Linde renewed Ovako Imatra steel mill’s bloom furnace burners in the summer of 2023. The goal of modernizing the furnace was to reduce the steel mill's use of fossil natural gas, improve the energy efficiency of this production phase and reduce associated emissions, as well as enable a transition to the use of hydrogen in the future.
As a result of the transition to the Linde’s REBOX® flameless oxyfuel solution, the bloom furnace’s natural gas consumption is reduced by approximately 25 percent. The furnace’s carbon dioxide emissions will decrease in the same proportion, and nitrogen oxides (NOx) are expected to decrease by more than 50 percent. Thanks to the modernization of the burners, the bloom furnace will comply with strict emissions permits in the future. Ovako's goal is to achieve a completely carbon-neutral steel production.
All the steel to be produced goes through the bloom furnace
The bloom furnace is a critical part of the Imatra mill’s production process, as all the steel produced at the mill passes through the walking beam furnace. The purpose of the bloom furnace is to bring the blooms to the correct temperature before rolling. During heating, the blooms’ structure and the temperature differences are equalized.
The new bloom furnace has 27 oxygen burners and 8 heat zones. The new burners have been placed on the walls of the furnace, while some of the old burners were located on the furnace ceiling. The positioning of the burners allows for a more even heating of the steel blooms and thus a better quality.
The new oxygen burner system enables the use of hydrogen
One important reason for Ovako to modernize the burner system of the bloom furnace was the possibility of switching to using green hydrogen as heating fuel in the future.
"The previous burners could only use fossil natural gas. The new REBOX solution is built ready for the use of hydrogen," says Linde's project manager Antti Mikkola.
Old burners used combustion air to support the combustion reaction. The new burners use oxygen from Linde's air separation unit, which enables greater production capacity and reduces the amount of flue gases.
With this project, also the safety at the bloom furnace improved significantly. The new safety system includes, among other things, flame monitoring and pressure difference measurements and is highly automated: for example, the furnace ignition cannot succeed unless everything is secured.
Deliver safely and on time
Linde planned and implemented the entire modernization project of the bloom furnace burner system at Ovako Imatra steel mill. The project group consisted of Finnish and Swedish experts, and the planning work began in 2022. The installation of the new REBOX solution was carried out in the summer of 2023 during the maintenance outage of the Imatra steel mill.
"The schedule was really tight, as there were only five weeks to install the new oxygen burners, gas network and safety system. However, we got the work done on schedule, and the furnace was taken into production use in week 33. I am also particularly satisfied that the work was done safely without anything to report. Cooperation between Ovako, Linde and the subcontractors was exemplary," Mikkola praises.
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REBOX in short
The REBOX technology developed by Linde can be used to increase the production capacity and operational flexibility of existing heating furnaces, reduce fuel costs and reduce carbon dioxide, NOx and SOx emissions. REBOX technology can also be applied to new furnaces.
Linde has already installed more than 180 REBOX systems in steel reheating and annealing furnaces around the world, improving energy efficiency, production flexibility and paving the way for the use of hydrogen as a fuel.
®REBOX is a registered trademark of Linde plc.
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