control of atmospheric pollutants

Question 1

what are the general methods of controlling air pollutants

Answer 1

1) legislation
2) energy conservation
3) fuel substitution

Question 2

give some examples of legislation in controlling atmospheric pollutants

Answer 2

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

Question 3

how can energy conservation be used to reduce atmospheric pollutants

Answer 3

1) bulk transport
2) use fo energy-efficient appliances
3) improve insulation
4) make car fuels more efficient
5) recover and recycle industrial energy

Question 4

how can fuel substitution be used to control atmospheric pollutants

Answer 4

some fuels produce more atmospheric pollutants than others ie

• coal = CO2, SO2 and particulates
• natural gas = CO2
• wind= no air pollutants

Question 5

what are some more specific methods to reduce or control atmospheric pollutants

Answer 5

1) sulfur dioxide reductions
2) nitrogen oxide reductions
3) particulate reductions

Question 6

list the ways sulphur dioxide can be reduced

Answer 6

1) wet flue-gas desulphurization

2) dry flue-gas desulphurization

Question 7

explain coal desulphurisation

Answer 7

• 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

Question 8

explain the process of dry flue-gas desulphurisation (gas)

Answer 8

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

Question 9

explain the process of wet flue-gas desulphisation (gas)

Answer 9

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

Question 10

How can NOx be reduced or controlled

Answer 10

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

Question 11

how can hydrocarbons be controlled

Answer 11

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

Question 12

list some ways to control atmospheric particulates

Answer 12

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