Abstrict
An apparatus for chemical froth suppression in a fermenter comprises
a vessel containing a chemical froth suppressor and communicating
via a pressure pipe with the fermenter. The pressure pipe has arranged
at a preselected level with respect to the froth height a nozzle
intended to form a jet of froth suppressor which enters a chamber
through an inlet port thereof. This chamber is accommodated inside
the fermenter substantially above the level of froth therein. The
jet of froth suppressor is reflected from the concave wall of the
chamber to be conveyed along the discharge pipe by a pneumatic or
suction pump into the vessel containing the froth suppressor. The
discharge pipe is provided at tne end thereof inside the vessel
with a nozzle intended to form a jet of the chemical froth suppressor
flowing along this discharge pipe into the vessel. A gas zone of
the vessel containing the chemical froth suppressor is communicable
with a gas zone of the fermenter by a pipe having provided therein
a throttle means serving to maintain a required pressure inside
the pressure pipe.
Claims
What is claimed is:
1. An apparatus for chemical froth suppression comprising:
a fermenter;
a vessel containing a chemical froth suppressor;
a pressure pipe connecting said vessel with said fermenter;
a first nozzle having an outlet opening and disposed in said fermenter,
said nozzle being positioned on said pressure pipe at a preselected
level of said froth so as to form a jet of froth suppressor which
escapes through said outlet opening;
a chamber accommodated inside said fermenter above the level of
said froth and having an inlet port coaxial with said outlet opening
of said nozzle for said jet of froth suppressor escaping from said
outlet opening to enter said inlet port, said chamber having an
outlet, and a concave wall opposite to said inlet port for reflecting
said jet of froth suppressor which enters said chamber through said
inlet port thereof to said outlet;
a discharge pipe connecting the outlet of said chamber with said
vessel containing said chemical froth suppressor to withdraw said
jet of froth suppressor reflected from said concave wall and convey
it to said vessel;
a pneumatic pump disposed in said discharge pipe to suck said chemical
froth suppressor from said chamber;
a second nozzle secured on said discharge pipe in said vessel containing
said chemical froth suppressor to form a jet of said chemical froth
suppressor flowing along said discharge pipe into said vessel containing
said chemical froth suppressor;
a third pipe communicating a gas zone of said fermenter overlying
said froth with a gas zone of said vessel containing said chemical
froth suppressor overlying the level of said chemical froth suppressor;
and
a throttle means disposed in said third pipe and serving to maintain
a predetermined pressure in said vessel containing said chemical
froth suppressor during circulation therethrough by said pneumatic
pump of said chemical froth suppressor to maintain thereby a required
pressure in said pressure pipe.
Description FIELD OF THE INVENTION
This invention relates to apparatus for chemical froth suppression,
and more particularly to apparatus for chemical froth suppression
in a fermenter.
The invention can find application in the microbiological, medical
and chemical industries, as well as in research practice.
BACKGROUND OF THE INVENTION
Steady froth formation is an undesirable phenomenon occuring 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 outlet
ports;
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 withdrawn at the same rate while retaining the total volume unchanged)
the gas content varies, hence the liquid volume of the culture medium
becomes uncontrollable.
There is known an interface controller between two liquid media
in a vessel used in a process of microbiological synthesis for suppressing
froth in a fermenter by surface-active substances (froth suppressors)
as exemplified in USSR Inventor's Certificate No. 485,423, [IPC
C 05 d 9/12].
The above controller comprises a throttle installed in the interior
of the fermenter at a preselected froth level and connected by a
pipe to a comparator to control the feed rate of the froth suppressor
into the fermenter. Another pipe connecting the comparator with
the fermenter accommodates a pump providing for closed circulation
of a gas mixture. The controller also comprises a vessel containing
the froth suppressor and a pipe having a means for controlling the
rate of feed of the froth suppressor from the vessel to the fermenter
when an error signal is received by the comparator.
The aforedescribed apparatus operates as follows.
When froth in the fermenter is short of coming into contact with
a throttle port, the pump acts to force the gas mixture via the
throttle and the comparator from the fermenter and return the mixture
back to the fermenter, the comparator remaining unengaged.
Conversely, when the froth reaches the throttle port, it is pumped
by the pump whereby resistance in the throttle tends to increase
sharply to result in an error signal received by the comparator
which issues a control signal to the means for controlling the rate
of feed of the froth suppressor for more froth suppressor to be
fed to the fermenter.
The froth suppressor which is conveyed to the fermenter acts to
suppress the froth thereby relieving the throttle port of the froth
to result in a reduced flow resistance therein, the comparator assuming
its initial state. Therewith, the means for controlling the feed
rate of the froth suppressor terminates the supply of the froth
suppressor to the fermenter.
The above apparatus may be employed both in large-scale production
fermenters and in laboratories.
Inherent in such apparatus are disadvantages residing in that the
provision for gas circulation through the comparator constituting
a focal point of microorganism decay upsets the aseptic conditions
for carrying out a microbiological process. In addition, supply
of the froth suppressor by samples into the fermenter tends to result
in overconsumption of the froth suppressor, since froth formation
during a fermentation process is normally not programmable. On the
other hand, the froth suppressor in the vessel is susceptible to
stratification due to lack of stirring whereby froth suppression
in the fermenter may be affected.
There is further known an apparatus for chemical froth suppression
in a fermenter comprising a vessel containing a chemical froth suppressor
fed to the fermenter by a pneumatic pump along a pressure pipe adapted
to connect the vessel containing the froth suppressor with the fermenter,
a nozzle disposed inside the fermenter at a preselected level of
froth therein and connected by the pressure pipe with the vessel
containing the chemical froth suppressor, the nozzle serving to
form a jet of the froth suppressor for this jet to be received by
an inlet port of a chamber accommodated in the interior of the fermenter,
the inlet port being disposed coaxially with an outlet opening of
the nozzle, a wall of the chamber opposite to the inlet port thereof
being concaved to reflect the jet of froth suppressor escaping from
the nozzle for the thus reflected froth suppressor to be sucked
off and conveyed to the vessel containing the froth suppressor along
a discharge pipe connecting this chamber with the froth suppressor
containing vessel, and a throttle means serving to maintain a required
pressure in the pressure pipe (cf. U.S. Pat. No. 4,302,545, Cl.
[435-289].
In the above apparatus the pneumatic pump is arranged in the pressure
pipe, while the throttle and the nozzle are positioned in succession
downstream of the chemical froth suppressor subsequent to the pneumatic
pump in the pressure pipe. This arrangement provides for a gravity
drain of the froth suppressor into the vessel containing the chemical
froth suppressor along the discharge pipe.
Discharge of the froth suppressor by gravity from the chamber causes
suction or underpressure resulting in air bubbles affecting the
rate at which the froth suppressor is withdrawn from the chamber
which in turn may cause overflow of the chamber with the chemical
froth suppressor and accidental discharge thereof through the inlet
port of the chamber back into the fermenter.
The gravity drain of the chemical froth suppressor also fails to
provide a sufficiently vigorous stirring thereof which may result
in stratification, clogging of the throttle and loss of control
over froth suppression.
One more disadvantage is that the gravity discharge of the chemical
froth suppressor limits structural and operational capabilities
of the apparatus requiring a careful selection of the flow area
and height of the discharge pipe depending on the viscosity of the
chemical froth suppressor employed.
The use of the discharge pipe for two purposes, particularly for
discharging the chemical froth suppressor and equalizing pressure
in the fermenter and the vessel containing the chemical froth suppressor
affects the reliability of the apparatus. For example, when pressure
in the fermenter drops due to reduced air supply for aeration, this
pressure tends to equalize subsequent to the overflow of air along
the discharge pipe from the vessel containing the chemical froth
suppressor into the fermenter which may result in an accidental
discharge of the froth suppressor into the fermenter.
Further, the arrangement of the throttle in the pressure pipe downflow
of the pneumatic pump produces an overpressure in the pressure pipe
which makes pressure sealing of the apparatus more complicated,
affects operation of the pneumatic pump and brings down its operational
reliability.
SUMMARY OF THE INVENTION
It is an object of this invention to prevent discharge of the chemical
froth suppressor into the fermenter without the froth affecting
the jet of froth suppressor.
Another object is to provide mixing of the chemical froth suppressor
in a vessel containing the froth suppressor to prevent stratification
thereof.
One more object is to prevent the chemical froth suppressor from
flowing along the discharge pipe back into the fermenter due to
pressure variations in the fermenter.
Yet another object is to improve the operational reliability of
the apparatus for chemical froth suppression in a fermenter.
The objects are attained by that in an apparatus for chemical froth
suppression in a fermenter comprising a vessel containing a chemical
froth suppressor fed to the fermenter by a pneumatic pump along
a pressure pipe connecting the vessel containing the chemical froth
suppressor with the fermenter, a nozzle disposed inside the fermenter
at a preselected level of froth and connected by the pressure pipe
with the vessel containing the chemical froth suppressor to form
a jet of the froth suppressor and withdraw the froth suppressor
through an inlet port of a chamber accommodated inside the fermenter
coaxial with an outlet opening of the nozzle into this chamber a
wall of which opposite to the inlet port is concaved to reflect
the jet of the froth suppressor and convey it into the vessel containing
the froth suppressor along a discharge pipe connecting the chamber
with the vessel containing the chemical froth suppressor, and a
throttle intended to maintain a required pressure in the pressure
pipe, according to the invention, the pneumatic pump is disposed
in the discharge pipe for sucking the chemical froth suppressor
from the chamber, while there are provided one more nozzle arranged
on the discharge pipe in the vessel containing the chemical froth
suppressor to form a jet of the chemical froth suppressor conveyed
along the discharge pipe into the vessel containing the chemical
froth suppressor and one more pipe communicating a gas zone of the
fermenter with a gas zone of the vessel containing the chemical
froth suppressor, a throttle being disposed in this pipe to stabilize
pressure in the vessel containing the chemical froth suppressor
during circulation therethrough by means of the pneumatic pump of
the chemical froth suppressor to maintain thereby a required pressure
in the pressure pipe.
Such an arrangement of the apparatus for chemical froth suppression
in a fermenter enables one to prevent discharge of the chemical
froth suppressor into the fermenter without affecting the jet of
froth suppressor, mix the chemical froth suppressor in the vessel
containing the chemical froth suppressor to prevent stratification
thereof, prevent penetration of the chemical froth suppressor along
the discharge pipe into the fermenter caused by pressure variations
therein, improve the operational reliability of the apparatus, prevent
overconsumption of the costly chemical froth suppressor, and use
the apparatus embodying the invention in fermenters of various size,
including large-scale production industrial fermenters. The apparatus
according to the invention further makes it possible to control
the flow of the chemical froth suppressor consumed during fermentation
without accidentally discharging the chemical froth suppressor to
the fermenter.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described in greater detail with reference
to a specific embodiment thereof taken in conjunction with the accompanying
drawings the sole FIGURE of which illustrates schematically a longitudinal
sectional view of an apparatus for chemical suppression of froth
in a fermenter.
DETAILED DESCRIPTION OF THE INVENTION
An apparatus 1 for chemical froth suppression in a fermenter 2
comprises a vessel 3 containing a chemical froth suppressor 4 which
is fed into the fermenter 2 by means of a pneumatic pump 5 along
a pressure pipe 6 communicating the vessel 3 containing the chemical
froth suppressor 4 with the fermenter 2.
The apparatus 1 further comprises accommodated inside the fermenter
2 a chamber 7 arranged to overlie froth 8 formed therein as a result
of a fermentation process occuring in a culture medium 9 stirred
by a stirrer 10 of the fermenter 2, and a nozzle 11 positioned at
a preselected level of the froth 8, the nozzle 11 being connected
by the pressure pipe 6 with the vessel 3 containing the chemical
froth suppressor 4 to feed the froth suppressor 4 through an inlet
port 13 of the chamber 7 into this chamber 7. An outlet opening
14 of the nozzle 11 is arranged coaxially with the inlet port 13
of the chamber 7. A wall 15 of the chamber 7 opposite to the inlet
port 13 of the chamber 7 is concave (hereinafter referred to as
the concave wall 15) to reflect a jet of the chemical froth suppressor
4 to convey the latter into the vessel 3 along a discharge pipe
16 communicating the chamber 7 with the vessel 3.
The pneumatic pump 5 is arranged in the discharge pipe 16 to suck
the chemical froth suppressor 4 from the chamber 7. The discharge
pipe 16 is provided with a nozzle 17 letting out into the interior
of the vessel 3 and intended to produce a jet 18 of the chemical
froth suppressor 4 conveyed along the discharge pipe 16 to the vessel
3.
A gas zone 19 of the fermenter 2 occupying a space above the froth
8 is communicable with a gas zone 20 of the vessel 3 containing
the chemical froth suppressor 4, this gas zone occupying a space
in the vessel 3 above the level of the froth suppressor 4 by way
of a pipe 21 having a throttle 22 to maintain a stable preselected
pressure in the vessel 3 when the pneumatic pump 5 acts to charge
thereinto and discharge therefrom the chemical froth suppressor
4 and to thereby maintain a required pressure in the pressure pipe
6.
The pipes 6, 16 and 21 are secured in the vessel 3 by means of
a rubber plug 23 and introduced into the fermenter 2 through its
cover plate 24.
The apparatus 1 for chemical suppression of froth in a fermenter
2 operates in the following manner.
Initially, the vessel 3 is filled with the chemical froth suppressor
4 and hermetically sealed by the rubber plug 23, the nozzle 11 of
the apparatus 1 being positioned in the gas zone 19 of the fermenter
2 at a preselected level of the froth 8. The pneumatic pump 5 is
engaged whereafter by manipulating the throttle 22 a required pressure
is set in the vessel 3 containing the chemical froth suppressor
4, which froth suppressor 4 when acted upon by this pressure is
caused to be conveyed toward the nozzle 11 and escape from its outlet
opening 14 to form a jet 12 which without touching the edges of
the opening 13 of the chamber enters thereinto and after being thrust
against the concave wall 15 thereof is sucked away by the pneumatic
pump 5 along the discharge pipe 16 back into the vessel 3. While
escaping through the nozzle 17 the froth suppressor 4 forms the
jet 18 acting on the froth suppressor contained in the vessel 3
to actively mix it to prevent stratification.
A positive pressure in the vessel 3 containing the chemical froth
suppressor 4 which is produced during operation of the pneumatic
pump 5 is restored by the throttle 22 by a gas overflow via the
pipe 21 connecting the gas zone 19 of the fermenter 2 with the gas
zone 20 of the vessel 3.
Froth is continuously produced in the course of stirring the culture
medium 9 by the stirrer 10. Therewith, the froth tends to rise above
the opening 14 of the nozzle 11 to thereby come into contact with
the jet 12 of the chemical froth suppressor 4. At this point, adhesive
forces cause the jet 12 of the chemical froth suppressor 4 to deflect
or deviate to be discharged into the layer of froth 8 rather than
enter the inlet port 13 to thereby suppress the froth resulting
in bringing down the level of froth for the jet 12 to come out of
engagement with the froth 8 and start again entering the port 13
of the chamber 7 thereby recommencing the closed circulation of
the froth suppressor 4.
The apparatus according to the invention provides a self-controllable
process of froth tracing and froth suppression by a chemical froth
suppressor accompanied by rationing the amount of chemical froth
suppressor expended for suppressing the froth depending on the rate
of froth formation and the stability of the froth to the effect
produced by the chemical froth suppressor employed.
In addition, the suction of froth suppressor from the chamber and
the provision of a throttle means in a pipe enabled to have the
working assembly of the apparatus, particularly the chamber, the
nozzle, the pressure and discharge pipes, be embodied as a cylindrical
rod-like member easily insertable into a fermenter through the cover
plate thereof and adjustable in height.
Specific and narrow terminology has been used for the sake of clarity
in the description of the present invention. The invention is not,
however, limited by the terms employed, and it stands to reason
that each term covers every equivalent element having a similar
function and used for accomplishing the same object.
Though the invention has been described as applied to the preferred
embodiments thereof, it is understood that various alternative modifications
and changes may be introduced without departing 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. |