Filtration for the EGCS scrubber systems

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Filtration for the EGCS scrubber systems

ECGS scrubber system - the oceanic ships emit massive amounts of contaminants that affect not only the population living alongside the costs and the ports, but also those who live on the mainland, far from the seaside. The diesel engines generate substantial emissions of NOx, fine dust particles (PM2.5) and sulphur dioxide (SOx). The most important regulation for the gas emissions is IMO Global Sulphur Cap, that has come into force on January, 1st 2020 and sets the limit for sulphur content of ship’s fuel oil at 0.5%, whereas earlier it was set at 3.5%.
This reduction will abate the airborne emissions of sulphur oxides (SOx) and other particulates that are very harmful for the environment and humans.

In order to comply with this regulation, all the ships operating outside Emission Control Areas (ECA) must use fuel oil that contains maximum 0.5% of sulphur oxide. Meanwhile for the vessels operating inside the EAC area the limit is set at 0.1%.
Otherwise the ship owners can keep the HFO (heavy fuel oil) system that are largely installed and used and abate the emissions throughout systems that treat the exhaust gas (Exhaust Gas Cleaning System-EGCS) or most known as scrubber.

Sea Water Scrubber (SWS) use liquid to wash unwanted pollutants from a gas stream before it reaches the atmosphere. The scrubbers are cylindric elements, positioned inside the chimney through which the exhausted gases are expelled meanwhile sea water is sprinkled.
In this manner the sulphur oxides are largely reduced, due to two distinct processes: one is the dissolving of the SOx in the water droplets and the other is the reaction between the alkaline substances (naturally present in the sea water) and the dissolved SOx.
Both for open and close loop Scrubber system the water used has to be filtrated. In the open loop system, the quantity of water used is very substantial (arriving at 1400m3/h).

Alfa Water has developed huge experience in this sector and is able to provide solutions for the different phases of the water usage in the scrubber filtration:

a. Prefiltration of the feed water for the scrubber: our SAF 2205 (DUPLEX) filters protect the spray nozzles;

b. Filtration of the wash water from the scrubber that prevents the release of contaminant suspended solids in the sea. After the sulphur combustion takes place the discharged water becomes acidic (pH 2-3) and the content of oil, heavy metals, IPA and hydrocarbons reaches very high level. Filters in SMO 254 are used for this application.

c. For the storage and the treatment of the water used in the filtration process (pos b.) we propose the multibag filters in GRP or polyethylene, or the complete system ABF Vacuum Band Filter.

d. Polishing unit – at the filter drain, the AMT automatic magnetic filter in SMO 254 attracts the heavy metals present in the water.

Alfa Water systems developed specifically for the pos. a, b, c & d the water discharged from the scrubber is in compliance with the regulations in all three versions of the ECGS technology, i.e. open loop, closed loop and hybrid.

Application Scheme

The filter installed in the Wash water line, during the cleaning cycle can be pressurized by the supply line of the scrubber with filtered water under pressure.
In this way the pressurization of the filter is always ensured during the cleaning cycle to ensure a good suction effect of the contaminant from the suction pads.

The sea water is sucked on board through a coarse filtered intake to separate the larger sized impurities, then passes through a basket filter with a filtration degree of 1 mm and is pumped to AVC automatic filters with filtration degrees generally between 500 and 50 microns.
The filtered water is pressurized to the various utilities of the ship, the discharges resulting from the automatic cleaning of the filters are returned to the sea or further collected in the ABF filter for the separation of any oily compounds or for the collection of microplastics.

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