U.S. patent application number 16/476099 was filed with the patent office on 2019-10-31 for electrocoagulation unit and a method for operating the same.
The applicant listed for this patent is Muddy River Technologies Inc.. Invention is credited to Michael Stephen GARDNER, Peter Douglas JACK, Robert John STEPHENSON.
Application Number | 20190330086 16/476099 |
Document ID | / |
Family ID | 62783943 |
Filed Date | 2019-10-31 |
United States Patent
Application |
20190330086 |
Kind Code |
A1 |
STEPHENSON; Robert John ; et
al. |
October 31, 2019 |
Electrocoagulation Unit and a Method for Operating the Same
Abstract
An electrocoagulation unit for removing one or more dissolved
constituents from an untreated feedstock comprises a
non-electrically conductive housing having a fluid inlet, a fluid
outlet and an interior surface; a cathode and anode arranged within
the housing, the cathode and anode each having an ionizing surface,
the ionizing surfaces of the anode and cathode in opposed facing
relation so as to define a gap having a separation distance
therebetween; the cathode and the anode configured to be
electrically coupled to a DC power supply in a DC electrical
circuit so as to ionize and dissolve the ionizing surface of the
anode; and a controller configured to maintain the separation
distance at a set value as the ionizing surface of the anode
dissolves. A method for using a plurality of electrocoagulation
units in series is also provided.
Inventors: |
STEPHENSON; Robert John;
(Vancouver, CA) ; GARDNER; Michael Stephen;
(Delta, CA) ; JACK; Peter Douglas; (Delta,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Muddy River Technologies Inc. |
Delta |
|
CA |
|
|
Family ID: |
62783943 |
Appl. No.: |
16/476099 |
Filed: |
January 3, 2018 |
PCT Filed: |
January 3, 2018 |
PCT NO: |
PCT/CA2018/000002 |
371 Date: |
July 4, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62442603 |
Jan 5, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F 1/46109 20130101;
C02F 2001/46171 20130101; C02F 2001/46133 20130101; C02F 2201/4617
20130101; B01D 19/0005 20130101; C02F 2103/10 20130101; C02F
2301/046 20130101; C01G 49/02 20130101; C02F 2201/4612 20130101;
C01B 17/74 20130101; C02F 2001/46123 20130101; C02F 2101/16
20130101; C02F 1/56 20130101; E21B 43/40 20130101; C02F 1/5245
20130101; C02F 1/20 20130101; C02F 9/00 20130101; C02F 2101/101
20130101; B01D 17/045 20130101; C02F 1/463 20130101; C02F 2101/206
20130101; C02F 2101/32 20130101; B01D 17/06 20130101; C02F 2101/322
20130101; C02F 1/52 20130101; C02F 1/74 20130101; C02F 1/66
20130101; C02F 1/008 20130101; C02F 2101/203 20130101; C02F 2103/06
20130101; C02F 1/24 20130101 |
International
Class: |
C02F 1/463 20060101
C02F001/463; C02F 1/56 20060101 C02F001/56; C02F 1/00 20060101
C02F001/00; C02F 1/461 20060101 C02F001/461; C02F 9/00 20060101
C02F009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 5, 2017 |
CA |
2953591 |
Claims
1. An electrocoagulation unit for removing one or more dissolved
constituents from an untreated feedstock, the unit comprising: a
non-electrically conductive housing having a fluid inlet, a fluid
outlet and an interior surface, a cathode and an anode arranged
within the housing, the cathode and anode each having an ionizing
surface, the ionizing surfaces of the anode and cathode in opposed
facing relation so as to define a gap having a separation distance
therebetween, the cathode and the anode configured to be
electrically coupled to a DC power supply in a DC electrical
circuit so as to ionize and dissolve the ionizing surface of the
anode, and a controller configured to maintain the separation
distance at a set value as the ionizing surface of the anode
dissolves.
2. The unit of claim 1 wherein the cathode includes an inlet
surface opposite the cathode's ionizing surface and at least one
aperture extending through the cathode from the inlet surface to
the ionizing surface, the cathode mounted to and sealed against the
interior surface of the housing so as to orient the inlet surface
towards the fluid inlet, wherein the at least one aperture defines
a flow path for the untreated feedstock to flow from the fluid
inlet to the gap.
3. The unit of claim 1 wherein the controller comprises at least
one non electrically-conductive spacer, the at least one spacer
sandwiched between the cathode and the anode so as to
simultaneously contact the ionizing surface of the cathode and the
ionizing surface of the anode.
4. The unit of claim 3 wherein the anode is weighted so as to
maintain contact between the ionizing surface of the anode and the
at least one spacer.
5. The unit of claim 1 wherein the anode is replaceable.
6. The unit of claim 1 wherein the cathode is mounted to and sealed
against the interior surface of the housing and the controller
comprises an actuator operatively coupled to cause relative
movement between the anode and cathode.
7. The unit of claim 6 wherein the actuator is actuated when a
measurable parameter attains a threshold value.
8. The unit of claim 7 wherein the parameter is selected from a
group comprising: unit operation time, voltage, current.
9. The unit of claim 8 wherein, when actuated, the actuator is
configured so as to translate the anode towards the cathode so as
to contact the ionizing surfaces of the anode and the cathode and
then translate the anode away from the cathode so as to separate
the ionizing surfaces of the anode and cathode by the separation
distance.
10. The unit of claim 1 wherein the one or more constituents of the
untreated feedstock includes at least dissolved metal ions and
wherein the anode comprises magnesium so as to facilitate removal
of the at least dissolved metal ions from the untreated
feedstock.
11. A method of treating an untreated feedstock using the
electrocoagulation units of claim 1, the method comprising:
providing a plurality of units of claim 1, connecting each unit of
the plurality of units in series by connecting the fluid outlet of
one unit of the plurality of units to the fluid inlet of an
adjacent unit of the plurality of units, wherein a first unit of
the plurality of units has a free fluid inlet and a last unit of
the plurality of units has a free fluid outlet, operatively
connecting at least one DC power supply to the anode and cathode of
each unit of the plurality of units, flowing a volume of the
untreated feedstock into the free fluid inlet, wherein a coagulated
amount of at least one dissolved constituent of the volume of
untreated feedstock increases within each unit of the plurality of
units as the volume of untreated feedstock flows from the first
unit to the last unit.
12. The method of claim 11, wherein providing the controller of
each unit of the plurality of units includes providing an actuator
operatively coupled to the anode so as to selectively translate the
anode relative to the cathode, detecting when a measurable
parameter of any unit of the plurality of units attains a threshold
value, identifying the unit of the plurality of units in which the
parameter has attained the threshold value, actuating the actuator
so as to adjust the separation distance of the identified unit so
as to optimize the separation distance.
13. The method of claim 12 wherein the step of actuating the
actuator further includes: translating the anode towards the
cathode so as to contact the ionizing surface of the anode against
the ionizing surface of the cathode, translating the anode away
from the cathode until the separation distance is optimized.
14. The method of claim 12 wherein the measurable parameter is
selected from a group comprising: unit operation time, voltage,
current.
15. The method of claim 11 wherein the plurality of units connected
in series includes a conduit for conducting an intermediate
feedstock from the fluid outlet of one unit to the fluid inlet of
an adjacent unit, wherein the method further comprises the step of
adding an anionic polymer to the intermediate feedstock as the
intermediate feedstock flows through the conduit so as to
flocculate the intermediate feedstock.
16. The method of claim 15 wherein the one or more constituents of
the untreated feedstock includes at least dissolved metal ions and
wherein the anode comprises magnesium so as to facilitate removal
of the at least dissolved metal ions from the untreated feedstock.
Description
RELATED APPLICATIONS
[0001] This Patent Cooperation Treaty patent application claims
priority to U.S. Provisional Patent Application No. 62/442,603
filed on Jan. 5, 2017 and Canadian Patent Application No. 2,953,591
filed on Jan. 5, 2017, each of which are incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present disclosure relates to electrocoagulation (EC)
units for treating wastewater, otherwise referred to herein as a
feedstock, and methods for operating same; in particular, the
present disclosure relates to improved EC units for removing
targeted constituents in a feedstock.
BACKGROUND
[0003] Various methods and processes for treatment of feedstock are
known. The term "feedstock", as used herein, includes various types
of water or wastewater, including but not limited to waste water
from hydraulic fracturing; so called fracking, oily water, mining
water, brine, industrial wastewater, municipal wastewater,
anaerobic digester effluent, landfill leachate, and groundwater.
The feedstock is therefore an aqueous mixture which may contain or
include one or more contaminants, constituents or components
(hereinafter, referred to by the term "constituent"), which one or
more constituents need to be removed from the feedstock.
[0004] Feedstock may need to be treated to remove one or more
constituents from the feedstock for the following reasons: (a) for
feedstock obtained from or produced by an industrial process, it
may be desirable to re-use that feedstock in the same industrial
process so as to conserve water resources and/or prevent discharge
of contaminated feedstock to the environment. However, one or more
constituents may need to be removed from the feedstock prior to
re-using the feedstock in the industrial process; (b) to remove
constituents from the feedstock so as to reduce potential harm to
people or the air, water, land environment when the feedstock is
discharged to the environment; or (c) so constituents, such as
metals, nutrients, algae or other materials can be removed and
recovered or harvested for other uses.
[0005] Amongst the various known processes and methods for treating
feedstocks to remove targeted constituents, are conventional EC
units. A conventional EC unit typically includes multiple pairs of
anodes and cathodes, with a gap provided between each anode and
cathode. The feedstock to be treated is forced to flow through the
series of gaps between the multiple anode/cathode pairs, which
electrodes are typically contained within a non-conductive cell
housing with a feedstock influent connection and a treated
feedstock outlet connection. An electrical power supply is
connected to the pairs of anodes and cathodes by electrical cables.
The electrical power requirement is relatively small to treat
feedstocks at relatively low flow rates, requiring relatively long
total hydraulic residence times of the influent feedstock stream
within the gaps between the electrodes. The current density
(electric current per total electrode area) of a conventional EC is
relatively small.
[0006] Conventional EC units may either use direct current (DC),
where the anodes and the cathodes are unchanging, or alternating
current (AC), where the plates that serve as anodes and cathodes
change their function when the polarity of the current is
reversed.
[0007] Feedstock is introduced into an EC unit, otherwise referred
to interchangeably herein as an EC cell, so as to flow through the
gaps between multiple pairs of metallic anodes and cathodes.
Typically, the anodes are constructed from carbon steel or aluminum
plates, however, the anodes may also be constructed from magnesium,
stainless steel, titanium, copper, or zinc, or other materials such
as graphite. The anodes and cathodes are each electrically
connected to either an AC or DC power supply. In use, electrical
current flows from the anode through the influent feedstock to the
cathode, gradually causing the anode to dissolve into the
feedstock. The dissolved metallic anode ions, which are positively
charged, serve to coagulate negatively charged constituents of the
feedstock, increasing the constituents' particle size.
Electrocoagulation also causes hydrolysis of water, whereby
hydrogen (H.sub.2) and oxygen (O.sub.2) gas bubbles and hydroxide
(OH.sup.-) ions are produced as by-products. The produced oxygen
may oxidize feedstock constituents, which may result in the
destruction of those constituents as their oxidation to other
species (for example, Fe.sup.2+ is oxidized to Fe.sup.3+, which is
less soluble), and their subsequent removal through solid-liquid
separation techniques. The produced hydrogen and oxygen escape as
gas bubbles from the feedstock. These gas bubbles may be used to
separate coagulated solids by gas flotation. The produced hydroxide
may increase the pH of the treated feedstock, depending on the
feedstock composition and the anode material.
[0008] A conventional EC unit includes multiple pairs of anodes and
cathodes, typically configured as sets of parallel metal plates
having fixed positions relative to each other. A gap between each
anode and cathode set is provided so feedstock can only flow
through the gap. This requires that the side edges of each anode
and cathode be sealed against the cell housing so the feedstock
flows between each anode and cathode pair without by-passing the
gap, the feedstock then exiting the EC unit through a treated
feedstock outlet connection.
[0009] Electrical current dissolves the anodes. Therefore, the
magnitude of electrical current controls the rate of feedstock
treatment by EC. For typical EC cell configurations, as the supply
of electrical current dissolves the metal anodes to treat the
feedstock, the gaps between the anodes and cathodes eventually
increase over time as the surface of the anode facing the cathode
gradually dissolves. Where feedstock conductivity and DC current
power supply remain constant, as the size of the gap between
electrodes increases, the voltage increases linearly. However,
because voltage increase does not result in an increase of the rate
of feedstock treatment by EC, in order to minimize electrical power
cost (the product of current and voltage), the electrode gap would
ideally be maintained at a relatively small and constant distance.
Once the anode is consumed to a significant extent, the electrode
plates may therefore need to be re-positioned so as to maintain the
gap between the anode and the cathode at the small and
substantially constant distance.
[0010] Typical EC cells use multiple sets of anodes and cathodes
configured as parallel plates, each plate having a thickness of
approximately one inch or less, and positioned so as to have an
initial gap of approximately one inch or less between the anode and
cathode of each set of electrodes. As each anode is dissolved by EC
treatment, the gap between each anode and cathode pair gradually
increases.
[0011] Typically, the edges of each anode and cathode plate are
sealed against the cell housing so the feedstock flows between each
anode and cathode pair without flow by-pass. Therefore, when the
voltage becomes too high, indicating excessive electrode gaps, or
when the electrodes become plugged, or when the anodes are
dissolved to the extent that they cannot prevent by-pass and direct
flow of feedstock between the anodes and the cathodes, EC cell
maintenance is required.
[0012] Performing maintenance on the multiple sets of electrodes in
a conventional EC unit involves removing the electrodes from the
cell so they may be cleaned of fouled material, replaced, and/or
mechanically reset so as to adjust the distance of the gap between
the anodes and the cathodes. Such maintenance is labour intensive
and costly, resulting in a loss of productivity as the EC unit is
taken out of service during maintenance.
SUMMARY
[0013] In some embodiments of the present disclosure, an improved
EC unit includes one anode and one cathode. One small and nearly
constant gap between the anode and cathode is maintained by one or
more spacers positioned between the anode and cathode, or in other
embodiments, the nearly constant gap distance may be maintained by
controls which trigger the adjustment of the anode relative to the
cathode, based on measured voltage, or alternatively, based on
current or treatment time.
[0014] Feedstock flows through one or more holes in the cathode to
enter into the gap between the cathode and the anode. Feedstock may
flow upwardly through the EC cell so the gas bubbles that are
by-products of the electrochemical reactions rise with the flowing
feedstock to exit the EC cell along with treated feedstock, rather
than accumulating inside the cell where the gas bubbles may
decrease conductivity of the liquid feedstock within the gap
between the anode and cathode and risk explosion. In some
embodiments, the cathode may be stationary and sealed against the
cell housing. In one embodiment, treated feedstock exits the gap at
the periphery of the anode and flows up around the outside
cylindrical wall surface of the anode towards the EC cell treated
feedstock discharge connection. The anode is not sealed against the
cell housing, but is configured to be translated within the cell
housing either towards or away from the fixed cathode, thereby
enabling for periodic adjustment of the distance of the gap between
the anode and the cathode as the anode slowly dissolves. Typically,
the EC cell housing may be constructed from PVC pipe, rubber lined
steel, or other suitable materials which are non
electrically-conductive and resistant to corrosion; ideally, the EC
cell housing may be constructed of materials that are relatively
inexpensive and which are capable of accommodating a small pressure
drop.
[0015] Although in some embodiments the electrodes may be
constructed of sections of a round bar enclosed within a
cylindrical EC cell housing, it will be appreciated that such
geometry is not intended to be limiting, provided the one anode is
configured to be translatable within the cell housing so as to
enable adjustment of the distance of the gap between the anode and
cathode. Furthermore, the anode may be a single anode, or, in other
embodiments, the anode may be a plurality of anodes, provided that
the plurality of anodes are in electrical communication with each
other and connected to the power supply. In the embodiments
described herein, the cathode is held in a fixed position within
the EC cell housing and the anode is configured so as to be
translatable within the cell housing, such that the anode may be
moved towards or away from the fixed cathode. However, the
Applicant notes that other embodiments providing for relative
motion between the anode and cathode; for example, in which the
anode is held in a fixed position within the cell housing and the
cathode is configured so as to be translatable towards or away from
the fixed anode, for maintaining a substantially constant gap
distance G between the anode and cathode, one also intended to be
included within the scope of the present disclosure.
[0016] An electrical power supply is connected to the translatable
anode and stationary cathode by electrical cables. The electrical
cable connected to the anode may be of sufficient length so as to
maintain an electrical connection between the power supply and the
anode until the anode is entirely dissolved. Advantageously, by
maintaining a substantially constant distance between the anode and
cathode within the EC cell, the electrical power requirement is
relatively large but consistent to treat feedstock at a relatively
high flow rate, thereby enabling a hydraulic residence time in the
gap of approximately one second. With the high flow rate, small EC
cell disclosed herein, the current density (current per electrode
area) of embodiments of the EC unit disclosed herein is high
compared to conventional EC units, although the electrical current
requirement per mass of targeted constituent to be removed is
similar to that of conventional EC cells. For example, without
intending to be limiting, the EC unit embodiments disclosed herein
may have a current density in substantially the range of 0.1
A/cm.sup.2 to 1 A/cm.sup.2, and the flow velocity of the feedstock
through the EC cell gap may be in the range of 1 cm/s to 10 cm/s.
In one example of an EC unit according to the present disclosure,
the EC unit's electrodes have a current density of substantially
0.24 A/cm.sup.2 and operate at a feedstock flow velocity through
the EC cell gap of substantially 2.3 cm/s.
[0017] Electrical power supplies are rated according to their
capacity to deliver electrical current at a specified voltage. In
addition to lowering operating costs, minimizing voltage
requirements minimizes the capital cost of power supplies.
Consequently, the distance across the electrode gap needs to be
maintained substantially constant and relatively small so as to
reduce power costs.
[0018] Using EC to treat feedstocks that have only small electrical
conductivity requires high voltage in order to provide enough
electrical current to dissolve the anode. Minimizing the gap
between the electrodes minimizes voltage requirements and lowers
the capital cost of the power supply.
[0019] Furthermore, maintaining a substantially constant gap
distance helps to ensure that consistent treatment of feedstock is
achieved. Because increasing the gap distance increases the voltage
across the gap and thus, may decrease current, EC treatment will
decrease. Thus, a small and constant gap between the electrodes is
desirable.
[0020] Maintaining a small gap maximizes fluid turbulence as
feedstock flows through the gap between the anode and the cathode.
Maximizing turbulence maximizes contact between the feedstock and
the anode surface, so the dissolved metal efficiently contacts
feedstock constituents for their effective coagulation.
[0021] For a given flow rate, a small electrode gap maximizes
turbulent contact and scouring by the feedstock with the anode
surface, thus minimizing fouling of the anode surface.
[0022] A small and constant electrode gap minimizes voltage and
thus enables high current to be delivered from a power supply, thus
providing high current density that helps prevent electrode
fouling.
[0023] In an aspect of the present disclosure, an
electrocoagulation unit for removing one or more dissolved
constituents from an untreated feedstock comprises a
non-electrically conductive housing having a fluid inlet, a fluid
outlet and an interior surface; a cathode and an anode arranged
within the housing, the cathode and anode each having an ionizing
surface, the ionizing surfaces of the anode and cathode in opposed
facing relation so as to define a gap having a separation distance
therebetween; the cathode and the anode configured to be
electrically coupled to a direct current (DC) power supply in a DC
electrical circuit so as to ionize and dissolve the ionizing
surface of the anode; and a controller configured to maintain the
separation distance at a set value as the ionizing surface of the
anode dissolves. In some embodiments, the electrocoagulation unit's
cathode includes an inlet surface opposite the cathode's ionizing
surface and at least one aperture extending through the cathode
from the inlet surface to the ionizing surface, the cathode mounted
to and sealed against the interior surface of the housing so as to
orient the inlet surface towards the fluid inlet, and the at least
one aperture defines a flow path for the untreated feedstock to
flow from the fluid inlet to the gap. In some embodiments, the
anode may be replaceable.
[0024] In another aspect of the present disclosure, the controller
of the electrocoagulation unit may comprise at least one non
electrically-conductive spacer, the at least one spacer sandwiched
between the cathode and the anode so as to simultaneously contact
the ionizing surface of the cathode and the ionizing surface of the
anode. In some embodiments, the anode may be weighted so as to
maintain contact between the ionizing surface of the anode and the
at least one spacer.
[0025] In another aspect of the present disclosure, the cathode may
be mounted to and sealed against the interior surface of the
housing and the controller comprises an actuator operatively
coupled to cause relative movement between the anode and cathode.
In some embodiments, the actuator is actuated when a measurable
parameter attains a threshold value, and the measurable parameter
may be selected from a group comprising: unit operation time,
voltage, current. In some embodiments, when actuated, the actuator
is configured to translate the anode towards the cathode so as to
contact the ionizing surfaces of the anode and the cathode and then
translate the anode away from the cathode so as to separate the
ionizing surfaces of the anode and cathode by the separation
distance.
[0026] In some embodiments, the one or more constituents of the
untreated feedstock includes at least dissolved metal ions and the
anode comprises magnesium so as to facilitate removal of the at
least dissolved metal ions from the untreated feedstock.
[0027] In another aspect of the present disclosure, a method of
treating an untreated feedstock using the electrocoagulation units
comprises the steps of: [0028] providing a plurality of EC units,
such as those described above, [0029] connecting each EC unit of
the plurality of EC units in series by connecting the fluid outlet
of one EC unit of the plurality of EC units to the fluid inlet of
an adjacent unit of the plurality of EC units, wherein a first unit
of the plurality of EC units has a free fluid inlet and a last unit
of the plurality of EC units has a free fluid outlet, [0030]
operatively connecting at least one DC power supply to the anode
and cathode of each EC unit of the plurality of EC units, [0031]
flowing a volume of the untreated feedstock into the free fluid
inlet, [0032] wherein a coagulated amount of at least one dissolved
constituent of the volume of untreated feedstock increases within
each EC unit of the plurality of EC units as the volume of
untreated feedstock flows from the first unit to the last unit.
[0033] In another aspect of the present disclosure, providing the
controller of each EC unit of the plurality of EC units includes
providing an actuator operatively coupled to the anode so as to
selectively translate the anode relative to the cathode; detecting
when a measurable parameter of any unit of the plurality of EC
units attains a threshold value; identifying the EC unit of the
plurality of EC units in which the parameter has attained the
threshold value; and actuating the actuator so as to adjust the
separation distance of the identified EC unit so as to optimize the
separation distance.
[0034] In some embodiments, the step of actuating the actuator may
further include translating the anode towards the cathode so as to
contact the ionizing surface of the anode against the ionizing
surface of the cathode and then translating the anode away from the
cathode until the separation distance is optimized. In some
embodiments, the measurable parameter may be selected from a group
comprising: unit operation time, voltage, current.
[0035] In another aspect of the present disclosure, the plurality
of EC units connected in series may include a conduit for
conducting an intermediate feedstock from the fluid outlet of one
unit to the fluid inlet of an adjacent unit, wherein the method
further comprises the step of adding an anionic polymer to the
intermediate feedstock as the intermediate feedstock flows through
the conduit so as to flocculate the intermediate feedstock. In some
embodiments, the one or more constituents of the untreated
feedstock includes at least dissolved metal ions and the anode
comprises magnesium so as to facilitate removal of the at least
dissolved metal ions from the untreated feedstock.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a cut-away view of an embodiment of an EC unit in
accordance with the present disclosure.
[0037] FIG. 2 is a cut-away view of an embodiment of an EC unit in
accordance with the present disclosure.
[0038] FIG. 3 is a flow diagram of an embodiment of a method for
maintaining a gap distance within an EC unit in accordance with the
present disclosure.
[0039] FIG. 4 is a flow diagram of an embodiment of a method for
maintaining a gap distance within an EC unit in accordance with the
present disclosure.
[0040] FIG. 5 is a schematic illustrating an embodiment of a method
for using a plurality of EC units in series in accordance with the
present disclosure.
DETAILED DESCRIPTION
[0041] In some embodiments of the present disclosure, the improved
EC unit includes one anode and one cathode. The anode and cathode
are contained in a non electrically-conductive cell housing with a
feedstock influent connection and a treated feedstock outlet
connection. Typically, the cell housing may be constructed from PVC
pipe or rubber lined steel pipe. The diameter or inside dimensions
of the cell housing is sized to accommodate flow of the feedstock
between the typically cylindrical anode and the cell housing.
[0042] In some embodiments, such as illustrated in FIG. 1, the
anode 130 consists of a metal round bar, which may typically range
from three to 12 inches diameter D, or larger. The length L of a
new anode, prior to use, may typically be in the range of 24
inches, but could be as small or as large as needed, taking into
consideration the factors of treatment requirements, anode weight
and interior volume of the housing. Because the anode 130 dissolves
over time while the EC unit 198 is operating, a larger diameter D
or longer length L of anode 130 would allow the heavier anode to be
in service for a longer period of time before requiring
replacement. The diameter D of the anode is selected to provide
treatment while maintaining a high current density and a high flow
velocity of the untreated feedstock as it flows through the gap 111
between the anode 130 and the cathode 124, so as to provide
efficient mass transfer and to minimize electrode fouling by fluid
turbulence. The shape of the active area between the anode and
cathode may be selected so as to provide a constant pressure drop
between the one or more inlet apertures 126 in the cathode and the
periphery of the electrode gap 111.
[0043] The anode 130 may be manufactured of aluminum, carbon steel,
magnesium, copper, zinc, or any other suitable material which
releases positively charged ions upon dissolution wherein the
positively charged ions are suitable for coagulation of dissolved
constituents in the feedstock. The time to dissolve the entire
anode for EC treatment of feedstock is directly proportional to the
electrical current, the duration of treatment operation, and the
mass of the anode. The cathode 124 is made of electrically
conductive material that is resistant to chemical degradation under
the conditions of treating the feedstock. For example, not intended
to be limiting, the cathode may be constructed from aluminum,
stainless steel, carbon steel, titanium, or graphite.
[0044] In some embodiments, a pipe connection is attached to the
base of the cathode to serve as the fluid inlet 116 to the EC cell
198. The cathode 124, which may be in the form of a plate, is sized
such that the ionizing surface 125 of the cathode, facing the
ionizing surface 129 of the anode, and the inlet surface 123 of the
cathode opposite the ionizing surface 125, substantially occupies
the entire cross-sectional area of the cell housing 110, and the
cathode 124 is mounted to an interior surface 109 of the cell
housing 110, such that all incoming feedstock flows through the gap
111 between the anode and the cathode. Feedstock flows through a
flow path, whereby untreated feedstock enters the EC unit 198
through the fluid inlet 116 and through one or more apertures 126
which extend through the cathode 124 from the inlet surface 123 of
the cathode to the ionizing surface 125 of the cathode, the one or
more apertures 126 typically located near the center of the inlet
and ionizing surfaces 123, 125 of the cathode, so as to enter the
gap 111 between the cathode and the anode. The number of apertures,
and the total surface area of those apertures, is preferably
selected to create a pressure drop across each aperture to minimize
risk of plugging the one or more apertures during operation of the
EC unit. Feedstock then flows through the gap in a radial direction
to exit the gap at the perimeter of the anode and the cathode
160.
[0045] After feedstock exits the gap 111 between the anode and the
cathode, it flows between the perimeter 160 between the anode 130
and the interior surface 109 of the EC cell housing and then exits
out the top of the EC cell housing through a fluid outlet
connection 122.
[0046] An electrical cable 151 may be attached to an outlet surface
of the anode 131, the outlet surface positioned opposite the
ionizing surface of the anode and facing towards the fluid outlet
of the EC unit, and the electrical cable is configured to connect
to a direct current (DC) power source 150. The length of the
electrical cable may be selected so as to accommodate the complete
dissolution of the anode, as the ionizing surface of the anode will
gradually dissolve over time while the EC unit is operating,
thereby causing the outlet surface 131 of the anode to gradually
move towards the cathode 124 as the ionizing surface 129 of the
anode dissolves. An electrical cable 152 is also attached to the
cathode 124 so as to supply DC electrical current from the DC power
source 150 to the cathode; for example in some embodiments, the
electrical cable 152 may be attached to the edge of the cathode and
is configured to be connected to the DC power source 150.
[0047] In one embodiment of the EC unit 198, illustrated in FIG. 1,
during operation the anode 130 rests loosely on top of one or more
non-conductive spacers 128 that are mounted on the cathode 124 to
provide a gap 111 between the anode 130 and the cathode 124, the
gap 111 having a set distance G. As the ionizing surface 129 of
anode 130 is dissolved into the feedstock that flows through the
electrode gap 111, the weight of the anode 130 causes the anode to
continue to rest on the spacers and thus maintain a gap 111 having
a substantially constant distance G between the ionizing surfaces
129, 125 of the anode and cathode respectively. In general,
maintenance of the EC cell 198 may not be required until the anode
130 is fully dissolved, at which time a replacement anode 130 may
be connected to the electrical cable 151 and dropped into place on
the spacers 128.
[0048] In a preferred embodiment of the present disclosure, such as
illustrated in FIG. 1, the cathode 124 remains in a fixed position
within the cell housing 110, such as by mounting the cathode to the
interior surface 109 of the cell housing 110, whereas the anode 130
is not affixed to the cell housing 110 and is therefore free to
move within the cell housing 110. Optionally, so as to ensure the
anode 130 remains in contact with the spacers 128 during
dissolution of the ionizing surface 129 of the anode, a weight 134
may be positioned so as to apply a downward force in direction X to
the outlet surface 131 of the anode 130.
[0049] Spacers can be made from any non-fragile and non-conductive
material, such as plastic or nylon or hardened rubber, for example,
which materials do not degrade in the environmental conditions
within the EC cell and which materials are capable of supporting
the weight of the anode 130 without significant deformation. The
spacers are preferably narrow, for example having a width W in the
range of not more than 0.5 inches, so as to reduce the impact of
the shadow effect, whereby non-conductive materials in the gap
between the anode and the cathode result in localized increased
electrical resistance, and thus less electrical current, in the
area 115 of the ionizing surface 129 of the anode which is
proximate to the one or more spacers 128. In areas in the gap where
the electrical current is less, the rate of anode dissolution is
correspondingly less. Consequently, non-conductive materials such
as spacers result in unequal anode consumption on the ionizing
surface 129 of the anode. Therefore, using narrow spacers 128
reduces the impact of the shadow effect on the consumption of anode
130.
[0050] When a new anode 130 is initially put into service, the
ionizing surface 129 is substantially flat and the ionizing surface
129 will be preferentially dissolved in the areas not contacted by
the spacers 128, and the anode surface area 115 which is in contact
with or proximate to the spacers 128 will dissolve at a slower rate
compared to the rest of the ionizing surface 129. However, over
time, because the anode surface 115 that contacts or is proximate
to each spacer 128 forms the smallest local distance to the cathode
124, depending on the current density and the width dimension W of
each spacer 128, the shadow effect of the spacers may eventually be
overcome, so the localized electrical resistance in the localized
area 115 becomes approximately equal to the electrical resistance
where the spacers 128 do not contact the ionizing surface 129. The
factors of higher current density and smaller width W of each
spacer 128 reduces the shadow effect, thereby producing a smaller
and shallower raised area on the ionizing surface 129 of anode 130.
Although the anode surface is uneven, the Applicant observes the
wear pattern is generally steady during routine operations until
the anode 130 is almost completely dissolved.
[0051] The spacers 128 may take various shapes and geometries; for
example, without intending to be limiting, the one or more spacers
128 may include plates, rods, nubs, balls, spirals or any
combination thereof. Preferably, the spacers 128 are held in place
by attaching them to the cathode through screws, mating slots or
any other suitable means, such that the spacers 128 do not shift
position during flow of the feedstock through the gap 111. The
spacers 128 are ideally configured so as to enable approximately
uniform flow of feedstock through the electrode gap 111 from the
inlet apertures 126 to the periphery 160 of the anode 130. The gap
111 between the anode and cathode is preferably configured to have
a set distance G of substantially 1/8 of an inch or less, although
this is not intended to be limiting, as in other EC cell
configurations the set distance G may range up to substantially one
inch.
[0052] In other embodiments, the EC unit may include a controller
for moving the anode towards the cathode, so as to maintain the
distance of the gap between the anode and the cathode at a set
value, upon detecting a parameter of the EC unit attaining a
specified value. In such embodiments, the anode may be mounted on a
vertically movable platform, such as a piston, inside the EC cell
housing. Moving the platform may be accomplished by actuating an
actuator operatively connected to the platform. Examples of
actuators may include, for example, a hydraulic or pneumatic
piston, a mechanical screw, or a lifting jack. Actuating the
actuators may be accomplished by electromechanical means, or in the
alternative, actuation may occur by an operator manually actuating
the actuator. As one example of a parameter of the EC unit, changes
in voltage may be monitored. As operation of the EC unit dissolves
the anode, thereby increasing the distance of the gap between the
anode and cathode, the voltage required to treat the feedstock
increases. Once the parameter of the voltage supplied to the
electrodes is detected to reach a set value, thereby indicating the
distance between the anode and cathode has become too large, an
actuator operatively connected to the movable platform moves the
anode towards the cathode until a lower, desired voltage is
reached.
[0053] In another embodiment, a set period of operation for the EC
unit may be used as a parameter to trigger the actuation of the
platform so as to move the anode closer to the cathode. The set
period of operation may be selected based on the electric current
and thus the approximate rate of dissolution of the ionizing
surface of the anode. In some embodiments, upon reaching the set
period of operation of the EC unit, the DC power supply is turned
off, and then the actuator is actuated so as to lift the anode
until it comes into contact with the cathode. Then, the anode is
lowered until the distance of the gap between the anode and cathode
reaches the set value. The DC power supply is then resumed.
[0054] FIG. 2 depicts further embodiments of an EC unit 298, which
maintains the distance G of the gap 211 between a cathode 224 and
an anode 230 at a relatively constant value, utilizing a hydraulic
piston and hydraulic pump as the actuator for moving the anode
towards the cathode, as described above. However, it will be
appreciated by a person skilled in the art that the following
description of the embodiment depicted in FIG. 2 is not intended to
be limiting, and that, for example, other types of actuators,
whether manually or mechanically or electromechanically actuated,
are intended to be included within the scope of the present
disclosure.
[0055] The EC unit 298 comprises a housing 210, two end flanges
212, 214, the cathode 224, the anode 230, a platform such as a
hydraulic piston 217 and an actuator such as a hydraulic pump 234.
The housing 210 and two end flanges 212, 214 may define a
substantially fluid tight plenum that houses the cathode 224, the
anode 230 and the hydraulic piston 217. Fluid inlet 216 conducts a
volume of untreated feedstock into the EC unit 298, for example
through end flange 214 proximal to the cathode 224. Fluid outlet
222 conducts treated feedstock from the EC unit 298. The volume of
feedstock within EC cell 298 may be drained via a drain including a
valve 221 and conduit 218, for example when servicing the EC cell
298.
[0056] The housing 210, the end flanges 212, 214, the cathode 224
and anode 230 may be manufactured from the same materials as
described above for the corresponding components of the EC unit
198. The hydraulic piston 217 can be made from similar
non-conductive and thermally resistant materials as the end flanges
212, 214. The cathode 224 also comprises at least one aperture 226,
which is similar to the at least one aperture 126 described above
in relation to EC cell 198. Furthermore, the anode 230 includes an
ionizing surface 229 and the cathode includes an ionizing surface
225, oriented towards the ionizing surface 229 of the anode
230.
[0057] The hydraulic piston 217 is contained within the housing 210
and positioned adjacent a piston surface 231 of the anode 230,
opposite the ionizing surface 229 of the anode. The hydraulic
piston 217 is in fluid communication with the hydraulic pump 234
via manifold 238. The end flange 212 includes one or more inlet
ports 212'. The inlet ports 212' provide fluid communication
between the manifold 238 and the interior of the housing 210. The
hydraulic pump 234 is in fluid communication with a supply
reservoir 236 of hydraulic fluid. In one example, the hydraulic
fluid may include the untreated feedstock. Optionally, the drain
218, 221 may be in fluid communication with the supply reservoir
236 via conduit 218 for providing fluid to the supply reservoir
236. The hydraulic pump 234 may comprise one or more of a fixed or
variable displacement pump. For example, the hydraulic pump 234 may
be one or more of a gear pump, a peristaltic pump, an axial pump
with or without a swash plate, a screw pump or a rotating vane
pump.
[0058] The hydraulic piston 217 further comprises annular seals 201
that are positioned between a circumferential edge of the hydraulic
piston 217 and the inner surface 209 of the housing 210. The
annular seals 201 form a fluid tight seal, such that as the
hydraulic pump 234 introduces and removes hydraulic fluid into the
housing 210 via the manifold 238, the hydraulic fluid will push or
pull the hydraulic piston 217 towards or away from the anode 230.
Alternatively, the hydraulic pump 234 may only introduce hydraulic
fluid to move the hydraulic piston 217 towards the anode 230. A
valve 221 of the drain may be activated to drain hydraulic fluid
and allow the hydraulic piston 217 to move away from the anode 230,
for example by gravity. Optionally, the valve 221 may be an
electrically controlled solenoid.
[0059] During operation of the EC unit 298 a direct electrical
current is provided by a direct current (DC) power source 250,
resulting in the dissolution of the ionizing surface 229 of anode
230 and delivering highly reactive, positively charged ions; for
example, not intending to be limiting, the positively charged ions
may be Al.sup.3+, Fe.sup.3+ or Mg.sup.2+, depending on whether the
anode is constructed of aluminum, iron or magnesium respectively.
The positively charged ions are released into the gap 211 where
they come into contact with the influent feedstock, causing
coagulation of negatively charged constituents in the feedstock.
Negatively charged constituents may include, for example, petroleum
hydrocarbons, suspended solids, or phosphate; although it will be
appreciated by persons skilled in the art that such examples of
negatively charged constituents in a volume of untreated feedstock
are not intended to be limiting, and may include any type of
negatively charged constituent which is desired to be removed from
the volume of untreated feedstock. Operation of the EC unit also
causes hydrolysis of the water in the untreated feedstock, to
produce O.sub.2 (oxygen) gas, H.sub.2 (hydrogen) gas and dissolved
OH.sup.- (hydroxide). For volumes of untreated feedstock containing
dissolved chloride, operation of the EC unit on the untreated
feedstock also produces Cl.sub.2 (chlorine) gas. The anode/cathode
electrode pair(s) may be positioned in any orientation as long as
the entire volume of untreated feedstock flows through the gap 211
between the anode and cathode, and the above gaseous by-products
produced within the EC unit during operation will flow through the
fluid outlet 222 rather than accumulate within the cell housing
210.
[0060] The controller, consisting of an actuator such as the
hydraulic pump 234 and piston 217 as shown in FIG. 2, may maintain
a substantially constant distance G of the gap 211 between the
anode 230 and the cathode 224, for example by one or more of the
processes described in FIGS. 3 and 4, by which a parameter of the
EC cell 298 is monitored and the actuator is actuated upon
detection of the parameter reaching a set value. For example, as
illustrated in FIGS. 2 and 3, process 1100 comprises the steps of
setting a time interval at step 1110 which is a time interval
during which the EC unit 298 is operated prior to moving the anode
towards the cathode; attaining the set time interval, at step 1113;
interrupting the DC power supply to the electrodes, at step 1115;
actuating the actuator at step 1120, such as by pumping the
hydraulic fluid, so as to move the anode 230 in direction X towards
the cathode 224; at step 1130, contacting the ionizing surface 229
of the anode 230 with the ionizing surface 225 of the cathode 224;
at step 1150, actuating the actuator so as to move the anode in
direction Y away from the cathode, such as by releasing hydraulic
fluid, until the distance G of the gap 211 reaches the set
value.
[0061] The step 1110 of setting a time interval is based upon the
expected rate of anode consumption; for example, the time interval
may be set to an EC unit operation time of 30 minutes, or any other
suitable time interval. For example, a higher rate of anode
consumption would result in the distance G of the gap 211
increasing at a faster rate, thereby requiring a lower set time
interval for triggering actuation of the anode so as to decrease
the distance G of the gap 211; and conversely, a lower rate of
anode consumption would result in the distance G of the gap 211
increasing at a slower rate, in which case the selected set time
interval may be longer before actuating the actuator so as to
decrease the distance G of the gap 211. Upon detecting that the set
time interval has been attained, the actuator, which may be a
hydraulic pump 234, is actuated so as to pump hydraulic fluid to
move the hydraulic piston 217 and the anode 230 in direction X
until the anode 230 briefly contacts the cathode 224. While various
hydraulic fluids may be used, untreated feedstock or other aqueous
fluids are preferred because minor leaks past the seals 201 and
into the volume of untreated feedstock contained within the other
portions of the EC unit 298 are of minimal consequence. The contact
between the anode 230 and the cathode 224 causes the DC current to
momentarily spike and the voltage to decrease to near zero.
Creating a current spike at step 1130 may, in some embodiments,
result in activating the valve 221 and releasing hydraulic fluid
from below the hydraulic piston 217 for moving the anode 230 out of
contact with the cathode 1150, thereby re-establishing the gap 211
at a set distance G between the anode 230 and the cathode 224.
Advantageously, utilizing the unit operation time as the parameter
for actuating the actuator so as to adjust the distance G of the
gap 211 may be used to establish a relatively constant distance G
between the anode and cathode, even where the conductivity of the
influent, untreated feedstock is variable.
[0062] FIGS. 2 and 4 depict a further embodiment of controlling the
distance G of the gap 211. Process 1200 comprises the steps of
setting a threshold value of voltage or current, at step 1210;
detecting when the threshold value is attained, at step 1215, for
example by monitoring the DC power source 250; actuating the
actuator, at step 1220, for example by pumping hydraulic fluid so
as to move the piston and the anode 230 towards the cathode 224;
and reducing the distance G of the gap 211 to the set value of
distance G, at step 1230. For example, with reference to FIG. 2,
during operation of the EC unit 289, if the direct current source
250 operating voltage exceeds a threshold voltage, for example 10
volts, hydraulic fluid is pumped from below the hydraulic piston
217 in housing 210 to move up the hydraulic piston 217. This causes
the anode 230 to move closer to the cathode 224 and reduce the
distance G of gap 211. The reduced gap reduces the operating
voltage of the DC power source 250. Pumping continues until the
operating voltage of the DC power source 250 reduces to less than
the threshold voltage and then the pumping stops. This approach for
controlling the distance G of the gap 211 may preferably be used
when the conductivity of the influent feedstock is relatively
constant.
[0063] In some embodiments, either one of the processes 1100 and
1200 may be automated. For example, the controller may be
configured to monitor the EC unit 298 and control the hydraulic
pump 234 by the set time interval (as in process 1100) or by
monitoring the voltage or current output of the DC power source 250
(as in process 1200). The processes 1100, 1200 maintain a
relatively constant gap distance G, advantageously enabling the EC
unit 298 to operate without intervention or maintenance until the
entire anode 230 is dissolved. In some embodiments, when the anode
230 is entirely dissolved, the voltage or current cannot be reduced
when the actuator is actuated, in which case the controller may
include a high voltage or high current alarm, signaling to the
operator that a replacement anode 230 is required.
[0064] Optionally, the EC units 198 or 298 may further comprise a
removable cap 132 or 232. A removable cap 132 or 232 may be
positioned above the anode 130 or proximate the anode 230 to
provide access so the anode 130 or 230 may be placed inside the
housing 110 or 210 and one or more electrical cables may be
connected between the anode 130 or 230 and the DC power source 150
or 250.
[0065] The use of spacers 128 in the EC unit 198 and the processes
1100, 1200 in the EC unit 298, as described above, are preferred
approaches. There are other ways to adjust the gap G in response to
detected changes in current, voltage, and/or pressure drop across
the EC units 198, 298. Such means of automated electrode
positioning may include: a hydraulic piston, ram or jack; a
pneumatic piston, ram or jack; or a mechanical screw or a range of
mechanical jack configurations.
[0066] The smallest practical gap distance G is limited by pressure
drop as feedstock flows through the EC unit 198 or 298. As G
decreases, the pressure drop increases. This effect is more
pronounced at elevated flow rates. As the pressure drop across the
EC units 198, 298 increases, more energy is required to pump the
feedstock through the EC units 198, 298. The preferred gap distance
G is one where a target flow rate of feedstock is achieved while
the sum of the energy input for the direct current source 150, 250
and for pumping water through the EC units 198, 298 is
minimized.
[0067] The anode 230 may be replaced following these steps: turning
off the direct current power source 250; stopping the flow of
feedstock into the EC unit 298; releasing the volume of feedstock
that may be trapped within the EC unit 298, for example by opening
drain 231 in cap 232; removing cap 232; removing any remnants of
the used anode 230; disconnecting the electrical connection between
the anode 230 and the direct current source 250; placing a
replacement anode 230 upon the hydraulic piston 217; connecting the
replacement anode 230 to the direct current source 250; opening
drain 218, 221 to release hydraulic fluid trapped between the
hydraulic piston 217 and the end flange 212; replacing cap 232 and
closing drain 231 therethrough; closing drain 218; resuming the
flow of feedstock into the EC unit 298; turning the current source
250 back on; activating the hydraulic pump 234 to re-establish the
set gap distance G, which may be in response to a current spike or
a threshold voltage value, for example, depending on the embodiment
of a controller utilized to maintain the distance G at the set
value.
[0068] In another aspect of the present disclosure, as EC units
operate to dissolve, for example, an aluminum or carbon steel anode
to deliver positively charged aluminum or iron ions for coagulating
constituents in the feedstock, the dissolved hydroxide (OH--) that
is also produced as a by-product of hydrolysis reacts with the
dissolved metal ions, thus removing hydroxide from the feedstock
and resulting in only a minor change of pH levels in the feedstock.
With their hydroxide-consuming properties, aluminum and iron are
acid-producing metals.
[0069] In contrast with aluminum and iron, using a magnesium anode
within an EC unit delivers dissolved magnesium and a surplus of
hydroxide ions, resulting in significant pH increase. Compared with
steel or aluminum anodes, magnesium anodes consume far less of the
produced dissolved hydroxide. Advantageously, this increase in the
pH level may therefore facilitate removal of dissolved metal
constituents in the feedstock, through formation of insoluble metal
hydroxides between the dissolved metal constituents and the surplus
dissolved hydroxide, in addition to removal of negatively charged
constituents in the feedstock.
[0070] Treating feedstock with EC produces both positive and
negative charges. Dissolved metals may be positively charged but
dissolved metal hydroxides are negatively charged. EC introduces
positively charged dissolved metal ions which coagulate negatively
charged feedstock constituents. Therefore, following treatment of
feedstock in an EC unit with flocculation using anionic polymer
produces negative charges that attach to positive charges,
resulting in agglomeration of constituents to increase the size of
the formed particles. Repeating this cycle of EC unit treatment and
flocculation one or more times may remove both negatively and
positively charged constituents to form agglomerations of larger
particle sizes. As these agglomerated particles become larger, they
are more readily separated by liquid: solid separation techniques
such as flotation, sedimentation, or filtration.
[0071] For feedstock constituents such as with iron, manganese, or
sulphide where oxygen reacts with these constituents to render them
less soluble, multiple stages of EC units in series may
advantageously improve treatment performance. Initially, the
constituents are oxidized to form less soluble solids that are then
subsequently separated by coagulation, flocculation, and
flotation.
[0072] The EC units disclosed herein also deliver dissolved
hydroxide that reacts with dissolved metals to form insoluble metal
hydroxides. Multiple stages of EC units in series can improve
removal of these metal hydroxides that carry a negative charge. By
each cycle of EC unit treatment and flocculation, the constituents
form metal hydroxides (negative charge), and subsequently they are
coagulated by EC (positive charge), and flocculated (negative
charge). This cycle is repeated until the concentration of soluble
metals meets treatment objectives and the agglomerated particles
are large enough to favour their separation from the treated
feedstock. The on-going production of excess hydroxide in EC units,
particularly when using magnesium anodes, helps to provide a
chemical environment that favours insolubility of the formed metal
hydroxides.
[0073] Employing multiple stages of EC and flocculation is more
than just additive. For each of these mechanisms, employing
multiple stages of EC and flocculation may result in performance
synergies to remove constituents from feedstock. Operating EC and
flocculation in series may be performed when the solubility of
constituents is decreased by changes in pH or by oxidation due to
EC, to remove dissolved constituents that are present in small
concentrations, or where constituents need to be removed until they
are present in reduced concentrations, depending on the desired
parameters for the treated feedstock.
[0074] This approach of multiple stages of EC and flocculation in
series may either be employed utilizing the EC units disclosed
herein, or by using conventional EC units. However, with
conventional EC unit designs which employ low flow rates and low
current density, electrode fouling by agglomerated insoluble
particles formed by EC and flocculation is more likely to occur,
whereas such electrode fouling is reduced or eliminated by the EC
units disclosed herein, due to the increased efficiency of the EC
units described above which enable higher flow rates for the
influent untreated feedstock.
[0075] In addition to current density, a key parameter to prevent
electrode fouling is to provide a feedstock flow velocity
sufficient to scour the electrode surfaces via turbulent fluid flow
through the electrode gap. However, for some applications,
increasing the feedstock flow velocity may not be feasible due to
the limitations of using a single DC power supply, which may limit
the ability to increase the current supplied to the electrodes so
as to achieve suitable performance of constituent removal at an
increased feedstock flow rate. Because EC treatment involves
applying electric current to dissolve an anode in proportion to the
mass of the constituent to be removed, increasing the flow rate
increases the mass of the constituent to be removed, so increased
electric current is required to increase the dissolution of the
anode for satisfactory treatment performance. In the alternative,
the total current required to achieve satisfactory treatment at an
increased flow rate may be reached by using multiple EC cells, each
with their own DC power supply. In this way, multiple stages of EC
may be used by connecting a plurality of EC units in series, so as
to achieve overall improvements in treatment performance at the
increased the flow rate.
[0076] As illustrated in FIG. 5, in one embodiment of the present
disclosure a plurality of EC units 1, such as the EC units 198 or
298 described above, are connected in series whereby the fluid
outlet 12 of a first EC unit 10 is in fluid communication with
fluid inlet 24 of a second EC unit 20, fluid outlet 22 of EC unit
20 is in fluid communication with fluid inlet 34 of a third EC unit
30, and fluid outlet 32 of EC unit 30 is in fluid communication
with fluid inlet 44 of the last EC unit 40 of the plurality of EC
units. The conduit 16, between fluid outlet 12 of EC unit 10 and
fluid inlet 24 of EC unit 20, may be in fluid communication with a
polymer pump 18, which adds an anionic polymer to the feedstock as
it flows from EC unit 10 to EC unit 20; similarly, conduits 26 and
36 are in fluid communication with polymer pumps 28 and 38 which
introduce the anionic polymer to the feedstock as it flows between
EC units 20 and 30 and EC units 30 and 40. As described above, this
alternating treatment of the feedstock with EC units and
flocculation through addition of anionic polymer further increases
the efficiency of removing both positively and negatively charged
constituents from the feedstock. In some embodiments, feedstock
exiting EC unit 40 may be delivered to other apparatuses for
further treatment. It will be appreciated by a person skilled in
the art that the example illustrated in FIG. 5, showing four EC
units connected in series, is not intended to be limiting and that
less than or greater than four EC units may be connected in series
for treatment of feedstock.
* * * * *