Apparatus useful for foam breaking

An apparatus useful for foam breaking operations and particularly useful for fermentation processes is described having a foam breaking body wherein the foam breaking surfaces are created by a multitude of elements arranged in contact with each other and defining a multitude of paths for the foam and fluids there through. This body is arranged for rotation and the gas phase is withdrawn from said body at or near the rotational axis.

This invention relates to a foam breaking process and an apparatus which 
can be used for foam breaking. More specifically, the invention relates to 
a process in which a foam following a pressure gradient is passed through 
moving surfaces to separate the liquid and the gas. 
BACKGROUND OF THE INVENTION 
In a variety of technologies foams are generated in one step and have to be 
broken in a further step. Such foams usually consist of a continuous 
liquid phase with small gas bubbles entrapped therein. Generally, the 
separation becomes more difficult the smaller the bubbles are. 
In the fermentation art foam breakers have become widely known which 
comprise a plurality of frustoconically shaped surfaces coaxially arranged 
with a constant distance between them. These surfaces, when put into rapid 
rotation, cause the foam to be broken apart with the heavier liquid 
leaving the foam breaker at its circumference whereas the gas is withdrawn 
from an axial central conduit. It is a continuing goal in the industry to 
provide apparatus and processes allowing to carry out a foam breaking step 
in an efficient and economically more feasible manner than heretofore 
possible. 
THE INVENTION 
It is one object of this invention to provide a new apparatus that can be 
used for foam breaking and is simple in construction. 
Another object of this invention is to provide an apparatus useful for foam 
breaking operations that can be adapted to varying foam compositions. 
A further object of this invention is to provide a process for breaking a 
fermentation foam. 
These and other objects, advantages, details, features and embodiments of 
this invention will become apparent to those skilled in the art from the 
following detailed description of the invention, the appended claims and 
the drawing which shows a schematic cross section through an apparatus in 
accordance with this invention. 
The apparatus of this invention comprises as its main feature a rotatably 
arranged foam breaking body of a specific structure. This foam breaking 
body comprises a plurality of elements which are in contact with each 
other leaving a multitude of fluid paths in this body. These fluid paths 
provide fluid connections between an outer and an inner surface. The terms 
"outer" and "inner" refer to an axis of rotation in the sense that the 
inner surface is closer to this axis of rotation than the outer surface. 
The foam breaking body is arranged for rotation around this axis. When a 
pressure gradient is generated between the outer and the inner surface a 
foam present at the outer surface will move toward the inner surface. The 
rotation of the foam breaking body will cause the liquid to follow the 
stronger centrifugal forces and move along the paths toward the outer 
surface whereas the gas will move toward the inner surface following the 
pressure gradient and thus separating the liquid phase and the gas phase. 
The moving surfaces of the individual elements contacting the foam 
together with the forces described cause a foam breaking effect. 
Thus, in accordance with a first embodiment of this invention, an apparatus 
useful for breaking foam is provided. This apparatus comprises housing 
which can hold foam and a foam breaking body. This foam breaking body 
comprises a plurality of elements arranged in contact with each other. 
These elements are of such a structure and arrangement as to lead a 
multitude of fluid paths in the body. These paths provide fluid 
connections between an outer and an inner surface. The outer surface of 
the body is in fluid communication with the interior of the housing 
whereas the inner surface is in fluid connection with conduit means 
providing the fluid connection between this inner surface and an area 
outside of the housing. 
In accordance with a second embodiment of this invention an improved 
fermentation process is provided for. In this process a mixture comprising 
a nutrient medium and a microorganism is subjected to fermentation 
conditions. A foam comprising a liquid phase of nutrient medium and cells 
and a gas phase is generated. The foam is passed through a foam breaking 
operation wherein the foam is separated into the liquid phase and into the 
gas phase by passing this foam in contact with a rapidly rotating 
surfaces. In accordance with this invention this process is improved by 
using as the surfaces path defining surfaces formed in a foam breaking 
body by a multitude of elements that are in contact with each other and 
that are shaped and arranged such as to form a large number of fluid paths 
between an outer an an inner surface of said body. A pressure gradient is 
generated between the outer and the inner surface of the body and the 
outer surface is arranged in contact with the foam. A gas phase is 
withdrawn from the inner surface. The liquid phase leaves the foam 
breaking body from at least a portion of the outer surface and is 
preferably returned into the fermentation step or collected for further 
processing. If the liquid is tacky or sticks to the surface of the padding 
material, it is preferred to backflush the foambreaking device 
periodically and thereby wash of some or all of the materials held by the 
foambreaking device. 
The following details apply both to the apparatus and the process 
embodiments where feasible. 
The individual elements forming the foam breaking body can also be 
described as a packing material. This packing material can consist of 
typical packing material as used in for instance distillation columns. 
Packing materials that can also be used if they are compatible with the 
fermentation process, are plastic mesh, e.g. mesh material knitted or 
woven from plastic yarns or other fibrous material, fiberglass reinforced 
or unreinforced foamed plastic, e.g. foam (open cells) or foam particles 
(open cells or closed cells, the latter having weight reduction function 
only, the former constituting additional channels) from such plastics as 
polystyrene, polytetrafluoroethylene, and polypropylene, metal, glass or 
ceramic rings (slotted or unslotted) or saddles; mixtures of two or more 
different kinds of packing materials can be used in a random form of a 
mixture or in the form of annular rings of packings of various kinds 
separately. The elements preferably are wire elements which are knitted or 
woven into wire mesh segments and a plurality of these segments form the 
foam breaking body. The advantage of the large number of elements used and 
the thereby created large number of fluid paths contributes to the 
efficiency of the foam breaking operation in that a larger surface 
spinning around the rotational axis is provided for along which a foam has 
to move as compared to the geometrically well defined frustoconically 
shaped foam breaking surfaces. The foam breaking surfaces of this 
invention can be also described as multichannel arrangements. The 
individual paths can be statistically arranged and do not have a 
geometrically defined pattern. 
The shape of the foam breaking body is not particularly critical and can 
for instance be spherical, cylindrical, or frustoconical. The presently 
preferred shape of the foam breaking body is a cylindrical shape. The 
individual elements of the foam breaking body may be confined in a solid 
casing having openings smaller than the elements which are in contact with 
the casing. In case of a cylindrically shaped foam breaking body this 
casing comprises a top portion, a bottom portion and a cylindrical 
circumferential portion with openings through the cylindrical 
circumferential portion as well as through at least the outer area of the 
top and bottom portion of the casing. 
The foam breaking body is preferably connected to a conduit having openings 
therein allowing the withdrawal of gas from the interior of the foam 
breaking body and the flow of the gas through this conduit into an area 
outside of the confining housing. 
For typical fermentation purposes the surface area of the foam breaking 
body will be in the range of 1.0 to 25 in.sup.2 /in.sup.3. Another way of 
describing the foam breaking body for such fermentation operations is by a 
number of paths above 500. The size of the paths is best described by an 
average diameter of such a path of in the range between 0.04 and 1 inches. 
It should be understood that rotation of the foam breaking body will in 
effect decrease the average path diameter and increase the number of 
pathways.

The foam breaking device 5 comprises a casing 6 which is composed of a top 
cover plate 7, a bottom cover plate 8 and a cylindrical confining portion 
9. The top cover plate 7, the bottom cover plate 8 and the cylindrical 
confining section 9 are provided with openings 10 which are large enough 
to allow the foam to pass through, but not large enough to allow those 
elements of the foam breaking body 11 that are in contact with this casing 
to pass through. The casing is attached to a hollow conduit 12 which is 
supported in the casing by means of a bearing 13. The foam breaking unit 5 
can be put into rapid rotation by means of a motor drive unit 14. The 
conduit 12 is closed at the bottom to prevent any direct flow of foam into 
this conduit. Openings 15 are provided at the lower end of the conduit 12. 
The geometrical arrangement of the openings 10 through which the foam 
enters the foam breaking body 11 and the openings 15 through which gas 
leaves the foam breaking body 11 are such that the fluid has to migrate 
through a substantial length of its way along one or more of the paths in 
the foam breaking body. In other words, the shortest geometrical distance 
between the openings 10 in plates 7 and 8 into the foam breaking body 11 
and any of the openings 15 at the inner surface of the foam breaking body 
11 is significant and in the range of about 0.4 to 1.5 of the radial 
extension of the foam breaking body 11. 
Reasonable variations and modifications which will become apparent to those 
skilled in the art can be made in this invention without departing from 
the spirit and scope thereof.