U.S. patent application number 10/567415 was filed with the patent office on 2007-07-12 for power efficient flow through capacitor system.
This patent application is currently assigned to BIOSOURCE, INCORPORATED. Invention is credited to Marc D. Andelman, Shihab Kuran, Jon Zulkiewicz.
Application Number | 20070158185 10/567415 |
Document ID | / |
Family ID | 34135182 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070158185 |
Kind Code |
A1 |
Andelman; Marc D. ; et
al. |
July 12, 2007 |
Power efficient flow through capacitor system
Abstract
The invention features a flow-through capacitor system that
achieves enhanced power efficiency by sequential control and
actuation of at least two or more flow-through capacitor cells
within the flow-through capacitor system. Alternatively or in
addition, power efficiency is enhanced by integrating the
purification stages of the system, for example, by placing more
than one cell within a single cell casing. Preferably, integrated
stage flow-through capacitors are controlled sequentially.
Inventors: |
Andelman; Marc D.;
(Worcester, MA) ; Kuran; Shihab; (Green Brook,
NJ) ; Zulkiewicz; Jon; (Palmer, MA) |
Correspondence
Address: |
LESLIE MEYER-LEON, ESQ.;IP LEGAL STRATEGIES GROUP P.C.
1480 FALMOUTH ROAD
P.O. BOX 1210
CENTERVILLE
MA
02632-1210
US
|
Assignee: |
BIOSOURCE, INCORPORATED
1200 MILLBURY STREET, SUITE 7F
WORCESTER
MA
01607
|
Family ID: |
34135182 |
Appl. No.: |
10/567415 |
Filed: |
August 6, 2004 |
PCT Filed: |
August 6, 2004 |
PCT NO: |
PCT/US04/25582 |
371 Date: |
February 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60492938 |
Aug 6, 2003 |
|
|
|
Current U.S.
Class: |
204/229.7 ;
204/267 |
Current CPC
Class: |
C02F 1/4604 20130101;
C02F 2103/08 20130101; C02F 2201/4615 20130101; C02F 2001/46152
20130101; C02F 2201/4611 20130101; C02F 2201/4613 20130101; C02F
2209/005 20130101; C02F 1/4691 20130101 |
Class at
Publication: |
204/229.7 ;
204/267 |
International
Class: |
C25B 9/18 20060101
C25B009/18 |
Claims
1. A flow-through capacitor system comprising a plurality of
flow-through capacitor cells, each of said plurality of cells in
electrical communication with a charge cycle sequence
controller.
2. The flow-through capacitor system of claim 1, further comprising
a plurality of current collectors and a flow spacer shared among
said plurality of current collectors.
3. The flow-through capacitor system of claim 1, which is operated
such that multiple concentration bands exist simultaneously within
a given material layer.
4. The flow-through capacitor system of claim 1, further comprising
a conductivity controlled valve between at least two of said
plurality of current collectors.
5. The flow-through capacitor system of claim 1, further comprising
a flow stream parallel to at least two of said plurality of current
collectors, with continuous purification and concentration streams
directed to separate collection paths.
6. The flow-through capacitor system of claim 4, wherein fluid is
manipulated to form adjacent purification and concentration streams
that are separately collected without need for a valve.
7. The flow-through capacitor system of claim 1, wherein valves are
individually triggered with charge cycles in order to produce a
purified product stream.
8. The flow-through capacitor system of claim 1, wherein said
flow-through capacitor system has a staging efficiency of 50% or
more.
9. The flow-through capacitor system of claim 2, wherein said
flow-through capacitor system has a power efficiency of 50% or
more.
10. The flow-through capacitor system of claim 1, wherein the
charge cycles of individual cells are synchronized to correspond
with the arrival of a segment of purified water traveling serially
through multiple cells.
11. The flow-through capacitor system of claim 1, wherein voltage
is incremented in a step wise fashion as cells are sequentially
powered by adding them in series.
12. The flow-through capacitor system of claim 1, wherein cells are
powered by sequentially switching them together in parallel.
13. The flow-through capacitor system of claim 1, whereby the
voltage varies along the flow path.
14. The flow-through capacitor system of claim 1, wherein charged
capacitor cells are used to power discharged capacitor cells.
15. The flow-through capacitor system of claim 14, comprising a DC
to DC converter between cells or groups of cells.
16. The flow-through capacitor system of claim 1, wherein
individual flow-through capacitor cells, or groups of cells, are
controlled in a timed sequence.
17. The flow-through capacitor system of claim 16, wherein each of
said cells is contained in a cell holder and each cell holder
contains no more than one of said cells, said cell holder being a
container, a cartridge holder, or a casing.
18. The flow-through capacitor system of claim 16, wherein the
charge cycles between individual flow-through capacitor cells are
either asynchronous or out of phase by at least one quarter
second.
19. The flow-through capacitor system of claim 16, wherein the
charge cycles are actuated by a timer, a conductivity reading, a
voltage, or pH.
20. The flow-through capacitor system of claim 16, wherein valves
to individual cells or groups of cells that dispose of waste,
deliver purified fluid, or which recycle in flow loops are
triggered synchronously or asynchronously together with the above
charge cycles.
21. The flow-through capacitor system of claim 16, comprising for
reducing peak wattage by at least 30%.
22. The flow-through capacitor system of claim 16, wherein each of
said cells is actuated between one and 359 degrees out of
phase.
23. The flow-through capacitor system of claim 16, wherein
sequential operation of charge cycles follows the direction of
flow.
24. The flow-through capacitor system of claim 16, comprising a
power management system for sharing power between the flow through
capacitor cells, said power management system comprising one or
more of a battery, a fuel cell, and a generator.
25. The flow-through capacitor system of claim 16, wherein failed
or short circuited cells are bypassed by means of a sensing
circuit.
26. The flow-through capacitor system of claim 16, wherein either
the purified product or concentrated waste segments of water from
one or more cells or cell groups are combined together.
27. The flow-through capacitor of claim 26, wherein said system
achieves better than 40% recovery or purification.
28. The flow-through capacitor of claim 26, wherein said segments
of water are combined through a manifold.
29. The flow-through capacitor system of claim 16, wherein a dead
volume due to the flow spacer is larger than the dead volume
between the capacitor cell and the inside of the cartridge
holder.
30. The flow-through capacitor system of claim 2, wherein two or
more cells are contained within a single cell holder, said cell
holder being a container, a cartridge holder, or a casing.
31. The flow-through capacitor system of claim 30, wherein the
plurality of current collectors bracket a stack of true series
electrode assemblies.
32. The flow-through capacitor system of claim 10, wherein current
declines with each successive charge cycle.
33. The flow-through capacitor system of claim 10, wherein at least
one of said cells differs in size from at least one other of said
cells.
34. A method of charging a flow through capacitor system,
comprising providing a source of DC power and distributing said DC
power in sequential fashion to individual flow through capacitor
cells in order to minimize a capacitive charging power surge.
35. The method of claim 34, further comprising using a voltage or
amperage sensor to control sequence of actuation among a group of
cells.
Description
REFERENCE TO PRIOR APPLICATION
[0001] This application is based on and claims priority from U.S.
provisional patent application Ser. No. 60/492,938, filed Aug. 6,
2003, which is hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The field of the invention is systems for capacitive
deionization of fluids by the use of flow through capacitors.
BACKGROUND OF THE INVENTION
[0003] It is generally recognized that, in order to purify
concentrated water, flow-through capacitor purification systems
need to be staged. It is an objective of the present invention to
improve the staging and power efficiency of flow-through
capacitors. Power efficiency is a measure of how well power is
distributed in a multi-cell system, and is defined here as the
averaged percent of power needed by a flow-through capacitor system
divided by the system's peak power needs. Staging efficiency is a
measure of how well a staged system is designed to limit the
inter-stage mixing caused by inter-stage dead volume, and is
defined here as the percent purification achieved by a multi-cell
or multi-stage system divided by the sum of the percent
purifications of each individual cell or stage. In the past, each
cell or stage of a flow-through capacitor system has been housed
within a separate housing or cartridge holders, which were charged
or discharged together, either in parallel or in series. See, e.g.,
US 2004/0121204 A1. A dead volume mixes with the water which is
purified in each stage, and decreases the resolution of the band of
purified water, due to band broadening, as it moves from one stage
to another. The mixing effect also leads to a need to operate with
greater numbers of stages, and may reach a lower voltage limit, as
voltage is lowered when used with concentrated water such as sea
water. Therefore, a need exists for an improved flow-through
capacitor which has less mixing of purified or concentrated water
with each other or with the feed water, and for a method and system
which allows the capacitor to operate more efficiently at lower,
energy saving voltages.
[0004] In addition, capacitors exhibit a charging characteristic
whereby upon initial application of a voltage, they require peak
power. Charging banks or stages of capacitors all at once
multiplies this peak power, thereby increasing the wattage rating
and cost of power supplies needed to provide this power. Therefore,
an additional need exists to more efficiently distribute power to
banks of flow-through capacitor cells which may be fluid or
electrically staged in a combination of parallel or in series.
SUMMARY OF THE INVENTION
[0005] Sequentially powered and controlled flow-through capacitor
systems of the present invention control individual flow-through
capacitor cells, or groups of cells, in a timed sequence, with
individual cells out of phase with each other. The system of the
present invention may be configured with one cell per cartridge
holder. Preferably, the flow-through capacitor system is configured
to have one or more integrated stages, by which is meant that two
or more purification stages occupy a common housing, i.e., are
within the same container or cartridge holder. When one
flow-through capacitor cell represents a discreet purification
stage, integral staging is achieved by housing two or more
flow-through capacitor cells within a single container or cartridge
holder.
[0006] The integrated stage design embodiment of the present
invention eliminates the need, cost, and complication of connecting
separate cartridge holders per stage by containing multiple stages
within the same cartridge holder. This integrated stage design
reduces the band broadening that would otherwise be caused by
mixing of the band of purified water with dead volume as it moves
from stage to stage. Staging efficiencies of 50% or more are
possible by using sequential charge cycles coupled with integrated
stage design. Another advantage achieved by organizing a
flow-through capacitor system so that some or all stages are
physically integrated is to diminish the amount of dead volume that
otherwise exists between the capacitor layers and the inside the
walls of the cartridge holder or capacitor container.
[0007] The integrated stage design of the present invention
incrementally sharpens purified and concentrated bands of feed
solution as it flows from stage to stage. In individually staged
capacitors of the prior art, a dead volume exists between each
multilayer capacitor cell and the internal walls of the housing of
the cartridge holder. In the integrated stage embodiment, each
stage shares common capacitor material layers. Only the current
collectors, or, where electrodes are conductive enough not to need
a current collector, the electrodes, are independently actuated and
electrically separated from each other. Therefore, multiple stages
can share the same cartridge holder, thereby eliminating the need
for separate current collectors. Eliminating excess dead volume
through integrated staging allows operation of the capacitor at
lower voltage while, at the same time, obtaining a deep
purification peak. The result of this is that the capacitor may be
operated at lower, more energy efficient voltages.
[0008] One special use of integrated staging is for low energy
desalination of sea water. The present invention achieves that end
by removing a little bit of salt at a time at low energy, and then
amplifying this signal by virtue of synchronous charging of
multiple capacitor stages that share the same capacitive material,
spacer, and optional charge barrier layers in order to sharpen
bands of purified and concentrated water. This band sharpening
method uses staging to refine or sharpen concentration bands,
analogous to other staged methods such as chromatography,
distillation, and absorption.
[0009] An additional advantage of the sequential charging system of
the present invention is to provide power in steps between multiple
cells in order to optimize peak power usage to allow use of lower
wattage, less expensive power supplies, so as to avoid the
requirement for peak power at the initial application of voltage
and distribute power to banks, or stages, of flow-through capacitor
cells which may be fluid or electrically staged in a combination of
parallel or in series. By sequentially spreading out the
application of peak power to individual cells in a multi-cell
system, power efficiencies of up to 50% to 100% are possible. In
other words, power usage may approach the averaged power needed
over the sum of the individual cell cycles.
[0010] The flow-through capacitor of the present invention can make
use of the same layers used in prior flow-through capacitors
systems, such as, for example, U.S. Pat. No. 6,413,409 and U.S.
Pat. No. 6,709,560 ("Charge barrier flow-through Capacitor").
Preferably, in a flow-through capacitor system of the present
invention, in place of integral current collectors backing one or
more electrode layers, multiple current collectors are arranged
sequentially along a fluid flow path. In the integrated stage
embodiment, these are arrayed within the same cartridge holder.
These current collectors are made to be charged or discharged
according to various sequences and times. The sequential charging
of the multiple current collectors may either be done in series or
in parallel, and in addition, within the context of either a series
or a parallel flow cell.
[0011] Load leveling may be achieved by such sequential control of
flow-through capacitors cells according to the present invention
whereby capacitor cells are charged or discharged in a timed
sequence. In doing so, the present invention avoids the
multiplication of peak power needs, thereby minimizing the size and
cost of power supplies required to power a multiple flow-through
capacitor system. The cells may be progressively powered or charged
in parallel, or in series. If powered or charged in series, the
voltage is stepped up as each cell is switched in an additive
sequence onto the others in series. Parallel cells may be powered
or charged by switching onto a common bus. Individual cells may
have individual or common power supplies. Flow-through capacitor
cells can be integrated within a single cartridge holder, or may be
discrete cells in a combination of series or parallel electrical or
fluid flow. Upstream cells within an integrated stage cartridge
holder, or individual stages with one cell per cartridge holder, or
groups of cells, may be charged first, then additional downstream
stages or cells are charged with a time delay. Cells connected
together, either singly or in groups, in parallel or series in an
electrical or fluid flow sense, may be sequentially actuated or
controlled according to the present invention. This time delay may
be selected so that the peak capacitive charging peaks do not
overlap, in order to obtain a lower average peak charging
current.
[0012] It is desirable for the present invention to cut the peak
wattage of power supplies needed by 30% to 50% or more. In order to
level the watt, amperage, or power load of the flow-through
capacitor system, charge cycles of individual cells or groups of
cells, either in series or parallel, are preferably actuated
sequentially, or between 1 and 359 degrees out of phase, such as by
charging or discharging, or reversing the cell polarities in
increments that vary between one and one hundred seconds. For
example, cells can be charged or discharged in increments of
between five and thirty seconds. Sequential operation of the charge
cycles may also follow other patterns than the direction of flow.
For example, where it is important to quickly reduce the output
conductivity, it may be preferable to charge the downstream cells
first. In lieu of time, a voltage or an amperage sensor may relay
data from individual cells to a logic chip or circuit in order to
control the sequence of actuation of a series of flow-through
capacitor cells or groups of cells.
[0013] The circuits used to distribute power to flow-through
capacitor system preferably provide DC power in a sequential
fashion in order to minimize the capacitive charging power surge.
Circuits designed for stepwise charging of multiple batteries,
multiplex charging or discharge of banks of batteries may be used
to distribute power to the flow-through capacitor cells according
to the present invention; examples of such circuit design include,
without limitation, U.S. Pat. Nos. 6,140,799, 6,326,768, 6,140,799,
6,750,631, 5,506,456, 5,461,264, 5,483,643, 5,514,480, and
5,710,504 (each hereby incorporated by reference). Where batteries
or battery banks are replaced by flow-through capacitor cells or
capacitor banks, and with the addition of a necessary switches,
relays, or FET circuits that sequentially switch in or switch out
flow-through capacitor cells using a timer, voltage sensor, or
amperage sensor logic of the present invention. Power sequencer
circuits designed to distribute power across multiple loads, such
as those known to those skilled in the art to be used to charge
banks of batteries, capacitors, lights, motors, or other multiple
loads, and preferably which are designed to avoid power surges when
charging multiple loads, can be adapted to provide DC power and
used in the flow-through capacitor system of the present invention,
where the loads are multiple flow-through capacitors. Examples of a
power sequencer circuit include, but are not limited to, U.S. Pat.
Nos. 6,766,222 and 6,239,510 (each hereby incorporated by
reference), circuits used in solar power distribution such as U.S.
Pat. No. 6,685,334 (hereby incorporated by reference) where the
solar power source is replaced by a DC power source, power
distribution circuits where DC power is provided or substituted for
AC outputs and used to provide sequential power control according
to the present invention. One example, without limitation, of a
timer circuit that may be used for sequential control of
flow-through capacitor cells according to the present invention is
described in U.S. Pat. No. 6,011,329 (hereby incorporated by
reference). Power Field Effect Transistors (FETS) or thyristors may
be also used as mechanical contacts or relays in various timer
circuits that may be employed, for one example, an H Bridge FET
circuits such as described by Blanchard, Eugene
(http://www.armory.com/.about.rstevew/Public/Motors/H-Bridges/Blanchard/h-
-bridge.htm; last visited Aug. 6, 2004).
[0014] Power may be distributed to multiple stages of the present
invention by using a power distribution or power management system
circuits designed to control peak loads, or a sequential power
distribution circuit. Useful examples of circuits that may be used,
where the electric loads are multiple flow-through capacitor cells,
include without limitation U.S. Pat. No. 5,119,014, U.S. Pat. No.
4,093,943, U.S. Pat. No. 4,180,744, RE29560, U.S. Pat. No.
6,385,057, U.S. Pat. No. 5,070,440, U.S. Pat. No. 5,969,435, and
U.S. Pat. No. 4,894,764 (each hereby incorporated by reference). In
an additional embodiment, power sharing schemes where batteries,
fuel cells, or generators are used to receive or give power to or
from either the flow-through capacitor system of the invention or a
prior art flow-through capacitor system may also be used. An
example of such a power sharing system is described in, but not
limited by, U.S. Pat. No. 5,969,435 (hereby incorporated by
reference). The present invention may be combined with various
power sharing circuits that may also be used to level the load,
distribute power, or conserve energy during the charging of
multiple capacitor cells or stages. Systems described for charging
multiple batteries may be used, with capacitors replaced for some
or all of the batteries. Examples are described in but not limited
to U.S. Pat. Nos. 6,444,159, 5,757,163, 5,955,868, and 6,157,867
(each hereby incorporated by reference).
[0015] A sequential power circuit similar to ones used to generate
current pulses, including but not limited to U.S. Pat. Nos.
4,001,598, 5,952,735, and 5,585,758 (each hereby incorporated by
reference) can also be used to sequentially charge and discharge
flow-through capacitor loads to a power source in order to offset
by between 1 and 100 seconds the peak amp and power requirements of
individual flow-through capacitor cells in a multiple cell system.
Failed or short circuited cells may be bypassed by using a current
or voltage sensing or voltage drop circuit such as without
limitation U.S. Pat. Nos. 6,087,035, 5,362,576, and 5,650,240 (each
hereby incorporated by reference) to close valves into or out of
individual cells . In addition, another way to cut peak power needs
is to use charged capacitors to power discharged capacitors, using
an optional DC to DC converter between cells or series groups of
cells to save additional energy if desired.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic illustration of an integrated stage
flow-through capacitor and system of the present invention.
[0017] FIG. 2 is a detail view of a flow-through capacitor cell
assembly.
[0018] FIG. 3 is an illustration of an integrated stage
flow-through capacitor cell.
[0019] FIG. 4 is a schematic illustration of a spiral wound
integrated stage flow
[0020] FIG. 5 is a representation of a nested current collector
flow-through capacitor.
[0021] FIG. 6 is a representation of a series or series array
flow-through capacitor.
[0022] FIG. 7 is an illustration of concentration stream manifold
22 and purification stream manifold 23 combining together the
concentration streams 20 and purification streams 21 produced by
multiple electrode or electrode assembly layers 8.
[0023] FIG. 8 is a graphical illustration of sequential charging
current of an eight cell flow-through capacitor system.
DETAILED DESCRIPTION
[0024] FIG. 1 is a schematic of an integrated stage flow-through
capacitor cell and system of the present invention, showing a
controller or logic means 1, a power supply 2, e.g., a capacitor
power supply, a switch power supply 3, ground 4, switches, relays,
or FETS, e.g., switches 5, a cartridge or cell holder 6 as a casing
for one or more capacitor cells, inlet 7, electrode or electrode
assembly 8, outlet 9, flow path 10, individual current collector
11, individual current collector lead 12, circuit 13, e.g., an
integrated circuit, programmable logic chip, digital input/out, or
printed circuit; cell assembly 14, and sensor 15. A computer or
controller 1 and a additional digital input/output 13 controls and
actuates switches, relays, or FETS 5 in either a pre-programmed or
feed-back controlled sequence using conductivity, pH, or other
composition data, or flow, amperage, or voltage data supplied to
controller 1 by sensor 15. Switch 5 can be multiple switching, and
can also be an integrated circuit or chip with multiple outputs,
can be triggered to ground 4 and thereby allow flow of current to
current collector leads 12 into individual current collectors 11.
Cell assembly 14 is made of electrode or electrode assembly layers
8 with flow spacer or spacers 16 (shown in FIG. 2), and individual
current collectors 11. Multiple switching 5 can be controlled by a
programmable chip, computer, controller, logic, timer, or in
response to amp, voltage, or conductivity sensor data input, to
sequentially charge or power the individual collector leads 12.
[0025] FIG. 2 represents a detailed view of a flow-through
capacitor cell assembly 14 of the present invention showing
optional electrical insulating spacers 15, insulating electrodes or
electrode assemblies 8 one from the other. Electrode assemblies 8
are backed by individual current collectors 11 which are
individually connected to individually actuated electrical leads
12.
[0026] FIG. 3 represents an integrated stage flow-through capacitor
cell of the present invention with individual current collectors
11, current collector leads 12, against electronically conducting
electrode or electrode assembly 8. The electrode or electrode
assembly 8 is spaced apart by flow space or flow spacer 16 with
optional flow or series electrical isolation gaskets 14. Flow path
10 is shown cutting across the multiple current collectors 11
connected to individual electrical leads 12. The multiple current
collectors shown in FIG. 3 may be thin enough to be wires, for
example, less than two millimeters in diameter.
[0027] FIG. 4 represents a spiral or concentric flow-through
capacitor of the present invention with electrodes or electrode
assembly 8, flow path 10 intercepting multiple current collectors
11 connected to individual electrical leads 12.
[0028] FIG. 5 represents a nested integrated stage flow-through
capacitor single electrode assembly layer 8 with associated
individual current collectors 11 and current collector leads 12,
flow path 10 and flow inlet our outlet.
[0029] FIG. 6 represents a flow-through capacitor of the present
invention with a matrix series connection such that individual
cells may be connected in series both horizontally and vertically.
FIG. 6 illustrates cartridge holder or capacitor casing 6, inlet or
outlet 7, outlet or inlet 9, current collectors 11, individual
current collector leads 12, and series separator 18, and high
resistive series cell separator flow path 10. Only individual
current collectors 11 and current collector leads 12 are shown,
with the addition of inter-cell series separators 18. An optional
high resistive flow path 19 is included for use when current
collectors 11 are connected in series across the stack. Either a
parallel or a series cell, not shown, would be placed between the
end current collectors 11. Where series cells are used, and where
each of these cells is in turn connected in series, the resulting
capacitor cell would form a series matrix, with resulting voltage
upon charge of the matrix the multiple of the series voltage of the
individual cells times the number of series cells further connected
together in series. Cartridge holder or capacitor casing 6 contains
the matrix connected flow-through capacitor formed by these
components plus additional electrodes or electrode assembly layers
8 and flow spacers 16 shown in FIG. 2
[0030] FIG. 7 represents a flow-through capacitor of the present
invention with the flow parallel to the current collector 11, which
may be used to provide continuous concentration streams 20 and
purified solution flow channel 21 to provide a purification stream.
Concentration stream 22 is a flow channel for concentrated
solution. Purification stream 23 is a flow channel for purified
solution. Concentration stream 22 and purification stream 23 are
connected by manifolds so as to combine together the concentration
streams 20 and purification streams 21 produced by multiple
electrode or electrode assembly layers 8.
[0031] In FIG. 8, curves 11 through 18 represent eight separate
charging currents of eight flow-through capacitor cells
sequentially charged at constant voltage in an eight cell
integrally staged flow-through capacitor system. Optionally,
constant current schemes can also be used. This charging scheme can
be applied to either integrated or individual flow-through
capacitor cells. Notice how each current trace, 11 through 1 8, has
a typical capacitive charging shape, with peak current in the time
equals less than one seconds, then leveling off rapidly after that
over a period of 1 to 60 seconds or more. If, for example, the
multiple cells have been charged together in parallel or in series,
there would only have been one charging curve with a maximized peak
wattage. This is undesirable because it requires a larger, more
expensive power supply. By offsetting the peak amperage and power
curves as in FIG. 8, the additive power is reduced. Optimally, the
additive power can be averaged over multiple cells in this way, to
comprise the average power usage over a charge cycle averaged over
a number of cells. The charge cycles can be synchronized to
correspond with the arrival of a traveling purification segment or
peak as it moves serially from cell to cell, in order to trigger
progressive removal of total dissolved solids from that
purification peak. Flow can also be parallel through a number of
cells with asynchronous charge cycles. A charge cycle may be a
combination of constant voltage, constant current, reverse
polarity, and optional shunt cycles, with each such portion of a
charge cycle lasting between zero and 300 seconds or more, for
example 60 seconds, or 5000 seconds. Charge cycles between
individual flow-through capacitor cells may be asynchronous or out
of phase between one quarter and 300 seconds or more, for example,
100 seconds or 10,000 seconds. Charge cycles may be triggered by a
timer, a conductivity reading, a voltage, a pH, or other data.
Valves to individual cells or groups of cells that dispose of
waste, delivered purified fluid, or which recycle in flow loops may
be triggered synchronously or asynchronously together with the
above charge cycles. For example, it may be desirable to trigger
individual valves from individual cells in a multi-cell system at
the same time the purification or waste part of a charge cycle is
triggered. The purified product or concentrated waste segments of
water from individual cells or cell groups may subsequently be
combined together, such as through a manifold, in order to maximize
the level of purification or concentration, for example, to than
40% purified and better than 40% recovery or more, for example
90%.
[0032] In one embodiment, the integrated stage flow-through
capacitor of the present invention utilizes multiple current
collectors 11 individually connected to current collector leads 12
with common flow path layers 14, and electrode or electrode
assembly layers 8 that may be optionally separated by inter
electrode insulators 19. The current collectors are multiple in the
sense that a plurality of current collectors are transected by a
common flow path 10, share common electrode or electrode assemblies
8, or are placed within the same cartridge holder or capacitor
casing 6. A stage is represented by a pair of current collectors
typically perpendicular to, but optionally parallel to, the flow
path 10. Flow path 10 therefore typically intersects oppositely
charge current collector pairs. As the fluid in flow path 10 flows
across these current collector pairs, the current collectors,
through individual current collector leads 12, are activated in a
sequence. This sequence can either be programmed or may be trigged
by a sensor 17. Each time a pair of current collectors is activated
with a voltage, additional materials are either removed from or
added to a band of water which flows from cell to cell, where cell
may be defined as a oppositely charged pair of current collectors
charged together in time as part of a charge sequence among many
pairs of current collectors. The multiple current collectors 11 of
the present invention within each cartridge holder may bracket a
stack of electrode assemblies 8 that are electrically insulated
from each other in true series fashion, such as in U.S. Pat. No.
6,628,505 (hereby incorporated by reference), or the current
collectors can be bundled together in parallel, to form anode and
cathode, with geometries as known to those skilled in the art,
including but not limited to the geometries of U.S. Pat. No.
5,192,432, "Flow Through Capacitor"; U.S. Pat. No. 5,196,115,
"Controlled Charge Chromatography System"; U.S. Pat. No. 5,200,068,
"Controlled Charge Chromatography System"; U.S. Pat. No. 5,360,540,
"Chromatography System"; U.S. Pat. No. 5,415,768, "Flow-Through
Capacitor"; U.S. Pat. No. 5,538,611, "Planar, Flow-Through,
Electric, Double Layer Capacitor And A Method Of Treating Liquids
With The Capacitor"; U.S. Pat. No. 5,547,581, "Method Of separating
Ionic Fluids With A Flow Through Capacitor"; U.S. Pat. No.
5,620,597, "Non-Fouling Flow-Through Capacitor"; U.S. Pat. No.
5,748,437, "Fluid Separation System With Flow-Through Capacitor";
U.S. Pat. No. 5,779,891, "Non-Fouling Flow-Through Capacitor
System"; U.S. Pat. No. 6,127,474, "Strengthened Conductive Polymer
Stabilized Electrode Composition And Method of Preparing"; U.S.
Pat. No. 6,325,907, "Energy And Weight Efficient Flow-Through
Capacitor, System And Method"; U.S. Pat. No. 6,413,409,
"Flow-Through Capacitor And Method Of Treating Liquids With It
(each of which are hereby incorporated by reference). Those skilled
in the art will also be guided by WO93/13844, "Chromatography
System With flow-Through Capacitor And Method"; WO94/26669, "A
Planar, Flow-Through, Electric, Double Layer Capacitor And A Method
Of Treating Liquids With The Capacitor"; WO95/21674, Flow-Through
Capacitor And Chromatographic System And Method"; WO97/13568,
"Non-fouling, Flow-fouling, Flow-Through Capacitor system And
Method Of separation"; WO00/14304, "Flow-Through Capacitor And
Method Of Treating Liquids With It"; WO 01/09907 A1, Flow-Through
Capacitor And Method"; WO 01/13389 A1, "Flow-through Capacitor
system And Method"; WO 01/66217 A1, "Low Pore Volume electrodes
With Flow-Through Capacitor And energy Storage Use And Method"; WO
01/95410 A1, "Fluid and electrical connected flow-Through
Electrochemical Cells, System Cells, System And Method"; and WO
02/29836 A1, "Fringe-Field Capacitor Electrode For Electrochemical
Device". In addition to the stacked layer geometries shown here,
individual electrodes shown in the electrode array WO 03/009920 A1
may be sequentially charged according to the present invention in
order to form flow through capacitor stages according to the
present invention.
[0033] The electrode assembly 8 can include a combination
flow-through capacitor electrodes and optional current collector,
ion perm selective membranes, or charge barrier material. (U.S.
Pat. No. 6,709,560, hereby incorporated by reference). For example,
the electrode can be comprised of high capacitance particles,
including carbon or ceramics, held together with a binder material
including a hydrogel or functional charge barrier material,
fibrillated polypropylene or PTFE, latex, or cross linked or
sintered polymer or hydrocarbon materials. For example, if a charge
barrier material is used as a binder, it may be a fluorine
containing ionomer, an elastomeric or thermoformable hydrogel
containing either or both of strong acid or strong base
functionality. Materials of use as charge barriers are known to
those skilled in the art. (See, e.g., Toshikatsu Sata, Ion Exchange
Membranes, The Royal Society of Chemistry, publ., 2004).
[0034] An important aspect of the invention is the ability to vary
the voltage, current, or power, either perpendicular or parallel to
the flow path within a single cartridge holder, or among a group of
single cartridge holder cells. In the integrated stage embodiment,
this is accomplished by incorporating multiple current collectors
within a single cartridge holder, where the current collectors can
have individual electrode, charge barrier, and flow spacer layers,
or can share one or more of these layers in order to simplify
manufacture. A fluid, solution, or solute to be purified of
concentrated is introduced into each cell. As this fluid flows
through each cell, the multiple current collectors are
independently synchronously actuated with a purification or a
concentration peak that forms as the flow moves through each cell.
This is analogous to the peaks formed in chromatography systems.
For example, a small amount of total dissolved solids can be
purified from water each time the flow stream passes a particular
current collector, or pair, or set of current collectors. This
produces a slightly purified aliquot of water. As this aliquot
moves along its flow path, additional current collectors are
actuated. Where this flow path cuts across multiple current
collectors, the flow stream is separated into purification and
concentration peaks that can be separated, e.g., by a valve. Where
the flow is parallel to the multiple current collectors, the fluid
will be separated into side by side purification and concentration
streams.
[0035] Where electrode layers are shared between multiple current
collectors, it is important that the current collectors are
electrically isolated. To do this, the distance between current
collectors has to be wide enough so that the current collectors
have a fair degree of electrical isolation between them. Generally,
wider than one sixty-fourth of an inch, and optimally, under three
inches, such as between one eight and one quarter inch, will
suffice to isolate the cells. Cells are sufficiently isolated when
the width between current collectors backing an adjacent electrode
material of a given conductivity is such that the overall
conductivity of the combined current collector--electrode
combination is 1 ohm cm or greater. Resistance between individual
current collectors is preferably 0.1 ohm or more.
[0036] Prior flow-through capacitor systems reach a practical limit
of efficiency due to the fact that less total dissolved solids and
other contaminants are removed from water per charge cycle as
voltages are lowered. The flow rate utilization per gram of carbon
needs to be lowered in order to provide a given percent
purification at a lowered voltage and energy usage level. This
slowing of the flow rate was necessary in prior systems, because
sufficient levels of purification must be maintained in order to
overcome the mixing effects of the cartridge holder dead volume.
The capacitor of the present invention minimizes this cartridge
holder dead volume by eliminating inter-stage cartridge holders.
For example, with integrated staging, the dead volume due to the
flow spacer may be larger than the dead volume due to the volume
that exists between the capacitor cell and the inside of the
cartridge holder. The capacitor cell is defined as the electrode,
flow spacer, and a current collector and charge barrier layers.
Therefore, focused bands of purified water may be obtained at low
voltages and therefore low energy usage levels. An advantage of the
present invention is that energy may be saved by charging an
integrated stage cell many times at lower voltages. Percent
utilization of the cell may be increased by virtue of operating the
cell so that more than one concentration band is present at a given
time within a given material layer or cartridge holder. To obtain
purified water at a desired purification level, a valve coupled
with a conductivity sensor selects out water desired purification
and concentration levels. Percent recovery may also be pre-selected
by presetting conductivity control based upon a mass balance
between purified, feed, and/or waste concentrations.
[0037] An additional advantage of the present invention is that it
allows operation without a valve, achieving continuous
purification. In this case, flow may be parallel to the current
collectors, and fluid concentration may be modulated within the
plane of the flow. FIG. 7 depicts how water may be purified in
purification stream 21 between one set of current collectors and
concentrated in concentration stream 20 between adjacent sets of
current collectors, with purification streams 21 and concentration
streams 20 being coplanar in the direction of flow. These coplanar
streams are brought together by, e.g., manifolds, to form a
continuously purified stream 23 and concentrated stream 22.
Optionally, ions can be manipulated by operation of the current
collectors in order to form a central flow path of one
concentration and side flow paths of another. In either case,
adjacent concentration bands are formed which may be directed to
separate collections paths or separately collected from separate
outlets in the cell casing provided for this purpose. A valve is
not except when it is desirable to switch concentration and
purification streams by polarity reversal or otherwise
electronically manipulating the charge cycle sequence.
[0038] Individual current collectors may be pre-manufactured onto
electrode layers by lamination or by continuously coating a banded
pattern of current collector material onto an electrode material.
The current collector material may be a conductive material less
than 1 ohm cm in resistance, including a graphite material, or, may
be a metal foil, in particular, metal foil protected by a
conductive vinyl or a form of carbon-polymer composite layer using
carbon black, nanotubes, graphite powders, etc. mixed in with a
thermoplastic, olefin, fluorocarbon, or a other polymer, used with
a metal backing to form a current collector where the metal is
protected from water by the thin polymer layer, with the polymer
layer typically under 0.03 cm thick. Conversely, a capacitance
containing electrode material may be discontinuously formed in a
banded pattern upon a suitably conductive current collector layer.
A carbon containing material may be used. Microparticulate titanium
oxide powder is also advantageous.
[0039] Electrode materials may include carbon black, activated
carbons, sintered carbons, aerogels, glassy carbons, carbon fibers,
nanotubes, graphite, and other forms of carbon in particular those
with surface areas over 400 BET, nanotube gels, conductive
polymers, ceramics, anatase titanium oxide, or another material
that has a capacitance above 1 Farad per square meter when applied
in a layer 0.1 cm or less thick. A binder material may be used
which holds the electrode capacitive particles together, including
hydrogels, latex, thermoplastics, and fluoropolymers. Charge
barrier materials may be an ion exchange polymer, hydrogel, cross
linked polymer, or membrane, preferably with a charge density of
over 0.1 milli-equivalents per gram. The charge barrier material
can also function as a binder or adhesive, which is used cause
capacitance containing electrode particles together to form an
electrode sheet, or to adhere them to a current collector.
[0040] To manufacture the present invention, current collector,
electrode, and a charge barrier layers may be laminated or layered
together in a stacked configuration, then cut to length and
inserted into a cartridge holder. As many layers as can be cut
effectively at one time are layered and pre cut together. The
blocks of materials so formed can in turn be layered on top of one
another and inserted into a cartridge holder designed to fit them.
Current collector tabs may overlap out either end, and be bundled
together in parallel or connected in series. If graphite foil is
used as a current collector, the end tabs may be infiltrated with
an oily material or a polymer so that they do not wick water. A
metal compression contact may be formed with a nut, bolt, and-or
washer arrangement to the bundled graphite tabs. This contact may
be protected from water by a compression nut containing a gasket
which screws down over the top in order to cover underlying metal
contacts. Inert metals such as titanium, tantalum, including
palladium or platinum coated or infused valve metals, may be used
to form metal to graphite contacts. It is preferable that contact
resistance be less than 1 ohms. Metal contact to graphite
compression over 10 psi, and metal to graphite contract areas over
1 cm.sup.2 may be used to achieve this.
[0041] In FIG. 8 the current declines with each successive charge.
This is because a volume of feed water was being successively
purified as it passed through each of the eight sequentially
charged cells. As the water becomes more purified, it increases the
resistance as it passes through subsequent cells, thereby causing
them to draw less current and power. The fact that all the cells
are not charged at once allows the purification peak to be
deepened, allowing greater peak purification, for example, 50%
purification or more. Using integrated flow-through capacitors to
cut dead volume we have been able to achieve 70% purification of
sea water in an eight cell system at only 0.3 Volts. Based upon
energy measurements in single cells, this low voltage is likely to
be in the 15 watt hour per gallon range. Significant purification
in the 20% range has been measured with as low as 0.1 volts, which
represents very little energy. The percent purification can be
increased by adding a sufficient number of stages.
[0042] Cells within a sequentially controlled train of flow through
capacitor individual cell stages need not all be the same size. For
example, downstream cells, which experience a partly purified
stream of water compared to upstream cells, may be sized smaller in
order to save cost, or in order to design shorter charge cycles
that match the charge cycles of upstream cells. On the other hand,
a downstream cell may also be sized larger where it is important to
increase the percentage of purification or concentration in the
last stage compared to the previous stages.
* * * * *
References