Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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K 263
EMULSIFYING ARRANGEMENT
The invention concerns an emulsifying arrangement with
an emulsifying chamber having inlets and outlets for a fluid
mixture consisting of at least two fluid fractions or,
respectively, an emulsion to be mixed or to be dispersed in
accordance with claim 1.
An emulsifying arrangement is used for the mixing of at
least two fluid flows which are not soluble in one another or
only to a limited extent in order to form an emulsion. An
emulsion is a finely distributed disperse mixture of at least
two fluidic phases.
Herein at least one of the phases is
bound, while forming droplets, as a disperse phase into a
common carrier phase forming a common coherent matrix. This
forms a disperse phase in a carrier phase mixture. Classic
examples are oil-in-water or water-in-oil emulsions.
An
emulsion is considered to practically be stable over a
certain period, that is, it dissociates only slowly.
Non-soluble fluid phases have an interface tension which
must be overcome for introducing energy into the fluid
mixture.
The interface tension increases with decreasing
droplet size of the disperse phase, that is in an emulsifying
arrangement with constant energy input, for example an
agitator vessel, the droplet size in the carrier phase the
droplet size is reduced until an equilibrium is established
on the basis of the increasing interface energy.
Consequently, the droplet size in the emulsion can be
varied by the amount of energy input into the emulsifying
arrangement.
In this way, an emulsifying arrangement is
different from a dispersing arrangement in which a solid
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material component part of changeable particle size is mixed
into a liquid. Emulsifiers, preferably tensides, are mixed
into the liquid phase. They assist an emulsifying process
and stabilize the emulsion in that they reduce the interface
tensions of the disperse phases relative to the carrier
phase.
Known emulsifying arrangements utilize agitators by
which the fluid mixture is not only mixed but additionally
large sheer impulses are applied in a homogenous manner.
A first basic form of an emulsifying arrangement
including a container arrangement with an agitator is
disclosed for example in DE 348 667.
DE 23 39 530 discloses a more up-to-date mixer
development with an agitator device including several
serially arranged agitator blades and an outlet at the last
chamber for a continuous mixing an emulsifying of a mixture
comprising several components.
However, agitator devices include agitator arms, blades
and other movable parts disposed in the mixing areas.
Movable parts are not only subject to wear but they are
basically also a source of undesired contamination.
In
addition, the possibilities for miniaturization and also
covering all volume areas of the mixing chambers are limited.
EP 0 545 334 B1 discloses an example of an emulsifying
arrangement for a continuous emulsifying arrangement for a
continuous emulsifying of Diesel fuel and water which does
not include any movable parts. The emulsions are formed in
several stages in turbulence chambers which are in
communication via nozzles and bores, wherein a rapid change
between pressurizing and depressurizing promotes the
emulsifying process.
Turbulence chambers, in particular in cooperation with
nozzles provide for high and therefore advantageous shearing
loads in the emulsion being formed but they increase the
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probability for larger and therefore disadvantageous
residence time differences of the emulsion components in the
emulsifying arrangement.
EP 2 123 349 discloses a continuous emulsifying
arrangement for at least two fluid fractions which are not
mixable and wherein such back-mixing is avoided.
It is
proposed to introduce a first fluid tangentially and a second
fluid axially into a round mixing chamber.
In the mixing
chamber, the first fluid flows around the second fluid
generating a shearing action between the two fluids. In the
process, the fluid mixture begins to emulsify and is
conducted as axially rotating emulsion strand to an axial
outlet in which it is further emulsified.
However, in the last-mentioned emulsifying arrangement
the largest energy input for forming an emulsion occurs at
the beginning of the procedure that is, with the first
engagement between the fluid fractions.
There is a rapid
initial emulsification whereas in the following sections in
which a further droplet size reduction should take place
there are small speed differences and consequently small
energy inputs are generated between the fluid fractions. But
it is exactly the further emulsifying stages where a high
energy input would be important if the particle sizes in the
emulsion are to be further reduced. However, the impulses
generated by shearing and consequently the energy input
continuously decrease.
Furthermore, the last mentioned arrangement requires for
each fluid fraction an input line leading directly into the
mixing chamber which could curb a parallel arrangement of a
multitude of emulsifying arrangement of a multitude of
emulsifying arrangement for capacity expansion.
Based hereon, it is the object of the present invention
to propose a continuous emulsifying arrangement of the type
referred to initially which does not have the disadvantages
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and limitations mentioned above, which has no movable parts,
and which avoids back-mixing and furthermore is based on a
simplified design.
This object is solved by the characterizing feature of
claim I; the sub-claims referring thereto include
advantageous embodiments of this solution.
For solving the object, an emulsifying arrangement with
at least one tubular emulsifying chamber with two end
sections is proposed. It is provided with a number of inlets
for at least two dispersing fluid fractions with in each case
at least one inlet into the emulsifying chamber and at least
one outlet from the emulsifying chamber.
Preferably all
inlets are arranged exclusively in one of the end areas
whereas the outlets are preferably arranged in the other end
area.
The inlets are treated technically as at least one inlet
for a fluid mixture of two non-mixable fluid fractions which
includes an introduction of fluid via separate as well as
common inlets.
If more than one inlet as provided for, the inlets for
the fluid fractions are preferably distributed over the
circumference of the emulsifying chamber, that is, not at the
front face, but in alternating order and in one or several
planes.
The emulsifying chamber includes between the two end
areas a cross-section which is symmetrical about an axis of
symmetry.
Inlets and/or outlets extend preferably skewed
with respect to the axis of symmetry. They extend preferably
in the flow direction tangentially or at an acute angle with
respect to the tube wall area around the wall area
surrounding directly the area where they are connected to the
emulsifying chamber. In the emulsifying chamber in this way
a spiral flow is formed between the inlet and the outlet with
a spiral shaped flow direction around the axis of symmetry.
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It is essential that the axis of symmetry and the
emulsifying chamber have at least one curved area. While the
spiral flow is subjected in a straight emulsifying chamber to
a constant centrifugal force component which is oriented
radially away from the axis of symmetry, the spiral flow in a
curved chamber is subjected to a centrifugal force which
extends radially outwardly from the center point of curvature
of the tubular emulsifying chamber.
The two centrifugal
forces are combined, that is, added.
The flow volume
components in the spiral flow are subjected in the curved
flow not only alone to the constant centrifugal force but
also, by the superimposed centrifugal force resulting from
the curvature to a cyclically changing force input. In this
way, in an advantageous manner, a cyclical change between a
compression and decompression is generated in the fluid flow
which introduces pulsed energy into the fluid mixture. This
dynamics does not only advantageously cause a speed-up of the
emulsifying process but also improves the chances of
obtaining smaller droplet sizes in comparison with not
curved, straight-line emulsifying chamber.
A possible embodiment of the emulsifying arrangement is
characterized in that the axis of symmetry is spiral-shaped.
In this way, curved emulsifying chamber sections of increased
length and consequently a longer effectiveness of pulsed
energy input to the fluid mixture can be realized. In
particular with such an arrangement also longer curved
emulsifying chamber sections with small radii of curvature
can be realized. The centrifugal force components resulting
from the curvature increase with decreasing radius of
curvature, that is smaller radii of curvature result
advantageously in an increased amplitude of the energy input
to the volume components of the spiral flow and consequently
the effect and the speed of the emulsifying process.
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A further embodiment of the emulsifying arrangement is
characterized in that the axis of symmetry of subsequent
curved sections is oriented in different space directions
and/or the cross-section of the emulsifying chamber changes
continuously or preferably in an abrupt manner along the line
of symmetry. This measure provides for additional impulses.
A change in direction additionally results in energy inputs
in additional directions and consequently in disturbances in
the cyclically effective centrifugal forces in their fluid
flow. In this way, not only an advantageous process
acceleration is achieved but also established emulsifying
processes are interrupted and, by the change in direction,
the miniaturization of the droplets in the emulsion is
advanced.
For forming a stable spiral flow which remains in place
also with regard to the curvature-caused force effects, it is
advantageous if, in addition to the form of the above-
mentioned inlet and outlet structures, the cross-section of
the emulsifying chamber extends around the axis of symmetry
in a rotationally symmetric manner.
Preferably, the
emulsifying chamber has a round elliptical, rectangular or
square cross-section.
Basically, the cross-section of an emulsifying chamber
is round. The cross-section corresponds to the extension of
the spiral-shaped flow minus a boundary layer at the
emulsifying chamber wall.
As a result of the centrifugal
force components, which are directed constantly radially
outwardly from the axis of symmetry, the spiral-like flow is
particularly stable. In addition, in particular a circular
cross-section can be produced with simple preferably
standardized means, for example, by galvanic deposited rod
shaped bodies.
The round material preferably consists of
electrically conductive, coated plastic because it can easily
be removed thermally or chemically.
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An elliptical cross-section of the emulsifying chamber
is advantageous in connection with a spiral flow formed in
adaptation to the cross-section of the emulsifying chamber.
With the elliptical chamber shape alone a cyclically
increasing centrifugal force is effective on the fluid
mixture (also without curvature). Basically, the effect is
comparable with the centrifugal force effective on the flow
by the curvature.
The frequency of the swelling force is
twice as large as a result of the elliptical shape (two
maxima at a 360 pass of the spinal flow in the ellipse).
Together with a curvature the forces effective on the flow
are added vectorally and also the advantageous effects
thereof. With the dynamics generated hereby the emulsifying
process is in this manner accelerated and the obtainable
droplet size is further reduced.
A cross-section with corners, preferably a rectangular
or square cross-section of the emulsifying chamber provide in
an advantageous manner for an improved manufacturing
capability, preferably in a foil stack design as established
by micro-process engineering.
Preferably, the emulsifying
chamber extends as planar structure in at least one plane,
each being formed preferably by foils.
The emulsifying
chambers and other fluid guides are technically formed by
grooves or openings in the foil stacks.
The inlets and
outlets extend preferably also parallel or normal to the
planes wherein the axis of symmetry is disposed on, or
parallel to, a plane.
An integration as a component in
micro-engineering arrangements is particularly advantageous
with this form. The spiral flow is not guided by the carrier
cross-section but is only delimited. They are formed in a
free core area of the cross-section preferably as a rounded
or elliptical flow, whereas the corner areas cross-sections
become passive dead areas with little flow activity.
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Embodiments may also be provided which have emulsifying
chamber temperature control means. If the emulsifying chamber
is an integral part of a micro-engineering arrangement the
temperature control arrangement comprises preferably a micro-
channel structure through which a cooling or heating medium
flows.
It is further preferred if in the emulsifier chamber a
core extending over the full length thereof is arranged. The
core may be arranged so as to extend along and around the
axis of symmetry in a rotationally symmetric form. The fluid
volume of the emulsifying chamber is reduced thereby to an
annular gap volume between the core and the inner wall of the
emulsifying chamber.
This embodiment has the additional
advantage of providing additional solid walls by which the
spiral-shaped flow is delimited by boundary layers which are
formed along the walls and provide for additional shear
effects in the spiral flow.
The process of repeated compression and expansion in the
spiral flow which enhances the emulsifying is improved with
the above mentioned core in that the annular gap volume has
angle-dependent (starting from the line of symmetry)
dimension differences in the open width and the spiral flow
has corresponding angle-dependent cross-section increases or
reductions.
These dimensional differences are realized by
arranging the core either eccentrically with respect to
symmetry or that they are provided with axial disruptive
structures such as cutouts, grooves, flat areas or steps
while otherwise the core has a preferably round rotation-
symmetric cross-section.
Optional embodiments provide an emulsifying chamber with
a cross-section which changes along the axis of symmetry and
which cause backup pressures or pressure wherein in the
spiral flow.
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The invention as well as details thereof will be
described below based on an exemplary embodiments with
reference to the following drawings. It is shown in:
Fig. 1 a perspective representation of an emulsifying
chamber of a first embodiment with in- and outlets for
explanation of the principle of the invention,
Figs. 2a and 2b a perspective view and respectively a
cross-sectional view of a technical embodiment of the concept
shown in Fig. 1,
Figs. 3a to 3c additional embodiments, each in a
perspective view, and
Figs. 4a and 4b a further embodiment of a layered
design.
The first embodiment according to Fig. 1 shows
schematically a tubular emulsifying chamber 1 with a first
end area 2 provided with an inlet 3 and a second end area 4
provided with an outlet 5, and an axis of symmetry 6.
A
fluid mixture flow 7 enters the emulsifying chamber via the
inlet and forms in the chamber a spiral flow 8 around the
axis of symmetry in the direction toward the outlet. The
spiral flow extends over the whole emulsifying chamber
between the two end areas 2 and 4. Between the two end areas
2 and 4 the emulsifying chamber has a cross-section which is
symmetrical around an axis of symmetry.
With increasing
travel distance in the emulsifying chamber the emulsifying
process, by the effects of a pulsating and at the same time
its direction changing force, causes an increasing conversion
of the material mixture to an emulsion which then leaves the
emulsifying chamber as an emulsion flow 9 via the outlet. As
mentioned above the curved orientation as well as the fluid
forces effective in the flow cause the mentioned pulsating
force and also the changes of the direction of the force.
The main inlet flow direction of the fluid mixture flow
7 into the emulsifying chamber is preferably along a smooth
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part without a kink or deflection tangentially in the main
flow direction of the spiral flow 8.
Herein the flow
direction of the spiral flow in the emulsifying chamber is
determined or affected.
Also, the exit 4 for emulsion flow extends preferably
tangentially to the main flow direction of the spiral flow 8
at the end area. Following these design criteria, the inlet
and the outlet join the wall of the emulsifying chamber
tangentially or at an acute angle.
The tangential orientation of the inlets and outlet with
regard to spiral flow with as little as possible flow
deflection provides for a laminar inlet and outlet of the
fluid flow into or, respectively, out of, the emulsifying
chamber.
This measure ensures primarily a buildup and a
stabilization of the spiral flow at the two end areas. This
guide effect may be even improved by providing the end areas
with a rotationally symmetrical core (annular gap area only
in the end areas), which narrows down away from the end areas
and ends with a tip. The emulsifying process is affected by
a laminar inlet and outlet flow only indirectly by the
generation of the stable spiral flow in the curved areas of
the emulsifying chamber.
Figs. 2a and 2b show in a perspective view and a cross-
sectional view a technical implementation of the embodiment
of Fig. 1.
Starting with two round discs (lower disc 10, upper disc
11), a groove 12, each preferably with a semicircular cross-
section, is cut into each disc so that by placing the disc on
one another a hollow space with circular cross-section is
formed between the discs 10, 11 (Fig. 26). The inlet 3 and
the outlet 5 are, in accordance with the mentioned design
criteria, preferably drilled (round channel area) and/or
formed by electoerosion (cornered channel area)into the lower
disc 10. Upon placement of the two discs on top of one
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another and joining them by for example clamping, cementing,
diffusion welding or another material- or force locking
joining procedure as shown in Fig. 2, the disc compound is
cut into two halves at the level of the inlet and outlet
openings (see Fig. 2a). In this way, two half-disc compounds
or formed which then are covered at the front along the
cutting plane 13 (see Fig. 2a) by a cover foil.
Figs. 3a - 3c show in perspective views schematically
other embodiments. Figs. 3a and 3b disclose for example an
emulsifying arrangement wherein the axis of symmetry has
subsequent curvatures 14 in different spatial directions. In
the embodiment shown in Fig. 3a, the curved areas are joined
by areas with larger transition radii 15 than in the
arrangement as shown in Fig. 3b. Hereby there is a continuous
change of the curvature radius that is the admission
stretches in the emulsifying chamber, which additionally
stabilize the spiral flow before entering a curved section.
The curved sections comprise only the curves 14 with inlet
and outlet areas Fig. 3c shows an emulsifying arrangement
wherein the axis of symmetry extends spirally. The
arrangement permits the realization of longer curved areas
also with small radius.
An exemplary embodiment in layer construction with
stacked structured individual foils 16 is shown in Figs. 4a
and 4b. The emulsifying chamber 1 is realized in the foil in
the form of a slot-shaped cutout 17, which is covered at both
sides by adjacent foils. The adjacent foils themselves have
openings forming an inlet 3 and an outlet 5.
The cross-
section of the emulsifying chamber 1 is rectangular (See
sectional view Fig. 4). The
foils are joined by known
procedures such as preferably cementing or diffusion welding.
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Reference Numerals
1 Emulsifying chamber
2 First end area
3 Inlet
4 Second end area
Outlet
6 Axis of symmetry
7 Fluid mixture flow
8 Spiral flow
9 Emulsion flow
Lower disc
11 Upper disc
12 Groove
13 Cutting surface
14 Curvature
Transition radius
16 Individual foil
17 opening
12
