填料塔气体吸收实验实验报告英文Word下载.docx

填料塔气体吸收实验实验报告英文Word下载.docx

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Objectives

Thisexperimentisdesignedforstudyingthetheoryofhydrodynamicsandabsorptionprocessesinapackedtower.Improvetheskillofsolvingopen-endedquestionisalsoexpectedinthisexperiment.

Introduction

Absorptionisatypicalmasstransferprocesswhichiswidelyusedinseparationprocess.Theremovalofoneormoreselectedcomponentsfromamixtureofgasesbyabsorptionintoasuitableliquidisthesecondmajoroperationofchemicalengineering.Packedtoweriswildlyusedasoneoftheoutstandingrequirementstoabsorbwithdifferentphasesolventinbothindustryandlaboratory.

Inthisexperiment,amixtureofCO2andairisutilisedinthepackedtower,andCO2isconsideredasthetargetgaswhichshouldbeabsorbed.WaterisusedassolventliquidtosoluteCO2.Bymeasuringtheinletandtheoutletconcentration,CO2absorbedcanbedetermined.

Backgroundtheory

Themeasureoftheefficiencyoftheabsorptionprocesscanbeexpressedinthetermsofoverallheightofliquidfilmtransferunit,HOL.ThesmallertheHOLis,themoreefficienttheabsorptionprocesswillbe.Theheightofthecolumn（m）Zisdefinedas:

Where,

L

kmol/（m2.s）

themolarflowrateofliquidperunitcrosssectionalarea

kmol/（m3.s）

overallliquidtransfercoefficient

dimensionless

thenumberoftransferunitsbasedonoverallliquidfilmcoefficient

m

theheightofatransferunitbasedonoverallliquidfilmcoefficient

KXAisavariablewhichcanindicatetheefficiencyofgasabsorption.

AsKXA=L/HOL,itcanbedeterminedthatthelargerKXAvalue,thebetterefficiencyofthesystem.

Andtheabsorptionfactorisdefinedas:

A

absorptionfactor

molarflowrateofliquid

G

molarflowrateofgas

slopeoftheequilibriumlineonamolefractionbasis

ThebalanceequationisyA=mxA

Wherem=E/P

Eisthehenry’sconstant,E=f（t）

Pisthetotalpressure

xAisthemolarfractionofthecontaminantinthegasphaseatequilibrium.

yAisthemolarfractionofthecontaminantdissolvedintheliquidphaseatequilibrium

AfterAisgiven,thefollowingequationcanbeusedtodeterminethenumberoftransferunitsbasedonoverallliquidfilmcoefficient（

）:

CO2concentrationintheinletgas

CO2concentrationintheoutletliquid

CO2concentrationintheinletliquid

Followstepsneedtobedoneinthisexperiment,

∙Determinationofgasflowrateandliquidflowrate

∙Determinationoftheheight（Z）ofthepackingandthediameter（D）ofthecolumn

∙Determinationofy1andy2

Fordataanalyse,alog-logdiagramwillbeusedinthisexperiment.Itisatwo-dimensionalgraphofnumericaldatathatuseslogarithmicscalesonbothaxes.Morespecific,inCartesiancoordinationtheunitis1whileinthelog-logsystem,theunitforbothaxesarethelogX.

Apparatus

1-

liquidoutletV4

2-airblower

3-liquidoutletV5

4-gasoutlet

5-outletgassampling

6-Utubemanometer

7-Packing

8-Liquiddistributor

9-Inletgassampling

10-Gasflowmeter

11-Gasflowmeter

12-Liquidflowmeter

13-GasinletvalveV1

14-GasinletvalveV2

15-LiquidinletvalveV3

16-Watertank

17-Waterpump

18-Liquidinlettemperature

19-Mixedgastemperature

20-Blowerbypassvalve

21-Procedure

Figure1,theCADdiagramofexperimentalapparatus.

Specification:

heightofthecolumnis2000mm

Diameterofthecolumnis100mm

Procedureandnotes

∙Checkthevalveatbottomofgasmixertoletcondensateout.

∙Turnonthepoweratthepanel,turnonthegauge.

∙Fillthewatertankwithtapwaterandcheckthelevelperiodically,keepitinastablerange.

∙Switchonthewaterpump.Adjusttheliquidinletvalvetoachieveadesertwaterflowrate.OperateV4andV5tocontrolthewaterlevelatbottomofthecolumnbelowtheairinlet.

∙Turnontheairblower.TurnontheCO2cylindervalveandthereadingislargerthan3

∙V1andV2arethevalvethatadjustCO2rotameter（suggestedgasflowrateis3-5m3/h,liquidflowrateis0.6-0.8m3/h,CO2flowrateis2-3L/min）

∙Letthecolumnrunforafewminutes,duringthetimeyoucanadjustlevelwater,pressuredroptomakesureitreaches“steady-state”conditions.

∙AnalysetheinletgasandoutletgasrespectivelybyGC:

open（inlet/outlet）valve---（2min）---turnonthesamplebottom---click“start”---closesamplevalve—close（inlet/outlet）valve

∙Recordingallthenecessarydata

Notes:

∙Thewaterlevelshouldkeepinastablerange;

neverthelessitwillcauseinstabilityofrotameterofliquid.

∙ThetotalgasflowrateequalsthesumflowofV1andV2

∙BeforesamplingtotheGC,opentheinlet/outletvalvefor1-2minutessothatmeasuredgascouldfillupwithpipe.Otherwise,theoutletcarbondioxidepercentagemaybelargerthaninletoneintheresult.

Calculationandresults:

Thedataofthreegroupsarelistedasfollowing:

T（Liquid）（⁰C）

T（Gas）（⁰C）

Pressuredrop（Pa）

Liquidflowrate

（Nm3/h）

Gasflow

rate

InletCO2

Con.y1

（Vol%）

OutletCO2

Con.y2

1

12.7

21.8

90

0.6

10.06

5.493

5.308

2

21.6

200

12.56

5.540

5.406

3

220

15.08

4.806

4.719

Table1ExperimentData

Chosegroup1asanexample:

Tosimplifythecalculation,roomtemperatureisassumedas25⁰Candtheroompressureis1atm.

Thehenry’sconstantofcarbondioxidedissolvedinwaterat25⁰C1atmcanbefoundbylookinguptheengineeringhandbookwhichis1635atm

Thus,

m=1635/1=1635（dimensionless）.

Fromtheexperimentdata,

L=0.6*998/18=32.267kmol/h

G=PV/RT=1*10.06/（0.082*298）=0.412kmol/h

Y1=5.493%

Y2=5.308%

Accordingtothebalanceequation:

L*（X1-X2）=G*（Y1-Y2）;

X2=0

X1=G*（Y1-Y2）/L=0.412*（5.493%-5.308%）/32.267=2.362*10-5

Inaddition,

A=L/mG

Thus,A=32.267/（1635*0.412）=0.048

TakeAintotheequation

=1.239

Because,

Then,

1.142

log（HOL）=0.208

log（KXA）=log（L/HOL）=-0.150

log（G）=log（0.412*1000）=2.615

Accordingtoprocessabove,othertwogroupscanbedeterminedaswellintheTable2.

L（kmol/h）

G（kmol/h）

x1

x2

NOL

HOL

KXA

log（HOL）

log（G）

log（KXA）

32.267

0.412

0.048

2.362*10-5

1.238

1.616

0.707

0.208

2.615

-0.151

0.514

0.038

4.444*10-5

1.008

1.983

0.576

0.297

2.711

-0.240

0.617

0.032

3.902*10-5

0.844

2.371

0.482

0.375

2.790

-0.317

Table2CalculationResults

Afterwards,thelog-loggraphcanbedrawn

0.297.

Table3

Figure2log（HOL）-log（G）diagram

Figure2showstherelationshipbetweenlog（G）andlog（HoL）,whichhasadirectproportionwithpositive.Thefunctionisabouty=0.0832x+0.1271

log（G）G）

Table4

Figure3log（KXA）-log（G）diagram

Figure3isthediagramofTable4thatindicatesthatthereisanegativerelationshipbetweenlog（Kxa）andlog（G）,whichhasadirectproportionwithnegative.Thefunctionisabouty=-0.0832x-0.0695

log（HOL）G）

Table5

Figure4log（HOL）-log（KXA）diagram

Figure4showstherelationshipbetweenlog（Kxa）andlog（HoL）directlywhichillustratestheyhavealinearrelation.Thefunctionofthelineisabouty=0.0832x+0.1271

Figure5Operatinglineandequilibriumlines

Figure5showstheoperatinglineinthesituationofdifferentinletgasflowratecomparetothesameequilibriumline.Theslopeofoperatinglineandequilibriumlinehasabigdifference.However,whenx=0,thesethreeoperatinglinesarenotequals0.Asaresult,theremusthaveintersection,inotherwords,itexistsminimumflowrate.

Discussion:

Experimenterrors

Readingerrorsinthisexperimentcannotbeavoided.Itwillbemainlycreatedinreadingtheflowrateofbothliquidandgas.

Thetemperatureoftheroomkeepschangingduringtheexperiment,whichcertainwillmakeintersection.

Thedeviceitselfhaserror.ForexampleCO2gasmayberevealedfromtheapparatusatsomecomponents.

Thereaddingwrittenisnoinstable-state

BeforeenterthesampletoGCmachine,thevalvemaybenotimmersedbymeasuredgascompletely,whichbecausetherearesomeimpuritiesinthesampleandtheresultisinfluenced.Inaddition,theerrorwillbeveryobviouslyduetothesensitivityofGC.

Calculationerrors:

Thefirstnotablethingduringthecalculationistheunits.Mistakesareeasytobemadeifunits’transformationsarenotgettingenoughattention.

Thelog-logdiagramdrawnaccordingtotheresultsoftheexperimentisnotexactlystraightlinesandthefunctionofthegraphisestimated,thus,thisexperimentmusthaveintersectionorsmallerrors.

Tomakethecalculationeasytoget,wehaveassumedtheroomtemperatureis25˚C;

however,theroomtemperatureoftheexperimentisnearly21.8˚C.Theinaccurateofthetemperaturewillmakethehenry’sconstantofcarbondioxidedissolvedinwaterweuseincalculationisnottheactuarialone,anditwillmakeadifferenceinresults.

OneofthereasonstochoosetheHenry’sconstantunder25˚Cisthatitiscommontobeusedasstandardsituation,theotherisitisneartherealvaluerelatively.

Duetotheexperienceofformerexperiment,theinfluenceofKxaandHoLforpackingcolumnisthatthelargerKxais,themoreefficiencycolumnwillhas.Onthecontrary,largeHoLvaluemeanslowabsorptionefficiency.Moreover,dependingonthethreelog-logdiagrams,log（G）-log（HoL）,log（G）-log（Kxa）andlog（Kxa）-log（HoL）diagramasfigure2,3and4,itiseasilytofindtheyarealllinearrelationship,firstoneamongthesethreeistheonlyonewithpositivetrend.ItillustratesthatonlyGandHoLhavepositivedirection,whenGincrease,HoLwillalsoincrease.Inotherwords,theincreasinggasflowratewillhavenegativeeffectontheefficiencyofgasabsorption.Theothertwogroupsareonopposite.KxawillreducedependingonG’sincrease.SodoKxa（X-axis）andHoL（Y-axis）.Inaddition,comparedtofigure2andfigure3,becausetheyhavethesameX-axiselement,itcanbefoundoutthatwhenlog（G）increases,log（Kxa）fallsdownandlog（HoL）ri