09-07-2012, 02:42 PM
THE NRG PROCESS
58194_Project_Sheet_7_-_NRG_-_The_Process.pdf (Size: 772.93 KB / Downloads: 138)
1. Coal arrives on site by train and is dumped onto a system of conveyor belts to be checked and weighed before being moved to
the coal bunkers or the stockpile.
2. The coal is dispersed to and from the stockpile by two stacker reclaimers at a rate of 800 tonnes per hour.
3. The coal travels on conveyor belts.
4. Coal transfer tower.
5. Coal bunkers, where coal is fed into pulverising mills.
6. At the pulverising mills the coal goes through pulverisers and crushed into a fine granular state by crusher hammers. This
granular coal then passes through a two-stage pulverising process: first it gets rubbed on coal pegs to reduce the particle size, and
then it is rubbed on other coal until the right minute particle size is reached.
7. Air Inlet: An electric air heater is used to completely dry the coal. The coal and hot air mix in the chute to the mill, and all the
moisture is driven off as steam in the crusher-dryer section of the pulveriser.
8. The forced draught fan forces air through pre-heaters.
9. Air pre-heaters.
10. Hot air duct where hot air is directed to burners or pulverising mills.
11. Burners.
12. Furnace, where coal mixes with hot air and burns at high temperatures.
13. Tubes inside the boiler. (Heat produced in the boiler raises the temperature of water circulating in the tubes to produce steam.)
14. Steam drum where steam passes through at high pressure (16,890 kilopascals)
The Energy Process
15. Steam is heated further in superheater.
16. Steam is fed through high pressure cylinder of the steam turbine at 541°C, returned to the reheater and then passed
through the intermediate and low pressure cylinders of the turbine. (The steam turbine converts steam energy into mechanical
energy in the form of a turning rotor).
17. Intermediate and low pressure cylinders.
18. Reheater.
19. Steam cooled in condenser.
20. Seawater from Auckland Inlet is used to cool steam in the condenser.
21. Feed pump pumps condensed steam (condensate) through the economiser.
22. Condensate pumped through the economiser goes back to the steam drum (14) to be reheated.
23. Combustion gases pass through the air preheaters to the fabric filters consisting of 7,500 bags that remove any ash dust
particles before discharging it up the stack.
24. The induced draught fan forces cleaned gases into the main flue and out through the 153 metre chimney.
25. Chimney.
26. Rotating alternator converts mechanical energy into electrical energy, generating electricity.
27. Generator transformer converts electricity to high voltage for connection to state power grid.