How Salzgitter AG intends to avoid greenhouse gases in the future

Salzgitter AG's integrated steel mill at the site of the same name is already almost energy self-sufficient and recycles residual materials and by-products either within the plant or also in other sectors. As a result, losses are thus constantly minimised - but this is by no means the end of development. Together with external partners such as various Fraunhofer Institutes, the aim is to test the limits of the natural sciences.

"SALCOS" - this stands for "SAlzgitter Low CO2-Steelmaking" and is still a rather young project of Salzgitter AG to reduce the carbon dioxide emissions of its own plants to a minimum. Every year, the Salzgitter steel mill produces around eight million tonnes of CO2, which cannot be avoided under the current technical conditions.

Therefore, "new ways are to be tried out and innovative process technologies explored", as the official website of the project states. Although SALCOS will initially only be tested in Salzgitter, it will in principle be extended to every location with so-called "integrated" steel production.

Classic reduction with coke and coal

While other companies process CO2 chemically or store it underground, Salzgitter AG intends to use this innovative concept to largely avoid its production. In Europe, iron ore is almost exclusively reduced by means of carbon in the form of coke, coal and hydrocarbons such as oil and natural gas. However, this is where the greenhouse gas comes from.

This could nevertheless become expensive in the future. "European steel producers must reckon with rapidly rising costs due to the purchase of contamination rights from the EU certificate trade", said CEO Heinz Jörg Fuhrmann on "Deutschlandfunk".

Carbon is replaced by hydrogen

In so-called direct reduction plants, or "DRP" for short, carbon is greatly simplified and replaced by hydrogen. As the hydrogen required is mainly produced from natural gas, such plants have so far only been used in countries with low-cost natural gas deposits. These can be found, for example, in the Middle East, the USA and Russia.

The framework conditions for SALCOS are manifold. For one thing, there are the political conditions such as the climate targets of the European Union or the aforementioned trade in rights, the demands of society or the needs of employees and responsibility for the region. Of course, SALCOS must also fit in with its own "sustainability concepts and economic criteria".

Above all, however, the technical feasibility and the examination of how the new plants can be integrated into the existing steel mill are major issues. Last but not least, a continuation in the international competitive environment must also be guaranteed.

EU research project for regenerative hydrogen production

However, it is not enough to only replace carbon with hydrogen in the direct reduction process. Hydrogen production must also be based on renewable energies. Since March 2016, Salzgitter AG, together with Sunfire GmbH amongst others, has therefore been participating in the EU research project "GrInHy". This is short for "Green Industrial Hydrogen via reversible high-temperature electrolysis". Salzgitter claims the title for the currently "most powerful reversible high-temperature electrolyser in the world".

"The technology of high-temperature electrolysis enables the reversible operation of the pilot plant. While in the electrolysis process, it converts industrially generated steam from waste heat into hydrogen with the highest electrical efficiency, in the reverse case - fuel cell operation - it produces electricity and heat from hydrogen or natural gas," the company explains.

The electrolytically produced hydrogen can already be used as a protective gas in the annealing processes for steel production. Hydrogen will be displaced on a fossil basis. For the future, the use as a substitute for carbon for the direct reduction of iron oxide would be conceivable, even with significantly larger capacities.