(176a) Design of Non-Isothermal Multicomponent Process Water Networks

This paper presents a new method for solving the water reuse/recycle with heat integration problem in process complexes. Despite the fact that many methods have been developed for the optimization of process water networks, solving the problem considering heat recovery has been addressed only by a handful of methods, none of them in one single one-step mathematical programming procedure.

The procedure is based on mixed integer non-linear mathematical programming (MINLP). A new superstructure for heat exchanger network (HEN) synthesis capable of exploiting unique features of water networks, like non-isothermal mixing of different streams (providing potentially more cost-effective solutions) is proposed. The model is an extension of the Yee and Grossmann model for heat exchangers, allowing for streams to have variable temperature targets and also allows them to mix/split. This model is used in conjunction with a multicomponent water allocation set of constraints. Water from each process can either mix with other wastewater or with freshwater and be sent to another process or to the HEN for temperature conditioning.

An example is presented to illustrate the synthesis of heat integrated water networks using the proposed approach.