This paper presents a steady state analysis of a multi-effect thermal vapor compression desalination plant (MED-TVC) installed in the Tunisian Chemical Group (GCT) factory. A thermodynamic model includes mass and energy balances of the system are presented. An economic model is developed to estimate the cost of produced water ($/m 3 ). The proposed models to minimize the total annualized cost (TAC) of the desalination unit are based on a combination between the process simulator Aspen HYSYS and Matlab. The effects of the operating parameters variations on the system's performance were studied. The simulation results show a good agreement with the industrial data of the pilot unit.