U.S. patent application number 13/698265 was filed with the patent office on 2013-04-04 for apparatus for removal of ions, and a method of manufacturing an apparatus for removal of ions from water.
This patent application is currently assigned to VOLTEA B.V.. The applicant listed for this patent is Piotr Edward Dlugolecki, Hank Robert Reinhoudt, Albert Van Der Wal. Invention is credited to Piotr Edward Dlugolecki, Hank Robert Reinhoudt, Albert Van Der Wal.
Application Number | 20130081949 13/698265 |
Document ID | / |
Family ID | 42751940 |
Filed Date | 2013-04-04 |
United States Patent
Application |
20130081949 |
Kind Code |
A1 |
Reinhoudt; Hank Robert ; et
al. |
April 4, 2013 |
APPARATUS FOR REMOVAL OF IONS, AND A METHOD OF MANUFACTURING AN
APPARATUS FOR REMOVAL OF IONS FROM WATER
Abstract
An apparatus and a method to remove ions from water. The
apparatus includes a housing, an inlet to let water into the
housing, an outlet to let water out of the housing, a first and
second electrode connected to a power supply configured to create
an electrical potential difference between the first and the second
electrodes, and a spacer between the first and second electrodes to
allow water to flow in between the first and second electrodes, the
spacer comprising a pillar structure.
Inventors: |
Reinhoudt; Hank Robert;
(Delft, NL) ; Van Der Wal; Albert; (Oegstgeest,
NL) ; Dlugolecki; Piotr Edward; (Gdansk, PL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Reinhoudt; Hank Robert
Van Der Wal; Albert
Dlugolecki; Piotr Edward |
Delft
Oegstgeest
Gdansk |
|
NL
NL
PL |
|
|
Assignee: |
VOLTEA B.V.
Sassenheim
NL
|
Family ID: |
42751940 |
Appl. No.: |
13/698265 |
Filed: |
May 17, 2011 |
PCT Filed: |
May 17, 2011 |
PCT NO: |
PCT/EP2011/058000 |
371 Date: |
December 7, 2012 |
Current U.S.
Class: |
204/672 ;
204/660; 29/825 |
Current CPC
Class: |
C02F 1/4691 20130101;
C02F 2201/46115 20130101; Y10T 29/49117 20150115; C02F 2303/16
20130101 |
Class at
Publication: |
204/672 ;
204/660; 29/825 |
International
Class: |
C02F 1/469 20060101
C02F001/469 |
Foreign Application Data
Date |
Code |
Application Number |
May 17, 2010 |
EP |
10163021.8 |
Claims
1. An apparatus to remove ions from water, the apparatus
comprising: a housing; an inlet to let water into the housing; an
outlet to let water out of the housing; a first and second
electrode connected to a power controller configured to apply an
electrical potential difference between the first and second
electrodes; and a spacer between the first and second electrodes
for to allow water to flow in between the first and second
electrodes, the spacer comprising a pillar structure.
2. The apparatus according to claim 1, wherein the first and second
electrodes each have a substantially flat surface and the pillar
structure is located between the electrodes to keep the electrodes
at a substantially constant distance from each other.
3. The apparatus according to claim 2, wherein the pillar structure
is sandwiched in between the flat surfaces of the first and second
electrodes or a membrane of the first or second electrode.
4. The apparatus according to claim 1, wherein the pillar structure
is physically or chemically attached onto a surface of the first or
second electrode or a membrane on a surface of the first or second
electrode.
5. The apparatus according to claim 1, wherein the pillar structure
is located between the electrodes perpendicular to the flow
direction.
6. The apparatus according to claim 1, wherein the spacer comprises
a netting framework to keep pillars of the pillar structure at a
substantially fixed distance from each other.
7. The apparatus according to claim 6, wherein the netting
framework is constructed and arranged to keep the longitudinal axis
of the pillar structure substantially perpendicular with respect to
the flow direction of the water flowing between the first and
second electrodes.
8. The apparatus according to claim 1, wherein the center part of
the pillar structure is attached to a netting framework.
9. The apparatus according to claim 6, wherein the netting
framework and/or pillar structure creates movement of water
substantially perpendicular to the flow direction of the water
flowing between the first and second electrodes.
10. The apparatus according to claim 1, wherein the pillar
structure comprises a thicker middle portion to provide for an
increased flow resistivity in the center of a flow channel between
the first and second electrodes.
11. The apparatus according to claim 1, wherein the thickness of
the pillar structure decreases from the center of the pillar
structure to an edge of the pillar structure.
12. The apparatus according to claim 1, wherein the pillar
structure is spherical, elliptical, rhombus, egg or ball
shaped.
13. The apparatus according to claim 6, wherein the netting
framework is in the middle of a flow channel.
14. The apparatus according to claim 1, wherein the pillar
structure is made out of one piece extending over the full width of
a flow channel between the first and second electrodes.
15. A method of manufacturing an apparatus to remove ions from
water, the method comprising: providing a spacer comprising a
pillar structure to a first electrode; and providing a second
electrode to the spacer.
16. The method according to claim 15, further comprising providing
a membrane to the first electrode before providing the spacer to
the first electrode.
17. The method according to claim 15, wherein providing the spacer
comprises attaching the pillar structure to the first electrode or
a membrane.
18. An apparatus to remove ions from water, the apparatus
comprising: a housing; an inlet to let water into the housing; an
outlet to let water out of the housing; a first and second
electrode connected to a power controller configured to apply an
electrical potential difference between the first and the second
electrodes; and a spacer between the first and second electrodes to
allow water to flow in between the first and second electrodes, the
spacer comprising a helical structure.
19. The apparatus according to claim 18, wherein the first and
second electrodes each have a substantially flat surface at a
substantially constant distance from each other and the helical
structure is sandwiched in between the flat surfaces of the first
and second electrodes.
20. The apparatus according to claim 18, wherein the helical
structure forces the water to twist along the helical
structure.
21. The apparatus according to claim 18, wherein the helical
structure forces the water further away from the electrodes to a
position closer to the electrodes.
Description
FIELD
[0001] The invention relates to an apparatus to remove ions.
BACKGROUND
[0002] In recent years one has become increasingly aware of the
impact of human activities on the environment and the negative
consequences this may have. Ways to reduce, reuse and recycle
resources are becoming more important. In particular, clean water
is becoming a scarce commodity. Therefore, various methods and
devices for purifying water have been published.
[0003] A method for water purification is by capacitive
deionization, using an apparatus having a flow through capacitor
(FTC) to remove ions in water. The FTC functions as an electrically
regenerable cell for capacitive deionization. By charging
electrodes, ions are removed from an electrolyte and are held in an
electric double layer at the electrodes. The electrodes can be
(partially) electrically regenerated to desorb such previously
removed ions without adding chemicals.
[0004] The apparatus to remove ions comprises one or more pairs of
spaced apart electrodes (a cathode and an anode) and may comprise a
spacer, the spacer separating the electrodes and allowing water to
flow between the electrodes.
[0005] The apparatus comprises a housing comprising a water inlet
to let water in the housing and a water outlet to let water out of
the housing. In the housing of the apparatus, the layers of
electrodes (and spacers) are stacked in a "sandwich" fashion by
compressive force, normally by mechanical fastening.
SUMMARY
[0006] The efficiency of the apparatus during purification is
significant because it is indicative of the amount of water that
may be purified by the apparatus over a period of time.
[0007] It is desirable, for example, to improve the efficiency of
the apparatus to remove ions.
[0008] According to an embodiment of the invention, there is
provided an apparatus to remove ions from water, the apparatus
comprising:
[0009] a housing;
[0010] an inlet to let water into the housing;
[0011] an outlet to let water out of the housing;
[0012] a first and second electrode connected to a power controller
configured to apply an electrical potential difference between the
first and the second electrodes; and
[0013] a spacer between the first and second electrodes to allow
water to flow in between the first and second electrodes, the
spacer comprising a pillar structure.
[0014] According to a further embodiment of the invention, there is
provided a method of manufacturing an apparatus to remove ions from
water, the method comprising:
[0015] providing a first electrode;
[0016] providing a spacer comprising a pillar structure to the
first electrode; and
[0017] providing a second electrode to the spacer.
[0018] According to a further embodiment, there is provided an
apparatus to remove ions from water, the apparatus comprising:
[0019] a housing;
[0020] an inlet to let water into the housing;
[0021] an outlet to let water out of the housing;
[0022] a first and second electrode connected to a power controller
configured to apply an electrical potential difference between the
first and the second electrodes; and
[0023] a spacer between the first and second electrodes to allow
water to flow in between the first and second electrodes, the
spacer comprising a helical structure.
BRIEF DESCRIPTION OF THE FIGURES
[0024] Embodiments of the invention will be described, by way of
example only, with reference to the accompanying schematic drawings
in which corresponding reference symbols indicate corresponding
parts, and in which:
[0025] FIG. 1 shows a schematic representation of an embodiment of
an electrode for use in an embodiment of the invention;
[0026] FIG. 2 shows a schematic representation of a stack of
electrodes for use in an embodiment of the invention;
[0027] FIG. 3 shows a schematic representation of an apparatus to
remove ions for use in an embodiment of the invention;
[0028] FIG. 4 shows schematically the ion concentration between two
electrodes;
[0029] FIGS. 5a-c show schematic cross-sections of a part of an
apparatus to remove ions according to an embodiment of the
invention;
[0030] FIG. 6 shows a schematic cross-section of two spacers;
[0031] FIG. 7 shows a schematic arrangement of an apparatus to
remove ions for use in an embodiment of the invention;
[0032] FIGS. 8a to 8c show apparatus to remove ions according to an
embodiment of the invention; and
[0033] FIGS. 9a to 9e show apparatus to remove ions according to an
embodiment of the invention.
DETAILED DESCRIPTION
[0034] FIG. 1 shows a schematic cross section of an embodiment of
an electrode, being a first or a second electrode. In this example,
the electrode 11 has a sheet like shape with a rectangular form,
but other shapes, such as a round, polygonal or hexagonal shape are
possible. In the electrode a hole 12 is provided, which may have a
rectangular shape or another shape, such as a round shape. When
electrode 11 is in use, water may be flowing along the electrode
from the outer edge(s) towards the hole, as is indicated by the
dotted arrows 13 in FIG. 1. Typically, the outer dimensions of the
electrode 11 are about 16.times.16 cm and the dimensions of the
hole 12 are about 3.times.3 cm.
[0035] An advantage of a rectangular or a hexagonal shape of the
electrode may be that this type of electrode may be efficiently
produced with respect to use of material. An advantage of a round
shaped electrode with a round hole in the center may be that
distance between the outer edge and the inner edge (i.e. the
distance the water will flow along the electrode) is substantially
constant for all flow directions.
[0036] FIG. 2 shows a stack of electrodes. The first electrodes 21
and the second electrodes 22 each comprises a current collector,
indicated by 34 in FIG. 3, and an ion storage material, indicated
by 35 in FIG. 3. The current collector is connected to a power
controller PC configured to apply an electrical potential
difference between two adjacent electrodes. The ion storage
material may store ions that have been removed from the water. The
ion storage material may be a so-called high surface area material
with more than 500 m.sup.2/gr, more than 1000 m.sup.2/gr, or more
than 2000 m.sup.2/gr. The material may comprise activated carbon,
carbon aerogel, graphene, carbon nanofiber and/or carbon nanotube
on both sides of the electrode which are in contact with the
water.
[0037] FIG. 3 shows a schematic representation of an apparatus to
remove ions for use with an embodiment of the invention. The
apparatus has a housing 31 comprising a water inlet 32 and a water
outlet 33. During ion removal from the water, the water will flow
from the inlet 31 to the outlet 33 through the flow through
capacitor (FTC), comprising a pair of a first electrode 21 and an
adjacent second electrode 22. The flow of water is indicated by the
dotted arrows.
[0038] Between two adjacent electrodes a spacer 36 may be provided.
The spacer 36 may have a shape as is depicted in FIG. 1. A main
function of a spacer is to separate the first electrode from the
second electrode, for example by maintaining a substantially
constant or fixed distance between the two electrodes.
[0039] By applying an electrical potential difference between the
first and second electrodes by a power controller PC, for example
by applying a positive voltage to the first electrode (the anode)
21 relative to the second electrode (the cathode) 22, the anions of
the water flowing through the spacer 36 are attracted to the first
electrode 21 and the cations are attracted to the second electrode
22. In this way the ions (anions and cations) will be removed from
the water flowing through the spacer 36.
[0040] To increase the ion removal efficiency of the apparatus, the
electrodes may have a charge barrier, for example an ion exchange
membrane or an ion selective membrane. For example, the membrane
provided on or to the cathode may be permeable for cations and only
substantially allow the transport of cations and substantially
block the transport of anions and the membrane provided on or to
the anode may be permeable for anions and substantially block the
transport of cations.
[0041] The electrical potential difference between the anode and
the cathode is rather low, for example lower than 2 Volts, lower
than 1.7 Volts or lower than 1.4 Volts. A power controller is used
to control the conversion of the voltage and electrical current
from a power supply to the desired voltage difference over the
first and second electrodes.
[0042] An element of the efficiency of the apparatus is the ion
flux, where the ion flux may be defined as the number of ions
removed from the water, for example from the water in a spacer, to
one of the electrodes per unit time per projected electrode
area.
[0043] FIG. 4 shows two adjacent electrodes in an apparatus to
remove ions. The dotted line 41 indicates the concentration of ions
in the water flowing between the two electrodes. As can be seen in
FIG. 4, near the surface of electrodes the ion concentration is
lower than in the center. For example, the ion concentration in the
water in region 42 may be lower than the ion concentration in
region 43. Although in FIG. 4 only two regions are depicted, it
should be understood that the ion concentration may decrease
gradually or even linearly with the distance from one of the
electrodes and that therefore the choice of regions is arbitrary.
Where ion exchange membranes or ion selective membranes are used,
which are placed between the electrode and the spacer, a similar
situation may occur, where the ion concentration in the water in
region 42 may be lower than the ion concentration in region 43.
[0044] A low ion concentration close to the electrode (or membrane)
may result in a low ion flux to the electrode (or through the
membrane) to the electrode. By increasing the ion concentration
close to the electrode (or the membrane) the ion flux may be
increased, hence improving ion removal efficiency. The ion
concentration near the electrodes may be increased for example by
mixing the water, by the displacement of the water in a
substantially direction perpendicular to electrodes or by
increasing the mobility of the ions in the water.
[0045] According to an embodiment, the ion improvement device
comprises a mixing device. The mixing device may be a spacer with a
special structure that causes mixing of the water and which may
even cause turbulence in the water. The spacer may have a spiral or
a helical structure.
[0046] A helical spacer may influence the water flow by forcing the
fluid to twist along the spacer. The effect may be a faster local
velocity of the water or it may result in that water with higher
ion concentration further away from the electrode (or membrane) is
brought closer to the electrode (or membrane), which may increase
the ion flux towards the electrode. A helical spacer may improve
the ion flux by a factor up to two times compared to a non-helical
spacer. Furthermore, a helical spacer may increase the mixing of
the water where the flow is still laminar. A helical spacer may
promote turbulence in the flow channel, which may further improve
the mixing of the water.
[0047] According to a further embodiment, the mixing device causes
an unsteady flow in the water. In an unsteady flow, the flow
profile is not constant, i.e. it changes over time. For example the
flow velocity at a certain point may change over time and/or its
direction.
[0048] Additionally or alternatively, the ion flux improvement
device may comprise a turbulence creator to create a turbulent flow
in the water in the spacer or a recirculation circuit with a pump
and a storage facility. In the storage facility, water from the FTC
with low ion concentration may be mixed with water in the storage
facility with a higher ion concentration. The storage water may be
used for other purposes, for example as a swimming pool, or for
irrigation.
[0049] According to an embodiment the ion flux improvement device
comprises a spacer, which is ion-conductive or comprises
ion-conductive material. An ion-conductive spacer may improve the
ion mobility towards one of the electrodes. An ion-conductive
spacer may comprise a membrane (for example: anion exchange
membrane, cation exchange membrane, a mosaic membrane (for mixed
charges) and/or a bipolar membrane) or an ion exchange resin (for
example anion exchange resin, cation exchange resin or mixed ion
exchange resin). An ion-conductive spacer allows the passage of
charged species such as ions and may increase the mobility of the
ions towards one of the electrodes.
[0050] FIG. 5a shows a schematic cross section of a first and a
second electrode, between which water is flowing. The elements in
FIG. 5, such as electrodes 21 and 22 and their sizes and mutual
distances are depicted schematically. It may be that the flow of
water through the spacer is more or less laminar, e.g. the water
flows in more or less constant layers (parallel to the electrodes)
without mixing of the water or without water flowing with a
direction component perpendicular to the electrodes. In region 61
the flow velocity of a laminar flow parallel to the electrodes is
depicted, wherein the length of the straight arrows indicates the
velocity of the flow: a longer arrow indicates a higher
velocity.
[0051] According to an embodiment, the ion improvement device may
comprise a velocity adjuster 64 configured to adjust a flow
velocity of a first portion of the water with respect to a second
portion of the water, wherein, in use i.e. during ion removal from
the water, in the first portion an ion concentration is higher than
in the second portion. If a portion of water experiences the
electrical potential difference for a longer period of time (i.e.
its flow velocity is lower) than another portion of water, then at
the same ion concentration in the water the number of ions removed
from this portion will be higher than from another portion of water
that experiences the electrical potential difference for a shorter
period of time.
[0052] Velocity adjuster 64 may be located in the spacer, along the
spacer, or outside the spacer or it may be incorporated in the
spacer. Without the velocity adjuster 64 the flow in the flow
channel will follow a parabolic ("Poisseuille") profile with a
maximum flow velocity in the center of the flow channel and zero
flow at both electrode surfaces. The velocity adjuster 64 is
constructed to change the velocity of the water in such a way, that
a portion of the water flowing further away from one of the
electrodes (for example in region 63) is flowing slower relative to
a portion flowing closer to one of the electrodes (for example in
region 62). Region 65 depicts a possible effect on the flow
velocity of the water, wherein the length of the straight arrows
indicates the absolute velocity of the flow: a longer arrow
indicates a higher velocity and the orientation of the arrow
indicates the direction of the flow. In FIG. 5 a situation is
depicted where the velocity adjuster 64 has reduced the velocity of
the water so much that the velocity in the center of the flow
channel has become lower than closer to the electrodes.
Nevertheless, in another embodiment of the velocity adjuster 64, a
lower reduction of the flow velocity in the center may be achieved,
where the flow will only gradually decrease from the center to
close to the electrodes. In another embodiment the velocity
adjuster may cause the velocity to be more uniform inside the
spacer, where the flow velocity will be substantially independent
from the distance from the electrode.
[0053] The velocity adjuster 64 may comprise a porous material,
wherein the flow resistance in the center of the velocity adjuster
is larger than in one or more edges, causing the velocity of the
water passing through the center of the velocity adjuster 64 (for
example in region 63) to be reduced compared to the water passing
through the edge of the velocity adjuster 64 (for example in region
62). The flow resistance of this velocity adjuster may be
continuously increasing from an edge, near one of the electrodes,
towards the center of the velocity adjuster, i.e. the central axis
of the spacer. For example, the porosity of the velocity adjuster
64 may be varied from a value larger than 70%, larger than 80%, or
larger than 90% close to an electrode (e.g. region 62) to a value
of smaller than 70%, smaller than 60% or smaller than 50% towards
the center of the velocity adjuster (e.g. region 63). Porosity may
be measured as a percentage of the volume of voids over the total
volume.
[0054] The velocity adjuster 64 for use in the apparatus to remove
ions according to an embodiment of the invention may comprise a
spacer with multiple layers between the electrodes and the layer(s)
close to the electrode(s) may have a low flow resistance and the
layer(s) further away from the electrode(s) a relatively higher
flow resistance. The low flow resistance may cause a higher
velocity of the water close to an electrode and the higher flow
resistance may cause a lower velocity of the water further away
from the electrode. Without the velocity adjuster 64 less ions will
be removed from the water in the center of the flow channel or
spacer, because these ions will have to migrate over a larger
distance whereas the residence time of the ion in the center of the
flow channel or spacer is lower than that closer to an electrode.
Since the water further away from an electrode will be less easily
de-ionized than the water closer to the electrode it is
advantageous to have a lower velocity to the water further away
from the electrode so that the water stays longer between the
electrodes resulting in more time for the electrodes to attract the
ions. Water close to an electrode may be relatively quickly
de-ionized because of the close proximity of the electrode and
therefore shorter migration distance for the ions and this water
may therefore stay a relatively shorter time between the
electrodes. The layers in the spacer may comprise a porous material
with a low flow resistance in a first direction and a higher flow
resistance in a second direction. This may be achieved by orienting
fibers in the spacer substantially parallel to the first direction
and/or perpendicular to the second direction. The layer in the
spacer close to an electrode may be oriented such that the first
direction is substantially equal to the water flow direction. The
water may therefore experience a low flow resistance close to the
electrode and the speed of the water may therefore be relatively
high. A layer in the spacer further away from the electrode is
oriented such that the second direction is substantially equal to
the water flow direction so that the water further away from the
electrode experiences a higher resistivity resulting in a lower
velocity of the water. The thickness of the spacer with the
velocity adjuster may be 20-300 micrometers, 40-200 micrometers,
60-150 micrometers or 70-120 micrometers.
[0055] A further example of a velocity adjuster comprises a
material that closes off the spacer but has several small channels
in the longitudinal direction of the spacer through which water may
pass from one side to the other. The overall cross-section of the
channels in the region near an edge may be larger than the overall
cross-section of the channels in the central region of the velocity
adjuster 64.
[0056] FIG. 5b is an example of such a velocity adjuster 64 for use
in an apparatus to remove ions according to an embodiment of the
invention. The velocity adjuster 64 has channel walls creating
small channels 67, 68 in the spacer 64. The channel walls are
permeable for water and/or ions flowing through them but they
create a resistivity for the water flow. As depicted the channel
walls are substantially parallel to the electrodes but they may be
more randomly oriented. A small channel 68 in the middle of the
spacer creates a higher flow resistivity than a larger small
channel 67 closer to an electrode. The flow velocity of the water
flowing in the flow direction substantially parallel to the channel
walls is thereby adjusted so that the flow velocity is lower in the
middle of the spacer than the flow velocity closer to the
electrodes 21, 22. The flow resistance of the small channels may be
continuously increasing from a larger small channel 67 near the
edge, near one of the electrodes 21, 22, towards the middle, i.e.
the central small channel 68 of the spacer. The water further away
of an electrode may get a lower velocity so that it stays longer
between the electrodes and there is more time by the electrodes 21,
22 to attract the ions. Water close to an electrode may be
relatively quickly de-ionized because of the close proximity of the
electrode and may therefore be for a relatively short time between
the electrodes. The water further away from the electrode may
because of the higher flow resistance further away from the
electrode also be moved towards an electrode so that the ions are
more easily attracted to an electrode.
[0057] FIG. 5c discloses a cross-section of the velocity adjuster
64 of FIG. 5b perpendicular to the flow direction. FIG. 5c
discloses that the small channels have a total cross section which
is decreasing close to the center 68 of the flow channel and which
is increasing closer 67 to the electrodes 21, 22.
[0058] Another example of a velocity adjuster may be a shifted
spacer, as is depicted in FIG. 6. The spacer may comprise a grid
structure 71. The grid structure will influence the velocity of the
water flowing through the spacer. It may also cause mixing of the
water or cause a displacement of the water in a direction
perpendicular to electrodes. By shifting or rotating the
orientation of the grid with respect to the electrode, these
effects may be further optimized. FIG. 6 shows a shifted grid
structure 72. The shift or rotation of the orientation may be
around 45 degrees, where the threads of the spacer are at an angle
of around 45 degrees with respect to the side of one of the
electrodes, as can be seen from FIG. 6. Or in other words, the
threads of the spacer are substantially parallel to the diagonal of
the electrode. Note that the dimensions of the spacer are about the
same as the dimension of the electrode shown in FIG. 1 or may be a
bit larger, for example 17.times.17 cm.
[0059] FIG. 7 shows another embodiment of an ion flux improvement
device, comprising an electrical current measurement device A and a
flow controller FC. The current measurement device A measures the
current flowing to the first electrode 21 or to the second
electrode 22. The ion flux is a function of the electrical current
and the electrical current may thus be used as a measure for the
ion flux. The current measurement device A provides a current
signal to the flow controller FC, which may adjust the water flow
depending on the measured electrical current. The flow controller
FC may be configured to adjust the flow velocity of the water, for
example by controlling the pump P, via a control signal. In this
way, the ion flux may be controlled via the flow controller.
[0060] By increasing the flow velocity, the ion flux may increase
to one of the electrodes (or to the ion exchange membrane or ion
selective membrane), because of an increased ion concentration
nearby, for example in region 42 in FIG. 4.
[0061] However, at a high flow velocity, a further increase of the
flow may not result in an increased ion flux. An optimum ion flux
to the electrode (or membrane) may be obtained when the percentage
of ions removed from the water per cycle is relatively low, for
example below 80%, below 60%, below 40% or below 20%. In one cycle
the water flows once between two FTC electrodes.
[0062] A high ion flux may thus be obtained for example at a flow
velocity higher than 1 liter/m.sup.2 projected electrode area/min,
or higher than 2 liters/m.sup.2 projected electrode area/min or
even higher than 3 liters/m.sup.2 projected electrode area/min or
even higher than 4 liters/m.sup.2 projected electrode area/min.
[0063] Although increasing the flow velocity may cause the number
of ions or percentage of ions removed from the water per cycle to
be lower, the ion flux, which is defined per unit time per
projected electrode area, may increase because the number of cycles
per unit time may also increase with higher flow velocity.
[0064] In an embodiment, the ion flux improvement devices may
comprise a deionization rate measurement device to measure the
deionization rate (i.e. the percentage of ions removed from the
water) per cycle. The deionization rate measurement device may
comprise two ion concentration measurement devices, one measuring
the ion concentration of the water before the water flows between
the electrodes and one measuring the ion concentration of the water
after flowing between the electrodes. The deionization rate
measurement device may comprise only one of these two ion
concentration measurement devices and an electrical current
measurement device as described above. The deionization rate
measurement device may calculate the deionization rate on the basis
of one measurement of the ion concentration and the measurement of
the current flowing to one of the electrodes. The deionization rate
measurement device may provide a deionization rate signal
indicating the measured or calculated deionization rate.
[0065] The ion flux improvement device may further comprise a flow
controller to control the water flow in response to the
deionization rate signal. In this way, it is possible to
(automatically) maintain a certain deionization rate per cycle by
adjusting the flow velocity, for example a deionization rate per
cycle below 20%, where only up to 20% of the ions in the water are
removed per cycle. It is possible to increase the percentage of ion
removal per cycle, for example from 20% in the first cycle to 40%
in the second cycle to 60% in the third cycle and to 80% in the
fourth cycle and effectively almost complete removal in the fifth
cycle.
[0066] Using the above mentioned device to remove salt from water,
the ion flux may be higher than 0.5 grams salt per m.sup.2
projected electrode area per min, higher than 1.0 gram salt per
m.sup.2 projected electrode area per min, higher than 1.5 grams
salt per m.sup.2 projected electrode area per min or higher than
2.0 grams salt per m.sup.2 projected electrode area per min.
[0067] Increasing the flow velocity may cause the flow regime to
change from a laminar flow to an unsteady or turbulent flow. In the
laminar regime the pressure drop shows a linear relationship with
the flow velocity. However, in an unsteady or turbulent regime, the
pressure drop over the spacer or flow channel is no longer linear
with the flow velocity, but increases more rapidly with the flow.
This involves more pumping energy. To prevent the flow from
changing from laminar to (semi) turbulent flow, the pressure drop
should be limited, for example in the range of 0-20 bar per m.sup.2
projected electrode area, in the range of 15-18 bar per m.sup.2
projected electrode area or in the range of 2-10 bar per m.sup.2
projected electrode area. The pressure drop may be limited to
0.1-20 bar per m.sup.2 projected electrode area or 1-15 bar per
m.sup.2 projected electrode area.
[0068] FIG. 8a discloses a cross-section of an apparatus to remove
ions according to a further embodiment of the invention comprising
a first and second electrode 21, 22 and a spacer between the first
and second electrodes 21, 22. The spacer may have a helical
structure 81. The thickness of the spacer with the helical
structure 81 may be 20-300 micrometers, 40-200 micrometers, 60-150
micrometers or 70-120 micrometers. The helical structure 81 may
influence the principal water flow 83 by forcing the fluid to twist
along the helical structure in a direction 85. The effect may be a
faster local velocity of the water or it may result in that water
with a higher ion concentration further away from the electrode (or
membrane) may be brought closer to the electrode (or membrane),
which may increase the ion flux towards the electrode. A helical
structure in the spacer may improve the ion flux by a factor up to
two times compared to a spacer without a helical structure.
Furthermore, a helical structure may increase the mixing of the
water where the flow is still laminar. A helical structure may
promote turbulence in the flow channel, which may further improve
the mixing of the water. The electrodes may comprise a flat surface
and multiple helical structures may be sandwiched between the flat
surface of the first electrode and the flat surface of the second
electrode. One of the functions of the spacer is to keep the
surfaces of the two electrodes at a substantial constant distance
of, for example, between 0.02 and 0.5 mm. This is significant
because if the distance between the electrodes is irregular then
this may affect the flux of ions towards the electrode, with lower
fluxes where the spacer is thicker. The helical structure 81 may
provide seven twists over the length of the helical structure.
Seven twists would assure that the water is flowing along each
electrode at least seven times. The porosity of the spacer with the
helical structure may be larger than 50%, larger than 60%, larger
than 70% or larger than 80%.
[0069] FIG. 8b discloses a cross-section of an apparatus to remove
ions according to a further embodiment of the invention comprising
a first and second electrode 21, 22 and a spacer between the first
and second electrodes 21, 22. The spacer has a helical structure 81
having a less steep torsion and only half a twist in total. An
advantage may be that the flow resistance in such a case is lower
and that the water will rotate along an electrode. An optimum
between low flow resistance and sufficient interaction with the
electrodes may be with a number of twists between 0.5 and 7,
between 1 and 5 or between 2 and 4.
[0070] FIG. 8c discloses a cross-section of an apparatus to remove
ions according to a further embodiment of the invention. FIG. 8c
gives a top view of a spacer with one of the electrodes removed so
that multiple adjacent helical structures 81 on top of the flat
surface of the electrode 22 can be seen. The helical structures
have four and half twists and the twists of two adjacent helical
structures 81 are opposite. The helical structures 81 cause the
water to twist 85 around the principal flow direction 83 of the
water and since two adjacent helical structures 81 have an opposite
twist the water in between the helical structures 81 move in the
same direction substantially perpendicular to the principal flow
direction 83. This may improve the flow of the water towards an
electrode at a position 89 in between the helical structures 81.
Since two adjacent helical structures are co-operating there may be
a relatively low increase of the flow resistance.
[0071] The twist direction of two adjacent helical structures 81
may also be the same which causes turbulence in between the helical
structures and improved mixing. The helical structures in FIG. 8c
have a support 87 in the center. This forces the water out of the
center of the helical structure towards the electrodes where the
water is de-ionized.
[0072] Any embodiment of the above described apparatus to remove
ions may be used for the removal of ions from water in a swimming
pool, from water in a storage tank or from water in a factory plant
or from ground water.
[0073] FIG. 9a discloses a cross-section of an apparatus to remove
ions according to a further embodiment of the invention comprising
a first and second electrode 21, 22 and a spacer between the first
and second electrodes 21, 22. The spacer may have a structure as a
pillar 91 to keep the electrodes at a substantially fixed distance.
The thickness of the spacer with the pillar structure may be 20-300
micrometers, 40-200 micrometers, 60-150 micrometers or 70-120
micrometers. The pillar structure 91 may be produced in a netting
structure or framework 93 to form a layer which may form the
spacer. The spacer is electrically insulating and at the same time
open enough for water and ions to move through. The term pillar is
to be interpreted as a structural element that keeps the first and
second electrodes at a distance. The netting 93 keeps the pillar 91
substantially perpendicular compared to the main direction of the
spacer. The netting framework causes a higher flow resistivity in
the middle of the flow channel between the electrodes 21, 22
thereby forcing the water in the flow channel to move closer to the
first or second electrode resulting in increased de-ionization of
water. The netting framework and the pillars may cause better
mixing of the water in the flow channel, which may increase the ion
flux towards an electrode. An advantage of the spacer comprising
pillars and a netting is that it creates a very open spacer
(particularly in the flow direction) with a low flow resistivity,
which may result in a lower pressure drop over the channel, or
increased flow in the flow channel and it may also result in a
reduced risk of fouling of the spacer. The porosity of the spacer
with the pillar structure may be larger than 50%, larger than 60%,
larger than 70% or larger than 90%.
[0074] The electrodes may have a flat surface and multiple pillars
held by the netting may be sandwiched between the flat surface of
the first electrode and the flat surface of the second electrode.
One of the functions of the spacer is to keep the surfaces of the
two electrodes at a substantially constant or fixed distance of,
for example, between 0.02 and 0.5 mm. This is significant because
if the distance between the electrodes is irregular, then the ion
flux towards the electrodes may be affected.
[0075] FIG. 9b gives a top view of a part of a spacer with one of
the electrodes removed so that the multiple adjacent pillars 91 on
top of the flat surface of the electrode 22 which are held in the
netting 93 can be seen. The netting 93 provides support over the
full surface of the electrode so that it keeps the pillars 91
substantially perpendicular to the surface of the electrode as well
as at a substantially fixed distance with respect to each
other.
[0076] FIG. 9c discloses a cross-section of an apparatus to remove
ions according to a further embodiment of the invention. The pillar
95 in this embodiment may comprise a spherical, elliptical or egg
shape so that the pillar structure may have a thicker middle
portion so as to provide for a higher flow resistivity in the
middle of the flow channel in order to force the water flowing in
the center part of the flow channel between the electrodes 21, 22
in the direction of an electrode. At the same time the flow
velocity in the center of the flow channel may be reduced compared
to that of the water flowing closer to the first and/or second
electrode. The pillar may have a conical or rhombus structure,
which is thicker in the middle than at an edge. The spacer may
comprise a netting 97 to keep the pillars 95 in position. The
netting of FIG. 9c may be constructed similarly as the netting in
FIG. 9b.
[0077] FIG. 9d discloses a cross-section of an apparatus to remove
ions according to a further embodiment of the invention. This
embodiment is the same as the embodiment of FIG. 9c except that the
netting is omitted. The pillars 97 may be spherical, elliptical,
conical, rhombus or ball shaped so as to provide a higher flow
resistivity further away from the electrode 21, 22 and hence
increasing the residence time of the water in the center of the
channel compared to that of an edge of the spacer. The pillars 97
may be attached to the electrodes so that the electrodes keep the
pillars substantially perpendicular to the electrode surface by,
for example, a glue or a specific coating. The pillars may also be
produced by printing the pillars on an electrode with, for example,
a 3D printer and subsequently providing another electrode on top of
the already printed electrode. The pillars may be printed on top of
an additional layer, for example an ion exchange membrane, which
may be placed on top of the electrode as a separate layer or as a
coating or laminate.
[0078] FIG. 9e discloses a cross-section of an apparatus to remove
ions according to a further embodiment of the invention. This
embodiment is the same as the embodiment of FIGS. 9a and 9b except
that the netting is omitted. The pillars 99 may be connected to the
electrodes so that the electrodes keep the pillars substantially
perpendicular to the electrodes. The pillars may be produced by
printing the pillars on an electrode with, for example, a 3D
printer.
[0079] An advantage of the pillars without a netting is that a very
open spacer may be created in which the flow resistivity is reduced
as well as the risk of fouling is reduced.
[0080] Furthermore, the description also explains how ions may be
removed by providing a method comprising: providing an electrical
potential difference between a first and a second electrode in a
housing; allowing water to flow between the first and second
electrodes from an inlet in the housing to an outlet in the
housing; and improving the ion flux from the water to the first
and/or second electrode.
[0081] An apparatus to remove ions from water is described, the
apparatus may comprise a housing, an inlet to let water in the
housing, an outlet to let water out of the housing, a first and a
second electrode connected to a power controller configured to
apply an electrical potential difference between the first and the
second electrodes, and an ion flux improvement device configured to
improve the ion flux from the water flowing between the first and
second electrodes to one of the first and the second electrode. The
ion flux improvement device may comprise a mixing device
constructed and arranged to mix the water, or an unsteady flow
creator configured to create an unsteady flow in the water, or a
turbulence creator configured to create turbulence in the water, or
a spacer between the first and second electrodes configured to
allow water to flow in between the first and second electrodes, the
spacer having a spiral structure to change a flow profile of the
water. The mixing device may comprise a recirculation circuit
constructed and arranged to recirculate water flowing between the
first and second electrodes, the recirculation circuit may comprise
a pump and a storage facility. The ion flux improvement device may
comprise a spacer between the first and second electrodes to allow
water to flow in between the first and second electrodes, the
spacer may comprise ion-conductive material to increase a mobility
of ions towards the first electrode or the second electrode. The
ion flux improvement device may comprise a spacer between the first
and second electrodes to allow water to flow in between the first
and second electrodes, the first and second electrodes and the
spacer may have a substantially rectangular sheet-like shape, in
which a hole may be provided; and the spacer may comprise a grid
structure and an orientation of the grid structure may be rotated
with respect to a straight side of the first and second electrodes
by at least 30 degrees, in the range of 30-50 degrees or about 45
degrees. The ion flux improvement device may comprise a velocity
adjuster constructed and arranged to adjust a flow velocity of a
first portion of the water with respect to a second portion of the
water, wherein, in use, i.e. when removing ions from water, in the
first portion an ion concentration is higher than in the second
portion. The ion flux improvement device may comprise an electrical
current measurement device arranged and constructed to measure an
electrical current between the first and the second electrodes and
to provide a current signal indicating the electrical current; and
a flow controller arranged and constructed to receive the current
signal and adjust a flow velocity at which the water is flowing
between the first and second electrodes in response to the current
signal. The flux improvement device may comprise a deionization
rate measurement device arranged and constructed to measure a
deionization rate per cycle of the water flowing between the first
and the second electrodes and provide a deionization rate signal
indicating the deionization rate; and a flow controller arranged
and constructed to receive the deionization rate signal and adjust
a flow velocity at which the water is flowing between the first and
second electrodes in response to the deionization rate signal. The
flow controller may be arranged and constructed to maintain the
deionization rate below 60%, below 40% or below 20% of ions removed
per cycle. Alternatively, the percentage of ion removal per cycle
may be increased for example from 20% in the first cycle to 40% in
the second cycle to 60% in the third cycle and to 80% in the fourth
cycle and effectively almost complete removal in the fifth cycle.
The flow controller may be arranged and constructed to maintain the
flow velocity higher than 2 liters/m.sup.2 projected electrode
area/min, higher than 3 liters/m.sup.2 projected electrode
area/min, or higher than 4 liters/m.sup.2 projected electrode
area/min. The flow controller may be constructed and arranged to
provide a control signal to a pump, the pump being constructed and
arranged to receive the control signal and pump the water between
the first and second electrodes with a flow velocity in response to
the control signal.
[0082] Embodiments may also be provided in the following numbered
clauses:
1. An apparatus to remove ions from water, the apparatus
comprising:
[0083] a housing comprising: [0084] an inlet to let water into the
housing, [0085] an outlet to let water out of the housing, and
[0086] a first and a second electrode connected to a power
controller configured to apply an electrical potential difference
between the first and the second electrodes;
[0087] a velocity adjuster constructed and arranged to adjust a
flow velocity of a first portion of the water flowing between the
first and second electrodes with respect to a second portion of the
water flowing between the first and second electrodes.
2. The apparatus according to clause 1, wherein the velocity
adjuster is constructed and arranged to adjust the flow velocity of
the first portion of the water to be reduced compared to the flow
velocity of the second portion of the water. 3. The apparatus
according to clause 1 or clause 2, wherein the first portion of the
water is flowing further away from the first electrode and/or the
second electrode than the second portion of the water. 4. The
apparatus according to any of clauses 1-3, wherein the first
portion of the water is flowing through the center of the velocity
adjuster. 5. The apparatus according to any of clauses 1-4, wherein
the second portion of the water is flowing through an edge of the
velocity adjuster. 6. The apparatus according to any of clauses
1-5, wherein the second portion of the water is flowing closer to
the first electrode and/or the second electrode in the velocity
adjuster. 7. The apparatus according to any of clauses 1-6, wherein
the velocity adjuster comprises a material with a flow resistance
which may be adjusted to adjust the flow velocity of the water. 8.
The apparatus according to any of clauses 1-7, wherein the velocity
adjuster comprises a porous material, wherein a flow resistance in
the center of the velocity adjuster is larger than closer to an
edge, causing the velocity of the water passing through the center
of the velocity adjuster to be reduced compared to the water
passing through the edge of the velocity adjuster. 9. The apparatus
according to any of clauses 1-8, wherein the velocity adjuster
comprises a porous material, where the porosity increases from the
center of the velocity adjuster to the first electrode and/or the
second electrode. 10. The apparatus according to any of clauses
1-9, wherein the flow resistance of the velocity adjuster
continuously increases from near the first electrode and/or the
second electrode, towards the center of the velocity adjuster. 11.
The apparatus according to any of clauses 1-10, wherein the
velocity adjuster is provided along the spacer, outside the spacer
or incorporated in the spacer. 12. The apparatus according to any
of clauses 1-11, wherein the velocity adjuster comprises a spacer
having a grid structure which is shifted and/or rotated with
respect to the first electrode and/or the second electrode to
adjust the velocity of the water flowing through the spacer. 13.
The apparatus according to any of clauses 1-12, wherein the
velocity adjuster comprises a spacer with multiple layers between
the first and second electrodes and a layer close to the first
electrode and/or the second electrode has a low flow resistance and
a layer further away from the first electrode and/or the second
electrode has a relatively high flow resistance. 14. The apparatus
according to clause 13, wherein the layers comprise a porous
material with a low flow resistance in a first direction and a
higher flow resistance in a second direction, where a layer close
to the first electrode and/or the second electrode is oriented such
that the first direction is substantially equal to the water flow
direction. 15. The apparatus according to clause 14, wherein a
layer further away from the first electrode and/or the second
electrode is oriented such that the second direction is
substantially equal to the water flow direction. 16. The apparatus
according to clause 1, wherein the velocity adjuster comprises a
material having small channels and the cross-section of a channel
in a region closer to the first electrode and/or the second
electrode may be larger than the cross-section of a channel in the
center of the velocity adjuster. 17. The apparatus according to
clause 16, wherein the velocity adjuster comprises a material that
closes off the spacer but has several small channels in the
longitudinal direction of the spacer through which water may pass
from one side to the other and the total cross-section of the
channels in the region near an edge may be larger than the total
cross-section of the channels in a central region of the velocity
adjuster. 18. A method to remove ions, the method comprising:
[0088] providing an electrical potential difference between a first
and the second electrode in a housing;
[0089] allowing water to flow between the first and second
electrodes from an inlet of the housing to an outlet of the
housing; and
[0090] adjusting a flow velocity of a first portion of the water
with respect to a second portion of the water.
19. The method according to clause 18, wherein the flow velocity of
the first portion of the water is lower than the flow velocity of
the second portion of the water and the first portion of the water
is flowing further away from the first electrode and/or the second
electrode than the second portion of the water. 20. An apparatus to
remove ions from water, the apparatus comprising:
[0091] a housing comprising: [0092] an inlet to let water into the
housing, [0093] an outlet to let water out of the housing, and
[0094] a first and a second electrode connected to a power
controller configured to apply an electrical potential difference
between the first and the second electrodes;
[0095] a spacer between the first and second electrodes to allow
water to flow in between the first and second electrodes, the
spacer comprising a helical structure.
21. The apparatus according to clause 20, wherein the first and
second electrodes each comprise a substantially flat surface at a
substantially constant distance from each other. 22. The apparatus
according to clause 21, wherein the helical structure is sandwiched
in between the flat surface of the first and second electrodes. 23.
The apparatus according to any of clauses 20-22, wherein the
helical structure forces the water to twist along the helical
structure. 24. The apparatus according to any of clauses 20-23,
wherein the helical structure forces the water further away from
the first electrode and/or the second electrode to a position
closer to the first electrode and/or the second electrode. 25. The
apparatus according to any of clauses 20-24, wherein the helical
structure creates turbulence in between the first and second
electrodes to improve mixing of water. 26. The apparatus according
to any of clauses 20-25, wherein the spacer comprises multiple
helical structures. 27. The apparatus according to any of clauses
20-26, wherein the spacer comprises multiple helical structures and
the rotational direction of adjacent helical structures is
opposite. 28. The apparatus according to any of clauses 20-27,
wherein the water flow through the spacer has a principal direction
substantially parallel to the first electrode and/or the second
electrode and the helical structure is oriented substantially
parallel to the principal direction. 29. The apparatus according to
clause 28, wherein the helical structure forces the water to rotate
in direction substantially perpendicular to the principal
direction. 30. The apparatus according to clause 29, wherein two
adjacent helical structures rotate the water in opposite direction.
31. The apparatus according to clause 29, wherein two adjacent
helical structures rotate the water in the same direction. 32. The
apparatus according to any of clauses 20-31, wherein the helical
structure comprises a support in the center of the helical
structure. 33. A method to remove ions, the method comprising:
[0096] providing an electrical potential difference between a first
and the second electrode in a housing; [0097] allowing water to
flow between the first and the second electrodes from an inlet of
the housing to an outlet of the housing; [0098] forcing the water
to rotate in a rotational direction around a principal axis
substantially parallel to the first electrode and/or the second
electrode; and [0099] improving the ion flux from the water to the
first electrode and/or the second electrode. 34. An apparatus to
remove ions from water, the apparatus comprising:
[0100] a housing comprising: [0101] an inlet to let water into the
housing, [0102] an outlet to let water out of the housing, and
[0103] a first and a second electrode connected to a power
controller configured to apply an electrical potential difference
between the first and the second electrodes;
[0104] a spacer between the first and second electrodes to allow
water to flow in between the first and second electrodes, the
spacer comprising a pillar structure.
35. The apparatus according to clause 34, wherein the first and
second electrodes each have a substantially flat surface and the
pillar structure is between the first and second electrodes to keep
the first and second electrodes at a substantially constant
distance from each other. 36. The apparatus according to clause 35,
wherein the pillar structure is sandwiched in between the flat
surface of the first and second electrodes or a membrane of the
first electrode and/or the second electrode. 37. The apparatus
according to any of clauses 34-36, wherein the pillar structure is
physically or chemically attached onto a surface of the first
electrode and/or the second electrode or a membrane of the first
electrode and/or the second electrode. 38. The apparatus according
to any of clauses 34-37, wherein the pillar structure is, between
the electrodes, substantially perpendicular to the flow direction.
39. The apparatus according to any of clauses 34-38, wherein the
spacer comprises a netting framework to keep pillars of the pillar
structure at a substantially fixed distance from each other. 40.
The apparatus according to clause 39, wherein the netting framework
is constructed and arranged to keep the longitudinal axis of the
pillar structure substantially perpendicular with respect to the
flow direction of the water flowing between the first and second
electrodes. 41. The apparatus according to any of clauses 34-40,
wherein the center part of the pillar structure is attached to a
netting framework. 42. The apparatus according to any of clauses
39-41, wherein the netting framework and/or pillar structure
creates movement of water substantially perpendicular to the flow
direction of the water flowing between the first and second
electrodes. 43. The apparatus according to any of clauses 34-42,
wherein the pillar structure comprises a thicker middle portion in
order to provide for an increased flow resistivity in the center of
a flow channel in between the first and second electrodes. 44. The
apparatus according to any of clauses 34-43, wherein the thickness
of the pillar structure decreases from the center of the pillar
structure to an edge of the pillar structure. 45. The apparatus
according to any of clauses 34-44, wherein the pillar structure is
spherical, elliptical, rhombus, egg or ball shaped. 46. The
apparatus according to any of clauses 39-45, wherein the netting
framework is provided in the middle of a flow channel in between
the first and second electrodes. 47. The apparatus according to any
of clauses 34-46, wherein the pillar structure is made out of one
piece extending over the full width of a flow channel between the
first and second electrodes. 49. A method of manufacturing an
apparatus to remove ions from water, the method comprising:
[0105] providing a spacer comprising a pillar structure to a first
electrode; and
[0106] providing a second electrode to the spacer.
50. The method according to clause 49, further comprising providing
a membrane to the first electrode before the spacer is provided to
the first electrode. 51. The method according to clause 49 or
clause 50, wherein providing the spacer comprises attaching the
pillar structure to the first electrode or the membrane.
[0107] It is to be understood that the disclosed embodiments are
merely exemplary of the invention, which can be embodied in various
forms. Therefore, specific structural and functional details
disclosed herein are not to be interpreted as limiting, but merely
as a basis for the claims and as a representative basis for
teaching one skilled in the art to variously employ the present
invention in virtually any appropriately detailed structure.
Furthermore, the terms and phrases used herein are not intended to
be limiting, but rather, to provide an understandable description
of the invention.
[0108] The terms "a" or "an", as used herein, are defined as one or
more than one. The term another, as used herein, is defined as at
least a second or more. The terms including and/or having, as used
herein, are defined as comprising (i.e., not excluding other
elements or steps). Any reference signs in the claims should not be
construed as limiting the scope of the claims or the invention. The
mere fact that certain measures are recited in mutually different
dependent claims does not indicate that a combination of these
measures cannot be used to advantage. The scope of the invention is
only limited by the following claims.
* * * * *