U.S. patent number 3,731,800 [Application Number 05/093,038] was granted by the patent office on 1973-05-08 for counter-current centrifugal device and use.
This patent grant is currently assigned to Polaroid Corporation. Invention is credited to William J. Timson.
United States Patent |
3,731,800 |
Timson |
* May 8, 1973 |
COUNTER-CURRENT CENTRIFUGAL DEVICE AND USE
Abstract
An apparatus which includes a housing defining a chamber
therein, at least two rotatable plates in spaced, face-to-face
relationship defining a channel therebetween; at least one inlet
for feeding fluid material into the channel; a plurality of spaced
outlets for removing the processed material, at least one of which
is spaced radially from the center of rotation of the plates, and
means for interrupting the laminar flow in said channel, preferably
by means of a zig-zag configuration in at least a portion of the
surface of said plates, more preferably adjacent the periphery. A
counter-current flow pattern is provided by introducing a
displacement fluid into the channel. Preferably, the plates are
mounted on the same shaft and the inlet for material to be
processed is through one plate adjacent to the shaft, and one
outlet is through the other plate adjacent to the shaft. The
apparatus can be used as a classifier, concentrator, or for washing
materials of different density or the same density and different
mass.
Inventors: |
Timson; William J. (Belmont,
MA) |
Assignee: |
Polaroid Corporation
(Cambridge, MA)
|
[*] Notice: |
The portion of the term of this patent
subsequent to March 3, 1987 has been disclaimed. |
Family
ID: |
22236536 |
Appl.
No.: |
05/093,038 |
Filed: |
November 27, 1970 |
Current U.S.
Class: |
209/210; 241/251;
209/155; 209/724; 366/294 |
Current CPC
Class: |
B04B
5/12 (20130101) |
Current International
Class: |
B04B
5/00 (20060101); B04B 5/12 (20060101); B04b
005/12 () |
Field of
Search: |
;209/211,144,145,148
;210/512 ;55/17 ;233/15 ;241/188A,251,255 ;252/359R,359A,359C,360
;259/105,6 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Miles; Tim R.
Assistant Examiner: Hill; Ralph J.
Claims
What is claimed is:
1. An apparatus which comprises:
a housing defining a chamber therein;
at least a first and second plate in opposed spaced
relationship;
said plates defining a channel therebetween said channel being
disposed in a radial direction;
means for rotating said plates;
means for introducing a first fluid material into said channel;
a plurality of spaced outlet means for removing said fluid
material, at least one of said outlet means being spaced radially
from one other of said outlet means;
means for interrupting radial laminar flow of said fluid material
in said channel; and
a second means for introducing fluid material.
2. The apparatus as defined in claim 1 wherein said interruption
means comprises a zig-zag configuration in said plates.
3. The apparatus as defined in claim 1 wherein said interruption
means comprises baffles on said plates.
4. The apparatus as defined in claim 1 wherein said first and
second plates are mounted on first and second rotatable shafts
respectively.
5. The apparatus as defined in claim 1 wherein said means for
rotating said plates comprise a single shaft.
6. The apparatus as defined in claim 4 wherein said means for
introducing said first fluid material and at least one of said
outlet means for removing material are associated with said
rotatable shafts.
7. The apparatus as defined in claim 1 which includes baffle means
associated with said means for introducing said first fluid
material to provide distribution of said material in said
channel.
8. The apparatus as defined in claim 1 wherein at least one of said
outlet means is located in the periphery of one of said plates.
9. The apparatus as defined in claim 8 wherein said second means
for introducing a fluid material is spaced radially from the center
of rotation of said plates.
10. The apparatus as defined in claim 9 wherein said second means
for introducing a fluid material is spaced radially from said first
means for introducing a fluid material.
11. The apparatus as defined in claim 10 wherein said first means
for introducing a fluid material is associated with said first
plate and said second means for introducing a fluid material is
associated with said second plate.
12. The process for the separation of materials into fractions with
respect to density or mass which comprise the steps of introducing
a first fluid material containing elements of differing density or
mass into a channel intermediate a first and second plate in
face-to-face spaced relationship, rotating said plates to provide a
centrifugal force to said material in said channel, introducing a
second fluid into said channel to provide a counter-current flow
with respect to said centrifugal force providing a radial laminar
flow of fluid in said channel, interrupting the radial laminar flow
in said channel, thereby separating said elements as a function of
their density of mass, and collecting at least one fraction of said
first material so separated.
13. The process as defined in claim 12 wherein a lower density or
mass fraction is collected adjacent the center of rotation of said
plates and a higher density or mass fraction is collected at a
location spaced radially from said center of rotation.
14. The process as defined in claim 12 wherein said first material
is photographic silver halide dispersed in a polymeric matrix.
15. The process as defined in claim 13 wherein the fluid for
providing said counter-current flow is water.
Description
BACKGROUND OF THE INVENTION
This invention relates to an improved counter-current centrifugal
exchange device and to the method of separating materials of
different densities or materials of the same density and different
mass.
U. S. Pat. No. 3,498,454 is directed to a particularly preferred
counter-current centrifugal exchange device for separating
materials of different densities or materials of the same density
and different mass. The device disclosed therein includes a housing
defining a changer therein, at least two rotatable plates in
spaced, face-to-face relationship defining a channel therebetween,
means for introducing fluid material into the channel and outlets,
preferably spaced radially from the center of rotation of the
plates, preferably at the periphery of the plates or in the wall of
the housing. In operation, a fluid containing, e.g., material of
different particle size, is introduced between the rotating plates
which set up a centrifugal force in the channel driving the
particles toward the periphery of the plates. Simultaneously, a
counter-current flow is established by the introduction of fluid
into the housing from a point spaced apart from the center of
rotation which serves to carry the smaller particles back towards
the center of the plates, thus providing the desired separation of
the different particle sizes.
However, when the rotatable plates employed are relatively flat, a
radial laminar flow pattern is established in the channel wherein
the material of relatively smaller density of mass moves toward the
periphery of the plates substantially adjacent to the surfaces of
the plates in a low velocity fluid area, thus reducing to some
degree the efficiency of the system by, in effect, removing some of
the relatively less dense material from the full effect of the
counter-current flow.
A device has not been found which provides a more efficient
separation operation.
SUMMARY OF THE INVENTION
The novel apparatus of the present invention comprises a housing
defining a chamber therein which contains at least a first and
second rotatable plate defining a channel therein; means for
introducing fluid material into said channel; means for removing
processed material; means for providing a counter-current flow in
said channel; and means for interrupting the radial laminar flow in
said channel. Preferred means for interrupting said flow comprise
plates defining a tortuous path therebetween.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal section through the novel apparatus
illustrating the general construction thereof;
FIG. 2 is a longitudinal section illustrating an alternative
embodiment of the novel apparatus of the present invention;
FIG. 3 is a longitudinal section illustrating still another
embodiment of the novel apparatus of the present invention; and
FIG. 4 is a longitudinal section illustrating still another
alternative embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The novel apparatus of the present invention comprises a housing
defining a chamber which contains at least a first and second
rotatable plate or disc mounted therein in face-to-face
relationship and defining a tortuous channel therebetween. The
plates are preferably mounted on shafts. Inlet means are provided
for introducing the material to be processed into the channel.
Outlets for removing processed material are provided with at least
one outlet spaced radially from the center of rotation of the
plates. Preferably, material to be processed is introduced into the
space between the plates near the shaft, that is, near the center
of rotation of the plates. An outlet for the processed material of
lower density or mass is also preferably located in proximity to
one of the shafts. Baffle means, or distribution means are
optionally employed, to aid the distribution or the prevent a
direct flow of the material to be processed through the housing
from the inlet to the outlet without being processed by the
centrifugal forces set up by the rotation of the plates.
Counter-current force is applied to the material in the housing by
the introduction of a fluid from a point spaced apart from the
center of rotation of the plates. An outlet for the material of
greater density or mass is located spaced apart from the center of
rotation of the plates since this material will be forced towards
the periphery of the plates and toward the housing walls by the
centrifugal force exerted by the rotating plates. The inlet for a
displacement fluid or washing fluid to provide the counter-current
flow is preferably located in one of the plates adjacent the
periphery. In still another alternative embodiment, baffles are
provided on the housing walls to prevent channeling, to provide
uniform turbulent flow in the housing and to prevent rotation of
the fluid. If desired, filtering means are employed in conjunction
with the outlets or inlets to provide still further classification
of materials.
In employing the novel apparatus of the present invention, the
fluid material to be processed is introduced into the housing into
the space or channel between the plates. The inlet, which is
located close to, or preferably through a hollow shaft, i.e., at or
near the center of rotation, introduces the material into a channel
formed by the rotation of the plates where it is subject to the
centrifugal and counter-current forces. Also in close proximity to
a shaft is an outlet for the material of lower density or size. The
channel is preferably baffled to prevent the direct passage of the
material through the housing without undergoing the action of the
centrifugal force and counter-current treatment in the channel
between the plates.
If desired, the devices are operated in series or in various
combinations, for example, with the exit stream from one device
feeding into the inlet of another to provide any combination of
separation, washing, or classification operations.
The action of the rotating plates sets up a centrifugal force which
drives the materials of greater density or mass toward the
periphery of the plates and the walls of the housing while the
material of lesser density or mass move, as a result of the
counter-current flow pattern provided by the introduction of a
fluid into the chamber from a point spaced apart from the center of
rotation, toward the center of the plates, i.e., the center of
rotation where the centrifugal force is minimal. The less dense
material or smaller particle size material, as stated above, is
preferably drawn off from a point near the shaft or through the
shaft, while the material of greater density is drawn off from an
outlet in the plates adjacent to the periphery. Preferably, an
inlet is located adjacent to the periphery of one of the plates to
provide for the insertion of displacement or washing fluid into the
housing, which provides counter-current action to drive the
material of lesser density or mass towards the center of
rotation.
By interrupting the radial laminar flow in the channel of the
material to be separated, the material moving toward the periphery
of the plates under the influence of the centrifugal force is
thrown into more intimate contact with the counter-current action
and away from proximity to the walls of the channels, i.e., the
faces of the plates, whereby the counter-current flow will act upon
the material of relatively less density or mass carrying it towards
the center of rotation. The material of relatively large density or
mass, of course, will be substantially unaffected by the
counter-current action and will continue toward the periphery of
the plates under the influence of centrifugal force.
It is preferred that the interruption in the radial laminar flow be
accomplished by providing at least a portion of the channel with a
tortuous path which will divert the material of less density or
mass near the walls into the center of the higher velocity flow
region of the laminar flow profile from the low velocity flow
region, towards the center of channel under the influence of
counter-currents thereby obtaining greater efficiency of the
counter-current action.
The tortuous path is provided by modifying at least a portion of
the plates, preferably adjacent the periphery, with baffles or
undulations, i.e., successive raised and depressed areas which will
direct the material of lesser density or mass away from its low
fluid velocity path into more intimate contact with the higher
velocity counter-current flow. More preferably, at least a portion
of the plates contain a zig-zag configuration.
It is only necessary that a relatively small portion of the plates
be modified in order to disrupt the radial laminar flow and obtain
the increased efficiency. However, the greater the degree of
modification, the greater the disruption or prevention the escape
of the material of lesser density or mass along the plate walls in
the laminar flow pattern and the resultant increase in efficiency
in separation.
The degree of rotation of the plates is selected with regard to the
speed with which the materials are to be separated and the
composition of the material introduced into the apparatus. The
plates may be rotated in the same or in opposite directions;
preferably the rotation is in the same direction. In a particularly
preferred embodiment, the plates are rotated at the same speed in
the same direction. If the plates are rotating in the opposite
direction, a differential in the rotational speed is necessary to
provide the centrifugal force.
As stated above, the outlet for the material of greater density or
mass is preferably located in the periphery of one or more of the
plates or in the wall of the housing; that is, in the area of the
greater concentration of material driven outward by the centrifugal
force. In an alternative embodiment, a hollow or channeled plate is
employed with ports located at varying spaced positions on the face
of said plate whereby material of varying density or particle size
fractions can be removed from the apparatus. In still another
embodiment, a series of ports of different cross sections can be
located in the periphery of the plate.
While the face of the plates is preferably flat, the plates or
portions thereof may be parabolic in configuration.
In employing plates with a series of ports on the face thereof for
the removal of various fractions, sections of the face of the
plates are preferably parabolic to provide a predetermined balance
of flow rate to centrifugal force at various points along the face
of the plate so that material of a specific density or mass would
stop its outward movement at a pre-selected point along the face of
the plate and remain suspended at this particular point, thereby
permitting the removal of this particular fraction through the
aforementioned ports.
The spacing of the plates, i.e., the width of the channel, is not
critical and can range from the size of the largest particle of
material to be processed to a spacing many multiples of the
particle size. The selection of the particular spacing is,
therefore, determined by the material to be processed and the
desired speed with which the separation or other procedure is
accomplished. The length of the channel defined by the plates
(radices of the plate) is not critical.
In one example, an apparatus of the present invention having a
channel 21/2 inches long with a 1/2 inch zig-zag configuration
adjacent the periphery of the plates and a spacing between the
plates of about 0.1 centimeter was able to separate particulate
matter in a fluid to an accuracy of .+-. 0.1 micron in diameter,
where the particle size ranged from 0.4 to 5.0 microns in the
material introduced into the channel.
Referring now to the drawings, FIG. 1 shows housing 10 having
mounted therein plates 11 and 12 mounted on rotatable shafts 13 and
14; said plates being spaced apart and defining tortuous channel 20
therebetween by virtue of the zig-zag configuration 30 located
adjacent the periphery of the plates 11 and 12. The material to be
processed is introduced into the apparatus through conduit 15 and
inlet 16 and distributed by baffle 27 into channel 20. The
centrifugal and counter-current forces exerted on the material in
channel 20 directs the material of greater density or mass away
from the center of the plates and toward the outer walls of the
housing, from which it is removed from the apparatus through outlet
21. Radial laminar flow in channel 20 is interrupted when the
material to be processed passes zig-zag 30. Inlet 22 in the housing
wall provides means for introducing a washing or displacement fluid
into the housing to provide counter-current forces and to also
facilitate the removal of the higher density material through
outlet 21. The lower density or mass material passes through
conduit 18 in shaft 14 and is removed from the apparatus through
outlet 19.
FIG. 2 illustrates an alternative embodiment showing housing 10
having mounted therein plates 11 and 12 mounted on rotatable shafts
13 and 14; said plates being spaced apart and defining tortuous
channel 20 therebetween by virtue of the baffles 35 located
adjacent the periphery of the plates 11 and 12. The material to be
processed is introduced into the apparatus through conduit 15 and
inlet 16 and distributed by baffle 27 into channel 20. The
centrifugal and counter-current forces exerted on the material in
channel 20 directs the material of greater density or mass away
from the center of the plates and toward the periphery of the
plates, from which it is removed from the apparatus through outlet
36 through conduit 37 and outlet 38. Radial laminar flow in channel
20 is interrupted when the material to be processed passes baffles
35. Inlet 39 in shaft 13 provides means for introducing a washing
or displacement fluid into the housing through conduit 41 and inlet
42 to provide counter-current force and to also facilitate the
removal of the higher density material through outlet 36. The lower
density or mass material passes through conduit 18 in shaft 14 and
is removed from the apparatus through outlet 19.
FIG. 3 illustrates an apparatus similar in construction to that
shown in FIG. 1 except that plates 11 and 12 are mounted on a
single shaft 14. The material to be processed enters the channel
through ports 50 and lower density material exits into conduit 18
through ports 51 and shaft 14.
FIG. 4 is still another alternative embodiment of the present
invention similar in construction and operation to the apparatus
shown in FIG. 2 except that the inlet for displacement fluid 39 is
located in shaft 14 and outlet 38 is located in shaft 13.
In the above indicated figures, means for rotating the shafts
comprise electric motors M.
The novel apparatus of the present invention may be employed for a
variety of processing applications. As described above, it may be
employed for separating materials of different densities or masses.
The material to be processed is introduced into the channel between
the plates at a point near the center of the plate and a first
outlet means is provided near the center of the plate and a first
outlet means is provided near the center of the plate or through
the shaft for the material of lesser density or mass and a second
outlet spaced away from the center of rotation of the plates,
preferably in the periphery of the plates or in the wall of the
housing, provides for the removal of material of greater density or
mass which moves away from the center of rotation as a result of
the centrifugal action set up by the rotation of the plates.
Counter-current action is provided by the displacement fluid, such
as wash water, which is introduced into the housing from a point in
the wall of the housing on the periphery of the plates.
In alternative embodiments, various combinations of open and closed
inlets and outlets can be employed to provide a variety of effects.
A gross separation of materials can be achieved by closing the
inlet for the displacement fluid and also closing the outlet spaced
apart from the center of rotation to provide removal of smaller
particles and retension of the larger particles in the
apparatus.
The apparatus is also employed as a concentrator wherein only the
liquid is removed. For example, the novel apparatus of the present
invention has especial utility in separating insoluble salt in
fluids by removal of the liquid alone while the salts are
concentrated within the housing. Material is fed at a relatively
slow rate so that all the particulate material will move away from
the outlet in the shaft. When the concentration of the particulate
salt reaches a point wherein the efficiency of the apparatus is
substantially decreased, a port in the wall of the housing may be
opened to bleed-off the relatively high concentration of the
particulate matter.
In still another embodiment, the novel apparatus may be employed as
an emulsifier by the introduction of material to be emulsified into
the channel and then closing all of the inlet and outlet ports in
the apparatus. The transverse shear set up by the rotating plates
would provide the emulsification action. In this matter, the novel
apparatus can also be employed as a colloid mill. As an
illustrative example, the rotation of one plate at 5,000 rpm and
the second plate at 25,000 rpm will provide a colloid having a
particle of less than micron size.
The novel apparatus of the present invention possess great utility
for a broad spectrum of counter-current mass transfer operations
involving (a) solid-liquid systems, (b) liquid-liquid systems and
(c) gas-liquid systems and combinations thereof.
The apparatus can process materials of different densities, or the
materials of the same density and different masses. Unlike prior
art devices, the apparatus processes sticky and hard to handle
materials with ease since there are no small passages or
perforations in bands which can plug or otherwise become fouled.
The combined centrifugal and counter-current action provides a
cleaning operation during the processing.
The novel apparatus of the present invention is particularly useful
in processing silver-halide-gelatin photographic emulsions. The
apparatus is employed to perform a variety of processing operations
on the emulsion. For example, efficient washing of flocculated
emulsions may be achieved; emulsion grains may be classified into
desired distribution ranges; silver halide grains may be
concentrated into a smaller volume of fluid and the continuous
phase of an emulsion may be displaced by a second continuous
phase.
As illustrative of the novel process of the present invention, the
classification of a photographic emulsion into the desired particle
size range is described. The emulsion to be of is introduced into
the channel between the rotating plates. The centrifugal force
drives the larger, coarser particle fraction of the emulsion toward
the outer periphery of the plate where it leaves the apparatus by
an appropriate exit passage located near the periphery of the plate
either in the wall of the housing or in the plate itself. The
removal of the coarser particle size material is facilitated by the
introduction of distilled water as a wash liquid into the area of
the greater concentration of the coarse material. The finer
particle size emulsion material is displaced toward the center od
the rotating discs by the counter-current flow and is removed from
the rotation.
The following non-limiting example illustrates the employment of
the novel apparatus of the present invention to separate a material
according to particle size.
EXAMPLE
Employing an apparatus similar to that set forth in FIG. 2, a
conventional photographic silver halide gelatin emulsion, having a
particle size distribution from about 0.4 to 5.0 microns (as
determined by Histogram), was introduced into the channel between
two plates of 5 inch O.D. The length of the baffle portion of the
channel was one-half inch with the distance between the baffles on
opposite plates one thirty-second inch. The two plates were
rotating in the same direction at a speed of about 2,400 rpm, The
the material passing through the small particle outlet 18 in plate
12 was less than 1 micron in diameter. Particles having a diameter
of one to two microns were removed continuously through outlet 36
in plate 11. Materials greater than 2 microns in diameter remained
in the apparatus and were removed from time to time to prevent
excessive build-up of the larger particle size in the
apparatus.
The novel apparatus of the present invention is also of particular
value in processing photographic silver halide-gelatin emulsions,
in that the present invention provides a method by which
unflocculated grains can be washed. In the past, it was necessary
to carry out the washing step for the removal of soluble salts,
such as potassium nitrate, which are formed during the emulsion
preparation, by treating a flocculated emulsion or noodling the
emulsion. By means of the present invention, however, the
individual grains can now be washed, thereby providing greater
efficiency of salt removal, and emulsions with greater uniformity
or particle size which heretofore has not been obtainable on a
commercial scale.
By employing the novel apparatus of the present invention, it is
also possible to prepare a silver halide-gelatin emulsion and then
replace the gelatin phase of the emulsion with another suspending
polymer, such as polyvinyl alcohol. In such an exchange operation,
the silver halide gelatin emulsion would be introduced into the
channel between the rotating plates while at the same time
polyvinyl alcohol would be introduced into the apparatus through an
inlet in the housing. The centrifugal force and counter-current
forces set up would be such that the gelatin would move to the
center of the plates and be removed through the outlet in the shaft
while the silver halide particulate matter would be driven toward
the periphery of the rotating plates. Outlets for the particulate
matter would be closed thereby retaining it in the housing during
the exchange of the gelatin for the polyvinyl alcohol.
* * * * *