Heuristic Evolutionary Synthesis with Non-sharp Separators

Abstract If, in undertaking a process separation task, such as separating the constituent minerals of an ore to the most profitable extent, we allow limited separation in each process unit (as against requiring a “perfect split”), the number and connection of the units have to be found. Here it is done by building up the required flowsheet unit by unit, stopping when further addition does not increase the profit. Recycle of streams is allowed, the extent being controlled by an arbitrary parameter over which a search may be made. Simulation is sequential modular, with convergence and the necessary process optimization of each intermediate flowsheet carried out by infeasible path successive quadratic programming. As heuristics guide the construction, “good”, not necessarily “the best”, flowsheets are obtained, which may be further ranked, such as by controllability and/or process flexibility. The approach is here developed for “homogeneous” flowsheets (all process units identical), with minerals flotation separation as an example, using a very simple first-order kinetic flotation model. While countercurrent circuits are synthesized as limiting cases of the heuristics, flowsheets more profitable than these are also obtained. The paper reviews critically the heuristics and their application.