Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1992-10-01
1995-08-08
Niebling, John
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204269, 204272, 204275, 204290R, 204290F, C02F 1461
Patent
active
054395763
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an apparatus for the sterilization of water by means of anodic oxidation comprising a reactor through which water flows and which has at least one anode and one cathode and also a power supply means.
Apparatus of this kind is for example known from DE-OS 2757 854. There the anodes and cathodes are formed by bars which are arranged in a grid-like manner and extend transversely through the reactor. The bars of the anode and of the cathode are respectively electrically combined with one another by a connection element which is connected in each case to the power supply. Between the bar grid of the anode and the bar grid of the cathode there are arranged a plurality of subsidiary electrode bar grids which extend parallel to the bars of the anode and the bars of the cathode. In this arrangement bar grid planes which lie behind one another in the flow direction are displaced in such a way that one bar of a subsequent bar grid plane is laterally displaced approximately into the centre of the spacing between two bars of a preceding bar grid plane.
This arrangement of electrodes or subsidiary electrodes is intended to ensure that the liquid passes through a region of changing potentials with turbulence.
A reactor is known from DE-PS 28 61 889 in which the electrodes are formed as bar or grid-like individual elements and through which water flows in cross-flow. In this manner, a turbulent flow is obtained in the reactor to improve of the convective material exchange at the electrode-phase boundary.
These known devices bring about considerable generation of electrolysis gases in addition to sterilization and these electrolysis gases adhere to the electrode surfaces and are intended to be carried away by the eddying of the flow.
SUMMARY OF THE INVENTION
It is the object of the present invention to devise an apparatus of the initially named kind in such a way that a reliable sterilizing effect is obtained with a longer life time of the electrodes and with a simultaneous reduction in the formation of undesired gas bubbles and side reactions in the reactor.
This object is satisfied in the apparatus of the invention, in that a gap of constant gap width is provided between the mutually confronting surfaces of the anode and cathode. The gap width is dimensioned such that a pronounced and preferably laminar flow forms between the mutually confronting surfaces of the anode and cathode in the water flowing through the gap. The and in that the anode consists of a material which has an anode overpotential greater with respect to the generation of oxygen than with respect to the generation of chlorine from chloride ions.
The constant gap width over the surface of the electrodes which lie opposite to one another thereby ensures the laminar flow and thus the formation of an essentially homogenous electrical field between the electrodes.
As a result of the laminar flow between the mutually confronting surfaces of the anode and cathode, it is ensured that even with only low concentrations of dissolved chloride ions in the water, the chloride ions are transported by means of electrostatic migration in the homogenous potential field uniformly to the anode boundary layer without being hindered in their migratory movement by turbulent flow vectors. At the same time it is ensured, through the choice of the anode material in accordance with the invention, that the undesired generation of molecular oxygen (and thus the undesired gas bubble formation on the electrode surfaces) is reduced with respect to the generation of chloroxy acids, their salts and other oxidants which can be determined as chlorine equivalents (such as for example all oxidants which can be detected with DPD (Diethyl-p-phenylidene diamine, predominantly HOCl and OCl).
The core of the anode consists of a valve metal, such as for example titanium, niobium or tantalum ensuring that it forms a protective stable oxide layer in the electrolyte. Thus no corrosion of the anode core arises in regions in which the coating of
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patent: 4997540 (1991-03-01), Howlett
patent: 5062940 (1991-11-01), Davies
patent: 5094734 (1992-03-01), Torrado
patent: 5108563 (1992-04-01), Cook
Niebling John
Phasge Arun
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