Double-acting batch-RO system for desalination of brackish water with high efficiency and high recovery

Davies, Philip A.; Afifi, A.; Khatoon, Fehmeeda; Kuldip, G.; Javed, Shahryar; Khan, Sohail

doi:10.5004/dwt.2021.26995

Cited by 6 publications

(9 citation statements)

References 7 publications

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“…Second, controlling and minimizing downtime between cycles is challenging. Various methods, such as a double-acting piston configuration [14], reciprocating piston configuration [61], free-piston work exchanger [62], and a flexible bladder [63], have been introduced to minimize mixing and downtime. However, scalability and size could pose a constraint.…”

Section: Global Swro State-of-the-art and Practical Minimum Savingsmentioning

confidence: 99%

Practical Minimum Energy Use of Seawater Reverse Osmosis Facilities

Warsinger,

Alnajdi,

Beni

et al. 2024

Preprint

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The global challenges of climate change and water scarcity demand increased energy efficiency of desalination technologies, especially the dominant seawater reverse osmosis (SWRO). While many studies have assessed individual improvements to SWRO like energy recovery devices, their combined potential for maximizing system energy efficiency has not been systematically explored. Therefore, this study combines a comprehensive data collection from 64 facilities, with detailed modeling of conventional, state-of-the-art, and practical minimum energy use configurations. For each of these three efficiency levels, we synthesized performances benchmarks for pump efficiency, membrane permeability, membrane spacer mass transfer coefficient, and pre- and post treatment. We use these parameters to benchmark potential efficiency gains of 39 of the facilities, examine performance across different recovery ratio and feed salinity, and prioritize the most promising innovations. The methodology encompasses detailed process- and component-level modeling, and includes the derivation of a maximum membrane mass trans- fer coefficient from the Chilton-Colburn J-factor analogy. We found that the combined state-of-the-art methods, including semi-batch reverse osmosis, could save 69% of the energy excess beyond the thermodynamic minimum, while the practical minimum, including batch RO, could save 82% of excess energy. The compiled data also show that modern facilities achieve a lower specific energy consumption (SEC) when using isobaric–energy recovery devices (ERD) compared to older devices like Pelton turbines. Factors affecting SEC and energy savings (i.e., capacity, equipment efficiency, and year of installation) are also analyzed for 39 of the SWRO facilities. Further substantial savings can be obtained by improving membrane spacers and shifting to more batch efficient configurations

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Section: Global Swro State-of-the-art and Practical Minimum Savingsmentioning

confidence: 99%

Practical Minimum Energy Use of Seawater Reverse Osmosis Facilities

Warsinger,

Alnajdi,

Beni

et al. 2024

Preprint

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“…More detailed diagrams for batch RO operation in a cyclic mode are available in the literature. 12,13 Consider an ideal batch RO process that has an initial volume of V 0 . The applied pressure P is allowed to vary during the entire duration of operation from 0 to t f .…”

Section: Mathematical Modelmentioning

confidence: 99%

“…If the tank size is much larger than the void space for feed flow in the RO element, it is reasonable to assume that the permeation flux is only a function of time. More detailed diagrams for batch RO operation in a cyclic mode are available in the literature. , …”

Section: Mathematical Modelmentioning

confidence: 99%

“…They further developed a double-acting system that allowed continuous production of water following a pressurization−purge−pressurization−purge cycle. 13 Retentate recycling is an intrinsic feature of batch RO that allows the hydraulic energy in the pressurized concentrate to stay in the system. However, its role in batch RO is yet to be clarified.…”

Section: Introductionmentioning

confidence: 99%

“…They proposed a piston–cylinder assembly that can be used to operate the batch RO without mixing the feed with the solution that is already in the cylinder. They further developed a double-acting system that allowed continuous production of water following a pressurization–purge–pressurization–purge cycle …”

Section: Introductionmentioning

confidence: 99%

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Dynamic Operation of Batch Reverse Osmosis and Batch Pressure Retarded Osmosis

2020

Ind. Eng. Chem. Res.

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Optimal control theory is applied to dynamic operation of batch reverse osmosis (RO) for seawater desalination and batch pressure retarded osmosis (PRO) for power generation. It is proved that the water flux should be constant during the entire operation in order to minimize specific energy consumption (SEC) in RO or to maximize specific energy production (SEP) in PRO. A dimensionless parameter γ = A m L p π 0 t f /V 0 , similar to that used in continuous osmotic membrane processes, is proposed to characterize the energy performance. While the SEC in RO is a monotonic function of recovery and γ, the SEP in PRO is solely a monotonic function of γ. It is shown that batch RO/ PRO excels continuous RO/PRO because it mitigates the spatial variation of flux in a long pressure vessel observed in the latter. The batch operation provides an elegant way to implement continuous multistage RO with interstage pumps and an energy recovery device as well as continuous multistage PRO with interstage turbines. Some trade-off between the energy efficiency and flux is deemed necessary. A preliminary cyclic diagram to operate the batch PRO is proposed.

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