WO2009156840A2

WO2009156840A2 - Electronic fluid treatment apparatus and method

Info

Publication number: WO2009156840A2
Application number: PCT/IB2009/006065
Authority: WO
Inventors: Ian Douglas Vroom; Mark Baden Cooper
Original assignee: Conequipt Cc
Priority date: 2008-06-26
Filing date: 2009-06-26
Publication date: 2009-12-30
Also published as: EP2307322A4; EP2307322A2; WO2009156840A3

Abstract

Electronic fluid treatment apparatus is provided comprising an electrode assembly (5) mounted in a housing (9, 15) having an inlet (10, 16) and an outlet (11, 17, 18). The electrode assembly has multiple electrodes (1 ) held in parallel spaced relationship relative to each other. A power supply (8) is connected to the electrodes such that alternate electrodes are interconnected so as to be similarly energised by the power supply. The power supply is adapted to provide a pulsed voltage at an amplitude and frequency dependent on the construction of the individual electrodes, the spacing between them and the dielectric properties of the fluid in which the electrodes are to operate such that the electrodes, in use, provide a capacitive effect. Typically an inductance is connected in parallel with the electrodes so as to create a resonant circuit. The apparatus is able to provide three distinct actions against microorganisms contained in the fluid.

Description

ELECTRONIC FLUID TREATMENT APPARATUS AND METHOD

FIELD OF THE INVENTION

This invention relates to electronic fluid treatment apparatus of the general type including electrodes that are operatively in contact with a fluid being treated for the purpose of destroying or simply killing biological species, especially micro-organisms including bacteria, viruses as well as other pathogenic species contained within the fluid. The invention also relates to a method of treating fluids using such apparatus.

The fluid may be a gas but it is envisaged that the most common applications will be in the purification of water of numerous different forms including ballast water, whether fresh water or seawater, potable water, effluent water, grey water, as well as black water.

The apparatus of this invention has the general nature of electrolytic apparatus that has the ability to cause dissociation of chemical species and the creation of active, typically ionic, species that act to destroy or kill microorganisms. The invention is, however, in no way limited to apparatus the use of which results in electrolytic dissociation of species contained within the fluid in order to generate active species as the apparatus of the invention can be effective irrespective of any electrolytic action or the presence of any compounds that dissociate into active species.

BACKGROUND TO THE INVENTION

Numerous different water treatment methods and apparatus are employed for various different purposes. The chemical sterilisation of water typically uses chlorine, ozone, sodium hypochlorite and many other compounds that utilise oxidation as the basis for their effectiveness. Many chemicals, however, represent a danger to personnel that apply the compounds, the public at large, and animals. Chemically treated potable water also carries the danger that the chemicals may be harmful if not maintained within predetermined limits. Many of the chemicals are not environmentally friendly and disposal thereof represents a threat to the environment or a substantial cost to a company or authority responsible for removing some or all of them.

As regards the treatment of ballast water transported by ships from one place to another and that, in the absence of suitable treatment, deposit undesirable aquatic species at a destination where the ballast water is discharged, international patent publication number WO2007049139 to RESOURCE BALLAST TECHNOLOGIES (PTY) LTD sets out the prior art as applicant understands it. That publication also describes a method and apparatus for destroying or killing aquatic species using cavitation created by a rapid decrease in pressure in a stream of pumped water. Conventionally spaced electrodes may be used simultaneously to electrolyse dissolved salts including sodium and bromium chlorides to produce chlorine or bromine in the usual way as well as oxygen and hydrogen all of which are active against aquatic organisms.

A purely electrolytic method for the treatment of ballast water is described in international patent publication number WO2007032577 to KOREA OCEAN RESEARCH AND DEVELOPMENT INSTITUTE. The electrical energy that is applied to the electrodes is preferably DC current with the polarity being switched periodically by a timer in order to minimise scale build-up. OBJECT OF THE INVENTION

It is an object of this invention to provide electronic fluid treatment apparatus and a method whereby fluids can be treated for the reduction of live micro- organisms in the fluid in an enhanced manner.

SUMMARY OF THE INVENTION

In accordance with one aspect of this invention there is provided electronic fluid treatment apparatus comprising an electrode assembly mounted in a housing having an inlet and an outlet, the electrode assembly having multiple electrodes held in parallel spaced relationship relative to each other, and a power supply for the electrodes and wherein alternate electrodes are interconnected so as to be similarly energised by the power supply, the apparatus being characterised in that the power supply is adapted to provide a pulsed voltage at an amplitude and frequency dependent on the construction of the individual electrodes, the spacing between them and the dielectric properties of the fluid in which the electrodes are to operate such that the electrodes, in use, provide a capacitive effect.

Further features of this aspect of the invention provide for the frequency of the pulsed voltage power supply to be in the range of from 5 kHz to 200 kHz and preferably in the range of from 10 kHz to 150 kHz; for the voltage of the pulsed voltage to be from 5 volts to 200 volts and preferably 10 volts to 150 volts; for the individual electrodes to be designed and mounted such that they are able to vibrate, at least to some extent; for the amplitude and frequency of the pulsed voltage to be selected according to the design of an associated electrode assembly and fluid in which it is to operate such that the electrodes resonate, in use; and for the variables to be selected in order to provide a desired operative peak current density between the individual electrodes, of from 80 to 1000 amps and preferably from 500 to 700 amps. The individual electrodes are typically in the form of cut metal plates with or without a coating and preferably able to vibrate along a major part of their length. The electrodes are therefore preferably of elongate shape being mounted at one end and having suitable spacers at or towards the other end. The length of such electrodes may be 2 to 6 times the width of the electrodes and typically about 5 times the width. The materials of construction are selected according to the duty to be performed and the chemical and electrochemical properties of the fluid in which the electrodes are to operate.

The invention also provides an electrode assembly comprising a base having multiple electrodes extending in parallel spaced relationship therefrom and wherein the electrode assembly is particularly adapted to form part of apparatus as defined above.

In accordance with a second aspect of the invention there is provided a method of treating a fluid containing microbiological species in order to destroy or kill same, the method comprising passing the fluid through apparatus as defined above whilst applying electrical energy to the electrodes by way of the power supply such that at least a portion of the fluid passes between the individual electrodes of each electrode assembly.

It is within the scope of this invention that apparatus as defined above may be used on its own or may be used in combination with other apparatus aimed at achieving a similar purpose.

Typically the fluid will be water selected from ballast water, whether it be freshwater or seawater, potable water, waste water and sewage effluent water. However, it can also be a gas such as air that requires purification or sterilisation and it may also be an organic liquid. Of course, the variables of the apparatus and method will be selected according to the basic properties of the fluid being treated. The invention thus provides apparatus that may have a threefold effect in purifying or sterilising fluids by destroying or killing microbiological species therein. These effects include those consequent on electrolysis of constituents in the fluid; those consequent on the high-frequency effect of the pulsed voltage applied to the alternate electrodes that act on molecules having a dipole, including water that can break down and cause the formation of hydrogen peroxide and ozone; and the capacitive action in which the electrodes vibrate to form pressure waves between with the accompanying destructive effect on microbiological species as will be more fully described below.

In order that the above and other features of the invention may be more fully understood a description of different embodiments and an expanded description of the invention follow with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:-

Figure 1 is an elevation of a single electrode;

Figure 2 is an isometric view of one electrode assembly including electrodes as illustrated in Figure 1 and illustrating a simple single housing as one alternative of housing;

Figure 3 is an elevation of the assembly as illustrated in Figure 2;

Figure 4 is a plan view thereof; Figure 5 is a side view of one apparatus according to the invention including plural electrode assemblies as illustrated in Figures 2 to 4;

Figure 6 is a sectional view taken a long line Vl to Vl in Figure 5;

Figure 7 is an isometric view of the apparatus illustrated in Figures 5 and 6;

Figure 8 is a sectional view similar to Figure 6 but illustrating the inclusion of additional apparatus for having an additional destructive effect on microbiological species contained in a fluid being treated; and,

Figure 9 is a schematic circuit diagram of the apparatus.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In the embodiments of the invention described below individual electrodes (1 ) are cut from a suitable metal plate. In an application in which the electrode assemblies are used in relation to water, one general form of electrode is cut from a 1 mm thick titanium grade 1 plate. Numerous other materials could be used according to the fluid to be treated; the constituent species that are expected to be present in such fluid, and the required lifespan of the electrodes. In this particular instance the electrodes are coated by electroplating them with the platinum group metal ruthenium.

The electrodes are made to an elongate shape, in this particular instance with a length that is equal to 5 times the width, and in one particular application with a width of 50 mm and a length of about 250 mm. An integral laterally offset terminal tab (2) is formed at one end and perforated for receiving an electrically connecting bolt (3) (see Figure 2). Even numbers of electrodes are connected to a base (4) that is suitable for mounting the electrode assembly (generally indicated by numeral (5)) in a housing therefor. Alternate electrodes serve as an anode set and the remaining interposed electrodes serve as a cathode set with the electrodes of each set being electrically connected together by means of the bolts (3) that pass through their aligned tabs (2) that are alternately located on opposite sides with respect to the longitudinal centreline of the electrodes. The spacing between the individual electrodes is selected to provide the capacitive effect of the invention and in this particular instance, the spacing is 4.5 mm apart. Clearly, the spacing will depend on the nature of the power supply and, in any event, a different spacing will quite possibly apply to a different fluid material.

Because of the long and relatively flexible nature of the individual electrodes, electrically insulating silicon grommets (6) are associated with holes (7) provided towards the ends of the electrodes remote from the base. These grommets serve to maintain the required spacing between oppositely charged electrodes, in use, and prevent the individual electrodes from touching each other and thereby causing a short circuit in the power supply. This arrangement enables the individual electrodes to vibrate or oscillate under the influence of mutual attraction in response to the pulsed voltage applied in use by the power supply that is indicated by numeral (8).

For small capacity applications such as production of potable water, a single electrode assembly could be installed in a simple tubular housing (9) having an inlet (10) and an outlet (11 ) for water.

However, for larger applications such as in the treatment of ballast water or sewage effluent, and with reference to the Figures 5 to 7 of the drawings, a variety of electrode assemblies may be installed on a single housing. In the embodiment of the invention illustrated there are six equally angularly spaced parallel electrode assemblies arranged in a circular path around a central axis of a cylindrical housing (15). An inlet (16) and an outlet (17) extend radially outwards at opposite ends of the housing in an arrangement aimed at maximising the flow of fluid between the electrodes of the various electrode assemblies.

Figure 8 illustrates a simple arrangement except for the fact that the outlet (18) is directed axially from an inner compartment (19) that is provided with components (20) of the aforementioned international patent publication number WO2007049139 wherein the components are targeted at creating cavitation and associated destruction of microbiological species.

Turning now to the power supply, and as indicated above, the power supply is adapted to provide a pulsed d. c. voltage at an amplitude and frequency dependent on the construction of the individual electrodes, the spacing between them and the dielectric properties of the fluid in which the electrodes are to operate such that the electrodes, in use, provide a capacitive effect.

In the present example, the power supply is adapted to provide a pulsed voltage of about 10 volts at a frequency of about 10 kHz with the duration of each pulse being approximately equal to the time period between pulses. The pulses are applied to the one electrode set whilst the other electrode set is relatively connected to ground. This arrangement has been found to be particularly effective in the treatment of ballast sea water. The resultant peak current density is about 700 amps.

Irrespective of this, it is to be understood that with the electrode design and the electrode assembly as described above, the individual electrodes are able to vibrate or oscillate, at least to some extent and the amplitude and frequency of the pulsed voltage are in any event selected and adjusted so that the electrodes resonate, in use. The variables that need to be taken into consideration include the dielectric constant of the fluid; the distance between the individual electrodes; the surface area, shape, dimensions and other physical properties of the individual electrodes; and the other components of the electrical circuit, especially the components contributing towards the resonant tank circuit that is formed with the electrode assembly.

Turning now to the schematic circuit diagram illustrated in Figure 9, the electrical circuit may be of the type illustrated and include a low pass (third order) input filter (30) connected to an A/C mains supply that feeds a first quadrant full control Thyristor bridge (31). The resultant DC bulk supply output (32) is fed to a half bridge inverter (33) that has a quasi-resonant switch mode with insulated gate bipolar transistors operating at zero voltage or zero current. A variable frequency control (34) enables pulse width modulation regulation from 0 to 20% duty cycle at 20 to 40 kHz.

The output from the half bridge inverter is fed to a high frequency pulse transformer (35) with the number of turns of each winding being selected to provide the required voltage output. The output from the transformer is fed by way of a full bridge pulse rectifier (36) to a parallel load circuit (37) that includes a suitable inductor (38) and the two electrode sets indicated by numeral (39) of each electrode assembly (5). The load arrangement is, as indicated above, designed to resonate in operation.

The invention thus provides apparatus that may have a threefold effect in purifying or sterilising fluids by destroying or killing microbiological species therein. These effects include those consequent on electrolysis of constituents in the fluid are typically in the instance of seawater, the electrolytic production of chlorine and bromine from dissolved salts thereof with their well-known sterilising effect. Secondly, there are produced other ionic compounds in consequence of the high-frequency effect of the pulsed voltage applied to the alternate electrodes that acts on molecules having a dipole. In particular, water can break down to form hydrogen peroxide and ozone both of which have a well-known oxidative sterilising effect.

Thirdly, the capacitive action of the electrodes in the circuit can cause the electrodes to vibrate or oscillate and form pressure waves between adjacent individual electrodes as well as within the body of the liquid with the accompanying destructive effect on microbiological species.

The combined effect of these three actions creates a very strong sterilisation action on organisms and organic compounds present in the aqueous medium.

Whilst the invention has been described above is being applied to the treatment of water, especially ballast water, it has numerous other applications. These include treatment of gases and in that regard there may be mentioned that it is envisaged that apparatus of this nature can be used to purify air in air-conditioning systems and water in numerous other systems, as indicated above. In each instance the electrode design may be different and the power supply is designed to achieve the desired result.

Claims

CLAIMS:

1. Electronic fluid treatment apparatus comprising an electrode assembly (5) mounted in a housing (9, 15) having an inlet (10, 16) and an outlet (11, 17, 18), the electrode assembly having multiple electrodes (1) held in parallel spaced relationship relative to each other, and a power supply (8) for the electrodes and wherein alternate electrodes are interconnected so as to be similarly energised by the power supply, the apparatus being characterised in that the power supply is adapted to provide a pulsed voltage at an amplitude and frequency dependent on the construction of the individual electrodes, the spacing between them and the dielectric properties of the fluid in which the electrodes are to operate such that the electrodes, in use, provide a capacitive effect.

2. Electronic fluid treatment apparatus as claimed in claim 1 in which the frequency of the pulsed voltage power supply is in the range of from 5 kHz to 200 kHz.

3. Electronic fluid treatment apparatus as claimed in claim 2 in which the frequency of the pulsed voltage power supply is in the range of from 10 kHz to 150 kHz.

4. Electronic fluid treatment apparatus as claimed in any one of the preceding claims in which the voltage of the pulsed voltage is from 5

Volts to 200 Volts.

5. Electronic fluid treatment apparatus as claimed in claim 4 in which the voltage of the pulsed voltage is from 10 Volts to 150 Volts.

6. Electronic fluid treatment apparatus as claimed in any one of the preceding claims in which the individual electrodes are designed and mounted such that they are able to vibrate or oscillate, at least to some extent.

7. Electronic fluid treatment apparatus as claimed in any one of the preceding claims in which the amplitude and frequency of the pulsed voltage is selected according to the design of an associated electrode assembly and fluid in which it is to operate such that the electrodes resonate, in use.

8. Electronic fluid treatment apparatus as claimed in any one of the preceding claims in which the variables are selected in order to provide a desired operative peak current density between the individual electrodes, of from 80 to 1000 amps.

9. Electronic fluid treatment apparatus as claimed in any one of the preceding claims in which the individual electrodes are in the form of cut metal plates with or without a coating.

10. Electronic fluid treatment apparatus as claimed in claim 9 in which the electrodes are of elongate shape and are mounted at one end (2) and have suitable spacers (6) at or towards the other end with the length of such electrodes being from 2 to 6 times the width of the electrodes.

11. An electrode assembly comprising a base (4) having multiple electrodes extending in parallel spaced relationship therefrom and wherein the electrode assembly is particularly adapted to form part of apparatus as claimed in any one of the preceding claims.

12. A method of treating a fluid containing microbiological species in order to destroy or kill same, the method comprising passing the fluid through apparatus as defined in any one of claims 1 to 10 whilst applying electrical energy to the electrodes by way of the power supply such that at least a portion of the fluid passes between the individual electrodes of each electrode assembly.

13. A method as claimed in claim 12 in which the fluid is water.

14. A method as claimed in claim 13 in which the water is ballast water.