USING TWO TYPES OF HEAT RECOVERY STEAM GENERATOR FOR FULL REPOWERING A STEAM POWER PLANT AND ITS ANALYSIS BY EXERGY METHOD

Repowering is defined as adding gas turbine unit(s) to a steam cycle and using exhaust gases to increase cycle efficiency. There are two main methods of repowering: full repowering and partial repowering. Full repowering method is used as a common and tested method to reconstruct old steam powerplants and enhance their efficiency. In this research Be’sat steam powerplant in Tehran has been considered as a reference steam power plant. This old power plant has been designed by General Electric Corporation with 31.46% efficiency, while its current efficiency is 26.81%. Two separate combined cycles with two different heat recovery steam generators have been designed by full repowering (dual pressure, single pressure). Thermal and exergy efficiencies of the repowered cycles have been computed by exergy analysis; their weaknesses and strengths in using gas turbine exhaust gas exergy have been investigated. It has been indicated by the results that thermal effiency and exergy for single pressure state are 41.84%, 43.24% and for dual pressure state are 43.06%, 44.39% respectively. It can be inferred from results that in both cycles combustion chamber in the gas section and HRSG in the steam section have the highest exergy losses

Keywords:

Steam cycle , Repowering , Heat Recovery Steam Generator , Exergy analysis , Efficiency