Case Valmet flue-gas cleaning units

Courtney Tenz


Ships operating in the EU after 2015 needed to meet a directive limiting their sulphur concentration to below 0.1 percent. Ships therefore needed to install flue-gas desulphurization units to remove sulphur dioxide.


Finnish company Valmet used several grades of stainless steel for two 20-tonnes desulphurization units. The grades provide superior corrosion resistance for the harsh environment.


Steel grade: Outokumpu Forta SDX 2507, Forta DX 2205, Ultra 254 SMO and Supra 316L/4404
Product form: coil, sheet and plate

Stainless solution for greener ships

Emissions reduction is a collective agenda today. With countries around the world implementing regulations to prevent the release of greenhouse gases, companies like Valmet have stepped up with advanced air pollution control tools.

After an EU directive went into effect in 2015 that required ships operating in the EU to limit their sulphur concentration to below 0.1%, Valmet designed two flue-gas desulphurization units to be used in the Baltic and Northern Seas. Each unit weighs some 20 tonnes and is approximately 12 meters tall.


Pollutant prevention

With these units, the harmful organic and inorganic substances that are created during combustion are no longer discharged into the atmosphere. Instead, with a flue-gas desulphurization unit, carbon dioxide, sulphur dioxide, dust and soot can be concentrated and deposited safely underground.

Several studies have been conducted to determine which material is best for use in such a harsh environment. Sulphuric acid condensation has been long recognized as a cause of corrosion in flue-gas desulphurization units. Sulphur, seawater and heat placed together require highly corrosion resistant materials.


A harsh environment

“The environment in the flue-gas desulphurization unit is harsh and varies depending on where ships are sailing. Sulphur, seawater and heat put together require highly corrosion resistant materials. Due to the presence of such demanding environments, we decided to use duplex stainless steel grades,” says Juha Laukka at Valmet.

For the two units, Outokumpu provided 40 tonnes in total, consisting of four high-alloyed stainless steel grades – Outokumpu Forta SDX 2507 super duplex stainless steel, Forta DX 2205 duplex stainless steel, Ultra 254 SMO austenitic stainless steel and Supra 316L/4404 austenitic stainless steel.

“We get good benefits of Outokumpu’s duplex grades in flue-gas cleaning, where material is under a lot of pressure. Duplex is an excellent material in this use,” says Laukka.

Recommended products and insights

Energy and heavy industry

In energy and heavy industry, failure is simply not an option. When one single mishap can explode into a full-blown crisis, only stainless steel can deliver the assurance of control that you depend on.


The Forta range contains duplex and other high strength stainless steels that enable thinner structures and weight reduction (measured in Rp0.2 > 400 MPa. PRE 16 to 43).


The Ultra range contains stainless steel products meant for extremely corrosive environments (PRE of more than 27).

Hot rolled stainless steel coil, strip and plate

Offering exceptional versatility, Outokumpu hot rolled coil, strip and plate are used in virtually all industries and markets. In addition to plates, Outokumpu produces quarto plate that is available in thicknesses up to 130 mm. 


Stainless steel is a superb material for sustainable solutions as it is 100% recyclable, efficient and long-lasting. Our vision is to become the customers’ first choice in sustainable stainless steel.

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