A rigorous, mixed-integer, nonlineal programming model (MINLP) for synthesis and optimal operation of cogeneration seawater desalination plants

Abstract

This paper presents a rigorous mixed-integer nonlinear programming (MINLP) model for optimal synthesis and design of dual-purpose seawater desalination plants. The proposed superstructure considers more alternative configurations than the model recently proposed by Mussati et al. [1] and all process equipment is modelled in a rigorous way. The MINLP model introduces binary variables in order to select equipment for the cogeneration plant. The detailed model for the MSF desalter developed by Mussati et al. [2] was considered. The MSF mathematical model involves the real-physical constraints for the evaporation process. Nonlinear equations are used to model all plant equipment rigorously in terms of chemico-physical properties (enthalpies, entropies, vapor pressure) and design equations (efficiencies, NEA, BPE, heat transfer coefficients, momentum balances, among others). The proposed model is not only useful for synthesis, but also for analyzing different design alternatives. The model has been implemented in a general algebraic modelling system [4]. Several study cases were successfully solved by applying the MINLP model. A case study is presented in order to illustrate the model's capabilities.