U.S. patent application number 14/752420 was filed with the patent office on 2016-12-29 for multi-disk spinning disk assembly for atomization and encapsulation.
This patent application is currently assigned to SOUTHWEST RESEARCH INSTITUTE. The applicant listed for this patent is Darren E. Barlow, Jeffrey N. Harris, Mark R. Heistand, George T. Lamberson, Albert M. Zwiener. Invention is credited to Darren E. Barlow, Jeffrey N. Harris, Mark R. Heistand, George T. Lamberson, Albert M. Zwiener.
Application Number | 20160375420 14/752420 |
Document ID | / |
Family ID | 57601880 |
Filed Date | 2016-12-29 |
United States Patent
Application |
20160375420 |
Kind Code |
A1 |
Zwiener; Albert M. ; et
al. |
December 29, 2016 |
Multi-Disk Spinning Disk Assembly For Atomization and
Encapsulation
Abstract
A multi-disk spinning disk assembly for atomization and
encapsulation applications. A number of disks 17a and spacers (33,
40) are stacked to form a disk stack 17 having a feed well 31 in
the center core of the stack. The fluid to be atomized or
encapsulated is delivered to the feed well 31. The fluid then flows
into spacer channels (37, 41) within or on the surface of the
spacers. The channels (37, 41) communicate the fluid toward the
outer edges of the disks 17a. The disk surface past the spacers
(33, 40) can have various configurations, such as teeth, weirs, or
a bigger or smaller diameter, as desired for particular atomization
or encapsulation characteristics.
Inventors: |
Zwiener; Albert M.;
(Helotes, TX) ; Barlow; Darren E.; (Floresville,
TX) ; Heistand; Mark R.; (San Antonio, TX) ;
Lamberson; George T.; (San Antonio, TX) ; Harris;
Jeffrey N.; (San Antonio, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zwiener; Albert M.
Barlow; Darren E.
Heistand; Mark R.
Lamberson; George T.
Harris; Jeffrey N. |
Helotes
Floresville
San Antonio
San Antonio
San Antonio |
TX
TX
TX
TX
TX |
US
US
US
US
US |
|
|
Assignee: |
SOUTHWEST RESEARCH
INSTITUTE
San Antonio
TX
|
Family ID: |
57601880 |
Appl. No.: |
14/752420 |
Filed: |
June 26, 2015 |
Current U.S.
Class: |
425/5 |
Current CPC
Class: |
B05B 3/1064 20130101;
B01J 13/04 20130101; B05B 3/1007 20130101 |
International
Class: |
B01J 13/04 20060101
B01J013/04 |
Claims
1. A multi-disk spinning disk assembly for atomizing or
encapsulating feed stock fluids during rotation of the assembly,
comprising: a disk stack, comprising a number of annular disks
arranged one atop the other, each disk having a center opening; an
annular spacer associated with each disk, each spacer having a
center opening and having a radius the same as or smaller than that
of each disk; wherein the spacers are arranged between disks such
that their center openings and the center openings of the disks
form an inner well within the disk stack; and wherein each spacer
has each plurality of channels, each channel operable to provide
fluid communication in an uninterrupted path, the path extending
from the inner well to the outer periphery of the spacer, and the
path being parallel to the plane of the disks or sloped in a single
direction.
2. The assembly of claim 1, wherein the disks have teeth around
their perimeters.
3. The assembly of claim 1, wherein the channels of each spacer
have a spoke configuration.
4. The assembly of claim 1, wherein the channels each have the same
dimensions along their length.
5. (canceled)
6. The assembly of claim 1, wherein the channels are slanted
upward.
7. The assembly of claim 1, wherein the channels deliver fluid
directly onto the underside or topside of a disk.
8.
9.
10. (canceled)
11.
12.
13. The assembly of claim 1, further comprising an inner cone
extending upwardly from the center of the feed well, and having a
cone shaped upper surface for distributing fluid entering the feed
well.
14. The assembly of claim 1, wherein each channel has a varying
height along its length.
15. The assembly of claim 1, wherein all disks are uniform in size
and shape.
16. The assembly of claim 1, wherein each spacer is an integral
portion of a disk.
17. The assembly of claim 1, wherein the spacers are separate
pieces installed between disks.
18. The assembly of claim 1, further comprising a weir around the
periphery of each disk.
Description
BACKGROUND OF THE INVENTION
[0001] Micro-encapsulation is a process in which tiny particles or
droplets are surrounded by a coating to result in tiny capsules.
Micro-encapsulation may be used to encapsulate food ingredients,
enzymes, cells or a vast number of other materials on a micro
scale.
[0002] There are a number of different micro-encapsulation
techniques. These can be broadly categorized as either physical or
chemical processes. One type of physical process is referred to as
"spinning disk" encapsulation.
[0003] The spinning disk encapsulation process uses a disk that
rotates at high speeds, driven by a motor or other drive equipment.
A spray is created by passing a fluid across or through the
rotating disk. Centrifugal energy translates the fluid into a fine
horizontal droplet spray.
[0004] The spinning disk process may be used for other types of
atomization in addition to encapsulation. Numerous improvements to
spinning disk atomizers (and encapsulators) have been made. A
drawback of single disk atomizers is that the amount of liquid
passing through the flow area is small. To obtain higher
throughput, one improvement has been the use of multi-layered
disks.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] A more complete understanding of the present embodiments and
advantages thereof may be acquired by referring to the following
description taken in conjunction with the accompanying drawings, in
which like reference numbers indicate like features, and
wherein:
[0006] FIG. 1 illustrates an example of a spinning disk system.
[0007] FIG. 2 is a cross sectional view of one embodiment of a
spinning disk assembly.
[0008] FIG. 3 illustrates one embodiment of the disk stack of FIG.
2.
[0009] FIG. 3A is a top plan view of a spacer and channels from the
disk stack of FIG. 3.
[0010] FIG. 4 is an isometric view of a portion of another
embodiment of a disk stack.
[0011] FIG. 5 is a top plan view along section A-A of FIG. 2.
[0012] FIG. 6 is a detailed view of spacers and channels.
[0013] FIG. 7 illustrates an alternative view of spacers and
channels.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The following description is directed to improved spinning
disk equipment and methods for atomization and encapsulation.
Spinning disks used for these applications are sometimes more
generally referred to as a type of centrifugal atomizer.
[0015] FIG. 1 depicts an example of a spinning disk system 100,
which has a multi-disk spinning disk assembly 105. The system has a
"bottom-mount" configuration, that is, the drive shaft that enables
the spinning motion is located beneath the disks. In "top mount"
systems, the disk assembly 105 may be driven from the top, such as
in conventional rotary atomizers used for spray drying and
prilling.
[0016] Spinning disk assembly 105 is coupled to a drive motor 115
by connecting rod 120. As an alternative to drive motor 115 mounted
inside chamber 160, motor 115 may be replaced by a bearing
assembly, which is driven by a motor located outside chamber 160
and a flexible drive shaft routed through motor mounting frame
125.
[0017] Various embodiments of assembly 105 are described herein,
and it should be understood that these embodiments could be used in
either a bottom-mount or top-mount system, and with various drive
motor configurations.
[0018] Spinning disk assembly 105 is typically substantially
cylindrical. A typical range of diameter sizes of spinning disk
assembly 105 is between about 10 mm and about 300 mm. As will be
described in greater detail below, spinning disk assembly 105
comprises a stack of disks separated by spacers. The spacers have
special channels to receive feed fluid and to achieve a desired
flow onto the disk peripheries.
[0019] Drive motor 115 is supported within spinning disk apparatus
100 by a motor mounting frame 125. Motor 115, which may be driven
hydraulically, pneumatically or electrically, is operable to rotate
spinning disk assembly 105 via connecting rod 120. Motor 115
includes a speed control system operable to rotate spinning disk
assembly 105 at various speeds.
[0020] Spinning disk apparatus 100 also includes a fluid feed
delivery system 130, which typically has one or more feed
containers 135, one or more pumps 140, and a fluid delivery system
145. As an alternative to a pump, fluid may be fed to the disk
assembly 105 via pressurization of feed container 135 and/or by
gravity. Fluid delivery system 145 typically comprises a tube
through which the materials to be processed by disk apparatus 100
are introduced onto spinning disk assembly 105. Feed container 135
may have an agitation means 150, such as a stirrer, to facilitate
mixing of materials.
[0021] For use with feeds that are molten or thermally gellable,
proximate spinning disk assembly 105 is a heater 155, which may be
in contact with or integral to spinning disk assembly 105 as shown,
or alternatively, located in close, non-contacting proximity
thereto. Heater 155 may be located above and/or below disk assembly
105. Suitable heaters 155 include, but are not limited to,
capacitance heaters, impedance heaters, liquid circulation heaters,
hot air guns, and the like.
[0022] Spinning disk apparatus 100 includes a process chamber 160,
which seals a space surrounding spinning disk assembly 105. Chamber
160 is typically connected to a gas source (not shown) to maintain
the environment within process chamber 160 under a controlled
atmosphere. Process chamber 160 may optionally include a vacuum
source (not shown) adapted to control the pressure within process
chamber 160. The gaseous environment maintained within process
chamber 160 may comprise air or some inert gas or gases which are
supplied to the process chamber 160 by a gas feed means (not
shown). Process chamber 160 may comprise internal surfaces designed
for characteristics such as thermal control or thermal
conductivity.
[0023] Spinning disk apparatus 100 can further include a product
collection system 165, as well as an evacuation system 170, which
can include one or more filters 175, one or more blowers 180, one
or more air flow control valves 185, and one or more vents 190.
[0024] FIG. 2 is a cross sectional view of one embodiment of
spinning disk assembly 105, which is configured for a top-mount
system spinning disk system. An insulated housing 20 is generally
cylindrical in shape. A hollow shaft 14 delivers the liquid feed
material to the hollow core of housing 20, and provides a drive
connection for the motor. Shaft 14 and housing 20 comprise an
assembly such that they rotate at the same speed.
[0025] Housing 20 supports the top and bottom of a stack of disks
17. Housing 20 is typically closed at its ends, other than an
opening for fluid intake, and is typically insulated.
[0026] Disk stack 17 comprises a number of disks 17a, which are
uniform in shape and size. Each disk 17a has an annular shape, that
is, it is a flat round disk with an inner opening. The disks 17a
are stacked one atop the other such that the inner openings are
aligned and form an inner cylindrical feed well 31 within a core of
housing 20.
[0027] In other embodiments, the disks 17a need not necessarily be
uniform in shape or size. For example the disk stack 17 might
comprise a stack of disks having tapering diameters.
[0028] Spacers 16 between the disks have channels, not explicitly
shown in FIG. 2, but described in detail below. As explained below,
these spacers 16 and their channels provide communication of fluid
from the feed well 31 to the peripheries of the disks 17a. As well
as separating the disks 17a and providing fluid communication from
feed well 31 toward the exterior edges of disk stack 17, spacers 16
provide mechanical support and integrity to the disk stack 17.
[0029] As further explained below, a "spacer" may be an integral
portion of a disk, or equivalently, a "spacer" may be a separate
piece of material inserted or otherwise installed between disks. In
various embodiments, disks and spacers may be of the same or
different materials. The disk stack can be a machined assembly.
Disks can be made from thin foils, as thin as 0.03 inches or less.
Or, the entire disk stack 17 could be a composite assembly made by
stereo lithography or similar rapid prototyping techniques.
[0030] Feed shaft 14 delivers fluid into feed well 31 and rotates
the disk assembly 105. In the embodiment of FIG. 2, the feed well
31 has an inner cone 21 extending upward from the bottom center of
the feed well 31. The cone 21 has a sloped (conical) upper surface.
The fluid drops onto the sloped surface of cone 21. This conical
top surface of feed cone 21 provides tangential distribution of
liquid before it spills into feed well 31.
[0031] Optionally, the inner diameter of feed well 31 may be
slightly enlarged just below the cone-shaped top of feed cone 21,
forming a shelf 22 at the top of the disk stack 17. This allows
liquid to spill from cone 21 to the top of the disk stack 17.
Because disk assembly 105 is rotating, this distribution of fluid
onto the top of the disk stack 17 at shelf 22 is tangential. If
desired a small lip 22a may be added to improve fluid distribution
at low speeds.
[0032] In other embodiments, such as the embodiment of FIG. 3, feed
cone 21 and/or shelf 22 may be omitted and the fluid may drop
directly into feed well 31. The rotation of the spinning disk
assembly 105 causes the fluid to spread down and across the surface
of the feed well.
[0033] From feed well 31, fluid enters channels in the spacers 16,
which distribute fluid toward the periphery of the disks. After
exiting the channels, fluid flows at least some distance on the
flat surface of the disks. The flat surface of each disk between
the channels and the edges of the disk provides distance for liquid
discharging from the channels to acquiesce to the film thickness
driven by fluid properties, flow rate, and disk speed. Empirically
validated equations have been developed to represent the
theoretical steady state film thickness of fully developed laminar
flow on a spinning disk.
[0034] FIG. 3 illustrates one embodiment of the disk stack 17 of
FIG. 2. In the example of FIG. 3, disk stack 17 has five disks
17a.
[0035] Housing 20 has a top plate 32 and bottom flange 33. These
define air gaps at the top and bottom of disk stack 17 for
insulation purposes. These spaces could also be filled with
insulating material. A feed well 31 receives fluid flow into its
top end via feed shaft 14, and is configured as a hollow
cylinder.
[0036] Each disk 17a has an annular spacer 33 that separates that
disk 17a from the disk above. Each spacer 33 has a center opening
that coincides with the openings of the disks 17a. However, the
diameters of the spacers 33 are smaller than that of the disks.
Thus, the diameters of spacers 33 do not extend the entire diameter
of the disk stack 17. In the example of FIG. 3, the radius of the
spacers 33 is about one-third to one-half the radius of the
disks.
[0037] Each spacer 33 has at least one channel 37 that extends from
the center opening of that spacer outward to the perimeter of that
spacer 33. Each channel 37 provides fluid communication from the
feed well 31, via an inlet opening of the channel 37, to the
perimeter of the spacer, via an outlet opening of the channel 37.
In the example of FIG. 3, the spacer channels 37 are substantially
horizontal, relative to the horizontal plane of the disks.
[0038] The space between disks 17a past spacers 33 forms a
circumferential groove 38 near, but not at, the outer perimeter of
the disk 17a. A peripheral weir 39 around the periphery of each
disk 17a interrupts groove 38, but allows passage of fluid outward
from the outer edge of the disk, to further distribute fluid
tangentially.
[0039] Referring to both FIGS. 2 and 3, in operation, as disk stack
assembly 105 rotates, feed shaft 25 delivers fluid to the feed well
31, which distributes liquid tangentially around its inner surface.
The spacer channels 37 open into the sides of the feed well 31. The
spacer channels 37 communicate fluid to groove 38, where it is
distributed to the periphery of the disks.
[0040] FIG. 3A is a top plan view of a spacer 33 and an example of
its channels 37. Here, channels 37 are "spoke" type channels,
extending horizontally and radially across or through spacer 33. As
indicated by the arrows, fluid flows from feed well 31 radially
outward through channels 37. The fluid then spills into groove 38
where it distributes around the outer circumference of the disk and
is expelled from the disk perimeter.
[0041] In the example of FIG. 3A, channels 37 are the same geometry
along their length; they are typically round but may have any
closed geometry. They are generally horizontal, in a plane parallel
to that of the disks. However, in other embodiments, the channels
could be of varying geometry along their length, such as by
becoming narrower or wider toward the end away from the feed well
31. Also, in other embodiments, the channels could be slanted up or
down, relative to the plane of the disks, within their associated
spacer. Further, the channels may change in shape and/or aspect
ratio, for example, by becoming taller or shorter along their
length.
[0042] The text below accompanying FIGS. 4-6 describes an
embodiment of a disk stack 17 having spacers with channels, similar
to FIG. 3. However, in FIGS. 4-6, the channels are of varying
dimensions along their length, in a geometry designed for optimal
fluid distribution.
[0043] FIG. 4 is an isometric view of a portion of another
embodiment of a multi-disk stack, such as stack 17. The view of
FIG. 4 is sectioned at the bottom of a feed well 31. Feed well 31
may be configured like the feed well 31 of either FIG. 2 or 3. An
example of a suitable thickness of each disk 17a is 0.03''
thick.
[0044] Disk stack 17 has spacers 40, one spacer 40 between each
pair of adjacent disks 17a. The spacers 40 extend radially outward
from feed well 31 for a portion of the radial distance of the
disks. In the example of FIG. 4, each spacer 40 extends radially
outward about half the radial length of the disks.
[0045] Each spacer 40 has a number of channels 41 that provide
liquid flow from feed well 31, past the outer edge of the spacer,
to the underside of the disk above the spacer 17a. In other
embodiments, the liquid flow could be toward the upper surface of
the disk below the spacer.
[0046] The arrows indicate the path of the liquid feed material. It
is to be understood that the spinning disk assembly 105 is
rotating. As indicated, fluid first spills onto shelf 22 at the top
of the disk stack 17, and distributes tangentially. The fluid then
falls into vertical troughs 42. The communication of fluid from
these vertical troughs 42, through the channels 41 in spacers 40,
and to the perimeter of disks 17a is described in further detail
below in connection with FIGS. 5 and 6.
[0047] In the example of FIG. 4, with vertical troughs 42, axially
aligned flow on or within the inner surface of feed well 31
accomplishes disk-to-disk fluid distribution and circumvents
localized Coriolis effects that tend to cause flow variation. In
other embodiments, the feed delivery into channels 41 could be like
that of FIG. 2 or 3. Feed fluid would drop into the feed well 31
and be distributed by rotation into the channels 41 without
vertical troughs 42.
[0048] FIG. 4 further illustrates disks 17a having serrated
(teethed) edges. These serrated edges can be formed on the disks of
any of the embodiments of this description, and help improve
desired atomization and encapsulation characteristics.
[0049] FIG. 5 is a top plan view of section A-A of FIG. 2, and
illustrates one embodiment for delivering fluid into vertical
troughs 42. The top surface of the top-most disk 17a is shown. The
fluid that drops onto shelf 22 meets a plurality of openings 51
that communicate fluid flow into the disk stack 17. If desired,
holes 51 can be angled. If angled toward the direction of rotation,
holes 51 provide restriction for tangential distribution. If angled
opposite the direction of rotation, holes 51 enhance fluid pumping.
Referring again to FIG. 4, holes 51 may provide vertical fluid flow
to the vertical troughs 42 at the inner well of the disk stack
17.
[0050] FIG. 6 is a detailed view of a spacer 40 and its channels
41. Each channel 41 is in fluid communication with fluid delivered
to feed well 31. As its length goes from its inlet end to its
outlet end (at the outer edge of spacer 40), each channel 41 widens
and flattens. Adjacent channels 41 may widen to the extent that
they merge to the same plane at the edge of the spacer 40 and at
the underside of the disk above the spacer.
[0051] Fluid flow is indicated by arrows. Fluid enters channels 41
via the feed well 31 and into channels 41. Fluid flows through
channels 41 onto the underside of the disk above the spacer 40.
Each channel 41 begins with an approximately rectangular shape and
ends with near-zero depth, merging with adjacent channels. In other
words, the channels 41 are more narrow and deeper at their inlet
ends, and become more shallow and wider toward their outlet ends
where they discharge fluid directly onto the surface of the
disks.
[0052] This channel geometry acts to receive fluid from the feed
well 31 into the channels 41, and re-shapes the fluid into a
film-like geometry as the fluid transitions from the spacer 40 to
the disk 17a. Furthermore, the use of variable depth and width
fluid distribution channels 41 overcomes the need for substantial
flow restriction to accomplish fluid distribution.
[0053] After the fluid exits channels 41, it traverses an
additional radial distance over the disk surface. This allows any
channel disturbance to dissipate and the liquid to consolidate into
a film thickness. In alternative embodiments, the outer disk edge
could be closer to, or the same as, the edge of spacer 40, in which
case the liquid is atomized more quickly, or immediately.
[0054] The distance between the outer edge of the spacers 40 and
the outer diameter of the disks 17a is referred to as D (periphery)
in FIG. 6. A longer distance provides more space for the fluid to
interact with the disk surface prior to atomization. A shorter
distance reduces space for surface spreading, and can be merely the
size of the teeth.
[0055] The spacing, H, between disks 17a is designed to be
sufficiently large to avoid over-flooding of the disk periphery.
However, smaller spacing can be used to maintain flooding to the
disk periphery under sufficiently low flow rates to avoid sheet
break-up.
[0056] At their inlet ends, an example of a suitable channel
dimension (for the example disk assembly of this description) is
about 0.05 inches wide with a depth of about 0.02 inches. In
general, these dimensions are easily scaled to accommodate fluids
having various solid particles and viscosities. A typical range of
channel inlet widths is 0.005 inches to 0.5 inches. A typical range
of channel inlet depths is 0.005 inches to 0.25 inches. The aspect
ratio of width to depth can vary. A useful range of dimensions for
the vertical troughs 42 is 0.05 inches to 1 inch wide and 0.05
inches to 1 inch deep.
[0057] FIG. 7 illustrates an alternative embodiment of channels 41.
Here, channels 41 decrease in depth from their inlet ends to zero
depth at their outlet ends, merging with adjacent channels.
[0058] In this embodiment, an additional spacer 40A with a flat,
sheet-like geometry is used to control the gap between the outlet
end of spacer 40 and the adjacent disk 17a. These spacers 40A are
constructed from a very thin material, and control an annular gap
between the spacer 40 and disk at the outer edge of the spacer 40.
Spacers 40A have a diameter less than spacer 40 such that fluid
communication from the channels 41 to the disk is maintained. An
example of a suitable material for spacers 40A is shim stock. A
range of suitable thicknesses may be from 0.001'' to 0.07''.
[0059] The use of spacers 40A provides a degree of freedom for
controlling the liquid thickness flowing onto the disk. As a result
the disk assembly can adapt to various feed formulations and
resultant fluid properties without re-manufacturing spacers with
channels.
[0060] FIG. 7 also illustrates disk 17a having an outer perimeter
edge 71 that is beveled as well as serrated.
[0061] In still other embodiments, the width of channels 41 could
alternatively be constant. In the latter case, the channels would
have a constant geometry along their length as in the channels 37
of FIG. 3.
[0062] Referring to FIGS. 2-7, it can be seen that in all
embodiments, fluid distributes into a feed well 31. In some
embodiments, fluid is encouraged into axially aligned troughs 42 in
the feed well surface, which provide disk-to-disk fluid
distribution. The fluid then flows into spacers (33, 40) between
the disks 17a, and more specifically into spacer channels (37, 41)
within or on the surface of the spacers. The channels (37, 41)
communicate the fluid toward the outer edges of the disks 17a. The
disk surface past the spacers (33, 40) can have various
configurations, such as teeth, weirs, or flatness, designed for
particular desired atomization or encapsulation
characteristics.
* * * * *