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Thermodynamic and Economic Study of the Performance Improvement of Hybrid Desalination Plants

Ghofrani, Iraj | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54107 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Mousavi, Ali
  7. Abstract:
  8. In the present study, for cost-effective brine elimination of desalination plants, a hybrid system consisting of a multiple-effect distillation unit and a humidification-dehumidification unit is proposed. The development process of the hybrid system was carried out in two main steps: 1) evaluation of electricity-driven and heat-driven humidification-dehumidification brine concentrators 2) redesigning the humidification-dehumidification unit according to the results of step one and hybridization the unit with a multiple-effect distillation system. All the steps are assessed using the energy, exergy, exergoeconomics, and exergoenvironmental tools.Among the three heat-driven and electricity-driven configurations for the humidification-dehumidification unit, the heat-driven design was considered to hybridize with the multiple-effect distillation unit because of the higher exergy efficiency. Then the second law efficiency of the humidification-dehumidification system is enhanced by implementing bubble-column humidifiers and dehumidifiers and employing the multi-staging technique. Finally, the improved humidification-dehumidification unit is combined with the multiple-effect distillation unit with a thermocompressor, such a way that a large portion of the steam of the final effect of the multiple-effect distillation unit is condensed in the heater of the humidification-dehumidification unit instead of the condenser.A jump in the values of the specific exergy destruction, fresh water cost, and fresh water environmental impact was seen in the hybrid systems with a single-stage BRHDH system. However, the specific exergy destruction and cost of the fresh water production of the hybrid system with two and three-stage BRHDH systems are comparable with that of the MED-TVC system. Therefore, in the case of Iran, the proposed hybrid system eliminates the negative environmental effects of the brine discharge by 7 to 23% increase in the cost of fresh water compared to multiple-effect distillation units. As a result, this system can have cost-effective water production along with the brine discharge elimination. If the multi-stage distillation system is not hybridized with the humidification-dehumidification system with a thermocompressor, the water cost increase by up to 10%, and the environmental impact increase by 12% compared to the hybrid design. Also in Iran condition, using the solar parabolic collector to supply some portion of the input heat of the hybrid system reduce the environmental impact between 23 and 32 percent relative to the hybrid system while the fresh water cost was increased between 32 and 53 percent
  9. Keywords:
  10. Desalination ; Solar Desalination ; Exergo Economic Analysis ; Hybrid Desalination ; Minimum Liquid Discharge ; Exergoenvironmental Analysis ; Zero Liquid Discharge

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