Activated coke reduces energy consumption in the blast furnace

An extensive study by Swerea shows how coke properties change in various zones of the blast furnace. Valuable results will help to minimize energy use and emissions.

Some 1.2 Mt of coke is used in blast furnace iron production annually in Sweden, causing major CO2 emissions. In a doctoral thesis at Luleå University of Technology, by Maria Lundgren of Swerea in collaboration with SSAB and LKAB, presents important results showing how coke properties are affected in various blast furnace zones during different process conditions. This knowledge can be used to minimize energy use.

“The reaction rate can be increased and energy consumption reduced by activating the coke surface with Fe and Ca containing compounds. This increases the reactivity of coke with CO2, causing CO to form, which is important for iron oxide reduction. The method requires a lower temperature than normal, which is both conomical and climate-smart. 

By mixing activated screened nut coke with iron oxide pellets a more favourable environment for the formation of iron is created and total coke consumption is reduced,” says Maria Lundgren.

The outflow of flue dust has been studied, where the ascending gas lift force, dust particle size and density are important parameters. By  understanding and controlling factors influencing coke strength, emission of fine coke particles can be reduced. Studies conducted in laboratory, pilot and industrial scale have given broader insight into the role of coke in the blast furnace. 

The next step is to study the process with briquetted residual products with biomass. Hopefully, this will result in further energy and environmental gains.