Air Quality & SO2

Fossil Fuel provides Power (& SO2, etc.)

What is Coal

Coal-fired Power Plant

Flue Gas Cleanup – Nox, SO2, Hg, Ash

Coal-fired Power Plant Flue Gas Cleanup

FGD Absorber Schematic

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 https://en.wikipedia.org/wiki/File:Titolazione.gif

Dibasic Acid Titration https://en.wikipedia.org/wiki/File:Titolazione.gif

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

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

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

Village Green https://www.airnow.gov/index.cfm?action=airnow.villagegreen