A mathematical model for water network synthesis involving mixed batch and continuous units

This paper presents a mathematical model for the synthesis of water networks for systems consisting of process units of different operation modes, namely, truly batch, semicontinuous, and continuous units. By treating a continuous process as a special case of a semicontinuous process, the original problem becomes to synthesize a batch water network comprised of truly batch and semicontinuous units operated cyclically with a fixed schedule. The model is formulated as a mixed-integer nonlinear program based on a unit-tank superstructure including all possible network interconnections. Three modified literature examples are used to illustrate the proposed approach, with both in-plant and interplant water integration analyzed.