PROCESS DESIGN STRATEGIES FOR AIR POLLUTION CONTROL

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PROCESS DESIGN STRATEGIES FOR AIR POLLUTION
CONTROL
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Example Removal of NOx from a Process Stream
Cross flow
Problem identified Emission of NOx
Counter flow
Co-current flow

• PRELIMINARY DATA
• Stream composition
• Flow rate
• Temperature
• Pressure
• Operating parameter variations

Decision Point 3
Condensation
Decision Point 1
Decision Point 2
Continuous Packed column
Absorption
Stage-wise
Adsorption
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Energy and Mass Balances Basis for Process
Design
Q, heat transferred
Ws shaft work on system
Stream A
SYSTEM
Stream C
Stream B
ZA
ZC
ZB
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Overall mass balance MA MB MC xAA MA xBB
MB xAC MC
Overall Energy Balance
Note First subscript represents component and
second subscript represents Stream.
Enthalpy H U PV where V 1/? is the
specific volume. ?H calculated from ?Cp dT.

• Uj internal energy, Pj pressure, ?j
  density, Vj average stream velocity,
• - correction factor (1 for turbulent and 0.5 for
  laminar flow), g acceleration

due to gravity, gc gravitational constant.
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Mean Mixing Depth
(dt/dz)env
MMD
MMD
MMD
T0
T0
Denotes environmental profile
Denotes adiabatic profile
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Holzworth, G.C. (1972) "Mixing heights, wind
speeds, and potential for urban air pollution
throughout the contiguous United States", Office
of Air Prog. pub. AP-101,USEPA, RTP, NC.
Mean summer afternoon mixing height (meters)
Mean summer morning mixing height (meters)
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Effect of Terrain Roughness on Wind Speed Profile
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Wind Rose
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