work of shershah amarkhail

7/26/2019 Work of Shershah Amarkhail

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Islamic republic of Afghanistan

Ministry of higher education

Kabul polytechnic university

Faculty o f chemical technology

Theworkwasrealizedincooperationwith

SLOVAK UNIVERSITY OF TECHNOLOGY IN BRATISLAVA

FACULTYOF CHEMICAL AND FOOD TECHNOLOGYINSTITUTE OF CHMICAL AND ENVIRONMENTAL ENGINEERING

Air Separation

Diplomaproject

Thisdiplomaworkwasrealized

Intheframeworkoftheproject

No.SAMRS2009/09/02

DevelopmentofhumanresourcecapacityofKabulpolytechnicuniversity

Funded

by

Bratislava2010 ShershahAmarkhail


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Acknowledgement:

The author would like to express his appreciation for the Scientific Training Program to

Institute of Chemical and Environmental Engineering, Faculty of Chemical and Food

Technology of the Slovak University of Technology and Slovak Aid program

(SMARS/2009/09/02) for financial support of this project. I would like to say my hearth

thank to Doc. Ing. Juma Haydary, PhD. for his guidance and assistance during the all time of

my training visit in Slovakia. My thank belongs also to Prof. Dr. Noor Mohammad Zamani

and Prof Ahmad Ali Farhat my supervisors at the Kabul Polytechnic University for their kind

guidance and support.


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Content

Introduction 1

2.Theoreticalparts 3

1.2Airproperties 3

2.2Air separat iontechnologies 8

2.2.1CryogenicAirseparation 10

2.2.2Airclearing 15

2.2.3Aircompression 17

2.2.4CoolingofAir 20

2.2.5Airdistillation 23

2.3ProductsofAirseparationandtheirapplications 24

3.Practicalparts 30

3.1Thermodynamicofairseparation 30

3.2CalculationofairdistillationbyMcCabeThielemethod 34

3.3Aspensimulationofairseparationprocess 42

3.3.1TechnicalspecificationsofKT1000Mplant 43

3.3.2ResultsofASPENsimulation 47

4.Mechanicalaspectsofairdistillationtower 61

4.1Basicparametersofcalculations 61

4.1.1Calculated

pressures

61

4.1.2CalculatedTemperature 63

4.1.3Reactionarylongitudinalmodel 63

4.1.4CoefficientSutureStabilityWeld 64


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4.2Specifiedstructuralsurpluses 65

4.2.1SelectionoftheVirtualInjections 66

4.3MechanicalCalculationofdistillationtower 68

4.3.1CalculationCylindricalBodyofthetower 69

5.Safetyaspectsofairdistillationprocess 73

5.1MajorhazardsofchemicalProduction 73

5.2Materialpropertiesinplant(separationofair)wasplanning 73

5.3Majorrisks

in

the

production

system

(air

separation)

74

5.4SafeConditionsfromoperationofcompressor 75

5.5FacilityforDefenseemployeesindividual 75

5.6Sourcesoffireignitionmaterials 76

5.7Wayofmakingofffire 76

5.8Electrical

safety

77

5.9RulesofthetechnicalRepairofCompressorwhenitsbenotdanger 78

5.10Ventilationproductsanditskinds 79

6.Controlofairdistillationcolumns 80

6.1Capitalinvestmentcosts 80

6.2ControllingPressureinDistillation 81

6.2.1VenttoAtmosphere 82

6.2.2CoolingWater 82


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6.2.3FloodedCondenser1 83

6.2.4FloodedCondenser2 84

6.3Controlling

Tops

Composition

in

Distillation

85

6.3.1RefluxRate 85

6.3.2RefluxRatio 86

6.3.3DistillateRate 86

6.4DistillationColumnControlExamples 87

6.Economicevaluationofairdistillation 92

6.1Capitalinvestmentcosts 92

6.2Operationalcosts 93

Summary 97

Conclusion 98

Symbols 98

References 101


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1

1. Introduction

Thecomponentspresented inair(Nitrogen,Oxygen,Argonetc.)areveryoftenapplied

componentsinchemicaltechnology.Largequantitiesofhighpurityairproductsareusedin

severalindustries, includingthesteel,chemical,semiconductor,aeronautical,refining,foodprocessing,andmedicalindustries.

Airatlowertemperatures(196oC)becomesinliquidandsowecandothedistillationofthe

airtoitscomponents.Distillationofair iscurrentlythemostcommonlyusedtechniquefor

productionofpureoxygen,nitrogen andArgon on an industrial scale.An exampleof an

industrialprocessthatrequirespureoxygenandnitrogenisanIGCC(integratedgasification

combinedcycle),wheretheoxygenisfedtoagasifiedandthenitrogentoagasturbine.The

Historyofairseparationhaslongtime,in1895Worldsfirstairliquefactionplantonapilot

plantscale,commercialscale,productionscale,1904 World's firstairseparationplant for

the recoveryofnitrogen,1910World's first air separationplantusing thedouble column

rectification process, 1950 First LindeFrankl oxygen plant without pressure recycle and

stonefilledreactors,1954World'sfirstairseparationplantwithairpurificationbymeansof

absorbers,1978Internalcompressionofoxygenisappliedtotonnageairseparationplants,

1984World's largestVAROXairseparationplantwithvariableoxygendemandadjustment,

1990World'sfirsttalecontrolledairseparationplantwithunmannedoperation.Pureargon

productionbyrectification.1991World's largestairseparationplantwithpackedcolumns,

1992Airseparationplantsproducemegapuregases,and1997Linedsetsanewmilestone

inair separationhistory.Fournitrogengeneration trainsarebeingprovided,each in itself

constituting the largest air separation plant ever built. Nitrogen capacity 1,200 MMSCFD

(40,000 t/d). 2000 Development of the advanced multistage bath type condenser. In

chemical technology we need to allot of oxygen, nitrogen and argon. Air separation has

becomeaprocessintegraltomanymanufacturingprocesses.

Thelargestmarketsforoxygenareinprimarymetalsproduction,chemicalsandgasification,

clay, glass and concrete products, petroleum refineries, andwelding. The use ofmedical

oxygen is an increasingmarket.Gaseousnitrogen isused in the chemical andpetroleum

industriesanditisalsousedextensivelybytheelectronicsandmetalsindustriesforitsinert

properties.Liquidnitrogenisusedinapplicationsrangingfromcryogenicgrindingofplastics


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2

to food freezing.Argon, the thirdmajor componentofair, findsusesasan inertmaterial

primarily in welding, steelmaking, heat treating, and in the manufacturing processes for

electronics.

The separation of air into its components is an energy intensive process.The companies

designing air separation processes have aggressively reduced the required energy to the

pointthat it ispossibletosellatruckloadof liquidnitrogenfor is lessthanmanycommon

consumer products. This surprising result hasbeen accomplished by advances in process

design,processoperation,manufacturingapproachesandtechniques,andimprovementsin

supply chain management. Process designs have increasingly utilized mass and energy

integration.Substitutedprocessoperationshave increasedtheabilitytooperateefficiently

at awider rangeofproducton requirements, significantly improvedproductivity through

pervasiveAutomationandadvanced controldeveloped thecapability toefficientlyhandlerapid production rate and product split changes, and leveraged advances in remote

communications. Supply chain improvements have ranged from improved purchasing

practicestooptimizedschedulingofproductdeliverytocoordinatedoperationofseparate

facilities.

Muchhasbeenwrittenconcerningthedesignofairseparationprocessesandcertainlythe

worldwide patent activity for flow sheet and equipment innovation continues. Advanced

controlhasbeenpracticedintheairseparationbusinessfordecades.Thefirstapplicationof

computercontrol foranairseparationplantwascompleted in theearly1970s.Since that

time,mostadvancedcontroltechnologieshavebeenapplied inanattemptto improvethe

efficiencyandproductivityofairseparationfacilities.

Thecurrentworkaimstodescribetheairseparationprocess includingheatexchangeand

cryogenicdistillation.AnASPENPlus simulationof cryogenic air separation intoNitrogen,

OxygenandArgon iscreated.The influenceofdifferentprocessparametersondistillation

efficiencyisanalyzed.


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3

2. THEORETICALPART

2.1 Airproperties

Airisamixtureofgases,consistingprimarilyofnitrogen(78%),oxygen(21%)and

theinertgasargon(0.9%).Theremaining0.1%ismadeupmostlyofcarbondioxideandthe

inertgasesneon,helium,kryptonandxenon.Aircanbeseparatedintoitscomponentsby

meansofdistillationinspecialunits.Airisusuallymodeledasauniform(novariationor

fluctuation)gaswithpropertiesaveragedfromtheindividualcomponents.

Figure1:Aircomposition

DryAir: DryAir is relativelyuniform in composition,withprimary constituents as shown

below.Ambientair,mayhaveuptoabout5%(bycvolume)watercontentandmaycontain

anumberofothergases(usuallyintraceamounts)thatareremovedatoneormorepoints

intheairseparationandproductpurificationsystem.

Thetwomostdominantcomponents indryairareOxygenandNitrogen.Oxygenhasa16

atomicunitmassandNitrogenhas14atomicunitsmass.Sincebothoftheseelementsare


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diatomic inair O2andN2,themolecularmassofOxygen is32andthemolecularmassof

Nitrogenis28.Table1showssomepropertiesofaircomponents.

Table1:Somepropertiesofaircomponents

Gas

RatiocomparedtoDryAir(%) Molecular

Mass

M

(kg/kmol)

Chemical

Symbol

BoilingPoint

Byvolume Byweight (K) (oC)

Oxygen 20.95 23.20 32.00 O2 90.2 182.95

Nitrogen 78.09 75.47 28.02 N2 77.4 195.79

CarbonDioxide 0.03 0.046 44.01 CO2 194.7 78.5

Hydrogen 0.00005 ~0 2.02 H2 20.3 252.87

Argon 0.933 1.28 39.94 Ar 84.2 186

Neon 0.0018 0.0012 20.18 Ne 27.2 246

Helium 0.0005 0.00007 4.00 He 4.2 269

Krypton 0.0001 0.0003 83.8 Kr 119.8 153.4

Xenon 9106 0.00004 131.29 Xe 165.1 108.1

Othercomponentsinair:

Sulfurdioxide SO2 1.0parts/million(ppm)

Methane CH4 2.0parts/million(ppm)

Nitrousoxide N2O 0.5parts/million(ppm)

Ozone O3 0to0.07parts/million(ppm)


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400 1.0135 0.7264 1.395 2.286 3.365 0.688 2.591 0.8824

450 1.0206 0.7335 1.391 2.485 3.710 0.684 3.168 0.7844

500 1.0295 0.7424 1.387 2.670 4.041 0.680 3.782 0.7060

CommonPressureUnitsfrequentlyusedasalternativeto"oneAtmosphere"

76Centimeters(760mm)ofMercury

29.921InchesofMercury

10.332MetersofWater

406.78InchesofWater

33.899FeetofWater

14.696PoundForceperSquareInch

2116.2PoundsForceperSquareFoot

1.033KilogramsForceperSquareCentimeter

101.33Kilopascal

Table3:Someotherphysicalpropertiesofaircomponents:

Nitrogen Oxygen

NormalboilingpointK 126.1 154.4

criticalpressure at 34.6 51.3

CriticaltemperatureK 77.35 90.19

Oxygenhasthehighestboilingpointofthethreemaincomponentsand istakenfromthe

bottomoftheLPcolumn.NitrogenistakenfromthetopoftheLPorHPcolumns.Anargon


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richstreamcanbeproductinotherdistillationcolumnswithdrawnfromthemiddleoftheLP

column. Figure 2 (Source: reference [9] www.engineeringtoolbox.com/dryairproperties

d_973.html)showstheairdensityversustemperatureandpressure.

Figure2:Airdensityversustemperatureandpressure


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8

2 . 2 A i r s e p a r a t i o n t e c h n o l o g i e s

Air separation plants are designed to generate oxygen, and argon from air through the

process of compression, cooling, liquefaction and distillation of air. Air is separated for

production of oxygen, nitrogen, argon and in some special cases other rare gases

(krypton,xenon,helium,neon) throughcryogenic rectificationofair.Theproducts canbe

produced in gaseous form for pipeline supply or as cryogenic liquid for storage and

distributionbytruck.OneofthelargestproducersofairseparationplantsisLinedCompany.

Ithasbuiltapprox.2,800cryogenicairseparationplantsinmorethan80countries(Source:

http://tnsansoplant.com/en/air.html [4]) and has the leading market position for air

separationplants.

Figure3:airseparationscheme

Aircanbeseparated into itscomponentsbymeansofdistillation inspecialunits.Socalled

air fractionating plants employ a thermal process known as cryogenic rectification to

separate the individual components from one another in order to produce highpurity

nitrogen,oxygenandargoninliquidandgaseousform.

Differenttypeofairseparationtechnologieswasdeveloped:


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9

CryogenicAirseparation

MembraneAirseparation

Separationbyadsorption

Other

Differenttechnologiesareapplicablefordifferentrequirementonamountandpurityofthe

products. Figure (4) shows theOxygen production process selection grid.A similar graph

describingtherangesforwhichthedifferentnitrogenprocessesareapplicablecanbeseen

inFig.(4)

Figure4:Oxygenproductionprocessselectiongrid

Methodssuchasmembraneseparationarealsoavailablebuttheyarecurrentlyusedfarless

pervasivelythantheothertwoapproaches.


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Inthecryogenicgasprocessing,variousequipmentisusedlikethedistillationcolumns,heat

exchangers, cold interconnectingpipingetc.whichoperate at very low temperatures and

hencemustbewellinsulated.Theseitemsarelocatedinsidesealed"coldboxes".Coldboxes

aretallstructureswitheitherroundorrectangularcrosssection.Dependingonplanttype,

sizeandcapacity,coldboxesmayhaveaheightof15to60metersand2to4metersona

side.

Basicstepsofcryogenicairseparation:

FirstStep:Thefirststepinanycryogenicairseparationplantisfilteringandcompressingair.

Afterfiltrationthecompressedairiscooledtoreachapproximatelyambienttemperatureby

passingthroughaircooledorwatercooledheatexchangers.Insomecases it iscooled ina

mechanical refrigeration system to a much lower temperature. This leads to a better

impurity removal,andalsominimizingpower consumption, causing less variation inplant

performancedue to changes in atmospheric temperature seasonally.After each stage of

coolingandcompression,condensedwaterisremovedfromtheair.

Second Step:Thesecondstep is removingthe remainingcarbondioxideandwatervapor,

which must always be removed to satisfy product quality specifications. They are to be

removedbeforetheairentersthedistillationportionoftheplant.Theportionisthatwhere

thevery low temperaturecanmake thewaterandcarbondioxide to freezewhichcanbedepositedonthesurfaceswithintheprocessequipment.Therearetwobasicmethodstoget

ridofwatervaporandcarbondioxide molecularsieveunitsandreversingexchangers.

ThirdStep:The thirdstep inthecryogenicairseparation isthetransferofadditionalheat

againstproduct andwaste gas so as to bring the air feed to cryogenic temperature. The

cooling isusuallydone inbrazed aluminumheat exchangers. They let theheat exchange

between the incoming air feed and cold product and waste gas streams leave the air

separationprocess.Theverycoldtemperaturesrequiredfordistillationofcryogenic

Products are formed by a refrigeration process comprising expansion of one or more

elevatedpressureprocessstreams.

FourthStep:Thisstepinvolvestheuseofdistillationcolumnstoseparatetheairintodesired

products.Forexample,thedistillationsystemforoxygenhasboth"high"and"low"pressure


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columns.Nitrogenplantscanhaveoneortwocolumn.Whileoxygenleavesfromthebottom

ofthedistillationcolumn,nitrogenleavesfromthetop.Argonhasaboilingpointsimilarto

that of oxygen and it stays with oxygen. If however high purity oxygen is needed, it is

necessarythatatanintermediatepointargonmustberemovedfromthedistillationsystem.

Impureoxygenproducedinthehigherpressuredistillationcolumnisfurtherpurifiedinthe

lower pressure column. Plants which produce high purity oxygen, nitrogen or other

cryogenicgasesrequiremoredistillationstages.

Figure4 shows thebasic stepsofcryogenicair separationprovidedbyMESSER.Thebasic

stepsofthistechnologyaredescribedas:

Compressionofair:Ambientair isdrawn in,filteredandcompressedtoapprox6bar

byacompressor.

Precookingofair:Toseparateairintoitscomponents,itmustfirstbeliquefiedatan

extremelylowtemperature.Asafirststep,thecompressedairisprecooledwithchilled

water.

Purificationofair:Impuritiessuchaswatervaporandcarbondioxidearethen

removedfromtheairinasocalledmolecularsieve.

Cooling of air: Because the gases which make up air only liquefy at very low

temperatures,thepurifiedair inthemainheatexchanger iscooledtoapprox. 175C.The

cooling is achieved by means of internal heat exchange, in which the flows of cold gas

generatedduringtheprocesscoolthecompressedair.Rapidreductionofthepressurethen

causes thecompressedair tocool further,whereby itundergoespartial liquefaction.Now

theairisreadyfortheseparatingcolumn,wheretheactualseparationtakesplace.


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Figure6:Basicstepsofairseparation

Separationofair:Separationofairintopureoxygenandpurenitrogenisperformedin

twocolumns,themediumpressureandthelowpressureColumns.Thedifferenceinboiling

pointoftheconstituentsisexploitedfortheseparationprocess.Oxygenbecomesaliquidate

183Candnitrogenat196C.Thecontinuousevaporationandcondensationbroughtabout

bytheintenseexchangeofmatterandheatbetweentherisingsteamandthedescending

liquidproducespurenitrogenatthetopofthelowpressurecolumnandpureoxygenatthe

bottom.Argonisseparatedinadditionalcolumnsandinvolvessomeextrastepsinthe

process.

Withdrawalandstorage:Gaseousoxygenandnitrogenarefedintopipelinesfor

transporttousers,e.g.steelworks.Inliquidform,oxygen,nitrogenandargonarestoredin

tanksandtransportedtocustomersbytankerLorries.


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under the right conditions,providebetteroveralleconomics thaneither an allbulkliquid

supplyoranewcryogenicnitrogenplantwithastandardinternalrefrigerationcycle.

2.2.2 Airclearing

Beforedistillationtheairshouldbeclearedfromdifferent impuritiesandcomponents.The

exitsof impurity likecompass ,wet ,carbondioxide,andanother impurity inairmake the

problemsinairdistillationsowehavetocleartheairbeforethethatprocess.

ClearingtheairfromcompassandDryit:

Thecontentofcompass inair isabout0.0020.02g/m

3 so forclearing theair from this

impureweusetheoilfilters.Airpassesthesefiltersandclearsfromcompass.Inabigplant

withlargecapacityofproductsweusetheseveralsectionsofautomaticfilterswithapatch

orsectionoflocomotive.Wetinairbelongstothestatusoftheweathers.Valueofthewet

inairwhenairbee100%saturatebyitinthebelowtable.

Table4: correlationofairwithwetfromtC

Dryingoftheaircanberealizedwithoneoftheseforms:

1 Adsorption with SiO2.H2O : We can get the SiO2.H2O by sluice hydrate of aced of

SiO2.H2Oanditsbaitsizeis37mm.afterdryingbySiO2.H2Ocontainofthewetis0.03

g/m3

decreaseanditsdewdotis52.

Co wet g/m3 tC Cowet g/m

3tC

2.31

1.01

0.44

0.117

0.038

10

20

30

40

50

50.91

30.21

17.22

9.93

4.89

40

30

20

10

0


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2AdsorptionbyActiveAl2O3.H2O: ActiveAl2O3.H2OandanotheroxidantisSiO,Na2O,and

OFproductviasluicetrayhydroidoxidantAlmonium.

ActiveAl2O3.H2OpossessorofverybettermechanicalsubstancethenSiO2.H2Oanditbetter

suction thewet.After thedryingwithAl2O3.H2O thecontentofwet inair0.005g/m3

be in

decrease.Anditmachwiththe64dotofdew.RedactionoftheadsorbentbyHatenitrogen

upto170180CforSiO2.H2OforAl2O3.H2O245270C.

Foradsorptionofairfromwetalsoweusethealmoniumsilicates,sodium,andetc.

3Making ice: Insameoftheairseparationplantthatworkwithtwopressurecycleand

frizzingwithNH3.Dryingtheair inheatexchangeratfirstcoolingbythegutteroxygenand

nitrogenupto5CafterthatwithebullientNH3upto 4045Cbeecooled.Usuallyweuse

twoammonicheatexchangerthatworkautomaticwhenoneofthemhatestheotherone

becooled.

Airclearingfromcarbondioxide:

Inbegplant thathasbegcapacityclearing theair fromCO2 in the scrubberofalkali that

washed by SOLUTION of the sodium hydro oxide or potassium hydroxide. Same time in

regeneratorsofoxygenandnitrogendo that.During thepassageofair from regenerators

theCO2becomefreezeontheabsorbentoftheO2,N2.ThefreezeCO2thenclearsfromair

and the CO2 on absorbent clearing by the predicted O2and N2. There also use two

regenerators thatworkonperiodic system and aftera fewmintschange theyareplaces.

ContentofCO2afterscrubberofalkaliandregenerator1520cm3/m

3anditwillbeinthe

liquid form the air or same times it is like a ingredient suspension so it canmake same

problemsinvalvesandshuttheholeofplatesinseparationtower.

Clearingairfromacetylene:

Airclearing fromacetylenebecause itsverydangerous for theairseparationplant so its

importanttoclearairfromitbecauseifacetyleneaggregationitwillbeexplosion.Acetylene

haslowpartpressureintheairsoitcantdistantinheatexchangerandinregeneratorand

itsaggregationinliquid.Acetylenehaslowsolubilityinair,oxygenandnitrogensoitcanbe

veryeasycleaninSiO2.H2Ofilters. UsethedifferentmarkoftheSiO2.H2O.


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Somevapor iscondensed,andthe latentheatofthevapor isdischargedfrom4to7.Then,

thesaturatedairat7isexpandedandcooledtothecoolairat8intheturbine.Thecoolair

at8isthenductedtotheairconditionedrooms.Thecoolwaterisheatedinthesurfaceheat

exchanger. Water injection before the axial compressor aims to decrease both the

temperatureoftheworkingfluidandthepolytrophicexponentinthecompressionprocess.

Thus,wecansavesomecompressionwork.Thismethodhasbeenusedinajetenginewhen

a fighterplane increases itsspeed.However,thedifference isthatwhat is injected inajet

engineiswater,alcohol,etc.Thewatervaporinthecompressedaircaneasilybeextracted

by a surface heat exchanger. With the same temperature, the humidity ratio of the

saturatedwetairathighPressureP4isonlyaboutP3/P4ofthatatpressureP3.Themethod

ofusing compressed air to acquiredry airhasbeenused in someworkshops the system

abovediffersfromaconventionalaircyclesystem.Therearemanycharacteristicsinthisairvaporrefrigerationcircle.

Firstly,anaxialcompressorandaturbineareusedintheabovesystem.

Thecharacteristicsofturbomachinesarelargemassflowrateandhighefficiency.Theother

types of compressor and expander have none of the above advantages. Secondly, these

refrigerationsystem intakesprecooledwetairwith finewaterdroplets,andsomevapor is

condensedduringtheaircoolingfrom4to7.

Theamountofwaterextractedfromthehighpressurewetaircanreach1830g/kg(d.a.),

and the amountof latentheatdischarged from the vapor condensed, about4575 kJ/kg

(d.a.), exceeds the sensible heat from the air, 3050 kJ/kg (d.a.). For this reason, the

refrigeration load in this airvapor refrigeration systemdependsona combinationof the

sensible

Thehumidityratioofwetair,D,isobtainedfrom

(2.1)

Theenthalpyofwetair,H,iscalculatedfrom

H=1.006t+0.001D(2501+1.805t) (2.2)


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Theadoptedrelationforwatervaporbetweensaturation

Pressureandsaturationtemperature,Ps=f(ts),isselectedfromRef[2]

Tocalculatethesaturatedtemperatureofthewetairfromthesaturatedenthalpy,Esq.(1)

and(2)andPs=f(ts)areused.

Axial

compressor

During the compression process of the wet air, the fine water droplets in the air may

evaporate. Because the evaporation of water takes in heat, we can regard the ideal

compressionprocessofthewetair inthecompressorasapolytrophicprocess.Therefore,

wecanobtaintheidealworkofthecompressorperkilogramdryair,WC,from

Wc=

(Rair+0.001DRvapor)T3[1(p4/p3)n1/n

] (2.3)

inwhichnisthepolytrophicexponentforthecompressionprocess.

Thepracticalworkconsumedby theaxialcompressor isWc/gc inwhichgc is the thermal

efficiencyofthecompressor.

Turbine

ThesaturatedairwithapressureofP7andatemperatureofT7beforetheturbinehasbeen

dehumidified in the surface heat exchanger by coolingwater.At point 7, the amount of

vapor included in the saturated air is very small, about P3/P7 of the amount included in

saturatedairatP3.Thus,thewatercondensedintheairisinfog.Nevertheless,expansionof

thesaturatedairintheturbinecannotberegardedasanadiabaticexpansionofanidealgas.

With thedecreaseof thewetairpressure in the turbine, the temperatureof thewetair

decreases,andsomeheat isdischargedduringthecondensationofsomewatervapor.The

heatdischargedmaycause increasesinboththetemperatureoftheturbineoutletandthe

workdoneintheexpansion.Forthisproblem,wecan imaginethatnophasechangeexists

and that there is someheatadded to thewetairduring theexpansionprocesswhenwe

calculatetheworkdonebytheexpansionprocess.Accordingtotheaboveassumption,this

problem can be simplified to a problem of the polytrophic expansion of an ideal gas.


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becomesliquidagain.Forcreationofliquidnitrogen,O2,H2,airetc.thereconditecoolis

used.

Ingeneralforovertakeofreconditecoolweusethreesystemsasbelow:

1. Cascadevaporization

2. Fastpressuredropbytransmissionofgas

3. Adiabaticallyexpansionofgaswithexternalwork

Thefirstonecreatesmediumcool,thesecondandthirdarecreatingreconditecool.Two

kindoftransmissioneffectwehave:

1. Differentialeffect

2. Integraleffect

Thechangeoftemperaturecausedbyaverysmallchangeofpressureiscalleddifferential

effectoftransmission. Anditisshownbythisformula

i=[]i=cont (2.4)

Thechangeoftemperaturecausedbyalargechangeofpressureiscalledintegraleffectof

transmission. Anditisshownbythisformula

Ti=T1 T2=

(2.5)

T1,T2are gastemperaturebeforeandafterthetransmission.Thetransmissioneffectof

everygascanbepositive,negativeorzero.Thetemperaturethatequalszerobytheeffectof

transmissioniscalledchangepoint.

Adiabaticallyexpansionofgaswithexternalwork

One of another way to create low temperature is adiabatically expansion of gas withexternalworkthatoccurs inturbomachineor incompressors.Theadiabaticallyexpansion

effectoftransmissionofgasisequaltothe:

s= scont (2.6)


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By adiabatic expansion the decrease of temperature is more significant than the

transmissionofgas.

Theworkdonebyadiabaticexpansionisequaltothedifferenceofairenthalpiesintheenter

andexitofmachine.

L=i1i2 kj/kg

Whends=0thefinaltemperaturecanbefindfromthisformula

=(

)

k1/k

T2,T1 aretemperaturesofgasbeforeandaftertheexpansion.

P1,P2 firstandsecondpressureofgas.

K Adiabaticallycharacteristic.

By increaseofthepressureandreductionoftemperaturethequantityof sreducesand it

becomenearorclosetotheiquantity.Andneartotheclimacterictemperatureareaboth

affectofadiabaticallyexpansionandeffectofTransmissionofgasare the sameand they

createidenticalcool.

Reconditecoolcycles:

1 CyclesthatusingeffectofTransmissionofgas:

a) CycleofonestageTransmissionofgas

b) Cyclewithtowpressureofair

c) Cyclewithrotationoflowpressure

2 CyclebyusingAdiabaticallyexpansion:

a) Clodcycle

b) Kapisacyclec) Lirozacycle

d) Compositecycle

Formoredetailsofaircoolingcyclessee(Reference:lessenchapter[3])


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2.2.5 Airdistillation

Inanairseparationunitforseparatingairbycryogenicprocess,therebyrecoveringoxygen,

nitrogenandArgon,columnofduplextyperectificationtowerisused.Theairisfedintothe

lowercolumnwithhigherpressure.Liquidnitrogenisintroducedintotheuppercolumnasa

reflux from lower column and a oxygen reached stream from the bottom of the lower

column is fed to the bottom of the higher column. Distillate from the upper column is

practicallypureNitrogen,bottomof this column inOxygen andArgon reached stream is

removedfromthemiddlepartoftheuppercolumn.

Airdistillationcolumn

Distillationcolumncombinedfrombottom

column(2),condenserandreboiler(3)and

uppercolumn(4).Bottomcolumnwork

under5.5 6.5atpressureandits

allocationforpreliminarydistillationofair

intonitrogenandmixedofoxygenandair

thathas6065%nitrogenand3540%

oxygen. Inuppercolumnthatworksat1.3

1.4atforfinallydistillationofmixed

oxygenandairintonitrogenandoxygen.

1 Liquidoxygenandair

2 Bottomcolumn3 condenserreboiler4

uppercolumn5stages

6 Liquidnitrogenpacket7 valve

8 pipes

Figure9:airdistillationcolumn

Inthemedalofbottomanduppercolumncondenserandreboilerlocatedthatcondensing

ofnitrogenforbottomcolumnandvaporizingoxygenforuppercolumn.Condensation

temperatureofnitrogeninbottomcolumnis9697Kandoxygenvaporization

temperatureinuppercolumnis9293K.


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Compressedairin120200atinsidingatthelowerpartsofcolumn2bytemperatureof145

155Kafterthatotherprocessaccomplishmentonit.Attheendgasesnitrogenproducts

from topofcolumn4,oxygenproducts from the topofcondenser3andArgon from the

medalof column 4 .numberof theoretical stage inupper column are about 36up to 56

stagesandinbottomcolumn24upto36stages.

TheproducedNitrogen,OxygenandArgonpurityis:

Molfractionofoxygen98.7%,molfractionofnitrogen99.0%,molfractionofArgon99.5%.

2.3 Productsofairseparationandtheirapplications

ThesearetheAirproducts:

Oxygen: Oxygenmakesup21percentoftheairwebreathe.Ourbodiesneedoxygento

supportlife,sooxygenhasmanymedicalandhealthcareuses.

Oxygenisalsousedinmanyindustries,incloudingmetalandglassmanufacturing,chemicals

andpetroleumprocessing,pharmaceuticals,pulpandpaper,aerospace,wastewater

treatmentandevenfishfarming.

Chemicalformula:O2othernames:oxygengas,gaseousOxygen(GOX),liquidoxygen(LOX)

PhysicalandChemicalProperties

Oxygenhasnocolororsmell.Oxygenisslightlyheavierthanairandslightlywatersoluble.

Oxygen combines readily with many elements to form compounds called oxides. One

example is ironoxide,orrust,thatformson iron inthepresenceofoxygenandmoisture.

Although oxygen itself is nonflammable, combustible materials burn more strongly in

oxygen.Eventhoughmostapplicationsuseoxygeninthegasform,itcanbecooledtoapale

Blue liquid at extremely low temperatures (297F/183C). To put that temperature into

perspective,waterfreezesat32F/0C.

UsesandBenefits

Ourbloodstreamabsorbsoxygenfromtheairinourlungstofuelthecellsinourbodies.

Healthcareprovidersusemedicaloxygenforpatientsinsurgeryandforthosewhohave

difficultybreathing.Forhomeuse,lightweightPortableoxygencylindersgivepatients

freedomtogoutintothecommunity.


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Oxygenpromotescombustion,soithelpmanufacturerssaveuplandenergyandreducethe

emissionofgreenhousegasessuchascarbondioxide,nitrogenoxideorsulfuroxide.

Using oxygenenriched air increases production efficiency in steel, rocket fuel, glass,

chemicalandmetallurgicalprocessingapplications.

Manufacturersofaluminum,copper,goldand leaduseoxygentoremovemetalsfromore

moreefficiently.Asaresult,theycanoftenuse lowergradeoresandrawmaterials,which

helpsconserveandextendournaturalresources.Formetalfabrication,oxygenisoftenused

withacetylene,propane,andothergasestocutandweldmetals.

Thechemicalandpetroleumindustriescombineoxygenwithhydrocarbonbuildingblocksto

makeproductssuchasantifreeze,plasticandnylon.

Thepulpandpaper industryusesoxygen to increasepaperwhitenesswhile reducing the

need forotherbleachingchemicals.Theyalsouse it to reduceodorsandotheremissions.Municipalandindustrialwastewaterplantsuseoxygentomakethetreatmentprocessmore

efficientandincreasebasincapacityduringplantexpansionsorplantupsets.Municipal

Waterplantsuseoxygenasfeedgastotheirozonesystemstoremovetaste,odorandcolor

fromdrinkingwater.Oxygenatedwateralsoimprovesthehealthandsizeofthefishforfish

farmingoperationssofarmersaroundtheworldcansupplyhighqualityfood.

Industrial Use:Weshipoxygenasahighpressuregasoracold liquid.Weoftenshipand

store largerquantitiesofoxygen in liquid form,because itoccupiesmuch less space that

way.Dependingonhowmuchoxygengasourcustomeruses,westoreandship it inhigh

pressure cylinders and tubes. Industry guidelines cover the storage and handling of

compressedgascylinders.Workersshouldusesturdyworkgloves,safetyglasseswithside

shieldsandsafetyshoeswhenhandlingcompressedgascylinders.Westoreandship liquid

oxygen in three different types of containersdowers, cryogenic liquid cylinder sand

cryogenicliquidtanks.Thesecondtrainersaresimilartoheavydutyvacuumbottlesusedto

keep your coffee hot or your water cold. Because of its low temperature, liquid oxygen

shouldnot come in contactwith skin. Ifworkershandle containersof liquidoxygen, it is

importanttowearafullfaceshieldoversafetyglassestoprotecttheeyesandface.Workers

shouldalsowearclean,loosefitting,thermalinsulatedgloves;alongsleevedshirtandpants

withoutcuffs;andsafetyshoes.

Theriskoffireincreaseswhenoxygenlevelsintheairarehigherthannormal.Clothingand

hairreadilytrapoxygenandarehighlycombustible.Itisimportanttohavegoodventilation


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shield over safety glasses to protect the eyes and face.Workers should alsowear clean,

closefitting, thermalinsulated gloves; a longsleeved shirt and pants without cuffs; and

safetyshoes.Topreventsuffocation,itisimportanttohavegoodventilationwhenworking

with argon. Confined workspaces must be tested for oxygen levels prior to entry. If the

oxygen level is lower than 19.5 percent, personnel, including rescueworkers, shouldnot

entertheareawithoutspecialbreathingequipment.


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The model has option codes which can be used to customize the model, by selecting a

differentalphafunctionandothermodeloptions.Forbestresults,thebinaryparameterkij

mustbedeterminedfromregressionofphaseequilibriumdatasuchasVLEdata.TheAspenPhysicalPropertySystemalsohasbuiltinkij fora largenumberofcomponentpairs inthe

EOSLITdatabank.Theseparameters areused automaticallywith the PENGROBproperty

method.Valuesinthedatabankcanbedifferentthanthoseusedwithothermodelssuchas

SoaveRedlichKwongorRedlichKwongSoave,andthiscanproducedifferentresults.

UsingthePeng Robinsonequationofstatetheisobarict,xyandx,ydiagramsofN2O2and

ArO2binarysystemsatdifferentpressureswerecalculated:

a)P=1.4at

Figure10:T,X,Y diagram,N2O

2


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Figure11:X,Ydiagram,N2 O2

b)P=5at

Figure12:T,X,Y diagram,N2O2


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Figure13:X,Ydiagram,N2O2

bOxygen,Argon,P=1.4at

186.5

186

185.5

185

184.5

184

183.5

183

0 0.2 0.4 0.6 0.8 1

t(C)

X


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Figure14:T,X,Y diagram,Ar O2

Figure15:X,Y diagram,ArO2

AsitresultsfromtheisobaricphaseequilibriumdiagramstherelativevolatilityofN2toO2isquite

highitmeansthatseparationofN2fromO2isnotverydifficult.ButtherelativevolatilityofArtoO2is

verylow.Forthisreasonforseparationofthesecomponentswewillneedlargenumberof

theoreticalstagesandlargerefluxratios.

3.2CalculationofairdistillationbyMcCabeThielemethod

Materialbalancesystem:

Thequantityofoxygenandnitrogenthatinteriorwithairinplantisequaltothequantityof

thosegasesthatoutsidewiththeproductoftheplant.Ifweknowtheproductoxygenand

nitrogenConcentrationwecanknowthequantityofthemebyMaterialbalanceequation.

Weconsiderthat191.94kmol/hofabubbleliquidairconsistingof79mol%N2and 21mol%

O2 is distillated continuously in a distillation tower at a pressure of 1.4 atmospheres.

Distillatecontains98mol%oflightcomponentandBottoms98mol%ofheavycomponent.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.2 0.4 0.6 0.8 1

Y

X


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Therefluxratiois1.45timesofminimumrefluxratio.Followingisdescribedthecalculation

of:

a Numberoftheoreticalstagesandoptimumfeedstagelocation.

b Steam requirement in reboilerand requirementofcoolingAir in totalcondenser if

the steam pressure is 0.14 Map and cooling Air is preheated by 20oC, only

condensation heat of the steam is used and reflux is returned to the column at

boilingpoint.

Data:

EquilibriumdataofAirin1.4at(molfrictions)

XfN2 = 0.79 t=tfBP

XfO2 = 0.21 q=1

XDN2 = 0.98

XwN2 = 0.02

Nf =6048.9kmolh1

Heatofevaporationataveragecolumntemperature:t=190C

vhN2=6661.1kJ/kmol vhO=5487kJ/kmol

MN2= 28kg/kmol MO2=32kg/kmol

x 0 0.05 0.1 0.15 0.2 0.25 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.95 1

y 0 0.1732 0.3078 0.4146 0.501 0.5722 0.6318 0.7259 0.7972 0.8534 0.8993 0.9378 0.9709 0.9859 1


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Figure17:XYdiagram,vaporandliquidN2

3 SelectondiagrampointF,DandW

Figure18:SelectionofxFandxD

0

0.1

0.2

0.3

0.4

0.50.6

0.7

0.8

0.9

1

0 0.2 0.4 0.6 0.8 1

Y

X

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.2 0.4 0.6 0.8 1

Y

X


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4 Drawqline

qlineisgraphicalinterpretationofmaterialbalanceofthefeedstage;qrepresentsthe

amountofliquidthataccumulatesatthefeedstagebyfeedingof1kmolofthefeed.

qline

equation:

nv=nL+nD (3.5)

nvyi=nLxL+nDxD

L Di i D

v v

n ny x x

n n= + (3.6)

11

=

q

xxi

q

qyi F

ForbubbleliquidAir,q=1,theslopofqlineequationiso

q

qtg 90

1==

=

Figure19:XYdrawingofqline

00.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.2 0.4 0.6 0.8 1

Y

X

( 1) ( 1)

D Di i D

R ny x x

R Rn= ++ +


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5 Calculationofminimumrefluxration

ForcalculationminimumrefluxrationRmintheoperatinglineintherectifyingsectionofthe

columnforatRminshouldbedrawn.

11 minmin

min

+

+

+

=

R

xx

R

Ry D (3.7)

Wehavetwopointsofthislineoneistheintersectionofqlineandequilibriumcurveand

anotherintheintersectionof45olineandxDline.

Figure20:XYminimumrefluxratio

Theminimumrefluxratiocanbecalculatedfromtheslopeofthisline

''

'min

xy

yxR D

=

(3.8)

Orfromthesection1min +R

xDontheyaxisforx=0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.2 0.4 0.6 0.8 1

Y

X


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6 Calculaterefluxratio(R)asR=2Rmin.

R=2Rmin (3.9)

''

'min

xy

yxR D

=

Rmin=

R=2*0.727=1.45

7 Calculatethesection1+R

xDontheyaxisforx=0

40.0145.1

98.0

1=

+

=

+

=

R

x

y D

i

8 Drawtheoperatinglineoftherectifyingsectionofthecolumnbyconnectingpoints(0,

1+R

xD)and(xD,yD)

9 Drawtheoperatinglineofthestripingsectionofthecolumn,byconnectingintersection

pointofqlineandoperatinglineofrectifyingsectionwithpoint(xw,yw)

Figure21:XYDrawingofoperatinglines

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.2 0.4 0.6 0.8 1

Y

X


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10 Drawstepsbetweenequilibriumcurveandoperatinglines

Numberoftheoreticalstages=numberofsteps1(reboiler)

Optimalfeedstage=intersectionofqlineandoperatinglines

Enthalpybalanceofreboiler:

QRe=[nD(R+1)+nF(q 1)]vhw (3.10)

vhw=vhwO2Xw

O2+vhw

N2Xw

N2 (3.11)

vhw=54870.98+6661.10.02=5510.5kJ/kmol

QRe=[4652.612(1.4+1)+6048.9(11)]5510.5=61531724kJ/hr=17.092MW

Figure22: XYdiagram,vaporandliquidN2


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Enthalpybalanceoftotalcondenser:

Qcon=nD(R+1)vhD (3.12)

vhD=vhNXDN+vhOXDO (3.13)

vhD=6661.10.98+54870.02=6637.62kJ/kmol

Qcon=4652.612(1.4+1)6637.62=74117449kJ/hr=20.59MW

3.3Aspensimulationofairseparationprocess

For calculation and design of air separation process we have used the ASPEN Plus air

separationprogram. Itsanewsciencetechnology fordoingthecalculationofengineering

process.

In this project we have designed the air separation process and distillation of air to its

components. A special attention was devoted to separation of Argon. However, the

simulationofallprocessincludingaircoolingwasdone.

FollowingaredescribedthebasicstepsofsimulationbyASPENPlus

1. UsingAspenpropertyanalysisandPengRobinsonequationofstate,thermodynamic

analysisofairseparationwasdone.Theresultsarepresentedinthesection3.1.

2. Designanddrawingoftheprocessflowsheet

Descriptionoftheairseparationprocessflowsheet:

ThisschemeisgenerallyusingforproducingArgonthathasdifferentuse.

Thebasic formoftheair (3500m3/hratoperationalconditions (t=20C,P=5at)or (727.5

kmol/hr) thatcleared fromdustandcompressed inacompressorup to5atpressureafter

crossing refrigerator and separator of wet goes to inside of oxygen and nitrogen

refrigerators.Airiscooledhereupto( 160, 170C).Therefrigeratorsworkautomatically.

Airscrossingonetherefrigeratorso inthis timethereversedproceedinggasofO2andN2

arecrossinganotherrefrigeratorandafterafewminuteschangingthemarereplaced.After

thatclearedandcooledairgoestothelowerpartsoftheairseparationcolumn(C1).Second

partsoftheair(800m3/hratoperationalconditions(t=20C,P=160at))or(5321.4kmol/hr)


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thatcompressedupto(150200at)atfirstandupto(120160at)pressureduring normal

work in several stage compressor. Thehigh pressure airdivided in to twoproceedingor

parts,onepartsoftheair(550m3/hr) iscrossingheatexchanger(EH1)andcoolingupto(

130C)therebyreversinggasofnitrogenandafterthatexpandringupto5atandenters to

lowerpartsofcolumnC1.Theanotherpartsofhighpressureair(250m3/hr) isgoestothe

expanderandexpandsupto5atpressuresothispartsofairalsoenterstothe lowerparts

of air separation columnC1. in the resultofexpand ration the temperaturebecome (

130C).

Inthe lowerpartsofcolumnC1iscollected liquidairbymol fractionof3538%oxygen.

Vaporswith98%nitrogenareremovedfromthepartialcondenserLiquiddistillatenitrogen

iscollectedinthenitrogenpackets.ThisnitrogenaftercrossingHE3expandringtothetop

of columnC2. Themixtureof liquid air andoxygen from thebottomof columnC1 after

crossingHE2expandringtothe20stageofcolumnC2.Nitrogengasproductedfromthetop

of column C2 crossing heat exchanger (HE3) and nitrogen refrigerator it goes to use for

technologicalaim.AlsoproducedoxygenfromlowerpartsofcolumnC2aftercrossingHE4

andoxygenrefrigeratortocoolairthatcomingatfirsttoprocessgoestogascooler.From

themiddlepartofcolumnC2anstream reachedbyargon (line38)goes to thecolumnC3

where Argon is separated from Oxygen. From lower part of this column a product with

99.9%ofoxygenisremovedsothisO2mixedwithC2oxygenandaftercrossingHEO2goesto

useinotherprocesssothisoxygenhasapurityof98.7%molfraction.

From the top of C3 Argon with same nitrogen goes to column C4. From the top of this

columnproductsnitrogenand fromthebottomofthiscolumnArgon isreceived.TheMol

fraction of produced Argon is 99.5%. Nitrogen produced in C4 is mixed with Nitrogen

producedinC2.

3:3:1TechnicalspecificationsofKT1000Mplant:

Volumeflowoftheair m3/hr:

Highpressureair 800m3/hr atpressure160at 5321.4kmol/hr

Lowpressureair 3500m3/hr atpressure 5at 727.5kmol/hr

Volumeofproductedoxygen 1243.877kmol/hr


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Volumeofproductednitrogen 4760.309kmol/hr

VolumeofproductedArgon 44.714 kmol/hr

Molfractionofoxygen 98.7%

Molfractionofnitrogen 99.0%

MolfractionofArgon 99.5%

3. Selectingcomponentsandpropertymethod

Figure23:componentsandpropertymethodforairseparation


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4. Specifyingenteringair

Highpressureair

Pressure: 160at

Temperature: 20C

Molarflow: 5321.4kmol/hr

Composition: N2=0781,O2=0.209,Ar=0.0093

Lowpressureair

Pressure: 5 6at

Temperature: 20C

Molarflow: 727.5kmol/hr

Composition: N2=78.1,O2=20.9,Ar=1

Figure24:streamspecificationinASPENPlus


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5. Specifyingofequipments

HEO2:Hotstreamoutlettemperature:130C

HEN2:Hotstreamoutlettemperature:130C

HE1:Hotstreamoutlettemperature:130C




ColumnC1:Numberoftheoreticalstages:26,Airfeedstage:26,Condenserpressure: 6at

columnpressuredrop:0.5at

Distillaterate:3500kmol/hr

ColumnC2:Numberoftheoreticalstages:40,feedstage:40,Condenserpressure: 1.4at


Distillaterate:4751.99kmol/hr,N2purity: 0.99 ,N2recovery0.997

ColumnC3:Numberoftheoreticalstages:100,feedstage:50,Condenserpressure: 1at


Distillaterate:53.03kmol/hr, O2purity:0.999inbottom ,O2recovery0.999inbottom

ColumnC4:Numberoftheoreticalstages:15,feedstage:11,Condenserpressure: 1at


Distillaterate:44.71kmol/hr, Arpurity:0.995,Arrecovery0.998


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Figure25:exampleofblockspecificationinASPENPlus

3.3.2ResultsofASPENsimulation

Figure(26)showsthesimulationschemeofairseparationbasedontheabovedescribed

inputdata. Theresultsofmaterialandenthalpybalanceforallblocksandstreamsare

showninTable(5).

OtherresultsofdistillationcolumnsareshowninTable(6)


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Table6:Resultsofdistillationcolumns

TemperatureprofileofC1

ThisdiagramshowsthetemperetureindifferentstageofcolumnC1.

Itshowstheteperaturewillbehigherupfromlowertothebottomofcolumn1

Figure27:Temperatureprofileofcolumn C1

17 6

175.5

17 5

174.5

17 4

173.5

17 3

172.5

17 2

171.5

17 1

0 5 10 15 20 25 30

t(

C)

N

Col

condensar Reboiler

T(C) Headduty

(Watt)

Distillrate

(kmol/hr)

Refluxerate

(kmol/hr)

Refluratio T(C) Heatduty

(Wat)

Bottomsrate

(kmol/hr)

Boiluprate

(kmol/hr)

Boilupratio

C1 175.35 6472347.3 3500 1910.764 0.5459 171.48 0 2548.9 2620.192 1.0279

C2 192.74 91411835 4751.9924 58422.27 12.29 180.297 91000347.4 1196.907 49392.546 41.266

C3 188.872 1715098.2 53.03 923.076 17.4066 183.313 1710731.19 46.9698 910.819 9 19.39 1

C4 195.71 106960.11 8.316 68.6828 8.2588 186.123 120270.311 44.7138 67.5344 1.5103


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54

Figure29: Temperatureprofileofcolumn C2

CompositionprofileofC2

Thisdiagramshowsthe compositionofoxygen,nitrogenand Argonindifferentstage

numberofcolumn2.

Figure30: CompositionprofileocfolumnC2

19 4

19 2

19 0

18 8

18 6

18 4

18 2

18 0

17 8

0 10 20 30 40 50

t(

C)

N

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 5 10 15 20 25 30 35 40 45

X

N

N2

O2

AR


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TemperatureprofileC3



Figure31:TemperatureprofileofcolumnC3

CompositionprofileC3

Thisdiagramshowsthe compositionofoxygen,nitrogenand Argonindifferentstage

numberofcolumn3.

190

189

188

187

186

185

184

183

1 11 21 31 41 51 61 71 81 91 101 111

t

(

C)

N


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Figure32: CompositionprofileofcolumnC3

TemperatureprofileC4



Figure33: DiagramofTemperatureprofileC3

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100 110

X

N

N2

O2

AR

19 8

19 6

19 4

19 2

19 0

18 8

18 6

18 4

0 2 4 6 8 10 12 14 16

t(C)

N


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Figure35:DistillateflowrateincolumnC1versuscompositionofArgoninthesideArgonstreaminColumnC2

InfluenceofdistillateflowrateintheColumnC1onrefluxratioincolumnC2:

ThisdiagramshowsthedistillateflowrateincolumnC1versusrefluxratioincolumn

C2.Wherethepurityandrecoveryofproductswereholdatconstantvalues. Thedistillate

flowrate incolumnC1effectstherefluxratiointhecolumnC2. AswecanseeonFigure

(36)adistillateflorrateofaround3400kmol/hrshowsaminimumforrefluxrationin

columnC2.

Figure36: DistillateflowrateincolumnC1versusrefluxratio inthecolumnC2

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

1100 1600 2100 2600 3100 3600 4100 4600 5100

XArC2

nDC1

5

7

9

11

13

15

17

19

21

23

25

1100 1600 2100 2600 3100 3600 4100 4600 5100

R

C2

nDC1


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4.Mechanicalaspectsofairdistillationtower

TargetofmechaniccalculationssetsizeandpartsofHerbsdevicewasplannedthatshould

providestrengthanddurabilitytothemachine.Calculate,includingbasicpartstationmechanic

andpartsofthefollowingdevicesarechemicalvalence.Bodies(cylindersE.)depthring

strengthbyseparateducts,fittingsFlange,byrelyingonstrengthandHerbspartsdevices.

Devicesinthecapacitypressures(lessandadditional)undervacuumoroutsidepressureworks

and shouldalso theyare in the fieldsagainstwind loadeffectsandbe tested inearthquake

force.

Ifyouneedtocalculatetheeffectofsimultaneousmultipleadverseconditionswhentheother

operation canbeperformed.When computing thedeviceelementsmechanicwith stainless

defense wall ML plastic the creatures lining etc. It will not be considered.

Todeterminecastdevices thatconsistof several segmentsof the same formula thatcanbe

usedtodeterminethewallthicknessoftwoRinddevicesareused.Ifthedifferenceinthermal

expansioncoefficientofmetalsegments(3cm+X18H10T)thereisInthiscase,thethicknessof

cortical thickness saturate devices the basic forms (thick carbon steel) but also in such

conditions,socalculatedagainstsurplusesrustyarenotlooking.Whenplanningunitsofplants

inselectedcaseofbuildingsandusingnormalStandardnumbersthatareneededtotestthe

calculations and can be performed. The purpose of computing tentative is defining the

authorizedpressureInjectionsvirtualmachinesthatcanbeharvested.ForCalculationsstability

andstrengthofthemachinesthisnormsOH26011365/H103965areapplied.

4.1Basicparametersofcalculations

4.1.1Calculatedpressures

Pressure in the formula calculating machines and container wall thickness and stability,

including in Stabilityhasbeennamed and supposedly learned saturatepressure term is the

workingpressure.Astheworkingpressure,thelargeexcesspressureincaseofnormalflowof

Practicaltechnologyarise, isconsidered. Ifthefluid filleddevice isset inMeanwhileSaturate


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pressureisneededtomakethatpushhydrostaticalsoisconsidered,althoughinthatcasethe

quantityof2.5%oftheexcessgaspressureishigh.Insomecases,verysensitivetothepossible

increase in working pressure as 10% of the time delay in opening the valve is considered

discretionary.Fordevicesthattheexistenceofexplosive,toxicorpotentsubstancesarequickly

Activity Saturate pressure than the pressure of working long enough to accept 0.10.2MPa.

Saturate pressure on devices that maintain and filtration combustion and explosive

environmentsandGasesliquidusedinthetable(7)hasbeeninserted.

Table7:Saturatepressuresindevices

Forelementspaceswithdifferentpressuresfortheformationofseparate(forexample inthe

machine with warm shirt or cover) as the Saturate pressure is necessary to separate any

pressureorpressuregreaterwallthicknesscalculationtakestheelementstobeaccepted.Ifthe

effectofsimultaneouspressurecomes,runcalculationsinthiscasethepressuredifferencesare

allowed.Testunderpressureincontainersordevicesshouldbeconsideredunderthepressure

tocontroltestAssured,safetyandfunctionalityKaranoccurs.

PMPacalculationpressure

PCMPaeffectivepressure

0.01 liquidGaswithoutpressure

0.1 0.050.07

1.2PC upto 0.3 >0.07

0.06


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4.1.2CalculatedTemperature

Temperature directlynot included in calculated formula, but knowingwhere to get profile

material is necessary. Wall material calculated temperature of the device is equal to the

ambienttemperaturethatwall iscontact it, istaken. Iftheexistenceofthermal insulation in

thedeviceequaltothetemperaturelevelwiththewallinsulationtomakecontactwithplus20

Cistaken.Ifthemachineis heatedbyopenedflamesorelectricheatersandopenupstillhot

by Gases temperature 250 C and the more heated, the temperature equal to ambient

calculatedtemperaturetheliningistobe,adding50Cbutnotlessthan250Cistaken.

4.1.3Reactionarylongitudinalmodel ShowstheabilityofMaterialsanditsstandtough

againstdeformation.ReactionarylongitudinalmodelPricesfor highcarbonsteelsandmuch

Lagerincommunicatewithtemperatureshaveinsertinthetable(8)

Table8:Reactionarylongitudinalmodel

E.105

MPa UnderthefollowingtemperatureC

steel

350 300 250 200 150 100 20

1.64 1.71 1.76 1.81 1.86 1.91 1.99 Carbonation

1.86 1.91 1.94 1.97 1.99 2.00 2.00muchbeen

laager

steel

E.105

MPa UnderthefollowingtemperatureC

400450500550600650

Carbonation1.551.40

muchbeenlaager1.811.751.681.611.531.45


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64

4.1.4CoefficientSutureStabilityWeld

In the calculation of containers anddevices thathas Suture Stabilitywelding,mustbe

includedtheStabilityofconstant factor intheformula .Thiscoefficientshowsconnection

betweenStabilityofweldandconstructionofbasicmaterials(papersupplement).Priceofthe

Coefficient Suture Stability Weld is belongs to the Building of weld (connection) and how

somethingwillbeWeld.AutomaticandManualWeldandbilateralthanunilateralbetter.

Table9:WeldcoefficientStabilitySutureweldofcontainersanddevices

ofweldSutureshape

If stitchlengthwelding

100%1050%

Tiptotip,orheadtoheadtwowayapproachto,bare

Automaticorsemiautomatic1.00.90

Headonstitchesfromthebuttorheadtoheadbare

handatwoway1.00.90

Onewayheadonwithlayers0.90.80

Headtohead0.80.65

Headononesidedsemiautomaticorautomatic0.90.80

Headononewaymanually0.90.65


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66

Surplusformetalcorrosionrateequaltothemetalcorrosion(mm/year)vbeatupduringthe

system t (typically 1210 years) are: C = v t Corrosion of metal speed manual or book of

laboratorytestset.Surplusformetalcorrosionusually12mm,whichisasfast0.10.2mm/year,

mustaccept.

Iftwowaycontactwiththemetalcorrosionsurplusenvironmentformetalcorrosionshouldbe

increased to compensate. Compensation technologically Surplus wall thinning or elements

within thedevice inoperation technology: cake,bendpipes,etc.areanticipated.C1andC2

Surplusof themodesconsider thepriceof5%of their total thicknessexceedsnormal sheet

metal.

4.2.1SelectionoftheVirtualInjections

Injectionsinwhichcertainwork(safety)devicewithoutprovidingsubstanceiscalledBuilding

VirtualInjectionsberemembered.VirtualInjectionsrelatedtomechanicpropertiesmaterials,

propertiesBarranditsworkingconditions.VirtualInjectionsdeterminedbythefollows

formula:

Dop= (4.3)

Here: seizure authorized under heat normal Saturate MPa wall of the opinion that the

constructionmaterialsdevices calculatedunderthetablesaretaken,correctionfactorofthe

device inwhichworking conditions are considered. Systems for constructionmaterialshave

negativethermalliningthem;agreethattheirseizuresarethesameasnormfpermittedto20

Cis.

IfyouuseNormativeMaterialspresentedinTableseizuresarenotpermittedorintheabsence

ofheatsaturatepricesinthistable,theseizuresNormativepermittedtobereceivedasfollows:

1 Ifthetemperatureofcarbonsteelssaturatewallto380Cforsteels3of420Cforsteel

andmanyofLaagernotexceed525C,inthiscaseastheseizureofthetwopricesNormative

permittedunderthefollowingisselected:


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=B/nB , =T/nT (4.4 )

Here:BandT LeastlimitorderpriceStabilityfluidityundertemperaturelimitSaturate,

nB=2.6andnT=1.5 thecoefficientofstorage,respectively,totheextentStabilitycomment

andismuchfluidity.

Table11:coefficientsamendmentsauthorizedseizure

2 IfthewallnormativetemperatureofSaturatepricesparagraph(a)exceedstheseizureas

permittedunderthefollowingNormativetwopricesthatareacceptable:

=D/nD , =T/nT (4.5)

Here:D Stabilitylongtermaveragepricelevelof100thousandhoursundertemperatures

SaturateandnD=1.5 savingfactorStabilitycommentistoolongStability.

FortestingconditionsHydrolytedishesanddevicesoflargesteelLaagerbeenauthorized

seizureofthefollowingformulatodetermine:

Manner

riskof

chemical

substances

Permissible

concentrationlimit

ofthehealth

Consideringthe

Norm mg/m3

Muchlower

abilitytoblast%

Spontaneous

ignition

temperatureto

inflammationCCorrectionfactor

ILessthan5Lessthan1Lessthan5170.85

II505513001750.90

III1000511064503010.95

IVMorethan1000Morethan10Morethan 4501.00


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68

/nT (4.6)20

2.0 []np=

Here:quantitypricelevelflowconditions(underwhichtheseizureremainingelongation

makesup0.2%)andisnT=1.1.

4.3MechanicalCalculationofdistillationtower

Initialfigures:

1 Internaldiameterofthelowertower: D.=1200mm

2 LowerTowerHeight: H=1.1M

3 Temperature: tn=185C

4 Pressure: P=6 2

g

5 MuchStability =3000 2

g

6 SavethelimitofstrengthStability: n=2.6

7 Internaldiameteroftheuppertower: D.=1040mm

8 UpperTowerHeight: H=3240mm

9 Temperature: t=192C

10 Pressure: P=1.6 2

g

11 Inadditiontoaskingforcompensationofmetalcorrosion:C=2mm

12 ConstructionMaterial: L62


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69

4.3.1CalculationCylindricalBodyofthetower

ACylinderwallthickness(bottom)determinewithhelpofthisrelationshipasfollows:

Cp

DP

S

+

= ][2

.

(4.7)

28.11536.2

3000][

==

mmcmS 12.5512.02.0312.02.06.2301

0.7202.0

618.11532

0.1206==+=+=+

=

TheS=6mmwallthicknessareacceptable.

Permissiblepressureintheselectedwallthickness[P]andseizureagainstthetopwallare

calculatedas

)(

)]([2][

CSD

CSP

+

=

(4.8)

267.74.120

84.923

)2.06.00.120(

)2.06.0(8.115312][

P ==+

=

22.78592.0

4.722

)2.06.0(13.2

)2.06.00.120(6

)(3.2

)(

CS

CSDP==

+=

+=

B Cylindricalbodywallthickness(upper)determinedwithhelpoffollowsrelationship:

CP

DPS +

=

][2. (4.9)

mmcmS 72.2272.02.0072.02.02306

4.1663.0

6.118.11532

0.1046.1==+=+=+

=


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70

TheS=6mmwallthicknessareacceptable

Permissiblepressureintheselectedwallthickness[P]andseizureagainstthetopwallby

formula(4.8)arecalculatedas:

)(

)]([2][

CSD

CSP

+

=

284.84.104

04.923

)2.06.00.104(

)2.06.0(8.115312][

P ==+

=

25.18192.0

04.167

)2.06.0(13.2

)2.06.00.104(6.1

)(3.2

)(

CS

CSDP==

+=

+=

4.3.2Calculationofellipticalcapandbottom

A Ellipticalbottomwallthicknessdeterminedbythehelpoffollowingformula:

CP

RPS +

=

][2 (4.10)

mmcmS 12.5512.02.06.2301

0.7202.0

68.11532

0.1206==+=+

=

Thebottomwallthicknessequalto6mmisaccepted.

AuthorizedPressureandseizureonthetopwall arecalculatedas:


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72

Permittedpressure[P]andseizureagainstthewallabovebyformula(4.11)arecalculatedas:

284.84.104

923

)2.06.0(0.104

8.11531)2.06.0(2

][

P ==+

=

28.2088.0

04.167

1)2.06.0(2

)2.06.00.104(6.1

)(2

)(

CS

CSRP==

+=

+=


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73

5.Safetyaspectsofairdistillationprocess

5.1MajorhazardsofchemicalProduction

Keyrisksandchemicalrisksfollow:

1 Level entitywarm, sharp steam flow, if thatmakes combustion acid thermal burns and

chemicalrepresented.Opinionbecause37%occurinunfortunatesituations.

2 Mechanicinjuriesthatcausehazardsandrepresentedmechanicinjuriesadversescenarios.

Is14%constituted?

3 Levelentityharmfulgases,toxicsubstances,toxicthatareuniquelypoisoningmakeup13%

oftheseeventsscenarioshorrible.

4 Theexistenceisofelectriccurrentsbecauseelectricaldamageandeventsrepresented.This

happenedof11%formalladversescenarios.

5 Otherhazardssuchasfallsfromhighway,trafficoccursinsidethefactoryandothersmake

up25%ofevents.

5.2Materialpropertiesinplant(separationofair)wasplanning

Nitrogen: Nitrogen look fromPhonologyTl, theconcentrationof large In theair than82%

(lowratioOxygen)consistsoftherepression.

Nitrogenpureformofindustrialpressureballoon150atthesteelissoldgreen.Inthechemical

industry,gastransmissionpipelinesNitrogen,aredenotedingreen.

Oxygen:isthemostabundantchemicalelement.InadditiontoitspresenceasMolecule

diatomicO2intheair,ascombinedwiththeHydrogenH2O,withmetalsandotherelements,

canbefound.Inaddition,manymembersalsocontaincitrusOxygenatomsare.OxygenO2gas

iscolorlessandodorless.Oxygennotburned,butburningofothermaterialsisnecessary.

Oxygenpureliquidformintanksasacoldorhasgashighpressure,uptoabout150at,insteel

blueballoonistransportation.Inthechemicalindustry,transportNellOxygenmarkedwith


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74

blueare.

Carbondioxide:odorlessgasis.Thantwotimesheavierthanair,andcausedshortagesin

Oxygenair.

5.3Majorrisksintheproductionsystem(airseparation)

a liquiddecompositionproductsexistthathavetheairtemperatureislow,allowingaportion

oftheicefrostsuchasonthehumanbody,hands,etc.footshasplaces.

bNitrogenexistenceandthepossibilityofcreatingcarbonTetracollaredarechokingand

poisoning.

c SodiumHydroxidepossiblesolutionsexisttocreatechemicalburnsintheeye,zinc,etc.are

available.

dAttributepossiblecauseexplosionsapartpressure,thetransitionandtheinjuryisNell.

e AttributeflowmaybecausedelectricalfiresLane.

f AttributeUsefulmovingpartsandopenMechanicalvectormaybecausinginjurymechanic.

g Theexistenceofsteam,hotpartsCondensateandequipmentmaybecausingtheburning

partBodyhumans.

h CottonGlassattributes(cottoncandy)maycauseeyeirritationandillnessistherespiratory

tract.

i Theexistenceofammoniaintheneighboringbranchesmaybecausingtoxicity.

j OxygenentitymixedOxygenAirFirelessmaterialsmaycausefireandexplodeFireless

materialsareclothingandhair.


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5.4SafeConditionsfromoperationofcompressor

Practical contraction inGases dangers with increasing pressure, temperature and chemical

operations can lead toexplosionsand injure,Updatedrawn. If the temperatureCompressor

contractingasevereformofincreasedgasanditwillbecalculatedbythefollowingformula.

mmPPTT /11212 )/(

=

(5.1)

Here:

T2 AbsolutetemperatureofgasaftercontractingtheCalvinK

T1 AbsolutetemperatureofthegaspriortocontractingCalvinK

P1 Absolutepressuregaspriortocontraction

P2AbsolutepressureofgastoContraction

m IndicatorsMonetaryTrope

Ifthecontractionofairoranyothergaswithoutmakingcold(Practicaladiabatic)temperature

willincreasestrongly.Iftemperaturesincreaseenergyconsumptionforcontractionwastoo

muchgas,metalTightlyCompressorbeenlow,extremelyfastdecompositionOilsGreasyand

thepossibilityexplosionwerecaused.

5.5FacilityforDefenseemployeesindividual

Individualmeansofprotection for employees include gasmask, glasses defense, special

clothing is and shoe.Allemployees frommaterialsnoxious anddingerorganismmeans that

intoxicationAndfromPowerlossorlossofsightcausedvolumesofburnsismaintainedpicks.

ForthemembersofsubstancesharmfultotherespiratorygasmaskstoprotectIwouldusethe

shouldbe.Gasmaskstothemembersofthehumanorganismbreathingnoxiousfumesofthe

impact it will protect. In separators provides protection from dust. Comment gas masks to

protectthefilterPrincipevisitorsaredivided intoandvisitors.Aidedgasmaskfilterbreathing

vapoursvisitorsdropbyaspreliminaryfilterandclearandwillbreathethroughit.Insulatorgas


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76

mask filterwithadifferenceofvisitors fromallmembersofthehumanrespiratoryeffectsof

harmfulsubstancesshallprotect.

5.6Sourcesoffireignitionmaterials

Fireignitionsourcematerialsinclude:

1.Heatsources,sparkignition,hotsurfacesandopenfire.

Sparks shotor a resultof frictionwitheachothermetallicmaterialsora resultofelectric

charge arise.Toavoidproducingsparksinhazardousenvironmentsandexplosivecombustion

bytheapplicationofcoppercoveredsteelanddevisessecondlybytheapplicationoffattyoilin

theirneighborhoodsandthirdcarpetmaterialnotbematchedstones.Fireandtheninfactory

do soWelding,D. R.Dash around in smoking effects stop smoking comes and for grow on

smoking should consider pulling be special place to be. Not working at Welding Gases and

combustiblevaporspenetrate,theDashshouldbesothatthetower isroundandreactors In

effectof FlameWind It shouldbe close todangerousgear.TheDash then separatedby the

wallsofthegearis.DashandcontinuestoturnoffthefirebyfirefightersLaneisavailable.

2.Electronicresources(Staticselectronicresources)

PowerIneffectofStaticsusuallywillfillandemptygastank,opentheflowofgasolinewith

airpowercreatesChargeStaticsistheresultwecanconnecttotheearthdestroyed.

IfChargeengendersnegativeandpositiveaircleanerincaselightningcomestheresultcanalso

connect to the earth destroyed to prevent ignition sources said and from. Explosive device

when production comes from about the explosives concentrations in the air exceeds its

allowed. Prevent the need for room and is explosive places Gases wind is available and is

equippedwithfireequipment.

5.7Wayofmakingofffire

Makingoffthroughfireinclude:

1) ComethroughPinetemperaturematerialsfireplace.


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77

2)StopmakingOxygenreachthefireposition.

Howinclusionofwaterwordsaremakingofffire.Firestilldifferentbysomesolublesalt,soda

anddrawnoff.

Andsolutionbluewatershouldbeusedisthefollowing:

1. Gasesfireformakingoff.

2.Formakingoffundervoltageelectricalplantsareworking.

FormakinglowconcentrationortocutofftheflowOxygenpositionPalmthefireisused.For

example,inafiretakesplacethisdeviceintothedevicewhenPalmmakeallthemateriallevel,

tissuesandorganswilloccupyfirepreventionOxygenreachthesurfacematerialisfire.Palmas

tononinterruptedwhilefire isofftakesplace.Howeveractuallymakingoff inkusedtofire if

the fuel tankswhichwill fire simultaneously into the tanks are Palm out by the coldwater

make.InadditiontobeingsomeGases,Moblaile,ammonia,electricalwirefireriskVequipment

andmarkscarbonmonoxidevisitorscounterfirePalmDP3andDP5isused.F.Antifirecarbon

dioxideconsistsofconventionalsteelballoonfilledwithcarbondioxide is.Valveballoonneck

closedwith visitorsNell sailfony length is 13meters above the valveopened anti fire over

sourceoffireistopushtheballoonPashaspalmproducingabatchistoopenthevalveandthe

balloon and the acid solutionAlkali there. In case of opening valvesAlkalimixedwith acid,

resulting inpalm interaction isproduced. In addition to fireoff the sand andotherbuilding

materialsarealsoused.

5.8Electricalsafety

HighelectricalcurrentthehumanorganismtoseveredamagedGaywontheRemyand

sometimesleadtodeath.Thusallstaffandpersonnelregulationsandaseriesoffactoriesto

securityPolytechnicTotalbenefitknow.Electricalequipmentinfactoriesbecausethepumps

andhighvoltagecompressor(watt380)providesthatintermsoftechnicalworkisdangerous.

Thefactoryworkersmusttakethefollowingrulesshallobservegoodandaccurate.

1.AllelectricalappliancesmustbespecifiedunderNormusedtobethrown.


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78

2.Allpartsoftheelectricalequipmentofthepowerpassesmustbeinsulatedcover.

3.CrosssectionofnonconducivetoanyformofelectricityshouldnotTransitelectricity.

4.ElectricmachinegunmustSignalserversandautomaticallyturnoffelectricalcurrentdonors

indangeroussituations.

5.Electricaldevicesmustconnecttoprotectiveearthorbywirefailureisprotective.

6.Whilerepairingelectricaldevicesshouldbediscontinued.

7.WithmachineryandelectricaldevicesmustbetheonlyoneDowork.

5.9RulesofthetechnicalRepairofCompressorwhenitsbenotdanger

Whilecompressorrestoredfollowingtherulesandregulationsbeinattention

1.Compressorofconformityinstructionsgivenareatostopworking.

2.Compressorwillbeemptyfrompressure

3.PressureRestabsencedeinthecompressorisgivenbyMonometer.

4. Compressorisemptyfromgas.

5.Electricityiscuttingfromcompressor.

6. CompressorbyNitrogenthatamountuntiltheventilationintheneithercombustionGases

ventilationnormorethen%5/0is.

7.Compressorconnectionofotherequipmenttobedisconnected.

8.CompressorisdrawinguntiltheamountofairOxygenlessthan21percentinvolumeand

valueGasesharmfulandtoxicnotexceedthelimits.

9.DuringrepairoperationsmustberestoredCompressoremployeesTechnicalrecipessafeto

observejoinsseriously.


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79

5.10Ventilationproductsanditskinds

VentilationProductsAirDirtytomakeoutofworkandintoneighborhoodswherefreshairand

tocontinuetoavoidcreatinganexplosiveconcentrationisconsidered.Becauseotherwiseit

mightwork,therecomestoexplosiveconcentrations.Practicalinmanufacturing,especiallyin

thepumphouse,houseandCPOCompressorcomposedofartificialventilationareused.Itis

stillroomairfieldisalsoconsidered.AirProductsmustmeetthefollowingdemands.

1. Concentrationinthecombustionmixtureshoulddropislessthanexplosive.

2. Ventilationshouldbetheultimatelimitofconcentrationtoholdtherooms.

3. ForStartingFanElectronicmotorswithStartingvisitorsmustsecurepointwithexplosive

wasused.

4. Topreventtheformationoffrictionorimpactsparks,iftherouterFanbodyismadeof

coloredmetals.

5. VentilatedroomsmeansaroominwhichheisFanshouldbeplacedwithnoncombustion

materialsandtheproductionoftheroomsarecompletelyseparate.


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6.Controlofairdistillationcolumns

We start by analyzing the degrees of freedom to establish how many and which control

parameters it ispossibletocontroland/ormanipulate.Thenwemoveontodiscussdifferent

waystocontrolmanyvariables.Generally,thevariablesintable( )needtobecontrolled.

Table12:Typicalvariablesthathavetobemaintainedinadistillationcolumn.

Thetwomostimportantparameters:compositionatthetopofthecolumnandthepressureof

thecolumn.Differentcontrolstructures.

6.1DegreesofFreedomAnalysis

Todeterminethenumberofcontroldegreesoffreedominadistillationcolumn.Therearetwo

equivalentproceduresbasedontheequation C.D.F.=TotalNo.ofStreamsNo.ofPhases

Present+1Allwehavetodoiscountallthestreamsintheprocess.Separatelycountthetotal

numberofextraphasesi.e.addupalloccurrencesofphasesgreaterthanoneinallunits.The

numberofcontroldegreesoffreedomisthedifferencebetweenthesetwonumbers.Figure(39

)belowshowsthismethod.


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81

Figure39: DegreesofFreedomAnalysisofDistillationColumn

TotalStreams=8

ExtraPhases=3

DegreesofFreedom=5

So the number of degrees of freedom is 5. However, a typical control strategy for such a

processwoulduseonly4of these federate,columnpressure, topandbottomcomposition.This is because the column and condenser are normally maintained at the same pressure.

However,avalvecouldbeplaced in the linebetween.Thiswouldactuallybeundesirableas

reducingthecondenserpressurewilldecreasethetemperaturedrivingforceavailablefromthe

coolingmedium.

6.2ControllingPressureinDistillationInadistillationcolumnitisusuallynecessarytoregulate

thepressureinsomeway.Belowtherearefivedifferentmethodsdescribedfordoingthis.

VenttoAtmosphere

CoolingWater

FloodedCondenser 1

FloodedCondenser 2


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PartialCondenser

Onethingtonoteisthatinnoneofthemisavalvesimplyplacedonthevapourline.This

wouldleadtotheuseofalargeexpensivecontrolvalve.Insteadthepressureiscontrolled

indirectlyinvolvingtheuseofthecondenserand/orrefluxdrum.

6.2.1VenttoAtmosphereFigure(40)belowshowstheeasiestwaytocontrolthepressureina

columnoperatingatatmosphericpressure.

Figure40:VenttoAtmosphere

Inthiscasethecoolingwaterflowstaysconstantandtherefluxdrumisventedtoatmosphere.

Thus the reflux drums and hence the top of the column are at atmospheric pressure. The

advantageofthisschemeisthatitrequiresonelesscontrolvalve.Thedisadvantageisthatthe

topshavetobesubcooledsothataminimalamountofvapourislostthroughthevent.Hence

moreenergyisrequiredfromthereboilerwhentherefluxisaddedtothetopofthecolumn.

6.2.2CoolingWater:Figure(41)showsthemostcommonmethodforcontrollingthepressure

adjustmentofthecoolingwaterflow.


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Figure41:CoolingWater

Inthiscaseifthecoolingwaterflowisincreasedthenmorevapouriscondensedandthe

vapourpressureisreduced(andviceversa).

6.2.3FloodedCondenser 1:Figure(42)showstheclassicfloodedcondenserapproach.

Figure42FloodedCondensers 1

Againinthissetup,aswiththefirstexample,thereisnovalveonthecoolingwater.Insteadthe

valveisintheliquidlinebetweenthecondenserandrefluxdrum.Ifthisvalveisclosedthenthe

condensedvapori.e.liquidwillbuildupandfloodthecondenser.Thishastheeffectofreducing


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85

Figure44:PartialCondenser

Theaboveschemeisusediftheoverheadproductisrequiredasavapour.

6.3ControllingTopsCompositioninDistillation:Aswellaspressure,theotherparametermost

likelytobecontrolledisthecompositionofthetopsproduct.Thereasonisthatthefinal

productwillmostprobablycomefromthetopofthecolumnanditisimportanttoknowits

composition.Again,aswithpressure,therearemanydifferentwaysofcontrollingthetops

composition.Threemethodsaredescribedbelow.

RefluxRate

RefluxRatio

DistillateRate

6.3.1RefluxRateInthisfirstexampletherefluxrateisadjustedtocontrolthecompositionof

thetopsproduct.Astheamountofrefluxischangedsothetemperatureprofileinthecolumn

changesandhencethecomposition.


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Figure45:RefluxRate

6.3.2RefluxRatioThesecondexampleusestherefluxratioasthecontrolparameter

Figure46:RefluxRatio

Whendesigningadistillationcolumnitisusuallytherefluxratiothatisdetermined.Thiscanbe

keptconstantthroughoutoperationbyusingtwoflowindicatorsandaratiocontroller.

6.3.3DistillateRateThethirdexampleisforhighpuritytops.Itusesthedistillateflowrateto

controlthedistillatecomposition.


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Figure47:DistillateRate

Itcanbeshownthatforahighpuritycolumni.e.onewithalargereflux,thatthecomposition

ofthedistillateissensitivetothedistillateflowbutinsensitivetotherefluxrate.Thereforefor

ahighpuritycolumnthecontrolschemeoutlinedaboveisused.Itshouldbenotedthattight

controlonthelevelintherefluxdrumisrequiredusingtherefluxrate.

6.4DistillationColumnControlExamples

Thefollowingexamplesdescribealternativecontrolstrategiesoffairlystandardform.

Pressure,OverheadsRateandComposition

Pressure,BottomsRateandComposition

Pressure,BottomsRateandOverheadComposition,WithPartialCondenser

Pressure,OverheadRateandBottomsComposition

Pressure,BottomsRate,OverheadRateandComposition

Inallcasesactualcompositioncontrollersareshown.Thesecouldofcoursebereplacedby

inferentialmeasurementfromtemperature,withorwithoutcascadeofasloweranalyzer.

Unlessotherwisestated,ithasbeenassumedthatthefeedratetothesystemisnotavailable

asamanipulatedvariable.


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88

1.Pressure,OverheadsRateandCompositionThisisafairlystandardconfigurationforasingle

product column, i.e. when the bottoms streams is a byproduct, recycle or goes to further

processing.Althoughtheoverheadscompositionisregulatedbyadjustingthesteamrateatthe

baseofthecolumn,theresponseofthecolumntoheatinputchangesisquiterapid,andsothis

strategy is acceptable.Pressure controlon condenser coolingwater is shown;of course any

otherpressurecontrolschemewouldbeacceptable.

Figure48:OverheadsRateandComposition

2. Pressure, Bottoms Rate and Composition This is the analogous situation to theprevious

case, in the rather less usual circumstances where a main product is withdrawn from the

bottom of the column. This does not work well, since either the bottom level, as here, or

composition,hastoberegulatedbyadjustingtherefluxrate.Ineithercasetheloopinvolvesa

longdelaydue to thehydraulic lagsoneachtray. It isprobablymarginallybetter to regulate

compositionbysteamratesincethisisamoreimportantquantitythanlevel,althoughthetwo

loopscouldbeinterchangedwiththesteamadjustingthelevel,whichisquiteagoodscheme,

andtherefluxmanipulatingthebottomscomposition,whichisverypoor.Fortunatelythisisan

unusual requirement, as main products normally come from the top of columns for other

reasons.Astandardfloodedcondenserpressurecontrolsystemisshown.


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89

Figure49:BottomsRateandComposition

3.Pressure,BottomsRateandOverheadComposition,WithPartialCondenser

Thisisnotaparticularlycommonstrategy,butthearrangementsforacolumnwithpartial

condenseraretypical.Thepressureinsuchasystemisalmostalwaysmanipulatedbyavalve

onthevaporproductline.Thereisnorefluxdrum,andrefluxrateisoftensetimplicitlyby

adjustingthecoolingloadonthecondenser.

Figure50:BottomsRateandOverheadComposition,WithPartialCondenser


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90

4.Pressure,OverheadRateandBottomsCompositionThisschemeshouldworksatisfactorily

asalladjustmentsaremadeatthesameendofthecolumnastherelatedmeasurements.The

pressurecontrolschemeisthesocalledhotgasbypass.Notethatthelayoutofcondenserand

refluxdrumshown iscriticaltotheoperationofthismethod,which isactuallyavariationon

thefloodedcondenserapproach.Thebypass isaverysmallpipewhichbleedsvapor into the

refluxdrumwhere itdoesnot immediatelycondense.Thepressure inthesystemrisesasthe

bypassvalveisopened.

Figure51:OverheadRateandBottomsComposition

5.Pressure,BottomsRate,OverheadRateandComposition:Sincethreeregulatedquantities

are specified, the feed to theunitmustbe available as an adjustment.Apart from this, the

arrangementsaresimilartothoseofthefirstexample.Levelcontrolonthecolumnbaseisnot

verysatisfactoryduetothelagsbetweenthefeedandthebottomofthecolumn,butanyother

arrangementwouldbeworse.


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91

Figure52:BottomsRate,OverheadRateandComposition


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92

6.Economicevaluationofairdistillation

Inthischaptertheeconomicsoftheairdistillationprocessisevaluated.Forbuildinganair

distillationplanttheinitialcostofequipmentsandoperationalcostsareimportant.

6.1Capitalinvestmentcosts

Inanairdistillationplantthereareusedanumberofexpensivedevices.Mostimportantof

themarecompressors,distillationcolumns,andheatexchangers.UsingAspenEconomic

Evaluationwehavecalculatedthecostofequipmentusedinthesimulationscheme(Figure26)

andalsofeedaircompressors.TheresultsofthesecalculationsareshowninTable13.Thetotal

Investmentcostswerecalculatedas29720000USD.Consideringa15yearperiodofplant

operationtheannuallyinvestmentcostsare:1981333USD.

Table13:calculationofinvestmentcosts

NO Name Type DirectCost

(USD)

NO Name Type Direct

Cost(USD)

1 B1 DGCCNTRIF 15726500 15 C3refluxpump DCPCENTRIF 34800

2 B2 DGCCNTRIF 2163300 16 C3tower DTWTRAYED 2758400

3 B4 DHEFLOATHEA 90500 17 C4cnodacc DHTHORIZDRU 127200

4 C1condacc DHTHORIZDRU 219500 18 C4reb DRBUTUBE 65400

5 C1 refluxpump DCPCENTRIF 61200 19 C4refluxpump DCPCENTRIF 24100

6 C1 tower DTWTRAYED 450700 20 C4tower DTWTRAYED 165900

7 C2 cond DHEFIXEDTS 572400 21 Expander DTURTURBOEX 63000

8 C2reb DRBUTUBE 143000 22 HE1 DHEFLOATHEA 294600

9 C2refluxpump DCPCENTRIF 338600 23 HE2 DHEFLOATHEA 207200

10 C2tower DTWTRAYED 5183100 24 HE3 DHEFLOATHEA 278700

11 C3cond DHEFIXEDTS 25 HE4 DHEFLOATHEA 374700

12 C3condacc DHTHORIZDRU 147600 26 HEN2 DHEFLOATHEA 94000

13 C3 reb DRBUTUBE 41600 27 HEO2 DHEFLOATHEA 94000

14 total 25138000 28 total 4582000

TOTAL = 29720000USD


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93

6.2Operationalcosts

Theoperationalcostincludesmainlythefollowing:

a Costofrawmaterials,basicmaterialsandsemimanufacturingproductsandauxiliary

materials.

b FuelcostsfortheStateoftechnologicalwork

c Water

d Electricity

e Steam

f workers,technicalengineeringemployees

Table14: calculatethebasicmaterialcostsandauxiliarymaterials,fuelcosts,electricity,watervaporandair

Costsofrawmaterials,electricity,waterandsteamaregiveninTable14.Thestaffcostis

calculatedandincludedinTable15.

NO NameMeasurement

Unit

Normof

consumptio

nunit

Annual

production

capacity

Thetotal

consumptio

ninyear

Pricesper

unit

Thetotal

priceof

(USD)

1 A 2 3 4 5 6 7

1 at. Air Nm3/hr 135572

222688000m

3

O2

1084576000 0.01 10845760

2 Silicagel kg/27836m3O2 0.08 640 0.5 320

3sodiumhydro

oxidekg/27836Nm

3O2 2.8 22400 0.375 8400

4 Aluminiumoxide kg/27836Nm3O2 0.06 480

work of shershah amarkhail

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