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Aeration / Degassing

Liquid degassing with straws?

There are various methods for degassing of water/ liquids. The best known techniques are intensive aeration in stripping towers or (multiple) plate aerators. These techniques work by bringing water containing dissolved gases into intensive contact with air. With these technologies, low values ​​of gases in water can only be achieved for certain types of gases; for example, this does not apply to oxygen and CO2. See https://www.logisticon.com/en/technologies/aeration-degassing  

If however low values ​​of dissolved gases (such as low values for oxygen O2 and carbon dioxide CO2) are required in the water, for example for boiler feed water, there are other known technologies such as vacuum-degassing, chemical dosing and thermal degassing (using steam) or combinations of these methods.

Logisticon Water Treatment uses the 3M-Liqui-cel membrane contactors for degassing of liquids.

In addition to these methods, Logisticon Water Treatment now also uses a technique that uses membranes. With special membranes (3M Liqui-Cel membrane contactors) it is possible to remove gases from an aqueous phase. The degassing membrane contactor consists of thousands of micro-porous polypropylene hollow fiber membranes (a type of straws) that are wound around a distribution pipe. Because the hollow fiber membranes are hydrophobic (water-repellent), the water stream cannot penetrate through the pores of the membrane, but the gases can. The gases can be removed via the pores by applying a higher pressure on the aqueous side than on the gas side. If very low values ​​of dissolved gases are to be achieved, it is possible to apply a vacuum on the suction side, possibly in combination with a stripping gas. We call this sweep gas and usually nitrogen is used. This forms a driving force that brings dissolved gases from the water phase into the gas phase.

By applying a vacuum on the suction (gas) side, possibly in combination with a sweep gas (mostly Nitrogen), oxygen O2 levels <20 ppb can be achieved. These results are achieved with industrial grade nitrogen instead of technically pure nitrogen which results in a considerable saving of operational costs.

Methane removal using membrane degassing

In addition to removing well known gases such as ammonium NH3, oxygen O2 and carbon dioxide CO2 , it is also possible to remove methane CH4 from water with membrane contactors of Liquicel. Various studies, with installations of Logisticon Water Treatment together with Dutch water companies, show that methane can be removed from groundwater to low values. In some cases, this methane can even be recovered and used as an energy source.

Advantages of membrane degassing/ membrane contactors

  • No use of chemicals
  • Low energy consumption
  • No increase in temperature
  • Compact (small footprint)
  • Modular design
  • Very low residual values ​​of gases possible
  • Fast results after start-up

Applications of membrane degassing/ membrane contactors

  • Production of boiler feed water without chemicals
  • Degassing of permeate between two reverse osmosis plants (double pass RO)
  • Removal of gasses such as carbon dioxide (CO2), oxygen (O2), methane (CH4) and ammonium (NH3) from water
  • Production of oxygen-free water for district heating