Abstract
A novel thermo-economic performance indicator for a waste heat power system, namely, MPC, is proposed in this study, which denotes the maximum net power output with the constraint of EPC ≤ EPC0, where EPC is the electricity production cost of the system and EPC0 refers to the EPC of conventional fossil fuel power plants. The organic and steam Rankine cycle (ORC, SRC) systems driven by the flue gas are optimized to maximize the net power output with the constraint of EPC ≤ EPC0 by using the Non-dominated Sorting Genetic Algorithm-II (NSGA-II). The optimization process entails the design of the heat exchangers, the instantaneous calculation of the turbine efficiency, and the system cost estimation based on the Aspen Process Economic Analyzer. Six organic fluids, n-butane, R245fa, n-pentane, cyclo-pentane, MM (Hexamethyldisiloxane), and toluene, are considered for the ORC system. Results indicate that the MPC of the ORC system using cyclo-pentane is 39.7% higher than that of the SRC system under the waste heat source from a cement plant with an initial temperature of 360 °C and mass flow rate of 42.15 kg/s. The precondition of the application of the waste heat power system is EPC ≤ EPC0, and the minimum heat source temperatures to satisfy this condition for ORC and SRC systems are obtained. Finally, the selection map of ORC versus SRC based on their thermo-economic performance in terms of the heat source conditions is provided.
Highlights
Large quantities of waste heat are generated during the working processes of internal combustion engines, gas turbines, and many industries [1,2]
The results indicated that the net power output of the steam Rankine cycle (SRC)
The cost of the system is estimated by Aspen PEA, the cost of operation and Focusing on the power recovery of flue gas waste heat, a novel thermo-economic performance maintenance is assumed as 1.5% of the system cost, and the interest rate and life time of the system indicator MPC, which refers to the maximum net power output of the system with the constraint of are set as 5% and 20 years, respectively
Summary
Large quantities of waste heat are generated during the working processes of internal combustion engines, gas turbines, and many industries [1,2]. Recovering the waste heat helps reduce fossil energy consumption and the related emissions of CO2 and atmospheric pollutants. One of the feasible ways is to convert the waste heat to electricity via power cycle systems. Flue gas waste heat is generally discharged to the environment after heat release from the system; we intend to recover as much electricity from the flue gas as possible. We want to reduce the electricity production cost (EPC) of the waste heat power system, since the cost represents the energy and material resources consumed by the system from its manufacturing to operation and maintenance. The EPC reveals the utilization efficiency of the total energy and material resources of the system
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