Ozone Production, Concentration, and Solubility

Ozone generation is made possible through specialized equipment known as ozone generators. These devices employ electrical discharges to convert oxygen into ozone. Ozone generators find applications in various fields, including water disinfection treatment, air purification, and food preservation. This post will delve into ozone production, concentration, solubility, and mass transfer. Understanding these fundamental concepts is crucial for harnessing the power of ozone safely and effectively.

Ozone gas Production

Ozone is produced using industrial ozone generators. These generators use electrical discharges to convert oxygen into ozone gas. Ozone production refers to the mass of ozone produced over time, measured in grams per hour. It is closely related to the flow of oxygen/air at the generator inlet. The ozone production rate determines the efficiency and capacity of an ozone generator.

Ozone Concentrations

Ozone Concentration refers to the amount of ozone in a given air volume. It is commonly expressed as a Part per million (ppm), grams per cubic meter (g/m³), or percentage by weight (% w/w).

Higher ozone gas concentration is crucial for the economical and effective use of ozone in water treatment, air purification, and other applications. High ozone concentrations mean a higher solubility ratio.

For example, when comparing these two ozone generators

Generador “A” is a 30 g/h ozone generator that produces ozone gas at 2.9wt% and will require a feed oxygen flow of 13 SLPM.

Generator “B” also produces 30 g/h but at 9.1 wt% and will need only 4.0 SLPM of oxygen.

Even though the two generators produce the same amount of ozone over time, they make it at different concentrations. For this reason, there can be a significant difference in their ozone solubility and, consequently, in their efficacy. Generator A can only dissolve 30% of the ozone in water; in other words, only 9 g/h of ozone can be dissolved from the 30 g/h produced, whereas Generator B can dissolve 85-95%. 

Ozone Solubility:

Solubility measures the ability of ozone to dissolve in a particular medium, such as water. So, Dissolved ozone is the portion of ozone that has been transferred from the gas phase to the liquid phase and is available for oxidation reactions. The ozone solubility depends on water temperature, pressure, ozone production, concentration, and mass transfer efficiency. An important fact is that not all ozone is soluble in water. Henry’s Law dictates (simplified) that the higher the ozone concentrations, the higher the solubility ratio of ozone in water. The ozone concentration is essential for the solubility of ozone in water, but no one wants to discuss it.

Ozone mass transfer:

Ozone mass transfer refers to the process by which ozone is transferred from the gaseous phase to the liquid phase. An efficient injection method is critical for achieving the desired dissolved ozone level and ozone treatment efficiency. Initially, static mixers and ozone bubble columns were commonly used to dissolve ozone. However, nowadays, venturi injection is regarded as the most efficient method.
We have seen the following dependency:

O3 Concentration %wt	Percentage of O3 dissolved in water
1% wt	10%
3% wt	20-30%
5-7% wt	50-70%
8-10% wt	80-90
10-14% wt	95%
14-22% wt	97%

WHY OZONE PRODUCTION, OZONE CONCENTRATION, AND OZONE SOLUBILITY IN WATER ARE IMPORTANT?

A while ago, I received a call from Bob, an engineer responsible for water treatment and disinfection at a large industrial plant, after buying two 60 g/h ozone generators for USD 15,000. After the ozone system ran for over an hour, only 18 grams of the 120 grams of ozone he produced were dissolved in water. The amount of ozone produced was considerable, but the concentration was deficient. As we mentioned, the ozone concentration is essential to ozone solubility in water.

Following my advice, we replaced his two 60 g/h low-concentration ozone generators with one high-concentration 30 g/h Absolute Ozone ATLAS 30 ozone generator, which illustrates the issue.

His new system successfully dissolved 27 g of ozone into the water (no 18) for less than a quarter of the price.

ANOTHER CUSTOMER’S NIGHTMARE.

Some years ago, we learned about a customer who had to install an air-fed ozone generator for his 100 m3 swimming pool. The generator was purchased from one of North America’s largest manufacturers. The manufacturer claimed that his equipment produced enough ozone to disinfect the swimming pool.
His ozone generator was rated at 16 g/h. However, the ozone produced from that generator was only 1% weight. At that concentration, it is possible to dissolve 1.6 g of ozone in water (16 g x 10% = 1.6 g), creating a low concentration of 0.004 ppm (a concentration of 0.04-0.07 ppm is recommended for chemical-free pools, more than ten times more).
We suggest installing our Atlas30 generator. Its 30 g/h of ozone generation at a 9% Wt concentration will be enough to provide a happy customer with a crystal-clear, chemical-free swimming pool.

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Challenges and Considerations

Ozone production, concentration, and solubility are critical factors in harnessing the power of ozone safely and effectively. However, several challenges and considerations must be addressed to optimize ozone treatment systems.

One of the main challenges is achieving high dissolved ozone concentrations in water. Ozone is highly reactive and rapidly interacts with contaminants in the water . Selecting the right ozone generator and injection technique is crucial. In addition, the choice of injection technique, such as using a diffuser or venturi, can impact the efficiency of ozone mass transfer and the overall effectiveness of the treatment.

Conclusion

Ozone is a powerful oxidant with numerous industrial and consumer applications. However, its production, concentration, and solubility are critical factors in harnessing its power safely and effectively. Understanding the physical and chemical properties of ozone and its environmental impacts is essential for effective ozone treatment.

Addressing the challenges and considerations of ozone production, concentration, and solubility can optimize ozone treatment systems to achieve high dissolved ozone concentrations and effective treatment outcomes. Additionally, reducing ozone precursors and mitigating ozone air pollution can minimize the negative impacts of ozone on human health and the environment.