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Treatment of highly saline brines using a static freeze crystallisation process

Mansour Ahmed, Darren Oatley-Radcliffe Orcid Logo, Paul Williams Orcid Logo

DESALINATION AND WATER TREATMENT, Volume: 213, Pages: 1 - 25

Swansea University Authors: Darren Oatley-Radcliffe Orcid Logo, Paul Williams Orcid Logo

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DOI (Published version): 10.5004/dwt.2021.26672

Abstract

Pilot and semi-pilot plants using the static freeze crystallisation process were investigated for concentrating reverse osmosis (RO) brines with different salinities. The pilot plant results revealed that the crystallisation experiments (without a sweating process) operating at a temperature of –4°C...

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Published in: DESALINATION AND WATER TREATMENT
ISSN: 1944-3994 1944-3986
Published: Desalination Publications 2021
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URI: https://cronfa.swan.ac.uk/Record/cronfa56319
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Abstract: Pilot and semi-pilot plants using the static freeze crystallisation process were investigated for concentrating reverse osmosis (RO) brines with different salinities. The pilot plant results revealed that the crystallisation experiments (without a sweating process) operating at a temperature of –4°C achieved a permeate concentration and water recovery ratio of 3.46 wt.% and 73%, respectively, indicating permeate of near ocean seawater standards. As a result, the treated water can be further desalted by the seawater RO plant. As for the case of concentrated RO brine (9.78 wt.%), a semi-pilot plant using feed stage with and without the sweating process was assessed. Before perform-ing the sweating process, the results showed that the permeate concentration was reduced from 9.78 to 8.40 wt.% by decreasing the cooling rate of the crystallisation process from –0.80 to –0.48°C/ min. For the case of the crystallisation rate of –0.80°C/min with the sweating process, the permeate concentration was reduced from 9.78 to 4.50 wt.% when the crystal mass ratio reached 35.64%. For the case of the crystallisation rate of –0.48°C/min, the permeate salinity was further reduced by the sweating process, where the permeate concentration was lowered from 8.40 to 3.68 wt.% when the crystal mass ratio reached 36.25%. In general, the salt rejection ratio increased whereas the water recovery ratio decreased as the cooling rate, crystal mass ratio, and sweating time increased.
Keywords: Freeze-melting process, Freezing desalination technologies, Melt crystallisation process, Reverse osmosis (RO) concentrate, RO retentate
College: Faculty of Science and Engineering
Start Page: 1
End Page: 25