Open Loop vs Closed Loop Scrubbers: Engineering Trade-Offs Shipowners Should Understand
Exhaust gas cleaning systems are an important part of maritime emission compliance, but not all scrubber configurations behave the same in operation. For shipowners, the choice between open loop, closed loop or hybrid scrubber operation is not only a regulatory decision. It is an engineering decision that affects water chemistry, pump load, energy consumption, maintenance and long-term operational flexibility. Open Loop and Closed Loop: The Core Difference In an open loop scrubber, seawater is used as the scrubbing medium. The natural alkalinity of seawater neutralizes the acidic components created when sulphur oxides are removed from the exhaust gas. In a closed loop scrubber, the washwater is recirculated inside the system. Instead of relying mainly on seawater alkalinity, the system uses chemical dosing to control pH and maintain the scrubbing process. This creates two very different engineering profiles. Open loop systems are typically more dependent on high seawater flow and local water conditions. Closed loop systems offer greater chemical control, but require more process equipment, monitoring and operational discipline. Water Chemistry: ... Read more
