An apparatus for chemical froth suppression in a fermenter comprises
a froth sensor installed in the fermenter for tracing the froth
and a vessel containing a chemical froth suppressor which is fed
to the froth sensor and to the fermenter. The froth sensor comprises
a hollow chamber accommodating a throttle and a nozzle. The chamber
has a through opening with the walls having two ports congruent
to and coaxial with the outlet orifice of the nozzle, through which
passes a jet of the froth suppressor leaving the outlet orifice
of the nozzle to fly past the through opening and to get into the
chamber to be reflected from its concave wall for being removed
into the vessel containing the chemical froth suppressor.
What is claimed is:
1. An apparatus for chemical froth suppression in a fermenter,
a vessel containing a chemical froth suppressor;
a take-off pipe connected to said vessel;
a pneumatic pump connected to said take-off pipe for taking-off
said froth suppressor from said vessel along said take-off pipe;
a pneumatic pulse generator pneumatically coupled to said pneumatic
pump to drive said pump continuously during operation of said fermenter;
a froth sensor installed in said fermenter for tracing the froth
which is formed therein as a result of a process occurring in the
fermenter, said froth sensor comprising a throttle installed downstream
from said pneumatic pump in the direction of flow of said chemical
froth suppressor and connected thereto, a nozzle having an outlet
orifice from which a jet of said froth suppressor flows and which
is installed downstream of said throttle, and in fluid connection
therewith, in the direction of flow of said chemical froth suppressor
and a hollow chamber accommodating said throttle and nozzle, whereby
the jet of froth suppressor flowing from said nozzle traverses said
hollow chamber when no froth is present, and contacts said froth,
when froth is present within the hollow chamber, and having a drain
pipe at the opposite side of said hollow chamber, said drain pipe
being connected to said chemical froth suppressor and having a through
opening formed by first, second, and third walls, a first port in
the first wall of said through opening, which is congruent to and
coaxial with said outlet orifice of said nozzle, a second port in
the third wall of said through opening, which is congruent to and
coaxial with the first port, said jet of said froth suppressor passing
through said ports after leaving said nozzle to fly past said through
opening and into said hollow chamber, having a concave wall arranged
opposite to said second port and reflecting said jet of said froth
suppressor and removing it through said drain pipe to said vessel
containing said chemical froth suppressor thereby forming a closed
circuit for circulation of said chemical froth suppressor when froth
is below the level of the jet in said hollow chamber.
2. An apparatus according to claim 1, wherein said outlet orifice
of said nozzle is arranged approximately above the normal level
of said froth in said fermenter; said concave wall of said hollow
chamber being arranged above said outlet orifice.
FIELD OF THE ART
The invention relates to apparatus for chemical froth suppressors,
and more particularly, to apparatus for chemical froth suppression
The invention may be used in the microbiological, medical and chemical
industries and in research applications.
BACKGROUND OF THE INVENTION
Steady froth formation is an undesirable phenomenon occurring in
aerating media containing organic matter. Stability of froth is
associated with the composition of complex media or products of
metabolism of microorganisms which are not identified in many instances,
and the fight against froth formation is frequently conducted on
an empirical basis.
Negative effect of froth formation consists in the following:
a culture with froth may be let out of the fermenter through air
the value of KL.sub.a (efficiency of oxygen absorption) decreases;
in chemostatic cultures (cultures with complete stirring to which
a culture medium is added at a constant rate and from which a culture
is taken-off at the same rate while retaining the total volume unchanged)
the gas content changes, hence the liquid volume becomes uncontrollable.
Froth formation is generally prevented by using froth suppressors
which may be classified in the following manner:
elimination of froth-forming substances and action on the froth
with physico-chemical facilities;
destruction of froth by mechanical, hydro- and aerodynamic methods;
acoustic froth suppression using audio and ultrasonic frequency
thermal froth suppression using saturated steam or heated liquid;
electrical froth suppression;
stabilization of froth level and temporary suspension of air supply
for aeration or temporary suspension of mechanical stirring or discharge
of excessive froth from the apparatus;
Among all the above-mentioned froth suppressors only chemical and
mechanical ones have found a widespread use in the microbiological
industry since all remaining froth suppressors are poorely studied
and not applied in practice for various reasons. Thus, the works
on the use of ultrasonic oscillations for froth suppression are
still at the laboratory stage and, according to preliminary estimations,
this method for suppressing large quantities of froth in fermenters
are bound to prove economically inefficient. The use of thermal
froth suppressors is limited by the sensitivity of many microorganisms
to high temperature, while the knowledge of the influence of electric
field, especially of .alpha.-particles on microorganisms is still
inadequate so that their use in the microbiological applications
Various mechanical froth suppressors are recommended.
One of the simplest modifications consists in using a rapidly rotating
rotor (cf. British patent specification No. 8,922,505, Cl. 14(2)L,
publ. in 1962).
Such froth suppressors are generally mounted in a confining device
of the cyclone type which can be connected to a vacuum chamber.
The prior art teaches a mechanical froth suppressor comprising
a perforated plate having two impellers installed thereon of which
one--the upper impeller--is arranged with the vanes up and the other--the
lower impeller--is arranged with the vanes down. For destructing
froth over the liquid surface, there is provided a turbine rotating
about its axis so that during rotation of the turbine an ascending
gas flow is formed under the turbine, which takes-in the froth to
be thrown away by the turbine blades in the form of liquid jets.
The working member comprises a perforated plate submerged in the
froth and connected with a vibratory drive (cf. U.S. Pat. No. 2,610,155,
publ. in 1962). Known in the art is an apparatus for mechanical
froth suppression, comprising a rotary perforated plate having partitions
in the form of hollow truncated cones mounted on the plate with
spaces therebetween for the passage of liquid (cf. USSR Inventor's
Certificate No. 107900, Cl. C 12B 1/18, publ. in the Off. Bull.
No. 9, 1957, page 16).
An apparatus for froth suppression, comprising a stack of conical
plates on a hollow shaft is widely used in practice (cf. Swiss Pat.
No. 1660, publ. in 1968).
The apparatus is installed on an independent shaft. The apparatus
are used both in laboratory and commercial installations.
Known in the art is a mechanical blade froth suppressor with a
horizontally extending working shaft. To improve the efficiency
of froth suppression, a partition wall is provided inside the froth
suppressor vessel to divide the vessel into two communicating compartments,
one compartment having at the bottom thereof a pipe having its inlet
end arranged immediately under impellers, and the outlet end is
incorporated in the partition wall (cf. USSR Inventor's Certificate
No. 246446, Cl. C 12C, publ. in the Off. Bull. No. 21, 1969, page
A hydraulic and pneumatic system for collecting, removing and destructing
froth was contemplated, featuring recirculation of concentrated
solution and having two pumps. Froth suppression is effected by
means of pumps, one pump being designed for processing gas and liquid
emulsions. A portion of waste gas is fed for recirculation for pneumatic
froth suppression. The second pump takes-off the liquid from the
settling basin and also feeds it for recirculation (cf. U.S. Pat.
No. 3,339,345, Cl. 55-178, publ. in 1967).
All above-described froth suppressors are rarely used in the microbiological
applications in spite of their large structural variety. Such apparatus
either cannot provide for complete suppression of froth or they
impose considerable power requirements. In addition, such systems
are cumbersome and do not permit the useful space of the fermenter
to be completely utilized so that the filling ratio of fermenters
is from 0.5 to 0.6 of the total volume. The free space is used for
compensation of the level rise which generally does not exceed 10%
owing to gas content after the aeration is put on, and also for
controlling the froth level.
Automatic control of processes occurring during cultivation of
microorganisms, including the froth suppression process, is very
important for operation of fermenters. In principle, this problem
should be very simple to resolve: a mechanical stirrer and an actuator
for adding a chemical froth suppressor are to be mounted in the
fermenter, the devices being operable by means of a mechanism actuated
in response to the presence of froth above an admissible level.
A simple solution resides in an installation of a sensor--a contact
electrode--at a preset level producing a signal when the froth is
in contact with the electrode. Not every froth is, however, electrically
conducting. A-c or d-c voltage of 10-30 V is fed for the electrode
supply and a current of 5 to 20 mA and over flows through the froth.
In case d-c supply is used, such voltage and amperage cause polarization
of the electrode so that its sensitivity appreciably changes during
fermentation. The use of alternating current results in erosion
of the electrode, while metal ions getting to the culture liquor
negatively affect the process of cultivation of microorganisms.
The use of electrodes is not always justified as a comparably large
area of contact of the forth with electrode is required, and the
froth sticking to the electrode causes changes in its operating
Therefore, various contactless froth level indicators have been
contemplated. Photocells are in a widespread used (cf. USSR Inventor's
Certificate No. 128827, Cl. C 12 B 1/18, publ, in the Off. Bull.,
No. 11, 1960) incorporated in the fermenter wall, which, after the
froth cuts-off the light beam, turn on actuators, such as an electric
motor of a gear pump for feeding a chemical suppressor.
Culture media generally contain various quantities of mineral salts
which, after dissolution, form relatively well electrically conducting
froth having various electrical resistance. Therefore a contact
electrode was contemplated for indicating the froth level (cf. M.
Zh. Kristapsons, L.Ya. Latsis, Coll, or Art. "Controlled Microbeal
Synthesis" (in Russian), Riga, Znanie Publ., 1973), to be inserted
in an arm of a bridge circuit. This enables the electrode supply
with an a-c voltage of 0.2 V so that maximum current flowing through
the froth does not exceed 100 .mu.A. Such amperage and voltage cannot
have any negative influence in the microbiological process and life
activity of microorganisms.
An interesting solution involves the installation of a contact
electrode on a float which is movable up and down depending on the
froth level (cf. GDR Pat. No. 76454, Cl C 12 B, publ. in 1970).
The use of apparatus for chemical froth suppression enables more
efficient control of froth formation thereby improving the filling
ratio of a fermenter. It should be, however, noted that the control
of froth suppressor flow rate requires additional systems which
are sophisticated expensive in the manufacture and do not always
comply with the requirements imposed by microorganism cultivation
conditions; besides they do not exclude overconsumption of froth
Also known in the art is an apparatus for chemical froth suppression
in a fermenter having a froth sensor tracing the froth in the fermenter,
and a vessel containing a chemical suppressor which is fed to the
fermenter by means of a pneumatic pump along a take-off pipe (cf.
Technical Description and Operation Manual "Complex of Cultivation
Equipment" (in Russian), SKB Biologicheskogo priborostroenia
AN SSSR, Pushchino, 1978, pp. 37-40).
In this apparatus, the froth sensor comprises a capillary tube
installed in the interior of the fermenter at a preset level and
connected by means of a pipeline to a sensor member having a magnetic
contact. Another pipeline connecting the sensor member to the interior
of the fermenter is provided with a pump for pumping air along the
resultant closed circuit.
The apparatus also comprises an actuating mechanism having a vessel
containing a chemical froth suppressor provided with a take-off
pipe having a pinch valve for feeding the froth suppressor from
the vessel containing the chemical froth suppressor to the fermenter
following a signal from the sensor member.
The apparatus functions in the following manner.
When froth in the fermenter does not touch the opening of the capillary
tube, the pump pumps a gas mixture from the fermenter through the
capillary tube and sensor member to return it back to the fermenter.
The sensor member is so adjusted that its membrane having a permanent
magnet secured thereto is stationary, the magnetic contact is open,
and the pinch valve of the actuating mechanism is closed. When the
froth approaches the opening of the capillary tube, the pump starts
feeding the froth, the resistance of the capillary tube abruptly
increases so that the pump causes a pressure reduction in the sensor
member. The membrane starts displacing until the magnetic contact
is closed, to open the pinch valve for feeding a froth suppressor.
The froth suppressor is admitted to the fermenter to destruct the
froth thereby cleaning the capillary tube so that the resistance
of the capillary tube again decreases, and the sensor member returns
back to its initial position to open the magnetic contact. The pinch
valve is again closed to interrupt the admission of the chemical
froth suppressor to the fermenter.
This apparatus for chemical froth suppression may be used in both
commerical and laboratory fermenters.
The provision of the gas circulation circuit passing through the
sensor member which becomes a focus of decay for microorganisms
when clogged with froth breaks the septic conditions of microbiological
process. In addition, pulse feeding of froth suppressor to the fermenter
does not exclude overconsumption of froth suppressor as the process
of froth formation cannot be forecast by a researcher. The absence
of stirring of froth suppressor causes its stratification thereby
changing the character of its action on the froth layer.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a structurally simple
apparatus for chemical froth suppression in a fermenter which is
capable of stabilizing a froth layer at any preset level with a
chemical froth suppressor without overconsumption of the froth suppressor.
Another object of the invention is to prevent stratification of
This is accomplished by that in an apparatus for chemical froth
suppression, comprising a froth sensor for tracing the froth in
the fermenter and a vessel containing a chemical froth suppressor
which is fed to the fermenter by means of a pneumatic pump through
a take-off pipe, according to the invention, the froth sensor is
installed in the fermenter and comprises a throttle and a nozzle
installed in series one downstream the other in the direction of
flow of the chemical froth suppressor downstream the pneumatic pump
and connected thereto, and a hollow chamber which accommodates the
throttle and the nozzle, communicates, via a drain pipe, with the
vessel containing the chemical froth suppressor and has a through
opening, the walls of the opening having two ports congruent to
and coaxial with an outlet orifice of the nozzle, through which
passes a jet of the froth suppressor leaving the outlet orifice
of the nozzles to fly past the through opening and to get into the
chamber, the wall of the chamber arranged opposite to the port most
distant from the nozzle being concave to reflect the jet of the
froth suppressor and to remove it through the drain pipe to the
vessel containing the chemical froth suppressor.
The outlet orifice of the nozzle is preferably arranged at about
the level of froth in the fermenter, and the concave wall of the
chamber is arranged above the outlet orifice.
This construction of the apparatus for chemical froth suppression
in the fermenter according to the invention enables an automatic
tracing of froth and its stabilization owing to the feeding of a
froth suppressor to the froth layer necessary to maintain a preset
height of froth independent of the rate and time of froth formation.
In addition, permanent circulation of froth suppressor prevents
it from stratifying thus ensuring more stable action of froth suppressor
on the froth, improving reliability of operation of the apparatus
and lowering the cost.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects of the invention will become apparent from
reading the following description of specific embodiments thereof
with reference to the accompanying drawings, in which:
FIG. 1 is a general diagrammatic view (in longitudinal section)
of an apparatus for chemical froth suppression in a fermenter, according
to the invention;
FIG. 2 is another embodiment (in longitudinal section) of the apparatus
according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
An apparatus 1 (FIG. 1) for chemical froth suppression in a fermenter
2, according to the invention, comprises a froth sensor 3 installed
in the fermenter 2 for tracing a froth 4 which is formed therein
as a result of a fermentation process occurring in a culture medium
5 stirred by means of a stirrer 6 of the fermenter 2.
The apparatus 1 also comprises a vessel 7 containing a chemical
froth suppressor 8 which is fed to the sensor 3 of the froth 4 as
shown by arrow A along a take-off pipe 9 by means of a well known
pneumatic pump 10 which is pneumatically coupled to a well known
pneumatic pulse generator 11.
The sensor 3 of the froth 4 comprises a throttle 12, a nozzle 13
and a hollow chamber 14. The throttle 12 and the nozzle 13 are mounted
in series one downstream the other in the direction of flow of the
froth suppressor 8 downstream the pneumatic pump 10 and are connected
thereto. The nozzle 13 is installed within the hollow chamber 14.
The hollow chamber 14 is connected by means of a drain pipe 15
to the vessel 7 containing the chemical froth suppressor 8 and has
a through opening 16. Walls 17 and 18 of the opening 16 have two
ports 20 and 21 congruent to and coaxial with an outlet orifice
19 of the nozzle 13, through which passes a jet 22 of the froth
suppressor 8 leaving the outlet orifice 19 of the nozzle 13 to fly
past the through opening 16 and to get into the chamber 14.
A wall 23 of the chamber 14 arranged opposite to the port 21 most
distant from the nozzle 13 is concave to reflect the jet 22 of the
froth suppressor 8 and to remove it as shown by arrow B through
the drain pipe 15 to the vessel 7 containing the chemical froth
suppressor 8 so as to form a closed circuit for circulation of the
froth suppressor 8.
In this embodiment of the apparatus 1 the outlet orifice 19 of
the nozzle 13 is arranged somewhat above the level of the froth
4, and the concave wall 23 of the chamber 14 is above the outlet
The take-off pipe 9 and the drain pipe 15 are secured in the vessel
7 containing the chemical froth suppressor 8 using gaskets 24 and
The apparatus 1 shown in FIG. 2 is most efficient for suppressing
froth in the fermenter 2.
The apparatus 1 shown in FIG. 2 is similar to the apparatus 1 of
FIG. 1, and only some structural differences relating to the sensor
3 of the froth 4 will be described below.
In this embodiment the sensor 3 of the froth 4 comprises a throttle
26, a nozzle 27 and a hollow chamber 28. The throttle 26 and the
nozzle 27 are installed in series one downstream the other downstream
the pneumatic pump 10 in the direction of flow of the froth suppressor
8 in the hollow chamber 28.
The hollow chamber 28 is connected by means of the drain pipe 15
to the vessel 7 containing the chemical froth suppressor 8 and has
a through opening 29. Walls 30 and 31 of the opening 29 have two
ports 33 and 34 congruent to and coaxial with an outlet orifice
32 of the nozzle 27, through which passes the jet 22 of the froth
suppressor 8 leaving the nozzle 27 to fly past the opening 29 and
to get into the chamber 28. A wall 35 of the chamber 28 arranged
opposite to the port 34 most distant from the nozzle 27 is concave
to reflect the jet 22 of the froth suppressor and to remove it as
shown by arrow B through the drain pipe 15 to the vessel 7 containing
the chemical froth suppressor 8 thus enabling, similarly to the
apparatus 1 of FIG. 1, the provision of a closed circuit for circulation
of the froth suppressor 8.
In this embodiment of the apparatus 1 the outlet orifice 32 of
the nozzle 27 is arranged at the level of the froth 4 and the concave
wall 35 of the chamber 28 is arranged above the outlet orifice 32.
Operation of the apparatus 1 for chemical froth suppression in
the fermenter 2 is the same for the embodiments shown in FIGS. 1
and 2 and based on the use of the jet 22 of the chemical froth suppressor
8 moving freely along a preset path and changing the flying path
upon touching the froth 4.
The chemical froth suppressor 8 is pumped from the vessel 7 along
the take-off pipe 9 by means of the pneumatic pump 10 to the throttle
12 (26) and leaves its outlet orifice 19 (32) in the form of the
jet 22. The jet 22, if it does not touch the froth 4 flies past
the opening 16 (29) to get into the chamber 14 (28) wherein it is
reflected from its wall 23 (25) and is removed through the drain
pipe 15 to the vessel 7 thus forming a closed circuit for circulation
of the froth suppressor 8. The contact of the froth 4 with the jet
22 of the froth suppressor results in a change in the flying path
of the jet 22, which gets in the froth 4 to suppress it. (The reference
numerals in the parentheses are given for the embodiment shown in
The useful result of the invention resides in that the feeding
of froth suppressor to the froth occurs owing to the direct contact
of the froth with the outflowing jet of the chemical froth suppressor
thus preventing overconsumption of froth suppressor and enabling
stabilization of the fermentation process in terms of the froth
height. Permanent closed circulation of froth suppressor prevents
it from stratifying. Simplicity of manufacture and reliability in
operation ensure widespread application of the apparatus according
to the invention for chemical froth suppression in a fermenter.
Specific and narrow terminology was used for the description of
the specific embodiments of the invention. The invention is not,
however, limited by the terms used, and it should be born in mind
that each term covers all equivalent elements having the same function
and used for accomplishing the same object.
Through the invention has been described as applied to the preferred
embodiment thereof, it is understood that various modifications
and changes may be introduced without departure from the spirit
and scope of the invention as will be readily apparent to those
skilled in the art. Such modifications and changes will be considered
as not deviating from the spirit and scope of the appended claims.