Chemistry of inorganic compounds – Oxygen or compound thereof – Superoxide or ozone
Reexamination Certificate
1999-07-14
2001-12-25
Langel, Wayne (Department: 1754)
Chemistry of inorganic compounds
Oxygen or compound thereof
Superoxide or ozone
C423S579000
Reexamination Certificate
active
06333017
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for producing ozone. One particular aspect of the invention relates to a method for producing ozone utilizing supersonic expansion of monoatomic oxygen.
BACKGROUND TO THE INVENTION
Ozone is a very powerful oxidant, and has many commercial applications. One application of ozone is in the purification of drinking water. Ozone may be used to purify drinking water either on a small scale or on a large scale. For example, existing municipal water treatment facilities have been upgraded to use ozone to purify drinking water. One of the benefits of using ozone as a water purifier is that at standard water treatment conditions it decomposes into molecular oxygen very quickly, leaving little residual contaminants.
Ozone is typically produced by the reaction between molecular oxygen and monoatomic oxygen. The equilibrium of the chemical reaction may be represented by equation I:
O
2
+O<= = = = = = = = =>O
3
(I)
One significant problem encountered in the commercial production of ozone is that the required monoatomic oxygen exists only at temperatures above about 2300° K. However, ozone is stable only at lower temperatures, eg. below about 1000° K. At temperatures above about 1000° K, ozone dissociates to form molecular oxygen and monoatomic oxygen. At temperatures below 2300° K, monoatomic oxygen recombines to form molecular oxygen. This is problematic since temperatures above 2300° K are necessary to form the monoatomic oxygen required to produce ozone, yet the ozone itself is almost immediately destroyed at temperatures above 1000° K.
In an effort to overcome this significant problem, attempts have been made to commercially produce ozone at low temperatures (below about 500° K) in order to increase its useful life. While attempts to date have been moderately successful, they have significant drawbacks, in that the total volume of ozone capable of being produced is small.
A typical method for the commercial production of ozone uses high voltage corona discharges. These discharges produce energized electrons which are supplied to a source of molecular oxygen, causing the molecular oxygen to dissociate into monoatomic oxygen. Some of the monoatomic oxygen then reacts with molecular oxygen, via a three-body interaction, to form ozone. Because the gas source of molecular oxygen is maintained at a low temperature (below 500° K), a significant portion of the ozone produced survives to its point of use. However, overall this method is inefficient because only a small amount of molecular oxygen is converted into monoatomic oxygen by the excited electrons. That is, a very large number of electrons (and a correspondingly large amount of energy to produce the electrons) is required to produce a very small amount of monoatomic oxygen. This is the rate limiting step in the production of ozone by this method. These types of systems are only capable of producing a small net amount of ozone.
Alternately, ozone may be produced with ultraviolet radiation. In this method, ultraviolet light photons are bombarded at molecular oxygen, causing molecular oxygen to dissociate into monoatomic oxygen. The monoatomic oxygen then reacts with molecular oxygen via the three bodied interaction to form ozone. This reaction proceeds by the Chapman mechanism, which is essentially how ozone is created in the upper atmosphere of the earth. As with the high voltage method of creating ozone, ozone production with ultraviolet light is limited since the vast majority of ultraviolet radiation passes through oxygen without causing the molecular oxygen to dissociate. That is, the limiting step in the formation of ozone is the formation of monoatomic oxygen.
In each of these systems, it is only possible to obtain a significant production of ozone by operating a large number of systems in parallel. This results in large acquisition and operating costs. Therefore, there remains a need to develop a method of producing significant quantities of ozone on a cost effective, commercial scale basis, and which has a useful life before deterioration.
SUMMARY OF THE INVENTION
The present invention provides a method for producing ozone utilizing conditions which favour both the formation of monoatomic oxygen and the formation of ozone from the monoatomic oxygen. The monoatomic oxygen is transported to the ozone production stage in a frozen flow state so as to deliver monoatomic oxygen in substantial quantities to the ozone production stage. By operating different steps of the process at conditions which favour these reactions, an energy efficient method of producing ozone is provided. Thus, an ozone flow rate of up to 0.5 kg/s may be achieved.
In one aspect of the present invention, there is provided a method of producing ozone comprising providing a supply of monoatomic oxygen at a first temperature and pressure at which the equilibrium between monoatomic oxygen and molecular oxygen lies in favour of production of monoatomic oxygen, supersonically expanding and cooling the monoatomic oxygen to a second temperature lower than the first temperature (eg. below about 1000° K) to obtain supersonically cooled and expanded monoatomic oxygen, and combining the supersonically cooled and expanded monoatomic oxygen to form ozone.
In one embodiment, the step of producing monoatomic comprises subjecting a gas containing molecular oxygen to conditions which shift the equilibrium to the right side of the equation:
O
2
<= = = = = =>2O
to favour the production of monoatomic oxygen over the production of molecular oxygen. The monoatomic oxygen may be formed by heating a gas (eg. to a temperature above about 2300° K) containing molecular oxygen to favour the production of monoatomic oxygen.
In another embodiment, the step of expanding and cooling the monoatomic oxygen comprises passing the monoatomic oxygen through a convergent-divergent nozzle.
In another embodiment, the step of combining the supersonically cooled and expanded monoatomic oxygen to form ozone is conducted under conditions which shifts the equilibrium to favour the production of ozone.
In another embodiment, the supersonically cooled and expanded monoatomic oxygen is subjected to an elevated pressure to assist in the formation of ozone.
In another embodiment, the method further comprises the step of introducing molecular oxygen to the supersonically cooled and expanded monoatomic oxygen to form ozone. The molecular and monoatomic oxygen may be mixed under conditions which shift the equilibrium to the right hand side of the equation:
O+O
2
<= = = = = =>O
3
to favour production of ozone (eg. at a temperature below about 1000° K and/or under pressure).
In another aspect of the present invention, there is provided a method of producing ozone comprising providing a supply of monoatomic oxygen at conditions at which the equilibrium between monoatomic oxygen and molecular oxygen lies in favour of the production of monoatomic oxygen, transporting the monoatomic oxygen as a flow stream under frozen flow state conditions from a first location to a second location, and combining the monoatomic oxygen to form ozone.
In one embodiment, the monoatomic oxygen is combined at conditions at which the equilibrium between monoatomic oxygen and ozone lies in favour of the production of ozone.
In another embodiment, molecular oxygen is introduced to the monoatomic oxygen to form ozone. The monoatomic oxygen and the molecular oxygen may be combined at conditions at which the equilibrium between monoatomic oxygen, molecular oxygen and ozone lies in favour of the production of ozone. The molecular oxygen may be introduced to the monoatomic oxygen while the monoatomic oxygen is in the frozen flow state and the flow stream is then subjected to conditions at which the equilibrium between monoatomic oxygen, molecular oxygen and ozone lies in favour of the production of ozone.
Conrad Wayne Ernest
Szylowiec Ted
Hale and Dorr LLP
Langel Wayne
Omachron Technologies, Inc.
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