Graphical performance characterization of membrane modules for RO and PRO processes
Date
2022-11-05
Authors
Moreira, Luiz
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Abstract
Environmental issues have been stricken our planet in different areas. Current
worldwide problems, for instance, water shortage and the increasing demand for energy
can be mitigated by employing technological mechanisms, such as a well-established
osmotic process for salt water desalination known as reverse osmosis (RO), and a
promising technology for generating power from salinity gradient sources, called
pressure retarded osmosis (PRO). This work aims to mathematically model the core
component of RO and PRO systems, which is the membrane module, working in
different conditions and graphically characterize its efficiency using performance
indicators to support researchers and people in industry to design and implement RO
and PRO systems in a less complex and more reliable way. To reach this goal,
segmented mathematical models of a 5-inch scale Toyobo HP5255SI-H3K hollow fibers
membrane module were developed for the RO and PRO processes using the solution-diffusion and friction-concentration polarization transport models, mass balances and
pressure drop equations. After validating the models and performing simulations, the
performance curves obtained were able to provide the optimum values of inlet
parameters for both RO and PRO processes that led to generate the best results in
terms of volume flow rate and salinity of permeate, recovery ratio, salt rejection rate,
power density and net power output. In addition, some interesting discoveries were
acquired from the results such as an unused portion of membrane area in the radial
direction and the influence of flow velocities on entropy generation, salt and water
fluxes within the membrane module in the RO process, as well as how input
parameters as hydraulic pressures and flow rates impact power generation in PRO
systems and how to mitigate the reverse salt flux in this process. Finally, the possibility
of integrating RO and PRO systems to desalinate salt water and produce power from
the resulting permeate and brine solutions is also discussed and arguments on the
reasons why such systems would not work with current technology are presented.
Description
Keywords
Reverse Osmosis, Pressure Retarded Osmosis, Performance Curves