We will present an approach to the modelling and optimization of mass and energy flows in these general processes. A network representation of the process flowsheet is utilized wherein the network nodes are the characteristic thermodynamic states or possible pinches in the process, and interconnecting arcs embody various methods of material flow between the states. Heat exchange flows are included to account for utility costs with heat integration. Simplification of the multicomponent thermodynamic behavior is not required. For fixed states, linear programming is used to optimize the network to determine the optimal flowsheet topology and flowrates.
Nonlinear programming is used to vary the states and to identify locally optimal flowsheets.
Application to some distillation-based examples including air separation and ethane recovery will be described, where interesting flowsheet improvements are sometimes indicated.