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. N 2 and O 2 produce NO 2 nitrogen dioxide C and O 2 produce CO 2 and CO carbon dioxide carbon monoxide H 2 and O 2 produce H 2 O water O 2 reacts with the other elements. P and O 2 produce P 2 O 5 (not released into the atmosphere) phosphorus pentoxide S and O 2 produce SO 2 and then SO 3 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 (HNO 3 ) Carbon dioxide reacts with water to form carbonic acid (H 2 CO 3 ) Sulfur dioxide reacts with oxygen to form sulfur trioxide. Sulfur trioxide reacts with water to form sulfuric acid (H 2 SO 4 )

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 NO 2 1.Reduce amount of extra air in the boiler. (O 2 will combine with fuel rather than N 2 ). 2.Keep temperature in burner low (also reduces plant’s efficiency). CO 1.Keep temperature in burner high. 2.Maintain high O 2 flow (form CO 2, not CO) SO 2 1.Use coal containing less S. 2.Wash coal with water to remove S before burning.

9. How can NCHOPS emissions be reduced? Remove them from flue gases NO 2 Use scrubbers (chemicals) to convert NO 2 to fertilizers (costly, but removes 90% of NO 2 ) CO 2 Scientists exploring possibility of capturing and storing underground SO 2 Use scrubbers (limestone) to convert SO 2 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 NO 2 High Temperature = Reduced CO Why? What Price is Better? Cheaper electricity with higher emissions Expensive electricity with lower emissions Why?