2.1.3. Process Drive Operation

Steam turbines, like compressors, can be modeled on many levels—from basic enthalpy balance with constant isentropic efficiency to more complex approaches comprising turbine characteristics and correction curves [20,30]. Aspen Plus® did not provide the option to model turbines with the same precision as the compressors. Therefore, the characteristics and correction curves had to be input "manually", via a calculator block. As only isentropic calculations were predefined for turbines, the model first calculated the turbine steam consumption based on the characteristics (required power output) and correction curves (live steam pressure, live steam temperature, exhaust pressure, and compressor revolutions). Then, the model iteratively calculated the isentropic efficiency of the turbine so that, based on the before-calculated steam consumption and enthalpy balance, the provided power output correlated with the required value.
