Thermoeconomic design of a multi-effect evaporation mechanical vapor compression (MEE-MVC) desalination process

A. S. Nafey, H. E S Fath, Abdelnasser Aboukhlewa

Research output: Contribution to journalArticle

86 Citations (Scopus)

Abstract

This work presents thermoeconomic design for a multi-effect evaporation-mechanical vapor compression (MEE-MVC) desalination process. Exergy and thermoeconomic mathematical models of the considered process units are developed and presented in this work. The design data of an existing MEE-MVC (1500 m3/day) desalination process is used for the present analysis. The effect of using external steam to initiate the evaporation process is investigated. The MEE-MVC without external steam is investigated under different operating conditions. The developed Visual Design and Simulation (VDS) package is utilized as a powerful tool for the present analysis. The energy analysis shows that the thermal performance ratio of the considered system with external steam is 8% less than that the system without external steam. Thermoeconomic analysis shows the unit product cost is 29% higher in the system of external steam. The unit product cost of the desalted water at the normal operation (without external steam) is calculated by 1.7 $/m3. For system without external steam, by reducing the pressure ratio of the vapor compressor from 1.35 to 1.15, the capital cost of the compressor is reduced by 16%. The specific power consumption is also reduced by 50%. Sequentially, the unit product cost is reduced from 1.7 to 1.24 $/m3 (27% reduction). Thermoeconomic results show that, reducing the splitter ratio of the brine re-circulation flow rate from 0.5 to 0.25 while the compression ratio is specified by 1.15, the unit product cost decreases to 1.21 $/m3. Using the design condition of the considered MEE-MVC desalination plant, thermoeconomic results show that the minimum unit product cost is obtained at three evaporators. As the unit product cost at two evaporators and three evaporators are almost the same and due to the complexity and maintenance requirements, the system of two evaporators is preferable. By increasing the capacity of the considered process from 1500 m3/day to 5000 m3/day, the results show that the unit product cost at two and three evaporators are almost the same. Design calculations show that increasing the required capacity of the considered system, the unit product cost decreases.

Original languageEnglish
Pages (from-to)1-15
Number of pages15
JournalDesalination
Volume230
Issue number1-3
DOIs
Publication statusPublished - 30 Sep 2008
Externally publishedYes

Fingerprint

Desalination
desalination
Steam
Evaporation
evaporation
Vapors
compression
Evaporators
cost
Costs
Compressors
effect
exergy
product
Exergy
brine
Chemical reactions
Electric power utilization
Flow rate
Mathematical models

Keywords

  • Desalination
  • Exergy
  • Mechanical vapor compression (MVC)
  • Multi-effect evaporation (MEE)
  • Thermoeconomics
  • Unit product cost

ASJC Scopus subject areas

  • Filtration and Separation

Cite this

Thermoeconomic design of a multi-effect evaporation mechanical vapor compression (MEE-MVC) desalination process. / Nafey, A. S.; Fath, H. E S; Aboukhlewa, Abdelnasser.

In: Desalination, Vol. 230, No. 1-3, 30.09.2008, p. 1-15.

Research output: Contribution to journalArticle

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AB - This work presents thermoeconomic design for a multi-effect evaporation-mechanical vapor compression (MEE-MVC) desalination process. Exergy and thermoeconomic mathematical models of the considered process units are developed and presented in this work. The design data of an existing MEE-MVC (1500 m3/day) desalination process is used for the present analysis. The effect of using external steam to initiate the evaporation process is investigated. The MEE-MVC without external steam is investigated under different operating conditions. The developed Visual Design and Simulation (VDS) package is utilized as a powerful tool for the present analysis. The energy analysis shows that the thermal performance ratio of the considered system with external steam is 8% less than that the system without external steam. Thermoeconomic analysis shows the unit product cost is 29% higher in the system of external steam. The unit product cost of the desalted water at the normal operation (without external steam) is calculated by 1.7 $/m3. For system without external steam, by reducing the pressure ratio of the vapor compressor from 1.35 to 1.15, the capital cost of the compressor is reduced by 16%. The specific power consumption is also reduced by 50%. Sequentially, the unit product cost is reduced from 1.7 to 1.24 $/m3 (27% reduction). Thermoeconomic results show that, reducing the splitter ratio of the brine re-circulation flow rate from 0.5 to 0.25 while the compression ratio is specified by 1.15, the unit product cost decreases to 1.21 $/m3. Using the design condition of the considered MEE-MVC desalination plant, thermoeconomic results show that the minimum unit product cost is obtained at three evaporators. As the unit product cost at two evaporators and three evaporators are almost the same and due to the complexity and maintenance requirements, the system of two evaporators is preferable. By increasing the capacity of the considered process from 1500 m3/day to 5000 m3/day, the results show that the unit product cost at two and three evaporators are almost the same. Design calculations show that increasing the required capacity of the considered system, the unit product cost decreases.

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