System and method for controlling chlorate generation in an electrolytic cell

Abstract

The present invention provides a system and method for controlling the generation of chlorate in an electrolytic cell. The method can prepare a hypochlorite-containing solution having a chlorate to free available chlorine ratio of less than 0.1 by contacting a chloride-containing brine stream with an aqueous feed stream to produce a mixture. The technology disclosed in the present invention also includes adjusting at least one of the flow rate of the chloride-containing brine and the chloride ion concentration of the chloride-containing brine to produce a hypochlorite-containing product solution.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Patent Application No. 62 / 750,598, “Electrolysis Method,” filed October 25, 2018, the entirety of which is incorporated herein for any and all purposes. Technical Field

[0003] The present disclosure relates to the field of electrolytic methods for producing hypochlorite-containing solutions using a continuous electrolytic flow cell. Background Art

[0004] Chlorate (ClO3 - ) is a common water pollutant that can be harmful to the environment and to human and animal health. Chlorate is primarily introduced into water as an undesirable byproduct of the water chlorination process used to disinfect water, especially drinking water. In addition to drinking water suppliers, the food and beverage industry and agricultural users use the chlorination process to disinfect water. Therefore, these industries are also sensitive to the presence of chlorate.

[0005] Many regulatory agencies, including the United States Environmental Protection Agency (US EPA), are proposing stricter regulations that would limit the amount of chlorate that can be present in drinking water. Currently, the World Health Organization's interim guideline is 700 ppb chlorate in drinking water, and the US EPA's health reference level is 210 ppb. As a result, municipal water authorities and water managers in affected industries are developing methods to reduce the introduction of chlorate into the water supply.

[0006] The chlorination process disinfects water by introducing a solution containing hypochlorite into the water being treated. Typically, the hypochlorite solution contains chemicals such as hypochlorous acid (HOCl), hypochlorite (ClO - ) ions, molecular chlorine (Cl2) and mixtures thereof. These solutions are known to have broad-spectrum antibacterial and antimicrobial properties.

[0007] Three chlorination methods are commonly used to prepare hypochlorite-containing solutions. First, large amounts of sodium hypochlorite (e.g., bleach) can be added directly (e.g., diluted) to water. This can be done by quantitatively adding a small amount of concentrated sodium hypochlorite solution to the water to be treated.

[0008] Second, chlorine gas can be diffused directly into the water to be treated, which generally results in the production of hypochlorous acid and hypochlorite ions. Third, the hypochlorite-containing solution can be electrolytically generated by an electrolytic system, such as a continuous electrolytic system, such as an on-site generation (OSG) system or an on-site sodium hypochlorite generation (OSHG) system.

[0009] The electrolytic production of hypochlorite-containing solutions generally involves the production of chloride ions (Cl - ) solution (e.g., NaCl brine). During the electrolysis, Cl - Oxidized to Cl2 (Equation (1)) and further reacting with water to produce hypochlorous acid (HOCl) (Equation (2)), which can be further converted to hypochlorite ions in the water being treated (depending on the pH of the water being treated):

[0010] 2Cl - →Cl2+2e - Equation (1)

[0011] Cl2+H2O→HOCl+HCl Equation (2)

[0012] However, when sodium hypochlorite is used in large quantities or sodium hypochlorite produced by electrolysis to disinfect water, undesirable chlorate ions may also be produced by a number of chemical and electrochemical mechanisms.

[0013] When large amounts of hypochlorite are used, the primary mechanism for chlorate formation is through disproportionation of hypochlorite. In this process, the hypochlorite ion (ClO - ) is converted into chlorate ions (ClO3 - ) and chloride ions:

[0014] 3ClO - →ClO3 - +2Cl - Equation (3)

[0015] At lower pH values, when hypochlorite ions (ClO - ) and hypochlorous acid (HOCl), a reaction may occur between the hypochlorous acid and the hypochlorite ion to produce the chlorate ion according to equation (4):

[0016] 2HOCl+ClO - →ClO3 - +2Cl - +2H + Equation (4)

[0017] When the electrolysis system is used to electrolyze a solution containing chloride ions, a variety of electrochemical pathways lead to the undesirable production of chlorate ions. Equations (5) and (6) represent how hypochlorite or hypochlorous acid is oxidized in the presence of water to produce chlorate ions, while equation (7) represents a reaction pathway in which chloride ions can be directly oxidized to chlorate ions in the presence of water.

[0018] 6ClO - +3H2O→3 / 2O2+2ClO3 -+4Cl - +6H + +6e - Equation (5)

[0019] 6HOCl+3H2O→3 / 2O2+2ClO3 - +4Cl - +12H + +6e - Equation (6)

[0020] Cl - +3H2O→ClO3 - +6H + +6e - Equation (7)

[0021] Continuous electrolysis systems offer many advantages over adding large amounts of hypochlorite and diffusing chlorine gas for chlorination of water. Continuous electrolysis systems allow for the production of hypochlorite-containing solutions "on demand" from inexpensive, readily available chloride-containing raw materials (e.g., NaCl). Thus, continuous electrolysis systems do not require the transportation, storage, and handling of hazardous and corrosive solutions of concentrated sodium hypochlorite, oxidizing solids such as calcium hypochlorite (Ca(OCl)2), or toxic gases such as chlorine gas (Cl2), providing significant environmental, health, and safety benefits.

[0022] The on-site generation system is a continuous electrolysis system that allows the formation of a hypochlorite-containing solution "on demand". The on-site generation system generates the hypochlorite-containing solution by electrolyzing a chloride-containing solution, and is configured to meter the hypochlorite-containing solution into a second water source to disinfect the second water source. For example, the on-site generation system can be used to meter the hypochlorite-containing solution into a water stream (e.g., "on-line" metering), or meter into a (storage) reservoir.

[0023] However, recent studies (Stanford et al., Chlorate, perchlorate, and bromate in on-site generated hypochlorite systems, Journal American Water Works Association, 2013, 105, pp. E93-E102) have shown that there is no clear correlation between the operating conditions used in an electrolytic on-site generation system and the amount of chlorate generated. Therefore, despite the efforts of those skilled in the art, there has long been a need to develop new electrolytic methods to produce hypochlorite-containing solutions in which the chlorate level can be controlled. Summary of the invention

[0024] To meet the long-felt need, the present disclosure provides a method for reducing the concentration of chlorate in hypochlorite-treated water produced using a continuous electrolysis system.

[0025] In one non-limiting aspect, the present disclosure provides a method for preparing a hypochlorite-containing solution having a chlorate to free available chlorine ratio of less than 0.1, comprising the steps of: (a) providing a chloride ion-containing feed having a chloride ion concentration of at least 40 mmol / L (e.g., 40 mmol / L to 5000 mmol / L); and (b) passing the chloride ion-containing feed through a continuous electrolytic cell operated at an inter-plate voltage of less than or equal to 10 volts and preferably less than 8 volts to form a hypochlorite-containing solution.

[0026] The interplate voltage may be, for example, less than or equal to 8 V, more preferably less than or equal to 7 V, and most preferably less than or equal to 6 V. In some embodiments, the interplate voltage is about 3.5 V to about 4 V.

[0027] In another aspect, the present disclosure provides a method for preparing a hypochlorite-containing product solution having a chlorate to free available chlorine (FAC) ratio of about 0.005 to about 0.1, comprising: contacting a chloride-containing brine stream with an aqueous feed stream to produce a mixture, the stream having a flow rate, the chloride-containing brine having a chloride ion concentration, and the chloride ion concentration of the mixture and / or the chloride-containing brine is optionally in the range of about 200 mmol / L to about 2500 mmol / L; passing the mixture through a continuous electrolysis cell to produce a hypochlorite-containing product solution; and adjusting at least one of the flow rate of the chloride-containing brine and the chloride ion concentration of the chloride-containing brine to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1.

[0028] Also provided are methods comprising: contacting a chloride-containing brine stream with an aqueous feed stream to form a mixture, the chloride-containing brine having a chloride ion concentration therein; passing the mixture through a continuous electrolysis cell to produce a hypochlorite-containing product solution, the continuous electrolysis cell optionally being operated (i) at a substantially constant interplate voltage therein, or (ii) at a substantially constant current therein; identifying characteristics of the flow rate of the chloride-containing brine to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1.

[0029] Also disclosed is a system comprising: an electrolysis cell configured to be in fluid communication with a chloride-containing brine and an aqueous feed, the electrolysis cell configured to output (e.g., by electrolyzing a mixture comprising the chloride-containing brine and the aqueous feed) a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1, the system configured to adjust at least one of a flow rate of the chloride-containing brine and a chloride concentration of the chloride-containing brine to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1. 0.1 of a hypochlorite-containing product solution, the system optionally being configured to (i) adjust at least one of the flow rate of the chloride-containing brine and the chloride ion concentration of the chloride-containing brine (which in turn can affect the chloride ion concentration in the mixture being electrolyzed) to maintain a substantially constant inter-plate voltage in the continuous electrolysis cell, (ii) adjust at least one of the flow rate of the chloride-containing brine and the chloride ion concentration of the chloride-containing brine to maintain a substantially constant current supplied in the continuous electrolysis cell, or (i) and (ii).

[0030] The present inventors have surprisingly discovered that when the voltage of the electrolytic cell and the chloride concentration of the chloride-containing brine are controlled in accordance with the present disclosure, a hypochlorite-containing solution having a surprisingly low chlorate to free available chlorine ratio can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the drawings, which are not necessarily drawn to scale, like reference numerals may describe similar components in different views. Like reference numerals with different letter suffixes may represent different instances of similar components. The accompanying drawings generally illustrate various aspects discussed in this document by way of example and not limitation. In the drawings:

[0032] Figure 1 An exemplary embodiment of an apparatus suitable for performing the method of the present disclosure is provided;

[0033] Figure 2 Another exemplary embodiment of an apparatus suitable for performing the method of the present disclosure is provided; and

[0034] Figure 3 Yet another exemplary embodiment of an apparatus suitable for performing the method of the present disclosure is provided. DETAILED DESCRIPTION

[0035] The present disclosure may be more readily understood by reference to the following detailed description in conjunction with the accompanying drawings and examples which form a part of this disclosure. It should be understood that the present disclosure is not limited to the specific apparatus, methods, applications, conditions or parameters described and / or illustrated herein, and that the terminology used herein is for the purpose of describing specific embodiments by way of example only and is not intended to limit the claimed technology.

[0036] In addition, as used in the specification including the appended claims, the singular forms "a", "an" and "the" include plural, and unless the context clearly dictates otherwise, references to a particular numerical value include at least that particular value. As used herein, the term "plurality" means more than one. When a range of values ​​is expressed, another embodiment includes from one particular value and / or to another particular value. Similarly, when a value is expressed as an approximation by using the antecedent "about", it should be understood that the particular value forms another embodiment. All ranges are inclusive and combinable, and it should be understood that the steps can be performed in any order.

[0037] It should be understood that, for clarity, certain features of the invention described herein in the context of separate embodiments may also be provided in combination with a single embodiment. Conversely, various features of the invention described in the context of a single embodiment for brevity may also be provided separately or in any sub-combination. All documents cited herein are incorporated herein by reference in their entirety for any and all purposes.

[0038] In addition, references to values ​​in ranges include every value within the range. In addition, the term "comprising" should be understood to have its standard, open-ended meaning, but should also be understood to encompass "consisting of." For example, a device that includes part A and part B may include parts other than part A and part B, but may also be formed of only part A and part B.

[0039] The preferred and / or optional features of the present invention will now be listed. Unless the context otherwise requires, any aspect of the present invention can be combined with any other aspect of the present invention. Unless the context otherwise requires, any preferred and / or optional features of any aspect can be combined with any aspect of the present invention individually or in combination.

[0040] In some aspects, the present disclosure relates to methods of preparing hypochlorite-containing solutions, for example, such solutions having a chlorate to free available chlorine ratio of less than 0.1.

[0041] The term "free available chlorine" is understood to mean the total combined concentration of hypochlorite ions (ClO - ), hypochlorous acid (HOCl) and molecular chlorine (Cl2).

[0042] Free available chlorine can be determined by methods known to those skilled in the art, for example by spectrophotometric determination using N,N-diethyl-p-phenylenediamine.

[0043] For the avoidance of doubt, terms such as "chlorate concentration", "hypochlorite concentration" and "chloride ion concentration" include the concentration of free ions, salts and conjugate acids. For example, the term "hypochlorite concentration" should be understood to include hypochlorites (e.g., NaOCl, KOCl, etc.), hypochlorous acid (HOCl) and hypochlorite ions (ClO - ) concentration, and the term "chlorate concentration" should be understood to include chlorates (such as NaClO3, KClO3, Ca(ClO3)2, etc.), chloric acid (HClO3) and chlorate ions (ClO3 - ).

[0044] As used herein, the chlorate to free available chlorine (FAC) ratio refers to the chlorate concentration in mg / L divided by the free available chlorine concentration in mg / L.

[0045] The chlorate concentration can be determined by methods known to those skilled in the art, for example by ion chromatography.

[0046] The present disclosure provides, inter alia, a method for electrolyzing a chloride-containing feed to produce a hypochlorite-containing solution having a chlorate to free available chlorine (FAC) ratio of less than 0.1.

[0047] Preferably, the chlorate to free available chlorine ratio may be less than 0.075, less than 0.05, less than 0.025, less than 0.02, less than 0.015, or less than 0.01.

[0048] The present disclosure includes the step of providing a chloride ion-containing feed having a chloride ion concentration of at least 40 mmol / L.

[0049] The feed containing chloride ions may have a chloride ion concentration of at least 100 mmol / L, at least 200 mmol / L, at least 250 mmol / L, at least 500 mmol / L, at least 1000 mmol / L, at least 1500 mmol / L, or at least 2000 mmol / L. The feed containing chloride ions may have a chloride ion concentration of less than 5000 mmol / L, less than 4000 mmol / L, less than 3000 mmol / L, or less than 2500 mmol / L.

[0050] Typically, the chloride ion-containing feed may have a chloride ion concentration of 100 mmol / L to 2000 mmol / L, 200 mmol / L to 2000 mmol / L, 500 mmol / L to 2000 mmol / L, 1000 mmol / L to 2000 mmol / L, or 1500 mmol / L to 2000 mmol / L.

[0051] The chloride-containing feed can be prepared by dissolving a chloride-containing compound in water; the chloride-containing feed can also be prepared by mixing a source brine with an aqueous feed. The chloride-containing compound used to prepare the chloride-containing feed is not particularly limited. Preferably, the chloride-containing compound used to prepare the chloride-containing feed is sodium chloride (NaCl). Those skilled in the art will recognize alternative chloride-containing compounds suitable for preparing a chloride-containing solution.

[0052] The method according to the present disclosure also includes the step of passing the chloride ion-containing feed through a continuous electrolytic cell, wherein an inter-plate voltage of less than or equal to 12 volts is applied.

[0053] The continuous electrolytic cell comprises two or more electrodes separated by a fluid path. The two or more electrodes can be independently an anode and a cathode. The electrolytic cell may also include one or more intermediate electrodes. The number of intermediate electrodes used in the electrolytic cell is not particularly limited, for example, the electrolytic cell may include two or more intermediate electrodes, three or more intermediate electrodes, four or more intermediate electrodes, or a plurality of intermediate electrodes. The intermediate electrode may be a bipolar electrode.

[0054] The electrolytic cell may comprise an anode and a cathode.The electrolytic cell may comprise an anode, a cathode and one or more intermediate electrodes.

[0055] The continuous electrolysis cell includes an inlet and an outlet that form part of a fluid path. The inlet and the outlet are in fluid communication with each other and allow a solution (eg, a chloride-containing feed) to continuously pass through the electrolysis cell.

[0056] As the solution passes through the fluid path of the electrolytic cell, it passes between two electrodes (eg, an anode and a cathode) where an inter-plate voltage is applied.

[0057] As used herein, the term "interplate voltage" refers to the voltage between any two electrodes in an electrolytic cell. For example, in an electrolytic cell containing an anode and a cathode, the interplate voltage will be the voltage between the anode and the cathode. For example, in an electrolytic cell containing an anode, a cathode, and an intermediate electrode, the interplate voltage will be the voltage between the anode and the intermediate electrode, and the voltage between the intermediate electrode and the cathode. Those skilled in the art will know how to configure an electrolytic cell to achieve the interplate voltage required for the present disclosure.

[0058] The voltage between the electrolytic plates may be less than or equal to 12 volts, less than or equal to 8 volts, less than or equal to 7 volts, less than or equal to 6 volts, less than or equal to 5.5 volts, or less than or equal to 5 volts.

[0059] The voltage between the electrolytic plates may be greater than or equal to 2 volts, greater than or equal to 3 volts, or greater than or equal to 4 volts.

[0060] The voltage between the electrolytic plates may be in the range of about 2 volts to about 8 volts, about 3 volts to about 7 volts, about 4 volts to about 7 volts, about 4.5 volts to about 6 volts, about 5 volts to about 6 volts.

[0061] The electrolytic cell forms part of an electrolytic system, such as a continuous system. It should be understood that a continuous system is not an intermittent system. A continuous system is understood to be a system configured so that the chloride ion-containing solution feed passes through the electrolytic cell only once.

[0062] In contrast, an intermittent system is understood to include a system in which a solution containing a large amount of chlorine (e.g., as a feed) is electrolyzed in a single container or vessel. In an intermittent system, the solution feed containing chloride ions can be electrolyzed multiple times. For example, an intermittent system includes electrolysis in a single container, wherein the solution feed containing chloride ions is not removed from the single container during the electrolysis process, and multiple electrolysis can be performed. Intermittent systems also include closed systems that are configured so that after electrolysis of the solution feed containing chloride ions, the resulting hypochlorite-containing solution is recycled through the electrolytic cell (i.e., the hypochlorite-containing solution can be electrolyzed a second time or subsequently).

[0063] After the electrolysis of the chloride-containing solution feed, a solution containing hypochlorite is prepared. The hypochlorite concentration may be greater than 500 mg / L, greater than 1000 mg / L, greater than 2000 mg / L, greater than 3000 mg / L, greater than 5000 mg / L or greater than 7000 mg / L. Typically, the chloride-containing feed is electrolyzed in an electrolytic cell, for example, for an average electrolysis residence time between 30 seconds and 600 seconds. In one embodiment, the average electrolysis residence time may be greater than 30 seconds, greater than 35 seconds, greater than 40 seconds or greater than 45 seconds.

[0064] In another embodiment, the average electrolysis residence time may be less than 120 seconds, less than 110 seconds, or less than 100 seconds. In yet another embodiment, the residence time in the electrolytic cell may be between 260 seconds and 600 seconds, between 250 seconds and 590 seconds, between 240 seconds and 580 seconds.

[0065] In certain embodiments of the present disclosure, the electrolytic cell is used in an on-site generation system.The disclosed method for preparing a hypochlorite-containing solution is particularly suitable and beneficial for use in an on-site generation system.

[0066] In certain embodiments of the present disclosure, the electrolytic cell includes a control system and one or more sensors at the inlet and outlet of the electrolytic cell.

[0067] The sensor may be used to detect, but is not limited to, one or more of the following: (i) the chloride ion concentration in the chloride ion-containing feed supplied to the electrolytic cell; (ii) the hypochlorite concentration of the solution leaving the electrolytic cell; (iii) the chlorate concentration of the hypochlorite solution leaving the cell; (iv) the temperature of the chloride ion-containing feed or the hypochlorite-containing solution; (v) the flow rate of the chloride ion-containing feed entering the cell. The sensor may also be used to detect the concentration of chloride ions in a stream in contact with the feed, for example, the concentration of chloride ions in a brine added to an aqueous stream to constitute the chloride ion-containing feed supplied to the electrolytic cell.

[0068] The sensor is in communication with a control system. The control system can be used to effect changes in any of the conditions used in the disclosed methods (e.g., applied plate voltage, flow rate, chloride ion concentration in the chloride ion-containing solution, etc.). If, for example, the chlorate concentration of the solution leaving the electrolysis cell is higher than a desired chlorate concentration, it may be desirable to control the conditions under which the electrolysis is conducted.

[0069] Figure 1 One embodiment of an electrolysis system is shown. In this embodiment, a chloride-containing solution, such as a sodium chloride solution, is prepared in a container 1 and passed to a continuous electrolysis cell 3 along an inlet 2. An inter-plate voltage is applied to the solution in the electrolysis cell before the resulting hypochlorite-containing solution leaves the cell along an outlet 4. The hypochlorite-containing solution is then collected in a container 5. Sensors (6a and 6b) are placed on the inlet (2) and outlet (4), which feed data back to a control system (7). The control system (7) can then change the conditions according to the present disclosure to prepare a hypochlorite-containing solution having a desired chlorate to free available chlorine (FAC) ratio.

[0070] Figure 2 One embodiment of an on-site generation system is shown. A solution containing chloride ions (e.g., feed) is prepared in a container 1 and passed to an electrolytic cell 3 along an inlet 2. An interplate voltage is applied to the solution in the electrolytic cell before the resulting hypochlorite-containing solution leaves the cell along an outlet 4. The hypochlorite-containing solution is then metered into a continuous flow of secondary water in a pipe (6) by a metering device (5).

[0071] Figure 3 Another embodiment of an on-site generation system is shown. Here, water enters the system through line 1. A saturated brine containing chloride ions is prepared in container 2 and transferred along line 3 to combine with the contents of line 1, thereby producing a mixture that is then fed into an electrolysis system 4. Container 2 can be a tank or other vessel and can be configured to receive additional salt and / or solvent (e.g., water) before, during, or even after operation of the system.

[0072] Not shown in this figure are specific components of the electrolysis system 4, which one skilled in the art will appreciate includes the system, including the electrolysis cell, power supply, various pumps, and control system. In addition, it should be understood that not all of these components need to be included in a single structure in order to practice the present disclosure.

[0073] Once the electrolysis of the diluted brine is completed, the electrolytic solution will leave the electrolysis system 4 along pipeline 5 to container 6, where the solution is temporarily stored. (It should be understood that container 6 is optional.) When necessary, the electrolytic solution is transported from container 6 to the application point via pipeline 7 by applying a mechanism not specifically shown here.

[0074] As a reference Figure 3 As a non-limiting example, a mixture may be formed by contacting an aqueous feed 1 with a flow of a chloride-containing brine (or "source brine") 3, which is supplied by element 2. (Element 2 may be, for example, a container, a tank, or a brine generator). The chloride-containing brine may be, for example, a saturated NaCl solution, but it may also be an unsaturated NaCl solution, for example, a solution within about 10% of saturation. The chloride ion level in the source brine may be maintained manually, but may also be maintained in an automated manner.

[0075] The mixture is then passed through an electrolysis system 4, in which the mixture is electrolyzed to produce a hypochlorite-containing product solution 5. The solution 5 can in turn be stored in a container 6 and can be discharged from the storage container 6 via a line 7.

[0076] Example

[0077] The following examples are illustrative only and are not intended to limit the scope of the present disclosure or the appended claims.

[0078] The disclosed technology will now be described with reference to the following examples, which are provided to aid understanding of the disclosure and are not intended to limit the scope thereof.

[0079] Example 1

[0080] A chloride-containing solution (prepared from sodium chloride) having a NaCl concentration of 15 g / L (equivalent to a chloride concentration of 257 mmol / L) was electrolyzed using a continuous (undivided) electrolytic cell with an applied interplate voltage between 3 and 6 volts. The electrolytic cell included a main anode, a main cathode, and a single intermediate electrode. The electrolytic active dimensions of each electrode were 1" x 3". After these solutions were electrolyzed, the pH and free available chlorine content of the samples were measured using standard laboratory methods. A portion of the electrolyzed solution was then quenched by adding an excess of malonic acid, and these quenched solutions were then used for the measurement of chlorate in the solution. The results in Table 1 show that increasing the voltage used to electrolyze the chloride-containing solution resulted in an increase in the ratio of chlorate to free available chlorine from 0.002 to 0.028.

[0081] Table 1: Exemplary results.

[0082]

[0083] Without being bound by any particular theory, it is believed that at relatively high current densities, the current efficiency decreases. This decreased efficiency, in turn, leads to a relative increase in the production of chlorate and other low efficiency products.

[0084] Example 2

[0085] A sodium chloride solution with a NaCl concentration between 2.5 g / L and 50 g / L (equivalent to a chloride ion concentration of 43 mmol / L to 1711 mmol / L) was electrolyzed using a continuous electrolytic cell at an inter-plate voltage of 6 volts. In this embodiment, the electrolytic cell consists of a main anode, a main cathode, and a single intermediate electrode. The electrolytic active size of each electrode is 1"×3". After these solutions are electrolyzed, the free available chlorine (FAC) content of the sample is measured by spectrophotometry using N,N-diethyl-p-phenylenediamine, and the pH is measured. A portion of the electrolytic solution is then quenched by adding an excess of malonic acid, and these quenched solutions are then used for the measurement of chlorate in the solution by ion chromatography. As can be seen from the results presented in Table 2, increasing the chloride ion content of the chloride-containing solution causes the ratio of chlorate to free available chlorine in the electrolytic solution to decrease from 0.066 to 0.005.

[0086] Table 2: Exemplary results

[0087]

[0088] The data show that as the chloride concentration increases, the chlorate to free available chlorine ratio decreases. Surprisingly, operating at an interplate voltage of 6 volts or less in combination with a chloride concentration greater than 40 mmol / L results in a hypochlorite-containing solution having a very low chlorate to free available chlorine ratio.

[0089] Example 3

[0090] Using a continuous electrolysis system (including two intermediate plates in addition to the main anode and cathode), a sodium chloride solution with a NaCl concentration between 5g / L and 75g / L was electrolyzed with an inter-plate voltage between 3.0V and 4.6V and an applied current between 5.1A and 12.7A. After these solutions were electrolyzed, the free available chlorine (FAC) content of the sample was measured using N,N-diethyl-p-phenylenediamine by spectrophotometry, and pH was measured. A portion of the electrolytic solution was then quenched by adding an excess of malonic acid, and these quenching solutions were then used for the measurement of the chlorate radical in the solution by ion chromatography. As can be seen from the results presented in Table 3, increasing the chloride content of the solution containing chloride ions causes the chlorate radical in the electrolytic solution to be reduced to 0.069 with the free available chlorine ratio from 0.022.

[0091] Table 3: Exemplary results.

[0092]

[0093] Example 4

[0094] Using a continuous electrolysis system, a sodium chloride solution with a NaCl concentration between 15.8g / L and 31.7g / L was electrolyzed with an interplate voltage between 3.4V and 4.3V and an applied current of 65A. After these solutions were electrolyzed, the free available chlorine (FAC) content of the sample was measured by iodine titration. A portion of the electrolytic solution was then stabilized by adding excessive sodium hydroxide and diluted with distilled water to maintain a pH between pH 11-11.5. These stabilized solutions were then used to measure the chlorate ions in the solution by ion chromatography. As can be seen from the results presented in Table 4, increasing the chloride ion content of the solution containing chloride ions causes the chlorate radical in the electrolytic solution to be reduced to 0.039 with the free available chlorine ratio from 0.005.

[0095] Table 4: Exemplary results.

[0096]

[0097] Example 5

[0098] Use something like Figure 1The continuous electrolysis system shown electrolyzes a sodium chloride solution having a NaCl concentration between 5.8 g / L and 12.9 g / L by passing the solution through an electrolytic cell at a flow rate of 1.64 ml / min (Table 5) or 8 ml / min (Table 6). After the NaCl solution is electrolyzed, the resulting oxidant solution is characterized by measuring the oxidant FAC content and the oxidant chlorate content. As with the other examples, brines containing a higher initial NaCl content produce an oxidant solution having a lower chlorate content when electrolyzed.

[0099] In the following non-limiting Tables 5 and 6, Faraday's Law was used to calculate Chlorine (g / hr) = (A)(B)(C)(D)(E), where A = 35.45 g / gm-Eq; B = 1 gram Eq / 26.8 amp-hours; C = number of compartments (in this case, 1 compartment); D = operating amps; and E = efficiency. The cell area is 19.35 cm 2 , and the flow rate was 1.64 ml / min.

[0100] Table 5: Exemplary results.

[0101]

[0102] Table 6: Exemplary results.

[0103]

[0104] Example 6

[0105] Use something like Figure 3 The continuous flow electrolysis cell described in was used to electrolyze sodium chloride brines with similar brine total dissolved solids (TDS) content at two different total system flow rates. After the NaCl solution was electrolyzed, the resulting oxidant solution was characterized by measuring the oxidant FAC content and the oxidant chlorate content.

[0106] Table 7: Exemplary results.

[0107]

[0108] Implementation

[0109] The following embodiments are exemplary only and are not intended to limit the scope of the present disclosure or the appended claims.

[0110] Embodiment 1. A method for preparing a hypochlorite-containing product solution having a chlorate to free available chlorine (FAC) ratio of about 0.005 to about 0.1, comprising: contacting a chloride-containing brine stream with an aqueous feed stream to produce a mixture, the stream having a certain flow rate, the chloride-containing brine having a certain chloride ion concentration and the mixture having a certain chloride ion concentration, and the chloride ion concentration of the chloride-containing brine and / or the chloride ion concentration of the mixture is optionally in the range of about 200 mmol / L to about 2500 mmol / L; passing the mixture through a continuous electrolysis cell to produce a hypochlorite-containing product solution; and adjusting at least one of the flow rate of the chloride-containing brine and the chloride ion concentration of the chloride-containing brine to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1.

[0111] For example, the chloride ion concentration of the chloride ion-containing solution and / or mixture can be adjusted to maintain a chlorate to FAC ratio in the hypochlorite-containing product solution at about 0.005 to about 0.1, or about 0.005 to about 0.08, or about 0.005 to about 0.07, or about 0.005 to about 0.05, or about 0.005 to about 0.03, or about 0.005 to about 0.003, or about 0.005 to about 0.002, or about 0.005 to about 0.001. The chloride ion concentration of the chloride ion-containing solution and / or mixture can be adjusted to maintain a chlorate to FAC ratio in the hypochlorite-containing product solution at about 0.005 to about 0.1, or about 0.005 to about 0.08, or about 0.005 to about 0.07, or about 0.005 to about 0.05, or about 0.005 to about 0.03, or about 0.005 to about 0.003, or about 0.005 to about 0.002, or about 0.005 to about 0.001.

[0112] The chloride concentration of the chloride-containing solution and / or mixture can be adjusted to maintain a chlorate to FAC ratio in the hypochlorite-containing product solution from about 0.007 to about 0.05, or from about 0.007 to about 0.03, or from about 0.007 to about 0.02, or even from about 0.007 to about 0.01.

[0113] For example, the chloride ion concentration in the mixture can be adjusted by, for example, producing an increased or decreased chloride ion concentration in the salt water. This can be achieved by, for example, adding more chloride ion sources (e.g., NaCl, in pure or concentrated form). Alternatively, the relative amount of solvent and chloride ion in the ion-containing salt water and / or mixture (e.g., by adding water or other solvents) can be increased to reduce the chloride ion concentration in the mixture. The chloride ion-containing solution can include, for example, NaCl and water. Other solvents other than water can also be used.

[0114] In addition to or as an alternative to adjusting the chloride ion concentration of the chloride ion-containing brine and / or mixture, the flow rate of the chloride ion-containing brine flow (or even the mixture) can also be adjusted. This can be achieved by valves, pumps and other elements known to those of ordinary skill in the art. Thus, either or both of the flow rate of the chloride ion-containing brine flow and the chloride ion concentration of the chloride ion-containing brine can be adjusted.

[0115] The chloride ion concentration of the chloride ion-containing brine (which may be referred to as "source brine") and / or the mixture may be, for example, from about 200 mmol / L to about 2500 mmol / L, or from about 250 to about 2300 mmol / L, or from about 300 mmol / L to about 2100 mmol / L, or from about 400 mmol / L to about 1900 mmol / L, or from about 500 mmol / L to about 1700 mmol / L, or from about 600 mmol / L to about 1500 mmol / L, or from about 700 mmol / L to about 1300 mmol / L, or from about 800 mmol / L to about 1200 mmol / L, or even from about 900 mmol / L to about 1100 mmol / L. Chloride ion concentration is about 200mmol / L to about 2500mmol / L, or about 250mmol / L to about 2300mmol / L, or about 300mmol / L to about 2100mmol / L, or about 400mmol / L to about 1900mmol / L, or about 500mmol / L to about 1700mmol / L, or about 600mmol / L to about 1500mmol / L, or about 700mmol / L to about 1300mmol / L, or about 800mmol / L to about 1200mmol / L, or even about 900mmol / L to about 1100mmol / L mixture is considered suitable. However, it should be understood that the above concentrations and ranges are exemplary only, not restrictive or required.

[0116] The chloride-containing brine may be saturated with chloride (eg, the chloride-containing brine may be a saturated NaCl solution). The chloride-containing brine may also have a chloride ion concentration less than the saturation concentration (eg, about 80% to about 99% of the saturation concentration).

[0117] The chloride-containing brine may have a chloride ion concentration that is maintained within 10%, within 5%, or even within about 1% of the saturation concentration. The chloride-containing brine may be supplied, for example, by a brine generator. An exemplary brine generator is a source of a saturated (or nearly saturated) chloride solution, such as NaCl. The brine generator may be manually operated, but may also be operated in an automated manner.

[0118] For example, an aqueous feed (e.g., process water) can be contacted with a flow of a chloride ion-containing solution (or "source brine"). The source brine can be a saturated salt solution (e.g., a saturated NaCl solution), but this is not a requirement, as the source brine can have less than a saturated concentration of salt dissolved therein. The source brine can be provided by a brine generator that is configured to maintain (either by manual means or automatically) the chloride ion level in the source brine, but this is not a requirement.

[0119] The mixture can then be conveyed to a continuous electrolysis cell where electrolysis is performed to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1 The product can then be conveyed downstream (e.g., to a process unit), but can also be held (e.g., in a storage tank) until needed.

[0120] Embodiment 2. The method according to embodiment 1 further includes adjusting at least one of the flow rate of the chloride-containing brine and the chloride ion concentration of the chloride-containing brine to (i) maintain a substantially constant inter-electrolytic plate voltage in the continuous electrolytic cell, or (ii) maintain a substantially constant current supplied in the continuous electrolytic cell. For example, one or both of the flow rate of the chloride-containing brine (and / or mixture) and the chloride ion concentration of the chloride-containing brine (and / or mixture) can be adjusted to maintain a substantially constant inter-electrolytic plate voltage in the continuous electrolytic cell. For another example, one or both of the flow rate of the chloride-containing brine and the chloride ion concentration of the chloride-containing brine can be adjusted to maintain a substantially constant current supplied in the continuous electrolytic cell. One or both of the flow rate of the mixture and the chloride ion concentration of the mixture can be adjusted to maintain a substantially constant current supplied in the continuous electrolytic cell.

[0121] The continuous electrolysis cell may be operated at a substantially constant inter-plate voltage therein. The continuous electrolysis cell may be operated at a substantially constant current supplied thereto.

[0122] Embodiment 3. The method according to any one of Embodiments 1-2 further comprises adjusting the current supplied in the continuous electrolysis cell to maintain a substantially constant voltage between the electrolysis plates in the continuous electrolysis cell.

[0123] Embodiment 4. The method according to any one of embodiments 1-2 further comprises adjusting the inter-plate voltage in the continuous electrolysis cell to maintain a substantially constant current supplied in the continuous electrolysis cell.

[0124] Embodiment 5. The method according to any one of embodiments 1-4, wherein the hypochlorite-containing solution has a chlorate to FAC ratio of less than 0.075. Exemplary such ratios are, for example, less than 0.075, less than 0.070, less than 0.065, less than 0.060, less than 0.055, less than 0.050, less than 0.045, less than 0.040, less than 0.035, less than 0.030, less than 0.025, less than 0.020, less than 0.015, less than 0.010, less than 0.009, less than 0.008, less than 0.007, or even less than 0.006.

[0125] Embodiment 6. The method according to embodiment 5, wherein the hypochlorite-containing solution has a chlorate to FAC ratio of less than 0.025. Exemplary such ratios are, for example, 0.005 to 0.024, 0.005 to 0.022, 0.006 to 0.020, 0.007 to 0.018, 0.008 to 0.016, or even 0.009 to 0.014.

[0126] Embodiment 7. The method of embodiment 6, wherein the hypochlorite-containing solution has a chlorate to FAC ratio of less than 0.010.

[0127] Embodiment 8. The method according to any one of embodiments 1-7, wherein the chloride ion concentration of the chloride ion-containing brine, the mixture, or both is from about 250 mmol / L to about 2500 mmol / L.

[0128] Embodiment 9. A method according to embodiment 8, wherein the chloride ion concentration of the chloride ion-containing brine, the mixture, or both is at least 500 mmol / L, for example, at least 600 mmol / L, at least 700 mmol / L, at least 800 mmol / L, at least 900 mmol / L, at least 1000 mmol / L, at least 1100 mmol / L, at least 1200 mmol / L, at least 1300 mmol / L, at least 1400 mmol / L, at least 1500 mmol / L, at least 1600 mmol / L, at least 1700 mmol / L, at least 1800 mmol / L, at least 1900 mmol / L, at least 2000 mmol / L, at least 2100 mmol / L, at least 2200 mmol / L, at least 2300 mmol / L, or even at least 2400 mmol / L.

[0129] Embodiment 10. The method of embodiment 9, wherein the chloride ion concentration of the chloride ion-containing brine, the mixture, or both is at least 1000 mmol / L.

[0130] Embodiment 11. The method of embodiment 10, wherein the chloride ion concentration of the chloride ion-containing brine, the mixture, or both is at least 1500 mmol / L.

[0131] Embodiment 12. The method of embodiment 11, wherein the chloride ion concentration of the chloride ion-containing brine, the mixture, or both is at least 2000 mmol / L.

[0132] Embodiment 13. The method according to any one of embodiments 1-12, wherein the chloride-containing brine comprises sodium chloride. Other chloride-containing salts may be used, such as potassium chloride, potassium chloride, calcium chloride, and other metal chlorides. Sodium chloride is considered particularly suitable, but sodium chloride is exemplary only and not limiting.

[0133] Embodiment 14. A method according to any of Embodiments 1-13, wherein the inter-plate voltage of the continuous electrolysis cell is less than or equal to about 8 volts, less than or equal to about 7 volts, less than or equal to about 6 volts, less than or equal to about 5.5 volts, or less than or equal to about 5 volts.

[0134] Embodiment 15. The method according to any one of embodiments 1-14, wherein the concentration of hypochlorite present in the hypochlorite-containing product solution is about 500 mg / L to about 10,000 mg / L. The concentration of hypochlorite present in the hypochlorite-containing product solution can be, for example, about 500 mg / L to about 10,000 mg / L, or about 600 mg / L to about 9000 mg / L, or about 800 mg / L to about 8500 mg / L, or about 900 mg / L to about 8000 mg / L, or about 950 mg / L to about 7500 mg / L, or about 1000 mg / L to about 7000 mg / L, or about 1000 mg / L to about 6500 mg / L. , or about 1500 mg / L to about 6000 mg / L, or about 1800 mg / L to about 5800 mg / L, or about 2000 mg / L to about 5400 mg / L, or about 2200 mg / L to about 5000 mg / L, or about 2500 mg / L to about 4500 mg / L, or about 2800 mg / L to about 4200 mg / L, or about 3000 mg / L to about 3900 mg / L, or about 3200 mg / L to about 3500 mg / L. The above ranges are exemplary only and are not intended to limit the present disclosure.

[0135] Embodiment 16. The method according to any one of embodiments 1-15, wherein the pH of at least one of the chloride-containing brine and the mixture is in the range of about 6 to about 10. The pH of the chloride-containing brine (or mixture) may be about 6 to about 10, or about 6.2 to about 9.8, or about 6.4 to about 9.6, or about 6.6 to about 9.4, or about 6.8 to about 9.2, or about 7 to about 9, or about 7.2 to about 8.8, or about 7.4 to about 8.6, or about 7.6 to about 8.4, or about 7.8 to about 8.2, or even about 8. A pH of about 6 to about 8 is believed to be particularly suitable.

[0136] Embodiment 17. The method according to any one of embodiments 1-16, wherein the average residence time of the mixture in the electrolytic cell is about 30 seconds to about 600 seconds. The residence time can be, for example, about 10 seconds to about 600 seconds, or about 15 seconds to about 550 seconds, or about 20 seconds to about 500 seconds, or about 25 seconds to about 450 seconds, or about 30 seconds to about 400 seconds, or about 40 seconds to about 350 seconds, or about 45 seconds to about 300 seconds, or about 50 seconds to about 270 seconds, or about 60 seconds to about 240 seconds, or about 80 seconds to about 220 seconds, or about 100 seconds to about 200 seconds, or about 120 seconds to about 180 seconds, or about 140 seconds to about 160 seconds.

[0137] Embodiment 18. The method according to any of embodiments 1-17, wherein the electrolytic cell comprises an intermediate electrode. The electrolytic cell may comprise one, two, three, four or more intermediate electrodes.

[0138] Embodiment 19. The method according to any one of embodiments 1-18, wherein the electrolytic cell is used in an on-site generation system, such as an on-site hypochlorite generation system. The electrolytic cell can also be used in a portable system, such as a portable hypochlorite generation system.

[0139] Embodiment 20. The method of any of Embodiments 1-19, wherein the electrolytic cell comprises a control system and comprises one or more sensors at an inlet or outlet of the electrolytic cell. The sensor can be configured to monitor a characteristic of the flow rate of the chloride-containing brine, such as the flow rate of the solution, the chloride concentration of the solution, or both. The sensor can be configured to monitor a characteristic of the flow rate of the mixture, such as the flow rate of the mixture, the chloride concentration of the mixture, or both.

[0140] The sensor can also be configured to monitor characteristics of the product solution containing hypochlorite. These characteristics can include, for example, the hypochlorite concentration of the solution, the FAC concentration of the solution, the flow rate of the solution, etc.

[0141] Embodiment 21. A method according to embodiment 20, wherein the control system is configured to adjust at least one of the flow rate of the chloride ion-containing brine, the inter-plate voltage in the continuous electrolysis cell, the current supplied in the continuous electrolysis cell, and the chloride ion concentration of the chloride ion-containing brine, for example in response to signals collected by one or more sensors.

[0142] The control system may also be configured to adjust at least one of the flow rate of the chloride-containing brine, the interplate voltage within the continuous electrolysis cell, the current supplied within the continuous electrolysis cell, or the chloride concentration of the chloride-containing brine in response to manual or automatic input. Such input may (but need not) be based on signals collected by one or more sensors.

[0143] Embodiment 22. A method comprising: contacting a chloride-containing brine stream with an aqueous feed stream to form a mixture, the chloride-containing brine having a chloride ion concentration therein, the mixture having a chloride ion concentration therein; passing the mixture through a continuous electrolysis cell to produce a hypochlorite-containing product solution, the continuous electrolysis cell optionally operating (i) at a substantially constant interplate voltage therein, or (ii) at a substantially constant current therein; identifying characteristics of the flow rate of the chloride-containing brine to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1.

[0144] Without being bound by any particular theory, use or application, the foregoing method can be used, for example, to configure a system before the system is delivered to a user or customer. More specifically, the foregoing method can be used to select and set operating parameters of the system so that the system is configured to achieve desired characteristics in the product, for example, a desired chlorate to FAC ratio.

[0145] For example, a stream of chloride-containing brine (also referred to as "source brine") can be contacted with an aqueous feed stream to produce a mixture. The mixture is then conveyed to a continuous electrolysis cell where electrolysis is performed to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1. The flow rate of the source brine can be adjusted to obtain a hypochlorite-containing product solution having a desired FAC ratio.

[0146] Embodiment 23. The method of embodiment 22, wherein the characteristic of the flow rate of the chloride-containing brine is at least one of (i) the chloride ion concentration in the chloride-containing brine and (ii) the flow rate of the chloride-containing brine. Thus, a chloride ion concentration (or even a range of chloride ion concentrations) can be identified that produces a chlorate-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1.

[0147] For example, the chloride concentration of the chloride-containing brine (and / or mixture) can be adjusted to maintain a chlorate to FAC ratio in the hypochlorite-containing product solution of about 0.005 to about 0.1, or about 0.005 to about 0.08, or about 0.005 to about 0.07, or about 0.005 to about 0.05, or about 0.005 to about 0.03, or about 0.005 to about 0.003, or about 0.005 to about 0.002, or about 0.005 to about 0.001. The chloride concentration of the chloride-containing brine (and / or mixture) can be adjusted to maintain a chlorate to FAC ratio in the hypochlorite-containing product solution of about 0.005 to about 0.1, or about 0.005 to about 0.08, or about 0.005 to about 0.07, or about 0.005 to about 0.05, or about 0.005 to about 0.03, or about 0.005 to about 0.003, or about 0.005 to about 0.002, or about 0.005 to about 0.001.

[0148] The chloride concentration of the chloride-containing brine (and / or mixture) can be adjusted to maintain a chlorate to FAC ratio in the hypochlorite-containing product solution from about 0.007 to about 0.05, or from about 0.007 to about 0.03, or from about 0.007 to about 0.02, or even from about 0.007 to about 0.01.

[0149] Embodiment 24. The method of any of Embodiments 22-23, comprising identifying characteristics of the flow rate of the chloride-containing brine (and / or mixture) to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.05.

[0150] Embodiment 25. The method of embodiment 24, comprising identifying characteristics of the flow rate of the chloride-containing brine (and / or mixture) to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.03.

[0151] Embodiment 26. A system comprising: an electrolysis cell configured to receive a mixture comprising a brine stream containing chloride ions and an aqueous feed, the brine stream containing chloride ions having a flow rate and a chloride ion concentration, the electrolysis cell configured to output a product solution containing hypochlorite having a chlorate to FAC ratio of about 0.005 to about 0.1, the system configured to adjust at least one of the flow rate of the brine containing chloride ions and the chloride ion concentration of the brine containing chloride ions to produce a chlorate to FAC ratio of about 0.005 to about 0.1. A hypochlorite-containing product solution having a FAC ratio of about 0.005 to about 0.1, the system optionally being configured to (i) adjust at least one of the flow rate of the chloride-containing brine and the chloride ion concentration of the chloride-containing brine to maintain a substantially constant inter-plate voltage in the continuous electrolysis cell, (ii) adjust at least one of the flow rate of the chloride-containing brine and the chloride ion concentration of the chloride-containing brine to maintain a substantially constant current supplied in the continuous electrolysis cell, or (i) and (ii).

[0152] As described in other aspects of this invention, the chloride-containing brine can be supplied, for example, from a tank or a brine generator. The chloride-containing brine can be a saturated solution, such as a saturated NaCl solution, but other chloride-containing salts (i.e., in addition to NaCl) can be used. The chloride-containing brine can also include chlorides at less than a saturation concentration (e.g., within about 10% of saturation).

[0153] As described herein, the system can be configured to adjust one or both of the flow rate of the chloride-containing brine and the chloride concentration of the chloride-containing brine to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1. The system can be configured to adjust only the flow rate of the chloride-containing brine. The system can also be configured to adjust only the chloride concentration of the chloride-containing brine.

[0154] For example, the chloride concentration of the chloride-containing brine can be adjusted to maintain a chlorate to FAC ratio in the hypochlorite-containing product solution at about 0.005 to about 0.1, or about 0.005 to about 0.08, or about 0.005 to about 0.07, or about 0.005 to about 0.05, or about 0.005 to about 0.03, or about 0.005 to about 0.003, or about 0.005 to about 0.002, or about 0.005 to about 0.001. The chloride concentration of the chloride-containing brine can be adjusted to maintain a chlorate to FAC ratio in the hypochlorite-containing product solution at about 0.005 to about 0.1, or about 0.005 to about 0.08, or about 0.005 to about 0.07, or about 0.005 to about 0.05, or about 0.005 to about 0.03, or about 0.005 to about 0.003, or about 0.005 to about 0.002, or about 0.005 to about 0.001. By adjusting the chloride concentration (and / or flow rate) of the chloride-containing brine, the system can adjust the chloride concentration of the mixture.

[0155] The chloride concentration of the chloride-containing brine may be adjusted to maintain a chlorate to FAC ratio in the hypochlorite-containing product solution of about 0.007 to about 0.05, or about 0.007 to about 0.03, or from about 0.007 to about 0.02, or even about 0.007 to about 0.01.

[0156] Embodiment 27. The system of embodiment 26, further comprising a sensor system comprising sensors configured to monitor one or more characteristics of the hypochlorite-containing product solution. The sensor can be, for example, a sensor configured to monitor hypochlorite levels in the product solution or a sensor configured to monitor chlorate levels in the product solution.

[0157] Embodiment 28. The system of embodiment 27, wherein the sensor system includes a module configured to adjust one or more parameters of the electrolytic cell in response to the signal from the sensor. These parameters include but are not limited to current, interplate voltage, and residence time.

[0158] Embodiment 29. A system according to any of Embodiments 26-28, wherein the electrolytic cell is operated at an interplate voltage of less than or equal to about 12 volts.

[0159] Embodiment 30. A system according to Embodiment 29, wherein the electrolytic cell is operated at an interplate voltage of less than or equal to about 10 volts.

[0160] Embodiment 31. A system according to embodiment 30, wherein the electrolytic cell is operated at an interplate voltage of about 2 volts to about 8 volts.

[0161] Embodiment 32. The system of any one of Embodiments 26-31, wherein the chloride ion concentration of the chloride ion-containing feed is from about 40 mmol / L to about 5000 mmol / L.

[0162] Embodiment 33. A system according to any of Embodiments 26-32, wherein the electrolytic cell comprises an anode, a cathode and optionally one or more intermediate electrodes.

[0163] Embodiment 34. A system according to any of Embodiments 26-33, wherein the hypochlorite-containing product solution is characterized by a hypochlorite concentration greater than about 500 mg / L, such as about 500 mg / L to about 10,000 mg / L.

[0164] It should also be understood that the system may include a processor configured to perform one or more operations related to the operation of the system. This can be performed based on instructions stored on a temporary or non-temporary medium. For example, the system may include a processor configured to adjust at least one of the flow rate of the chloride-containing brine and the chloride ion concentration of the chloride-containing brine to produce a hypochlorite-containing product solution having a chlorate to FAC ratio of about 0.005 to about 0.1. The processor may also be configured to adjust the flow rate of the chloride-containing brine flow in addition to or as an alternative to adjusting the chloride ion concentration of the chloride-containing brine. The processor may be configured to perform the aforementioned (or other) steps in response to signals collected by components (e.g., sensors) of the system.

Claims

1. A method for preparing a hypochlorite-containing product solution having a chlorate to free available chlorine (FAC) ratio of 0.005 to 0.1, the method comprising: - contacting a chloride ion-containing brine stream with an aqueous feed stream to produce a mixture, The salt water flow containing chloride ions has a certain flow rate, The chloride ion-containing salt water flow has a certain chloride ion concentration, The mixture has a certain chloride ion concentration, and The chloride ion concentration of at least one of the chloride ion-containing brine and the mixture is optionally in the range of 200 mmol / L to 2500 mmol / L; - passing the mixture through a continuous electrolytic cell having an anode and a cathode disposed therein and separated by a fluid path so that the mixture passes between the anode and the cathode to produce the hypochlorite-containing product solution; as well as - adjusting at least one of the flow rate of the chloride-containing brine and the chloride concentration of the chloride-containing brine to produce the hypochlorite-containing product solution having a chlorate to FAC ratio of 0.005 to 0.

1.

2. The method of claim 1 , further comprising adjusting at least one of the flow rate of the chloride ion-containing brine and the chloride ion concentration of the chloride ion-containing brine to (i) maintain a substantially constant inter-plate voltage within the continuous electrolysis cell, or (ii) maintain a substantially constant current supplied within the continuous electrolysis cell.

3. The method according to any one of claims 1 to 2, further comprising - regulating the current supplied to the continuous electrolysis cell to maintain a substantially constant inter-plate voltage within the continuous electrolysis cell; or - regulating the voltage between the plates in the continuous electrolysis cell to maintain a substantially constant current supplied in the continuous electrolysis cell.

4. The method of any one of claims 1-2, wherein the hypochlorite-containing solution has a chlorate to FAC ratio of less than 0.

075.

5. The method of claim 4, wherein the hypochlorite-containing solution has a chlorate to FAC ratio of less than 0.

025.

6. The method of claim 5, wherein the hypochlorite-containing solution has a chlorate to FAC ratio of less than 0.

010.

7. The method according to any one of claims 1-2, wherein the chloride ion concentration of at least one of the chloride ion-containing brine and the mixture is 250 mmol / L to 2500 mmol / L.

8. The method of claim 7, wherein the chloride ion concentration of at least one of the chloride ion-containing brine and the mixture is at least 500 mmol / L.

9. The method of claim 8, wherein at least one of the chloride ion-containing brine and the mixture has a chloride ion concentration of at least 1000 mmol / L.

10. The method of claim 9, wherein at least one of the chloride ion-containing brine and the mixture has a chloride ion concentration of at least 1500 mmol / L.

11. The method of claim 10, wherein at least one of the chloride ion-containing brine and the mixture has a chloride ion concentration of at least 2000 mmol / L.

12. The method of any one of claims 1-2, wherein the chloride-containing brine comprises sodium chloride.

13. The method of any one of claims 1-2, wherein the inter-plate voltage of the continuous electrolysis cell is less than or equal to 8 volts, less than or equal to 7 volts, less than or equal to 6 volts, less than or equal to 5.5 volts, or less than or equal to 5 volts.

14. The method of any one of claims 1-2, wherein the hypochlorite is present in the hypochlorite-containing product solution at a concentration of 500 mg / L to 10,000 mg / L.

15. The method of any one of claims 1-2, wherein the pH of at least one of the chloride-containing brine and the mixture is in the range of 6 to 10.

16. The method according to any one of claims 1-2, wherein the average residence time of the mixture in the electrolytic cell is from 30 seconds to 600 seconds.

17. The method of any one of claims 1-2, wherein the electrolytic cell comprises an intermediate electrode.

18. The method of any one of claims 1-2, wherein the electrolytic cell is used in an on-site generation system.

19. The method of any one of claims 1-2, wherein the electrolytic cell comprises a control system and comprises one or more sensors at an inlet or outlet of the electrolytic cell, wherein the control system is configured to adjust at least one of the flow rate of the chloride-containing brine, the inter-plate voltage within the continuous electrolytic cell, the current supplied within the continuous electrolytic cell, or the chloride ion concentration of the chloride-containing brine in response to signals collected by the one or more sensors.

20. A method comprising: contacting a chloride ion-containing brine stream with an aqueous feed stream to form a mixture, The chloride ion-containing salt water has a certain chloride ion concentration therein, The mixture has a concentration of chloride ions therein; passing the mixture through a continuous electrolytic cell having an anode and a cathode disposed therein and separated by a fluid path such that the mixture passes between the anode and the cathode to produce a product solution containing hypochlorite, The continuous electrolysis cell is optionally operated (i) at a substantially constant interplate voltage therein, or (ii) at a substantially constant current therein; as well as identifying a characteristic of the chloride-containing brine stream so as to produce the hypochlorite-containing product solution having a chlorate to FAC ratio of 0.005 to 0.1 and selecting and setting operating parameters to achieve the identified characteristic, wherein the characteristic of the chloride-containing brine stream is at least one of (i) a chloride ion concentration in the chloride-containing brine and (ii) a flow rate of the chloride-containing brine.

21. The method of claim 20, wherein the method comprises identifying characteristics of the chloride-containing brine stream to produce the hypochlorite-containing product solution having a chlorate to FAC ratio of 0.005 to 0.

05.

22. The method of claim 21, comprising identifying characteristics of the chloride-containing brine stream to produce the hypochlorite-containing product solution having a chlorate to FAC ratio of 0.005 to 0.

03.

23. A system comprising: a continuous electrolysis cell configured to receive a mixture comprising a brine stream containing chloride ions and an aqueous feed, The continuous electrolytic cell has an anode and a cathode disposed therein such that the mixture passes between the anode and the cathode, The chloride-containing salt water flow has a certain chloride ion concentration and a certain flow rate therein, The electrolytic cell is configured to output a hypochlorite-containing product solution having a chlorate to FAC ratio of 0.005 to 0.1, The system is configured to adjust at least one of the flow rate of the chloride-containing brine and the chloride concentration of the chloride-containing brine to produce the hypochlorite-containing product solution having a chlorate to FAC ratio of 0.005 to 0.1, The system is optionally configured to (i) adjust at least one of the flow rate of the chloride ion-containing brine and the chloride ion concentration of the chloride ion-containing brine to maintain a substantially constant inter-plate voltage within the continuous electrolysis cell, (ii) adjust at least one of the flow rate of the chloride ion-containing brine and the chloride ion concentration of the chloride ion-containing brine to maintain a substantially constant current supplied within the continuous electrolysis cell, or (i) and (ii).

24. The system of claim 23, further comprising a sensor system comprising sensors configured to monitor one or more properties of the hypochlorite-containing product solution, wherein the sensor system comprises a module configured to adjust one or more parameters of the electrolytic cell in response to signals from the sensors, wherein the electrolytic cell operates at an interplate voltage of less than or equal to 12 volts.

25. The system of claim 24, wherein the electrolytic cell is operated at an interplate voltage of less than or equal to 10 volts.

26. The system of claim 25, wherein the electrolytic cell operates at an interplate voltage of 2 to 8 volts.

27. The system of any one of claims 23-26, wherein at least one of the chloride-containing brine and the mixture has a chloride concentration of 40 mmol / L to 5000 mmol / L, wherein the electrolysis cell comprises an anode, a cathode, and optionally one or more intermediate electrodes, and wherein the hypochlorite-containing product solution is characterized by a hypochlorite concentration of greater than 500 mg / L.

28. The method of claim 5, wherein the hypochlorite-containing solution has a chlorate to FAC ratio of less than 0.010, wherein at least one of the chloride-containing brine and the mixture has a chloride ion concentration of at least 500 mmol / L, and wherein the interplate voltage of the continuous electrolysis cell is less than or equal to 8 volts.

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