Evaluation of low and high level integration options for carbon capture at an integrated iron and steel mill

Abstract

To achieve climate goals, the iron and steel industry needs to find energy efficient and cost saving pathways for implementing CO2 capture. This paper evaluates two integration alternatives of excess-heat powered CO2 capture at an integrated iron and steel plant using the concept of partial capture. The two sources of CO2 investigated were the blast furnace gas (BFG) and flue gas from the combined heat and power (CHP) plant, representing a high and low level integration alternative, respectively. An amine capture system was simulated in Aspen Plus, and optimized for low energy requirement. To analyze the effects on the iron and steel system and the level of available excess heat, an in-house model was used containing interlinked energy and mass balances of each process step available. The results show that high level integration of CO2 capture gives a lower specific heat demand and improves the overall energy efficiency of the steel plant, resulting in more available heat. For this reason, it is possible to capture 3% more from BFG without any extensive alterations to the plant to recover excess heat. The total available excess heat at the plant will sustain capture of up to 46% of the steel plants total CO2 emissions, and beyond that point steam has to be imported.