Specialized equipment called ozone generators can artificially produce ozone by using electrical discharges to convert oxygen into ozone. Ozone generators are employed for countless applications such as water disinfection treatment, air purification, and food preservation.
The performance of an ozone generator is typically evaluated based on two important measurements: ozone concentration (% wt or g/m³) and ozone production (g/hr). It is crucial to understand the significance of both these measurements and their relationship with ozone solubility. In order to utilize ozone in a safe and effective manner, it is essential to comprehend key concepts such as ozone production, concentration, solubility, and mass transfer.
Generation of Ozone
Industrial ozone generators are used for producing ozone gas by utilizing electrical discharges to convert oxygen into ozone. The production of ozone refers to the amount of ozone generated per unit time, measured in grams per hour, and is closely linked to the flow rate of oxygen or air at the inlet of the generator.
The term “Ozone Concentration” denotes the quantity of ozone present in a particular volume of air or water. It is determined by the ratio of the total gas input to the ozone production and is measured in g/m³ or % by weight. A higher concentration of ozone gas is of utmost importance for achieving cost-effective and efficient results in various applications, such as water treatment and air purification. This is due to the fact that higher ozone concentrations result in a higher solubility ratio.
To illustrate, let’s compare two ozone generators. Generator “A” is capable of producing 30 g/h of ozone gas at a concentration of 3wt% and requires a feed oxygen flow rate of 12.5 SLPM. On the other hand, Generator “B” also produces 30 g/h of ozone gas but at a concentration of 10wt%, and requires only 4.0 SLPM of oxygen.
Despite their apparent similarities, the two generators exhibit a significant difference in terms of the achievable ozone solubility. While Generator A can dissolve only 1-2% of ozone in water, Generator B is capable of dissolving 10-12%.
Solubility refers to the maximum amount of solute that can be dissolved in a given solvent to form a solution. In the context of ozone, dissolved ozone refers to the portion of ozone that has been transferred from the gas phase to the liquid phase, and is therefore available for oxidation reactions. The solubility of ozone is influenced by several factors, including water temperature, water pressure, ozone production, ozone concentration, and mass transfer efficiency.
It is essential to note that not all ozone is readily soluble in water. According to Henry’s Law, which is simplified, the solubility ratio of ozone in water increases with higher ozone concentrations. Although ozone concentration plays a crucial role in the solubility of ozone in water, it is often overlooked and not discussed.
Ozone Mass Transfer
Ozone mass transfer refers to the mechanism by which ozone is transferred from the gaseous phase to the liquid phase. To achieve the desired dissolved ozone level and treatment efficiency, it is crucial to employ an efficient injection method. In the past, static mixers and ozone bubbles column were commonly used to dissolve ozone, but nowadays, venturi injection is considered the most efficient method.
We have observed the following correlation:
O3 Concentration (wt) vs. O3 Dissolution Percentage in Water
1% vs. 10%
3% vs. 20-30%
5-7% vs. 50-70%
8-10% vs. 80-90%
10-14% vs. 95%
14-22% vs. 97%
The Reason Why They Are Important
We have done experiments on the relationship between ozone concentration and solubility. We used 2 sets of 60g/h ozone generators to dissolve ozone into the water. Over the course of more than 1 hour, only 18g of the 120g of ozone generated had been dissolved into the water. The amount was considerable, but the concentration is extremely low. The concentration of ozone is critical to its solubility in water.
After the 2 sets of 60g/h ozone generators were replaced by 1 high concentration 30g/h ozone generator, the problem was effectively solved. In this way, 24g of ozone can be successfully dissolved into the water for 1/4 of the price.
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