Calculations: Air vs. Oxygen as Feed Gas for Generating Ozone

Ozone Generation: Air Feed

Air is one method for ozone generation. The ozone concentrations achieved by using air as the feed gas are low. The maximum concentration achievable with the best technology is 5%. The effectiveness of the ozone however, is not in anyway inferior to the effectiveness of ozone produced with oxygen as the feed gas.

The process requirement is what determines whether you should use air or oxygen as the feed gas. The rule of thumb is: the larger the volume of water, the more volume of gas is required and therefor air is most suitable. E.G. municipal water ozonation. The lower the volume of water, the better it is to use oxygen as feed gas. E.G. waste water treatment.

The effectiveness of ozone is governed by Henrys law, Chicks law, etc., in most cases. Air only contains 21% oxygen and requires 4 times the volume of air to generate the same quantity of ozone as oxygen being the feed gas. For large requirements of ozone, like for industrial applications such as effluent treatment, processing etc., ozone is best produced with oxygen. The total costs of ozone generation for large doses of ozone will be much lower for ozone produced with air instead of oxygen. For smaller requirements of ozone, production with air will be more economical than with oxygen.

Calculations

Molecular weight of air: 1293 (1 m3 of air weighs 1293 grams) Air Feed 1% ozone concentration: 1293 x 1/100 = 12.96 g/m3 of air 2% ozone concentration: 1293 X 2/100 = 25.86 g/m3 of air 3% ozone concentration: 1293 x 3/100 = 38.79 g/m3 of air 4% ozone concentration: 1293 x 4/100 = 51.72 g/m3 of air 5% ozone concentration: 1293 x 5/100 = 64.64 g/m3 of air

Oxygen Feed

It may be better to use oxygen as feed gas in areas that water quantities are low. That way the gas quantity will be low and easily manageable, the high concentration are likely to increase ozone dissolution, per Henrys law.

Molecular weight of oxygen: 1428 (1 m3 of oxygen weighs 1428 grams)

Oxygen Feed

6% ozone concentration: 1428 x 6/100 = 74.88 g/Nm3 of O2

7% ozone concentration: 1428 x 7/100 = 99.96 g/Nm3 of O2

8% ozone concentration: 1428 x 8/100 = 114.24 g/Nm3 of O2

9% ozone concentration: 1428 x 9/100 = 128.52 g/Nm3 of O2

10% ozone concentration: 1428 x 10/100 = 142.80 g/Nm3 of O2

11% ozone concentration: 1428 x 11/100 = 157.08 g/Nm3 of O2

12% ozone concentration: 1428 x 12/100 = 171.36 g/Nm3 of O2

It is very dif´Čücult to economically produce 13% concentration and beyond. Since the higher the concentration the power is consumed and at 13% this becomes disproportional to be economically viable.

The converse calculations will be used to determine the quantity of air/oxygen required to produce ozone at a predetermined concentration of ozone.

Let us assume that you want to produce ozone say 2000 grams of ozone at 8% concentration with oxygen as feed gas. Then the quantity of oxygen required will be: (2000/0.08) / molecular weight of oxygen: i.e. = (2000/0.08)/1428 = 17.5 m3 of oxygen /hour. You will than design the oxygen plant accordingly. Of course, you will adjust the quantity based on the purity of oxygen and atmospheric pressure.

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