3 air pollution control technology 08

7/30/2019 3 Air Pollution Control Technology 08

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Chapter 12Chapter 12

Air Pollut ion Cont rolAir Pollut ion Cont rol

A. Cont rol of Gaseous Pollu tant sA. Cont rol of Gaseous Pollu tant s

B. Cont rol of Part iculates Pollut antsB. Cont rol of Part iculates Pollut ants

A. Cont rol of Gaseous Pollu tant sA. Cont rol of Gaseous Pollu tant s

Absorption (Wet Scrubbing)Absorption (Wet Scrubbing)

AdsorptionAdsorption CombustionCombustion

FGDFGD


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AbsorptionAbsorption

Adsorption SystemsAdsorption Systems

consist of a bed of adsorbing materialconsist of a bed of adsorbing material

activated carbonactivated carbon adsorbing material is housed within aadsorbing material is housed within a

pressure vessel through which thepressure vessel through which the

contaminated air passescontaminated air passes

pollutants are transferred from air to adsorberpollutants are transferred from air to adsorber

AdsorptionAdsorption


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AdsorptionAdsorption


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Incineration or flaringIncineration or flaring

used to oxidize:used to oxidize:

carbon monoxidecarbon monoxide

organic air pollutantsorganic air pollutants

organics containing chlorine, sulfur, and nitrogenorganics containing chlorine, sulfur, and nitrogen

to carbon dioxide and waterto carbon dioxide and water direct flame combustion and catalyticdirect flame combustion and catalytic

combustioncombustion

IncinerationIncineration

IncinerationIncineration


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Vertical Venturi ScrubberVertical Venturi Scrubber

Packed Bed ScrubberPacked Bed Scrubber


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Control Technologies forControl Technologies forNitrogen OxidesNitrogen Oxides

PreventivePreventive

minimizing operatingminimizing operating

temperaturetemperature

fuel switchingfuel switching

low excess airlow excess air

flue gas recirculationflue gas recirculation staged combustionstaged combustion

secondary combustionsecondary combustion

Post combustionPost combustion

selective catalyticselective catalyticreductionreduction

selective nonselective non--catalyticcatalyticreductionreduction

B. Cont rol of Part iculate Pollut antsB. Cont rol of Part iculate Pollu tants

Settling chambersSettling chambers

based onbased on StokeStokess LawLaw

practical lower limit is 50practical lower limit is 50--100100 mm

CycloneCyclone lower limit = 10lower limit = 10 mm

Bag house filterBag house filter

removes very small particlesremoves very small particles

Liquid scrubbingLiquid scrubbing

Electrostatic precipitation (ESP)Electrostatic precipitation (ESP)


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based onbased on StokeStokess LawLaw

practical lower limit is 50practical lower limit is 50--100100 mm

Settling ChambersSettling Chambers

CyclonesCyclones

can be used for 50can be used for 50--100100 m size particlesm size particles

simple economical unitsimple economical unit

no moving partsno moving parts

relies on inertial effectsrelies on inertial effects


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Cyclones.Cyclones.

For particle sizes greater than about 10For particle sizes greater than about 10 m inm in

diameter, the collector of choice is the cyclonediameter, the collector of choice is the cyclone

(Figure 6(Figure 6--30). This is an inertial collector with no30). This is an inertial collector with no

moving parts.moving parts.

The particulateThe particulate--laden gas is accelerated throughladen gas is accelerated through

a spiral motion, which imparts a centrifugal forcea spiral motion, which imparts a centrifugal force

to the particles.to the particles.

The particles are hurled out of the spinning gasThe particles are hurled out of the spinning gas

and impact on the cylinder wall of the cyclone.and impact on the cylinder wall of the cyclone.


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CycloneCyclone

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2

5.0

9

=

gpQ

HBd

( )212 LLH

+=

De

L3D2

L1

L2

Dd

H

B

d0.5 = cut diameter at 50% removal

= dynamic viscosity of gas, Pa-sB = width, m

H = height, m

p = particle density, kg/m3Qg = gas flow rate, m3/s = effective number of turns


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Ex. 6-9Given:

D2 = 0.5 m

Qg = 4 m3/s

T = 25 oC

p = 800 kg/m3

For standard Cyclone:

B = 0.25 D2 = 0.13 m

H = 0.5 D2 = 0.25 mL1 = L2 = 2 D2 = 1 m

Q = What is the removal efficiency

for particles with ave

diameter of 10 m?

( ) 7.371)1(225.0

=+=

)(41.2

1041.2)7.37)(4)(800(

)25.0()13.0)(105.18(9 65.0

26

5.0

m

xxd

=

=

=

@ d =10 m 15.441.2

10

5.0

==d

d

= 0.95


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Cyclone Installation at Wood Working Plant

http://www.fkinc.com/cyclones.htm

BaghouseBaghouse FilterFilter

similar to conventional homesimilar to conventional home

vacuum cleanervacuum cleaner

particle size smaller that 10particle size smaller that 10mm

High removal efficiency for < 5High removal efficiency for < 5 m particlesm particles cannot be used forcannot be used for

wet air systemswet air systems

corrosive gasescorrosive gases

gases above 260gases above 260ooCC


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Air FiltrationAir Filtration

Air FiltrationAir Filtration

ImpactionImpaction

DiffusionDiffusion

Straining (Interception)Straining (Interception)

ElectrostaticsElectrostatics


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Wet ScrubberWet Scrubber

can be used wherecan be used where

air is wetair is wet

corrosivecorrosive

hothot

wherewhere baghousesbaghouses can not be usedcan not be used

for even higher efficiencies, a combinationfor even higher efficiencies, a combination

of a venturi scrubber and cyclone and canof a venturi scrubber and cyclone and can

be usedbe used


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ScrubberScrubber

VenturiVenturi

Liquid ScrubberLiquid Scrubber


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ESPESP


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ESPESP


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Effectiveness of Air PollutionEffectiveness of Air Pollution

Control DevicesControl Devices

0.00001 0.0001 0.001 0.01 0.1 1 1 10 100 1000 10,000

Pollutant diameter (m)

Electrostatic precipitator

Bag filter

Adsorber

Scrubber

Incinerator

Cyclone

Settling chamber

Wet scrubber

Comparison of Air PollutionComparison of Air Pollution

Control DevicesControl Devices

A Setling Chamber

B Simple Cyclone

C H igh efficiency cyclone

D E le ctr osta tic P rec ipita to r

E Spray Tower Wet Scrubber

F Venturi Scrubber

G Bag Filter

3 air pollution control technology 08

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