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Systematic analysis and optimization of power generation in pressure retarded osmosis: Effect of multistage design
Author(s) -
Li Mingheng
Publication year - 2018
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.15894
Subject(s) - pressure retarded osmosis , dimensionless quantity , work (physics) , limit (mathematics) , stage (stratigraphy) , mechanics , thermodynamics , overall pressure ratio , power (physics) , flux (metallurgy) , osmotic power , mathematics , control theory (sociology) , chemistry , gas compressor , forward osmosis , computer science , reverse osmosis , physics , membrane , mathematical analysis , paleontology , biochemistry , control (management) , organic chemistry , artificial intelligence , biology
This work presents a systematic method for analysis and optimization of specific energy production (SEP) of pressure retarded osmosis (PRO) systems employing single‐stage configuration as well as multistage design with interstage hydro‐turbines. It is shown that the SEP normalized by the draw solution feed osmotic pressure increases with the number of stages as well as a dimensionless parameterγ tot= A totL pπ 0 / Q 0. As compared to the single‐stage PRO, the multistage arrangement not only increases flux and volume gain, but also allows a stage‐dependent, progressively decreasing hydraulic pressure, both of which contribute to enhanced SEP and power density. At the thermodynamic limit where γ tot goes to infinity, the theoretical maximum SEP by an N‐stage PRO system is N ( 1 − q tot − 1 / N)π 0, where q tot is the ratio of the draw solution flow rate at the outlet to the inlet on the system level. For single‐stage PRO, it is no more than π 0 . For infinite number of stages, the theoretical limit becomes ( ln q tot) π 0. SEP under realistic conditions and practical constraints on multistage design are discussed. © 2017 American Institute of Chemical Engineers AIChE J , 63: 144–152, 2018