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Open-loop and hybrid scrubbers

Yara Marine offers open-loop scrubbers and scrubbers that can operate in both open- and closed-loop mode. The latter are known as “hybrid” scrubbers. Pure closed-loop scrubbers are practically non-existent, but can also be offered.

Open-loop scrubbers

In open-loop mode, sea water is pumped from the sea chest through the scrubber and discharged back to the sea. The natural alkalinity of the seawater neutralizes the discharged water. Continuous monitoring at the inlet and outlet ensures that the discharged water quality is well within regulatory limits and has minimal impact on ports, marine environments, and aquatic life.

Hybrid scrubbers

With a hybrid scrubber system, you can switch from open- to closed-loop mode through simple commands.

When operating in closed-loop mode, the water is recirculated through the scrubber, with a small amount of bleed-off taken from the loop for treatment. The water is treated by adding a small amount of alkali and removing particulate matter. The treated water can be discharged or led to a holding tank when in areas of zero discharge.

In closed-loop mode, alkali injection is required for the scrubbing to work over time. Without alkali injection, the seawater used to wash the exhaust would gradually lose its ability to absorb SO2 from the SOx emissions. Our scrubbers can operate on multiple types of alkali when in closed-loop mode, such as magnesium oxide, caustic soda, and sodium carbonate.

Our water treatment systems can be customized to fit any vessel’s needs. The systems are highly automated, made from high-quality materials, and based on well-established filtration principles, such as crossflow membrane filtration. This ensures optimal closed-loop operation and a long lifetime for the system.

Selection criteria

The choice between open-loop and hybrid scrubbers depends on the vessel’s trading and voyage patterns.

Yara Marine Technologies offers scrubbers that can operate in pure open-loop mode or by combining open- and closed-loop mode. With a hybrid scrubber, the vessel is able to switch between modes depending on the specific water discharge regulations in the area.