U.S. patent application number 14/563334 was filed with the patent office on 2015-06-18 for microclarification system and method.
The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Jason Louis Davis, Craig Patrick Galligan, Rachel Marie Gettings, Jason Michael Nichols, Daniel George Norton, Christopher Michael Puleo.
Application Number | 20150165347 14/563334 |
Document ID | / |
Family ID | 53367219 |
Filed Date | 2015-06-18 |
United States Patent
Application |
20150165347 |
Kind Code |
A1 |
Nichols; Jason Michael ; et
al. |
June 18, 2015 |
MICROCLARIFICATION SYSTEM AND METHOD
Abstract
A microclarification system is disclosed which can be used to
separate solid particulates dispersed within a base fluid such as
water. The microclarification system includes a plurality of
microfluidic separator units disposed between and in fluid
communication with a fluid inlet manifold and a fluid outlet
manifold. The microclarification system enforces lamellar flow of
fluid though it and as a result the rate at which particles settle
is enhanced within a collection chamber associated with each
microfluidic separator unit and through which the fluid being
purified must pass. Each microfluidic separator unit includes a
microfluidic outlet microchannel disposed between the microfluidic
collection chamber and the fluid outlet manifold, and a gas-liquid
flushing module configured to purge particulates from the
collection chamber during a collection chamber purge cycle.
Optionally, each microfluidic separator unit may include a
microfluidic inlet microchannel. The system holds promise in
municipal water purification among other applications.
Inventors: |
Nichols; Jason Michael;
(Schenectady, NY) ; Puleo; Christopher Michael;
(Niskayuna, NY) ; Davis; Jason Louis; (Albany,
NY) ; Norton; Daniel George; (Niskayuna, NY) ;
Galligan; Craig Patrick; (Niskayuna, NY) ; Gettings;
Rachel Marie; (Albany, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Family ID: |
53367219 |
Appl. No.: |
14/563334 |
Filed: |
December 8, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61916379 |
Dec 16, 2013 |
|
|
|
Current U.S.
Class: |
435/261 ;
210/322; 210/803; 435/308.1 |
Current CPC
Class: |
B01L 2400/0421 20130101;
B01L 2200/0652 20130101; B01D 21/10 20130101; B01L 3/502761
20130101; B01L 2400/0457 20130101; C02F 1/24 20130101; C02F
2201/002 20130101; B01L 2200/0668 20130101; C02F 1/444 20130101;
C02F 2101/32 20130101; B01D 21/02 20130101; B01L 2300/0851
20130101; B01L 2400/043 20130101; C02F 2103/10 20130101; B01D
21/0006 20130101; B01L 3/502753 20130101; B01L 2200/0631 20130101;
B01L 2400/0469 20130101; B01D 21/2433 20130101; B01D 2221/04
20130101; C12N 5/0641 20130101; C02F 1/48 20130101; C02F 2103/08
20130101; C12M 47/02 20130101; B01D 21/0087 20130101; B01D 21/245
20130101; B01L 2300/0681 20130101; B01D 17/02 20130101; B01D
21/2444 20130101; C02F 1/00 20130101; C02F 2001/007 20130101; B01D
21/0042 20130101 |
International
Class: |
B01D 21/24 20060101
B01D021/24; C02F 1/00 20060101 C02F001/00; B01D 21/02 20060101
B01D021/02; C12M 1/00 20060101 C12M001/00; B01D 21/00 20060101
B01D021/00 |
Claims
1. A microclarification system for separating particulates
dispersed within a base fluid, the system comprising: a plurality
of microfluidic collection chambers disposed between and in fluid
communication with a fluid inlet manifold and a fluid outlet
manifold; a plurality of outlet microchannels disposed between the
microfluidic collection chambers and the fluid outlet manifold; and
a gas-liquid flushing module configured to purge particulates from
the collection chamber during a collection chamber purge cycle.
2. The system according to claim 1, wherein the plurality of
collection chambers are characterized by a critical height of less
than one centimeter.
3. The system according to claim 1, wherein the fluid inlet
manifold and the fluid outlet manifold are configured in
parallel.
4. The system according to claim 1, wherein the fluid inlet
manifold and the fluid outlet manifold are configured radially.
5. The system of claim 1, wherein the outlet microchannels have an
average height in a range from about 1 micron to about 200 microns
(.mu.m).
6. The system of claim 1, wherein the outlet microchannels have a
length in a range from about 1 millimeter to about 1
centimeter.
7. The system according to claim 1, wherein a plurality of inlet
microchannels are disposed between the fluid inlet manifold and the
microfluidic collection chambers.
8. The system according to claim 7, wherein the inlet microchannels
have an average height in a range from about 1 micron to about 500
microns.
9. The system according to claim 7, wherein the inlet microchannels
have length in a range from about 1 millimeter to about 10
centimeters.
10. The system of claim 1, wherein the gas-liquid flushing module
is configured to purge the collection chamber with a combination of
a gas and a purge liquid.
11. The system of claim 10, wherein a ratio of gas to purge liquid
employed is in a range from about 1:10 to about 10:1.
12. The system according to claim 10, wherein the gas is
appreciably soluble in the purge liquid.
13. The system according to claim 10, wherein the gas is selected
from the group consisting of air, carbon dioxide, oxygen, nitrogen,
argon, and mixtures of two or more of the foregoing gases.
14. The system of claim 1, wherein the collection chambers are
divided into at least two portions by a microporous body.
15. The system according to claim 14, wherein the microporous body
comprises pores with an average diameter between about 10 microns
and about 500 microns.
16. The system of claim 1, wherein the particulates are
characterized by an average particle size in a range from about 2
to about 100 .mu.m and the base fluid comprises water.
17. The system according to claim 1 configured to produce potable
water.
18. The system according to claim 1 configured for use in treating
municipal sewage, indigenous water produced from a hydrocarbon
reservoir, water produced as a by-product from hydraulic
fracturing, water produced as a by-product of oil reservoir
flooding, water produced as a by-product of a mining operation,
water produced as a by-product of boiler operation, water as a
by-product of bitumen extraction and combinations of two or more of
the forgoing.
19. The system according to claim 1 configured for use with a
biomass reactor.
20. The system according to claim 1, wherein configured for use in
a water desalination facility.
21. A method for separating particulates dispersed within a base
fluid, the method comprising: (a) introducing, as part of a fluid
purification cycle, a fluid comprising particulates dispersed
within a base fluid into a fluid inlet manifold of a
microclarification system comprising: (i) a plurality of
microfluidic collection chambers disposed between and in fluid
communication with the fluid inlet manifold and a fluid outlet
manifold; (ii) a plurality of microchannels disposed between the
microfluidic collection chambers and the fluid outlet manifold; and
(iii) a gas-liquid flushing module; wherein the system is
configured such that the particulates dispersed within the base
fluid pass from the fluid inlet manifold into the plurality of
microfluidic collection chambers wherein a substantial portion of
the particulates are captured and through which a substantial
portion of the base fluid passes and emerges at the fluid outlet
manifold as a processed fluid depleted in particulates; and (b)
introducing via the gas-liquid flushing module, as part of a
collection chamber purge cycle, a gas and a purge liquid which
together function as a collection chamber purge medium; and (c)
repeating steps (a) and (b).
22. The method according to claim 21, wherein over a plurality of
fluid purification cycles and following collection chamber purge
cycles the particulate capture capacity of the system remains
essentially constant.
23. The method according to claim 21, wherein the fluid inlet
manifold and the fluid outlet manifold are configured in
parallel.
24. The method according to claim 21, wherein the fluid inlet
manifold and the fluid outlet manifold are configured radially.
25. A microclarification system for separating particulates from
water, the system comprising: a plurality of microfluidic
collection chambers disposed between and in fluid communication
with a fluid inlet manifold and a fluid outlet manifold; a
plurality of outlet microchannels disposed between the microfluidic
collection chambers and the fluid outlet manifold; a plurality of
inlet microchannels disposed between the inlet manifold and the
microfluidic collection chambers; and a gas-liquid flushing module
configured to purge particulates from the collection chamber during
a collection chamber purge cycle; wherein the microfluidic
collection chambers are characterized by a critical height of less
than one centimeter; and wherein the outlet microchannels have an
average height between about 1 micron and about 200 microns (.mu.m)
and a length in a range from about 1 millimeter to about 1
centimeter; and wherein the inlet microchannels have an average
height in a range from about 1 micron to about 500 microns and a
length in a range from about 1 millimeter to about 10 centimeters;
and wherein the gas-liquid flushing module is configured to purge
the collection chamber with a combination of a gas and a purge
liquid.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/916,379, entitled "Systems for Separation of
Particulates and Associated Methods and Devices", filed Dec. 16,
2013, and which is incorporated herein by reference in its
entirety.
BACKGROUND
[0002] The invention relates to microfluidic separation systems,
devices and methods useful for separating particulate materials
from fluids. In a particular aspect, the invention relates to a
method for separating solid particulates from fluid mixtures
comprising such particulates.
[0003] While a substantial body of knowledge pertaining to the
separation of solids from fluids such as water, for example as is
practiced in municipal water treatment facilities, further
enhancements and efficiencies are needed to keep pace with the
needs of the world's people.
BRIEF DESCRIPTION
[0004] In one embodiment, the present invention provides
microclarification system for separating particulates dispersed
within a base fluid, the system comprising: a plurality of
microfluidic collection chambers disposed between and in fluid
communication with a fluid inlet manifold and a fluid outlet
manifold; a plurality of outlet microchannels disposed between the
microfluidic collection chambers and the fluid outlet manifold; and
a gas-liquid flushing module configured to purge particulates from
the collection chamber during a collection chamber purge cycle.
[0005] In an alternate embodiment, the present invention provides a
method for separating particulates dispersed within a base fluid,
the method comprising: (a) introducing, as part of a fluid
purification cycle, a fluid comprising particulates dispersed
within a base fluid into a fluid inlet manifold of a
microclarification system comprising: (i) a plurality of
microfluidic collection chambers disposed between and in fluid
communication with the fluid inlet manifold and a fluid outlet
manifold; (ii) a plurality of microchannels disposed between the
microfluidic collection chambers and the fluid outlet manifold; and
(iii) a gas-liquid flushing module; wherein the system is
configured such that the particulates dispersed within the base
fluid pass from the fluid inlet manifold into the plurality of
microfluidic collection chambers in which a substantial portion of
the particulates are captured and through which a substantial
portion of the base fluid passes and emerges at the fluid outlet
manifold as a processed fluid depleted in particulates; and (b)
introducing via the gas-liquid flushing module, as part of a
collection chamber purge cycle, a gas and a purge liquid which
together function as a collection chamber purge medium; and (c)
repeating steps (a) and (b).
[0006] In yet another embodiment, the present invention provides a
microclarification system for separating particulates from water,
the system comprising: a plurality of microfluidic collection
chambers disposed between and in fluid communication with a fluid
inlet manifold and a fluid outlet manifold; a plurality of outlet
microchannels disposed between the microfluidic collection chambers
and the fluid outlet manifold; a plurality of inlet microchannels
disposed between the inlet manifold and the microfluidic collection
chambers; and a gas-liquid flushing module configured to purge
particulates from the collection chamber during a collection
chamber purge cycle; wherein the microfluidic collection chambers
are characterized by a critical height of less than one centimeter;
and wherein the outlet microchannels have an average height between
about 1 micron and about 200 microns (.mu.m) and a length in a
range from about 1 millimeter to about 1 centimeter; and wherein
the inlet microchannels have an average height in a range from
about 1 micron to about 500 microns and a length in a range from
about 1 millimeter to about 10 centimeters; and wherein the
gas-liquid flushing module is configured to purge the collection
chamber with a combination of a gas and a purge liquid.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0007] Various features, aspects, and advantages of the present
invention will become better understood when the following detailed
description is read with reference to the accompanying drawings in
which like characters may represent like parts throughout the
drawings. Unless otherwise indicated, the drawings provided herein
are meant to illustrate key inventive features of the invention.
These key inventive features are believed to be applicable in a
wide variety of systems which comprising one or more embodiments of
the invention. As such, the drawings are not meant to include all
conventional features known by those of ordinary skill in the art
to be required for the practice of the invention.
[0008] FIG. 1 illustrates a microclarification system provided by
the present invention.
[0009] FIG. 2 illustrates a microclarification system provided by
the present invention.
[0010] FIG. 3 illustrates a microclarification system provided by
the present invention.
[0011] FIG. 4 illustrates a microclarification system provided by
the present invention.
[0012] FIG. 5 illustrates a microclarification system provided by
the present invention.
[0013] FIG. 6 illustrates a microclarification system provided by
the present invention.
[0014] FIG. 7 illustrates a microclarification system provided by
the present invention.
[0015] FIG. 8 illustrates a microclarification system provided by
the present invention.
[0016] FIG. 9 illustrates a microfluidic separator unit provided by
the present invention.
[0017] FIG. 10A illustrates a microfluidic separator unit provided
by the present invention.
[0018] FIG. 10B illustrates a microfluidic separator unit provided
by the present invention.
[0019] FIG. 11 illustrates a microclarification system for
preparing drinking water provided by the present invention.
[0020] FIG. 12 illustrates a sewage treatment system provided by
the present invention.
[0021] FIG. 13 illustrates a system for purifying a liquid product
from a bioreactor provided by the present invention.
[0022] FIG. 14 illustrates a desalination system provided by the
present invention.
[0023] FIG. 15 illustrates a system provided by the present
invention.
DETAILED DESCRIPTION
[0024] In the following specification and the claims, which follow,
reference will be made to a number of terms, which shall be defined
to have the following meanings.
[0025] The singular forms "a", "an", and "the" include plural
referents unless the context clearly dictates otherwise.
[0026] "Optional" or "optionally" means that the subsequently
described event or circumstance may or may not occur, and that the
description includes instances where the event occurs and instances
where it does not.
[0027] Approximating language, as used herein throughout the
specification and claims, may be applied to modify any quantitative
representation that could permissibly vary without resulting in a
change in the basic function to which it is related. Accordingly, a
value modified by a term or terms, such as "about" and
"substantially", are not to be limited to the precise value
specified. In at least some instances, the approximating language
may correspond to the precision of an instrument for measuring the
value. Here and throughout the specification and claims, range
limitations may be combined and/or interchanged, such ranges are
identified and include all the sub-ranges contained therein unless
context or language indicates otherwise.
[0028] As noted, in one embodiment, the present invention provides
a microclarification system for separating particulates within a
base fluid. The systems and methods provided by the present
invention are especially promising for use in water purification
processes which involve one or more settling steps to effect
removal of suspended particulate matter. The present invention acts
to enhance the rate at which suspended particles can be separated
from a base liquid under the influence of gravity. The liquid to be
purified, at times herein referred to as the unprocessed fluid, is
passed through a microfluidic device, the microfluidic separator
unit, which enforces a lamellar flow regime on the flowing liquid
in which particle settling rates are maximized in the absence of
turbulent flow. The dimensions of the microfluidic device are such
that the distance is minimized between a particle falling under the
influence of gravity and a surface upon which the particle alights
and is removed from a stream of horizontally flowing liquid. The
devices can be operated at flow rates corresponding to particle
residence times which are longer than the time required for a
suspended particle to settle into contact with the bottom surface
of the device collection chamber. As shown experimentally herein,
the systems provided by the present invention are capable of
particulate removal at much higher rates than conventional
systems.
[0029] The microclarification systems provided by the present
invention comprise a plurality of microfluidic collection chambers
connected to and in fluid communication with a fluid inlet manifold
and a fluid outlet manifold. Typically, the system is configured
such that an unprocessed fluid requiring removal of particulates
enters the collection chamber at a collection chamber fluid inlet
and flows along the length of the collection chamber to a
collection chamber fluid outlet. The dimensions of the collection
chamber are microfluidic, meaning that at least one of the
dimensions of the collection chamber is appropriately reported in
microns. Table 1 of the Experimental Section of this disclosure
provides specific, non-limiting examples of microfluidic collection
chambers.
[0030] The collection chambers are characterized by a dimension, at
times herein referred to as a critical height. This critical height
is important for several reasons, among them, the critical height
dimension is important to the enforcement of lamellar flow within
the collection chamber and determines the distance a particle
falling under the influence of gravity must travel before
contacting the bottom of the collection chamber where it separates
from the liquid flowing through the collection chamber. Particle
behavior within the collection chamber is such that once coming
into contact with the bottom surface of the collection chamber a
particle is immobilized until its removal in a back flushing step.
In one or more embodiments, the collection chambers are
characterized by a critical height of less than one centimeter,
i.e. less than 10000 microns, and corresponds to the average depth
of the collection chamber.
[0031] The fluid inlet manifold is configured to deliver a fluid to
be processed to the plurality of collection chambers. Thus, the
fluid inlet manifold is sized appropriately to deliver a flow of
unprocessed fluid at a controlled flow rate to each collection
chamber with which it is in fluid communication. Fluid
communication between the fluid inlet manifold and the collection
chamber may be direct, with no intervening structure, or may be
indirect, as when fluid from the inlet manifold must first pass
through an inlet microchannel prior to entering the collection
chamber. In one or more embodiments the fluid inlet manifold is
configured such that during back flushing, particles trapped within
the collection chamber are directed through the fluid inlet
manifold and to a waste collection vessel and/or a waste collection
conduit. At times herein, particulate matter recovered from the
collection chamber during a back flushing step is referred to as
sludge.
[0032] The fluid outlet manifold is configured to receive processed
fluid from the collection chamber and to direct the processed fluid
to a processed fluid collection vessel and/or a processed fluid
collection conduit. The fluid outlet manifold may be in direct
fluid communication with the collection chamber or may be separated
from the collection chamber by an intervening outlet microchannel.
One purpose of the outlet microchannel is to create sufficient
restriction at the outlet of the collection chamber such that a
slight back pressure is created uniformly across each of the
collection chambers of the microclarification system. While such
outlet microchannels are not a requirement for operability of
microclarification systems provided by the present invention, the
outlet microchannels act to assure more uniform performance among
the plurality of microfluidic collection chambers both from the
stand point of uniform throughput and particle capture
efficiency.
[0033] Inlet microchannels and outlet microchannels have dimensions
smaller than the collection chamber. In one or more embodiments,
the inlet microchannels and outlet microchannels are of uniform
dimensions which are smaller than the dimensions of the collection
chambers. In one or more embodiments, collection chambers, the
inlet microchannels, and the outlet microchannels are of uniform
height, such that the height of the inlet microchannels and outlet
microchannels is a in a range from about one twentieth to about one
tenth the height of the collection chambers. In one or more
embodiments, the inlet microchannel and the outlet microchannels
are characterized by an average height in a range from about 1
micron to about 200 microns (.mu.m). In one or more embodiments,
only outlet microchannels are present and are characterized by an
average height in a range from about 1 micron to about 200 microns
(.mu.m).
[0034] In one or more embodiments, the inlet microchannel and the
outlet microchannels are characterized by a length in a range from
about 1 millimeter to about 1 centimeter. In one or more
embodiments, only outlet microchannels are present and are
characterized by a length in a range from about 1 millimeter to
about 1 centimeter.
[0035] In one or more embodiments, both an inlet microchannel and
an outlet microchannel are present in each microfluidic separator
unit of the microclarification system provided by the present
invention. Under such circumstances, a plurality of inlet
microchannels are disposed between the fluid inlet manifold and the
microfluidic collection chambers. In one such embodiment, the inlet
microchannels have an average height in a range from about 1 micron
to about 500 microns. In another such embodiment, inlet
microchannels have length in a range from about 1 millimeter to
about 10 centimeters.
[0036] In one or more embodiments, the gas-liquid flushing module
is configured to deliver a mixture of gas and purge liquid to the
collection chamber in order to clear collected particles from the
collection chamber during a collection chamber purge cycle. The
mixture of gas and purge liquid is at times herein referred to as a
combination of a gas and a purge liquid. Upon entry of the
combination of the gas and purge liquid, the limited height of the
collection chamber causes rapid coalescence of gas bubbles
dispersed in the purge liquid. As shown experimentally herein, this
combination of a purge gas and purge liquid are especially
effective at removal of captured solids from the collection chamber
and maintaining collection chamber particle capture capacity, purge
cycle after purge cycle. In one or more embodiments, the ratio of
purge gas to purge liquid is in a range from about 1:10 to about
10:1.
[0037] Suitable purge gases include air, carbon dioxide, oxygen,
nitrogen, argon, and mixtures of two or more of the foregoing
gases. In one or more embodiments, the purge gas is primarily
carbon dioxide. In an allied set of embodiments, the purge gas is
greater than 95% carbon dioxide. In one or more embodiments, the
purge gas employed is appreciably soluble in the purge liquid. For
reference, carbon dioxide having a solubility in water at room
temperature of about 0.9 mL CO.sub.2 per mL of water is considered
appreciably soluble in the purge liquid when the purge liquid is
water.
[0038] Suitable purge liquids include water, aqueous ethanol, and
clarate produced by the microclarification system. In one or more
embodiments the purge liquid is water.
[0039] The microclarification system provided by the present
invention may be operated essentially continuously through a
plurality of full cycles each comprising a priming cycle, a fluid
purification cycle, and a collection chamber purge cycle. Upon
system start-up and following each purge cycle, the
microclarification system is primed in order to eliminate trapped
gas within the system. In various embodiments disclosed herein, the
microclarification system is valved appropriately to bleed trapped
gases out of the system. Suitable priming fluids include clarate
produced by the system, water, aqueous ethanol, aqueous acetic acid
and combinations of two or more of the foregoing priming fluids. In
one or more embodiments, it may be useful to degas the priming
fluid prior to its introduction into the system.
[0040] The microclarification systems provided by the present
invention are anticipated to be useful in a host of applications
and may be configured for use in treating municipal sewerage,
indigenous water produced from a hydrocarbon reservoir, water
produced as a by-product from hydraulic fracturing, water produced
as a by-product of oil reservoir flooding, water produced as a
by-product of a mining operation, water produced as a by-product of
boiler operation, water as a byproduct of bitumen extraction, and
combinations of two or more of the forgoing applications.
[0041] As noted, the present invention provides a method for
separating particulates dispersed within a base fluid using one or
more of the microclarification systems disclosed herein. As will be
appreciated by those of ordinary skill in the art and having read
this disclosure, the microclarification systems disclosed herein
provide for essentially continuous operation in which, over a
plurality of fluid purification cycles and following collection
chamber purge cycles, the particulate capture capacity of the
system remains essentially constant.
[0042] Turning now to the drawings, FIG. 1 illustrates essential
features of microclarification systems 10 and associated methods
provided by the present invention. For the sake of simplicity in
illustrating the principles of operation of the microclarification
systems provided by the present invention, FIG. 1 features only one
collection chamber 14 and microfluidic separator unit 44 comprising
such collection chamber. Thus, a slurry tank 5 holding a mixture of
particulates 2 disposed in a base fluid 4 is linked via an inlet
manifold 16 to a microfluidic separator unit 44 comprising
collection chamber 14 having critical height 6 (h). The collection
chamber is linked to and is in fluid communication with inlet
manifold 16 via inlet microchannel 21. The limited height
dimensions of the inlet microchannel 21 and the collection chamber
14, both are microfluidic as defined herein, enforce lamellar flow
within the inlet microchannel and the collection chamber while
allowing for relatively high throughput rates. Such a lamellar flow
regime minimizes the time required for a particle entering the
collection chamber to settle to the bottom of the collection
chamber and become trapped there. An outlet microchannel 20 acts
both as a weir-creating structure to further inhibit passage of
particulates out of the collection chamber and as a back pressure
regulating feature which helps assure uniform performance of a
plurality of microfluidic separator units when such separator units
are linked to a single inlet manifold. Further uniformity is
achieved by providing for turbulent flow within both the slurry
tank and the inlet manifold.
[0043] Outlet microchannel 20 is linked to and in fluid
communication with outlet manifold 18 which is linked to pump 12
which serves to draw the suspension of particulates 2 in base fluid
4 through the microfluidic separator unit 44 to provide processed
fluid comprising base fluid 4 which is substantially depleted in
particulates 2. As used herein and with respect to a processed
fluid, substantially depleted means that at least fifty percent of
the particulates originally present in the fluid to be processed
have been removed by the system. In the embodiment shown, the
processed fluid is collected in a vessel, at times herein referred
to as a clarate recovery tank 11. The term clarate may at times
herein be used interchangeably with the term processed fluid. The
microclarification system 10 may be operated in fluid purification
mode until the collection chamber becomes saturated with
particulates and particle capture efficiency begins to drop from
optimal performance. Particulate breakthrough may be deemed to have
occurred at any time during the fluid purification cycle but is
typically associated with a rise in particulate level in the
processed fluid following a period of operation in which the
processed fluid remains substantially depleted in particulates.
[0044] Upon particulate breakthrough, the fluid purification cycle
is replaced by a fluid purge cycle. The system is equipped with a
gas-liquid flushing module 30 configured to flush captured
particulate matter from the collection chamber. During the purge
cycle a relatively small volume of the clarate is drawn by pump 13
and mixed with a purge gas from purge gas source 17 and passed
through purge cycle inlet line 7 into collection chamber 14. During
the purge cycle valve 34 may be opened to allow a concentrated
mixture of particulates and purge fluid to pass along purge cycle
exit line 8 and into sludge recovery tank 9. Inlet manifold 16 may
comprise valves as appropriate (not shown) to prevent fluid
communication between slurry tank 5 and the collection chamber
during the purge cycle. In a typical purge cycle, less than 10
percent of the clarate produced in the fluid purification cycle is
expended in the purge cycle. In various embodiments, less than 5
percent of the clarate produced in the fluid purification cycle is
expended in the purge cycle.
[0045] Following the purge cycle, the microclarification system is
primed to eliminate gas bubbles, particularly within the
microfluidic separator unit 44. In the embodiment shown, the system
is configured to utilize a relatively small volume of the clarate
as the priming fluid in the absence of the purge gas. In a typical
priming cycle, less than 10 percent of the clarate produced in the
fluid purification cycle is expended in the priming cycle. In
various embodiments, less than 5 percent of the clarate produced in
the fluid purification cycle is expended in the priming cycle. In
one or more embodiments less than the volume of the collection
chamber is required to effectively prime the system. Various
wetting agents such as surfactants, ethanol, acetic acid and
polethyelene glycol may aid in minimizing the volume of priming
fluid required to effectively prime the system.
[0046] Referring to FIG. 2, the figure represents a portion of a
microclarification system 10 provided by the present invention
featuring a microfluidic separator unit 44 disposed between an
inlet manifold 16 and an outlet manifold 18. The inlet manifold is
shown as containing a fluid to be processed by the unit and
comprising particulates 2 dispersed within a base fluid 4. The
fluid to be processed enters the microfluidic separator unit via
inlet microchannel 21 having average height 24 and length 25. In
the embodiment shown, the inlet microchannel of uniform dimensions
and the average height is simply the height of the inlet
microchannel along its length 25. As noted, the inlet microchannel
serves to enforce lamellar flow on the fluid to be processed, and
this lamellar flow continues in the collection chamber 14 and
particles 2 settle rapidly to the bottom in the absence of
turbulent flow. Lamellar flow is indicated in FIG. 2 and elsewhere
herein as two or more parallel arrows. Collection chamber 14 is
microfluidic in the sense that it is characterized by a critical
height 6 which appropriately measured in microns and is under
10,000 microns, typically in a range from about 100 microns to
about 2000 microns. Collection chamber 14 must be appropriately
sized such that lamellar flow is enforced within it, but any
pressure drop across the length of the collection chamber will be
minimal. In the embodiment shown, the collection chamber is of
uniform dimensions with a single critical height 6. The
microfluidic separator unit 44 comprises an outlet microchannel 20
having height 22 and length 23. Together, the outlet microchannel
and the inlet microchannel create a tub-like structure in which
particulates are captured. Processed fluid exits the outlet
microchannel and enters outlet manifold 18.
[0047] Referring to FIG. 3, the figure represents a portion of a
microclarification system 10 provided by the present invention and
features a plurality of microfluidic separator units of the type
shown in FIG. 2. The microfluidic separator units are essentially
identical and each comprises a collection chamber 14 disposed
between and in fluid communication with fluid inlet manifold 16 and
fluid outlet manifold 18.
[0048] Referring to FIG. 4, the figure represents a portion of a
microclarification system 10 provided by the present invention
wherein the microfluidic separator units each comprise a
microporous body 26 which divides the collection chamber into an
upper portion and a lower portion, the critical height 6 being
shown as the distance between the top of the collection chamber 14
and the bottom of the collection chamber where particulates 2 are
shown as accumulating.
[0049] In one or more embodiments, the microporous body 26 may be a
membrane or a solid body through which holes have been created. In
one or more embodiments the microporous body comprises pores
originating at a first surface of the microporous body and
terminating at a second surface of the microporous body. In one or
more embodiments, the microporous body is a film through which
pores have been created. For example, pores traversing a film may
be created by chemical etching techniques and/or laser ablative
techniques. The term microporous is used herein because the pores
have dimensions appropriately measured in microns (e.g., the
average pore diameter is 1000 microns or less). In one embodiment,
the pores have an average diameter between about 1 micron and about
500 microns. In an alternate embodiment, the pores have an average
diameter between about 10 microns and about 250 microns. In yet
another embodiment, the pores have an average diameter between
about 20 microns and about 100 microns. In one embodiment, the
porosity of the microporous body is between about 10 and about 75
percent. In an alternate embodiment, the porosity of the
microporous body is between about 20 and about 65 percent. In yet
another embodiment, the porosity of the microporous body is between
about 30 and about 60 percent.
[0050] As noted, in one embodiment, the microporous body may be a
microporous film such as a monofilament screen or mesh made from,
for example, polyester, nylon, polypropylene, or a combination of
such polymeric substances). Alternatively, the microporous body may
be a chemically-etched KAPTON, titanium, or NiTinol film. In one
embodiment, the microporous body is a laser etched organic film
made from an organic polymeric material such as KAPTON.
[0051] Referring to FIG. 5, the figure represents a portion of a
microclarification system 10 provided by the present invention in
which the microfluidic separator units do not comprise an inlet
microchannel 21, but do comprises an outlet microchannel 20. Thus,
collection chamber 14 is in direct fluid communication with fluid
inlet manifold 16. In the embodiment shown, fluid enters the
collection chambers initially as turbulent flow and is converted to
lamellar flow within the collection chamber. Processed fluid passes
through outlet microchannels 20 into fluid outlet manifold 18.
[0052] Referring to FIG. 6, the figure represents a
microclarification system 10 provided by the present invention and
features a plurality of collection chambers 14 disposed between and
in fluid communication with a fluid inlet manifold 16 and a fluid
outlet manifold 18, the fluid inlet manifold and fluid outlet
manifold being configured in parallel. Each of the collection
chambers 14 is in fluid communication with the fluid outlet
manifold 18 via an outlet microchannel as in, for example, FIG. 3,
FIG. 4 and FIG. 5. The microclarification system 10 operates as
outlined in the description of FIG. 1 with the exception that the
gas-liquid flushing module 30 utilizes a purge liquid drawn from
purge liquid supply tank 32 which is separate from clarate recovery
tank 11. The microclarification system comprises valves 34 which
may be used to isolate purge cycle inlet and outlet lines 7 and 8
from fluid inlet manifold 16 and fluid outlet manifold 18 during
purification cycles in which feed line 15 is in fluid communication
with outlet conduit 19 and clarate recovery tank 11 via fluid inlet
manifold 16, collection chambers 14 and fluid outlet manifold 18.
Similarly, during collection chamber purge cycles, valves 34 may be
used to isolate feed line 15 and outlet conduit 19 from the inlet
and outlet manifolds while passing purge liquid and purge gas from
the gas-liquid flushing module 30 into fluid outlet manifold 18,
collection chambers 14 and fluid inlet manifold 16 and collecting
particulates in sludge recovery tank 9.
[0053] Referring to FIG. 7, the figure represents a portion of a
microclarification system 10 provided by the present invention and
features a plurality of collection chambers 14 disposed between and
in fluid communication with a fluid inlet manifold 16 and a fluid
outlet manifold 18, the fluid inlet manifold and fluid outlet
manifold being configured radially.
[0054] Referring to FIG. 8, the figure represents the
microclarification system shown in FIG. 7 but revealing additional
system details. As noted with respect to FIG. 7, the fluid inlet
manifold 16 and fluid outlet manifold 18 are arranged radially with
the collection chambers 14 configured like the spokes of a wheel
linking fluid inlet manifold 16 (the wheel hub) with the fluid
outlet manifolds 18 (the wheel rim). The embodiment shown in FIG. 8
comprises a plurality of fluid outlet manifolds 18 arrayed along
the axis of a single fluid inlet manifold 16. The collection
chambers 14 are in fluid communication with fluid inlet manifold 16
and fluid outlet manifolds 18 via inlet microchannel 21 and outlet
microchannel 20 (not shown). During a fluid purification cycle a
mixture particulates 2 dispersed within a base fluid 4 passes from
slurry tank 5 into fluid inlet manifold 16 in response to the
action of forward pump 12. The mixture of particulates 2 dispersed
within a base fluid enters the microfluidic separator units
comprising collection chambers 14 wherein a lamellar flow regime is
enforced as a result of the limited heights of the collection
chambers and associated inlet and outlet microchannels.
Notwithstanding the appearance in FIG. 8 and the reference to wheel
spokes, the microfluidic separator units 44 shown in FIG. 8 and
comprising collection chambers 14 are shaped essentially like
flattened boxes (or pie wedges) adapted for coupling to and fluid
communication with the fluid inlet manifold 16 at one end and fluid
outlet manifold 18 on the other. Processed fluid emerging from the
microfluidic separator units 44 passes from each of the fluid
outlet manifolds 18 to clarate recovery tank 11 via outlet conduits
19, valve 34 and forward pump 12.
[0055] Still referring to FIG. 8, during a collection chamber purge
cycle slurry tank 5 and clarate recovery tank 11 are isolated from
the system by closing one or more valves 34 while introducing a gas
and a purge liquid which together function as a collection chamber
purge medium into each of the fluid outlet manifolds 18 via purge
cycle inlet line 7 while simultaneously collecting in sludge
recovery tank 9 a mixture comprising particulates driven from the
collection chambers 14 and purge liquid from purge liquid supply
tank 32.
[0056] Referring to FIG. 9, the figure represents a portion of a
microfluidic separator unit 44 which may be adapted for use in
microclarification systems comprising either a radial or a parallel
arrangement of the fluid inlet and fluid outlet manifolds. In the
embodiment shown, the microfluidic separator unit is an orthotope
open at each end and containing flow channel blocking members 46 at
each end which create an inlet microchannel (not shown) and an
outlet microchannel 20. The microfluidic separator unit may be made
from simple plastic rectangles joined one to each of two others
with adhesive 47. Flow blocking members 46 are joined with adhesive
47 to three of the rectangles but are not joined to upper portion
48. Alternatively, microfluidic separator unit 44 may be prepared
using one or more art recognized plastics processing techniques,
such as injection molding and/or extrusion. In one or more
embodiments, one or more components of the microfluidic separator
unit is prepared using an additive manufacturing technique.
[0057] Referring to FIG. 10A and FIG. 10B, these figures further
exemplify techniques for building microfluidic separator units 44
which may be used according to one or more embodiments of the
present invention. These figures are discussed in detail in the
Experimental Part of this disclosure.
[0058] Referring to FIGS. 11-14, the figures illustrate the use of
microclarification systems 10 provided by the present invention in
key human activities: the purification of fresh water for human
consumption (FIG. 11); the treatment of sewage (FIG. 12); process
steps involving the removal of particulates in a biological process
such as the production of ethanol from sugarcane bagasse (FIG. 13);
and the desalination of seawater (FIG. 14).
[0059] Referring to FIG. 11, system 50 is a system for producing
drinking water from fresh, but otherwise non-potable water 51, the
element 52 is a screen filter, the element 53 is a clarate stream
produced by microclarification system 10, the element 54 is a
sludge stream produced by the microclarification system 10, the
element 55 is filtration unit configured to filter clarate stream
53; the element 56 is the filtrate produced by filtration unit 55,
the element 57 is a stream of material rejected by the filtration
unit 55 which is added to sludge stream 54 for sludge disposal. The
element 58 is a disinfection unit which produces drinking water
59.
[0060] Referring to FIG. 12, the figure represents a sewage
treatment system 60 in which the element 61 is raw sewage, the
element 62 is an aeration tank, the element 63 is an activated
sludge reactor, the element 64 is a stream of water recovered from
activated sludge reactor 63, the element 65 is a stream of sludge
produced by the activated sludge reactor, the element 66 is an
overflow stream from aeration tank 62, and the element 67 is
treated water from the sewage treatment plant. All other elements
shown have been defined elsewhere in this disclosure.
[0061] Referring to FIG. 13, the figure represents a system 70 for
conducting a biological manufacturing process in which 71
represents a feed stock serving as the starting material for the
biological transformation, for example chopped bagasse to be
converted into a mixture of sugars useful in ethanol production via
fermentation. The element 72 is a stream of air used in the
biological transformation which takes place in aerated bioreactor
73. The element 74 is the product stream from the bioreactor. The
elements 10, 53, 54 and 55 have been defined elsewhere in this
disclosure. The element 75 represents a stream of material rejected
by filtration unit 55. The element 77 represents a stream of clean
product produced by system 70.
[0062] Referring to FIG. 14, the figure represents a system 80 for
the desalination of seawater 81. In one or more embodiments, the
element 81 is brackish water. The elements 10, 52, 53 and 54 have
been defined elsewhere in this disclosure. The element 82 is a
filtration device. In one or more embodiments the element 82 is a
microfilter. In one or more embodiments the element is an
ultrafilter. The element 83 is an aqueous stream produced by
filtration device 82. The element 84 is a stream of material
rejected by filtration device 82. The element 85 represents a
reverse osmosis separation membrane unit. The elements 86 and 87
represent a substantially salt free permeate stream and a salt rich
concentrate stream respectively. The elements 58 and 59 have been
defined elsewhere in this disclosure.
[0063] Referring to FIG. 15, the figure represents a
microclarification system 10 provided by the present invention in
which the fluid inlet manifold is configured as an immersion tank.
In the embodiment shown, the microfluidic separator units 44 are
arranged as a stack of flattened cylinders having a largely open
rim defining the inlet of the collection chamber 14 and closed
upper 48 and lower surfaces 28. The collection chambers are in
fluid communication with a cylindrical fluid outlet manifold 18 via
outlet microchannels 20. The immersion tank serving as the fluid
inlet manifold 16 comprises a raised surface 94 which may support
the stack of cylindrical microfluidic separator units 44 and the
fluid outlet manifold 18, and defines a particulate sump 92. In the
embodiment shown, the immersion tank serving as the fluid inlet
manifold 16 is configured to receive a vented (See valved vents 134
and 136)tank cover 96 which prevents tank overfill during fluid
purification cycles and allows gas pockets introduced during a
collection chamber purge cycle to be escape from the immersion
tank.
EXPERIMENTAL PART
Methods and Materials
[0064] Silica particle standards were purchased from Fisher
Scientific and used as received. Influent and effluent turbidity
was measured using an OAKTON.RTM. TN-100/T-100 portable
turbidimeter. Particle size distributions were measured by forward
light scattering method. Medical grade polyamide woven mesh
(purchased from SEFAR (MEDIFAB, 07-40/40)) was employed in
embodiments comprising a microporous body and had 40 micron pores
and 40% porosity. Rapid prototyping of microfluidic separator unit
components was performed at a commercial vendor using a
photopolymerizable acyronitrile-butadiene-styrene (ABS) copolymer
(DSM Somos WaterShed XC 11122). Pressure sensitive adhesive (VHB
double-sided pressure sensitive adhesive tape) used in the
construction of microfluidic separator units was purchased from
3M.
Microfluidic Separator Device Construction
[0065] A series of microfluidic separator devices (Devices 1-8)
were assembled from three parts created on the rapid prototyping
instrument. With the exception of Device 1, which comprised a
microporous body made of a polyamide woven mesh dividing the
collection chamber into an upper and a lower portion, all of the
Devices possessed undivided collection chambers. A set of pressure
sensitive adhesive films appropriately sized and shaped were used
to join the component parts of the microfluidic separator units
together into a unitary whole. Useful reference may be made to
FIGS. 10A and 10B and Table 1 below. Dimensions for 1-8 are given
in Table 1 below. Reference elements A-H and J-K are illustrated in
FIGS. 10A and 10B and wherein:
A is the height of the of the microfluidic separator unit measured
from surface 28 of base 49 (FIG. 10B) to the top of the inlet
microchannel (21), where A=E=H; B is the height of the inlet
microchannel (21); C is the length of the inlet microchannel (21);
D is the length of the collection chamber (14); E is height of the
collection chamber (14) where E=A=H; F is the length of the outlet
microchannel (20); G is the is the height of the outlet
microchannel (20); H is the height of the of the microfluidic
separator unit measured from surface 28 of base 49 (FIG. 10B) to
the top of the outlet microchannel (20) where H=A=E; J is the width
of the inlet microchannel (21); K is the width of the collection
chamber (14); and L is the width of the outlet microchannel
(20).
TABLE-US-00001 TABLE 1 Dimension A B C D E F G H J K L mm mm mm mm
mm mm mm mm cm cm cm Device 1 2.0 0.1 16.5 40.0 2.0 16.5 0.1 2.0
1.0 1.0 1.0 Device 2 2.0 0.1 16.5 40.0 2.0 16.5 0.1 2.0 1.0 1.0 1.0
Device 3 0 0 0 40.0 2.0 0 0 0 0 1.0 0 Device 4 2.0 0.1 66.5 40.0
2.0 16.5 0.1 2.0 1.0 1.0 1.0 Device 5 0 0 0 262 2.0 0 0 0 0 25.4 0
Device 6 0 0 0 40.0 4.0 0 0 0 0 1.0 0 Device 7 0 0 0 40.0 6.0 0 0 0
0 1.0 0 Device 8 0 0 0 222 2.0 0 0 0 0 38 0
[0066] The following exemplifies the construction of a microfluidic
separator device 44 comprises an inlet microchannel 21, an outlet
microchannel 20 and a microporous body 26 from three components
prepared on the rapid prototyping instrument. Again, useful
reference may be made to FIGS. 10A and 10B. A first part 41 (FIG.
10A) comprising a fluid inlet 42 linked to an inlet microchannel 21
and fluid outlet 43 linked to an outlet microchannel 20. The second
part 45 (FIG. 10B) substantially defined the depth of collection
chamber 14. A third part 49 (FIG. 10B) served as the base of the
device and served as the bottom surface 28 of the collection
chamber 14. Device components could be joined with appropriately
cut pressure sensitive adhesive films 47. For example, a 50 micron
(.mu.m) thick pressure sensitive adhesive 47 may be used to secure
the first part 41 to the surface of the microporous body 26 and
create thereby a channel extending from upper portion 48 of the
microfluidic separator device to the upper surface of the
microporous body 26. Appropriately shaped pressure sensitive
adhesive comprised features cut out using a cutter/plotter
(Graphtec Craft Robo ProS). Additional cut adhesive films 47 were
used to fix the second part 45 to the lower surface of the
microporous body 26 and the third part 49 respectively. In one or
more embodiments, the collection chamber 14 had dimensions of 40
millimeters by 10 millimeters and varied in depth from 2
millimeters (Devices 1-4), to 4 millimeters (Device 6), to 6
millimeters (Device 7). Devices 1-4, 6 and 7 had collection chamber
volumes ranging from about 750 to about 2250 microliters (.mu.L).
Devices 5 and 8 had collection chamber volumes of about 13.3
cm.sup.3 and 16.9 cm.sup.3 respectively.
Laboratory Operation of Microfluidic Separator Devices
[0067] In a typical experiment, a feed suspension was prepared by
addition of about 40 mg of a silica particle standard in a single
portion to 100 mL of deionized water, creating a 0.04 wt %
suspension in a 200 mL glass beaker. The feed suspension was
stirred throughout the experiment. Turbidity measurements are
reported in Nephelometric Turbidity Units (NTU).
[0068] The feed line was connected between the device inlet 42
(FIG. 10A) and the beaker containing the stirred feed suspension. A
syringe pump was attached to the device outlet 43 and was used to
pull the feed suspension through the device inlet at a controlled
flow rate. The effluent (clarate) was collected in the syringe in
10 mL increments. The experiments were run in batch mode, with no
recirculation of the effluent stream. Syringe pump flow rates were
confirmed by recording the volume increase in the syringe over
time. In general, an amount of feed suspension equivalent to ten
times the volume of the collection chamber was processed before
measuring effluent turbidity to ensure the device had reached a
representative state of operation.
Example 1
Effect of Microporous Body
[0069] Devices 1 and 2 (Table 1) comprised collection chambers
having dimensions 40 mm.times.10 mm.times.2.0 mm. Each device
comprised inlet and outlet microchannels having dimensions of 16.5
mm.times.10 mm.times.0.1 mm. Device 1 comprised a 40 .mu.m mesh
microporous body 26 screen whereas, Device 2 did not. A feed
suspension containing 0.04 w/v % of 2 .mu.m silica standard
particles and a measured turbidity of 560 NTU was prepared in
deionized water. The feed suspension was presented to each device
at a feed rate of 200 microliters per minute (.mu.L/min) and
corresponded in each case to a residence time of approximately 4
minutes. The residence time is arrived at by dividing the nominal
volume of the device (800 .mu.L) by the 200 .mu.L/min throughput
rate. The effluent turbidities of the device with and without the
microporous body were 105 NTU and 135 NTU respectively. This result
demonstrates that while the presence of the microporous body
incrementally improves the performance of the device under the
conditions of this Example 1, the device may achieve a substantial
clarifying effect in the absence of such microporous body as
well.
Example 2
Effect of Particle Size
[0070] Device 2 was presented sequentially with two feed
suspensions; first a 1,600 NTU suspension containing 0.08 w/v % of
2 .mu.m silica particles, and second a 1,087 NTU suspension
containing 0.04 w/v % 10 .mu.m silica particles. Each feed
suspension was prepared in deionized water and presented to the
device at a throughput rate of 200 .mu.l/min. The effluent
turbidities of the 2 .mu.m and 10 .mu.m particle experiments were
320 NTU and 2.3 NTU respectively, and indicated both the
effectiveness of the device in removing the smaller particles, and
the greater susceptibility of larger particles to capture in the
collection chamber.
Example 3
Effect of Inlet and Outlet Microchannels
[0071] In this experiment the performance of Device 2 comprising
16.5 mm long inlet and outlet microchannels and was compared with
the performance of Device 3 having no inlet and outlet
microchannels. A feed suspension containing 0.04 w/v % of 2 .mu.m
silica standard particles was prepared in deionized water. Each
device was tested against the feed suspension processed at 200
.mu.L/min. The height of the collection chamber was 2.0 millimeters
in each case. The measured influent and effluent turbidities from
the device with the microchannels (Device 2) were 589 and 175 NTU
respectively. The measured influent and effluent turbidities from
the device with no microchannels (device 3) were 597 and 236 NTU
respectively. The experimental results illustrate an incremental
beneficial effect of the inlet and outlet microchannels on product
clarate quality.
Example 4
Effect of Inlet Microchannel Length
[0072] Device 2 comprising a 16.5 mm long inlet and 16.5 mm long
outlet microchannel was compared with Device 4 comprising a 66.5 mm
long inlet and 16.5 mm long outlet microchannel. A 700 NTU feed
suspension containing 0.04 w/v % of 2 .mu.m silica standard
particles was prepared in deionized water. Each device was tested
against the feed suspension processed at 200 .mu.L/min (a 4 min
residence time). The effluent turbidities from the devices with
16.5 mm and 66.5 mm long inlet microchannels were 274 NTU and 135
NTU respectively suggesting that a longer inlet microchannel can
substantially improve clarate quality.
Example 5
Effect of Device Scale
[0073] The performance of Device 3 having a nominal collection
chamber volume of 0.8 cm.sup.3 was compared with the performance of
Device 5 having a nominal collection chamber volume of 13.3
cm.sup.3. Neither device comprised an inlet or outlet microchannel,
and thus the feed suspension was presented directly through the
device fluid inlet into the collection chamber. Processed fluid
exited directly from the collection chamber through the device
fluid outlet. Each device was presented with a 526 NTU feed
suspension containing a 0.04 w/v % 2 .mu.m silica standard
particles prepared in deionized water. The 0.8 cm.sup.3 and 13.3
cm.sup.3 devices were tested against the feed suspension processed
at 0.2 mL/min and 2.0 mL/min respectively, corresponding to a 4 min
residence time in each device. The effluent turbidities of the 0.8
cm.sup.3 and 13.3 cm.sup.3 devices were 206 NTU and 137 NTU,
respectively, and indicated that performance observed for smaller
device may be scaled to larger devices at correspondingly higher
flow rates.
Example 6
Continuous Operation and Solids Clearance
[0074] A 22.2.times.3.8.times.0.2 cm device (Device 8) without
microchannels or a microporous sieve was assembled and its
performance evaluated. In a typical experiment, 6 g of tan clay
particles were added in a single portion to 3,000 mL of deionized
water, creating a 2,000 mg/L suspension in a 4 L glass beaker. The
solution was stirred for the entirety of the experiment. A
schematic of the lab process for monitoring solid settling in the
device and collection chamber (tub) clearance using different
backwashing designs is provided in FIG. 1 with the exception that
no inlet microchannel 21 or outlet microchannel 20 was present, the
feed suspension being introduced directly into the collection
chamber 14. Prior to the experiment, the device was primed with
deionized water and placed on a balance. The balance was tared and
the system was configured to record weight change in the device
over time. During forward operation, a peristaltic pump attached to
the device outlet pulled the feed suspension through the device
inlet and controlled flow rates. The effluent was collected in a
graduated cylinder in 1,200 mL increments. The experiments were run
in batch mode, with no recirculation of the effluent stream. Pump
flow rates were confirmed by recording the volume increase in the
cylinder over time. The solids accumulation in the device was
recorded from the balance every 15 seconds until 1,200 mL of
processed liquid had collected. Following forward processing, one
of several solids clearance protocols was implemented in the
reverse direction to flush out the accumulated solids into a waste
beaker in a backwash cycle. Following a backwash cycle, the device
was re-primed in the forward direction to begin a new forward
cycle. The weight remaining in the collection chamber represented
the amount of solids that could not be cleared using the solids
clearance protocol employed. Several cycles consisting of a forward
and back wash mode were run for each protocol tested. The
accumulated solids in the collection chamber following each
backwash cycle was recorded for the total volume of feed
processed.
Protocol 1: High Flow Backflush--Water Only
[0075] Device 8 (Table 1) was tested against a 2,000 mg/L TAN clay
feed suspension processed at 24 mL/min. After each 1200 mL of
volume processed, the pump direction was reversed and deionized
water was pumped through the device at 300 mL/min for 60 seconds.
The flushed solids were emptied into a separate waste container.
Following the 60 second water backwash, the pump speed was
decreased back to 24 mL/min and the system was placed back into
forward service. The weight remaining in the device was recorded on
the balance after the device had been re-primed. This forward and
back wash cycle was repeated three times and in each case 1,200 mL
processed was collected in each cycles. The data are shown in Table
2.
TABLE-US-00002 TABLE 2 Performance of Device 8 Over Three Cycles
Water Only Backflush Cycle Data Cycle 1 Cycle 2 Cycle 3
Irreversible Solid Accumulation (g) 1.43 2.15 2.9 Cycle Collection
Chamber Capacity 1.34 2.33 3.11 % Collection chamber Clearance 0
7.7 6.8 (cycle to cycle) Cycle Time (min) 45.5 48.75 49.25 Volume
Processed (mL) 1092 1170 1182 % Water Recovery 72.5 74.4 74.6
Cumulative Volume Processed (mL) 1092 2262 3444
Protocol 2 Alternating Air-Water Backflush
[0076] Device 8 (Table 1) was tested against a 2,000 mg/L TAN clay
feed solution processed at 24 mL/min. After 1200 mL of the feed
solution had been processed, the pump direction was reversed and
deionized water was pumped through the device at 300 mL/min for 45
seconds. During this time, the deionized water inlet was lifted out
of the beaker every 5 seconds for durations of 5 seconds to draw
into the flush line an approximately 25 mL confined air bubble
followed by a 5 second flush with deionized water. Alternating
air-water cycles were repeated 5 times during a single back wash
cycle. The flushed solids were emptied into a separate waste
container. Following the 45 second confined air bubble and water
backwash, the pump speed was decreased back to 24 mL/min and the
system was placed back into forward service. The weight remaining
in the device was recorded on the balance after the device
re-primed. This forward and back wash cycle was repeated after
every additional 1,200 mL processed volume for a total of three
complete cycles. The data are gathered in Table 3.
TABLE-US-00003 TABLE 3 Performance of Device Using Alternating
Air-Water Backflush Protocol Cycle Data Cycle 1 Cycle 2 Cycle 3
Irreversible Solid Accumulation (g) 0.96 1.02 1.28 Average
Breakthrough Capacity (g)* 1.49 % Collection Chamber Clearance*
35.6 31.5 14.1 Cycle Breakthrough Capacity (g) 1.13 1.59 1.75 %
Clearance (cycle to cycle) 15 35.8 26.9 Cycle Time (min) 45 47.75
46.75 Volume Processed (mL) 1080 1146 1122 % Water Recovery 83.8
84.7 84.4 Cumulative Volume Processed (mL) 1080 2226 3348
Protocol 3 Low and High Flow Dual Fluid--Air/Water Backflush.
[0077] Device 8 was tested against a 2,000 mg/L TAN clay feed
solution processed at 24 mL/min. After 1,200 mL of volume
processed, the pump direction was reversed and a mixture of
deionized water and air was fed into device for 45 seconds. The
water flow rate was 150 mL/min and the air flow rate was 0.1 scfh.
After 45 seconds of air and water flushing, the air flow feed line
was switched off and water-only was flushed back through the device
for an additional 15 seconds completing the back wash cycle. The
flushed solids were collected in a separate waste container.
Following the 60 second low velocity air and water flush, the pump
speed was decreased back to 24 mL/min and the system was placed
back into forward service. The weight remaining in the device was
recorded on the balance after the device had been fully re-primed,
i.e. there were no visible air bubbles or air pockets within the
device. This forward and back wash cycle was repeated after every
additional 1,200 mL processed volume for a total of four complete
cycles. The data are shown in Table 4. An analogous experiment was
carried out over five cycles at a water flow rate of 300 mL/min and
an air flow rate of 0.2 scfh during the back wash cycles. The data
are shown in Table 5.
TABLE-US-00004 TABLE 4 Low Flow Dual Fluid Solids Clearance
Protocol Cycle Data Cycle 1 Cycle 2 Cycle 3 Cycle 4 Irreversible
Solid Accumulation 0.21 0.6 0.8 0.9 (g) Average Breakthrough
Capacity 1.31 (g)* % Collection chamber Clearance* 83.9 54.1 38.8
31.2 Cycle Breakthrough Capacity (g) 1.01 1.08 1.68 1.46 %
Collection chamber Clearance 79.2 44.4 52.4 38.4 (cycle to cycle)
Cycle Time (min) 45.5 48.25 50.75 53.5 Volume Processed (mL) 1092
1158 1218 1284 % Water Recovery 86.3 87 87.7 88.3 Cumulative Volume
Processed 1092 2250 3468 4752 (mL) *Average of solids accumulated
each cycle- used to calculated % clearance
TABLE-US-00005 TABLE 5 High Flow Dual Fluid Solids Clearance
Protocol Cycle Data Cycle Cycle Cycle Cycle Cycle 1 2 3 4 5
Irreversible Solid 0.24 0.24 0.22 0.24 0.2 Accumulation (g) Average
Breakthrough 0.9025 Capacity (g)* % Collection chamber 73.4 73.4
75.6 73.4 77.8 Clearance* Cycle Breakthrough 0.91 0.94 0.91 0.7
0.85 Capacity (g) % Collection chamber 73.6 74.5 75.8 65.7 76.5
Clearance (cycle to cycle) Cycle Time (min) 46.5 49 47.5 51 48.75
Volume Processed (mL) 1116 1176 1140 1224 1170 % Water Recovery
73.1 74.5 73.7 75.5 74.4 Cumulative Volume 1116 2292 3432 4656 5826
Processed (mL) *Average of solids accumulated each cycle- used to
calculated % clearance
Discussion of Experimental Results
[0078] A simple relationship between device critical height, i.e.
the height of the device collection chamber and residence time
accounts for nearly all of the performance variations in the
devices studied. As demonstrated herein, the device can be
optionally configured with and without inlet and outlet
microchannels, and with or without a microporous body. It should be
noted that a single outlet microchannel, or a combination of an
inlet microchannel and an outlet microchannel can confer enhanced
performance characteristics, as can the presence of a microporous
body. The key performance governing dimension of the device is the
height between the top of the device inlet (or the top of the
device outlet) and the floor of the collection chamber (14). This
dimension is at times herein referred to as the critical height,
largely determines device performance, and corresponds to the
height of the collection chamber. Highly efficient particle
separation can be achieved when the critical height is matched to
the settling characteristics the particulates being removed.
[0079] A series of experiments established the relationship between
device critical height and particle settling characteristics. The
devices (Devices 3, 6 and 7) had 4.times.1 cm collection chambers
with varying depths and had no microchannels or microporous sieves.
A transfer function was established which accounted for 99.4% of
the performance variability and the relationship between residence
time and critical height for a monodisperse sample of 2 nm silica
particles. The experimental results were used to generate the
transfer function. A time to capture was calculated using Stoke's
settling velocity and the critical height for each experiment. The
capture time results can also be found in Table 6.
TABLE-US-00006 TABLE 6 Critical Turbidity Turbidity Expt. Particle
Capture Height V t.sub.R F IN OUT Capture Time RUN (cm) (cm.sup.3)
(sec) (mL/min) (NTU) (NTU) (%) (s) 1 0.60 2.4 480 0.30 656 364 45
1775 2 0.60 2.4 240 0.60 759 387 49 1775 3 0.20 0.8 480 0.10 679 58
91 600 4 0.60 2.4 360 0.40 822 464 44 1775 5 0.40 1.6 240 0.40 717
426 41 1183 6 0.20 0.8 240 0.20 534 204 62 600 7 0.40 1.6 480 0.20
717 306 57 1183 8 0.20 0.8 360 0.13 633 137 78 600
[0080] The trend in capture efficiency mirrors the trend in capture
time relative to residence time. The highest capture efficiency
occurs when the residence time is closest to the particle capture
time at a given critical height (Run 3). Conversely, the worst
efficiency occurs when the residence is much shorter than the
theoretical particle capture time (Runs 1, 2, and 4). Additional
factors contribute to particle capture in the device beyond
particle settling physics, and these factors include edge effects,
dead volumes, variable device height as the collection chamber
becomes saturated with particulates. Edge effects, dead volumes,
and variations in collection chamber height resulting from
sedimentation likely account for some of the additional capture
efficiency observed over that predicted by the capture times in
Table 6.
[0081] As noted, improved particle removal was observed when the
microfluidic devices comprised inlet and/or outlet microchannels
and a microporous body subdividing the collection chamber. Capture
efficiencies for 2 .mu.m particles with various device
configurations are presented in Table 7. The devices had a
4.times.1.times.0.2 cm collection chamber and feed rates were
employed such that the residence time of a particle traversing the
device was about 240 seconds. Microchannel lengths were varied at
the device inlet and outlet between 0 and 66.5 mm. The effect of
the presence or absence of a 40 .mu.m microporous body dividing the
collection chamber was also examined. The baseline capture
efficiency for a device with neither microchannels nor a
microporous sieve was 60% (Entry 1). Incorporation of an inlet
microchannel resulted in increased capture efficiencies of up to
81% (Entries 1-3). Alternatively, the presence of a microporous
body also increased capture efficiencies up to 81% (Entries 2 and
4).
TABLE-US-00007 TABLE 7 Microchannel Length, Microporous Sieve
Capture Efficiency Entry mm (Inlet/Outlet) (+/-) (%) 1 0/0 - 60 2
16.5/16.5 - 71 3 66.5/16.5 - 81 4 16.5/16.5 + 81
[0082] Fluid dynamics models suggested that the presence of one or
more microchannels influences particle trajectories within the
device to reduce the effective critical height. A COMSOL fluid
dynamics package was used to model the particle settling behavior
in the microclarification device. The model incorporated settling
physics, drag force, lift force, and edge effect parameters. While
the model could not fully predict all of the particle capture
behavior observed, it reliably predicted important behavioral
trends. Thus, the predicted 50% capture efficiency for 2 .mu.m
particles at a 240 second residence time was a modest
underestimation of the 60% capture efficiency observed
experimentally. The underpinning physical behavior was modeled well
enough to understand the impact of microchannel geometry on capture
efficiency.
[0083] Predicted particle trajectories and flow line patterns were
calculated using the COMSOL fluid dynamics modeling package. The
model suggests that during operation the particles in the lower
portions of the inlet microchannel enter the collection chamber
along trajectories tracking the lower portions of the collection
chamber. It is believed that the limited height of the microchannel
allows particles to settle into the bottom portion of the flow
volume in the relatively short time required for the particles to
traverse the microchannel and enter the collection chamber. Thus,
the effective critical height in the collection chamber is
decreased, and capture efficiency is increased, compared to a
chamber without an inlet microchannel. The phenomenon can be
understood by considering the expansion of lamellar flow lines from
the microchannel into the collection chamber. As a particle passes
from the inlet microchannel into the collection chamber, it follows
its respective lamellar flow line and the particle distribution is
preserved as a function of relative channel height. The
microchannel acts as a high speed concentrator for the lowest flow
line and decreases the time required to capture particles in the
collection chamber resulting in increased capture efficiency at
equivalent residence times.
[0084] The COMSOL model was used to evaluate flow characteristics
in the presence and absence of a microporous body. The COMSOL model
suggested that the microporous body tends to influence lamellar
flow within the collection chamber improves particle capture
efficiency. It is believed that the microporous body acts like a
weir and directs flow towards the bottom of the collection chamber
and creates dead volumes near the top of the collection chamber.
The particles do not have enough inertia under the lamellar flow
conditions to exit the flow lines and are carried toward the bottom
of the collection chamber. Synergy between microchannel and
microporous body occurs because the inlet microchannel concentrates
particles and directs them towards the lowest flow lines within the
collection chamber. Moreover, the microporous body increases the
total fraction of flow in the bottom of the collection chamber. The
increased flow carries more particles deeper into the collection
chamber thereby reducing the effective critical height of the
collection chamber and increasing capture efficiency.
Example 7
Chemical Treatment and Particle Size
[0085] Device 8 having a 22.2.times.3.8.times.0.2 cm collection
chamber but configured without inlet and outlet microchannels or a
microporous body. A tan clay slurry with a turbidity of 1484 NTU
was prepared in deionized water at a particle concentration of 2000
mg/L and presented to the device at a flow rate corresponding to a
residence time of 170 seconds. The processed fluid collected from
the device outlet had a turbidity of 384 NTU, which corresponds to
75% particle capture efficiency.
[0086] The 170 second residence time was chosen to be intermediate
between a theoretically high capture efficiency of 10 .mu.m
particles and low capture efficiency for 2 .mu.m particles.
Particle size analysis of the influent, effluent, and sludge
produced by back flushing the device show the enrichment of small
particles in the effluent and large particles in the sludge. The
particle size distribution in the sludge was centered above 10
.mu.m while that of the effluent was centered near 2 .mu.m.
Treating the TAN clay feed suspension with 5 mg/L of the coagulant
PC2700 re-centered the particle size distribution at nearly 100 nm.
The PC2700 treated feed was presented to the device at a flow rate
corresponding to a residence time of 40 seconds yielded an effluent
having a turbidity of 15 NTU; which corresponds to 98% particle
capture efficiency. The increased capture efficiency despite the
shorter residence time is a direct result of the coagulant and its
effect on particle size distribution.
Particle Clearance and Continuous Operation
[0087] A key feature of a practical inline clarification device is
the ability to clear the accumulated solids and maintain a
continuous process. Four different back flushing protocols were
examined with the objective of fluidizing particles captured during
fluid purification and clearing them from the device using a
minimal amount of water. Incomplete clearance of captured particles
was shown to result retained solids after each back wash over a
series of cycles and was shown to result in a progressive loss of
collection chamber capacity over time. An efficient protocol would
minimize retained solids and have a collection chamber capacity
loss rate near 0 mg/mL.
[0088] The initial back flush protocol relied on water at high flow
to clear the solids. The small scale of the microfluidic separation
devices enforces lamellar flow for most flow regimes less than 6
L/min. A flow rate of 300 mL/min was used to establish a baseline
with respect to the other strategies employed. The high flow water
protocol resulted in 0.74 g of retained solids and a capacity loss
rate of approximately 0.6 mg/mL of processed volume. A confined air
bubble strategy was tested where a series of approximately 25 mL
air bubbles were used to push the solids from the device at an
air-water interface. The air bubble strategy resulted in similar
retained solids value of 0.77 g, but decreased the collection
chamber capacity loss rate to 0.1 mg/mL. A dual fluid strategy was
tested in which both air and water were used simultaneously at low
flow without creating a uniform air water interface. The dual fluid
strategy reduced the retained solids value to 0.35 g, but only
marginally reduced the loss rate to 0.12 mg/mL. Doubling the
air/water flows in the dual fluid approach slightly improved
retained solids to 0.25 g, but yielded an optimal clearance
protocol where the capacity loss rate was negligible. The
microclarifier system was continuously run for five cycles using
the high flow air/water backwash at a water recovery rate of
85%.
Comparative Example
[0089] A comparative test was performed using 2 .mu.L particles in
both the microfluidic separation device provided by the present
invention and a labscale upflow clarifier. A residence time of 8
minutes was used for each device and a rise rate of 12.2
LPM/m.sup.2 (0.3 gpm/ft.sup.2) was maintained in the upflow
clarifier. The microfluidic separation device captured 90% of
particles reducing turbidities to 58 NTU from 560 NTU. The upflow
clarifier captured only about 2% of particles reducing turbidities
to 541 NTU from 551 NTU. At equivalent residence times the use of
the microfluidic separation device provided by the present
invention was clearly superior to the conventional clarification
technique.
[0090] The foregoing examples are merely illustrative, serving to
illustrate only some of the features of the invention. The appended
claims are intended to claim the invention as broadly as it has
been conceived and the examples herein presented are illustrative
of selected embodiments from a manifold of all possible
embodiments. Accordingly, it is the Applicants' intention that the
appended claims are not to be limited by the choice of examples
utilized to illustrate features of the present invention. As used
in the claims, the word "comprises" and its grammatical variants
logically also subtend and include phrases of varying and differing
extent such as for example, but not limited thereto, "consisting
essentially of" and "consisting of." Where necessary, ranges have
been supplied, those ranges are inclusive of all sub-ranges there
between. It is to be expected that variations in these ranges will
suggest themselves to a practitioner having ordinary skill in the
art and where not already dedicated to the public, those variations
should where possible be construed to be covered by the appended
claims. It is also anticipated that advances in science and
technology will make equivalents and substitutions possible that
are not now contemplated by reason of the imprecision of language
and these variations should also be construed where possible to be
covered by the appended claims.
* * * * *