Separation of Particulate Matter from Marine Scrubber Washwater Using a High-speed Separator

New stringent legislations are currently being introduced in the maritime sector, effectively changing the way ship owners operate their vessels and even more stringent legislation is expected in the nearest future. It is expected that the continued use of scrubbers will rely on efficient water cleaning of the scrubber washwater, since several ports and countries around the world have prohibited the use of open-loop operation in near-coastal waters and ports. To continue using scrubbers in these areas, the scrubber must operate in closed-loop, where the particulate matter (PM) is separated from the water.

Alfa Laval’s water cleaning system (WCS) consists of a high-speed separator (HSS) and a static flocculator. The suspended PM holds a charge, resulting in stable single particles effectively repelling one another. To destabilize the PM, chemical coagulant and flocculant are added to the scrubber washwater in the static flocculator, to make the PM agglomerate into larger flocs, which increases the separation efficiency of the HSS. A multiphase numerical model of the WCS will be developed using a coupling of computational fluid dynamics (CFD) and discrete element method (DEM), to describe the agglomeration, breakage and separation of the PM in the static flocculator and HSS.

The main objective of the project is to increase the separation efficiency of the WCS, thereby more effectively separating the pollutants from the scrubber washwater. This will be done by describing the performance of the WCS with the CFD-DEM model and validating it against lab-scale experimental work as well as a unique, large-scale 2 MW marine engine testbed.

The project is carried out in cooperation with Alfa Laval Aalborg A/S, where the unique, large-scale marine testbed is available. The marine testbed will be operated under various test conditions, where the data will be used to validate the numerical model.

Collaborator: Alfa Laval Aalborg A/S.
Funding: Alfa Laval Aalborg and Innovation Fund Denmark.