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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
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