ENV 462 cont...

SOURCES OF AIR POLLUTION
Two main categories


Stationary sources such as power stations, oil refineries

Mobile sources such as motor vehicles

STRATEGIES TO CONTROL AIR
POLLUTION

Stationary sources

Siting of industries
Should be sited far away from residential areas
Install pollution control equipment and have tall stacks for dispersion of air pollutants


Fuel quality
Control type and quality of fuel
E.g. Use fuel with sulphur content not exceeding 2% by weight


Pollution control equipment
Equipment/processes which give rise to emissions are designed to be able to comply with emission standards

Industries encouraged to adopt cleaner technologies
Wet & Dry collectors (scrubbers)
Cyclones
Fabric filters
Electrostatic Precipitators

Tax incentives

Enforcement
Regular inspections to ensure that pollution control equipment and facilities are properly maintained

Mobile sources

Fuel quality
Use of unleaded petrol
Sulphur content of diesel is 0.05% by weight
Fitted with catalytic converters

Emission standards

Inspection and enforcement
Mandatory periodic inspections

Air pollution
Air Pollution

is the presence of any chemical, physical (e.g. particulate matter), or biological agent that modifies the natural characteristics of the atmosphere.

The atmosphere is a complex, dynamic natural gaseous system that is essential to support life on planet earth.

Worldwide air pollution is responsible for large numbers of deaths and cases of respiratory diseases


Types of air pollutants

Main gaseous pollutants

Sulphur dioxide (SO2)
Oxides of nitrogen (NO and NO2)
Carbon monoxide (CO)
Hydrocarbons (HC)
Ozone (O3)


Main non-gaseous pollutants
Suspended particulate matter
Lead


Sources of air pollution
Stationary sources
any fixed emitter of air pollutants

Fossil fuel burning power stations
Petroleum/Oil refineries
Petrochemical plants
Food processing plants
Heavy Industrial sources


Mobile sources
non-stationary source of air pollutants

automobiles, buses, trucks, ships, trains, aircraft and various other vehicles
tobacco smokers

Sources of air pollution
Sulphur dioxide

Largest single source of SO2 is the combustion of sulphur – containing fossil fuel both for electric power generation and for process heat

Some important industrial emitters

Nonferrous smelters

Except iron and aluminum, metal ores are suphur compounds

When ore is reduced to pure metal, sulphur in the ore is oxidized to SO2


Oil refining

Sulphur and hydrogen are constituents of crude oil

Hydrogen sulphide is released as gas during catalytic cracking

Hydrogen sulphide is more toxic then sulphur dioxide

It is flared to sulphur dioxide before release into air


Pulp and paper manufacture

Sulphite process for wood pulping use hot sulphiric acid

Thus emits sulphur dioxide into air

Kraft pulping process produces hydrogen sulphide, that is flared to sulphur dioxide

Natural sources

Volcanic eruptions
Sulphur containing geothermal sources – hot springs


Oxides of nitrogen

formed by the combustion of nitrogen - containing compounds

and thermal fixation by atmospheric nitrogen

NOx is created when nitrogen and oxygen in combustion air are heated to high temperature

The equilibrium constant for the reaction: N2 + O2 2NO

All high temp processes produce NO, that is oxidized to NO2 in the ambient air

Carbon monoxide

Product of incomplete combustion of carbon-containing compounds

Most of the CO in ambient air comes from vehicle exhaust

Internal combustion engines do not burn fuel completely to CO2 and water

Some unburned fuel will always be exhausted, with CO as a component

Tobacco smoke

Hydrocarbons

Major source
vehicles

Stationary sources

Petrochemical manufacture
Oil refining
Incomplete incineration
Paint manufacture and use
Dry cleaning


Particulate matter

Every industrial process is a potential source of dust, smoke 0r aerosol emissions

Waste incineration
Coal combustion
Petrochemical industry
Smelting

Agricultural operations
major source of dust – dry farming

Demolition and construction
Great quantities of dust

Fires
Major sources of airborne particulate matter, HC, CO

Tobacco smoke
CO, organic tars, metal oxides particles

Wood – burning stoves and fireplaces
Produce smoke that contains partly burned HC, tars, dioxins


Airborne lead
Vehicle exhaust
Leaded paint