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Chemistry of Coal

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Chemistry of Coal

  1. 1. DO NOW <ul><li>What is “pollution”? </li></ul><ul><li>Name one pollutant or chemical that pollutes the AIR </li></ul><ul><li>Name one pollutant or chemical that pollutes the WATER </li></ul><ul><li>Name one pollutant or chemical that pollutes the LAND </li></ul>
  2. 2. Coal <ul><li>From where does it come? </li></ul><ul><li>What happens when it is burned? </li></ul>
  3. 3. From where does coal come? <ul><li>Plants and animals! </li></ul>
  4. 4. Of what elements do plants and animals consist? <ul><li>Nitrogen </li></ul><ul><li>Carbon </li></ul><ul><li>Hydrogen </li></ul><ul><li>Oxygen </li></ul><ul><li>Phosphorus </li></ul><ul><li>Sulfur </li></ul>
  5. 5. An Easy Way to Think of This <ul><li>NCHOPS </li></ul>
  6. 6. How are pollutants formed when coal is burned? <ul><li>NCHOPS are released into the air. </li></ul><ul><li>N 2 and O 2 produce NO 2 nitrogen dioxide </li></ul><ul><li>C and O 2 produce CO 2 and CO carbon dioxide carbon monoxide </li></ul><ul><li>H 2 and O 2 produce H 2 O water </li></ul><ul><li>O 2 reacts with the other elements. </li></ul><ul><li>P and O 2 produce P 2 O 5 (not released into the atmosphere) phosphorus pentoxide </li></ul><ul><li>S and O 2 produce SO 2 and then SO 3 sulfur dioxide sulfur trioxide </li></ul>
  7. 7. What happens to these compounds when it rains? <ul><li>NCHOPS produce acid rain. </li></ul><ul><li>Nitrogen dioxide reacts with water to form nitric acid (HNO 3 ) </li></ul><ul><li>Carbon dioxide reacts with water to form carbonic acid (H 2 CO 3 ) </li></ul><ul><li>Sulfur dioxide reacts with oxygen to form sulfur trioxide. Sulfur trioxide reacts with water to form sulfuric acid (H 2 SO 4 ) </li></ul>
  8. 8. How can NCHOPS emissions be reduced? <ul><li>Two main methods </li></ul><ul><ul><li>Prevent them from being formed </li></ul></ul><ul><ul><li>Remove them from flue gases. </li></ul></ul>
  9. 9. How can NCHOPS emissions be reduced? <ul><li>Prevent them from being formed </li></ul><ul><ul><li>NO 2 </li></ul></ul><ul><ul><li>Reduce amount of extra air in the boiler. (O 2 will combine with fuel rather than N 2 ). </li></ul></ul><ul><ul><li>Keep temperature in burner low (also reduces plant’s efficiency). </li></ul></ul><ul><ul><li>CO </li></ul></ul><ul><ul><li>Keep temperature in burner high. </li></ul></ul><ul><ul><li>Maintain high O 2 flow (form CO 2 , not CO) </li></ul></ul><ul><ul><li>SO 2 </li></ul></ul><ul><ul><li>Use coal containing less S. </li></ul></ul><ul><ul><li>Wash coal with water to remove S before burning. </li></ul></ul>
  10. 10. How can NCHOPS emissions be reduced? <ul><li>Remove them from flue gases </li></ul><ul><ul><li>NO 2 </li></ul></ul><ul><ul><ul><li>Use scrubbers (chemicals) to convert NO 2 to fertilizers (costly, but removes 90% of NO 2 ) </li></ul></ul></ul><ul><ul><li>CO 2 </li></ul></ul><ul><ul><ul><li>Scientists exploring possibility of capturing and storing underground </li></ul></ul></ul><ul><ul><li>SO 2 </li></ul></ul><ul><ul><ul><li>Use scrubbers (limestone) to convert SO 2 into wet paste or dry powder - disposed of in landfill rather than released into the atmosphere </li></ul></ul></ul>
  11. 11. Tradeoffs <ul><li>What Temperature is Better? </li></ul><ul><ul><li>Low Temperature = Reduced NO 2 </li></ul></ul><ul><ul><li>High Temperature = Reduced CO </li></ul></ul><ul><ul><ul><li>Why? </li></ul></ul></ul><ul><li>What Price is Better? </li></ul><ul><ul><li>Cheaper electricity with higher emissions </li></ul></ul><ul><ul><li>Expensive electricity with lower emissions </li></ul></ul><ul><ul><ul><ul><li>Why? </li></ul></ul></ul></ul>

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