Combined cycle power station

In combined cycle power stations there are two types of turbines gas turbine and a steam turbine. Gas turbine has three stages compressor, combustion chamber and turbine. Then flue gas from the gas turbine is sent to the steam power station. In some combined cycle power station flue gases flows through a diversion damper. Therefore that plants can be operated as both combined cycle and open cycle. (Ex: Kalanithissa CCP in Sri Lanka).

The flue gases from the gas turbine is sent to the heat recovery steam generator (HRSG). It recover heat from the flue gases and produce high pressure and low pressure steam.  

Heat recovery steam generator (HRSG)

Upper part of HRSG is LP part and the bottom part is HP part. Water from treatment plant is preheated and send to the feed water tank. Before store in feed water tank dearator is used to remove oxygen from the water. From this tank preheated LP preheater and HP economizer. Let’s take the LP part. After preheating that water is sent to the LP drum where saturated water and steam is in equilibrium. Saturated water from LP drum is taken out and continuously heated by LP evaporator. Saturated steam in the drum is taken out to drive the LP steam turbine.

Similar procedure for HP also. HP steam is fed to the HP turbine and then they are sent to the LP steam turbine.