1. Air Quality & SO2

2. Fossil Fuel provides Power (& SO2, etc.)

3. What is Coal

4. Coal-fired Power Plant

5. Flue Gas Cleanup – Nox, SO2, Hg, Ash

6. Coal-fired Power Plant Flue Gas Cleanup

7. FGD Absorber Schematic

8. Basic Limestone FGD Reactions
SO2 + CaCO3 → CaSO 3·½ H2O (s) + CO2 (g) ↑
SO2 + CaCO3 → CaSO3 ·½H2O + CO2 (g) + O2 → CaSO4 ·2H20 (Gypsum)
Dibasic Acid additive

9. Dibasic Acid Titration

10. FGD Technology Development
EPA and industry sponsored
SO2 gas to liquid transfer – H2SO3
Sorbent, e.g., CaCO3, dissolution
SO3/CO3 replacement, CaSO3 formed
CaSO3 oxidized to CaSO4
CaSO4 removed as insoluble solid
Later versions used dibasic acid buffers, e.g., adipic acid, to increase mass transfer
See scrubber train on board

11. FGD Summary Points
The 1990 Clean Air Act Amendments required > 90% SO2 removal (acid rain)
More than 350 operating units in U.S., ¾ are lime/limestone wet scrubbers

12. Air Quality Conclusion Success and Challenges
Automotive emissions reduced 90% per mile driven,
Average lead concentrations in children’s blood have fallen over 90%, removing lead from gas
Aggregate emissions of six key air pollutants have fallen by 68% since 1970, population growth 54%
Tens of thousands of early deaths avoided per year
Some US cities still not meet health-protective standards
Premature deaths from fine particle and ozone continuing concern
Greenhouse gases and climate change

13. Village Green