Design of a Thermal Separation Process for Draw Solution Recovery in Forward Osmosis Desalination Plant

Abstract

The optimal design of a draw solution recovery process for a forward osmosis desalination plant is studied. The previous researches in forward osmosis (FO) desalination are mainly focused on the water permeability and salt rejection of semi-permeable membrane. However, relevant engineering issues such as recovery of draw solution and energy efficiency of process should be also resolved to commercialize a FO desalination process.

In this study, a continuous process is designed using a distillation column to separate draw solution and permeated water. The optimal design of the process is suggested achieving the minimum production cost while purity of product water is maintained at drinkable level. For case studies, ammonium bicarbonate, ammonium hydroxide and ethanol are employed as draw solutes which are selected by the screening method based on property database in our previous research. Each draw solute system is individually designed to handle redissolving or reconcentrating problems of each case.