1. Can Coal be used for Power Generation by an Environmentally Responsible Society? An Overview of “Clean Coal” Technologies Ben Bayer November 20, 2006 ChE 384

2. U.S. Dependence on Coal

3. Coal Consumption Will Rise  Energy usage to increase 1.1% per year  Coal usage expected to increase 53% by 2030

4. Is the Pollution Avoidable?  Burning of coal responsible for pollution (2005) –10,222,547 tons SO 2 – acid rain –3,633,313 tons NOx – smog, smog acid rain –2,539,805,219 tons CO2 – greenhouse gas –50 tons Hg (debatable) – developmental difficulties  “Clean” options for coal use –Current and future pollution control technologies for traditional coal combustion –FutureGen – Integrated Gasification Combined-Cycle (IGCC) electricity generation

5. SO 2 Scrubbing  SO 2 +H 2 0 → H 2 SO 4  Coal cleaning is insufficient  Wet Flue Gas Desulfurization (FGD) is dominant technology – “scrubs” SO 2 out of flue gas Absorption SO2 + H2O → H2SO3 Neutralization CaCO3 + H2SO3 → CaSO3 + CO2 + H2O Oxidation CaSO3 + ½ O2 → CaSO4 Crystallization CaSO4 + 2H2O → CaSO4∙2H2O

6. SO 2 Scrubbing – FGD Diagram

7. Potential SO 2 Emissions  10,222,547 → 3,020,000 tpy w/ 90% capture

8. NOx Control  NOx emissions responsible for ground-level ozone and acid rain (HNO 3 )  NOx is a function of the heat of combustion  Combustion and post combustion control –Combustion – low excess air, overfire air, low NOx burners, fuel reburning, flue gas recirculation –Post Combustion – selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR)

9. NOx Control Options  3,633,313 → 477,000 tpy w/ 90% capture

10. HAPs / CO 2 Control  Hazardous Air Pollutants (HAPs) – mercury, arsenic, cadmium –Sorbent technologies / traditional pollution control devices  Greenhouse Gas Control –Pure oxygen feed – membrane technologies  Sequestration  Feedstock –Microbial degradation → biofuels

11. FutureGen Coal Gasification  “Zero” emissions power plant –45% thermal efficiency  Integrated Gasification Combined Cycle (IGCC)  Coal is reduced in gasifier to CO and H 2 –CO “shifted” to CO2  H 2 combusted in turbine –Potential feedstock

12. IGCC Process Flow

13. Coal Gasification Emissions  Sulfur in coal reduced to H 2 S –Elemental sulfur is recovered – salable product –99.4% removal efficiencies, no sludge  Nitrogen in fuel is converted to N 2, NH 3, and small amounts of HCN  Metals either contained in glasslike slag or water stream – 10x fewer air emissions  15-20% less CO 2 due to increased efficiencies

14. Conclusions  Pollution control is promising for new coal burning plants –Pure oxygen research should continue –Metals could be problematic  FutureGen is still off in the future… –Technical difficulties –Promising technologies

15. Questions