1. Boiler

Types of boilers:

a)Water tube

b)Fire tube

c)Special boiler

The function of the boiler is, to provide pressure containment and heat transfer in the form of pressure vessels and tubes for the transmission of heat from the furnace combustion process to the boiler water, steam and reheat steam circuits for generation of high pressure superheated steam and medium pressure reheated steam for the turbine.

Firstly to produce steam we need water. Water is supplied from Jabatan Bekalan Air. This water is sent to the water treatment plant to remove the impurities. From the WTP water is then pumped to the RFWT. From the RFWT water is filled in the boiler drum up to the normal working level, via gravity or by boiler filling pump.

Next we need to heat up the water to produce steam and for that we need fuel to burn. The types of fuel available are natural gas, residual fuel oil and coal.

When fuel is burnt with the mixture of air in the furnace, heat is generated. This heat heats up the water in boiler tubes. The hot water rises to the boiler drum. At the drum the steam is separated from the water and flow to various superheaters and finally to the HP turbine. After the HP turbine the steam is rerouted to the reheater to raise the temperature and flow to the IP turbine and LP turbine.

After the LP turbine the steam flow into the condenser to change its status from steam to water. This water is called as condensate and recycled back to the boiler.

1.1Main components of the boiler

a)Economizer

b)furnace water wall

c)boiler drum

d)stop valves

e)safety valves, air vents, and drainage system

f)superheaters and desuperheaters

g)reheater

h)HP/LP bypass

i)furnace

Furnace:

It is an enclosed area where mixture of air and fuel is burnt. The burnt product is called heat in the form of flue gas. Surrounding the furnace are water wall tubes where, water in the tube is heated up.

a)Boiler Steam Drum

The function of the boiler steam drum is to receive feedwater from the economizer, distribute feedwater to the furnace water wall tubes and receive a mixture of steam and water from the water wall tubes. Internals in the drum separate the steam/water mixture to dry saturated steam and water. The drum distributes the dry saturated steam to the superheaters for further addition of heat.

b)Superheater

The function of the super heater is to add heat to the saturated steam which has been generated in the water walls. As this addition of steam takes place without increasing pressure, the saturated steam is converted to superheated steam.

bb) De super Heater

The function of the de super heater is to reduce the temperature of superheated steam to the designed value by spraying low temperature feed water into steam

c)Reheater

Reheater functions to add further heat, utilizing the heat from boiler flue gas to the exhaust steam from turbine HP cylinder before it’s entry to the intermediate pressure cylinder.

d)Economizer

The function of the economizer is to preheat the feedwater before it enters the steam drum. The economizer consists of number tubes, which are arranged along the gas path.

e)Flue gas

The product of combustion is called flue gas. This flue gas heats up the water, steam and air.

f)Rotary Air heater

The function of the rotary air heater is to raise the atmospheric air from 320C to 2500C by the flue gas.

  1. TURBINE

The function of the turbine is to convert the energy in the steam from the boiler, to mechanical energy to operate the generator.

There are other components associated together with the turbine, such as:

  1. Condenser
  • receive the exhaust steam from the LP turbine and condense it into water.
  • Receive condensate drain.
  • Supply water to extraction pump suction
  1. Condenser cooling water

Sea water or river water flowing through the tubes is used to condense the exhaust steam from the LP turbine.

  1. Lube oil

The function of the lube oil are:

  • To provide lubrication for the bearings
  • To carry away heat generated in the bearings
  • To provide high pressure oil to the hydraulic servo motors for the stop valves
  • To provide actuator oil and lubricating oil to barring gear
  • Supply oil to seal oil system
  1. Extraction steam system

The function of the turbine extraction steam is:

  • to heat condensate water in the LP heater
  • to remove dissolve O2 in the deaerator
  • to heat feed water before it is delivered to the boiler
  1. Condensate system

The exhaust steam becomes condensate water and collected at the condenser hot well. This water is recycled backed to the boiler. From the condenser hot well the water flow to the deaerator via:

  1. Extraction pump
  2. Gland steam condenser
  3. Air ejector
  4. Drain cooler
  5. LP heater
  1. Extraction pump

The function of the extraction pump is to supply sufficient water to the deaerator

  1. Gland steam condenser

The function of the gland steam condenser is to preheat the condensate by using gland steam from the turbine glands.

  1. Air ejector

The function of the air ejector is to remove non condensable gases and vapor from the condenser to maintain a good vacuum and to preheat the condensate water.

  1. Drain Cooler

The function of the drain cooler is to preheat the condensate by using condensate drains from the LP heater

  1. Low Pressure Heater

The function of the LP heater is to preheat the condensate before admission to the deaerator, using the extraction steam from the LP turbine.

  1. Deaerator

The function of the deaerator is to remove dissolve O2 from the condensate and preheat the feed water

  1. High Pressure Heaters(HP)

The function of the HP heaters are to further heat the feed water from the deaerator by utilising extraction steam from the turbine before admission to the economizer.

  1. Generator

The function of the generator is to convert the rotational mechanical energy of the turbine into electrical energy and to supply this energy to plant electrical system and to the national grid.

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