Particle Lagrangian CFD Simulation and Experimental Characterization of the Rounding of Polymer Particles in a Downer Reactor with Direct Heating
Abstract
:1. Introduction
2. Materials and Methods
2.1. Rounding Setup
2.2. Particle Characterization
2.2.1. Scanning Electron Microscopy
2.2.2. Particle Sizing
2.2.3. Light Microscopy
2.3. Mathematical Model
2.3.1. Governing Equations
2.3.2. Computational Domain and Meshing
2.3.3. Boundary Conditions and Material Properties
2.3.4. Numerical Solution
2.3.5. Post-Processing of the Particle Tracks
3. Results and Discussion
3.1. Effect of the Process Parameters on the Radial Solids Concentration in the Downer
3.2. Influence of Process Parameters on the Particle Residence Time
3.3. Influence of Process Parameters on Temperature Distribution and Effective Rounding Time
3.4. Effect of the Effective Rounding Time on Powder Properties
4. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Appendix A. Governing Equations
Gas phase (Continuous phase) |
Mass conservation equation |
Momentum conservation equation |
Turbulent kinetic energy |
Production of k due to buoyancy |
Dissipation rate equation of turbulent energy |
Viscous stress tensor equation |
Turbulent stress tensor equation |
Eddy viscosity equation |
with |
and |
Strain-rate tensor |
Deviatory part of the strain-rate tensor |
Rate of rotation tensor |
Realizable k-ε model constants |
Instantaneous gas velocity |
Velocity fluctuation |
Characteristic lifetime of eddy |
Eddy length scale |
Energy equation |
Total energy equation |
Sensible enthalpy |
Effective thermal conductivity |
Turbulent thermal conductivity |
Heat source term |
Solid phase (disperse phase) |
Particle force balance |
Drag force per unit particle mass |
Particle Reynolds number |
Drag coefficient |
Energy balance |
Heat transfer coefficient |
Particle crossing time |
Particle relaxation time |
Interaction time of particle with eddy |
Coupling between discrete and continuous phases at each control volume (CV) |
Momentum exchange |
Heat exchange |
Appendix B. Additional Experimental and Simulation Setup
Appendix B.1. Mesh Independeny Study
Appendix B.2. Setup for Temperature Measurements and Determination of Heat Fluxes through the Reactor Wall
Appendix B.3. Determination of the Residence Time Distribution of Aerosol Gas in the Downer
Appendix B.3.1. Measurement Setup
Appendix B.3.2. Simulation of the Residence Time Distribution of the Aerosol Gas
Appendix B.4. Validation Results
Appendix B.4.1 Axial Temperature Profiles (Figure A5)
Appendix B.4.2. Residence Time Distribution of Aerosol Gas (Figure A6)
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Property | Value | Reference |
---|---|---|
Solid density | 907 kg/m3 | [31] |
Powder loose Packing density | 332.1 kg/m3 | [31] |
Sauter diameter | 87.8 µm | [31] |
Flow function ffc @1300 Pa consolidation | 1.39 ± 0.04 | [31] |
Melting temperature (melting peak) | 167.4 °C | [31] |
Melting onset | 159 °C | [31] |
Specific surface area | 0.40 m2/g | [31] |
Heat conductivity | 0.22 W/K∙m | [32] |
Specific heat capacity | 1.7 J/g∙K | [32] |
Parameter Set | Mass Flow Sheath Gas ṁsheath/kg/h | Set Temperature Sheath Gas Tsheath,set/°C | Mass Flow Aerosol Gas ṁaerosol/kg/h | Powder Mass Flow ṁparticles/kg/h | Averaged Solid Volume Fraction at Aerosol Inlet (1 − ε)av,aer/− |
---|---|---|---|---|---|
Variation of Tsheath,set | |||||
1 | 8.9 | 240 | 1.35 | 0.24 | 1.79 × 10−4 |
2 | 8.9 | 260 | 1.35 | 0.24 | 1.69 × 10−4 |
3 | 8.9 | 280 | 1.35 | 0.24 | 1.70 × 10−4 |
Variation of ṁparticles | |||||
1 | 8.9 | 240 | 1.35 | 0.24 | 1.79 × 10−4 |
4 | 8.9 | 240 | 1.35 | 0.46 | 3.42 × 10−4 |
5 | 8.9 | 240 | 1.35 | 0.69 | 5.41 × 10−4 |
Variation of ṁsheath | |||||
6 | 5 | 240 | 1.35 | 0.24 | 1.77 × 10−4 |
1 | 8.9 | 240 | 1.35 | 0.24 | 1.79 × 10−4 |
7 | 10.7 | 240 | 1.35 | 0.24 | 1.78 × 10−4 |
Variation of ṁaerosol | |||||
1 | 8.9 | 240 | 1.35 | 0.24 | 1.79 × 10−4 |
8 | 8.9 | 240 | 2.28 | 0.24 | 1.14 × 10−4 |
9 | 8.9 | 240 | 2.91 | 0.24 | 9.24 × 10−5 |
Parameter Set | Mean Velocity Sheath Gas/m/s | Measured Temperature Sheath Gas/°C | Mean Velocity Aerosol Gas/m/s | Measured Temperature Aerosol Gas/°C |
---|---|---|---|---|
1 | 0.39 | 210.8 | 1.57 | 96.4 |
2 | 0.40 | 227 | 1.65 | 116.2 |
3 | 0.41 | 244 | 1.65 | 114.8 |
4 | 0.39 | 210.8 | 1.57 | 96.4 |
5 | 0.39 | 210.8 | 1.57 | 96.4 |
6 | 0.21 | 187 | 1.58 | 99.7 |
7 | 0.47 | 215.8 | 1.57 | 96.9 |
8 | 0.39 | 210.8 | 2.47 | 71.0 |
9 | 0.39 | 210.8 | 3.04 | 59.0 |
Simulation Case | Mean Residence Time t50/s | Standard Deviation σ/s | Skewness/- |
---|---|---|---|
Variation of Tsheath,set | |||
240 °C | 1.02 | 0.31 | 0.11 |
260 °C | 1.00 | 0.31 | 0.12 |
280 °C | 1.04 | 0.32 | 0.12 |
Variation of ṁparticles | |||
0.24 kg/h | 1.02 | 0.31 | 0.11 |
0.46 kg/h | 0.94 | 0.31 | 0.16 |
0.69 kg/h | 0.89 | 0.31 | 0.21 |
Variation of ṁsheath | |||
5 kg/h | 1.40 | 0.61 | 0.42 |
8.9 kg/h | 1.02 | 0.31 | 0.11 |
10.7 kg/h | 0.93 | 0.25 | 0.08 |
Variation of ṁaerosol | |||
1.35 kg/h | 1.02 | 0.31 | 0.11 |
2.28 kg/h | 0.86 | 0.69 | 0.48 |
2.91 kg/h | 0.76 | 0.71 | 0.51 |
Simulation Case | Median Effective Rounding Time tr,50/s | 99th Percentile of the Effective Rounding Time tr,99/s |
---|---|---|
Variation of Tsheath,set | ||
240 °C | 0.62 | 1.46 |
260 °C | 0.75 | 1.52 |
280 °C | 0.80 | 1.64 |
Variation of ṁparticles | ||
0.24 kg/h | 0.62 | 1.46 |
0.46 kg/h | 0.37 | 0.84 |
0.69 kg/h | 0.22 | 0.58 |
Variation of ṁsheath | ||
5 kg/h | 0 | 0.02 |
8.9 kg/h | 0.61 | 1.46 |
10.7 kg/h | 0.66 | 1.33 |
Variation of ṁaerosol | ||
1.35 kg/h | 0.62 | 1.46 |
2.28 kg/h | 0 | 0.28 |
2.91 kg/h | 0 | 0.18 |
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Gómez Bonilla, J.S.; Unger, L.; Schmidt, J.; Peukert, W.; Bück, A. Particle Lagrangian CFD Simulation and Experimental Characterization of the Rounding of Polymer Particles in a Downer Reactor with Direct Heating. Processes 2021, 9, 916. https://doi.org/10.3390/pr9060916
Gómez Bonilla JS, Unger L, Schmidt J, Peukert W, Bück A. Particle Lagrangian CFD Simulation and Experimental Characterization of the Rounding of Polymer Particles in a Downer Reactor with Direct Heating. Processes. 2021; 9(6):916. https://doi.org/10.3390/pr9060916
Chicago/Turabian StyleGómez Bonilla, Juan S., Laura Unger, Jochen Schmidt, Wolfgang Peukert, and Andreas Bück. 2021. "Particle Lagrangian CFD Simulation and Experimental Characterization of the Rounding of Polymer Particles in a Downer Reactor with Direct Heating" Processes 9, no. 6: 916. https://doi.org/10.3390/pr9060916