Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – With means applying electromagnetic wave energy or...
Reexamination Certificate
2001-09-05
2004-04-27
Mayekar, Kishor (Department: 1753)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
With means applying electromagnetic wave energy or...
Reexamination Certificate
active
06726885
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ozone generator and a method for generating ozone by exposing oxygen to a high frequency alternating current with high voltage over a dielectric.
BACKGROUND OF THE INVENTION
Ozone has strongly oxidizing features and is used, preferably diluted, to sterilize water. For example may wastewater be treated for purpose of breaking down or eliminating substances dangerous for the environment or the health as well as unpleasant smells from the water, and the drinking water may be pre-treated for purpose of improving the water quality. Other fields of application are e.g. as bleaching agent in the paper industry, for air purification purposes, and to perform certain oxidizing reaction in organic chemistry.
Ozone mixed with oxygen is produced by passing oxygen gas or gas rich in oxygen through an electric discharge. Oxygen gas or gas rich in oxygen is thereby made to flow through a chamber in an ozone generator or ozonizer, which chamber either is delimited by two tubes having the same axis or by plates in series, between which an electric discharge occurs. In this description the expressions space and chamber are used as representing the same, i.e. the place in the ozone generator where existing oxygen gas or gas rich in oxygen is converted to ozone.
The first mentioned type of ozone generator is for industrial purpose very large and space demanding and also difficult and expensive to produce and maintain. The second type of ozone generator is more economic and less space demanding, but has still certain sealing and strength problems and does not operate optimally.
A problem related to ozone generators is connected to that the chamber in which the oxygen in the form of oxygen gas or gas rich in oxygen is converted to ozone at least has one delimiting surface constituted of a dielectric material, a dielectric. This dielectric is utilized for the purpose of generating a corona at the discharge between a high voltage electrode and earth, and is generally composed of a ceramic or a glass material. High gas pressures and not the least pressure variations in the gas supplied to the chamber, for example caused by pressure shocks in the system when the gas supply is engaged or disengaged, generates high stresses on the ceramic with the consequence of the ceramic risking to crack.
Another problem is related to the sealing required between said dielectric and the opposite delimiting surface of the chamber, which opposite surface generally constitutes electric earth. This sealing is exposed to the influence of high gas pressure and pressure shocks. In addition the sealing is a problem for the useful life and the reliability of the ozone generator since ozone is particularly reactive, whereby common rubber gaskets tend to break down and cause leakage.
Concrete exemplary embodiments of ozone generators have been described in a manifold of publications, i.a. in the following:
In U.S. Pat. No. 5,354,541 A1 is thus a tubular ozone generator described comprising i.a. a helical spring electrode
12
, a tube
14
of dielectric material surrounding the electrode
12
and also a tubular, earthed and cooled second electrode
15
. Between the second electrode
15
and the tube
14
is an annular chamber
16
for ozone generation delimited. Supply of oxygen to the only annular chamber
16
for ozone generation occurs one-sided, whereby in the beginning also the pressure influence is one-sided. During operation a pressure influence is continuously present from the outside against the tube
14
, and this pressure influence varies instantaneously by pressure shocks, which may occur during the operation. Altogether this causes major stresses on the construction and major risk for damages and leakage.
In U.S. Pat. No. 4,960,570 A1 a complex and material demanding ozone generator is described with i.a. tubes
3
,
8
of a dielectric material, alternatively tubes having an outer coating of dielectric material. The tubes
3
,
8
have internally a metallic film
4
constituting one electrode, alternatively show a separate electrode
10
inside the tubes
3
. The tubes
3
are located between two flat external electrodes
1
,
2
, which are cooled. Spaces or chambers
6
and
11
, respectively, for ozone generation are found between the tubes
3
and the plate electrodes
1
,
2
, and possibly also in the tubes
3
between the inside of the tubes and the electrode
10
therein. It is not evident from the publication how the spaces
6
, between the details
3
,
8
of dielectric material and the cooled electrodes
1
,
2
, are supplied with oxygen for ozone generation, and consequently nor how these details are affected by the pressure from the supplied oxygen or by pressure shocks arising during operation.
Through WO, A1 9701507 an ozone generator is known, which comprises two plates
2
of a dielectric material, and between them is a thread or net shaped electrode
3
located, over which electrode
3
is a high frequency alternating current with high voltage is applied and, on the outside of the plates
2
, earthed and cooled electrodes
4
. A space for ozone generation is delimited between the plates
2
and a frame
3
′. The ozone generator is, from the inside of the space for ozone generation, exposed to pressure influence, whereby the plates
2
tend to separate. Instantaneously, at pressure shocks, this pressure influence may increase. Major risks for damages and sealing problems for the ozone generator exists. There are no spaces for ozone generation outside the plates
2
.
In U.S. Pat. No. 5,435,978 A1 is finally also a flat ozone generator with two electrodes
1
described, which intermediately form a space
2
for ozone generation. On the respective electrode
1
a layer of dielectric material is applied. In order to compensate the pressure in the internal space
2
for ozone generation, an external pressure is applied on the ozone generator by locating it in a pressure vessel, in which a gas under pressure is supplied. Instantaneous pressure differences due to pressure shocks, which occur during operation of the ozone generator, are however hard to handle. The risk for damages is large at these occasions. Yet another ozone generator design is shown in “High Density Ozone Generation In a Very Narrow Gap By Silent Discharge” by M. Kuzumoto, Y. Tabata and S. Yagi, Mitsubishi Electric Corporation, from the 12
th
World Ozone Congress, May 15-18, 1995, Lille, France, Vol. 2, pages 51-58. The proposed design discloses a thin circular one-sided discharge chamber between a ceramic plate and an earth electrode. Gas inlets to the chamber are arranged in the periphery of the chamber, while an outlet is arranged in the center of the chamber through a hole in the earth electrode. The ceramic plate rests, on the opposite side of the chamber, against a stress buffering plate of unknown kind, which in its turn is adjacent to a metal plate. Towards the stress buffering plate the ceramic plate is coated with a metal layer, which forms a high voltage electrode. The depth of the chamber is defined by a metal spacer located therein and comprises radially extending support element.
PURPOSE WITH THE INVENTION
A purpose with the present invention is to provide an ozone generator and a method for ozone generation, which overcomes the problems with the prior art. An aspect of this purpose is to use a simple, compact and less costly design to increase the power and improve the conversion efficiency compared to known ozone generators, and moreover to prevent components of the apparatus to be damaged or to deteriorate in efficiency due to the overpressure of supplied gas and due to pressure shocks arising during the operation of the apparatus.
A further aspect of this purpose is to provide a design, which gives a uniform pressure distribution over the delimiting surfaces of the gas chamber.
Another aspect of this purpose is to provide a design that is adapted to protect a sealing, arranged between a dielectric and an opposite delimiting surface, from wear as a consequence of t
Boyle Fredrickson Newholm Stein & Gratz S.C.
Mayekar Kishor
Ozonator Limited
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