Lesson 2 Notes

Lesson 2 Notes - Lesson 2 Describing how electricity is...

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Lesson 2 Describing how electricity is generated from coal, natural gas, nuclear, wind, hydroelectric, etc. ...... Discussing electricity growth and conservation Articulate electricity deregulation Explaining fluidized beds Linking energy generation with pollution formation Explaining efficiency limitations in electricity production Describe Gasification and Vision 21 Steam and Industrial Revolution This was one of the first uses of the steam engine, to pump water out of coal mines, (and tin mines in Cornwall). The steam engine was used to turn looms (used in cloth manufacturing), pump water, turn belts, stir beer, and carry hops up to the upper floors of breweries. This revolution altered the distribution of the populace, enabled mass production, and created the intricate network of communications (road, rail and canals) so that goods could be moved to different markets. We will see that most of our electricity is still generated from steam. Energy is the ability to do Work Power is the rate (speed) of performing work Pulverized Coal Combustion The concept is simple; through the process of combustion release the trapped chemical energy from the coal producing heat, which we can change into electricity, which we then use to do work. Coal is stockpiled into great piles, this is the reserve supply of the coal so the power plant can operate even if there are transport (rail strike) problems, supply problems (miners’ strikes etc.) or weather related issues. The coal is moved via a conveyor belt to the pulverizers where the coal is crushed into a fine dust (about 35 microns in size) Particle size reduction helps to speed up the process of burning the coal particles. If the particle size is smaller, then there is more surface area for the same weight. Thus, the coal particle will burn quicker and the combustor can be smaller in size. There might be 12 or 24 burners in a boiler wall with the burners outlet poking through the water wall of the boiler. There are different configurations of burners, but simply put, the inside of the boiler is very hot (1,500 °C) causing the coal to devolatilize, give off gases, which combust, then the remaining char particle combusts(exothermic). Water flows through the pipes and is transformed into steam. But not just any steam. By using high pressures and special materials (so they can withstand the temperature) the steam can reach very high temperatures above 500 ° C. The combustion gases that leave the boiler are known as flue gases. The steam passes through a turbine, which spins at a very fast rate. If you recall that energy cannot be created or destroyed, then you will realize that making the turbine spin in excess of a 1,000
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revolutions a minute takes some of the energy from the steam. To help the flow process, the low temperature steam is cooled to transform it back into water. Water takes much less volume than steam and so the resulting pressure drop helps pull the steam through
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Lesson 2 Notes - Lesson 2 Describing how electricity is...

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