If you are exploring ozone generator options, you may spoken to manufacturers of ozone generators and inquired how much ozone their generators produce. One respondent might have said parts per million (ppm), another might have said grams per hour (gph), another could have said percent, and still another could have said grams per meter cubed. So there are different units to determine ozone generator performance.
Despite your best efforts, you may have ended up more confused than before. I believe that consistent answers from all parties would be extremely valuable for evaluating the type and size of ozone generator to be installed.
For a better understanding of why such standards are necessary, let me illustrate some of the many factors affecting a generator’s performance, as well as factors affecting the application’s performance.
Performance Parameters of Ozone Generator
First, let’s look at the performance parameters of the generator. In practice, ozone is produced by passing oxygen-containing gas through an electrical device (corona discharge) or by exposure to an ultraviolet light source. As an oxygen feed gas for the generator, air is used almost exclusively for POE/POU water treatment. However, only a small proportion of oxygen in the air is converted to ozone by this method of production. Therefore, as much as 1-3% by weight of ozone is obtained by corona discharge.
On the other hand, generation by ultraviolet radiation produces much lower concentrations, on the order of .1% for 184 nanometer UV generators down to .01% for 254 nanometer UV generators, about 10 to 300 times less than those generated by corona discharge.
In addition to the air flow rate, another major factor involves the rate at which ozone is formed. Simply put, as air flow increases, the relative rate of ozone production increases until it reaches an optimum level, flattens out, and then starts to decline.
A second variable that must be considered is the amount of heat generated. Excessive heat leaves the generator unable to operate at its best. Increasing the airflow decreases the concentration of ozone gas. In addition to the flow rate and temperature of air passing through the generator, the amount of heat generated by the generator is also determined by the amount of air moving through it. Because of this, it is necessary for the ozone generator manufacturer to perform extensive testing before they can determine the desired air flow rate.
It has been shown that water vapor in the feed gas is a critical factor in the production of ozone, particularly in the case of corona discharge technology. For UV-type generators, water vapor is less of an issue. In conventional corona discharge units, ozone yields typically decline by 30% when the dew point of the gas feed drops from -40°C to -20°C.
Another factor that influences ozone production, as well as its quality, is the voltage level applied to the corona area, the frequency at which the voltage is applied, the pressure of the feed gas, the amount of desiccant fines in the feed air, and the uniformity of the corona gap.
An ozone generator manufacturer is responsible for taking all of these factors into account when designing a generator that is as efficient and reliable as possible. In this case, ozone concentration may be the most important factor (especially for your application).
Ozone dissolves in water more readily at higher ozone concentrations in neighboring air, which in turn will perform more oxidative and/or disinfective changes to the water.
We can conclude from the effect of airflow that an ozone generator capable of producing 2 grams per hour (gph) may not be as effective as one capable of producing 1.5 gph. It is possible that the 1.5 gpm unit has a concentration twice that of the 2.0 gpm unit, which will lead to a higher amount of ozone being dispersed into the water.
Thus, while looking for how much ozone their generators produce, it is important to understand more than just one parameter. The company’s representatives should be able, and indeed should be obligated, to provide them information about the percent by weight, the air flow rate, and the relative yield per hour.
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