Design and 4E Analysis of a Hybrid Air Supply System for Blast Furnaces Driven by Excess Pressure and Waste Heat Recovery

In pursuit of energy-efficient solutions for air supply systems in steel plants, this study introduces a novel hybrid air supply system, amalgamating Waste Heat Recovery (WHR) and Excess Pressure Recovery (EPR) units. The system integrates an expander in the WHR unit and a gas turbine in the EPR unit, coaxially aligning them with the blower. A 4E model is established to evaluate the system’s energy, exergy, economic, and environmental performance. Results highlight R236ea as optimal, boasting a net power output of 1072.07 kW and an exergy efficiency of 35.62%. The WHR and EPR units contribute 73.36 and 26.64%, respectively, resulting in an electricity saving of 8.38% for the blast furnace. The minimum cost per unit of net power output with R236ea is 0.0229 $/kWh, with a dynamic payback period of 1.66 years. Compared to traditional electro-driven systems, the proposed system yields a 14.23% total cost saving. R1233zd(E) facilitates the largest net emission reduction at 202.86 kt per year, operating at an evaporation temperature of 84.3 °C. This hybrid air supply system demonstrates significant practical value, offering simultaneous benefits in energy savings, cost reduction, and emission reduction, suggesting a promising avenue for future research and development in air supply systems.