Design and multiobjective optimization of ORC for determination of pinch point temperature and power generation potential

Increasing energy demand in the world day by day increases the need for alternative energy sources, renewable energy sources and energy recovery methods. A large part of the energy produced in order to maintain the supply-demand balance in the world is consumed in the industrial sector. Iron and steel production sector is one of the sectors with the highest energy consumption share among industrial facilities. In this study, the temperature and flow rate values of the exhaust gas discharged from the annealing furnace of an iron and steel factory were analyzed and recorded for one year. Considering these data, an organic Rankine cycle system was designed based on the annual average exhaust gas temperature and flow rate. Within the scope of the study, six different fluids were selected, two wet types (ethanol, methanol), two isentropic (acetone, butene) and two dry types (cyclohexane, benzene). In the first stage, the optimum pinch point temperature differences of the fluids were determined in line with the data obtained from the annealing furnace, and in the second stage, the effects of these pinch point temperature differences on the system performance were investigated. Finally, environmental and economic analyzes of these fluids were made. As a result of this study, the highest thermal efficiency was obtained in benzene fluid with 17.05%, while the highest exergy efficiency was obtained in methanol with 58.76%. In addition, among the selected fluids, the highest CO2 emission reduction was achieved in benzene fluid with 1935.9 tons/year. In addition, although benzene and methanol are the fluids with the highest initial investment costs, they are the fluids with the highest profitability with payback periods (3.6 years and 3.7 years), respectively.