IT202000013945A1 - ELECTROCHLORINATION PROCESS WITH HIGH COULOMBIAN EFFICIENCIES - Google Patents

Description

Of the Patent Application for Industrial Invention entitled:

?Electrochlorination process with high Coulomb efficiencies?

The invention relates to the field of electrochlorinators and, in particular, to an electrochlorination process which shows higher Coulomb efficiencies? high compared to the prior art. BACKGROUND OF THE INVENTION

Electrochlorination technology is often used for the production of chlorine for water treatment in swimming pools and offers, among other things, the advantage of reducing the storage and handling of chemicals as well as a constant generation of chlorine with minimal maintenance. In order to ensure low maintenance requirements, electrochlorination of swimming pools typically uses one of two electrical profiles, in order to avoid the formation of deposits on the electrode surfaces. One of these profiles? disclosed in U.S. Pat. 5,034,110 issued July 23, 1991.

The electrical profile disclosed in U.S. Pat. 5,034,110 ? known as the polarity profile? reverse. Element 110 describes a circuit capable of providing direct current which increases to a maximum positive level, decreases to zero, increases to a maximum negative value [e.g. increases to a maximum value in the opposite direction (-) of the original direction (+)], then returns to zero and cycles through this sequence in a pre-selected time period of 4, 8, 16, 24 or 48 hours or other periods. The transition from a positive level to a negative level? known as reverse polarity? or polarity reversal. FIG. 1 of the present disclosure graphically shows this profile found in U.S. Pat. 5,034,110.

US patent no. 5,034,110 further discloses a dc converter which is operated to provide a step dc current output to the electrochemical cell.

According to 110, this output ranges from zero, 50%, 100%, 50%, zero, -50%, -100%, -50% to 0 in a repeating sequential fashion. Does this particular profile reverse the polarity? but also keeps the circuit open (DC output = 0) for a period of time. FIGURE. 2 of the present disclosure graphically shows this profile found in U.S. Pat. 5,034,110. FIGURE. 3 of this description graphically shows the polarity? reverse when the direct current circuit is not ? never open and the polarity? it simply switches between positive (+) and negative (-).

US patent no. 5,034,110 describes ?? been found in practice that the switching of the polarity? of electrolytic coordinators under normal operating power loads causes rapid deterioration of electrode efficiency. This deterioration is believed to result from an electrical "shock" causing the brittle electrocatalytic coating to crack and flake under such shock loads. This problem ? particularly evident with the coordinators line which normally operate at voltages of 25-32 volts and a density? of current of 25-30 amps / dm?. Although the polarity of line coordinators can be switched between cycles of operation to minimize electric shock loads, do you feel that the shock loads associated with simply turning the chain on and off are too high to maintain longevity? economical in electrode assemblies. "

US patent no. 5,034,110 claims to solve this problem by using the controllable power supply to gradually increase the power from minimum to maximum during the turn-on phase and vice versa during the turn-off phase, thus relieving the substantially electric shock loads.

US patent no. 7,722,746 issued May 25, 2010 discusses in detail electrode erosion problems caused by reverse polarity? and the buildup of mineral deposits on the electrode.

The deposit buildup problems noted in U.S. Pat. 7,722,746 are well known. The accumulation of deposits occurs because? water typically used in residential pools contains other dissolved salts (e.g. calcium, magnesium, barium, strontium). These salts precipitate at the high pH levels found at the negative electrode interface. These deposits will eventually passivate the electrode and cause degradation or even complete interruption of performance. Ultimately, the passivation due to the precipitates? a primary mechanism of cell failure. ? for this reason that the direct current is pure without polarity reversal? it is rarely used commercially.

US patent no. 7,722,746 claims to solve the polarity reversal problem? applying a direct current in only one direction for a long period of time. FIGURE. 4 of the present description graphically shows the profile associated with the application of direct current without inverting the polarity.

US patent no. 7,22,746, dissolves mineral deposits, especially calcium deposits, by isolating the electrolyte chamber and adding a pH reducing agent, e.g. muriatic acid, to the room while there? flow of electrolyte through the chamber.

According to US patent no. 7,722,746 this dissolution step "is only needed about once every two weeks".

US patent no. No. 7,722,746 summarizes the problem and its solution that in traditional bipolar chambers, both sides of the plates (electrodes) must be coated. However, the present invention [of U.S. Pat. 7,722,746 which does not reverse the polarity?] requires that only one side of each plate be coated since? Is the electric charge delivered from only one end? of the room.

According to US patent no. 7,722,746, the elimination of the need? to reverse the polarity? it also has the benefit of allowing the electrolytic chlorine generator to operate at low salt levels without increasing the required flow rate.

However, ? known that during the constant current operation that constantly applies current in the same direction and at a speed? constant, the anodes and cathodes develop reactive boundary layers which lead to increased mass transport overpotentials, lower chlorine evolution and subsequently lower efficiency of chlorine evolution (compared to oxygen evolution).

The effects of mass transport on the electrodes also increase with higher reactant concentrations. low (i.e. chloride salts, traditionally sodium chloride).

These problems with running on DC power when adding additional reactants to the feed water are not possible or simply not wanted. For example, adding salt may not be an option due to lack of operator impact or lack of availability. of salt in remote water treatment plants. Another example, what? also referenced in U.S. Pat. 7,722,746, ? the residential swimming pool with low salt content (for example 1 g of salt / L) where not? desirable that operators add salt.

Current electrochlorination processes in these low-salt residential pools typically have a Coulomb efficiency (E.C.) of around 35%. The Coulomb efficiency measures the quantity? of current used to produce chlorine compared to other reaction products. At low reactant concentrations, greater efficiencies are needed to produce larger quantities. of chlorine economically. So is there a need? of a new process capable of achieving greater efficiency at similar production rates.

SUMMARY

The present description discloses a process for the production of chlorine (Cl2) in an electrochemical cell. Does the process include a plurality? of polarization cycles comprising at least one polarization cycle, N, having a polarization cycle time (tPCN), a chlorine production time (tCPN), and a chloride enrichment time (tCRN).

The process comprises the steps of (a) applying a bias, to induce a chlorine production feed flow for the chlorine production time (tCPN), (b) reducing the bias to a chloride enrichment feed flow for the chloride enrichment time (tCRN); where the polarization cycle time (tPC) must not equal the polarization cycle time (tPC) of any other polarization cycle, the chlorine production time (tCP) must not equal the chlorine production time (tCP) of any other chlorine production time, the chloride enrichment time (tCR) cycle shall not be the same as the chloride enrichment time (tCR) of any other cycle; and the total number of bias cycles, TNPC, ? an integer in the range between 1 and 2,160 and N ? an integer in the range of 1 to 2,160 and indicates a particular polarization cycle N of a total number of polarization cycles.

? further disclosed that the chloride enrichment time (tCRN) of at least one of the polarization cycles, ? less than or equal to its chlorine production time (tCPN), so that tCRN ? tCPN.

The disclosure further discloses that the chloride enrichment time (tCRN) of each polarization cycle ? less than or equal to its chlorine production time (tCPN), so that tCRN ? tCPN.

? It is also disclosed that the bias cycle time of at least one of the bias cycles can? equal the sum of the time of production of chlorine pi? the chloride enrichment time (tPCN = tCPN tCRN).

In another embodiment, the bias cycle time of each of the bias cycles is equal to the sum of the time of production of chlorine pi? the chloride enrichment time (tPCN = tCPN tCRN).

The description also discloses that N pu? be at least 2 and that at least two of the bias cycles N are applied consecutively.

In another embodiment, all N bias cycles are applied consecutively.

The description addresses the relationship between chloride enrichment feedflow and chlorine production feedflow. In one embodiment, the ratio of chloride enrichment feedflow to chlorine production feedflow of any polarization cycle ? in the range from 0 to 0.95.

In another embodiment, the ratio of chloride enrichment feedflow to chlorine production feedflow of any polarization cycle ? in the range from 0 to 0.5.

In yet another embodiment, the ratio of chloride enrichment feedflow to chlorine production feedflow of any polarization cycle is ? in the range greater than 0 to 0.06.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an example of the polarity profile? inverse (waveform) of the prior art. FIG. 2 illustrates a different example of the polarity profile? inverse (waveform) of the prior art.

FIG. 3 illustrates a different example of the polarity profile? inverse (waveform) of the prior art in which there is no? open circuit time.

FIG. 4 illustrates an example of the polarity profile? direct current (waveform) of the prior art.

FIG. 5 depicts a sample waveform of the invented pulse profile.

FIG. 6 illustrates the components of the invented pulse profile.

FIG. 7 depicts a comparison between two profiles of the prior art with the invented profile. DETAILED DESCRIPTION

Are polarity pulse profiles described here? for an applied field that achieve higher Coulomb efficiency than previously known profiles. These profiles allow the use of low salt concentration water (NaCl) to produce more water. efficient chlorine for chlorination without reversing polarity. This process will find its use in remote water chlorination facilities and low salt applications, such as residential swimming pools. will find? also use in normal water chlorination and other types of pools.

The pulse profiles found involve a bias cycle consisting of a chlorine production step having a direct pulse for a chlorine production time (tCPN) followed by a chloride enrichment step where the bias is maintained in a pulse of "interruption of polarization" for a chloride enrichment time (tCRN).

This ?interruption of polarization? ? called ?interruption of polarization? In short. Whether voltage or current controlled, the forward impulse field applied during the disruption of the bias (i.e. chloride enrichment charge flow)? low enough to make s? that the faradic reaction of chloride to chlorine is ?interrupted? with very little or no generation of either oxygen or chlorine. However, the forward biased field applied during the polarization break? also high enough to keep the cell polarized at a level such that the cell voltage ? greater than about the open circuit voltage for the standard electrode potential of chlorine at the anode, the potential of the standard electrode of hydrogen at the cathode, adjusted for temperature and concentration at the electrodes. Appendix C of "Electrochemical Methods: Fundamentals and Applications," 2nd Edition, teaches these standard potentials in Appendix C, and in Chapter 2 teaches the equations and relationships of how these standard potentials change with pH and concentration. Pi? specifically, the forward biased field applied during the polarization interruption? high enough to keep the cell polarized at a level such that the cell voltage is greater than the open-circuit voltage for the anode chlorine standard electrode potential, the cathode hydrogen standard electrode potential, and the value of reference of the generation of sodium hydroxide adjusted for temperature and concentration at the electrodes. In general, the upper limit of the field applied during the "interruption of polarization" phase (i.e. the chloride enrichment phase), also known as the chloride enrichment charge flow, is ? substantially less or just less than the chlorine production feedstock flow during the chlorine production phase. The applied field is not reversed when the feedflow is reduced from the chlorine production feedflow to the chloride enrichment feedflow, ie? the flow of charge during the phase of interruption of the polarization (that is? flow of charge of enrichment of chloride) ? in the same direction as the chlorine production feedstock flow during the chlorine production phase.

In other words, the chloride enrichment feedstock flow ? such as to be in the range from the quantity? required to maintain the cell voltage greater than approximately the open-circuit voltage for the anode chlorine standard electrode potential, the cathode hydrogen standard electrode potential, and the regulated sodium hydroxide generation setpoint for temperature and concentration at the electrodes, to a quantity? lower than the chlorine production feedstock flow.

In a first embodiment, the chlorine production process can understand a plurality of polarization cycles comprising at least one polarization cycle, N, having a polarization cycle time (tPCN), a chlorine production time (tCPN), a chloride enrichment time (tCRN), and comprising the following steps.

First, applying a bias, to induce a chlorine production charge flow for the chlorine production time (tCPN).

Then bias reduction to a chloride enrichment feedflow for the chloride enrichment time (tCRN) with the chloride enrichment feedflow in the same direction as the chlorine production feedflow. The sentence ?with the chloride enrichment feedstock flow in the same direction as the chlorine production feedstock flow? can? be said alternatively as ?with the chloride enrichment feedstock flow maintained in the same direction as the chlorine production feedstock flow?.

Also, for this first embodiment, the bias cycle time (tPC) need not be the same as the bias cycle time (tPC) of any other bias cycle. The chlorine production time (tCP) must not be equal to the chlorine production time (tCP) of any other chlorine production time. The chloride enrichment time (tCR) cycle should not be the same as the chloride enrichment time (tCR) of any other cycle.

In a second embodiment, the chlorine production process can understand a plurality of polarization cycles comprising at least one polarization cycle, N, having a polarization cycle time (tPCN), a chlorine production time (tCPN), a chloride enrichment time (tCRN), and comprising the following steps.

First, applying a bias, to induce a chlorine production charge flow for the chlorine production time (tCPN).

Then bias reduction to chloride enrichment feedflow for chloride enrichment time (tCRN) with chloride enrichment feedflow in the same direction as chlorine production feedflow with enrichment feedflow of chloride high enough to maintain the electrochemical cell voltage greater than an open circuit voltage for a standard electrode potential of chlorine at the anode and a standard electrode potential of hydrogen at the cathode that have been adjusted for temperature, concentration, pH at the electrodes. As in the first embodiment, the statement ?with the chloride enrichment feedstock flow in the same direction as the chlorine production feedstock flow? can? be said alternatively as ?with the chloride enrichment feedstock flow maintained in the same direction as the chlorine production feedstock flow?.

Like the first embodiment, in this second embodiment the bias cycle time (tPC) need not be equal to the bias cycle time (tPC) of any other bias cycle. The chlorine production time (tCP) must not be equal to the chlorine production time (tCP) of any other chlorine production time. The chloride enrichment time (tCR) cycle should not be the same as the chloride enrichment time (tCR) of any other cycle.

A chlorination manufacturing process, such as those described in Embodiments 1 and 2, can also understand more polarization cycles. Will there be a total number of polarization cycles, TNPC, in each chlorination treatment. The total number of polarization cycles in a chlorination treatment can be in the range from 1 to 2,160. While a chlorination treatment can include up to 2,160 cycles of polarization, you can apply more? successive chlorine treatments. In one scenario, a swimming pool is constantly chlorinated over a long period of time. In this scenario, there would be more chlorination treatments applied one after the other.

A given chlorination treatment, such as those described in Embodiments 1 and 2, can also include many different types of polarization cycles, one of which ? the invented bias cycle having the bias on state and the "bias off" state. However, the number of polarization cycles invented need not equal the total number of polarization cycles in a chlorination treatment.

When are you there? more of 1 invented polarization cycle having a chloride enrichment time (i.e., a polarization stop state), the invented polarization cycles, such as those described in Embodiments 1 and 2, can be further applied consecutively such that there are no other polarized profiles among the invented polarization cycles.

The cycle of polarization invented avr? a polarization cycle time (tPCN) composed of chlorine production times chlorine production time (tCPN) followed by chloride enrichment times chloride enrichment time (tCRN).

The bias cycle time (tPC) of a given bias cycle must not equal the bias cycle time (tPC) of any other bias cycle. Similarly, the chlorine production time (tCP) of a given polarization cycle must not equal the chlorine production time (tCP) of any other polarization cycle and the chloride enrichment time (tCR) of each cycle polarization cycle must not be equal to the chloride enrichment time (tCR) of any other polarization cycle.

The polarization cycle time of at least one of the N polarization cycles ? equal to the sum of the timeN of chlorine production pi? the chloride enrichment timeN (tPCN = tCPN tCRN).

To increase chorus production, the chloride enrichment timeN of at least one of the polarization cyclesN should be less than or equal to its chlorine production timeN (tCRN ? tCPN).

The production of chlorine, what is it? as described in embodiments 1 and 2, ? moreover increased when the timeN of chloride enrichment of at least 50% of the cyclesN of polarization ? less than or equal to its chlorine production timeN (tCRN ? tCPN). Consequently, the greater quantity of chlorine? produced when the chloride enrichment time N of each of the N polarization cycles ? less than or equal to its chlorine production timeN (tCRN ? tCPN).

In the chlorine production phase of the experimental examples, the polarization field ? was a direct impulse to a density? of current of 300 A / m<2 >of the anode area (or at a corresponding voltage) for the time of chlorine production. While 300 A / m<2 >? a typical operating condition, other conditions are considered valid.

When checking the field for current, a typical forward bias ? in the range from 100 to 10,000 A / m<2>.

When checking the field for voltage, a typical forward bias ? in the range from 2 to 30 V / cell with one anode and one cathode.

The chlorine production phase begins with a direct charge pulse. A bias is applied during the chlorine production step to induce chlorine production charge flow in a charge flow direction between the anode and cathode. The charge flow direction of chlorine production is from the electrolyte to the anode.

While the examples show a constant waveform during the chlorine build time, the waveform during the chlorine build time can be any combination of waveforms, which substantially produce, or simply produce, chlorine. For example, the profile or waveform during the chlorine production time could be a sine wave, small triangle waves, several rectangular waves, as long as chlorine is being produced. Why is chlorine produced? the applied potential ? greater than the open circuit potential for chlorine at the anode.

It should be understood that there are different ways to control bias, for example through current or voltage control. One could fix the current and observe a varying voltage during the forward pulse. Alternatively, one could fix the voltage and observe a varying amperage during the direct pulse.

The experiments used a chlorine production time (tCPN) in the range of 1-30 seconds and the bias interrupt pulse was ? verified for the chloride enrichment time (tCRN), which was in the range of 0.1 to 5 seconds. Could the chlorine production time be longer? long and the enrichment of chloride could be more? short depending on salt concentration and electrolyte flow rate past the electrode. concentrations more high levels of chloride will allow "times of production of chlorine" more? long. Similarly, speed? flow pi? high levels of the electrolyte over the electrode will reduce the? enrichment of chloride and the ci? allow? "times of production of chlorine" pi? long.

Again, the chloride enrichment time could be longer. long depending on the salt concentration, temperature and electrolyte flow rate past the electrodes.

For example, the time it takes for the the chloride concentration on the electrode approaches the mass concentration during the polarization interrupt pulse, i.e. the chloride enrichment time, ? less when the electrolyte flow past the electrode ? high. Alternatively, the time to enrich the chloride ? more long when the flow of the electrolyte ? inferior. Consequently, the flow rate of the electrolyte during the chloride enrichment time could be increased to reduce the time in which very little chlorine is formed.

There are many ways to relate the control attributes of the chlorine production period to the chloride enrichment period. One way to express the relationship called charge ratio, which ? the ratio of the chloride enrichment charge flow (current) of one polarization cycle to the chlorine production charge flow (current) of the same polarization cycle. This charge ratio? in the range from greater than 0 to less than 1.0. If the feedrates are variable during the chlorine production time or the chloride enrichment time, the feedrate used? the average feedrate flow for the respective chlorine production feedrate during the chlorine production time and the chloride enrichment feedrate during the chloride enrichment time.

Accordingly, such systems, such as those described in Embodiments 1 and 2, would operate in the following ranges with the lower limit greater than 0. Therefore, the charge ratio can? be in the range of greater than 0 to 0.95 or even greater than 0 to 0.75. In practice the charge ratio should be in the range greater than 0 to 0.5, with the range greater than 0 to 0.2 being more? preferred, with the range greater than 0 to 0.08 even more? preferred with the range from greater than 0 to 0.06 being the range pi? favorite.

there ? an advantage in maintaining the ratio between the charge flow (current) of chloride enrichment of a polarization cycle and the charge flow (current) of chlorine production of the same polarization cycle, i.e. the charge ratio, the pi? as low as possible but greater than 0 provided the cell voltage is such that it is greater than or approximately the open circuit voltage for the reference values of anode chlorine evolution and hydrogen evolution and hydrogen generation 'sodium hydroxide at the cathode regulated for the temperature and concentration at the electrodes to a quantity? lower than the chlorine production feedstock flow. This advantage ? that with a low charge ratio, very little chlorine is produced and the chloride enrichment time ? much more short compared to the chlorine production time. Consequently, chlorine production increases when the charge ratio ? greater than when? inferior.

An example profile? shown in FIG. 4 showing three cycles of polarization. As shown in FIG.5, the first polarization cycle begins at time = 0, with the applied field, the polarity, appearing from its maximum.

As further shown in FIG. 5, the applied field ? reduced in a position of "interruption of the polarization" in which there? little or no chlorine or oxygen production, but the anode remains in a charged state. In fig.5 this ? for a period of 1 second.

fig. 6 illustrates a description pi? detail of the elements of a single invented polarization cycle. As shown in FIG.6, the production of chlorine occurs when the forward pulse, also called polarization activation, is applied. The time in which the direct pulse is applied, activation of the polarization, is called the chlorine production time.

As further shown in FIG. 6, the time when the "interruption of polarization" pulse is applied ? called time of enrichment of chloride why? This ? when the electrode concentration of the reaction product/s ? decreased as the chloride (reagent) is enriched to electrode concentration levels close to or equal to the chloride concentration in the bulk electrolyte.

Not ? It is necessary for the electrolyte to pass through the cell during the chloride enrichment time. However, ? preferable that the mass of electrolyte pass through the cell during the time of enrichment of chloride because? There? will it improve? mass transport and will minimize? the time required to bring the concentration at the electrodes back to the concentrations of the mass of electrolyte. Indeed, speed? of electrolyte flow pi? high temperatures increase the diffusion of the reactants around the electrode allowing to reduce the polarization interruption time and to extend the chlorine production time in each cycle.

fig. 7, details the differences between the prior art waveforms and the invented waveform. The clear difference? that the invented waveform does not reverse the polarity? compared to the waveforms of the prior art.

EXPERIMENTAL PART

Experiments were conducted at a NaCl concentration of 1 g/L in two different cells. The first cell was a monopolar cell with 66.5 cm<2 > of anode area and a 30 gallon (133.6 L) reservoir with a flow rate of 13.3 L/min at 80?F (26.7?C ) to simulate a 500-gallon (1.893 L) cell with a 13-blade 3-terminal bipolar cell.

The second cell was a true 500-gallon (1,893 L) system with a 13-blade, 3-lead bipolar cell with a flow rate of 30 gal/min (113.5 L/min).

Each test ? been performed for more of 40 minutes and the concentration of free chlorine of the system ? was measured every 10 minutes during the test.

Equations 1 and 2 were used to calculate the Coulomb efficiencies (E.C.). Free chlorine at 100% efficiency = (equation 1.) Where

MW = 70.906 g/mol for Cl2

n = 2 mol e-/mol Cl2

F = 96485 A*s/mol e-, where A = Amps, s = seconds

Coulomb efficiency(%) = (equation 2). Equation 1 can? be resolved for the speed? theoretical production of free chlorine:

Four sets of experiments were conducted in each cell. The first experiment? was the comparative example (CEx 1) by applying a direct current without inverting the polarity? as described in the art. The second set of experiments ? was a comparative example (CEx 2) in which the polarity? ? been reversed as described in the art. The third set of experiments was a comparative example (CEx 3) using a forward, interrupt pulse, then a polarity pulse. reverse as described in the art.

The fourth set of experiments are the working examples (WEx) applying a direct, bias-on pulse, followed by a bias-off pulse, with no polarity reversal, as described above.

Table 1. Coulomb efficiency (E.C.) in 1 g/L NaCl at 300 A/m<2 >for each forward ON time (tfor) and each polarization non-break time (OFF), reverse ON times (trev ) and specific times of ?interruption of polarization? and current (POL. @ 0.1 A).

Such a group of experiments ? conducted on the same cell by checking the voltage.

Similar results were obtained in comparison to the comparative examples.

Table 2. Coulomb efficiency (E.C.) in 1 g/L NaCl at 7 V for each forward ON time, each bias non-interruption time (OFF or Open Circuit), each inversion time and specific ?bias interruption? (POL. @ 0.5V or 2.45V).

Coulomb efficiency? was evaluated in the 500 gallon configuration using 1 g/L of electrolyte operating at 263.8 A / m<2 > while controlling the applied voltage. The Coulomb efficiency for 40 V constant direct current was 46%. The working examples of 40V for 10s and 10V for 0.5s and 1s achieved Coulomb efficiencies of 49% and 50%, respectively. Three other invented profiles that vary the applied voltage and/or the time of the bias cut-off state have demonstrated Coulomb efficiency above 50%.

Claims (10)

1. A process for producing chlorine (Cl2) in an electrochemical cell, said process comprising a plurality of of polarization cycles comprising at least one polarization cycle, N, having a polarization cycle time (tPCN), a chlorine production time (tCPN), a chloride enrichment time (tCRN), and comprising the steps of A. Apply a bias, to induce a chlorine production charge flow for the chlorine production time (tCPN); B. Reduce the bias to one chloride enrichment feedrate flow per chloride enrichment time (tCRN) with the chloride enrichment feedflow in the same direction as the chlorine production feedflow; where the polarization cycle time (tPC) must not equal the polarization cycle time (tPC) of any other polarization cycle, the chlorine production time (tCP) must not equal the chlorine production time (tCP) of any other chlorine production time, the cycle chloride enrichment time (tCR) shall not be equal to the chloride enrichment time (tCR) of any other cycle; and the total number of bias cycles, TNPC, ? an integer in the range from 1 to 2,160 and N ? an integer in the range of 1 to 2,160 and indicates a particular polarization cycle N of a total number of polarization cycles. 2. The process of claim 1 wherein the chloride enrichment time (tCRN) of at least one of the polarization cycles, ? less than or equal to its chlorine production time (tCPN), such that tCRN ? tCPN. 3. The process of any of claims 1 and 2, wherein the chloride enrichment time (tCRN) of each of the polarization cycles ? less than or equal to its chlorine production time (tCPN), such that tCRN ? tCPN. 4. The process of any of claims 1 to 3, wherein the bias cycle time of at least one of the bias cycles is? equal to the sum of the time of production of chlorine pi? the chloride enrichment time (tPCN = tCPN tCRN). 5. The process of any of claims 1 to 4, wherein the bias cycle time of each of the bias cycles is? equal to the sum of the time of production of chlorine pi? the chloride enrichment time (tPCN = tCPN tCRN). 6. The process of any one of claims 1 to 5, wherein N ? at least 2 and at least two of the bias cycles N are applied consecutively. 7. The process of claim 6 wherein all the N bias cycles are applied consecutively. 8. The process of any of claims 1 to 7, wherein the ratio of the chloride enrichment feedstock flow to the chlorine production feedstock flow of any polarization cycle is ? in the range from 0 to 0.95. 9. The process of any of claims 1 to 7, wherein the ratio of the chloride enrichment feedstock flow to the chlorine production feedstock flow of any polarization cycle is ? in the range from 0 to 0.5. 10. The process of any of claims 1 to 7, wherein the ratio of the chloride enrichment feedstock flow to the chlorine production feedstock flow of any polarization cycle is ? in the range greater than 0 to 0.06.