Fouling in the High Pressure LDPE Process

Transcription

1 Engineering Conferences International ECI Digital Archives Polymer Reaction Engineering IX Proceedings Spring Fouling in the High Pressure LDPE Process Sebastian Fries Technische Universität Darmstadt, Germany Markus Busch Technische Universität Darmstadt, Germany Diego Mauricio Castañeda-Zúñiga Saudi Basic Industries Corporation, The Netherlands Jan Duchateau Saudi Basic Industries Corporation, The Netherlands Peter Neteboom Saudi Basic Industries Corporation, The Netherlands See next page for additional authors Follow this and additional works at: Recommended Citation Sebastian Fries, Markus Busch, Diego Mauricio Castañeda-Zúñiga, Jan Duchateau, Peter Neteboom, and Carolina Toloza Porras, "Fouling in the High Pressure LDPE Process" in "Polymer Reaction Engineering IX", E. Vivaldo-Lima, UNAM; J. Debling, BASF; F. Zaldo-Garcia, CP-COMEX; J. Tsavalas, Univ. of New Hampshire Eds, ECI Symposium Series, (2015). polymer_rx_eng_ix/4 This Conference Proceeding is brought to you for free and open access by the Proceedings at ECI Digital Archives. It has been accepted for inclusion in Polymer Reaction Engineering IX by an authorized administrator of ECI Digital Archives. For more information, please contact

2 Authors Sebastian Fries, Markus Busch, Diego Mauricio Castañeda-Zúñiga, Jan Duchateau, Peter Neteboom, and Carolina Toloza Porras This conference proceeding is available at ECI Digital Archives:

3 Fouling in the High Pressure LDPE Process Experimental and Computational Investigation Approach Sebastian Fries, Markus Busch Technische Universität Darmstadt, Germany Diego Mauricio Castañeda-Zúñiga, Jan Duchateau, Peter Neuteboom, Carolina Toloza Porras Saudi Basic Industries Corporation, The Netherlands Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 1

4 What is LDPE Fouling? low-density polyethylene (LDPE) is produced under high temperatures (140 C 330 C) and pressures (1000 bar 3500 bar) fouling mechanisms still not understood fouling impacts: insulating effect MWD tailing productivity operating safety product quality Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 2

5 Investigation Strategy validation modeling 1D model experiments radial model prediction compartment model understanding fouling formation application of countermeasures Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 3

6 Experiments: Preliminary Considerations MWD tailing pronounced at higher surface-to-volume ratios and even existent at technical scales fouling formation within the laminar boundary layer reasonable idea: lab-scale reactor with as much laminar flow as possible 100 ml autoclave 15 ml autoclave pilot scale tubular reactor w log M w log M M / (g mol -1 ) M / (g mol -1 ) Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 4

7 Experiments: Setup combined autoclave and tubular reactor setup autoclave 100 ml premixing, preheating p = 2000 bar tubular reactor laminar flow heated L = 2 m, d = 4.8 mm ~ 30 sec residence time Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 5

8 Experiments: Results w log M sample 01 IR sample 02 IR sample 03 IR sample 04 IR sample 01 LS sample 02 LS sample 03 LS sample 04 LS fouling material strongly branched indication for polymerrich environment time evolution M / (g mol -1 ) pronounced MWD tailing with increasing running time intrinsic viscosity (ml/g) a = 0.67 d f = 1.80 sample 04 linear reference M / (g mol -1 ) a = 0.13 d f = Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 6

9 Modeling: Model Family 1D module radial module compartment module plug flow (ODEs) complex reaction network with primary and secondary radicals rigorous MWD radial profiles (PDEs) laminar velocity profile wall temperature from 1D module (boundary condition) simplified kinetic scheme two ideally mixed compartments for center and wall layer (ODEs) temperatures and velocities from radial module rigorous MWD Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 7

10 Modeling: Model Family 1D module radial module compartment module in increasing information about polymeric microstructure near the wall Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 8

11 Modeling: 1D Module w log M simulation experiment IR experiment LS slow heating due to laminar flow M / (g mol -1 ) T / C satisfying agreement of modeled distribution with main MWD L / m reactor jacket Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 9

12 Modeling: Radial Module r / mm r / mm L / m 2 1 temperature contour plot faster heat transport in the outer area M n contour plot L / m T / C slightly lower M n at the wall more transfer to CTA M n / (g mol -1 ) Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 10

13 Modeling: Radial Module r / mm X / % D polymer = D monomer X wall = 5.4% X avg = 2.7% r / mm X / % D polymer = 1/10 D monomer X wall = 11.9% X avg = 1.9% r / mm L / m X / % D polymer = 1/20 D monomer X wall = 15.7% X avg = 1.8% Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 11

14 Modeling: Radial Module 1x10-3 D polymer = 1/10 D monomer 0.20 predicted flow ideal laminar flow η / Pas 8x10-4 6x10-4 4x10-4 w / (m s -1 ) x r / mm 0.05 L = 2 m D polymer = 1/10 D monomer r / mm viscosity gradient influences velocity profile description via Stokes law possible Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 12

15 Modeling: Radial Module higher friction leads to lower wall speeds fouling as a self-acclerating process as proposed by Krasnyk et al. implementation in radial module follows higher viscosity higher polymer concentration lower flow speed higher residence time higher conversion M. Krasnyk et al. Proceedings of the 22nd ESCAPE Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 13

16 Modeling: Compartment Module D polymer = D monomer ṁ shell = 1/100 ṁ total compartment module 1D module experiment IR significant broadening even for fast diffusing polymer same prediction as radial w log M module regarding M n core shell M / (g mol -1 ) M n (kg/mol) M w (kg/mol) M n (kg/mol) M w (kg/mol) Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 14

17 Summary generating of tailed distributions with the chosen experimental setup possible fouling material highly branched model family delivers coherent results polymer diffusion speed crucial for buildup of higher polymer concentrations close to the wall indication that fouling is the result of a self-accelerating process; effects are to be investigated Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 15

18 Acknowledgements Computing in Technology GmbH, Rastede, Germany Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 16

19 Fouling in the High Pressure LDPE Process Experimental and Computational Investigation Approach Sebastian Fries, Markus Busch Technische Universität Darmstadt, Germany Diego Mauricio Castañeda-Zúñiga, Jan Duchateau, Peter Neuteboom, Carolina Toloza Porras Saudi Basic Industries Corporation, Netherlands Technische Universität Darmstadt Sebastian Fries Polymer Reaction Engineering IX 17