control of atmospheric pollutants Flashcards
what are the general methods of controlling air pollutants
1) legislation
2) energy conservation
3) fuel substitution
give some examples of legislation in controlling atmospheric pollutants
1) Clean air act 1956- restricted use of fossil fuels that produce smoke in large urban areas of the UK
2) Montreal protocol- international agreement to phase out the use of ozone-depleting substances
3) Geneva convention on long-range air pollutants- an international agreement to reduce emissions of sulfur dioxide by 30% by 1992
how can energy conservation be used to reduce atmospheric pollutants
1) bulk transport
2) use fo energy-efficient appliances
3) improve insulation
4) make car fuels more efficient
5) recover and recycle industrial energy
how can fuel substitution be used to control atmospheric pollutants
some fuels produce more atmospheric pollutants than others ie
- coal = CO2, SO2 and particulates
- natural gas = CO2
- wind= no air pollutants
what are some more specific methods to reduce or control atmospheric pollutants
1) sulfur dioxide reductions
2) nitrogen oxide reductions
3) particulate reductions
list the ways sulphur dioxide can be reduced
1) wet flue-gas desulphurization
2) dry flue-gas desulphurization
explain coal desulphurisation
- coal can be washed reducing the release of sulfur by 15%
- coal can be crushed to remove more chemically bound sulfur but is more expensive
- sulfur is removed from gas to decrease corrosion to distribution infrastructure
explain the process of dry flue-gas desulphurisation (gas)
sulfur dioxide is passed over a bed of crushed limestone
the acid sulfur dioxide reacts with the base forming calcium sulfate which can be used commercially as a component of plaster
explain the process of wet flue-gas desulphisation (gas)
waste gases (which SO2 is a part of) are bubbled through a sodium sulfite solution
this produces hydrogen sulphite
this is heated producing previous reactants-
sulfur dioxide is now more concentrated and captured individually and used in industry
How can NOx be reduced or controlled
1) catalytic converters= reduces NOx back into atmospheric oxygen and nitrogen
2) urea sprays= solution of ureas sprayed into the flue-gases of a combustion chamber, this reacts at high temps with NOx removing it from the flue gas
how can hydrocarbons be controlled
1) catalytic converters- oxidize hydrocarbons into CO2 and water
2) collect vapors at filling stations, condense them and return them to the main fuel tank
3) collect and pass vapors through an activated carbon filter where hydrocarbons pass onto carbon filter
list some ways to control atmospheric particulates
1) cyclone separators = flue gases are passed into a rapidly spinning chamber where particles are thrown to the sides and collected- clean gas is released
2) scrubbers= flue gas passed through fine sprays of water that forms a mist which sticks to particles that fall to the bottom
3) fabric filters= waste gases passed through long tubes of bags of fabric 99% efficient