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Some Engineering Opportunities and Challenges when Producing Polymer Materials from Oil and Gas

Nigerian Academy of Engineering June 2013. Some Engineering Opportunities and Challenges when Producing Polymer Materials from Oil and Gas. by W. Harmon Ray. University of Wisconsin - Madison Dept. of Chemical Engineering. W. Harmon Ray. Vilas Research Professor Emeritus

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Some Engineering Opportunities and Challenges when Producing Polymer Materials from Oil and Gas

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  1. Nigerian Academy of Engineering June 2013 Some Engineering Opportunities and Challenges when Producing Polymer Materials from Oil and Gas by W. Harmon Ray University of Wisconsin - Madison Dept. of Chemical Engineering

  2. W. Harmon Ray Vilas Research Professor Emeritus US National Academy of Engineering (Class of 1991)

  3. OUTLINE • INTRODUCTION • FUNDAMENTALS • PROCESS DESIGN AND OPERATIONS • General Considerations • Production in Nigeria • LOW VOLUME PRODUCTION • CONCLUSIONS

  4. Background; Polymer Production Basics (Worldwide & Nigeria) INTRODUCTION

  5. Powertrain Fuel Tanks HDPE Electrical/Electronics Polyacetal Coatings Body Interior Safety Glass Polyvinylbutyral Body Exterior Impact PP Polymers in our Automobiles

  6. Polymers in our Clothing • Dacron Polyester (PET) (Polyethylene Terephthalate) • Lycra Spandex • Gore-Tex (Polytetrafluoroethylene) • Nylon 66 (HMD/AA) (Hexamethylene diamine/Adipic acid) • Polypropylene (PP)

  7. Polymers in Food Packaging Polyethylene & ethylene copolymers (LDPE, LLDPE, EVA) Polystyrene (PS) Polyethylene Terephthalate (PET) & High-density Polyethylene (HDPE)

  8. HDPE/PP/PVC Nylon/Polyesters PolyTFE ABS/HIPS/PP PS/PC Nylon/ABS Polyformaldehyde Copolymers of Styrene, Methacrylates, Acrylates, Epoxies. Solvent borne, Latex emulsion, Powder coat. (Particle size distribution and particle morphology are critical) ABS/HIPS/PC Polymers in Everyday Life

  9. Polymers in Protective Apparel No melting point; stable beyond 350 C Nomex (Poly-metaphenylene isophthalamide) Liquid Crystal Polymers Kevlar (aromatic nylon) (Poly-paraphenylene terephthalamide)

  10. Worldwide Scale of Polymers: ~ 300 Million tons/yr

  11. Some Polymer Production in Nigeria High Density and Linear Low Density Polyethylene: • Sclairtech (Nova Chem) HDPE/LLPDE (1-butene) 250,000 tons/yr(Port Harcourt) • Methanol to Olefins Project underway to add 400,000 tons/yr of HDPE (Port Harcourt) Polypropylene: • Spheripol (Basell) PP homopolymer/High Impact PP 95,000 tons/yr(Port Harcourt) • Older PP Plant 35,000 tons/yr (Warri) • Methanol to Olefins Project underway to add 400,000 tons/yrof PP (Port Harcourt) Bottle Grade Polyethylene Terephthalate (PET): • Buehler Two Stage Solid State Process 75,000 tons/yr (Port Harcourt) _________________________ Business Monitor International (Jan 2013) Special Chem Industry News (July 2012)

  12. Annual Cost of Polymer Imports to Nigeria in 2010 High Density Polyethylene (HDPE)*: $85 Million Low Density Polyethylenes (LDPE/LLDPE)*: $376 Million Other Polyethylene*: $38 Million Polypropylene (PP, all types)*: $150 Million Polyethylene Terephthalate (PET)*: $45 Million Polyvinyl Chloride (PVC)*: $125 Million Polystyrene (PS, EPS)*: $13 Million All Imports of Synthetic Polymers~ $1 Billion/yr _________________________ *United Nations Commodity Trade Statistics

  13. Separation Purification Cracking Catalytic Conversion Purification Methanol to Olefins Dr.K.R.Krishnamurthy (2009)

  14. Ethylene and Propylene Production

  15. Project Currently underway in Nigeria Dr.K.R.Krishnamurthy (2009)

  16. Zeolite Catalysts for Olefins from Methanol For Ethylene For High Propylene yield

  17. Polymerization Kinetics and Mechanisms FUNDAMENTALS

  18. Fundamental Kinetic Mechanisms Polycondensation Addition Polymerization Chain Terminated Living Catalyzed Uncatalyzed Ionic/Group Transfer Living Free Radical Trans Metal Catalysis Ionic Free Radical Trans Metal Catal Polymerization Kinetics

  19. Initiation • P D k k / k n f n r d • I ßR k • i • + R M P 1 + C Termination (incl. chain transfer) + A Propagation Transfer to dormant state k pij • • Pi + Pj Mj n n +1 + • • T + P D P n 1 n / Dn+Dm k k tc tf D • • + P n+m P n m H H H H H H • X& Y are functional groups with specific properties • Monomer addition at each step is statistical based on kpij and M1/M2 ratio • The chain length is also statistical depending on relative rates of initiation, propagation, and termination C C C C C C H H H X Y Y • CH CH CH CH 2 2 X Y Addition Polymerization Kinetics or

  20. Number average = Mn Viscosity average Weight average= Mw Polymer mass Molecular Weight Distributions Polydispersity: Mw/Mn=2 - 20 for commodities; as low as 1.1 for some specialities For “narrow” distribution of Mw/Mn=2, σ= Mn !! Chain length Molecular weight MWD’s are usually very Broad!

  21. Sequence Length Distributions (% 1’s, 2’s, 3’s, ... in a row for each monomer): • controls crystal structure and total crystallinity • controls chain stiffness • related to material strength, elasticity, etc. • controls side chain functionality for surface properties, cross-linking, etc. Composition Distribution (% of each Monomerin each Polymer chain) Random (most common) Alternating Block Graft Syndiotactic, Isotactic, or Atactic addition is equivalent to having different comonomers! Distributions with Multiple Monomers

  22. Key to control of Polyethylene properties --> Branching Ethylene Unbranched Polyethylene (rare) Short-chain Branched PE Short and Long-chain Branched PE HDPE & LLDPE LDPE • For high pressure LDPE, short and long-chain branches are formed naturally and are controlled by reaction conditions (temperature and pressure). • For HDPE and LLDPE, short-chain branches are formed by copolymerization with α-olefins such as butene, hexene, or octene. No long-chain branching occurs except with special catalysts allowing polymer chains to be inserted.

  23. Examples: Distributions: • Short chains per 1000 C • Branch sequence - long runs vs short runs - concentrated in long chains vs short chains • Long chains per 1000 C • Morphology of Long chains: - generations - gel formation Linear molecule ca. 4 to 10 short side chains per 1000 C - atoms Both short and long-chain branching Linear Low-Density Polyethylene - LLDPE Linear molecule ca. 10 to 35 short side chains per 1000 C – atoms With Special Catalysts Branching Distributions High-Density Polyethylene HDPE Very High Pressure Low-Density Polyethylene LDPE

  24. Why be interested in crystallinity effects? Monomer swells amorphous polymer, not crystals Crystallites act like “tie” segments in polymer networks Polymer properties depend on crystal and tie molecule size distributions Short Chain Branching influences degree of Crystallinity in Semi-Crystalline Polymers S S S S S S S S S S S S S S S S S S S S S S

  25. Branched 106 Linear Viscosity (Poise) 104 102 10-2 100 102 104 Shear Rate γ (Sec-1) Effect of Long-Chain Branches on Polymer Viscosity Alteration of viscosity-shear rate behavior due to the presence of long branches.

  26. General Considerations; Polymer Production in Nigeria PROCESS DESIGN & OPERATIONS

  27. Making polymers at low cost and in quantity – polymerization process issues • Batch, semi-batch orcontinuous process? • In solution/melt or multiphase suspension, emulsion, or dispersion? • Can we scale-up (heat removal, mixing, mass transfer) to produce the polymer we made in the lab? • Can we control the process in order to obtain reproducible quality? • Will the costs of production be low enough? • More than 85% of all polymer production is by Exothermic Addition Polymerization! Can we control the reactor temperature and prevent process runaway? • Will the process be safe and friendly to the environment?

  28. Thermal Parameters for Addition Polymerization Dynamics Heat of Pure Mon Adiab. Heat Removal Poly Conc Temp Rise Duty Monomer Kcal /Mol mol/lit C Kcal /Kg Ethylene 25.9 14.2 1609 922 Propylene 20.1 12.3 850 476 1-Butene 19.9 10.6 647 355 Isobutylene 11.5 10.6 395 204 1,3-Butadiene 17.4 11.5 589 322 Isoprene 17.9 10.0 496 263 Styrene 17.4 8.7 398 167 alpha- Methylstyrene 8.4 7.7 173 71 Vinyl chloride 17.2 14.6 803 275 Vinylidene chloride 17.4 12.5 655 180 Tetrafluoroethylene 38.9 15.2 1447 390 Acrylic Acid 16.0 14.6 464 222 Acrylonitrile 18.3 15.2 774 344 Maleic Anhydride 14.1 15.3 491 144 Vinyl acetate 21.0 10.8 519 244 Methyl acrylate 18.6 11.1 452 216 Methyl methacrylate 13.4 9.4 260 134 Methacrylic acid 18.6 11.8 488 216 Butyl acrylate 18.6 7.0 310 145 A Major Design and Control Problem!

  29. To recycle Product Catalyst TC Polymerization Reactors • Features • Single phase Solution (liquid or supercritical fluid) • Multiphase with particle in liquid or gas dispersion • Heat removal by wall cooling, recycle cooling or • evaporative cooling CW Monomer Hydrogen Polymer

  30. Some Polymer Production in Nigeria High Density and Linear Low Density Polyethylene: • Sclairtech (Nova Chem) HDPE/LLPDE (1-butene) 250,000 tons/yr(Port Harcourt) • Methanol to Olefins Project underway to add 400,000 tons/yr of HDPE (Port Harcourt) Polypropylene: • Spheripol (Basell) PP homopolymer/High Impact PP 95,000 tons/yr(Port Harcourt) • Older PP Plant 35,000 tons/yr (Warri) • Methanol to Olefins Project underway to add 400,000 tons/yrof PP (Port Harcourt) Bottle Grade Polyethylene Terephthalate (PET): • Buehler Two Stage Solid State Process 75,000 tons/yr (Port Harcourt) _________________________ Business Monitor International (Jan 2013) Special Chem Industry News (July 2012)

  31. Dupont/Nova Sclairtech HDPE/LLDPE Solution Process(Polyethylene Process used at Port Harcourt Plant) Flexible process: products range from clear film (ρ=0.91) to bottles (ρ=0.96) (1-Butene or 1-Octene) (Transition Metal) (Cyclohexane) Reactor Adiabatic to 300 C, 140 bar. Res time ~ 30 min 1 or 2 Reactors Meyers, R.A. “Handbook of Petrochemical Production Processes” Soares, J.B.P. & T.F.L. McKenna “Polyolefin Reaction Engineering”

  32. Dupont/Nova Sclairtech HDPE/LLDPE Solution ProcessSome Possible Products MolWt (chain length)-> VLDPE LLDPE HDPE (Crystallinity)

  33. OTHER POLYETHYLENE PROCESSES

  34. LDPE AUTOCLAVE REACTOR Monomer • Adiabatic reactor • 190 to 270 °C • 2000 to 3000 bar (supercritical fluid) • 10 to 20 % conversion • DuPont type (L/D = 2 - 4) • 10 to 120 sec residence time • Reactor temperature is controlled by the amount of initiator in the feed Initiator T TC Products

  35. POLYMERIZATION vs DECOMPOSITION 10+06 Decompositionvs Polymerization • Heat of Rxn 40% larger • ActivationEnergy 900% larger • Runaway starts at T ~ 300C with fast reaction w/o initiator 10+04 Decomposition of Ethylene 10+02 1 Reaction Rate, mol/lt-sec 10-02 Polymerization 10-04 10-06 10-08 110 190 270 350 430 510 Temperature, °C

  36. CONTINUATION AND STABILITY DIAGRAMEFFECT OF RESIDENCE TIME ON TEMPERATURE - PERFECT MIXING MODEL 3000 STABLE It would be practically impossible to operate a reactor with this small operating window, and yet these reactors actually operate! ?? 1000 Temperature, °C UNSTABLE 300 STABLE UNSTABLE STABLE 100 0 100 200 300 400 500 Residence Time, sec

  37. Simple compartment models are adequate to explain curves of initiator consumption in LDPE autoclave reactors (Marini and Georgakis, 1984) Experiments show that changing feed location, velocity, or agitator design will strongly affect initiator efficiency! 0.10 0.09 van der Molen et al. (1982) 0.08 Imperfect Mixing Initiator Consumption, g/kg polymer 0.07 0.06 Perfect Mixing 0.05 IMPERFECT MIXING 200 220 240 260 280 300 Temperature, °C Evidence of Imperfect Feed Mixing Carlos Villa

  38. QR = RQO QF QR I III II QO MIXING INTENSITY = RECYCLE RATIOEFFECT OF RESIDENCE TIME ON TEMPERATURE - IMPERFECT MIXING MODEL 300 100 500 50 R = 10 250 Good reactor design involves understanding and controlling the degree of imperfect mixing 200 Temperature, °C 150 100 50 150 250 350 450 Residence Time, sec

  39. 3.41 55.4 1.71 27.6 0.00 0.00 Ncompart CFD results Stable Unstable Limit point Computational Fluid Mechanics (CFD) combined with Compartment Models allow detailed information decomp active (shaded region) Contours of Radical Conc. x 107mol/L 580 Temp. rise: 0.65 K/ppm C A B out 540 in 500 Exit Temperature (K) 300 ppm TBPOA feed Temp. rise: 4.67 K/ppm out 460 A: 1 B: 3 C: 100 420 in 400 0 200 600 30 ppm TBPOA feed Initiator Feed Fraction (ppm) • Decomp active at temperatures above about 560 K; modeled using approach of Zhang et al. (1996) Tfeed = 360 K (87 °C); 200 rpm stirring rate; t = 32 sec

  40. Title Decomp Safety Equipment Ethylene & Molten Polymer Vented to the Neighborhood  LDPE Reactor Emergency Relief Valves Emergency Relief Valves

  41. Consequences of LDPE Decomp • Burnt and molten polymer rains down on the surrounding area, leading to possible difficulties inside the plant, but also coats the employees cars in the parking lot, and dumps material on neighbors • A large ethylene cloud on a windless day could be ignited by flames from other equipment inside the plant or on neighboring properties.In this case the explosion can damage other equipment leading to leaks that can ignite and cause a fire or the release of toxic chemicals. • If the ethylene cloud moves safely away from the plant to an open area, it can be ignited with a flare.

  42. Heterogeneous Catalytic Processes for Polyolefins

  43. Fluidized Bed Reactors (Union Carbide (now Univation), BP, and in-house technology) -the most widely used process for making catalytic polyethylene products (high density (HDPE) and linear low density (LLDPE) Polyethylene)

  44. Macroscale Purge Cooler Emulsion Phase Catalyst Cocatalyst Bubble Phase Poison Product Hydrogen Monomers Gas Phase Fluidized Bed Polyethylene Process Microscale kpij Pkn,i* + Mj Pkn+1,j* (Growth of a polymer chain) Mesoscale C2H4 The particle size distribution (PSD) depends on: • the PSD of the original catalyst support, • the catalyst activity kinetics, • the residence time distribution of the reactor The particle is the micro-reactor inside the fluidized bed which is the macro-environment. Catalyst Polymer Particle Inlet Stream

  45. 108 g/g-cat 12 g/g-cat 880 g/g-cat Kakugo, M., H. Sadatoshi, & J. Sakai, Catalytic Olefin Polymerization, T. Keii & K. Soga,Editors; Elsevier (1990), pp 345-354 Chakraborti, S.,A.K. Datye, & N. J. Long, J. Catalysis,108, p 444 (1987) Heterogeneous Catalytic Olefin Polymerization Breakup of catalyst and growth of polymer particle (TEM showing catalyst fragments inside polymer microparticles) Metal catalyst (TiCl4, Cr, Zr, etc) supported on SiO2 30 nm

  46. Comonomer Comonomer Multistage Fluidized Bed Polyethylene Process

  47. Particle Growth Behavior Surface area 9 4 1 (g pol/g cat)

  48. Fluidized Bed Particle Temperatures Melted Quasi-steady state particle temperature, fully activated Temperature difference DT [C] Dynamic particle temperature Direct injection, fast activation 15C temp rise Prepolymerization or slow activation dpmin dcat Particle diameter dP [mm] Sticky particles adhere to the reactor wall and attract more particles. After some buildup, the polymer sheets on the wall fall down and disrupt the fluidization, causing the entire polymer bed to melt.

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