SSAB cuts compressed air production emissions

Global steel company SSAB aims for fossil-free steel production from mines to end users. The SSAB steel mill in Raahe in Finland has tested the replacement of coal with biochar, among other things. A new energy-efficient turbocompressor has been installed to reduce the emissions of compressed air production.

The Raahe steel mill produces standard, premium, and special-purpose steel. The mill uses hot rolling to turn 30-ton slabs into different sheets and strips such as directly hardened reels. Steel production is carbon-intensive. Just the SSAB Raahe steel mill is responsible for some seven per cent of Finland’s total CO2 emissions.

It was only natural for SSAB to investigate how technology could be used to mitigate climate change and reduce the carbon footprint of production. SSAB chose to replace the fossil coal and coke in its production with fossil-free electricity and hydrogen. Now instead of carbon dioxide, the process emits water vapour. The new production method is based on direct reduction that reduces pellets into iron without smelting them. At the production line, blast furnaces are replaced with electric arc furnaces.

SSAB aims to produce fossil-free steel in commercial quantities in its Sweden unit in 2026 and in all three Nordic units by 2040.

SSAB has long worked to reduce the environmental impacts and emissions of its production. For example, the Raahe steel mill has reduced its CO2 emissions per ton of steel produced by improving its energy efficiency. Recycled steel is also used in production.

A major investment was made to the secondary dust removal system, and the mill’s waste heat is recovered into the town’s district heating network. The mill also uses liquefied natural gas (LNG) to replace oil-based fuels.

The next step in the process was to recover the waste air exhausted by the oxygen plant for compressed air production, as this would increase the overall compressed air production capacity. The target was set at producing 300 cubic metres per minute with exhaust air, which is about 60 per cent of the mill’s compressed air consumption.

The new model can achieve this target with two turbocompressors and two screw compressors. The old screw compressors are kept in the new model as a backup.

SSAB chose an oil-free 450 kW SM6000 series turbocompressor manufactured by Hanwha and delivered by Sarlin. Virsiheimo highlights the model’s large range of adjustment, 170 to 350 cubic metres pre minute. The turbocompressor was commissioned a little over a year ago.

- We ordered the compressor without any logic and asked for other customisation of the standard equipment because we wanted to modify the software and automation ourselves. We were satisfied by how accommodating the manufacturer was about the changes. They also delivered the turbo quickly. This is a unique package, says Virsiheimo.

The life cycle costs of the turbocompressor were an important element of the purchase. The maintenance costs are now lower than before, which is reflected in the total cost. A separate 170 square metre step-up station was built at the mill for the new turbocompressor.

Virsiheimo says that collaboration with Sarlin was smooth and customer-oriented. In his opinion, Sarlin could see the mill as a whole and respond to the customer’s ideas about development. Sarlin also successfully communicated SSAB’s wishes to the Hanwha factory in South Korea.

Key Account Manager Jukka Järventaus of Sarlin found the SSAB compressed air system modification and modernisation project to be an interesting one because the turbocompressors will be able to run optimally and bring true savings in energy costs.

The data produced by Sarlin Balance was also a concrete help. Reporting makes monitoring and hence everyday work easier.