COMPARATIVE ENERGY AND EXERGY ANALYSES OF A SIMPLE THERMAL GAS

ABSTRACT

In this project, a thermodynamic analysis of a simple gas turbine system based on the model at Ihovbor Gas Power Plant has been carried out. The analysis considered the first and second laws of thermodynamics, and compared its performance with that of a gas turbine retrofitted with a steam injection module with the aim of power augmentation and optimization for load fluctuations and peak load seasons. The plant efficiencies, rate of irreversibility, and optimal amount of steam to be injected were determined in order to determine the specific features that affect power optimization, and see how they can be improved. The model was simulated using Engineering Equations Solver (EES) by varying selected external and internal factors (ambient temperature, turbine inlet temperature, pressure ratio, steam fraction injection). There was a notable overall increase in the produced power and efficiency of the gas turbine when retrofitted with steam injection. At a steam injection ratio of 0.13% on a total mass basis (0.15% on a mass flow rate of air basis), power went from 126.816MW to 164.311MW, and cycle efficiency went from 33.92% to 36.79%. The highest exergy destruction rate occurs in the combustion chamber, and experienced a notable decrease when steam injection was used. There was also a slight decrease in exergy destruction in the gas turbine, and the effects of steam injection on the compressor was negligible. There was an overall increase in the exergetic efficiency of the plant, and this was due to increased mass flow rate through the system without a corresponding increase in compressor work.