Coalescence Modelling for Settler Design David Leleu, Andreas - PowerPoint PPT Presentation

Coalescence Modelling for Settler Design David Leleu, Andreas Pfennig dleleu@uliege.be Products, Environment, and Processes (PEPs) Department of Chemical Engineering Université de Liège www.chemeng.uliege.be/Pfennig 1

agenda  motivation  basic understanding  coalescence modelling  settler simulation 2

gravity settler 3

pilot-plant settler with internals 4

stirring cell 5

settling of dispersion Henschke, 2002 6

stirring-cell experiment 0.18 0.16 stirring cell height in m 0.14 0.12 0.10 0.08 sedimentation curve 0.06 0.04 coalescence curve 0.02 0.00 0 5 10 15 20 25 30 time in s 7

modelling coalescence of drops effect description influenced by frequency at which equipment type, drops meet fluid dynamics, holdup drops bounce at high equipment type, relative velocity fluid dynamics, operating conditions time drops stay in equipment type, contact, t contact fluid dynamics, operating conditions characteristic time material system,  drops need to drop size coalesce, t coalescence 8

settling of dispersion Henschke, 2002 9

close-packed zone  drops deformation  film drainage Arnaud Saint-Jalmes, 2006 10

continuous flow counterflow Δ P hydrodynamic  v εΔ h  Δ P hydrostatic droplets Δ P total = Δ p hydrostatic - Δ P hydrodynamic 11

ReDrop (Representative Drop) simulation definition of the system • material properties • simulation parameters time loop local holdup evaluated for each height element drop loop • drop velocity • update of the vertical position of each drop • coalescence evaluation 12

iso-optical settling experiment 13

experimental measurement of the holdup measured hold up 0.18 1.000 0.16 0.8750 0.14 0.7500 cell height in m 0.12 0.6250 0.10 0.5000 0.08 0.3750 0.06 0.2500 0.04 0.1250 0.02 0.000 0.00 0 10 20 30 40 50 60 time in s 14

settling simulation 180 160 140 cell heigth in mm 120 100 80 60 40 20 0 20 40 60 80 100 120 time in s 15

summary  consistent coalescence model  calibrated setup for model validation  simulation tool based on ReDrop  model able to characterize settling behavior for any system 16

Coalescence Modelling for Settler Design David Leleu, Andreas Pfennig dleleu@uliege.be Products, Environment, and Processes (PEPs) Department of Chemical Engineering Université de Liège www.chemeng.uliege.be/Pfennig 17

coalescence probability: fundamental t coalescence p coalescence,Coulaloglou&Tavlarides = exp − t contact Coulaloglou & Tavlarides, Chem. Eng. Sci., 1977 18

coalescence probability: fundamental p non−coal, nΔt = p non−coal, Δt n p non−coal, Δt = ex p − Δt t contact t coal n= tcontact p non−coal ,nΔt = exp − nΔt Δt t coal ∆t p non−coal = exp − t contact t coal p coal = 1 − exp − t contact t coal 19