The established steel production route via blast furnace in an integrated iron and steel works is energy intensive, but highly efficient. Its operation is close to minimum carbon and energy consumption levels that are theoretically possible. The steel industry is continuously implementing energy efficiency measures to reduce energy consumption and energy-related carbon dioxide emissions. However, Energy consumption and carbon dioxide emissions mostly arise due to the process related use of carbon from fossil fuels in order to reduce iron ores in the blast furnace.
The possibilities to reduce CO2 emissions by using renewable energy at an integrated iron and steel works are limited. To that effect and coupled with the energy efficient use of waste heat, hydrogen from a high-temperature electrolyzer can provide another option for integrating electricity from renewables.
Therefore, green industrial hydrogen holds the potential for further optimization regarding the Carbon Footprint of steel products by either reducing indirect or avoiding of direct CO2 emissions, Carbon Direct Avoidance (CDA). Besides simply substituting natural gas as a fuel (e.g. for heating furnaces) green hydrogen may be used for different applications.
One example is using green hydrogen as inert gas for annealing atmosphere:
Annealing is a heat treatment for processed steel to restore its ductility. Depending on the required material properties the steel is heated to a suitable temperature in an inert atmosphere with shares of hydrogen. Hydrogen fulfills two functions:
prevention of oxidation during the process, and
increasing the heat transfer of the inert atmosphere due to its higher heat transfer coefficient than most other inert gases.
In context with life cycle assessment the use of green hydrogen for annealing processes in comparison to hydrogen from fossil sources has a positive impact e.g. on indirect CO2 emissions and the Product Carbon Footprint, respectively.