Imatra steel mill's bloom furnace modernization reduces CO2 emissions of the bloom heating by approximately 25 percent
Ovako Imatra's bloom furnace burners were upgraded during the summer maintenance shutdown in 2023, with an investment value of approximately 3 million euros. The main contractor for the project was the Swedish company Linde. The goal of the investment is to reduce the use of fossil natural gas, improve energy efficiency in this production phase, and reduce associated emissions.
As a result of the burner upgrades, natural gas consumption in the bloom furnace will decrease by about 25 percent. The bloom furnace consumes about one-third of all natural gas used at the mill. Carbon dioxide (CO2) emissions from this production phase will decrease proportionally, and nitrogen oxides (NOx) are expected to decrease by more than 50 percent.
"Based on preliminary measurements, NOx emissions have dropped to about half of the previous levels. However, we will have more precise results after comprehensive measurements," says Development Engineer Otto Kankaanpää.
With the burner upgrade, the mill's bloom furnace will comply with strict air emissions permits in the future.
Ovako's goal is to achieve a completely carbon-neutral steel production regarding fossil carbon. The company is compensating for carbon emissions from production until this goal is achieved. Carbon offsetting will gradually decrease as the company continues to invest in new technology and more advanced processes.
Ready for Hydrogen
The bloom furnace is a critical part of the steel production process at Imatra mill, as all steel produced at the mill passes through the bloom furnace. The purpose of the bloom furnace is to bring the blooms to the correct temperature before rolling. During heating, the blooms' structure and temperature differences are equalized.
"The renewed furnace was put into production in week 33. We are currently fine-tuning the furnace. The project's schedule was initially tight, but I am really pleased that we managed to stay on schedule throughout the project," says Project Manager Tomi Karvinen.
The upgraded bloom furnace has 27 burners, and there are 8 heat zones. The new burners are placed on the walls of the furnace, as some of the old burners were located on the furnace ceiling. The positioning of the burners allows for a more even heating of the blooms.
"Previously, most of the heat came from above the bloom, leaving more shadow areas below. Now that the heat is blown from both above and below, we achieve more uniform heating of the blooms, in turn improves their quality," explains Karvinen.
According to Karvinen, one important factor behind the burner upgrade was also the readiness to use other gases in the furnace. Previously, combustion air used to support the combustion reaction was replaced with oxygen, requiring the construction of a new oxygen main pipeline at the site. The 250-meter-long pipeline runs from the site's oxygen valve station to the bloom furnace.
"The previous burners could only use fossil natural gas. The new burners are combination burners, so they can burn other gases, such as hydrogen. The entire burner system, including controls and gas control panels, has been built ready for hydrogen use."
Safety at the bloom furnace also significantly improved with these upgrades."The safety system is modern, including features such as flame monitoring and pressure differential measurements, and it is highly automated. For example, the furnace ignition cannot succeed unless everything is secured," says Karvinen.
This extensive project employed over 30 companies operating regionally and nationally. Ovako received support for the investment from Business Finland, with the energy support being approximately 0.7 million euros.