US20140026971A1

US20140026971A1 - System and method for industrial cleaning

Info

Publication number: US20140026971A1
Application number: US14/111,087
Authority: US
Inventors: Kenneth J. Roach; Henry von Rege
Original assignee: Diversey Inc
Current assignee: Diversey Inc
Priority date: 2011-04-12
Filing date: 2012-04-12
Publication date: 2014-01-30
Also published as: EP2697409A4; EP2697409A2; WO2012142243A2; WO2012142243A3

Abstract

Provided herein are systems and methods useful for the cleaning, sanitizing, and/or microbial control of industrial equipment such as, for example, conveyance and production/manufacturing systems.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Ser. No. 61/474,677, filed on Apr. 12, 2011, which is incorporated herein by reference in its entirety.

BACKGROUND

Electrolyzed water can be produced by passing a brine solution through an electrolytic cell. In the electrolytic cell, an anode and a cathode apply a low direct-current voltage. As a result, two types of water are produced: at the anode, an anolyte that includes hypochlorous acid, and at the cathode, a catholyte that includes hydroxide. The anolyte can be used as a cleanser, detergent, provide microbial control, and/or disinfectant, and the catholyte can similarly be used as a cleanser or detergent.
Typically, methods for the regular cleaning of industrial equipment such as, for example, equipment used in the manufacture, processing, and packaging of foods and beverages require that the chemicals and/or solvents and diluents used in such methods be purchased, shipped, and stored until needed. While costs associated with the shipping and storage of such chemicals are a consideration, reducing the need for transport and handling of hazardous concentrated chemicals is desirable. While the on-site generation of such chemicals has been suggested previously, such as by using electrochemically activated (ECA) water or brine solution, such methods have not been widely accepted as they are labor-intensive and are difficult to monitor effectively (e.g., requiring manual titration of available chlorine, pH measurement, etc.). Thus, systems and methods that allow for the simple generation of ECA solutions and for the subsequent use thereof in cleaning applications would reduce the need for handling, storage, and transport of concentrated chemical products that are associated with typical cleaning applications, as well as reduce the burden on personnel.

SUMMARY

In an aspect the disclosure relates to an industrial cleaning system comprising: an electrochemical activation unit that is capable of generating an anolyte from a brine solution, the anolyte having a concentration of available chorine; an anolyte dosing pump that is connected to the electrochemical activation unit; a chlorine probe capable of measuring the concentration of available chlorine in a diluted anolyte; and a controller unit operatively coupled to the chlorine probe and the anolyte dosing pump, wherein the controller unit activates the anolyte dosing pump when the measured concentration of available chlorine is lower than a predetermined concentration of available chlorine.
In an aspect the disclosure relates to a method for maintaining the concentration of available chlorine in an industrial cleaning system, wherein the method comprises providing an electrochemically activated solution comprising an amount of available chlorine; measuring the concentration of available chlorine in the solution using a chlorine probe, wherein the chlorine probe has a linear or substantially linear response to the concentration of available chlorine up to at least 50 ppm and a flat or substantially flat response over a given pH range; and providing an additional amount of available chlorine to the system when the measured concentration is lower than a predetermined concentration of available chlorine.
In an aspect the disclosure relates to a method for cleaning a system, the method comprising: providing an electrochemically activated solution having a concentration of available chlorine; determining a concentration of available chlorine that is suitable for cleaning at a given pH of the electrochemically activated solution; measuring the concentration of available chlorine in the electrochemically activated solution; activating a dosing pump when the measured concentration of available chlorine is lower than the determined concentration of available chlorine; and contacting the system with the electrochemically activated solution.
Other aspects and embodiments are encompassed within the scope of the disclosure and will become apparent in light of the following description and accompanying Drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a non-limiting embodiment of an industrial cleaning system falling within the scope of the disclosure.

FIG. 2 is a schematic representation of a non-limiting electrochemical activation unit suitable for use with the industrial cleaning system as described herein including, for example, FIG. 1.

FIG. 3 is a generalized qualitative graph plotting the various chlorine species in an electrolyzed water solution as a function of the pH of the electrolyzed water solution generated in the electrochemical activation unit as described herein including, for example, of FIGS. 1 and 2.

FIG. 4 illustrates the testing and evaluation of a chlorine probe. FIG. 4A plots the ratio of available chlorine concentration (chlorine probe/titration) as a function of pH and illustrates a response that is linear or substantially linear to chlorine concentration, and has a flat or substantially flat chlorine probe response over a pH range (see Examples). FIG. 4B illustrates, for purposes of contrast, a chlorine probe response that is not flat or substantially flat (the line has a non-zero slope) as a function of pH (plotted ratio of chlorine probe:titration). FIG. 4C plots the chlorine concentration as measured by a probe against the concentration as measured by titration demonstrating a linear or substantially linear response to chlorine concentration. The diagonal line represents the theoretical 1:1 correspondence FIGS. 4D and 4E illustrate chlorine concentrations of identical solutions as measured using a probe (4D) and by titration (4E), each versus pH. Like FIG. 4A, the data depicted in 4D and 4E demonstrates that the chlorine concentration is independent from solution pH.

DETAILED DESCRIPTION

It should be understood that the claims are not limited in application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings that depict non-limiting embodiments of the disclosure.
The methods and systems described herein may comprise, consist of, or consist essentially of the indicated steps or components. It should be noted that, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
It is specifically understood that any numerical value recited herein (e.g., ranges) includes any and all values from the lower value to the upper value, i.e., all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application. For example, if a range is stated as 1% to 50%, it is intended that values such as 2% to 40%, 10% to 30%, or 1% to 3%, etc., are expressly enumerated in this specification. In some instances particular numbers may be recited as examples falling within a disclosed range, however these are only examples of what is specifically intended.
In a general sense, the inventors have unexpectedly found that a combination of available electronic control systems and chlorine probes (e.g., electrodes) can be used to construct an industrial cleaning system that allow for on-site generation of electrochemically activated (ECA) water solutions that can be used for on-demand cleaning, sanitizing, disinfecting, and/or microbial control of equipment in industrial settings such as, for example, food and beverage manufacturing and conveyance equipment. Generally in ECA clean in place (CIP) applications, concentrated anolyte is diluted with water to give a final “use” solution. For example, a typical use solution can include an available chlorine concentration of about 40 ppm, which is usually adequate to provide an appropriate or acceptable kill (i.e., microbial control) against microorganisms (e.g., typically pathogenic and/or spoilage microorganisms). Prior to the methods and systems provided herein, prior art systems and methods could not provide for the accurate and convenient measurement of chlorine concentrations in a range above 1-2 ppm (e.g., in swimming pools) and below several hundred ppm (e.g., hard surface disinfectants). One challenge in the industry is that the source of the dilution water that is added to an anolyte concentrate is often from a local source (e.g., tap) and as such its composition can vary widely between various localities (e.g., water from a particular municipality may have increased buffering capacity relative to water from another municipality because of differing local water treatment(s)). The final pH in the chlorine use solution (or diluted anolyte, anolyte use solution, etc.) determines the ratio of hypochlorite to hypochlorous acid. Thus there is a need in such ECA applications for a reliable control of available chlorine independently from differing water quality, composition, and pH. One advantage that both the methods and apparatus disclosed herein provide is that they allow for establishing a linearity between an amperometric signal and the read out of available chlorine within a given pH window (slight acid to slight alkaline) and at available chlorine (or “FAC”) levels which are typical for CIP applications (e.g. a target FAC of 40 ppm for a sanitizing step in CIP). In addition the disclosure provides this advantage without the need for an additional buffer component addition to the cell such as are currently found in the art, or without the need for additional components (e.g., acidification units). Thus, once the system and method disclosed herein is calibrated it no longer requires multiple manual titration measurements in order to determine the concentration of chlorine in an anolyte solution or the correlation of the chlorine concentration to available chlorine concentration as a function of the solution pH. Further, the methods and systems disclosed herein allow for the use of any type or source of potable water to be used in connection with the system. That is, once the methods and systems disclosed herein are calibrated, a change in the potable water supply will not result in a change in the reading of available chlorine concentration (i.e., potable water source independent). It will be appreciated that periodic probe calibration should be incorporated according to the probe manufacturer's recommendations (e.g., biweekly, monthly, etc.). The system and method disclosed herein can be adapted for use in any number of industrial manufacturing, processing, and conveyance systems and associated cleaning systems.
Suitably, the method and system disclosed herein can be adapted for and/or applied to equipment generally cleaned using clean-in-place (“CIP”) cleaning procedures, and find general use in any industrial setting/application where soils need to be removed (e.g., food and beverage, oil processing, industrial agriculture, and ethanol processing). CIP processing is generally well-known and can include contacting (applying) one or more cleaning solution that includes one or more diluted cleaning agents with the surface to be cleaned. The solution flows on the surface at a particular rate (e.g., 0.5 to 6 feet/second) or for a particular contact time (e.g., 1, 2, 3, 4, 5, 10, 15, 30, 60, etc. minutes), and removes the soil. The process can include one or more steps that apply new cleaning solution to the surface, or the process and system can be set up to recirculate and reapply the same solution to the surface. Common CIP processes can include any number of steps depending on the type of soil to be removed and/or the type of system to be cleaned (e.g., pretreatments, fresh water rinses, alkaline solution washes, acid solution washes, oxidizing solution washes, prolonged washing protocols for heavy cleaning, quick washing protocols for light cleaning, etc.).
As used herein, “by weight” refers to the total weight of the composition. For example, if a composition has a total weight of 100 grams and comprises 40% (by weight) of a component, the composition comprises 40 grams of that component.
As used herein, the term “about” refers to variability in the recited numerical quantity that can occur because of, for example, typical measuring and liquid handling procedures used for making concentrates or use solutions, through inadvertent error and propagation of error in these procedures; through differences in the manufacturing method, source, or purity of the ingredients used to make the compositions or components used to carry out the methods; and the like. The term “about” also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture.
As used herein, chlorine species that are present in an aqueous solution in an oxidized form, such as hypochlorous acid (HOCl) or hypochlorite anion (OCl⁻, or commonly, bleach), are interchangeably called “free chlorine,” “available chlorine,” or “free available chlorine.” Merely as a point of reference (and as generally known) recreational bodies of water, e.g., swimming pools, hot tubs, spas, etc., typically contain available chlorine from 1 to 3 parts per million.
An “electrochemical activation unit” or “ECA unit” as used herein includes a system that is capable of generating an anolyte from a brine solution and typically comprises an anode and a cathode. ECA units are known in the art and are commercially available from a number of manufacturers and suppliers. Suitably the activation unit generates a catholyte and an anolyte from a brine solution. An “electrochemically activated (ECA) solution,” “ECA water solution,” or “electrolyzed oxidizing water” as used herein includes solutions generated from the action of the electrochemical activation unit on the brine solution such as, for example, an anolyte comprising a concentration of available chlorine and a catholyte having a concentration of caustic. An “anolyte” as used herein includes the solution that is produced in the electrochemical activation unit at the anode, and suitably comprises a concentration of free chlorine. A “catholyte” as used herein includes the solution that is produced in the electrochemical activation at the cathode, and suitably comprises a concentration of caustic. “Brine” as used herein relates to an aqueous solution that includes some concentration of a salt such as, for example, an alkali metal chloride (e.g., NaCl, KCl, or LiCl). Brines can be generated manually to have a particular salt concentration and/or conductivity and can be readily determined and prepared by one of ordinary skill in the art (e.g., by addition of salts as solids or concentrated solutions to water to achieve a desired composition). Brines can also be derived from a natural source such as, for example, tap water or well water sources. In some embodiments, a brine can comprise a conductivity of about 3 to about 5 mS/cm.
A “dosing pump” as used herein includes any pump that can circulate a liquid at a particular flow rate, such as a peristaltic pump or a metering pump.
A “controller unit” as used herein includes any programmable controller that is suitable for use in monitoring and/or controlling automation of electromechanical processes, for example in response to an input condition/signal.
A “chlorine probe” as used herein includes an electrochemical sensor (electrode) suitable for measuring the chlorine concentration in water, as generally known in the art. In some embodiments a chlorine probe exhibits certain performance characteristics as described herein.
A “chlorine tank” as used herein includes a tank that contains a chlorine working solution (or anolyte use solution), such as is found in some clean-in-place systems.
A “caustic” as used herein includes a basic solution (e.g., high pH), suitably hydroxide solution.
“Maintaining” when used herein with respect to “maintaining” a concentration of available chlorine also includes continuous and/or periodic monitoring of the concentration of available chlorine in a solution to ensure the concentration remains at or near a particular level or threshold (e.g., within 10% of a desired concentration, above a particular minimum threshold concentration, etc.).
In an aspect the disclosure relates to an industrial cleaning system comprising: an electrochemical activation unit that is capable of generating an anolyte from a brine solution, the anolyte having a concentration of available chorine; an anolyte dosing pump that is connected to the electrochemical activation unit; a chlorine probe capable of measuring the concentration of available chlorine in a diluted anolyte (or anolyte use solution); and a controller unit operatively coupled to the chlorine probe and the anolyte dosing pump, wherein the controller unit activates the anolyte dosing pump when the measured concentration of available chlorine is lower than a predetermined concentration of available chlorine.
In embodiments, the chlorine probe can be selected from any type of commercially available chlorine probe (electrode) that can provide a linear or substantially linear response to the concentration of available chlorine in ranges of about 1 ppm to about 50 ppm or more, and a flat or substantially flat response to changes in pH from about 5-9 (i.e., where changes in pH do not cause a change in detected chlorine concentration). In some embodiments the concentration of available chlorine can be, for example, about 1 ppm, 2 ppm, 3 ppm, 4 ppm, 5 ppm, 6 ppm, 7 ppm, 8 ppm, 9 ppm, 10 ppm, 11 ppm, 12 ppm, 13 ppm, 14 ppm, 15 ppm, 16 ppm, 17 ppm, 18 ppm, 19 ppm, 20 ppm, 21 ppm, 22 ppm, 23 ppm, 24 ppm, 25 ppm, 26 ppm, 27 ppm, 28 ppm, 29 ppm, 30 ppm, 31 ppm, 32 ppm, 33 ppm, 34 ppm, 35 ppm, 36 ppm, 37 ppm, 38 ppm, 39 ppm, 40 ppm, 41 ppm, 42 ppm, 43 ppm, 44 ppm, 45 ppm, 46 ppm, 47 ppm, 48 ppm, 49 ppm, 50 ppm, 51 ppm, 52 ppm, 53 ppm, 54 ppm, 55 ppm, 56 ppm, 57 ppm, 58 ppm, 59 ppm, or 60 ppm, or more. “Substantially linear response” as used herein includes a response that provides a concentration of available chlorine within 15% (including all values to within 1%) of the particular available chlorine concentration. A “linear response” typically includes a response that provides a concentration of available chlorine within 1% of the particular available chlorine concentration, or alternatively within the known tolerance/error of the chlorine probe. A linear or substantially linear response can be evaluated using a series of standard or stock chlorine solutions of known concentration, or evaluated using another method or kit for determining chlorine concentration such as, for example, colorimetric methods, titration (amperometric, iodometric, etc.), orthotolidine, syringaldazine (FACTS), or other methods and kits that are known in the art and/or commercially available (e.g., from Hach Company).
As noted above, the probe can provide a chlorine concentration response that is flat or substantially flat in response to changes in solution pH including, for example, pH values from about 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, or about 9.0. In embodiments, the probe provides a flat or substantially flat response to the concentration of available chlorine in solutions having a pH range of about 4 to about 9, about 5 to about 9, about 6 to about 8, about 6.5 to about 8, about 6.5 to about 7.5, or about 7 to about 7.5. Suitably the probe provides a flat or substantially flat response in a solution having about a neutral pH or alternatively, a pH of a local water source (e.g., tap water, well water, and the like). A probe having a “flat or substantially flat response” relates to chlorine probes that provide a reading or measurement of chlorine concentration that does not vary substantially in response to a change in solution pH. In some embodiments a flat or substantially flat response relates to 0% to about 10% variance in chlorine concentration over a pH range, including all values falling within that range, (e.g., about 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.25, 1.5, 1.75, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or about 10%). In some embodiments a flat or substantially flat response relates to a variance of no more than about 10% in chlorine concentration over a pH range. In some embodiments, a flat or substantially flat response relates to 0% to about 5% variance in chlorine concentration over a pH range, including all values falling within that range, (e.g., about 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.25, 1.5, 1.75, 2.0, 2.5, 3.0, 4.0, or about 5.0%). In some embodiments a flat or substantially flat response relates to a variance of no more than about 5% variance in chlorine concentration over a pH range. Some embodiments provide a probe with a linear or substantially linear response to available chlorine concentrations of about 40 ppm to about 50 ppm and flat or substantially flat response to changes in pH from about 5 to about 9. A non-limiting example of a chlorine probe includes a TARAline chlorine probe manufactured by Reiss GmbH in Weinheim, Germany. Other chlorine probes are similarly useful in the systems and methods described herein as long as they provide a linear or substantially linear response to the concentration of available chlorine and a flat or substantially flat response over a range of solution pH values such as, for example, the conditions described herein. Suitably, the probe can be set up using a single calibration based on the source of available water (e.g., local tap water source, well water, and the like) and/or brine solution.
In embodiments, the predetermined concentration of available chlorine can be determined/identified by one of skill in the art depending on the particular cleaning that is necessary or desired (e.g., light cleaning, heavy cleaning, etc.) as well as the industrial equipment and soils that are to be cleaned. In some embodiments, the predetermined concentration is a value within the linear or substantially linear range of the chlorine probe. In some embodiments the predetermined concentration is a value within the linear or substantially linear range of the chlorine probe in a solution within a pH range in which the chlorine probe has a flat or substantially flat response with respect to changes in pH. In some embodiments, for example for microbial control, the predetermined value is about 40 ppm at a pH range of about 4 to about 9, about 5 to about 9, about 6 to about 8, about 6.5 to about 8, about 6.5 to about 7.5, or about 7 to about 7.5. In some embodiments, the predetermined value can be adjusted to a higher or lower value (e.g., about 10 ppm, 11 ppm, 12 ppm, 13 ppm, 14 ppm, 15 ppm, 16 ppm, 17 ppm, 18 ppm, 19 ppm, 20 ppm, 21 ppm, 22 ppm, 23 ppm, 24 ppm, 25 ppm, 26 ppm, 27 ppm, 28 ppm, 29 ppm, 30 ppm, 31 ppm, 32 ppm, 33 ppm, 34 ppm, 35 ppm, 36 ppm, 37 ppm, 38 ppm, 39 ppm, 40 ppm, 41 ppm, 42 ppm, 43 ppm, 44 ppm, 45 ppm, 46 ppm, 47 ppm, 48 ppm, 49 ppm, 50 ppm, 51 ppm, 52 ppm, 53 ppm, 54 ppm, 55 ppm, 56 ppm, 57 ppm, 58 ppm, 59 ppm, or about 60 ppm, or more) for solutions within the same range of pH values.
In embodiments, the system further comprises a tank, such as a chlorine tank, that receives the anolyte from the anolyte dosing pump and an optional water source for dilution of anolyte to particular desired concentrations or pH ranges. The chlorine tank suitably contains a working anolyte solution for various methods described herein, such as clean-in-place (CIP). Suitably, a chlorine tank can be used to recycle/recover anolyte solution after a cleaning application, or alternatively can provide a single use solution (i.e., subsequently routed for disposal).
In one aspect, the industrial cleaning generally includes an electrochemical activation unit that is capable of generating an anolyte from a brine solution. Any known and commercially available ECA unit can be used in connection with the instant disclosure. FIG. 1 is a schematic representation of one embodiment of a cleaning-in-place system or industrial cleaning or cleansing system 10 that can be adapted for any industrial setting such as, for example, a food production facility or a beverage facility (e.g., a soft-drink production facility). One of skill in the art will recognize that such systems are generally known and can include additional or alternative components, and include the components in alternative arrangements, relative to the illustrative depiction in FIG. 1. The industrial cleaning system 10 includes an electrochemical activation unit 12 that receives reverse osmosis (RO) water or softened water and sodium chloride (NaCl), and passes the resulting brine solution through an electrolytic cell 14. Referring also to FIG. 2, the electrochemical activation unit 12 generates at the anode side 15 an anolyte that has a concentration of hypochlorous acid, by the following reaction:
Cl⁻+H₂O→HOCl+H⁺+2e ⁻ (1)
The electrochemical activation unit 12 also generates at the cathode side 17 a catholyte that has a concentration of hydroxide or caustic, by the following reaction:
2e ⁻+2H₂O→2OH⁻+H₂(g) (2)
In the example illustrated in FIG. 1, the anolyte and the catholyte are separated in the electrochemical activation unit 12 by a permeable membrane 16. The electrochemical activation unit 12 thus forms a dual-stream system that generates both the anolyte and the catholyte, the anolyte having a concentration of available chlorine and the catholyte having a concentration of caustic. In an alternative construction, the electrochemical activation unit 12 does not include a membrane 16 that separates the anolyte and the catholyte, thereby forming a single-stream system. In the single-stream system, the acid generated at the anode side 15 is neutralized by the hydroxide at the cathode side 17.
The concentrations of the anolyte and catholyte can be proportionate to factors such as the brine flow rate and salt concentration in the feed solution. At the cathode, the electrochemical activation unit 12 can generate a catholyte concentrate that has a concentration of caustic in the amount of about 800 to about 1000 ppm. Other caustic concentrations are possible depending on the usage requirements or operating parameters of the electrochemical activation unit 12. The hydrogen gas generated at the cathode can be about 400 ppm. At the anode, the electrochemical activation unit 12 can generate an anode concentrate that has a concentration of hypochlorous acid in the amount of about 600 to about 800 ppm. Other hypochlorous acid concentrations can be achieved depending on the usage requirements or operating parameters of the electrochemical activation unit 12. The anolyte in its raw form has a pH of about 2. This can be corrosive to industrial equipment that are made, of or contain components that are made of, soft metals and stainless steel (e.g., equipment in food and beverage processing applications). To raise the pH of the anolyte and bring it closer to neutral, the anolyte can be blended with the catholyte. In one embodiment, 60% of the generated catholyte is added to the anolyte, bringing the anolyte to a pH of about 4.0 to about 7.0. In a further embodiment, the anolyte is also diluted with tap water, bringing it to a pH of about 6.5 to about 7.5. Thus, some embodiments provide for an anolyte that is diluted and/or buffered so as not to be corrosive to metals, such as those used in industrial manufacturing equipment. Further, other well known components can be added to anolyte solutions (e.g., surfactants, builders, stabilizers) so long as those components do not affect the response of the probe to chlorine concentration, as described herein.
The industrial cleaning system 10 further includes an anolyte dosing pump 18 that is connected to the electrochemical activation unit 12. The anolyte can then be streamed to an anolyte dosing pump 18 that is connected to the electrochemical activation unit 12. When activated, the anolyte dosing pump 18 can send the anolyte to a chlorine tank 20. In some embodiments, the industrial cleaning system 10 further includes a water source and a water flow meter 22 that is connected to the chlorine tank 20. The chlorine tank 20 thus receives anolyte from the anolyte dosing pump 18 and can further dilute the anolyte into an anolyte working solution. In other embodiments (not depicted in FIG. 1) the anolyte may flow directly from the electrochemical activation unit 12 to contact the industrial production system without requiring the chlorine tank 20. The anolyte concentrate from the electrochemical activation unit 12 in this case can be diluted directly from a water source that is controlled, for example, by a water flow meter.
The industrial cleaning system 10 further includes a controller unit that acts (action/signal depicted by 28) and is operatively coupled to the anolyte dosing pump 18 and a chlorine probe 30. The chlorine probe 30, discussed herein, is capable of measuring the concentration of available chlorine in the anolyte working solution of the chlorine tank 20 (or anolyte that is otherwise diluted to form an anolyte working solution). When the measured concentration of available chlorine is lower than a predetermined concentration of available chlorine, the controller unit 28 activates the anolyte dosing pump 18 to provide an additional amount of available chlorine to the anolyte working solution. In some embodiments the predetermined concentration of available chlorine can be suitably about 40 ppm at a pH range of about 4.0 to about 9.0. The predetermined concentration of available chlorine can also be about 40 ppm at a pH range of about 5 to about 9, about 6 to about 8, about 6.5 to about 8, about 6.5 to about 7.5, or about 7 to about 7.5. An anolyte working solution with this concentration of available chlorine (e.g., at least 40 ppm) can provide effective microbial control (kill and/or removal from equipment). In a further embodiment, the water flow meter 22 can generate a signal for the controller unit 28 to initially charge the chlorine tank 20 with a proportionally controlled volume of water from the water flow meter 22 and anolyte from the anolyte dosing pump 18. Subsequently, the controller unit 28 controls makeups of the anolyte working solution by monitoring the concentration of available chlorine through the chlorine probe 30. The controller unit 28 can thus automate the monitoring and controlling of the anolyte working solution in a user-friendly manner.
In some embodiments, the industrial cleaning system 10 may include a catholyte dosing pump 32 that is operatively coupled to the controller unit 28. The catholyte dosing pump 32 can be activated by the controller unit 28 by conductivity when the concentration of caustic is lower than a predetermined concentration of caustic. The catholyte can be an effective cleaner for sugar-based soil such as soft-drink concentrates, and other water-soluble soils such as coffee, milk, and soy milk. For cleaning more difficult/tenacious soils such as orange juice or higher soil loads, additives containing surfactants, builders and/or other functional cleaning components, such as Kompleet or Brightwash, both available from Diversey (Sturtevant, Wis.), can be used with the catholyte. Increasing the temperature of the catholyte, for example to 50° C., can also have a positive effect on the cleaning properties of the catholyte. The catholyte can also be diluted with water.
Referring to the illustrative embodiment depicted in FIG. 1, in operation, the anolyte working solution flows from the chlorine tank 20 through a cleaning-in-place pump 24 and cleaning-in-place flow meter 26 to contact the industrial equipment (e.g., food and beverage production system). The anolyte working solution can return from the industrial production system to the chlorine tank 20, as shown in the extended dashed arrow 36. The anolyte working solution can also be for single use, not returning to the chlorine tank 20, as shown in the solid arrow 34.
As noted above, the industrial cleaning system 10 includes a chlorine probe capable of measuring the chlorine concentration in a diluted anolyte solution. While the oxidizing potential of the particular species of available chlorine is the same, the particular efficacy in microbial control is different between various chlorine species. Referring to FIG. 3, the anolyte working solution is generally in the pH range of about 4.0 to about 9.0, about 5 to about 9, about 6 to about 8, about 6.5 to about 8, about 6.5 to about 7.5, or about 7 to about 7.5 where the hypochlorous acid is in equilibrium with the hypochlorite anion OCL. As described herein, the chlorine probe suitably measures chlorine concentration with a linear or substantially linear response to changes in chlorine concentration, and provides a flat or substantially flat response for chlorine concentrations over a range of solution pH (e.g., see FIG. 4A, contrast from FIG. 4B). Referring again to FIG. 3, each chlorine species can follow a different response curve as a function of the pH of the anolyte working solution. At lower pH, available chlorine consists predominantly of HOCl and chlorine gas (Cl_2(g)). Above a pH of 7.5, OCl⁻ starts to dominate, and above a pH of 9.5, available chlorine consists almost entirely of OCl⁻.
In an aspect the disclosure relates to a method for maintaining the concentration of available chlorine in an industrial cleaning system, wherein the method comprises providing an electrochemically activated solution comprising an amount of available chlorine; measuring the concentration of available chlorine in the solution using a chlorine probe, wherein the chlorine probe has a linear or substantially linear response to the concentration of available chlorine up to at least 50 ppm or more, and a flat or substantially flat response to changes in solution pH (i.e., changes in pH from about 5-9 do not cause a change in detected chlorine concentration); and providing an additional amount of available chlorine to the system when the measured concentration is lower than a predetermined concentration of available chlorine. In some embodiments the method is used in a system for a CIP method.
In embodiments, the flat or substantially flat response is at a pH range of about 4 to about 9, about 5 to about 9, about 6 to about 8, about 6.5 to about 8, about 6.5 to about 7.5, or about 7 to about 7.5.
The method generally includes providing an electrochemically activated solution comprising an amount of available chlorine, optionally diluting the solution, measuring and/or monitoring the concentration of available chlorine in the solution using the chlorine probe 30, and providing an additional amount of available chlorine to the system when the measured concentration is lower than a predetermined concentration of available chlorine. As one of skill in the art will appreciate, the general method disclosed herein can be adapted to or incorporated into any number of cleaning methods that can comprise other steps that are known in any cleaning protocol such as, for example, CIP (e.g., soaking, pretreatment, rinses, etc.). Referring also to FIG. 4A, the chlorine probe exhibits a substantially flat response to available chlorine up to at least about 50 ppm within pH range of about 4.0 to about 9.0. In a further embodiment, the chlorine probe 30 has a substantially flat response to available chlorine up to at least 50 ppm at a pH of about 4 to about 9, about 5 to about 9, about 6 to about 8, about 6.5 to about 8, about 6.5 to about 7.5, or about 7 to about 7.5. The data plotted in FIG. 4A is summarized in Tables 2-4 in the Examples below.
In some embodiments of the method, the chlorine probe can be a single electrode calibrated for the anolyte working solution, showing a response in less than about 2 minutes. The temperature exposure of the chlorine probe can be limited to less than 45° C., but is suitably robust up to about 50° C. with some embodiments providing for a chlorine probe that can self-compensate for temperature. As disclosed in connection with the cleaning system, the chlorine probe used to measure/monitor the amount of available chlorine is suitably coupled to (i.e., is in electronic communication with) any suitable programmable logic controller unit known in the art such as, for example, Webmaster manufactured by Walchem in Hollison, Mass.; BiOx from Diversey (Sturtevant, Wis.); or LABView manufactured by National Instruments in Austin, Tex. The logic controller, in response to one or more chlorine concentration reading inputs from the probe, can initiate an adjustment (increase or decrease) in the amount of anolyte added to the use solution (e.g., via a dosing pump), the amount of dilution water, or the amount of catholyte, depending on the predetermined value of chlorine concentration used in the method.
Accordingly, the aspects disclosed herein also provide a method for cleaning a system, the method comprising: providing an electrochemically activated solution having a concentration of available chlorine; determining a concentration of available chlorine that is suitable for cleaning at a given pH of the electrochemically activated solution; measuring the concentration of available chlorine in the electrochemically activated solution; activating a dosing pump when the measured concentration of available chlorine is lower than the determined concentration of available chlorine; and contacting the system with the electrochemically activated solution for a time or in an amount sufficient to provide an amount of cleaning.
In embodiments, the method includes a second electrochemically activated water solution provided at a concentration that is suitable for optional dilution with water. In some embodiments the second ECA solution comprises catholyte.
In some embodiments, the method can be used for cleaning a system that comprises manufacturing, production, or conveyance equipment. In some embodiments the equipment is used in the food or beverage industry. In some embodiments the method is used in a clean-in-place system.
The Examples that follow provide illustration of several aspects and embodiments that fall within the scope of the disclosure and should not be interpreted as limiting the scope of the appended claims.

EXAMPLES

In order to identify an appropriate chlorine probe for use in the methods and cleaning systems described herein, commercially available chlorine probes were used to measure chlorine concentration for a series of NaOCl and mixed anolyte solutions that were diluted in tap water sourced from Sturtevant, Wis.
A test apparatus including a recirculation pump, a chlorine probe and a fluid reservoir was assembled. The recirculation pump was a magnetic drive pump [Model MD20RZT-115NL, Iwaki] capable of maintaining a continuous flow of 0.5 L/min across the face of the chlorine probe.
The data using a TARAline chlorine probe (Dr. Reiss GmbH, Weinheim, Germany) is summarized in the Tables that follow. Table 1 shows that the pH of the diluent water was experimentally adjusted at a titrated chlorine concentration of 52.5 ppm. The ratio of measured concentration to titrated concentration in this case showed a linear correlation to the pH (measured using a pH meter [model 51875-60, Hach Company]). To compensate for this effect of pH on the measured concentration of available chlorine, the chlorine probe was calibrated at a given pH of the diluent water (in Sturtevant, Wis.). Within a range of the calibrated pH, the chlorine probe thus suitably maintains the ratio of measured concentration to titrated concentration close to 1.000 (a flat or substantially flat response).

TABLE 1

			Mea-	Ratio
	Titrated		sured	(measured/
Diluent water	conc.	pH	conc.	titrated)

NaOCl	Sturtevant tap	45.0	7.9	45.0	1.000
NaOCl	Sturtevant tap	37.5		38.4	1.024
NaOCl	Sturtevant tap	52.5	8.3	48.0	0.914
NaOCl	Sturtevant tap	52.5	8.1	49.0	0.933
NaOCl	Sturtevant tap	52.5	7.6	54.2	1.032
NaOCl	Sturtevant tap	52.5	7.2	58.7	1.118
NaOCl	Sturtevant tap	52.5	6.9	61.9	1.179

To set up the experiments summarized in Tables 2-4, the fluid reservoir was charged with 5 litres of the selected diluent water and the solution was circulated across the face of the chlorine probe. A sample of mixed anolyte (62.5% anolyte, 37.5% catholyte) was collected from an ECA unit [model MC1, Atlantis]. The sample was titrated to determine the concentration of available chlorine.
Sufficient mixed anolyte was added to the circulating solution in the test apparatus to provide a solution concentration of between 35 and 40 ppm available chlorine. After addition of the mixed anolyte, the system was allowed to circulate until the diluted mixed anolyte solution was homogeneous. The concentration reading was recorded and a sample collected and titrated via a standard iodometric method using a kit available from Diversey (Kit #BT409790) to determine the “true” concentration. The pH of the sample was measured using a pH meter [Hach Company].
An additional aliquot of mixed anolyte was added to the test solution to increase the available chlorine concentration by about 10%. The system was allowed to circulate until homogeneous and the concentration reading was recorded. A second sample was collected, titrated and the pH was measured. A second aliquot of mixed anolyte was added to the test solution to increase the available chlorine concentration by about 10%. Again the system was allowed to circulate until homogeneous and the concentration reading was recorded. A third sample was collected, titrated and the pH was measured.
The test solution was then discarded and replaced with a fresh 5 litres of selected diluent water. A fresh sample of mixed anolyte was collected from the ECA unit and the above cycle was repeated.
Table 2 summarizes measurements of the TARAline chlorine probe for various mixed anolyte solutions diluted by tap water (Sturtevant, Wis.).

TABLE 2

			Mea-	Ratio
	Titrated		sured	(measured/
Diluent water	conc.	pH	conc.	titrated)

mixed	Sturtevant tap	35.0	6.9	35.3	1.009
anolyte - 1
mixed	Sturtevant tap	37.5	6.7	37.5	1.000
anolyte - 1
mixed	Sturtevant tap	40.0	6.6	39.4	0.985
anolyte - 1
mixed	Sturtevant tap	30.0	6.6	33.4	1.113
anolyte - 2
mixed	Sturtevant tap	42.5	6.7	39.1	0.920
anolyte - 2
mixed	Sturtevant tap	47.5	6.6	44.2	0.931
anolyte - 2
mixed	Sturtevant tap	40.0	7.1	36.5	0.913
anolyte - 3
mixed	Sturtevant tap	45.0	7.1	40.0	0.889
anolyte - 3
mixed	Sturtevant tap	47.5	7.1	43.6	0.918
anolyte - 3
mixed	Sturtevant tap	37.5	6.7	36.8	0.981
anolyte - 4
mixed	Sturtevant tap	40.0	7.0	40.4	1.010
anolyte - 4
mixed	Sturtevant tap	45.0	7.0	44.0	0.978
anolyte - 4
mixed	Sturtevant tap	37.5	6.5	36.6	0.976
anolyte - 5
mixed	Sturtevant tap	42.5	7.0	39.4	0.927
anolyte - 5
mixed	Sturtevant tap	45.0	7.1	42.7	0.949
anolyte - 5

Table 3 summarizes measurements of the TARAline chlorine probe for various mixed anolyte solutions diluted by water that includes 200 ppm of HCO₃ ⁻ and 0 ppm of hardness.

TABLE 3

			Mea-	Ratio
	Titrated		sured	(measured/
Diluent water	conc.	pH	conc.	titrated)

mixed	200 ppm HCO₃ ⁻,	37.5	7.4	37.5	1.000
anolyte - 6	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	40.0	7.5	40.1	1.003
anolyte - 6	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	42.5	7.4	43.7	1.028
anolyte - 6	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	37.5	7.3	37.5	1.000
anolyte - 7	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	42.5	7.3	41.7	0.981
anolyte - 7	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	47.5	7.3	45.6	0.960
anolyte - 7	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	35.0	7.4	33.6	0.960
anolyte - 8	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	42.5	6.9	39.9	0.939
anolyte - 8	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	45.0	7.0	44.0	0.978
anolyte - 8	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	37.5	7.2	30.7	0.819
anolyte - 9	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	40.0	7.2	35.1	0.878
anolyte - 9	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	42.5	7.2	39.1	0.920
anolyte - 9	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	37.5	7.1	34.3	0.915
anolyte - 10	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	42.5	7.1	38.9	0.915
anolyte - 10	0 ppm hardness
mixed	200 ppm HCO₃ ⁻,	45.0	7.1	43.1	0.958
anolyte - 10	0 ppm hardness

Table 4 summarizes measurements of the TARAline chlorine probe for various mixed anolyte solutions diluted by water that includes 200 ppm of HCO₃ ⁻ and 200 ppm of hardness.

TABLE 4

			Mea-	Ratio
	Titrated		sured	(measured/
Diluent water	conc.	pH	conc.	titrated)

mixed	200 ppm HCO₃ ⁻,	37.5	7.2	36.0	0.960
anolyte - 11	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	40.0	7.2	41.0	1.025
anolyte - 11	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	45.0	7.2	45.6	1.013
anolyte - 11	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	37.5	7.1	35.4	0.944
anolyte - 12	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	40.0	7.2	40.8	1.020
anolyte - 12	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	42.5	7.2	45.4	1.068
anolyte - 12	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	35.0	7.3	36.4	1.040
anolyte - 13	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	40.0	7.0	41.1	1.028
anolyte - 13	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	45.0	7.0	46.8	1.040
anolyte - 13	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	37.5	7.3	34.7	0.925
anolyte - 14	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	40.0	7.2	40.1	1.003
anolyte - 14	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	45.0	7.3	44.3	0.984
anolyte - 14	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	37.5	7.1	36.5	0.973
anolyte - 15	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	42.5	7.2	41.7	0.981
anolyte - 15	200 ppm hardness
mixed	200 ppm HCO₃ ⁻,	45.0	7.3	46.4	1.031
anolyte - 15	200 ppm hardness

The data above for the TARAline chlorine probe demonstrates that it has a linear or substantially linear and flat or substantially flat response over relevant available chlorine concentrations and solution pH, and can be used in the systems and methods described herein. Thus, the methods and apparatus disclosed herein provide and establish a linearity between the amperometric signal and the read out of available chlorine within a pH range (exemplified above in a range from slightly acidic to slightly alkaline) and at available chlorine concentrations typical for CIP applications (e.g. about 40 ppm for a sanitizing step in CIP). The methods and apparatus disclosed herein do not require additional buffers or equipment (e.g., acidification units) for proper operation.

Claims

1. An industrial cleaning system comprising:

an electrochemical activation unit that is capable of generating an anolyte from a brine solution, the anolyte having a concentration of available chorine;

an anolyte dosing pump that is connected to the electrochemical activation unit;

a chlorine probe capable of measuring the concentration of available chlorine in a diluted anolyte; and

a controller unit operatively coupled to the chlorine probe and the anolyte dosing pump, wherein the controller unit activates the anolyte dosing pump when the measured concentration of available chlorine is lower than a predetermined concentration of available chlorine.

2. The industrial cleaning system of claim 1, wherein the chlorine probe has a substantially linear response to the concentration of available chlorine up to at least 50 ppm.

3. The industrial cleaning system of claim 2, wherein the chlorine probe has a substantially flat response to changes in pH within a range of about 4.0 to about 9.0.

4. The industrial cleaning system of claim 1, wherein the predetermined concentration of available chlorine is about 40 ppm at a pH range of about 4.0 to about 9.0.

5. The industrial cleaning system of claim 1, further comprising a chlorine tank that receives the anolyte from the anolyte dosing pump.

6. The industrial cleaning system of claim 1, further comprising a source of potable water connected to the system.

7. The industrial cleaning system of claim 1, further comprising

a catholyte dosing pump operatively coupled to the controller unit,

wherein the electrochemical activation unit is capable of further generating a catholyte, the catholyte having a concentration of caustic, and wherein the controller unit is capable of activating the catholyte dosing pump when the concentration of caustic is lower than a predetermined concentration of caustic.

8. The industrial cleaning system of claim 7 wherein the catholyte is diluted with water.

9. A method for maintaining the concentration of available chlorine in an industrial cleaning system, the method comprising:

providing an electrochemically activated solution comprising an amount of available chlorine;

measuring the concentration of available chlorine in the solution using a chlorine probe, wherein the chlorine probe has a substantially linear response to the concentration of available chlorine up to at least 50 ppm, and a substantially flat response to the concentration of available chlorine over a pH range; and

providing an additional amount of available chlorine to the system when the measured concentration is lower than a predetermined concentration of available chlorine.

10. The method of claim 9, wherein the substantially flat response is at a pH range of about 4 to about 9.

11. A method for cleaning a system, the method comprising:

providing an electrochemically activated solution having a concentration of available chlorine;

determining a concentration of available chlorine that is suitable for cleaning at a given pH of the electrochemically activated solution;

measuring the concentration of available chlorine in the electrochemically activated solution;

activating a dosing pump when the measured concentration of available chlorine is lower than the determined concentration of available chlorine; and contacting the system with the electrochemically activated solution.

12. The method of claim 11, wherein the concentration of available chlorine is about 40 ppm at a pH of about 4.0 to about 9.0.

13. The method of claim 11, further comprising

providing a second electrochemically activated solution having a concentration of a caustic;

measuring the concentration of caustic in the second electrochemically activated solution;

activating a dosing pump that is connected to (a) the second electrochemically activated solution and (b) the system; and

contacting the system with the second electrochemically activated solution.

14. The method of claim 13, wherein the second electrochemically activated water solution is diluted with water.

15. The method of claim 11, wherein the system is associated with industrial manufacturing.

16. The method of claim 11, wherein the system comprises production equipment.

17. The method of claim 11, wherein the system comprises conveyance equipment.

18. The method of claim 11, wherein the system comprises food or beverage production equipment.