7.6 - Reduction of Air Pollutants

Question 1

Reducing Emissions

Answer 1

• Reducing emissions = reducing air pollutants
• drive less, walk/bike/bus more
• conserve electricity (smart appliances)
• eat more plants, elss meat
• renewable, non-pollution emitting energy (solar, wind, hydro)

Question 2

Laws/Regulation

Answer 2

Clean Air Act
- Allows EPA to set acceptable levels for criteria air pollutants
- monitor emission levels from power plants and other facilities
- tax/sue/fine corporations that release emissions above levels

Pollution Credits
- Similar to ITQs for fish
- Companies that reduce emissions well below EPA-set levels earn pollution credits
- they can sell these to companies that release more than acceptable levels

CAFE Vehicle Standards
- (Corporate Average Fuel Economy) standards require the entire US “fleet” of vehicles to meet certain average fuel
- requires vehicle manufacturers to work to make more efficient vehicles
- More efficient vehicles burn less gasoline and release less NOx, PM, CO, and CO2

Question 3

Redcuing Vehicle Air Pollutants

Answer 3

Vapor Recovery Nozzle
- Capture hydrocarbon VOCs released fromg asoline fumes during refueling
- seperate tube insidenozzel captures vapors and returns them to underground storage tank beneath the gas station
- reduces VOCs which contribute to smog and irritate resp tracts
- Also reduces bensene (carcinogen) releaed fromg asoline vapors

Catlytic Converter (CC)
- required on all vehicles after 1975
- Contains metals (platinum and palladium) that bind to NOx and CO
- CC conerts NOx, CO, and other hydrocarbons into CO2, N2, O2, and H2O

Question 4

Reducing SOx and NOx

Answer 4

Crusehd Limestone (SO2)
- Used to reduce SO2 from coal power plants
- Crushed coal mixed with limestone (calcium carbonate) before being burned in boiler
- Calcium carbonate in limestone combines SO2 to produce calcium sulfate, reducing the SO2 being emitted
- Calcium sulfate can be used to make gypsum wallboard or sheetrock for home foundations

Fluidized Bed Combustion (NOx)
- Fluidizing jet of air pumped iunto combustion “bed”
- Jets of air bring more O2 into rxn, making combustion more efficient and brining SO2 into more contact with calcium carbonate in llimestone
- also allowscoal to be combusted at lower temperature which emits less NOx

Question 5

Wet and Dry Scrubbers

Answer 5

Dry Scrubbers (NOx, SOx, VOCs)
- large column/tube/pipe filled with chemicals that absorb or neutralize oxides (nOx, SOx, VOCs) from exhaust steams (emissions)
- Calium oxide is a common dry srubber additivew hich reacts with SO2 to form calcium sulflite

Wet scrubbers (NOx, SOx, VOCs, PM)
- many involve chemical agents that absorb or neutralize NOx, SOx, VOCs but also include mist nozzels that trap PM in water droplets as well
- mist droplets with pollutants and PM trapped in them fall to bottom of scrubber or get traped at top by mist eliminator
- Sludge collection system traps polluted water for dispsal

Question 6

Reducing PM

Answer 6

Electrostatic Precipitator
- Power plant/factory emissions passed through device with a negative charged electrode, giving particles a negative charge
- negative charged particles stick to positive chargaed collection plates, trapping them
- plates discharged occasionally so particles fall down into collection hopper for disposal in ladnfills

Baghouse Filter (PM)
- Karge fabuc bag filters that trap PM as air form combustion/industrial process passes through
- Shaker device knocks trapped particles loose into collection hopper below
- PM collected and taken to landfill