An Energetic and Exergetic Analysis is conducted on a Steam Turbine Power Plant of an existing Phosphoric Acid Factory. The heat recovery systems used in different parts of the plant are also considered in the analysis. Mass, thermal and exergy balances are established on the main components of the factory. A numerical code is established using EES software to perform the calculations required for the thermal and exergy plant analysis. The effects of the key operating parameters such as steam pressure and temperature, mass flow rate as well as seawater temperature, on the cycle performances are investigated. The minimum Exergy Destruction Rates are obtained for the condensers and deaerators followed by the blowers and turbines. The Steam Turbine Generator STGI presents the maximum irreversibility rates of about 4.1 MW. For the explored ranges of HP steam pressure, the energy efficiencies of steam turbine generators STGI and STGII increase of about 1.37 % and 8.8 % respectively. While the exergy efficiencies increase of about 2.46 for STGI and 6.8 % for STGII. In the same way optimum HP steam flow rate values, leading to the maximum exergy efficiencies are defined.