Abstract
Compared with the basic organic and steam Rankine cycles, the organic trans-critical cycle (OTC), steam flash cycle (SFC) and steam dual-pressure cycle (SDC) can be regarded as the improved cycle configurations for the waste heat power recovery since they can achieve better temperature matching between the heat source and working fluid in the heat addition process. This study investigates and compares the thermodynamic performance of the OTC, SFC, and SDC based on the waste heat source from the cement kiln with an initial temperature of 320 °C and mass flow rate of 86.2 kg/s. The effects of the main parameters on the cycle performance are analyzed and the parameter optimization is performed with net power output as the objective function. Results indicate that the maximum net power output of SDC is slightly higher than that of SFC and the OTC using n-pentane provides a 19.74% increase in net power output over the SDC since it can achieve the higher use of waste heat and higher turbine efficiency. However, the turbine inlet temperature of the OTC is limited by the thermal stability of the organic working fluid, hence the SDC outputs more power than that of the OTC when the initial temperature of the exhaust gas exceeds 415 °C.
Highlights
A great deal of waste heat energy with exhaust gas as the carrying medium is available in the industrial processes
The purpose of this study is to investigate and compare the thermodynamic performance of the steam flash cycle (SFC), steam dual-pressure cycle (SDC), and organic trans-critical cycle (OTC) based on the exhaust gas waste heat source from the cement industry with a medium temperature and capacity
For the basic steam Rankine cycle (SRC) driven by the waste heat, the pinch point temperature difference between working fluid and heat source usually occurs at the bubble point of the working fluid
Summary
A great deal of waste heat energy with exhaust gas as the carrying medium is available in the industrial processes. The temperature matching between the exhaust gas and working fluid in the organic Rankine cycle (ORC) is better than the SRC. Multiple evaporation pressure and flash are other possible options to improve the temperature match between exhaust gas and working fluid, so as to achieve better use of the available heat and smaller exergy loss in the heat absorption process [12,13]. Results indicated that the steam dual-pressure cycle reaches higher net power outputs at high engine loads, while the ORC reaches higher performance at low engine loads when the two cycles are compared based on the same turbine efficiency. The purpose of this study is to investigate and compare the thermodynamic performance of the SFC, SDC, and OTC based on the exhaust gas waste heat source from the cement industry with a medium temperature and capacity. Description of described the System correlations in Ref. [18]
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