PARTICULATE AIR POLLUTANT & IT’S CONTROL
Particulate Matter~
“Particulate matter,” also known as particle pollution or PM, is a complex mixture of extremely small particles and liquid droplets.
*Particle pollution is made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles.
*The EPA is concerned about particles that are 10 micrometers in diameter or smaller because those are the particles that generally pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects.
*Sea salt is considered the second-largest contributor in the global aerosol budget, and consists mainly of sodium chloride originated from sea spray.
Types of Particle~
EPA (Environmental Protection Agency) groups particle pollution into two categories:
• “Inhalable coarse particles,” such as those found near roadways and dusty industries, are larger than 2.5 micrometers and smaller than 10 micrometers in diameter.
• “Fine particles,” such as those found in smoke and haze, are 2.5 micrometers in diameter and smaller. These particles can be directly emitted from sources such as forest fires, or they can form when gases emitted from power plants, industries and automobiles react in the air.
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‘I’ll go out for a breath of fresh air’ is an often-heard phrase. But how many of us realize that this has become irrelevant in today’s world, because the quality of air in our cities is anything but fresh. The moment you step out of the house and are on the road you can actually see the air getting polluted; a cloud of smoke from the exhaust of a bus, car, or a scooter; smoke billowing from a ...
Composition~
The composition of particles depends on their source, from where they comes originated.
*Particulates may have an anthropogenic origin (from fossil fuel or coal combustion) and a natural biogenic origin.
*In addition, sea spray aerosols may contain organic compounds, which influence their chemistry. Sea salt does not absorb.
*Organic matter (OM) can be either primary or secondary, the latter part deriving from the oxidation of VOCs; organic material in the atmosphere may either be biogenic or anthropogenic.
*Another important aerosol type is constitute of elemental carbon (EC, also known as black carbon, BC): this aerosol type includes strongly light-absorbing material and is thought to yield large positive radiative forcing.
*The composition of particulate matter that generally causes visual effects such as smog consists of sulphur dioxide, nitrogen oxides, carbon monoxide, mineral dust, organic matter, and elemental carbon also known as black carbon or soot.
*The particles are hydroscopic due to the presence of sulphur, and SO2 is converted to sulphate when high humidity and low temperatures are present. This causes the reduced visibility and yellow color.
*The chemical composition of the aerosol directly affects how it interacts with solar radiation.
*The chemical constituents within the aerosol change the overall refractive index. The refractive index will determine how much light is scattered and absorbed.
Sources of Particulate Matter~
Sources of fine particles include all types of combustion activities (motor vehicles, power plants, wood burning, etc.) and certain industrial processes.
*Particles with diameters between 2.5 and 10 micrometers are referred to as “coarse.” Sources of coarse particles include crushing or grinding operations, and dust from paved or unpaved roads.
*Other particles may be formed in the air from the chemical change of gases. They are indirectly formed when gases from burning fuels react with sunlight and water vapor. These can result from fuel combustion in motor vehicles, at power plants, and in other industrial processes.
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Media source effects on Airlines Industry. British Airways Airline operating business generates some of the highest revenues out of all types of truly global businesses. However, the revenues always have costs. Probably the highest costs of all for airline companies are those related to advertising. Today the market requires new approaches to the questing of correct product positioning and ...
*Some common sources are:
-Motor vehicle
-Power plants
-Wood burning
-non road vehicles
-Space heating
-Industrial source
-Sea spray
-Forest fire
Effects
Health Effects-
The size of particles is directly linked to their potential for causing health problems.
*Small particles less than10 micrometers in diameter pose the greatest problems, because they can get deep into your lungs, and some may even get into your bloodstream.
*Exposure to such particles can affect both lungs and heart.
*The Clean Air Act requires EPA to set air quality standards to protect both public health and the public welfare (e.g. crops and vegetation).
Particle pollution affects both.
*Particles, especially fine particles, can cause variety of problems on exposure:
• increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing;
• decreased lung function;
• aggravated asthma;
• development of chronic bronchitis;
• irregular heartbeat;
• nonfatal heart attacks; and
• premature death in people with heart or lung disease.
*People with heart or lung diseases, children and older adults are the most likely to be affected by particle pollution exposure.
However, a healthy person, may experience temporary symptoms from exposure to elevated levels of particle pollution, called “asthma”.
Environmental Effects
Visibility reduction~
Fine particles (PM2.5) are the major cause of reduced visibility (haze) in parts of the world. e.g. Smog etc.
Environmental damage~
Particles can be carried over long distances by wind and then settle on ground or water. The effects of this settling include: making lakes and streams acidic; changing the nutrient balance in coastal waters and large river basins; depleting the nutrients in soil; damaging sensitive forests and farm crops; and affecting the diversity of ecosystems.
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Approved by: Chair of Committee, Committee Members, Robert A. Wattenbarger Goong Chen Christine Ehlig-Economides Bryan Maggard Stephen Holditch Head of Department, May 2009 Major Subject: Petroleum Engineering iii ABSTRACT Rate Transient Analysis in Shale Gas Reservoirs with Transient Linear Behavior. (May 2009) Rasheed Olusehun Bello, B. Sc. , University of Lagos, Nigeria; M. Sc. , University of ...
Aesthetic damage~
Particle pollution can stain and damage stone and other materials, including culturally important objects such as statues and monuments. e.g. Acid Rain.
Effects on vegetation
Particulate matter can clog stomatal openings of plants and interfere with photosynthesis functions. In this manner high particulate matter concentrations in the atmosphere can lead to growth stunting or mortality in some plant species.
Control of Particulates
The various collecting devices and techniques employed for the particulate air pollutants:
Gravity Techniques~
It is simple type of equipment used for the collection of solid particles. The gravitational technique use a settling chamber in which the carrier gas velocity is reduced, so as to allow the particulates to settle down out of moving stream under the action of gravity on the base of chamber. The gas velocity in the chamber is kept sufficiently low, so that the settling time of a particle entering the chamber at the top is same or less than the time taken by the flue gas to pass through the chamber.
e.g. Settling Chamber; Cyclone; etc.
Filtration Techniques~
Particulate matter can be filtered, if the fumes containing them are forced to pass through a filtering device.
The particles are held, while the gases pass through the media. Cloth fabric or fibrous medium, like mats of wool, cellulose, etc. may be used as separator (or filter media).The most common type of fabric collector, used in industries, is `Bag Filter`.
It consist of numerous vertical bags, 120-400mm. diameter & 2-10m. long. Dust laden fumes are passed through, under pressure.
Periodically, the bag contents are shaken out in dust collection containers, which are hopper shaped from where the dust particle are removed.
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A particle cloud chamber is a device that makes visible to the human eye the presence of certain particles and cosmic rays. This paper will discuss the process in which a successful chamber prototype was developed. This paper will also discuss how the chamber utilizes the properties of a supersaturated environment to detect these particles. Finally, plans for the future development of a larger ...
Precipitation Techniques~
It involves the precipitation of the particulate matter. It is of two types:
Thermal precipitation~
When exposed to a high temperature gradient, suspended particles tend to move to the lower temperature region. This principle may be applied for collecting aerosol particles in the range 0.001-10µ. The technique can also be used efficiently for collecting radio-active particulates.
Wet Precipitator~
These are also called `Wet Collectors`. These utilizes water or any other specific liquid to assist in the removal of particulates as well as gases by absorption or adsorption. The simplest type is `spray tower`. Gas is passed countercurrent to falling drops of water or liquid from a number of spray nozzles. These can remove particulate matter of less than 0.2µm in diameter.
e.g. Spray Tower; Cyclone Scrubber; etc.
Electrostatic Precipitator~
In this technique, electrical charge is used to force radio-active or other particulates in the range of 0.001-10µ to migrate out of the air stream onto a collecting surface. When the dust laden fumes enter the ESP, the large size particles settle down due to gravity, while the smaller charged particle settle on the oppositely charged electrode surface, and on getting accumulated ,they gradually fall down, and pass out of the cylinder from the bottom outlet.
