Investigation into design parameters in seawater reverse osmosis (SWRO) and pressure retarded osmosis (PRO) hybrid desalination process: a semi-pilot scale study

Abstract

The performance of a seawater reverse osmosis and pressure retarded osmosis (SWRO-PRO) hybrid system for power generation and seawater desalination was investigated using a pilot-scale system. The draw and feed solutions of the PRO process were SWRO brine and permeate, respectively. The PRO system performed better, meaning it had a higher energy recovery rate, at higher draw solution salinities. The PRO performance was further improved by increasing the flow rate of the draw solution as this reduced the concentration polarization effect in the PRO membrane. The performance of the PRO module was investigated experimentally, and the results were compared with simulations. The maximum power density of the PRO membrane module was 14 W/m² at 28 bar using a solution with 70,000 mg/L of sodium chloride (NaCl) and draw and feed solution flow rates of 20 LPM and 4 LPM, respectively. We estimated the performance of the PRO membrane module using a simulation that incorporated the temperature of the draw solution. Our model can be used to predict the effects of operational conditions including solution concentrations, the flow rate, the flow ratio of the draw and feed solutions, and the temperature of the draw solution in the PRO system.

Keywords:

• Desalination
• Seawater reverse osmosis (SWRO)
• Pressure retarded osmosis (PRO)
• Energy recovery
• Power density

Acknowledgments

This research was supported by a grant (code 13IFIP-B065893-01) from Industrial Facilities and Infrastructure Research Program funded by the Ministry of Land, Infrastructure and Transport of Korean government.

Notes

Presented at 2015 Academic Workshop for Desalination Technology held in the Institute for Far Eastern Studies Seoul, Korea, 23 October 2015