Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – With means applying electromagnetic wave energy or...
Reexamination Certificate
1999-05-21
2001-11-27
Gorgos, Kathryn (Department: 1741)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
With means applying electromagnetic wave energy or...
C422S186180
Reexamination Certificate
active
06322759
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns an ozonizer having a first electrode and a second electrode between which a discharge gap is formed, a dielectric being arranged between the first electrode and the second electrode.
The invention moreover concerns a method for the manufacture of an ozonizer.
An ozonizer of this kind is known from DE 195 11 001 A1.
The known ozonizer comprises a, for example, tubular support element made of glass, on the outer side of which a first metallic electrode is applied by thermal spraying. Applied in turn onto this metallic electrode, by thermal spraying, is a dielectric film which can be made, for example, of aluminum oxide, titanium oxide, or hafnium oxide. A discharge gap for ozone generation is provided between the dielectric film and a concentrically arranged outer electrode.
What is used as the dielectric in the known ozonizer is not the glass tube, but only the sprayed-on ceramic film. The glass tube thus serves only as a support element.
A relatively high ozone yield is achieved with this arrangement, since the dielectric is configured only as a relatively thin film and it is known that ozone yield, to a first approximation, is proportional to the dielectric constant and inversely proportional to the thickness of the dielectric. The ozone yield is, at the same time, further increased by the fact that what is used as the dielectric, instead of glass, is aluminum oxide, titanium oxide, hafnium oxide, or a mixture thereof, which results in a higher dielectric constant.
The known ozonizer nevertheless suffers from certain disadvantages. For example, in order for the thermally sprayed dielectric film to have sufficient dielectric strength, it must have a film thickness on the order of approximately 1 mm. Application of a film of this kind by thermal spraying is relatively complex and expensive. In addition, newer ozonizers are usually no longer operated from the standpoint of maximum ozone yield (i.e. mass fraction of ozone generated as a function of electrical energy used), but rather an effort is made to achieve the greatest possible ozone concentration in the oxygen mass flow used as the basis. An effort is thus made, possibly with greater use of electrical energy, to minimize oxygen consumption while generating a predefined quantity of ozone. A high oxygen concentration can only be achieved, however, with higher operating voltages. In the ozonizer known from DE 195 11 001 A1, however, the dielectric strength is relatively limited, since the thermally sprayed dielectric film has a relatively high porosity and is naturally, for cost reasons and for reasons of improved ozone yield, coated only with a film thickness on the order of 1 mm.
As compared to conventional glass ozonizers in which the glass tube is equipped with an inner electrode and the glass tube itself serves as a dielectric, what is achieved according to DE 195 11 001 A1 is thus a higher ozone yield but a lower ozone concentration than with conventional glass ozonizers.
It is thus the object of the invention to create an improved ozonizer which allows the greatest possible ozone concentration to be achieved, simultaneously with a relatively good ozone yield.
SUMMARY OF THE INVENTION
This object is achieved according to the present invention, in an ozonizer of the kind cited initially, in that the dielectric comprises a support element made of glass or glass ceramic onto which a ceramic dielectric film is applied.
The object of the invention is completely achieved in this fashion.
Surprisingly, it has been found that thermal spraying of a thin ceramic film as an additional dielectric film onto the support element made of glass or glass ceramic already results in improved ozone yield. At the same time, the ozonizer according to the present invention makes it possible to achieve both a higher ozone yield as compared to conventional glass ozonizers in which the glass tube serves as a dielectric and which are equipped with an inner electrode, and an improved ozone concentration as compared to ozonizers in which the glass tube serves exclusively as a. support element onto which first the electrode and then a dielectric film is applied.
The ozonizer according to the present invention makes possible improved discharge characteristics as compared to conventional ozonizers. A particularly homogeneous discharge profile is achieved, which is advantageous in terms of achieving a high ozone concentration in the carrier gas simultaneously with a high yield.
It is believed that a certain understoichiometric structure, such as TiO
2−x
or certain contaminations, both achieved by the thermal spraying process, is necessary to achieve a higher surface conductibility of the dielectric film. This leads to an improved discharge behavior of the micro-filaments of the dielectric barrier and thus to a considerably improved ozone yield.
At the same time the ozonizer can be operated at higher voltages, since the dielectric strength is ensured by the support element made of glass or glass ceramic. It is thus possible, with the ozonizer according to the present invention, to attain considerably elevated ozone concentrations in the carrier gas.
In a preferred development of the invention, the first electrode is provided on a first side, facing away from the second electrode, of the support element.
To the extent that the ozonizer is configured as a tube ozonizer, the first electrode is thus provided on the inner side of the support element, while the second electrode is provided on the inner side of a second tube which concentrically surrounds the support element.
According to a further embodiment of the invention, the ceramic film is provided on a second side, facing toward the second electrode, of the support element.
The arrangement of the first electrode on the first side of the support element, and of the ceramic film on the second side, faces toward the second electrode, of the support element, allows easy manufacture by thermal spraying.
In this context, the first electrode can be produced by thermal spraying using an laterally bent lancet that is introduced axially into the glass tube. The ceramic film can then in turn be produced on the outer side of the support element, preferably by plasma spraying.
Since the dielectric strength of the ozonizer is provided by the inherently gas-tight support element made of glass or glass ceramic, which can be manufactured with high precision, the ceramic dielectric film applied on the support element as an additional dielectric film can be configured with a relatively thin film thickness of approximately 10 to 100 &mgr;m, preferably approximately 20 to 70 &mgr;m, in particular approximately 30 to 50 &mgr;m.
A thin dielectric film of this kind can be generated relatively cost-effectively by thermal spraying. At the same time, surprisingly, despite the fact that the additional dielectric film is so thin, an improved ozone yield is achieved as compared to conventional ozonizers in which only a glass tube is used as dielectric and which are equipped with an inner electrode.
According to a further preferred embodiment of the invention, the ceramic film contains at least aluminum oxide, titanium oxide, or zirconium oxide.
In an additional development of this embodiment, the ceramic film contains a mixture of titanium oxide and aluminum oxide which has up to approximately 10 wt % titanium oxide. It has been found in this connection that a concentration of 5 to 10 wt %, preferably on the order of approximately 7 wt % titanium oxide, is particularly advantageous. At higher titanium oxide levels, a large proportion of the titanium oxide is no longer dissolved in the aluminum oxide lattice, which causes the ceramic layer to become conductive so that the necessary dielectric strength can no longer be attained.
According to a further embodiment of the invention, the ceramic film contains zirconium oxide that is stabilized with yttrium oxide, magnesium oxide, or calcium oxide.
It has been found in this context that stabilization in particular with magnesium ox
Friedrich Christian
Gadow Rainer
Gunther Siegfried
Killinger Andreas
Riege Gunter
Gorgos Kathryn
Nicolas Wesley A.
Oppenheimer Wolff & Donnelly LLP
Schott-Gerate GmbH
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