Feasibility study of a forward osmosis/crystallization/reverse osmosis hybrid process with high-temperature operation: Modeling, experiments, and energy consumption

Abstract

This paper presents a comprehensive analysis of a forward osmosis (FO)/crystallization/reverse osmosis (RO) hybrid process with high-temperature operating conditions to assess its feasibility as desalination technology. A process configuration and draw solute candidates are suggested. A mathematical model was developed to describe transport phenomena at the described operating conditions and an experimental study was conducted to investigate the amounts of water and reverse salt fluxes and to validate the developed model. Based on the experimental data, suitable membrane parameters for each process were estimated, and the applicability of the operating conditions was confirmed. An energy consumption model for the hybrid process was also developed and a comparative study with the conventional seawater reverse osmosis (SWRO) process was conducted. The equivalent work in the hybrid process is around 1.66-2.72 kW h/m(3) when heat-electricity energy cost conversion is considered. The energy requirement of the hybrid process is competitive with that of conventional SWRO process. Of the total energy requirement of the process, thermal energy comprises 0.6-1.1 kW h/m(3). Thus, the energy requirement can be lowered to less than 1.0 kW h/m(3) if very cheap waste energy is available.