4.2.1 Steam Turbine Description
Steam turbine takes the steam from HRSG and converts its energy (thermal and kinetic) into rotational mechanical energy. The steam turbine consist of high pressure turbine, intermediate pressure turbine and low pressure turbine .the condenser condensate the steam from LPT and the turbine shaft connected with generator to produce electric energy as shown in Fig.(4.10)
The exhaust rejected from the exhaust stack is at high temperature around 600 oC, so we use the combined cycle that is generally defined as one or more gas turbines with heat recovery steam generators in the exhaust, producing steam for a steam turbine generator, so the efficiency will be increased up to 60% and the exhaust rejected from the HRSG stack is at low temperature around 110 oC as shown in Figure (4.11).
The mean purpose of the HRSG is to extract the heat losses of the exhaust and convert the feed water to superheated steam at pressure of 120 bar and temperature of 560 oC which is the specifications required for the operation of the steam turbine. The HRSG system consists of Economizer, Evaporator, Superheater, Steam drums (LP drum, IP drum and HP drum) and Deaerator.
Preheated is receiving condensate water from the condenser, heating up this water. Then water is fed to the deaerator dome, where de-aeration of the non-condensable gases from the water occurs before arriving into the feed water tank. Feed water for LP, IP and HP system is taken from the feed water tank to the drums.
Superheated (SH) steam from the outlet of the HP stage of the steam turbine is fed from the HRSG through the main steam (MS) line and is supplied to the steam turbine and the deaerator. The cold reheat steam flow from the outlet of the HP stage of the steam turbine is mixed with the superheated steam from IP system.
The total steam amount is superheated in the reheater and is expanded through IP turbine. Then the outlet of IP turbine is mixed with the LP superheated (LP SH) steam from LP superheater and is expanded through LP turbine.
The steam is let from the IP turbine to the LP turbine. Before entering the LP turbine LP steam is added via stop and control flap MAC31AA001/011. From the LP turbine the steam is fed to the condenser. During normal operation the whole steam generated in the HRSG flows through the HP/IP/LP steam turbine. The steam is condensed in the condenser.
The bypass stations are installed in parallel to the turbine. Their task is to control the HP and re-heater steam pressure and reduce the steam to conditions suitable for the re-heater (HP bypass) and the condenser (HRH-bypass). They are used for starting and shut down of the steam turbine and in cases when steam turbine is tripped.
Steam turbine takes the steam from HRSG and converts its energy (thermal and kinetic) into rotational mechanical energy. The steam turbine consist of high pressure turbine, intermediate pressure turbine and low pressure turbine .the condenser condensate the steam from LPT and the turbine shaft connected with generator to produce electric energy as shown in Fig.(4.10)
The exhaust rejected from the exhaust stack is at high temperature around 600 oC, so we use the combined cycle that is generally defined as one or more gas turbines with heat recovery steam generators in the exhaust, producing steam for a steam turbine generator, so the efficiency will be increased up to 60% and the exhaust rejected from the HRSG stack is at low temperature around 110 oC as shown in Figure (4.11).
The mean purpose of the HRSG is to extract the heat losses of the exhaust and convert the feed water to superheated steam at pressure of 120 bar and temperature of 560 oC which is the specifications required for the operation of the steam turbine. The HRSG system consists of Economizer, Evaporator, Superheater, Steam drums (LP drum, IP drum and HP drum) and Deaerator.
Preheated is receiving condensate water from the condenser, heating up this water. Then water is fed to the deaerator dome, where de-aeration of the non-condensable gases from the water occurs before arriving into the feed water tank. Feed water for LP, IP and HP system is taken from the feed water tank to the drums.
Superheated (SH) steam from the outlet of the HP stage of the steam turbine is fed from the HRSG through the main steam (MS) line and is supplied to the steam turbine and the deaerator. The cold reheat steam flow from the outlet of the HP stage of the steam turbine is mixed with the superheated steam from IP system.
The total steam amount is superheated in the reheater and is expanded through IP turbine. Then the outlet of IP turbine is mixed with the LP superheated (LP SH) steam from LP superheater and is expanded through LP turbine.
The steam is let from the IP turbine to the LP turbine. Before entering the LP turbine LP steam is added via stop and control flap MAC31AA001/011. From the LP turbine the steam is fed to the condenser. During normal operation the whole steam generated in the HRSG flows through the HP/IP/LP steam turbine. The steam is condensed in the condenser.
The bypass stations are installed in parallel to the turbine. Their task is to control the HP and re-heater steam pressure and reduce the steam to conditions suitable for the re-heater (HP bypass) and the condenser (HRH-bypass). They are used for starting and shut down of the steam turbine and in cases when steam turbine is tripped.
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