Exhaust Gas Cleaning

Wärtsilä has long been at the forefront of sustainable technology development. Just as cleaning wastewater or reducing air emissions are important contributors to a cleaner environment, engine efficiency is also central to sustainability. With years of experience in exhaust gas cleaning for marine applications, Wärtsilä has developed efficient, safe, and certified products for eliminating air emissions.

SOx Reduction

The reduction of sulphur oxide (SOx) emissions from marine vessels has been a priority for some time now, due to the harmful impact they have on both human health and the environment. Rules have been introduced stipulating both global limits and specified Emission Control Areas (ECA) limits. Wärtsilä has developed a full wet scrubber portfolio to fit our customer needs.  All Wärtsilä scrubbers have been tested and certified according to the IMO guidelines, thus ensuring safe operation and compliance with MARPOL Annex VI , Regulation 4.  Wärtsilä strives continuously for technological excellence, and to minimize the environmental impact of our scrubber systems.  This is why our scrubber systems not only reduce SOx, but also remove large levels of particulate matter (PM) and black carbon. Each system has water treatment units installed to clean the scrubbing water before discharge. Wärtsilä has made it easy for customers to get exactly what they want, and our packages range from equipment only to full turnkey installations.

Scrubber Designs

Wärtsilä has developed two kinds of standard scrubber designs to better meet the demands of our customers. Wärtsilä can offer the conventional venturi scrubber design, as well as the more compact inline scrubber system.

Both scrubber designs have benefits and drawbacks dependent on vessel type and layout, so it’s important to look at the specific project needs. Both designs can be utilized for open loop, closed loop and hybrid scrubber systems.

Wärtsilä Scrubber Designs

Open Loop Scrubber System

Wärtsilä exhaust gas cleaning technology is an economical and environmentally friendly solution for tackling all existing and future SOx emission regulations, and provides flexibility and reliable operations wherever you operate. The scrubber system is designed to remove SOx from the exhaust and operates utilising seawater.

The open loop scrubber system is our most straightforward scrubbing method. It utilizes the natural alkalinity in seawater for scrubbing, and does not need caustic soda. This method can be used in most seas around the world, where alkalinity levels are high.

Exhaust gas enters the scrubber and is sprayed with seawater, the SOx 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 to ensure that it conforms to MEPC 184(59) criteria and can be discharged into the sea with no risk of harm to the environment.

Wärtsilä Open Loop Scrubbers

Hybrid Scrubber System

Wärtsilä provides hybrid scrubber system solutions which have the flexibility to operate in both open and closed loop using seawater to remove SOx from the exhaust. This provides a flexibility of operation in low alkaline waters, as well as the open ocean.

When at sea the switch can be made to open loop using only seawater. The sulphur oxides in the exhaust react with the water to form sulphuric acid. Chemicals are not required since the natural alkalinity of seawater neutralizes the acid.

When required to switch to closed loop, for instance whilst entering a port in a low alkalinity area, the natural alkalinity of seawater is boosted by an alkali which uses caustic soda (NaOH) as a buffer.

Wärtsilä Hybrid Scrubber System

Retrofit Services

Wärtsilä Retrofit Services supports its customers throughout the lifecycle of a retrofit project by providing excellent engineering capabilities, by minimizing risks, keeping downtime to a minimum, and through reduced customer project management costs. As a professional project organization, we are capable of managing retrofit projects of all kinds wherever you are in the world, including EPC (Engineering Procurement and Construction), class and statutory approvals, commissioning, and crew training. Wärtsilä develops tailored retrofit solutions in close cooperation with the customer – from the very first enquiry until the system is successfully delivered and the project complete. By working very closely with the customer, we can establish the precise needs, and then validate the solutions at the conclusion of each phase of the project. After the project is completed, Wärtsilä’s global services network is there to support customers throughout the lifecycle of the ship.

Wärtsilä Retrofit Services

Useful Downloads

SOx Scrubber Technology Guide


Scrubber Retrofit


Choosing the right scrubber