Sizing of Ozone Equipment
This article provides Ozone equipment sizing guidelines to get your ozone systems sized correctly.
Ozone is created when oxygen (O2) molecules are dissociated by an energy source into oxygen atoms and collide with an oxygen molecule to form an unstable gas which is one of the most potent oxidants. Although ozone can be applied as a gas, in most applications, ozone is utilized in an aqueous solution (ozonation or ozonization). The effectiveness and usefulness of ozone have been demonstrated over the years with its wide range of applications, for example, in water treatment or the food industry. With an oxidation-reduction potential of 2.07 V, ozone is one of the strongest and most reactive known sanitizers that makes microorganisms significantly easily destroyed by it.
An ozone generator is a device that produces ozone by breaking apart oxygen (O2) molecules into single atoms, which are attached to other oxygen molecules to form ozone (O3). Ozone generators produce ozone (O3) by applying an electrical charge to the oxygen molecules (O2) passes through which causes the oxygen atoms to part ways and temporarily recombine with other oxygen molecules.
Ozone is generated industrially by Plasma Ozone Generators. These generators work on the principle of dielectric barrier discharge. As the electrical charge passes through the oxygen, it ionizes the gas to a point where it becomes electrically conductive and forms a Plasma. Plasma Ozone generators can generate ozone gas concentrations of 10-15%.
Ozone generators are categorized by their ozone production in grams per hour (or pounds per day). You can find a small unit with nominal ozone production of 15 g/h (NANO 15) or more capable with 200 g/h (Magnum 200). Essentially, this is only the grams of ozone produced in a time. Although it may sound self-evident, it is crucial to understand that there is missing vital information for you. The production of 15 g/h of ozone using an oxygen flow rate of 4 (slpm) will have a higher concentration in comparison to the production of 15 g/h using a flow rate of 12 (slpm). Therefore, you always need to know your concentration as well. The absence of a performance table is usually a sign that the generator is not performing well. Ozone Concentration is the ratio of total feed-gas to ozone production, measured in g/m³ or % by weight.
For example, as you can see in this performance chart. At 20 PSI and 4, SLPM Atlas 30 produces ozone at 10 wt%
Ozone mass transfer is the movement of a gas phase into water. In most Ozone applications, ozone needs to be dissolved into water. Ozone gas is partially soluble in the liquid. However, using proper methods and equipment high mass transfer efficiencies can be reached. Ozone can be transferred by either bubbling or mixing with a venturi mass transfer system. Initially, diffusion stones were the primary method for transferring ozone mass to water. Currently, venturi-based mass transfer systems are the preferred method for dissolving ozone in water due to their simplicity, economy, and effectiveness. In addition, a venturi injector has about 90% efficient and can be up to 99% efficient at dissolving ozone into the water. Check this for more information: Mass Transfer of High Concentration Ozone with High-Efficiency Injectors, Ozone Mass Transfer Beginners Guide.
Ozone Dosage for Water Treatment
The following information is necessary to determine the Ozone Dosage for Water Treatment:
- Water quality and Ozone demand (via water sample analysis)
- Ozone dosage
- Inline pressure
- The volume of water (for recirculating systems)
Water Quality and Ozone Demand
To remove contaminants from water using ozone, it is important to understand how the amount of ozone required is affected by the amount of ozone demand. Ozone is not selective; therefore “contaminants” in the water will consume ozone, affecting the ozone dosage. A water sample is required for analysis to ensure the correct dosage is provided. For reference, this table shows the typical demand required for different contaminants.
Iron 0.14 to 0.50 mg/l
Manganese 0.88 mg/l
Hydrogen Sulfide 3.0 mg/l
The ozone dosage required per mg/liter of contaminant is as follows – this figure must be added to the target dosage to ensure there is enough ozone to be effective:
Dosage is the required amount of ozone, it is expressed in mg/l (milligrams per liter) or ppm (parts per million). Either value is the same.
There is a large range of applications requiring different dosages.
Bottled water 0.05-0.3 ppm
Cooling towers 0.05 – 0.3 ppm
Reclaimed water 0.2 – 0.5 ppm
Bacteria & Virus 0.2 – 1.0 ppm
If you need help with the dosage required in your applications contact us now. We have more than 30 years of experience in a wide range of ozone applications. Our personnel will be happy to assist you.
There is two distinct type of application – single pass and recirculating. Single-pass applications are bottling lines, discharge water, etc. Recirculating systems are fruit and vegetable washing, cooling towers, etc. Where the ozone level remains constant.
For single-pass applications, you can calculate the ozone dosage (grams per hour) by multiplying the dosage required by contaminant level by flow rate.
For example, the dosage required is 2 ppm – contaminant level (demand) is 8 mg/l – flowrate is 4000 liters per hour
= 2 (mg/l) x 8 (mg/l) x 4000 (l/h)
= 64000 (mg/h) + 25% safety factor
= 80000 (mg/h)
= 8 (g/h)
There are two important points to mention here. The first is that is not possible to dissolve all the ozone produced in water, the higher the concentration, the higher the mass transfer efficiency. For this, it is essential to choose a high-performance ozone generator.
Second, is the decomposition of Ozone, Ozone in an aqueous solution has a self-decomposition reaction. The decomposition reaction is a function of temperature. For example, you need to add 25% more for every extra 6 degrees in the water temperature. Check this for more information: How to Compensate for Half-Life of Ozone in Water, Half-life of Ozone.
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