Coal Fired Power Plant Process1. Coal Supply
- Coal from the mine is delivered to the coal hopper, where it is crushed to five centimetres (2 inches) in size.
- The coal is processed and delivered by a conveyor belt to the generating plant.
2. Pulverizer
- The coal is then pulverized, or crushed, to a fine powder, mixed with air and blown into the boiler, or furnace for combustion.
3. Boiler
- The coal / air mixture ignites instantly in the boiler.
- Millions of litres of purified water are pumped through tubes inside the boiler.
- Intense heat from the burning coal turns the purified water in the boiler tubes into steam, which spins the turbine (see number four) to create electricity.
4. Precipitator, stack
- Burning coal produces carbon dioxide (CO2), sulphur dioxide (SO2) and nitrogen oxides (NOx).
- These gases are vented from the boiler.
- Bottom ash, which is made of coarse fragments that fall to the bottom of the boiler, is removed.
- Fly ash, which is very light, exits the boiler along with the hot gases.
- An electrostatic precipitator (a huge air filter) removes 99.4 per cent of fly ash before the flue gases are dispersed into the atmosphere.
5. Turbine, generator
- Water in the boiler tubes picks up heat from the boiler and turns into steam.
- The high-pressure steam from the boiler passes into the turbine (a massive drum with thousands of propeller blades).
- Once the steam hits the turbine blades, it causes the turbine to spin rapidly.
- The spinning turbine causes a shaft to turn inside the generator, creating an electric current.
6. Condensers and the cooling water system
- Cooling water is drawn into the plant and circulated through condensers, which cools steam discharged from the turbine.
- Steam from the turbine also passes through the condensers in separate pipes from cooling water.
- The cold water is warmed by the steam, which condenses back into pure water and circulates back to the boiler to begin the process of generating electricity again.
- Cooling water, now warm from the heat exchange in the condensers, is released from the plant.
7. Water treatment plant: water purification
- To reduce corrosion, water must be purified for use in the boiler tubes.
- Other wastewater systems within the plant collect water used to clean pipes and other equipment, and sludge from the water purification process and other processes.
- Waste water is pumped out of the plant and into the holding ponds.
8. Precipitator, Ash systems
- Ash that builds up on the precipitator's plates is vibrated off and collected in large hoppers or bins.
- Fly ash and bottom ash are removed from the plants and hauled to disposal sites or ash lagoons.
- Depending on the market demand, fly ash produced from TransAlta's three plants is sold to the cement industry for construction.
9. Substation, transformer, transmission lines
- Once the electricity is generated, transformers increase the voltage so it can be carried across the transmission lines.
- Once electricity is delivered to substations in cities and towns, the voltage flowing into the distribution lines is reduced, and then reduced again to distribute electricity to customers.
