AIR POLLUTION CONTROLS

Chapter 24

A.P.E.S.

Is Dilution the Solution?

• Years ago polluting factors were moved to more remote locations

• Used taller smokestacks to disperse pollution further up into air so it would dissipate over a wide area & come down in “harmless traces”

PARTICULATE REMOVAL

1. Filters – Cotton or fiberglass

cloth traps particles from effluent stream (waste gas), allowing clean air to pass thru.

– Similar to filter on car or vacuum- but bigger and more of them.

– Often stored in a “baghouse”

PARTICULATE REMOVAL

2. Electrostatic precipitators– Most common in

powerplants– Ash passes over

electrodes & pick up an electrostatic surface charge

– Ash particles passed along & accumulate on a collecting plate that is removed and disposed of as solid waste in landfill

– 99% effective- depends on particle size, chemistry, strength of electric field

– Still poses solid waste problems

SULFUR REMOVAL

1. Fuel Switching• Use low sulfur fuel from

softer coal• Will affect jobs in areas

that mine harder coals

• Natural gas• Difficult to ship,

expensive

• Nuclear power• Uncertain dangers

• Alt. Energy source• Becoming more

competitive

SULFUR REMOVAL

2. Fuel Cleaning• Coal can be crushed,

washed, and gasified to remove sulfur

• Creates water pollution that must be cleaned- expensive

SULFUR REMOVAL

3. Limestone Injection• Mix limestone with coal

before going to boiler• CaCO3 reacts with sulfur

to make CaSO3, CaSO4, or gypsum.

• Sometimes produces a residue called slag that reduces efficiency & must be disposed of

SULFUR REMOVAL4. Fluidized Bed Combustion

• 1 meter thick layer of coal & limestone cover perforated plate

• Air is forced up thru perforation to push coal & limestone up- making it seem like a fluid.

• Oil is sprayed into mix to “start the fire”

• Steam/water pipes are immersed in mix

• This makes burning more efficient & prevents build up of slag

• 90% of sulfur is captured by limestone & nitrogen cmpds are reduced due to lower temperatures used.

• Can use cheaper fuel (lignite)

SULFUR REMOVAL

5. Flue Gas Scrubbing (wet scrubbing)– Crushed limestone, lime

slurry, or alkali (sodium bicarbonate) are injected into gas stream

– Inexpensive & effective– Maintenance is difficult-

chip off plaster like residue regularly

– Causes metal erosion of pipes

– Dispose of solid waste

SULFUR REMOVAL

6. Dry alkali injection• Spray dry sodium

bicarbonate into gases

• Expensive• Trade off- reduce air

pollution problem but increase solid waste/water problem when wastes have to be disposed of.

NITROGEN OXIDE REMOVAL

• Staged burners– Burn at slower rate

reduces NOx

• Catalytic converters– Use platinum-

palladium-rhodium to remove 90% of NOx, hydrocarbons, & CO from your cars exhaust

CLEAN AIR ACT

• 1963- 1st national air pollution legislation

• Revamped in 1970’s– Identified 6 criteria

pollutants– Est. national ambient air

quality standards (NAAQS)• Primary standards- protect

human health• Secondary standards-

protect property, crops, climate, visibility, personal comfort

CLEAN AIR ACT• Extensively revamped in 1990

– Acid rain• Cut SO2 by more than ½ from

1990-2000– Urban smog

• ↓ tailpipe emissions, deadlines est. for cities that do not meet standards

– Toxic Air Pollutants• Factories must reduce toxic

pollutant production by 90% by 2003

– Ozone Protection• CFC’s & CCl4 phased out.

Recovery & recycling programs for CFCs est. Hydrofluorocarbons phased out by 2030

– Marketing pollution rights• Corporations can offset their

pollution levels by buying, selling, and banking pollution

– Volatile organic cmpds

CLEAN AIR ACT

• And yes… Changed again in 1997• Ambient ozone standards lowered from 0.12 ppm(1 hr

avg) to 0.08 ppm (8 hr avg)• Soot & dust emissions apply to particles 2.5 microns vs.

10 previously• Cap and Trade program devised by President Bush is

designed to allow utilities not in compliance with EPA NAAQS to buy, sell, or trade pollution credits for sulfur dioxide, nitrogen dioxide and particulates. The expense of these credits is a strong incentive to utilities to decrease their emissions to reduce their overall costs.

• A timeline of the Clean Air Act:• http://www.edf.org/documents/2695_cleanairact.htm

Clean Air Act http://www.epa.gov/air/oaq_caa.html

• Title I - Air Pollution Prevention and Control– Part A - Air Quality and Emission Limitations

– Part B - Ozone Protection (replaced by Title VI)

– Part C - Prevention of Significant Deterioration of Air Quality

– Part D - Plan Requirements for Nonattainment Areas

• Title II - Emission Standards for Moving Sources– Part A - Motor Vehicle Emission and Fuel Standards

– Part B - Aircraft Emission Standards

– Part C - Clean Fuel Vehicles

• Title III - General• Title IV - Acid Deposition Control• Title V - Permits• Title VI - Stratospheric Ozone Protection

Be familiar with which part does what…

Comparison of 1970 and 1999 Emissions

Other Countries…THE GOOD

• Sweden, W. Germany cut sulfur emissions by 2/3

• Austria & Switzerland over 2/3 & they control motorcycle emissions

• 26 of 37 cities on the Global Environmental Monitoring System have decreased particulate levels

• 20 out of 37 have decreased sulfur emissions

• Cubatao, Brazil was called “Valley of Death” due to dangerous pollution from oil refinery, chemical & fertilizer companies, steel plant; end of military rule allowed people to voice concern, invested money & reduced pollution significantly.

THE BAD & THE UGLY

• Many other countries do not have air pollution controls or legislation.

• China- almost entire pop. uses coal cakes to heat home; some places have particulate levels 9x those of max U.S. standards

• S. Poland, N. Czech Republic covered in smog most of the time, acid rain huge, gardens contaminated

• Copsa Mica, Romania- notorious “black town” from mining dust, birth defects, decreased life expectancy