| In this thesis, a systematic design methodology to synthesize mass exchange networks (MEN) that accomplish separation tasks in the process industries has been developed. Specifically, MEN synthesis methods are employed to determine the minimum utility cost required to achieve a given separation target for waste reduction problems. Three problems have been tackled with this approach.; First, a novel problem, that of the synthesis of an MEN with variable supplies and targets for single key component systems has been proposed and solved. Its formulation leads to a mixed integer nonlinear program (MINLP) that is proven to possess certain properties. Through a stream decomposition approach, this MINLP is shown to have an exact linear programming (LP) formulation, which is employed to determine the minimum utility cost for the problem. It is shown that, for several waste minimization problems, considering variable targets leads to lower utility costs over fixed targets.; Next, MEN synthesis is considered for species with several transferrable components. The state space approach is employed for the first time in the mathematical formulation of this design problem. First, multicomponent mass exchange with thermodynamic relations for each component that are independent of the other components is considered. Through this formulation, networks of isothermal absorbers, adsorbers, extractors and strippers can be synthesized.; Finally, with a view to solve the general multicomponent problem including heat exchange and mass exchange with component dependent equilibria, as in distillation networks, a model for a multicomponent mass exchanger has been developed. This model is shown to possess complex roots for real columns. An algorithm, employing this model, for the design of such countercurrent mass exchangers with finite plates is also presented.; The MEN synthesis methodology developed in this work helps: (1) quantify the economics of plant integration by identifying the minimum utility cost for an MEN, (2) identify the waste reduction and recycling potential existing in a process, and (3) evaluate alternative technologies for a given separation task.; These benefits have been demonstrated through the solution of several waste minimization case studies. |
