Energy absorption during impact of wet particles in the fluidized bed: experiment and DEM simulation Sergiy Antonyuk Institute of Solids Process Engineering and Particle Technology Hamburg University of Technology, Germany Chair of Particle Process Engineering University of Kaiserslautern PIKO Workshop Liquid Energy Bridges absorption Experimental during impact and of simulation wet particles methods Paderborn July 5-6, 204
Particle formulation in fluidized beds exhaust air Agglomeration mechanisms in fludized beds porous structure binder liquid fluidized particles nozzle sprayed droplets primary particle Time liquid bridge solid bridge blackberry-like structure fluidization air Fluidized bed spray agglomeration dried milk agglomerate aerogel agglomerate Energy absorption during impact of wet particles July 5-6, 204 2
Micro mechanisms of agglomeration processes wetting particle-droplet impact spray droplets rebound overspray rebound breakage rupture of the liquid bridge particle collision binder drying agglomeration, sintering Energy absorption during impact of wet particles July 5-6, 204 3
Temperature [ C] Micro mechanisms of wet collision Mechanism I - Softening Force Kraft F in in N [N] 20 80 40 0 glassy: elastic rubbery: vidcoplastic 0 5 0 5 Water content [%wb] Glass transition temperature of maltodextrin DE2 - model material for an amorphous food powder) Dopfer, D., Heinrich, S., Fries, L., Antonyuk, S., Haider, C., Salman, A.D., Palzer, S.: Adhesion mechanisms between water soluble particles, Powder Technology 238 (203), 35-49. Antonyuk, S. (2006) Deformations- und Bruchverhalten von kugelförmigen Granulaten bei Druck- und Stoßbeanspruchung, Dissertation, Docupoint Energy Verlag. absorption during impact of wet particles July 5-6, 204 4 5 4 3 2 dry X W = 0 E diss,dry F v B F E diss,wet Influence of moisture X w on the forcedisplacement behaviour during the compression of a sodium benzoate granule (v = 20 µm/s) F s F wet X W = 0.2 0 0 0. 0, 0,2 0.2 0.3 0,3 0.4 0,4 Weg s in mm Displacement s [mm] s
Micro mechanisms of wet collision Mechanism II Liquid layer at the contact V Liquid shear flow (viscose force) Contact force, formation of a liquid bridge time Rebound: capillary and viscous forces V R > 0 V R =0 rebound V R or agglomeration High speed recording of the wet impact of a glass particle = mpa s, d p =.0 mm, h s = 300 µm, v imp = 0.95 m/s Energy absorption during impact of wet particles July 5-6, 204 5
Important adhesion forces Energy adsorption at static and dynamic loading static F tot = F cap + F tension dynamic F tot = F cap + F tension + F vis F tot / d p 8 6 la d p ) 4 = 0 V l /V s = V l h s d p V s F tot / R p v h s R p velocity ( m/s) 0. 2.5 5 0 2 0 0 0. 0.2 0.3 0.4 0.5 h s /d p h s /d p Schubert (976): static tensile tests the static tension of a liquid bridge between the particle and the wall h s /R p Pitois et al. (2000): liquid bridge apparatus Oil bridge between ruby spheres (8 mm) Simons et al. (2003): micro-force balances device Oil bridge between glass spheres (45 m) Energy absorption during impact of wet particles July 5-6, 204 6
Measurement of the energy adsorption by a wet impact Energy absorption during impact of wet particles July 5-6, 204 7
Measurement of the energy loss Restitution coefficient e = elastic no adhesive 0 < e < elastic-plastic adhesive e = 0 plastic adhesive Energetic restitution coefficient E E v diss E E v kin,r e = = - kin kin R v R /v relative rebound/impact velocity E kin,r elastic rebound energy E kin impact energy E diss irreversible absorbed energy Energy absorption during impact of wet particles July 5-6, 204 8
Measurement of the energy loss Setup for measuring wet restitution coeff. vacuum nozzle E kin,r e = = E kn i v v R f h * ( s,, v,, R ) high-speed camera steel target confocal sensor polymer film v R /v relative rebound/impact velocity E kin,r elastic rebound energy E kin impact energy precisions table Antonyuk, S., Heinrich, S., Deen, N.G. and J.A.M. Kuipers: Influence of liquid layers on energy absorption during particle impact, Particuology 7 (2009). high speed recoding of the normal and oblique impact steel wall Energy absorption during impact of wet particles July 5-6, 204 9
Measurement of the energy loss Setup for measuring wet restitution coeff. vacuum nozzle Particles: -Al 2 O 3 high-speed camera steel target precisions table confocal sensor polymer film Property Value Diameter [mm].75 0.05 Density [kg/m 3 ] 040 E-Modulus [kn/mm 2 ] 4.62 0.3 Liquid: water solutions of hydroxypropyl methylcellulose (0 0 mass - %) Objectives of the study: Antonyuk, S., Heinrich, S., Deen, N.G. and J.A.M. Kuipers: Influence of liquid layers on energy absorption during particle impact, Particuology 7 (2009). Influence factor Range Viscosity [mpa s] 300 Thickness h s [ m] 00 000 Impact velocities v [m/s] 0.3-3.0 Energy absorption during impact of wet particles July 5-6, 204 0
Measurement of the energy loss Influence of viscosity and thickness h S restitution coefficient en 0.8 0.6 0.4 0.2 0 e n (h s = 0) viscosity in mpa. s: 0 200 400 600 800 000 layer thickness h s in m.0 4.5 5.0 50.0 sticking e n (h s,st ) = 0 en 0.75 0.5 0.25 0 h St e n 0.0 00 in mpa s 0.75 0.5 0.25 0 hst in mm Parameters -Al 2 O 3 granules d 50 =.75 mm impacted on the flat steel wall of experiments: v imp = 2.4 ± 0.2 m/s Sticking takes place at a minimum layer thickness h st = f (, v) Energy absorption during impact of wet particles July 5-6, 204
Measurement of the energy loss Sticking layer thickness & sticking velocity Sticking layer thickness h st [µm] Images from high-speed recording mm real time in ms: 000 0 4.5 0.8 23.5 750 500 sticking s Viscosity in mpa s 22 62 Sticking conditions: Impact velocity: v v st Liquid layer thickness: h s h st 250 Viscosity st 0 0.5.5 2 2.5 3 Sticking velocity v st [m/s] Energy absorption during impact of wet particles July 5-6, 204 2
Modeling of the wet collision mm real time in ms: 0 0.38.3.88 2.38 3.3 4.50 4.88 I. Penetration of particle into liquid layer II. Contact with the wall (loading-unloading) III. Emergence of particle IV. Formation and rupture of the liquid bridge Energy absorption during impact of wet particles July 5-6, 204 3
Modeling of the wet collision Force and energy balances m p Force dx 2 dt 2 n Fi surface tension i Model Ftx, dp sin sin( ) la E E E F E kin,imp kin,r abs abs mgh,br x capillary force contact force viscous force buoyancy force F 2 F E R x m k x 3 F 2 2 cap la p R R2 * * 3 * / 4 c c d el c vis R sin 2 6 Rp dx h x dt s 2 2 Fb x (3 Rp x ) l g 6 dx dt c S. Antonyuk et al. Influence of liquid layers on energy absorption during particle impact, Particuology 7 (2009), 245-259. Energy absorption during impact of wet particles July 5-6, 204 4
Modeling of the wet collision Force and energy balances energy in J restitution coefficient en 0.8 0.6 0.4 0.2 0 simulation experiment 0 200 400 600 800 layer thickness h s in m 0 0. 0.0 E dis,tot h s,st E kin =00% E vis =67 % E c =28 % E t +E cap = 4% E mgh =% sticking 00 300 500 700 layer thickness h s in m Calculation for an impact velocity 2.36 m/s and viscosity 4.5 mpa s Contributions of viscous (E vis ) and contact forces (E c ) to energy dissipation (E diss ) are of great importance. The other forces are significant only at small impact velocities. Energy absorption during impact of wet particles July 5-6, 204 5
Modeling of the wet collision Simulation via VOF-IB methods Simulation of particle impact on thin liquid films using Experiment (high speed recording) Siumation with a combined Volume-of-Fluid and Immersed Boundary Method (Cooperation with Prof. J.A.M. Kuipers (Eindhoven University of Technology) Jain, D., Deen, N., Kuipers, J.A.M., Antonyuk, S. and S. Heinrich: Direct numerical simulation of particle impact on thin liquid films using a combined volume of fluid and immersed boundary method, Chemical Engineering Science 69 (202), 530-540.Particle Impact on Thin Liquid Films Using VOF & IB Method Energy absorption during impact of wet particles July 5-6, 204 6
Basic model parameters Restitution coefficient of particles by wet impact Restitution coefficient en 0.8 0.7 0.6 CFD model vel=.0 vel=2.36 Antonyuk model vel=.0 vel=2.36 Experimental vel=.0 vel=2.36 0.5 0.4 0.3 0.2 0. 0.0 0 200 400 600 800 000 Layer Thickness (µm) Jain, D., Deen, N., Kuipers, J.A.M., Antonyuk, S. and S. Heinrich: Direct numerical simulation of particle impact on thin liquid films using a combined volume of fluid and immersed boundary method, Chemical Engineering Science 69 (202), 530-540.Particle Impact on Thin Liquid Films Using VOF & IB Method Energy absorption during impact of wet particles July 5-6, 204 7
Important adhesion forces Predominant force between wet particles Flow stress Str* [-] 0 3 0 2 0 Region I Capillary number (Saffman Taylor): viscous force Ca tension force v imp liquid viscosity v imp impact velocity la surface tension of the liquid wetting angle Region II la Ca < 0-4 F cap > F vis Ca 0-4 F cap << F vis F cap > F vis F cap << F vis 0-0 0-4 Ca [-] * Iveson, S.M., Beathe, J.A., Page, N.W. The dynamic strength of partially saturated powder compacts: the effect of liquid properties. Powder Technology 27 (2002), 49-6. Energy absorption during impact of wet particles July 5-6, 204 8
Interactions stress conditions in fluidized beds Motivation Which adhesion mechanisms is dominant in the fluidized bed? Method Simulation of the particle dynamics in the fluidized bed apparatus with coupled DEM-CFD method particle-wall Interactions impact forces Stress conditions droplet-wall particle-particle-droplet gas-particle/droplet adhesion (viscous, capillary, solid bridge etc.) field (gravitation etc.) drag F d, flow pressure F p p Example of a DEM-CFD simulation of a spouted bed apparatus: Salikov, V., Antonyuk, S., Heinrich, S., Sutkar, V.S., Deen, N.G. and J.A.M. Kuipers. Characterisation of flow regimes and CFD-DEM modelling of a novel prismatic spouted bed, Powder Technology in Press. Energy absorption during impact of wet particles July 5-6, 204 9
Coupling Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD) Particle Description via Newtonian/Euler motion equations: z F d Translation dvp n mp Fp, i F g + F Fa +Fd F.. F dt i c p n v y, p y w p v p F c F g Rotation dw p I p = k Mp,j dt j= F c v n v t w p x v x, p z v z, p z y F p, M p v p, w p M p, I p Force and torque acting on a particle Translational and angular velocity mass and mass moment of inertia of a particle F a Fluid CFD: Description via volumeaveraged Navier-Stokes equations Energy absorption during impact of wet particles July 5-6, 204 20
Important adhesion forces Absolute relative velocities in fluidized beds Wurster-Coater Rotor granulator Spouted bed granulator Kinematic parameters Identical parameters for three granulators: Wurster coater Rotor granulator air flow = 360 m³/hr, total mass = 0.94 kg (50.000 particles), d p = 2 mm Spouted bed Average particle velocity [m/s] 0.47 0.59 0.6 Average collision particle velocity [m/s] 0.3 0.044 0. Fries L., Antonyuk, S., Heinrich, S., Dopfer, D., Palzer, S.: Collision dynamics in fluidized bed granulators: A DEM- CFD study, Chemical Engineering Science 86 (203), 08-23. Energy absorption during impact of wet particles July 5-6, 204 2
Important adhesion forces What is the predominant force? Cumulative distribution P(Ca) [-] P(Ca) [- ] P(v) [-] Typical distributions relation of Ca-Number of particle and & Impact impact velocity for in fluidized bed granulators 0.8 0,8 0.6 0,6 0.4 0,4 particle impact velocity v imp Ca >> 0-4 Capillary forces are negligible in comparison with viscous forces 0.20,2 0 particle velocity v p 0 0,000 0,00 0,0 0 0.5 0, 0.5 Geschwindigkeit velocity v [m/s] Ca-Number [-] v [m/s] The relative impact velocity are much smaller than absolute particle velocity Energy absorption during impact of wet particles July 5-6, 204 22
Cumulative distribution P( ) [-] P( ), [- ] Important adhesion forces Impact angle of particles in fluidized bed 0.8 particle-particle particle-wall 0.6 0.4 0.2 0 0 30 60 90 Impact angle [deg] steel wall High speed recording of wet impact = 2 mpa s d p =.75 mm v imp = 0.95 m/s imp = 30 Antonyuk S., Heinrich, S., Smirnova, I.: DEM study of particle dynamics in a spouted bed apparatus, Chem. Eng. Technol. 35 (202) 8. Energy absorption during impact of wet particles July 5-6, 204 23
Conclusions Measurements of restitution coefficient: Influence of the layer viscosity and thickness, impact velocity on the energy absorption by impact. Obtained sticking condition can be used in the DEM. DPM study of different granulators: small impact velocities and dominantly oblique impacts of particles: Contribution of viscous forces to energy dissipation is dominant Tangential force (tangential restitution coefficient!) became dominant Contact model with viscous forces. Energy absorption during impact of wet particles July 5-6, 204 24
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