Comparison of toluene and cyclohexane as a working fluid of an organic Rankine cycle used for reheat furnace waste heat recovery

An organic Rankine cycle (ORC) is set up to recover waste heat from the flue gas of a reheat furnace. The calculations show that, under the same conditions, the gross power production, energy and exergy efficiencies are 490.63 kW, 16.62% and 35.64% for ORC with cyclohexane and 457.83 kW, 17.08% and 31.96% for ORC with toluene, respectively. After the comparison of working fluids, the ORC with cyclohexane was optimised at different turbine inlet pressures (from 26 bar to 38 bar) and turbine inlet temperatures (from 260°C to 320°C). The best performance of the cycle is obtained at the turbine inlet pressure of 38 bar and turbine inlet temperature of 280°C. The gross power production, energy and exergy efficiencies were evaluated as 527.67 kW, 17.65% and 37.37%, respectively, for optimised ORC with cyclohexane.