Evaluation of advanced three-stage membrane desalination technologies for efficient industrial brine concentration

Graph of osmotic pressure versus NaCl concentration, showing different pressure-driven reverse osmosis regimes up to saturation. The development of energy-efficient concentration processes is essential to facilitate the industrial reuse of brine. This study assesses a calculated three-stage membrane process, comparing configurations operating at 80 and 120 bar using experimentally characterized, commercially available 4-inch spiral wound membrane elements. Experiments are conducted across a systematic range of NaCl feed concentrations from 60 to 110 g/L and target final concentrations of 220–280 g/L. Based on the experimental results, a process design is proposed, and the energy demand as well as the required membrane area are calculated. The results demonstrate that, under the selected experimental correlations and calculation assumptions, the 120 bar configuration outperforms the 80 bar variant in terms of specific energy consumption and required membrane area, primarily due to reduced internal recycle streams. Across all investigated scenarios, the specific electric energy consumption ranges from 16.5 to 37 kWh/m3 at 80 bar and from 9.4 to 17.5 kWh/m3 at 120 bar. The 80 bar configuration approaches the energy demand of mechanical vapor compression (20 – 35 kWh/m3), while the 120 bar configuration maintains a competitive advantage across all investigated scenarios. The contribution of energy recovery is found to be modest, not exceeding 15%.