Thermo-Economic Evaluation of Water and Power Cogeneration Process through Thermal Desalination near a Back Pressure Combined Cycle

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Abstract

In this paper a comprehensive model is proposed to simulate combined cycle water and power process (CCWP) based on thermal desalination. In order to verify the performance of model, Al-Taweelah cogeneration plant in UAE is thermodynamically simulated by Thermoflex V.19 and the results are compared with actual operating conditions. Considering shortcomings of mentioned unit, a cogeneration combined cycle is configured based on conventional power generation units in Iran. In this configuration, thermal desalination units utilize exhausting steam from a back pressure turbine as energy source. Desalination processes which are investigated in present study include Multi-Stage Flash (MSF) and Multi-Effect Distillation (MED). Results show that increasing the backpressure from 6 to 40 bars decreases the electrical efficiency of cogeneration unit from up 20%, compared to a single-purpose one. It also leads to increment of power generation cost up to 67 %, but results in 23% of fuel saving. The electric power consumption of MSF unit is very high, about 3.3 times of that of MED. This fact implies that the production cost of MSF is 12.5% more than that of MED, which remains almost constant at 0.88 $.m-3 by changing the backpressure

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