Performance of the Pressure Assisted Forward Osmosis-MSF Hybrid Desalination Plant

Daoud Khanafer,Namuun Ganbat,John Zhou,Ali Altaee,Alaa H Hawari,Sudesh Yadav

doi:10.3390/w13091245

Daoud Khanafer, Namuun Ganbat + Show 4 more

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https://doi.org/10.3390/w13091245

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Journal: Water	Publication Date: Apr 29, 2021
Citations: 9	License type: CC BY 4.0

Affiliation: University of Technology Sydney, Qatar University

Abstract

An osmotically driven membrane process was proposed for seawater pretreatment in a multi-stage flashing (MSF) thermal plant. Brine reject from the MSF plant was the draw solution (DS) in the forward osmosis (FO) process in order to reduce chemical use. The purpose of FO is the removal of divalent ions from seawater prior the thermal desalination. In this study, seawater at 80 g/L and 45 g/L concentrations were used as the brine reject and seawater, respectively. The temperature of the brine reject was 40 °C and of seawater was 25 °C. Commercial thin-film composite (TFC) and cellulose triacetate (CTA) membranes were evaluated for the pretreatment of seawater in the FO and the pressure-assisted FO (PAFO) processes. Experimental results showed 50% more permeation flux by increasing the feed pressure from 1 to 4 bar, and permeation flux reached 16.7 L/m2h in the PAFO process with a TFC membrane compared to 8.3 L/m2h in the PAFO process with CTA membrane. TFC membrane experienced up to 15% reduction in permeation flux after cleaning with DI water while permeation flux reduction in the CTA membrane was >6%. The maximum recovery rate was 11.5% and 8.8% in the PAFO process with TFC and CTA membrane, respectively. The maximum power consumption for the pretreatment of seawater was 0.06 kWh/m3 and 0.1 kWh/m3 for the PAFO process with a TFC and CTA membrane, respectively.

Highlights

Published: 29 April 2021Seawater desalination has become a strategic source of clean water worldwide and in the area of the Middle East, where the natural resources are limited [1,2].Reverse Osmosis (RO) represents the primary membrane technology for desalination, while thermal technologies are mainly the Multi-Stage Flushing (MSF) and, to a less extent, the Multi-Effect Distillation (MED) [3,4,5]
In the pressure-assisted FO (PAFO) experiments, a feed pressure between 1 and 4 bar with 1 bar interval was applied to the FS
Results show that permeation flux at 0 bar was around 7.4 Lmh compared to 14.8 Lmh at 4 bar for the thin-film composite (TFC) forward osmosis (FO)

Summary

Introduction

Published: 29 April 2021Seawater desalination has become a strategic source of clean water worldwide and in the area of the Middle East, where the natural resources are limited [1,2].Reverse Osmosis (RO) represents the primary membrane technology for desalination, while thermal technologies are mainly the Multi-Stage Flushing (MSF) and, to a less extent, the Multi-Effect Distillation (MED) [3,4,5]. Despite RO being more energy-efficient [6], thermal desalinations are still prominent in the Middle East especially in the Gulf countries due to their high performance in treating FS of high salinity and low-quality seawater, reliability, and no need for intensive pretreatment of FS [5,7,8]. Besides the fact that the thermal desalination plants produce high-quality freshwater they suffer from scale formation on the heat exchangers, which is one of the drawbacks that affect the efficiency of the desalination process [5]. Scale precipitation adversely impacts the performance of thermal desalination plants and the energy requirements for Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations

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Conclusion