Energy and economic optimization of regenerative organic Rankine cycle with in the energy recovery system of a steel plant

The use of energy recovery is increasing in various industries. One type of these cycles that converts waste heat into electricity at low temperatures is the organic Rankine cycle. this paper provided the design, analysis, and optimization of regenerative ORC for waste heat recovery in a steelworks facility. A feedwater heater was installed in the system to further increase thermal efficiency. The system was examined by energy, exergy, and thermoeconomic approaches. To achieve the highest performances, the selection of various parameters was carried out using NSGA-II optimizing both exergy efficiency and total annual cost at the same time. The software MATLAB interfaced with the REFPROP library was used for modeling, and design variables included turbine inlet pressure, superheat temperature difference, condenser pressure, and the isentropic efficiencies of the rotating components. Thus, it has been shown that a proper tuning of some of these parameters may bring a satisfactory compromise between thermodynamic and economic performance. The optimum design gave a maximum exergy efficiency of 64.88%, an energy efficiency of 38.23%, a net power output of 1756.2 kW, and an estimated annual cost of $14.88 million. These results suggest that optimization of ORC systems could be a viable and practical solution for better energy utilization in heavy industries.