Coal-fired Power Station

COAL
 

Coal is a fossil fuel formed by the decomposition of land plants that have accumulated in swampy
or low-lying areas. 

Millions of years ago, the continual build-up of decaying plants started the process of becoming coal. Humification, or the rapid decaying of plant materials, results in the formation of peat. The peat becomes covered with new sediment layers. The lack of air reaching the peat starts the second step of the coalification process. 

The combined effects of time, temperature, and pressure convert the peat into brown coal, then
sub-bituminous coal, bituminous coal, and finally anthracite. The last three coals in this process
are usually called black coal, the coal mined for power generation at Hazelwood and Loy Yang B
is brown coal, in which the process of coalification began 45 million years ago.  

The main difference between brown and black coal is brown coal has a much higher moisture content. The brown coal at Hazelwood and Loy Yang B has between 60% and 70% moisture, whereas black coal has between 8% and 12%.   


THE ELECTRICITY GENERATING PROCESS

Hazelwood Power Station   

The Hazelwood mine covers an area of over 800 hectares. The coal is mined by bucket-wheel dredgers and is transported to the power station by a 40 kilometre conveyor system and into
a pulverising mill.  

To reduce the high water content, it is crushed and dried into a very fine powder which allows it to burn more easily. The intense heat from burning the coal turns water in the boilers into super-heated steam. The water in the boiler is contained within thousands of pipes. When the coal is burnt a lot
of ash is produced.  

This ash by-product is processed by electro-static precipitators which capture 95-99 per cent
of the dust before allowing the hot gases to escape into the atmosphere via giant chimneys.
The high pressure steam from the boiler is injected onto the blades in the steam turbine causing
the blades to rotate at 3000 revolutions per minute. 

The turbine turns a generator (which contains an electromagnet) at very high speed, (about 50 times
a second), inside copper wire conductors. This generates electricity. As the steam leaves the turbine
it is converted back into water in the condenser. The pipes inside the condenser are full of cool water. The majority of power stations use river water and cooling towers to cool the steam from the turbines.

Hazelwood uses a different cooling system which is a purpose built artificial lake rather than cooling towers as a cooling medium.  

The power station deals with the huge volumes of heated water using an artificial lake southeast of the power station. Known as the Hazelwood Pondage, this artificial lake accepts the station’s water and allows the waste heat to escape safely into the air.  

Hazelwood pumps water at about 35 degrees into the eastern channel of the Pondage.
This circulates, cools to about 23 degrees and is pumped back into the station where it is used
in the condensers to cool the super-heated turbine steam.  

The electricity that is generated at the plant has to be transformed into a higher voltage (500 kV)
so that it can travel across the National Grid. It is then transformed into lower voltage (240 V)
to be used in our homes, schools and factories.    

QUICK FACTS  

The BoilersThe PrecipitatorsThe Chimneys The Turbine Generators

Please click on the link below to access information about the electricity generation process
of our other brown coal power plant, Loy Yang B.
Loy Yang B Technical Overview.