Air Pollution Calculation
Air Pollution Calculation
Air Pollution Calculation
&
Control Technologies
Presentation by:
Dr. Gazala Habib
Room 303, Block IV
Department of Civil Engineering
IIT Delhi
Commonly Used Methods For Air Pollution Control
PARTICULATE
Cyclones
Electrostatic Precipitators
Fabric Filter
Wet Scrubbers
GASES
Adsorption Towers
Thermal Incineration
Catalytic Combustion
Cyclones
• Based upon principle of inertia separation.
• Step 2:
Determine final composition after ESP.
25% - (25% x 0.9) = 2.5%
• Step 3:
Determine overall efficiency
hoverall = (initial – final)/ initial
= 100% - 2.5%100% = 97.5%
Definition of Aerodynamic Diameter
• Aerodynamic diameter is the diameter of a unit
density particle (1 gm/cm3) that has the same
settling velocity as the particle.
Equal settling
velocities means
equal aerodynamic
diameters
Calculation of terminal settling velocity in the Stokes region
Where:
= particle density (g cm-3)
p d p2 gC p
VTS dp = physical diameter (cm)
18 g = gravitational acceleration
Cp = Cunningham correction
factor
= viscosity
= shape correction factor
Centrifugal Separators
Centrifugal Separators
• If a body moves in a circular path with radius r and
velocity vc along the path, then it has angular velocity
ω = vc / r, and
m c
2
Centrifugal force m r
2
r
Example
2
111.8 #
Gravity force mg 32.2 ft / s
m = mass,
vc = velocity
r = radius
g = acceleration due to gravity
Terminal Velocity
• The constant speed that a freely falling object eventually
reaches when the resistance of the medium through which
it is falling prevents further acceleration
c2 D 2 p
t , centrifugal (5)
18 r
• vc = velocity
• D = Aerodynamic diameter
• ρp = the density of the particle.
• μ = coefficient of viscosity of air (1.8 *10^-5 kg/m/s)
• r = radius
Problem
Compute the terminal settling velocity of a particle in a
circular gas flow with velocity vc = 60 ft/s (18.29 m/s) and
radius 1 ft (0.3048 m).
6
8.85 10 C / V / m 10 m 300 kV / m
2
q 3 12 6
62
17 1.602 1019 electrons
1.88 10 C 300 electrons #
C
Electrostatic force
• F=qEp
• Ep= the local electric field strength
causing the force
• Two subscripts on Es remind us that one
represents the field strength at the time of
charging the other instantaneous (local)
field strength. For all practical purpose we
take average E (E0=Ep=E).
Drift velocity
Example
Out ESP has a measured efficiency of 90%.
We wish to upgrade it to 99%. By how much must we
increase the collecting area?
25
Solution
Aexisting
pexisting 1 existing 0.1 exp
Q
Anew
pnew 1 new 0.01 exp
Q
26
Solution
27