From molecules to dollars: integrating molecular design into thermo-economic process design using consistent thermodynamic modeling

Abstract

Thermo-economically optimal design = optimal molecule + optimal process + optimal equipment.

Integrating superstructure‐based design of molecules, processes, and flowsheets

“…For each flowsheet configuration, we perform the integrated design of working fluids, processes, and equipment considering the net present value NPV and the specific investment cost SIC as objective. For a fixed flowsheet configuration, the integrated design of working fluids, processes, and equipment corresponds to our previous work presented by Schilling et al Thus, the present work avoids the enumerative evaluation of all possible configuration by directly identifying the optimal flowsheet.…”

“…Due to their physical basis, the pure component parameters show good relation to the molecular structure making the parameters suitable for optimization by relaxation strategies and GC methods . The strong predictive power of the PC‐SAFT EoS to calculate equilibrium and transport properties allows for a clear distinction of the identified molecules if the molecular structures are not too similar, for example, propene and propane, as demonstrated in an uncertainty analysis by Schilling et al…”

“…The present value annuity factor PVAF is calculated from the lifetime n = 25a and the rate of return i = 0.08 . The total capital investment TCI is calculated as sum of the purchased‐equipment cost PEC i multiplied by factors for additional direct and indirect costs (for details see Schilling et al): where PEC RE, m denotes the purchased‐equipment cost of the rotating equipment m and PEC HE, n indicates the purchased equipment cost of the heat exchanger n (see Section 3.2). The net power output P net is calculated as: where P T, j denotes the power output of the turbine j and P P, k indicates the power input of the pump k .…”

“…The binary structural decision variables w are used to deactivate fixed purchased‐investment costs of optional units if a unit is not selected. For the calculation of the purchased‐equipment cost PEC, we consider the chemical plant cost index to account for inflation and development of raw materials with CEPCI 2016 = 541.7 and an exchange rate of 1,136$/€ (details see Schilling et al). The purchased‐equipment cost PEC RE of the rotating equipment (pumps and turbines) are calculated from the power input ( P P ) and output ( P T ), respectively .…”

“…Since only a thermo‐economic model is used within 1‐stage CoMT‐CAMD, the identified molecular structures have to be subsequently assessed regarding further non‐thermodynamic properties, for example, toxicity or environmental impacts. These non‐thermodynamic properties can be directly integrated into 1‐stage CoMT‐CAMD if an accurate prediction method is available, for example, a GC method or QSPR method . Otherwise, the ranking can be assessed a posteriori.…”