Working principle of CCPP

At first air is extracted from the atmosphere & then filtered by the air filters. The filtered air is then sent to the air compressor in order to compress at high pressure. After that compressed air and gas are sent to the combustion chamber which is ignited by the spark plug. Due to this combustion of the gas high temperature is produced in the combustion chamber and lies between 800 0C to 850 0C.

The hot flue gas produced in combustion chamber then passes through the turbine blades of 2 stages. The produced hot flue gas first enters into the static blade of turbine which acts as a nozzle to increase the velocity of the flue gas. This hot flue gas having high velocity strikes the rotating blade of turbine which in turn rotates the shaft connecting to the rotating blade. This shaft is also connected with the compressor as well as generator. Hence it is called single shaft turbine unit.

Due to the rotation of the shaft, magnet existing in the rotor of generator rotates and produces magnetic flux. This magnetic flux cuts the conductor situated in the stator which eventually produces electricity. This turbine has two sections. One is called HP (High Pressure) turbine and other is called LP (Low Pressure) turbine. While passing through the HP turbine, the temperature & pressure of the flue gas drops to some extent. The flue gas then passes through the LP turbine and temperature reduces to 500 0C. Consequently the flue gas goes to the damper as exhaust & is released to the atmosphere through stock.

In case of GT-1, this exhaust gas is passed through a waste heat recovery unit (WHRU) where a boiler which uses heat from flue gases to produce steam. WHRU consists of a column of evaporator through which water is circulated to produce steam. It also consists of an Hp drum, deareator and some centrifugal pumps. At first, water is pumped into the deareator to remove all kind of dissolved gases such as O2, CO2 etc.

From deareator water is pumped by LP pump to LP evaporator to take some heat from exhaust gas and then again sent to the deareator. Next water is pumped to the forced flow section by feed pump to take more heat from exhaust gas and sent to the HP steam drum. In HP steam drum there resides actually a mixture of steam and water.

This saturated steam from HP steam drum is then sent to the HP evaporator by HP pump to pressurize it. This high pressure steam is then sent to the super heater to become superheated steam. This superheated steam is then sent to turbine by an arrangement of pipe system through CIES valve. The thermal energy contained in the steam rotates the steam turbine blades.

The shaft connected to the turbine blades also rotates the magnet of generator. Due to the rotation of electromagnet, magnetic flux cuts on the generator winding. In this way, a voltage is induced in the conductor and electricity is produced. When steam is passed through the HP turbine section the pressure and temperature of the steam becomes very high and then gradually decreases while passing through the LP turbine.

The exhaust low pressure steam came out from the LP turbine is condensed in the condenser by the help of river water. This condensed steam is termed as condensate. This condensate is then again passed to the deareator by condensate pumps. If there is any shortage in condensate then some make up water is pumped by makeup pump to compensate the loss.