After performing successfully in a series of tests, the Wärtsilä sulphur oxides (SOx) scrubber has been granted the Sulphur Emission Control Area (SECA) Compliance Certificate by the classification societies Det Norske Veritas and Germanisher Lloyd. A scrubber is an after treatment technology for cleaning exhaust gases of sulphuric oxides. Wärtsilä's solution is the first ever marine scrubber to be awarded this certification.
Prior to the successful Wärtsilä tests, the use of scrubbers as an efficient and cost-effective alternative to the use of low sulphur fuel for reducing SOx emissions from ships, had been questioned. The full-size SOx scrubber test plant was installed on board the MS Suula, and was used to clean the exhaust gases from the ship's four-cylinder in-line Wärtsilä 20 auxiliary diesel engine. This Neste Oil owned, Finnish registered product tanker operates mainly in the SECA Baltic Sea area, where regulations governing sulphuric oxide emissions are very stringent.
The tests were performed with both high sulphur (3.4%) and low sulphur (1.5%) heavy fuel oil, and verified that the Wärtsilä scrubber system efficiently removes SOx from the exhaust gases. The measurements, which were part of the certification process and made by an accredited independent body, demonstrated a sulphur dioxide removal efficiency exceeding 99% in all operating conditions, even when using high sulphur fuel. This high level of efficiency was consistent throughout the load range and with all fuels. The efficiency of nitrogen oxides removal was 3-7%. The removal of particulate matter was in the range of 30-60%. The approvals covered also the safety of the installation, as well as the performance.
The International Maritime Organisation (IMO) as well as other regulating bodies will gradually limit the sulphur content in marine fuels. The most common fuels used in marine diesel engines are heavy fuel oils with sulphur contents typically of 1.5 to 3.5 per cent. Such engines can readily burn low-sulphur fuel oils as well, though the associated problems are known and suitable operating guidance is available. Scrubbing exhaust gases is an environmentally friendly and cost-effective alternative for reducing sulphur oxide emissions down to 0.1%.