Electricity

1. Electricity Part 5: Coal Power Plants, Particulate Mater, Flue Gases, Carbon Capture and Storage

2. What percent of U.S. energy is used to generate electricity? • 40% • 28% • 32%

3. What percent of electricity in the U.S. is generated by coal? • 12% • 19% • 27% • 39% • 67%

4. Stationary Source Air Pollution Control • 40% energy in U.S. used to generate electricity • 67% of electricity in U.S. generated by fossil fuels • 39% generated by coal • Coal has the most emissions of any fossil fuel

5. Typical Coal Fired Power Plant

6. Emissions from Coal-Fired Plants • Gases • CO2 • SO2 • NOx • Particulates • Soot & Fly ash • Mercury • Thorium

7. Emissions from Coal-Fired Plants • Different means needed to remove various types of pollutants.

8. Particulates • The majority of particles are very small with sizes < 0.1 m • ~ 95% of the mass is made up by larger particles

9. Sizes of various “particles”

10. Particulates • The rate at which particles precipitate (fall) out of atmosphere depends on size. • Smaller particles fall more slowly. This allows them to travel long distances

12. Old Pollution Control • Build a tall chimney and make it someone else’s problem.

13. Old Pollution Control • Build a tall chimney and make it someone else’s problem.

14. Old Pollution Control: Build a tall smoke stack and make it someone else’s problem

15. Prevailing Winds Can Take Pollution Thousands of Miles

16. Particulate Control Devices • Gravitational Collector • Cyclonic Collector • Electrostatic Precipitator • Mechanical Filters

17. Gravitational Collector Works for Particles > 50m

18. Cyclonic Collector Works for particles down to 5m

19. Electrostatic Precipitator: • Works for particles down to 1m • Collects 99% of the total mass but only 5% of total number of particles • Uses about 50,000 Volts

20. Mechanical Filters • Can use fabric filters to remove particles smaller than 1m. • Similar to a filter on a vacuum cleaner • Removes up to 99.9% of particles • Effective for particles down to 0.1m.

21. Gravitational Collectors work for particles • Bigger than 50 mm • Smaller than 50 mm • Between 10 and 30 mm • Less than 1 mm

22. To filter out very small particles we use • Gravitational collectors • Cyclonic collectors • Electrostatic precipitators • Mechanical filters

23. Most of the mass of particulates from coal-fired plants is in • Large particles • Small particles

24. Which particulates from coal-fired plants are a greater health concern? • Large particles • Small particles

25. Other Air Pollution • Sulfur Dioxide • Acid Rain • Carbon Dioxide • Greenhouse gas • Nitrogen Oxides • Respiratory Diseases

26. Sulfur Dioxide

27. Acid Rain H2O (l) + CO2 (g) → H2CO3 (aq)

28. In the gas phase sulfur dioxide is oxidized by reaction with the hydroxyl radical via an intermolecular reaction: SO2 + OH· → HOSO2· which is followed by: HOSO2· + O2 → HO2· + SO3 In the presence of water, sulfur trioxide (SO3) is converted rapidly to sulfuric acid: SO3 (g) + H2O (l) → H2SO4 (l)

29. Also Nitrogen dioxide reacts with OH to form nitric acid: NO2 + OH· → HNO3

30. Effects of Acid Rain

31. pH Tolerance of Aquatic Animals

32. Sulfur Dioxide • Use Smoke Stack Scrubbers to remove. • Gases pass through a water solution spray and SO2 reacts with calcium carbonate (Limestone) to form Calcium Sulfate and Carbon dioxide. (Flue Gas Desulfurization) • SO2 + CaCO3 CaSO3 + CO2 • Removes 98% of SO2. • Gas is reheated to regain buoyancy.

33. A 1000 MW power plant burning 10,000 tons of coal per day can generate 4000 tons per day of concentrated aqueous waste. Big disposal problem. But • Aerobic oxidation of the CaSO3 gives CaSO4, gypsum. Most gypsum sold in Europe comes from flue gas desulfurization

34. Gypsum is used for wallboard, cement, soil conditioning, and plaster

35. Flue gas desulfurization accounts for 10-15% of construction costs in new power plants. Energy required is 3-7% of plant output.

36. As of 2016, China is the world's largest sulfur dioxide polluter, with 2014 emissions estimated to be 30 million tons China started reductions in 2007 50% reduction from 2012 to 2014

37. As of 2016, China is the world's largest sulfur dioxide polluter, with 2014 emissions estimated to be 30 million tons China started reductions in 2007 50% reduction from 2012 to 2014 India is 2nd highest polluter 2014 emissions estimated 12 million tons Levels doubled between 2012 and 2014

38. SO2 Emissions • 2007

39. SO2 Emissions • 2007 2014

40. Fluidized Bed Combustion • Sulfur is “removed” during the actual combustion. • Old technology but just now making its way into power industry. • Could signal a rebirth of use in high sulfur coal.

41. Carbon Dioxide Naturally occurring gas in the atmosphere but recent significant increase due to human activity. One of many Greenhouse Gases. Only recently counted as a pollutant. 12/07/2009 WASHINGTON – After a thorough examination of the scientific evidence and careful consideration of public comments, the U.S. Environmental Protection Agency (EPA) announced today that greenhouse gases (GHGs) threaten the public health and welfare of the American people.

42. Current atmospheric concentration ~404 ppm, up from ~280 ppm before industrial revolution. • Contributor to global climate change.

43. Oceans have absorbed ~50% of carbon released from burning fossil fuels. • Caused a pH decrease in the ocean of ~0.1 • The rate at which reef-building corals produce their skeletons decreases. • The ability of marine algae and free-swimming zooplankton to maintain protective shells is reduced. • The survival of larval marine species, including commercial fish and shellfish, is reduced."

44. Carbon Capture and Storage

45. Underground/water Storage • Pump pressurized gas into deep, permanent storage locations. • In deep ocean, pressure is high enough thatCO2 is a liquid that is denser than water. Should stay there, …but will it? • Contributes to acidification of oceans.\ • Will CO2 find ways to escape from deep well storage? Cracks in rocks.

46. Lake Nyos CameroonOver 1700 people killed by sudden release of CO2 from lake.

47. Potential uses for captured Carbon Dioxide • Convert it into hydrocarbons where it can be stored or reused as fuel or to make plastics. • Stimulate growth of algae to produce biodiesel. • Enhanced production of conventional oil. • Enhanced coal bed methane production

48. A one-year study by the National Research Council looked at many costs of energy production and the use of fossil fuels that aren't reflected in the price of energy. The $120 billion sum was the cost to human health from U.S. electricity production, transportation and heating in 2005, the latest year with full data.The report also looks at other hidden costs from climate change, hazardous air pollutants such as mercury, harm to ecosystems and risks to national security, but it doesn't put a dollar value on them. Coal-fired power and motor-vehicle transportation accounted for roughly 99 percent of those costs The report looks at the sulfur dioxide, nitrogen oxide and particulate emissions from 406 coal-fired plants in the lower 48 states, which produce 95 percent of the nation's coal-generated electricity. There were wide differences among plants in the amount of pollution each produced. The estimated health damages ranged from less than half a cent per kilowatt hour to more than 12 cents. The average was 3.2 cents per kilowatt hour. Read more: http://www.mcclatchydc.com/2009/10/19/77423/report-looks-at-hidden-health.html#ixzz0idRmBTdQ

49. Usually use multiple stages of pollution control

50. SO2 can be removed from flue gases by • Cold precipitation • Filtration • Stack scrubbers • None of the above