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 SMOand 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 insight

Automotive and transportation

In transportation, today’s solutions must be dynamic enough to carry us to the future. Safe, strong, economical, durable and sustainable: Stainless steel delivers a new dimension of unmatched performance.


The Supra range contains stainless steel products designed for highly corrosive environments. Outokumpu Supra range stainless steels have a good resistance to uniform corrosion in many organic and inorganic chemicals. The addition of molybdenum enhances the alloy’s corrosion resistance in many acidic environments.

Eskilstuna, Sweden

Sweden’s long steelmaking tradition is showcased in the unique expertise found at the Eskilstuna Coil Service Center. Through outstanding quality and short lead times, the service center shows its commitment to the customer.