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Design of a Desalination System with High Recovery Using Membrane Based Systems

Naderi Beni, Ali | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54840 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Mousavi, Ali; Nouri Borujerdi, Ali
  7. Abstract:
  8. Osmotically assisted reverse osmosis (OARO) assimilates high efficiency due to non-thermal processes and accessing high salinity. This makes it suitable for high water recovery for the purpose of zero- and minimal liquid discharge desalination. Moreover, forward osmosis (FO) has low fouling efficiency which makes the operating costs of cleaning and replacement lower. This study aims at incorporating OARO and FO in a novel configuration with multiple inlet of the diluted draw solution to the regeneration section. Pinch analysis with simplifying assumptions was carried out for FO and OARO standalone stages. The results showed that pinch point in FO resides either on the beginning or at the end of the stage while in OARO it can be located between the beginning and end of the membrane. Furthermore, pinch concentration depends on the flow rate and salinity ratios of the interacting streams. Next, simulation is carried out with considering indispensable phenomena for economic optimization using CONOPT solver in GAMS due to the nonlinearity of the problem. The results of the optimization for dewatering influent streams with 75, 75, and 125 g/l and with 50%, 70%, and 50% water recovery showed that the integrated system with 2, 3, and 4 stages of the osmotically assisted reverse osmosis will be needed, and the unit water cost of the product water were 3.67, 5.48 , and 9.21 $/m3. Specific energy consumption for these operating cases were 8.43, 10.71, and 16.95 kWh/m3. Capital and operating cost of the membrane were significant contributions of the unit water cost. Optimal spacer porosity was the minimum possible value so as to reach the minimum structural parameter to contain internal concentration polarization which is the dominant resistance in mass transfer. Finally, sensitivity analysis was done for the cases with constant number of OARO stages for several design and cost parameters. The results showed that optimizing water permeability coefficient in FO and OARO has little effect in decreasing the costs, while optimizing the channel height, increasing the maximum operating pressure of the OARO, and decreasing the structural parameter of the FO has positive and significant effect on saving costs. This configuration can concomitantly address the high energy consumption and fouling issues in brine concentration and is expected to mitigate the environmental consequences of brine disposal for the future in which brine production will be increased
  9. Keywords:
  10. Desalination ; Waste Treatment ; Forward Osmosis ; Reverse Osmosis ; Zero Liquid Discharge ; Osmotically Assisted Reverse Osmosis (OARO) ; Minimal Liquid Discharge

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