Carbon Dioxide Capture in the Iron and Steel Industry: Thermodynamic Analysis, Process Simulation, and Life Cycle Assessment

The iron and steel sector is one of the dominant drivers behind economic and social progress, but it is also very energy-intensive and hard-to-abate, making it a major cause of global warming. Improving energy efficiency, introducing hydrogen for direct reduction, and utilising CCS technologies are the three most viable options for reducing CO2 emissions from steel mills. This investigation deals with a life cycle comparison of three different carbon capture processes, the inventory data of which have been obtained using process simulation based on rigorous phase and chemical equilibrium equations. In-silico models for the absorption of carbon dioxide employing MDEA, membranes, or sodium hydroxide to produce sodium bicarbonate have been developed and compared from a life cycle viewpoint. The research findings showed a variable amount of CO2 removal in the three cases, where membranes achieved the best performance (95 % CO2 removal). Since NaOH absorption produces a valuable by-product (sodium bicarbonate, which is commonly produced by Solvay process), the other two technologies were modified to integrate the utilisation of CO2 for the synthesis of sodium bicarbonate with NaOH rather than transporting and storing the carbon dioxide. As a result, this production pathway for sodium bicarbonate generates lower environmental burdens than traditional Solvay process. The environmental performances of the alternatives are nearly equal, even though the environmental impacts associated with capturing the CO2 and subsequently reacting with NaOH are always slightly higher than those involved with reacting directly during absorption. Among the evaluated alternatives, the direct conversion to sodium bicarbonate appears to be the most promising approach for converting CO2 emissions in the steel sector.