Energy requirements of ammonia–carbon dioxide forward osmosis desalination

The energy requirements of ammonia–carbon dioxide forward osmosis (FO) desalination are predicted by the use of chemical process modeling software (HYSYS). The FO process is modeled using single or multiple distillation columns to separate draw solution solutes from the product water for solute recycling within the FO system. Thermal and electrical energy requirements of the process are calculated, as well as a combined term for equivalent electrical work. The results of the simulations are compared to the energy requirements of current desalination technologies. Energy savings of FO compared to current technologies, on an equivalent work basis, are projected to range from 72% to 85%. Forward osmosis desalination is in an early stage of its development, and several areas of future work promise opportunities to improve its energy utilization and cost.