred into the motive liquid stream would be limited by the motive stream flow rate and its saturation value, and (3) any gaseous oxygen that carries through the motive stream cycle may exit in a state of dispersion which is unfavorable for mass transfer.
Notwithstanding the foregoing it was decided to develop a prototype and conduct tests of such a system. The results were completely and unexpectedly favorable. FIG. 3 illustrates the substantial increase in absorption efficiency of an aeration system embodying the principles of the present invention and utilizing high purity oxygen as contrasted with a conventional jet aeration system also using high purity oxygen. The curve entitled "Jet Oxygenation" corresponds to the similarly entitled curve shown in FIG. 2. On the other hand, the curve entitled "Pre-injection Jet Oxygenation" dis- -closes the much higher absorption efficiencies available from a jet aeration system constructed in accordance with the prin-ciples of the present invention. Both curves illustrate the variation in absorption efficiency which results from varia-tions in the mass-flow ratio of gaseous oxygen and waste liquid.
FIG. 4 illustrates a conventional prior art jet aeration system and corresponds to the system which was used in developing the curves shown in FIG. 1, the curve entitled "Prior Art Jet Aeration"shown in FIG~ 2 and the aurve entitled "~et Oxygenation" shown in FIG. 3. The system includes a large aeration tank or reservoir indicated generally at ref-erence numeral 10 which contains a body of liquid 11 being oxygenated. The surface of the liquid 11 is shown at refer-ence character lla and it is noted that the surface of the liquid may very closely approach an open upper end 12 of the , ': ' ' ' ': ' . .. . .
. . .. . . . . .
'; . ' :, : .
1342S~9 aeration tank 10. A side wall 13 of the tank 10 is, in the illustrated embodiment, cylindrically shaped, but it will be appreciated that the particular configuration of the tank 10 is not critical to the present invention. Unlike presently known high purity oxygen systems, however, the top 12 of the tank 10 is not closed or covered but instead is fully open to the atmosphere surrounding the tank 10.
A jet aerator 14 is located within the aeration tank 10 below the surface of the liquid 11. In the system which was actually used in the course of these investigations and experiments, the jet aerator 14 comprised a single unit (which may be referred to as a jet cluster) having a plur- ~ :
ality-of liquid nozzles 15 arranged radially about a verti--al axis and communicating with a common manifold 16 to which --is connected a conduit 17 which extends through the side wall 13 of the tank 10 and to a discharge side 18 of a liquid pump 19. Another condu.t 20 is connected at one end 21 there^f to the suction or inlet side of the pump 19, whereas an opposite end 22 communicates with the interior of the tank 10.
valve 23 is mounted in the high pressure liquid conduit 17 whereas a similar valve 24 is mounted in the low pressure liquid conduit 20.
Re~erring again to the jet aerator 14, a series of gas-liquid nozzles 26, corresponding in number and location to the liquid no~zles 15, communicate with an air manifold 27 to which is connected an air conduit 28 which extends through the side wall 13 of the aeration tank 10 to an air blower ( not shown).
In the operation of the conventional jet aeration - 30 system shown in FIG. 4, liquid 11 from the aeration tank 10 - is pumped through the conduit 20 by the liquid pump 19 and conducted through the conduit 17 to the liquid nozzles 15 of .
.:
.:
~Z569 the jet aerator 14. Liquid ~rom the nozzles 15 issues in the form of high velocity liquid jets and mixes with air being con-ducted through the conduit 28 to the manifold 27 surrounding the liquid nozzles 15. The admixture of liquid and air then issues in the form of high velocity jets from the air-liquid nozzles 26 extending radially about the axis of the jet aera-tor 14.
While the illustrated embodiment of the jet aerator 14 includes a plurality of liquid and air-liauid nozzles, the principles of the conventional jet aeration do not require a multi-nozzle jet aerator or cluster and in 'act many systems utilize one or more jet aerators, each of which comprises only a single liquid nozzle surrounded by an air-liquid nozzle.
FIG. 6 illustrates an aeration system embodying the principles of the present invention and a comparison of FIGS.
~ and 6 illustrates .he essential similari ~i25 O' an~ distinc-tions between the two systems. Those parts or components of the system shown in FIG. 6 which correspond to those shown in FIG. 4 are identified with the similar reference characters, and it is noted that the system shown in FIG. 6 does not utilize an air conduit 28. As a consequence the jet aerator chamber 27, which previously served as an air manifold, is now in direct communication with the liquid 11, and the air-liquid nozzles 26 merely serve to produce secondary liquidjets surrounding the jets which issue from the liquid nozzles lS.
In the system shown in FIG. 6 a conduit 30 has been added to interconnect the high pressure liquid conduit 17 and the low pressure conduit liquid 20. In the illustrated em-bodiment the diameter of the conduit 30 is significantly less than the diameter of either the conduit 17 or the conduit 20, ' ` . '" `', ' : `
.
, .: .
1~25~9 and mounted in the conduit 30 is an eductor 31, as well as a pair of valves 32 and 33 mounted on the opposite sides of the eductor 31. Another conduit indicated at reference numeral 34 is connected to the eductor 31 and has mounted therein a valve 36. The conduit 34 is connected to a source of high purity oxygen (not shown) although the principles of the present invention are applicable even though the percent of oxygen in the gas is substantially less than 100%.
Referring to FIG. 7, the eductor 31 comprises a liquid nozzle section 37, a mixing chamber 38 and a diffuser section 39. The precise embodiment of the eductor 31 is not critical to the present invention, however, and indeed it is not necessary that an eductor be used for the purpose of -.
introducing the oxygen into the liquid. What is important --. --is that the oxygen be introduced into the liquid in the form of fine bubbles, and for that purpose an eductor 31 is par- `- ~.
ticularly well suited. - ~`
.
In operation of the system disclosed in FIG. 6, the liquid pump 19, which is connected to an electric motor l9a, draws liquid from the tank 10 through the low pressure con-:-: duit 20 and discharges the liquid back into the tank 10 through the high pressure liquid conduit 17 and the liquid nozzles 15. A small poriton of the liquid being circulated : through the pump 19 and being discharged back into the tank 10 through the high pressure liquid conduit 17 is by-passed thorugh the conduit 30 back to the low pressure liquid con-duit 20. As this small portion of the liquid stream is con-ducted through the conduit 30, relatively high purity oxygen ~
is introduced into the liquid by virtue of the eductor 31. : - -30 Thus in the embodiment shown in FIG. 6, the oxygen is added . .
to the liquid stream on the suction side rather than the dis-charge side of the liquid pump 19.
, ~ .
i~42S~9 In the test facilities in which the investigations and experimentations were undertaken, the eductor or injector 31 produced oxygen bubbles in the order of about 2 millimeters or less in diameter, resulting in a specific interfacial area of about 30,000 cm /liter of gas. Based upon these investigations, it is believed that the very high absorption efficiencies resul-ting from the present invention may be obtained regardless of whether the oxygen is introduced into the low pressure liquid conduit 20 on the suction side of the pump 19 or in the high pressure liquid conduit 17 on the discharge side of the pump 19, and it is also believed that absorption efficiencies in the same order of magnitude as those achieved in the specific test fac-ility utilized can be obtained regardless of the manner in which the oxygen is introduced into the conduits 17 and 20, provided the specific interfacial area of the oxygen to the liquid is about 30,000 cm2/liter or gas, or greater.
That hydraulic circuitry, including the liquid nozzles 15, the high pressure liquid conduit 17, the liquid pump 19 and .the low pressure liquid conduit 20, by which the liquid 11 is circulated from the tank 10, through the circuitry and then back to the tank 10, is indicated generally at reference num-eral 36. -It is apparent that the principles of the present invention do not require any specific geometry or configura-tive relationships with respect to the hydraulic circuitry36. Nor is it required that the oxygen be introduced at any particular point in the hydraulic circuitry 36 as long as it is subjected to a minimum residence time therein. What is apparent, however, is that the liquid stream in the hydraulic circuitry 36 must be in a state of turbulence upstream of the liquid nozzles 15 to provide mixing of the oxygen bubbles in the liquid stream. By turbulence is meant a state of distur-bance of the liquid stream to produce relatively violent agi-. . . . .
. . . . . . . . .
-. . ~ .
,. ~
.
. .
.. . . .
, 1~4ZS69 tation or perturbation of the liquid.
It has been estimated that the Reynolds number of - the hydraulic circuitry 36 in the test facility was probably between 200,000 and 400,000. In the course of these inves-tigations, however, a considerable effort was made to varythe Reynolds number, and upon observation it was noted that there was no appreciable variation in absorption efficiency as a consequence of variation in Reynolds number. As noted, it is only necessary that the liquid stream be maintained in ` -a state of turbulence upstream of the liquid nozzles 15, but it is anticipated that, ~ith respect to any particular system, and depending upon the diameter of the pipes, the number of elbows and other fittings and the like, some adjustment with respect to the valves 23 and 24 and other experimentation may be required in order to obtain the maximum absorption efficiency.
The curve snown in FIG. 8 illustrates variation in absorption efficiency of the system shown in FI~.6 as the level of submergence of the jet aerator 14 is varied. The ~ -tests in connection with which this curve was developed were conducted at a fixed gas flow rate of 5 lbs. per hour per liquid iet nozzle 15. Actually, the jet aerator indicated at reference numeral 14 which was used in the test facility .
diagrammatically indicated in FIG. 6 comprised a total of 12 - 25 liquid nozzles 15 extending radially outwardly from a single casing. Experimentation indicates, however, that the absorp-tion efficiencies available from the invention do not depend upon the numbex of liquid jet nozzles involved, although it is apparent that the total rate of dissolution of oxygen in the liquid will vary in accordance with the number of liquid jet~.
FIG. 8 indicates that the absorption effiaiency of , . . . ~ , .
: .,.. ,...... , . . ~ . . , ~ .
1¢~4;~
the invention approaches almost 50~ even when the liquid jet approaches the very surface lla of the liquid 11 in the tank 10. Absorption efficiency increases upon an increase in li~uid jet submergence level and very nearly 100~ absorption efficiency was obtained when the liquid jets were located approximately 20 feet below the surface lla of the liquid 11.
In the course of the tests the liquid 11 in the tank 10 was tap water at standard conditions, but based upon com-parative test data the greatly increased absorption effic-iencies which the invention is capable of producing are alsoobtainable in the waste liquid introduced into the aeration tanks of activated sludge waste treatment systems. Beyond that, however, it would,appear as though the principles of the invention are applicable in any situation in which it is desirable to dissolve a gas into a liquid at greatly enhanced absorption efficiencies.
Based upon the results of these investigations, var-iations in the pressure drop across the liquid nozzles 15 ~'~
shown in FIG. 6 have a definite effect on the absorption ' 20, efficiency of the system. As illustrated in the curve shownin FIG. 9, the absorption efficiency of a system constructed in accordance with the principles of the invention probably requires a liquid nozzle pressuredrop of about 5 psia in order ' to provide a viable or practically commercial system, and the ', ~ , pressure may be advantageously increased to about 10-12 psia.
Further pressure drop, however, does not appear to enhance absorption efficiency to any significant degree and, on the other hand, requires the expenditure of additional energy.
Tests were conducted in an effort to determine whether the residence time of the liquid within that hydraulic circuitry bears some significant relationship to absorption efficiency. FIG. 10 discloses a curve which indicates varia- -.,;' ~, . ,, , ' .
1~4Z5~9 tions in absorption efficiency with variations in liquid res-idence time, that is, the time which elapses from the time that the liquid in the hydraluic circuitry 36 is first in-troduced to the gaseous oxygen until the liquid is discharged from the liquid nozzles 15 into the body of liquid 11. This curve indicates that, within limits, an increase in residence time produces an increase in absorption efficiency, but it -~
also indicates that a residence time of at least about five seconds is required to produce a co~mercially acceptable ab-sorption efficiency.
It will be understood, of course, that with respect to any given system it may be desirable to adjust flow rates of the gaseous oxygen and-of the recirculated liquid to pro-vide maximum absorption efficiency for that system in accor-dance with the principles of the invention described herein,but these adjustments fall within the purview of one having ordinary skill in the art. --Tests were also conducted in which the liquid nozzles 15 discharged directly into the liquid 11 both with and with- -out the benefit o the gas-liquid nozzles 26 surrounding the liquid nozzles 15. FIG. 11 illustrates that absorption efficiency is somewhat enhanced when the high velocity jets issuing from the liquid nozzles 15 are surrounded by the noz-zles 26 which, in the embodiment shown in FIG. 6, merely serve as shrouds to produce secondary liquid streams surrounding the jets issuing from the nozzles 15. Since the cost involved in providing the shrouds of nozzles 26 is quite nominal, the preferred embodiment should include the nozzles 26 to in-crease the absorption efficiency as the curve shown in FIG.
11 would indicate.
In the tests, the mean velocity of the liquid stream in the hydraulic circuitry 36 was between the range of about , .; . . : .
. .
~42S69 4 to 8 feet per second. It would appear that variations in liquid mean velocity may produce some variations in absorp-tion efficiency, but once again it is apparent that the only requirement relating to velocity is that it be sufficient to produce a state of turbulence of the liquid within the hydrau-lic circuitry so that the gaseous oxygen is mixed with the liquid.
It will be understood by those skilled in the art that any aeration system which can be considered commercially acceptable and economical must, in addition to providing acceptable absorption efficiencies at acceptable gas trans-fer rates, also be capable of producing such absorption effi-ciencies and gas transfer rates at acceptable energy require-ments. . ;
FIG. 3 discloses that the present invention is cap-able of producing extremely high absorption efficiencies at -~-economically acceptable sas .rar,sfer rates. FIG. 12 discloses that these high absorption efficiencies and rates are obtain- -- able at relatively low and entirely acceptable energy require-ments. Indeed FIG. 12 discloses that the present invention requires much less energy for dissolution of the oxygen in the liquid than does the conventional jet aeration system, regardless of whether air or high purity oxygen is utilized as the oxygenation medium.
In comparing the absorption efficiencies of systems constructed and operated in accordance with the principles of this invention with the absorption efficiencies a pre-viousl~ known "oxygeD~' s~stems which require a succession of completely enclosed tanks or cells, it is apparent that the 30 present invention compares favorably in terms of efficiencies, -but in addition attains such efficiencies in an open tank, one-pass contacting system.
In FIG. 5 the details of the jet aerator 14 are shown in greater detail. The air conduit 28 is shown con-nected to jet aerator 14 in the manner illustrated in FIG. 4, but in the system shown in FIG. 6 the conduit 28 is elimin-ated, as mentioned hereinabove. Again it should be empha-sized that while the embodiment of the jet aerator 14 illus-trated herein comprises a plurality of liquid jet nozzles arranged in a "cluster" form, the principles of the invention are equally applicable to systems in which individual and dis-tinct liquid jet nozzles are used for producing the.high velo-city jets in the aeration tank 10.
Although minor modifications might be suggested by . ~
those versed in the art, it should be understood that in- ~. ; . .
cluded within the scope of the patent warranted hereon all such modifications as reasonably come within the scope of t.he present contribution to the art.
..
~ , -
Claims (15)
1. A method of dissolving gaseous oxygen into liquid comprising the steps of; confining a body of liquid into which gaseous oxygen is to be dissolved, continually removing a portion of the liquid from said confined body, pressurizing the liquid removed from said confined body, injecting gaseous oxygen into said pressurized liquid to oxygenate said liquid, causing said oxygenated liquid to reside in a pressurized state for at least about five seconds while removed from said confined body, and returning said oxygenated liquid to said confined body and causing it to be discharged into said confined body through a discharge nozzle while undergoing a pressure drop in the range of approximately 5 to 12 psia.
2. The method as defined in Claim 1 in which said gaseous oxygen is introduced to said liquid on the suction side of said fluid pump.
3. The method as defined in Claim 1 in which said gaseous oxygen is introduced to said liquid through a liquid-oxygen injector.
4. The method as defined in Claim 1 in which said gaseous oxygen is introduced into said pressurized liquid in the form of small bubbles having an average diameter of approximately 2mm or less.
5. The invention as defined in Claim 1 wherein the velocity of said liquid stream upstream of said liquid nozzle is at least about 4 feet per second.
6. The invention as defined in Claim 1 in which the gaseous oxygen is dissolved in the liquid in said stream at a rate of at least about 10 lbs. of oxygen per 1,000,000 lbs.
of liquid.
of liquid.
7. The invention as defined in Claim 1 including the step of providing a shroud surrounding said liquid nozzle for inducing liquid from said body of liquid to flow between said liquid nozzle and said shroud and to mix with liquid issuing from said liquid nozzle.
8. The method as defined in Claim 1 wherein said gaseous oxygen is injected into said pressurized liquid such that the specific interfacial area of oxygen to the liquid is at least about 30,000 cm2 per liter of gas.
9. Apparatus for dissolving gaseous oxygen in a liquid comprising, in combination, reservoir means for confining a body of liquid into which gaseous oxygen is to be dissolved, circulating means comprising hydraulic circuitry connected to said reservoir means and including fluid conduit means externally of said reservoir means, fluid flow and pressure producing means connected in said fluid conduit means externally of said liquid confining means for circulating and pressurizing liquid from said confined liquid body through said fluid conduit means and returning said removed fluid back to said reservoir means, injector means connected in said fluid conduit means for injecting gaseous oxygen into the liquid in said fluid conduit means to oxygenate said liquid, said circulating means further including nozzle discharge means disposed within said reservoir means for discharging the oxygenated liquid from said hydraulic circuitry into said confined liquid body, said fluid flow means and hydraulic circuitry being operative to maintain said oxygenated liquid within said circuitry for a minimum period of approximately five seconds prior to discharge through said nozzle discharge means, said nozzle discharge means being adapted to effect a pressure drop of between approximately 5 to 12 psia as said oxygenated liquid is discharged into said confined liquid body.
10. Apparatus as defined in Claim 9 wherein said fluid flow and pressure producing means comprises a hydraulic pump, and in which said injector means comprises means for introducing said gaseous oxygen into the liquid in said hydraulic circuitry on the suction side of said hydraulic pump.
11. Apparatus as defined in Claim 10 in which said gaseous oxygen is introduced into said liquid stream upstream of that portion of the stream at which the liquid therein is pressurized.
12. Apparatus as defined in Claim 9 wherein said fluid flow and pressure producing means comprises a liquid pump having an inlet conduit to receive liquid from said confined liquid body and having an outlet to discharge fluid from said liquid pump, and wherein said conduit means includes a gas-liquid injector interconnecting said inlet and outlet conduits across said liquid pump.
13. Apparatus as defined in Claim 9 wherein said means for circulating and pressurizing liquid from said confined body includes a liquid pump, and wherein said conduit means is constructed and arranged to introduce the gaseous oxygen into said hydraulic circuit means on the upstream or low pressure side of said liquid pump.
14. Apparatus as defined in Claim 9 wherein said means for circulating and pressurizing liquid from said confined body includes a liquid pump, and wherein said liquid pump is constructed and arranged to provide a velocity of the liquid in said hydraulic circuitry upstream of said nozzle discharge means of at least 4 feet per second.
15. Apparatus as defined in Claim 9 wherein said injector means is constructed and arranged to introduce the oxygen into the liquid in said fluid conduit means in the form of bubbles having an average diameter of about 2 mm or less.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US46101474A | 1974-04-15 | 1974-04-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1042569A true CA1042569A (en) | 1978-11-14 |
Family
ID=23830898
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA224,228A Expired CA1042569A (en) | 1974-04-15 | 1975-04-09 | Method of and apparatus for the dissolution of gaseous oxygen into a liquid |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5328257B2 (en) |
| CA (1) | CA1042569A (en) |
| DE (1) | DE2516371A1 (en) |
| GB (1) | GB1469049A (en) |
| ZA (1) | ZA752273B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE7611981L (en) * | 1975-10-31 | 1977-05-01 | Albert Blum | DEVICE FOR INFORMATION OF GASES, IN PARTICULAR AIR, IN VETSKOR. |
| DE2634494C2 (en) * | 1976-07-31 | 1983-04-14 | Bayer Ag, 5090 Leverkusen | New injectors for liquid gassing |
| DE2713210A1 (en) * | 1977-03-25 | 1978-10-05 | Albert Blum | Submersible aerator for fluids e.g. sewage - with pump and blower driven at adjustable speed ratio |
| US4139579A (en) * | 1977-07-15 | 1979-02-13 | Albert Blum | Apparatus for introducing air into a liquid including a liquid pump mounted within an aerator pressure chamber |
| US4152259A (en) * | 1977-12-22 | 1979-05-01 | Clevepak Corporation | Backflushing method |
| JPS54170665U (en) * | 1978-05-23 | 1979-12-03 | ||
| JPS55114394A (en) * | 1979-02-24 | 1980-09-03 | Eiichi Sugiura | Water suction pipe air intake type vapor-liquid mixing pressure aerator for polluted water treatment |
| JPS5615831A (en) * | 1979-07-18 | 1981-02-16 | Nishihara Environ Sanit Res Corp | Aerator |
| GB8401781D0 (en) * | 1984-01-24 | 1984-02-29 | Boc Group Plc | Dissolving gas liquid |
| SE457349B (en) * | 1986-03-04 | 1988-12-19 | Purac Ab | DEVICE FOR TREATMENT OF LIQUIDS WITH AIR IN A TREATMENT POOL |
| JPH01139196A (en) * | 1987-11-24 | 1989-05-31 | Kazuaki Yokota | Ejector structure in water treating device |
| JP7299591B2 (en) * | 2019-10-16 | 2023-06-28 | 住友金属鉱山株式会社 | Method of operating the reactor |
-
1974
- 1974-08-01 JP JP8861974A patent/JPS5328257B2/ja not_active Expired
-
1975
- 1975-04-08 GB GB1437275A patent/GB1469049A/en not_active Expired
- 1975-04-09 CA CA224,228A patent/CA1042569A/en not_active Expired
- 1975-04-09 ZA ZA00752273A patent/ZA752273B/en unknown
- 1975-04-15 DE DE19752516371 patent/DE2516371A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5328257B2 (en) | 1978-08-14 |
| ZA752273B (en) | 1976-03-31 |
| JPS50133974A (en) | 1975-10-23 |
| GB1469049A (en) | 1977-03-30 |
| DE2516371A1 (en) | 1975-10-23 |
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