1. Tuesday 2/21/12week 23 objective – SWBAT identify products of coal combustion and their effects on the environment. HW – Read p. 89 Combustion of Fossil Fuels. Define combustion, fossil fuel, ash, ecosystem (DEJ) and answer AQ 1, 3, & 4 on p. 99 (looseleaf paper, full sentences, name & date upper right, assignment title/p. # center, no shreds, no crossing out) BR – Summarize how electricity is produced from coal in a diagram or words.

2. Coal Where does it come from? What happens when it is burned?

3. Where does coal come? Plants (mostly) and animals! The coal we burn today is from forests that died MILLIONS of years ago.

4. What elements make up living things? Nitrogen Carbon Hydrogen Oxygen Phosphorus Sulfur

5. An Easy Way to Think of This NCHOPS

6. 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

7. Isn’t the air we breathe mostly oxygen? NO! Nitrogen = 78% Oxygen = 21% Everything else – 1% So why is it a problem if NCHOPS go into the air?

8. Well here’s what happens when it rains - 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 ) NCHOPS produce acid rain !!

9. How can NCHOPS emissions be reduced? Two main methods Prevent them from being formed Remove them from flue (smokestack) gases.

10. How can NCHOPS emissions be reduced? Prevention 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.

11. How can NCHOPS emissions be reduced? Removal from smoke stack 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

12. Tradeoffs Which is better? Low burner temperature = Reduced NO 2 High burner temperature = Reduced CO Why? What price is better? Cheaper electricity with higher emissions Expensive electricity with lower emissions Why?