Open Loop / Closed Loop

Open Loop / Closed Loop / Hybrid Ready

With the Open Loop operating mode, the natural alkalinity of the sea-water is used to neutralize the exhaust gas sulphur content. The filtered water is collected from the sea chest and delivered to the scrubber. The water is then collected, analyzed and discharged overboard.

It is the simplest and the most economical operating configuration :

  • No reagents needed (minimum OPEX)
  • Minimum equipment installed and integration impact (minimum CAPEX)
  • Not allowed in some harbors and areas due to the discharged washwater flow


Btn Ref Djibouti.jpg


With the Closed Loop operating mode, the water is continuously recirculated and a reagent is used to neutralize the exhaust gas sulphur content. Only a limited water bleed is treated, analyzed and discharged overboard (or stored in a tank in case of zero discharge operation).

  • The sulphur and the soot are concentrated in the sludge tank and the discharge overboard is reduced
  • Ships can operate in all areas where there is legal discharged regulations (harbors, SECA areas, canals, territorial waters…) with  maximum flexibility
  • Reagents shall be stored on board (MgO or NaOH)
  • The system can be switched to Open Loop mode (Hybrid) anytime


Btn Ref GNV.jpg


A special Open loop - called Hybrid ready configuration is offered to minimize the first investment, reduce the dry-dock time and allow a simplified future conversion to Closed Loop.



Btn Ref Fabiola.jpg