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Water Treatment Capacity of Forward-Osmosis Systems Utilizing Power-Plant Waste Heat

Zhou, Xingshi, Gingerich, Daniel B., Mauter, Meagan S.
Industrial & Engineering Chemistry Research 2015 v.54 no.24 pp. 6378-6389
air, distillation, electric power, energy efficiency, engineering, heat recovery, hydrodynamics, mathematical models, osmosis, power generation, reaction kinetics, steam, wastewater, water treatment, United States
Forward osmosis (FO) has the potential to improve the energy efficiency of membrane-based water treatment by leveraging waste heat from steam electric power generation as the primary driving force for separation. In this study, we develop a comprehensive FO process model, consisting of membrane separation, heat recovery, and draw-solute regeneration (DSR) models. We quantitatively characterize three alternative processes for DSR: distillation, steam stripping, and air stripping. We then construct a mathematical model of the distillation process for DSR that incorporates hydrodynamics, mass- and heat-transport resistances, and reaction kinetics, and we integrate this into a model for the full FO process. Finally, we utilize this FO process model to derive a first-order approximation of the water production capacity given the rejected-heat quantity and quality available at U.S. electric power facilities. We find that the upper bound of FO water treatment capacity using low-grade heat sources at electric power facilities exceeds process water treatment demand for boiler water makeup and flue-gas-desulfurization wastewater systems.