When liquid contains dissolved oxygen (DO), deoxygenation treatment may be performed in chemical plants to prevent potential explosions during chemical reactions and to prevent dissolved oxygen from inhibiting reactions, as well as in the beverage industry to increase their products’ shelf lives. One common method is to blow nitrogen gas (N2) into the liquid. This decreases the concentration of DO by increasing the concentration of dissolved N2 — in other words, O2 gas is substituted for N2 gas and DO is removed.

Conventional methods that simply blow the N2 gas into the liquid are extremely inefficient in terms of both time and money. When the target deoxygenation rate is high (e.g. 95%, 99% or 99.9% removal), a large amount of N2 gas is required in a large tank over times as long as 24 hours. These problems increase lead times and reduce factory productivity.

With the OHR method, highly efficient deoxygenation is easy to achieve. For example, even in a particularly difficult case where a DO of 10.0 mg/L is to be reduced down to 0.2 (i.e. an oxygen removal rate of 98%), the deoxygenation treatment can be completed in a matter of seconds via continuous processing. There is absolutely no need for pressurization, depressurization or added deoxygenation agents. If you would like to learn more about our deoxygenation method, please contact us for extra materials containing illustrations and independent test results.

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First, all N2 deoxygenation methods follow these three principles:
1. Air dissolved in water (at 20°C and 1 atm) is saturated at a level of approximately 24 mg/L. In other words, 24 mg of air dissolves into 1 liter of water with a composition of 15 mg of N2 and 8.84 mg of O2, plus trace gases. Since N2 gas comprises 78% of air, water with a high DO must also contain a high level of dissolved N2.
2. During deoxygenation, high-purity N2 gas is dissolved into water up to the saturation level of 19 mg/L (at 20°C and 1 atm).
3. This increases the concentration of N2 gas by a mere 4 mg/L (from 15 up to 19 mg/L). As described in point 1 above, water with high DO already contains a high concentration of N2 gas; as a result, only the newly-added 4 mg/L of N2 is available to displace and remove DO. This is why conventional methods require large amounts of both gas and time to reduce DO to near zero.

How, then, can DO be quickly and continuously removed from liquid? To this end, N2 gas must be dissolved to the point of the supersaturation.
The OHR MIXER can achieve this at a supersaturation level of 130% — that is, 30% beyond the saturation limit of 100%. Note that 5% or 10% oversaturation is not enough to instantaneously remove DO. This requires a powerful gas–liquid mixing technology capable of dissolving 25 mg/L of N2 gas in water.

In the case of oxygen dissolution, the graph on the right shows OHR’s DO supersaturation capabilities compared with two other common pieces of equipment. This test was conducted by the Tokyo University of Marine Science and Technology.
●Company F’s micro/nano-bubble generator reaches a mere 104.4%, or 4.4% oversaturation.
●OHR’s micro/nano-bubble generator reaches 130.7%, or 30.7% oversaturation. OHR’s ability to achieve 130% supersaturation of O2 in water naturally means that it can also achieve 130% supersaturation of N2.

The above test data demonstrates that there is a significant difference in the performance of microbubble generators available today. For more information on how to compare and evaluate different microbubble generators, please follow the link below.
Criteria for judging superiority/inferiority of microbubble generators

The OHR method’s highly efficient deoxygenation is thanks to its exceptionally powerful gas–liquid mixing and reaction capabilities. This makes it possible to quickly reduce 10 mg/L of DO down to just 0.2.