The Linear Polyethylene Family

Transcription

1 HDPE Technology

2 Content HDPE, MDPE and LLDPE linear polyethylenes Application History Catalysts HDPE processes Process control Key equipment Investment cost Cost of production 2

3 The Linear Polyethylene Family HDPE, MDPE, LLDPE: linear polyethylenes Classification by density determined by short chain branching through comonomer content No of SCB LLDPE MDPE HDPE 0,915 0,926 0,940 0,970 Properties Melt index 0,03 - >100 g/10 min (190 C/2,16 kg) Melting point C Polydispersity (TVK grades) Monomodal 6-8 Bimodal

4 Application HDPE end-use 16% 8% 26% film fibre 5% injection moulding 27% 18% blow moulding pipe others LLDPE end-use 5% 4% 5% 5% 81% film injection moulding rotomoulding other extrusion others 4

5 Application by properties 100 Narrow MWD 10 Medium MWD Broad MWD LLDPE INJECTION MOULDING MDPE ROTOMOULDING HDPE INJECTION MOULDING 1 LLDPE BLOWN & CAST FILM MDPE YARN FILAMENTS HDPE BLOW MOULDING 0,1 LLDPE-MDPE-HDPE WIRE AND CABLE (Medium to broad MWD) HDPE FILM PIPES 0,01 0,890 0,900 0,910 0,920 0,930 0,940 0,950 0,960 0,970 5

6 History HDPE discovered in 1951 by P. Hogan and R. Banks Mid 1950s: commercial HDPE production in slurry process (Hoechst) and solution process (Phillips Petroleum) 1961: slurry loop reactor technology by Phillips Petroleum 1968: first gas phase process by Union Carbide Mid 1970s: first LLDPE process by Union Carbide Various processes available up to 400 kt/y capacity Consumption, 2015 Global: HDPE 39 million t and LLDPE 28 million t Domestic:HDPE 90 kt and LLDPE 25 kt MPK (TVK) HDPE plants 1986: Phillips slurry loop process 140 kt/y, debottlenecked to 200 kt/y 2004: Mitsui slurry, cascade reactor technology 200 kt/y (presently 220 kt/y) 6

7 Catalysts Chromium Silica supported hexavalent Cr Activation at high temperature before use Cocatalyst not necessary Medium to broad molecular weight distribution Ziegler(-Natta) MgCl 2 supported TiCl 4 Metal alkyl cocatalyst necessary Narrow molecular weight distribution Preferred for bimodal products in cascade reactor technology very broad MWD Metallocene (single site) Still developing Cocatalyst necessary Very narrow molecular weight distribution Bimodal capability in single reactor technology 7

8 HDPE LLDPE Processes and Products Gas phase processes Melt index limit Solution processes High quality film grades Best for blow moulding and pipe grades Slurry processes Loop slurry only with density limit 8

9 Gas Phase Processes Characteristics Catalyst: chromium, Ziegler, (metallocene) Fluidized bed reactor C bar Long residence time Swing technology: LLDPE HDPE capability Simple process design Low investment and operating cost Bimodal capability with two reactors 9

10 Gas Phase Process Polymerization Gas blow er Blow dow n Catalyst Ethylene and nitrogene separation Catalyst feed tank Reactor Comonomer separator Ethylene treater Ethylenen Purge column Comonomer treater Nitrogene Comonomer Degassing tank Product to pow der silo 10

11 Gas Phase Process Additivation and Pelletizing 11

12 Solution Processes Characteristics Catalyst: Ziegler, (metallocene) Polymerization takes place in solution bar C Short residence time Broad product range: LLDPE HDPE Bimodal capability with cascade reactors Higher investment and operating cost 12

13 Solution Process Blow down Recycle compressor Feed tank Comonomer treater Separator Solvent treater Solvent Ethylene treater H2 Comonomer 1. reactor Comonomer column Solvent column Ethylene Catalyst Flash tank Cocatalyst H2 Polymer wax 2. reactor Vacuum pump Flash heater Vacuum flash tank Melt to pelletizer Gear pump 13

14 ChevronPhillips Slurry Loop Process Characteristics Catalyst: chromium, Ziegler, (metallocene) Chromium catalyst activation Fluidized bed activator Heat treatment in air at C Reaction in loop reactor C; 42 bar 3-6 % ethylene concentration Isobutane diluent Heat removed by coolant in reactor jacket very good surface/volume ratio Flash separation 10 bar; 80 C Degassing 85 C; 0,1 bar 14

15 ChevronPhillips Slurry Loop Process Polymerization 15

16 Phillips Process at MPK (TVK) Polymerization Hexene-1 Purification Ethylene Purification Ethylene Compressor Hexene-1 Comonomer Ethylene Flash Gas Compressor Loop Reactor Isobutane Distillation and Purification Catalyst Flash Tank Flash Gas Filter Circulating Pump Dryer Isobutane and Nitrogen Recovery Unit Settling Legs and Product Take off Valves Purge Column Powder silo 16

17 Phillips Process at TVK Additivation and Pelletizing Extruder hopper Spin dryer Classifier Additive blender Dewatering screen Main feeder Rotary feeder Premix feeder Pellet water tank CIM Air blower Extruder Pellet water pump 17

18 Slurry Process - CSRT Process Characteristics Catalyst: Ziegler, (metallocene) Low reaction pressure and temperature 6-8 bar, C Reaction heat removed by Overhead condensators Slurry coolers Reactor jacket Bimodal product capability Different molecular weight polymer in 1st and 2nd reactor Comonomer built into high molecular weight polymer Diluent and polymer separation by centrifuge Diluent cleaning for low polymer removal 18

19 Slurry Process CSRT- Cascade Stirred Reactor Technology Catalyst Catalyst dosing Cocatalyst Compressor Flash tank Hexane Ethylene treater 1. reactor Polymer wax (Low polymer) Ethylene Hexane recovery and cleaning unit 2. reactor Buten-1 treater Mother liquer tank Buten-1 Centrifuge Rotary dryer To powder silo 19

20 Slurry Process CSRT Reactor and Surroundings 20

21 Process Control Melt index Ziegler catalyst [H 2 ]/[Et] MI Chromium catalyst: T, [Et], [H 2 ] T MI [Et] MI [H 2 ] MI Density [comonomer] D Molecular weight distribution Catalyst type Reactors operated at different parameters 21

22 Key Equipment Reactors Loop with axial circulating pump Gas phase Decanter centrifuge in CSTR only Extrusion line 22

23 Reactors Loop reactors Long jacketed pipe straight vertical sections interconnected by elbows at top and bottom Built in axial pump to circulate slurry Good surface to volume ratio easy reaction heat removal Gas phase reactors Vertical pressure vessel with increased top section to reduce polymer carry over Long residence time Reaction heat removed by external heat exchanger in recycle gas stream Difficult reaction control 23

24 Loop Reactor Circulating Pump 24

25 Decanter Centrifuge 25

26 CMP Extrusion Line Arrangement 26

27 CMP Elements 27

28 Investment Cost Basis: WE 2015Q2 Process slurry Capacity, kt/yr 300 Investment costs million EUR ISBL 115 OSBL 90 Total investment: 205 Specific investment, EUR/ton

29 Cost of Production Basis: WE 2015Q2 Process slurry 100% Capacity, kt/yr % Fix costs Production costs EUR/ton Raw materials 918,1 Utilities 32,2 Fix costs 39,6 Total cash cost 989,9 80% 70% 60% 50% 40% Utilities Raw materials 29