Deoxygenation by substitution with N2

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One special pipe applying aerodynamics goes beyond conventional reaction and mixing levelsOHR MIXER

The OHR method is the most efficient and fastest deoxygenation treatment on the market

When oxygen (O2) is dissolved in liquid, deoxygenation treatment is carried out in chemical plants when there is a danger of an explosion in the chemical reaction process or where dissolved oxygen (DO) inhibits the chemical reaction. A common deoxygenation process in chemical plants is a method of blowing nitrogen (N2) gas into liquid. DO concentration decreases by the increase of the dissolved N2 concentration. In other words, O2 gas is substituted with N2 gas and DO is removed.

Conventional methods require a large amount of N2 gas bubbling for a long time

Deoxidation by N2 gas is very difficult

Conventional methods of simply supplying N2 gas into liquid waste much time and money. It is necessary to blow large amounts of N2 gas in a large tank, and a very long time such as 24 hours is required when the targeted deoxygenation rate is high (e.g. 95%, 99% or 99.9% removal). These problems increase lead times and reduce factory productivity.

The OHR method can quickly remove DO from 10.0 mg/L to 0.2 mg/L

High efficiency deoxygenation can be easily done with the OHR method. For example, even in a very difficult case where the DO value of 10.0mg/L should be deoxidized to 0.2mg/L (oxygen removal rate is 98%), the treatment can be done continuously in just a few seconds. No need for pressurization/decompression or adding chemicals at all.
You can learn about the OHR high-efficiency deoxygenation treatment in our other documents containing illustrations and test data. Please contact us.


Why the OHR method can deoxidize with high efficiency

There is no technology other than OHR to raise the dissolved N2 concentration in liquid to supersaturation to 130%

  • (1) The saturation value of ‘air’ dissolved in water (at 20°C, 1 atm) is approximately 24mg/L. This means 24mg of air dissolves in 1 liter of water. The breakdown of the 24mg/L is 15mg/L of N2 gas and 8.84mg/L of O2 gas. N2 gas occupies 78% of the air, hence much N2 gas is also dissolved in the water with high DO.
  • (2) During the deoxygenation treatment, almost 100% concentration of N2 gas (pure N2 gas) is supplied/dissolved in water. Then the dissolved N2 gas concentration increases up to 19mg/L (saturation value of N2 gas at 20°C, 1 atm).
  • (3) Supplying pure N2 gas increases the dissolved N2 gas concentration by only 4mg/L (from 15 to 19mg/L). As described in (1) above, water with high DO already has much dissolved N2 gas. Therefore, DO must be displaced with only 4mg/L of increasing dissolved N2 gas. This is why the conventional methods require large amounts of N2 gas and a long time to reduce DO to near zero.
  • (4) Then, how can we remove DO in liquid quickly and continuously? To do this, it is necessary to dissolve N2 gas at once to an ‘oversaturated point’. The OHR MIXER can dissolve N2 gas up to 30% oversaturation level (saturation value is set at 100%, OHR can dissolves gas up to 130%). 5 or 10% oversaturation is not enough. In order to instantaneously remove DO, a powerful gas-liquid mixing technology that increases the dissolved N2 gas concentration up to 25mg/L is necessary.

See the graph on the right. The graph shows how much DO can be oversaturated using three kinds of equipment.
(Measured by Tokyo University of Marine Science and Technology)

F company’s micro/nano bubble generator reaches only 104.4%, which means 4.4% oversaturation.
OHR micro/nano bubble generator reaches 130.7%, which means 30.7% oversaturation.

OHR’s ability to dissolve the O2 concentration at 130% means that likewise OHR has the ability to oversaturate the N2 concentration to 130%. The above data shows that there is a big difference in the performance of microbubble generators that are sold on the market.
For details on how to judge the superiority/inferiority of microbubble generators, please see the link below.
The OHR method can achieve highly efficient deoxygenation treatment because of its very powerful gas-liquid mixing/reaction ability. Therefore 10mg/L of DO can be reduced to 0.2mg/L quickly.
Criteria for judging superiority/inferiority of microbubble generators