AIR POLLUTION CONTROL DEVICES.pptx

8/10/2019 AIR POLLUTION CONTROL DEVICES.pptx

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EQUIPMENTS TO

CONTROL AIR

POLLUTION

ARUN. S


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COMMON CONTROLDEVICES

POLLUTANTS EXAMPLES WHERE USED

Packed towers, spray chambers, venturiscrubbers

Gases, vapours, sulphur oxides, solidparticles, liuid droplets

Asphalt and concrete batch plants, coalburnin! power plants

"arbon absorbers #apour phase #$"s, %a&ardous AirPollutants '%APs(

Soil remediation )acilities, oil re)ineries,steel mills, printers

*abric )ilters or ba!houses Particulate +atter 'P+( Asphalt batch plants, steel mills,)oundries, )ertili&er plants,

"atalytic reactors #$"s, Gases -and )ills, oil re)ineries, printin! or paintshops

"yclones -ar!e P+ ood shops, pharmaceuticalmanu),acture rock crushers, cementplants

/SPs P+ Power plants, steel 0 paper mills,smelters, cement plants, re)ineries

1ncinerators #$"s, !ases, )umes, %aps, P+ Soil contaminated with !asoline, ink andprintin!, ha&ardous waste disposal

2io)ilters #$"s, odours, %3S, marcaptans astewater treatment plants


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PARTICULATE CONTROLEQUIPMENT Basic Mechanisms

Gravitational settlin!

"entri)u!al impaction

1nertial impaction

4irect interception

4i))usion

/lectrostatic perception


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GRAVITATIONAL SETTLINGCHAMBERS

5o remove lar!e, abrasive particles )rom !as streams

Reuire simple maintenance

5he particulate matter is settled by its own wei!ht by

lowerin! the )lue !as velocity.

1t essentially consists o) a chamber in which the

velocity o) the carrier !as is decreased so that

particles in the !as settle down by !ravity.

#elocity o) a !as is reduced by expandin! the ductin!

into a chamber o) a suitable dimension so that a low!as velocity is obtained. 1ts e))iciency can be

increased by providin! plates or ba))les


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CYCLONE SEPARATOR

Used )or the separation o) solids )rom )luids

Separation based both on particle si&e and

particle density

1t uses centri)u!al )orce to e))ect the separation 1t consists essentially a short vertical cylinder

closed at the top and by a conical bottom. 5he air

with its load o) solid introduced tan!entially at the

top, solids particles drop into the hopper and outlet

air pass throu!h the top central portion.

idely used )or the collectin! o) wood chips

,heavy and coarse dusts


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FABRIC FILTERS OR BAGHOUSES

*abric collectors use )iltration to separate dust particulates

)rom dusty !ases.

5he most e))icient and cost e))ective types o) dust collectors

available and can achieve a collection e))iciency o) more

than 667 )or very )ine particulates. 4ust8laden !ases enter the ba! house and pass throu!h

)abric ba!s that act as )ilters. 5he ba!s can be o) woven or

)elted cotton, synthetic, or !lass8)iber material in either a

tube or envelope shape.

5heir advanta!es include retention o) )inest particles,collection o) particulates in dry )orm and low pressure drop

As classi)ied by cleanin! method, three common types o)

ba! houses are9


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Mechanical shaker

Reverse je

Reverse air


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ELECTROSTATIC PRECIPITATOR

Particulate collection device that removes

particles )rom a )lowin! !as 'such as air( usin!

the )orce o) an induced electrostatic char!e.

%i!hly e))icient )iltration devices that minimallyimpede the )low o) !ases throu!h the device,

and can easily remove )ine particulate matter

such as dust and smoke )rom the air stream.

/SP applies ener!y only to the particulatematter bein! collected and there)ore is very

e))icient in its consumption o) ener!y


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ACID GAS (SO2

CONTROL)


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FLUE GAS DESULPHURISATION

Used to remove S$3)rom the exhaust )lue !ases o) )ossil )uel power

plants.

+ost *G4 systems employ two sta!es9 one )or )ly ash removal and

the other )or S$3removal.

1n wet scrubbin! systems, the )lue !as normally passes )irst throu!h a

)ly ash removal device, either an electrostatic precipitator or a wetscrubber, and then into the S$3absorber.

1n dry in:ection or spray dryin! operations, the S$3is )irst reacted with

the sorbent and then the )lue !as passes throu!h a particulate control

device.

%ydrodesul)uri&ation o) )uel has been used )or treatin! )uel oils be)oreuse.

*luidi&ed bed combustion adds lime to the )uel durin! combustion.

5he lime reacts with the S$3to )orm sul)ates which become part o)

the ash.


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HYDRODESULPHURIATION %4S is a catalytic chemical process widely used

5he industrial hydrodesulphuri&ation processes include

)acilities )or the capture and removal o) the resultin! %3S

!as which is converted into byproduct elemental sul)ur or

sul)uric acid "3%;S% < %3= "3%>< %3S

Reaction takes place in a )ixed8bed reactor at

elevated temperatures ran!in! )rom ?@@ to @@ B" and

elevated pressures ran!in! )rom ?@ to C?@ atmospheres

in the presence o) a catalyst consistin! o)

an alumina base impre!nated

with cobalt and molybdenum 'usually called a "o+o(

catalyst or nickel and molybdenum 'called Ni+o(


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DRY SCRUBBER

4ry scrubbin! systems are o)ten used )or the removal

o) odorous and corrosive !ases

4ry scrubbin! systems can be cate!ori&ed as dry

sorbent in:ectors '4S1s( or as spray dryer absorbers

'S4As( Dr! s"r#en injeci"ninvolves the addition o)

an alkaline material 'usually hydrated lime or soda

ash( into the !as stream to react with the acid !ases.

1n s$ra! %r!er a#s"r#ers, the )lue !ases areintroduced into an absorbin! tower 'dryer( where the

!ases are contacted with a )inely atomi&ed

alkaline slurry.


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!ET SCRUBBER

5he polluted !as stream is brou!ht into contact with the

scrubbin! liuid, by sprayin! it with the liuid or by

)orcin! it throu!h a pool o) liuid, so as to remove the

pollutants.

5he reaction takin! place in wet scrubbin! usin! a"a"$?'limestone( slurry can be expressed as9

CaCO&'s"li%( ) SO*'+as( , CaSO&'s"li%( )

CO*'+as(

hen wet scrubbin! with a +!'$%(3'ma!nesiumhydroxide( slurry

M+'OH(*'s"li%( ) SO*'+as( , M+SO&'s"li%( ) H*O

'li-.i%(


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VENTURI SCRUBBER


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A conver!in!Ddiver!in! section o) duct.

5he conver!in! section accelerates the !as stream to

hi!h velocity. hen the liuid stream is in:ected at the

throat, which is the point o) maximum velocity, the

turbulence caused by the hi!h !as velocity atomi&esthe liuid into small droplets, which creates the sur)ace

area necessary )or mass trans)er to take place.

5he hi!her the pressure drop in the venturi, the

smaller the droplets and the hi!her the sur)ace area. 5he penalty is in power consumption.

*or simultaneous removal o) S$3and )ly ash, venturi

scrubbers can be used.


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PAC"ED BED SCRUBBER

"onsists o) a tower with packin! material inside

in the shape o) saddles, rin!s, or some hi!hly

speciali&ed shapes desi!ned to maximi&e

contact area between the dirty !as and liuid.

Packed towers typically operate at much lower

pressure drops than venturi scrubbers and are

there)ore cheaper to operate. 5hey also typically

o))er hi!her S$3removal e))iciency.

5he drawback is that they have a !reater

tendency to plu! up i) particles are present in

excess in the exhaust air stream.


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SPRAY TO!ERS

5he simplest type o) scrubber.

1t consists o) a tower with spray no&&les,

which !enerate the droplets )or sur)ace

contact. Spray towers are typically used when

circulatin! a slurry .

5he hi!h speed o) a venturi would causeerosion problems, while a packed tower

would plu! up i) it tried to circulate a slurry.


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VOC ABATEMENT


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ADSORPTION SYSTEMS

1nvolves the molecular attraction o) !ases or

vapours onto the sur)ace o) adsorbent solids E

activated carbon or molecular sieves

5he attraction maybe physical or chemical

A)ter the activated carbon is saturated with #$"s,

it is treated to strip o)) the collected #$"s

#$"s E )urther treatment 0 "arbon E reused in

adsorption reactor

"ommonly used )or removin! !ases )rom

contaminated soil, oil re)ineries, industrial paint

shops and steel mills


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FLARE


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Also known as a /lare sack,it is an elevated

vertical conveyance )ound accompanyin! the

presence o) oil wells, !as

wells,ri!s, re)ineries, chemical plants, natural

!as plants, and land)ills.

5hey are used to eliminate waste !as which is

otherwise not )easible to use or transport. 5hey

also act as sa)ety systems )or non8waste !asand is released via pressure relie) valve when

needed to ease the strain on euipment.


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THERMAL O#IDIERS ORINCINERATORS


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A process unit )or air pollution control in many chemical plants that

decomposes ha&ardous !ases at a hi!h temperature and releases

them into the atmosphere.

Used to destroy %APs and #$"s )rom industrial air streams.

Pollutants are destroyed via thermal combustion where they are

chemically chan!ed to )orm "$3and %3$. /ner!y recovery e))iciency can reach 6;7

4i))erent types include 9

Re!enerative thermal oxidi&er 'R5$(

Re!enerative catalytic oxidi&er 'R"$(

#entilation air methane thermal oxidi&er '#A+5$F(

5hermal recuperative oxidi&er

"atalytic oxidi&er

4irect )ired thermal oxidi&er 8 a)terburner


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CRYOGENICCONDENSERS "ryo!enic condensation is a process that allows

recovery o) volatile or!anic compounds '#$"s( )or

reuse.

5he condensation process reuires very low

temperatures so that #$"s can be condensed andhence liuid nitro!en has emer!ed as a viable substance

)or use in the extremely low8temperature or cryo!enic

'less than 8C>@ de!rees "( condensation process.

"ryo!enic condensation is best suited to exhaust

streams with low )lowrates 'below 3@@@ standard )t?Dmin(andDor vapor concentrations above C@@ parts per million

on a volumetric basis 'ppmv(.


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NOXCONTROL


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SELECTIVE CATALYTIC REDUCTION

A means o) convertin! nitro!en oxides, also re)erred to

as N$xwith the aid o) a catalyst 'ceramic as carrier, and

oxides o) base metals like # 0 ( into N3, and %3$ usin!

a !aseous reductant 8 anhydrous N%?, aueous N%?

or urea, at a temp between >?@ and 3@ H. Application8 lar!e utility 0 industrial boilers

'reduce N$xby @86;7(. 4iesel en!ines 0 !as turbines.

Reactions

N$ < N%?< $3= N3< >%3$

3N$3< N%?< $3= ?N3< >%3$

N$ < N$3< 3N%?= 3N3< ?%3$


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Se$ec%i&e n'n(ca%a$)%ic *e+,c%i'n

A method to lessen N$x emissions in conventional

power plants that burn biomass, waste and coal by

in:ectin! N%? or urea into the boiler at a location

where the )lue !as is betweenC,@@ 0 3,@@@ B*

producin! N3, "$30 %3$. N%3"$N%3< %3$ 8I 3N%?< "$3

N$ < N%?< $38I N3< > %3$

1t can achieve the same e))iciency o) about 6@ 7

as S"R, but practical constraints o) temperature, time,and mixin! exist.

SN"R has an economical advanta!e as the cost o)

the catalyst isnt there.


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E#HAUST GAS RECIRCULATION

1t is a N$x emissions reduction techniue used in petrol

and diesel en!ines.

Recirculates a portion o) the en!ines exhaust !as back to

the en!ine cylinders. 1n a !asoline en!ine, this inert

exhaust displaces the amount o) combustible matter in thecylinder. 1n a diesel en!ine, the exhaust !as replaces

some o) the excess oxy!en in the pre8combustion mixture.

5he exhaust !as, added to the )uel, oxy!en, and

combustion products, increases the speci)ic heat

capacity o) the cylinder contents, which lowersthe adiabatic )lame temperature. 2ecause N$x )ormation

pro!resses much )aster at hi!h temperatures, /GR

reduces the amount o) N$x the combustion !enerates


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CATALYTIC CONVERTER

A device used to reduce the toxicity o) emissions )rom an 1" en!ine.

orks by usin! a catalyst to stimulate a chemical reaction in which

toxic by8products o) combustion are converted to less8toxic

substances.

6@7 conversion o) carbon monoxide, hydrocarbons, and nitro!en

oxides into less harm)ul !ases in automobiles. Pt8Rh E reduction catalyst 0 Pt8Pd E oxidation catalyst

5wo way 9 3"$ < $3= 3"$3

"x%3x


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MERCURY

CONTROL


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DIOXIN AND

FURAN CONTROL


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Sources o) dioxins and )urans include

waste incinerators, cement production,

)ossil8)uel8)ired combustors,

and )orest )ires.

4ioxin and )uran compound emissions

are calculated in

two di))erent ways9

As the total dioxin and )uran compound concentrations

As the T"0ic E-.ivalenc! 1."ien'5/L(

concentration


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CONTROL TECHNIQUES

2oth dioxin and )uran compounds are destroyed when

the !as temperatures exceeds approximately C@@B*

5hese temperatures usually exist in the combustion

&ones o) incinerators and )ossil8)uel8)ired boilers.

5he )ormation mechanisms decrease to ne!li!ible rateswhen the !as stream temperature decreases below

@@B*. 5he !as stream should be su))iciently cooled prior

to the air pollution control system can eliminate this

)ormation mechanism.

5he best way to control dioxin and )uran emissions ispreventin! their )ormation by reducin! or eliminatin! the

chlorine in the )uel and waste material bein! burned.


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AIR POLLUTION CONTROL DEVICES.pptx