Shipping is a global industry and the harmful emissions created from shipping fleets affect many regions worldwide. As a consequence the marine industry will in the coming years face tougher legislation on emissions around the world. These rules and regulations will force the marine industry to make difficult choices, however the benefits are a much cleaner air, resulting in a greener future for us all.
The rules range from the International Maritime Organization’s MARPOL Annex VI, regulation 4 as detailed in resolution MEPC 259(68) to the European Union Directives 2012/33/ EU. Some areas may also be faced with national or local rules. Business as usual is no longer an option. To comply with incoming rules, ship owners must switch to costly low Sulphur fuel, or choose abatement technology. The requisite for sulphur levels in Emission Control Areas (ECA) is now 0.1% and will be 0.5% worldwide by either 2020, therefore the marine industry needs to choose a path on how to achieve compliance
OPEN LOOP SCRUBBER SYSTEM
The system operates in an open loop utilising seawater to remove SOX from the exhaust. Exhaust gas enters the scrubber and is sprayed with seawater in three different stages. The sulphur oxide in the exhaust reacts with water and forms sulphuric acid. Chemicals are not required since the natural alkalinity of seawater neutralises the acid. Wash water from the scrubber is treated and monitored at the inlet and outlet to ensure that it conforms with the MEPC 184(59) discharge criteria. It can then be discharged into the sea with no risk of harm to the environment
CLOSED LOOP SCRUBBER SYSTEM
Closed loop scrubber system works continuously in closed loop, which means that one does not need to worry about sea water alkalinity levels. This system is best suited for full time operation in low alkalinity areas (e.g. Great Lakes). In a closed loop scrubber system, the exhaust gas enters the scrubber and is sprayed with sea water that has been mixed with caustic soda (NaOH). The sulphur oxides in the exhaust react with this mixture and are neutralised. A small bleed-off is extracted from the closed loop and treated to fulfil IMO requirements. Cleaned effluents can be safely discharged overboard with no harm to the environment. If operation in zero discharge mode is requested, the effluent can be led to a holding tank for scheduled and periodical discharge.