Raising forward osmosis brine concentration efficiency through flow rate optimization
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Desal_2015.pdf
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1.95 MB
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Author(s)
Tow, Emily W.
McGovern, Ronan Killian
Lienhard, John H
Date Issued
November 2014
Journal
Desalination
Publisher
Elsevier
Citation
Tow, Emily W., Ronan K. McGovern, and John H. Lienhard V. “Raising Forward Osmosis Brine Concentration Efficiency through Flow Rate Optimization.” Desalination 366 (June 2015): 71–79.
Version
Author's final manuscript
Abstract
An exergetic efficiency is defined in order to compare brine concentration processes including forward osmosis (FO) across a wide range of salinities. We find that existing FO pilot plants have lower efficiency than reverse osmosis plants in the brackish and seawater salinity ranges. High salinity FO, in its current form, is still less efficient than mechanical vapor compression. We show that efficiency is the product of FO exchanger and draw regenerator efficiencies, and therefore FO system energy efficiency benefits from improvements to both. The mass flow rate ratio (between draw and feed flow rates) is identified as a crucial parameter in the design of efficient FO systems because of its effect on exchanger efficiency. We demonstrate a method of thermodynamically balancing an FO system by choosing flow rates that lead to equal osmotic pressure differences at both ends of the exchanger, and show the method's potential to increase the efficiency of current systems by 3–21%.
MIT Department
Massachusetts Institute of Technology. Abdul Latif Jameel World Water & Food Security Lab
Massachusetts Institute of Technology. Department of Mechanical Engineering
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
https://doi.org/10.1016/j.desal.2014.10.034
