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Coal

Coal. From where does it come? What happens when it is burned?. From where does coal come?. Plants and animals!. Of what elements do plants and animals consist?. Nitrogen Carbon Hydrogen Oxygen Phosphorus Sulfur. An Easy Way to Think of This. NCHOPS.

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Coal

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  1. Coal From where does it come? What happens when it is burned?

  2. From where does coal come? • Plants and animals!

  3. Of what elements do plants and animals consist? • Nitrogen • Carbon • Hydrogen • Oxygen • Phosphorus • Sulfur

  4. An Easy Way to Think of This • NCHOPS

  5. How are pollutants formed when coal is burned? NCHOPS are released into the air. N2 and O2 produce NO2nitrogen dioxide C and O2 produce CO2 and CO carbon dioxide carbon monoxide H2 and O2 produce H2O water O2 reacts with the other elements. P and O2 produce P2O5(not released into the atmosphere) phosphorus pentoxide S and O2 produce SO2 and then SO3 sulfur dioxide sulfur trioxide

  6. What happens to these compounds when it rains? NCHOPS produce acid rain. • Nitrogen dioxide reacts with water to form nitric acid (HNO3) • Carbon dioxide reacts with water to form carbonic acid(H2CO3) • Sulfur dioxide reacts with oxygen to form sulfur trioxide. Sulfur trioxide reacts with water to form sulfuric acid (H2SO4)

  7. How can NCHOPS emissions be reduced? • Two main methods • Prevent them from being formed • Remove them from flue gases.

  8. How can NCHOPS emissions be reduced? • Prevent them from being formed • NO2 • Reduce amount of extra air in the boiler. (O2 will combine with fuel rather than N2). • Keep temperature in burner low (also reduces plant’s efficiency). • CO • Keep temperature in burner high. • Maintain high O2 flow (form CO2, not CO) • SO2 • Use coal containing less S. • Wash coal with water to remove S before burning.

  9. How can NCHOPS emissions be reduced? • Remove them from flue gases • NO2 • Use scrubbers (chemicals) to convert NO2 to fertilizers (costly, but removes 90% of NO2) • CO2 • Scientists exploring possibility of capturing and storing underground • SO2 • Use scrubbers (limestone) to convert SO2 into wet paste or dry powder - disposed of in landfill rather than released into the atmosphere

  10. Tradeoffs • What Temperature is Better? • Low Temperature = Reduced NO2 • High Temperature = Reduced CO Why? • What Price is Better? • Cheaper electricity with higher emissions • Expensive electricity with lower emissions Why?

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