Integrated waste heat and cold energy recovery using Organic Rankine Cycles for a Direct Reduced Iron (DRI) process

The iron and steel industry, as one of the most energy-intensive sectors, faces growing challenges related to energy efficiency and carbon emissions. This study proposes an integrated energy recovery approach for a 1.5 Mtpa Direct Reduced Iron (DRI) process by simultaneously utilizing waste heat from flue gases and cold energy from Liquefied Natural Gas (LNG) regasification through Organic Rankine Cycle (ORC) systems. LNG storage and regasification offer a reliable and flexible energy supply solution, enabling buffering against disruptions and supporting continuous operation. Four ORC configurations (Basic, internal heat exchanger, Regenerative, and Dual fluid) were modeled and optimized. The working fluid selection was guided by stringent environmental and safety criteria, narrowing an initial pool of refrigerants to viable candidates. Two optimization objectives were evaluated: maximizing net power output and minimizing the Levelized Cost of Electricity (LCOE). Results show that while the Dual fluid configuration achieves the highest power output (14.14 MW), the Regenerative one offers the lowest LCOE (5.22 c$/kWh), striking a balance between efficiency and economic viability. To assess robustness, a Monte Carlo-based uncertainty analysis was conducted, accounting for variations in turbine power output, pump consumption, heat exchanger areas, and operation and maintenance costs. The results revealed narrow confidence intervals across all configurations, indicating high robustness of the optimal designs. • Integrated ORC design recovers both waste heat and LNG cold energy in DRI process. • Four ORC configurations modeled and optimized for power and cost performance. • Working fluids screened by environmental and safety-related properties constraints. • Dual fluid configuration yields the highest output (14.14 MW). • Regenerative configuration shows lowest LCOE (5.22 c$/kWh).