Exergy Analysis and Performance Improvement of the Wasit Thermal Power Plant Using Particle Swarm Optimization with Reduced Exergy Destruction

Abstract

: Increasing electricity demand and the reduced efficiency of steam power plants operating below their design load highlight the need to improve the performance of existing generating units rather than relying solely on constructing new power plants. This study aims to enhance the exergy performance of the Wasit Thermal Power Plant by adjusting controllable operating variables without modifying the existing plant design or equipment. A component-level exergy analysis was first performed using actual steady-state operating data to identify the major sources of irreversibility. The boiler, turbine group, and condenser accounted for approximately 98% of the total exergy destruction. Based on the exergy diagnosis and sensitivity analysis, four controllable operating variables within safe operating ranges were selected because of their direct influence on the major sources of exergy destruction: main steam pressure (13.5–15.5 MPa), main steam temperature (525 ○ C–540 ○ C), reheat steam temperature (525 ○ C– 540 ○ C), and condenser pressure (0.007–0.013 MPa). These variables were simultaneously optimized using Particle Swarm Optimization (PSO) to maximize the overall exergy efficiency while maintaining a constant fuel flow rate. Thermodynamic and operational constraints related to low-pressure turbine (LPT) outlet steam quality, heater terminal temperature difference (TTD), and drain cooler approach (DCA), condenser feasibility, and mass balance were imposed to ensure physically realistic and safe operating conditions. The optimal values of the main steam pressure, the main reheat steam temperatures, and the condenser pressure are 13.5 MPa, 540 ○ C, 540 ○ C, and 0.008219 MPa, which achieved the highest overall exergy efficiency and the lowest total exergy destruction. As a result, the overall exergy efficiency increased from 34.7% to 36.3%, total exergy destruction decreased by approximately 11.81 MW, and turbine shaft work increased from 249 to 261 MW. The results demonstrate that diagnosis-driven constrained optimization of controllable operating variables can effectively improve the exergy performance of existing steam power plants without design modifications.