Device for admixing a gaseous and a liquid phase

An upright vessel for the liquid phase has a cylindrical baffle located in it extending upwardly from the lower region of the vessel. The baffle has a lower open end at which an impeller is located and an upper open end which is formed with a constriction. A member provided with passages through which the gaseous phase is discharged, is located in the constriction so that the passages discharge the gaseous phase at the narrowest cross-section of an annular clearance formed between the constriction and the member.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a device for admixing liquid and 
gaseous phases, and more particularly to a device for mixing a gaseous 
phase into a liquid phase which is particularly suitable for aerobic 
microbiological processes and the like. 
Devices of the type in question are already known. They have vessels which 
accommodate the liquid phase, and it is known to provide a tubular guide 
baffle in such a vessel, forming the guide baffle with apertures in its 
circumference, and providing adjacent one end of the guide baffle an 
impeller which draws the liquid phase through the openings and into the 
guide baffle from the space surrounding the same. The gaseous phase is 
admitted into the vessel, and as it is drawn through the openings into the 
guide baffle together with the liquid phase, the two become mixed. 
There are circumstances in which the vessel of such an apparatus must be 
tall and substantially cylindrical but can have only a relatively small 
diameter. One of these is the fact that frequently space is at a premium 
and larger-diameter vessels cannot be accommodated. If such a relatively 
high vessel is used, then the hydrostatic pressure of the liquid phase in 
the filled vessel is considerable in the lower region thereof, due to the 
column of liquid located in the upper regions. This pressure can be so 
great that the gaseous phase must be forcibly pressed into the interior of 
the vessel by means of compressors. If the vessel is large, and therefore 
requires substantial quantities of the gaseous phase, such installations 
are very expensive both as to their construction and operation, and 
therefore quite frequently cannot be operated economically. 
SUMMARY OF THE INVENTION 
It is, therefore, a general object of the invention to overcome the 
disadvantages of the prior art. 
More particularly, it is an object of the present invention to provide an 
improved device for admixing gaseous and liquid phases, which is not 
possessed of the aforementioned disadvantages. 
Another object of the invention is to provide such a device which is 
simpler to construct and to operate than those known from the prior art. 
A further object of the invention is to provide such a device wherein the 
pressure required to force the gaseous phase into the interior of the 
device is substantially reduced over those of the prior art, so that 
instead of compressors it is possible to use fans or other low-pressure 
blowers which are less expensive to construct and to operate. 
In keeping with the above objects and with others which will become 
apparent hereafter, one feature of the invention resides, in a device for 
admixing a gaseous and a liquid phase particularly in a reaction vessel or 
a fermentor, in a combination which comprises an upright vessel for the 
liquid phase, and a substantially cylindrical baffle extending in the 
vessel upwardly from a lower region thereof. The baffle has a lower open 
end and an upper end provided with a constriction which forms a throat. 
Impeller means is provided in the region of the lower open end for 
impelling a flow of the liquid phase through the baffle. Admitting means 
is provided for admitting the gaseous phase into the baffle in the region 
of the throat thereof. 
The novel features which are considered as characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawing in detail, it will be seen that in the exemplary 
embodiment which has been illustrated a vessel 1 is of cylindrical shape 
and has an upright orientation. In the region of the bottom of the vessel 
there is located in the interior an impeller 2 which axially draws the 
contents in terms of liquid and gaseous phase, and which throws the 
contents in radial direction. In other words, the contents are drawn 
downwardly in the vessel 1, and are expelled in radial direction. An 
electromotor 3 is provided which drives the impeller 2 via a transmission 
4. 
Located within the vessel 1, extending axially thereof in upright direction 
and having its lower open end located above the impeller 2 is a tubular 
guide baffle 5 which extends into the upper region of the vessel 1 and 
which has a constriction 6 at its upper end. Located in this upper end is 
a gas-admitting body 7 which is constructed as a hollow double-conical 
member and which is mounted on a hollow supply tube 9, which is in turn so 
mounted that it can be shifted vertically, that is axially of the baffle 
5. The body 7 defines with the throat of the constriction 6 an annular gap 
the cross-section of which can be varied when the body 7 and the tube 9 
are shifted in axial direction. The body 7 has gas outlet openings 8 which 
are located in a common plane transverse to the elongation of a body 7. 
The tube 9 is mounted in the stuffing box 10 which serves to seal the 
upper end of the vessel 1 and also to hold the tube 9 for such shiftable 
displacement. 
The liquid phase which is to have a gaseous phase admixed with it, and 
which may be for instance a nutrient medium with microorganisms, is 
admitted into the vessel 1 either batch-wise or continuously, and a 
gaseous phase -- such as air -- is blown through the tube 9. When the 
impeller 2 is operated, the liquid phase is drawn axially in downward 
direction through the baffle 5, entering the latter at the upper open end, 
and is expelled radially at the bottom end thereof. It therefore can move 
upwardly outside the guide baffle 5, whereas inside the guide baffle 5 it 
moves downwardly. Depending upon the axial position of the body 7, the 
latter defines with the wall bounding the constriction 6 of the guide 
baffle 5 an annular gap of greater or lesser cross-section, in which the 
liquid phase reaches its highest flow speed, so that a suction is exerted 
at the location at which the openings 8 are provided. Since the body 7 is 
located in the upper region of the vessel 1, the hydrostatic pressure 
which heretofore was objectionable in the prior art cannot act to prevent 
the ready introduction of the gaseous phase, especially as there is in 
this region an underpressure resulting from the Venturi effect of the flow 
of the liquid phase through the throat of the constriction. 
The construction according to the present invention overcomes fully the 
disadvantages of the prior art, and in most instances it is actually not 
necessary to provide any blower at all, because it has been found that in 
most instances the suction effect exerted by the liquid phase which rushes 
through the annular gap where the constriction 6 forms the throat, is 
sufficient to draw air or other gaseous medium through the openings, the 
body 7 and the tube 9. This substantially increases the economy of 
operation of the device, since no energy is required for a blower or the 
like to blow the gaseous phase into the vessel 1, and it also reduces the 
expenses of constructing the device since no blower or similar element 
need be provided. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
device for admixing a gaseous and a liquid phase, it is not intended to be 
limited to the details shown, since various modifications and structural 
changes may be made without departing in any way from the spirit of the 
present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.