Synthesis of integrated membrane desalination and salt production networks

The development of desalination processes that are coupled with simultaneous salt production opportunities are increasingly receiving attention by the scientific community. This work is the first to propose a superstructure-based optimization approach that enables a systematic identification of high performance designs for such systems. The approach considers hybrid seawater reverse osmosis (SWRO) and nanofiltration (NF) membrane desalination together with salt production processes (SPPs). The proposed mathematical formulation has been developed based on a membrane superstructure, which mainly consists of SWRO, NF, and SPP as its primary synthesis units. The various connectivity options between synthesis units has also been explored in this work. For instance, SWRO and NF membranes follow slightly different connectivity patterns due to NF membrane's lower rejections for monovalent ions. The objective function identifies the minimum cost network embedded in the superstructure. The proposed method is illustrated with an example involving SWRO and NF membrane units as well as two different SPP options. The example highlights potential savings in water production cost as a consequence of salt value extraction. It further illustrates the benefits of integrated design of membrane desalination systems coupled with salt production processes over sequential designs of desalination processes followed by end-of-pipe salt production.