Air pollution control and its mechanism and techniques

Seminar Report on Air Pollution Control And its Mechanism and Techniques

2014-2015Chetan Sharma M.Sc. III sem.

School Of Studies In Environment Management

Vikram University, Ujjain

Synopsis

IntroductionTechniques for control air pollutionAcid Gas (SO2 Control)Electrostatic precipitatorDioxin and Furan ControlConclusion References

Introduction

Air pollution is the introduction of particulates, biological molecules, or other harmful materials into Earth's atmosphere, causing disease, death to humans, damage to other living organisms such as food crops, or the natural or built environment.Air pollution control, the techniques employed to reduce or eliminate the emission into the atmosphere of substances that can harm the environment or human health. The control of air pollution is one of the principal areas of pollution control, along with wastewater treatment, solid-waste management, and hazardous-waste management.

PARTICULATE CONTROL EQUIPMENT and Basic Mechanisms

Gravitational settling

)

Predation

GRAVITATIONAL SETTLING CHAMBERS

To remove large, abrasive particles from gas streams

Require simple maintenanceThe particulate matter is settled by its own

weight by lowering the flue gas velocity.It essentially consists of a chamber in which

the velocity of the carrier gas is decreased so that particles in the gas settle down by gravity.

CYCLONE SEPARATOR

Used for the separation of solids from fluidsSeparation based both on particle size and

particle densityIt uses centrifugal force to effect the separationIt consists essentially a short vertical cylinder

closed at the top and by a conical bottom. The air with its load of solid introduced tangentially at the top, solids particles drop into the hopper and outlet air pass through the top central portion.

Widely used for the collecting of wood chips ,heavy and coarse dusts

FABRIC FILTERS OR BAGHOUSES

Fabric collectors use filtration to separate dust particulates from dusty gases.

The most efficient and cost effective types of dust collectors available and can achieve a collection efficiency of more than 99% for very fine particulates.

Dust-laden gases enter the bag house and pass through fabric bags that act as filters. The bags can be of woven or felted cotton, synthetic, or glass-fiber material in either a tube or envelope shape.

ACID GAS (SO2 CONTROL)

WET SCRUBBER

The polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the liquid or by forcing it through a pool of liquid, so as to remove the pollutants.

A wet scrubber operates by introducing the dirty gas stream with a scrubbing liquid – typically water. Particulate or gases are collected in the scrubbing liquid. Wet scrubbers are generally the most appropriate air pollution control device for collecting both particulate and gas in a single system.

WET SCRUBBER

DRY SCRUBBER

Dry scrubbing systems are often used for the removal of odorous and corrosive gases

Dry scrubbing systems can be categorized as dry sorbent injectors (DSIs) or as spray dryer absorbers (SDAs)

Dry sorbent injection involves the addition of an alkaline material (usually hydrated lime or soda ash) into the gas stream to react with the acid gases.

Dry scrubbing systems are used to remove acid gases (such as SO2 and HCl) primarily from combustion sources.

FLARE

Flare

Also known as a flare stack, it is an elevated vertical conveyance found accompanying the presence of oil wells,gaswells,rigs,refineries,chemical plants, natural gas plants, and landfills.

They are used to eliminate waste gas which is otherwise not feasible to use or transport.

BIOFILTERS

Uses living material to capture and biologically degrade process pollutants.

Common uses include processing waste water, capturing harmful chemicals or silt from surface runoff, and microbiotic oxidation of contaminants in air.

Examples of biofiltration include Bioswales, Biostrips, Biobags, Bioscrubbers, and Trickling filters Constructed wetlands and Natural wetlands, Slow sand filters, Treatment ponds.

ELCTROSTATIC PRECIPITATOR

An electrostatic precipitator (ESP) is an device that removes dust particles from a flowing gas (such as air) using the force of an induced electrostatic attraction (i.e, like charges repel; unlike charges attract).Electrostatic precipitators are highly efficient filtration devices that allow the flow of gases through the device, and can easily remove fine particulate matter such as dust and smoke from the air stream.

Electrostatic precipitation is a method of dust collection that uses electrostatic forces, and consists of discharge wires and collecting plates. A high voltage is applied to the discharge wires to form an electrical field between the wires and the collecting plates, and also ionizes the gas around the discharge wires to supply ions. When gas that contains an aerosol (dust, mist) flows between the collecting plates and the discharge wires, the aerosol particles in the gas are charged by the ions. The Coulomb force caused by the electric field causes the charged particles to be collected on the collecting plates, and the gas is purified.

20 – 80 KV dc

BASIC DIAGRAM OF AN ELECTROSTATIC PRECITATOR

440V, 50Hz

Control cabinet High voltagetransformer

Rectifier Dust gas

Clean gas

Hooper

Discharge electrode

Collectorelectrode

DIOXIN AND FURAN CONTROL

Source

Sources of dioxins and furans include waste incinerators, cement production, fossil-fuel-fired combustors, and forest fires.Dioxins and furans is the abbreviated or short name for a

family of toxic substances that all share a similar chemical structure. Dioxins, in their purest form, look like crystals or a colorless solid. Most dioxins and furans are not man-made or produced intentionally, but are created when other chemicals or products are made. Of all of the dioxins and furans, one, 2,3,7,8-tetrachloro-p-dibenzo-dioxin (2,3,7,8 TCDD) is considered the most toxic

CONTROL TECHNIQUES

Both dioxin and furan compounds are destroyed when the gas temperatures exceeds approximately 1400°F

These temperatures usually exist in the combustion zones of incinerators and fossil-fuel-fired boilers.

The best way to control dioxin and furan emissions is preventing their formation by reducing or eliminating the chlorine in the fuel and waste material being burned.

CONCLUSION

VegetationandZoning,, are also very helpful methods to reduce air pollution in our atmosphere . Plants contribute towards controlling air-pollution by utilizing carbon dioxide and releasing oxygen in the process of photosynthesis.

Thank you..

References

Mazzone, P. J. (2008). "Analysis of Volatile Organic Compounds in the Exhaled Breath for the Diagnosis of Lung Cancer". Journal of Thoracic Oncology.

http://www.hitachi-infra.com.sg/services/energy/dustcollection/principle/dustcollection.html

http://www.indiastudychannel.com/resources/140937-Working-of-electrostatic-precipitators-with-its-advantages-and-disadvantages.aspx

Kay, Jane (November 13, 2008). "Bad air costing state's economy billions". San Francisco Chronicle. Retrieved August 14, 2012

Air Pollution Control Technology Handbook by by Karl B. Schnelle Jr. (Author), Charles A. Brown (Author)