Abstract
Salinity gradient resource presents an essential role for power generated in the process of pressure-retarded osmosis (PRO). Researchers proposed several designs for coupling the PRO process with the desalination plants, particularly reverse osmosis technology for low-cost desalination but there is no study available yet on the utilization of the concentrated brine reject from a thermal desalination plant. This study evaluates the feasibility of power generation in the PRO process using thermal plant brine reject-tertiary sewage effluent (TSE) salinity gradient resource. Power generation in the PRO process was determined for several commercially available FO membranes. Water flux in Oasys Forward Osmosis membrane was more than 31 L/m2h while the average water flux in the Oasys module was 17 L/m2h. The specific power generation was higher in the thin film composite (TFC) membranes compared to the cellulose triacetate (CTA) membranes. The specific power generation for the Oasys membrane was 0.194 kWh/m3, which is 41% of the maximum Gibbs energy of the brine reject-TSE salinity gradient. However, the Hydration Technology Innovation CTA membrane extracted only 0.133 kWh/m3 or 28% of Gibbs free energy of mixing for brine reject-TSE salinity gradient. The study reveals the potential of the brine reject-TSE salinity gradient resource for power generation and the dilution of brine reject.
Highlights
Renewable energy by mixing solutions of different concentrations have been investigated for power production by retarded pressure osmosis (PRO) technology [1,2]
The PRO process was proposed for power production and mitigating the environmental impact of brine reject on seawater
The concentration of brine reject was reduced from 80 g/L before the PRO process to about 49 g/L after the PRO process
Summary
Renewable energy by mixing solutions of different concentrations have been investigated for power production by retarded pressure osmosis (PRO) technology [1,2]. The theory of the PRO process dates back to the sixties, to harvest the mixing energy of two solutions having different osmotic pressures. The concentrated solution is partially pressurized before pumping in the PRO membrane to serve as the draw solution in the PRO process. The low concentration feed solution will be on the other side of the PRO membrane. The chemical potential transforms into a hydraulic pressure when the freshwater passes across the PRO membrane. Different designs and hybrid systems were suggested to increase the energy output in the PRO process [4,5,6].
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