Integrated ۴E Assessment of a Cascaded Supercritical CO₂–Organic Rankine Cycle for Waste Heat Recovery from Dry Slag Granules Using a Moving Bed Heat Exchanger

High-temperature metallurgical slags contain substantial thermal exergy that is commonly dissipated during conventional cooling, thereby representing a significant opportunity for industrial energy recovery. However, most slag-based waste heat recovery studies idealize the moving bed heat exchanger and neglect pressure drop, auxiliary fan power, and inter-cycle exergy recovery. The present study addresses these gaps by developing a physically consistent ۴E assessment (Energy, Exergy, Economic, and Environmental) of a cascaded supercritical CO₂–Organic Rankine Cycle (SCC–ORC) system, in which a Moving Bed Heat Exchanger (MBHE) extracts sensible heat from dry slag granules and supplies the recovered heat to the power cycles. Industrial data from a copper flash smelting furnace are adopted as a representative case, while the proposed modeling framework remains applicable to a broad range of slag-generating processes. The MBHE model incorporates gas–solid heat transfer, airflow resistance, and auxiliary fan power to better represent practical operating conditions. Under design conditions, the cascaded SCC–ORC configuration produces ۵.۰۴۲ MW of net electrical power, with thermal and exergy efficiencies of ۲۰.۷۸% and ۳۷.۰۴%, respectively. Complementary exergy formulations are introduced to clarify cascade utilization by distinguishing recoverable exergy from destroyed exergy within the system. The proposed configuration enables annual indirect CO₂ emission reductions of (۲.۲۲–۳.۴۳) × ۱۰⁴ tons, depending on the grid carbon intensity. The thermo-economic assessment yields a levelized cost of electricity of approximately ۵۹.۹۵ USD/MWh, indicating economically viable performance for a fuel-free industrial heat recovery system. Overall, the proposed cascade provides a scalable pathway for metallurgical waste heat recovery and industrial decarbonization.

کلیدواژه ها:

Dry slag granulation ، Moving Bed Heat Exchanger ، Supercritical CO₂ cycle ، Organic Rankine Cycle ، Waste heat recovery