Investigation of 2-phase evaporative reacting flows in micro-scale

2016 ANSYS Convergence Conference
30 June, Electra Palace Hotel, Athens, Greece
ANSYS Hall of Fame 2016 Competition Winner - Academic:
Investigation of 2-phase evaporative reacting flows in micro-scale
Dr. Nikolaos Nikolopoulos, PhD cand. Ilias Malgarinos, and Prof.
Manolis Gavaises

http://www.ansys.com/Other/Hall-of-Fame/CUL

Presentation Outline
Activities Ideas Possibilities
Current Activities
 Droplet Dynamics
 Fluidized Beds
Ideas (Prospects)
 CFD application prospects in FCC industry
Ideas for collaboration
Ansys Convergence 2016, Slovenia

Droplet Dynamics
Drop-gas Solid Surface Phase Change Reactions+ + +
Validated 2-phase flow model VOF in wide range of cases

Model Features
 Navier-Stokes Momentum-Continuity
 Volume of Fluid Method (VOF) for interphase tracking
 Phase change Evaporation Model
Drop motion
 Dynamic local refinement
Droplet Dynamics
 Surface Reactions

Application in FCC industry
FCC (Fluid Catalytic Cracking), from large scale to micro scale
Large Scale
(FCC reactor)
Meso Scale
(injection zone)
Micro Scale
(drop-particle collisions)

Why study the micro scale?
 Investigate the reasons for catalyst pore blocking (due to
non-evaporated liquid or coke formed) originating in direct
solid-liquid contact
 Improve selectivity
 Optimize injection strategy
 Injection is a micro-scale phenomenon

Parameters investigated
Particle Droplet Gas
Position static moving
D (μm) 75 75-150
U (m/s) 15-30
T (K) 800-1000 550 800
P (atm) 2
Constant conditions
Parameters
Cracking Pathway assumed
 Cracking rates from
Gianetto et al. (1994)
Gianetto, A., et al., Fluid Catalytic Cracking
Catalyst for Reformulated Gasolines. Kinetic
Modeling. Industrial & Engineering Chemistry
Research, 1994. 33(12): p. 3053-3062.
C25H52(l) C25H52(g) C7H16(g)

Case 1 (2D), 1 drop – 1 particle
Dd = Dp 2D
 Effect of particle T on collision outcome
thin liquid expanding radially
torus breakup
τ=0.1 τ=0.7 τ=1.1 τ=1.7
Uo = 15m/s
1000K800K
Tp
Formation of vapour layer

2D
encapsulation
Dd = 2Dp
15m/s
Tp = 800K
 Effect of impact velocity on collision outcome
30m/s
Uo τ=0.1 τ=0.5 τ=1.0 τ=1.4
thick (compared to the previous where we had a
“thin”) ejecta sheet - expanding radially
under specific conditions may
lead to satellite droplets
detachment

Vapour layer prediction-a decisive parameter (Leidenfrost phenomenon)
 Drop is levitated by a vapour layer on hot catalysts
2D

Cracking Predictions
 Hotter catalysts promote cracking reactions/gasoline production
 Low impact velocity promotes cracking reactions/gasoline production
2D

Droplet info
 Small over large droplets (compared to catalytic particles)
evaporate faster and cool down slightly in the process
2D

3D

Vapour layer prediction-Leidenfrost phenomenon
 Drop is levitated by a vapour layer on hot catalysts
3D
h

Droplet break-up mechanism in 3D
3DDd = Dp
Uo = 15m/s
Tp = 1000K

Case 3 (3D), 1 drop – many particles
3DDd = 2Dp
Uo = 30m/s
Tp = 1000K

Droplet impact onto a cluster
 Many different liquid shapes (ligaments, sheet, fingers)/ Gasoline prediction
3DDd = 2Dp
Uo = 30m/s
Tp = 1000K

 Cluster formations promote cracking reactions/gasoline production
compared to 1drop-1particle collisions
3DDroplet impact onto a cluster

 Droplets on clusters evaporate faster and heat up in the process
3DDroplet impact onto a cluster

CUL-CERTH-video-Malgarinos.mpg
3DExhibited Dynamics

Case 4 (2D), 4 chain drops – 1 particle
2D

Case 4 (2D), 4 chain drops – 1 particle
2D
 Solution of particle cells for prediction of particle cooling from impact

Particle cooling characterization
(4 chain drops on 1 particle)
 Similar trend of particle temperature decrease for different chain impact
periods and initial particle temperatures
2D
a dimensionless character for time periods up to 12 μs (800 K) a dimensionless character for time periods up to at least 24 μs (1000 K)

 Wall heat flux prediction for different chain impact periods (6, 12, 24 μs
between each impact) and initial particle temperatures
Particle cooling characterization
(4 chain drops on 1 particle)
2D
a higher WHF for 1000 K (compared to 800 K) – this controls the necessary regeneration rate of catalytic particles

Fluidized Beds
Fluidized bed modeling
CERTH/CPERI Expertise
 10 Year Experience in Fluidized Bed simulation
 Hydrodynamic simulations
 Reacting Flows
 Full-loop simulations
 Custom built model (EMMS)
for the formation of clusters

CFD application in FCC industry
FCC (Fluid Catalytic Cracking), large scale reactors
• Investigate back-mixing effects
• Investigate Feed spray arrangement; Optimize catalyst / liquid oil
mixing
• Use of micro-scale results to predict accurately droplet / catalytic
particles fluid mechanics

CFD application in FCC industry
FCC (Fluid Catalytic Cracking), micro scale
• Help in minimization of coke deposits in the feedstock injection
zone originating from droplet-particle direct contact
• Investigate cooling rate for particle cluster
• Identify configuration which promote light molecule gas yields
and catalytic particle temperature reduction

 Experiments? Correlate particle insertion temperature
with deactivated catalyst rate in outlet
Collaboration
Internal Meeting
 Experiments? Bring closer the region of injection with
the region of particle insertion for increased
possibility of drop levitation. Correlate
injection/particle insertion regions overlapping with
deactivated catalyst rate in outlet
 Experiments? Find the optimum temperature of
droplet injection for maximization of evaporation rate.
Correlate droplet T with deactivated catalyst number
in outlet

CERTH CFD competencies
Collaboration with Industrial partners

PF and FB combustion
 Fluent commercial code (licenses for parallel processing), fully validated UDFs (PF
and FB boilers)
 New cluster computing system for parallel processing
 House built validated developed models integrated in ANSYS/Fluent:
 Char combustion
 Devolatilization
 Boudouard reaction
 Radiation
 NOx emissions
 Drag Scheme (EMMS)
 Full-loop simulation
 Reacting flow
 Homogeneous and
heterogeneous reactions
 NOx emissions
Fluidized Bed TechnologyPulverized alternative fuel Technology
(WRF/SRF, Sludge, Biogenic Fuels)

 Numerical Grid of 2.5 million tetrahedral cells (High computational cost)
 The true geometry is fully respected. Detailed design of burners
Primary air
Secondary air
Burner wall
OFA
Labels
Recircualation
Ducts
Oil burners
Ag. Dimitrios PP
An example of a Greek PF boiler

An example of a German FB reactor
- The EMMS scheme developed increases the accuracy of the model especially in the dense
bottom region which is hard to model, and in which the majority of CO2 capture takes place.
CFD modeling of plexi-glass cold model (Carbonator) of USTUTT

Real geometry RVE RVE with Backstays
Wall heat flux as a BC
Anisotropic stiffness matrix (xml file)
Far-Field Analysis
FEM tubes analysis in a German PP

Far-Field stress/strain fields Near-Field stress field
Near-Field Analysis
FEM tubes analysis in a German PP

Thank you for your attention!
The European Commission for funding this work, by the Marie Curie
Fellowship (FP7-PEOPLE-2012-IEF), GA No 329500 entitled as “Non Flat
Impingement” is gratefully acknowledged

Appendix
 Adaptive local grid
refinement
 Saves computational cost
 Increases accuracy at the interface
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Investigation of 2-phase evaporative reacting flows in micro-scale

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