Lean duplex stainless steel is proving to be an ideal construction material for new generation biogas tanks. In addition to saving substantially in weight, Börger of Germany was able to make its tanks larger than before.
New grade recommended
Biogas tanks have traditionally been built from cement or enameled, zinc-coated or coated carbon steel. This has not been the case with the German company Börger, which has considered the stainless steel as the best defense against corrosive conditions in tanks, caused by hydrogen sulfide. So when Börger contacted Outokumpu for a new project, they had austenitics in mind. Outokumpu, however, recommended a lean duplex solution, with the newly launched lean duplex grade LDX 2404® playing the starring role.
Larger tanks, less material
Following an increasing trend, Börger too was convinced by the lean duplex solution, and decided to use the new grade for storage and process tanks. "The main reason for the selection of LDX 2404® for the tank system was its high strength, which allowed us to use 25% less material. Additionally, for the first time we could create a storage tank with a capacity greater than 5 000 cubic meters," says Gerd Buβ, Sales Manager at Börger GmbH.
Summing up the benefits
"Outokumpu LDX 2404® achieves its high-strength with low nickel content, while providing corrosion resistance that exceeds austenitic 316. Moreover, our new duplex has excellent mechanical properties," says Bernd Beckers, Global Product Manager Duplex at Outokumpu. The duplexes benefit also from the fact that stainless steel tanks are maintenance free and easy to maintain and their size and design can be flexibly adapted to meet the needs of customers.
The duplex biogas tanks manufactured by Börger are now up and running in West-Münsterland, Germany. The tanks are bolted, which allows for individual and flexible design, and thus the possibility to choose between different lid types. Dismantling and re-assembling the tanks at a different location is also possible. So, after 2020, when current regulations for the renewable energy policy will expire, the tanks could be used for different purposes if necessary.