Acid Rain Flashcards
What is the source of SOx?
S from coal, 99% is SO2
What is the source of NOx?
High T combustion, NO emitted and forms NO2 in air.
Consequence of Al mobilised?
Fish loss in Scandinavia
Consequence of Mg depletion?
Forest death in Germany
What happened in 1952 London?
4000 excess deaths led to tall chimneys and clean air acts.
Liming soil and lakes
Low S coal, dash to gas
FGD plants
Cost millions (expensive), Radcliffe on Soar and Drax, Turns limestone to gypsum
Production methods of coal gasification
Favours gas turbine over steam turbine.
Health effects
SOx, aerosols and NO2 causes respiratory distress
Major source of SOx and NOx?
SOx - coal, increasing NOx source - vehicles
All acid deposition
Snow, mist, dry, direct impact on trees and buildings
Rain pH
Dissolved CO2 rain pH 5-6
SOx and NOx input
Fossil fuels - acid vinegar
SOx and NOx
S oxidation in fuel and N high temperature combustion from N2 and O2 in air, catalytic ally and photochemically oxidised
SO4(2-)
Not deposited, less prone to dry composition than SO2 , travels in atmosphere - days, falls by wet deposition, rainout and wash out
Impacts
Spring - acid flush, affect spawning, Al mobilised, reduce fish ability to take salt in through gills
Forest death
Deciduous trees less affected, foliage low surface area, leaves shed, photochemical oxidants O3
Crops
Yield reduction, others stimulated, sulphur deficiency consequence of fGD
Human health
Heavy metals in water, fish food + drinking water, high Cu levels
Building materials
Metals and stone (marble) corroded
1980s early 1990s
Dense acid hazes
Short term solutions
Limit lakes and streams, low S fuels, Fluidized bed combustion system, FGD, vehicle, catalysts, lean burn engines
FGD Flue Gas Desulphurisation
Wet scrubbing, 90% efficient in removing SOx, expensive, produce sludge - environmental problem, water demand 4000 gallons/ min, 1000 mega watts
Fluidized bed combustion FBC
Efficient - upward air flow, boilers direct contact with bed - heat, transferred by conduction, lower temperature 3000 degrees, lees NOx produced, 90% S removed, emissions comparable to natural gas
Integrated gasification/ combined cycle (IGCC)
Clean burning fuel, turbines driven by hot gases from coal combustion, waste heat used to produce steam, efficient electrical power, particulates trapped, low emissions, loss water used, emissions comparable to natural gas
SOx
1-2% in SO3
Anthropogenic SO2
SO2 from coal combustion, no effective way of removing S from coal matrix compared to oil and gas
SO2 characteristics
Unstable at high temperature, independent of O2 in contrast to C. Most soluble of gaseous pollutants
SO2 Fate
No catalyst - slow process, dry deposition or acid rain
