U.S. patent application number 14/527805 was filed with the patent office on 2016-11-10 for apparatus for purifying a fluid and method for purifying a fluid, in particular by means of the aforesaid apparatus.
The applicant listed for this patent is IDROPAN DELL'ORTO DEPURATORI S.R.L. Invention is credited to Tullio SERVIDA.
Application Number | 20160326027 14/527805 |
Document ID | / |
Family ID | 54068181 |
Filed Date | 2016-11-10 |
United States Patent
Application |
20160326027 |
Kind Code |
A9 |
SERVIDA; Tullio |
November 10, 2016 |
Apparatus for purifying a fluid and method for purifying a fluid,
in particular by means of the aforesaid apparatus
Abstract
Apparatus for purifying a fluid, which comprises at least one
ion absorption cell (2) with an operating chamber (4, 5) at its
interior through which a first operative fluid (F1) flows and an
evacuation chamber (13, 13') through which a second operative fluid
(F2, F2') flows and which is separated from the operating chamber
(4,5) by a filtering membrane (100). A porous electrical conductor
(18) is housed in the evacuation chamber (13, 13') and is traversed
by the second operative fluid (F2, F2'). Two electrodes (A, B) have
the aforesaid operating chamber (4, 5) and evacuation chamber (13,
13') interposed, and are supplied with opposite polarities in order
to generate an operative electric field in the operating chamber
(4, 5) and a limited electric field in the evacuation chamber (13,
13'), the latter with value lower than the operative electric
field, due to the shielding effect of the porous electrical
conductor (18). The charged particles contained in the operating
chamber (4, 5) are susceptible of traversing the filtering membrane
(100) under the action of the operative electric field generated by
the electrodes (A, B), and be evacuated by the second operative
fluid (F2, F2') in the evacuation chamber (13, 13'), in which they
are subjected to the action of the limited electric field.
Inventors: |
SERVIDA; Tullio; (Milano,
IT) |
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Applicant: |
Name |
City |
State |
Country |
Type |
IDROPAN DELL'ORTO DEPURATORI S.R.L |
Milano |
|
IT |
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|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20150259224 A1 |
September 17, 2015 |
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|
Family ID: |
54068181 |
Appl. No.: |
14/527805 |
Filed: |
October 30, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14215094 |
Mar 17, 2014 |
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14527805 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 61/48 20130101;
C02F 1/4693 20130101; C02F 2201/461 20130101; B01D 61/422 20130101;
C02F 2201/46 20130101; C02F 1/4695 20130101; B01D 61/445 20130101;
C02F 2103/08 20130101 |
International
Class: |
C02F 1/469 20060101
C02F001/469 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2013 |
IT |
PD2013A000065 |
Sep 15, 2014 |
IT |
PD2014A000234 |
Claims
1. Apparatus for purifying a fluid, characterized in that it
comprises: at least one ion absorption cell (2) traversed by at
least one first operative fluid (F1) containing charged particles,
provided with a containment structure (3) defining at its interior:
at least one operating chamber (4, 5) provided with an inlet
opening (6, 7) and an outlet opening (8, 9), through which said at
least one first operative fluid (F1) is susceptible to flow; at
least one chamber (13, 13') for evacuating said charged particles,
which is provided with an inlet section (14, 14') and with an
outlet section (15, 15'), through which at least one second
operative fluid (F2, F2') flows; said at least one operating
chamber (4,5) and said at least one evacuation chamber (13, 13')
being separated from each other by at least one filtering membrane
(100). a porous electrical conductor (18) housed in said at least
one evacuation chamber (13, 13') and traversed by said at least one
second operative fluid (F2, F2'), a first and a second electrode
(A, B) separated from each other with said at least one operating
chamber (4, 5) and said at least one evacuation chamber (13, 13')
interposed, and suppliable with power by an electrical power supply
source (12) with opposite polarities in order to generate an
operative electric field in said at least one operating chamber (4,
5) and a limited electric field in said at least one evacuation
chamber (13, 13'), with value lower than said operative electric
field, due to the shielding effect of said porous electrical
conductor (18); the charged particles contained in said operating
chamber (4, 5) being susceptible of traversing said filtering
membrane (100) under the action of the operative electric field
generated by said first and second electrode (A, B), of being
evacuated by said at least one second operative fluid (F2, F2') in
said at least one evacuation chamber (13, 13'), in which they are
subjected to the action of said limited electric field.
2. Apparatus for purifying a fluid according to claim 1,
characterized in that it comprises at least one first and one
second operating chamber (4, 5), respectively provided with: a
first and a second inlet opening (6, 7); a first and a second
outlet opening (8, 9), through which said at least one first
operative fluid (F1) flows; and at least one first and second wall
(10, 11) for containing said at least one first operative fluid
(F1), respectively having associated said first and said second
electrode (A, B); said at least one chamber (13, 13') for
evacuating said cationic particles and/or anionic particles, being
interposed between said first and second operating chamber (4, 5)
and being provided with a third (16, 16') and a fourth wall (17,
17') each comprising said filtering membrane (100); said third and
fourth wall (16, 17) delimiting, together with said first wall (10)
and with said second wall (11), respectively said first operating
chamber (4) and said second operating chamber (5).
3. Apparatus for purifying a fluid according to claim 1,
characterized in that it comprises at least one first and one
second evacuation chamber (13, 13'), each delimited by a third wall
(16, 16') and a fourth wall (17, 17'), respectively provided with a
first and a second inlet section (14, 14'); with a first and second
outlet section (15, 15'), through which said at least one second
operative fluid (F2, F2') flows; at least said third walls (16,
16') respectively of said first and said second evacuation chamber
(13, 13') each comprising a filtering membrane (100) and between
them delimiting said at least one operating chamber (4) interposed
between said first and second evacuation chamber (13, 13'); said
first electrode and said second electrode (A, B) being associated
with the fourth walls (17, 17') respectively of said first and said
second evacuation chamber (13, 13').
4. Apparatus for purifying a fluid according to claim 1,
characterized in that said electrical power supply source (12) is
susceptible of periodically reversing the polarities of said first
and second electrode (A, B), in order to force said cationic
particles and said anionic particles contained in said at least one
operating chamber (4, 5) to enter into a same said at least one
evacuation chamber (13, 13') through said at least one filtering
membrane (100).
5. Apparatus for purifying a fluid according to claim 1,
characterized in that said filtering membranes (100) are selected
from among microfiltration membranes, ultrafiltration membranes,
nanofiltration membranes and reverse osmosis membranes.
6. Apparatus for purifying a fluid according to claim 1,
characterized in that said electrodes (A, B) are protected by a
cover layer (38, 38'), in particular obtained from a filtering
membrane (100).
7. Apparatus for purifying a fluid according to claim 6,
characterized in that each said cover layer (38, 38') is spaced
from the corresponding said electrode (A, B) in order to define
therewith a secondary chamber (39, 39') for the passage of at least
one washing fluid (F3, F3').
8. Apparatus for purifying a fluid according to claim 1,
characterized in that the pressure in said at least one first
evacuation chamber (13, 13') is adjusted with respect to the
pressure in said at least one operating chamber (4, 5) to a value
susceptible of limiting the leakage of operative flows (F1, F2)
through said filtering membrane (100) preferably between 0 and
20%.
9. Apparatus for purifying a fluid according to claim 1,
characterized in that it comprises a plurality of operating
chambers (4, 5) and a plurality of evacuation chambers (13, 13'),
distributed in succession with each other according to one or more
of the preceding claims, with pairs of said first and second
electrodes (A, B) with, interposed, said at least one operating
chamber (4, 5) and said at least one evacuation chamber (13, 13')
electrically in series.
10. Apparatus for purifying a fluid according to claim 9,
characterized in that at least two intermediate electrodes (A, B)
of said succession of pairs of electrodes (A, B) are substituted by
at least one bipolar membrane (40).
11. Apparatus for purifying a fluid according to claim 1,
characterized in that in said at least one operating chamber (4,
5), at least one isolating porous spacer separator (19) is housed,
susceptible of being traversed by said first operative fluid
(F1).
12. Apparatus for purifying a fluid according to claim 11,
characterized in that said isolating porous spacer separator (19)
is a granular material of definite size equal to the distance
between the walls of each operating chamber.
13. Apparatus for purifying a fluid according to claim 1,
characterized in that the porous electrical conductor (18) of said
at least one evacuation chamber (13, 13') comprises at least one
net made of conductive material, in particular interposed as a
spacer between said third and fourth wall (16, 16' 17, 17').
14. Apparatus for purifying a fluid according to claim 1,
characterized in that it comprises at least one ion exchange resin
(36) contained inside said at least one operating chamber (4, 5) in
order to interfere with the passage of said first operative fluid
(F1), and maintained herein by means of retention means (37).
15. Apparatus for purifying a fluid, characterized in that it
comprises: at least one ion absorption cell (2) traversed by a
fluid to be treated (F1) containing cationic particles and/or
anionic particles, provided with a containment structure (3)
defining at its interior: at least one first operating chamber (4)
provided with: a first inlet opening (6) and a first outlet opening
(8), through which said fluid to be treated (F1) is susceptible to
flow, at least one first wall (10) for containing said fluid to be
treated (F1), having a first electrode associated that can be power
supplied by an electrical power supply source (12) to a first
polarity; at least one second operating chamber (5) provided with:
a second inlet opening (7) and a second outlet opening (9), through
which said fluid to be treated (F1) flows, at least one second wall
(11) for containing said fluid to be treated (F1), having a second
electrode associated that can be power supplied by said electrical
power supply source (12) to a second polarity opposite the first;
at least one third chamber (13) for evacuating said cationic
particles and/or anionic particles, which is: interposed between
said first and second operating chamber (4, 5); provided with a
third inlet opening (14) and a third outlet opening (15), through
which a washing fluid (F2) flows, delimited by a third and a fourth
wall (16, 17), substantially impermeable to said fluid to be
treated F1 and to said washing fluid F2, opposite each other,
which, alongside said first wall (10) and said second wall (11),
respectively further delimit said first operating chamber (4) and
said second operating chamber (5); said third and fourth wall (16,
17) each having associated at least one ion-selective area that is
susceptible to being traversed by charged particles with
corresponding polarity contained in said first and second operating
chamber (4, 5), and the action of the electric field generated by
said electrodes acts on such particles; said third evacuation
chamber (13) comprising a porous electrical conductor (18)
interposed between said third and fourth wall (16, 17) and
traversed by said washing fluid (F2), said porous electrical
conductor (18) being susceptible to limit, inside said third
evacuation chamber (13), the electric field generated by said first
and second electrode; the ion-selective areas of said third and
fourth wall (16, 17) being susceptible to achieve a barrier against
the charged particles with corresponding polarity contained in said
third evacuation chamber (13) and subjected to the action of said
electric field limited by said porous electrical conductor
(18).
16. Apparatus for purifying a fluid according to claim 15,
characterized in that said third and fourth wall (16, 17) are each
provided with two or more adjacent ion-selective areas (16A, 16B,
17A, 17B), of which at least one is cation-phobic and at least one
anion-phobic; said electrical power supply source (12) being
susceptible to periodically reverse the polarities of said first
and second electrode, in order to force said cationic particles and
said anionic particles contained in said first and second operating
chamber (4, 5) to enter into said third evacuation chamber (13)
through said corresponding ion-selective areas (16A, 16B, 17A,
17B).
17. Apparatus for purifying a fluid according to claim 15,
characterized in that the third and fourth wall (16, 17) of said
third evacuation chamber (13) comprise a sheet-form support, in
which the ion-selective areas (16A, 16B, 17A, 17B) are silk screens
or prints of ion-selective paints.
18. Apparatus for purifying a fluid according to claim 17,
characterized in that said ion-selective silk screen or print areas
(16A, 16B, 17A, 17B) are a plurality of silk screens or prints in
adjacent positions with ion-selective paints, alternately with
opposite ion-selectivity.
19. Apparatus for purifying a fluid according to claim 15,
characterized in that the ion-selective areas (16A, 16B, 17A, 17B)
of said third and fourth wall (16, 17) are obtained with membranes
selectively of anionic exchange type and cationic exchange
type.
20. Apparatus for purifying a fluid according to claim 15,
characterized in that, between the first wall (10) of said first
operating chamber (4) and the third wall (16) of said third
evacuation chamber (13), at least one first isolating porous spacer
separator (19) is interposed, susceptible to being traversed by
said fluid to be treated (F1), and between the second wall (11) of
said second operating chamber (5) and the fourth wall (17) of said
third evacuation chamber (13) at least one second isolating porous
spacer separator (20) is interposed, susceptible to being traversed
by said fluid to be treated (F1).
21. Apparatus for purifying a fluid according to claim 15,
characterized in that the porous electrical conductor (18) of said
third evacuation chamber (13) comprises at least one net made of
conductive material, in particular interposed as spacer between
said third and fourth wall (16, 17).
22. Apparatus for purifying a fluid according to claim 15,
characterized in that it comprises at least one ion exchange resin
(36) contained inside at least one of said first and second
operating chambers (4, 5) in order to interfere with the passage of
said fluid to be treated (F1), and maintained here by means of
retention means (37).
23. Apparatus for purifying a fluid according to claim 15,
characterized in that said cell (2) comprises: a plurality of
superimposed purification layers, each comprising a first, a second
and a third chamber (4, 5, 13); a first supply section (21)
provided in said containment structure (3), which supplies the
fluid to be treated (F1) to the first inlet opening (6) and the
second inlet opening (8) of said first and second operating chamber
(4, 5) of the aforesaid purification layers; a first extraction
section (22) provided in said containment structure (3), which
receives the treated fluid from the first outlet opening (7) and
from the second outlet opening (9) of said first and second
operating chamber (4, 5) of the aforesaid purification layers; a
second supply section (23) provided in said containment structure
(3), which supplies the washing fluid (F2) to the third inlet
opening (14) of said third evacuation chamber (13) of the aforesaid
purification layers; a second extraction section (24) provided in
said containment structure, which receives the washing fluid (F2)
from the third outlet opening (15) of said third evacuation chamber
(13) of the aforesaid purification layers.
24. Apparatus for purifying a fluid according to claim 23,
characterized in that said second extraction section (24) provided
in said containment structure (3), is extended said purification
layers, in particular in a central zone of said chambers (4, 5,
13), traversing said first, second, third and fourth wall (10, 11,
16, 17) with corresponding through holes.
25. Apparatus for purifying a fluid according to claim 23,
characterized in that the first and second electrodes of each said
purification layer is provided with a projection (25) externally
projecting for the connection with said electrical power supply
source (12).
26. Apparatus for purifying a fluid according to claim 15,
characterized in that said third evacuation chamber (13) is
obtained in duct form and for such purpose is laterally closed with
two lateral walls (26, 26') placed to join said third and fourth
wall (16, 17) at two opposite edges thereof.
Description
FIELD OF APPLICATION
[0001] The present invention regards an apparatus for purifying a
fluid and a method for purifying a fluid, in particular by means of
the aforesaid apparatus, according to the preamble of the
respective independent claims.
[0002] More in detail, the apparatus and the method according to
the invention are intended to be advantageously employed for
removing ionized particles from a fluid, for the purpose of
facilitating the recovery or removal of such particles. The latter
can be typically constituted by ions of salts dissolved in a liquid
or by metal ions, for example of industrial process fluids, or by
polarizable organic substances.
[0003] The present apparatus can be intended for multiple
applications, both in industrial and civil fields, such as the
desalination of sea water, the softening of particularly hard
waters, the removal of salts (such as chlorides and sulfates) from
water, as well as the removal from any liquid of, for example,
nitrates, nitrites, ammonia, heavy metals, organic substances
(whether provided with an intrinsic electric charge or susceptible
to polarization due to the electric field present that induces an
electric dipole in the organic substance) or micropollutants in
general, or for the deionization of fluids, for example of
industrial processes or for the concentration of polluting
substances that are difficult to dispose of or advantageous to
recover for a reuse.
[0004] The apparatus, object of the present invention, can also be
incorporated in a machine, in particular for domestic use. In this
case, it will allow purifying the water intended for such machine,
allowing the latter to better achieve the functionalities for which
it is used; such functions for example may include producing
drinks, cleaning dishes, clothes etc.
[0005] The present invention is therefore generally inserted in the
industrial field of the production of apparatuses for removing
ionized particles from fluids.
STATE OF THE ART
[0006] Apparatuses are known for purifying fluids that exploit the
principle of capacitive deionization for removing ionized particles
from a fluid. Such apparatuses comprise at least one cell composed
of an assembly of flow-through capacitors; the cell is more in
detail formed by a plurality of superimposed electrodes, between
which a flow of fluid to be purified is made to pass. The
electrodes face each other and are charged with opposite polarities
by a direct current power supply unit.
[0007] Operatively, such known apparatus provides for the
alternation of operating steps, in which the ions present in the
fluid are captured on the opposite electrodes, and regeneration
steps, in which the ions accumulated on the electrodes are removed
by means of a washing fluid. The electrodes of the flow-through
capacitors electrostatically absorb and release the ionic charge
contaminants and actively participate in the process of
deionization of the liquid to be treated.
[0008] The electrodes are also usually fed by collectors, for
example made of graphite, and they are made of electrically
conductive porous materials (e.g. typically made of carbon) in
order to absorb high quantities of ionized particles on their
surface.
[0009] Flow-through capacitors of the above-indicated known type
are for example described in the patents U.S. Pat. No. 6,413,409
and U.S. Pat. No. 5,360,540.
[0010] The aforesaid operating and regeneration steps for the cells
translate, with reference to the interaction between electrodes and
ions, into the following operative steps: [0011] a step for
absorbing the ions on the porous surface of the carbon of the
electrodes supplied with opposite voltages; the energy expended for
such step is proportional to the quantity of ions that are
captured; [0012] a step of electrostatic liberation of the ions
from the carbon of the electrodes, providing the latter with the
previously absorbed quantity of charge, so as to neutralize the
electrostatic attraction with the ions; [0013] a step for moving
away the ions that are no longer electrostatically bound, to
outside the porous electrodes, by means of charging the ions with
reversed polarity, with the consequent possibility to remove them
from the cell by means of the passage of the washing liquid. The
apparatuses with flow-through capacitors, present on the market and
which exploit the principle of capacitive deionization according to
the cyclically repeated operative steps mentioned above, have
proven in practice that they have numerous drawbacks.
[0014] A first drawback lies in the fact that the apparatuses with
flow-through capacitors have intermittent and hence discontinuous
operation, which strongly negatively affects their productive
efficiency/output. Such drawback is intrinsic in the operating
principle itself of such apparatuses that leads the cell to purify
the fluid for a time that varies between 50 and 75% of its
operation, which stems from the need to subject the electrodes to
the different above-indicated steps in order to operate in
different times and modes on the ions (absorbing them, neutralizing
them, moving them away).
[0015] In addition, the alternation of the operating and
regeneration steps leads to queues of diluted fluid that cannot be
exploited and which contributes to further negatively affecting the
performances of the cell.
[0016] A second drawback lies in the fact that within the cell,
high salinity concentrations can be reached with the consequent
precipitation of salts, and hence the formation of fouling. A
widespread problem in the cells with flow-through capacitors indeed
pertains to the need to prevent the solutes from precipitating
between the electrodes of the capacitor, obstructing the fluid
passage channels and thus rendering the cell useless in the long
term.
[0017] It must also be considered that the capacity of the
electrodes to capture the ions in solution, and more generally the
charged particles, is a characteristic that positively affects the
operation of the capacitor. Nevertheless, the ions, after having
been captured by the electrodes in the operating step, must be
easily releasable into the flow of the washing liquid of the
regeneration step.
[0018] For such purpose, numerous different embodiments of
electrodes have been developed aimed to attempt to optimize the
physical and electrical relation between the surface of the same
electrodes and the ions to be treated upon varying the
abovementioned operative steps (absorption, liberation, moving
away). For example, electrodes have been designed made of spongy
active carbon, molded in the form of sheets or fibers, as described
for example in the U.S. Pat. No. 6,413,409 or sheets of a mixture
comprising PTFE as described for example in the U.S. Pat. No.
6,413,409.
[0019] However, it is clear that not all the obtained electrodes
can have optimal efficiency, since it is always necessary to
balance the opposing needs of first retaining, then releasing the
ions, making compromises in the process.
[0020] Apparatuses for purifying fluids are known which exploit the
principle of electrodialysis for removing ionized particles from a
fluid. Through dialysis, it is possible to obtain the separation of
positive and negative ions dissolved as solutes inside a solution,
by the traversing of selectively-permeable membranes of anionic and
cationic type.
[0021] In order to accelerate the dialysis phenomenon, rather slow,
a direct potential difference is normally established by means of
the application of electrodes with opposite sign, such that the
ions are stimulated to migrate towards the electrode with charge
opposite their own.
[0022] More in detail, the apparatuses for purifying a fluid by
means of electrodialysis comprise a sequence of membranes
alternately semi-permeable to cations and anions. Such membranes
define parallel chambers; the aqueous solution to be purified is
made to travel through these chambers. At the ends of the sequence
of membranes, a potential difference is applied. Consequently, the
ions migrate towards the electrode with opposite polarity, coming
to form salt concentration chambers and salt dilution chambers. In
other words, since the arrangement of the membranes is alternated
with respect to their disposition to allow the ionic migration, the
following come to be stabilized in the chambers: electrolyte trap
compartments and purified solution (e.g. water) compartments.
[0023] The electrodialysis is thus based on the application of a
direct electric field capable of forcing the ionic components to
traverse the respective ion-selective and water-impermeable
membranes.
[0024] A first drawback of the electrodialysis apparatuses lies in
the fact that in order to prevent the staining of the
semi-permeable membranes by the ions, it is necessary to use
numerous expedients that can provide for filtering systems, the use
of chemical agents, as well as temporary modifications in the
operation of the electrodialysis apparatus, such as polarity
reversal. All these expedients render the apparatus and its
operation method complex and not very practical, such to require
high, costly maintenance.
[0025] A second drawback of the electrodialysis apparatuses lies in
the fact they are not adapted to treat fluids with low salinity,
such to determine low conductivity in the fluid to be purified.
[0026] Otherwise, it is known to arrange paints on electrodes that
are capable of making positive or negative ions selectively
pass.
[0027] Apparatuses for purifying fluids are known which exploit the
principle of electrodeionization for removing ionized particles
from a fluid. Such apparatuses described in the patents WO
00/44477, WO 2012/170192, JP 2003145164, WO 2005/011849, US
2012/031763 comprise at least one ion absorption cell traversed by
a fluid to be treated containing ionized particles and provided
with a containment structure that defines at least one first
operating chamber through which the fluid to be treated flows and
provided with a first wall having a first electrode associated
provided with a first polarity, at least one second operating
chamber through which the fluid to be treated containing ionized
particles flows and provided with a second wall having a second
electrode associated that is provided with a second polarity
opposite the first, at least one first chamber for evacuating the
ionized particles interposed between the first and the second
operating chamber through which a washing fluid flows and provided
with a third and a fourth wall opposite each other.
[0028] In addition, the third and the fourth wall delimit,
alongside the first and the second wall, respectively the first and
the second operating chamber. The third and the fourth wall each
have at least one ion-selective area associated, susceptible to
being traversed by ionized particles with corresponding polarity
contained in the first and second operating chamber, which pass
from the first and second operating chamber to the first evacuation
chamber under the action of the electric field generated by the
electrodes.
[0029] In accordance with the above-described prior apparatuses,
the electric field always present in the first evacuation chamber
between the third and the fourth wall acts on the ionized
particles, pushing them to exit, in this manner reducing the
efficiency of purification of the fluid to be treated.
[0030] With reference to the apparatus described in the patent US
2012/031763, it is specified that an intermediate electrode is
provided at ground potential between two electrodes with opposite
polarities. Such electrode does not decrease the electric field
between the electrodes with opposite polarities and does not define
any volume where the electric field maintains substantially
constant potential value and where the fluid to be treated flows.
Such apparatus has the same limits as the other apparatuses
described above.
PRESENTATION OF THE INVENTION
[0031] In this situation, the problem underlying the present
invention is therefore to eliminate the abovementioned problems of
the prior art, by providing an apparatus for purifying a fluid and
a method for purifying a fluid, in particular by means of the
aforesaid apparatus, which are capable of removing high quantities
of ionized particles with a high capture efficiency.
[0032] Another object of the present invention is to provide an
apparatus and a method for purifying a fluid, which are capable of
removing the ionized particles with high energy efficiency.
[0033] Another object of the present invention is to provide an
apparatus and a method for purifying a fluid, which are capable of
removing the ionized particles with high efficiency/output.
[0034] Another object of the present invention is to provide an
apparatus and a method for purifying a fluid, which are capable of
purifying fluids contaminated by salts of different ionic
species.
[0035] Another object of the present invention is to provide an
apparatus and a method for purifying a fluid, which require a low
consumption of washing liquid.
[0036] Another object of the present invention is to provide an
apparatus for purifying a fluid that is simple and inexpensive to
obtain and entirely reliable in operation.
[0037] Another object of the present invention is to provide an
apparatus for purifying a fluid, which allows being employed in a
versatile manner in different applications, for industrial
processes as well as in machines for home use, in plants in civil
field for the purification of water and in plants for the
desalination of sea water.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] The technical characteristics of the finding, according to
the aforesaid objects, are clearly found in the contents of the
below-indicated claims and the advantages thereof will be clearer
from the following detailed description made with reference to the
enclosed drawings, which represent several merely exemplifying and
non-limiting embodiments of the invention, in which:
[0039] FIG. 1 schematically shows the apparatus for purifying a
fluid object of the present invention in its minimum structural
components;
[0040] FIG. 2 shows a general electrical and hydraulic operation
scheme of the apparatus for purifying a fluid, object of the
present invention;
[0041] FIGS. 3A and 3B schematically show, in two cross section
views, a portion of the cell of the apparatus for purifying a fluid
object of the present invention in two different operative moments
in accordance with a first embodiment;
[0042] FIG. 4 schematically shows, in a cross section view, a
portion of the cell of the apparatus for purifying a fluid object
of the present invention in accordance with one embodiment;
[0043] FIG. 5 shows a first embodiment variant of the example of
FIG. 4;
[0044] FIG. 6 schematically shows, in perspective view, the
apparatus for purifying a fluid in accordance with the embodiment
of FIG. 5 in which the elementary layers or cells are repeated in
succession;
[0045] FIGS. 7, 8, 9 and 10 show several embodiment variants of the
example of FIGS. 3A and 3B;
[0046] FIG. 11 schematically shows, in cross section view, the
apparatus for purifying a fluid in accordance with the embodiment
of FIGS. 3A and 3B in which the elementary layers or cells are
repeated in succession;
[0047] FIG. 12 schematically shows, in a perspective view, a
portion of the cell of the apparatus for purifying a fluid of FIG.
11;
[0048] FIG. 13 shows a general electrical and hydraulic operation
scheme of a variant embodiment of the apparatus for purifying a
fluid, according to the present invention;
[0049] FIGS. 14 and 15 schematically show, in cross section views,
a portion of the cell of the apparatus for purifying a fluid of
FIG. 13 in two different operative moments;
[0050] FIG. 16 schematically shows a detail of the apparatus for
purifying a fluid of FIG. 13 relative to an evacuation chamber with
substantially equipotential volume of a cell.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0051] With reference to the set of drawings, reference number 1
indicates overall an embodiment of an apparatus for purifying a
fluid, object of the present invention.
[0052] The apparatus 1, according to the invention, is adapted to
be employed for removing ionized particles present in fluids, such
particles susceptible of being affected by the presence of an
electric field, such as ions in solution.
[0053] Hereinbelow, the term ionized particles will generically
indicate any contaminant dissolved in a fluid F1 to be treated,
capable of being attracted by an electrostatic field, such as in
particular the ions dissolved in a fluid.
[0054] The ionized particles will therefore not only comprise
dissolved ions such as salts, chlorides, sulfates, nitrates,
nitrites, ammonia and heavy metals, but also organic substances or
micropollutant substances in general whether provided with an
intrinsic electric charge or susceptible of polarization due to the
electric field present (as indicated hereinbelow) which induces an
electric dipole in the substance itself.
[0055] The apparatus 1 is therefore adapted to operate for the
deionization of industrial process fluids and for the deionization
of water, in particular for softening the water of the water supply
system and for the desalination of sea water; it is particularly
capable of removing, from its interior, salts in solution (such as
chlorides and sulfates), nitrates, nitrites, ammonia, and other
polarized contaminants of organic substances or micropollutants in
general.
[0056] The apparatus 1 is also adapted to concentrate ionized
particles within fluids, particularly of industrial processes, in
order to facilitate the recovery or the disposal of such particles.
In addition, the apparatus 1 is also adapted to be integrated in
apparatuses or machines, for example for home use, in order to
previously treat the water from the latter employed for their
various use functions.
[0057] In accordance with the present invention and with the scheme
of the general FIG. 1, the apparatus 1 comprises at least one ion
absorption cell 2, which is traversed by a first operative fluid F1
(for example a fluid to be treated) containing charged particles
e.g. cationic and/or anionic particles, such as water with high
degree of mineralization, i.e. mineral salts dissolved therein, and
in particular with high hardness or with high quantities of calcium
and magnesium salts contained therein. As indicated above, the
first operative fluid F1 can also be a solution of organic type
containing mineral salts to be removed or an organic solution where
it is necessary to carry out a separation between the components of
the solution itself on the basis of the electric charge and/or
molecular weight.
[0058] The apparatus can provide for multiple cells in series or
parallel in a per se known manner in order to improve the
purification of the fluid or treat high flow rates.
[0059] The aforesaid cell 1, illustrated in partial schematic form
in the enclosed figures, is provided with a containment structure
3, e.g. made of plastic material, which at its interior contains at
least one operating chamber 4 and at least one chamber 13 for
evacuating the charged particles.
[0060] The operating chamber 4 is provided with an inlet opening 6
and an outlet opening 8, through which the aforesaid first
operative fluid F1 is susceptible to flow while the evacuation
chamber 13 is provided with an inlet section 14 and an outlet
section 15, through which at least one second operative fluid F2
flows (e.g. a washing fluid).
[0061] As specified hereinbelow, multiple operating chambers 4 and
multiple evacuation chambers 13 can also be provided for each cell
1, or a plurality of elementary cells can be provided, each
provided with one or more operating chambers and one or more
evacuation chambers 13, as specified hereinbelow in the various
illustrated examples.
[0062] According to the idea underlying the present invention, the
operating chamber 4 and the evacuation chamber 13 are separated
from each other by a filtering membrane 100.
[0063] The filtering membrane can therefore advantageously be with
reverse osmosis, nanofiltration, ultrafiltration, microfiltration
or even, in accordance with the example of FIG. 13-16, an
ion-selective membrane.
[0064] The filtering membrane will therefore be susceptible of
separating components of fluids on the basis of size or weight
characteristics in the case of reverse osmosis, nanofiltration,
ultrafiltration or microfiltration membranes and on the basis of
electrical characteristics in the case of filtering membrane with
ion exchange (ion-selective membrane).
[0065] The aforesaid filtering membranes, which separate the fluid
components on the basis of size or weight characteristics, are
usually classified based on their MWCO "molecular weight cut off"
acronym, rather than on the size of the particles that they are
capable of filtering.
[0066] The measurement unit MWCO of the filtering membranes is the
Dalton that expresses the mass of the single atoms, molecules,
ions, radicals and elementary particles. If MWCO is >10,000
Dalton, this is ultrafiltration; if MWCO is <500 Dalton this is
reverse osmosis (RO). The size of the "pores" of a membrane
describes the characteristics of the membrane and the size of the
particles that can be repelled. In the microfiltration membranes,
the size of the pores various from 10 to 0.1 mm. This is the
membrane with the largest pores and is suitable for allowing the
passage of a flow even in the presence of low pressures. In the
ultrafiltration membranes, the size of the pores varies from 0.1 to
0.01 mm. In the nanofiltration membranes the size of the pores
varies from 0.01 to 0.001 mm. In the reverse osmosis membranes the
size of the pores varies from 0.001 to 0.0001 mm.
[0067] The filtering membrane will advantageously form, in a
complete manner without requiring another support layer, the
separation wall between the operating chamber 4 and the evacuation
chamber 13.
[0068] Inside the evacuation chamber 13, a porous electrical
conductor 18 is housed, which is traversed by the second operative
fluid F2 parallel along the plane of extension of the same porous
electrical conductor. The latter also simultaneously forms a spacer
for the walls of the evacuation chamber 13, as will be specified
hereinbelow.
[0069] The apparatus 1 further comprises a first and a second
electrode A, B separated from each other with at least one
aforesaid operating chamber 4 and at least one aforesaid evacuation
chamber 13 interposed.
[0070] The two electrodes A, B are power supplied by an electrical
power supply source 12 with opposite polarities in order to
generate, respectively, an operative electric field in the
operating chamber 4 and a limited electric field in the evacuation
chamber 13.
[0071] The electric field in the evacuation chamber 13 has lower
value than the operative electric field in the operating chamber 4,
due to the shielding effect exerted by the porous electrical
conductor 18.
[0072] Consequently, the charged particles contained in the
operating chamber 4 are susceptible of traversing the filtering
membrane 100 under the action of the operative electric field
generated by the electrodes A, B, and then be evacuated by the
second operative fluid F2 once they have reached the evacuation
chamber 13.
[0073] Indeed, the charged particles, once they have reached the
evacuation chamber 13, remain substantially confined at its
interior, since herein they are subjected to the small action of
the limited electric field due to the presence of the porous
electrical conductor, while they are subjected to the evacuation
action by the second operative fluid F2.
[0074] The power supply source 12 will be adapted to supply the
aforesaid electrodes with the aforesaid negative and positive
voltages, with direct power supply or with pulsed power supply
having average voltage value respectively positive and
negative.
[0075] The electrical power supply source 12 will be susceptible of
periodically reversing the polarities of the two electrodes A, B in
order to force said cationic particles and the anionic particles
contained in the operating chamber 4 to enter into a same
evacuation chamber 13 by traversing the filtering membrane 100.
[0076] Advantageously, the pressure in the first evacuation chamber
13 is therefore regulated with respect to the pressure in the
contiguous operating chambers 4, 5 to a value susceptible of
limiting the leakage of flows F1 or F2 through the filtering
membrane 100, preferably between 0 and 20%.
[0077] Preferably, in the operating chamber 4, an isolating porous
spacer separator 19 is housed that is susceptible of being
traversed by the first operative fluid F1. It is obtained, for
example, by means of a granular material or by means of a net,
which have definite size equal to the distance between the walls of
the operating chamber 4.
[0078] The apparatus 1 according to the invention can comprise a
plurality of operating chambers 4 and a plurality of evacuation
chambers 13, distributed in succession with each other according
for example to one of the configurations illustrated hereinbelow,
with a plurality of pairs of first and second electrodes A, B
electrically connected in series and with each pair at least one
respective operating chamber 4 and one evacuation chamber 13 being
interposed.
[0079] Between the first wall 10 of the first operating chamber 4
and the third wall 16 of the first evacuation chamber 13, a first
isolating porous spacer separator 19 is preferably interposed,
susceptible of being traversed in its extension by the first
operative fluid, F1.
[0080] In accordance with an advantageous characteristic of the
invention, the apparatus 1 comprises at least one ion exchange
resin 36 contained inside the operating chamber 4 in order to
interfere with the passage of the first operative fluid F1, and
maintained herein by means of retention means 37.
[0081] In operation, the apparatus described up to now mainly from
the structural standpoint operates as specified hereinbelow.
[0082] The positively and/or negatively charged particles contained
in the first operative fluid F1 which flow in a continuous manner
into the operating chamber 4 are forced by the action of the
electric field produced by the two electrodes A, B to migrate
respectively towards the cathode (negative electrode) and towards
the anode (positive electrode). In such migration, the positive
cationic particles and negative anionic particles contained in the
fluid of the operating chamber 4 encounter the filtering membrane
100 and are forced by the electric field to traverse it, passing
through the meshes of the material constituting the membrane until
they enter into the evacuation chamber 13. The charged particles
with different polarity can traverse a same membrane 100 following
the polarity reversal of the electrodes, or two separate membranes
100 in order to enter into two separate evacuation chambers if the
evacuation chamber 13 is placed next to two operating chambers 4,
or if two successive operating chambers 4 are provided which
traverse electric fields with different polarity according to the
descriptive examples illustrated hereinbelow.
[0083] Once they have entered the evacuation chamber 13, the
charged particles are subjected herein to a small action of the
electric field and hence they are no longer able to cross the
filtering membrane 100, remaining confined in the substantially
equipotential volume of the evacuation chamber 13, in order to then
be conveyed towards the drain by the flow of the second operative
fluid F2 which advances in the evacuation chamber 13.
[0084] Through the operative electric field present in the
operating chamber 4, the charged particles present therein are
moved into a volume constituted by the evacuation chamber 13, with
limited electric field lower than that of the operative electric
field, passing through a check barrier constituted by the filtering
membrane 100 which (at least partly) separates the operating
chamber 4 from the evacuation chamber 13.
[0085] The porous electrical layer 18, for example constituted in
accordance with a possible abovementioned embodiment by a metallic
net possibly assisted by a porous and conductive filler, causes the
isopotentiality of the third chamber 13, like a Faraday cage, with
shielding of the electric field in order to prevent conducting the
charged particles to outside the same chamber 13 once they have
entered inside.
[0086] In accordance with the embodiment illustrated in the
enclosed FIGS. 3A, 3B, 7, 8, 9 and 10, at least one first and one
second operating chamber are provided, respectively indicated with
the reference numbers 4 and 5, respectively provided with a first
and a second inlet opening, 6, 7 and with a first and second outlet
opening 8, 9, through which the first operative fluid F1 is
susceptible of flowing.
[0087] The aforesaid first and second operating chamber 4, 5 are
respectively provided with a first and second wall 10, 11 for
containing the first operative fluid, with which the first and
second electrode A, B are correspondingly associated; such
electrodes are power supplied by the electrical power supply source
12 to a first and a second polarity that are opposite each other.
Advantageously, in accordance with a preferred but non-limiting
embodiment of the present invention, the first and the second
containment wall 10, 11 themselves achieve the two electrodes,
given that they are constituted by a conductor material, such as
graphite. The electrodes can be of the type with high surface area,
of the type widely described in the literature for capacitive
deionization. These electrodes with high porosity and surface area
in fact allow an improved creation of the electric field,
especially in the case of power supply with alternating polarity of
the cell as described hereinbelow.
[0088] For such reason, the electrodes A, B coincide in the figures
in accordance with this example with the same two containment walls
10, 11.
[0089] For some specific requirements, such as for example
improving the ease of cleaning and/or sterilizing the cell, in some
embodiments it may be advantageous to add, in front of the
electrodes, a porous separation membrane similar to that indicated
above and further considered hereinbelow.
[0090] According to the present invention in accordance with this
embodiment, the first evacuation chamber 13 of the cationic
particles and/or anionic particles absorbed from the two operating
chambers 4, 5 is interposed between the first operating chamber 4
and the second operating chamber 5, and is provided with a third
inlet opening 14 and a third outlet opening 15, through which the
second operative fluid F2 flows.
[0091] The third chamber 13 is delimited by a third and fourth wall
16, 17, parallel to and opposite each other, which separately
delimit, together with the first wall 10 and the second wall 11,
respectively the first operating chamber 4 and the second operating
chamber 5.
[0092] The third and the fourth wall 16, 17 each comprise the
filtering membrane 100, which as said can be with reverse osmosis,
nanofiltration, ultrafiltration or microfiltration.
[0093] The electric field in the first evacuation chamber 13 is
present in a much more limited manner due to the presence of the
porous electrical conductor 18 inside the same first evacuation
chamber 13. Such porous electrical conductor 18 is provided, in
accordance with this embodiments and advantageously in accordance
with all the embodiments of the present invention, with a thickness
and hence with a corresponding volume susceptible of being
traversed at its interior by the washing fluid F2, along the
thickness of the conductor. This porous electrical conductor 18 is
interposed between the third and the fourth wall 16, 17 and is in
close contact with the same third and fourth wall 16, 17, thus
reducing, inside the first evacuation chamber 13, the electric
field generated by the first and second electrode 10, 11. Such
porous electrical conductor causes a shielding effect of the
electric field due to the volume subtended between the third and
the fourth wall 16, 17 such that the charged particles contained in
the first evacuation chamber 13 do not have the force to pass
through the membranes.
[0094] The porous electrical conductor 18 extends its shielding
substantially up to the internal surface of the third and fourth
separation wall 16, 17, with the first operative fluid F1, that
flows into the two operating chambers 4, 5 and which obviously has
higher resistivity.
[0095] The aforesaid porous electrical conductor 18 is
advantageously formed by at least one three-dimensional porous
structure (provided with thickness), in particular interposed as a
spacer between the third and fourth wall 16, 17, and made of
conductive material such as a metal, porous active carbon, possibly
expanded graphite, carbon aerogel or other materials with similar
characteristics. The three-dimensional structure of the material
will allow the passage of the fluid at its interior (in the same
lying plane thereof) and will thus attain the electrostatic
shielding. The aforesaid porous electrical conductor 18 can also be
advantageously formed by a net made of conductive material, e.g.
made of metal, it too interposed as a spacer between the third and
fourth wall 16, 17 and provided with a three-dimensional structure
in order to allow the passage of the fluid in its same lying
plane.
[0096] Therefore, the above-described configuration of the cell 2
provides for making the second operative fluid F2 flow into the
first evacuation chamber 13 interposed adjacent between the two
operating chambers 4, 5 where the first fluid F1 (e.g. the fluid F1
being the fluid to be treated and the fluid F2 the washing fluid)
moves; the first evacuation chamber 13 is separated from the two
operating chambers 4, 5 by means of the filtering membranes of the
third and fourth wall 16, 17 which are substantially not permeated
by a flow of fluid F1 or F2 but which allow the selective crossing,
under the action of the electric field generated by the electrodes
A, B, of the ionized particles contained in the first operative
fluid F1.
[0097] The filtering membranes that constitute the walls 16, 17
would allow a significant flow of liquid to cross them only in the
presence of a pressure difference at their sides; at the same time,
due to their porosity, they do not constitute an insulator capable
of interrupting the electric field and the ion conduction.
[0098] The pressure in the first evacuation chamber 13 is therefore
regulated with respect to the pressure in the contiguous operating
chambers 4, 5 to a value susceptible of limiting the leakage of
flows F1 or F2 preferably between 0 and 20%.
[0099] Therefore, as indicated above, preferably the pressure in
the first evacuation chamber 13 will be regulated with value lower
than that of the two operating chambers 4, 5 so as to prevent or
limit a leakage of fluid F2 from such first evacuation chamber 13
to the two operating chambers 4, 5. Advantageously, in fact, the
leakage if provided will be directed from the operating chambers
4,5 to the evacuation chamber 13.
[0100] Preferably, the filtering membrane 100 will not exert a
filtering action on a flow of fluid moving through the membrane due
to a difference of pressures between the operating chambers 4, 5
and the evacuation chamber 13, since such flow will not be
advantageously present; rather, it will only exert a filtering
action on a flow of charged particles which are moved by the
electric field.
[0101] The filtering membrane 100 will also allow selecting the
ionic particles that move into the evacuation chamber 13 as a
function of its filtering characteristics (e.g. as a function of
the size of the charged particles). Multiple evacuation chambers 13
can be provided in succession in different apparatuses 1 or in the
same apparatus and delimited by filtering membranes 100 of
different type in order to selectively separate ionic species of
particles with different size or weight, or in any case particles
that can be differently filtered by means of the different membrane
types.
[0102] It will also be possible to insert, inside the same cell,
more than one evacuation chamber 13 for the purpose for example of
being able to advantageously obtain permeate fluids through the
filtering membranes 100, with particles with opposite polarity.
[0103] Even if preferably the filtering membrane 100 is not per se,
due to its nature and material, impermeable to the fluid F1 or F2,
it will in operation--due to the regulation of the pressure in the
operating chambers 4, 5 and in the evacuation chamber
13--substantially behave in an impermeable manner with respect to a
fluid flow but in a permeable manner to the ionized particles
capable of traversing the membrane.
[0104] The filtering membranes 100 that delimit the evacuation
chamber 13, in accordance with the abovementioned embodiment
illustrated in the enclosed FIGS. 3A, 3B, 7, 8, 9 and 10, are
therefore susceptible of being traversed by charged particles
contained in the first and second operating chamber 4 and 5, which
are acted upon by the action of the operative electric field
generated by the electrodes A, B. At the same time, the filtering
membranes 100 are adapted to confine, within the same first
evacuation chamber 13, the cationic particles or the anionic
particles or particles of both polarities, which crossed the
filtering membrane 100, maintaining them inside the same first
evacuation chamber 13 due to the small movement force induced
thereon by the electric field in such first evacuation chamber
13.
[0105] The filtering membranes 100 can face the electrodes for the
entire extension thereof or they can be composed of side-by-side
portions of membranes with different filtration characteristics in
order to select ionized particles that can be differently
filtered.
[0106] Advantageously, the aforesaid electrodes A, B (with
reference to the specific example as illustrated in FIG. 8, with
reference to a subsequent example illustrated in FIG. 5 and also
with reference to the general principle of the present invention)
can be protected by a cover layer 38, such as an analogous
filtering membrane with reverse osmosis, nanofiltration,
ultrafiltration or microfiltration, for the purpose of protecting
from dirtying due to the attraction of the ionized particles
towards the electrodes A, B themselves. The porosity of the
filtering membranes 100 is capable of preventing the electrical
isolation of the electrodes A, B from the fluid.
[0107] Such cover layer 38 of the electrodes, if advantageously
provided, can be made both in contact with the face of each
electrode A, B, and spaced therefrom in order to define with each
electrode a further secondary chamber 39 for the passage of a
secondary fluid F3, as is schematized in FIG. 8 (and in FIG. 5 with
reference to a further example described hereinbelow).
[0108] The secondary fluid F3 can also have the purpose of
improving the conduction of the electrodes A, B with respect to the
first operative fluid F1 and simultaneously maintaining clean the
surfaces of the electrodes A, B themselves.
[0109] Between the first wall 10 of the first operating chamber 4
and the third wall 16 of the first evacuation chamber 13, a first
isolating porous spacer separator 19 is preferably interposed,
susceptible of being traversed in its extension by the first
operative fluid F1.
[0110] Analogously, between the second wall 11 of the second
operating chamber and the fourth wall 17 of the first evacuation
chamber 13, a second isolating porous spacer separator 20 is
preferably interposed, also susceptible of being traversed by the
fluid F1 to be treated. The abovementioned cell 2 is advantageously
obtained by means of a plurality of superimposed purification
layers, affected upstream and downstream by a common hydraulic
circuit.
[0111] For example, in accordance with the aforesaid embodiment
illustrated in the enclosed FIGS. 3A, 3B, 7, 8, 9 and 10, each
purification layer comprises a first 4, a second 5 and a third
chamber 13 in addition to the electrodes.
[0112] More in detail, in such embodiment, the cell 2 is for such
purpose provided with: [0113] a first supply section 21 obtained in
its containment structure 3, and adapted to supply, with the first
operative fluid F1, the first inlet opening 6 and the second inlet
opening 7 respectively of the first and the second operating
chamber 4, 5 of all the purification layers; [0114] a first
extraction section 22 obtained in its containment structure 3, and
adapted to receive the treated fluid F1 from the first outlet
opening 8 and from the second outlet opening 9 of the first and of
the second operating chamber 4, 5 of the aforesaid purification
layers; [0115] a second supply section 23 obtained in the
containment structure 3, which supplies, with the second operative
fluid F2, the third inlet opening 14 of the first evacuation
chamber 13 of the aforesaid purification layers; [0116] a second
extraction section 24 obtained in the containment structure 3,
which receives the washing fluid from the third outlet opening 15
of the first evacuation chamber 13 of the aforesaid purification
layers.
[0117] The electrical connection between the first and the second
electrodes A, B of each purification layer is made by means of
terminals (not shown) which are connected to respective projections
25 externally projecting from the electrodes A, B themselves;
preferably the projections 25 of the positive and negative
electrodes A, B are extended from opposite sides or in any case
sides of the respective electrodes A, B that are spaced from each
other. The two supply liquids of the cell, i.e. the first operative
fluid F1 and the second operative fluid F2, can also be constituted
by the same liquid (for example water to be treated and washing
water), also by arranging a common supply.
[0118] The apparatus further comprises: [0119] a first solenoid
valve or manual interception and/or regulation valve 28 in the
supply duct 29 to the first inlet section 21; [0120] a second
solenoid valve 30, or in its place a first manual adjustment tap,
placed on the delivery duct 31 to the users and connected to the
first extraction section 22; [0121] a third solenoid valve 32 on
the supply duct 33 of the second operative fluid F2 connected to
the second inlet section 23; [0122] a fourth solenoid valve 34 on
the drain duct 35, connected to the second extraction section 24,
or preferably in its place a second tap for adjustably varying the
ratio between the first operative fluid F1 and the second operative
fluid F2.
[0123] In accordance with a particular characteristic of the
present invention illustrated in FIGS. 9 and 10 in accordance with
the first embodiment of the invention but also applicable to the
other embodiments and to the general principle of the invention,
ion exchange resins 36 are provided, contained inside at least one
of the two operating chambers 4 and 5 in order to interfere with
the passage of the first operative fluid F1. The resins are
maintained inside the operating chamber without being evacuated
from the first operative fluid F1 by means of retention means
37.
[0124] Preferably, such ion exchange resins are of anionic and
cationic type mixed together, both resin types preferably inserted
in both the operating chambers 4, 5.
[0125] Preferably, the aforesaid retention means 37 are obtained
with a porous separator, e.g. fixed to the operating chambers 4, 5
at the outlet opening 8, 9 thereof, susceptible of allowing the
continuous passage of the first operative fluid F1 and
simultaneously of retaining the resins 36, preventing the exit
thereof together with the first operative fluid F1.
[0126] In operation, the resins allow slowing the advance of the
cationic and anionic ions to the interior of the chambers together
with the first operative fluid F1, increasing the possibility that
they will be electrostatically attracted towards the evacuation
chamber 13. More in detail the anionic and cationic resins 36 will
be more greatly worn in proximity to the inlet openings 6, 7 of the
operating chambers 4, 5, being able to retain a limited number of
ions, while they will be more active towards the outlet openings 8,
9 where the ions are less numerous and where, therefore, due to
their ion retention contribution, they allow the ions to have a
greater possibility to cross the ion-selective areas and enter into
the evacuation chamber 13.
[0127] In accordance with a preferred embodiment of the present
invention, the electrical power supply source 12 is advantageously
susceptible of periodically reversing the polarities of the first
and second electrode 10, 11 in order to force the cationic
particles and the anionic particles contained in the first and
second operating chamber 4, 5 to enter into the third chamber 13 by
traversing the corresponding filtering membrane.
[0128] Preferably, in accordance with the aforesaid embodiment,
i.e. also with the others illustrated in the present description,
the polarity reversal frequency varies in an interval comprised
between 0.5 Hz and 100 Hz.
[0129] In accordance with this polarity reversal, the two operating
chambers 4, 5 are traversed in parallel by the first operative
fluid 1 since the anionic and cationic particles, due to the
polarity reversal, can cross through the filtering membranes that
delimit the first evacuation chamber 13, in order to then be
removed from the second operative fluid F2 (hence with washing
function) coming from either the first or the second operating
chamber 4, 5.
[0130] Of course, the single purification layer of the cell 2,
shown in FIG. 12 in perspective view, can be repeated n times as
illustrated in FIG. 2 in order to obtain a greater filtering
action. In this case, preferably, as illustrated in the same FIG.
11, each intermediate electrode 10, 11 (excluding only the final
electrodes) will act as a containment wall for two first operating
chambers 4 or for two second operating chambers 5 of two adjacent
and consecutive purification layers.
[0131] Preferably, moreover, the second extraction section 24 is
extended substantially transversely to the purification layers,
preferably in a central zone of the chambers 4, 5, 13, traversing
the first 10, the second 11, the third 16 and the fourth wall 17
with corresponding through holes. In addition, in accordance with
the embodiment characteristic illustrated in the detail of FIG. 7,
but in general also referable as a variant of the present
invention, the first evacuation chamber 13 is obtained in duct form
and for such purpose is laterally closed with two lateral walls 26,
26' placed to join the third and fourth wall 16, 17 at two opposite
edges thereof so as to create a duct for conveying the evacuation
fluid. The latter is preferably extended with its ends beyond
provided spacer separators 27, which delimit the extension of the
first and second walls 4, 5 and separate the liquid to be treated
F1, with which the first and the second chamber 4, 5 are supplied,
from the washing liquid F2.
[0132] In accordance with a further embodiment of the present
invention illustrated in the detail of FIGS. 7 and 10, but also
generally referable as a variant of the present invention, polarity
reversal is not provided at the electrodes and the flow to be
treated F1 sequentially traverses at least two operating chambers
delimited by electrodes with opposite polarity in order to allow
both the positive and negative ionic particles to traverse the
filtering membranes under the action of the electric field. For
such purpose, the two operating chambers are advantageously
traversed in countercurrent and can be sequentially connected by
connector sections made of electrically isolating material,
indicated with the dashed line in FIGS. 7 and 10 and of course
arranged in positions of the cell that are susceptible to not
interfere with the walls 16, 17 that delimit the first evacuation
chamber 13.
[0133] In operation, the apparatus described up to now mainly from
the structural standpoint operates as specified hereinbelow, with
reference to the embodiment of FIGS. 3A, 3B.
[0134] The positively and negatively charged particles contained in
the liquid to be treated F1, which continuously flow into the first
and second chamber 4, 5, are forced by the action of the electric
field produced by the two electrodes A, B to respectively migrate
towards the cathode (negative electrode) and towards the anode
(positive electrode). In such migration, the positive cationic
particles contained in the fluid of the operating chamber opposite
that delimited by the cathode (first operating chamber 4 in
accordance with FIG. 3A) and the negative anionic particles
contained in the fluid of the operating chamber opposite that
delimited by the anode (second operating chamber 5 in accordance
with FIG. 3A) which encounter the filtering membranes of the third
wall 16 and fourth wall 17 are forced by the electric field to
traverse them by passing through the meshes of the material
constituting the filtering membranes, until they enter into the
first evacuation chamber 13.
[0135] Once they have entered into the first evacuation chamber 13,
the charged particles are subjected here to a small action of the
electric field, and thus they are no longer able to traverse the
filtering membranes of the third 16 and fourth wall 17, remaining
confined in the substantially equipotential volume of the third
chamber 13, before then being conveyed towards the drain by the
washing fluid flow F2 which continuously advances into the first
evacuation chamber 13.
[0136] Through the electric field present in the first and in the
second chamber 4, 5, the charged particles present herein are then
moved into a volume constituted by the third evacuation chamber 13
with limited electric field, overcoming a check barrier constituted
by the filtering membranes of the same walls 16, 17 of the third
chamber 13.
[0137] In accordance with a further embodiment of the invention
illustrated in FIGS. 4, 5 and 6, at least one first and one second
evacuation chamber 13, 13' are provided (advantageously a
succession of such chambers are provided as illustrated in FIG. 6),
each delimited by a third wall 16, 16' and a fourth wall 17, 17',
respectively provided with a first and a second inlet section 14,
14', with a first and second outlet section 15, 15', through which
the second operative fluid F2, F2' flows. The aforesaid third walls
16, 16', respectively of the first and the second evacuation
chamber 13, 13', each comprises a filtering membrane 100 and
delimit between them the provided at least one operating chamber 4
(and advantageously a succession of such operating chambers 4 as
illustrated in FIG. 6), which therefore remains interposed between
the first and the second evacuation chamber 13, 13'.
[0138] The first electrode and the second electrode A, B are
associated with the fourth walls 17, 17' respectively of the first
and the second evacuation chamber 13, 13'.
[0139] With the term "associated" referred to an electrode and to a
wall (in this example or more generally according to the
invention), it must be intended that the electrode itself forms the
wall or a direct mechanical connection, i.e. without the
interposition of other chambers or layers, an indirect mechanical
connection, with the interposition of other chambers or layers). In
any case, the electric field generated by the electrode A, B will
be particularly active with respect to such wall.
[0140] In accordance with this embodiment, the electrical power
supply source 12 will preferably be susceptible of maintaining
unchanged the polarity of the two electrodes A, B in order to force
the cationic particles and the anionic particles contained in the
operating chamber 4 to enter into respective two different
evacuation chambers 13, 13' through respective filtering membranes
100.
[0141] In such a manner, as illustrated in FIG. 6, in the two
evacuation chambers 13, 13' one can obtain the concentration for
example of acids and bases at the outlet of the two corresponding
second operative fluids F2 and F2', starting from an operative
liquid F1 with a salt dissolved. In the example of FIG. 6, the case
of sea water with sodium chloride dissolved is reported. In
accordance with the embodiment variant illustrated in FIG. 5, the
electrodes A, B are protected by a cover layer 38, 38', it too
obtained by a filtering membrane 100, advantageously spaced from
the corresponding electrode A, B in order to define therewith a
secondary chamber 39, 39' for the passage of at least one washing
fluid of the electrode. In the case of the example of FIG. 6, two
separate washing flows F3, F3' were provided respectively for the
positive electrode A and for the negative electrode B.
[0142] As already seen for the general case and illustrated herein
in FIG. 6 with reference to the above-described particular
embodiment, the apparatus can comprise a plurality of operating
chambers 4 and a plurality of evacuation chambers 13, 13',
distributed in succession and with, in the case of this example,
each operating chamber 4 interposed between two evacuation
chambers. Pairs of first and second electrodes A, B electrically in
series are provided; in this example, an operating chamber 4 and
two evacuation chambers contiguous on opposite sides are
interposed.
[0143] More clearly, therefore, in the embodiment exemplified in
FIGS. 4, 5 and 6, it can be observed that the cell is adapted such
that it can separately recover the removed cationic and anionic
particles.
[0144] In order to transfer relatively large quantities of charged
particles, it is possible to connect in parallel to a certain
number of base cells; in this manner, nevertheless, the overall
operative current could reach high values. Since the cost of a
power supplier increases with the increase of the operative
current, to a greater extent than that which occurs with the
increase in voltage, it is recommended to electrically connect the
cells together in series. Also the electrodes represent a
considerable cost in making the cells, since they require
electrical connections to the power supply.
[0145] The intermediate electrodes A, B of the succession of pairs
of electrodes A, B can be substituted or better yet obtained by
means of a bipolar membrane 40.
[0146] In FIG. 6, a cell is described that provides for the
connection in series and the use of bipolar membranes 40 instead of
conventional electrodes.
[0147] It is known that the bipolar membranes are constituted by
the joining of cation and anion exchange membranes by means of a
rolling process. Creating an electric field with suitable potential
difference, these membranes are capable of generating H+ and OH-
ions, separating the water.
[0148] More in detail, in accordance with such embodiment
illustrated in FIG. 6, it is possible to superimpose a plurality of
operating chambers 4 and evacuation chambers 13, 13', preventing
the insertion of the electrodes in each chamber group but
exploiting the capacity of the bipolar membranes to separate water
into Hydrogen and Hydroxyl ions and then close the electric circuit
of the connection in series, while maintaining the superimposed
chambers separated from the chemical standpoint. In this manner,
one will obtain an electrically in series connection of the
chambers while it becomes possible to select a hydraulic connection
of the chambers both in parallel and at least partially in
series.
[0149] For this purpose, in FIG. 4, one can observe the presence of
only one operating chamber 4 for two chambers 13 and 13'
respectively intended for the recovery of the particles with
positive and negative charge.
[0150] The insertion is observed of two further chambers 39 and 39'
intended for washing the electrodes in order to prevent possible
gas bubbles (emitted in case the operating voltage is increased in
order to increase the purification efficiency/output) from
partially isolating the electrode or causing excessive internal
pressures. Advantageously the two second operative flows F2 and F'
can be partially recirculated in order to increase the
concentration of the recovered acids and bases.
[0151] The washing flows F3 and F3' can in turn be recirculated and
possibly also crossed if advantageous.
[0152] The first operative flow F1 conveys the liquid to be
purified, from which the ionized particles will be extracted.
[0153] By coupling these membranes to the evacuation chambers 13,
as indicated in FIG. 6, one can create a basic unit composed of two
evacuation chambers 13 and 13' and an operating chamber 4. The
chambers 13, 13' are respectively delimited on the cationic side
with a bipolar membrane in a chamber and on the anionic side with
the subsequent bipolar membrane in the opposite chamber. Both
chambers 13, 13' are facing a same operating chamber 4. The
chambers 13 and 13' are opposite each other and each is separated
from the upper 13' and lower 13 evacuation chamber of the series by
a bipolar membrane that substitutes the two electrodes and the
respective electrical connection in the connection in series. The
bipolar membrane will have opposite insertion sense between the
lower chamber and upper chamber. In the two evacuation chambers 13,
13', two second operative flows, respectively F2 and F2', will
flow; these will convey the acidic and basic particles thus
separated. This basic unit can be duplicated "n" times, thus
rendering the apparatus more effective.
[0154] The bipolar membranes are capable of operating at rather
high current densities, up to 30-50 ma/cm2. And at these current
densities, they maintain a voltage at their ends that is on the
order of 1-1.2V based on the density of operative current. The
evacuation chambers 13, 13' however maintain at their ends a
voltage that is close to zero (or in any case quite low). This fact
makes the apparatus 1 according to the invention very efficient, if
compared to the conventional electrodialysis cells which, due to
the ion exchange membranes present, cannot reach comparable current
densities or they sustain voltage drops due to the membranes that
are certainly much bigger.
[0155] A typical cationic membrane often exceeds 10 ohm/cm2 and
hence at a current density of 30 ma/cm2 generates a drop of 0.3V.
Given that a cell of electrodialysis with bipolar membranes uses at
least two membranes (one cationic and one anionic), there is clear
energy savings obtainable with the described configuration, object
of the present invention.
[0156] Another advantage of the present finding is to be able to
easily operate on organic solutions where there are charged
particles with often high molecular weight, which due to their
nature cannot easily traverse a conventional ion exchange
membrane.
[0157] Illustrated in FIGS. 13-16 is a variant of the embodiment of
the enclosed FIGS. 3A, 3B, 7, 8, 9 and 10. With reference to such
variant, the operative fluid F1 is advantageously the fluid to be
treated containing cationic particles and/or anionic particles,
such as water with a high degree of mineralization, i.e. mineral
salts dissolved therein, and in particular with high hardness or
with high quantities of calcium and magnesium salts contained
therein, while the operative fluid F2 is the washing fluid.
[0158] In accordance with this embodiment, the third and fourth
wall 16, 17, which together delimit the third chamber 13 and which
together with the first wall 10 and the second wall 11 respectively
delimit the first operating chamber 4 and the second operating
chamber 5, are substantially impermeable.
[0159] With the term substantially impermeable it must be intended
that there can be a flow leakage between the third evacuation
chamber 13 and one or both operating chambers 4, 5 comprised
between 0 and 20%.
[0160] Preferably the pressure in the third evacuation chamber 13
will be adjusted to a value less than that of the two operating
chambers 4, 5 so as to prevent or limit a fluid leakage from such
third evacuation chamber 13 to the two operating chambers 4,5.
[0161] Therefore, the above-described configuration of the cell 2
provides for making the washing fluid F2 flow into a third
evacuation chamber 13 interposed contiguously between the two
operating chambers 4, 5 where the fluid F1 to be treated transits;
fluid F2 is separated from fluid F2 by means of the third and the
fourth wall 16, 17 which are substantially impermeable to the
fluid. F1 and to the washing fluid F2 but which allow the selective
traversing, under the action of the electric field generated by the
electrodes 10, 11, of the ions contained in the fluid to be treated
F1.
[0162] For such purpose, the third and the fourth wall 16, 17 each
have one or more ion-selective areas associated, such areas
susceptible of being traversed by charged particles with
corresponding polarity contained in the first and in the second
operating chamber 4 and 5; the action of the electric field
generated by the electrodes 10, 11 acts on such particles. At the
same time, the ion-selective areas are adapted to retain, within
the same third evacuation chamber 13, the cationic particles or the
anionic particles, even if with polarity corresponding to the
membrane, keeping them inside the same third evacuation chamber,
due to the small movement force induced thereon by the electric
field when the charged particles are contained in the third
evacuation chamber 13. With the term "corresponding polarity" it is
intended to consider that the anionic ion-selective membrane is
more easily permeable to anions than cations and vice versa the
cationic ion-selective membrane is more easily permeable to cations
than anions.
[0163] Inside the third evacuation chamber 13, the above-described
porous electrical conductor 18 is contained. It is susceptible of
being traversed by the washing fluid F2, it is interposed between
the third and the fourth wall 16, 17 and is in close electrical
contact with the same third and the fourth wall 16, 17, thus
reducing, inside the third evacuation chamber 13, the electric
field generated by the first and by the second electrode 10, 11.
Such porous electrical conductor determines a shielding effect of
the electric field for the volume subtended between the third and
the fourth wall 16, 17 such that the charged particles contained in
the third evacuation chamber 13 do not have the force to overcome
the ion-selective areas, with low electrical resistivity, of the
third and fourth wall 16, 17 even though they have corresponding
polarity.
[0164] The ion-selective areas are a good electrical conductor and
therefore extend the shielding outside the third evacuation chamber
13 up to the outer surface of the third and fourth separation wall
16, 17 with the fluid to be treated F1 that flows into the two
operating chambers 4, 5 which of course has higher resistivity.
[0165] The ion-selective areas of the third and fourth wall 16, 17
are advantageously obtained with membranes selectively of anionic
exchange type and of cationic exchange type, each of which can be
extended for the entire area of an electrode or, otherwise, each
can regard portions of both electrodes as will be clarified in the
examples reported hereinbelow.
[0166] In accordance with a possible embodiment selection, the
third and the fourth wall 16, 17 of the third evacuation chamber 13
each comprise a sheet-form support on which prints of ion-selective
areas are provided, and in particular for example silk screens of
ion-selective areas, obtained starting from anionic and cationic
ion-selective paints, for example of the type described in the
patent EP 2463242 in the paragraphs 18-28 enclosed here for
reference purposes. Such anionic and cationic ion-selective areas
thus obtained can each cover the entire extension of an electrode
or they can regard adjacent portions with different ion-selectivity
of each electrode, in accordance with the two embodiment selections
specified hereinbelow.
[0167] The sheet-form support can for example be made with a TNT
sheet of 10-30 grams per m.sup.2, preferably electrically
conductive, with the ion-selective areas--obtained by means of silk
screen printing, or more generally by means of a printing
process--preferably made of a material that is substantially
electrically conductive.
[0168] As in the above-described case of the enclosed FIGS. 3A, 3B,
7, 8, 9 and 10, the abovementioned cell 2 is advantageously
obtained by means of a plurality of superimposed purification
layers, affected upstream and downstream by a common hydraulic
circuit.
[0169] The two supply liquids of the cell, i.e. the liquid to be
treated F1 and the washing liquid F2) can also be constituted by
the same liquid (e.g. water to be treated and washing water), also
by arranging a common supply.
[0170] In accordance with a first embodiment of the aforesaid
variant of FIGS. 13-16 illustrated in the FIGS. 14, 15 and 16, the
third and the fourth wall 16, 17 are each provided with two or more
adjacent ion-selective areas, and preferably with a plurality of
adjacent ion-selective areas, respectively indicated with 16A, 16B
and 17A, 17B, of which at least one is anionic 16A, 17A or
cation-phobic (indicated with tilted lines rising towards the right
in the enclosed FIGS. 4A, 4B) and at least one is cationic 16B, 17B
or anion-phobic (indicated with tilted lines rising towards the
left in the enclosed FIGS. 4A, 4B).
[0171] In accordance with such embodiment, i.e. in the presence of
ion-selective areas with opposite polarity on each third and fourth
wall 16, 17, the electrical power supply source 12 is
advantageously susceptible of periodically reversing the polarities
of the first and second electrode 10, 11 in order to force the
cationic particles and the anionic particles contained in the first
and second operating chamber 4, 5 to enter into the third chamber
13, by traversing the corresponding ion-selective area 16A, 16B and
17A, 17B.
[0172] Preferably, in accordance with the aforesaid embodiment, the
polarity reversal frequency varies in an interval comprised between
0.5 Hz and 100 Hz.
[0173] In accordance with this embodiment, the two operating
chambers 4, 5 are traversed in parallel by the fluid to be treated
F1 since the anionic and cationic particles, due to the polarity
reversal and to the presence of ion-selective areas with opposite
polarity on each wall that delimits the third evacuation chamber
13, can enter into the latter chamber 13 in order to then be
removed, whether they are coming from both the first or the second
operating chamber 4, 5.
[0174] Of course, the single purification layer of the cell 2
schematized for example in FIGS. 12, 14 and 15 can be repeated n
times as illustrated in FIG. 11 in order to obtain a greater
filtering action. In this case, preferably, as illustrated in the
same FIG. 11, each intermediate electrode 10, 11 (except for only
the final electrodes) will act as containment wall for two first
operating chambers 4 or for two second operating chambers 5 of two
adjacent and consecutive purification layers.
[0175] Preferably, in addition, the second extraction section 24 is
extended substantially transverse to the purification layers,
preferably in a central zone of the chambers 4, 5, 13, traversing
the first 10, the second 11, the third 16 and the fourth wall 17
with corresponding through holes. Otherwise, in accordance with a
second embodiment of the aforesaid variant of FIGS. 13-16, the
ion-selective areas with opposite polarity are each associated with
the entire extension of an electrode 10, 11. In this case, polarity
reversal is not provided at the electrodes (equivalent to the
example of FIG. 10) and the flow to be treated F1 sequentially
traverses at least two operating chambers delimited by electrodes
with opposite polarity in order to allow both the positive and
negative ionic particles to traverse the ion-selective areas with
corresponding polarity under the action of the electric field. For
such purpose, the two operating chambers can be traversed in
countercurrent and can be sequentially connected by connector
sections made of electrically isolating material, indicated with
dashed line in FIG. 10 and of course arranged in positions of the
cell that are susceptible to not interfere with the walls 16, 17
that delimit the third evacuation chamber 13.
[0176] Functionally, the apparatus described up to now mainly from
the structural standpoint operates as specified hereinbelow, with
reference to both embodiments of the variant of FIGS. 13-16.
[0177] The positively and negatively charged particles contained in
the liquid to be treated F1, which continuously flow into the first
and second chamber 4, 5, are forced by the action of the electric
field produced by the two electrodes 10, 11 to migrate respectively
towards the cathode (negative electrode) and towards the anode
(positive electrode). In such migration, the positive cationic
particles contained in the fluid of the operating chamber opposite
that delimited by the cathode (first operating chamber 16 in
accordance with FIG. 4A) and the negative anionic particles
contained in the fluid of the operating chamber opposite that
delimited by the anode (second operating chamber 17 in accordance
with FIG. 4A) which encounter the ion-selective areas, respectively
cationic (16B) and anionic (17A) of the corresponding third wall 16
and fourth wall 17, are forced by the electric field to traverse
them, overcoming the potential barrier, represented by the
ion-selective area, until they enter into the third evacuation
chamber 13.
[0178] Once they have entered into the third evacuation chamber 13,
the charged particles are subjected here to a small action of the
electric field, and thus they are no longer able to traverse the
ion-selective areas of the third 16 and fourth wall 17, remaining
confined in the substantially equipotential volume of the third
chamber 13, before then being conveyed towards the drain by the
washing fluid flow F2 which continuously advances in the third
evacuation chamber 13.
[0179] Through the electric field present in the first and in the
second chamber 4, 5, the charged particles present herein are then
moved into a volume constituted by the third evacuation chamber 13
with limited electric field, overcoming a check barrier allowed by
the ion-selective areas of the same walls of the third chamber
13.
[0180] The porous electric layer 18, advantageously constituted in
accordance with the abovementioned preferred embodiment by a metal
net, determines the isopotentiality of the third chamber 13, like a
Faraday cage, with shielding of the electric field in order to
prevent conducting the charged particles to outside the same
chamber 13 once they have entered inside.
[0181] Also forming an object of the present invention is a method
for purifying a fluid, which in particular can advantageously but
not exclusively employ the above-described apparatus 1; for the
sake of simplicity, the same reference numbers and nomenclature of
the apparatus 1 will be maintained hereinbelow.
[0182] The aforesaid method, according to the idea underlying the
present invention, provides for the following operations.
[0183] The continuous flow is provided of the first operative fluid
F1 containing cationic particles and anionic particles through at
least one operating chamber 4 (or multiple operating chambers 4, 5
in accordance with the above-described examples) from the
respective inlet opening to the respective outlet opening, as well
as the flow of a second operative fluid through at least one
evacuation chamber 13 (or multiple evacuation chambers 13, 13' in
accordance with the above-described examples), from its inlet
section 14 to its outlet section 15.
[0184] The evacuation chamber 13 at its interior comprises the
porous electrical conductor 18, which is thus traversed by the
second operative fluid F2, and is separated from the operating
chamber 4 by the filtering membrane 100.
[0185] The method provides for the generation of an electric field
between the two electrodes A, B (or between a plurality of pairs of
electrodes in accordance with the above-reported examples) between
which at least one operating chamber and at least one evacuation
chamber 13 are interposed.
[0186] For such purpose, electrodes A, B are direct voltage or
average direct voltage power supplied with opposite polarities, in
a manner such that the porous electrical conductor 18 is
susceptible of reducing, inside the evacuation chamber 13, the
electric field generated by the electrodes.
[0187] There is then a migration into the evacuation chamber 13, by
traversing the filtering membrane 100, of at least one part of the
charged particles under the action of the operative electric field
during the flow of the first operative fluid F1 into the operating
chamber 4. It is thus possible to obtain the evacuation, through
the passage of the second operative fluid F2, of the charged
particles migrated through the filtering membrane 100 into the
evacuation chamber 13 and subjected herein to the action of the
limited electric field.
[0188] The generation of the electric field can occur with periodic
reversal of the polarity at the electrodes A, B in order to force
the charged particles with opposite polarity to migrate through a
same filtering membrane 100 at different times, passing from the
operating chamber 4 to the evacuation chamber 13.
[0189] More in detail, in accordance with the embodiment
illustrated in the enclosed FIGS. 3A, 3B, 7, 8, 9 and 10, the
generation of an electric field is provided between the electrodes
A, B associated with the first and second wall of the two operating
chambers 4, 5 by means of direct voltage power supply or average
direct voltage power supply of the same electrodes with opposite
polarities.
[0190] There is thus the migration of at least part of the cationic
particles and/or anionic particles contained in the two operating
chambers 4, 5 under the action of the electric field, during the
flow of the first operative fluid F1 into the aforesaid operating
chambers 4, 5, with their movement from the first and from the
second operating chamber 4, 5 to the first evacuation chamber 13,
by traversing the filtering membranes under the action of the
electric field generated by the electrodes A, B.
[0191] In accordance with the embodiment illustrated in the FIGS.
3A, 3B, the flow of the first operative fluid F1 occurs in parallel
into the two operating chambers 4, 5; otherwise, in accordance with
the embodiment illustrated in FIG. 7, the flow of the first
operative fluid F1 occurs sequentially into at least two operating
chambers 4, 5 delimited by electrodes with opposite polarity. The
traversing sequence provides for the passage of the fluid first
through all or only a group of operating chambers at a first same
polarity of the purification layers, and then subsequently the
passage of the fluid through all or only a group of operating
chambers at the second polarity of the purification layers.
[0192] There follows the treatment of the cationic particles and/or
anionic particles which have migrated into the first evacuation
chamber 13 passing through the filtering membranes provided with
the third and fourth wall 16, 17, due to the barrier action exerted
by the same filtering membranes contained in the first evacuation
chamber 13 and subjected herein to the action of the limited
electric field due to the shielding effect produced by the porous
electrical conductor 18.
[0193] In the case of FIGS. 3A and 3B, in which the generation of
the electric field occurs with periodic reversal of the polarity at
the electrodes A, B, there is a migration both of the cationic
particles and of the anionic particles contained in the first and
second operating chamber 4, 5 towards the first evacuation chamber
13 by traversing the filtering membranes both of the third and
fourth wall 16, 17.
[0194] The method for purifying a fluid according to the embodiment
of FIGS. 13-16 provides for the following operations.
[0195] The continuous flow is provided of the fluid to be treated
F1, containing cationic particles and anionic particles, through
the first operating chamber 4 and the second operating chamber 5,
as described above, from their respective first and second inlet
openings 6, 7 to their first and second outlet openings 8, 9; also
provided is the flow of a washing fluid F2 through the third
evacuation chamber 13, as described above, from its third inlet
opening 14 to its third outlet opening 15.
[0196] More in detail, in accordance with the first embodiment of
the aforesaid variant of FIGS. 13-16, i.e. illustrated in FIGS. 14,
15 and 16 in which the third and fourth wall 16, 17 are each
provided with two or more side-by-side ion-selective areas, the
flow of the fluid to be treated F1 occurs in parallel in the
different operating chambers 4, 5.
[0197] Otherwise, in accordance with the second embodiment of the
aforesaid variant of FIGS. 13-16, i.e. with the ion-selective areas
with opposite polarity each associated with the entire extension of
an electrode 10, 11, the flow of the fluid to be treated F1 occurs
sequentially in at least two operating chambers delimited by
electrodes with opposite polarity. The traversing sequence can
provide for the passage of the fluid first through all or only a
group of operating chambers with a first same polarity of the
purification layers and then subsequently the passage of the fluid
through all or only a group of operating chambers with the second
polarity of the purification layers.
[0198] It is then provided, for both embodiments, to generate an
electric field between the electrodes 10, 11 associated with the
first and the second wall of the two operating chambers 4, 5 by
means of direct voltage power supply, or average direct power
supply, of the same electrodes with opposite polarities.
[0199] Thus, there is the migration of at least part of the
cationic particles and/or anionic particles contained in the two
operating chambers 4, 5 under the action of the electric field,
during the flow of the fluid to be treated F1 into the aforesaid
operating chambers 4, 5, with their movement from the first and
from the second operating chamber 4, 5 to the third evacuation
chamber 13, traversing the ion-selective areas with corresponding
polarity under the action of the electric field generated by the
electrodes 10, 11.
[0200] There follows the retention of the cationic particles and/or
of the anionic particles that migrated into the third evacuation
chamber 13, passing through the ion-selective areas provided for on
the third and fourth wall 16, 17, due to the barrier action exerted
by the same ion-selective areas towards the charged particles with
corresponding polarity contained in the third evacuation chamber 13
and subjected therein to the action of the electric field limited
due to the shielding effect produced by the porous electrical
conductor 18.
[0201] More in detail, in accordance with the first embodiment
described above, in which multiple ion-selective areas are provided
on both the third and fourth wall defining the third evacuation
chamber 13, the generation of the electric field occurs with
periodic reversal of the polarity at the electrodes 10, 11.
Consequently, the migration forces the cationic particles and the
anionic particles contained in the first and second operating
chambers 4, 5 to enter into the third evacuation chamber 13 by
traversing ion-selective areas provided adjacent on each third and
fourth wall 16, 17, of which at least one is cation-phobic and at
least one is anion-phobic. The apparatus and the method thus
conceived therefore attain the pre-established objects.
[0202] In particular, by providing for a continuous operation, the
apparatus allows considerably increasing the efficiency/output with
respect to apparatuses of known type operating in intermittent
manner, such as the apparatuses with flow-through capacitors.
[0203] In addition, the apparatus according to the invention does
not provide for forcing a fluid flow against the filtering
membranes, as instead is provided for by the apparatuses that
employ the principle of electrodialysis; consequently, the
apparatus, object of the present invention, does not lead to any
particular obstruction of the same filtering membranes, i.e. it
does not require costly maintenance work. The same net of the
porous electrical conductor 18 is adapted to prevent the
obstruction of the walls 16, 17 that it spaces.
[0204] Advantageously, inside the evacuation chamber 13, both ionic
species absorbed from the contiguous operating chambers 4, 5 are
found, so that excessively acidic or alkaline solutions are not
obtained, i.e. fouling problems are avoided. This is particularly
in accordance with the first embodiment described above, since the
presence of a variable electric field does not allow the
development of considerable variations in the ionic balance of the
first operative fluid.
[0205] The components employed by the apparatus, object of the
present invention, allow obtaining cells at extremely limited
costs.
[0206] Given that double layers of ionization are not provided for,
as in the apparatuses with flow-through capacitors, it is not
necessary to provide high current peaks with the power supply
source, and consequently it is not necessary to employ costly
electronics.
* * * * *