Saturday, July 2, 2011

Introduction to Ozone Generation Techniques - Corona, UV and Electrochemistry

, Siemens has developed the first ozone generator, which was based on corona discharge in 1957. Today, ozone is produced several different methods and commercially in the laboratory.

ozone generation involves the creation of high atomic oxygen radicals which can react with molecular oxygen. All processes that can separate the molecular oxygen into oxygen radicals have the potential for ozone generation. Energy sources that make this action possible electron or photon energy. Electrons can be used from high voltage sources Corona discharge from nuclear sources, and the electrolysis process. Suitable photon quantum energy comprises ultraviolet rays of wavelengths less than 200 nm, and γ-rays.

In nature, ozone generation occurs when molecular oxygen reacts in the presence of an electric discharge, eg, lightning activity and high energy electromagnetic radiation. Some electrical appliances inadvertently creates ozone levels that can be easily smelled;. This is especially true if there is a spark or a very high voltage

Corona Discharge ozone generation

Corona discharge in the dry process gas containing oxygen is the most widely used method of ozone generation process vode.Corona or plasma is created in an ozone generator using a high voltage between two electrodes Ozone is formed by the following reaction:.

1 / 2 O2 = The heat of reaction = 59.1 kcal

B = O + O2 O3, heat of reaction B = -24.6 kcal

AB 3 / 2 O2 = O3 reaction heat AB = 34.5 kcal

The overall reaction (AB), which produces ozone requires energy and endothermic reaction that generates energy from the electric discharge ozone generation of the basic system consists of the following:. Gas source (compressed air or oxygen), gas dryers, and ozone generators.

It is of utmost importance that the process of dry gas is applied to corona discharge. Limiting the nitric acid formation is also important to protect the generator and increase the efficiency of the process generation. In normal operation of properly designed system, most 3-5 g of nitric acid gets produced per kilogram of ozone with air. If increased amounts of water vapor present, large amounts of nitrogen oxides are formed when the spark discharges occur. Also, hydroxyl radicals are formed which combine with oxygen radicals and ozone. Both reactions reduce the efficiency of ozone generation. Consequently, the dry process gas is important in order to obtain a good yield of ozone. Moreover, with air, nitrogen oxides can form nitric acid, which can cause corrosion.

the formation of ozone through electrical discharge in the process gas is based on corona discharge in air. The ozone generator here are numerous and distributed micro-electrical discharge (arc or plasma), which generate ozone efficiently. It seems that each individual micro-discharge takes only a few nanosekundi.Gustoća current varies between 100 and 1000 Amps/cm2. Using oxygen or oxygen-enriched air process, the production capacity of certain ozone generator can be increased by a factor ranging from 1.7 to 2.5 compared to air alone. Whether by air or oxygen, food energy is lost as heat, cooling, process gas is very important. In smaller systems, it is often down through the air to cool one or both electrodes. In larger systems, cooling is usually done with water, usually on the ground electrode.

Other methods of ozone generation are as follows:

photochemical ozone generation

the formation of ozone from oxygen exposed to UV light at 140-190 nm was first reported by Lenard in 1900 and fully assessed Goldstein 1903rd He soon recognized that the active wavelengths for the technical generation below 200 nm. Given the current technology with mercury-based UV-emission lamps, 254-nm wavelength is transmitted along with the 185-nm wavelength, so that destruction of ozone occurs simultaneously with the generation. Moreover, the relative emission intensity of 5 to 10 times more at 254 nm compared with 185-nm wavelength. Thus only a small amount of ozone can be produced.

Attempts to reach an appropriate photo steady state ozone with mercury lamps are uspjeli.Glavni reason for this is that the failure Thermal decomposition is a side effect of ozone. Apart from minor uses or synergistic effect, UV-photochemical generation of ozone has not found wide application.

Electrolytic Ozone Generation

Electrolytic generation of ozone has historical importance as a synthetic ozone was first discovered by Schonbein in 1840 by electrolysis of sulfuric kiseline.Jednostavnost equipment can make this process attractive to small users and users in remote areas.

Many potential advantages are associated with electrolytic generation, including the use of low voltage DC current, without the preparation of food supply, reduced size of equipment, you can create ozone at high concentrations, and generation in the water, removing water-ozone contacting process. Problems and disadvantages of the method include: corrosion and erosion of the electrodes, thermal overload due to the anode over-voltage and high current density, the need for a separate electrolyte or water with low conductivity, and on-site generation process, incrustations and deposits are formed on the electrode, and production free chlorine in conjunction with the process when chloride ions are present in water or electrolyte used.

radiochemical Ozone generation

high-energy radiation, oxygen radioactive rays may promote the formation of ozone. Even with the favorable thermodynamic process yields and interesting use of waste fission isotopes, cheminuclear ozone generation process is not yet postalaznačajan use in water or wastewater treatment plant due to its complicated application process.


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