GB2033770A - Method and apparatus for aerating liquids - Google Patents

Method and apparatus for aerating liquids Download PDF

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Publication number
GB2033770A
GB2033770A GB7844503A GB7844503A GB2033770A GB 2033770 A GB2033770 A GB 2033770A GB 7844503 A GB7844503 A GB 7844503A GB 7844503 A GB7844503 A GB 7844503A GB 2033770 A GB2033770 A GB 2033770A
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gas
supply pipe
gas supply
liquid
aeration tank
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GB2033770B (en
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INST TEKH TEPLOFIZIKI AKAD
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INST TEKH TEPLOFIZIKI AKAD
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Priority to DE19782854557 priority patent/DE2854557A1/en
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    • 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
    • C02F3/1284—Mixing devices
    • 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
    • B01F31/00—Mixers with shaking, oscillating, or vibrating mechanisms
    • B01F31/65—Mixers with shaking, oscillating, or vibrating mechanisms the materials to be mixed being directly submitted to a pulsating movement, e.g. by means of an oscillating piston or air column
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/34—Treatment of water, waste water, or sewage with mechanical oscillations
    • 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
    • C02F3/20—Activated sludge processes using diffusers
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M27/00—Means for mixing, agitating or circulating fluids in the vessel
    • C12M27/18—Flow directing inserts
    • C12M27/24—Draft tube
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M29/00—Means for introduction, extraction or recirculation of materials, e.g. pumps
    • C12M29/12—Pulsatile flow
    • 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

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  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Wood Science & Technology (AREA)
  • Microbiology (AREA)
  • Zoology (AREA)
  • Bioinformatics & Cheminformatics (AREA)
  • Health & Medical Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Water Supply & Treatment (AREA)
  • Environmental & Geological Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Biotechnology (AREA)
  • Sustainable Development (AREA)
  • Biomedical Technology (AREA)
  • Biochemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • General Health & Medical Sciences (AREA)
  • Genetics & Genomics (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Mechanical Engineering (AREA)
  • Apparatus Associated With Microorganisms And Enzymes (AREA)

Abstract

A method of aerating liquids in an aeration tank 1 having at least one gas supply pipe 2 comprises feeding gas to the pipe under an alternating pressure, thereby, imparting an oscillatory motion to the liquid in the gas supply pipe under the action of the alternating pressure which forms a gas-liquid emulsion, dispersing the emulsion formed by expelling it from the gas supply pipe into the aeration tank. Alternate feeding and removal of gas is arranged to cause reciprocations of the gas-liquid interface in the gas supply pipe at a frequency ranging from 40 to 200 c/min and with an amplitude from 0.05 to 2 m. The pipe or pipes 2 extend, substantially vertically into the aeration tank 1 and communicate at the upper portion thereof with switchover 3,4,5&7 means for alternately connecting the gas supply pipe to the gas supply source and to the gas removal system. The apparatus may be automatically controlled. <IMAGE>

Description

SPECIFICATION Method and apparatus for aerating liquids The present invention relates to methods and apparatus for aerating liquids and can be used in biological treatment of sewage, as well as in fermentation of culture media in the microbiological, food, and pharmaceutical industries.
The invention provides a method for aerating liquids in an aeration tank having a gas supply pipe extending substantionally vertically therein, the method comprising the steps of feeding a gas to the gas supply pipe in batches to create an alternating pressure; imparting an oscillatory motion to the liquid within the gas supply pipe under the action of the alternating gas pressure in such a manner as to cause reciprocations of the gas-liquid interface within the gas supply pipe ranging from 40 to 200 c/min and with the amplitude ranging from 2 to 0.05 m; forming a gas-liquid emulsion in the layer adjacent the gas-liquid interface in the gas supply pipe during the feeding of each batch of the gas; dispersing the resultant emulsion by expelling the same from the gas supply pipe into the aeration tank to aerate the liquid therein; alternately removing the gas from and feeding it into the gas supply pipe to fill said gas supply pipe with the liquid from the aeration tank at regular intervals.
With the gas being fed in batches into and removed from the gas supply pipe in the intervals between two successive feedings of the batches, the pressure of liquid within the aeration tank varies by jumps thus resulting in a blow-up type destruction of the film of surface-active agents as a result of an abrupt change in the volume of gas bubbles. Emulsification intensity under the above conditions is such that there is no need in foaming agents.
These very factors make it possible to intensify the mass exchange between the liquid and gaseous phases and reduce gas consumption for aeration.
To aerate liquids having a viscosity from 10 to 30 cP, gas is preferably fed to and removed from the gas supply pipe in such a way as to cause the reciprocations of the gasliquid interface within the pipe at a frequency of at least 40 c/min and with maximum amplitude of 2 m.
To aerate liquids having a viscosity from 1 to 3 cP, gas is preferably fed to and removed from the gas supply pipe so as to cause the reciprocations of the gas-liquid interface within the pipe at maximum frequency of 200 c/min and with an amplitude of at least 0.05 m.
In fermentation of culture media for the production of streptomycin, penicillin, and similar antibiotics gas is preferably fed to and removed from the gas supply pipe as to cause the reciprocations of the gas-liquid interface within the pipe at a frequency about 95 c/min and with an amplitude of about 1.2 m.
In fermentation of nutritive antibiotics, for instance foodgrysine and the like, gas is preferably fed to and removed from the gas supply pipe so as to cause the reciprocations of the gas-liquid interface within the pipe at a frequency of about 76 c/min and with an amplitude of about 0.5 m.
In biological purification of waste waters having a concentration of activated sludge from 1 to 4 mg/l gas is preferably fed to and removed from the gas supply pipe so as to cause reciprocations of the gas-liquid interface within the gas supply pipe at a frequency of about 45 c/min and with an amplitude of about 0.7 m.
To provide for effective suppression of foaming at the surface of liquid, gas feeding to the gas supply pipe is preferably interrupted after the gas-liquid interface is displaced from the pipe into the aeration tank and a gas cavity is formed ascending along the pipe to the surface in the aeration tank.
Such a cavity, having reached the level of the gas-liquid interface within the aeration tank, collapses to impart to the foam bubbles a lateral impact shear thus suppressing the foam layer over the major part of the liquid surface within the aeration tank.
The most efficient is such an embodiment of the method, wherein gas feeding to the gas supply pipe is interrupted after the consumption of gas for forming the gas cavity amounts from 5 to 7% of that gas quantity required for producing a gas-liquid emulsion and for aerating the liquid in the aeration tank.
The nature of the invention will become clear from the following detailed description of modifications of the method and apparatus taken in conjunction with the accompanying drawings in which:~ Figure 1 diagrammatically shows the apparatus for carrying out the method according to the invention; Figure 2 shows a functional diagram of a gas feeding and removal switch-over means for alternately connecting a gas supply source and a gas removal system to a gas supply pipe, according to the invention; Figure 3 shows an embodiment of the apparatus comprising a control mechanism having contactors connected to sensors for sensing limit levels of the gas-liquid interface in the gas supply pipe, according to the invention; Figure 4 shows an embodiment of the apparatus comprising a valve-type gas distributor in the form of a two-way plug valve, according to the invention;; Figure 5 shows an embodiment of the apparatus comprising a valve-type gas distributor in the form of two solenoid valves, according to the invention; Figure 6 shows an embodiment of the apparatus comprising a valve-type gas distributor in the form of a two-position sliding spool valve, according to the invention; Figure 7shows an embodiment of the apparatus comprising a tubular member arranged co-axially with the gas supply pipe, according to the invention; Figure 8 is a perspective view of an embodiment of the gas supply pipe and tubular member which are of cylindrical shape, according to the invention; Figure 9 shows an embodiment of the apparatus comprising a conical tubular member, according to the invention; Figure 10 shows an embodiment of the apparatus comprising a concave deflector, according to the invention;; Figure 11 is a perspective view of an embodiment of the deflector in the form of a cone, according to the invention; Figure 12 is a perspective view of an embodiment of the concave deflector in the form of a hollow pyramid, according to the invention; Figure 13 is a perspective view of an embodiment of the apparatus for biological purification of waste waters, according to the invention.
A method for aerating liquids according to the invention is carried out in an apparatus comprising an aeration tank (Fig. 1) which is provided with a gas supply pipe 2 extending substantionally vertically therein. The gas supply pipe 2 communicates at its upper end with a gas supply source 3. According to the invention, the gas supply pipe 2 at its upper end communicate with a gas-removal system 4. The gas supply source 3 and the gas removal system 4 are connected through an alternate switch-over means 5 provided at the inlet of the gas supply pipe 2. The upper part of the aeration tank 1 is provided with a pipe 6 for removing the excess gas from the space over the liquid.
As shown in Fig. 2, the alternate switchover means 5 comprises a valve-type gas distributor 7 having a drive 8 which is connected to a control mechanism 9.
It will be readily understood that the control mechanism 9 adapted to control the drive 8 may comprise any programmed controller, specifically, a timer (not shown) inserted in a supply circuit (not shown) of the drive 8 of the valve-type gas distributor 7. This embodiment of the apparatus is used for aeration of liquids, viscosity of which changes insignificantly through the entire aeration process, for instance, in biological purification of waste waters.
Fig. 3 shows an embodiment of the apparatus which is preferably used for aerating liquids, viscosity of which substantially changes through the entire of aeration process. As may be seen in this figure, the control mechanism 9 adapted to control the drive 8 comprises contactors 10 and 11 inserted in a supply circuit 12 of the drive 8 of the valvetype gas distributor 7. The contactors 10 and 11 have their coils 13 and 14 which are connected to sensors 15 and 16 respectively for sensing the upper and lower limit levels, respectively of a gas-liquid interface 17 in the gas supply pipe 2.
It should be noted that the valve-type gas distributor 7 may be of various designs.
Referring to Fig. 4, the gas valve-type distributor 7 may be made as a two-way plug valve 18 having a rotary plug 19 which is made with passages defined by walls 20 and 21 and is mechanically coupled to the drive 8. The drive 8 comprises a reversible rotary drive and is connected to the control mechanism 9. The gas supply source 3, the gas removal system 4 and the gas supply pipe 2 are connected to the two-way plug valve 18.
This embodiment is mainly suitable for smallvolume, apparatus operating under low pressure and flow rate of the supplied gas.
Reference is now made to Fig. 5 showing an embodiment of the apparatus for industrial application of the method for aerating liquids according to the invention. In this embodiment the valve-type gas distributor 7 comprises solenoid valves 22 and 23. Solenoids 24 and 25 of said valves 22 and 23 perform the function of the drive 8 and are connected to the control mechanism 9. The solenoid valve 22 is inserted between the gas supply source 3 and the gas supply pipe 2, and the solenoid valve 23 is inserted between the gas removal system 4 and the gas supply pipe 2.
This embodiment of the apparatus is preferably when carrying out fermentation or biological purification of large volumes of waste waters.
It is to be noted that the valve-type gas distributor 7 may be variously otherwise constructed. Fig. 6 shows another embodiment of the apparatus, wherein the valve-type gas distributor 7 comprises a two-position sliding spool valve 26. A spool 27 of the twoposition sliding spool valve 26 includes pistones 28 and 29 which are rigidly secured to a common piston rod 30. The common piston rod 30 is rigidly fixed to the drive 8. The drive 8 comprises a reciprocatory drive 31, such as a hydraulic cylinder or pneumatic cylinder. The reciprocatory drive 31 is connected to the control mechanism 9. The inner space of the sliding spool valve 26 intermediate between the pistons 28 and 29 communicates with the gas supply pipe 2. The pistons 28 and 29 are spaced apart on the common piston rod 30 at such a distance that when the spool 27 is displaced they cut-off either the gas removal system 4 or a passage 32 of the gas supply source 3.
Reference is now made to Fig. 7 which shows an embodiment of the apparatus of the present invention comprising a tubular member 33. The tubular member is arranged coaxially with and extends around the gas supply pipe 2 over the major part of its length.
The tubular member 33 has a flare portion 34 at its lower end. The upper end face of the tubular member 33 is disposed below the liquid level in the aeration tank 1.
It is to be understood that the gas supply pipe 2 and the tubular member 33 can be variously shaped. The simplest modification is deemed to be one involving cylindrical gas supply pipe 2 and tubular member 33 as shown in Fig. 8. Preferably the ratio of the diameter D of the tubular member 33 to the diameter d of the gas supply pipe 2 is from 1.1 to 1.7.
Alternatively, the gas supply and the tubular member 33 may have cylindrical and conical shape, respectively, as shown in Fig. 9.
The conical tubular member 33 has a flare portion 35 at its upper end in addition to a flare portion 34 at its lower end. Thus the clearance between the gas supply pipe 2 and the tubular member 33 first decreases and then increases upwardly.
The above described embodiments shown in Figs. 8 and 9 are preferred when the aeration of liquids is accompanied by an intense foaming in the aeration tank 1.
Reference is now made to Fig. 10 showing an embodiment of the apparatus comprising a concave deflector 36 arranged opposite to the lower end face 37 of the gas supply pipe 2.
The concave deflector 36 improves the conditions for the formation of a gas cavity within the liquid. The concave deflector 36 may be of various shapes. Specifically, it may have a conical form as shown in Fig. 11 or the form of a hollow pyramid with a downwardly directed apex, as shown in Fig. 12. It will be appreciated that the concave deflector 36 may be of a more intricate configuration, for instance, it may have the form of a paraboloid (not shown).
It is to be understood that the number of gas supply pipes and their relative arrangement in the aeration tank 1 may be of a most diversified character, specifically, as shown in Fig. 13, for biological purification of waste waters an embodiment of the apparatus is preferably used which comprises several gas supply pipes 2 which are arranged in a single line along the aeration tank 1 and communicating, via a manifold 38 to the alternate switch-over means 5 for connecting the gas supply source 3 and the gas removal system 4 to the pipe 2.
The idea of the method will become more apparent from the following description of operation of the apparatus in conjunction with the specific examples illustrating practical realization of the process according to the invention.
The method for aerating liquids using the above-described apparatus is carried out as follows. The aeration tank 1 is filled with a liquid to be aerated such as a culture medium in case of fermentation, or activated sludge in case of biological purification of waste waters.
The liquid thus fills the gas supply pipe 2 up to the same level as that in the aeration tank 1. To create the alternating pressure, a gas from the gas supply source 3 is fed in batches into the gas supply pipe 2 via the switch-over means 5 for alternately connecting the gas supply source 3 and gas removal system 4 to the gas supply pipe 2. Under the action of cyclically changing pressure of gas, an oscillatory motion is imparted to the liquid contained within the gas supply pipe 2 so that, according to the invention, the liquid-gas interface reciprocates at a frequency within the range from 40 to 200 c/min and with an amplitude ranging from 0.05 to 2 m. As each batch of the gas is fed an intense turbulization and formation of a gas-liquid emulsion within the gas supply pipe 2 occur in the layer of liquid adjacent the gas-liquid interface.The resultant gas-liquid emulsion undergoes dispersion by expelling it into the liquid contained within the aeration tank 1. The bubbles of the gasliquid emulsion are diminished to a size ranging from 20 to 60 fiA. Alternately with the gas supply from the source 3 and the gas is removed from the gas supply pipe 2 via the alternate switch-over means 5 which is conducive and the system 4, which results in a regular filling the gas supply pipe 2 with the liquid taken from the aeration tank 1 during the oscillatory motion of liquid with the abovespecified parameters.
The steps of feeding of gas with subsequent formation, expulsion and dispersion of the gas-liquid emulsion, alternating with the gas removal from the gas supply pipe 2 result in the liquid pressure fluctuation within the aeration tank 1. The pressure fluctuation cases an abrupt change in the volume of bubbles of the gas-liquid emulsion being dispersed and bursting of the film of surface-active agents enveloping these bubbles. An intense mass exchange between the gaseous phase of the gas bubbles floating to the surface, and the liquid contained within the aeration tank 1 occurs under these conditions, to cause an aeration of the liquid being treated. The pressure fluctuation and periodic expulsion of the gasliquid emulsion from the gas supply pipe 2 causes an agitation of the liquid within the aeration tank 1 and provides for uniform saturation of the liquid with the gas.
In case waste waters having exhibiting high concentration of surface-active agents undergo fermentation or biological purification, it is advisable to use the embodiment of the method, wherein according to the invention, the gas supply from the gas supply source 3 into the gas supply pipe 2 is interrupted after the gas-liquid interface has been displaced from said pipe 2 and a gas cavity has been formed. The gas cavity ascends to the liquid surface along the pipe 2 and collapses upon reaching the gas-liquid interface in the aeration tank 1. The foam on the liquid surface in the aeration tank 1 is subjected to a lateral impact shear. As a consequence, a major part of the foam is suppressed.The most efficient and economical performance involves the interruption of gas supply to the gas supply pipe 2 when the quantity of gas required for the formation of cavity amounts from 5 to 7% of that required for the formation gas-liquid emulsion and aeration of the liquid within the aeration tank.
Such operation conditions of the aeration process, according to the invention, are maintained by acting at regular intervals upon the valve-type gas distributor 7 by the drive 8 receiving signals from the control mechanism 9 (Fig. 2).
Specifically, in the course of fermentation of culture media with viscosity which substantially varies during the aeration process the oscillation frequency varies automatically, since the signals are fed directly from the sensors 15 and 16 for sensing the limit levels of the gas-liquid interface to the control mechanism 9 (see Fig. 3). It is to be understood that since the rate of filling the gas supply pipe 2 with the liquid varies with variation of its viscosity a signal to the drive 8 for connecting the gas supply source 3 through the valve-type gas distributor 7 should be sent only after the gas-liquid interface reaches its uppermost level. In this embodiment the control mechanism 8 sends such a signal in response to operation of the sensor 15 and contactor 11.The system will response in a similar manner when the gas-liquid interface reaches its lowermcist level in the gas supply pipe 2, the signal from the sensor 16 being fed to the coil 13 of the contactor 10. The contactor 10 makes the supply circuit of the drive 8 so that the valve-type gas distributor 7 driven by the drive 8 disconnects the gas supply source 3 from the gas supply pipe 2 and connects gas removal system 4 to the gas supply pipe 2.
The embodiment of the apparatus shown in Fig. 4. operates in the following way when carrying out the method according to the invention. Control signals are fed from the control mechanism 9 to the rotary drive 8.
The rotary drive 8 alternately turns the plug 19 of the valve 18 into one of the two limit positions. The gas supply pipe 2 first is connected to the gas supply source 3 through the passage 20 and then to the gas removal system 4 through the passage 21.
The embodiment of the apparatus shown in Fig. 5 operates in the following way when carrying out the method according to the invention. Control signals are fed from the control mechanism 9 alternately to the solenoids 24 and 25 of the solenoid valves 22 and 23 which are normally Closed. When the solenoid 24 is energized, the solenoid valve 22 is opened to establish communication between the gas supply source 3 and the gas supply pipe 2. An intense formation of a gasliquid emulsion occurs in the gas supply pipe 2 which is dispersed when expelled into the aeration tank 1 to aerate the liquid in the tank. Then, the solenoid 24 is deenergized, and the solenoid 25 is energized. The solenoid valve 22 is closed, and the solenoid valve 23 is opened. The gas supply pipe 2 communicates with the gas removal system 4, and the liquid from the aeration tank 1 fills the gas supply pipe 2.
The embodiment of the apparatus shown in Fig. 6 operates in the following way when carrying out the method according to the invention. Control signals are fed from the control mechanism 9 to the reciprocatory drive 31 to reverse it. The drive 31 displaces the spool 27 of the two-position sliding spool valve 26 into one of its limit positions. With the spool 27 displaced into its left-hand position, the piston 29 shuts-off the passage 32 to disconnect the gas supply source 3, and the piston 28 opens the inlet of the gas removal system 4 to connect the system to the gas supply pipe 2. The gas supply pipe 2 is filled with the liquid from the aeration tank With the spool 27 displaced into its righthand position, the piston 28 shuts-off the gas removal system 4 and the piston 29 opens the passage 32 to connect the gas supply pipe 2 to the gas supply source 3.
The embodiment of the apparatus shown in Fig. 7 is used to carry out the method according to the invention mostly in applications where liquids to be aerated are characterized by a high content of surface-active substances which cause an intense foaming in the space over the liquid in the aeration tank 1. This embodiment operates in the following way.
The alternate switch-over means 5 connects the gas supply pipe 2 the gas supply source 3. In the layer adjacent the descending gasliquid interface an intense formation of a gasliquid emulsion occurs. When the gas-liquid interface is displaced from the gas supply pipe 2, the gas-liquid emulsion is expelled through the flare portion 34 into the liquid in the aeration tank 1 to aerate the liquid contained therein. A gas cavity formed in the flare portion 34 ascends to the surface through the annular space between the gas supply pipe 2 and the tubular member 33. At the same time, the alternate switch-over means 5 disconnects the gas supply source from the gas supply pipe 2 and connects gas supply pipe to the gas removal system 4. The liquid from the aeration tank 1 fills the pipe 2. The gas cavity ascending to the surface expels the liquid from the annular space between the gas supply pipe 2 and the tubular member 33.
The displaced liquid is erupted into the space over the liquid in the aeration tank 1 in the form of a dispersed annular jet, the drops of the jet falling down to partly suppress the foam on the surface of the liquid in the aeration tank 1. Upon displacing the liquid and reaching the level of the gas-liquid interface in the aeration tank 1, the gas cavity collapses to impart a lateral impact shear to the foam bubbles thereby suppressing the remaining foam.
The embodiment of the apparatus shown in Fig. 9 operates in a similar way. The advantage of this embodiment resides in a higher velocity of liquid eruption from the annular space between the gas supply pipe 2 and the tubular member 33.
The embodiment of the apparatus shown in Fig. 10 operates likewise the embodiment described above and shown in Fig. 7. However the gas-liquid emulsion is expelled through the annular space between the edges of the concave deflector 36 and flare portion 34, and the formation of the gas cavity takes place within the concave deflector 36. This eliminates a premature collapse of the gas cavity, improves the conditions for its formation and reduces the gas consumption.
- The invention will now be explained with reference to specific examples of carrying out the method with different liquids.
Example 1.
The method for aerating liquids according to the invention was used for the fermentation of a culture medium with a viscosity ranging from 10 to 30 cP. The capacity of the aeration tank employed for the fermentation was 15 m3. The volume of a culture medium in the aeration tank was 10 m3. During the fermentation, the gas was fed and removed in such a manner that the gas-liquid interface reciprocated in the gas supply pipe at a frequency of 40 c/min. The amplitude of the oscillatory motion of the gas-liquid interface was 2 m. Specific gas consumption was 0.64 m3. per 1 m3 of the culture medium per minute. The velocity of gas-liquid interface within the gas supply pipe was 2.7 m/s. The gas-liquid emulsion was formed without adding any foaming agents.During the fermentation, foam was suppressed both due to the expulsion of liquid from the annular space between the gas supply pipe and the tubular member and collapse of the gas cavity, so that a foam suppressor was dispensed with.
The aeration time was 80 hr.
Example 2.
The method for aerating liquids according to the invention was used for the fermentation of a culture medium with a viscosity ranging from I to 3 cP. The capacity of the aeration tank employed for the fermentation was 1.0 m3. The volume of a culture medium in the aeration tank was 0.8 m3. During the fermentation the gas was fed and removed in such a manner that the gas-liquid interface reciprocated within the gas supply pipe at a frequency of 200 c/min. The amplitude of the oscillatory motion of the gas-liquid interface was 0.5 m. Specific gas consumption was 0.1 m3 per 1 m3 of the culture medium per minute. The velocity of gas-liquid interface within the gas supply pipe was 0.33 m/s.
The gas-liquid emulsion was intensely formed under these conditions without adding any foaming agents. During the fermentation, foam was suppressed both due to the expulsion of the liquid from the annular space between the gas supply pipe and the tubular member and collapse of the gas cavity, so that a foam suppressor was dispensed with.
The aeration time was 40 hr.
Example 3 The method for aerating liquids according to the invention was used for the fermentation of streptomycin. The capacity of the aeration tank employed for the fermentation was 15 m3. The volume of the culture medium in the aeration tank was 10 m3. During the fermentation, gas was fed and removed in such a manner that the gas-liquid interface reciprocated within the gas delivery pipe at a frequency of 95 c/min. The amplitude of the oscillatory motion of the gas-liquid interface was 1.2 m. Specific gas consumption was 0.7 m3 per 1 m3 of the culture medium per minute. The velocity of gas-liquid interface within the gas supply pipe was 7 m/s. The gas-liquid emulsion was intensely formed under these conditions without any foaming agents.During the fermentation foam was suppressed both due to the expulsion of liquid from the annular space between the gas supply pipe and the tubular member and collapse of the gas cavity, so that a foam suppressor was dispensed with. The aeration time was 140 hr.
Example 4.
The method for aerating liquids according to the invention was used for the fermentation of food antibiotics such as food grysine. The capacity of the aeration tank employed for the fermentation was 16 m3. The volume of a culture medium was 12 m3. During the fermentation, gas was fed and removed in such a manner that the gas-liquid interface reciprocated within the gas delivery pipe at a frequency of 76 c/min. The amplitude of the oscillatory motion of the gas-liquid interface was 0.5 m. Specific gas consumption was 0.8 m3 per 1 m3 of the culture medium per minute. The velocity of gas-liquid interface within the gas supply pipe was 1.27 m/s.
The gas-liquid emulsion was intensely formed under these conditions without any foaming agents. During the fermentation, foam was suppressed both due to the expulsion of the liquid from the annular space between the gas supply pipe and the tubular member and collapse of the gas cavity so that a foam suppressor was dispensed with. The aeration time was about 50 hr.
Example 5.
The method for aerating liquids according to the invention was used for the biological purification of waste waters wherein the concentration of active sludge was within 1 to 4 mg/l. The aeration was carried out in a tank having the following dimensions: length, 60 m; width, 1.5 m; depth, 1.5 m. Four gas supply pipes were provided along the aeration tank. The volume of liquid filling the aeration tank was 96 m3. During the fermentation, gas was fed and removed in such a manner that the gas-liquid interface reciprocated in the gas delivery pipe at a frequency of 45 c/min. The amplitude of the oscillatory motion of the gasliquid interface was 0.7 m. Specific gas consumption was 0.084 m3 per 1 m3 of the liquid per minute. The velocity of gas-liquid interface within the gas supply pipe was 1.05 m/s. The gas-liquid emulsion was intensely formed without any foaming agents added.
While the invention has been described herein in terms of the preferred embodiments thereof, numerous other modifications of the method and apparatus may be made without departing from the scope of invention as set forth in the appended claims.

Claims (23)

1. A method for aerating liquids within an aeration tank having a gas supply pipe extending substantially vertically therein, the method comprising the steps of feeding a gas to the gas supply pipe in batches to generate an alternating pressure; imparting an oscillatory motion to the liquid within the gas supply pipe under the action of the alternating gas pressure in such a manner as to cause reciprocations of the gas-liquid interface within the gas supply pipe at a frequency ranging from 40 to 200 c/min and with an amplitude from 0.05 to 2 m; forming a gas-liquid emulsion in the layer adjacent the gas-liquid interface in the gas supply pipe upon feeding each batch of the gas; dispersing the resultant emulsion by expelling it from the gas supply pipe into the aeration tank to aerate the liquid contained therein; removing the gas from the gas supply pipe alternately with feeding of the gas to fill said gas supply pipe with the liquid from the aeration tank at regular intervals.
2. A method as claimed in Claim 1, wherein the gas is fed to and removed from the gas supply pipe in such a manner that the gas-liquid interface reciprocates in the pipe at a frequency of at least 40 c/min and with a maximum amplitude of 2 m.
3. A method as claimed in Claim 1, wherein the gas is fed to and removed from the gas supply pipe in such a manner that the gas-liquid interface reciprocates in the pipe at a maximum frequency of 200 c/min and with an amplitude of at least 0.05 m.
4. A method as claimed in Claim 1, wherein the.gas is fed to and removed from the gas supply pipe in such a manner that the gas-liquid interface reciprocates in the pipe at a frequency of about 95 c/s and with an amplitude of about 1.2 m.
5. A method as claimed in Claim 1, wherein the gas is fed to and removed from the gas supply pipe in such a manner that the gas-liquid interface reciprocates in the pipe at a frequency of about 76 c/m and with an amplitude of about 0.5 m.
6. A method as claimed in Claim 1, wherein the gas is fed to and removed from the gas supply pipe in such a manner that the gas-liquid interface reciprocates at a frequency of about 45 c/min and with an amplitude of about 0.7 m.
7. A method as claimed in Claim 1, wherein the gas feeding to the gas supply pipe is interrupted upon the displacement of the gas-liquid interface from the gas supply pipe into the aeration tank and formation of a gas cavity ascending to the surface in the aeration tank along the pipe.
8. A method as claimed in Claims 1 and 7, wherein the gas feeding to the gas supply pipe is interrupted when the gas consumption for the formation of the cavity amounts from 5 to 7 % of the gas consumption for the formation of the gas-liquid emulsion and for aeration of the liquid in the aeration tank.
9. An apparatus for carrying out the method claimed in Claim 1, comprising an aeration tank; a gas supply pipe extending substantially vertically within the aeration tank; a gas supply source for feeding gas under alternating pressure communicating with the upper end of the gas supply pipe, a gas removal system communicating with the gas supply pipe at the upper end thereof; an alternate switch-over means for alternately connecting the gas supply source and the gas removal system to the gas pipe provided at the inlet of the gas supply pipe supply to feed gas in batches and alternate removal thereof to impart an oscillatory motion to the liquid in the gas supply pipe.
10. An apparatus as claimed in Claim 9, wherein the alternate switch-over means comprises a valve-type distributor and a drive having a control mechanism.
11. An apparatus as claimed in Claim 10, wherein the control mechanism comprises a timer inserted in a supply circuit of the drive of the valve-type gas distributor.
12. An apparatus as claimed in Claim 10, wherein the control mechanism comprises contactors which are inserted in a supply circuit of the drive of the valve-type gas distributor and connected to sensors for sensing the limit levels of the gas-liquid interface in the gas supply pipe.
13. An apparatus as claimed in Claim 10, wherein the valve-type gas distributor com prises a two-way plug valve.
14. An apparatus as claimed in Claims 10, wherein the valve-type gas distributor comprises two solenoid valves.
15. An apparatus as claimed in Claim 10, wherein the valve-type gas distributor comprises a two-position sliding spool valve.
16. An apparatus as claimed in Claim 9, wherein the aeration tank has a tubular member co-axially enclosing the gas supply pipe and having a flare portion at its lower end.
17. An apparatus as claimed in Claims 9 and 16, wherein the gas supply pipe and the tubular member are cylindrical, the ratio between their diameters ranging from 1.1 to 1.7.
18. An apparatus as claimed in Claims 9 and 16, wherein the tubular member is conical and has a flare portion at its upper end so that the clearance between the tubular member and the gas supply pipe first decreases and then increases upwardly.
19. An apparatus as claimed in Claims 9, 16 through 18, wherein there is provided a concave deflector arranged opposite to the lower end face of the gas supply pipe.
20. An apparatus as claimed in Claim 19, wherein said concave deflector is conical.
21. An apparatus as claimed in Claim 19, wherein the concave deflector is a hollow pyramid.
22. A method for aerating liquids substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.
23. An apparatus for carrying out the above-described method substantially as hereinbefore described with rererence to, and as shown in the ccompanying drawings.
GB7844503A 1978-11-14 1978-11-14 Method and apparatus for aerating liquids Expired GB2033770B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB7844503A GB2033770B (en) 1978-11-14 1978-11-14 Method and apparatus for aerating liquids
DE19782854557 DE2854557A1 (en) 1978-11-14 1978-12-18 METHOD FOR VENTILATING LIQUID AND DEVICE FOR IMPLEMENTING IT

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB7844503A GB2033770B (en) 1978-11-14 1978-11-14 Method and apparatus for aerating liquids

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GB2033770A true GB2033770A (en) 1980-05-29
GB2033770B GB2033770B (en) 1982-11-03

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2484447A1 (en) * 1980-06-13 1981-12-18 Saps Anticorrosion AEROBIC BIOTRANSFORMATION METHOD AND DEVICE
FR2552101A1 (en) * 1983-09-21 1985-03-22 Inst Biokhim I Fiziol Mikroorg INSTALLATION FOR BIOCONVERSION OF VEGETABLE RAW MATERIALS

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2220974B (en) * 1988-05-04 1992-11-18 Apv Uk Aseptic processing system
DE202010017463U1 (en) * 2010-03-19 2012-03-30 Ech Elektrochemie Halle Gmbh Device for improving the effect of light on microalgae suspensions in bioreactors

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2484447A1 (en) * 1980-06-13 1981-12-18 Saps Anticorrosion AEROBIC BIOTRANSFORMATION METHOD AND DEVICE
FR2552101A1 (en) * 1983-09-21 1985-03-22 Inst Biokhim I Fiziol Mikroorg INSTALLATION FOR BIOCONVERSION OF VEGETABLE RAW MATERIALS

Also Published As

Publication number Publication date
DE2854557A1 (en) 1980-09-18
GB2033770B (en) 1982-11-03

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