Gas absorption by aladwani

7/23/2019 Gas absorption by aladwani

http://slidepdf.com/reader/full/gas-absorption-by-aladwani 1/16

Al-Balqa' Applied University

Faculty of Engineering Technology

Department of Chemical Engineering

eport of Control !a"oratory

#as A"sorption

Edited "y$

%haled &aad %halaf ayaif

(eshari )amed A!shammari(ohmmad

2



T*T!E+A#E

A"stract,

*ntroduction

Aims.

Theory.

Apparatus and (aterials/-0

(ethodology1-2

esults3-

Calculations45-4

Discussion4.

Conclusion4/

ecommendations40

eferemces41

AB&TACT

Gas absorption is a process in which the soluble parts of mixture are

transferred to a liquid.Gas absorption is done in a packed column .This report

are done as to examine the air pressure drop across the column as a function

of air ow rate for dierent water ow rates through the column. When the

1



air pressure drop to certain limit, the phenomena known as ‘ooding will

occur in which the s!stem can no longer operate as it is. "ence the ‘ooding

point is to be determined as to make sure that the process should be made

to operate under the ‘ooding point.

*T6DUCT*6

Gas absorption is a process in which the soluble parts of a gas mixture are

transferred to or dissol#ed in a liquid. The re#erse process, called desorption

or stripping, is used to transfer #olatile parts from a liquid mixture to a gas

$%& . Therefore there will be mass transfer of the component of the gas from

the gas phase to the liquid phase. The solute transferred is said to be

absorbed b! the liquid. 'n gas desorption (or stripping), the mass transfer is

in the opposite direction, of which the transfer is from the liquid phase to the

gas phase. The principles for both s!stems are the same. *ut from here and

2



on, we are onl! interested in gas absorption . There are + t!pes of absorption

processes ph!sical absorption and chemical absorption,depending on

whether there is an! chemical reaction between the solute and the

sol#ent(absorbent).

When water and h!drocarbon oils are used as absorbents, no signi-cant

chemical reactions occur between the absorbent and the solute, and the

process is commonl! referred to as ph!sical absorption. When aqueous

sodium h!droxide (a strong base) is used as the absorbent to dissol#e an

acid gas, absorption is accompanied b! a rapid and irre#ersible neutraliation

reaction in the liquid phase and the process is referred to as chemical

absorption or reacti#e absorption.

A*(&

To examine the air pressure drop across the column as a function of air ow

rate for dierent water ow rates through the column.

T)E67

/nother de-nition of gas absorption0desorption is ,a process in which a

gaseous mixture is brought into contact with a liquid and during this contact

a component is transferred between the gas stream and the liquid stream.

The gas ma! be bubbled through the liquid, or it ma! be passed o#er

streams of the liquid, arranged to pro#ide a large surface through which the

mass transfer can occur. The liquid -lm in this latter case can ow down the

sides of columns or o#er packing, or it can cascade from one tra! to another

3



with the liquid falling and the gas rising in the counter ow. The gas, or

components of it, either dissol#es in the liquid (absorption) or extracts a

#olatile component from the liquid (desorption). $+&

'n e#er! packed tower with a gi#en sie of packing and t!pe , has an upper

limit to the rate of gas ow known as ooding #elocit! of which the tower

cannot operate abo#e the #elocit! mentioned earlier. /t low gas #elocities

the liquid ows downward through the packing uninuenced b! the upward

gas ow. /s the gas ow rate increases at low gas #elocities the pressure

drop starts to rise at higher rate. The liquid accumulation increases as the

gas ow rate is increased . /t the ooding point, the liquid will no longer

ha#e the abilit! to ow down through the pack column and later is blown out

with or b! the gas. $1&

A++AATU&

The apparatus used in this experiment are

234T567689 /bsorption column (:odel *; <=%7*)

The material used in this experiment is water and air.

4



(ET)6D6!6#7 8 +6CEDUE&

A9 #eneral start-up

%. /ll #a#l#es are closed except the #entilation #al#e 8%1.

+. /ll gas connections are ensured of properl! -tted.

5



1. The #al#e on the compressed air suppl! line is opened. The suppl!

pressure is setted up in between + to 1 bar b! turning the regulator knob

clockwise.

>. The shut7o #al#e on ?3+ gas c!linder is opened. The ?3+ gas c!linder

pressure is ensured to be su@cient.

=. The power for the control panel is turned on.

B9 E:perimental +rocedures $ )ydrodynamic of a +ac;ed Column

<=et Column +resssure Drop9

%. The general start up procedures are carried out

+. The recei#ing #essel *+ is -lled with =A 4 of water b! opening #al#e 81

and 8=.

1. 8al#e 81 is closed.

>. 8al#e 8%A and #al#e 8B are slightl! opened. The ow of water from #essel

*% through pump ;% is obser#ed.

=. ;ump % is switched on then #al#e 8%% is slowl! opened and adCusted to

gi#e a water ow rate of around % 40min. Water is allowed to enter the top

of column D%, ow down the column and accumulate at the bottom until it

o#erows back to #essel *%.

6



E. 8al#e %% is opened and and adCusted to gi#e a water fow rate of A.= 40min

into column D%.

<. 8al#e 8% is opened and adCusted to gi#e an air ow rate of >A40min into

column D%.

F. The liquid and gas ow in the column % are obser#ed , the pressure drop

across the column at d;T7+A% is recorded.

B. 2teps E to < are repeated with dierent #alues of air ow rate, where each

time is increased b! >A40min while the same water ow rate is

maintained.

%A. 2teps = to F are repeated with dierent #alues of water ow rate, of

which each time is increased b! A.=40min b! adCusting #al#e %%.

C9 #eneral &hut-Do>n +rocedures

%. ;ump % is switched o.

+. 8al#es 8%,8+ and 81 are closed

1. The #al#es on the compressed air suppl! line is closed and the suppl!

pressure is exhausted b! turning the regulator knob counterclockwise all

the wa!.

>. The shut7o #al#es on ?3+ gas c!linder is closed

=. /ll liquid in the column in D% is drained b! opening #al#e 8> and 8=.

E. /ll iquid from recei#ing #essels *% and *+ are drained b! opening #al#es

8< and 8F.

<. /ll liquid from pump % is drained b! opening #al#e 8%A.

7



F. The power for the control panel is turned o.

E&U!T& AD CA!CU!AT*6&

9low rate

)40min(

;ressure drop (mm"+3)

/ir

water

+A>AEAFA%AA%+A%>

A

%E

A

%F

A

%.AA+E<B%A%F+%=F

+.AF+A1B1A=177

1.AA+<%11B7777

Table % ;ressure rop for Wet column

8



9igure % ;ressure rop #s. /ir 9low Hate

&ample Calculations

ata

ensit! of air I %.%<=kg0m1

ensit! of waterI BBEkg0m1

?olumn diameter I FAmm

/rea of packed column diameter I A.AA=A+<m+

;acking 9actor I BAA m%

Water #iscosit! I A.AA%Js0m+

Theoretical Flooding +oint$

GG, gas ow rate (kg0m+

s)

9



GG I G!Kp 0 /

I

IA.A<<Bkg0m+s

Capacity parameter? y-a:is

I

IIA.A%=>

G4 , liquid owrate per unit column cross7sectional area

I

I

I1.FBEx %A71 kg0m+

9low parameter , x7 axis

x7axisI

10



I1.A1+

Water 9low Hate (40min)G4 (kg0m+s)

%.A1.FBEx %A71

+.AE.EAA>

1.AB.BAAE

Table + Water 9lowrate and G4 , 4iquid 9lowrate per Lnit ?olumn ?ross7

sectional /rea

Table 1 /ir 9lowrate

,gas ow rate

(kg0m+s) abr#. GG

,capacit! parameter

and ow parameter.

9igure +

Theoretical ;ressure

rop ?orrelation

?hart 9or Handom

;ackings

11

/ir

ow

rate

(40min)

GG

)kg0m+

s(

?apac

it!

;aram

eter

(!7

axis)

9low parameter (x7axis)

+AA.A<<BA.A%=

>

%.A4;:+.A4;:1.A4;:

>AA.%==<A.AE%

>

1.A1++.B%A+>.1E=1

EAA.+11EA.%1F

1

%.>=EA%.>=EA+.%F>A

FAA.1%%=A.+>=

B

A.B<A=A.AAB<A=%.>==<

%AAA.1FB1A.1F>

%

A.<+<FA.=F+1%.AB%<

%+AA.>E<+A.==1

+

A.AA=F+

1

A.>F=>A.F<1=

%>AA.E++BA.<=1

%

A.<=1%A.>%EAA.<+<B

%EAA.E++BA.BF1

+

A.BF1+A.1E1BA.=>=B



Water 9low

Hate

)40min(

Theoretical

9looding /ir

9lowrate

(40min)

5xperimental

9looding /ir

9lowrate

(40min)

5rror(M)

%.A%FA%EA%%.%

+.A%>A%+A%>.+F

1.A%AAFA+A

Table > comparison of theoretical and correlation of ooding point

D*&CU&&*6

'n this experiment, the interest is to examine the air pressure drop across the

column as a function of air ow rate for dierent water ow rates through the

column. The experiment based on the ow rate of liquid and gas in the

packed.

9irstl! the water ow rate is kept constant to % 40min and the air ow rate is

then recorded after a % minute inter#al. /ir ow rate is kept rising at constant

b! +A 40min b! each = minutes. /ll reading of pressure drop are then

recorded until the ooding point is reached. The pressure drop for ow rate of

air are A,+,E,<,B,%A,%1,+%,=F mm "+A respecti#el! to

+A,>A,EA,FA,%AA,%+A,%>A,%EA and %FA 40min of air.

The ow rate of water is then adCusted to + 40min, the data recorded are

12



F,+,A,1,B,1A,=1 mm "+A respecti#el! to +A,>A,EA,FA,%AA,%+A,%>A,%EA 40min

of air. 't cannot reach %FA 40min of air ow rate as the water will spra!ed out

from the column due to the high ow rate. Theoreticall!, the pressure drop

will increase as the air ow rate of air is increased, howe#er at the beginning

of the experiment , the pump suddenl! failed to work as an o#erow occurs

hence Ceoparding the s!stem of which being experimented.

/s the water ow rate is increased to 1 40min, the datas are , A,+,<,%1,1B mm

"+A respecti#el! to +A,>A,EA and FA 40min of air . *e!ond FA 40min of air , the

ooding occurs.

The graph of column ;ressure rop #s. /ir 9low Hate is plotted and in which

the results from the plotted graph shown the higher the gas ow rate , the

higher the pressure drop.

9or correlated #alue of the pressure drop,calculations has ben made and a

graph of capacit! parameter against ow rate parameter is plotted. The

capacit! parameter is indirectl! proportional to ow rate parameter

C6C!U&*6

'n conclusion, the air pressure drop across the column increases as the air

ow rate increases as well as the water ow rate through the column. 9rom

the experiment, the #alue of experimental pressure drop is higher compared

to the correlated #alues for packed column. 9or packed column of water

owrate of % 4;:, the error in#o#led is the lowest that is %%.% M, followed b!

that of water owrate of + 4;: which is %>.+F M . /t water owrate of 1 4;:,

the error in#ol#ed is +AM . These percentage errors between theoretical andcorrelated calculations of ooding point are slightl! high due to some

13



unexpected instrumental error as the pump suddenl! shut o in the middle

of the experiment. "ence, all instruments must be checked before an!

experiment is conducted to ensure the accurac! of the outcomes.

EC6((EDAT*6&

2ome suggestion in impro#ing the safet! are to alwa!s check and rectif! an!

leak and all operating instructions supplied with the unit must be carefull!

read and understood before attempting to operate the unit. Jext, be

extremel! careful when handling haardous, ammable or polluting materials

such as ?3+. :ake sure the s!stem is su@cientl! #entilated when working at

atmospheric pressure.

14



EFEECE&

$%&;err!, Hobert "., and Green. ;err!Ns ?hemical 5ngineersN "andbook. Jew

Oork :cGraw7"ill, 'nc. (%BF>), pp%>7E,%F7++7+

$+&Hetrie#ed on %+th :arch,+A%= from

http00www.nifst.org.n0unitoperations0conteqseparationF.htm

$1&Geankoplis, ?.P. (+AA1). Transport ;rocesses and 2eparation ;rocess

;rinciple, >th 5dition. Jew Oork ;rentice "all,ppE=<7EEA

$>&Hetrie#ed on %+th

:arch,+A%= from

)http00www.separationprocesses.com

15

http://www.nzifst.org.nz/unitoperations/conteqseparation8.htm

http://www.nzifst.org.nz/unitoperations/conteqseparation8.htm

Documents

Gas absorption by aladwani