Chlorine dioxide generator for the efficient generation of chlorine dioxide in dilute solutions

Abstract

Disclosed is an apparatus and method for the safe and efficient generation of chlorine dioxide. Chlorine dioxide is produced safely and efficiently by diluting a source of chlorite in water to produce less than or equal to 5000 ppm measured as ClO2 while achieving at least 80 wt%, more preferably 90 wt %, and most preferred at least 95 wt % conversion of chlorite anion to chlorine dioxide.

Description

RELATED APPLICATIONS

This Utility Application is a continuation of Provisional Application No. 61/743,436 filed on Sep. 04, 2012.

BRIEF DESCRIPTION

Chlorine dioxide generators come in a variety of configurations and use a range of generating techniques. Generators that use chlorite, hypochlorite, and acid often comprise an eductor to form a vacuum to extract a highly concentrated stream of chlorine dioxide gas and dilute it with water to produce a chlorine dioxide solution.

These techniques have the potential to cause explosion and/or significant harm to personnel due to contact with highly concentrated chlorine dioxide in the event of a malfunction. The invention provides a system and method for producing a dilute chlorine dioxide solution with a concentration ranging from 250 ppm to 5000 ppm as chlorine dioxide without the need for combining concentrated streams of chemical reagents and producing potentially dangerous concentrations of chlorine dioxide gas.

The invention provides for the safe and efficient generation of chlorine dioxide with at least 80 wt %, more preferably at least 90 wt %, and most preferably at least 95 wt % conversion of chlorite anion to chlorine dioxide without the need of forming concentrated streams of chlorine dioxide prior to dilution with water.

DEFINITIONS

As used herein, “safe and efficient generation of chlorine dioxide” describes the inventions ability to produce chlorine dioxide with high conversion of chlorite anion to chlorine dioxide without producing a process stream of chlorine dioxide that has a concentration of chlorine dioxide gas that is potentially explosive. The term “safe” refers to the inventions inherent safe generation of chlorine dioxide achieved by diluting a source of chlorite in water to achieve a concentration of chlorite anion necessary to provide less than or equal to 5000 ppm chlorine dioxide. By diluting the source of chlorite before generating chlorine dioxide, at no time is the concentration of chlorine dioxide at explosive levels. The term “efficient” describes the efficient generation of chlorine dioxide resulting from the conversion of chlorite anion (as ClO₂) to chlorine dioxide (ClO₂) of at least 80 wt %, more preferably 90 wt %, and most preferably 95 wt % conversion of chlorite anion to chlorine dioxide. The wt % (weight percent) conversion of chlorite anion to chlorine dioxide can be determined by dividing the parts per million of chlorine dioxide by the parts per million of chlorite anion multiplied by 100. The equation is exemplified by: [ClO₂ (ppm)/ClO₂⁻ (ppm)]×100=wt % conversion of chlorite anion to chlorine dioxide.

As used herein, “dilute aqueous solution of chlorine dioxide” describes the effluent aqueous solution discharged from the reaction chamber having a chlorine dioxide concentration of less than or equal to 5000 ppm measured as ClO₂.

As used herein, “flow sensor” describes a device that can detect a liquid flowing through a pipe. The flow sensor can measure, but is not required to measure the flow rate. The flow sensor detects motive water in the pipe. One non-limiting example of a flow sensor is Rotorflow® Flow Sensors available by Gems™ Sensors and Controls.

As used herein, “control panel” describes a system that is used to control at least, but is not limited to, chemical feed systems. Non-limiting examples of how the control panel can be used to control chemical feed systems include: actuating chemical feed; varying the rate of chemical feed; energizing an electronic device such as a chemical feed pump, solenoid valve, modulating control valve; stopping chemical feed; and/or initiating a flushing cycle that removes residual chemicals from the chemical feed system by either rinsing with water and/or neutralizing chemicals exemplified by sodium sulfite. The control panel comprises at least relays that may function as a switch or as a contactor. The control panel can also comprise microprocessors, programmable logic controllers, and timers and/or receive input from externally sourced microprocessors, programmable logic controllers, timers, and sensors. The control panel can be used to receive and process information from external sensors for determining ORP, amperometric, flow-rate measurement, temperature, pH and the like to optimize the feed-rate of the chemical feed systems and optimize the feed rate of chlorine dioxide.

As used herein, “energize” and “energizing” and its variations describes the activation of an electrical device by closing a circuit that delivers an electrical current to the electrical device so that the electrical device performs a desired function. For example, a flow sensor detects motive water followed by the control panel energizing the chemical feed systems. In contrast, when motive water is no longer confirmed by the flow sensor, the control panel stops the chemical feed systems.

As used herein, “actuated” and “actuating” and its variations is an action initiated by the control panel to cause something to happen such as initiating chemical feed, stopping chemical feed, initiating a flushing cycle and the like.

As used herein, “flushing cycle” describes a process of rinsing at least the injection manifold and reaction chamber with water or a neutralizing solution that neutralizes chlorine dioxide, and acidified chlorine and/or their respective chemical sources exemplified by sodium chlorite, sodium hypochlorite, and hydrochloric acid. One example of a neutralizing solution is a solution of sodium sulfite.

As used herein, “signal contact” describes the ability of an electronic device exemplified by a flow sensor to communicate with a control panel. The methods of communication may comprise a signal transmitted by electromagnetic means &/or by hard wiring. Electromagnetic means is exemplified by the non-limiting example radio transmissions, whereas hard wiring in a physical connection between the electronic device and the control panel by wire.

As used herein, “electrical contact” describes the hard wire connection. One non-limiting example is a wire connection between the control panel and the chemicals feed systems. The electrical contact can either provide a signal to energize the chemical feed system or provide the electrical current to directly energize the chemical feed system.

As used herein, the term “efficient” describes the conversion of chlorite anion (as ClO₂) to chlorine dioxide (ClO₂) of at least 80 wt %, more preferably 90 wt %, and most preferably 95 wt % conversion of chlorite anion to chlorine dioxide. The wt % conversion of chlorite anion to chlorine dioxide can be determined by dividing the parts per million of chlorine dioxide by the parts per million of chlorite anion multiplied by 100. The equation is exemplified by: [ClO₂ (ppm)/ClO₂ ⁻ (ppm)]×100=wt % conversion of chlorite anion to chlorine dioxide.

As used herein, “fluid contact” describes intimate contact between conduits capable of transporting liquid between the different conduits.

As used herein, “chemical feed systems” describe any convenient device that is fluid contact with both the chemicals for the generation of chlorine dioxide and the injection manifold. The chemical feed systems can be controlled to deliver the desired amount of reagent to generate the chlorine dioxide. Non-limiting examples of chemical feed systems include: chemical metering pumps, educators, modulating control valves and the like.

As used herein, “chemicals for the generation of chlorine dioxide” describes chemicals (reagents) for producing an aqueous solution of acidified chlorine and chlorite anions used to generate a dilute aqueous solution of chlorine dioxide.

As used herein, “source of acidified chlorine” describes reagents needed to produce an aqueous solution of acidified chlorine comprising chlorine gas (Cl₂) and/or hypochlorous acid (HOCl). Non-limiting examples of sources of acidified chlorine may comprise a two reagent treatment comprising hydrochloric acid and sodium hypochlorite injected separately into the injection manifold having a source of motive water to form acidified chlorine in-situ, a mixture of a source of chlorine and an acid source injected together into the injection manifold, or a source of chlorine comprising gaseous chlorine that hydrolyzes in the source of motive water to form hydrochloric acid and hypochlorous acid.

As used herein, “injection manifold” describes a manifold with at least two and preferable at least three inlet ports to inject a source of chlorite into a source of motive water separately from the other reagents for the generation of acidified chlorine used to generate chlorine dioxide. One non-limiting example of an injection manifold with two inlet ports injects a source of chlorite into one inlet port and a source of acidified chlorine into the other inlet port. One non-limiting example of a three inlet port manifold injects a source of chlorite, source of chlorine, and an acid source separately through the different inlet ports, wherein the source of chlorine and acid source produce acidified chlorine in-situ.

As used herein, “reaction chamber” describes a chamber wherein the aqueous solution comprising water, a source of chlorite, and acidified chlorine react to produce a dilute aqueous solution of chlorine dioxide. Non-limiting examples of reaction chambers include: static mixer, a chamber to increase contact time, or a length of pipe or hose that increases the contact time to provide at least 80 wt % conversion, more preferably at least 90 wt % conversion, and most preferably 95 wt % conversion of chlorite anion to chlorine dioxide. Non-limiting examples of a reaction chamber include: a static mixer, a chamber providing increased volume that increases reactants contact time, and/or a length of pipe or hose that increase the reactants contact time. The reaction chamber improves the efficiency by improving the kinetics through either increasing mixing (e.g. static mixer) and/or the reaction time to allow the reactions to approach completion (increased volume).

As used herein, “source of chlorite” describes a compound that releases chlorite anions having the general formula ClO₂⁻ when dissolved in water. Non-limiting examples of a source of chlorite include: sodium chlorite, potassium chlorite, and calcium chlorite.

As used herein, “chlorite anion” describes the precursor having the general formula ClO₂⁻ that is converted into chlorine dioxide ClO₂ when reacted with acidified chlorine.

As used herein, “source of chlorine” is any convenient source of chlorine that releases chlorine gas and/or hypochlorous acid when dissolved in an acidified aqueous solution. Non-limiting examples include: gaseous chlorine, sodium hypochlorite, lithium hypochlorite, calcium hypochlorite, dichloroisocyanuric acid, trichloroisocyanuric acid, dichlorodimethyl hydantoin and the like.

As used herein, “acid source” describes any convenient source of a hydrogen ions (H⁺) that reduce the pH when dissolved in water. An acid source can comprise mineral acids and/or organic acids. Non-limiting examples include: hydrochloric acid, phosphoric acid, sulfuric acid, citric acid, tartaric acid, fumaric acid and the like.

As used herein, “chemical feed systems are slaved together” describes the ability to control the chemical feed-rate in such as way so that altering the output of one chemical (exemplified by the source of chlorite) automatically and proportionally alters the feed-rate of the other chemicals used to generate chlorine dioxide (e.g. acidified chlorine). This proportional slaving of the chemicals feed systems allows for consistent efficiency in the conversion of chlorite anion to chlorine dioxide while providing variability in the production rate of chlorine dioxide. The production rate of chlorine dioxide can be automatically adjusted by the control panel using on feed-back and/or feed-forward control.

As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a composition containing “a compound” includes a mixture of two or more compounds. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

DESCRIPTION OF FIGURES

FIG. 1—Flow sensor (501) is in position to detect a source of motive water being supplied to the injection manifold and in signal contact with control panel (502). Control panel (502) is in electrical contact with the chemical feed systems (101).

Chemical feed systems (101) are in fluid contact with the chemical (reagents) for the generation of chlorine edioxide (non-limiting examples NaClO₂, NaOCl, and HCl) and the injection manifold (201). The injection manifold (201) is in fluid contact with the reaction chamber (301). The dilute aqueous solution of chlorine dioxide from the reaction chamber (301) is sent to the application.

DETAILED DESCRIPTION

The invention is an apparatus and method for the safe and efficient generation of chlorine dioxide using chemicals (reagents) without producing a concentrate of chlorine dioxide. The invention comprises a plurality of chemical feed systems in fluid contact with an injection manifold flooded with water by a source of motive (flowing) water. The plurality of chemical feeds deliver chemicals for the generation of chlorine dioxide (reagents) comprising a source of acidified chlorine and a source of chlorite to produce a dilute aqueous solution of chlorine dioxide. The motive water, acidified chlorine, and chlorite anion flow through a reaction chamber and convert at least 80 wt %, more preferably 90 wt %, and most preferably 95 wt % of the chlorite anion to chlorine dioxide before being applied to the application.

In one preferred method the control panel actuates the chemical feed systems only when motive (flowing) water is confirmed using a flow sensor and a sufficient period of time is allowed to lapse to ensure at least the injection manifold is flooded with motive water before chemical feed is actuated.

In another preferred embodiment, the control panel varies the feed-rate of the chemical feed systems and subsequent production rate of chlorine dioxide based on input from external sensors in fluid contact with the water system. The sensor(s) monitor parameters exemplified by the non-limiting examples ORP, chlorine dioxide concentration, and/or flow-rate. The control panel automatically varies the chemical feed-rate of the chemical feed systems using feed-back and/or feed-forward control.

In another preferred embodiment, chemical feed systems are slaved together providing proportional variability in chemical feed rates resulting in consistent efficiency in the conversion of chlorite anions to chlorine dioxide while providing variability in the production rate of chlorine dioxide.

The invention allows for the safe and efficient generation of dilute aqueous solution of chlorine dioxide without the need to combine concentrated reagents that generate potentially dangerous concentrations of chlorine dioxide exemplified by U.S. Pat. No. 6,855,294 and other prior art. Combining concentrated solutions of acidified chlorine and liquid chlorite rapidly generates concentrations of chlorine dioxide that can exceed the explosive concentration threshold of chlorine dioxide. Any interruption in water flow across the educator can lead to catastrophic events include injury or death.

The invention provides for a chlorine dioxide generating system that dilutes the source of chlorite to achieve a chlorite anion concentration necessary to produce a dilute aqueous solution of chlorine dioxide of preferably less than or equal to 5000 ppm measured as ClO₂. Using this method, the concentration of chlorine dioxide is sustained well below the explosive threshold of chlorine dioxide, while achieving the efficiency of generators that react concentrated solutions of reactants.

The chemical feed systems are controlled by a control panel. The control panel can adjust the chlorine dioxide production rate based on feed-back and/or feed-forward control. For example, oxidation reduction potential (ORP) and/or amperometric sensors can be used to monitor the water being treated with chlorine dioxide. The feed-back from these sensors can be used to automatically adjust the amount of chlorine dioxide being produced by altering the feed-rate of the chemicals used to generate chlorine dioxide. An example of feed-forward is a device that measures flow-rate and provides data to the control panel so that the feed-rate of chlorine dioxide is variable based on flow-rate. Feed-back and feed-forward control can be combined to further optimize chlorine dioxide product rate and feed-rate.

Sensors can also be used to monitor and subsequent allow the control panel to vary the feed-rate of chemicals used to optimize the production of chlorine dioxide. For example, pH monitoring of the chlorine dioxide solution can be used to optimize the feed-rate of an acid source used to produce the acidified chlorine. Other sensors can be used to monitor useful parameters. Non-limiting examples of sensors include: oxidation reduction potential (ORP), amperometric, reagent based automatic titrator, pH, conductivity, temperature, and ion specific probes.

Feed-back control can be used to optimize the production rate and feed-rate of chlorine dioxide. Oxidation reduction potential (ORP) is one non-limiting example of a control parameter that can be used as a feed-back control to optimize the feed-rate of chlorine dioxide. As oxidant demand and/or flow-rate change, the ORP controller can provide feed-back that automatically varies the production rate and feed-rate of chlorine dioxide in order to sustain the desired millivolt potential. Depending on the application, proportional, proportional integral, proportional integral differential, or time based proportional control may be used to optimize the generation and feed-rate of chlorine dioxide.

The invention provides a method for safe and efficient generation of chlorine dioxide for the treatment of water systems. Non-limiting examples of water systems include: oil and gas hydraulic fracking water, oil and gas down-hole water, oil and gas produced water, hydraulic fracking flow-back water, cooling water, food intervention, and waste-water.

Oil and gas hydraulic fracking water (frac water) is water used to create hydraulic fracturing in a rock layer, as a result of the action of a pressurized fluid. The fracturing of the rock layer allows trapped oil and gas to be recovered. Frac water must be treated to kill waterbome bacteria to prevent contamination of

Oil and gas down-hole treatment comprises using water treated with chlorine dioxide often combined with other chemicals such as surfactants, chelants, acids and the like to increase the oil and/or gas production of the well. Wells can become sour from anaerobic bacteria producing hydrogen sulfide which sours the oil and gas. Bacterial bio-films, iron sulfide deposits, and corrosion byproducts can foul the well and reduce oil and gas production. Down-hole treatment with at least chlorine dioxide can increase productivity by removing the foulants.

Flow-back water and produced water is water that is returned to the surface from gas and oil wells. Flow-back water is treated frac water that contains frac chemicals such as surfactants, dissolved solids, suspended solids and often oil. Produced water occurs after the frac process that contains the oil and/or gas resulting from the production of the well. Both the frac water and produced water can be treated with chlorine dioxide to induce coagulation of organics, removal of oxidant demand such as hydrogen sulfide, and disinfect the water for re-use in frac operations.

Cooling water can be once-through or circulated for the use of cooling process equipment such as heat exchangers. Circulated cooling water is often passes across cooling towers, or spray ponds to induce evaporation to lose heat of vaporization.

Chlorine dioxide is an effective biocide for treating water used in “food intervention” for the treatment of a food product or food, and/or food processing systems to killing one or more of the food-borne pathogenic bacteria associated with a food product, such as Salmonella typhimurium, Salmonella javiana, Campylobacter jejuni, Listeria monocytogenes, Escherichia coli O157:H7, and the like.

A “food product” or “food” refers to any food or beverage item that may be consumed by humans or mammals. Some non-limiting examples of a “food product” or “food” include the following: meat products including ready-to-eat (“RTE”) meat and poultry products, processed meat and poultry products, cooked meat and poultry products, and raw meat and poultry products including beef, pork, and poultry products; fish products including cooked and raw fish, shrimp, and shellfish; produce including whole or cut fruits and vegetables and cooked or raw fruits and vegetables; eggs, and egg-based products.

The “food processing systems” refers to the surfaces of equipment and surroundings used to process food. Food processing systems includes the equipment and building structures used to process, produce, store, wash, move, sanitize, cut, and package consumable food items.

Waste-water can be treated with chlorine dioxide to oxidize odors exemplified by the non-limiting examples hydrogen sulfide and mercaptans, kill microbiological organisms, oxidize organics, and induce coagulation. Waste-water is any source of water that is discarded and is not deemed suitable for discharge to NPDES regulated waterways or for use by mammals for washing or consumption.

Claims

1) An apparatus for the safe and efficient generation of chlorine dioxide comprising:

a control panel that controls chemical feed systems,

chemical feed systems in fluid contact with chemicals for the generation of chlorine dioxide and an injection manifold,

chemicals for the generation of chlorine dioxide comprising a source of chlorite and a source of acidified chlorine,

a reaction chamber; and

wherein a source of motive water passing through the injection manifold is treated by the chemical feed systems with a source of chlorite and a source of acidified chlorine, and the motive water treated with a source of chlorite and a source of acidified chlorine flows through the reaction chamber generating a dilute aqueous solution of chlorine dioxide.

2) The apparatus according to claim 1, further comprising: a flow sensor for detecting the motive water; the flow sensor being in signal contact with the control panel; and wherein the control panel actuates the chemical feed systems only when motive water is confirmed.

3) The apparatus according to claim 1, wherein the efficient generation of chlorine dioxide comprises converting the source of chlorite to chlorine dioxide with at least 80 wt % conversion of chlorite anion to chlorine dioxide.

4) The apparatus according to claim 1, wherein the efficient generation of chlorine dioxide comprises converting the source of chlorite to chlorine dioxide with at least 90 wt % conversion of chlorite anion to chlorine dioxide.

5) The apparatus according to claim 1, wherein the dilute aqueous solution of chlorine dioxide comprises less than or equal to 5000 ppm measured as ClO2.

6) The apparatus according to claim 1, wherein the chemical feed systems are slaved together providing proportional variability in chemical feed rates and in the production rate of chlorine dioxide.

7) The apparatus according to claim 1, wherein the control panel automatically varies the chemical feed-rate of the chemical feed systems using feed-back and/or feed-forward control.

8) The apparatus according to claim 7, wherein the feed-back control comprises oxidation reduction potential.

9) A method for safe and efficient generation of chlorine dioxide for the treatment of water systems according to claim 1.

10) A method according to claim 9, wherein the water system comprises oil and gas hydraulic fracking water.

11) A method according to claim 9, wherein the water system comprises oil and gas down-hole water.

12) A method according to claim 9, wherein the water system comprises oil and gas produced water.

13) A method according to claim 9, wherein the water system comprises hydraulic fracking flow-back water.

14) A method according to claim 9, wherein the water system comprises cooling water.

15) A method according to claim 9, wherein the water system comprises food intervention.

16) A method according to claim 9, wherein the water system comprises waste-water.