134
• Sulphur dioxide
• Unburnt hydrocarbons
Toxic chemicals emitted in minor quantity include the following:
• Aldehydes
• Benzene
• Butadiene
• Ethers
• Methanol
Pollutants from engine exhaust depend on the following
• Air-conditioning and other accessories
• Deterioration of emission control equipment
• Driving conditions
• Fuel properties and quality
• Maintenance of vehicle
• Quality of tyres
• Type of engine
• Use of leaded fuel
Internal combustion engines (ICE) can be classified by ignition type, fuel type,
power, etc. Figure 6.5 shows one such classification.
Conventional air pollution control from mobile sources includes the following:
1. Vehicle design change
2. Clean fuels
3. Positive crankcase ventilation (PCV) system
4. Adsorption system
5. Post-combustion control equipment
(a) Diesel particulate filters (DPF)
(b) Catalytic systems
Table 6.1 (continued)
Type of
control
equipment
Types of
pollutants
removed
Examples of
pollutants
Control
efficiency
Device
considerations
and restrictions
Common
applications
Catalytic
reactors
Gaseous
compounds
NO x , other
VOCs and
gases
90+% (for
NO x )
99.99% (for
other gaseous
pollutants)
Catalyst
contamination
will lead to
efficiency
reduction
Oil refineries
Biofilters
Gaseous
compounds
Water-soluble
biodegradable
organic
compounds
Feasible for
biodegradable
air pollutants
Food processing,
pharmaceuticals
a ESD of a non-spherical particle is the diameter of a spherical particle that shows the same properties such as hydrodynamic, aerodynamic, optical and electrical
6 Air Pollution Control