Step 1 - Coal Supply
Coal for Liddell and Bayswater power stations comes from NSW coal mines. Coal is transported via rail or overland conveyors into the power stations. Once at the stations the coal is fed into the mills. The milling process pulverises the coal into a fine powder.
Step 2 - The Boiler
The pulverised coal is then blown into the boiler furnace chamber, where it is burned to convert water into high pressure steam. The typical boiler furnace temperature is 1500 degrees.
The boilers convert purified fresh water to steam in over 450km of tubes which line the boiler furnace walls.
The burning of coal results in the production of ash and various gases. The ash is captured and then stored or used in road manufacture and cement production. The gases are filtered to remove all particulate matter and then released through the emission stack.
Step 3 - Steam Turbine
The steam created in the boiler is then injected at high pressure into the turbine cycle. The steam turns turbine blades which are mounted along the turbine drive shaft.
For maximum efficiency, the steam is returned to the boiler and reheated after its energy is partially spent driving the first stage of the turbine cycle. The first stage is the High Pressure Turbine, where the blades are smallest in diameter.
The reheated steam then passes to the second stage or Intermediate Pressure Turbine, which has larger blades. Then as heat and pressure drops, the steam reaches the last stage or Low Pressure Turbines, where the blades are largest.
The spent steam is then cooled back to water for re-use as it passes over a series of condenser tubes through which cold water is circulated.
Step 4 - Electrical Generator and Transmission
The electrical generator consists of two main sections. The first is a revolving section called the rotor, which is directly joined to the turbine drive shaft. The second is the stator, which is a series of coils grouped cylindrically in the stationary shell around the rotor.
The rotor, which is really an electro-magnet, revolves at high speed courtesy of the turbine cycle, and generates electricity in the stator.
The electricity is produced by the generators at 23,000 volts. It then passes through a transformer which increases the voltage to 330,000 volts.
From the transformer the electricity is passed into the adjacent power station switchyard. Transmission lines carry the electricity from the switchyard to cities and towns across south eastern Australia.
Step 5 - Water Supply
The generation of electricity in coal-fired power stations requires large amounts of water. There are two separate water systems required, one for the steam production cycle, and one for cooling purposes.
Most of the water in both systems is used over and over again. Lake Liddell is the cooling water source for Liddell Power Station. Bayswater Power Station has cooling towers that use an evaporative draught cooling system.
