COAL FIRED POWER PLANTS

Coal-Fired Power Plant:

 

 How a Coal-fired Power Plant works:

1. 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.