Designing and mathematical modeling of a Multi-Effect Desalination (MED) System Applicable in the Steam Power Plant and Similar Industries

Document Type : Review

Authors

1 M.Sc. Student of Chemical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

2 Associate Professor of Chemical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

Abstract

Using a thermal multi-effect desalination (MED) system for sea water desalination in areas facing with a shortage of appropriate drinking, agricultural or industrial water is a way to get fresh water, which acts on the basis of the evaporation- distillation methods. The incoming seawater temperature together with the other factors is among the main parameters affecting the efficiency of these systems. In this study, to increase the efficiency of the MED system we have presented a new proposal, which includes two condensers and a heat exchanger, and is used to increase the temperature of the input feed. In addition to reduce steam consumption through vapor condensation exited from the flash tank in an attached condenser, the rate of the fresh water production also increases by the proposed design. Mathematical modeling on the basis of mass and energy balance equations, which is implemented in MATLAB software, is used to investigate the influence of various parameters on the efficiency of the process. The modeling results show that the performance ratio (PR) of a multi-effect process with a low and a high number of steps will be increased by using the proposed procedure more than one and 3.5 units, respectively. According to the results, the temperature of the steam entering the first effect has been chosen to be 60oc. Furthermore, With regard to the concentration factor and thermo-compressor efficiency, the optimal effect count of stages will be 3. The number of effects will be decreased to 2 ones, if the new system works with the same performance ratio of old system.

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