Using Double Pressure Heat Recovery Steam Generator Equipped with Duct Burner for Full Repowering a Steam Power Plant and Its Analysis by Exergy Method

摘要

Repowering is defined as adding gas turbine unit(s) to steam cycle and using exhaust gases to increase cycle efficiency. Repowering methods are divided into two main ways: full repowering and partial repowering. In this research Be'sat steam power plant in Tehran has been considered as reference steam power plant. This old power plant has been designed by General Electric Corporation with 31.46% efficiency, whereas its current efficiency is 26.81%. In this research by using full repowering a combined cycle have been designed with double pressure heat recovery steam generator equipped with duct burner and through exergy analysis, the functional parameters of the repowered cycle has been studied in the two states of no duct burner and various modes with duct burner (in terms of the fuel flow feed to duct burner). The results showed that thermal and exergy efficiencies for repowered cycle at without duct burner state are 44.39%, 43.06 % respectively and in other states of using burner in general state thermal and exergy efficiencies are higher than reference cycle. It has been shown by results that in repowered cycle combustion chamber in the gas section and HRSG in the steam section have the highest exergy losses. Also The results showed that by using duct burner and increasing the feed fuel, in general state thermal and exergy efficiencies of repowered cycle, decrease and the temperature of the exhaust gas from stack and the exergy losses by it, the generated steam flow and the generation power increases.