Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND
Field of the Invention
This invention relates to treatment of waste water and, more particularly, to
novel systems and
methods for heavy metals removal from a waste water stream.
Background Art
Prior art systems exist for various types of waste water treatment. For
example, recycling
waste water from sewage systems in cities is classic and well established.
Moreover, production water
from petroleum production and coal-bed methane production is also well
established.
Typically, removal of heavy metals in particular is accomplished in a vat or
tank dedicated to
an electrochemical, water treatment process. In this process, conventional
systems focus on a balance
between problems. For example, fouling occurs as a result of flocculation and
precipitant
accumulation on electrodes and other reactive surfaces. Engineers balance
between throughput or flow
rate of waste water treated and efficiency measured with respect to the amount
of surface area
available on reaction plates, and so forth.
Typically, maintenance is excessive in many designs. In fact, much of the
prior art is dedicated
to the issue of maintenance of systems particularly with regard to cleaning
off reaction plates
(electrodes). Various deposits may accumulate as a direct result of chemical
reactions in the waste
water treated and the electrical activity near the electrode.
As a practical matter, maintenance, and particularly cleaning of electrode
plates, is at the center
of much of the prior art literature and accepted as a given, or requirement.
It is simply inescapable,
due to the nature of the processes occurring in the reactor tank. For example,
an electrochemical
reaction occurs at each of two electrodes. Typically, a sacrificial anode or
simply an anode will donate
positive current (draw electrons) in order to generate certain ions.
At an opposite, cathodic, electrode, electrons are donated to ions, such as
ions of hydrogen.
This generates hydrogen gas as a byproduct of the freeing up of ions for
reaction in the tank. The
release of hydrogen and formation of hydrogen ions into hydrogen gas are a
direct result of balancing
the electrochemical reaction. Stated another way, the balanced half reaction
of the hydrogen
necessarily involves acceptance of electrons and formation of the hydrogen
gas.
Another aspect of the prior art is the attention to certain electrical schemes
created for the
purpose of interference with, reduction of, or reversal of the plating out or
coating of undesirable
materials over electrodes. Coating of electrodes tends to interfere with their
effectiveness, system
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efficiency, and so forth. As a practical matter, reversing polarity between
electrodes is a common
approach to reversing the coating process.
Nevertheless, it has been found by the inventors that such coating processes
are not necessarily
reversible. In fact, they tend to resist reversal, and require effectively
undercutting the coating in order
to remove it. In other words, the coating often becomes an effective
dielectric or insulation barring
free flow of electrons in the reactions at the electrodes.
In other prior art systems, the generation of hydrogen bubbles, and their
natural tendency to
rise, are relied upon as an agitation source to scrub or remove coatings from
surfaces. As a practical
matter, due to boundary layer theory of fluids, these actually tend to simply
disrupt the formation
process, and are largely ineffective, for actually removing deposits that have
already been deposited on
an electrode.
In short, myriad schemes for manipulating polarities, cycle times,
frequencies, and the like
exist in the prior art. Regardless of attempts to optimize surface areas,
optimize resistance to coating
by insulating reaction products, minimize fouling by flocculating
compositions, and the like have
largely been effective only in slowing the process of coating, and not
effectively eliminating extensive
maintenance operations and costs. Thus, what is needed is a system that
operates with a minimum of
maintenance. In fact, it would be a great advance in the art to provide an
electrochemical reaction
system that is effectively self-cleaning, resistant against coating of
electrodes, or both. It would be a
further advance in the art to remove the common practice of de-rating systems
according to their actual
capacity compared to their engineered capacity.
Moreover, their capacity over time degrades far below their initial capacity.
For example, the
frequent and necessary process of maintenance or disassembly for cleaning is
so ubiquitous that
systems are de-rated so that they may be properly sized by being over-
designed. This effectively
amounts to reducing the expectations of performance in place to comport with
reality. Between actual
disassembly for cleaning at periodic times, the intervening performance
degradation must be properly
accommodated.
Thus, it would be a great advance in the art to provide a system that had a
consistent, high
fraction of available operational time. It would be a further advance to
effectively eliminate routine
cleaning if possible.
If possible, it would be a great advance in the art to relegate maintenance to
replacement of
consumed sacrificial anodes, in due course, rather than cleaning those or
other electrodes. It would be
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another advance in the art to develop a process for design of a system that
operates within a set of
operational parameter values that effectively preclude cleaning as a
requirement.
It would be another advance in the art to develop a process for design, and a
system so
designed, that result in uniform sacrificial donation of ions from a surface
of a sacrificial anode.
It would be an advance to provide a consistent measure of efficiency over time
and
predictability of replacement.
It would be another advance in the art to create a system, and a method for
designing systems,
that would be responsive to variations in the incoming waste water treated.
For example, different
petroleous formations have inherent geological differences, resulting in
different chemistries for the
to surrounding water or production water. Thus, waste water treatment may
be subject to large variations
in the constitution of heavy metals and other constituents such as dissolved
solids, salinity, and the
like. Accordingly, it would be an advance in the art to provide a system and a
method for designing
systems that can be responsive to changes in the constitution of incoming
waste water without altering
the reduced maintenance, operational efficiency, and so forth.
Another advance in the art would be to provide an increased efficiency of
precipitation of
heavy metal compositions separated out from the waste water stream. In this
regard, it would be a
further advance in the art to provide a system for designing a predictable
performance of precipitation
of the extracted materials. This may be expressed as a precipitation
efficiency of a system.
BRIEF SUMMARY OF THE INVENTION
An alternative to electro-coagulation isolates ion generation and
precipitation of target ions
from one another. For example, each is relegated to a subsystem optimized for
accomplishing its own
objective (e.g., ionization and precipitation, respectively) to the virtual
exclusion of others.
Performance of all functions is improved, electrical efficiency is improved,
power use is reduced,
heating of treated fluids is reduced or eliminated, and separation of target
ions (e.g., heavy metals) is
improved.
Conventional pitting, channeling, variations in surface texture, and the like
that typically result
from coating are eliminated. Stated another way, coating is eliminated, so the
effective degradation of
a sacrificial anode is a direct function of uniform reduction of thickness. In
the case of a cylindrical
sacrificial anode, the radius uniformly decreases smoothly along the entire
length and about the entire
circumference during operation.
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In one method of reclamation of a flow of waste water, a system of pumps
control head, which
thus controls pressure, velocity, mass flow rate, and the turbulence that will
exist in conduits carrying
the fluid. Plug flow is enforced within at least the ion generator. Along the
entire length thereof, plug
flow exists, meaning that the Reynolds number is well into the turbulent
region, well beyond any
critical zone in the transition region. Typically this involves Reynolds
numbers much greater than five
thousand, typically greater than ten thousand, and often on the order of
twenty thousand to thirty
thousand.
Plug flow represents a hyper-turbulent condition at a Reynolds number well
above the critical
zone range. The typical critical zone of the transition region for the
Reynolds number is between about
two thousand and five thousand. Below a Reynolds number of about one thousand
is very stably
laminar flow. That is, flows at Reynolds number values below one thousand are
well into the laminar
range and not susceptible to changes with disturbance. Similarly, flows having
a Reynolds number
greater than five thousand are turbulent. At a Reynolds number greater than
ten thousand, a flow is
well into the turbulent region, and incapable of dropping back to a laminar
flow absent a radical
change in operating parameters, such as the velocity, diameter, significant
length, or the like.
Thus, plug flow is maintained along the entire operating length of an anode in
a cell of an ion
generator in accordance with the invention. Plug flow indicates that a
velocity profile is substantially
all at a single value of velocity, except in a very thin layer near a wall,
such as from about one percent
to about ten percent of the overall available diameter or available radius.
Similarly, the flow is unidirectional throughout an ion generator. The bulk
flow direction is
axial, not twisting, turning, reversing, crossing, or the like in other
directions.
A system in accordance with the invention may provide for recirculation. The
system may
recirculate certain output water that has already been cleaned, in order to
control the concentration of
incoming water to be remediated. The circulation pump may be controlled by a
control valve which
effectively trims the head (pressure, typically measured in terms of a height
at some standard
acceleration, such as the value of gravity) that results from the circulation
pump.
A main pump delivering fluid to be remediated will typically not overcome a
recirculation
pump through a control valve. The recirculation pump, when throttled back with
the control valve,
cannot overcome or dominate the flow from the main drive pump. Thus, the flow
from both pumps
may be combined in order to pass into an ion generator at a condition of
concentration (constitution of
water with its constituent ions and in total dissolved solids) that can be
effectively handled by the
system.
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An ion generator may include a conduit in which a hyper-turbulent, plug flow
operates in a
unidirectional mode, progressing axially along the conduit. Effectively no
radial component nor back
component to bulk velocity exists. Near the wall thereof, the hydrodynamic
boundary layer will
provide some slight amount of recirculation as understood in boundary layer
theory. However, this is
not even a significant portion of the volumetric flow rate (cubic feet per
minute or liters per minute).
In one embodiment, stagnation points are not permitted along a conduit in an
ion generator.
The flow is preferably directed through a cross-sectional area that has little
or no change in area,
dimension, shape, or the like along the length thereof.
Necessarily, certain guides may be required in order to position an anode
along a central axis of
a conduit. These may occasion a slight amount of interference with the cross-
sectional area, but will
add to turbulence. They will not tend to make the flow any more nearly
laminar, nor generate
stagnation eddies. By stagnation eddy is meant a region where flow may
actually come to a stop or
reverse in the axial direction or main direction of flow.
The Reynolds number is greater than the critical zone value at all significant
points within the
conduit. This is typically from about two to about six times the value of
Reynolds number in the
critical zone of the transition region's end (maximum value). Likewise, there
may be a single transition
area at an entrance to the conduit, wherein fluid may come in perpendicularly
or from a conduit of
another diameter in order to feed into a particular cell of an ion generator.
Similarly, a single transition
at the exit will typically be downstream of the sacrificial anode. That anode
may be configured as a
cylindrical rod passing axially along the center of a conduit carrying the
fluid to be remediated. The
rod furnishes ions as the sacrificial anode.
The hydrodynamic boundary layer near any walls adjacent to the hyper-turbulent
flow provides
mechanical shear selected to overcome weak chemical bond forces, and
specifically Van der Waal's
forces. Only ionic bonds may survive the turbulence and the laminar shear (at
a solid boundary) extant
throughout the lumen of a conduit in the generator.
Tripping devices, or trippers may be used in order to trip flows in regions
where the possibility
of reduced Reynolds number may exist. Textures on surfaces, ridges, dams,
disruptions, or changes in
direction at highly localized locations and the like may trip a laminar
boundary layer, turbulent
boundary layer, or both in order to maintain thorough, actual turbulence.
Calculation and design of a system may require assessment of hydraulic
diameter of a conduit,
selection of the velocity, investigation and accommodation of fluid
properties, minimizing a
hydrodynamic boundary layer, maintaining a constant axial cross-sectional area
of flow, and the like.
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It may benefit from maintaining all flow parallel to an anode surface, such
that net ion migration or
diffusion exists only perpendicular to the anode surface. This results in an
effective electrodynamic
machining process actually carrying ions away from the contact surface of an
anode in the conduit of a
cell of the ion generator.
The hydrodynamic boundary layer is minimized by the hyper turbulence of the
flow.
Meanwhile, the diffusion boundary layer is minimized in that it is coincident
with the entire laminar
portion of the hydrodynamic boundary layer, and then may extend into a micro
eddy portion of the
transition region to turbulent flow. For example, transition from laminar flow
to turbulent flow at a
solid boundary will typically involve micro eddies that have a circulation
component while still
moving axially along the path of the boundary.
Thus, diffusion is minimized in the direction toward the anode throughout the
diffusion
boundary layer. The flow of current, drawing electrons from any metals in the
flow will result in a
plethora of ions (a comparatively high concentration) near the surface of the
anode. By matching the
mass transport rate of convective processes carrying ions out of the diffusion
boundary layer and into
the bulk plug flow of the conduit will assure that no effective precipitation
can occur in the ion
generator.
Rather, sacrificial metal ions are driven into the bulk flow by a flux,
effectively approaching
saturation with respect to the maximum current output by a current source
driving the ion generator.
Meanwhile, a radial flow of ions is matched with an axial flow of fluid with
thorough and immediate
mixing of ions into the bulk flow. Thus, only in a core region near the anode
is any diffusion gradient
extant, and not actually distinguishable, as a practical matter. That is, the
hydrodynamic and diffusion
boundary layers are simply too thin to include a significant portion of the
flow. The constant, radial,
cross-sectional area provides a diffusion per unit length that is
substantially constant and thus
represents a linear curve along the entire length of a cell of the ion
generator.
Moreover, a unidirectional, axial, mechanical load on the anode results from
centering the
anode in a seat of a holder or guide engineered for the purpose near the exit
end of the cell.
Meanwhile, another guide positions the upstream end of the anode near the flow
entrance within the
conduit. The conduit itself, meanwhile, operates as a cathode.
There is no need nor benefit to alternating the current flow or the roles of
the anode and
cathode. There is no benefit to swapping polarity. A system in accordance with
the invention
precludes coating out any significant precipitants on the anode. There is no
need to try minimizing that
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coating, nor trying to reverse that coating, by acidifying the fluid in order
to scavenge hydroxides from
the fluid.
In one embodiment of an apparatus and method in accordance with the invention,
no
manipulation of the polarity, modulation, reversal, change of magnitude, or
the like is required in order
to avoid precipitation in the ion generator. Rather, isolation of
precipitation is physical. The ion
generator has a separate device, containment, and flow path from a
precipitation reactor. They occupy
no coincident physical space. Moreover, the hydrodynamic, hyper-turbulent flow
regime within the
ion generator precludes precipitation and precludes any agglomeration of
precipitants. The
hydrodynamic shear precludes any agglomeration of ions under weak forces, such
as Van der Waal's
forces. Moreover, no acid need be added to the water to be treated upstream
from the ion
generator. No hydroxide ion scavenging is necessary. Rather, the availability
of hydroxide ions need
not be manipulated nor controlled. Hydrodynamic effects simply assert control
over the agglomeration
process, thus effectively precluding them from the ion generator.
Stated another way, the hyper-turbulent flow and the comparatively high rate
of shear in the
hydrodynamic boundary layer will preclude agglomeration of precipitants, and
even tend to reverse
any occasional, statistically random, chance precipitation of constituents.
This is because the
availability of hydroxide ions, heavy metal ions, and sacrificial ions, is so
ubiquitous, yet extra charge
is not available. This system does not run excess currents similar to electro-
coagulation systems.
Thus, a system in accordance with the invention isolates precipitation
physically, isolates ion
generation from precipitation reactions by hydrodynamic shear, and does not
require acid or other
hydroxide scavengers in order to manipulate the availability of hydroxide ions
to metal ions.
Downstream from the ion generator, the addition of flocculating polymers,
adjustments of pH in order
to optimize the availability of reactants for precipitation in the
precipitation reactor, and so forth may
be considered and included. The reactor operates in the laminar flow regime,
and may even be
completely quiescent. Stagnation is not necessarily general. A certain amount
of mixing may be
beneficial to provide availability of ions to one another for reactions.
Nevertheless, the laminar flows
that have a Reynolds number value less than half that of the critical zone
(e.g., less than half of about
two thousand) may be considered to be well within the laminar flow regime.
One may analyze water, and create a report. One may analyze ion concentrations
and types
based on the report of inductively coupled plasma (ICP), chromatography, or
other testing systems.
Accordingly, one may determine by calculation of electrons required for
ionization a current limit. For
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example, the numbered ions times the charge per unit is the current required
to remove all those ions at
their charges. The sum of all species of ions provides the total charge.
That amount of charge per unit volume, and the volumetric flow rate, will
control the amperage
required. Amperage is the current flow of electrons needed per unit of time to
match the reaction of
the number of ions passing per unit of time through the precipitation reactor
portion of a system.
Electrical energy need not be devoted to overcoming resistance of coatings.
Very little energy is
wasted as heat.
The amperage is a function of ion generation, and is largely independent from
any resistance.
Typically, the only resistance to be overcome is that inherent in
thermodynamic processes of
ionization. The electrical energy need only be sufficient to break bonds of
metals with electrons, in
order to create metal ions. There is no need to provide excessive additional
current. Energy is needed
to the extent that thermodynamics requires the minimum of losses required by
its first and second laws
for a process to occur.
Meanwhile, a system does not need the amount of electrical energy common in
the prior art
(e.g., Electrocoagulation or EC). Prior art systems need to overcome the
electrical resistance of
dielectric coatings of precipitants on electrodes, such as a sacrificial
anode. Moreover, electrical
energy is required for electrophoresis of ions through the thickened prior art
fluids. Here, mechanical
mixing provides all the diffusion required outside the boundary layers.
A system in accordance with the invention may optimize a curve of operation
representing
electrical conductivity (proportional to ion concentration) as a function of
current in a separate ion
generator. The mass transport (transfer) limit may be calculated initially
from the principles of heat
and mass transport as well as chemical diffusion through boundary layers of
fluids. A definition of a
mass transport limit and an electric current limitation will establish an
envelope within which the
operation of curve will be found. It is typically desirable to improve the
operational curve toward the
limits of the envelope established by the current limit and the mass transport
limit.
The system may also track independent variables, which include current, flow,
and chemical
constitution. Typically, current, flow, and, to a lesser extent, the
constitution of the fluid may be
manipulated by individual controls. The constitution may be manipulated by
diluting an incoming
fluid stream to be remediated. On the other hand, flow and current are
typically controlled almost
directly. As a practical matter, current may be controlled by a feedback
control loop on a current
generator between the cathode and anode.
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The system may measure and track the dependent variables such as electrical
conductivity,
temperature, and pH within the flow of a fluid. The system may accordingly
adjust the operation of
the curve within the mass transport limitation and the current limitation of
the system. Sensors may
measure conductivity variations as current is increased and reduced.
Accordingly, process controllers
may evaluate the comparison of slopes, and determine whether the benefits of
increased current will
provide sufficient increase in ionization of anode metal. The system may test
the slope operating of
the curve at various conditions and thereby limit the processes to avoid
operating in a fouling region in
which too much current applied to an anode results in coating out of
precipitants on the anode.
In certain embodiments of apparatus and methods in accordance with the
invention, an ion
generator may be fed by a current source to treat a flow of incoming water. In
certain embodiments, a
precipitation reactor may be connected to receive the output of the ion
generator. As a practical matter,
it has been found effective to separate the ion generator from a precipitation
reactor in order that the
processes of precipitation, flocculation, and the like be completely isolated
from the generation of ions.
In certain embodiments, it has been found most effective to maintain a high-
velocity, well
established, turbulent flow throughout the ion generator. Thus, the
electrochemical reaction driven by
the current source is effective to generate large (comparatively) masses of
metal ions from a sacrificial
anode into a very turbulent flow (Reynolds number well into the turbulent
region, and consistently well
away from any laminar-to-turbulent transition).
It has also been found effective to rely on a channel or lumen that is annular
in shape. The
sacrificial anode is best made a cylinder axially aligned in a cylindrical
tube acting as the cathode.
Thus, the sacrificial anode is completely surrounded by treated fluid. The
high velocity, high
turbulence, and generalized mixing of plug flow results in a rapid carriage of
ions into the bulk of the
stream. This also causes a minimization of hydrodynamic boundary layer,
diffusion boundary layer,
and any tendency to coat out the anode.
A flocculent polymer may be injected into the flow between the ion generator
and the
precipitation reactor. This provides several benefits. For example, the
precipitation reactor is separate
from the ion generator. The flocculent source provides a source of
flocculating polymer. Thus, the
precipitation reaction and flocculation of precipitants cannot be effective,
and cannot overcome the
turbulent flow and boundary layer shear within the ion generator.
Moreover, in contrast to prior art systems, separating the precipitation
reactor from the ion
generator provides for a flow in the precipitation reactor that may range from
quiescent to laminar
flow. In electro-coagulation systems, ion generation and precipitation
reactions commonly compete
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with one another in the same tank. Thus, prior art systems would damage the
flocculation process if
turbulence were allowed. Meanwhile, such quiescence or laminar flow in the
presence of an anode
will increase hydrodynamic boundary layers, and the diffusion boundary layer,
both resulting in higher
rates of coating out and fouling.
In a system and method in accordance with the invention, ion generation takes
place in an
environment optimizing the rate of ion creation, and minimizing the processes
or effects contributing
to coating. Meanwhile, the precipitation reactor is optimized specifically for
flocculation. Turbulence
is effectively eliminated by maintaining the flows well within Reynolds
numbers below turbulent
transition. Moreover, in certain embodiments, the Reynolds number is often
double the Reynolds
number at the high end of the critical zone of the transition region or
greater.
The Reynolds number in the precipitation reactor is often in the range of half
the beginning
critical zone of the transition Reynolds number. This may be a value of one
thousand or less. Thus,
each of the ion generator and precipitation reactor may be optimized to
maximize the effectiveness of
the process to which it is dedicated.
In order to provide low Reynolds numbers (e.g., slow to quiescent flows) with
some modicum
of mixing sufficient to promote precipitation reactions, the precipitation
reactor may include elements
such as baffles, channel obstructions, flow path variations, and the like.
Gates, and the like may
maintain laminar bulk flows while still providing the exposure required to
create molecular availability
or atomic availability for reactions.
Typically, the actual separation of flocculated precipitants may be conducted
in a clarification
unit. Typical clarification units include induced gas flotation (IGF),
dissolved air flotation (DAF),
settling tanks or settlers, or the like. Typically, such systems rely on time,
gravitational separation of
heavy materials from lighter materials, and so forth. Typically, the reference
in such systems is to
"scraping" or separating off the lighter materials appearing near the top of a
processing tank, while
augering out sediments from the bottom of such tanks. A water outlet
therebetween removes the water
separated from the contaminants.
A post processing unit may be added. For example, a distillation process,
reverse osmosis,
activated carbon filter, or the like may be placed in line with the output
from a clarification unit. The
post processing unit may thus return the treated waste water to a condition
suitable for subsequent use.
Such subsequent uses may include, for example, irrigation, drinking water,
process water, and so forth.
In some embodiments, a certain amount of the water output from the
clarification unit may be
recycled in a bypass or circulation loop. The circulation loop may be driven
by a circulation pump
CA 3058876 2019-10-16
restricted by a control valve in order to control incoming concentration by
providing a certain amount
of make up water into the ion generator. An alternative is to use fresh water
or a separate source of
clean water to dilute the concentration of a particular incoming waste water
stream.
In the petroleum production industry, commonly called the oil and gas
industry, water may
simply be reinjected into an injection well drilled for the purpose. Thus, the
production water removed
from the earth as a byproduct of petroleous production may be reinjected into
another dry well, below
underground aquifers
Notwithstanding the fact that the water is reinjected, it is desirable that
the water not contact
aquifers. Nevertheless, the purification requirements are such that the
possibility of eventual contact
with aquifers is still kept in mind. For example, heavy metals are removed
permanently.
As a practical matter, the injection wells are typically drilled to a depth
consistent with
petroleum production. In the oil and gas industry, the removal of heavy metals
and compounds of
heavy metals also serves to prevent fouling of the injection well itself, the
bores as well as the
formation into which the water is injected. Otherwise, over time, fouling will
eventually block access
and destroy the utility of an injection well.
Similarly, water used for formation fracturing (commonly referring to as
fracking) also has
environmental limitations as well as fouling concerns. Thus, removal of heavy
metals and their
compounds reduces fouling and increases the longevity of a particular well and
a formation.
In another system and method in accordance with the invention, a control
scheme has been
developed by which the system may be operated, designed, trimmed, and
monitored. In certain
embodiments, a current limit is established, as well as a mass transfer limit.
These correspond,
respectively to the electrochemical reaction rates available at the surface of
a sacrificial anode and the
diffusion and mass transfer processes due to hydrodynamic and diffusion
boundary layers within the
system. Accordingly, it has been found that a system may be
controlled to optimize capital
expenditure or balance capital expenditure on systems against the operating
costs, such as power costs.
Likewise, maintenance costs may be so balanced or optimized. Fouling may be
effectively eliminated
by controlling a system within parametric values in accordance with the
apparatus and method.
The operating envelope may be bounded by the current limit and mass transfer
(mass transport)
limit. These govern the relationship of ion concentration (as reflected in the
electric conductivity) as a
function of the current input for a sacrificial anode.
By maintaining values of operational parameters within the envelope defined by
the current
limit and mass transfer limit, an operational limit on performance may be
established. For example, by
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tracking a suitable dependent variable, such as electrical conductivity of the
waste water stream, the
effectiveness of reactions along the path of that stream may be tracked and
controlled.
In this example, an initial period of ion generation may effectively
degenerate to a linear curve
that may be relied upon consistently. Meanwhile, the decay of electrical
conductivity as the
precipitation and flocculation processes proceed may also be measured,
characterized, and
parameterized to provide suitable predictions of performance.
In fact, depending on whether the incoming stream is effectively clean water
with heavy metals
in it, brine containing heavy metals, or some combination containing only
metals, only salts, or the
like, certain operational parameters may be established, and an operating
envelope may be defined.
These operating envelopes have been established by experiment and demonstrated
to be operative.
In certain embodiments, a quick release system for replacement of anodes has
been developed
to provide rapid replacement of individual cells. Taking a cell offline,
minimizes downtime for
replacement of anodes. The only operational degradation of that anode is
consumption. Current may
be maintained at a constant value regardless.
In order to break an emulsion or coalesce small liquid droplets in a dilute
dispersion, an
alternate process may pass the emulsion or dilute dispersion through the
EcoReactor system. Since
aluminum is not required in the process, the current between electrodes may be
turned down so low the
potential of the electric field (voltage) is low enough that no aluminum is
oxidized into ions.
Alternatively, the process may use an anode and cathode of material more noble
than aluminum
(e.g., stainless steel, gold, etc.) with higher voltage. A less noble metal
may also be used if a more
noble metal is electroplated or sputtered on it to prevent corrosion or
oxidation.
Such a device acts as a coalescer (EcoCoalescer). As far as process operation,
it operates very
similarly. The device does not remove heavy metals, and has significantly less
onerous maintenance
requirements (e.g., no anodes to replace). Operation costs are on the order of
70% less as well.
Potential candidate emulsions or dilute dispersions are heavy or light phase
effluent from a
liquid / liquid separator (e.g., centrifugal, gravity, etc.), drilling mud,
used motor oil, used lube oil,
dilute silica in water mixtures, effluent from a flotation or settling
operation, etc.
When the emulsion or dispersion passes into the coalescer, it experiences an
electric field
gradient. The electric field gradient causes electrophoretic movement of the
droplets and distortion of
the droplets. This movement, distortion, or both will cause the small, dilute
droplets to coalesce more
quickly due to closer proximity or favorable reduction, distortion, or both of
the zeta potential. This
method of coalescence works with any droplet or particle where the droplet or
particle has an
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unbalanced electric charge (e.g., oil, clay, etc.) or with any droplet or
particle where an unbalanced
electric charge may be induced (e.g., oil, silica, etc.).
It is important in the design and operation of the coalescer that the flow be
such that the
residence time of the fluid be sufficient for coalescence to occur, but not so
long as to waste power.
The flow also needs to be quiescent enough not to break up any coalesced
droplets but not so quiescent
as to require undue capital costs for equipment size.
It has been found that streams or flows of water having extremely high
dissolved solids content,
such as greater than 150,000, and especially over 200,000, parts per million
may have excessively
reduced electrical resistance (increased conductivity) within the stream
itself. Accordingly, it is
difficult to maintain the voltage necessary between an anode and a cathode to
drive ions from the
sacrificial anode. In order to increase resistivity along the electrical path
of ions and electrons passing
between the anode and cathode, it has been found effective to modify the
surface area available to
participate in the electrical exchange.
One method for increasing the effective resistance due to low electrical
resistivity is by
reducing the area on the anode. This may be done by masking a portion of the
anode until after the
anode has been eroded (sacrificed) sufficiently to increase the distance
between the anode and the
cathode to a value suitable to maintain a suitable voltage (typically greater
than two volts across two
inches). Masking techniques may involve films, cylinders, coatings, various
plastics or dielectric
materials, and the like used to coat a portion of an anode, a cathode, or
both. Masking may be
accomplished in stages. In alternative embodiments, masking of the cathode may
also result in
additional reduction of effective conductivity and therefore increase the
resistance and voltage between
the anode and cathode.
In yet another embodiment, masking may be done by hydrodynamic means, such as
a curtain of
extremely fine bubbles generated to pass upward along the hydrodynamic
boundary layer attached to
the anode or to the cathode. The net effect of the curtain of the bubbles is
to increase the physical path
length required for an ion to traverse between the anode and the cathode.
The air or other gas in each bubble represents an effective dielectric region.
Thus, ions must
pass through the minimized, residual liquid surrounding each bubble. This
creates a tortuous path
through the bubble curtain. Increasing resistance and effective resistivity
increases the voltage upward
towards that required to drive ions from the sacrificial anode toward the
cathode.
A method for removing metals from a flow of liquid may include providing a
flow of a liquid
containing target ions of a target metal. Providing a cathode, as a conduit,
and an anode, formed of a
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sacrificial metal passing axially through the conduit, leaves an annulus
therebetween. The anode is
capable of providing sacrificial ions of the sacrificial metal.
Limiting a surface area of the anode exposed to the flow increases resistance
by masking a
portion of the anode. Flow through the conduit receives sacrificial ions from
the anode, released into
the flow by applying an electrical potential voltage between the anode and
cathode.
Reaction between the target ions and the sacrificial ions within the annulus
is blocked by
maintaining a comparatively thin, (compared to laminar flow) hydrodynamic
(liquid) boundary layer
therebetween resulting from hyper-turbulence in the annulus. Liquid shear
forces are easily capable of
overcoming "weak forces" (e.g., Vander Waal's forces) between products of
reaction that may react in
the annulus, by the hyper-turbulence. By thus limiting flocculation, in the
annulus, by precipitants
(reacted constituents) comprising the sacrificial ions and the target ions the
hyper-turbulence in the
bulk of the flow in the annulus does double duty. It keeps boundary layer
thinned and close to the
anode, but thoroughly shears and mixes the bulk (vast majority) of the flow.
This amounts to resisting precipitation of reactants composed of the
sacrificial ions and target
ions by mechanically isolating the target ions from the anode by maintaining a
hydrodynamic
boundary layer of the flow corresponding to a hyper-turbulent condition in the
flow. Then, the flow
continues resisting flocculation of reactants by a combination of resisting
reaction of the target ions
and sacrificial ions and by overcoming weak forces of aggregation of reaction
products by maintaining
a hyper-turbulent condition in the annulus and a boundary layer corresponding
to hyper-turbulence
proximate the anode. This may be called "plug flow" since the volumetric flow
rate is so high and so
very turbulent that it flows at a single bulk velocity across the entire
annulus except in the very thin
boundary layer.
Controlling the quantity of sacrificial ions exposed to the flow may also
occur by controlling
the area of the exposed surface of the anode or of the cathode. This results
in maintaining a migration
of the sacrificial ions into the flow by increasing the resistance (V=IR) and
electrical potential
(voltage) for any given current (I) between the anode and cathode. Voltage
will continue to rise in
response to receding (eroding, sacrificing ions) by the anode, thus increasing
its distance away from
the cathode.
Masking is temporary. Removing a portion the masking from the anode may be
done as a
maintenance step in response to at least one of a reduction of the surface
area of the anode due to
migration of sacrificial ions, a rise in the electrical potential required to
maintain a current flow
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between the anode and cathode at a pre-determined value, and a reduction in
electrical conductivity
through the flow.
An apparatus for removing contaminants, comprising metals, from a flow of
liquid may include
an inlet connectable to and capable of introducing a flow of a liquid
containing target ions of a target
metal. A cathode, operably connected to the inlet may act as a conduit capable
of conducting the flow.
An anode, formed of a sacrificial metal, passes axially through the conduit to
form an annulus
therebetween. The anode is capable of providing sacrificial ions of the
sacrificial metal into the flow;
A mask is capable of controlling exposure to the flow of a surface area of the
anode by
selectively covering a portion of the surface area. An electrical source, of
electrons as an electrical
current at an electrical potential (voltage), is capable of controlling at
least one of the electrical current
and the electrical potential, between the cathode and the anode, at a pre-
determined value.
The liquid typically comprises water and dissolved solids as contaminants,
including at least
one of a hydrocarbon, other organic material, a heavy metal, an earthen
material, a surfactant, a
chemical waste product. At least one of the contaminants contains the target
metal ions. The
sacrificial ions are reactive with water in the liquid to form a dipole
capable of collecting thereon a
target-metal-ion-bearing contaminant as a target contaminant.
A reactor tank is operably connected to receive the flow from the cathode
(conduit) and flows
quiescently to be capable of reacting a majority of the sacrificial ions with
water to form dipoles. A
precipitator is even more quiescent, perhaps almost stagnant, to be capable of
flocculating the dipoles
with the target contaminants as a flocculent. Later a clarification unit
receives the flocculent and
removes it from the flow. A post processing unit is capable of filtering out
from the flow suspended
solids of a predetermined size.
One method of removing contaminants by flocculation based on target metal ions
in a flow,
includes providing a cathode, as a conduit capable of conducting a flow
comprising water carrying
contaminants containing target metal ions; providing an anode, formed of a
sacrificial metal as a
source of sacrificial ions, the anode forming an annulus by passing axially
through the conduit; and
limiting a surface area of the anode exposed to the flow by applying a mask
onto a portion of the
anode.
The method may direct the flow through the annulus while imposing an
electrical potential
between the cathode and anode. The sacrificial ions are generated at the anode
and released into the
flow in response to the electrical potential. The desired value of the
electrical potential may be
controlled in response to an increase in distance between the anode and
cathode, resulting from erosion
CA 3058876 2019-10-16
and migration of the sacrificial ions into the flow. One way to do so is by
exposing an additional
surface area of the anode by removing at least a portion of the mask in
response to the exposed anode
decay or erosion, which increases the electrical potential to a value about
that required to maintain the
migration of the sacrificial ions.
The method may be improved by resisting interaction between the target ions
and the sacrificial
ions within the annulus by maintaining a boundary layer therebetween resulting
from hyper-turbulence
in the annulus. This also results in hydrodynamic shear forces in the bulk
flow overcoming weak
forces (e.g., Vander Waal's forces) between products of reaction of the
sacrificial ions as sacrificial
dipoles and target-ion-bearing contaminants as target contaminants in the
annulus, as a consequence of
the hyper-turbulence. This results in limiting agglomeration into flocculants
by the sacrificial dipoles
and the target contaminants through a combination of resisting reaction of the
target ions with the
water in the flow and the overcoming of the weak forces required for such
aggregation
(agglomeration).
The method may control quantities of sacrificial ions exposed to the flow by
controlling the
area of the exposed surface of the anode. Masking maintains voltage required
to initiate migration of
the sacrificial ions into the flow by increasing the electrical potential
between the anode and cathode
by limiting available area and distance. Later, increased distance develops
between the anode and
cathode as the anode erodes (sacrifices) mass.
As voltage increases or tends to go beyond the voltage of the current sources
removing a
portion the masking from the anode reduces voltage in response to at least one
of a reduction of the
surface area of the anode due to migration of sacrificial ions, a rise in the
electrical potential required
to maintain a current flow between the anode and cathode at a pre-determined
value, and a reduction in
effective electrical conductivity (increased total resistance) across the flow
in the annulus.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing features of the present invention will become more fully
apparent from the
following description and appended claims, taken in conjunction with the
accompanying drawings.
Understanding that these drawings depict only typical embodiments of the
invention and are, therefore,
not to be considered limiting of its scope, the invention will be described
with additional specificity
and detail through use of the accompanying drawings in which:
Figure 1 is a schematic block diagram of an apparatus and process in
accordance with the
invention;
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Figure 2 is a schematic diagram of the chain of reactions occurring in the
system of Figure 1;
Figure 3 is a schematic diagram of the flow within the annulus of an ion
generator in
accordance with the invention, indicating velocity profiles, concentration
profiles, and geometric
relationships;
Figure 4 is a schematic diagram of the ionic reactions at the electrodes,
anode and cathode, of
an ion generator in accordance with the invention;
Figure 5 is a graph indicating the curves of current limit, mass transfer
limit, and the electrical
conductivity performance curve of a system and method in accordance with the
invention;
Figure 6 is a schematic block diagram of a process in accordance with the
invention for setting
up, evaluating, and controlling the performance of a system along the
performance curve of Figure 5;
Figure 7 is a graph showing the electrical conductivity, reflecting ionic
concentrations within a
waste water treatment stream, as a function of distance through the system,
including passage through
the ion generator and precipitation reactor of Figure 1;
Figure 8 is a chart showing a least squares fit of data in a log-log format
showing the
correlation of actual experimental data to the calculated predictions of a
system in accordance with the
invention;
Figure 9 is a chart showing a least squares fit of data in a log-log format
showing the
correlation of actual experimental data to the calculated predictions of a
system in accordance with the
invention, according to another series of tests; and
Figure 10 is a partial, side-elevation, cross-sectional view of one embodiment
of a quick-
change-out cell system for the ion generator in accordance with the invention,
including its sacrificial
anode, which must be replaced periodically;
Figure 11 is a partially cut away, side-elevation, cross-sectional view of one
embodiment of ion
generator having a portion of the anode masked by a dielectric layer;
Figure 12 is a top plan view of one embodiment of a support for the anode;
Figure 13 is a side-elevation view of an alternative embodiment of a
dielectric layer having
score marks at which to tear off portions of the height of the dielectric mask
as necessary in order to
expose additional area of the anode;
Figure 14 is a side-elevation view of an alternative embodiment of a mask
involving segments
or tubular plastic collars having a slit or gap that may be opened in order to
snap each length of tubing
around the anode, leaving exposed only a portion thereof, which portion may be
increased by selective
removal of the collars over time;
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Figure 15 is a top plan view of an alternative embodiment of a support for the
anode;
Figure 16 is a side-elevation view of an alternative embodiment of a
dielectric mask involving
a tape-like wrapping around the anode, which wrapping may be selectively
removed over time in order
to expose additional area of the anode;
Figure 17 is a side-elevation view of an alternative embodiment of a tubular
dielectric film or
layer that may be drawn down to expose additional area of the anode to the
flow, with the excess film
being collected or cut off;
Figure 18 is a side-elevation, cross-sectional view of an alternative
embodiment of a dielectric
mask involving telescoping sections of tubing that may be compressed or
shortened in order to expose
additional surface area of the anode;
Figure 19 illustrates an alternative embodiment of a dielectric layer applied,
such as by
spraying or dipping an anode, later to be removed by a sharp-edged tool
scraping the mask away from
the anode;
Figure 20 is a top plan view of the tool of Figure 19;
Figure 21 is a side, elevation, cross-sectional view thereof;
Figure 22 is an upper perspective view thereof;
Figure 23 is a side-elevation view of an anode illustrating an uppermost or
first portion that has
been exposed for some time to sacrificing ions into a surrounding flow
(stream), a second, central
portion that has just been exposed by removal of a mask, and a lower portion
that remains masked;
Figure 24 is a sectioned view of a cathode having a portion of its area masked
by a dielectric
layer;
Figure 25 is a side-elevation, cross-sectional view of a cathode having a
perforated mask
providing partial masking and partial open gaps, also including optional vanes
for engaging the flow,
and thereby rotating the mask within the cathode; and
Figure 26 is a side-elevation, cross-sectional view of an alternative
embodiment of ion
generator cell relying on injection of gas bubbles, such as air, around a
circumference of very small
orifices creating a curtain of bubbles in front of an electrode, illustrated
as the cathode, but also
possible in an anode configuration.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
It will be readily understood that the components of the present invention, as
generally
described and illustrated in the drawings herein, could be arranged and
designed in a wide variety of
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different configurations. Thus, the following more detailed description of the
embodiments of the
system and method of the present invention, as represented in the drawings, is
not intended to limit the
scope of the invention, as claimed, but is merely representative of various
embodiments of the
invention. The illustrated embodiments of the invention will be best
understood by reference to the
drawings, wherein like parts are designated by like numerals throughout.
Referring to Figure 1, a system 10 in accordance with the invention may
include an ion
generator 12 responsible for generating ions of a metal anode. The anode
referred to as a sacrificial
anode, delivers ions into a solution of waste water to be remediated.
Waste water may arise in a variety of industrial circumstances. Tail water
from mining,
production water from petroleous production, production water from coal-bed
methane production,
industrial process waste water, irrigation tail water, city sewer systems and
surface drainage, and the
like may all give rise to water containing contaminants. Certain biological
contaminants are handled
by conventional mechanisms. In accordance with the invention, a principal
contaminant is heavy
metals.
A system 10 in accordance with the invention may include other elements (not
shown)
responsible for handling volatile organic compounds (VOCs), other organic
materials, biological
matter, or the like. Meanwhile, salinity may be another issue to be addressed
by additional
mechanisms or ignored, depending on final disposition such as Re-use versus Re-
injection. In the
illustrated embodiment, the principal concern is heavy metals that are
difficult to remove from water
streams. The difficulty is related partly to the chemistry of those metals,
and partly to the trace
amounts in which they exist. Efficiently processing such constituents out of a
waste water stream may
be problematic, and has historically been so.
Thus, a system 10 in accordance with the invention may be augmented by
additional
components responsible for managing VOCs, organic compounds, salts, biological
compounds, and
the like. Alternately, some may be permitted to remain.
Downstream from the ion generator 12 may be located a precipitation reactor
14. The
precipitation reactor 14 is responsible for agglomerating various compounds
made up of sacrificed
metal ions from the ion generator, along with hydroxide ions derived from the
water itself, and other
heavy metal ions. In general, the precipitation reactor 14 may include
flocculation by addition of
suitable compounds discussed hereinbelow (e.g., polymers).
A precipitation reactor 14 differs from an ion generator 12 in a significant
manner. In
contradistinction to prior art systems, such as, for example, electro
coagulation (EC) systems, whether
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open or closed as to containment of the treated fluids, the ionization process
is isolated to the ion
generator 12. The precipitation process is isolated to the precipitation
reactor 14, for all practical
purposes.
Ionization, reaction, and the like as chemical processes, are inherently
statistical in nature.
Thus, at any given moment, any particular chemical atom or composition may
enter into a reaction
with another. Nevertheless, as a statistical probability, such processes
typically occur at an
appreciable, significant, or measurable rate only under certain conditions.
Thus, the ion generator 12 is
specifically designed to provide conditions of highly turbulent flow (well
above the critical zone of the
transition Reynolds number range).
In contrast, the precipitation reactor 14 is maintained at a quiescent or at
most stably laminar
flow (e.g., a Reynolds number of much less than the initiation of transition
to turbulence, and typically
even on the order of half that value).
The ion generator 12 is designed, described, defined, and operated to provide
minimal
residence time. One reason this is so is that the ion generator 12 is driven
electrically, as a function of
flow rather than depending upon or balancing other processes present. For
example, the ion generator
12 is driven at a high velocity, very high Reynolds number, in a highly
turbulent plug flow. This
ensures a minimal boundary layer at all surfaces, and in both hydrodynamic and
diffusion boundary
layers.
In contrast, the precipitation reactor 14 may include baffles, weirs, dams,
obstructions, gates,
serpentine paths, or the like. These may provide a certain amount of mixing at
very low Reynolds
numbers (well below values of two thousand, and frequently less than half that
value) in order to
assure laminar flow, agglomeration of molecules and associations of ions by
"weak forces" that might
otherwise be disrupted by any effective turbulence in the flow. This supports
flocculation,
development of gels and polymeric reactions, absorption of water molecules
into flocculating
polymers, and association of large groups of ions including metallic ions from
the ion generator 12 and
the constituent heavy metals, and so forth.
Thus, the ion generator 12 need not be designed to tolerate nor foster the
weak forces, such as
Van der Waal's forces. In direct contrast, the precipitation reactor 14 by its
well-laminarized to
quiescent flow exactly fosters flocculation, agglomeration, chemical reaction,
precipitation and so
forth.
In certain embodiments, a clarification unit 16 may be a settling tank that
simply provides
space and time for materials to separate in a quiescent environment.
Typically, sediments representing
CA 3058876 2019-10-16
heavy precipitates may be augured out of the bottom portion of such a unit 16
while lighter
compositions and mixtures may be "skimmed" from the upper reaches thereof.
A clarification unit 16 may be any of several suitable types. For example, an
induced gas
flotation system (IGF) may foster agglomerating reactions of various ions that
will include (e.g.,
scavenge) the heavy metals ions desired to be removed from the waste water. To
that end, an IGF
system, or a dissolved air flotation system (DAF) may operate similarly.
For example, these systems may foster flocculation and flotation of certain
compositions,
resulting in a froth or gel that may be separated, skimmed, or "scraped" from
near the surface of a tank
of a clarification unit 16. By the same token, smaller particles that are not
involved in flocculation,
and thus have not entrained air, or trapped air or other lighter species, may
simply drift downward to
the bottom of such a tank, becoming sediment. Various types of scrapers may
operate near the top of
such a tank in order to remove lighter compounds and mixtures. Meanwhile,
augers and the like may
remove heavy sediments settled out at the bottom of the clarification unit 16.
A post processing unit 18 may provide additional steps in remediating a flow.
Typically, post
processing units 18 may include desalinization, reverse osmosis, and other
types of purification
processes. Such processes executed by post processing units 18, which may be
included as one or
more individual process units 18, are typically directed to preparing a
remediated stream for its specific
use.
For example, reinjection of production water from petroleous production does
not require
removing salt. Thus, brines are often suitable for reinjection. Nevertheless,
if water is being prepared
for irrigation, culinary purposes, or the like, then desalinization and other
processes may be included in
a post processing unit 18.
Any type of post processing 18, including those referenced in the prior art as
final "polishing
steps" or processes may be included. The operating specifications will tell
what is required as the
output of a system 10 in accordance with the invention. Nevertheless, as a
practical matter, a system
10 may be used in combination with a variety of other prior art systems, in
order to accomplish the
functions of those prior art systems. Thus, the existence or utility of such a
prior art system does not
obviate the utility and special functionality of a system 10 in accordance
with the invention.
A major distinction between an apparatus and method in accordance with the
invention and
prior art systems for removing heavy metals from waste water treatment streams
is the isolation of the
ion generator 12 in order to maximize ion generation. In contradistinction to
prior art systems, there is
not a direct balancing, in a single vessel, of the ion generation function of
the ion generator 12 and the
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precipitation reaction processes of the precipitation reactor 14. Rather, each
of these is designed,
sized, and optimized for its own function, within its own environment, and its
own respective, isolated,
system 12, 14.
In general, waste water 20 or a feed 20 may be passed into a pump 22 for
raising the pressure in
a downstream line 46. Typically, the pump 22 may be augmented by a bypass line
24 or recirculation
line 24. Herein, one may speak of the line 20, 24, or the flow 20, 24, since
is each is connected to the
other.
In general, a bypass flow 24 or bypass line 24 may be driven by a pump 26.
Typically, a
control valve 28 may be set as a resistance against the free flow in the line
24. Accordingly, the pump
26 may actually be set to pump against the resistance of valve 28. A resulting
flow is added to the
incoming raw water 20 introduced into the ion generator 12 as the flow 30.
The flow 30 may simply be the flow 20 directed into the ion generator 12.
Nevertheless, in
certain situations, concentration may be desired to be controlled. The bypass
line 24 or recirculation
line 24 may provide recirculation of part of the output of the clarification
unit 16. Thus, the precise
concentration may be provided for one of several reasons.
Briefly, some of those reasons may simply be the capacity of the ion generator
12, the capacity
of the precipitation unit 14, or the capacity of the clarification unit 16. If
concentrations vary, which
they often will between various production units and over time, then increases
may otherwise
overwhelm or overrun portions 12, 14, 16, of the system 10. Instead, the flow
20 may simply be
diluted by recirculating comparatively clean (e.g., cleaned) water in the
recirculation line 24.
Likewise, the ion generator 12 in accordance with the invention is constructed
in a modular
fashion such that additional cells 90 may be added to the ion generator 12.
They may simply be taken
on and off line within a battery of such cells 90 in the ion generator 12.
Thus, the capacity of the ion
generator 12 may be modular even while online, in order to accommodate rapid
variations, need for
dilutions, or the like while still maintaining a specified throughput or
treatment of an incoming raw
waste water stream 20.
The ion generator 12 may be engaged by cells 90 in a modular fashion to
maintain a specific
throughput rate for a precipitation reactor 14. Rather than tying the
capacities of the precipitation
reactor 14 and the ion generator 12 together, each may be adjusted to operate
according to the
parameters or the constitution of the incoming water 20. They may adjust
independently from one
another, in order to maintain each within its preferred operating envelope at
optimal performance.
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The line 34 may include a pH adjuster 31 to add an acid or a base into the
line 34. For
example, acidity may affect reaction rates, solubility of the heavy metal
precipitates, or both. Thus, the
addition of acid or base in the output 34 of the ion generator 12 may be
accomplished, resulting in an
adjusted pH in the line 36 entering the precipitation reactor 14.
By the same token, and for similar reasons, a flocculent source 32 may inject
certain polymers
into the line 34, thus adding to the line 36 additional polymeric materials
effective for IGF, DAF, and
so forth.
The output 34 from the ion generator will eventually, after augmentation by
the pH adjuster 31
flocculent source 32 pass into the precipitation reactor 14. The entire
quantity or content of the line 34
will typically pass into the precipitation reactor 14.
The reactor output 38 includes all the content introduced by the output 34
from the ion
generator 12, as well as any constituents from the pH adjuster 31 and the
flocculent source 32, as
modified by reactions and flocculation within the precipitation reactor 14.
Therefore, the clarification
unit 16 may include not only an output 39 of the cleaned water stream, but an
output 41 of the lighter
materials removed from the top of the unit 16, and the heavy sediments as an
output 42 from the
bottom of the unit 16. Thus, after the post processing unit 18 may have
further processed the output
39, the final output 40 is the flow of "cleaned" water output from the system
10, and suitable for the
designated use.
A current source 50 is electrically connected to the ion generator 12. Each
cell within the ion
generator 12 receives current through the line 54 (positive charge, in an
electrical engineering
convention), and electrons in the electrical line 52 (physicist, electron
point of view). As a practical
matter, the current source 50 may be configured in a variety of forms.
Typically, sensors within the
ion generator 12, or elsewhere may detect voltage drops or other variations in
voltage as a result of
changes of conditions. For example, a sacrificial anode may decay with
time, increasing
distance to the cathode, thus altering the required voltage required to
maintain current. Nevertheless,
by whatever control mechanism is implemented, of which several are available,
the current source 50
generates a current set and maintained at an operational level.
In general, the current source 50 is designed to provide a flow of electrons
sufficient to liberate
from a sacrificial anode, the metallic ions, according to the charge of each.
Thus, for example, in one
embodiment, an aluminum rod may act as the sacrificial anode. Accordingly,
three electrons are
required to liberate an aluminum ion from the matrix of the metal, or the
close association with its
metallic, atomic neighbors. The current source 50 may be designed to provide
that amount of
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electrical charge (remove that many electrons) required to generate the
required number of ions (e.g.,
aluminum ions). The number of ions released is the number required to support
the eventual
precipitation of the requisite number of incoming heavy metal ions. The
current and sacrificial ions
balance the reaction constituting the incoming flow 20. Both types exit the
ion generator 12, then react
in the precipitation reactor 14.
Referring to Figure 2, while continuing to refer generally to Figures 1
through 10, a process 60
represents a chemical reaction as a chain 60 of individual, intermediate,
chemical reactions. In the
illustrated embodiment, the various interactions are statistical in nature.
For example, an aluminum
ion 65 may leave a sacrificial anode 92 and be resident in an aqueous
solution. On the other hand,
statistically, periodically, certain of those ions may actually re-embed in
the anode 92 or combined
with other atoms. Nevertheless, in the main, on a statistically calculable
basis, the various illustrated
processes will take place at calculable rates.
For example, a continuous ion-generation process 62 constitutes the upper
portion of the
process 60 of Figure 2. This generation process 62 occurs within the ion
generator 12. The current
provided by the current source 50 into the anode 92 introduces ions into the
source water 30 ion
generator 12.
The precipitation reaction process 64 represents a series of reactions
occurring in the
precipitation reactor 14. In contradistinction to prior art systems (e.g., EC
systems), manipulation of
the acidity, or the pH in general, need not be reckoned before the output 34
of the ion generator 12.
The acidic nature of certain waters 20 introduced into any reclamation system
may tend to maintain,
fortify, reduce, inhibit, or otherwise interfere with the processes in the
precipitation reactor 14.
According to convention, acids may be introduced to lower the pH in prior art
systems. Specifically,
acid may resist scaling or coating of anodes 92 in the ion generator 12. Prior
art systems do not isolate
an ion generator 12, but maintain some type of combined reaction system. Thus,
in order to reduce
coating of an anode 92 with insulating precipitants, acid may be introduced,
thus reducing the pH,
acidifying the water 30, and scavenging free hydroxide ions 63 within the
system 10.
In the illustrated embodiment, a particular metal, such as aluminum, may be
introduced as an
ion 65 in a solution of water molecules 67. By increasing the availability 66
of the aluminum ion 65 in
the water 67, a reaction 68 may be initiated. In the illustrated embodiment,
an aluminum ion 65 may
combine with a hydroxide ion 63 derived from the water 67. This leaves a free
hydrogen ion 69 in
solution.
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Meanwhile, the aluminum hydroxide ion 70 becoming available 72 to additional
water
molecules 71 undergoes a reaction 74 in which the aluminum hydroxide ion 75
now contains multiple
hydroxide ions with the aluminum ion 65.
The reaction 74 leaves another free hydrogen atom 76. Meanwhile, additional
availability 78
of aluminum ions 77 results in a reaction 80 that continues to add hydroxyl
groups or ions to a
compound 81 or ion 81. However, in the illustrated embodiment, additional ions
77 may react 80 with
the aluminum hydroxide 75 to create larger compounds 81 of aluminum and
hydroxides.
Ultimately, the availability 82 of other metal ions 83, such as heavy metal
ions 83 results in a
reaction 84 by the metal ion 83 with the compound 81 or ion 81. The result is
the compound 85. At
this point, one may question just how strong each individual bond is as the
hydroxide ions, aluminum
ions, other metal ions, and so forth continue to agglomerate. The settling of
such compounds 85 will
be driven, to a certain extent, by their density as sediments. However,
ongoing reactions 86 continue
to make larger compounds 87, held together by weaker and weaker forces.
As a practical matter, the early reaction 68 is largely ionic in nature. Thus,
the compound 70 of
aluminum hydroxide, although still ionic in nature and unbalanced in charge,
is maintained by a
comparatively large, ionic force. However, the continued precipitation of the
compound 81, and more
so the compound 85, results in much lower strength bonds. Ultimately, the long
chains of the end
compounds 87 may actually be "bonded" more by Van der Waal's forces. Thus, a
system 10 in
accordance with the invention recognizes the dichotomy in requirements for
maximum generation of
ions 65 versus maximum precipitation. Countervailing principles control clean
ionization into hyper-
turbulent flows, versus the limited amount of disruption to which a large
compound 87 may be
subjected during reaction and growth.
Referring to Figure 3, an individual cell 90 within an ion generator 12 may
define the line 89 of
radial symmetry. In the illustrated embodiment, a radius 91, in general, may
be defined as a distance
from the center line 89. In the illustrated embodiment, an anode 92 may be
configured as a rod 92 or a
cylinder 92 of consistent length, and having a surface 93 that stands
electrically opposite to a surface
95 of a cathode 94. The cathode 94 is electrically isolated from the anode 92
(at least as for direct
current exchange). Thus, the surface 93 of the anode 92 and the surface 95 of
the cathode 94 will pass
current through the intervening fluid within the lumen 96 or annulus 96 of the
cell 90.
Typically, a radius 97 represents the inside radius 97 of a tube 94 that acts
as a cathode 94.
Here, a cylindrical geometry, or a right-circular-cylindrical geometry,
defines each cell 90.
Accordingly, an anode 92, and specifically its outer surface 93 establishes
with the inner surface 95 of
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a cathode 94 at a radius 97 the annular space 96 in which the fluid 30 will
flow. Thus, a lumen 96 or
annulus 96 is defined by those radii 97, 111 between the surface 93 and the
surface 95. They define
the lumen 96 or annulus 96 of the system 10, and particularly each cell 90 of
the ion generator 12
within the system 10.
Typically, a hydrodynamic boundary layer 98 will be created near a surface 93.
According to
boundary layer theory, a molecule of a liquid is, nevertheless, stationary at
a stationary wall or other
interference. The thickness 99 of a hydrodynamic boundary layer 98 will be
established by the fluid
properties of any fluid flowing through the lumen 96.
A diffusion boundary layer 100 will also be established, but typically extends
to a location
different from the hydrodynamic boundary layer 104. In the illustrated
embodiment, a thickness 107
of the diffusion boundary layer 106 will identify exactly how far chemical
diffusion will extend, or
how far a concentration gradient of an ion 76 will persist.
Typically, a diffusion boundary layer 106 may have a thickness 107 dictated
partially by
hydrodynamics, and partially by the chemical concentration of materials. For
example, a convection
component tends to provide mixing in certain regions nearer the bulk center.
By contrast, other
regions near solid surfaces 95 tend to be dominated by simple, straightforward
diffusion of species. In
this case, the aluminum ion 65 is being released at highest concentration at
the anode 92.
Typically, one may define a diffusion boundary layer 106 as including the
hydrodynamic
boundary layer 104 but going further, into a buffer zone 108. The buffer zone
108 may be thought of
as a region 108 of transition in which micro eddies or small-scale turbulence
provides additional
convection between a laminar region 98, and the somewhat circulating,
convecting region 102.
The thickness 109 near the cathode 94 need not be the same size as the
thickness 103 of the
buffer zone 102. Stated another way, each of the zones 108 and 102 is a buffer
zone 108, 102,
respectively. Yet, each is affected by the diffusion of its species, including
metal ions at the anode 92,
and hydrogen ions at the cathode 94.
Typically, a velocity 110 of the bulk flow 130 results in a bulk plug flow
130. For example, a
velocity 110 across virtually the entire expanse of the lumen 96 results in a
very flat profile 112.
The flow of a remediated fluid in a cell 90 will typically be a bulk plug flow
130 through an
annulus 96 or lumen 96 defined by a radius 97 and the radius 111 of the right,
circular cylinder that is
the sacrificial anode 92. Typically, the velocity 110 of the fluid within the
lumen 96 generates a
velocity profile 112 that spans from the radius 111 at a wall face 93 to the
radius 97 at the face 95 on
the wall 94 that forms the cathode 94.
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Note that these polarities need not change in the apparatus 10 in accordance
with the invention.
Instead, hyper-turbulence prevents flocculation and resists precipitation. The
diffusion boundary layer
100 extends a comparatively short distance 101 from the face 93 of the anode
92. Thus, the boundaries
93, 125, define the diffusion boundary layer 100. Similarly, the boundaries
93, 123 establish the
hydrodynamic boundary layer 98 between the face 93 and the boundary 123.
Similarly, at the opposite electrode 94, where the wall 94 of a tube operates
as a cathode 94, the
hydrodynamic boundary layer 104 may have a distinct thickness 105. Likewise,
the diffusion
boundary layer 106 may have its own distinct thickness 107. The fact that
hydrogen is being
reconstituted at the cathode 94, while ions 65 are leaving the anode 92, with
ions 113 being generated
in the flow 130 will dramatically affect the response, and consequent
diffusion layers 100, 106.
In either case, a buffer zone 102, 108 may be thought of as a region 102, 108
of thickness 103,
109, respectively, wherein the hydrodynamic boundary layer 98, 104 is
effectively absent, yet the fully
involved turbulence may not yet be present. A laminar flow 122 will exist
within each of the boundary
layers 98, 104. Typically, the concentration 114 of hydrogen ions is reflected
in the profile 116
extending a distance 115 from the face 95 of the cathode 94. Meanwhile, the
aluminum concentration
120 may be reflected in a profile 118 of concentration within the lumen 96.
Thus, in general, a hydrodynamic profile 112 reflects the variation in
velocity 110 within the
bulk flow 130 or which becomes bulk plug flow 130 within a lumen 96.
Meanwhile, the laminar
boundary layers 98, 104 reflect the dramatic variation in velocity radially
across a region 98, 104.
The buffer layers 124 proximate either surface 93, 95 each represent a
transition in which ions
are eventually diffused to have a uniform concentration 120 reflected in the
flat profile 118, similar to
the flat profile 110 of a fully developed velocity. Similarly, near the
cathode 94, within some distance
115 may be a concentration 114 of hydrogen ions 116.
The regions 98, 102, 104, 106 are thus defined by the boundaries 93, 123, 125,
95, 127, 128.
Meanwhile, the buffer layers 102, 109 are defined by their adjacent boundaries
123, 125, and 127, 128,
respectively.
Typically, the distances 100, 107 are comparatively small, on the order of
less than ten percent,
and often less than one percent of the overall radius 97 across the lumen 96.
Thus, the profiles 112,
116, 118 develop comparatively quickly (e.g., close to solid objects 92, 94).
One reason for the existence of the upper zones 103, 108, is the nature of the
distinction
between laminar flow 122 and bulk, turbulent, plug flow 130. The regions 102,
108 involve turbulent
eddies 124 in transition. Meanwhile, the turbulent eddies 124 represent the
transition between the
27
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laminar flow 122 within the regions 98, 104. The bulk plug flow 130 of the
system 10 reflects the bulk
turbulence 126 or large, turbulent circulations with no net motion except
axial flow.
In contradistinction to prior art electro coagulation (EC) systems and
processes, a system 10 in
accordance with the invention relies on the ion generator 12 maintaining plug
flow. Plug flow is so
absolutely dominated by turbulence throughout that the hydrodynamic boundary
layers 98, 104
represent an insignificant fraction of the overall flow 130 in the lumen 96.
This causes the flat velocity
profile 112 in which the velocity 110 throughout the lumen 96 may be assumed
to be the maximum
velocity 110, to the exclusion of the laminar flow 122 existing in the
hydrodynamic boundary layers
98, 104.
The result of plug flow 130 in the lumen 96 of the cells 90 in the ion
generator 12 is that the
micro turbulence 124 in the buffer region 108 effectively sweeps clear all
ions generated at the surface
93 of the sacrificial anode 92. They are carried through the diffusion
boundary layer 100. In fact, the
actual diffusion process actually occurs almost exclusively within the laminar
hydrodynamic boundary
layer 98. In the buffer region 102, the convection of micro turbulence 124
rapidly mixes all
constituents, thus bringing the concentration 120 of the sacrificial ions 65
(e.g., aluminum 65, in the
illustrated example) up to the level of the bulk profile 118 thereof as
illustrated.
This bulk plug flow 130 is maintained pervasively across substantially the
entire radius 97 of
the annulus 96 or lumen 96. It is also typically maintained throughout the
entire length of each cell 90,
from inlet to outlet thereof, particularly the length of the anode 92.
This sustained, persistent, pervasive bulk plug flow 130 cannot be achieved in
plate types of
systems as known in the prior art. Stagnation, back eddies, dead spaces, wide
disparity in velocity
profile, and the like, are not permitting of this flow. Moreover, geometries
preclude such uniformity.
In contradistinction to other prior art attempts at agitation, "turbulence,"
or other periodic or
location-specific turbulence, plug flow turbulence is a direct consequence of
maintaining specific
conditions at a comparatively very high rate of flow. This means a very high
Reynolds number (where
Reynolds number is density multiplied by velocity and a significant length,
such as a diameter,
hydraulic diameter, or the like, all divided by the viscosity of a fluid) at
values well into the turbulent
region.
Flow near the critical zone of the transition region does not qualify, and
will not develop bulk
plug flow 130. Thus, whereas the word "turbulence" or "agitation" may be
tossed about in prior art, it
is clear that such systems as described in prior art references simply do not
maintain, cannot maintain,
do not suggest, and do not rely on nor benefit from bulk plug flow 130 driven
by hyper-turbulence.
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Typically, in a system 10 in accordance with the invention, Reynolds numbers
are maintained above
values of five thousand, and typically at values of more than ten thousand.
Thus, in a system 10 in
accordance with the invention, Reynolds numbers on the order of twenty to
thirty thousand, or more
are typical. Thus, this is a full order of magnitude larger than the initial
value of Reynolds number in
the critical zone of the transition region, which starts at about two
thousand. At that point, laminar
flow begins to be left behind and transition begins. Typically, turbulence is
fully developed beyond
the critical zone at a Reynolds number of about five thousand. Here, Reynolds
numbers of many times
that value assure bulk plug flow 130.
The ultimate effect of bulk plug flow 130 in the lumen 96, is a reduction,
virtually to the point
of eradication, of any effective coating of a cathode 94. Precipitation and
inward, radial diffusion of
ions 65 from the sacrificial anode 92 by any reactants or precipitants simply
has no mechanism. The
ionic reactions of metals of any type (sacrificial or heavy metals to be
removed) from the incoming
water stream 20 is resisted by the flood of ion 65 and paucity of electrons.
Hence, the ion generator 12
is maintained under hydrodynamic, electrical, and chemical conditions to
assure that it is substantially
exclusively an ion generator 12. This occurs to the exclusion of precipitation
reactions. They are
reserved for the precipitation reactor 14. Any pretreatment requirements,
acidification, or other
prophylactics to forestall, slow, or retard precipitation reactions do not
occur here as in other prior art
systems that do not maintain flows within these Reynolds number ranges.
The order of magnitude of the thickness 99 of the hydrodynamic boundary layer
98 may be of
the order of magnitude of the buffer layer 102. Thus, the incursion of
precipitants is effectively
prohibited. The laminar flow 122 is still vigorous with high shear stress, but
is thinned down by the
bulk plug flow 130. Thus, the opportunity for any statistically significant
diffusion in a reverse
direction by precipitants toward the face 93 of the anode 92 has been
virtually eradicated.
Accordingly, coating out of precipitants on the sacrificial anode 92, is
effectively precluded at any
significant quantity or with any significant persistence.
Thus, scrubbing, although effectively present, by the vigorous flow 130 in the
lumen 96, need
not even be relied upon. Rather, the reverse diffusion of chemical species
toward the anode 92, as it
donates its entire surface 93 in ions, simply does not brook any coating out
of precipitants on
electrodes 92, 94. Moreover, the high power densities, the net current driven
(electrons received) by
the current source 50 into the anode 92, weights the reaction, or the ionic
formation process in favor of
driving aluminum ions 65 from the anode 92 into the bulk plug flow 130.
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Coating (which depends on quiescence, or laggard, laminar flows and
stagnation) simply is not
permitted at any measurable or calculable rate. As a practical matter the mass
transport and
electrochemical balance in the region 98 is so dominating and so matched to
the ability of the bulk
plug flow 130 to carry away the ions, that no species of heavy metals in the
bulk flow 130 can migrate
to the surface 93 at any appreciable rate.
Ions near the electrodes 92 are immediately treated as the ions leaving the
anode 92, themselves
losing, not gaining, electrons. Thus, there is effectively no point at which a
precipitated heavy metal
ion can land. Hence, in experiments operated by Applicants, the pitting common
to electrodes in
conventional electro coagulation systems was completely absent. A precisely,
electrodynamically
machined, outer surface 93 persisted at all radii 111 of the anode 92, from
new installation, to complete
decimation. Thus, a system 10 in accordance with the invention provides
electrostatic machining of
the sacrificial anode 92, as precisely and effectively as electrodynamically
machining (EDM) in the
manufacturing industry.
An apparatus and method in accordance with the invention rely on the bulk plug
flow 130 as a
flow regime that is so hyper-turbulent that it virtually precludes any
precipitation reaction within the
ion generator 12. For example, (e.g., EC) prior art systems typically rely on
a tank of some
configuration in which generation of ions from a sacrificial anode occurs in
the same continuous and
contiguous medium as the precipitation and coagulation reactions. Large
molecules or ions are made
up of multiple metal ions and hydroxide ions. Isolation of the ion generation,
as created in the ion
generator 12, from the precipitation reactor 14 and its precipitation
reaction, is impossible in typical
prior art approaches.
In an apparatus and method in accordance with the invention, the incoming flow
30 received by
the ion generator 12 does not include any manipulation of the pH (basic or
acidic nature) of the
influent water 20. Rather than manipulate the pH to make the flow 30 more
acid, an ion generator 12
in accordance with the invention hydrodynamically isolates heavy metal ions,
that are to be removed
from the flow 130, from the sacrificial anode 92.
For example, the hydrodynamic boundary layer 98 is so vigorous in its
hydrodynamic intensity,
that migration of ions of heavy metals from the flow 130 to the anode 92 is
effectively eliminated.
First, the anode 92 is contributing sacrificial ions 65 at the maximum
possible rate available based on
the current source 50. The approach of some random heavy metal ions may be
occasioned due to the
fact that the flow 30 does contain those ions. Accordingly, any metal ions 83
in the liquid in the
hydrodynamic boundary layer 98 will be treated by the anode 92 as if they were
the same as the ions
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65. The anode 92 will simply receive an electron from that metal, and return
it into the flow 130 as a
metal ion.
Moreover, any compound in which a heavy metal may be found in the flow 130
might
approach the anode 92, but would immediately be subjected to the electrostatic
potential available
from the anode 92, ionizing the compound, and dismembering the ions or atoms
from one another.
Thus, the electrostatic potential near the anode 92 tends to drive metal ions
into solution, not
precipitate them out. The fact that the diffusion boundary layer 100 and the
hydrodynamic boundary
layer 98 are so comparatively thin compared to the overall radius 97 between
the anode 92 and the
cathode 94, militates against any precipitation and coagulation.
The hyper-turbulence occasioned by the extremely high (comparatively; on the
order of ten to
thirty thousand, typically) Reynolds number within the flow 130 presents so
much shear in the laminar
flow 122, as to overcome any Van der Waal's forces that might exist due to any
of the reactions 64.
That is, the agglomeration of ions by forces weaker than ionic attractions are
overcome by the
mechanical shear forces existing between stream lines in the laminar flow 122
of the hydrodynamic
boundary layer 98. Thus, precipitation and flocculation are effectively
precluded mechanically and
electrically within the ion generator 12.
The cross-sectional area is substantially constant along the entire length of
each cell 90. There
is no appreciable change in velocity or direction along the length thereof.
This results in a uniformly
severe condition of shear in the hydrodynamic boundary layer 98. Thus, each
cell 90 provides a
hydrodynamically isolated ion generator 12 completely separated from the
precipitation reactor 14 and
its processes. Mechanically, the precipitation reactor 14 is a different
physical containment structure.
However, the very processes of the reactions 64 are precluded by the vigor of
the boundary layers 98,
100, the high rate of viscous shear therein, and the inability of any
agglomeration of precipitants to
mechanically survive. Thus, the inertial forces as represented in the Reynolds
number completely
dominate, and will reverse if present, any agglomeration due to Van der Waal's
forces or other
similarly weak attraction.
Referring to Figure 4, reactions 140 are illustrated schematically. Individual
reactions 140, or
individual instances of the reactions 140 include a release 142 of a metal ion
65, shown here as an
aluminum ion 65 occur at an anode 92. Electrons 144 driven by a power source
50 through the lines
52, 54 facilitate the reaction 142, converting elemental aluminum to aluminum
ions 65.
Meanwhile, a migration 146 may be thought of as a reaction 146 inasmuch as the
hydrogen
ions 69, 76 from the flow or fluid carrier in which ions 65, 69, 76 are
present may involve several
31
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reactions intermediate the anode 92 and the cathode 94. Those reactions result
in a certain degree of
electrophoresis. That is, ions 65, 69, 76, will tend to drift or diffuse,
under electrostatic force, through
the carrier liquid (e.g., water). Also, reactions may occur at one location,
facilitating release of
electrons, facilitating other reactions elsewhere. Hydrogen ions 69, 76 may or
may not originate near
the anode 92 or the cathode 94. On the other hand, the ultimate reaction that
provides the ions 69, 76
may simply be the last in a long chain, dependent upon the rapid transfer of
electrons between various
species and solution.
The result is a donation 146 of the hydrogen ions 69, 76 at the cathode 94
where electrons are
available for facilitating a reaction 148 generating hydrogen molecules 147.
The equation 143 governs
the generation 142 or reaction 142 creating aluminum ions 65. Meanwhile, the
reaction 149 governs
the conversion of hydrogen ions 69, 76 with the electrons to form hydrogen gas
147 or hydrogen
molecules 147 at the cathode 94. This completes the reaction 148 of the
equation 149.
The electrons 144 are released to an anode 92. It accepts electrons from the
elemental
aluminum, causing generation of the aluminum ion 65. Meanwhile, the lines 52,
54 carry those
electrons to the cathode 94, where they may readily donated to hydrogen ions
69, 76, resulting in
neutralization of their charge, and their stabilization in a covalent bond in
the hydrogen molecule 147.
Referring to Figure 5, the mass transfer (transport) limit 158 depends on such
dimensionless
parameters (well defined in the fluid mechanics and the heat and mass
transport technology) as the
Nusselt number, the Prandtl number, and the Reynolds number as reported in the
heat and mass
transport literature. Properties of consequence are densities, fluid
viscosities, heat transfer areas,
thermal conductivities, specific heat capacities of materials, and so forth.
The correlations between
Reynolds number, Prandtl number, Nusselt number, and other similar
dimensionless parameters that
may be applicable to the establishing of mass transfer limit 158 on the
theoretical basis are not
repeated here, but are available in any suitable text on heat and mass
transport.
The graph 150 is actually one single graph 150 from an entire family of graphs
150. For
example, this graph 150 illustrates the variation of electrical conductivity
154 as a function of current
152 introduced into the ion generator 12, or a cell 90 thereof.
However, the entire family corresponds to different settings for additional
parameters taken as
constants, unvarying throughout the domain of this instant graph 150. Some of
those other parameters
will vary, thus moving into a different plane of operation as represented by
the axes 152, 154.
Parameters may include, for example, the constitution of waste water 20 being
treated. Another such
parameter that is fixed for the purposes of the graph 150 is the actual
volumetric flow rate Q (Q dot).
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Others are the material properties and geometries associated with the Reynolds
number, Prandtl
number, and Nusselt number, and so forth. For example, density, viscosity,
significant length, thermal
conductivity, specific heat, and the like are considered non-variant for the
chart 150. Variation of one
or more of those parameters may generate a different chart 150, and
specifically a different curve 160.
The experiments conducted by Applicant demonstrate the existence of the curve
160, and the
qualitative relationship illustrated in the chart 150. In the illustrated
embodiment, the curve 160 has a
slope 162 or tangent 162 at any and every point. The slope 162 represents the
rate of change of the
curve 160 at the point of tangency. Several tangent points 160, 164, 168, 170
are illustrated. Each has
significance.
For example, the point 164 represents an optimum 164, or an operational point
164 that
balances several competing considerations. Meanwhile, the boundary line 165
defined by the optimum
164 establishes a region 166 of all electrical current levels greater than
that associated with the point
164. This region 166 represents a region in which excessive power usage from
the current source 50
will be likely if additional power is drawn.
Accordingly, in currently constituted embodiments used in experimentation, a
length of a cell,
and thus the length of an anode 92 and the effective length of an ion
generator 12 have been defined.
The annulus 96 between the anode 92 and the cathode 94 or the tube 94
surrounding the anode 92 is
defined. Meanwhile, a mass flow rate or volumetric flow rate of fluid based on
the Reynolds number
has been established at a bulk plug flow 130 for the regime.
The fluid properties were identified in accordance with the prevailing
temperatures and so
forth, in order to establish all pertinent fluid parameters. Under these
conditions, the concentration of
the aluminum ion may be directly reflected in the electrical conductivity or
sigma (a) as identified on
the y axis 154 of the graph 150.
Meanwhile, the concentration of the aluminum ion 65 or the donated ion 65 from
the anode 92
is equal to current divided by a constant representing certain material
properties characteristic of the
material of the anode 92. It is also divided by the volumetric mass flow rate.
Of course, the units must
be consistent in order to maintain dimensional consistency throughout the
equation. The result of that
concentration is that the electrical conductivity 154 is also proportional to
that concentration. In fact,
the change in concentration between the maximum concentration in the system
10, and the maximum
electrical conductivity 154 at any point reflects ions removed from solution.
Electrical conductivity is
proportional to a constant times the concentration of the ion in question,
aluminum in this example.
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Thus, the rise in electrical conductivity is proportional to the rise in
concentration of aluminum ion,
multiplied by that constant.
Stated another way, or in consequence thereof, the net electrical conductivity
of a fluid having
a constitution of ions therein is a summation of the individual electrical
conductivities, where each
electrical conductivity is proportional to a constant peculiar to the
material, multiplied by the
concentration of that material in the flow. In order to calibrate back to
reality from this theoretical
calculation, a parameter zeta (). Values of zeta are typically in the range of
from about 0.4 to about
0.7. The value of zeta is proportional to concentration multiplied by a
constant of proportionality
(18.34 for aluminum) multiplied by the volumetric flow rate of water divided
by current and divided
by the molecular weight of the species whose conductivity and concentration
are in question.
The foregoing relationship, when written in mathematical equation form, is the
equation by
which one may determine the initial set point 164 or optimum 164 at which to
operate the system 10.
The operational point 164 represents an optimum according to the
representation that the
precipitation efficiency, called zeta, is equal to the concentration of the
ion in question multiplied by a
constant of proportionality (18.34 for aluminum) and multiplied by the
volumetric flow rate of the
incoming water 20 divided by the current and the molecular weight of the ion
in question. Thus, this
zeta () principally defines the electrical conductivity 154 in the chart 150.
Operation above the point 168 is within a region 169 bounded by the boundary
167 above
which excessive maintenance will be required. Excessive maintenance will be
required because the
system 10 will periodically pass into the fouling region 172 identified by the
point 170, a zero value of
the slope 162, the first derivative 162 of the curve 160.
The boundary 171 defines the region 172 in which fouling will absolutely
occur. Fouling
occurs because the mass transfer limit 158 has been met, and the current is
continuing to increase, thus
creating ion species that will precipitate and foul the anode 92. Meanwhile,
to operate above the point
168, is to add current 152 within the excessive maintenance region 169.
Operation is above the border
167 or boundary 167. Variations in temperature, fluid properties, constitution
of the fluid 20, and the
like may result, and typically will therefore result, in periodic excursions
into the fouling region 172
from the point 168.
Thus, a set point 164 provides a certain amount of protection against such
excursions into the
excessive maintenance region 169, the fouling region 172, or both. Meanwhile,
the marginal increase
in electrical conductivity 154, and thus ions dissolve in solution, above the
point 164 has a diminishing
return. Note the increase in current 152 between the points 164 and 168. Note
the difference in
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electrical conductivity 154 between the points 164 and 168. The marginal
increase in electrical
conductivity 154 as a result of increases in current 152 is simply too
marginal to be worth the risk of
excessive maintenance or fouling.
Likewise, however, the point 174 is operating at a lower current 152. This
results in a lower
electrical conductivity 154 reflecting fewer ions in solution. The region 175
defined by the boundary
173 coincident with the point 174 represents excess capital cost. For example,
too much capacity is
being required as infrastructure, in the way of the ion generator 12
specifically, and probably as well in
the precipitation reactor 14. This excessive infrastructure is due to an
unwillingness to push the
current 152 above the value represented by the point 174.
Meanwhile, the marginal increase in electrical conductivity 154 by increasing
the current above
the value corresponding to the point 174 is significant. This represents
little risk of passing into the
fouling region 172, and thus the region 175 is an excess capital region 175.
Too much infrastructure is
created without being effectively used. Without an undue amount of power
expense, additional current
may be delivered from the current source 50 into each cell to achieve the
increased ion concentrations,
reflected by the electrical conductivity 154, without undue increases in
current 152.
The excessive power region 166 established by the boundary 165 reflects the
fact that the point
164 achieves an optimal value of electrical conductivity 154 (ion
concentration in solution) at a modest
or reasonable input of current 152. Note that the slope 162 begins to drop off
substantially at values of
current 152 above the point 164. For example, above the point 168, almost
no perceptible benefit
in electrical conductivity 154 is achieved, while a substantial increase in
current 152 is required. Thus,
the marginal value of power increases between the points 168 and 170 clearly
militates against
operating anywhere within that range. Meanwhile, the risks discussed
hereinabove are not worth
operating above the point 168. On the other hand, the excessive power region
166 suggests that more
capacity can be built more cheaply than excessive power can be purchased.
This optimization may be done by comparing the economic value in distributed
value of money
over time, present value of expenditure, or simply the advertised cost per
barrel of water treated. Thus,
when the cost-per-barrel of increased power in the excessive power region 166
warrants, then the
additional capital expenditure for adding cells may be warranted.
In one embodiment, cells may be taken offline while in operation. Accordingly,
automatically
switching may simply provide for optimizing the operation at the point 164 or
thereabouts, within
some tolerance region. This may be done in order to maximize the value of
power purchased for
driving the current source 50, while still obtaining maximum dissolved ions as
represented by the
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electrical conductivity 154. Thus, one may optimize economically to find the
point 164 at which the
economics of maintenance, power costs, and capital investment are best
balanced according to
financial considerations or economics.
In certain embodiments, a sensitivity of the curve 160 to variations in flow
rate, current,
operational efficiency, and the like may result in the curve 160 shifting. For
example, the curve 160
may move in a direction 178a if the mass transfer limit 158 or mass transport
limit 158 is reduced.
Similarly, increases in the mass transfer limit 158 or mass transport limit
158 may result in the curve
160 moving higher at the point 170 where contact is made.
Considered another way, a current limit 156 may be controlled by physical
phenomena such as
electrical conductivity, area, current density, and the like. Ultimately, the
current limit 156 may
depend on a variety of physical parameters and physical material properties.
Thus, a point of
intersection 159 at which the current limit 156 intersects the mass transport
limit 158 may actually
move upward or downward. Accordingly, the curve 160 may shift in a direction
178a or a direction of
178b as a result of the change of the mass transfer limit 158.
However, the directions 178a, 178b also represent the process of optimization.
For example,
the current limit 156 is a theoretical limitation on the ability to drive
current 152 through the anode 92
and into the flow 130. Thus the discrepancy measured in the direction of the x
axis 152 or the current
axis 152 between the current limit 156 and the curve 160 represents an
inefficiency. That inefficiency
is measurable as the amount of current 152 that is effectively lost to
ionizing the metal ions 65. It is
consumed in the thermodynamic losses incident to all actual physical
processes.
For example, in accordance with the second law of thermodynamics, a
theoretical limitation on
how a process may occur is a matter of certain analyses. Nevertheless, the
realities of time, space,
material properties, and various losses in processes result in some efficiency
less than the theoretical
maximum. Thus, the current limit 156 may be simply calculated. However, it
will typically never be
achieved in an actual physical system. Rather, the curve 160 is qualitatively
the actual relationship
between conductivity 154 (which represents ions in solution) and the current
152 actually applied to an
anode 92.
In optimizing performance, it is desired to move the curve 160 in a direction
178b, toward the
current limit 156, and the mass transport limit 158. Any failure of the curve
160 to match the curves
156, 158 represents inefficiency. That inefficiency represents the addition of
current between the
operational point 164 and the current limit 156. The ionization or electrical
conductivity 154 lost is
represented by the distance between the point 164 of operation and the mass
transfer limit 158.
36
CA 3058876 2019-10-16
Optimization is desirable and possible in a system 10 in accordance with the
invention. The
processes incident to EC documented in the prior art may be represented by a
depressed or reduced
mass transport limit 158a considerably below the original mass transfer limit
158 of a system 10.
Accordingly, the resulting curve 160a in prior art systems represents the
electrical conductivity in their
quiescent fluids.
For example, prior art systems combine in a single reactor both the processes
of ionization and
precipitation. In fact, many combine the processes in the exact same physical
space between electrode
plates. As a direct result, the curve 160a is limited not only by the current
limit 156, but also by the
reduced mass transfer limit 158a. The difference between the mass transport
limit 158a and the mass
transport limit 158 is a direct consequence of the quiescence of prior art
systems, compared to the
vigorous, hyper-turbulent, high-Reynolds-number flow in the lumen 96 of a cell
90 in accordance with
the invention.
Consequences falling out of that quiescence include a point 170a at which
fouling begins if
current 152 is increased. Thus, the decay in the curve 160a begins at the
point 170a at which the mass
transport limit 158a limits any further ability to benefit from an increase in
the available current 152
supplied. The curve 160a is shifted to a much lower curve and has a zero value
of slope at a point
170a representing a much lower current 152. It also has a higher fraction of
that current devoted to
losses as represented by the distance between the point 170a and the current
limit 156 along the mass
transport limit 158a.
One may note that the optimization of a curve 160a is circumscribed by the
same current limit
156, but at a much lower value of current 152. Likewise, the curve 160a is
limited by the mass
transport limit 158a and is much reduced because of the lack of the hyper-
turbulent convection of plug
flow in the cell 90 of a system 10 available with the invention. Thus, the
point of intersection 159a at
which the current limit 156 intersects the mass transport limit 158a
represents a theoretical optimum or
maximum that the curve 160a may fit.
However, the same thermodynamic limitations exist. Moreover, additional
electrical losses
occur due to the inefficiencies of ion generation. This is a direct result of
the quiescence and the
coexistence of ionization, precipitation, and flocculation in the same
physical space. They act as
retardants to both the process of ionization and the process of precipitation.
Referring to Figure 6, a process 180 for controlling the operational point 164
is illustrated. The
process 180 involves not only an initial selection of an operating point 164,
but also a sensitivity
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CA 3058876 2019-10-16
analysis. A system 10 may perturb the conditions about the point 164, in order
to determine whether it
may be further improved or optimized.
Referring to Figure 6, as a very real and practical matter, conditions for
waste water streams 20
being remediated are not in a steady state condition. Waste water constitution
(the catalog or list of
constituent dissolve solids, salts, heavy metals, and so forth) may vary day
to day and hour to hour as
waste water is delivered by tank, truck, train, pipeline, or the like to a
system 10 in accordance with the
invention.
Therefore, to maintain operation at currents 152 well below the excess
maintenance boundary
167 represented by the point 168, it is imperative that a control mechanism be
developed. In one
embodiment of an apparatus and method in accordance with invention, a process
180 may be used for
continuing monitoring and feedback control of the system 10 in accordance with
the invention.
Initially, determining 181 a metal concentration may involve selection of a
particular metal.
Calculation of the total concentration will be required in order to treat the
particular constitution in a
waste water stream 20.
For example, the concentration of the candidate sacrificial anode metal
required is equal to a
level of current multiplied by the molecular weight of a constituent to be
removed, divided by the
constant relating to the candidate metal (18.34 in the case of aluminum) also
divided by the volumetric
flow rate through the system 10. This is all multiplied by the precipitation
efficiency, zeta.
The system 10 may determine 181 the concentration expected in solution of the
flow 130 for
each and every metal type to be removed from the flow 130 as described
hereinabove. The summation
of the requirements for each metal to be scavenged or removed will result in
the net concentration
required of the sacrificial metal ions 65 to be constituted in the anode 92.
Next, determining 182 a maximum current 152, or the current corresponding to
the operating
point 164, involves additional equations expressing the relationship between
the incoming waste water
stream 20 and its constitution, from the water analysis report. Also, the
current is a function of
experimental data indicating operation of theoretical equations as discussed
herein, the concentration
of the sacrificial metal, and so forth.
One may note that the precipitation efficiency, zeta, is a rating factor or
reality factor adjusting
theoretical numbers. Thus, such empirical information will reveal the value of
zeta. In initial analyses,
a value of zeta within the range from about 0.4 to about 0.7 may be selected,
and parametric variations
may be run to establish the range of the variables effecting the current 152
at the set point or
operational point 164.
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Next, a system may be put in operation and the current 152 may be set at a
value corresponding
to the point 164 as determined from the step 182. Setting 183 the current 152
may be followed by
starting 184 the system 10 and running it to a steady state condition. The
electrical conductivity 154
will be a constant without substantial variation for a particular flow rate of
a constitution involved with
the water 20 being remediated. Steady state simply means that the system has
come to an operating
point 164 that is not varying substantially over time. As a practical matter,
the conductivity at the
outlet 38 of the precipitation reactor 14 should likewise be a constant. In
other words, the system is
operating at a steady state.
Measuring 185 the electrical conductivity 154, at the inlet flow 30 into the
ion generator 12, as
well as the maximum electrical conductivity 154 at the outlet line 34 of the
ion generator 12 will
establish a point 164. The pH adjuster 31 and flocculent polymer source 32
should not affect the
electrical conductivity 154.
Similarly, the electrical conductivity 154 at the outlet 38 of the
precipitation reactor 14 can also
be measured. An effective electrical conductivity 154 change or delta (6) will
be the difference
between the electrical conductivity 154 in the outlet 38 from the
precipitation reactor 14 less the initial
electrical conductivity 154 at the inlet line 30 to the ion generator 12.
Testing 186 determines whether the delta or change in electrical conductivity
154 is greater
than zero. If so, then the operational point 164 is to the left of the point
170 on the chart 150 of Figure
5. If, for any reason, the change in electrical conductivity 154 is near zero
or negative, the system 10
should be shut down immediately and evaluated against the water analysis
report and the theoretical
operating point 164.
The reason for this is that a negative slope 162 on the curve 160 indicates
that operation has
drifted into the fouling region 172. This is inappropriate, intolerable, and
contrary to the design
concept for a system 10 in accordance with the invention. Alternatively, a
value of about zero,
without a negative value may indicate that no change in conductivity is
occurring. Thus, no heavy
metals are present to which to bond, and no heavy metals are present to alter
conductivity. The
presence of the sacrificial metal ions 65 is not effective to remove non-
present target metals. This
indicates as a general proposition a change in the constitution of the
influent 20.
A process 180 may include setting 187 a current at a high or incremented
value. This
corresponds to moving current to the right from the point 164 along the curve
160. Accordingly, some
incremental increase in current 152 may be added to the current at the point
164, with a consequent
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CA 3058876 2019-10-16
movement of the operational point 164 to the right along the curve 160. This
may be chosen as some
fraction, such as a small percentage or small fraction on the order of five,
ten, or fifteen percent.
Typically, one desires to not perturb the current 152 beyond the point 164 to
approach a point
168. Definitely anathema is to pass the point 170. This will not destroy the
system, but will cause
immediate incipience of fouling in the system. Fouling is difficult to recover
from, and an apparatus
and method in accordance with the invention should effectively eradicate
fouling. Thus, there is really
no percentage in operating under fouling conditions.
Next, measuring 188 the electrical conductivity 154 at the outlet 38 reflects
the electrical
conductivity 154 on the curve 160. This indicates how far the point 164 has
moved upward and to the
right along the curve 160. Similarly, setting 189 the current 152 at a value
departing from the initial
position of the point 164, downward to the left, represents a negative
increment or a decrement in the
current 152. This may similarly be done as a proportion or fraction of the
current 152 at the point 164.
Measuring 190 the electrical conductivity 154 at this new value of the point
164 will result in a
new slope 162, as well as a new value of conductivity 154. Stated another way,
both the value of
conductivity 154, and the rate of change of conductivity about the point 164,
have now been
determined. Accordingly, an analysis 191 involves computing and comparing the
slope to the left of
the initial point 164, to the slope to the right. This will indicate where on
the curve 160 the point 164
is relative to such pivotal points as the point 174, the point 168, the point
170, and so forth.
Here, the change in electrical conductivity 154 may represent the
perturbations about the point
164. The points 176 corresponds to an increase in current 152, and the point
171 corresponds to a
decrease in current 152. Thus, if the difference in electrical conductivity
154 between the points 176
and 164 divided by or per the amount of change in the current 152
therebetween, becomes negative,
then operation is transferred into the fouling region 172.
Nevertheless, a value of difference in electrical conductivity 154 per
difference in current 152
may be represented as a fraction for the point 176, and a different fraction
for the point 177. If either
of the slopes 162 corresponding to either of the points 177, 176 is negative,
then the system 10 is in the
fouling region 172. It should be shut off, and the process 180 should be begun
with new information
and evaluation of the system 10. Meanwhile, the slopes 162 corresponding to
the points 176 and 177
should actually be decreasing in value with increased current 152. Thus, the
curve 160 should be
changing in slope, decreasing in slope, flattening out, and approaching the
point 170.
In one embodiment, a fraction of the slope 162 of the current limit 156 may be
used. For
example, if a slope 162 has decreased to less than about one third, then the
trade off of electrical
CA 3058876 2019-10-16
conductivity 154 for current 152 is particularly poor. Stated another way, the
marginal value of an
increase in current 152 is a very limited increase in electrical conductivity
154, and thus in the
presence of additional ions 65. After a few tests, and a sensitivity analysis
for different ranges of
constituents in the incoming water 20, a specific fraction may be selected.
The slope 162 should never
be allowed to decline below that fraction of the initial current limit 156.
This depends very much on
the sensitivity of the system 10 to the changes in temperature, fluid
properties, constitution of the
incoming influent stream 20, and so forth.
Adjusting 192 current 152 for the point 164 may be thought of as a function of
the ratio of the
slopes 162 corresponding to the points 176 and 177. Likewise, the net change
in the functional value,
that is, the actual electrical conductivity 154, is also an independent
variable on which the adjusted
current 152 will depend. Typically, adjustment 192 may be based on experiment,
theory, or curve fits
according to "numerical methods." That term of art is well understood and
defined in the arts of
mathematics and engineering modeling.
In one embodiment, a threshold minimum slope 162 may be established, even
somewhat
arbitrarily. For example, one third of the slope 162 of the current limit line
156 should be a reasonable
proportion, based on the principle of cosines. That is, most of the benefit to
be achieved along the
curve 160 is achieved well before the point 170 of a zero value of slope 162.
A return 193 to continuing operation will typically involve a return 193 to
the step 184 of
running the system 10 in a steady state. Periodic repetition of the steps 184
through 192 will maintain
the system 10 sensitive to and responsive to changes in environment,
constitution of the incoming
water stream 20, and so forth. Meanwhile, the intrinsic material properties or
fluid properties such as
viscosity, density, and so forth as they may be affected by temperature and
constitution may also be
factored into the sensitivity analysis of the method 180 or process 180.
Referring to Figure 7, while continuing to refer generally to Figures 1
through 10, a chart 194
or graph 194 illustrates an origin 195 at which a distance axis 196 identified
as x intersects a
conductivity axis 198 representing electrical conductivity 154. Electrical
conductivity may be
measured in micro Siemens per centimeter. Similarly, conductivity 154 may be
described in terms of
inverse Ohms per unit distance. In the graph 194, the data rise 199 represents
an offset 199 between
the origin 195 and an initial value of electrical conductivity 154.
The point 202 represents a starting point 202 or an initial value 202 of
electrical conductivity
198. Within the ion generator 12, the curve 203, which is linear, typically,
progresses with an increase
in distance 196 along the length of a cell 90 of the ion generator 12 to a
maximum value 204.
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CA 3058876 2019-10-16
In the illustrated embodiment, the electrical conductivity at the point 204 is
a function of the
mass flow rate, the current, the type of material at the anode, as well as the
constitution (e.g., the
overall suite of constituents within the incoming water 20), and so forth.
In fact, the data rise 199 reflects the electrical conductivity 154 of an
initial stream 20 passed
into the ion generator 12 through the flow 30. Thus, the electrical
conductivity 198 at the point 202
reflects any number of constituents that may have an effect on electrical
conductivity thereof Thus,
the rise in electrical conductivity 198 between the points 202 and 204
represents the increase in
electrical conductivity as a result of adding ions 65 from the sacrificial
anode 92. Thus, the linearity of
the curve 203 is following the current limit curve 156 of Figure 5. A
correspondence exists.
Nevertheless, as illustrated in Figure 5, the curve 160 departs from the
current limit 156. Thus,
the curve 203 may depart somewhat from an exact linearity, or from a slope
exactly consistent with the
current limit 156.
Nevertheless, the increase in electrical conductivity 198 between the points
202 and 204 is a
direct function or has a direct variation with flow rate, current, and the
length of the anode. Each of
these directly affects, and thus is directly proportional to, the increase in
electrical conductivity 198 in
traversing a curve 203 to the point 204.
The decay curves 205a, 205b, 205c are simply instances of a generalized decay
curve 205.
Thus, herein it is proper to speak of all the curves 205, or any numbered item
according to that
reference numeral. Meanwhile, a trailing letter simply means a specific
instance of the item
corresponding to the reference numeral. Thus, it is proper to illustrate,
refer to, or designate using a
trailing reference letter or to refer only to the generalized reference
numeral.
The decay curves 205a, 205b, 205c refer to different conditions that depend on
the incoming
water 20 to be treated. For example, the curve 205a represents clean water
absent brine, such as
sodium chloride, and without heavy metals. Accordingly, the rise in electrical
conductivity 198 to the
point 204 is entirely due to the addition of the sacrificial anode ions 65.
Meanwhile, the drop in
electrical conductivity indicates that the heavy metal content has been
eliminated by the ion generator
12 and precipitation reactor 14. Thus, the value of the electrical
conductivity drops to the lowest value,
reflected by the point 206a.
Similarly, the curve 205b represents brine containing heavy metals.
Accordingly, upon
increase of the electrical conductivity 198 to the value at the point 204, the
decay curve 205b decreases
the electrical conductivity 198 according to the removed heavy metals, and the
removed sacrificial ions
65. This results in the electrical conductivity 198 dropping to the point
206b. Note that the point 206b
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CA 3058876 2019-10-16
is still above the axis 196, indicating that residual electrical conductivity
198 is resulting from the
brine, which has not been removed by the system 10.
The decay curve 205c results in termination at a point 206c, because the water
20 being treated
is water having brine and no heavy metals. Accordingly, the rise in electrical
conductivity from the
point 202 to the point 204 is entirely due to the donated metal ions 64 from
the anode 92. Once those
metal ions are removed, the decay curve 205c settles back to the original
value at the point 206c, which
reflects the presence of brine, and no heavy metals.
In general, the region between the curves 205a and 205c is the operating
envelope of the
system 10. Thus, whether the water is completely clean of heavy metals, or
laden with heavy metals,
these extrema are indicated by the graph 194.
It will be appreciated that conductivity (a) is but one of conductivity,
acidify (pH), and
temperature (T) that can be ascertained at points 202, 204, 206 such that an
apparatus and method in
accordance with the invention may be similarly optimized and controlled.
Referring to Figures 8 and 9, the experimental work giving rise to the graphs
150, 194 was
validated by comparing predicted to actual experimental performance of a
system 10 in accordance
with the invention. For example, each of the charts 210 includes an x axis 212
or horizontal axis 212
representing a change in electrical conductivity as predicted. That change in
electrical conductivity is
the value of electrical conductivity at a point 206 compared to electrical
conductivity at a point 202.
Each of the values is represented as a logarithm of the actual measured value.
Thus, each of the
charts 210 represents a log-log comparison. Thus, they axis 214 or vertical
axis 214 represents the
change in electrical conductivity actually measured in the experimental system
10.
The curves 216 represents a leased squares fit of the data. The median 218 is
illustrated by a
dashed line. The individual data points 220 of individual experiments are
distributed in the graphs
210. The correlation quality is evident from the "Pvalue" indicated by the
letter p in each case, that
ratio is less than four significant figures behind the decimal point. Thus,
the "Pvalue" is less than one
ten thousandth. This represents a high degree of statistical significance to
the correlation.
The r squared value indicating the degree of correlation is indicated by the
expression RSq and
has a value of 0.95 in the first series of tests, and a value of 1.87 in the
second series of tests.
Similarly, the root mean square of the error represented by the moniker RMSE
is also illustrated.
Thus the charts 210 of Figures 8 and 9 evidence that the physical system 10
illustrated in
Figures 1 through 4 indeed operates according to the qualitative
representations of Figures 5 and 7.
Nevertheless, the specific values of any particular curve 160, 200 will depend
upon the specific
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CA 3058876 2019-10-16
constitution of the incoming water 20, the value of current 50, the material
properties of the fluids, the
flow rate, and so forth as described hereinabove.
Referring to Figure 10, while continuing to refer generally to Figures 1
through 10, in one
embodiment of a cell 90 in accordance with the invention, a specific
embodiment of a sacrificial anode
92 may be encased within a tube 94 representing a cathode 94. In the
illustrated embodiment, a cap
222 may be formed to include a sleeve 223. The sleeve 223 will engage with a
seal 236 and otherwise
secure mechanically to the tube 94. Any suitable mechanism will operate.
Various seals 236, such as '0' rings 236 or the like may be used to seal
individual surfaces
from passing any fluids, such as vapors, liquids, or the like therethrough. In
certain embodiments, a
washer 238 may act as a compression fitting 238 activated or distorted by the
tube 94 as it fits within
the sleeve 225 of the cap 222. In this embodiment, an axial load along the
axial direction of the anode
92 may be enforced between the wall of the tube 94, and the washer 238. Thus,
the washer will distort
in an axial direction, shrinking in that direction in response to force or
stress. Meanwhile, the washer
238 will expand in a radial direction in direct consequence thereof according
to the Poisson effect,
which represents a conservation of mass in solidous materials.
A feed pipe 240 may be secured, such as by welding to feed the flow 30 into
the annulus 96
within the tube 94. An anchor 242 may be secured against a surface 243 such as
by threading. In one
embodiment, a lug 244 held by the anchor 242 against the surface 243 of the
tube 94 will feed power
from a power line 246 or power cable 246 connected to the current source 50.
Various switching and
control mechanisms may intervene in order to control application of current,
control flow direction into
the feed pipe or port 240 and so forth.
The anode 92 may be positioned by guides 248. In the illustrated example,
guides 248 are
positioned near the top end of the anode 92, and near the bottom end thereof.
Typically, the guides
248 may be spoked or includes spokes 250 that represent radial supports 250
positioning the anode 92.
The guide 248 may include an outer rim 251 and inner rim 252.
Each of the spokes 250 may extend along a length or axial direction and
present a vane 253 that
tends to rotate or spin the flow within the annulus 96. In this way,
additional turbulence may be
initiated in the lumen 96 or annulus 96. The lower guide 248 may be similarly
situated, but may also
be adapted to act as a seat 248 for the lower end of the anode 92.
For example, in the illustrated embodiment, the anode 92 may be tapered to a
reduced diameter
and fitted into a seat 248 in order to be self-piloting. The spokes 250 and
their vanes 253 may simply
be integrated. For example, a face 253 of a spoke 250 may extend radially,
axially, and twist
44
CA 3058876 2019-10-16
circumferentially in order to induce spinning in the flow. It may assure that
the flow 130 passes
through or between the spokes 250, and has sufficient cross-sectional area and
hydraulic diameter to
maintain the flow velocity, volumetric flow rate, and so forth. Reductions of
area that may be
occasioned by the interference by spokes 250 will simply increase velocity,
and turbulence.
In the illustrated embodiment, a load block 256 may be a right circular
cylinder, which may or
may not include spokes 250 and intervening spaces to promote flow
therethrough. In the illustrated
embodiment, the flow 130 passes through the blocks 256, which support the
lower guide 248 axially.
Ultimately, the flow 130 will pass through the guide 248 and the load block
256 that stands the guide
248 off away from the outlet port 258 or outlet line 258. It provides
sufficient cross-sectional area and
hydraulic diameter. Hydraulic diameters is a term of art defined
mathematically in engineering science
as four times the cross-sectional area divided by the wetted perimeter of a
conduit of any shape or
passage of any shape.
In accordance with the operational approach for the cells 90, additional
variations in diameter,
effective roughness, trip lines, or the like may be added to the interior of
the tube 94, such as along the
surface 95. In order to assure turbulent flow immediately. Typically, flows
develop over a distance.
Accordingly, boundary layer theory predicts the establishment of flows. In
order to maximize
turbulence, roughness, features that may trip, such as projections, ridges,
and the like, as well as the
spokes 250, the vanes 253, integral thereto, or the like may be added to the
surface 95, in order to
quickly develop turbulence and a bulk plug flow 130 within the annulus 96.
Referring to Figures 11-23, various embodiments are illustrated for masking an
electrode
(anode or cathode) in a system 10 in accordance with the invention. In
particular, an ion generator 12
having a centrally located anode 92 spaced from a cathode 94 a distance
selected to provide an annulus
96 carrying a flow 130 of liquid to be remediated may have too high a solids
content (totally dissolved
solids or TDS). The consequence of too high solids, typically comes with an
ionic solution of sodium
chloride and possibly other salts. Thus, not only the contribution of the TDS,
but also the salts result in
a very high electrical conductivity through the flow 130, corresponding to a
very low electrical
resistivity. Accordingly, the net electrical resistance between the anode 92
and cathode 94 may not
support the voltage necessary to free ions (e.g., A13+) from the anode 92.
It has been found that various mechanisms may result in an increase in the
overall electrical
resistance through the flow 130. One mechanism is to limit the area of the
surface 93 of the anode 92.
The effect of reducing the available surface 93 of the anode 92 is to create a
limitation on how many
ions may gain access to the flow 130 in order to migrate away from the anode
92. This "traffic
CA 3058876 2019-10-16
congestion" is simply a result of limiting a surface area available in a
transport process to participate in
the ionization at that surface. Aluminum picks up two electrons to become an
aluminum ion (A13+).
By the same token, the surface 93 of the cathode 94 available to contribute
electrons into the
flow 130 in order to match the charge of the flow of ions may also be limited
by masking to limit the
portion of the surface 95 available to participate or contact the flow 130.
The cathode 94 sponsors a
half reaction constituted by a splitting of water molecules. A hydrogen splits
off and joins another
hydrogen atom to produce hydrogen gas (H2). Meanwhile, hydroxide ions (OH)
having picked up an
electron each are left behind in the flow 130. These are available for later
construction of the dipoles
necessary for creation of pin flock and agglomeration by flocculation. Thus,
the surface area 95
available controls the transport process of water molecules accessing the
cathode, picking up an
electron, and moving back into the flow 130.
Referring to Figures 11-12, a general concept of a mask 260 illustrates the
anode 92 with an
exposed portion 262 accessible to the flow 130 in the annulus 96. That exposed
area 262 is free to
participate fully, within the limitations of boundary layer dynamics as
discussed in detail hereinabove.
A mask 260 results in a covered portion 264 not exposed to the flow 130, and
therefore
unavailable to donate ions into that flow 130. The mask 260 may be formed of
any suitable material.
Typically, a good mask 260 or effective mask 260, should be impervious to the
flow 130, although the
mask 260 need not be "air-tight" nor "liquid-tight" with respect to the
surface 93 of the anode 92. The
distance across the annulus 96 is selected to maintain the appropriate
voltage, typically about two volts
or more across a one-inch annular gap, required to free ions from the anode
92. In the illustrated
embodiment, any portion of the anode 92 in the covered portion 264 will
necessarily have little or no
access to the flow 130.
As a practical matter, electrical access to any portion of the flow 130 that
may seep between the
mask 260 and the anode 92 will be limited by both the cross-sectional area of
such a gap between the
electrode 92, 94 and the mask 260, as well as the distance of any point along
the anode 92 in the
covered portion 264, from the edge of the mask 260. In other words, the
voltage or potential for
ionization will be satisfied along the exposed portion 262, to the exclusion
of any part of the covered
portion 264, which will be separated by a greater resistance.
Referring to Figure 13, a technician may periodically service an individual
cell (combination of
an anode 92 and corresponding cathode 94). In the embodiment of Figure 13, a
mask 260 may be
formed as a tubular column fitted closely about the anode 92. The mask 260 may
be formed in
portions 260a, 260b, 260c, and so forth separated by score lines 268 or tear
lines 268 having
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CA 3058876 2019-10-16
considerably smaller thickness. Thus, a technician may cut or tear at a
section 260a, separating it from
the segment 260b along the intervening tear line 268. In this way, additional
area of anode 92 may be
exposed at different times, when the distance has increased between the
exposed portion 262 and the
corresponding cathode 94.
Referring to Figures 14-15, a comparatively thinner dielectric, from a finger
print thickness of
microns or under a mil, is completely suitable for forming a mask 260.
Nevertheless, in this
embodiment, a comparatively thicker (greater than one sixteenth inch or two
millimeters) segment of
tube is formed as mask segments 260a, 260b, 260c. Here, the material and
thickness of each of the
masks 260a, 260b, 260c is selected to maintain a grip about the anode 92. The
individual masks 260a,
260b, 260c may be stacked to form an overall mask 260. By opening a split 266
in each mask 260a,
260b, 260c each may clamp over the anode 92 with the overall stack 260 that
constitutes the mask 260.
Accordingly, each mask 260a, 260b, 260c may be removed by simply drawing it
away from the anode
92, thereby opening the split 260 or brake 266. That split may be in any
shape, from the line illustrated
to a serpentine shape, a saw tooth shape, or the like.
As a practical matter, each of the masks 260 in Figures 11-15 may suitably be
applied to an
anode 94 rather than a cathode 92. This results in a somewhat different
process for manufacture and
installation, as well as a somewhat different operational principle.
For example, the anode 92 contributes sacrificial metal ions that will be used
as described
hereinabove with respect to Figure 2. Masking the cathode 94 results in
limiting the surface area
available to participate electrically. Thus, the electrical resistance may be
raised by artificially limiting
the area and distance, when the resistivity of the specific flow 130 is
entirely too low. Thus, if the
electrical conductivity of the flow 130 is too high to maintain the necessary
voltage needed between
the anode 92 and cathode 94 to free ions from the anode 92, area and effective
distance may be
modified.
Referring to Figure 16, a mask 260 may be wrapped on as a tape 260, a portion
thereof being
removed by a technician periodically to uncover additional exposed portions
262 of the anode 92. In
this embodiment, the mask 260 may be wrapped over itself, or the edges thereof
may be abutted
against one another. Any small gaps between individual turns of a wrap 260
operating as a mask 260
(just as in Figures 14-15) may expose a portion of the anode 92, which may
therefore sacrifice and
diminish. However, transport processes within such potential gaps are
typically an order of magnitude
too slow, inasmuch as they are below the boundary layer 106 as discussed
hereinabove, have limited
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area, and their depths are restrictive. Thus, such potential gaps represent no
significant effect on the
useful operation of a mask 260 over the anode 92.
Referring to Figure 17, a mask 260 may be configured as a thin sheath over a
covered portion
264. The exposed portion 262 may thus be selected to be any amount of the
anode 92 desired. In this
embodiment, the mask 260 may be configured as a fitted sleeve 260 over the
anode 92 to be drawn off
and rolled up or discarded. For example, at some cut line 272, a technician
may draw down and cut off
any excess amount of the mask 260 from the anode 92, in an axial direction
with respect thereto.
Referring to Figure 18, an alternative embodiment may simply involve a
telescoping mask 260
comprising segments 260a, 260b, 260c that are telescoped together, rather than
separated off as in
embodiments described immediately hereinabove. The segments 260a, 260b, 260c
may be provided
with some mechanism 276 as a detent 276. For example, a rim may be provided on
one surface and
matched by a relief into which that rim can fit. That is, a ring projecting
away from the surface,
whether inner or outer, may fit into one of several relief regions matched in
shape. In other
embodiments, mere friction, due to a compression fit or an interference fit
may result in stabilizing the
mask 260 by stabilizing the segments 260a, 260b, 260c with respect to one
another.
Of course, more segments 260a, 260b, 260c may be added. Meanwhile, any type of
a detent
276 that will typically cause an interference between a portion of one segment
260a, 260b, 260c, and
any other fitted thereto may act to stabilize the telescoping mask 260. In
fact, a technician may simply
push down on the outermost or highest segment 260a, and allow relative
movement between any pair
of segments 260a, 260b, 260c that move first. The entire covered portion 264
remains shielded,
thereby presenting a higher resistance, and resulting voltage requirement,
than does the exposed
portion 262.
Referring to Figures 19-22, anodes 92 may simply be manufactured with a dipped
coating. It
may be useful to provide a release 278 such as some type of mold release
between the mask 260 and
the anode 92. This will assist in separating the mask 260 when a portion
thereof needs to be peeled
away from the anode 92 in order to uncover additional exposed area 262.
Nevertheless, it has been found that a dielectric coating as thin as an oily
fingerprint of a person
may be sufficient to coat an anode 92, and render that particular region
ineffective to participate
reliably in donating ions into the flow 130. Accordingly, the release material
278 would best serve if it
is an easily dissolved material. Thus, it could be something as simple as a
cornstarch powder, salt
powder, or the like that would immediately dissolve in the flow 130 upon
exposure thereto.
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In this embodiment, a tool 280 may be used to separate or peel the mask 260
from the anode
92. The tool 280 may have an aperture 281 fitted to the full diameter of the
anode 92, terminating at
the lower edge 282 with a sharp edge 282 that will peel or cut the mask 260
away from the anode 92.
A handle 283 may be provided for a user, extending from the principal frame
284 or guide 284 that
forms the principal structure 284 of the tool 280.
In other embodiments, a basic industrial knife, such as a box cutter or the
like may simply score
the mask 260 parallel to the longitudinal direction of the anode 92, and then
cut around a
circumference of the anode 92. Thus, no tool 280 need be left in the flow 130.
Referring to Figure 23, an anode 92 is illustrated with portions 262a, 262b,
264 in three
conditions. The top portion 262a condition is that which exists following
considerable loss of ions by
the sacrificial anode 92. That is, in experiments, the anode 92 decreases in
diameter cleanly and
uniformly throughout, as if it were machined very precisely. The resistance,
and therefore the voltage
requirement will increase between the anode 92 and the cathode 94 as a result
of the reduction in
diameter of the exposed portion 262a, as a result of the increase in distance
therebetween as well as the
reduction in surface area.
Meanwhile, the central section 262b illustrates a portion of the anode 92 that
has barely been
exposed, to become part of the exposed portion 262, as compared with the
eroded or sacrificed,
exposed region 262a thereabove. Accordingly, the exposed area 262b or exposed
region 262b has an
additional area, still limited and at a reduced distance, which is still
reduced from that of the full anode
92, and therefore effective to elevate resistance and support a voltage
required to participate in
donating ions into the flow 130.
Finally, the covered portion 264 is surrounded by the remaining mask 260. In
due course, the
exposed portion 262b will come to look like the exposed portion 262a. Inasmuch
as the proximity and
surface area on the exposed portion 262b are more favorable, and require less
voltage, although
sufficient to effect the migration of ions, the exposed portion 262a will not
decay in diameter
appreciably during the operation of the exposed portion 262b. Of course,
ultimately, the entirety of the
mask 260 is removed over the covered portion 264, rendering it again another
exposed portion 262.
Referring to Figure 24, each of the previously discussed masks 260 may be
adapted to use
against an inner surface 95 of the cathode 94. As a practical matter, the
adaptation of each mask 260
will be somewhat different being on an interior surface 95 of the cathode 94,
rather than the outer
surface 93 of anode 92.
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For example, the thinnest of coatings a few thousandths of an inch (several
microns) provides
sufficient dielectric interference to mask 260 a covered portion 264 of the
anode 92. Meanwhile,
mechanically, tensile forces in a shrink-type wrap 260, or simply a fitted
wrap 260 may be sufficient to
maintain the mask 260 in place over an anode 92. In contrast, the mask 260
over the inside surface 95
of a cathode 94 may need sufficient structural stability and grip against the
cathode 94 to maintain its
position at the cathode 94 within the flow 130, or rather surrounding the flow
130. Thus, the thickness
of the mask 260 may be required to be self-supporting of the mask 260.
Referring to Figure 25, in certain embodiments, a mask 260 may actually be
provided with
vents 286 or gaps 286 to expose, or to define the exposure areas of, the
cathode 94. Long single slits
286, short elliptical gaps 286, or the like may be provided. Since the anode
92 sacrifice ions, it will
decay. In contrast, the cathode 94 contributes only electrons. Thus, it is not
degraded or eroded.
Thus, there is not the same requirement that the mask 260 continue to expose a
different portion of the
surface 95 of the cathode 94. Nevertheless, it may be necessary to open up
more area on the surface
95, which may then be done by removal of the masking material 260 as done in
the anodic masks 260
described hereinabove.
Referring to Figure 26, in keeping with the vigorous flow 130 maintained in
the annulus 96, a
significant improvement may be made in the adjustability and effectiveness of
masking 260, generally.
It has been found and tested that a line 288 may be attached to feed a plenum
289 around the supports
250 or the outer rim 251 of the supports 250 described hereinabove.
As it turns out, a curtain 290 of tiny bubbles 291, which may actually be too
small to be seen
individually by the naked eye, may be injected through orifices 292. By
suitable selection of the flow
rate of air or other gas through the line 288, and the sizing of the orifices
292, the bubbles 291 may be
maintained effectively within the boundary layer 106 as discussed above with
respect to the anode 92,
at the inside surface 95 of the cathode 94.
The bubbles 291, as contained gas, represent dielectric gaps in the flow 130.
Thus, resistivity,
effective (a material property) or effective resistance (net overall effect)
between the anode 92 and
cathode 94 is increased by an increasing path length for electrons and ions
passing around bubbles 291
in the boundary layer 106 of the surrounding flow 130. This increase in
distance is effectively
increasing the effective width of the annulus 96 (effective electrical path
length) between the anode 92
and the cathode 94.
In fact, the need for masking 260, in general, is one of initial voltage
management in highly
conductive flows 130. For example, above about 100,000 parts per million of
total dissolved solids,
CA 3058876 2019-10-16
the combination of solids and typical salts in solution will begin to provide
an electrical conductivity
so high as to not maintain a required voltage (e.g., voltage is equal to
current times resistance) needed
to move ions from the anode 92 into the flow 130. As the decay of the diameter
of the anode 92
proceeds, that distance becomes larger, as long as the voltage is sufficient.
When the required voltage becomes too high such that the current source fails,
it cannot be
used. Current and voltage cannot be maintained to supply the flow of electrons
and ions. Then, the
remaining, thinned anode 92 must be removed and replaced. In certain of the
embodiments
immediately hereinabove, additional area may then be exposed. However, the
basic reason for the
management of available electrical area and effective path length is to
provide either a constriction or
liberation of the flow of electrons and ions as necessary, to match a current
source to an electrical
conductivity of a flow 130.
Thus, the bubble curtain 290 provides a path length, providing a virtual
lengthening of the path
across the annulus 96. The bubble curtain does provide masking 260 to some
extent, but is effectively
doing so by providing dielectric bubbles 290, close to an electrode 92, 94 in
order to increase
resistivity or effective electrical resistance across the annulus 96 to
support a voltage requirement.
Analytical experiments (computer modeling of components and configurations to
calculate
certain dependent variables based on other independent variables) have been
executed to determine the
effect of masking. The "electrical path" between anode 92 and cathode 94 is
necessarily complex
when both are not identical in length and registration (no offset
vertically/axially from one another).
The liquid in such cases presents a virtually infinite number of parallel
paths for electrons and ions to
traverse the annulus 96. It has been shown that such a masking of a portion of
either the anode 92 or
cathode 94 results in an increase in voltage therebetween for a given TDS or
its consequently increased
electrical conductivity (decreased resistivity).
The practical effect is that high values of TDS, such as 150,000 ppm, 200,000
ppm, and even
250,000 ppm do not fail the system 10. Saturation occurs at about 280,000 ppm
TDS. Nevertheless,
the 1.69 volts required to free ions from the anode 92 can still be imposed
across the annulus 96 by
masking a sufficient area of the anode 92 to increase the overall resistance
across the annulus.
Controls simply need to provide an electrical current at a desired value
(current in Amperes translates
directly to Coulombs of charge in the ionic reactions) for the number of ions
to be introduced into the
flow 30.
If voltage is determined to be too low (below 1.69 volts), by analytical or
empirical methods,
due to too short a distance or too high a conductivity, masking off a portion
of the area of the anode 92
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or cathode 94 may be implemented. Meanwhile it has been found that the power
supply 50 or current
source 50 most typically available at an installation produces about 10K VA of
energy. Meanwhile,
voltage across a 1-inch (2.54 cm) annulus needs to be at least 1.69 volts, but
will often increase to
about 24 volts when anode erosion approaches another inch of gap (with
associated loss of surface
area). Thus, to maintain operational currents on the order of 100 to 400
Amperes or more to match ion
production needs, the systems 10 need to operate within these limiting
parameters.
An empirical model of the bubble curtain was created with square flat plates,
about a foot
square (30 cm x 30 cm) and an inch apart. Between the plates, acting as anode
92 and cathode 94,
water containing dissolved salts increased electrical conductivity.
Maintaining suitable voltages and
currents was done for various levels of salinity up to an equivalent
resistivity/conductivity
corresponding to 250,000 ppm TDS. The pressure-controlled introduction of an
air bubble curtain
290, successfully increased the effective electrical resistivity between the
plates sufficiently to support
the 1.69 volts needed to release anodic ions, even at this upper extreme of
actual conductivity. Voltage
may then be increased and the curtain 290 removed as the anode recedes due to
sacrificing ions.
One may wonder why a feedback control could not be implemented based on
incoming
conductivity and outgoing conductivity. Conductivity results from dissolved
solids and other ions,
particularly salt. Although salt is useful to establish electrical
conductivity in experiments to show
voltage control by use of masks 50 and bubble curtains 290, it is actually a
background material. Its
presence raises conductivity, but often relegates TDS to a small portion of
the overall contribution to
electrical conductivity. Thus, a system 10 in accordance with the invention
cannot rely on the
accuracy of measurements of conductivity incoming and outgoing, as the TDS
contribution thereto is a
small difference in two numbers orders of magnitude (often 3 or more) larger
than their difference.
Thus, the system 10 reduces boundary layer thickness with "plug flow" or
"hyper-turbulent
flow," and current is set to match the ions needed to match the mass flow rate
and TDS. Normally, it
is best to maintain a constant current and adjust voltage to the minimum
required, which minimum
increases as distance across the annulus (anode to cathode) increases and as
available area exposed (at
anode 92 or cathode 94) decreases (typically at the anode 92 as it sacrifices
ions). Thus current
controls the ion flow, and voltage is adjusted to maintain the current flow.
Voltage may require an
increase as distance increases or area decreases.
The present invention may be embodied in other specific forms without
departing from its
purposes, functions, structures, or operational characteristics. The described
embodiments are to be
considered in all respects only as illustrative, and not restrictive. The
scope of the invention is,
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therefore, indicated by the appended claims, rather than by the foregoing
description. All changes
which come within the meaning and range of equivalency of the claims are to be
embraced within their
scope.
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