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E nvironmental consequences of combustion processes – Part I (Smog, Acid Rain, and ozone depletion)

CHAPTER # 3. E nvironmental consequences of combustion processes – Part I (Smog, Acid Rain, and ozone depletion). Dr. Hassan Arafat Department of Chem. Eng. An-Najah University. (these slides were adopted, with modification, from Ms. Paulina Bohdanowicz , KTH Institute, Sweden). Combustion.

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E nvironmental consequences of combustion processes – Part I (Smog, Acid Rain, and ozone depletion)

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  1. CHAPTER # 3 Environmental consequences of combustion processes – Part I(Smog, Acid Rain, and ozone depletion) Dr. Hassan Arafat Department of Chem. Eng. An-Najah University (these slides were adopted, with modification, from Ms. Paulina Bohdanowicz , KTH Institute, Sweden)

  2. Combustion Source: WCI 2005

  3. Combustion chamber

  4. Combustion • Emissions of concern: • Particulates/fly and bottom ash • Carbon dioxide • Sulphur oxides • Nitrogen oxides • Carbon monoxide • Waste

  5. Flue gas composition from a typical coal-fired power plant Source: Liss R., Saunders A., Power generation and the Environment, Oxford 1990; Turns S.R., An introduction to combustion, concepts and application, Singapore 2000

  6. Air Pollutants • Carbon monoxide • colorless, odorless, non-irritating poison • attaches to hemoglobin; reduces oxygen carrying capacity • results in headaches, drowsiness and asphyxiation • Hydrocarbons • denotes a large group of volatile organic compounds • some are carcinogens, poison etc.

  7. Air Pollutants • Sulfur Dioxide • colorless corrosive gas • respiratory irritant and poison • can result in H2SO4 • Particulates • small pieces of solid or liquid materials dispersed in the atmosphere • 0.005-100 um • reduction in visibility, respiratory problems

  8. Air Pollutants • Nitrogen Oxides • critical component for smog formation • compounds acid precipitation problems • Photochemical Oxidants • products of secondary atmospheric reactions driven by solar energy • e.g., O3 PAN (peroxyacetyl nitrate), acrolein • strong oxidants, eye irritant etc.

  9. Air Pollutants • Lead • released as metal fumes or suspended particles • 2 million metric tons per year • 5-10 times more in urban than rural areas when leaded gas is used • major source was leaded gasoline • Carbon Dioxide • generally considered non-toxic and innocuous • not listed as air pollutant • increasing concentrations have been related to global warming

  10. Results of emissions • Local pollution with particulates and gases • Smog • Acid rains • Greenhouse effect/ Global warming • Thermal pollution from cooling waters • Waste generation

  11. Local air pollution

  12. Layers of Earth’s Atmosphere

  13. Composition of the Atmosphere

  14. Atmospheric concentration of selected species Source: Siemiński M., Środowiskowe zagrożenia zdrowia, Warszawa 2001

  15. Smog

  16. Form of air pollution in which atmospheric visibility is partially obscured by a haze consisting of solid particulates and/or liquid aerosols Occurs mainly in urban areas but not exclusively Smoke + fog = smog Smog

  17. History dates back to the 14th century the "Killer Smog" reported in 1952, claimed 4000 fatalities in London - by far the most devastating event of this type in recorded history. Mechanism Inefficient combustion of high-sulphur coal => high concentration of unburned carbon soot and other particulates, acidic sulfate aerosols (such as sulfuric acid, H2SO4) as well as elevated levels of sulphur dioxide. SO2 and soot, => sulphuric acid, sulfate aerosols Characteristic brownish haze - formed usually under conditions of high humidity and relatively low temperatures, characterised by reducing and acidic properties. In case of humid atmospheres carbon particulates serve as condensation nuclei for water droplets resulting in formation of fog, highly irritant. Classical smog can persist for days when atmospheric conditions allow. Sulphur smog / London smog

  18. Sulphur smog / London smog Batter Sea power station, London, UK

  19. Impacts Deterioration of human made structures and materials Deterioration of flora Respiratory problems, allergies, asthma, lung damage Mitigation Burning of lower S-content coal Desulphurisation of flue gases Clean Air Acts, Sulphur Protocol Sulphur smog / London smog

  20. process by which ozone is being created at low altitudes – ground level encountered in automobile rich cities – with specific climatic conditions History mid-1940s - repeated occurrence of heavy injury to vegetable crops in the Los Angeles area - traced to high concentrations of ozone that appeared to be created at low altitudes Photochemical smog / LA smog

  21. Photochemical smog / LA smog

  22. Photochemical smog / LA smog Los Angeles

  23. Photochemical smog / LA smog LA Santiago Las Vegas

  24. Impacts Impaired visibility Eye and respiratory system irritants Damage to lung tissue Vegetation damage Contribution to acidic deposition Materials destruction (rubber and some plastics) Photochemical smog / LA smog

  25. Photochemical smog / LA smog • How to reduce smog (main goal is to reduce VOC and NOx): • PCV valves • Leak-proof caps • Tune-up • Emission tests • Catalytic converters • Public transportation

  26. Acid Rain

  27. History First studies on rain chemistry were conducted in late 1800s, but modern investigations date back to 1960s. Nowadays the chemistry of atmospheric precipitation is fairly well known. The phenomenon of acid rain has been known and studied from 1950s. 1960 – lowered fish production in Scandinavian lakes In 1972 it became an international public policy issue at the first United Nations Conference on the Environment held in Stockholm. The transboundary effect of atmospheric pollution has been officially accepted, based on the fact that sulphur and nitrogen oxides are commonly emitted in one location while the acid deposition occurs in distant area. In Sweden and Norway around 90% of the acid deposition comes from other countries, primarily UK, Germany, Poland and other Central Europe countries. Canada receives major acid contribution form the US. Acid Rain Source: Van Loon G.W., Duffy S.J., 2000.

  28. Acid Rain • Rain that is more acidic than normal because it contains sulfuric acid or nitric acid • result of SOx, NOx, acidic particulates in air • involves all forms of acid deposition, even if rain is not involved • Utility plants contribute to 70% SO2 production and 30% NOx production in USA • Coal contains as high as 5% sulfur

  29. Mechanism of acid rain formation

  30. Acidification of water ecosystems Natural surface waters - pH of 6-8, acidified waters pH 3 (conditions unbearable for many aquatic species, which eventually die, and lakes become lifeless) Today some 14000 lakes in Sweden are affected by acidification. Similar situation is in Canada Nitrogen can induce eutrophication, which results in depletion of oxygen in water, further affecting the aquatic flora and fauna Impacts of acid rain

  31. Damage of flora A 1999 survey of European forests - one out of every four trees suffered the loss of 25% or more leaves or needles Decay of structural materials Marble, sandstone, rubber, metals Herten, Germany, 1908 & 1969 Impacts of acid rain

  32. Human health problems respiratory problems including lung disorders, asthma, and bronchitis due to suspended atmospheric sulphates indirect effect of acidification on humans is related to the presence of toxic metals in the food chain Impacts of acid rain

  33. Conventions/Targets the Convention on Long Range Transboundary Air Pollution (1994 Sulphur Protocol) – with amendments 5th Environmental Action Programme and by the Council of Ministers of the Environment) 1999 Gothenburg Protocol to Abate Acidification, Eutrophication and Ground-Level Ozone Mitigation

  34. Ozone Depletion

  35. Ozone Depletion • Stratospheric Ozone absorbs harmful ultraviolet (<340nm) radiation from the Sun • 1% loss of ozone = 2% increase in UV radiation = 106 extra cancers • ozone hole = 7.7 million sq. miles • CFCs & HCFCs are the primary causes

  36. Ozone hole above the the Antarctic on October 3, 1999 (NASA satellites) A record size of ozone hole was 10.5 million square miles on Sept 19, 1998 Red color would denote high ozone levels; blue denotes low Antartic/Arctic ozone hole

  37. Impacts Humans (a 10% drop in stratospheric ozone levels is likely to lead globally to 300000 more skin cancers, 1.6 million more eye damage – cataracts) per year Reptiles (damage to eggs) Plants (reduced photosynthesis, increased sensitivity to stress) Damage to marine ecosystems (direct and indirect) Ozone layer depletion

  38. Ozone: What’s Being Done? • Montreal Protocol (1985) • complete phase-out of CFCs by 2000 • critical need to come up with inexpensive non-halogenated coolants • if everyone abides, ozone loss should peak between 2001 and 2005 • ozone levels should return to normal

  39. Chlorine Content in Stratosphere

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