CLOSED loop scrubbers

The CLOSED loop is the most frequently used system. The seawater used in the process is continuously re-circulated. Detailed information can be found in our brochure. Download here.

How does it work?

  • From the bottom of the scrubber exhaust gases are led through the scrubber to the top.
  • The seawater is fed into the top of the scrubber through nozzles. This results in an equally divided spray.
  • The outgoing exhaust gases are washed with seawater in the scrubber.
  • The seawater (process water) is continuously re-circulated.
  • The sulphur in the exhaust gases dissolves in the process water pumped from a circulation tank and binds with the caustic soda (NaOH) as a salt.
  • Based on conductivity level a certain amount of process water is drained out of the system automatically.
  • If needed clean seawater is then added to the process water tank and also NaOH, if needed.
  • The process water is pumped through the separator.
  • This separator will separate solids and oil from the process water.
  • The remaining sludge is pumped to the sludge storage tank on the ship.
  • The process water with high conductivity level will be discharged directly back to sea while complying fully to the IMO regulations.
  • The pH, turbidity and concentration of PAH are constantly measured in accordance with MARPOL Annex VI resolution MEPC.184 (59).
  • The clean exhaust gases exit the scrubber, removed from sulphur and particulates, through a demister.


“We were intrigued by the simplicity of the AEC scrubbing system. Their technology works without filters. There is no pollution on the deck, no filters to clean and no maintenance. After testing the AEC closed loop scrubber on the Schleswig-Holstein we were so convinced, we ordered scrubbing systems for three more vessels.”

Fini Alsted Hansen, Technical Superintendent Fleet Management at Scandlines.

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