Clean Coal Technology Sam Harris 20chunks.j pg.
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Transcript of Clean Coal Technology Sam Harris 20chunks.j pg.
Clean Coal TechnologySam Harris
http://i.treehugger.com/images/2007/5/24/coal%20chunks.jpg
Overview
● Burning and current use of Coal● “Clean” coal technologies● Is “clean” coal actually clean?● The future of clean coal and politics● Summary
Types of Coal
– Lignite (brown coal) - 25% to 35% carbon, around 70% when dry
– Subbituminous – 35% to 45% carbon– Bituminous – 45% to 86% carbon
– Anthracite (black coal) – 86% to 98% carbon
Coal and Electricity
● There are about 600 U.S. coal plants.● Coal generates 54% of our electricity● There are 249 projected coal power plants to be
built between 1999 and 2009, another 483 by 2019, and another 710 by 2030
Burning of Coal
● In 2002 fossil fuels released 23 billion tons of CO2 into the atmosphere
● of the 23 billion tons 41% was from coal● Burn 1 ton of black coal and you get 4 tons of
CO2● Anthracite releases 67% more CO2 than methane
and brown coal releases 130% more CO2 emissions than methane
● Coal also contains trace amounts of sulfur and Nitrogen that when burned can cause environmental issues
The Effects of Sulfur Dioxide from Coal
● In the 1960s trees as well as aquatic life in lakes were dying
● Due to acid rain from sulfur dioxide emissions from burning of coal
● Created “scrubbers” to clean the coal● The sulphates had reflected light back into space
keeping the earth cooler● Once the sulphates were gone the temperature of
the earth rose
Why is coal still used?● Cheapest for power stations relative to the amount
of heat it generates when burnt
http://www.economist.com/business/displaystory.cfm?story_id=10145492
How does a coal power plant work?
http://www.cs.wright.edu/~egr190/Alternative%20energy/coalart.gif
http://upload.wikimedia.org/wikipedia/commons/d/d6/Coal_power_plant_Datteln_2_Crop1.png
So what is clean coal?
● It is actually a vague term that does not describe any one process
● Can include the removal of nitrogen and sulfur that create acid rain
● Can include the storage of CO2● The term “clean coal” is abused
“Clean” Coal Technologies
● Coal washing● Wet scrubbers● Low NOx burners● Electrostatic precipitators● Gasification● Carbon Capture and Storage (CCS)● Fuel Cells● Magnetohydrodynamics
Coal Washing● Grinding coal into pieces and passing it through
gravity filtration● One technique: Putting coal into a barrel with a
liquid with a specific density where the coal floats and the impurities sink
http://news.bbc.co.uk/1/hi/sci/tech/4468076.stm
Wet Scrubbers
● When the emissions reach the flue of the furnace limestone and water are sprayed
● The SO2 reacts with the calcium carbonate (limestone) to form gypsum (calcium sulfate)
● The gypsum is collected and used for construction
● 99% effectivehttp://news.bbc.co.uk/1/hi/sci/tech/4468076.stm
Nitrogen Oxides (NOx)
● Use of ● First stage: combustion occurs in an oxygen
deficient zone where NOx is usually formed● Second Stage: hydrocarbons are formed which
react with the already formed NOx● Third Stage - internal air staging completes the
combustion but may result in additional NOx formation, which can be minimized by completing the combustion in an air lean environment
Electrostatic Precipitators (Particle emissions)
● Creates an electrical field that removes unwanted charged particles
● 99% effective
http://news.bbc.co.uk/1/hi/sci/tech/4468076.stm
Gasification
● Coal is reacted with oxygen and steam to form a “syngas” (mostly hydrogen and part CO)
● Syngas is cleaned and burned which then turns a turbine
● As gas cools it heats water, which turns another turbine
http://news.bbc.co.uk/1/hi/sci/tech/4468076.stm
Gasification (continued)● Gasification is seen as part of zero-emission system● Improved SO2 and NOx emissions (already low)● Unproven on widespread scale● Up to 45% efficient ● Currently only demonstration units exist on a trial
basis● Right now syngas being cleaned at low
temperatures. In the future will be cleaned at higher temperatures, increasing efficiency
● Costly, but current coal power plants can be modified
Carbon Capture and Storage (CCS)
● Capturing CO2 and storing it underground (geosequestration)
http://news.bbc.co.uk/1/hi/sci/tech/4468076.stm
CSS (continued)
● There are many problems with CSS● CO2 is hard to capture● Once captured it needs to liquified which takes
20% of the energy yielded from the coal● Where the CO2 is stored needs to be monitored● There are only so many places that are good for
mass storage● Transportation could be costly
Fuel Cells
● Allow hydrogen from coal to react with oxygen to produce electricity electrochemically
● Still in early development● Costly
http://www.australiancoal.com.au/cleantech.htm#fuelcell
Magnetohydrodynamics
● Coal is burned to form an extremely hot gas or plasma
● Given electrical charge by adding a compound like potassium salt
● The charged gas or plasma is passed through a magnetic field and electricity is produced
● The heat from the combustion gases is used to turn a steam turbine too
● Still in development● Costly
So is “clean” coal really clean?
● Unfortunately there is no way to make coal clean● Processes like gasification can make coal burning
more efficient, but it still burns plenty of CO2● CO2 can be stored underground using CSS, but
that could lead to more problems in the future● Best solution: STOP USING COAL!!!!
“Clean” Coal and Politics● Barack Obama has said that he would develop
five first-of-their-kind coal-fired plants with CCS technology
● Wants to spend $150 billion over 10 years for renewable energy sources such as wind, solar, biofuels, plug-in hybrids and clean-coal technology
● Wants to cut carbon-dioxide emissions from power plants, oil companies and other industries.
● But we're talking politics.
Summary
● Coal is very inefficient and is a huge cause of global warming, but cheap
● Clean coal is a term that describes many different technologies
● Clean coal is by no means clean● CSS will be put in use in the near future, which
may or may not be a good thing
Works Cited
● "Clean Coal Technologies - Examples." Australian Coal Association. Australian ● Clean coal technology: How it works." BBC News. 28 Nov. 2005. BBC News. 6 ● "Coal power Still going strong." The Economist 15 Nov. 2007.● Davidson, Paul. "Major issues await Obama." USA Today 6 Nov. 2008.● Flannery T. 2005. The Weather Makers: How Man is Changing the Climate and ● "IEA Clean Coal Centre." IEA Clean Coal Centre. IEA Clean Coal Centre. 6 Nov. ● Schirber, Michael. "What Exactly Is Clean Coal?" Foxnews.com. 3 Nov. 2008. Fox