Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND DEVICE FOR OBTAINING A FREE DISPERSE SYSTEM IN LIQUID
Technical Field
The present invention relates to a method of obtaining a free disperse system
in liquid which
will make it possible to produce a controlled hydrodynamic cavitation and to
regulate the intensity
parameters of a hydrodynamic cavitation field. Selection of the parameters
with regard to the
properties of components of the fluid under treatment which in turn will make
it possible to
effectively treat the components with different physio-chemical
characteristics. The invention
particularly relates to a cavitation device for effecting this method with a
baffle body of such a
construction which will allow the multiplicity of treatment to be regulated
along with an increase in
degree of cavitation which will substantially improve the quality of an
obtained free disperse system
and will substantially extend technological capabilities of the method.
Bacl~round Art
Widely known in the prior art are methods of obtaining free disperse systems
and particularly
lyosols, diluted suspensions and emulsions, using the effect of cavitation.
These systems are fluidic
and particles of a dispersed phase have no contacts, participate in a random
beat motion and freely
move by gravity. In these methods, the emulsification and dispersion processes
are accomplished
due to cavitation effects expediently set up in the flow under treatment by
hydrodynamic means at
the expense of a sharp change in geometry of the flow.
Also known in the prior art are devices for effecting these methods of which
the basic
element is presented by a baffle body installed in a flow channel in the
direction of a hydrodynamic
flow Phenomenon of the hydrodynamic cavitation resides in the formation of
cavities fllIed with a
vapor-gas mixture inside the liquid flow or at the boundary of the baffle body
due to a local pressure
drop caused by movement of the fluid. Mixing, emulsification homogenization
and dispersion effects
of the hydrodynamic cavitation result from a substantial plurality of force
effects on the treated
mixture of components due to the collapse of cavitation bubbles. The collapse
of cavitation bubbles
near the boundary of "liquid-solid particles" phases results in dispersion of
these particles in the fluid
and in formation of the suspension, while in the "liquid-liquid" system one
fluid is atomized in the
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other fluid and results in formation of the emulsion. In both cases, the
boundary of solid phases is
destroyed, i.e. eroded, and a dispersive medium and a dispersed phase are
formed.
For the most part, the models explaining the mechanism of emulsification and
dispersion
processes accomplished by means of cavitation are based at the present time on
the use of a
cumulative hypothesis of the cavitation effect on a surface to be destroyed.
The process of
dispersion by means of cavitation is associated with the formation of
cumulative microjets. It is
supposed, that due to the interaction of a shock wave set up by the collapse
of cavitation bubbles
with the bubbles arranged at the boundary of the phases, the cumulative
microjets are formed.
Intensive mixing and dispersion is explained by the formation of high-
intensity microvortices and by
a sequential disintegration of the cumulative microjets. The process of the
fluid atomization is
caused by tangential stresses acting on the referred fluid and occurring at
the boundaries of cavitation
microvortices, while the dispersion of solid particles is accomplished due to
a hydrodynamic
penetration of a cumulative microjet into a particle.
In addition to erosion effects caused by the collapse of cavitation bubbles,
other physio-
chemical effects occur serving as additional factors in the intensification of
technological processes.
It should also be noted that physical characteristics of the mixture of
components in the flow
under treatment have a substantial influence on the erosion activity of
cavitation bubbles. For
example, increase of viscosity, decrease of surface tension and density of the
fluid, as well as increase
of the gas content therein reduce the efficiency of the cavitation effect.
There is also known, a method of obtaining a free disperse system, i.e. a
suspension of fibrous
materials, involving the passage of a hydrodynamic flow of fibrous materials
through a channel
internally accommodating a baffle body installed across the flow for providing
a local contraction
of the flow and forming downstream of the referred body a hydrodynamic
cavitation field acting on
the flow of fibrous materials until the suspension of the referred materials
is formed.
An attempt was made for effecting the method described hereinabove, in which a
device was
proposed consisting of a housing with inlet and outlet openings, a contractor,
an internal flow
channel accommodating a solid cylindrical baffle body and a diffuser (U.S.A.
Patent No. 3,834,982)
arranged in succession on the inlet opening side and connected together.
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It must be emphasized that there are fundamental differences between the
Cavitation Method
and Device described and claimed in the present Patent Application and the
other prior art devices
such as static mixers. The static mixers ofthe prior art references (i.e.
Durrieu et a1, U.S. Patent No.
4,464,057, Wiemers et al, U.S. Patent No. 5,145,256 and Japanese patent 45 -
40634) rely on
turbulence or high Reynolds Numbers to produce their desired result. They may
experience
cavitation during their operation but such cavitation is incidental to their
operation. The claimed
Cavitation Device differs fundamentally from prior art devices due to the fact
that controlled
cavitation is a fundamental requirement and an achieved accomplishment for the
successful operation
of the claimed invention.
The shape of the internal baffle body used in the claimed Cavitation Device is
different from
conventional devices due to the fact that it is designed specifically to
produce controlled cavitation.
Mixing and homogenization processes in the claimed Cavitation Device are based
on using
hydrodynamic cavitation connected with physical and mechanical effects
(including but not limited
to shock waves, cumulative effects of bubble collapse, self excited
oscillations, vibroturbolization,
and straightened diffusion) occurring at a collapse of cavitation bubbles.
Disclosure of the Invention
The invention is essentially aimed at providing a method of obtaining a free
disperse system
in liquid which will make it possible to regulate the intensity of a
hydrodynamic cavitation field and
to select its parameters with due regard to properties of components of the
flow under treatment.
This in turn will make it possible to effectively treat the components with
different physio-chemical
characteristics and to develop a device for effecting this method with a
baffle body of such a design
which will allow the multiplicity of treatment to be regulated along with
increasing the degree of
cavitation which will substantially improve the quality of an obtained free
disperse system in liquid
and will substantially extend technological capabilities of the method.
This is attained by, that in a method of obtaining a free disperse system in
liquid involving
- the passage of a hydrodynamic flow of components through a channel
internally accommodating a
baffle body providing a local constriction of the flow, a hydrodynamic
cavitation field is formed
downstream of this body which affects the flow of components under treatment
and forms a flow
of the free disperse system. According to the invention, the local
constriction of the flow is
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accomplished in at least one section of the flow channel emanating from the
condition of maintaining
the ratio of the cross-sectional portion of the hydrodynamic flow in the local
constriction to the
cross-sectional portion of the flow in the flow channel to 0.8 or less,
maintaining the velocity of the
hydrodynamic flow of components in the local constriction to at least 14
meters/seconds which
provides for the development of a hydrodynamic cavitation field downstream
from the baffle body
having a degree of cavitation of at least 0.1, and, processing the flow of
components mixture in the
hydrodynamic cavitation field downstream from the baffle body. Furthermore,
the local flow
constriction of the components mixture created on the periphery of the
flow,its path accommodated
by the bale body, is established at or near to the center of the flow-through
passage, as well as, the
local flow constriction of the components mixture created in or near the
center of the flow, its path
accommodated by the bafirle body, is established near the walls of the flow-
through passage, are in
both cases, according to the invention, are feasible and conditional for the
method of obtaining a free
disperse system in liquid. Although the invention is described herein in terms
of constriction, the
terms "impingement" or "contraction" of the flow are equally applicable.
Such a method makes it possible to obtain high-quality aggregate-stable
lyosols, emulsions
and suspensions from components, having different physio-chemical
characteristics, at the expense
of a more complete utilization of erosion activity of the field of cavitation
microbubbles and energy
of the flow of components under treatment.
Maintenance ofthe above-mentioned values of the referred parameters (velocity
and degree
of cavitation) is an indispensable condition for setting up and developing the
hydrodynamic cavitation
under the referred conditions.
The ratio of the cross-sectional portion of the hydrodynamic flow in the local
constriction
to the cross-sectional portion of the flow in the flow channel to 0.8 or less
is an important condition
to maintain.
With such a ratio of the cross-sectional portion of the flow in the local
constriction and flow
channel and due to the set-up of hydrodynamic effects, shock waves are formed
and intensively affect
the cavitation field of bubbles which collapse and form cumulative jets. Due
to this fact, conditions
are set up for coordinated collapse of groups of cavitation bubbles in a local
volume along with the
formation of high-energy three-dimensional shock waves whose propagation
intensifies the
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disintegration of cavities and collapse of groups of cavitation bubbles, found
in the process of
collapse. In the case of a coordinated collapse of cavitation bubbles having
the same characteristic
dimensions, the intensity and energy potential of the cavitation field is
approximately one order of
magnitude higher than at a single non-coordinated collapse of bubbles.
Thus, the energy is concentrated and the erosion effect is enhanced on the
flow of
components under treatment. Secondary shock waves formed as a result of
impacts of microjets on
the walls of cavitation bubbles during their interaction are also intensively
affecting this flow. All of
this provides conditions for initiation of vibro-turbulent effects due to
which the components are
intensively mixed and redistributed in the local volume of the flow channel,
and subjected to
additional treatment. Furthermore, the effects described hereinabove
facilitate disintegration of the
cavities formed downstream of the baffle body into a more homogenous field of
relatively small
cavitation bubbles, thereby causing a high efficiency of their coordinated
collapse. In addition, using
the ratio of the cross-sectional portion, the hydrodynamic flow in the local
constriction and flow
channel of 0.8 or less, allows to exclude the possibility of the processing
flow slipping through and
past the field of collapsing cavitation bubbles.
The method, according to the invention, makes it possible to regulate the
intensity of an
occurring hydrodynamic cavitation field as applied to specific technological
processes.
Still other benefits and advantages of the invention will become apparent to
those skilled in
the art to which it pertains upon a reading and understanding of the following
detailed specification.
Brief Description of the Drawings
Some specific examples of embodiments are presented of the herein - proposed
method of
obtaining a free disperse system in liquid, according to the invention,
presented with reference to the
accompanying drawings, wherein:
Figure 1 is a schematic of a longitudinal section view of a device for
carrying out the herein -
proposed method into effect, featuring a cone-shaped baffle body;
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Figure 2 is a longitudinal section view of another embodiment of a device for
carrying out the
herein - proposed method into effect, featuring a flow-throttling baffle body
shaped as the Venturi
tube;
Figures 3A-3D is a fragmentary longitudinal section view of a flow-through
passage ofthe device
of Figure l, featuring the diversely shaped bare body; and
Figures 4A-4D is a fragmentary longitudinal section view of a flow-through
passage of the device
of Figure 2, featuring a flow-throttling diversely shaped baille body.
Best Mode for Carraring out the Invention
The method, according to the invention, consists of feeding a hydrodynamic
flow of a mixture
of liquid components via a flow-through passage, wherein a baffle body is
placed, with the bafrle
body having such a shape and being so arranged that the flow of liquid
components is constricted
on at least one portion thereof. The cross-sectional profile design of the
flow constriction area is
selected so as to maintain such a flow velocity that provides for the creation
of a hydrodynamic
cavitation field past the baffle body. The flow velocity in a local
constriction is increased while the
pressure is decreased, but not less than 14 meters/second, with the result
that the cavitation cavities
or voids are formed in the flow past the baffle body, which on having been
disintegrated, form
cavitation bubbles which determine the structure of the cavitation field.
The cavitation bubbles enter into the increased pressure zone resulting from a
reduced flow
velocity, and collapse. The resulting cavitation effects exert a physio-
chemical effect on the mixture
of liquid components, thus initiating improved mixing, emulsification,
homogenization, dispersion.
In order to utilize the energy generated in the cavitation field to the best
advantage, the
degree of cavitation of the cavitation field must not be below 0.1.
The ratio of the cross-sectional portion of the hydrodynamic flow in the local
constriction
to the cross-sectional portion of the flow in the flow channel to 0.8 or less
is an important condition
to maintain.
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A device schematically presented in Figures 1 and 2 is used for carrying- into
erect the
method, according to the invention.
Reference is now being directed to the accompanying Drawings:
Figure 1 presents the device, comprising a housing 1 having an inlet opening 2
and an outlet
opening 3, and arranged one after another and connecting to one another a
convergent nozzle ~, a
flow-through passage 5, and a divergent nozzle 6.
The flow-through passage 5 accommodates a frustum-conical baffle body 7 which
establishes
a local flow constriction 8 having an annular cross-sectional profile design.
The baffle body 7 is held
to a rod 9 coaxially with the flow-through passage 5. Rod 9, for example, is
attached to stud 10,
mounted to divergent 6 near inlet 2.
The hydrodynamic flow of a mixture of liquid components moves along the arrow
A through
the inlet opening 2 and the convergent nozzle 4 to enter into the flow-through
passage 5 and moves
against the bai~le body 7.
Further along, the flow passes through the annular local constriction 8. When
flowing about
the cone-shaped baffle body 7, a cavity is formed past the baffle body which,
after having been
separated, the cavity is disintegrated in the flow into a mass of cavitation
bubbles having different
characteristic dimensions. The resulting cavitation field, having a vortex
structure, makes it possible
for processing liquid components throughout the volume of the flow-through
passage 5.
The hydrodynamic flow moves the bubbles to the increased pressure zone, where
their
coordinated collapsing occurs, accompanied by high local pressure (up to 1500
MPa) and
temperature (up to 15,000 ° K), as well as by other physio-chemical
erects which initiate the
progress of mixing, emulsification, homogenization and dispersion.
After the flow of a mixture of liquid components is processed in the
cavitation field, the
qualitatively and quantitatively changed mixture of liquid components flow is
then discharged from
the device through the divergent nozzle 6 and the outlet opening 3.
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Figure 2 presents an alternative embodiment of the device for carrying into
effect the herein-
proposed method, according to the invention, characterized in that the bafi~le
body 7 is shaped as the
Venturi tube and fitted on the wall of the flow-through passage 5. The local
flow constriction 8 is
established at the center of the flow-through passage 5.
The hydrodynamic flow of liquid components flowing along the direction of the
arrow A
arrives at the flow-through passage 5 and is throttled while passing through
the annular local
constriction 8. The resultant hydrodynamic field is featured by its high
intensity which is accounted
for by the high flow velocity and pressure gradient. The stationary-type
cavitation voids are
relatively oblong-shaped, and, upon their disintegration, form rather large-
sized cavitation bubbles
which, when collapsing, possess high energy potential. This cavitation field
provides for improved
mixing, emulsification, homogenization and dispersion of a mixture of liquid
components.
In order to control the intensity of the hydrodynamic cavitation field, the
baffle body 7 placed
in the flow-through passage 5 is shaped as a sphere, ellipsoid, disk, impeller
as shown in Figures 3A
-3D, respectively.
Moveable cavitation voids develop past the baf~Ie body 7 shaped as a sphere or
ellipsoid
(Figures 3A, B). Cavitation bubbles, resulting from disintegrated voids and
then collapsing in the
increased pressure zone, exert a more "severe" effect on the mixture of liquid
components under
processing, because the energy potential of the resultant cavitation field is
adequately high. This
being the case, a considerable improvement occurs in the qualitative
processing of liquid
components.
The process of mixing, emulsification, homogenization and dispersion of liquid
components
in the cavitation field, developing past the disk-shaped baffle body 7 (Figure
3C), proceeds as
described with reference to the embodiment of Figure 1. When the impeller-
shaped baffle body 7
is used (Figure 3D), the hydrodynamic flow is made to rotate, and a relatively
larger amount of liquid
components under processing are involved in the formed vortex cavitation field
than in the case of
the baif(e bodies 7, described before.
When using the bale body 7 shaped as a washer, perforated disk, or bushes
having conical
or toroidal internal wall surfaces as shown in Figures 4A - 4D, respectively,
the flow is throttled at
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the local flow constriction locations 8, which results in a local flow zone
featuring high transverse
velocity gradients. The baffle bodies 7 (Figures 4A, B, D) establish the
constriction locations 8 at
the center of the flow-through passage S, while the disk- shaped baffle body 7
(Figure 4B) establishes
the constrictions arranged parallel to one another in the same cross-section
of the passage 5.
The geometry of the baffle body 7 creates an accelerated flow of the mixture
of liquid
components, which promotes the development of a cavitation field having high
energy potential due
to the formation of the lower pressure zone within the local areas of high
transverse velocity
gradients around the sink flow streams. It is readily apparent that baffle
body 7 may possess a
variety of geometries to effect a high degree of mixing, emulsification,
homogenization and
dispersion of liquid components.
The hydrodynamic flow of a mixture of liquid components is fed to the device
by a pump.
Depending on a required result ofthe technological process, the flow may be
fed through the device
either once or repeatedly according to a recirculation pattern.
The desired quality of the obtained emulsion is evaluated by the volumetric
mean diameter
size of the disperse phase droplet or particle. The quality of emulsion is
effected by variances in the
constriction ratio, flow rate and the degree of cavitation.
Some specific examples of embodiments describing practical implementation of
the method
and carved out on pilot specimens of the device, according to the invention,
as presented in Figures
1 and 2, are described as follow:
EXAMPLE 1
A hydrodynamic flow of a mixture, comprised of 98 mass % water and 2 mass % of
vegetable oil, is fed at a velocity rate of 6 meters/second through inlet
opening 2 in the device, as
shown in Figure 1. A static pressure at the inlet of the flow-through passage
5 is 0.43 MPa, and, at
the outlet, 0.31 MPa. The ratio of the cross-sectional flow portion in the
local constriction 8 to the
cross-sectional flow portion of the flow-through passage 5 is 0.8. The flow
velocity at the Local
constriction 8 is 14 meters/second. The flow of components passes along the
flow-through passage
and flows in a conical shape in accordance with the cone-shaped baffle body 7.
After the baf~Te
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body 7, a cavitation zone is created with a degree of cavitation of 0.1. The
flow of processed _
components, flowing along the flow-through passage S and flowing along the
cone-shaped bathe
body 7, is subjected to the cavitation effect which initiates the progress of
a high degree of
emulsification. The quality of the obtained emulsion is evaluated by the
volumetric mean diameter
size of the disperse phase (oil) droplet or particle. In this example, the
volumetric mean diameter
size of the oil droplets is 22.4 microns.
EXAMPLE 2
A hydrodynamic flow of a mixture, comprised of 98 mass % water and 2 mass % of
vegetable oil, is fed at a velocity rate of 6 meters/second through inlet
opening 2 in the device, as
shown in Figure 1. A static pressure at the inlet of the flow-through passage
5 is 0.91 MPa, and, at
the outlet, 0.35 MPa. The ratio of the cross-sectional flow portion in the
local constriction 8 to the
cross-sectional flow portion of the flow-through passage S is 0.31. The flow
velocity at the local
constriction 8 is 36.2 meters/second. The flow of components passes along the
flow-through
passage S and flows in a conical shape in accordance with the cone-shaped
baffle body 7. After the
baffle body 7, a cavitation zone is created with a degree of cavitation of I
.7. The flow of processed
components, flowing along the flow-through passage S and flowing along the
cone-shaped baffle
body 7, is subjected to the cavitation effect which initiates the progress of
a high degree of
emulsification. The volumetric mean diameter size of the disperse phase (oil)
droplet or particle of
this example is S.7 microns.
EXAMPLE 3
A hydrodynamic flow of a mixture, comprised of 98 mass % water and 2 mass % of
vegetable oil, is fed at a velocity rate of 6 meters/second through inlet
opening 2 in the device, as
shown in Figure 1. A static pressure at the inlet of the flow-through passage
S is 7.95 MPa, and, at
the outlet, O.S6 MPa. The ratio of the cross-sectional flow portion in the
local constriction 8 to the
cross-sectional flow portion of the flow-through passage S is 0.10. The flow
velocity at the local
constriction 8 is I12.S meterslsecond. The flow of components passes along the
flow-through
passage S and flows in a conical shape in accordance with the cone-shaped
baffle body 7. After the
baffle body 7, a cavitation zone is created with a degree of cavitation of
4.2. The flow of processed
components, flowing along the flow-through passage S and flowing along the
cone-shaped bathe
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body 7, is subjected to the cavitation effect which initiates the progress of
a high degree of
emulsification. The volumetric mean diameter size of the disperse phase (oil)
droplet or particle of
this example is 2.8 microns.
EXAMPLE 4
A hydrodynamic flow of a mixture, comprised of 98 mass % vegetable oil and 2
mass % of
water, is fed at a velocity rate of 5.7 meters/second through inlet opening 2
in the device, as shown
in Figure 2. A static pressure at the inlet of the flow-through passage 5 is
2.67 MPa, and, at the
outlet, 0.42 MPa. The ratio of the cross-sectional flow portion in the local
constriction 8 to the
cross-sectional flow portion of the flow-through passage 5 is 0.2. The flow
velocity at the Iocal
constriction 8 is 45.6 meters/second. The flow of components passes through
the flow-through
passage 5 and the internal flow constriction 8 created by the Venturi tube-
shaped baffle body 7.
After the baffle body 7, a cavitation zone is created with a degree of
cavitation of 1.3. The flow of
components through the cavitation zone are effected by producing a high degree
of emulsification.
The quality of the obtained emulsion is evaluated by the volumetric mean
diameter size of the
disperse phase (water) droplet or particle. It has a measurement of 6.2
microns.
While the invention has been described in connection with specific embodiments
and
applications, no intention to restrict the invention to the examples shown is
contemplated. It will be
apparent to those skilled in the art that the above methods may incorporate
changes and
modifications without departing from the general scope of this invention. It
is intended to include
all such modifications and alterations in so far as they come within the scope
of the appended claims
or the equivalents thereof.
Having thus described the invention, it is now claimed:
