填料塔气体吸收实验实验报告英文.docx
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填料塔气体吸收实验实验报告英文
DivisionofEngineering
AssessedReport
DepartmentofChemicalEngineering
EH1SPF:
GasAbsorptioninapackedcolumn
Tobecompletedbystudent
StudentName
JohnSmith
StudentID
669665
Groupnumber
Dateofexperiment
Datesubmitted
Officeuseonly
Gradeawarded
Penalty
Finalgrade
MarkersSignature
Abstract
Packedtoweriswellknownasoneofthemostwildlyusedmethodinabsorptionzonetoseparatedifferentgasbyliquidphase.Inthisexperiment,theaimistocalculatetheoverallliquidtransfercoefficientKxabytheequation
ThevalueofKxainthreegroupsarechangeableandonlytwoofwhichcanworkoutKxavalue.TheKxavalueofgroup2andgroup3is0.014and0.012.Inaddition,boththeKxavalueisbelow1sothatlog（Kxa）isalwaysnegative.Moreover,theGandHoLhaveapositivelinearratio.However,GandKxahaveanegativerelationship,sodoesKxaandHoL.Thesethreediagramsillustratethatthegasflowratehasnegativeinfluenceontheefficiencyofgasabsorption.Andtheheightofatransferunitalsohasaninverseratiototheefficiency.
Content
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:
Where,
A
absorptionfactor
L
molarflowrateofliquid
G
molarflowrateofgas
m
slopeoftheequilibriumlineonamolefractionbasis
ThebalanceequationisyA=mxA
Wherem=E/P
Eisthehenry’sconstant,E=f（t）
Pisthetotalpressure
xAisthemolarfractionofthecontaminantinthegasphaseatequilibrium.
yAisthemolarfractionofthecontaminantdissolvedintheliquidphaseatequilibrium
AfterAisgiven,thefollowingequationcanbeusedtodeterminethenumberoftransferunitsbasedonoverallliquidfilmcoefficient（
）:
Where,
A
absorptionfactor
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
（Nm3/h）
InletCO2
Con.y1
（Vol%）
OutletCO2
Con.y2
（Vol%）
1
12.7
21.8
90
0.6
10.06
5.493
5.308
2
12.7
21.6
200
0.6
12.56
5.540
5.406
3
12.7
21.6
220
0.6
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
Thus,
=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）
A
x1
x2
NOL
HOL
KXA
log（HOL）
log（G）
log（KXA）
1
32.267
0.412
0.048
2.362*10-5
0
1.238
1.616
0.707
0.208
2.615
-0.151
2
32.267
0.514
0.038
4.444*10-5
0
1.008
1.983
0.576
0.297
2.711
-0.240
3
32.267
0.617
0.032
3.902*10-5
0
0.844
2.371
0.482
0.375
2.790
-0.317
Table2CalculationResults
Afterwards,thelog-loggraphcanbedrawn
log（G）
log（HOL）
2.615
0.208
2.711
0.297.
2.790
0.375
Table3
Figure2log（HOL）-log（G）diagram
Figure2showstherelationshipbetweenlog（G）andlog（HoL）,whichhasadirectproportionwithpositive.Thefunctionisabouty=0.0832x+0.1271
log（KXA）
log（G）G）
-0.151
2.615
-0.240
2.711
-0.317
2.790
Table4
Figure3log（KXA）-log（G）diagram
Figure3isthediagramofTable4thatindicatesthatthereisanegativerelationshipbetweenlog（Kxa）andlog（G）,whichhasadirectproportionwithnegative.Thefunctionisabouty=-0.0832x-0.0695
log（KXA）
log（HOL）G）
-0.151
0.208
-0.240
0.297
-0.317
0.375
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
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