LECTURE 6. AIR POLLUTION CONTROL TECHNOLOGIES Dr. Oleksandr Kovrov, Associate Professor of the Department of Ecology, National Mining University (Dnipropetrovsk, Ukraine) IUR 4025: ENVIRONMENTAL ENGINEERING 1

Outlines Air pollution related questions Sources of air pollutants Major Air Pollutants Environmental Effects of Air Pollution Air Pollution Control Devices Engineering considerations Preliminary conclusions and discussions 2

Answer the questions in complete sentences. 1.What is air pollution? 2.What causes air pollution? 3.What is an example of air pollution in the text? 4.What is at least one negative outcome of air pollution? 5.How can air pollution be prevented? 6.What is something you could do to reduce air pollution? 3

Air pollution is the emission of gases, chemicals, and particulate matter into the atmosphere. Air pollution primarily comes from burning fossil fuels such as natural gas, petroleum, and coal as well as mining and processing raw minerals. Air Pollution ©2009 abcteach.comabcteach.com 4

Primary Pollutants Secondary Pollutants Sources Natural Stationary CO CO 2 SO 2 NO NO 2 Most hydrocarbons Most suspended particles SO 3 HNO 3 H 2 SO 4 H2O2H2O2H2O2H2O2 O3O3O3O3PANs Most andsalts NO 3 – Mobile SO 4 2 – 5

Major Sources of Primary Pollutants Stationary Sources Mining and processing of minerals and raw materials, industrial processes etc. Combustion of fuels for power and heat – Power Plants Other burning such as wood & crop burning or forest fires Solvents and aerosols Mobile Sources Highway: cars, trucks, buses and motorcycles Off-highway: aircraft, boats, locomotives, farm equipment, RVs, construction machinery, and lawn mowers 6

Major Air Pollutants Major Air Pollutants (known as “Criteria” Pollutants) –Particulate Matter (PM) –Lead (Pb) –Sulfur Dioxide (SO 2 ) –Carbon Monoxide (CO) –Nitrogen Dioxide (NO 2 ) –Ozone (O 3 ) Toxic Air Pollutants –Not criteria pollutants –188 substances defined as hazardous air pollutants 7

Environmental Effects of Air Pollution Acid Rain –SOx and NOx react in the atmosphere to form acids –Acid rain falls on the soil and water bodies making the water unsuitable for fish and other wildlife –Speeds the decay of buildings, statues and sculptures. The Greenhouse Effect –Ozone, methane, CO 2, and other gases may contribute to global warming 8

Wind Transformation to sulfuric acid (H 2 SO 4 ) and nitric acid (HNO 3 ) Nitric oxide (NO) Acid fog Ocean Sulfur dioxide (SO 2 ) and NO Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Farm Lakes in deep soil high in limestone are buffered Lakes in shallow soil low in limestone become acidic Wet acid deposition (droplets of H 2 SO 4 and HNO 3 dissolved in rain and snow) AcidicPrecipitation 9

Greenhouse effect 10

Environmental Effects of Air Pollution (cont.) Stratospheric Ozone Depletion –Certain substances deplete the amount of ozone in the stratosphere, increasing the amount of UV-b radiation Mercury –Mercury in the air can settle into water bodies where it can change it into methylmercury, a highly toxic form that builds up in fish, shellfish and animals that eat fish. Agriculture Impacts Photochemical Smog 11

Ozone Depletion Ozone (O 3 ) –Triatomic form of oxygen in which three atoms of oxygen are bonded. –Strong oxidant and chemically reacts with many materials in the atmosphere. –In the lower atmosphere, ozone is a pollutant. –Highest concentration of ozone in the stratosphere

Solar radiation Ultraviolet radiation NO Nitric oxide P h o t o c h e m i c a l S m o g H 2 O Water NO 2 Nitrogen dioxide Hydrocarbons O 2 Molecular oxygen HNO 3 Nitric acid PANs Peroxyacyl nitrates Aldehydes (e.g., formaldehyde) O 3 Ozone O Atomic oxygen Photochemical Smog 13

Smog Photochemical smog reaction involves sunlight, nitric oxides and VOCs –Directly related to automobile use Sulfurous smog is produced by the burning of coal or oil at large power plants. 14

Particulate Matter PM10 is made up of particles less than 10μm in diameter –Present everywhere but high concentrations and/or specific types dangerous –Much particulate matter easily visible as smoke, soot, or dust –Includes airborne asbestos and heavy metals 15

Particulate Matter Of particular concern are very fine pollutants –PM 2.5- less than 2.5 μm in diameter –Easily inhaled into the lungs, then absorbed into the bloodstream –Ultrafine particles- <0.18 μm released by automobiles. Related to heart disease 16

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General Effects of Air Pollution Affect human health in several ways Toxic poisoning, cancer, birth defects, eye irritation, and irritation of respiratory system. Increased susceptibility to viral infections, causing pneumonia and bronchitis. Increased susceptibility to heart disease. Aggravation of chronic diseases, such as asthma and emphysema. 18

Air Pollution Control The most reasonable strategies for control have been to reduce, collect, capture, or retain the pollutants before they enter the atmosphere. Particulates emitted from fugitive, point or area stationary sources are much easier to control. Point and area sources can be controlled by –Settling chambers or collectors which cause particulates to settle out Fugitive sources –Protecting open areas, controlling dust, reducing effects of wind. We deal mostly with the problems of particulate matter!!! (PM:gas compounds = 20:80) 19

General applicability of particulate control systems 20

Dust collectors (settling chambers) 21 The gas stream enters a chamber where the velocity of the gas is reduced. Large particles drop out of the gas and are recollected in hoppers. Because settling chambers are effective in removing only larger particles, they are used in conjunction with a more efficient control device. Settling chambers use the force of gravity to remove solid particles.

Cyclones The general principle of inertia separation is that the particulate- laden gas is forced to change direction. As gas changes direction, the inertia of the particles causes them to continue in the original direction and be separated from the gas stream. - The walls of the cyclone narrow toward the bottom of the unit, allowing the particles to be collected in a hopper. - Cyclone dust collectors have been used as a pre-filter before a cartridge or baghouse collector, - Effective for larger, more abrasive dust particles that can easily damage standard media filters. 22

(Multi-) Cyclone Mechanical collectors Efficiency – % For PM – μm 23

Settling chamber and cyclones in operation Dust collectorCyclone 24

Venturi scrubbers 25 Efficiency – % For PM 1-10 μm Venturi scrubbers use a liquid stream to remove solid particles. In the venturi scrubber, gas laden with particulate matter passes through a short tube with flared ends. The gas stream speeds up when the pressure increases. The reduced velocity at the expanded section of the throat allows the droplets of water containing the particles to drop out of the gas stream. Venturi scrubbers are effective in removing small particles, with removal efficiencies of up to 99 percent. One drawback of this device, however, is the production of wastewater.

Wet scrubber in operation 26

Baghouse Filter 27 "Baghouse" is an example of surface filtration (similar to vacuum cleaner). Fabric filters, or baghouses, remove dust from a gas stream by passing the stream through a porous fabric. The fabric filter is efficient at removing fine particles and can exceed efficiencies of 99 percent in most applications. It is usually the cake on the filter that stops particles from flowing through

Baghouse Filter 28 Efficiency – % For PM μm

Bag Filter in operation 29

Electrostatic Precipitator (ESP) 30 Electrostatic precipitators have collection efficiency of 99%, but do not work well for fly ash with a high electrical resistivity (as commonly results from combustion of low-sulfur coal). Fly ash is a common emission from the burning of fossil fuels

Electrostatic Precipitator (ESP) 31 Efficiency – 90 % For PM μm

ESP in operation 32

Engineering considerations EquipmentAdvantagesDisadvantages (Multi-) cyclone mechanical collectors Efficiency – low (70- 85%) but operational costs low as well Collects for PM of average size μm Small particles thrown out ScrubbersEfficiency – high %. Excellent for PM 1-10 μm. Removes some gaseous emissions. High capital and operational costs. We obtain new problem of wastewater treatment! Baghouse filterEfficiency – high % For PM μm Baghouses are very sensitive to operational conditions (temp., gas velocity, properties, dust conc. etc.) Electrostatic precipitatorsEfficiency – 90 % for PM μm High capital and operational costs! 33

Preliminary conclusions and discussions 34 1.Do we resolve the air pollution problem by implementing appropriate equipment? (PM:gas compounds = 20:80). 2.What kind of air pollution control equipment is the best choice for environmental engineering in terms of collection efficiency? 3.What is your opinion about removal of gaseous compounds from technological emissions? 4.Do you believe that air quality standards are achievable in the near future? Please, provide your suggestions on this case.