Waste Heat Recovery in Decarbonized Ironmaking: A Process Simulation Approach : Evaluating Thermodynamic and Technical Limits of Waste Heat Utilization in H2-Based Ironmaking

Sammanfattning

This thesis conducts a techno-economic analysis of a waste heat recovery system integrated into a Direct Reduced Iron (DRI) steel production process. The study focuses on utilizing high-temperature off-gases from the shaft furnace to generate saturated steam via shell-and-tube heat exchangers. The recovered thermal energy can be reused within the plant for process heating or directed to hydrogen production units, thereby delivering both energy cost savings and substantial reductions in overall plant carbon emissions. Engineering simulations were conducted using Aspen Plus and ChemCAD to model the heat recovery process, evaluate the performance of the heat exchanger, and determine the steam generation capacity. The economic feasibility of the system was evaluated using capital expenditures (CAPEX), operating expenditures (OPEX), and key financial indicators, including net present value (NPV) and return on investment (ROI). The model was applied to assess regional viability under varying electricity prices and carbon intensities of the grid. The results demonstrate that recovering process heat for steam production significantly reduces energy consumption and associated carbon emissions, providing a strong case for industrial decarbonization and economic competitiveness in DRI steelmaking.