Analysis of sCO₂ Waste Heat Recovery System for Application in a Cement Plant

The industrial sector contributes approximately 28% of global CO₂ emissions. CO₂ emissions from energy-intensive industries can be reduced by converting waste heat into electricity. This represents a low-cost, zero-emissions power generation option with near-term deployment opportunities. One energy-intensive industry is cement production. Two cement plant heat sources are flue gas streams from preheater and clinker cooler, with temperatures of 250–450 °C. Potential energy conversion systems include Organic Rankine (ORC), steam Rankine (SRC), and supercritical CO₂ (sCO₂) power cycles. ORC/SRCs have been commercially deployed in cement plants. However, sCO₂ power cycles offer benefits such as high thermal stability of CO₂, higher cycle efficiencies, and compact power generation equipment. The paper is focused on multi-objective optimization of four sCO₂ cycle layouts (Recuperated, Re-compression, Partial recuperative, and cascade) and comparison with ORCs/SRCs. The optimization considers waste heat temperatures of > 300°C. The results show that sCO₂ power cycles can reach cycle efficiencies up to 30 %, which is higher than corresponding ORCs and almost similar to SRCs. However, cycle efficiency is not the only parameter to evaluate waste heat utilization. More meaningful parameters are the net power and capital costs. Results show higher power outputs from the sCO₂ cycle compared to ORCs and SRC.