Thermal Power Station Plant

Introduction• 150 MW Thermal power station plant,

produce 450t/hr steam at full load

• The max steam pressure is 150 bar with Super heated steam temperature (537 °C ) and Reheat steam temperature (537 °C )

Unit Overview

• 2 Force Draft Fan is providing the air inlet to the boiler

• FD fan capacity is 330,000 m3 /hr at full load.

• Condenser water pump is used to transfer the condensate water to low pressure heaters (LPH) and feed water tank.

• 3 feed water pump ( FWP)(multi stage pump)is used to transfer water from feed water tank to the boiler

BOILER OVERVIEW

• The boiler has 3 levels of burners.• Level (A):4 burners Level (B): 4 burners• Level (C): 4 burners• The fire type is diagonal.• The Flame detector sensor is used to detect

the flame of the burner

Cooling fan is used to cool The Flame detector sensors from high temperatures

Boiler Fuel System

There are three types of fuel used :• Natural gas• Heavy fuel oil (mazot)• Light oil ( solar )Natural gas is usually used in start up due to it’s low flame

temperature to avoid the thermal stress in the boiler tubes at starting.

• The flame temperature of any fuel must not exceed 1600 °C to avoid ( NOx)

• At the starting the boiler temperature is very low so it will absorb a lot of quantity of heat from flue gas temperature, if the fuel contain a sulfur and it’s temperature equal the dew point temperature, Sulfuric acid (H2SO4 ) will produce and make Corrosion in the chimney and air pre heaters.

• So, it’s not recommended to use ( HFO ) at starting.

BURNERS

HFO burner:• Fuel burner valve • Atomizing steam valve • Cooling steam valve

One igniter for HFO burner and natural gas burner

One air damper for HFO burner and natural gas burner

• Atomizing steam pressure in HFO burner must be above 1 bar of the (HFO) pressure for good atomization.

Thermal Power steam start up• Start up sequence :1. Boiler purge2. Natural gas leak test3. Start firing to build a steam pressure in the

drum ( 60 bar )4. Start sealing system5. Start ejectors to make vacuum pressure in the

condenser6. Synchronization

Boiler Purge• Boiler purge means getting air in the boiler with

high velocity to get rid of any flue gases and ashes .• There are condition must be achieved to start purge.• Air flow must be 30% from total air flow to start

purge• ALL main fuel valves and ignition valves must be

closed and all fuel valve vents and ignition vents must be opened to ensure no fuel getting in the boiler during purge.

• Purge time= 300 Sec

Natural gas leak test• The importance of natural gas leak test process is to

detect leakage in the burners.• BY compressing natural gas to the burners with

constant pressure, main natural gas valve closed and all the vents are closed.

• IF there is a leakage in the burner, the natural gas constant pressure will decrease.

• IF there is no leakage, the natural gas constant pressure remains constant.

Sealing System

• Portion of steam is used as sealing steam (labyrinth seal) to prevent leak in and leak out in the turbine.

• Leak out: ( leakage steam from turbine to atmospheric air)

• Leak in: ( air leakage from atmospheric air inside LP turbine and condenser)

• Leak out occurs in ( HP & IP ) turbines due to the high pressure of the steam.

steam pressure is greater than the atmospheric air pressure in (HP&IP).

• Leak in occurs in LP turbine due to the atmospheric air pressure is greater than the steam in LP turbine

Synchronization

• Synchronization: is the process of matching the speed ,frequency

and voltage of a generator to a running network.