EXHAUST SYSTEM WITH SILENCER

•     Function of Exhaust System:
  

−The exhaust system guides exhaust gas from the gas turbine via the exhaust diffuser to the heat recovery steam generator (HRSG) of a combined cycle power plant and finally to the atmosphere through the main stack.−After leaving the last stage of the gas turbine, the exhaust gases are directed through an exhaust system, which includes an exhaust plenum mounted on the outlet end of the turbine. The exhaust plenum directs the exhaust gas into the exhaust ductwork, which transports the hot gases into the inlet ductwork of the heat recovery steam generator (HRSG) for utilization of its thermal energy. The exhaust system includes an expansion bellows that allows for the thermal movements of the plenum and exhaust ductwork.−Silencer is installed in the HRSG main stack. Silencer should be installed to reduce noise at stack outlet because hot temperature exhaust gases from gas turbine makes noise. Therefore, splitter in silencer made of material to absorb noise. Silencer outlet sound level shall be maintained 85 dB(A) at all operating condition.

• The major parameters of the exhaust system are:

−Exhaust gas flow at base load    :  616.2 kg/s (When Fuel is Gas)

                                                               610.9 kg/s (When Fuel is Oil)
−Exhaust gas temperature with compressor  :  607.6°C (When Fuel is Gas)

   inlet temperature 35°C at base load                  557.4°C (When Fuel is Oil)
−Pressure loss at turbine outlet for both  :  36.3 mbar  fuel (i.e. gas and oil)

• The major components of the exhaust system are:

−Exhaust Diffuser
−Exhaust Plenum
−Expansion Joint
−Exhaust Duct

•     Exhaust Diffuser:

−Gas turbine exhaust is fed through the exhaust diffuser, the downstream exhaust system and into the main stack to utilize the maximum thermal energy from hot exhaust flue gases in the HRSG; in the process static pressure increases as a function of the decrease in velocity.−A manhole located in the upper portion of the exhaust diffuser is provided to permit access into the exhaust diffuser during inspections.

• Exhaust Plenum:

−The function of the exhaust plenum is to direct the gas turbine exhaust gases into the exhaust ductwork.

• Expansion Joint:

−The function of the expansion joint is to allow for the thermal movements of the exhaust plenum and exhaust ductwork.

• Exhaust Duct:

−The function of the exhaust duct is to transport exhaust gases from the outlet of the gas turbine into the inlet ductwork of the heat recovery steam generator (HRSG).

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