WO2007065228A1

WO2007065228A1 - Continuous hypochlorite generator

Info

Publication number: WO2007065228A1
Application number: PCT/AU2006/001872
Authority: WO
Inventors: Kenneth Roland Varcoe
Original assignee: Kenneth Roland Varcoe
Priority date: 2005-12-09
Filing date: 2006-12-08
Publication date: 2007-06-14
Also published as: US20090000944A1; AU2006322658A1; CN101360686A; EP1971553A1; EP1971553A4

Abstract

A continuous hypochlorite generator is disclosed. The apparatus includes a brine tank (9), a make-up water line (15), a flow controlled electrolysis cell (19) fitted with electrodes (20), a salinity / flow sensor (31), a temperature sensor (27), a dosing line (23) and control means accepting input from each of said salinity / flow and temperature sensors and controlling said brine source and said make up water supply to maintain salinity and flow in said electrolysis cell and apply power to the electrodes within respective preselected ranges.

Description

CONTINUOUS HYPOCHLORITE GENERATOR

Field of the Invention. ,

The present invention relates to a continuous hypochlorite generator. This invention has particular but not exclusive application to a continuous hypochlorite generator for swimming pool water treatment, and for illustrative purposes reference will be made to such application. However, it is to be understood that this invention could be used in other applications, such as treating spas, hot tubs, drinking water, water in tanks or containments, process water and waste streams.

B ackground Art.

Hypohalites and particularly hypochlorites are an economical antimicrobial for water treatment, and general industrial disinfection. Chlorine gas and

Sodium hypochlorite predominate in the market, with the hypochlorite either being produced in bulk for distribution in containers from tanks, through drums to domestic dispensing containers, or being produced in situ by electrolytic generators.

The process of electrochlorination to produce an anti-microbially effective source of available chlorine as sodium hypochlorite solution is well known and basically consists of converting common salt (Sodium Chloride, NaCl) to low strength (up to 1 %) liquid chlorine equivalent by electrolysis. It is important that drinking water, wastewater, process water and swimming pool water is correctly disinfected to ensure safety and environmental responsibility.

The principle reactions occurring in the electrolytic cell that produces sodium hypochlorite are quite simple, as shown in the following:

Oxidation of the chloride ion occurs at the anode:

2Cl-—— — *^2C1₂ + 2e-

Followed by a rapid hydrolysis of the chlorine:

Cl₂ + H₂O— *~HOC1 + HCl

Reduction of the sodium ion occurs at the cathode:

Na+ + e — ~~*~Na

Followed by a rapid reaction of the sodium with water:

Na + H₂O *- 1/2H₂ + NaOH

The acids (HCl and HOCL) produced at the anode react with the base (NaOH) produced at the cathode: HCl + NaOH— *-NaCl + H₂O and,

HOCl + NaOH *~NaOCl + H₂O

The net reaction of electrolysis is:

NaCl + H₂O + energy'—— HVaOCl + H₂

Electrochlorinators generally comprise an electrolysis cell, a power supply to electrodes, a salt water supply and a control system, which allow the production of the hypochlorite solution by electrolysis from sodium, potassium, magnesium or other cationic chlorides, or a combination of such chlorides.

Electrochlorination is commonplace in recirculated systems such as swimming pools and the like, where the water in the pool is dosed with salt according to an approximate measure of concentration and the cell simply processes the water during the filtration cycle. Such a system is not applicable when it is not appropriate or desirable to add salt to the body of water or for use in a reticulated systems such as drinking water supplies and process water treatment.

It is known that on-site hypochlorite generators may be used for reticulated systems. These systems operate most efficiently when the salinity of the solution to be electrolysed is around 3% by weight. In known systems, the salt is fed from a brine tank holding a concentrated salt solution (26% by weight), which is diluted to 3% by mechanical means, such as valves and rotameters.

It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

Summary of the Invention.

The present invention is directed to a continuous hypochlorite generator, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

In a first form, the invention resides broadly in a continuous hypochlorite generator including:

a) a brine source,

b) an electrolysis cell, said electrolysis cell having internal recirculation to increase the fluid velocity over the electrodes to increase hypochlorite production efficiency. In a more particular form, the invention resides in a continuous hypochlorite generator including:

a. a concentrated brine source,

b. a water supply,

c. a salinity sensor,

d. a flow sensor,

e. a temperature sensor,

f. an electrolysis cell and a dosing outlet, and

g. control means accepting input from each of said salinity, flow and temperature sensors and controlling level and flow from said brine source and dilution water supply to maintain salinity in said electrolysis cell within respective preselected ranges.

The concentrated brine source may take any suitable form. For example, the concentrated brine source may comprise a brine storage tank wherein brine is replenished periodically. Alternatively, the saturated brine source may comprise a substantially continuous brine source such as a salt mass in a brine tank into which is passed water under the control of level maintenance means. For example, there may be provided metering means such as a pump or valve under control of the control means and adapted to maintain the correct liquid level in the brine storage tank. The level control means may comprise a mechanical cistern type arrangement or an electrical sensing mechanism which allows the water to be maintained at a preset level.

The chemical composition and relative amounts of different salts in the salt mass may be adjusted to provide additional therapeutic or synergistic effects. The preferred salts used in the salt mass will typically include monovalent or divalent cations such as calcium, magnesium, potassium and manganese, but may also include other metal salts such as salts of zinc (studies have shown that zinc salts mediate antiviral activity on respiratory syncytial virus (RSV) by altering the ability of the cell to support RSV replication Effect of Zinc Salts on Respiratory Syncytial Virus Replication, Rahaman O. Suara¹ and James E. Crowe, Jr.), gold (active progressive rheumatoid arthritis, and progressive juvenile chronic arthritis), or ammonium salts which have been shown to be effective against some forms of cancer. For example, a preferred salt mass may comprise a combination of Sodium, Potassium and Magnesium Chlorides in proportions from 0 - 100% and other additives may be used to enhance the therapeutic or agricultural benefits of the solution.

Therefore, in an alternative form, the invention may reside in a salt mass composition including at least two salts from the group including the alkali metals, the alkaline earth metals, the transition metals, the halogens or the rare earth elements. The salts chosen and the actual composition of the individual salts chosen will preferably be adjusted according to the purpose. Typically all salt masses will include at least a chlorine salt component.

The electrolysis cell may be supplied by the brine source by any suitable means. For example, there may be provided metering means such as a pump or valve under the control of the control means and adapted to meter brine into the electrolysis cell. The dilution water may be supplied by any suitable means. For example, there may be provided metering means such as a pump or valve under the control of the control means and adapted to control the dilution water flow into the electrolysis cell

There may be a single or multiple electrolysis cells which may take the form of one or more pairs of electrodes across which is maintained a suitable potential difference. The electrodes may comprise one or more of plates, mesh screens, membranes or the like. Potential difference may be applied continuously, on demand, on a timer or under control of the control means. The electrodes may be permanently assigned a polarity or may be periodically reversed as to polarity. By polarity reversal means the inevitable electrolytic deposits on the electrodes are at the least distributed evenly across all electrodes and at best are significantly reduced by electrolytic reversal of the polarity. The electrolysis cell may be designed so that the dilute brine flow is controlled so that it exceeds a minimum flow velocity over the electrode plates. This may be by controlling the dilute brine flow, the electrode cross sectional area and using multiple internal circulation paths so that the required minimum velocity is achieved.

Also, the interior of the electrolytic cell is preferably configured to provide internal recirculation of the electrolyte to increase the fluid velocity over the electrodes to increase hypochlorite production efficiency. It is understood that the driving force of the electrolysis and therefore the efficiency of the electrolytic cell is dependant upon the concentration of ions. It is also known that the concentration profile is typically highest near the electrolyte inlet and lowest near the electrolyte exit, resulting in the electrodes nearest the electrolyte inlet having a high driving force and those near the outlet having a low driving force. Using internal recirculation according to the present invention will preferably even out the concentration profile of electrolyte in the cell.

By maintaining a high concentration of the desired salt ion near the anode, the efficiency of the cell is increased. It is also realized that it is disadvantageous to have localized areas of low concentration. Also important to the function of the present invention is the increase of flow velocity over the electrodes to promote more even electrolyte concentration.

The internal recirculation of electrolyte may be accomplished in a number of ways. For example, a circuitous flow pathway through the cell may be provided with return channels to circulate electrolyte. A separate channel or duct may be provided inside the cell to recirculate the electrolyte.

The duct may have only upper (top) and lower (bottom) openings. Accordingly, gas bubbles evolving at an electrode, which tend to flow upward, are prevented from entry into the duct so that a difference in gross density of electrolyte takes place readily between the exterior and interior of the duct. Down flow occurs in the duct while upward flow occurs outside of the duct to produce natural circulation of electrolyte in the cell. Thus, the natural circulation in an electrolytic cell of the invention serves to equalize distribution of concentration therein and to rapidly remove evolved gas. Generally, a larger current density brings a wider range of distribution of concentration in the cell, and, also, a larger current density increases the gas evolution, which leads to a greater difference in gross density between the exterior and interior of a duct to cause greater circulation. Consequently, the cells of the invention can effectively maintain uniform or equal distribution of concentration even under high current density.

Generally, deviation of concentration is evident not only in a vertical direction, but also in a horizontal or transverse direction. Recirculation may therefore be provided in both directions. Therefore, a duct having a horizontal part as well as vertical part is well suited to maintaining a more uniform concentration in the cell. For example, an L-shaped duct is preferred with electrolyte circulation occurring between areas with the lowest concentration and areas with the highest concentration. Therefore, an upper opening of a duct should be adjusted close to an outlet hole for spent electrolyte and electrolytic product. Likewise, a lower opening of a duct should be adjusted close to an inlet hole for fresh electrolyte.

The duct may be of any cross-sectional shape. The dimension of the duct may be chiefly determined according to that required for circulation, which depends upon current efficiency of the electrodes employed, utilization degree of brine, construction of an electrolytic cell and electrode area.

The salinity sensor may take any suitable form. For example, the salinity sensor may measure the conductivity, steady state current and/or voltage between electrodes, or other electrical parameter of the solution in the electrolysis tank, and provide an output that may be correlated against standard range values corresponding to concentrations for salt in solution. The salinity sensor may comprise the Electrolyser electrodes, a dedicated pair of electrodes, or an independent sensor.

The flow sensor may take any suitable form. For example, the flow sensor may measure the presence of liquid by conductivity or other electrical parameter. The flow sensor may comprise the Electrolyser electrodes, a dedicated pair of electrodes, or an independent sensor and it may be combined with the salinity sensor.

The temperature sensor may take any suitable form. For example the temperature sensor may measure the liquid temperature by electrical, mechanical or any suitable means. The temperature sensor may comprise the Electrolyser electrodes or an independent sensor.

If a hypochlorite storage tank is used, the level sensing means may comprise a float arrangement that either is of a reed switch type that goes open and closed circuit at selected of levels. Alternatively, the level sensing means may comprise one or more ground referenced contacts that sense the level with reference to the conductivity of, or ultrasonic measurement means, or reduced capacitance relative to air of, the solution in the hypochlorite storage tank, hi a yet further embodiment, the level sensing means may comprise one or more pairs of discrete sensor electrode pairs disposed at a selected level or levels in the hypochlorite storage tank. The hypochlorite storage tank and the dosage outlet may take any suitable form and will be in part determined by the nature of the process stream being dosed. For example, the dosage outlet may comprise a pump or venturi supplying hypochlorite solution to the process water either continuously or on an on demand basis, hi one embodiment of the present invention, a sensor is provided in an intermittently flowing process line to activate the dosage outlet in response to commencement of flow. In other embodiments, the process line includes a flow meter and / or chlorine analyser and / or Redox potential analyzer in response to which the dosage outlet and / or hypochlorite generator is operated.

The control means accepting inputs from each of the level sensing means and salinity sensor and controlling the brine source, dilution and make up water supply may comprise an electromechanical logic apparatus, programmable logic controller or the like.

If a hypochlorite storage tank is not employed, the flow through the electrolysis cell and into the process water will be controlled by the control means and by brine and dilution water pumps or valves. The process may be activated by the control means in response to inputs from a time clock or inputs from instruments, such as a flow meter and / or chlorine analyzer and / or redox potential analyzer.

In the case of the substantially continuous brine source, salt is tipped into a brine tank and the water supply thereto operated by a float valve or level sensing means and / or pump designed to add make up water to maintain a constant level. Brine is then transferred to the electrolysis cell by operation of a pump, controlled by the control means. Water is added to dilute the brine flowing to the electrolysis cell to 2.0 to 3.5% by operation of a pump or solenoid valve, controlled by the control means. A heat exchange coil or chiller may or may not be fitted to effectively cool the solution in the case where temperatures exceed a preset level during the hypochlorite generation process.

A water heater may or may not be fitted for particular applications, especially where the dilution water may be supplied at temperatures for example < 18°C.

The salinity may then be checked for a short period of time, initially, periodically or continuously during the hypochlorite generation process and if the salinity is for example > 0.5% the main hypochlorite generating electrodes may be activated by the control means for a set period of time. During this time the level in the storage tank may be checked. Also during this time, the temperature and flow of the liquid may be checked.

The control means may include indicator means adapted to indicate the condition of the apparatus. If the salinity is checked and is for example < 1.5% and > 0.5% a visual indicator, such as an LED labeled "Low Salt" may illuminate indicating the need for additional mass salt to be added to the brine tank. If for example the salinity is checked and is for example < 0.5% a visual and / or audible indicator such as an LED labeled "No Salt" and / or a buzzer may be activated and the system may be shut down to halt any further operation, until mass salt is added and the apparatus is restarted. Similar alarms and indications may be activated in the event of no flow or high temperature.

For example, the hypochlorite generation period may be signaled by an audible and / or visual indicator such as an LED labeled "Cell on". If the low level control sensor in the hypochlorite storage tank has been reached, the control means may illuminate an LED labeled "Dosing On" and an LED labeled "Hypo Ready", indicating that there is sufficient liquid in the tank to allow the dosing of hypochlorite.

If the upper level control sensors in the hypochlorite storage tank have not been reached the control means may automatically continue the process and will continue to do so whenever the liquid level falls below both the top and intermediate control points. If the dosing flow is greater than the hypochlorite production, the level in the hypochlorite storage tank will fall until the lower level control sensor is reached and the control means may extinguish the LED labeled "Dosing On" indicating that the hypochlorite tank is effectively empty. This condition may be transmitted by the control means to the hypochlorite dosing apparatus to allow dosing to cease.

The control means may also include safety features such as audio and/or visual indications. For example, if the salinity is checked and found to be high, for example > 4.0%, a "No Water" or "Flow Fault" LED and / or audible buzzer may be activated. In another example, if during the hypochlorite generation cycle the hypochlorite temperature exceeds a preset value, for example 45°C, an "Overload or Temp High" LED and / or audible buzzer may be activated.

The control means may include means for varying the power to the electrodes, or cycling the power or other means of power management. However, it is preferred that the electrodes run at full power when they are on. The reversing of the polarity of the electrodes may or may not be used for the electrodes responsible for the salinity checking and may or may not be used for the main hypochlorite generating electrodes. The reversing period maybe selectable or fixed.

The control means may be fitted with supplementary electromechanical apparatus allowing the display of operating parameters such as "Volts", "Amps", "Operating Hours" and "Status" and may allow alarms and other operating variables to be transmitted to other external devices by electromechanical means.

On the hypochlorite dosing outlet side of the apparatus, under constant flow conditions the dosing system may operate normally whenever required. Where the flow is intermittent, the dosing system may be controlled to only operate when a flow detector indicates that there is flow. Dosing may be achieved by either a solenoid vale operated by the control means or by a separate dosing pump or preferably by turning the complete system on / off or which may be controlled by time, flow and / or chlorine analysis and / or Redox potential.

Brief Description of the Drawings.

Various embodiments of the invention will be described with reference to the following drawings, in which:

Figure 1 is a diagrammatic view of a process according to a preferred embodiment of the present invention.

Detailed Description of the Preferred Embodiment.

According to the embodiment of the invention illustrated in Figure 1, there is provided a sterilant generator comprising a brine tank 9 of about 25 litres, pumps 12, 13, 14 and an electrolysis cell 19. A water supply 10 flows through a control valve 11 and is then manifolded to provide a brine tank make up water supply

15 controlled by a float valve or sensor 16 and pump 12 and a dilution water supply

25 controlled by pumpl4. The brine tank 9 contains a salt mass 24, and is fitted with a brine manifold 26 in the base of the tank. Operation of the brine pump 13 and the dilution water pump 14 effects transfer of brine and water to the dilute brine flow line 18.

The electrolysis cell 19 is provided with hypochlorite generation electrodes 20 connected by power leads 21, a flow sensor 31 and the waterways are configured to ensure optimum flow velocities are achieved. A temperature sensor 27 is fitted to the outlet of the hypochlorite generation cell 19 to measure the temperature of the solution 23. A control valve 22 is provided to allow isolation of the cell. The process water flow line 29 is fitted with a non return valve 28. A flow sensor or other analysis equipment 30 may be provided in the flow line 29.

In use, 20 kg salt (sodium chloride and / or potassium chloride and / or magnesium chloride) is tipped into the brine tank 9 to become the salt mass 24. The brine tank float valve 16 opens and pump 12 runs until the brine tank 9 is filled with make-up water. If the control mechanism calls for the machine to start, the brine pump 13 will transfer brine through the brine manifold 26 into the brine line 17 and the dilution water pump 14 will start allowing brine to be diluted and to flow through the dilute brine line 18. The dilute brine flows through the electrolysis cell 19 which is powered to allow the electrolysis process to occur and salinity, flow and temperature checks are made. The salinity is checked by reference to the current passed for an applied voltage, which may be correlated against salinity. Ideally, the salinity will be in the range 2.0% - 4.0%. If the salinity < 1.5% the process will operate but the "Low Salt" LED will be activated to advise the need for fresh salt to be added to the brine tank 9. If the salinity is < 0.5% the "No Salt" LED and an audible buzzer will be activated and the process will not operate until fresh salt is added and the process is reset. If the salinity is > 4.0% the "Flow Fault" LED and an audible buzzer will be activated and the process will not operate until the water flow is restored and the process is reset. Salinity, flow and temperature will be regularly checked during the hypochlorite generation process.

If the temperature 27 of the hypochlorite solution exceeds a preset value, for example 45⁰C, an "Overload or Temp High" LED and / or audible buzzer may be activated and the process may be stopped.

When the control mechanism instructs the process to stop, power to electrolysis cell 19 is stopped and after a delay dilution water pump 14 is stopped and brine pump 13 is stopped. The control apparatus goes to stand-by mode until the timer or other inputs request generation of hypochlorite, at which time the process restarts.

The present embodiment provides a simple, reliable machine which can be set up and operated by relatively unskilled people to allow disinfection of water, particularly where previously such disinfection may not have occurred or may not have had the same level of automation and therapeutic and / or agricultural benefit.

In the present specification and claims (if any), the word "comprising" and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

Claims

1. A continuous hypochlorite generator including

a. a brine source,

b. at least one electrolysis cell, said electrolysis cell having internal recirculation to increase the fluid velocity over the electrodes to increase hypochlorite production efficiency.

2. A continuous hypochlorite generator as claimed in claim 1 wherein the brine source includes a premixed concentrated brine storage tank wherein brine is replenished periodically.

3. A continuous hypochlorite generator as claimed in claim 1 wherein the brine source includes a substantially continuous brine source of a salt mass in a brine tank into which is passed water under the control of level maintenance means.

4. A continuous hypochlorite generator as claimed in claim 1 wherein a metering means is provided to meter brine into the electrolysis cell.

5. A continuous hypochlorite generator as claimed in claim 1 wherein the brine is diluted prior to entry into the electrolytic cell by dilution water supplied by a suitable dilution means.

6. A continuous hypochlorite generator as claimed in claim 1 including multiple electrolysis cells.

7. A continuous hypochlorite generator as claimed in claim 1 wherein the electrolysis cell includes at least two electrodes and the polarity of the electrodes is periodically reversed.

8. A continuous hypochlorite generator as claimed in claim 1 wherein the electrolysis cell is configured so that the brine flow exceeds a minimum flow velocity over the electrodes.

9. A continuous hypochlorite generator as claimed in claim 1 wherein the interior of the electrolytic cell is configured to provide internal recirculation of the electrolyte to increase the fluid velocity over the electrodes to increase hypochlorite production efficiency by creating uniform or equal distribution of concentration within the electrolytic cell.

10. A continuous hypochlorite generator as claimed in claim 9 wherein the internal recirculation of electrolyte is accomplished through providing a circuitous flow pathway through the cell with return channels to circulate electrolyte.

11. A continuous hypochlorite generator as claimed in claim 9 wherein a separate channel or duct is provided inside the cell to recirculate the electrolyte.

12. A continuous hypochlorite generator as claimed in claim 9 wherein electrolyte recirculation provided in more than one direction within the electrolytic cell.

13. A continuous hypochlorite generator as claimed in claim 11 wherein an L- shaped duct is provided with electrolyte circulation occurring between areas with the lower concentration and areas with the higher concentration.

14. A continuous hypochlorite generator as claimed in claim 13 wherein an upper opening of the duct is provided adjacent to an outlet from the electrolytic cell and a lower opening of the duct is provided adjacent to an inlet to the electrolytic cell.

15. A continuous hypochlorite generator as claimed in claim 1 further including a hypochlorite storage tank.

16. A continuous hypochlorite generator as claimed in claim 1 wherein flow of hypochlorite from the electrolysis cell is introduced to process water and is controlled by the control means and by brine and dilution water pumps or valves.

17. A continuous hypochlorite generator as claimed in claim 3 wherein the chemical composition of the salt mass includes a combination of Sodium, Potassium and Magnesium Chlorides in proportions from 0— 100%.

18. A continuous hypochlorite generator including

a. a concentrated brine source,

b. a water supply,

c. a salinity sensor,

d. a flow sensor,

e. a temperature sensor,

f. an electrolysis cell and a dosing outlet, and

g. control means accepting input from each of said salinity, flow and temperature sensors and controlling level and flow from said brine source and dilution water supply to maintain salinity in said electrolysis cell within respective pre-selected ranges.

19. A salt mass composition for a hypochlorite generator, the composition including at least two salts from the group including the alkali metals, the alkaline earth metals, the transition metals, the halogens or the rare earth elements.

20. A salt mass composition for a hypochlorite generator according to claim 18 wherein the chemical composition and relative amounts of different salts in the salt mass is adjusted to provide additional therapeutic or synergistic effects.

21. A salt mass composition for a hypochlorite generator according to claim 18 wherein the chemical composition includes a combination of Sodium, Potassium and Magnesium Chlorides in proportions from 0 - 100%.

22. A continuous hypochlorite generator including

a. a brine source,

b. at least one electrolysis cell, said electrolysis cell having an internal configuration to increase the fluid velocity over the electrodes to increase hypochlorite production efficiency.