Libro Air Pollution Manual

5/19/2018 Libro Air Pollution Manual

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AIR

POLLUTION

MANUAL

Pa

rt

ll-Control

Equipment

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Published

by

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lndustrial

Hygiene Association

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2/158

Copyright

1969

by

A-r,trnrcax

Ixnusrmar

Hycmxr

printed

in

U.S,A.

3?/gsf

t

Copies

availabie

from:

AssocrarroN

George

D.

Clayton,

Executive

Secretarv

14L25

prevost

-

t

AIdmrcAN

Lvpusrnrer.

Hyerexe

Assoqerrorv.

Detoit,

Michigan

4g222

price

$15.00

ii


3/158

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I

PREFACE

I,'

"\

t\\

1

s

+

ft

{l

I

THIS VIANUAL

is ttrb second

in

a

two-volume

set

on the

zubject of

Air

Pollution.

Volume

I

covers

tle

geoeral

aspects

oj

air

qollution,

its efiects;

sampiing,

and

administration

of

control

progralns.

This

Volume

is

concerned

solbly-

with

the

equipment for

conkol

of air

pollutibn

sourcesi It is written

for

the'practicing

plant

or

process engineer.

l

'

rn deslibing coJuol-equipment,_the

au$op

hav-_e attempted

to provide

enough

information

so

the reader

may

understand

the collection

mechani-sms

u.tilized

L

the equipment he is

considering,

and may

select the appropriate

type

of

equip-

ment for

the

problem

at hand.

Discussion

of the major

;nrometeiJof

per}onir-

ance, it

is hoped, will

be helpfuJ

in

evaluation

of

performance,

rn

maintponce;

and

in

bouble

shooting, as well

zu

in.

the

originai. selection

o[ equipment.

Confrol

of

automobile

exhaust as

a

source

of air

pollution

ii

omitted

from this

book. This

subject is

not covered

because

the source is

essentiall.7

nonind1156ix1,

because

the

application

will

be by

regulatory Iaw

wi&out

much applicafion

engr-

neering to indinidual

cases,

and

because

the technology is

in

a

rapidly

developing

state

of flux

as this book is

being written. For

similar

reasons,

cont'ol

of open

burning

is

also

ordtted.

In

addition

to

the

descriplons

of

major

classes

of

control equipmeut, severa.l

innovations

have been made for

a manual

of

this type.

Chapter-2 attempts to

build

a

foundation

of

particie

techrology

for

better'understandihg

of

the

mech-

anisms

of equipment

described later.

Chapter

3

highlights

the number

and

importance

of

the

various process

engineering factors that affect the

selection

'and

perfornnance

of control

equipment

In

Chapter

12,

an attempt is made,to present

a

rational

philosophy

for

perform-

anee

testing.

Speciffc

test

methods and

codes

vary widely

in

applicability,

orig-

inate

from a

large variety

of

organizations

and

are

constantly being set

forth

or

revised.

It is

our hope that an understanding

of

pu4>ose

and objective of

per-

formance testing,

and some

of

the

general

pidails

tl:erein,

will

dnabie

the

engineer

to

more

intelligentiy

use

auy applicable

codes, or

provid,e

guideiines

for testing

in

areas

that are

not

covered.

At

the

end of

the

Manual,

Chapter

13

dilcusses

t{re

botheqsome

sublect of

ffnal

disposal

of

conta:rdnant that has beei removed fiom a

gas

tci'pievqg an_-qir.pollu-

tion

problem.

This

subject

in

itself

is

so

broad

as to

defy

complete

coverage

except

in

an additional

book,

but ChaErter.l3

should serve

at least

as

a rer,rinder

that

something

must be done; and a

biJad

guride

ai to

what can

be

done. Altiiough

this

manual

was,

o&erwise.

written

by

AIIIA.

members,

we

are indebted to Dr.

C. Fred

Gur:nham,

Illinois,'Institute

of

Technolo

gr,

for

this

chapter.

.

;

:

In spite

of

innovations,:the

nain

theme+of this

work is

the control equipmeut

itself,

covered' in

Chapters 4

thrmgb

11.

"Of

these

eight

&+ptii'6

the,

firJt

four

are

devoted

to

equipment

tFpes

uiually

usid fo-r collecting

particulate

air

con-

tamiuants,

and

the latier

group

is-devot&to.con&ol of:gaseou512:Tuagix

.r{q-

inates,

In

general

the

equipment

classes are

based

oa

,thdpredominatihg

phyiieal

and

chemical

phenomena

that separate eontaminant

from

carrier

gas.

Unfortu-

nately,

most sir

pollution

control devices utilize

two

or

more of

these

phenome-na,

and

which

is

"predominaut"

is sometimes a moot

point.

Rigid adherence to

iliis

theoretical

classiffcation

scheme

would lead

to

a complex

hierarchy,

confusing

and

of

little

practiepl

use

to tha Utended reader. Accoidingly,

it

wdll be obr.ious

ir-

lr

D

i

I

t

\

I


4/158

PREFACE

lo

tu

already-expert reader

that

in

-rrrany-

instances,

the

relesatiou

of

a speci-fic

kind

of machine to

one

or

another

ciass

of equipment

has

beia

rather arbitr'r.y.

Mosi of the commiitee

members,

both present

and

past,

contibuted

significantiy

to

the efort.

Those who

authored

various

sections

or

subsectioos

"r-th.,

oo*

exist

are:

Indusbial Health

Engineering

Div.

Harvard

school

of

public

Health

Bethlehem Steel

Corporaiion

6&5

Hunting.ton

Avenue

Bethlehern,

Pennsylvania

Boston,

-Vlaisachusetts

Deyo M. Al.oeRSoN

Cnarurs E. Bu.uvcs

Manager

Aerosol Physics

Department

GCA Corporation

Bedford,

Massachusetts

Roamr

A.

Brre

Chief

Engineer

Fluid

Purifi

cation Division

MSA

Research

Cortrrcration

Evans

City,

Pennsylvania

C.

Fnxp

Gr::aNne.w

Professor

of Environmental

Engineering

Illinois

Instjtute

of Techaology-

Chicago,

Illinois

Rosffir

A.

Hmmcr5

5

D

5

D


24/158

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1

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14

AIR

POLLUTION

IvIANUAL

II

:,i

tl

:rl

i,l

,r,i

il

,li

ril

ril

:iii

ril

'al

il

,i.

,i

a

crossover

point

in

the

operation

of these

mech-

anisms

in

the

vicinify

of

0.5

micron 31

is6in:.1

filter veiocities

of

a

few

feet

per minute,

'i/hich

leads

to

a

maiomum

in

particie penebation (a point

A is irojectory of

porlicl

cenler

which

lust

touches cylindricol

fiber

INERT]AL

IMPACTION

I

is

troiesrory of

porticle

cenler ond

fluid

streomiine.

Porricle surtoce

touches fiber st

point

of

closesl opprooch.

DIRECT

INTERCEPTION

efiect

becomes

operable

o

high

velocities.

Filter

perfor

plicated

by

addltional

caoh

[ected

material

(

if

solid

)

.

act

as

targets

for

other

airb

operation

proceeds

long

enou

of

granular

particulate

ma

mary separator;

the

filter

,

secondarily

as

a

collector,

it

'

ing

to maintain

the

granula

sur{ace.

Elecbostatic

*J"*rri

o

collecting

objeci

or the

part

electrostatic

charge,

or act

t

applied electric

field. They

a

and

are

most

amenable

to

th

electrical

precipitation.

In

tatorlT

the

particle

is

charge

value

by high

voltage

discha

then

subsequently

collected

o

the opposite

sigrr

or

ground

omefies

can

be adequaElYb

tical

operating

diftculties

ar

see-and

solution'

must

freq

perience.

The

eiectrostatic

efiect

has

tion

in

certain

limited

applica

wool

filter

(use,&-in

respirat

bag fflters

for air

pollution

c

static

effects-

due.Jo

-natir

charge

may

also

be

importan

static

fflters

operated

at low

non has

not

6een adequately

BEFERENC

1. Hsnpall,

C.,

Sdill

Porticte

Inc.,

New

York,

i1960..

Onn,

C.,

and

J.

M. O*ru

V

urr

"ni,

Vlacmillin

Co.,

Ne

Ceora"

R.

D.,

Padicle

Size

Publications,

Inc.,

New

York

C

is

poth

of

porticle

csnter

due

to

fluid molion

ond rondom

diffuslon:

DTFFUSTOU

Figure

2-8.

Mechailisms

of

mechanica

filtration.

of

minimurr

efficiency

for

a

given

particle

size)'

Higher velocities,yield

higher

efficiencies

dhe

to

in-

cte"ased

impaction,

Iowei

veiocities

yaield

higher

efteiencies

iue

to

increased

difusidn,

Forpaiticles

above

a

ferv sdcrons,

the

diffusion

effeetbectmes

negligible.

For very

small

particles''the

ihipn"ction

2.

"3.

Trojectory

o,

porlicJe

center

0,1

5EPARAr6il

rur6Ei,

*'-

Figure

2-9.

Calcula:-.d

impaclion

tion

nsmber

for ideal flow

amund


25/158

il

PROPERTIES

OF

AEROSOLS

4.

D.

o.

8.

o

10.

il

I

r

I

I

I

11.

Ina,''rr,

R. R.,

*ud

C. F.

Caur, Patticle

Size.

Measure-

menl-Ioterptetd,iat

arui.

Appli"cotialt,

Johl

Wiley &

Sons,

Inc.,

New

York,

L963.

American

Society

of Mecha.i.cal

Engiueers,

"Determin-

ing

the

Properbes"

of

Fine:.

Parricu.late r\Iatter,"

Polver

Test

Code

28, 1965.

:

Dn-nl

n, P.,

aod

T.

Hercrl

hdilstridl

Dvst,2r:.d, ed.,

VlcCraw-Hill

Book

Company,

New York, 1954.

DrxNrs,

R.,

L. Sr-vr-m1,ry, C. E. Bu-r.a.rcs,

E.

Katst.rr.,

D.

M.

lvlrnsoN,

anci

P.

Dnnrrm,

"Air

Clearing

Studies

Progress

Reporc ior

July

1,

1955

to

June

30,

1956,"

USAIC

Report

NYO-1809, Harvard

Uaiversity,

March

i959.

Wrrnrw-Gnav,

R, and H.

H.

P.r,rrsnsoN,

Smofte,

Edwarti

Arnold

a

Co.,

London,

1932-

llcCnoNs,

W.

C., anri I.

A. Ser-zaxsrtoi,

"The

llicrosccpic

Identiication

of

Atmospheric

Particulaies,"

APCA

Annual

Meeting Paper.6l-10,

APCA,

Pittsburgb,

Pe.,

i961.

Fnsr,

[.

W.,

"Iostrumentation

for

Particle

Sizing,"

n

Enctlcloped.ia.

of

lnstrumefltotion

for

lndustrial

HU-

giene,

litive*ity

of llichigan.

Aan

Arbor,

1956.

Yrrrrr,

C.

D.,.

D. H. Bvrns;

and

A.

D.

Hosrr,

eds.,

E

nc1cloped,b

of

lnstrumentdion'for

hdustri,al

H1giefl"e,

University

of Michigan,

,{.un

Arbor, 1956.

12.

American

SocietrT

for

Testiag and

Materia'ls,

"Sym-

..

posium

on ?articie Size

Measurement,"

ASTII

Special

Techdcal Publibation

No.

234, ASTM,

Philadelphia,

1959.

13.

Laos,

L.

B.,

*The

Basic )Iechauisrns

of

Siatic

Elecki-

fication]

Science

102,

573.

(1945).

14. W:lre,

H.

J.,

in

Ebctrbal

Prechttditvo

Fqviome&ak,

Eng. Proc.,

The

Pennsylvaoia

State

University,

Uni-

versity

Park, Pa.,

1961,

p.

39.

15.'

CarxN,

H.

L.,

and

1V. R. Lexr,

Paiicubte Clouds,

E.

& F. N.

Spon,

Ltd.. London,

t957.

16.

American Industrial

Hygiene

Assu., Ah Polbtiat

Manual-Pcrt

I,

Eoahlation,

AIII-4,

1960,

pp.

17-30.

17. Wryr:s,

H.

1.,

In"&BtrbL

EloAro*aic

Prech,itAioq

Adciison-Wesley

Publishing

Company,

Inc..

Reading,

\lass., 1963.

18. Laeyr,:, C. E.,

io Chem,bal Engineers'

Haadbook,

VlcGraw-Hill Bock Company,

New York,

196O.

19. fuc:r,r.msoN, E. G.,

ed.,

Aerod4rcnvic

Capture

of Par-

ticbs,

Perg^on

Press, Odord"

1960.

BIBLIOGR{PHT

.

l. D,rnres,

C.

N.,

ed."

Inhahd

Particies

aui

Yapouts,

Pergarron

Press,

Oford,

1961.

il

'I

I

I

I

I

t

I

I

I

I

*


26/158

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3.2

3.1

Oontrsl

Equipment

Types

3.1.1

Filters

3.1.2

Electrical precipitators

3.1.3

Cyclones

3.1.4

Mechanical

coltectors

3:1.5

Wet

collectors

(Scrubbers)

3.'1.6

Adsorbers

3.1.7

Combustion

3.5

Flow

Characteristics

of

the

Carrier

Gas

3.5.1

Carrier

gas

flow

rate

3.5.2

Variations

in

carrier

gas

fiow

ra

l.:

g

Changes

in

carrier

gi

properti

3.5.4

Relationship

to

air

moirer'cha

istics

3.5

Propeilies

of

the

Contaminant

.6.1

Contaminantcomposition

3.6.2

Contaminant

loading

9.6.4

Contaminant

Sotubitity

9.6.5

Contaminant

sorhabilitT

3.5.6

Contaminantcombusti6ility

3.6.?

Contaminantreactivity

3.5.8

Electricat

and

sonic

pioperties

contam.inant

Control

Equipment

Selection

3.2.1

Amount

of

contaminant

discharged

to

atmosphere

Amount

of

contaminant

entering

the

collector

3.3

3.4

.?.3

Collectorefficiency

3.2.4

Collectorselectiori

Process

Characterization

in

Control

Equip-

ment

Selection

Properties

of

the

Garrier

Gas

1.1.1

Carrier gas

composition

1.+.?

Carrier gas

temferature

3.4.3

Carrier

gas

pressure

1.1.1

Carrier

gas

viscosity

1.1{

Carrier gas

density'

1.1.9

Carrier gas

humidity

1.1.7

Canier

gas

combusiiUility

Contaminant

toxicitv

Particle.size,

shape,

and

density

Co

nta

m inant

hygioicop

icity

Aggtomerating

characteristics

contaminant

9.q.

q

FIow properties

of

the

contamin

3.5.14 Catalyst poisoning

by

the

co

inant

3.7

Representative

Sample

of

Contaminant

contaminant

it

is

censidered-

a

scrubber.

Difi

types

of equipment

are

frequently

used

in

serie

;omejmes_incorporated

into

the

pame

equip

housing.

Thus

0lters

commonly

incorporate

a

tegral

settJing

chamber,

a form

of

*ihanica

lector.

3.1.1

Filfers

Filters-are:devices

for

removal

of

ai""irl"

rnatter_fronr.gas

stre4lq$_by

retenUon

o

y,r:oo.r

jo

or

ola

porous

structure

througb

w

the gas

flows.

The

porous

structure

is

m"ost

monly

_a

woven

or

felted

fabric

but

can

inc

pierced,

woven,

or

sintered

metal;

*al"a.

Iarge

variety

of

zubstances

such'as

ffberr,

*

111ings,

coke,

slag

wool,

and

,*oa-.

TJ.rs

are

operated

wet

to

keep

the

intestices

a

ffItss

in general

iroprove

i,

,"t"otiorl

"E'ii"o"

3.6.9

3.6.'t0

3.6.11

3.5.'t2

1..]t

;;,i

li;

lil

till

tiri

ii

';

il

il

:lir

lii

:'ri:

i,,ii

;fi

:ii.

ril

irli

rli

rill

;ijll

:ll

.1il

r,i

,i

:,il

I

,lr

rii

;il

iil

:]"i1

ril

4

I

rt

ti

rl

3/

PROCESS

FACTORS

AFFECTI

N

EQUTP{wENT

SELECT\ON

3.2.2

3.+.9

Carrier gas

reactivity

3.4.9

Carrier

gas

toxicity

'

3./

coNrRoi

EQU

tP/.ilENT

TYPES

,Conhol-equipment

may

be

classiffed

into-sEv_

erat

genera-l

t-ypes:

fllters,

electical

precipitators,

cyclones,

mechanical

-

collectors

(othir

tb""

"y-

:flf)l

scrubbers,

adsorbers,

*a

"qrip-*t

io

which

the

contaminant

is

burned

as

thi

ieans

for

its

control.

This

last

category

includes

afterburn_

11:

.rttdc

combustion,-and

similar

appaxatus.

Some

equipment

combines

elements

of

mole

than*

o"g.

RT:.

.For

examplg

there

are

cyclones

in

which

-.",1q*d

is

sprayed"

and

there

are

scrubbers

in

ytuc

cyc.lonic

action

is

employed

to

remove

the

,iqyd

$ogl9rs.-

Packed

i:e,t'filieri

operated

wet,

a3a

qlcked bed

scrubbers

are

alike

in'consbuction,

the

difference

being

that

when

,f"

a"1."

is

de.

rrfl"d

to

rernove

particulate

matter

it

iS

a flter

and

',vhen

it

is

designed

to

remove

a gas

or vapor

phase

16

CONTENTS

t 3,4.10

Eiectrical

and sonic properties

carner

gas


27/158

il

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I

the

interstices

in

the

porous

structure

begin

to

be

nlf"a

Uy coilected

p*iti"l"t.'

These

collected

par-

ticles

form

a porous

structure

of

their

ow '

suD-

.orted

bv

the

filter,

and

have

the

ability-

to

inier-

I""t r"a

sstein

other

particles.

This

increase

in

."LoUoo

effcienc'r

is

acccmpanied

by--an

increase

;;-;;;t*"

drop

'through

th"

fllter'

-Therefore'

io

;";;;;

d"*""t.

m

c;

f.ow.

the

filter

must

be

5t,h"t

continuousiv

o.

periodicallv

cleaned'

or

oeriodicsllY

iePlaced'

'

Ir,

,p""i"1'applications,

filters

a;e

used

to

remove

nm

or'rrpo,

by

teaction

with

the

parficuiate

mat-

ier

reteined

on

or

in

the

porous

smrcture'

3.1.2

Electrical

PreciPiiafors

Derrices

in

which

one

or

more

high

intensilv

eLectrical

fields

cause

particles

to

acquire

"o

.i""t'i"ri

charge

and

migrate

to

a

collecdng

,*f"""

are

electriial

precipitators'

The

collecling

,*fr""

may

be

either

dry

oi

wet' Since

the

collect-

ioe

fo.""

is

applied

only

to

the parricles,-not

to

the

n^",

tn"

pr"rriri"

drop

of

the

gaJis

onlv

that

of

flow

iUro"gi,

duct

having

the

co-nfiguration

of

the

col-

lector]

Hence,

pr"ttrri"

drop

is

very

low

and

does

not

tend

to

inciease

with

time.

In'general,

collec-

tion

efficiency

increases

with

length

of

passage

iLo"gh

an

electrical

precipitator'

Therefore,

addi-

tional-precipitator

seciions

ar-e

employed

in

series

to

obtain

higher

collection

efficiency'

PROCESS

FACTORS

AFFECTINC

EQUIPVIET_T

SELE

TION

3.1.4

Mechanical

Collectors

(ofher

than

cyclones)

This

category

rncludes

devices

"virich

colleoi

particulate

m*tt"r

by

gravity

or

centri'iugal

force

b,].t

which

do

not

depend

uPon

a

vortex,

as

in

the

case

of cyclones.

These

devdces

include

set'iling

cham,bers,

bafied

chambers,

Iouvered

chambers,

and

de.rices

in

which

ihe

carrier

gas-oarticulate

ma,iter

inixture

passes

through

a

fan in

winbh

separation

o".*J.

In

general,

coilectors'

of

this

"liss

are

of

leiati'relv

low:

coliection

eficieacy

They

are

frequently

used'as

pre-cleaners

preceding

other

qrpes

ci

collectcrs.

3.1.5

Wei

Collectors

iScrubbersi

These

are

devices

in

which

the

prime

means

of

collection

is

a

liquid

introduced

irto

thb

collector

for

contact

w-ith

ihe aerosoi.

Scrubbers

are primarily

emploved

to remove

gases

and

vapor

phase

contaminants

from

the car-

ri."r

gas,

but

ire sometirnes

used to

remove

par"icu-

late

-matter.

The

liquid

may

either

dissolve

or

chemicaiiy

react

witi the contaminant

collected''

Methods'of

efieeting

contact between

scrubbing

liquid

aad carrier

gi io"lrd",

spraying

the

liquid

inio

open

chambers,

or chambers

containing

vari-

ous

fdrrns

of

baflesfgrilles,

or

packing;

flowing

the

tiquid

into

ihese

suuctures

over

weirs;

bubbiing

the

g"s

through

tanks

or

houghs-

of

liquid;

and

"tiliing

grt

i'o*

to

create

droplets

from

liqurd

intro


28/158

18

jjlj

i,l

iir,

1rl

iii:

,]i,

rlll

ili

iil'

ri

,il

-tti

il;

i:i

i

irl:

:rii

-.ii

; iil

:rii

lrlt[

tlil

ll;

,|ii:

ll;

\li

'ri

iljj

rili

rl

lr

iIll

l ri

.il

fil

1

AiR

POLLUTION

IVIANUAL

ii

quentll/

protected

from pluggrng

by

particulate

matter

b;z

preceding

it

wrth

a filter

so that

the

gases

passing

through

t}'e

adsorption

bed

are free

of

particles.

In

true

adsorption, there is

no

irreversible

cherrical

reaction

beiween

the

adsorbent

and

the

adsorbed

gas otlpor.

The

adsorbed gas

or

vapor

can therefore

be driven

off

the

adsorbent

by

heat,

vabuum,

steam,

or

other

means. In some adsorbers,

the

adsorbent is

regenerated in

this

man-rier for

re.

use. In

other

applicail.ons

the

spent

adsorbent

is

discarded

anil

replaced

with

fresh

adsorbent-

P.res-

sure

drop

through

an

adsorber

that does

aot handle

gas

contaminateci

b;r particulate

matter

should not

increase

with time,

but

should

increase with

gas

flow

rate. Tne

relationship

betw-een

adsorption

efficiency

and

gas

flow

rate depends

upon

desig::

and

the materjal

being

adsorbed.

3.1.7

Combustion

In deyices

of this

ciass,

combustible

organic

contaminants

are burned

by tle

oxvgen in

the

carrier

gas

to

products

of

as

complete combus-

tion

as

possible.

fn some

cases, combustion

takes

place

on the

surface

of

a

catalyst; in

others no

catalyst is

necessary.

Combustion

is

used

mostly

for

contaminant

organic

gases

and

vapors,

rareiy

for

particulate

contaminants:

3.2

CONTROT

EQU

:P/AENT

SElfCr/ON

The prime

determinant

in

the

selection

of con-

toi

equipment is

the

maximum

amount

of

contam-

inant

to

be

discharged

to the

atmosphere.

Wiih

hrowledge

of

this

amount

plus

knowledge

of

the

amount

of

contaminant

entering

the

collectory.the

required

collection

eficiency

can be

computed

fiom

the

equation:

,

faro

o*

@i''h"nrl

f.Mt

oi

nffi'nt

die]

.

( atqiug

de

@ilector

j

-

i

ctqged tp the aEtrgh@

l

Ldr6ry

ffide'w=

mt

of

cotubst

ltailg

ths

milador

Other

forms

of this

equatiou

Eue

more

suitable

for

various

practical

circumstances

and

are

&scussed

in

Chapter

12.

3.2.1

Amount

of

Contaminant

Discharged

to the

Atmosphere

The

amount

of

contaminant

&scharged

to

the

atrnosphere

is,

in

some

locaiities,

prescribed

by air

pollutiou

control

regulations.

Where

not so

prescribed,

or

where

it

may

be desirable

to

dis-

4*gg

less than

is

permitted,

it

is

necessary

to

d+.

cide

the amount

to

be

dischareed.

This decision

shouid

be

based

upon

the

adveEe

effects

likely

to

be

caused

by tfie

discharge.

To

evaiuate

fects,

computations

will

have to

be

ma

concenkation

of contaminant at ground

1e

stuctures

above

ground resultiag from

under

tle conditjons.cottemplated.

it

s

recognized

that stack height,

disc.harge

ve

temperahrre,

wind

_directicn

and

veloci

pheric-stabfiy,

and local

topography

all'

rground

ievel conceurrafions.

Hence,

lu

a

compuiaii.ons,

it mav

be Cesirabie

io

have

nel

tests

made of

a

model

of

the

propose

tion.

Tnese

several

considerationJ

are

dis

Volume

I

of this

NIanual.

3.2.2

Amount

of

Contarninanf

E

the

Collector

The

amount

of

contaminant

the

coilector

is,

for

an

existing installatio

mine


29/158

il

r

pRocESS

F-\croRS

-\FFECT'NG

EeuiplvtENT

sELECTioN

19

f

3.3

PRocFss

]HARACTER:.ATI)N

/N

measure

of

the

ease

with

which

the

poilutant

mav

coNrRor

EQU

p

l;.ENi-srrcrloN

H#i"""Jt"'?n*fi:

Hhlli,",i;'::L#r"::?i,;

I

Control

equipment

seleclion

involves

two

basic

considered'

Exampies

of

these

latter

are

tiose

for

steps:

first,

the

chii"e

from

among

'u

'oul*to'

tvpo

:""H:X'#'IrTgilrl$t:;j

tH"T"i::"H'"7

I

:1,fru*::,:l.T::*:,iTlfi*,'nH",T,-T#

to

f.o"id.

a direct

measure

or

"corlectibiritv"

bv

a

those

meetjng

the

requir",,'"ot'"-oJ:

iL'

q''i

+{

f":;L,t:,"}X',X;;Tro#"1"j,i:tJdl#'ffi:ff""J

I

fl**ift;:1X",:,il'f',;fr:

ffif".trul

wta"

.hi

p'o"""

I'

o

ti'"

dra*"gboaid

ind

the

gas

and

t'e

contaminanis

it can-ies.

-lvitl:T,*:j:

Xt[:X

;X,3"t.'"ff:ft

,T

"',.i:',t:L*:""'X*f;

ihe

carrier

gas,

cne

must

know

its

phvsica.t ano

pi-ants

,rri

p.o."rres.

Wtere such

erperience

does

I

.t

"*1.,t

pro:pert'es'

rts

rate

of

fow'

and

variations

not

erist.

one

must

compute

those

pr-operties

such

r

li$m::"1,t':l':":;f":',rffi

T"::iHi:;l'"x

;;;;;;;;;'ri;rtTaft';Y;1J#,?:x'

reac'liviqv'

r

must

also

kaow

their

ph,vsicai

"oi

"h'*i"'I

propgr-

ffii-i]::T:iiiX

*:li,';:,

*n::i,il'i:fj::

I

,i*,

,l"it

concentratibn

or

loading

in

-the

caTer

for

the

advance

computation

of

many

of

ihe

prop-

grt,

,"a

vanaiions

in

boih

loading

and

properties

utti"r,

,r"h

as those

of

the

particulate

phase,

tlat

I

;li*"JJfi"1ltJJl.tr'or,r,"

carner

gas

and

*irt".:"':il"'i::i"tH#:11i::?X.f

;,,l*l

the

contaminant

aie

known,

it

is

generally

urrneces-

process,

it

is

frequentlv

possible

to

base

desigo

r

sarv

to

have

precise

larcwledge

of

their

chemical

,po.,

. closely

parallel

existing

process..

To

pro'

I

.J,,poritlor..

i{o*-"r"r,

in

the

case

of

a

ne\^i

Pro-

,id"

, margin

for

error

in

the

assumptions

made,

cess,

these

physical

properties

rnust

be

computed

it is

wise

irr"s',-,ch

cases

to

incorPorate

a.saielv

fac-

ahead

of

ttr.'oo

the-bails

of

an

assumed

chemical

ior

in the

design

so

tlat

changes

required

to

im-

I

torpositiorr.

Where

the

acfual

phvsical

properties

prove

collection

eficiency

after

the

piant

goes

into

I

-

p.ou"

to

be

difierent

than

those

computed,

lt

may

operation

will

not

necessitate

major

reconstruction.

be

necessary

to

precisely

determine

chemical

com-

il"f,

*i"ty

factors

inciude,

for

example,

the

initial

f

position

to

compute

more

accurately

those

physical

provision

of

motors

somewhat

larger

than

the

I

iitf"ttl",

dlfficult

to

measure

in

a

field

installation'

-irriorrr'o

horsepower

computed'

^

fh"

prime

physical

properties

of

&e

carrier

gas'

I-ternpqgtu" "#

p."tti'",

"t*

usuallv

independenl

:

,4

PROPERT/ES

OF

THE

CARR/ER

G/5

t

;;:

1H: '',"fi:".#ffi;,r'6,,"i;.ffi;-;;J.ii" :

As

was,p'"":9:'+ofl*:

ii'

composi-

bicat

"nd

sJni""ft;;;;-'lrr""y

#'these

latter

rion

is

important

o"iy3

it

*Iecis

its

physical

and

depend

.po"

l.*'p.irture

and

p.Lr*r"

as

well

as-

_

chemical

prop-erties.

fh3

ch,eTi_cai

prcperties

are

I

Hfi;i5;mposition.

if reactiviry-[

.o"rtr""a

,i

-

i*portrnt'to

ihe

extent

that

thele

may

be chemical

r

ffiffi;,;ilili"rlrala-*L"liiitz,

the

above

list

;JG";

b't*."o

the

gas, the

contaminant,

and

the

of

prop"lto-"ppiiJ;r;Jii"

the'contaminant

as

coilEtor-its

structure

or

its

contents'

One com-

I

;;',h;1;;,

g"r.

mon

example

of

reaction

between

gas components

In the

special

case

where the

contaminant

is

""d

eqoip'ment

is

w-here

gases containing

zulfur

:

particulate,

there

is

an

ad&rio"ri;;;;'pnyrl""r

oxides

arr-d

water

'*po'

"oi'ode

metallic

parts

of

r

lilxx"'1l.;:#*i1ffi"'f;1':?':r".5"sg,":*

:::fi1:il,"i.llu:'**ffiff*T,=5*E#::^i,i:

I

H*ei;mi":,r*:*#"Ls[d:"ffi

#l

342

Hl';:::l;iL?""J::.r,emper

packing pr;;"";;;.

;f-;i;";;'[""t"d-*rt".irt,.

ature

are

og

th9

vohine,of

the carrier

gas

and

on

I

;*jf

*#,:,

"*;"*t*16r,'m

lhr::ffii':"::."?ffi*r;:J:*JJ"["":1T0.*i

using

accepted

techniques.

Fo*o*l-of

the

proper-

l'

aud tte

concenfation

of

the

contaminant

per unit

r

ties

mentioned,

there

are

no

""c"6U

tu"niiqi'"t' ',.,

:l-Lol-r11"'.IT-th't'r*;1';1i tt:T:tt3:::"Tf;:

il-i-}rem;iut

-iomposition

uniess

constituents

are

,"""tirrg

chemicalli.

The

major

properties

a,ene1{-

3

4..,

Carrier

Gas

Composiiion

elrt

upon

composition

are

density,

viscosity,

humid-

J

'

ties

mentioned'

there

are

no

acuEP\.*

**n1;;-;,,,.-:*.,centation

is

itself

the

dri..iog

force for

removatr.

B"tl" p."pl*a;s

are

not

always

translatabl'

:.q-i :

:,

i

,

ti;.


30/158

20

rii

:ir,

;f

,ii

il:

irl

rill

:ii

;l.i

:ti:

il]

ii

:

i.i'

;:;l

'lrl

ill

lit;

:iill

.;li

iii

jtl

,iil

jil

;ll

.,rl

'jill

.tlt

.l l

rlril

ill

,ll

,rl

I

0

.500

looo

t50c

GAs

TEMPEFATURE

AT

CLOTH

F]LTER

Figu.re

3-1.

Change

in

fiitering

power

requirements

'ccoling

of

carriet

gas.

Viscosity,

density,

_and

other

gas

properties

AIR

POLLUTION

\,IANU,{L

U

from

a

power

siandpoint

(cooliog

by

tion-convectiou

or

evaporatiou

will

oot

cantly io

the total mass- "i"g

h,ndle

crease

p

power

that would

iesult from

required

mass

of

diluent

ail

is

oearly

c

reducdons

in both r-iscosity

and

,oio

efiuent

when

it is

cooled from

elevate

tr:res

to 750"F.

Temperature

of

the

"

1

may

have

other indepea{ent

signrfican

to a

-particular

contr-oi

iechnique.

Adsorption

processes

are

generally

a1d

ge-

irnpra-cticable

at

fugher

tempe

aCsorbabilitv

being

inverselv

proporti

temperatures

(w-hen

the

reacdon is

prim

cal

and

is not

inf,.uenced

by

accompany

reaction

).

Similarly,

in absorption

(

solubfity

depeads

on

tle

temoerature

veni)

ternperature

efiects

may

b9

cf

sig

the

concentation

of the

soluble

mate

that

appreciable

temperature

rise

resul

bustion

as a

means

for

contaminant

re

gas

temperatr:re

affeais

the

heat

balanc

ihe

yital

factor in

the process.

In eiectu

cipitation,

both dust

resistivity

and

th

lstrength

of

the

gas

are

temperature

dep

Wet

processes

cannot

be

used

at te

'

-where

the

liquid

wouid

either

freeze,

boi

rate

too rapidly.

Filter

rnedia

can

be u

the

temperature

range

within

which

they

The

stucture

must

be

of materials

that

integrilz

at

their

operating

temperaturqs

Last,

low

temperafure

gases

from

a

st

ing

control

equipmeut

&sperse

in

the

less

efrectjvely

than

high temperair:re

g

sequently,

benefits

derived

from pariial

c

companied

by

cool{ag

may-be

offset.if

the

gas

cannot

be well

dispersed.

This

is

.,

rmportance'in

wet"'cleaaing

prbcesses

for

where

the

advantage

gained

by

cleanin

times

offset near

the

plant

by

down-w-as

stack because

tle

stack

gas

is

cooled.

3.4.3 Carrie-r

Gas

Pressure

_

I"-

g_9gg-rtl,,-carrier

gas

pres

higher or lorvei

than,

aturospheric pressu

that

the

confrel-"equipment-bedesigned

sure

vessel.

Some

types

of

equipmeut

more_amerable

to being

designed

ioto

pr

sels.

than others.

For

example,

catalydc

are

incorp_orated

in

pressure

processls

io

duction

of

nikjc

acid

and

piovi


31/158

l---

-

3.4.6

Carrier

Gas

HumidiiY

EQUTPi/ENT

SEL-ECTION

71-

above

reasons,

scrubbers

or

ad.sorpdon

tow'ers

may

be

particularly

aopropriate

de'rices.

3.4.7

Carrier

Gas

Cornbustibility

The

handling

of

a.

carrier

gas

that

is

flammable

or

erplosive

will

iequire

certajn

precau-

tions.

Tae

most

important

ol'

these

precautions

is

makjng

sure

that

the

can-ier

gas

is

either

above

'&e

upp.r*erolosive

limit

or

beiow

ihe

lower

explosive

li*ii

t*

lnv

au-admirture

ihat

may

arist

or occur'

-

The

use

of

water

scrub'bing

or

aCsorptron

rrav

be

an

efiective

means

o{

minimizing

ihe

hazards

ia

some

instances.

Electicstatj.c

precioiiators

are

oiten

im-

pracdcai,

since

thev

tenci

io spark

anC

mav

ignite

ihe

gas.

3.4.8

Carrier

Gas

ReaciivitY

A

reactive

carier

gas

presents speclal

problems.

In

filtratjon,

for

exarrpl-e,

tie

p-resence

if

""r"oo,

fluorides

may

eliminate

tJle possibilitv

of

higi-,

temperatr:re

flltratioa

using

glass

fiber

fabrics'

Il."-udro.ption.

carrier

gas must

not

react

preferen-

tirn.r-

*ii\

'&e

adsorbents.

For

example,

sllica

gel

is not

aprropriate

for

adsorpdon

oI

contaminants

*h.r,

*iie,

i-apor

is

present

as a

comPonent

of

the

carri.er

gas

steam-

A-lso

the maglitude

of

this

p.olt*t"*"."

be

greater

when

one

is

de4ng-wi&

"

n

gf, temperatur:e

process'

On

the

one

hand'

de-

ui*i*"ot"mg

the

use

of

waier

may

be

eliminaieC

from

consid"r"rtioo

if

the

carrier

gas

reacts

with

water.

On

the

other

hand,

scrubbers

may

be

espe-

cially

appropriate

in ihat

thqz

tend

to

be

relativei-'z

r*a.il

u"h

r-equire

small

amounts

of

constuction

material

so

that corrosi.on

resistant

components

may

PF.OCESS

FACTORS

AFFECTINC

I

I

T

r

I

I

I

I

I

I

I

I

I

t

T

erties.

It

may,

however-

be

of

itnlortance

in cer-

ir*

,p""irt

,i*rtioor,

as

w-here

&e

droice

is be-

#"":b-+

eficienry

scrubbers

and

other

devices

i"r

""U."=o""

of

pariculate'

The

available

source

-;;;;

can

be

,rsed

to

overcome

&e

b'igh

pres'

y,:::";;.;"tor.

th.

scmbber,

reducing

the

high

i.I*"r tJ"r*ement

thai

cften

limits

the

utilizatioo

5i

r"*tu}tt.

In

adsorptLon,

high

pressure

favors

r"*o"rl

and

mav

be

required

in

some

situations'

3.4.4

Carrier

Gas

ViscositY

V;scosiY

is of

imporiance

to

collection

techaiques

in

lwo

respects'

First'

it

is unportant

to

,ill#"trr

*ecranisls

in

many

siruadons

(

inertial

Iott""t.o",

Sa'rit,v

collectior,

ald

eiectrostatic

pre-

"i"rir"""j.=

Pariculate

removal

techniques

often

-t""f""

-lgtahon

of

the

partrcies

through

th9

gas

;";

""aL

e'r"

iofuence

of

some

removal

force'

irr"

&

migradon

decreases

with

increasing

vis-

.*lq"

,f

tf,"

g.t

stieam'

Second'

riscositv

in-

flr"o"",

tle

preisure

drcp

acros-s

the

collector

and

th"r"by

becomes

a

Power

consideration'

3.4.5

Carrier

Gas

DensitY

Density

appears

to

have

no

signficaqt

efiec

ia

most

real

gaicieaniog

processes'

aithough

,1"

-difi"t"oc"

betieeo

particle

densilv

and

gas

density

apPears

as

a

facior

in

the

theoretical

an-

alvsis

of

ili

g'ar,iiational

anC

ceafifugal

ccilection

a;;;";.

Par"ticle

density

is

so

much

greater

tJran

sas

density

that

the

usual

changes

in

gas

density

f,a,re

neglig:ble

efiect.

Humi&t,v

of

the

carrifi

gas

stream

may

be

used

with

lower

reiative

lncrease

in

cost'

be

important

to the

seiestion

or

ge.rfonn1u"",.*

too.

t,o1equipmentin""r;;;-;;aibasicai1ydifier1n-t3.4.9CarrierGes=TojrLcity

ffIl"f,l#.:ffi1?"0*lJ,i?ELx';;HTffi;-soeciar**"S;:T"1H'*1J';"J:"Iffi'il":

$#ifl"ix1x"fr:

i:,}:YL:et:.

"ffi"T:::

$,ffi:1Tlr;

H"$:.:%:i1#J,r,::*'

":i

tion

and

aggravation

of

corosion

probleml'

ts

'O-

;";h" ;;"k

rho"ld

be

i:nder

negative

pressure

and

dition, thJpresence

of

water

vap-or

may

tnflu3,1e

[;-r*k

must

be

ottight

constructiou.

Sibce

the

lh;",:Hi"TT**#,.",i

1ffi#:":";".rff::^ff

;:t*:xrs""

ffiIeHi:1,,,H:H#t':'

":x

catalytic

combuition

ft

qry

be.an

important

con- i"*1""",

from

thi

hoppers,

i{

eo*eetiun

i.

by

1*y

sid.eration

in the

heat

balance

that

Inust

be

mntn-

tained.

rn

adsorption

it

mav

tend

to.r-?ffi

::#"t::.tffiffiLH:::"ff:""ffi*Y?y#"#

capacity of the

bed

if

water

is

prefe'rentiaily-or

cc1-

;;;i."

currentiv adsorbed

with

the

contaminant'

jlven

in.

fiffi;

;;),

,"f;"

,gg1o*.r"tiou

and

pro-

3.4.10

Electrical

and

Sonic

Properiies

duce

subtle

ellects.

The

above-mentioned

-con-

of

the

Carrier

Gas

siderations are

the

66jrl

limitations

upoa

ihe

utiliza-

tion

of

evaporariou

;Ud;

;btrio

tne

obvious

Electrical

properties

will

be important

power

advantage

,u"#il?i-,r#n

i";;;d;t

to-

elechostatic

precipitation

because

the

rate

or

ease

where

humidity

is

a

serious

pioblem

tot

oo"

ol-tf";,,

of

io1+1 9n.yri11

i4ry"S'removal.

mechanisn:5'

'

::i

'*.1-

'


32/158

i,;

{xr

ril

ii

r;i

rli

i,iil

iltl

til

;ltl

ili

,i,l:l

:rill

l;ri

iI

,;il

1rl

rilii

trll

rI

iii,i

llll

;il

ll

itl

lltl

ill

fi,I

iil

,il

ti

dl

#l

ii

j[l

il

iill

jil

rili

'[l

ilr

ill

flr

il

{r

dl

l

{i

$'

tr

li

il

1i

It

r1

Ii

ti

li

ll

it

ri

il

ri

ii

i,l

i

ll

I

i'

ll

i

ir

ili

L

rl

i;

il

ri

.i

I

E

i

l

r

a.

f

tf,

,,1

AIR

POLLUTION

ivlA.\U-{L

il

Generally

speaking,

iatensity of Brswnian

motion

and

gas

viscosity

both

increase

wiiir

gas tempera-

hrre.

These

factors

are im,portant

gas

st'eam

char-

acteristics

that rolate

to

&e

"sonic

prope*ies"

of the

streaq..

Increases

in ei&er

property

will

tend

to in-

crease

the

effectiveness

-wiii

which

sonic

enerey

can

be

used

to

produce

pariicie

agglomeration.

3.5

FLOW

CHARAC'TER/S7JCs

OF

CARR/ER

G/5

3.5.1

Carrier

Gas

Flow

Raie

The

rate of

evolution

lrom

the

process,

the

iemperature

of

the efluent,

and

the-degree

ald

th"

**ot

by

which

it is

cooled

if

cooliag

is

used

fl*

tl"

rate

at

which

carrjer

gases

must

be

beated,

and

therefore

the

size of

rernoval equipment

and

the

rate

at

which

gas

passes

through

it'

-

For

eco'

"o*i"

reasrls

it

is f,esirable

to

minimize

the

size

of

th"

*qoipor"ot.

Optimizing

the

size^

and

velocii

-eta.tlc.tiip

involv6s

consideration

of

iwo

efiects:

I 1 t

redr:cion

in

size

results

in

increased

power

re-

quiements

for

handling

a

gyen

amount

of

gas

be=

J",-,r"

of

increased

pt"r-t*J

ioss

within

the contol

a"J""

*a

(2) the

efiect

of

velocity

or

the

removal

*eah*oitmt'

must

be

considered'

For

exarnple'

higher

velocities

favor

removal

in

inertiai

"q"ip-

*3"t

"p

to'the

point

ot

turbuleace

but

beyond

this

increasid

velocity

results

in

decreased

eficiency'

In

gravity settling

chambers,

flow

velocitv

deter-

*i"Zr

rrr"

smallei

size

that

will

be

rernoved'

In

"""t*i

scrubbers,

eficiency

is

directly

proportionai

;ielo"t,y

rl"""gi

tn"

t,rtilm.

Io

"utoti'titi",

"4o"-

ity

af"cts

fibn relistance

to.mass

transfer'

In

fflt'a-

dtn,

the

resistance

of

the

medium

will

often

vary

*itil

,"locity

because

of

cnanges

in

dust

cake

per-

meability

*ith

flo*.

In

adsorgtion,

velocily-across

the

bed'should

not

exceed

&e

ma:rimum

that

pEr-

mits

efiective

removal.

Optimum

veloities

have

not

generally

been

established

with

certainty

Jor

*v o"f

the

cont'ol

processes

because

they

are highiy

t rlir"rr"td

by

the

iroperties

crf

tle contaminant

and

carrier

g*t

"t

*"11

"i

by

the

design

of

the

equlp-

ment.

3.5.2

Variaiions

in Carrier

Gas

Flow

Rite

Rate

variations

result

in

veiocity

changes

and

thereby

influence

equlpmgnt

eftcienc,v

*ai."tt*"

drop.

Various

control

lgchliques

have

aie"l"g

abilitiei

to

adjus

to

fow.

&ange;'

In

situatiois

where

rate

variations

are

inescapable'

it

ir

""""tt".y

to:

(1)

design

for.extreme.conditions'

i;t

;;p%y d",.i.""t

thit

wix

conect

for

flow

ihrog"r,'

ot

1S

I

use

a

collector

&at

is

inhe-rently

positive

in

its operation.

Filtlation

is

most

''adapted

to

extreme

rate

variatj.ons

becau

posiiive

barner

ior

-particulate

iro""rr

is,

ho.rever.

subject

to pre

tons

and

general.lv

rhe+u

nouing

not

deliver

at

a

ccnstant

rate

wh

increases.

In

most

other

conkol

tions

in

fow

.riil

result

in'change

ness of

removai.

One

means

icr

coping

with rat

use

of

iwolpectors

ia serles,

one

oer{ormance

with.ircreasing

fo

multicycJ.one)

and

de

whose

creases

with

increasinq

flo:'

(

ele

\a(Vr

r.

-

3.5.3

ChanS.S-lF

Carrier

.r,

",,

f;i,"

Y#:H":iffi

*+

"^i=i*,

gis flows;

and

thoselg[ere'r

are

cauied

by

pro55s

changes

'

varjation

in the

composition

qggm

carrier

gas.

Var+ations

in

contarqj

and coiposition

na7#ur

simu

many

carrier

gas

properJibs

chang

tion

and

temPeratue

change,

eq

must

give

these

changes

recog-nit

Cariier

gas

properlirFrn{r

aiso

There

**

pto""ts"s

where

flow

ra

ablv

unifc^rm

over

a

process

cy-c

composition

goes

thror:gh

a cyc

problems are

essentialiy

the

same

variation of

both

composition

and

3.5.4

RelationshiP

to

Air

Characteristics

C6ot'oi

&6eiques

&

*essively

increasing

collector

p

Eme

will require

that

cbnsideratio

efiect

on

air

mover

selection'

Fab

fr""t

tfru

best

illustration

of

this

;;"

"it;

cake

during

the

filteri

incred5ti4'resistance

to

flow'

Th

;;;

generallY

reduces

centr

lVhere

#e-r"tolt*t

fl.ow

var

tol"i"t"d

[v

the

prcce$EJlos

biowers

or

other

special

precaut

oioved.

'

Lotlr.,

meihod

of

coPing

wi

to

maintain

constar.t

fl.ow

by

inc

sure

operated

dbmper-

i"

S"

*+

or"ttr-ri"

drop

across

the

flter

is

il

"ft;t

cleaiing,

the

damper

is

in

position

to

addlressrue

drop

to

p."s.or*

drop

aooss

the

fi1tar

in

Lola"p

orr

ih" fabric,

the

dam


33/158

il

;

PROCESS

FACTORS

.{f'FECTINC

EQUIPNIENT SEJ

ECT1ON

I

changes

in

ioading.

I

Contaminant

loading

from

many

proce-sses:aries

3.6.5

Contaminant

Sorbabiliiy

I

opens,enough

to

maintain

the

sum

of

the

filter

pres-

of

phase

ai

temperatures

nea.r

those

normally

erist-

Juie

drop

ôd

th"

damper

pressure

drop

constaat,

irg

i::

conventional collection

equrpment

(unless

ihereby

foaintainine

eoistanlcy of

flow rate

through such

change

of

phase

is

relatC

io

'.he

actual

re-

ilffi,"*:

"ix*

lT;'

i

"ilfjff

T

ijil

[:::

"

f

^

"H:

.6

1RO1ERTIES

OF

TtjE

sii-.rations

determinafion

o{

.*e,

temperature

at

f

ciNr

aulNANr

[]f",,ti"?f,ir'**1":","ff",1#'""1"ffii:t

3.6.1

Contaminant

Composifion

&e

contaminant.

For

exartple,

ah:minum

Clorjde

r

iamjnani,,&::lfrii,t';",rxll:Hi,*i:"fi

iU'3;""$fx1L1*LIH:':i#ffi*&jffi

chemicai

p,opJ.ti".

*"d

the chesrical

pr-operdes

are,

#d,l}r:'rl""Xn|irlt.fn[:f,fn:J"';"f,;:

;1r*:l

f

*

*T,

important

mainl;

as

thgv

affect

physicai

iemoeratures

that

co*or"only

edst in

*an;z

i,"p"r

"r

propeJtiel',

As

a separare

ccnsideracon,

composi-

.."""i-"i*p*.,, selection

and

conh-ol.

of

&e

ton

directly

afrects

the use

or

value

of

the

collected

r

*"::i:[:l::ii"Hilxr"*ri+i*

ffxt

frt?'i-r:#

:'*H:i}i r:it"i#?:#ifi

material

is to be

used

ul proc,ess

ot

shipped

dr-r, a

&e

{umes

of

difier#

*-",rf,

;"dr*r;"i

banks

oi

r

H;:i:Ji;i'tffit'f,::,':

*L":["":l*

x-

r1,;:',t ;':'rff,x**;-,,

"t';U*:i:t

ector

is

indicated.

Just

as

the

ca::ier

gas

composition can

change

i:T:TH:*::;Jlr:",""f::1i##:1il1*"]j:1

I

T:lgh""'.

a

cyclic

process,

so can-the

composition

all

other

metals

p.i.r".rt in the gas

remaining

in the

of

the

contaminant'

In

the

seccndary

5msltjng^

of

vapor

phase.

A drop

ot

tempEratrue

betwien

the

aluminurr,

**

p"-ttod oJ

evolution

of extremely

ffne

first and

second

collector

bank

condenses

another

I

#"i:P:J"#tfi,:,"' t,ll*rffitii"*l,i

t*T

metat

rume

which

is

+,rren

cotlected

in the

bank,

and

physical properties vary

with

composition,

a collec-

so

forth

until

all

metals

present

have been

removed'

r

tor must

be able to

cope

with

cyclic composition

3.6.4

Contarninanf

Solubiliiy

I

changes.

Solubility

of

contaminant

is important

3.6.2

Contaminanf Loading

to

adsorptiorr,

absorpton,and scnrbbTg.

In

ilt-o.p-

I

--,

-

Load.rng influsase5

different

types

cf

tion,

the degree

of solubiliry is

one

indication of

rhe

r

.-

;;;;:-;,:*-;_-::*;

""^=^_

ease of

removal of the ccntaminani.

In

adsorption,

collectors in different way-s'

For

example'-

cyclone

sohrbfihy

mav

be imoortant to

,,Ie

ease

uritl

which

effciency

increases markedlv

at

high dusi

loadings.

-----

-

-

---

I

converslly,

extremely

higir loading may

overta-r

the adsorbent

may be

regenerated' In

scrubbing

to

I

;"pp;;,

;;;per,

o*h'"k",

iap"cilv,

hocesses

zuch

.

remove

pardculate'

solgbrlity

-will

provide a secorr-

as

sonic agglomeration

"rL

quite

sensitive

to

dary removai mechanisrn

to

aid

the basic separafing

forces.

over

a wide

range

for

the

operating

cycle.

Ten

to

1

.

r

1r

I

ne

sorbabilrty,

or

ease

wlu] wficn

a

r

oDe

varlauon

m loaClt.trg is not uncoutmou. uEe

ex-

_^_ -_j-

r_^ _^*^.1^;

L.,

^,J^^-.l1-

I

;;il;;;;

a

process

is &e ope4

hearth

furnace,

contaminaat

can

be

-removed

by

adsôrption

or

ab-

"n.:th""

is soot blowiag

in

a

steam

boiler.

sorption

techniques'

is-a

function of

a number

of

^-

,-

.

,

, 1. ,

.::i":;-I"

ô-iar

moie basic

properties.

Generally

adsorptiou.is

de-

_

tjontarninant

l6zding may also

vary

with carrier

;::; ::t:'::^::_

I s"'-r;;';;.

A

priml

example

is

dy

ash

in

fue

lo"9.as

the

procesl-P;:g*--ffi+]3e,l1t:,1'

.,4

gas

rrom

a

stor(er

ured

coal

rumace.

an

mcrease

m

Iiquids

are erposed

t:

i?d

Tl::""flT^:-1Pjit*:

fid

true

sas

now

rate is the resurt or

an rncrease

1D up-

li:,

"-':

*: lg::^t: ::I1-.'*l'^:T*"^,1i.^1

I

*"rd-velocity

sf

air

thoueh

th.

coal bed

and

u-

igi' '?l;i'j

-1i"T^*^"j?1::"-'^:?Iie

eltner

I

----

r

'.^1^^r--,..

,r-.]e,_-.^..

r . . i

.

r

Uqud or

sold

and

tne

ColTlDlnatron

ls

moTe

Per-

ereased

gas

veiocliv

in &e F.gnace,'.rot},

of

wirich

.

r, r

.

.l

:- ?,

-

--

^:

^,

r_^_ rL-

f_-^,

L^l

r^ rL^

-^-

mrflent

Decause

it 1s

accomDarueq

DJ/

cDemlciu.

re-

lncreasethecarryoverlromt-heruelDeorotnegas

,., 1

.tr

\

,r

I

ste"T

--

_

tTH;f[?il:';:i.T,:'H:';:XTl,T"ri3l:

'

3.6.3 Contaminanf

Phase

erties

of

temperafure,

pressure

of

the

system, &"rir-

_

In most air cleaning

operations,

the ical

,composition-_of

gornfqYnin4nf

and

sorbent,

and

I

contamjaant

to

be removed

w-ill

oo1

ood.rgo

chauge

,.

plubilitl,

as

well as

r:ndefined

properties

such

as


34/158

x ril

f

,ril

I

1':

l,rl

il

,rl,

:ii

iii

ti.l

,il:

:iii

iri.

',ii

",::i

;:ii

lli

-ll

illi

Il

.x

.r,il

.lil

al

.tii

lll

.i

lrl

,ill

tll

.tii

:ill

rl

'll

il

',il

,

------'-.-

I

j

-.:-=::::-_=:.=.

.:____:_:-::..:.

i

tll

$i

rll

'::'j

l;il

:'ii,i

ill

jlii

.ri+

fii

'{i

illl

iill

rfl

rti

rll

,fii

ri,i

iill

i|

iltl

[i

#t

i[l

il

,#i

Cenerally,

it

is

not

desirable

to

use

a

colection

ry-stem

that

permits

accumulrtion

of

"pockets"

o{

contaminant

i.hen

,e"

"L"tr**ant

co1_

lected

is

explosive.

Systems

t

""df*g

such

ma-

teriais

nust

be

protectld

against

acc.imulat

on

of

staric

-cnarges.

Elech.osiatic

precipitators

are

not

suiiabie

,because

ot

.their

tendency:

to

spark.

Wet

collecton

by

scrubbrag

or

adsorptioo

*dthod,

*ru

be

.especiaily

rpp."prl"t".

ifo*-""".,-roo.

"air?u

suci

as-

magnesium

are

.owophor:c

rn

the

presence

of

small

amounts

of

wat6r.

h

"ombustion

i*th

o.

lithoqt

a

catalyst),

explosibfitT

must

te

con_

sicierec.

3.6.7

Confaminani

Reacfiviiy

Certarn

obvrous

precautions

must

be

iaken

in

the

selection

of

equiiment

for

the

collec-

tion

of

reactive

contaminanis.

Jn

filtraticn,

selection

of the

filtering

media

may

present

a

speciai

proUf"*.

In

adsorption,

certain

situa-tions

,"qrrl"

that

the

ad_

sorbed

contaminant

react

with

tie

adsorbent

so

that

the

degree-of

reactivrty

will

be

important.

For

uses

where

scrubbers

are

considered,

agryavation

of

corrosive

conditions

must

be

balanci"against

the

savings

that

are

possibie

because

corrosion

resistant

construcijon

requires

relativeiy

small

amounts

of

material.

3.6.8

Elecfrical

and

Sonic

properties

of

the

Contaminani

The

electrical

propertie,

of

thrl"oo_

taminant

may

influence

the

^perio.rrrance

of

several

col-lector

types.

Electrical

prlperti.,

"r"-.oosldered

:?

o",l

contributing

fact'or-

influencing

the

build_up

ot

soiids

in

inertial

colleCors.

Ii=

eiectostafic

precipitators,

the

electical

properties

of

the

con-

taminant

are

of paramount

importance

in

determin-

ing

cailection

eficiency

and

;n-fnsn.e

the ease

witb

yhich

it

is

removed

by periodi*

.t"r"lng.

ln

fabric

filbaUon,

elech-ostatjc'

pl"rro*.rm

may

iave

direct

and

observable

in{uenie

upon

th" prl""r.

of

cake

formation

aod

the

subsequeirt

ur."

Jf

cal


35/158

PROCESS

FACTORS

AFFECTINC

EQUIPMENT

SELECTION

I

I

il

il

il

il

I

I

t

i$il

size

distibution

will

largely

deiermiae

the

overall

eficiency

of

a

parlicuiar piece

of

conkol

equipment.

Generally,

the

smaller ihe

size to be

removed,

the

qeater is

ihe

erpenciiiure

requireC

for

power

or

Jq*p."rt

or

both. To

inerease

the

eficiencjes ob-

tarnable

wiih

scrubbers

it

is

necessary

to

expend

additionai

power

either

to

oroduce

high

gas

stream,

velocities

as

in the

venturi

scrubber

or to produce

fineiy

divided

spray

water.

Cyclones

will

require

that

a

iarger

number

of small

uniis be

used

for

lugher

eficiencv

in a

-ziven

situation.

Both the

power

cost

(because

of

',he

increased

pressure

drcp

)

and

equipment cost

(

ior

a

muluple

unit

in-

staiiation)

will

be

increased-

Iligher

eficiencies

{or

elecrrostatrc

precipitaiors

'vr1I

re-quire

iiat

a num-

bel

of

'aniis

be

used in

series because ihere is an

approximately

inveise

logarithmic

relafionship

be-

rween

outlet

concenh'ation and

the

size

of

collec-

tion

equipment.

A_

precipitaior giving

gO%

effcienqr

must be doubled

in

size

to

give

99{5

effcjency

and

uipied

in

size

to

give

gg.9%

eficiency.

3.6.1'l

Confaminant Hygroscopicity

Hvgroscopicity

is

not

specifically

re-

laied

to

any

removal

mechanism. However,

it may

be

a measure of how

readilv particulate

will

cake

or

tend to

accumulate

in

equipmeut

i.f

moisture

is

present.

If such accumulation

occurs

on

a,fabric--

filter,

it mav

completely

blind

it

and prevent gas

flow.

3.6.12

Agglomerating

Characieristics

o{

the

Coniaminant

Collectors

are

sometimes

used

in

series

wiih the

first

collector

aciing

as

an aggiomerator

and

the

second

coilecting

the particies

aggiomerated

in

ihe

first

one.

Carbon

black

collection is Brl x:

.

ample

of a

process

where

extremely fine particles

are first

agglomerated

so

ihat they

may

be

made-

-

pracficably

collectabie.

3.6,13

Flow

Properiies

of

the

Contaminant

These properti,es

are

maiuly reiated

to

&e ease

with

which

the collected

dust mav

be

&s-

charged

from

the

collector.

Extreme

stickiness

may

elimiaate the possibility

of

using

equipment

such

,s

fabric

filters.

Hopper

size

depeuds

in

part on

ihe

packing

characteristjcs

or

bulk density

of

the

collected

material.

3.614

Cafalyst

Poisoning

by

the

Contaminant

Tte

presence

of

traces

of

materials

such

as

silicones, which

on

decomposition

leave

a

deposit

of

silicon

(or

an

oxicie

of

silicon), and

metals

such

as

mercury,

lead,

and zinc,

may make

caialytic combusfi.cn

impractical

even

though

ef-

fluent

stream

characieristics

are

such that

it wouid

otierwise be a

suiiabls

lgcl']nique. Other

than by

mechanical

attrition,

cataivsts

are deteiorated

bv

four

phenomena associated.

witi

stream

content

oi

condiiion:

(

1

)

surface coaiing

of

the

granular

stuucture

by

particulate

contaminants

within

the

gas

ttieam,

(2

)

coatrng

by

parUcuJate products of

oxidation,

(

3

) chen:ical

reacCon with gaseous

com-

ponents

c{

the

stieam,

and

(4)

bed

temoeraiure

levels

',Iai

wrll

cause

sinterins

of

&e

catalyst.

These

often

overlooked

ccnsiderations

must be. taken

into

account when

selecting

a caralytic

o;adation

system.

3,7

REPRESENTATIVE

CONTA#IN,ANT

SA/APLE

OF

In order

to

evaluate

anv

contaminant

and

predict

the ease

or eficiency

wiih

which

it

can

be

collected,

lt is

nec:ssary io procure

a

sample rep-

resentatjve of

the

way the

contaminant

erists

in

the

gas

stream.

Such evaluation

is

seidom

possible

because

the

process

of coilecting

the

sample,

re-

dispersing it

for

measurement,

and measuring

the

properties

of interest ail

involve handling

ihaf

may

change

such fundamenial properties

as

effective

particle

size.

For

tlis

reason,

laboratory

investiga-

rions

and

evaluatjons

of

a

contaminant,

while

they

provide ihe

best avaiiable basis

for

design, are

deff-

nitely

limited

in

their utilily.

Because

of

this, the preferred

way

of

evaluating

'-the

ability of a collector

type

to

collect

a

con-

taminant

is

io pass a

poriion

Ofl

th-e

gas

stream

con-

taining

the

contaminant into

,

a so-call

"test

unit"

brought

to the

plani site.

The'test unit is a

pilot

plant

sized

collector

employing',-he

same

eiements

and forces on a fraction

of the

prccess

gas fl.ow

as

a

fulI scaie

unit

would

apply

to the

total

gas

fow.

Thus the

test

unit

operates

on

a

sampie

of the con-

taminant

as

it

exists

in

&e

gas

steam.

A

test

unit

seldom

gives

results identieai to tlose

from

a

fulI

--scale

unit

because

SEdje

bfects alE-ffirays a

factor

in

performance.

However, test units

give

more

re-

liable results

than

laboratorv

tests using redispersed

dust.

lVhere

it

is.

not

practicabie

to

use a test unit,

testing

must

be

done

on

a

collected

dust

sanple,

koblems of

contaminant

collection

and redispersion

do

uot

exist, of

course,

if the

contaminant

is

a

well-

defined

gaseeus substance,

not reacting

witl

the

carrier

gas

or

other

contaminants.


36/158

4/

MECHANICAL

COLLECTORS

.1 lntroduction

4.4.3

Jet

Type

42

Qr-av_ity

Settling

Chamhers-

t

4.4.4

Loniiir.tion

4.2.1

combination

settling

chambers

and

4.4.s

afii;i;;.y'-

,-.*,.-

adiant

Gooring

Devices

1.1.i

Fowei'Cinsumption

.2.?

chip..rraps

4.4.t

niiiiiiiitv'--

4.3

Cyclone

Collectors

4.4.9

Costs

'--'

4.3.1

Principles

of

0peration

4.5

Dynamic

-Fiicipitator

4.3.2

constiuction

4'5

t. .1

principres

of

operition

4.3.3

Efficiency

4.5.2

ot;;t,-;;

iiraracteristics

iii

fti,5;,ili'umption

f:i;i

iilrmU:ful,iil;-

.3.5

Costs

4.5.5

C;,i;;{il;

Emoien.y

,nd.

Retiabitity

4.4xHi-E :lii&1]il]^'?t^g.?l...1I i{mi':l.diil.-..-,

4.4.2

Principles

of

Operation-Saffte

Type

4.s.7

Applications

-

4.t

INTRODUCTION

The

reason

for keeping

collector

&mensions

*1arge

sp*# ..?:::::

i.fl"JT

il*ET'

d***ti

ilffi

r#::,{.:,iil+:{,,J:'fdij*1"*

Thre-e

of

these-gravity,

centrj,fugal

force,

-and

in-

tinguishing

feature

of

mechanical

collectors.

ertial.impacdon-.-ar,e..the

most

im-portant ihat

dis-

[tect"oi]ca

colectors

rrray

be

,convenienti

llsoitn

the

so-called

"mechanicaf'equipment

class..

grouped

into

two

major

types,

gravity

ana

ine*ia

The

last

two

mechanisms

invorve

4

s'nstreined

a"peoaug

on

the

*"jo,

,'"p"rriog

f6rce.

Th"

d;

---eblaga-of

fuiddirection

at

such

a rate tha

e1-

g6op,

g'"*y

derices,-

is

"o*it

ua

,of"fy

'oi

icle

motion

is determined

more

-

by

partcle-

in-

r"ttfig

Ia"-*tior

""J

il

oi

only

d1"",

ir.p"rtt""

ertia

thau

by

fuid

drag

forces,

wilh

the

result that

The

se-cond,

much

larger,

group

consists oi

"y"lo

.i:1,rf"ry'&i*i5t%":"*'-

"rsn::.

H::

ffi

:i;g:

r'au:::ru:i*tl;::,"rf,.nffi

mechanical"

coilection

equipment

may be-thought

the

fuid

st'eam

--i-o

m-o'ffio

a

corh,ed

,rort"*

*itil

of

as

that

qorP.

of

devices that

depends

on-gqar-itn

_

in

which

inertiai

forces-cordirutnwlg

proar".-

*{;f:'f,ffifi"l::,::#H'*-'*TTf,j",'."i,1u

'

*1,?:ili*?l?.":"i;y*ri*,:t*"r,mx

resistance,

increase

dt

ah.

square

of

particle

in

operaion-except

thlt

th"

change

lo

il;

;t

*;

&ameter

(see

Chapter.2)._ThuJ.hrgest.pgtia"s

d.ueiggn.is

usuilty

db;;t";;

l;;";#il

re

separated

most

easily.

From

the

itandlioint

of

chamberi).

F-rr-ally,

dynamic

separators

*"

* *-"]

dirnensions

of

the

collector,

the smaller'the

re.

cial

class'wherein'ihe'fl*d;;;;'lf'"#,,-"

quaed

&stance

of

tiavei

across

streamlines,

the

rotating

imfm,:.tret:"G"

ir

th;

dl "|nbd"n";

reater

i3

the

removal

eficieocr.

ftereforfiy -

"19yr"n;

.ri:s{ogtj-p"cuonetirst

the

elemeut

,,:

minimizing

the.se

collector

dime.t*ions

even

com-

self

or

its housLg.

paratively

-small

particles

could, be sepaSglg{.

b7

.

It

should be

nlted

that

many

mecianical

eol_

these

two

ibrces.

It

rs

a

seccnd

basc charaiTe.ristic

lectors

can

be operaterl

a*lo,

*ei:

Ho*erer,

;h;

of

"mechanicaf'

equipmert,

however,

that

these water

is

used,

ii

p*.fo*r

"rb';

;""#;

#"

drmensions

are

still

ver,v

large,

when_

erpressed

as

tiou such

as

the

cleansing

of

collector-;*f;";-

multiples

of,

the

partigie

Ai*"t"i-

tl*kor",

thi,

in

some

cases, it

ma;,

form

part

of

the

llurd.

"l*o.1.

equipmeat-has

an

inhelenl

]Fper

limit_on

per-

Theuseof

waterinthesea;;L;;;ffi;;

formance

that

i1 determmed

by'p.article

dia-meter.

^

t "* as scrubbers,

since

i*r"*.bb.r-r-ih;;;;i

..,.

26

:

;.

,:.

r_..

_

-,.t,.";

.

Documents

Libro Air Pollution Manual