How is Ozone Produced?
OZONE GENERATION TECHNIQUES
Ozone cannot be stored and transported like other industrial gases because it quickly decays into oxygen and must therefore be produced on-site.
In the atmosphere, ozone is generated when UV light splits oxygen molecules into single oxygen atoms (radicals). When ozone is generated industrially it is produced either with cold plasma (also called dielectric barrier discharge method), corona discharge or UV-light.
Cold plasma (dielectric barrier discharge)
Cold plasma is defined as a gas that is partially ionized (a few per cent) and is created at room temperature or lower. The ionization of the gas, in this case, pure oxygen takes place between two electrodes which are separated by an insulating barrier (dielectric barrier). When the plasma is formed oxygen molecules are split into single oxygen atoms which then recombine with O2 and forms ozone (O3).
Cold plasma ozone generators utilize oxygen as the input source and are used to produce ozone with a concentration of about 5-7%. Recently developed technology enhancements make it possible to produce ozone with a concentration of up to 20% or more from on-site-produced oxygen.
Corona discharge method
The production of ozone with the corona discharge method is very common for industrial applications. It produces ozone by channelling air into a corona discharge tube, in which plasma is created by applying a strong electrical field. The plasma created disassociates single oxygen atoms which then are free to recombine with oxygen molecules and thus create ozone. The difference between the cold plasma ozone generation and the corona discharge ozone generation method lies in the means used to create the plasma and the feed gas used. Corona discharge generators also create nitrogen oxides (NOx) which will if water is present react and produce corrosive nitric acid (HNO3).
The difference between available ozone generators lies in the arrangement and design of the high-voltage electrodes. The gas temperature is an important factor when it comes to ozone generation efficiency. The gas temperature is often controlled by cooling water and the cooler the water the better will the ozone synthesis work. Ozone reactors can only be built with a few materials due to the high reactivity of the ozone. Materials like stainless steel, aluminium, glass, polytetrafluorethylene, or polyvinylidene fluoride may be used. Viton may also be used but only for a limited time and with the restriction of constant mechanical forces and the absence of humidity.