GB2256649A - Electrolytic device for water treatment for modifying scale - Google Patents

Abstract

Device for electrolytic treatment of water, for example as in Figure 1, comprises a tubular outer case (10) having end connections (14) to be coupled into a supply pipe, and an electrode sub-assembly (16) removably located therein comprising anode(s) eg. of Zn and cathodes eg. of Cu containing a substance of different electric potential from the anode(s). The sub-assembly may comprise a cathode in the form of an outer sleeve (18) and one (or more) anodes (20), eg a metal bar, located in spaced relationship within the sleeve. The electrodes may be electrically interconnected and a resistance (26) may be incorporated. Electric current may be applied across the electrodes. Other dispositions of cathode(s) and anode(s) in such sub-assemblies are described. <IMAGE>

Description

WATER TREATMENT This invention relates to the treatment of water and more specifically to treatment for mitigating the adverse effect of hardness of water by modifying the manner in which scale is precipitated therefrom, e.g. on heating. Hard water is commonly defined as water containing concentrations over 100 mgl CaC03 and this carbonate will precipitate to form scale when the water is heated above BOO. The harmful effects of this scale in heat exchanging equipment such as boilers, in pipework, and in domestic appliances such as kettles is well known; the scale is hard, very durable, and difficult to remove.

It is known to provide an electrolytic device for acting on incoming water supply to influence the properties of the scale forming compounds in the water so that they either remain in suspension on heating or, if precipitated, form a crystalline or non-crystalline substance having greatly reduced tendency to deposit on surfaces and/or, if so deposited, are of a friable nature so that they can be removed, possibly by the flow of water itself, or by a simple and speedy maintenance operation, e.g. by simple brushing.

Examples of electrolytic devices of this type are described in GB-A-1Z88552 and in EP-B-0194012.

The object of the present invention is to provide an electrolytic device of the above type which is easily assembled, readily dis-assembled for maintenance or replacement of its electrodes (having in mind that the anode will be eroded and wasted in operation), and which enables the characteristics of the device to be readily monitored and adjusted if necessary to suit the particular operating conditions of an installation, e.g.

the water flow rate and the degree of hardness and other properties of the water itself.

According to the invention there is provided an electrolytic device for treatment of a flow of water to modify the manner in which hardness will be precipitated therefrom including one or more anodes, and one or more cathodes in a spaced relationship to the anode or anodes and formed from or containing a substance or substances having a different electric potential from that of the anode or anodes; whereby substances in the water, which acts as the electrolyte, have their properties modified characterised in that all the electrodes are located and secured together to form a unitary sub-assembly which can be installed in or removed from the device as an integral unit.

Some or all of the cathodes may be electrically interconnected with some or all of the anodes and, for some applications, an electric current, e.g. from a battery, may be applied across the respective electrodes to enhance the electrolytic action.

Said sub-assembly may include a plurality of electrodes of either or both types, e.g. a plurality of anodes of the same or different metals or other electropositive substances could be used in conjunction with a common cathode or with a plurality of cathodes of or containing a substance or substances which is or are electro-negative relative to the anodes.

Some examples of the invention are now more particularly described with reference to the accompanying drawings, wherein: Figure 1 is a longitudinal section of one form of electrolytic device, Figure 2 is a section on line 2-2 of Figure 1 Figure 3 is a longitudinal section of a modified form of the device, Figures 4, 5 and 6 are respective cross sections to show alternative arrangements of electrodes in a device of the type shown in Figure 3, Figure 7 is a longitudinal section of a further form of the device, and Figure 8 is a cross section on line 8-8 of Figure 7 Referring firstly to Figure 1 which shows a basic form of the device, a cylindrical watertight outer case 10 comprises a tubular main body portion 11 with removable end caps 12.The latter are provided with coaxial spigot portions 14 which can be coupled into a run of piping by means of couplings or unions in conventional manner. The casing is preferably formed from material which is non-electrically conducting and electrolytically inert so that the active parts of the device are isolated from the pipe run. Thus the components of the casing may be formed of a plastics material, glass or ceramic.

However, for some applications, a metal casing may be acceptable.

Inner end parts of the caps 12 define rebates which locate and centre a cylindrical electrode sub-assembly 15 co-axially.

Said sub assembly, which acts as an electrolytic cell, comprises an outer sleeve 18 formed from or including a substance acting as the cathode of the cell.

The sleeve itself may be metal or its internal surface may be plated or otherwise coated with metal film.

This example of the device incorporates a single anode of or incorporating a substance which is electropositive with respect to the cathode. Typically said anode 20 is a metal bar centred co-axially in spaced relationship to sleeve 18 by electrically insulating supporting spiders 22 at each end of sleeve 18. Thus the water is directed to flow between the spaced electrodes i.e. anode 20 and the cathode constituted by outer sleeve 18, the water acting as the electrolyte of the cell.

Said electrodes are electrically interconnected by a conductor 24 carried by an arm of one of the spiders 22 and said electrical connection may incorporate a resistor 26 of preselected fixed or variable rating which will control and smooth any fluctuations in the action of the cell due to small variations in flow rate of the water and in the rate of release of ions under the electrolytic action.

It will be seen that sub-assembly 16 is of unitary construction in that it can be pre-assembled to locate and secure the electrodes in their working relationship independently of the structure of the main body 11. Thus sub-assemblies can readily be interchanged by re-moving one of the end caps 12 of the main body. This facilitates manufacture and assembly and has further advantages in that replacement sub-assemblies can be provided to reactivate the device when necessary e.g.

when the anode has become wasted by dissolution under the electrolytic action. Moreover sub-assemblies having different electrolytic characteristics can readily be substituted to provide the most effective action suited to the degree of hardness and other properties of the water being treated and the rate of flow of the latter.

This enables testing and evaluation to be carried out on site to match the action to each particular installation, and to check for optimum operation, with easy re-assembly thereafter.

A variety of substances may be used as the cathode, any substance which is electro-chemically negative with respect to the chosen anode substance will provide some electrolytic effect. Copper will commonly be used, for example outer sleeve 18 could be a copper tube. It is also contemplated that noble metals e.g. silver, gold etc could be used and these could be provided as vacuum depositions onto a plastics sleeve or other forms of plating of the interior surface of e.g. a plastics outer sleeve 18 could be employed. Metals such as titanium, iron, vanadium, chromium, nickel or manganese or alloys of these metals are also contemplated as well as graphite in various forms e.g. pyrolytic.

The anode 20 can also be constructed of a wide range of substances provided it is electro chemically positive with respect to the cathode. Thus zinc could be used e.g. in combination with a copper cathode or other metals or alloys could be employed. Concentrations of the anode substance released into the water will need to be controlled to take regard

maximum levels permitted by health regulations e.g. for drinking water, this will obviously be affected by the velocity and volume of water passing through the device and its composition and temperature.Control can be effected by selection of anode and cathode materials as referred to above and the shaping, e.g. surface areas of the electrodes as well as the potential and current flow between them e.g. by use of a resistor referred to above or, in some applications, electric current may be applied across the electrodes from a secondary source, e.g. a small dry battery.

The device will normally be designed to operate effectively with water having a pH (acidity/alkalinity) conforming with World Health Organisation and E E C levels for potable water, i.e. 6.5 - 8.5. The cell design could be adapted to treat water outside this pH range or the water itself could be pre-treated to bring it within this range prior to its inflow to the device.

The interior flow passage or passages of the device may be adapted to induce turbulence in the through flow for some applications, e.g. the arms of the spider 22 could include angled side faces to induce a swirling action.

For some applications, e.g. where large volumes of water have to be treated, a plurality of the devices, e.g. as in Figure 1, could be employed, preferably acting in parallel though series connection of devices is also contemplated. However, this has the disadvantage of increasing the pipework necessary to interconnect the devices and also greatly increases the overall bulk of the installation.

Figures 3-6 show modified forms of electrode subassembly for a larger capacity device of compact construction which can be connected into a single run of pipework as described above. Referring firstly to Figures 3 and 4 the outer casing 10 of the device is as previously described though it will normally be of greater overall volume, particularly of increased diameter. Within it is located a unitary electrode subassembly 316 having a tubular outer sleeve 318 forming the cathode (which will have increased effective surface area by reason of its greater diameter) as referred to above.Supported in spaced relationship within sleeve 18 by means of appropriately shaped spiders 322a,b,or c (Figures 4,5 and 6) are a plurality of rod shaped anodes 320 disposed in spaced parallel relationship equiangularly about the axis of the sub-assembly, for example three (Figure 4), four (Figure 5) or six (Figure 6) anodes may be provided and they will each be electrically interconnected with the cathode as referred to above with or without the use of respective resistors.

In another arrangement (not shown) a plurality of sub-assemblies 18 or 318 may be disposed within a common outer casing.

The further form of a device of the invention shown in Figures 7 and 8 is of substantially different construction to the above.

A cylindrical outer casing 710 comprises a tubular main body 711 closed by end caps 712 incorporating coaxial spigots 714 for connection of the device into pipework as referred to above.

The electrode sub-assembly 716 of this device is removably located directly within main body 711. It comprises a plurality (in this example five) disc shaped anodes 720, e.g. of zinc or zinc alloy though they may be made of other substances as referred to above spaced equi-distantly along a supporting rod 718. Anodes 720 are a sliding fit within main body 711 so that they serve to locate the sub-assembly co-axially therein and they are provided with through apertures 719 so that the water can flow therethrough.

Four cylindrical cathodes 730a-d have central openings mounting them on rod 718, each cathode being mounted between a respective pair of anodes 720 and they are spaced axially therefrom by spacing washers carried on the rod. The outer diameter of the cathodes is substantially less than that of the anodes 720 so that the water can flow past them. The electrodes are located on a sleeve covering rod 18 and are clamped in their operative relationship by a nut 732 engaged with a threaded end portion of the rod so that the whole subassembly is secured together as a unitary structure and can be inserted into and removed from outer casing 710.

Again various substances may be used to form the cathodes 730. In this example a graduated electrolytic action is provided longitudinally of the device in that the cathode 730a at the inflow end sz the device is formed from or coated with platinum, the next cathode 730b is formed from or coated with gold, the third cathode 730c is formed from or coated with silver and the final cathode 730d toward the outflow end of the device is formed from or coated with copper; these cathodes acting in conjunction with the zinc or zinc based anodes 720. Thus the electric potential of the portions of the cell longitudinally of the device are graded with respect to the throughflow of water.

It will be appreciated that the characteristics of the cell can very readily be varied according to requirements by substitution of sub-assemblies 718 having different electrolytic characteristics and/or shaping and dimensions of their electrodes, e.g. by changing the metals or other substances used, and the number and dimensions of the electrodes of each type.

Claims (1)

1. An electrolytic device for treatment of a flow of water to modifiy the nanner in which hardness will be precipitated therefrom including one or more anodes, and one or ore catiiodes in a spaced relationship to the anode or anodes and formed from or containing a substance or substances having a different electric potential from that of tile anode or anodes;; whereby substances in the water, which acts as the electrolyte have their proper ties nods fled characterised in that all the electrodes are located and secured together Lo for a unitary subrassenbly which can be installed in or cemove@ from the device as an integral unit.

2. A device as in Claim 1 whierein some or all of the cathodes are electrically interconnected with some or @@@ of the anodes.

2. A vice as ito Claii:i 2 including a resistance electrically connected between the catood e or catilocles and the anode or anodes.

device as in Claim 2 including means for applying an electric current across the respective electrodes to p@hance the electrolytic action.

5. A @cvice as in Clain 4 wherein said @eans is a battery.

6. A device as in any preceding claim wherein said sub assembly includes a plurality of electrodes of either or both types.

7. A device as in Claim 6 wherein the sub-assembly includes a plurality of anodes of tile sane or different electro positive substances.

8. A device as in Claim 6 or 7 wherein the subrasse bly includes a plurality of cathodes of the same or different electro negative substances.

9. A device as in Claim 7 wherein the sub@assembly includes an outer sleeve comprising or constituting the cathode and a plurality of anodes located i in mutually spaced parallel relationship within and spaced @rom said sleeve Ill. A device as in Claim 7 wherein tIoc sub@assembly includes an outer sleeve and a plurality of anodes located in a series spaced longitudinally of each other within the sleeve.

11. A device as in Claim 16 wherein the sub@assembly ferther includes a plurality of cathodes each pou@ted space @elatonship between a respective pair of the anodes.

12. A device as in Claim 11 wherein the outer disneter of the cathodes is substantially less than that of the ') ',: C'S 13. n device as in Claim 12 wherein the anodes define through apertures for the flow of water through the sleeve and past the outer peripheries of the cathodes in use 14. A device as in Claim 11. 12 or 13 wherein the cathodes are each formed from a different electr@@ hegative substance graded in electrical potostial longitudinally of the device.

15. A device as in any preceding claim wherein at least one sail' electrode comprises a body of plastics or other bestral material having a surface coating of the electropositive or electro@negative substance.

16. An electrolytic device for water treatment substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 Figures 3. 4. 5 or or Figures 7 and 8 of the accompanying drswings.