How does a corona discharge ozonator work

It reacts, then quickly disappears. We know it as the ozone layer. Ozone exists when oxygen O 2 is exposed to ultraviolet light, or exposed to high voltages of lightning.

That fresh, clean smell that we notice after a rain storm, is ozone. It provides a natural, clean disinfectant that can also be used in a controlled environment used in water and air treatment applications. As the oxygen molecules O 2 are exposed to these energy fields, they dissociate and split, forming atoms O 1.

These wandering oxygen atoms then recombine with other O 2 molecules in the air stream, forming ozone O 3. Ozone is nothing more than another molecular form of oxygen. Because ozone is highly reactive, it readily oxidizes breaks down organic matter. When ozone encounters another compound, one oxygen atom will break away, attach itself to the compound, and oxidize clean or purify it. Good ozone protects us from harmful UV radiation from the sun.

Another form of ozone we are familiar with is a component of air pollution found in the lower atmosphere. We call that bad ozone. Bad ozone is formed when carbon dioxide given off by cars and industrial fumes reacts with sunlight UV at ground level. About 95 percent of these chemicals come from human activity from the burning of coal, gasoline, and oil in motor vehicles, homes, industries, and power plants.

The result is smog, the air pollution we see. When smog levels are discussed, ozone is targeted because it is relative to smog conditions and is much easier to measure than other components that smog form. Ozone is actually there to help eliminate smog. Ozone is an oxidizer and disinfectant commercially available for water and air treatment. Ozone systems require only cold water, reduces the need for chemicals, and are made on-site, on-demand.

It is a more innovative alternative to salt, chlorine, and other chemicals. It can oxidize and reduce microorganisms such as bacteria, fungus, and viruses in water faster than chlorine and faster than bromine. Ozone reduces odor and color. It can also be used for the flocculation of organic material, which simplifies mechanical filtration. It is generated at the point of use and then reverts back to oxygen.

When used correctly, ozone is very effective for many applications, especially at high concentrations.

To break down the remaining ozone after use, ozone destructors are applied. The mechanism of an ozone destructor can be based on different principles. Usually a catalyst is applied, which accelerates the decomposition of ozone into oxygen e.

Important factors that influence ozone generation are: oxygen concentration inlet gas, humidity and purity of inlet gas, cooling water temperature and electrical parameters.

To minimize the energy that is used at a high ozone yield, it is important that these factors are optimal. Cooling water temperature The generation of ozone is accompanied by heat formation. This makes it important to cool the generator. An ozone reaction is reversible and this increases when temperatures rise.

Figure 2 illustrates the relation between cooling water temperature and the yield of ozone generation. This figure shows that an increasing cooling water temperature results in a decreasing ozone production [1,5].

It is important that the temperature of the inlet air is not too high. Humidity inlet air Before the feed gas enters the ozone generator, air dryers should dry the air. Ambient air contains moisture, which reacts with ozone. This leads to a reduction of the ozone yield per kWh.

An additional problem of high humidity is that undesired reactions occur in the corona unit. When increased amounts of water vapor are present, larger quantities of nitrogen oxides are formed when sparks discharge occurs. Nitrogen oxide can form nitric acid, which can cause corrosion. Furthermore, hydroxy-radicals are formed that combine with oxygen radicals and with ozone. Al these reactions reduce the capacity of the ozone generator [3,5]. Figure 3 shows the influence of the humidity on the capacity of an ozone generator.

The two descending lines illustrate the capacity of the generator: 'oxygen' for an oxygen-fed generator and 'air' for an air-fed generator. To prevent these side-reactions, inlet air first passes a drying chamber before ozone is generated. For drying, an aluminum compound can be used, comparable with silica gel. In an ozone generator two or more drying chambers are used alternately.

When a drying chamber is used for a certain period of time, humid air is led to the other drying chamber, while the first is regenerated. Purity of gas inlet The presence of organic impurities in gas feed must be avoided, including impurities arising from engine exhausts, leakages in cooling groups, or leakages in electrode cooling systems.

The gas supply of the generator must be very clean. An example is given in figure 4, where the concentration of hydrocarbons is related to the ozone yield. Pure oxygen can be generated from ambient air by an oxygen generator. The ozone concentration an ozone generator delivers is dependant on the oxygen concentration among other things. This is clarified by figure 7, where the oxygen concentration is outlines against the ozone concentration.

The diverse lines demonstrate the ozone generators with different energy use. Summarising, one can claim that the ozone production increases by a factor 1,7 to 2,5 when pure oxygen is used, at constant electrical power [3,5]. Figure 7: influence of oxygen concentration on ozone production at different electrical current.