On comparison of three multi-feed osmotic-mediation-based configurations for brine management: Techno-economic optimization and exergy analysis

This study aims at analyzing the performance of three units known as low salt rejection reverse osmosis (LSRRO), split-feed counterflow reverse osmosis (SF-CFRO), and split-brine counterflow reverse osmosis (SB-CFRO) and implementing them in a modified multi-stage multi-feed counter-current membrane with cascade recycle for dewatering hypersaline streams to the salinity appropriate for crystallizers' feed. Exergy and primitive pinch analysis showed that dewatering is limited in SF-CFRO as the permeate inlet dictates the maximum salinity difference at the pinch point as well as high frictional pressure loss in the permeate channel. SB-CFRO and LSRRO units can reach high salinities by increasing permeate to concentrate flow rate and salt permeability, respectively but their efficiency drops due to transport-stemming exergy destruction. Optimizing the multi-stage systems showed that SB-CFRO, LSRRO, and SF-CFRO implemented systems can dewater 70 g/L influent to 234 g/L effluent with unit water cost of 3.44, 3.77, and 3.63 $/m(3) and with corresponding specific energy consumption of 8.66, 16.82, and 9.47 kWh/m(3), respectively. Furthermore, it was shown that the influent with salinity less than 70 g/L should be delivered to the first inlet while at higher salinities up to 90 g/L it should be given to the second inlet.

Automated summary

This study analyzes the performance of three units (LSRRO, SF-CFRO, and SB-CFRO) and their implementation in a modified membrane system for dewatering hypersaline streams. The optimized systems can achieve high salinities and reduce water cost, with varying specific energy consumption. The findings also suggest the appropriate inlet for different influent salinities.