Stirring arrangement
Description
The invention relates to a stirring arrangement with a rotating stirring body for
stirring fluids, with stirring blades attached on a stirring body hub. The stirring
device also includes a gas supply device which supplies a gas, such as air, for
dispersing with the stirring body.
In many chemical reactors or bioreactors with a stirring arrangement, reactions
occur wherein at least one reaction partner is present as a gaseous starting
component. The stirring arrangement is provided to finely distribute the gaseous
component and to thus provide a large boundary surface between the gaseous
component or the fluid such that the gaseous component goes at least partially or
entirely into solution and takes part in the reaction progressing in the reactor.
Accordingly, there are applications where the stirring arrangement must disperse
a gas. The task of dispersing a gas occurs in practice mostly in conjunction with
additional primary tasks, for example mixing of fluid flows having different
viscosities used to introduce additional reaction partners, suspending solid
materials, transferring heat to heat exchange elements, circulating the fluid to the
surface for evaporating solvents, precipitating and crystallizing solid materials,
etc.
To optimally solve the primary tasks, various stirring bodies have been previously
developed, which may differ with respect to the transport direction, namely radial
and/or axial, the number of stirring blades, the shape of the stirring blades and
the number of stirring stages.
For example, US 4 371 480 A and in DE 92 01 820 U1 describe stirring
arrangements are disclosed wherein a gas is drawn in by the stirring body.

Conversely, stirring arrangements with "external gas supply" are known, meaning
that the gas is not drawn in by the stirring body, but is supplied by a blower or
compressor or from a pressure reservoir. Several examples for conventional
stirring arrangements will now be described.
WO 2008/083673 A2 discloses a stirring arrangement with a stirring body and a
gas supply device of the aforedescribed type. This gas supply device supplies
gas below or on the sides of the stirring body, wherein this gas is dispersed by
the stirring body. With this design of the stirring arrangement, the gas is supplied
and distributed either on the sides and/or below the stirring body at a relatively
large distance from the stirring body.
EP 0 847 709 A1 discloses a stirring body which is used, in particular, as gas
supply stirring body for stirring fluids. A gas, for example air, is supplied to the
fluids. In this gas supply stirring body, the gas is supplied via a supply tube with a
discharge port located below the stirring axis of the stirring body. Optionally,
several supply tubes may be provided below and/or on the side spaced from the
stirring body. The gas is supplied via these tubes to the outflow of the stirring
body of the stirring arrangement.
EP 1 055 450 B1 shows a stirring arrangement, wherein the gas is supplied via
co-rotating distribution elements.
As can be seen from the aforedescribed stirring arrangements, stirring
arrangements having an external gas supply can be divided into two different
cases.
The gas may be supplied via stationarily installed supply lines, for example via
tubes arranged below the stirring body or tubes arranged on the side next to the
stirring body or a ring-shape gas distributor, a so-called ring shower arranged
below the stirring body. Such ring shower has several openings distributed along

its circumference, through which the gas to be supplied to the stirring body can
exit.
Gas can also be supplied through co-rotating distribution elements, as is the case
for the stirring arrangement described in EP 1 055 450 B1. However, if the
stirring body of this stirring arrangement must satisfy one of the aforementioned
primary tasks in addition actually supplying the gas, the rotating distribution
elements for supplying gas are arranged outside the actual stirring body,
preventing an optimal gas supply.
The conventional embodiments of gas supply devices include several individual
and separate components which require associated rigid supports to prevent
flow-induced oscillations. It may also be necessary to use expensive materials,
duplex steels, alloys or titanium to prevent corrosion. Overall, the conventional
gas supply devices are therefore complex, include several components and are
complex and cost-intensive to manufacture.
It is therefore an object of the invention to provide a gas supply to the stirring
body of a stirring arrangement, which has a very simple structure while
simultaneously attaining a significant cost reduction, and to also achieve a
targeted gas discharge at any location of the stirring body or the stirring blades
desired for the flow mechanics. In particular, the gas should be optimally
dispersed without adversely affecting the primary task of the stirring
arrangement.
According to the invention, a stirring arrangement with a rotating stirring body for
stirring fluids is provided, wherein the stirring body has stirring blades mounted
on a stirring body hub, and with a gas supply device supplying a gas, such as air,
for dispersing with the stirring body, wherein the stirring arrangement is
distinguished in that the gas supply device includes a distribution bushing which
rotates with the hub of the stirring body and which has an interior space for

receiving the gas, wherein the interior space is in fluid communication with co-
rotating outlet lines. The invention is characterized in that outlet openings of the
outlet lines are arranged in immediate vicinity of the stirring blades and within the
volume swept by the stirring body or in the immediate outflow zones and
discharge the gas at desired locations in the corresponding desired flow
direction.
In the stirring arrangement according to the invention, co-rotating outlet lines with
outlet openings are provided in the immediate vicinity of the stirring blades,
simplifying their support and attachment. These outlet lines also allow
discharging the gas in a targeted manner at any location of the stirring body
and/or of the stirring blades favorable for the flow mechanics. The gas is
conducted from the distribution bushing to the corresponding desired outlet
openings through the co-rotating outlet lines. By arranging the outlet openings of
the outlet lines according to the invention in the immediate vicinity of the stirring
blades and within the volume swept by the stirring body or in the immediate
outflow zones, the gas is optimally dispersed, while simultaneously preventing
any interference with fulfillment of a primary task of the stirring arrangement.
The gas supply device preferably also includes a standing supply line, which is in
sealed fluid communication with the interior space of the rotating distribution
bushing. The gaseous component is supplied to the stirring body through a single
central supply line, thus significantly simplifying the structure of a stirring
arrangement which includes a stirring body and a gas supply device. The
standing central supply line is in sealed fluid communication with the interior
space of a central distribution bushing which rotates with the hub of the stirring
body.
The design of the stirring arrangement according to the invention thus includes a
central gas supply line, which is then in fluid communication with co-rotating
devices, such as a distribution bushing, with the likewise co-rotating outlet lines.

In this way, a structurally significantly simplified gas supply is realized with this
type of stirring arrangement with gas supply device.
In order to attain a very compact structure of the stirring arrangement, the
rotating distribution bushing is arranged coaxially and below the stirring body
hub. This produces an optimal space-saving arrangement and structure of the
rotating distribution organ.
In particular, according to the invention, the gas supply locations formed by the
outlet openings of the outlet lines are located within the volume swept by the
stirring body. The outlet lines thereby allow in the stirring arrangement according
to the invention a free selection of the optimal locations for releasing the gas in
the immediate vicinity of the stirring blades. Both the outflow direction of the
supplied gas as well as the outflow location can be optimally selected by taking
into account the respective design of the stirring body.
The outlet lines coming off the distribution bushing may extend separate from the
stirring blades and their discharge openings, or outlet openings may be located
above the blade height or the blade periphery. The discharge openings or outlets
of the outlet lines may be located in the region of the stirring body blades; other
designs are possible where the discharge openings are located between the
stirring body blades.
According to an alternative embodiment, the outlet lines may be integrated in the
stirring blades of the stirring body.
The transition from the standing supply line and the distribution bushing co-
rotating with the stirring body, wherein the outlet lines are in fluid communication
with the interior space of the distribution bushing, should be designed such that
the quantity of lost fluid at the transition from standing to rotating part is as small
as possible, thus providing a reliable seal in the transition region. According to

the invention, a hydrostatic seal may be provided in this transition region, or a
substantially wear-free arrangement with an axial or radial gap implementing the
desired sealing function may be provided.
In summary, it is important with the stirring arrangement according to the
invention to arrive at a structurally simplified supply line to the stirring body with
the smallest possible number of individual parts. Accordingly, a single central gas
supply is provided with the invention which is stationary and cooperates with a
rotating distribution bushing having an interior space forming a gas receiving
space. The co-rotating outlet lines are then supplied from this central co-rotating
distribution bushing, and these co-rotating outlet lines with outlet openings
disposed in the immediate vicinity to the stirring blades and within the volume
swept by the stirring body or in the immediate outflow zones can then discharge
the supplied gas at the respective most favorable locations in order to optimize
the stirring arrangement and to thereby also impart a desired flow direction on
this supplied gas flow so as to improve the participation of the gas in the reaction.
Preferred embodiments of the invention will now be described in more detail with
reference to the appended drawing which only exemplary and does not represent
a limitation. The drawing shows in:
FIG. 1 a schematic side view of a stirring arrangement with a stirring body and
a gas supply device according to the invention; and
FIG. 2 a schematic side view of a stirring arrangement with a stirring organ
and a gas supply device according to a modified embodiment of the
invention.
In the figures of the drawing, identical or similar elements are labeled with
identical reference symbols.

FIG. 1 shows a first embodiment of a stirring arrangement having the overall
reference symbol 1. The stirring arrangement 1 has a rotating stirring body 2
designed for stirring liquids. The stirring body 2 includes a stirring body hub 3 to
which stirring blades 4 are attached. The sealing blades 4 may have any desired
shape and design.
The stirring arrangement 1 also includes a gas supply device indicated with the
overall reference symbol 5, which supplies a gas, such as air, to the stirring
organ 2 for dispersing. The gas supply device 5 includes a distribution bushing 6
co-rotating with the stirring body hub 3 of the stirring organ 2. The distribution
bushing 6 encloses an interior space configured to receive gas. The distribution
bushing 6 and/or the interior space thereof are in fluid communication with co-
rotating outlet lines 7 which discharge the gas at respective desired locations with
the corresponding.desired flow direction. The gas supply device 5 furthermore
includes a standing supply line 8 which is in sealed fluid communication with the
interior space of the rotating distribution bushing 6. In this exemplary embodiment
illustrated in FIG. 1, the co-rotating outlet lines 7 are formed separate from the
stirring blades 4.
In the stirring arrangement illustrated in FIG. 1, a single central standing supply
line 8 is provided for a gas to be supplied. The distribution bushing 6 is arranged
coaxially and below the stirring body hub 3 having the interior space for receiving
gas. The standing or stationary supply line 8 and the rotating distribution bushing
6 are in sealed fluid communication with each other. The structure is hereby
selected such that the quantity of lost fluid at the seal of the transition between
standing supply line 8 and rotating distribution bushing 6 is as small as possible.
For this purpose, a hydrostatic seal can be provided at this transition region, or
the sealed connection between stationary supply line 8 and rotating distribution
bushing 6 is implemented with a wear-free arrangement having an axial or radial
gap.

In the design of the stirring arrangement 1 according to the invention, the gas
introduced into the interior space of the rotating distribution bushing 6 through the
stationary supply line 8 is released through the co-rotating outlet lines 7 of the
gas supply device 5 at a respective desired suitable location, wherein the supply
locations are located within the volume swept by the stirring organ 2. However,
the gas can also be discharged and released at the discharge openings of the
co-rotating outlet lines 7 with a corresponding desired flow direction. These
discharge openings of the outlet lines 7 may be located in the region of the
stirring blades 4, or they may also be arranged between the stirring blades 4.
However, they are always arranged in the immediate vicinity of the stirring blades
and within the volume swept by the stirring body. These discharge openings of
the outlet lines 7 may also be located above or below the height of the stirring
blades 4. The most favorable locations for the outlet openings of the outlet lines 7
and the most favorable discharge directions may be optimally selected
depending on the type of the stirring organ 2. In particular, savings in installation
costs and/or material cost can be achieved with the compact design of the gas
supply device 5. Because the outlet lines 7 also co-rotate, the rigid supports for
the outlet lines for preventing flow-induced oscillations can be eliminated.
The stirring arrangement 1 according to the invention is relatively cost-effective
due to its inventive design and also has a simpler structure. The stirring body 2 of
the stirring arrangement 1 according to the invention is therefore able to very
efficiently disperse the supplied gas, so that optimal reaction conditions of gas
and fluid in a reactor can be realized.
FIG. 2 shows examples of alternative embodiments of the outlet lines 7 as well
as well of the orientations and arrangements of the discharge openings thereof.
In an illustrated example, the outlet line 7 is integrated in the associated stirring
blade 4. All additional details of the stirring arrangement 1' according to FIG. 2
are identical with the details of the stirring arrangement 1 according to FIG. 1. A
more detailed explanation is therefore unnecessary.

The invention is not limited to the details of the illustrated embodiments, and
numerous changes and modifications are possible which the skilled artisan will
make as needed without going beyond the scope of the invention. For example,
combinations of the embodiments of outlet lines 7 are also feasible, wherein the
outlet lines 7 are partially integrated in the stirring blades 4 and partially separate
from the stirring blades. The discharge openings of the co-rotating outlet lines 7
may then be alternatingly arranged at different locations in relation to the stirring
body 2, and the discharge openings themselves may also be formed differently to
impart the respective desired flow direction component on the exiting gas flow.
However, according to the invention, these discharge or outlet openings should
be located in the immediate vicinity of the stirring blades and within the volume
swept by the stirring body.

We Claim:
1. Stirring arrangement with a rotating stirring body (2) for stirring fluids,
wherein the stirring body (2) has stirring blades (4) mounted on a stirring
body hub (3), and with a gas supply device (5) supplying a gas, such as
air, for dispersing with the stirring body, wherein the gas supply device
comprises a distribution bushing (6) which rotates with the hub (3) of the
stirring body (2) and includes an interior space for receiving the gas, said
interior space being in fluid communication with co-rotating outlet lines (7),
characterized in that outlet openings of the outlet lines (7) are arranged in
immediate vicinity of the stirring blades (4) and within the volume swept by
the stirring body (2) or in the immediate outflow zones, and discharge the
gas at desired locations in a corresponding desired flow direction.
2. Stirring arrangement according to claim 1, characterized in that the gas
supply device (5) comprises a standing supply line, which is in sealed fluid
communication with the interior space of the rotating distribution bushing
(6).
3. Stirring arrangement according to claim 1 or 2, characterized in that the
rotating distribution bushing (6) is arranged coaxially and below the stirring
body hub (3).
4. Stirring arrangement according to one of the claims 1 to 3, characterized
in that the outlet lines (7) run separate relative to the stirring blades (4).
5. Stirring arrangement according to one of the claims 1 to 3, characterized
in that the outlet lines (7) are integrated in the stirring blades (4).

6. Stirring arrangement according to one of the claims 1 to 5, characterized
in that the sealed connection between stationary supply line (8) and
rotating distribution bushing (6) is implemented with a hydrostatic seal.
7. Stirring arrangement according to one of the claims 1 to 5, characterized
in that the sealed connection between stationary supply line (8) and
rotating distribution bushing (6) is implemented with wear-free, axial or
radial gap arrangement.

ABSTRACT

The invention relates to a stirring arrangement having a rotating stirring body (2)
for stirring fluids. The stirring body (2) has stirring blades (4) attached on a
stirring body hub (3). The stirring body further includes a gas supply device (5)
supplying a gas, such as air, for dispersing with the stirring body (2). The gas
supply device (5) includes a distribution bushing (6) which rotates with the hub
(3) of the stirring body (2) and has an interior for receiving the gas. The
distribution bushing (6) and the interior thereof are in fluid communication with
co-rotating outlet lines (7). Outlet openings of the outlet lines (7) are disposed in
the immediate vicinity of the stirring blades (4) and within the volume swept by
the stirring body (2) or in the immediate outflow zones, and discharge the gas at
respective desired locations in the corresponding desired flow direction.