Staged implementation of alternative processes in an existing integrated steel mill for improved performance and reduced CO2 emissions – Part I: Technical concept analysis

• Replacing coal and increasing oxygen to blast furnace improve top gas heating value.
• Replacing gas boiler power plant with low-BTU gas turbine increases electric output.
• Removing CO2 prior to gas turbine significantly reduces total CO2 emissions.
• Selexol absorption shows the most promising results.
• Staged implementation of modifications enables reduced investment and technology risk.

In this study, an alternative operational concept for the blast furnace has been evaluated for an integrated iron and steel mill. The integrated iron and steel mill evaluated was based on the blast furnace and basic oxygen furnace (BF + BOF) hot metal production route equipped with a gas boiler power plant for power production. The alternative assessed was increased pulverized coal injection (PCI) as reducing agent to the blast furnace. Accompanied with a higher rate of oxygen feed to the blast furnace, this reduces the coke consumption in the blast furnace and increases the blast furnace top gas calorific value. The increased calorific value enables combustion of the blast furnace top gas in a high efficiency gas turbine for power production. Combining this modified blast furnace concept with pre-combustion carbon capture will enable a reduction in the total CO2 emissions from the steel mill. Three concepts were evaluated: a modified blast furnace concept without carbon capture, a modified blast furnace concept with MEA-based pre-combustion CO2 capture and a modified blast furnace concept with Selexol-based pre-combustion CO2 capture. All cases were compared to an integrated iron and steel reference case based on the BF + BOF route. Results show that replacing part of the blast furnace coke with increased PCI injection and replacing the gas boiler with a high efficiency gas turbine significantly reduces total CO2 emissions (up to 1.8 Mt/a) from the steel mill. The modified concept imposes significant changes in electricity production on site and becomes an important factor for steel producers operating in the national grids. The different concepts can be implemented stage wise, minimizing the investment and technology risks.