LDPE LDPE TechnologyTechnology20102010

ElElőőadadóó: Csernyik Istv: Csernyik Istváánn

22

ContentContentWhat is LDPEWhat is LDPEApplicationApplicationHistoryHistoryProcess theoryProcess theoryAutoclave processAutoclave processTubular processTubular processProcess stepsProcess stepsProcess controlProcess controlProcess safetyProcess safetyKey equipmentKey equipmentInvestment costInvestment costCost of productionCost of production

33

What is LDPEWhat is LDPE

LLow ow DDensity ensity PPolyolyEEthylenethyleneTypical propertiesTypical properties

DensityDensity 0,910,9155--0,930,9355Melt indexMelt index 0,30,3-->>20 g/10 min (190 C/2,16 20 g/10 min (190 C/2,16 kg)kg)Melting pointMelting point 120 C120 CPolydispersityPolydispersity 5,5 5,5 –– 6 (TVK tubular6 (TVK tubularggradesrades))

44

ApplicationApplication

Film65%

Extrusion coating

10%

Other14%

Injection moulding

7%

Blow moulding

4%

55

Application by PropertiesApplication by Properties

0,1

1

10

100

0,915 0,92 0,925 0,93 0,935

EXTRUSION COATING

FILM EXTRUSION

INJECTION MOULDINGEXTRUSION COATING

BLOW MOULDING

MI,

g/10

min

/190

C

Density, kg/dm3

66

HistoryHistoryLDPE was discovered by ICI in 1933 LDPE was discovered by ICI in 1933 →→ autoclave autoclave processprocess inin 19381938BASF developed the first tubular process during WW IIBASF developed the first tubular process during WW IIHigh variation of autoclave and tubular processes by High variation of autoclave and tubular processes by different licensorsdifferent licensorsNowadays licences available up to 400 Nowadays licences available up to 400 kt/ykt/y plant plant capacitycapacityGlobal consumptionGlobal consumption inin 2009:2009: 1188 million million ttTVK LDPE plantsTVK LDPE plants

1970 1970 -- ICI autoclave process 24 ICI autoclave process 24 kt/ykt/y –– debottleneckeddebottlenecked to 50 to 50 kt/ykt/y1991 1991 -- BASF tubular process 60 BASF tubular process 60 kt/ykt/y

77

Process TheoryProcess Theory 11

Free radical reactionFree radical reactionInitiationInitiation

I I →→

RR··

+ R+ R··Initiators: typically organicInitiators: typically organic

peroxidesperoxides

PropagationPropagationRR··

+ CH+ CH

22

CHCH

2 2 →→ RCHRCH

22

CHCH

22

··R(CHR(CH

22

CHCH

22

))

nn--11

CHCH

22

CHCH

22

··

++

CHCH

22

CHCH

2 2 →→

R(CHR(CH

22

CHCH

22

))

nn

CHCH

22

CHCH

22

··

TerminationTerminationCombinationCombinationRR

xx

··

++

RR

yy

··→→

PP

xx+y+y

DisproportionDisproportioningingRR

xx

··

++

RR

yy

··→→

PP

x x + + PP

yy

88

Process TheoryProcess Theory 22

Other reactionsOther reactionsChain transfer Chain transfer –– important to control important to control molecular weightmolecular weight

RRxx

··

+ CH+ CH22

CHCH22

→→PPx x + R+ R11

··

by monomerby monomerRRxx

··

+ + MM→→PPxx

+ M+ M··

by modifierby modifierCracking Cracking –– results in shorter chainsresults in shorter chainsRRxx

··→→PPyy

+ R+ Rxx--yy

··

99

Process TheoryProcess Theory 33

Branching Branching –– LDPE characterised by high degree LDPE characterised by high degree of short and long chain branchingof short and long chain branching

Short chain branching Short chain branching –– responsible for densityresponsible for densityIntramolecularIntramolecular

chain transfer and copolymerisation result in chain transfer and copolymerisation result in

short chain branchesshort chain branches

Long chain branchingLong chain branchingIntermolecular chain transfers give long chain branchesIntermolecular chain transfers give long chain branches

CC

HC C

C

C C C C

C C CH

C C C

C C C

1010

LDPE LDPE -- Autoclave ProcessAutoclave Process

Initiators(Peroxides)

Autoclavereactor

Secondarycompressor

Primarycompressor

280 bar250 C

HP separator

Waxseparator

0,5 bar250 C

LP separator

Extruder

Ethylene

Oilseparator

250 bar

1400 bar

170 C

240 C

280 C

BaggingBulk loading

Degassing

1111

AutoclaveAutoclave ReactorReactorAutoclave reactor MK 10

L = 4750 mm d = 18”

Thermocouple 1(1st T control)

Thermocouple 2

Thermocouple 4(2nd T control)

Thermocouple 5

Thermocouple 6

Thermocouple 7(control 2nd zone T)

Thermocouple 8

Thermocouple 9(control 3rd zone T)

Thermocouple 10(control 4th zone T)

Thermocouple 3

Top Zone

2nd Zone

3rd Zone

4th Zone

Total 725 l

ethylene

peroxides

1212

LDPE LDPE -- Tubular ProcessTubular Process

Modifier

Fresh Ethylene

Purge

Initiator(Oxygen)

PrimaryCompressor

SecondaryCompressor

Preheater

Precooler

Reaction Zone I

Reaction Zone II

HP Separator

LP Separator

Extruder

HP RecycleLP Recycle

280 bar250 C

0,5 bar250 C

2400-2900 bar

180-310 C

250 bar

BaggingBulk loading

Degassing

1313

Autoclave vs. Tubular ProcessAutoclave vs. Tubular Process

AutoclaveAutoclaveConversion up to 21% Conversion up to 21% --adiabatic, reaction heat adiabatic, reaction heat removed by reactant onlyremoved by reactant only13001300--2000 bar operating 2000 bar operating pressurepressureHigher capacity of hyperHigher capacity of hypercompressorcompressorOrganic peroxide initiators onlyOrganic peroxide initiators onlySpecialty polymer capability Specialty polymer capability ––EVA copolymers over 40% EVA copolymers over 40% vinyl acetatevinyl acetateLower reactor capacity Lower reactor capacity –– 150 150 kt/ykt/y

TubularTubularConversion up to 36% Conversion up to 36% --rreaeactionction heat partly removed heat partly removed by coolantby coolant25002500--3200 bar operating 3200 bar operating pressurepressureLower capacity of hyper but Lower capacity of hyper but higher loadhigher loadCheaper oxygen initiator Cheaper oxygen initiator possiblepossibleFilm Film grades with higher claritygrades with higher clarity,,EVA up to 10% vinyl acetateEVA up to 10% vinyl acetateReactor capacity up to 400 Reactor capacity up to 400 kt/ykt/y

1414

Process Steps 1Process Steps 1

CompressionCompressionIncrease make up ethylene Increase make up ethylene pressure to reaction pressure to reaction pressurepressureRecycle Recycle unreactedunreacted ethyleneethyleneInject modifier and Inject modifier and comonomercomonomer

ReactionReactionInjection of initiatorsInjection of initiatorsControl temperatures for Control temperatures for required product propertiesrequired product propertiesOne phase reaction One phase reaction –– two two phase only at lower phase only at lower pressure and temperaturepressure and temperatureShort residence time Short residence time ––some minutessome minutes

1515

Process Steps 2Process Steps 2

HP separatorHP separatorSeparate melt LDPE and Separate melt LDPE and unreactedunreacted ethyleneethylene

LP separatorLP separatorRemove Remove unreactedunreacted ethyleneethyleneFeed tank for extruderFeed tank for extruder

HP recycleHP recycleRemove low molecular weight Remove low molecular weight polymer (wax)polymer (wax)Cool down recycle ethyleneCool down recycle ethylene

LP recycleLP recycleRemove low molecular weight Remove low molecular weight polymer (wax, oils)polymer (wax, oils)Cool down recycle ethyleneCool down recycle ethylene

1616

Process Steps 3Process Steps 3

ExtrusionExtrusionHomogenizationHomogenizationAdditive dosingAdditive dosingPelletizingPelletizing

DegassingDegassingRemove residual Remove residual ethylene (generally ethylene (generally less than 1000 less than 1000 ppmppm) ) from LDPE from LDPE –– to avoid to avoid explosive gas mixturesexplosive gas mixtures

1717

Melt index (Molecular weight)Melt index (Molecular weight)PP↑↑ MIMI↓↓ (M(Mww↑↑))TT↑↑ MIMI↑↑ (M(Mww↓↓))[Modifier][Modifier]↑↑ MIMI↑↑ (M(Mww↓↓))

DensityDensityPP↑↑ DD↑↑TT↑↑ DD↓↓

Pressure range: 1300Pressure range: 1300--3000 bar3000 barTemperature range: 160Temperature range: 160--310 C310 C

Process ControlProcess Control

1818

Risk of decompositionRisk of decompositionDecomposition: ethylene or polyethylene Decomposition: ethylene or polyethylene decompsdecomps to C and Hto C and H22

High temperature, high pressure, contaminations favour High temperature, high pressure, contaminations favour decompositiondecomposition

Reactor and HP separator in confined area Reactor and HP separator in confined area –– generally generally behind concrete wallbehind concrete wallInterlock system toInterlock system to

avoid decomposition andavoid decomposition andprotect equipmentprotect equipment

Special metal gaskets at high pressuresSpecial metal gaskets at high pressuresGas detectorsGas detectorsFire fighting systemFire fighting system

Process SafetyProcess Safety

1919

Key EquipmentKey Equipment

CompressorsCompressorsPrimary compressor (Primary compressor (Booster+PrimaryBooster+Primary))

5 stages5 stages0,1 bar suction; 250 bar discharge0,1 bar suction; 250 bar discharge

Secondary compressor (Hyper)Secondary compressor (Hyper)Two stagesTwo stages250 bar suction; 3000 bar discharge250 bar suction; 3000 bar discharge

ExtruderExtruderHot melt extruder for homogenizationHot melt extruder for homogenization

2020

HyperHyper CompressorCompressor ArrangementArrangement

2121

HyperHyper CompressorCompressor CylinderCylinder

2222

ExtruderExtruder ArrangementArrangement

2323

SingleSingle--screwscrew ExtruderExtruder

2424

Investment costInvestment cost Basis: USGC 2008Q1Basis: USGC 2008Q1

Process Autoclave Autoclave TubularPlant size 135 kt 3x135 kt 400 kt

ISBL 91,7 231,6 130,1OSBL 60,6 142,3 118,4Other project cost 61,2 160,5 125,1Total investment 213,5 534,4 373,6

Specific investment, USD/t 1581 1320 934

million USD

2525

Cost of ProductionCost of Production Basis: USGC 2008Q1Basis: USGC 2008Q1

Autoclave Autoclave Tubular135 kt 3x135 kt 400 kt

USD/tEthylene 1354 1354 1347Catalysts&chemicals 8 8 5Additives 14 14 14Total raw materials 1376 1376 1366

Power 51 51 58Other utilities 9 9 7Steam credit -34Total utilities 60 60 31

Direct cash cost 34 22 14Allocated cash cost 37 27 18Total fixed costs 71 49 32

Total cash cost 1507 1485 1429

80%

85%

90%

95%

100%

135 kt 3x135 kt 400 kt

Autoclave Autoclave Tubular

Total fixed costsTotal utilitiesTotal raw materials

2626

Appendix: Metal GasketAppendix: Metal Gasket

2727

Appendix: Hyper compressor cylinderAppendix: Hyper compressor cylinder

2828

Appendix: Appendix: Blown Film ExtrusionBlown Film Extrusion

2929

Appendix: Appendix: Extrusion CoatingExtrusion Coating