SMALL PORTABLE ELECTROLYTIC SODIUM HYPOCHLORITE ON SITE GENERATORS
The present invention describes four preferred embodiments of an apparatus aimed to the production of a dilute solution of sodium hypochlorite. It uses the process of the electrolysis of a dilute solution of sodium chloride in water by means of two metallic electrodes immersed in the solution. The electricity needed may be delivered by a range of sources like disposable cells (alkaline), rechargeable batteries, photovoltaic modules (PVM) or electromechanical generators, like alternators or dynamos, moved by human power. All the apparatus described operate in batch mode. They are small lightweight portable units, easily transportable anywhere, in remote areas or emergency situations where chemicals or electricity is not available. Main use is the purification of drinking water, but also the production of sterilizing solutions for wound disinfection, washing etc.
A number of electrochemically generated oxidants may be used to purify water: for instance Hydrogen Peroxide and ozone, which are difficult and critical to produce with simple devices to be operated on site and in the field. Therefore the most traditional oxidizing agent in these circumstances is Sodium Hypochlorite solutions or chlorine in the form of solid compounds. It should be noted that this compounds are quite critical to storage and deliver, particularly in hot and remote areas. The alternative solution is to produce Sodium Hypochlorite on site. It can be easily obtained by simple electrolysis of a dilute solution of Sodium Chloride in water.
The electrolysis process is well known. It is carried out by preparing a solution of Sodium Chloride in water, of proper concentration, and place it into an electrolysis cell composed of a container equipped with two electrodes, one anode and one cathode, through which is passed a dc electric current.
The electrodes are made of a chemically inert metal, like Titanium coated with oxides of noble metals like Ruthenium, Titanium, Lanthanum, Iridium, etc. They have semiconductor properties and are excellent catalysts for chlorine generation. This electrodes are named DSA (dimensionally stable anodes) and the coatings are proprietary.
In a cell of this type the anode and cathode are placed in the cell cavity without diaphragm or membranes separating them. In this way the electrochemical reaction products, Chlorine at the anode and Sodium Hydroxide at the cathode, react producing Sodium Hypochlorite.
The current density on the electrodes can vary from 0.05 to 0.5 Amp/cm2.
The current efficiency depends on temperature. (a high temperature should be avoided as it promotes the formation of undesired Chlorates ClO3), from pH of the solution. The energy conversion efficiency depends on the concentration of the saline solution, on the gap between the electrodes, and from the geometry of the cell: all this parameters influence the conductivity of the solution and consequently the ohmic losses of the cell itself.
SUMMARY OF THE INVENTIONThe present invention is related to the production of Sodium Hypochlorite by means of electrolysis of a solution of Sodium Chloride in water.
This device has been conceived to fulfill the following specifications:
a) produce Sodium Hypochlorite in batch mode, delivering always the same quantity of equivalent chlorine. In other words the hypochlorite amount produced must be reproducible irrespective from the saline solution concentration or cell voltage,
b) have a current efficiency from 80 to 90%,
c) have an energy conversion efficiency as high as possible (in terms of Wh/g of equivalent Chlorine produced), of the order of 2.5 to 3.5 Wh/g.
d) operate in a sure and reliable way for a wide range of concentrations of the saline solution, from 1 to 5% by weight,
e) operate with renewable sources of energy,
f) be portable and lightweight
g) be low-cost.
h) be maintenance free,
i) last for many years (5-10)
Points b), c), and e) allow the use of this device powered by: solar PV modules, rechargeable batteries or manually operated electromechanical generators. All this can be obtained by means of a small electrolytic cell equipped with titanium DSA electrodes, powered by a power supply circuit that delivers a specified quantity of electricity (Amp*sec), this circuit being powered by a source of electromotive force (emf), in order to produce a specified quantity of sodium hypochlorite. For this reason this device is very useful when employed in isolated or remote sites, where electricity or chemicals are not available.
The apparatus is made essentially of three parts:
1—An electrolytic cell made of a plastic transparent cylindrical vessel that has means to measure a specific quantity of water. The vessel is provided with a lid provided with a small cavity which is used to measure the quantity of salt to be introduced into the cell.
The cell capacity ranges from 10 to 50 ml, depending on the quantity of the Sodium Hypochlorite to be produced. The amount of salt measured with the cavity on the lid is such as to form, together with the quantity of water measured in the cell, a solution of specified concentration, which can vary from 1 to 5% by weight. The cell is equipped with two or more titanium DSA electrodes, whose dimensions are related to the applied current and to the amount of Sodium Hypochlorite that has to be produced.
2—An electronic power supply management circuit.
3—An electromotive force (emf) source that could be of many types: disposable cells, rechargeable batteries, supercapacitors, solar photovoltaic modules, and electromechanical generators (alternators or dynamos) moved by hand or pedal power.
The power supply management circuits related to the four embodiments illustrated in
A circular line 10 is engraved on the inside wall of the cell to indicate the water level. The cell is closed with the lid 4 in which a cavity 5 is used to measure the quantity of salt necessary to prepare the solution. In the compartment 6 is placed the electronic power supply as described below. The diaphragm 7 separates the power supply compartment 6 from the battery compartment 8. In this example the unit is equipped with a couple of 1,5 Volts alkaline D cells (disposable). From manufactured prototypes the operating characteristics were the following: a saline concentration raging from 1.5 to 2.5% by weight, a cell current ranging from 300 to 500 mA, and the quantity of electricity delivered to the cell ranging from 4.5 to 7.5 Amp×sec. Under these conditions the cycle duration was about 15 seconds and the equivalent Chlorine produced ranged from 1.2 to 2.2 mg. The dimensions of the unit are approx. 250 mm length and 50 mm diameter.
It is obvious that the same embodiment can be made using rechargeable batteries (NiMH or NiCd). In this case the power management circuit will be provided with a battery charging circuit powered by an external extension to be plugged to the electricity grid. Another embodiment comprised in the one described above could be one with larger batteries and consequently larger electrolytic cell. All this in order to produce larger amounts of sodium hypochlorite.
The electronic power supply block diagram relative to the first embodiment (
The first is illustrated in
The second is of the same type as the one for the following embodiment (
A third embodiment is illustrated in
With a saline concentration of 1.65%, and a current of 2 Amp lasting one minute a quantity of equivalent chlorine of 40 mg has been obtained, at an efficiency near to 90%. The dimensions of this example are 26×16×12 cm.
The power supply employed for the above described embodiment, as already anticipated is illustrated in
A fourth example is shown in
With reference to
Claims
1. Portable apparatus for the production of Sodium Hypochlorite by means of the electrolysis of a dilute solution of Sodium Chloride in water, comprising a container in which is enclosed an electrolytic cell which is composed by a vessel equipped with at least two electrodes made of metal like titanium or titanium coated with noble metals like ruthenium, tantalum, lanthanum oxides, suited to contain a predetermined quantity of diluted sodium chloride solution, an autonomous source of electric energy and a circuit for connecting said source of electric energy to the electrodes of the aforesaid electrolytic cell.
2. Portable apparatus as claimed in claim 1 wherein said connecting circuit comprises means for interrupting the operation of said electrolytic cell after a time delay in relation to the current intensity and time supplied to the electrodes of said electrolytic cell, and to the concentration of the solution introduced into said electrolytic cell.
3. Portable apparatus as claimed in claim 1 and 2 wherein said connecting circuit comprises means for stabilizing the current and/or the voltage delivered by said autonomous source of electric energy to said electrodes of the electrolytic cell.
4. Portable apparatus as claimed in any one of the preceding claims wherein said means for interrupting the operation of the electrolytic cell comprises an integrator circuit of the current delivered, in relation to time, to said electrodes of the electrolytic cell, the output of said integrator being connected to a comparator circuit that compares the value of the current integral provided by said integrator circuit with a predetermined reference value, said comparator being connected to a switch in order to interrupt the current supplied to the electrolytic cell when said current integral has reached a predetermined value.
5. Portable apparatus as claimed in any one of the preceding claims comprising a circuit which interrupts the electric energy supply to said electrolytic cell in case of absence of Sodium Chloride solution in said electrolytic cell.
6. Portable apparatus as claimed in any one of the preceding claims wherein said circuit comprises a comparator circuit whose input is connected to the electrodes of said electrolytic cell, and whose output is connected to said switch.
7. Portable apparatus as claimed in any one of the preceding claims wherein said switch consists of a mechanical relay.
8. Portable apparatus as claimed in any one of the preceding claims wherein said switch consists of a solid state relay.
9. Portable apparatus as claimed in any one of the preceding claims wherein said electrical energy in the form of voltage or current delivered by the emf source is detected by a threshold circuit of the Schmitt trigger type.
10. Portable apparatus as claimed in any one of the preceding claims wherein said means for voltage stabilization includes a dc (direct current) voltage stabilizer.
11. Portable apparatus as claimed in any one of the preceding claims wherein said means for current stabilization includes a dc constant current stabilizer.
12. Portable apparatus as claimed in any one of the preceding claims wherein said means for voltage stabilization includes a converter from ac (alternate current) current to dc current.
13. Portable apparatus as claimed in any one of the preceding claims wherein said power supply circuit includes a pushbutton switch to turn on said portable apparatus, said pushbutton switch being connected in series with aforesaid switch.
14. Portable apparatus as claimed in any one of the preceding claims wherein said threshold circuit when it senses a preset value of the constant current delivered to said electrodes of the electrolytic cell, a pulse generator is activated and connected to a counter which is set to a specific preset count. When the counter stops a shut-off pulse is sent to the said constant current stabilizer shutting off the current to said electrodes of said electrolytic cell.
15. Portable apparatus as claimed in any one of the preceding claims wherein said pulse generator is connected between said constant current stabilizer and said counter.
16. Portable apparatus as claimed in any one of the preceding claims wherein said counter is set to a number of counts which determine the quantity of electric energy delivered to the electrodes of said electrolytic cell.
17. Portable apparatus as claimed in any one of the preceding claims wherein said electrolytic cell comprises a vessel suited to contain a predetermined quantity of Sodium Chloride diluted solution, said vessel being fitted with said electrodes and being closed with a removable cover.
18. Portable apparatus as claimed in any one of the preceding claims wherein said vessel is made of transparent material bearing a reference notch to indicate the level of the solution when poured into said electrolytic cell.
19. Portable apparatus as claimed in any one of the preceding claims wherein said cover has a cavity suitable for dosage of the Sodium Chloride to be introduced into said electrolytic cell in order to prepare the diluted Sodium Chloride solution.
20. Portable apparatus as claimed in any one of the preceding claims wherein said cover has a cylindrical form with an eccentric hole. Said cover is free to rotate in a cylindrical housing having on its bottom a hole of the same diameter of the hole in said rotating cover, the two holes being coincident for a specific position of said rotating cover.
21. Portable apparatus as claimed in any one of the preceding claims wherein said electrodes of the electrolytic cell have a rectangular shape, having a surface area comprised between 1 and 15 square centimeters and being placed parallel to each other with a gap comprised between 1 and 5 mm.
22. Portable apparatus as claimed in any one of the preceding claims wherein said anode and said cathode are made of Titanium coated with noble metal oxides like ruthenium, tantalum, titanium, lanthanum, etc., said coating being proprietary.
23. Portable apparatus as claimed in any one of the preceding claims wherein said connecting circuit is fitted into a sealed compartment (hereinafter called first compartment) separated from said electrolytic cell and from another compartment (hereinafter called second compartment) containing said autonomous electric energy source.
24. Portable apparatus as claimed in any one of the preceding claims wherein said part of said container, called first compartment, is permanently connected to the part of said container, called second compartment, being provided means for an electrical connection between said connecting circuit, fitted in the first compartment, and said electric energy source fitted in said second compartment.
25. Portable apparatus as claimed in any one of the preceding claims wherein said connecting circuit is provided with a cable for the connection to an external source of electric energy.
26. Portable apparatus as claimed in any one of the preceding claims wherein said autonomous electric energy source comprises at least one electric cell (disposable type).
27. Portable apparatus as claimed in any one of the preceding claims wherein said autonomous electric energy source comprises at least one rechargeable battery.
28. Portable apparatus as claimed in any one of the preceding claims wherein said autonomous electric energy source comprises at least one supercapacitor.
29. Portable apparatus as claimed in any one of the preceding claims wherein said autonomous electric energy source comprises an alternator or dynamo.
30. Portable apparatus as claimed in any one of the preceding claims comprising means for hand driving of said alternator or dynamo.
31. Portable apparatus as claimed in any one of the preceding claims wherein said autonomous electric energy source comprises a photovoltaic module (PVM).
32. Portable apparatus for the production of Sodium Hypochlorite by means of the electrolysis of a diluted solution of Sodium Chloride comprising any one of the characteristics as herein described with reference to and as shown in the accompanying drawings.
Type: Application
Filed: Mar 1, 2007
Publication Date: Sep 4, 2008
Inventor: Giovanni Del Signore (Firenze)
Application Number: 11/680,632
International Classification: C25D 17/00 (20060101); C25D 21/12 (20060101);