Entropy generation in multi-stage flash desalination plants

Snoussi, Ali; Chekir, Nihel; Brahim, Ammar Ben

doi:10.1007/s40095-020-00337-1

“…During the last two decades, a great number of RO desalination stations have been installed and thermal projects are under study. In parallel to this development, there is a growing research effort in the field of desalination [17][18][19][20]. The present work constitutes a continuation of a previous paper [19] where we dealt with the economic assessment of MED-TVC plants using the data of an existing triple-effect unit.…”

Section: Introductionmentioning

confidence: 94%

Second-Law Analysis of a Double-Effect Evaporator with Thermal Vapor Compression

Snoussi

¹

,

BenHamad

²

2021

J. Adv. Therm. Sci. Res.

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In this paper, we present a steady-state analysis of a double-effect evaporator with thermal vapor compression (MED-TVC) installed in the Tunisian Chemical Group (GCT) factory. A thermodynamic model including mass and energy balances of the system is developed and integrated in a Matlab program. The model resolution yields to the determination of the operating parameters of the plant and the Gain Output Rate (GOR) was found to be roughly equal to 5. In a second step, the simulation results served to conduct a second law analysis of the unit. The performance criterion used in this analysis is the second law efficiency, i.e., the ratio of the least theoretical work of separation to the actual work input to the plant. The second law efficiency was found to be 2.4%. The distribution of the irreversibility between the different components of the plant was, in addition, assessed. As a conclusion, it was established that the most irreversibility occurs in the thermo-compressor which contributes with more than 50% to the global imperfection and which presents an exergy efficiency of less than 77%. The remaining irreversibility comes from the three exchangers (the two evaporators and the condenser) with an average contribution of 16%. As it is very difficult to introduce modifications into an existing unit, we assume that the importance of the results is not limited to the studied unit. They serve, rather, as an aid to the future design of a MED-TVC plant.

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“…Nonetheless, it is possible to produce 9000 m 3 /day of distilled water in MSF plants with 30,000 m 3 /day of brine, albeit with exergy destruction rates of 71% [98]. In addition, entropy analysis for various MSF configurations have shown that heat transfer is responsible for 65% to 85% of total exergy irreversibility for each MSF stage [99]; however, it is possible to attenuate the consumption of the water specific energy by using condensing steam turbines [100]. On the other hand, an energy analysis carried out at MSF shows that the greatest destruction of exergy occurs in the pumps and motors of the system [101].…”

Section: Multi Stage Flash Distillation (Msf)mentioning

confidence: 99%

Commercial Thermal Technologies for Desalination of Water from Renewable Energies: A State of the Art Review

Feria-Díaz

¹

,

López-Méndez

²

,

Rodríguez-Miranda

³

et al. 2021

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Thermal desalination is yet a reliable technology in the treatment of brackish water and seawater; however, its demanding high energy requirements have lagged it compared to other non-thermal technologies such as reverse osmosis. This review provides an outline of the development and trends of the three most commercially used thermal or phase change technologies worldwide: Multi Effect Distillation (MED), Multi Stage Flash (MSF), and Vapor Compression Distillation (VCD). First, state of water stress suffered by regions with little fresh water availability and existing desalination technologies that could become an alternative solution are shown. The most recent studies published for each commercial thermal technology are presented, focusing on optimizing the desalination process, improving efficiencies, and reducing energy demands. Then, an overview of the use of renewable energy and its potential for integration into both commercial and non-commercial desalination systems is shown. Finally, research trends and their orientation towards hybridization of technologies and use of renewable energies as a relevant alternative to the current problems of brackish water desalination are discussed. This reflective and updated review will help researchers to have a detailed state of the art of the subject and to have a starting point for their research, since current advances and trends on thermal desalination are shown.

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“…Steam temperature is the only factor that has a significant and positive effect on the distillate flow rate and the production/profit ratio. [93] Entropy analysis for various MSF configurations…”

Section: Multi Stage Flash Distillation (Msf)mentioning

confidence: 99%

Commercial Thermal Technologies for Desalination of Water from Renewable Energies: A State of the Art Review

Feria-Díaz¹,

López-Méndez²,

Sandoval-Herazo³

et al. 2021

Preprint

10

0

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Thermal desalination is yet a reliable technology in the treatment of brackish water and seawater; however, its demanding high energy requirements have lagged it compared to other non-thermal technologies such as reverse osmosis. This review provides an outline of the development and trends of the three most commercially used thermal or phase change technologies worldwide: Multi Effect Distillation (MED), Multi Stage Flash (MSF), and Vapor Compression Distillation (VCD). First, state of water stress suffered by regions with little fresh water availability and existing desalination technologies that could become an alternative solution are shown. The most recent studies published for each commercial thermal technology are presented, focusing on optimizing the desalination process, improving efficiencies, and reducing energy demands. Then, an overview of the use of renewable energy and its potential for integration into both commercial and non-commercial desalination systems is shown. Finally, research trends and their orientation towards hybridization of technologies and use of renewable energies as a relevant alternative to the current problems of brackish water desalination are discussed. This reflective and updated review will help researchers to have a detailed state of the art of the subject and to have a starting point for their research, since current advances and trends on thermal desalination are shown.

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Entropy generation in multi-stage flash desalination plants

Cited by 8 publications

References 20 publications

Second-Law Analysis of a Double-Effect Evaporator with Thermal Vapor Compression

Second-Law Analysis of a Double-Effect Evaporator with Thermal Vapor Compression

Commercial Thermal Technologies for Desalination of Water from Renewable Energies: A State of the Art Review

Commercial Thermal Technologies for Desalination of Water from Renewable Energies: A State of the Art Review

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